Sr原子自电离谱线的观察和分析

本文报道了用偏振光束分步激发的方法,对Sr原子(5p_(1/2~(ns)))_(J-1)及(5P_(1/2~(nd))_(J-1,3)自电离谱的观察,测定了Sr的(5P_(1/2~(ns))_(J-1)系列(n=10～26)的自电离能级位置和量子亏损,并对(5P_(1/2~(ns))_(J-1)及(5P_(1/2~(nd))_(J-1,3)两种自电离谱线的不同特点进行了分析.     

纯位移核磁共振氢谱及其应用

J耦合引起的核磁共振(NMR)信号多重裂分的数目和耦合常数反映了磁性原子核之间的化学键数目和空间位置信息,是研究分子结构的重要依据之一.但是当分子中磁性原子核数目增加时,NMR谱图特别是一维核磁共振氢谱(1D ~1H NMR)中,J耦合所致的多重裂分造成谱图重叠,严重干扰结构指认和定量分析.利用纯位移(亦称宽带同核去耦)~1H NMR谱图可以消除J耦合效应(即将相邻质子间耦合所引起的多重裂分融合成一个单峰),得到与去耦碳谱相似的、只含化学位移信息的谱图.该文首先介绍了三种最受关注的获取纯位移核磁共振氢谱技术——BIRD、ZS和PSYCHE的基本原理,随后综述了纯位移~1H NMR谱图的典型应用.     

钕、铽(Ⅲ)硝酸盐、水杨醛乙二胺双席夫碱、二甲亚砜三元配合物的NMR研究

用NMR的方法研究了新型稀土配合物:钕、铽(Ⅲ)硝酸盐与N,N-二亚水杨基乙二胺双席夫碱、二甲亚砜三元配合物的结构,并利用二维质子NOE谱和异核多量子相关谱完全归属了它们的质子和¹³C信号.     

新型菁类染料聚集体构筑和它的非线性光学特性研究

采用旋涂法制备了一种五甲川菁染料的超薄膜,利用原子力显微,椭偏仪、UV-Vis吸收光谱、红外光谱、小角X射线衍射等对薄膜的形貌和线性光谱性质进行了研究表征,结果表明染料在薄膜中形成了有序而稳定的J-聚集体,前向简并四波混频(DFWM)技术研究表明由于分子的聚集作用引起三阶非线性极化率的增大(χ(3)=2.55×10-12esu),利用激子耦合模型初步分析和讨论了产生非线性效应增强的内在机制。     

多脉冲序列可编程辅助控制器及其应用

本文描述了一种以单板机为基础的多脉冲序列可编程辅助控制器(PCMP),在常规液体NMR谱仪上实现多脉冲实验。应用PCMP获得了固体的J-耦合化学位移各向同性谱、化学位移缩窄谱,同时也可以完成时间平均旋进频率交叉极化实验以及组合脉冲宽带去耦实验,进一步开拓了常规液体谱仪的功能。     

用1H-NMR-Eu (fod)3位移谱研究3-(2,2,2-三氯乙烯基)-2,2-二甲基环丙烷羧酸甲酯的立体构型

本文用¹H-NMR-Eu （fod）₃位移谱鉴定了(1RS)-3-(2,2,2-三氯乙烷基)-2,2-二甲基环丙烷羧酸甲酯的顺、反异构体,测出其三元碳环质子的耦合常数³J=5.5Hz (顺式)、4Hz (反式),并以此确定构型。根据质子极限位移的测定值与假接触位移公式,求出两种配位物合理的配位参数,并由此计算出其顺、反异构体的羰基与Eu（fod）₃配位能力的比值。     

N—甲基异靛蓝在不同溶剂中的^1H—NMR研究

用选择照射方法研究了N-甲基异靛蓝(isoindigatin)在(CD_3)_2CO、CDCl_3、DMSO-d_6溶剂中及重水交换后的~1H NMR谱。得到了化学环境极为类似的两芳环质子在不同溶剂中的NMR谱线归属和偶合常数。     

晶体NiX2(X=Cl,Br,I)的光谱和电子顺磁共振谱研究

在强场耦合图像中,采用双自旋-轨道耦合(SO)参量模型建立了过渡族3d2(3d8)离子的三角对称下全组态光谱能级和电子顺磁共振(EPR)公式.与经典的晶体场理论(仅考虑中心金属离子的自旋-轨道耦合作用)相比较,该公式还包括了配体离子的自旋-轨道耦合作用的贡献,这一模型在应用于计算共价性较强的晶体光谱和电子顺磁共振谱可得到合理的结果.作为验证,用完全对角化方法研究了品体NiX2(X=Cl,Br,I)的光谱和电子顺磁共振谱,结果表明,理论与实验很好地符合.建立的全组态谱能级和电子顺磁共振公式为更精确地计算光谱和电子顺磁共振谱提供了一条可行方法.     

尼龙6结晶和动力学的固体高分辨^13C NMR研究

用MSL—400核磁共振(NMR)波谱仪记录了尼龙6的~(13)C交叉极化魔角旋转(CP/MAS)NMR谱,发现固态下ω碳原子有两个峰,尼龙6记为ω_1和ω_2。在同一样品的~(13)C NMR溶液谱中,这两个峰合并成一个峰,证明固态尼龙6中两种晶区是共存的。在固态,ω_2峰比ω_1峰向高场偏移2.2ppm。测量了尼龙6—系列不同接触时间的CP/MAS NMR谱以研究动态行为。用SIMPLEX非线性最小二乘法拟合技术计算了交叉极化速率和质子T_(1ρ)~H用Ngai公式计算了固态尼龙6的运动参数。     

2D EXSY实验和几何平均法研究水与天然化合物的羟基之间的化学交换速率常数

利用二维核磁共振交换谱(2DEXSY)研究了三种天然产物的羟基质子与水的交换,三种天然产物分别含有四到八个羟基质子.较为简单的几何平均法(GA)被用来进行数据处理.GA法在假定体系和实际体系中,与全矩阵分析和初级速率近似比较,结果尚好。     

Peculiarities of the spectral-angular distribution of transition radiation from a relativistic particle in a dihedral angle

The spatial distributions of transition radiation from relativistic particles entering and exiting the edge of a dihedral angle formed by perfectly conducting flat surfaces have been investigated. The angular distributions of the radiation intensity in dihedral angles with various opening angles have been calculated. The angular distributions of forward radiation (when the particle exits the dihedral angle) and backward radiation (when the particle enters the dihedral angle) are shown to differ significantly.     

Torsional barriers and nonlinear optical properties of 2-, 3-, 4-phenylpyridine molecules

The torsional barriers and nonlinear optical properties for all phenylpyridine molecules were calculated by using Hartree-Fock (HF) theory and Becke three-parameter functional (B3LYP) hybrid approaches within the density functional theory framework with the 6-31++G(d, p) basis set, and via the GAUSSIAN 98W. The torsional barrier computations show that dihedral angle between the two rings increases with the number of H-H vicinal interactions and torsional barriers with dihedral angles for 3-, 4-phenylpyridines are too similar for both HF and B3LYP level calculations. Also, HOMO-LUMO energy gaps, polarizabilities, anisotropy of polarizabilities, and static hyperpolarizabilities are calculated as a function of dihedral angle between benzene and pyridine rings. The study reveals that the phenylpyridines show very low nonlinear optical properties. The calculated torsional barrier, equilibrium dihedral angle and molecular dipole moment results for these molecules were compared with available experimental and other results determining from different computational methods.     

Transition radiation in a dihedral angle formed by perfectly conducting planes

The spatial distribution of the field of transition radiation generated by a relativistic particle flying into a dihedral angle formed by perfectly conducting plane surfaces is determined. The cases when particles are injected from the edge and from a plane of the dihedral angle are considered. The angular distributions of radiation intensity in dihedral angles of different values are calculated.     

Improving amplitude-modulated signals by re-scaled and twice sampling vibrational resonance methods

Quantum chemical calculations have been employed to study the molecular effects produced by \(\hbox {Cr}_{2}\hbox {O}_{3}/\hbox {SnO}_{2}\) optimised structure. The theoretical parameters of the transparent conducting metal oxides were calculated using DFT / B3LYP / LANL2DZ method. The optimised bond parameters such as bond lengths, bond angles and dihedral angles were calculated using the same theory. The non-linear optical property of the title compound was calculated using first-order hyperpolarisability calculation. The calculated HOMO–LUMO analysis explains the charge transfer interaction between the molecule. In addition, MEP and Mulliken atomic charges were also calculated and analysed.     

New method for calculating reflected wave fronts of acute retroreflectors with tuned dihedral angle

An acute retroreflector having dihedral angles of 45, 60 and 90 deg exactly reflects incident rays in the opposite direction. Beam pattern or wave front of the reflected light of the acute retroreflector can be controlled by tuning dihedral angles. We present here a new method for calculating the reflected wave front of the acute retroreflector, in which the wave front is calculated with high accuracy and in a shorter calculation time than by the conventional ray trace method.     

由NMR获取原子间距离约束计算蛋白质三维结构

提出一种以核磁共振(NMR)技术获取蛋白质分子多肽链中原于对(主要是H—H对)的距离约束,来计算蛋白质在溶液中的三维结构的方法。这种方法把肽平面之间的二面角当作独立变量,通过从局部到整体逐渐最优化的方法使适当构造的目标函数最小,计算出这些二面角,以及主链每个残基上六种原子N、H~N、C~α、H~α、C′、O的空间坐标.本方法已编写成计算程序DISNMA,并以碱性胰蛋白酶抑制剂(BPTI)为标准结构,得到了很好的验证.     

Fluorimetric Determination of Morphine in Codeine

Abstract

Two easy to handle, sensitive and specific fluorimetric methods for the detection and determination of morphine in codeine are described. In method A the codeine sample investigated is treated with alkaline potassium ferricyanide, whereby morphine when present will produce the fluorescent dimer pseudomorphine. In method B, the codeine sample is thermally treated with gaseous ammonia on a chromatographic plate where morphine, if present, is converted to a highly fluorescent derivative. The limits of detection were 10 ng and 20 ng for methods A and B respectively.     

Transient radiation of particles in dihedral and trihedral angles

The image method is used for determining the field of transient radiation emitted by a charged particle intersecting a dihedral angle formed by ideally conducting charged planes. The spectral-angular distributions of radiation intensity in a dihedral angle with different corner angles are calculated. The effect of the direction of motion of the particle and of the position of the point at which the particle intersects the plane on radiation parameters is considered. Transient radiation distributions in a trihedral angle are also obtained.     

PMR Assay of Natural Products in Pharmaceuticals. IV Assay of Codeine and Simultaneous Detection of Morphine

A rapid, accurate and precise PMR method is presented for the quantitative determination of codeine and codeine phosphate as bulk drugs and in tablet dosage form. The determination is based on the integration of the C-3 methylprotons or the two aromatic protons of codeine or its salt relative to that of the nine protons of t-butanol. Standard deviations of ± 1.39, 0.27 and 0.65% were obtained for codeine, codeine phosphate bulk drug and codeine phosphate tablets respectively. The method furnishes a specific means of identification of codeine as well as of the simultaneous detection and possible determination of morphine; thus fulfilling one of the most important pharmacopeial requirements for the purity of codeine.     

THE PHONON DENSITY OF STATES AND THE NEUTRON SCATTERING FACTOR FOR A DISORDERED POLYMER CHAIN

In this paper we calculated the phonon density of states and the neutron scattering factor in a model of a random polymer chain embedded as a self-avoiding walk on a diamond lattice by using the equation of motion method of Green's function. The Iiadltonian of the mdel includes stretching force, bending force and dihedral force. The result showea that the gap near ω=0 disappeared,which is in good agreement with experiment. It is also found that peaks of the spectrunr at low frequencies are sensitive to the degree of crystallization. This indicates that they are related only to the vibration of the crystalline region.