On using lens-assisted hologram interferometry to investigate semiconductor device behaviour

The paper analyses some of the causes that limit the performance of the hologram interferometry method when used for the study of the behaviour of semiconductors devices. Then some results are shown obtained by the authors using a method of lens-assisted microscope hologram interferometry for studying such structures. The method allows detection of defects and, besides, it renders quantitatively the structure local non-uniformities during the normal operation of the semiconductor devices.     

The exterior Dirichlet problem for quasi-linear elliptic equations with small boundary data

It is shown that if the order of non-uniformity of a quasi-linear elliptic equation is h,10,2(h–1)/h norm. For 0h1,existence of a bounded solution is guaranteed without any smallness assumption on the given boundary data.More precise information is given for the special case of the minimal surface equation.     

利用可见-近红外-中红外超快光谱揭示离子交换法制备的少层MoS2中缺陷介导的载流子动力学

本文结合可见-近红外-中红外瞬态吸收光谱技术对离子交换法制备的少层MoS₂中缺陷介导的载流子动力学进行了详细的解析. 在近红外瞬态吸收光谱中观察到的宽带漂白信号表明少层MoS₂纳米片带隙中分布着大量的缺陷态. 实验结果明确揭示了载流子被缺陷态的快速捕获以及进一步的复合过程,证明带隙中的缺陷态对MoS₂光生载流子动力学过程起着至关重要的作用. 在中红外瞬态吸收光谱中观察到的正信号到负信号的转变进一步证实了在导带下小于0.24 eV处存在被载流子占据的缺陷态. 这些在少层MoS₂纳米片中存在的缺陷态可以作为有效的载流子捕获中心来辅助光生载流子在皮秒时间尺度内完成非辐射复合过程.     

Modified Gerchberg–Saxton (G-S) Algorithm and Its Application

The Gerchberg–Saxton (G-S) algorithm is a phase retrieval algorithm that is widely used in beam shaping and optical information processing. However, the G-S algorithm has difficulty obtaining the exact solution after iterating, and an approximate solution is often obtained. In this paper, we propose a series of modified G-S algorithms based on the Fresnel transform domain, including the single-phase retrieval (SPR) algorithm, the double-phase retrieval (DPR) algorithm, and the multiple-phase retrieval (MPR) algorithm. The analysis results show that the convergence of the SPR algorithm is better than that of the G-S algorithm, but the exact solution is not obtained. The DPR and MPR algorithms have good convergence and can obtain exact solutions; that is, the information is recovered losslessly. We discuss the security advantages and verification reliability of the proposed algorithms in image encryption. A multiple-image encryption scheme is proposed, in which n plaintexts can be recovered from n ciphertexts, which greatly improves the efficiency of the system. Finally, the proposed algorithms are compared with the current phase retrieval algorithms, and future applications are discussed. We hope that our research can provide new ideas for the application of the G-S algorithm.     

Observation of laser driven supercritical radiative shock precursors

We present a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using targets filled with xenon gas at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured shock quantities (electronic density and propagation velocity) are shown to be in good agreement with theory and numerical simulations.     

单级G-M 150制冷机性能实验研究

为满足高温超导和低温气体处理系统等工程应用项目的大冷量需求,单级大冷量G-M制冷机成为目前国内外的研究热点。文章中描述了以G-M150为基础的制冷机综合性能测试方法及实验平台,并对其制冷温度和制冷量两个主要性能的影响因素进行实验研究,为探讨20K单级大冷量G-M制冷机的研究提供参考。     

Simultaneous Determination of Acetylsalicylic Acid and Caffeine in Pharmaceutical Formulation by First Derivative Synchronous Fluorimetric Method

A sensitive, rapid, and specific assay has been developed for the simultaneous determination of acetylsalicylic acid and caffeine in commercial tablets based on their natural fluorescence. The mixture of these drugs was resolved by first derivative synchronous fluorimetric technique using two scans. At Δλ=106 nm, using first derivative synchronous scanning, only acetylsalicylic acid yields a detectable signal at 316 nm (peak to zero method) which is unaffected by caffeine. At Δλ=30 nm, the signal of caffeine at 288 nm (peak to zero method) is not affected by acetylsalicylic acid. The range of application is between 0.021 and 41.62 μg ml⁻¹ (correlation coefficient, R=0.9995) for acetylsalicylic acid and between 0.4486 and 44.86 μg ml⁻¹ (correlation coefficient, R=0.99786) for caffeine. The recovery range of 98.40–102% for acetylsalicylic acid and 90–100.5% for caffeine from their synthetic mixture was reported. Overall recovery of both compounds about 97–99% for acetylsalicylic acid and 97–98% for caffeine was obtained from real sample analysis. The detection limits are 0.0013 μg ml⁻¹ and 0.0306 μg ml⁻¹ for acetylsalicylic acid and caffeine, respectively. The relative standard deviation (n=10) for 20 μg ml⁻¹ of acetylsalicylic acid is 2.75% and for 2.2 μg ml⁻¹of caffeine is 1.7%.     

The effect of disulfide bonds on protein folding,unfolding, and misfolding investigated by FT–Raman spectroscopy

Disulfide bond is relevant to many protein folding/unfolding functions and conformational diseases. To elucidate the effects of disulfide bonds on protein folding, unfolding, and misfolding, we performed Fourier transform–Raman measurements on serial chemical‐induced denaturations of bovine serum albumin (BSA). By directly monitoring Raman stretching at S–S (~507 cm⁻¹), S–H (~2566 cm⁻¹), amide I (1655 cm⁻¹ for α‐helix; 1667 cm⁻¹ for β‐sheet structure), and amide III (>1300 cm⁻¹ for α‐helix; 1246 cm⁻¹ for β‐sheet structure), the status of disulfide bonds and secondary structure of BSA at different states were elucidated. Both disulfide bonds and secondary structure (mostly in α‐helix) of BSA appeared relatively stable even when the protein was unfolded by urea solution. However, disulfide bonds were completely reduced and protein secondary structure changed from α‐helix to a relatively β‐sheet dominant when the protein was modified by the mixed solution of urea and dithiothreitol (urea/DTT). Adhering to these structural changes, the protein proceeded to different degrees of polymerization. BSA would aggregate into a high molecular mass (over 700 kDa) of protein ensemble when it was exposed to the mixed urea/DTT solution. An irreversible change in S–S/S–H conversion and secondary structure was responsible for protein misfolding. We demonstrate here that Fourier transform–Raman directly probe S–S/S–H conversion and secondary structural change of BSA at different states, and these results clearly indicate that disulfide bonds and secondary structure of BSA serve as concrete frameworks to stabilize protein structure. As the frameworks collapse, the protein undergoes an irreversible structural change and results in protein misfolding. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of RGO/Cu8S5/PPy Composite Nanosheets with Enhanced Peroxidase‐Like Activity for Sensitive Colorimetric Detection of H2O2 and Phenol

In this paper, a novel strategy for the fabrication of reduced graphene oxide (rGO)/Cu₈S₅/polypyrrole (PPy) composite nanosheets with Cu₈S₅ nanoparticles and PPy layer anchored on the surface of rGO as peroxidase‐like nanocatalyst is reported. During the synthesis, graphene oxide (GO)/CuO composite nanosheets are prepared first and used as templates, then the sulfuration of CuO and polymerization of pyrrole are accompanied with the reduction of GO, resulting in ternary rGO/Cu₈S₅/PPy composite nanosheets. The synthesized Cu₈S₅ nanoparticles with a diameter in the range from tens to hundreds of nanometers are dispersed within PPy decorated rGO nanosheets. The resultant ternary rGO/Cu₈S₅/PPy composite nanosheets exhibit a higher peroxidase‐like catalytic activity toward the oxidation of 3,3′,5,5′‐tetramethylbenzidine in the presence of H₂O₂ than GO/CuO and rGO/CuS composite nanosheets, revealing a synergistic effect on their activity. The as‐prepared rGO/Cu₈S₅/PPy platform provides a simple colorimetric approach for the detection of H₂O₂ and phenol with a high sensitivity. This work offers a new way for the fabrication of rGO‐based nanocomposite with superior enzyme‐like activity, which displays great potential applications in biocatalysis and environmental monitoring.