The spall strength limit of matter at ultrahigh strain rates induced by laser shock waves

New results concerning the process of dynamic fracture of materials (spallation) by laser-induced shock waves are presented. The Nd-glass laser installations SIRIUS and KAMERTON were used for generation of shock waves with pressure up to 1 Mbar in plane Al alloy targets. The wavelengths of laser radiation were 1.06 and 0.53 μm, the target thickness was changed from 180 to 460 μm, and the laser radiation was focused in a spot with a 1-mm diameter on the surface of AMg6M aluminum alloy targets. Experimental results were compared to predictions of a numerical code which employed a real semiempirical wide-range equation of state. Strain rates in experiments were changed from 106 to 5 × 107 s−1. Two regimes of spallation were evidenced: the already known dynamic regime and a new quasi-stationary regime. An ultimate dynamic strength of 80 kbar was measured. Finally, experiments on targets with artificial spall layers were performed showing material hardening due to shock-wave compression

PROBLEMS OF MEASUREMENT OF DENSE PLASMA HEATING IN LASER SHOCK-WAVE COMPRESSION

Experimental results of heating measurements of matter carried out in a study of laser-driven shock waves in aluminum (Batani et al. 1997) are discussed. The measured temporal evolution of the "color" temperature of the rear surface of the target is compared with that computed by a numerical code. It has been established that the target preheating can substantially affect optical signal features recorded from the rear side of the target, and consequently influence upon the accuracy of temperature and pressure measurements of the material behind the shock wave front

ANALYSIS OF THE MORTALITY STRUCTURE IN HEMODIALYSIS PATIENTS

Studies of the mortality structure in patients receiving hemodialysis (HD) remain relevant and are the basis for developing measures and recommendations directed to increase the lifetime of patients. Aim. The aim was to study the assessment of death causes in patients who received programmed hemodialysis, based on the demographic and gender characteristics, the duration of dialysis treatment. Methods. Mortality causes in 137 patients who received programmed hemodialysis from 2007 to 2011 years in Kyiv City Scientific and Practical Center of Nephrology an Dialysis were analyzed. Results. The leading cause of death was cardiovascular complications, but their decreasing has been observed since 2008. Fatality rate in young and middle- aged women with cardiovascular diseases (CVD) was almost two times higher than that of men. At the same time CVD is a predominant cause of men’s death at the age older than 44. Cerebrovascular complications were permanently in the second place of the mortality structure. About 30% of deaths occurred during the first 90 days of HD treatment, 72,5% of them were among males. Conclusion. Gender characteristics influence the structure of death causes in patients received programmed hemodialysis depending on age