Multiresidue Determination of Organophosphorus Pesticides in Fruits and Vegetables by Gas Chromatography-Negative Chemical Ionization-Mass Spectrometry

建立同时分析果蔬中多种有机磷农药残留。果蔬样品经乙酸乙酯提取剂提取与flOrISIl硅藻土层析柱净化后,以乙硫磷为内标物,采用气相色谱-负化学离子化-质谱法同时的选择离子监测方式对多种有机磷农药残留进行定性与定量分析。结果表明:此方法快速、简便、灵敏度高和选择性好;9种有机磷农药残留的检测限为0.12~1.21μg/kg,平均回收率为76.5%~112%,相对标准偏差为1.45%~11.0%。A gas chromatography-negative chemical ionization-mass spectrometry(GC-NCI-MS) method was established to simultaneously determine 9 organophosphorus pesticide residues in fruits and vegetables.Samples were extracted with ethyl acetate and cleaned up on a Florisil column before GC-NCI-MS analysis in a selective ion-monitoring(SIM) mode.The internal standard used was ethion.The presented method was rapid,simple,sensitive and selective.The detection limits of this method for 9 organophosphorus pesticides were in the range of 0.12-1.21 μg/kg.The average recovery rates of 9 organophosphorus pesticides varied from 76.5% to 112% with a relative standard deviation of 1.45%-11.0%.江西省自然科学基金项目(2009GQH0018);江西省教育厅科学技术研究项目(GJJ09580

A LOCKING GRANULARITY - BASED DISTRIBUTED fflGH PRIORITY TWO PHASE LOCKING CONCURRENCY CONTROL MODEL

本文通过分析并发控制中的几种锁模型及其在分布式环境下的拓展,提出了一种基于加锁粒度的分布式高优先级两段锁模型。在该模型中,引入一种加锁检测机制,通过该机制可以确定哪些冲突事务可以通过降低加锁粒度来解决冲突。同时提出了该模型的算法。该算法在避免死锁、提高事务的并发度上有很大的改善。The present paper deals with some lock models in concurrency control and how to using them on the distributed environment, and presents a locking granularity - based distributed high priority two phase locking model. At this model, a locking checking scheme is introduced, and some conflicts can be solved by decreasing locking granularity with this scheme. At last the algorithm of this model is presented. Deadlock can be avoided and increasing transaction concurrency can be increased by this algorithm

Optimization of Join Queries of Distributed Database System

在分布式数据库系统中,查询优化是一极其重要的问题,其中联接查询的优化因其应用的广泛性而显得尤为关键.本文介绍了在分布式数据库系统中对联接查询的一般处理方法,详细论述了笔者提出的一种在分布式数据库中基于事先测试的优化联接查询技术,并进行了分析与总结.Query optimization is a key point of distributed database (DDB) system, while optimization of join queries is especially important considering it's been widely used. In this paper, we discuss common optimization method of join queries within DDB system, and then give an intensive description of join optimization based on pre-test technology we applied, we make final analyses and conclusions of this paper at last

AN INTERACTIVE CONCEPT-BASED WEB SEARCH MODEL

当前基于关键字查询的大多数搜索引擎都没有提供个性化的用户服务 ,搜索结果主要根据关键字与文档的相似度来排序 ,这很难满足用户对日益膨胀的信息资源的需求。面对用户越来越难以迅速精确地检索到所需信息的现状 ,本文提出一种应用于LAN中的基于概念的三层搜索引擎模型 :通过用户交互的方式 ,使得搜索具有个性化、智能化的特点。Most search engines nowadays based on keyword retrieval can't afford personal retrieval service.Users can't be satisfied with the results which mainly ranked by the similarity between keywords and documents in an ever-growing information world.Faced with the fact that users become more and more difficult to find needed information quickly and correctly,we present an interactive concept-based Web search model applied in a LAN environment in the paper.With the help of interactivity,information search becomes personal and intelligent.福建省自然科学基金项目资助(A0 31 0 0 0 8

Cloning and analysis of phosphoenolpyruvate carboxylase （PEPC） gene of Dunaliella salina

为研究杜氏盐藻（Dunaliella salina）磷酸烯醇式丙酮酸羧化酶（phosphoenolpyruvate carboxylase,PEPC）基因的功能, 根据莱茵衣藻（Chlamydomonas reinhardtii）、拟南芥（Arabidopsis thaliana）、花生（Arachis hypogaea）等真核生物PEPC 基因高度保守序列, 设计一对简并引物, 通过RT-PCR 的方法获得杜氏盐藻PEPC 基因部分序列, 然后采用RACE 的方法分别克隆到5′端和3′端序列, 拼接后得到全长cDNA, 其长度为3 523bp, 包含2 949 bp 的完整开放阅读框, 编码982 个氨基酸, 相对分子质量为110560.5。氨基酸序列与已知物种PEPC 序列的同源性依次为： Chlamydomonas reinhardtii 69%, Chlorellavariabilis 55%, Ostreococcus tauri 50%和Ostreococcus lucimarinus CCE9901 49%, 表明所克隆的序列确为杜氏盐藻PEPC cDNA 序列

Research of the Optimization Method for Distributed Heterogeneous Database Based on CORBA

提出了一个基于CORBA中间件的分布式多层异构数据库信息共享结构模型,在该模型中将数据库的访问集成到CORBA中间件中,并重点提出了一种对数据库的操纵以及应用服务器与数据库服务器连接的优化策略和设计方法;笔者采用Java和CORBA技术结合的方法构建分布式异构系统,以解决系统的通信及交互性、安全性、扩展性问题,从而实现了一个不依赖于表示层编程语言的透明访问机制.In the paper,a information share structure model of Distributed Mutil-tier Heterogeneous Database based on CORBA is presented. In the model,we integrate database's accessing to CORBA middle software, present a database operation and optimization strategy and design method for connecting application server with database server.The authos designed a Distributed Heterogeneous System by using Java and CORBA technic,and resolve some question about system communications,alternating property,security,expansibility.At last we implement a transparent accessing mechanism that independent of express-tier program language.福建省自然科学基金计划(A0310008);; 福建省高新技术研究开发计划重点项目(2003H043)资

Electrodeposition of Cu-Co Multilayer Thin Films

采用旋转圆盘电极、双脉冲电位法从单一的含有铜离子和钴离子的镀液中电沉积Ｃｕ－Ｃｏ纳米多层膜、并用ＴＥＭ．ＡＥＳ和Ｘ－射线衍射研究镀层的形貌和组成。结果表明：多层膜结构为纯铜和含有少量铜的铜钴合金层交替组成，铜在钴层中的含量，随镀液中的铜含量的增大和转速的提高而提高。A method has been developed to produce Cu-Co Multilayer from a single electrolyte by electredeposition. The effects of the concentration of copper ions,current density and the speed of rotation were investigated,and the Cu-Co electrodeposition films were analysed by TEM. AES and X-ray diffraction.The results indicated that the film was alternating pure copper and coppercobalt alloy layers. If the content of copper in cobalt layer is to be small,the concentration of its ions in solution must be small and the rotation speed must be low.作者联系地址：北京科技大学表面科学与腐蚀工程系Author's Address: Department of Surface Science and Corrosion Engineering,University of Science and Technology,Beijing 10008

Mechanism of Electrodeposition of Cu/Co Multilayer Thin Films

采用动电位扫描、循环伏安以及电化学交流阻抗等方法研究了铜钴纳米多层膜的电沉积机理．结果表明：在所研究的体系中，铜的沉积是扩散控制的可逆电极过程，而钴的沉积是首先形成Ｃｏ（ＯＨ）ａｄｓ的吸附中间产物，而后在电极上进一步还原为原子态．基于研究结果，提出了铜钴沉积的机制．The mechanism of electrodeposition of Cu/Co multilayer thin films has been studied by means of potentodynamic sweep, cyclic voltammetry sweep and AC impendance. The results indicated that the copper deposition is mass transfer controlled process and the cobalt deposition is related to the absorbed intermediate species such as Co(OH)ads. The cobalt ions first form Co(OH)ads, then was deoxygenated to cobalt on the electrode surface.作者联系地址：北京科技大学表面科学与腐蚀工程系Author's Address: Department of Surface Science and Corrosion Engineering University of Science and Technology, Beijing, Beijing 10008