5,144 research outputs found

    Vacuum fluctuations of a scalar field near a reflecting boundary and their effects on the motion of a test particle

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    The contribution from quantum vacuum fluctuations of a real massless scalar field to the motion of a test particle that interacts with the field in the presence of a perfectly reflecting flat boundary is here investigated. There is no quantum induced dispersions on the motion of the particle when it is alone in the empty space. However, when a reflecting wall is introduced, dispersions occur with magnitude dependent on how fast the system evolves between the two scenarios. A possible way of implementing this process would be by means of an idealized sudden switching, for which the transition occurs instantaneously. Although the sudden process is a simple and mathematically convenient idealization it brings some divergences to the results, particularly at a time corresponding to a round trip of a light signal between the particle and the wall. It is shown that the use of smooth switching functions, besides regularizing such divergences, enables us to better understand the behavior of the quantum dispersions induced on the motion of the particle. Furthermore, the action of modifying the vacuum state of the system leads to a change in the particle energy that depends on how fast the transition between these states is implemented. Possible implications of these results to the similar case of an electric charge near a perfectly conducting wall are discussed.Comment: 17 pages, 8 figure

    Identificação varietal de algumas videiras cultivadas no Rio Grande do Sul.

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    Esta publicraçã contém a descrição ampelográfica das copas que comumente apresentam dificuldades para identificação. bem como dos principais porta-enxertos difundidas na MRH 311.bitstream/item/40787/1/cir11.pdf2. ed. rev

    Zoneamento climático da Heveicultura no Brasil.

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    Para o zoneamento da aptidão climática da heveicultura no Brasil, considerou-se as exigências climáticas da espécie a ser cultivada e da principal doença que afeta a cultura. Neste trabalho, utilizou-se a temperatura média anual do ar, a deficiência hídrica no solo e a temperatura média do mês mais frio, como condicionantes do desempenho da cultura e da ocorrência de surtos epidêmicos do Microcyclus ulei (P. Henn) V. Arx., principal patógeno da seringueira no Brasil e causador do "mal-das-folhas". Considerando esses fatores, elaborou-se uma carta de aptidão climática da heveicultura no Brasil, baseada em isolinhas de temperatura, precipitação, e de outros fatores de interesse, estabelecendo-se, assim, as regiões brasileiras com condições climáticas aptas, restritas, marginais e inaptas para o cultivo comercial da seringueira.bitstream/CNPM/1254/1/d24_heveic_fin.pd

    Comportamento de nove cultivares de videira destinadas a elaboração de vinho branco, em diferentes locais da Microrregião Homogênea 311.

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    bitstream/item/60787/1/CNPUV-PESQ.AND.-15.pd

    A cultivar de videira sémillon: características e comportamento no Rio Grande do Sul.

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    bitstream/item/40375/1/cir08.pd

    Avaliação De Impacto De Alterações Na Temperatura Em Biomphalaria Glabrata Variantes Melânica E Albina Infectadas Com Schistosoma Mansoni

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    Fluctuations in population density of planorbid hosts of S. mansoni are influenced by climatic factors. The knowledge about interference from changes in water temperature in these populations is an important aspect of the epidemiology of schistosomiasis. In this experiment, it is explored the influence of different temperatures on the development of Schistosoma mansoni in Biomphalaria glabrata melanic and albino variants. The results indicated an intrinsic relationship between temperature and development of the parasite in the intramollusc phase, independent of the pigmentation of the mantle of the molluscs. The higher the temperature, the shorter the period necessary for the development of the parasite was while the higher the mortality of infected mollusks. It is concluded that, in the presence of climate change, the increasement of temperature in cold and flooded regions may encourage the establishment of new foci of transmission of schistosomiasis by changing the geographic extent and extending the epidemiological transmission potential. In warm climates, higher temperatures, however, could compromise the transmission of the disease because of biological stress suffered by parasite and host. Under these conditions, it can result in the death of the parasite or a change in their ability to infect new host species of molluscs in new areas. Mantle pigmentation patterns in molluscs have not shown significant interference in the development of the parasite.77

    Recomendações técnicas para produção eficiente de leite.

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    bitstream/CPPSE-2010/19155/1/PROCICircT60ACC2009.00419.pd

    Efeito da alta pressão hidrostática na cor de presunto fatiado embalado a vácuo.

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    bitstream/CTAA-2009-09/9982/1/ct104-2006.pd
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