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Responses of structure and mineral content in weight-bearing bones to 1-week hindlimb suspension were studied in growing rats. The weight, volume, and length of femur, tibia, and fibula were less in suspended rats than cage controls, although there was no significant difference in the weight/volume ratio. The diameter of mid-shaft, the thickness of cortical bone, and the ratio of cortical bone thickness to femur diameter were significantly less in the suspended rats. The width of marrow space showed no differences, suggesting that the cortical bone was mainly affected. The sum of mineral content and the mineral content per diameter in the cross section of femurs were decreased following suspension, suggesting a change in the internal structure of cortical bone. Data also indicated that the reduction of femur diameter was caused by decreased thickness which is accompanied by the decreased mineral content of the cortical bone. It was suggested that there is a close relationship between the responses of bones and muscles to hindlimb suspension of young rats, although the degree of weight loss was greater in muscles than in bones.

To study the structure of the core of an edge dislocation in ionic crystal, we measured the amplitude dependence of internal friction by automated Marx's composite oscillator method and the vibrational current caused by charged dislocations. The phase angle between vibrational current and strain suddenly changed by 180 degrees at a strain amplitude of 10-6. From this fact we discuss the structure of the dislocation core.

Marx's composite oscillator method has been successfully automated for measuring internal friction and Young's modulus. The apparatus automatically finds the mechanical resonant frequency of the composite oscillator and keeps the strain amplitude constant, so that internal friction and the modulus can easily be measured and directly recorded on an X-t recorder. This device enables us to observe continuously the time dependence of the pinning and unpinning processes of dislocation by point defects. The error in strain amplitude is suppressed to within ±0.1%, while the internal friction value changes by 2 orders of magnitude. The operation of this system has been analyzed by automatic control theory, and the theoretical results are in good agreement with the experiment results. The analysis and the application of this method are presented here together with some experimental results.

By automated Marx's composite oscillator method, changes of internal friction with the pressure of nitrogen, oxygen, and argon were measured. The range of the measurement was from a pressure of 103 mbar to 10-5 mbar. An application to a wide range vacuum gauge was discussed.