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831.
832.
Dysamide U,a new tricblorinated diketopiperanne(1)along with seven known ones(2-8)were isolated from the sponge of Dysidea sp.collected from the Pacific ocean.The structure of dysamide U(1)was elucidated by high resolution FARMS and 1H NMR data induding COSY and RCT-COSY. 相似文献
833.
Jian Gong SHI Han Qing Wang Min WANG Guang Xiong ZHOU. Yong Chun YANG Wen Yan HU 《中国化学快报》2000,11(3):225-228
In a previous paper' we reported two optically active pyridine-2, 6 (l H. 3H)-dionealkatoids speranskalines A and B from SPeranskia luberculala (Bge.) (Euphorbiaceae)We report here the isolation and structural elucidation of two novel poly-oxygenbipyridine alkaloids named speranculatines A (l) and B (2) from this plant.The acetone (or methanol) extract of the air-dried whole plants of .q. IllhelT.lllaluwas subjected to column chromatography on St gel to afford a fraction. whichdemonstrate… 相似文献
834.
A new way to Prepare ts-2 with Silica sol as Silicon Source 总被引:3,自引:0,他引:3
The addition of suitable amounts of aqueous ammonia into precursor gel with silica sol as silicon source, TS-2 with small particle size and high titanium content has been successfully synthesized. It displays the same excellent performance in hydroxylation of phenol as the sample prepared with TEOS as silicon source. 相似文献
835.
索赔次数为复合Poisson-Geometric过程的常利率风险模型的罚金函数 总被引:3,自引:0,他引:3
讨论了常利率下索赔次数为复合Poisson-Geometric过程的风险模型的罚金函数,得到了罚金函数的期望所满足的积分方程,并由所得到的积分方程推出了破产概率所满足的积分方程,初始盈余为0时,得到了罚金函数的期望及破产概率的精确解. 相似文献
836.
Xie Wen Xiong Caidong Wang Xiangru Wang Zhigang Liu Yuming 《International Journal of Infrared and Millimeter Waves》2008,29(4):406-415
In this paper, a new type of gain guiding fiber is presented, with a parabolic-profile for both the gain and index guiding.
Theoretical investigation shows that the core diameter of such fiber may be up to 200 μm while propagating with single-mode. 相似文献
837.
Walter C. P. M. Blondel Bertrand Lehalle Gérard Maurice Xiong Wang Jean-François Stoltz 《Rheologica Acta》2000,39(5):461-468
Cryopreservation is widely used to preserve blood vessels for a while but is controversially suspected to affect the mechanical
behavior of these allografts. The aim of this study was to determine whether differences in the three-dimensional mechanical
behavior exist or not between fresh and cryopreserved arteries. Using a previously developed experimental system, in vitro
inflation tests were performed on twenty segments of human fresh and cryopreserved arteries, in static conditions. Opening
angles were also measured from images of rings in zero-stress state. The initial reference state was chosen as the unloaded
state and tests were performed on specimens stretched at natural “in vivo” length. Mechanical measures calculated are “natural”
(Hencky) strains (finite deformations), “true” (Cauchy) stresses in radial, circumferential, and longitudinal directions as
well as strain energy per unit volume. Tangent moduli are derived from radial and circumferential stress-strain characteristics
using non-linear curve fitting. Values of incremental and pressure-strain elastic parameters, wall stiffness, and compliance
per unit length are also calculated. Results are presented in terms of characteristics of stresses and strains in the three
directions, axial force, tangent moduli vs strains or stresses, and energy per unit volume, for both types of artery, with
reference to transmural pressure. Detailed numerical results are given at mean transmural pressure or in the physiological
range. Significant differences are indicated by statistic Student T-tests. Results obtained show that significant differences
exist between rheological properties of fresh and cryopreserved segments of human artery. Strains, stresses, axial force,
strain energy, and wall stiffness values highlight those differences whereas elastic parameters, compliance, and opening angle
do not. The usefulness of some parameters to compare the mechanical behavior existing between fresh and cryopreserved arteries
is therefore underlined.
Received: 3 January 2000 Revision received: 12 April 2000 Accepted: 8 May 2000 相似文献
838.
839.
840.
Jianhui Wang Tao Liu Dr. Guotao Wu Dr. Wen Li Yongfeng Liu Dr. C. Moysés Araújo Dr. Ralph H. Scheicher Dr. Andreas Blomqvist Rajeev Ahuja Prof. Zhitao Xiong Dr. Ping Yang Dr. Mingxia Gao Dr. Hongge Pan Prof. Ping Chen Prof. 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2009,121(32):5942-5946