Fluorescent Conjugated Polyelectrolytes for Bioimaging

This Feature Article summarizes the recent advances of water‐soluble fluorescent conjugated polyelectrolytes (CPEs) in bioimaging. Apart from a brief overview of traditional linear CPEs, a special emphasis is placed on CPEs that can self‐assemble into or are born with three‐dimensional nano‐architectures, including grafted CPEs, hyperbranched CPEs, and polyhedral oligomeric silsesquioxanes(POSS)‐based CPE derivatives. These CPEs naturally form nanoparticles with sizes ranging from 3 to 100 nm in aqueous media, and possess reactive functional groups for bioconjugation or complexation with desired biorecognition elements. The tunable size, low cytotoxicity, good photostability, and ease of surface modification ultimately enable these CPEs with wide applications in in vitro intracellular protein sensing, cell detection, in vivo cell imaging and drug tracking. Moreover, traditional linear CPEs can be transformed into uniform nanoparticles by complexation with oppositely charged biomolecules to allow for cell detection and in situ drug release monitoring. The work featured herein not only reveals the important molecular design principles of CPEs for different imaging tasks, but also highlights the promising directions for the further development of CPE‐based imaging materials.     

光纤金属腐蚀传感器的应用及研究现状

随着经济的高速发展,金属材料腐蚀时刻影响着安全生产,对国民经济造成了重大损失,因此如何有效地监控金属材料腐蚀就显得特别重要。对目前用于金属材料腐蚀监控的光纤金属腐蚀监控技术进行了分类,分析了各种技术的优缺点以及光纤金属腐蚀传感器的工作原理、研究应用现状及发展趋势。     

CaF2衍射光学元件的金刚石车削工艺优化

为了提高单点金刚石车削CaF2衍射光学元件(DOE)的表面质量和衍射效率,首先基于Beckman标量散射理论和有效面积法,建立了表面粗糙度误差和表面轮廓误差对衍射效率影响的数学模型.然后,结合CaF2的车削特性和DOE的结构特点,优化了CaF2 DOE的车削模型.同时,给出了不同工艺条件下半圆金刚石刀具的最佳车削位置和最优刀具半径,实现了对CaF2 DOE表面粗糙度的控制.最后,在该优化模型的指导下,获得了表面粗糙度为3.4 nm、阴影区域宽度为28.7μm的高表面质量的CaF2 DOE,验证了所提优化车削模型的可靠性.所提车削模型对提高包含CaF2 DOE折-衍混合光学系统的成像质量具有重要意义.     

Damage detection method in complicated beams with varying flexural stiffness

A damage detection method for complicated beam-like structures is proposed based on the subsection strain energy method (SSEM), and its applicability condition is introduced. For a beam with the continuously varying flexural stiffness and an edge crack, the SSEM is used to detect the crack location effectively by numerical modal shapes. As a complicated beam, the glass fiber-reinforced composite model of a wind turbine blade is studied based on an experimental modal analysis. The SSEM is used to calculate the damage index from the measured modal parameters and locate the damage position in the blade model successfully. The results indicate that the SSEM based on the modal shapes can be used to detect the damages in complicated beams or beam-like structures for engineering applications.     

Vertical cavity surface emitting laser transverse mode and polarization control by elliptical hole photonic crystal

The polarization of traditional photonic crystal(PC) vertical cavity surface emitting laser(VCSEL) is uncontrollable,resulting in the bit error increasing easily.Elliptical hole photonic crystal can control the transverse mode and polarization of VCSEL efficiently.We analyze the far field divergence angle,and birefringence of elliptical hole PC VCSEL.When the ratio of minor axis to major axis b/a = 0.7,the PC VCSEL can obtain single mode and polarization.According to the simulation results,we fabricate the device successfully.The output power is 1.7 mW,the far field divergence angle is less than 10°,and the side mode suppression ratio is over 30 dB.The output power in the Y direction is 20 times that in the X direction.     

Mechanical stress effect on the crystallization behavior of Ge2Sb2Te5 films studied by electrical resistance measurement

The mechanical stress effect on the crystallization behaviour of Ge₂Sb₂Te₅(GST) thin films is carefully investigated by electrical resistance measurements. It is found that the crystallization temperature of GST films increases as external compressive stress is applied, while the crystallization temperature decreases under tensile stress. We also find that the uneven distribution of extrinsic stress can widen the span of transition temperature. These results clearly demonstrate that mechanical stress plays an important role during the crystallization process of GST films and may further influence the reliability and storage speed of relevant devices. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

适用于表面分析的小型低能电子显微镜

介绍并表征了一套单法兰集成的低能电子显微镜. 这套显微镜中采用了10o偏转角的磁分束器,从而有利于将其集成到一个10 in的法兰上. 电子光学系统中的一些修正单元被简化,以使其结构简单,容易操作. 样品被置于地电位,方便各静电透镜浮在高电压上. 通过几个实验展示了这台显微镜在典型的低能电子成像、低能电子衍射和光电子成像模式下的性能. 低能电子成像的空间分辨率为51 nm. 利用飞秒激光做光源,相应的非线性光电子发射过程使得这台设备非常适合进行光学近场现象的观察,并获得110 nm的光电子成像空间分辨率.     

基于遗传算法的斜入射窄带滤光片膜系优化设计

根据薄膜窄带滤光片在斜入射时的偏振特性,提出了基于遗传算法的斜入射薄膜窄带滤光片膜系优化设计方法.根据开发的程序,设计并制备了一组可用于18°倾斜入射的0.8纳米信道间隔的五腔薄膜窄带滤光片.该滤光片能有效地抑制斜入射时偏振光中心波长的分离现象,降低器件的偏振相关损耗,通过角度调谐能实现选择波长的改变.通过与针法设计的滤光片膜系相比,遗传算法得到的膜系具有更高的矩形度、更大的波长调谐范围以及更低的偏振相关损耗.实验结果表明其满足设计要求并有超过25纳米的波长调谐范围.     

Research on meat species and freshness identification method based on spectral characteristics

This paper proposed a method of meat recognition method based on the artificial neural network of wavelet denoising. In this study, visible reflected spectra (from 380 nm to 780 nm) of beef and pork with different freshness were measured with fiber sensor spectrometer. The wavelet multi-resolution analysis was employed and the ideal way of decomposing layers was selected to eliminate the burr noise or abnormal data caused by absorption and scattering spectra signals in optical fiber. Then a kind of with a double-hidden layer was applied to analyze meat spectral reflectance data, and the back propagation-artificial neural network (BP-ANN) was trained by Polak–Ribiere conjugate gradient learning algorithm. The experimental results show that the method can analyse the complex spectrum signals and achieve a good identification on the species and freshness of meat.     

基于表面等离子体共振增强的硅基锗金属-半导体-金属光电探测器的设计研究

金属-半导体-金属光电探测器的光栅结构可激发表面等离子体, 有效增强探测器的吸收. 为深入研究器件结构对于表面等离子体的激发及共振增强的影响, 本文提出了一种具有超薄有源层的硅基锗金属-半导体-金属光电探测器的设计方法. 采用时域有限差分的方法详细分析了光栅周期、光栅厚度、 光栅间距及有源层厚度对于表面等离子体共振增强器件性能的影响, 通过仿真模拟获得了器件的最佳结构, 详细地分析了各个界面激发的表面等离子体及其共振模式对于光谱吸收增强的机理. 仿真结果表明, 有源层锗的厚度为400nm的超薄器件在通信波段具有较高的吸收, 尤其在1550nm波长处器件的归一化的光谱吸收率可以高达53.77%, 增强因子达7.22倍. 利用共振效应能够极大地提高高速器件的光电响应, 为解决光电探测器响应度与响应速度之间的相互制约关系提供了有效途径. 关键词： 表面等离子体 锗探测器 时域有限差分仿真