Guiding synchrotron X‐ray diffraction by multimodal video‐rate protein crystal imaging

Synchronous digitization, in which an optical sensor is probed synchronously with the firing of an ultrafast laser, was integrated into an optical imaging station for macromolecular crystal positioning prior to synchrotron X‐ray diffraction. Using the synchronous digitization instrument, second‐harmonic generation, two‐photon‐excited fluorescence and bright field by laser transmittance were all acquired simultaneously with perfect image registry at up to video‐rate (15 frames s^?1). A simple change in the incident wavelength enabled simultaneous imaging by two‐photon‐excited ultraviolet fluorescence, one‐photon‐excited visible fluorescence and laser transmittance. Development of an analytical model for the signal‐to‐noise enhancement afforded by synchronous digitization suggests a 15.6‐fold improvement over previous photon‐counting techniques. This improvement in turn allowed acquisition on nearly an order of magnitude more pixels than the preceding generation of instrumentation and reductions of well over an order of magnitude in image acquisition times. These improvements have allowed detection of protein crystals on the order of 1 µm in thickness under cryogenic conditions in the beamline. These capabilities are well suited to support serial crystallography of crystals approaching 1 µm or less in dimension.     

Identification and Determination of Lsd in Illicit Preparations Using Synchronous Spectro Fluorimetry

Abstract

Molecular fluorescence is much in use nowadays as an analytical technique, particularly for the determination of traces of toxic fluorescent substances. The authors describe a spectrofluorimetric method, called the synchronous excitation method, which is more sensitive and more selective than the classical spectrofluorimetry and which can be used for the direct determination, in the presence of other hallucinogens, of LSD in confiscated samples. They also propose the application, under certain conditions, of the method as a rapid test for the presence of LSD.     

基于无源性理论自适应镇定具有v/f输入的永磁同步电动机的混沌运动

首先利用无源性理论,构造自适应反馈控制器使具有v/f控制输入的混沌永磁同步电动机(PMSM)等效为闭环无源系统,然后证明该无源系统可以实现在平衡点的稳定,从而达到镇定PMSM混沌运动的目的.数值仿真结果表明,该控制策略不仅行之有效,对参数的不确定性具有较强的鲁棒性.研究结果对保证具有v/f控制输入的PMSM的稳定运行有较好的参考价值.     

The spectral gap for quasi-birth and death processes

For a reversible quasi-birth and death process, we generalize and refine the decomposition method, by constructing a birth-death process and a sequence of restriction processes. The spectral gap for the quasi-birth and death process is estimated in terms of the spectral gaps for these processes, and in some special cases, the estimation is sharp. With the aid of the symmetrization procedure, the result is also applied to two queueing models: M/M/1 in random environment and M/M/c with synchronous vacation.     

300 kA直线型变压器驱动源模块实验研究

介绍了14支路并联的300 kA百ns直线型变压器驱动源单级模块的结构和关键部件。模块通过采用双端引出电极电容器以及小型多间隙串联气体火花开关,可以并联更多的支路数,减小回路电感,提高储能密度;通过采用非晶磁芯,减小磁芯损耗,提高模块耦合效率。实验研究了初级气体开关工作系数对模块输出的影响,实验结果表明:模块开关电压工作系数达到0.7,多间隙串联开关才能较好同步放电;给出了快直线型变压器模块的初步调试实验结果,在模块充电90 kV,开关气压0.32 MPa情况下,匹配负载电流峰值可达到302 kA,上升时间约100 ns,负载上获得的峰值功率为23 GW。     

基于SOA的环形腔激光器在全光信号处理中的应用

半导体光放大器（SOA）因其具有良好的光光互作用特性,包括交叉增益调制、交叉相位调制、交叉偏振调制以及四波混频等,在全光信号处理技术中已经获得了广泛的应用。利用SOA与光纤反馈可构成环形腔激光器S_FRL。在S—FRL中将SOA的光一光互作用特性与反馈条件相结合,可以改变孓FRI．的起振、抑制、选频等多种状态,从而构成不同功能的全光信号处理器件。在分析S—FRL激光振荡原理的基础上,提出了双环耦合的S-FRL,并以此为基础构成一种双环耦合的双稳态触发器,进而构成一种同步脉冲展宽器;还提出了一种级联的S-FRL,由此构成一种基于负逻辑的全光判决器。