14,179 research outputs found
The Boltzmann Equation in Classical and Quantum Field Theory
Improving upon the previous treatment by Mueller and Son, we derive the
Boltzmann equation that results from a classical scalar field theory. This is
obtained by starting from the corresponding quantum field theory and taking the
classical limit with particular emphasis on the path integral and perturbation
theory. A previously overlooked Van-Vleck determinant is shown to control the
tadpole type of self-energy that can still appear in the classical perturbation
theory. Further comments on the validity of the approximations and possible
applications are also given.Comment: 22 pages, 3 eps figures. Version to appear in Physical Review
Concurrent investigation of global motion and form processing in amblyopia: an equivalent noise approach
PURPOSE: Directly comparing the motion and form processing in neurologic disorders has remained difficult due to the limitations in the experimental stimulus. In the current study, motion and form processing in amblyopia was characterized using random dot stimuli in different noise levels to parse out the effect of local and global processing on motion and form perception. METHODS: A total of 17 amblyopes (8 anisometropic and 9 strabismic), and 12 visually normal subjects monocularly estimated the global direction of motion and global orientation in random dot kinematograms (RDK) and Glass patterns (Glass), whose directions/orientations were drawn from normal distributions with a range of means and variances that served as external noise. Direction/orientation discrimination thresholds were measured without noise first then variance threshold was measured at the multiples of the direction/orientation threshold. The direction/orientation and variance thresholds were modelled to estimate internal noise and sampling efficiency parameters. RESULTS: Overall, the thresholds for Glass were higher than RDK for all subjects. The thresholds for both Glass and RDK were higher in the strabismic eyes compared with the fellow and normal eyes. On the other hand, the thresholds for anisometropic amblyopic eyes were similar to the normal eyes. The worse performance of strabismic amblyopes was best explained by relatively low sampling efficiency compared with other groups (P < 0.05). CONCLUSIONS: A deficit in global motion and form perception was only evident in strabismic amblyopia. Contrary to the dorsal stream deficiency hypothesis assumed in other developmental disorders, deficits were present in both motion (dorsal) and form (ventral) processing
Transient electrophoretic current in a nonpolar solvent
The transient electric current of surfactants dissolved in a nonpolar solvent
is investigated both experimentally and theoretically in the parallel-plate
geometry. Due to a low concentration of free charges the cell can be completely
polarized by an external voltage of several volts. In this state, all the
charged micelles are compacted against the electrodes. After the voltage is set
to zero the reverse current features a sharp discharge spike and a broad peak.
This shape and its variation with the compacting voltage are reproduced in a
one-dimensional drift-diffusion model. The model reveals the broad peak is
formed by a competition between an increasing number of charges drifting back
to the middle of the cell and a decreasing electric field that drives the
motion. After complete polarization is achieved, the shape of the peak stops
evolving with further increase of the compacting voltage. The spike-peak
separation time grows logarithmically with the charge content in the bulk. The
time peak is a useful measure of the micelle mobility. Time integration of the
peak yields the total charge in the system. By measuring its variation with
temperature, the activation energy of bulk charge generation has been found to
be 0.126 eV.Comment: 7 pages, 5 figure
Event-by-event fluctuations of the charged particle ratio from non-equilibrium transport theory
The event by event fluctuations of the ratio of positively to negatively
charged hadrons are predicted within the UrQMD model. Corrections for finite
acceptance and finite net charge are derived. These corrections are relevant to
compare experimental data and transport model results to previous predictions.
The calculated fluctuations at RHIC and SPS energies are shown to be compatible
with a hadron gas. Thus, deviating by a factor of 3 from the predictions for a
thermalized quark-gluon plasma.Comment: This paper clarifies the previous predictions of Jeon and Koch
(hep-ph/0003168) and addresses issues raised in hep-ph/0006023. 2 Figures,
10pp, uses RevTe
White organic light-emitting diodes with an ultra-thin premixed emitting layer
We described an approach to achieve fine color control of fluorescent White
Organic Light-Emitting Diodes (OLED), based on an Ultra-thin Premixed emitting
Layer (UPL). The UPL consists of a mixture of two dyes (red-emitting
4-di(4'-tert-butylbiphenyl-4-yl)amino-4'-dicyanovinylbenzene or fvin and
green-emitting 4-di(4'-tert-butylbiphenyl-4-yl)aminobenzaldehyde or fcho)
premixed in a single evaporation cell: since these two molecules have
comparable structures and similar melting temperatures, a blend can be
evaporated, giving rise to thin films of identical and reproducible composition
compared to those of the pre-mixture. The principle of fine color tuning is
demonstrated by evaporating a 1-nm-thick layer of this blend within the
hole-transport layer (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl
(\alpha-NPB)) of a standard fluorescent OLED structure. Upon playing on the
position of the UPL inside the hole-transport layer, as well as on the premix
composition, two independent parameters are available to finely control the
emitted color. Combined with blue emission from the heterojunction, white light
with Commission Internationale de l'Eclairage 1931 color coordinates (0.34,
0.34) was obtained, with excellent color stability with the injected current.
The spectrum reveals that the fcho material does not emit light due to
efficient energy transfer to the red-emitting fvin compound but plays the role
of a host matrix for fvin, allowing for a very precise adjustment of the red
dopant amount in the device
Polarized Gluon Distribution Function from Production
Using the recently proposed effective vertex, we investigate the
production of from gluon fusion in polarized pp collisions. We show
that by measuring in production, one can extract the polarized
gluon distribution at Q^2 \sim 1 \GeV^2 and in a wide range
of x.Comment: 11 pages, 3 figure
Searching for the QCD Critical Point Using Particle Ratio Fluctuations and Higher Moments of Multiplicity Distributions
Dynamical fluctuations in global conserved quantities such as baryon number,
strangeness, or charge may be observed near a QCD critical point. Results from
new measurements of dynamical , , and ratio fluctuations
are presented. The commencing of a QCD critical point search at RHIC has
extended the reach of possible measurements of dynamical , , and
ratio fluctuations from Au+Au collisions to lower energies. The STAR
experiment has performed a comprehensive study of the energy dependence of
these dynamical fluctuations in Au+Au collisions at the energies
= 7.7, 11.5, 39, 62.4, and 200 GeV. New results are compared to
previous measurements and to theoretical predictions from several models. The
measured dynamical fluctuations are found to be independent of
collision energy, while dynamical and fluctuations have a
negative value that increases toward zero at top RHIC energy. Fluctuations of
the higher moments of conserved quantities (net-proton and net-charge)
distributions, which are predicted to be sensitive to the presence of a
critical point, are also presented.Comment: 4 pages, 2 figures, Proceedings of the 21st International Conference
On Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2011), Annecy,
France, May 23 - May 28, 201
Coherence Time in High Energy Proton-Nucleus Collisions
Precisely measured Drell-Yan cross sections for 800 GeV protons incident on a
variety of nuclear targets exhibit a deviation from linear scaling in the
atomic number A. We show that this deviation can be accounted for by energy
degradation of the proton as it passes through the nucleus if account is taken
of the time delay of particle production due to quantum coherence. We infer an
average proper coherence time of 0.4 +- 0.1 fm/c, corresponding to a coherence
path length of 8 +- 2 fm in the rest frame of the nucleus.Comment: 11 pages in LaTeX. Includes 6 eps figures. Uses epsf.st
B-4. A review on feeding system for deer production(Abstracts of the International Symposium on Recent Advances in Animal Science(IS-RAAS),Joint meeting of 2^<nd> IS-AS and 3^<rd> IS-IFS)
Deer farmingvelvet productionfeed sourcemedicinal her
Black Hole Feedback On The First Galaxies
We study how the first galaxies were assembled under feedback from the accretion onto a central black hole (BH) that is left behind by the first generation of metal-free stars through self-consistent, cosmological simulations. X-ray radiation from the accretion of gas onto BH remnants of Population III (Pop III) stars, or from high-mass X-ray binaries (HMXBs), again involving Pop III stars, influences the mode of second generation star formation. We track the evolution of the black hole accretion rate and the associated X-ray feedback starting with the death of the Pop III progenitor star inside a minihalo and following the subsequent evolution of the black hole as the minihalo grows to become an atomically cooling galaxy. We find that X-ray photoionization heating from a stellar-mass BH is able to quench further star formation in the host halo at all times before the halo enters the atomic cooling phase. X-ray radiation from a HMXB, assuming a luminosity close to the Eddington value, exerts an even stronger, and more diverse, feedback on star formation. It photoheats the gas inside the host halo, but also promotes the formation of molecular hydrogen and cooling of gas in the intergalactic medium and in nearby minihalos, leading to a net increase in the number of stars formed at early times. Our simulations further show that the radiative feedback from the first BHs may strongly suppress early BH growth, thus constraining models for the formation of supermassive BHs.Astronom
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