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651.
Wei Ming ZHU Xin HONG Yue Mao SHEN Bi Tao ZHAO Hong Ping HE Xiao Jiang HAO* Laboratory of Phytochemistry Kunming Institute of Botany Chinese Academy of Sciences Kunming Department of Chemistry Yunnan Normal Universite Kunmi 《中国化学快报》2001,(7)
The genus plants Polyalthia, being rich in bioactive diterpenoids and alkaloids1,2, have been attracting much attention. Polyalthia cheliensis Hu is a bush mainly distributed in Xishuangbanna, Yunnan Province of China. The previous researches1 reported the isolations of four clerodane diterpenes from the stem bark of this plants. Recent phytochemical work on its dried leaves results in the elucidations of a new benzosesquiterpenoid dimer, 3((, 3(((-bispolycerasoidol (1) and its monomer, a kn… 相似文献
652.
Shui Hua TANG Bao Chun LIU Qi LIANG Li Zhen GAO Liang Fu ZHANG Zuo Long YU* Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu 《中国化学快报》2001,(1)
It is well known that NO is one of the most predominant pollutants. It is the main source of acid rain and has strong carcinogenicity. Therefore, removal of NO is one of the key environmental subjects in the world nowadays. With the discovery of carbon nanotubes and their large-scale synthesis1-2, attention is now being focused on their potential application in various fields of materials research. In the field of heterogeneous catalysis, numerous carbon materials have been used to disperse … 相似文献
653.
Man Zhou ZHU Qi Hua WU Qing Xiang GUO* Department of Chemistry University of Science Technology of China Hefei 《中国化学快报》2001,(9)
Delivery of exogenous DNA into cells of various origins plays an important role not only in basic research, but also in clinical application in gene therapy. Great efforts have been made towards the development of viral and nonviral vectors for these purposes1~6. However, at the present stage, none of the vectors can claim to be the panacea. Although most viral vectors can transfer gene efficiently and some of them can be used for gene transfer into tissue cells in vivo, they suffer from immu… 相似文献
654.
Zhan Zhu LIU Ye Feng TANG Shi Zhi CHEN* Institute of Materia Medica Chinese Academy of Material Sciences & Peking Union Medical College Beijing 《中国化学快报》2001,(11)
1,2,3,4-tetrahydroisoquinoline-3-carboxylic acids (TIC) are of considerable interest due to their biological activity and as an important structural element in several important alkaloids and other medically useful products1. Moreover, TIC is a phenylalanine analogue in which the dihedral angle is limited to a very small range because of its bicyclic nature2. In connection with the design of topographically constrained peptides, TIC has been utilized in several instance as a replacement o… 相似文献
655.
The title compound, (H2en)3H3O{Mo8V4O36(VO4) (VO)2} ?4H2O, was hydrothermally synthesized and structurally characterized by means of IR, ESR spectrum and single crystal X-ray diffraction. It crystallized in a monoclinic system with space group P21/c, a=1. 980 4(4) nm, 6=2. 063 4(4) nm, c=l. 192 0(2) nm, =94. 76(3)?and deep black colour. The compound contains V-centered bi-capped a-Keggin fragments {Mo8V7O42} that are linked together by edge-shared units V O5 via V桹梀 bonds, forming a chain. 相似文献
656.
Gang Li 《高等学校计算数学学报(英文版)》2007,16(4):358-369
The Helmholtz equation is sometimes supplemented by conditions that include the specification of the boundary value of the divergence of the unknown.In this paper, we study the vector Helmholtz problem in domains of both C~(1,1)and Lipschitz.We es- tablish a rigorous variational analysis such as equivalence,existence and uniqueness. And we propose finite element approximations based on the uncoupled solutions.Fi- nally we present a convergence analysis and error estimates. 相似文献
657.
Shuang Xi MEI Yun Xin DENG Quan Bin HAN Zhong Wen LIN Han Dong SUN* Laboratory of Phytochemistry Kunming Institute of Botany Academia Sinica Kunming Department of Pharmacy Guiyang Medical College Guiyang 《中国化学快报》2001,(2)
The genus Isodon has been shown to be a rich source of diterpenes, especially the highly oxidized ent-kaurene diterpenoids with various biological activities1-3. The chemical constituents of Isodon forrestii was reported by Yun Long Xu et al.4. We have investigated the titled plant collected in another place, from the 70% acetone extract of the aerial parts of I. forrestii, seven compounds including a new diterpene glycoside 1 were isolated by a combination of silica gel, preparative TLC an… 相似文献
658.
NaLI Qi Tai ZHENG Zhi Da MIN* Department of Natural Products Chemistry China Pharmaceutical University Nanjing Institute of Materia Medica Chinese Academy of Medical Sciences & Peking Union Medical College Xian Nong Tan street Beiji 《中国化学快报》2001,(10)
Pueraria peduncularis (Grah. ex Benth.) Benth. is a plant of Leguminosae which grows in the southwest of China. Different from other plants of Pueraria, it could not be used as a medicine due to its toxicity1. In order to use the Pueraria plants safer, we studied the constituents of P. peduncularis. Previous phytochemical studies of an n-BuOH extract afforded three triterpenoid saponins2-3. The continuing investigation on CHCl3 extract led to the isolation of a new indole alkaloid. … 相似文献
659.
In previous paper and work, we reported the synthesis and cytotoxicity studies of a novel series of short chain peptide conjugates of the cytotoxic agent 2, 6-dimethoxyhydro -quinone-3-mercaptoacetic acid1 (DMQ-MA). The DMQ-MA is a derivative of 2,6-dimethoxybenzoquinone, which is a natural product of fermented wheat germ and found to have a wide spectrum of cytotoxicity against various tumor cell lines under the synergistic activation of L-ascorbic acid (AH2)2,3. Compared with DMQ, DMQ… 相似文献
660.
力链是颗粒体系研究中的重要概念,是微观现象的集中体现,对宏观颗粒物质体系起着重要作用。采用光弹方法对受竖向荷载作用的混合直径颗粒体系进行加压实验,结合数字图像处理技术和G2值法(彩色梯度均方值算法),分析了颗粒体系在竖向荷载作用下几何结构的变化以及接触力、力链网络的分布情况。首先通过数字图像处理技术统计出颗粒体系在不同竖向荷载作用下的接触向量角度分布情况,发现其集中分布区间只是在区间分布频率上出现小幅波动,竖向荷载的增大并不会对整体分布产生影响。然后通过G2值法求出了颗粒体系的G2值,并对单个颗粒的G2值和平均接触力F的关系进行了拟合,结果表明,光弹颗粒的G2值随着F的增大而增大,接触点少的颗粒G2值反而偏大。接着通过拟合公式计算出单个颗粒的接触力,根据其与平均接触力的比值频率统计结果画出接触力频率分布曲线,从曲线结果来看,竖向荷载的增大能够让颗粒体系中直径较小的颗粒接触力更加接近平均接触力,分布更加统一;直径较大的颗粒能够支撑起更多的荷载并接触到更多其他... 相似文献