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本文总结了进五年来,基于RoHS指令下,在测定电子电器产品中多澳联苯和多溴联苯醚含量的研究中,测定前处理技术和定量分析技术方面的研究进展. 相似文献
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以汞灯为光源研究了4-一溴联苯醚在有机溶剂中的光化学反应特性,探讨了初始浓度、紫外光源和溶剂介质对其光解速率的影响。结果表明,4-一溴联苯醚在有机溶剂中的紫外光降解均符合准一级动力学规律;300 W汞灯下,4-一溴联苯醚在不同有机溶剂中的光解速率存在明显差异,其在正己烷中的降解速率与甲醇接近,分别为1.22 min-1和1.20 min-1,而在丙酮中光解速率显著降低,仅为0.0082 min-1;光源强度越高,4-一溴联苯醚降解速率越快;因竞争吸光作用,溶液初始浓度也对4-一溴联苯醚的光解反应有影响,初始浓度增高其降解速率减慢。 相似文献
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目的：建立一种高效液相色谱法测定小儿清热化痰栓中黄芩苷的含量。方法：用十八烷基硅烷键合硅胶为填充剂;以甲醇-水-磷酸（47：53：0．2）为流动相;流速为1．0ml／min;检测波长为276nm。结果：黄芩苷与其它成分分离良好,在11．28μg／ml～101．52μg／ml浓度范围内,黄芩苷浓度与峰面积呈良好的线性关系;平均加样回收率为98．8％,RSD为0．69％;中间精密度试验不同分析人员之间的RSD为1．71％,小于3．0％;样品溶液在10小时内稳定;重复性RSD为1．22％,小于3．0％。结论：该方法简便、快速、准确,可以作为小儿清热化痰栓中黄芩苷的含量测定方法。 相似文献
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在表面活性剂存在下及硫酸介质中,70℃恒温水浴中,铜（Ⅱ）催化溴酸钾氧化亚甲基蓝褪色。据此建立了测定痕量铜的方法。铜（Ⅱ）浓度的线性范围为0-0．1mg．L^-1,最大吸收波长为660nm,摩尔吸光系数为2．2×10^4L．g^-1．cm^-1,检出限为3．82×10^-6g·L^-1。方法简单快速、选择性好,用于测定水中铜含量时,测定结果与AAS法的结果相近,所得结果的RSD值均小于3．2％,回收率在99—104％。 相似文献
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目的:建立一种高效液相色谱法测定玫芦消痤凝胶中苦参碱的含量.方法:用十八烷基硅烷键合硅胶为填充剂;以0.2％磷酸溶液-三乙胺-乙腈(96∶0.2∶4)为流动相;流速为1.0ml/min;检测波长为210nm.结果:苦参碱与其它成分分离良好,在0.1～1.0μg浓度范围内,苦参碱进样量与峰面积呈良好的线性关系;平均加样回收率为99.67％,RSD为1.40％;中间精密度试验不同分析人员之间的RSD为1.25％,小于3.0％;样品溶液在8小时内稳定;重复性RSD为1.23％,小于3.0％;苦参碱的检测限为0.5ng.结论:该方法简便、快速、准确,可以作为玫芦消痤凝胶中苦参碱的含量测定方法. 相似文献
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巢湖沉积物及水体中四溴双酚A浓度分布及时空分布特征 总被引：1，自引：0，他引：1
通过TBBPA检测方法的优选,对湖泊水体、底泥样品TBBPA及其代谢物含量进行准确测定和分析,根据研究结果揭示其在湖泊中的时空分布特征。应用建立的分析方法测定了巢湖中TBBPA的水平,在已监测的环境沉积物、水体样品中TBBPA含量分别为21.96-481.80μg/kg和0-4.77μg/L,其含量随着水华爆发而增大,主要为人为污染。由于在巢湖各位置中都能测出溴代阻燃剂TBBPA的存在,且较国外有关文献报道值高,有必要引起有关部门对巢湖溴代阻燃剂的污染高度重视与关心。 相似文献
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建立电感耦合等离子体-原子发射光谱法（ICP-AES）测定饲料中铜、铁、锌、钙、镁、磷等元素含量的方法,优化选择消解体系及仪器工作条件。结果表明样品各元素回收率为90%-105%,精密度（RSD）均小于5%。 相似文献
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A research group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol-a chemical found in the skins of red grapes in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said. 相似文献
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Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
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A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
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Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
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《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
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Active biological molecules functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery disease diagnosis therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction. 相似文献
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《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
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Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
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Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
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Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 相似文献