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Advanced methods of phosphorus-31 nuclear magnetic resonance spectroscopy provided a method whereby biological phosphonates and phosphates can be determined on simple lipid fractions of biological origin. The spectra consist of two easily distinguished resonance bands; one corresponds to families of phosphonates, and the other corresponds to families of orthophosphates. 相似文献
54.
Thompson LG Mosley-Thompson E Davis ME Lin PN Henderson KA Cole-Dai J Bolzan JF Liu KB 《Science (New York, N.Y.)》1995,269(5220):46-50
Two ice cores from the col of Huascarán in the north-central Andes of Peru contain a paleoclimatic history extending well into the Wisconsinan (Würm) Glacial Stage and include evidence of the Younger Dryas cool phase. Glacial stage conditions at high elevations in the tropics appear to have been as much as 8 degrees to 12 degrees C cooler than today, the atmosphere contained about 200 times as much dust, and the Amazon Basin forest cover may have been much less extensive. Differences in both the oxygen isotope ratio zeta(18)O (8 per mil) and the deuterium excess (4.5 per mil) from the Late Glacial Stage to the Holocene are comparable with polar ice core records. These data imply that the tropical Atlantic was possibly 5 degrees to 6 degrees C cooler during the Late Glacial Stage, that the climate was warmest from 8400 to 5200 years before present, and that it cooled gradually, culminating with the Little Ice Age (200 to 500 years before present). A strong warming has dominated the last two centuries. 相似文献
55.
Burlingame AL Calvin M Han J Henderson W Reed W Simoneit BR 《Science (New York, N.Y.)》1970,167(3918):751-752
The carbon concentration in Apollo 11 lunar fine material is of the order of 200 ppm. By far the largest single amount of this carbon appears to be in carbon monoxide. Some of this seems to be in the form of gas bubbles in the glass spheres, but most of it could be in some complex form other than gas. This result would be consistent with the idea that most of the fines passed through a high temperature and that the carbon was oxidized by mineral oxides at that time. 相似文献
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Brain weight increases resulting from environmental enrichment: a directional dominance in mice 总被引:2,自引:0,他引:2
N D Henderson 《Science (New York, N.Y.)》1970,169(947):776-778
A genetic analysis of brain weights of 544 mice reared in either enriched or standard laboratory environments indicated significant directional dominance in the percentage of increase in brain weight as a result of enrichment. 相似文献
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Since 1962 the crown-of-thorns starfish, Acanthaster planci, has caused the devastation of living coral in large tracts of the Great Barrier Reef, Australia. Some authorities view this as a modern phenomenon, resulting from ecological disturbance caused by man. Evidence from skeletal remains in sediment suggests that large A. planci populations have been part of the Great Barrier Reef ecosystem for at least 8000 years. Coral predation by A. planci is likely to have influenced the morphological fabric of the Great Barrier Reef in its post-glacial development and may also have influenced species richness of the reef biota. 相似文献
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A simple method was developed for measuring extensive intact leaves of monocots on a minute-by-minute basis. Growth was markedly reduced by a slight reduction in leaf water potential. When plants mildly deficient in water were irrigated, growth resumed virtually instantly. The transitional rapid growth aftr watering suggests that water deficit increased cell extensibility. 相似文献