We analyze the effective diffusivity of a passive scalar in a two-dimensional, steady, incompressible random flow that has mean zero and a stationary stream function. We show that in the limit of small diffusivity or large Peclet number, with convection dominating, there is substantial enhancement of the effective diffusivity. Our analysis is based on some new variational principles for convect...

BACKGROUND Schizophrenia is associated with often widespread changes in white matter structure. Most studies have investigated changes in fractional anisotropy, whereas alterations in radial or axial diffusivity have barely been investigated until now. AIMS To investigate radial diffusivity as a potential marker of dysmyelination in direct relation to abnormalities in neural activation. MET...

Recent MRI studies have indicated that regions of the temporal lobe including the superior temporal gyrus (STG) and the temporal stem (TS) appear to be abnormal in autism. In this study, diffusion tensor imaging (DTI) measurements of white matter in the STG and the TS were compared in 43 autism and 34 control subjects. DTI measures of mean diffusivity, fractional anisotropy, axial diffusivity, ...

We use Brownian dynamics with hydrodynamic interactions to calculate both the Kirkwood (short-time) diffusivity and the long-time diffusivity of DNA chains from free solution down to channel confinement in the de Gennes regime. The Kirkwood diffusivity in confinement is always higher than the diffusivity obtained from the mean-squared displacement of the center-of-mass, as is the case in free s...

A moving finite element-based inverse method for determining the temperature on a moving surface is developed. The moving mesh is generated employing the transfinite mapping technique. The proposed algorithms are used in the estimation of surface temperature on a moving boundary with high velocity in the burning process of a homogenous low thermal diffusivity solid fuel. The measurements obtain...

The drying behavior of green peas is investigated in a pilot scaled Fluidized Bed Dryer (FBD) with inert particles assisted by an Infra Red (IR) heat source. The variation of shrinkage and moisture diffusivity with temperature and moisture content were investigated. The experimental drying curves were adjusted to the diffusion model of Fick’s law for spherical particles. The result was that...

A technique of the temperature dependent thermal diffusivity investigation has been analysed. The technique is based on the modified Ångström method utilising periodic temperature oscillations in a slab specimen. The additional modification consists of imposing linear temperature changes – application of linear scans. This scanning mode procedure enables investigation of the thermal diffusivity...

Recent studies in rodents have demonstrated that diffusion imaging is highly sensitive to differences in myelination. These studies suggest that demyelination/dysmyelination cause increases in the radial diffusivity from diffusion tensor imaging (DTI) measurements and decreases in the restricted diffusion component from high b-value diffusion-weighted imaging experiments. In this study, the sha...

BACKGROUND AND PURPOSE Diffusion tensor metrics are potential in vivo quantitative neuroimaging biomarkers for the characterization of brain tumor subtype. This meta-analysis analyzes the ability of mean diffusivity and fractional anisotropy to distinguish low-grade from high-grade gliomas in the identifiable tumor core and the region of peripheral edema. MATERIALS AND METHODS A meta-analysis...

In this study, nanofluids of Chromium (Cr) in water, Ethylene Glycol and Ethanol have been prepared using single step method. The thermal conductivity and diffusivity of these nanofluids were measured via hot wire-photothermal deflection technique. Based on finite difference method (FDM) temperature distribution and photothermal deflection caused by the hot wire inside nanofluids was obtained. ...