Aspergillines K and L,Two New Anti-TMV Indole Alkaloids from Fungus Aspergillus versicolor Derived from Tobacco

Chemistry of Natural Compounds - Two new (1 and 2) and four known (3–6) CPA-type indole alkaloids were isolated from the fungus Aspergillus versicolor. Their structures were determined by...     

Effects of pulse energy ratios on plasma characteristics of dual-pulse fiber-optic laser-induced breakdown spectroscopy

Laser-induced plasmas of dual-pulse fiber-optic laser-induced breakdown spectroscopy with different pulse energy ratios are studied by using the optical emission spectroscopy(OES)and fast imaging.The energy of the two laser pulses is independently adjusted within 0–30 m J with the total energy fixed at 30 m J.The inter-pulse delay remains 450 ns constantly.As the energy share of the first pulse increases,a similar bimodal variation trend of line intensities is observed.The two peaks are obtained at the point where the first pulse is half or twice of the second one,and the maximum spectral enhancement is at the first peak.The bimodal variation trend is induced by the change in the dominated mechanism of dual-pulse excitation with the trough between the two peaks caused by the weak coupling between the two mechanisms.By increasing the first pulse energy,there is a transition from the ablation enhancement dominance near the first peak to the plasma reheating dominance near the second peak.The calculations of plasma temperature and electron number density are consistent with the bimodal trend,which have the values of 17024.47 K,2.75×10¹⁷cm;and 12215.93 K,1.17×10¹⁷cm;at a time delay of 550 ns.In addition,the difference between the two peaks decreases with time delay.With the increase in the first pulse energy share,the plasma morphology undergoes a transformation from hemispherical to shiny-dot and to oblate-cylinder structure during the second laser irradiation from the recorded images by using an intensified charge-coupled device(ICCD)camera.Correspondingly,the peak expansion distance of the plasma front first decreases significantly from 1.99 mm in the single-pulse case to 1.34 mm at 12/18(dominated by ablation enhancement)and then increases slightly with increasing the plasma reheating effect.The variations in plasma dynamics verify that the change of pulse energy ratios leads to a transformation in the dual-pulse excitation mechanism.     

三维电磁扩散场数值模拟及磁化效应的影响

采用矢量有限元法实现了三维电磁扩散场数值模拟,并成功将其应用在大地电磁的正演研究中.为灵活精确地拟合起伏地形和地下不规则构造,采用由不规则四面体单元组成的非结构化网格,可根据模型设计的需要调整网格的大小.引入了基于二次场理论,将解析的一次场从总场中扣除,直接计算二次场,使得误差仅局限于相对较小的二次场,以提高总场计算精度.常规的节点有限元法不满足电性分界面上法向电场不连续和无源区单元内电流密度无散,违反麦克斯韦方程组.为克服节点有限元法的弊端,使用矢量有限元法求解基于二次电场的偏微分方程.另外,在算法设计中,考虑了磁导率参数的变化,可以模拟磁导率不均匀的模型.通过与COMMEMI模型已发表的结果对比,证明了本文算法的正确性和精确性.为突显非结构网格优势,计算了椭球异常体模型和任意地形模型的MT响应,并详细讨论了地形和磁化效应对三维数值模拟结果的影响.     

Room-Temperature Photonic Crystal Laser in H3 Cavity on InGaAsP/InP Slab

We fabricate and investigate two-dimensional photonic crystal H3 microcavities in an InGaAsP slab. The lasing action at room temperature is observed. The lasering threshold is 7mW under the pulsed pump of 0.75% duty cycle. The Q factor and the lasing mode characteristics are simulated by three-dimensional finite difference time domain method. The simulation result matches well with the experiment.     

光子晶体微腔中高偏振单偶极模的研究

三角晶格排列的光子晶体微腔中的偶极模式是简并的,通过改变其晶格的对称性可以消除模式简并.晶格的整体形变破坏了晶格对称性从而影响光场的分布,同时还改变了电磁场的偏振分布.晶格整体形变使得简并的偶极模式分离成x极和y极偶极模式.通过计算分析发现分离后的模式具有良好的偏振特性,从而为实现单偏振光子晶体激光器提供了一种很好的途径.文中针对光子晶体薄板结构的微腔,主要计算了偶极模中x极偶极模式在不同拉伸时以及不同填充因子情况下的Q值,并分别计算了x关键词： 光子晶体 偶极模 品质因子 偏振度     

C_(36)聚合体电子结构的理论研究

采用PM3 和DFT/B3LYP方法对2D六方网状,以及1D链状C36聚合体的构型进行全优化,探讨了其电子结构和稳定性;并在从头算水平上计算了相应的能带结构。研究发现,C36形成聚合体后构型发生了显著变化; 与0D 的结构比较,C36聚合为1D或2D结构后,笼内CC键长变化明显。计算表明C36聚合后稳定性提高,呈半导体或绝缘体性质。聚合后C36内部CC键定域化程度的增强是其稳定性提高的主要因素。     

Structures and solvatochromic phosphorescence of dicationic terpyridyl-platinum(II) complexes with foldable oligo(ortho-phenyleneethynylene) bridging ligands

A series of binuclear organoplatinum(II) complexes, [(tBu3tpy)Pt--(C[triple chemical bond]C--1,2-C6H4)n--C[triple chemical bond]C--Pt(tBu3tpy)][ClO4]2 (1-7, n=1, 2, 3, 4, 5, 6, 8; tBu3tpy=4,4',4'-tri-tert-butyl-2,2':6',2'-terpyridine) with foldable oligo(ortho-phenyleneethynylene) linkers were prepared and characterized by spectroscopic methods and/or X-ray crystallographic analyses. In the crystal structures of 32.5 CH3OH, 5CH3CN, and 64 CH3CN, each of the bridging ortho-phenyleneethynylene ligands has a partially folded conformation. In aerated water/acetonitrile mixtures with water percentages larger than 40 %, the emission of complexes 3-7 are red-shifted and enhanced when compared to those recorded in acetonitrile. The red-shift in emission energy and enhanced emission intensity can be attributed to the inter- and/or intramolecular interactions induced by the addition of water to solutions of the platinum(II) complexes in acetonitrile. Data from dynamic light scattering and transmission electron microscopy studies revealed that these binuclear platinum(II) complexes aggregated into nanosized particles in acetonitrile/water mixtures. Hydrophobic folding of the ortho-phenyleneethynylene linkers in acetonitrile/water mixtures is postulated.     

烯丙基溴化钐与α,β-不饱和醛酮反应合成高烯丙基醇

烯丙基溴与金属钐在室温条件下、THF溶剂中反应生成中间体烯丙基溴化钐,烯丙基溴化钐再与α,β-不饱和醛、酮反应生成高烯丙基醇.烯丙基溴化钐与α,β-不饱和醛、酮发生1,2-加成反应,其与α,β-不饱和酮的反应几乎定量进行,表明该反应具有很好的区域选择性.产物的结构通过IR,1H NMR和MS光谱确证.     

胆囊组织、组织细胞膜及细胞株的FTIR研究

研究了不同病理生理状态的胆囊组织、胆囊组织细胞膜及胆囊癌细胞株的傅里叶变换红外光谱的相关性.结果显示,与正常组织比较,胆囊癌组织中脂质相关谱带(2955,2920,2870,2850和1740 cm-1)与蛋白相关谱带(1550 cm-1)强度降低;胆囊癌细胞株中脂质相关谱带与蛋白相关谱带(1550 cm-1)强度明显增加;胆囊癌组织细胞膜中脂质相关谱带强度明显增加;核酸相关吸收谱带强度变化在胆囊癌组织和胆囊癌细胞株中一致,在细胞膜中消失;I1460/I1400比值在组织、细胞株和细胞膜层面变化一致,与正常组织相比均有所减少.结果表明,与胆囊癌组织相比,胆囊癌细胞株和胆囊癌组织细胞膜的红外光谱发生了显著变化:癌组织的脂类和蛋白质的相对含量降低;癌细胞株的脂质和蛋白相对含量增加;胆囊癌组织细胞膜的脂质和蛋白相对含量升高.从组织、细胞和细胞膜3个层面阐述了癌变的分子光谱变化.I1460/I1400比值的变化在组织、细胞株和细胞膜层面变化一致,对此指标的深入研究有望获得一个良好的临床诊断指标.     

R404A/CO2复叠式制冷系统的熵分析

为了研究R404A/CO₂复叠式制冷系统的性能,对其进行了热力学分析。采用理论计算和熵产最小法分析蒸发温度T_e、冷凝温度T_k、冷凝蒸发器的传热温差△T等参数对该系统的性能、部件及整个系统的熵产的影响。结果表明,给定T_e、T_k和△T时,在最佳低温级冷凝温度下,系统COP取得最大值,系统总熵产取得最小值;高温级节流阀和压缩机、冷凝蒸发器和低温级压缩机的熵产约占总熵产的80%。