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12,800 |
Suppose that you have an abstract for a scientific paper: long - term time variabilities of the o ( 0.57 kev ) emission in the soft x - ray diffuse background were studied using six suzaku annual observations of blank sky towards the lockman hole made from 2006 to 2011 .
after time intervals in which the emission was enhanced on time scales of a few tens of ks were removed , the o intensity was found to be constant from 2006 to 2009 within the 90% statistical errors .
the intensity in 2010 and 2011 was higher by @xmath0 lu ( @xmath1 ) than the earlier values .
the most plausible origin of the fast variable component is solar wind charge exchange ( swcx ) .
the intensity increase is not positively correlated with the proton flux at the l1 point .
since all the observations were made in the same season of a year , the variation can not be explained by parallax of the swcx induced x - ray emission from the heliosphere .
we consider that it is related to the geometrical change of slow and fast solar wind structures associated with the 11 year solar activity .
the observed variation was compared with that expected from the swcx induced x - ray emission model . .
And you have already written the first three sentences of the full article: the charge exchange process of solar wind ions with neutrals ( swcx ) is considered to contribute to the diffuse x - ray background , especially at energies under 1 kev ( @xcite ) . when solar wind ions interact with neutral atoms ( mainly h and he ) , electrons bound in the neutral
are transferred to the excited state of the ion , and move to the ground state by emitting x- rays corresponding to the de - excitation energy .
thus the swcx consists of emission lines , among which the o triplet at 0.57 kev is the most prominent and has been observed with x - ray ccd spectrometers on board chandra , xmm - newton and suzaku ( @xcite , @xcite ) ..
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the swcx - induced diffuse emissions are considered to arise from collisions with neutrals of two different origins .
one is the earth s geocorona , thus the emission is called `` geocoronal swcx '' . according to @xcite ,
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12,801 |
Suppose that you have an abstract for a scientific paper: we have developed an ensemble density functional theory which includes spin degrees of freedom for nonuniform quantum hall systems .
we have applied this theory using a local - spin - density approximation to study the edge reconstruction of parabolically confined quantum dots . for a zeeman splitting below a certain critical value
, the edge of completely polarized maximum density droplet reconstructs into a spin - unpolarized structure . for larger zeeman splittings ,
the edge remains polarized and develops an exchange hole . .
And you have already written the first three sentences of the full article: the recent development of nanofabrication technology has made it possible to manufacture semiconductor systems with reduced dimensionality and very high electron mobility .
these technological advances have led to the discovery of such fascinating phenomena as the fractional and integer quantum hall effects ( qhe ) @xcite .
these occur in a two - dimensional electron gas in a magnetic field @xmath0 perpendicular to the electron system @xcite . a quantum treatment of the motion of an infinite.
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, homogeneous system shows that the kinetic energy takes discrete values @xmath1 , where @xmath2 is the landau level index ( @xmath3 ) and @xmath4 is the cyclotron frequency .
each landau level contains @xmath5 states per unit area , or one state for each magnetic flux quantum @xmath6 , giving rise to a macroscopic landau level degeneracy .
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12,802 |
Suppose that you have an abstract for a scientific paper: we present atacama large millimeter / submillimeter array ( alma ) 860 @xmath0 imaging of four high - redshift ( z=2.8 - 5.7 ) dusty sources that were detected using the south pole telescope ( spt ) at 1.4 mm and are not seen in existing radio to far - infrared catalogs . at 1.5 resolution , the alma data reveal multiple images of each submillimeter source , separated by 1 - 3 , consistent with strong lensing by intervening galaxies visible in near - ir imaging of these sources .
we describe a gravitational lens modeling procedure that operates on the measured visibilities and incorporates self - calibration - like antenna phase corrections as part of the model optimization , which we use to interpret the source structure .
lens models indicate that spt0346 - 52 , located at z=5.7 , is one of the most luminous and intensely star - forming sources in the universe with a lensing corrected fir luminosity of @xmath1 and star formation surface density of 4200 yr@xmath2 kpc@xmath3 .
we find magnification factors of 5 to 22 , with lens einstein radii of [email protected] and einstein enclosed masses of 1.6 - 7.2@xmath510@xmath6 .
these observations confirm the lensing origin of these objects , allow us to measure the their intrinsic sizes and luminosities , and demonstrate the important role that alma will play in the interpretation of lensed submillimeter sources . .
And you have already written the first three sentences of the full article: half of the energy produced by all objects in the history of the universe has been absorbed and reemitted by dust @xcite .
the cosmic infrared background , first detected by the cosmic background explorer satellite @xcite , is the aggregate emission from individual dusty galaxies across cosmic time ( e.g. , * ? ? ?
the brightest of these dusty star - forming galaxies ( dsfgs ) were discovered in deep submillimeter - wavelength images of the sky @xcite , and have luminosities in excess of @xmath7 emitted primarily at rest wavelength in the far - infrared . with star formation rates.
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@xmath8 yr@xmath2 , this population of dsfgs contributes a significant fraction of the total star formation density of the universe at @xmath9 , where their abundance peaks ( e.g. , * ? ? ?
these objects are the progenitors of the massive galaxies we observe today . despite the enormous total luminosity of the brightest dsfgs ,
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12,803 |
Suppose that you have an abstract for a scientific paper: we discuss kraan - van baal - lee - lu ( kvbll ) solutions of the classical yang - mills equations with temperature in the context of @xmath0 lattice gauge theory .
we present discretized lattice versions of kvbll solutions and other dyonic structures , obtained by cooling in order to understand their variety and signature .
an analysis of the zero modes of the lattice dirac operator for different fermionic boundary conditions gives clear evidence for a kvbll - like background of finite @xmath1 lattice subensembles with @xmath2 .
using ape - smearing we are able to study the topological charge density @xmath3 of the configurations and to corroborate this interpretation . .
And you have already written the first three sentences of the full article: the discovery of new caloron solutions with non - trivial holonomy @xcite has revived hopes for a semiclassical description of yang - mills theory at @xmath5 , in particular of the deconfinement transition .
a new aspect of these solutions is the interplay between topological charge and the local and asymptotic polyakov loop .
one new feature , the separation of a @xmath6 object ( caloron ) into @xmath7 dyonic ( @xmath8 ) constituents , happens only in some part of the parameter space which seems to be statistically enhanced in the confinement phase ..
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for a couple of years some of us have been searching @xcite for this type of semiclassical background in @xmath4 lattice monte carlo configurations at finite @xmath1 , mostly using cooling . besides of opening a zoo of possible lattice solutions ,
a remarkable outcome was that , near @xmath9 , the confinement phase is distinguished from deconfinement by a finite yield of non - trivial caloron configurations with 2 dyonic constituents .
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12,804 |
Suppose that you have an abstract for a scientific paper: the amount of dust estimated from infrared to sub - millimetre ( submm ) observations strongly depends on assumptions of different grain sizes , compositions and optical properties . here
we use a simple model of thermal emission from cold silicate / carbon dust at a range of dust grain temperatures and fit the spectral energy distribution ( sed ) of the crab nebula as a test .
this can lower the derived dust mass for the crab by @xmath050% and 30 - 40% for astronomical silicates and amorphous carbon grains compared to recently published values ( @xmath1 and @xmath2 , respectively ) , but the implied dust mass can also increase by as much as almost a factor of six ( @xmath3 and @xmath4 ) depending on assumptions regarding the sizes / temperatures of the coldest grains .
the latter values are clearly unrealistic due to the expected metal budget , though .
furthermore , we show by a simple numerical experiment that if a cold - dust component does have a grain - temperature distribution , it is almost unavoidable that a two - temperature fit will yield an incorrect dust mass estimate .
but we conclude that grain temperatures is not a greater uncertainty than the often poorly constrained emissivities ( i.e. , material properties ) of cosmic dust , although there is clearly a need for improved dust emission models .
the greatest complication associated with deriving dust masses still arises in the uncertainty in the dust composition .
[ firstpage ] stars : agb and post - agb , supernovae : general , individual : crab nebula ; ism : dust , extinction .
And you have already written the first three sentences of the full article: observations suggest ly@xmath5 systems , quasars and gamma - ray burst hosts at high-@xmath6 contain very large amounts of dust ( see , e.g. * ? ? ?
* ; * ? ? ?
* ; * ? ? ?.
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* ; * ? ? ?
* ; * ? ? ?
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12,805 |
Suppose that you have an abstract for a scientific paper: successful isolation of graphene from graphite opened a new era for material science and condensed matter physics . due to this remarkable achievement , there has been an immense interest to synthesize new two dimensional materials and to investigate their novel physical properties .
silicene , form of si atoms arranged in a buckled honeycomb geometry , has been successfully synthesized and emerged as a promising material for nanoscale device applications . however , the major obstacle for using silicene in electronic applications is the lack of a band gap similar to the case of graphene .
therefore , tuning the electronic properties of silicene by using chemical functionalization methods such as hydrogenation , halogenation or oxidation has been a focus of interest in silicene research . in this paper
, we review the recent studies on the structural , electronic , optical and mechanical properties of silicene - derivative structures . since these derivatives have various band gap energies , they are promising candidates for the next generation of electronic and optoelectronic device applications . .
And you have already written the first three sentences of the full article: layered bulk materials consisting of two dimensional ( 2d ) sheets which are hold together with weak , interlayer van der waals interaction have been the focus of interest for more than a century@xcite . with the advancement of synthesis and characterization techniques it has been possible to isolate ultra thin films down to a monolayer of these materials which became feasible in the last decade .
monolayer forms of these layered bulk materials often exhibit different physical properties than their bulk counterparts .
the first isolated 2d material is known to be graphene , a one - atom - thick carbon sheet , with extraordinary physical properties@xcite ..
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after the successful exfoliation of graphene by novoselov and geim , researchers have been searching for several other 2d materials that can exist in single layer form such as hexagonal monolayer crystals iii - v binary compounds@xcite , transition metal dichalcogenides ( tmds)@xcite and the group iv elements ( silicene , germanene , stanene)@xcite . among these 2d monolayer materials ,
graphene and silicene are known to posses semi - metallic character while the members of tmds family compounds generally display semiconducting behavior with a band gap of 1 - 2 ev . in all of these 2d materials silicene
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12,806 |
Suppose that you have an abstract for a scientific paper: maximum entropy principle does not seem to distinguish between the use of tsallis and renyi entropies as either of them may be used to derive similar power - law distributions . in this paper
, we address the question whether the renyi entropy is equally suitable to describe those systems with power - law behaviour , where the use of the tsallis entropy is relevant .
we discuss a specific class of dynamical systems , namely , one dimensional dissipative maps at chaos threshold and make our study from two aspects : i ) power - law sensitivity to the initial conditions and the rate of entropy increase , ii ) generalized bit cumulants .
we present evidence that the tsallis entropy is the more appropriate entropic form for such studies as opposed to renyi form . _
pacs number(s ) : 05.45.-a , 05.20.-y , 05.70.ce_ .
And you have already written the first three sentences of the full article: as it is evident , an enormous variety of systems in nature fall into the domain of validity of boltzmann - gibbs ( bg ) thermostatistics . on the other hand , it is also well - known since long that a variety of anomalous systems exists for which the powerful bg formalism exhibits serious difficulties .
some of the examples for such anomalous cases could be the long - ranged interacting systems @xcite , two - dimensional turbulence @xcite , nonmarkovian processes @xcite , granular matter @xcite , cosmology @xcite , high energy collisions @xcite , among others . in order to handle some of these anomalous systems ,
an attempt has been performed in 1988 @xcite , which is based on the generalization of the standard bg formalism by postulating a nonextensive entropy ( tsallis entropy ) of the form s_q ( q ) , [ st]and it recovers the standard bg entropy @xmath0 in the @xmath1 limit ..
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this generalization is usually called in the literature as nonextensive thermostatistics or tsallis thermostatistics ( tt ) @xcite , and it has been ( still continues to be ! ) a matter of intensive studies during the past decade @xcite both from the point of theoretical foundations of the formalism and its applications to various physical systems .
the apparent success of tt gave rise to an increase of the studies with new entropy definitions @xcite .
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12,807 |
Suppose that you have an abstract for a scientific paper: the adsorption of potassium on the cu(111 ) surface in a @xmath0 pattern has been simulated with all - electron full - potential density functional calculations .
the top site is found to be the preferred adsorption site , with the other highly symmetric adsorption sites being nearly degenerate . the bond length from potassium to the nearest copper atom
is computed to be 2.83 .
population analysis and density of states indicate that there is no evidence for covalent bonding so that the binding mechanism appears to be a metallic bond . .
And you have already written the first three sentences of the full article: the study of adsorbates on metal surfaces is of high importance for scientists as well as for industry with potential applications , for example in catalysis .
alkali metals are relatively simple systems to consider as adsorbates .
initially , it was assumed that they would always occupy high - coordination sites ..
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it was therefore a big surprise when a first system was discovered where cs , adsorbed on the cu(111 ) surface , occupied the top site and not the threefold hollow site @xcite . meanwhile , further systems of alkali metals with top adsorption have been found typically heavier alkali atoms ( from k on ) on closed packed surfaces ( for a review , see references ) .
the situation is thus more complex than in the case of halogens where the adsorption site on closed - packed surfaces is usually the threefold hollow site . due to the increase in computational power ,
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12,808 |
Suppose that you have an abstract for a scientific paper: we present two methods for determining spectroscopic redshifts of galaxies in the deep2 survey which display only one identifiable feature , an emission line , in the observed spectrum ( `` single - line galaxies '' ) .
first , we assume each single line is one of the four brightest lines accessible to deep2 : h@xmath0 , [ oiii ] @xmath1 , h@xmath2 , or [ oii ] @xmath3 .
then , we supplement spectral information with @xmath4 photometry .
the first method , parameter space proximity ( psp ) , calculates the distance of a single - line galaxy to galaxies of known redshift in @xmath5 , @xmath6 , @xmath7 , @xmath8 parameter space .
the second method is an artificial neural network ( ann ) .
prior information , such as allowable line widths and ratios , rules out one or more of the four lines for some galaxies in both methods .
based on analyses of evaluation sets , both methods are nearly perfect at identifying blended [ oii ] doublets . of the lines identified as h@xmath0 in the psp and ann methods ,
91.4% and 94.2% respectively are accurate .
although the methods are not this accurate at discriminating between [ oiii ] and h@xmath2 , they can identify a single line as one of the two , and the ann method in particular unambiguously identifies many [ oiii ] lines . from a sample of 640 single - line spectra
, the methods determine the identities of 401 ( 62.7% ) and 472 ( 73.8% ) single lines , respectively , at accuracies similar to those found in the evaluation sets . .
And you have already written the first three sentences of the full article: photometric redshifts ( photo-@xmath9s ) save astronomers from expensive spectroscopy by determining redshifts from efficient broadband photometry .
however , photo-@xmath9 precision can not compare to spectroscopic redshift precision .
@xcite compare five state - of - the - art methods to determine redshifts from sloan digital sky survey ( sdss ) photometry ..
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neural networks , which are non - linear regression tools , perform the best , but the rms error in the photo-@xmath9s is @xmath10 at best .
this precision is sufficient to study large scale structure and some forms of redshift evolution , but not local environments @xcite , kinematic pairs , or the low - redshift luminosity function , where precise luminosities require precise redshifts . at a spectral resolution @xmath11 ,
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12,809 |
Suppose that you have an abstract for a scientific paper: we present algorithms for distributed verification and silent - stabilization of a dfs(depth first search ) spanning tree of a connected network .
computing and maintaining such a dfs tree is an important task , e.g. , for constructing efficient routing schemes .
our algorithm improves upon previous work in various ways .
comparable previous work has space and time complexities of @xmath0 bits per node and @xmath1 respectively , where @xmath2 is the highest degree of a node , @xmath3 is the number of nodes and @xmath4 is the diameter of the network . in contrast
, our algorithm has a space complexity of @xmath5 bits per node , which is optimal for silent - stabilizing spanning trees and runs in @xmath6 time .
in addition , our solution is modular since it utilizes the distributed verification algorithm as an independent subtask of the overall solution .
it is possible to use the verification algorithm as a stand alone task or as a subtask in another algorithm . to demonstrate the simplicity of constructing efficient dfs algorithms using the modular approach
, we also present a ( non - silent ) self - stabilizing dfs token circulation algorithm for general networks based on our silent - stabilizing dfs tree .
the complexities of this token circulation algorithm are comparable to the known ones . tolerance , self- * solutions , silent - stabilization , dfs , spanning trees .
And you have already written the first three sentences of the full article: a clear separation is common between the notions of computing and verification in sequential systems .
a similar separation in the context of distributed systems has been emerging . distributed verification of global properties like minimum spanning trees have been devised @xcite .
an area of distributed systems that can greatly benefit from this separation is that of self - stabilization ..
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self - stabilization is the ability of a system to recover from transient faults .
a self - stabilizing distributed system can be started in any arbitrary configuration and must eventually converge to a desired legal behavior .
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12,810 |
Suppose that you have an abstract for a scientific paper: regular and black - hole solutions of the spontaneously broken einstein - yang - mills - higgs theory with nonminimal coupling to gravity are shown to exist .
the main characteristics of the solutions are presented and differences with respect to the minimally coupled case are studied . since
negative energy densities are found to be possible , traversable wormhole solutions might exist .
we prove that they are absent .
+ + + + + + + + + + + freiburg - thep 00/1 + march 2000 + * regular and black - hole solutions of the einstein - yang - mills - higgs equations ; + the case of nonminimal coupling * + j.j . van der bij and eugen radu + _ albert - ludwigs - universitt + _ fakultt fr physik + _ freiburg germany + _ _ _ .
And you have already written the first three sentences of the full article: in the light of the no - hair @xcite and no - go theorems @xcite for the classical glueball solutions with or without gravity , the discovery of both smooth and black - hole solutions of the self - gravitating non - abelian gauge theories was a big surprise ( for a review see @xcite ) . among such solutions a physically interesting case is that of a spontaneous broken eymh theory examined in @xcite , where both regular and black - hole solutions , i.e. gravitating sphalerons and sphaleron black - holes have been found .
the stability analysis of this system has shown that the solutions are unstable @xcite . because of the physical importance of these objects , it is worthwhile to study generalizations of the couplings of the flat - space lagangian to gravity .
one of the simplest and best motivated extensions is the inclusion of an explicit coupling between the scalar field @xmath0 and the curvature of the spacetime @xmath1 of the form @xmath2 , where @xmath3 is a dimensionless coupling constant ..
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there are many reasons to believe that a nonminimal coupling term appears .
a nonminimal coupling is generated by quantum corrections even if it is absent in the classical action and is required in order to renormalize the theory @xcite . in many physical situations ,
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12,811 |
Suppose that you have an abstract for a scientific paper: in this paper , we study the thermodynamics of quantum harmonic oscillator in the tsallis framework and in the presence of a minimal length uncertainty .
the existence of the minimal length is motivated by various theories such as string theory , loop quantum gravity , and black - hole physics .
we analytically obtain the partition function , probability function , internal energy , and the specific heat capacity of the vibrational quantum system for @xmath0 and compare the results with those of tsallis and boltzmann - gibbs statistics without the minimal length scale . .
And you have already written the first three sentences of the full article: various approaches to quantum gravity such as string theory @xcite , noncommutative geometry @xcite , and loop quantum gravity @xcite motivate the existence of a minimal measurable length .
these theories argue that near the planck scale , the heisenberg uncertainty principle ( hup ) should be replaced by the so - called generalized uncertainty principle ( gup ) ( see refs .
@xcite and references therein ) ..
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the effects of gravity play an important role in the limit of small distances around the planck length , @xmath1 , where @xmath2 is newton s constant , @xmath3 is the planck constant , and @xmath4 is the speed of light .
equivalently , these effects are dominant in the limit of high energies near the planck energy @xmath5 . in nonrelativistic quantum mechanics , a particle with an arbitrary energy can be accurately localized and its exact location can be obtained . according to the quantum filed theory and based on heisenberg uncertainty principle , only particles with infinite energy can be localized . however , in quantum gravity theories that try to combine the effects of gravity with quantum mechanics , the localization of particles completely disappear . in general relativity , it is possible to access the path of particles that is impossible to obtain in quantum mechanics .
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12,812 |
Suppose that you have an abstract for a scientific paper: cavity optomechanics is showing promise for studying quantum mechanics in large systems . however , smallness of the radiation - pressure coupling is a serious hindrance . here
we show how the charge tuning of the josephson inductance in a single - cooper - pair transistor can be exploited to arrange a strong radiation pressure -type coupling @xmath0 between mechanical and microwave resonators . in a certain limit of parameters ,
such a coupling can also be seen as a qubit - mediated coupling of two resonators .
we show that this scheme allows reaching extremely high @xmath0 .
contrary to the recent proposals for exploiting the non - linearity of a large radiation pressure coupling , the main non - linearity in this setup originates from a cross - kerr type of coupling between the resonators , where the cavity refractive index depends on the phonon number .
the presence of this coupling will allow accessing the individual phonon numbers via the measurement of the cavity .
recent experiments on cavity optomechanical systems have shown how the parametric coupling between an electromagnetic ( either optical or microwave ) cavity and a mechanically vibrating resonator can be exploited to take the latter to its quantum mechanical ground state @xcite .
such schemes rely on amplifying the intrinsically weak radiation pressure coupling @xmath0 between the two systems via a strong pumping of the cavity , making the effective coupling between the systems linear .
however , linearly coupled oscillators constitute a linear system lying in the correspondence limit , where quantum effects can be seen only in signal fluctuations @xcite .
therefore , the emphasis of this research has shifted to the regime of strong radiation pressure coupling .
there are many recent theoretical proposals of the ensuing dynamics of the system in the strong coupling regime @xcite , but reaching this regime in any other system than cold atom gases @xcite in practice is challenging @xcite .
the ultimate aim would be to....
And you have already written the first three sentences of the full article: we start by writing the electromagnetic energy of the tripartite quantum system : @xmath167 where we have allowed also for the mechanical modulations of the gate charge @xmath168 , and introduced the flux @xmath65 through the cavity loop .
we denote with @xmath169 the average phase , i.e. , the phase that minimizes the total energy . for a vanishing flux , @xmath68 .
we quantize the cavity and the mechanical oscillator by defining the annihilation operators @xmath170\\ a&=\frac{1}{\sqrt{2\hbar m\omega_m^0}}(m\omega_m^0x + i p ) , \end{split}\ ] ] of single quanta in the cavity and the oscillator , respectively ..
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the conjugate variables can now be written as @xmath171 where @xmath172 .
we end up with @xmath173\cos \phi_i - ( e_{j1}-e_{j2})\sin\big[\eta(c^{\dag}+c)+\phi_a/2\big]\sin \phi_i , \end{split}\ ] ] where @xmath174 and we have expanded the josephson potentials using trigonometric identities . in the most relevant limit @xmath8 , and it is enough to concentrate on the two charge states closest to @xmath9 , defining @xmath10 $ ] as the deviation of @xmath9 from the lower integer value .
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12,813 |
Suppose that you have an abstract for a scientific paper: we provide an expanded and clarified proof of the famous result of bowen and ruelle giving an asymptotic formula for the hausdorff dimension of quasi - circles corresponding to the julia sets of @xmath0 for small @xmath1 .
the proof does not contain new material but has been rewritten to make it more accessible to msc or phd students with an interest in dimension theory .
+ _ mathematics subject classification _ 2010 : 37c45 , 28a80 , 37f50 .
+ _ key words and phrases _ : julia set , quasi - circle , hausdorff dimension . .
And you have already written the first three sentences of the full article: julia sets are an extremely important example of fractals , ( see figure [ pic : julia ] ) , which are repellers of certain complex analytic functions .
they display approximate self - similarity , as well as being compact , uncountable and perfect .
they can be defined in the following way ..
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the _ julia set _ of a function @xmath2 , denoted @xmath3 , is the closure of all repelling periodic points of @xmath2 . for more on the theory of julia sets including the proofs of the aforementioned properties see @xcite , chapter 14 .
one of the most fundamental ways to study a fractal set is via its hausdorff dimension . for a definition and much more on hausdorff dimension see @xcite , chapter 2 . ]
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12,814 |
Suppose that you have an abstract for a scientific paper: we present multi - epoch high - resolution optical spectroscopy , uv / radio / x - ray imaging , and archival _ hubble _ and _ spitzer _ observations of an intermediate luminosity optical transient recently discovered in the nearby galaxy ngc300 .
we find that the transient ( ngc300ot2008 - 1 ) has a peak absolute magnitude of @xmath0 mag , intermediate between novae and supernovae , and similar to the recent events m85ot2006 - 1 and sn2008s .
our high - resolution spectra , the first for this event , are dominated by intermediate velocity ( @xmath1 km s@xmath2 ) hydrogen balmer lines and emission and absorption lines that point to a complex circumstellar environment , reminiscent of the yellow hypergiant irc+10420 .
in particular , we detect broad h&k absorption with an asymmetric _ red _ wing extending to @xmath3 km s@xmath2 , indicative of gas infall onto a massive and relatively compact star ( blue supergiant or wolf - rayet star ) ; an extended red supergiant progenitor is unlikely .
the origin of the inflowing gas may be a previous ejection from the progenitor or the wind of a massive binary companion .
the low luminosity , intermediate velocities , and overall similarity to a known eruptive star indicate that the event did not result in a complete disruption of the progenitor .
we identify the progenitor in archival _ spitzer _ observations , with deep upper limits from _
hubble _ data .
the spectral energy distribution points to a dust - enshrouded star with a luminosity of about @xmath4 l@xmath5 , indicative of a @xmath6 m@xmath5 progenitor ( or binary system ) .
this conclusion is in good agreement with our interpretation of the outburst and circumstellar properties .
the lack of significant extinction in the transient spectrum indicates that the dust surrounding the progenitor was cleared by the outburst .
we thus predict that the progenitor should be eventually visible with _ hubble _ if the transient event marks an evolutionary transition to a dust - free state , or with _....
And you have already written the first three sentences of the full article: in recent years dedicated searches and serendipitous discoveries have uncovered several optical transients with luminosities intermediate between the well - studied classes of nova eruptions ( @xmath7 mag ) and supernova ( sn ) explosions ( @xmath8 mag ) . as can be expected from the wide gap in luminosity , these intermediate luminosity optical transients ( hereafter , ilots )
appear to be diverse in their properties and origins .
some have been classified as low luminosity core - collapse sne , with inferred energies and @xmath9ni masses that are at least an order of magnitude below typical sn events ( e.g. , @xcite ) ..
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others , sometimes initially classified as type iin sne , have been subsequently tagged with the catch - all designation of `` sn impostors '' ( e.g. , @xcite ) , that includes events resembling luminous blue variable ( lbv ) eruptions .
finally , a small number of somewhat dimmer events have been recently grouped under the proposed name `` luminous red novae '' ( lrne ; @xcite ) , based on their red optical colors ; the origin of lrne and their relation to each other remain unclear .
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12,815 |
Suppose that you have an abstract for a scientific paper: the total @xmath0 hadronic width can be accurately calculated using analyticity and the operator product expansion .
the result turns out to be very sensitive to the value of @xmath1 , providing a precise determination of the strong coupling constant .
the theoretical description of this observable is updated , including the recently computed @xmath2 contributions .
the experimental determination of @xmath1 and its actual uncertainties are discussed . .
And you have already written the first three sentences of the full article: the inclusive hadronic decay width of the @xmath0 lepton provides one of the most precise measurements of the strong coupling @xcite .
moreover , the comparison of @xmath1 with @xmath3 determinations at higher energies constitutes the most accurate test of asymptotic freedom , successfully confirming the predicted running of the qcd coupling at the four - loop level .
the calculation of the @xmath2 contribution @xcite has triggered a renewed theoretical interest on the @xmath1 determination , since it allows to push the accuracy to the four - loop level @xcite ..
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however , the recent theoretical analyses slightly disagree on the final result , giving rise to a range of different values for @xmath1 .
the differences among these results , shown in table [ tab : alpha - pub - values ] , are too large compared with the claimed @xmath2 accuracy and originate in the different inputs or theoretical procedures which have been adopted . in the following
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12,816 |
Suppose that you have an abstract for a scientific paper: in a recent paper @xcite , we introduced `` dynamical dark matter , '' a new framework for dark - matter physics , and outlined its underlying theoretical principles and phenomenological possibilities . unlike most traditional approaches to the dark - matter problem which hypothesize the existence of one or more stable dark - matter particles , our dynamical dark - matter framework is characterized by the fact that the requirement of stability is replaced by a delicate balancing between cosmological abundances and lifetimes across a vast ensemble of individual dark - matter components .
this setup therefore collectively produces a time - varying cosmological dark - matter abundance , and the different dark - matter components can interact and decay throughout the current epoch . while the goal of our previous paper was to introduce the broad theoretical aspects of this framework ,
the purpose of the current paper is to provide an explicit model of dynamical dark matter and demonstrate that this model satisfies all collider , astrophysical , and cosmological constraints .
the results of this paper therefore constitute an `` existence proof '' of the phenomenological viability of our overall dynamical dark - matter framework , and demonstrate that dynamical dark matter is indeed a viable alternative to the traditional paradigm of dark - matter physics .
dynamical dark matter must therefore be considered alongside other approaches to the dark - matter problem , particularly in scenarios involving large extra dimensions or string theory in which there exist large numbers of particles which are neutral under standard - model symmetries . .7ex
.7ex # 1*\{#1 } * = cmss10 = cmss10 at 7pt epsf .
And you have already written the first three sentences of the full article: the nature of what constitutes the non - baryonic dark matter in our universe remains one of the most fundamental mysteries in particle physics @xcite .
the most precise measurements of the relic abundance of this dark matter to date are those derived from wmap data @xcite , which yield a value @xmath0 where @xmath1 is the hubble constant . beyond this , we know very little about the properties of this dominant constituent of the matter density in our universe , save that its interactions with the fields of the standard model ( sm ) are extremely weak .
one of the reasons why the nature of the dark matter remains so elusive is its apparent stability ..
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observational constraints on the lifetime @xmath2 of any decaying dark - matter candidate @xmath3 are quite stringent .
indeed , for any particle with a relic abundance @xmath4 , current limits @xcite from cosmic microwave background ( cmb ) measurements , , require that @xmath5 for this reason , most models of the dark sector posit the existence of a single dark - matter particle ( or , in the case of certain multi - component dark - matter scenarios @xcite , a small number of such particles ) which is either absolutely stable ( with that stability usually conferred by some additional symmetry , such as r - parity in supersymmetric models , kk - parity @xcite in universal extra dimensions @xcite , or t - parity @xcite in little - higgs theories @xcite ) , or else sufficiently long - lived as to satisfy the bound in eq .
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12,817 |
Suppose that you have an abstract for a scientific paper: the rapid worldwide spread of severe viral infections , often involving novel modifications of viruses , poses major challenges to our health care systems .
this means that tools that can efficiently and specifically diagnose viruses are much needed . to be relevant for a broad application in local health care centers
, such tools should be relatively cheap and easy to use .
here we discuss the biophysical potential for the macroscopic detection of viruses based on the induction of a mechanical stress in a bundle of pre - stretched dna molecules upon binding of viruses to the dna .
we show that the affinity of the dna to the charged virus surface induces a local melting of the double - helix into two single - stranded dna .
this process effects a mechanical stress along the dna chains leading to an overall contraction of the dna .
our results suggest that when such dna bundles are incorporated in a supporting matrix such as a responsive hydrogel , the presence of viruses may indeed lead to a significant , macroscopic mechanical deformation of the matrix .
we discuss the biophysical basis for this effect and characterize the physical properties of the associated dna melting transition . in particular , we reveal several scaling relations between the relevant physical parameters of the system .
we promote this dna - based assay for efficient and specific virus screening . .
And you have already written the first three sentences of the full article: modern means of transportation , civil aviation traffic in particular , effect extremely rapid global spreading of diseases @xcite , contrasting the much slower spreading dynamics by traveling fronts , for instance , during the black death in europe @xcite .
concurrently , new infectious diseases keep emerging constantly , driven by human or ecologic reasons @xcite , while disease - causing microorganisms are developing various forms of multiple drug resistance @xcite .
this development puts considerable strain on modern health care systems , requiring rapid , reliable , and specific diagnosis of infectious agents ..
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there exist a number of modern techniques to detect viral and bacterial pathogens .
however , most of these methods require considerable time and resources .
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12,818 |
Suppose that you have an abstract for a scientific paper: we consider the energy current correlation function for the fpu-@xmath0 lattice . for small non - linearity one can rely on kinetic theory .
the issue reduces then to a spectral analysis of the linearized collision operator .
we prove thereby that , on the basis of kinetic theory , the energy current correlations decay in time as @xmath1 .
it follows that the thermal conductivity is anomalous , increasing as @xmath2 with the system size @xmath3 . .
And you have already written the first three sentences of the full article: with the availability of the first electronic computing machines , fermi , pasta , and ulam @xcite investigated the dynamics of a chain of nonlinear oscillators , in particular , their relaxation to thermal equilibrium .
their work had a , in retrospect surprisingly , strong impact .
we refer to the special issue @xcite which accounts for the first fifty years . in our contribution.
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, we will study the @xmath0-chain .
this is a linear chain of equal mass particles which are coupled to their nearest neighbors by nonlinear springs with a potential of the form @xmath4 , with @xmath5 , and @xmath6 being the string elongation .
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12,819 |
Suppose that you have an abstract for a scientific paper: the two- and three - nucleon interaction derived in chiral effective field theory at next - to - next - to - leading order is used to obtain the binding energy of nuclear matter .
saturation is found at a binding energy per particle @xmath0 mev and a fermi momentum @xmath1 @xmath2 , where the uncertainty is due to the cut - off dependence of the two - nucleon interaction .
the sensitivity of these values to the three - nucleon force is also studied . nuclear matter , equation of state of nuclear matter , forces in hadronic systems 21.65.-f , 21.65.mn , 21.30.-x .
And you have already written the first three sentences of the full article: within the last two decades , effective field theory ( eft ) has provided new methods for nuclear structure investigations . both two- and three - nucleon interactions based on the most general chiral effective pion - nucleon lagrangian have been developed utilizing weinberg s power counting scheme .
the phase shifts of the nucleon - nucleon interaction below the pion production threshold are reproduced with a precision that is comparable with the one achieved by modern phenomenological two - nucleon potentials , when pushing the expansion to the order n@xmath3lo , see refs.@xcite .
these forces together with three - nucleon forces at n@xmath4lo have been applied to a cornucopia of reactions . in particular ,.
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a good description of most of the low - energy nucleon - deuteron scattering observables at order n@xmath4lo has been reported .
the binding energies of @xmath3he and @xmath5he are also correctly reproduced once the leading three - nucleon force is included . within the framework of the no - core shell model , the chiral forces have been used to study nuclei with @xmath6 systems , in particular the sensitivity to the three - nucleon force . for details , see @xcite .
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12,820 |
Suppose that you have an abstract for a scientific paper: in general relativity , spacetime singularities raise a number of problems , both mathematical and physical . one can identify a class of singularities with smooth but degenerate metric which , under a set of conditions , allow us to define proper geometric invariants , and to write field equations , including equations which are equivalent to einstein s at non - singular points , but remain well - defined and smooth at singularities .
this class of singularities is large enough to contain isotropic singularities , warped - product singularities , including the friedmann - lematre - robertson - walker singularities , _
etc._also a big - bang singularity of this type automatically satisfies penrose s weyl curvature hypothesis . the schwarzschild , reissner - nordstrm , and kerr - newman singularities apparently are not of this benign type , but we can pass to coordinates in which they become benign .
the charged black hole solutions reissner - nordstrm and kerr - newman can be used to model classical charged particles in general relativity .
their electromagnetic potential and electromagnetic field are analytic in the new coordinates
they have finite values at @xmath0 .
there are hints from quantum field theory and quantum gravity that a dimensional reduction is required at small scale . a possible explanation is provided by benign singularities , because some of their properties correspond to a reduction of dimensionality .
http://www.jinr.ru/news_article.asp?n_id=1246[seminar held at jinr , dubna , may 15 , 2012 . ] .
And you have already written the first three sentences of the full article: there are two big problems in general relativity : 1 .
it predicts the occurrence of _ singularities _ @xcite .
2 . the attempts to _ quantize gravity _ seem to fail , because it is perturbatively nonrenormalizable @xcite . are these problems signs that we should _ give up general relativity _ in favor of more radical approaches ( superstrings , loop quantum gravity _ etc ..
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? there is another possibility : the limits may be in fact not of gr , but of our tools .
understanding how much we can push the boundaries of gr would be helpful , even in the eventuality that a better theory will replace gr .
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12,821 |
Suppose that you have an abstract for a scientific paper: coherent control of complex quantum systems is a fundamental requirement in quantum information processing and engineering .
recently developed notion of shortcut to adiabaticity ( sta ) has spawned intriguing prospects .
so far , the most experimental investigations of sta are implemented in the ideal thermal gas or the weakly interacting ultracold bose gases . here
we report the first demonstration of a many - body sta in a 3d anisotropically trapped unitary fermi gas .
a new dynamical scaling law is demonstrated on such a strongly interacting quantum gas . by simply engineering the frequency aspect ratio of a harmonic trap ,
the dynamics of the gas can be manipulated and the many - body state can be transferred adiabatically from one stationary state to another one in short time scale without the excitation .
the universal scaling both for non - interacting and unitary fermi gas is also verified .
this could be very important for future many - body quantum engineering and the exploration of the fundamental law of the thermodynamics .
understanding the adiabatic dynamics of complex quantum systems , often in the presence of strong correlations between constituent particles , is crucial for solving many fundamental problems in physics .
the quantum states are typically prepared and transferred by driving the system very slowly deterministically from an initial state to a desired target state in order to suppress excitation .
recently , a scheme of shortcut to adiabaticity ( sta ) @xcite has been proposed to speed up a quantum adiabatic process and relax the limitations of the environmentally - induced decoherence . the tremendous progress has been made on this field , with developments in optimal control theory including different driving mechanism @xcite , preparation of many - body states @xcite and shining new light on the fundamental law of the thermodynamics @xcite .
ultracold quantum gases provide unprecedented opportunities for studying such phenomena under controlled....
And you have already written the first three sentences of the full article: our experimental setup was presented in @xcite . a large atom number magneto - optical trap ( mot )
is realized by a laser system of 2.5-watts laser output with raman fiber amplifier and intracavity - frequency - doubler , as shown in fig .
[ fig : sfig1](a ) . after the loading stage.
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, @xmath72 cold atoms is obtained .
then mot is compressed to obtain atoms of near doppler - limited temperature of 280 @xmath73 and a density of @xmath74 @xmath75 . following this compressed stage ,
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12,822 |
Suppose that you have an abstract for a scientific paper: the space of phase - parameters ( sky - position , frequency , spindowns ) of a coherent matched - filtering search for continuous gravitational waves from isolated neutron stars shows strong global correlations ( `` circles in the sky '' ) . in the local limit
this can be analysed in terms of a parameter - space metric , but the global properties are less well studied . in this work we report on our recent progress in understanding these global correlations analytically for short to intermediate ( less than a month ,
say ) observation times and neglecting spindowns .
the _ location _ of these correlation - circles in parameter - space is found to be determined mostly by the orbital velocity of the earth , while the spin - motion of the detector and the antenna - patterns only contribute significantly to the amplitude of the detection statistic along these circles . .
And you have already written the first three sentences of the full article: continuous gravitational waves from , for example , rotating neutron stars with non - axisymmetric deformations such as mountains or oscillation - modes , are one of the primary targets of current - generation detectors of both interferometric- ( e.g. see @xcite ) as well as bar - detector design @xcite . in this paper we restrict ourselves to gravitational waves emitted from isolated neutron stars with negligible proper motion , for which the signal can be assumed to be a nearly monochromatic sinusoidal ( with slowly decreasing frequency ) in the solar - system barycenter frame ( ssb ) .
the corresponding signal received at the detector will be doppler - modulated by the spin of the earth and its orbital motion around the sun .
the phase of the received signal therefore depends not only on its intrinsic frequency @xmath0 and spindowns @xmath1 , but also on the sky - position ( denoted by @xmath2 and @xmath3 for right ascension and declination ) of the source and on the detector location ..
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in addition there is a time - dependent amplitude modulation of the signal depending on its polarisation angle @xmath4 and amplitudes @xmath5 and @xmath6 .
however , as shown in @xcite , one can eliminate these `` amplitude parameters '' together with the initial phase of the signal @xmath7 by analytically maximising the detection statistic over these parameters .
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12,823 |
Suppose that you have an abstract for a scientific paper: we study the suppression of qubit dephasing through uhrig dynamical decoupling ( udd ) in nontrivial environments modeled within the spin - boson formalism .
in particular , we address the case of ( i ) a qubit coupled to a bosonic bath with power - law spectral density , and ( ii ) a qubit coupled to a single harmonic oscillator that dissipates energy into a bosonic bath , which embodies an example of a structured bath for the qubit .
we then model the influence of random time jitter in the udd protocol by sorting pulse - application times from gaussian distributions centered at appropriate values dictated by the optimal protocol . in case ( i )
we find that , when few pulses are applied and a sharp cutoff is considered , longer coherence times and robust udd performances ( against random timing errors ) are achieved for a super - ohmic bath . on the other hand , when an exponential cutoff is considered a super - ohmic bath is undesirable . in case ( ii )
the best scenario is obtained for an overdamped harmonic motion .
our study provides relevant information for the implementation of optimized schemes for the protection of quantum states from decoherence . .
And you have already written the first three sentences of the full article: quantum systems are highly susceptible to perturbations coming from imprecise experimental control and undesirable interactions with the surrounding environment . in general
, system - environment coupling causes the vanishing of the off - diagonal matrix elements of the density operator for the system , wiping out its superposition aspects as time evolution occurs in a process called decoherence .
the existence of such a phenomenon in realistic situations has motivated scientists and engineers to devise methods to protect quantum information , with quantum error correction and the use of decoherence - free subspaces as important examples @xcite ..
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the technique of dynamical decoupling ( dd ) has emerged as a complementary and powerful means to combat decoherence experimentally . in general , it requires less physical resources than the aforementioned techniques and can , in principle , be used in a great variety of system - environment couplings . in dd , a sequence of strong and short electromagnetic pulses is applied to the system in order to time reverse the effects of the system - bath interaction hamiltonian .
the idea stems from the spin - echo technique in liquid nuclear magnetic resonance ( nmr ) developed in 1950 by hahn @xcite .
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12,824 |
Suppose that you have an abstract for a scientific paper: we report magnetization ( @xmath0 ) measurements close to the ferromagnetic quantum phase transition of the d - metal alloy ni@xmath1v@xmath2 at a vanadium concentration of @xmath3 . in the diluted regime ( @xmath4 )
, the temperature ( @xmath5 ) and magnetic field ( @xmath6 ) dependencies of the magnetization are characterized by nonuniversal power laws and display @xmath7 scaling in a wide temperature and field range .
the exponents vary strongly with @xmath8 and follow the predictions of a quantum griffiths phase .
we also discuss the deviations and limits of the quantum griffiths phase as well as the phase boundaries due to bulk and cluster physics . .
And you have already written the first three sentences of the full article: magnetic quantum phase transitions ( qpt ) have been studied in transition metal alloys and in heavy - fermion compounds tuned , e.g. , by pressure or chemical substitution .
they still offer challenges to theory and experiment ( see ref .
@xcite for a recent review ) ..
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quantum critical behavior is signified by singularities in thermodynamic and transport properties .
usually , specific power laws with characteristic exponents have been predicted at the quantum critical point ( qcp ) for `` clean '' homogeneous systems , while `` disordered '' inhomogeneous systems , driven , e.g. , by chemical substitution , may show different behavior @xcite . in the case of metallic ( itinerant ) heisenberg magnets ,
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12,825 |
Suppose that you have an abstract for a scientific paper: we consider the braid groups @xmath0 on finite simplicial complexes @xmath1 , which are generalizations of those on both manifolds and graphs that have been studied already by many authors .
we figure out the relationships between geometric decompositions for @xmath1 and their effects on braid groups , and provide an algorithmic way to compute the group presentations for @xmath0 with the aid of them . as applications ,
we give complete criteria for both the surface embeddability and planarity for @xmath1 , which are the torsion - freeness of the braid group @xmath0 and its abelianization @xmath2 , respectively . .
And you have already written the first three sentences of the full article: the braid group @xmath3 on a 2-disk @xmath4 was firstly introduced by e. artin in 1920 s , and fox and neuwirth generalized it to braid groups @xmath0 on arbitrary topological spaces @xmath1 via _ configuration spaces _ , which are defined as follows . for a compact , connected topological space @xmath1 , the _ ordered configuration space @xmath5 _
is the set of @xmath6-tuples of distinct points in @xmath1 , and the orbit space @xmath7 under the action of the symmetric group @xmath8 on @xmath5 permutting coordinates is called the _ unordered configuration space _ on @xmath1 .
@xmath9 where @xmath10 let @xmath11 and @xmath12 be basepoints for @xmath5 and @xmath7 , respectively . then the _ pure @xmath6-braid group _ @xmath13 and _ ( full ) @xmath6-braid group @xmath14 _ are defined to be the fundamental groups of the configuration spaces @xmath5 and @xmath7 , respectively ..
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we will suppress basepoints and denote these groups by @xmath15 and @xmath0 unless any ambiguity occurs .
however , most of research on braid groups has been focused on braid groups on manifolds , more specifically , on surfaces , until the end of 20th century when ghrist presented a pioneering paper @xcite about braid groups on _ graphs @xmath16 _ which are finite , 1-dimensional simplicial complexes . in 2000 , abrams defined in his ph .
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12,826 |
Suppose that you have an abstract for a scientific paper: we observe the shift of rydberg levels of rubidium close to a copper surface when atomic clouds are repeatedly deposited on it .
we measure transition frequencies of rubidium to @xmath0 and @xmath1 rydberg states with principal quantum numbers @xmath2 between 31 and 48 using the technique of electromagnetically induced transparency .
the spectroscopic measurement shows a strong increase of electric fields towards the surface that evolves with the deposition of atoms . starting with a clean surface , we measure the evolution of electrostatic fields in the range between 30 and from the surface .
we find that after the deposition of a few hundred atomic clouds , each containing @xmath3 atoms , the field of adsorbates reaches for a distance of from the surface .
this evolution of the electrostatic field sets serious limitations on cavity qed experiments proposed for rydberg atoms on atom chips . .
And you have already written the first three sentences of the full article: the large electric polarizability of rydberg atoms leads to a large response to electric fields @xcite .
this property is an enormous advantage for applications that require fast coupling between atoms and photons , such as the entanglement of rydberg atoms via the electromagnetic modes of radio - frequency and microwave cavities @xcite .
several quantum computation schemes have been proposed based on rydberg atoms coupled to superconducting coplanar cavities @xcite . in the proposed scenarios ,.
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cold atomic gases are first positioned near a coplanar resonator .
the atoms are subsequently laser excited into rydberg states which interact with the electromagnetic modes of the resonator .
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12,827 |
Suppose that you have an abstract for a scientific paper: an important property of high - performance , low complexity codes is the existence of highly efficient algorithms for their decoding .
many of the most efficient , recent graph - based algorithms , e.g. message passing algorithms and decoding based on linear programming , crucially depend on the efficient representation of a code in a graphical model . in order to understand the performance of these algorithms , we argue for the characterization of codes in terms of a so called _ fundamental cone _ in euclidean space which is a function of a given parity check matrix of a code , rather than of the code itself .
we give a number of properties of this fundamental cone derived from its connection to unramified covers of the graphical models on which the decoding algorithms operate .
for the class of cycle codes , these developments naturally lead to a characterization of the fundamental polytope as the newton polytope of the hashimoto edge zeta function of the underlying graph . .
And you have already written the first three sentences of the full article: whenever information is transmitted across a channel , we have to ensure its integrity against errors .
while data may originate in a multitude of applications , at some core level of the communication system , it is usually encoded as a string of zeros and ones of fixed length .
protection against transmission errors is provided by intelligently adding redundant bits to the information symbols , thus effectively restricting the set of possibly transmitted sequences of bits to a fraction of all possible sequences ..
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the set of all possibly transmitted data vectors is called a code , and the elements are called codewords . a classical measure of goodness of a code is the code s _ minimum hamming distance _ , i.e. , the minimum number of coordinates in which any two distinct codewords differ .
in fact , a large part of traditional coding theory is concerned with finding the fundamental trade - offs between three parameters : the length of the code , the number of codewords in the code , and the minimum distance of the code .
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12,828 |
Suppose that you have an abstract for a scientific paper: we present a case study for the relevance of the r - mode instability for accreting compact stars .
our estimates are based on approximations that facilitate back - of - the - envelope calculations .
we discuss two different cases : 1 ) for recycled millisecond pulsars we argue that the r - mode instability may be active at rotation periods longer than the kepler period ( which provides the dynamical limit on rotation ) as long as the core temperature is larger than about @xmath0 k. our estimates suggest that the instability may have played a role in the evolution of the fastest spinning pulsars , and that it may be presently active in the recently discovered 2.49 ms x - ray pulsar sax j1808.4 - 3658 as well as the rapidly spinning neutron stars observed in low mass x - ray binaries .
this provides a new explanation for the remarkably similar rotation periods inferred from khz quasi - periodic oscillations in the lmxbs .
the possibility that the rotation of recycled pulsars may be gravitational - radiation limited is interesting because the gravitational waves from a neutron star rotating at the instability limit may well be detectable with the new generation of interferometric detectors .
2 ) we also consider white dwarfs , and find that the r - mode instability may possibly be active in short period white dwarfs .
our order of magnitude estimates ( for a white dwarf of @xmath1 and @xmath2 composed of @xmath3 ) show that the instability could be operating for rotational periods shorter than @xmath4 s. this number is in interesting agreement with the observed periods ( @xmath5 s ) of the rapidly spinning dq herculis stars . however , we find that the instability grows too slowly to affect the rotation of these stars significantly
. = -1.5 cm = .0 cm = 18.8 cm .
And you have already written the first three sentences of the full article: the recent discovery of a new instability in rotating relativistic stars has revived interest in problems concerning mechanisms that may limit the rotation rate of neutron stars . as was first shown by one of us ( andersson 1998 ) , the so - called r - modes ( papaloizou and pringle 1978 ) are formally unstable at all rates of rotation in a perfect fluid neutron star ( see also friedman and morsink 1998 ) . the mechanism behind the instability is the familiar one that was discovered by chandrasekhar ( 1970 ) , friedman and schutz ( 1978 ) : the modes are unstable due to the emission of gravitational waves ( see stergioulas ( 1998 ) for a review on nonaxisymmetric instabilities in rotating relativistic stars ) .
even more surprising than the actual existence of the instability are the results of recent estimates of the time - scale at which the r - mode instability will grow ( lindblom , owen and morsink 1998 ; andersson , kokkotas and schutz 1998 ) .
it seems that the r - mode instability has the potential to slow down newly born neutron stars dramatically , and that the r - mode instability is considerably stronger than the previously considered one for the f - mode of the star ( cf ..
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the results of lindblom 1995 ; stergioulas and friedman 1998 ) .
the new results suggest that , assuming that a neutron star is born spinning as fast as it possibly can ( at the kepler frequency @xmath6 , i.e. with a period @xmath7 ms ) , the r - mode instability will force the star to spin down to a period of roughly @xmath8 ms in the first year or so .
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12,829 |
Suppose that you have an abstract for a scientific paper: models for the seds of infrared galaxies are reviewed , with particular application to hyperluminous infrared galaxies .
infrared : galaxies - galaxies : starburst - galaxies : active .
And you have already written the first three sentences of the full article: the key ingredients for models for the spectral energy distributions ( seds ) of infrared galaxies are * ( 1 ) a model for interstellar dust grains . *
detailed models have been provided by mathis et al ( 1977 ) , draine and lee ( 1984 ) , rowan - robinson ( 1986 , 1992 ) , desert et al ( 1990 ) , siebenmorgen and krugel ( 1992 ) , dwek ( 1998 ) . *
( 2 ) an assumed density distribution for the dust . *.
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detailed physical density profiles have been developed by yorke ( 1977 ) for hii regions , by efstathiou and rowan - robinson ( 1991 ) for protostars and by eftathiou et al ( 2000 ) for starbursts .
however most authors have followed the approach of rowan - robinson ( 1980 ) , who explored models with n(r ) @xmath0 .
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12,830 |
Suppose that you have an abstract for a scientific paper: we consider the semilinear elliptic boundary value problem @xmath0 in a bounded smooth domain @xmath1 of @xmath2 for supercritical exponents @xmath3 until recently , only few existence results were known .
an approach which has been successfully applied to study this problem , consists in reducing it to a more general critical or subcritical problem , either by considering rotational symmetries , or by means of maps which preserve the laplace operator , or by a combination of both .
the aim of this paper is to illustrate this approach by presenting a selection of recent results where it is used to establish existence and multiplicity or to study the concentration behavior of solutions at supercritical exponents .
key words : nonlinear elliptic boundary value problem ; supercritical nonlinearity ; nonautonomous critical problem .
2010 msc : 35j61 ( 35j20 , 35j25 ) . .
And you have already written the first three sentences of the full article: consider the model problem@xmath4{ll}% -\delta u=\left\vert u\right\vert ^{p-2}u & \text{in } \omega,\\ \text { \ \ \ \ } u=0 & \text{on } \partial\omega , \end{array } \right .
\tag{$\wp_p$}\label{mainprob}%\ ] ] where @xmath5 is the laplace operator , @xmath1 is a bounded domain in @xmath2 with smooth boundary , @xmath6 and @xmath7 despite its simple form , this problem has been an amazing source of open problems , and the process of understanding it has helped develop new and interesting techniques which can be applied to a wide variety of problems .
the behavior of this problem depends strongly on the exponent @xmath8 ..
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it is called subcritical , critical or supercritical depending on whether @xmath9 @xmath10 or @xmath11 where @xmath12 is the so - called critical sobolev exponent . in the subcritical case ,
standard variational methods yield the existence of a positive solution and infinitely many sign changing solutions .
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12,831 |
Suppose that you have an abstract for a scientific paper: lytic polysaccharide monooxygenase ( lpmo ) enzymes have attracted considerable attention due to their ability to enhance polysaccharide depolymerization , making them interesting in respect to production of biofuel from cellulose .
the lpmos are metalloenzymes that contain a mononuclear copper active site that can active dioxygen .
however , many details of this activation are unclear , and have previously been investigated from a computational angle . yet
, these studies have either employed only molecular mechanics ( mm ) , which are inaccurate for metal active sites , or they have described only the active site with quantum mechanics ( qm ) and neglected the effect of the protein . here , we employ hybrid qm and mm ( qm / mm ) methods to investigate the first steps of the lpmo mechanism , which is reduction of of cu@xmath0 to cu@xmath1 and formation of a cu@xmath0superoxide complex . in the latter complex , the superoxide can bind either in an equatorial or an axial position .
for both steps we obtain structures that are markedly different from previous suggestions , based on vacuum calculations .
our calculations show that the equatorial isomer of the superoxide complex is over 60 kj / mol more stable than the axial isomer , being stabilized by interactions with a second - coordination - sphere gln residue , showing a possible role for this residue .
coordination of superoxide in this manner is in agreement with recent experimental suggestions . .
And you have already written the first three sentences of the full article: employing cellulose in biofuel production can make this advancing technology a highly competitive alternative to fossil fuel . as a major component of biomass , cellulose is non - expensive and the most abundant polysaccharide on earth@xcite .
however , the application of cellulose in biofull production requires degradation of it into smaller sugars , which has shown to be a major obstacle , requiring both hydrolytic enzymes and thermal work .
this remarkable stability is caused by the structure of very long glucan chains , which are comprised of glucose monomers , coupled together by @xmath2 - 1,4 glycosidic linkages ..
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the glucan chains interact with each other by an extensive network of inter- and intra - molecular hydrogen bonds invovling the three hydroxyl groups of each glucose monomer , which limits the accessibility of hydrolytic enzymes to the glycosidic linkages.@xcite lately , a class of fungal and bacterial enzymes called lytic polysaccharide monooxygenases ( lpmos ) have attracted considerable attention due to their ability to enhance polysaccharide depolymerization , thereby providing a route to efficient conversion of cellulose into fermantable sugars@xcite .
the first industrial applications have already been seen for ethanol production.@xcite , scaledwidth=75.0% ] initially , lpmo enzymes@xcite were assumed to be solely hydrolytic and were classified as belonging to the glycoside hydrolase 61 ( gh61 ) and carbohydrate - binding modules 33 ( cbm33 ) families . an initial report questioning whether gh61 indeed were hydrolases occurred in 2008@xcite , but the role of lpmos in polysaccharide degradation was first demonstrated in 2010 , when a lpmo from the gh61 family was shown to be able to disrupt the surface of recalcitrant cellulose by an oxidative mechanism.@xcite .
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12,832 |
Suppose that you have an abstract for a scientific paper: the polaron binding energy and effective mass in a degenerate polar gas is calculated in the fractional - dimensional approach under plasmon pole approximation.the effect of carrier densities on the static and dynamic screening correction of the electron - phonon interaction and electron - electron interaction to the polaronic propertis is calculated from electron self - energies within the second - order perturbation method .
the hubbard local field factor has been used for the static screening correction in the polaronic properties .
we found that polaronic properties decrease with increase with carrier density and dimensionality of the system . .
And you have already written the first three sentences of the full article: when an electron in the bottom of the conduction band of a polar semiconductor moves , its coulomb field displaces the positive and negative ions with respect to each other producing polarization field .
the electron with the associated phonon cloud is known as a polaron .
the density oscillation in a medium creates plasmons ..
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the interaction between an electron and plasmons can be described by frlich hamiltonian .
the interaction of the electron with plasmon cloud is termed as the plasmapolaron .
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12,833 |
Suppose that you have an abstract for a scientific paper: we consider the coupled einstein - dirac - maxwell equations for a static , spherically symmetric system of two fermions in a singlet spinor state .
soliton - like solutions are constructed numerically .
the stability and the properties of the ground state solutions are discussed for different values of the electromagnetic coupling constant .
we find solutions even when the electromagnetic coupling is so strong that the total interaction is repulsive in the newtonian limit .
our solutions are regular and well - behaved ; this shows that the combined electromagnetic and gravitational self - interaction of the dirac particles is finite . .
And you have already written the first three sentences of the full article: in the recent paper @xcite , we studied the coupled einstein - dirac ( ed ) equations for a spherically symmetric system of two fermions in a singlet spinor state . using numerical methods , we found particle - like solutions and analyzed their properties . in this letter , we extend our results to the more physically relevant system where the einstein - dirac equations are coupled to an electromagnetic field .
we find particle - like solutions which are linearly stable ( with respect to spherically symmetric , time - dependent perturbations ) , and have other interesting properties .
the general einstein - dirac - maxwell ( edm ) equations for a system of @xmath0 dirac particles are @xmath1 where @xmath2 is the sum of the energy - momentum tensor of the dirac particles and the maxwell stress - energy tensor . here.
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the @xmath3 are the dirac matrices , which are related to the lorentzian metric via the anti - commutation relations @xmath4 @xmath5 is the electromagnetic field tensor , and @xmath6 are the wave functions of fermions of mass @xmath7 and charge @xmath8 .
the dirac operator is denoted by @xmath9 ; it depends on both the gravitational and the electromagnetic field ( for details , see e.g. @xcite ) . in order to get a spherically symmetric system , we consider , as in @xcite , two fermions with opposite spin , i.e. a singlet spinor state . using the ansatz in @xcite ,
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12,834 |
Suppose that you have an abstract for a scientific paper: we present a method to determine the nodal structure of the energy gap of unconventional superconductors such as high @xmath0 materials .
we show how nonlinear electrodynamics phenomena in the meissner regime , arising from the presence of lines on the fermi surface where the superconducting energy gap is very small or zero , can be used to perform `` node spectroscopy '' , that is , as a sensitive bulk probe to locate the angular position of those lines . in calculating the nonlinear supercurrent response , we include the effects of orthorhombic distortion and @xmath1 plane anisotropy . analytic results presented demonstrate a systematic way to experimentally distinguish order parameters of different symmetries , including cases with mixed symmetry ( for example , @xmath2 and @xmath3 ) .
we consider , as suggested by various experiments , order parameters with predominantly @xmath4-wave character , and describe how to determine the possible presence of other symmetries .
the nonlinear magnetic moment displays a distinct behavior if nodes in the gap are absent but regions with small , finite , values of the energy gap exist . .
And you have already written the first three sentences of the full article: in recent years a very significant effort , both experimentally and theoretically , has been made to determine the symmetry of the pairing state@xcite in high temperature superconductors ( htsc s ) .
it is usually held that such an identification would provide significant clues towards a better understanding of the microscopic mechanism responsible for superconductivity .
the symmetry properties of the pairing state itself , being connected to those of the superconducting energy gap , have important physical and technological implications ..
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there is a large body of experimental results , supported by theoretical work , that is generally interpreted as indicative of a pairing state at least predominantly of the @xmath4-wave type @xcite , ( although there are experiments@xcite which are difficult to interpret in that framework . ) by this , it is meant a pairing state which has an order parameter ( op ) which vanishes , or nearly so , along four lines on the fermi surface ( fs ) .
the angle between such lines of nodes ( or `` quasinodes '' ) is presumed to be near @xmath5 , but , because of the orthorhombic symmetry of htsc materials ( as exemplified by the strong anisotropy of superconducting properties@xcite in the @xmath1 plane ) this is unlikely to be precisely correct .
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12,835 |
Suppose that you have an abstract for a scientific paper: the surface magnetic field strength of white dwarfs is observed to vary from very little to around @xmath0 g . here
we examine the proposal that the strongest fields are generated by dynamo action during the common envelope phase of strongly interacting stars that leads to binary systems containing at least one white dwarf .
the resulting magnetic field depends strongly on the electrical conductivity of the white dwarf , the lifetime of the convective envelope and the variability of the magnetic dynamo .
we assess the various energy sources available and estimate necessary lifetimes of the common envelope . in the case of a dynamo that leads a randomly oriented magnetic field
we find that the induced field is confined to a thin boundary layer at the surface of the white dwarf .
this then decays away rapidly upon dispersal of the common envelope .
the residual field is typically less than @xmath1 times the strength of the external field . only in the case where there is some preferential direction to the dynamo - generated field
can an induced field , that avoids rapid decay , be produced .
we show that a surface field of magnitude a fewper cent of the external field may be produced after a few myr . in this case
the residual field strength is roughly proportional to the lifetime of the dynamo activity .
[ firstpage ] .
And you have already written the first three sentences of the full article: surveys of the galactic white dwarf ( wd ) population have discovered magnetic field strengths ranging up to about @xmath2 @xcite . typically wds fall into two categories , those with field strengths of the order @xmath3 or higher and those with fields weaker than around @xmath4 .
we focus here on highly magnetic wds ( hereinafter mwds ) with field strengths greater than @xmath3 .
@xcite proposed a fossil field mechanism based on the evolution of ap / bp stars but it is difficult to argue that such a field can survive stellar evolution in which all parts of the star have passed through convective phases . here.
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we build on the proposal of @xcite that the origin of such fields lies in the interaction between the wd and its companion star in a binary system .
this assertion is based on observations from the sdss that approximately @xmath5per cent of isolated wds are highly magnetic @xcite as are @xmath6per cent in cataclysmic variables @xcite while there are none to be found in wide detached binary systems . of the 1253 binary systems comprising a wd and non - degenerate m - dwarf star surveyed in the sdss data release five @xcite none
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12,836 |
Suppose that you have an abstract for a scientific paper: based on kitaev - heisenberg model with dzyaloshinskii - moriya ( dm ) interactions , we studied nature of possible magnetic phases in frustrated hyperkagome iridate , na@xmath0ir@xmath1o@xmath2 ( na-438 ) . using monte - carlo simulation , we showed that the phase diagram is mostly covered by two competing magnetic ordered phases ; z@xmath3 symmetry breaking ( sb ) phase and z@xmath4 sb phase , latter of which is stabilized by the classical order by disorder .
these two phases are intervened by a first order phase transition line with z@xmath2-like symmetry .
the critical nature at the z@xmath4 sb ordering temperature is characterized by the 3d xy universality class , below which u(1 ) to z@xmath4 crossover phenomena appears ; the z@xmath4 spin anisotropy becomes irrelevant in a length scale shorter than a crossover length @xmath5 while becomes relevant otherwise .
a possible phenomenology of polycrystalline na-438 is discussed based on this crossover phenomena .
u l .
And you have already written the first three sentences of the full article: an interplay between spin and orbital degree of freedom enriches the physics of mott insulators @xcite . a strong relativistic spin - orbit interaction in cubic iro@xmath4 octahedra endows ir electron with spin - orbit entangled kramers doublet ( pseudo - spin doublet ) , @xcite which opens a new root to `` @xmath6 '' mott insulators with coordinate - dependent pseudo - spin - anisotropic exchange interactions .
@xcite mott insulating materials with bond - dependent spin - anisotropic interactions possibly stabilize gapless quantum spin liquid state with exotic excitations such as majorana fermions @xcite .
honeycomb - lattice na@xmath3iro@xmath7 , @xcite @xmath8 , @xmath9 , @xmath10-li@xmath3iro@xmath7 , @xcite and hyperkagome - lattice na@xmath0ir@xmath7o@xmath2 ( na-438 ) @xcite are being intensively explored along this research interest . throughout thermodynamic measurements , @xcite resonant inelastic x - ray @xcite and neutron scattering experiments @xcite ,.
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the nature of low - temperature magnetic phases in all the honeycomb iridate compounds has been mostly clarified .
meanwhile nature of a low-@xmath11 phase of na-438 is still veiled in mystery , although possible magnetic , @xcite nematic @xcite , valence bond solid , @xcite and spin liquid phases @xcite are being proposed theoretically .
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12,837 |
Suppose that you have an abstract for a scientific paper: we develop a unified treatment of pumping and nonequilibrium thermodynamics .
we show that the pumping current generated through an adiabatic mechanical operation in equilibrium can be expressed in terms of the stationary distribution of the corresponding driven nonequilibrium system .
we also show that the total transfer in pumping can be evaluated from the work imported to the driven counterpart .
these findings lead us to a unified viewpoint for pumping and nonequilibrium thermodynamics . for centuries
, heat pumping has been considered an important topic .
the carnot engine showed the direct relation between mechanical work and pumping of heat .
pumping induced by electric current known as the peltier effect , was explained by the linear response theory as an example of the reciprocal relation . in molecular scales ,
the possibility of realizing heat pumps with thermal ratchets is suggested in @xcite apart from heat pumps , ion pumps or the directive transport of biomolecules are theoretically intensively studied .
these are modeled using flashing ratchets @xcite as stochastic pumps in molecular scales .
the mechanism of pumping in flashing ratchets is related to geometric effects in the parameter space @xcite . the same property in heat pumps
has also been discussed @xcite .
these studies suggest that the universal characteristics of pumps exist in various designs . in this paper , we develop a unified viewpoint on pumping and nonequilibrium thermodynamics , from which one can derive the universal characteristics of pumps as well as examine efficient protocols for pumping . by pumping , we mean an equilibrium process in which the parameters of the system are varied through an external agent according to a fixed protocol in order to invoke the desired type of current through the system . for each setup of pumping
, we introduce a corresponding `` _ driven counterpart _ '' , i.e. , a nonequilibrium system in which the current flows spontaneously owing to an applied driving....
And you have already written the first three sentences of the full article: we employ a classical system with a hamiltonian @xmath0 , where @xmath1 denotes the system s microstate .
the hamiltonian depends on a set of parameters @xmath2 .
we assume a time - reversal symmetry for the hamiltonian @xmath3 , where @xmath4 ..
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we do not limit the number of the system s degrees of freedom .
it may be one or the avogadro number .
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12,838 |
Suppose that you have an abstract for a scientific paper: we analyze nonlinear collective effects near surfaces of semi - infinite periodic systems with multi - gap transmission spectra and introduce a novel concept of _ multi - gap surface solitons _ as mutually trapped surface states with the components associated with different spectral gaps .
we find numerically discrete surface modes in semi - infinite binary waveguide arrays which can support simultaneously two types of discrete solitons , and analyze different multi - gap states including the soliton - induced waveguides with the guided modes from different gaps and composite vector solitons .
10 s. g. davidson and m. steslicka , _ basic theory of surface states _ ( oxford science publications , new york , 1996 ) . i. e. tamm , `` a possible kind of electron binding on crystal surfaces , '' z. phys .
* 76 , * 849850 ( 1932 ) .
p. yeh , a. yariv , and c. s. hong , `` electromagnetic propagation in periodic stratified media .1 .
general theory , '' j. opt .
. am .
* 67 , * 423438 ( 1977 ) .
p. yeh , a. yariv , and a. y. cho , `` optical surface waves in periodic layered media , '' appl
. phys . lett .
* 32 , * 104105 ( 1978 )
. w. j. tomlinson , `` surface wave at a nonlinear interface , '' opt . lett . * 5 , * 323325 ( 1980 ) .
a. d. boardman , p. egan , f. lederer , u. langbein , and d. mihalache , `` third - order nonlinear electromagnetic te and tm guided waves , '' in _ nonlinear surface electromagnetic phenomena _
, vol .
29 of _ modern problems in condensed matter sciences _ ,
h. e. ponath and g.i .
stegeman , eds . , ( north - holland , amsterdam , 1991 ) , pp . 73287
. d. mihalache , m. bertolotti , and c. sibilia , `` nonlinear wave propagation in planar structures , '' in _ progress in optics _ , e. wolf , ed . , ( north - holland , amsterdam , 1989 ) , vol .
xxvii , pp .
229313 .
yu .
s. kivshar , f. zhang , and s. takeno , `` multistable nonlinear surface modes , '' physica d * 119 , * 125133 ( 1998 ) .
k. g.....
And you have already written the first three sentences of the full article: interfaces separating different physical media can support a special class of transversally localized waves known as _
surface waves_. linear surface waves have been studied extensively in many branches of physics @xcite , and the structure of surface states in periodic systems is associated with the specific properties of the corresponding bloch waves .
such linear surface waves with _ staggered _ profiles are often referred to as _ tamm states _.
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@xcite , first identified as localized electronic states at the edge of a truncated periodic potential , and then found in other systems , e.g. for an interface separating periodic and homogeneous dielectric optical media @xcite .
_ nonlinear surface waves _ have been studied most extensively in optics where both te and tm surface modes were predicted and analyzed for the interfaces separating two different homogeneous nonlinear dielectric media @xcite .
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12,839 |
Suppose that you have an abstract for a scientific paper: we discuss a possible scenario for radiation mechanism of pulsed gev @xmath0-rays from magnetars .
the magnetars have shown frequent x - ray bursts , which would be triggered by crust fractures and could release the energy of order of @xmath1 .
if the location of the crust cracking of the magnetic field is close to the magnetic pole , part of the released energy may excite the alfv@xmath2n wave that can propagate into outer magnetosphere .
the oscillation of the magnetic field induces the available potential drop @xmath3 volts , which can accelerate the electrons and/or positrons to the lorentz factor @xmath4 in the outer magnetosphere .
the curvature radiation process at outer magnetosphere can produce gev @xmath0-rays .
if the radiation process is occurred above @xmath5 cm from the stellar surface , the emitted gev @xmath0-rays can escape from the pair - creation process with the x - rays and/or the magnetic field .
the expected luminosity of the gev emissions is order of @xmath6 , and the radiation process will last for a temporal scale of years .
the expected pulse profiles have a broad shape with sometimes sharp peaks .
we apply the model to axp 1e 2259 + 586 .
[ firstpage ] .
And you have already written the first three sentences of the full article: soft gamma - ray repeaters and anomalous x - ray pulsars ( axps ) have been discussed in terms of `` magnetar '' model , in which the activities of the neutron star are powered by the dissipation of the extremely strong magnetic field ( thompson & duncan 1995 ; thompson , lyutikov & kulkarni 2002 ; woods & thompson 2006 ; mereghetti 2008 ) .
the magnetar s emissions mainly appear in the x - ray bands , which are described by the blackbody component ( with hard tail ) below 10 kev plus a hard power law component above 10 kev ( kuiper et al .
the power law components are often explained by the resonant compton scattering process of the mildly relativistic electrons and/or positrons below 10 kev ( fern@xmath7ndez & thompson 2007 ; rea et al ..
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2008 ) and of the relativistic pairs above 10 kev ( beloborodov & thompson 2007 ; baring & harding 2007 ; beloborodov 2012 ) , respectively .
although no pulsed gev emissions from the magnetars have been confirmed , it has not been conclusive that the magnetars are intrinsically dark in the gev radiation or present sensitivity of the @xmath8 telescope is not enough to detect any pulsed gev emission from magnetars .
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12,840 |
Suppose that you have an abstract for a scientific paper: we analyze high multiplicity proton - proton ( @xmath0 ) collision data in the framework of the string percolation model ( spm ) that has been successful in describing several phenomena of multiparticle production , including the signatures of recent discovery of strongly interacting partonic matter , the quark gluon plasma ( qgp ) , in relativistic heavy - ion collisions .
our study in terms of the ratio of shear viscosity and entropy density ( @xmath1 ) and the ( lqcd ) predicted signature of qcd change of phase , in terms of effective number of degrees of freedom ( @xmath2 ) , reiterates the possibility of strongly interacting collective medium in these events .
the quark - gluon plasma ( qgp ) @xcite , an exotic state of matter of partonic degrees of freedom , is predicted @xcite by quantum chromodynamics ( qcd ) the theory of strong interaction .
experiments with relativistically colliding heavy nuclei at the relativistic heavy ion collider ( rhic ) at brookhaven national laboratory revealed features @xcite , expected from qgp - like dense partonic medium .
relativistic hydrodynamics helped in identifying the collective nature of the medium .
unpredictably , however , the ratio of the shear viscosity and the entropy density ( @xmath3 ) , the measure of fluidity , at the rhic heavy - ion collisions reached a value @xcite close to that for a perfect fluid , indicating formation of a strongly interacting medium , termed as sqgp .
recent heavy - ion data from the large hadron collider ( lhc ) at cern with heavier nuclei and at higher energy corroborates @xcite most of the rhic findings . in this scenario of the qgp study , an unexpected feature , namely the `` ridge '' in the long range near side angular correlation , in distinct class of `` high multiplicity '' events of proton - proton collisions @xcite at @xmath4 7 tev at lhc
has triggered revival of an old school of thought @xcite of the possibility of formation of a collective medium in @xmath0 collisions also .
several of subsequent....
And you have already written the first three sentences of the full article: i. bautista was supported by conacyt grant .
we would like to thank c. pajares and b. k. srivastava for fruitful discussions .
99 collins , j. c. and perry , m. j.,phys ..
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lett . * 34*,1353 - 1356(1975 ) .
shuryak , e. , phys .
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Suppose that you have an abstract for a scientific paper: in the ultracold gases of alkali - earth ( like ) atoms , a new type of feshbach resonance , i.e. , the orbital feshbach resonance ( ofr ) , has been proposed and experimentally observed in ultracold @xmath0yb atoms .
when the ofr of the @xmath0yb atoms occurs , the energy gap between the open and closed channels is smaller by two orders of magnitudes than the van der waals energy . as a result
, quantitative accurate results for the low - energy two - body problems can be obtained via multi - channel quantum defect theory ( mqdt ) , which is based on the exact solution of the schr@xmath1dinger equation with the van der waals potential . in this paper
we use the mqdt to calculate the two - atom scattering length , effective range , and the binding energy of two - body bound states for the systems with ofr . with these results
we further study the clock - transition spectrum for the two - body bound states , which can be used to experimentally measure the binding energy .
our results are helpful for the quantitative theoretical and experimental researches for the ultracold gases of alkali - earth ( like ) atoms with ofr . .
And you have already written the first three sentences of the full article: feshbach resonance @xcite is a powerful tool for the control of interaction between ultracold atoms @xcite . in ultracold gases of alkali atoms the magnetic feshbach resonances
are widely used for the tuning of @xmath2-wave scattering lengths @xcite . for the gases of ultracold alkali - earth ( like ) atoms , recently we found a new type of feshbach resonance , i.e. , the orbital feshbach resonance ( ofr ) @xcite . with the help of ofr , one can precisely control the @xmath2-wave scattering length between two fermionic alkali - earth ( like ) atoms in @xmath3 and @xmath4 electronic orbital states with different nuclear spin , by changing the magnetic field @xcite .
ofr has been experimentally observed in the ultracold gases of @xmath0yb atoms @xcite ..
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it is also shown that using the ultracold gases of alkali - earth ( like ) atoms with ofr one can study several interesting problems , including the kondo effect , the strong - interacting ultracold fermi gases with narrow feshbach resonance and the leggett mode , _ et .
_ @xcite .
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12,842 |
Suppose that you have an abstract for a scientific paper: many complex systems are characterized by broad distributions capturing , for example , the size of firms , the population of cities or the degree distribution of complex networks . typically this feature is explained by means of a preferential growth mechanism .
although heterogeneity is expected to play a role in the evolution it is usually not considered in the modeling probably due to a lack of empirical evidence on how it is distributed .
we characterize the intrinsic heterogeneity of groups in an online community and then show that together with a simple linear growth and an inhomogeneous birth rate it explains the broad distribution of group members . .
And you have already written the first three sentences of the full article: many complex systems are characterized by distributions , _ e.g. _ , zipf s law ( originally used to describe the frequency of words @xcite ) , pareto s law ( originally describing the wealth of nations @xcite ) , and more recently scale - free topologies ( capturing the degree distribution of complex networks @xcite ) @xcite .
this property is typically perceived as a symptom of the rich - gets - richer principle , and models implementing some degree of preferential growth are usually the first approach to explain heavy - tailed distributions @xcite . in line with the rich - gets - richer principle , the gibrat s law suggests that the expected growth of a firm , a city or social activity is proportional to its size @xcite .
however , in general , less attention has been devoted to the time evolution of complex systems probably due to the lack of empirical data along time ( for some exceptions see @xcite ) . in many network growth models the time unit.
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is mapped to the number of new arriving elements , which makes it difficult to compare the results with real data . moreover
, many models assume that the elements are born identical leading to correlations between age and frequency ( of words , wealth , degree or size ) which are not fully supported by empirical observations @xcite . in many real systems , especially in social systems , individuals or elements
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12,843 |
Suppose that you have an abstract for a scientific paper: recent experimental evidence [ gruji _ et al . _ , plos one * 5 * , e13749 ( 2010 ) ] on the spatial prisoner s dilemma suggests that players choosing to cooperate or not on the basis of their previous action and the actions of their neighbors coexist with steady defectors and cooperators .
we here study the coexistence of these three strategies in the multiplayer iterated prisoner s dilemma by means of the replicator dynamics .
we consider groups with @xmath0 and @xmath1 players and compute the payoffs to every type of player as the limit of a markov chain where the transition probabilities between actions are found from the corresponding strategies .
we show that for group sizes up to @xmath2 there exists an interior point in which the three strategies coexist , the corresponding basin of attraction decreasing with increasing number of players , whereas we have not been able to locate such a point for @xmath3 .
we analytically show that in the limit @xmath4 no interior points can arise .
we conclude by discussing the implications of this theoretical approach on the behavior observed in experiments .
evolution ; prisoner s dilemma ; cooperation ; conditional cooperation ; game theory ; replicator dynamics .
And you have already written the first three sentences of the full article: in the past few years , different mechanisms have been proposed to explain the origin and stability of cooperation @xcite .
one of these mechanisms involves assortment of cooperators @xcite , in particular through the existence of a spatial or social structure dictating who interacts with whom ( cf .
network reciprocity in @xcite ) ..
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cooperators might then interact mainly with each other and keep the benefits of cooperation to the extent that they perform better than defectors or free riders in peripheral positions .
this idea stems from the work by @xcite , who carried out a simulation of the iterated prisoner s dilemma ( pd ) @xcite on a lattice in which every individual interacted with her eight nearest neighbors .
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12,844 |
Suppose that you have an abstract for a scientific paper: we use a large n - body simulation to examine the detectability of hi in emission at redshift @xmath0 , and the constraints imposed by current observations on the neutral hydrogen mass function of galaxies at this epoch .
we consider three different models for populating dark matter halos with hi , designed to encompass uncertainties at this redshift .
these models are consistent with recent observations of the detection of hi in emission at @xmath1 . whilst detection of @xmath2 emission from individual halos requires extremely long integrations with existing radio interferometers , such as the giant meter radio telescope ( gmrt ) , we show that the stacked @xmath2 signal from a large number of halos can be easily detected
. however , the stacking procedure requires accurate redshifts of galaxies .
we show that radio observations of the field of the deep2 spectroscopic galaxy redshift survey should allow detection of the hi mass function at the @xmath3 level in the mass range @xmath4 , with a moderate amount of observation time . assuming a larger noise level that corresponds to an upper bound for the expected noise for the gmrt , the detection significance for the hi mass function is still at the @xmath5 level .
we find that optically undetected satellite galaxies enhance the hi emission profile of the parent halo , leading to broader wings as well as a higher peak signal in the stacked profile of a large number of halos .
we show that it is in principle possible to discern the contribution of undetected satellites to the total hi signal , even though cosmic variance limitation make this challenging for some of our models .
methods : n - body simulations , cosmology : large scale structure of the universe , galaxies : evolution , radio - lines : galaxies .
And you have already written the first three sentences of the full article: observations show that the cosmic star formation rate ( sfr ) has declined by more than an order of magnitude since @xmath0 @xcite .
however , a combined census of the cold gas , the fuel for star formation , and stellar components is still largely missing in observations .
the cold gas fraction of a halo is a crucial ingredient in models of galaxy formation and constitutes the link to how galaxies obtain gas and subsequently convert it to stars ..
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hence , measurements of hi in the post - reionization era can place tight constraints on different models of galaxy formation @xcite .
after the epoch of reionization , the neutral hydrogen ( hi ) survives in dense clouds , e.g. damped lyman-@xmath6 systems ( dlas ) and lyman - limit systems ( lls ) , that are high - redshift equivalents of the hi - rich galaxies that we see at the present epoch .
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12,845 |
Suppose that you have an abstract for a scientific paper: we analyze the structure of the malvenuto - reutenauer hopf algebra @xmath0 of permutations in detail .
we give explicit formulas for its antipode , prove that it is a cofree coalgebra , determine its primitive elements and its coradical filtration , and show that it decomposes as a crossed product over the hopf algebra of quasi - symmetric functions .
in addition , we describe the structure constants of the multiplication as a certain number of facets of the permutahedron . as a consequence
we obtain a new interpretation of the product of monomial quasi - symmetric functions in terms of the facial structure of the cube .
the hopf algebra of malvenuto and reutenauer has a linear basis indexed by permutations .
our results are obtained from a combinatorial description of the hopf algebraic structure with respect to a new basis for this algebra , related to the original one via mbius inversion on the weak order on the symmetric groups .
this is in analogy with the relationship between the monomial and fundamental bases of the algebra of quasi - symmetric functions .
our results reveal a close relationship between the structure of the malvenuto - reutenauer hopf algebra and the weak order on the symmetric groups . .
And you have already written the first three sentences of the full article: malvenuto @xcite introduced the hopf algebra @xmath0 of permutations , which has a linear basis @xmath1 indexed by permutations in all symmetric groups @xmath2 .
the hopf algebra @xmath0 is non - commutative , non - cocommutative , self - dual , and graded . among its sub- , quotient- , and subquotient-
hopf algebras are many algebras central to algebraic combinatorics ..
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these include the algebra of symmetric functions @xcite , gessel s algebra @xmath3 of quasi - symmetric functions @xcite , the algebra of non - commutative symmetric functions @xcite , the loday - ronco algebra of planar binary trees @xcite , stembridge s algebra of peaks @xcite , the billera - liu algebra of eulerian enumeration @xcite , and others .
the structure of these combinatorial hopf algebras with respect to certain distinguished bases has been an important theme in algebraic combinatorics , with applications to the combinatorial problems these algebras were created to study .
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12,846 |
Suppose that you have an abstract for a scientific paper: nearby gamma - ray bursts ( grbs ) are likely to have represented a significant threat to life on the earth .
recent observations suggest that a significant source of such bursts is compact binary mergers in globular clusters .
this link between globular clusters and grbs offers the possibility to find time intervals in the past with higher probabilities of a nearby burst , by tracing globular cluster orbits back in time .
here we show that the expected flux from such bursts is not flat over the past 550myr but rather exhibits three broad peaks , at 70 , 180 and 340myr ago .
the main source for nearby grbs for all three time intervals is the globular cluster 47tuc , a consequence of its large mass and high stellar encounter rate , as well as the fact that it is one of the globular clusters which comes quite close to the sun .
mass extinction events indeed coincide with all three time intervals found in this study , although a chance coincidence is quite likely .
nevertheless , the identified time intervals can be used as a guide to search for specific signatures of grbs in the geological record around these times .
[ firstpage ] globular clusters : general gamma - ray burst : general galaxy : kinematics and dynamics astrobiology .
And you have already written the first three sentences of the full article: globular clusters , densely packed groups of old stars , can efficiently produce close stellar binaries by dynamical interactions of their member stars .
examples for such dynamically formed binaries include low - mass x - ray binaries ( e.g. * ? ? ?
* ; * ? ? ?.
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* ) , cataclysmic variables @xcite and milli - second pulsars ( mspsrs , * ? ? ?
* ; * ? ? ?
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12,847 |
Suppose that you have an abstract for a scientific paper: cichlid fishes are one of the best model system for the study of evolution of the species
. inspired by them , in this paper we simulated the splitting of a single species into two separate ones via random mutations , with both populations living together in sympatry , sharing the same habitat .
we study the ecological , mating and genetic conditions needed to reproduce the polychromatism and polymorphism of three species of the midas cichlid species complex .
our results show two scenarios for the _ a. citrinellus _ speciation process , one with and the other without disruptive natural selection . in the first scenario ,
the ecological and genetic conditions are sufficient to create two new species , while in the second the mating and genetic conditions must be synchronized in order to control the velocity of genetic drift . .
And you have already written the first three sentences of the full article: the evolution of a single population into two or more species without prevention of gene flow through geographic segregation is known as sympatric speciation @xcite .
cichlid fishes , _ amphilophus zaliosus _ , are one possible example of evolution by sympatric speciation in nature @xcite .
the midas cichlid species complex @xcite are distributed in the great lakes of nicaragua as well as in several crater lakes in the area ..
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combined , they represent by far the largest biomass of any fish species in nicaragua freshwaters
. there are substantial morphological differences between them , for example , some of them have cryptic colouring , grey or brown with dark bars or spots , known as normal morph , or a conspicuous form , which lacks melanophores , resulting in brightly red , orange , or yellowish coloured fish , gold morph .
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12,848 |
Suppose that you have an abstract for a scientific paper: = 100 in the error box of , the brightest as - yet unidentified egret source at intermediate galactic latitude , we find a weak , ultrasoft x - ray source at energies @xmath0 kev in the all - sky survey .
deep optical imaging at the location of this source , as pinpointed by an observation with the hri , reveals a blank field to a limit of @xmath1 .
the corresponding lower limit on @xmath2 is 300 , which signifies that the x - ray source is probably a thermally emitting neutron star .
considering our previous complete multiwavelength survey of the region which failed to find any other notable candidate for identification with , we propose that this x - ray source , , is a rotation - powered @xmath3-ray pulsar which is either older or more distant than the prototype geminga .
we see marginal evidence for variability between two hri observations . if real
, this would indicate that the x - ray emission has an external origin , perhaps due to intermittent heating of the polar caps by a variable particle accelerator
. could even be an old , recycled pulsar , which may nevertheless have a high @xmath3-ray efficiency . .
And you have already written the first three sentences of the full article: the nature of the persistent high - energy ( @xmath4 mev ) @xmath3-ray sources in the galaxy remains an enigma three decades after their discovery .
ever since the identification of the mysterious @xmath3-ray source geminga as the first radio quiet but otherwise ordinary pulsar ( see review by bignami & caraveo 1996 ) , it has been argued that rotation - powered pulsars likely dominate the galactic @xmath3-ray source population ( e.g. , yadigaroglu & romani 1997 ) , and that many of them will be radio quiet . that geminga is a bright egret source at a distance of only @xmath5 pc ( carveo et al .
1996 ) begs for it not to be unique ..
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several excellent neutron - star candidates for egret sources have emerged from x - ray observations in recent years .
one is present in the supernova remnant cta1 which is close to 3eg j0010 + 7309 ( brazier et al .
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12,849 |
Suppose that you have an abstract for a scientific paper: we study the increase in per - sample differential entropy rate of random sequences and processes after being passed through a non minimum - phase ( nmp ) discrete - time , linear time - invariant ( lti ) filter @xmath0 . for lti discrete - time filters and random processes
, it has long been established that this entropy gain , @xmath1 , equals the integral of @xmath2 .
it is also known that , if the first sample of the impulse response of @xmath0 has unit - magnitude , then the latter integral equals the sum of the logarithm of the magnitudes of the non - minimum phase zeros of @xmath0 ( i.e. , its zeros outside the unit circle ) , say @xmath3 .
these existing results have been derived in the frequency domain as well as in the time domain . in this note , we begin by showing that existing time - domain proofs , which consider finite length-@xmath4 sequences and then let @xmath4 tend to infinity , have neglected significant mathematical terms and , therefore , are inaccurate .
we discuss some of the implications of this oversight when considering random processes .
we then present a rigorous time - domain analysis of the entropy gain of lti filters for random processes .
in particular , we show that the entropy gain between equal - length input and output sequences is upper bounded by @xmath3 and arises if and only if there exists an output additive disturbance with finite differential entropy ( no matter how small ) or a random initial state .
unlike what happens with linear maps , the entropy gain in this case depends on the distribution of all the signals involved . instead , when comparing the input differential entropy to that of the entire ( longer ) output of @xmath0 , the entropy gain equals @xmath3 irrespective of the distributions and without the need for additional exogenous random signals .
we illustrate some of the consequences of these results by presenting their implications in three different problems . specifically : a simple derivation of the rate - distortion function for....
And you have already written the first three sentences of the full article: in his seminal 1948 paper @xcite , claude shannon gave a formula for the increase in differential entropy per degree of freedom that a continuous - time , band - limited random process @xmath5 experiences after passing through a linear time - invariant ( lti ) continuous - time filter .
in this formula , if the input process is band - limited to a frequency range @xmath6 $ ] , has differential entropy rate ( per degree of freedom ) @xmath7 , and the lti filter has frequency response @xmath8 , then the resulting differential entropy rate of the output process @xmath9 is given by ( * ? ? ?
* theorem 14 ) @xmath10 the last term on the right - hand side ( rhs ) of can be understood as the _ entropy gain _.
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( entropy amplification or entropy boost ) introduced by the filter @xmath8 .
shannon proved this result by arguing that an lti filter can be seen as a linear operator that selectively scales its input signal along infinitely many frequencies , each of them representing an orthogonal component of the source . the result
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12,850 |
Suppose that you have an abstract for a scientific paper: both observations and numerical simulations show that stellar convective motions are composed of semi - regular flows of convective rolling cells and the fully developed turbulence .
although the convective rolling cells are crucial for the properties of the stellar convection that transports heat and mixes materials in the stellar interior , their contributions have not been included in turbulent convection models proposed up to now .
we simplify the structure of the convective rolling cells as a cellular pattern moving circle by circle with different angular velocities around the center , estimating their typical size by solving approximately for the temperature difference over the stationary temperature background and their average shear of velocity by evaluating approximately their kinetic energy transformed by themselves working as thermal engines from the heat involved in the convective rolling cells .
we obtain a steady state solution in the fully local equilibrium which is similar to what is obtained in the standard mixing - length theory , by applying such model assumptions to the standard @xmath0-@xmath1 model and properly choosing the model parameter @xmath2 .
accordingly , we propose a @xmath0-@xmath3 model to include the transport effect of turbulence in stars .
preliminary results of their applications to the sun and other stars with different masses and in different evolutionary stages show good agreements with results of the standard mixing - length theory and results of numerical simulations for the stellar convection . .
And you have already written the first three sentences of the full article: thermal convection is a common phenomenon in the stellar interior .
convective flows are driven in stars by the thermal buoyancy , which results from unstable density stratifications .
both observations and numerical simulations show that convective motions are characterized by deterministic structures of different scales such as unsteady convective rolls and semi - regular convective cells created by large - scale instabilities of the buoyancy , along with the fully developed turbulence due to extremely high reynolds numbers in the stellar convection zones ..
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the bulk of a convection zone is stochastically filled up with numerous unsteady convective rolls pushing each other and leaving little space in between @xcite .
close to the boundaries of the convective region , semi - regular convective cells jostle onto the surface and roughly line up seen for examples as the rayleigh - bnard convection @xcite and the solar granulation @xcite .
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12,851 |
Suppose that you have an abstract for a scientific paper: charge reversal of the planar electrical double layer is studied by means of a well known integral equations theory . by a numerical analysis ,
a diagram is constructed with the onset points of charge reversal in the space of the fundamental variables of the system . within this diagram
two regimes of charge reversal are identified , referred to as oscillatory and non oscillatory .
we found that these two regimes can be distinguished through a simple formula .
furthermore , a symmetry between electrostatic and size correlations in charge reversal is exhibited .
the agreement of our results with other theories and molecular simulations data is discussed . .
And you have already written the first three sentences of the full article: charged particles are naturally adsorbed onto an oppositely charged surface , however , temperature prevents them to completely condensate producing a diffuse ionic concentration profile known as the electrical double layer ( edl ) .
intuitively one might expect that the adsorbed counterions in the edl are just the necessary to compensate the surface s charge , however , for certain conditions , they overcompensate it producing a surface _
charge reversal_. hence , an inversion of the local electric field takes place next to the first counterions layer and , consequently , coions are attracted to form a second layer referred to as _.
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charge inversion _ of the edl .
charge reversal ( cr ) and charge inversion ( ci ) have motivated a large number of studies in the past @xcite .
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12,852 |
Suppose that you have an abstract for a scientific paper: photometric redshift estimation is an indispensable tool of precision cosmology .
one problem that plagues the use of this tool in the era of large - scale sky surveys is that the bright galaxies that are selected for spectroscopic observation do not have properties that match those of ( far more numerous ) dimmer galaxies ; thus , ill - designed empirical methods that produce accurate and precise redshift estimates for the former generally will not produce good estimates for the latter . in this paper
, we provide a principled framework for generating conditional density estimates ( i.e. photometric redshift pdfs ) that takes into account selection bias and the covariate shift that this bias induces .
we base our approach on the assumption that the probability that astronomers label a galaxy ( i.e. determine its spectroscopic redshift ) depends only on its measured ( photometric and perhaps other ) properties @xmath0 and not on its true redshift . with this assumption
, we can explicitly write down risk functions that allow us to both tune and compare methods for estimating importance weights ( i.e. the ratio of densities of unlabeled and labeled galaxies for different values of @xmath0 ) and conditional densities .
we also provide a method for combining multiple conditional density estimates for the same galaxy into a single estimate with better properties .
we apply our risk functions to an analysis of @xmath110@xmath2 galaxies , mostly observed by sdss , and demonstrate through multiple diagnostic tests that our method achieves good conditional density estimates for the unlabeled galaxies .
[ firstpage ] galaxies : distances and redshifts galaxies : fundamental parameters galaxies : statistics methods : data analysis methods : statistical .
And you have already written the first three sentences of the full article: photometric redshift ( or photo - z ) estimation is an indispensable tool of precision cosmology .
the planners of current and future large - scale photometric surveys such as the dark energy survey ( @xcite ) and the large synoptic survey telescope ( @xcite ) , which combined will observe over one billion galaxies , require accurate and precise redshift estimates in order to fully leverage the constraining power of cosmological probes such as baryon acoustic oscillations and weak gravitational lensing .
numerous estimators currently exist that achieve good " point estimates of photo - z redshifts at low redshifts ( @xmath3 ) , where good " means that photo - z and spectroscopic ( or spec - z ) estimates for the _ same galaxy _ largely match , with only a small percentage of catastrophic outliers ..
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these estimators are conventionally divided into two classes : template fitters , oft - used examples of which include bpz ( @xcite ) and eazy ( @xcite ) , and empirical methods such as annz ( @xcite ) .
the former utilize sets of galaxy sed templates that are redshifted until a best match with a galaxy s observed photometry is found , whereas the latter utilize spectroscopically observed galaxies to train machine learning methods to predict the redshifts of those galaxies that are only observed photometrically .
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12,853 |
Suppose that you have an abstract for a scientific paper: we use the world data on the pion form factor for space - like kinematics and a technique previously used to extract the proton transverse densities to extract the transverse pion charge density and its uncertainty due the incomplete knowledge of the pion form factor at large values of @xmath0 and the experimental uncertainties .
the pion charge density at small values of impact parameter @xmath1 0.1 fm is dominated by this incompleteness error while the range between 0.1 - 0.3 fm is relatively well constrained .
a comparison of pion and proton transverse charge densities shows that the pion is denser than the proton for values of @xmath1 0.2 fm .
the pion and proton transverse charge densities seem to be the same for values of @xmath2=0.3 - 0.6 fm .
future data from thomas jefferson national accelerator facility ( jlab ) 12 gev and the electron - ion collider ( eic ) will increase the dynamic extent of the form factor data to higher values of @xmath0 and thus reduce the uncertainties in the extracted pion transverse charge density .
nt@uw-14 - 05 .
And you have already written the first three sentences of the full article: measurements of form factors play an important role in our understanding of the structure and interactions of hadrons based on the principles of quantum chromodynamics ( qcd ) .
one of the simplest hadronic systems available for study is the pion , whose valence structure is a bound state of a quark and an antiquark .
its elastic electromagnetic structure is parameterized by a single form factor @xmath3 ..
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calculations of the pion charge form factor have been used to investigate the transition from the low - momentum transfer confinement region to the regime where perturbative methods are applicable@xcite .
there is a long history of experimental measurements @xcite-@xcite . in particular , @xmath3 has been measured at space - like momentum transfers through pion - electron scattering and pion electroproduction on the nucleon with high precision up to @xmath0=2.5 gev@xmath4 , and new measurements are planned with the 12 gev era at the thomas jefferson national accelerator facility ( jlab ) @xcite and envisioned for a future electron - ion collider ( eic ) @xcite . the concept of transverse charge densities @xcite has emerged recently @xcite as a framework providing an interpretation of electromagnetic form factors in terms of the physical charge and magnetization densities .
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12,854 |
Suppose that you have an abstract for a scientific paper: this paper deals with change detection of utility maximization behaviour in online social media .
such changes occur due to the effect of marketing , advertising , or changes in ground truth .
first , we use the revealed preference framework to detect the unknown time point ( change point ) at which the utility function changed .
we derive necessary and sufficient conditions for detecting the change point .
second , in the presence of noisy measurements , we propose a method to detect the change point and construct a decision test .
also , an optimization criteria is provided to recover the linear perturbation coefficients . finally , to reduce the computational cost , a dimensionality reduction algorithm using johnson - lindenstrauss transform is presented .
the results developed are illustrated on two real datasets : yahoo !
tech buzz dataset and youstatanalyzer dataset . by using the results developed in the paper ,
several useful insights can be gleaned from these data sets .
first , the changes in ground truth affecting the utility of the agent can be detected by utility maximization behaviour in online search .
second , the recovered utility functions satisfy the single crossing property indicating strategic substitute behaviour in online search .
third , due to the large number of videos in youtube , the utility maximization behaviour was verified through the dimensionality reduction algorithm .
finally , using the utility function recovered in the lower dimension , we devise an algorithm to predict total traffic in youtube
. + social media , youtube , utility maximization , revealed preference , dimensionality reduction , change point detection .
And you have already written the first three sentences of the full article: the interaction of humans on social media platforms mimic their interactions in the real world @xcite . hence , as in the real world
, `` utility maximization '' underpins human interaction on social media platforms .
utility maximization is the fundamental problem humans face , wherein humans maximize utility given their limited resources of money or attention ..
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detection of utility maximization behaviour is therefore useful in online social media .
however , a key difference for agents in online social media is the absence of economic incentives .
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12,855 |
Suppose that you have an abstract for a scientific paper: the light scalar meson nonet above 1 gev ( _ i.e . _
the @xmath0 , @xmath1 and @xmath2 ) are studied within the framework of qcd sum rules . in conventional qcd sum rules ,
the calculated masses of this nonet are degenerate , and the mass of @xmath1 is always larger than the @xmath0 in contradiction with the observed spectrum . after improving the correlation function by including instanton effects ,
the masses are well separated from each other . in particular ,
our results shows glueball content plays an important role in the underlying structure of @xmath3 .
the decay constants are also discussed . .
And you have already written the first three sentences of the full article: the @xmath4 classification of strongly - interacting particles originally proposed by gell - mann @xcite and zweig @xcite has been a very successful paradigm in particle physics .
it is observed from the hadronic spectrum that the results following from this naive quark model ( nqm ) agree better with the heavy meson systems than the light ones .
this is understandable because the heavy quarks inside a heavy meson are non - relativistic , and hence we can deal with their kinematics in the framework of nonrelativistic quantum mechanics as a good approximation ..
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however , for light mesons where the light components are relativistic , it is hard to say whether the nonrelativistic approximation is applicable .
we can see that there is more complexity in light mesons than the heavy ones from the observed spectrum .
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12,856 |
Suppose that you have an abstract for a scientific paper: the response of an array of plastic phoswich detectors to ions of @xmath0 has been measured from @xmath1=12 to 72 mev .
the detector response has been parameterized by a three parameter fit which includes both quenching and high energy delta - ray effects .
the fits have a mean variation of @xmath2 with respect to the data . .
And you have already written the first three sentences of the full article: in recent years a number of large arrays using plastic and/or csi scintillators have been built for heavy ion experiments . while these arrays offer a relatively inexpensive way of covering large solid angles , the nonlinear response of various scintillators as a function of the incident particle s energy , charge , and mass poses a challenge in their calibration . to understand the nonlinear response of various scintillators ,
calibration data covering a wide range of projectile energy , charge and mass are required .
these requirements , combined with the large number of elements in an array , make it virtually impossible to do a detailed calibration after each experiment.
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. thus a procedure by which the calibration of large scintillator arrays can be achieved during or after an experiment with only a few calibration points would be valuable .
the essential ingredient in such a procedure is an understanding of the scintillator response to a wide variety and energy of incident particles .
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12,857 |
Suppose that you have an abstract for a scientific paper: we revisit the issue of the quark masses and mixing angles in the framework of large extra dimension .
we consider three identical standard model families resulting from higher - dimensional fields localized on different branes embedded in a large extra dimension .
furthermore we use a decaying profile in the bulk different form previous works . with the higgs field
also localized on a different brane , the hierarchy of masses between the families results from their different positions in the extra space .
when the left - handed doublet and the right - handed singlets are localized with different couplings on the branes , we found a set of brane locations in one extra dimension which leads to the correct quark masses and mixing angles with the sufficient strength of _ cp_-violation .
we see that the decaying profile of the higgs field plays a crucial role for producing the hierarchies in a rather natural way .
ftpi - minn-06/21 + hep - ph/0606158 + + + * ckm pattern from localized generations in extra dimension * c. matti 0.05 in _ william i. fine theoretical physics institute , university of minnesota , minneapolis , mn 55455 , usa _ .
And you have already written the first three sentences of the full article: the origin of the quark masses and their mixing angles is still one of the mysteries of the standard model ( sm ) .
the great hierarchy of scale between the sm yukawa couplings should be justified in a fundamental theory .
we usually thought about low - energy constants as resulting from some breaking of higher symmetry operators ..
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several years ago , new mechanisms were proposed by @xcite to explain the hierarchy of the yukawa couplings from geometry of extra space without any new flavor symmetries . in these models ,
we consider the sm four - dimensional fermionic fields as zero modes of higher - dimensional fields localized at different positions in an extra dimension .
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12,858 |
Suppose that you have an abstract for a scientific paper: the protonation of n@xmath0 bound to the active center of nitrogenase has been investigated using state - of - the - art density - functional theory calculations .
dinitrogen in the bridging mode is activated by forming two bonds to fe sites , which results in a reduction of the energy for the first hydrogen transfer by 123kj / mol . the axial binding mode with open sulfur bridge is less reactive by 30kj / mol and the energetic ordering of the axial and bridged binding modes is reversed in favor of the bridging dinitrogen during the first protonation .
protonation of the central ligand is thermodynamically favorable but kinetically hindered .
if the central ligand is protonated , the proton is transferred to dinitrogen following the second protonation .
protonation of dinitrogen at the mo site does not lead to low - energy intermediates . .
And you have already written the first three sentences of the full article: although dinitrogen is the main part of the atmosphere , it is , in its molecular form , inaccessible to biological organisms .
its inactivity is caused by the triple bond
one of the strongest covalent bonds in nature ..
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while high pressure and high temperature are required to convert n@xmath0 to nh@xmath1 in the industrial haber - bosch process , biological nitrogen fixation achieves the same goal at ambient conditions . for this purpose nature employs the enzyme nitrogenase , which is one of the most complex bioinorganic catalysts in nature .
nitrogenase converts n@xmath0 to biologically accessible ammonia.@xcite during the reaction , non - stoichiometric@xcite amounts of hydrogen are produced .
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Suppose that you have an abstract for a scientific paper: in this paper , we present the concept of the one - way unlocalizable quantum discord and investigate its properties .
we provide a polygamy inequality for it in tripartite pure quantum system of arbitrary dimension .
several tradeoff relations between the one - way unlocalizable quantum discord and other correlations are given .
if the von neumann measurement is on a part of the system , we give two expressions of the one - way unlocalizable quantum discord in terms of partial distillable entanglement and quantum disturbance .
finally , we also provide a lower bound for bipartite shareability of quantum correlation beyond entanglement in a tripartite system . .
And you have already written the first three sentences of the full article: entanglement plays a key role in quantum computation and quantum information , which is a kind of quantum correlation not available in classical world @xcite . on the other hand
, there exists some other quantum correlations different from entanglement , for example , quantum discord is also a quantum correlation not present in classical system @xcite .
it is supposed that quantum discord might be responsible for the advantage of a quantum algorithm , the deterministic quantum computation with one qubit @xcite , which surpasses any corresponding classical algorithms while with vanishing entanglement but non - zero quantum discord ..
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it is also noticed that though different from entanglement , quantum discord is closely related with entanglement and may have interesting operational interpretations in quantum information processing @xcite , and also see the reviews @xcite .
we know that entanglement is an invaluable resource for quantum information processing , and thus it can not be shared freely among multiparities .
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Suppose that you have an abstract for a scientific paper: we present here a self - consistent , tridimensional model of a disc galaxy composed by a number of ellipsoidal distributions of matter having different flattening and density profile .
the model is self - consistent and takes into account the observed luminosity distribution , the flattening profile and the stellar rotation- and velocity dispersion- curves . in this paper
we considered the particular case of a disc galaxy composed by two spheroidal bodies : an exponential disc and a bulge following the @xmath0 law .
we studied the behavior of the stellar rotation- and velocity dispersion- profiles along the sequence of s0s and spirals , identified by an increasing disc - to - bulge ratio .
inside every class , kinematic curves were produced by changing the relative concentration of the two components and the inclination of the galaxy with respect to the line of sight .
the comparison with observational data requires only two scaling factors : the total mass of the galaxy , and the effective radius .
the model allows also to detect the presence of anisotropy in the velocity distribution . in the special case of s0s
, we explored the sensitivity of the kinematics of the model by changing the anisotropy and the flattening of the bulge .
for intermediate flattening ( @xmath1 ) it is possible to distinguish a change of anisotropy of 15% to show a real case , the model has been applied to the photometric and kinematic data of ngc 5866 . we plan to apply these models to a larger database of s0 galaxies in a future paper . .
And you have already written the first three sentences of the full article: the study of the light distribution and the _ stellar _ kinematics in disk galaxies is an important tool to understand their structure .
it is the only way to study stellar systems which are gas poor such as the s0s , and may be crucial to distinguish between different scenarios of galaxy formation .
it allows to discuss if a bulge is flattened by rotation or by anisotropic residual velocities and how the different components of a galaxy mutually interact . in the past , in front of the success achieved in studying the _ gas _ kinematics of disk galaxies , much less attention has been paid to the modeling of their _ stellar _ kinematics from the observations ..
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a reason of this was the lower extension of the available stellar rotation curves , based on absorption lines , with respect to that obtained with emission lines ( optical or 21 cm ) .
however , the inner part of the galaxies is often poor of cold gas , and can be studied with data from the stellar component only . in addition , the progresses in detectors and data analysis techniques ( sargent et al . 1977 , bertola 1984 , kuijken & merrifield 1993 ) extended the range explored with stellar data and produced a large quantity of stellar rotation- and velocity dispersion- curves , making compulsory the creation of realistic theoretical models for their interpretation .
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12,861 |
Suppose that you have an abstract for a scientific paper: we examine the characteristics of nucleosynthesis in hypernovae , i.e. , supernovae with very large explosion energies ( @xmath0 ergs ) .
we carry out detailed nucleosynthesis calculations for these energetic explosions and compare the yields with those of ordinary core - collapse supernovae .
we find that both complete and incomplete si - burning takes place over more extended , lower density regions , so that the alpha - rich freezeout is enhanced and produces more ti in comparison with ordinary supernova nucleosynthesis .
in addition , oxygen and carbon burning takes place in more extended , lower density regions than in ordinary supernovae .
therefore , the fuel elements o , c , al are less abundant while a larger amount of si , s , ar , and ca ( `` si '' ) are synthesized by oxygen burning ; this leads to larger ratios of `` si''/o in the ejecta .
enhancement of the mass ratio between complete and incomplete si - burning regions in the ejecta may explain the abundance ratios among iron - peak elements in metal - poor stars .
also the enhanced `` si''/o ratio may explain the abundance ratios observed in star burst galaxies .
we also discuss other implications of enhanced [ ti / fe ] and [ fe / o ] for galactic chemical evolution and the abundances of low mass black hole binaries . .
And you have already written the first three sentences of the full article: massive stars in the range of 8 to @xmath1 150@xmath2 undergo core - collapse at the end of their evolution and become type ii and ib / c supernovae unless the entire star collapses into a black hole with no mass ejection ( e.g. , arnett 1996 ) .
these type ii and ib / c supernovae ( as well as type ia supernovae ) release large explosion energies and eject explosive nucleosynthesis materials , thus having strong dynamical , thermal , and chemical influences on the evolution of interstellar matter and galaxies .
therefore , the explosion energies of core - collapse supernovae are fundamentally important quantities , and an estimate of @xmath3 ergs has often been used in calculating nucleosynthesis ( e.g. , woosley & weaver 1995 ; thielemann et al ..
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1996 ) and the impact on the interstellar medium .
( in the present paper , we use the explosion energy @xmath4 for the final kinetic energy of explosion . ) a good example of this estimate is sn1987a in the large magellanic cloud , whose energy is estimated to be @xmath5 - 1.5 ) @xmath6 @xmath7 ergs from its early light curve ( shigeyama et al .
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Suppose that you have an abstract for a scientific paper: photonic crystals and metamaterials have emerged as two classes of tailorable materials that enable precise control of light .
plasmonic crystals , which can be thought of as photonic crystals fabricated from plasmonic materials , bragg scatter incident electromagnetic waves from a repeated unit cell . however , plasmonic crystals , like metamaterials , are composed of subwavelength unit cells . here , we study terahertz plasmonic crystals of several periods in a two dimensional electron gas .
this plasmonic medium is both extremely subwavelength ( @xmath0 ) and reconfigurable through the application of voltages to metal electrodes .
weakly localized crystal surface states known as tamm states are observed . by introducing an independently controlled plasmonic defect that interacts with the tamm states , we demonstrate a frequency agile electromagnetically induced transparency phenomenon . the observed 50% _ in - situ _ tuning of the plasmonic crystal band edges should be realizable in materials such as graphene to actively control the plasmonic crystal dispersion in the infrared .
photonic band gaps@xcite , strong light - matter interaction@xcite , slow light@xcite , and negative refractive index@xcite arise in photonic crystal@xcite structures due to bragg scattering of electromagnetic waves from a repeated unit cell .
however , the electromagnetic properties of photonic crystals engineered from bulk semiconductors , metals , and dielectrics generally are weakly tunable , if at all .
material systems such two dimensional electron gases ( 2degs ) embedded in semiconductors@xcite and graphene@xcite offer a substantially more flexible electromagnetic medium .
these plasmonic materials can both be lithographically patterned and electronically tuned , giving rise to a variety of subwavelength plasmonic devices that may be broadly controlled via an applied dc electric field . when a periodic structure is engineered from these systems ,
plasmonic band structure can be realized@xcite .
....
And you have already written the first three sentences of the full article: in this article , we examine the complex interplay between surface states known as tamm states@xcite , plasmonic defect ( pd ) modes , and the pc band structure in tunable thz plasmonic band gap devices engineered from a gaas / algaas 2deg .
the studied pc devices , samples a and b , are pictured in fig .
both are integrated at the vertex of an antenna having bandwidth from 100 ghz to 1 thz ..
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these plasmonic structures are based upon a four period pc formed below gate g1 with an adjacent independently controlled plasmonic defect ( pd ) @xcite controlled by gate g2 .
a pd is induced when g2 is tuned to a different voltage than g1 .
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12,863 |
Suppose that you have an abstract for a scientific paper: we first presented an isochrone database that can be widely used for stellar population synthesis studies and colour - magnitude diagram ( cmd ) fitting .
the database consists of the isochrones of both single star and binary star simple stellar populations ( ss - ssps and bs - ssps ) .
the ranges for the age and metallicity of populations are 015 gyr and 0.00010.03 , respectively .
all data are available for populations with two widely used initial mass functions ( imfs ) , i.e. , salpeter imf and chabrier imf . the uncertainty caused by the database ( about 0.81% )
is designed to be smaller than those caused by the hurley code and widely used stellar spectra libraries ( e.g. , basel 3.1 ) when the database is used for stellar population synthesis . then based on the isochrone database
, we built a rapid stellar population synthesis ( @xmath0 ) model and calculated the high - resolution ( 0.3 @xmath1 ) integrated spectral energy distributions ( seds ) , lick indices and colour indices for bs - ssps and ss - ssps .
in particular , we calculated the @xmath2 colours , @xmath3 colours and some composite colours that consist of magnitudes on different systems
. these colours are useful for disentangling the well - known stellar age
metallicity degeneracy according to our previous work . as an example for applying the isochrone database for cmd fitting , we fitted the cmds of two star clusters ( m67 and ngc1868 ) and obtained their distance moduli , colour excesses , stellar metallicities and ages .
the results showed that the isochrones of bs - ssps are closer to those of real star clusters .
it suggests that the effects of binary interactions should be taken into account in stellar population synthesis .
we also discussed on the limitations of the application of the isochrone database and the results of the @xmath0 model .
[ firstpage ] galaxies : stellar content galaxies : elliptical and lenticular , cd . .
And you have already written the first three sentences of the full article: stellar population synthesis is a widely used technique to model the spectra and photometry evolution of galaxies .
it is also an important method to estimate the stellar contents of galaxies from spectra ( e.g. , @xcite ) or photometry data ( e.g. , @xcite ; @xcite ) .
a lot of models such as @xcite ( galaxev ) , @xcite , @xcite , @xcite ( pegase ) , and @xcite have been brought forward for studying stellar populations , but most of them did not take binary interactions into account . similarly , the popular models for galaxy formation and evolution ( e.g. , @xcite , @xcite , @xcite ) did not take binary interactions into account , either ..
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therefore , most results of stellar population studies are derived from single star stellar population ( ss - ssp ) models , e.g. , @xcite , @xcite , @xcite , while only a few results from binary star stellar population ( bs - ssp ) model @xcite .
a reason for those works using ss - ssps rather than bs - ssps is that the evolution of binaries is much more complicated than single stars .
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12,864 |
Suppose that you have an abstract for a scientific paper: broad emission - line outflows of active galactic nuclei ( agns ) have been proposed for many years but are very difficult to quantitatively study because of the coexistence of the gravitationally - bound and outflow emission .
we present detailed analysis of a heavily reddened quasar , sdss j000610.67 + 121501.2 , whose normal ultraviolet ( uv ) broad emission lines ( bels ) are heavily suppressed by the dusty torus as a natural `` coronagraph '' , thus the blueshifted bels ( bbels ) can be reliably measured .
the physical properties of the emission - line outflows are derived as follows : ionization parameter @xmath0 , column density @xmath1 @xmath2 , covering fraction of @xmath3 and upper limit density of @xmath4 @xmath5 .
the outflow gases are located at least 41 pc away from the central engine , which suggests that they have expanded to the scale of the dust torus or beyond .
besides , ly@xmath6 shows a narrow symmetric component , to our surprise , which is undetected in any other lines . after inspecting the narrow emission - line region and the starforming region as the origin of the ly@xmath6 narrow line , we propose the end - result of outflows , diffusing gases in the larger region , acts as the screen of ly@xmath6 photons .
future high spatial resolution spectrometry and/or spectropolarimetric observation are needed to make a final clarification . .
And you have already written the first three sentences of the full article: the blueshifted emission lines ( blueshifted - els ) and broad absorption lines ( bals ) , which are the typical presentations of active galactic nuclei ( agns ) outflows , have been widely studied .
they are potentially one of the most important pieces of feedback from agns and may play a crucial role in galaxy formation and evolution , connecting the central supermassive black holes ( smbhs ) to their host galaxies and regulating their co - evolution ( e.g. , granato et al . 2004 ; scannapieco & oh 2004 ; hopkins et al . 2008 ) .
previous works suggested that the agn outflows can reach from the small scale ( at or outside of the broad - line region ( belr ) , e.g. , zhang et al ..
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2015b ; williams et al .
2016 ) , to the intermediate scale ( the dusty torus , e.g. , leighly et al .
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12,865 |
Suppose that you have an abstract for a scientific paper: hot dense helium is studied with first - principles computer simulations . by combining path integral monte carlo and density functional molecular dynamics ,
a large temperature and density interval ranging from 1000 to 1@xmath0000@xmath0000 k and 0.4 to 5.4 g@xmath0@xmath1 becomes accessible to first - principles simulations and the changes in the structure of dense hot fluids can be investigated .
the focus of this article are pair correlation functions between nuclei , between electrons , and between electrons and nuclei .
the density and temperature dependence of these correlation functions is analyzed in order to describe the structure of the dense fluid helium at extreme conditions . .
And you have already written the first three sentences of the full article: in the interiors of solar and extrasolar @xcite giant planets , light elements such as hydrogen and helium are exposed to extreme temperature ( @xmath210000k ) and pressure ( 10 1000 gpa ) conditions .
shock wave measurements @xcite are the preferred experimental technique to reach such conditions in the laboratory
. lasers @xcite , magnetic fields @xcite , and explosives @xcite have recently been used to generate shock waves that reached megabar pressures ..
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the challenge of these experiments is first to reach such extreme conditions and secondly to characterize the properties of the material with sufficient accuracy so that planetary interior model actually can be improved .
single shock experiments yield the highest accuracy to the equation of state ( eos ) .
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12,866 |
Suppose that you have an abstract for a scientific paper: in this article we will apply the first- and second - order supersymmetric quantum mechanics to obtain new exactly - solvable real potentials departing from the inverted oscillator potential .
this system has some special properties ; in particular , only very specific second - order transformations produce non - singular real potentials .
it will be shown that these transformations turn out to be the so - called complex ones .
moreover , we will study the factorization method applied to the inverted oscillator and the algebraic structure of the new hamiltonians .
supersymmetric quantum mechanics ; darboux transformations ; harmonic oscillator ; inverted oscillator + * pacs * 03.65.-w , 03.65.fd , 02.20.sv .
And you have already written the first three sentences of the full article: let us consider the following hamiltonian @xmath0 where @xmath1 has units of mass and @xmath2 of frequency .
in order to simplify , we are going to use natural units , such that @xmath3 , to obtain @xmath4 moreover , by choosing appropriately the value of @xmath2 , three essentially different cases can be obtained : @xmath5 these are three rare examples of exactly - solvable potentials in quantum mechanics . the first one , the harmonic oscillator , is a very well known system from which the technique of creation and annihilation operators and the whole formalism of the factorization method come from .
the second , the free particle , has also been largely studied ..
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this simple system allows us to work close to the limits of quantum theory , for example , with non - square - integrable wavefunctions with plenty of physical applications such as the plane waves .
the third case is not so familiar : it is called either _ inverted oscillator _ , _ repulsive oscillator _ , _ inverse oscillator _ , or _
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12,867 |
Suppose that you have an abstract for a scientific paper: we construct an effective model for gravity of a central object at large scales . to leading order in the large radius expansion we find a cosmological constant , a rindler acceleration , a term that sets the physical scales and subleading terms .
all these terms are expected from general relativity , except for the rindler term .
the latter leads to an anomalous acceleration in geodesics of test - particles .
gravity at large distances poses some of the most difficult puzzles in contemporary gravitational physics . the cosmological constant problem @xcite and the nature of dark matter @xcite are the most prominent ones . at a somewhat smaller scale , both in terms of actual size and in terms of scientific credibility
, there are fly - by anomalies @xcite and the pioneer anomaly @xcite .
the word `` anomalous '' here refers to the difference between the observed trajectory of a test - particle in the gravitational field of a central object and the calculated trajectory .
the pair test - particle / central object can mean e.g. galaxy / cluster , star / galaxy , sun / pioneer spacecraft , earth / satellite , etc . conceptually , there are three ways to resolve the anomalies .
either we modify the matter content of the theory ( dark matter ) , or we modify the gravitational theory itself .
the third alternative is that we might not be applying the theory correctly or beyond its realm of validity .
namely , even though effects that go beyond general relativity ( gr ) or its newtonian limit are small locally , they may accumulate over large distances and/or through averaging , see @xcite for various approaches that advocate this idea and implement it in different ways . in this letter
we advocate a new approach to describe gravity at large distances that is agnostic about the issue which of these three alternatives is realized in nature .
the main strength of our method lies in its rigidity there is only one new free parameter and in its _ ab initio _ nature .
one well -....
And you have already written the first three sentences of the full article: to address the issue of anomalous acceleration of test - particles in the gravitational field of a central object we first simplify the underlying theory as much as possible .
we assume that spacetime is described by a spherically symmetric metric in four dimensions ( see e.g. @xcite ) @xmath0 the 2-dimensional metric @xmath1 and the surface radius @xmath2 depend only on the coordinates @xmath3 .
our task is now clear : we should describe the dynamics of the fields @xmath4 and @xmath5 ..
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it is possible to do this in two dimensions , since the metric @xmath6 and the scalar field @xmath5 are both intrinsically 2-dimensional objects .
each solution of the equations of motion ( eom ) of that 2-dimensional theory leads to a 4-dimensional line - element , so the former faithfully captures the classical dynamics of the latter .
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12,868 |
Suppose that you have an abstract for a scientific paper: a @xmath0-user cascade gaussian z - interference channel is a subclass of the general @xmath0-user gaussian interference channel , where each user , except the first one , experiences interference only from the previous user . under simple han - kobayashi schemes assuming gaussian inputs and no time sharing
, it is shown that the maximum sum rate is achieved by each user transmitting either common or private signals . for @xmath1 ,
channel conditions under which the achieved sum rate is either equal to or within 0.5 bits to the sum capacity are identified . .
And you have already written the first three sentences of the full article: gaussian interference channel ( gic ) models a communication scenario where the received signal is not only subject to gaussian noise but also the interference coming from other transmissions . despite its simple form ,
the capacity region of the 2-user gic is unknown except for some special cases such as the strong interference regime @xcite .
additionally the sum capacity in the noisy regime was derived concurrently in @xcite@xcite@xcite . for a general 2-user gic the best achievable rate region.
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is given by the han - kobayashi ( hk ) scheme @xcite where the information is split into common and private components .
however the computation of the general hk rate region is very difficult due to a large degrees of freedom involved and the lack of knowledge of the optimal input distribution . nevertheless in @xcite etkin ,
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12,869 |
Suppose that you have an abstract for a scientific paper: we investigate the breathing mode of harmonically trapped bosons in an optical lattice at small site occupancies . the bose - hubbard model with a trapping potential
is used to describe the breathing - mode dynamics initiated through weak quenches of the trap strength .
we connect to results for continuum bosons ( lieb - liniger and gross - pitaevskii results ) and also present deviations from continuum physics .
we take a spectral perspective , identifying the breathing mode frequency with a particular energy gap in the spectrum of the trapped bose - hubbard hamiltonian .
we present the low energy eigenspectrum of the trapped many - boson system , and study overlaps of the initial state with eigenstates of the quenched hamiltonian .
there is an intermediate interaction regime , between a `` free - boson '' limit and a `` free - fermion '' limit , in which the bose - hubbard breathing mode frequency approaches the gross - pitaevskii prediction .
in addition , we present a striking failure of the time - dependent gutzwiller approximation for describing breathing modes . .
And you have already written the first three sentences of the full article: controlled and tunable experimental realizations of confined quantum systems with ultra - cold atoms enables non - equilibrium studies of quantum many - body states in novel geometries .
a common feature of many cold - atom experiments is the confinement of a many - body system in a harmonic trap .
trapping introduces many distinctive features which have no analog in uniform many - body states , such as collective excitations like breathing modes , dipole modes , and scissors modes ..
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such trap - related collective modes have been widely studied both experimentally and theoretically for continuum systems , especially in the mean - field regime , since the early days after quantum degeneracy was achieved with trapped atoms @xcite . in a well - known recent experiment @xcite
, breathing modes have been used for a one - dimensional ( 1d ) system of continuum bosons to characterize mean - field and non - mean - field regimes , as well as states obtained by quenching to large negative interactions . with the addition of optical lattices , it should be possible to study collective modes in lattice systems beyond the mean field regime . in this work , we study the breathing mode for interacting bosons on a 1d lattice , described by the bose - hubbard model and subject to an additional trapping potential .
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12,870 |
Suppose that you have an abstract for a scientific paper: we have undertaken a pilot survey for faint qsos in the ukidss ultra deep survey field using the kx selection technique .
these observations exploit the very deep near - infrared and optical imaging of this field from ukirt and subaru to select candidate qsos based on their @xmath0 colours and morphologies .
we determined redshifts for 426 candidates using the aaomega spectrograph on the aat in service time .
we identify 17 qsos ( @xmath1 ) in this pilot survey at @xmath23.29 .
we combine our sample with an x - ray selected sample of qsos in the same field ( a large fraction of which also comply with our kx selection ) to constrain the surface density of qsos with @xmath3 , deriving limits on the likely surface density of 85150deg@xmath4 .
we use the good image quality available from our near - infrared imaging to detect a spatially extended component of the qso light which probably represents the host galaxies .
we also use our sample to investigate routes to improve the selection of kx qsos at faint limits in the face of the significant contamination by compact , foreground galaxies .
the brightest examples from our combined qso sample will be used in conjunction with a large vlt vimos spectroscopic survey of high redshift galaxies in this region to study the structures inhabited by gas , galaxies and growing super - massive black holes at high redshifts in the ukidss uds .
galaxies : active quasars : general . .
And you have already written the first three sentences of the full article: simulations of the distribution of baryons in the universe predict that much material is spread out in a `` cosmic web '' between the galaxies , groups and larger structures visible in conventional surveys .
the main components of this material are the ly@xmath5 forest , which traces highly ionized hydrogen of low neutral column density and low chemical enrichment distributed through the lower density regions , and metal absorption lines which trace massive galaxy halos ( and hence higher density regions ) via their metal - enriched gas . to probe this material and investigate its 3-dimensional distribution we must exploit qsos as bright background sources to trace the web through its absorption .
an optimal survey of the cosmic web would use a grid of distant bright qsos as probes of the intervening matter , with the redshift and equivalent width of these absorbers providing information on the relative distribution and clustering of gas around galaxies and larger structures , as well as providing insights into the chemical enrichment and heating of this material ( e.g. morris & januzzi 2006 ) ..
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studies comparing the results from high - redshift galaxy surveys around individual bright qsos have provided unique insights into the effect of star formation on the gas surrounding young galaxies ( e.g. adelberger et al .
however , these studies are observationally expensive it would be much more efficient if a large number of galaxies and qsos could be compared within a single field as the number of absorber
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12,871 |
Suppose that you have an abstract for a scientific paper: for a graph @xmath0 the random @xmath1-lift of @xmath0 is obtained by replacing each of its vertices by a set of @xmath1 vertices , and joining a pair of sets by a random matching whenever the corresponding vertices of @xmath0 are adjacent .
we show that asymptotically almost surely the random lift of a graph @xmath0 is hamiltonian , provided @xmath0 has the minimum degree at least @xmath2 and contains two disjoint hamiltonian cycles whose union is not a bipartite graph . .
And you have already written the first three sentences of the full article: the notion of a random lift was proposed by amit and linial @xcite as a discrete version of the topological notion of covering maps , which are `` locally bijective '' homomorphisms . for graphs @xmath0 and @xmath3 , a map @xmath4 is a _ covering map _ from @xmath3 to @xmath0 if for every @xmath5 the restriction of @xmath6 to the neighborhood of @xmath7 is a bijection onto the neighborhood of @xmath8 . in particular , for every vertex @xmath5 the degree of @xmath7 must be the same as the degree of @xmath9 .
the set of all vertices which are mapped onto a vertex @xmath7 is called the _ fiber above @xmath7 _ and denoted by @xmath10 . since the term covering has been already widely used in graph theory , following amit and linial , we use the term _ lift _ instead .
for instance , we say that @xmath3 from the previous example is a lift of @xmath0 ..
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we often denote the lift of @xmath0 by @xmath11 .
if for every vertex @xmath12 the fiber @xmath10 has size @xmath1 , then we call such a lift an _ @xmath1-lift_. we denote the set of all @xmath1-lifts of a given graph @xmath0 by @xmath13 and call @xmath0 the _ base graph_. a random @xmath1-lift of @xmath0 is a graph chosen uniformly at random from the set @xmath13 .
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12,872 |
Suppose that you have an abstract for a scientific paper: we examine the variation of the fine structure constant in the context of a two - field quintessence model .
we find that , for solutions that lead to a transient late period of accelerated expansion , it is possible to fit the data arising from quasar spectra and comply with the bounds on the variation of @xmath0 from the oklo reactor , meteorite analysis , atomic clock measurements , cosmic microwave background radiation and big bang nucleosynthesis .
that is more difficult if we consider solutions corresponding to a late period of permanent accelerated expansion
. 0.5 cm 0.5 cm .
And you have already written the first three sentences of the full article: the recent claim that the spectra of quasars ( qsos ) indicates the variation of the fine structure constant , @xmath0 , on cosmologically recent times @xcite has raised considerable interest in examining putative sources of this variation . in most models a possible variation of the fine structure constant is studied by arbitrarily coupling fields to electromagnetism , as suggested by bekenstein @xcite .
thus the proposals put forward sofar consider a scalar field @xcite ( with an additional coupling to dark matter and to a cosmological constant in the former case ) and quintessence @xcite .
in fact , as discussed in ref ..
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@xcite , the couplings of gravito - scalar fields , such as the axion or the dilaton , to electromagnetism naturally arise in @xmath1 supergravity in four dimensions , making this model particularly interesting .
it is worth mentioning that , in the latter model , the mass of these scalars can drive the accelerated expansion of the universe , transient or eternal @xcite . in this work
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12,873 |
Suppose that you have an abstract for a scientific paper: we investigate the global persistence properties of critical systems relaxing from an initial state with non - vanishing value of the order parameter ( , the magnetization in the ising model ) .
the persistence probability of the global order parameter displays two consecutive regimes in which it decays algebraically in time with two distinct universal exponents .
the associated crossover is controlled by the initial value @xmath0 of the order parameter and the typical time at which it occurs diverges as @xmath0 vanishes .
monte - carlo simulations of the two - dimensional ising model with glauber dynamics display clearly this crossover .
the measured exponent of the ultimate algebraic decay is in rather good agreement with our theoretical predictions for the ising universality class . .
And you have already written the first three sentences of the full article: in spite of many efforts during the last decades , a detailed description of the non - equilibrium dynamics of statistical systems is still lacking .
in addition to disordered and glassy systems @xcite even simpler ones ( , pure magnets ) have revealed unexpected non - equilibrium dynamical behaviors such as aging @xcite .
close to _ critical _ points , some aspects of these collective behaviors become largely independent of the microscopic details of the system ( _ universality _ ) and therefore they can be very effectively investigated by means of simplified models , among which field - theoretical ( ft ) @xcite ones . within this approach one studies , for instance , the non - equilibrium relaxation from a state with non - vanishing value @xmath0 of the time - dependent average order parameter @xmath1 ( , the magnetization of a ferromagnet ) ..
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it turns out @xcite that , after a non - universal transient , @xmath1 grows in time as @xmath2 for @xmath3 whereas , for @xmath4 , @xmath1 decays algebraically to zero as @xmath5 .
these different time dependences are characterized by the universal exponents @xmath6 ( the so - called initial - slip exponent @xcite ) and @xmath7 , where @xmath8 , @xmath9 and @xmath10 are the usual static and dynamic ( equilibrium ) critical exponents , respectively .
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12,874 |
Suppose that you have an abstract for a scientific paper: we study the chern - simons black holes in @xmath0dimensions and we calculate analytically the quasi - normal modes of the scalar perturbations and we show that they depend on the highest power of curvature present in the chern - simons theory .
we obtain the mass and area spectrum of these black holes and we show that they have a strong dependence on the topology of the transverse space and they are not evenly spaced .
we also calculate analytically the reflection and transmission coefficients and the absorption cross section and we show that at low frequency limit there is a range of modes which contributes to the absorption cross section . .
And you have already written the first three sentences of the full article: chern - simons black holes are special solutions of gravity theories in higher than four dimensions which contain higher powers of curvature
. these theories are consistent lanczos - lovelock theories resulting in second order field equations for the metric with well defined ads asymptotic solutions . for
spherically symmetric topologies , these black holes are labelled by an integer @xmath1 which specifies the higher order of curvature present in the lanczos - lovelock action and it is related to the dimensionality @xmath2 of spacetime by the relation @xmath3 @xcite ..
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these solutions where further generalized to flat and hyperbolic topologies @xcite . for spherical topologies
the chern - simons black holes have similar causal structure as the ( 2 + 1)-dimensional btz black hole @xcite , and they have positive specific heat and therefore thermodynamical stability . for hyperbolic topologies , the chern - simons black holes resemble to the topological black holes @xcite in their zero mass limit , and their thermodynamic behaviour was studied in @xcite .
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12,875 |
Suppose that you have an abstract for a scientific paper: we have performed numerical simulations of the interplanetary transport of solar cosmic rays .
the particles form a coherent pulse within @xmath0 au after their injection .
the gradual decrease of a pulse s speed and anisotropy can be understood in terms of an equilibrium between pitch - angle scattering and focusing .
the results should be useful for estimating times of particle injection . .
And you have already written the first three sentences of the full article: much of the current research on solar cosmic rays aims to determine the time distribution of their emission during solar flares .
the major obstacle is that no spacecraft has approached closer than @xmath1 au from the sun , so interplanetary scattering has greatly broadened the observed temporal distributions .
this problem is least severe when the detector is magnetically reasonably well - connected to the flare ..
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if strong anisotropies are observed , they also aid the determination of the scattering mean free path and the injection profile ( kallenrode , wibberenz , and hucke 1992 ) .
the key phenomenon underlying the strong anisotropy observed for many well - connected events is that charged particles of a given energy tend to travel together as a highly anisotropic `` coherent pulse , '' which can survive long enough to be observed near the earth .
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Suppose that you have an abstract for a scientific paper: the twofold degenerate anderson impurity model [ 1 - 4 ] is investigated and the strong electronic correlations of d - electrons of impurity ion are taken into account by elaborating suitable diagram technique .
we discuss the properties of the slater - kanamori model [ 2 - 4 ] of d - impurity electrons . after finding the eigenfunctions and eigenvalues of all 16 local states ,
we determine the local one - particle propagator .
then we construct the perturbation theory around the atomic limit of the impurity ion and obtain the dyson type equation for the renormalized one - particle propagator .
diagrammatic theory has been developed and correlation function determined . special diagrammatic approximation was discussed and summation of diagram has been considered .
pacs numbers : 71.27.+a , 71.10.fd .
And you have already written the first three sentences of the full article: the theory of strongly correlated electron systems plays a central role in contemporary condensed matter physics .
the essence of the problem is the competition between the localization tendency originated by the coulomb repulsion of d electrons and itinerancy tendency arising as a result of hybridization of electron orbitals .
the orbital degeneracy can be completely eliminated in solid substances but in many of them , for example , new superconductors based on @xmath0 and @xmath1 materials orbital degeneracy is not completely eliminated and orbital effects are important ..
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for instance , orbital degeneracy plays essential role in the mott metal - insulator transition . here the effects of hund s rule coupling in our orbitally degenerated model are studied with diagrammatic approach .
we study the influence of the intra - atomic coulomb interactions of the two electrons with opposite spins situated on the same or different orbitals and intra - atomic exchange is analyzed .
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12,877 |
Suppose that you have an abstract for a scientific paper: we consider the klein - gordon equation in the non - relativistic limit regime , i.e. the speed of light @xmath0 tending to infinity .
we construct an asymptotic expansion for the solution with respect to the small parameter depending on the inverse of the square of the speed of light . as the first terms of this asymptotic
can easily be simulated our approach allows us to construct numerical algorithms that are robust with respect to the large parameter @xmath0 producing high oscillations in the exact solution .
[ multiblock footnote omitted ] .
And you have already written the first three sentences of the full article: the klein - gordon equation is a fundamental physical equation describing the motion of a spin - less particle , see for instance @xcite , @xcite and @xcite for a physical introduction on this topic and @xcite , @xcite and the references therein for the mathematical analysis , and in particular @xcite for some long time results when the equation is set on a compact domain , the case mainly considered in the present work . in the relativistic regime ,
i.e. the speed of light @xmath1 , the klein - gordon equation ( as a non - linear wave equation ) is numerically well studied , see for instance @xcite , @xcite , @xcite , and , for long time behavior results in the weakly nonlinear regime , @xcite , @xcite and @xcite .
here we are interested in the klein - gordon equation in the non - relativistic limit regime , i.e. the speed of light @xmath0 tending to infinity ..
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thus , our model problem reads @xmath2 where we will consider essentially the case @xmath3 , @xmath4 , assume that the initial condition @xmath5 and @xmath6 do not depend on @xmath0 , and consider periodic boundary conditions in the space variable . in this regime the klein - gordon equation has recently gained a lot of attention , see for instance @xcite , @xcite and @xcite ( when equation is set on the whole space @xmath7 ) .
numerically , the highly oscillatory nature of the exact solution is very challenging as standard numerical schemes require severe time step restrictions depending on the large parameter @xmath8 , see for instance @xcite , @xcite and @xcite for a numerical overview on highly oscillatory problems . in the recent work @xcite , gautschi - type exponential integrators ( proposed in @xcite for equations with high frequencies generated by the linear part ) were applied to the non - relativistic klein - gordon equation , which allow time steps of order @xmath9 . following the one - term asymptotics results given in @xcite we study in this paper the existence of a complete asymptotic expansion of the exact solution of in terms of @xmath10 over a @xmath0 -independent interval @xmath11 , and for smooth initial data .
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12,878 |
Suppose that you have an abstract for a scientific paper: the cross section of the process @xmath0 was measured in the snd experiment at the vepp-2 m collider in the energy region @xmath1{s}<1000 $ ] mev .
this measurement was based on about @xmath2 selected collinear events , which include @xmath3 @xmath4 , @xmath5 @xmath6 and @xmath7 @xmath8 selected events .
the systematic uncertainty of the cross section determination is 1.3 % .
the @xmath9-meson parameters were determined : @xmath10 mev , @xmath11 mev , @xmath12 nb as well as the parameters of the @xmath13-parity suppressed decay @xmath14 : @xmath15 nb and @xmath16 degree . .
And you have already written the first three sentences of the full article: the cross section of the @xmath6 process in the energy region @xmath17{s}<1000 $ ] mev can be described within the vector meson dominance model ( vdm ) framework and is determined by the transitions @xmath18 of the light vector mesons ( @xmath19 ) into the final state .
the main contribution in this energy region comes from the @xmath20 and from the g - parity violating @xmath14 transitions .
studies of the @xmath6 reaction allow us to determine the @xmath9 and @xmath21 meson parameters and provide information on the @xmath13-parity violation mechanism . at low energies.
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the @xmath6 cross section gives the dominant contribution to the celebrated ratio @xmath22 , which is used for calculation of the dispersion integrals .
for example , for evaluation of the electromagnetic running coupling constant at the @xmath23-boson mass @xmath24 , or for determination of the hadronic contribution @xmath25 to the anomalous magnetic moment of the muon , which nowadays is measured with very high accuracy @xmath26 @xcite . assuming conservation of the vector current ( cvc ) in the isospin symmetry limit , the spectral function of the @xmath27 decay can be related to the isovector part of the @xmath6 cross section .
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Suppose that you have an abstract for a scientific paper: black - hole accretion systems are known to possess several distinct modes ( or spectral states ) , such as low / hard state , high / soft state , and so on .
since the dynamics of the corresponding flows is distinct , theoretical models were separately discussed for each state .
we here propose a unified model based on our new , global , two - dimensional radiation - magnetohydrodynamic simulations . by controlling a density normalization we could for the first time reproduce three distinct modes of accretion flow and outflow with one numerical code .
when the density is large ( model a ) , a geometrically thick , very luminous disk forms , in which photon trapping takes place .
when the density is moderate ( model b ) , the accreting gas can effectively cool by emitting radiation , thus generating a thin disk , i.e. , the soft - state disk .
when the density is too low for radiative cooling to be important ( model c ) , a disk becomes hot , thick , and faint ; i.e. , the hard - state disk
. the magnetic energy is amplified within the disk up to about twice , 30% , and 20% of the gas energy in models a , b , and c , respectively .
notably , the disk outflows with helical magnetic fields , which are driven either by radiation pressure force or magnetic pressure force , are ubiquitous in any accretion modes . finally , our simulations are consistent with the phenomenological @xmath0-viscosity prescription , that is , the disk viscosity is proportional to the pressure . .
And you have already written the first three sentences of the full article: the extensive study of disk accretion flows started in the 1960 s .
the standard disk model , and then the slim disk model and the radiatively inefficient accretion flow ( riaf ) model were proposed for explaining a variety of accretion modes ( @xcite ; @xcite ; @xcite ; @xcite ; @xcite ) . these models are successful , but have some limitations .
for example , the disk viscosity , the most important key ingredient for the accretion disk theory , is prescribed by a phenomenological @xmath0-viscosity model , whereby the viscous torque is proportional to the pressure @xcite , although its physical basis is not clear ..
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they are ( radially ) one - dimensional models so that they can not describe multi - dimensional motion , such as outflow and internal circulation .
complex coupling between radiation , magnetic fields , and matters is not accurately solved , either .
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12,880 |
Suppose that you have an abstract for a scientific paper: we propose an extension to the standard model where three exotic fermion 5-plets and one scalar 6-plet are added to the particle content . by demanding that all interactions are renormalizable and standard model gauge invariant , we show that the lightest exotic particle in this model can be a dark matter candidate as long as the new 6-plet scalar does not develop a nonzero vacuum expectation value .
furthermore , light neutrino masses are generated radiatively at one - loop while the baryon asymmetry is produced by the cp - violating decays of the second lightest exotic particle .
we have demonstrated using concrete examples that there is a parameter space where a consistent solution to the problems of baryon asymmetry , dark matter and neutrino masses can be obtained . .
And you have already written the first three sentences of the full article: the observation of neutrino oscillations @xcite , which provides compelling evidence for nonzero neutrino masses , has long indicated to us that the minimal standard model ( sm ) is incomplete and must be extended .
meanwhile , astrophysical and cosmological data have given us ample important hints regarding the missing mass of the universe @xcite , prompting many theorists to build new models for accommodating such dark matter ( dm ) .
so , there is no shortage of motivation for developing physics beyond the sm ..
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in addition to these , it is well - known that the problem of generating a primordial baryon asymmetry @xcite must also bring together the studies of particle physics and cosmology .
most notably , in models of thermal leptogenesis @xcite , the sm is extended to include lepton violating interactions so that baryogenesis can be originated from a lepton asymmetry while neutrino masses are naturally generated via the type - i seesaw mechanism @xcite . in the light of this , it is perhaps most interesting to explore extensions to the sm that can address all three issues of baryon asymmetry , dark matter and neutrino masses simultaneously . to construct a model that can achieve this , we first note that a popular candidate for the role of the non - baryonic dm is the weakly interacting massive particle ( wimp ) @xcite .
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12,881 |
Suppose that you have an abstract for a scientific paper: as part of an ongoing program to better understand the early stages of massive star cluster evolution and the physical conditions for their formation , we have obtained @xmath0 , @xmath1 , and @xmath2 ( 10.8 @xmath3 m ) images of the nuclear region of the starburst galaxy he 2 - 10 .
the @xmath2-band images were obtained with the gemini north telescope . in only ten minutes of on - source integration time with gemini
we were able to detect three of the five enshrouded clusters , or `` ultradense h regions '' ( udhs ) recently discovered in radio maps .
none of these sources appears in either the optical hst images or the near - infrared ( @xmath0 , @xmath4 , and @xmath1 ) images .
these sources comprise about 60% of the total @xmath2-band flux from he 2 - 10 and ,
we suspect , a similar fraction of the total far infrared flux measured by iras . the inferred spectra of the udhs are strikingly similar to those of galactic ultracompact h ii regions .
we have modeled the radio+ir spectrum of these udhs under the assumption that they are scaled - up " galactic ultracompact h ii regions . from this model , the bolometric luminosity of the brightest cluster alone
is estimated to be @xmath5 l@xmath6 .
the total mass of the dust and gas in this udh is @xmath7 .
we have also used the observed spectra to place constraints on the masses and ages of the stellar clusters enshrouded within the udhs . for the brightest udh , we find that the stellar mass must be @xmath8 and the age must be @xmath9 yr , with the most probable age @xmath10 yr .
if we assume that the region is pressure confined and enforce the requirement that the star formation efficiency must be less than @xmath11% , we find that the age of this stellar cluster must lie within a very narrow range , @xmath12 yr . all of the clusters within the udhs in he 2 - 10 are estimated to have ages less than about @xmath13 yr and masses greater than about @xmath14 .
we find that the logarithmic ratio of the radio to far - infrared flux....
And you have already written the first three sentences of the full article: images of starburst galaxies obtained with the _ hubble space telescope ( hst ) _ have resolved the sites of active star formation into numerous compact star clusters ( see e.g. , schweizer 1999 ; whitmore 2000 and references therein ) . these so - called `` super star clusters '' ( sscs ) comprise approximately 20% of the total observed ultraviolet flux , and therefore represent a major mode of star formation in starburst galaxies ( meurer et al .
the radii of these sscs are typically a few pc and masses , estimated from both theoretical mass - to - light ratios and from direct measurements of velocity dispersions , are in the range @xmath19 .
the oldest of these sscs have ages significantly greater than their dynamical timescales and hence must be bound ..
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the masses , sizes , stellar densities , and ages of sscs suggest that the most massive examples may be the progenitors of globular clusters .
sscs may also be intimately related to nuclear stellar clusters recently found in the centers of exponential bulges in spiral galaxies ( carollo , stiavelli , & mack 1998 ; carollo 1999 ; bker , van der marel , & vacca 1999 ; bker et al .
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12,882 |
Suppose that you have an abstract for a scientific paper: below a ( comparatively large ) measure of non - hermiticity @xmath0 of a @xmath1 symmetrically complexified square well , bound states are constructed non - numerically .
all their energies prove real and continuous in the ( hermitian ) limit @xmath2 . beyond the threshold @xmath3 ( and , in general , beyond @xmath4 at @xmath5 ) the lowest two real energies ( i.e. , @xmath6 and @xmath7 ) are shown to merge and disappear .
pacs 03.65.ge , 03.65.fd .
And you have already written the first three sentences of the full article: an interest of physicists in complex potentials @xmath8 with the generalized symmetry property v(x ) = rev(-x ) ,
v(x ) = -imv(-x ) [ pts ] dates back to the perturbative study of imaginary cubic anharmonic oscillators v(x ) = x^2 + ix^3 [ ixnatri ] by caliceti et al @xcite . in the early nineties ,
an increase of this interest @xcite was inspired by the role of the imaginary cubic anharmonicity in field theory where eq ..
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( [ pts ] ) mimics the fundamental parity times time - reversal (= @xmath1 ) symmetry of phenomenological lagrangians @xcite . under certain circumstances ,
the @xmath1 symmetric and hermitian models can even prove mathematically equivalent @xcite . in the late nineties , bender and
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12,883 |
Suppose that you have an abstract for a scientific paper: the study of turbulent flows calls for measurements with high resolution both in space and in time . we propose a new approach to reconstruct high - temporal - high - spatial resolution velocity fields by combining two sources of information that are well - resolved either in space or in time , the low - temporal - high - spatial ( lths ) and the high - temporal - low - spatial ( htls ) resolution measurements . in the framework of co - conception between sensing and data post - processing
, this work extensively investigates a bayesian reconstruction approach using a simulated database . a bayesian fusion model is developed to solve the inverse problem of data reconstruction .
the model uses a maximum a posteriori estimate , which yields the most probable field knowing the measurements .
the dns of a wall - bounded turbulent flow at moderate reynolds number is used to validate and assess the performances of the present approach .
low resolution measurements are subsampled in time and space from the fully resolved data .
reconstructed velocities are compared to the reference dns to estimate the reconstruction errors .
the model is compared to other conventional methods such as linear stochastic estimation and cubic spline interpolation .
results show the superior accuracy of the proposed method in all configurations .
further investigations of model performances on various range of scales demonstrate its robustness .
numerical experiments also permit to estimate the expected maximum information level corresponding to limitations of experimental instruments . .
And you have already written the first three sentences of the full article: turbulence , though governed by navier - stokes equations , is extremely hard to predict due to its spatiotemporally intermittency as well as three - dimensional and irregular properties .
it is also a multi - scale phenomenon where a very wide range of scales from the largest eddies to kolmogorov micro - scales co - exist and interact . since the ratio between the largest and the smallest scales increases with reynolds number as @xmath0 , flows with high reynolds are the most challenging .
wall bounded flows are particularly difficult to model due to the overlap of several scaling regions as a function of distance to the wall ..
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coherent structures in such flows can extend up to several boundary layer thickness .
the modeling of such structures and scales therefore requires extremely detailed flow information in both space and time . despite a constant progress ,
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12,884 |
Suppose that you have an abstract for a scientific paper: traditionally the charge ratchet effect is considered as a consequence of either the spatial symmetry breaking engineered by asymmetric periodic potentials , or time asymmetry of the driving fields . here
we demonstrate that electrically and magnetically driven quantum dissipative systems with spin - orbit interactions represent an exception from this standard idea .
in contrast to the so far well established belief , a charge ratchet effect appears when both the periodic potential and driving are symmetric .
we show that the source of this paradoxical charge ratchet mechanism is the coexistence of quantum dissipation with the spin flip processes induced by spin - orbit interactions . .
And you have already written the first three sentences of the full article: a system of particles in a periodic potential and driven by a time - dependent external force may exhibit a net current even if the force has zero time average .
this so - called particle ratchet effect @xcite is used e.g. in nano - generators of direct charge currents @xcite . to excite the particle ratchet current
it is traditionally believed that the asymmetry of either the periodic potential or driving force is a must . in the quantum regime.
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a more stringent conclusion has been obtained : in quantum systems in which charged particles populate only one bloch band the charge ratchet effect does not exist , even if the periodic potential is asymmetric , unless time asymmetry is provided by the driving field @xcite .
indeed , the ratchet effect exists in a single - band system which is driven by a field with harmonic mixing @xcite .
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12,885 |
Suppose that you have an abstract for a scientific paper: the e1(t=1 ) isovector dipole giant resonance ( gdr ) in heavy and super - heavy deformed nuclei is analyzed over a sample of 18 rare - earth nuclei , 4 actinides and three chains of super - heavy elements ( z=102 , 114 and 120 ) .
basis of the description is self - consistent separable rpa ( srpa ) using the skyrme force sly6 .
the self - consistent model well reproduces the experimental data ( energies and widths ) in the rare - earth and actinide region .
the trend of the resonance peak energies follows the estimates from collective models , showing a bias to the volume mode for the rare - earths isotopes and a mix of volume and surface modes for actinides and super - heavy elements .
the widths of the gdr are mainly determined by the landau fragmentation which in turn is found to be strongly influenced by deformation .
a deformation splitting of the gdr can contribute about one third to the width and about 1 mev further broadening can be associated to mechanism beyond the mean - field description ( escape , coupling with complex configurations ) . .
And you have already written the first three sentences of the full article: the isovector giant dipole resonance ( gdr ) is a most prominent and much studied excitation mode of nuclei , see e.g. @xcite .
nonetheless , it remains a subject of actual interest as there are many aspects which deserve more detailed investigations as , e.g. , photo - excitation cross sections in exotic nuclei which play a role in astrophysical reaction chains @xcite or isotopic trends of the gdr including the regimes of deformed nuclei .
the present paper aims at a theoretical survey of the gdr in isotopic chains of heavy and super - heavy nuclei ..
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the high importance of the gdr has triggered since long many theoretical surveys analyzing the intriguing aspects of nuclear collective motion , starting from a purely collective description @xcite and slowly establishing a link to microscopic models in the framework of the random - phase approximation ( rpa ) @xcite .
the theoretical description has much developed over the years .
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12,886 |
Suppose that you have an abstract for a scientific paper: the inelastic collapse of stochastic trajectories of a randomly accelerated particle moving in half - space @xmath0 has been discovered by mckean and then independently re - discovered by cornell et .
al .
the essence of this phenomenon is that particle arrives to a wall at @xmath1 with zero velocity after an infinite number of inelastic collisions if the restitution coefficient @xmath2 of particle velocity is smaller than the critical value @xmath3 .
we demonstrate that inelastic collapse takes place also in a wide class of models with spatially inhomogeneous random force and , what is more , that the critical value @xmath4 is universal .
that class includes an important case of inertial particles in wall - bounded random flows . to establish how the inelastic collapse influence the particle distribution
, we construct an exact equilibrium probability density function @xmath5 for particle position and velocity .
the equilibrium distribution exists only at @xmath6 and indicates that inelastic collapse does not necessarily mean the near - wall localization . .
And you have already written the first three sentences of the full article: the models of a randomly accelerated particles which collide inelastically with a wall arise naturally in different contexts ranging from driven granular matter to dynamics of confined polymers ( see e.g. @xcite and relevant references therein ) . in the simplest one - dimensional model , a particle is subjected to gaussian white noise and instantaneously loses a certain part of its velocity at the moments of reflection from the wall .
the first rigorous results for this problem go back to mckean @xcite , who discovered that trajectory tends to touch the origin of phase space ( particle velocity turns zero on the wall ) if the restitution coefficient of particle velocity is smaller that some critical value .
subsequently , this phenomenon was named the inelastic collapse and has been extensively studied in physics @xcite and mathematics @xcite literature . in particular , it has been established that inelastic collapse does not necessarily force the particle to remain at the wall forever @xcite ..
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more recently there has been significant interest in specific generalization of the aforementioned classical model , which includes viscous damping together with inhomogeneous noise whose intensity increases with distance to the wall .
first of all , the inhomogeneous generalization is relevant to the single - particle dynamics in turbulent environment .
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12,887 |
Suppose that you have an abstract for a scientific paper: the xmm - newton x - ray observatory pointed the galactic black hole candidate and microquasar grs 1758 - 258 in september 2000 for about 10 ks during a program devoted to the scan of the galactic center regions .
preliminary results from epic mos camera data are presented here .
the data indicate that the source underwent a state transition from its standard low - hard state to an intermediate state . for the first time in this source
the ultra - soft component of the accretion disk , which black hole binaries display in intermediate or high - soft states , was clearly detected and measured thanks to the high spectral capabilities of xmm - newton . .
And you have already written the first three sentences of the full article: the source grs 1758 - 258 was discovered in 1990 with the sigma soft @xmath0-ray telescope at about 5@xmath1 from the galactic center @xcite .
the hard spectrum extending up to 200 - 300 kev @xcite , very similar to the cyg x-1 spectrum , strongly suggests that this source is an accreting black hole in a galactic binary system with a low mass companion star .
the source was then observed in radio and two symmetrical radio lobes were detected at 6 cm with the vla @xcite on either sides of a point - like radio source close to the x - ray source ..
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the radio point source position was compatible with both the sigma error circle and the much smaller rosat error circle ( 10@xmath2 radius ) of grs 1758 - 258 . in spite of a large drop in hard x - ray flux detected with sigma in 1991 - 1992 and some claims of sporadic appearence of a soft component @xcite ,
no spectral transitions have ever been clearly observed from this source .
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12,888 |
Suppose that you have an abstract for a scientific paper: we have made a serendipitous discovery of a massive ( @xmath0@xmath1 ) cd galaxy at z=1.096 in a candidate rich cluster in the hudf area of goods - south .
this brightest cluster galaxy ( bcg ) is the most distant cd galaxy confirmed to date .
ultra - deep hst / wfc3 images reveal an extended envelope starting from @xmath2 and reaching @xmath3 in radius along the semi - major axis .
the spectral energy distributions indicate that both its inner component and outer envelope are composed of an old , passively - evolving ( specific star formation rate @xmath4 ) stellar population .
the cd galaxy lies on the same mass - size relation as the bulk of quiescent galaxies at similar redshifts .
the cd galaxy has a higher stellar mass surface density ( @xmath5 ) but a similar velocity dispersion ( @xmath6 ) to those of more - massive , nearby cds .
if the cd galaxy is one of the progenitors of today s more massive cds , its size ( @xmath7 ) and stellar mass have had to increase on average by factors of @xmath8 and @xmath9 over the past @xmath10 gyrs , respectively .
such increases in size and stellar mass without being accompanied by significant increases in velocity dispersion are consistent with evolutionary scenarios driven by both major and minor dissipationless ( dry ) mergers .
if such cd envelopes originate from dry mergers , our discovery of even one example proves that some bcgs entered the dry merger phase at epochs earlier than @xmath11 .
our data match theoretical models which predict that the continuance of dry mergers at @xmath12 can result in structures similar to those of massive cd galaxies seen today . moreover , our discovery is a surprise given that the extreme depth of the hudf is essential to reveal such an extended cd envelope at @xmath13 and , yet , the hudf covers only a minuscule region of sky ( @xmath14 ) . adding that cds are rare , our serendipitous discovery hints that such cds may be more common than expected , perhaps even ubiquitous .
images reaching hudf depths of....
And you have already written the first three sentences of the full article: cd galaxies are the most luminous and most massive galaxies in the local universe and are mostly located close to the centers of galaxy clusters .
earlier studies have characterized cd galaxies by their excess light ( ` envelopes ' ) over the de vaucouleurs ( or @xmath15 , de vaucouleurs 1948 ) profile or s@xmath16rsic ( or @xmath17 , s@xmath16rsic 1968 ) profile at large radii ( e.g. , * ? ? ?
* ; * ? ? ?.
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* ; * ? ? ?
more recent studies have identified cd galaxies using improved petrosian @xcite parameter profiles @xcite .
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12,889 |
Suppose that you have an abstract for a scientific paper: we present observations of hdco and h@xmath0co emission toward a sample of 15 class 0 protostars in the orion a and b clouds . of these , eleven protostars are _
herschel_-identified pacs bright red sources ( pbrs ) and four are previously identified protostars .
our observations revealed the chemical properties of the pbrs envelope for the first time .
the column densities of hdco and h@xmath0co are derived from single dish observations at an angular resolution of @xmath120@xmath2 ( @xmath18400 au ) .
the degree of deuteration in h@xmath0co ( [ hdco]/[h@xmath0co ] ) was estimated to range from 0.03 to 0.31 .
the deuterium fractionation of most pbrs ( 70% ) is similar to that of the non - pbrs sources .
three pbrs ( 30% ) exhibit high deuterium fractionation , larger than 0.15 .
the large variation of the deuterium fractionation of h@xmath0co in the whole pbrs sample may reflect the diversity in the initial conditions of star forming cores .
there is no clear correlation between the [ hdco]/[h@xmath0co ] ratio and the evolutionary sequence of protostars . .
And you have already written the first three sentences of the full article: observing deuterated species is useful for probing the physical and chemical conditions of star - forming regions @xcite .
the deuterium to hydrogen ( d / h ) ratio in the local interstellar medium is low , about @xmath3 , which is the d / h elemental abundance as predicted by the nucleosynthesis @xcite .
by contrast , higher molecular d / h ratios have been observed from objects associated with star formation , such as molecular clouds @xcite , pre - stellar cores @xcite , and protostellar cores @xcite ..
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many observations and chemical models showed that deuterium - bearing molecules are enhanced during the cold prestellar core phase and released into the gas when a heating event , such as the formation of a protostar or the passage of a shock , evaporates the ice @xcite .
formaldehyde ( h@xmath0co ) is one of the key species in the synthesis of more complex organic molecules .
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12,890 |
Suppose that you have an abstract for a scientific paper: the phase structure of the polyakov loop - extended chiral quark
meson model is explored in a nonperturbative approach , beyond a mean - field approximation , in the presence of a magnetic field .
we show that by including meson fluctuations one can not resolve the qualitative discrepancy on the dependence of the crossover transition temperature in a non - zero magnetic field between effective model predictions and recent lattice results ( arxiv:1111.4956 ) .
we compute the curvature of the crossover line in the @xmath0 plane at a non - zero magnetic field and show that the curvature increases with increasing magnetic field . on the basis of qcd inequalities , we also argue that , at least in the large @xmath1 limit , a chiral critical end point and , consequently , a change from crossover to a first - order chiral phase transition are excluded at zero baryon chemical potential and non - zero magnetic field . .
And you have already written the first three sentences of the full article: the phase diagram of strongly interacting matter in the presence of an external magnetic field has been been explored in model studies and in first principle lattice quantum chromodynamics ( lqcd ) calculations .
these investigations has an importance for physics of heavy - ion collisions at top rhic and lhc energies , where according to the estimates ( see refs .
@xcite and @xcite ) , the magnitude of the magnetic field may reach extremely large values of @xmath2 ..
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model studies ( see e.g. refs .
@xcite ) have revealed a general structure of the phase diagram in the temperature - magnetic field ( @xmath3 ) plane .
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12,891 |
Suppose that you have an abstract for a scientific paper: hamiltonian and eigenstate problem is formulated for a bilayer graphene in terms of clifford s geometric algebra _ _ cl__@xmath0 and respective multivectors .
it is shown that such approach allows to perform analytical calculations in a simple way if geometrical algebra rotors are used .
the measured quantities are express through spectrum and rotation half - angle of the pseudospin that appears in geometric algebra rotors .
properties of free charge carriers pseudospin , velocity and berry phase in a bilayer graphene are investigated in the presence of the external voltage applied between the two layers . .
And you have already written the first three sentences of the full article: bilayer graphene ( blg ) consists of two graphene monolayers a and b that are typically aligned in the bernal stacking arrangement .
the study of blg has started in 2006 after the appearance of e. mccann s and v. i. falko s paper @xcite .
a unique feature of the blg is its tunable energy band structure by external voltage applied between a and b layers ..
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the opening of the gap in exfoliated bottom - gated blg was demonstrated experimentally by a. b. kuzmenko et al @xcite .
a comprehensive description of blg properties and respective references can be found in review articles @xcite and monograph @xcite . the geometric algebra ( ga ) , or more precisely a family of algebras _
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12,892 |
Suppose that you have an abstract for a scientific paper: in this paper , the support genus of all legendrian right handed trefoil knots and some other legendrian knots is computed . we give examples of legendrian knots in the three - sphere with the standard contact structure which have positive support genus with arbitrarily negative thurston - benniquin invariant .
this answers a question in @xcite . .
And you have already written the first three sentences of the full article: in his seminal paper @xcite , giroux established the surprising one - to - one correspondence between the contact structures up to isotopy and the open book decompositions up to positive stabilizations on a given closed oriented three - manifold .
see @xcite for details .
it becomes natural and convenient for topologists to study contact structures in the viewpoint of open book decompositions ..
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for legendrian knots , akbulut and ozbagci @xcite showed that for any legendrian link @xmath0 in @xmath1 with the standard contact structure @xmath2 , there exists a compatible open book such that @xmath0 sits in a page of the open book , furthermore , the framing of l given by the page of the open book agrees with the contact framing .
see also @xcite
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12,893 |
Suppose that you have an abstract for a scientific paper: the dft / vdw - wf2s1 method , recently developed to include the van der waals interactions in the density functional theory and describe adsorption processes on metal surfaces by taking metal - screening effects into account , is applied to the case of the interaction of xe and graphene with a transition - metal surface , namely ni(111 ) . in general the adsorption of rare - gas atoms on metal surfaces
is important because is prototypical for physisorption processes .
moreover , the interaction of graphene with ni(111 ) is of particular interest for practical applications ( efficient and large - scale production of high - quality graphene ) and , from a theoretical point of view , is particularly challenging , since it can be described by a delicate interplay between chemisorption and physisorption processes .
the first - principles simulation of transition metals require particular care also because they can be viewed as intermediate systems between simple metals and insulating crystals . even in these cases
the method performs well as demonstrated by comparing our results with available experimental data and other theoretical investigations .
we confirm that the rare gas xe atom is preferentially adsorbed on the top - site configuration on the ni(111 ) surface too .
our approach based on the use of the maximally localized wannier functions also allow us to well characterize the bonds between graphene and ni(111 ) . .
And you have already written the first three sentences of the full article: the interaction of graphene with transition metal surfaces is of great importance because the growth of graphene on these substrates is probably at present the most perspective way for the large - scale preparation and production of high - quality graphene.@xcite in particular , the ni(111 ) surface is very interesting , being the closest matched interface with respect to graphene of all transition metals ( with a lattice mismatch of about 1% ) , and has been therefore intensively investigated.@xcite in fact , the close lattice match allows graphene to adapt itself to the ni(111 ) lattice and enables the formation of a well - ordered _
p(@xmath0 ) _ over - structure on the ni(111 ) surface , which is much simpler than the complex moir patterns commonly found in other transition metal surfaces.@xcite moreover , given the ferromagnetic properties of ni , graphene on ni surface has also been proposed as a promising spin - filtering device needed in spintronics.@xcite due to the strong interaction between graphene @xmath1 and ni @xmath2 electrons , the graphene electronic structure is heavily modified if compared to the electronic structure of free - standing graphene .
the most important change is the gap opening resulting from sublattice symmetry breaking . from a fundamental point of view.
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, the nature of the bonds at the graphene - metal interface has not been completely elucidated yet .
basically , by taking the c - c covalent bonds as a reference , the interaction of graphene with a metal substrate can be classified as weak ( with ir(111 ) , au(111 ) , cu(111 ) , pt(111 ) , al(111 ) , and pd(111 ) ) or strong
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12,894 |
Suppose that you have an abstract for a scientific paper: the problem to be studied in this work is within the context of coefficient identification problems for the wave equation .
more precisely , we consider the problem of reconstruction of the refractive index ( or equivalently , the dielectric constant ) of an inhomogeneous medium using one backscattering boundary measurement . the goal of this paper is to analyze the performance of a globally convergent algorithm of beilina and klibanov on experimental data acquired in the microwave laboratory at university of north carolina at charlotte .
the main challenge working with experimental data is the the huge misfit between these data and computationally simulated data .
we present data pre - processing steps to make the former somehow look similar to the latter .
results of both non - blind and _ * blind * _ targets are shown indicating good reconstructions even for high contrasts between the targets and the background medium . * keywords * : coefficient identification , wave equation , globally convergent algorithm , experimental data , data pre - processing . * ams classification codes : * 35r30 , 35l05 , 78a46 . .
And you have already written the first three sentences of the full article: in this paper , we consider the problem of the reconstruction of the refractive indices ( equivalently , the relative permittivities , or dielectric constants ) of unknown targets placed in a homogeneous medium using experimental measurements of back - scattered electromagnetic waves in time domain .
mathematical speaking , this is a coefficient inverse problem ( cip ) for the time - dependent wave - like equation : we reconstruct a spatially varying coefficient of this equation using measurements on a part of the boundary of the domain of interest .
potential applications of this problem are in the detection and characterization of explosives , including improvised explosive devices ( ieds ) . note that ieds are often located above the ground surface @xcite , which is somewhat close to our case of targets located in the air ..
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the case when targets are buried in the ground will be reported in a future publication .
different imaging methods have been applied to this type of measurements to obtain geometrical information such as shapes , sizes and locations of the targets , see e.g. @xcite
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12,895 |
Suppose that you have an abstract for a scientific paper: we present the discovery of the first t dwarf + white dwarf binary system lspm1459 + 0857ab , confirmed through common proper motion and spectroscopy .
the white dwarf is a high proper motion object from the lspm catalogue that we confirm spectroscopically to be a relatively cool ( @xmath0 = 5535@xmath145k ) and magnetic ( b@xmath22 mg ) hydrogen - rich white dwarf , with an age of at least 4.8gyrs .
the t dwarf is a recent discovery from the ukirt infrared deep sky survey ( ulas1459 + 0857 ) , and has a spectral type of [email protected] and a distance in the range 43 - 69pc . with an age constraint ( inferred from the white dwarf ) of @xmath34.8gyrs
we estimate @xmath0 = 1200 - 1500k and @xmath4 = 5.4 - 5.5 for ulas1459 + 0857 , making it a benchmark t dwarf with well constrained surface gravity .
we also compare the t dwarf spectra with the latest lyon group atmospheric model predictions , which despite some shortcomings are in general agreement with the observed properties of ulas1459 + 0857 .
the separation of the binary components ( 16,500 - 26,500au , or 365 arcseconds on the sky ) is consistent with an evolved version of the more common brown dwarf + main - sequence binary systems now known , and although the system has a wide separation , it is shown to be statistically robust as a non spurious association .
the observed colours of the t dwarf show that it is relatively bright in the @xmath5 band compared to other t dwarfs of similar type , and further investigation is warranted to explore the possibility that this could be a more generic indicator of older t dwarfs .
future observations of this binary system will provide even stronger constraints on the t dwarf properties , and additional systems will combine to give a more comprehensively robust test of the model atmospheres in this temperature regime .
[ firstpage ] stars : low mass , brown dwarfs - stars : white dwarfs - binaries : general .
And you have already written the first three sentences of the full article: large scale near infrared ( nir ) and optical surveys such as the 2-micron all sky survey ( 2mass ) , the sloan digital sky survey ( sdss ) , and the ukirt infrared deep sky survey ( ukidss ) are aiding the identification of a rapidly increasing number of @xmath6field@xmath6 brown dwarfs ( bds ) ( e.g. @xcite , @xcite , @xcite ) , as well as probing down into new cooler temperature regimes ( @xcite , @xcite , @xcite , @xcite , @xcite ) .
in general the estimation of properties of these bds ( e.g. age , mass , metallicity ) currently relies on model fitting .
however , the models are very sensitive to a variety of poorly understood processes in bd atmospheres , such as the formation of dust condensates @xcite and non - equilibrium chemistry @xcite , and the spectroscopic fitting of atmospheric properties ( @xmath0 , @xmath4 , [ m / h ] ) is a major challenge ..
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crucially , the nature of bd evolution means that the mass - luminosity relation depends strongly on age , and in the absence of well constrained atmospheric properties there is no way to accurately determine mass and age .
identifying objects where one can pin down these properties independently can help aid the calibration of models .
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12,896 |
Suppose that you have an abstract for a scientific paper: a theoretical framework is developed for a precise control of spatial patterns in oscillatory media using nonlinear global feedback , where a proper form of the feedback function corresponding to a specific pattern is predicted through the analysis of a phase diffusion equation with global coupling .
in particular , feedback functions that generate the following spatial patterns are analytically given : i ) 2-cluster states with an arbitrary population ratio , ii ) equally populated multi - cluster states , and iii ) a desynchronized state .
our method is demonstrated numerically by using the brusselator model in the oscillatory regime .
experimental realization is also discussed . .
And you have already written the first three sentences of the full article: feedback control is a powerful method of regulating spatio - temporal dynamics and has been studied in a wide variety of fields including physics , chemistry , biology , and medical science @xcite . for example ,
formation of various clustering patterns has been realized in the belousov - zhabotinsky reaction @xcite and in the catalytic co oxidation reaction on pt @xcite .
the catalytic co oxidation systems have also been studied for the suppression of chemical turbulence @xcite . moreover ,.
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considerable attention has been paid to feedback devices that suppress the pathological synchronization in the brain of parkinson s disease patients @xcite . in many cases systems to be controlled are spatially extended , and reaction - diffusion systems provide a good model for the study of pattern controlling .
theoretical analyses based on reaction - diffusion systems have been done for the belousov - zhabotinsky reaction @xcite and co oxidation @xcite .
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12,897 |
Suppose that you have an abstract for a scientific paper: the dynamic behavior of microtubules in solution can be strongly modified by interactions with walls or other structures .
we examine here a microtubule growth model where the increase in size of the plus - end is perturbed by collisions with other microtubules .
we show that such a simple mechanism of constrained growth can induce ordered structures and patterns from an initially isotropic and homogeneous suspension .
first , microtubules self - organize locally in randomly oriented domains that grow and compete with each other . by imposing even a weak orientation bias , external forces like gravity or cellular boundaries
may bias the domain distribution eventually leading to a macroscopic sample orientation . .
And you have already written the first three sentences of the full article: biological processes like cell division , transport of certain organelles , morphogenesis and organization in the cell are mediated by rod like structures known as microtubules , which form various arrays , radial spindles , parallel and antiparallel bundles @xcite .
the microtubule self - assembly in living organisms is regulated by different factors : microtubule - associated proteins ( maps ) which stabilize , destabilize and crosslink microtubules @xcite , diverse kinesin - like motor proteins , which organize and link microtubules , @xmath0-tubulin ring complex which serves as a template for nucleation sites for microtubule polymerization in centrosomes @xcite .
these factors combine with the physical and chemical properties of the solution to determine , by mechanisms not yet well understood , the spatial structure and the orientation of the microtubules ..
Please generate the next two sentences of the article
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each individual microtubule is a highly dynamic self - assembled rod , which is permanently growing or shrinking .
this ability for being in an everlasting state of changing length as won microtubules the name of `` searching devices '' for specific targets in the cell @xcite .
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12,898 |
Suppose that you have an abstract for a scientific paper: we report a discovery of a companion candidate around one of _ kepler _ objects of interest ( kois ) , koi-94 , and results of our quantitative investigation of the possibility that planetary candidates around koi-94 are false positives .
koi-94 has a planetary system in which four planetary detections have been reported by _
kepler _ , suggesting that this system is intriguing to study the dynamical evolutions of planets .
however , while two of those detections ( koi-94.01 and 03 ) have been made robust by previous observations , the others ( koi-94.02 and 04 ) are marginal detections , for which future confirmations with various techniques are required .
we have conducted high - contrast direct imaging observations with subaru / hiciao in @xmath0 band and detected a faint object located at a separation of @xmath1 from koi-94 .
the object has a contrast of @xmath2 in @xmath0 band , and corresponds to an m type star on the assumption that the object is at the same distance of koi-94 .
based on our analysis , koi-94.02 is likely to be a real planet because of its transit depth , while koi-94.04 can be a false positive due to the companion candidate .
the success in detecting the companion candidate suggests that high - contrast direct imaging observations are important keys to examine false positives of kois . on the other hand ,
our transit light curve reanalyses lead to a better period estimate of koi-94.04 than that on the koi catalogue and show that the planetary candidate has the same limb darkening parameter value as the other planetary candidates in the koi-94 system , suggesting that koi-94.04 is also a real planet in the system . .
And you have already written the first three sentences of the full article: one of the best ways to determine orbital parameters of extrasolar planets ( exoplanets ) is the transit method .
particularly the _ kepler _ satellite , launched in 2009 , has executed successful transit observations , resulting in discovery of more than 3,500 planet candidates .
it drastically increases the number of exoplanets we know and has found many multi - transiting planetary systems ..
Please generate the next two sentences of the article
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the principal problem related to the transit method is a possibility of a false positive .
a false positive in transit surveys means misidentifying a signal caused by an object other than a planet orbiting the target star as its true planetary companion . in transit surveys ,
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12,899 |
Suppose that you have an abstract for a scientific paper: we report circumstantial evidence for the first detection of pulsed high - energy @xmath0-ray emission from a millisecond pulsar , psr j0218@xmath14232 , using data collected with the energetic gamma ray experiment ( egret ) on board the compton gamma ray observatory ( cgro ) .
the egret source 3eg j0222 + 4253 is shown to be spatially consistent with psr j0218@xmath14232 for the energy range 100 - 300 mev . above 1 gev
the nearby bl lac 3c 66a is the evident counterpart , and between 300 mev and 1 gev both sources contribute to the @xmath0-ray excess . folding the 100 - 1000 mev photons with an accurate radio ephemeris of psr j0218@xmath14232
yields a double peaked pulse profile with a @xmath2 modulation significance and with a peak separation of @xmath3 similar to the 0.1 - 10 kev pulse profile .
a comparison in absolute phase with the 610 mhz radio profile shows alignment of the @xmath0-ray pulses with two of three radio pulses .
the luminosity of the pulsed emission ( 0.1 - 1 gev ) amounts @xmath4 which is @xmath5 % of the pulsar s total spin - down luminosity .
the similarity of the x - ray and @xmath0-ray pulse profile shapes of psr j0218@xmath14232 , and the apparent alignment of the @xmath0-ray pulses with two radio pulses at 610 mhz , bears resemblance to the well - known picture for the crab pulsar .
this similarity , and the fact that psr j0218@xmath14232 is one of three millisecond pulsars ( the others are psr b1821 - 24 and psr b1937 + 21 ) which exhibit very hard , highly non - thermal , high - luminosity x - ray emission in narrow pulses led us to discuss these millisecond pulsars as a class , noting that each of these has a magnetic field strength near the light cylinder comparable to that for the crab .
none of the current models for @xmath0-ray emission from radio pulsars can explain the @xmath0-ray spectrum and luminosity of psr j0218@xmath14232 . .
And you have already written the first three sentences of the full article: pulsed high - energy emission from millisecond ( ms ) pulsars has so far been detected at x - ray energies below @xmath6 10 kev for only five pulsars : psr j0437 - 4715 ( @xcite ) , psr j2124 - 3358 ( @xcite ) , psr b1821 - 24 ( @xcite ) , psr j0218 + 4232 ( @xcite ) and psr b1937 + 21 ( @xcite ) .
the first two exhibit broad x - ray pulses , have soft spectra and relatively low luminosities in the x - ray window , about 3 orders of magnitude lower than derived for the latter three ( @xmath7 assuming emission in a 1 sr beam ) .
in addition to the higher luminosity , these have very narrow x - ray pulses ( intrinsically @xmath8 or narrower ) and hard power - law shape spectra measured up to @xmath6 10 kev ( @xcite , @xcite , @xcite , respectively ) , the two hardest spectra having indices as hard as @xmath6 -0.65 ..
Please generate the next two sentences of the article
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this short observational summary suggests that this small sample can de devided in two distinct classes of ms pulsars : _ class _ i , ms pulsars with soft , low - luminosity x - ray emission in broad pulses ; _ class _ ii , with highly non - thermal , high - luminosity x - ray emission in narrow pulses .
millisecond pulsars not only differ from normal radio pulsars in that their spin periods are 1 to 2 orders of magnitude shorter , reducing correspondingly their light cylinder radii , but particularly their surface magnetic field strengths are 3 to 4 orders of magnitude weaker .
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