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Qian Y Engel MH Macko SA Carpenter S Deming JW 《Geochimica et cosmochimica acta》1993,57(14):3281-3293
Dipeptide hydrolysis and amino acid decomposition appear to follow a first-order rate law. The hydrolysis rate increases exponentially with increasing temperature in aqueous solution at both 265 atm and water steam pressures over the temperature range of 100 to 220 degrees C. Dipeptide hydrolysis has a lower apparent activation energy at 265 atm (44.1 KJ/mol) than at water steam pressure (98.9 KJ/mol). At lower temperatures (<200-220 degrees C), the rate of peptide bond hydrolysis is faster at 265 atm than at water steam pressure. At higher temperatures (>200-220 degrees C), however, peptide bond hydrolysis is slower at 265 atm than at water steam pressure. In aqueous solution, amino acid decomposition rates also increase exponentially with increasing temperature. Amino acid decomposition rates are much higher at 265 atm than at water steam pressure over the entire temperature range investigated. 相似文献
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H2 is the most abundant molecule in the universe. We demonstrate that this molecule may be an important component of interstellar and possibly intergalactic ices, both because it can be formed in situ, within the ices, and because gas phase H2 can freeze out onto dust grains in some astrophysical environments. The condensation-sublimation and infrared spectral properties of ices containing H2 are presented. We show that solid H2 in H20-rich ices can be detected by an infrared absorption band at 4137 cm-1 (2.417 micrometers). The surface binding energy of H2 to H2O ice was measured to the delta Hs/k = 555 +/- 35 K. Surface binding energies can be used to calculate the residence times of H2 on grain surfaces as a function of temperature. Some of the implications of these results are considered. 相似文献
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The condensation and vaporization behavior of ices containing SO2, H2S, and CO2: implications for Io
In an extension of previously reported work on ices containing CO, CO2, H2O, CH3OH, NH3, and H2, measurements of the physical and infrared spectral properties of ices containing molecules relevant to Jupiter's moon Io are presented. These include studies on ice systems containing SO2, H2S, and CO2. The condensation and sublimation behaviors of each ice system and surface binding energies of their components are discussed. The surface binding energies can be used to calculate the residence times of the molecules on a surface as a function of temperature and thus represent important parameters for any calculation that attempts to model the transport of these molecules on Io's surface. The derived values indicate that SO2 frosts on Io are likely to anneal rapidly, resulting in less fluffy, "glassy" ices and that H2S can be trapped in the SO2 ices of Io during night-time hours provided that SO2 deposition rates are on the order of 5 micrometers/hr or larger. 相似文献
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“大科学”时代的“小科学”具有独特的优势。在“大科学”时代,“小科学”并没有失去它存在的价值。相反,现代科学技术的发展,反而使“小科学”亦得更为重要。“小科学”也可以以一定的方式“演化”成“大科学”本文中提出了两种模式:逾渗模式和成核模式。 相似文献
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从大陆地震震源的观测研究、震源力学的理论研究和震源物理实验三个方面,评述了90年代以来中国震源物理研究的进展.这些进展包括:大陆地震的震源参数测定;利用数字地震资料进行的“现代”震源参数的反演;地震断裂力学的应用和发展;非线性物理学在震源研究中的应用;岩石破裂实验的发展;地震前兆的物理机制的实验研究等.指出了新技术的发展和现代物理科学的发展对90年代以来震源物理研究的重要影响.展望了跨世纪的我国震源物理研究的发展方向,指出震源物理研究的进展必将在大陆地震预测和减轻地震灾害方面发挥积极的作用. 相似文献
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Though the forecast and prediction of earthquakes is a commonly accepted difficult problem in science, thestep towards the exploration and knowledge of the generation and occurrence of earthquakes has never stopped. Ithas strong scientific exploration nature and great social efficacy in disaster reduction. For this reason, it has alwaysbeen the object and motivation pursued assiduously by earthquake researchers. It is beyond doubt that the study ofseismicity is still one of the important infor… 相似文献