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991.
Yun Long ZHANG Liang Ren ZHANG* Zhen Jun YANG Ji Mei MIN Li He ZHANG* Yang LU Ning Bo GONG Qi Tai ZHENG National Research Laboratory of Natural Biomimetic Drugs Peking University Beijing Institue of Materia Medica Chinese 《中国化学快报》2001,(5)
Tubercidin (4-amino-7--D-riobofuranosyl-7-H-pyrrolo[2,3-d]pyrimidine) 1, an antibio-tic substance produced in the culture broth of Streptomyces tubericidus1, is an adenosine analog in which N-7 is replaced by a carbon atom. It has attracted much attention due to the biological activities for the growth inhibition of certain tumors, and many derivatives of tubercidin have been synthesized2-5.For the synthesis of tubercidin analogs, 4-chloro-7-H-pyrrolo[2,3-d]pyrimidine-2,3,5-tri-O-acetyl--D-r… 相似文献
992.
L.tibeticaHook.f.etThorns.isanimportantTibetanmedicineusedfortreatmentofmanydiseases'.Thelignanglycosidesandtriterpenesfromthisplanthavebeenreported"'byHuidiZhangetal.ThispaperdescribesthestructureelucidationofanewIignanglucoside,namedtibeticosideA1... 相似文献
993.
La (III), Y(III) complexes wit11 diglycol aldehyde his-arginine (H2DAAR) and tetraglycol aldehyde bislysine (H2TALY) Schiff bases were synthesized. Thcy were characterized and formulated as La (H2DAAR) (NO3)3. 6H20 and Y (H2TALY) (NO3)3. 5H20 separately by elemental analyses. The obtained complexes were investigated in detail by high resolution solid state (HRSS)13C NMR using cross polarization, magic angle spinning (CPMAS). and total suppression of sidebands (TOSS) techniques. The results
are supported by the liquid state 2D-’H-13C COSY NMR spectra. Some new information about the splitting peaks of13C for -CH = N- group and alkene carbon bands, etc. in HRSS13C NMR spectra are given. 相似文献
994.
用半经典理论分析了含多勒普加宽的斯塔克效应调制,使用密度矩阵近似,导出了吸收线附近NH3分子的吸收系数和调制度表达式,实验研究了10.784μm波长的斯塔克效应调制特性,调制频率1MHz时,调制度达到33%。 相似文献
995.
Shuang Cai Taoguang Huo Ning Li Zhili Xiong Famei Li 《Biomedical chromatography : BMC》2009,23(7):782-786
An UPLC/MS/MS based metabonomic method was developed and applied to the elucidation of biomarker of metformin action. The plasma metabolite profiling in healthy volunteers before and after per os metformin was determined with UPLC/MS/MS and analyzed by using multivariate statistics. Significant difference in endogenous metabolite profiles was revealed before and after administration of metformin. Four biomarkers found were lysophosphatidylcholines (LPCs), and their structures were tentatively identified to be 16:0 LPC, 18:0 LPC, 18:1 LPC and 18:2 LPC according to the molecular ions information and corresponding fragments of product ion scan. Lysophosphatidylcholine in blood may be involved in metformin treatment. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
996.
The implantation of intravascular stent (IVS) is a kind of coronary angioplasty to restore the blood flow perfusion to the downstream of the heart muscle tissue. The superior mechanical properties of a stent guarantee the successful implantation. This paper intends to improve the mechanical properties of MAC STENTTM by utilizing optimization theory instead of the conventional trial-and-error approach. In order to achieve this goal, firstly, a reliable procedure of finite element analysis (FEA) is established based on a parametric geometric model. The FEA overcomes the difficulties due to nonlinearities such as elasto-plasticity, large deformation, large strains and contact. It can simulate the stent's deformations during a loading scheme of three phases without any possible failures or irregularities. Secondly, a single objective function, which includes the main mechanical properties of stents, is proposed to replace the initial multi-objective function and then an optimization model is formulated. An optimal design of MAC-J09-3.0 stent is obtained after successful execution of the optimizing process using 41 loops. Its comprehensive mechanical properties are largely improved. It is concluded that the optimization theory is very useful and efficient in the studies of coronary artery stents, although the optimization task encounters many severe difficulties and requires extensive calculation. The result also shows that the single objective function proposed in this paper is practical. 相似文献
997.
998.
Yu‐Liang Yang Dr. Wen‐Ying Liao Wan‐Yun Liu Chih‐Chuang Liaw Dr. Chia‐Ning Shen Dr. Zih‐You Huang Shih‐Hsiung Wu Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11573-11580
Six photosensitive polyketides, malbranpyrroles A–F, were discovered from the thermophilic fungus Malbranchea sulfurea by using intact‐cell desorption/ionization on silicon mass (ICD‐MS) and LC‐SPE‐NMR. These two strategies facilitate the searching and structural determination of unstable natural products. The ICD‐MS indicated that only brown hyphae of M. sulfurea can produce malbranpyrroles. The biosynthetic pathway of malbranpyrroles was evidenced by 13C isotope precursors and amino acid feeding experiments. The cytotoxicity data revealed that the conformation of the conjugated system in malbranpyrroles does not affect cytotoxic potency against cancer cell lines. In addition, the chlorine atom was shown to be the pharmacophore for cytotoxicity. 相似文献
999.
GalnAsSb是直接带隙、窄禁带的半导体材料,其波长范围为0. 87-12μm,粗盖了2-4 m, 3-5μm和8-12μm三个重要的红外应用波段,可制作室温下工作的红外光电器件,在光纤通信、环境监测、资源勘探、空间技术及军事等方面有广泛的应用前景. 相似文献
1000.
Hua Ning LIU Wen Peng ZHANG 《数学学报(英文版)》2007,23(1):77-82
The main purpose of this paper is to use the generalized Bernoulli numbers, Gauss sums and the mean value theorems of Dirichlet L-functions to study the asymptotic property of one class of number-theoretic functions, and to give four interesting hybrid mean value formulae. 相似文献