Wettabilities of SiO2, BN, pBN and graphite substrates with molten InGaAs were measured under Ar atomosphere at temperatures of 1200, 1300 and 1400°C. Molten InGaAs spouted through a hole of substrates even when pushing by a piston was stopped at the position where a top of the melt appeared just above the hole. This might be due to high arsenic dissociation pressures at measure ment temperatures. In addition, migration of drops on pBN and BN substrates was observed. BN and pBN sustrates showed poor wettability, namely appropriate properties as crucible materials. SiO2 and graphite showed high wettability, namely insufficient properties.
Protein crystal growth in space and on earth is conceptually explained in terms of both thermodynamics and kinetics, and the results of crystallization of hen egg-white lysozyme using space shuttles and the space station MIR are summarized. In a microgravity environment in space, single crystals which have a good molecular packing appear, although crystal growth proceeds at a slower rate than that on earth. However, they are not always of an optimal shape and size for X-ray diffraction experiments. It is speculated that crystal shape is influenced by the characteristics of the molecular surface of the protein in space than it is more greatly on earth. Furthermore, it was observed that hen egg-white lysozyme happened to grow in single crystals of two different kinds of space groups in the same crystallization apparatus. The reasons why these phenomena occurred in space are discussed.
In order to simulate weightlessness adequately, we constructed a new three-dimensional (3-D) clinostat equipped with two rotation axes placed at right angles. In the clinostat, the rotation achieved with two motors is computer-controlled and monitored with encoders attached to the motors. By rotating plants three-dimensionally at random rates on the clinostat, their dynamic stimulation by gravity in every direction can be eliminated. Some of growth processes dependent on the grav ity vector, such as morphogenesis, were shown to be influenced by the 3-D clinostat rotation. On the clinostat, shoots and roots of maize exhibited curvatures in three different portions. These spontaneous curvatures occurred independent of graviperception or the early steps of gravity signal transmission. It was also shown that different modifications of cell wall metabolism were involved in such
curvatures. The 3-D clinostat is a valuable device in simulating weightlessness and will contribute to deepen our knowledge of the role of gravity in regulation of plant growth and development .
The self-diffusion coefficient of liquid germanium, which shows the semiconducting properties in the solid crystalline state, was measured by the long capilary method under the microgravity due to the launch of the fifth TR-IA rocket. The obtained self-diffusion coefficient, 0.84 X 10- 4 cm2s- 1 at 1273 K, is 20% smaller than the previous data on the ground. The present self-diffusion coefficient and its temperature dependence are far larger than the cases of simple liquid metals. From the point of view of hard sphere model, it is concluded that these features are derived from the loose packing of liquid structure.
Shear Cell method is one of diffusion coefficient measuring method, and this method can make it possible to measure Diffusion coefficient accurately. Development of Shear Cell method was performed in this investigation. Preliminary investigation as fluid simulation was performed to decide best design for Shear Cell cartridge. Diffusion coefficient of germanium semiconductor melt was measured in microgravity environment using this Shear Cell cartridge. Experiment temperature is 1200°C, experiment time is 357 sec. These experiment conditions are decided to utilize microgravity environment in sounding rocket fully. Concentration distribution of experiment sample is measured by SIMS after flight experiment. Diffusion coefficient is calculated as 1.94 X 10-4 cm2 / s from this results. Technological development of Shear Cell method was achieved from this experiment.
In April and July, the first microgravity science laboratory missions (STS-83 and STS-94) were done, respectively. The mission done in April (STS-83) returned after only 4 days because of an accident involving fuel cells. NASA promptly set the reflight mission (STS-94) for July. Five organizations from USA (NASA), Japan (NASDA), Germany (DARA and DLR) and Europe (ESA) provided 13 experimental facilities, and 28 experimental themes were performed. NASDA was responsible for the Large Isothermal Furnace (LIF), with which the experimental programs of four Japanese (Drs. Yamamura, Itami, Uchida and Yoda) and two American (Drs. German and Mattiesen) principal investigators were carried out through 25 experiments.
This paper describes the outline of these two missions related with the NASDA activity on experiment operations with the LIF.