恒星的初始-终止质量关系     

韩占文 《中国天文和天体物理学报》1997,(4)

本文研究了星族ＩＲＧＢ／ＡＧＢ星外壳结合能为零时的核质量与其初始质量的关系，发现此关系与Ｗｅｉｄｅｍａｎｎ和Ｋｏｅｓｔｅｒ观测得到的初始终止质量关系相符，并与Ｚｈａｎｇ和Ｋｗｏｋ得到的行星状星云核质量分布的观测结果相符合．采用相同的假设，本文还得到了星族ＩＩ恒星的初始终止质量关系．对于相同的初始质量，星族Ｉ恒星的终止质量比星族Ｉ的大～１０％－２０％．  相似文献   

Time-dependent greenhouse warming computations with a coupled ocean-atmosphere model     

Ulrich Cubasch  Klaus Hasselmann  Heinke Höck  Ernst Maier-Reimer  Uwe Mikolajewicz  Benjamin D Santer  Robert Sausen 《Climate Dynamics》1993,9(3):165-165

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The geochemistry of gem opals as evidence of their origin     

Eloïse Gaillou  Aurlien Delaunay  Benjamin Rondeau  Martine Bouhnik-le-Coz  Emmanuel Fritsch  Guy Cornen  Christophe Monnier 《Ore Geology Reviews》2008,34(1-2):113

Seventy-seven gem opals from ten countries were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) through a dilution process, in order to establish the nature of the impurities. The results are correlated to the mode of formation and physical properties and are instrumental in establishing the geographical origin of a gem opal. The geochemistry of an opal is shown to be dependant mostly on the host rock, at least for examples from Mexico and Brazil, even if modified by weathering processes. In order of decreasing concentration, the main impurities present are Al, Ca, Fe, K, Na, and Mg (more than 500 ppm). Other noticeable elements in lesser amounts are Ba, followed by Zr, Sr, Rb, U, and Pb. For the first time, geochemistry helps to discriminate some varieties of opals. The Ba content, as well as the chondrite-normalized REE pattern, are the keys to separating sedimentary opals (Ba > 110 ppm, Eu and Ce anomalies) from volcanic opals (Ba < 110 ppm, no Eu or Ce anomaly). The Ca content, and to a lesser extent that of Mg, Al, K and Nb, helps to distinguish gem opals from different volcanic environments. The limited range of concentrations for all elements in precious (play-of-color) compared to common opals, indicates that this variety must have very specific, or more restricted, conditions of formation. We tentatively interpreted the presence of impurities in terms of crystallochemistry, even if opal is a poorly crystallized or amorphous material. The main replacement is the substitution of Si⁴⁺ by Al³⁺ and Fe³⁺. The induced charge imbalance is compensated chiefly by Ca²⁺, Mg²⁺, Mn²⁺, Ba²⁺, K⁺, and Na⁺. In terms of origin of color, greater concentrations of iron induce darker colors (from yellow to “chocolate brown”). This element inhibits luminescence for concentrations above 1000 ppm, whereas already a low content in U (≤ 1 ppm) induces a green luminescence.  相似文献   

土壤中氟的形态分析   总被引：11，自引：3，他引：8  

桂建业  韩占涛  张向阳  刘福亮 《岩矿测试》2008,27(4):284-286

以宁夏盐池地区高氟土壤为例,采用连续提取法对土壤样品中各形态氟进行提取,离子色谱法测定各形态氟的含量。根据研究目的及土壤特点将氟的形态划分为水溶态、离子交换态、可还原态、可氧化态及残渣态5种形态;对各种形态连续提取过程中使用的提取液进行了选择。采用建立的方法获得提取土壤中F-的检出限为0.76μg/g;方法精密度(RSD,n=7)各形态氟为水溶态氟11.3%,离子交换态氟13.5%,可还原态氟10.7%,可氧化态氟8.9%。  相似文献   

Shear strength characterization of municipal solid waste at the Suzhou landfill, China   总被引：5，自引：0，他引：5  

Tony L.T. Zhan  Y.M. Chen  W.A. Ling 《Engineering Geology》2008,97(3-4):97-111

The current practice of slope stability analysis for a municipal solid waste (MSW) landfill usually overlooks the dependence of waste properties on the fill age or embedment depth. Changes in shear strength of MSW as a function of fill age were investigated by performing field and laboratory studies on the Suzhou landfill in China. The field study included sampling from five boreholes advanced to the bottom of the landfill, cone penetration tests and monitoring of pore fluid pressures. Twenty-six borehole samples representative of different fill ages (0 to 13 years) were used to perform drained triaxial compression tests. The field and laboratory study showed that the waste body in the landfill can be sub-divided into several strata corresponding to different ranges of fill age. Each of the waste strata has individual composition and shear strength characteristics. The triaxial test results showed that the MSW samples exhibited a strain-hardening and contractive behavior. As the fill age of the waste increased from 1.7 years to 11 years, the cohesion mobilized at a strain level of 10% was found to decrease from 23.3 kPa to 0 kPa, and the mobilized friction angle at the same strain level increasing from 9.9° to 26°. For a confinement stress level greater than 50 kPa, the shear strength of the recently-placed MSW seemed to be lower than that of the older MSW. This behavior was consistent with the cone penetration test results. The field measurement of pore pressures revealed a perched leachate mound above an intermediate cover of soils and a substantial leachate mound near the bottom of the landfill. The measurements of shear strength properties and pore pressures were utilized to assess the slope stability of the Suzhou landfill.  相似文献   

Coupled redox transformations of catechol and cerium at the surface of a cerium(III) phosphate mineral     

Javiera Cervini-Silva  Benjamin Gilbert  Sirine Fakra  Stephan Friedlich  Jillian Banfield   《Geochimica et cosmochimica acta》2008,72(10):2454-2464

Highly insoluble Ce-bearing phosphate minerals form by weathering of apatite [Ca₅(PO₄)₃.(OH,F,Cl)], and are important phosphorous repositories in soils. Although these phases can be dissolved via biologically-mediated pathways, the dissolution mechanisms are poorly understood. In this paper we report spectroscopic evidence to support coupling of redox transformations of organic carbon and cerium during the reaction of rhabdophane (CePO₄·H₂O) and catechol, a ubiquitous biogenic compound, at pH 5. Results show that the oxic–anoxic conditions influence the mineral dissolution behavior. Under anoxic conditions, the release of P and Ce occurs stoichiometrically. In contrast, under oxic conditions, the mineral dissolution behavior is incongruent, with dissolving Ce³⁺ ions oxidizing to CeO₂. Reaction product analysis shows the formation of CO₂, polymeric C, and oxalate and malate. The presence of more complex forms of organic carbon was also confirmed. Near edge X-ray absorption fine structure spectroscopy measurements at Ce-M_4,5 and C-K absorption edges on reacted CePO₄·H₂O samples in the absence or presence of catechol and dissolved oxygen confirm that (1) the mineral surface converts to the oxide during this reaction, while full oxidation is limited to the near-surface region only; (2) the Ce valence remains unchanged when the reaction between CePO₄·H₂O and O₂ but in the absence of catechol. Carbon K-edge spectra acquired from rhabdophane reacted with catechol under oxic conditions show spectral features before and after reaction that are considerably different from catechol, indicating the formation of more complex organic molecules. Decreases in intensity of characteristic catechol peaks are accompanied by the appearance of new π^* resonances due to carbon in carboxyl (ca. 288.5 eV) and carbonyl (ca. 289.3 eV) groups, and the development of broad structure in the σ^* region characteristic of aliphatic carbon. Evolution of the C K-edge spectra is consistent with aromatic-ring cleavage and polymerization. These results further substantiate that the presence of catechol, O₂ (aq) causes both the oxidation of structural Ce³⁺ and the transformation of catechol to more complex organic molecules. Scanning Transmission X-Ray Microscopy measurements at the C K and Ce M_4,5 edges indicate three dominant organic species, varying in complexity and association with the inorganic phase. Untransformed catechol is loosely associated with CeO₂, whereas more complex organic molecules that exhibit lower aromaticity and stronger CO π^* resonances of carboxyl-C and carbonyl-C groups are only found in association with the grains. These results further serve as basis to postulate that, in the presence of O₂, CeO₂ can mediate the oxidative polymerization of catechol to form higher molecular weight polymers. The present work provides evidence for a pathway of biologically-induced, non-enzymatic oxidation of cerium and formation of small CeO₂ particles at room temperature. These findings may have implications for carbon cycling in natural and cerium-contaminated soils and aqueous environments.  相似文献   

Evidence for crustal degassing of CF₄ and SF₆ in Mojave Desert groundwaters     

Daniel A. Deeds  Martin K. Vollmer  Justin T. Kulongoski  Benjamin R. Miller 《Geochimica et cosmochimica acta》2008,72(4):999-1013

Dissolved tetrafluoromethane (CF₄) and sulfur hexafluoride (SF₆) concentrations were measured in groundwater samples from the Eastern Morongo Basin (EMB) and Mojave River Basin (MRB) located in the southern Mojave Desert, California. Both CF₄ and SF₆ are supersaturated with respect to equilibrium with the preindustrial atmosphere at the recharge temperatures and elevations of the Mojave Desert. These observations provide the first in situ evidence for a flux of CF₄ from the lithosphere. A gradual basin-wide enhancement in dissolved CF₄ and SF₆ concentrations with groundwater age is consistent with release of these gases during weathering of the surrounding granitic alluvium. Dissolved CF₄ and SF₆ concentrations in these groundwaters also contain a deeper crustal component associated with a lithospheric flux entering the EMB and MRB through the underlying basement. The crustal flux of CF₄, but not of SF₆, is enhanced in the vicinity of local active fault systems due to release of crustal fluids during episodic fracture events driven by local tectonic activity. When fluxes of CF₄ and SF₆ into Mojave Desert groundwaters are extrapolated to the global scale they are consistent, within large uncertainties, with the fluxes required to sustain the preindustrial atmospheric abundances of CF₄ and SF₆.  相似文献   

(GIS).Evolution of Yellow River Sub-aqueous Delta Since 1996     

LIU Zhan  BAN Li  LIU Zhan 《水文》2008,28(4)

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低风速下海面附近气温场对海气动量通量的影响     

程展  吴少华 《海洋预报》1995,12(1):1-6

实用测的海上和层平均风剖面数据和温度剖面数据，通过数据回归和迭代方法计算出了在不同大气稳定情况下的海面阻力系数。得到了与前人理论计算一致的结论：海面阻力系数随海面大气稳定度的增加而减小，另外，我们还发现：在海面风速小于１３ｍ／ｓ时，不能认为气温剖面外推到海面的值与海面水温的是一致的。这样若用海气温差作为衡量海面上方大气的稳定程度，难于得到上面给出了理结论。这一点同前人的理论计算结果是不相同的。  相似文献   

东亚温带气旋及其长期预报（二）：预报应用分析     

战淑芸  杨淑瑞 《海洋预报》1995,12(1):26-30

本文以赤道东太平洋海温作为主导因子，分析其与东亚温带气旋的关系。得出：高海温多气旋，低海温少气旋的对应关系较为明显。并进一步对不符合这种主要关系的年份从环流型。下垫面海温等作了分类鉴别分析。  相似文献