• Journal of Electrochemical Science and Technology
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• v.2 no.4
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• pp.187-192
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• 2011

Photoelectrochemical performances of ZnO electrodes are enhanced by coupling with cobalt-based catalyst (CoPi) in phosphate electrolyte (pH 7). For this study, hexagonal pillar-shaped ZnO nanorods are grown on ZnO electrodes through a chemical bath deposition, onto which CoPi is deposited with different photodeposition times (10-30 min). A scanning electron microscopic study indicates that CoPi deposition does not induce any change of ZnO morphology and an energy-dispersive X-ray spectroscopic analysis shows that inorganic phosphate ions (Pi) exist on ZnO surface. Bare ZnO electrodes generate the current of ca. $0.36mA/cm^2$ at a bias potential of 0.5 V vs. SCE, whereas ZnO/CoPi (deposited for 10 min) has ca. 50%-enhanced current ($0.54mW/cm^2$) under irradiation of AM 1.5G-light ($400mW/cm^2$). The excess loading of CoPi on ZnO results in decrease of photocurrents as compared to bare ZnO likely due to limited electrolyte access to ZnO and/or CoPi-mediated recombination of photogenerated charge carriers. The primary role of CoPi is speculated to trap the photogenerated holes and thereby oxidize water into molecular oxygen via an intervalency cycle among Co(II), Co(III), and Co(IV).

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.298-305
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• 2016

The development of non-precious metal based electrocatalysts is highly desired for the oxygen reduction reaction (ORR) as alternates to noble metal based ORR electrocatalysts. Herein, we report mononulcear copper(II) complex $[CuLbpy]ClO_4$ (L=4-[(2-hydroxyphenylimino)methyl]benzoic acid) containing poly(allylamine.HCl) polymer (PAlACuLbpy) as an electrocatalyst for oxygen reduction reaction (ORR). PAlACuLbpy was mixed with poly(acrylic acid) and tetraethylortho silicate to prepare a composite and then deposited on the screen printed electrode surface. The modified electrode (PAlACuLbpy/PCE) is highly stable and showed a quasi-reversible redox behavior with $E_{1/2}=-0.2V$ vs. Ag/AgCl(3 M KCl) in 0.1 M phosphate buffer at pH 7 under argon atmosphere. PAlACuLbpy/PCE exhibited a remarkable ORR activity with an onset potential of -0.1 V vs Ag/AgCl in 0.1 M PB (pH 7) in the presence of oxygen. The kinetics for ORR was studied by rotating disk voltammetry in neutral aqueous medium and the results indicated that the number of electrons involving in the ORR is four and the conversion products are water and hydrogen peroxide.

• Korean Journal of Agricultural Science
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• v.39 no.4
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• pp.467-471
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• 2012

In this study, we investigated the antioxidative and antiaging activity of Perilla frutescens using LLC-$PK_1$ porcine renal epithelial cell and WI-38 human diploid fibroblast cell. The extract from Perilla frutescens showed strong protective effect against nitric oxide (NO) and superoxide ($O_2{^-}$)-induced oxidative stress generated by sodium nitroprusside (SNP) and pyrogallol, respectively. The result showed that P. frutescens increased the cell viability and showed scavenging activity of NO and $O_2{^-}$. In addition, the extract of P. frutescens exerted the protective effect against peroxynitrite ($ONOO^-$) induced by 3-morpholinosydnonimine. It suggests that P. frutescens would have the protective role against $ONOO^-$ itself and its precursors, NO and $O_2{^-}$. Furthermore, the aging model of hydrogen peroxide ($H_2O_2$)-treated WI-38 human diploid fibroblast was employed to investigate the anti-aging effect of P. frutescens. $H_2O_2$-treated WI-38 cells showed the loss of cell viability, however before-treatment with P. frutescens to WI-38 cells under premature senescence could delay the cellular aging process. The present study suggests the antioxidative and antiaging potential against free radical-induced oxidative damage of P. frutescens.

• YAKHAK HOEJI
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• v.53 no.4
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• pp.222-227
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• 2009

Human topoisomerase I (Topo I) plays a pivotal role in cell replication, transcription and repair and, therefore, is an important anti-cancer target. 20S-camptothecin (CPT) is a representative Topo I inhibitor. Compounds belonging to CPT family inhibit the religation step of Topo I-DNA by binding to the DNA cleavage site. Computational docking studies with Surflex-Dock were carried out to investigate the binding modes between Topo I-DNA binary complex structure and the ligand such as 20S-CPT and 9,10-substituted 20S-CPT analogues. The docking results demonstrated that most of the compounds with $IC_{50}$ value under $0.5{\mu}M$ intercalated exactly between the -1 and +1 DNA bases, deeply toward the cleavage site. The complex was stabilized by hydrogen-bonding and hydrophobic interactions with both the enzyme and the DNA. The compounds with $IC_{50}$ value above $0.5{\mu}M$ were poorly docked and did not intercalate. In addition, the docking results confirmed the overall correlation between the $IC_{50}$ values and docking scores, indicating the possible use of the modeling for the prediction of biological activity and design of potential inhibitors.

• The Journal of Natural Sciences
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• v.7
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• pp.47-51
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• 1995

In order to develope new asymmetric catalyst, we synthesized the following new sulfonamide derivatives start from S-Indoline-2-Carboxylic Acid via the following 5 steps. Hydroxy methyl derivative(1) was thus treated with methane sulfonyl chloride in the presence of triethylamine as base to give mesylated derivative(2) in 85% of isolated yield. The mesylate compound (2) was treated with excess sodium azide to give Azido derivative (4) in 95% isolated yield. Azido compound (3) was then reduced to the corresponding amino derivative in near quntitative yield by the hydrogenation under hydrogen atmospere in the presence of catalytic amount of Pd-C. The amino derivative (4) was converted to its sulfonamide derivatives by the treatment of compound(4) with triisopropyl benzene sulfonyl chloride in the presence of triethyl amine as base. Finally t-BOC group of the compound(5) was removed by the treatement of excess Trifluoro-acetic acid in near quantitative yield to give the target sulfonamide derivative (7) .in this paper we prepared compound(6) in 49% overall yield via the 5 steps of synthesis starting from t-Boc- 2-hydroxy methyl indoline(1) which cab be easily prepared from commercial available S-indoline-2-carboxylic acid by known methods. we plan to apply this new catalyst for the asymmetric reduction , diels-alder reaction, aldolcondensation reaction in due courses.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.671-686
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• 2004

The shock-induced combustion ramjet (shcramjet) is a hypersonic airbreathing propulsion concept which over-comes the drawbacks of the long, massive combustors present in the scramjet by using a standing oblique detonation wave (a coupled shock-combustion front) as a means of nearly instantaneous heat addition. A novel shcramjet combustor design that makes use of wedge-shaped flameholders to avoid detonation wave-wall interactions is proposed and analyzed with computational fluid dynamics (CFD) simulations in this study. The laminar, two-dimensional Navier-Stokes equations coupled with a non-equilibrium hydrogen-air combustion model based on chemical kinetics are used to represent the physical system. The equations are solved with the WARP (window-allocatable resolver for propulsion) CFD code (see: Parent, B. and Sislian, J. P., “The Use of Domain Decomposition in Accelerating the Convergence of Quasihyperbolic Systems”, J. of Comp. Physics, Vol. 179, No. 1,2002, pages 140-169). The solver was validated with experimental results found in the literature. A series of steady-state numerical simulations was conducted using WARP and it was deter-mined by means of thrust potential calculations that this combustor design is a viable one for shcramjet propulsion: assuming a shcramjet flight Mach number of twelve at an altitude of 36,000 m, the geometrical dimensions used for the combustor give rise to an operational range for combustor inlet Mach numbers between six and eight. Different shcramjet flight Mach numbers would require different combustor dimensions and hence a variable geometry system in or-der to be viable.

• Journal of Pharmacopuncture
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• v.14 no.3
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• pp.55-61
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• 2011

Objectives: Reactive Oxygen Species(ROS) are continuously produced at a high rate as a by-product of aerobic metabolism. Since tissue damage by free radical, ROS such as hydrogen peroxide($H_2O_2$), nitric oxide(NO) increases with age. Several lines of evidence provided that ROS appears to cause to develop aging-related various diseases such as cancer, arthritis, cardiovascular disease. In this study, we have conducted to investigate the pharmacological effects of red ginseng for the development possibility to pharmacopuncture drug sources or healthy aid foods. Methods: For our aims, it was investigated the biological activities of Red Ginseng ethanol extracts (RGEE) by measuring total polyphenol contents, total flavonoid contents, DPPH radical scavenging activity, ABTS radical scavenging activity and cell viability of MCF 10A and SK-MEL-2 in vitro with MTT assay method. Results: The total polyphenol contents of RGEE was 3.06${\pm}$0.11mg/g in 10mg/ml, the total flavonoid contents of RGEE was 1.35${\pm}$0.01mg/g in same concentration. The ABTS radical scavenging activity was about 80% and that of DPPH activity was 65% in 50mg/ml of RGEE. The cell viability of SKMEL-2, skin cancer cell line was decreased and that of MCF 10A, skin normal cell line was increased. Conclusions: We conclude that RGEE may be useful as potential functional foods or pharmacopuncture drug sources on the diseases induced by oxidant stress.

• The Korean Journal of Physiology and Pharmacology
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• v.24 no.5
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• pp.373-384
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• 2020

Paeonol, quercetin, β-sitosterol, and gallic acid extracted from Moutan Cortex had been reported to possess anti-oxidative, anti-inflammatory, and anti-tumor activities. This work aimed to illustrate the potential anti-oxidative mechanism of monomers in human liver hepatocellular carcinoma (HepG2) cells-induced by hydrogen peroxide (H₂O₂) and to evaluate whether the hepatoprotective effect of monomers was independence or synergy in mice stimulated by carbon tetrachloride (CCl₄). Monomers protected against oxidative stress in HepG2 cells in a dose-response manner by inhibiting the generation of reactive oxygen species, increasing total antioxidant capacity, catalase and superoxide dismutase (SOD) activities, and activating the antioxidative pathway of nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1 (Nrf2/Keap1) signaling pathway. We found that the in vitro antioxidant capacities of paeonol and quercetin were better than those of β-sitosterol and gallic acid. Furthermore, paeonol apparently diminished the levels of alanine transaminase and aspartate aminotransferase, augmented the contents of glutathione and SOD, promoted the expressions of Nrf2 and heme oxygenase-1 proteins in mice stimulated by CCl₄. In HepG2 cells, paeonol, quercetin, β-sitosterol, and gallic acid play a defensive role against H₂O₂-induced oxidative stress through activating Nrf2/Keap1 pathway, indicating that these monomers have anti-oxidative properties. Totally, paeonol and quercetin exerted anti-oxidative and hepatoprotective effects, which is independent rather than synergy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6411-6418
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• 2015

To respond the climate change and environmental pollution, the studies on renewable energy policies are increasing. The renewable energy is a new growth engine technology represented by the green industry and green technology. At present, the investments for the renewable energy supply and technology development projects of three main strategy sectors such as sunlight, wind power and hydrogen fuel cell are implemented in our country, while they are still in the early stage, accordingly reducing those uncertainty for the research direction and investment fields is the most urgent issue among others. Thus, this study applied text mining method and multinominal topic model among the big data analysis methods on our country's newspaper articles concerning the renewable energy over the last 10 years, and then analyzed the core issues and global research trend, forecasting the renewable energy fields with the growth potential. It is predicted that these results of the study based on information and communication technology will be actively applied on the renewable energy fields.

• Korean Journal of Medicinal Crop Science
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• v.25 no.5
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• pp.315-321
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• 2017

Background: Glycyrrhiza uralensis Radix (GR) is a crude drugs used in Asian countries that has been reported to prevent the progression of neurodegenerative diseases such as Alzheimer's disease. The present study examined whether GR and its active compounds, glycyrrhizic acid (GA) and isoliquiritigenin (IL), exerted protective effects on $H_2O_2$-induced oxidative damage in C6 glial cells. Methods and Results: We exposed C6 glial cells to hydrogen peroxide ($H_2O_2$) for 24 h and investigated the cellular response to GR and its active compounds by evaluating cell viability, reactivie oxygen species (ROS) production, and apoptosis-related protein expression. GR successfully mitigated the reduced cell viability and ROS production induced by $H_2O_2$ in C6 glial cells, IL and GA significantly increased the cell viability and decreased ROS production. In addition, IL and GA down-regulated apoptotic Baxdependent caspase-3 activation, but each compound exerted different mechanisms, i.e., IL dose-dependently decreased ROS production and, GA up-regulated anti-apoptotic Bcl-2 expression. Conclusions: These results demonstrated that GR and its active components, IL and GA, exhibit potential for use as natural neurodegenerative agents for the modulation of apoptosis in C6 glial cells.