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https://www.readbyqxmd.com/read/28429787/heat-temperature-and-clausius-inequality-in-a-model-for-active-brownian-particles
#1
Umberto Marini Bettolo Marconi, Andrea Puglisi, Claudio Maggi
Methods of stochastic thermodynamics and hydrodynamics are applied to a recently introduced model of active particles. The model consists of an overdamped particle subject to Gaussian coloured noise. Inspired by stochastic thermodynamics, we derive from the system's Fokker-Planck equation the average exchanges of heat and work with the active bath and the associated entropy production. We show that a Clausius inequality holds, with the local (non-uniform) temperature of the active bath replacing the uniform temperature usually encountered in equilibrium systems...
April 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28415284/theory-of-linear-sweep-voltammetry-with-diffuse-charge-unsupported-electrolytes-thin-films-and-leaky-membranes
#2
David Yan, Martin Z Bazant, P M Biesheuvel, Mary C Pugh, Francis P Dawson
Linear sweep and cyclic voltammetry techniques are important tools for electrochemists and have a variety of applications in engineering. Voltammetry has classically been treated with the Randles-Sevcik equation, which assumes an electroneutral supported electrolyte. In this paper, we provide a comprehensive mathematical theory of voltammetry in electrochemical cells with unsupported electrolytes and for other situations where diffuse charge effects play a role, and present analytical and simulated solutions of the time-dependent Poisson-Nernst-Planck equations with generalized Frumkin-Butler-Volmer boundary conditions for a 1:1 electrolyte and a simple reaction...
March 2017: Physical Review. E
https://www.readbyqxmd.com/read/28415177/influence-of-atomic-kinetics-in-the-simulation-of-plasma-microscopic-properties-and-thermal-instabilities-for-radiative-bow-shock-experiments
#3
G Espinosa, R Rodríguez, J M Gil, F Suzuki-Vidal, S V Lebedev, A Ciardi, J G Rubiano, P Martel
Numerical simulations of laboratory astrophysics experiments on plasma flows require plasma microscopic properties that are obtained by means of an atomic kinetic model. This fact implies a careful choice of the most suitable model for the experiment under analysis. Otherwise, the calculations could lead to inaccurate results and inappropriate conclusions. First, a study of the validity of the local thermodynamic equilibrium in the calculation of the average ionization, mean radiative properties, and cooling times of argon plasmas in a range of plasma conditions of interest in laboratory astrophysics experiments on radiative shocks is performed in this work...
March 2017: Physical Review. E
https://www.readbyqxmd.com/read/28333590/mean-first-passage-memory-lifetimes-by-reducing-complex-synapses-to-simple-synapses
#4
Terry Elliott
Memory models that store new memories by forgetting old ones have memory lifetimes that are rather short and grow only logarithmically in the number of synapses. Attempts to overcome these deficits include "complex" models of synaptic plasticity in which synapses possess internal states governing the expression of synaptic plasticity. Integrate-and-express, filter-based models of synaptic plasticity propose that synapses act as low-pass filters, integrating plasticity induction signals before expressing synaptic plasticity...
March 23, 2017: Neural Computation
https://www.readbyqxmd.com/read/28325129/lobectomy-for-non-small-cell-lung-carcinoma-a-nationwide-study-of-short-and-long-term-survival
#5
G N Oskarsdottir, H Halldorsson, M I Sigurdsson, B M Fridriksson, K Baldvinsson, A W Orrason, S Jonsson, M Planck, T Gudbjartsson
INTRODUCTION: Lobectomy is the standard curative treatment for non-small cell carcinoma (NSCLC) of the lung. Most studies on lobectomy have focused on short-term outcome and 30-day mortality. The aim of this study was to determine both short-term and long-term surgical outcome in all patients who underwent lobectomy for NSCLC in Iceland over a 24-year period. MATERIAL AND METHODS: The study involved 489 consecutive patients with NSCLC who underwent lobectomy with curative intent in Iceland, 1991-2014...
March 21, 2017: Acta Oncologica
https://www.readbyqxmd.com/read/28306551/master-equations-and-the-theory-of-stochastic-path-integrals
#6
Markus F Weber, Erwin Frey
This review provides a pedagogic and self-contained introduction to master equations and to their representation by path integrals. Since the 1930s, master equations have served as a fundamental tool to understand the role of fluctuations in complex biological, chemical, and physical systems. Despite their simple appearance, analyses of master equations most often rely on low-noise approximations such as the Kramers-Moyal or the system size expansion, or require ad-hoc closure schemes for the derivation of low-order moment equations...
April 2017: Reports on Progress in Physics
https://www.readbyqxmd.com/read/28297849/continuous-time-limits-of-the-utterance-selection-model
#7
Jérôme Michaud
In this paper we derive alternative continuous time limits of the utterance selection model (USM) for language change [G. J. Baxter et al., Phys. Rev. E 73, 046118 (2006)PLEEE81539-375510.1103/PhysRevE.73.046118]. This is motivated by the fact that the Fokker-Planck continuous time limit derived in the original version of the USM is only valid for a small range of parameters. We investigate the consequences of relaxing these constraints on parameters. Using the normal approximation of the multinomial approximation, we derive a continuous time limit of the USM in the form of a weak-noise stochastic differential equation...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28243720/extracting-cellular-automaton-rules-from-physical-langevin-equation-models-for-single-and-collective-cell-migration
#8
J M Nava-Sedeño, H Hatzikirou, F Peruani, A Deutsch
Cellular automata (CA) are discrete time, space, and state models which are extensively used for modeling biological phenomena. CA are "on-lattice" models with low computational demands. In particular, lattice-gas cellular automata (LGCA) have been introduced as models of single and collective cell migration. The interaction rule dictates the behavior of a cellular automaton model and is critical to the model's biological relevance. The LGCA model's interaction rule has been typically chosen phenomenologically...
February 27, 2017: Journal of Mathematical Biology
https://www.readbyqxmd.com/read/28208407/stochastically-gated-local-and-occupation-times-of-a-brownian-particle
#9
Paul C Bressloff
We generalize the Feynman-Kac formula to analyze the local and occupation times of a Brownian particle moving in a stochastically gated one-dimensional domain. (i) The gated local time is defined as the amount of time spent by the particle in the neighborhood of a point in space where there is some target that only receives resources from (or detects) the particle when the gate is open; the target does not interfere with the motion of the Brownian particle. (ii) The gated occupation time is defined as the amount of time spent by the particle in the positive half of the real line, given that it can only cross the origin when a gate placed at the origin is open; in the closed state the particle is reflected...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28208350/l%C3%A3-vy-flights-in-the-presence-of-a-point-sink-of-finite-strength
#10
Deepika Janakiraman
In this paper, the absorption of a particle undergoing Lévy flight in the presence of a point sink of arbitrary strength and position is studied. The motion of such a particle is given by a modified Fokker-Planck equation whose exact solution in the Laplace domain can be described in terms of the Laplace transform of the unperturbed (absence of the sink) Green's function. This solution for the Green's function is a well-studied, generic result which applies to both fractional and usual Fokker-Planck equations alike...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28157360/redefining-the-axion-window
#11
Luca Di Luzio, Federico Mescia, Enrico Nardi
A major goal of axion searches is to reach inside the parameter space region of realistic axion models. Currently, the boundaries of this region depend on somewhat arbitrary criteria, and it would be desirable to specify them in terms of precise phenomenological requirements. We consider hadronic axion models and classify the representations R_{Q} of the new heavy quarks Q. By requiring that (i) the Q's are sufficiently short lived to avoid issues with long-lived strongly interacting relics, (ii) no Landau poles are induced below the Planck scale; 15 cases are selected which define a phenomenologically preferred axion window bounded by a maximum (minimum) value of the axion-photon coupling about 2 times (4 times) larger than is commonly assumed...
January 20, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28157343/critical-number-of-fields-in-stochastic-inflation
#12
Vincent Vennin, Hooshyar Assadullahi, Hassan Firouzjahi, Mahdiyar Noorbala, David Wands
Stochastic effects in generic scenarios of inflation with multiple fields are investigated. First passage time techniques are employed to calculate the statistical moments of the number of inflationary e-folds, which give rise to all correlation functions of primordial curvature perturbations through the stochastic δN formalism. The number of fields is a critical parameter. The probability of exploring arbitrarily large-field regions of the potential becomes nonvanishing when more than two fields are driving inflation...
January 20, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28089383/-long-term-psychiatric-hospitalizations
#13
L Plancke, A Amariei
BACKGROUND: Long-term hospitalizations in psychiatry raise the question of desocialisation of the patients and the inherent costs. METHODS: Individual indicators were extracted from a medical administrative database containing full-time psychiatric hospitalizations for the period 2011-2013 of people over 16 years old living in the French region of Nord-Pas-de-Calais. We calculated the proportion of people who had experienced a hospitalization with a duration of 292 days or more during the study period...
February 2017: Revue D'épidémiologie et de Santé Publique
https://www.readbyqxmd.com/read/27993627/an-open-loop-approach-to-calculate-noise-induced-transitions
#14
Farzaneh Maleki, Attila Becskei
Bistability permits the co-existence of two distinct cell fates in a population of genetically identical cells. Noise induced transitions between two fates of a bistable system are difficult to calculate due to the intricate interplay between nonlinear dynamics and noise in bistable positive feedback loops. Here we opened multivariable feedback loops at the slowest variable to obtain the open-loop function and the fluctuations in the open-loop output. By the subsequent reclosing of the loop, we calculated the mean first passage time (MFPT) using the Fokker-Planck equation in good agreement with the exact stochastic simulation...
December 18, 2016: Journal of Theoretical Biology
https://www.readbyqxmd.com/read/27967083/time-dependent-probability-density-function-in-cubic-stochastic-processes
#15
Eun-Jin Kim, Rainer Hollerbach
We report time-dependent probability density functions (PDFs) for a nonlinear stochastic process with a cubic force using analytical and computational studies. Analytically, a transition probability is formulated by using a path integral and is computed by the saddle-point solution (instanton method) and a new nonlinear transformation of time. The predicted PDF p(x,t) in general involves a time integral, and useful PDFs with explicit dependence on x and t are presented in certain limits (e.g., in the short and long time limits)...
November 2016: Physical Review. E
https://www.readbyqxmd.com/read/27967014/statistics-of-the-stochastically-forced-lorenz-attractor-by-the-fokker-planck-equation-and-cumulant-expansions
#16
Altan Allawala, J B Marston
We investigate the Fokker-Planck description of the equal-time statistics of the three-dimensional Lorenz attractor with additive white noise. The invariant measure is found by computing the zero (or null) mode of the linear Fokker-Planck operator as a problem of sparse linear algebra. Two variants are studied: a self-adjoint construction of the linear operator and the replacement of diffusion with hyperdiffusion. We also access the low-order statistics of the system by a perturbative expansion in equal-time cumulants...
November 2016: Physical Review. E
https://www.readbyqxmd.com/read/27820827/effect-of-ionic-diffusion-on-extracellular-potentials-in-neural-tissue
#17
Geir Halnes, Tuomo Mäki-Marttunen, Daniel Keller, Klas H Pettersen, Ole A Andreassen, Gaute T Einevoll
Recorded potentials in the extracellular space (ECS) of the brain is a standard measure of population activity in neural tissue. Computational models that simulate the relationship between the ECS potential and its underlying neurophysiological processes are commonly used in the interpretation of such measurements. Standard methods, such as volume-conductor theory and current-source density theory, assume that diffusion has a negligible effect on the ECS potential, at least in the range of frequencies picked up by most recording systems...
November 2016: PLoS Computational Biology
https://www.readbyqxmd.com/read/27782504/cdpd-a-new-dissipative-particle-dynamics-method-for-modeling-electrokinetic-phenomena-at-the-mesoscale
#18
Mingge Deng, Zhen Li, Oleg Borodin, George Em Karniadakis
We develop a "charged" dissipative particle dynamics (cDPD) model for simulating mesoscopic electrokinetic phenomena governed by the stochastic Poisson-Nernst-Planck and the Navier-Stokes equations. Specifically, the transport equations of ionic species are incorporated into the DPD framework by introducing extra degrees of freedom and corresponding evolution equations associated with each DPD particle. Diffusion of ionic species driven by the ionic concentration gradient, electrostatic potential gradient, and thermal fluctuations is captured accurately via pairwise fluxes between DPD particles...
October 14, 2016: Journal of Chemical Physics
https://www.readbyqxmd.com/read/27739815/entropy-production-by-active-particles-coupling-of-odd-and-even-functions-of-velocity
#19
Debasish Chaudhuri
Nonequilibrium stochastic dynamics of several active Brownian systems are modeled in terms of nonlinear velocity dependent force. In general, this force may consist of both even and odd functions of velocity. We derive the expression for total entropy production in such systems using the Fokker-Planck equation. The result is consistent with the expression for stochastic entropy production in the reservoir that we obtain from probabilities of time-forward and time-reversed trajectories, leading to fluctuation theorems...
September 2016: Physical Review. E
https://www.readbyqxmd.com/read/27739760/diffusion-in-an-expanding-medium-fokker-planck-equation-green-s-function-and-first-passage-properties
#20
S B Yuste, E Abad, C Escudero
We present a classical, mesoscopic derivation of the Fokker-Planck equation for diffusion in an expanding medium. To this end, we take a conveniently generalized Chapman-Kolmogorov equation as the starting point. We obtain an analytical expression for the Green's function (propagator) and investigate both analytically and numerically how this function and the associated moments behave. We also study first-passage properties in expanding hyperspherical geometries. We show that in all cases the behavior is determined to a great extent by the so-called Brownian conformal time τ(t), which we define via the relation τ[over ̇]=1/a^{2}, where a(t) is the expansion scale factor...
September 2016: Physical Review. E
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