珠江入海口水体中多氯联苯及其归趋分析

以气质联用仪检测了珠江八大入海口水样中19种PCBa单体.结果显示:PCBs在溶解相和颗粒相中的总含量分别为0.02～2.55 ng/L和0.05～5.14 ng/L;水体PCBs的logK1∝范围为4.70 -5.18,与其log K1∝值表现为非线性相关,表明水体溶解相与颗粒相间PCBs分配的非平衡状态；第三相胶体...     

双层钙钛矿锰氧化物(La_(0.9)Eu_(0.1))_(4/3)Sr_(5/3)Mn_2O_7的磁性和磁熵变研究

本文采用传统固相反应法制备多晶样品(La_(0.9)Eu_(0.1))_(4/3)Sr_(5/3)Mn_2O_7,并对其磁性和磁卡效应进行研究.研究表明:在低温部分出现反铁磁和铁磁相互竞争,在三维铁磁有序转变温度(T_c~(3D)≈75 K)至二维铁磁转变温度(T_c~(2D)≈227 K)范围内出现铁磁顺磁共存;此外,在T_c~(3D)附近,出现了较大的磁熵变,当外加磁场为1 T时其最大磁熵变值为1.69 J/(kg K),这表明该材料可能适合在液氢温区内作为一种磁制冷材料.     

Teeming stream protection using an argon shroud during casting of steel ingots

Two kinds of argon shroud protection devices with two different basic structures were designed and investigated. Industrial experiments and numerical simulations were used to examine the protection effect, and the mechanism of air entrapment during the casting of steel ingots was analyzed. The influence of the structure of the argon shroud protection device on the protection effect was investigated. An argon shroud protection device mounted to the nozzle holder on the bottom of the ladle does not provide a good protection effect because air can easily flow into the teeming system and cause reoxidation of molten steel during teeming. By contrast, an argon shroud protection device seated on the top of the central trumpet provides an excellent protection effect, where air has little chance of flowing into the teeming system during casting. The feasibilities of the argon shroud protection devices are discussed.     

国有企业有关纪委监察的思考

随着我国社会经济和科学技术的发展,社会主义市场经济体制建立起来,企业体制改革逐渐得到深化,我国的国有企业也开始向现代企业体制转变,从而成为一个自己做主的经济主体,企业活力也得到了很大的提升。但是作为一种法制经济,在发展社会主义市场经济的同时,还应该加强国有企业纪检监察组织的监督职能。随着新形势的到来,国有企业纪检监察组织遇到了很多难以解决问题的,这会对其职能作用的发挥产生重大阻碍作用。所以,应该有效解决国有企业纪检监察组织遇到的难题,加强其监督职能,这也是现如今国有企业发展的重要问题。     

山寨软件忽悠，如何筑起“防火墙”？

忽如一夜春风来，百行千业皆山寨。“康帅博”的饮料、“啃他鸡”的快餐、“阿迪王”的皮鞋、“宝马”的电风扇、“NOKLA”手机，乃至山寨明星、山寨春晚等纷至沓来，让人眼花缭乱，就连软件业同样也出现什么“山寨播放器”、“山寨杀毒软件”、“山寨版”百度、“山寨版”QQ等，甚至山寨OA、HR、ERP都有。     

用矛盾定律分析查新委托技术资料存在的问题

目的:履行查新人的职业道德,规范查新委托人的学术行为;方法:应用矛盾定律评判问题,应用逻辑推理分析问题;结果:分析出查新委托技术资料存在问题的结症;结论:提醒科研人员在填报查新委托技术资料中要实事求是,科学严谨.     

4G的诱惑

移动高清会议、移动高清视频监控、移动高清视频点播、便携视传、高速上网……在上海世博园浦西片区的移动通信馆,理论峰值传输速率是现行3G网络十几倍的TD-LTE(TD-SCDMA演进技术)演示网,曾给参观者留下了深刻的印象。而进入2011年,3G建设方兴未艾,运营商们已开始在"后世博经济"大潮中部署4G网络的商用战略了——无线传输堪比固网,视频通话就像聊天——4G的诱惑的确令人神往,然而在手机终端、建设成本等一系列因素制约下,4G商用离我们究竟有多远?     

“十一五”期间泉州市区大气环境质量状况分析及防治对策

该文对"十一五"期间泉州市区大气环境质量监测结果进行统计分析,得出"十一五"期间泉州市区大气质量总体上保持在较好水平,以及大气中主要污染物的变化趋势。同时,根据监测结果,结合泉州市区具体情况,提出具体的大气污染防治措施。     

C++面向对象程序设计教学改革与实践简

C++是目前众多高校计算机相关专业开设的一种面向对象的程序设计课程,是一门重要的专业基础课和平台课.针对C++课程教学中存在的一些问题,从教学内容、教学手段、实验教学以及课程考核等方面开展了一系列教学改革.教学实践表明,这些措施在提高课程教学质量,提升学生知识运用能力等方面均取得了良好效果.     

Recognition of DNA damage by the Rad4 nucleotide excision repair protein

Mutations in the nucleotide excision repair (NER) pathway can cause the xeroderma pigmentosum skin cancer predisposition syndrome. NER lesions are limited to one DNA strand, but otherwise they are chemically and structurally diverse, being caused by a wide variety of genotoxic chemicals and ultraviolet radiation. The xeroderma pigmentosum C (XPC) protein has a central role in initiating global-genome NER by recognizing the lesion and recruiting downstream factors. Here we present the crystal structure of the yeast XPC orthologue Rad4 bound to DNA containing a cyclobutane pyrimidine dimer (CPD) lesion. The structure shows that Rad4 inserts a beta-hairpin through the DNA duplex, causing the two damaged base pairs to flip out of the double helix. The expelled nucleotides of the undamaged strand are recognized by Rad4, whereas the two CPD-linked nucleotides become disordered. These findings indicate that the lesions recognized by Rad4/XPC thermodynamically destabilize the Watson-Crick double helix in a manner that facilitates the flipping-out of two base pairs.