Showing papers by "Universidade de Pernambuco published in 1994"
TL;DR: In this paper, an IR pump beam is used to heat the electron distribution and changes in electron temperature are measured with a visible probe beam at the d band to Fermi-surface transition, showing that the subpicosecond optical response of gold is dominated by delayed thermalization of the electron gas.
Abstract: Femtosecond electron thermalization in metals was investigated using transient thermomodulation transmissivity and reflectivity. Studies were performed using a tunable multiple-wavelength femtosecond pump-probe technique in optically thin gold films in the low perturbation limit. An IR pump beam is used to heat the electron distribution and changes in electron temperature are measured with a visible probe beam at the d band to Fermi-surface transition. We show that the subpicosecond optical response of gold is dominated by delayed thermalization of the electron gas. This effect is particularly important far off the spectral peak of the reflectivity or transmissivity changes, permitting a direct and sensitive access to the internal thermalization of the electron gas. Using a simple rate-equation model, line-shape analysis of the transient reflectivity and transmissivity indicates a thermalization time of the order of 500 fs. At energies close to the Fermi surface, longer thermalization times \ensuremath{\sim}1--2 ps are observed. These results are in agreement with a more sophisticated model based on calculations of the electron-thermalization dynamics by numerical solutions of the Boltzmann equation. This model quantitatively describes the measured transient optical response during the full thermalization time of electron gas, of the order of 1.5 ps, and gives new insight into electron thermalization in metals.
642 citations
TL;DR: The radiological evaluation indicate a precise correlation between clinical picture and the distribution and course of lumbar spinal cord degenerations and a strong correlation was also found with hernias, roots and the bony sequalae of spinal cord dystrophy found in Scheuermann disease.
Abstract: The author reports the case of a patient with spinal cord compression by a thoracic herniated disc without paraplegia as well as a cauda equina syndrome due to spondylotic and discai lesions, with small protrusions of the L4-L5 and L5-S1 discs associated with Scheuermann disease. There was complete recovery in six months with clinical treatment. The radiological evaluation using standard radiography, myelography, computed tomography, magnetic resonance imaging of the vertebral column, and electromyographic evaluation indicate a precise correlation between clinical picture and the distribution and course of lumbar spinal cord degenerations. Furthermore, a strong correlation was also found with hernias, roots and the bony sequalae of spinal cord dystrophy found in Scheuermann disease.
TL;DR: In this paper, an estudo retrospectivo comparativo das Legislacoes de 16 Paises da America Latina, a saber Argentina, Bolivia, Brazil, Colombia, Costa Rica, Chile, Cuba, Equador, Guatemala, Honduras, Mexico, Panama, Paraguai, Peru, Republica Dominicana e Venezuela, do periodo de 1963 to 1992, enfatizando-se os aspectos eticos referentes a doacao, determinacao da morte, conflito de interesses, selecao do
Abstract: Respeitando recomendacoes da OMS, foi feito estudo retrospectivo comparativo das Legislacoes de 16 Paises da America Latina, a saber Argentina, Bolivia, Brasil, Colombia, Costa Rica, Chile, Cuba, Equador, Guatemala, Honduras, Mexico, Panama, Paraguai, Peru, Republica Dominicana e Venezuela, do periodo de 1963 a 1992, enfatizando-se os aspectos eticos referentes a doacao, determinacao da morte, conflito de interesses, selecao do receptor, comercializacao e intercâmbio internacional de orgaos.