锶特效树脂萃取色谱耦合热电离同位素质谱法测定海水中锶同位素研究

采用锶特效树脂,以萃取色谱法将锶离子自基体中分离,详细介绍了锶特效树脂萃取原理,进行了实验条件优化。采用HNO3消解海水样品,以HNO3(8.0mol/L)为介质上柱,用HNO3(8.0mol/L)淋洗,样品中的锶离子被强烈吸附在树脂柱上,再以HNO3(0.05mol/L)洗脱,Sr被解吸。收集淋洗液,蒸干,采用热电离同位素质谱仪测定海水样品中的87Sr/86Sr比值。结果表明,利用锶特效树脂,可将锶与基体元素(K,Na,Mg,Ba)分离,并能有效分离同位素测定中干扰元素Ca和Rb。消除了基体干扰,提高了分离效率,达到灵敏测定。     

液相色谱-电化学衍生-光学检测技术研究进展

综述了以反相键合相为主的高效液相色谱-柱后电化学衍生-荧光检测(RP-HPLC/ED/FD)技术的研究进展。对RP-HPLC/ED/FD存在的主要问题进行了讨论。并介绍了离子色谱-柱后电化学衍生-光学联用装置的构建及其在极性有机物和金属离子的测定方面的应用研究。     

气相色谱法测定环境空气中的微量丙烯腈

 建立了测定环境空气中丙烯腈的Tenax GC吸附-热解吸气相色谱法。方法的回收率为85.6%～105.4%,RSD为4.5%～6.2%。当采样体积为2 L时,最低检测限为0.01 mg/m3 。     

利用WRF数值模拟分析小型超强台风“桑美”

利用中尺度数值模式WRF,结合WRF Var三维变分系统,同化了雷达资料和常规、非常规观测资料,对2006年第8号小型超强台风“桑美”进行数值模拟试验.结合实况验证,WRF较好地模拟本次台风暴雨过程,基本反映实况台风演变过程.利用模式输出的具有高时空分辨率的模拟结果对“桑美”台风短时强暴雨进行诊断分析,表明“桑美”台风具有较好的对称性结构,涡旋结构紧密,云团内部气流强烈辐合上升,这是降水高度集中的动力因素;中尺度辐合带以及强回波带始终环绕中心眼区呈同心圆形状逆时针旋转,验证了台风螺旋云带的形成是产生台风暴雨的一个必要条件,“桑美”螺旋辐合带靠近台风中心,范围小、弧状明显;风切变所产生的低层辐合为强对流低层发生的动力之一;“桑美”引起的暴雨属于台风区内暴雨,具有相当充沛的水汽条件,并且水汽对降水的作用主要在中低层,以低层最强;各物理量场相互之间都有很好的对应,说明台风暴雨的发生和维持需要大尺度环境场、动力条件和水汽条件等的配合.     

Circle detection using scan lines and histograms

Circle detection is significant in image processing and pattern recognition. We present a new algorithm for detecting circles, which is based on the global geometric symmetry of circles. First, the horizontal and vertical midpoint histograms of the edge image are obtained by using scan lines. Then, we apply the peak-finding algorithm to the midpoint histograms to look for the center of the circle. The normalized radius histogram is finally used to verify the existence of the circle and extract its radius. Synthetic images with different levels of pepper noise and real images containing several circles have been taken to test the performance. Experimental results demonstrate that the proposed algorithm has the advantage of computational efficiency as compared with the randomized Hough transform and some other algorithms.     

固相萃取-亲水相互作用液相色谱法同时测定环境水样中3种酰胺类化合物

基于亲水相互作用液相色谱(Hydrophilic Interaction Liquid Chromatography,HILIC)技术,建立了同时测定环境水样中丙烯酰胺、N,N-二甲基甲酰胺和N,N-二甲基乙酰胺的液相色谱分析方法.水样采用石墨化碳黑固相萃取柱净化,上样1.0 mL,并最终用1.0 mL乙腈洗脱,洗脱液进样色谱分析.选择Waters HILIC色谱柱,以乙腈/水作为流动相,等度洗脱,二极管阵列检测器200 nm条件下检测.在优化的分析条件下,3种酰胺类化合物在11 min内实现基线分离.所有目标化合物浓度在0.05～ 100 mg/L范围内线性良好,相关系数均大于0.9999;检出限达0.01 mg/L.加标回收率为84.1％～106％;相对标准偏差1.8％～10.4％.本方法具有简便快捷、灵敏准确等特点,能够满足环境水样中痕量酰胺类污染物检测的要求.     

A convenient phosphoryloxylactonization of pentenoic acids with catalytic hypervalent iodine(III) reagent

A novel and convenient catalytic method for phosphoryloxylactonization of pentenoic acids is available: the cyclization of 4-pentenoic acids with phosphates using iodobenzene as a recyclable catalyst in combination with m-chloroperbenzoic acid as the terminal oxidant was easily carried out in CF₃CH₂OH at room temperature, giving phosphoryloxylactons in good yields, some of them had two diastereoisomers.     

Comparative research on activation technique for GaAs photocathodes

The properties of GaAs photocathodes mainly depend on the material design and activation technique. In early researches, high-low temperature two-step activation has been proved to get more quantum efficiency than high-temperature single-step activation. But the variations of surface barriers for two activation techniques have not been well studied, thus the best activation temperature, best Cs–O ratio and best activation time for two-step activation technique have not been well found. Because the surface photovoltage spectroscopy (SPS) before activation is only in connection with the body parameters for GaAs photocathode such as electron diffusion length and the spectral response current (SRC) after activation is in connection with not only body parameters but also surface barriers, thus the surface escape probability (SEP) can be well fitted through the comparative research between SPS before activation and SEP after activation. Through deduction for the tunneling process of surface barriers by Schrödinger equation, the width and height for surface barrier I and II can be well fitted through the curves of SEP. The fitting results were well proved and analyzed by quantitative analysis of angle-dependent X-ray photoelectron spectroscopy (ADXPS) which can also study the surface chemical compositions, atomic concentration percentage and layer thickness for GaAs photocathodes. This comparative research method for fitting parameters of surface barriers through SPS before activation and SRC after activation shows a better real-time in system method for the researches of activation techniques.     

Electrostatic precipitation of airborne bio-aerosols

In this study, we report electrostatic precipitation of Escherichia Coli- and Yeast-aerosols in air. The aerosol size distribution and their electrostatic precipitation efficiency are monitored by using an Electrical Low Pressure Impactor. The results indicate that the E. Coil-aerosols are mainly around 0.8 μm in aerodynamic diameter and the Yeast-aerosols are in the range of 1.3–3.1 μm, respectively. At an average electric field of 1 kV/cm, the precipitation efficiencies of E. Coli- and Yeast-aerosols are about 31% and 5%, respectively. They rise to 79% and 71% when the field strength rises to 7.5 kV/cm. For H₂O-aerosols, the diameter is about 0.02 μm and the efficiency is almost 100% under the same condition.     

Tour time in a two-route traffic system controlled by signals

We study the dynamic behavior of vehicular traffic in a two-route system with a series of signals (traffic lights) at low density where the number of signals on route A is different from that on route B. We investigate the dependence of the tour time on the route for some strategies of signal control. The nonlinear dynamic model of a two-route traffic system controlled by signals is presented by nonlinear maps. The vehicular traffic exhibits a very complex behavior, depending on the cycle time, the phase difference, and the irregularity. The dependence of the tour time on the route choice is clarified for the signal strategies.