Optical characterization of polycarbonate: Influence of additives on optical properties

In laser transmission welding of thermoplastics the optical properties of the joining parts determine the quality of the welding result. Especially, the scattering of laser radiation in the transparent welding part has an impact on weld seam properties. This scattering is caused by additives. For polycarbonate (PC) with different additives the transmittance, the reflectance and the collimated transmittance are measured with a UV‐VIS‐NIR spectrometer. From this data, the optical properties, such as scattering coefficient, absorption coefficient, and anisotropy factor are calculated. The calculations are made with the aid of the four‐flux model of radiation transport in the diffusive approximation. The results show that the additives have a significant influence on the scattering coefficient. For most additives under consideration the scattering is forward directed, which means that most of the radiation is transmitted into the absorbing welding part. However, the power density distribution of the transmitted radiation may differ significantly from PC without additives. So, the weld seam may also differ due to different additives. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 451–455, 2010     

Evaluation of isotope-coded protein labeling (ICPL) in the quantitative analysis of complex proteomes

An evaluation of the ICPL (isotope-coded protein labeling) non-isobaric labeling technique was performed using two different biological models. Two samples containing phage T4 capsids were mixed in a 1:1 ratio after being labeled with the light or heavy versions of the ICPL reagent. The analysis of this proteome demonstrated the feasibility of this approach for differential quantitative proteomics and was employed to optimize the experimental parameters of the ICPL workflow. ICPL-mediated analysis of two more complex proteomes, those of a Salmonella enterica serovar Typhimurium virulent strain and an isogenic attenuated mutant, and its comparison with the results obtained in a 2D-PAGE “classical” approach confirmed that ICPL is a valuable alternative to other labeling techniques currently in use. In addition, our results suggest that labeling at the peptide level instead of following the standard ICPL workflow should increase both the number of proteins quantified and the reliability of the quantification.     

Quantification of Photosensitized Singlet Oxygen Production by a Fluorescent Protein

Fluorescent proteins are increasingly becoming actuators in a range of cell biology techniques. One of those techniques is chromophore‐assisted laser inactivation (CALI), which is employed to specifically inactivate the function of target proteins or organelles by producing photochemical damage. CALI is achieved by the irradiation of dyes that are able to produce reactive oxygen species (ROS). The combination of CALI and the labelling specificity that fluorescent proteins provide is useful to avoid uncontrolled photodamage, although the inactivation mechanisms by ROS are dependent on the fluorescent protein and are not fully understood. Herein, we present a quantitative study of the ability of the red fluorescent protein TagRFP to produce ROS, in particular singlet oxygen (¹O₂). TagRFP is able to photosensitize ¹O₂ with an estimated quantum yield of 0.004. This is the first estimation of a quantum yield of ¹O₂ production value for a GFP‐like protein. We also find that TagRFP has a short triplet lifetime compared to EGFP, which reflects relatively high oxygen accessibility to the chromophore. The insight into the structural and photophysical properties of TagRFP has implications in improving fluorescent proteins for fluorescence microscopy and CALI.     

Rapid Prototyping of Low‐Loss IR Chalcogenide‐Glass Waveguides by Controlled Remelting

A method for fabricating infrared‐transmitting waveguides that yields low optical losses and strong confinement of light is presented. The method minimises the number of fabrication steps by exploiting the photosensitivity of arsenic trisulfide glass, using it both as a photoresist and as a waveguiding material. Controlled annealing/remelting of the waveguides minimises scattering due to fluctuations in refractive index at the interface between the waveguide and the surrounding medium, allowing low losses to be realised. Bends and Y‐splitter structures have been realised, as well as the longest As₂S₃ serpentine planar waveguides yet reported.     

激光防护技术的发展现状

为了对抗日趋严重的激光致盲威胁 ,世界各国加速发展激光防护技术 ,并已取得了相当大的进展。本文综述激光防护技术的发展现状     

氦氖激光纵模脉冲检测及其数据处理

在分析常用低噪声快速光电探测器的基础上,选择PIN光电二极管来探测氦氖激光纵模脉冲。通过合理设计降低前放电路的噪声,根据被测脉冲频率设计探测电路的带宽,达到提高信噪比的目的。同时在后端的数据处理中,根据激光脉冲的波形函数,利用曲线拟合的方法来进一步去除测量中的各种噪声,从而准确地了解脉冲的形状、相位等信息,大大地提高了在现有硬件设备条件下测量的准确性,减小了测量误差。     

Application of enthalpy method for moving boundary problem in laser surface melting

A numerical analysis was carried out to study the moving boundary problem in the physical process of pulsed Nd-YAG laser surface melting prior to vaporization. The enthalpy method was applied to solve this two-phase axisymmetrical melting problem. Computational results of temperature fields were obtained, which provide useful information to practical laser treatment processing. The validity of enthalpy method in solving such problems is pressented. Supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences     

A ‘tree’ for generation and identification of the colour symmetry point groups

A flow chart (inverted ‘tree’) for generating and identifying the 58 magnetic and 18 polychromatic point groups using a classification for the 32 generating crystallographic point groups is suggested. The idea of colour generator is explored for generating the colour symmetry point groups. The advantages in presenting the identification of colour groups through a tree are discussed.     

Calorimetric study of laser-irradiated thin foil targets

Hydrodynmaic efficiency of laser-irradiated thin aluminum and gold-coated aluminum targets was experimentally determined using a specially designed cone calorimeter. Velocity of the accelerated target and ablation pressure were also estimated from the experimental data. The laser irradiance range used in the experiments was between 10¹² and 10¹³ watts/cm². Experiments indicate that the fall in the hydrodynamic efficiency due to gold coating on aluminum target is about 12% at an irradiance of 8 × 10¹² W/cm².     

氩团簇高信噪比13—23nm软x射线辐射谱实验观察

用150fs的掺钛蓝宝石激光系统, 在功率密度约为5×10¹⁵ W/cm²时 激励氩(Ar)团簇，利用具有空间分辨能力的平场光栅谱仪观察到13—23nm波段Ar的软x射线谱，并观察到Ar的11阶离子谱线.在较宽的激光脉宽和较低的激光功率密度情况下，通过激励Ar团簇，获得 了Ar的高阶电离度的实验结果，且谱线的信噪比明显好于光场感应电离的情况，说明团簇的 形成大幅度地提高了激光能量的吸收效率. 关键词： Ar团簇 超短强激光 软x射线辐射