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Sang‑Wook Kim,Hyeon‑Woo Son,Taek‑Kyun Jung,Young‑Bum Chun,Yi‑Hyun Park,Ji‑Woon Lee,Soong‑Keun Hyun 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
The hot deformation behavior of advanced reduced-activation alloy (ARAA) was investigated using hot torsion tests. Thefl ow stress decreased as deformation temperature increased and as strain rate decreased. The fl ow behavior demonstratedthe typical dynamic recrystallization (DRX). Based on the constitutive analysis of peak stress, the activation energy for hotdeformation was found to be 330.3 kJ mol −1 . Peak stress was analyzed as a function of the Zener–Hollomon parameter, andcalculated and experimental values were in good agreement. A DRX kinetic model for ARAA was derived with deformationconditions based on the Avrami-type model. It was confi rmed that the volume fraction of dynamically recrystallized grainsincreased as deformation temperature increased and as strain rate decreased. The necklace structure and grain boundarybulging were observed in the deformed microstructure of ARAA. The suggested DRX mechanism for ARAA during hotworking is discontinuous DRX.
산업단지 및 일반생활 지역의 공기 중 톨루엔에 대한 개인노출 및 생체시료의 상관성 분석
이병준(Byoungjun Lee),허 정(Jung Heo),정다영(Dayoung Jung),김순신(Sunshin Kim),류현수(Hyeon-Su Ryu),최민지(Min-Ji Choi),솨이지엔페이(Jian-Fei Shuai),임성국(Sung-Guk Im),양원호(Wonho Yang) 한국환경보건학회 2017 한국환경보건학회지 Vol.43 No.4
Objectives: The purpose of this study was to assess the correlation relationship between personal exposure and urinary hippuric acid in biological monitoring for airborne toluene in an industrial complex and in general environments. Methods: Personal exposure to toluene and its metabolite, hippuric acid, in urine were simultaneously measured in occupational environments area near an industrial complex and in general environments. The study subjects were divided into three types: 137 workers who use organic solvents in the workplace, 210 residents living near a dyeing industrial complex, and 379 residents living in general environments. The toluene exposures of workers and residents were measured by a passive sampler for four days. The urine of participants was sampled when the passive samplers of personal exposure were collected. Results: The toluene and hippuric acid concentrations of workers were the highest, followed by the concentrations of residents living near a dyeing industrial complex and residents living in general environments. The coefficient of correlation between the concentrations of toluene and hippuric acid among workers was 0.749 (p<0.01) in the workplace. On the contrary, correlations between the concentrations of toluene and hippuric acid among residents living near a dyeing industrial complex and residents living in general environments were all not significant. The relationship between the concentrations of hippuric acid and toluene in three types could be described by the exponential growth model. Conclusions: This study analyzed the relationships between toluene exposure and the concentrations of hippuric acid in urine in high, middle, and low exposure environments, and could be described by the exponential growth model.
Choi, Dukhyun,Choi, Min-Yeol,Choi, Won Mook,Shin, Hyeon-Jin,Park, Hyun-Kyu,Seo, Ju-Seok,Park, Jongbong,Yoon, Seon-Mi,Chae, Seung Jin,Lee, Young Hee,Kim, Sang-Woo,Choi, Jae-Young,Lee, Sang Yoon,Kim, Jo WILEY-VCH Verlag 2010 ADVANCED MATERIALS Vol.22 No.19
<B>Graphic Abstract</B> <P>The cover shows an image of fully rollable transparent nanogenerators synthesized using chemical vapor deposition grown large-scale graphene sheets as transparent electrodes and piezoelectric ZnO nanorod arrays. Sang-Woo Kim, Jae-Young Choi, and co-workers report on p. 2187 the electrical and structural stability of the nanogenerators, with excellent charge scavenging performance under external mechanical loads such as bending and rolling. This study shows that graphene-based nanogenerators are very promising for self-powered rollable transparent device applications. <img src='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content.gif' alt='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content'> </P>
Lee, Hyeon-Ji,Kim, Jung-Hwan,Won, Ji-Hye,Lim, Jun-Muk,Hong, Young Taik,Lee, Sang-Young American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.11
<P>We demonstrate highly flexible, proton-conductive silicate glass electrolytes integrated with polyimide (PI) nonwoven fabrics (referred to as “b-SS glass electrolytes”) for potential use in medium-temperature/low-humidity proton exchange membrane fuel cells (PEMFCs). The b-SS glass electrolytes are fabricated via in situ sol–gel synthesis of 3-trihydroxysilyl-1-propanesulfonic acid (THPSA)/3-glycidyloxypropyl trimethoxysilane (GPTMS) mixtures inside PI nonwoven substrates that serve as a porous reinforcing framework. Owing to this structural uniqueness, the b-SS glass electrolytes provide noticeable improvements in mechanical bendability and membrane thickness, in comparison to typical bulk silicate glass electrolytes that are thick and easily fragile. Another salient feature of the b-SS glass electrolytes is the excellent proton conductivity at harsh measurement conditions of medium temperature/low humidity, which is highly important for PEMFC-powered electric vehicle applications. This beneficial performance is attributed to the presence of a highly interconnected, proton-conductive (THPSA/GPTMS-based) silicate glass matrix in the PI reinforcing framework. Notably, the b-SS glass electrolyte synthesized from THPSA/GPTMS = 9/1 (mol/mol) exhibits a higher proton conductivity than water-swollen sulfonated polymer electrolyte membranes (here, sulfonated poly(arylene ether sulfone) and Nafion are chosen as control samples). This intriguing behavior in the proton conductivity of the b-SS glass electrolytes is discussed in great detail by considering its structural novelty and Grotthuss mechanism-driven proton migration that is strongly affected by ion exchange capacity (IEC) values and also state of water.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-11/am400836h/production/images/medium/am-2013-00836h_0010.gif'></P>
Lee, Seung‐,Hwan,Ha, Hee‐,Sung,Park, Young‐,Jun,Lee, Jin‐,Hee,Yim, Hyeon‐,Woo,Yoon, Kun‐,Ho,Kang, Moo‐,Il,Lee, Won‐,Chul,Son, Ho‐,Young,Park, Yong Blackwell Publishing Ltd 2011 Clinical endocrinology Vol.75 No.4
<P><B>Summary</B></P><P><B>Objective </B> To investigate the prevalence and identify the phenotype of individuals suspected to be metabolically obese but normal weight (MONW).</P><P><B>Design and subjects </B> Eight thousand nine hundred and eighty‐seven nondiabetic subjects aged over 40 years were selected from the Chungju Metabolic disease Cohort study performed in 2003–2006 in Korea. Those within the highest quartile in the homeostasis model assessment of insulin resistance (HOMA‐IR) with a normal body mass index (BMI) between 18·5 and 23 kg/m<SUP>2</SUP> were classified as MONW.</P><P><B>Measurements </B> Data on anthropometry, lipid profiles and HOMA‐IR values were analysed.</P><P><B>Results </B> The prevalence of MONW was 14·2% for men and 12·9% for women amongst normal‐weight subjects. Multiple logistic regression analysis showed that total cholesterol (TC) levels over 5·17 m<SMALL>m</SMALL> (odds ratio, OR = 1·481; 95% confidence intervals, CI 1·086–2·021), triglyceride (TG) levels over 1·69 m<SMALL>m</SMALL> (OR = 1·507; 95% CI 1·093–2·077) and high‐density lipoprotein‐cholesterol levels lower than 1·03 m<SMALL>m</SMALL> (OR = 1·580; 95% CI 1·053–2·371) independently had higher odds of diagnosing MONW amongst men. For women, a BMI over 21·5 kg/m<SUP>2</SUP> (OR = 1·405; 95% CI 1·034–1·909), TC levels over 5·17 m<SMALL>m</SMALL> (OR = 1·524; 95% CI 1·112–2·090) and TG levels over 1·69 m<SMALL>m</SMALL> (OR = 1·799; 95% CI 1·302–2·487) were independently associated with a diagnosis of MONW.</P><P><B>Conclusions </B> More than 10% of normal‐weight subjects were classed as MONW in this cohort. Identification of these subjects based on lipid profiles could aid in the early detection of a high risk group of developing cardiometabolic diseases.</P>
Sang-Rae Cho,Kuldeep Kumar,Seong-Heum Yeon,Sung-Hwan Lee,Ui-Hyung Kim,Ki-Yong Chung,Hyeon-Shup Kim,Myeung Sik Lee,Chang-Seok Park,Byoung-Chul Yang 한국수정란이식학회 2014 한국동물생명공학회지 Vol.29 No.4
The present study was performed on farm animals to test the effectiveness of progesterone-releasing intravaginal device (Cue-Mate® 1.56 g) and injection of prostaglandin F2α (PGF2α) for synchronization estrus in Hanwoo cattle. The cattle were at random stage of the estrus cycle. The cows were artificially inseminated at day 7 after Cue-Mate withdrawal, using commercial semen from Korean native bulls. There was a season effect on the estrus synchronization rate. It was higher in spring (94.3%) followed by winter (93.3%), autumn (90.4%) and summer (67.2%). In summary, The results of this study revealed that season has influences on estrus behavior of cattle with no significant effect on pregnancy rate. In summary, we suggest summer reproductive management to alleviate the effects of heat stress. It should be based on intensive cooling combined with hormonal treatment. Given that different subgroups of cows benefit differently from the treatments, selective hormonal administration should be considered.
Lee, Kang Hyuck,Shin, Hyeon-Jin,Lee, Jinyeong,Lee, In-yeal,Kim, Gil-Ho,Choi, Jae-Young,Kim, Sang-Woo American ChemicalSociety 2012 NANO LETTERS Vol.12 No.2
<P>Hexagonal boron nitride (h-BN) has received a great dealof attention as a substrate material for high-performance grapheneelectronics because it has an atomically smooth surface, lattice constantsimilar to that of graphene, large optical phonon modes, and a largeelectrical band gap. Herein, we report the large-scale synthesis ofhigh-quality h-BN nanosheets in a chemical vapor deposition (CVD)process by controlling the surface morphologies of the copper (Cu)catalysts. It was found that morphology control of the Cu foil ismuch critical for the formation of the pure h-BN nanosheets as wellas the improvement of their crystallinity. For the first time, wedemonstrate the performance enhancement of CVD-based graphene deviceswith large-scale h-BN nanosheets. The mobility of the graphene deviceon the h-BN nanosheets was increased 3 times compared to that withoutthe h-BN nanosheets. The on–off ratio of the drain currentis 2 times higher than that of the graphene device without h-BN. Thiswork suggests that high-quality h-BN nanosheets based on CVD are verypromising for high-performance large-area graphene electronics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2012/nalefd.2012.12.issue-2/nl203635v/production/images/medium/nl-2011-03635v_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl203635v'>ACS Electronic Supporting Info</A></P>
Lee, Ha-Na,Jin, Hyeon-Ok,Park, Jin-Ah,Kim, Jin-Hee,Kim, Ji-Young,Kim, BoRa,Kim, Wonki,Hong, Sung-Eun,Lee, Yun-Han,Chang, Yoon Hwan,Hong, Seok-Il,Hong, Young Jun,Park, In-Chul,Surh, Young-Joon,Lee, Jin Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.4
Piperlongumine, a natural alkaloid isolated from the long pepper, selectively increases reactive oxygen species production and apoptotic cell death in cancer cells but not in normal cells. However, the molecular mechanism underlying piperlongumine-induced selective killing of cancer cells remains unclear. In the present study, we observed that human breast cancer MCF-7 cells are sensitive to piperlongumine-induced apoptosis relative to human MCF-10A breast epithelial cells. Interestingly, this opposing effect of piperlongumine appears to be mediated by heme oxygenase-1 (HO-1). Piperlongumine upregulated HO-1 expression through the activation of nuclear factor-erythroid-2-related factor-2 (Nrf2) signaling in both MCF-7 and MCF-10A cells. However, knockdown of HO-1 expression and pharmacological inhibition of its activity abolished the ability of piperlongumine to induce apoptosis in MCF-7 cells, whereas those promoted apoptosis in MCF-10A cells, indicating that HO-1 has anti-tumor functions in cancer cells but cytoprotective functions in normal cells. Moreover, it was found that piperlongumine-induced Nrf2 activation, HO-1 expression and cancer cell apoptosis are not dependent on the generation of reactive oxygen species. Instead, piperlongumine, which bears electrophilic ${\alpha},{\beta}$-unsaturated carbonyl groups, appears to inactivate Kelch-like ECH-associated protein-1 (Keap1) through thiol modification, thereby activating the Nrf2/HO-1 pathway and subsequently upregulating HO-1 expression, which accounts for piperlongumine-induced apoptosis in cancer cells. Taken together, these findings suggest that direct interaction of piperlongumine with Keap1 leads to the upregulation of Nrf2-mediated HO-1 expression, and HO-1 determines the differential response of breast normal cells and cancer cells to piperlongumine.