Probing the gluon density of the proton in the exclusive photoproduction of vector mesons at the LHC: A phenomenological analysis

The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken - $x$ variable and low values of the hard scale $Q^2$. An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon - hadron and hadron - hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrizations for the gluon distribution and estimate the exclusive vector meson photoproduction cross section at HERA and LHC using the leading logarithmic formalism. We perform a fit of the normalization of the $\gamma h$ cross section and the value of the hard scale for the process and demonstrate that the current LHCb experimental data are better described by models that assume a slow increasing of the gluon distribution at small - $x$ and low $Q^2$.Comment: 8 pages, 6 figures, 1 table. Version published in European Physical Journal

Clustering Properties of Dynamical Dark Energy Models

We provide a generic but physically clear discussion of the clustering properties of dark energy models. We explicitly show that in quintessence-type models the dark energy fluctuations, on scales smaller than the Hubble radius, are of the order of the perturbations to the Newtonian gravitational potential, hence necessarily small on cosmological scales. Moreover, comparable fluctuations are associated with different gauge choices. We also demonstrate that the often used homogeneous approximation is unrealistic, and that the so-called dark energy mutation is a trivial artifact of an effective, single fluid description. Finally, we discuss the particular case where the dark energy fluid is coupled to dark matter.Comment: 5 page

Mapping the train model for earthquakes onto the stochastic sandpile model

We perform a computational study of a variant of the ``train'' model for earthquakes [PRA 46, 6288 (1992)], where we assume a static friction that is a stochastic function of position rather than being velocity dependent. The model consists of an array of blocks coupled by springs, with the forces between neighbouring blocks balanced by static friction. We calculate the probability, P(s), of the occurrence of avalanches with a size s or greater, finding that our results are consistent with the phenomenology and also with previous models which exhibit a power law over a wide range. We show that the train model may be mapped onto a stochastic sandpile model and study a variant of the latter for non-spherical grains. We show that, in this case, the model has critical behaviour only for grains with large aspect ratio, as was already shown in experiments with real ricepiles. We also demonstrate a way to introduce randomness in a physically motivated manner into the model.Comment: 14 pages and 6 figures. Accepted in European Physical Journal

Differential mesenteric fat deposition in bovines fed on silage or concentrate is independent of glycerol membrane permeability

© The Animal Consortium 2011In the meat industry, the manipulation of fat deposition in cattle is of pivotal importance to improve production efficiency, carcass composition and ultimately meat quality. There is an increasing interest in the identification of key factors and molecular mechanisms responsible for the development of specific fat depots. This study aimed at elucidating the influence of breed and diet on adipose tissue membrane permeability and fluidity and their interplay on fat deposition in bovines. Two Portuguese autochthonous breeds, Alentejana and Barrosã, recognized as late- and early-maturing breeds, respectively, were chosen to examine the effects of breed and diet on fat deposition and on adipose membrane composition and permeability. Twenty-four male bovines from these breeds were fed on silage-based or concentrate-based diets for 11 months. Animals were slaughtered to determine their live slaughter and hot carcass weights, as well as weights of subcutaneous and visceral adipose depots. Mesenteric fat depots were excised and used to isolate adipocyte membrane vesicles where cholesterol content, fatty acid profile as well as permeability and fluidity were determined. Total accumulation of neither subcutaneous nor visceral fat was influenced by breed. In contrast, mesenteric and omental fat depots weights were higher in concentrate-fed bulls relative to silage-fed animals. Membrane fluidity and permeability to water and glycerol in mesenteric adipose tissue were found to be independent of breed and diet. Moreover, the deposition of cholesterol and unsaturated fatty acids, which may influence membrane properties, were unchanged among experimental groups. Adipose membrane lipids from the mesenteric fat depot of ruminants were rich in saturated fatty acids, and unaffected by polyunsaturated fatty acids dietary levels. Our results provide evidence against the involvement of cellular membrane permeability to glycerol on fat accumulation in mesenteric fat tissue of concentrate-fed bovines, which is consistent with the unchanged membrane lipid profile found among experimental groups.This study was supported by Fundação para a Ciência e a Tecnologia (FCT) through grant PTDC/CVT/2006/66114 and individual fellowships to Ana P. Martins (SFRH/BD/2009/65046), Ana S. H. Costa (SFRH/BD/2009/61068) and Susana V. Martins (SFRH/BPD/2009/63019). Paula A. Lopes is a researcher from the program ‘‘Ciência 2008’’ from FC

Desenvolvimento de um laboratório de ciências para os primeiros anos de escolaridade

A presente comunicação visa apresentar uma proposta de laboratório de ciências para os primeiros anos de escolaridade. Assim, pretende-se: (i) fundamentar a relevância de infraestruturas, equipamentos e recursos de suporte ao ensino das ciências e apresentar princípios orientadores apontados pela literatura para o desenvolvimento de laboratórios escolares e (ii) descrever o processo de concepção, validação e implementação inerente ao desenvolvimento de um laboratório de ciências numa escola do 1.º Ciclo do Ensino Básico (CEB), tendo por base o marco teórico de suporte ao desenvolvimento do mesmo

Resonance induced by repulsive interactions in a model of globally-coupled bistable systems

We show the existence of a competition-induced resonance effect for a generic globally coupled bistable system. In particular, we demonstrate that the response of the macroscopic variable to an external signal is optimal for a particular proportion of repulsive links. Furthermore, we show that a resonance also occurs for other system parameters, like the coupling strength and the number of elements. We relate this resonance to the appearance of a multistable region, and we predict the location of the resonance peaks, by a simple spectral analysis of the Laplacian matrix

Emoções e promoção da saúde

Ser capaz de gerir os próprios afectos bem como as relações inter-sociais ao longo do tempo, são a proposta do estudo que a seguir se apresenta. Parte-se do pressuposto que uma das formas mais profundas de assegurar a Promoção da Saúde intra e interpessoal, é aprender a tornar-se emocionalmente competente (Veiga Branco, 2004; 2007). Ser emocionalmente competente é ser capaz de encontrar soluções, a partir de recursos internos que emergem das emoções, e substancialmente da gestão das emoções e da automotivação que os sujeitos podem encontrar. Este conjunto de destrezas parece potencializar a percepção de uma vida psicoafectiva à qual parecem estar ligados o êxito social, individual, sucesso profissional e felicidade conjugal (Goleman, 1995; 2000). A Promoção e Educação para a Saúde insere o bem-estar da pessoa como um todo, o que envolve: o homem é razão, mas também emoção. Métodos Estudo exploratório, quantitativo e transversal. Utiliza o instrumento desenvolvido para estudos anteriores “Escala Veiga de Competência Emocional” (EVCE), (Veiga Branco, 2004, a),b) e 2007), cujas respostas – submetidas à Análise de Componentes Principais e analisadas por Alpha de Cronbach – foram tratadas através do programa SPSS 13.0. A amostra do estudo é constituída por 183 sujeitos, com idades compreendidas entre os 18 e77 anos, residentes em Bragança. Destes, 58 eram do sexo masculino e 125 do sexo feminino. Objectivos: Conhecer e analisar o perfil de Competência Emocional de uma amostra da população de Bragança; Identificar as diferenças entre os estudos apresentados no construto e os dados recolhidos no trabalho empírico.Resultados Qual é o Perfil de Competência Emocional encontrado? Verifica-se que os estudantes Pouco Frequentemente vivem a Auto-consciência de Fenómenos Emocionais. Também fazem a Gestão de Emoções com Pouca Frequência tal como a Auto motivação. Mas têm a percepção que Por Norma, vivem a Empatia e a Gestão de Emoções em Grupo. Todavia é preocupante que ocorram frequentemente Alterações relacionadas e racionais (x 3,80+ dp1.6); e que Por norma, 25% dos estudantes vivam uma Percepção negativa de si: ruminação e absorção emocional (x 3.17+ dp 1,53); e sobretudo que 20% dos estudantes adopte por norma as Estratégias: isolamento, intrusão, explosão e percepção de perigos (x 3,27+ dp 1,60); e ainda que 20% se sintam Iliteratos e manipulados por pensamentos negativos (x 3,07+ dp 1,50). Estes resultados apontam para alguma necessidade de intervenção em Educação Emocional