Effect of Mn and C on Age Hardening of Fe–Mn–Al–C Lightweight Steels

Sung‑Won Park,Jun Young Park,Kyong Mox Cho,Jae Hoon Jang,Seong‑Jun Park,Joonoh Moon,Tae‑Ho Lee,Jong‑Ho Shin 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.3

The effects of Mn and C content on the age hardening of Fe–Mn–Al–C lightweight steels, which have austenitic or duplex(austenite and ferrite) microstructures, were investigated. An increase in Mn content induced a delay of the age hardeningthat is caused by the formation of intra-granular κ-carbides. In order to interpret the effect of Mn content, first-principlescalculations were conducted using the supercells of Fe24Al8C8,Fe24Al8C7,Fe24(Al7Mn)C8, and Fe24(Al7Mn)C7. The calculationsshowed that an increase in Mn content could be the source of the delay of the intra-granular κ-carbide formation bysuppressing C atom’ occupation of the vacancy at the body-centered site of L12. An increase in C content accelerated theformation of intra-granular κ-carbides, which induced the intense age hardening, and coarse inter-granular κ-carbides, whichresulted in significant decrease in impact absorbed energy due to inter-granular fracture.

Association Between Vitamin D Deficiency and Suspected Nonalcoholic Fatty Liver Disease in an Adolescent Population

Cho, Young Hoon,Kim, Ju Whi,Shim, Jung Ok,Yang, Hye Ran,Chang, Ju Young,Moon, Jin Soo,Ko, Jae Sung The Korean Society of Pediatric Gastroenterology 2019 Pediatric gastroenterology, hepatology & nutrition Vol.22 No.3

Purpose: Vitamin D deficiency is a condition widespread throughout the world. Recent studies have suggested that vitamin D deficiency was associated with obesity and metabolic syndrome. The purpose of the study was to examine the relationship between vitamin D deficiency and nonalcoholic fatty liver disease (NAFLD) in adolescents. Methods: The data were obtained from the Korean National Health and Nutrition Examination Survey from 2008-2014. A total of 3,878 adolescents were included in the study. Vitamin D deficiency was defined as a 25-hydroxyvitamin D concentration <20 ng/mL and suspected NAFLD was defined as an alanine transaminase concentration >30 U/L. Results: Vitamin D deficiency was noted in 78.9% of the studied population. Age, body mass index, waist circumference, and blood pressure, glucose, cholesterol, and triglyceride levels were significantly higher in adolescents with suspected NAFLD than in adolescents without suspected NAFLD, while the mean vitamin D level was significantly lower in adolescents with suspected NAFLD. The multivariate-adjusted odds of suspected NAFLD were higher with increased age, male gender, obesity, and metabolic syndrome. Individuals with vitamin D deficiency were at higher risk of suspected NAFLD (odds ratio, 1.77; 95% confidence interval, 1.07-2.95) after adjusting for age, gender, obesity, and metabolic syndrome. Conclusion: Vitamin D deficiency was associated with suspected NAFLD, independent of obesity and metabolic syndrome, in adolescents.

Dkk-1 Promotes Angiogenesis through Epithelial-Mesenchymal Transition in Hepatocellular Carcinoma

( Sang Hyun Seo ),( Hye Jung Park ),( Kyungjoo Cho ),( Hye Won Lee ),( Beom Kyung Kim ),( Jun Yong Park ),( Do Young Kim ),( Sang Hoon Ahn ),( Seung Up Kim ) 대한간학회 2020 춘·추계 학술대회 (KASL) Vol.2020 No.1

Aims: Dickkopf-1(DKK1), a negative regulator of the Wnt/ ß-catenin pathway, has been recently found to be up-regulated in hepatocellular carcinoma (HCC). However, the biological function of DKK1 in HCC has not yet been well documented. Our previous in vitro data suggest that DKK1 can enhance angiogenesis by endothelial cell, independent of the Wnt signaling pathway. This study aimed to investigate the tumorigenic potential and angiogenic role of DKK1 in mouse model. Methods: We assessed tumorigenic functions of DKK1 in Hep3B cells expressing endogenous DKK-1 and in DKK1-deficient Hep3B cells created using CRISPR/Cas9 technology. These edited cells were injected subcutaneously in immunosuppressed mice and tumor growth was followed for 6 weeks. With the evidence of tumorigenic potential in DKK1, transgenic mouse models expressing DKK-1 or luciferase were developed using hydrodynamic transfection. Transposons encoding an activated form of human H-RAS were mixed with transposons encoding either DKK1 or luciferase. All mice were monitored at least twice per week and sacrificed when moribund. Subcutaneous tumors and tumor-bearing livers were formalin fixed for hematoxylin- eosin and immunofluoroscence staining. Results: DKK1-deficient Hep3B xenografts exhibited significantly less growth compared to control Hep3B cells expressing DKK1. In addition, the forced expression of DKK1 with H-RAS through the hydrodynamic transfection formed many tumors in the liver, compared to luciferase liver. We investigated the expression of angiogenesis markers, including CD31, VEGFR2 and mesenchymal markers, including vimentin, fibronectin in the subcutaneous tumors and tumor-bearing livers. Quantity of angiogenic and mesenchymal cells were found to be reduced in the established DKK1 homozygous knockout mice (all P<0.05). Taken together, it was confirmed that the expression of CD31 (P<0.0001), VEGFR2 (P<0.0001), vimentin, and fibronectin (P<0.0001) were up-regulated with DKK1 in the mouse liver. Conclusions: Our findings indicate that DKK1 appears to facilitate angiogenesis, and the progression of HCC through inducing the EMT.

Analysis of Clip-induced Ischemic Complication of Anterior Choroidal Artery Aneurysms

Cho, Min-Soo,Kim, Min-Su,Chang, Chul-Hoon,Kim, Sang-Woo,Kim, Seong-Ho,Choi, Byung-Yon The Korean Neurosurgical Society 2008 Journal of Korean neurosurgical society Vol.43 No.3

Objective: The surgical approach for anterior choroidal artery (AChA) aneurysm is typically similar to those used for other supraclinoid internal carotid artery (ICA) lesions. However, the surgical clipping of this aneurysm is complicated and as a result. can result in postoperative ischemic complications. The purpose of this study was to clarify the risk of clip-induced ischemic complication in AChA aneurysm and to get the benefits for helping decision making. Methods: We retrospectively investigated 53 cases (4.0%) of AchA aneurysm treated surgically. We divided the AChA aneurysm to 3 subtype according to the origin of aneurysmal neck; A type originating from the AChA itself. J type from junction of AChA and ICA and I type from the ICA itself. We evaluated brain CT about 1 week post-operative day to confirm the low density in AChA territory. Results: Ruptured aneurysm was 26 cases and unruptured aneurysm 27 cases. The aneurysmal subtype of A, J, and I was 13, 17, and 23 cases. Of the 53 cases who performed surgical neck clipping, twelve (22.6%) had postoperative AChA distribution infarcts. Increased infarct after neck clipping had statistic significance in non-I subtype (r=0.005) Conclusion: AChA aneurysm surgery carries a significant risk of postoperative stroke. Don't always stick to clipping only, especially in non-I type of incidental small aneurysm, which has high risk of post-clip ischemic complications.

MiR-22-3p Alleviated Hepatic Lipogenesis via Inhibiting the SIRT1-PPAR Gamma Signal Pathway in Non-Alcoholic Fatty Liver Disease

( Sung Woo Cho ),( Jung Hoon Cha ),( Na Ri Park ),( Won Hee Hur ),( Pill Soo Sung ),( Jong Young Choi ),( Seung Kew Yoon ),( Si Hyun Bae ),( Hee Chul Nam ) 대한간학회 2020 춘·추계 학술대회 (KASL) Vol.2020 No.1

Aims: Non-alcoholic fatty liver disease (NAFLD) is a metabolic- related disorder ranging from simple steatosis to more severe forms, but the exact mechanism of progression remains unknown. MicroRNAs(miR), a class of small noncoding RNAs, are implicated in controlling a variety of biological processes. The aim of this study is to investigate the regulatory and protective role of miR-22-3p in NAFLD progression. Methods: Both in vitro and in vivo models of NAFLD were generated by treating HepG2 and Huh-7 cells with palmitic acid (PA) and by feeding mice a high-fat diet (HFD), respectively. HE and Oil Red O staining were used to examine liver tissue morphology and lipid deposition, respectively. qRT-PCR (quantitative real time polymerase chain reaction) was used for investigate expression of miR, SIRT1, and proteins involved in lipogenesis Results: HFD-mice hepatic tissues and PA-treated HepG2 and Huh-7 cells presented excess lipid production. Both in vitro and in vivo NAFLD model displayed decreased miR-22-3p and SIRT1 expression as evidenced by qRT-PCR. Overexpression of miR-22-3p induced downregulation of FAS, PPAR gamma and SREBP-1c via upregulation of SIRT1 expression. Reduction of hepatic lipid accumulation was observed by Oil red O staining. Conclusions: In this study, miR-22-3p had a role in ameliorating hepatic lipogenesis by regulation of SIRT1 signal pathway in NAFLD model. The overexpressed miR-22-3p protects hepatocytes from lipid metabolism and suppresses hepatic lipogenesis, suggesting as a potential target for the therapeutic strategy of NAFLD.

Determinants of Hedging and their Impact on Firm Value and Risk: After Controlling for Endogeneity Using a Two-stage Analysis

Sang-Ik Seok,Tae-Hyun Kim,Hoon Cho,Tae-Joong Kim 한국무역학회 2020 Journal of Korea trade Vol.24 No.1

Purpose – In this study, we investigate determinants of hedging with derivatives and its effect on firm value and firm risk for Korean firms. Design/methodology – To avoid the endogeneity problem pointed out in previous studies, we use a two-stage analysis by using gains and losses from derivatives as instrument variable for hedging with derivatives. Findings – Our analysis on the determinants of hedging shows that firms that are more leveraged and less profitable, and with more growth opportunities are likely to hedge through derivatives. Additionally, large firms, firms less diversified into industry, and firms more diversified geographically are likely to use derivatives. Our two-stage analysis shows that indicators of hedging with derivatives have an insignificant effect on firm value, and the indicator of futures/forwards use and of swaps use have significant negative effect on firm value. Whereas, the extent of hedging with derivatives has positive effect on firm value for all types of foreign currency derivatives, which suggests that moderately low hedgers use derivatives inefficiently, but extensive hedgers use derivatives properly. With regard to firm risk, hedging with derivatives increases market-based risk, but decreases accounting-based risk. Thus, we conclude that Korean firms use derivatives to manage operational volatility rather than to manage market risk, and accounting-based risk reduction through hedging is not directly translated into higher firm value. Originality/value – This is not the first study to investigate hedging behavior of Korean firms, but the sample period that that this study analyzed is the longest and various method are used to control the endogeneity problem. We investigate not only total foreign currency derivatives but also by types of derivatives, including futures/forwards, options, and swaps.

Macroscopic Nonlinear Optical Properties of Tricyanopyrrolidene Chromophore Containing Amorphous Polycarbonate: Effect of Molecular Lateral Moiety in the Conjugative Structure

Cho, Min-Ju,Lee, Sang-Kyu,Jin, Jung-Il,Choi, Dong-Hoon The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.6

Tricyanopyrrolidene chromophores were prepared in order to compare their macroscopic nonlinear optical (NLO) properties with a conjugated structure through the long molecular axis. A thiophene or phenyl ring was tethered to an ethylenic bond; it may act as a lateral moiety to disrupt the planarity of a chromophore and lessen the electrostatic interaction. Thin film composites of these chromophores dissolved in amorphous polycarbonate (APC) were fabricated. Real time pole and probe method was employed to investigate the change of electro-optic (EO) signal during poling. The EO properties and their relaxation behaviors of the guest-host systems containing newly synthesized chromophores were investigated in detail.

Acyclic Diterpenoids from the Leaves of Capsicum annuum

Cho, Jin-Gyeong,Lee, Dae-Young,Lee, Jae-Woong,Lee, Do-Gyeong,Lee, Youn-Hyung,Kim, Se-Young,Kim, Sung-Hoon,Baek, Nam-In The Korean Society for Applied Biological Chemistr 2009 Applied Biological Chemistry (Appl Biol Chem) Vol.52 No.2

The leaves of Capsicum annuum L. were extracted with 80% aqueous MeOH, and the concentrated extract was partitioned successively with EtOAc, n-BuOH, and $H_2O$. Three acyclic diterpenoids were isolated from the EtOAc fraction through repeated silica gel column chromatography. The physico-chemical and spectroscopic analyses including NMR, EI-MS, and IR indicated that the three compounds correspond to ${\alpha}$-tocopherol (1), phytol (2), and vitamin E quinone (3). This is the first time these compounds have been isolated from the leaves of C. annuum.

Determinant of Hedging and Its Impact on Firm Value : After Controlling Endogeneity Problem Using a Two-Stage Analysis

Sang Ik Seok,Tae Hyun Kim,Hoon Cho,Tae Joong Kim 한국유통과학회 2017 KODISA ICBE (International Conference on Business Vol.2017 No.-

A derivative market in Korea was used to be one of the biggest markets in the world, but it has dramatically decreased after 2011, and now, trading volume of Korea Exchange becomes 1/3 compared to that in 2011. Given that the unprecedented change in the derivative market in Korea, in this study, we suggest that it is caused by the inefficient use of derivatives by Korean firms which led to significant financial loss by analyzing the relation between hedging and firm value. To avoid endogeniety problem between these two variables, we use a two-stage analysis. At a first stage, we regress hedging on several control variables which are known to affect hedging theoretically or empirically, and we calculate the predicted value of hedging. Then we put this predicted value into a second stage model as an independent variable. The result of the first stage analysis also provides information about the determinant of hedging. The result of a second stage analysis shows that the use of derivatives itself significantly reduces firm value, but if a firm has decided to use derivative, then the extent of hedging increases its value. Thus, we conclude that a decision to use derivatives for hedging is, in fact, harmful for firm value in Korea because Korean firms may use them inefficiently. However, extensive users utilize derivative more efficiently than moderate users do.

Template-Assisted Electrochemical Growth of Hydrous Ruthenium Oxide Nanotubes

Cho, Sanghyun,Liu, Lichun,Yoo, Sang-Hoon,Jang, Ho-Young,Park, Sungho Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.5

We demonstrate that ruthenium oxide ($RuO_2$) nanotubes with controlled dimensions can be synthesized using facile electrochemical means and anodic aluminum oxide (AAO) templates. $RuO_2$ nanotubes were formed using a cyclic voltammetric deposition technique and an aqueous plating solution composed of $RuCl_3$. Linear sweep voltammetry (LSV) was used to determine the effective electrochemical oxidation potential of $Ru^{3+}$ to $RuO_2$. The length and wall thickness of $RuO_2$ nanotubes can be adjusted by varying the range and cycles of the electrochemical cyclic voltammetric potentials. Thick-walled $RuO_2$ nanotubes were obtained using a wide electrochemical potential range (-0.2~1 V). In contrast, an electrochemical deposition potential range from 0.8 to 1 V produced thin-walled and longer $RuO_2$ nanotubes in an identical number of cycles. The dependence of wall thickness and length of $RuO_2$ nanotubes on the range of cyclic voltammetric electrochemical potentials was attributed to the distinct ionic diffusion times. This significantly improves the ratio of surface area to mass of materials synthesized using AAO templates. Furthermore, this study is directive to the controlled synthesis of other metal oxide nanotubes using a similar strategy.