"The study of the toxicity of Ra and MsTh(Ra/sup 228/) in humans was continued. Several Thorotrast cases were also examined. Physical and clinical studies were made on 151 persons. In all cases possible gamma ray measurements were made of Ra and MsTh decay products retained in the body, alpha -ray measurements of Rn and Rn/sup 220/ in breath, a complete medical history was taken, a complete x-ray examination was made of the skeleton, and urinalysis, hematological, and blood chemistry studies were made."

"The performance of the Model I electrostatic precipitator sampler in recent field and laboratory tests is described and discussed. Two of the four precipitator-bearing balloon flights during this interval reached the floating altitude of approximates 105,000 feet, and the precipitator operated efficiently on both. One sample was collected at the nominal design flowrate of approximates 100 cfm, and the second at approximates -200 cfm. Comparison of the deposition profiles of the stratospheric samples with those obtained under controlled conditions in the altitude chamber indicates that the field samples were collected with >90% efficiency. The laboratory tests also showed that the performance capability of the precipitator improves with increasing precipitator current, and with increasing altitude. One of the above balloon flights carried two Model A-I altimeters with recorder outputs. The two records were identical within plus or minus 250 feet. In addition, variations in altitude indications were consistent with the less sensitive aneroid barocoder measurements from the same flight. A revised Model A-I altimeter with a telemeterable output signal has been designed and constructed. The frequency of the signal is a function of the altitude. A preliminary design concept for a flowmeter with negligible flow resistance is described. It would utilize …

"Results of the continuing stratospheric flight test evaluation program for the Del Model I Electrostatic Precipitator Sampler and the Del Electrical Discharge Altimeter are described and discussed. Only one of four balloon launches reached floating altitude. The altimeter obtained an altitude recording consistent with concurrent aneroid barocoder readings. The reported gross gamma concentration for the precipitator sampler was approximates 25 and 80% higher than those of the two simultaneous direct flow filter samples. The completion of the design and construction of two prototype units of the Del Electrical Discharge Altimeter and their laboratory evaluation are described. A preliminary design concept is presented for an operational high volume electrostatic precipitator sampler to operate with high collection efficiency at an ambient flowrate of 500 cfm throughout the altitude range 100,000 to 150,000 ft."

"Design work was completed and construction initiated on a prototype field altimeter based on the gas density dependence of Townsend discharge current in an electrical discharge. The design of an ion tracer air velocity meter for laboratory applications, and construction of three units were successfully completed. Theoretical and experimental support is presented, showing the applicability of the ion tracer system to the accurate measurement of linear gas velocity. The operating range of the laboratory meter is 150 to 2500 ft/min at ambient pressures between 200 mu and 30.0 mm Hg. Further investigations on the application of the ion tracer concept to flowrate measurements are presented. By generating velocity profile curves with an ion tracer calibrated thermoanemometer, it was possible to determine the flowrate for 2 flow and pressure conditions; 37.5 cfm at 19.6 mm and 75 cfm at 9.8 mm Hg. Comparison with a calibrated Rotameter technique was within 5% in both cases. Also presented are some preliminary investigations leading to the development of a generalized ion tracer flowmeter for low gas densities. Results of some supplemental electrical discharge experiments in rarefied atmospheres are described. It was observed that electrical oscillations could be produced in a low density gas discharge, …

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"Research in thermal contact resistance at MIT and advances made during the past year are summarized. The problem of predicting cortact resistance is examined in an analysis of a model for the contact which relates the geometry of actual surfaces in contact to the contact model, and a deformation analysis which relates the contact geometry to the load carried by the surfaces. Experimental procedures are described and are applied to two stainless steel surfaces in contact and to W and graphite surfaces in contact. A significant result is that a surface may be described by two measurable parameters which may be combined with two such parameters of any other surface to completely determine the geometry of the interface if they are placed in contact. It thus remains to construct a device which will readily measure these two parameters."