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991.
Yu Lu Hui Xiong Hong Li Teng Guang Zhong Yang Zhi Nan Mei 《Helvetica chimica acta》2011,94(7):1296-1303
Three new C21 steroidal glycosides with a cinnamoyl group at C(12) and a 2‐methylbutanoyl group at C(20), and a straight sugar chain at C(3), namely cyanoauriculosides C–E ( 1 – 3 , resp.), together with three known steroidal derivatives, were isolated from the roots of Cynanchum auriculatum (Asclepiadaceae). Their structures were determined by spectroscopic analyses and chemical methods. The known constituents were identified as wilfoside K1N ( 4 ), cynanauriculoside II ( 5 ), and auriculoside IV ( 6 ). 相似文献
992.
Archiv der Mathematik - Let $$m\in \mathbb {N}$$ and $$\vec {b}=(b_{1}, \ldots ,b_{m})$$ be a collection of locally integrable functions. It is proved that $$b_{1},b_{2}, \ldots , b_{m}\in BMO$$ if... 相似文献
993.
We report the electrical bistability of cadmium sulfide (CdS) nanoparticles (NPs) capped by dodecanethiol, which are sandwiched between aluminum tris (8-hydroxyquinoline) (Alq3) layers. The current density–voltage (J–V) characteristics of the device with Al/Alq3/CdS NPs/Alq3/Al structures show the high- and low-conducting state at the same voltage, and the two states are reproducible by applying different negative sweeping voltages. The Ohmic model and the space–charge limited model are proposed and supported by the current density–voltage results, which give a possible transport mechanism for the electrical bistability of our devices. 相似文献
994.
Dingying Zhou Hongxiang Teng Koutarou Koike Yasuhiro Koike Yoshiyuki Okamoto 《Journal of polymer science. Part A, Polymer chemistry》2008,46(14):4748-4755
Fluoroalkyl methacrylates, 2,2,2‐trifluoroethyl methacrylate ( 1 ), hexafluoroisopropyl methacrylate ( 2 ), 1,1,1,3,3,3‐hexafluoro‐2‐methyl‐2‐propyl methacrylate ( 3 ), and perfluoro t‐butyl methacrylate ( 4 ) were synthesized. Homopolymers and copolymers of these fluoroalkyl methacrylates with methyl methacrylate (MMA) were prepared and characterized. With the exception of the copolymers of MMA and 2,2,2‐trifluoroethyl methacrylate ( 1 ), the glass transition temperatures (Tgs) of the copolymers were found to deviate positively from the Gordon‐Taylor equation. The positive deviation from the Gordon‐Taylor equation could be accounted for by the dipole–dipole intrachain interaction between the methyl ester group and the fluoroalkyl ester group of the monomer units. These Tg values of the copolymers were found to fit with the Schneider equation. The fitting parameters in the Schneider equation were calculated, and R2 values, the coefficients of determination, were almost 1.0. The refractive indices of the copolymers, measured at 532, 633, and 839 nm wavelengths, were lower than that of PMMA and showed a linear relationship with monomer composition in the copolymers. 2 and MMA have a tendency to polymerize in an alternating uniform monomer composition, resulting in less light scattering. This result suggests that the copolymer prepared with an equal molar ratio of 2 and MMA may have useful properties with applications in optical devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4748–4755, 2008 相似文献
995.
Da Teng Sheng Xia Shimin Tao Lijiu Gao Youjian Feng Liangce Rong 《Research on Chemical Intermediates》2013,39(2):561-568
An efficient and convenient method for the preparation of 3-aryl-2,3-dihydr-othiophene-2-carboxamide derivatives in absolute ethyl alcohol by thiazolidine-2,4-dione, aromatic aldehyde, malononitrile and n-butylamine without using any other catalysts was reported. This methodology has the advantages of high yields, simple work-up procedure and mild reaction conditions. 相似文献
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A series of highly porous 4,8-connected isoreticular MOFs of the scu topology [Cu(4)(L(1))(H(2)O)(4)]·20DEF, [Cu(4)(L(2))(H(2)O)(4)]·16DMF·5H(2)O, and [Cu(4)(L(3))(H(2)O)(4)]·14DMF (L(1)-L(3) are (R)-1,1'-binaphthyl-derived octacarboxylate bridging ligands) were synthesized and characterized by single-crystal X-ray crystallography. Although the frameworks exhibit some distortion during the solvent removal process, the high-connectivity nature of the building blocks helps in stabilizing the frameworks, leading to high surface areas (S(BET) = 1189-2448 m(2)/g) and significant hydrogen uptake of up to 1.8 wt % (77 K, 1 atm). 相似文献
1000.
In this work, an efficient CuSO(4)-catalyzed S-arylation of thiols with aryl and heteroaryl boronic acids at room temperature is established. This catalytic system can tolerate a wide variety of thiols and arylboronic acids in the presence of only 5 mol % of CuSO(4) as the catalyst and inexpensive 1,10-phen·H(2)O as the ligand. Moreover, this catalytic system used environment-friendly solvent (EtOH) and oxidant (oxygen). 相似文献