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氧化物催化剂表面过剩氧与氧化活性 总被引：1，自引：0，他引：1
本文采用肼法测定了金属氧化物催化剂表面过剩氧的浓度，并考察了吡啶的氧化活性。催化剂的氧化活性与表面氧浓度成正比。氧化活性和表面氧浓度的顺序为：Ｃｕ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｍｎ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｃｒ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｆｅ－Ｏ／Ａｌ＿２Ｏ＿３≥Ｃｏ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｎｉ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｃｅ－Ｏ／Ａｌ＿２Ｏ＿３．随着催化剂焙烧温度的提高，催化剂表面氧浓度和氧化活性均下降。Ｃｕ－Ｏ／ＳｉＯ＿２催化剂中添加ＣｅＯ＿２后，催化剂表面氧浓度和氧化活性均有明显提高，同时催化剂的热稳定性也明显增加。 相似文献
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固体超强酸催化缩醛、酮化反应 总被引：21，自引：0，他引：21
研究了固体超强酸ＳＯ／ＴｉＯ＿２￣－ＳｎＯ＿２催化碳基化合物与乙二醇的缩醛、酮化反应，考察了催化剂活化温度、反应物摩尔比及反应时间等对缩醛、酮产率的影响。 相似文献
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茶多酚抗突变和消除自由基作用的研究 总被引：6，自引：0，他引：6
采用Ｅ．ＣｏｌｉＳＯＳ显色法，小鼠骨髓细胞微核及染色体畸变试验和体外自由基消除实验等方法测定了茶多酚复合物（ＴＰ）的抗突变和消除自由基作用．结果表明：（１）ＴＰ的终浓度在２．５和５ｍｇ／ｍｌ时，对由阳性致突变物ＭＮＮＧ，ＥＭＳ和ＮａＮ＿３诱导的ＳＯＳ应答反应均具有明显的抑制作用；（２）小鼠每日ｉｇ４０、８０和１２０ｍｇ／ｋｇ剂量的ＴＰ能明显抑制由环磷酰胺（ＣＰ）诱发的骨髓ＰＣＥ的ＭＮＣＦ，三种剂量ＴＰ的抑制率分别为４０．９８％、６６．７６％和６５．９４％；（３）ＴＰ对ＭＭＣ诱发的骨髓细胞染色体畸变（ＣＡ）的抑制率分别为６２．５６％、５５．７１％和４７．９５％；（４）在Ｘ／ＸＯ－ＥＳＲ、Ｘ／ＸＯ／Ｌｕｍｉｎｏｌ－ＢＣＬ和ＩＲ／ＮＢＴ－ＳＰＭ三种模型中ＴＰ对超氧阴离子Ｏ＿２自由基均具有极强的消除作用，消除率分别为９８±６％、９８±１．２％和９５±１．５％，对Ｏ＿２的消除效率明显强于维生素Ｃ和Ｅ，对不同工艺制备的ＴＰ消除活性氧自由基作用的测定结果显示：脱咖啡碱程度高，ＥＧＣ和Ｌ－ＥＧＣＧ含量比例高的ＴＰ－３制剂消除Ｏ＿２的效率最高．因此，ＴＰ消除有害自由基，中断或终止自由基的氧化反应是抗突变，抗肿瘤作用的主要机制 相似文献
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研制并考察了Ｐｔ、Ｐｄ及其双组份蜂窝燃烧催化剂的催化性能，并运用ＸＲＤ和ＴＰＤ－ＭＳ等实验技术研究了催化剂的耐热性和催化氧化性能与其物相结构和表面氧性能之间的联系，实验结果表明，由于Ｐｔ、Ｐｄ的共助作用，有利于催化剂上活性氧的脱出和恢复，致使Ｐｔ、Ｐｄ双组份催化剂对ＣＯ和有机物有较高的催化氧化活性，反应温度在１１０～３００℃下，转化率可达９８％以上。此外，该催化剂有良好的耐热稳定性，可耐受１０００℃以下的高温冲击。高温活性下降的主要原因是载体γ－Ａｌ＿２Ｏ＿３完全转变成α－Ａｌ＿２Ｏ＿３的结果。初步考察了该催化剂在烘漆废气治理方面的应用，有良好的使用效果。 相似文献
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超微LaMO3（M=Fe,Cr,Mn,Co）的导电性与粒度的关系 总被引：1，自引：0，他引：1
用Ｓｏｌ－Ｇｅｌ法合成了ＬａＭＯ＿３（Ｍ＝Ｆｅ，Ｃｒ，Ｍｎ，Ｃｏ）超微粉末．Ｘ射线衍射分析表明，不同焙烧温度下所合成的化合物均为单相．ＳＥＭ分析表明，粒子呈球形，室温电阻率测量表明，电阻率随粒度的变化呈两种类型：ＬａＦｅＯ＿３，ＬａＣｒＯ＿３随粒度的增大，电阻率增加；而ＬａＭｎＯ＿３，ＬａＣｏＯ＿３随粒度的增大，电阻率减小． 相似文献
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大气中污染物的浓度与气象条件的关系极为密切,取决于大气扩散稀释能力。而大气扩散稀释大气污染物的能力则取决于大气的活动情况,即取决于大气的稳定性。大气的稳定性越差,则活动能力越强,扩散稀释大气污染物的能力也就越强。任何能够影响大气稳定性的因素都会影响大气对污染物扩散稀释的能力。 相似文献
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鸭梨果实采后生理及其气调贮藏气体组分研究 总被引：5，自引：0，他引：5
鸭梨果实采后在２０±１℃时，随着其后熟进程，ＡＣＣ含量和乙烯释放量急剧增加，分别于采后第１５天和第２１天达到峰值，同时伴随出现呼吸跃变．采后果实的果心组织不仅对ＣＯ＿２极为敏感，而且还对低氧敏感．两者导致组织伤害的症状相同，但集中表现的时间不同．ＣＯ＿２伤害多出现在贮藏前期，而低氧伤害则主要在贮藏中、后期出现．鸭梨果实气调贮藏的适宜气体组分为７％～１０％Ｏ＿２和０％Ｃ０＿２． 相似文献
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污染物排入大气后,能否引起严重的大气污染,一方面取决于污染源的状况,另一方面则取决于污染物在大气中的扩散稀释速率。当一定数量的污染物排入大气后,如果在近地层大气中不易扩散而聚积,就可能造成严重的污染。可见,气象条件是影响大气污染物扩散的重要因素。 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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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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《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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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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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
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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