Surface plasmon-assisted widefield non-linear imaging of gold structures

In this paper, we demonstrate how the confinement and enhancement of optical fields by surface plasmon resonance can allow non‐linear microscopy to be performed in a simple, cost‐effective widefield configuration, rather than the more usual laser‐scanning arrangement. We present second harmonic and two‐photon luminescence widefield images of dielectric and gold samples obtained with both prism‐based and high numerical aperture objective (‘prismless’) microscope arrangements.     

Colour centres and thermally stimulated luminescence of Na2ZnCl4

Thermally stimulated luminescence (TSL) of Na₂ZnCl₄ single crystals showed three glow peaks having their peak maxima at 343, 425 and 475 K. Optical absorption (OA) data of unirradiated samples revealed an absorption band at 272 nm while X-irradiation caused additional bands at 462 and 723 nm. Growth and room temperature annealing studies of TSL and OA supported the idea of attribution of 425 K glow peak and 462 nm absorption band to F-centres. The 272 nm OA band is due to Zn²⁺ centres whereas the 723 nm absorption band and 475 K glow peak have been assigned to Zn⁺ centres.     

Single Photon Detection of InGaAs／InP APD Based on Gated-mode Operation at Telecom Wavelengths

Based on the commercially available avalanche photodiodes, the basic needs of gated-mode operation for single photon are discussed. Gated-mode technique based on the experimental data for detection of single photon is analyzed at communication wavelengths so that the basic operation parameters can decide properly for efficient detection of single photon. The bias voltage has related to the punch-through voltage in combining the cooling technique with synchronization to decrease the dark counts.     

Subpixel position measurement using 1D, 2D and 3D centroid algorithms with emphasis on applications in confocal microscopy

The accuracy with which centroid algorithms in 1D, 2D and 3D can estimate an object's position has been investigated. Three factors that can influence the method's accuracy have been investigated: systematic error of the algorithm, influence of photon noise and the influence of perturbations such as scanning nonlinearity. The variation of the accuracy with parameters that are relevant for confocal microscopy, such as object diameter and photon noise/pixel, has been considered. Theory and simulations presented show that the variation of the accuracy with respect to such parameters can differ drastically between the 1D, 2D and 3D cases. Experiments performed using microspheres show that the magnitudes of the three types of error can be approximately the same under normal operating conditions and that it is therefore necessary to take all three into account when assessing the total error.     

Characterization of ancient Indian iron and entrapped slag inclusions using electron, photon and nuclear microprobes

Compositional and structural information were obtained from an ancient 1600-year old Indian iron using microprobe techniques (EDS, μXRD and μPIXE). Several different local locations in the iron matrix and in the entrapped slag inclusions were analyzed. The P content of the metallic iron matrix was very heterogeneous. Lower P contents were observed in the regions near slag inclusions. This was correlated to the dephosphorization capacity of the slag. The crystallized phases identified in the slag inclusions were wüstite and fayalite. The compositions of the slag inclusions were relatively homogeneous.     

时间相关单光子计数记录快速荧光寿命图像

基于时间相关单光子计数(TCSPC)的荧光寿命成像(FLIM)的获取时间取决于成像的图像尺寸、样品寿命的精度及样品计数率.对于高密度荧光团样品,如染色组织或植物细胞,当前可用的样品计数率与TCSPC荧光寿命成像技术最高的计数率接近.该文描述了在高计数率下TCSPC性能,并估计计数损失及堆积效应.结果表明,整个体系的寿命误差比预料的要小.因此,TCSPC FLIM可在获取时间低于1 s的情况下记录寿命图像.为增加FLIM时间序列记录,利用存储交换技术,在采集下一个光子期间读取正在记录的数据,使用两个平行TCSPC模块,可以每秒两幅图像记录荧光寿命时间序列.该技术可应用于活体植物组织叶绿素的瞬态测量.     

X射线脉冲星导航探测器的微通道板甄选

根据应用于X射线脉冲星导航系统的大面阵X射线探测器对微通道板(MCP)性能的要求,研究了甄选微通道板的方法。确定了甄选微通道板的4个关键参量,分别是增益的均匀性、阻抗匹配、暗计数率、增益系数。针对这4个参量设计了相应的测试实验,制定了甄选MCP的流程,并对采用该流程甄选出的MCP进行了幅值和计数率的测试。测试结果显示:采用单通道阳极接收信号时,每一个探测单元的幅值存在的相对误差各不相同,第i个探测单元输出的信号幅值的最大相对误差Δ1i和最小相对误差Δ2i的波动分别为7%~13.5%,3%~6.7%;而采用四通道共享阳极时输出信号的Δ1i为7.8%、Δ2i为3.1%;单通道阳极计数率之和(n=n1+n2+n3+n4)与四通道共享阳极计数率N的相对误差为4.38%,小于预估值10%。上述实验结果表明该甄选方法能够甄选出满足探测器要求的MCP。     

Automatic quantification of mitochondrial fragmentation from two‐photon microscope images of mouse brain tissue

The morphology of mitochondria can inform about their functional state and, thus, about cell vitality. For example, fragmentation of the mitochondrial network is associated with many diseases. Recent advances in neuronal imaging have enabled the observation of mitochondria in live brains for long periods of time, enabling the study of their dynamics in animal models of diseases. To aid these studies, we developed an automatic method, based on supervised learning, for quantifying the degree of mitochondrial fragmentation in tissue images acquired via two‐photon microscopy from transgenic mice, which exclusively express Enhanced cyan fluorescent protein (ECFP) under Thy1 promoter, targeted to the mitochondrial matrix in subpopulations of neurons. We tested the method on images prior to and after cardiac arrest, and found it to be sensitive to significant changes in mitochondrial morphology because of the arrest. We conclude that the method is useful in detecting morphological abnormalities in mitochondria and, likely, in other subcellular structures as well.     

相干光时域反射仪中受激布里渊散射的抑制

采用对分布反馈半导体激光器(DFB-LD)直接进行小信号电流调制的方法抑制相干光时域反射仪(COT-DR)中的受激布里渊散射(SBS),分析了DFB-LD受到小信号电流调制时的频谱特性以及SBS阈值和频谱宽度的关系,设计了实验电路和光路抑制光纤中SBS。理论分析和实验结果表明,在低频调制电流处,光源频谱宽度随调制频率增加而减小,随调制幅度增加而增加,而SBS随频谱宽度增加而减弱,直接用电流调制激光器可抑制COTDR中的SBS。