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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>
( Sang Eun Lee ),( Hyeon Beom Seo ),( Hye Ji Kim ),( Ji Hyeon Yeon ),( Kyung Hwan Jung ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.11
In this study, a galactooligosaccharide (GOS) was synthesized using active β-galactosidase (β-gal) inclusion bodies (IBs)-containing Escherichia coli (E. coli) cells. Analysis by MALDI-TOF (matrix-assisted laser desorption/ionizationtime of flight) mass spectrometry revealed that a trisaccharide was the major constituent of the synthesized GOS mixture. Additionally, the optimal pH, lactose concentration, amounts of E. coli β-gal IBs, and temperature for GOS synthesis were 7.5, 500 g/l, 3.2 U/ml, and 37˚C, respectively. The total GOS yield from 500 g/l of lactose under these optimal conditions was about 32%, which corresponded to 160.4 g/l of GOS. Western blot analyses revealed that β-gal IBs were gradually destroyed during the reaction. In addition, when both the reaction mixture and E. coli β-gal hydrolysate were analyzed by highperformance thin-layer chromatography (HP-TLC), the trisaccharide was determined to be galactosyl lactose, indicating that a galactose moiety was most likely transferred to a lactose molecule during GOS synthesis. This GOS synthesis system might be useful for the synthesis of galactosylated drugs, which have recently received significant attention owing to the ability of the galactose molecules to improve the drugs solubility while decreasing their toxicity. β-Gal IB utilization is potentially a more convenient and economic approach to enzymatic GOS synthesis, since no enzyme purification steps after the transgalactosylation reaction would be required.
Lee, Kil Sung,Seo, Hyeon Kyeong,Hwang, Woo Chae,Kim, Jung Ho,Yang, Yong Jun,Yang, In Young Trans Tech Publications, Ltd. 2008 Materials science forum Vol.580 No.-
<P>Currently, the most important objective in designing automobiles is to focus on environment-friendly and safety performance aspects. For the environment-friendly aspect, the issues relate to the shift towards lightweight automobile production, for improving fuel-efficiency and reducing exhaust fumes. However, in contrast, the issues of the safety performance such as crash safety, comfort level and muti-functional programs demand increase of automobile’s weight. Therefore, the design of automobile should be inclined towards the safety aspects, but at the same time, it also should consider reducing the structural weight of an automobile. In this study, for lightweight design of side member, CFRP side member was manufactured from CFRP unidirectional prepreg sheet. The stacking condition related to the energy absorption of composite materials, is being considered as an issue for the structural efficiency. Therefore, the axial collapse tests were performed with change of the stacking condition, such as fiber orientation angle and interlaminar number. The collapse modes and energy absorption characteristics were analyzed according to fiber orientation angle and interlaminar number.</P>
Hyeon, Yuhwan,Jung, Su-Ho,Jang, Wonseok,Kim, Mansu,Kim, Byung-Sung,Lee, Jae-Hyun,Nandanapalli, Koteeswara Reddy,Jung, Namgee,Whang, Dongmok American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.5
<P>In MoS<SUB>2</SUB>-carbon composite catalysts for hydrogen evolution reaction (HER), the carbon materials generally act as supports to enhance the catalytic activity of MoS<SUB>2</SUB> nanosheets. The carbon support provides a large surface area for increasing the MoS<SUB>2</SUB> edge site density, and its physical structure can affect the electron transport rate in the composite catalysts. However, despite the importance of the carbon materials, direct observation of the effects of the physical properties of the carbon supports on the HER activity of MoS<SUB>2</SUB>-carbon composite catalysts has been hardly reported. In this work, we conduct an experimental model study to find the fundamental and important understanding of the correlation between the structural characteristics of carbon supports and the HER performance of MoS<SUB>2</SUB>-carbon composite catalysts using surface-modified graphitic carbon shell (GCS)-encapsulated SiO<SUB>2</SUB> nanowires (GCS@SiO<SUB>2</SUB> NWs) as support materials for MoS<SUB>2</SUB> nanosheets. The surface defect density and the electrical resistance of GCS@SiO<SUB>2</SUB> NWs are systematically modulated by control of H<SUB>2</SUB> gas flow rates during the carbon shell growth on the SiO<SUB>2</SUB> NWs. From in-depth characterization of the model catalysts, it is confirmed that the intrinsic catalytic activity of MoS<SUB>2</SUB>-carbon composites for the HER is improved linearly with the conductance of the carbon supports regardless of the MoS<SUB>2</SUB> edge site density. However, in the HER polarization curve, the apparent current density increases in proportion to the product of the number of MoS<SUB>2</SUB> edge sites and the conductance of GCS@SiO<SUB>2</SUB> NWs.</P> [FIG OMISSION]</BR>
Alteration of Apoptosis during Differentiation in Human Dental Pulp-Derived Mesenchymal Stem Cell
Hyeon-Jeong Lee,Byung-Joon Park,Ryoung-Hoon Jeon,Si-Jung Jang,Young-Bum Son,Sung-Lim Lee,Gyu-Jin Rho,Seung-Joon Kim,Won-Jae Lee 한국동물생명공학회(구 한국수정란이식학회) 2019 한국동물생명공학회지 Vol.34 No.1
Because mesenchymal stem cells (MSCs) maintain distinct capacities with respect to self-renewal, differentiation ability and immunomodulatory function, they have been highly considered as the therapeutic agents for cell-based clinical application. Of particular, differentiation condition alters characteristics of MSCs, including cellular morphology, expression of gene/protein and cell surface molecule, immunological property and apoptosis. However, the previous results for differentiation-related apoptosis in MSCs have still remained controversial due to varied outcomes. Therefore, the present study aimed to disclose periodical alterations of pro- and anti-apoptosis in MSCs under differentiation inductions. The human dental pulp-derived MSCs (DP-MSCs) were differentiated into adipocytes and osteoblasts during early (1 week), middle (2 weeks) and late (3 weeks) stages, and were investigated on their apoptosis-related changes by Annexin V assay, qRT-PCR and western blotting. The ratio of apoptotic cell population was significantly (p < 0.05) elevated during the early to middle stages of differentiations but recovered up to the similar level of undifferentiated state at the late stage of differentiation. In the expression of mRNA and protein, whereas expressions of pro-apoptosis-related makers (BAX and BAK) were not altered in any kind and duration of differentiation inductions, anti-apoptosis marker (BCL2) was significantly (p < 0.05) elevated even at the early stage of differentiations. The recovery of apoptotic cell population at the late stage of differentiation is expected to be associated with the response by elevation of anti-apoptotic molecules. The present study may contribute on understanding for cellular mechanism in differentiation of MSCs and provide background data in clinical application of MSCs in the animal biotechnology to develop effective and safe therapeutic strategy.
A crucial role of WW45 in developing epithelial tissues in the mouse
Lee, Joo-Hyeon,Kim, Tae-Shin,Yang, Tae-Hong,Koo, Bon-Kyoung,Oh, Sang-Phil,Lee, Kwang-Pyo,Oh, Hyun-Jung,Lee, Sang-Hee,Kong, Young-Yun,Kim, Jin-Man,Lim, Dae-Sik Wiley (John WileySons) 2008 The EMBO journal Vol.27 No.8
<P>The role and molecular mechanisms of a new Hippo signalling pathway are not fully understood in mammals. Here, we generated mice that lack WW45 and revealed a crucial role for WW45 in cell-cycle exit and epithelial terminal differentiation. Many organs in the mutant mouse embryos displayed hyperplasia accompanied by defects in terminal differentiation of epithelial progenitor cells owing to impaired proliferation arrest rather than intrinsic acceleration of proliferation during differentiation. Importantly, the MST1 signalling pathway is specifically activated in differentiating epithelial cells. Moreover, WW45 is required for MST1 activation and translocation to the nucleus for subsequent LATS1/2 activation upon differentiation signal. LATS1/2 phosphorylates YAP, which, in turn, translocates from the nucleus into the cytoplasm, resulting in cell-cycle exit and terminal differentiation of epithelial progenitor cells. Collectively, these data provide compelling evidence that WW45 is a key mediator of MST1 signalling in the coordinate coupling of proliferation arrest with terminal differentiation for proper epithelial tissue development in mammals.</P>