Time-Delayed transfer functions simulations for LMXBs

Recent works (Steeghs & Casares 2002, Casares et al. 2003, Hynes et al. 2003) have demonstrated that Bowen flourescence is a very efficient tracer of the companion star in LMXBs. We present a numerical code to simulate time-delayed transfer functions in LMXBs, specific to the case of reprocessing in emission lines. The code is also able to obtain geometrical and binary parameters by fitting observed (X-ray + optical) light curves using simulated annealing methods. In this work we present the geometrical model for the companion star and the analytical model for the disc and show synthetic time-delay transfer functions for different orbital phases and system parameters.Comment: Contribution presented at the conference "Interacting Binaries: Accretion, Evolution and Outcomes", held in Cefalu, Sicily (Italy) in July 2004. To be published by AIP (American Institute of Physics), eds. L. A. Antonelli, L. Burderi, F. D'Antona, T. Di Salvo, G.L. Israel, L. Piersanti, O. Straniero, A. Tornambe. 4 pages, 4 figure

Effect of the Gribov horizon on the Polyakov loop and vice versa

We consider finite temperature SU(2) gauge theory in the continuum formulation, which necessitates the choice of a gauge fixing. Choosing the Landau gauge, the existing gauge copies are taken into account by means of the Gribov-Zwanziger (GZ) quantization scheme, which entails the introduction of a dynamical mass scale (Gribov mass) directly influencing the Green functions of the theory. Here, we determine simultaneously the Polyakov loop (vacuum expectation value) and Gribov mass in terms of temperature, by minimizing the vacuum energy w.r.t. the Polyakov loop parameter and solving the Gribov gap equation. Inspired by the Casimir energy-style of computation, we illustrate the usage of Zeta function regularization in finite temperature calculations. Our main result is that the Gribov mass directly feels the deconfinement transition, visible from a cusp occurring at the same temperature where the Polyakov loop becomes nonzero. In this exploratory work we mainly restrict ourselves to the original Gribov-Zwanziger quantization procedure in order to illustrate the approach and the potential direct link between the vacuum structure of the theory (dynamical mass scales) and (de)confinement. We also present a first look at the critical temperature obtained from the Refined Gribov-Zwanziger approach. Finally, a particular problem for the pressure at low temperatures is reported.Comment: 19 pages, 8 .pdf figures. v2: extended section 3 + extra references; version accepted for publication in EPJ

Contrasting roles of axonal (pyramidal cell) and dendritic (interneuron) electrical coupling in the generation of neuronal network oscillations

Electrical coupling between pyramidal cell axons, and between interneuron dendrites, have both been described in the hippocampus. What are the functional roles of the two types of coupling? Interneuron gap junctions enhance synchrony of γ oscillations (25-70 Hz) in isolated interneuron networks and also in networks containing both interneurons and principal cells, as shown in mice with a knockout of the neuronal (primarily interneuronal) connexin36. We have recently shown that pharmacological gap junction blockade abolishes kainate-induced γ oscillations in connexin36 knockout mice; without such gap junction blockade, γ oscillations do occur in the knockout mice, albeit at reduced power compared with wild-type mice. As interneuronal dendritic electrical coupling is almost absent in the knockout mice, these pharmacological data indicate a role of axonal electrical coupling in generating the γ oscillations. We construct a network model of an experimental γ oscillation, known to be regulated by both types of electrical coupling. In our model, axonal electrical coupling is required for the γ oscillation to occur at all; interneuron dendritic gap junctions exert a modulatory effect

Double non-perturbative gluon exchange: an update on the soft Pomeron contribution to pp scattering

We employ a set of recent, theoretically motivated, fits to non-perturbative unquenched gluon propagators to check in how far double gluon exchange can be used to describe the soft sector of pp scattering data (total and differential cross section). In particular, we use the refined Gribov--Zwanziger gluon propagator (as arising from dealing with the Gribov gauge fixing ambiguity) and the massive Cornwall-type gluon propagator (as motivated from Dyson-Schwinger equations) in conjunction with a perturbative quark-gluon vertex, next to a model based on the non-perturbative quark-gluon Maris-Tandy vertex, popular from Bethe-Salpeter descriptions of hadronic bound states. We compare the cross sections arising from these models with "older" ISR and more recent TOTEM and ATLAS data. The lower the value of total energy \sqrt{s}, the better the results appear to be.Comment: 14 pages, 8 .pdf figures. To appear in Phys.Rev.

Porque comemos o que comemos?: determinantes psicossociais da selecção alimentar

Este artigo apresenta uma breve análise sobre os determinantes psicossociais do comportamento alimentar. É essencial compreendermos os factores subjacentes às escolhas alimentares dos indivíduos, isto é, compreendermos porque é que comemos os alimentos que comemos e porque comemos a quantidade de alimentos que comemos, se pretendemos intervir neste domínio, seja ao nível da promoção da saúde, seja ao nível da prevenção ou tratamento da doença. No presente trabalho, apresenta-se uma análise sobre alguns dos determinantes psicológicos e sociais da regulação do comportamento alimentar, bem como uma síntese de alguns dos modelos explicativos da selecção alimentar (Modelo Desenvolvimental e Modelo Cognitivo). Procedemos, ainda, a uma reflexão sobre a relação entre alimentos, emoções, cognições e comportamentos, assim como a uma reflexão sobre a relação entre o stress e o comportamento alimentar. ------ ABSTRACT ------ This paper presents a brief analysis of the psychosocial determinants of eating behaviour. It is essential to understand the factors underlying food selection, that is to say, the factors that contribute to the individual eating, what he/she eats and how much he/she eats. In this paper, we present an analysis of some of the psychological and social factors which regulate eating behaviour, as well as some of the theoretical models that try to explain eating behaviour regulation (namely the Developmental Model and the Cognitive Model). We also discuss some issues concerning the relation between food, emotion, cognition and behaviour, and the relation between stress and eating behaviour

Equilibrium moisture content and heat of desorption of garlic

Desorption isotherms for 1 mm thick garlic slices were determined by a static gravimetric method at temperatures between 5 and 45ºC, in the relative humidity range from 11 to 98%. The experimental desorption data obtained in this study was fitted to BET and GAB equations to predict the desorption behavior of garlic. It was found that the GAB model was the most satisfactory model for representation of the sorption data. The results obtained in this study, are now being used in the development of a drying unit for garlic, by a suitable technique