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Veeder GJ Hanner MS Matson DL Tedesco EF Lebofsky LA Tokunaga AT 《The Astronomical journal》1989,97(4):1211-1219
We report 10 micrometers infrared photometry for 22 Aten, Apollo, and Amor asteroids. Thermal models are used to derive the corresponding radiometric albedos and diameters. Several of these asteroids appear to have surfaces of relatively high thermal inertia due to the exposure of bare rock or a coarse regolith. The Apollo asteroid 3103, 1982 BB, is recognized as class E. The Jupiter-crossing Amor asteroid 3552, 1983 SA, is confirmed as class D, but low albedos remain rare for near-Earth asteroids. 相似文献
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大平原北部的蛋白石植物岩中封存碳的１３Ｃ／１２Ｃ比值可作为重建古气候的依据。宿主植物的碳同位素组成与植物岩中有机质的碳同位素组成之产存在着明显的相关关系。沿气候梯度土壤表层分布的植物岩的１３Ｃ／１２Ｃ比值反映了当前植被中Ｃ３和Ｃ４植物的比例。土壤中植物岩的δ＾１３Ｃ值随土壤深度的变化而变化，而这种变化是由多种作用引起的；尘土对土壤表面的埋藏作用，生物扰动和可能由雨水的渗透而引起的淋滤作用。此外，尘 相似文献
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本文阐述了天线准确定位的重要性，提出了影响天线相位中心与测站标志之间准确关系的误差来源，也提出了能够减少误差，检测粗差的外业方法和设备改进意见。 相似文献
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设计州平面坐标系适用于测量员、工程师及其它人员利用国家大地参考坐标系精测成果的平面直角坐标。它很有效用，但有不完全之处：（１）ＮＧＲＳ精测成果不能支持特别数据集和计算能力。（２）人们避免使用他们不理解的州平面坐标系。（３）坐标格网距离与地面水平距离不同。这些障碍通过培训和计划可以克服，同时，用现有个人计算机资源来解决更具吸引力，通过设计完成局部（县）坐标系，可以保留所利用ＮＧＲＳ成果和现有州平面坐 相似文献
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Elevated nutrients have the potential to disrupt reproduction in scleractinian corals, with consequent impacts on population dynamics. Reproduction in broadcast spawning (Montipora capitata) and brooding (Pocillopora damicornis) species was assessed following exposure to elevated ammonium in a microcosm experiment. Planulation in P. damicornis ceased following 4 months of ammonium exposure and did not recover until 3 months after termination of nutrient enrichment. Larval settlement and survivorship were not affected by ammonium enrichment. Few significant changes were found for reproductive parameters of M. capitata. There was a significant but small decrease in egg size (430 microm in control eggs to 408 microm in eggs from ammonium enrichment treatments), but no differences in total fecundity or fertilization success. This may be related to the presence of zooxanthellae in the eggs of M. capitata, in contrast to changes in reproduction previously reported in Acropora species, whose eggs do not contain zooxanthellae. 相似文献