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61.
H. Klein H.U. Walter A. Bewersdorff J. Pöttschke 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(5):57-62
The evolution of a dispersion under the action of temperature gradients and solidification was followed optically in a transparent molten salt (CsCl) with inclusions of Pb-droplets and gas bubbles. This system is believed to model a solidifying metallic alloy. Rejection of Pb-particles by the solidification front was observed, while large gas bubbles were incorporated. Thermocapillary convection at the gas bubbles considerably distorted the temperature field and even caused local remelting. Marangoni migration of bubbles was not observed, contrary to expectations. 相似文献
62.
G. Götz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(4):15-21
The space-based sub-system of the composite observing system, operated during the Operational Year of the Global Weather Experiment, played an indispensable role in the acquisition of data and in transmitting data from surface-based and airborne observational platforms to data-processing centres. The sub-system comprised both geostationary and near-polar orbiting meteorological satellites and special efforts were undertaken to keep the performance of the system as close as possible to that which had been anticipated during the planning stage of the Experiment.Five geostationary satellites were spaced at approximately uniform intervals around the equator. They were used primarily to derive wind vectors by measuring the displacement of clouds. The satellites also provided communication support for the Aircraft to Satellite Data Relay system, by which flight level meteorological data were automatically transmitted to ground receiving stations.Three polar orbiting satellites provided data simultaneously during the whole Operational Year. Vertical temperature soundings, clear-radiance data, sea-surface temperature and wind speed data, and total atmospheric water vapour data were produced for inclusion in the research data set of the Experiment. Two of these satellites /TIROS-N and NOAA-6/ carried a new data collection and platform location system, a basic component of the Tropical Constant Level Balloon System and the Drifting Buoy System of FGGE. 相似文献
63.
64.
G.W. Prölss 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(12):31-34
Dissipation of magnetospheric energy leads to an upper atmospheric disturbance zone whose extent varies with local time. A statistical analysis of ESRO 4 data reveals that (1) in the afternoon/evening sector the boundary location is determined by the region of electric current dissipation along the auroral oval; (2) in the midnight/early morning sector dynamical effects extend the disturbance zone to lower latitudes; and (3) in the late morning sector direct heating effects are superimposed on the residuals of the early morning disturbance. 相似文献
65.
Oligonucleotides are structurally similar to short RNA strands. Therefore, their formation via non-enzymatic reactions is highly relevant to Gilbert's RNA world scenario (1986) and the origin of life. In laboratory synthesis of oligonucleotides from monomers, it is necessary to remove the water molecules from the reaction medium to shift the equilibrium in favor of oligonucleotide formation, which would have been impossible for reactions that took place in dilute solutions on the early Earth. Model studies designed to address this problem demonstrate that montmorillonite, a phyllosilicate common on Earth and identified on Mars, efficiently catalyzes phosphodiester-bond formation between activated mononucleotides in dilute solutions and produces RNA-like oligomers. The purpose of this study was to examine the sequences and regiospecificity of trimer isomers formed in the reaction of 5'-phosphorimidazolides of adenosine and uridine. Results demonstrated that regiospecificity and sequence specificity observed in the dimer fractions are conserved in their elongation products. With regard to regiospecificity, 61% of the linkages were found to be RNA-like 3',5'-phosphodiester bonds. With regard to sequence specificity, we found that 88% of the linear trimers were hetero-isomers with 61% A-monomer and 39% U-monomer incorporation. These results lend support to Bernal's hypothesis that minerals may have played a significant role in the chemical processes that led to the origin of life by catalyzing the formation of phosphodiester bonds in RNA-like oligomers. 相似文献
66.
Tardigrades as a potential model organism in space research 总被引:1,自引:0,他引:1
Jönsson KI 《Astrobiology》2007,7(5):757-766
Exposure of living organisms to open space requires a high level of tolerance to desiccation, cold, and radiation. Among animals, only anhydrobiotic species can fulfill these requirements. The invertebrate phylum Tardigrada includes many anhydrobiotic species, which are adapted to survive in very dry or cold environmental conditions. As a likely by-product of the adaptations for desiccation and freezing, tardigrades also show a very high tolerance to a number of other, unnatural conditions, including exposure to ionizing radiation. This makes tardigrades an interesting candidate for experimental exposure to open space. This paper reviews the tolerances that make tardigrades suitable for astrobiological studies and the reported radiation tolerance in other anhydrobiotic animals. Several studies have shown that tardigrades can survive gamma-irradiation well above 1 kilogray, and desiccated and hydrated (active) tardigrades respond similarly to irradiation. Thus, tolerance is not restricted to the dry anhydrobiotic state, and I discuss the possible involvement of an efficient, but yet undocumented, mechanism for DNA repair. Other anhydrobiotic animals (Artemia, Polypedium), when dessicated, show a higher tolerance to gamma-irradiation than hydrated animals, possibly due to the presence of high levels of the protective disaccharide trehalose in the dry state. Tardigrades and other anhydrobiotic animals provide a unique opportunity to study the effects of space exposure on metabolically inactive but vital metazoans. 相似文献
67.
68.
Kobayashi Masanori Shibata Hiromi Nogami Ken’ichi Fujii Masayuki Hasegawa Sunao Hirabayashi Masatoshi Hirai Takayuki Iwai Takeo Kimura Hiroshi Miyachi Takashi Nakamura Maki Ohashi Hideo Sasaki Sho Takechi Seiji Yano Hajime Krüger Harald Lohse Ann-Kathrin Srama Ralf Strub Peter Grün Eberhard 《Space Science Reviews》2020,216(8):1-49
Space Science Reviews - In this chapter, we review the contribution of space missions to the determination of the elemental and isotopic composition of Earth, Moon and the terrestrial planets, with... 相似文献
69.
C. Zeitlin D. M. Hassler R. F. Wimmer-Schweingruber B. Ehresmann J. Appel T. Berger E. Böhm S. Böttcher D. E. Brinza S. Burmeister J. Guo J. Köhler H. Lohf C. Martin D. Matthiä A. Posner S. Rafkin G. Reitz Y. D. Tyler M. Vincent G. Weigle Y. Iwata H. Kitamura T. Murakami 《Space Science Reviews》2016,201(1-4):201-233
70.
K. G. Rönnmark 《Space Science Reviews》1985,42(3-4):411-428
In this paper, I outline the solution of Vlasov-Maxwell's equations with given initial conditions. When transients have died out, the temporal evolution of each spatial Fourier component is completely determined by a dispersion relation. I derive the electrostatic dispersion relation and discuss the resonant interaction between particles and electrostatic waves. A new derivation of the wave energy density in a plasma with arbitary dissipation is given. The numerical solution of the dispersion relation of waves in a Maxwellian plasma is discussed, and finally I show some examples of numerically evaluated dispersion surfaces. 相似文献