2,407 research outputs found

    Convex Neighbourhoods and Complete Finsler Spaces

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    In this paper, it is shown that a large set of connections on a suitable sub-bundle of the tangent bundle of a Finsler Manifold can be used to study all the properties of convex neighbourhoods with respect to the Finsler Metric, which are needed to see that any Complete Finsler Space is Geodesically Connected.Comment: 17 page

    Gravitational clustering in N-body simulations

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    In this talk we discuss some of the main theoretical problems in the understanding of the statistical properties of gravity. By means of N-body simulations we approach the problem of understanding the r\^ole of gravity in the clustering of a finite set of N-interacting particles which samples a portion of an infinite system. Through the use of the conditional average density, we study the evolution of the clustering for the system putting in evidence some interesting and not yet understood features of the process.Comment: 5 pages, 1 figur

    Clustering in N-Body gravitating systems

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    Self-gravitating systems have acquired growing interest in statistical mechanics, due to the peculiarities of the 1/r potential. Indeed, the usual approach of statistical mechanics cannot be applied to a system of many point particles interacting with the Newtonian potential, because of (i) the long range nature of the 1/r potential and of (ii) the divergence at the origin. We study numerically the evolutionary behavior of self-gravitating systems with periodical boundary conditions, starting from simple initial conditions. We do not consider in the simulations additional effects as the (cosmological) metric expansion and/or sophisticated initial conditions, since we are interested whether and how gravity by itself can produce clustered structures. We are able to identify well defined correlation properties during the evolution of the system, which seem to show a well defined thermodynamic limit, as opposed to the properties of the ``equilibrium state''. Gravity-induced clustering also shows interesting self-similar characteristics.Comment: 6 pages, 5 figures. To be published on Physica

    Spillover and diffraction sidelobe contamination in a double-shielded experiment for mapping Galactic synchrotron emission

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    We have analyzed observations from a radioastronomical experiment to survey the sky at decimetric wavelengths along with feed pattern measurements in order to account for the level of ground contamination entering the sidelobes. A major asset of the experiment is the use of a wire mesh fence around the rim-halo shielded antenna with the purpose of levelling out and reducing this source of stray radiation for zenith-centered 1-rpm circular scans. We investigate the shielding performance of the experiment by means of a geometric diffraction model in order to predict the level of the spillover and diffraction sidelobes in the direction of the ground. Using 408 MHz and 1465 MHz feed measurements, the model shows how a weakly-diffracting and unshielded antenna configuration becomes strongly-diffracting and double-shielded as far-field diffraction effects give way to near-field ones. Due to the asymmetric response of the feeds, the orientation of their radiation fields with respect to the secondary must be known a priori before comparing model predictions with observational data. By adjusting the attenuation coefficient of the wire mesh the model is able to reproduce the amount of differential ground pick-up observed during test measurements at 1465 MHz.Comment: 14 pages, 17 eps + 1 gif figures and 4 Tables. Accepted for publication in A&AS. Fig.7 available at full resolution from http://www.das.inpe.br/~tello/publications.ht

    Perfil sócio-econômico dos alunos da creche Irmã Anísia Rocha da cidade de Sobral, CE no ano de 2005.

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    O estudo é parte do projeto "Manipulação de constituintes e prospecção de propriedades funcionais do leite de cabra" financiado pelo Macroprograma 2 da Embrapa e, liderado pela Embrapa Caprinos, que teve objetivo geral: Conhecer o efeito de estratégias nutricionais para manipulação do perfil de caseínas e de ácidos graxos do leite de cabra e seus impactos sobre a saúde humana na prospecção de propriedades funcionais. Além de conhecer melhor o aluno, trata-se de gerar subsídios para melhorar a qualidade do ensino e prestação de serviços pela Creche Irmã Anísia Rocha.bitstream/CNPC/20815/1/cot84.pd
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