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For years, crop science has been balkanized, with specialists in rice, corn, and soybeans, for example, working on their own commodities and attending their own meetings. But at the First International Crop Science Congress, held in July in Ames, Iowa-an 8-day event 3 years in the making-the discipline displayed a newfound hybrid vigor. More than 1000 researchers of various persuasions, including plant molecular biology, classical plant breeding, agronomy, and soil science, representing 85 countries, shared their expertise in basic and applied studies. Here are a couple of proposals for expanding world food production and another that shows the diverse roles crops can play. 相似文献
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The structure of a silicate liquid changes with temperature, and this substantially affects its thermodynamic and transport properties. Models used by geochemists, geophysicists, and glass scientists need to include such effects. In situ, high-temperature nuclear magnetic resonance (NMR) spectroscopy on (23)Na, (27)A1, and (29)Si was used to help determine the time-averaged structure of a series of alkali aluminosilicate liquids at temperatures to 1320 degrees C. Isotropic chemical shifts for (29)Si increase (to higher frequencies) with increasing temperature, probably in response to intermediate-range structural changes such as the expansion of bonds between nonbridging oxygens and alkali cations. In contrast, isotropic chemical shifts for (27)Al decrease with increasing temperature, indicating that more significant short-range structural changes take place for aluminum, such as an increase in mean coordination number. The spectrum of a sodium aluminosilicate glass clearly indicates that at least a few percent of six-coordinated aluminum was present in the liquid at high temperature. 相似文献
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Flam F 《Science (New York, N.Y.)》1992,257(5077):1726-1727