Influence of microstructure on galling resistance of cold-work tool steels with different chemical compositions when sliding against ultra-high-strength steel sheets under dry condition

Ko, D.C.,Kim, S.G.,Kim, B.M. Elsevier Sequoia [etc.] 2015 Wear: An international journal on the science and Vol.338 No.-

The objective of this study was to determine the influence of a microstructure on the galling resistance of three variations of D2-grade steels that are used for the stamping of ultra-high-strength steel (UHSS) sheets. Standard D2 steel and two other types of D2-grade steel, having different microstructures, were used as the pins in a pin-on-flat galling test, and a dual-phase 980 (DP 980) sheet was used as the counterface. The friction coefficient was monitored as a function of the sliding distance, and the critical sliding distance for the onset of severe galling was indicated by the transition to a high and unstable friction coefficient. The best galling resistance was observed for the steel that contained a large amount of relatively small secondary carbides, whereas the worst galling resistance was obtained for standard D2 steel, which contained a large amount of coarse primary carbides. The test data also indicated that the galling resistance of the cold-worked tool steels was influenced by the type, size, and distribution of the carbides rather than simply by the total amount of carbides. Furthermore, it was inferred that the galling resistance of cold-worked tool steels could be improved by larger amounts of secondary carbides, smaller mean free paths between secondary carbides, and smaller mean diameters of both primary and secondary carbides.

A limited series of synthetic tetrahydroisoquinoline alkaloids reduce inflammatory gene iNOS via inhibition of p-STAT-1 and suppress HMGB1 secretion in LPS-treated mice lung tissue

Ko, Y.S.,Park, E.J.,Kim, Y.M.,Kim, H.J.,Yun-Choi, H.,Lee, D.H.,Chang, K.C. ELSEVIER 2017 INTERNATIONAL IMMUNOPHARMACOLOGY Vol.52 No.-

Tetrahydroisoquinoline alkaloids (THIs) have shown to increase survival and beneficial effect on animal model of sepsis, partly due to heme oxygenase-1 (HO-1) induction. Here, we aimed to compare a limited series of synthesized THIs on HO-1 induction and inhibitory effect of iNOS and COX-2 expression in lipopolysaccharide (LPS)-activated RAW264.7 cells. To the end, most promising compound (THI-61) was tested whether this compound reduces iNOS protein expression and inflammatory markers (HMGB1, TNF-α) in LPS-treated mice lung tissue. The results indicated that N-carbonyl substituted THI seem to affect HO-1 induction depending on which functional group is attached to C1 position. All compounds that reduce LPS-activated NF-κB-luciferase activity showed to preferential inhibition of iNOS/NO but not COX-2/PGE<SUB>2</SUB> that was partly related to inhibition of STAT-1 phosphorylation. In particular, THI-61 induced translocation of Nrf2 from cytosol into the nucleus by an increased Nrf2-ARE binding activity, and reduced IL-1β production in LPS-activated RAW264.7 cells. The reduced expression of iNOS/NO by THI-61 was reversed by siHO-1RNA-transfection. In LPS-treated mice, THI-61 significantly reduced iNOS protein in lung tissues, and HMGB1 and TNF-α levels in the BALF. We concluded that 1) lipophilic moiety of 1C substituent is much more important in N-carbonyl substituted THI for induction of HO-1, 2) newly synthesized THI-61 may be beneficial for treatment of lung injury.

Protective effect and mechanism of action of diallyl disulfide against acetaminophen-induced acute hepatotoxicity

Ko, J.W.,Park, S.H.,Shin, N.R.,Shin, J.Y.,Kim, J.W.,Shin, I.S.,Moon, C.,Heo, J.D.,Kim, J.C.,Lee, I.C. Pergamon ; Elsevier Science Ltd 2017 Food and chemical toxicology Vol.109 No.1

The aim of this study was to investigate the potential protective effects of diallyl disulfide (DADS) against acetaminophen (AAP)-induced acute hepatotoxicity and elucidate the molecular mechanisms underlying these protective effects in rats. Treatment with AAP caused acute hepatotoxicity manifested by elevated levels of aspartate aminotransferase and alanine aminotransferase with corresponding histopathological changes and high levels of oxidative stress in the livers. AAP treatment also caused hepatocellular apoptosis with phosphorylation of c-Jun-N-terminal protein kinase (JNK). In addition, AAP caused activation of nuclear factor kappaB (NF-κB) concurrent with induction of inflammatory mediators. In contrast, pretreatment with DADS effectively attenuated acute liver injury and oxidative stress caused by AAP. DADS pretreatment suppressed cytochrome P450 2E1 (CYP2E1) levels in a dose-dependent manner and inhibited elevation of CYP2E1 activity induced by AAP. DADS pretreatment suppressed the phosphorylation of JNK and attenuated hepatocellular apoptotic changes. In addition, DADS inhibited the nuclear translocation of NF-κB and subsequent induction of inflammatory mediators. Overall, these results indicate that DADS confers a protective effect against oxidative stress-mediated JNK activation and apoptotic changes caused by AAP in the rat livers. This may be due to its ability to inhibit CYP2E1, enhance antioxidant enzymes activities, and suppress NF-κB activation.

Rebamipide abolishes Helicobacter pylori CagA-induced phospholipase D1 expression via inhibition of NFκB and suppresses invasion of gastric cancer cells

Kang, D W,Hwang, W C,Park, M H,Ko, G-H,Ha, W-S,Kim, K-S,Lee, Y-C,Choi, K-Y,Min, D S Macmillan Publishers Limited 2013 Oncogene Vol.32 No.30

Infection with cagA-positive Helicobacter pylori is a risk factor for the development of severe gastritis and gastric cancer (GC). CagA protein is injected into gastric epithelial cells and deregulates a variety of cellular signaling molecules. Phospholipase D (PLD) is elevated in many different types of human cancers and has been implicated as a critical factor in inflammation and carcinogenesis. In this study, we show that infection with cagA-positive H. pylori in GC cells significantly induces PLD1 expression via CagA-dependent activation of nuclear factor κB (NFκB). Interestingly, the level of PLD1 protein and IκBα phosphorylation is aberrantly upregulated in H. pylori-infected human GC tissues. Infection with cagA-positive H. pylori and expression of CagA enhanced the binding of NFκB to the PLD1 promoter, and two functional NFκB-binding sites were identified within the PLD1 promoter. Rebamipide, a mucosal-protective antiulcer agent, abolished H. pylori cagA-induced PLD1 expression via inhibition of binding of NFκB to the PLD1 promoter, and also inhibited PLD activity. Moreover, rebamipide suppressed H. pylori-induced matrix metalloproteinase-9, interleukin-8 and activation-induced cytidine deaminase expression as well as invasion of GC cells through downregulation of PLD1. Our data suggest that H. pylori cagA targets PLD1 for invasion of GC cells, and rebamipide might contribute to the antitumorigenic effect of GC cells via inhibition of the H. pylori cagA-NFκB-PLD1 signaling pathway.

CO₂ 레이저 광의 조사조건에 따른 치아의 치수강내 온도상승에 관한 연구

고동섭(D.S. Ko),박용환(Y.H. Bak),신상훈(S.H. Shin),엄효순(H.S. Eom),김웅(U. Kim),이찬영(C.Y. Lee) 한국광학회 1990 한국광학회지 Vol.1 No.2

본 연구에서는 레이저와 치아조직과의 상호작용에 대한 연구의 일환으로, CO₂ 레이저의 발진파장인 10.6㎛의 레이저 빔 조사시에 일어나는 치아의 온도변화를 조사하기 위하여 CO₂ 레이저 발진장치를 제작하여 여러 가지 조사에너지, 조사시간에 대하여 발거된 치아의 치수강의 온도변화를 측정 분석하였다. 측정한 data를 분석하여 최대 상승온도 ΔTm를 추정할 수 있는 다음과 같은 실용적인 경험식을 얻었다.<br/> ΔTm=αPΔτexp(-βd)<br/> 여기서 P는 레이저의 출력(W)이고 Δτ는 조사시간(sec), d는 치아의 두께(㎜)이다. This study was performed to obtain fundamental data on temperature increases in the dental tissues irradiated by 10.6㎛ laser radiation. For this purpose a experimental facility was established, which was composed of a CO₂ laser, a shutter unit and a temperature sensing device. The temperature changes in the pulp chamber of extracted molars, during and after the laser irradiation, were measured as function of laser power, the time of irradration and the thickness of the sample. An empirical formula for the maximum temperature increases. ΔTm was derived from the measured data as follows;<br/> ΔTm=90PΔτ exp(-1.5d)<br/> where P. Δτ rand d are the laser power(W), irradiation time(sec) and the thickness(㎜) between pulp chamber and occlusal surface, respectively.<br/> Also a theoretical calculation model based on simplified assumptions were established and the results from the calculation were compared with the measured temperature data. A fairly good agreement was obtained.

우리나라의 기름 감식ㆍ분석시스템 연구

고성덕(S.D. Ko),천명철(M.C. Chon),김만중(M.J. Kim),윤주용(J.Y. Yoon) 한국해양환경·에너지학회 2011 한국해양환경·에너지학회 학술대회논문집 Vol.2011 No.11

해양오염사고에 의한 기름 유출은 대부분 선박에서 발생하고 있으며 오염 행위자를 밝히지 못하면 피해당사자의 보상문제 뿐만아니라 사고초기에 방제전략 수립 등이 어렵다. 더욱이 선박은 이동성 및 국제항행 특수성이 있어 오염사고 주변해역을 지나간 수백척의 선박을 짧은 시간안에 조사하는 것은 매우 어렵다. 따라서 오염행위자를 적발하기 위해서는 정확한 유출유의 유종 파악과 유출시간 추정을 통해 조사대상을 압축하여 정밀조사하는 것이 효과적이다. 우리나라에서는 이러한 문제를 해결하기 위해 국내에 도입되는 모든 원유, 제품유에 대한 유지문D/B를 구축 하여 활용하고 있으나 해상에 유출된 기름이 주변해역의 기상, 수온 및 경과시간 등 자연조건변화에 따라 물리화학적 특성이 변화한 경우에는 정확한 유종파악에 많은 시간이 소요되며 유출시간을 추정하는 것이 매우 제한적이다. 본 연구에서는 경시변화된 기름의 형광분광광도계를 이용한 감식ㆍ분석방법과 다양한 해역조건에 따라 미국 해양대기청(NOAA)의 ADIOS 2를 활용한 유출시간 추정 방법 등 효율적인 기름 감식ㆍ분석시스템에 대해 연구하였다. Generally oil spill incidents come from vessel. If it happened, especially in case of unknown oil spill incidents, it is difficult to ferret out criminals and compensation for victim grows all the more serious. Besides, It is much difficult to find criminal’s vessel among many vessels. Therefore, it is important to analyse the kind of spilled oil and spilled time of oil because that is one of useful method how to be able to summarize research subjects. KCG(Korea Coast Guard) makes full use of oil fingerprint D/B about crude oil, petroleum oil imported from overseas. But, because the characteristics of spilled oil is changed by weather, temperature and weathering time etc, it is difficult to analyse the oil sample and estimate to spilled time, too. In this study, we introduced how to forensic identify weathering oil by using spectrofluorometer and we studied about oil analysing system by using ADIOS 2 program to be made by NOAA(National Oceanic and Atmospheric Administration).

The interaction domains of transient receptor potential canonical (TRPC)¼ and TRPC1/5 heteromultimeric channels

Myeong, J.,Ko, J.,Hong, C.,Yang, D.,Lee, K.P.,Jeon, J.h.,So, I. Academic Press 2016 Biochemical and biophysical research communication Vol.474 No.3

Transient receptor potential canonical (TRPC) family contains a non-selective cation channel, and four TRPC subunits form a functional tetrameric channel. TRPC4/5 channels form not only the homotetrameric channel but also a heterotetrameric channel with TRPC1. We investigated the interaction domain required for TRPC¼ or TRPC1/5 heteromultimeric channels using FRET and the patch-clamp technique. TRPC1 only localized at the plasma membrane (PM) when it was coexpressed with TRPC4 or TRPC5. The TRPC¼ or TRPC1/5 heteromultimeric showed the typical outward rectifying I/V curve. When TRPC1 and TRPC4 form a heteromeric channel, the N-terminal coiled-coil domain (CCD) and C-terminal 725-745 region of TRPC1 interact with the N-terminal CCD and C-terminal 700-728 region of TRPC4. However, when TRPC1 and TRPC5 form a heteromeric channel, the N-terminal CCD and C-terminal 673-725 region of TRPC1 interact with the N-terminal CCD and C-terminal 707-735 region of TRPC5. In conclusion, the N-terminal CCD of TRPC channels is essential for the heteromultimeric structure of TRPC channels, whereas specific C-terminal regions are required for unique heteromerization between subgroups of TRPC channels.

기상 환원제를 사용하는 선택적 환원촉매에서 유동혼합 개선에 관한 연구

고상철(S.C. Ko),이범호(B.H. Lee),조승환(S.H. Cho),이상헌(S.H. Lee),홍성태(S.T. Hong),이대엽(D.Y. Lee) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.1

Since emission regulations for vehicles have become more stringent, SCR technology has drawn a strong attention in order to reduce NOx emissions. Optimal design of a reductant injection nozzle and a multi-hole plate located between the cone and catalyst is critical in that the uniform distribution of reductant is necessary to maximize the NOx conversion efficiency and minimize the slip of reductant in SCR. In this work, an LPG fuel(C3H8 in vapor state) was used as a reductant for LPG vehicles. A Realizable k-ε model is used for turbulence, and SCR body is defined as porous media with inertia and viscous resistances measured in this work. Effect of the number of nozzle holes on the flow mixing index was analyzed, which revealed that a four hole nozzle shows the best performance in terms of uniformity of flow. An installment of a multi-hole plate at the entrance of catalyst was evaluated with flow mixing index, uniformity of flow, and pressure drop. A multi-hole plate with gradual hole diameter change in three steps showed the best uniformity of flow within the conditions suggested in this work.

중년 사무직 남성의 직무스트레스와 허리둘레, 체질량지수의 관계에 관한 연구

강수임,고보경,김지영,노정연,리청,송주은,이현영,이혜민,최유경,정덕유,이민경 이화여자대학교 간호과학대학 2016 이화간호학회지 Vol.- No.50

Purpose: The purpose of this study was to determine the relationship between job stress, body mass index and waist circumference among middle aged male workers. Methods: Using a descriptive correlation study design, a total of 122 middle aged male workers were recruited through convenience sampling from November 8 to December 13, 2015. The questionnaire included in this study were general characteristics and the Korean Occupational Stress Scale-Short Form (KOSS-SF). Data were statistically analyzed using SPSS windows version 22 program with Pearson’s correlation coefficient. Results: A significant relationship was found between job stress, body mass index (p=.043) and waist circumference (p=.007). Conclusion: These results suggest that high job stress are significantly associated with both body mass index and waist circumference of middle aged male workers. This implies a need for intervention that focuses on reducing obesity and metabolic syndrome influenced by job stress.

哺乳動物 卵胞卵의 琉璃化凍結後 FDA-test에 의한 生存性 判定

康珉秀,張德支,梁柄哲,金重桂,高敬來,高赫辰 제주대학교 방사능이용연구소 1995 연구보고 Vol.9 No.-

本 實驗은 琉璃化凍結 融解된 포유동물 卵胞卵의 生存性을 FDA-test에 의한 판정을 규명하기 위하여 실행되었으며 Oocytes는 卵丘細胞의 부착 상태에 따라 3 group 분류하였다. A oocyte는 卵丘細胞가 밀착되어 부착된 것(tight oocytes)이며 B oocyte는 卵丘細胞가 部分的으로 부착된 것(partial oocytes) 그리고 C oocyte는 卵丘細胞가 빈약하게 부착된 것(poor oocytes)이다. 琉璃化 凍結液은 1992년 金 등에 의한 연구에서 개발된 것으로서 glycerol 20 %, ethylene glycol, 10%, Ficoll 30% 와 sucrose 10% 로 구성되어 있다. Oocyte(7-10)는 10분의 평형시간을 경과한 후 0.25 ㎖ straw에 넣어 상온에서 직접 액체질소 container(-196℃)에 침지시켜 동결을 완료시켰다. 凍結融解한 A 그룹 난자의 FDA-score는 rat(4.2)에서 rabbit(3.9), cow(3.8), mouse(3.4)와 porcine(2.4)보다 높았지만 cumulus cell의 경우는 rabbit(4.7)에서 rat(4.1), cow(2.9), porcine(2.6)과 mouse(1.4)보다 높았다. 凍結融解한 B 그룹 난자들의 FDA-score는 각각 3.1(cow), 2.9(rabbit), 2.9(mouse), 2.6(rat) 그리고 2.5(porcine)이였다. 하지만 cumulus cell의 경우는 rabbit(3.7)에서 porcine(2.6), rat(2.3), cow(1.7) and mouse(0.3)보다 높았다. 凍結融解한 C 그룹 난자의 FDA-score는 mouse(4.1)에서 cow(2.9), rabbit(2.6), rat(1.3)과 porcine(1.1)에서 보다 높았다. 以上의 結果에서 mouse를 제외하고 일반적으로 난포난의 琉璃化 凍結融解 후 group A의 난자가 group B와 C에서 난자보다 生存率이 높았으며 FDA-test를 하였을 때 oocytes는 물론 cumulus cell에서도 발광을 나타내어 卵丘細胞의 생존판정여부를 확인할 수 있는 가능성을 제시하였다. This experiment was carried out to study the determination of survival of vitrified and thawed mammal follicular oocytes by FDA-test. Oocytes were divided into 3 groups according to attachment of cumulus cell. Group A oocytes were tightly surrounded by cumulus cell, group B oocytes were partially surrounded by cumulus cell, and group C oocytes were poorly surrounded by cumulus cell. Vitrification solution developed by our previous study (Kim et al, 1992) which consisted of permeable agent (20% glycerol + 10 % ethylene glycol) and nonpermeable agent (30 % Ficoll + 10 % sucrose). Oocytes (7-10) loaded into 0.25 ㎖ straw after 10 min equilibration were plunged into liquid nitrogen (-196℃) directly. The FDA-score of vitrified and thawed group A oocytes was higher in rat (4.2) than in rabbit (3.9), cow(3.8), mouse (3.4) and porcine(2.4), however that of cumulus cell was higher in rabbit (4.7) than in rat (4.1), cow(2.9), porcine(2.6) and mouse (1.4). The FDA-score of vitrified and thawed group B oocytes were 3.1(cow), 2.9 (rabbit), 2.9 (mouse), 2.6 (rat) and 2.5(porcine), respectively. However that of cumulus cell was higher in rabbit (3.7) than in porcine(2.6), rat(2.3), cow(1.7) and mouse(0.3). The FDA-score of vitrified and thawed group C oocytes was higher in mouse (4.1) than in cow(2.9), rabbit(2.6), rat(1.3) and porcine(1.1). As shown in the above results, The survival rates of oocytes were higher in group A than in group B and C except in mouse and cow. These results suggest that the survival of cumulus cell as well as follicular oocytes can be reliably judged by their fluorescence with FDA-test.