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21.
Modern drug development requires technologies that allow rapid translation from the preclinical to the clinical stage. It is obvious that non-invasive imaging modalities such as magnetic resonance imaging (MRI) will play a central role in this regard. This article reviews the use of structural and functional MRI readouts for characterization of central nervous system (CNS) disorders and evaluation of the efficacy of potential CNS drugs. Examples comprise dementia of Alzheimer's type, cerebral ischemia, and neuroinflammation covering both clinical and preclinical aspects. In these examples MRI has been used to obtain relevant structural information on brain atrophy, on the location and extent of ischemic brain areas, and on the number and distribution of demyelinated plaques. These structural data are complemented by readouts assessing the functional consequences associated with the pathomorphological changes. In the last decade, MRI has evolved into a standard tool for the development of CNS drugs. With regard to target-specific/molecular imaging applications MRI is limited by its inherently low sensitivity; complementary imaging modalities utilizing optical and radionuclear reporter systems will thus be required.  相似文献   
22.
唐子龙 《有机化学》2006,26(8):1059-1065
综述了含硅路易斯酸R3SiX [X=I, OTf, NTf2, C(C6F5)Tf2等]和(R3SiX+MLn)的发展、合成以及它们在有机合成中的应用. 它们主要被用来催化Aldol, 烯丙基化, Diels-Alder, Ene和Friedel-Crafts等反应. 催化剂的用量一般为0.5~20 mol%, 并随着催化剂的活性不同, 反应产率从一般到良好不等. 催化剂活性顺序为R3SiNTf2>R3SiOTf, (R3SiX+MLn)>R3SiX. 也对近年出现的手性含硅路易斯酸的发展和应用进行了概述, 当手性双-(多氟甲磺酰)-亚胺基硅烷用于催化环戊二烯和丙烯酸甲酯的Diels-Alder反应时, ee值高达54%.  相似文献   
23.
报道了对JEE-4x型真空镀膜仪蒸发装置的改进以及建立蒸发材料回收装置的具体方法,并介绍了改进后该仪器在高分辨扫描电镜样品制备上的应用实例.实验证明,上述改进不但扩展了JEE—4x型真空镀膜仪的制样功能又节省了蒸发材料,集中了离子溅射法及常规高真空镀膜法的优点,完全满足SEM样品的分析要求,该方法简单易操作.  相似文献   
24.
Retrieving definitional content for ontology development   总被引:1,自引:0,他引:1  
Ontology construction requires an understanding of the meaning and usage of its encoded concepts. While definitions found in dictionaries or glossaries may be adequate for many concepts, the actual usage in expert writing could be a better source of information for many others. The goal of this paper is to describe an automated procedure for finding definitional content in expert writing. The approach uses machine learning on phrasal features to learn when sentences in a book contain definitional content, as determined by their similarity to glossary definitions provided in the same book. The end result is not a concise definition of a given concept, but for each sentence, a predicted probability that it contains information relevant to a definition. The approach is evaluated automatically for terms with explicit definitions, and manually for terms with no available definition.  相似文献   
25.
手性氨基酚配体及其衍生物在不对称催化中的应用   总被引:1,自引:0,他引:1  
综述了手性氨基酚配体及其衍生物的研究进展, 着重介绍其在不对称催化烷基化、烯基化、Michael加成、aldol反应及环丙化等反应中的应用.  相似文献   
26.
银络合物在催化核上的还原反应   总被引:2,自引:0,他引:2  
研究了尿嘧啶银络合物在胶态金属及其硫化物核上被对苯二酚还原的反应,并以Ag和Pt电极代替催化核与对苯二酚显影剂和银络合物组成原电池作为电化学模型,分别测定该络合物阴极反应和对苯二酚阳极反应的电流。结果表明,原电池的电流大小与反应速度成正比关系,从而为物理显影电极理论提供实验依据。  相似文献   
27.
MAA存在下VAc/BA核壳乳液聚合过程中的胶粒形态研究   总被引:1,自引:0,他引:1  
用TEM和电位滴定法对不同配方和工艺条件得到的胶粒形态结构和羧基分别进行了表征。结果表明:加入甲基丙烯酸有利于胶粒的稳定和形成规则的核壳胶粒。半连续加料不会形成完全反转的核壳结构,但是,核层在反应过程中由于聚合物簇的迁移会造成形变。由于胶粒中聚合物浓度高,粘度大,因而胶粒形态变化受动力学影响甚大,羧基分布主要是由动力学确定的。  相似文献   
28.
超临界流体萃取仪器的研制   总被引:1,自引:1,他引:1  
崔兆杰  张新保 《分析化学》1995,23(12):1462-1466
本文报道了以国产原配件为基础,成功地研制了分析规模的超临界流体萃取仪器、并对仪器性能进行了全面考察,仪器性能稳定,重现性良好(RSD<3.1%),定量线性关系可靠,可满足定量萃取的要求。  相似文献   
29.
The parameters for the OPLS-AA potential energy function have been extended to include some functional groups that are present in macrocyclic polyketides. Existing OPLS-AA torsional parameters for alkanes, alcohols, ethers, hemiacetals, esters, and ketoamides were improved based on MP2/aug-cc-pVTZ and MP2/aug-cc-pVDZ calculations. Nonbonded parameters for the sp(3) carbon and oxygen atoms were refined using Monte Carlo simulations of bulk liquids. The resulting force field predicts conformer energies and torsional barriers of alkanes, alcohols, ethers, and hemiacetals with an overall RMS deviation of 0.40 kcal/mol as compared to reference data. Densities of 19 bulk liquids are predicted with an average error of 1.1%, and heats of vaporization are reproduced within 2.4% of experimental values. The force field was used to perform conformational analysis of smaller analogs of the macrocyclic polyketide drug FK506. Structures that adopted low-energy conformations similar to that of bound FK506 were identified. The results show that a linker of four ketide units constitutes the shortest effector domain that allows binding of the ketide drugs to FKBP proteins. It is proposed that the exact chemical makeup of the effector domain has little influence on the conformational preference of tetraketides.  相似文献   
30.
During the last decade, it has become increasingly important that researchers demonstrate that research is conducted to the highest standards. The implementation of quality assurance for research laboratories will enable all fields of research and development to be judged impartially. There are no specific standards for research laboratories but where possible, existing standards can be adapted. This review is structured around two approaches. The first considers research to be a logical extension of testing, and it is assumed that testing standards can be applied methodically to each step in a research project. The second advocates a flexible approach, with research-specific criteria for assessing quality. The important papers published on this topic have been reviewed. The conclusions are that the general quality management approach, encompassed by the ISO 9000 series of standards with the emphasis on customer satisfaction and ‘fitness for purpose’, is suitable for implementing quality assurance in research laboratories.  相似文献   
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