15,858 research outputs found

    Modelagem de crescimento e produção usando o modelo Simflora.

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    Importância da modelagem de dinâmica florestal na Amazônia Brasileira; Modelagem de crescimento e produção usando o Simflora; Outros documentos disponíveis; Instalação; Simulações únicas; Dados; Começando; Janelas de exibição; Rodando o modelo; Resultados; Simulando silvicultura; A escolha de módulos e valores dos parâmetros; Exemplo; Simulações múltiplas; Começando uma simulação múltipla; Criando um arquivo de dados de saída; Rodando simulações múltiplas; Examinando e analisando os resultados; Experiências de uso do Simflora e suas implicações para políticas públicas; Indonésia; Guiana Inglesa; Brasil; Padrões observados em relação à exploração madeireira e às lacunas de conhecimento de dinâmica florestal de diferentes países tropicais

    The HERMES Solar Atlas and the spectroscopic analysis of the seismic solar analogue KIC3241581

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    Solar-analog stars provide an excellent opportunity to study the Sun's evolution, i.e. the changes with time in stellar structure, activity, or rotation for solar-like stars. The unparalleled photometric data from the NASA space telescope Kepler allows us to study and characterise solar-like stars through asteroseismology. We aim to spectroscopically investigate the fundamental parameter and chromospheric activity of solar analogues and twins, based on observations obtained with the HERMES spectrograph and combine them with asteroseismology. Therefore, we need to build a solar atlas for the spectrograph, to provide accurate calibrations of the spectroscopically determined abundances of solar and late type stars observed with this instrument and thus perform differential spectral comparisons. We acquire high-resolution and high signal-to-noise spectroscopy to construct three solar reference spectra by observing the reflected light of Vesta and Victoria asteroids and Europa (100<S/N<450) with the \Hermes spectrograph. We then observe the Kepler solar analog KIC3241581 (S/N~170). We constructed three solar spectrum atlases from 385 to 900 nm obtained with the Hermes spectrograph from observations of two bright asteroids and Europa. A comparison between our solar spectra atlas to the Kurucz and HARPS solar spectrum shows an excellent agreement. KIC3241581 was found to be a long-periodic binary system. The fundamental parameter for the stellar primary component are Teff=5689+/-11K, logg=4.385+/-0.005, [Fe/H]=+0.22+/-0.01, being in agreement with the published global seismic values confirming its status of solar analogue. KIC 3241581 is a metal rich solar analogue with a solar-like activity level in a binary system of unknown period. The chromospheric activity level is compatible to the solar magnetic activity.Comment: 12 pages, 8 figures, accepted for publication in A&

    Cobertura florestal secundária em pequenas propriedades rurais na Amazônia: implicações para a agricultura de corte e queima.

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    Geometric dynamical observables in rare gas crystals

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    We present a detailed description of how a differential geometric approach to Hamiltonian dynamics can be used for determining the existence of a crossover between different dynamical regimes in a realistic system, a model of a rare gas solid. Such a geometric approach allows to locate the energy threshold between weakly and strongly chaotic regimes, and to estimate the largest Lyapunov exponent. We show how standard mehods of classical statistical mechanics, i.e. Monte Carlo simulations, can be used for our computational purposes. Finally we consider a Lennard Jones crystal modeling solid Xenon. The value of the energy threshold turns out to be in excellent agreement with the numerical estimate based on the crossover between slow and fast relaxation to equilibrium obtained in a previous work by molecular dynamics simulations.Comment: RevTeX, 19 pages, 6 PostScript figures, submitted to Phys. Rev.

    Glutathione Deficit Affects the Integrity and Function of the Fimbria/Fornix and Anterior Commissure in Mice: Relevance for Schizophrenia.

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    Structural anomalies of white matter are found in various brain regions of patients with schizophrenia and bipolar and other psychiatric disorders, but the causes at the cellular and molecular levels remain unclear. Oxidative stress and redox dysregulation have been proposed to play a role in the pathophysiology of several psychiatric conditions, but their anatomical and functional consequences are poorly understood. The aim of this study was to investigate white matter throughout the brain in a preclinical model of redox dysregulation. In a mouse model with impaired glutathione synthesis (Gclm KO), a state-of-the-art multimodal magnetic resonance protocol at high field (14.1 T) was used to assess longitudinally the white matter structure, prefrontal neurochemical profile, and ventricular volume. Electrophysiological recordings in the abnormal white matter tracts identified by diffusion tensor imaging were performed to characterize the functional consequences of fractional anisotropy alterations. Structural alterations observed at peri-pubertal age and adulthood in Gclm KO mice were restricted to the anterior commissure and fornix-fimbria. Reduced fractional anisotropy in the anterior commissure (-7.5% ± 1.9, P&lt;.01) and fornix-fimbria (-4.5% ± 1.3, P&lt;.05) were accompanied by reduced conduction velocity in fast-conducting fibers of the posterior limb of the anterior commissure (-14.3% ± 5.1, P&lt;.05) and slow-conducting fibers of the fornix-fimbria (-8.6% ± 2.6, P&lt;.05). Ventricular enlargement was found at peri-puberty (+25% ± 8 P&lt;.05) but not in adult Gclm KO mice. Glutathione deficit in Gclm KO mice affects ventricular size and the integrity of the fornix-fimbria and anterior commissure. This suggests that redox dysregulation could contribute during neurodevelopment to the impaired white matter and ventricle enlargement observed in schizophrenia and other psychiatric disorders

    Metodologia para estudo socioeconômico de pequenos produtores rurais do nordeste paraense Belém, PA - Brasil.

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    New evidence for a massive black hole at the centre of the quiescent galaxy M32

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    Massive black holes are thought to reside at the centres of many galaxies, where they power quasars and active galactic nuclei. But most galaxies are quiescent, indicating that any central massive black hole present will be starved of fuel and therefore detectable only through its gravitational influence on the motions of the surrounding stars. M32 is a nearby, quiescent elliptical galaxy in which the presence of a black hole has been suspected; however, the limited resolution of the observational data and the restricted classes of models used to interpret this data have made it difficult to rule out alternative explanations, such as models with an anisotropic stellar velocity distribution and no dark mass or models with a central concentration of dark objects (for example, stellar remnants or brown dwarfs). Here we present high-resolution optical HST spectra of M32, which show that the stellar velocities near the centre of this galaxy exceed those inferred from previous ground-based observations. We use a range of general dynamical models to determine a central dark mass concentration of (3.4 +/- 1.6) x 10^6 solar masses, contained within a region only 0.3 pc across. This leaves a massive black hole as the most plausible explanation of the data, thereby strengthening the view that such black holes exist even in quiescent galaxies.Comment: 8 pages, LaTeX, 3 figures; mpeg animation of the stellar motions in M32 available at http://oposite.stsci.edu/pubinfo/Anim.htm
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