Label‐Free Imaging of Nanoparticle Uptake Competition in Single Cells by Hyperspectral Stimulated Raman Scattering

Imaging and quantification of nanoparticles in single cells in their most natural condition are expected to facilitate the biotechnological applications of nanoparticles and allow for better assessment of their biosafety risks. However, current imaging modalities either require tedious sample preparation or only apply to nanoparticles with specific physicochemical characteristics. Here, the emerging hyperspectral stimulated Raman scattering (SRS) microscopy, as a label‐free and nondestructive imaging method, is used for the first time to investigate the subcellular distribution of nanoparticles in the protozoan Tetrahymena thermophila. The two frequently studied nanoparticles, polyacrylate‐coated α‐Fe₂O₃ and TiO₂, are found to have different subcellular distribution pattern as a result of their dissimilar uptake routes. Significant uptake competition between these two types of nanoparticles is further discovered, which should be paid attention to in future bioapplications of nanoparticles. Overall, this study illustrates the great promise of hyperspectral SRS as an analytical imaging tool in nanobiotechnology and nanotoxicology.     

Al2O3:C光致荧光剂量计初步研究

采用液体成膜法制备了Al₂O₃:C光致荧光剂量计（OSLD），开展了剂量学性能的初步研究。退火后本底为0.03 mGy，均匀性优于2%，在0.02 mGy~10 Gy测量范围内具有良好线性响应，线性相关系数R²=0.999 6，对β、γ射线响应系数差异约10%，对中子响应系数约为β、γ射线的4%~7%，剂量计多次测量响应信号无明显衰减，照后两个月响应变化为5%，可用于一定周期内剂量存档、复测。上述结果表明，液体成膜方法制备的OSLD具有良好的剂量学性能，证明该方法可行。     

Dielectric spectroscopy for the determination of the glass transition temperature of pharmaceutical solid dispersions

The purpose of this study was to evaluate analytical techniques for the measurement of the glass transition temperature of HPMC and formulated solid dispersions thereof. Unmodified samples of various grades of HPMC and solid dispersions of HPMC and itraconazole produced by hot melt extrusion were analyzed by thermomechanical analysis, differential scanning calorimetry, thermally stimulated depolarization current and dielectric spectroscopy. It was found that dielectric spectroscopy offers the best accuracy and reproducibility for analysis of the base HPMC powders regardless of the substitution type or viscosity grade and that the obtained results were not frequency dependent. The results of dielectric measurements of solid dispersions prepared by hot melt extrusion were compared with predicted values of the Gordon–Taylor equation. It was found that time–temperature superposition effects and small molecule frequency dependence makes broadly applying determination of the glass transition temperature in drug dispersions by dielectric spectroscopy prohibitively difficult.     

Time-correlated single photon counting system and light-collection system for studying fluorescence emitters under high-vacuum conditions: Use of immersion objective and ionic liquid

In this paper, we introduce a time-correlated single photon counting system and an efficient light-collection system for studying fluorescence emitters under high-vacuum conditions; the latter system has an immersion objective, and an ionic liquid is used as a refractive index matching medium. The ionic liquid is positioned in high vacuum. The time-correlated single photon counting system has modified photomultiplier tubes that act as photon detectors. The light-collection system is designed to be simple, compact, and easy to use. In order to verify the performance of these systems, the optical properties of colloidal semiconductor nanocrystals (CdSe/ZnS) and fluorescent dye molecules are studied as examples.     

Understanding excitation energy transfer in metalloporphyrin heterodimers with different linkers,bonding structures,and geometries through stimulated X-ray Raman spectroscopy

We present simulations of stimulated X-ray Raman (SXRS) signals from covalently bonded porphyrin heterodimers with different linkers, chemical bonding structures, and geometries. The signals are interpreted in terms of valence electron wavepacket motion. One- and two-color SXRS signals can both mark excitation energy transfer (EET) between the porphyrin monomers. It is shown that the SXRS signals provide a novel window into EET dynamics in multiporphyrin systems, and can be used as a powerful tool to monitor the subtle chemical environment which affects EET.     

Thermally Stimulated Depolarization Current

Abstract

Thermally stimulated discharge or thermally stimulated polarization and depolarization current is becoming a valuable technique in discerning transitions having a small relaxation strength. Polymer liquid crystals (PLCs) are a group of such materials. This article provides a review of the different experimental techniques associated with the technique and their application to PLCs. Experimental results for thermotropic longitudinal PLCs are presented.     

一种测量超窄激光线宽的新方法

提出使用布里渊光纤环形激光器产生的二阶Stokes光作为参考光测量超窄激光线宽的新方法.分析了布里渊光纤环形激光器的一阶和二阶Stokes光的线宽压缩特性,指出输出的二阶Stokes光线宽可以压缩到亚Hz量级.理论上分析了使用零线宽参考光的拍频法测量激光线宽的特点,结果表明参考激光为理想零线宽时,拍频频谱与待测激光频谱线型形状完全相同.最后指出该方法可以有效测量<100kHz的激光线宽,并且具有装置简单、测量精度高和测量波段宽的优点.     

固体拉曼激光器

简要介绍了固体拉曼激光器的研究现状,总结了几种常用的固体拉曼晶体[LiIO3,Ba(NO3)2,CaWO4]的受激拉曼实验特性,并对如何设计各种形式的拉曼激光装置以取得良好的频率转换做了分析。最后对固体拉曼激光器的发展做了展望。