Density functional theory calculations of nuclear quadrupole coupling constants with calibrated 14N quadrupole moments

Density functional calculations of the electric field gradient tensor at the nitrogen nucleus in 13 test molecules, containing 14 nitrogen sites, have been performed using the linear combination of Gaussian-type orbital Kohn-Sham density functional theory (LCGTO-KSDFT) approach. Local and gradient corrected functionals were used for all-electron calculations. All the molecular structures were optimized at their respective levels of theory with extended basis sets. Calibrated ¹⁴N nuclear quadrupole moments were obtained through a fitting procedure between calculated electric field gradients and experimental nuclear quadrupole coupling constants of the test set of molecules for each basis set and functional considered. With these calibrated ¹⁴N nuclear quadrupole moments, the nuclear quadrupole coupling constants of the following selected systems were determined: fluoromethylisonitrile, pyridine, pyrrole, imadazole, pyrazole, 1,8-bis(dimethyl-amino)naphthalene, cyclotetramethylenetetranitramine, cocaine and heroin.     

金属卟啉催化条件下有机化合物与二氧化碳的电羧化反应Ⅰ. 金属卟啉对苄基氯电羧化催化活性的研究

本文研究了系列金属卟啉对苯基氯(phCH~2Cl)和CO~2电羧化反应的催化活性.用熔点,MS,IR,UV鉴别产物为苯乙酸卟脂,利用高效液相色谱(HPLC)定量分析了羧化产物,选出最佳电羧化电解电位为-1.6v(相对于饱和甘汞电极,vs.SCE,下同). 并对催化活性较高的钴卟啉系列配合物进行了深入研究. 探讨了金属卟啉具有催化活性的原因,认为能形成M(Ⅰ)中间体的金属卟啉配合物.具有较高的催化活性.     

AN APPROXIMATE PROJECTION SCHEME FOR INCOMPRESSIBLE FLOW USING SPECTRAL ELEMENTS

An approximate projection scheme based on the pressure correction method is proposed to solve the Navier–Stokes equations for incompressible flow. The algorithm is applied to the continuous equations; however, there are no problems concerning the choice of boundary conditions of the pressure step. The resulting velocity and pressure are consistent with the original system. For the spatial discretization a high-order spectral element method is chosen. The high-order accuracy allows the use of a diagonal mass matrix, resulting in a very efficient algorithm. The properties of the scheme are extensively tested by means of an analytical test example. The scheme is further validated by simulating the laminar flow over a backward-facing step.     

THE PROTONATION OF A RETINYL SCHIFF BASE

The hydrogen bonding-protonation equilibrium for retinyl Schiff base/propionic acid or 3-chloropropionic acid systems was examined by Fourier transform infrared spectroscopy in non polar solutions at temperatures ranging from 25 degrees C to about -150 degrees C. The spectra give evidence for the gradual increase in the degree of protonation as temperature is lowered. The bearing of this on applying low temperature spectroscopic results to physiological conditions in rhodopsin research is discussed.     

D and D meson production near 4 GeV in e+e− annihilation

We have studied momentum spectra for D⁰ ($\text{D}$⁰) and D^± mesons produced near 4 GeV in e⁺e^? annihilation and find that production is dominated by two-body reactions involving D and D¹ states where the D¹ (charged and neutral) have masses near 2.01 GeV/c². A detailed study of D momentum spectra near E_cm = 4.028 GeV allows determination of masses and branching ratios of D and D¹ states. Lastly we find that events containing a D⁰ meson conserve strangeness, thus establishing upper limits on D⁰-$\text{D}$⁰ mixing and on the effects of charm changing neutral currents.     

Linear dynamical systems with integer constraints

We study properties of dynamic discrete-time linear systemswith the input or the state constrained to have integer components.The reachability of input-constrained systems is investigated,and consistency conditions for state-constrained systems aregiven.     

钾蒸气中的偶极禁戒双光子共振四波混频和混合激发能量转移受激辐射

本文首次报道了由钾分子-原子系统的混合激发和碰撞能量转移过程产生4F→3D受激辐射以及由钾原子的4S→4F偶极禁戒双光子共振产生4F→3D受激辐射和四波混频的研究结果。     

液氦温区两级4K脉冲管制冷机数值模拟

为模拟和动态显示工作在液氦温区的两级4K脉冲管制冷机内部工作过程和参数变化规律,发展了一种新的欧拉法-拉格朗日法数值计算模型。采用拉格朗日方法,直接跟踪脉冲管中气体微元随周期性压力波动的具体运行轨迹;采用欧拉法,直接模拟蓄冷器内部的动态参数变化。本文简单介绍该模型,并模拟了一典型两级4 K脉冲管制冷机各参数的变化情况,分析了多层磁性蓄冷材料对制冷机性能的影响情况。     

[H_2N(C_2H_4)_2NH_2]_4(H_3O)[PMo_2~VMo_6~(VI)V_4~(IV)O_(40)(V~(IV)O)_2]·H_2O: A New Highly Reduced, Bicapped Pseudo-Keggin Vanadylpolymolybdophosphate

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GLOBAL ANALYSIS OF THE TIME-RESOL VED FLUORESCENCE OF α-CHYMOTRYPSINOGEN A AND α-CHYMOTRYPSIN POWDERS AS A FUNCTION OF HYDRATION

The time-resolved tryptophyl fluorescence of alpha-chymotrypsin A and alpha-chymotrypsin in the crystalline state and in buffer solution at room temperature was analyzed globally. Triple-exponential decay functions are necessary to adequately describe the tryptophyl fluorescence decay surfaces of the protein powders as a function of hydration and in solution. The fluorescence lifetimes of alpha-chymotrypsinogen A (tau 1 = 0.32, tau 2 = 1.30 ns, tau 3 = 3.98 ns) and alpha-chymotrypsin(tau 1 = 0.66 n s, tau 2 = 2.26 ns, tau 3 = 5.40 ns) are constant over the entire hydration range. The spectral positions of the decay-associated spectra of the hydrated powders do not shift as a function of hydration. This indicates that the structures of the zymogen and the active enzyme are unaffected by hydration. The lifetimes of alpha-chymotrypsinogen A in phosphate buffer pH 7.4 are tau 1 = 0.37 ns, tau 2 = 1.17 ns and tau 3 = 3.44 ns while the respective values of alpha-chymotrypsin are tau 1 = 0.47 ns, tau 2 = 1.40 and tau 1 = 3.89 ns.