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891.
Gengliang Yang Haiyan Liu Haiying Li Yanhuan Wang Zhiwei Li Yi Chen 《Chromatographia》2003,57(3-4):245-247
Summary A high-performance liquid chromatographic method is proposed for the simultaneous separation of two pairs of isomers:N-(trans-4-isopropylcyclohexylcarbonyl)-d-phenylalanine, (Nateglinide) andN-(cis-4-isopropylcyclohexylcarbonyl)-d-phenylalanine,trans-4-isopropylcyclohexane-carboxylic acid andcis-4-isopropyl-cyclohexanecarboxylic acid using a C18 column. The mobile phase is a ternary mixture of acetonitrile-methanol-0.1 M ammonium dihydrogen phosphate buffer, pH 3.0
(5:2:4 v/v/v) and UV detection at 210 nm. Precision, linearity, limit of detection and recovery were also evaluated for each
compound. Satisfactory results were obtained. 相似文献
892.
893.
Xinping Huang Zhiwei Deng Xiaobin Zhu Leen vanOfwegen Peter Proksch Wenhan Lin 《Helvetica chimica acta》2006,89(9):2020-2026
Four new pregnane‐type steroids, krempenes A–D ( 1 – 4 ), were isolated from the marine soft coral Cladiella krempfi. Their structures were elucidated on the basis of 1D‐ and 2D‐NMR analyses, as well as MS experiments. Krempene A ( 1 ) contains a very unusual structural motif, with a hexacyclic oxadithiino unit fused to the steroidal ring A. Krempene B ( 2 ) is a 19‐norpregnane steroid, the 19‐Me group formally being transferred to position 4. Furthermore, krempene D contains an unusual C?C bond at C(7) of the pregnane skeleton. 相似文献
894.
Takeshi Hattori Zhiwei Tong Yoshiyuki Kasuga Yoshikazu Sugito Tatsuto Yui Katsuhiko Takagi 《Research on Chemical Intermediates》2006,32(7):653-669
The hybridization of two different types of organic polycations, 1,1’-dimethyl-4,4’-bipyridinium dications (methyl viologen,
MV2+) and 5,10,15,20-tetrakis(N-methyl-pyridinium-4-yl)-21H,23H-porphine tetracations (TMPyP4+), into layered niobates was investigated to construct an efficient dye-modified semiconductor for solar conversion and storage.
Two different methods were employed for the direct intercalation of the cationic species, i.e., conventional ion-exchange
with K4Nb6O17 · 3H2O as the starting host and a novel acid-base neutralization method with H4Nb6O17 as the starting host. These two methods showed totally different behavior and the characteristic features of both will be
discussed in relation to the structure of the hybrid formed, the amount of absorption observed for the guest molecules and
the intercalation rates. An analysis of the photo-induced electron-transfer reactions will also be discussed to show how control
of the intercalation of guest molecules affects the photofunctionality of these unique hybrids. 相似文献
895.
Photocatalytic H2 evolution reactions on pristine graphitic carbon nitrides (g-C3N4), as a promising approach for converting solar energy to fuel, are attractive for tackling global energy concerns but still suffer from low efficiencies. In this article, we report a tractable approach to modifying g-C3N4 with vanadyl phthalocyanine (VOPc/CN) for efficient visible-light-driven hydrogen production. A non-covalent VOPc/CN hybrid photocatalyst formed via π-π stacking interactions between the two components, as confirmed by analysis of UV-vis absorption spectra. The VOPc/CN hybrid photocatalyst shows excellent visible-light-driven photocatalytic performance and good stability. Under optimal conditions, the corresponding H2 evolution rate is nearly 6 times higher than that of pure g-C3N4. The role of VOPc in promoting hydrogen evolution activity was to extend the visible light absorption range and prevent the recombination of photoexcited electron-hole pairs effectively. It is expected that this facile modification method could be a new inspiration for the rational design and exploration of g-C3N4-based hybrid systems with strong light absorption and high-efficiency carrier separation. 相似文献
896.
Falk Lissner Karl Krmer Thomas Schleid Gerd Meyer Zhiwei Hu Günter Kaindl 《无机化学与普通化学杂志》1994,620(3):444-450
The Chlorides Na3xM2–xCl6 (M = La? Sm) and NaM2Cl6 (M = Nd, Sm): Derivatives of the UCl3-Type of Structure. Synthesis, Crystal Structure and X-Ray Absorption Spectroscopy (XANES) Single crystals of the derivatives of the UCl3-type structure Na3xM2–xCl6 (M = La/x = 0.364(4); Ce/0.349(5); Pr/0.318(8); Nd/0.305(5); Sm/0.246(4)) and NaSm2Cl6 were grown by different methods generally under reducing conditions. They are addition [Na(Sm2)Cl6] and addition/substitution variants [Na2x(NaxM2–x)Cl6] of the UCl3 structure type [□(U2)Cl6]. X-Ray Absorption Spectroscopy (XANES) at the LIII edge characterizes NaSm2Cl6 and NaNd2Cl6 as mixed-valence compounds with valences of +2 and +3 in statistical distribution (approximately 1:1) for Sm and Nd, respectively. 相似文献
897.
据自由电子激光原理,利用变参数摇摆器设计可以大幅度提高自由电子激光放大器的效率,在分析文献中所提出的“单电子共振”和“磁场指数下降法”基础上,提出了变参数摇摆器的“多电子自洽设计和最佳选择”的设计方法。经数值计算证明,所提出的方法明显优于其它方法。 相似文献
898.
899.
900.