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Yin QZ Jacobsen SB McDonough WF Horn I Petaev MI Zipfel J 《The Astrophysical journal》2000,536(1):L49-L53
We report new Zr isotope evidence for live (92)Nb (mean life: tau&d1;92Nb=52 Myr) within the early solar system resulting in &parl0;92Nb&solm0;93Nb&parr0;initial approximately 10-3. The meteoritic minerals rutile and zircon have, respectively, very high and very low Nb/Zr ratios and are ideal for exploring the (92)Nb-(92)Zr chronometer. Rutiles exhibit high positive straightepsilon92Zr ( approximately 14-36) while a zircon has a negative straightepsilon92Zr ( approximately -4), as would be expected if (92)Nb was live in the early solar system. The meteoritic rutiles appear to be young, with apparent times of formation of approximately 80-220 Myr subsequent to the origin of the solar system. The initial (92)Nb/(92)Mo for the solar system is broadly compatible with a model of uniform production if the (92)Nb/(92)Mo production ratio for Type II supernova (SNII) sources with neutrino-driven winds is used. Data for all the now extinct p-process nuclides ((92)Nb, (97)Tc, and (146)Sm) are consistent with these isotopes being derived by uniform production from SNII sources and a free decay interval of approximately 10 Myr. Consideration of a range of models indicates that the average p-process production ratio of (92)Nb/(92)Mo needs to be at least in the range of 0.06-0.25. 相似文献
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GPS技术在金川露天矿边坡变形监测中的应用 总被引：6，自引：0，他引：6
本文结合金川露天矿边坡变形GPS监测研究,主要论述监测基点的选择,基点WGS-84坐标的确定,变形监测网的布设,GPS数据采集、处理和质量,坐标转换的实施等,给出反演推出的若干四等三角点及其它控制点的变形数据,这些数据和造成变形的物理成因符合得很好,最后概括出GPS技术应用于变形观测的若干优点。 相似文献
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The temporal variability of 210Po and 210Pb was examined in the overlying water of the Zhubi Coral Reef flat to detect nutrient-like behavior of 210Po. Different mechanisms influencing their geochemical behaviors were observed. Excess 210Po relative to 210Pb revealed an additional input of 210Po other than in situ production from 210Pb. The 210Po input comes from the reef flat sediment through diffusion. The diffusion contributes 62% of the total 210Po. This diffusion of 210Po directly highlights its nutrient-like behavior. No input, but the slight removal, of 210Pb was observed. Fractionation factors indicate that particulate matter prefers to adsorb 210Po rather than 210Pb. In combination with particulate composition, 210Po diffusion was closely related to organic matter. These results reveal that 210Po might be a potential tracer for quantifying nutrient recycling in the Coral Reef system. 相似文献
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