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21.
Zong Xin PI Hou Wen XIN* Department of Chemical Physics University of Science Technology of China Hefei 《中国化学快报》2001,(3)
IntroductionStochastic resonance (SR) is a nonlinear effect which describes the optimal detection of a weak periodic signal by the action of external noise in nonlinear systems. SR was originally proposed to account for periodicity in the Earth's ice ages1, and it has been observed in a wide range of biological2-4 , physical5 and chemical6 systems. The systems mentioned above which may give rise to SR have a denominator despite many examples of SR in different scientific areas. It is noted… 相似文献
22.
1INTRODUCTIONInrecentyears,ourresearchgrouphasstudiedsystematicalycycloadditionreac tionsoftheC=Ndoublebondsinthebenzoheteroa... 相似文献
23.
Cui Hua XUE Qi Ming MU Shu Hua CHEN* The Faculty of chemistry Sichuan University Chengdu 《中国化学快报》2001,(5)
Molecular tweezers is a novel type of artificial receptors, which not only offer the advantage of efficient construction but also their surfaces can be tailored for specific applications. The clefts of molecular tweezers are particularly effective in regard to complementarity with substrates since functional groups attached to the interior of the cleft converge on substrates held inside1. So, in recent years, the molecular tweezers receptors have attracted more and more attention in molecular … 相似文献
24.
Gang ZHOU Xiao Lei GAO Yu Kun GUAN Wei Dong LI Yu Lin LI* National Laboratory of Applied Organic Chemistry Institute of Organic Chemistry Lanzhou University Lanzhou 《中国化学快报》2001,(5)
Sesquiterpenic compounds of the Eudesmane family have attracted considerable attention due to their intriguing biological properties1,2, particularly significant antifeedant activity, cell growth inhibitory and plant growth regulating activities.In 1996, J. Hu and co-workers3 had isolated eudesmane sesquiterpene 5?-hydroxy-isopterocarpolone 1 from the aerial parts of chinese folk medicine Artemisia eriopoda and elucidated its structure by spectropic methods. Herein, we reported the first tota… 相似文献
25.
Hong Ping LI Hai Fei ZHANG Jun LIU Bu Xing HAN* Center for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2001,(4)
There are some unique advantages for chemical reactions in SCFs. For example, reaction rates, yields, and selectivity can be tuned by pressure or small amount of cosolvent. SCFs can be used to replace environmentally undesirable solvents. It is not surprised that in recent years the use of SCFs as solvents for chemical reaction media has received much attention. However, mechanism for the effect of pressure and cosolvents on chemical reactions is not very clear. Tautomeric reactions are id… 相似文献
26.
Ming Xia LI Yan Ming WANG Ru Ru CHEN* Research Institute of Elemento-Organic Chemistry Nankai University Tianjin Pittsburgh University Medical Center Pittsburgh PA U. S. A 《中国化学快报》2001,(6)
The chiral diols ((,(,((,((-Tetraaryl-1,3-dioxolane-4,5-dimethanols) have been used for the formation of cyclic titanates and similar derivatives of Mg, Al and Zr. These complexes of oxophilic metal centers were employed in catalytic and stiochiometric enantioselective reactions such as enantioselective addition reactions of carbon-centered nucleophiles to aldehydes1, [2+2] cycloadditions2, and Diels-Alder reactions3. So far, the two hydrogen atoms of all this type of diols are in trans form… 相似文献
27.
Our group have explored the reaction of allylsamarium bromide with a variety of substrates, such as N-(2-aminoalkyl)benzotriazoles1, imines2, nitriles3, diorgano diselenides4, disulfides5, isocyanates6 and nitroalkenes7. Here we wish to report the monoallylation of gem-diacetates with allylsamarium bromide. Gem-diacetates are stable in neutral and basic media, thus they are frequently used to protect aldehydes8. However, the presence of two leaving groups at the same carbon may make carbon … 相似文献
28.
XI Shang-Zhong 《结构化学》2001,20(4)
1 INTRODUCTIONAtrope alkaloids, which exist in eggplant plants, such as atrope and scopolamine, are used as a series of important drugs in medical science [1,2]. The typical character of atrope alkaloid is that these compounds contain the main skeleton of 8-azabicycle[3,2,1]octane , which results in the very complicated synthetic routine[3]. During our research for the reaction of 1,3,5,7-tetraphenyl-4- nitro-1,7-heptadione with low-valent titanium reagent, we easily synthesized the title … 相似文献
29.
Si WANG Pei Cheng ZHANG Ruo Yun CHEN De Quan YU* Institute of Materia Medica Chinese Academy of Medical Sciences 《中国化学快报》2001,(9)
Goniothalamus cheliensis Hu (Annonaceace) is a small tree or shrub in Yunnan Province, southwest of China. Acetogenins, styryllactones and alkaloids1-3 from the genus were reported in the previous literature and many of them showed strong cytotoxic activities against a number of human cancer cell lines4. The titled plant has been the subject of our investigation due to the impressive cytotoxicity of its organic extract against mouse lymphocytic leukemia cells in preliminary pharmacological s… 相似文献
30.
采用水热法,使用碳源蛋白胨制得荧光碳量子点(CQDs)。使用透射电镜、X射线光电子能谱(XPS)和红外光谱对其进行了表征。该CQDs溶液的荧光能够被Cu2+猝灭,草酸能够使CQDs的荧光恢复。据此建立了碳量子点“关-开”型荧光探针测定草酸的新方法。荧光恢复程度与草酸浓度在8~65μg/mL范围内呈线性关系,检出限为1.8μg/mL。通过紫外光谱、荧光光谱和荧光寿命探究了CQDs对草酸的荧光响应机理。Cu2+能够对CQDs的荧光产生动态猝灭,C2O42-与Cu2+结合,减少了溶液中游离的Cu2+,导致CQDs的荧光恢复。该方法可用于实际样品西红柿和圣女果中草酸的分析检测。 相似文献