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1.
甲苯等为带水剂,对甲苯磺酸为催化剂,对苯二酚为阻聚剂,丙烯酸与十八醇进行酯化反应,用阿贝折射仪测定丙烯酸和水混合液中的水量,非线性最小二乘法计算得到在１２２±１℃下酯化反应动力学方程式为：ｄｘ／ｄｔ＝ ０．０４５８（ Ｃ Ａ０ － ｘ）（ Ｃ Ｂ０ － ｘ）（ｘ 为反应生成的丙烯酸十八酯浓度, Ｃ Ａ０、 Ｃ Ｂ０ 分别为反应物丙烯酸和十八醇的初始浓度）, 讨论了催化剂用量、温度等对丙烯酸与十八醇酯化反应的影响,并测定了本实验条件下的活化能（１５８．５ ｋ Ｊ／ｍ ｏｌ）⒚该反应体系的反应动力学方程为：ｒ＝ ｄｘ／ｄｔ＝ ［３．１２３ Ｅ１０１９×ｅｘｐ（－ １９０６０／ Ｔ）］×（ Ｃ Ａ Ｏ－ ｘ）（ Ｃ Ｂ Ｏ－ ｘ 相似文献
2.
乳清酸的单扫示波极谱研究 总被引：1，自引：0，他引：1
乳清酸在０．１ｍｏｌ／ＬＨＣｌＯ４＋０．０２ｍｏｌ／ＬＮａＣｌＯ４底液中，于ＪＰ－２型示波极谱仪上，有一良好的二阶导数峰Ｅｐ＝－０．８６０±０．０１Ｖ（ＳＣＥ），浓度在１×１０－７～６×１０－５ｍｏｌ／Ｌ范围内，与峰高成线性关系，检测限为７．５×１０－８ｍｏｌ／Ｌ．实验证明，电极过程为具有催化性质的双电子可逆过程． 相似文献
3.
人IFNγ／TNFβ杂交蛋白的初步纯化及其抗癌效应研究 总被引：1，自引：0，他引：1
采用国产的微孔玻璃珠吸附层析法分离纯化人干扰素γ／肿瘤坏死因子β重组杂交蛋白，它具有抗病毒和抗肿瘤的双重功能活性，其抗病毒活性为１．７×１０￣６ｕ／ｍｇ蛋白，细胞毒活性为１．４×１０￣６ｕ／ｍｇ蛋白。该杂交蛋白在体外对人宫颈癌细胞株（ＭＥ１８０），人胃癌细胞株（７９０１）和人肺癌细胞株（Ｇ６）均有明显的杀伤作用，并都显著地高于单一的ＩＦＮγ或ＴＮＦβ对这些肿瘤细胞的杀伤。本文还对γＴＮＦβ的抑瘤机理进行了初步探讨。 相似文献
4.
高效液相色谱法测定饲料中色氨酸含量 总被引：3，自引：0，他引：3
样品用淀粉－氢氧化钡溶液１１０℃封管水解２４ｈ水解物用４ｍｏｌ／ＬＨＣｌ溶液调节ｐＨ至５～６以含１５％甲醇的０．０２ｍｏｌ／ＬＮａＡｃ缓冲溶液（ｐＨ＝４．５）为流动相,经高效液相色谱Ｃ１８柱分离,ＵＶ２８０ｎｍ检测,测定了饲料样品中色氨酸含量,方法简便,重现性好,回收率在９７．７％～１０４．１％之间。 相似文献
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报道了Ｉｏｄｏｇｅｎ法碘化标记单克隆抗体（单抗）的最佳条件和对标记单抗免疫活性影响的实验结果，结果表明，当Ｉｏｄｏｇｅｎ：ＭｃＡｂ＝１：４缓冲液ｐＨ＝７．４，旋涡搅拌１０ｍｉｎ时，标记率、放化纯和峰值百分率均较高，标记单抗的免疫活性与标记前比较没有统计学差异（Ｐ＞０．０５）。￣１３１Ｉ－ＨＣＭ８３和￣１２５Ｉ－ＶＣＭＣ与阳性对照结合率为３８．２％和３０．１％，Ｐ／Ｎ为９．１和３０．１。此通用技术具有推广应用价值。 相似文献
7.
一阶导数光谱法测定杞菊地黄丸中丹皮酚含量 总被引：2，自引：0，他引：2
杞菊地黄丸为滋肾养肝药,由八种中药组成,本文采用一阶导数光谱法,不经分离对丹皮酚进行含量测定,实验证明,用△Ａ＝Ａ２６７－Ａ２６３测定其含量较准确,在３．０１８～８．０４８ｍｇ／ｍｌ浓度范围内呈良好线性关系,回归方程Ａ＝０．００３７２４＋０．０１４０６Ｃ、ｒ＝０．９９９６,回收率为１０１．９５％（ＲＳＤ＝１．７４％ｎ＝５）。 相似文献
8.
运用连续增长速度消除因素分析中的“共变”影响汪道明（安徽大学经济学院２３００３９）在宏观经济研究中，常需计算经济增长速度，一般采纳的公式是：（１）增长速度（以Ｒ表示）Ｒ＝（ｙｔ－ｙ０）／ｙ０＝ｙｔ／ｙ０－１＝△ｙ／ｙ０（２）平均增长速度（仍以Ｒ表示）... 相似文献
9.
以低温冲击试验、金相和扫描电镜研究了３０Ｍｎ２０Ａ１３低温钢及其用配套的Ｆｅ－Ｍｎ－Ａｌ焊丝由手工钨极氩弧焊焊接该钢的焊缝全属的低温韧性、组织结构和断裂方式．实验结果表明，３０Ｍｎ２０Ａ１３低温钢的低温韧性优于两相区处理（１０７３Ｋ１ｈ·ＷＱ＋９４３Ｋ１ｈ·ＷＱ＋８５８Ｋ１ｈ·ＡＣ）的９％Ｎｉ钢和固溶处理的奥氏体不锈钢１Ｃｒ１８Ｎｉ９Ｔｉ；焊缝金属７７Ｋ的冲击韧性相当于两相区处理的９％Ｎｉ钢，且高于１Ｃｒ１８Ｎｉ９Ｔｉ．焊缝金属为单相奥氏体组织，它与母材在７７Ｋ呈现塑性韧窝断裂。３０Ｍｎ２０Ａ１３低温钢可作为低温结构材料用于７７Ｋ以上温区，配套的Ｆｅ－Ｍｎ－Ａｌ焊丝适合于３０Ｍｎ２０Ａ１３低温钢结构件的焊接。 相似文献
10.
本文使用相转移催化剂（ＴＢＡＢ）合成了空间位阻大、碳链长的６个含特丁基的三羟甲基烷烃ｔ－Ｂｕ（ＣＨ２）ｎＣ（ＣＨ２ＯＨ）３（ｎ＝０、１、２、３、４、６），测定了这些化合物的熔点，进行了元素分析、质谱、红外光谱鉴定。 相似文献
11.
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
12.
《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
13.
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
14.
《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
15.
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
16.
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
17.
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
18.
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
19.
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
20.
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