Association between gait variability and brain ventricle attributes: a brain mapping study.

Background: It remains unknown which brain regions are involved in the maintenance of gait dynamic stability in older adults, as characterized by a low stride time variability. Expansion of lateral cerebral ventricles is an indirect marker of adjacent brain tissue volume. The purpose of this study was to examine the association between stride time variability and the volume of sub-regions of the lateral cerebral ventricles among older community-dwellers.

Automated algorithm to measure changes in medial temporal lobe volume in Alzheimer disease.

Background: The change in volume of anatomic structures is as a sensitive indicator of Alzheimer disease (AD) progression. Although several methods are available to measure brain volumes, improvements in speed and automation are required. Our objective was to develop a fully automated, fast, and reliable approach to measure change in medial temporal lobe (MTL) volume, including primarily hippocampus.

A novel MRI-compatible brain ventricle phantom for validation of segmentation and volumetry methods.

Purpose: To create a standardized, MRI-compatible, life-sized phantom of the brain ventricles to evaluate ventricle segmentation methods using T(1) -weighted MRI. An objective phantom is needed to test the many different segmentation programs currently used to measure ventricle volumes in patients with Alzheimer's disease.

Materials And Methods: A ventricle model was constructed from polycarbonate using a digital mesh of the ventricles created from the 3 Tesla (T) MRI of a subject with Alzheimer's disease.

Constitutive relations in dense granular flows.

We use simulations to investigate constitutive relations in dry granular flow. Our system is comprised of polydisperse sets of spherical grains falling down a vertical chute under the influence of gravity. Three phases or states of granular matter are observed: a free-fall dilute granular gas region at the top of the chute, a granular fluid in the middle and then a glassy region at the bottom.

Velocity fluctuations in dense granular flows.

We use simulations to investigate velocity fluctuations in dry granular flow. Our system is comprised of mono- and polydisperse sets of spherical grains falling down a vertical chute under the influence of gravity. We find three different classes of velocity distributions depending on factors such as the local density.

Granular circulation in a cylindrical pan: simulations of reversing radial and tangential flows.

Granular flows due to simultaneous vertical and horizontal excitations of a flat-bottomed cylindrical pan are investigated using event-driven molecular dynamics simulations. In agreement with recent experimental results, we observe a transition from a solidlike state to a fluidized state in which circulatory flow occurs simultaneously in the radial and tangential directions. By going beyond the range of conditions explored experimentally, we find that each of these circulations reverses its direction as a function of the control parameters of the motion.