508 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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    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

    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

    How will Mahanarva spectabilis (Hemiptera: Cercopidae) respond to global warming?

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    The aim of this study was to determine the favorable constant temperature range for Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae) development as well as to generate geographic distribution maps of this insect pest for future climate scenarios. M. spectabilis eggs were reared on two host plants (Brachiaria ruziziensis (Germain and Edvard) and Pennisetum purpureum (Schumach)), with individual plants kept at temperatures of 16, 20, 24, 28, and 32C. Nymphal stage duration, nymphal survival, adult longevity, and egg production were recorded for each temperature*host plant combination. Using the favorable temperature ranges for M. spectabilis development, it was possible to generate geographic distribution. Nymphal survival was highest at 24.4C, with estimates of 44 and 8% on Pennisetum and Brachiaria, respectively. Nymphal stage duration was greater on Brachiaria than on Pennisetum at 20 and 24C but equal at 28C. Egg production was higher on Pennisetum at 24 and 28C than at 20C, and adult longevity on Pennisetum was higher at 28C than at 20C, whereas adult longevity at 24C did not differ from that at 20 and 28C. With these results, it was possible to predict a reduction in M. spectabilis densities in most regions of Brazil in future climate scenarios

    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

    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

    Analysis of grassland degradation in Zona da Mata, MG, Brazil, based on NDVI time series data with the integration of phenological metrics.

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    Abstract: There is currently a lot of interest in determining the state of Brazilian grasslands. Governmental actions and programs have recently been implemented for grassland recovery in Brazilian states, with the aim of improving production systems and socioeconomic indicators. The aim of this study is to evaluate the vegetative growth, temporal vigor, and long-term scenarios for the grasslands in Zona da Mata, Minas Gerais State, Brazil, by integrating phenological metrics. We used metrics derived from the normalized difference vegetation index (NDVI) time series from moderate resolution imaging spectroradiometer (MODIS) data, which were analyzed in a geographic information system (GIS), using multicriteria analysis, the analytical hierarchy process, and a simplified expert system (ESS). These temporal metrics, i.e., the growth index (GI) for 16-day periods during the growing season; the slope; and the maximum, minimum, and mean for the time series, were integrated to investigate the grassland vegetation conditions and degradation level. The temporal vegetative vigor was successfully described using the rescaled range (R/S statistic) and the Hurst exponent, which, together with the metrics estimated for the full time series, imagery, and field observations, indicated areas undergoing degradation or areas that were inadequately managed (approximately 61.5%). Time series analysis revealed that most grasslands showed low or moderate vegetative vigor over time with long-term persistence due to farming practices associated with burning and overgrazing. A small part of the grasslands showed high and sustainable plant densities (approximately 8.5%). A map legend for grassland management guidelines was developed using the proposed method with remote sensing data, which were applied using GIS software and a field campaign

    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

    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
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