5d过渡金属原子掺杂氮化铝纳米管电子结构、磁性性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理计算方法, 研究了5d过渡金属原子(Lu、Hf、Ta、W、Re、Os、Ir、Pt、Au、Hg)取代AlN纳米管(AlNNTs)中的铝原子或氮原子时体系的几何结构、电子结构和磁性性质; 并且以理想AlN纳米管(AlNNTs)、Al缺陷体系(VAl)和N缺陷体系(VN)的结果作为对比. 研究发现: 5d 原子取代Al(Al5d)时体系的局域对称性接近于C3v, 但是取代N(N5d)时体系的局域对称性偏离C3v对称性较大; 当掺杂的5d元素相同时, Al5d的成键能比N5d的成键能大; 当掺杂体系相同时(Al5d或N5d), 其成键能基本上随着5d原子的原子序数的增大而降低; 掺杂体系中出现了明显的杂质能级, 给出了态密度等结果; 不同掺杂情况的磁矩不同, 总磁矩呈现出较强的规律性. 利用C3v对称性和分子轨道理论解释了过渡金属原子取代Al时杂质能级的产生和体系磁性的变化规律.     

Thermochromatium tepidum外周捕光天线蛋白LH2在脂质体及表面活性剂胶束中的光谱性质

采用动态光散射、透射电子显微镜、紫外-可见吸收光谱和拉曼光谱对比研究了处于表面活性剂胶束和脂质体磷脂双分子层中的Thermochromatium(Tch.)tepidum LH2的光谱响应.结果表明,与在表面活性剂胶束中相比,双分子层脂膜中LH2的Spirilloxanthin(一种含有13个共轭双键的类胡萝卜素)构象有明显差异;表面活性剂及磷脂分子端基的荷电状态对B850-Qy吸收谱有显著影响;Ca2+结合导致B850 Qy吸收谱带红移和增色,而H+结合则使该吸收谱带蓝移和减色.对LH2脱辅基蛋白氨基酸序列的分析结果表明,Ca2+和H+的结合位点可能位于α脱辅基蛋白的C-端一侧.B850 Qy吸收谱带对Ca2+和H+的响应特性可能与Tch.tepidum适应其生存环境的能力有关.     

气相色谱-质谱联用法测定维生素C泡腾片中的甜蜜素

采用气相色谱-质谱(GC-MS)选择离子监测法(SIM),建立了准确可靠、灵敏度高、快速简便的测定维生素C泡腾片中甜蜜素含量的新方法.样品中的甜蜜素衍生后用有机试剂提取,在选择离子模式下进行测定,以保留时间和特征离子比例进行定性,单离子定量.甜蜜素的线性范围为0.05-10mg/L,检出限为0.6mg/kg,回收率为90.5%-96.9%,相对标准偏差小于4.4%.方法分析所用时间短,结果准确可靠,选择性好,适用于维生素C泡腾片中甜蜜素含量的检验.     

Low-threshold, high-efficiency, high-repetition-rate optical parametric generator based on periodically poled LiNbO3

We report a high-repetition-rate optical parametric generator (OPG) with a periodically poled lithium niobate (PPLN) crystal pumped by an acousto-optically Q-switched CW-diode-end-pumped Nd:YVO_4 laser. For the maximum 1064nm pump power of 970mW, the maximum conversion efficiency is 32.9% under the conditions of 250℃, 1064nm pulse repetition rate of 22.6kHz and pulse width of 12ns, and the PPLN OPG threshold in the collinear case is less than 23.7μJ. The output power increases with the increase of the crystal temperature. The 1485－1553nm signal wave and 3383－3754nm idler wave are obtained by changing the temperature and the angle of the PPLN crystal.     

Power distribution in Yb3+-doped double-cladding fiber laser

The distribution of pump light and signal light in Yb3+-doped double-cladding fiber laser is analyzed based on a rate equation model.Numerical simulation results are obtained.The numerical solution of the rate equation is shown to be in excellent agreement with the experimental data.     

Power distribution in Yb~(3+)-doped double-cladding fiber laser

The distribution of pump light and signal light in Yb3+-doped double-cladding fiber laser is analyzed based on a rate equation model. Numerical simulation results are obtained. The numerical solution of the rate equation is shown to be in excellent agreement with the experimental data.     

Experimental 511 W Composite Nd：YAG Ceramic Laser

We demonstrate a 511 W laser diode pumped composite Nd：YAG ceramic laser. The optical pumping system is consisted of five laser diode stacked arrays arranged in a pentagonal shape around the ceramic rod whose size is φ6.35×144mm. When the pumping power is 1600 W, the cw laser output up to 511 W at 1064nm can be obtained with a linear piano-piano cavity, and the optical-to-optical efficiency is 31.9%. To our knowledge, this is the highest value of laser output by using a newly invented composite Nd：YAG ceramic rod as the gain medium.     

Light-Gradient-Induced Spiral Wave Drifts in a Belousov-Zhabotinsky Reaction

The dynamic behaviour of spiral tip in the light-sensitive Belousov-Zhabotinsky reaction under the influence of an externally applied light gradient was experimentally studied. The gradient causes different drifts for different spiral patterns. The centre of the spiral wave moved toward the region of lower light intensity. The direction of an additional perpendicular drift depended on the chirality of the spiral wave. The dependences of the drifting angle and the drifting velocity on light gradient have been measured.     

High-Average-Power Nanosecond Quasi-Phase-Matched Single-Pass Optical Parametric Generator in Periodically Poled Lithium Niobate

A pulsed nanosecond optical parametric generator (OPG) in periodically poled lithium niobate (PPLN) crysal is presented. The pump laser is an acousto-optically Q-switched Nd:YVO4 laser with the maximum average power of 6.58 W. When the repetition rate is 50kHz and the pulse width of the pump source is 80ns, the maximum average total output power of the single-pass PPLN OPG is about 1.9 W, which includes 1.322 W of 1.536μm signal radiation. The length of the PPLN crystal is only 38.7mm (at room temperature) with a grating period of 28.93μm (at room temperature). The 1.502-1.536μm signal radiation and 3.652-3.465μm idler radiation are obtained by adjusting the PPLN crystal temperature from 155℃ to 250℃.     

甲壳素色谱柱富集－柱前显色分光光度法快速测定痕量铜

本文研究了甲壳素柱快速吸附Ｃｕ（Ⅰ）－２，９－二甲基－４，７－二苯基－１，１０－邻菲罗啉－十二烷基苯磺酸钠橙红色的缔合物，用乙醇－乙酸的混合液洗脱后，在分光光度计上直接测定洗脱液的吸光度，方法简便，快速，富集倍数高，可用于水样中痕量铜的测定。