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Quan Xiang WE Xia LIU Yan Ping SHI 《中国化学快报》2005,16(11):1477-1480
A novel dimeric eremophilane, ligulolide B, was isolated from the alcoholic extract of the whole plant of Ligularia virgaurea spp. oligocephala. The structure was elucidated by various spectroscopic methods including intensive 2D NMR techniques (^1H-^1H COSY, gHMQC, gHMBC and ^1H-^1H NOESY) and HR-ESI-MS. 相似文献
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基于可调谐光纤环形镜滤波器的多波长布里渊掺铒光纤激光器 总被引:7,自引:7,他引:0
通过使用非线性放大的光纤环形 镜滤波器(AFLMF),构造了一种新颖的多波长布里渊掺铒光纤激光器(E DFL)线形结构。非线性AFLMF由掺铒光纤放大器(EDFA,由980n m泵浦抽运 一段EDF构成)、偏振控制器(PC)和耦合器构成,减少了腔内基于波长的损耗,并且能够灵 活地控制反射 光以及激光腔内输入和输出光的强度。在布里渊泵浦功率为25mW、 980nm泵浦功率为200mW时,获得了波 长间隔为0.08nm的14个波长的激光输出以及50nm的可调谐范围。通过调节980nm抽运光功率、PC以及布里渊泵浦光波长,实现了可调谐的多波长输出。研究 了980nm抽运光功率以及PC对斯托克斯光波数的影响。 相似文献
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以香豆素为基用以识别氟离子的新型比色化学传感器 总被引:2,自引:1,他引:1
以香豆素作为发色团,胺基为氢键供体,以—C=N键桥连设计合成了可裸眼识别氟离子的化学传感器1,吸收光谱结果表明在乙腈中它可以高选择性识别氟离子,光谱红移70 nm,溶液颜色由橙色变为蓝紫色,而其它离子如Cl~-、Br~-、I~-、H_2PO_4~-、NO_3~-、HSO_4~-、AcO~-等均不影响其对氟离子的识别.通过核磁共振氢谱考察其识别机制,表明传感分子通过与F~-间的质子转移反应,使整个体系电子离域,分子内电荷转移更加显著,从而导致吸收光谱大幅红移. 相似文献
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By means of a noncommutative differential calculus on function space of discrete Abelian groups and that of the regular lattice with equal spacing as well as the discrete symplectic geometry and a kind of classical mechanical systems with separable Hamiltonian of the type H(p, q) = T(p) + V(q) on regular lattice, we introduce the discrete symplectic algorithm, i.e., the phase-space discrete counterpart of the symplectic algorithm including original symplectic schemes and the jet-symplectic schemes in terms of the discrete time jet bundle formalism, on the regular lattice. We show some numerical calculation examples and compare the results of different schemes. 相似文献
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Research suggests that pretrial publicity influences trials. Past research has relied heavily on experimental methods. Several commentators have questioned the ecological validity of the studies, and hence the value of the findings. The present study, one of the first to examine actual trials, focused on all federal murder trials over a 3-year period. The results suggested that (a) greater probability of conviction was associated with low rather than high levels of publicity; (b) defendants fared better under moderate rather than no publicity levels; and for defendants who were convicted, any degree of pretrial publicity was associated with longer sentences. In general, the results obtained from studying actual trials differed in important ways from the results obtained in laboratory research. 相似文献