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建立顶空气相色谱内标法快速测定面包、糕点中丙酸钙的定量方法.方法:样品在顶空进样瓶酸化后,丙酸盐转化为丙酸,用自动进样顶空气相色谱/FID检测,用乙酸为内标物定量.测定丙酸钙方法最低检出限为0.5mg/kg,其在2～1000mg/kg范围内呈线性关系,相关系数均大于0.9996,RSD均小于5%,回收率为81.2%～87.8%之间.结论:本法灵敏度高,操作简单,稳定性和重复性好,可同时连续检测大量样品,能满足快速检测面包、糕点中丙酸钙的需要. 相似文献
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采用微波消解样品处理技术和原子荧光光谱法,测定了水果样品中铅和汞的含量。确定了微波消解样品的条件,优化了仪器的最佳工作参。铅和汞的回收率分别为98.3%和85.7%。铅和汞的检出限分别为0.005mg/kg和0.00015 mg/kg。试验表明,该方法用于实际样品测定,与石墨炉原子吸收法对比,结果令人满意。 相似文献
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本文采用了微波消解后紫外分光光度法测定城市污泥中总磷。系统地研究了微波消解污泥的方法,实验基于将成分复杂的污泥样品经硝酸、过氧化氢、高氯酸微波消解,溶解出污泥样品中总磷,使其全部以正磷酸盐形式存在于分析液中。将其经GB/T 11893方法测定。总磷检出限为2mg/kg(0.01 mg/L),加标回收率在90.0～96.0%。本方法简便、准确、可靠。 相似文献
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建立了凝胶渗透色谱(GPC)净化,气相色谱-质谱联用法(GC-MS)检测口鱼片中残留的禾草丹、呋喃硫威、扑草净三种农药残留.样品以乙腈为萃取溶剂,经凝胶渗透色谱(GPC)净化预处理,N-丙基乙二胺(psA)填料再净化,由气相色谱-质谱分时段选择离子监测技术进行测定与确证,外标法定量.3种农药在0.05～10mg/L范围内线性均良好;方法的灵敏度高,定量限(LOQ)均低于或等于0.01mg/kg;方法的准确度和精密度高,在0.01、0.005、01、05mg/kg4个添加水平下三种农药的回收率均在80%～100%之间,RSD≤8.4%.方法的最低检测限和添加回收率均符合农药残留分析的要求. 相似文献
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市场中现有的软泥产品大多在生产过程中加入硼元素,若硼砂含量大于标准值,会影响儿童身体健康,因此设计应用电感耦合等离子体发射光谱法测定软泥产品硼砂含量的方法。准备实验仪器及试剂,设定实验仪器工作参数。预处理软泥样品,分别测试萃取时间与仪器功率对萃取效率的影响,优化雾化气流量及压力参数。分别测定10种软泥样品中硼测定范围及标准偏差,因其标准偏差均不超过5%,则该实验中的测试结果可用。10种软泥样品中的硼砂含量分别为832、925、4261、944、1007、748、845、345、536、1735 mg/kg,参考欧盟标准硼元素限量值为300 mg/kg,这10种软泥产品均达不到标准,存在较大风险。 相似文献
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<正>我厂23万t/a气体分馏装置是以液态烃原料,经过碱洗、气分、精制等工艺,脱去硫、水、C2、C4、丙烷,最后生产出高纯度的精丙烯产品。在整个生产过程中,丙烯塔的 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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《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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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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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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Prof. SUN Changpu from the CAS Institute of Theoretical Physics coworkers from University of Basel in Switzerland have worked out a way - at least in theory - to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams is similar to the famous Stern-Gerlach effect whereby a beam of atoms passing through a magnetic field is split in two according to the atoms' spin states 《中国科学院院刊(英文版)》2008,22(1):23-23
Prof. SUN Changpu from the CAS Institute of Theoretical Physics and coworkers from University of Basel in Switzerland have worked out a way --at least in theory --to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams and is similar to the famous Stern-Gerlach effect, whereby a beam of atoms passing through a magnetic field is split in two according to the atoms＇ spin states （Phys. Rev. Lett. 99 130403）. 相似文献
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Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
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Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献