气相色谱-质谱法测定当归粉、当归原药材中的邻苯二甲酸二丁酯

建立了气相色谱-质谱法测定当归粉和当归原药材中邻苯二甲酸二丁酯（DBP）的方法。在国家标准的基础上,通过单因素试验,优化了提取方法和提取溶剂,确定了以正己烷为提取剂从水中液液萃取的方法。方法学试验结果表明,DBP浓度在0．01～1．00μg／mL范围内与色谱峰面积呈良好的线性关关系,线性相关系数r^2=0．9995,检出限为0．05μg／g（全扫描）,不同水平的加标回收率在90％～100％之间,测定结果的相对标准偏差小于5％（n=3）。该方法适合当归粉和当归原药材中DBP的日常检测。     

副溶血弧菌的热激亚致死损伤与显微红外光谱检测

采用传统的平板计数法作为对照,利用显微红外光谱技术(4000~400 cm!1)并结合化学计量学,研究了在55℃水浴中热激处理不同时间(0,2,4,6和8 min)对副溶血弧菌失活和亚致死损伤的作用效果。二维主成分分析(PCA)表明,正常细菌与受损细菌能够各自聚类,明显区分,而且损伤程度不同的细菌也能够基本区分。载荷图分析(LPA)发现,加热处理后,副溶血弧菌中的多糖、结构蛋白、脂质、核酸都发生了变化,其细胞壁、细胞膜和DNA皆遭受损伤。类模拟软独立建模(SIMCA)的结果表明,一般情况下,受不同程度热损伤的细菌均有80%以上的预测率,能够被有效区别开。研究表明,显微红外光谱技术具有检测热激后亚致死损伤的副溶血弧菌的潜力。     

Dark count in single-photon avalanche diodes:A novel statistical behavioral model

Dark count is one of the inherent noise types in single-photon diodes,which may restrict the performances of detectors based on these diodes.To formulate better designs for peripheral circuits of such diodes,an accurate statistical behavioral model of dark current must be established.Research has shown that there are four main mechanisms that contribute to the dark count in single-photon avalanche diodes.However,in the existing dark count models only three models have been considered,thus leading to inaccuracies in these models.To resolve these shortcomings,the dark current caused by carrier diffusion in the neutral region is deduced by multiplying the carrier detection probability with the carrier particle current at the boundary of the depletion layer.Thus,a comprehensive dark current model is constructed by adding the dark current caused by carrier diffusion to the dark current caused by the other three mechanisms.To the best of our knowledge,this is the first dark count simulation model into which incorporated simultaneously are the thermal generation,trap-assisted tunneling,band-to-band tunneling mechanisms,and carrier diffusion in neutral regions to evaluate dark count behavior.The comparison between the measured data and the simulation results from the models shows that the proposed model is more accurate than other existing models,and the maximum of accuracy increases up to 31.48%when excess bias voltage equals 3.5 V and temperature is 50℃.