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Ion microprobe analyses show that solar wind nitrogen associated with solar wind hydrogen implanted in the first tens of nanometers of lunar regolith grains is depleted in 15N by at least 24% relative to terrestrial atmosphere, whereas a nonsolar component associated with deuterium-rich hydrogen, detected in silicon-bearing coatings at the surface of some ilmenite grains, is enriched in 15N. Systematic enrichment of 15N in terrestrial planets and bulk meteorites relative to the protosolar gas cannot be explained by isotopic fractionation in nebular or planetary environments but requires the contribution of 15N-rich compounds to the total nitrogen in planetary materials. Most of these compounds are possibly of an interstellar origin and never equilibrated with the 15N-depleted protosolar nebula.  相似文献   

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介绍了储粮害虫土耳其扁谷盗的标本采集,以及土耳其扁谷盗标本的两种制作方法。  相似文献   

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Cellulosic ethanol. Biofuel researchers prepare to reap a new harvest   总被引:1,自引:0,他引:1  
Service RF 《Science (New York, N.Y.)》2007,315(5818):1488-1491
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