Datasets:

wckwan

/

M4LE

like 3

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: smc 3 is one of the symbiotic systems in the magellanic clouds . the system contains a wd and an m giant with an orbital period of 4.5 years ( eg . it is a supersoft x - ray source powered by a steady hydrogen burning on the surface of the white dwarf ( orio _ et al . _ 2007 ) . because the system contains a massive white dwarf ( m@xmath01.18 m@xmath1 ; orio _ et al . _ @xcite ) with a high accretion rate ( @xmath2 m@xmath1/yr ; kahabka @xcite ) it is considered as one of the most promising supernova ia progenitors among the known symbiotic population . to estimate the mass of the red giant we used the fact that it pulsates with a period of 110 days ( kahabka @xcite ) . smc 3 lies on the sequence b in the k - log(p ) plane ( wood 2000 ) which suggests the first overtone pulsation . assuming the pulsation constant of q=0.04 we derived the mass of 2.3@xmath3 m@xmath1 . to carry out our analysis we used the startrack population synthesis code ( belczyski _ et al . _ the code includes the wind accretion through bondi - hoyle mechanism , roche - lobe overflow , @xmath4 roche - lobe overflow and @xmath5 roche - lobe overflow . as initial conditions we adopted the current parameters of the system and then we modeled its future evolution . we assumed @xmath6=1.44 m@xmath1 and , since we studied the system in the sn ia context , a co wd . for all of our models the system went trough a common envelope ( ce ) after @xmath7 yrs and for none of the models system wd managed to accumulate enough matter to become a type ia supernova . the orbital separation after the ce was relatively big ( a@xmath8r@xmath1 ) , which makes a merger in the hubble time unlikely . the obtained parameters of the system are presented in fig . we predict that the system will not become a type ia supernova in contrary to what was suggested in the literature ( orio _ et al . _ the caveat is that our predicted mass transfer rate is somewhat lower then the one expected for the steady hydrogen burning on the surface of the white dwarf ( nomoto _ et al . _ a lower @xmath9 then expected could be due to the fact that our model underestimates the rg mass loss trough wind by treating it as in the single star scenario , whereas there is a strong observational evidence that this wind is significantly enhanced due to tidal interactions in syst ( mikoajewska _ et al . _ large roche lobe filling factor suggests ellipsoidal variability in the system . 99 belczyski k. 2008 , apjs , 174 , 223 kahabka p. , 2004 , a&a , 416 , 57 kato m. 2013 , apj , 763 , 5 nomoto k. 2007 , apj , 663 , 1269 mikoajewska j. 2002 , adspr , 30 , 2045 orio m. 2007 , apj , 661 , 1105 wood p.r . , 2000 , pasa , 17 , 18 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the distant globular cluster palomar 13 has been found to have a very high m / l ratio of @xmath0 and its profile can be well fitted either by a king profile with a power - law tail or a nfw model [ 1 ] with scale radius @xmath1pc and central density @xmath2 . a possible explanation is that this distant cluster @xmath3 is one of the numerous dark clumps predicted by cdm scenarios , which was not destroyed by the galactic tidal field . it may be a disrupted cluster as well , out of dynamical equilibrium . here we assume that the nfw profile is the signature of a halo made of cold particles . physics beyond the standard model could be supersymmetry . the lowest massive supersymmetric particle , i.e. the neutralino , is a natural candidate for cdm . if r - parity is conserved the neutralino is stable , is its own antiparticle and has a very small cross - section for annihilation . we assume that the halo of palomar 13 is made of neutralinos and calculate the flux in high energy @xmath4-rays due to their annihilation . theoretical physics beyond the standard model is reviewed by j. ellis in this book . the susy benchmark models have been proposed to provide a common way of comparing the discovery potential of future accelerators [ 2 ] . these scenarios correspond to 13 configurations of the 5 msugra parameters with the trilinear coupling parameter @xmath5 set to 0 . the models fulfill the conditions imposed by lep measurements , @xmath6 result and relic density constraint @xmath7 . we calculate the @xmath4 fluxes for the benchmark models bcgil in the `` bulk '' region with our current mc simulation programs : darksusy [ 3 ] and suspect [ 4 ] . the simultaneous use of the suspect and darksusy package allows to perform the rge evolution from the gut scale to the ewsb scale . the fluxes ( in @xmath8 ) obtained by varying the threshold energy and integrated within @xmath9 are shown in the following figure . the main points are that we need to work at low energy threshold and very low flux @xmath10 . these fluxes are not out of reach but ground - based ongoing instruments will have to be improved by one order of magnitude for that purpose . an array of 5 hesses ( each including four 15-m class telescopes like in hess ) , operating in adjacent areas at 5000 m altitude , would reach a flux limit of @xmath11 at 25 gev in 400 h. * with that flux limit most of the neutralino parameter space in the galactic center could be explored . this is roughly the instrument needed to demonstrate or disprove supersymmetry in astrophysics . * p. cot , s.g . djorgovski , g. meylan , s. castro , j.k . mccarthy , 2002 astro - ph/0203410 j. ellis , j.l . feng , a. ferstl , , k.t . matchev , & k. olive , 2001 , astro - ph/0110225 http://www.physto.se/~ edsjo / darksusy/ http://www.lpm.univ - montp2.fr:7082/~ kneur / suspect.html Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the polcor instrument is a combined imager , coronograph and polarimeter built for the nordic optical telescope ( not ) . polcor provides sharp images ( resolution down to 02 ) , has a well - defined psf ( resulting in a higher image contrast ) and a high - quality polarimeter . + we observed three sources using polcor / not : the binary s - type agb star w aql , and the two detached shell carbon stars u cam and dr ser . observations of the polarized light around the stars trace the circumstellar dust distribution and thus enables the search for structures and asymmetries in the circumstellar envelope . though this study the geometry of the mass loss can be investigated which will give important clues not only to the processes at play , but also to the transition from the agb phase to the planetary nebula phase . the circumstellar dust distribution around the binary star w aql is mapped and found to be asymmetric , both on large ( 10 ) and on smaller ( 1 ) scales ( fig . 1 ) . the large - scale images show what appears to be a dust - density enhancement on the south - west side of the star and the inner region appears bi - polar through the coronographic mask . these structures are in agreement with what could be expected from binary interaction . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: intermediate scale disk galaxies with starbursts are relatively common in the nearby universe . about 5% of galaxies with @xmath017 @xmath1 m@xmath2 @xmath321 have evidence for starbursts . many of these occur in smaller galaxies , produce blue colors and strong emission lines , and are in gas rich systems , as indicated by their relatively large fractional hi content . the more luminous nearby blue starbursts structurally and spectroscopically resemble the faint blue compact narrow emission line galaxies ( cnelgs ) , which become common at redshifts of z@xmath40.3 ( e.g. , guzman et al . they are less well - matched to high redshift blue galaxies , which have a combination of high uv luminosities and huge star formation rates that are not common in nearby extreme starbursts . this difference probably reflects secular evolution in the lives of galaxies ; for example , systems at high redshift may be subject to frequent , strong mergers that trigger hyperactive star formation ( e.g. conselice et al . 2001 in prep ) . nearby starbursts frequently show evidence for being dynamically cool , that is they contain strong spiral arms or bars , features that are found in rotationally supported galactic disks . thus the processes that produced these starburst did not severely disrupt the disk , or the disk reformed during the starburst event . local analogs to the cnelgs include profound starbursts arising from minor perturbations ( see figure 1 ) . moderate interactions ( glancing collisions between equals , minor mergers ) are apparently the sources of many starbursts . evidence for this includes subtle optical structural features such as wisps , faint tails , or moderately disturbed kinematics in starbursts , as well as the more ubiquitous signatures of disturbed hi . furthermore , in some starbursts where an interaction is the likely trigger , the outer regions of the optical disk appear to be relatively symmetric and relaxed . three possible explanations for this behavior are : @xmath5 blue starbursts are commonly associated with disk galaxies : near face - on systems can transmit uv light through areas where the disk has been cleaned out by supershells , supernova , etc . ( e.g. conselice et al . 2000 ) . @xmath5 low inclination disks can mimic the kinematics of low mass galaxies due to their narrow line widths ( homeier & gallagher 1999 ) . some intermediate redshift cnelgs could be low inclination disks of moderate mass rather then extreme dwarf starbursts . @xmath5 undisturbed intermediate mass galaxies , such as extreme late - type and superthin spirals ( e.g. , matthews et al . 1998 ) can be inefficient star - formers and thereby store interstellar gas , the fuel for starbursts , over cosmic time scales . @xmath5 uv - bright regions of starbursts frequently occur in features associated with disks , such as rings or arms ( e.g. conselice et al . 2000 ) which may represent star forming environments not yet accessible to severely disturbed high luminosity starbursts in the distant universe . conselice , c.j . 2000 , aj , 119 , 79 + guzman , r. et al . 1998 , apj , 495 , l13 + homeier , n. & gallagher , j.s . 1999 , apj , 522 , 199 + matthews , l. , van driel , w. , & gallagher , j. 1998 . aj , 116 , 1169 + mihos , c. & hernquist , l. 1996 , apj , 464 , 641 + Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the ultimate fate of the gas which cools in cooling flows is still unknown . a possibility is that a fraction of the gas forms cold molecular clouds @xcite . as a result of fragmentation we expect the formation of small clouds with higher density and possible production of molecules in particular @xmath0 and traces of @xmath1 and @xmath2 . + taking into account radiative transfer effects we computed analytically in @xcite the cooling function @xmath3 for the transition between the ground state and the first rotational level . this way we determined a lower limit of @xmath4 . + meanwhile we improved this calculation by including numerically all rotational transitions which are relevant at low temperatures ( i.e. up to @xmath5 ) . + the following column densities are adopted for a typical small cloud ( with @xmath6@xmath7 ) : @xmath8 , which corresponds to a @xmath2 abundance : @xmath9 . for @xmath1 instead we assume the primordial ratio @xmath10 . + in figure 1 we plotted the molecular cooling function @xmath3 taking into account @xmath2 , @xmath1 and @xmath0 in the range 3 - 300 k. @xmath2 is the main coolant in the range of temperatures 3 - 80 k , @xmath1 in the range 80 - 150 k and @xmath0 dominates above 150 k. the heating is given by the external x - ray flux as produced from the hot intracluster gas . the thermal balance between heating and cooling leads to an equilibrium temperature for the clouds . we have calculated the minimum equilibrium temperature @xmath11 of the clumps inside the cooling flow region . table 1 shows the equilibrium temperature for different clusters . for comparison we give the values we find using our analytical approximation ( @xmath12=1 ) and the ones by taking into account higher excited rotational levels ( @xmath12=5 ) . one clearly sees that the inclusion of the higher excited levels into the calculations lowers the equilibrium temperature , particularly for hot clusters such as for instance abell 478 . + we conclude that thermal equilibrium can be achieved at very low temperatures inside the cooling flow region mainly due to @xmath2-cooling . other molecules than @xmath2 , for example @xmath13 or @xmath14 , could also be important . thus the study of the chemistry in cooling flows might lead to important insight . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: catalogs of galaxy clusters with a large range of redshifts and cluster x - ray luminosities are an ideal basis for the test of cosmological parameters ( e.g. henry 2000 ; borgani et al . 2001 ) and the study of cluster formation and evolution . the bright and southern serendipitous high redshift archival rosat cluster ( sharc ) surveys provide a sample of clusters detected in rosat observations over two decades of x - ray luminosities ( 10@xmath2 l@xmath3erg / s ) with redshifts between 0.2 and 0.8 ( romer et al . 2000 ; collins et al . 1997 ; burke et al . 1997 ) . we present here preliminary results based on the follow - up observations of three of these selected galaxy clusters with xmm newton : rx j0256.5 + 0006 , rx j2237.0 - 1516 and rx j1200.8 - 0328 . for the first time , the new generation of x - ray observatory , like xmm - newton and _ chandra _ give capabilities to do precise spectroscopic and imaging analysis at the same time ( see e.g arnaud et al . 2002a ) . our analysis is based on the three epic cameras , mos1&2 and pn . throughout the paper , we use a cosmology with h@xmath4km / s / mpc , @xmath5 and @xmath6 . the error bars are given with a confidence level of 90% . all the data presented here are treated with the version 5.2 of the sas ( science analysis software ) . we select event patterns and time intervals of low background as described in majerowicz et al . table 1 shows the effective exposure time of our observations after flare rejection . this suggests that this cluster does not host a strong cooling flow . this was already seen in rx j1120.1 + 4318 , a relaxed cluster at z=0.6 ( arnaud et al . 2002a ) also found in the sharc survey . the global temperature for this cluster is 5.1@xmath1kev . its surface brightness profile is fitted by a @xmath7-model and the parameters are : @xmath7=0.64 and @xmath80.51@xmath9228kpc . arnaud , m. , neumann , d.m . , aghanim , n. , et al , 2001 , , 365 , l80 arnaud , m. , majerowicz , s. , lumb , d. , et al , 2002a , in press , astro - ph/0204306 arnaud , m. , 2002b , this issue borgani , s. , rosati , p. , tozzi , p. , et al , 2001 , , 561 , 13 burke , d.j . , collins , c.a . , sharples , r.m . , et al , 1997 , , 488 , l83 collins , c.a . , burke , d.j . , romer , a.k . , et al , 1997 , , 479 , l117 henry , j.p . , 2000 , apj , 534 , 565 lumb , d. , 2002 , xmm - soc - cal - tn-0016 majerowicz , s. , neumann , d.m . & reiprich , t.h . , 2002 , submitted to , astro - ph/0202347 neumann , d.m . & bhringer , h. 1997 , , 289 , 123 roettiger , k. , loken , c. & burns , j.o . , 1997 , , 109 , 307 romer , a.k . , nichol , r.c . , holden , b.p . , et al , 2000 , , 126 , 209 schindler , s. & mller , e. , 1993 , , 272 , 137 snowden , s.l . , egger , r. , freyberg , m.j . , et al , 1997 , , 485 , 125 takizawa , m. , 1999 , , 520 , 514 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the disk - galaxies are constructed in dynamical equilibrium ( hernquist , 1993 ) and consist of an exponential stellar disk , a bulge with a hernquist profile , and a pseudoisothermal dark halo ( units as in hernquist , 1993 ) . the two merging galaxies approach each other on nearly parabolic orbits at a pericenter distance of 2 scale lengths of the larger disk . the large galaxy is realized with 20000 disk particles , 6666 bulge particles and 40000 halo particles , respectively . the smaller galaxy contains @xmath1 of the mass and of the particles in each component and has a disk scale length of@xmath2 compared to the more massive galaxy . we tested 14 different relative orientations for every mass ratio . the time integration was performed using the special purpose hardware grape . after the remnants settled into equilibrium an artificial image of the remnant was created ( see also heyl , hernquist & spergel , 1994 ) . following the definition of bender , dberreiner & mllenhoff ( 1988 ) we determined the characteristic isophotal shape @xmath3 , ellipticity @xmath4 , the ratio of major axis rotation and central velocity dispersion , @xmath5 , and the anisotropy parameter @xmath6 for 500 random projections of each of the 14 orbital geometries . these values were used to calculate a probability density for a given simulated remnant to be observed at a given location in the two dimensional parameter plane , adopting that mergers occur randomly without any preferred relative inclination . figure 1 shows the result for 1:1 , 2:1 , 3:1 and 4:1 merger remnants . from these results we conclude that most of the global properties of elliptical galaxies can be explained by a sequence of stellar mergers between disk galaxies of mass ratios between 1:1 and 4:1 . 1:1 mergers completely erase the structure of the initial disk . in the 3:1 and 4:1 case the remnants seem to remember their initial state ( see barnes , 1998 ) . in this sense the sequence of mass ratios is a sequence of disk disruption . however , even with 4:1 remnants we fail to reproduce the fastest observed rotators with @xmath7 at one effective radius ( figure 1 ) . recent observations of fast rotating low luminosity ellipticals ( rix , carollo & freeman , 1999 ) show that the disagreement is even stronger at larger radii ( see cretton , naab , rix & burkert , this conference ) barnes , j. , 1998 , in galaxies : interactions and induced star formation , ed . d. friedli , l. mertinet , & d.pfenniger ( saas - fee advanced course lecture notes , no . 26 : berlin : springer ) , 275 bender , r. , dberreiner , s. & mllenhoff , c. , 1988 , , 278 hernquist , l. , 1993 , , 86 , 389 heyl , j. s. , hernquist , l. & spergel , d. n. , 1994 , , 427 , 165 naab , t. , burkert , a. & hernquist , l. , 1999 , , 523 , l133 rix , h. w. , carollo , c. m. & freeman , k. , 1999 , , 513 , l25 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: this paper documents some of the dynamics observed when a gas is injected into a shallow pool of liquid . these dynamics are visible to the naked eye , but benefit from the high - frame rate and low exposure time offered by a high - speed camera . the high - speed video discussed in this paper is available in the accompanying http://ecommons.library.cornell.edu/bitstream/1813/11469/3/bird_dfd2008_mpeg1.mpg[movie ] , submitted to the 2008 american physical societies division of fluid dynamic s gallery of fluid motion . the experimental setup consists of a 7 gauge metal needle placed into a 5-millimeter deep pool of 10 cst silicon oil , such that part of the needle tip contacts the bottom of the container . similar regimes have been observed in other liquids , although the dynamics are less crisp . helium is pumped through the needle at a modest flowrate of 3 ml / s . the advantage of helium is that it is well - characterized , inert , and readily available ; we suspect that the dynamics shown in the movie are independent of the gas properties . the flow of helium into the silicon oil distorts the interface between the silicon oil and surrounding air . the precise dynamics of this deformation depend on the angle of needle , flowrate of the gas , and the depth and material properties of the liquid . in this study we have held the flowrate and pool depth constant while varying the angle of the needle , @xmath0 . at low needle angles ( @xmath1 ) , the air - silicon oil interface is in static equilibrium . once the angle approaches @xmath2 , ripples propagate across the surface . due to the size and speed of the ripples , we believe that they are capillary waves , that is waves that are regulated by surface tension . as the angle of the needle continues to increase , the amplitude of the capillary waves grows such that an oscillating bulge develops . at higher angles , the bulge becomes both larger and more focused , developing into periodic jets . once the jet aspect ratio of the jet becomes sufficiently small ( @xmath3 ) , the tip of the jet pinches off to form a spherical droplet . the droplets formed from the periodic jets float over the interface , similarly to how drops avoid coalescence over a vibrating fluid @xcite . it is worthwhile to note that the droplets often coalesce with each other before coalescing with the interface , implying that it is unlikely that natural surfactants are responsible for the floating behavior . as the angle of the needle increases , the height of the upward jets increase . at sufficient jet height ( @xmath4 ) , the jets break into two drops , leading to both a high parabolic arch and a lower droplet stream . between ( @xmath5 ) , the jet dynamics breakdown so that the droplet streams appear chaotic . large bubbles sporadically form at the fluid interface , often with jets emitting from the bubble surface . droplets are still emitted from the jets , but the resulting bubble streams are incoherent . we have found that injecting gas into shallow liquid can lead to a rich variety of interfacial dynamics . by sweeping the angle of the gas - injecting needle , we observe a smooth transition between static deformation , juggling and tumbling of droplet streams , and an incoherent mix of bubbles and jets , reminiscent of a daredevil shooting out of a canon . this combination of dynamics provides an aesthetically pleasing show of liquid acrobatics . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: recent years have seen a rapid increase in the interest in finite quantum spin systems , also known as molecular magnets or nanomagnets @xcite . molecular magnets typically consist of clusters of interacting spins that are magnetically isolated from the other clusters in the molecular solid by nonmagnetic ligands . formally , molecular magnets are materials in which the ground state has nonzero total spin . here we generalize this definition to include all systems of largely isolated clusters of interacting quantum spins . these materials are interesting both as simple model systems for the study of quantum magnetism and because they have possible applications as nanoscale computer memory elements @xcite . many realizations of finite spin clusters with various ionic spins , ground state spins and geometries have been reported in the literature ; some recent examples with s=1/2 ions are given in table [ materials ] . theoretical results for the properties of finite s=1/2 quantum spin systems have appeared in several recent references , primarily in the context of experimental studies of specific materials . dimer results are reported in several studies of the s=1/2 spin dimer vo(hpo@xmath0)@xmath10.5h@xmath2o ; see for example johnson _ @xcite , tennant _ et al . _ @xcite and koo _ et al . theoretical properties of s=1/2 spin trimers have similarly been given in studies of candidate trimer materials ; see for example refs.@xcite . rather few general theoretical results have been reported for s=1/2 spin tetramers , since the results are more complicated and there are many more independent geometries and sets of superexchanges . specific cases of tetramers are considered by procissi _ et al . _ @xcite ( s=1/2 square tetramer ) , gros _ et al . _ @xcite and jensen _ et al . _ @xcite ( an unsymmetric s=1/2 tetrahedral model of cu@xmath2te@xmath2o@xmath3(br@xmath4cl@xmath5 ) ) , kortz _ et al . _ @xcite ( unsymmetric tetramer model of k@xmath6na[cu@xmath0k@xmath2(h@xmath2o)@xmath7(@xmath8-asw@xmath9o@xmath10)@xmath2]@xmath15.5h@xmath2o ) , and ciftja @xcite ( symmetric trimer with apical spin ) . more general reviews of quantum spin systems have been published by kahn @xcite ( thermodynamics ) and whangbo _ et al . _ @xcite ( local origins of magnetism , thermodynamics properties , and materials ) . studies of the dynamics of heisenberg spin clusters using a quasiclassical formalism have been reported in a series of papers by ameduri , efremov and klemm @xcite . waldmann @xcite has carried out calcuations of the inelastic neutron structure factor for cyclic heisenberg spin clusters which are quite similar to the results presented here . this increased level of interest in molecular magnets motivates more detailed theoretical investigation of the properties of finite quantum spin systems . for simple theoretical models such as the heisenberg model , clusters that consist of only a few interacting magnetic ions can be treated analytically , and closed - form results can be obtained for many physical observables . one especially interesting quantity is the inelastic neutron scattering structure factor , which is required for the interpretation of inelastic neutron scattering experiments . inelastic neutron scattering is very well suited to the investigation of magnetic interactions at interatomic scales , since the measured structure factor is sensitive to the local geometry and interactions of the magnetic ions . as this work is intended in part to facilitate future neutron scattering studies , the evaluation of this structure factor is one of our principal concerns . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: we have recently completed a search of 56 unidentified mid - latitude egret @xmath0-ray sources for pulsations using the parkes telescope and the multibeam receiver . this survey covered @xmath1140 square degrees of sky at galactic latitudes @xmath2 and revealed six new pulsars , three of which are in binary systems . here we present initial timing results for the three binaries . the properties of the three new binaries are summarized in table 1 and their pulse profiles are shown in figure 2 . .newly discovered binaries [ cols="<,^,^,^,^,^,^ " , ] @xmath3 assuming a pulsar mass ( @xmath4 ) of 1.4m@xmath5 . + @xmath6 dm distance from the ne2001 electron density model of the galaxy ( cordes & lazio 2002 , astro - ph/0207156 ) . + psr j1614@xmath72230 is a recycled millisecond pulsar with a very low inferred magnetic field ( @xmath8 g ) . it has the highest minimum companion mass of the @xmath150 binary pulsars with spin periods lower than 8ms , suggesting a possible non - standard evolution . compared with the orbital period versus companion mass relationship of rappaport et al . 1995 ( mnras , 273 , 731 ) the orbital period of psr j1614@xmath72230 is short by a factor @xmath910 for its companion mass . the companion may be a cno white dwarf or a low - mass degenerate dwarf . the spin - down rate of psr j1614@xmath72230 gives an @xmath10 erg s@xmath11 , which is just barely consistent with the flux measured from the @xmath0-ray source in whose error box this pulsar was found . if the pulsar is the counterpart it would demand a very high @xmath0-ray efficiency , or a significantly closer distance than what is inferred from the dm . psr j1614@xmath72318 is likely partially recycled ( @xmath12 g ) . it has the lowest minimum companion mass of any binary pulsar with spin period between 10 and 100ms . the pulse profile is relatively wide at 1.4ghz ( @xmath130% of the pulse period at fwhm ) . at @xmath1350mhz the higher signal - to - noise ratio of the profile shows that there are wings on either side of the main pulse ( see figure 1 ) . it is possible that we are seeing emission from the core and cone of the beam . psr j1744@xmath73922 was also independently discovered by the parkes multibeam galactic plane survey ( a. lyne , private communication ) . it is possibly partially recycled ( @xmath13 g ) and is one of only @xmath116 binary pulsars with spin periods greater than 50ms ( of these it has the shortest orbital period and the third smallest minimum companion mass ) . it is difficult to detect at times , as it seems to shut off and turn on on timescales as short as a few tens of seconds ( see figure 2 ) . since its dm is relatively high , it is unlikely that scintillation is responsible for the many non - detections of the pulsar . psr j1744@xmath73922 has also been very difficult to detect at wavelengths other than @xmath11.4ghz . observations with the gbt have improved the detection rate of this strange pulsar . we have applied for exploratory observations of all three pulsars presented here with the 8-m gemini - south optical telescope in order to determine the magnitudes and colors of their binary companions and to see if they are consistent with being white dwarfs . these observations may lead to future spectroscopic observations of the companions , which could allow us to determine the neutron star masses and distances to the systems . with a clearer picture of the nature of the companion stars we would also be in a better position to comment on how these systems fit in with theories of binary evolution . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: nuclear spirals are known to be preponderant in active galaxies ( reagan & mulchaey 1999 ; martini et al . they have a variety of morphology , from the grand - design symmetric two - armed spirals to chaotic ones ( martini et al . the flocculent nuclear spirals are considered to be formed by the acoustic instability proposed by montenegro , yuan , & elmegreen ( 1998 ) , whereas the grand - design nuclear spirals are thought to be formed by the hydrodynamical instability caused by the gas inflow driven by the non - axisymmetric potentials ( englmaier & shlosman 2000 ) . it is well known that the response of gaseous disk to the imposed non - axisymmetric potentials depends not only on the potential shape of the model galaxy but also on the hydrodynamic properties of the gaseous disk ( ann & lee 2000 ; englmaier & shlosman 2000 ; maciejewski et al . however , the effects of smbhs on the gas flow inside the ilrs have not been studied much . here , we present some results of numerical experiments including smbh for the formation of nuclear spirals , based on smoothed particle hydrodynamics ( sph ) . we have assumed that a barred galaxy is made up of three stellar components ( bulge , disk , bar ) and two dark ones ( smbh , halo ) . we adopt simple analytic forms for the potential generated by each component . the properties of all the potential generating components are assumed to be invariant in time . we considered mass models which are thought to resemble early type galaxies ( @xmath0 sba ) by assuming the bulge - to - disk mass ratios as @xmath1 . we assumed a strong bar which has the fractional mass of 0.2 and the axial ratio ( a / b ) as 3 . the bar rotation period is @xmath2 years . we used isothermal assumption for the gas but we explored the effect of gas temperature by varying the sound speed of gas . we adopted @xmath3 and @xmath4 for the artificial viscosity coefficients . the self - gravity of gas was also included . fig . 1 shows snapshots of the evolution of the nuclear regions of gaseous disks at the evolution time of 20 bar rotations . the three models have the same mass distributions except for the central smbhs . the model m1 has no smbh , while the other two models ( m2 , m3 ) have a smbh whose mass is about @xmath5 of the total mass of the visible components ( disk , bulge and bar ) but they assumed different sound speeds in the gas ; 10 km / s for m2 and 15 km / s for m3 . the sound speed in the gas of m1 model is the same as that of the model m2 . as shown clearly in fig . 1 , the nuclear regions of the gaseous disk of m1 model evolves to leading spirals between the iilr and oilr , whereas those of m2 and m3 develop trailing spirals whose detailed shapes depend on the sound speeds in the gas . the cold gaseous disk assumed in the model m2 shows ring - like spirals , while the hot gaseous disk of the model m3 shows tightly wound spirals whose innermost parts reach close to the center . thus , it seems quite clear that the tightly wound trailing nuclear spirals can be developed in the hot interstellar medium when there is a smbh whose mass is large enough to remove the iilr . this is the reason why nuclear spirals are frequently observed in active galaxies . ann , h.b . , & lee , h.m . 2000 , jkas , 33 , 1 englmaier , p. , & shlosman , r.s . 2000 , , 528 , 677 maciejewski , w , teuben , p.j . , sparke , l.s . , & stone , j.m . 2002 , , 329 , 502 martini , p. , regan , m.w . , mulchaey , j.s . , & pogge , r.w . 2003 , , 146 , 353 montenegro , l. e. , yuan , c. , & elmegreen , b. g. 1999 , , 520 , 592 regan m.w . , & mulchaey j.s . , 1999 , , 117 , 2676 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: regge calculus @xcite is used to re - examine a particular class of brill wave spacetimes @xcite investigated by miyama @xcite , and more recently , holz @xcite and alcubierre @xcite . in particular , we study the formation of apparent horizons within the simplicial initial data , and confirm recent findings regarding the appearance of such horizons @xcite . brill wave initial data was first constructed using regge calculus by dubal @xcite , although we show elsewhere @xcite that his procedure is unable to capture the full structure of complex axisymmetric initial data sets . by using an improved lattice ( which is described in full in ref . @xcite ) , we are able to accurately reproduce the continuum solution , and find apparent horizons in excellent agreement with recent two and three - dimensional calculations @xcite . we proceed as follows . in the next section , we briefly survey the approach taken by brill @xcite in the construction of gravitational wave initial data . in section [ sec : regge ] we describe the axisymmetric lattice used to construct brill waves using regge calculus . in section [ sec : trapped ] we describe the method used to find apparent horizons at a moment of time symmetry , and in section [ sec : horizons ] we investigate the appearance of apparent horizons in the brill wave space as the wave amplitude is increased . .mass estimates for the regge ( @xmath0 ) and continuum solutions ( @xmath1 ) . the mass is calculated from the decay of @xmath2 in the asymptotic region . we also show the results of previous calculations by holz @xcite and alcubierre @xcite , which are in excellent agreement . all our results were calculated on a @xmath3 grid . [ cols="^,^,^,^,^",options="header " , ] + using the technique outlined in section [ sec : trapped ] , we now search for apparent horizons in the brill wave initial data constructed in sections [ sec : continuum ] and [ sec : regge ] . we find that in both the regge and continuum solutions an apparent horizon first appears at a critical amplitude @xmath4 , which lies in the range @xmath5 $ ] . as the amplitude @xmath6 is increased above this critical value , two trapped surfaces are present , and these gradually separate . these results are in complete agreement with the recent calculations of alcubierre @xcite . figure [ fig : horizons]_a _ shows a projection of the trapped surfaces found for a wave amplitude of @xmath7 , calculated using both the continuum and regge solutions . there is a slight difference between the surfaces calculated using these two independent sets of initial data , but the discrepancy is found to reduce as the second power of the grid spacing . in figure [ fig : horizons]_b _ , we show the position @xmath8 of both trapped surfaces along the @xmath9-axis as a function of the brill wave amplitude . the quadratic fit to this data allows us to improve the estimate of the critical wave amplitude at which an apparent horizon first forms . we estimate that @xmath10 for the simplicial solution , and @xmath11 for the solution to the continuum equation . both solutions predict that the single horizon at @xmath12 passes through @xmath13 . the value of the critical amplitude @xmath4 , at which an apparent horizon first forms , differs from that obtained in an earlier calculation by some of us @xcite . the discrepancy in the earlier work was due to the relatively weak convergence criteria used for the trapped surface finder . qualitatively , the previous work agrees with both the present calculations and those of alcubierre @xcite . we have used regge calculus to confirm recent numerical findings regarding the formation of apparent horizons in a particular class of brill wave spacetimes , while demonstrating that regge calculus provides an alternative and competitive technique for use in numerical relativity . brill wave spacetimes provide a challenging test - bed for the future development of simplicial gravity . work is currently underway on the development of a simplicial trapped surface finder for regge calculus , as well as the time evolution of the initial data constructed here , in both @xmath14 and @xmath15-dimensions . we gratefully acknowledge support from a los alamos national laboratory ldrd grant . one of us ( apg ) acknowledges support from the sir james mcneill foundation at monash university , and from the center for nonlinear studies . # 1 , # 2 , # 3 , # 4 # 1 , * # 2 * , # 3 ( # 4 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: in our computations we adopt an initial helium content @xmath1 . we consider the complete sets of reactions for the pp - chain and cno tri - cycle , and the most important alpha - capture reactions for heavy elements up to mg . nuclear rates are taken from caughlan & fowler ( 1988 ) . the nuclear network is implicitly solved for all the considered h- and he - burning reactions , and without any additional assumption for nuclear equilibria . overshooting from stellar cores is applied according to the bressan et al . ( 1981 ) formalism . mass - loss from massive stars ( @xmath2 ) is described according to chiosi ( 1981 ) . stellar evolution is calculated throughout the nuclear h - burning phase up to the he - flash at the rgb tip for low - mass models , and throughout nuclear h- and he - burning phases up to the beginning of the tp - agb phase and carbon ignition for intermediate- and high - mass models , respectively . figure [ fig_hrd ] presents the evolutionary tracks in the h - r diagram . the appearance of short - lived loops is caused by the ignition of the 3-@xmath3 reaction during core and/or shell h - burning , leading to the first activation of the cno - cycle . in the case of low - mass stars ( @xmath4 ) a loop develops near the end of central h - burning ( @xmath5 ) , whereas for more massive stars ( @xmath6 ) a similar feature also occurs at the formation of the he - shell . as far as the critical stellar masses for non - degenerate nuclear ignition are concerned , we find that @xmath7 corresponds to the minimum initial mass for a star to avoid the he - flash , and @xmath8 the minimum initial mass for a star to avoid carbon deflagration . the first dredge - up is practically absent in all models . only for stars with @xmath9 a very small amount ( less than 0.003 @xmath0 ) of he is dredged - up to the surface . the second dredge - up is experienced by stars with @xmath10 , being quite efficient in models with @xmath11 . it turns out that the surface composition is enriched almost only in he ( reaching @xmath12 @xmath13 at increasing stellar mass ) and negligibly in cno elements ( @xmath14 @xmath15 in mass fraction ) . massive stars , with @xmath16 , do not show any trace of surface chemical pollution due to dredge - up episodes . only models calculated with mass - loss may expose nuclearly processed material to the surface . with the adopted prescription for mass - loss , stellar winds are never able to strip off h - exhausted layers in models with @xmath17 . in these cases , at most , the h - burning shell is eaten up , with consequent surface enrichment in he and small amounts of cno . for more massive models with @xmath18 , wind stripping is able to reach the co - enriched region left by convective he - burning . in these cases , the corresponding yields of c and o are considerable ( @xmath19 @xmath20 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the radiation emitted by physical processes ongoing in active galaxies sculpt a spectral energy distribution ( sed ) that spreads on a wide range of the electromagnetic spectrum . multi - wavelength photometry is thus a rich source of information about the agn nature . one method to extract this information is through sed fitting , which consist in comparing the observed photometric data to a combination of physical models for agn components . it is customary to perform sed fitting using optimization methods as @xmath0-minimization , which defines the best fit as the combination of parameters which models the whole sed showing the minimal @xmath0 value . however , this method is statistically correct only under the assumption that the parameters are fully independent from each other and thus have a gaussian probability distribution . this assumption is a drawback of this method since the parameters describing agn physics are in most cases highly degenerated . to solve this issue we present agn__fitter _ _ , a bayesian sed fitting code for agn that allows an integral calculation of the posterior probability distributions of the model parameters taking into account degeneracies and correlations existing among them . agn__fitter _ _ samples the parameter space built by the agn models parameters using a markov chain monte carlo method . this consists in a random walk that is biased for regions of higher probability in the parameter space , making the code fast and efficient since no time is lost in non - interesting regions . built on the published code emcee ( ( * ? ? ? * ; * ? ? ? * ; * ? ? ? * foreman - mackey et al . 2011 ) ) our mcmc code increases its efficiency taking advantage of multiprocessing by parallel tempering , i.e. exploring the parameter space with several chains simultaneously . [ 0.96 ] the dimension of the parameter space sampled by agn__fitter _ _ is constructed in this first version by 10 parameters , which rule the modeling of four agn components : the accretion disk radiation , the nuclear hot dust emission and the radiation emitted by the host galaxy and the star burst regions . for the accretion disk radiation ( big blue bump ) we use the model by ( * ? ? ? * ; * ? ? ? * richards et al . ( 2006 ) ) , while the hot dust surrounding the disk is modeled by a continuous torus ( ( * ? ? ? * silva et al . 1994 ) ) . the contribution of the host galaxy to the full source radiation is modeled using ( * ? ? ? * ; * ? ? ? * ; * ? ? ? * bruzual & charlot ( 2003 ) ) templates , while the cold dust radiation produced in star burst regions is simulated using ( * ? ? ? * dale & helou ( 2002 ) ) templates . since many of these models cover equal regions of the spectrum it is important to take correlations into account . l0.48 agn__fitter _ _ constructs seds from existing physical models ( fig . 1 ) and calculate physical parameters that are interesting to agn physics , such as relevant integrated luminosities ( @xmath1 , @xmath2 , @xmath3 ) and parameters ruling the physics of the host galaxy , such as age , stellar mass @xmath4 and star formation rate ( sfr ) . moreover , agn__fitter _ _ provides both the marginalized and two - dimensional posterior density functions ( pdf ) of the parameters listed above . in this way degeneracies can not only be better visualized but also analyzed and treated ( fig.2 ) . finally , due to the code s bayesian methodology , the user is able to take advantage of prior constraints on the parameters distributions . in this way the information given by the likelihood function can be complemented , calculating robustly posterior probabilities of the parameters . agn__fitter _ _ is a robust statistical tool to model agn seds and to infer physical parameters from multiwavelength photometrical data . our code provides a vast statistical information about the inferred parameters allowing in this way an analysis of multiwavelength photometry cognizant of degeneracies and correlations , which is necessary for agn studies of general purpose . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: we examined the vlba imaging and polarimetry survey ( vips , ( * ? ? ? * helmboldt et al . 2007 ) ) . it contains 1127 agn observations taken at 5 ghz with the very long baseline array ( vlba ) . the calibrated vlbi visibility data sets can be downloaded from the vips data collection index page . the original field of view of the interferometer was @xmath01.5 arcsec but the imaging was typically preformed only in the central area of 128 mas@xmath1128 mas . even though large structures were reported in the original publication and subsequent studies ( ( * ? ? ? * helmboldt et al . 2007 ) , ( * ? ? ? * tremblay et al . 2016 ) ) , we could find further objects in the full - field images with structures extending beyond the central area . the large sample size and the extended fields motivated us to image the sources and analyse the data in an automated way . the imaging and model fitting were performed through standard procedures using difmap ( ( * ? ? ? * shepherd et al . 1994 ) ) . we modeled the visibility data with a central elliptical gaussian component . in addition , extended structures were fitted with circular gaussians . the number of these components was determined by the signal - to - noise ratio ( snr ) in the residual map . we applied a 6-@xmath2 threshold for fitting a new component , as done in ( * ? ? ? * helmboldt et al . ( 2007 ) ) . thereafter , we calculated the separation of the circular components from the central elliptical gaussian . we marked the sources with at least one fitted component farther away than 50 mas from the centre as candidates for having large - scale structure within the full vlba field of view . we found 60 sources as candidates with extended structure among the 1127 vips sources . to check the quality of the candidate sample , we visually inspected all the wide - field images . we found that in a few cases the distant components are unreliable because of the low flux density of the fitted components . an increased snr threshold in the automated model - fitting procedure would eliminate these questionable cases . further quantitative classification of the sample is needed ( and planned ) . published information from the literature , analysis of archival data , and eventually new targeted observations would be necessary to reveal the true nature of these objects , on a case - by - case basis . these sources show great diversity in morphology and brightness . the large , typically @xmath00.11 kpc structures could most probably be extended jet structures . however , the possibility of dual radio agn or gravitationally lensed radio sources should also be investigated . as an illustration , we present an example from the candidate sample ( fig.[fig1 ] ) . 200 milli - arcseconds ( mas ) south of the central component . follow - up multi - frequency observations could be useful to decide if this is a kpc - separation dual radio agn , a gravitationally lensed background source with two images , or an agn core plus a hot spot embedded in an extended lobe that is resolved out with the vlba . the area originally imaged in vips is enclosed by the dashed line.,width=336 ] this work was supported by the hungarian national research , development and innovation office ( otka nn110333 ) . kr thanks the nkp-16 - 2 new national excellence program of the ministry of human capacities for support . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the star formation history ( sfh ) of stellar populations ( e.g. galaxies and clusters ) may be derived using the synthetic cmd method ( scm ) based on the interpolation in mass and age of the stellar evolutionary models ( sem ) . to perform systematic studies and comparisons of the sfh of galaxies , the sems should have : _ i _ ) a dense grid over a large masse range ( up to 100 m@xmath0 ) to cover the entire age of the universe ; _ ii _ ) a homogeneous input physics ; _ iii _ ) a dense grid in metallicity ( z ) to cover the large range in metallicity of the stellar populations . at present , only a few sems datasets satisfy two of the previous points : padova94 ( @xcite ) dataset is one of them , but its grid in metallicity is too coarse , particularly in the z range 0.0004 - 0.004 , that is the most commonly used . to compensate for this limitation , we have interpolated in this metallicity range the padova94 models . in this work , we discuss ( section 2 ) our cares and prescriptions to obtain the interpolated tracks for z=0.001 ( fig . the comparison between our results and ( * ? ? ? * hereafter g00 ) models , of the same metallicity , are shown in section 3 , in order to emphasize the reliability of the interpolation . the interpolation in metallicity require special care to avoid spurious features in the resulting grid . our procedure goes through three steps : 1 . the subdivision of the tracks in specific evolutionary phases with : _ i _ ) the same internal burning processes ; _ ii _ ) comparable lifetimes ; _ iii _ ) similar behaviors on the hrd . + the subphases differ for the low , intermediate or high masses because of the different structures on the hrd . interpolations are performed at constant fractionary age within each subphase . we have performed several tests within padova94 sets to get the reliable interpolation method . we have found that an average of linear and logarithmic factor in z gives us the best result . the age has been linearly interpolated . we choose the transition masses for the selected metal content taking into account the trend of the transition masses over all the metallicity range . g00 models are similar to padova94 models , although some differences are present because of different input physics . we test our interpolated tracks by comparing them with g00 models at z=0.001 : 1 . the @xmath1 $ ] of the _ h - burning phase _ is less than 2% for m @xmath2 m@xmath0 . and smaller than 15% for m @xmath3 m@xmath0 . the latter discrepancy reflects the different definition of the overshooting parameter in the mass range 1 - 1.4 m@xmath0 . 2 . the @xmath4 of the _ he - burning phase _ is less than 15% for m @xmath5 m@xmath0 and smaller than 7% for m @xmath6 m@xmath0 . for m=1.7 m@xmath0 the he - burning lifetime of our model is two times larger than that of g00 . this is because in our set the m=1.7 m@xmath0 is adopted to be below the transition mass , while in g00 models it is close to the transition mass . taking into account the differences in the input physics , we find a good general agreement by comparing the interpolated tracks with the g00 models ( e.g. the lifetime of the major phases are reasonably well evaluated ) although some difference are present especially in the extention and luminosity of the blue loops . the results showed here refers to a specific choice of z. the same interpolation algorithm has been succesfully applied to other interpolated dataset ( z=0.002,0.003 ) and for other metallicity range ( z=0.004 - 0.008 ) . bressan a. , fagotto f. , bertelli g. , chiosi c. , 1993 , a&as , 100 , 647 fagotto f. , bressan a. , bertelli g. , chiosi c. , 1994 , a&as , 105 , 29 fagotto f. , bressan a. , bertelli g. , chiosi c. , 1994 , a&as , 104 , 365 girardi l. , bressan a. , bertelli g. , chiosi c. , 2000 , a&as , 141 , 371 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: we have observed the pulsar vela with a range of australian telescopes . using the long baseline array ( lba ) we have measured the parallax of pulsar , and thus the distance . using the australia telescope compact array ( atca ) we have found the radio pulsar wind nebula ( pwn ) that surrounds the x - ray pwn . using the university of tasmania s dedicated pulsar monitoring telescope in hobart we have detected the core interaction in the spin up of the pulsar in the glitch of 2000 . the pulsar monitoring telescope at hobart is a fourteen meter radio telescope dedicated to timing the vela pulsar . it collects three frequencies ( 635 , 990 , 1340-mhz ) , and the central one is collected unfolded for high resolution timing analysis ( @xcite ) . the ` fast component ' observed , which was fitted with a decay time 1.2 minutes , has been reanalysed with a more realistic model . we marginally detect the core interaction in the spin up ( @xcite ) . the atca has been used to map the radio pwn at 21 cm , 13 cm , 6 cm and 3 cm . because we used compact configurations with better sensitivity to low surface brightness objects we are able to map the whole nebula , unlike previous observations ( @xcite ) . we have used a single baseline from the lba to measure the on sky motion of the vela pulsar compared with the extra galactic source vela - g . we have measured the proper motion and parallax of the vela pulsar to an unprecedented accuracy ( @xmath0 @xmath1 , @xmath2 mas ) , and have been able to convert these back to the space velocity and position angle of the pulsar in its local environment with greater precision that previously possible ( @xmath3 @xmath4at @xmath5 ) , because of the unambiguity in the radio reference frame . we have found an arithmetic error in @xcite and , once corrected , their results agree with ours ( caraveo , personal comms ) . we have funding for a coherently dedispersed 30mhz backend for the 635mhz if on the pulsar timing telescope . this should allow us an increase in sensitivity of an order of magnitude over the previous observations . we plan to observe at the atca the radio nebula at higher frequencies to find the turn over frequency , and model the emission from the x - rays down to the radio frequencies . we are observing at the vla to get sensitive rapid observations to measure changes associated with the recently discovered x - ray outer jet ( @xcite ) . the limitation in the accuracy of the vlbi observation is the solar motion parameters , and we can not improve on this . nevertheless we are planning to use vela as a demonstration source in a baseband e - vlbi experiment . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: what has been available to eso up to now are efficiency curves provided by the vimos consortium that are averaged over the four quadrants and were determined with laboratory measurements , not by observing standard stars . prompted by user requests to have separate efficiency estimates for each quadrant , two spectrophotometric standard stars were observed in 2006 : hiltner 600 for all filters , and ltt7379 for the u and b band . these observations were performed with the broadest possible slit ( 5@xmath0 ) and the grisms lr - blue ( for u , b , and v ) and lr - red ( for r , i , and z ) . under the assumption that the total star - light is contained in the slit , the efficiency curve is derived from the measured flux . the required input consists of the tabulated standard star flux , the extinction curve , and the grism transmission as provided by the vimos consortium . the resulting curves are shown in fig . [ smieske : fig1 ] . they are also available from the public vimos web - pages . there is good agreement between the newly derived efficiency estimates and those from the consortium . the substantial sensitivity drop in quadrant 3 for the u - band is found independently for both ltt 7379 and hiltner 600 ( note that the measurement for hiltner 600 was not used for the efficiency estimate in the u - band since it suffered from flux loss in all four quadrants , due to a slight misalignment of the standard within the slit ) . since the u - band photometric zero - points for q3 do not show such a strong drop , a centring problem due to instrument flexure is a possible reason for this lack of measured flux . in addition , the consortium estimate of the grism transmission in q3 for l@xmath13800 may be too high . we suggest that the efficiency estimates especially in the u - band be always re - scaled to the ( integrated ) photometric zero - points . in addition to the total instrument+telescope efficiency estimates , we used the continuum lamp screen flats taken with and without inserted filter to measure the filter transmissions for each quadrant . the results are shown in fig . [ smieske : fig3 ] and compared with the consortium estimates . there is very good agreement for the v , r , i , and z filters . for the u - band , the consortium estimates are about 20% above those derived from the screen flats . also for the b - band , the consortium estimates are about 5 - 10% higher . unlike in the consortium filter transmission curves from fig . [ smieske : fig3 ] , we do _ not _ detect a red leak of the u - band filter around 4200 . only in q4 , there is a very minor leak at about 4850 ( see fig . [ smieske : fig2 ] ) . the measured telescope+instrument efficiency curves for the vimos broad band filters agree very well with the consortium estimates . a discrepancy in the u - band is observed for one quadrant , possibly due to flexure and low grism transmission at short wavelengthes . the filter transmissions also agree very well , except for the b and especially u - band , where the newly measured transmission is about 20% lower . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: it has been suggested that the most massive planets in a planetary system can be formed by a process of gas collapse , independently of metallicity , whilst the lighter components would have formed via core accretion . this can lead to a situation in which massive planets that have originated relatively far away from the inner system , migrate inwards into it ( see * ? ? ? * and contribution by font - ribera et al . in this same volume ) . in this process , these more massive planets with larger semi - major axis , cross the gas disc centred around the central sun . when going through this dissipative process , the planets lose kinetic energy because of the friction with the gas . as a consequence , the inner disc is heated up and the semi - major axis of the planet shrinks . after some passages , the planet is trapped in the disc with a residual eccentricity . we propose this scenario as a plausible way of explaining the existence of massive planets distributed around a sun with non - zero eccentricities . we give results based on high - accurate dynamical simulations about the distribution of the orbital elements of the trapped objects in the disc . we find that the massive planets are typically captured after some @xmath0 yrs and the final eccentricity is non - negligible ( @xmath1 ) . we have recently developed an integrator bhint specialised for dynamical processes in the vicinity of a very massive particle , which relies in the assumption that the very massive particle dominates the motion of the smaller ones @xcite . for this new mechanism , we retain the hermite scheme as a basis . the bottleneck is , of course , the number of particles to be used . nonetheless , we resort to special - purpose hardware , the grape , a card specially developed to integrate the calculation of newtonian gravitational forces . the peak performance of one of these cards is of 130 gflop , roughly equivalent to 100 single pcs , which makes possible long simulations with a realistic particle number . we set initially a disc made out of @xmath2 small particles which is `` hosting '' a sun in the centre and follows a simple @xmath3 profile . the integrated mass is of some 5 jupiters and the radius of some @xmath4 au . the thickness of the disc is of about the diameter of the central sun and has a gap around the central sun which extends @xmath5 au . the mass of the central sun is @xmath6 . the mass forming the disc are all single - mass . the massive planet , a massive particle of 5 jupiters is set in an orbit such that the initial eccentricity with the sun is of @xmath7 . initially , the particle is 100 au away from the sun and the inclination angle is @xmath8 degrees . the system ( disc plus interloper ) is integrated until the interloper is trapped by the disc . in the figure we show the evolution of the orbital parameters . whilst we can not discuss them in detail because of the publication limits , we note that after some @xmath9 yrs the inclination has almost not changed as compared to its initial value . then , after a short time of @xmath10 yrs elapses , it abruptly decays from almost 80 degrees to a very small number , to be finally trapped in the disc after @xmath11 yrs . the energy , whilst it decays from the initial high value of 0.95 , is of @xmath1 when the massive planet is totally trapped in the disc , within a final semi - major axis which is well within the range of expectation . an extended and detailed scrutiny of the parameter space of this capture process we propose will be soon published elsewhere @xcite . the adressing of this scenario has direct bearing on our understanding of planetary dynamics and migration mechanisms . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: in the relativistic jets of agns or grbs , the observed flux is related to their intrinsic flux by @xmath0 , where @xmath1 is doppler factor , @xmath2 and @xmath3 are the observed and intrinsic flux respectively , and @xmath4 is the spectral index ( ( * ? ? ? * blandford & knigl 1979 ) ) . if @xmath1 is greater than 1 , then the observed flux will be enhanced , which is called doppler boosting effect . on the other hand , if @xmath5 is less than 1 , the observed flux is attenuated , which is named to doppler deboosting effect . the doppler factor of a jet can be described by the following equation , @xmath6 where @xmath7 is the velocity , @xmath8 is the lorentz factor , and @xmath9 is the viewing angle . for a counter relativistic jet where @xmath10 , the doppler factor @xmath1 is always less than 1 , which can easily be derived from equation [ eqn1 ] . so a counter jet is always doppler deboosted . for a forward relativistic jet , the situation is more complex . provided that the viewing angle of jet @xmath11 ( when @xmath12 , @xmath1 is always greater that 1 ) , the doppler factor can be greater than 1 as well as less than 1 ( see figure [ fig01 ] for detail ) . therefore , both doppler boosting and deboosting effects could happen in forward jets . in many radio loud agns , the large scale jets share some common features in their profiles . firstly , there are compact and bright cores in the center of jets . secondly , adjacent to the cores , the flux of the jets drops down very quickly , even form some gaps where the jets are undetectable . thirdly , the jets will be re - brightened in the outer region . recently , the swift found some interesting properties in grbs . five grbs x - ray light curves are characterized by a rapid fall - off for first few hundred seconds , followed by a less rapid decline lasting several hours . the light curves also show discontinuity ( ( * ? ? ? * tagliaferri et al . ( 2005 ) ) ) . @xcite found that there were bright x - ray flares in grb afterglows . * stage i : the jets are accelerating and boosting , which relates to the bright cores of agns and the bursts of grbs . the initial acceleration of relativistic jets has been detected in 3c 273 by @xcite and modeled by @xcite . in this stage , @xmath8 is usually less than a few tens , and @xmath1 increase very quickly . * stage ii : the jets are accelerating but deboosting . as the acceleration continues , @xmath8 will be very large ( @xmath13 ) . therefore , the jets will enter into the deboosting area , i.e. @xmath14 . in this stage , the observed flux of the jets decreases very quickly , and often forms the gaps between inner and outer jets in agns and the rapid decays and discontinuous light curves in grbs . * stage iii : the jets are decelerating and boosting . the acceleration , however , wo nt last forever because of radiation loss and the interaction between the jets and the surrounding medium . thus , the jets will decelerate and their @xmath1 will increase again . consequently , the doppler boosted jets will appear again in the profiles of agns or in the light curves of grbs . * stage iv : the jets are decelerating and deboosting . finally , due to the same reasons in stage iii , the jets will gradually disappear . blandford , r.d . , knigl arieh , 1979 , _ apj _ , 232 , 34 burrows , d.n . , romana , p. , falcone , a. et al . , 2005 , _ science _ , 309 , 1833b krichbaum , t.p . , graham , d.a . , witzel , a. et al . , 2001 , _ particles and fields in radio galaxies , asp conference series _ tagliaferri , g. , goad , m. , ghincarini , g. et al . , 2005 , _ nature _ , 436 , 985 t zhou , j.f . , zheng , c. , li , t.p . et al . , 2004 , _ apj _ , 616l , 95z Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: imaging of extrasolar planets is a very challenging goal because of the very large luminosity contrast ( of the order 10@xmath1 for young giant planets and of the order of 10@xmath2 - 10@xmath3 for old giant and rocky planets ) and the small angular separation ( few tenths of arcsec for a planet at @xmath410 au around a star at some tens of pc ) between the host star and the companion objects . however , a number of different project are either now running ( e.g. project 1640 at the 5 m palomar telescope - see ( * ? ? ? * crepp et al . 2011 ) ) or are going to begin like the gemini planet imager ( gpi ) at the gemini south telescope ( ( * ? ? ? * macintosh et al . 2006 ) ) or sphere at the eso very large telescope ( ( * ? ? ? * beuzit et al . 2006 ) ) . this last instrument , in particular , includes three scientific channels that are a differential imager and dual band polarimeter called irdis operating in the near infrared between the y and the ks band ( ( * ? ? ? * dohlen et al . 2008 ) ) , a polarimeter called zimpol that will look for old planets at visible wavelengths ( ) and an integral field spectrograph ( ifs ) operating in the near infrared between the y and the h band ( ( * ? ? ? * claudi et al . 2008 ) ) . in the next paragraphs we will present the results of the laboratory tests on the ifs . tests on the ifs instrument were held in january and february 2013 at the _ institut de planetologie et dastrophysique de grenoble _ ( ipag ) facility with the aim to validate functionality of the science and calibration templates and to preliminary estimate the performances of the instrument . the tests were performed both in the yj ( 0.95@xmath51.35 micron ) and in yh ( 0.95@xmath51.65 micron ) mode using the appropriate combination of lyot coronagraph and apodized mask . data were then reduced exploiting the data reduction and handling ( drh ) software that allows to perform all the required calibrations and the speckle subtraction procedure through the spectral deconvolution ( sd ) method ( ( * ? ? ? * sparks & ford 2002 ) ) . a further speckle suppression can be obtained applying angular differential imaging ( adi ) ( ( * ? ? ? * marois et al . 2006 ) ) . given that we do can not perform any rotation of the field of view during our tests , we can just perform a simulation of the method so that our results have to be regarded as just an estimation of the contrast that we will be able to get . in figure [ fig2 ] we display the 5@xmath6 contrast plot that we can get for the ifs operating both in the yj - mode ( left panel ) and in the yh - mode ( right panel ) . a contrast better than 10@xmath1 can be obtained for both the modes appropriately combining sd and adi . to further confirm this results we add a number of simulated planets to the raw data at different separations and with luminosity contrast of 10@xmath7 and 10@xmath1 and reduced these data following the same procedure . all simulated planets are visible with a s / n greater than 5 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: in this configuration , the brunt - visl frequency is simply proportional to the radial distance . many mathematical results are known ( friedlander & siegmann 1982 ) concerning the shape of critical surfaces and characteristics of the governing mixed type operator . we confirm all these results by calculating the orbits of characteristics which propagate in the hyperbolic domain . in particular , we find that characteristics can be focused along attractors leading to associated singular velocity fields ( dintrans et al . we study , using the anelastic approximation , the low - frequency oscillations of a typical @xmath0-doradus star . hence , we show that dealing with rotation by the means of a second - order perturbative theory is not correct for rotation periods less than 3 days . using the same geometric formalism as above ( i.e. calculations of orbits of characteristics ) allows us to compute the frequencies of oscillations in the rapid rotation rgime ( rotation periods @xmath1 1 day ) . we find again that wave attractors are a common feature of rapidly rotating fluids and conclude that they are promising features for the transport of angular momentum and chemicals in the radiative zone of rotating stars ( dintrans & rieutord , 1999 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: monitoring known radial velocity ( rv ) planets at predicted transit times , particularly those planets in relatively eccentric orbits , presents an avenue through which to investigate the mass - radius relationship of exoplanets into unexplored regions of period / periastron space beyond ( kane & von braun 2008 , 2009 ) . here we describe techniques for refining ephemerides and performing follow - up observations ( kane et al . these methods are used by the transit ephemeris refinement and monitoring survey ( terms ) . the transit window as described here is defined as a specific time period during which a complete transit ( including ingress and egress ) could occur for a specified planet . the size of a transit window will increase with time due to the uncertainties in the fit parameters , and thus follow - up of the transit window as soon as possible after discovery is optimal . figure 1 ( left panel ) shows the size of the transit window for a sample of 245 exoplanets . the transit windows of the short - period planets tend to be significantly smaller than those of long - period planets since , at the time of discovery , many more orbits have been monitored to provide a robust estimate of the orbital period . terms chooses targets that have small transit windows , medium - long periods , and a relatively high probability of transiting the host star . [ cols="^,^ " , ] the transit ephemeris for a particular planet can often be significantly improved with the addition of a handful of high - precision rv data . for example , the planet orbiting the star hd 231701 ( fischer et al . 2007 ) has a current transit window of @xmath082 days based upon the discovery data . the addition of four subsequent measurements as shown in figure 1 ( right panel ) would improve both the precision of the period and time of periastron passage , resulting in a reduction of the transit window to 3.7 days - a factor of almost 25 ! through selective observations at optimal times , we produce viable targets for photometric follow - up . a considerable number of high transit probability targets are difficult to monitor adequately during their transit windows because the uncertainties in the predicted transit mid - points are too high . the acquisition of a handful of new rv measurements at carefully optimised times can reduce the size of a transit window by an order of magnitude . this is described in more detail by kane et al . ( 2009 ) . figure 2 presents data acquired with the t10 0.8 m automated photoelectric telescope ( apt ) during a predicted transit time of hd 114762b . the transit window was refined to less than a day using lick rv data , and the transit of this planet was subsequently ruled out . the observations from this survey will lead to improved exoplanet orbital parameters and ephemerides even without an eventual transit detection . the results from terms will provide a complementary dataset to the fainter magnitude range of the _ kepler _ mission , expected to discover many intermediate to long - period transiting planets . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the discovery of type1-like broad emission lines in the polarized spectrum of the type2 seyfert galaxy ngc1068 @xcite led to the foundation of the so - called unification model ( um ) of agns ( e.g. * ? ? ? * ) in which the orientation of a dusty torus plays a crucial role in the spectroscopic classification of the agn for a given observer . while this um is now well accepted for the lower luminosity agns , a key question is whether it applies to higher luminosity objects like quasars since the presence of the dusty torus may be affected by the higher radiation flux . in order to get some insights into the quasar inner structure , we investigate the possible existence of a correlation between the direction of the linear optical polarization ( @xmath0 ) and the orientation of the major axis ( @xmath1 ) of the host galaxy / extended emission surrounding rq and rl quasars . the sample used in our study is made of type1 and type2 rq / rl quasars for which high resolution visible / near - ir images are available and with optical polarization data reported in the literature . we determined the @xmath1 for the objects with missing measurements by using the mcs deconvolution method @xcite . from this compilation , we selected a sub - sample of objects for which we have relevant and accurate data and then computed the acute angle @xmath2 between the directions defined by the @xmath1 and @xmath0 angles . further details about the quasar sample and the determination of the @xmath1 are available in @xcite . the behavior of the angle @xmath2 as a function of the observation wavelength @xmath3 as measured in the quasar rest - frame is illustrated in the left panel of fig . 1 . from the analysis of the data plotted , we conclude that while no particular behavior is noted at redder wavelengths ( @xmath3 @xmath4 ) , a clear dichotomy appears in the uv / blue domain where the type1 quasars tend to have their ee preferentially aligned ( @xmath5 ) with the polarization direction , these two axes being mainly orthogonal ( @xmath6 ) in the type2 objects . moreover , the observed alignment effect seems to be independent of the radio - loudness . in the case of the type2 quasars , this behavior is known as the _ alignment effect _ reported by @xcite and @xcite where the extended uv / blue emission resolved in images is interpreted as an electron / dust polar region , scattering off the nuclear light and explaining the anti - alignment . in type1 quasars , the alignment can be explained by assuming a two - component scattering model ( see fig . 1 ) , similar to the one proposed for the seyfert galaxies by @xcite . in this scenario , an equatorial scattering region located inside the dusty torus produces a polarization aligned with the torus symmetry axis . the resulting polarization , the sum of the polar and equatorial contributions , is dominated by the equatorial component because of the higher symmetry of the polar region at smaller viewing angles ( see * ? ? ? * ) . antonucci , r. , & miller , j. 1985 , , 93 , 785 antonucci , r. 1993 , , 31 , 473 borguet , b. , hutsemkers , d. , letawe , g. , et al . 2008 , , 478 , 321 cimatti , a. , di serego - alighieri , s. , fosbury , r. , et al . 1993 , , 264 , 421 magain , p. , courbin , f. , & sohy , s. 1998 , , 449 , 472 smith , j.e . , robinson , a. , alexander , d. , et al . 2004 , , 350 , 140 zakamska n. , strauss , m. , krolik , j. , et al . 2006 , , 132 , 1496 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: it is widely accepted that cold and luminous submillimeter ( submm ) galaxies ( smgs ) are dominant contributors to the star formation history of the universe at redshifts @xmath0 @xcite . on the other hand , the host galaxies of long - duration gamma - ray bursts ( grbs , originating in the collapses of very massive stars , e.g. * ? ? ? * ) are found to be subluminous @xcite and low - mass @xcite . four of them ( grbs 980703 , 000210 , 000418 and 010222 ) have been firmly detected in submm and/or radio ( @xcite @xcite ; @xcite @xcite ; @xcite @xcite ) . in this paper we discuss the possibility that these submm - bright grb hosts may represent the hotter counterparts of smgs . for details see @xcite and @xcite . in order to model the spectral energy distributions ( seds ) of grb hosts we used the grasil software @xcite . it is a numerical code that calculates the spectrum of a galaxy by means of a radiative transfer method , applied to photons produced by a stellar population , and reprocessed by dust . in figure [ fig : t_l ] we compare the total infrared luminosities and dust temperatures of grb hosts ( derived from the sed fits ) with well - studied galaxies both local and at high-@xmath1 . it is apparent that grb hosts are hotter than smgs with the same luminosity . this gives a hint that grb events may pinpoint a population of ultraluminous infrared galaxies ( ulirgs ) at high redshifts with dust hotter than in typical smgs . the search for such galaxies is important because they likely contribute to the star formation history at the same level as smgs . we note that the majority of the galaxies shown in figure [ fig : t_l ] also have higher dust temperatures compared to smgs . however , all of them are local galaxies , so can not be considered as counterparts of high - redshift smgs and their submm emission has been detected only because of their proximity . grb hosts may be consistent with a population of optically faint radio galaxies ( ofrgs ) having similar infrared luminosities and ( likely ) temperatures . although the majority of ofrgs lie at @xmath2 @xcite , some of them are within the redshift range of the grb hosts discussed here ( ) . ofrgs have been suggested to be hotter counterparts of smgs @xcite , so the same may be true for grb hosts . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the grb050730 afterglow was observed 4.0 hours after the trigger . we find seven main absorption systems at z=3.968 , 3.564 , 2.2536 , 2.2526 , 2.2618 , 1.7729 and 1.7723 the grb050922c afterglow was observed 3.5 hours after the trigger . we find four main absorption systems at z=2.199 , 2.077 , 2.008 and 1.9985 . the grb060418 afterglow was observed 10 minutes after the trigger . we find four main absorption systems at z=1.489 , 1.106 , 0.655 and 0.602 . the resolution of all spectra is r 40,000 ( 7.5 km / s in the observer frame ) . data sets were reduced using uves pipeline for midas . all afterglows are clearly detected in the range 3300 - 10000 . fine structure lines for cii , oi , feii and siii have been identified in all the grbs . such lines convey information on the temperature and electron density of the absorbing medium , provided that they are excited by collisional processes ( j. n. bahcall , r. a. wolf et al . _ apj _ , 152 , 701 , 1968 ) . to constrain these parameters we need to estimate the fine structure column densities for two different ions and compare them . for grb050730 , two out of five components show fine structure lines ( fig . [ ciietc ] ) . reliable values for temperature and electron density are t a few @xmath1 k and @xmath2 @xmath3 ( second component ; the components are numbered according to decreasing z ) and @xmath4 @xmath3 ( third component ) . the other components do not show fine structure features : this is an indication that they refer to a clumpy environment . metallicity in grbs can be measured comparing the column densities of heavy elements to that obtained for hydrogen by fitting the ly@xmath5 , @xmath6 and @xmath7 profiles . both for grb050730 and grb050922c , we find metallicities between @xmath8 and @xmath9 with respect to the solar values . since metals tend to form dust , that then does not contribute to the absorption lines , this result is affected by some uncertainties . in grb060418 we identify crii and znii lines . such elements tend to stay in the gas state , minimizing the uncertainty when estimating the metallicity . no h features are present in this grb spectrum , so we derive the @xmath10 column from the x - ray data , leading to : z(cr ) @xmath11 and z(zn ) @xmath12 , a bit higher than for the other two grbs , but still below the solar values . the absorption spectra of grb afterglows are extremely complex , featuring several systems at different redshifts . both high and low ionization lines are observed in the circumburst environment , but their relative abundances vary from component to component , indicating a clumpy environment consisting of multiple shells . fine structure lines give information on the temperature and electron density of the absorbing medium , provided that they are excited by collisional effects . different components have different densities , suggesting a variable density profile . metallicity can be derived from the metal column densities ; crii and znii are the best indicators , since they do not form dust . metallicity values around @xmath9 with respect to the solar ones have been found . more details can be found in v. delia , f. fiore , e.j.a meurs et al . 2006 ( submitted to a&a , astro - ph/0609825 , 2006 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: recent measurements of o stars winds indicate that their mass loss rates , @xmath0 , may be significantly less than previous estimates and expectations ( e.g. , massa et al . 2003 , repolust et al . 2004 , bouret et al . 2005 , fullerton et al . the primary mass loss diagnostic used in these analyses is p v @xmath1 . although wind models predict that the ion fraction of p@xmath2 should approach 100% in the winds of mid- to late o stars , this is a na - like ion , and can be quite fragile . consequently , it is important to verify the results based on p v. like phosphorus , sulfur is a non - cno element with a relatively low cosmic abundance . three sulfur mass loss diagnostics are available : the s iv @xmath3 1062 , 1072 and s vi @xmath4 933 , 944 resonance doublets , and the s v @xmath5 1502 excited state line populated by the s v @xmath5 786 resonance line . for wind conditions , the lower level of 1502 is populated exclusively by radiative excitation . in this case , its radial optical depth in the wind is ( see , lamers et al . , 1987 ) : @xmath6_{\nu}\ ] ] thus , while sulfur provides access to three adjoining stages of ionization , it introduces a model dependency through the flux term , @xmath7_{\nu}$ ] . s iv , s v and s vi occur together in luminous o4 o 6 stars with massive winds . s v was analyzed in both lmc and galactic stars , using the sei code ( lamers et al . , 1987 ) and rotationally broadened tlusty models were used for both the uv and euv continua . the results are shown in figure 1 . the derived @xmath8s v ) should be accurate to better than @xmath9% . preliminary sulfur results give _ total _ sulfur mass loss rates , @xmath10 , between 0.04 0.18 times smaller than those expected from either theoretical ( vink et al . 2000 ) or radio or h@xmath11 determinations ( see , fullerton et al . these results are similar those determined by the p v analyses . clumping and porosity can influence the results , and must be incorporated into the analysis to determine exact factors . nevertheless , it seems that the mass loss rates of o stars will have to be revised downward by some amount . we intend to extend the current analysis to a much larger sample and to investigate the effects of clumping more closely . * figure 1 : * fits to the program stars . the data are faint , solid curves , and the fits are heavy solid curves . models with @xmath12 equal to twice and half of the best fit values are shown as dashed curves . the values of @xmath13 implied by the fits are between 0.04 and 0.18 of the expected values . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the diffuse intra - group light ( igl ) component is a useful tool to measure the intensity of the tidal interactions suffered by the galaxies and to map the extension and shape of the groups gravitational potential and the dark matter halo . in order to isolate the igl we used the `` trous '' wavelet transform with a multi - scale vision model ( ov_wav epitcio pereira , rabaa & da rocha 2005 ; da rocha & mendes de oliveira 2005 ) , which does not depend on `` a priori '' information . the process detects different characteristic size structures , separating the types of light source in the image . we have studied 3 hickson compact groups ( hickson 1982 ) , in different evolutionary stages , ( hcg 79 , hcg 88 and hcg 95 ) as a pilot study for an igl survey . simulated images were analyzed with ov_wav and showed that we are able to detect low - surface brightness extended structures , down to a @xmath3 per pixel , which corresponds to a 5-@xmath4-detection level in wavelet space . we have detected igl in hcg 79 and hcg 95 . hcg 79 has an irregular igl distribution , which closely matches the x - ray distribution ( pildis et al . 1995 ) and is bluer than the galaxies ( ( b - r ) = 1.5 ) , possibly a mix of stripped material from the outer parts of the galaxies and blue dwarf galaxies destruction . hcg 95 has an almost spherical igl distribution , with colors typical of old stellar populations . non - detection of igl in hcg 88 indicating an early stage of dynamical evolution . we suggest an evolutionary sequence : hcg 79 , in an advanced stage of dynamical evolution ; hcg 95 , intermediate stage ; and hcg 88 , initial epoch still without igl . the presence of an igl component indicates gravitationally bound configurations in which tidal encounters already stripped a considerable fraction of mass from the member galaxies and an advanced stage of dynamical evolution , providing a test for formation and evolution models of groups . to @xmath5 magnitudes for hcg 79 ( left ) and from @xmath6 to @xmath7 magnitudes for hcg 95 ( right ) . [ figdif],title="fig:",width=136 ] to @xmath5 magnitudes for hcg 79 ( left ) and from @xmath6 to @xmath7 magnitudes for hcg 95 ( right ) . [ figdif],title="fig:",width=147 ] da rocha , c. & mendes de oliveira , c. 2005 , mnras , in press epitcio pereira , d. n. , rabaa , c. r. & da rocha , c. 2005 , in preparation hickson , p. 1982 , apj , 255 , 382 pildis , r. a. , bregman , j. n. & evrard , a. e. 1995 , apj , 443 , 514 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: dv psc is a rs cvn - type eclipsing binary with high - level surface activity , which is characterized by the light - cuvre asymmetries ( robb et al . , 1999 ; vanko et al . , 2007 ; zhang & zhang , 2007 ; zhang et al . , 2010 ; parimucha et al.,2010 ) and @xmath1 h & k emission ( beer 1994 ) . therefore , it is a very intriguing object for studying stellar magnetic activity . our new ccd photometric observations of dv psc ( fig . 1 ) were made in four observing runs : 2010 nov . 19 , 20 , and 2011 oct . 12 and 13 , dec . 08 and 10 with 85 cm telescope ( zhou et al . , 2009 ) at xinglong station of the national astronomical observatories of china ( @xmath2 ) . the spectroscopic observations of dv psc were obtained with the 2.16 m telescope at xinglong station on 2012 feb . 2 ) . the omr spectrograph centered at about 4280 @xmath3 with a reciprocal dispersion of 1.03 @xmath3 ( fang et al . , 2010 ) . + multi - color light - curve analyses were carried out using the wilson- devinney program ( wilson & devinney 1971 ; etc ) . the spot models are used to explain light - curve asymmetry based on the prior photometric solution ( zhang et al . the theoretical and observed light - curve are both displayed in figure 1 . the normalized spectra of dv psc were analyzed in the @xmath1 h & k , h@xmath4 and h@xmath5 lines with the spectral subtraction technique , which was described in detail by barden ( 1985 ) and montes et al . + h&k , h@xmath5 and h@xmath4 lines . the dotted lines represent the synthesized spectra and the upper are the subtracted ones.,title="fig:",width=96 ] h&k , h@xmath5 and h@xmath4 lines . the dotted lines represent the synthesized spectra and the upper are the subtracted ones.,title="fig:",width=96 ] h&k , h@xmath5 and h@xmath4 lines . the dotted lines represent the synthesized spectra and the upper are the subtracted ones.,title="fig:",width=96 ] the results can be summarized as follows : 1 . an updated linear ephemeris formula min.i = jd(hel.)2454026.1424(2 ) + 0.30853609(8)e was obtained . fitting all available light minimum times with a polynomial function showed that the orbital period of dv psc increased ( fig . our photometric and spectral results demonstrate that dv psc is very active . new four flare events of dv psc were found and the flare rate is about 0.017 flares per hour ( fig . the three flare - like events might be detected firstly in one period . the relation of the flare maximum amplitude and the flare duration of late - type stars ( kozhevnikova et al . , 2006 ; vida et al . , 2009 ; qian et al . , 2012 ; zhang et al . 2012 , etc ) are displayed in figure 3 . the magnetic active cycle may be 9.26(@xmath60.78 ) year , which was analyzed by the variabilities of max.i - max.ii ( fig . 3 ) . we will monitor later . we are very grateful to dr . montes d. , gu s. h. , han j. l. , zhou a. y. , zhou x. , jiang x. j. , zhao y. h. , and fang x. s. the work is supported by the _ nsfc _ under grant no . 10978010 , 11263001 , 11203005 and 10373023 . this work is partially supported by the open project program of the key laboratory of optical astronomy , _ naoc , cas_. Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the creation of public archives of high - value observational data ( e.g. , nasa s hsearc ) has been a great boon to astronomical research in the past decade . it has given rise to a new kind of astronomer the archival astronomer who is free to check the methods and results of the data s authors , as well as to pursue independent , and sometimes novel , lines of inquiry . archival astronomy is expected to grow in scope and importance in the coming decade . by creating this archive of simulated x - ray clusters , we hope to extend this concept into the computational realm where simulations are growing in size and complexity . our goal is to produce large , statistical catalogs of @xmath1 100 clusters simulated at high resolution for two cases : ( 1 ) with , and ( 2 ) without non - adiabatic physical processes , in order to : @xmath2 understand the role of non - adiabatic processes in x - ray clusters , + @xmath2 make definitive predictions of the xlf evolution in both cases , + @xmath2 compare degree of cluster substructure with observational samples , + @xmath2 determine frequency of cooling flows as a function of @xmath3 . + we simulate a @xmath0cdm model with parameters @xmath4 . the survey volume is @xmath5 mpc on a side . we employ a new hydro+n - body code @xcite which uses adaptive mesh refinement to place high resolution grids where needed . first , a survey calculation was performed with @xmath6 cells , @xmath7 particles , and two levels of refinement everywhere to locate the clusters in our sample . then , each cluster is recomputed with up to 7 levels of refinement within the cluster environment . the dm mass resolution is @xmath8 ; the l7 spatial resolution is @xmath9 kpc . the adiabatic ( control ) sample is near completion and being analyzed . preliminary results focusing on the ten brightest clusters have been reported in @xcite and a second , more extensive paper is in preparation . amr simulation data structures are hierarchical and complex , and require specialized software for their manipulation and analysis @xcite . one of the design goals of the sca was to shield the user from the complexity ( and size ) of amr simulation data . we accomplished this by developing the sca as a workbench - style system that lets users interact with the archived data over the web . the user begins by selecting a cluster from a catalog list or a 3d vrml map . the server then retrieves the raw amr data from ncsa s mass storage system . once the data is on the sca web server , the user extracts from the amr files particle data and field data sampled to a uniform grid of user - specified size and resolution . at this point , the user may export the extracted data as hdf files for local analysis or use the suite of analysis tools provided as a part of the sca . the tools , which include 2d and 3d visualization tools , x - ray and sz imager , and graphing tool , are implemented as thin java applets in a client- server model . more detail can be found in @xcite . 99 bryan , g. l. & norman , m. l. , 1999 , in _ structured adaptive mesh refinement ( samr ) grid methods _ , eds . s. baden et al . , i m a vol . 117 , ( springer , new york ) , p. 165 burns , j. , loken , c. , rizza , e. , bryan , g. & norman , m. 1999 , in _ proceedings of @xmath10 texas symposium _ , eds . j. paul , t. montmerle & e. aubourg , _ in press _ daues , g. , currie , c. , anninos , p. , kohler , l. , shalf , j. & norman , m. 1999 , in _ astronomical data analysis software and systems viii _ , eds . d. mehringer , r. plante & d. roberts , asp vol . 172 , ( asp , san francisco ) , p. 241 norman , m. , shalf , j. , levy , s. & daues , g. 1999 , _ ieee computing in science and engineering _ , july / august , p. 36 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: from its beginnings , progress in qcd at low energies has been impeded because there are no good analytical tools available in order to work with strongly coupled yang mills theories . nevertheless , in the last few years the ads / cft ideas has provided a new approach that could improve this situation . at present a dual to qcd is unknown , but a simple approach known as bottom - up has been quite successful in several concrete qcd applications , such as in hadronic scattering processes @xcite , hadronic spectra @xcite , hadronic couplings and chiral symmetry breaking @xcite , mesonic wave function @xcite , among other applications . here we summarize the main ideas developed in @xcite , where a soft wall holographical model that describes hadronic spectra with an arbitrary number of constituents was proposed . the present work has been structured as follow . section ii is a summary of the model considered . in section iii we give some examples , and finally in iv we present some conclusions . we begin by considering an asymptotically ads space defined by @xmath0 and an action for arbitrary spin modes ( which depends on the spin of the hadron described ) . [ cols="^,^ " , ] on the other side , solutions to rarita - schwinger equation in ads space are more difficult to get , but its spectrum is similar to the dirac case , as you can see for example in ref . @xcite . as is possible to see in fig 2 , again the results are somewhat high , but using @xmath1 , adjusted to @xmath2 resonances gives better results . the holographical model discussed here allowed us to obtain hadronic spectra with regge behavior , not only for the integer spin case , but also for spins 1/2 and 3/2 , and also to calculate masses for exotics . in order to do this we considered anomalous dimensions for operators that create hadrons , and the dilaton that was used has a form suggested by einstein s equations , corresponding to the ads metric . this two traits allowed the model to reproduce regge spectra in all cases considered , and therefore the model can describe hadronic masses in a unified phenomenological model . j. polchinski and m. j. strassler , phys . lett 88 , 031601 ( 2002 ) ; r. a. janik and r. peschanski , nucl . phys b565 , 193 ( 2000 ) ; s. j. brodsky and g. f. de tramond , phys . lett b582 , 211 ( 2004):e . levin , j. miller , b. kopeliovich and i. schmidt , e - print : arxiv:0811.3586 [ hep - ph ] s. j. brodsky and g. f. de tramond , phys . lett 94 , 201601 ( 2005 ) ; a. karch , e. katz , d. t. son and m. a. stephanov , phys . rev d74 , 015005 ( 2006 ) ; s. j. brodsky and g. f. de tramond , arxiv : 0802.0514 v1 [ hep - ph ] . l. da rol and a. pomarol , nucl . phys b721 , 79 ( 2005);j . erlich , e. katz , d. t. son and m. a. stephanov , phys . lett 95 , 261602 ( 2005 ) ; p. colangelo , f. de fazio , f. giannuzzi , f. jugeau and s. nicotri , phys . d * 78 * , 055009 ( 2008 ) [ arxiv:0807.1054 [ hep - ph ] ] . s. j. brodsky and g. f. de teramond , phys . * 96 * , 201601 ( 2006 ) [ arxiv : hep - ph/0602252 ] ; s. j. brodsky and g. f. de teramond , phys . d * 77 * , 056007 ( 2008 ) [ arxiv:0707.3859 [ hep - ph ] ] ; a. vega , i. schmidt , t. branz , t. gutsche and v. e. lyubovitskij , phys . d * 80 * , 055014 ( 2009 ) [ arxiv:0906.1220 [ hep - ph ] ] . i. kirsch , jhep09 ( 2006 ) 052 . w. de paula , t. frederico , h. forkel and m. beyer , phys . d * 79 * , 075019 ( 2009 ) [ arxiv:0806.3830 [ hep - ph ] ] ; u. gursoy and e. kiritsis , jhep0802 : 032 , 2008 ; u. gursoy , e. kiritsis and f. nitti , jhep0802 : 019 , 2008 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: rooted in the book of job , `` behemoth '' is a worthy accolade to bestow upon the class of red supergiants . this finds reason in the popular use of the word . thinking of the namesake polish death metal band , red supergiants are dying stars , and their explosive death sparks the production and distribution of metals . in the cult game final fantasy , behemoths are beasts most feared for their magic spell `` meteor '' ; indeed , red supergiants fabricate dust grains , a process enshrouded in mystery . princeton university s farlex wordnet describes behemoths as `` abnormally large and powerful '' , `` unusual '' , `` of exceptional importance and reputation '' , and that `` strongly influence the course of events '' all applicable to red supergiants . and they are , simply put , `` whoppers '' . descendent from stars with birth masses in the region of 830 m@xmath0 , red supergiants become large , hundreds of r@xmath0 up to more than a thousand r@xmath0 , because their mantles become convective . the reason they become convective is because the energy production rate in the core can no longer be balanced by radiative diffusion and instead bulk motion is induced to transport the energy to the surface . this causes a drastic restructuring of the mantle , with a much shallower density gradient . it becomes optically thin at much larger radial distance from the core , and hence the temperature of the plasma where this happens is relatively low , @xmath14000 k , such that equilibrium is maintained ( @xmath2 ) . to put this in perspective , a massive main sequence star would easily fit within the orbit of mercury , but its red supergiant progeny could swallow jupiter . at that point , it would take more than a decade to travel around its surface at a speed of 10 km s@xmath3 , which is little more than the thermal motions in the star s atmosphere but only a few times smaller than the escape speed from its surface . hence red supergiants oscillate on timescales of years , and their winds have speeds of just a few tens of km s@xmath3 taking tens of thousands of years for matter to move out to one parsec distance . this means that we may be able to read the immediate past of the red supergiant even if it is no longer there in the story told by its circumstellar medium . the low escape speed makes it easy for these stars to lose mass , but it critically depends on how long they spend their time doing this , how much mass they eventually will have lost . it also means that rotation at the mere km s@xmath3 level may already affect these stars . red supergiants matter , as actors and probes in processes that drive galaxy evolution . but there are some important aspects of their formation , evolution and behaviour that need to be better understood : + + and finally , if close binary interaction does affect the evolution of a large fraction of the massive star population ( ( * ? ? * de mink ( 2014 ) ) , then observational and theoretical efforts must be promoted that aim to quantify these effects . 2012 , _ a&a _ , 548 , 113 2014 , _ apj _ , 782 , 7 2009 , _ a&a _ , 508 , 923 2014 , _ apj _ , 782 , l2 2015 , _ mnras _ , 447 , 3973 2009 , _ a&a _ , 504 , 115 2011 , _ a&a _ , 531 , 117 2015 , _ apj _ , 799 , 50 2006 , _ apj _ , 645 , 1102 2007 , _ apj _ , 667 , 202 2013 , _ a&a _ , 560 , 16 2011 , _ science _ , 333 , 1258 2015 , , 575 , 60 2012 , _ nature _ , 482 , 375 2013 , _ mnras _ , 433 , 1246 2015 , _ pasa _ , 32 , 16 2015 , _ apj _ , 799 , 158 2010 , _ aspc _ , 425 , 279 2013 , _ eas _ , 60 , 307 1999 , _ a&a _ , 351 , 559 2005 , _ a&a _ , 438 , 273 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: @xcite has suggested that bulges in spiral galaxies can be classified into _ classical bulges _ or _ pseudobulges_. classical bulges are thought to form through galactic merger . pseudobulges are discussed to form through secular evolution caused by non - axisymmetric structures in a galactic disc . @xcite demonstrated that clumpy structures form due to gas instability , which could also explain some clumpy galaxies observed in the high - redshift universe . these galaxies are referred to as clump clusters ( chain galaxies ) . @xcite suggested that these clumpy stellar structures fall into the galactic centre by dynamical friction and merge into a single bulge at the galactic centre , a clump - origin bulge . clump - origin bulges form through ` _ _ mergers of the clumps _ _ ' in a galactic disc , neither the galactic merger nor the secular evolution . therefore , properties of clump - origin bulges could be different from those of the conventional ones , classical bulges nor pseudobulges . i perform a similar numerical simulation to @xcite using an isolated halo model by a @xmath0-body / sph code and study the naive natures of clump - origin bulges in details . our initial condition follows the spherical model that was used to study the formation of disc galaxies in an isolated environment . i assume an equilibrium system with the nfw profile with a virial mass @xmath1 . baryon mass fraction of the system is set to @xmath2 . the details of my simulation settings are given in @xcite . in fig . [ fig:1 ] , i plot the azimathally averaged surface density and density map from the edge - on view . the fitting is given by the srsic index , @xmath3 indicating a nearly exponential density profile . as seen from the central panel , it clearly appears that this bulge is a boxy bulge from the edge - on view . furthermore , i find that this bulge shows a significant rotation with a value of @xmath4 , the rotation ( spin ) is _ not _ negligible in kinematics . these are indicating pseudobulge signatures @xcite . however , i find that the clump - origin bulge consists of stars with an over - solar metallicity @xcite . additionally , this bulge formation scenario , the clump cluster phase , is expected to happen only at the high - redshift . therefore , the clump - origin bulge consists of old stars . such old and metal - rich natures are better similar to classical bulges rather than pseudobugles @xcite . the mw bulge is also known to be an ambiguous bulge . the mw bulge shows a nearly exponential profile , an oblate peanut shape ( x - shape ) and a significant rotation , which are similar to pseudobulges . at the same time , the mw bulge is made of old and metal - rich stars , which are classical bulge signatures @xcite . these properties of the mw bulge are consistent with the clump - origin bulge obtained in this study . such unclassifiable bulges ( old pseudobulge ) are also observed in some other disc galaxies @xcite . my simulation results imply that such old pseudobulges like the mw bulge may be a clump - origin bulge and the mw might use to be a clump cluster . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the cyg x-1 data presented here were obtained by the pca onboard rxte , mostly gained through our monitoring campaign 19982002 ( for a description of the data see @xcite ) . we split each light curve into segments of 1s length and determine the mean flux of each segment . the segments are binned into 41 equally segmented flux bins , for each of which we calculate the power spectral density ( psd ) of all contained lightcurve segments via the dft ( see , e.g. , ) . from all periodograms of each flux bin the mean psd is determined using standard methods . for better statistics we chose to take into account only flux bins containing at least 20 periodograms . integrating the poisson noise corrected psd over the range @xmath0@xmath1hz , we arrive at the squared fractional rms variability . in a next step we multiply the fractional rms variability by the mean flux of the bin , to obtain the absolute rms variability @xmath2 . for all bins of each observation we plot @xmath2 over flux @xmath3 and fit a linear function in two different representations . by fitting @xmath4 , two characterizing values are determined : slope @xmath5 and intercept @xmath6 on the @xmath2 axis . the gradient of the @xmath2-@xmath3-trend @xmath5 is equivalent to the fractional rms variability of the light curve . alternatively to intercept @xmath6 , it was proposed to determine the physically meaningful intercept @xmath7 on the @xmath3 axis by fitting @xmath8 @xcite . if @xmath5 is interpreted as the variable component of the lightcurve , then @xmath7 represents a second component of it which does not follow the linear @xmath2-@xmath3-trend . in deriving results , it should be kept in mind that @xmath7 , which is identical to @xmath9 , and @xmath5 are not independent values for the characterization of the rms - flux - relation . generally , there is a good linear relationship between @xmath2 and @xmath3 in the hard state , which is reflected by the stable pearson correlation coefficient in fig . [ fig : rmsfluxvstime ] . we also notice coincidence of the change of the general long term behavior of cyg x-1 from a `` quiet hard state '' to a `` flaring hard state '' in 1998 may @xcite with a shift in the values of slope @xmath5 and the intercepts . the shape of the rms - flux - relation in the soft states of 1996 and 2001/2002 changes continuously between waviness and approximate linearity ( see fig . [ fig : softstate ] ) . during `` failed state transitions''(fst ) , i.e. , during times when the source reached its intermediate state , the linear rms - flux relation breaks down . we examined four fst : 1998 july 15 , 1999 dec 05 , 2000 nov 03 , and 2001 jan 29 ( indicated in fig . [ fig : rmsfluxvstime ] by dotted lines ) . comparing these events with the neighboring hard state observations , we notice that the rms - flux - relations of 1999 december 05 and 2000 november 03 being strictly linear before and after change to an arch - like appearance during the fst itself ( see fig . [ fig : failed ] ) . the other two examined fst also deviate from the linear relation , but these deviations are not as prominent . an explanation of the rms - flux - relation seems to be the modification of a theory which explains the psd of gbhc by the superposition of accretion disk ( ad ) instabilities occuring at several radii in the ad that are propagated towards the innermost region of the disk . local @xmath10 variations , which are caused by short term changes of the disk viscosity and whose time scale is dependent on radius , are superimposed on long term @xmath10 modulations . if the fractional amplitude of the @xmath10 variations is independent of the long term @xmath10 , a linear flux - rms relation will be observed @xcite . the rms - flux - relation will break down if the corona is severely disturbed this seems to be the case during the intermediate state of cyg x-1 , in agreement with earlier results for the behavior of x - ray time lags @xcite . here , the observed x - ray time lag is much larger than during the normal hard state , which could indicate changes in the geometry of the ad corona , possibly related to the observed radio emitting outflow . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: since its discovery in 1974 , the @xmath0 meson has provided a useful laboratory for quantitative tests of quantum chromodynamics ( qcd ) and , in particular , of the interplay of perturbative and nonperturbative phenomena . the factorization formalism of nonrelativistic qcd ( nrqcd ) @xcite provides a rigorous theoretical framework for the description of heavy - quarkonium production and decay . this formalism implies a separation of short - distance coefficients , which can be calculated perturbatively as expansions in the strong - coupling constant @xmath3 , from long - distance matrix elements ( mes ) , which must be extracted from experiment . the relative importance of the latter can be estimated by means of velocity scaling rules , i.e. the mes are predicted to scale with a definite power of the heavy - quark ( @xmath4 ) velocity @xmath5 in the limit @xmath6 . in this way , the theoretical predictions are organized as double expansions in @xmath3 and @xmath5 . a crucial feature of this formalism is that it takes into account the complete structure of the @xmath7 fock space , which is spanned by the states @xmath8 with definite spin @xmath9 , orbital angular momentum @xmath10 , total angular momentum @xmath11 , and colour multiplicity @xmath12 . the hierarchy of the mes predicted by the velocity scaling rules is explained for the @xmath0 , @xmath13 , and @xmath14 mesons in table [ tab : vsr ] . in particular , this formalism predicts the existence of colour - octet ( co ) processes in nature . this means that @xmath7 pairs are produced at short distances in co states and subsequently evolve into physical , colour - singlet ( cs ) quarkonia by the nonperturbative emission of soft gluons . in the limit @xmath15 , the traditional cs model ( csm ) @xcite is recovered . the greatest triumph of this formalism was that it was able to correctly describe @xcite the cross section of inclusive charmonium hadroproduction measured in @xmath16 collisions at the fermilab tevatron @xcite , which had turned out to be more than one order of magnitude in excess of the csm prediction . .values of @xmath17 in @xmath18\right\rangle\propto v^k$ ] for @xmath19 . [ cols="^,^,^",options="header " , ] inclusive @xmath0 production in dis lends itself as a sensitive probe of the co mechanism . as for @xmath20 , the h1 data @xcite generally confirms nrqcd and disfavours the csm @xcite . however , nrqcd predicts at lo a distinct rise in cross section as @xmath21 , which is not reflected by the h1 data . this anomaly is familiar from photoproduction , and it is likely to be resolved by the inclusion of higher - order corrections @xcite , possibly in combination with intrinsic-@xmath22 effects and/or nonperturbative shape functions . as for @xmath23 , the chorus central value for the total cross section @xcite exceeds the lo prediction @xcite by almost one order of magnitude . however , the experimental error is still rather sizeable . as for @xmath24 , co processes are dominant , diffractive ones are absent , and the experimental signature is spectacular , so that a measurement would be worthwhile @xcite . inclusive @xmath0 production in cc dis represents a challenge for hera and thera . cdf collaboration , f. abe et al . lett . 69 ( 1992 ) 3704 ; 71 ( 1993 ) 2537 ; 79 ( 1997 ) 572 ; 79 ( 1997 ) 578 ; d0 collaboration , s. abachi et al . , phys . b 370 ( 1996 ) 239 ; d0 collaboration , b. abbott et al . , phys . rev . lett . 82 ( 1999 ) 35 . m. beneke and m. krmer , phys . d 55 ( 1997 ) 5269 ; a.k . leibovich , phys . d 56 ( 1997 ) 4412 ; m. beneke , m. krmer , and m. vnttinen , phys . d 57 ( 1998 ) 4258 ; b.a . kniehl and j. lee , phys . rev . d 62 ( 2000 ) 114027 ; s. fleming , a.k . leibovich , and i.z . rothstein , phys . d 64 ( 2001 ) 036002 . todorova - nov , in _ proceedings of the xxxi international symposium on multiparticle dynamics ( xxxi - ismd ) _ , datong , china , september 17 , 2001 , edited by b. yuting , y. meiling , and w. yuanfang , econf c010901 ( 2001 ) ; m. chapkin , talk presented at _ 7th international workshop on meson production , properties and interaction ( meson 2002 ) _ , krakow , poland , 2428 may 2002 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: during the recent gregorian upgrade of the arecibo telescope , considerable effort was put into drift scan searches of the arecibo sky ( @xmath0 ) for new pulsars . the stsci / naic group was assigned declination strips centered at 1.5@xmath1 , 6.5@xmath1 , 11.5@xmath1 , 16.5@xmath1 , 21.5@xmath1 , 26.5@xmath1 , 31.5@xmath1 , and 36.5@xmath1 . a list of 20 candidates was compiled from a search in these areas between 1994 and 1998 . we have so far confirmed eight new pulsars as a result of these observations . the nominal parameters based on the confirmation observations are summarized in table 1 . barycentric periods have uncertainties of order one unit in the last digit quoted , while a conservative estimate of the uncertainty in the dispersion measures ( dm ) is @xmath2 @xmath3 pc . the positions are presently uncertain by of order @xmath4 arcmin in right ascension and declination equivalent to the half power beam size of the telescope at 430 mhz . although we presently have no long - term estimates of the flux densities of the new pulsars , it is already clear that they are weak sources with typical flux densities of order 0.5 to 1 mjy . some of the initial detections were probably significantly facilitated by flux amplifications due to interstellar scintillation . inferred 430-mhz luminosities , based on their fluxes and dispersion measures estimates range between 3 and 30 mjy kpc@xmath5 . these pulsars , along with those discovered by other groups during the arecibo upgrade , should greatly assist future statistical studies of the low end of the pulsar luminosity function . more accurate measurements of the flux densities , as well as the spin and astrometric parameters for each source are presently underway at arecibo as part of a regular timing program using the penn state pulsar machine . llllll psr & r.a . & decl . & period & epoch & dm + & & ( sec ) & ( mjd ) & @xmath3 pc + j0137 + 16 & 01:37:31 & + 16:55 & 0.41477 & 51264 & 26 + j0329 + 16 & 03:29:13 & + 16:54 & 0.8933 & 51257 & 35 + + j1549 + 21 & 15:49:41 & + 21:14 & 1.262 & 51335 & 55 + j1822 + 11 & 18:22:17 & + 11:22 & 1.787 & 51261 & 112 + + j1838 + 16 & 18:38:52 & + 16:53 & 1.902 & 51261 & 36 + j1849 + 06 & 18:49:07 & + 06:07 & 2.219 & 51258 & 236 + + j1905 + 06 & 19:05:21 & + 06:23 & 0.9897 & 51261 & 262 + j2040 + 16 & 20:40:13 & + 16:54 & 0.8656 & 51261 & 51 + Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: 55 cancri (= hd 75732 ) is a late g / early k dwarf / subgiant currently known to host five extrasolar planets with periods between around 0.7 days and 14 years and minimum masses between 0.026 and 3.84 @xmath5 . the super - earth 55 cnc e was recently discovered to transit ( winn et al . 2011 , demory et al . 2011 ) , prompting a number of studies of the properties of this system ( e.g. , kane et al . 2011 , von braun et al . we used the chara interferometric array to directly measure the stellar angular diameter , which , when combined with hipparcos parallax measurement and calculation of bolometric flux based on spectral templates and literature broad - band photometry , yields the physical @xmath6 and @xmath7 ( von braun et al . details of our observations and calculations of stellar properties are described in von braun et al . ( 2011b ) . we give our results in table 1 . of particular interest are the location and extent of the circumstellar habitable zone ( hz ) , based on the equations of jones & sleep ( 2010 ) , and the physical radius of the transiting super - earth , based on simply the measured flux decrement during transit and our calculated stellar radius value . 1 illustrates that planet f , with its elliptical orbit ( @xmath8 ) , spends about 74% of its year inside the hz , while its equilibrium temperature varies between 221k ( apastron ) and 302k ( periastron ) for the assumption of perfect efficiency in the redistribution of energy received from the star ( von braun et al . 2011b ) . coupled with the recent literature values of assumed planetary mass and measured flux decrement during transit , our measured stellar radius implies @xmath9 and @xmath10 ( for @xmath11 = @xmath12 ; winn et al . 2011 ) , and @xmath13 and @xmath14 ( for @xmath11 = @xmath15 ; demory et al . 2011 ) . .stellar properties of the 55 cancri system . @xmath16 and @xmath17 correspond to the uniform disk and limb - darkening corrected angular stellar diameters , respectively . @xmath17 corresponds to the angular diameter of the rosseland , or mean , radiating surface of the star . [ cols=">,^ " , ] Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: entanglement is one of the potential sources of quantum theory . it is the key concept and major resource for quantum communication and computation @xcite . in the last few years , enormous efforts has been made to investigate various aspects of quantum entanglement and its benefits in a number of setups , such as teleportation of unknown states @xcite , quantum key distribution @xcite , quantum cryptography @xcite and quantum computation @xcite . recently , the study of quantum entanglement of various fields has been extended to the relativistic setup @xcite and interesting results about the behavior of entanglement have been obtained . the study of entanglement in the relativistic framework is important not only from quantum information perspective but also to understand deeply the black hole thermodynamics @xcite and the black hole information paradox @xcite . the earlier investigations on quantum entanglement in the relativistic framework is mainly focused by considering isolated quantum systems . in fact , no quantum system can be completely isolated from its environment and may results in a non - unitary dynamics of the system . therefore , it is important to study the effect of environment on the entanglement in an initial state of a quantum system during its evolution . the interaction between an environment and a quantum system leads to the phenomenon of decoherence and it gives rise to an irreversible transfer of information from the system to the environment @xcite . [ cols="^,^,^ " , ] if we compare the single qubit and the both qubits decohering situations , it becomes obvious that the entanglement loss is rapid when both the qubits are coupled to the noisy environment . for example , in the case of bit flip channel the concurrence behaves as a linear function of @xmath0 for single qubit decohering case whereas in the case of both qubits decohering case it varies as a parabolic function . nevertheless , the sudden death happens at the same value of @xmath0 , irrespective of the acceleration , for both cases under the action of bit flip and phase damping channels . for depolarizing channel , however , this is not true . in conclusion , we have investigated that the entanglement in dirac fields is strongly dependent on coupling with a noisy environment . this result is contrary to the case of an isolated system in which the entanglement of dirac fields survives even in the limit of infinite acceleration of rob s frame . in the presence of decoherence , the entanglement rapidly decreases and entanglement sudden death occurs even for zero acceleration . under the action of phase flip channel , the entanglement can regrow when both qubits are coupled to a noisy environment in the limit of large values of decoherence parameter . the entanglement disappears , irrespective of the acceleration , under the action of phase damping channel only when the channel is fully decohered both for single qubit and the two qubits decohering cases . however , under the action of depolarizing channel an early sudden death occurs for larger acceleration when both qubits are coupled to the environment . in summary , the entanglement generated by unruh effect in noninertial frame is strongly influenced by decoherence . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: in order to have an idea on the types of objects we can expect at flux levels accessible with ska we have modeled the main classes of sources detected at mjy and sub - mjy levels : steep agns ( radio galaxies ) modeled following dunlop & peacock ( 1990 , mnras , 247 , 19 ) ; flat agns ( sy1 and qso ) , for which we have assumed the quasar optical lf and evolution ( boyle et al 1988 , mnras , 235 , 935 ; 1991 , asp conf . 21 , p. 191 ; schmidt et al 1995 , aj , 109 , 473 ) ; the star - forming galaxies ( rlf from sadler et al 2002 , mnras , 329 , 227 ) composed by a fraction ( assumed 50% ) of non - evolving normal spirals and a fraction ( 50% ) of evolving starburst galaxies ( @xmath1 ) . passive optical evolution has been assumed whenever necessary ( poggianti 1997 , a&as , 122 , 399 ) . + a number of available surveys at the mjy , sub - mjy and jy level can provide important boundary conditions to any modelling of the radio sky . the radio counts are constrained by using all the samples available in the literature , while we focused on samples with optical spectroscopy follow - up to get constraints on the redshift and magnitude distributions of the sources . in particular we refer to the following samples : first ( magliocchetti et al . 2000 , mnras , 318 , 1047 ) , atesp - eis ( prandoni et al . 2001b ) , pdf ( phoenix deep field , georgakakis et al . 1999 , mnras , 306 , 708 ) , mf ( marano field , gruppioni et al . 1999 ) , b93 ( sample collection studied by benn et al . 1993 , mnras , 263 , 98 ) , h00 ( collection studied by haarsma et al . + the models used here provide a good fit to the observed number counts along the entire flux range spanned by the counts ( @xmath2 @xmath0jy - 1 jy ) and can reproduce the total number of sources in the comparison samples within a factor of 2 . the models can trace with good accuracy both the magnitude and the redshift distributions of the sources in the given samples . the models above have been used to simulate the radio sky at fainter flux levels than reached by the current surveys . the composition of the radio sky changes with flux as shown in figure [ eps1 ] . the figure clearly shows that radio galaxies , which dominate ( together with qso ) the mjy population , reappear in large proportions going to nanojy levels ( @xmath3 at @xmath4 njy ) ! + on the other hand , starburst galaxies and their evolution can be suitably studied with less sensitive surveys ( e.g. @xmath5 njy ) . the other main population at nanojy level is represented by non - evolving spirals , whose contribution shows a bump ( mainly due to @xmath6 galaxies ) in the range @xmath7 njy . + this work demonstrates that nuclear activity could be important at nanojy flux levels . deeper data are strongly needed to better constrain the models and provide more reliable simulations . this kind of analysis can provide very useful constraints to the design of ska . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the origin of ultra - high energy cosmic rays remains a fundamental and unsolved problem in astroparticle physics . promising clues could be provided by the associated high energy neutrinos since they would neither interact with intergalactic or interstellar media nor be deflected by the magnetic fields . various detectors have been proposed for detecting high energy neutrinos . some of them rely on measuring the air shower by the so - called earth - skimming @xmath1 , for which horizontal showers are generated by the ensuing @xmath2 decay@xcite . in this paper , we investigate the shower properties by simulations . equipped with the knowledge of the @xmath1 induced air shower , we are able to calculate the induced geosynchrotron radiation . in sec . ii , we present the corsika@xcite simulated shower profile to be employed in the calculation of geosynchrotron radiation in sec . our calculation is based on the coherent geosynchrotron emission scenario initiated in 1970s@xcite and further developed by huege and falcke@xcite . in sec . iv , we summarize and conclude our work . the tau decay induced air shower is initiated by the decay product . using corsika code , we simulate the shower initiated by electrons at five different energies . table [ stat ] presents the statistics of these simulations . the simulation shows that the shower particles reside in a shower thickness less than @xmath3 . compared with the radiation which traverses a distance of @xmath4 @xmath5 , the shower front at the shower maximum is treated as longitudinally coherent . the remaining structures are the lateral profile and lorentz factor distribution representing the spatial and energy distribution of the shower particles . .shower statistics [ cols="<,^,^,^ " , ] fig . [ gamma ] and [ lateral ] show the energy and position distributions of the shower particles at shower maximum for different energies . both are displayed in the unit normalized to the total number at the corresponding energies . having determined the spatial structure and energy distribution of shower particles , we can calculate the emission from the shower maximum . [ interfere ] depicts the expected electric field at different receiver locations . the interference pattern arises from the scale of the shower front . in fig . [ pulse ] , we calculate the pulse measured by the receiver with a given bandwidth . this plot indicates how large the separation between antennae can be for the current technology . for the maximum of a @xmath6 shower at the observation distance of @xmath7 . curves in blue , red and yellow represent signals in observing frequencies of @xmath8 , @xmath9 and @xmath10 , respectively.,width=302 ] shower at the observation distance of @xmath7 , using an idealized rectangular filter spanning @xmath11 . curves in blue , red and yellow denote pulses measured at center , at lateral distances of @xmath12 and @xmath13 , respectively.,width=302 ] in this work , we investigate properties of the earth - skimming tau neutrino induced shower . the universal behavior of the shower particle allows a simple parametrization which will be helpful in future calculations of the geosynchrotron radiation . our calculations also provide useful information for the future experiments . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: ship bow waves exhibit both large and small scale features . the most prominent small scale feature is the bow wave crest formation of thin overturning sheets which break up into spray . re and we scale effects are large such that replication of full scale phenomena of the small scale features of ship bow waves is difficult even with large models . however , experimental studies for wedge flows display and document the small scale structures of bow waves . herein , flows around a wedge - shaped bow are numerically simulated with the aim of investigating the wave breaking mechanism and small scale features of ship bow waves . the side length of the wedge is l = 0.75 m , and the height of the wedge is h = 1.0 m. the half wedge angle is @xmath0 = @xmath1 and the flare angle @xmath2 = @xmath3 . the water depth is d = 0.0745 m and the upstream velocity is u = 2.5 m / s , the corresponding reynolds number , re = @xmath4 , and the froude number , fr = 2.93 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the vimos integral field unit ( hereafter ifu ) allows to obtain one spectrum for each resolution element of its field of view , thanks to a square array of microlenses , each one coupled to an optical fiber . technical details about vimos ifu can be found in prieto et al . see also le fvre et al . ( 1998 ) . vimos ifu can be used in various configurations , outlined in table [ tab : ifuconf ] [ tab : ifuconf ] cccc field of view & spatial resolution & spectral resolution & number of fibers + 54@xmath0 54 & 067 & 250 & @xmath1 + 27@xmath0 27 & 033 & 250 & @xmath1 + 27@xmath0 27 & 067 & 700 , 2500 & @xmath2 + 13@xmath0 13 & 033 & 700 , 2500 & @xmath2 + ifu data reduction presents new challenges and requires to set up new data reduction techniques with respect to `` traditional '' mos data . two main aspects that have to be taken into account for the data reduction of every ifu are the high density of spectra on the detector , causing some degree of crosstalk ( overlapping of light from neighbouring spectra ) and the sky subtraction , demanding special care , since the sky must be evaluated using different fibers for different observations . for vimos ifu in particular a third aspect is the high number of spectra collected in a single exposure ( up to 6400 spectra on four 2k@xmath04k ccds ) , requiring at least a partial automatization of the reduction process . once data have been reduced , exploiting their scientific content is even more challenging . for this reason a european network has been set up , formed by all the european institutes involved in ifu instrument development , with the purpose to provide the european astronomical community with powerful 3d data analysis tools . the fact that an ifu can obtain spectra for all the objects in the field of view at once makes it much more efficient than a mos in very crowded field , where complete sampling is required . this is especially true in the case of high - z clusters , where the numbers of interlopers is roughly 90% of all the field objects . this can have great advantages regarding spectroscopic confirmation of clusters and dynamical studies of cluster cores , where just one ifu observation ( or a few ones , if using the smaller size and higher resolution configuration ) could obtain the same result as several mos exposures . it is clear that medium and high - z clusters , being of a smaller angular size , are ideal targets for ifu observations , as shown by figure 1 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: after the completion of the palomar - quest northern sky survey in september 2008 the quest large field camera ( ( * ? ? ? * baltay et al . 2007 ) ) was moved and installed on the 1.0-m eso schmidt in la silla and had first light on april 24 , 2009 . since september 2009 , the southern survey has been in routine observations ( ( * ? ? ? * andrews et al . 2008 ) ) and the telescope and camera are controlled from yale and fully robotic . we have 90@xmath1 of the time on the telescope with 10@xmath1 allocated to chile . the quest camera consists of 112 ccds of 600 @xmath2 2400 sarnoff thinned pixels , back illuminated devices with 13 @xmath3 m x 13 @xmath3 m pixel pitch . the camera covers an area of 4.6@xmath4 @xmath2 3.6@xmath4 on the sky and a plate scale of 0.86 arcsec / pixel . the survey covers @xmath51000 square degrees per night , primarily between @xmath625@xmath4 to allow for follow up from both hemispheres . the lsq variability ( sn and transient ) survey uses 60 sec exposures ( and the tno survey-180 sec ) taken twice a night with a cadence of 2 nights in one broad band filter of 4000 to 7000 ( qst*-band ) . the seeing at la silla for the 60 sec exposures is 1.7 arcsec fwhm , reaching depth of 20.5 mag . the lsq survey subtraction pipeline has started producing between 400 and 900 transient candidates each night ( fig.[fig3 ] ) . the lsq rr lyrae star ( rrls ) survey is searching the galactic halo for rrls that have v magnitudes between roughly 14 and 20 . because rrls are excellent standard candles , they provide a powerful probe of the density distribution of the halo , which is being examined for halo substructure . plotted are the v magnitude light - curves for three type ab rrls ( fig.[fig5](a ) ) , which illustrate the typical photometric precisions at these magnitudes . from their mean v magnitudes , we estimate that rrab 12574 , 10770 , and 5381 lie 7 , 13 , and 52 kpc from the sun , respectively . a deep eclipsing cataclysmic variable ( ( * ? ? ? * rabinowitz et al . 2011a ) ) was discovered with eclipse depths @xmath75.7 magnitudes , orbital period 94.657 min , and peak brightness v@xmath518 at j2000 position 17h 25 m 54.8s , -64 deg 38 min 39 sec . light curves in b , v , r , i , z and j were obtained with smarts 1.3-m and 1.0-m telescopes at cerro tololo and spectra from 3500 to 9000 with the soar 4.3-m telescope at cerro pachon . the optical light curves ( fig.[fig5](b ) ) show a deep , 5-min eclipse immediately followed by a shallow 38-min eclipse and then sinusoidal variation . no eclipses appear in j. during the deep eclipse the measure of v - j @xmath7 7.1 corresponds to a spectral type m8 or later secondary . the spectra show strong hydrogen emission lines , doppler broadened by 600 - 1300 km s-1 , oscillating with radial velocity that peaks at mid deep eclipse with semiamplitude 500 @xmath6 22 km s-1 . it is suggested that lsq172554.8 - 643839 is a polar with a low - mass secondary viewed at high inclination . an apparent dwarf nova was discovered ( ( * ? ? ? * rabinowitz et al . 2011b ) ) on june 11.046 ( when the variable was at magnitude r = 16.3 ) and june 11.063 ut ( at r = 16.0)(fig.[fig6](a ) and ( b ) ) . a faint source is reported at this position in the guide star catalog v2.3.2 ( with bj = 20.76 ) . simultaneous visible and j - band observations were taken with andicam on the 1.3-m smarts telescope at cerro tololo . a spectrum ( range 0.350 - 0.966 nm ) taken on june 26 with gmos on the gemini south telescope reveals strong h - alpha and h - beta emission lines , with h - alpha clearly double - peaked , indicating the presence of an accretion disk with rotational velocity 1000 km / s . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: compact groups of galaxies are associations of three to seven galaxies , where the projected distances between them is of the order of their diameters , and where the group shows a low velocity dispersion , making compact groups an ideal place to study galaxy interaction and intergalactic star formation ( e.g. ( * ? ? ? * torres - flores et al . 2010 ) , ( * ? ? ? * de mello et al . 2008 ) , ( * ? ? ? * de mello , torres flores & mendes de oliveira 2008 ) , ( * ? ? ? * mendes de oliveira et al . 2004 ) ) . the main goal of this work is to search for a link between the evolutionary stage of a group and the presence of young intergalactic objects which may have formed during galaxy interactions . for this , we analyze a subsample of seven compact groups ( hcg 2 , 7 , 22 , 23 , 92 , 100 and ngc 92 ) which span a wide range of evolutionary stages , from hi rich groups to strongly interacting groups , where the galaxies show tidal tail features and a deficiency in neutral hi gas . in order to analyze the evolutionary stage of each group , we used new fabry - perot velocity maps , galex / uv data and optical r - band images . the velocity fields and rotation curves help constraining the evolutionary stage of each compact group while ultraviolet light contains important information regarding the age of the young stellar population that may be present in the intragroup medium . we searched for ultraviolet emitting regions in the vicinity of all seven targets , using the sextractor software ( se , ( * ? ? ? * bertin & arnouts 1996 ) ) in the fuv , nuv and r sky - subtracted images of our compact group sample . we compare the field density of regions detected in the compact group with a control sample outside the group . hcg 92 and hcg 22 have the highest field density in this study . no excess was found in hcg 2 , hcg 7 , hcg 23 , hcg 100 and ngc 92 ( ( * ? ? ? * torres - flores et al . 2009 ) ) . in order to constrain the evolutionary stage of each compact group , we inspected the velocity field and rotation curve of each galaxy to search for interaction indicators , in a similar way to that done by ( * ? ? ? * plana et al . ( 2003 ) ) and ( * ? ? ? * amram et al . ( 2003 ) ) . in the case of ngc 92 , it shows a prominent tidal tail in its velocity field . at the tip of this tail , there is a tidal dwarf galaxy candidate , having an age of about 40 myrs ( ( * ? ? ? * torres - flores et al . 2009 ) ) . we used multiwavelength data to study the evolutionary stages of the compact groups of galaxies hcg 2 , 7 , 22 , 23 , 92 , 100 and ngc 92 . new fabry - perot velocity fields , rotation curves and galex nuv / fuv images were analyzed for four and seven of these groups respectively . groups hcg 7 and 23 are in an early stage of interaction whereas hcg 2 and 22 show limited interaction features and hcg 92 , 100 and ngc 92 are in a late stage of evolution , having hi gas in the intragroup medium , galaxies with peculiar velocity fields and several young star - forming regions in the intergalactic medium . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: we present the characteristics and performances of a demonstrative experiment devoted to the observation of ultra high- energy cosmic rays extensive air showers using a radiodetection technique . the codalema ( cosmic ray detection array with logarithmic electromagnetic antennas ) experiment was set up at the nanay radio observatory in 2003 . it uses 6 of the 144 log - periodic antennas ( in the 1 - 100 mhz frequency band for codalema ) constituting the decametric array ( dam ) @xcite . in the first period of observation @xcite , the setup ( see fig . [ fig : setup ] ) was self - triggered using one devoted antenna : its signal was filtered in an appropriate noise - free frequency band ( 33 - 65 mhz ) chosen after an exhaustive study in the observed local noise frequency spectrum , before entering the adc . the wide band waveform signals ( 1 - 100 mhz ) of the other antennas were registered when a voltage threshold was reached on the trigger antenna . the trigger threshold was set at 4 @xmath1 ( @xmath1 : the rms sky background noise ) , leading to an electric field sensitivity of 4 @xmath2v / m . on figure [ fig : triggerlevel ] the evolution of the average counting rate at nancay is presented as a function of the trigger level expressed in unit of @xmath1 . the counting rate evolves greatly with the anthropic activities in the vicinity of the station of nancay and with the weather conditions . except for the trigger antenna , transient signals on the antennas were hidden by radio transmitters signals . consequently , a numerical passband filter ( same as trigger frequency band ) was applied , offline , in order to observe coincidences involving several antennas @xcite . using the position and the timing differences between antennas , it was also possible to perform the trajectory reconstruction of the electromagnetic plane wave using a triangulation techniques across the array @xcite . this level of analysis enables us to bring in light several cosmic ray air shower candidates . in the second phase operating since mid 2004 , the above setup ( see fig . [ fig : setup2 ] ) has been completed with four double plastic scintillators @xcite placed at the corner of the dam array ( @xmath3 ) . the trigger of the experiment is made of the four particle detectors in coincidence , resulting on an event rate of 0.8 event / mn . all the antennas have now the same role and are passband filtered ( 24 - 82 mhz ) in order to increase the signal to noise ratio . the observation of coincident events on antennas and charged particle detectors ( fig . [ fig : r248e1782 ] ) demonstrates the association of antenna transient signals with the occurrence of extensive air showers . this unambiguous evidence of radio signals through the simultaneous detection of shower particles will allow , for the first time , the characterisation of the shape and amplitude of air showers associated radio pulses . a preliminary event rate of 1/(8 hours ) is observed with antenna multiplicity ranging from 3 to 6 . from the corresponding deposited energy distribution in scintillators , one can infer the location of the air shower core . the time delays between the particle detectors allow the reconstruction of the shower axis . from these information , impact parameter effects can be studied especially those related to non vertical showers . the latter are expected @xcite to generate amplitude and shape field variations which will better show up in large atmosphere volumes accessible with radiodetection method . purposely , 5 antennas will be installed ( up to 400 m from the dam ) on a east - west line crossing the existing array . two effects , namely cerenkov emission and the classical far field , contribute to the radio emission of a shower @xcite . the line will also allow to study their respective influences and asseses the interest for designing a larger antenna array dedicated to ultra high energy cosmic rays . http://www.obs-nancay.fr/ and http://www - subatech.in2p3.fr/. ravel o. _ et al . * a518 * , 213 - 215 ( 2004 ) . dallier r. _ et al . sf2a 2003 scientific highlights _ , ed f. combes _ et al . _ ( edp sciences , 2003 ) . a. belltoile _ et al . _ , astro - ph/0409034 ( 2004 ) . m. boratav _ et al _ , _ proc . of the @xmath4icrc _ , rome , 954,(1984 ) . t. gousset , o. ravel and c. roy , _ astroparticle physics _ , * 22 * , 103 - 107 ( 2004 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: since the discovery of the far - infrared background ( firb ; @xcite ) , successive surveys have aimed to identify the discrete sources ( primarily galaxies ) responsible for this emission . with the launch of the esa _ herschel _ space observatory @xcite , with its large ( 3.5 m ) telescope and high sensitivity , it is now possible to resolve a much greater fraction of the firb . an essential element of this is to have methods for identifying individual sources from _ herschel _ data . this paper describes the generation of single - band point source catalogues from scan - map observations at 250 , 350 and 500@xmath0 m made using the photometer array of the spire instrument on _ herschel_. the spire instrument , its in - orbit performance , and its scientific capabilities are described by @xcite , and the spire astronomical calibration methods and accuracy are outlined by @xcite . the observations described here have been taken as part of the _ herschel _ multi - tiered extragalactic survey ( hermes ; oliver et al . , in preparation ) , using data from the science demonstration phase ( sdp ) of the survey . these observations cover approximately 20deg@xmath1 in five regions located in four extra - galactic fields , chosen for their minimal galactic emission at far - infrared wavelengths , and for the amount of high - quality multi - wavelength ancillary data available in those fields ( oliver et al . , in preparation ) . details of the observations are given in table [ tbl : wcs ] . the observations in the spitzer first look survey ( fls ) field were taken in spire pacs parallel mode , at scan speed 20 arcsec per second , while the other observations were taken in spire - only mode , at scan speed 30 arcsec per second ( abell 2218 , goods - north and lockman - north ) or 60 arcsec per second ( lockman - swire ) . standard spire observing modes were used for all observations . the number of repetitions is indicated in table [ tbl : wcs ] ; for each spire - only repetition , the field is scanned in both the nominal and orthogonal directions , while for spire pacs parallel mode ( fls ) , one of the repetitions is in the nominal direction and the other is in the orthogonal direction . for the lockman - swire field , two separate observations were taken , offset from one another , in order to produce a more uniform coverage . the abell 2218 ( a2218 ) data were obtained through two observations , each consisting of 50 repetitions , separated by 38 days , giving complementary scan directions . all observations were taken with nominal bias mode . more details are given by @xcite ( @xcite ; in preparation ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the gaia cornerstone mission by esa ( perryman et al . 2001 ) , scheduled for launch around 2010 , will record during its 5-year lifetime an average of @xmath2100 spectra for each of all the stars brighter than @xmath317.5 mag ( @xmath4 objects ) , over the wavelength range 84808740 and at a resolution 10000@xmath5 20000 , corresponding to dispersions 0.22 @xmath6 / pix @xmath6 0.44 in the nyquist fwhm=2 pix sense . the main aim of such spectra is to support the mission micro - arcsec accurate astrometry with the 6@xmath7 component of the phase - space via determination of the radial velocities . however , this huge number of spectra will not only provide radial velocities but will also carry the whole usual astrophysical content ( munari 2002 ) , which will be pretty large given the adopted high spectral resolution and the diagnostic potential of this wavelength region dominated by the caii triplet , the head of the paschen series , multiplet # 1 and # 8 of ni , and a forest of fei , tii lines and of many other metals . the study of the cool component of symbiotic stars will particularly benefit from the choice of this wavelength region for the gaia mission , as much as the spectral observations performed from the ground ( cf . marrese et al . , this volume ) . in fact , the 84808740 region is the only astrophysically relevant wavelength interval longward of h@xmath8 free from telluric absorption interference ( cf . munari 1999 ) , and is within the reach of many of the currently available high - resolution spectrographs . we have identified and calibrated , over this wavelength interval , a family of diagnostic line ratios that provide good estimate of temperature ( spectral type ) and surface gravity ( luminosity ) . the whole set of ratios will be described elsewhere , with only a sample of them presented here . other diagnostic ratios have been presented by munari ( 2002 ) . the line ratios have been investigated on the available high - resolution spectral atlases in this region , both observational ( munari and tomasella 1999 ) and synthetic ( munari and castelli 2000 , castelli and munari 2001 ) ones . the relations here presented come entirely from observational material , mainly referring to mkk standards ( thus bright , solar neighborhood stars ) . figure 1 presents temperature ( spectral type ) sensitive indicators for supergiant , giant and dwarf cool stars , built on the ratio of equivalent widths . to _ blend 8680 _ contribute mainly lines of fei ( 8679.638 ) , si ( 8678.927 , 8679.620 , 8680.411 ) and ni ( 8680.282 ) , and the extremes for equivalent width integration extends from 8678.0 to 8681.6 . the extremes for caii 8542 extend from 8522.0 to 8565.0 , to fully cover the line wings ( even if including several weak metallic lines ) . those for fei 8675 go from 8673.0 to 8676.5 , for tii 8683 from 8681.6 to 8684.0 , for fei 8688 from 8688.5 to 8690.5 . figure 2 offers surface gravity ( luminosity class ) sensitive indicators for supergiant , giant and dwarf cool stars , built on the ratio of equivalent widths . the extremes for equivalent width integration of fei 8688 and fei 8675 are the same for in figure 1 , while for tii+mgi 8735 it is 8734.38737.7 , for sii+fei 8728 is 8726.78729.5 , for fei 8514 is 8512.58515.8 and for tii 8518 it is 8516.68519.6 . castelli f. & munari u. 2001 , , 366 , 1003 munari u. 1999 , baltic astron . 8 , 73 munari u. 2002 , in _ gaia : an european space project _ , les houches , o.bienaym and c.turon ed.s , eas pub . series , edp sciences , pag . 39 munari u. & castelli f. 2000 , , 141 , 141 munari u. & tomasella l. 1999 , , 137 , 521 perryman m.a.c . 2001 , , 369 , 339 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the distribution of the duration of gamma - ray bursts shows an indication of two distinct groups from earlier experiments@xcite@xcite@xcite@xcite . data from burst and transient source experiment ( batse ) have confirmed the bimodal distribution of the duration of gamma - ray bursts . in terms of the parameter t90 , which is the time interval during which the integrated counts of a burst go from 5% to 95% of the total integrated counts , the bursts are separated into two groups around t90 @xmath0 2 s @xcite . time dilation , an evidence for the cosmological origin of grbs , was found in the long grbs @xcite . it is not yet known whether the two kinds of bursts are different or not . a recent study on the pulses in grbs suggests that the duration of the equivalent width of each pulse and the mean duration of individual pulse are bimodal @xcite . in this paper , we present a different approach to investigate the average pulse width of grbs . light curves of the batse grbs in 4b catalogue are studied . the light curves are from concatenated discla , preb and discsc data , and were obtained from compton observatory science support center ( cossc ) . they have been arranged into 64 ms time bins . first we subtract batse background from grb light curves . the batse background were estimated by a 5-degree polynomial . the total number of grbs with visually acceptable background estimate is 1186 . then we calculate the average pulse width @xmath1 of each grb as follows . first we calculate the auto - correlation of the light curve of each grb . the auto - correlation coefficients of the grb , @xmath2 , are defined as follows : @xmath3 where @xmath2 ( @xmath4 ) the auto - correlation coefficient at @xmath5 . we define the average pulse width @xmath1 as @xmath6 where 0.25 represents the average time shift of the central bin of the auto - correlation coefficient a(0 ) , and @xmath7 the maximum of @xmath8 with @xmath9+@xmath2 no less than 0.0 in the main peak of the auto - correlation . + the auto - correlation coefficients of batse trigger no.143 is shown in fig.1 . the data in the shaded region is used to calculate @xmath1 . we calculate @xmath1 of each grb and study the distribution of the average pulse width of the 1186 grbs . we have obtained the following results from the study of the average pulse width @xmath1 * the distribution of @xmath1 of grb is bimodal . this suggests that the average pulse width is bimodally distributed , and grbs can be divided into two groups , namely shot - pulse bursts and long - pulse bursts . the distribution of @xmath1 is peaked at about 0.5 s and 14 s for the two groups , respectively . they are roughly separated around 2 s. this is shown in fig.2 . * the average pulse width of the dim long - pulse bursts are longer than the bright long - pulse bursts . however , the average pulse width of the short - pulse bursts does not show a simple relation with grb peak flux . this is shown in fig.3 . we have presented our preliminary analyses of 1186 batse grb light curves in order to study the bimodal distribution of the duration of grbs . we conclude * the duration of the average pulse width in grbs are bimodally distributed . this is consistent with a different approach ( mitrofanov et al . * long - pulse bursts show the evidence for the time dilation effect . this is nt shown for the short - pulse bursts . further study of the short - pulse bursts is need , and probably need to include correction of the batse selection effect and to study short grbs with high time resolution tte data . wy appreciate various assistances by dr . r. s. mallozzi at msfc / uah . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: in order to explain the differences observed between type 1 and type 2 agn it has been proposed that an axially symmetric dusty structure ( the torus ) beyond the accretion disk absorbes a considerable fraction of the radiation emitted at wavelengths shorter than 1 @xmath0 m ( the agn unified scheme ) . the dust in this torus typically reaches temperatures of a few hundred degrees and therefore its emission peaks somewhere at ir wavelengths . it is therefore in this wavelength regime that the torus can be detected allowing us to determine its properties . we have obtained images for 49 seyfert 2 galaxies in 6 ir bands : j ( 1.25 @xmath0 m ) , h ( 1.65 @xmath0 m ) , k ( 2.2 @xmath0 m ) , l ( 3.78 @xmath0 m ) , m ( 4.66 @xmath0 m ) and n ( 10.36 @xmath0 m ) using the vlt at paranal , ntt at la silla and gemini at pachn . these galaxies were selected from the _ extended 12 @xmath0 m galaxy sample _ @xcite . we obtained the surface brightness profiles of each galaxy and modeled them to separate the contribution from a nuclear point source and a stellar component ( disk+bulge , figure 1 ) to construct the nuclear spectral energy distributions ( seds ) for each galaxy . the seds are then fitted using theoretical models of the emission of the dusty torus from @xcite , who solved the radiative transfer problem of a clumpy torus including absorption , emission and scattering . in figure 2 we show results for mcg -2 - 40 - 004 and mcg -3 - 34 - 64 , both galaxies classified as type 2 seyfert galaxies in @xcite , but in @xcite mcg -2 - 40 - 004 is classified as a type 1.9 seyfert , and mcg -3 - 34 - 64 as a type 1 due to the detection of broad polarized balmer lines . following @xcite definitions , for mcg -2 - 40 - 004 we obtained a torus of 100 pc in size , with 5 clouds along the line of sight ( each with a @xmath1=20 ) and an inclination of 60@xmath2 . for mcg -3 - 34 - 64 we obtained a torus of 30 pc in size , with 5 clouds along the line of sight ( each with a @xmath1=40 ) and a face on inclination . this sed is clearly more consistent with a type 1 seyfert classification . complementary data for our study comes from x - ray , spectropolarimetry , isocam and spitzer observations . together with our observations , we will use this information to further constrain the seds of our targets and determine the geometrical and physical parameters that govern the ir emission from agns . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: we observed the central parsec of the galactic center using an h band filter and seven intermediate band filters covering the k band with the ao assisted instrument naco at the eso vlt on paranal . this yielded eight point spectral energy distributions ( seds ) for 5914 sources . the spectral feature we used for stellar classification is the co bandhead absorption ( @xmath0 m ) , which allows the separation of late and early type stars . we determined its presence by fitting the seds with an extincted blackbody . our method produces reliable results for stars as faint as 15.5 mag in the k band ( k2iii or b2v stars , considering extinction and distance modulus ) , much deeper than previous studies . we classfied 322 stars as early type candidates and 2955 as late type . for the first time , it is now possible to study the early and late type population separately at this depth . only the latter can be expected to be dynamically relaxed due to its age ( gyrs ) . our new results show that the late type population indeed lacks the predicted cusp structure , showing a core instead ( see e.g. * ? ? ? the steep decline of the projected early type density towards the outer parts of the cluster ( e.g. * ? ? ? * ; * ? ? ? * ) could be confirmed here as well ( for both see fig.[fig1 ] ) . , resp . @xmath1 and @xmath2 for @xmath3 , red : late type stars , fitted with @xmath4 and @xmath5 for @xmath6 , blue : all identified stars , light blue : @xcite sources , right : klfs for different populations in the gc , with fitted power laws . ] the total k band luminosity function of the central parsec is considerably flatter than that of the galactic bulge , with a power law index @xmath7 @xcite compared to @xmath8 @xcite . the power law slope we fitted to the late type klf alone agrees very well with that of the bulge , a surprising result since the gc cluster is assumed to be a dynamically separate entity ( see fig.[fig1 ] ) . we can also confirm the much flatter klf found for the early type stars ( e.g. * ? ? ? * ) to a much greater depth ( k@xmath915.5 instead of k@xmath913 - 14 ) . these new results have enhanced our knowledge of the stellar population in the gc considerably , although several points remain unclear . instead of a cusp , we find a depletion of giants in the very center , as already found by e.g. @xcite , for giants with k@xmath912 , with @xcite confirming our own results spectroscopically only recently . several possible causes for this have been suggested , such as collisions / envelope stripping , mass segregation and imbh / smbh infall scenarios ( see e.g. * ? ? ? the fact that the power law slopes of the bulge and the late type klf agree within errors points to a similar mass function and stellar evolution . how this agrees with both being dynamically separate entities needs to be determined . for our further results and a more detailed treatment of the issues mentioned above , please see @xcite . bartko , h. , martins , f. , trippe , s. , fritz , t. , genzel , r. , et al . 2010 , apj , 708 , 834b buchholz , r. m. , schdel , r. , eckart , a. 2009 , a&a , 499 , 483 dale , j. , davies , m. , church , r. , freitag , m. 2009 , mnras 393 , 1016 do , t. , ghez , a. , morris , m. , lu , j. , et al . 2009 , apj 703 , 1323d figer , d. , rich , r. , sunsoo , s. , morris , m. , & serabyn , e. 2004 , apj , 601 , 319 genzel , r. , schdel , r. , ott , t. , eisenhauer , f. , et al . 2003 , apj , 594 , 812 haller , j. w. , rieke , m. j. , rieke , g. h. , et al . 1996 , apj , 456 , 194 merritt , d. 2009 , arxiv:0909.1318 paumard , t. , genzel , r. , martins , f. , et al . 2006 , apj , 643 , 1011 - 1035 schdel , r. , eckart , a. , alexander , t. , et al . 2007 , a&a , 469 , pp.125 - 146 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the standard neutrino theory involves diagonalization of the neutrino mass matrix @xmath1 by use of the mixing matrix @xmath0 : the matrices @xmath5 and @xmath0 are restricted by experimental data . merging information from neutrino oscillation experiments with neutrinoless double beta and tritium decay data @xcite-@xcite , the absolute neutrino masses can be found to be in the range : .the allowed absolute values of the neutrino mass squared differences @xmath7 , @xmath8 and the allowed absolute values of the neutrino mixing matrix elements @xmath9 . @xmath10 and @xmath11 are the central values and the @xmath12 uncertainties , respectively . [ cols="^,^,^,^",options="header " , ] Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: observations of occultations of compact radio sources by solar system planets may be interesting for several astronomical and physical applications , such as testing gr @xcite , improvement of planet orbits and their tie to icrf @xcite , and planetary researches @xcite . our previous computations of occultations of astrometric radio sources by planets and their close approaches were published in @xcite . in this paper we present the updated list of the forthcoming occultations that may be interesting for radio astronomy observations . the main differences with the previous work are the use of an extended astrometric source list , and computation of event maps to help better planning of observations . most computations of the circumstances of occultations of geodetic radio sources by planets were performed using the codes approach and occult , which utilize the ephemeride package for objects of the solar system ( epos ) data and environment . source coordinates were taken from the catalog of astrometric radio source positions of leonid petrov , version 2009c the list of occultations is presented in table [ tab : occulttaions ] with their basic circumstances . one can see that most of the events are visible in regions with radio astronomy observatories , and several of them can be observed on many antennas . the nearest most interesting event is the occultation of the source 1946200 by mars in february 2011 visible in north america with vlba , vla , gbt and other radio astronomy facilities . figure [ fig : maps ] and table [ tab : details1 ] present the detailed circumstances of the several nearest events that can be observed in regions with several geodetic vlbi antennas . the maps of shadow path are shown in fig . [ fig : maps ] . table [ tab : details1 ] presents the detailed circumstances of the several nearest events , such as the elevation , azimuth , and position angle on the planetary limb at the beginning and the end of the occultation . the circumstances for other events are available on request . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: a large number of low mass x - ray binaries ( lmxb ) are believed to harbor neutron stars , rotating rapidly due to accretion - induced angular momentum transfer . these systems show many complex spectral and temporal behaviors . one of the main purpose for studying such behaviors is to understand the properties of very high density @xmath0 g @xmath1 matter at the neutron star core . such high densities can not be created in the laboratory and only the study of these sources can give a possible answer to this fundamental question of physics . here we calculate the equation of state ( eos ) dependent model spectra of the accretion disks around rapidly rotating neutron stars . these models , when fitted to the observed spectra , can in principle help to constrain eos models and hence to understand the properties of core - matter of neutron stars . we compute the structure of a rapidly rotating neutron star for realistic eos models , gravitational masses and rotational speeds using the same procedure as cook , shapiro , & teukolsky ( 1994 ) . we use the axisymmetric metric ( see bhattacharyya et al . 2000 for description ) @xmath2 to calculate the metric coefficients and the bulk structure parameters of the neutron star , we solve einstein s field equations and the equation of hydrostatic equilibrium simultaneously . for a thin blackbody disk , we compute the temperature profile ( see bhattacharyya et al . 2000 ) and hence the spectrum ( see bhattacharyya , bhattacharya , & thampan 2001b ) considering the effect of the doppler shift , gravitational redshift and light - bending effects . we calculate the spectra for different eos models , which therefore gives a way to constrain eoss when fitted to the observed spectra . however , the computation of the complete spectrum in this manner is rather time - consuming and therefore not quite suitable for routine use . therefore , in order to make our results available for routine spectral fitting work , we intend to present a series of approximate parametric fits to our computed spectra in a forthcoming publication . as a first step towards this aim , here we present an analytical function which describes both the relativistic spectra and the newtonian spectra well . this function with three free parameters @xmath3 and @xmath4 is given by ( see bhattacharyya , misra , & thampan 2001a for details ) @xmath5 where , @xmath6 , @xmath7 is the energy of the photons in kev and @xmath8 is in units of photons / sec/@xmath9/kev . the value of @xmath10-parameter is @xmath11 for the newtonian case , while it ranges from @xmath12 to @xmath13 for the relativistic cases ( if the value of inclination angle is not too high ) . therefore , constraining this parameter by fits to future observational data may indicate the effect of strong gravity in the observed spectrum . this work is a step forward towards constraining eos models of neutron stars by fitting the observed spectra of lmxbs . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the analysis of the trends of abundances of light elements with respect to [ fe / h ] for the oldest metal - poor stars is a direct way to provide some clues on their production mechanism and evolution . in a recent work on non - lte effects in iron abundances , thvenin & idiart ( 1999 ) ( ti99 ) obtained that for metal - poor dwarf stars fe abundances ( [ fe / h ] ) are affected by significant non - lte effects and , moreover , surface gravities ( logg ) derived by lte analysis also need corrections . this logg corrections should be crucial for beryllium abundances determination , since be ii resonance lines normally used to estimate be abundances are much sensitive to this stellar parameter . in this work we examine the consequences of non - lte corrections to logg and [ fe / h ] for logn(be / h ) vs. [ fe / h ] ( or be - fe ) diagram . in section 2 we present a short summary of our results obtained in ti99 for fe and in section 3 the results for be abundances . ti99 performed statistical equilibrium calculations for fe i and fe ii to estimate non - lte effects in iron abundances . the main results are showed in figure 1 ( see ti99 for details ) . we re - estimate n(be / h ) abundances for 21 stars also analised by boesgaard et al.(1999 ) using @xmath0 , logg and [ fe / h ] given by ti99 . be abundances were calculated assuming lte conditions , since the non - lte corrections are negligible for be ii lines considered here ( @xmath1 3130 and 3131 ) , as demonstrated by garcia lopez et al . ( 1995 ) , for example . figure 2 shows our results . we conclude that for the range of metal - poor objects -3 @xmath2 [ fe / h ] @xmath2 -1.5 , non - lte corrections for [ fe / h ] compensate changes in be abundances ( as result of logg corrections ) in the be - fe diagram , recovering the same linear behavior of lte derived abundances ( boesgaard et al.1999 ) . similar results are found for boron ( see primas 1999 , this colloquium ) . thvenin , f . & idiart , t . 1999 , , 521 , 753 boesgaard , a.,constantine , p.,king , j.,ryan , s. vogt , s . , 1999 , , 117 , 1549 garcia lopez , r . , severino , g . & gomez , m . , 1995 , , 297 , 787 primas f. , 1999 , this colloquium Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the three - quark ( 3q ) potential is one of the most important fundamental quantities in the hadron physics , because it is directly responsible to the baryon properties and is the key quantity to clarify the quark confinement in baryons . we perform the first systematic study of the ground - state 3q potential @xmath0 and the excited - state 3q potential @xmath1 using su(3 ) lattice qcd @xcite . for more than 300 different patterns of the spatially - fixed 3q systems , we perform the thorough calculation for the ground - state potential @xmath0 in lattice qcd with @xmath3 at @xmath4 and with @xmath5 at @xmath6 at the quenched level . for the accurate calculation , we construct the quasi - ground - state of the 3q system using the smearing method @xcite . as an important conclusion , the static ground - state 3q potential @xmath0 is found to be well described by the coulomb plus y - type linear potential " , i.e. , y - ansatz , @xmath7 within the 1%-level deviation @xcite . here , @xmath8 denotes the minimal value of total flux - tube length , as shown in fig.1 . such a y - type flux - tube profile is actually observed in recent lattice qcd @xcite , as shown in fig.2 . from the comparison with the q-@xmath9 potential , @xmath10 , we find the universality of the string tension as @xmath11 and the one - gluon - exchange result as @xmath12 @xcite . of the total flux - tube length . there appears a physical junction linking the three flux tubes at the fermat point p , and one finds @xmath13 . , width=168 ] 0.5fm in the maximally - abelian projected qcd @xcite . , width=432 ] we study also the excited - state potential @xmath1 in the spatially - fixed 3q systems in lattice qcd with @xmath5 at @xmath14 @xcite . the energy gap between @xmath0 and @xmath1 physically means the excitation energy of the gluon field in the presence of the spatially - fixed three quarks , and the gluonic excitation energy , @xmath2 , is found to be about 1gev , as shown in fig.3 . note that the gluonic excitation energy is rather large compared with the excitation energy of quark origin , and the present result predicts that the hybrid baryon expressed as @xmath15 should be heavier than 2gev . 1 gev / fm . in the flux - tube picture , the gluonic excitation is described as the flux - tube vibration , and the flux - tube vibrational energy is expected to be large , reflecting the large string tension . the large gluonic - excitation energy of about 1gev leads to the absence of the gluonic mode in low - lying hadrons , which would play the key role to the success of the quark model without gluonic excitation modes . , width=672 ] we show in fig.4 a possible scenario from qcd to the massive quark model . in terms of the flux - tube picture , the large gluonic - excitation energy is conjectured to originate from the large string tension as a result of strong color confinement . the large gluonic - excitation energy would be responsible to the absence of the gluonic mode and the success of the quark model for low - lying hadrons . 9 t.t.takahashi , h.matsufuru , y.nemoto , h.suganuma , phys.rev.lett . 86 ( 2001 ) 18 . t.t.takahashi , h.suganuma , y.nemoto , h.matsufuru , phys.rev . d65 ( 2002 ) 114509 . t.t . takahashi and h. suganuma , ( 2003 ) 182001 . takahashi , h. suganuma , h. ichie et al . a721 ( 2003 ) 926 . h. ichie , v. bornyakov , t. streuer and g. schierholz , nucl . a721 ( 2003 ) 899 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: temporal variation of the vorticity magnitude during the falling procedure is demonstrated here . a high vorticity region is obvious on top of the troplet . the more the fragments , the more the complexity in the carrier phase . two of the crucial parameters for the case of falling droplets are size and velocity of the fragments . this video shows the variation of falling velocity over the interface . using the integration , the falling velocity and size of the fragments can be easily and accurately achieved . since an accurate prediction of the radius of curvature and vorticity magnitude are essential to the breakup process , these parameters are considered as refinement criteria , while the latter is also important to resolve the local turbulent eddies generated in the continues phase and close to the interface . in this part , the detailed mechanism of thin liquid sheet breakup is shown where the instability growth over the interface generates several punctures . the retraction of punctures produces a network of ligaments rapidly disintegrates into several number of small droplets . a video presenting the results obtained via direct numerical simulation is presented . outcomes demonstrates the capability of the current numerical methods to investigate the complex problem of falling droplets . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the term _ patience sorting _ was introduced in 1962 by c.l . mallows @xcite as the name of a card sorting algorithm invented by a.s.c . ross . this algorithm works by first partitioning a shuffled deck of @xmath0 cards ( which we take to be a permutation @xmath1 ) into sorted subsequences @xmath2 called _ piles _ and then gathering the cards up in order from the tops of these piles . the procedure used in forming @xmath3 can be viewed as an iterated , non - recursive form of the schensted insertion algorithm for interposing values into the rows of a young tableau ( see @xcite and @xcite ) . given @xmath1 , we call this resulting collection of piles ( given as part of the more general algorithm [ alg : extendedpsalgorithm ] below ) the _ pile configuration _ corresponding to @xmath4 and denote it by @xmath5 . given a pile configuration @xmath6 , one forms its _ reverse patience word _ @xmath7 by listing the piles in @xmath6 `` from bottom to top , left to right '' ( i.e. , by reversing the so - called `` far - eastern reading '' ) as illustrated in example [ eg : pileconfigurationexample ] below . in recent work @xcite the authors used g. viennot s ( northeast ) shadow diagram construction ( defined in @xcite and summarized in section [ sec : geometricrsk : neshadowdiagrams ] below ) to characterize these words in terms of the following pattern avoidance condition : given @xmath1 , each instance of the generalized permutation pattern @xmath8 in @xmath9 must be contained within an instance of the pattern @xmath10 . we call this restricted form of the generalized permutation pattern @xmath8 a _ ( generalized ) barred permutation pattern _ and denote it by @xmath11 . this notational convention is due to j. west , et al . , and first appeared in the study of two - stack sortable permutations @xcite . as usual , we denote the set of permutations @xmath1 that avoid the pattern @xmath11 by @xmath12 . ( see bna @xcite for a review of permutation patterns in general . ) [ eg : pileconfigurationexample ] let @xmath13 . then , using a simplified form of algorithm [ alg : extendedpsalgorithm ] below , @xmath4 has the pile configuration @xmath14 , which is visually represented as the following array of numbers : d. aldous and p. diaconis . `` longest increasing subsequences : from patience sorting to the baik - deift - johansson theorem '' , _ bull . * 36 * ( 1999 ) , 413432 . available online at ` http://www.ams.org/bull/1999-36-04/ ` g. viennot . `` une forme gomtrique de la correspondance de robinson - schensted '' , in _ combinatoire et reprsenatation du groupe symtrique _ , d. foata , ed . lecture notes in mathematics 579 . springer - verlag , 1977 , pp . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: csma / eca instruct nodes to get out of the contention when their mac queue empties . these nodes @xmath0 upon receiving a new packet in the mac queue @xmath0 will rejoin the contention picking a random backoff counter @xmath1 $ ] . this behavior brings again a transitory state , where nodes that just rejoined the contention will attempt to make a successful transmission and get back into the collision - free state . our first attempts to take a look at what happens under this condition were unsuccessful mainly for the lack of code considering this scenario , i.e. : packet erasure from the mac queue upon successful transmissions or retransmission attempts , delay measures and the determination of when was it really an unsaturated system . nevertheless , those times are behind us . in the following sections we will take a look at some of the results , namely : * throughput , * delay , * number of packets in the mac queue at the end of each simulation , * number of times a mac queue empties , * average backoff stage at the end of each simulation , and * average collisions . we can see form figure [ unsat : throughput ] that as each tested protocol enters in saturation , it deviates from the straight line ( which is the offered traffic load ) . the delay metric that we are using in this report measures the time elapsed between the moment a packet enters the mac queue , up until an acknowledgement for this ( these ) packet(s ) is received . csma / eca offers lower delay than csma / ca , nevertheless we can see an otherwise strange behavior at around 60 nodes . what happens ? if we take a closer look at what happens with the delay curves ( using a logarithmic scale ) , the `` _ _ bumb _ _ '' appears again at 60 nodes . this bumb is related to the saturation of csma / eca . we can see from figure [ unsat : delaylog ] , that this behavior is similar to csma / ca when it is about to enter in saturation . if we use the `` csma / ca unsaturated with maximum aggregation '' curve as an example : * from around 20 to around 35 contenders , this curve seems to be concave ; as both csma / eca curves are from around 20 to 60 contenders . * the concavity ends at around 35 contenders ( which coincides with the saturation point , see figure [ unsat : throughput ] ) , just to change to another concavity from the saturation point forward . * for the csma / eca curves this behavior seems to be the same , but this time at around csma / eca s saturation point ( around 60 nodes ) . this increase in the delay at saturation point will be appreciated as a rapid increase in the number of packets in the mac queue , see figure [ unsat : qsize ] . csma / eca eliminates collisions while in saturation and for a limited number of contenders in 802.11 networks . in figure [ unsat : collisions ] an increase on the average number of collisions is appreciated in the csma / eca curves . this is the result of many nodes emptying their mac queue and rejoining the contention . figure [ unsat : qempties ] provides evidence of this event , where from 20 to 60 nodes csma / eca s nodes empty their mac queue sometime in the simulation and collide . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the study of the kinematics of spiral galaxies is an active area of astronomical research . the construction of fabry - perot interferometers have greatly increased the kinematical knowledge of these objects . in this contribution , we present preliminary results from a fabry - perot study of ngc 5457 ( m101 ) . the observations were carried out during the night of july 23 - 24 , 2001 , with the unam scanning fabry - perot interferometer ( sfpi ) puma attached to the f/7.9 ritchey - chretien focus of the 2.1 m telescope at the observatorio astronmico nacional at san pedro mrtir , b.c . the main characteristics of puma can be found in rosado et al . the data reduction was performed using the adhoc package ( boulesteix 1993 ) . the reduction procedure followed a `` standard '' scheme and the details will be published elsewhere ( puerari et al . , in preparation ) . one of the main results obtained from fabry - perot data is the radial velocity field . by using this field , and the geometrical parameters of the galaxy ( inclination and position angles , kinematical center ) as well as the recession velocity , the rotation curve can be calculated . for ngc 5457 , we have derived the rotation curve presented in fig . 1 ( left panels ) . this curve is in agreement with that one of comte et al . ( 1979 , see their fig . 6 ) , but our results present less dispersion , due to the better resolution and signal / noise ratio of our observations . assuming a distance of 7.2 mpc ( sandage & tammann 1974 ) , we have calculated a total mass of 9.8@xmath1 10@xmath2 m@xmath3 inside a radius of 48 ( or 10 kpc ) , also in agreement with comte et al . ( 1979 ) . we have also obtained the velocity dispersion of the hii region population . we fitted a gaussian to each hii region velocity profile and corrected the final value by the instrumental , thermal and intrinsic broadenings . the distribution of velocity dispersion values presents a normal behavior ( see fig . 1 , right panel ) . the mean value of this distribution is 30 km sec@xmath4 ( i.e. , supersonic dispersion ) ; this result must be checked with fabry - perot studies at other lines ( eg . , [ sii ] ) . boulesteix , j. 1993 , `` adhoc reference manual '' , publications de lobservatoire de marseille ( http://alpha2.cnrs-mrs.fr/adhoc/ ) comte , g. , monnet , g. , rosado , m. 1979 , a&a , 72 , 73 rosado , m. et al . 1995 , rev . y astrof . , 3 , 263 sandage , a. , tammann , g.a . 1974 , apj , 194 , 223 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: almost all hgmn stars exhibit a strong absorption feature at 3984 , which has been identified as a line of . the wavelength at which this line is observed depends on the isotopic mix of hg ( white et al . 1976 ) , which ranges from the terrestrial mix to nearly pure @xmath0hg . mercury is not the only very heavy element observed in hgmn stars . lines of ( dworetsky & vaughan 1973 ) and ( guthrie 1985 ) are also observed . dworetsky & vaughan ( 1973 ) studied the @xmath1 line in a sample of nine hgmn stars . this line is the strongest pt line at optical wavelengths , and in the nine stars studied it is shifted toward longer wavelengths by 0.04 to 0.09 , with respect to the centroid of the terrestrial platinum line . these shifts are interpreted as an isotopic effect . the corresponding anomalies are analogous to those found for hg , in the sense that the heavier isotopes tend to dominate in cooler stars . neither radiatively driven diffusion nor any other theory until now can account satisfactorily for the variations in the hg and pt isotope mix among the hgmn stars ( leckrone et al . 1993 ) . the main purpose of the work reported here was to provide additional observational constraints to guide the theorists in the understanding of the isotopic anomalies in hgmn stars , improving upon previous studies through the much better data quality obtainable now . thanks to the availability of new laboratory measurements of isotope shifts in ( engleman 1989 ) it became possible to identify more definitely the isotopes . .isotopic compositions [ cols= " < , > , > , > , > , > , > " , ] spectra were obtained with the eso 1.4 m coud auxiliary telescope and the coud echelle spectrograph long camera at a resolving power r = @xmath2 and @xmath3 . the observed wavelength ranges are 39654000 and 40184035 . synthetic spectra and model atmospheres were computed with the synthe and atlas9 codes ( kurucz 1997 ) , respectively . a code similar to the tefflogg code of moon & dworetsky ( 1985 ) , but based on new computed uvbybeta indices , was used to obtain the stellar parameters ( castelli & kurucz 1994 ) . observed indices were taken from the mermilliod , mermilliod , & hauck catalogue ( 1997 ) and were dereddened using the uvbybeta code of moon ( 1985 ) . for all the stars we assumed zero microturbulent velocity , while the rotational velocity was derived from the comparison of the observed and computed spectra , after having degraded the computed spectra for the broadening due to the instrumental profile . for the whole transition of 3983 we adopted @xmath4 ( dworetsky 1980 ) . for each isotopic and hyperfine component this value was scaled in agreement with each observed relative intensity . for reference , the terrestrial intensities from kurucz ( 1993 ) and from smith ( 1997 ) were adopted . for the transitions of 4023.8 , 4034.2 , and 4046.4 we adopted log @xmath5 , and @xmath6 , respectively ( dworetsky & vaughan 1973 ) . the isotopic and hyperfine shifts and intensities were either taken directly from engleman ( 1989 ) or were derived from engleman ( 1989 ) and kalus et al . one of the programme stars with very sharp lines is the double - lined spectroscopic binary @xmath7 lup . an updated version of the binary code of kurucz ( 1993 , cd - rom 18 ) has yielded as final computed spectrum the spectrum resulting from the contribution of both components . the atmospheric parameters of the secondary star and ratio of the radii of the primary to the secondary stars in @xmath7 lup were taken from wahlgren et al . ( 1994 ) . for five programme stars with extremely sharp spectral lines ( @xmath8 km / s ) the isotopic composition could be studied in greater detail . the results are summarized in table 1 . all stars have hg overabundance by more than 5 dex compared with the solar abundance . the largest overabundance of pt ( 4.69 dex ) was found in the star hr 7775 . no star shows terrestrial isotopic proportions . the most pronounced deviation from the terrestrial composition is found in the stars @xmath7 lup and hr 7775 , which are the coolest ones in our sample . castelli f. , kurucz r.l . : 1994 , poster paper presented at the jd no . 12 of the 22nd iau general assembly kalus g. , johansson s. , wahlgren g.m . , leckrone d.s . , thorne a.p . , brandt j.c . _ astrophys . j. _ , in press kurucz r.l . : 1997 , private communication moon t.t . : 1985 , _ comm . . london obs._*78 * Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: we come up with the formalism in several stages . first , we write down the standard propagation equations of stokes parameters @xmath2 @xmath3 @xmath4 @xmath5 in the uniform thermal plasma @xcite in a locally flat co - moving reference frame with synchrotron emissivities / absorptivities from @xcite . we take faraday rotation / conversion coefficients from @xcite , as the other published derivation of faraday conversion coefficients @xcite is a very crude approximation . second , we parallel propagate the basis vectors along the null geodesic from the observer s plane to account for gr rotation of the basis . third , with proper gauges on wave vector potential we write down the covariant equations of polarized radiative transfer . following @xcite , we assume that the matrix of absorptivities and propagation coefficients generalizes in the polarized transfer analogously to the unpolarized case . the dynamical model used in the transfer starts with adiabatic 3d grmhd simulations of thick accretion flow onto the kerr black hole ( bh ) with spins @xmath6 @xmath7 @xmath8 @xmath9 we average the flow velocity , magnetic field , rms magnetic field , gas density and pressure for the quasi - steady period of the developed accretion and separate the electron temperature @xmath10 from the proton temperature @xmath11 by applying the heating prescription from @xcite . the dynamical model is smoothly extended to large radii @xmath12 to take into account the faraday rotation effect at large distances from the bh . we perform the gr polarized radiative transfer for each spin for a set of inclination angles @xmath13 and compare the specific fluxes , linear polarization fractions ( lp ) , and circular polarization fractions ( cp ) to observations . we find , that the extreme spins @xmath14 @xmath15 do not fit all the observations well . they require lower density @xmath16 @xmath17 near bh to fit the flux at @xmath18 ghz , but faraday depolarization fails at these densities leading to high lp at @xmath19 ghz compared to the observed value @xcite . the preferred value of the inclination angle @xmath1 is coincident with that in @xcite . the spin value @xmath0 gives the best fit ( see fig . [ fig ] ) , though spin @xmath20 produces good fits as well . imaging produces some unexpected results . as our simulation appears to be substantially sub - keplerian and have significant thermal support , the innermost stable circular orbit ( isco ) loses its importance and the black hole shadow is not always seen . huang , l. , liu , s. , shen , z .- q . , yuan , y .- f . , cai , m. j. , li , h. , & fryer , c. l. 2009 , apj , 703 , 557 macquart , j .- bower , g. c. , wright , m. c. h. , backer , donald c. , falcke , h. 2006 , , 646 , l111 marrone , d. p. , moran , j. m. , zhao , j. , & rao r. , 2007 , , 654l , 57 melrose , d. b. 1971 , 12 , 172 melrose , d. b. , mcphedran , r. c. 1991 , `` electromagnetic processes in dispersive media '' , ( cambridge university press : cambridge ) sharma , p. , quataert , e. , hammett , g. w. , & stone , j. m. 2007 , , 667 , 714 shcherbakov , r. v. 2008 , apj , 688 , 695 yuan , f. , quataert , e. , narayan , r. 2004 , , 606 , 894 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the fruit fly is considered to be one of the smallest flying insects with a wingspan of about 6 mm . it flies at about 200 wingbeats per second , which yields a reynolds number of about 120 . however , there is a large variety of flying insects that are much smaller in size . one group includes parasatoid wasps . the jewel wasp is one example and has a wingspan of about 3 mm , flying at a reynolds number of about 60 . another group includes _ thysanoptera _ , commonly known as thrips . these insects are characterized by bristled wings and fly at reynolds numbers around 10 . in typical insect flight , lift is produced when a leading edge vortex is formed and remains attached to the wing , and a trailing edge vortex is formed and separates from the wing during each stroke . for tiny insect flight , neither the leading nor trailing edge vortices separate from the wing during the duration of each stroke . as the reynolds number is lowered from 100 to 1 , the relative lift forces produced during flapping flight decrease while drag forces increase significantly . these transitions are associated with a change in the behavior of the vortex wakes behind the flapping wings @xcite . thrips were collected during july and august locally on the university of north carolina campus . fruit flies were obtained from a local collection in the unc department of biology . jewel wasps were ordered from carolina biological . high speed videos of the insects were taken at 4000 hz . in each case , one or two cameras were focused on a standard pipette tip from which the insects were filmed during takeoff . immersed boundary simulations @xcite were performed for a two - dimensional wing with a fixed angle of attack of @xmath3 immersed in a channel . reynolds number was calculated as @xmath4 , where @xmath5 was the maximum velocity in the channel , @xmath6 was the dynamic viscosity of the fluid , @xmath7 was the density of the fluid , and @xmath8 was the chord length of the wing . the initially velocity of the channel was set to zero and then linearly increased to a set velocity determined by the desired reynolds number . particle image velocimetry was used to quantify the flow fields around a dynamically scaled physical model of a wing that rotated about its base . the velocities of particles illuminated in the laser sheet were determined from sequential images analyzed using a cross - correlation algorithm ( lavision inc . software ) . image pairs were analyzed with shifting overlapping interrogation windows of decreasing size ( @xmath9 pixels then @xmath10 pixels ) . lift and drag forces were also measured using a dynamically scaled physical model that rotated about its base @xcite . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the centers of galaxy clusters are the densest regions of galaxy populations in the universe . they are the places where the most frequent interactions between galaxies are expected to have taken place during the cluster formation epoch ( and maybe also in the present ) . some striking properties of galaxy cluster centers are : 1 ) a very rich globular cluster system ( gcs ) around the central galaxy ( e.g. harris 1991 ) , 2 ) an extended stellar halo ( cd halo ) around the central galaxy ( e.g. schombert 1988 ) , and 3 ) an abundant population of early - type dwarf galaxies clustered towards the center ( e.g. ferguson & binggeli 1994 ) . how do these findings come together ? can they be the result of a common scenario in which galaxy disruption played a major role ( see hilker et al . nearby galaxy clusters provide an ideal laboratory to study the different stellar components in detail . the hydra i galaxy cluster is dynamically evolved , has a regular core shape and an isothermal x - ray gas halo that can be followed out to about 160 kpc . the centaurus cluster is dynamically young with two merging sub - groups , a main cluster component ( cen30 ) around the cd galaxy ngc 4696 and a smaller group component ( cen45 ) around ngc 4709 . both galaxy clusters are located at a distance of about 45 mpc . both galaxy clusters were observed at dark time and under photometric conditions in the filters @xmath2 and @xmath3 with fors1 at the vlt ( eso , paranal ) . the seeing in all fields was in the range 0.5 to 0.7 arcsec , thus providing a very homogeneous data set . as one can see in fig . 1 , globular cluster candidates are spread all over the core of the two galaxy clusters , well outside the tidal radii of the central galaxies . the red gcs ( @xmath4 ) are more concentrated towards the galaxy s bulges than the blue gcs ( @xmath5 ) . the intra - cluster gcs are not uniformly distributed around the central galaxies . in the centaurus cluster , they show a tidal tail - like structure between the two dominant giant ellipticals . in hydra i , they occupy the same space as the abundant ( newly found ) dwarf spheroidal galaxies . also there exists a population of very blue ( @xmath6 ) , probably young clusters close to ngc 3311 . these clusters might have been stripped from the late - type group of galaxies around ngc 3312 that is passing by the core of hydra i. in both clusters , a population of very bright ( @xmath7 ) cluster or compact dwarf galaxy candidates seems to exist . in the near future we intend to 1 ) construct a density map of the intra - cluster gc population , in order to define its center and compare it to that of the x - ray gas halo , 2 ) model the cd halo light to study the local specific frequency all over the galaxy cluster , 3 ) study in detail the individual gcss of all member galaxies down to the dwarf galaxy regime , and 4 ) confirm the membership of dwarf galaxies and bright compact objects by follow - up spectroscopy . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: agile , the 4@xmath1 gamma - ray satellite , is a bridge between the compton gamma ray observatory ( cgro ) , switched off in 2000 , and the gamma ray large area space telescope ( glast ) to be launched at the end of 2006 . the agile instrument is designed to detect and image gamma - ray and hard x - ray photons by means of the gamma ray imaging detector ( grid ) and the hard x - ray imager super - agile ( sa ) . grid , sensitive in the energy range 30mev@xmath050gev , is made of 12 si - w planes and the mini calorimeter , sensitive in the energy range 0.3@xmath0100mev and positioned at the bottom of the instrument . sa , sensitive in the energy range 10@xmath040kev , with its 4 si - detectors and the ultra - light coded mask system is positioned on top of the first grid tray . the asi science data center ( asdc ) will host the agile data center ( adc ) . the adc includes the agile team processing group and the agile science support group . agile data from the malindi ground station will be received by the operational and control center ( aocc ) in italy and then they will be transfered to adc . + the adc@asdc will be in charge of the following tasks @xcite : * running the quick look analysis * running the standard data reduction analysis * performing , when necessary , the interactive data analysis * managing announcement of opportunities * contributing to the agile management of the pointing program * archiving the data ( raw , cleaned and calibrated , scientific ) * distributing the data to the scientific community * providing scientific support to the users community * interfacing the project for both data and proposals + via dedicated web pages * providing the standard software support for data analysis the pipeline that will be running at asdc will drive the automated data analysis for both grid and sa data . figure [ memola1 ] shows a preliminary flow chart concerning the grid data analysis . the software modules needed to process the data are under development by the agile team , while the pipeline itself will be built by professional programmers of the agile science support group at asdc , in collaboration with the agile team . the grid telemetry packets will be pre - processed in order to get files in the standard fits format . the event list undergoes a complex process of background subtraction and track reconstruction analysis in order to get a cleaned @xmath2-photon list . then , standard products as spectra , light curves and images will be made available to the scientific community via a set of dedicated web pages . agile data will be part of the permanent multi - mission interactive archive at asdc . the scientific goals of the agile mission include the detailed study of active galactic nuclei . figure [ memola2 ] ( _ top _ ) shows the simulated all - sky intensity map above 100mev @xcite as well as the spectral energy distributions ( seds ) of the blazars mkn 501 ( _ bottom , left _ ) and 3c 273 ( _ bottom , right _ ) . the multi - frequency data have been retrieved from the nasa / ipac extragalactic database ( ned ) , the second version of the guide star catalog ( gsc - ii ) and from _ beppo_sax . by accounting for agile - grid and super - agile limiting sensitivity we plan to select the blazars currently known that might be suitable candidates for agile observations . according to the predictions of a synchrotron - self compton ( ssc ) spectral model ( _ dashed _ , _ dashed - dotted lines _ ) , mkn 501 and 3c 273 would be visible to both agile - grid and super - agile . the seds of all the blazars observed by _ beppo_sax during its first five years of operations @xcite and the corresponding ssc predictions together with the plotted agile - grid and super - agile limiting sensitivity can be found at the following web address : http://www.asdc.asi.it/blazars/ agile science management plan , asi document , 2002 + giommi p. , capalbi m. , fiocchi m. , memola e. , et al . , 2002 , in _ blazar astrophysics with bepposax and other observatories _ , frascati , italy , december 2001 , p. giommi , e. massaro , g. palumbo eds . , asi special publication p.63 + science with agile , agile document ap , issue 25 , march 6 , 2003 : http://agile.mi.iasf.cnr.it/homepage/index.shtml Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: rx j2115 - 5840 ( euve 211658.6 ) was discovered during the _ rosat _ ( voges et al 1996 ) and _ euve _ ( bowyer et al 1996 ) all sky surveys . subsequent ground based observations confirmed the source as a polar . schwope et al ( 1997 ) suggested that the orbital and spin periods of rx j2115 - 5840 differ by @xmath01% . this would make it the fourth near synchronous polar and the first one below the 23 hr period gap . we obtained 2 weeks of white light polarimetric observations in july - aug 1997 at saao to investigate this possibility . the circular polarisation data are shown in fig . [ cpol ] : the circular polarisation is generally either close to zero or shows positive excursions . however , there are occasions when negative polarisation is seen ( hjd 2450000 + 659 , 666 and 672 ) . these observations suggests that rx j211558 is not fully synchronised . ( 6,8 ) ( -3,-2 . ) to investigate the circular polarisation data more closely , we used a discrete fourier transform to obtain an amplitude spectrum ( fig [ power ] ) . the highest amplitude peak corresponds to a period of 110.889 mins similar to the spectroscopic period of 110.8 mins reported by vennes et al ( 1996 ) . the second highest peak corresponds to a period of 109.547 mins similar to the shorter of the two possible optical photometric periods , 109.84 and 109.65 mins , reported by schwope et al ( 1997 ) . if we assume that the binary orbital period is @xmath1=110.889 min and the spin period of the white dwarf is @xmath2=109.547 min we find the following more complex frequencies in the amplitude spectrum : 3@xmath1 , 2@xmath2 , 3@xmath2 , @xmath3 , 2@xmath4 , 4@xmath13@xmath2 . any other frequencies which are present have amplitudes lower than 1% . the spin - orbit beat frequency corresponds to a period of 7.1 days . ( 8,7 ) ( -4,-28.5 ) to make a more detailed investigation of these data we folded the circular polarimetry on the proposed spin and orbital periods and the spin - orbital beat period ( the left hand panel of fig [ beat_phase ] ) . folding the data which correspond to a discrete beat phase on the proposed spin period of the white dwarf , we find that the polarisation curve shows a negative excursion lasting approximately half the spin cycle . at other spin phases the polarisation is close to zero ( the right hand panel of fig [ beat_phase ] ) . at @xmath5=0.20 the polarisation is not significantly modulated . at other beat phases a prominent positive hump is seen in the folded spin polarisation curves , the peak of which advances in phase as @xmath5 increases . ( 8,7 ) ( -3.5,-29.5 ) in fully synchronous polars , the accretion flow is locked with respect to the binary orbital rotation frame and the bulk of the accretion flow is thought to be directed onto the geometrically preferred magnetic pole of the white dwarf . however , in the case of near - synchronous polars , the accretion flow rotates around the magnetic field of the white dwarf on the spin - orbit beat period . this has the effect that the accretion flow will be directed preferentially onto first one then the other magnetic pole of the white dwarf . at two phases of the spin - orbit beat period we expect that the flow will be equally directed onto both poles . this ` pole - switch ' will manifest itself most obviously in the circular polarisation curves where the polarisation will change sign after the accretion flow has ` switched ' poles . this is seen in the right hand panel of fig [ beat_phase ] where at @xmath60.00 the polarisation is modulated with a positive hump , but at @xmath60.07 and 0.17 it is modulated with a negative hump . we consider two accretion scenarios which are described in fig [ scenario ] . the phasing of the data on the spin , orbital and beat phases requires that the accretion flow must be directed onto the same magnetic field line at all spin - orbit beat phases implying that at some phases the flow must follow a path around the white dwarf before accreting . this is difficult to reconcile with simple views of how the accretion stream attaches onto the magnetic field of the white dwarf . possible reasons for this are described in a more detailed paper that has been submitted to _ Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the standard - model extension ( sme ) provides a general field - theoretic framework for studying lorentz violation@xcite , including rotation - invariance violation . to highlight the basic ideas of lorentz - symmetry breaking , we consider rotation - invariance violation in newton s second law:@xcite @xmath0 here @xmath1 is a symmetric direction - dependent inertial mass ( we consider conventional gravitational mass ) . this yields a valid and more general form that newton himself could have chosen . our effective inertial mass can be generated as a low - energy limit of the sme:@xcite @xmath2 here @xmath3 is a coefficient for lorentz violation found in the fermion sector , taken as symmetric . it is depicted with background diamonds in fig . 1 . a similar construction can also be found associated with other sme coefficients for lorentz violation . @xcite using a block on an inclined plane , we show that observer rotation invariance holds , while a particle rotation changes the experiment s outcome , violating lorentz symmetry . examine a block on an inclined plane devoid of friction . the @xmath4-axis points down the plane while the @xmath5-axis is perpendicular to the surface as shown in the left - hand diagram of fig . 1 . let the block s effective inertial mass be diagonal : @xmath6 solving for the particle s acceleration under the constraint @xmath7 yields @xmath8 where @xmath9 is the acceleration down the ramp . the only difference here from the conventional problem is the presence of @xmath10 . qualitatively , the motion is down the plane with constant acceleration , as in the absence of lorentz violation . perform an observer rotation on the original experiment ; that is , consider the same problem in new coordinates as shown in the left - hand diagram of fig . 1 . here , @xmath11 is the mass in the new coordinates obtained via @xmath12 , @xmath13 being a rotation matrix . components are related by , for example , @xmath14 again solving , we find up to @xmath15 the components @xmath16 however , the acceleration is again along the ramp with the magnitude found in eq . ( [ eq1 ] ) , which is obtained from @xmath17 and @xmath18 by @xmath19 and a substitution for @xmath20 in terms of @xmath3 . hence , both observers agree on the outcome of the experiment . -40pt a particle rotation of the original system leaves the mass matrix as in eq . , but alters the direction of the gravitational field relative to the background as shown in the right - hand diagram of fig . 1 . this produces an observably different acceleration . solving for the motion of the particle subject to the constraint yields @xmath21 here the component along the ramp is @xmath22 which is different from the first cases , revealing observable lorentz violation . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the tunka eas cerenkov array is located in tunka valley , at an altitude of 675 m a.s.l . , and was described in [ 1 ] . the new fitting function ( ldf ) for the eas cerenkov light lateral distribution , derived from corsika code simulation [ 2 ] , has been applied to tunka data . the primary energy @xmath0[@xmath1 has been obtained from the measured cherenkov light flux at a distance 175 m from the shower core @xmath2[@xmath3 with corsika sumulated relation : @xmath4 the absolute energy calibration is based on the results obtained with the quest experiment [ 3 ] . a monte carlo simulation of the experiment has shown that the energy resolution is better than 18% . the spectrum is derived from data taken in 300 hours , spread over 51 clear moonless nights , with a trigger rate of about 1.8 hz . to construct a spectrum with energy threshold @xmath5 ev , showers with zenith angles @xmath6 and a core position inside the geometrical area of the array have been selected . for the range from @xmath7 to @xmath5 ev , events with zenith angles @xmath8 falling inside a 5 times smaller area around the array center have been selected . lateral and time distributions of eas cherenkov light provide two independent methods to estimate the maximum depth . the simulation shows , that the ldf steepness @xmath9 is related to the linear distance ( in [ km ] ) from the array to the eas maximum position : @xmath10 . the cherenkov light pulse fwhm [ ns ] at distances larger than 200 m from the eas axis is related to the relative position of the eas maximum by @xmath11 [ g/@xmath12 , where @xmath13 is the total depth of the atmosphere and @xmath14 is the zenith angle of the shower . this relation depends only on the distance to the eas axis . for example , for distance of 250 m : @xmath15 . this method gives a better theoretical accuracy , than the first one . moreover , the @xmath16 estimate does not depend on assumptions about the primary nucleus . figure 2 presents the mean depth of the eas maximum , derived with the two methods described above , as a function of primary energy . it is seen that the threshold of the fwhm method is higher than that of the ldf steepness method , but the mean depths , obtained with the two different methods are in good agreement . the mean values of @xmath16 from fig.2 can be easily transformed to the mean logarithmic mass @xmath17 of primary particles . figure 3 represents the result . a slight correction , derived from mc simulations of the experiment ( assuming a 4-group mass composition , p : he : cno : fe = 0.3:0.3:0.2:0.2 ) has been applied . according to these data the mass composition has almost no energy dependence in the range from @xmath5 to @xmath18 ev and is compatible with the hypothetical composition with @xmath19 mentioned above . at energies above @xmath18 ev , however , a steep increase of the average mass is observed . a similar increase in average mass is observed in almost all experiments . points of the present work coincide with kascade data [ 4 ] at the energy of the knee . authors are thankful to professor gianni navarra and eas - top collaboration for the opportunity to carry out the calibration experiment quest at the eas - top array . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the jet studies are known to be a good tool to test perturbative qcd effects . it was pointed out already some time ago that dijet production in dis could be a method to study the onset of bfkl dynamics both in photo- @xcite and electroproduction @xcite . unfortunately in practice , due to unavoidable cuts on transverse momenta of jets , one samples rather large values of the gluon longitudinal momentum fraction @xmath0 , where it is not completely clear what is the underlying dynamics and in particular what unintegrated gluon distribution should be used . this presentation is based on ref . @xcite where we have discussed the jet production beyond the familiar collinear approximation and have focused on how more exclusive and more differential jet production observables probe the unintegrated gluon distribution . based on the unintegrated gluon distributions found recently @xcite from the phenomenological analysis of @xmath1 we have explored dijet azimuthal correlations . at the parton level the total cross section for quark - antiquark dijet production @xmath2 can be written in a compact way as : @xmath3 where @xmath4 and @xmath5 are standard kinematical variables . in the formula above @xmath6 is the unintegrated gluon distribution and @xmath7 is the transverse momentum of the exchanged gluon . it is related to the quark / antiquark jet transverse momenta @xmath8 and @xmath9 as : @xmath10 we have written explicitly lower cuts on the transverse momenta of jets in ( [ total_dijets ] ) . the indices @xmath11 and @xmath12 refer to transverse and longitudinal photons , respectively . the auxilliary quantities @xmath13 introduced in ( [ total_dijets ] ) are given explicitly in @xcite . @xmath14 is evaluated at @xmath15 where @xmath16 is flavour dependent . it is obvious then that at large transverse momenta of jets one samples larger values of @xmath0 than in the case of total cross section . the gluon momentum @xmath17 is responsible for the jets being not exactly back - to - back in contrast to the conventional collinear approximation to leading order . in the following we limit ourselves to the region of @xmath18 1 , where the jets are dominantly produced from the quark box on the very top of the gluonic ladder . the following simple two - component ansatz was adopted in @xcite @xmath19 for unintegrated gluon distribution . the parameters @xmath20 and @xmath21 determine the scale of the transition from the hard to soft gluon region @xcite . the details concerning both components can be found in @xcite . the hard perturbative component is calculated from known conventional dglap parametrizations as derivative @xcite . the results presented in this note and in @xcite were obtained based on a recent mrst98 lo parametrization @xcite . the two - component structure ( [ decomposition ] ) of the unintegrated gluon distribution leads to interesting consequences for the dijet azimuthal correlations . here for illustration only two examples will be discussed . a more complete analysis can be found in @xcite . the cross section for the dijet production strongly depends on cuts imposed on kinematical variables . in order to better demonstrate the effect of coexistence of perturbative and nonperturbative effects we have imposed cuts on kinematical variables in the so - called hadronic center of mass ( hcm ) sytem . in the present purposefully simplified analysis we impose the cuts on the parton level and avoid extra cuts in the laboratory frame . in fig.[fig_x_dep ] , we present @xmath22 as a function of hcm azimuthal angle between jets for two different values of photon virtuality @xmath5 = 4 gev@xmath23 ( left panel ) and @xmath5 = 16 gev@xmath23 ( right panel ) for a series of bjorken @xmath4 . in this calculation , we have restricted the transverse momenta of jets to @xmath24 4 gev and summed over light flavours @xmath25 , @xmath26 and @xmath27 . one can observe a strong dependence of the azimuthal angle decorrelation pattern on bjorken @xmath4 . a closer inspection of both panels simultaneously leads to the conclusion that averaging over a broad range of @xmath5 would to a large extent destroy the effect as it involves automatically averaging over a certain range of @xmath0 , the most crucial variable for the effect to be observed . the experimental identification of the effects discussed here requires good statistics in the data sample . in practice @xcite , one averages over broader range of bjorken @xmath4 , photon virtuality and jet transverse momenta . most of the effects are then washed out and the information about the small-@xmath4 dynamics is to a large extent lost . in the model in ref.@xcite the total ( real ) photoproduction cross section at energies @xmath28 100 gev is dominated by the soft component . only at very high , not yet available , energies the hard component would dominate . at `` intermediate '' energy available at hera , the two components coexist and their fraction is a smooth function of initial @xmath29 energy . in principle , the same stays true for the dijet production and has interesting consequences for the jet azimuthal correlations @xcite . there is another interesting prediction of the two - component model . let us concentrate on the cases ( events ) with one hard ( @xmath30 ) jet and one soft ( @xmath31 ) `` jet '' . in this single jet event @xmath32 1 , because the transverse momentum of the single quark(antiquark ) jet is compensated by a transverse momentum of a much softer gluon . we shall call such cases `` one jet '' events for simplicity . let us compare the rate of such `` one jet '' events to the previously discussed cases of two hard jets in photoproduction . as an example in fig.[fig_1vs2 ] we compare the cross section for the two cases with the lower cut on transverse momentum @xmath33 = 4 gev . firstly , we observe that the cross section for both cases are of similar order . furthermore we observe a significantly stronger rise of the cross section for the `` one jet '' case than for the `` two jet '' case . this is related to different @xmath0 and @xmath17 sampled in both cases . for example for w = 100 gev and @xmath33 = 4 gev in the `` one jet '' case @xmath34 0.01 is substantially lower than in the `` two jet '' case @xmath34 0.02 . both numbers are , however , substantially larger than average @xmath34 0.005 sampled in the case of total cross section . the effect of @xmath17 is more complicated as averaged @xmath17 strongly depends on @xmath35 for the `` two jet '' case . the interplay of the two effects ( @xmath0 and @xmath17 ) causes @xmath14 to be sampled differently in the `` one jet '' and `` two jet '' cases . this , potentially allows the possibility of a further nontrivial test of @xmath14 . it would be valuable to compare the present predictions with the predictions of standard ( collinear ) nlo approach . based on the recent model determination @xcite of the unintegrated gluon distribution in the proton we have explored the impact of the soft gluon component and the onset of the perturbative regime on the dijet azimuthal correlations . we have predicted a strong dependence of the azimuthal correlation pattern on bjorken @xmath4 , photon virtuality and the cut on the jet transverse momenta . the effects in the electroproduction could be verified now at hera , provided a careful differential ( @xmath4 , @xmath5 , transverse momentum cut ) studies of the dijets are made . it would be important to compare the results of the model discussed here with the result of the standard collinear approach to understand the potential of such a dijet study to shed more light on the low-@xmath4 dynamics which has been studied up to now in rather inclusive processes . finally , we have found that the study of the energy dependence of the `` one jet '' ( defined in the text ) cross section would be a new test of unintegrated gluon distributions . i am indebted to coauthors of ref.@xcite for collaboration on the subject of this presentation . this work was partially supported by the german - polish dlr exchange program , grant number pol-028 - 98 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: shortly after the burst of nova persei 1901 , a light echo was observed to emerge with superluminal expansion . it was later properly explained ( couderc 1939 ) to be the nova light scattered by dust nearby which reached us later than the unscattered photons due to light travel effects . the possibility of observing such an effect with supernovae was later discussed by many authors ( e.g. zwicky 1940 , schaefer 1987 ) . more than its splendid appearance , a light echo also sheds light on the circumstellar and interstellar environments through which it passes and the most famous example is from sn 1987a in large magelanic cloud . observations of re - emission from the rings around sn 1987a provide us the information on the geometry , distribution and composition of its circumstellar medium ( e.g. , lundqvist et al 1991 ) , help us to infer the stellar wind history of its pregenitor , and even enable us to determine an accurate distance to sn 1987a ( panagia et al . also , the monitoring of its scattered light echoes enables a three dimenional mapping of the structure of the interstellar medium in front of sn 1987a ( xu et al . 1995 ) , which reveals aspects of dense clouds and superbubbles that are difficult to reveal by other means . this phenomenon has also been found in distant galaxies . for example , sn 1991 t , a luminous type ia supernova in ngc 4527 , exhibited a nearly flat light curve more than 950 days after maximum light , and spectral features that , although were present in earlier spectra , were substantially narrower and blueshifted on a significantly bluer continuum ( schmidt et al . schmidt et al . attributed these features to a light echo , which was later confirmed by hst foc observations ( sparks et al . similar photometric and spectroscopic behaviors in the late - time observations of sn 1998bu have led to suspicion of a light echo ( cappellaro et al . 2001 ) , but it has yet to be confirmed by direct high - resoulution imaging . due to limited spatial resolution , direct imaging observations of supernova light echoes are possible only in our local supercluster , which makes these phenomena rare events . thus far , only nova persei 1901 , sn1987a , sn1991 t and sn1998bu are reported to have associated light echoes in the literature . here we report on a light echo around sn1993j , the fourth such event . the supernova sn1993j exploded on march 28 , 1993 in the spiral galaxy m81 , and due to its proximity ( 3.6 mpc ) , it has been observed and at wavebands from radio to @xmath0-ray regions . it began as a type ii supernova , but changed later to type ib at the nebular stage , and was classified as type iib . a series of observations with the very large baseline interferometer revealed an expanding radio shell that was decelerating ( bartel et al . 1999 ) , reflecting the interaction between the shock front and the circumstellar medium . intensive photometric and spectroscopic observations also showed an infrared excess after day 50 , which may be indictive of an infrared echo ( lewis et al . 1994 ) . in this paper we report an optical scattered light echo around sn 1993j that was dicovered in an hst wfpc2 observation . in @xmath12 , we discuss our observations showing the light echo , and another archive hst wfpc2 observation with a nondetection of such a light echo . models for this light echo are discussed in @xmath13 , which give the geometry and dust properties . for the distance to sn 1993j , we use the distance to m81 , i.e. , 3.63 mpc ( @xmath2 , freedman et al . 1994 ) . as part of an observation of a different target , the wfpc2 was oriented so that sn1993j fell on a wide field chip ( wf4 ) during our 2000 second hst observations in the b , v , and i bands ( f450w , f555w , and f814w ) . the observation was obtained on june 4 , 2001 , 8.2 years after its explosion ; the data were analyzed following standard procedures . a light echo is clearly visible around sn1993j , as shown in fig . 1 . this ring , which is most obvious in the f555w image , has a radius of about 1.9 ( 19 pixels ) and about 0.2 in width . this ring is a partial arc with the brightest part about 4.3 in length . for comparison , another wfpc2 observation on jan . 31 , 1995 ( i.e. , 1.8 years after sn1993j ) with supernova centered on the planetary camera was also extracted from the mast archive . there was no evidence of similar light echoes or partial arcs in the 1995 . the mean surface brightness of the arc was computed from those arc pixels that are brightest in the f555w image , excluded were those pixels that show a faint source in the f814w image . the background mean and sigma were computed from a square box centered on the arc , but excluding the arc and point sources . the net count rates ( in @xmath3 ) were then converted to surface brightness ( in @xmath4 ) using zeropoints appropriate for standard bvi photometry . the measured surface brightness and lower / upper limits in units of @xmath4 for @xmath5 errors in count rates are listed in table 1 . for the 1995 observation , the @xmath6 detection threshold in the f555w image , defined by the standard deviation of the mean of a region which includes the positions of the observed 1.9 arc and the postulated 0.9 arc ( see section 3 ) , is @xmath7 , about 15 times fainter than the observed light arc . .surface brightness of the light echo [ cols="^,^,^,^",options="header " , ] we have presented the wfpc2 observation of a light echo around sn 1993j after 8.2 years of supernova explosion . this light echo is due to light scattered from a dust cloud about @xmath8 in front of sn 1993j , about @xmath9 thick and @xmath10 wide , revealing the existence of a sheet of dust ( and gas ) in another galaxy . the dust inferred from the light echo surface brightness is 1000 times denser than the intercloud dust . the graphite to silicate fraction can not be determined by our bvi photometric measurements , however , a pure graphite model can be excluded based on comparison with the data . aside from studying the geometric structure of the interstellar medium in other galaxies , a light echo can be used to determine the distance to the host galaxy . to accomplish this , one needs to measure the expansion rate of the light echo . with future observations , we should be able to determine this expansion rate and obtain a measurement of the distance independent of that obtained by using cepheid variables . allen , c.w.,1976 , astrophysical quantities , 3rd edition , p.265 bartel , n. , bietenholz , m. f. et al . , 2000 , science , 287,112 bohlin , r. , avage , b. d. & drake , j. f. 1978 , , 224 , 132 bromage , g.e . & nandy , k. 1983 , mnras , 204 , 29 cappellaro , e. et al . , 2001 , , 549,l215 couderc , p. 1939 , ann . dap.,2,271 lewis , j. et al . 1994 , mnras , 266,27 lundqvist , p. & fransson , c. 1991 , , 380 , 575 mathis , j. , rumpl , w. & nordsieck , k. 1977 , , 217,425 panagia , n et al . 1991 , , 380 , l23 richmond , m. et al . 1994 , , 107,1022 schaefer , b. , 1987 , , 323,l47 schmidt , b. et al . 1994 , , 434 , l19 sparks , w. et al . 1999 , , 523,585 xu , j. , crotts , a. & kunkel , w. 1995 , , 451 , 806 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: what powers the nuclei of nearby galaxies ? many of them show evidence for emission - lines similar to those seen in active galactic nuclei ( agn ) but on a much lower level ( ho et al . 1997a ) therefore they are called low - luminosity agn ( llagn ) . in some cases broad lines are seen and hence one infers the presence of a central black hole ( ho et al . 1997b ) . in most cases , however , even a moderate starburst might be able to explain the observed optical spectra ( alonso - herrero et al . 1999 ) , especially those residing in liner galaxies ( heckman et al . 1983 ) . another method to identify the nature of the activity is to search for compact , flat - spectrum radio cores with high brightness temperatures , since this is a typical feature of many agn and can not be explained by star formation . for llagn the nature of these radio cores is largely unclear . it has been proposed that the compact radio emission could be produced either by emission from an advection dominated accretion flow ( adaf ; e.g. narayan et al . 1998 ) or from scaled - down agn jets ( falcke & biermann 1996 ; 1999 ) . we have therefore performed a vla survey of two samples of nearby galaxies with optical emission - lines to identify such compact radio cores . follow - up observations with the vlba of these cores have been made that shed further light on their nature . the first sample we observed consisted of 48 galaxies with mainly liner - like emission spectra that were part of ongoing studies at other wavelengths . in a second project we expanded this sample to a distance - limited sample of galaxies with emission - lines within 19 mpc . both samples were observed with the vla in its largest configuration at 15 ghz . in the final data reduction we reached a 10 @xmath2 detection limit of @xmath3 mjy . the resolution was about 0.15@xmath4 which corresponds to a linear scale of 14 pc for a galaxy at a distance of 19 mpc . all sources which were detected with compact emission above 3 mjy in either sample were then observed with the vlba at 5 ghz with a resolution of 2.5 mas ( @xmath5 pc at 19 mpc distance ) and a detection limit around 2 mjy . we are going to restrict the following discussion to the detection of compact core emission . the detection rate in our first llagn sample was 35% ( 17 of 48 ) , higher than similar deep surveys of normal galaxies ( wrobel & heeschen 1991 ) . only two sources had steep spectra and only one out of eighteen sources with optical classification as transition sources ( ho et al . 1997a ) was detected . the other detections are all in llagn with either seyfert or liner spectra . this is confirmed by the results of our distance - limited survey : 44% of llagn with seyfert or liner spectra have compact cores , but only 12% of transition objects do . these results suggest that galaxies with seyfert and liner spectra are black hole powered , while transition objects are dominated by star formation . the evidence for black hole powered engines is further strengthened by our vlba results . even though our detection limit was close to our selection threshold , 19 out of 20 galaxies showed compact radio emission with brightness temperatures of the order @xmath6 k. the one non - detected source had a steep - spectrum and hence is the exception which confirms the rule that also in llagn flat - spectrum radio cores are a sign of high-@xmath7 agns . we find that the six brightest sources in our vlbi sample all show typical core - jet structures . the fainter cores probably have too low dynamic range and signal - to - noise to show any significant extended structure . figure [ ha ] ( left panel ) shows the distribution of spectral indices between our total 6 cm ( vlba ) and 15 ghz ( vla ) flux densities ( @xmath8 ) . even though comparing vlba with vla fluxes and our selection at 15 ghz is biased towards highly inverted spectra , none of the spectral indices has @xmath9 , in conflict with the prediction of the adaf model ( e.g. yi & boughn 1998 ) but quite consistent with the predictions of jet models ( falcke & biermann 1999 ) . the average is @xmath10 . for the vlbi - sample , i.e. the well - detected cores above 3 mjy , for which we have basically established that the radio emission is agn - related , we also looked at correlations between radio , emission - line , and bulge luminosities . figure [ ha ] ( right panel ) shows that there is a trend for galaxies with higher h@xmath11 emission to have more luminous radio cores . interestingly , elliptical and spiral host galaxies are offset from each other . does this reflect a radio - loud / radio - quiet dichotomy for llagn ? however , there is another important factor : the galaxy bulge luminosity . we do see a weak trend for the radio luminosity to be related to bulge luminosity ; also the ratio between radio and h@xmath11 luminosity tends to increase with increasing bulge luminosity . hence , galaxies apparently become more efficient in producing radio emission relative to h@xmath11 in bigger bulges . this also holds if we look at the enitre vla detected sample ( fig . whether this is due to increasing obscuration , effects intrinsic to the agn , or a selection effect is unclear . since ellipticals and spirals in our sample are nicely separated between the top and bottom end of the bulge luminosity distribution , an apparent dichotomy in fig . [ ha ] is a natural consequence of this trend . we find that at least 40% of optically selected llagn with seyfert and liner spectra have compact radio cores . vlbi observations show that these cores are similar to radio jets in more luminous agn with high brightness temperatures , jet - like structures , and flat radio spectra ( e.g. falcke & biermann 1996 ; 1999 ) . the radio emission seems to be related to the luminosity of the emission - line gas and hence both are probably powered by genuine agn operating at low powers . we found no evidence for high frequency components with highly inverted spectra predicted in adaf models . hence , for these models one should probably not include radio fluxes in broad - band spectral fits . we also find only a weak correlation between radio and bulge luminosity . together with the radio - h@xmath11 correlation this makes it very unlikely that the black hole mass could be reliably determined from the radio data in contrast to what is occasionally suggested . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: correlations between spatially separated cosmic ray events would indicate that the particles have some common history . extensive air showers are well - known to produce correlated signals on the earth s surface over distances of several kilometers . however , it is possible that isolated primary cosmic ray events separated by @xmath2 km could arrive in time coincidence . such correlated cosmic ray events could result , for example , from the photodisintegration of heavy nuclei ( _ i.e. _ , iron ) by solar photons @xcite . in a previous study @xcite , there was some episodic evidence for time correlations up to @xmath3 s in events separated by @xmath4 km . more recently , laas @xcite searched for correlated events at large distances @xmath5 km and found a few candidate events . however , these events were consistent with interpretation as accidental coincidences between uncorrelated events . we have studied data obtained with the chicos array during january 2003 through june 2005 and searched for evidence of correlated air shower events separated by @xmath6 km with energy threshold @xmath7 ev . the california high school cosmic ray observatory ( chicos ) observes cosmic ray induced air showers with an array of detector sites located on school roofs in the los angeles area ( lat . @xmath8 , long . @xmath9 , average 250 m above sea level ) . the sites are separated by distances of typically @xmath10 kilometers , with the overall array covering an area of @xmath11 km@xmath12 . during this study , the number of operational sites increased from 31 to 66 . each detector site contains two plastic scintillator detectors , separated by @xmath13 meters . the detector typically has @xmath14 m@xmath1 area and @xmath15 cm thickness . data are stored on local hard disk and automatically transferred to caltech via internet every night by the computer located at each site . `` trigger '' events are defined as those where both detectors at a site record signals greater than 2 single vertical particles within a 100 ns time window . most trigger events are isolated single events ( _ i.e. _ , no nearby sites are hit ) which are generated by low energy showers with a threshold of about @xmath7 ev . the rate of these triggers ( about 1000 per day per site ) is comparable to expectations based on the previously measured flux @xcite and computer simulations of air showers with the aires code @xcite . large showers that generate a trigger at one site with coincident single hits at several neighboring sites must have extremely high energies of @xmath16 ev . we do observe such large air shower events with the chicos array , presently at a rate of about one per month . however , even the largest air showers with primary energy @xmath17 ev would not generate 2 triggers in sites separated by more than 1 km . in this work we search for double trigger events where two sites , separated by more than 1 km , both record trigger events within a certain coincidence time . such a signal could indicate the existence of isolated correlated cosmic ray events separated in distance by up to 60 km ( the largest distance between two chicos sites ) . the data sample for this analysis is the time - stamped sequence of trigger data from the operational sites , which forms a complete record of all the events detected by the array with sufficient energy to trigger a single site . in order to examine these data for time correlations , a randomized data set was constructed directly from the real data , as in @xcite , by offsetting the sequence of triggers at each site by some integer number of seconds relative to the other sites . since a shift of several seconds is small compared to the time for drift in the average trigger rate , the randomized data should reproduce all aspects of the real data associated with accidental coincidences . deviations of correlations observed in the real data relative to the randomized data could be indications of significant correlations ( _ i.e. _ , not accidental ) in the data . given a coincidence time interval @xmath18 , we define @xmath19 as the number of excess event pairs ( relative to the randomized data sample ) with that time difference , which may be positive or negative . if both members of a successive pair are from the same site , that pair is not counted ( to eliminate instrumental effects such as pmt afterpulsing ) . in order to search for correlations on any time scale less than 1 second , we compute the probability of an excess coincidence per site for the cumulative time interval @xmath20 according to @xmath21 in which @xmath22 is the average number of operational sites and @xmath23 is the total number of trigger pairs . we compute a 90% confidence interval for @xmath24 using the method in @xcite , and interpret the upper limit as the 90% confidence level upper limit for the excess probability per site for the interval @xmath25 . the results , for 17 months of data from january 2003 through july 2004 are shown in fig . [ fccis ] @xcite . as discussed in @xcite , the data in fig . [ fccis ] indicate an excess of events at time scales of order @xmath26 s , or @xmath27s . the excess heals itself at larger @xmath28 as we add more data that show ( apparently ) no correlations . to study this possible signal further , we have repeated this analysis with an independent data set from august 2004 through may 2005 . in fig . [ timediffs ] we show the results of the analysis of the new data . it is clear from the new data that there is no evidence of the apparent excess displayed in fig . [ fccis ] . therefore , the excess in the earlier dataset is interpreted as a statistical fluctuation . a search for time correlations in cosmic ray data collected by the chicos project has been performed . the results are consistent with a lack of any real correlation between isolated events . earlier observations that indicated an excess of events at shorter times are interpreted as a statistical fluctuation . the excess coincidence probabilities displayed in fig . [ fccis ] can be properly interpreted as 90% cl upper limits for the incidence of correlated pairs of cosmic rays above @xmath7 ev separated by distances between 1 and 60 km . we are grateful for the generous support of caltech and the weingart foundation in initiating the chicos project . the donation of the detectors by the cygnus collaboration is gratefully acknowledged . support from the nsf ( grants phy-0244899 and phy-0102502 ) and the donation of computers for the project by ibm corporation are also acknowledged . the volunteer efforts of many high school and middle school teachers have been essential in the deployment and operation of the chicos array , and we are delighted to acknowledge their participation . o. carrel and m. martin , physics letters * b325 * , ( 1994 ) 526 . n. ochi , _ et al . _ , j. phys . g. : nucl . * 29 * ( 2003 ) 1169 . m. nagano and a. watson , rev . phys . * 72 * , ( 2000 ) 698 . aires webpage : + g. feldman and r. cousins , phys * d57 * , ( 1998 ) 3873 . b. e. carlson , _ et al . _ , journ . phys . g : nucl . part 31 * , 409 ( 2005 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: for the vacuum state of qcd and the properties of low - temperature qcd the existence of non - trivial topological excitations is important . well known are instantons @xcite as classical solutions in euclidean space . the role of topology for the solution of the famous @xmath0 problem has been recognized very early @xcite . it is known by now from lattice qcd that the ( fractal ) dimensionality of the topological structures in the vacuum depends very strongly on the resolution scale @xcite . in particular , infrared instantons structures are believed to explain chiral symmetry breaking @xcite . the gluon fields contributing to the path integral at finite temperature correspondingly may contain calorons @xcite . because of non - trivial holonomy they consist of dyons and therefore , have a richer structure than instantons . their changes they experience at the qcd phase transition are presently under study @xcite . some time ago the gluonic topological structure and the famous axial anomaly have been proposed to be immediately observable ( and controllable ) through the generation of @xmath1 and @xmath2 violating domains in heavy ion collisions @xcite . it has been demonstrated by detailed numerical calculations @xcite that macroscopic domains of ( anti)parallel color - electric and color - magnetic field can emerge in a heavy ion collision creating an increasing chiral imbalance among the quarks which are deconfined due to the high temperature . in this situation , the magnetic field created by the spectator nucleons may initiate a charge separation relative to the reaction plane ( parallel to the electro - magnetic field ) @xcite . the resulting charge asymmetry of quarks would become observable in terms of recombined hadrons ( chiral - magnetic effect ) @xcite . the strength ( and particularly the dependence on the collision energy ) of this effect has been theoretically studied and proposed to be a measure for the transient existence of liberated quarks @xcite . in recent years the dependence of the chiral and deconfinement transitions on the magnetic field has been investigated both in models and ab - initio lattice simulations , see e.g. @xcite . it remains an open question whether the phase transition from quarks to hadrons , i.e. the onset of confinement and chiral symmetry breaking ( and vice versa ) , depends on the chiral imbalance . in this article we study the change of the phase structure by an equilibrium lattice simulation . we mimic the topological content ( of a topologically nontrivial gluonic background in heavy ion collisions ) by a standard of chiral imbalance , which is provided by a chiral chemical condensate . in this form , the modification of the phase diagram by the chiral chemical potential @xmath3 has been studied mainly in effective models @xcite with which we will compare our results . on the lattice , contrary to the ordinary chemical potential ( for quarks , i.e. baryonic charge ) , simulations with non - zero @xmath3 are not hampered by a sign problem . they are accessible to standard hybrid monte carlo algorithms . such lattice simulations with @xmath4 were already performed in ref . the main goal of these papers , however , was the chiral magnetic effect . therefore , the phase diagram was not systematically studied . in our study we perform simulations with the @xmath5 gauge group . one reason is that less computational resources are required for this pilot study than for full qcd . the second one is that we have already carried out two - colour qcd computations with an external magnetic field @xcite . we have performed simulations with the @xmath5 gauge group . we employ the standard wilson plaquette action @xmath6 for the fermionic part of the action we use staggered fermions @xmath7 where the @xmath8 are the standard staggered phase factors : @xmath9 for @xmath10 . furthermore , @xmath11 denotes the lattice spacing , @xmath12 the bare fermion mass , and @xmath3 the value of the chiral chemical potential . in the chirality breaking term @xmath13 , @xmath14 represents a shift to a diagonally located site of a spatial elementary cube . the combination @xmath15 is connecting sites @xmath16 and @xmath17 symmetrized over the @xmath18 shortest paths between these sites . in the continuum limit ( [ eq : staggeredaction ] ) can be rewritten in the dirac spinor - flavor basis @xcite as follows @xmath19 it should be noted here that the usual baryonic chemical potential @xcite and also the chiral chemical potential @xcite are introduced to the action as a modification of the temporal links by corresponding exponential factors in order to eliminate chemical potential dependent quadratic divergencies . for staggered fermions this modification can be performed as well for the baryonic chemical potential . however , for the chiral chemical potential such a modification leads to a highly non - local action @xcite . therefore , we decided to introduce @xmath3 in eq . ( [ eq : staggeredaction ] ) in an additive way similar to the mass term leaving aside the question of arising singularities for the time being . we expect that the polyakov loop will not contain @xmath3 dependent singular terms . we have performed simulations with two lattice sizes @xmath20 . the measured observables are * the polyakov loop @xmath21 * the chiral condensate @xmath22 * the polyakov loop susceptibility @xmath23 * the disconnected part of the chiral susceptibility @xmath24 the polyakov loop and the corresponding susceptibility are sensitive to the confinement / deconfinement phase transition , while the chiral condensate in principle responds to chiral symmetry breaking / restoration . the simulations have been carried out with a cuda code to run the hybrid monte carlo algorithm on gpu s . the dependence of the lattice spacing on the coupling parameter @xmath25 was taken from @xcite . for our simulations with the lattice size @xmath26 the fermion mass was kept fixed in lattice units at @xmath27 while changing @xmath25 . e.g. for @xmath28 this corresponds to a pion mass value @xmath29 . for the larger lattice size @xmath30 and for various @xmath25 values we have chosen the same bare quark mass in physical units @xmath31 , which corresponds to @xmath32 . [ cols="^,^ " , ] to confirm our results we carried out simulations also for the larger lattice size @xmath30 . in fig . [ fig : largeobs ] we present results for varying @xmath3 and fixed values of @xmath33 and @xmath34 , which for a vanishing chiral chemical potential correspond to temperatures below the transition , to the transition region , and to the high temperature phase , respectively . as can be seen from this figure , in the confinement phase the polyakov loop remains almost constant with increasing chiral chemical potential . it means , that if the system was in the confinement phase at @xmath35 , it remains confined at @xmath36 . moreover , we observe the polyakov loop to drop down both in the deconfinement phase and in the transition region . thus , the system goes into the confinement phase for sufficiently large @xmath3 . with other words , we conclude that the critical temperature increases with an increasing chiral chemical potential in agreement with our results obtained on the smaller lattice . notice that in case of the larger lattice we have kept fixed the bare fermion mass in physical units at @xmath31 for all three @xmath25 values , while changing @xmath3 . it is worth mentioning that the behavior described above looks quite similar as that obtained for two - color qcd in an external magnetic field @xcite . our results are in contradiction to those of the models studied in @xcite , where the critical temperature of the transition was observed to decrease . furthermore , in these papers at some critical value of the chiral chemical potential the transition was reported to become first order . in our simulations we do not see such a behavior . however , the results obtained have a tendency towards a sharper phase transition at nonzero chiral chemical potential . although the analytic results are only derived in models and not in full qcd also in our approach there are some differences to qcd . we use the @xmath5 gauge group instead of @xmath37 and four flavor degrees of freedom . moreover , the pion mass value used here is higher than the physical one . the situation can change , when one arrives at smaller quark masses . we want to address this question in a future work . the authors are grateful to v. i. zakharov and v. g. bornyakov for interesting and stimulating discussions . the simulations were performed at gpus of supercomputer k100 and computers of the berlin group . the work was supported by fefu grants no . 12 - 02 - 13000-fefu_a and 13 - 09 - 617-m_a , rfbr grants 14 - 02 - 01185-a , 13 - 02 - 01387-a , grant of the president of the rf md-3215.2014.2 and grant of the fair - russia research center . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: very low mass eclipsing binary millisecond pulsars occupy a unique niche in pulsar parameter space , between accreting x - ray binaries and isolated neutron stars . in these systems , mass loss in the secondary is driven either by roche lobe overflow or by winds induced by heating of the secondary by pulsar irradiation . the resulting mass flow eclipses the pulsar signal at inferior conjunction . at this conference , the results of two observational studies related to eclipsing binary pulsars were given . first , multifrequency observations of orbital and pulse - phase variability of eclipsing binary pulsars b1744@xmath024a and b1957 + 20 were presented . this work will be published elsewhere . second , a search for eclipses in very low mass pulsar binaries not previously seen to eclipse was described . this paper summarizes the findings of the latter experiment . there are more than a dozen known very low mass eclipsing binary pulsar systems . there are also several pulsar binaries with similar orbital characteristics but in which no eclipses have been detected ( see table 1 of paulo freire s contribution to these proceedings ) . the mass functions of the non - eclipsing systems are moderately smaller than those of the eclipsing systems . the question arises : why do these systems not exhibit eclipses ? there are three possibilities : 1 . these systems are qualitatively different from eclipsing binaries . perhaps the pulsar irradiation is insufficient to drive mass loss in the secondaries . ( the spin - down luminosities of this project s target pulsars are not known . ) or perhaps the low mass functions indicate low secondary star masses which , for whatever reason , are less prone to mass loss . these systems are similar to eclipsing systems , with secondaries nearly filling their roche lobes , but mass flow is `` turned off '' at the present epoch . in this scenario , eclipsing systems can become non - eclipsing systems , and vice versa , perhaps on a time scale of years . orbital elements of eclipsing systems exhibit small perturbations on timescales of years , but it is hard to see how they would influence the mass flow . these systems are not different than eclipsing systems , but our viewing geometry is not favorable for detecting eclipses . their orbital inclinations are much less than 90@xmath1 , i.e. , they are not viewed `` edge on . '' this is consistent with the low mass functions of these binaries if there is a relatively narrow range of secondary masses among the low mass binaries . ( see the discussion by paulo freire in these proceedings ) . it is a common property of very low mass eclipsing systems that the eclipse characteristics depend on frequency . for example , the eclipse lengths , @xmath2 , of psrs b1744@xmath024a and b1957 + 20 scale inversely with frequency , @xmath3 , as @xmath4 , where @xmath5 and @xmath6 , respectively ( nice et al . 1990 ; fruchter et al . 1990 ) . since eclipses observed at low frequencies are extended along the orbital plane , it is reasonable to suppose that they are extended off the orbital plane as well , so that , for lines of sight far from the plane ( i.e. , at low inclination ) eclipses might be detectable only at low frequencies . observations of eclipsing binary psr j2051@xmath00827 provide further evidence that eclipses are more dramatic , and hence easier to detect , at low radio frequencies . past observations of this pulsar found no change in flux density , and only small dispersion delays , at 1400mhz at inferior conjunction , while the system was completely eclipsed at 660 mhz ( stappers et al . 1996 ; but see below ) . we made low frequency observations of very low mass binary pulsars psr j1807@xmath02459 and psr b1908 + 00 . their orbital periods are 1.7 and 3.4 hours , respectively , and companion masses are around 0.01 and 0.02m@xmath7 under conventional assumptions . previous observations of these systems at 1400mhz did not show eclipses ( damico et al . 2001 , deich et al . 1993 , ransom et al . 2001 ) . observations of eclipsing binary pulsar psr j2051@xmath00827 were made at some of the same epochs as the other pulsars . while not originally a target of the eclipse - search project , these data are relevant to it ( see below ) . the pulsars were observed with the 100 m robert c. byrd green bank telescope ( gbt ) at numerous frequencies between 575mhz and 1660mhz . the superior gain , frequency agility , and tracking ability of this telescope make it ideal for low - frequency observations of compact binary pulsars . in a typical session , a pulsar would be continuously observed for several hours often a complete orbit or longer . data were collected by the spectral processor , a fourier transform spectrometer . spectra were folded on - line modulo the pulse period over intervals of 0.5 to 5.0 minutes . off - line , the folded spectral data were de - dispersed , and pulse times of arrival were extracted using conventional techniques . we found no evidence for eclipses of psr j1807@xmath02459 or psr b1980 + 00 . eclipses would have been detected either by absence or systematic reduction in flux around inferior conjunction or , in case of partial eclipses , by systematic delays of the pulsed signal as it passed through the ionized eclipsing medium . neither of these observational signatures was detected . the data are shown in figures 1 and 2 . residual pulse arrival times are shown after subtracting a model for the orbit . the ascending node is at orbital phase @xmath8 ; eclipses would be at @xmath9 . both pulsars are visible at @xmath9 , at frequencies as low as 575 mhz ( j1807@xmath02459 ) and 820 mhz ( b1908 + 00 ) . limits on the electron column density of ionized eclipsing material can be derived from limits on the pulse time of arrival delays , @xmath10 , at @xmath9 . for j1807@xmath02459 , we estimate that @xmath11s , at 800mhz at conjunction , so the maximum excess column density is @xmath12 . for b1908 + 00 , @xmath13s at 820mhz yields these are both smaller than , for example , the past eclipses of j2051@xmath00827 , for which @xmath15 ( stappers et al . 1996 , 2001 ) . but psrj2051@xmath00827 presents a puzzle . its eclipses are known to be variable , but it has always shown complete eclipses at low frequency at some point near conjunction ( stappers et al . observations of this pulsar with the gbt are shown in figures 3 and 4 . surprisingly , it is visible throughout the eclipse region , albeit attenuated as much as 80@xmath090% . further , the maximum time delay at conjunction is no more than @xmath16s at 585mhz , which gives a column density of @xmath17 , an order of magnitude less than earlier measurements . clearly the eclipses are much weaker than previously observed . neither of the target pulsars exhibited eclipses . the question of whether the lack of eclipses is intrinsic to the binaries or whether it is a geometric effect remains open . the surprisingly weak eclipses in binary j2051@xmath00827 , with at least an order of magnitude less ionized material around the secondary than seen in previous observations , adds to the mystery . while there is no evidence that these systems completely `` turn off '' ( as in scenario no . 2 above ) , it is clear that the eclipse depths can vary greatly . we thank scott ransom for discussing previous observations of some target pulsars . this work was supported by nsf grant 0206205 and by an nserc ufa and discovery grant . the gbt / nrao is a facility of the nsf , operated by associated universities , inc . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the energy exchange between neutrino beams and plasma collective modes can be a crucial mechanism e.g. for shocks in type ii supernovae @xcite . the associated neutrino charge coupling @xcite leads to kinetic effects such as neutrino landau damping @xcite , as well as to the generation of quasi - static magnetic fields @xcite the orthodox approach to the neutrino - plasma interaction problem is to assume specific medium properties , and then to solve the dynamical equations , either in approximate or numerical forms . in this respect , one can have sinusoidal variations of the electron density @xcite , @xcite , @xcite , @xcite , general time - dependent media @xcite , stochastic backgrounds @xcite , @xcite as well as instabilities due to electron density ripples @xcite . in an inverse way , in the present work a certain electron density profile is assumed , and then the corresponding medium properties are unveiled . the procedure is restricted to two - flavor neutrino populations . no further approximations are needed . the work is organized as follows . section ii describes the general method , leading to eq . ( [ e8 ] ) , the central result of the paper . section iii briefly discuss the cases of exponentially decaying or oscillating electron neutrino populations . section iv is reserved to final remarks . the equations for neutrino - flavor oscillations in a plasma are well known @xcite and we present them in the form @xmath0 where @xmath1 is the three - dimensional flavor polarization vector , such that the density matrix can be written as @xmath2 using the total neutrino number @xmath3 and the pauli matrices @xmath4 , with @xmath5 being the electron ( muon ) neutrino populations . in eq . ( [ e1 ] ) , @xmath6 where we have introduced the characteristic oscillation frequency @xmath7 , with @xmath8 being the square mass difference between mass eigenstates and @xmath9 the energy associated to the neutrino dirac spinor , while @xmath10 is the pertinent mixing angle . finally , we have @xmath11 being the coupling function between the neutrino and the embedding plasma medium , where @xmath12 is the fermi constant and @xmath13 the electron plasma density . in our analysis , it is important to keep in mind that @xmath14 . from the first and the last equations in eq . ( [ e1 ] ) we get @xmath15 substituting the results shown in eq . ( [ e4 ] ) into the mid equality in eq . ( [ e1 ] ) and integrating once yields @xmath16 where @xmath17 is a constant of motion , @xmath18 . the last equality in eq . ( [ e5 ] ) follows from @xmath19 and the normalization condition , @xmath20 . our central result comes from the fact that eq . ( [ e5 ] ) can be solved up to a sign choice for @xmath21 in terms of @xmath22 , or @xmath23 correspondingly , using eqs . ( [ e4 ] ) and ( [ e6 ] ) we find @xmath24 therefore , we have a very simple recipe to generate exact solutions for the two - flavor neutrino - plasma oscillation equations . instead of prescribing a given plasma density @xmath25 as usual , one can start choosing @xmath26 , which is interpreted as the normalized difference between neutrino flavor populations . afterward , eqs . ( [ e6 ] ) and the last in eq . ( [ e4 ] ) gives resp . the coherences @xmath27 and @xmath28 . finally , eq . ( [ e7 ] ) gives the corresponding @xmath29 , which is linked to the plasma medium properties . to have meaningful solutions at least some requirements should be taken into account , namely @xmath30 , otherwise one would eventually get negative flavor populations . in addition , @xmath22 should be a double - differentiable function of time . alternatively , we can use @xmath31 to express the results in terms of the electron neutrino population . from eqs . ( [ e4 ] ) , ( [ e6 ] ) and ( [ e7 ] ) we get @xmath32 where @xmath33 . the results in eq . ( [ e8 ] ) compactly represents the basic findings of this work . as a first example , consider the case of an exponentially decaying electron neutrino population , @xmath34 which models the change of the electron number density along the path of the solar neutrinos moving radially from the central region to the surface of the sun @xcite , @xcite . in this context @xmath35 is the scale height and @xmath36 is the distance traveled by the neutrinos . to have meaningful solutions from eq . ( [ e8 ] ) ( or , real @xmath37 ) one should have @xmath38 , as can be readily verified . we use stretched time and space variables so that @xmath39 . moreover , the mixing angle satisfy @xmath40 , so that @xmath41 . finally , we chose @xmath42 , which assures the produced solutions to be non - complex . the resulting polarization vector components are shown in fig . [ fig1 ] , while @xmath43 is shown in fig . [ fig2 ] , with the plus sign chosen in eq . ( [ e8 ] ) . it can be shown that in this case one has the asymptotic dependence @xmath44 when @xmath45 . evidently , an infinite class of profiles can be generated via the same procedure . one can e.g. consider the case of an oscillating electron neutrino population , discussed in the following . ) and ( [ e9 ] ) . parameters , @xmath39 , @xmath40 , @xmath42 . ] for an exponentially decaying electron neutrino population , according to eqs . ( [ e8 ] ) and ( [ e9 ] ) and the same parameters as in fig . [ fig1 ] . ] now consider an initially unpolarized electron neutrino beam , @xmath46 including an amplitude parameter @xmath47 and an arbitrary frequency @xmath48 . a simple analysis shows that @xmath49 is the condition to avoid singularities . the corresponding polarization vector components and @xmath43 function are shown resp . in figs . [ fig3 ] and [ fig4 ] , for @xmath41 as before and for @xmath50 . ) and ( [ e10 ] ) . parameters , @xmath51 . ] for an oscillating electron neutrino population , according to eqs . ( [ e8 ] ) and ( [ e10 ] ) and the same parameters as in fig . [ fig3 ] . ] in this work the usual route for solving the two - flavor neutrino - plasma oscillation equations has been subverted . namely , instead of setting a certain electron plasma density and then looking for the polarization vector components , here the third component @xmath52 and equivalently the electron neutrino population @xmath53 are chosen _ ab initio_. consequently , simple formulas for the coherences @xmath54 are readily found . the necessary condition for the recipe to work is to adjust the function @xmath43 and hence the electron plasma density @xmath55 so that eq . ( [ e7 ] ) holds . the results can be expressed in terms of the electron neutrino population only , see eq . ( [ e8 ] ) . in a sense , our exact neutrino flavor solution has similarities with the celebrated bernstein - greene - kruskal equilibria for the vlasov - poisson system @xcite , where arbitrarily chosen electrostatic potentials can be constructed provided specific trapped electron distributions are set . * acknowledgments * + fernando haas acknowledge cnpq ( conselho nacional de desenvolvimento cientfico e tecnolgico ) for financial support . this work is dedicated to the memory of prof . padma kant shukla . 99 r. bingham , l. o. silva , j. t. mendona , p. k. shukla , w. b. mori and a. serbeto , neutrino plasma coupling in dense astrophysical plasmas . plasma phys . fusion * 46 * , b327b334 ( 2004 ) . a. serbeto , l. a. rios , j. t. mendona and p. k. shukla , neutrino ( antineutrino ) effective charge in a magnetized electron - positron plasma . plasmas * 11 * , 13521357 ( 2004 ) . l. o. silva , r. bingham , j. m. dawson , j. t. mendona and p. k. shukla , neutrino driven streaming instabilities in a dense plasma . lett . * 83 * , 27032706 ( 1999 ) . p. k. shukla , r. bingham , j. t. mendona and l. stenflo , neutrinos generating inhomogeneities and magnetic fields in the early universe . plasmas * 5 * , 28152817 ( 1998 ) . j. p. kneller , g. c. mclaughlin and k. m. patton , stimulated neutrino transformation with sinusoidal density profiles . g. : nucl . phys . * 40 * , 055002 ( 2013 ) . m. koike , t. ota , m. saito and j. satoa , fourier analysis of the parametric resonance in neutrino oscillations . b * 675 * , 6972 ( 2009 ) . p. i. krastev and a. y. smirnov , parametric effects in neutrino oscillations . b * 226 * , 341346 ( 1989 ) . a. schafer and s. e. koonin , influence of density fluctuations on solar neutrino conversion . b * 185 * , 417420 ( 1987 ) . s. hollenberg and h. ps , adiabatic and nonadiabatic perturbation theory for coherence vector description of neutrino oscillations . d * 85 * , 013013 ( 2012 ) . e. torrente - lujan , finite dimensional systems with random external fields and neutrino propagation in fluctuating media . d * 59 * , 073001 ( 1999 ) . f. benatti and r. floreanini , dissipative neutrino oscillations in randomly fluctuating matter . phys . rev . d * 71 * , 013003 ( 2005 ) . p. k. shukla , amplification of neutrino oscillations by a density ripple in dense plasmas . j. plasma phys . * 77 * , 289291 ( 2011 ) . g. g. raffelt , stars as laboratories for fundamental physics . ( university of chicago press , chicago , 1996 ) . s. t. petkov , exact analytic description of two - neutrino oscillations in matter with exponentially varying density . b * 200 * , 373379 ( 1988 ) . s. t. petkov , describing analytically the matter - enhanced two - neutrino transitions in a medium . phys . b * 406 * , 355365 ( 19997 ) . i. b. bernstein , j. m. greene and m. d. kruskal , exact nonlinear plasma oscillations . phys . rev . * 1087 * , 546550 ( 1957 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: with the introduction of new telescopes and instruments to the scientific astronomical community , and the rapid increase of sky surveys such as sdss and rave , tremendous amount of spectral data is being acquired on a daily basis and with an increasing rate . therefore , these challenges urged the need of efficient and automated techniques to handle and analyze this huge amount of information . such automated procedures for classification of stars have been discussed recently using different codes and mathematical approaches . as an example , one can mention the methods used to analyze a spectral library described in @xcite . + in this work , we present a dimensionality reduction technique called pca , applied to a huge database of synthetic spectra . pca searches in a high dimensional space for possible correlations , and finds an optimal basis for representing the data in a compact way . due to the high number of spectra in each synthetic database ( @xmath2200000 ) , and the high number of data points in each spectral domain ( @xmath22500 . same as observation , see section 2 ) , such technique is crucial for inverting stellar parameters of observed targets from gaia eso survey . using pca , data can be represented in a fewer number of data points , allowing a fast nearest neighbor(s ) " search between the observed data set and the synthetic spectra . this study is an extension of @xcite where the h - r domain of application has been extrapolated to stars of types earlier than f , and the training database used in this work is a set of synthetic spectra . the procedure is applied to more than 800 stars , members of the open clusters ngc3293 , ngc6705 , and trumpler14 . the observations are part of the gaia eso public survey and consist of 2 spectral ranges , one samples the h@xmath3 line region [ 4030 - 4200]and the second samples the [ 4400 - 4550](hr5 ) region . these spectra were taken using giraffe / flames spectrograph at a resolution r @xmath4 25000 , and reduced by the ges . balmer lines , due to the broadening caused by the stark s effect , are excellent indicators of effective temperature and surface gravity @xcite . the reason behind studying h@xmath3 in particular is because this line is formed in deep enough atmospheric layers where lte can still be considered as a reasonable assumption . moreover , the hr5 region was chosen since metallic lines ( namely feii , mgii , tiii , ... ) are potentially good indicators of rotational velocity and metallicity . lte model atmospheres were calculated using atlas9 code @xcite and were used as input to the spectrum synthesis code synspec48 @xcite in order to compute a large grid of synthetic line profiles , over the same spectral regions as the observations . spectra were calculated for t@xmath5 between 5000 and 15000 k , gravities between 2.0 and 5.0 cgs , rotational velocities between 0 and 200 @xmath6 , and metalicities between -0.6 and 0.4 dex ( only for the hr5 region , whereas a solar [ fe / h ] was assumed for the @xmath7 region ) , all at a microturbulence of 2 @xmath6 and at a resolution of 25000 . the central idea of principal component analysis is to reduce the dimensionality of a data set in which there are a large number of interrelated variables , while retaining as much as possible of the variation present in the data set @xcite . pca searches for basis vectors that represent most of the variance in a given database . these vectors ( @xmath8 ) are in fact the eigenvectors of the variance - covariance matrix ( [ var - covar ] ) of the synthetic data set * s*. @xmath9 where @xmath10 being the mean spectrum over all the database . once the basis is obtained ( adopted a set of 12 vectors , i.e @xmath11 ) , the synthetic spectra and each observation ( o ) are projected unto this basis to obtain the projected coefficients ( [ proj synth ] & [ proj obs ] ) @xmath12 @xmath13 then , a standard chi - squared ( [ chi - sqr ] ) is performed in this low dimensional space in order to achieve a fast inversion of stellar parameters of the observed targets . the parameters of the synthetic spectrum having the minimum _ d _ will be considered as the observation fundamental parameters . @xmath14 the observation spectra were radial velocity corrected , and those with low signal - to - noise ratio were filtered out . upon starting the inversion process , the technique showed to be very sensitive to normalization of spectra , thus an iterative re-"normalization procedure was performed according to @xcite . in general , inversion based on this technique was performed over the selected stars , and the fundamental parameters of the targets were estimated . an example of the nearest neighbor search is given in figures [ hdelta ] and [ met ] . the parameters derived by pca , along with the non - official parameters obtained by wg13 of ges are detailed in table [ table ] . .results derived using pca along with parameters given by wg13 of ges [ cols="<,^,^,^,^,^,^,^,^ " , ] [ table ] with pca , we will be contributing by determining stellar parameters to the next ges data release . line of the star 10361733 - 5809031 member of ngc3293 cluster , with a synthetic spectrum . blue being the observed spectrum , while red the fitted synthetic.,scaledwidth=80.0% ] pca proved to be a fast and reliable inversion technique , with an ease to implement . an attempt to increase the size of the synthetic database is being performed in order to improve the accuracy in the parameters obtained . moreover , the merging of two spectral ranges in a one data set is also considered as a future work . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: qcd is expected to undergo a transition to a deconfined state , where thermodynamics can no longer be described by hadronic degrees of freedom but should be described in terms of elementary quark and gluon degrees of freedom . in addition , the chiral symmetry which is broken in qcd vacuum is expected to be restored above some temperature . in the limit of zero quark masses the restoration of the chiral symmetry is expected to be a true phase transition . however , for the quark masses realized in nature this transition turns out to be an analytic crossover @xcite . a question naturally arises whether the deconfinement and the chiral transitions are closely related . early lattice calculations with large quark masses and/or coarse lattices suggested that deconfinement and chiral transition happen at the same temperature @xcite . however , more recent investigations that use so - called stout staggered quark action and finer lattices found that these two transitions are no longer interconnected @xcite . in this paper we are going to discuss the deconfinement and chiral transition in qcd at non - zero temperature using highly improved staggered quark ( hisq ) action and tree - level improved gauge action . we refer to this combination of quark and gauge actions as hisq / tree action . to control discretization effects calculations have been performed at three values of the lattice spacing corresponding to temporal extent @xmath0 and @xmath1 . to fix the lattice spacing we used the @xmath2 scale of the static quark potential @xcite and the kaon decay constant @xmath3 . additional calculations using the asqtad action with @xmath4 and @xmath1 have been performed to demonstrate the consistency of the results obtained with different actions , since the asqtad action was extensively used in the past to study qcd at non - zero temperature @xcite . the breaking of the chiral symmetry in qcd vacuum is signaled by non - zero expectation value of quark condensate @xmath5 . at non - zero temperature the quark condensate is expected to decrease , signaling the restoration of the chiral symmetry . however , the quark condensate needs a multiplicative , and for non - zero quark mass , also an additive renormalization . therefore following ref . @xcite we consider the following quantity , which we will call the renormalized chiral condensate @xmath6 here @xmath7 and @xmath8 refer to quark condensate at zero and non - zero temperatures , @xmath9 and @xmath10 for light and strange quarks , respectively . the numerical results are shown in fig . [ fig : deltals ] using the lattice spacing determined by @xmath2 parameter and @xmath3 . we also show the continuum estimate for @xmath11 obtained with the stout action in fig . [ fig : deltals ] . we use the value @xmath12fm @xcite and @xmath13mev @xcite when setting the scale in mev . when @xmath2 is used to set the scale we see large deviations for asqtad action , while for hisq / tree action these deviations are largely reduced . interestingly enough , when @xmath3 is used to set the scale almost no cutoff effect is seen in @xmath11 both for hisq / tree and asqtad action . this feature was first noticed for stout action @xcite . the difference in the stout action and our result is due to the small difference in the light quark mass @xmath14 . in our calculation @xmath15 , while the stout calculations correspond to @xmath16 . here @xmath17 is the physical strange quark mass . if we perform interpolation in the quark mass using @xmath18 scaling , which can describe the quark mass dependence of the chiral observables obtained with p4 action very well @xcite , to the value @xmath16 we get a very good agreement with the stout results . is compared with the continuum extrapolated data obtained with the stout action @xcite ( left panel ) . the temperature @xmath19 is converted into physical units using @xmath2 in the left panel . in the right panel we show the temperature dependence of the same subtracted chiral condensate for the hisq / tree and asqtad actions using @xmath3 to set the scale . the black diamonds show hisq / tree results for @xmath4 after interpolation to the physical quark mass @xmath16 . , title="fig:",scaledwidth=45.0% ] is compared with the continuum extrapolated data obtained with the stout action @xcite ( left panel ) . the temperature @xmath19 is converted into physical units using @xmath2 in the left panel . in the right panel we show the temperature dependence of the same subtracted chiral condensate for the hisq / tree and asqtad actions using @xmath3 to set the scale . the black diamonds show hisq / tree results for @xmath4 after interpolation to the physical quark mass @xmath16 . , title="fig:",scaledwidth=45.0% ] quark number susceptibilities , i.e. fluctuations of the quark numbers are sensitive probe of deconfinement . these can be defined as second derivatives with respect to quark chemical potential evaluated at zero chemical potentials @xmath20 at low temperatures quark number fluctuations are determined by massive hadrons and therefore are quite small , while at high temperatures they are determined by light quark degrees of freedom and thus proportional to @xmath21 . the deconfinement transition can bee seen as a rapid change between these two limiting behaviors and thus the quark number susceptibilities are expected to show a rapid increase . in fig . [ fig : chiq ] we show the light and strange quark number susceptibilities and we clearly see the expected rapid rise in these quantities . as before the lattice spacing was fixed using @xmath2 and @xmath3 . if @xmath3 is used to fix the scale cutoff effects turn out to be very small . the rapid rise in the light quark number susceptibilities happens at temperatures , where @xmath11 sharply decreases . the strange quark susceptibility shows a rapid rise at somewhat higher temperatures . note , however , that this behavior of quark number susceptibilities is not related to different transition temperatures . the inflection points of quark number susceptibilities are dominated by the regular part of the free energy density , and the difference in the inflection points is simply due to the difference in the quark mass . is used to set the lattice scale , while in the right panel we use @xmath3 . the filled squares correspond to @xmath22 . , title="fig:",scaledwidth=49.0% ] is used to set the lattice scale , while in the right panel we use @xmath3 . the filled squares correspond to @xmath22 . , title="fig:",scaledwidth=49.0% ] the polyakov loop is an order parameter for the deconfinement transition in pure gauge theory , which is governed by @xmath23 symmetry . for qcd this symmetry is explicitly broken by dynamical quarks . there is no obvious reason for the polyakov loop to be sensitive to the singular behavior close to the chiral limit although speculations along these lines have been made @xcite . the polyakov loop is related to the screening properties of the medium and thus to deconfinement . after proper renormalization , the square of the polyakov loop characterizes the long distance behavior of the static quark anti - quark free energy ; it gives the excess in free energy needed to screen two well - separated color charges . the renormalized polyakov loop has been studied in the past in pure gauge theory @xcite as well as in qcd with two @xcite , three @xcite and two plus one flavors @xcite . the renormalized polyakov loop , calculated on lattices with temporal extent @xmath24 , is obtained from the bare polyakov loop @xmath25 where @xmath26 and @xmath27 is the additive normalization of the static potential chosen such that it coincides with the string potential at distance @xmath28 with @xmath29 being the sommer scale . this procedure of normalizing the polyakov loop follows ref . some earlier calculations used the singlet free energy in coulomb gauge to estimate the renormalized polyakov loop @xcite . while the former procedure is expected to be more precise both procedures give the same results within errors . the numerical results for the renormalized polyakov loop for the hisq / tree action are shown in the right panel of fig . [ fig : tc_and_lren ] as function of @xmath30 , with @xmath31 being the transition temperature . as one can see from the figure the cutoff ( @xmath32 ) dependence of the renormalized polyakov loop is small . we also compare our results with the continuum extrapolated stout results @xcite and the corresponding results in pure gauge theory @xcite . we find good agreement between our results and the stout results . we also see that in the vicinity of the transition temperature the behavior of the renormalized polyakov loop in qcd and in the pure gauge theory is quite different . ( right ) . for the hisq / tree data we used the values of @xmath31 discussed in @xcite , while for stout data we used the value of @xmath33 mev from the inflection point of renormalized chiral condensate @xcite.,width=294 ] in this contribution we discussed different quantities , which characterize the deconfinement and chiral transition in qcd at non - zero temperature and studied their cutoff dependence . we showed that when the kaon decay constant @xmath3 is used to set the scale ( lattice spacing ) the cutoff effects in different quantities are quite small and calculations performed with the asqtad and hisq / tree actions are in good agreement with calculations performed with the stout action . we pointed out that it is difficult to define the deconfinement temperature . different observables that are used to characterize the deconfinement transition show rapid rise at different temperatures , which in turn , could be different from the chiral transition temperature . this is due to the fact that the observables used to study the deconfinement transition are not sensitive to the singular part of the free energy density or have limited sensitivity to it . this work has been supported in part by contracts de - ac02 - 98ch10886 and de - fc02 - 06er-41439 with the u.s . department of energy and contract 0555397 with the national science foundation . the numerical calculations have been performed using the usqcd resources at fermilab as well as the bluegene / l at the new york center for computational sciences ( nyccs ) . y. aoki _ et al . _ , phys . b * 643 * , 46 ( 2006 ) y. aoki _ et al . _ , jhep * 0906 * , 088 ( 2009 ) s. borsanyi _ et al . _ [ wuppertal - budapest collaboration ] , jhep 1009 , 073 ( 2010 ) c. aubin _ et al . _ , phys . rev . d * 70 * , 094505 ( 2004 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: we are currently in a renaissance for x - ray astronomy , with two major missions , _ chandra _ and _ xmm - newton _ , currently operating . these missions are producing large amounts of archival data , which is supplementing existing databases from missions such as _ rosat _ and _ asca_. historically , only x - ray `` experts '' usually attempted the analysis of x - ray data . this is because there were fundamental differences in the analysis of x - ray data compared with other bandpasses , most notably the fact that individual photons are detected as opposed to the accumulation of ( only ) spectra or images . most modern x - ray detectors are imaging spectrometers so each observation results in a photon list from which images , spectra and light curves can be extracted . in general the numbers of photons are small so poissonian rather than gaussian statistical methods must be used . the spectral and spatial resolution of most detectors is moderate at best and forward - fitting convolution methods are needed to properly fit the data . all of these factors limit the accessibility of the x - ray data to non - experts . in addition each mission tends to have its own unique software package for the reduction and analysis of the data , and x - ray data often require reprocessing as the calibration improves . these latter two factors also limit the ability of experts to take advantage of all available data for a given project , particularly large - scale surveys . we have developed a software package to address these concerns . xassist is capable of performing data reduction and preliminary analysis for _ rosat _ , _ chandra _ and _ xmm - newton _ data . it is fully automatic making it well - suited for surveys , as well as for the reprocessing of existing data . below we will discuss its capabilities and prospects for the future . xassist currently has the following capabilities : * downloads data * reprocesses data * creates exposure maps and detector masks ( if possible ) * detects sources ( using built - in routine for _ rosat _ and _ asca _ , ciao wavdetect for _ chandra _ , etc . ) * fits each source with `` simple '' ( i.e. , not including point - spread function ) model to establish source extent and ( poisson - correct ) significance ( using the stand - alone python program ) * flags extended , confused and problematic sources * computes median ( or mean ) background level * excludes times of high background * extracts spectra , `` postage stamp '' images , and light curves of each source for more detailed analysis ( a simple power - law model is fit to sources with more than 100 sources ) * optionally performs chip - by - chip analysis ( relevant just for _ chandra _ right now ) * analysis can be restricted to an energy band * large emphasis on detailed reporting * looks for correlations of x - ray sources with astronomy databases and provides links on the detailed source web reports to query simbad ( see below ) note that in the case of _ chandra _ analysis , most of the data reduction steps are based on the `` threads '' reported in the . most parameters controlling xassist are read from iraf / ftools - style parameter file , and can be set on the command - line as well ( allowing for the automated setup of xassist for surveys ) . xassist can be run ( and configured ) interactively ( with a text - based interface ) . figure [ n1569_chandra_dss_fig ] shows images created as part of the report for the processing of the _ chandra _ observation ngc 1569 . figure [ n1569_chandra_src2_fig ] shows the detailed report generated for a source . while there are admittedly `` warts '' that occur ( as in any automated system ) , this example demonstrates that even in moderately crowded fields the system performs well and continues to the point of fitting a power - law spectrum model to the source spectrum . obviously , this opens a powerful possibility for virtual observatories , namely that searches could be performed on high - level quantites such as spectral slope . even though human inspection would of course still be necessary for science - grade results , an automated system such as this could cull samples and produce useable results for many of the sources , both of which would be particularly useful prior to observing proposal deadlines ( especially if the data of interest had only recently become publically available and had not been published yet ) . queries are also submitted to heasarc to find correlations of x - ray sources with 2@xmath0ass , usno , first , and other catalogs . to demonstrate xassist s capabilities , have been set up to run xassist on _ rosat _ hri and _ chandra _ observations of rc3 galaxies . the _ rosat _ analysis is nearing completion , and crontab jobs are checking for the public release of _ chandra _ observations that may containing rc3 galaxies in the fov of view , and these data sets are downloaded ( using the script cda.py also available for download ) . _ xmm - newton _ has recently been added as a supported mission , and we are in the process of establishing a pipeline for public _ xmm _ data . the pipeline products are searchable and work is in progress to allow users to request fields to be added to the processing lists . * finishing off details ( especially for _ asca _ and _ rosat _ pspc analysis ) * better installation and configuration support ( including the creation of a gui ) * web access to xassist * web services : limited status reporting is already available using soap and it will be possible to request full or partial processing of data via soap requests Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the flight management infrastructure ( fmi ) product is intended to keep the aircraft from interfering with preplanned observations on the sky . it predicts the ground tracks necessary to execute its mission , and corrects the plan for actual conditions while airborne . to support this , it contains both a planning component that can run on the ground and in the air , and an execution component that runs in the air . the planning component manages a set of ordered observations and optional aircraft repositioning requests . the execution component compares the plan to actual conditions in flight and requests headings ( indirectly ) from the autopilot . sofia mission planning differs from satellite or ground based observatory planning in a few key areas . most importantly , the observatory position is a function of observation target history , which prevents observations from being considered as time - slots alone . assignment of flight dates is also nontrivial targets can not be localized on the sky or the observatory will always fly in about the same direction ( requiring nearly equivalent dead time to return ) ; this suggests entire flight series should be considered at once , for greater target variety . flight planning and execution differs from conventional as well . all conventional aircraft fly from point to point along specified paths on the ground , and `` drift '' the aircraft to compensate for winds . typical drift angles ( course - heading ) exceed 3@xmath0 , and the worst possible case approaches 30@xmath0 , so sofia can not necessarily observe in this manner . expected winds can be planned for using a weather forecast . correcting course for _ unexpected _ winds can be accomplished by adjusting observation durations , by relocating the aircraft between observations , or by `` observation triage '' as a last resort . this requires an astronomically - aware airborne monitoring function to compare current conditions to plan . aircraft capabilities are a strong function of fuel weight , which argues against simple parametrizing by time , in favor of fuel . in addition to the geometrical and practical constraints described above , the sofia flight planning problem also has a number of external constraints , all of which prevent a truly automated , or even rigorously sequential , flight planning process . for instance , special use airspace ( sua ) incursions may require external approval , and it can not be known ahead of time whether such approval will be forthcoming in all cases . national airspace boundaries require international agreements . over - ocean operations are prohibited for safety reasons for the first flights ; for later flights , fairly complex fuel reserve constraints are required . gross takeoff weight has a hard limit of 700,000 pounds , which limits the duration of sofia missions . some science - driven constraints require interaction with scientists or detailed knowledge of the observations ; especially , trading off water vapor overburden estimates with altitude and duration , and for trading off observations against each other . prior to any particular mission , several iterations of flight planning are performed . this is expected to include fully integrated automated flight planning ( frank , gross , & krkl 2004 ) , routinely . manual choice of observation ( including order ) will occur subsequently . upon execution , replanning might occur if conditions are sufficiently different from assumptions . figure [ fig : sampleflight ] shows a color - processed screenshot of a simulated flight intended for april , 2008 , from palmdale , ca . actual conditions for the simulation shown differ from planned only by small timing errors of the order of several seconds between segments and at takeoff . as mentioned earlier , it is advantageous to consider entire flight series at once , in order to trade observations between flights . the data structure supporting this is shown in fig . [ fig : flightseries ] . fmi requires substantial input data in order to accurately predict a flight track and its constraints . weather forecast time - series are taken from the national center for environmental prediction global forecasting system , quadrilinearly interpolated . an alternative is required for dates more than several days in the future , since accurate forecasts are not available then ; we use a set of stacked monthly means for 19972001 ( the last years available ) from the european center for medium ranger weather forcasting 40 year reanalysis ( uppala et . al . 2005 ) also quadrilinearly interpolated . aircraft performance is interpolated from tables generated by boeing inflt runs , for cruising , thrust - limited climbs , and descents . planned flight track intersections with special use airspace ( sua ) boundaries ( including non - us zones , from the us national imagery and mapping agency ) are evaluated using a quadtree - based search on the 8000 + sua boundaries for each flight segment . observation segments are treated as initial value problems in cartesian coordinates , others may be boundary or initial problems , as appropriate . desired headings are calculated during execution from planned ( not actual ) sky coordinates and actual position ; direct steering by the telescope can not be allowed for safety reasons . in order to test fmi components and integrate other systems , as well as for training purposes , we use a simulation environment . this includes a medium - fidelity aircraft simulator , an automated pilot simulator , a method to set the time arbitrarily , and a telescope simulator ( brggenwirth , gross , nelbach , & shuping 2008 ) . while airborne , the fmi software components interact with the airborne data acquisition software to acquire the aircraft s position and attitude . while on the ground , the planner portion of fmi interacts with observers planning software and must support multiple simultaneous planning sessions . the airborne configuration is shown in fig . [ fig : dataflow ] ; the ground configuration is similar , except there is no flight executor nor mccs data ( except in testing configurations ) , and there is a connection to the observation planning database . sofia presents a unique flight planning problem due to the nature of astronomical observation . fmi provides a connection between scientific needs of an observatory with the practical constraints of operating an aircraft , without introducing excessive safety considerations or pilot workload , or planner effort . brggenwirth , s. , gross , m. a. k. , nelbach , f. j. , & shuping , r. y. 2009 , , 485 frank , j. , gross , m. a. k. , & krkl , e. 2004 , in proc . 16th conf . on innovative applications of artificial intelligence , ed . d. l. mcguinness & g. ferguson ( boston : mit press ) , 828 uppala , s. m. et al . 2005 , quart . j. r. meterol . soc.,131 , 2961 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the magnetic dipole moments @xmath4 of neutron stars are observed to decrease with accreted mass , @xmath5 . evidence of this trend is found in a variety of systems , e.g. low- and high - mass x - ray binaries , and binary radio pulsars with white - dwarf and neutron - star companions @xcite , although there is some debate over whether the trend is monotonic @xcite . several theoretical mechanisms have been proposed to explain the @xmath6 data , including accelerated ohmic decay @xcite , fluxoid - vortex interactions @xcite , and magnetic screening or burial @xcite . with regard to the latter mechanism , @xcite ( hereafter pm04 ) calculated a sequence of two - dimensional , hydromagnetic ( grad - shafranov ) equilibria describing the structure of the magnetically confined mountain of material accreted at the magnetic poles of the neutron star . the mountain is confined by magnetic stresses near the equator , where the field is compressed @xcite . these solutions are the first of their kind to explicitly disallow cross - field transport of material as the mountain evolves from its initial to its final state ( cf . * * ) , as required in the ideal - magnetohydrodynamic ( ideal - mhd ) limit . pm04 found that @xmath4 is screened substantially above a critical accreted mass @xmath7 , well above previous estimates of @xmath8 @xcite . pm04 calculated equilibria up to @xmath9 , falling short of the mass required ( @xmath10 ) to spin up a neutron star to millisecond periods @xcite . this is supplied by a large class of mass donors like lmxbs @xcite , even given nonconservative mass transfer @xcite . grad - shafranov calculations are stymied above @xmath11 by physical effects ( e.g. magnetic bubbles form above the stellar surface ) and numerical effects ( e.g. steep magnetic gradients hinder iterative convergence ) . in this paper , we extend the @xmath6 relationship to @xmath12 by loading equilibria with @xmath11 into zeus-3d , a multi - purpose time - dependent , ideal - mhd code for astrophysical fluid dynamics , and adding extra mass quasistatically through the outer boundary of the simulation volume . pm04 also left open the important question of the stability of the hydromagnetic equilibria . distorted magnetic configurations , in which the polar flux is buried beneath the accreted overburden and compressed into a narrow belt at the magnetic equator , are expected prima facie to be unstable . indeed , the grad - shafranov analysis in pm04 hints at the existence of an instability by predicting ( informally ) the existence of magnetic bubbles as steady - state solutions . in this paper , we systematically explore the stability of the equilibria by evolving them in zeus-3d , subject to linear and nonlinear perturbations . the structure of the paper is as follows . in section [ sec : stability2 ] , the necessary theory is summarised and the solution method described . the formalism of pm04 is again used here . the numerical grad - shafranov solver is described in appendix b of pm04 and appendix c of @xcite . in section [ sec : burialsetup ] , we verify zeus-3d against a set of test cases relevant to the problem of magnetic burial ; the implementation is described thoroughly in appendix a. in section [ sec : lateburial ] , we explore the late stages of magnetic burial ( @xmath13 ) by adding mass quasistatically to equilibria from pm04 in zeus-3d . in section [ sec : stability ] , we discuss the linear and nonlinear stability of the equilibria in the regime @xmath14 . the paper concludes , in section [ sec : stabilityconclusion ] , with a discussion of the limitations of our analysis and suggestions for future numerical work . during accretion onto a neutron star from a binary companion , matter piles up on the polar cap , funnelled by the magnetic tension of the polar magnetic flux tube . once @xmath5 exceeds @xmath15 , the hydrostatic pressure at the base of the accretion column overcomes the magnetic tension and matter spreads over the stellar surface towards the equator , dragging along frozen - in polar field lines ( pm04 ) . the distorted magnetic field leads to screening currents which act to decrease the magnetic dipole moment . figure [ fig : smalla](a ) illustrates the magnetic ` tutu ' formed for @xmath16 , cut off at ten density scale heights . the polar mountain of accreted material ( dashed contours ) and the pinched , flaring , equatorial magnetic belt ( solid contours ) are plainly seen . at first glance , one might expect such equilibria , with their steep density and magnetic field gradients , to be unstable . interestingly , this expectation is largely false , as we show in section [ sec : stability ] . we summarise the key equations and notation of magnetic burial here ( pm04 ) . the steady - state ideal - mhd equations for an isothermal atmosphere ( @xmath17 , i.e. adiabatic index @xmath18 ) reduce to the force equation @xmath19 . for an axisymmetric configuration in spherical polar coordinates @xmath20 , a flux function @xmath21 generates the magnetic field @xmath22 via @xmath23 . the flux function satisfies the grad - shafranov equation @xmath24 , \label{eqn : gradshafranov}\ ] ] where @xmath25 , @xmath26 , @xmath27 , @xmath28 , @xmath29 , and @xmath30 denote the matter density , pressure , gravitational potential , surface gravitational potential , sound speed , and grad - shafranov operator respectively ( pm04 ) . in the limit @xmath31 , @xmath32 , where @xmath33 is the mass of the neutron star and @xmath34 is its radius , mass - flux conservation in ideal mhd provides the integral constraint @xmath35 \right\}^{-1 } \ , , \\ \label{fpsiparker } \end{split}\ ] ] we prescribe the mass - flux distribution to be @xmath36 , where @xmath37 is the flux enclosed by the inner edge of the accretion disk at a distance @xmath38 and @xmath39 is the hemispheric flux . for the boundary conditions , we fix @xmath40 to be dipolar at @xmath41 , assume north - south symmetry , fix the @xmath42 field line , and leave the field free at large @xmath43 . equations ( [ eqn : gradshafranov ] ) and ( [ fpsiparker ] ) are solved numerically using an iterative relaxation scheme @xcite . the mean residual as a function of iteration number is shown in figure [ fig : smalla](b ) , corresponding to the grad - shafranov equilibrium for @xmath44 displayed in figure [ fig : smalla](a ) . the form of @xmath45 , found from ( [ fpsiparker ] ) , varies from @xmath46 to @xmath47 in the manner displayed in figure [ fig : smalla](c ) . here we give the formulae for converting between the grad - shafranov code and zeus-3d . furthermore , we detail the effects of converting from a small ( @xmath49 ) to a realistic ( @xmath50 ) star . with @xmath51 fixed , but allowing @xmath48 to vary , we have @xmath52 m , @xmath53 , and @xmath54 @xmath51 is the dimensionless unit of length . the dimensionless units in the grad - shafranov code ( subscript ` g ' ) are @xmath55 @xmath56 kg m@xmath57 , @xmath58 t. in zeus-3d ( subscript ` z ' ) , @xmath59 , @xmath60 t. for conversion from the equilibrium code to zeus-3d , the factors are @xmath61 , and @xmath62 . pm04 concentrated maximum grid resolution near the equator and stellar surface where @xmath63 and @xmath64 are greatest , by employing logarithmic stretching : @xmath65 @xmath66\ , .\ ] ] to implement these coordinates in zeus-3d , set ggen1:x1rat to @xmath67 , where @xmath68 and @xmath69 controls the ` zoom ' . radial logarithmic scaling gives less grid resolution near the outer boundary where the density is least and thus @xmath70 is greater and zeus-3d runs for a longer time . when importing a grad - shafranov equilibrium ( pm04 ) , whose grid is linear in @xmath71 , into zeus-3d , whose grid is ( in many cases ) logarithmic in @xmath72 , there is no trivial multiplicative factor relating @xmath73 and the required logarithmic @xmath74 scaling through ggen1:x2rat . the problem can be overcome by rewriting the grad - shafranov code such that its grid is logarithmic in @xmath74 . this problem is an obstacle in certain sorts of numerical experiments e.g. the bootstrapping method in 4.2 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the possibility of fundamental constants to vary is predicted by theories unifying gravity with other interactions ( see , e.g. review by uzan @xcite ) . there is an evidence found in quasar absorption spectra that the fine structure constant @xmath5 ( @xmath6 ) might be smaller in early cosmological epoch @xcite . however , similar analysis applied by other authors to different sets of data does not support this claim @xcite . recent progress in improving atomic clocks and developing optical frequency standards ( see , e.g. @xcite ) made it possible to put strong constrains on possible time variation of fundamental constants in laboratory measurements . in particular , constrains obtained for the fine structure constant @xmath5 need only about one order of magnitude improvement to see whether they are consistent with the quasar absorption spectra data if the same rate of change is assumed over cosmological time . these constrains were obtained with the full use of the technique developed for highly accurate optical standards . however , the choice of atomic transitions was not optimal for searching of variation of the fine structure constant . frequencies used so far change at about the same rate as @xmath5 if @xmath5 changes , i.e. there is no enhancement . an alternative approach was suggested in refs.@xcite . it was proposed to measure small frequency between two close states with different dependence on @xmath5 . here small change of @xmath5 may lead to orders of magnitude larger relative change in frequency . the enhancement factor @xmath7 can be expressed as @xmath8 , where @xmath9 is the difference in relativistic energy shifts of two levels and @xmath10 is transition frequency . a good candidate for such experiments is dysprosium atom @xcite . it has two almost degenerate states of opposite parity and corresponding enhancement factor is of order of @xmath11 @xcite . the measurements for dysprosium are currently underway at berkeley @xcite . while it is hard to find anything better than dysprosium in terms of enhancement factor , it has its disadvantages too . the levels involved are not so narrow . while one of the states lives long enough to cause no problem the other level does not . one has to work inside the line width to have the desirable accuracy . this puts certain limitations on achievable constrains on @xmath5-variation . therefore , it would be important to find something which combines the advantages of having metastable states and strong enhancement . a number of such transitions were considered in recent work @xcite . it has been suggested to look at close metastable states of different configurations . energies of different configurations change at different rates when @xmath5 is changing . this , together with small energy intervals between the states ensures strong enhancement @xcite . in present work we consider slightly different possibility . we suggest to study anomalously small fine structure intervals in ground configurations of many - electron atoms . the use of the ground state fine structure multiplet ensures that states are metastable . they can only decay via @xmath12-transitions which are very much suppressed due to small value of transition frequency . on the other hand , configuration interaction in many - electron atoms can reduce fine structure intervals and lead to strong sensitivity to the change in the fine structure constant . in next sections we consider in detail fine structure of the ground state of tellurium and discuss some other possibilities . to study sensitivity of atomic frequencies to variation of the fine structure constant @xmath5 it is convenient to present them in the vicinity of the physical value of @xmath5 ( @xmath13 ) in the form @xmath14 where @xmath15 and coefficient @xmath16 defines the sensitivity of the frequency to variation of @xmath5 . in general , its value can be found from atomic calculations . if @xmath5 changes the relative frequency changes at the rate @xmath17 where @xmath18 is enhancement factor . to search for variation of the fine structure constant one needs to compare atomic frequencies with different enhancement factors over long period of time . the larger this difference the more sensitive the experiment to variation of @xmath5 . note that @xmath7 can have negative value which means that changes of @xmath5 and frequency go in opposite directions : frequency decreases when @xmath5 increases and vise versa . for `` normal '' fine structure intervals which are proportional to @xmath19 formula ( [ omegaq ] ) is valid for all values of @xmath5 , @xmath20 . therefore , @xmath21 and @xmath22 . in other words , the factor @xmath7 is the same for all `` normal '' fine structure intervals and comparison between them can not reveal any drift of @xmath5 . these fine structure intervals can still be used in search for variation of the fundamental constants if they are compared to hyperfine structure or to frequencies of suitable optical transitions . situation changes dramatically if fine structure multiplet is strongly perturbed by configuration interaction with neighboring states . we consider neutral tellurium atom in its ground state as an example . experimental and theoretical energies of the ground state @xmath23 configuration of tellurium are presented in table [ tab1 ] . there are strong anomalies in the fine structure multiplet @xmath2p@xmath1 . the @xmath2p@xmath24 - @xmath2p@xmath3 and @xmath2p@xmath3 - @xmath2p@xmath4 intervals have opposite signs and differ in value more than hundred times . this is because of configuration interaction between the @xmath2p@xmath24 and @xmath25d@xmath24 states and between the @xmath2p@xmath4 and @xmath25s@xmath4 states while the @xmath2p@xmath3 state has no close neighbors to mix with . configuration interaction leads to accidental almost exact cancellation between spin - orbit and coulomb terms in the energy interval between the @xmath2p@xmath3 and @xmath2p@xmath4 states . since spin - orbit interaction is much more sensitive to the change of @xmath5 than the coulomb term , it is natural to expect that the @xmath2p@xmath3 - @xmath2p@xmath4 energy interval is very sensitive to the variation of @xmath5 . to check how strong is sensitivity of the fine structure intervals of te i we perform model configuration interaction ( ci ) calculations for the @xmath23 configuration of the atom . first , we perform hartree - fock calculations for open shells to find the @xmath26 and @xmath27 states of neutral tellurium . then we use the ci technique to construct four - electron states of the @xmath23 configuration and to calculate their energies ( in fact , in this approximation ci technique is reduced to diagonalization of the interaction hamiltonian describing direct mixing of different @xmath23 states ) . it turns out that some extra fitting is needed to have good agreement with experiment . namely , we reduce the value of the @xmath28 coulomb integral by 25% . this reduction simulates the effect of screening of coulomb interaction between valence electrons by core electrons . the results for energies are presented in table [ tab1 ] . one can see that in spite of simple approximation used in calculations the agreement with experiment is very good . coefficients @xmath16 ( see eq.([omegaq ] ) ) are found by varying @xmath5 in computer codes : @xmath29 the results for @xmath16 are also presented in table [ tab1 ] . since we have good agreement with experiment for the energies it is natural to assume that the accuracy for the @xmath16-coefficients is also good . .[tab1]experimental and theoretical energies and @xmath16-coefficients ( @xmath30 ) for the @xmath23 ground - state configuration of te i. [ cols="^,^,>,>,>",options="header " , ] calculations for ce ii are more difficult than for te i and po i because of valence states of high angular momentum ( @xmath31 and @xmath32 ) . therefore we believe that it is premature to attempt them now . the presence of enhancement is obvious but its actual value would become important only on the stage of planning the measurements . we are ready to perform the calculations if there is any interest from experimentalists . cases of fine structure anomalies similar to what is presented here for ce ii can be easily fond in spectra of many other rare - earth elements . which of them are suitable for the search of @xmath5 variation is the question which needs further consideration . we present an alternative way to search for variation of the fine structure constant in laboratory measurements . we propose to use fine structure intervals in the ground or low excited states of many - electron atoms which are strongly perturbed by configuration interaction with neighboring states . this method has double advantages . on one hand , the use of low states ensures that they are metastable . this is important for very accurate frequency measurements . on the other hand , strong perturbation may lead to anomalously small fine structure interval and strong enhancement of the relative sensitivity of the frequencies to the change of the fine structure constant . because of the high relative sensitivity one does need extremely accurate absolute measurements of the frequencies ( this is the difference with conventional atomic clock measurements ) . large value of the effect / frequency ratio may also help to reduce importance of some systematic effects ( e.g. the doppler shift and broadening ) . note , however , that we do not consider in this paper any practical measurement scheme . enhanced and highly non - linear dependence of the small fine structure intervals on the magnitude of the relativistic corrections also presents certain theoretical interest . this work was supported by the australian research council and department of energy , office of nuclear physics , contract no . w-31 - 109-eng-38 . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: a challenging issue in cosmology today consists in explaining the current accelerated cosmic expansion or dark energy. even if the standard model of cosmology reproduces current observations , the cosmological constant can not explain the coincidence issue and faces a fine - tuning problem . the most simple alternative is to introduce a dynamical scalar field , potentially originating from the gravity sector . however , such models are a dangerous business since they have to pass stringent constraints in the solar system and in lab experiments . to do so , models invoking a screening mechanism , like the chameleon@xcite , have been built : in dense environment like the solar system , the scalar field is suppressed while it acts on sparse environment , like in the cosmos at late time . recently , a new lab experiment based on atom interferometry with a test mass inside a vacuum chamber has been designed for testing modified gravity models@xcite . the idea is that , even if their nuclei appear to be dense , atoms are so small that the scalar field is unsuppressed . additional acceleration on individual atoms due to the chameleon field gradient inside the vacuum chamber in the presence of the test mass could be measured . analytical calculations derived so far in refs . , show that most of the chameleon parameter space is constrained by such an experiment . nevertheless , the authors assumed that the wall effect is negligible and the value of the scalar field at the center of the chamber is then determined as a function of the size of the chamber@xcite . we provide numerical computations with the following minimal assumption@xcite : the chameleon field reaches its equilibrium value @xmath0 in the outside atmosphere . our results reveal that the scalar field amplitude inside the chamber is related to @xmath0 instead of the chamber size , in the case where the test mass perturbs weakly the chameleon profile . we also study the _ strongly _ perturbing case where _ thin shell _ appears . in both cases , we provide forecasts for the acceleration due to the scalar field @xmath1 which is related to the scalar field gradient inside the vacuum chamber , experimental constraint@xcite being @xmath2 , with @xmath3 the earth gravitational acceleration . we also highlight the effects of the test mass density and size , a result which can be interesting for designing further experiments . in this section , we briefly remind the chameleon model . we start from the general scalar - tensor theory action written in the einstein frame , s=^4x + s_m , with @xmath4 , the scalar curvature , @xmath5 , @xmath6 being the planck mass , @xmath7 the matter fields , @xmath8 the chameleon potential ( in the following , we will consider @xmath9 , @xmath10 and @xmath11 being the parameters of the potential ) and @xmath12 a general coupling function ( in the following , we will consider @xmath13 , @xmath14 being a parameter ) . for a static and a spherically symmetric spacetime in the non - relativistic limit , the klein - gordon equation is given by , + = , = + a^3 , with @xmath15 the effective potential , @xmath16 the density written in the jordan frame@xcite such as it obeys to the energy conservation @xmath17 , a prime denoting a derivative with respect to the radial coordinate . the effective potential minimum @xmath18 is given by , _ = ( ) ^1/(+1 ) , in the limit @xmath19 . depending on the environment , the scalar field is suppressed ( dense environment ) or not ( sparse environment ) . in order to constrain the acceleration due to the scalar field @xmath20 , we solve the klein - gordon equation inside the test mass , the vacuum chamber , the wall and in the air outside the vacuum chamber with the minimal assumptions : the scalar field reaches its equilibrium value @xmath21 at spatial infinity and the solution should be regular at the origin of coordinates and everywhere continuous . we use a solver for multi - point boundary value problem with unknown parameters@xcite , the boundary conditions being given by @xmath22 and a yukawa profile far in the exterior environment , = _ + , with @xmath23 , the constant of integration @xmath24 being a parameter to be determined by the numerical algorithm . we compare the numerical and analytical profiles of the scalar field and the acceleration on fig . [ plot : profiles ] for various @xmath14 ( @xmath25 and corresponding @xmath11 being obtained from the cosmological constraints coming from sne ia observations@xcite ) . the numerical results differ by up to one order of magnitude for the acceleration compared to previous analysis@xcite , indicating that the effect of the wall can not be neglected in a precise investigation of the chameleon parameter space . indeed , varying the wall density by two orders of magnitude ( see dotted lines on the scalar field profile of fig . [ plot : profiles ] ) , we show that the wall perturbs more or less importantly the field profile . the effect remains however negligible for the acceleration profile that is related to the gradient of the field . another important result is the determination of the central value of the scalar field : in ref . , it is given by the size of the chamber while the numerical simulations show that it is better approximated by @xmath21 . [ plot : simu_near ] , we study the effect of @xmath10 and @xmath14 on the acceleration at 8.8 mm far from the test mass ( refers as the _ near _ position in ref . ) where the acceleration is measured experimentally . we conclude that the experiment presented in ref . is able to rule out the chameleon model presented in the previous section for @xmath26 gev whatever @xmath10 . discrepancies due to @xmath10 in the determination of the acceleration highlighted on fig . [ plot : simu_near ] , appears when the limit @xmath27 is no more valid . we also studied the thin shell regime and our results validate the analytical approximations to a good accuracy . [ plot : profiles ] [ plot : simu_near ] as stated in the sec . i , in the case where the scalar field is _ weakly _ perturbed by the test mass , we observe only a small deviation with respect to @xmath0 . this is due to the presence of the wall chamber . it stabilizes the scalar field and gives it a kick for reaching @xmath0 . furthermore , on fig . [ plot : profiles ] , we see that the wall density is responsible for a variation of two orders of magnitude in the scalar field profiles . since in the experimental setup proposed in ref . the wall and test mass are similar in size and density , we expect similar effects while varying test mass density and size . the acceleration profiles for the test mass made of aluminum and tungsten with a radius of 5 mm , 1 cm and 3 cm are reported on fig . [ plot : geom ] . we show that , choosing a test mass which is denser and bigger , the acceleration can differ by almost a factor 10 . [ plot : geom ] we derived numerically forecasts for the experiment of ref . for various chameleon models in the _ weakly perturbing regime_. we showed that analytical and numerical acceleration forecasts and constraints differ by up to one order of magnitude . we also highlight that the numerical simulations can be helpful for precise investigation of the parameter space of the chameleon models as well as for optimizing the experimental setup . the same numerical method has been used to derive constraints on other chameleon potentials in ref . for the thin shell regime . our numerical method could be easily extended to other modified gravity models like the symmetron . we warmly thank holger mller for the discussion during the mg meeting and the following conversation where justin khoury , benjamin elder and philipp haslinger took part . we also warmly thank clare burrage and christophe ringeval for useful comments and discussion . is supported by the fnrs - fria , s.c . is partially supported by the _ return grant _ program of the belgian science policy ( belspo ) and a. f. is partially supported by the arc convention no . 11/15 - 040 . 00 j. khoury , a. weltman , _ phys.rev.lett . _ * 93 * , 171104 ( 2004 ) . j. khoury , a. weltman , _ phys.rev . _ * d69 * , 044026 ( 2004 ) . p. hamilton , m. jaffe _ _ , _ science _ , * 349 * , 849 - 851 ( 2015 ) c. burrage , e. j. copeland , e. hinds , _ jcap _ * 1503 * , 042 ( 2015 ) . s. schlgel , s. clesse and a. fzfa , arxiv:1507.03081 _ probing modified gravity with atom - interferometry : a numerical approach _ , 2015 . a. hees and a. fzfa , _ phys.rev . _ * d85 * , 103005 ( 2012 ) . shampine , i. gladwell , and s. thompson , _ solving ode s with matlab _ ( cambridge university press , 2003 ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: images from the hubble space telescope ( hst ) advanced camera for surveys ( acs ) suffer from strong geometric distortion : the square pixels of its detectors project to trapezoids of varying area across the field of view . the tilted focal surface with respect to the chief ray is the primary source of distortion of all three acs detectors . in addition , the hst optical telescope assembly induces distortion as does the acs m2 and im2 mirrors ( which are designed to remove hst s spherical aberration ) . the sbc s optics include a photo - cathode and micro - channel plate which also induce distortion . here we describe our method of calibrating the geometric distortion using dithered observations of star clusters . the distortion solutions we derived are given in the idc tables delivered in nov 2002 , and currently implemented in the stsci calacs pipeline . this paper is a more up to date summary of our results than that presented at the workshop . an expanded description of our procedures is given by meurer ( 2002 ) . * observations*. the acs smov geometric distortion campaign consisted of two hst observing programs : 9028 which targeted the core of 47 tucanae ( ngc 104 ) with the wfc and hrc , and 9027 which consisted of sbc observations of ngc 6681 . additional observations from programs 9011 , 9018 , 9019 , 9024 and 9443 were used as additional sources of data , to check the results , and to constrain the absolute pointing of the telescope . the ccd exposures of 47 tucanae were designed to well detect stars on the main sequence turn - off at @xmath0 in each frame . this allows for a high density of stars with relatively short exposures . the f475w filter ( sloan g ) was used for the ccd observations so as to minimize the number of saturated red giant branch stars in the field . for the hrc two 60s exposures were taken at each pointing , while for the wfc which has a larger time overhead , only one such exposure was obtained per pointing . simulated images made prior to launch , as well as archival wfpc2 images from gilliland et al . ( 2000 ) were used to check that crowding would not be an issue . for calibrating the distortion in the sbc we used exposures of ngc 6681 ( 300s - 450s ) which was chosen for the relatively high density of uv emitters ( hot horizontal branch stars ) . the pointing center was dithered around each star field . for the wfc and hrc pointings , the dither pattern was designed so that the offsets between all pairs of images adequately , and non - redundantly , samples all spatial scales from about 5 pixels to 3/4 the detector size . for the sbc pointings , a more regular pattern of offsets is used augmented by a series of 5 pixel offsets . * distortion model*. the heart of the distortion model relates pixel position ( @xmath1 ) to sky position using a polynomial transformation ( hack & cox , 2000 ) given by : @xmath2 here @xmath3 is the order of the fit , @xmath4 is the reference pixel , taken to be the center of each detector , or wfc chip , and @xmath5 are undistorted image coordinates . the coefficients to the fits , @xmath6 and @xmath7 , are free parameters . for the wfc , an offset is applied to get the two ccd chips on the same coordinate system : @xmath8 @xmath9 are 0,0 for wfc s chip 1 ( as indicated by the fits ccdchip keyword ) and correspond to the separation between chips 1 and 2 for chip 2 . the chip 2 offsets are free parameters in our fit . @xmath10 correspond to tangential plane positions in arcseconds which we tie to the hst @xmath11 coordinate system . next the positions are corrected for velocity aberration : @xmath12 , @xmath13 , where @xmath14 here * u * is the unit vector towards the target and * v * is the velocity vector of the telescope ( heliocentric plus orbital ) . neglect of the velocity aberration correction can result in misalignments on order of a pixel for wfc images taken six months apart for targets near the ecliptic . finally , we must transform all frames to the same coordinate grid on the sky @xmath15 : @xmath16 where the free parameters @xmath17 are the position and rotation offsets of frame @xmath18 . * calibration algorithm*. we use the positions of stars observed multiple times in the dithered star fields to iteratively solve for the free parameters in the distortion solution : fit coefficients @xmath19 ; chip 2 offsets @xmath20 ( wfc only ) ; frame offsets @xmath21 ; and tangential plane position @xmath22 of each star used in the fit . the stars are selected by finding local maxima above a selected threshold . the centroid in a @xmath23 box about the local maximum is compared to gaussian fits to the @xmath24 profiles , if the two estimates of position differ by more than 0.25 pixels , the measurement is rejected as likely being effected by a cosmic ray hit or crowding . further details of the fit algorithm can be found in meurer et al . ( 2002 ) . * low order terms*. originally only smov images taken with a single roll angle were used to define the distortion solutions . the solution using only these data is degenerate in the zeroth ( absolute pointing ) and linear terms ( scale , skewness ) . so we used the largest commanded offsets with a given guide star pair to set the linear terms . however , comparison of corrected coordinates to astrometric positions showed that residual skewness in the solution remained . hence , as of november 2002 , the idc tables for wfc and sbc are based on data from multiple roll angles . the overall plate scale is set by the largest commanded offset . for the hrc , the linear scale is set by matching hrc and wfc coordinates , since the same field was used in the smov observations . the zeroth order terms ( position of the acs apertures in the hst @xmath25 frame ) was determined from observations of an astrometric field . .summary of fit results [ cols="<,^,>,>,^,>,^,^,^ " , ] the distortion in all acs detectors is highly non - linear as illustrated in fig . [ f : nonlin ] . we find that a quartic fit ( @xmath26 ) is adequate for characterizing the distortion to an accuracy much better than our requirement of 0.2 pixels over the entire field of view . table [ t : res ] summarizes the rms of the fits to the various datasets . the wfc and hrc fits were all to f475w data as noted above . to check the wavelength dependence of the distortion we used data obtained with f775w ( wfc and hrc ) and f220w ( hrc ) from programs 9018 and 9019 . we held the coefficients fixed and only fit the offsets in order to check whether a single distortion solution is sufficient for each detector . table 2 shows that there is a marginal increase in the rms for the red data of the wfc , little or no increase in the fit rms for the red hrc data , but a significant increase in the rms using the uv data . an examination of the hrc f220w images reveals the most likely cause : the stellar psf is elongated by 0.1 " . a similar elongation can also be seen in sbc psfs . we attribute this to aberration in the optics of either the acs m1 or m2 mirrors or the hst ota ( hartig , et al . , the aberration amounts to 0.1 waves at 1600 , but is negligible relative to optical wavelengths , hence it is not apparent in optical hrc images . while it was expected that the same distortion solution would be applicable to all filters except the polarizers , recent work ( by tom brown , stsci , and our team ) has shown that at least one other optical filter ( f814w ) induces a significant plate scale change ( factor of @xmath27 ) . in the long term , the idc tables will be selected by filter in the stsci calacs pipeline . while a quartic solution is adequate for most purposes , binned residual maps ( fig . [ f : resid ] ) show that there are significant coherent residuals in the wfc and hrc solutions . these have amplitudes up to @xmath28 pixels . the small - scale geometric distortion is the subject of the anderson & king contribution to this proceedings . hack , w. , & cox , c. 2000 , isr acs 2000 - 11 , stsci . hartig , g. et al . 2002 , in `` future euv and uv visible space astrophysics missions and instrumentation '' , eds . blades & o.h . siegmund , proc . spie , vol . 4854 , in press [ 4854 - 30 ] . gilliland , r.l . 2000 , apj , 545 , l47 . meurer , g.r . 2002 , in `` future euv and uv visible space astrophysics missions and instrumentation '' , eds . blades & o.h . siegmund , proc . spie , vol . 4854 , in press [ 4854 - 30 ] . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: in the family of frustrated magnets , the kagom and pyrochlore lattices have attracted special attention both experimentally and theoretically . experimentally such magnets display a wide variety of unusual low temperature behaviors @xcite signatures of different kind of collective low energy degrees of freedom . the first - neighbor classical heisenberg model on such lattices has a t=0 entropy @xcite . on these lattices , the heisenberg model can be rewritten as the sum of the square of the total spin of corner sharing units @xmath2 ( triangles for the kagom lattice , tetrahedra in the pyrochlore ) : @xmath3 thus a classical ground - state is obtained whenever @xmath4 for all @xmath2 . it is a straightforward exercise to show that such ground - states have a continuous local degeneracy . thermal fluctuations select planar spin configurations on the kagom lattice @xcite , but are unable to build order from disorder in the pyrochlore lattice@xcite . a simple maxwellian counting has been done by the last authors : the number of degrees of freedom of @xmath5 heisenberg spins with a given length is @xmath6 . the number of constraints to realize a classical ground - state is @xmath7 where @xmath8 is the number of spins on each @xmath2 unit . assuming that these constraints are linearly independent , one finds a @xmath9 extensive entropy ( @xmath10 ) for the pyrochlore and zero entropy ( @xmath11 ) in the kagom case . although the assumption is known to fail for the kagom magnet this naive counting suggests that the degeneracy of the classical ground - state in the pyrochlore magnet is larger than in kagom magnet , in qualitative agreement with the thermal behavior of the two magnets . lately , palmer and chalker have studied the heisenberg problem on the checker - board lattice@xcite . this lattice built out of corner sharing 4-spin squares ( see fig . [ checkerboard2 ] ) is the two dimensional analog of the pyrochlore lattice . the classical heisenberg model on the checker - board lattice has a similar ground - state degeneracy and behave the same way at low temperature ( and with additional dipolar interactions)@xcite . the effect of quantum fluctuations on these different structures remains to be fully understood . in the large s , first - order spin - wave approximation , all these magnets remain disordered@xcite . higher order approximations have been devised for the kagom lattice and lead to selection of order out of disorder by quantum fluctuations@xcite . there is no spin long range order ( lro ) in the pyrochlore magnet@xcite . the spectrum of low lying excitations of the spin-1/2 kagom magnet obtained from exact diagonalizations has been a real surprise@xcite : whereas it probably has a small gap for @xmath12 excitations ( transitions @xmath13 ) , there is no gap to singlet excitations ( transitions @xmath14 ) and the density of low lying @xmath15 states is so large that the system has a t=0 residual entropy . the discovery of a second model with a similar spectrum of low lying excitations on the triangular lattice with 4-spin exchange interaction lead us to speculate that this could be a generic new type of magnets@xcite . a natural question thus arises : do the 2-dimensional and the true pyrochlore quantum magnets belong to this generic class ? the results obtained from their classical and semi - classical counterparts support the speculation that the answer might be positive ! as exact diagonalizations are up to now limited to systems of @xmath16 spins , the problem of the true spin-1/2 pyrochlore magnet might remain open for still a long time . the 2-d pyrochlore looks more promising : palmer and chalker@xcite have computed the spectra of clusters up to @xmath17 spins . from their results , they were able to conclude that the system has no nel lro ; it does not break @xmath18 at @xmath9 and probably has a large spin gap . yet these sizes were not large enough to be sure that this magnet was really in the same class as the kagom magnet . in this work we extend such diagonalizations up to @xmath0 . the technical aspects of these diagonalizations have been previously described@xcite . besides these diagonalizations in the full hilbert space , we also have peformed diagonalizations in the restricted space of first neighbor dimer coverings ( denoted in the following fnss , for first neighbor singlet subspace ) . the size of this restricted subspace is smaller than the @xmath15 sector of the full hilbert space and it increases slower with the system size ( @xmath19 compared to @xmath20 ) . in this restricted basis we have studied samples up to @xmath1 . the fnss calculations for @xmath1 have required an order of magnitude less of computer memory than the full hilbert space calculations for @xmath0 . as usual , periodic boundary conditions are applied to the samples . spectrum of the heisenberg model in the full hilbert space . energy per spin in the ground - state @xmath21 and energy gaps @xmath22 between the @xmath23 energy level of the @xmath24 spin sector and the @xmath25 level of the @xmath26 sector . second line : spin gap . third line : gap between the absolute ground - state and the first singlet excitation . fourth line : gap between the second and third level in the @xmath15 sector . fifth line : gap between the third level in the @xmath15 sector and the first triplet excitation . following lines : @xmath27 is the number of singlet states in the spin gap ( including degeneracies ) . the starred columns correspond to samples which have the extra symmetries of the pyrochlore lattice . the three first columns are 4-spins tubes . [ cols="^,^,^,^,^,^,^,^,^",options="header " , ] Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: circulators are important passive nonreciprocal components which are used both in microwave and optical frequency region . these devices permit mitigate the harmful influence of reflections on the sources of electromagnetic waves . in microwaves , the most popular circulators are based on waveguide and microstrip technology with magnetized ferrite elements @xcite . optical circulators have been also discussed in literature @xcite . in thz region , one of the promising tendencies is graphene technology which allows one , in particular , to construct nonreciprocal devices . recently , an interesting idea of an edge - guided graphene circulator was suggested in @xcite . the device consists of multi - layer graphene - dielectric waveguides and this can complicate its production technology . in this paper , we suggest a graphene circulator with a very simple structure which can be used in thz and infrared frequency region . it consists of graphene nanostrip waveguides connected to a graphene circular resonator . the schematic representation of the circulator is shown in fig . [ figure1]a and [ figure1]b . the width of the waveguides are @xmath0 nm and @xmath1 , that are connected to a circular graphene resonator with the radius @xmath2 nm . the waveguides and the resonator are placed on a lossless dielectric substrate of silicon and silica with the thickness @xmath3 200 nm and @xmath4 600 nm , with relative permittivity @xmath5 11.9 and @xmath5 2.09 , respectively . is dc magnetic field . ] in numerical simulations by the commercial software comsol @xcite , we have used the following parameters of the graphene conductivity tensor @xcite : @xmath6 where @xmath7 is the drude weight , @xmath8 is the miminum conductivity of graphene , @xmath9 is related to chemical potential of graphene @xmath10 is the cyclotron frequency , @xmath11 is the reduced planck s constant , @xmath12 is the electron charge , @xmath13 is the relaxation time , @xmath14 is the frequency of the incident wave and @xmath15 . for numerical proposition , graphene is modeled as a bulk material with a bulk conductivity tensor given by @xmath16 = [ \sigma_s]/\delta$ ] , being @xmath17 $ ] the surface conductiviry tensor , which its component are given by ( [ eq : sig1])-([eq : sig2 ] ) , and @xmath18 is the thickness of the graphene . in all calculations @xmath19 nm . it is well known that graphene stips can suport two kinds of guided surface plasmon polaritons ( spp ) modes , namelly a guide mode and edge mode , which are discussed in details in @xcite . in our case , we have chosen the former one , once the eletromagnetic field in that mode is concentrated in the center of the ribbon , as shown in the insert in fig [ fig : neff ] . the dependence of effective refractive index for different values of frequency , with respect to width of the geraphene ribbon is shown in fig . [ fig : neff ] . profile of guided mode in graphene strip . ] in the following , the transmission coefficient @xmath20 of a signal injected in port @xmath21 and received by port @xmath22 was calculated . the percentage bandwidth of circulator is defined as @xmath23 , where @xmath24 and @xmath25 are the limit frequency value so that the transmission level on a transmission port remain above - 2 db and the isolation level on the isolation port remain below - 15 db at the same time . @xmath26 is the central frequency of operation . the working principle of the circulator is similar to that of the microstrip one . the guided spp wave in the input waveguide excites in the circular resonator in the non - magnetic state two degenerate clockwise @xmath27 and anticlockwise @xmath28 rotating modes . these two modes produce a dipole aligned to the input waveguide , which leads to a transmission in both output ports , as shown in fig . [ fig : desdob]a . a dc magnetic bias of @xmath29 t brakes the degenerency and makes the field pattern of the standing wave to rotate by 60@xmath30 aligning thus the node of dipole with the isolation of port 3 as shown in fig . [ fig : desdob]b . the dependency of these two rotating dipole modes with respect to magnetic field is shown in fig . [ fig : desdob]c . field profile for a ) nonmagnetized and b ) magnetized case , and c ) magnetic field dependency of rotating modes . ] the calculated frequency characteristics are shown in fig . [ fig : s21s31 ] . at a central frequency of 8.23 thz , the device presents a transmission coefficient of -1.2 db , a isolation of -33 db , with a bandwidth of 6.98 % in a transmission level of -2 db and a isolation level of -15 db . by changing chemical potential of graphene , one can change the carrier density in the ribbon , and consequently , the values of the conductivity tensor components . this leads to a possibility of dynamical control of the circulator responses . one can see from , fig . [ fig : mucdep ] , that the central frequency of circulator operation shifts to higher frequencies , when the chemical potencial increases . the opposite situation occurs by diminishing this value . besides by changing @xmath31 , the values of the insertion losses and the bandwidth get worst than those for @xmath32 ev . it can be explained by the fact that the stationary dipole is not property aligned to the output port , but one can see that for values between 0.12 ev and 0.20 ev , these levels are acceptable , as shown in the same figure . in this work we have suggested and confirmed by numerical simulations a possibility of a controllable three - port circulator graphene - based circulator . this component with a very simple structure can be used in thz and infrared circuits . 99 saib , a. , darques , m. , piraux , l. , vanhoenacker - janvier , d. , and huynen , i. , `` an unbiased integrated microstrip circulator based on magnetic nanowired substrate '' , _ microwave theory and techniques , ieee transactions on _ , vol . 53 , no . 6 , 20432049 , 2005 . dmitriev , v. , kawakatsu , m.n . , and de souza , f.j.m . , `` compact three - port optical two - dimensional photonic crystal - based circulator of w - format '' , _ optics letters _ , vol . 37 , no . 15 , 31923194 , 2012 . nikitin , a. yu et al . `` edge and waveguide terahertz surface plasmon modes in graphene microribbons . '' _ physical review b , vol . 84 , no . 16 , p. 161407 he , sailing ; zhang , xizhou ; he , yingran . `` graphene nano - ribbon waveguides of record - small mode area and ultra - high effective refractive indices for future vlsi.''__optics express , vol . 21 , no . 25 , 30664 - 30673 , 2013 . sheng , shiwei et al . analysis of a tunable band - pass plasmonic filter based on graphene nanodisk resonator . optics communications , v. 336 , p. 189 - 196 , 2015 . wang , q. , ouyang , z. , lin , m. and liu , q .. , `` compact photonic crystal circulator with flat - top transmission band created by cascading magneto - optical resonance cavities '' , _ applied optics _ , 54 , no . 33 , 97419746 , 2015 . _ _ _ crassee , i , . levallois , j. , walter , a. l , . ostler , m , . bostwick , a , . rotenberg , e , . seyller , t. , van der marel , d , . and kuzmenko , a. b.,``giant faraday rotation in single - and multilayer graphene '' , _ nature physics . _ , vol . 7 , no . 1 , 48 , 51 , 2011 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: learning from multi - label data has received a lot of attention from the machine learning and data mining communities in recent years . this is partly due to the multitude of practical applications it arises in , and partly due to the interesting research challenges it presents , such as exploiting label dependencies , learning from rare labels and scaling up to large number of labels @xcite . in several multi - label learning problems , the labels are organized as a tree or a directed acyclic graph , and there exist approaches that exploit such structure @xcite . however , in most multi - label learning problems , flat labels are only provided without any accompanying structure . yet , it is often the case that implicit deterministic relationships exist among the labels . for example , in the imageclef 2011 photo annotation task , which motivated the present study , the learning problem involved 99 labels without any accompanying semantic meta - data , among which certain deterministic relationships did exist . for example , among the 99 labels were several groups of mutually exclusive labels , such as the four seasons _ autumn , winter , spring , summer _ and the person - related labels _ single person , small group , big group , no persons_. it also included several positive entailment ( consequence ) relationships , such as @xmath0 and @xmath1 . hierarchies accompanying multi - label data model positive entailment via their is - a edges , but do not model exclusion relationships . these observations motivated us to consider the automated learning of such deterministic relationships as potentially interesting and useful knowledge , and the exploitation of this knowledge for improving the accuracy of multi - label learning algorithms . while learning and/or exploiting _ deterministic _ relationships from multi - label data is not new @xcite , little progress has been achieved in this direction since then . past approaches exhibit weaknesses such as being unsuccesful in practice @xcite , lacking formal theoretical grounding @xcite and being limited to existing is - a relationships @xcite . given an unlabeled instance @xmath2 , multi - label models can output a bipartition of the set of labels into relevant and irrelevant to @xmath2 , a ranking of all labels according to relevance with @xmath2 , marginal probabilities of relevance to @xmath2 for each label or even a joined probability distribution for all labels . the latter is less popular due to the exponential complexity it involves @xcite . among the rest , marginal probabilities are information richer , as they can be cast into rankings after tie breaking and into bipartitions after thresholding . they are also important if optimal decision making is involved in the application at hand , which is often the case . this work presents a sound probabilistic method for enforcing adherence of the marginal probabilities of a multi - label model to automatically discovered deterministic relationships among labels . we focus on two kinds of relationships . the first one concerns pairwise _ positive entailment _ : pairs of labels , where presence of one label implies presence of the other in all instances of a dataset . the second one concerns _ exclusion _ : sets of labels that do not coexist at the same instances of a dataset . these relationships are represented with a bayesian network . marginal probabilities are entered as soft evidence in the network and adjusted through probabilistic inference . our approach offers robust improvement in mean average precision compared to the standard binary relavance approach across all 12 datasets involved in our experiments . the discovery process helps interesting implicit knowledge to emerge , which could be useful in itself . the rest of this paper is organized as follows . section 2 introduces our approach . in particular , section 2.1 discusses the discovery and section 2.2 the exploitation of entailment relationships . section 3 presents related work and contrasts it with our approach . section 4 presents the empirical work , with section 4.1 discussing datasets and experimental setup , section 4.2 presenting samples of the knowledge discovered by our approach and section 4.3 discussing comparative prediction results against binary relevance . finally , section 5 summarizes the conclusions of this work and suggests future work directions . let @xmath3 and @xmath4 be two labels with domain @xmath5 . for simplicity , we will be using the common shortcut notation @xmath6 , @xmath7 , @xmath8 and @xmath9 instead of @xmath10 , @xmath11 , @xmath12 and @xmath13 respectively . the following four entailment relationships can arise between the two labels : 1 . @xmath14 and equivalent contrapositive @xmath15 ( positive entailment ) 2 . @xmath16 and equivalent contrapositive @xmath17 ( positive entailment ) 3 . @xmath18 and equivalent contrapositive @xmath19 ( exclusion ) 4 . @xmath20 and equivalent contrapositive @xmath21 ( coexhaustion ) figure [ fig : contingency ] presents a contingency table for labels @xmath3 and @xmath4 , based on a multi - label dataset with @xmath22 training examples . positive entailment corresponds to @xmath23 or @xmath24 , exclusion to @xmath25 and coexhaustion to @xmath26 . furthermore , @xmath27 corresponds to mutually exclusive and completely exhaustive labels , while @xmath28 corresponds to equivalent labels . [ cols="^,^,^",options="header " , ] + [ tbl : both ] this work has introduced an approach that discovers entailment relationships among labels within multi - label datasets and exploits them using a sound probabilistic approach that enforces the adherence of the marginal probability estimates of multi - label learning with the discovered background knowledge . we believe that our approach can be further extended and improved in a number of directions . an important issue concerns the statistical validity of the extracted relationships , especially when based on infrequent labels . we are working on automatically selecting the minimum support per relationship in order to separate chance artifacts from confident findings , which we expect not only to improve accuracy results , but also to reduce the complexity of the discovery process . on the opposite direction , it would be also interesting to investigate whether approximate relations , where the contingency table frequencies may not necessarily be zero due to noise , can be exploited with improved results . another important direction is the generalization of our approach so as to be able to discover all types of entailments among any number of labels . on the empirical part of this work , we intend to apply our approach to additional datasets and to employ evaluation measures , such as log loss and squared error , that assess the quality of the predicted probabilities . we also intend to drill - down the accuracy results and discuss the extend of improvement for each label involved in one or more relationships . finally , we also intend to investigate the effect that the quality of predicted probabilities has on our approach . dembczynski , k. , cheng , w. , hllermeier , e. : bayes optimal multilabel classification via probabilistic classifier chains . in : proceedings of the 27th international conference on machine learning ( icml ) . ( 2010 ) agrawal , r. , srikant , r. : fast algorithms for mining association rules in large databases . in : proceedings of the 20th international conference on very large data bases . vldb 94 , san francisco , ca , usa , morgan kaufmann publishers inc . ( 1994 ) 487499 zhang , m.l . , zhang , k. : multi - label learning by exploiting label dependency . in : proceedings of the 16th acm sigkdd international conference on knowledge discovery and data mining . kdd 10 , new york , ny , usa , acm ( 2010 ) 9991008 niculescu - mizil , a. , caruana , r. : predicting good probabilities with supervised learning . in : proceedings of the 22nd international conference on machine learning . icml 05 , new york , ny , usa , acm ( 2005 ) 625632 trohidis , k. , tsoumakas , g. , kalliris , g. , vlahavas , i. : multilabel classification of music into emotions . in : proc . 9th international conference on music information retrieval ( ismir 2008 ) , philadelphia , pa , usa , 2008 . ( 2008 ) thomee , b. , popescu , a. : overview of the imageclef 2012 flickr photo annotation and retrieval task . in forner , p. , karlgren , j. , womser - hacker , c. , eds . : clef ( online working notes / labs / workshop ) . ( 2012 ) pestian , j.p . , brew , c. , matykiewicz , p. , hovermale , d.j . , johnson , n. , cohen , k.b . , duch , w. : a shared task involving multi - label classification of clinical free text . in : proceedings of the workshop on bionlp 2007 : biological , translational , and clinical language processing . bionlp 07 , stroudsburg , pa , usa , association for computational linguistics ( 2007 ) 97104 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the basis for the work presented here is our set of chemically consistent spiral galaxy models with a range of star formation histories ( * sfhs * ) specifying the spectral types @xmath0 . our models are very simple 1-zone models without any dynamics meant to describe global quantities of average galaxies of the respective types . our approach is to use the simplest models possible with the smallest number of parameters in order to see how far we can get and what kind of sophistications are required by a comparison with observed galaxy properties . our unified spectrophotometric and chemical evolutionary synthesis models allow to have a large number of observational constraints spectrophotometric properties including gaseous emission and stellar absorption features as well as ism abundances to restrict the small number of model parameters , basically the imf and the sfh . while in the local universe a 11 - correspondance between spectral types and morphological types is a long - standing matter of fact it is also clear that this correspondance has to break down at some yet unknown stage when going back towards the earliest phases of galaxy evolution and formation . the choice of sfhs for the various spectral types is determined by a number of observational constraints . these include type - averaged luminosities , colours from uv through nir for nearby galaxy samples , emission and absorption line properties , template spectra , and hii region abundances that our model galaxies have to match after a hubble time as well as a comparison with observed galaxy luminosities and colours over a large redshift range ( cf . _ 1999 ) . here , we present the chemical evolution aspect of our spectroscopically successful spiral galaxy models and compare to abundances for a series of elements observed in damped ly@xmath1 ( * dla * ) absorbers over the redshift range from @xmath2 through @xmath3 , which corresponds to lookback times of more than 90 % of the age of the universe . originally , dla absorption was thought to arise in intervening ( proto-)galactic disks along the lines of sight to distant qsos ( wolfe 1988 ) . this view is supported by arguments based on mass estimes from column densities and absorber sizes at @xmath4 as well as by kinematic features consistent with rotation at velocities of order 200 @xmath5 ( prochaska & wolfe 1997a , b , 1998 ) . more recently , on the basis of [ @xmath1/fe ] and [ n / o ] abundance ratios and their large scatter , an origin of dla absorption in dwarf or low surface brightness galaxies is also discussed ( matteucci _ et al . _ 1997 , vladilo 1998 , jimenez _ et al . our aim is to see , if and in how far very simple spiral galaxy models are compatible with the observed dla abundance evolution over the large redshift range accessible . in this context it does not matter if dla galaxies at the highest redshifts are not yet fully assembled massive disks but rather consist of galactic building blocks as suggested by haehnelt _ et al . _ our sfhs in this case are meant to describe sf in all the fragments bound to end up in one disk by z @xmath6 . in a second step , we then present the spectrophotometric properties of those galaxy models that succesfully describe the dla galaxy population and discuss them in the context of the large campaigns designed to optically identify dla galaxies both at low and at high redshift . as opposed to star clusters which basically form their stars `` all at the same time '' , i.e. within @xmath7 yr , any stellar system with a sfh more extended than this is expected to feature finite distributions both in age and metallicity . our spectrophotometric and chemical evolutionary synthesis models are * chemically consistent * in the sense that we account for the increasing initial metallicity of successive generations of stars . we keep track of the ism abundance at birth of each star and use various sets of input physics for metallicities in the range @xmath8 \leq + 0.3}$ ] . in particular , we use stellar evolutionary tracks and lifetimes from the padova group ( bressan _ et al . _ 1993 , fagotto _ et al . _ 1994 a , b , c for 0.6 @xmath9 , and from chabrier & baraffe 1997 for @xmath10 , stellar yields and remnant masses from v. d. hoek & groenewegen ( 1997 ) for @xmath11 and from woosley & weaver ( 1995 ) for stars @xmath12 , and model atmosphere spectra and colour calibrations from lejeune _ et al . _ snia contributions are included as described by matteucci & greggio ( 1986 ) and matteucci & tornamb ( 1987 ) with snia yields from nomoto _ et al . _ ( 1997 ) . we use a salpeter imf and sfhs for the various spiral types as follows : @xmath13 @xmath14 + @xmath15 @xmath16 ( g : gas mass , m : total mass ) . characteristic timescales for sf @xmath17 as defined by @xmath18 are [ cols=">,>,^ " , ] we thus would * not * expect low - z dla galaxies to be more easily identified than at least the brighter ones among the high - z dlas . on the basis of these luminosities we understand the non - detection of dla galaxies at z @xmath19 down to @xmath20 @xmath21 ( steidel _ et al . _ 1998 ) and the small number of dla candidates ( 2/10 ) at @xmath22 to k @xmath23 by aragon - salamanca _ et al . _ ( 1996 ) . the galaxies identified by steidel _ et al . _ ( 1994 , 1995 ) as candidates for dla absorbers at @xmath24 indeed have luminosities @xmath25 typical of late - type spirals . however , for their sample of 7 dla identifications in the range @xmath26 le brun _ et al . _ ( 1997 ) find a variety of morphologies : spirals as well as compact and lsb objects . at high redshift , djorgovski _ et al . _ ( 1996 ) and djorgovski ( 1998 ) report identifications of a bright disk galaxy ( @xmath27 ) with sfr @xmath28 in agreement with our models at @xmath29 , and of an @xmath30 galaxy with low sfr at @xmath31 . the two early - type dla galaxies ( @xmath32 ) put foreward by lanzetta _ et al . _ ( 1997 ) at @xmath33 and by miller _ et al . _ ( 1999 ) ( ngc 4203 at @xmath34 ) both show counterrotating gas disks . hi mapping shows ngc 4203 to be abnormally gas - rich ( van driel _ et al . _ these two cases raise the issue that recent accretion or merging may provide favourable conditions for dla absorption . we use very simple spiral galaxy models with standard imf and sfhs chosen as to agree with chemical and spectrophotmetric properties of nearby galaxies as well as with the observed redshift evolution of luminosities and colours . when combined with a chemically consistent description of their chemical evolution and a standard cosmology , we find good agreement with the observed redshift evolution of dla abundances over more than 90 % of the hubble time . we claim that at @xmath35 all spiral types can give rise to dla absorption while towards lower redshifts only the gas - rich metal - poor late spiral types do so . the spectrophotometric properties given by our models for average spiral types are consistent with the few optical identifications of dla galaxies both at low and high - z in large observing programs . steidel , c. c. , pettini , m. , dickinson , m. , persson , s. e. , 1994 , aj 108 , 2046 steidel , c. c. , bowen , d. v. , blades , j. c. , dickinson , m. , 1995 , apj 440 , l45 steidel , c. c. , dickinson , m. , meyer , d. m. , adelberger , k. l. , sembach , k. r. , 1997 , apj 480 , 568 steidel , c. c. , adelberger , k. l. , dickinson , m. , giavalisco , m. , pettini , m. , kellogg , m. , 1998 , apj 492 , 428 de la varga , a. , reimers , d. , 1999 , in _ chemical evolution from zero to high redshift _ , _ in press _ Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the quark model has been introduced fifty years ago @xcite as a realization of the @xmath1 symmetry and it has been used with success for the description of many important properties of hadrons , as the existence of multiplets , their quantum numbers and the magnetic moments @xcite . the idea of quarks as effective particles ( constituent quarks ) emerged very early @xcite and was further developed with the introduction of the colour quantum numbers . here we shall concentrate ourselves on constituent quark models ( cqm ) for baryons . after the pioneering work of isgur and karl ( ik ) @xcite a series of cqm followed : the relativized capstick - isgur model ( ci ) @xcite , the algebraic approach ( bil ) @xcite , the hypercentral cqm ( hcqm ) @xcite , the chiral goldstone boson exchange model ( @xmath2cqm ) @xcite , the bonn instanton model ( bn ) @xcite and the interacting quark - diquark model @xcite . all models reproduce the baryon spectrum , which is the first quantity to be approached when building a model for the baryon structure , but have been widely used to describe baryon properties . in some cases the calculations referred to as a cqm one are performed using a simple h.o . wave function for the internal quark motion either in a nonrelativistic ( ho ) or relativistic framework ( rho ) . the photocouplings for the excitation of the baryon resonances have been calculated in various models , among others we quote ho @xcite , ik @xcite , ci @xcite , bil @xcite , hcqm @xcite ( for a comparison among these and other previous approaches see e.g. @xcite ) . the calculations reproduce the overall trend , but the strength is systematically lower than the data . the fact that quite different models lead to similar results can be ascribed to their common @xmath3 structure . as for the nucleon elastic form factors there are the calculations performed by bil @xcite with the algebraic method and by the rome group @xcite within a light front approach based on the ci model . the hcqm has been firstly applied in the nonrelativistic version with lorentz boosts @xcite and then it has been reformulated relativistically @xcite . a quite good description of the elastic form factors is achieved also using the gbe @xcite and the bn @xcite models , both being fully relativistic . the same happens for the interacting quark - diquark model @xcite , specially in its relativistic version @xcite . a sensible test of both the energy and the short range properties of the quark structure is provided by the @xmath0 behaviour of the helicity amplitudes for the electromagnetic excitation to the baryon resonances . in the ho framework , there are various calculations of the transverse helicity amplitudes , among them we quote refs . @xcite , while a systematic rho approach has been used by @xcite . a light cone calculation , using the ci @xcite model , has been performed @xcite and then successfully applied to the @xmath4 @xcite and roper excitations @xcite . for more recent light cone approaches , see ref . @xcite and references therein . the algebraic method has been also used for the calculation of the transverse helicity amplitudes @xcite . the hcqm , in its nonrelativistic version , has produced nice predictions for the transverse excitation of the negative parity resonances @xcite and , recently , for both the transverse and longitudinal helicity amplitudes of all resonances having a sensible excitation strength @xcite . the calculation of the helicity amplitudes in a relativistic hcqm is in progress and some preliminary results for the @xmath4 resonance are now available @xcite . helicity amplitudes have been calculated also by the bonn group , both for the nonstrange @xcite and strange resonances @xcite . the models have been applied also to the decays of baryons . the strong decays have been quite soon calculated with the ik model @xcite and in its relativized versions @xcite . there are also calculations in other models , namely bil @xcite , gbe @xcite . as for the hcqm , there are some preliminary calculations @xcite . there are also calculations of the semileptonic decays of baryons in the bn model @xcite . finally we quote calculations of the axial nucleon form factors in the gbe @xcite and bn @xcite . the possibility of a nonrelativistic description of the internal quark dynamics was considered very early @xcite after the introduction of the quark model . in this framework , one can introduce the three - quark wave function @xmath5 , factorized according to the various degrees of freedom : @xmath6 in agreement with the pauli principle , the wave function @xmath7 must be totally antisymmetric for the exchange of any quark pair . baryons must be colour singlets and the corresponding wave function @xmath8 is by itself antisymmetric , therefore the remaining factors must be completely symmetric . actually a symmetric quark model has been formulated before the introduction of the colour quantum numbers and the symmetric three - quark states have been classified @xcite . early lattice qcd calculations @xcite showed that the quark interaction can be split into a long range part , which is spin and flavour independent and contains confinement , and a short range spin - dependent one @xcite . this means that one can assume the dominant part to be @xmath3 invariant and the wave function of eq . ( [ 3q ] ) becomes @xmath9 in order to satisfy pauli principle , the product @xmath10 must be symmetric and then both factors @xmath11 and @xmath12 must have the same permutation symmetry , that is symmetric ( s ) , antisymmetric ( a ) or one of the two mixed symmetry types ( ms , ma ) , which are distinguished by the symmetry or the antisymmetry with respect to a quark pair . it should be reminded that each quark belongs to the fundamental @xmath3 representation with dimension 6 and that with three quarks one can obtain the following @xmath3-representations : @xmath13 the corresponding symmetry type is , respectively , a , m , m , s. the suffixes in the r.h.s . denote the multiplicity @xmath17 of the @xmath18 spin states and the underlined numbers are the dimensions of the @xmath1 representations . this means for instance that the @xmath19 representation contains a spin-@xmath20 @xmath1 octect and a spin-@xmath21 @xmath1 decuplet . the various baryon resonances can be grouped into @xmath3-multiplets , the energy differences within each multiplet being at most of the order of @xmath22 as in the case of @xmath23 mass difference and of the splittings within the @xmath1 multiplets . in fig . [ baryon ] we report the experimental non strange baryon spectrum , including only the three- and four- star states @xcite . the notation for the @xmath3-multiplets is @xmath24 , where @xmath25 is the dimension of the @xmath3-representation , @xmath26 is the total orbital angular momentum of the three - quark state describing the baryon and @xmath27 the corresponding parity . an alternative but equivalent notation is @xmath28 , where t is the symmetry type of the @xmath3 representation . the fact that the @xmath29 and @xmath30star non strange resonances can be arranged in @xmath3 multiplets indicates that the quark dynamics has a dominant @xmath3 invariant part accounting for the average multiplet energies , while the splittings within the multiplets are obtained by means of a @xmath3 violating interaction , which can be spin and/or isospin dependent and can be treated as a perturbation . the various constituent quark models are quite different , but they have a simple general structure in common , since in any case , analogously to what stated above , the quark interaction @xmath31 can be split into a spin - flavour independent part @xmath32 , which is @xmath3-invariant and contains the confinement interaction , and a @xmath3-dependent part @xmath33 , which contains spin and eventually flavour dependent interactions @xmath34 in tables [ statpos ] and [ statneg ] , we give the explicit form of the three - quark states with positive and negative parity , respectively . in these tables the hyperradial wave functions @xmath35 are solutions of the hyperradial equation eq . ( [ hyrad ] ) of the text ; their form depends of course on the hypercentral potential . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: observations of galaxies in optical wavebands are strongly influenced by selective extinction which is hard to take into account due to inhomogeneous distribution of dust . by this reason the maps of color and brightness may give distorted picture of photometrical structure of galaxies and distribution of star - formation tracers . in paper @xcite it was proposed to use the combined color index @xmath1 whose value does nt depend on selective attennuation of light to trace the structure of galaxies . in general case for photometric bands a , b , c one can define combined index @xmath2 as @xmath3 to make it as far insensitive to extinction as possible . here @xmath4 is the ratio of color excesses . we have assumed its values for vbri system to be equal to standart values for our galaxy according to @xcite : @xmath5 = 0.840 , @xmath6 = 0.413 , @xmath7 = 2.033 , @xmath8 = 0.681 . as it was shown in @xcite , these ratioes do not depend practically on whether we observe the source through the dust screen or dust and stars are well mixed . similar approach was later used in @xcite to investigate the structure of m 51 . two spiral galaxies - and were observed in bvri colors ( cousins system ) 21 - 22 jan 1988 at 1-m reflector of special astrophysical observatory of russian academy of science . ccd camera 512x512 with scale 0."37/pix was used . data processing was carried out with the help of midas package . asymmetric distribution of colors on the color maps of and gives evidence that they are dusty objects . combined colors indices do not describe neither `` real '' colors nor the value of the extinction . they may be considered as some conditional color indices free ( or nearly free ) of color excesses . the values of @xmath2 depend on stellar population , stellar abundances and , if r band is involved , on the presence of @xmath9 emission ( see @xcite ) . as an illustration , fig.1a shows how the values of @xmath10 , @xmath1 , @xmath0 and @xmath11 change when young stars formed in the single burst with the age t=0.1 gyr are overlapped onto the the old population ( t=13 gyr ) for different relative mass of young stars . the evolution program by + g.worthey ( see @xcite ) was used adopting salpeter imf and [ fe / h]=0 . fig.1b illustrates the dependence of q s on the burst ages for a fixed ( 1@xmath12 ) fraction of young stars . fig 1c shows a variation of q s with the adopted metallicity of the old population for the same parameters of burst as in fig 1b . as it follows from figures 1a - 1c , @xmath0 is the most sensitive to the fraction of young stars . the change of @xmath1 is less significant , but on the other hand this index should allow to localize giant emission regions where @xmath13 line locally increases r luminosity of the disk . in fig.2 and 3 the maps of @xmath0 and @xmath1 distribution for our galaxies are presented . maps are bounded by the ellipses whose major axes equal to @xmath14 . they appear to be much more symmetrically distributed than color indices . curiously a ring - like zone at about 15 " ( 4.7 kpc for @xmath15 ) from the center appears in which is not noticeable at the color maps . it enables to consider this system as the galaxy , where star formation is enhanced in the ring . note that is absent in catalog of a ring galaxies by @xcite ) . @xmath1 map of reveals a clear 3-armed spiral - like structure where the values of @xmath1 have local maxima which may be explained by enhanced emission in @xmath13 ( local equivalent width @xmath16 100 @xmath17 ) . however blue stars do not form a clear spiral structure in this region as one can see from @xmath0 map of the galaxy . we can compare the relative intensity of star formation in different regions of a galaxy using @xmath0 @xmath1 diagram . the toy - model of a galaxy with exponential decreasing @xmath18 was developed using worthey s program ( from @xcite ) . the model values of q s which do not take into account recently formed stars ( t @xmath19 @xmath20 yr ) are shown by continious curve in fig.4 . dashed curve shows the values of the combined indices when the burst of sf is added to the previous model ( young population contains 30@xmath12 of the mass of the background population , has solar metallicity and the age of 0.1 gyr ) . the arrow in fig.4 . shows how @xmath21 emission shifts the point in the diagramm . the model curves show that the increasing of the fraction of young stellar population change mostly @xmath0 . on the other hand the @xmath22 shifts points horizontally . it enables to use the diagram as the diagnostic one for comparizon of star formation in different parts of a galaxy . as an example we put average values of q s for more than hundred points of central region ( diamond ) , regions of sf - ring ( triangle ) and outer regions ( square ) of on the diagram in fig.4 . mean errors of position of the points is about @xmath23 . regions in the center and in the sf - ring have the same @xmath0 which enables to conclude that they have similar fraction of young stars . the difference in @xmath1 may be explained by the presence of @xmath24 emission ( local @xmath25 ) . the outer regions of the galaxy contain a less amount of blue stars . these examples illustrate the ability to investigate structure and distribution of star formation tracers in dusty galaxies using optical broad - band photometry . combined photometrical indices @xmath0 and @xmath1 which are weakly affected by the selective extinction may be used successfully to restore the photometrical structure of galaxies with non - homogeneous dust distribution , even if their dust - free colors remain unknown . index @xmath0 depends on the presence of blue stars which enables to use it to localize regions of recent star formation . on the other hand , @xmath1 weakly depends on the light of blue stars but is sensitive to young star population through the emission in @xmath9 line . whereas color distribution is asymmetric in and due to internal absorption , their @xmath0 and @xmath1 maps are relatively symmetric and allow to reveal structure details hidden by the dust . in a ring - like region evidently related to active star formation is clearly visible at q - maps . in three armed spiral structure and active star formation reveal themselves in @xmath1 map of the galaxy . this research was suported by russian grants rfbr 98 - 02 - 17102 and federal program astronomy . d.b . very appreciates financial support of european space agency to participate to the 33rd eslab symposium . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: quasars , and agn in general , are often supposed to be powered by accretion of gas into supermassive black holes ( bhs ) . in this case , large dormant bhs are expected in the nuclei of nearby galaxies ( soltan 1982 ; rees 1984 ; cavaliere & padovani 1986 ) . assuming accretion at a known fraction of the eddington rate and efficiency of radiation of 10% in units of @xmath0 , it is possible to estimate the expected mass function of dormant bhs . this mass function implies a number density of large bhs ( @xmath1 m@xmath2 ) compatible with the hypothesis that a bh is present in each bright bulge . recent detailed observations of the cores of nearby galaxies have lead to the discovery of massive dark objects in most cases ( magorrian et al . 1998 ; van der marel 1999 ) . even though many details are still uncertain , many authors agree in claiming a correlation between the mass of the massive dark object and the host bulge . interpreting these dark objects as the expected dormant bhs , the bh bulge correlation strongly suggests a connection between quasar activity and the formation of galactic bulges . it is assumed that the accretion of matter onto a bh of mass @xmath3 is a fixed fraction @xmath4 of the eddington rate , so that the quasar luminosity is @xmath5 , where @xmath6 . the efficiency of accretion @xmath4 is assumed to increase from 0.1 for the smallest bhs ( @xmath7 m@xmath2 ) to 1 for the largest ones ( @xmath8 m@xmath2 ) . then , the mass function of dormant bhs is calculated by integrating the luminosity function of quasars ( see salucci et al . 1999a for details ) . we assume that a significant fraction of agns are heavily obscured , and give the dominant contribution to the hard x - ray cosmological background ( see , e.g. , celotti et al . 1995 ; comastri et al . 1995 ; fiore et al . we include such objects using the model of comastri et al . ( 1995 ) . the resulting expected mass function of dormant bhs is shown in fig . 1 ( dashed line ) , for @xmath9 km / s / mpc and @xmath10 . the mass function of dormant bhs residing in nearby galaxies is estimated with two independent methods ( see salucci et al . 1999a for details ) . firstly , the mass function of galactic bulges is convolved with a fiducial bh bulge relation ( a lognormal , with width 0.3 dex and average @xmath11 ) . 1 shows the resulting mass function ( continuous line ) . secondly , exploiting the correlation between radio power from the core of elliptical galaxies and bh mass ( @xmath12 , where @xmath13 , see also franceschini et al . 1998 ) , the radio luminosity function of elliptical cores is convolved with a bh radio power relation to obtain another estimate of the mass function of the dormant objects . the result is again shown in fig . 1 ( points with errorbars ) . the three determinations of the mass function of dormant bhs agree for reasonable values of the parameters involved . this highlights a dichotomy ( in a statistical sense ) in the behaviour of bhs . larger objects ( @xmath14 m@xmath2 ) are hosted in ellipticals , shine as bright quasars at high redshift , almost at the eddington luminosity , are hardly reactivated and hardly obscured , while smaller bhs ( @xmath15 m@xmath2 ) are hosted in the bulges of spiral galaxies , shine also at low redshift with a lower luminosity ( in eddington units ) , and may be reactivated and obscured . the abundance of bhs in the bulges of spiral galaxies is more difficult to estimate . upper limits have been determined by salucci et al . ( 1999b ) by analyzing nearly a thousand rotation curves for spirals . we have constructed an analytical model for the joint formation of ellipticals and quasars in the framework of hierarchical cdm models . the details are given in monaco , salucci & danese ( 1999 ) . in a bulge , quasar activity and the main burst of star formation , which mark the main `` shining phase '' of a galactic dark matter halo , are likely to be close in time ( see , e.g. , hamann & ferland 1993 ; see also best , these proceedings ) . it is supposed that the shining phase of a galactic halo is delayed with respect to its dynamical formation . this delay is assumed to be small for the halos corresponding to large ellipticals , and increasingly larger for smaller halos . in this way the hierarchical order is inverted for halo shining . this is done to reproduce the apparent anti - hierarchical evolution of quasars while preserving a correlation between bulge and bh mass . the mass of the bh formed during the shining phase is assumed to depend on the halo mass , and to be modulated by the same variable which determines the morphological type , so as to obtain a bh - bulge relation . this variable is assumed to be either the spin of the dark matter halo or the fraction of the merging masses at the formation time . the model reproduces successfully the main observable quantities relative both to elliptical galaxies and quasars ; see monaco et al . ( 1999 ) for details . the results shown in this paper are for a flat cdm model with @xmath16 , cosmological constant and @xmath9 km / s / mpc . 2 shows the predicted mass function for the dark matter halos of ellipticals , compared with that inferred from the luminosity function and reasonable hypotheses on the mass - to - light ratios of ellipticals . 3 shows the comparison between the predicted and observed quasar luminosity functions at different redshifts . the data are taken from pei ( 1995 ) , boyle et al . ( 1993 ) ( @xmath17 to 3 ) and kennefick , djorgovski and meylan ( 1996 ) ( @xmath18 ) . boyle b. j. , griffiths r. e. , shanks t. , stewart g. c. , georgantopulos i. , 1993 , mnras , 260 , 49 cavaliere a. , padovani p. , 1988 , apj , 333 , l33 celotti a. , fabian a. c. , ghisellini g. , madau p. , 1995 , mnras , 277 , 1169 comastri a. , setti g. , zamorani g. , hasinger g. , 1995 , a&a , 296 , 1 fiore et al . 1998 , nature , in press franceschini a. , vercellone s. , fabian a. , 1998 , mnras , 297 , 817 hamann f. , ferland g. , 1993 , apj , 418 , 11 kennefick j.d . , djorgowski s.g . , meylan g. , 1996 , aj , 11 , 1816 magorrian j. , tremaine s. , richstone d. , bender r. , bower g. , dressler a. , faber s.m . , gebhardt k. , green r. , grillmair c. , kormendy j. , lauer t. , 1998 , aj , 115 , 2285 monaco p. , salucci p. , danese l. , 1999 , mnras , in press ( astro - ph/9907095 ) pei y.c . , 1995 , apj , 438 , 623 rees , m. j. , 1984 , ara&a , 22 , 471 salucci p. , szuszkiewicz e. , monaco p. , danese l. , 1999a , mnras , 307 , 637 salucci p. , ratnam c. , monaco p. , danese l. , 1999b , mnras , submitted ( astro - ph/9812485 ) soltan a. , 1982 , mnras , 200 , 115 van der marel r.p . , 1999 , aj , 117 , 744 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: quantum chromodynamics ( qcd ) is a gauged theory of the strong interactions . exquisitely predictive in the perturbative high - energy regime , at present a description of the physical states is beyond the reach of the theory . meson spectroscopy allows a more complete understanding of qcd in this non - perturbative realm . heavy meson spectroscopy provides unique insight into the underlying theory without the additional complications associated with the the lighter ( and more relativistic ) mesons . heavy mesons have been studied at @xmath1 colliders for nearly 30 years , however , only selective states compatible with the quantum numbers of the @xmath1 beams are produced directly : other states are populated via subsequent hadronic or electromagnetic decays . often , as is the case with the @xmath2(ns ) mesons , the relevant branching ratios are very small . photon interactions provides a mechanism by which some of these inaccessible mesons are produced directly . in a way that is complementary to @xmath1 interactions , @xmath0 interactions produce particles having final states with @xmath3 of + 1 , where @xmath3 is the charge conjugation number . participating photons can be either virtual or real . virtual photons are an irreducible description of charged particle beams : all e@xmath4e@xmath5 colliders generate virtual @xmath0 luminosity - in the case of pep - ii or kek - ii the virtual luminosity can rival the e@xmath4e@xmath5 luminosity . an alternate mechanism for producing @xmath0 luminosity is with real photons . typically , low energy photons are made to compton - backscatter off of an energetic charged particle beam to produce highly boosted photons . opposing photon beams are kinematically focused and interact to produce real @xmath0 luminosity . although this production mechanism requires the added complication of introducing a laser and associated optics into the interaction region , the substantial benefits include control over the @xmath0 luminosity profile , polarization and magnitude . technology advances in optics and lasers have progressed to the point that one could construct a low energy @xmath0 testbed as a proof - of - principle for the nlc , where it would be possible to singly produce the higgs boson ( whereas it must be produced in pairs at e@xmath4e@xmath5 colliders ) . the potential this offers for doing precision higgs studies is a major driving force behind the impetus for a @xmath0 option at the nlc . for the purposes of this study , however , we restrict our attention to photons with a center of mass energy of 60 gev , which is sufficient for an engineering demonstration . one possible site for the testbed is the stanford linear collider , where polarized electron beams meet opposing positrons beams at center - of - mass energies up to the mass of the z@xmath6 . in this proceeding we demonstrate that with suitable choice of laser and optics parameters the resulting @xmath0 luminosity can be made to exceed the virtual @xmath0 luminosity from e@xmath4e@xmath5 colliders . this luminosity can thus serve as the basis for a physics program at the testbed facility , e.g. , heavy quarkonia studies . in subsequent sections we compare and contrast real and virtual @xmath0 luminosities and discuss the implications for heavy quark meson spectroscopy . depending on the energy transfer scale the structure of an otherwise featureless photon can be resolved , resulting in an irreducible hadron and leptonic background that would complicate precision higgs measurements . hence , a primary goal of a @xmath0 testbed would be to measure the @xmath0 luminosity and compare the result with simulation . in this study compton - backscattered luminosity was simulated with cain 2.1e @xcite using the laser and beam parameters listed in table [ tab : t1 ] , where the electron and laser polarizations refer to circular polarization . .beam and laser parameters used to characterize the real photon luminosity at linx . [ cols="^,^,^,^ " , ] the phythia interface to pandora allows events to be written in stdhep format @xcite , which in turn are read in by the lcdroot @xcite - a detector simulation and analysis framework based on root @xcite . in this analysis the p@xmath7 final states and background were propagated through a small version of a hypothetical nlc detector whose electromagnetic and hadronic calorimeters reside in 5 t magnetic field . details of the detector @xcite are not crucial to the results . passage of p@xmath7 through the detector simulation results in momenta smearing . in the hadronic calorimeter the momenta is inferred . for this analysis only inclusive decays to p@xmath7 are considered , thus all particles reaching the hadronic calorimeters were assumed to have the mass of a proton . with this information and the total energy measured in the electromagnetic calorimeter the four vector is constructed and the invariant mass is calculated . figure [ fig : events ] is a reconstruction of the invariant mass of events leaving a track in the hadronic calorimeter subject to the restriction that @xmath8 0.6 and @xmath9 2.75 gev . the total number of reconstructed events ( 26,494 ) found in the last column of [ tab : final ] is significantly fewer than the 32,527 stdhep events input into lcdroot . this is an artifact stemming from the fact that kinematic cuts were not imposed on the meson events within pandora but rather inside lcdroot . for the isotropically decaying mesons the fraction lost is consistent with the restricted phase space imposed by the angular cuts . the meson events clearly stand out above the p@xmath7 background , although additional analysis is needed to determine whether it is possible to separate out @xmath10 and @xmath11(2s ) events . a thorough description of these results , including a complete treatment of the non - isotropic decay of the @xmath12 , will appear elsewhere . a @xmath0 interaction region has been proposed for the nlc using compton - backscattered photons . technical challenges integrating the optical , laser and mechanical subsystems suggest the desirability of a low - energy testbed . in this paper we address one aspect of a physics program that could accompany such a test bed - heavy meson production - and compare it with similar meson production expected where virtual photons are the means of production . we find that after a single year of operation the number of charmed mesons seen at a linx facility equals or exceeds the number generated at either babar+belle or lep to - date . linx is especially dominant when producing bottom mesons , offering the exciting possibility of discovering @xmath2(ns ) mesons before the lhc begins delivering data toward the end of this decade . the authors would like to thank prof . robert nisius for helpful insight into the virtual photon methodology . http://opal.web.cern.ch/opal/ k. f. von weizsacker , z. physik 88 , 612 ( 1934 ) , + e. j. williams , phys . 45 , ( 1934 ) 729 . http://www-sldnt.slac.stanford.edu/nld/new/docs/generators/pandora.htm delphi collaboration , j. abdallah , et al , eur . c31 ( 2003 ) 481 aleph collaboration , phys.lett . b530 , ( 2002 ) 56 v. m. budnev et al . 15 , ( 1975 ) 181 ch .- ch . kuo et al . , nucl . phys.b ( proc . suppl . ) 126 , ( 2004 ) 313 http://www-cpd.fnal.gov/psm/stdhep/ http://www-sldnt.slac.stanford.edu/nld/new/docs/lcd_root/root.htm http://root.cern.ch/ http://wwwal.kuicr.kyoto-u.ac.jp/www/accelerator/sspm/iwasaki.pdf Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: black holes are the most enigmatic objects in the universe . last forty years , several space missions have gathered data from these objects , and yet , a true and complete understanding of the physical processes around black holes has remained a mystery . while the quality and quantity of data have gone up exponentially , they were motivated by general properties of compact objects and not by specific properties of black holes . for example , none of them were geared towards capturing the outcome of solutions around black holes . because of these even after watching hundreds of objects ( in random time intervals ) , the model builders have to explain each object on a case by case basis . theoreticians have lesser choice , as they believe that whatever is observed are to be explained from solutions of equations with appropriate boundary conditions . thus continuous observations would allow them to refine the equations , adding more terms and obtain better solutions . day by day , it becoming clearer from the observational facts ( e.g. , soria et al . 2001 ; smith et al . 2001 , 2002 , 2007 ; wu et al . 2002 ; shaposhnikov & titarchuk , 2006 ; shaposhnikov et al . 2007 ) that accretion flows have a substantial amount of sub - keplerian components as was predicted long ago ( chakrabarti , 1990 ; chakrabarti & titarchuk , 1995 ; chakrabarti , 1996 ) . with a pair of cspobs ( chakrabarti et al . 2007 ) , for the first time , we will be able to answer questions like : how should the standard model of accretion of matter be modified ? what are the roles played by a non - keplerian or sub - keplerian flow and how do they change with time ? how does the variation of the accretion rates of the keplerian and sub - keplerian flow reflected in the light curves , spectral and timing properties ? can we distinguish between various models of compton cloud which range from a magnetic corona to the puffed up post - shock flow called cenbol ? what is the origin of the fast oscillations ( quasi - periodic oscillations or qpos ) observed at high energies and , why do they occasionally appear with frequencies in certain ratios ? how important is the magnetic field in the dynamics of the accretion flow and the jet ? is there a relationship between iron the line emission shape and the qpo frequencies ? do we really know where the iron line comes from , the disk or the jet ? etc . the instruments that we plan to fabricate is simple and is solely dedicated to observe only half a dozen black holes ( unless , of course , some more exciting transient black holes divert its attention ) in its lifetime . the payloads are restricted to be about 20 kilograms each . each cspob will be a 640 @xmath0 si - pin photo - diode based array of detectors which is sensitive in the @xmath1 kev range . large area si drift detectors are also being studied as an alternative . both would be equally good to have @xmath2 energy resolution . the data in 256 energy channels will be stored every 100 sec and thus time resolved spectra would be obtained and time lags / leads in keplerian and sub - keplerian components , light curve variations of intriguing objects such as grs 1915 + 105 etc . there would be two all sky proportional counters ( aspcs ) . it will revolve with the satellite and scan the sky for new outbursts . indian centre for space physics is developing si - pin detectors and also collaborating with other national and international organizations to fly this simple tool in near future . a multi - wavelength large scale mission is _ not _ suitable for our purpose . to our knowledge no mission has been proposed so far to observe a single celestial body other than cspob if one excludes bodies within our solar system . we now briefly summarize the reasons why we believe that continuous observation is essential . first of all , black holes having kerr radius @xmath3 is very small , about @xmath4 km for a nano - quasar of with a rapidly spinning black hole of mass @xmath5 . the light crossing time is only @xmath6s . a black hole accretion being necessarily transonic ( chakrabarti , 1990 ) , the flow close to the black hole is relativistic . the infall time - scale in a keplerian flow vary with viscosity and it can take a few days for the matter to come from the outer edge to the inner edge . but the net inflow is known to have a substantial amount of almost freely falling sub - keplerian matter and indeed this determines the emitted spectrum and its variability unless the spectrum is very very soft . high frequency qpos suggest that the emitted intensity does change in a matter of a few tens of milliseconds . the low and intermediate frequency qpos , which are more common , change in a matter of seconds or less and are well explained by rapidly oscillating shocks originating in sub - keplerian flow . class transitions in objects like grs 1915 + 105 take place in a matter of few seconds , and their nature change totally in a matter of a few hours ( chakrabarti et al . 2004 ; choudhury et al . this volume ) . some of these involve luminosity variations by orders of magnitude . thus it is obvious that all these can happen only if the local effects are important which are triggered by sub - keplerian flows . a constant vigil is required to really understand how the accretion rates of the keplerian and sub - keplerian flows change with time . constant observation of black body and power - law components would give the variation of geometry close to the inner edge since the power - law component is produced from the interception of the soft - components . we justify the goal to observe continuously celestial objects other than the sun and present a viable mechanism to do a thorough study using a pair of small satellites . we require to observe both the soft and the hard components of the galactic black hole candidates . we are studying the feasibility of the si - pin based photo - diodes ( bhoumik et al . this volume ) as well as si drift detectors for this purpose . details will be presented elsewhere . 12 chakrabarti , s.k . , 1990 , theory of transonic astrophysical flows , world scientific publications , singapore . chakrabarti , s.k . , 1996 , apj , 464 , 664 chakrabarti , s.k . , nandi , a. , choudhury , a. & chatterjee , u. 2004 , astrophys . j. 607 , 406 chakrabarti , s.k . et al . , 2007 , isro - proposal for small satellite , csp - technical report-01/07 . chakrabarti , s.k . & titarchuk , l.g . , 1995 , apj , 455 , 623 smith , d. , heindl , w.a . & swank , j.h . , 2002 , apj , 569 , 362 smith , d.m . , heindl , w.a . , markwardt , c.b . & swank , j.h . , 2001 , apj , 554 , l41 smith , d.m . , dawson , d.m . & swank , j.h . , 2007 , apj , 669 , 1138 soria , r. , wu , k. , hannikainen , d. , mcmollough , m. & hunstead . , r. , 2001 , in ` x - ray emission from accretion onto black holes ' , eds . t. yaqoob and j.h . krolik , p. 65 , astro - ph/0108084 shaposhnikov , n. et al . , 2007 , apj , 655 , 434 shaposhnikov , n. & titarchuk , l. g. , apj , 2006 , 643 , 1098 ( st06 ) wu , k. , soria , r. , campbell - wilson , d. , et al . , 2002 , apj 565 , 1161 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: among the most important unsolved questions concerning the behavior of matter inside neutron stars , it is the knowledge of the thermodynamic conditions at which the deconfinement transition to quark matter would occur @xcite . the analysis of such problem is complicated by the uncertainties in the knowledge of the equation of state ( eos ) above the nuclear saturation density , as well as by the lack of a satisfactory description of both hadronic a deconfined matter within a unified description ( however see @xcite for work in this direction ) . a possible approach , is to analyze the transition within a two - phase description in which an hadronic model valid around the nuclear saturation density @xmath2 is extrapolated to larger densities and a quark model that is expected to be valid only for asymptotically large densities is extrapolated downwards . within this kind of analysis some work has been performed recently in order to determine the effect of different hadronic and quark equations of state , as well as the effect of different astrophysical environments : e.g. different temperatures , effect of color superconductivity , effect of neutrino trapping @xcite . an important characteristic of the deconfinement transition in neutron stars , is that quark and lepton flavors must be conserved during the transition @xcite . as a consequence , just deconfined quark matter is transiently out of equilibrium with respect to weak interactions ( for a short period of @xmath3 s ) . when color superconductivity is included together with flavor conservation , the most likely configuration of the just deconfined phase is two - flavor color superconducting ( 2sc ) provided the pairing gap is large enough @xcite . in a recent paper @xcite we have investigated the role of color superconductivity in the deconfinement transition in protoneutron star ( pns ) conditions employing the nambu - jona - lasinio ( njl ) model for just deconfined quark matter . while early calculations showed that neutrino trapping may preclude the transition in pnss @xcite , the results in ref . @xcite show that color superconductivity compensates this effect resulting a transition density that is nearly constant throughout the deleptonization stage . however , a full calculation including both effects has not been done yet within the mit bag model . in the present paper we shall analyze the deconfinement transition in protoneutron star conditions employing for hadronic matter a nonlinear walecka model which includes hadrons , electrons , and electron neutrinos in equilibrium under weak interactions . for the just deconfined quark matter we shall employ the mit bag model including the effect of color superconductivity and neutrino trapping . according to numerical simulations @xcite , during the first tens of seconds of evolution the protoneutron star cools from @xmath4 mev to temperatures below @xmath5 mev . in the same period , the chemical potential of the trapped neutrinos evolves from @xmath6 mev to essentially zero . this paper extends previous calculations performed in ref . @xcite . in that paper we showed that the transition density for bubbles with radii around @xmath7 fm is almost coincident with the bulk transition density and that the nucleation rate of such droplets is huge . this fully justifies a more detailed treatment of several aspects of the deconfinement transition , without including surface effects at all . in view of this , we investigate here the effect of other parametrizations of the hadronic equation of state ( gm1 and nl3 ) , the effect of hyperons in the hadronic phase , we explore more parameters of the quark model , and analyze in more detail the effect of trapped neutrinos and color superconductivity . the article is organized as follows . in sec . 2 we present the main aspects of the equations of state . in sec . 3 we study the deconfinement transition at finite temperature for different parametrizations of the equations of state and different neutrino trapping conditions . 4 we discuss our results and compare them with previous calculations using the njl model in the description of quark matter . for the hadronic phase we use a non - linear walecka model @xcite for matter with and without hyperons . for matter with hyperons we include the whole baryon octet , electrons , electron neutrinos , and the corresponding antiparticles . for matter with no hyperons we consider nucleons , electrons , electron neutrinos , and the corresponding antiparticles . the lagrangian is given by @xmath8 where the indices @xmath1 , @xmath9 and @xmath10 refer to baryons , mesons and leptons respectively . for the baryons we have @xmath11\psi_b,\end{aligned}\ ] ] with @xmath1 extending over the nucleons @xmath12 , @xmath13 and the following hyperons @xmath14 , @xmath15 , @xmath16 , @xmath17 , @xmath18 , and @xmath19 . the contribution of the mesons @xmath20 , @xmath21 and @xmath22 is given by @xmath23 where the coupling constants are @xmath24 electrons and neutrinos are included as a free fermi gas , @xmath25 , in chemical equilibrium with all other particles . for details on the explicit form of the equation of state derived from this lagrangian the reader is referred to ref . the equation of state can be solved numerically by specifying three thermodynamic quantities , e.g. the temperature @xmath26 , the mass - energy density @xmath22 and the chemical potential of electron neutrinos in the hadronic phase @xmath27 . the constants in the model are determined by the properties of nuclear matter and hyperon potential depths known from hypernuclear experiments @xcite . in the present work we use the gm1 parametrization given by @xcite and the nl3 parametrization given by @xcite , as shown in table [ table1 ] . for each parametrization we construct an equation of state including nucleons plus leptons and another one including the baryon octet plus leptons . they are labeled as gm1npe@xmath28 , gm1hyp@xmath28 , nl3npe@xmath28 and nl3hyp@xmath28 . the maximum masses @xmath29 of hadronic stars are 1.78 @xmath30 for gm1npe@xmath28 , 2.32 @xmath30 for gm1hyp@xmath28 , 1.95 @xmath30 for nl3npe@xmath28 and 2.7 @xmath30 for nl3hyp@xmath28 . except for gm1npe@xmath28 , these masses are compatible with the masses of the pulsars psr j1614 - 2230 with @xmath31 @xcite and psr j0348 + 0432 with @xmath32 @xcite . the parametrization for the hyperon coupling constants in the case of gm1 is @xmath33 , @xmath34 and @xmath35 @xcite . for nl3 we use @xmath36 , @xmath37 , @xmath38 , @xmath39 , @xmath40 and @xmath41 @xcite . .parameters of the hadronic equation of state . the parametrizations for the hyperon coupling constants and the maximum masses of hadronic stars are given in the text . [ cols="^,^,^,^,^,^",options="header " , ] the final configuration of the star after the transition depends on many issues that are out of the scope of the present paper , such as the presence or absence of mixed phases , the phase diagram of color superconducting quark matter in beta equilibrium , or the effect of rotation . in particular , we notice that the maximum allowed mass for each model is strongly affected by the distribution of the angular velocity in the radial direction and by the consequent degree of differential rotation @xcite . in view of this , having @xmath42 through the integration of a simple static tolman - oppenheimer - volkoff equation should not be considered as a necessary condition for consistency of our calculations with observations . anyway , we notice that some of the here used models give static stable stars when the quark phase is in the cfl state and no mixed phases are considered . for example , for @xmath1=80 mev @xmath43 and large enough @xmath44 stable cfl strange stars with @xmath42 are obtained by @xcite . for stable static hybrid stars with @xmath1 = 337 and 353 mev @xmath43 the reader is referred to @xcite and references therein . a final comment is worthwhile concerning the formation of mixed hadron - quark phases , in which the electric charge is zero globally but not locally , i.e. the two phases have opposite charges @xcite . mixed phases can not form in the here studied just - deconfined phase @xcite , because the flavor conservation condition guarantees that a just - deconfined quark - matter drop initially has exactly the same electric charge as the hadronic drop from which it originated ( i.e. zero ) . of course , charge separation could occur later on ( if energetically preferred ) and a mixed phase could form . however , notice that debye screening effects and the surface tension can prevent mixed phases to form ( see e.g. @xcite and references therein ) . in any case , this study of mixed phases concerns the state of the system at times that are much longer than the ones that are addressed in this paper . within the mit bag model , the expected effects on protoneutron star evolution are as follows . when a pns is formed it is hot and it has a large amount of trapped neutrinos . if color superconductivity were not considered , cooling will increase the transition density while deleptonization will decrease it @xcite . since both effects compete which each other it is possible that the transition is inhibited in the initial moments of the evolution of neutron stars @xcite . as shown in the present paper , when color superconductivity is taken into account , the decrease of temperature decreases the transition density ( due to the increase of the pairing gap ) . therefore , both cooling and deleptonization of the pns increase the probability of deconfinement as the pns evolves . t. a. s. do carmo acknowledges the financial support received from capes . g. lugones acknowledges the financial support received from fapesp . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: there has been considerable recent interest on the general dynamics of the glass transitions in bulk polymer systems@xcite . a central experimental law which controls the rate of transition was long ago formulated by vogel , fulcher and tammann@xcite ; the empirical vft law of transition rates reads @xmath0 \right\ } , \label{intro1}\ ] ] wherein @xmath1 is the free energy of thermal activation . the vft thermal activation law is quite similar to the well known arrhenius@xcite thermal activation law except for the temperature singularity in the denominator on the right hand side of eq.([intro1 ] ) . the singularity occurs at a dynamical temperature @xmath2 which is somewhat lower than the thermodynamic glass transition temperature @xmath3 . the singularity is thereby never quite attained . nevertheless , the critical slowing down of the vft eq.([intro1 ] ) is experimentally well obeyed in bulk polymer glasses . there exist somewhat different physical views@xcite as to why the vft law might theoretically be true . nevertheless there is presently no agreed upon theory of eq.([intro1 ] ) . our purpose is to derive the vft thermal law through the following quite simple quantum mechanical considerations . the transition rate per unit time for an activated process involves an absolute squared transition amplitude ( matrix element ) times a density of final states . the logarithm of the density of final states represents the final entropy . thus , the quantum mechanical rule for computing transition rates is that @xmath4 , \label{intro2}\ ] ] wherein @xmath5 is the entropy of activation to a state with energy @xmath6 . the theoretical problem is to deduce the nature of the excitations@xcite and compute the entropy of activation from the the logarithm of the final state phase space magnitude @xmath7 the polymer glass excitation configurations@xcite pictured in fig.[fig1 ] are of two types : ( i ) there are - in the bulk of the polymer - closed chains of atoms referred to as _ closed _ strings . ( ii ) also , there are open polymer chains which begin and end on the boundary surfaces of the bulk polymer and are referred to as _ open _ strings . it will be shown below that the closed strings have an entropy obeying the vft thermal activation eq.([intro1 ] ) . on the other hand , the open string configurations with end points in the neighbourhood of surface boundaries obey shifted thermal activation laws . the distinction between the thermal activation properties of open and closed strings is crucial for an understanding of surface effects which are of importance for thin films@xcite . the vft thermal activation law holds only for the bulk polymer . by contrast , the dynamical sinularity temperature @xmath2 decreases as the ratio of boundary surface are to the bulk volume , @xmath8 , increases . consequently , the singularity temperature is sharply lowered@xcite when @xmath9 is decreased to a few nanometers . closed polymer chains in the form of `` polygons '' are treated as a self avoiding random polygons . the number of _ closed self avoiding polygon _ polymer chains containing @xmath10 links is thought to obey@xcite @xmath11 wherein @xmath12 denotes the connectivity . the de gennes scaling law@xcitein @xmath13 dimensions for the exponent @xmath14 is given by @xmath15 wherein @xmath16 is the fractal dimension of the complete closed chain configuration . in mean field theory@xcite we have @xmath17 if @xmath18 denotes the activation energy per link for a mobile closed chain ( closed string ) , then the energy @xmath19 determines the entropy via eqs.([intro3 ] ) , ( [ closed1 ] ) and ( [ closed4 ] ) according to @xmath20 wherein @xmath21 the activation entropy as a function of energy exhibits a minimum as shown in fig . [ fig2 ] . for stable entropy functions , the maximum entropy principle dictates upward convexity while metastable entropy functions exhibit downward convexity . since the density of final states @xmath22 , rates become slower as the minimum activation entropy is approached . in terms of the temperature @xmath23 , @xmath24 we have at @xmath2 the activated energy singularity @xmath25 . \label{closed8}\ ] ] eqs.([closed3 ] ) , ( [ closed5 ] ) and ( [ closed8 ] ) imply @xmath26 \nonumber \\ & \ & \ -(3-\alpha)k_b\ln \left[\frac{(t}{(t - t_0)}\right ] . \label{closed9}\end{aligned}\ ] ] using eqs.([intro2 ] ) , ( [ closed3 ] ) and ( [ closed9 ] ) , we may now complete the proof that the closed chain activation law has the vft form given by eq.([intro1 ] ) . explicitly , we have @xmath27^{2.8 } \nu_\infty e^{s_\infty /k_b}\ . \label{closed10}\end{aligned}\ ] ] in practice , the vft activation process is often observed by measuring viscosity , @xmath28 wherein @xmath29 is the mass density and @xmath30 is the length scale of the polymer links . in this regard , the prediction for the activation free energy @xmath31 is subject to an experimental test of the scaling critical index in eq.([closed2 ] ) . consider the problem of how much activation energy would be required to remove a given section of chain from the condensed matter piece of polymer . if the given section of chain were deep within the polymer , the removal would be quite difficult . for example , if one exerted a force on the given chain section , then it would become knotted with other polymer chain sections and would be rendered immobile . on the other hand , if the given section of chain was entirely located in the neighborhood of the surface boundary of the polymer , then it would be relatively easier to peel the chain off the surface . let us consider , in more detail , the activation energy to slide a section of polymer chain along a given path . such an activation energy has been denoted above as @xmath32 per link of the chain section . furthermore , let @xmath33 denote the distance from a chain link to the boundary surface . by the above physical arguments we expect @xmath34 to sharply decrease as @xmath35 . from eq.([closed6 ] ) we expect , for uniform connectivity ( @xmath36 ) , the dynamical singularity temperature to be a decreasing function of @xmath33 varying as @xmath37 in a local density theory@xcite , @xmath38 may be parameterized by @xmath39 in which the coherence length is related to the density @xmath40 the @xmath41 relation invalidates the vft eq.([intro1 ] ) for the case of very thin polymer films . a derivation has been provided for vft activated transition rates in bulk polymer glasses . our derivation depends on the micro - canonical counting of the number of closed polymer chain configurations within the bulk glassy system . the configuration counting is mapped into the self avoiding polygon problem . the activation energy @xmath18 per link determining the chain mobility also determines the dynamical glass transition temperature in the empirical vft law . the critical indices employed are calculated as in flory s theory . the chain movements also lend strong support to `` co - operative '' motion inside the bulk . it is also to be stressed that the dynamical glass transition temperature , @xmath42 , varies with the distance from the surface boundary through that a coherence length scale of about a few nanometers . this surface effect is due to the fact polymer strings localized near the surface boundary are more mobile than the polymer chains embedded in the bulk . for sufficiently thin films , the vft activation law thereby becomes modified as in eqs . ( [ se1 ] - [ se3 ] ) . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: young pulsars are relatively rare objects in the pulsar population because they evolve rapidly , so on average their distance is relatively high . they are usually found at low galactic latitudes , close to their places of birth , where their detection is limited by the high background temperature and by the broadening of pulses due to dispersion and interstellar scattering . on the other hand , they are interesting objects for many reasons : they are likely to be @xmath0ray sources ; they exibhit rotational _ glitches _ , which are of interest in the understanding of the interior structure of neutron stars ; they are likely to be associated with supernova remnants . high frequency ( @xmath1 @xmath2 1400 mhz ) surveys ( clifton et al , 1992 ; johnston et al 1992 ) and searches ( kaspi et al , 1996 ; manchester , damico & tuohy , 1985 ) for young , low latitude distant pulsars proved to be successful , because the contribution of the galactic synchrotron radiation to the radiotelescope system temperature is highly reduced , because the effect of dispersion is more easlily removed , and because the broadening of pulses due to interstellar scattering varies with frequency aproximately as @xmath3 . .three 20 cm pulsar surveys [ cols="<,<,<,<",options="header " , ] triggered by the above motivations , we are undertaking a new survey for pulsars along the galactic plane at 1.4 ghz , using the 13-element multibeam receiver recently installed on the 64-m parkes radiotelescope . in this paper we present the experiment configuration , the survey plan and the preliminary results of about 50% of the survey . each beam of the multibeam receiver system at parkes is approximately 0.23@xmath4 wide and the beams centres are spaced 2 beamwidth apart ( see fig . the survey pointings are interleaved to give complete sky coverage on a hexagonal grid containing a total of 2670 pointings of 13 beams each . the parameters of the present experiment and those of two previous high frequency surveys of the galactic plane are summarized in table 1 . thanks to the long integration time adopted ( 35-min ) and the high sensitivity of the new receiver system , the present survey has a sensitivity 7 times better than previous surveys . fig 2 . shows the theoretical sensitivity as a function of the pulsar period and dispersion measure . so far we have observed about 1600 pointings , 90% of which are analysed , corresponding to about 50% of the total survey region . the data reduction system is similar to that used in the parkes low frequency survey ( manchester et al , 1996 ) , and is carried out on a network of workstations . because of the relatively long integrations adopted , we complement the standard search analysis with `` acceleration search '' to take into account possible binary motions . to date we have discovered 513 new pulsars , and have detected 190 known pulsars . accounting for the fact that so far we searched the regions closest to the galactic plane , we believe that the number of new discoveries for the entire survey should be somewhat over 800 . timing observations of the newly discovered pulsars are carried out at jodrell bank and parkes . observations are made at intervals of 4 8 weeks , or more closely spaced when pulse - counting statistics need to be resolved . full timing solutions have been obtained so far for 80 pulsars . at least eight of the new discoveries are young pulsars ( @xmath5 @xmath6 10@xmath7 years ) . two radio pulsars with the highest known surface magnetic field have been discovered ( kaspi et al , these proceedings ) . one of these objects , psr j1119 - 6127 is very young , with as characteristic age , @xmath5 = 1600 years . for this pulsar we also measured a braking index @xmath8=3.0@xmath90.1 . so far , eight of the newly discovered pulsars proved to be members of binary systems , including a pulsar ( psr j1811 - 1736 ) in a highly eccentric binary system ( lyne et al 1999 ) and a pulsar ( psr j1740 - 3052 ) with a very massive companion ( @xmath2 11 m@xmath10 ) . the basic parameters of the binary pulsars are shown in table 2 . lcccccc psr j & @xmath11 & @xmath12 & distance & @xmath13 & ecc . & @xmath14 + & ( ms ) & ( @xmath15 y ) & ( kpc ) & ( d ) & & ( @xmath16 ) + j1232@xmath176501 & ! 88.28 & 1400 & 10.0 & ! ! 1.863 & 0.00 & ! 0.15 + j1904 + 04 & ! 71.09 & & ! 4.0 & ! 15.750 & 0.04 & ! 0.23 + j1810@xmath172005 & ! 32.82 & 4000 & ! 4.0 & ! 15.012 & 0.00 & ! 0.29 + j1453@xmath1758 & ! 45.25 & & ! 3.3 & ! 12.422 & 0.00 & ! 0.88 + j1435@xmath1760 & ! ! 9.35 & & ! 3.2 & ! ! 1.355 & 0.00 & ! 0.90 + + j1811@xmath171736 & 104.18 & ! 950 & ! 5.9 & ! 18.779 & 0.83 & ! 0.87 + j1141@xmath176545 & 393.90 & ! ! ! 1.45 & ! 3.2 & ! ! 0.198 & 0.17 & ! 1.01 + + j1740@xmath173052 & 570.31 & ! ! ! 0.36 & 10.8 & 231.039 & 0.58 & 11.07 + Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the draco dwarf spheriodal galaxy was first extensively studied by baade & swope ( 1961 ) , who identified 260 variable stars in their survey , determining periods and photographic b light curves of 138 variables . goranskij ( 1982 ) and nemec ( 1985 ) reanalyzed the baade & swope observations , finding 10 double - mode rr lyraes ( rrd ) . in this current survey of draco , we present our photometric results of 268 rr lyraes and 8 anomalous cepheids . the draco dwarf spheroidal galaxy is a metal poor system with an @xmath0 } \rangle$ ] @xmath1 ( mateo , 1998 ) . draco has a well populated red horizontal branch ( hb ) . however , compared to a metal poor globular cluster such as m15 , draco has a sparsely populated blue horizontal branch . the data were obtained from two sources : the 1.0 m telescope at the united states naval observatory ( usno ) - flagstaff station and the 2.3 m telescope at the wyoming infrared observatory ( wiro ) . the observations spanned over two years , from june 1993 to july 1995 . there were between 40 to 60 observations in @xmath2 and @xmath3 . the images were reduced using the standard iraf ccd reduction packages while the photometry was done with the stand alone versions of daophot ii and allframe ( stetson , 1987 , 1994 ) . to find the periods , two methods were utilized : a date compensated discrete fourier transform supplemented by phase dispersion minimization ( stellingwerf , 1978 ) . we have increased the number of rrd stars from the original 10 to at least 26 . prior to this work , five anomalous cepheids were known to be in the draco dwarf galaxy , and to this number we have added three more . in the period - magnitude diagram , fig.1 , a clear separation between the ab and cd type rr lyraes is shown . nemec ( 1988 ) proposed that two period - luminosity ( p - l ) relationships exist depending on the pulsational mode ( fundamental or first overtone ) of anomalous cepheids for five dwarf spheroidal galaxies . three of the newly discovered anomalous cepheids of draco fall close to nemec s fundamental mode p - l relation , but it is not clear if the draco cepheids fall along two distinct p - l relations . = 6.5 cm a period - amplitude diagram for draco rr lyraes is presented in figure 2 . here we have overlaid the oosterhoff i ( m3 ) and oosterhoff ii ( @xmath4 centauri ) trend lines for rrab stars ( clement & rowe , 2000 ) . the draco rrab stars appear to mostly fall along or are close to the oosterhoff i line . in comparison , galactic globular clusters that are more metal poor than [ fe / h ] = -1.7 are classified as oosterhoff ii . = 6.5 cm lee et al . ( 1990 ) provide a plausible explanation for this contradiction in oosterhoff classification in draco . rr lyraes in oosterhoff ii globular clusters are originally on the blue horizontal branch and evolve away from their zero - age horizontal branch positions . as they evolve , the stars become brighter and redder . according to ritter s relation , as the star gets brighter , the period becomes longer . since draco has a sparsely populated blue horizontal branch , this is not the best description for this system . if the draco rrab stars are not as evolved as those in a metal poor globular cluster , then these stars are fainter , have shorter periods , and hence fall closer to the oosterhoff i trend line . however , the rrc and rrd stars of draco have periods similar to those found in oosterhoff ii globular clusters . only one rrd star was found to be similar to oosterhoff i globular cluster rrd stars . some c - type rr lyraes are also like oosterhoff i stars , but a majority of them are oosterhoff ii . detailed modeling for different evolutionary scenarios is needed to see how difficult it is to explain the different oosterhoff properties of rrab and rrcd stars . in this paper we presented our results from @xmath2 band photometry only . @xmath2 and @xmath3 colors are being determined . we will also be investigating the prevalence of the blazhko effect among the rr lyraes in draco and the radial distributions of the variable stars . this work has been supported in part by the national science foundation under grants ast-9528080 and ast-9986943 . snyder was partially supported by the nsf reu grant 991221 . baade , w. & swope , h. 1961 , , 66 , 300 clement , c. & rowe , j. 2000 , , 120 , 2579 goranskij , v. p. 1982 , astronomicheskij tsirkulyar , 1216 , 5 grillmair , c. j. et al . 1998 , , 115 , 144 lee , y. w. , demarque , p. & zinn , r. 1990 , , 350 , 155 mateo , m. 1998 , , 36 , 435 nemec , j. 1985 , , 90 , 204 nemec , j. , mendes de oliveira , c. , & wehlau , a. 1988 , in asp conf . ser , vol . 4 , the extragalactic distance scale , eds . s. van den bergh & c. pritchet , ( san francisco asp ) , 180 stellingwerf , r. f. 1978 , , 224 , 953 stetson , p. b. 1987 , , 99 , 191 stetson , p. b. 1994 , , 106 , 250 _ d. laney : _ could the peculiar distribution of rr lyrae stars with respect to oosterhoff i and ii be explained by an age distribution different from that found in typical oosterhoff i and ii globular clusters ? + [ 0.2 cm ] _ k. kinemuchi : _ grillmair et al . ( 1998 ) discuss a lack of multiple main sequence turnoffs ; thus no multiple star formation episodes . from their analysis , there is no large age distribution in draco . + [ 0.4 cm ] _ g. kovcs : _ the p - a diagram may not necessarily be the best way to estimate cluster metallicity . for rrab stars , there is a much better correlation with p and @xmath5 . also , amplitudes might be affected in the case of crowded field photometry . concerning the latter effect , do you have an estimation on the severity of crowding in the case of your data set ? + [ 0.2 cm ] _ k. kinemuchi : _ draco is not a very compact object , so crowding does not usually become an issue . we do have problems with near neighbors , but almost all of that is taken care of with our photometry programs . we have not yet looked into the @xmath5 values of our rrab light curves . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: a major gap in our understanding of low - mass star formation concerns the origins of binary stars . about 30 to 50% of low - mass main - sequence stars have companions , and the frequency of young ttauri binary systems in nearby star - forming regions is nearly twice as high . binary systems have been observed in all pre - main - sequence stages of evolution and there is growing evidence for proto - binary systems , although the numbers are still very small ( e.g. , fuller et al . 1996 ; looney et al . 1997 ) . both theory and observations support the hypothesis that binary systems form during the gravitational collapse of molecular cloud cores . most scenarios propose bar formation and fragmentation in rotating and accreting protostellar cloud cores or circumstellar disks as a formation mechanism ( e.g. , burkert & bodenheimer 1996 ; boss & myhill 1995 ; bonnell et al . 1991 ; boss 1999 ) . to understand the formation process of binary stars , high angular resolution studies of the earliest stages of star formation are required . we have , therefore , started a program to search for multiplicity among low- and intermediate - mass protostars ( class0 and i ) using the owens valley radio observatory ( ovro ) millimeter array . our program aims at sub - arcsecond resolution corresponding to linear resolutions of 150 to 450au . later , with alma , we aim for 0.1 arcsec resolution , or 15 - 45 au , close to the peak of the pre - main sequence binary separation distribution . the mm continuum emission is used to trace the optically thin thermal dust emission . the molecular gas is traced by the c@xmath1o(1@xmath20 ) and n@xmath3h@xmath4(1@xmath20 ) lines at 110 and at 93ghz , respectively . n@xmath3h@xmath4(1@xmath20 ) comprises seven hyperfine components and , compared to other molecules , depletes later and more slowly onto grains ( bergin & langer 1997 ) . it is , thus , a very reliable gas tracer of the the morphology of protostellar cores . initial results presented here are based on observations conducted at ovro in september and october 1999 . the 1 mm and 3 mm continuum maps have 1@xmath5 rms sensitivities of 4mjy / beam for hpbw 2.0@xmath61.5 and 0.7mjy / beam for hpbw 5.2@xmath64.2 , respectively . the n@xmath3h@xmath4 images were obtained at low resolution only and have a velocity resolution of 0.2km / s and a 1@xmath5 sensitivity of 110mjy / beam for hpbw 13@xmath69.4 . the nir , submm , and 1.2 mm continuum observations were performed at the 3.5 m calar alto telescope ( magic ) , the 15 m jcmt ( scuba ) , and the iram 30 m telescope ( 19-channel bolometer array ) . we wish to thank th . henning , r. zylka , r. lenzen , d. ward - thompson , and j. kirk who are involved in these programs . cb230 is a bok globule located at a distance of @xmath0450pc . it contains a strong submm / mm continuum source ( launhardt & henning 1997 ; launhardt et al . 1998 , 2000 ) and a dense cs core which shows spectroscopic signature of mass infall ( launhardt et al . 1997 ) . the dense core is associated with two nir reflection nebulae separated by @xmath010 ( yun 1996 ; launhardt 1996 ) . the western nebula is bipolar with a bright northern lobe perfectly aligned with the blue lobe of a well - collimated co outflow ( yun & clemens 1994 ) . the much fainter southern ( red ) part of this bipolar nebula seems heavily obscured possibly by the infalling envelope . no star is visible and the nir morphology can be interpreted as light emerging from a deeply embedded yso and scattered outward through the outflow cone directed towards us . the eastern nir nebula is much fainter and redder and displays no bipolar structure . previous single - dish mm continuum and molecular line observations did not resolve the central part of the dense core . but they demonstrated that the mm emission has a core - envelope structure and peaks at the origin the western bipolar nir nebula ( fig . 1 , top row ) . the slight extension of the continuum emission to the south east suggests that the faint eastern nir source is also associated with circumstellar material . the new ovro continuum maps at 1 mm and 3 mm ( fig . 1 , bottom row ) show only one unresolved component clearly associated with the origin of the western bipolar nebula . the compactness and location of the 1 mm continuum source observed ( @xmath7400au e - w extent ) , together with the bipolar structure of the nir nebula , suggest the presence of a circumstellar disk . the compact source contains @xmath010% of the total 1 mm continuum flux in the iram map . a significant contribution by free - free emission can be ruled out since the bolometric luminosity of the entire cloud core of 11l@xmath8 points to a low - mass protostar with no capability to ionize its environment ( launhardt et al . . the eastern source may be too faint to detect ( @xmath9mjy at 3 mm and @xmath10mjy at 1 mm ) or no compact disk is associated with it . in contrast to the dust continuum emission , all seven hyperfine structure components of the n@xmath3h@xmath4(10 ) line are detected at both nir positions . the n@xmath3h@xmath4 data resolve the molecular cloud core into two separate components each of which is spatially coincident with one of the two nir nebulae ( fig . the projected separation of the two sources is @xmath05000au . the double core seems to rotate around an axis perpendicular to the connecting line and approximately parallel ( in projection ) to the outflow of the western source . a comparison of the kinetic , gravitational , and rotational energy of the double core system shows that the two cores are gravitationally bound . this is consistent with the assumption that the double core formed due to rotational fragmentation from a single cloud core and with the orientation of the assumed circumstellar accretion disk around the western protostar . the angular resolution is not yet high enough to derive the rotation curves of the individual cores , but planned observations should improve the resolution considerably . the projected separation of @xmath05000au is at the upper end of the pre - main - sequence binary separation distribution , nevertheless , these preliminary results suggest that the bok globule cb230 contains a `` true '' wide binary protostar system . bergin , e.a . , & langer , w.d . 1997 , , 486 , 316 bonnell , i. , martel , h. , bastien , p. , et al . 1991 , , 377 , 553 boss , a.p . , & myhill , e.a . 1995 , , 451 , 218 boss , a.p . 1999 , , 520 , 744 burkert , a. , & bodenheimer , p. 1996 , , 280 , 1190 fuller , g.a . , ladd , e.f . , & hodapp , k .- w . 1996 , , 463 , l97 launhardt , r. 1996 , phd thesis , university of jena launhardt , r. , & henning , th . 1997 , , 326 , 329 launhardt , r. , evans ii , n.j . , wang j. , et al . 1997 , , 119 , 59 launhardt , r. ward - thompson , d. , & henning th . 1998 , , 288 , l45 launhardt , r. , henning , th . , & zylka , r. 2000 , in preparation looney , l.w . , mundy , l.g . , & welch , w.j . 1997 , , 484 , l157 yun , j.l . & clemens , d.p . 1994 , , 92 , 145 yun , j.l . 1996 , , 111 , 930 Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the eclipses of the 11th magnitude star ee cep have been observed with a period of 5.6 yr from the early 1950-ies . their depths change in a wide range from about @xmath0 to @xmath1 ( see * ? ? ? * ) , however all of them show the same features : they are almost gray and have the same asymmetric shape ( descending branch of every eclipse has longer duration than the ascending one ) . in all eclipses it is possible to distinguish five phases ( shown in fig . 1 ) : ingress ( 12 ) and egress ( 34 ) , respectively preceded and followed by the extended atmospheric parts ( 1@xmath21 and 44@xmath2 ) , and the slope - bottom transit ( 23 ) . the most plausible explanation of the observed photometric behavior was proposed by @xcite . they suggested that the secondary consists of a dark disk , with opaque interior and semi - transparent exterior , around a low luminosity central object . the inclination of the disk to the line of sight and the tilt of its cross - section to the direction of motion are changed by precession . this causes the changes in the depth and the duration of the eclipses . a significant impact parameter is responsible for the observed asymmetry of the eclipses . this model can explain the shallow ( @xmath3 ) , flat - bottomed eclipse observed in 1969 if we assume a nearly edge - on and non - tilted projection of the disk . an observational campaign organized during the 2003 eclipse @xcite , brought very good quality photometric @xmath4 data with a dense time coverage . for the first time it was possible to analyze the color evolution during the eclipse and not only their amplitudes . the preliminary photometric results of this campaign were described by @xcite . the eclipse turned out to be quite shallow and in accordance with expectations almost gray . the eclipse achieved depths from about @xmath0 in @xmath5 to @xmath6 in @xmath7 passbands . in fig . 2 , the @xmath8 light curve and the color indices are presented . each point represents the average of all measurements obtained in a given passband during a single night . the color indices from the 2003 eclipse show two blue maxima , about nine days before and after the mid - eclipse . simultaneously , weak maxima in the @xmath8 light curve are clearly visible . the blue maxima observed in the color indices can be understood if we assume that a hot star , rotationally darkened at the equator and brightened at the poles , is eclipsed by a disk divided into two parts by a gap ( fig . the spectra obtained in 2003 indicate indeed that the hot component is a rapidly rotating be star @xcite . a comparison of the balmer absorption lines in the spectrum of ee cep with theoretical profiles gives @xmath9 km / s ( see * ? ? ? * ) , which implies strong equatorial darkening . the difference between the polar and the equatorial temperatures can reach even 5 - 6 @xmath10 k. therefore , when the hot polar area appears in the gap the blue maxima are observed . in fig . 3 two eclipse models are presented : with a solid disk and with a disk having a gap . the first model gives quite a good fit to the light curve and the global color changes , but it does not explain in details the color evolution during the eclipse . the disk model with a circular gap fits the observed color changes quite well . it was not possible to obtain a good fit to the light and color curves simultaneously , most likely because the assumed formula for the density of the disk was too simple . the fruitful observational campaign in 2003 did not provide answers to a number of questions : ( i ) is the be star ( primary ) in the ee cep system indeed eclipsed by a dark , precessing disk ? ( ii ) does the gap in the disk really exist ? ( iii ) what is the nature of the central body surrounded by the disk and what is its contribution to the total flux ? an excellent opportunity for answering these questions came with the next eclipse , which took place at the turn of 2008 , with a minimum occuring on january 10 , 2009 . the invitation to the observational campaign was announced in a short paper in _ ibvs _ @xcite . the strong interest among observers , who took part in the observations , resulted in a large amount of the collected data . the @xmath4 light curves presented in fig . 4 are composed of more than 1600 individual data points in total ! surprisingly , the last eclipse with depths @xmath11 in @xmath7 and nearly @xmath12 in @xmath5 passbands , turned out to be the shallowest in the observing history of ee cep . in fig . 5 , we present the _ b _ light curve and the color indices . each point represents the average of all measurements obtained in a given filter during the first and second part of a particular julian day . the accuracy of the photometry is excellent , reaching a few mmag . the features observed during the previous eclipse , including the two blue maxima , occur also in the 2008/9 eclipse . the bump preceding the minimum , at jd 2454836 ( fig . 4 and 5 ) is much more pronounced than previously . the differences in the phase and strength of these features can be caused by the changes in the spatial orientation of the disk . the observed variations in the _ i _ passband before and after the eclipses during the last decade @xcite would give additional support for this idea . a comparison of the photometric and spectroscopic data obtained during the last two eclipses ( see fig . 6 ) reveals some new characteristics of the eclipsing disk in the ee cep system . the durations of last two eclipses were longer than we expected ( about 90 days ) , and they both were preceeded and followed by very shallow minima which are perhaps repeatable in each orbital cycle . the 2008/9 campaign results confirmed the existence of a gap in the disk . additionaly , the data present some indications of the existence of a second , outer gap in the disk . the possible multi - ring structure of the eclipsing disk in ee cep suggests the existence of some massive bodies that could be responsible for their formation . this means that we may observe signs of planet formation in a circumstellar disk in ee cep . the results presented here show that the disk in ee cep system is very similar to the multi - ring structure observed in @xmath13 aurigae @xcite . during the ee cep eclipses additional components appear in the @xmath14 emission line and in the nai absorption doublet . towards the mid - eclipse an absorption component appears and grows in the @xmath14 profile and during the minimum it is very deep and broad . the sodium doublet line profiles evolve during the eclipse and in the minimum multi - component structure with at least two additional absorption components can be seen . during the shallow minimum at orbital phase 0.017 an additional nai absorption component was also present , while it was absent soon after the egress . the spectra from the last two eclipses suggest that the absorption lines evolution is the same during each cycle . unfortunately spectroscopic observations coverage of the last eclipse was very bad . many more spectroscopic observations during the next eclipse would be needed to understand the nature of ee cep . photometry in the infrared _ jhk _ passbands and the radial velocity variations of the hot component could be invaluable as well . a part of the observations used were taken through courtesy of the aavso and the sonoita research observatory . this study was supported by mnisw grant no . n203 018 32/2338 and umk promotor s grants no . 366-a and 367-a . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the solar neutrino problem and the atmospheric anomaly belong to the category of long base - line phenomena using natural neutrino sources . along with the short base - line oscillation experiments the long base - line projects with man - made neutrino sources are very promising . among them the recent chooz project using reactor neutrinos was completed with a negative effect @xcite . most others are planned for installation at high energy accelerators . the k2k project @xcite has taken the first run recently and has shown a preliminary first cc - event @xcite . minos at fermilab - soudan @xcite and icarus at cern - gran sasso @xcite are in a preparatory stage . the traditional interpretation of the origin of neutrino anomalies is the oscillation mechanism . another approach is the possibility of decay of conventional massive neutrinos , which may decay in some mixing components into a singlet majoron and another neutrino , as summarised in ref . this decay theory is restricted by very low upper limits on neutrino masses . as an alternative , we suggested in ref . @xcite a three - body decay mechanism to explain the existing oscillation hints , which considers neutrinos as time - like leptons and where the heavier neutrinos may decay according to the dual principle in the super - luminous lorentz transformation ( slt ) . the idea is based on the symmetry between space - like and time - like bradyons , following e. recami et al . @xcite , according to which we may suggest that in the super - luminous lorentz transformation the space and the time dimensions should replace each other . as a result , tachyons may travel in a 3-dimension time while moving in an unique space direction . a very severe problem is that no tachyon was ever observed in an experiment . on the other hand , neutrinos are an exception with the following appearances of tachyon properties : - there is a very high symmetry between neutrinos and space - like leptons which is enhanced in the electro - weak unification ; - each neutrino has its unique space direction , left or right , described by a definite helicity ; - neutrinos never stop in a space position , similarly as a space - like particle can never stop in a moment of time - evolution . a big challenge is the fact that all neutrinos seem to have very small mass , which disturbs the lepton - neutrino symmetry . to solve this problem we assumed in ref . @xcite that neutrinos are realistic tachyons , however due to weak interaction their transcendent masses m being complex have to be strongly suppressed . we suggested that the real part of mass is roughly equal to @xmath0 , where @xmath1 is the decay width of the unstable lepton and @xmath2 is its rest mass . the imaginary part of tachyon mass is suppressed by the factor @xmath3 , i.e. to the first order by the fermi constant @xmath4 . this means that the imaginary part may be measured in parity non - conserving experiments by interference of the weak interaction and electro - magnetic or nuclear force . generally , we may vary the rest mass @xmath2 as a free parameter to fit the experiments . in this work , however , we prefer to test the first order approximation by making the extreme assumption of time - space symmetry , i.e. that the absolute value of the transcendent mass of a neutrino is equal to the rest mass of its bradyon partner . for unification of the formalism we extend a similar formula for @xmath5 of unstable leptons to the electron , which does not harm the conclusion that electron neutrinos as time - like electrons should be stable . as a result , we have got a formalism almost without free parameters in our calculation . in table [ tab : mass ] we show the observable transcendent masses of space - like neutrino - tachyons or time - like leptons : ' '' '' ' '' '' ' '' '' .observable transcendent masses of neutrino - tachyons [ tab : mass ] [ cols="^,^,^,^",options="header " , ] ' '' '' ' '' '' ' '' '' 2 for @xmath6 protons on target ( p.o.t . ) at k2k , if the muon neutrino decay works , only @xmath7 cc - events will be collected and if the particle identification ( pid ) works well only electron - like events , but no muon - like events will be seen . here we can not exclude the possibility that the electron neutrinos are majorana . in this case only the dirac component may be detected , as in the solar neutrino flux and , as a result , the total amount of electron - like events may be decreased up to 50% ( for the maximum mixing @xcite ) . for the oscillation mechanism there are different possibilities : i/ when the ( @xmath8 ) version works , we may have more electron - like events @xmath9 from the oscillation and an amounts of muon - like ones @xmath10 from the survivors of the initial muon neutrino spectrum ; ii/ when the ( @xmath11 ) version works , we may see the same amount of muon - like events from the surviving muon neutrinos , however the rate of cc - events from the tauon neutrinos decreases significantly , due to the high threshold of the @xmath12n reaction and the low ratios of tauon decay into muon or electron , which are 17.9% and 17.4% , respectively @xcite . the first run of k2k at super - k has seen the first cc - event @xcite . we have to wait for the next run in year 2000 , for sufficient statistics before making any definite conclusion . according to table [ tab : ratev ] , minos will give more statistics to identify the origin of the oscillation hints . in the super - k long base - line detector we expect to identify muon - like events from electron - like ones as a criteria to test the three - body decay of muon neutrinos . the shape of the spectra and the quantity of cc - events are also sensitive to the origin of the oscillation hints . if the decay mechanism works , we suggest to the next long base - line experiments to use intensively the shorter base - line detectors . the optimal condition for observation is to get significant amounts of neutrino decays to see electron - like events , not to harm the intense flux to see also a proportion of muon - like events , that a decay rate larger than say 20% is desirable . it leads to a ratio @xmath13 and the base - line @xmath14(km ) equal to : 2.1 ; 15.3 and 41.8 km respectively , for the kek front detector , cosmos and jura . the experiments with modified shorter base - line detectors might collect a significant statistics for a short period . for example , 0.5 kton fiducial volume of the kek front detector at the distance 2.1 km may see @xmath15 muon - like and about ( 4 - 8)@xmath16 electron - like events for @xmath6 p.o.t . this work was funded by the basic research program of the ministry of science , technology and environment of vietnam . we appreciate prof . p. darriulat ( cern ) for very useful discussion . we thank dr . y. yano ( riken ) , prof . a. masaike ( kyoto ) and dr . y. suzuki ( super - k ) for supporting the first author to attend the present workshop . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: the spectra of quasars and seyfert galaxies show strong emission lines superimposed onto a bright continuum . the continuum contains a significant feature in the optical - ultraviolet region , known as `` the big blue bump '' . due to the huge photoelectric opacity of the galaxy , the spectral energy distribution ( sed ) of the ionizing continuum , between the lyman limit and the soft x - rays ( euv x ) , is hardly known . fortunately , owing to the redshift effect and the transparency of the quasar environment , it has been possible to infer the sed of quasars down to @xmath1350 . composite energy distributions were derived by zheng etal . ( 1997 ) and later by telfer etal . ( 2002 ) using archived hst - fos spectra . before averaging , each spectrum was dereddened for galactic absorption as well as statistically corrected for the absorption due to intergalactic ly@xmath2 absorbers and lyman limit systems . a striking feature of the composite quasar sed is that a significant steepening occurs around 1100 , leading to a far - uv powerlaw of index @xmath3 ( @xmath4 ) . korista , ferland & baldwin ( 1997 ) pointed out the difficulties of reproducing the equivalent widths of the high ionization lines of heii ( 1640 ) , civ ( 1549 ) and ovi ( 1035 ) , assuming a powerlaw as soft as @xmath5 . state of the art photoionization models favor a much harder sed , one that peaks in the extreme - uv beyond 22ev ( e.g. casebeer , leighly & baron 2006 ; korista etal . 1997 ; baldwin etal . the far - uv break is clearly seen in individual spectra ( see binette etal . 2005 : hereafter b05 ) . the amount of steepening varies considerably from object to object . binette & krongold ( 2006 ) recently analyzed the spectrum of ton34 ( @xmath6 ) , which is the object with the steepest break known , with a far - uv behavior given by @xmath7 . however , strong emission lines of ovi and civ are present . there is no generally accepted interpretation of the nature of the far - uv break . we review below possible absorption mechanisms that would give rise to the break and at the same time allow the emergence of an upturn in the extreme - uv , in order that the ionizing sed be as hard as needed in photoionization calculations of the emission lines . we hereafter assume that the far - uv break results from absorption and will consider two possibilities : ( i) hi [ ly@xmath2 , @xmath8 , @xmath9 ... and bound - free ] and ( ii) interstellar dust . we will consider four locations for the absorbing medium : ( @xmath10 ) intergalactic , ( @xmath11 ) local to the quasar ism , ( @xmath12 ) accretion disk photosphere and ( @xmath13 ) accelerated outflow from quasars . the resulting eight cases are illustrated in fig.1 with labels 14 for hi and a d for the dust . the aim is to resolve the problem of the ionizing sed , which appears to be too soft . among the eight cases reviewed , some have the potential to resolve the softness problem , either because the local belr sees a different sed ( intergalactic absorption ) , or because the absorption in the uv is followed by a flux upturn at higher energies . case binette etal . ( 2003 ) studied this possibility . they assumed an hi behavior ( as a function of @xmath14 ) proportional to the gas density expected from the warm - hot intergalactic medium . although they could reproduce the tz02 composite , they rejected this possibility , since their model predicted a jump in flux blueward of 1216 ( observer - frame ) that is not observed . an absorber at the quasar redshift results in a sharp absorption edge at 912 as well as in an ly@xmath2 absorption line . such pronounced and sharp features do not match the far - uv steepening discussed above . state of the art ` naked ' accretion disk ( nad ) models predict a steepening ( i.e. lyman edge ) near ly@xmath2 . however , the far - uv break is not reproduced well by nad models ( c.f . fig.22 in hubeny etal . the lyman edge from a nad model is not followed by a flux upturn at higher energies , hence the softness problem remains unresolved . the same may be said of the comptonized accretion disk model although in that case the uv break is well reproduced ( zheng etal . 1997 ) . eastman , macalpine & richstone ( 1983 ) could generate a steepening of the continuum by having absorptions clouds progressively accelerated up to 0.8@xmath15 . exploration of a different behavior of the hi opacity with velocity would be welcomed , as these calculations might shift the break position to the observed value near 1100(instead of 1216 ) , and possibly produce a flux upturn beyond 20ev . furthermore , by including hei opacity , such models might explain the curious dip observed at 500 in one of the most studied quasar , he2347@xmath164342 ( see fig.2 ) . interestingly , both the 1100 and 500 breaks are blueshifted by comparable amounts with respect to rest - frame hei and hi ly@xmath2 ( at 584 and 1216 , respectively ) . case b05 studied the possibility of intergalactic dust consisting of nanodiamond grains ( other dust compositions were unsuccessful ) . they could reproduce the dip displayed by the far - uv indices when plotted as a function of redshift . this possibility was rejected , since it required too much intergalactic dust ( @xmath117% of the cosmic carbon ) . it also required that only nanodiamond dust is formed . assuming a nanodiamond dust component intrinsic to each quasar , b05 successfully reproduced the far - uv break observed in individual quasars of the tz02 sample . the flux upturn taking place below 650 in these models near allow the intrinsic sed to be much harder than indicated by extrapolating of the flux near the uv break . such an upturn was identified in 4 quasar spectra . an example , pg1008 + 1319 , is shown in the left panel of in fig.1 . from a spectrum that combines various archives , binette & krongold ( 2006 ) reported a far - uv rise in ton34 . a 6th example is provided by he2347@xmath164342 ( see upturn shortward of 700 in fig.2 ) . shang etal . ( 2005 ) explored the possibility of ism and smc - like extinction . it would be interesting to compute the sed emerging from a nad photosphere that contains small amounts of nanodiamond dust . if the break is accounted for by dust , much harder ( hotter ) disk seds could be envisaged . nanodiamonds have so far been identified in emission around 3 stellar disks . a large uv fluence may facilitate dust formation . we consider the hypothesis of an accelerating dust outflow not to be needed nor useful for the purpose of explaining the far - uv break . we find that the three cases 4 , b , and c are worth exploring further , as they may reconcile the observed downturn in the far - uv with the need of a harder sed to account for the high ionization emission lines . the exploration of absorption by an intrinsic crystalline carbon dust screen ( case c ) is at this stage the most developed hypothesis . we are currently exploring its consequences in the infrared and uv in order to provide ways to falsify such models . Abstract:

Write an abstract for the following acadamic paper.

Paper: we have recorded the flight of a fly during take off and landing using digital high speed photography . it is shown that the dynamics of flexible wings are different for these procedures . during this observation fly flew freely in a big box and it was not tethered . Abstract: in this fluid dynamics video , we demonstrated take off and landing of a fly . the deformation of wings is in focus in this video . Paper: in the last several years , many systems have been analyzed unraveling the way in which their constituents interact which each other . surprisingly , many seemingly diverse phenomena found in biological , social and technological systems @xcite share a complex interaction topology that is in most cases characterized by the existence of a few key nodes that participates in a large number of interactions @xcite . this observation is in sharp contrast to previous studies that in order to model the dynamical aspects of biological , social and technological processes assumed a regular or a random distribution of interactions for the system s units . obviously , the new approach to the topology of networked systems has important bearings on their dynamics and functioning as have been pointed out during the last few years @xcite . a first step is then the characterization of the topological properties in order to get better insights into the dynamics , functioning and new designs of natural and man - made networked systems . peer - to - peer ( p2p ) networks form a kind of open , decentralized overlay network on top of the internet @xcite , on which distributed users communicate directly to find and share resources , often music and movie files . these networks may be one of the few largest distributed computing systems ever , and more surprisingly , they can run with great stability and resilient performance in face of possibly the most ferocious dynamics . the number of hosts running on gnutella was reported to be 1,800,000 in august 2005 @xcite . recent studies have extensively investigated the traffic , shared files , queries and peer properties of some widely applied p2p systems such as gnutella and kazaa @xcite . it has also been reported that node connectivity ( the number of partners a node interacts with ) in gnutella follows a combination of a power - law distribution ( usually for nodes with more than 10 connections ) and a quasi - constant distribution ( for nodes with fewer connections ) @xcite . this may be due to the arbitrarily created connections : peers establish connections to others by searching presently available peers on the overlay , in addition to a few links to well known hosts provided by the system . peer connections in these systems only suggest routes of traffic and usually have no relation to peer properties , e.g. , peer interests or resources held by peers . [ cols= " < , < , < , < , < , < , < " , ] this paper presents the first study on social associations of distributed peers in peer - to - peer networks . several peer social networks have been constructed from the real user data collected from the gnutella system . basic properties of the social networks , including degree distributions , local topological quantities and degree - degree correlations have been particularly studied in this paper . the results have proved that peer social networks are small world networks , as peers are clustered and the path length between them is small . moreover , most of the peers ( nearly 98.5% ) are pure resource providers , contributing to the high resource reliability and availability of p2p networks in resource sharing . comparatively , free riding peers that do not contribute any resources are only a small fraction ( less than 1% ) of the whole network . for peers that have more than one connection , their undirected , directed ( including out and in ) and weighted degree distributions follow a clear power - law distribution . the exponents are greater than 2 for undirected and in degrees and nearly 1 for out degrees . investigations on betweenness and correlations suggest that dynamics of peer social networks are not dominated by a few highly connected peers . in fact , the peer degrees are generally disassortative mixing , except some @xmath0 and @xmath1 , suggesting that active providers are connected between each other and by active requesters . the collected social networks studied in this paper are only some small snapshots of the large - scale and continuously changing p2p networks . however , the kind of study performed here allows us to touch upon the real network topologies that are difficult to obtain with existing network models . the analysis results will give useful hints for the future design of effective p2p systems , by considering their acyclic topologies and small world architecture . in the future , the joint relation of the social network topology and the topology of the underlying peer - to - peer network ( e.g. , gnutella ) will be studied to examine their commonness and discrepancy . on top of the kind of network found in the study , simulations of processes can be enabled to investigate spreading processes @xcite , modeling of traffic flow @xcite and optimization of network resources @xcite . based on the current study on peer betweenness and degree correlations , we will further investigate network hierarchy , peer work load and dynamic properties of p2p social networks . the authors are grateful to di liu for his work on gnutella data collection , dr . kun yang and weibo chen for their help on early data calculation and the anonymous referees for their valuable comments . y. m. thanks v. latora for helpful discussions on several aspects of this work . y. m. is supported by mec ( spain ) through the ramn y cajal program and by the spanish dgicyt project fis2004 - 05073-c04 - 01 . Abstract: