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991.
In order to further study on minor diterpenoid constituents of lsodon rubescens, wereinvestigated this species, which was collected in Taibai mountain, Shaanxi Province.TWo new diterpenoids, taibairubescensins A (l) and B (2), were isolated. In this paper,we present the structure elucidation of these two new diterpenoids.Taibairubescensin A (l ), C,.H,#O, (FABMS m/z 435[M 11 ), an amorphous powder,showed UV and iR absorption bands for the existence of hydroxyl, acetoxyl and a fivemembe… 相似文献
992.
993.
994.
Xu J. Z. Tian C. M. Ma Z. G. Gao M. Guo H. Z. Yao Z. H. 《Journal of Thermal Analysis and Calorimetry》2000,63(2):501-506
The effects of some kinds of metal ions used as chemical modifications on the thermal properties of the modified polyacrylonitrile
(PAN) fibers were studied by DTA, TG, GC and cone calorimetry. The apparent activation energies for the decomposition of the
unmodified and modified PAN fibers were determined using Kissinger equation and Broido equation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
995.
Youxin Yao Wenju Zeng Bin Zhang Yunqi Liu Daoben Zhu 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):e90-e91
The title complex, C14H20O4S8+.BF4?, is a charge‐transfer complex with typical charges for the donor and anion of +1 and ?1, respectively. Two centrosymmetrically related donors form a face‐to‐face π‐dimer with a strong intermolecular S?S interaction. These π‐dimers stack along the a axis to form a donor column. The structure is extensively hydrogen bonded. 相似文献
996.
Huanrong Li Yingming Yao Qi Shen Linhong Weng 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):747-748
The title complex, [Y2(C6H7)4(C3H7O)2], is a centrosymmetric dimer bridged through the O atoms of the isopropoxide ligands. The Y2O2 unit is planar and the geometry around the eight‐coordinate Y atom is distorted pseudo‐tetrahedral. The Y—O distances are 2.2228 (19) and 2.2432 (19) Å, and the O—Y—O angle is 74.86 (7)°. 相似文献
997.
A novel ion-selective sensor for procaine hydrochloride has been proposed and applied successfully to analysis of pharmaceutical
preparations. The sensor is based on modification of the Ag-electrode of an AT-cut piezoelectric quartz crystal with a PVC
membrane containing procaine tetraphenylborate. A linear relation between the logarithm of the response frequency and the
logarithm of the procaine hydrochloride concentration was found experimentally and could be explained by combination of a
modified Sauerbrey equation and the Freundlich isotherm. The detection range was from 8.3 × 10−8 to 5.0 × 10−3 M with a detection limit of 8.3 × 10−8 M. The selectivity of the sensor and the influence of experimental parameters such as solution pH and detection time were
investigated.
Received February 10, 1999. Revision October 10, 1999. 相似文献
998.
A new type of two-dimensional network was found in the hydrogen-bonded molecular assemblies of copper(II) α,β-unsaturated
carboxylate complexes with TMP [OP(OMe)3], {Cu2A4(H2O)2[OP(OMe)3]}
n
[(1) A = CH2=CHCO2
−; (2) A = CH2=C(Me)CO2
−]. The crystal structure of (1) has been determined by single-crystal X-ray diffraction. Both complexes are unique in terms of a sheet structure brought
about by O—H ⋯ O hydrogen-bonded interactions both between neighbouring Cu2A4(H2O)2 units and between Cu2A4(H2O)2 and OP(OMe)3 molecules. The electronic reflectance spectra in the solid state suggest a square pyramidal coordination environment around
the copper(II) atom. Room temperature X-band e.s.r. spectra of powered samples and variable-temperature magnetic susceptibility
studies indicate the presence of strong antiferromagnetic exchange interactions between two copper(II) atoms, with 2J = −310 cm−1 for (1) and 2J = −304 cm−1 for (2) respectively.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
999.
Zhang Lei Xu Chao Guo Yaohao Zhu Guangpu Cai Shiyu Wang Xin Jing Wenlong Sun Hai Yang Yongfei Yao Jun 《Transport in Porous Media》2021,140(3):713-725
Transport in Porous Media - Pore scale immiscible displacement is crucial in oil industry. The surface roughness of throat is an important factor affecting water–oil interface movement. In... 相似文献
1000.
Zhao Xiaopeng Köbis Markus A. Yao Yonghong Yao Jen-Chih 《Journal of Optimization Theory and Applications》2021,190(1):82-107
In this paper, we propose a projected subgradient method for solving constrained nondifferentiable quasiconvex multiobjective optimization problems. The algorithm is based on the Plastria subdifferential to overcome potential shortcomings known from algorithms based on the classical gradient. Under suitable, yet rather general assumptions, we establish the convergence of the full sequence generated by the algorithm to a Pareto efficient solution of the problem. Numerical results are presented to illustrate our findings.
相似文献