• Title, Summary, Keyword: STM

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A Theoretical Study on STM image of Carbon Nanotube (탄소나노튜브 표면의 STM 이미지를 통한 전기적 특성 연구)

  • 문원하;황호정
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.314-317
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    • 2002
  • Since the early work of Tersoff and Hamann on the theory of the scanning tunneling microscope (STM), many theoretical approaches have been developed in order to gain further physical insight into the real space image that this technique provides. In this Paper, the STM image of Carbon nanotubes (CNT's) was calculated through the theoretical study. The optimized structure of CNT's was simulated using Brenner's hydrocarbon potential. The structure of simulation is (5. 5) armchair CNT and (10. 0) zigzag CNT. Also we have used that the extended Huckel tight binding (EHTB) theory already provides a fairly good qualitative description of the main processes that control the final contrast in the STM image. we found that the shape of the calculated images is hardly dependent on the exact electronic charge distribution at the surface. The STM images are not too sensitive to the precise electronic structure but, rather, they reflect its qualitative features. As a result of the simulation, The STM images of CNT's and the electronic density distribution were investigated. It found that the EHTB theory is appropriate for STM image calculation and that the STM images are in agreement with the result of Experiment.

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Swertiamarin ameliorates carbon tetrachloride-induced hepatic apoptosis via blocking the PI3K/Akt pathway in rats

  • Zhang, Qianrui;Chen, Kang;Wu, Tao;Song, Hongping
    • The Korean Journal of Physiology and Pharmacology
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    • v.23 no.1
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    • pp.21-28
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    • 2019
  • Swertiamarin (STM) is an iridoid compound that is present in the Gentianaceae swertia genus. Here we investigated antiapoptotic effects of STM on carbon tetrachloride ($CCl_4$)-induced liver injury and its possible mechanisms. Adult male Sprague Dawley rats were randomly divided into a control group, an STM 200 mg/kg group, a $CCl_4$ group, a $CCl_4+STM$ 100 mg/kg group, and a $CCl_4+STM$ 200 mg/kg group. Rats in experimental groups were subcutaneously injected with 40% $CCl_4$ twice weekly for 8 weeks. STM (100 and 200 mg/kg per day) was orally given to experimental rats by gavage for 8 consecutive weeks. Hepatocyte apoptosis was determined by TUNEL assay and the expression levels of Bcl-2, Bax, and cleaved caspase-3 proteins were evaluated by western blot analysis. The expression of $TGF-{\beta}1$, collagen I, collagen III, CTGF and fibronectin mRNA were estimated by qRT-PCR. The results showed that STM significantly reduced the number of TUNEL-positive cells compared with the $CCl_4$ group. The levels of Bax and cleaved caspase-3 proteins, and $TGF-{\beta}1$, collagen I, collagen III, CTGF, and fibronectin mRNA were significantly reduced by STM compared with the $CCl_4$ group. In addition, STM markedly abrogated the repression of Bcl-2 by $CCl_4$. STM also attenuated the activation of the PI3K/Akt pathway in the liver. These results suggested that STM ameliorated $CCl_4$-induced hepatocyte apoptosis in rats.

STM(Scanning Tunneling Microscope)의 제작 시 고려사항과 응용사례

  • 구자용
    • Proceedings of the Korea Crystallographic Association Conference
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    • pp.7-7
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    • 2002
  • 실공간 (real space)에서 원자분해능을 보여주는 STM의 작동원리를 핵심사항을 중심으로 설명하며 또한 실제 제작 시 고려해야 하는 사항들을 구체적으로 검토한다. 반도체의 경우 전자들이 원자부근에서 국소화가 잘 되므로 STM으로 표면의 원자상을 얻기가 비교적 쉽다. 특히 실리콘은 그 물질의 중요성과 결부되어 STM으로 많이 연구되어 왔으며 다른 방법으로는 알 수 없는 독특한 결과들을 보여주었다. STM의 응용사례로써 오랫동안 수수께끼였던 Si(001) 표면에서 생기는 점결함(point defect)과 계단 (step)부근의 원자구조 및 최근의 몇 가지 연구결과에 대한 기본적인 결과들을 소개한다.

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HAUSAT-2 STM(Structural-Thermal Model) Development and Launch Environment Test Result Analyses (HAUSAT-2 위성 STM 개발 및 발사환경시험 분석)

  • Chang, Jin-Soo;Hwang, Ki-Lyong;Chang, Young-Keun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.11
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    • pp.95-105
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    • 2005
  • The HAUSAT-2 nanosatellite which is scheduled to launch in 2008 is being developed by SSRL(Space System Research Lab.). The HAUSAT-2 STM(Structural-Thermal Model) was developed as the first system model to verify structural and thermal design margin. The qualification level vibration and thermal tests have been conducted on STM. This paper addresses the comparison of structural analysis and test results of HAUSAT-2 STM. It was shown that the natural frequency of HAUSAT-2 STM satisfies the stiffness requirements without structural damage in the random vibration test. The assembly and integration validity were also checked out through STM.

A Functional Design of Connection Control in the NG-SDG based Transport System (NG-SDH 기반 전송 시스템에서의 연결제어 기능 설계)

  • 김영화;예병호;이종현;유재철
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.40 no.10
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    • pp.110-118
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    • 2003
  • The paper describes a design process of the connection control function that performs overall procedures of optical network control system in the Next Generation - Synchronous Digital Hierarchy (NG-SDH) based transport system. Here, the NG-SDH means a new SDH technology that could perform automatic connection control with a granularity of VC-3 (about 50M) or VC-4 (about 150M) according to the increase and decrease of traffic, which is different from the existing technology that could perform connection control only with a granularity of a physical SDH link (STM-l, STM-4, STM-16, STM-64, STM-256 etc). The NG-SDH based connection control allows an ingress NG-SDH node to control the appropriate connection establishment process according to connection types such as Permanent Connection (PC), Soft Permanent Connection (SPC), Switched Connection (SC) over various SDH and Ethernet line cards.

Attributes and Expression of STM(Short-term Memorable) Information (STM(Short-term Memorable) Information의 속성 및 정보표현)

  • Han, Ji-Ae;You, Si-Cheon
    • The Journal of the Korea Contents Association
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    • v.10 no.9
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    • pp.201-211
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    • 2010
  • The aim of this study is to investigate the method to enhance user cognition for "STM information(Short-term Memorable Information)" that is relatively accessible to information in a short period of time in information design types. What stands out from this study is the design attributes and expression method of information in a broad perspective. By 4 visualization attributes of function variable; 'Operations', 'Events', 'Methods' and 'Use cases', STM information should be satisfied by the attribute of 'Understandable' and 'Accessibility' from the point of view of visual representation and by the attribute of 'Errorless' and 'Timeliness' from the point of view of user operation. As the expression method of each perspectives, I suggested "Attribution theory", "Cognitive model", "Maximization of Proactivity", "Minimization of surplus information" and "Using dual-code" in the point of view of visual representation, and "Context effect", "Using memory code" and "Two methods of information scanning" in the point of view of user operation. I assured that above-mentioned methods are efficient and cognitive pattern of user for STM information is found out by survey and interview.

Study on the Mophology Observation and Electrical Properties of Dipyridinium Organic Monolayer Using STM (STM을 이용한 Dipyridinium 유기 단분자막의 모폴로지 관찰 및 전기적 특성 연구)

  • Lee Nam-Suk;Shin Hoon-Kyu;Kwon Young-Soo
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.54 no.2
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    • pp.51-54
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    • 2005
  • In this work, the attempt has been made to investigate the morphology of self-assembled dipyridinium dithioacetate on Au(111) substrate by Scanning Tunneling Microscopy(STM). Also, we measured electrical properties(I-V) using Scanning Tunneling Spectroscopy(STS). Sample used in this experiment is dipyridinium dithioacetate, which contains thiol functional group, this structure that can be self-assembled easily to Au(111) substrate. The self-assembly procedure was used for two different concentrations, 0.5 mM/ml and 1 mM/ml. Dilute density of sample by 0.5 mM/ml, 1 mM/ml and observed dipyridinium dithioacetate's image by STM after self-assembled on Au(111) substrate. The structure of STM tip-SAMs-Au(111) substrate has been used measurement for electrical properties(I-V) using STS. The current-voltage(I-V) measurement result, observed negative differential resistance(NDR) properties.

Effects of Tunneling Current on STM Imaging Mechanism for Alkanethiol Self-assembled Monolayers on Au(111)

  • Mamun, Abdulla Hel Al;Son, Seung-Bae;Hahn, Jae-Ryang
    • Bulletin of the Korean Chemical Society
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    • v.32 no.1
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    • pp.281-285
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    • 2011
  • We investigated the effects of tunneling current on scanning tunneling microscopy (STM) images of 1-octanethiol (OT) and 1-decanethiol (DT) self-assembled monolayers (SAMs). At a low tunneling current, the domain boundaries and ordered alkanethiol molecules were clearly resolved. As the tunneling current was increased at a constant bias voltage, however, the STM images showed disordered structures of the OT and DT SAMs. As the tunneling current was reduced back to low values, the ordered structures of the alkanethiol molecules reappeared. The reversibility of the process suggests that the sulfur head groups did not rearrange under any of the tunneling current conditions. On the basis of our observations, which are inconsistent with the standard model for STM imaging of molecules on metal surfaces, we consider the STM imaging mechanism in terms of a two-region tunneling junction model.

Understanding Comprehensive Transcriptional Response of Salmonella enterica spp. in Contact with Cabbage and Napa Cabbage

  • Lee, Hojun;Kim, Seul I;Park, Sojung;Nam, Eunwoo;Yoon, Hyunjin
    • Journal of Microbiology and Biotechnology
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    • v.28 no.11
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    • pp.1896-1907
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    • 2018
  • Salmonellosis is commonly associated with meat and poultry products, but an increasing number of Salmonella outbreaks have been attributed to contaminated vegetables and fruits. Enteric pathogens including Salmonella enterica spp. can colonize diverse produce and persist for a long time. Considering that fresh vegetables and fruits are usually consumed raw without heat treatments, Salmonella contamination may subsequently lead to serious human infections. In order to understand the underlying mechanism of Salmonella adaptation to produce, we investigated the transcriptomics of Salmonella in contact with green vegetables, namely cabbage and napa cabbage. Interestingly, Salmonella pathogenicity island (SPI)-1 genes, which are required for Salmonella invasion into host cells, were up-regulated upon contact with vegetables, suggesting that SPI-1 may be implicated in Salmonella colonization of plant tissues as well as animal tissues. Furthermore, Salmonella transcriptomic profiling revealed several genetic loci that showed significant changes in their expression in response to vegetables and were associated with bacterial adaptation to unfavorable niches, including STM14_0818 and STM14_0817 (speF/potE), STM14_0880 (nadA), STM14_1894 to STM14_1892 (fdnGHI), STM14_2006 (ogt), STM14_2269, and STM14_2513 to STM14_2523 (cbi operon). Here, we show that nadA was required for bacterial growth under nutrient-restricted conditions, while the other genes were required for bacterial invasion into host cells. The transcriptomes of Salmonella in contact with cabbage and napa cabbage provided insights into the comprehensive bacterial transcriptional response to produce and also suggested diverse virulence determinants relevant to Salmonella survival and adaptation.

Comparison of Roughnesses of Polycrystalline Gold Electrode Calculated from STM Images, Oxygen Adsorption-Desorption and Adsorption of N-Docosyl-N'-methyl Viologen (STM 이미지와 산소 흡탈착 그리고 N-docosyl-N'-methyl viologen의 흡착으로부터 구한 다결정 금 전극 표면의 거칠기의 비교)

  • Lee Chi-Woo;Jang Jai-Man
    • Journal of the Korean Electrochemical Society
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    • v.3 no.2
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    • pp.104-108
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    • 2000
  • It is very important to know the real roughness of electrode surface in electrochemistry. But it is impossible to know absolute roughness of electrode surface for various reasons. In this work, we compared the roughnesses of polycrystalline gold electrode often used in electrochemistry calculated from the images of scanning tunneling microscopy (STM) and cyclic voltammetry with those of Au (111) and HOPG. The roughness of polycrystalline gold calculated from STM image was $1.1(\pm0.1)$, that from adsorption-desorption of oxygen was $2.4(\pm0.7)$ and that from adsorption of N-docosyl-N'-methyl viologen was $1.6(\pm0.1)$.