Viscosalines B1,2 and E1,2: Challenging New 3‐Alkyl Pyridinium Alkaloids from the Marine Sponge Haliclona viscosa

Four new 3‐alkyl pyridinium alkaloids, the viscosalines B₁ ( 1 a ), B₂ ( 1 b ), E₁ ( 2 a ), and E₂ ( 2 b ), were isolated from the Arctic sponge Haliclona viscosa. The structure elucidation of these isomeric compounds was challenging due to ambiguous fragments that derive during “standard” mass spectrometric fragmentation experiments. The final structure elucidation relied on the use of a combination of synthesis, liquid chromatography, and mass spectrometry. Three different mass spectrometers were used to differentiate between the synthetic structural isomers: a time‐of‐flight (TOF) mass spectrometer and two ion‐trap mass spectrometers with different ion‐transfer technologies (i.e., skimmer versus funnel optics). Although at first none of the spectrometers returned spectra that permitted structure elucidation, all three mass spectrometers provided analysis that successfully differentiated between the isomers after thorough method optimization. The use of in‐source collision‐induced dissociation (CID) with the ion trap and TOF instrument returned the most interesting results. The mode of fragmentation of the viscosalines under different experimental conditions is described herein. After successful optimization of the mass spectrometric method applied, the chromatographic method was improved to distinguish the previously inseparable isomers. Finally, both the liquid chromatography and mass spectrometric methods were applied to the natural products and the results compared to those from the synthetic compounds.     

Boron nitride nanotubes with quadrangular cross sections: Density functional studies

Density functional theory (DFT) calculations have been performed to investigate the availabilities and properties of boron nitride nanotubes (BNNTs) with quadrangular cross sections. To achieve the purposes, the original structure of a representative BNNT was individually decorated by the carbon and silicon atoms to make the C-BNNT and Si-BNNT models. The sp³ hybridizations were set for the C and Si atoms to make possible the formation of the quadrangular cross sections for the BNNTs. The optimized results indicated that the investigated models could be stabilized; however, they showed different properties. The atomic scale properties based on computations of quadrupole coupling constants (C_Q) also approved different properties for the C-BNNT and Si-BNNT models. Moreover, the C_Q parameters indicated that the properties of C-BNNT could be considered similar to the original BNNT; however, more discrepancies were observed for the Si-BNNT.     

730 eV电子碰撞He原子(e, 2e)电离的三重微分截面

考虑初态He原子电子间的关联效应、末态敲出电子与剩余束缚电子间的关联效应和末态屏蔽效应, 计算和分析了在共面、大能量损失和小动量转移这一特殊几何条件下730eV电子离化He原子的三重微分截面. 所得结果与Stevenson等人的相对实验数据和CCC理论计算结果进行比较发现: 所得到的理论曲线能够反映实验数据给出的三重微分截面的结构特征.     

O+DC1→OD+Cl反应在~3 A″势能面上的动力学研究(英文)

在~3A″势能面上,在散射能为14～20 kcal/mol的范围内,运用准经典轨线方法对O+DCl→OD+Cl进行了动力学研究.我们发现积分散射截面随着散射能的增加而增大,产物OD的振动分布发生了很强的粒子数的反转现象,且振动激发较弱、转动激发较强.后向散射居于主导地位,碰撞能的变化对产物转动取向的影响不大.     

基质折射率对反常色散散射体散射特性的影响

基于Mie散射理论,给出了散射强度、散射截面及吸收截面的计算公式,并对不同基质中碳化硅材料在反常色散区中的散射特性进行了数值计算与理论分析。结果表明,在反常色散区中,随着基质折射率的增大,散射强度的峰位发生红移,峰值增大;散射截面和吸收截面的峰位发生红移,峰值减小,这为该材料在反常色散区中的光学理论、实验及应用方面提供了理论参考。     

空气下无配体钯催化二苯胺和卤代芳烃的C—N偶联

研究了空气下无配体Pd(OAc)2在弱碱碳酸钾存在下催化二苯胺和溴代芳烃的C—N偶联合成三苯胺类化合物.与传统合成方法相比,该反应可以在无配体存在下在空气和温和的条件下进行,即,无需无水无氧操作条件,操作特别方便.催化剂用量、碱、溶剂、反应温度、反应时间等因素对反应的影响均做了考察.优化的反应条件是:在Pd(OAc)2(3 mol%)和K2CO3(1.5 equiv.)存在下,二苯胺和溴代芳烃在DMSO中在空气下在90℃加热24 h.溴代芳烃上的吸电子基团和二苯胺上的给电子基团有利于该偶联反应的进行,其中4-硝基三苯胺的产率高达93%.     

Theoretical investigation on electron scattering by benzene in the intermediate-energy range

We present a theoretical investigation on electron scattering by benzene (C₆H₆) in the intermediate-energy range. Calculated elastic differential, integral, and momentum-transfer as well as total (elastic + inelastic) and total absorption cross sections are reported for impact energies ranging from 20 to 500 eV. A complex optical potential is used to represent the electron-molecule interaction dynamics. A theoretical method based on the single-center-expansion close-coupling framework and corrected by the Padé approximant [F.A. Gianturco, R.R. Lucchese, N. Sanna, J. Chem. Phys. 102 (1995) 5743] is used to solve the scattering equations. The comparison of our calculated results with the experimental and theoretical data available in the literature is encouraging.     

散射粒子的相互作用对He(e,3e)五重微分截面的贡献

计算了敲出电子等能分享几何安排下,入射能量分别为5 599 eV和1 099 eV时He(e,3e)反应五重微分截面,并比较在He(e,3e)过程中散射粒子的相互作用和它们之间的干涉效应对五重微分截面的贡献.结果表明,理论计算数据在误差范围内与实验数据基本吻合,并且散射粒子的相互作用以及干涉效应对五重微分截面的影响都是不容忽视的.     

对酒精-水小孔周期性泄流的实验与分析

介绍酒精-水周期性泄流实验的装置,阐述实验现象,记录实验数据并进行归纳整理,用计算机软件描绘图形,通过反复实验和分析,得出与以往盐水-水等不一样的酒精-水小孔周期性泄流的振荡规律.