Collection of relevant results obtained with the Skylab images by the Institute for Space Research, INPE

There are no author-identified significant results in this report

Compressive Phase Contrast Tomography

When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. In- terference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher con- trast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).Comment: 5 pages, "Image Reconstruction from Incomplete Data VI" conference 7800, SPIE Optical Engineering + Applications 1-5 August 2010 San Diego, CA United State

Influência da cobertura morta no desenvolvimento de fruteiras tropicais.

bitstream/CNPAT-2010/7344/1/Dc-049.pd

Mudanças climáticas, agricultura irrigada e integração de modelos.

As mudanças climáticas podem afetar a disponibilidade e a demanda de água para a agricultura irrigada, a qual depende da evaporação e precipitação. O objetivo deste artigo é propor metodologia para análise de impactos de mudanças climáticas em nível de bacia hidrográfica, através de integração de modelos globais e locais. Os Modelos de Circulação Global (GCMs) geralmente utilizados para simular o clima presente e projetar o clima futuro simulam processos na escala global ou continental. O método usado para converter saídas dos Modelos de Circulação Global em variáveis meteorológicas locais requeridas para modelagem hidrológica viável é geralmente referido como técnicas de redução de escala. A definição de um modelo conceitual permite ainda a visualização da forma de integração dos modelos e verificação das respectivas compatibilidades das escalas temporais, avaliando-se a viabilidade da própria integração e necessidade de ajustes

Lateral Casimir-Polder force with corrugated surfaces

We derive the lateral Casimir-Polder force on a ground state atom on top of a corrugated surface, up to first order in the corrugation amplitude. Our calculation is based on the scattering approach, which takes into account nonspecular reflections and polarization mixing for electromagnetic quantum fluctuations impinging on real materials. We compare our first order exact result with two commonly used approximation methods. We show that the proximity force approximation (large corrugation wavelengths) overestimates the lateral force, while the pairwise summation approach underestimates it due to the non-additivity of dispersion forces. We argue that a frequency shift measurement for the dipolar lateral oscillations of cold atoms could provide a striking demonstration of nontrivial geometrical effects on the quantum vacuum.Comment: 12 pages, 6 figures, contribution to QFEXT07 proceeding

On the embedding of branes in five-dimensional spaces

We investigate the embedding of four-dimensional branes in five-dimensional spaces. We firstly consider the case when the embedding space is a vacuum bulk whose energy-momentum tensor consists of a Dirac delta function with support in the brane. We then consider the embedding in the context of Randall-Sundrum-type models, taking into account $Z_{2}$ symmetry and a cosmological constant. We employ the Campbell-Magaard theorem to construct the embeddings and are led to the conclusion that the content of energy-matter of the brane does not necessarily determine its curvature. Finally, as an application to illustrate our results, we construct the embedding of Minkowski spacetime filled with dust.Comment: 12 pages - REVTEX To appear in Classical and Quantum Gravit