Bone metabolism and formation of mice bred in a 2 G environment.

The purpose of this study is to reveal the effect of chronic hypergravity exposure on the bone formation and the bone metabolism when mammals produce offspring in a 2 G environment. We measured the length and width of the thighbone, the length of the pelvis, the width of the pelvic cavity and the width of the fourth cervical vertebra on the second (F2) and the third (F3) generation mice bred in a 2 G environment every ten days from 20 days old to 60 days old in an experiment on bone formation. In an experiment on bone metabolism, we measured calcium and phosphorus in the bones of the F3 in the 2 G group. Ratios of the thighbone length, pelvis length, pelvic cavity width, and fourth cervical vertebra width versus the body length were calculated. These ratios were higher in the 2 G group than the control group during all measuring periods. Calcium and phosphorus concentrations in the thighbone and the lumbar vertebra were lower in the 2 G group than in the control group. However, the calcium and phosphorus concentrations in the cervical vertebrae of the 2G group were higher. These results suggest that the influence of gravity load may vary in the bones.     

Differential positioning experiment using two geostationarysatellites

A ranging and positioning system for a ship or an aircraft using two geostationary satellites is described. This system has a ranging and positioning accuracy of 100 m and 1 km. Experiments to estimate this system were performed using a ship in the Pacific Ocean in a normal and a differential modes. This system leads to the development of fundamental ranging and positioning techniques for the cooperated independent surveillance     

X-ray observations of black-hole accretion disks

Our current theoretical and observational understandings of the accretion disks around Galactic black-holes are reviewed. Historically, a simple phenomenological accretion disk model has been used to interpret X-ray observations. Although such a phenomenological interpretation is still useful, high quality X-ray data from contemporary instruments allow us to test more realistic accretion disk models. In a simple and ideal case, the standard optically thick accretion disk model is successful to explain observations, such that the inner disk radius is constant at three times the Schwarzschild radius over large luminosity variations. However, when disk luminosity is close to or exceeds the Eddington luminosity, the standard disk model breaks, and we have to consider the “slim disk” solution in which radial energy advection is dominant. Recent observations of Ultra-luminous X-ray sources (ULXs), which may not be explained by the standard disk model, strongly suggest the slim disk solution. We compare theoretical X-ray spectra from the slim disk with observed X-ray spectra of ULXs. We have found that the slim disk model is successful to explain ULX spectra, in terms of the massive stellar black-holes with several tens of solar mass and the super-Eddington mass accretion rates. In order to explain the large luminosities (>10⁴⁰ ergs s⁻¹) of ULXs, “intermediate black-holes” (>100M) are not required. Slim disks around massive stellar black-holes of up to several tens of solar mass would naturally explain the observed properties of ULXs.