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分子折叠体是一类由非共价键稳定的、采用有序构象的寡聚物或聚合物. 我们设计并合成了三类非天然的折叠体，包括：1）由疏溶剂作用驱动的并入萘环板块的寡聚乙二醇折叠体，2）由分子内氢键驱动的寡聚酰肼折叠体，3）由分子内氢键驱动的并入锌卟啉板块的寡聚苯酰胺折叠体. 定性和定量的研究揭示，在有机溶剂中这些折叠体可以作为非天然受体分子高效络合或识别结构匹配的有机分子和离子，并且氢键驱动的折叠体可以通过络合作用实现超分子体系的手性诱导或手性放大. 相似文献
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对多年来垦东海区的调查资料分析表明,沉积体不稳定性比较突出,对海洋工程设施危害很大,主要表现在以下几个方面:(1)软弱层是沉积体不稳定的根本因素.(2)水下斜坡是垦东海区所在黄河三角洲上主要的工程不稳定区;(3)海底冲刷和海洋动力调整在海底形成的活动层对海底铺设的管线和构筑物造成危害,应引起高度重视. 相似文献
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目的:开发适合液质联用的聚合物检测方法,考察托西酸舒他西林的聚合物杂质.方法:采用ZORBAX Eclipse Plus C18色谱柱(4.6 mm×100 mm,3.5 μm),以甲酸盐缓冲液(0.01 mol/L甲酸铵溶液,甲酸调节pH至3.0)为流动相A,乙腈为流动相B,梯度洗脱,流速1mL/min;检测波长215 nm,柱温25℃,并联用质谱测试未知聚合物杂质峰的分子量.结果:在原料药杂质谱中识别出两个新聚合物杂质,分子量分别为721.2 m/z、926.3 m/z.结论:考察结果可为药品的质量控制提供参考. 相似文献
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为建立四方藤的指纹图谱,文章用高效液相色谱(HPLC)联合飞行时间质谱(TOF-MS)结合离子阱多级质谱(Ion-trap/MSn)分析研究不同产地四方藤中的化学物质。高效液相色谱配备DAD检测器及C_(18)色谱柱(250mm×4.6mm,5μm),在流动相为0.1%甲酸水-甲醇体系,流速为0.8mL/min,检测波长为254nm的条件下梯度洗脱。结果表明,不同产地的四方藤HPLC指纹图谱中有5个共有物质峰,该分析方法建立的指纹图谱可为四方藤质量标准的建立及质量评价提供实验依据。 相似文献
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生物标志化合物(或称分子化石)系指地质体中产出的特征有机化合物。由于它们具有生物体化合物的基本分子骨架,而能提供生物输入、沉积环境与成岩变化等多方面的信息,已在国内外石油勘探中发挥出重要作用。如进行原油对比、油源对比,有机质成熟度的判别、确定母质类型与生物输入源、生物降解油与重油研究,以及探讨石油的原生运移等,从而成为当代有机地球化学的重要生长点之一。 相似文献
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分析复杂地质体三维模型的构建方法,本地质体通过使用vbnet+Direct3D来建模实现.在Directx3D中,使用三种基本图元信息(点,线,和三角形面)来构建复杂的三维地质体模型.本三维地质体生成时,根据采集的离散数据,通过克里金插值算法生成地层表面,然后通过广义三棱柱法,将生成的地层表面通过三棱柱连接生成地质体模型. 相似文献
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对ZnO单晶材料不同温度下进行了光致发光研究。室温下ZnO单晶有两个发光峰,分别为375nm的紫外发光峰和570nm的可见光发光带。随着温度的降低,出现两个紫外发光峰,分别为自由激子(FX)和束缚激子(D0X)发光峰,并且束缚激子发光峰随着温度降低较自由激子变化明显。较低温度时在370nm到400nm出现多个发光峰,为声子(LO)参与的受主束缚激子(A0X)发光峰。10K时出现四个紫外发光峰,分别为自由激子(FX)、表面激子(SX)和束缚激子(D0X)发光峰。 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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《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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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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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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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
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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