有机溶剂与水溶液引入电感耦合等离子体电子密度和电子温度轴向分布的比较

为了研究有机ICP最佳分析条件与水溶液ICP明显不同的原因,本文在不同的等离子体操作条件下测量了Hβ486.133nm Stark变宽,分别计算了有机溶剂和水溶液引入1CP轴向的n_e和Te值,并进行了比较。有机溶剂引入ICP时,在固定的功率,观测高度及载气流量下其轴向ne和Te均比用水溶液引入时低一些。有机ICP的优异分析性能只有在比水溶液ICP有较高的入射功率和较低的载气流量条件下才能展现出来。     

A Systematic Analysis of Human Activity on Landform Evolution of Loess Plateau——Taking loess plateau area in Gansu Province as an example

It is common knowledge that landform evolutionary process is controlled bytwo processes,endogenic forces processes,and exogenic forces process.Endogenicforces and exogenic forces processes history is as long as the earth's history.Comparing with landform evolutionary history,human history is a very shortinstance.But people have to undertake cultivation,animal husbandry and otherproductive activities for their living since they came to the world.This affectslandform evolutionary process.Especially,the effect of human activity on landformevolution of loess plateau is becoming more and more violent for several thou-sand years.Watersoil erosion is one of very important landform evolution pheno-menon of loess plateau.The authors have studied water-soil erosion of loess pla-teau area in Gansu province as example,analyzed the effect of human activity onwater-soil erosion.Thus the position and the effect of human activity on landformevolution of loess plateau have been shown from one point.     

Fluorometric determination of microRNA based on strand displacement amplification and rolling circle amplification

The authors describe a fluorometric assay for microRNA. It is based on two-step amplification involving (a) strand displacement replication and (b) rolling circle amplification. The strand displacement amplification system is making use of template DNA (containing a sequence that is complementary to microRNA-21) and nicking enzyme sites. After hybridization, the microRNA strand becomes extended by DNA polymerase chain reaction and then cleaved by the nicking enzyme. The DNA thus produced acts as a primer in rolling circle amplification. Then, the DNA probe SYBR Green II is added to bind to ssDNA to generate a fluorescent signal which increases with increasing concentration of microRNA. The method has a wide detection range that covers the10 f. to 0.1 nM microRNA concentration range and has a detection limit as low as 1.0 fM. The method was successfully applied to the determination of microRNA-21 in the serum of healthy and breast cancer patients.

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Graphical abstract Schematic of a fluorometric microRNA assay based on two-step amplification involving strand displacement replication and rolling circle amplification. DNA probe SYBR Green II is then bound to ssDNA to generate a fluorescent signal which increases with increasing concentration of microRNA.

     

Retention Behavior of Nucleic Acid Bases and Purine Derivatives on Titania

The retention of nucleic acid bases and purine derivatives on titania was studied using a 0.4 mM acetic acid–sodium acetate buffer (pH 6.0) and 70% aqueous methanol as mobile phases. We observed that the retention strength of tested analytes on titania was dependent on the structural differences between pyrimidine and purine skeletons and the variety and number of substituents. The retention order was purine derivatives with methyl groups, pyrimidine bases and purine derivatives with hydrophilic functional groups, which were retained most strongly on titania. We concluded that the retention of each analyte was caused by the analyte’s hydrophobicity in the case of purine derivatives with methyl groups and pyrimidine bases. In the case of purine and its derivatives with hydrophilic functional groups, it was considered that the retention was dependent on the analyte’s ability to form chelates, and the variety and number of functional groups on C6 and C2.     

离子色谱法测定米酒中NO-3和NO-2

研究了用带电导检测器的离子色谱对米酒中阴离子NO3^-、NO2^－进行分离测定的方法。NO3^-、NO2^－的线性范围分别为0．5－80mg/L和0.1-20mg/L，检出限分别为0.5mg/L和0.1mg/L。该法适用于SO4^2-、CI^-的测定。     

Expansion of potential 1/r12 of c‐spherical harmonics

The expansion coefficient C^D_|L| of Coulomb potential 1/r₁₂ of atomic system in hyper‐spherical harmonics is derived and the explicit expression is given.     

Electron Transfer Reaction between M-C_6H_6 and M~ -C_6H_6 Complexes in the Gas Phase: Density Functional Theory Study

Significant progress has been made in understanding the nature of the transition state andthe paths for electron transfer, especially the influences of environmental factors and themolecular properties on the electron transfer rate. These classical and semi-classical, aswell as quantum-mechanical theory, have been very successful in rationalizing severalstructure-reactivity relationships and in predicting novel features of reactivity. Thesemodels established some links between the electron tra…     

Methods of rapid orbit forecasting after maneuvers for geostationary satellites

A geostationary (GEO) satellite may serve as a navigation satellite, but there is a problem that maneuvers frequently occur and the forces are difficult to model. Based on the technique of determining satellite orbits by transfer, a predicted orbit with high accuracy may be achieved by the method of statistical orbit determination in case of no maneuver force. The predicted orbit will soon be invalid after the maneuver starts, and it takes a long time to get a valid orbit after the maneuver ends. In order to improve ephemeris usability, the method of rapid orbit forecasting after maneuvers is studied. First, GEO satellite movement is analyzed in case of maneuvers based on the observation from the orbit measurement system by transfer. Then when a GEO satellite is in the free status just after maneuvers, the short arc observation is used to forecast the orbit. It is assumed that the common system bias and biases of each station are constant, which can be obtained from orbit determination with long arc observations. In this way, only 6 orbit elements would be solved by the method of statistical orbit determination, and the ephemeris with high accuracy may be soon obtained. Actual orbit forecasting with short arc observation for SINOSAT-1 satellite shows that, with the tracking network available, the precision of the predicted orbit (RMS of O-C) can reach about 5 m with 15 min arc observation, and about 3 m with 30 min arc observation. Supported by the National High Technology Research and Development Program of China (Grant No. 2006AA12Z322), the National Basic Research Program of China (Grant No. 2007CB815503), and the West Light Program of Chinese Academy of Sciences (Grant No. 2007LH01)