Visualizations of Light-induced Refractive Index Changes in Photorefractive Crystals Employing Digital Holography

We propose a novel approach to visualize the light-induced refractive index changes in photorefractive crystals employing digital holography. The holograms formed in a Mach-Zehnder interferometer are recorded by a two-dimensional CCD camera. From these holograms, the phase differences, which contain the information of the index changes in photorefractive crystals, are determined by utilizing digital holographic interferometry. Then the two-dimensional visualizations of index changes in the crystals can be obtained. This method is successfully demonstrated in LiNbO3:Fe, KNSBN:Ce and SBN:Cr crystals.     

Weierstrass逼近定理的一个初等証明

以下将给出Weierstrass定理的一个既初等又简短的证明。该定理是说:任何一个在闭区间[0,1]上连续的函数f(x)都可以用多项式一致逼近。作为辅助工具,只要用到Bernóulli不等式: (1+h)~n≥1+nh(h>-1,n为自然数)。它容易用归纳法证得。我们考察多项式 Q_n(x)=(1-x~n)~(2~n)。当x从0变到1时,Q_n(x)的值从1单调地变到0。在0≤x≤q<1/2中,Q_n(x)当n→∞时一致收敛于1,因为 1≥Q_n(x)≥Q_n(q)= =(1-q~n)~(2~n)≥1-2~nq~n=1-(2q)~n→1。     

扫描电子显微镜发展动态

扫描电子显微镜(简称扫描电镜)是近十余年朱迅速发展起来的一种大型精密电子光学仪器.它具有以下特点:(1)分辨本领高、景深长、成象富有立体感、试样制备简单;(2)和X光微区分忻仪、俄歇电子谱仪、电子能量损失谱仪、二次离子质谱仪以及通道电子衍射技术等相结合,可以在观察微区形貌的同时,逐点分析试样的化学成份及结构;(3)可用于观察半导体器件的工作状态,检查其失灵原因;(4)可用于研究材料的阴极发光性质,等等.因此它的应用范围日益广泛.自1965年末扫描电子显微镜开始有商品以来,到1973年的短短七、八年内,据不完全统计,全世界已有2500台…     

武勒(Whler)与生命力学说的推翻

麦克叶(McKie)曾经发表过这样的意见:由氰酸铵合成尿素并不标志着生命力学说崩溃的开始,而且武勒自己当时确实还坚持着生命力学说。此类意见,假若能够促使读者或教师亲自去查考一下论据的话,它们还是有价值的。但是,存在着这样一种危险,即这种所谓“揭露”会被人就其表面价值加以接受,而对于其论据却未加以批判的考查。这里就是这样。麦克叶的意见,自从被引用在一本通行的教科书中以后,已获得了信任。我已发现,在某些年事较轻的讲师或作者中,有这样开始他们的     

随机化应答调查方案的参数估计问题

随机化应答调查是一种特殊的数据采集技术,使得调查者既得到了某个敏感问题的信息又保护了被调查者的隐私,本文研究从两种随机化答调查方案采得数据后的参数估计问题,在应用Ｂａｙｅｓ估计时,给出了便于Ｍａｔｈｅｍａｔｉｃａ软件计算的后验均值和方差的公式,通过模拟实验,比较了两个方案所得估计量的优劣。     

TEAD4与子宫颈鳞状细胞癌增殖和侵袭的关系及分子机制探讨

探讨TEAD4表达与子宫颈鳞状细胞癌增殖和侵袭的关系。用免疫组化MaxVision法结合光密度分析检测目标蛋白的组织表达。通过真核表达质粒pCMV3-TEAD4转染子宫颈鳞癌SiHa细胞以获得TEAD4基因过表达;应用Western blotting法检测细胞中目标蛋白的表达。分别利用CCK-8实验和Transwell小室实验检测细胞的增殖和侵袭能力。子宫颈鳞癌组织中TEAD4平均表达水平(0.186±0.0355)显著高于正常宫颈上皮组(0.0494±0.0105,P<0.001),且TEAD4的表达与子宫颈鳞癌的淋巴结转移、脉管浸润和宫旁浸润有关(P<0.05),与子宫颈鳞癌的患者年龄、肿瘤大小、和分化程度无关。TEAD4的表达与MMP9的表达呈正相关关系(r=0.394,P<0.01)。TEAD4基因转染后的宫颈鳞癌细胞的增殖能力和侵袭能力显著增强。TEAD4基因转染诱导宫颈鳞癌细胞P-ERK1/2和MMP9蛋白表达上调,而ERK抑制剂(U0126)能显著抑制TEAD4诱导的MMP9上调。TEAD4高表达于子宫颈鳞癌,促进子宫颈鳞癌增殖和侵袭能力,其机制可能与TEAD4激活ERK1/2-MMP9信号通路有关。     

Degradation of current–voltage and low frequency noise characteristics under negative bias illumination stress in InZnO thin film transistors

The instabilities of indium–zinc oxide thin film transistors under bias and/or illumination stress are studied in this paper. Firstly, illumination experiments are performed, which indicates the variations of current–voltage characteristics and electrical parameters(such as threshold voltage and sub-threshold swing) are dominated by the stress-induced ionized oxygen vacancies and acceptor-like states. The dependence of degradation on light wavelength is also investigated. More negative shift of threshold voltage and greater sub-threshold swing are observed with the decrease of light wavelength.Subsequently, a negative bias illumination stress experiment is carried out. The degradation of the device is aggravated due to the decrease of recombination effects between ionized oxygen vacancies and free carriers. Moreover, the contributions of ionized oxygen vacancies and acceptor-like states are separated by using the mid-gap method. In addition, ionized oxygen vacancies are partially recombined at room temperature and fully recombined at high temperature. Finally, low-frequency noise is measured before and after negative bias illumination stress. Experimental results show few variations of the oxide trapped charges are generated during stress, which is consistent with the proposed mechanism.     

脂润滑条件下激光微精处理零件的抗擦伤性能研究

采用ＳＲＶ试验机和Ｔｉｍｋｅｎ试验机，对脂润滑条件下经激光微精处理的３种铸铁与ＧＣｒ１５钢的抗擦伤性能进行了研究。结果表明：激光微精处理使其抗擦伤性能均大幅度提高，其中合金铸铁经激光微精处理后可在蜗轮摩擦副中代替青铜使用。     

Nanomorph Silicon Thin Films Prepared by Using an HW-MWECR CVD System

We have prepared hydrogenated nano-amorph silicon (na-Si:H) films by using a hot-wire-assisted microwave electron-cyclotron-resonance (HW-MWECR) chemical vapour deposition (CVD) system. The films are deposited in two steps: in the first 9rain, a hydrogenated amorphous silicon layer is deposited by using hydrogen-diluted silane with a concentration of SiH4/(SiH4 H2) = 20%, and then a nanocrystalline silicon (nc-Si) layer is deposited by using various highly hydrogen-diluted silane. The Raman TO-like mode peak of the films was found in the range 497-508cm^-1. When the silane concentration used for preparation of the nc-Si layer is 14.3%, the film has a large crystalline volume fraction of 65.4%, a wide optical band gap of 1.89eV and a low hydrogen content of 9.5 at.%. Moreover, the na-Si:H films rather than nc-Si possess high photosensitivity of about 10^5.