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941.
A potentially useful thermochemical cycle developed for the production of hydrogen and oxygen from water consists of three chemical reactions that take place in the temperature range from 400 degrees to 1200 degrees K. The oxidation and reduction of chromium compounds by barium hydroxide and the hydrolytic disproportionation of barium chromate(IV) and barium chromate(V), the reactions which constitute the proposed cycle, have been demonstrated. 相似文献
942.
Diurnal variations in the hydroxyl radical concentration of ambient air were measured for the first time by the technique of laser-induced fluorescence. 相似文献
943.
Archibald RC 《Science (New York, N.Y.)》1942,96(2491):294-296
944.
An electrophoretically slow hemoglobin variant, in which the structural change involves the replacement of a glutamyl residue by alanyl at position beta-22, was reported in two groups of North American Indians: hemoglobin-G Coushatta, in Alabama-Coushatta Indians in Texas; and hemoglobin-G Saskatoon, in descendants of Santee Indians living in Canada. Hemoglobin-G Hsin-Chu, found in Taiwan in a Chinese from the northern Chinese province of Liaoning, is now shown to have the same structural anomaly. 相似文献
945.
Unit responses to photic stimuli were studied in cat visual cortex. After the baseline response pattern of a cell was determined, conditioning trials were given during which reinforcement was contingent upon increased firing during a selected segment of the poststimulus interval. Density of reinforcement increased substantially in about half the cells studied; significant increases in firing occurred within, but not outside, the criterion segment. 相似文献
946.
Bridge HS Lazarus AJ Scudder JD Ogilvie KW Hartle RE Asbridge JR Bame SJ Feldman WC Siscoe GL 《Science (New York, N.Y.)》1974,183(4131):1293-1296
Preliminary results from the rearward-looking electrostatic analyzer of the plasma science experiment during the Mariner 10 encounter with Venus are described. They show that the solar-wind interaction with the planet probably involves a bow shock rather than an extended exosphere, but that this is not a thin boundary at the point where it was crossed by Mariner 10. An observed reduction in the flux of electrons with energies greater than 100 electron volts is interpreted as evidence for somne direct interaction with the exosphere. Unusual intermittent features observed downstream of the planet indicate the presence of a comet-like tail hundreds of scale lengths in length. 相似文献
947.
Ontogenetic development of the human sleep-dream cycle 总被引:1,自引:0,他引:1
948.
949.
Nitrous oxide, methane, ammonia, and a number of other trace constituents in the earth's atmosphere have infrared absorption bands in the spectral region 7 to 14 microm and contribute to the atmospheric greenhouse effect. The concentrations of these trace gases may undergo substantial changes because of man's activities. Extensive use of chemical fertilizers and combustion of fossil fuels may perturb the nitrogen cycle, leading to increases in atmospheric N(2)O, and the same perturbing processes may increase the amounts of atmospheric CH(4) and NH(3). We use a one-dimensional radiative-convective model for the atmospheric thermal structure to compute the change in the surface temperature of the earth for large assumed increases in the trace gas concentrations; doubling the N(2)O, CH(4), and NH(3) concentrations is found to cause additive increases in the surface temperature of 0.7 degrees , 0.3 degrees , and 0.1 degrees K, respectively. These systematic effects on the earth's radiation budget would have substantial climatic significance. It is therefore important that the abundances of these trace gases be accurately monitored to determine the actual trends of their concentrations. 相似文献
950.