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141.
Based on the analysis of the courses and the investigation of students' online learning needs, an online teaching mode of "Tencent Classroom" and "Rain Classroom" with "split screen" is designed. This mode is used for the online teaching of "Foundation of Innovation and Entrepreneurship" and "Chemical Instrumentation and Automation". After two months of teaching practice, the teaching and learning were reflected and summarized, aiming to improve the performance of online teaching. 相似文献
142.
143.
Robert Werner Lang 《Helvetica chimica acta》1986,69(4):881-886
The title compound 1 , which can be regarded as a synthetic equivalent of substituted 1,1,1-trifluoroacetone 2 , is prepared by Zn-induced reductive addition of 1,1,1-trichloro-2,2,2-trifluoroethane ( 3 ) to formaldehyde ( 4 ). A brief survey of the scope of this C? C-bond formation leading to a variety of new CF3-containing synthetic building blocks is also given. 相似文献
144.
A new organic photochromic compound containing pyrazolone-ring photochromic functional unit: 1-phenyl-3-methyl-4-benzyl-5-one pyrazole S-methyl thiosemicarbazone (PMBP-smtsc) was synthesized. The photochromic properties and photochemical kinetics of PMBP-smtsc have been studied by UV reflectance spectra under irradiation of 365 nm light. The crystal structure analyses of photocolored product show the photochromism is due to the photoisomerization from enol form to keto form through an intermolecular proton transfer. 相似文献
145.
StudiesonArtificialImitationofGlutathionePeroxidasebyChemicalMutationDINGLan;ZHUZhen-qi;LUOGui-min;SUNQi-an;YANGTong-shuandSH... 相似文献
146.
147.
Summary This work describes the study of a degradation curve of Oxadixyl in field-treated potato and tomato samples. The residues
were extracted using classical and supercritical fluid (SFE) extraction methods and analyzed by HRGC/ECD. The extraction techniques
were compared and the results indicate the advantages of using SFE as an alternative method for pesticide analyses in these
samples. 相似文献
148.
引言我们曾研究了金属镍,铜,钛,钨,铝,铁,银,铂,钼等和非金属硅与石墨及ⅢA—VA与ⅡB—ⅥA化合物晶体等的弛豫、重构和吸附表而的60多个表面结构。本文报道研究Ag(100)c(2×2)—C1表面的结果。Zanazzi和Jona观测了Ag(100)c(2×2)—C1表面结构的21束LEED谱,并采用层—KKR(Korring—Kohn—Rostocker)法,对清洁的Ag(100)表面吸附C1原子时假设了4种结构模型。经理论计算与观测值的比较,提出了C1原子的单层吸附和C1原子与Ag原子 相似文献
149.
The electrochemical stability of 10 organic cations, which can be used in ionic liquids (IL), was investigated as solutes in acetonitrile (ACN). The stability of three of the salts, BenMe2EtNCl (salt III), 1-butyl-2-methyl pyrrolidium chloride (salt VI), and its structural isomer, BuMe2ProNCl (salt VII), were also compared in chloroaluminate ILs. The chloroaluminate ILs of salts VI and VII are investigated for the first time. The NaCl-neutralized ILs of salts VI and VII have melting points of 43.2 and 3.7 degrees C, respectively. The benzyl-substituted cation, salt III, was more easily reduced in ACN or as the neutral chloroaluminate IL than the alkyl-substituted cation, salt VII, due to the better leaving ability of the benzyl group. Mass spectroscopy measurements before and after electrolysis on the benzyl-substituted solutions confirmed that reduction involves the loss of an alkyl group. In ACN, salt VI was found to be the most difficult to reduce (1 mA/cm2 at -2.09 V) due to its cyclic structure. However, in the chloroaluminate IL, the pyrrolidinium cation was more easily reduced than salt III or its isomer, salt VII, resulting in an insoluble black deposit. This is consistent with the mass spectrometry data, which do not show formation of low-molecular-weight products, as in the reduction of salts III and VII. The IL of salt VII was the most stable in the presence of sodium. Sodium ions could be reduced and reoxidized with a maximum Coulombic efficiency of 94.1% versus 87.2% for salt VI. Reduction of the pyrrolidinium cation produces insoluble products, most likely through opening of the cyclic ring, and an inferior medium for sodium ion reduction compared to the benzyl- and butyl-substituted cations, even though reduction of the cation occurs at a more negative potential in acetonitrile. 相似文献
150.
Acid-catalyzed isomerization of the petrosterol side chain () proceeds stereospecifically to yield the naturally occurring 26-dehydro-25-epiaplysterol side chain (); in addition, a 1.5-hydride shift leading to 22-dehydro-25-epiaplysteryl acetate () has also been observed. 相似文献