The 4051-Angstroms band of C3 (A 1Piu-X 1Sigmag +, 000-000): perturbed low-J lines and lifetime measurements

Rotational analyses have been carried out at high resolution for the 000-000 and 000-100 bands of the A (1)Pi(u)-X (1)Sigma(g) (+) transition of supersonic jet-cooled C(3). Two different spectra have been recorded for each band, using time gatings of 20-150 and 800-2300 ns. At the shorter time delay the spectra show only the lines observed by many previous workers. At the longer time delay many extra lines appear, some of which have been observed previously by [McCall et al.Chem. Phys. Lett. 374, 583 (2003)] in cavity ring-down spectra of jet-cooled C(3). Detailed analysis of these extra lines shows that at least two long-lived states perturb the A (1)Pi(u), 000 state. One of these appears to be a (3)Sigma(u) (-) vibronic state, which may possibly be a high vibrational level of the b (3)Pi(g) state, and the other appears to be a P = 1 state with a low rotational constant B. Our spectra also confirm the reassignment by McCall et al. of the R(0) line of the 000-000 band, which is consistent with the spectra recorded towards a number of stars that indicate the presence of C(3) in the interstellar medium. Fluorescence lifetimes have been measured for a number of upper-state rotational levels. The rotational levels of the A (1)Pi(u) state have lifetimes in the range of 230-190 ns, decreasing slightly with J; the levels of the perturbing states have much longer lifetimes, with some of them showing biexponential decays. An improved value has been obtained for the nu(1) vibrational frequency of the ground state, nu(1) = 1224.4933 +/- 0.0029 cm(-1).     

新型4,4-二甲基异噁唑-3-酮衍生物的合成及生物活性研究

以Baylis-Hillman加成物为起始原料,设计并合成了5个结构新颖的4,4-二甲基异唑-3-酮衍生物。所合成的化合物经IR、1HNMR和元素分析确证。生物活性测试结果表明,所合成的目标产物在2000gai/ha的剂量下均具有较好的除草活性。中间体1-(2,4-二氯苯基)-2-溴甲基丙烯酸乙酯具有杀虫活性,在600gai/ha的剂量下对朱砂叶螨防效为100%。     

Optimization of peak power of passively Q-switched lasers by taking into account intracavity laser spatial distribution

The intracavity photon density and the initial population-inversion density in the diode-pumped passively Q-switched lasers are assumed to be Gaussian spatial distributions. The space-dependent rate equations are solved numerically. The key parameters of an optimally coupled passively Q-switched laser under Gaussian approximation are determined, and a group of general curves are generated for the first time. These key parameters include the optimal normalized coupling parameter and the optimal normalized saturable absorber parameter that maximize the peak power, and the corresponding normalized energy, normalized peak power, and normalized pulse width. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the saturable absorber, and the resonator. In addition, the importance including the space variation is also shown. The optimal calculations for a diode-pumped passively Nd:YVO₄ laser are presented to demonstrate the use of the curves and the related formulas.     

Optimization of the slowly actively Q-switched laser

By taking into account turnoff time of the slowly active Q-switch, the coupled equations of a slowly actively Q-switched laser are given. These rate equations are solved numerically. The key parameters of an optimally coupled actively Q-switched laser with the turnoff time are determined, and a group of general curves are generated for the first time. These key parameters include the optimal normalized coupling parameter which maximizes the output energy, and the corresponding normalized energy, normalized peak power and normalized pulse width. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium and the resonator. In addition, the importance of including turnoff time of the slowly active Q-switch is also shown. The optimal calculations for an actively Q-switched Nd:YVO₄ laser with acoustic–optic modulator are presented to demonstrate the use of the curves and the related formulas.     

Theoretical mechanisms of the superoxide radical anion catalyzed by the copper‐zinc superoxide dismutase

The disproportionation of superoxide radical anions catalyzed by copper‐zinc superoxide dismutase was investigated in detail using density functional theory. The structures of each stationary point and the transition states were located so that the reaction pathways were determined. The results indicate that the reactions proceed by two steps both for the oxidized process of superoxide radical anion and the reduced one. The rate for the determining step of the reaction (2) is in very good agreement with the experimental value. The solvation effect on the reaction was also discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

嗜热古细菌Sulfolobus tokodaii脱卤酶在D-乳酸生产中的应用

将来源于嗜热古菌Sulfolobus tokodaii的脱卤酶(L-HADST)基因克隆到载体p ET28b,转化大肠杆菌BL21(DE3)进行表达,在蛋白的N末端带有6个组氨酸融合标签,纯化后经聚丙烯酰胺凝胶电泳显示融合蛋白的分子量约为25000.融合蛋白催化2-氯丙酸(2-CPA)的最适反应温度为70℃,最适p H值为9.5.以外消旋2-CPA为底物生产D-乳酸,利用HPLC检测反应液中2-CPA及乳酸的变化,发现L-HADST只催化L-2-CPA脱氯反应.对酶催化反应条件进行了优化,结果表明,在p H值为9.5,温度为60℃的条件下,当反应体系中缓冲液浓度为3 mol/L,底物浓度为0.5 mol/L,酶浓度为3×104U/L时有较高的底物转化率及乳酸生成量.依据条件优化结果可知,影响反应速度的因素有底物浓度、缓冲液浓度以及酶浓度,其中底物浓度变化对转换率的影响最明显.     

Nonlinear dynamic analysis for coupled vehicle-bridge system with harmonic excitation

In this paper, a multi-degree-of-freedom lumped parameter coupled vehicle-bridge dynamic model is proposed considering the nonlinearities of suspension and tire stiffness/damping and the nonlinear foundation of bridge. In terms of modelling, the continuous expressions of the kinetic energy, potential energy and the dissipation function are constructed. The dynamic equations of the coupled vehicle-bridge system (CVBS) are derived and discretized using Galerkin’s scheme, which yield a set of second-order nonlinear ordinary differential equations with coupled terms. The numerical simulations are conducted by using the Newmark-β integration method to perform a parametric study of the effects on excitation amplitude, suspension stiffness and position relation. The bifurcation diagram, 3-D frequency spectrum and largest Lyapunov exponent are demonstrated in order to better understand the vibration properties and interaction between the vehicle and bridge with the key system parameters. It can be found that the nonlinear dynamic characteristics such as parametric resonance, jump phenomena, periodic, quasi-periodic and chaotic motions are strongly attributed to the interaction between vehicle and bridge. Significantly, under the combined internal and external excitations, the vibration amplitudes of the CVBS have a certain degree of dependence on the external excitation. Suspension stiffness could lead to complex dynamics such as the higher-order bifurcations increase and the chaotic regions broaden. The increasing of distance could effectively control the nonlinear vibration of CVBS. The application of the proposed nonlinear coupled vehicle-bridge model would bring higher computational accuracy and make it possible to design the vehicle and bridge simultaneously.     

LD泵浦Nd∶GdVO4晶体Cr4+∶YAG被动调Q激光特性研究

考虑腔内光子数密度的空间高斯分布以及晶体热效应的影响,给出了LD泵浦Nd∶GdVO4晶体Cr4+∶YAG被动调Q 1.06 μm激光的耦合速率方程组.数值求解该方程组获得了输出激光的脉冲宽度、重复率、峰值功率以及单脉冲能量随泵浦功率的变化特性,其理论值与实验结果相符.