A new dimeric iridal triterpenoid from Belamcanda chinensis with significant molluscicide activity

An unprecedented dimeric triterpenoid, designated dibelamcandal A, with a six-membered ring linking two iridal type triterpenoid nuclei, was isolated from the rhizome of Belamcanda chinensis. Its structure was determined by extensive spectroscopic measurements, including IR, ESI-MS, HR-ESI-MS, and 1D and 2D NMR. It demonstrated significant molluscicide activity against Pomacea canaliculata.     

固体中圆柱形空腔上爬波的光弹法实验研究

本文用光弹法在玻璃内直接看到了弹性波爬波现象,当超声垂直轴向投射于固体内的圆柱形空腔时,在声的几何阴影区会激发出一种沿空腔界面爬行的表面波,它边爬边辐射体波,从而在几阴影区产生超声的散射波。我们观察了纵波入射和横波入射两种情况,分别测量了爬波的脉冲速度。实验表明,纵波入射时,固体中情况和流体中情况大体一样,但横波入射时,固体中情况要复杂得多。 此外,还附带观察了超声波从圆弧一侧投射到玻璃内半圆柱形空腔时的爬波行为。     

Demonstration of a phosphazirconocene as a catalyst for the ring opening of epoxides with TMSCl

[reaction: see text] In this study, it was demonstrated for the first time that a phosphazirconocene catalyzes the ring opening of epoxides with TMSCl. This reactivity leads to a facile preparation of chlorohydrins. The late transition metal Fe analogue was found to catalyze the reaction at rates and stereoselectivity comparable to those of the Zr complex.     

光源参数及大气湍流对电磁光束传输偏振特性的影响

根据光束扩展理论,以部分相干的电磁高斯-谢尔光束为研究对象,分析了电磁光束传输时其偏振特性的变化机理.结果表明,光源参数和大气湍流对电磁光束分量扩展的影响是导致传输过程中电磁光束偏振特性变化的原因.在真空中传输时,电磁光束两分量的相干性存在差异,导致传输时电磁光束两分量扩展快慢不同,从而引起传输路径上光束谱偏振度的变化.在大气湍流中,电磁光束两分量扩展的快慢与光源参数和大气湍流强度均有关,当传输路径较短时,电磁光束偏振变化主要与光源参数有关,变化特性与在真空中传输时的情况类似,而传输距离较远时,电磁光束偏振变化受大气湍流的影响明显,变化特性与在真空中传输时的情形存在不同.     

超窄线宽激光——激光稳频原理及其应用

自从20世纪激光发明以来,激光的应用已经深入到我们生活的各个方面,如光刻机、激光3D打印、激光医疗、大型激光干涉引力波探测等。在科学研究上,激光是一种不可或缺的重要光源,它以其优异的光谱特性被应用于许多研究领域,尤其是超窄线宽的高稳定度激光可以作为一双独特“眼睛”,能够用来观察原子分子的微观物理世界。如果以这种高稳定度激光来探测原子或离子的光谱特征,并将激光频率锁定在原子或离子的能级跃迁上,能形成计时无比精准的“光学原子钟”。这种新型的时钟具有前所未有的计时精度,它的累积误差将可以做到从宇宙起源(137亿年前)至今仍小于1秒！获取这种超窄线宽的高稳定度激光是一项关键且非常重要的技术,文章详细介绍了该项技术的发展历程和基本原理,以及它的几项重要的用途和前沿进展。     

金纳米粒子-荧光素体系的光谱特性

纳米粒子具有量子尺寸效应和表面效应等许多特有的性质 [1] ,在光吸收、医药及新材料等方面具有广阔的应用前景 .纳米粒子具有较高的比表面能且带有电荷 ,当光子与其接近时 ,实际上是光子与纳米粒子的界面电子发生了作用 [2 ,3 ] .基于此建立的共振散射 (RS)光谱技术已成为一种高灵敏度和高选择性的分析技术 ,是研究生物化学和液相纳米粒子特性的良好手段 [4～ 9] .我们 [2 ,3 ] 研究发现 ,较大粒径纳米粒子和界面的形成是导致散射光增强的根本原因 ;金、银等液相纳米粒子产生 RS效应和 RS峰等 .荧光猝灭 (FQ)效应已用于分析化学和蛋白…     

Chemical Constituents from Notoseris Species

The genus Notoseris (Asteraceae) comprising of 14 species is endemic in China^[1]. Two new sesquiterpene lactones,notoserolides A and B,along with 12 known compounds were isolated from the aerial parts of N. Porphyrolepis^[2], but nothing is known about secondary metabolites of other N species.     

Enhanced optical absorption by Ag nanoparticles in a thin film Si solar cell

Thin film solar cells have the potential to significantly reduce the cost of photovoltaics. Light trapping is crucial to such a thin film silicon solar cell because of a low absorption coefficient due to its indirect band gap. In this paper, we investigate the suitability of surface plasmon resonance Ag nanoparticles for enhancing optical absorption in the thin film solar cell. For evaluating the transmittance capability of Ag nanoparticles and the conventional antireflection film, an enhanced transmittance factor is introduced. We find that under the solar spectrum AM1.5, the transmittance of Ag nanoparticles with radius over 160 nm is equivalent to that of conventional textured antireflection film, and its effect is better than that of the planar antireflection film. The influence of the surrounding medium is also discussed.     

Ionic crystals of {[Ni(phen)3]2Ge4S10}·xSol, showing solid-state solvatochromism and rapid solvent-induced recrystallization

Thiogermanates, {[Ni(phen)(3)](2)Ge(4)S(10)}·xSol (Sol = 4MeOH·12H(2)O (1) and 24H(2)O (2)) were prepared and characterized by single-crystal structure analysis. There are large quantities of the solvent molecules that cocrystallize with the anions and cations and form a strong hydrogen bonding network (O-H···S and O···H-O-H···O). Reversible yellow-pink color change with fast speed was found for these compounds, when the crystals were immersed in alcohol solvents and water alternately. The time of the solvent-induced color change relates to the molecular size and structure of the alcohols. The smaller the molecule is, the faster the color change will be. The fastest color change was found by using the methanol solvent that took only about one second. The color change also relates to the ratio of water/alcohol. The solvatochromism phenomenon is accompanied with a rapid solvent-induced recrystallization that is verified by the XRD patterns.