3,727 research outputs found
Non-Abelian Bremsstrahlung and Azimuthal Asymmetries in High Energy p+A Reactions
We apply the GLV reaction operator solution to the Vitev-Gunion-Bertsch (VGB)
boundary conditions to compute the all-order in nuclear opacity non-abelian
gluon bremsstrahlung of event-by-event fluctuating beam jets in nuclear
collisions. We evaluate analytically azimuthal Fourier moments of single gluon,
, and even number gluon, inclusive
distributions in high energy p+A reactions as a function of harmonic ,
%independent target recoil cluster number, , and gluon number, , at
RHIC and LHC. Multiple resolved clusters of recoiling target beam jets together
with the projectile beam jet form Color Scintillation Antenna (CSA) arrays that
lead to characteristic boost non-invariant trapezoidal rapidity distributions
in asymmetric nuclear collisions. The scaling of intrinsically
azimuthally anisotropic and long range in nature of the non-abelian \br
leads to moments that are similar to results from hydrodynamic models,
but due entirely to non-abelian wave interference phenomena sourced by the
fluctuating CSA. Our analytic non-flow solutions are similar to recent
numerical saturation model predictions but differ by predicting a simple
power-law hierarchy of both even and odd without invoking
factorization. A test of CSA mechanism is the predicted nearly linear
rapidity dependence of the . Non-abelian beam jet \br may thus
provide a simple analytic solution to Beam Energy Scan (BES) puzzle of the near
independence of moments observed down to 10 AGeV where
large valence quark beam jets dominate inelastic dynamics. Recoil \br from
multiple independent CSA clusters could also provide a partial explanation for
the unexpected similarity of in and non-central at same
multiplicity as observed at RHIC and LHC.Comment: 16 pages, 10 figure
Pion and Kaon Spectra from Distributed Mass Quark Matter
After discussing some hints for possible masses of quasiparticles in quark
matter on the basis of lattice equation of state, we present pion and kaon
transverse spectra obtained by recombining quarks with distributed mass and
thermal cut power-law momenta as well as fragmenting by NLO pQCD with intrinsic
{and nuclear} broadening.Comment: Talk given at SQM 200
Non-Extensive Quantum Statistics with Particle - Hole Symmetry
Based on Tsallis entropy and the corresponding deformed exponential function,
generalized distribution functions for bosons and fermions have been used since
a while. However, aiming at a non-extensive quantum statistics further
requirements arise from the symmetric handling of particles and holes
(excitations above and below the Fermi level). Naive replacements of the
exponential function or cut and paste solutions fail to satisfy this symmetry
and to be smooth at the Fermi level at the same time. We solve this problem by
a general ansatz dividing the deformed exponential to odd and even terms and
demonstrate that how earlier suggestions, like the kappa- and q-exponential
behave in this respect
3-D Simulations of Protostellar Jets in Stratified Ambient Media
We present fully three-dimensional hydrodynamical simulations of radiative
cooling jets propagating into stratified isothermal ambient media with
power-law density and pressure distributions. The parameters used are mainly
suitable for protostellar jets but results applicable to extragalactic jets are
also presented. Comparisons are made with previous simulations of jets through
homogeneous media. We find that for radiative cooling jets propagating into
regions where the ambient medium has an increasing density (and pressure)
gradient, the ambient gas tends to compress the cold, low-pressure cocoon of
shocked material that surrounds the beam and destroy the bow shock-like
structure at the head. The compressing medium collimates the jet and promotes
the development of Kelvin-Helmholtz instabilities which cause beam focusing,
wiggling and the formation of internal traveling shocks,
, via pinching along the beam. This remarkably resembles the structure of
some observed systems (e.g. Haro 6-5B northern and HH 24G jets). These effects
are larger for jets with smaller density ratio between jet and environment
(tested for =1, 3, and 10) and larger Mach number
(tested for 12 and 24, where is the jet velocity and the
ambient sound speed). In an ambient medium of decreasing density (and
pressure), the beam is poorly collimated and relaxes, becoming faint. This
could explain ''invisible'' jet sections, like the gap between the parent
source and collimated beam (e.g., in HH30 jet). Although, on average, jets
propagating into an increasing (decreasing) density environment are decelerated
(accelerated) by the increasing (decreasing) ram pressure of the ambient
medium, we find that their propagation velocities have an oscillating pattern.Comment: 33 pp, LaTeX file, 13 figures upon request. To appear in the
Astrophys. J., vol 471, nov. 10t
Correlation between nucleotide composition and folding energy of coding sequences with special attention to wobble bases
Background: The secondary structure and complexity of mRNA influences its
accessibility to regulatory molecules (proteins, micro-RNAs), its stability and
its level of expression. The mobile elements of the RNA sequence, the wobble
bases, are expected to regulate the formation of structures encompassing coding
sequences.
Results: The sequence/folding energy (FE) relationship was studied by
statistical, bioinformatic methods in 90 CDS containing 26,370 codons. I found
that the FE (dG) associated with coding sequences is significant and negative
(407 kcal/1000 bases, mean +/- S.E.M.) indicating that these sequences are able
to form structures. However, the FE has only a small free component, less than
10% of the total. The contribution of the 1st and 3rd codon bases to the FE is
larger than the contribution of the 2nd (central) bases. It is possible to
achieve a ~ 4-fold change in FE by altering the wobble bases in synonymous
codons. The sequence/FE relationship can be described with a simple algorithm,
and the total FE can be predicted solely from the sequence composition of the
nucleic acid. The contributions of different synonymous codons to the FE are
additive and one codon cannot replace another. The accumulated contributions of
synonymous codons of an amino acid to the total folding energy of an mRNA is
strongly correlated to the relative amount of that amino acid in the translated
protein.
Conclusion: Synonymous codons are not interchangable with regard to their
role in determining the mRNA FE and the relative amounts of amino acids in the
translated protein, even if they are indistinguishable in respect of amino acid
coding.Comment: 14 pages including 6 figures and 1 tabl
Magnetization of small lead particles
The magnetization of an ensemble of isolated lead grains of sizes ranging
from below 6 nm to 1000 nm is measured. A sharp disappearance of Meissner
effect with lowering of the grain size is observed for the smaller grains. This
is a direct observation by magnetization measurement of the occurrence of a
critical particle size for superconductivity, which is consistent with
Anderson's criterion.Comment: 7 pages, 5 figures, Submitted to PR
Chemical equilibration and thermal dilepton production from the quark gluon plasma at finite baryon density
The chemical equilibration of a highly unsaturated quark-gluon plasma has
been studied at finite baryon density. It is found that in the presence of
small amount of baryon density, the chemical equilibration for gluon becomes
slower and the temperature decreases less steeply as compared to the baryon
free plasma. As a result, the space time integrated yield of dilepton is
enhanced if the initial temperature of the plasma is held fixed. Even at a
fixed initial energy density, the suppression of the dilepton yields at higher
baryo-chemical potential is compensated, to a large extent, by the slow cooling
of the plasma.Comment: Latex, 19 pages, 8 postscript figures. To appear in Phys. Rev.
The developing cognitive substrate of sequential action control in 9- to 12-month-olds: Evidence for concurrent activation models
Infants interpret third-person sequential actions as goal directed by 6 months of age, around 9 months of age they start to perform sequential actions to accomplish higher order goals. The present study employed an innovative pupillometric and oculomotor paradigm to study how infants represent first-person sequential actions. We aimed to contrast chaining-, concurrent- and integrated models of sequential-action representation. 9- and 12- month olds were taught action sequences consisting of two elementary actions. Thereafter the secondary action was selectively activated to assess any interactions with the primary action. Results suggest that concurrent models best capture the representations formed
Chloride Ions in the Pore of Glycine and GABA Channels Shape the Time Course and Voltage Dependence of Agonist Currents
In the vertebrate CNS, fast synaptic inhibition is mediated by GABA and glycine receptors. We recently reported that the time course of these synaptic currents is slower when intracellular chloride is high. Here we extend these findings to measure the effects of both extracellular and intracellular chloride on the deactivation of glycine and GABA currents at both negative and positive holding potentials. Currents were elicited by fast agonist application to outside-out patches from HEK-293 cells expressing rat glycine or GABA receptors. The slowing effect of high extracellular chloride on current decay was detectable only in low intracellular chloride (4 mM). Our main finding is that glycine and GABA receptors "sense" chloride concentrations because of interactions between the M2 pore-lining domain and the permeating ions. This hypothesis is supported by the observation that the sensitivity of channel gating to intracellular chloride is abolished if the channel is engineered to become cation selective or if positive charges in the external pore vestibule are eliminated by mutagenesis. The appropriate interaction between permeating ions and channel pore is also necessary to maintain the channel voltage sensitivity of gating, which prolongs current decay at depolarized potentials. Voltage dependence is abolished by the same mutations that suppress the effect of intracellular chloride and also by replacing chloride with another permeant ion, thiocyanate. These observations suggest that permeant chloride affects gating by a foot-in-the-door effect, binding to a channel site with asymmetrical access from the intracellular and extracellular sides of the membrane
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