15,854 research outputs found
Multi-strange baryon production in Au+Au collisions near threshold
The centrality dependence of Xi^- and Lambda production in Au+Au interactions
at E_lab=6 AGeV is studied within a microscopic transport approach. In line
with recent data, a slight enhancement of the Xi^-/(Lambda+Sigma^0) ratio
toward central collisions is found. It is demonstrated that the observed
production of multiple strange baryons can be traced back to multi-step
meson-baryon interactions in the late stages of the collisions. Therefore, the
present analysis supports an interpretation of the observed Xi abundance in
terms of hadronic re-scattering.Comment: 5 pages, 6 figure
A Remark on the Geometry of Uniformly Rotating Stars
In this paper we classify the free boundary associated to equilibrium
configurations of compressible, self-gravitating fluid masses, rotating with
constant angular velocity. The equilibrium configurations are all critical
points of an associated functional and not necessarily minimizers. Our methods
also apply to alternative models in the literature where the angular momentum
per unit mass is prescribed. The typical physical model our results apply to is
that of uniformly rotating white dwarf stars
Bulk viscosity of Mixed nucleon-hyperon-quark Matter in Neutron stars
We calculate the coefficient of bulk viscosity by considering the
non-leptonic weak interactions in the cores of hybrid stars with both hyperons
and quarks. We first determine the dependence of the production rate of
neutrons on the reaction rate of quarks in the non-leptonic processes, that is
. The
conversion rate, in our scenario is a complicated function of baryon
number density. We also consider medium effect of quark matter on bulk
viscosity. Using these results, we estimate the limiting rotation of the hybrid
stars, which may suppress the r-mode instability more effectively. Hybrid stars
should be the candidates for the extremely rapid rotators .Comment: This paper contains 17 pages,8 figures and 1 table and is accepted by
Monthly Notices of the Royal Astronomical Societ
Study of color connections in annihilation
We replace in the event generator JETSET the color singlet chain connection
with the color separate state one as the interface between the hard and soft
sectors of hadronic processes. The modified generator is applied to produce the
hadronic events in annihilation. It describes the experimental data
at the same level as the original JETSET with default parameters. This should
be understood as a demonstration that color singlet chain is not the unique
color connection. We also search for the difference in special sets of
three-jet events arising from different color connections, which could subject
to further experimental test.Comment: 23 pages, 8 figures, 4 tables, Revtex
Canonical form of master equations and characterization of non-Markovianity
Master equations govern the time evolution of a quantum system interacting
with an environment, and may be written in a variety of forms. Time-independent
or memoryless master equations, in particular, can be cast in the well-known
Lindblad form. Any time-local master equation, Markovian or non-Markovian, may
in fact also be written in a Lindblad-like form. A diagonalisation procedure
results in a unique, and in this sense canonical, representation of the
equation, which may be used to fully characterize the non-Markovianity of the
time evolution. Recently, several different measures of non-Markovianity have
been presented which reflect, to varying degrees, the appearance of negative
decoherence rates in the Lindblad-like form of the master equation. We
therefore propose using the negative decoherence rates themselves, as they
appear in the canonical form of the master equation, to completely characterize
non-Markovianity. The advantages of this are especially apparent when more than
one decoherence channel is present. We show that a measure proposed by Rivas et
al. is a surprisingly simple function of the canonical decoherence rates, and
give an example of a master equation that is non-Markovian for all times t>0,
but to which nearly all proposed measures are blind. We also give necessary and
sufficient conditions for trace distance and volume measures to witness
non-Markovianity, in terms of the Bloch damping matrix.Comment: v2: Significant update, with many new results and one new author. 12
pages; v3: Minor clarifications, to appear in PRA; v4: matches published
versio
The Airlines’ Recent Experience Under the Railway Labor Act
Silky-feather has been selected and fixed in some breeds due to its unique appearance. This phenotype is caused by a single recessive gene (hookless, h). Here we map the silky-feather locus to chromosome 3 by linkage analysis and subsequently fine-map it to an 18.9 kb interval using the identical by descent (IBD) method. Further analysis reveals that a C to G transversion located upstream of the prenyl (decaprenyl) diphosphate synthase, subunit 2 (PDSS2) gene is causing silky-feather. All silky-feather birds are homozygous for the G allele. The silky-feather mutation significantly decreases the expression of PDSS2 during feather development in vivo. Consistent with the regulatory effect, the C to G transversion is shown to remarkably reduce PDSS2 promoter activity in vitro. We report a new example of feather structure variation associated with a spontaneous mutation and provide new insight into the PDSS2 function
Photoswitched DNA-binding of a photochromic spiropyran
The dramatically different DNA-binding properties of the two isomeric forms of a photochromic spiropyran have been demonstrated, enabling photoswitched DNA binding. The closed, UV-absorbing form shows no signs of interaction with DNA. Upon UV exposure the spiropyran is isomerized to the open form that binds to DNA by intercalation. The process is fully reversible as the corresponding dissociation process is induced by visible light. Copyright \ua9 2008 American Chemical Society
Numerical investigation of particles turbulent dispersion in channel flow
This paper investigates the performance of Reynolds-averaged Navier-Stokes model on dispersion of particles in wall turbulence. A direct numerical simulation of wall-bounded channel flow with particles suspensions was set as a benchmark. The standard k-ω model coupled with two different eddy interaction models was used in Reynolds-averaged Navier-Stokes model and compared to the direct numerical simulation. Detailed comparisons between direct numerical simulation and Reynolds-averaged Navier-Stokes model on particle distribution evolving over time were carried out
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