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771.
Summary Dichloro bis(5) molybdenum catalyses the reduction of organic halides by sodium borohydride smoothly and selectively. The reactions with representative organic monohalides and polyhalides are investigated. The ease of reduction depends on the structure of the halide and the solvent used. alkoxycarbonyl and cyano groups are unattacked in the reaction. An oxidative addition-reductive elimination mechanism is tentatively suggested. 相似文献
772.
Zhang Q Liang X Chen J Lu P Yediler A Kettrup A 《Analytical and bioanalytical chemistry》2002,374(1):93-102
A method has been developed for peak identification of PCBs in GC with ECD detection under different temperature programs and isothermal conditions on two commonly used columns (DB-5 and DB-1701). This was achieved by means of accurate calibration of retention times based on the concept of the relative retention index P (i) and retention times of the selected PCB internal standards. The P (i) was calculated from the predicted retention times with the database of the retention parameters (A, B) and the migration equations. Through comparison of the calibrated and experimental retention times of PCBs in technical samples, it was shown that the developed method was effective for correct PCB comprehensive, quantitative, congener-specific (CQCS) analyses. 相似文献
773.
哺乳动物体内氨基酸及蛋白质的非酶糖化反应(Mailard反应)与糖尿病及其并发症的关系已引起广泛关注[1],β-羧乙基锗倍半氧化物(Ge-132)具有预防糖尿病和调节糖代谢的作用[2],研究Ge-132对Mailard反应的抑制作用对于开发防治糖尿病... 相似文献
774.
考察氧化物担体对Fe-MnO催化剂反应性能影响的结果表明,担体的类型对Fe-MnO催化剂CO加氢反应性能影响很大,其低碳烯烃选择性相差悬殊,Al_2O_3、SiO_2和MgO担载的Fe-MnO催化剂都不利于低碳烯烃的生成,而TiO_2担载的Fe-MnO催化剂则具有较高的烯烃选择性和催化活性。从担体-金属相互作用本质的差异,研究了担体对金属活性组分化学状态的影响及催化活性相与F-T合成烯烃的关系,发现担体-金属间的电子效应有利于催化剂活性和选择性的提高,其它物理化学效应引起的相互作用则不利于改善催化剂性能;还表明Fe_(?)C是催化活性相,Fe~(2+)物种的存在不利于提高烯烃的选择性。 相似文献
775.
Nanofabrication: conventional and nonconventional methods 总被引:4,自引:0,他引:4
Nanofabrication is playing an ever increasing role in science and technology on the nanometer scale and will soon allow us to build systems of the same complexity as found in nature. Conventional methods that emerged from microelectronics are now used for the fabrication of structures for integrated circuits, microelectro-mechanical systems, microoptics and microanalytical devices. Nonconventional or alternative approaches have changed the way we pattern very fine structures and have brought about a new appreciation of simple and low-cost techniques. We present an overview of some of these methods, paying particular attention to those which enable large-scale production of lithographic patterns. We preface the review with a brief primer on lithography and pattern transfer concepts. After reviewing the various patterning techniques, we discuss some recent application issues in the fields of microelectronics, optoelectronics, magnetism as well as in biology and biochemistry. 相似文献
776.
High-quality online course materials were reconstructed through feedback from undergraduate students and online data analysis regarding constructed learning materials on the Chao Xing Learning Platform. They were used for studying organic chemistry courses online and offline in university for nationalities. This model, based on student-centered teaching, can effectively transform students from passively accepting knowledge to actively learning and internalizing knowledge. This strategy can also enhance the students' learning initiative and the effects of learning, and hopefully be helpful to the universities in multi-ethnic areas in developing fundamental disciplined construction of organic chemistry and other courses. 相似文献
777.
Lesaicherre ML Lue RY Chen GY Zhu Q Yao SQ 《Journal of the American Chemical Society》2002,124(30):8768-8769
We report here the first example using an intein-mediated expression system to generate biotinylated proteins suitable for immobilization onto avidin-functionalized glass slides. With this novel array, proteins are site-specifically immobilized on the glass surface and are able to retain their native activity. The advantage of the avidin/biotin linkage over his-tag/Ni-NTA strategies for protein immobilization is highlighted by its ability to withstand a variety of chemical conditions, which makes this new protein array compatible with most biological assays. 相似文献
778.
779.
烷基极化效应与X=O键伸缩振动频率 总被引:2,自引:0,他引:2
烷基取代物R’X=0的X=0键伸缩振动频率ν与烷基R的极化效应指数PEI(R)的关系可表示为:ν=a bPEI(R)。研究结果表明,烷基的极化效应使X=0键的伸缩振动频率降低。 相似文献
780.
The calculations of clusters modeling the fluorine-doping and oxygen deficiency of YBa2Cu307 have been performed by the method of all-electronab initio Hartree-Fock with self-consistent crystal field. Results show that in CuO planes electric charge significantly increases,
the chemical valence of Cu decreases and the covalent bonding of Cu-O greatly weakens owing to oxygen deficiency, while the
effect of F restores the local electronic structure of YBa2Cu3O7. The reported opinion that F occupied the oxygen vacancy in Cu-O chains seems disputable according to the calculated bonding
characteristics
Project supported by the National Natural Science Foundation of China. 相似文献