H-Theorems from Autonomous Equations

The H-theorem is an extension of the Second Law to a time-sequence of states that need not be equilibrium ones. In this paper we review and we rigorously establish the connection with macroscopic autonomy. If for a Hamiltonian dynamics for many particles, at all times the present macrostate determines the future macrostate, then its entropy is non-decreasing as a consequence of Liouville's theorem. That observation, made since long, is here rigorously analyzed with special care to reconcile the application of Liouville's theorem (for a finite number of particles) with the condition of autonomous macroscopic evolution (sharp only in the limit of infinite scale separation); and to evaluate the presumed necessity of a Markov property for the macroscopic evolution.Comment: 13 pages; v1 -> v2: Sec. 1-2 considerably rewritten, minor corrections in Sec. 3-

WILDCOMS

Disease and contaminants can both pose major risks to wildlife and human populations. Disease is a natural driver regulating the dynamics of wildlife populations, but some diseases warrant particular attention because they (i) cause major mortalities that lead to population crashes, (eg., VHD in rabbits), (ii) threaten wildlife species of high conservation concern (for example squirrelpox virus in red squirrels), or (iii) pose a potential threat to Man (eg., rabies, avian influenza). The wildlife Disease & Contaminant Monoitoring and Surveillance (WILDCOMS) Network is a collaborative project among the major disease and contaminant monitoring schemes for vertebrate wildlife that operate in the United Kingdom. These schemes are run by various government agencies and laboratories, research centres, institutes, and academia. The overall aim is to establish a network which will foster and facilitate knowledge exchange, harmonisation towards best practice, and productive collaboration between: (i) partner organisations; (ii) surveillance schemes and end-users. It will aim to provide end-users with an integrated overview of environmental disease and contaminant risk. The specific objectives will be to develop the network and use it to address common challenges, specifically maximising dissemination of information to stakeholders and harmonisation towards common operational procedures to facilitate interaction and collaboration

Household fish preparation hygiene and cholera transmission in Monrovia, Liberia.

BACKGROUND: In the 1980s Vibrio cholerae was found to be an autochthonous resident of aquatic environments. As result, ingestion of undercooked, contaminated fish has been associated with cholera transmission. An alternative mechanism of transmission associated with fish was hypothesised by Schürmann et al. in 2002. He described a cholera case that was more likely to have been infected by contamination on the patient's hands rather than by ingestion of contaminated fish. METHODOLOGY: With fish being the main diet in Liberia, we decided to examine fish samples and preparation techniques in Monrovia. Excreta of 15 fish, caught in the estuarine waters of Monrovia, were analysed for V. cholerae. In addition, fish preparation methods were observed in 30 households. RESULTS: Two fish samples were found positive. Observations revealed that hygiene measures during the gutting process of fish were limited; although hands were usually rinsed, in all cases soap was not used. Furthermore, contaminated water was frequently reused during food preparation. CONCLUSIONS: Since the cooking process of fish (and thus elimination of bacteria) in Monrovia usually consists of both frying and boiling, it seems plausible that in this context, the hypothesis by Schürmann et al. could be applicable. Further research is necessary to confirm this association, which could be a starting point for more context-specific health education campaigns addressing food preparation hygiene as risk factor for cholera

Nonequilibrium Linear Response for Markov Dynamics, II: Inertial Dynamics

We continue our study of the linear response of a nonequilibrium system. This Part II concentrates on models of open and driven inertial dynamics but the structure and the interpretation of the result remain unchanged: the response can be expressed as a sum of two temporal correlations in the unperturbed system, one entropic, the other frenetic. The decomposition arises from the (anti)symmetry under time-reversal on the level of the nonequilibrium action. The response formula involves a statistical averaging over explicitly known observables but, in contrast with the equilibrium situation, they depend on the model dynamics in terms of an excess in dynamical activity. As an example, the Einstein relation between mobility and diffusion constant is modified by a correlation term between the position and the momentum of the particle

A nonequilibrium extension of the Clausius heat theorem

We generalize the Clausius (in)equality to overdamped mesoscopic and macroscopic diffusions in the presence of nonconservative forces. In contrast to previous frameworks, we use a decomposition scheme for heat which is based on an exact variant of the Minimum Entropy Production Principle as obtained from dynamical fluctuation theory. This new extended heat theorem holds true for arbitrary driving and does not require assumptions of local or close to equilibrium. The argument remains exactly intact for diffusing fields where the fields correspond to macroscopic profiles of interacting particles under hydrodynamic fluctuations. We also show that the change of Shannon entropy is related to the antisymmetric part under a modified time-reversal of the time-integrated entropy flux.Comment: 23 pages; v2: manuscript significantly extende

An extension of the Kac ring model

We introduce a unitary dynamics for quantum spins which is an extension of a model introduced by Mark Kac to clarify the phenomenon of relaxation to equilibrium. When the number of spins gets very large, the magnetization satisfies an autonomous equation as function of time with exponentially fast relaxation to the equilibrium magnetization as determined by the microcanonical ensemble. This is proven as a law of large numbers with respect to a class of initial data. The corresponding Gibbs-von Neumann entropy is also computed and its monotonicity in time discussed.Comment: 15 pages, v2 -> v3: minor typographic correctio

Amplification of compressional MHD waves in systems with forced entropy oscillations

The propagation of compressional MHD waves is studied for an externally driven system. It is assumed that the combined action of the external sources and sinks of the entropy results in the harmonic oscillation of the entropy (and temperature) in the system. It is found that with the appropriate resonant conditions fast and slow waves get amplified due to the phenomenon of parametric resonance. Besides, it is shown that the considered waves are mutually coupled as a consequence of the nonequilibrium state of the background medium. The coupling is strongest when the plasma $\beta \approx 1$. The proposed formalism is sufficiently general and can be applied for many dynamical systems, both under terrestrial and astrophysical conditions.Comment: 14 pages, 4 figures, Accepted to Physical Review