315 research outputs found
Universality of residence-time distributions in non-adiabatic stochastic resonance
We present mathematically rigorous expressions for the residence-time and
first-passage-time distributions of a periodically forced Brownian particle in
a bistable potential. For a broad range of forcing frequencies and amplitudes,
the distributions are close to periodically modulated exponential ones.
Remarkably, the periodic modulations are governed by universal functions,
depending on a single parameter related to the forcing period. The behaviour of
the distributions and their moments is analysed, in particular in the low- and
high-frequency limits.Comment: 8 pages, 1 figure New version includes distinction between
first-passage-time and residence-time distribution
Maximal Violation of Bell's Inequalities for Continuous Variable Systems
We generalize Bell's inequalities to biparty systems with continuous quantum
variables. This is achieved by introducing the Bell operator in perfect analogy
to the usual spin-1/2 systems. It is then demonstrated that two-mode squeezed
vacuum states display quantum nonlocality by using the generalized Bell
operator. In particular, the original Einstein-Podolsky-Rosen entangled states,
which are the limiting case of the two-mode squeezed vacuum states, can
maximally violate Bell's inequality due to Clauser, Horne, Shimony and Holt.
The experimental aspect of our scheme and nonlocality of arbitrary biparticle
entangled pure states of continuous variables are briefly considered.Comment: RevTEX, 4 pages, no figure. An important note was adde
Classical and Thermodynamic work fluctuations
We have studied the nature of classical work () and thermodynamic work
() fluctuations in systems driven out of equilibrium both in transient and
time periodic steady state. As the observation time of trajectory increases, we
show that the number of trajectories which exhibit excursions away from the
typical behaviour i.e., , and dissipated heat
decreases as anticipated for macroscopic time scales. Analytical expressions
for such trajectories are obtained. Trajectory for which may not
correspond to or . The applicability of steady state
fluctuation theorems are discussed in our linear as well as nonlinear models.Comment: Based on the talk presented by Mamata Sahoo at the Condensed Matter
Days-Aug. 2008 held at Viswavarati University, Kolkata. 19 pages, 8 figure
Quantum dynamics in strong fluctuating fields
A large number of multifaceted quantum transport processes in molecular
systems and physical nanosystems can be treated in terms of quantum relaxation
processes which couple to one or several fluctuating environments. A thermal
equilibrium environment can conveniently be modelled by a thermal bath of
harmonic oscillators. An archetype situation provides a two-state dissipative
quantum dynamics, commonly known under the label of a spin-boson dynamics. An
interesting and nontrivial physical situation emerges, however, when the
quantum dynamics evolves far away from thermal equilibrium. This occurs, for
example, when a charge transferring medium possesses nonequilibrium degrees of
freedom, or when a strong time-dependent control field is applied externally.
Accordingly, certain parameters of underlying quantum subsystem acquire
stochastic character. Herein, we review the general theoretical framework which
is based on the method of projector operators, yielding the quantum master
equations for systems that are exposed to strong external fields. This allows
one to investigate on a common basis the influence of nonequilibrium
fluctuations and periodic electrical fields on quantum transport processes.
Most importantly, such strong fluctuating fields induce a whole variety of
nonlinear and nonequilibrium phenomena. A characteristic feature of such
dynamics is the absence of thermal (quantum) detailed balance.Comment: review article, Advances in Physics (2005), in pres
Long term outcome of cavotricuspid isthmus cryoablation for the treatment of common atrial flutter in 180 patients: A single center experience
Unmappable ventricular tachycardia after an old myocardial infarction. Long-term results of substrate modification in patients with an implantable cardioverter defibrillator
Purpose The frequent occurrence of ventricular tachycardia can create a serious problem in patients with an implantable cardioverter defibrillator. We assessed the long-term efficacy of catheter-based substrate modification using the voltage mapping technique of infarct-related ventricular tachycardia and recurrent device therapy. Methods The study population consisted of 27 consecutive patients (age 68 +/- 8 years, 25 men, mean left ventricular ejection fraction 31 +/- 9%) with an old myocardial infarction and multiple and/or hemodynamically not tolerated ventricular tachycardia necessitating repeated device therapy. A total of 31 substrate modification procedures were performed using the three-dimensional electroanatomical mapping system. Patients were followed up for a median of 23.5 (interquartile range 6.5-53.2) months before and 37.8 (interquartile range 11.7-71.8) months after ablation. Antiarrhythmic drugs were not changed after the procedure, and were stopped 6 to 9 months after the procedure in patients who did not show ventricular tachycardia recurrence. Results Median ventricular tachycardias were 1.6 (interquartile range 0.7-6.7) per month before and 0.2 (interquartile range 0.00-1.3) per month after ablation (P = 0.006). Nine ventricular fibrillation episodes were registered in seven patients before and two after ablation (P = 0.025). Median antitachycardia pacing decreased from 1.6 (interquartile range 0.01-5.5) per month before to 0.18 (interquartile range 0.00-1.6) per month after ablation (P = 0.069). Median number of shocks decreased from 0.19 (interquartile range 0.04-0.81) per month before to 0.00 (interquartile range 0.00-0.09) per month after ablation (P = 0.001). One patient had a transient ischemic attack during the procedure, and another developed pericarditis. Nine patients died during follow-up, eight patients due to heart failure and one patient during valve surgery. Conclusion Catheter-based substrate modification using voltage mapping results in a long-lasting reduction of cardioverter defibrillator therapy in patients with multiple and/or hemodynamically not tolerated infarct-related ventricular tachyarrhythmia
Stochastic dynamics and mean field approach in a system of three interacting species
The spatio-temporal dynamics of three interacting species, two preys and one
predator, in the presence of two different kinds of noise sources is studied.
To describe the spatial distributions of the species we use a model based on
Lotka-Volterra equations. A correlated dichotomous noise acts on \beta, the
interaction parameter between the two preys, and a multiplicative white noise
affects directly the dynamics of each one of the three species. We study the
time behaviour of the three species in single site for different values of the
multiplicative noise intensity, finding noise-induced oscillations of the three
species densities with an anticorrelated behaviour of the two preys.
Afterwards, by considering a spatially extended system formed by a
two-dimensional lattice with N sites and applying a mean field approach, we get
the corresponding moment equations in Gaussian approximation. Within this
formalism we obtain the time behaviour of the first and second order moments
for different values of multiplicative noise intensity, with \beta(t) subject
to the same dichotomous noise source. Finally, we compare our results with
those obtained by using a coupled map lattice model, consisting of a time
discrete version of the Lotka-Volterra equations.Comment: 21 pages, 7 figures. Submitted to Centr. Eur. J. Phy
Accountability in the East Asian economic miracle, crisis and recovery
Despite claims that accountability enables 'good governance' proper, its specific origins, character and limitations are not yet fully clear. In order to explicate the nature of accountability better this paper will, therefore, formulate and apply its own comparative framework to the case of the East Asian economic miracle, crisis and recovery in particular. In so doing it finds that, even when accountability emerged as a mid-crisis issue that was dramatically reconfigured for any due recovery later, it was not itself then sufficiently explicated for all the implications and consequences to be realized fully. Once it is explicated more fully, however, the further implications and consequences of changing accountability for economic governance question precisely what is to be expected from accountability per se
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