Synthesis,characterization and antifungal activity of glycylglycine Schiff base complexes of 3d transition metal ions

Summary Two new Schiff bases, N-4-hydroxysalicylidene-glycylglycine (K·GGRS·H₂O), N-O-vanillal-glycylglycine (K· GGVS·3H₂O) and their manganese(II), cobalt(II), nickel(II) and copper(II) complexes have been synthesized and characterized by elemental analysis, t.g.a., molar conductance, i.r. and u.v. spectral studies. The ¹³Cn.m.r. spectrum of one of the Schiff base ligands has been recorded. The results show that the ligand is coordinated to the central metal ion via amide nitrogen, imino nitrogen, phenolic oxygen and carboxyl oxygen to form a quadridentate complexes. Some of the complexes exhibit strong inhibitory action towards Candida albicans and Cryptococcus neoformans.     

Numerical methods for conjunctive two‐dimensional surface and three‐dimensional sub‐surface flows

Sophisticated catchment runoff problems necessitate conjunctive modeling of overland flow and sub‐surface flow. In this paper, finite difference numerical methods are studied for simulation of catchment runoff of two‐dimensional surface flow interacting with three‐dimensional unsaturated and saturated sub‐surface flows. The equations representing the flows are mathematically classified as a type of heat diffusion equation. Therefore, two‐ and three‐dimensional numerical methods for heat diffusion equations were investigated for applications to the surface and sub‐surface flow sub‐models in terms of accuracy, stability, and calculation time. The methods are the purely explicit method, Saul'yev's methods, the alternating direction explicit (ADE) methods, and the alternating direction implicit (ADI) methods. The methods are first examined on surface and sub‐surface flows separately; subsequently, 12 selected combinations of methods were investigated for modeling the conjunctive flows. Saul'yev's downstream (S‐d) method was found to be the preferred method for two‐dimensional surface flow modeling, whereas the ADE method of Barakat and Clark is a less accurate, stable alternative. For the three‐dimensional sub‐surface flow model, the ADE method of Larkin (ADE‐L) and Brian's ADI method are unconditionally stable and more accurate than the other methods. The calculations of the conjunctive models utilizing the S‐d surface flow sub‐model give excellent results and confirm the expectation that the errors of the surface and sub‐surface sub‐models interact. The surface sub‐model dominates the accuracy and stability of the conjunctive model, whereas the sub‐surface sub‐model dominates the calculation time, suggesting the desirability of using a smaller time increment for the surface sub‐model. Copyright © 2000 John Wiley & Sons, Ltd.     

单摆周期的数值计算

本文从理论上分析了单摆周期随角振幅变化的规律，并给出了数值计算结果     

Numerical experiments with several variant WENO schemes for the Euler equations

Numerical experiments with several variants of the original weighted essentially non‐oscillatory (WENO) schemes (J. Comput. Phys. 1996; 126 :202–228) including anti‐diffusive flux corrections, the mapped WENO scheme, and modified smoothness indicator are tested for the Euler equations. The TVD Runge–Kutta explicit time‐integrating scheme is adopted for unsteady flow computations and lower–upper symmetric‐Gauss–Seidel (LU‐SGS) implicit method is employed for the computation of steady‐state solutions. A numerical flux of the variant WENO scheme in flux limiter form is presented, which consists of first‐order and high‐order fluxes and allows for a more flexible choice of low‐order schemes. Computations of unsteady oblique shock wave diffraction over a wedge and steady transonic flows over NACA 0012 and RAE 2822 airfoils are presented to test and compare the methods. Various aspects of the variant WENO methods including contact discontinuity sharpening and steady‐state convergence rate are examined. By using the WENO scheme with anti‐diffusive flux corrections, the present solutions indicate that good convergence rate can be achieved and high‐order accuracy is maintained and contact discontinuities are sharpened markedly as compared with the original WENO schemes on the same meshes. Copyright © 2008 John Wiley & Sons, Ltd.     

Rate enhancement for nitroxide stable free radical polymerization of n‐butyl acrylate by dodecylbenzenesulfonic acid

Dodecylbenzenesulfonic acid, DDBSA, was chosen as a new rate‐accelerating additive for 2,2,6,6,‐teramethyl‐1‐piperidinyloxy (TEMPO)‐mediated stable free radical polymerization of n‐butyl acrylate (n‐BA) monomers with 2,2′‐azobisisobutyronitrile (AIBN). It was found that the number‐average molecular weight of polymers could reach about ten thousand with a narrow polydispersity index (PDI) of 1.4 in a few minutes, which was faster than other systems reported previously. But, at higher conversion, the molecular weight distribution of polymers became broad, and a bimodal distribution occurred. The macro‐initiators isolated from the former polymers with narrow PDI could be extended by polymerization with monomers by the addition of DDBSA. Furthermore, a proposed kinetic model demonstrated that the decay of the concentration of DDBSA would reduce the living polymer concentration and retard the growth of the polymers, which could be further propagated by the supplement of DDBSA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 42–49, 2005     

Numerical study on InGaAsN/GaAs multiple-quantum-well laser with GaAsP and GaAsN barriers

In this work, the multiple-quantum-well InGaAsN laser structures with indirect-GaAsP and direct-GaAsN barriers are investigated by using LASTIP simulation program. We vary the quantum-well number, from 1 to 5, to find appropriate barrier material for InGaAsN laser structures. The simulation results show that InGaAsN laser structure has higher characteristic temperature regardless of what quantum-well number is if the indirect-GaAsP barrier is utilized. Furthermore, for InGaAsN laser structure, the usage of indirect-GaAsP barrier is beneficial for reducing the threshold current when the quantum-well number is from 1 to 2 and the usage of direct-GaAsN barrier is beneficial for reducing the threshold current when the quantum-well number is from 3 to 5.     

A complete measurement of spin-observables for intermediate-energy inclusive quasielastic polarized proton scattering from C

The complete set of Wolfenstein parameters, the polarization, the asymmetry of scattering and the unpolarized double-differential cross section are presented for inclusive quasielastic proton scattering from ¹²C at a central momentum transfer of q = 1.9 fm⁻¹ and incident energies of 290 and 420 MeV. The spin observables D₀, D_x, D_y and D_z as well as the longitudinal-to-transverse ratio of spin-flip probabilities are extracted from the data. Across the quasielastic continuum, the experimental data is compared to the variations expected from a single-scattering Fermi-gas approximation using the free NN amplitudes. Medium effects are evident in the pronounced quenching of the polarization parameter relative to the free value.     

Improvement in piezoelectric effect of violet InGaN laser diodes

The laser performance of violet InGaN laser diodes is investigated numerically. The polarization-dependent properties, including overlap of electron and hole wavefunctions, threshold current, and slope efficiency, are studied through the use of step-like quantum well structure. Furthermore, the electron and hole wavefunctions, band diagrams, and emission wavelength are compared and analyzed. The simulation results show that the lowest threshold current and the highest slope efficiency are obtained when the step-like quantum well structure is designed as In_0.12Ga_0.88N (2.5 nm)-In_0.18Ga_0.82N (1 nm) or In_0.18Ga_0.82N (2.5 nm)-In_0.12Ga_0.88N (1 nm) for violet laser diodes due to sufficiently enhanced overlap of electron and hole wavefunctions.     

X射线衍射仪功能扩展的研究

通过软件实现了用 Ｐ Ｃ 机调用日本 Ｒｉｇａｋｕ 公司生产的 Ｄ／ ｍａｘ 一类 Ｘ 射线衍射仪测量数据，利用 Ｐ Ｃ 机的复杂计算功能，使原有仪器也可以进行新的结构分析工作，扩展了仪器的功能。