We start from the many-chain Smoluchowski equation that describes dynamics of dense polymer solutions and derive an effective diffusion equation for a tagged ~probe! chain distribution function. In the tagged chain diffusion equation the effects of the inter-chain interactions are incorporated through an effective friction tensor. We propose a simple phenomenological formula for the friction te...

BACKGROUND AND PURPOSE Quantitative MR imaging strategies may have considerable potential for in vivo assessment of neuropathologic changes associated with HIV. This investigation evaluated the prognostic significance of whole brain histogram-derived diffusion tensor imaging indices with respect to severity of cognitive impairment and measures of clinical status in cases of HIV. METHODS Quant...

Hydrogen diffusion has an important role in solute-dependent hydrogen embrittlement in metals and metallic alloys. In spite of extensive studies, the complexity of hydrogen diffusion in solids remains a phenomenon that needs to be clarified. In this paper, we investigate the anisotropy of hydrogen diffusion in pure nickel single crystals using both an experimental approach and a thermodynamic d...

A singularly perturbed reaction diffusion problem is considered. The small diffusion coefficient generically leads to solutions with boundary layers. The problem is discretized by a vertex-centered finite volume method. The anisotropy of the solution is reflected by using anisotropic meshes which can improve the accuracy of the discretization considerably. The main focus is on a posteriori erro...

The effect of different particle release time from the sources to the cosmic-ray (CR) spectrum below 10eV in the Galaxy are studied in detail. We discuss different possible forms of particle injection like the burst-like injection, continuous injection for a finite time, injection from a stationary source and energy dependent injection. When applied to the nearby known supernova remnants, it is...

The diffusion in voxels with multidirectional fibers can be quite complicated and not necessarily well characterized by the standard diffusion tensor model. High angular resolution diffusion-weighted acquisitions have recently been proposed as a method to investigate such voxels, but the reconstruction methods proposed require sophisticated estimation schemes. We present here a simple algorithm...

The steady-state polarization (or anisotropy) of the fluorescent dye 1,6-diphenyl-1,3-5-hexatriene in amniotic fluid samples and the lecithin/sphingomyelin ratio of the samples were correlated with development of respiratory distress syndrome in newborns. We found that clinical samples have a variable endogenous fluorescence that reduces the observed polarization (or anisotropy). This backgroun...