Laser induced fluorescence method has been employed for the remote, non-intrusive and instantaneous measurements of a fuel droplet flame under microgravity. A fuel droplet was doped with naphthalene and TMPD (N,N,N',N'-Tetramethyl-1,4--phenylendiamine). The fluorescene emis sion spectra from a droplet subjected to the incident nitrogen laser were measured with an image in tensified optical multichannel analyzer. The microgravity was generated in a capsule of the MGLAB (Micro-Gravity Laboratory of Japan) drop shaft. The results showed that the newly developed diagnostic system was found to be applicable successfully for the simultaneous measurements of diameters of droplet, flame and soot shell under microgravity. A droptet temperature could be determined from the measured result of the ratio of fluorescence emission intensities at two different wavelengths. The soot shell was located at the vicinity of the droplet surface at the early stage of the burning and moved away from the droplet with the lapse of time.
An experiment on pool boiling of subcooled water was performed in microgravity obtained by a parabolic flight of jet aircraft. A heating surface was a thin stainless steel plate with 20 mm in length, 5 mm in width and 0.1 mm in thickness. Water was maintained at the subcooled states of 10 K, 20 K, 30 K and 40 K below the saturation temperature. Alternative current was applied to the heating surface and the surface was exposed to burnout in microgravity. The bubble behaviors were observed by a CCD video system. At lower subcooling of water, bubbles became large with increasing of heating power, but they did not detach from the heating surface until the burnout occurred in microgravity. At higher subcool ing, the heating surface was covered entirely by coalesced bubbles and many fine bubbles generated on the surface were emitted explosively through the coalesced bubbles. The burnout heat flux obtained in the present experiment was 200 to 400% higher than the existing predictions.
The precise knowledge of thermophysical properties becomes increasingly important as progress is made in numerical simulations of complex processes. With the improvement of the models, the limiting factor in predicting the real process is determined by the accuracy of the input parameters characterising the material under study. For high temperature melts, such as liquid metals, containerless methods are the best choice for their measurement. They avoid contamination of the melt, give access to the undercooled regime and allow accurate measurements of thermophysical properties sensitive to surface contamination, such as surface tension. During the MSL-1 mission (Microgravity Science Laboratory), undercooling experiments were performed using the electromagnetic levitation facility TEMPUS (Tiegelfreies Elektro Magnetisches Prozessieren Unter Schwerelosigkeit) to measure thermophysical properties and to study the nucleation and growth phenomena of selected metals and alloys. Following thermophysical properties were measured: specific heat, thermal expansion, electrical conductivity, viscosity and surface tension. The range of materials investigated included pure metals, binary alloys, and multicomponent alloys. Among the latter, special attention was given to the new easy glassforming systems and to alloys with quasicrystalline symmetry. The experiments were very succesful: large undercoolings were obtained and many melt cycles could be performed. The large amount of scientific data, consisting of digital and video signals, requires an extensive analysis, which, to some extent, is still not complete. This paper reports on the experiments and some selected results already available.
In the MSL-1 mission the self-diffusion coefficient, D, in liquid Sn was investigated at five temperatures in the wide temperature range up to 1622 K. The long capillary (LC) method was adopted with the use of stable isotope 124Sn as a tracer. The concentration profiles of 124Sn were determined by the SIMS analysis. The D was determined by the analytical solution of the Fick's second law combined with the effective time, terr• In this effective time the effect of diffusion on both the heating and cooling periods was taken into account properly in addition to the keeping time. In the practical application the iteration method was adopted. The obtained self-diffusion coefficients remain to be small enough even at 1622 K contrary to the abrupt increase of the ground data in the literature due to the same LC method. The present data at 1622 K was in good agreement with D obtained by the shear cell technique, which was adopted in the present MSL-1 mission by NASDA. The extrapolation of present data to the low temperature range is in good agreement with the microgravity data of D due to Frohberg et al. The power index in the temperature dependence of Dis 1.81 for the present data and
2.04 for the all microgravity data of D though the latter index seems to be much affected by the data due to Frohberg et al. Obtained data was analyzed by the hard sphere model. Agreement between calculations and experiments is qualitatively good though 1.77 was obtained as the power index for the calculated temperature dependence of D. The prediction of the viscosity of some liquid metals was successfully performed by the hard sphere model, in which the present experimental information of D under microgravity is taken into account.
This study was conducted in order to elucidate the molecular mechanism of the response to microgravity in osteoblasts. Mouse osteoblast MC3T3-El cells were grown in il!-MEM supplement ed with 1% fetal calf serum and 10 mM Hepes and mounted in the newly developed cell culture experiment module (CCE) in sounding rocket TR-1A6. The cells were stimulated with EGF (100 ng/ ml) or forskolin (5 µM) for 5 min. under microgravity. Then, the cells were lysed with Isogen. Total RNA and protein were isolated from the returned lysates. The gene c-jos were detected by RT-PCR and MAPK by Western blotting. The EGF-induced c-jos expression in the cells were
suppressed under microgravity, while the forskolin-induced gene expression were not affected. These results suggest that microgravity restrains expression of c-jos which mediate protein kinase C signal transduction induced by EGF.