• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.2
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• pp.96-101
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• 2021

Developing effective and earth-abundant electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is critical for the commercialization of a water splitting system. In particular, the overpotential of the OER is relatively higher than the HER, and thus, it is considered that one of the important methods to enhance the performance of the electrocatalyst is to reduce the overpotential of the OER. We report effects of incorporation of metalloid into Ni(OH)2 microcrystal on electrocatalytic activities. In this study, Te incorporated Ni(OH)2 (��Te-Ni(OH)2) were grown on three-dimensional porous NF by a facile solvothermal method with �� = 1, 3 and 5. Homogeneous microplate structure on the NF was clearly observed for the Ni(OH)2/NF and ��Te-Ni(OH)2/NF samples. However, irregular and collapsed nanostructures were found on the surface of nickel foam when Te precursor ratio is (��) over 3. Electrocatalytic OER properties were analysed by Linear sweep voltammetry (LSV) and Electrochemical impedance spectroscopy (EIS). The amount of Te incorporation used in the electrocatalytic reaction was found to play a crucial role in improving catalytic activity. The optimum Te amount (��) introduced into the Ni(OH)2/NF was discussed with respect to their OER performance.

• Journal of the Korean Chemical Society
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• v.64 no.6
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• pp.350-353
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• 2020

The validity of the calculation method based on the local mode in hydrogen-bonded water molecules was investigated by comparing the frequencies of the local and normal modes of OH stretching vibration in water molecules. By calculating a monomer, dimer, and trimer of water molecules using a quantum chemical ab initio theory, we examined how the frequencies of the local and normal modes and the anharmonicity of local modes vary with molecular cluster size. It was shown that, as the number of molecules increases from monomer to trimer, the anharmonicity of OH bonds increases and the difference between local and normal mode frequencies decreases. This confirms that local-mode-based calculations that can easily handle the anharmonicity can be appropriate for the calculation of the OH stretching frequency of water molecules in the condensed phase.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.668-673
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• 2020

In this work, ultrathin and two-dimensional (2D) cobalt hydroxide [Co(OH)2] nanosheets were synthesized by a sonication assisted liquid-phase exfoliation of bulk Co(OH)2. The resulting exfoliated Co(OH)2 is a hexagonal mono-layered nanosheet with a high specific surface area of 27.5 ㎡ g-1. The depolymerization of polyethylene terephthalate (PET) based on glycolysis reaction was also performed using an exfoliated Co(OH)2 catalyst. Excellent catalytic reaction performances were demonstrated; a high PET conversion and bis(2-hydroxyethyl) terephthalate (BHET) yield of both 100% using the nanosheet catalyst were achieved within a reaction time and temperature of 30 min and 200 ℃, respectively. The long-term stability of exfoliated Co(OH)2 catalysts was also demonstrated by recyclability tests of the catalyzed glycolysis reaction of PET over four cycles, showing both 100% of high PET conversion and BHET yield.

• Nutrition Research and Practice
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• v.16 no.6
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• pp.745-754
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• 2022

BACKGROUND/OBJECTIVES: The incidence of cardiovascular diseases (CVDs) has increased worldwide. Although a low serum vitamin D level is known to be associated with the risk of CVD, the mechanism is not well understood yet. The aim of this study was to determine the relationship of serum 25-hydroxyvitamin D₃ (25[OH]D) with homocysteine and apolipoprotein B (ApoB). SUBJECTS/METHODS: Of 777 subjects recruited from one health promotion center for routine heath exam from January 2010 to December 2016, 518 subjects were included in this study. Serum 25(OH)D, serum homocysteine, and other metabolic parameters including ApoB were analyzed. Simple and partial correlations were carried out after adjustments. Simple linear regression analysis was used for precise correlation of parameters. Multivariate regression analysis was done to know which factor (serum homocysteine or ApoB) was more related to serum 25(OH)D after adjustments. Finally, logarithms of homocysteine concentrations according to tertiles of serum 25(OH)D were compared. RESULTS: After sex and age adjustments, serum 25(OH)D showed negative correlations with serum homocysteine (r' = -0.114) and ApoB (r' = -0.098). In simple linear regression analysis, serum 25(OH)D showed a significant negative correlation with ApoB (P = 0.035). However, in multivariate regression analysis, serum 25(OH)D was significantly associated with serum homocysteine after adjustments (P = 0.022). In addition, serum homocysteine concentration was significantly high in the lowest 25(OH)D group (P = 0.046). CONCLUSION: Serum 25(OH)D concentration showed a stronger negative association with serum homocysteine than with ApoB.

• The Korea Journal of Herbology
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• v.32 no.4
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• pp.39-46
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• 2017

Objectives : This study aims to provide basic data about Portulacae Herba (PH) extracts as natural antioxidants by considering diverse antioxidant activities of PH depending on solvents. Methods : The samples of PH were pulverized, and A hot water and a 70% EtOH were stir-extracted for two hours three times repeatedly in a water bath with a temperature of 95 degrees and at room temperature respectively to measure 7 kinds of antioxidant activities. Results : There were significant differences in total phenol content, because the total phenol content of the 70% EtOH extract was higher than the hot water extract's, and the total flavonoid content of the 70% EtOH extract($4.40{\mu}g/mg$) was nearly 3.8 times higher than the hot water extract's($1.16{\mu}g/mg$). DPPH and ABTS radical scavenging activities were 70% EtOH extract showed a little higher activity than the hot water extract, and at a concentration of $500{\mu}g/mg$, the highest scavenging activity was found in the 70% EtOH extract, not in the control group. Hydroxyl radical and $Fe^{2+}$ chelatingactivities were slightly higher in hot water extract than in 70% EtOH extract, and increased in a dose-dependent manner. Nitrite scavenging activities increased dose-dependently in the hot water and the 70% EtOH extract, regardless of the pH level, and scavenging activity of the 70% EtOH extract was higher at pH 1.2 than at pH 3.0. Conclusions : In conclusion, it is thought that PH hot water and 70% EtOH extract have antioxidant activities, and can be used as natural antioxidants in future.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2021.04a
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• pp.49-49
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• 2021

The roots of reed (Phragmites australis) were used in traditional medicine to treat respiratory problems, including symptoms such as high fever and cough. In this study, we identified the active ingredient from 70% EtOH reed root extract, and evaluated the whitening, wrinkle improvement and moisturizing effects. The content of p-coumaric acid, the active ingredient of the roots of P. australis, was slightly lower in 70% EtOH extract than in 100% EtOH extract. However, 70% EtOH reed root extract showed similar or higher effect in reducing power, DPPH, hydrogen peroxide scavenging, and nitric oxide scavenging activity compared to 100% EtOH extract. Moreover, 70% EtOH reed root extract markedly inhibited melanogenesis in B16F10 cells treated with α-melanocyte-stimulating hormone. 70% EtOH reed root extract significantly inhibited the mRNA expression of matrix metalloproteinase-1 (MMP-1) and reduced elastase activity in HDF human dermal fibroblasts. In addition, 70% EtOH reed root extract ameliorated hyaluronic acid synthase-2 (HAS-2) expression induced by ultraviolet B (UVB) stimulation in HaCaT keratinocytes. The results of this study suggest that 70% EtOH reed root extract has potential as a functional cosmetic material related to whitening, wrinkle improvement, and moisturizing.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1527-1533
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• 2011

The reaction of gas-phase atomic hydrogen with oxygen atoms chemisorbed on a silicon surface is studied by use of the classical trajectory approach. We have calculated the probability of the OH formation and energy deposit of the reaction exothermicity in the newly formed OH in the gas-surface reaction H(g) + O(ad)/Si${\rightarrow}$ OH(g) + Si. All reactive events occur in a single impact collision on a subpicosecond scale, following the Eley-Rideal mechanism. These events occur in a localized region around the adatom site on the surface. The reaction probability is dependent upon the gas temperature and shows the maximum near 1000 K, but it is essentially independent of the surface temperature. The reaction probability is also independent upon the initial excitation of the O-Si vibration. The reaction energy available for the product state is carried away by the desorbing OH in its translational and vibrational motions. When the initial excitation of the O-Si vibration increases, translational and vibrational energies of OH rise accordingly, while the energy shared by rotational motion varies only slightly. Flow of energy between the reaction zone and the solid has been incorporated in trajectory calculations, but the amount of energy propagated into the solid is only a few percent of the available energy released in the OH formation.

• KSBB Journal
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• v.29 no.5
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• pp.343-352
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• 2014

In the present study, antioxidant activities of two crude pigments (acetone and MeOH) and their solvent fractions (n-hexane, 85% aq.MeOH, n-BuOH, and water fractions) from red crab shell were evaluated by measuring 1,1-diphenyl-2-picryl hydrazyl (DPPH), peroxynitrites, and degree of production of reactive oxygen species (ROS) in HT 1080 cells as well as the extent of oxidative damage of genomic DNA purified from HT 1080 cells. From comparative analysis, 85% aq.MeOH fraction showed the strongest scavenging effect on both peroxynitrite in vitro and intracellular ROS in HT 1080 cells. Protective activities of these samples against hydroxyl radical-mediated genomic DNA damage were also investigated. 85% aq.MeOH and n-BuOH fractions significantly inhibited oxidative damage of purified genomic DNA. On the other hand, we investigated their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated Raw 264.7 cells. All samples significantly reduced NO production. Among the samples, n-hexane and water solvent fractions most effectively inhibited NO.

• KSBB Journal
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• v.30 no.6
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• pp.275-282
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• 2015

Dried samples of Ligustrum japonicum were extracted twice: with methylene chloride and with methanol (MeOH), respectively. The combined crude extracts were successively fractionated into n-hexane, 85% aqueous methanol (85% aq.MeOH), n-butanol (n-BuOH), and water fractions by liquid-liquid partition. Antioxidant activities of crude extract and its solvent fractions were evaluated by measuring authentic $ONOO^-$, and $ONOO^-$ generated from 3-morpholinsydnonimine (SIN-1) as well as degree of occurrence of intracellular ROS in HT 1080 cells, and genomic DNA oxidation. The 85% aq.MeOH and n-BuOH fractions exhibited the good antioxidant activity. Further purification of the 85% aq.MeOH fracition led to the isolation of Oleanolic acid (1), Maslinic acid (2), and Ursolic acid (3). All compounds showed the significant antioxidant effects in all assay systems.

• The Korean Journal of Food And Nutrition
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• v.22 no.2
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• pp.246-251
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• 2009

This study examined the possible hypoglycemic effects Angelica gigas Naki extracts in streptozotocin-induced diabetic rats(STZ+50%, STZ+100% EtOH and STZ+water). The studies showed that administration of the Angelica gigas Naki extract decreased high blood glucose levels(more than 300 mg/$d{\ell}$) to a normal level(104 mg/$d{\ell}$) in the STZ+50% EtOH group. Liver glucokinase levels were significantly increased in STZ+50% EtOH and STZ+100% EtOH groups compared to the STZ group. Moreover, the liver acetyl CoA carboxylase level was significantly increased in STZ+50% EtOH, STZ+100% EtOH and STZ+water groups compared to the STZ group. These results suggest that the Angelica gigas Naki extract in the STZ+50% EtOH group exerted an ameliorable effect and can be used as an anti-diabetic substance, either as a dietary supplements or as a new drug.