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타원편광분석법을 이용한 HgCdTe 양자우물구조에서의 계면 분석
공태호,김태중,김영동,인용섭 한국물리학회 2004 New Physics: Sae Mulli Vol.49 No.5
We discuss the ability and the accuracy of ellipsometric special anlysis on detecting interface layers in Hg$_{1-x}$Cd$_x$Te quantum-well systems. We observed that the conventional ellipso- metric analysis using the Bruggeman effective medium approximation could not easily detect the existence of an interface layer. Based on our results, we also suggest that analysis of interfaces should be done with caution and that the alloy dielectric function should be used for the interface. HgTe/CdTe 양자우물구조에서의 Hg$_{1-x}$Cd$_x$Te 계면(interface)의 존재유무를 타원편광분석법으로 분석해 보았다. 전통적인 방법으로 사용되어왔던 Effective-Medium-Approximation 방법을 이용하여 관찰하였을 경우에는 얇은(30 \AA 이하) 두께의 Hg$_{1-x}$Cd $_x$Te 계면의 존재유무는 확인하기 어려웠음을 알 수 있었고, 본 연구에서 제시하는 화합물유전함수를 사용하여 분석하는 경우, 그 계면이 물리적 혼합물이 아니라 주기적 구조를 갖는 화합물 형태로 구성된 경우 그 계면의 존재여부에 대한 측정민감도가 훨씬 뛰어나다는 것을 발견하였다.
공태호,박지민,장지현,C-Yoon Kim,배상훈,최유리,정윤화,김철,장성운,김주평,문지숙 생화학분자생물학회 2018 Experimental and molecular medicine Vol.50 No.-
Human placenta amniotic membrane-derived mesenchymal stem cells (AMSCs) regulate immune responses, and this property can be exploited to treat stroke patients via cell therapy. We investigated the expression profile of AMSCs cultured under hypoxic conditions and observed interesting expression changes in various genes involved in immune regulation. CD200, an antiinflammatory factor and positive regulator of TGF-β, was more highly expressed under hypoxic conditions than normoxic conditions. Furthermore, AMSCs exhibited inhibition of pro-inflammatory cytokine expression in co-cultures with LPS-primed BV2 microglia, and this effect was decreased in CD200-silenced AMSCs. The AMSCs transplanted into the ischemic rat model of stroke dramatically inhibited the expression of pro-inflammatory cytokines and up-regulated CD200, as compared with the levels in the sham-treated group. Moreover, decreased microglia activation in the boundary region and improvements in behavior were confirmed in AMSC-treated ischemic rats. The results suggested that the highly expressed CD200 from the AMSCs in a hypoxic environment modulates levels of inflammatory cytokines and microglial activation, thus increasing the therapeutic recovery potential after hypoxic-ischemic brain injury, and further demonstrated the immunomodulatory function of AMSCs in a stroke model.
Hardware Implementation of a Multi-Function Image Processing System
공태호,김남철,Kong, Tae-Ho,Kim, Nam-Chul The Institute of Electronics and Information Engin 1987 전자공학회논문지 Vol.24 No.2
Generally, general-purpose image processing system is so expensive that not so many users easily can access the system. In this paper attemps have been made to design and describe a general and economical image processing system for real-time aplications such as image data compression, pattern recognition and target tracking. The system comprises an operator console, image data acquisition/display sistem and IBM PC/XT. The system also utilizes a high speed Fairchild 16-bit microprocessor with ALU speed of 375 nsec for system control, algrithm execution and user computation. The system also can digitize /display a 256x 256x 8 bit image in real time and store two frames of images. All image pixels are directly accessible by the microprocessor for fast and efficient computation. Some experimental and illustrative results such as target tracking are presented to show the efficient performance of the system.
Interface Analysis of an AlGaAs Multilayer System by Using Spectroscopic Ellipsometry
공태호,김영동,데이비드에스프네스,D. S. Ko,J. Coleman,M. V. Klein,V. Elarde,김영운 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
We investigate the validity of the alloy interface model that we recently developed for the analysis of interfaces from ellipsometric data, which is an analysis where the eective medium approximation (EMA) has traditionally been used. For this purpose, an AlGaAs multilayer system was grown as a typical example, and its room-temperature dielectric function was measured by using variable angle spectroscopic ellipsometry (SE). To critically assess our results, we also measured the sample by using transmission electron microscopy to verify the sharpness of its interfaces and to determine its layer thicknesses independently.