1,185 research outputs found
Dynamical star-disk interaction in the young stellar system V354 Mon
The main goal of this work is to characterize the mass accretion and ejection
processes of the classical T Tauri star V354 Mon, a member of the young stellar
cluster NGC 2264. In March 2008, photometric and spectroscopic observations of
V354 Mon were obtained simultaneously with the CoRoT satellite, the 60 cm
telescope at the Observat\'orio Pico dos Dias (LNA - Brazil) equipped with a
CCD camera and Johnson/Cousins BVRI filters, and the SOPHIE \'echelle
spectrograph at the Observatoire de Haute-Provence (CNRS - France). The light
curve of V354 Mon shows periodical minima (P = 5.26 +/- 0.50 days) that vary in
depth and width at each rotational cycle. From the analysis of the photometric
and spectroscopic data, it is possible to identify correlations between the
emission line variability and the light-curve modulation of the young system,
such as the occurrence of pronounced redshifted absorption in the H_alpha line
at the epoch of minimum flux. This is evidence that during photometric minima
we see the accretion funnel projected onto the stellar photosphere in our line
of sight, implying that the hot spot coincides with the light-curve minima. We
applied models of cold and hot spots and a model of occultation by
circumstellar material to investigate the source of the observed photometric
variations. We conclude that nonuniformly distributed material in the inner
part of the circumstellar disk is the main cause of the photometric modulation,
which does not exclude the presence of hot and cold spots at the stellar
surface. It is believed that the distortion in the inner part of the disk is
created by the dynamical interaction between the stellar magnetosphere,
inclined with respect to the rotation axis, and the circumstellar disk, as also
observed in the classical T Tauri star AA Tau and predicted by
magnetohydrodynamical numerical simulations.Comment: Accepted by Astronomy and Astrophysic
Proposição de um índice de produção para bibliotecas com uso do Método MACBETH.
O artigo apresenta o uso de um método multicritério (MACBETH) para propor um índice de produção ponderado para bibliotecas
Confinement of bosonic and spinning particles in braneworlds
In this manuscript we study the confinement of bosonic and spinning test
particles in smooth Randall-Sundrum models. For this, we show that it is
possible to find an effective potential which describe the motion of the
particle over the extra dimension. For the bosonic case it is a known fact that
free test particles cannot be localized neither in thin nor thick branes.
Recently, a coupling to a scalar field has been used to localize a limited
range of masses. Up to now, no mechanism has been found that can trap test
particles of any mass over the brane. To solve this, we show that a coupling
with the dilaton can trap particles of any mass. Next we analyze the spinning
particle. The spin variables introduces an interaction with the
curvature Riemann tensor. This introduces a correction to the effective
potential. By analyzing it, we find that the spinning particle can be localized
at a position different of the brane. We also show that a spinning particle
over the brane can escape to infinity. Therefore, we can conclude that free
bosonic and spinning particles are not trapped to the brane
Desempenho produtivo de fêmeas das raças Canchim e Nelore. III. Produção de leite.
Comparar a produtividade de leite de vacas primiparas das raças Canchim e Nelore
Dynamical Mass Constraints on Low-Mass Pre-Main-Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion with a 1.0 Msun Primary and an 0.7 Msun Secondary
We report the discovery of a double-lined, spectroscopic, eclipsing binary in
the Orion star-forming region. We analyze the system spectroscopically and
photometrically to empirically determine precise, distance-independent masses,
radii, effective temperatures, and luminosities for both components. The
measured masses for the primary and secondary, accurate to ~1%, are 1.01 Msun
and 0.73 Msun, respectively; thus the primary is a definitive pre-main-sequence
solar analog, and the secondary is the lowest-mass star yet discovered among
pre-main-sequence eclipsing binary systems. We use these fundamental
measurements to test the predictions of pre-main-sequence stellar evolutionary
tracks. None of the models we examined correctly predict the masses of the two
components simultaneously, and we implicate differences between the theoretical
and empirical effective temperature scales for this failing. All of the models
predict the observed slope of the mass-radius relationship reasonably well,
though the observations tend to favor models with low convection efficiencies.
Indeed, considering our newly determined mass measurements together with other
dynamical mass measurements of pre-main-sequence stars in the literature, as
well as measurements of Li abundances in these stars, we show that the data
strongly favor evolutionary models with inefficient convection in the stellar
interior, even though such models cannot reproduce the properties of the
present-day Sun.Comment: Accepted by Ap
Análise de dinâmica de uso e de desempenho: o caso do web site da Embrapa Monitoramento por Satélite
A Embrapa Monitoramento por Satélite, há mais de uma década, utiliza a Internet como meio de difusão de resultados de pesquisa e de interação com clientes, parceiros e usuários. Com intuito de avaliar o uso do web site por esse público e o desempenho do sistema de comunicação eletrônica envolvido, tem-se utilizado o programa Webalizer, que monitora e elabora estatísticas de entradas e saídas do sistema, com base na análise de arquivos de log. Com os indicadores contabilizados pelo programa foi possível avaliar aspectos sobre a origem dos acessos, as ações executadas pelos usuários e sobre aspectos do desempenho do sistema em termos de respostas enviadas às solicitações dos usuários. Os resultados podem possibilitar a remodelagem do web site, de modo a melhorar a dinâmica de interação instituição-usuário e promover o desenvolvimento de uma abordagem própria de análise de logs
Towars web site user's profile: log file analysis.
The Internet is a remote, innovative, extremely dynamic and widely accessible communication medium. As in all other human communication formats, we observe the development and adoption of its own language, inherent to its multimedia aspects. The Embrapa Satellite Monitoring is using the Internet as a dissemination medium of its research results and interaction with clients, partners and web site users for more than one decade. In order to evaluate the web site usage and performance of the e-communication system the Webalizer software has been used to track and to calculate statistics based on web server log file analysis. The objective of the study is to analyze the data and evaluate the indicators related to requests origin (search string, country, time), actions performed by users (entry pages, agents) and system performance (error messages). It will help to remodel the web site design to improve the interaction dynamics and also develop a customized log file analyser. This tool would retrieve coherent and real information
Monitoramento e determinação do nível de ação do ácaro-rajado na cultura da uva.
bitstream/CPATSA/26987/1/CTE71.pd
Uso e desempenho de web sites: um estudo de caso.
A Internet é um meio de comunicação remota, inovador, extremamente dinâmico e, cada vez mais, amplamente acessível, que tem adotado uma linguagem própria, inerente à sua natureza multimídia. A Embrapa Monitoramento por Satélite, há mais de uma década, utiliza a Internet como meio de difusão de resultados de pesquisa e de interação com clientes, parceiros e usuários. Com intuito de avaliar o uso do web site por esse público e o desempenho do sistema de comunicação eletrônica envolvido, tem-se utilizado o programa Webalizer que monitora e elabora estatísticas de entradas e saídas do sistema, com base na análise de arquivos de log. Através dos indicadores pelo programa foi possível avaliar aspectos sobre a origem dos acessos, as ações executadas pelos usuários e sobre aspectos do desempenho do sistema em termos de respostas enviadas às solicitações dos usuários. Os resultados podem possibilitar a remodelagem do web site, de modo a melhorar a dinâmica de interação instituição-usuário e promover o desenvolvimento de uma abordagem própria de análise de logs
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