14,862 research outputs found
Tracing the magnetic field morphology of the Lupus I molecular cloud
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
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.
Resumo: Esse trabalho é parte de um survey amplo sobre a produção de ovinos no Ceará, incluindo a análise das características gerais das propriedades, perfil dos produtores, infraestrutura e nível de capitalização, indicadores financeiros, aspectos comerciais e tecnologia de produção. O objeto geral desse artigo é a descrição da tecnologia de produção adotada no estado. Para cumprir o objetivo, realizou-se uma pesquisa classificada quanto aos objetivos como descritiva e quanto à 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 Ceará. Estatísticas descritivas foram usadas na análise dos dados, com o uso do pacote estatístico SPSS, em especial o cálculo de médias e freqüências. Estes cálculos permitiram observar que o sistema de produção dominante é caracterizado por baixo nível geral tecnológico em todas as áreas ? manejo, alimentação, reprodução e sanidade. Abstract: The work is part of an extensive survey about sheep production in the Ceará 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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