Properties of iterative Monte Carlo single histogram reweighting

We present iterative Monte Carlo algorithm for which the temperature variable is attracted by a critical point. The algorithm combines techniques of single histogram reweighting and linear filtering. The 2d Ising model of ferromagnet is studied numerically as an illustration. In that case, the iterations uncovered stationary regime with invariant probability distribution function of temperature which is peaked nearly the pseudocritical temperature of specific heat. The sequence of generated temperatures is analyzed in terms of stochastic autoregressive model. The error of histogram reweighting can be better understood within the suggested model. The presented model yields a simple relation, connecting variance of pseudocritical temperature and parameter of linear filtering.Comment: 3 figure

Interaction Effects in the Mesoscopic Regime: A Quantum Monte Carlo Study of Irregular Quantum Dots

We address the issue of accurately treating interaction effects in the mesoscopic regime by investigating the ground state properties of isolated irregular quantum dots. Quantum Monte Carlo techniques are used to calculate the distributions of ground state spin and addition energy. We find a reduced probability of high spin and a somewhat larger even/odd alternation in the addition energy from quantum Monte Carlo than in local spin density functional theory. In both approaches, the even/odd effect gets smaller with increasing number of electrons, contrary to the theoretical understanding of large dots. We argue that the local spin density approximation over predicts the effects of interactions in quantum dots.Comment: Final Version, to appear in PRB as a Rapid Com

Longitudinal investigation of Salmonella spp. from farm to fork in the pig industry in Reunion Island

Salmonella is, after Campylobacter, the most reported zoonotic pathogen in Europe. Pork meat is frequently incriminated in salmonellosis. However, asymptomatic carrying of Salmonella by pigs makes its detection difficult. Despite its tropical situation, pig industry of Reunion Island is also concerned by this public health burden

Prevalence and risk indicators associated with Salmonella infection in farrow-to-finish farm in Reunion Island

Salmonella is the second cause of foodborne diseases in France and pork products are regularly incriminated. For the implementation of control measures in farms, it is necessary to better understand the risks of infection of pigs by Salmonella at farms. Our epidemiological study aims to determine Salmonella prevalence of fattening pigs in Reunion Island, oversea territory of France, and the main risk indicators for pig infection. Fifty farms (farrow-to finish and multiplier) were randomly selected and visited 4 times: at slaughtered previous batch, after cleaning and disinfection, beginning and end of the fattening period for the studied batch. Pools of fresh faeces, gauze socks and gauze swabs were sampled to assess the bacteriological status of these pig farms. A questionnaire was submitted to farmers and analysed for the further identification of risk indicators

Etude et réalisation d'un système à base de connaissances d'aide à la décision en cas d'intervention sur des accidents majeurs

National audienceL'accident majeur se caractérise par une forte dynamique, l'urgence et une part d'inconnue élevée. La complexité de ce type d'accident rend particulièrement délicate la gestion de l'intervention des services de secours. En particulier, le responsable de l'intervention éprouve des difficultés à dégager une vue d'ensemble de l'accident et de son contexte, et donc à prendre une décision. Le projet présenté a pour but d'étudier et réaliser un système à base de connaissances d'aide à la décision en intervention, non spécifique à un type d'accident particulier. On a pour cela modélisé l'expertise des sapeurs-pompiers sur la Méthode de Raisonnement Tactique (MRT). Le modèle formel d'expertise obtenu permet de définir une ontologie de l'intervention. Il sera utilisé pour mettre en oeuvre une base de connaissances sur l'intervention. L'architecture proposée pour le système informatique est articulée autour d'un Système de Gestion de Base de Connaissances (SGBC) qui permet à différents outils d'exploiter et de gérer les connaissances de la base. Dans un premier temps, un outil d'Enseignement Assisté par Ordinateur de la MRT permettra de valider le modèle en le testant sur un grand nombre de personnes. Le retour d'expérience permettra alors de spécifier ce que sera l'outil final d'aide à la décision sur le terrain

A biochemical study of the marine annelid worm, Thoracophelia mucronata: Its food, biochromes and carotenoid metabolism

Comparative biochemical studies of numerous marine invertebrates and fishes have indicated that the majority of such species so far examined selectively assimilate and store xanthophyllic or allied oxygenated carotenoids rather than carotenes, when consuming food containing both types of pigment. In some forms there is complete exclusion of carotenes, e.g., in several fishes, in the sea mussel (Mytilus californianus), in at least three brittle stars, and in some color-variants of the anemone Metridium senile. Some asteroid echinoderms store carotenes, but in far lower concentrations than xanthophylls, while four species of echinoids appear to assimilate relatively greater quantities of carotenes (Fox, Updegraff and Novelli, 1944)

Towards wave extraction in numerical relativity: the quasi-Kinnersley frame

The Newman-Penrose formalism may be used in numerical relativity to extract coordinate-invariant information about gravitational radiation emitted in strong-field dynamical scenarios. The main challenge in doing so is to identify a null tetrad appropriately adapted to the simulated geometry such that Newman-Penrose quantities computed relative to it have an invariant physical meaning. In black hole perturbation theory, the Teukolsky formalism uses such adapted tetrads, those which differ only perturbatively from the background Kinnersley tetrad. At late times, numerical simulations of astrophysical processes producing isolated black holes ought to admit descriptions in the Teukolsky formalism. However, adapted tetrads in this context must be identified using only the numerically computed metric, since no background Kerr geometry is known a priori. To do this, this paper introduces the notion of a quasi-Kinnersley frame. This frame, when space-time is perturbatively close to Kerr, approximates the background Kinnersley frame. However, it remains calculable much more generally, in space-times non-perturbatively different from Kerr. We give an explicit solution for the tetrad transformation which is required in order to find this frame in a general space-time.Comment: 13 pages, 3 figure

Primordial magnetic field and spectral distortion of cosmic background radiation

The role played by a primordial magnetic field during the pre-recombination epoch is analysed through the cyclotron radiation (due to the free electrons) it might produce in the primordial plasma. We discuss the constraint implied by the measurement or lack thereof COBE on this primordial field.Comment: to appear in International Journal of Mod. Phy