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Suppose that you have an abstract for a scientific paper: promoter strength , or activity , is important in genetic engineering and synthetic biology .
evidences show that a constitutive promoter with certain strength for one given rna can often be reused for other rnas .
therefore , the strength of one promoter is mainly determined by its nucleotide sequence .
one of the main difficulties in genetic engineering and synthetic biology is how to control the expression of certain protein in one given level .
one usually used way to achieve this goal is to choose one promoter with suitable strength , which can be employed to regulate the rate of transcription and then leads to needed level of protein expression . for this purpose , so far , many promoter libraries have been established experimentally .
however , theoretical methods to predict the strength of one promoter from its nucleotide sequence are desirable . since such methods are not only valuable in the design of promoter with specified strength , but also meaningful to understand the mechanism of promoter in gene transcription .
in this study , through various tests one theoretical model is presented to describe the relationship between promoter strength and its nucleotide sequence .
our analysis shows that , promoter strength is greatly influenced by nucleotide groups with three adjacent nucleotides in its sequence .
meanwhile , nucleotides in different regions of promoter sequence have different effects on promoter strength .
based on experimental data for _ e. coli _ promoters , our calculations indicate , nucleotides in -10 region , -35 region , and the discriminator region of promoter sequence are more important than those in spacing region for determining promoter strength . with model parameter values obtained by fitting to experimental data ,
four promoter libraries are theoretically built for the corresponding experimental environments under which data for promoter strength in gene expression has been measured previously . .
And you have already written the first three sentences of the full article: in cells , a small variety of expression of some protein may influence cell metabolism seriously . in synthetic biology , many models have been presented to describe the metabolic network @xcite . according to these models , it often needs to express a certain kind of protein ( especially enzyme ) in a specific intensity .
one of the widely used ways to do this is to adjust the nucleotide sequence of the corresponding promoter @xcite .
a promoter is a region of dna that initiates transcription of a particular gene @xcite , see fig ..
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[ figschematic ] . in gene expression ,
the genetic information coded in nucleotide sequence of dna should be firstly transcribed into message rna ( mrna ) , which is performed by enzyme rna polymerase ( rnap ) @xcite .
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11,601 |
Suppose that you have an abstract for a scientific paper: numerical solution of equations governing time domain simulations in computational electromagnetics , is usually based on grid methods in space and on explicit schemes for the time evolution .
a predefined grid in the problem domain and a stability step size restriction must be accepted .
evidence is given that efforts need for overcoming these heavy constraints .
recently , the authors developed a meshless method to avoid the connective laws among the points scattered in the problem domain . despite the good spatial properties , the numerical explicit integration used in the original formulation of the method provides , also in a meshless context , spatial and time discretization strictly interleaved and mutually conditioned .
afterwards , in this paper the stability condition is firstly addressed in a general way by allowing the time step increment get away from the minimum points spacing . meanwhile , a formulation of the alternating direction implicit scheme for the evolution in time is combined with the meshless solver .
the formulation preserves the leapfrog marching on in time of the explicit integration scheme .
the new method , not constrained by a gridding in space and unconditionally stable in time , is numerical assessed by different numerical simulations .
perfect matching layer technique is used in simulating open spatial problems ; otherwise , a consistency restoring approach is introduced in treating truncation at finite boundary and irregular points distribution .
three case studies are investigated by achieving a satisfactory agreement comparing both numerical and analytical results .
adi leapfrog method , meshless methods , smoothed particles electromagnetics . .
And you have already written the first three sentences of the full article: meshless methods have recently emerged as numerical techniques for electromagnetic modelling @xcite .
these methods do not require a predefined mesh , and use points scattered in the problem domain avoiding the need of information on the position among them .
one of the most popular meshless method , the smoothed particle hydrodynamics ( sph ) @xcite has been recently reformulated by the authors for computational electromagnetics ( cem ) problems ..
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maxwell s equations , which relate the electric and magnetic fields by means of a time dependent system of partial differential equations(pdes ) are considered @xcite . due to the coupling nature of the electric and magnetic field components , the points are in such a way that the electric points should be surrounded by those of magnetic field and vice - versa .
the method named as spem is applied in approximating the space field variables of the time domain maxwell s curl equations by using a kernel representation working with a cluster of scattered nodes .
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11,602 |
Suppose that you have an abstract for a scientific paper: longitudinal polarizations of different kinds of hyperons produced in @xmath0 annihilation at lep i and lep ii energies in different event samples are calculated using two different pictures for the spin structure of hyperon : that drawn from polarized deep inelastic lepton - nucleon scattering data or that using su(6 ) symmetric wave functions .
the result shows that measurements of such polarizations should provide useful information to the question of which picture is more suitable in describing the spin effects in the fragmentation processes . .
And you have already written the first three sentences of the full article: spin effects in high energy fragmentation processes have attracted much attention@xcite recently .
study of such effects provide useful information for the spin structure of hadron and spin dependence of high energy reactions . there
exist now two distinctively different pictures for the spin contents of the baryons : the static quark model picture using su(6 ) symmetric wave function [ hereafter referred as su(6 ) picture ] , and the picture drawn from the data for polarized deep inelastic lepton - nucleon scattering ( dis ) @xcite and su(3 ) flavor symmetry in hyperon decay [ hereafter referred as dis picture ] ..
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it is natural to ask which picture is suitable to describe the relationship between the polarization of the fragmenting quark and that of the produced hadron .
it has been pointed out in [ [ bl98 ] ] that measurements of @xmath1 longitudinal polarization in @xmath0 annihilation at high energies can provide useful information to answer this question .
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Suppose that you have an abstract for a scientific paper: we investigate the unruh effect on entanglement taking into account the spin degree of freedom of the dirac field .
we analyze spin bell states in this setting , obtaining their entanglement dependence on the acceleration of one of the partners .
then , we consider simple analogs to the occupation number entangled state @xmath0 but with spin quantum numbers for @xmath1 . we show that , despite their apparent similitude , while the spinless case is always qubit@xmath2qubit , for the spin case acceleration produces a qubit@xmath2qu4it state .
we also introduce a procedure to consistently erase the spin information from our setting preserving occupation numbers .
we show how the maximally entangled state for occupation number emerges from our setting .
we as well analyze its entanglement dependence on acceleration , obtaining a greater entanglement degradation than in the spinless case . .
And you have already written the first three sentences of the full article: despite their apparently separated application areas , general relativity and quantum information are not disjoint research fields . on the contrary , following the pioneering work of alsing and milburn @xcite a wealth of works
@xcite has considered different situations in which entanglement was studied in a general relativistic setting , for instance , quantum information tasks in the proximity of black holes @xcite , entanglement in an expanding universe @xcite , entanglement with non - inertial partners @xcite etc .
entanglement behavior in non - inertial frames was first considered in @xcite where the fidelity of teleportation between relative accelerated partners was analyzed ..
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after this , occupation number entanglement degradation of scalar @xcite and dirac @xcite fields due to unruh effect @xcite was shown .
recent works studied the effect of the instantaneous wigner rotations and thomas spin precession on entanglement @xcite,@xcite .
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11,604 |
Suppose that you have an abstract for a scientific paper: we present a systematic analysis of molecular oxygen ( o@xmath0 ) adsorption trends on bimetallic pt - ni clusters and their monometallic counterparts supported on mgo(100 ) , by means of periodic dft calculations for sizes between 25 up to 58 atoms .
o@xmath0 adsorption was studied on a variety of inequivalent sites for different structural motifs , such as truncated octahedral ( to ) , cuboctahedral ( co ) , icosahedral ( ih ) and decahedral ( dh ) geometries .
we found that o@xmath0 prefers to bind on top of two metal atoms , parallel to the cluster , with an average chemisorption energy of 1.09 ev ( pt - ni ) , 1.07 ev ( pt ) and 2.09 ev ( ni ) , respectively .
the largest adsorption energy values are found to be along the edges between two neighbouring ( 111)/(111 ) and ( 111)/(100 ) facets ; while fcc and hcp sites located on the ( 111 ) facets may show a chemisorption value lower 0.3 ev where often fast o@xmath0 dissociation easily occurs .
our results show that , even though it is difficult to disentangle the geometrical and electronic effects on the oxygen molecule adsorption , there is a strong correlation between the calculated general coordination number ( gcn ) and the chemisorption map . finally , the inclusion of dispersion corrections ( dft - d ) leads to an overall increase on the calculated adsorption energy values but with a negligible alteration on the general o@xmath0 adsorption trends . .
And you have already written the first three sentences of the full article: [ h ] [ 0.26 ] + [ h ] [ 0.26 ] + the development of novel mobility technologies for cleaner vehicle emissions is essential to mitigate the current high levels of pollution seen on internal combustion engines .
one foreseeable technology involves the electrochemical conversion of energy using polymer electrolyte membrane fuel cells ( pemfc)@xcite . used in cars , fuel cells currently provide the necessary power needed to travel even long - distances .
however , the costly use of platinum ( pt ) as an electrocatalyst inside pemfc has triggered an a vast active search for cheaper pt - based alloys ..
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one proposed solution is to combine it with other late transition metals such as nickel ( ni ) , cobalt ( co ) , chromium ( cr ) , copper ( cu ) and iron ( fe)@xcite . the goal of the alloyed material is to improve the catalytic activity towards the oxygen reduction reactions ( orrs ) offered by commercial pt cathode catalysts without the scaling costs . in this respect , recent studies have shown that a five - fold decrease in the amount of pt currently used in pemfc stacks is needed , in terms of pt costs and scarcity , in order to reach levels for mass - production and commercialisation in light - duty vehicles @xcite . among these alloys
, a promising one corresponds to pt - ni .
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11,605 |
Suppose that you have an abstract for a scientific paper: in order to understand the periodic and semi - periodic variations of luminous o- b- a - type stars , linear nonadiabatic stability analyses for radial and nonradial oscillations have been performed for massive evolutionary models ( @xmath0 ) .
in addition to radial and nonradial oscillations excited by the kappa - mechanism and strange - mode instability , we discuss the importance of low - degree oscillatory convection ( nonadiabatic g@xmath1 ) modes .
although their kinetic energy is largely confined to the convection zone generated by the fe opacity peak near @xmath2k , the amplitude can emerge to the photosphere and should be observable in a certain effective temperature range .
they have periods longer than those of the radial strange modes so that they seem to be responsible for some of the long - period microvariations of lbvs ( s dor variables ) and @xmath3 cyg variables .
moreover , monotonously unstable radial modes are found in some models whose initial masses are greater than or equal to @xmath4 with @xmath5 .
the monotonous instability probably corresponds to the presence of an optically thick wind .
the instability boundary roughly coincides with the humphreys - davidson limit .
[ firstpage ] stars : evolution stars : oscillations stars : massive stars : early - type supergiants . .
And you have already written the first three sentences of the full article: it is known that various instabilities occur in very luminous stars .
most luminous stars called luminous blue variables ( lbvs or s dor variables ) show major events ( sd(s dor)-eruptions and sd - phases ) with which mass loss from the star is thought to be enhanced greatly ( see e.g. , * ? ? ?
* ; * ? ? ?.
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* for reviews ) .
their distribution on the hr diagram seems to be bounded by the humphreys - davidson ( hd ; * ? ? ?
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11,606 |
Suppose that you have an abstract for a scientific paper: we compare the gram - schmidt and covariant phase - space - basis - vector descriptions for three time - reversible harmonic oscillator problems , in two , three , and four phase - space dimensions respectively .
the two - dimensional problem can be solved analytically .
the three - dimensional and four - dimensional problems studied here are simultaneously chaotic , time - reversible , and dissipative .
our treatment is intended to be pedagogical , for july 2011 publication in communications in nonlinear science and numerical simulation , and for use in the second edition of our book on _ time reversibility , computer simulation , and chaos_. comments are very welcome . .
And you have already written the first three sentences of the full article: it is lyapunov instability which makes statistical mechanics possible@xcite . for stationary boundary conditions , either equilibrium or nonequilibrium , the _ exponential growth _ , @xmath0 , of small phase - space perturbations @xmath1 or @xmath2 , `` sensitive dependence on initial conditions '' , provides longtime averages independent of initial conditions .
in addition to the coordinates and momenta @xmath3 , time - reversible `` thermostat variables '' @xmath4 can be used to impose _ nonequilibrium _ boundary conditions@xcite , such as velocity or temperature gradients .
a prototypical nonequilibrium problem simulates heat flow between two thermal reservoirs maintained at temperatures @xmath5 and @xmath6 . the resulting heat flow through an internal newtonian region , bounded by the two reservoirs ,.
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can then be studied and characterized@xcite . to describe the lyapunov instability for any of such systems , equilibrium or nonequilibrium , imagine the deformation of a small phase - space hypersphere @xmath7 , comoving with , and centered on , a deterministic `` reference trajectory '' @xmath8 .
as the motion progresses the hypersphere will deform , at first becoming a rotating hyperellipsoid with the long - time - averaged exponential growth and decay rates of the principal axes defining the lyapunov spectrum @xmath9 .
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11,607 |
Suppose that you have an abstract for a scientific paper: the hard x - ray source 4u 2206 + 54 is a peculiar high mass x - ray binary with a main - sequence donor star .
recent x - ray observations suggested that the compact object in 4u 2206 + 54 may be a neutron star .
the x - ray emission comes from the accretion of stellar winds from the massive donor stars , and variability of luminosity may be due to the changes of its orbit phase . to further reveal the nature of compact object , we studied 4u 2206 + 54 with integral / ibis observations in two years , and found that in most time , 4u 2206 + 54 undergone a quiescent state and sometime an active state . in the quiescent state the spectrum can be fitted by a power - law model of @xmath0 with a hard x - ray luminosity of @xmath1 erg s@xmath2 ( 20 100 kev ) . while in the active state
, the 20 100 kev hard x - ray luminosity reaches @xmath3 erg s@xmath2 and the spectrum is fitted by a thermal bremmstrahlung model of @xmath4 kev plus two cyclotron absorption lines at @xmath5 30 and 60 kev .
then we derived a magnetic field of 3.3@xmath6 g for the compact object in 4u 2206 + 54 . during the active state
, we found a pulsation period of @xmath5 5400 s in the light curve of 4u 2206 + 54 .
so the compact object in 4u 2206 + 54 should be a magnetic neutron star with a slow pulsation .
cyclotron absorption lines detected in the active state and non - detection in the quiescent state suggested that two different accretion states have possible different hard x - ray emission regions : surface of neutron star in the active state ; the magnetic - accretion pressure equivalent point in the quiescent state .
the re - analysis of the rxte / asm light curve found the modulation periods at @xmath7 days and 19.11 days , and the orbit period of 4u 2206 + 54 should be 19.11 days .
stars : individual ( 4u 2206 + 54 ) stars : neutron magnetic fields stars : binaries : close x - rays : binaries . .
And you have already written the first three sentences of the full article: the x - ray source 4u 2206 + 54 has been studied with numerous ground and space - based observations , but the nature of this source and origins of its variability patten are still unclear .
4u 2206 + 54 was identified with an optical counterpart bd + 53 2790 by steiner et al .
( 1984 ) which was initially classified as a be star ..
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however , in optical and uv bands the emission spectrum is complex , in particular the behavior of the h@xmath8 emission line , suggesting that this star is an o9.5v star ( negueruela & reig 2001 ; rib et al .
2006 ; blay et al .
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11,608 |
Suppose that you have an abstract for a scientific paper: we study the eigenvalue problem @xmath0u(z)=\lambda u(z)$ ] with the boundary conditions that @xmath1 decays to zero as @xmath2 tends to infinity along the rays @xmath3 , where @xmath4 is a polynomial and integers @xmath5 .
we provide an asymptotic expansion of the eigenvalues @xmath6 as @xmath7 , and prove that for each _ real _ polynomial @xmath8 , the eigenvalues are all real and positive , with only finitely many exceptions .
_ 2000 _ mathematics subject classification _
: 34l40 , 34l20
_ = 18pt .
And you have already written the first three sentences of the full article: for integers @xmath5 fixed , we are considering the `` non - standard '' non - self - adjoint eigenvalue problems @xmath9u(z,\lambda)=\lambda u(z,\lambda),\quad\text{for some $ \lambda\in{\mathbb c}$},\ ] ] with the boundary condition that @xmath10 where @xmath8 is a polynomial of degree at most @xmath11 of the form @xmath12 we let @xmath13 be the coefficient vector of @xmath14 .
we are mainly interested in the case when @xmath8 is real , that is , when @xmath15 .
however , some interesting facts in this paper hold also for @xmath16 ..
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so except for theorem [ main_theorem ] below , we will use @xmath16 .
if a nonconstant function @xmath17 satisfies with some @xmath18 and the boundary condition , then we call @xmath19 an _ eigenvalue _ of @xmath20 and @xmath17 an _ eigenfunction of @xmath20 associated with the eigenvalue @xmath19_. also , the _ geometric multiplicity of an eigenvalue @xmath19 _ is the number of linearly independent eigenfunctions associated with the eigenvalue @xmath19 . the operator @xmath20 in with potential @xmath21 is called _
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11,609 |
Suppose that you have an abstract for a scientific paper: we use integral field spectroscopy with the gemini north telescope to detect probable fluorescent ly@xmath0 emission from gas lying close to the luminous qso pss 2155 + 1358 at redshift 4.28 .
the emission is most likely coming not from primordial gas , but from a multi - phase , chemically enriched cloud of gas lying about 50 kpc from the qso .
it appears to be associated with a highly ionised associated absorber seen in the qso spectrum . with the exception of this gas cloud ,
the environment of the qso is remarkably free of neutral hydrogen .
we also marginally detect ly@xmath0 emission from a foreground sub - damped - ly@xmath0 absorption - line system .
[ firstpage ] intergalactic medium quasars : absorption - lines quasars : individual : pss 2155 + 1358 galaxies : high - redshift .
And you have already written the first three sentences of the full article: flows of gas play a crucial role in galaxy formation both the infalling primordial gas from which galaxies ultimately form , and outflows which enrich the intergalactic medium and regulate galaxy formation .
much attention has recently been placed on one possible way of directly observing this gas : ly@xmath0 fluorescence .
the idea , originally proposed by @xcite is that the plentiful ultraviolet ( uv ) radiation in the high redshift universe will be absorbed by any neutral gas , and some fraction of the incident ionising photons will be re - radiated as ly@xmath0 photons @xcite.
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. this fluorescent ly@xmath0 emission will be brightest where the uv radiation is strongest : close to luminous qsos . @xcite and @xcite predicted that qsos with sufficiently high redshifts should be surrounded by halos of ly@xmath0 emission , as the uv flux from the qso causes the still infalling primordial gas to fluoresce .
the predicted intensity of this flux is , however , very dependent upon assumptions on how the gas is clumped
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11,610 |
Suppose that you have an abstract for a scientific paper: interesting results from bes - ii and other experiments raised actually many new questions which shall be answered by its upgrade program , bepcii and bes - iii . the design and current status of bepcii and bes - iii are reported . .
And you have already written the first three sentences of the full article: in early 80 s , chinese government decided to build an @xmath0 collider running at the tau - charm energy region , called bepc , which is completed in 1989 .
the only detector at the machine is called beijing spectrometer(bes ) . in mid 90 s ,
there has been a minor upgrade of the detector , which is then called bes - ii . since then.
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, hundreds of papers have been published on the international journals , some with significant impacts to the community .
the upgrade of bepc was decided at the beginning of this century , called bepcii , which has a designed luminosity of @xmath1 , an increase of a factor of 100 .
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11,611 |
Suppose that you have an abstract for a scientific paper: we present predictions on the total cross sections and on the ratio of the real part to the imaginary part of the elastic amplitude ( @xmath0 parameter ) for present and future @xmath1 and @xmath2 colliders , and on total cross sections for @xmath3 hadrons at cosmic - ray energies and for @xmath4 hadrons up to @xmath5 tev .
these predictions are based on an extensive study of possible analytic parametrisations invoking the biggest hadronic dataset available at @xmath6 .
the uncertainties on total cross sections , including the systematic errors due to contradictory data points from fnal , can reach @xmath7 at rhic , @xmath8 at the tevatron , and @xmath9 at the lhc , whereas those on the @xmath0 parameter are respectively @xmath10 , @xmath11 , and @xmath10 . in recent works
@xcite , we have performed an exhaustive study of the analytic parametrisations of soft data at @xmath6 . for this purpose
, we gathered the largest available set of data at @xmath12 , which includes all measured total cross sections and ratios of the real part to the imaginary part of the elastic amplitude ( @xmath13 parameter ) for the scattering of @xmath14 @xmath15 , @xmath16 , @xmath17 , and total cross sections for @xmath18 , @xmath19 and @xmath20 @xcite .
several experiments are under way @xcite , or being planned , to measure the hadronic amplitudes at @xmath6 .
some authors @xcite also presented what they feel are reference values for the total @xmath21 and @xmath4 hadrons cross sections .
thus it is timely and appropriate to present independently our predictions for the forward observables at rhic , the tevatron - run ii and the lhc as well as for @xmath21 total cross section at cosmic - ray energies and for @xmath22 total cross sections up to 1 tev .
we can summarize the general form of the parametrisations by quoting the form of total cross sections , from which the @xmath0 parameter is obtained via analyticity .
the ingredients are the contribution @xmath23 of the highest meson trajectories ( @xmath0....
And you have already written the first three sentences of the full article: the compas group was supported in part by the russian foundation for basic research grants rfbr-98 - 07 - 90381 and rfbr-01 - 07 - 90392 .
k.k . is in part supported by the u.s .
contract de - fg-02 - 91er40688-task a. we thank professor jean - eudes augustin for the hospitality at lpnhe - universit paris 6 , where part of this work was done ..
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we thank o. selyugin for his corrections to the database , a. sobol for discussions on the soft physics program of the totem & cms , and yu.kharlov for discussions on possibilities for @xmath22 physics at rhic and at the lhc .
99 computerised models , parameter evaluation for theory and experiment .
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11,612 |
Suppose that you have an abstract for a scientific paper: here we describe the red msx source ( rms ) survey which is the largest , systematic , galaxy - wide search for massive young stellar objects ( mysos ) yet undertaken .
mid - ir bright point sources from the msx satellite survey have been followed - up with ground - based radio , millimetre , and infrared observations to identify the contaminating sources and characterise the mysos and uchii regions . with the initial classification
now complete the distribution of sources in the galaxy will be discussed , as well as some programmes being developed to exploit our sample . .
And you have already written the first three sentences of the full article: massive stars ( @xmath0@xmath18 m@xmath2 , @xmath3@xmath110@xmath4 l@xmath2 ) play a fundamental role in many areas of astrophysics .
they are the principal source of uv radiation and heavy elements in galaxies , and are responsible for injecting huge amounts of kinetic energy into the ism through powerful molecular outflows , strong stellar winds and supernova explosions .
the momentum imparted through these processes provides an important source of mixing and turbulence within the ism ..
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they are also thought to play a key role in regulating star formation , either by disrupting molecular clouds before stars have been able to form , or constructively through the expansion of their hii regions ( e.g. , collect and collapse ) or the propagation of strong shocks into their surroundings ( e.g. , radiatively driven implosion ) .
massive stars have an enormous influence not only on the physical structure and chemistry of their local environment , but also on the structure and evolution of their host galaxies . despite the importance of massive stars
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11,613 |
Suppose that you have an abstract for a scientific paper: electromotility of outer hair cells ( ohcs ) has been extensively studied with _ in vitro _
experiments because of its physiological significance to the cochlear amplifier , which provides the exquisite sensitivity and frequency selectivity of the mammalian ear . however , these studies have been performed largely under load - free conditions or with static load , while these cells function _ in vivo _ in a dynamic environment , receiving electrical energy to enhance mechanical oscillation in the inner ear .
this gap leaves uncertainties in addressing a key issue , how much mechanical energy an ohc provides .
the present report is an attempt of bridging the gap by introducing a simple one - dimensional model for electromotility of ohc in a dynamic environment .
this model incorporates a feedback loop involving the receptor potential and the mechanical load on ohc , and leads to an analytical expression for the membrane capacitance , which explicitly describes the dependence on the elastic load , viscous drag , and the mass .
the derived equation of motion was examined in a mass - less model system with realistic parameter values for ohc .
it was found that viscous drag is more effective than elastic load in enhancing the receptor potential that drives the cell .
for this reason , it is expected that ohcs are more effective in counteracting viscous drag than providing elastic energy to the system .
amplifier , mammalian ear , membrane capacitance .
And you have already written the first three sentences of the full article: considerable progress has been made in recent years in our understanding of the mechanism of prestin - based somatic motility , or `` electromotility , '' of outer hair cells ( ohcs ) in the cochlea , both on cellular- @xcite and the molecular levels @xcite , as well as clarifying its physical basis that it is based on electromechanical coupling @xcite .
for example , experiments on isolated ohcs have determined load - free displacement @xcite and isometric force production @xcite .
these experimental observations can be described by static models @xcite . nonetheless , these are the conditions under which those cells do not provide energy ..
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some theoretical works have addressed energy production by ohcs @xcite by extrapolating from these _ in vitro _ conditions .
however , these analyses do not provide an equation of motion or the dependence of nonlinear capacitance on external mechanical load , the essential features to describe the production of mechanical energy for amplifying acoustic signal .
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11,614 |
Suppose that you have an abstract for a scientific paper: gauge fields are central in our modern understanding of physics at all scales . at the highest energy scales known , the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons . at the largest length scales , our universe is ruled by gravity , whose gauge structure suggests the existence of a particle the graviton that mediates the gravitational force . at the mesoscopic scale ,
solid - state systems are subjected to gauge fields of different nature : materials can be immersed in external electromagnetic fields , but they can also feature emerging gauge fields in their low - energy description .
+ in this review , we focus on another kind of gauge field : those _ engineered _ in systems of ultracold neutral atoms . in these setups , atoms
are suitably coupled to laser fields that generate effective gauge potentials in their description .
neutral atoms feeling " laser - induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field , but also , the interaction of elementary particles with non - abelian gauge fields . here , we review different realized and proposed techniques for creating gauge potentials both abelian and non - abelian in atomic systems and discuss their implication in the context of quantum simulation . while most of these setups concern the realization of background and classical gauge potentials , we conclude with more exotic proposals where these synthetic fields might be made dynamical , in view of simulating interacting gauge theories with cold atoms . .
And you have already written the first three sentences of the full article: the laboratory realization of ultracold neutral atomic gases such as bose - einstein condensates @xcite and degenerate fermi gases @xcite quantum gases delivered remarkably versatile experimental systems that can realize physical effects with analogues throughout physics .
the coherence properties of bose - einstein condensates ( becs ) allow them to address concepts from optics and nonlinear optics : classical and quantum atom optics @xcite .
quantum gases have shed light on many effects predicted in the context of traditional condensed matter systems such as the bosonic superfluid to mott transition in optical lattices @xcite , and the bardeen - cooper - schrieffer crossover in degenerate fermi gases @xcite ..
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even phenomena commonplace in high energy physics can occur in ultracold settings , where higgs modes have been observed @xcite , unconventional `` color '' superfluidity @xcite is possible , and where confinement mechanisms @xcite and axion electrodynamics @xcite have been predicted .
atomic quantum gases are charge neutral , and therefore , they are not affected by external electromagnetic fields the way electrons are .
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11,615 |
Suppose that you have an abstract for a scientific paper: we consider principal component analysis ( pca ) in decomposable gaussian graphical models . we exploit the prior information in these models in order to distribute its computation . for this purpose ,
we reformulate the problem in the sparse inverse covariance ( concentration ) domain and solve the global eigenvalue problem using a sequence of local eigenvalue problems in each of the cliques of the decomposable graph .
we demonstrate the application of our methodology in the context of decentralized anomaly detection in the abilene backbone network .
based on the topology of the network , we propose an approximate statistical graphical model and distribute the computation of pca . .
And you have already written the first three sentences of the full article: we consider principal component analysis ( pca ) in gaussian graphical models .
pca is a classical dimensionality reduction method which is frequently used in statistics and machine learning @xcite .
the first principal components of a multivariate are its orthogonal linear combinations which preserve most of the variance . in the gaussian case.
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, pca has special properties which make it especially favorable : it is the best linear approximation of the data and it provides independent components . on the other hand , gaussian graphical models , also known as covariance selection models , provide a graphical representation of the conditional independence structure within the gaussian distribution @xcite . exploiting the extensive knowledge and literature on graph theory , graphical models allow for efficient distributed implementation of statistical inference algorithms , e.g. , the well known belief propagation method and the junction tree algorithm @xcite . in particular , decomposable graphs , also known as chordal or triangulated graphs ,
provide simple and intuitive inference methods due to their appealing structure .
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11,616 |
Suppose that you have an abstract for a scientific paper: we present recently defined jet - observables for hadron - hadron dijet production , which are designed to reconcile the seemingly conflicting theoretical requirement of globalness , which makes it possible to resum them ( automatically ) at nll accuracy and the limited experimental reach of detectors , so that they are measurable at the tevatron and at the lhc . .
And you have already written the first three sentences of the full article: event shapes and jet - rates are infrared and collinear ( irc ) safe observables , which describe the energy and momentum flow of the final state . they constitute an ideal compromise between simplicity and sensitivity to properties of qcd radiation .
they provide then a wealth of information , e.g. in measurements of the coupling @xmath0 and its renormalisation group running , in cross checks / measurements of the values of the colour factors of qcd and , most importantly , in studies of the connection between parton - level ( the perturbative ( pt ) description of quarks and gluons ) and hadron - level ( the real ) , for a review see @xcite .
irc - safety ensures that event - shape distributions can be computed within perturbation theory , however in the more exclusive phase space region where perturbative radiation is suppressed ( conventionally associated to almost vanishing values of the observable , @xmath1 ) large logarithmic corrections need to be resummed to all orders ..
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more specifically , given an event - shape @xmath2 , a function of all secondary final state momenta @xmath3 and of the set of recoiling born momenta @xmath4 , the probability of `` constrained events '' i. e. @xmath5 has a _ divergent _ pt expansion for @xmath6 @xmath7 i. e. there is a soft and collinear divergence [ @xmath8 for each emitted gluon . today
s state - of - the art accuracy accounts for all leading ( ll ) and next - to - leading logarithms ( nll ) as follows : @xmath9 furthermore resummations are matched to fixed order results at nlo .
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Suppose that you have an abstract for a scientific paper: near normal incident far - infrared reflectivity spectra of [ 111 ] dysprosium titanate ( dy@xmath0ti@xmath0o@xmath1 ) single crystal have been measured at different temperatures .
seven phonon modes ( eight at low temperature ) are identified at frequency below 1000 @xmath2 .
optical conductivity spectra are obtained by fitting all the reflectivity spectra with the factorized form of the dielectric function .
both the born effective charges and the static optical primitivity are found to increase with decreasing temperature .
moreover , phonon linewidth narrowering and phonon modes shift with decreasing temperature are also observed , which may result from enhanced charge localization .
the redshift of several low frequency modes is attributed to the spin - phonon coupling .
all observed optical properties can be explained within the framework of nearest neighbor ferromagnetic(fm ) spin ice model . .
And you have already written the first three sentences of the full article: recently , there has been a surge of interest in the properties of pyrochlore compound dy@xmath3ti@xmath3o@xmath4 , which is considered to be a model system of `` spin ice '' materials .
`` spin ice '' materials governed by the same statistical mechanics of so - called `` ice rule '' as the hydrogen atoms in the ground state of ordinary hexagonal ice i@xmath5 have macroscopically degenerate ground states down to almost zero temperature.nature99,prb04,nature01,apa02 , prb03,jpcm01,prl01,jpsj04,prb02 experimentally , the observed value of ( 1/2)rln(3/2 ) through specific heat measurement@xcite is consistent with what is expected by pauling s theory , while the spin entropy only freezes out below about 4 k.@xcite from magnetic susceptibility studies , a strongly frequency dependent cooperative spin freezing is observed at about 16 k , which is associated with a very narrow distribution of spin relaxation times and a sharp drop at about 2 k.@xcite neutron scattering studies performed by fennell et al.@xcite also well demonstrate the spin ice state and the coexistence of long range ferromagnetic and short range antiferromagnetic order in a magnetic field applied along the [ 110 ] axis of dy@xmath3ti@xmath3o@xmath6 . in theoretical aspect ,
melko and coworkers@xcite report numerical results on the low temperature properties of the dipolar spin ice model by the multicanonical monte carlo ( mc ) method and they find a first order transition to a long - range ordered phase ..
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other researchersjpsj04 also confirm the existence of the transition under a magnetic field along the [ 110 ] axis with mc simulation .
dy@xmath3ti@xmath3o@xmath4 has a typical a@xmath3b@xmath3o@xmath4 structure with the space group ( fd3 m , o@xmath5@xmath7 ) , no.227 .
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Suppose that you have an abstract for a scientific paper: studies of quasar absorption lines reveal that the low density intergalactic medium at @xmath0 is enriched to @xmath1 solar metallicity .
this enrichment may have occurred in an early generation of population iii stars at redshift @xmath2 , by protogalaxies at @xmath3 , or by larger galaxies at @xmath4 .
this paper addresses the third possibility by calculating the enrichment of the igm at @xmath5 by galaxies of baryonic mass @xmath6 .
we use already completed cosmological simulations to which we add a prescription for chemical evolution and metal ejection by winds , assuming that the winds have properties similar to those observed in local starbursts and lyman - break galaxies .
results are given for a number of representative models , and we also examine the properties of the galaxies responsible for the enrichment as well as the physical effects responsible for wind escape and propagation . we find that winds of velocity @xmath7 are capable of enriching the igm to the mean level observed , though many low - density regions would remain metal free .
calibrated by observations of lyman - break galaxies , our calculations suggest that most galaxies at @xmath5 should drive winds that can escape and propagate to large radii .
the primary effect limiting the enrichment of low - density ig gas in our scenario is then the travel time from high- to low - density regions , implying that the metallicity of low - density gas is a strong function of redshift . .
And you have already written the first three sentences of the full article: the detailed comparison of quasar absorption spectra with the predictions of cosmological hydrodynamic simulations has established that the ly@xmath8 absorption ` forest ' is caused by a smoothly - fluctuating neutral component of the intergalactic medium ( igm ) ( e.g. , cen et al .
1994 ; zhang , anninos , & norman 1995 ; hernquist et al .
the simulations also reveal a strong correlation between absorber hi column density and gas overdensity @xmath9 , so that the study of @xmath10 absorbers gives information about the igm for @xmath11 at @xmath5 ( e.g. zhang et al . 1998 ; dav et al ..
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furthermore , studies of civ , siiv and ovi have revealed that the low - density igm is not as was long expected chemically pristine , but has been enriched to @xmath12 ( with a scatter of @xmath13dex ) down to @xmath14 ( @xmath15 ) ( e.g. , meyer & york 1987 ; songaila & cowie 1996 ) , and perhaps to even lower overdensities ( e.g. , cowie & songaila 1998 ; ellison et al . 2000 ; schaye et al .
2000 ) .
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Suppose that you have an abstract for a scientific paper: in this paper , we study the formation and dynamical evolution of black hole - black hole ( bh - bh ) binaries in young star clusters ( yscs ) , by means of n - body simulations .
the simulations include metallicity - dependent recipes for stellar evolution and stellar winds , and have been run for three different metallicities ( @xmath0 ) .
following recent theoretical models of wind mass - loss and core - collapse supernovae , we assume that the mass of the stellar remnants depends on the metallicity of the progenitor stars .
we find that bh - bh binaries form efficiently because of dynamical exchanges : in our simulations , we find about 10 times more bh - bh binaries than double neutron star binaries .
the simulated bh - bh binaries form earlier in metal - poor yscs , which host more massive black holes ( bhs ) than in metal - rich yscs .
the simulated bh - bh binaries have very large chirp masses ( up to 80 m@xmath1 ) , because the bh mass is assumed to depend on metallicity , and because bhs can grow in mass due to the merger with stars .
the simulated bh - bh binaries span a wide range of orbital periods ( @xmath2 yr ) , and only a small fraction of them ( 0.3 per cent ) is expected to merge within a hubble time .
we discuss the estimated merger rate from our simulations and the implications for advanced virgo and ligo .
[ firstpage ] black hole physics
methods : numerical gravitational waves galaxies : star clusters : general binaries : general .
And you have already written the first three sentences of the full article: most stars are expected to form in young star clusters ( yscs , @xcite ; @xcite ; @xcite ) . like globular clusters ( gcs ) ,
the densest yscs are collisional systems : their two - body relaxation timescale is shorter than their lifetime , and they undergo intense dynamical evolution . on the other hand ,
yscs are considerably different from gcs : the former have generally lower mass ( @xmath3 m@xmath4 ) and smaller size ( half - mass radius @xmath5 pc ) than the latter ( see e.g. @xcite , for a recent review ) ..
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this explains why the central relaxation time of yscs is @xmath6 myr , orders of magnitude shorter than that of gcs ( e.g. @xcite ) .
yscs populate the disc of late - type galaxies , while gcs are spherically distributed in the host - galaxy halo .
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Suppose that you have an abstract for a scientific paper: we extend a special kind of localized state trapped at the intersection due to the geometric confinement , first proposed in a three - terminal - opening t - shaped structure [ euro .
. lett . * 55 * , 539 ( 2001 ) ] , into a ring geometry with a tangent connection to the wire . in this ring geometry
, there exists one localized state trapped at the intersection with energy lying inside the lowest subband .
we systematically study this localized state and the resulting fano - type interference due to the coupling between this localized state and the continuum ones .
it is found that the increase of inner radius of the ring weakens the coupling to the continuum ones and the asymmetric fano dip fades away .
a wide energy gap in transmission appears due to the interplay of two types of antiresonances : the fano - type antiresonance and the structure antiresonance .
the size of this antiresonance gap can be modulated by adjusting the magnetic flux . moreover , a large transmission amplitude can be obtained in the same gap area .
the strong robustness of the antiresonance gap is demonstrated and shows the feasibility of the proposed geometry for a real application . .
And you have already written the first three sentences of the full article: electrons in a t - shaped structure with three terminals opening , i.e. , three terminals extending to infinity , are classically extended . however , numerical study for the t - shaped structure by lin _
et al_. showed the existence of a localized state trapped at the intersection.@xcite after that , openov presented an analytical solution of this localized state in one - dimensional t - shaped quantum wires.@xcite moreover , he also showed the existence of the localized state trapped at the intersection in a four - terminal - opening cross - shaped structure .
the existence of such localized state essentially shows the confinement effect of the geometry in quantum region ..
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it is noted that the three - terminal - opening structure here is very different from the previously studied t - junction system,@xcite where only two terminals are open and the structure confinement is more like a kind of cavity confinement.@xcite very recently , xu _
et al_. investigated the localized state in the three - terminal - opening t - shaped graphene nanoribbons.@xcite as reported , the existence of the localized state due to the t - shaped confinement provides the discrete channel to interfere with the directly propagating channels since the localized state embeds in the continuum .
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Suppose that you have an abstract for a scientific paper: the one - dimensional effective hamiltonian for a planar curvilinear quantum wire with arbitrary shape is proposed in the presence of the rashba spin - orbit interaction .
single electron propagation through a device of two straight lines conjugated with an arc has been investigated and the analytic expressions of the reflection and transmission probabilities have been derived .
the effects of the device geometry and the spin - orbit coupling strength @xmath0 on the reflection and transmission probabilities and the conductance are investigated in the case of spin polarized electron incidence .
we find that no spin - flip exists in the reflection of the first junction .
the reflection probabilities are mainly influenced by the arc angle and the radius , while the transmission probabilities are affected by both spin - orbit coupling and the device geometry .
the probabilities and the conductance take the general behavior of oscillation versus the device geometry parameters and @xmath0 .
especially the electron transportation varies periodically versus the arc angle @xmath1 .
we also investigate the relationship between the conductance and the electron energy , and find that electron resonant transmission occurs for certain energy .
finally , the electron transmission for the incoming electron with arbitrary state is considered . for the outgoing electron ,
the polarization ratio is obtained and the effects of the incoming electron state are discussed .
we find that the outgoing electron state can be spin polarization and reveal the polarized conditions . .
And you have already written the first three sentences of the full article: recently , a new subdiscipline of condensed matter physics , spintronics , is emerging rapidly and generating great interests@xmath2}$ ] .
much attention has been focused , especially , on the spin - dependent transport dominated by the spin - orbit interaction ( soi)@xmath3}$ ] in the low dimensional semiconductor nanostructures , such as wires , rings , spirals , and other structures .
for example , the influence of spin on electrons moving in a mesoscopic ring have been studied in several contexts@xmath4}$ ] since the original proposal of the spin field effect transistor by datta and das@xmath5}$ ] . on the other hand.
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, many low - dimensional systems are curvilinear and more complicated in geometry , such as the v - shaped quantum wire@xmath6}$ ] , the spiral inductors@xmath7}$ ] , nanotubes@xmath8}$ ] , and so on . due to the potential of providing new physical features and new functionalities for electronic devices@xmath9}$ ] , the effects of the curvilinear geometry on electronic states and electron transports are the subjects of many recent works@xmath10}$ ] . especially , the influence of geometry on the soi is considered by some groups@xmath11}$ ] .
the systems concerned are quasi - one - dimensional circles or two - dimensional ( 2d ) nanostructures .
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Suppose that you have an abstract for a scientific paper: we deal with the efficient parallelization of bayesian global optimization algorithms , and more specifically of those based on the expected improvement criterion and its variants .
a closed form formula relying on multivariate gaussian cumulative distribution functions is established for a generalized version of the multipoint expected improvement criterion . in turn , the latter relies on intermediate results that could be of independent interest concerning moments of truncated gaussian vectors .
the obtained expansion of the criterion enables studying its differentiability with respect to point batches and calculating the corresponding gradient in closed form .
furthermore , we derive fast numerical approximations of this gradient and propose efficient batch optimization strategies .
numerical experiments illustrate that the proposed approaches enable computational savings of between one and two order of magnitudes , hence enabling derivative - based batch - sequential acquisition function maximization to become a practically implementable and efficient standard .
* keywords : * kriging , expected improvement , parallel optimization . .
And you have already written the first three sentences of the full article: since their beginnings about half a century ago @xcite , bayesian optimization algorithms have been increasingly used for derivative - free global minimization of expensive to evaluate functions . typically assuming a continuous objective function @xmath0 , single - objective bayesian optimization algorithms consist in sequentially evaluating @xmath1 at promising points under the assumption that @xmath1 is a sample realization ( _ path _ or _ trajectory _ ) of a random field @xmath2 .
such algorithms are especially popular in the case where evaluating @xmath3 requires heavy high - fidelity numerical simulations ( or _ computer experiments _ , see notably @xcite ) , where @xmath4 stands for some design parameters to be optimized over .
such expensive simulations are classically encountered in the resolution of partial differential equations from physical sciences , engineering and beyond @xcite . in recent years.
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, bayesian optimization also has attracted a lot of interest from the machine learning community @xcite , be it to optimize simulation - based objective functions @xcite or even to estimate tuning parameters of machine learning algorithms themselves @xcite . in both communities , a gaussian random field ( or _ gaussian process _ , gp ) model is often used for @xmath5 , so that prior information on @xmath1 is taken into account through a trend function @xmath6 and a covariance kernel @xmath7 .
once @xmath8 and @xmath9 are specified , possibly up to some parameters to be inferred based on data , the considered gp model can be used as an instrument to locate the next evaluation point(s ) via so - called infill sampling criteria , also referred to as _ acquisition functions _ or simply as _
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Suppose that you have an abstract for a scientific paper: radio relics detected in the outskirts of galaxy clusters are thought to trace radio - emitting relativistic electrons accelerated at cosmological shocks . in this study , using the cosmological hydrodynamic simulation data for the large - scale structure formation and adopting a diffusive shock acceleration ( dsa ) model for the production of cosmic - ray ( cr ) electrons , we construct mock radio and x - ray maps of simulated galaxy clusters that are projected in the sky plane .
various properties of shocks and radio relics , including the shock mach number , radio spectral index and luminosity are extracted from the synthetic maps and compared with observations .
a substantial fraction of radio and x - ray shocks identified in these maps involve multiple shock surfaces along line of sights ( loss ) , and the morphology of shock distributions in the maps depends on the projection direction . among multiple shocks in a given los ,
radio observations tend to pick up stronger shocks with flatter radio spectra , while x - ray observations preferentially select weaker shocks with larger kinetic energy flux . as a result
, the shock mach numbers and locations derived from radio and x - ray observations could differ from each other in some cases .
we also find that the distributions of the spectral index and radio power of the synthetic radio relics are somewhat inconsistent with those of observed real relics ; a bit more radio relics have been observed closer to the cluster core and with steeper spectral indices .
we suggest the inconsistency could be explained , if very weak shocks with @xmath0 accelerate cr electrons more efficiently , compared to the dsa model adopted here . .
And you have already written the first three sentences of the full article: since the discovery of a bow shock in the periphery of the bullet cluster 1e 0657 - 558 @xcite , it has been well established that shock waves exist in and around galaxy clusters .
using cosmological hydrodynamic simulations for the large - scale structure ( lss ) formation of the universe , the origin and nature of shock waves in the intracluster medium ( icm ) as well as in the intergalactic medium ( igm ) have been extensively studied @xcite .
these studies demonstrated that abundant shocks are produced by supersonic flow motions during the process of hierarchical clustering of nonlinear structures , and that they could be classified into two categories , according to their locations relative to the host structures . _.
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external shocks _ are formed at the outermost surfaces surrounding clusters , filaments , and sheets of galaxies by the accretion of cool ( @xmath1 k ) , tenuous gas in voids onto those nonlinear structures . since the accretion velocity around clusters can be as high as @xmath2 a few @xmath3 and the sound speed of accreting gas
is @xmath4 , external shocks are strong with mach number as large as @xmath5 . on the other hand , _ internal shocks _ are produced inside the nonlinear structures , where the gas has been already heated to high temperature by previous episodes of shock passage , so their mach number is typically low with @xmath6 . while most of internal shocks have @xmath7 , those with @xmath8 play the most important role in dissipating the shock kinetic energy into heat in the icm ( e.g. , * ? ? ?
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Suppose that you have an abstract for a scientific paper: we study the @xmath0 phenomenology for two extensions of the electroweak standard model ( sm ) which have an extra @xmath1 gauge factor .
we show the capabilities of the lhc in distinguishing the signals coming from these two extensions and both of them from the standard model background . in order to compare the behavior of these @xmath2 models we consider the reaction @xmath3 and
compute some observables as the total cross sections , number of events , forward - backward asymmetry , final particle distributions like rapidity , transverse momentum , and dimuon invariant mass , for two lhc regimes : @xmath4 tev ( @xmath5 ) and @xmath6 tev ( @xmath7 ) for @xmath8 = 1000 gev and 1500 gev .
we show that by using appropriate kinematic cuts some of the observables considered here are able to extract different properties of the @xmath0 boson , and hence providing information about to which @xmath2 model it belongs to .
pacs:14.70.pw , 12.60.cn , 12.15.ji [email protected] ; [email protected];[email protected] .
And you have already written the first three sentences of the full article: the starting up of the large hadron collider ( lhc ) operating in an energy range far above the electroweak scale , offers a possibility to reveal new phenomena and to explore the phenomenology extracted from the expected huge amount of experimental data . in this way
, it is expected new physics manifestations throughout the appearance of new degrees of freedom such as new charged and neutral fermions , superpartners , new gauge bosons , and higgs scalar(s ) . to take into account these new possible degrees of freedom
we must go beyond the sm ..
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there are many ways to construct extensions of the electroweak sm .
however , if we are concerned with new gauge bosons we must consider a larger gauge group .
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Suppose that you have an abstract for a scientific paper: we give skein theoretic formulas for minimal idempotents in the birman - murakami - wenzl algebras .
these formulas are then applied to derive various known results needed in the construction of quantum invariants and modular categories . in particular , an elementary proof of the wenzl formula for quantum dimensions
is given .
this proof does not use the representation theory of quantum groups and the character formulas . .
And you have already written the first three sentences of the full article: the birman - murakami - wenzl algebras are deformations of the brauer centralizer algebras @xcite .
they are quotients of the artin braid groups algebras , and have appeared in connection with the kauffman link invariant and the quantum groups of types b , c and d. the birman - murakami - wenzl algebras are generically semi - simple , and their structure was given by wenzl @xcite .
they play a key role in the construction of quantum invariants , modular categories and topological quantum field theories , as was shown by turaev and wenzl @xcite ..
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our purpose here is to study the structure of these algebras without using their representation theory . in a separate article
, we will pursue turaev and wenzl s program and construct four series of modular categories . together with the present paper
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Suppose that you have an abstract for a scientific paper: although marginally more complicated than the traditional laplace sum - rules , gaussian sum - rules have the advantage of being able to probe excited and ground states with similar sensitivity .
gaussian sum - rule analysis techniques are applied to the problematic scalar glueball channel to determine masses , widths and relative resonance strengths of low - lying scalar glueball states contributing to the hadronic spectral function .
a feature of our analysis is the inclusion of instanton contributions to the scalar gluonic correlation function .
compared with the next - to - leading gaussian sum - rule , the analysis of the lowest - weighted sum - rule ( which contains a large scale - independent contribution from the low energy theorem ) is shown to be unreliable because of instability under qcd uncertainties .
however , the presence of instanton effects leads to approximately consistent mass scales in the lowest weighted and next - lowest weighted sum - rules .
the analysis of the next - to - leading sum - rule demonstrates that a single narrow resonance model does _ not _ provide an adequate description of the hadronic spectral function .
consequently , we consider a wide variety of phenomenological models which distribute resonance strength over a broad region some of which lead to excellent agreement between the theoretical prediction and phenomenological models .
including qcd uncertainties , our results indicate that the hadronic contributions to the spectral function stem from a pair of resonances with masses in the range 0.81.6 gev , with the lighter of the two potentially having a large width . .
And you have already written the first three sentences of the full article: mass predictions for scalar @xmath0 glueballs extracted from qcd sum - rules have been problematic mainly due to discrepancies between analyses which are sensitive to the low - energy theorem for gluonic correlation functions and those which are insensitive to this quantity @xcite .
such a discrepancy would be indicative of two widely - separated states , a result which has already been seen to occur in explicit two - resonance analyses of laplace sum - rules even in the absence of mixing with quark scalar resonances @xcite .
however , there exists substantial evidence that these discrepancies are resolved by the inclusion of instanton @xcite effects in the laplace sum - rules for scalar glueballs @xcite ..
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recently , techniques for using gaussian sum - rules @xcite to predict hadronic properties have been developed @xcite .
in particular , these methods concentrate on normalized gaussian sum - rules which are independent of the finite - energy sum - rule constraint which is central to the original heat - evolution studies @xcite of the gaussian sum - rules
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Suppose that you have an abstract for a scientific paper: we present a possible scheme to tamper with non - local quantum correlations in a way that is consistent with relativistic causality , but goes beyond quantum mechanics . a non - local jamming " mechanism , operating within a certain space - time window , would not violate relativistic causality and would not lead to contradictory causal loops .
the results presented in this letter do not depend on any model of how quantum correlations arise and apply to any jamming mechanism .
15.0 cm -1.0 in -42pt plus 2 mm minus 2 mm taup-2263 - 95 + ` june 21 , 1995 + .
And you have already written the first three sentences of the full article: the question of non - local quantum correlations versus local realism , first raised in the famous epr paper @xcite , has held the interest of the physics community since .
j. s. bell @xcite showed that the predictions of quantum mechanics are incompatible with any model based on local realism . the pioneering experimental work of a. aspect
_ @xcite and others @xcite supports the predictions of quantum mechanics and contradicts local realism : bell inequalities applicable to the various experimental arrangements have been shown to be violated ..
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it should be mentioned that some aspects of the experimental setups have been criticized and questioned @xcite .
problems of experimental bias or enhancement of particular polarization states by detection systems were experimentally checked by t. haji - hassan _
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Suppose that you have an abstract for a scientific paper: in heavy - ion fusion reactions involving a well deformed nucleus , one often assumes that the orientation of the target nucleus does not change during the reaction .
we discuss the accuracy of this procedure by analyzing the excitation function of the fusion cross section and the fusion barrier distribution in the reactions of @xmath0sm target with various projectiles ranging from @xmath1c to @xmath2ar .
it is shown that the approximation gradually looses its accuracy with increasing charge product of the projectile and target nuclei because of the effects of finite excitation energy of the target nucleus .
the relevance of such inaccuracy in analyzing the experimental data is also discussed .
it is now well established that nuclear intrinsic degrees of freedom strongly influence the fusion cross section in heavy - ion reactions at energies near and below the coulomb barrier @xcite .
typical examples include the rotational excitation of a deformed target nucleus which leads to a large enhancement of the fusion cross section at low energies .
a characteristic in this case is that the excitation energy of the rotational motion is often much smaller than the curvature of the fusion barrier , which determines the time scale of the fusion process .
this is the case when , e.g. , one of the deformed rare earth nuclei or actinides is the target nucleus .
one then often calculates the fusion probability for each partial wave @xmath3 following @xcite @xmath4 where @xmath5 is the orientation of the deformed target , which will be specified later more precisely .
we call this the orientation average formula . the upper index @xmath6 stands for the sudden tunneling approximation .
@xmath7 is the fusion probability for a given orientation .
it is determined by solving a one - dimensional schrdinger equation for the relative distance between the projectile and target @xmath8 , where the potential consists of the nuclear and coulomb components given by @xmath9 } \label{nucl } \\....
And you have already written the first three sentences of the full article: we thank d.m . brink for useful discussions . this research was supported by the monbusho scholarship and the international scientific research program : joint research : contract number 09044051 from the japanese ministry of education , science and culture , and by the u.s .
department of energy under grant no .
de - fg03 - 00-er41132 ..
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w. reisdorf , f.p .
hessberger , k.d .
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Suppose that you have an abstract for a scientific paper: we consider an undirected graph @xmath0 with a set @xmath1 of terminals , and with nonnegative integer capacities @xmath2 and costs @xmath3 of nodes @xmath4 .
a path in @xmath5 is a _
@xmath6-path _ if its ends are distinct terminals . by a _ multiflow _
we mean a function @xmath7 assigning to each @xmath6-path @xmath8 a nonnegative rational _ weight _ @xmath9 , and a multiflow is called _ feasible _ if the sum of weights of @xmath6-paths through each node @xmath10 does not exceed @xmath2 .
the _ value _ of @xmath7 is the sum of weights @xmath9 , and the _ cost _ of @xmath7 is the sum of @xmath9 times the cost of @xmath8 w.r.t .
@xmath11 , over all @xmath6-paths @xmath8 .
generalizing known results on edge - capacitated multiflows , we show that the problem of finding a minimum cost multiflow among the feasible multiflows of maximum possible value admits _ half - integer _ optimal primal and dual solutions .
moreover , we devise a strongly polynomial algorithm for finding such optimal solutions
. _ keywords _ : minimum cost multiflow , bidirected graph , skew - symmetric graph .
And you have already written the first three sentences of the full article: for a function @xmath12 and a subset @xmath13 , we write @xmath14 to denote @xmath15 .
the _ incidence vector _ of @xmath16 in @xmath17 is denoted by @xmath18 , i.e. @xmath19 is 1 for @xmath20 and 0 for @xmath21 ( usually @xmath22 will be clear from the context ) .
when @xmath16 is a multiset , @xmath19 denotes the number of occurrences of @xmath23 in @xmath16 . in an undirected graph @xmath5 ,.
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the sets of nodes and edges are denoted by @xmath24 and @xmath25 , respectively .
when @xmath5 is a directed graph , we speak of arcs rather than edges and write @xmath26 instead of @xmath25 .
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Suppose that you have an abstract for a scientific paper: the impression gained from the literature published to date is that the spectrum of the stadium billiard can be adequately described , semiclassically , by the gutzwiller periodic orbit trace formula together with a modified treatment of the marginally stable family of bouncing ball orbits .
i show that this belief is erroneous .
the gutzwiller trace formula is not applicable for the phase space dynamics the bouncing ball orbits .
unstable periodic orbits close to the marginally stable family in phase space can not be treated as isolated stationary phase points when approximating the trace of the green function .
semiclassical contributions to the trace show an @xmath0 dependent transition from hard chaos to integrable behavior for trajectories approaching the bouncing ball orbits .
a whole region in phase space surrounding the marginal stable family acts , semiclassically , like a stable island with boundaries being explicitly @xmath0dependent .
the localized bouncing ball states found in the billiard derive from this semiclassically stable island .
the bouncing ball orbits themselves , however , do not contribute to individual eigenvalues in the spectrum . an ebk like quantization of the regular bouncing ball eigenstates in the stadium can be derived .
the stadium billiard is thus an ideal model for studying the influence of almost regular dynamics near marginally stable boundaries on quantum mechanics .
this behavior is generically found at the border of classically stable islands in systems with a mixed phase space structure .
+ pacs numbers : 05.45 , 03.65.sq .3 cm .3 cm .0 cm .0 cm 23.0 cm epsf .
And you have already written the first three sentences of the full article: the derivation of semiclassical periodic orbit formulas for the trace of the quantum green function led to a deeper understanding of the influence of classical dynamics on quantum spectra .
closed periodic orbit expressions have been given by gutzwiller @xcite and balian and bloch @xcite for `` hard chaos '' systems and by berry and tabor @xcite for integrable dynamics .
integrability and hard chaos represent the two extremes on the scale of possible hamiltonian dynamics ..
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the term `` hard chaos '' introduced by gutzwiller @xcite is , however , not well defined .
it implies , that all periodic orbits are unstable and `` sufficiently '' isolated to allow for the stationary phase approximations in the derivation of the trace formula .
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Suppose that you have an abstract for a scientific paper: we consider the penetration length @xmath0 of random walkers diffusing in a medium of perfect or imperfect absorbers of number density @xmath1 .
we solve this problem on a lattice and in the continuum in all dimensions @xmath2 , by means of a mean - field renormalization group . for a homogeneous system in @xmath3
, we find that @xmath4 , where @xmath5 is the absorber density correlation length . the cases of @xmath6 and @xmath7 are also treated . in the presence of long - range correlations
, we estimate the temporal decay of the density of random walkers not yet absorbed .
these results are illustrated by exactly solvable toy models , and extensive numerical simulations on directed percolation , where the absorbers are the active sites . finally , we discuss the implications of our results for diffusion limited aggregation ( dla ) , and we propose a more effective method to measure @xmath0 in dla clusters . .
And you have already written the first three sentences of the full article: the dynamics of random walkers diffusing in the presence of a finite density of perfect absorbers is a rich problem which has been widely discussed in the physical and mathematical literature @xcite . at very large times
, the density of surviving walkers does not decay exponentially as a simple mean - field argument would predict , but rather behaves as @xmath8 , \label{don}\ ] ] where @xmath1 is the absorber density , and @xmath9 is a numerical constant .
the physical interpretation is that the process is dominated by particles starting in very large absorber - free regions ( voids ) , of linear size @xmath10 . in @xmath2 dimensions ,.
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these regions have a probability of order @xmath11 for small @xmath1 . in a void of size @xmath10 , solving the diffusion equation with absorbing conditions on its surface shows that the density typically decays as @xmath12 . a saddle - point argument
then leads to the result of eq .
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Suppose that you have an abstract for a scientific paper: we report the first detection of @xmath0100 mev gamma rays associated with a behind - the - limb solar flare , which presents a unique opportunity to probe the underlying physics of high - energy flare emission and particle acceleration . on 2013
october 11 a goes m1.5 class solar flare occurred @xmath1 9.9 behind the solar limb as observed by _
stereo_-b .
_ rhessi_observed hard x - ray emission above the limb , most likely from the flare loop - top , as the footpoints were occulted .
surprisingly , the _ fermi_large area telescope ( lat ) detected @xmath0100 mev gamma - rays for @xmath130 minutes with energies up to 3 gev .
the lat emission centroid is consistent with the _ rhessi_hard x - ray source , but its uncertainty does not constrain the source to be located there .
the gamma - ray spectra can be adequately described by bremsstrahlung radiation from relativistic electrons having a relatively hard power - law spectrum with a high - energy exponential cutoff , or by the decay of pions produced by accelerated protons and ions with an isotropic pitch - angle distribution and a power - law spectrum with a number index of @xmath13.8 .
we show that high optical depths rule out the gamma rays originating from the flare site and a high - corona trap model requires very unusual conditions , so a scenario in which some of the particles accelerated by the cme shock travel to the visible side of the sun to produce the observed gamma rays may be at work . .
And you have already written the first three sentences of the full article: during its first six years in orbit , the _ fermi_large area telescope ( lat ; * ? ? ?
* ) has detected @xmath030 mev gamma - ray emission from more than 40 solar flares , nearly 10 times more than egret @xcite onboard the _ compton gamma - ray observatory _
, grs @xcite onboard the _ solar maximum mission _ ( _ smm _ ) and coronas - f @xcite ..
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the _ fermi_detections sample both the impulsive @xcite and the long - duration phases @xcite including the longest extended emission ever detected ( @xmath120 hours ) from the sol2012 - 03 - 07 goes x - class flares @xcite .
our understanding of solar flares has also been shaped by decades of hard x - ray ( hxr ) observations , notably by the detection of conjugate footpoint sources by _ smm _
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Suppose that you have an abstract for a scientific paper: in order to solve quantum field theory in a non - perturbative way , lagrangian lattice simulations have been very successful .
here we discuss a recently proposed alternative hamiltonian lattice formulation - the monte carlo hamiltonian . in order to show its working in the case of the scalar @xmath0 model
, we have computed thermodynamic functions like free energy , average energy , entropy and specific heat .
we find good agreement between the results from the monte carlo hamiltonian and standard lagrangian lattice computations .
however , the monte carlo hamiltonian results show less fluctuations under variation of temperature .
we address properties of the mc hamiltonian , like a finite temperature window , and scaling properties .
also we discuss possible future applications - like quantum chaos in many - body systems , the non - perturbative computation of wave functions of elementary particles , as well as scattering amplitudes in high energy physics . , , .
And you have already written the first three sentences of the full article: lagrangian lattice field theory has been for the last three decades the most successful non - perturbative technique to compute properties of elementary particles and to solve @xmath1 .
however , some problems have resisted to a solution even by this powerful technique .
for example , it is difficult to estimate wave functions and the spectrum of excited states ..
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wave functions in conjunction with the energy spectrum contain more physical information than the energy spectrum alone .
although lattice @xmath1 simulations in the lagrangian formulation give good estimates of the hadron masses , one is yet far from a comprehensive understanding of hadrons .
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Suppose that you have an abstract for a scientific paper: we have observed markarian 421 in january and march 2001 with the cangaroo - ii imaging cherenkov telescope during an extraordinarily high state at tev energies . from 14 hours observations at very large zenith angles , @xmath070@xmath1 , a signal of 298@xmath252 gamma - ray like events ( 5.7 @xmath3 ) was detected at @xmath4 tev , where a higher sensitivity is achieved than those of usual observations near the zenith , owing to a greatly increased collecting area . under the assumption of an intrinsic power - law spectrum , we derived a differential energy spectrum @xmath5 ph./@xmath6/sec / tev , which is steeper than those previously measured around 1 tev , and supports the evidence for a cutoff in the spectrum of markarian 421 .
however , the 4@xmath3 excess at energies greater than 20 tev in our data favors a cutoff energy of @xmath08 tev , at the upper end of the range previously reported from measurements at tev energies . .
And you have already written the first three sentences of the full article: markarian 421 ( mrk 421 , j1104 + 3812 ) is a nearby bl lacertae object ( @xmath7 ) and was the first extragalactic tev gamma - ray source discovered @xcite .
the tev gamma - ray flux is variable , with flaring behavior observed on time - scales of less than an hour @xcite .
extensive measurements have been performed by several experimental groups based on the imaging cherenkov technique @xcite ..
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multi - wavelength observations support the synchrotron self
compton ( ssc ) mechanism for the production of tev gamma - rays from this source ( see , e.g. , * ? ? ?
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Suppose that you have an abstract for a scientific paper: the emission of energetic gluons in @xmath0 production in @xmath1 annihilation can have important experimental consequences , in particular on top quark mass measurements .
we present compact , analytical expressions for the gluon energy distribution and its average value at first order in qcd perturbation theory .
our results are valid for arbitrary masses , collision energies and production currents .
we pay particular attention to top quark production near threshold , and show that in certain cases the soft gluon approximation is insufficient to describe the radiation spectrum .
# 1#1 12_12 dtp/94/14 + lu - tp943 + march 1994 + 1.cm * gluon radiation and energy losses + in top quark production * 1.cm yu.l .
dokshitzer .2 cm _ department of theoretical physics , university of lund + slvegatan 14a , s-22362 lund , sweden _
+ .4 cm v.a .
khoze@xmath2 .2 cm _ department of physics , university of durham + durham dh1 3le , england _
+ .4 cm and .4 cm w.j . stirling .2 cm _ departments of physics and mathematical sciences , university of durham + durham dh1 3le , england _ .
And you have already written the first three sentences of the full article: the discovery of the top quark one of the basic components of the standard model
is one of the most important goals for present and future experiments .
indirect evidence for the existence of top is very strong , see for example @xcite , and the chances that it will be detected at the fermilab @xmath3 collider in the next few years are very high ..
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once top is discovered , the next challenge for experiments is to measure its parameters in particular its mass @xmath4 as precisely as possible .
an unambiguous interpretation of experimental data and the determination of the top quark parameters relies on a clear quantitative understanding of the details of the production process , including the effects of gluon bremsstrahlung at the production stage @xcite . to quantify these effects
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Suppose that you have an abstract for a scientific paper: we discuss the curvaton scenario with the affleck - dine baryogenesis . in this scenario ,
non - vanishing baryonic entropy fluctuation may be generated even without primordial fluctuation of the affleck - dine field .
too large entropy fluctuation is inconsistent with the observations and hence constraints on the curvaton scenario with the affleck - dine baryogenesis are obtained .
we calculate the baryonic entropy fluctuation ( as well as other cosmological density fluctuations ) in this case and derive constraints .
implications to some of the models of the curvaton are also discussed .
tu-717 + hep - ph/0404253 + april , 2004 + .5 in * * curvaton scenario with affleck - dine baryogenesis .45 in maki ikegami and takeo moroi .45 in _ department of physics , tohoku university , sendai 980 - 8578 , japan _ .4 in .
And you have already written the first three sentences of the full article: recent precise measurement of the cosmic microwave background ( cmb ) anisotropies by the wilkinson microwave anisotropy probe ( wmap ) @xcite has provided detailed informations about the mechanism of generating the cosmic density fluctuations .
importantly , observed cmb anisotropies are highly consistent with those predicted from scale - invariant purely adiabatic primordial density fluctuations .
such a class of primordial density fluctuations is also consistent with the recent results by the sloan digital sky survey experiments @xcite . among various possibilities ,.
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inflation is one of the most famous scenarios of generating cosmic density fluctuations consistent with the observations .
another class of scenario of generating the scale - invariant adiabatic density fluctuations , however , exists , which is called the `` curvaton '' scenario @xcite.a similar study of the effect of extra scalar field other than the inflaton , see also @xcite .
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Suppose that you have an abstract for a scientific paper: we examine the problem of stability of persistent currents in a mixture of two bose gases trapped in an annular potential .
we evaluate the critical coupling for metastability in the transition from quasi - one to two - dimensional motion .
we also evaluate the critical coupling for metastability in a mixture of two species as function of the population imbalance .
the stability of the currents is shown to be sensitive to the deviation from one - dimensional motion . .
And you have already written the first three sentences of the full article: bose - einstein condensates of dilute vapors of atoms offer a very promising testing ground for questions associated with superfluidity for a number of reasons .
firstly , these gases are dilute as opposed , for example , to the `` traditional '' superfluid liquid helium . furthermore , the atomic gases can be manipulated in many different ways , including the shape of the confining potential , the strength and the sign of the effective interatomic interaction , the number of different species in multicomponent systems , etc . while the term `` superfluidity '' covers a whole collection of many different phenomena @xcite , we focus in the present study on the metastability of superflow in annular traps @xcite .
persistent flow has been observed recently in a bose - einstein condensate of sodium atoms confined in a toroidal trap @xcite . in this experiment , an initial angular momentum of @xmath0 per particle.
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was transferred to the atoms and the rotational flow was observed to persist for up to ten seconds , limited only by the trap lifetime and other experimental imperfections .
persistent currents with two units of angular momentum were also observed in the same experiment .
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Suppose that you have an abstract for a scientific paper: this is the first in a series of papers studying the variable stars in large magellanic cloud globular clusters .
the primary goal of this series is to better understand how the rr lyrae stars in oosterhoff - intermediate systems compare to those in oosterhoff i / ii systems . in this paper
we present the results of our new time - series @xmath0 photometric study of ngc 1466 .
a total of @xmath1 variables were identified in the cluster , of which @xmath2 are new discoveries .
the variables include @xmath3 rrab stars , @xmath4 rrc s , @xmath5 rrd s , @xmath6 candidate rr lyrae , @xmath7 long - period variables , @xmath6 potential anomalous cepheid , and @xmath8 variables of undetermined classification .
we present photometric parameters for these variables . for the rr lyrae stars
physical properties derived from fourier analysis of their light curves are presented .
the rr lyrae stars were used to determine a reddening - corrected distance modulus of @xmath9 .
we discuss several different indicators of oosterhoff type and find ngc 1466 to be an oosterhoff - intermediate object . .
And you have already written the first three sentences of the full article: studies of rr lyrae stars in the milky way globular clusters reveal what is traditionally known as the oosterhoff dichotomy ; the tendency for these clusters to be either oosterhoff i ( oo - i ) or oosterhoff ii ( oo - ii ) objects with a relatively clear zone of avoidance between these two groups .
the left panel of figure 5 in @xcite strikingly illustrates the oosterhoff dichotomy in a plot of the average period of the rr lyrae stars of bailey type ab ( rrab ) versus cluster metallicity for milky way globular clusters .
when one looks at the nearby dwarf galaxies and their globular clusters , one does not see an oosterhoff dichotomy as these objects fall not only into the oo - i / ii groups but also into the gap between those two groups ..
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in fact the distribution of these extragalactic objects seems to peak in the zone of avoidance @xcite .
the existence of oosterhoff - intermediate objects ( oo - int ) , objects that fall into the zone of avoidance , in the nearby dwarf galaxies poses a significant challenge to the hierarchical merger model for the formation of the milky way halo .
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Suppose that you have an abstract for a scientific paper: previous research on semiflexible polymers including cytoskeletal networks in cells has suggested the existence of distinct regimes of elastic response , in which the strain field is either uniform ( affine ) or non uniform ( non affine ) under external stress .
associated with these regimes , it has been further suggested that a new fundamental length scale emerges , which characterizes the scale for the crossover from non affine to affine deformations .
here , we extend these studies by probing the response to localized forces and force dipoles . we show that the previously identified nonaffinity length [ d.a .
head _
et al . _
pre * 68 * , 061907 ( 2003 ) . ] controls the mesoscopic response to point forces and the crossover to continuum elastic behavior at large distances . .
And you have already written the first three sentences of the full article: semiflexible polymers such as filamentous proteins resemble elastic rods on a molecular scale , while exhibiting significant thermal fluctuations on the scale of micrometers or even less .
this has made them useful as model systems allowing for direct visualization via optical microscopy .
but , semiflexible polymers are not just large versions of their more well - studied flexible cousins such as polystyrene ..
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filamentous proteins , in particular , have been shown to exhibit _ qualitatively _ different behavior in their networks and solutions .
a fundamental reason for this is the fact that the thermal _ persistence length _ , a measure of filament stiffness as the length at which thermal bending fluctuations become apparent , can become large compared with other important length scales such as the spacing between polymers in solutions , or the distance between chemical crosslinks in a network .
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Suppose that you have an abstract for a scientific paper: we study the power spectrum of the mass density perturbations in an inflation scenario that includes thermal dissipation .
we show that the condition on which the thermal fluctuations dominate the primordial density perturbations can easily be realized even for weak dissipation , _
i.e. _ , the rate of dissipation is less than the hubble expansion .
we find that our spectrum of primordial density perturbations follows a power law behavior , and exhibits a `` thermodynamical '' feature the amplitude and power index of the spectrum depend mainly on the thermodynamical variable @xmath0 , the inflation energy scale . comparing this result with the observed temperature fluctuations of the cosmic microwave background , we find that both amplitude and index of the power spectrum can be fairly well fitted if @xmath1 gev .
# 1@xmath2#1 .
And you have already written the first three sentences of the full article: in the past decade , there has been a number of studies on dissipative processes associated with the inflaton decay during its evolution .
these studies have shed light into the possible effects of the dissipative processes .
for instance , it was realized that dissipation effectively slows down the rolling of the inflaton scalar field @xmath3 toward the true vacuum ..
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these processes are capable of supporting the scenario of inflation @xcite .
recently , inspired by several new developments , the problem of inflation with thermal dissipation has attracted many re - investigations .
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Suppose that you have an abstract for a scientific paper: we have observed a large sample of compact planetary nebulae in the near - infrared to determine how the 2@xmath0p2@xmath0s hei line at 2.058@xmath1 m varies as a function of stellar effective temperature , @xmath2 .
the ratio of this line with hi br@xmath3 at 2.166@xmath1 m has often been used as a measure of the highest @xmath2 present in a stellar cluster , and hence on whether there is a cut - off in the stellar initial mass function at high masses .
however , recent photoionisation modelling has revealed that the behaviour of this line is more complex than previously anticipated .
our work shows that in most aspects the photoionisation models are correct .
in particular , we confirm the weakening of the 2@xmath0p2@xmath0s as @xmath2 increases beyond 40000k .
however , in many cases the model underpredicts the observed ratio when we consider the detailed physical conditions in the individual planetary nebulae .
furthermore , there is evidence that there is still significant 2@xmath0p2@xmath0s hei line emission even in the planetary nebulae with very hot ( @xmath4100000k ) central stars .
it is clear from our work that this ratio can not be considered as a reliable measure of effective temperature on its own .
infrared : ism : lines and bands
ism : planetary nebulae : general .
And you have already written the first three sentences of the full article: one of the fundamental parameters characterising any stellar population is its mass function , and in particular its _ initial _ mass function ( imf ) , defined simply as the number of stars per unit mass that are actually formed in any system . determining the form of the imf is vital to our understanding of star formation in our own and other star - forming galaxies , since it allows us to model the chemical and physical evolution of these systems . despite ongoing debate ( eg .
leitherer 1998 ) it is not clear whether the imf varies widely between galaxies or even within different star formation regions of our own galaxy . since starburst galaxies are generally dusty , ir indicators of the imf are preferable since they provide considerable improvement in sensitivity since the extinction is lower than in the optical , and perhaps as important , any error in the derived extinction value has a correspondingly smaller effect on any observed line ratio when the lines are close in wavelength .
indeed any method that relies on absolute flux values or widely separated line pairs is likely to lead to significant errors in the derived results when the extinction is large ..
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there are limited methods for directly measuring the current imf from stellar features at these wavelengths , so indirect methods are required .
most work has relied on inferring the nature of the stars present by comparing the ionisation structure of the enveloping nebular gas with the predictions of detailed photoionisation models .
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Suppose that you have an abstract for a scientific paper: we consider the problem of defining free energy and other thermodynamic functions when the entropy is given as a general function of the probability distribution , including that for nonextensive forms .
we find that the free energy , which is central to the determination of all other quantities , can be obtained uniquely numerically even when it is the root of a transcendental equation .
in particular we study the cases of the tsallis form and a new form proposed by us recently .
we compare the free energy , the internal energy and the specific heat of a simple system of two energy states for each of these forms . .
And you have already written the first three sentences of the full article: we have recently @xcite proposed a new form of nonextensive entropy which depends on a parameter similar to tsallis entropy @xcite , and in a similar limit approaches shannon s classical extensive entropy .
we have shown how the definition for this new form of entropy can arise naturally in terms of mixing of states in a phase cell when the cell is re - scaled , the parameter being a measure of the rescaling , and how shannon s coding theorem @xcite elucidates such an approach . in this paper
we shall adopt a more general attitude and try to develop the statistical mechanics of systems where the entropy is defined almost arbitrarily ..
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such a designer entropy @xcite may indeed be relevant in a specific context , but we shall not justify here any specific form .
the applicability of the tsallis form which leads to a levy - type pdf found in many physical contexts is now well established @xcite and in the earlier paper we have commented about how our form may also be more relevant in a context that demands a more stiff pdf . in this paper
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Suppose that you have an abstract for a scientific paper: we study the effect of backward scatterings in the tunneling at a point contact between the edges of a second level hierarchical fractional quantum hall states
. a universal scaling dimension of the tunneling conductance is obtained only when both of the edge channels propagate in the same direction .
it is shown that the quasiparticle tunneling picture and the electron tunneling picture give different scaling behaviors of the conductances , which indicates the existence of a crossover between the two pictures .
when the direction of two edge - channels are opposite , e.g. in the case of macdonald s edge construction for the @xmath0 state , the phase diagram is divided into two domains giving different temperature dependence of the conductance . .
And you have already written the first three sentences of the full article: it has been discovered that the edge mode of a fractional quantum hall ( fqh ) system is described as a chiral tomonaga - luttinger ( tl ) liquid @xcite .
when one makes a point contact between the edges , backward scatterings become possible only near that point contact .
such a system is expected to be described as a tl model with a scattering potential at @xmath1 @xcite . for a @xmath2 state ,.
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the model predicts a @xmath3 dependence of the tunneling conductance near the zero temperature @xcite which is consistent with the recent experiment @xcite . the result does not rely upon whether we start the renormalization group ( rg ) analysis with the picture where quasiparticles tunnel between the edges through the bulk fqh liquid ( quasiparticle tunneling picture ) or the picture where electrons tunnel through the vacuum between the edges of two condensates separated by the tunnel effect ( electron tunneling picture ) @xcite . to describe the bulk fqh liquids with a filling factor
@xmath4 hierarchy constructions are introduced @xcite . at a given filling one
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Suppose that you have an abstract for a scientific paper: we report the discovery of a large , sudden , and persistent increase in the spin - down rate of b0540 - 69 , a young pulsar in the large magellanic cloud , using observations from the and satellites .
the relative increase in the spin - down rate @xmath0 of @xmath1 is unprecedented for b0540 - 69 .
no accompanying change in the spin rate is seen , and no change is seen in the pulsed x - ray emission from b0540 - 69 following the change in the spin - down rate .
such large relative changes in the spin - down rate are seen in the recently discovered class of `` intermittent pulsars '' , and we compare the properties of b0540 - 69 to such pulsars .
we consider possible changes in the magnetosphere of the pulsar that could cause such a large change in the spin - down rate . .
And you have already written the first three sentences of the full article: b0540 - 69 is a young , rotationally powered pulsar in the large magellanic cloud ( lmc ) that is similar to the crab pulsar in many ways . with a rotation frequency @xmath2 of almost 20 hz ,
it is one of the most rapidly rotating young pulsars known .
its spin - down luminosity ( @xmath3 ) of @xmath4 erg @xmath5 , where @xmath6 is the moment of inertia of the neutron star ( ns ) in units of @xmath7 g @xmath8 , is also among the largest for all pulsars ..
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the spin - down rate of a pulsar is often described in terms of a braking index @xmath9 , in which @xmath10 . the slowdown of b0540 - 69 is relatively stable for a young pulsar , and it is one of only 8 young pulsars for which a braking index has been reliably measured ( lyne 2015 ) .
it has a characteristic spin - down age ( @xmath11 ) of @xmath12 years .
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Suppose that you have an abstract for a scientific paper: we study high energy particle collisions around higher dimensional black holes .
it is shown that the center of mass energy can be arbitrarily large in the vicinity of the event horizon like the baados , silk and west ( bsw ) process in four dimensions if the following two conditions are satisfied : ( i ) the horizon is extremal and ( ii ) the parameters of either of the two colliding particles are fine - tuned , which is called a critical particle condition . we also show that a test particle which satisfies the critical particle condition can reach the event horizon from a distant region for a simple case .
finally , we discuss the relation between the bsw process and the linear instability of test fields around extremal black holes , the latter of which has been recently found by aretakis @xcite . .
And you have already written the first three sentences of the full article: baados , silk and west pointed out that a rapidly rotating black hole may act as a particle accelerator to arbitrarily high energy @xcite .
we call this acceleration mechanism the baados - silk - west ( bsw ) mechanism or bsw process .
there are several discussions on the bsw process @xcite . from a purely relativistic point of view.
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, it is suggested in @xcite that an arbitrarily high energy collision induced by the bsw process implies that an extremal kerr black hole is linearly unstable .
if we consider the free - fall test particles with an arbitrarily small mass from the far region , we expect that the gravity induced by those test particles will be well described by a linear perturbation around the background spacetime .
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Suppose that you have an abstract for a scientific paper: we investigate electron transport through clean open quantum dots ( `` quantum billiards '' ) .
we present a semiclassical theory that allows to accurately reproduce quantum transport calculations .
quantitative agreement is reached for individual energy and magnetic field dependent elements of the scattering matrix .
two key ingredients are essential : ( i ) inclusion of pseudo - paths which have the topology of linked classical paths resulting from diffraction in addition to classical paths and ( ii ) a high - level approximation to diffractive scattering . within this framework of the pseudo - path semiclassical approximation ( psca )
, typical shortcomings of semiclassical theories such as violation of the anti - correlation between reflection and transmission and the overestimation of conductance fluctuations are overcome . beyond its predictive capabilities
the psca provides deeper insights into the quantum - to - classical crossover . .
And you have already written the first three sentences of the full article: the ability to controllably fabricate , manipulate and examine structures on the sub - micrometer scale has let to the observation of quantum phenomena in electron transport such as , e.g. , universal conductance fluctuations ( ucf ) in chaotic billiards and weak localization ( wl ) , which dominate transport at the nanoscale.@xcite by reducing the characteristic system size below the electronic inelastic mean free path , transport enters the so - called ballistic regime.@xcite ballistic electron transport is a prime candidate for semiclassical descriptions @xcite where the classical trajectories carry an amplitude which reflects the stability of the classical orbits and a phase which contains the classical action and accounts for quantum interference.@xcite on a more fundamental level , the semiclassical framework provides a conceptually powerful bridge between classical and quantum mechanics allowing an intuitive approach to quantum mechanics and quantum chaos in general , and to transport through open quantum dots or so - called quantum billiards in particular.@xcite + several semiclassical approximations ( scas ) based on the approximation of the constant - energy green s function for propagation in a billiard have been proposed and compared with numerical quantum transport calculations or experiment.@xcite while many qualitative features could be well reproduced , quantitative agreement on a system - specific level has remained a challenge .
+ one underlying difficulty is the multi - scale nature of the quantum - to - classical transition for transport through open quantum dots . for the semiclassical approximation to hold
, the de broglie wavelength @xmath0 should be vanishingly small compared to all characteristic dimensions of the device ..
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such asymptotic theories have been successfully employed to reproduce , upon ensemble averaging , random matrix theory ( rmt ) results for chaotic cavities ( see e.g. ref . ) .
a quantitative comparison on a system - specific level with full quantum calculations or experiments is , however , only possible in the non - asymptotic regime where @xmath0 is small compared to the linear dimension @xmath1 of the dot , @xmath2 , but still comparable to the width of the lead ( or quantum wire ) @xmath3 , @xmath4 .
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Suppose that you have an abstract for a scientific paper: identifying nucleation pathway is important for understanding the kinetics of first - order phase transitions in natural systems . in the present work , we study nucleation pathway of the ising model in homogeneous and heterogeneous networks using the forward flux sampling method , and find that the nucleation processes represent distinct features along pathways for different network topologies . for homogeneous networks
, there always exists a dominant nucleating cluster to which relatively small clusters are attached gradually to form the critical nucleus . for heterogeneous ones ,
many small isolated nucleating clusters emerge at the early stage of the nucleation process , until suddenly they form the critical nucleus through a sharp merging process . by analyzing the properties of the nucleating clusters along the pathway ,
we show that the main reason behind the different routes is the heterogeneous character of the underlying networks . .
And you have already written the first three sentences of the full article: nucleation is a fluctuation - driven process that initiates the decay of a metastable state into a more stable one @xcite .
it is usually involved in first - order phase transitions and along with growth of a new phase @xcite .
many important phenomena in nature , including crystallization @xcite , fractures @xcite , glass formation @xcite , and protein folding @xcite , to list just a few , are associated with nucleation . despite much attention , many aspects of nucleation processes in complex systems are still unclear and deserve more investigation . the ising model is a paradigm for many phenomena in statistical physics ..
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it has also been widely used to study the nucleation process .
for instance , in two - dimensional lattices , allen _ et al _ discovered that shear can enhance the nucleation rate and the rate peaks at an intermediate shear rate @xcite .
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Suppose that you have an abstract for a scientific paper: the isoscalar octupole response of a heavy spherical nucleus is analyzed in a semiclassical model based on the linearized vlasov equation .
the octupole strength function is evaluated with different degrees of approximation .
the zero - order fixed - surface response displays a remarkable concentration of strength in the @xmath0 and @xmath1 regions , in excellent agreement with the quantum single - particle response .
the collective fixed - surface response reproduces both the high- and low - energy octupole rsonances , but not the low - lying @xmath2 collective states , while the moving - surface response function gives a good qualitative description of all the main features of the octupole response in heavy nuclei .
the role of triangular nucleon orbits , that have been related to a possible instability of the spherical shape with respect to octupole - type deformations , is discussed within this model .
it is found that , rather than creating instability , the triangular trajectories are the only classical orbits contributing to the damping of low - energy octupole excitations . #
10= -.025em0 - 0 .05em0 - 0 -.025em.0433em0 @xcite pacs : 24.10.cn , 24.30.cz keywords : vlasov equation , isoscalar octupole resonances , octupole surface modes .
And you have already written the first three sentences of the full article: it is well known that there is an intimate connection between the shell structure in quantum systems like nuclei and metallic clusters and the properties of classical trajectories within these systems ( see e.g. , p. 579 ) . in particular , for nuclei it has been argued that closed orbits of triangular shape might lead to an instability of the spherical shape against octupole - type deformations in the region beyond @xmath3pb , p.560 . here
we would like to investigate in detail this possibility by using a semiclassical theory of nuclear response based on the linearized vlasov equation @xcite .
instabilities are expected to show up as some kind of pathological behaviour in response functions ( vanishing eigenfrequencies and diverging response ) and the semiclassical theory of @xcite and @xcite , that has already been shown to give good qualitative results for lower multipolarities @xcite , is an ideal tool to study the role played by classical trajectories in determining the response of large quantum systems . of course.
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quantum corrections are expected to modify the results of this theory @xcite , especially at very low energy , however having a clear picture of what should be expected already at the classical level might help in making progress .
we study the isoscalar octupole response of a sample `` nucleus '' of @xmath4 nucleons contained in a square - well potential of radius @xmath5 , with @xmath6 .
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Suppose that you have an abstract for a scientific paper: first observation of single - top - quark production in the @xmath0 channel is reported .
the result is based on the combination of the cdf and d0 measurements of the cross section in proton - antiproton collisions at a center - of - mass energy of 1.96 tev .
a summary of other recent single - top - quark results are also included . .
And you have already written the first three sentences of the full article: the top quark , with a mass of @xmath1 gev @xcite , is the most massive of the elementary particles of the standard model ( sm ) . in proton - antiproton collisions ,
top quarks can be produced singly through electroweak interactions and this process provides a unique opportunity to test the standard model and search for non - sm physics . in the sm , the single - top - quark production cross section is predicted to be proportional to the square of the magnitude of the quark - mixing cabibbo - kobayashi - maskawa matrix @xcite element @xmath2 .
consequently , measurements of the single - top - quark production rate could be sensitive to contributions from a fourth generation of quarks @xcite ..
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the two dominant production modes of the single - top - quark process are shown in fig .
[ fig : feynman_diagrams ] and are sensitive to different classes of sm extensions @xcite .
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Suppose that you have an abstract for a scientific paper: we present an expression of a deformed partition function for @xmath0 @xmath1 gauge theory on @xmath2 by using plethystic exponentials . `
hep - th/0611324 ` + ` ou - het 570 ` + november 2006 * plethystics and instantons on ale spaces * yui noma , toshio nakatsu and takeshi tamakoshi + _ department of physics , graduate school of science , osaka university , + toyonaka , osaka 560 - 0043 , japan + _ [ [ section ] ] recently @xmath0 instantons on ale spaces were studied in @xcite and applied to black hole physics in @xcite . in this short note
we point out an expression of a deformed partition function for @xmath0 @xmath1 gauge theory on @xmath2 by using plethystic exponentials .
plethystic exponentials have been used in @xcite and play a central role in counting the bps operators .
let us start with describing the partition function for @xmath0 @xmath1 gauge theory on @xmath2 .
the partition function was computed in @xcite and becomes as follows : @xmath3 where @xmath4 are parameters of the standard torus action on @xmath2 , and @xmath5 denotes a scale parameter for the gauge theory .
the sum in eq.([eq;partition for 4d ] ) is a summation over partitions ( the young diagrams ) .
we remark that any partition @xmath6 can be decomposed into a single partition @xmath7 and @xmath8-tuple partitions @xmath9 @xcite .
they are called respectively @xmath8-core and @xmath8-quotients .
this arises from a division algorithm for the young diagrams analogous to that for integers .
see appendix [ sec;appendix ] for details .
we may write @xmath10 to emphasize the decomposition .
the sum in eq.([eq;partition for 4d ] ) is restricted so that only partitions whose @xmath8-cores are empty contribute to the partition function .
@xmath11 denotes the empty partition .
the symbol @xmath12 is the number of boxes in the young diagram : @xmath13 . for a box @xmath14 in the young diagram , @xmath15 , @xmath16 and @xmath17
are respectively , as given in ( [ eq;arm and leg ] ) , the hook....
And you have already written the first three sentences of the full article: a partition @xmath6 is a nonincreasing sequence of non - negative integers : @xmath46 .
partitions are often identified with the young diagrams .
take a box @xmath47 and let @xmath48 be the hook ..
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@xmath49 the arm length , the leg length and the hook length are @xmath50 where @xmath51 is the dual partition .
the hook @xmath48 is called @xmath52-hook if @xmath53 . fix a positive integer @xmath8 .
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Suppose that you have an abstract for a scientific paper: the main features of a three dimensional , high resolution special relativistic hydro code based on relativistic riemann solvers are described . the capabilities and performance of the code
are discussed . in particular , we present the results of extensive test calculations which demonstrate that the code can accurately and efficiently handle strong shocks in three spatial dimensions .
results of the performance of the code on single and multi - processor machines are given .
simulations ( in double precision ) with @xmath0 computational cells require less than 1 gb of ram memory and @xmath1 cpu seconds per zone and time step ( on a sci cray origin 2000 with a r10000 processor ) .
currently , a version of the numerical code is under development , which is suited for massively parallel computers with distributed memory architecture ( like , e.g. , cray t3e ) . .
And you have already written the first three sentences of the full article: numerical relativistic hydrodynamics ( rhd ) has experienced an important step forward in recent years when modern high resolution shock capturing ( hrsc ) techniques began to be applied to solve the equations of rhd in conservation form .
prior to the advent of hrsc techniques the field was dominated for more than one decade by wilson ( 1979 ) s approach to relativistic hydrodynamics .
this approach relies on the use of artificial viscosity in order to handle the discontinuities ( shocks , contact discontinuities , etc . ) that may appear in the flow numerically ..
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however , techniques based on artificial viscosity are prone to severe numerical difficulties when simulating ultrarelativistic flows ( see , e.g. , centrella & wilson 1984 ) . using modern hrsc techniques instead ,
these difficulties are overcome ( see , e.g. , donat et al .
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Suppose that you have an abstract for a scientific paper: we argue that supersymmetric grand unification of gauge couplings is not incompatible with small @xmath0 , even without large gut - scale corrections , if one relaxes a usual universal gaugino mass assumption .
a commonly assumed relation @xmath1 is in gross contradiction with @xmath2 .
instead , small @xmath0 favors @xmath3 .
if this is indeed the case our observation casts doubt on another commonly used relation @xmath4 which originates from the same constraint of a common gaugino mass at the gut scale .
one firm prediction emerging within the small @xmath0 scenario with the unconstrained gaugino masses is the existence of a relatively light gluino below @xmath5 200gev .
@=11 caption#1[#2]#3 @=12 # 1 + * university of minnesota * tpi - minn-95/04-t + umn - th-1330 - 95 + hep - ph/9503358 + march 1995 + ( revised version ) l. roszkowski and m. shifman + .
And you have already written the first three sentences of the full article: one of the testing grounds for various models of grand unification is calculating the strong coupling constant @xmath6 using , as input , the experimental values of the electromagnetic coupling constant @xmath7 and @xmath8 , where @xmath9 is the weinberg angle .
these calculations have been repeatedly carried out in different models and under different assumptions ( for recent reviews see , _
e.g. _ , ref ..
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it has been shown , in particular , that the simplest grand unification based on the standard model ( sm ) and @xmath10 gauge group leads to too small a value of the strong coupling constant , @xmath11 @xcite and is , thus , ruled out @xcite .
in contrast , supersymmetric models generally predicted @xmath6 in agreement @xcite with experimental data available at that time .
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Suppose that you have an abstract for a scientific paper: we present a current and charge conserving theory for the low frequency admittance of a two - dimensional electron gas connected to ideal metallic contacts and subject to a quantizing magnetic field . in the framework of the edge - channel picture
, we calculate the admittance up to first order with respect to frequency .
the transport coefficients in first order with respect to frequency , which are called _ emittances , determine the charge emitted into a contact of the sample or a gate in response to an oscillating voltage applied to a contact of the sample or a nearby gate .
the emittances depend on the potential distribution inside the sample which is established in response to the oscillation of the potential at a contact .
we show that the emittances can be related to the elements of an electro - chemical capacitance matrix which describes a ( fictitious ) geometry in which each edge channel is coupled to its own reservoir .
the particular relation of the emittance matrix to this electro - chemical capacitance matrix depends strongly on the topology of the edge channels : we show that edge channels which connect different reservoirs contribute with a negative capacitance to the emittance .
for example , while the emittance of a two - terminal corbino disc is a capacitance , the emittance of a two - terminal quantum hall bar is a negative capacitance .
the geometry of the edge - channel arrangement in a many - terminal setup is reflected by symmetry properties of the emittance matrix .
we investigate the effect of voltage probes and calculate the longitudinal and the hall resistances of an ideal four - terminal hall bar for low frequencies . _ .
And you have already written the first three sentences of the full article: the quantized hall effect@xcite provides particularly interesting tests of our understanding of electrical transport .
application of a resistance formula which treats all contacts to a two - dimensional electron gas on equal footing@xcite has considerably revised the traditional picture of the quantized hall effect and has led to the successful explanation of many novel experiments@xcite .
it is the purpose of this work to approach the low frequency electrical transport in two - dimensional electron systems ( 2des ) subject to strong magnetic fields from a similar point of view ..
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in contrast to the dc - transport properties , which have become increasingly well understood , the ac - transport properties have found much less attention .
however , a charge and current conserving theory for the low frequency admittance @xmath0 of a general arrangement of mesoscopic conductors has recently been worked out @xcite .
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Suppose that you have an abstract for a scientific paper: we study massive charged fermionic perturbations in the background of a charged two - dimensional dilatonic black hole , and we solve the dirac equation analytically .
then , we compute the reflection and transmission coefficients and the absorption cross section for massive charged fermionic fields , and we show that the absorption cross section vanishes at the low and high frequency limits . however , there is a range of frequencies where the absorption cross section is not null .
furthermore , we study the effect of the mass and electric charge of the fermionic field over the absorption cross section . .
And you have already written the first three sentences of the full article: in order to find a clue on the quantum gravity problem in spacetime for which @xmath0 , a very rich model of different lower dimensional gravity has been developed . in the particular case of @xmath1 , it is well known that the einstein - hilbert action has been used as the gravity sector . however ,
this model is locally trivial because the einstein - hilbert action in @xmath1 is just a topological invariant ( gauss - bonnet theorem ) .
if we want to obtain the dynamical degree of freedom , we need to couple this action with different fields besides the gravitational one . under this perspective.
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, the dilatonic field has shown a very rich structure and includes black hole solutions .
the dilatonic field naturally arises , for instance , in the compactifications from higher dimensional gravity or from string theory .
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Suppose that you have an abstract for a scientific paper: the results from _ suzaku _ observations of the central region of the perseus cluster are presented .
deep exposures with the x - ray imaging spectrometer provide high quality x - ray spectra from the intracluster medium .
x - ray lines from helium - like cr and mn have been detected significantly for the first time in clusters .
in addition , elemental abundances of ne , mg , si , s , ar , ca , fe , and ni are accurately measured within @xmath0 ( or 220 kpc ) from the cluster center .
the relative abundance ratios are found to be within a range of @xmath1 times the solar value .
these abundance ratios are compared with previous measurements , those in extremely metal - poor stars in the galaxy , and theoretical models . .
And you have already written the first three sentences of the full article: heavy elements ( or metals ) in the universe are created in stars and supernovae ( sne ) .
these metals enrich the interstellar medium and are recycled into generations of stars .
some part of these should have been transported into intergalactic space via galactic winds or ram pressure stripping ..
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indeed , the intracluster medium ( icm ) contains an amount of metals comparable to the total amount of metals found in galaxies ( e.g. * ? ? ?
the distribution of these metals can be measured exclusively by x - ray spectroscopy .
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Suppose that you have an abstract for a scientific paper: this review discusses the dynamics of negative ion reactions with neutral molecules in the gas phase .
most anion - molecule reactions proceed via a qualitatively different interaction potential than cationic or neutral reactions .
it has been and still is the goal of many experiments to understand these reaction dynamics and the different reaction mechanisms they lead to
. we will show how rate coefficients and cross sections for anion - molecule reactions are measured and interpreted to yield information on the underlying dynamics .
we will also present more detailed approaches that study either the transient reaction complex or the energy- and angle - resolved scattering of negative ions with neutral molecules . with the help of these different techniques
many aspects of anion - molecule reaction dynamics could be unravelled in the last years
. however , we are still far from a complete understanding of the complex molecular interplay that is at work during a negative ion reaction . .
And you have already written the first three sentences of the full article: questions about the nature of chemical reactions , why and how they proceed and how this can be used to form certain desired chemical products are already very old .
in fact they are older than most other of the current research topics in atomic and molecular physics or physical chemistry .
the efforts to answer these questions have lead to numerous achievements over the centuries , starting maybe with the re - discovery of the discreet atomic structure of matter , leading to the invention of chemical catalysis , and including the understanding of the quantum mechanical nature of the chemical bond ..
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several technological advances have fertilised experimental research on the dynamics of chemical reactions . besides the development of versatile tunable laser source , one notes supersonic single and crossed molecular beams @xcite , multi - dimensional momentum imaging and coincidence detection @xcite , ultrafast time - resolved spectroscopy @xcite , and , most recently
, the preparation of cold and ultracold atoms and molecules @xcite .
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Suppose that you have an abstract for a scientific paper: we describe the structure of all codimension - two lattice configurations @xmath0 which admit a stable rational @xmath0-hypergeometric function , that is a rational function @xmath1 all whose partial derivatives are non zero , and which is a solution of the @xmath0-hypergeometric system of partial differential equations defined by gelfand , kapranov and zelevinsky .
we show , moreover , that all stable rational @xmath0-hypergeometric functions may be described by toric residues and apply our results to study the rationality of bivariate series whose coefficients are quotients of factorials of linear forms . .
And you have already written the first three sentences of the full article: let @xmath2 , be a configuration of lattice points spanning @xmath3 .
we also denote by @xmath0 the @xmath4 integer matrix with columns @xmath5 .
we say that the configuration @xmath0 is _ regular _ if the points of @xmath0 lie in a hyperplane off the origin ..
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the _ dimension _ of @xmath0 is defined as the dimension of the affine span of its columns and the _ codimension _ as the rank of the lattice @xmath6 following gelfand , kapranov and zelevinsky @xcite we associate to @xmath0 and a _ parameter _ vector @xmath7 a left ideal in the weyl algebra in @xmath8 variables @xmath9 as follows .
[ def : hypergeom ] given @xmath10 of rank @xmath11 and a vector @xmath12 , the _ @xmath0-hypergeometric system _ with parameter @xmath13 is the left ideal @xmath14 in the weyl algebra @xmath15 generated by the _
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Suppose that you have an abstract for a scientific paper: measuring the angles of muons and electrons in air showers is proposed as a method for studying the primary cosmic - ray mass composition near the knee of the cosmic - ray energy spectrum at a few @xmath0ev .
conventional tracking detectors at existing air shower arrays could serve this purpose , like the crt detectors at the hegra array .
when the average radial muon angles are examined as a function of shower core distance , the experimental resolution can be very well calibrated from the tangential angle distribution .
the method is particularly promising for measuring changes in the average mass number of the primary cosmic rays with energy .
the method is described and experimental and theoretical constraints are discussed . .
And you have already written the first three sentences of the full article: despite the fact that ultra - high energy ( uhe ) cosmic rays are known for decades , their sources and the acceleration mechanisms are still under debate .
sources are only detectable by @xmath1-rays produced in interactions near the sources . in the very - high energy ( vhe )
range near 1tev more and more @xmath1-ray sources are revealed by the imaging cherenkov technique . on the contrary ,.
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no clear source detections have been made in the uhe domain above about 100tev , except perhaps a few episodic cases .
mainly for reasons of the required power , the dominant sources of cosmic rays up to about 100tev and probably up to the _ knee _ of the cosmic - ray energy spectrum at a few @xmath0ev are believed to be supernova remnants in the sedov phase .
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Suppose that you have an abstract for a scientific paper: entanglement distillation is a process via which the strength and purity of quantum entanglement can be increased probabilistically .
it is a key step in many quantum communication and computation protocols . in particular
, entanglement distillation is a necessary component of the quantum repeater , a device which counters the degradation of entanglement that inevitably occurs due to losses in a communication line .
here we report an experiment on distilling the einstein - podolsky - rosen ( epr ) state of light , the workhorse of continuous - variable entanglement , using the technique of noiseless amplification .
in contrast to previous implementations , the entanglement enhancement factor achievable by our technique is not fundamentally limited and permits recovering an epr state with a macroscopic level of entanglement no matter how low the initial entanglement or how high the loss may be . in particular , we recover the original level of entanglement after one of the epr modes has passed through a channel with a loss factor of 20 . the level of entanglement in our distilled state is higher than that achievable by direct transmission of any state through a similar loss channel .
this is a key bench - marking step towards the realization of a practical continuous - variable quantum repeater and other cv quantum protocols . .
And you have already written the first three sentences of the full article: quantum technology protocols exploit the unique properties of quantum systems to achieve communication , computing and metrology tasks that are impossible , inefficient or intractable for classical systems @xcite . in many cases the distribution of entanglement ,
correlations between subsystems that exceed those possible for classical systems , is a necessary condition for quantum technology protocols to succeed .
however , entanglement is fragile and can easily be degraded by the communication or storage of the entangled quantum systems ..
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one solution to this problem is entanglement distillation @xcite . given an ensemble of weakly entangled quantum states , distillation techniques allow one to select or distill a smaller sub - ensemble of quantum states that are more strongly entangled .
this can be achieved using only local operations and classical communication . in this way
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Suppose that you have an abstract for a scientific paper: we present results from timing observations of 27 pulsars made at the pushchino observatory over 33.5 yr between 1978 july and 2012 february .
we also analyze archival jet propulsion laboratory data of 10 pulsars to extend individual data span to 43.5 yr .
we detected a new phenomenon in the timing behavior of two pulsars , b0823 + 26 and b1929 + 10 , that demonstrates a rapid change of pulsar rotation parameters such that the sign of the second derivative @xmath0 is reversed .
an analysis of the @xmath0 changes showed that this process can be considered as a modulation process in @xmath0 .
we showed that the process of rapidly changing of pulsar rotation parameters represents a new type of rotational irregularity that , together with three other types of rotational irregularities ( discrete glitches , slow glitches and quasi - periodic oscillations ) , forms a large - scale structure of timing noise .
these effects are all the cause of the deviation of the timing behavior of most ordinary pulsars from a simple @xmath1 spin - down model .
we found that all four types of observed rotational irregularities have evolving nature .
irregularities in pulsar rotation rate pass through three evolutional stages that show that a certain type of rotational irregularity can occur only at a certain stage of pulsar rotation evolution
. the age boundaries between different evolutionary stages are indistinct and diffusive .
this fact is because different pulsars having similar properties evolve along different paths .
the evolutionary scenario of the occurrence of rotational irregularities explains well many of the observed properties of pulsar rotation . .
And you have already written the first three sentences of the full article: according to theoretical suggestions , a regular secular decrease in the pulsar rotation frequency can be described by the relation @xmath2 , where @xmath3 is the braking index @xcite . for the vacuum dipole model , when the secular spin - down is due to magnetic dipole radiation , @xmath4 .
the direct way of defining the braking index , @xmath5 , is based on a measurement of the second derivative @xmath0 from the pulsar observations .
the early timing observations showed that the rotation rate of many pulsars is subject to irregularities such as glitches ( discrete jumps in the rotation rate ) and timing noise ( variations in the pulse arrival times ) ..
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these irregularities disturb the steady secular spin down and hinder a measurement of the deterministic values of @xmath0 . for ordinary pulsars ,
the values of @xmath0 due to slowdown are very small in comparison to the measurement uncertainties and a rotation phase should be well described by a simple @xmath1 spin - down model . in actuality , most ordinary pulsars show significant deviations from a simple spin - down model .
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Suppose that you have an abstract for a scientific paper: spontaneous breaking of time - reversal symmetry in superconductors with the @xmath0 symmetry of the order parameter allows for a class of effects which are analogous to the anomalous hall effect in ferromagnets .
these effects exist below the critical temperature , @xmath1 .
we develop a kinetic theory of such effects . in particular , we consider anomalous hall thermal conductivity , the polar kerr effect , the anomalous hall effect , and the anomalous photo- and acousto - galvanic effects . _ introduction : _ one of the leading candidates for @xmath2-wave pairing in electronic systems is sr@xmath3ruo@xmath4 .
there are numerous pieces of experimental evidence that the superconducting state of sr@xmath3ruo@xmath4 has odd parity , breaks time reversal symmetry and is spin triplet @xcite .
an order parameter consistent with these experiments is given by the chiral @xmath2-wave state @xcite which is an analog of @xmath5he-@xmath6 .
it has the form @xmath7 where @xmath8 is the fourier transform of @xmath9 .
however , the observation of power laws in specific heat @xcite and nmr @xcite , the absence of electric currents along edges @xcite , and the absence of a split transition in the presence of an in - plane magnetic field @xcite are inconsistent with the theoretically expected properties of a simple chiral superconductor .
consideration of additional experimental manifestations of spontaneous breaking of time - reversal symmetry in @xmath10 superconductors may clarify the nature of superconducting state in sr@xmath3ruo@xmath4 .
due to spontaneous breaking of time - reversal symmetry , @xmath0 superconductors must exhibit anomalous transport phenomena similar to those which exist in metallic ferromagnets ( see refs .
@xcite and @xcite for a review ) . in this article
we develop a theory of several such effects in @xmath0 superconductors : the anomalous hall effect , polar kerr effect for microwave radiation , anomalous hall thermal conductivity , and anomalous photo- and acousto -....
And you have already written the first three sentences of the full article: in this appendix we obtain the scattering probability @xmath162 in eq .
( [ eq : w_kk ] ) that gives rise to anomalous transport properties . for simplicity
we consider point - like impurities whose scattering matrix elements are independent of momentum , @xmath163 ..
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skew scattering appears beyond the lowest born approximation as a result of a particular structure of the order parameter in @xmath0 superconductors .
we note that even weak impurities , @xmath164 , lead to the existence of bound states in @xmath0 superconductors with binding energies @xmath165 @xcite .
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Suppose that you have an abstract for a scientific paper: getting people cycling is an increasingly common objective in transport planning institutions worldwide .
a growing evidence base indicates that high quality infrastructure can boost local cycling rates . yet for infrastructure and other cycling measures to be effective , it is important to intervene in the right places , such as along ` desire lines ' of high latent demand .
this creates the need for tools and methods to help answer the question ` where to build ? ' .
following a brief review of the policy and research context related to this question , this paper describes the design , features and potential applications of such a tool .
the propensity to cycle tool ( pct ) is an online , interactive planning support system which was initially developed to explore and map cycling potential across england ( see http://pct.bike/[www.pct.bike ] ) .
based on origin - destination data , it models and visualises cycling levels at area , desire line , route and route network levels , for current levels of cycling , and for scenario - based ` cycling futures ' .
four scenarios are presented , including ` go dutch ' and ` ebikes ' , which explore what would happen if english people cycled as much as dutch people and the potential impact of electric cycles on cycling uptake .
the cost effectiveness of investment depends not only on the number of additional trips cycled , but on wider impacts such as health and carbon benefits .
the pct reports these at area , desire line , and route level for each scenario .
the pct is open source , facilitating the creation of additional scenarios and its deployment in new contexts .
we conclude that the pct illustrates the potential of online tools to inform transport decisions and raises the wider issue of how models should be used in transport planning . .
And you have already written the first three sentences of the full article: cycling can play an important role in creating sustainable and equitable transport systems .
cycling already provides reliable , healthy , affordable , and convenient mobility to millions of people each day ( komanoff , 2004 ) and is one of the fastest growing modes of transport in cities such as london , new york and barcelona ( fishman , 2016 ) .
there is mounting evidence about the external costs of car - dominated transport systems ( e.g. han and hayashi , 2008 ; shergold et al . , 2012 ) , and the benefits of cycling ( de nazelle et al ..
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, 2011 ; oja et al . , 2011 ; tainio et al . ,
2016 ) . in this context
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Suppose that you have an abstract for a scientific paper: we present a multi - epoch x - ray spectral analysis of the seyfert 1 galaxy fairall 9 .
our analysis shows that fairall 9 displays unique spectral variability in that its ratio residuals to a simple absorbed power law in the 0.5 - 10kev band remain constant with time in spite of large variations in flux .
this behavior implies an unchanging source geometry and the same emission processes continuously at work at the timescale probed . with the constraints from _
nustar _ on the broad - band spectral shape , it is clear that the soft excess in this source is a superposition of two different processes , one being blurred ionized reflection in the innermost parts of the accretion disk , and the other a continuum component such as spatially distinct comptonizing region . alternatively , a more complex primary comptonization component together with blurred ionized reflection could be responsible . .
And you have already written the first three sentences of the full article: the radiation from the innermost regions of active galactic nuclei ( agn ) is primarily emitted in the x - ray band , making x - ray spectroscopy a prime tool for studying this region .
moreover , the variability of the radiation can provide additional diagnostics .
flux and spectral variations in agn are usually nothing out of the ordinary ..
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the drivers and nature of this variability are known to depend on the timescale of the variability .
for example , changes in the accretion rate govern the longest timescales , and lead the continuum to become softer when brighter in the x - ray band @xcite .
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Suppose that you have an abstract for a scientific paper: experimental projects using spherical antennas to detect gravitational waves are nowdays a concrete reality .
the main purpose of this paper is to give a possible way of interpreting output data from such a system .
responses of the five fundamental quadrupole modes and of the six resonators in tiga collocations are shown as a function of the incoming direction of the incident wave .
then , for a source lying in the galactic plane , sidereal time and galactic longitude dependence is given .
thus , once a candidate source of gravitational waves is considered , we can exactly predict the resonators response as a function of time . .
And you have already written the first three sentences of the full article: theoretical interest in spherical gravitational wave ( gw ) antennas dates back to the 1970s .
spherical antennas have a greater cross - section than a bar detectors of similar dimensions .
more importantly , they have both omnidirectional and omnipolarization sensitivity , and also the potential to detect the direction of wave provenance ..
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interest in experimental research into resonant spheres has increased over the past 15 years , and today spherical antennas are recognized to be the new generation of gravitational resonant detectors , to complement existing cylindrical antennas .
two experiments are under way : minigrail in leiden ( holland ) @xcite and the graviton project in sau paulo ( brasil ) @xcite .
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Suppose that you have an abstract for a scientific paper: the security of source has become an increasingly important issue in quantum cryptography . based on the framework of measurement - device - independent quantum - key - distribution ( mdi - qkd ) ,
the source becomes the only region exploitable by a potential eavesdropper ( eve ) .
phase randomization is a cornerstone assumption in most discrete - variable ( dv- ) quantum communication protocols ( e.g. , qkd , quantum coin tossing , weak coherent state blind quantum computing , and so on ) , and the violation of such an assumption is thus fatal to the security of those protocols . in this paper , we show a simple quantum hacking strategy , with commercial and homemade pulsed lasers , by eve that allows her to actively tamper with the source and violate such an assumption , without leaving a trace afterwards . furthermore , our attack may also be valid for continuous - variable ( cv- ) qkd , which is another main class of qkd protocol , since , excepting the phase random assumption , other parameters ( e.g. , intensity ) could also be changed , which directly determine the security of cv - qkd . .
And you have already written the first three sentences of the full article: quantum key distribution ( qkd ) @xcite allows two remote parties to share an unconditional secret key , which has been proven in theory @xcite and demonstrated in experiment @xcite .
however , the imperfections of practical devices will compromise the security of qkd systems @xcite .
so far , three main approaches have been proposed to bridge the gap between theory and practice ..
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the first one is to close specific loopholes of devices with security patches @xcite , but it could not close potential and unnoticed loopholes .
the second one is device - independent ( di- ) qkd @xcite . by testing bells inequality in a loophole - free setting
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Suppose that you have an abstract for a scientific paper: we explore prethermal floquet steady states and instabilities of the weakly interacting two - dimensional bose - hubbard model subject to periodic driving .
we develop a description of the nonequilibrium dynamics , at arbitrary drive strength and frequency , using a weak - coupling conserving approximation .
we establish the regimes in which conventional ( zero - momentum ) and unconventional [ @xmath0-momentum ] condensates are stable on intermediate time scales .
we find that condensate stability is _ enhanced _ by increasing the drive strength , because this decreases the bandwidth of quasiparticle excitations and thus impedes resonant absorption and heating .
our results are directly relevant to a number of current experiments with ultracold bosons .
periodically driven systems@xcite often exhibit exotic phenomena that are absent in their non - driven counterparts@xcite .
classic examples include the kapitza pendulum and the periodically kicked rotor .
recently , periodically modulating optical lattices has attracted interest as a way of controlling hopping processes@xcite in order to engineer gauge fields@xcite , topological band structures@xcite , and associated exotic states of matter .
such exotic states are known to exist in noninteracting systems and in certain mean - field models ; the extent to which they survive in the presence of interactions is a central open question .
it is believed , from the eigenstate thermalization hypothesis@xcite , that driven interacting systems will generically heat up to infinite temperature at sufficiently late times@xcite . nevertheless , in some parameter regimes these heating times will be parametrically slower than the system s characteristic time scales . in that case , the system will rapidly approach a `` prethermalized '' floquet steady state@xcite , which governs the dynamics until the much later heating time scales . in the present work , we study these prethermal states in the weakly interacting , two - dimensional , periodically....
And you have already written the first three sentences of the full article: in this appendix , we begin by discussing the transformation of the driven bhm from the lab frame to the rotating frame , before doing a bogoliubov stability analysis .
the rotating frame is defined by the unitary transformation @xmath88\cdot \sum_j { \bf r}_j n_j \right),\ \ \ \ \
b_j\to b_j e^{-i\mathcal{a}(t)\cdot{\bf r}_j},\end{aligned}\ ] ] where @xmath11.
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. this time - dependent change of basis is equivalent to the standard gauge transformation in electromagnetism @xmath89 .
physically , the transformation trades the fast time - dependence of the quasimomentum for a time oscillating dispersion relation .
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Suppose that you have an abstract for a scientific paper: the first results on the searches of the higgs boson appeared this summer from the lhc and tevatron groups , and has been recently backed up by the atlas and cms experiments taking data at cern s lhc . even though the excitement that this particle has been detected is still premature , the new data constrain the mass of the lightest higgs boson @xmath0 to a very narrow 120140 gev region with a possible peak at approximately 125 gev . in this communication we shortly present the higgs sector in a minimal supergravity model with broken @xmath1-parity . imposing the constraint on @xmath0
we show that there is a relatively large set of free parameters of the model , for which that constraint is fulfilled .
we indetify also points which result in the lightest higgs boson mass being approximately 125 gev .
also the dependence on the magnitude of the @xmath1parity admixture to the model is discussed . .
And you have already written the first three sentences of the full article: the standard model and most of its supersymmetric extensions suffer from being a theory of massless particles .
therefore a mechanism that would provide masses is required . among several possibilities the higgs mechanism plays a major role .
it assumes the existence of an additional scalar field , the higgs field , which has non - zero vacuum expectation value ( vev ) ..
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the correct implementation of this mechanism leads in the standard model not only to massive gauge bosons ( with the photon correctly remaining massless ) , but also to massive fermions , and a proper electroweak symmetry breaking from the weak gauge groups @xmath2 to the electromagnetism @xmath3 .
these features make this mechanism an extremely convenient and elegant solution
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Suppose that you have an abstract for a scientific paper: issues on the physics of , beamlines for , and detectors of neutrino oscillation discussed in working group 2 at nufact02 are summarized . .
And you have already written the first three sentences of the full article: the way people are thinking about neutrino oscillations and how a neutrino factory fits into a program of measurements has changed dramatically between previous nufact workshops and this one .
although we still consider a neutrino factory the ultimate facility to do precision oscillation measurements , we are becoming more aware of what one can learn with conventional neutrino beams . understanding how much of the possible parameter space one can explore with conventional beams , and how these experiments might complement neutrino factory measurements
has kept many phenomenologists busy this past year ..
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the oscillation working group also has included for the first time discussions on different proposals for these super conventional neutrino beams , as well as a new idea for making a pure @xmath0 or @xmath1 beam , which can be done by accelerating radioactive ions which undergo beta decay . with these new techniques for measurements , new issues
become relevant : cross sections , beam systematics , and backgrounds , the three things that were so straightforward to tackle in the case of neutrino factory experiments . while the experimental picture is changing ,
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Suppose that you have an abstract for a scientific paper: it has been recently shown that in the heisenberg ( anti)ferromagnet on the honeycomb lattice , the magnons ( spin wave quasipacticles ) realize a massless two - dimensional ( 2d ) dirac - like hamiltonian .
it was shown that the dirac magnon hamiltonian preserves time - reversal symmetry defined with the sublattice pseudo spins and the dirac points are robust against magnon - magnon interactions
. the dirac points also occur at nonzero energy . in this paper
, we propose a simple realization of nontrivial topology ( magnon edge states ) in this system .
we show that the dirac points are gapped when the inversion symmetry of the lattice is broken by introducing a next - nearest neighbour dzyaloshinskii - moriya ( dm ) interaction .
thus , the system realizes magnon edge states similar to haldane model for quantum anomalous hall effect in electronic systems .
however , in contrast to electronic spin current where dissipation can be very large due to ohmic heating , noninteracting topological magnons can propagate for long time without dissipation as magnons are uncharged particles .
we observe the same magnon edge states for the xy model on the honeycomb lattice .
remarkably , in this case the model maps to interacting hardcore bosons on the honeycomb lattice .
quantum magnetic systems with nontrivial magnon edge states are called topological magnon insulators .
they have been studied theoretically on the kagome lattice and recently observed experimentally on the kagome magnet cu(1 - 3 , bdc ) with three magnon bulk bands .
our results for the honeycomb lattice suggests an experimental procedure to search for honeycomb topological magnon insulators within a class of 2d quantum magnets and ultracold atoms trapped in honeycomb optical lattices . in 3d lattices , dirac and weyl points were recently studied theoretically , however , the criteria that give rise to them were not well - understood .
we argue that the low - energy hamiltonian near the weyl points should break time - reversal....
And you have already written the first three sentences of the full article: topological properties of fermion band theory have dominated research in condensed matter physics and other areas over the past decade or so @xcite . recently , it has been shown that the magnon bulk bands of heisenberg ( anti)ferromagnet on the honeycomb lattice exhibit dirac points at the corners of the brillouin zone ( bz ) @xcite .
the low - energy hamiltonian near these points realizes a massless 2d dirac - like hamiltonian with dirac nodes at nonzero energy
. this system preserves pseudo spin time - reversal ( @xmath0 ) symmetry ..
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it was also shown that the dirac points are robust against magnon - magnon interactions and any perturbation that preserves the pseudo spin @xmath0-symmetry of the bogoluibov hamiltonian . in this paper , we provide evidence of non - trivial topology ( magnon edge states ) in the magnon bulk bands of heisenberg ( anti)ferromagnet and xy model on the honeycomb lattice , when a gap opens at the dirac points . we show that the simplest practical way to open a gap at the dirac points is by breaking the inversion symmetry of the lattice , which subsequently breaks the pseudo spin @xmath0-symmetry of the bogoliubov hamiltonian . we show that this can be achieved by introducing a next - nearest neighbour dzyaloshinskii - moriya ( dm ) interaction .
the opening of a gap at the dirac points leads to magnon edge states reminiscent of haldane model in electronic systems @xcite . in the case of xy model
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Suppose that you have an abstract for a scientific paper: the normal state and superconducting properties are investigated in the phase diagram of k@xmath0sr@xmath1fe@xmath2as@xmath2 for 0@xmath3x@xmath31 .
the ground state upper critical field , h@xmath4(0 ) , is extrapolated from magnetic field dependent resistivity measurements .
h@xmath4(0 ) scales with the critical temperature , t@xmath5 , of the superconducting transition . in the normal state
the seebeck coefficient is shown to experience a dramatic change near a critical substitution of [email protected] .
this is associated with the formation of a spin density wave state above the superconducting transition temperature .
the results provide strong evidence for the reconstruction of the fermi surface with the onset of magnetic order . .
And you have already written the first three sentences of the full article: the discovery of high - temperature superconductivity in rare earth ( r ) oxypnictides , rofeas @xcite , has initiated extensive research activities in this class of compounds @xcite .
the main structural building block of the feas - based superconductors is the fe@xmath2as@xmath2 layer with tetrahedrally coordinated fe covalently bonded to 4 as atoms .
the fe@xmath2as@xmath2 blocks are the active layers for the observed superconductivity and they are separated by charge reservoir layers that can modify or change the average charge of the active layer through appropriate chemical substitutions . in rofeas the appropriate doping can be achieved by substituting f for o @xcite or by removing oxygen @xcite . however , the amount of charge carriers introduced is limited and attempts to achieve higher carrier densities in the fe@xmath2as@xmath2 layers of the rofeas system frequently results in chemical disproportionation and decomposition and the formation of impurity phases @xcite ..
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the fe@xmath2as@xmath2 layers are very rigid and the charge reservoir blocks can be replaced by different oxygen - free layers , for example , by single layers of alkali metal or alkaline earth ( ae = ca , sr , ba ) ions .
stable structures of kfe@xmath2as@xmath2 , csfe@xmath2as@xmath2 @xcite , and lifeas @xcite have been synthesized and found superconducting at different temperatures .
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Suppose that you have an abstract for a scientific paper: we have investigated the variation of magnetic helicity over a span of several days around the times of 11 x - class flares which occurred in seven active regions ( noaa 9672 , 10030 , 10314 , 10486 , 10564 , 10696 , and 10720 ) using the magnetograms taken by the michelson doppler imager ( mdi ) on board the @xmath0 @xmath1 @xmath2 @xmath3 ( @xmath4 ) . as a major result we found that each of these major flares was preceded by a significant helicity accumulation , ( 1.816)@xmath510@xmath6 mx@xmath7 over a long period ( 0.5 to a few days ) .
another finding is that the helicity accumulates at a nearly constant rate , ( 4.548)@xmath510@xmath8 mx@xmath7 hr@xmath9 , and then becomes nearly constant before the flares .
this led us to distinguish the helicity variation into two phases : a phase of monotonically increasing helicity and the following phase of relatively constant helicity .
as expected , the amount of helicity accumulated shows a modest correlation with time - integrated soft x - ray flux during flares .
however , the average helicity change rate in the first phase shows even stronger correlation with the time - integrated soft x - ray flux .
we discuss the physical implications of this result and the possibility that this characteristic helicity variation pattern can be used as an early warning sign for solar eruptions . .
And you have already written the first three sentences of the full article: magnetic helicity is a measure of twists , kinks , and inter - linkages of magnetic field lines ( berger & field 1984 ) and has been an important parameter in solar dynamo theories ( parker 1955 ) .
while the source of the magnetic helicity lies below the surface of the sun , it was recently recognized as a useful parameter in describing solar features observed above surface such as spiral patterns of sunspot fibrils , helical patterns in filaments and coronal mass ejections ( cmes ; for a review , see brown et al .
naturally magnetic helicity studies have been directed to the energy buildup and instability leading to eruptions and cmes ( e.g. , rust 2001 ; kusano et al ..
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2004 ; phillips et al . 2005 ) .
more recently , several studies were carried out to relate the change of magnetic helicity to the problem of impending or triggering solar flares .
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Suppose that you have an abstract for a scientific paper: the spin - orbit splitting of the electron levels in a two - dimensional quantum dot in a perpendicular magnetic field is studied .
it is shown that at the point of an accidental degeneracy of the two lowest levels above the ground state the rashba spin - orbit coupling leads to a level anticrossing and to mixing of spin - up and spin - down states , whereas there is no mixing of these levels due to the dresselhaus term .
we calculate the relaxation and decoherence times of the three lowest levels due to phonons .
we find that the spin relaxation rate as a function of a magnetic field exhibits a cusplike structure for rashba but not for dresselhaus spin - orbit interaction . .
And you have already written the first three sentences of the full article: recent years have seen an increasing interest in the spin properties of nanostructures @xcite .
manipulation and readout of spins in solids could open the way to the development of a generation of electronic devices such as spin transistors , spin filters , and spin memory devices .
in addition , the spin of an electron confined to a quantum dot ( qd ) is a promising candidate for a quantum bit @xcite ..
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owing to the zero dimensionality of qds , the electronic orbital states are quantized and the electron spin states are very stable due to a substantial suppression of spin - flip mechanisms @xcite .
progress in nanotechnology has allowed the fabrication of qds with desirable electronic and spin properties @xcite .
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Suppose that you have an abstract for a scientific paper: we study the dynamic structure factor of two coherent bright solitary waves in attractive bose - einstein condensates confined in a harmonic trap .
we demonstrate that the wave function of the two solitary waves with a fixed relative phase shows interference in momentum space .
the fringes are shifted depending on the values of the phase .
this momentum interference can be extracted from the dynamic structure factor of the system using stimulated two - photon bragg scattering .
thus our method provides a way to measure the relative phase directly . .
And you have already written the first three sentences of the full article: bose - einstein condensates ( becs ) with attractive two - body interaction are dynamically unstable in a trap if the number of condensed atoms reaches a critical value @xcite .
generally , hefty becs will collapse following a switch of the s - wave scattering length from a positive value ( or zero ) to a negative one via the use of a feshbach resonance @xcite .
however it was found that in such case the number of remnant condensate atoms can be above the critical number @xcite ..
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this was explained by the generation of bright solitary waves with repulsive interactions @xcite .
these repulsive interactions have been used to indirectly infer a repulsive relative phase @xmath0 @xcite between neighbor solitons @xcite .
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Suppose that you have an abstract for a scientific paper: we use the poor man s scaling approach to study the phase boundaries of a pair of quantum impurity models featuring a power - law density of states @xmath0 that gives rise to quantum phase transitions between local - moment and kondo - screened phases . for the anderson model with a pseudogap ( i.e. , @xmath1 )
, we find the phase boundary for ( a ) @xmath2 , a range over which the model exhibits interacting quantum critical points both at and away from particle - hole symmetry , and ( b ) @xmath3 , where the phases are separated by first - order quantum phase transitions .
for the particle - hole - symmetric kondo model with easy - axis or easy - plane anisotropy of the spin exchange , the phase boundary and scaling trajectories are obtained for both @xmath1 and @xmath4 ( the later case describing a density of states that diverges at the fermi energy ) .
comparison with nonperturbative results from the numerical renormalization group shows that poor man s scaling correctly describes the shape of phase boundaries expressed as functional relations between model parameters . .
And you have already written the first three sentences of the full article: the kondo problem the question of how an impurity local moment becomes screened at low temperatures by the conduction electrons of a host metal was highly influential in stimulating the development of theoretical and numerical methods for treating strongly correlated condensed matter @xcite .
perturbative treatments of the spin - flip scattering between local and delocalized spins necessarily break down below a characteristic kondo temperature scale , giving rise to a complex many body problem .
nonetheless , much valuable understanding of the kondo problem has come from perturbative renormalization - group ( rg ) @xcite and perturbative scaling @xcite approaches ..
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these were distilled into their simplest form in the poor man s scaling of anderson @xcite . in poor man
s scaling , electron states far from the fermi energy are progressively eliminated as the effective bandwidth is reduced with a compensating adjustment of a dimensionless measure of the effective impurity - band exchange coupling .
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Suppose that you have an abstract for a scientific paper: the size distribution and total mass of objects in the oort cloud have important implications to the theory of planets formation , including the properties of , and the processes taking place in the early solar system .
we discuss the potential of space missions like _ kepler _ and _ corot _ , designed to discover transiting exo - planets , to detect oort cloud , kuiper belt and main belt objects by occultations of background stars . relying
on published dynamical estimates of the content of the oort cloud , we find that _ kepler _ s main program is expected to detect between @xmath0 and @xmath1 occultation events by deca - kilometer - sized oort cloud objects .
the occultations rate depends on the mass of the oort cloud , the distance to its `` inner edge '' , and the size distribution of its objects .
in contrast , _ kepler _ is unlikely to find occultations by kuiper belt or main belt asteroids , mainly due to the fact that it is observing a high ecliptic latitude field .
occultations by solar system objects will appear as a photometric deviation in a single measurement , implying that the information regarding the time scale and light - curve shape of each event is lost .
we present statistical methods that have the potential to verify the authenticity of occultation events by solar system objects , to estimate the distance to the occulting population , and to constrain their size distribution .
our results are useful for planning of future space - based exo - planet searches in a way that will maximize the probability of detecting solar system objects , without hampering the main science goals . .
And you have already written the first three sentences of the full article: oort ( 1950 ) postulated the existence of a cloud of comets orbiting the sun with typical semi - major axes , @xmath2 , of @xmath3au .
this cloud is required to explain the existence of long period comets and the fact that a considerable fraction of these comets have orbital energies concentrated in a narrow range , corresponding to @xmath4 au@xmath5 . however , to date no direct observation of objects in the oort cloud exist .
dynamical simulations suggest that the oort cloud was formed by the ejection of icy planetesimals from the jupiter - neptune region by planetary perturbations ( e.g. , duncan et al 1987 ; dones et al ..
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2004 ) . on orbital
time scales , galactic tides and passage of nearby stars raised the perihelia of these comets above the region of the giant planets influence .
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Suppose that you have an abstract for a scientific paper: the nucleon electromagnetic form factors @xmath0 and @xmath1 are complex quantities in the time - like region .
the absolute values can be determined by measuring the angular distribution of the nucleons in @xmath2 .
the complex phase can only be determined by measuring one or more polarizations of the initial or final state . for pep - n
, we can use unpolarized @xmath3 and @xmath4 and measure the polarization of one of the outgoing nucleons . .
And you have already written the first three sentences of the full article: the electromagnetic form factors of the nucleons , @xmath5 and @xmath6 , depend on @xmath7 . in the space - like region
they are relatively real .
they have been measured using @xmath8 elastic scattering where @xmath9 is the is the absolute value of the four - momentum transfer from the incoming lepton to the nucleon ..
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the techniques used are : 1 .
rosenbluth separation : measurements made at at least two angles and fixed @xmath7 .
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Suppose that you have an abstract for a scientific paper: thanks to its intrinsic ability to preserve spin coherence , graphene is a prime material for spintronics . in this review article , we summarize recent achievements related to spintronics in graphene quantum dots and motivate this field from a spintronics and a materials science point of view .
we focus on theory but also discuss recent experiments .
the main sources of spin decoherence are interactions with lattice excitations and the hyperfine interaction with present nuclear spins .
we explain effective spin - phonon coupling in detail and present a generic power law for the spin relaxation time @xmath0 as a function of the magnetic field . for specific cases ,
we discuss spin relaxation in detail .
the heisenberg exchange interaction is paramount for coherent spin qubit operation and addressed in the context of magnetism in graphene nanoflakes .
nuclear spins in the host and surrounding material can be considered by several means and the influence of @xmath1c nuclei has been studied in detail .
impressive advances in general spintronics and the fabrication of graphene devices are likely to spark significant advances in spintronics with graphene quantum dots in the near future . .
And you have already written the first three sentences of the full article: spintronics and graphene are exciting , vigorous , and rather new areas of research with a rapid pace of new discoveries
. books and a multitude of review articles are available for those that want to learn about one of these fields [ ] .
the intersection of both provides fertile soil for an abundance of fascinating physics and its fruits have been partially reaped by previous reviews [ ] . here.
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, we put the cherry on the cake and review specifically spintronics in graphene quantum dots . while classical electronics relies on the charge for information processing , spin - based electronics or _
spintronics _ is the paradigm of an advanced technology where the spin degree of freedom complements or even replaces charge as the carrier of information . the expected benefits of spintronics encompass non - volatile data storage , faster and more energy efficient data processing , increased data density , and many more . in order to fully exploit the potential , efficient generation , transport , transfer , manipulation , and detection of spin polarization
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Suppose that you have an abstract for a scientific paper: we discuss the approximation of distributed null controls for partial differential equations .
the main purpose is to determine an approximation of controls that drives the solution from a prescribed initial state at the initial time to the zero target at a prescribed final time . as a non trivial example
, we mainly focus on the stokes system for which the existence of square - integrable controls have been obtained in _ [ fursikov & imanuvilov , controllability of evolution equations , 1996 ] ) _ via carleman type estimates .
we introduce a least - squares formulation of the controllability problem , and we show that it allows the construction of strong convergent sequences of functions toward null controls for the stokes system .
the approach consists first in introducing a class of functions satisfying _ a priori _ the boundary conditions in space and time - in particular the null controllability condition at time @xmath0 - , and then finding among this class one element satisfying the system .
this second step is done by minimizing a quadratic functional , among the admissible corrector functions of the stokes system .
we also discuss briefly the direct problem for the steady navier - stokes system .
the method does not make use of any duality arguments and therefore avoid the ill - posedness of dual methods , when parabolic type equation are considered . .
And you have already written the first three sentences of the full article: let @xmath1 , @xmath2 or @xmath3 be a bounded connected open set whose boundary @xmath4 is lipschitz .
let @xmath5 be a ( small ) nonempty open subset , and assume that @xmath6 .
we use the notation @xmath7 , @xmath8 and we denote by @xmath9 the outward unit normal to @xmath10 at any point @xmath11 . bold letters and.
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symbols denote vector - valued functions and spaces ; for instance @xmath12 is the hilbert space of the functions @xmath13 with @xmath14 for all @xmath15 .
this work is related to the null controllability problem for the non - stationary stokes system @xmath16 which describes a viscous incompressible fluid flow in the bounded domain @xmath10 .
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Suppose that you have an abstract for a scientific paper: we are carrying out a search for ly@xmath0 emitting galaxies at @xmath1 employing slitless spectroscopy at the vlt . in our 43 arcmin@xmath2 field
we find three isolated single emission lines with seds consistent with line emitting galaxies at @xmath3 . .
And you have already written the first three sentences of the full article: since the discovery of @xmath4 lyman break galaxies ( lbgs @xcite ) , many efforts are being made to select the whole population of star - forming galaxies at the highest possible redshifts ( see @xcite for a review ) , and to constrain the star formation history of the universe ( e.g. @xcite ) .
the detection of @xmath5 galaxies allows to study the modes of early galaxy formation and the interplay between the first galaxies and the intergalactic medium ( igm ) .
the redshift range @xmath6 is a very intriguing time during cosmic evolution , when hydrogen reionization is believed to be basically complete and the igm starts to be polluted with metals @xcite . because a significant part of the bolometric luminosity of primeval star - forming objects escapes as ly@xmath0 emission , especially if dust is not yet ubiquitous , it seems profitable to search for the redshifted ly@xmath0 line of high redshift galaxies ..
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the advent of ten meter class telescopes made this approach successful and efficient , and both narrow - band imaging and optical _ serendipitous _ spectroscopy found ly@xmath0 emitters at @xmath7 @xcite . thanks to the recently increased sensitivity of ccds at @xmath8 m , the discovery of @xmath9 galaxies has also become possible . using narrow band filters sensitive to wavelengths in the range @xmath10 , i.e. ly@xmath0 emission at @xmath11 and subsequent spectroscopy ,
two groups have detected the first three galaxies known at @xmath5 .
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Suppose that you have an abstract for a scientific paper: in recent years , a large number of geosynchronous satellites are being planned to provide augmentation services for enhancing the precision to global positioning systems , e.g. , gps , in applications such as aircraft landing . in this paper , we present a scheme for co - locating passive satellite observational facilities with a radio astronomy facility to open a new possibility of providing valuable data for radio astronomical imaging , ionospheric studies and satellite orbit estimation .
interferometry , navigation satellites , radio astronomy .
And you have already written the first three sentences of the full article: recent years , an increasing number of geosynchronous satellites are being planned to cope with the need of providing regional navigation services or augmentation to global systems like the gps . from various announcements made by the indian space research organization ( isro )
, one can expect at least 9 geosynchronous satellites to be commissioned by isro within the next few years with dual frequency synchronized payloads @xcite@xcite . among these
, the first satellite , gsat-8 , has been launched recently and is likely to commence regular broadcast of waas messages from september 2011 , as part of the gagan project @xcite ..
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gagan aims to enhance the precision achievable by gps - based systems for assisting air - craft landing .
a second geosynchronous satellite with a gagan payload has been announced for launch during early 2012 .
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Suppose that you have an abstract for a scientific paper: the physics responsible for gauge coupling unification may also induce small neutrino masses . we propose a novel gauge mediated radiative seesaw mechanism for calculable neutrino masses .
these arise from quantum corrections mediated by new ( 3 - 3 - 1 ) gauge bosons and the physics driving gauge coupling unification .
gauge couplings unify for a 3 - 3 - 1 scale in the tev range , making the model directly testable at the lhc . .
And you have already written the first three sentences of the full article: the fact that gauge coupling unification is a `` near - miss '' within the standard model ( sm ) provides an indication in favor of the idea of unification @xcite .
likewise , the existence of neutrino masses , required to account for neutrino oscillation data @xcite , also provides another motivation towards unified or gut ( grand unified theory)-like extensions of the sm .
however , the most characteristic feature of gut - type unification , namely matter instability , has so far defied experimental confirmation @xcite . on the other hand , neither the generation of neutrino masses nor the tilting in the evolution of the gauge couplings require unification in the conventional sense ..
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for instance , it is well known that the gauge couplings merge in the minimal supersymmetric extension the sm , provided that supersymmetric states lie around the tev scale @xcite .
so far , though , there has been no trace of such states in the lhc data @xcite .
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Suppose that you have an abstract for a scientific paper: we present the first global 3d simulations of thermal convection in the oblate envelopes of rapidly - rotating solar - type stars .
this has been achieved by exploiting the capabilities of the new compressible high - order unstructured spectral difference ( chorus ) code .
we consider rotation rates up to 85% of the critical ( breakup ) rotation rate , which yields an equatorial radius that is up to 17% larger than the polar radius .
this substantial oblateness enhances the disparity between polar and equatorial modes of convection .
we find that the convection redistributes the heat flux emitted from the outer surface , leading to an enhancement of the heat flux in the polar and equatorial regions .
this finding implies that lower - mass stars with convective envelopes may not have darker equators as predicted by classical gravity darkening arguments .
the vigorous high - latitude convection also establishes elongated axisymmetric circulation cells and zonal jets in the polar regions .
though the overall amplitude of the surface differential rotation , @xmath0 , is insensitive to the oblateness , the oblateness does limit the fractional kinetic energy contained in the differential rotation to no more than 61% .
furthermore , we argue that this level of differential rotation is not enough to have a significant impact on the oblateness of the star . .
And you have already written the first three sentences of the full article: most stars are born spinning rapidly . observations of young clusters reveal a wide range of rotation rates , with some stars spinning more than 100 times faster than the sun ( e.g. * ? ? ?
* ; * ? ? ?
* ; * ? ? ?.
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this scatter is generally attributed to the vortical nature of the turbulent interstellar clouds from which these stars form . though much of the initial angular momentum is lost during the gravitational collapse of a protostellar core , the dramatic decrease in the moment of inertia during
the collapse is enough to impart a substantial rotational velocity in a large fraction of young stars . as the stars age
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Suppose that you have an abstract for a scientific paper: we present a unified framework to derive fundamental stellar parameters by combining all available observational and theoretical information for a star .
the algorithm relies on the method of bayesian inference , which for the first time directly integrates the spectroscopic analysis pipeline based on the global spectrum synthesis and allows for comprehensive and objective error calculations given the priors .
arbitrary input datasets can be included into our analysis and other stellar quantities , in addition to stellar age , effective temperature , surface gravity , and metallicity , can be computed on demand .
we lay out the mathematical framework of the method and apply it to several observational datasets , including high- and low - resolution spectra ( uves , narval , harps , sdss / segue ) .
we find that simpler approximations for the spectroscopic pdf , which are inherent to past bayesian approaches , lead to deviations of several standard deviations and unreliable errors on the same data . by its flexibility and the simultaneous analysis of multiple independent measurements for a star
, it will be ideal to analyse and cross - calibrate the large ongoing and forthcoming surveys , like gaia - eso , sdss , gaia and lsst .
[ firstpage ] stars : fundamental parameters stars : distances techniques : photometric techniques : spectroscopic methods : statistical methods : data analysis .
And you have already written the first three sentences of the full article: observations are a central source of knowledge on almost any entity in astrophysics . over several centuries of intense research
, several principal observational techniques have been developed that are now routinely used to study stars and stellar populations in the milky way and other galaxies .
we have information from astrometry , photometry , spectroscopy , but also interferometry , and astroseismology , that give complementary information on the physical parameters of stars ( detailed chemical composition , gravities , temperatures , masses and ages ) and their kinematics ( radial velocities , distances , and orbital characteristics ) ..
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however , in contrast to e.g. cosmology , where sophisticated bayesian schemes are well established ( e.g. * ? ? ?
* ; * ? ? ?
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Suppose that you have an abstract for a scientific paper: we study plasma oscillations in a flux tube of the dual superconductor model of t hooft and mandelstam . a magnetic condensate is coupled to an electromagnetic field by its dual vector potential , and fixed electric charges set up a flux tube .
an electrically charged fluid ( a quark plasma ) flows in the tube and screens the fixed charges via plasma oscillations .
we investigate both type i and type ii superconductors , with plasma frequencies both above and below the threshold for radiation into the higgs vacuum .
we find strong radiation of electric flux into the superconductor in all regimes , and argue that this invalidates the use of the simplest dual superconductor model for dynamical problems . .
And you have already written the first three sentences of the full article: the confinement of color in quantum chromodynamics is explained if color electric fields form flux tubes .
these flux tubes appear readily in the bag model @xcite , but this is a geometric picture rather than a dynamical one .
hooft @xcite and mandelstam @xcite proposed that , just as magnetic flux tubes form in a superconductor @xcite , a condensation of magnetic charge in the qcd vacuum would lead to the formation of electric flux tubes and confinement ..
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this is the dual superconductor picture of confinement .
the analytical study of the confining flux tube depends largely on a classical , abelian model .
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Suppose that you have an abstract for a scientific paper: we show how to construct an algorithm to search for binary idempotents which may be used to construct binary ldpc codes .
the algorithm , which allows control of the key properties of sparseness , code rate and minimum distance , is constructed in the mattson - solomon domain .
some of the new codes , found by using this technique , are displayed .
* idempotents , polynomials and binary ldpc codes * + r. horan , c. tjhai , m. tomlinson , m. ambroze and m. ahmed + _ fixed and mobile communications research _ + _ university of plymouth , pl4 8aa , united kingdom _ + * * .
And you have already written the first three sentences of the full article: the use of idempotents in the construction of cyclic error correcting codes is well established and the resulting literature is extensive ( for example , see @xcite,@xcite,@xcite ) .
the basic building blocks for this theory are the primitive idempotents .
any cyclic code may be described by a unique idempotent and this idempotent is a sum of primitive idempotents . for binary cyclic codes ,.
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efficient algorithms exist for the calculation of these primitive idempotents .
another way of constructing idempotents in the binary case is by using cyclotomic cosets and it was this property which was exploited by shibuya and sakaniwa in @xcite .
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Suppose that you have an abstract for a scientific paper: we calculate nuclear suppression @xmath0 of heavy quarks produced from the initial fusion of partons in nucleus - nucleus collisions at rhic and lhc energies .
we take the shadowing as well as the energy loss suffered by them while passing through quark gluon plasma into account .
we obtain results for charm and bottom quarks at several rapidities using different mechanisms for energy loss , to see if we can distinguish between them . .
And you have already written the first three sentences of the full article: the heavy ion collision experiments at rhic and lhc are designed with a hope to explore the existence of a new form of matter known as quark gluon plasma ( qgp ) and to explore its properties .
the estimation for the energy density @xcite attained in these collisions using the bjorken formula @xcite is well beyond the energy densities where qgp is expected to be formed .
the temperatures reached at rhic , as revealed from several studies ( see e.g. , @xcite for a compilation ) are also much larger than the values provided by lattice qcd calculations for the critical temperature for a transition to qgp @xcite ..
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strong confirmation of the formation of the qgp is given by observation of a large elliptic flow @xcite , jet - quenching @xcite , and the recombination of partons as the mechanism of production of hadrons at intermediate transverse momenta @xcite .
still higher temperatures are likely to be reached at lhc .
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Suppose that you have an abstract for a scientific paper: we propose a new class of estimators for pickands dependence function which is based on the concept of minimum distance estimation .
an explicit integral representation of the function @xmath0 , which minimizes a weighted @xmath1-distance between the logarithm of the copula @xmath2 and functions of the form @xmath3 is derived .
if the unknown copula is an extreme - value copula , the function @xmath0 coincides with pickands dependence function .
moreover , even if this is not the case , the function @xmath0 always satisfies the boundary conditions of a pickands dependence function .
the estimators are obtained by replacing the unknown copula by its empirical counterpart and weak convergence of the corresponding process is shown .
a comparison with the commonly used estimators is performed from a theoretical point of view and by means of a simulation study .
our asymptotic and numerical results indicate that some of the new estimators outperform the estimators , which were recently proposed by genest and segers [ _ ann .
statist . _
* 37 * ( 2009 ) 29903022 ] . as a by - product of our results
, we obtain a simple test for the hypothesis of an extreme - value copula , which is consistent against all positive quadrant dependent alternatives satisfying weak differentiability assumptions of first . , and . .
And you have already written the first three sentences of the full article: the copula provides an elegant margin - free description of the dependence structure of a random variable . by the famous theorem of @xcite
, it follows that the distribution function @xmath4 of a bivariate random variable @xmath5 can be represented in terms of the marginal distributions @xmath6 and @xmath7 of @xmath8 and @xmath9 , that is , @xmath10 where @xmath11 denotes the copula , which characterizes the dependence between @xmath8 and @xmath9 .
extreme - value copulas arise naturally as the possible limits of copulas of component - wise maxima of independent , identically distributed or strongly mixing stationary sequences [ see @xcite and @xcite ] ..
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these copulas provide flexible tools for modeling joint extremes in risk management .
an important application of extreme - value copulas appears in the modeling of data with positive dependence , and in contrast to the more popular class of archimedean copulas they are not symmetric [ see @xcite or @xcite ] .
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Suppose that you have an abstract for a scientific paper: we compute spectral energy distributions ( seds ) for passive t tauri disks viewed at arbitrary inclinations .
semi - analytic models of disks in radiative and hydrostatic equilibrium are employed . over viewing angles for which the flared disk does not occult the central star , the sed varies negligibly with inclination . for such aspects ,
the sed shortward of @xmath080@xmath1 is particularly insensitive to orientation , since short wavelength disk emission is dominated by superheated surface layers which are optically thin .
the sed of a nearly edge - on disk is that of a class i source .
the outer disk occults inner disk regions , and emission shortward of @xmath030@xmath1 is dramatically extinguished .
spectral features from dust grains may appear in absorption .
however , millimeter wavelength fluxes decrease by at most a factor of 2 from face - on to edge - on orientations .
we present illustrative applications of our sed models . the class i source 04108 + 2803b is considered a t tauri star hidden from view by an inclined circumstellar disk
. fits to its observed sed yield model - dependent values for the disk mass of @xmath00.015 @xmath2 and a disk inclination of @xmath065@xmath3 relative to face - on .
the class ii source gm aur represents a t tauri star unobscured by its circumstellar disk .
fitted parameters include a disk mass of @xmath00.050 @xmath2 and an inclination of @xmath0@xmath4 . .
And you have already written the first three sentences of the full article: excess infrared ( ir ) emission from t tauri stars is thought to originate from circumstellar disks ( mendoza 1968 ; shu , adams , & lizano 1987 ; and references therein ) .
passive disks are the simplest to consider . by definition ,
they lack intrinsic luminosity and reradiate the energy they absorb from the central star ..
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hydrostatic , radiative equilibrium models for passive t tauri disks are derived by chiang & goldreich ( 1997 , hereafter cg ) .
the disk surface flares outward with increasing radius and intercepts more stellar radiation , especially at large distances from the central star , than a flat disk would ( kenyon & hartmann 1987 ) .
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Suppose that you have an abstract for a scientific paper: we present _ spitzer_/irac photometry on the star - forming h ii region
n 90 , related to the young stellar association ngc 602 in the small magellanic cloud .
our photometry revealed bright mid - infrared sources , which we classify with the use of a scheme based on templates and models of red sources in the milky way , and criteria recently developed from the _ spitzer _ survey of the smc ( bolatto et al .
2007 ) for the selection of candidate young stellar objects ( ysos ) .
we detected 57 sources in all four irac channels in a 62 @xmath0 48 field - of - view centered on n 90 ; 22 of these sources are classified as candidate ysos .
we compare the locations of these objects with the position of optical sources recently found in the same region with high - resolution hst / acs imaging of ngc 602 by schmalzl et al .
( 2007 ) , and we find that 17 candidate ysos have one or more optical counterparts .
all of these optical sources are identified as pre - main sequence stars , indicating , thus , ongoing clustered star formation events in the region .
the positions of the detected ysos and their related pms clusters give a clear picture of the current star formation in n 90 , according to which the young stellar association photo - ionizes the surrounding interstellar medium , revealing the h ii nebula , and triggering sequential star formation events mainly along the eastern and southern rims of the formed cavity of the parental molecular cloud . the postscript file is removed due to size limitations . + to see the figure download the corresponding jpg file : `` f1.jpg '' .
And you have already written the first three sentences of the full article: the _ spitzer _ space telescope opens a unique mid- and far - infrared window to the exploration of massive star formation not only in our galaxy but also in our neighboring dwarf galaxies , the large and small magellanic cloud ( lmc , smc ) .
stellar associations in both the magellanic clouds ( mcs ) contain the richest sample of young bright stars in these galaxies , and consequently our knowledge on their young massive stars has been collected from studies of such stellar systems ( see e.g. massey 2002 ) .
furthermore , almost every mcs association coincide with one or more h ii regions , as they have been earlier cataloged ( henize 1956 ; davies et al ..
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1976 ) , and it has been shown that the measured h fluxes are in excellent agreement with those expected from the ionizing flux of the detected massive stars ( massey 1993 ) .
however , mcs associations are not mere aggregates of young bright stars alone , but they also host large numbers of faint pre - main sequence ( pms ) stars , as recent hst studies showed for both the lmc ( gouliermis et al .
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Suppose that you have an abstract for a scientific paper: short period , high field undulators are used to produce hard x - rays on synchrotron radiation based storage ring facilities of intermediate energy and enable short wavelength free electron laser .
cryogenic permanent magnet undulators take benefit from improved magnetic properties of @xmath0 ( rare earth based magnets ) at low temperatures for achieving short period , high magnetic field and high coercivity .
using @xmath1 instead of @xmath2 , which is generally employed for undulators , avoids the limitation caused by the spin reorientation transition phenomenon , and simplifies the cooling system by allowing the working temperature of the undulator to be directly at the liquid nitrogen one ( 77 k ) .
we describe here the development of a full scale ( 2 m ) , 18 mm period @xmath1 cryogenic permanent magnet undulator ( u18 ) . the design , construction and optimization , as well as magnetic measurements and shimming at low temperature are presented .
the commissioning and operation of the undulator with the electron beam and spectrum measurement using the nanoscopmium beamline at soleil are also reported . .
And you have already written the first three sentences of the full article: accelerator based x - ray sources produce nowadays very intense radiation in a broad spectral range @xcite .
third generation synchrotron radiation light sources , with reduced emittance and large use of insertion devices provide a high brilliance with partial transverse coherence for users , enabling for example coherent imaging experiments @xcite . furthermore ,
fourth generation light source generally rely on the free electron laser ( fel ) process using relativistic electrons propagating in a periodic magnetic field as a gain medium ..
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fels provide additional longitudinal coherence and extremely short pulses , enabling to follow dynamics process of dilute species @xcite . +
a planar undulator of period @xmath3 and peak field @xmath4 emits with an observation angle @xmath5 a radiation at wavelength @xmath6 and its harmonics according to : @xmath7 with the deflection parameter given by @xmath8 \times \lambda_u[mm]$ ] , @xmath9 is the electron charge , @xmath10 the electron mass , @xmath11 the speed of light , and @xmath12 the normalized energy .
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Suppose that you have an abstract for a scientific paper: performances of several single gap ( gas gap 2 mm ) prototype resistive plate chambers ( rpc ) made of high resistive ( @xmath0 @xmath1 10@xmath2 - 10@xmath3 @xmath4 cm ) bakelite , commercially available in india have been studied in recent times . to make the inner electrode surfaces smooth ,
a thin coating of silicone has been applied .
an efficiency > 90% and time resolution @xmath1 2 ns ( fwhm ) have been obtained for both the streamer and the avalanche mode .
the induced charge distributions of those silicone coated rpc are studied and the results are presented .
a numerical study on the effect of surface roughness of the resistive electrodes on the electric field of the device has been carried out using garfield - nebem code .
a few results for a simplified model representing surface roughness , measured using a surface profilometer for the bakelite surfaces , have also been presented . , , , , , , , , rpc ; streamer mode ; avalanche mode ; bakelite ; cosmic rays ; silicone ; charge distribution ; garfield - nebem ; roughness 29.40.cs .
And you have already written the first three sentences of the full article: high resistive ( @xmath0 @xmath1 10@xmath2 - 10@xmath3 @xmath4 cm ) bakelite rpcs @xcite , prepared with a silicone compound coating on the inner electrode surfaces , were studied in a cosmic ray test bench to characterize its long term stability of operation @xcite .
need for the silicone compound coating had been illustrated through the measurement of variation of efficiency with applied high voltage ( hv ) in our earlier work @xcite .
study of variation of time resolution and cross - talk between neighbouring pick - up strips with applied hv were also reported earlier @xcite ..
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such high resistive electrode - based rpcs are being explored as active elements of a large scale iron calorimeter for the proposed india - based neutrino observatory ( ino ) @xcite .
one of the limitations of the streamer mode operation of high resistive bakelite rpcs is that the rate handling capability is relatively worse than that in the avalanche mode .
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Suppose that you have an abstract for a scientific paper: we perform a pixel - by - pixel analysis of 467 galaxies in the goods - vimos survey to study systematic effects in extracting substructure and properties of stellar populations ( age , dust , metallicity and star formation history ) from the pixel colors using the pixel-@xmath0 method .
several systematics are examined in this paper , including the effect of the input stellar population synthesis models whose seds are fitted to each pixel s colors , the effect of passband limitations and differences between the individual sed fits to pixels and global sed fitting to a galaxy s colors .
we find that with optical - only colors ( @xmath1 ) , the systematic uncertainties due to differences among stellar population synthesis codes are well constrained .
the largest impact on the stellar population age and sfr e - folding time estimates in the pixels arises from differences between the maraston ( 2005 ) models on one hand and the bruzual & charlot ( 2003 ) and charlot & bruzual ( 2007 ) models on the other , when optical - only ( @xmath1 ) colors are used .
this results in systematic differences larger than the @xmath2 uncertainties in over 10 percent of all pixels in the galaxy sample .
the effect of varying the number and choice of available passbands is more severe . in 26 percent of the pixels in the full sample ,
these limitations result in systematic biases in the age determination which are larger than the @xmath2 uncertainties in the measurements .
robust results can , however , still be obtained with a minimum of 3 optical filters provided they span the 4000 break .
near - ir data is also added to a subsample of 46 galaxies from the goods - nicmos survey and systematics arising from model differences are again investigated .
differences among the models in their predicted rest - frame red / nir colors manifest themselves as follows . for @xmath3 galaxies
the observed optical / nir colors span the rest frame uv - optical sed , and the use of different population synthesis models....
And you have already written the first three sentences of the full article: many galaxies at @xmath5 have morphologies that are very different from the galaxy population at @xmath7 ( lotz et al . 2004 ;
lotz et al . 2006 ; law et al . 2007 ; scarlata et al . 2007 ; elmegreen et al . 2007
; pannella et al ..
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however , the morphologies of these objects only tell one part of the story . at @xmath8 ,
rest - frame uv wavelengths , which are most impacted by dust obscuration and star formation , can be traced by high resolution optical imaging ( toft et al . 2007 ;
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Suppose that you have an abstract for a scientific paper: we present the formalism for calculating the femtoscopic correlation function directly in spherical harmonics . the numerator and denominator
are stored as a set of one - dimensional histograms representing the spherical harmonic decompositions of each .
we present the formalism to calculate the correlation function from them directly , without going to any three - dimensional histogram .
we discuss the practical implementation of the method and we provide an example of its use .
we also discuss the stability of the method in the presence of angular holes in the underlying data ( e.g. from experimental acceptance ) .
spherical harmonics are one of the most commonly used mathematical tools for the analysis of experimental data .
for example , geopotential models of the earth s gravitational field are matched to experimental data up to harmonic order @xmath0 @xcite .
measurements of the cosmic microwave background is expanded to by the cosmic background explorer ( cobe ) @xcite and successor experiments extend further to an impressive @xmath1 @xcite . in the femtoscopic measurements of particle emitting sources in heavy - ion collisions , one also finds it useful to expand the measured correlations and extracted sources in spherical harmonics @xcite . in nearly all applications of spherical harmonics
to data analysis and reduction , one is faced with the problem of `` holes in the data '' i.e. sampling bias @xcite . in the cobe analysis mentioned above , this bias occurs because the milky way masks a sizable solid angle of the sky .
when constructing potential maps of the earth , the problem is even more severe as one uses strips of data obtained from various satellite and balloon - borne experiments to derive the map @xcite . in heavy - ion collisions ,
the sampling bias most often arises because the detector acceptance does not span all of phase - space . unlike other applications ,
the femtoscopic correlation functions are actually ratios of two single particle distributions....
And you have already written the first three sentences of the full article: the femtoscopic correlation function , @xmath3 , is defined as a ratio of the probability to observe a correlated pair of particles at a given relative momentum in the same event ( numerator ) , @xmath4 , to the probability to observe such a pair in an uncorrelated state ( denominator ) , @xmath5 : @xmath6 the uncorrelated distribution is usually obtained by mixing particles from different events . here the relative momentum is given in the pair center of mass frame as @xmath7 for particles 1 and 2 . here
@xmath8 is the notation commonly used for femtoscopic correlations for pairs of two different types of particles , and will be used interchangeably with @xmath9 ( traditionally used in femtoscopic correlations of pairs of identical partilces ) later in the paper .
we expand the numerator , denominator and correlation function in spherical harmonics , e.g. : @xmath10 .conditions on the distribution imply relations between the different terms in the @xmath11 expansion ..
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condition 1 is always valid for the true and mixed pair distributions and the correlation function .
condition 5 is always valid for like pair correlation and the corresponding pairs distributions . by exploiting symmetries in 2 - 5
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Suppose that you have an abstract for a scientific paper: i review recent progress in the study of the large - scale structure of the universe through the distribution of clusters of galaxies , concentrating on new results using x - ray selected samples . after discussing the importance of understanding the properties of the tracers used to map structure and their relation to the underlying mass ,
i elaborate on the advantages and disadvantages of clusters of galaxies to this end .
i then present the most recent estimates of the power spectrum and correlation function of x - ray clusters in the local ( @xmath0 ) universe , and their implications for cosmological models .
finally , i briefly summarize most recent results from deep x - ray surveys as probes of the evolution of structure and highlight current ongoing observational efforts in this field . *s * _ med 3j_3 .
And you have already written the first three sentences of the full article: our quest for understanding the origin and evolution of galaxies and larger
scale structures is based on the exploration of large volumes of space through redshift surveys of luminous objects .
this short review concentrates on using clusters of galaxies as the basic bricks by which to study large - scale structure ( lss hereafter ) on the largest accessible scales ..
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in fact , with mean separations @xmath1 , clusters of galaxies are ideal objects for sampling efficiently long wavelength ( @xmath2 ) density fluctuations over large volumes , i.e. well in the linear regime where inhomogeneities are expected to fully reflect initial conditions as they emerged at recombination .
this means that , for example , we do not necessarily need to go through n
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Suppose that you have an abstract for a scientific paper: we have used the vlba to measure the annual parallax of the h@xmath0o masers in the star - forming region iras 00420@xmath15530 .
this measurement yields a direct distance estimate of @xmath2 kpc ( @xmath33% ) , which disagrees substantially with the standard kinematic distance estimate of @xmath44.6 kpc ( according to the rotation curve of * ? ? ?
* ) , as well as most of the broad range of distances ( [email protected] kpc ) used in various astrophysical analyses in the literature . the 3-dimensional space velocity of iras 00420@xmath15530 at this new , more accurate distance implies a substantial non - circular and anomalously slow galactic orbit , consistent with similar observations of w3(oh ) @xcite , as well as line - of - sight velocity residuals in the rotation curve analysis of @xcite .
the perseus spiral arm of the galaxy is thus more than a factor of two closer than previously presumed , and exhibits motions substantially at odds with axisymmetric models of the rotating galaxy . .
And you have already written the first three sentences of the full article: distance estimates to celestial objects are one of the most fundamental measurements in astronomy and astrophysics .
knowledge of the distance to astronomical sources in the sky are needed in order to estimate their physical properties , such as luminosities , masses , kinematics , and dynamics . in recent years
, the technique of very long baseline interferometry ( vlbi ) has been used to make precise astrometric measurements ( to a precision of of a few tens of microarcseconds for a single observation ) and thus holds the promise to extend the range of the direct distance measurements of annual parallax up to at least 10 kpc with 10% accuracy using radio telescopes such as the very long baseline array ( vlba ) of the national radio astronomy obsevatory ( nrao ) ..
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compact , bright radio - emitting objects such as pulsars and masers are choice beacons for vlbi distance measurements across the galaxy ( e.g. , * ? ? ?
* ; * ? ? ?
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Suppose that you have an abstract for a scientific paper: to investigate the fundamental principles of h@xmath0 formation in a giant molecular cloud , we derive the hi and h@xmath0 surface density ( @xmath1 and @xmath2 ) images of the perseus molecular cloud on sub - pc scales ( @xmath30.4 pc ) .
we use the far - infrared data from the improved reprocessing of the _ iras _ survey and the @xmath4-band extinction image provided by the complete survey to estimate the dust column density image of perseus . in combination with the hi data from the galactic arecibo l - band feed array hi survey and an estimate of the local dust - to - gas ratio
, we then derive the @xmath2 distribution across perseus .
we find a relatively uniform @xmath5 68 m@xmath6 pc@xmath7 for both dark and star - forming regions , suggesting a minimum hi surface density required to shield h@xmath0 against photodissociation . as a result
, a remarkably tight and consistent relation is found between @xmath8 and @xmath9 .
the transition between the hi- and h@xmath0-dominated regions occurs at @xmath10 @xmath3 ( 814 ) @xmath11 10@xmath12 cm@xmath7 .
our findings are consistent with predictions for h@xmath0 formation in equilibrium , suggesting that turbulence may not be of primary importance for h@xmath0 formation . however , the importance of warm neutral medium for h@xmath0 shielding , internal radiation field , and the timescale of h@xmath0 formation still remain as open questions .
we also compare h@xmath0 and co distributions and estimate the fraction of `` co - dark '' gas , @xmath14 @xmath3 0.3 .
while significant spatial variations of @xmath14 are found , we do not find a clear correlation with the mean @xmath4-band extinction . .
And you have already written the first three sentences of the full article: most of the dense molecular gas in galaxies is assembled into giant molecular clouds ( gmcs ) with masses from 10@xmath15 m@xmath6 to 10@xmath16 m@xmath6 and radii from 50 pc to a few hundred pc ( e.g. , fukui & kawamura 2010 ) .
as stars , the `` atoms '' of galaxies , are exclusively formed in these gmcs , physical processes that govern the conversion of hi into h@xmath0 clearly play an important role in determining the properties of gmcs and consequently the initial conditions for star formation .
therefore , understanding the properties of the interstellar regions where gas transitions from h@xmath17h@xmath0-dominated ( hi h@xmath0 transition hereafter ) is an important step toward a complete theory of star formation . from an observational point of view , the hi .
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transition has been investigated in the galaxy mainly via ultraviolet ( uv ) absorption measurements toward background sources .
for example , savage et al .
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Suppose that you have an abstract for a scientific paper: we examine recent claims that the t - type brown dwarf s ori 053810.1 - 023626 ( s ori 70 ) is a spectroscopically verified low mass ( 3@xmath0 m@xmath1 ) member of the 18 myr @xmath2 orionis cluster .
comparative arguments by martn & zapatero osorio asserting that s ori 70 exhibits low surface gravity spectral features indicative of youth and low mass are invalidated by the fact that their comparison object was not the field t dwarf 2mass 0559@xmath31404 but rather a nearby background star .
instead , we find that the 12.5 @xmath4 spectra of s ori 70 are well - matched to older ( age @xmath5 few gyr ) field t6t7 dwarfs .
moreover , we find that spectral model fits to late - type field t dwarf spectra tend to yield low surface gravities ( @xmath6 = 3.03.5 ) , and thus young ages ( @xmath7 5 myr ) and low masses ( @xmath7 3 m@xmath1 ) , inconsistent with expected and/or empirical values .
finally , we show that the identification of one t dwarf in the field imaged by zapatero osorio et al .
is statistically consistent with the expected foreground contamination .
based on the re - examined evidence , we conclude that s ori 70 may simply be an old , massive ( 3060 m@xmath1 ) field brown dwarf lying in the foreground of the @xmath2 orionis cluster .
this interpretation should be considered before presuming the existence of so - called `` cluster planets . '' .
And you have already written the first three sentences of the full article: the boundary between classical planets ( e.g. , jupiter ) and stars has been blurred by the discovery of brown dwarfs , objects which presumably form like stars but lack sufficient mass to sustain core hydrogen fusion @xcite .
known brown dwarfs exhibit a number of features similar to those of giant planets , including size = 7.15@xmath810@xmath9 cm and m@xmath1 = 1.90@xmath810@xmath10 g = 0.00095 m@xmath11 throughout this article @xcite . ]
( r @xmath5 r@xmath1 ) , atmospheric composition ( e.g. , ch@xmath12 , condensate clouds ) , and possibly mass ( of order 10 m@xmath1 ) ; but are typically found in stellar environments as isolated field and cluster objects and as wide companions to main sequence stars ..
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while brown dwarfs appear to be rare as close companions to stars @xcite , a regime occupied by solar and extrasolar planets , the possibility of planetary ejection @xcite or brown dwarf capture @xcite , and the identification of low mass ratio binaries with substellar secondaries ( e.g. , hr 7329ab ; lowrance et al .
2000 ) , makes it impossible to unambiguously deduce the origin of a particular substellar object .
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Suppose that you have an abstract for a scientific paper: recent measurements of high - redshift qso clustering from the sloan digital sky survey indicate that qsos at @xmath0 have a bias @xmath1 .
we find that this extremely high clustering amplitude , combined with the corresponding space density , constrains the dispersion in the @xmath2 relation to be less than 50% at 99% confidence for the most conservative case of a 100% duty cycle .
this upper limit to the intrinsic dispersion provides as strong a constraint as current upper limits to the intrinsic dispersion in the local @xmath3 relation and the ratio of bolometric to eddington luminosity of luminous qsos .
-1 cm dark matter large - scale structure of universe quasars : general .
And you have already written the first three sentences of the full article: it has recently become accepted that quasar activity and black hole growth are an integral part of galaxy evolution , however a detailed understanding of what triggers quasar activity and how they are fueled still eludes us . the leading contender for the identity of luminous
, high redshift qsos is that they are black holes fed by by major mergers of gas - rich galaxies @xcite .
recent incarnations of such models @xcite provide a good description of many observed properties of the qso population ..
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the situation is particularly interesting at high redshift , where the population of supermassive black holes that powers the qsos is growing rapidly ( see e.g. * ? ? ? * for a recent review ) . to further understand this important phase of black hole and galaxy evolution we would like to build a model in which qso activity is tied to the evolving cosmic web of dark matter halos .
the relationship between qsos and dark matter halos , their environments and duty cycles , can be constrained via observations of their space density and large - scale clustering @xcite .
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Suppose that you have an abstract for a scientific paper: in the context of the weakly coupled heterotic string , we propose a new model of mediating supersymmetry breaking . the breakdown of supersymmetry in the hidden sector is transmitted to anti - generation fields via gravitational interactions .
subsequent transmission of the breaking to the mssm sector occurs via gauge interactions .
it is shown that the mass spectra of superparticles are phenomenologically viable .
kgku-00 - 01 + hep - ph/0001323 * mediation of supersymmetry breaking + via anti - generation fields * masato ito@xmath0 and takeo matsuoka@xmath1 _ @xmath0department of physics , nagoya university , nagoya , japan 464 - 8602 + @xmath1kogakkan university , nabari , japan 518 - 0498 _ the dynamical mechanism of supersymmetry(susy ) breaking and its mediation to our visible world form the major unsolved problems of particle physics . as for the former ,
many models have been proposed@xcite . for phenomenological implications
it is of more importance to clarify how susy breaking is communicated to the visible sector .
two ways of transmitting susy breaking to the visible sector have been proposed .
the first is that gravitational interactions in @xmath2 supergravity theory play this role@xcite .
the second is that gauge interactions play the role of the messenger@xcite . in the framework of superstring theory
it seems that the gravity - mediated susy breaking scenario is plausible . in the context of the weakly coupled heterotic @xmath3 superstring ,
@xmath4 is considered to be the hidden sector gauge symmetry . if supersymmetric gauge dynamics in the hidden sector , such as gaugino condensation , cause susy breaking to occur , the effects of the susy breaking will be transmitted to the observable sector through gravitational interactions . in these types of simple models@xcite
, the @xmath5-components of moduli fields other than the dilaton are expected to develop their vacuum expectation values ( vevs ) .
the gauginos acquire their soft susy breaking masses....
And you have already written the first three sentences of the full article: a part of this work was done at the department of physics engineering , mie university , tsu , japan .
the authors are grateful to professor y. abe and assistant professor m. matsunaga for their hospitality .
one of the authors ( t. m. ) is supported in part by a grant - in - aid for scientific research from the ministry of education , science , sports and culture , japan ( no . 10640256 ) ..
Please generate the next two sentences of the article
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99 e. witten , nucl .
b188 * ( 1981 ) , 513 ; * b202 * ( 1982 ) , 253 .
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