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991.
992.
W.F. Ruddiman G.A. Jones T.-H. Peng L.K. Glover B.P. Glass P.J. Liebertz 《Sedimentary Geology》1980,25(4):257-276
Bioturbation is generally not a strongly size-dependent or shape-dependent process in deep-sea sediments. Different sizes of ash (11–250 μm) deposited during a single eruption are usually mixed about equally, although in a few cores we found minor tendencies toward greater mixing of finer ash. Platey volcanic ash and spherical microtektites initially deposited within a few centimeters of each other in the sediment column are mixed with roughly comparable intensity. Radiocarbon dating of three sizes of CaCO3 near the top of one box core produced ages within the analytical error; this also suggests no size dependency in the mixing process. Another core showed age differences opposite in sense to those that would be predicted if the finer fractions were more intensely mixed than the coarser fractions.The sizes examined (11–250 μm) encompass most of the sedimentary components used in paleoclimatic analyses of deep-sea cores. From these findings, we infer that significant artificial lead/lag offsets in paleoclimatic signals will not be created by size-selective or shape-selective mixing. Mixing models calibrated on one sediment size fraction should be generally applicable to other sizes and kinds of material. 相似文献
993.
994.
Thorium-230 dating on saline of the Lower Salt unit in pluvial Searles Lake, California, shows that this unit was formed between 24,500 and 32,000 years ago. The initial apparent 14C age of the lake is estimated to be about 900 years. After correcting for nonradiogenic 230Th and for the initial 14C age, excellent agreement between 230Th and 14C ages is obtained. The reliability of 230Th dating on salt deposit opens a new way for continuation of absolute chronology below the Lower Salt in Searles Lake. 相似文献
995.
关于黄土碳酸盐与气候环境关系探讨 总被引:1,自引:0,他引:1
黄土中碳酸盐与气候环境密切相关。从碳酸盐的成因看,干冷的气候利于原生碳酸盐的保存,而温湿的气候使大量的次生碳酸盐产生。碳酸盐的存在形式与降水量多少有关,降水量大可形成结核层和钙板等,而降水量小则形成各种胶膜。胶膜中各种不同形态的方解石胶膜又可反映不同的气候条件。黄土一古土壤中形成的碳酸盐实际上在古土壤期形成的碳酸盐要高于黄土期形成的,只是由于古土壤期强烈的风化淋溶作用,大量的碳酸盐从古土壤中淀积到下伏的黄土层中。黄土中CaCO3的淀积可分为连续淀积和不连续淀积两类。依据淀积深度和降水量的关系,可建立二者定量的关系。从黄土碳酸盐的不同方面,得到其与气候环境关系较为全面的认识。 相似文献
996.
We have investigated the correlations among color, morphology and luminosity for all LRGs, cut I LRGs, cut II LRGs, and Main
galaxies that are also classified as LRGs. It is found that the morphology of LRGs is tightly correlated with luminosity.
The rest-frame u-g color of cut I LRGs and cut II LRGs is nearly independent of luminosity, but the color of Main galaxies
is correlated with luminosity. For cut I LRGs and Main galaxies, the early type proportion apparently changes with color:
at the rest-frame u-g < 1.3 it increases strongly with increasing color, while at the rest-frame u-g > 1.3 it decreases with
increasing color. We also notice that the morphology of cut II LRGs is only a weak function of color.
Published in Astrofizika, Vol. 50, No. 3, pp. 335–345 (August 2007). 相似文献
997.
A mathematical model describing the constant pumping is developed for a partially penetrating well in a heterogeneous aquifer system. The Laplace‐domain solution for the model is derived by applying the Laplace transforms with respect to time and the finite Fourier cosine transforms with respect to vertical co‐ordinates. This solution is used to produce the curves of dimensionless drawdown versus dimensionless time to investigate the influences of the patch zone and well partial penetration on the drawdown distributions. The results show that the dimensionless drawdown depends on the hydraulic properties of the patch and formation zones. The effect of a partially penetrating well on the drawdown with a negative patch zone is larger than that with a positive patch zone. For a single‐zone aquifer case, neglecting the effect of a well radius will give significant error in estimating dimensionless drawdown, especially when dimensionless distance is small. The dimensionless drawdown curves for cases with and without considering the well radius approach the Hantush equation (Advances in Hydroscience. Academic Press: New York, 1964) at large time and/or large distance away from a test well. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
998.
Benot Noyelles 《中国天文和天体物理学报》2007,7(2):317-324
We describe and analyze observations of mutual events of Galilean satellites made at the Yunnan Observatory in February 2003 from CCD imaging for the first time in China. Astrometric positions were deduced from these photometric observations by modelling the relative motion and the photometry of the involved satellites during each event. 相似文献
999.
1000.
The rate of evaporation of seawater droplets in the air-sea boundary layer can be estimated by its salinity change compared
to the sea surface salinity. A micro-chemical method based on Farlow (1954) is developed for quantitative determination of
the salinity of an individual droplet without the error due to further evaporation after sampling. A halide ion-sensitive
sampling surface is prepared by colloidally dispersing brown silver dichromate into the gelatin layer of a commercially available
film. The reaction of soluble chlorides with the silver salt leaves a clear white halo with diametera on the brown film to reveal the volume of the droplet. After the film is developed in a water vapor saturated atmosphere,
the halo grows to diameterd with the original as the embryo to indicate the quantity of chloride ion involved in the action. The ratio ofd/(a1.5) is a function of the salinity of the droplet. The method can be used to determine the salinity of seawater droplet of 10−6 to 10−10 gram. Details of the principle and preparation, and calibration of the reagent film, are presented.
Contribution No. 1708 from the Institute of Oceanology, Academia Sinica. The research was supported by the Chinese National
Natural Science Foundation.
The paper was prepared while the author was a visiting scholar at the Department of Atmospheric Sciences, AK-40, University
of Washington, Seattle, Washington 98195, USA (from May to July, 1989), and Scripps Institution of Oceanography, A-030, University
of California, La Jolla, California 92093, USA (from September, 1989 to February, 1990). 相似文献