Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 2 de 2
Filtrar
Mais filtros

Base de dados
Ano de publicação
Tipo de documento
Intervalo de ano de publicação
1.
Opt Lett ; 35(9): 1311-3, 2010 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-20436552

RESUMO

Fused-silica microstructural changes associated with localized 10.6 microm CO(2) laser heating are reported. Spatially resolved shifts in the high-frequency asymmetric stretch transverse-optic phonon mode of SiO(2) were measured using confocal Raman microscopy, allowing construction of axial fictive temperature (T(f)) maps for various laser-heating conditions. A Fourier conduction-based finite-element model was employed to compute on-axis temperature-time histories, and, in conjunction with a Tool-Narayanaswamy form for structural relaxation, used to fit T(f)(z) profiles to extract relaxation parameters. Good agreement between the calculated and measured T(f) was found, yielding reasonable values for relaxation time and activation enthalpy in the laser-modified silica.

2.
Bone ; 36(2): 193-201, 2005 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15780945

RESUMO

We describe a new method for quantifying the orientation of trabecular bone from three-dimensional images. Trabecular lattices from five human vertebrae were decomposed into individual trabecular elements, and the orientation, mass, and thickness of each element were recorded. Continuous functions that described the total mass (M(phi,theta)) and mean thickness (tau(phi,theta)) of all trabeculae as a function of orientation were derived. The results were compared with experimental measurements of the elastic modulus in three principal anatomic directions. A power law scaling relationship between the anisotropies in mass and elastic modulus was observed; the scaling exponent was 1.41 (R2=0.88). As expected, the preponderance of trabecular mass was oriented along the cranial-caudal direction; on average, there was 3.4 times more mass oriented vertically than horizontally. Moreover, the vertical trabeculae were 30% thicker, on average, than the horizontal trabeculae. The vertical trabecular thickness was inversely related to connectivity (R2=0.70; P=0.07), suggesting a possible organization into either few, thick trabeculae or many thin trabeculae. The method, which accounts for the mechanical connectedness of the lattice, provides a rapid way to both visualize and quantify the three-dimensional organization of trabecular bone.


Assuntos
Osso e Ossos/fisiologia , Processamento de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Idoso , Idoso de 80 Anos ou mais , Osso e Ossos/anatomia & histologia , Humanos , Vértebras Lombares/anatomia & histologia , Masculino , Pessoa de Meia-Idade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA