유착에 의한 AGS 및 Hep-G2 세포 표면 구조의 변화

박동규 ( D. K. Park ),전훈재 ( H. J. Chun ),박재홍 ( J. H. Park ),박철희 ( C. H. Park ),진윤태 ( Y. T. Jeen ),이홍식 ( H. S. Lee ),이상우 ( S. W. Lee ),엄순호 ( S. H. Um ),최재현 ( J. H. Choi ),김창덕 ( C. D. Kim ),류호상 ( H. S. Ryu 대한소화기학회 2002 대한소화기학회 춘계학술대회 Vol.2002 No.-

<목적> 최근 H. pylori 유착에 의한 세포 표면 구조의 변화에 관한 연구가 시도되어지고 있으나 actin 의 변화여부 및 그 특성에 관해서는 아직 명확히 정립되지 못한 실정이다. Rho GTPase는 세포 표면의 미세돌기인 microvilli, filopodia 및 membrane ruffle의 형성과 관련이 있으며, 최근 AGS 세포에서 H. pylori가 Rac activation에 의하여 membrane ruffle을 형성한다는 것과 Rac

PHF2 histone demethylase acts as a tumor suppressor in association with p53 in cancer

Lee, K-H,Park, J-W,Sung, H-S,Choi, Y-J,Kim, W H,Lee, H S,Chung, H-J,Shin, H-W,Cho, C-H,Kim, T-Y,Li, S-H,Youn, H-D,Kim, S J,Chun, Y-S Macmillan Publishers Limited 2015 Oncogene Vol.34 No.22

Plant homeodomain finger 2 (PHF2) has a role in epigenetic regulation of gene expression by demethylating H3K9-Me2. Several genome-wide studies have demonstrated that the chromosomal region including the PHF2 gene is often deleted in some cancers including colorectal cancer, and this finding encouraged us to investigate the tumor suppressive role of PHF2. As p53 is a critical tumor suppressor in colon cancer, we tested the possibility that PHF2 is an epigenetic regulator of p53. PHF2 was associated with p53, and thereby, promoted p53-driven gene expression in cancer cells under genotoxic stress. PHF2 converted the chromatin that is favorable for transcription by demethylating the repressive H3K9-Me2 mark. In an HCT116 xenograft model, PHF2 was found to be required for the anticancer effects of oxaliplatin and doxorubicin. In PHF2-deficient xenografts, p53 expression was profoundly induced by both drugs, but its downstream product p21 was not, suggesting that p53 cannot be activated in the absence of PHF2. To find clinical evidence about the role of PHF2, we analyzed the expressions of PHF2, p53 and p21 in human colon cancer tissues and adjacent normal tissues from patients. PHF2 was downregulated in cancer tissues and PHF2 correlated with p21 in cancers expressing functional p53. Colon and stomach cancer tissue arrays showed a positive correlation between PHF2 and p21 expressions. Informatics analyses using the Oncomine database also supported our notion that PHF2 is downregulated in colon and stomach cancers. On the basis of these findings, we propose that PHF2 acts as a tumor suppressor in association with p53 in cancer development and ensures p53-mediated cell death in response to chemotherapy.

Comparison of HVOF Thermal Spray Coatings of T800 and WC-Co Powders

T. Y. Cho,J. H. Yoon,K. S. Kim,N. K. Baek,K. O. Song,S. J. Youn,S. Y. Hwang,H. G. Chun 한국표면공학회 2006 한국표면공학회지 Vol.39 No.6

Hard chrome plating has been used in surface hard coating over 50 years both for applying hard coating and re-building of worn components. Hard chrome plating solution and mist pollute environment with very toxic Cr??(hex-Cr) known as carcinogen which causes lung cancer. High velocity oxy-fuel (HVOF) thermal spray coatings of WC base cermet and Co-alloy powders are the most promising candidates for the replacement of the traditional hard chrome plating. Surface properties, wear, and friction behaviors of micron size Co-alloy (T800) and micron size WC-12Co (WC-Co) have been studied for the application as hard coatings. The temperature dependence of wear and friction behaviors of T800 and WC-Co have been investigated at the temperature of 25℃ and 538℃ for the application to high speed spindle.

Design and Implementation of Hybrid Multilevel Inverters

T.V. Tran,J.R. Ahn,T.W. Chun,H.H. Lee,H.G. Kim,D.W.Yoo 전력전자학회 2009 전력전자학술대회 논문집 Vol.2009 No.1

Hybrid and cascade multilevel inverter topology has presented a modern trend for reducing the power circuits of multilevel inverter in applications. A proper PWM control technique can maximize voltage range and obtain a PWM performance similar to that in conventional multilevel inverters. This paper will present a simple carrier PWM control technique for controlling the hybrid 5-level inverter, which consists of two-level and H-bridge inverter in series. While common sinusoidal PWM methods can produce only a limited voltage, the novel carrier PWM can extend the voltage at the largest range. Simulation and experimental results have been implemented to demonstrate the proposed PWM method.

Numerical modeling and experimental study of the influence of GDL properties on performance in a PEMFC

Chun, J.H.,Park, K.T.,Jo, D.H.,Kim, S.G.,Kim, S.H. Pergamon Press ; Elsevier Science Ltd 2011 International journal of hydrogen energy Vol.36 No.2

This work is to study the effect of properties of gas diffusion layer (GDL) on performance in a polymer electrolyte membrane fuel cell (PEMFC) by both numerical simulation and experiments. The 1-dimension numerical simulation using the mixture-phase model is developed to calculate polarization curve. We are able to estimate optimum GDL properties for cell performance from numerical simulation results. Various GDLs which have different properties are prepared to verify accuracy of the simulation results. The contact angle and gas permeability of GDLs are controlled by polytetrafluoroethylene (PTFE) content in micro-porous layers (MPLs). MPL slurry is prepared by homogeneous blending of carbon powder, PTFE suspension, isopropyl alcohol and glycerol. Then the slurry is coated on gas diffusion mediums (GDMs) surface with controlled thickness by blade coating method. Non-woven carbon papers which have different thicknesses of 200 μm and 380 μm are used as GDMs. The prepared GDLs are measured by surface morphology, contact angle, gas permeability and through-plane electrical resistance. Moreover, the GDLs are tested in a 25 cm<SUP>2</SUP> single cell at 70 <SUP>o</SUP>C in humidified H<SUB>2</SUB>/air condition. The contact angle of GDL increases with increasing PTFE content in MPL. However, the gas permeability and through-plane electrical conductivity decrease with increasing PTFE content and thickness of GDM. These changes in properties of GDL greatly influence the cell performance. As a result, the best performance is obtained by GDL consists of 200 μm thick non-woven carbon paper as GDM and MPL contained 20 wt.% PTFE content.

Highly selective iron-based Fischer-Tropsch catalysts activated by CO₂-containing syngas

Chun, D.H.,Park, J.C.,Hong, S.Y.,Lim, J.T.,Kim, C.S.,Lee, H.T.,Yang, J.I.,Hong, S.,Jung, H. Academic Press 2014 Journal of catalysis Vol.317 No.-

Fischer-Tropsch synthesis (FTS) was carried out over precipitated iron-based catalysts activated by syngas (H<SUB>2</SUB>+CO) with different amounts of CO<SUB>2</SUB> (0%, 20%, 33%, and 50%). The activation using CO<SUB>2</SUB>-containing syngas significantly suppressed the production of undesired products, CH<SUB>4</SUB> and C<SUB>2</SUB>-C<SUB>4</SUB> hydrocarbons, but facilitated the production of valuable products, C<SUB>5+</SUB> hydrocarbons. In particular, in the case of C<SUB>19+</SUB> hydrocarbons, the target products of low-temperature FTS (≤280<SUP>o</SUP>C), both selectivity and productivity showed a great increase with an increased inlet CO<SUB>2</SUB> content during activation. We attribute the advantageous performance of the catalysts activated by CO<SUB>2</SUB>-containing syngas to the improvement in the effective performance of active iron carbides, possibly induced by an increased ratio of ε'-carbide (Fe<SUB>2.2</SUB>C) to χ-carbide (Fe<SUB>2.5</SUB>C) and a decreased fraction of inactive bulk carbons.

Friction Behavior of High Velocity Oxygen Fuel (HVOF) Thermal Spray Coating Layer of Nano WC-Co Powder

T.Y. Cho,J.H. Yoon,K.S. Kim,W. Fang,Y.K. Joo,K.O. Song,S.J. Youn,S.Y. Hwang,H.G. Chun 한국표면공학회 2007 한국표면공학회지 Vol.40 No.4

High Velocity Oxygen Fuel (HVOF) thermal spray coating of nano size WC-Co powder (nWC-Co) has been studied as one of the most promising candidate for the possible replacement of the traditional hard plating in some area which causes environmental and health problems. nWC-Co powder was coated on Inconel 718 substrates by HVOF technique. The optimal coating process obtained from the best surface properties such as hardness and porosity is the process of oxygen flow rate (FR) 38 FMR, hydrogen FR 57 FMR and feed rate 35 g/min at spray distance 6 inch for both surface temperature 25℃ and 500℃. In coating process a small portion of hard WC decomposes to less hard W₂C, Wand C at the temperature higher than its decomposition temperature 1,250°C resulting in hardness decrease and porosity increase. Friction coefficient increases with increasing coating surface temperature from 0.55-0.64 at 25℃ to 0.65-0.76 at 500℃ due to the increase of adhesion between coating and counter sliding surface. Hardness of nWC-Co is higher or comparable to those of other hard coatings, such as A1₂O₃, Cr, Cr₂O₃ and HVOF Tribaloy 400 (T400). This shows that nWC-Co is recommendable for durability improvement coating on machine components such as high speed spindle.

Cowden's Disease - A Report on the First Case in Korea and Literature Review

Lee, H.-R Korean Academy of Medical Science 1997 Journal of Korean medical science Vol.12 No.6

Synthesis and characterization of crosslinked sulfonated poly(arylene ether sulfone) membranes for high temperature PEMFC applications

Park, K.T.,Chun, J.H.,Kim, S.G.,Chun, B.H.,Kim, S.H. Pergamon Press ; Elsevier Science Ltd 2011 International journal of hydrogen energy Vol.36 No.2

Sulfonated poly(arylene ether sulfone) copolymers containing carboxyl groups are prepared by an aromatic substitution polymerization reaction using phenolphthalin, 3,3'-disulfonated-4,4'-dichlorodiphenyl sulfone, 4,4'-dichlorodiphenyl sulfone and 4,4'-bisphenol A as polymer electrolyte membranes for the development of high temperature polymer electrolyte membrane fuel cells. Thin, ductile films are fabricated by the solution casting method, which resulted in membranes with a thickness of approximately 50μm. Hydroquinone is used to crosslink the prepared copolymer in the presence of the catalyst, sodium hypophosphite. The synthesized copolymers and membranes are characterized by <SUP>1</SUP>H NMR, FT-IR, TGA, ion exchange capacity, water uptake and proton conductivity measurements. The water uptake and proton conductivity of the membranes are decreased with increasing the degree of crosslinking which is determined by phenolphthalin content in the copolymer (0-15mol%). The prepared membranes are tested in a 9cm<SUP>2</SUP> commercial single cell at 80<SUP>o</SUP>C and 120<SUP>o</SUP>C in humidified H<SUB>2</SUB>/air under different relative humidity conditions. The uncrosslinked membrane is found to perform better than the crosslinked membranes at 80<SUP>o</SUP>C; however, the crosslinked membranes perform better at 120<SUP>o</SUP>C. The crosslinked membrane containing 10mol% of phenolphthalin (CPS-PP10) shows the best performance of 600mAcm<SUP>-2</SUP> at 0.6V and better performance than the commercial Nafion<SUP>(</SUP>R) 112 (540mAcm<SUP>-2</SUP> at 0.6V) at 120<SUP>o</SUP>C and 30 % RH.

Generation of Transgenic Mice Overexpression Mouse RESISTIN

J. R. Chun,S. J. Song,J. T. Do,K. S. Chung,Lee, H. T. 한국수정란이식학회 2002 한국수정란이식학회 학술대회 Vol.2002 No.1

The hormone resistin is associated with typeII diabetes mellitus in rodent model. Resistin impairs glucose tolerance and insulin action. A new class of anti-diabetic drugs were called thiazolidinediones (TZDs) downregulates a resistin which is induced during adipocyte differentiation. But the connection between increased adiposity and resistin remains unknown. The objectives of this study was to clone a mouse resistin cDNA and to generate transgenic mice overexpressing mouse resistin gene. The 555 bp of mouse resistin was amplified from mob cDNAS by polymerase chain reaction (PCR) and cloned into pCR(R)/ 2.1 TOPO T-vector. Mouse resistin mRNA on the basis of Genbank sequence (acession no. AF323080). Then, the PCR product was cloned into pTargeTTM/ mammalian expression vector that has pCMV promoter and chimeric intron. Restriction enzyme analysis with BamH I and Not I was carried out to determine an orientation of the insert in the vector. The pCMV-mus/resistin gene was prepared from previous recombinant pTargeTTM/-mus/resistin by digestion of Bgl II, and has used for microinjection into pronuclei of one cell embryos. The microinjected embryos were transfered to pseudopregnant foster-mother. Mouse resistin expression was detected in transgenic F1 mice by Reverse Transcriptase- Polymerase Chain Reaction (RT-PCR). Resistin gene expression mouse has heavier body weight which was measured higher level of plasma glucose than that of normal mouse. And in diet-induced experiments, the abdominal fat pads were isolated from each 24h starvation and re-feeding after fasting group mice that were assessed by RT-PCR analysis. In fasting group mice, resistin expression was higher than that of re-feeding group mice. This result suggests that the resistin gene overexpressing mice may be became to obesity and be useful as an animal disease model to be diabetes mellitus caused by insulin resistance of resistin.