Numerical Studies of Flow Between Rotating Coaxial Disks

A new algorithm, which is exceptionally fast for certain choicesof numerical parameters, is described for the study of nonlinear,incompressible flow between two rotating disks. Typical examplesfor Reynolds number R in the range 10 R 2000 are describedand discussed. Comparisons are made with the limited availableresults generated by other methods.     

SPECIES DIFFERENCES IN RESPONSE TO PHOTOHEMOLYTIC AGENTS

Species differences in red blood cell susceptibility to the photohemolytic agents chlorpromazine, menadione and tetracycline were examined in mouse, rat, dog, and human blood. Menadione and tetracycline (25 microM) hemolyzed mouse but not dog, rat, or human red blood cells (RBC) when irradiated with UV light but not in the dark. Chlorpromazine (25 microM) produced a photohemolytic response in all four species with mouse and rat RBC lysing fastest followed by human then dog cells. Investigations into the nature of these species differences suggested that the size of mouse RBC may contribute to its high sensitivity to photohemolytic agents. An investigation of the effect of UV light on key antioxidant enzymes revealed species differences in enzyme inactivation. These data suggest that mouse RBC may be particularly vulnerable to phototoxic agents, especially those compounds which produce active oxygen species and, therefore, may prove more useful than human RBC as a model for predicting phototoxic potential of some chemical entities.     

The effect of a changing diffusion coefficient in super-Case II polymer-penetrant systems

In certain polymer-penetrant systems, nonlinear viscoelasticeffects dominate those of Ficlcian diffusion. By introducinga dependence of the chemical potential on concentration history,this behaviour can be modelled by a memory integral. The mathematicalframework presented is a moving boundary-value problem wherethe boundary separates the polymer into two distinct states:glassy and rubbery. In each region, a different operator holdsat leading order. The problem which results is not solvableby similarity solutions, but can be solved by perturbation andintegral equation techniques. By introducing a new model wherethe diffusion coefficient changes with phase, asymptotic solutionsare obtained where sharp fronts initially move like t³/2. This‘super-Case II’ behaviour is found in various non-Fickianpolymer-penetrant systems.