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Microcoleus vaginatus isolated from a desert algal crust of Shapotou was cultured in BG-11 medium containing 0.2 mol l−1 NaCl or 0.2 mol l−1 NaCl plus 100 mg l−1 sucrose, extracellular polymeric substances (EPS) or hot water-soluble polysaccharides (HWP), respectively. Photosynthetic oxygen evolution rates, photosystem II activity (Fv/Fm) and dark respiration of NaCl-stressed cells were enhanced significantly by the added sucrose or EPS under salt stress conditions (0.2 mol l−1 NaCl). Compared with cells treated with salt alone, sodium contents in cells reduced significantly; the content of cellular total carbohydrate did not change, and intracellular sucrose, water-soluble sugar increased significantly following the addition of exogenous carbohydrates. Sucrose synthase (SS) activity of NaCl-stressed cells increased following the addition of sucrose, and sucrose phosphate synthase (SPS) activity of NaCl-stressed cells increased following the addition of exogenous sucrose, EPS or HWP compared with cells stressed with NaCl only. The results suggested that the extruded EPS might be re-absorbed by cells of M. vaginatus as carbon source, they could increase salt tolerance of M. vaginatus through the changes of carbohydrate metabolism and the selective uptake of sodium ions. 相似文献
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新山金矿属构造剪切带控制的典型金矿床,产于中元古界昆阳群美党组(Pt2m)中部变质石英砂板岩中。规模大、品位富、易采易选。矿区构造——含金剪切带与土壤地球化学金异常,是寻找该类金矿的重要标志。 相似文献
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Xinhui Bi Bernd R.T. Simoneit Guoying Sheng Shexia Ma Jiamo Fu 《Atmospheric Research》2008,88(3-4):256-265
Total suspended particles (TSP), collected during June 2002 to July 2003 in Guangzhou, a typical economically developed city in South China, were analyzed for the organic compound compositions using gas chromatography–mass spectrometry (GC/MS). Over 140 organic compounds were detected in the aerosols and grouped into different classes including n-alkanes, hopanoids, polycyclic aromatic hydrocarbons, alkanols, fatty acids, dicarboxylic acids excluding oxalic acid, polyols/polyacids, lignin products, phytosterols, phthalates and water-soluble sugars. The total amounts of the identified organic compounds including unresolved complex mixture (UCM) ranged from 3112 ng/m3 in spring to 5116 ng/m3 in winter, comprising on seasonal average 2.8% of TSP. Primary organic compounds peaked in winter although there are no heating systems burning fuels in Guangzhou. The highest saccharide levels occurred in fall due to agricultural activities. This study demonstrated that utilization of fossil fuels, biomass burning, soil resuspension and plastic/refuse burning are the major contributors to the identified organic compounds in the urban atmosphere of South China. 相似文献
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主要介绍新疆维吾尔自治区地震局放射性同位素碳测年实验室的１４Ｃ测年原理,样品的前处理、样品的化学制备,低水平放射性测量方法及测定年代。首次公布一批１４Ｃ年代测定数据。 相似文献
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新疆地震局＾１４Ｃ实验室为提供准确可靠＾１４Ｃ年代 数据,在选择,制备、测量本底苯,制备、测量糖碳苯,分析产品的淬灭对＾１４Ｃ年代的影响等方面进行了有效的试验与探讨。 相似文献
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Victor W. Truesdale 《Aquatic Geochemistry》2009,15(3):421-442
The dissolution of sieved sucrose crystals has been studied spectrophotometrically by observing the increase in dissolved
sucrose concentration with time. Equations recently derived from the shrinking sphere model for the batch dissolution of a
solid in under-saturated conditions tested successfully on both single crystal-size and mixtures of two sizes of sucrose crystals.
Single-sized crystals provided a straight line for the plot of the fraction of un-dissolved solid to the power one-third,
versus time ( vs. t). The dissolution of mixtures of two crystal sizes fitted the non-linear equation tested earlier on sodium chloride in water-propanone
mixtures. Together, these two sets of tests on ionic and covalent substances verify that many simple dissolutions will be
easily modelled using this physical model based on shrinkage, where the chemical composition of the solids is very much of
secondary importance. Consequently, there is an increased chance that the equations will describe the dissolution of biogenic
silica in seawater, the problem which originally inspired this study. More than this, though, the equations are discovered
to be mathematically generic; very many geometries other than the sphere satisfy the same equations, and the “shrinking object
dissolution model” is thereby defined. The approach should also apply even to non-aqueous dissolutions. A prototype plot of
shrinking object rate constant (obtained from numerical fitting of the model to sucrose) versus particle size is presented,
and it is shown how analogous treatments for other substances will be central to collection and use of much dissolution data
in the future. The study is placed in context with much earlier solid phase decomposition studies, concluding that the key
characteristic of the simplest of all dissolutions is that the interface between solid and liquid should advance at a uniform
linear rate. It is shown how this approach leads to equations of the same mathematical forms already discussed above. 相似文献
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