Recent developments in synchrotron vacuum ultraviolet photoionization coupled to mass spectrometry

In recent years, increasing attention has been paid to “soft” photoionization (PI), which will potentially become a standard, universal ionization method. Tunable synchrotron vacuum ultraviolet (SVUV) light, a quasi-continuous light with good energy resolution and high photon flux, has proved an ideal source for “soft” PI in various research fields (e.g., combustion chemistry and molecular imaging).This review focuses on combinations of SVUV light with commonly used techniques (e.g., molecular-beam sampling, laser desorption, ion desorption, and thermal vaporization). These couplings have successful applications in flame chemistry, organic analysis, chemical imaging and aerosol mass spectrometry.     

聚合物负载的钯-咪唑催化烯烃加氢

A polymer-supported palladium-imidazole catalyst was used to catalyze the hydrogenation of various olefins under mild conditions. The rate of hydrogenation was studied. The effects of factors such as substrate concentration,catalyst concentration,partial pressure of hydrogen and temperature on initial rate of reaction of selected olefins were investigated. A mechanism for the reaction was proposed from the rate equation. The effects of the solvent and structure of the olefin on the rate of hydrogenation were investigated. The catalyst showed good reusability without any leaching of metal from the support. The homologous analog of the polymer-supported catalyst could not be used as catalyst for the hydrogenation of olefins in methanol because there was precipitation of the metal during reaction.     

Photoconductivity of C60‐doping benzocarbazole‐substituted polysiloxanes on an operating wavelength of 633 nm

A novel polysiloxane having benzo[a]carbazole, benzo[a,i]carbazole, and benzo[a,g]carbazole pendant groups has been synthesized and characterized. We studied the electric‐field‐induced xerographic properties, the photogeneration efficiency, and the photoconductivity of C₆₀‐doping polymeric composites at a wavelength of 633 nm. C₆₀‐doping with benzo[a,g]carbazole‐substituted polysiloxane shows a photogeneration efficiency of 56.55 × 10^?5 and a photoconductivity of 52.2 pS/cm at E = 100 V/µm, which was found to be higher than that of the other benzocarbazole‐substituted polysiloxane composites. Copyright © 2009 John Wiley & Sons, Ltd.     

Hydrophobic polyphenylalanine-grafted hyperbranched polyethylenimine and its in vitro gene transfection

A series of amphiphilic multi‐armed PPn copolymers were prepared by ROP of Phe‐NCA with PEI‐25k as a macroinitiator. The particle size of the PPn/DNA complexes was about 100 nm and the zeta potentials were below 20 mV. An MTT assay demonstrated that all the PPn copolymers had lower cytotoxicity compared to PEI‐25k. In vitro gene transfection studies were also conducted in HeLa, 293 and CT 26 cells. The optimal quantity of hydrophobic phenylalanine segments in PP80 led to higher transfection efficiency in various cell lines based on this study. The results indicate that PP80 was the best candidate for gene delivery among these PPn copolymers.

     

Stochastic partial differential equations with unbounded and degenerate coefficients

In this article, using DiPerna-Lions theory (DiPerna and Lions, 1989) [1], we investigate linear second order stochastic partial differential equations with unbounded and degenerate non-smooth coefficients, and obtain several conditions for existence and uniqueness. Moreover, we also prove the L¹-integrability and a general maximal principle for generalized solutions of SPDEs. As applications, we study nonlinear filtering problem and also obtain the existence and uniqueness of generalized solutions for a degenerate nonlinear SPDE.     

Ostrowski type methods for solving systems of nonlinear equations

Four generalized algorithms builded up from Ostrowski’s method for solving systems of nonlinear equations are written and analyzed. A development of an inverse first-order divided difference operator for functions of several variables is presented, as well as a direct computation of the local order of convergence for these variants of Ostrowski’s method. Furthermore, a sequence that approximates the order of convergence is generated for the examples and it confirms in a numerical way that the order of the methods is well deduced.     

Pseudo-likelihood methodology for partitioned large and complex samples

Large data sets, either coming from a large number of independent replications, or because of hierarchies in the data with large numbers of within-unit replication, may pose challenges to the data analyst up to the point of making conventional inferential methods, such as maximum likelihood, prohibitive. Based on general pseudo-likelihood concepts, we propose a method to partition such a set of data, analyze each partition member, and properly combine the inferences into a single one. It is shown that the method is fully efficient for independent partitions, while with dependent sub-samples efficiency is sometimes but not always equal to one. It is argued that, for important realistic settings, efficiency is often very high. Illustrative examples enhance insight in the method’s operation, while real-data analysis underscores its power for practice.     

微极流体蠕动泵经由滑移边界管道输送的Stokes流动

计及管道边界条件滑移的影响,研究微极流体蠕动泵,经由圆柱形管道输运的Stokes流动.壁面运动的控制方程为正弦波方程.使用润滑理论,得到了轴向速度、微转动向量、流函数、压力梯度、摩擦力和机械效率的解析数值解.用图形表示出构成参数,如像耦合参数、微极参数和表征蠕流泵特性的滑移参数、摩擦力和俘获现象的影响.数值计算表明,当耦合参数较大时,需要蠕动泵的压力更大,而微极参数和滑移参数正相反.俘获团块的大小随耦合参数和微极参数的减小而缩小,而随滑移参数的增大而缩小.     

DEA模型在资金分配和管理中的应用

资金的合理使用,是经济活动中的一个非常重要的问题.利用DEA的理论、方法模型,探讨资金的使用效率、分配的合理性,以及最佳资金预算的确定方法.涉及的DEA模型结构属于非参数的最优化DEA模型,以及DEA平行网络结构.模型中所使用的生产可能集是可以评价是否呈现"拥挤"迹象的.     

银行间债券市场的外部效率:基于商业银行的视角

以参与我国银行间债券市场的商业银行为研究对象,运用面板数据模型检验银行间债券市场的外部效率对于商业银行经营绩效的影响.实证结果表明:我国银行间债券市场的发展对于商业银行的盈利能力和流动性管理水平均有较强的外部正效率,而对于商业银行传统盈利模式和风险管理则具有负面影响.建议商业银行应利用银行间债券市场的外部正效率提高其资产负债管理水平,通过提升自身经营管理水平来降低银行间债券市场外部负效率对自身的影响;此外监管当局还应该降低小型金融机构进入银行间债券市场的门槛,以发挥该市场外部正效率对化解区域金融风险的作用.