15,214 research outputs found

    Tracing the magnetic field morphology of the Lupus I molecular cloud

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    Deep R-band CCD linear polarimetry collected for fields with lines-of-sight toward the Lupus I molecular cloud is used to investigate the properties of the magnetic field within this molecular cloud. The observed sample contains about 7000 stars, almost 2000 of them with polarization signal-to-noise ratio larger than 5. These data cover almost the entire main molecular cloud and also sample two diffuse infrared patches in the neighborhood of Lupus I. The large scale pattern of the plane-of-sky projection of the magnetic field is perpendicular to the main axis of Lupus I, but parallel to the two diffuse infrared patches. A detailed analysis of our polarization data combined with the Herschel/SPIRE 350 um dust emission map shows that the principal filament of Lupus I is constituted by three main clumps acted by magnetic fields having different large-scale structure properties. These differences may be the reason for the observed distribution of pre- and protostellar objects along the molecular cloud and its apparent evolutive stage. On the other hand, assuming that the magnetic field is composed by a large-scale and a turbulent components, we find that the latter is rather similar in all three clumps. The estimated plane-of-sky component of the large-scale magnetic field ranges from about 70 uG to 200 uG in these clumps. The intensity increases towards the Galactic plane. The mass-to-magnetic flux ratio is much smaller than unity, implying that Lupus I is magnetically supported on large scales.Comment: 10 pages, 9 figures. Accepted for publication in Ap

    Phase transition for the frog model

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    We study a system of simple random walks on graphs, known as frog model. This model can be described as follows: There are active and sleeping particles living on some graph G. Each active particle performs a simple random walk with discrete time and at each moment it may disappear with probability 1-p. When an active particle hits a sleeping particle, the latter becomes active. Phase transition results and asymptotic values for critical parameters are presented for Z^d and regular trees

    Tecnologia de produção de ovinos no Ceará.

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    Resumo: Esse trabalho √© parte de um survey amplo sobre a produ√ß√£o de ovinos no Cear√°, incluindo a an√°lise das caracter√≠sticas gerais das propriedades, perfil dos produtores, infraestrutura e n√≠vel de capitaliza√ß√£o, indicadores financeiros, aspectos comerciais e tecnologia de produ√ß√£o. O objeto geral desse artigo √© a descri√ß√£o da tecnologia de produ√ß√£o adotada no estado. Para cumprir o objetivo, realizou-se uma pesquisa classificada quanto aos objetivos como descritiva e quanto √† natureza ou abordagem do problema como qualitativa e quantitativa. Quanto ao delineamento o estudo caracterizou-se por uma ampla pesquisa de campo em 170 propriedades produtoras de ovinos no estado do Cear√°. Estat√≠sticas descritivas foram usadas na an√°lise dos dados, com o uso do pacote estat√≠stico SPSS, em especial o c√°lculo de m√©dias e freq√ľ√™ncias. Estes c√°lculos permitiram observar que o sistema de produ√ß√£o dominante √© caracterizado por baixo n√≠vel geral tecnol√≥gico em todas as √°reas ? manejo, alimenta√ß√£o, reprodu√ß√£o e sanidade. Abstract: The work is part of an extensive survey about sheep production in the Cear√° state of Brazil. The general objective of this paper is to describe the prevalent production technology in farms sheep in this state. This objective was achieved through a survey of 170 sheep farmers. Descriptive statistics was applied in the data analysis with the use of SPSS package. From the analysis, it was possible to identify the prevalence of low technological level in the production of sheep, either in production, management, reproduction e feedin
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