Diagnostic value of nonlinear optical signals from collagen matrix in the detection of epithelial precancer

During precancer development in epithelium, neoplastic cells remodel the underlying stroma, for example, the basement membrane, capillaries, fibroblasts, and extracellular matrix. The purpose of this study is to investigate the relationship between the nonlinear optical signals from the collagen matrix in stroma and the progression of early epithelial carcinogenesis. Two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) signals were measured from the stroma of hamster oral cheek pouch in vivo. We found that three features, including the intensity ratio of TPEF over SHG, the spatial frequency distribution, and the texture feature of SHG images, provide the quantitative identification of epithelial precancer at different pathologic stages. We demonstrated that the combination of all three features by using a support vector machine algorithm can significantly improve the accuracy in the detection of epithelial precancer.     

医用生物材料的低温保存研究

生物材料的低温保存一般都要经历降温过程、低温储存过程及复温过程,其中降温过程中对生物细胞的影响最大.每一种生物细胞都有自己合适的降温速率,如能满足其这种降温速率,细胞所受到的低温损伤最小,则生物细胞的复活率最高.文中介绍程序控制变速降温装置的主要结构及几种典型生物体的降温过程.最后,对器官的低温保存进行分析讨论.     

聚乙烯基咔唑与Alq3混合薄膜的发光性能与能量传递过程

研究了Alq3与聚乙烯基咔唑(PVK)按不同比例的混合体系制备的薄膜的发光特性.通过对混合薄膜的吸收光谱、激发光谱和发射光谱的分析，研究了PVK与Alq3之间的 能量传递规律.当Alq3与PVK的质量比为1∶7时，能量传递效率最高.用一个由单链模 型扩展到包括杂质的哈密顿量对实验进行模拟，发现该模型能够较好地解释有关的实验结果. 关键词： 吸收光谱 激发光谱 发射光谱 能量传递     

基于无基底焦平面阵列红外热像仪的理论模型分析

基于双材料微悬臂梁热变形原理的光学读出非制冷红外探测阵列经历了从有基底结构向无基底结构的发展过渡,无基底阵列的红外成像结果和有限元模型分析均表明无基底阵列不满足恒温基底条件.本文结合电学比拟的方法,提出了一种新的基于无基底焦平面阵列(focal plane Array,FPA)的热传递分析的理论模型.分析采用整体考虑的思路,避开了无基底FPA阵列各单元热传递互相影响所产生的复杂热分布分析,并考虑了框架对热量的吸收与传递.理论模型采用外边框与环境等温的边界条件,虽不及有限元方法对边界条件的处理灵活,但也已取 关键词： 光学读出 无基底 非制冷红外成像 焦平面阵列     

The optical near-field speckles and their first order statistics on the basis of the integral equations of electromagnetic field

Speckle fields are the random light wave distributions produced when the light fields are scattered from random surfaces or a random medium. They appear in many optical phenomena that are related to light propagations[1,2] and have found wide appli-cations in a variety of scientific and technical fields. The examples of the recent impor-tant applications of speckles include the analysis of the movement of the granules[3], the three-dimensional imaging for the microstructures of metal nanocryst…     

Determination of path length difference by low coherence interference spectrum

Path length difference is the key parameter in two-beam interferometer, especially in low coherence interferometer. It determines the visibility of the interference fringes. In this study, we present a method to determine the path length difference between two arms of a fiber optic Mach–Zehnder interferometer by evaluating the peaks of power distribution of the interference spectrum with a wide band light source. The experimental results are in close agreement with the theoretical calculations.     

Nonvolatile photorefractive holographic recording in Sc:Ce:Cu:LiNbO3

In this paper experimental studies of nonvolatile photorefractive holographic recording in Ce:Cu:LiNbO₃ crystals doped with Sc(0,1,2,3 mol%) were carried out. The Sc:Ce:Cu:LiNbO₃ crystals were grown by the Czochralski method and oxidized in Nb₂O₅ powders. The nonvolatile holographic recording in Sc:Ce:Cu:LiNbO₃ crystals was realized by the two-photon fixed method. We found that the recording time of Sc:Ce:Cu:LiNbO₃ crystal became shorter with the increase of Sc doping concentration, especially doping with Sc(3 mol%), which exceeds the so-called threshold, and there was little loss of nonvolatile diffraction efficiencies between Sc(3 mol%):Ce:Cu:LiNbO₃ and Ce:Cu:LiNbO₃ crystals.     

四轮驱动全向底盘的控制方法研究

为提高机器人移动的灵活性和机动性,使机器人到任意位置均沿直线行走并改变姿态,需在传统的两轮驱动底盘上增加驱动轮,本文主要针对四轮驱动全向底盘的控制方法进行研究。本文对四轮驱动全向底盘进行运动学分析并建模,得到了控制系统传递函数,并进仿真验证;对四轮驱动全向底盘进行了动力学建模,分析了如何避免出现“打滑”现象;导航方式采用了经济、精度较高的全向码盘导航方式;控制上采用闭环控制,加入前置探测点和超前校正环节,并且考虑了实际过程中机体的加减速问题。实验结果表明,提出的控制方法可以使四轮驱动全向底盘实现预设功能,并且具有较高的控制精度,研究内容对机器人的灵活移动有着十分重要的意义。     

拓扑绝缘体(Bi0.5Sb0.5)2Te3薄膜中的线性磁阻

本文报道了拓扑绝缘体(Bi_0.5Sb_0.5)₂Te₃薄膜中线性磁阻问题的系统性研究工作. 此体系中, 线性磁阻在很宽的温度和磁场范围内出现: 磁场高达18 T时磁阻仍没有饱和趋势, 并且当温度不高于50 K时, 线性磁阻的大小对温度的变化不敏感. 栅压调控化学势可明显改变线性磁阻的大小. 当化学势接近狄拉克点时, 线性磁阻最为显著. 这些结果说明电荷分布的不均匀性是引起该材料线性磁阻的根源.     

Enhanced photovoltaic properties of polymer-fullerene bulk heterojunction solar cells by thermal annealing

The effect of a thermal annealing treatment on the performance of bulk heterojunction photovoltaic cells based on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) and fullerene (C₆₀) composites is investigated. Upon thermal annealing at 120 ^°C, short-circuit current and power conversion efficiency (η) are more than tripled, while a sharp rise by eight times in and η is found for the device annealed at 200 ^°C. It is concluded that the improved phase separation between MEH-PPV and C₆₀ leads to the enhancement of and η at 120 ^°C, while thermodynamic molecule arrangement at the higher temperature of ∼200 ^°C induces a significant increase in all photovoltaic parameters of composite devices except the open-circuit voltage .