3,209 research outputs found
Cross-Dimensional relaxation in Bose-Fermi mixtures
We consider the equilibration rate for fermions in Bose-Fermi mixtures
undergoing cross-dimensional rethermalization. Classical Monte Carlo
simulations of the relaxation process are performed over a wide range of
parameters, focusing on the effects of the mass difference between species and
the degree of initial departure from equilibrium. A simple analysis based on
Enskog's equation is developed and shown to be accurate over a variety of
different parameter regimes. This allows predictions for mixtures of commonly
used alkali atoms.Comment: 7 pages, 4 figures, uses Revtex 4. This is a companion paper to [PRA
70, 021601(R) (2004)] (cond-mat/0405419
A Model for Phase Transition based on Statistical Disassembly of Nuclei at Intermediate Energies
Consider a model of particles (nucleons) which has a two-body interaction
which leads to bound composites with saturation properties. These properties
are : all composites have the same density and the ground state energies of
composites with k nucleons are given by -kW+\sigma k^{2/3} where W and \sigma
are positive constants. W represents a volume term and \sigma a surface tension
term. These values are taken from nuclear physics. We show that in the large N
limit where N is the number of particles such an assembly in a large enclosure
at finite temperature shows properties of liquid-gas phase transition. We do
not use the two-body interaction but the gross properties of the composites
only. We show that (a) the p-\rho isotherms show a region where pressure does
not change as changes just as in Maxwell construction of a Van der Waals
gas, (b) in this region the chemical potential does not change and (c) the
model obeys the celebrated Clausius-Clapeyron relations. A scaling law for the
yields of composites emerges. For a finite number of particles N (upto some
thousands) the problem can be easily solved on a computer. This allows us to
study finite particle number effects which modify phase transition effects. The
model is calculationally simple. Monte-Carlo simulations are not needed.Comment: RevTex file, 21 pages, 5 figure
Velocity distributions in dissipative granular gases
Motivated by recent experiments reporting non-Gaussian velocity distributions
in driven dilute granular materials, we study by numerical simulation the
properties of 2D inelastic gases. We find theoretically that the form of the
observed velocity distribution is governed primarily by the coefficient of
restitution and , the ratio between the average number of
heatings and the average number of collisions in the gas. The differences in
distributions we find between uniform and boundary heating can then be
understood as different limits of , for and
respectively.Comment: 5 figure
Carboplatin/taxane-induced gastrointestinal toxicity: a pharmacogenomics study on the SCOTROC1 trial
Carboplatin/taxane combination is first-line therapy for ovarian cancer. However, patients can encounter treatment delays, impaired quality of life, even death because of chemotherapy-induced gastrointestinal (GI) toxicity. A candidate gene study was conducted to assess potential association of genetic variants with GI toxicity in 808 patients who received carboplatin/taxane in the Scottish Randomized Trial in Ovarian Cancer 1 (SCOTROC1). Patients were randomized into discovery and validation cohorts consisting of 404 patients each. Clinical covariates and genetic variants associated with grade III/IV GI toxicity in discovery cohort were evaluated in replication cohort. Chemotherapy-induced GI toxicity was significantly associated with seven single-nucleotide polymorphisms in the ATP7B, GSR, VEGFA and SCN10A genes. Patients with risk genotypes were at 1.53 to 18.01 higher odds to develop carboplatin/taxane-induced GI toxicity (P<0.01). Variants in the VEGF gene were marginally associated with survival time. Our data provide potential targets for modulation/inhibition of GI toxicity in ovarian cancer patients
Shear Viscosities from the Chapman-Enskog and the Relaxation Time Approaches
The interpretation of the measured elliptic and higher order collective flows
in heavy-ion collisions in terms of viscous hydrodynamics depends sensitively
on the ratio of shear viscosity to entropy density. Here we perform a
quantitative comparison between the results of shear viscosities from the
Chapman-Enskog and relaxation time methods for selected test cases with
specified elastic differential cross sections: (i) The non-relativistic,
relativistic and ultra-relativistic hard sphere gas with angle and energy
independent differential cross section (ii) The Maxwell gas, (iii) chiral pions
and (iv) massive pions for which the differential elastic cross section is
taken from experiments. Our quantitative results reveal that (i) the extent of
agreement (or disagreement) depends sensitively on the energy dependence of the
differential cross sections employed, and (ii) stress the need to perform
quantum molecular dynamical (URQMD) simulations that employ Green-Kubo
techniques with similar cross sections to validate the codes employed and to
test the accuracy of other methods.Comment: To be submitted to PR
Microcanonical Lattice Gas Model for Nuclear Disassembly
Microcanonical calculations are no more difficult to implement than canonical
calculations in the Lattice Gas Model. We report calculations for a few
observables where we compare microcanonical model results with canonical model
results.Comment: 7 pages, Revtex, 3 postscript figure
Thermodynamic entropy of a many body energy eigenstate
It is argued that a typical many body energy eigenstate has a well defined
thermodynamic entropy and that individual eigenstates possess thermodynamic
characteristics analogous to those of generic isolated systems. We examine
large systems with eigenstate energies equivalent to finite temperatures. When
quasi-static evolution of a system is adiabatic (in the quantum mechanical
sense), two coupled subsystems can transfer heat from one subsystem to another
yet remain in an energy eigenstate. To explicitly construct the entropy from
the wave function, degrees of freedom are divided into two unequal parts. It is
argued that the entanglement entropy between these two subsystems is the
thermodynamic entropy per degree of freedom for the smaller subsystem. This is
done by tracing over the larger subsystem to obtain a density matrix, and
calculating the diagonal and off-diagonal contributions to the entanglement
entropy.Comment: 18 page
Eur J Human Genet
Heterozygous missense mutations in the serine-threonine kinase receptor BMPR1B result typically in brachydactyly type A2 (BDA2), whereas mutations in the corresponding ligand GDF5 cause brachydactyly type C (BDC). Mutations in the GDF inhibitor Noggin (NOG) or activating mutations in GDF5 cause proximal symphalangism (SYM1). Here, we describe a novel mutation in BMPR1B (R486Q) that is associated with either BDA2 or a BDC/SYM1-like phenotype. Functional investigations of the R486Q mutation were performed and compared with the previously reported BDA2-causing mutation R486W and WT BMPR1B. Overexpression of the mutant receptors in chicken micromass cultures resulted in a strong inhibition of chondrogenesis with the R486Q mutant, showing a stronger effect than the R486W mutant. To investigate the consequences of the BMPR1B mutations on the intracellular signal transduction, we used stably transfected C2C12 cells and measured the activity of SMAD-dependent and SMAD-independent pathways. SMAD activation after stimulation with GDF5 was suppressed in both mutants. Alkaline phosphatase induction showed an almost complete loss of activation by both mutants. Our data extend the previously known mutational and phenotypic spectrum associated with mutations in BMPR1B. Disturbances of NOG-GDF5-BMPR1B signaling cascade can result in similar clinical manifestations depending on the quantitative effect and mode of action of the specific mutations within the same functional pathway
Caloric Curves for small systems in the Nuclear Lattice Gas Model
For pedagogical reasons we compute the caloric curve for 11 particles in a
lattice. Monte-Carlo simulation can be avoided and exact results are
obtained. There is no back-bending in the caloric curve and negative specific
heat does not appear. We point out that the introduction of kinetic energy in
the nuclear Lattice Gas Model modifies the results of the standard Lattice Gas
Model in a profound way.Comment: 12 pages, Revtex, including 4 postscript figure
- …