512 research outputs found

    Mapeamento de áreas de preservação permanentes em topos de morros para a Amazônia Legal usando metodologia apropriada a grande volume de dados.

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    Terceiro e quarto relatórios de avaliação do IPCC: comparação entre cenários futuros de distribuição geográfica do Sipha flava no Brasil.

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    O trabalho visou comparar os resultados da distribuição geográfica do Sipha flava com base no Terceiro e no Quarto Relatório de Avaliação do IPCC no território brasileiro. O afídeo apresenta ampla distribuição geográfica, e pode causar danos às diversas culturas utilizadas na alimentação do gado de leite. As imagens que contém as médias de temperatura com tamanho de 30? (meio grau) cada pixel, dos relatórios do IPCC foram classificadas de acordo com as faixas de temperatura de sobrevivência do inseto, realizadas em laboratório por Oliveira et al. (2009), assim foi possível gerar o cenário A2 para os anos 2020, 2050 e 2080 (cenário em que o aquecimento traria modificações drásticas para o clima) com base no Quarto Relatório (IPCC, 2007). O software ArcGIS foi utilizado na confecção dos mapas para o Quarto Relatório. A comparação dos mapas para os relatórios em questão mostrou que em termos de regiões, a favorabilidade continua com a mesma tendência para os meses de temperaturas médias mais altas no ano de 2020, mas com algumas modificações nos estados abrangidos. Observa-se um aumento das áreas não favoráveis nos anos de 2050 e 2080 nas regiões Norte, Nordeste e Centro-Oeste

    Studies of aging and HV break down problems during development and operation of MSGC and GEM detectors for the Inner Tracking System of HERA-B

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    The results of five years of development of the inner tracking system of the HERA-B experiment and first experience from the data taking period of the year 2000 are reported. The system contains 184 chambers, covering a sensitive area of about 20 * 20 cm2 each. The detector is based on microstrip gas counters (MSGCs) with diamond like coated (DLC) glass wafers and gas electron multipliers (GEMs). The main problems in the development phase were gas discharges in intense hadron beams and aging in a high radiation dose environment. The observation of gas discharges which damage the electrode structure of the MSGC led to the addition of the GEM as a first amplification step. Spurious sparking at the GEM cannot be avoided completely. It does not affect the GEM itself but can produce secondary damage of the MSGC if the electric field between the GEM and the MSGC is above a threshold depending on operation conditions. We observed that aging does not only depend on the dose but also on the spot size of the irradiated area. Ar-DME mixtures had to be abandoned whereas a mixture of 70% Ar and 30% CO2 showed no serious aging effects up to about 40 mC/cm deposited charge on the anodes. X-ray measurements indicate that the DLC of the MSGC is deteriorated by the gas amplification process. As a consequence, long term gain variations are expected. The Inner Tracker has successfully participated in the data taking at HERA-B during summer 2000.Comment: 29 pages, 22 figure

    Análise da savana e queimadas no Parque Indígena de Tumucumaque (PA) através de imagens de satélite Landsat.

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    The Tiriyós Savanna, inserted in the Indian Park of Tumucumaque (PA), and the occurrence of fires were analyzed using satellite images. The savanna common and permanent area in the years of 1986 and 2005 was 4.109,72 km2. The total retraction and expansion areas in the same years were 287,3 km2 and 151,8 km2, respectively. From the burnt area, 38,5% presented only one focus of fire in 9 years (from 1998 August to 2006 October); in 23,6% of the area there was fire each 4 and a half years; 25,3% each 31 months; 10,8% each 18 months and 1,8% each year. The total estimated burnt area was 4.086 km2, at maximum. The fires are considered one of the pressure factors for the advance of the amazon savannas and in the change of the coverage and usage of the earth in the Tiriyós savanna area, but the analysis of the satellite images in the years of 1986 and 2005 showed that there was a retraction of 135,5 km2 in 20 years

    Effect of Impurity Scattering on the Nonlinear Microwave Response in High-Tc Superconductors

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    We theoretically investigate intermodulation distortion in high-Tc superconductors. We study the effect of nonmagnetic impurities on the real and imaginary parts of nonlinear conductivity. The nonlinear conductivity is proportional to the inverse of temperature owing to the dependence of the damping effect on energy, which arises from the phase shift deviating from the unitary limit. It is shown that the final-states interaction makes the real part predominant over the imaginary part. These effects have not been included in previous theories based on the two-fluid model, enabling a consistent explanation for the experiments with the rf and dc fields

    Um cenário de balanço do carbono para Áreas de Preservação Permanentes em mesorregiões leiteiras usando SIG e dados de sensoriamento remoto.

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    O objetivo deste trabalho foi mapear algumas categorias de Áreas de Preservação Permanentes (APP), com base no Código Florestal de 1965, destinadas à recuperação por regeneração natural de florestas semidecíduas nas mesorregiões Zona da Mata e Campo das Vertentes, Minas Gerais, e a partir disto estabelecer qual é o impacto do emprego das APP?s sobre as áreas de pastagens e subsequente sequestro de carbono. Assim, o cenário de carbono fixo pelas florestas naturais e seu balanço foi considerado como um importante fator para a manutenção de ecossistemas naturais, que posteriormente poderá ser comparado com cenários para o novo código florestal. A partir das informações altimétricas de modelos digitais de elevação (MDE), foi possível extrair dados morfométricos e morfológicos para estimar a APP. Foram utilizadas imagens MODIS / Terra para a extração de áreas de pastagens com o uso de índices de vegetação NDVI para o cruzamento com as APP?s estimadas. Num cenário linear e determinístico de implantação das APP?s em substituição às áreas de pastagens haveria a retração dessas áreas ou impacto de aproximadamente 12% na produção de leite do Campo das Vertentes e 21,5% na produção de leite da Zona da Mata, com subsequente fixação de 48 milhões de toneladas de carbono até o clímax florestal, quando da implantação de florestas semideciduais, e com balanço positivo de 2 ton/ha/ano de carbono fixo, enquanto a pecuária produz 1 ton/ha/ano, se bem manejadas, revelando-se equilíbrio

    Pathotypic diversity of Hyaloperonospora brassicae collected from Brassica oleracea

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    Downy mildew caused by Hyaloperonospora brassicae is an economically destructive disease of brassica crops in many growing regions throughout the world. Specialised pathogenicity of downy mildews from different Brassica species and closely related ornamental or wild relatives has been described from host range studies. Pathotypic variation amongst Hyaloperonospora brassicae isolates from Brassica oleracea has also been described; however, a standard set of B. oleracea lines that could enable reproducible classification of H. brassicae pathotypes was poorly developed. For this purpose, we examined the use of eight genetically refined host lines derived from our previous collaborative work on downy mildew resistance as a differential set to characterise pathotypes in the European population of H. brassicae. Interaction phenotypes for each combination of isolate and host line were assessed following drop inoculation of cotyledons and a spectrum of seven phenotypes was observed based on the level of sporulation on cotyledons and visible host responses. Two host lines were resistant or moderately resistant to the entire collection of isolates, and another was universally susceptible. Five lines showed differential responses to the H. brassicae isolates. A minimum of six pathotypes and five major effect resistance genes are proposed to explain all of the observed interaction phenotypes. The B. oleracea lines from this study can be useful for monitoring pathotype frequencies in H. brassicae populations in the same or other vegetable growing regions, and to assess the potential durability of disease control from different combinations of the predicted downy mildew resistance genes

    Fermion localization on asymmetric two-field thick branes

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    In this paper we investigate the localization of fermions on asymmetric thick branes generated by two scalars ϕ\phi and χ\chi. In order to trap fermions on the asymmetric branes with kink-like warp factors, the couplings with the background scalars ηΨˉF(χ,ϕ)Ψ\eta\bar{\Psi}F(\chi,\phi)\Psi are introduced, where F(χ,ϕ)F(\chi,\phi) is a function of ϕ\phi and χ\chi. We find that the coupling ηΨˉχϕΨ\eta\bar{\Psi}\chi\phi\Psi do not support the localization of 4-dimensional fermions on the branes. While, for the case ηΨˉχΨ+ηΨˉϕΨ\eta\bar{\Psi}\chi\Psi+\eta'\bar{\Psi}\phi\Psi, which is the kink-fermion coupling corresponding to one-scalar-generated brane scenarios, the zero mode of left-handed fermions could be trapped on the branes under some conditions.Comment: v2: 11 pages, 4 figures, accepted by CQ

    Derivative Expansion and the Effective Action for the Abelian Chern-Simons Theory at Higher Orders

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    We study systematically the higher order corrections to the parity violating part of the effective action for the Abelian Chern-Simons theory in 2+1 dimensions, using the method of derivative expansion. We explicitly calculate the parity violating parts of the quadratic, cubic and the quartic terms (in fields) of the effective action. We show that each of these actions can be summed, in principle, to all orders in the derivatives. However, such a structure is complicated and not very useful. On the other hand, at every order in the powers of the derivatives, we show that the effective action can also be summed to all orders in the fields. The resulting actions can be expressed in terms of the leading order effective action in the static limit. We prove gauge invariance, both large and small of the resulting effective actions. Various other features of the theory are also brought out.Comment: 36 page

    Fermion localization on degenerate and critical branes

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    In this work we analyze the localization of fermions on degenerate and critical Bloch branes. This is done directly on physical coordinates, in constrast to some works that has been using conformal coordinates. We find the range of coupling constants of the interaction of fermions with the scalar fields that allow us to have normalizable fermion zero-mode localized on the brane on both, critical and degenerate Bloch branes. In the case of critical branes our results agree with those found in [Class. Quantum Grav. \textbf{27} (2010) 185001]. The results on fermion localization on degenerate Bloch branes are new. We also propose a coupling of fermions to the scalar fields which leads to localization of massless fermion on both sides of a double-brane.Comment: 16 pages, 6 figure
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