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Biomedical subjects

M W Collins

Publications and source records attributed to M W Collins.

4 recordsLinked to original sources
PubMed1992

Flow studies in canine artery bifurcations using a numerical simulation method.

Three-dimensional flows through canine femoral bifurcation models were predicted under physiological flow conditions by solving numerically the time-dependent three-dimensional Navier-stokes equations. In the calculations, two models were assumed for the blood, those of (a) a Newtonian fluid, and (b) a non-Newtonian fluid obeying the power law. The blood vessel wall was assumed to be rigid this being the only approximation to the prediction model. The numerical procedure utilized a finite volume approach on a finite element mesh to discretize the equations, and the code used (ASTEC) incorporated the SIMPLE velocity-pressure algorithm in performing the calculations. The predicted velocity profiles were in good qualitative agreement with the in vivo measurements recently obtained by Jones et al. The non-Newtonian effects on the bifurcation flow field were also investigated, and no great differences in velocity profiles were observed. This indicated that the non-Newtonian characteristics of the blood might not be an important factor in determining the general flow patterns for these bifurcations, but could have local significance. Current work involves modeling wall distensibility in an empirically valid manner. Predictions accommodating these will permit a true quantitative comparison with experiment.

Animals↗
PubMed1991

Oat gum lowers glucose and insulin after an oral glucose load.

Foods containing soluble dietary fibers delay glucose absorption and lower postprandial plasma glucose. This effect of oat bran has been attributed to oat gum (80% beta-glucan). However, purified oat gum has previously not been available for human studies. In this study the glucose and insulin responses to consuming 14.5 g of specifically prepared oat gum with 50 g glucose were compared with the response to guar gum with glucose and to glucose alone in nine healthy, fasting subjects. Plasma glucose and insulin increases after the glucose drink were greater than after both gum meals between 20 and 60 min (P less than 0.01). The responses to the two gum meals were nearly identical. These results establish that the more palatable oat gum lowers postprandial plasma glucose and insulin concentrations in humans and may be comparable with or of greater benefit than guar gum.

Adult↗
PubMed1990

A review of the numerical analysis of blood flow in arterial bifurcations.

Arterial bifurcation flow has been of special interest for some years because of its important role in the formation of atherosclerotic plaques and thrombi. To investigate the flow phenomena analytically, four major factors need to be accommodated--the three-dimensionality of a general bifurcation, the pulsatile nature of the laminar flow, the distensibility of the arterial wall and the non-Newtonian character of the blood. In this review, both engineering and medical aspects of each factor are carefully surveyed. It is demonstrated that the latest generation of computational fluid dynamics codes can treat this problem area and that it is both feasible and desirable to investigate the effects of each independent factor.

Arteries↗