A Novel Dimeric Eremophilane from Ligularia virgaurea spp. oligocephala

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.     

Determination of cerium in fission products by extraction with di(2-ethylhexyl)phosphoric acid

Summary The extraction of cerium, oxidized to the tetravalent state, from nitric acid medium by di(2-ethylhexyl)phosphoric acid in hexane was studied. The effect of nitric acid concentration, agent concentration, oxidizer amount, and carrier concentration on the yield of cerium extraction was investigated and the optimum conditions of the extraction were found. Under these conditions, the reproducibility of the method was determined and the extraction of other fission products (Sr, Cs, Zr, and Ru) was also tested. The procedure was verified by the determination of cerium in artificial and real mixtures of fission products.

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Zusammenfassung Es wurden Untersuchungen angestellt über die Extraktion von vierwertigem Cer aus salpetersaurer Lösung mit Hilfe von Di-(2-äthylhexyl)-phosphorsäure in Hexan. Im einzelnen wurde der Einfluß der Konzentration an Salpetersäure, Reagens, Oxydationsmittel und Träger auf die Extraktionsausbeute geprüft und die optimalen Bedingungen festgelegt. Weiterhin wurde die Reproduzierbarkeit des Verfahrens bestimmt und bei der Anwendung auf künstliche und natürliche Gemische von Spaltprodukten das Verhalten der anderen Elemente (Sr, Cs, Zr, Ru) untersucht.

     

一类齐次对称多项式上的切比雪夫不等式

本文借助于控制不等式及数学归纳法，将著名的切比雪夫不等式推广到m次一般齐次对称多项式上(如文中定理及引理7)，并将此结果用于对称平均等．旨在展示证明解析不等式的一些有效的方法和技巧，同时为数学研究特别是高维几何研究提供一些新的有趣而有用的解析不等式．     

Strengthening of some spinodal binary and pseudobinary copper alloys

Age hardening and microstructure (TEM) in the Cu-Ni-Sn and Cu-Ti alloys is studied. The annealing curves with a plateau and a double peak are discussed with respect to the structure development.     

用ZEMAX软件辅助迈克耳孙干涉仪实验教学

利用ZEMAX软件设计了迈克耳孙干涉仪实验光路.软件绘制的不同显示方式的实验光路外形图,使学生对实验光路建立起了清晰的图像.通过编写ZPL程序实现了对实验现象的动态模拟,使学生对理想情况下的实验现象有一个准确的把握.通过在软件中改变光路主要参数分析了不同方面和不同程度的误差对干涉条纹的影响,其结论对学生在实验中进行有效而准确的调节起到了指导作用.     

Multidimensional analyses of voicing offsets and onsets in female speakers

This study investigates cross-speaker differences in the factors that predict voicing thresholds during abduction-adduction gestures in six normal women. Measures of baseline airflow, pulse amplitude, subglottal pressure, and fundamental frequency were made at voicing offset and onset during intervocalic /h/, produced in varying vowel environments and at different loudness levels, and subjected to relational analyses to determine which factors were most strongly related to the timing of voicing cessation or initiation. The data indicate that (a) all speakers showed differences between voicing offsets and onsets, but the degree of this effect varied across speakers; (b) loudness and vowel environment have speaker-specific effects on the likelihood of devoicing during /h/; and (c) baseline flow measures significantly predicted times of voicing offset and onset in all participants, but other variables contributing to voice timing differed across speakers. Overall, the results suggest that individual speakers have unique methods of achieving phonatory goals during running speech. These data contribute to the literature on individual differences in laryngeal function, and serve as a means of evaluating how well laryngeal models can reproduce the range of voicing behavior used by speakers during running speech tasks.     

Noncommutative Differential Calculus Approach to Discrete Symplectic Schemes on Regular Lattice

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.     

以香豆素为基用以识别氟离子的新型比色化学传感器

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.