169,830 research outputs found
Generalized Jarzynski's equality in inhomogeneous Markov chains
No full textA rigorous mathematical theory of generalized Jarzynski's equality in inhomogeneous Markov chains is given. Then, we explain its physical meaning and applications through several previous work including the original works of Jarzynski [Phys. Rev. Lett. 78, 2690 (1997); Phys. Rev. E 56, 5018 (1997); J. Stat. Phys. 96, 415 (1999); J. Stat. Phys. 98, 77 (2000)] and Crooks [J. Stat. Phys. 90, 1481 (1998); Phys. Rev. E 60, 2721 (1999); Phys. Rev. E 61, 2361 (2000)], Hatano-Sasa equality [Phys. Rev. E 86, 3463 (2001)], and the Gibbs free energy differences in stoichiometric chemical systems. By the way, we also consider the denumerable case. (c) 2007 American Institute of Physics.Physics, MathematicalSCI(E)0ARTICLE5null4
Jarzynski Equality in PT-Symmetric Quantum Mechanics
No full textWe show that the quantum Jarzynski equality generalizes to PT-symmetric quantum mechanics with unbroken PT symmetry. In the regime of broken PT symmetry, the Jarzynski equality does not hold as also the CPT norm is not preserved during the dynamics. These findings are illustrated for an experimentally relevant system—two coupled optical waveguides. It turns out that for these systems the phase transition between the regimes of unbroken and broken PT symmetry is thermodynamically inhibited as the irreversible work diverges at the critical point.We thank C. M. Bender for insightful discussions. S. D. acknowledges financial support by the U.S. Department of Energy through a LANL Director’s Funded Fellowship.https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.15060
Jarzynski equality for the jepsen gas
No full textPACS. 02.50.-r – Probability theory, stochastic processes, and statistics. PACS. 05.70.Ln – Nonequilibrium and irreversible thermodynamics. PACS. 05.20.-y – Classical statistical mechanics. Abstract. – We illustrate the Jarzynski equality on the exactly solvable model of an ideal gas in uniform expansion or compression. The analytical results for the probability density P (W) of the work W performed by the gas are compared with the results of molecular dynamics simulations for a two-dimensional dilute gas of hard spheres, a prototype for a real, slightly non-ideal gas. Exactly solvable models play an important role in statistical mechanics. They complement and verify results that are derived from general and usually abstract arguments, while at the same time they offer insight and intuition. They are particularly useful in far-from-equilibrium situations, for which few generic exact results are available. In this letter, we focus on a remarkable result in nonequilibrium statistical mechanics, namely the Jarzynski equality [1,2], which has given rise to a certain amount of confusion about its validity and interpretation [3]. The Jarzynski equality relates the statistics of the amount of work W performed by a syste
Applying bi-directional Jarzynski methods to quasi-equilibrium states
No full textMeasuring free energy differences between states is of fundamental importance to understanding and predicting the behaviour of thermodynamic systems. The Jarzynski equality provides a method for measuring free energy differences using non-equilibrium work paths and represents a major advance of modern thermodynamics. Recent work has extended the theory by usingwork paths in both directions between the states to improve the accuracy of the free energy measurement. It has also been shown that the Jarzynski equality can be adapted to measure the free energy of quasi-equilibrium systems such as glasses. Here we combine these advances to accurately measure the free energy difference between a glassy state and equilibrium using bi-directional methods. For this system however, the result is not as accurate as that achieved using the work evaluated in a single direction
The quantum Jarzynski inequality for superconducting optical cavities
No full textThe quantum version of Jarzynski equality was theoretically investigated for the work operator in the interaction picture. Since the Hamiltonian is time-dependent, it does not commute with itself at different times, then we have solved analytically its dynamics with lie-algebraic techniques. The physical object is a superconducting optical cavity. It was shown that the quantum dynamics of a cavity does not obey Jarzynski’s equality in the small temperature regime , if we consider a quantum work operator defined in a protocol interaction picture. The case of higher temperatures we are in Jarzynski regime and Jarzynski equality can be used to obtain statistical information about work done on the cavity. Since, for all used parameters, the state is a thermal state and its dynamics is of the harmonic oscillator, then this quantum regime is related to the protocol action. The protocol can be implemented by injecting a field in the cavity, thus it creates quantum resources
The free energy of expansion and contraction: treatment of arbitrary systems using the Jarzynski equality
No full textThermodynamic integration, free energy perturbation, and slow change techniques have long been utilised in the calculation of free energy differences between two states of a system that has undergone some transformation. With the introduction of the Jarzynski equality and the Crooks relation, new approaches are possible. This paper investigates an important phenomenon – systems undergoing a change in volume/density – and derives both the Jarzynski equality and Crooks relation of such systems using a statistical mechanical approach. These results apply to systems with arbitrary particle interactions and densities. The application of this approach to the expansion/compression of particles confined within a vessel with a piston and within a periodic system is considered
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Temperature-extended Jarzynski relation: Application to the numerical calculation of the surface tension
No full textInternational audienceWe consider a generalization of the Jarzynski relation to the case where the system interacts with a bath for which the temperature is not kept constant but can vary during the transformation. We suggest to use this relation as a replacement to the thermodynamic perturbation method or the Bennett method for the estimation of the order-order surface tension by Monte Carlo simulations. To demonstrate the feasibility of the method, we present some numerical data for the 3D Ising model
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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