5,910 research outputs found
Weyl geometry, anti-De Sitter space, and -theory
We study the Gaussian approximation to the quantum fluctuations of the metric
of the four dimensional anti-De Sitter spacetime. The associated massless
scalar field has a quartic self interaction, for which we construct the
generating functional of the -point correlation functions. The concomitant
infrared divergence is cured by a mass renormalization provided by the
cosmological constant, which is also responsible for the renormalization of the
coupling constant of the field theory.Comment: 9 pages, 1 figur
A viabilidade da pequena propriedade, a viabilidade do pequeno produtor.
bitstream/item/119172/1/digitalizar0013.pd
Zoneamento climático da Heveicultura no Brasil.
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
Four-port coupled channel-guide device based on 2D photonic crystal structure
We have fabricated and measured a four-port coupled channel-waveguide device using W1 channel waveguides oriented along ΓK directions in a two-dimensional (2D) hole-based planar photonic crystal (PhC) based on silicon-on-insulator (SOI) waveguide material, at operation wavelengths around 1550 nm. 2D FDTD simulations and experimental results are shown and compared. The structure has been designed using a mode conversion approach, combined with coupled-mode concepts. The overall length of the photonic crystal structure is typically about 39 μm and the structure has been fabricated using a combination of direct-write electron-beam lithography (EBL) and dry-etch processing. Devices were measured using a tunable laser with end-fire coupling into the planar structure
Biodisponibilidade de ferro em amostra de músculo bovino in natura e processada termicamente.
A carne bovina é de grande importância na alimentação, sendo consumida por quase 50% da população brasileira. Encontrado na carne vermelha e em certas frutas e legumes, o ferro é um mineral essencial. O ferro participa do processo de produção da hemoglobina, que transporta o oxigênio pelo corpo através do sangue. Níveis baixos de ferro no organismo podem causar anemia ferropriva nos seres humanos. Os processos de conservação de carne, tais como a refrigeração e os processamentos térmicos, podem alterar a composição química da mesma. Este trabalho teve por objetivo analisar a biodisponibilidade de Fe em amostras de carnes bovinas in natura e processadas termicamente, utilizando o método gastrointestinal in vitro
Alternativas inovadoras para otimizar a transferência de tecnologia para a agricultura familiar.
Editado por Flávio Augusto Portela Santos, José Carlos de Moura, Vidal Pedroso de Faria
Vacuum fluctuations of a scalar field near a reflecting boundary and their effects on the motion of a test particle
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
Avaliação dos impactos econômicos, sociais e ambientais de tecnologias da Embrapa Pecuária Sudeste. 4. Técnicas de produção intensiva aplicadas a propriedades familiares produtoras de leite.
bitstream/CPPSE/16766/1/documentos-57.pd
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