7,342 research outputs found
Study of non-equilibrium effects and thermal properties of heavy ion collisions using a covariant approach
Non-equilibrium effects are studied using a full Lorentz-invariant formalism.
Our analysis shows that in reactions considered here, no global or local
equilibrium is reached. The heavier masses are found to be equilibrated more
than the lighter systems. The local temperature is extracted using hot Thomas
Fermi formalism generalized for the case of two interpenetrating pieces of
nuclear matter. The temperature is found to vary linearly with bombarding
energy and impact parameter whereas it is nearly independent of the mass of the
colliding nuclei. This indicates that the study of temperature with medium size
nuclei is also reliable. The maximum temperatures obtained in our approach are
in a nice agreement with earlier calculations of other approaches. A simple
parametrization of maximal temperature as a function of the bombarding energy
is also given.Comment: LaTex-file, 17 pages, 8 figures (available upon request), Journal of
Physics G20 (1994) 181
Scaling Behavior of Response Functions in the Coarsening Dynamics of Disordered Ferromagnets
We study coarsening dynamics in the ferromagnetic random bond Ising model in
d = 1; 2. We focus on the validity of super-universality and the scaling
properties of the response functions. In the d = 1 case, we obtain a complete
understanding of the evolution, from pre- asymptotic to asymptotic behavior.
The corresponding response function shows a clear violation of
super-universality. Further, our results for d = 1; 2 settle the controversy
regarding the decay exponent which characterizes the response function
Diastolic And Systolic Right Ventricular Dysfunction Precedes Left Ventricular Dysfunction In Patients Paced From Right Ventricular Apex
Background: Cardiac dysfunction after right ventricular (RV) apical pacing is well known but its extent, time frame of appearance and individual effect on left ventricular (LV), RV systolic and diastolic parameters has not evaluated in a systematic fashion.
Methods: Patients with symptomatic bradycardia and ACC-AHA Class I indication for permanent pacemaker implantation (PPI) were implanted a single chamber (VVI) pacemaker. They were followed prospectively by echocardiographic examination which was done at baseline, 1 week, 1 month and 6 months after implantation. Parameters observed were chamber dimensions (M-line), chamber volumes, cardiac output (modified Simpson's method), systolic functions (ejection fraction, pre-ejection period, ejection time and ratio) and diastolic functions( isovolumic relaxation time & deceleration time) of left and right heart.
Results: Forty eight consecutive patients (mean age 65.6±11.8 yrs, 66.7% males, mean EF 61.82±10.36%) implanted a VVI pacemaker were enrolled in this study. The first significant change to appear in cardiac function after VVI pacing was in diastolic properties of RV as shown by increase in RV isovolumic relaxation time (IVRT) from 65.89±15.93 to 76.58±17.00 ms,(p<0.001) at 1week and RV deceleration time (DT) from 133.84±38.13 to 153.09±31.41 ms, (p=0.02) at 1 month. Increase in RV internal dimension (RVID) from 1.26±0.41 to 1.44±0.44, (p<0.05) was also noticed at 1 week. The LV diastolic parameters were significantly altered after 1 month with increase in LV-IVRT from 92.36±21.47 to 117.24±27.21ms, (p<0.001) and increase in LV DT from 147.56±31.84 to 189.27±28.49ms,(p<0.01). This was followed by LV systolic abnormality which appeared at 6 months with an increase in LVPEP from 100.33±14.43 to 118.41±21.34ms, (p<0.001) and increase in LVPEP/LVET ratio from 0.34±0.46 to 0.44±0.10, (p<0.001)]. The reduction in LV EF was manifested at 6 months falling from 61.82±10.36% to52.52±12.11%, (p<0.05) without any significant change in the resting cardiac output.
Conclusion: The present study shows that dysfunction of right ventricle is the first abnormality that occurs in VVI paced patients, which manifests by 1 week followed by LV dysfunction which starts appearing by 1 month and the diastolic dysfunctions precede the systolic dysfunction in both ventricles
Nonequilibrium Dynamics of the Complex Ginzburg-Landau Equation. I. Analytical Results
We present a detailed analytical and numerical study of nonequilibrium
dynamics for the complex Ginzburg-Landau (CGL) equation. In particular, we
characterize evolution morphologies using spiral defects. This paper (referred
to as ) is the first in a two-stage exposition. Here, we present
analytical results for the correlation function arising from a single-spiral
morphology. We also critically examine the utility of the Gaussian auxiliary
field (GAF) ansatz in characterizing a multi-spiral morphology. In the next
paper of this exposition (referred to as ), we will present detailed
numerical results.Comment: 21 pages, 7 figure
Crossover in Growth Law and Violation of Superuniversality in the Random Field Ising Model
We study the nonconserved phase ordering dynamics of the d = 2, 3 random
field Ising model, quenched to below the critical temperature. Motivated by the
puzzling results of previous work in two and three di- mensions, reporting a
crossover from power-law to logarithmic growth, together with superuniversal
behavior of the correlation function, we have undertaken a careful
investigation of both the domain growth law and the autocorrelation function.
Our main results are as follows: We confirm the crossover to asymptotic
logarithmic behavior in the growth law, but, at variance with previous
findings, the exponent in the preasymptotic power law is disorder-dependent,
rather than being the one of the pure system. Furthermore, we find that the
autocorre- lation function does not display superuniversal behavior. This
restores consistency with previous results for the d = 1 system, and fits
nicely into the unifying scaling scheme we have recently proposed in the study
of the random bond Ising model.Comment: To be published in Physical Review
Growth Law and Superuniversality in the Coarsening of Disordered Ferromagnets
We present comprehensive numerical results for domain growth in the
two-dimensional {\it Random Bond Ising Model} (RBIM) with nonconserved Glauber
kinetics. We characterize the evolution via the {\it domain growth law}, and
two-time quantities like the {\it autocorrelation function} and {\it
autoresponse function}. Our results clearly establish that the growth law shows
a crossover from a pre-asymptotic regime with "power-law growth with a
disorder-dependent exponent" to an asymptotic regime with "logarithmic growth".
We compare this behavior with previous results on one-dimensional disordered
systems and we propose a unifying picture in a renormalization group framework.
We also study the corresponding crossover in the scaling functions for the
two-time quantities. Super-universality is found not to hold. Clear evidence
supporting the dimensionality dependence of the scaling exponent of the
autoresponse function is obtained.Comment: Thoroughly revised manuscript. The Introduction, Section 2 and
Section 4 have been largely rewritten. References added. Final version
accepted for publication on Journal of Statistical Mechanics: Theory and
Experimen
Amplification of Fluctuations in Unstable Systems with Disorder
We study the early-stage kinetics of thermodynamically unstable systems with
quenched disorder. We show analytically that the growth of initial fluctuations
is amplified by the presence of disorder. This is confirmed by numerical
simulations of morphological phase separation (MPS) in thin liquid films and
spinodal decomposition (SD) in binary mixtures. We also discuss the
experimental implications of our results.Comment: 15 pages, 4 figure
Generation of Werner states via collective decay of coherently driven atoms
We show deterministic generation of Werner states as a steady state of the
collective decay dynamics of a pair of neutral atom coupled to a leaky cavity
and strong coherent drive. We also show how the scheme can be extended to
generate -particle analogue of the bipartite Werner states.Comment: 4 pages, 1 figur
A Singular Perturbation Analysis for \\Unstable Systems with Convective Nonlinearity
We use a singular perturbation method to study the interface dynamics of a
non-conserved order parameter (NCOP) system, of the reaction-diffusion type,
for the case where an external bias field or convection is present. We find
that this method, developed by Kawasaki, Yalabik and Gunton for the
time-dependant Ginzburg-Landau equation and used successfully on other NCOP
systems, breaks down for our system when the strength of bias/convection gets
large enough.Comment: 5 pages, PostScript forma
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