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331.
Sulphur isotope evidence for an oxic Archaean atmosphere 总被引:1,自引:0,他引:1
The presence of mass-independently fractionated sulphur isotopes (MIF-S) in many sedimentary rocks older than approximately 2.4 billion years (Gyr), and the absence of MIF-S in younger rocks, has been considered the best evidence for a dramatic change from an anoxic to oxic atmosphere around 2.4 Gyr ago. This is because the only mechanism known to produce MIF-S has been ultraviolet photolysis of volcanic sulphur dioxide gas in an oxygen-poor atmosphere. Here we report the absence of MIF-S throughout approximately 100-m sections of 2.76-Gyr-old lake sediments and 2.92-Gyr-old marine shales in the Pilbara Craton, Western Australia. We propose three possible interpretations of the MIF-S geologic record: (1) the level of atmospheric oxygen fluctuated greatly during the Archaean era; (2) the atmosphere has remained oxic since approximately 3.8 Gyr ago, and MIF-S in sedimentary rocks represents times and regions of violent volcanic eruptions that ejected large volumes of sulphur dioxide into the stratosphere; or (3) MIF-S in rocks was mostly created by non-photochemical reactions during sediment diagenesis, and thus is not linked to atmospheric chemistry. 相似文献
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Taylor TD Noguchi H Totoki Y Toyoda A Kuroki Y Dewar K Lloyd C Itoh T Takeda T Kim DW She X Barlow KF Bloom T Bruford E Chang JL Cuomo CA Eichler E FitzGerald MG Jaffe DB LaButti K Nicol R Park HS Seaman C Sougnez C Yang X Zimmer AR Zody MC Birren BW Nusbaum C Fujiyama A Hattori M Rogers J Lander ES Sakaki Y 《Nature》2006,440(7083):497-500
Chromosome 11, although average in size, is one of the most gene- and disease-rich chromosomes in the human genome. Initial gene annotation indicates an average gene density of 11.6 genes per megabase, including 1,524 protein-coding genes, some of which were identified using novel methods, and 765 pseudogenes. One-quarter of the protein-coding genes shows overlap with other genes. Of the 856 olfactory receptor genes in the human genome, more than 40% are located in 28 single- and multi-gene clusters along this chromosome. Out of the 171 disorders currently attributed to the chromosome, 86 remain for which the underlying molecular basis is not yet known, including several mendelian traits, cancer and susceptibility loci. The high-quality data presented here--nearly 134.5 million base pairs representing 99.8% coverage of the euchromatic sequence--provide scientists with a solid foundation for understanding the genetic basis of these disorders and other biological phenomena. 相似文献
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Genetic complementation after fusion of Tay-Sachs and Sandhoff cells 总被引:11,自引:0,他引:11
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I. Spence D. D. Jamieson K. M. Taylor 《Cellular and molecular life sciences : CMLS》1979,35(2):238-239
Summary A marine natural product, farnesylacetone epoxide, which is chemically related to juvenile hormone, has anticonvulsant properties at nonsedative doses in mice. 相似文献
339.
I. M. Taylor 《Cellular and molecular life sciences : CMLS》1972,28(5):560-561
Zusammenfassung Verschiedene Fraktionen von Esterasen in embryonalem Gewebe und enzymatische Reifungsprozesse während der Ontogenese werden beschrieben.
I wish to thank ProfessorG. A. G. Mitchell, Dr. S. R. Choudhury andMr. A. M. Lundy for their help and advice. 相似文献
I wish to thank ProfessorG. A. G. Mitchell, Dr. S. R. Choudhury andMr. A. M. Lundy for their help and advice. 相似文献
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