Electro-oxidation of N-hydroxy imides for redox mediator in acetonitrile containing lutidine as a base

The electrochemical properties of two N-hydroxy imides, N-hydroxymaleimide and N-hydroxysuccinimide, at a glassy carbon electrode in acetonitrile were examined by cyclic voltammetry. N-hydroxysuccinimide, which contains no olefinic linkage, indicated a chemically reversible redox response, and its ability as a mediator for the oxidation of benzyl alcohol was confirmed by rotating disk electrode voltammetry.     

基于中间件的网络生物信息学数据库查询

随着网络的迅速发展,基于互联网的生物信息数据库也得到了快速的发展。浏览和查询机制的效率太低,如何采取对这些资源的充分的使用是一个大问题。文章提供一种以分布式异构数据库Mediator/Wrapper集成方式为基础提供具体查询应用解决方案,实现用户访问的集成检索与分析功能。     

多数据库集成环境下查询优化研究

在多数据库集成系统中，用户查询由中介系统转换为对各局部数据库的内部操作及局部数据库之间的数据传递。搜索一条访问相互连接数据源的路径以获得综合开销最小的查询策略，是多数据库集成环境向查询优化提出的新的挑战。文章设计了一个新的中介系统，将查询优化问题分为两个阶段，并在此基础上通过化简策略空间、有效的代价估算和策略搜索算法，以提高多数据库环境下查询优化器的工作效率。     

Electrochemical synthesis of 2,2-dinitropropanol

This paper describes electrochemical approaches to the synthesis of 2,2-dinitropropanol (DNPOH) and discusses the potential for pilot-plant scale synthesis. In this work, the anode of the electrochemical cell replaces the chemical oxidants used in the conventional synthesis for the purpose of reducing secondary waste and the consequent disposal cost. The electrosynthesis reactions described in this work use the common starting material, nitroethane (NE). The synthesis of the end-product DNPOH involves two steps: (1) electrochemical oxidative nitration (addition of a geminal NO₂ group); and, (2) condensation with formaldehyde. Electrochemical oxidation of NE was first attempted by direct oxidation on a Pt electrode surface resulting in low yield and significant generation of undesirable by-product. Alternatively, two different mediators were employed resulting in a dramatic improvement of yield for the oxidative nitration step. The two different mediators used, Ag⁺/Ag⁰ and Fe(CN)₆^−3/−4, were derived from the chemical oxidants known to perform the oxidative nitration. The Fe(CN)₆^−3/−4 mediator demonstrated the best promise for scale-up and industrial production due to the lower cost of the mediator and the solubility of the mediator lending it to greater ease-of-use in conventional electrochemical cell designs.     

Functionalized magnetic nanoparticle-reduced graphene oxide nanocomposite for enzymatic biofuel cell applications

Enzymatic biofuel cells (EBFCs) produce electrical energy from green and renewable fuels, by utilizing redox enzyme. However, the main issue of low power output and stability of the electrode still prevails in this field. Extensive research is going on to overcome this problem by improving the electrical communication between the enzyme and the current collector. In the light of this, a new electrode design based on reduced graphene oxide (rGO) and functionalized magnetic nanoparticles (f-Fe₃O₄ NPs) in polyaniline matrix has been proposed and employed for the purpose of the EBFCs application, in order to achieve efficient electron shuttling between enzyme glucose oxidase (GOx) and the electrode surface. The as-prepared rGO/PANI/f-Fe₃O₄ nanocomposite was examined by analytical techniques viz, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and the electrochemical behaviour of the rGO/PANI/f-Fe₃O₄ nanocomposite and rGO/PANI/f-Fe₃O₄/Frt/GOx bioanode was determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). The bioanode attained a maximum current density of 32.9 mA cm⁻² at the optimum glucose concentration of 50 mM.     

Voltammetric behavior of β-phosphonylated nitroxide and its application to electrocatalytic oxidation of alcohol

N-tert-Butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)]nitroxide (DEPN) as β-phosphonylated nitroxide was prepared using tert-butylamine, pivalaldehyde and phosphonic acid diethyl ether as starting materials. This nitroxide revealed a reversible redox peak in cyclic voltammetry at +0.81 V versus Ag/AgCl, and showed electrocatalysis for the oxidation of alcohol. A preparative electrocatalytic oxidation of 4-methylbenzyl alcohol on the nitroxide yielded 98% 4-methylbenzaldehyde by 10 h of electrolysis. The current efficiency, turnover number and pseudo-first-order kinetic constant of the reaction were 96.5%, 39 and 0.95×10⁻⁵ s⁻¹, respectively.     

The fabrication and characterization of an ex situ plated lead film electrode prepared with the use of a reversibly deposited mediator metal

In this paper an ex situ plated lead film electrode prepared with use of the mediator metal (Zn) was elaborated. The electrochemical method for lead film formation is based on a co-deposition of a metal of interest (Pb) with a reversibly deposited mediator metal (Zn) and then on an oxidation of zinc and further deposition of lead by the appropriate potential. This serves to increase the density of islands of lead atoms, promoting lead film growth. The lead-based sensors were characterized by optical method (atomic force microscopy (AFM)) and as well as cyclic, linear sweep and square wave voltammetry. The adsorptive system of folic acid was employed to investigate the electrochemical characteristics a novel type of lead film electrode. Well-formed stripping peaks and a linear dependence of the stripping current on the folic acid concentration were observed on the lead film electrode prepared with use of the mediator metal while comparative measurements attempted with the lead film electrode prepared without use of the mediator metal were unsuccessful.     

Toward a typology of construction mediator tactics

The use of assisted negotiation plays a pivotal role in dispute settlement. Mediation is a notable example and has gained popularity because of the cost and time advantages. In a mediation, the tactics used by the mediator can be decisive. Construction has been described as a litigious industry and despite the vast numbers of mediation conducted, research on mediator tactics remains few. This paper reports a study directed at developing a typology of tactics used in construction mediation. Mediator tactics and mediation outcomes were firstly long listed from review of literatures. Data on the usefulness of tactics used and the outcome achieved were solicited from practicing mediator. Exploratory Factor Analysis (EFA) and Cluster Analysis (CA) were then used to identify the group structures. The results obtained from these two statistical tools were compared using the approach suggested by Newby et al. [Associations of empirically derived eating patterns with plasma lipid biomarkers: a comparison of factor and CA methods. American Journal of Clinical Nutrition 2004;80:759–67]. As such, the group structure obtained from the EFA was preferred than those from the CA. This finding supports the general observation that the structure of EFA is more adaptive. The grouping is further confirmed by a structural equation modeling (SEM) and provides a convenient platform for further research in construction mediation. The potential applications of the typology include effectiveness of construction mediator, behavior and strategic choice of tactics. Furthermore, with a typology of construction mediator tactics, the application can also be extended to study the responses of disputants respective to mediator tactics. It is believed that these applications are of both academic and practical value to the development of construction mediation.     

基于XML的分布式异构地理数据集成与共享

地理信息系统的迅速发展和广泛应用积累了大量的地理数据资源，它们分别以不同的存储格式存放在不同地理位置的不同系统中，给数据综合利用和数据共享带来了很大的不便，特别是给数据在网络环境下的集成和共享构成了障碍。本针对目前GIS数据集成和共享的现状，提出了一个以XML为数据交换模型的分布式异构地理数据集成与共享的框架。