AFS-230E原子荧光光度计无荧光信号显示故障排除一例

原子荧光光度计无荧光信号输出,在检查试剂及进样流路、气路系统正常的情况下,应重点检查光电倍增管和相关的附属电路.本文介绍由于光电倍增管打拿极电阻断路导致的此类故障及排除.     

单分散上转换纳米荧光微粒的荧光寿命测量

为了表征上转换纳米荧光微粒的发光特性,设计了一个可以对单个纳米微粒进行荧光寿命测量的系统。该系统首先使用基于检流计振镜的双光子显微镜系统对单分散状态的上转换纳米微粒样品进行扫描成像。然后,通过单分子荧光纳米定位算法精确找出每个纳米微粒的准确位置,再依次将激光聚焦到每个纳米微粒上,在该点施加一个500μs宽度的激光脉冲,并通过光电倍增管探测随时间变化的荧光强度信号。最后对荧光衰减曲线进行拟合,计算得到该纳米微粒的荧光寿命。实验结果表明:单个上转换纳米荧光微粒的荧光发射曲线符合单指数衰减规律,其荧光寿命为195.3μs。与之相比,聚集状态的纳米微粒的荧光寿命为358.9μs。这表明聚集状态对上转换纳米微粒的发光特性有显著影响。     

SIPM在脉冲光检测系统中的应用研究

为了实现硅光电倍增管(silicon photomultiplier,SIPM)对超出光子计数极限的微弱脉冲光信号的测量,建立了基于SIPM积分工作模式的脉冲光检测系统。测试了SIPM在同一光信号照射下,偏置电压与增益以及信噪比之间的关系,并测试了同一增益条件下,SIPM对不同光信号的响应特性。结果表明:SIPM在积分工作模式下,其增益可以达到104以上,并随着偏置电压的增加而指数增长;其信噪比也随着电压的增加而增加,在光强比较微弱的情况下,SIPM对光强是线性响应的。所设计的系统可以在一定程度上替代光电倍增管进行微弱脉冲光信号的测量。     

化学荧光免疫定量检测仪的系统设计

介绍一种全自动化学荧光免疫定量检测仪的系统设计方法。选用光电倍增管作为感光器件，以TMS320F2407微处理器为主构成系统的智能控制器，配合运动控制系统、温度控制系统、试剂加注系统和信号处理系统实现高灵敏度荧光检测定量分析。     

藻类分类检测的设计与实现

叶绿素a在特定光照条件下产生的荧光光谱,提供了水体中藻类的种群结构及含量信息,通过研究该光谱,能够分析水体中藻类的种类及含量。设计的藻类分类检测仪,用五种特定波长的LED激发藻类溶液产生荧光信号,由光电倍增管接收该信号,并通过调制解调的方法实现了微弱荧光信号的检测。采用某公司的低功耗微处理器msp430F149做主控芯片,对检测到的模拟信号进行A/D转换,并通过串口与上位机通信,由上位机软件对数据进行实时分析或者对原始数据进行存储。     

芯片毛细管电泳激光诱导荧光检测系统的设计

介绍了毛细管电泳芯片的构造和原理，提出激光诱导荧光检测系统的设计方案及其主要器件的选择。分析了光电倍增管电压和共焦针孔对检测系统影响，并给出结果。实验表明，该系统主要技术指标达到了设计要求。     

大型光电倍增管

美国瓦里安(Varian)联合企业公司最近研制出一种新系列的光电倍增管产品,其光电阴极由砷化镓组成,直径达188mm。因而,其阴极面积为目前所常见的光电倍增管的九倍。这种新系列光电倍增管型号为VPM-192M,与同种用途的其他光电倍增管相比,它有三倍于后者的光灵敏度和二倍以上的峰值量子灵敏度。从而,它可以取代现有的的玻璃管封装式光电倍增管,可用于分析仪器、天文仪器和辐射测量等仪器中。该器件增益为10~4至10~6,最高可达10~7。脉冲频率范围可从0至30MHz,脉冲上升和下降时间(按10％至90％计算)为10nS或20nS。     

光纤内窥式微弱信号检测系统开发

针对肿瘤深部的微弱光信号检测问题,设计了一套基于微创光纤探头的内窥式荧光数据采集系统,用于评估光动力疗法治疗肿瘤的疗效。该系统分为光电检测和数据采集两个部分。其中光电检测部分以CR186光电倍增管为核心。数据采集部分基于PCI-6251数据采集卡,以Labview为软件平台,实现数据的实时显示和存储功能。该系统可实时反映肿瘤深部的光强变化,对于在体医疗器械的开发和研究,具有一定的应用价值。     

改进旧原子荧光光度计的灵敏度

对早期原子荧光光度计，可通过正确地调试荧光信号与解调信号的相位关系；清除光学元件污染，调整谐振腔，原子化器，光电倍增管的最佳位置，大大提高仪器的灵敏度。     

光电倍增管特性及应用

文章以光电子发射效应、二次电子发射和电子光学理论为基础介绍了光电倍增管的原理、特性和应用。在基本特性方面从灵敏度和光谱响应度、输出信号等方面对光电倍增管进行阐述 ,又结合使用特性在现代科技发展领域的应用发展方面作了介绍 ,最后对光电倍增管的发展前景作了展望     

叶绿素α的激光光致发光机理及其浓度测量新方法研究

介绍了一种以红光半导体激光器作为荧光激发光源,结合光纤光谱技术测量水体中叶绿素α浓度的新方法。通过分析叶绿素α的激光光致发光机理,得出了水体中叶绿素α荧光发射光谱的相对荧光峰值强度与叶绿素α浓度的近似线性关系。实验结果表明,在红光半导体激光器激励下根据叶绿素α的荧光发射光谱直观地判断叶绿素α的浓度这种方法完全可行,由此为研制叶绿素α荧光仪提供了一种新的光源选择,并为实现现场实时监测海水中叶绿素α浓度提供了实验依据。     

基于PCA的时间分辨油荧光光谱分析及优化

激光诱导荧光技术可广泛应用于油污染的监测中,然而普通的油荧光光谱技术只能实现油污染监测的粗分类,无法区分原油与燃料油的荧光特征。本文基于主成分分析方法(PCA)的时间分辨油荧光分类方法,实验测量了20种油样本的时间分辨荧光光谱特征,给出了对应的荧光寿命和时间分辨油荧光光谱的时序特征。在此基础上,利用前三个主成分构成的三维特征矢量空间,通过分析不同采集时刻下油样本矢量间相关距离的变化,对油样本的时间分辨荧光光谱进行聚类分析。为了体现油荧光变化的时序性,引入矢量距离的离散度参量,提出基于PCA进行时间分辨油荧光光谱分析的优化方法。实验结果表明,基于时间分辨油荧光光谱识别可实现原油与燃料油的光谱时序特征区分,具备良好的油荧光分类效果。     

基于激光诱导荧光技术的蒽检测系统

介绍了一种用Nd：YAG的三倍频（波长355nm）作为激发光,CCD作为探测单元,加上其他光学元件构成的激光诱导荧光检测系统,并测量了蒽的乙醇溶液的荧光光谱。分析了荧光强度与蒽溶液浓度的关系。实验结果表明,蒽溶液浓度在0．003～0．700mg／L范围内与荧光强度有良好的线性关系,相关系数为0．9987,检出限为1．3ng／mL,蒽的回收率在98％～106％范围内。系统适合用于蒽的激光诱导荧光检测。     

Dynamic range and background filtering in raster image correlation spectroscopy

Raster-scan image correlation spectroscopy (RICS) enables researchers to measure molecular translational diffusion constants and concentrations from standard confocal laser scanning microscope images and is suitable for measuring a wide range of mobility, especially fast-diffusing molecules. However, as RICS analysis is based on the spatial autocorrelation function of fluorescence images, it is sensitive to the presence of fluorescent structures within the image. In this study, we investigate methods to filter out immobile or slow moving background structures and their impact on RICS results. Both the conventional moving-average subtraction-based method and cross-correlation subtraction-based method are rationalized and quantified. Simulated data and experimental measurements in living cells stress the importance of optimizing the temporal resolution of background filtering for reliable RICS measurements. Finally, the capacity of RICS analysis to separate two species is studied.     

An integrated laser Raman optical sensor for fast detection of nitrogen and oxygen in a cryogenic mixture

An integrated fiber optic Raman sensor was designed for real-time, nonintrusive detection of liquid nitrogen (LN(2)) in liquid oxygen (LO(2)) at high pressures and high flow rates. This was intended to monitor the quality of LO(2) in oxidizer feed lines during the ground testing of rocket engines. Various issues related to optical diagnosis of cryogenic fluids (LN(2)/LO(2)) in supercritical environment of rocket engine test facility, such as fluorescence from impurity in optical window of feed line, signal-noise ratio, and fast data acquisition time, etc., are well addressed. The integrated sensor employed a frequency doubled 532-nm continuous wave Nd:YAG laser as an excitation light source. The other optical components included were InPhotonics Raman probes, spectrometers, and photomultiplier tubes (PMTs). The spectrometer was used to collect the Raman spectrum of LN(2) and LO(2). The PMT detection unit was integrated with home-built LABVIEW software for fast monitoring of concentration ratios LN(2) and LO(2). Prior to designing an integrated sensor system, its optical components were also tested with gaseous nitrogen (GN(2)) and oxygen (GO(2)).     

基于紫外荧光法的大气SO2气体浓度分析仪

本文详细介绍了紫外荧光法测量二氧化硫(SO2)浓度的原理和分析仪的电路系统设计.阐述了该分析仪硬件电路结构和软件系统结构与流程.分别实现了高温与制冷等温控电路对反应室、转换室和光电倍增管的温度控制;采用基于复杂可编程逻辑器件实现了对紫外荧光信号的信号拾取电路;实现了串行口与USB桥接电路;实现了并行口对GPIB接口电路模拟通信.在性能实验中,表明该分析仪样机能对浓度为0～143 mg/m3的SO2保持线性的和稳定的检测.与国外同类仪器的48 h连续工作对比情况表明,该分析仪具有检测灵敏度高、实时检测以及稳定性好等特点,达到了实际应用的水平.     

Three-dimensional diffusion measurements by scanning microphotolysis

Fluorescence microphotolysis techniques have been used widely to measure lateral diffusion in two-dimensional microsystems such as cell membranes. However, a general microphotolysis method for the analysis of truly three-dimensional diffusion processes has not been developed so far. Here we combine microphotolysis with confocal laser scanning microscopy and numerical data evaluation in such a manner that small volumes (≥ 0.5 μm³) can be photolysed within extended three-dimensional samples and that fluorescence changes can be monitored at high time resolution (measuring interval 0.5 ms) and evaluated for lateral diffusion coefficients. We show furthermore that diffusion measurements can be performed according to three different experimental modes: (i) the instantaneous mode, (ii) the continuous mode and (iii) the mixed mode. For the evaluation of experimental data in terms of diffusion coefficients we have developed and thoroughly characterized a theoretical framework which is based on the numerical simulation of appropriate reaction–diffusion systems. The theoretical framework is rather general and flexible and can be applied to any microphotolysis geometry, makes provision for photolysis during fluorescence monitoring and takes into account the convolution of concentration distributions with imaging point spread functions. The new method was tested employing simple well-defined model systems.     

Evaluation of a femtosecond fiber laser for two-photon fluorescence correlation spectroscopy

This work evaluates a femtosecond fiber laser for use in two-photon fluorescence fluctuation spectroscopy. Fiber lasers present an attractive alternative to Ti:Sapphire systems because of their compact size and portability. Autocorrelation of the second harmonic generation signal from the laser demonstrates that its stability is sufficient for two-photon fluorescence correlation spectroscopy. Fluorescence correlation spectroscopy autocorrelation traces were well fit by a Gaussian-Lorentzian squared model with a beam waist near the diffraction limit for the 810 nm wavelength. A photon counting histogram collected with this system also fit nicely to a single-species model, further demonstrating the quality of the focal shape. The authors conclude that the output from the femtosecond fiber laser is sufficiently stable and has a high enough quality beam shape for fluctuation fluorescence methods, and thus represents an effective, compact, readily portable two-photon excitation source.     

Multicolour analysis and local image correlation in confocal microscopy

Multiparameter fluorescence microscopy is often used to identify cell types and subcellular organelles according to their differential labelling. For thick objects, the quantitative comparison of different multiply labelled specimens requires the three-dimensional (3-D) sampling capacity of confocal laser scanning microscopy, which can be used to generate pseudocolour images. To analyse such 3-D data sets, we have created pixel fluorogram representations, which are estimates of the joint probability densities linking multiple fluorescence distributions. Such pixel fluorograms also provide a powerful means of analysing image acquisition noise, fluorescence cross-talk, fluorescence photobleaching and cell movements. To identify true fluorescence co-localization, we have developed a novel approach based on local image correlation maps. These maps discriminate the coincident fluorescence distributions from the superimposition of noncorrelated fluorescence profiles on a local basis, by correcting for contrast and local variations in background intensity in each fluorescence channel. We believe that the pixel fluorograms are best suited to the quality control of multifluorescence image acquisition. The local image correlation methods are more appropriate for identifying co-localized structures at the cellular or subcellular level. The thresholding of these correlation maps can further be used to recognize and classify biological structures according to multifluorescence attributes.     

Calibration of a planar laser induced fluorescence technique for use in large scale water facilities

A calibration process for planar laser induced fluorescence (PLIF) is presented and employed to investigate the mixing field of a co-flowing jet in a water channel flow. The calibration technique uses individual calibration curves for each pixel in the image array that correct for the non-uniformities of the laser sheet, optics and digital sensor and account for parameters that affect fluorescence efficiency of the dye. A unique commercial optic is introduced into the optical train to generate a thin laser sheet with an approximately uniform laser intensity distribution. The performance of the calibration procedure is investigated by analysis of the calibration data and through the investigation of a co-flowing jet. The results compare well with the results documented in the literature for this flow field. The work shows that the simple approach designed specifically for application in large-scale facilities is suitable for calibration of PLIF style techniques.