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Klein HP Horowitz NH Levin GV Oyama VI Lederberg J Rich A Hubbard JS Hobby GL Straat PA Berdahl BJ Carle GC Brown FS Johnson RD 《Science (New York, N.Y.)》1976,194(4260):99-105
Three different types of biological experiments on samples of martian surface material ("soil") were conducted inside the Viking lander. In the carbon assimilation or pyrolytic release experiment, (14)CO(2) and (14)CO were exposed to soil in the presence of light. A small amount of gas was found to be converted into organic material. Heat treatment of a duplicate sample prevented such conversion. In the gas exchange experiment, soil was first humidified (exposed to water vapor) for 6 sols and then wet with a complex aqueous solution of metabolites. The gas above the soil was monitored by gas chromatography. A substantial amount of O(2) was detected in the first chromatogram taken 2.8 hours after humidification. Subsequent analyses revealed that significant increases in CO(2) and only small changes in N(2) had also occurred. In the labeled release experiment, soil was moistened with a solution containing several (14)C-labeled organic compounds. A substantial evolution of radioactive gas was registered but did not occur with a duplicate heat-treated sample. Alternative chemical and biological interpretations are possible for these preliminary data. The experiments are still in process, and these results so far do not allow a decision regarding the existence of life on the plonet Mars. 相似文献
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Ozone uptake by bean leaves 总被引:4,自引:0,他引:4
The removal of ozone from the air by bean leaves is regulated by the same factors that control the exchange of water vapor between leaves and the atmosphere. 相似文献
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Systemically administered flunarizine enhanced neuronal survival in lumbar sensory ganglia in newborn rats after axotomy. Flunarizine-treated rats lost 71 percent fewer neurons than the untreated control rats at the end of 1 week. In cell culture, flunarizine at 30 to 40 microM also prevented neuronal death in nerve growth factor-dependent embryonic sensory and sympathetic neurons after the abrupt withdrawal of neurotrophic support. The drug may cause this effect by acting at an intracellular site, one distinct from its blockade of voltage-dependent calcium channels. 相似文献
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Atlas R Campbell P Cozzarelli NR Curfman G Enquist L Fink G Flanagin A Fletcher J George E Hammes G Heyman D Inglesby T Kaplan S Kennedy D Krug J Levinson R Marcus E Metzger H Morse SS O'Brien A Onderdonk A Poste G Renault B Rich R Rosengard A Salzburg S Scanlan M Shenk T Tabor H Varmus H Wimmer E Yamamoto K;Journal Editors Authors Group 《Science (New York, N.Y.)》2003,299(5610):1149
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Rich JL 《Science (New York, N.Y.)》1918,47(1202):43-44
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Rich JL 《Science (New York, N.Y.)》1948,107(2788):581-584
Summarizing in a few words the essence of the preceding analysis of goals and trends in research in Geology and Geography, we may say that the goal in Geology is a knowledge and understanding of the earth and of its history. In Geography it is a knowledge and understanding of the natural and human environments, to the end that they may best be utilized toward better living in the broadest sense. Trends in research in these sciences that seem not altogether desirable are those toward overorganization of research and overdirection from others than the ones who are to do the work; toward indiscriminate fact-gathering; toward lessening of critical analysis of, and discussion of, papers given at meetings and of the published results; and toward premature publication and excessive volume of publications resulting from the prevailing practice of soliciting papers for scientific meetings. Changes in methods of financing of research resulting from a great decrease in endowment incomes are noted, together with a strong tendency to look toward the Federal Government for the financing of university research, in spite of the obvious dangers to university freedom which such financing involves. 相似文献