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1.
通过超临界CO2萃取均匀设计实验和微波辅助萃取荷叶挥发油的正交实验比较,考察影响提取的主要因素,寻求最佳萃取工艺. 相似文献
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通过超临界CO2萃取均匀设计实验和微波辅助萃取荷叶挥发油的正交实验比较，考察影响提取的主要图素，寻求最佳萃取工艺。 相似文献
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本实验确定最佳工艺条件为:温度40℃,粒度40目,固定堆积密度为100克/罐,萃取压力30MPa,CO2流速10公斤/小时,时间2小时。本方法可靠、简单,可用于生产。本文对护肝片中五味子的超临界CO2萃取工进行研究。 相似文献
4.
用微波辅助萃取万寿菊残渣中的挥发油,并对挥发油抑制活性实验进行了研究,应用单因素实验研究了温度、料液比、时间对抑菌效果的影响,确定抑菌最优条件:在料液比1:6、微波炉功率为中火时,提取60s。通过对MIC的测定,得到微波萃取法提取的挥发油对酵母菌、金黄色葡萄球菌的MIC最小,对大肠杆菌的MIC最大。 相似文献
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超临界CO2萃取技术作为一种新型绿色的分离手段在中药中的应用日益广泛。本文简述了超临界CO2萃取技术的原理、流程、在中药提取分离中的应用及其优缺点,并探讨了影响中药超临界CO2萃取的因素。 相似文献
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一、引言用超临界流体作为萃取剂来分离、提纯化合物就是新近发展的超临界流体萃取技术。它不仅能在化工领域中应用,而且已为石油、食品、煤炭、医药、烟草等工业所采用。国外的研究非常活跃,国内也已起步。该技术开发的一个重点就是其基础理论的研究,包括相平衡的计算,分离效率的确定等。超临界流体萃取与其它萃取过程一样,属于平衡分离过程,因而在论证其方案,确定工艺指标和设备设计中,都需要有此过程中涉及的相平衡数据。我们针对超临界流体萃取技术用于醇——水体系分离和用超临界CO_2回收石油过程中涉及的部分相平衡关系,用状态方程法进行关联计算,作为研究超临界流体萃取技术的出发点。选用十个含超临界CO_2的二元系进行计算,考察了有关状态方程的适用性。 相似文献
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目的 针对石菖蒲挥发油的研究,通过超临界萃取得到的挥发油中主要成分为细辛醚类。该研究结合先前所制备的荧光碳量子点对细辛醚的特异性检测,建立了从石菖蒲挥发油物中细辛醚含量的定量研究方法。方法 将收集到的石菖蒲挥发油进行精制处理,采用DMF作为溶剂将挥发油按照浓度梯度配置成各种浓度的供试品备用,然后分别将不同浓度的挥发油供试品加入碳点溶液中,采用荧光分光光度计进行分析测试。将所得到的曲线导入origin中作出标曲,得到最终的标准方程检测线性范围和检测限。结果 由于细辛醚具有和碳量子点之间的电荷差异,从而聚集导致荧光猝灭,根据荧光强度变化实现细辛醚结构的分析检测。结论 通过该方式即可完成对挥发油组分的含量检测。 相似文献
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本文简要叙述了超临界萃取的原理、及其与其他萃取方法相比存在的优势,基于以上原理与优势,提出超临界萃取在中草药深加工应用方面具有深远的前景. 相似文献
10.
本文简要叙述了超临界萃取的原理、及其与其他萃取方法相比存在的优势，基于以上原理与优势，提出超临界萃取在中草药深加工应用方面具有深远的前景. 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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《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
17.
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
18.
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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Leah A. Lievrouw 《The Information Society》1998,14(2):83-96
The main premise of this article is that in information societies generally, and in virtual social contexts particularly, a distinctive style of interaction to facilitate the communication of difference, heterotopic communication , has emerged. It rests on two cultural foundations: an ideological belief in the positive, socially integrating power of communication, and a prevailing ethic of instrumental rationality, subjective individualism, and strategically practiced self-interest. The former is demonstrated by the use of simulation and spectacle as sources of information; exhibitionism/voyeurism as a communicative style; and the awareness of surveillance. The latter is seen in the competitive use of knowledge as a commodity; a surface globalism masking deep parochialism; lateral as well as vertical information inequity; and the use of public versus private as strategies for engagement rather than as spaces. Those who engage in heterotopic communication resort to their 'own devices' both in the sense of personal agendas, strategies, interests, and interpretations, and in the form of the telecommunication tools that help realize them. These personal and technological devices allow individuals with the right educational and technical resources to avoid exposure to disagreement, difference, or other information that does not serve their direct purposes or reflect their particular views of the world; yet they also help convey the appearance of openness, availability, and cooperation. This style of interaction is used strategically in combination with information and communication technologies to gain social or economic advantages, but it may encourage social separatism and parochialism, inhibit the negotiation of disputes, and emphasize competing interests. 相似文献