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71.
M.?BarmatzEmail author F.?Zhong A.?Shih 《International Journal of Thermophysics》2004,25(6):1667-1675
The earlier microgravity heat capacity measurements in SF6 by Haupt and Straub have been reanalyzed in this study. A simple power law as well as the minimal-subtraction renormalization (MSR) scheme were used to fit the measurements. In this paper the unexpected result that the SF6 heat capacity measurements appear to be within the asymptotic critical region all the way out to a reduced temperature |t| 10–2 is presented. This conclusion is in contradiction with the smaller asymptotic region |t| < 1.6× 10–4 found in the original investigation. These heat capacity measurements were found to be inconsistent with renormalization group predictions using SF6 compressibility measurements. 相似文献
72.
空间高温实时观察装置(SHITISOI)被用于观察和记录在Li2B4O7溶体中KNbO3胞状结晶的整个生长过程,并对胞状结晶生长过程中浮力对流和表面张力对流的影响进行了研究.首次观察到空间条件下,Li2B4O7溶体中稳态表面张力对流图像,它呈镜面对称的抛物线状.由于表面张力对流的作用,KNbO3胞晶生长且充满了整个的溶体.而在地面上,由于浮力抑制表面张力,降低了胞晶在流体中的生长速度,使溶质KNbO3胞晶在Li2B4O7溶体中分布不均匀,本文还提出了胞状结晶生长理论的模型.这个模型的主要特点是表面张力对流起始于KNbO3胞晶的界面上;这是由于KNbO3溶质扩散速率减少而引起的KNbO3溶质表面张力梯度.本模型的预言和实验所观察的现象吻合得比较好,这说明该理论模型是合理、可靠的. 相似文献
73.
74.
Cora S. Thiel Christian Vahlensieck Timothy Bradley Svantje Tauber Martin Lehmann Oliver Ullrich 《International journal of molecular sciences》2021,22(13)
Microgravity acts on cellular systems on several levels. Cells of the immune system especially react rapidly to changes in gravity. In this study, we performed a correlative metabolomics analysis on short-term and long-term microgravity effects on primary human macrophages. We could detect an increased amino acid concentration after five minutes of altered gravity, that was inverted after 11 days of microgravity. The amino acids that reacted the most to changes in gravity were tightly clustered. The observed effects indicated protein degradation processes in microgravity. Further, glucogenic and ketogenic amino acids were further degraded to Glucose and Ketoleucine. The latter is robustly accumulated in short-term and long-term microgravity but not in hypergravity. We detected highly dynamic and also robust adaptative metabolic changes in altered gravity. Metabolomic studies could contribute significantly to the understanding of gravity-induced integrative effects in human cells. 相似文献
75.
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77.
Shota Nemoto Shinsuke Ohnuki Fumiyoshi Abe Yoshikazu Ohya 《Yeast (Chichester, England)》2019,36(2):85-97
Reduction of gravity results in changes in gene expression and morphology in the budding yeast Saccharomyces cerevisiae. We studied the genes responsible for the morphological changes induced by simulated microgravity (SMG) using the yeast morphology data. We comprehensively captured the features of the morphological changes in yeast cells cultured in SMG with CalMorph, a high-throughput image-processing system. Statistical analysis revealed that 95 of 501 morphological traits were significantly affected, which included changes in bud direction, the ratio of daughter to mother cell size, the random daughter cell shape, the large mother cell size, bright nuclei in the M phase, and the decrease in angle between two nuclei. We identified downregulated genes that impacted the morphological changes in conditions of SMG by focusing on each of the morphological features individually. Gene Ontology (GO)-enrichment analysis indicated that morphological changes under conditions of SMG were caused by cooperative downregulation of 103 genes annotated to six GO terms, which included cytoplasmic ribonucleoprotein granule, RNA elongation, mitotic cell cycle phase transition, nucleocytoplasmic transport, protein–DNA complex subunit organization, and RNA localization. P-body formation was also promoted under conditions of SMG. These results suggest that cooperative downregulation of multiple genes occurs in conditions of SMG. 相似文献
78.
The behavior of sloshing dynamics modulated fluid systems driven by the orbital accelerations including gravity gradient and jitter accelerations with partially-filled rotating fluids has been studied. Present study is applicable to a full-scale Gravity Probe-B Spacecraft dewar tank with and without baffle. Results of slosh wave excitation along the liquid—vapor interface induced by jitter acceleration-dominated orbital accelerations provide a torsional moment with an up-and-down movement of bubble oscillations in the rotating dewar. The results show rightward and leftward movement of bubble oscillations transverse to the rotating axis, and up-and-down movement of bubble oscillations longitudinal to the rotating axis of dewar container. The orbital accelerations also induce an eccentric contour of bubble oscillations in a horizontal r—θ plane. As viscous force between liquid—solid interface, and surface tension force between liquid—vapor—solid interface can greatly contribute to the damping effect of slosh wave excitation, the rotating dewar with baffle provides more areas of liquid—solid and liquid—vapor—solid interfaces than that of a rotating dewar without baffle. Results show that the damping effect provide by a baffle reduce the amplitude of slosh wave excitation and reduce the degree of asymmetry in liquid—vapor distribution. Computation of bubble (helium vapor) mass center fluctuations also verifies that a rotating dewar with baffle produces less fluctuations than that of a rotating dewar without baffle. 相似文献
79.
Noncontact temperature measurement of a falling drop 总被引:1,自引:0,他引:1
W. H. Hofmeister R. J. Bayuzick M. B. Robinson 《International Journal of Thermophysics》1989,10(1):279-292
The 105-m drop tube at the Marshall Space Flight Center has been used in a number of experiments to determine the effects of containerless, microgravity processing on the undercooling and solidification behavior of metals and alloys. These experiments have been limited, however, because direct temperature measurement of the falling drops has not been available. Undercooling and nucleation temperatures are calculated from thermophysical properties based on droplet cooling models. In most cases these properties are not well known, particularly in the undercooled state. This results in a large amount of uncertainty in the determination of nucleation temperatures. If temperature measurement can be accomplished, then the thermal history of the drops could be well documented. This would lead to a better understanding of the thermophysical and thermal radiative properties of undercooled melts. An effort to measure the temperature of a falling drop is under way at Vanderbilt and Marshall Space Flight Center. The technique uses two-color pyrometry and high-speed data acquisition. The approach is presented along with some preliminary data from drop tube experiments. The results from droplet cooling models will be compared with noncontact temperature measurements.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
80.
The effectiveness of 10-s microgravity on thermophysical property measurements on molten materials, such as molten semiconductors, is discussed. The thermal conductivity of molten InSb was successfully measured under microgravity conditions on board the German sounding rocket TEXUS and in a drop shaft in Hokkaido, Japan. Surface tension measurements using an oscillating drop method was attempted in low gravity using a parabolic flight of the NASA KC-135 aircraft. Combined levitation and microgravity, which can provide a contamination-free and undercooled condition. is recommended as a novel approach to obtain missing thermophysical property data on undercooled melts of semiconductors.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29. 1995. Köln, Germany. 相似文献