Geometries of the Halocarbene anions HCF- and CF2-: ab initio calculation and Franck-Condon analysis

A theoretical method to calculate multidimensional Franck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectra of HCF- and CF2- radicals. Geometry optimization and harmonic vibrational frequency calculations have been performed on the (X) over tilde (1)A' state of HCF and (X) over tilde (2)A" state of HCF-, and (X) over tilde (1)A(1) state of CF2 and (X) over tilde B-2(1) state of CF2-. Franck-Condon analyses and spectral simulation were carried out on the first photoelectron band of HCF- and CF2- respectively. The theoretical spectra obtained by employing B3LYP/6-311 + G(2d,p) values are in excellent agreement with the observed ones. In addition, the equilibrium geometry parameters, R(CF) = 0.1475 +/- 0.0005 nm, of the (X) over tilde (2)A" state of HCF-, and r(FC) = 0.1425 +/- 0.0005 nm and angle(FCF) = 100.5 +/- 0.5degrees, of the (X) over tilde B-2(i) state of CF2-, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation. (C) 2003 Elsevier B.V. All rights reserved.

城市森林发展战略与生态规划

<正>1城市森林的概念及研究内容 1.1城市森林的提出及概念 城市森林这一概念的提出已有 30余历史,1962年,美国肯尼迪政 府在户外娱乐资源调查报告中,首 次使用“城市森林”这一名词。自 1965年加拿大Erik Jorgensen教授提 出城市林业概念以来,城市林业与 城市森林先后在北美、欧洲乃至全 球掀起了研究热潮。

基于GIS的绿地景观可达性研究——以沈阳市为例

目的利用GIS系统建立城市绿地可达性模型,评价绿地景观格局与服务功能,从而为城市绿地的规划、营建、格局优化、管理提供决策支持.方法基于物理势能模型,以人口密度、道路分布、土地利用以及绿地面积作为模型参数,建立了城市绿地景观可达性评价模型,该模型既强调城市绿地的空间分布格局的重要性,又强调城市绿地的为居民提供服务的有效性,并以沈阳市区城市绿地作为实例研究.结果研究表明(1)研究区可达性处于第1、2等级的绿地面积分别占68.08%、21.64%,沈阳市区的绿地分布格局基本合理,绿地可以为城市居民提供较好的服务;(2)研究区绿地可达性值分布存在一定空间聚集现象,显示较高的空间自相关性,明确了沈阳市区绿地建设的重点和方向.结论绿地景观可达性揭示了人们对城市绿地的利用程度,反映了城市绿地价值的空间分布,是城市绿地景观格局与功能评价的一次新尝试.

景观健康概念、特征及其评价

景观健康是近年来出现于景观生态学与新兴的生态系统健康学领域的一个新的生态学概念 ,旨在探讨人类强烈活动干扰下遭受严重污染与退化、甚至会逐渐消失的景观生态系统的健康问题 .本文针对目前所存在的有关景观健康的基本概念、景观健康的特征与标准进行了详细介绍 ,并就景观健康评价指标的确立、评价时空尺度与等级以及评价方法分别进行了探讨 .最后 ,还强调了在进行景观健康评价时应运用比较的、综合的以及发展的观点开展研究 .

Poly(L-lysine)-graft-chitosan copolymers: Synthesis, characterization, and gene transfection effect

Polypeptide/polysaccharide graft copolymers poly(L-lysine)-graft-chitosan (PLL-g-Chi) were prepared by ring-opening polymerization (ROP) of epsilon-benzoxycarbonyl L-lysine N-carboxyanhydrides (Z-L-lysine NCA) in the presence of 6-O-triphenylmethyl chitosan. The PLL-g-Chi copolymers were thoroughly characterized by H-1 NMR, C-13 NMR, Fourier transform infrared (FT-IR), and gel permeation chromatography (GPC). The number-average degree of polymerization of PLL grafted onto the chitosan backbone could be adjusted by controlling the feed ratio of NCA to 6-O-triphenylmethyl chitosan. The particle size of the complexes formed from the copolymer and calf thymus DNA was measured by dynamic light scattering (DLS). It was found in the range of 120 similar to 340 nm. The gel retardation electrophoresis showed that the PLL-g-Chi copolymers possessed better plasmid DNA-binding ability than chitosan. The gene transfection effect in HEK 293T cells of the copolymers was evaluated, and the results showed that the gene transfection ability of the copolymer was better than that of chitosan and was dependent on the PLL grafting ratio. The PLL-g-Chi copolymers could be used as effective gene delivery vectors.

Nature of the ring-banded spherulites in blends of aromatic poly(ether ketone)s

The ring-banded spherulites in liquid crystalline poly(aryl ether ketone) (LC-PAEK) and poly(aryl ether ether ketone) (PEEK) blends with a higher content (>50%) of LC-PAEK are investigated by polarizing light microscopy (PLM) and atomic force microscopy (AFM) techniques. The results indicate that the light core and rings of the ring-banded spherulites under PLM are mainly composed of an LC-PAEK phase, while the dark rings consist of coexisting phases of PEEK and a small amount of LC-PAEK. The formation of the ring-banded spherulites is attributable to structural discontinuity caused by a rhythmic radial growth.

H_2S气体在不同催化剂表面的电化学氧化行为

H2 S气体能对人体产生严重伤害。在环保、生产等领域对其进行检测 ,具有重要意义。本实验通过循环伏安、线性扫描、XPS等手段 ,研究H2 S、Pd、Pt、Rh和Au电极上的电化学氧化行为。实验表明 :Au在特定条件对H2 S具有良好的电催化活性 ,以Au为工作电极并选择合适工作条件 ,可以解决催化剂中毒问题 ,传感器灵敏度可达 0 .76 μA·m3 /mg。2　实验部分2 .1　仪器设备　三电极电化学池 ;CHI6 0 2电化学系统 (美国CHI公司 ) ;恒电位仪 (长春市环保分析仪器厂 )。2 .2　样品准备与测试条件　工作电极是将Pd、Pt、Rh和Au用树脂胶密封于玻璃管处理 ,备用 ;H2 S气体通过H3 PO4和Na2 S反应制得 ;电解质为 0 .5mol/L的H2 SO4;传感器电极制备是将胶体Au催化剂、铂黑催化剂喷涂到基底膜 ,淋洗、烧结后制成 ;电解槽内通入H2 S至饱和 ;光滑电极测试条件 :循环伏安扫描电位 - 1～ +1.6V ;XPS测试。传感器测试 :线性扫描曲线 (0 .0 0 1V/s) ;标准气体浓度 6 0、1976mg/m3 ;计时电流曲线 (0 .4 0...

1-苯基-3-甲基-4-苯甲酰基-吡唑酮-5与中性磷(膦)萃取剂协同萃取镧B

研究了 1 苯基 3 甲基 4 苯甲酰基 -吡唑酮 5 (HPMBP)和中性有机磷 (膦 )类萃取剂Cyanex 4 71X(TIBPS ,B)在硝酸介质中对稀土元素La 的萃取 ,用斜率法和恒摩尔法探讨了萃取机理 ,确定了萃合物的组成为La(NO3 ) 2 ·PMBP·B ,计算了萃取平衡常数。比较了HPMBP与Cyanex 4 71X、Cyanex 92 1、Cyanex 92 3、Cyanex 92 5、DEH/EHP、P35 0及TBP的单独及混合体系萃取La 的性能 ,结果表明 :所有混合体系对La 均有协同效应 ,其中HPMBP与Cyanex 92 3、Cyanex 92 1、Cyanex 92 5的混合体系是萃取La 的有效体系。

硝酸镥急性毒性的体液核磁共振氢谱研究

采用现代核磁共振技术 ,通过分析灌胃给药0.01、0.05、0.2、2、10和100mg/kg剂量Lu(NO3 )324h内大鼠尿液及24h后大鼠血清的核磁共振氢谱 (1HNMR) ,由体液中内源性代谢物浓度的变化研究了稀土化合物在动物体内急性毒性。较高剂量组体液中的氨基酸、尿囊素、柠檬酸、氮氧三甲胺和肌酸酐等重要内源性代谢物的核磁共振谱峰强度发生了明显的变化 ,说明动物体内的代谢物出现异常 :高剂量的稀土的引入可能使动物肾脏和肝脏均受到损害 ,且受损程度随稀土剂量的增高而渐趋严重。

原子力显微镜技术对生物样品的研究

评述了近几年原子力显微镜在生物样品中的应用情况。主要涉及利用原子力显微镜研究核酸 ,包括脱氧核糖核酸和核糖核酸、蛋白质、核酸与蛋白质复合物、细胞和病毒等 5个方面的最新进展。

Synthesis and properties of aromatic polyimides derived from 2,2,' 3,3 '-biphenyltetracarboxylic dianhydride

2,2,'3,3' -Biphenyltetracarboxylic dianhydride (2,2,'3,3'-BPDA) was prepared by a coupling reaction of dimethyl 3-iodophthalate. The X-ray single-crystal structure determination showed that this dianhydride had a bent and noncopolanar structure, presenting a striking contrast to its isomer, 3,3,'4,4'-BPDA. This dianhydride was reacted with aromatic diamines in a polar aprotic solvent such as N,N-dimethylacetamide (DMAc) to form polyamic acid intermediates, which imidized chemically to polyimides with inherent viscosities of 0.34-0.55 dL/g, depending on the diamine used. The polyimides from 2,2,'3,3'-BPDA exhibited a good solubility and were dissolved in polar aprotic solvents and polychlorocarbons. These polyimides have high glass transition temperatures above 283 degrees C. Thermogravimetric analyses indicated that these polyimides were fairly stable up to 500 degrees C, and the 5% weight loss temperatures were recorded in the range of 534-583 degrees C in nitrogen atmosphere and 537-561 degrees C in air atmosphere. All polyimides were amorphous according to X-ray determination. (C) 1999 John Wiley & Sons, Inc.

Electrochemical quartz crystal microbalance study of the electrochemical behavior of riboflavin at gold electrodes

The electrochemical and adsorption behaviors of riboflavin (RF) at gold electrodes has ken studied by using an electrochemical quartz crystal microbalance (EQCM). Useful information is obtained not only about electrochemical behavior but also about mass changes on the electrode surface. The electrochemical properties and frequency shifts were investigated in RF solutions at different pH values, concentrations and scan rates. Reversible voltammograms were observed for pH less than or equal to 9.71. There was no electrochemical reaction for pH > 9.71. The maximum current response was obtained at about pH 8. The current response was proportional to the square root of scan rates when the concentration of RF was lower than 1.0 x 10(-4) mol L-1 (pH 6.92). On the contrary, at concentrations higher than 1.0 x 10(-4) mol L-1 (pH 6.92), it was proportional to the scan rates.

1,4-二丙氧基-2,3二氰基萘的晶体结构

用 Siemens P4四圆衍射仪,测得了1,4-二丙氧基-2,3-二氰基萘的晶体结构。晶体属单斜晶系,空间群为 C2/C。晶格参数 a=14.987(3)A,b=10.527(2),c=11.755(2),β=118.98°(3),晶胞体积 V=1622.4(6)3,Z=4,Dc=1.205Kg/m~3,μ(MoK_α)=0.079mm~(-1),F(000)=624,T=293(2)K_o晶体结构应用直接法,解出最后的偏离因子 R=0.0554[1425个Ⅰ≥2σ(Ⅰ)衍射点]。结构分析表明,萘环的1,4和2,3位碳原子上的氢原子分别被丙氧基和氰基所取代,由于取代基的引入使萘环的结构有所改变。

Phase behavior in mixtures of a homopolymer and a block copolymer .4. SALS and SAXS studies

Phase behavior of blends of poly(vinyl methyl ether) (PVME) with four styrene-butadienestyrene (SBS) triblock copolymers, being of various molecular weights, architecture, and compositions, was investigated by small-angle light scattering. Small-angle X-ray scattering investigation was accomplished for one blend. Low critical solution temperature (LCST) and a unique phase behavior, resembling upper critical solution temperature (UCST), were observed. It was found that the architecture of the copolymer greatly influenced the phase behavior of the blends. Random phase approximation theory was used to calculate the spinodal phase transition curves of the ABA/C and BAB/C systems; LCST and resembling UCST phase behavior were observed as the parameters of the system changed. Qualitatively, the experimental and the theoretical results are consistent with each other. (C) 1996 John Wiley & Sons, Inc.