共查询到20条相似文献，搜索用时 62 毫秒
1.
通过对染色处理的黄色、黑色等养殖珍珠进行紫外-可见分光光度计、傅立叶变换红外光谱以及激光拉曼光谱测试,研究分析染色淡水养殖和染色海水养殖珍珠的光谱差异,结果表明:黄色养殖珍珠无论染色与否,以355nm为中心的紫外-可见光谱吸收宽谱带为珍珠自身有机致色因子所致,染色海水养殖珍珠和未染色淡水养殖珍珠样品在450~500nm左右都具有强吸收谱带。染色后无论淡水还是海水珍珠,703cm~(-1)、882cm~(-1)碳酸钙红外振动光谱峰降低或被掩盖,由文石引起的1086cm~(-1)拉曼光谱明显降低,染色淡水养殖珍珠具有较强的荧光背景,染色海水养殖不明显;未染色黑色海水养殖珍珠存在紫外-可见光谱690nm吸收峰有别于黑色淡水养殖染色珍珠,染色海水养殖珍珠无特征紫外可见谱峰,红外光谱难以区分染色与否。珍珠主要组成成分文石的特征拉曼峰谱在1080cm~(-1)都会出现,海水养殖珍珠染色的图谱中同时出现了1352cm~(-1)和1587cm~(-1)振动峰,而淡水养殖珍珠染色后荧光特征明显。 相似文献
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报道了C_(60)球烯的制备分离过程,并对所获得的纯C_(60)粉末样品和膜样品进行了~(13)C核磁共振,傅里叶红外以及Raman谱研究.结果表明:C_(60)样品在红外有4个吸收峰,分别位于528、578、1182、1429cm~(-1)处;在Raman谱中观察到3个峰,分别位于273、469、1465cm(-1)处;~(13)C核磁共振谱则表明在143.2 ppm化学位移处有一单峰,这些都与理论计算值相符,很好地证实了C_(60)的全碳和高度对称的球形结构. 相似文献
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牛奶中蛋白质和脂肪是影响牛奶营养品质的主要因素,常规方法分析奶粉比较费时,需要的样品量较多,而且每项指标要采用不同的方法、利用红外光谱法可以可简便、快速地分析和评价奶粉品质的优劣。利用红外光谱法对来自不同地区的牛奶进行分析。牛奶中脂肪含量高的谱图在1747cm^-1附近的C=0吸收峰和2926cm^-1附近的CH2吸收峰很强;蛋白质高的奶粉所对应的酰胺I带的C=0吸收峰在1650cm^-1附近和酰胺Ⅱ带的N—H及C—N吸收峰在1540cm^-1附近吸收强度较大;奶粉中碳水化合物所对应的C-0伸缩振动峰和环的振动峰在1150—900cm^-1范围内较显著、结果表明同一厂家不同年龄阶段奶粉的脂肪、蛋白质和碳水化合物的含量差异较大,红外光谱差异较显著。不同厂家生产的相同类型的全脂奶粉的脂肪、蛋白质和碳水化合物的含量差异较小。 相似文献
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通过溶胶凝胶法制得平均粒径10nm左右CeO2纳米晶,然后以此纳米晶在位分散聚合得到了聚苯胺/纳米CeO2复合材料,红外分析表明纳米CeO2的存在导致聚苯胺的红外光谱具有明显的蓝移现象,复合后的产品在2938cm-1处的红外吸收峰变得很弱,在拉曼光谱中1240cm-1和1352cm-1附近的特征峰,被认为是由于纳米CeO2的存在与聚苯胺之间的化学作用产生的,聚苯胺与CeO2之间有化学键的结合,它们之间的化学作用在N原子上。导电性研究表明,随着纳米CeO2含量的提高,电导率呈指数下降。 相似文献
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陈拥军 《中国科学院研究生院学报》1992,(3)
本文研究了以β二酮及酯作为配体的七种过渡金属配合物:Ti(acac)_2Cl_2、Ti(bzac)_2Cl_2、Tj(bzbz)_2Cl_2、Ti(etac)_2Cl_2、Ti(mesa)_2Cl_2、Sn(bzac)_2Cl_2及Zr(bzac)_2Cl_2的顺磁共振光谱,并将特征配合物Tj(bzac)_2Cl_2、Ti(bzbz)_2Cl_2的ESR谱值参数与其IR吸收峰及MS的特征碎片峰进行了比较。 相似文献
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对国产荚蒾属Viburnum Linn．植物花粉的光学显微镜及扫描电镜观察表明：1．花粉特征在组间的分类学意义不大，而在组内的每一种都具各自的花粉特征。2．表面纹饰类型包括(1)外壁具半覆盖层，网状纹饰，网脊光滑；(2)外壁具半覆盖层，网状纹饰，网脊上具瘤状突起；(3)外壁无覆盖层或部分成半覆盖层，具鼓锤状基柱或基柱网，基柱顶端具瘤状突起。3．沟类型包括：(1)沟沿处外壁无覆盖层；(2)沟沿处外壁具半覆盖层，网状纹饰；(3)沟沿处外壁具覆盖层；(4)在一极形成合沟。内孔类型包括(1)看不见明显的孔膜；(2)孔膜半球状，与外壁不连续；(3)孔膜半球状，与外壁相连续；(4)孔膜半椭圆球状，纵长；(5)孔膜半椭圆球状，横架于沟间而类似于桥。文中同时对若干组内分类学问题进行了探讨。 相似文献
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对天然蒙脱石矿物进行离子交换及有机化改性,获得有机蒙脱石基的快己离子导体,它的结构特点是d(001)由原15A左右显著增长至18～21A,表明其层间阳离子结合着二至三层有机分子,它们的IR谱出现了典型的有机基团振动吸收带并相对有机液态分子吸收带波数发生明显移动。有机蒙脱石基快离子导体具有良好的电性能,室温下的电导率为10~(-3)—10~(-2)Sm~(-1),导电激活能在0.2—0.3eV范围,它作为固体电解质在固态锂、镁电池中的应用是成功的。 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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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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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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《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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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)
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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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