Effective dimensionality of the Portevin - Le Chatelier effect

Tensile tests have been carried out by deforming polycrystalline samples of substitutional Al-2.5%Mg alloy at room temperature at a range of strain rates. The Portevin - Le Chatelier (PLC) effect was observed. From an analysis of the experimental stress versus time series data we have inferred that the dynamics of the PLC effect in a local finite time is controlled by a finite number of degrees of freedom and this effective dimension becomes reduced with increasing strain.Comment: 12 pages, 5 figure

Plasticity in polycrystalline thin films: A 2D dislocation dynamics approach

Thermal stress evolution in polycrystalline thin films is analyzed using discrete dislocation plasticity. Stress develops in the film during cooling from a stress-free configuration due to the difference in thermal expansion coefficient between the film and its substrate. A plane strain formulation with only edge dislocations is used and each grain of the polycrystal has a specified set of slip systems. The film-substrate interface and the grain boundaries are impenetrable for the dislocations. Results are presented for two film thicknesses, with higher hardening seen for the thinner films

Effects of the renin-angiotensin system on the reflex response of the adrenal medulla to hypotension in the dog.

We have studied the influence of the renin-angiotensin system on the control of catecholamine release from innervated and denervated adrenal glands of anaesthetized dogs. Captopril reduced the resting release of catecholamines and inhibited release evoked either by lowering carotid sinus pressure or by stimulating the peripheral end of the cut splanchnic nerve. Both responses were restored by exogenous angiotensin II, and the reflex response could also be restored by corticotrophin. Cycloheximide, in the presence of captopril, further reduced the resting release of catecholamines and prevented the restoration of the reflex response by angiotension II. Plasma renin activity did not rise during baroreceptor tests lasting 10 min, but catecholamine release was evoked from the first minute. We conclude that the response of the adrenal medulla to sympathetic activity requires a minimum circulating concentration of angiotensin II. It is severely impaired by inhibition of the renin-angiotensin system but function can be restored either by exogenous angiotensin II or by corticotrophin