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The influence of 20 kc/s ultrasound on precipitation-hardening kinetics in a copper-beryllium alloy has been investigated. Half-wavelength specimens were employed so that a resonant standing wave existed. The ultrasonically irradiated specimens were subjected to a maximum acoustic-stress amplitude of 3.5 × 108dynes/cm2(5100 lb/in2). Acoustic energy brought about a small acceleration of the precipitation rate, the increase in overall ageing kinetics being caused by acoustic enhancement of the grain-boundary precipitation reaction. Ultrasonic energy did not significantly change the apparent activation energy for precipitation or alter the time-dependence of the rates of precipitate nucleation and growth.

The influence of 20 kc ultrasonic energy on grain growth kinetics in O.F.H.C. copper was investigated. Half-wavelength specimens resulted in resonant standing waves with a maximum acoustic stress amplitude of 2·4 × 108 dynes/cm2. Acoustic energy caused an acceleration in grain growth rate. The grain growth exponent, n, in the equation D=βtn was increased from 0·11 to 0·31, where D is the grain diameter at growth time t and β is a constant.

Although occlusion of the cerebral arterial circulation has been of considerable value in temporarily controlling hemorrhage during the surgical treatment of intracranial vascular anomalies, its elective use for any prolonged length of time to facilitate the removal of otherwise inoperable lesions has been limited by the substantial risk of impairing neural function. Total cessation of the circulation under hypothermia has been pioneered by the cardiovascular surgeon to allow direct attack upon lesions of the heart and great vessels. The relatively short length of time which the central nervous system will withstand total ischemia even under hypothermic conditions, however, has restricted its usefulness and has stimulated the study of means to shunt the circulation around the diseased area in order to maintain the cerebral blood supply during surgery. As such techniques are of little value to the neurosurgeon, it is important to understand the conditions for deriving the maximum possible benefit

The word leprosy has cast a shadow of terror before it since times of antiquity. From biblical days, when the leper had to proclaim his presence with a cry of "unclean," to the present period, when he is summarily incarcerated, no other disease has had the tremendous religious, moral, and social implications of leprosy. Despite the fact that it is far less contagious than tuberculosis and infinitely less prevalent, leprosy is considered a much greater hazard by the general public and, perhaps, by the medical profession. If this attitude is found in the United States, with only 0.1% of the world's lepers, it is not difficult to conceive of the unfortunate lot of the remaining 5,000,000 lepers in the poverty-stricken, less enlightened areas of the world.Recently, with newer advances in chemotherapy, a belated hope has been tendered to lepers. In view of the greater efficacy of these drugs in