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991.
992.
Ai Jun HOU Hui YANG Bei JIANG Qin Shi ZHAO Yan Ze LIU Zhong Wen LIN Han Dong SUN Laboratory of Phytochemistry Kunming Institute of Botany Chinese Academy of Sciences Kunming Department of Phytochemistry Henan College of Traditional Chinese 《中国化学快报》2000,11(9)
In continuation of our research on diterpenoids in the Isodon species, several newcompounds"' were obtained from the leaves oflsodon xerophilus (C. Y. Wu et H. W. Li)H. Hara (Labiatae), a perennial shrub native to Yunnan province. Further fractionation ofthe EtOAc extract led to the isolation of tWo new enl-kauranoids, xerophilusin E (l) andxerophilusin F (2). This paper deals with the structUral elucidation of the newcompounds.Xerophilusin E (l), a minor constitUent, was obtained as p… 相似文献
993.
994.
负载贵金属光催化剂的光催化活性研究 总被引:13,自引:0,他引:13
在注入V离子的二氧化钛光催化剂上负载贵金属,制备了在可见光照射下具有高光催化活性的功能型光催化剂,研究在可见光和太阳光照射下丙炔的光催化水解反应,利用这些改性的二氧化钛构筑太阳能到化学能的转换系统.研究结果发现了V/Pt光催化剂在丙炔和水的光催化水解反应中,由于贵金属的存在,有利于促进发生加氢反应;导致丙烯的生成量增加.在可见光下的光催化活性也和负载贵金属所处的氧化状态有着密切的关系,贵金属完全被还原到0价是提高光催化活性的必要条件. 相似文献
995.
Bisfunctionalized m-phenylene ethynylene imine oligomers were polymerized in the polar solvent acetonitrile, resulting in high-molecular weight poly(m-phenylene ethynylene imine)s. It is hypothesized that this polymerization, which proceeds through the reversible metathesis of imine bonds, is driven by the folding of the long m-phenylene ethynylene imine chains. Upon conducting the polymerization in a series of solvents in which the m-phenylene ethynylene oligomers exhibit different folding stabilities, it was possible to correlate the molecular weight of the resulting poly(m-phenylene ethynylene imine)s with the helical stability of the corresponding oligomers. The polymerization was also demonstrated to be reversible and responsive to solvent and temperature changes. 相似文献
996.
Marta Gonzlez‐lvarez Gloria Alzuet Jos Luis García‐Gimnez Benigno Macías Joaquín Borrs 《无机化学与普通化学杂志》2005,631(11):2181-2187
Three flavonoid copper(II) complexes Cu2(quercetin)(CH3COO)3(CH3OH) ( 1 ), Cu(anthrarufin)(CH3COO)·1/2H2O ( 2 ) and Cu(naringin)(OCH3)(CH3OH)2 ( 3 ) have been synthesized and characterized by elemental analysis, IR, electronic absorption and EPR (X‐band) spectroscopy. The complexes have a strong protective action over the Δsod1 mutant of S. cerevisiae against reactive oxygen radicals generated by an external source of free radicals (H2O2 or the superoxide‐generating, menadione). On the other hand, the complexes cleave DNA efficiently even in the absence of reducing agents. The main reactive oxygen species responsible for the DNA strand cleavage have been determined using radical scavengers. A probably mechanism of the DNA damage is proposed. 相似文献
997.
The geometries of the most stable isomers of gold telluride systems AuTe, Au2Te, and AuTe2 are determined using the MP2 method. The aspect of gold—telluride interaction, the electron correlation, and relativistic
effects on geometry and stability are investigated at the MP2 and CCSD(T) theoretical levels. The results show that the electron
correlation and relativistic effects are responsible not only for gold—gold attraction but also for additional gold—telluride
interaction. The gold—telluride interaction is strong enough to modify the known pattern of bare gold clusters. Both effects
are essential for determining the geometry and relative stability of this type of systems. 相似文献
998.
Shi Liang HUANG Yi LUO Zhi Shu HUANG Xian Zhang BU Pei Qing LIU Lin MA Yue Ming LI Albert S. C. CHAN Lian Quan GU 《中国化学快报》2006,17(6):769-772
Mansonone compounds represent a series of naturally occurring o-quinones mainly isolated from the heartwood of Mansonia Altissima1 and Ulmus Glabra2. Mansonone F contained oxaphenalene skeleton which was a relatively novel structure and rarely existed in … 相似文献
999.
L.L. Chen H.P. He Z.Z. Ye Y.J. Zeng J.G. Lu B.H. Zhao L.P. Zhu 《Chemical physics letters》2006,420(4-6):358-361
Li-doped ZnO thin films were prepared on glass substrates by DC reactive magnetron sputtering. The influence of post-annealing temperature on the electrical, structural, and optical properties of the films was investigated. A conversion from p-type conduction to n-type in a range of temperature was confirmed by Hall measurement. The optimal p-type conduction is achieved at the annealing temperature of 500 °C with a resistivity of 57 Ω cm, carrier concentration of 1.07 × 1017 cm−3 and Hall mobility of 1.03 cm2 V−1 s−1. From the temperature-dependent PL analysis, the energy level of LiZn acceptor was determined to be 140 meV above the valence band. 相似文献
1000.
Study on oxidation of polymers treated by high LET radiation 总被引:2,自引:0,他引:2
Wang Ruiyu Ha Hongfei Wang Yugang Zhao Weijiang Yan Sha Jin Changwen Wang Guanghui Wu Jilan 《Radiation Physics and Chemistry》1998,52(1-6):251-256
The oxidation of medical silicone rubber and segmented polyether urethane which were bombarded with 11.2 MeV Si+ or F+ at the dose of 5 × 1014 ions/cm2 was studied. In XPS measurements, it was found that the oxygen concentration on the surface of the implanted polymeric membranes had been increasing in three months at least. ESR measurement showed that some free radicals existed in these membranes and their quantities decreased with time. Chemical analysis proved that peroxides were generated in the γ irradiated membranes. The reason for the increasing of oxygen concentration was that free radicals combined with oxygen in the air and produced peroxides on the membrane surface. Moreover, in order to demonstrate the radiation mechanism, low LET (γ rays) radiation of such polymeric membranes was carried out for comparison 相似文献