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Responses of microbial activities and soil physical-chemical properties to the successional process of biological soil crusts in the Gurbantunggut Desert,Xinjiang

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Journal of Arid Land 2015年第1期7卷 101-109页

作者： BingChang ZHANG XiaoBing ZHOU YuanMing ZHANG Key Laboratory of Biogeography and Bioresources in Arid Land Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences

Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0-2 cm. Varia- tions of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that micro- algal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients （organic C, total N, total P, available N, available P and available K） were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly decreased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme

关键词： chlorophyll a microbial biomass C soil enzyme physical-chemical properties biological soil crusts

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QSPR between physical-chemical properties and Molecule Parameters of Alkanes

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Wuhan University Journal of Natural Sciences 2005年第5期10卷 897-903页

作者： XU Qing-qing LI Liang-chao HU Li-ya Department of Chemistry Zhejiang Normal University Jinhua 321004 ZhejiangChina Department of Chemistry and Pharmaceutical of Zhejiang Industry University Quzhou 324006 Zhejiang China

A set of molecule parameters, namely, N, N′, p, q, n, were used to express the structures of alkanes. A correlative model was established between certain physical-chemical properties and molecular parameters of alkanes by regression method. Eight physical-chemical properties, such as evaporation heat （△vHm^20）, density（D^20 ）, capacity （C^20）, surface tension （δ^20）, boiling point （Tb）, critical temperature（Tc）, critical pressure（Pc） and critical volume（Vc）, of fifty-six C3-C16 alkanes were calculated directly from the model in this paper. The calculated values are in good accordance with the literature ones reported for alkanes, and the correlation coefficients （R） equal or exceed 0.99 . The research results indicate that the principle of the method is simple and clear, the method is practical, the correlativity is excellent, and the predicted data are credible.

关键词： alkane molecular parameters physical-chemical properties

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Development of Mould Powder for High Speed Continuous Casting of Medium Carbon Steel Slab

Development of Mould Powder for High Speed Continuous Castin...

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The4thInternationalConfe...

作者： CHEN Min~1 LI Xue-hui~(1,2) 1.School of materials and metallurgy, Northeastern University, Shenyang, Liaoning, 110004 China 2. Industry Co. Ltd,Anshan Iron and Steel Group Corporation, Anshan, Liaoning, 114000 China

Mold powder as an important supplemental material for continuous casting influences slab quality directly, and more strict requirements are necessary for the continuous casting of medium carbon steel duo to its solidification characters. The present work studied the effect of composition on properties of mould powder and developed a series of mould powder products for continuous casting of medium carbon steel. The results showed that both crystallization and breaking temperatures as well as grain size in the solidified flux film were all deceased by adding some special component such as BO, LiO, MnO. Consequently, by preventing deposit of high melting phases during cooling process, liquid flux film on the surface of solidified shell was formed to insure the greasing performance, and at the same time, the crystallized flux film was formed on the side of mould wall to maintain uniform weak heat transfer. Practical application of the developed serious mold powder products showed good performance and the slab quality was effectively improved for continuous casting of medium carbon steel.

关键词： continuous casting mould powder physical-chemical properties crystallizing behavior medium carbon steel casting

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