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Enhancement in the photodetection of ZnO nanowires by introducing surface-roughness-induced traps
Park, Woojin,Jo, Gunho,Hong, Woong-Ki,Yoon, Jongwon,Choe, Minhyeok,Lee, Sangchul,Ji, Yongsung,Kim, Geunjin,Kahng, Yung Ho,Lee, Kwanghee,Wang, Deli,Lee, Takhee IOP Pub 2011 Nanotechnology Vol.22 No.20
<P>We investigated the enhanced photoresponse of ZnO nanowire transistors that was introduced with surface-roughness-induced traps by a simple chemical treatment with isopropyl alcohol (IPA). The enhanced photoresponse of IPA-treated ZnO nanowire devices is attributed to an increase in adsorbed oxygen on IPA-induced surface traps. The results of this study revealed that IPA-treated ZnO nanowire devices displayed higher photocurrent gains and faster photoswitching speed than transistors containing unmodified ZnO nanowires. Thus, chemical treatment with IPA can be a useful method for improving the photoresponse of ZnO nanowire devices. </P>
Tumorigenicity Evaluation of Umbilical Cord Blood-derived Mesenchymal Stem Cells
Park, Sang-Jin,Kim, Hyun-Jung,Kim, Woojin,Kim, Ok-Sun,Lee, Sunyeong,Han, Su-Yeon,Jeong, Eun Ju,Park, Hyun-shin,Kim, Hea-Won,Moon, Kyoung-Sik Korean Society of ToxicologyKorea Environmental Mu 2016 Toxicological Research Vol.32 No.3
Mesenchymal stem cells (MSCs) have been identified in multiple types of tissue and exhibit characteristic self-renewal and multi-lineage differentiation abilities. However, the possibility of oncogenic transformation after transplantation is concerning. In this study, we investigated the tumorigenic potential of umbilical cord blood-derived MSCs (hUCB-MSCs) relative to MRC-5 and HeLa cells (negative and positive controls, respectively) both in vitro and in vivo. To evaluate tumorigenicity in vitro, anchorage-independent growth was assessed using the soft agar colony formation assay. hUCB-MSCs and MRC-5 cells formed few colonies, while HeLa cells formed a greater number of larger colonies, indicating that hUCB-MSCs and MRC-5 cells do not have anchorage-independent proliferation potential. To detect tumorigenicity in vivo, hUCB-MSCs were implanted as a single subcutaneous injection into BALB/c-nu mice. No tumor formation was observed in mice transplanted with hUCB-MSCs or MRC-5 cells based on macro- and microscopic examinations; however, all mice transplanted with HeLa cells developed tumors that stained positive for a human gene according to immunohistochemical analysis. In conclusion, hUCB-MSCs do not exhibit tumorigenic potential based on in vitro and in vivo assays under our experimental conditions, providing further evidence of their safety for clinical applications.
Park, Sujin,Lim, Jung Mi,Park, Seon Hwa,Kim, Suree,Heo, Sukyeong,Balla, Tamas,Jeong, Woojin,Rhee, Sue Goo,Kang, Dongmin Elsevier 2019 FREE RADICAL BIOLOGY AND MEDICINE Vol.131 No.-
<P><B>Abstract</B></P> <P>Binding of epidermal growth factor (EGF) to its cell surface receptor induces production of H<SUB>2</SUB>O<SUB>2</SUB>, which serves as an intracellular messenger. We have shown that exogenous H<SUB>2</SUB>O<SUB>2</SUB> reversibly inactivates the phosphatidylinositol 4-phosphate [PtdIns(4)P] phosphatase Sac1 (suppressor of actin 1) at the Golgi complex of mammalian cells by oxidizing its catalytic cysteine residue and thereby increases both the amount of Golgi PtdIns(4)P and the rate of protein secretion. Here we investigated the effects of EGF on Sac1 oxidation and PtdIns(4)P abundance at the Golgi in A431 cells. EGF induced a transient increase in Golgi PtdIns(4)P as well as a transient oxidation of Sac1 in a manner dependent on elevation of the intracellular Ca<SUP>2+</SUP> concentration and on H<SUB>2</SUB>O<SUB>2</SUB>. Oxidation of Sac1 occurred at the Golgi, as revealed with the use of the Golgi-confined Sac1-K2A mutant. Knockdown of Duox enzymes implicated these Ca<SUP>2+</SUP>-dependent members of the NADPH oxidase family as the major source of H<SUB>2</SUB>O<SUB>2</SUB> for Sac1 oxidation. Expression of a Golgi-targeted H<SUB>2</SUB>O<SUB>2</SUB> probe revealed transient EGF-induced H<SUB>2</SUB>O<SUB>2</SUB> production at this organelle. Our findings have thus uncovered a previously unrecognized EGF signaling pathway that links intracellular Ca<SUP>2+</SUP> mobilization to events at the Golgi including Duox activation, H<SUB>2</SUB>O<SUB>2</SUB> production, Sac1 oxidation, and PtdIns(4)P accumulation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> EGF elicits transient H<SUB>2</SUB>O<SUB>2</SUB> production at the Golgi by Ca<SUP>2+</SUP>-dependent Duox. </LI> <LI> This H<SUB>2</SUB>O<SUB>2</SUB> inactivates Sac1 at the Golgi by transiently oxidizing its catalytic Cys. </LI> <LI> Transient inactivation of Sac1 results in a transient increase in Golgi PtdIns(4)P. </LI> <LI> This new EGF signaling pathway links Ca<SUP>2+</SUP> to Golgi PtdIns(4)P via Duox-H<SUB>2</SUB>O<SUB>2</SUB>-Sac1. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Manikin families representing obese airline passengers in the US.
Park, Hanjun,Park, Woojin,Kim, Yongkang Multi-Science Pub 2014 Journal of healthcare engineering Vol.5 No.4
<P>Aircraft passenger spaces designed without proper anthropometric analyses can create serious problems for obese passengers, including: possible denial of boarding, excessive body pressures and contact stresses, postural fixity and related health hazards, and increased risks of emergency evacuation failure. In order to help address the obese passenger's accommodation issues, this study developed male and female manikin families that represent obese US airline passengers. Anthropometric data of obese individuals obtained from the CAESAR anthropometric database were analyzed through PCA-based factor analyses. For each gender, a 99% enclosure cuboid was constructed, and a small set of manikins was defined on the basis of each enclosure cuboid. Digital human models (articulated human figures) representing the manikins were created using a human CAD software program. The manikin families were utilized to develop design recommendations for selected aircraft seat dimensions. The manikin families presented in this study would greatly facilitate anthropometrically accommodating large airline passengers.</P>