• Carbon letters
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• v.6 no.2
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• pp.71-78
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• 2005

Anti-oxidation coatings are the key technique for carbon/carbon (C/C) composites used as the thermal structural materials. The microstructure and oxidation behavior of several kinds of high-performance ceramic coatings for C/C composites prepared in Northwestern Polytechnical University were introduced in this paper. It showed that the ceramic coatings such as SiC, Si-$MoSi_2$, SiC-$MoSi_2$, $Al_2O_3$-mullite-SiC and SiC/yttrium silicate/glass coatings possessed excellent oxidation resistance at high temperatures, and some of these coatings were characterized with excellent thermal shock resistance. The SiC-$MoSi_2$ coating system has the best oxidation protective property, which can effectively protect C/C composites from oxidation up to 1973 K. In addition, the protection and failure reasons of some coatings at high temperature were also provided.

• Korean Journal of Materials Research
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• v.23 no.2
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• pp.123-127
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• 2013

The electrolytic reduction of a spent oxide fuel involves liberation of the oxygen in a molten LiCl electrolyte, which is a chemically aggressive environment that is too crosive for typical structural materials. Therefore, it is essential to choose the optimum material for the process equipment for handling a molten salt. In this study, the corrosion behavior of pyro-carbon made by CVD was investigated in a molten LiCl-$Li_2O$ salt under an oxidation atmosphere at $650^{\circ}C$ and $750^{\circ}C$ for 72 hours. Pyro-carbon showed no chemical reactions with the molten salt because of its low wettability between pyro-carbon and the molten salt. As a result of XRD analysis, pyro-carbon exposed to the molten salt showed pure graphite after corrosion tests. As a result of TGA, whereas the coated layer by CVD showed high anti-oxidation, the non-coated layer showed relatively low anti-oxidation. The stable phases in the reactions were $C_{(S)}$, $Li_2CO_{3(S)}$, $LiCl_{(l)}$, $Li_2O$ at $650^{\circ}C$ and $C_{(S)}$, $LiCl_{(l)}$, $Li_2O_{(S)}$ at $750^{\circ}C$. $Li_2CO_{(S)}$ was decomposed at $750^{\circ}C$ into $Li_2O_{(S)}$ and $CO_{2(g)}$.

• Corrosion Science and Technology
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• v.21 no.5
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• pp.412-417
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• 2022

Proton exchange membrane fuel cells (PEMFCs) provide zero emission power sources for electric vehicles and portable electronic devices. Although significant progresses for the widespread application of electrochemical energy technology have been achieved, some drawbacks such as catalytic activity, durability, and high cost of catalysts still remain. Pt-based catalysts are regarded as the most efficient catalysts for sluggish kinetics of oxygen reduction reaction (ORR). However, their prohibitive cost limits the commercialization of PEMFCs. Therefore, we proposed a NiCo@Au core shell structure as Pt-free ORR electrocatalyst in PEMFCs. NiCo alloy was synthesized as core to introduce ionization tendency and autoxidation reaction. Au as a shell was synthesized to prevent oxidation of core NiCo and increase catalytic activity for ORR. Herein, we report the synthesis, characterization, electrochemical properties, and PEMFCs performance of the novel NiCo@Au core-shell as a catalyst for ORR in PEMFCs application. Based on results of this study, possible mechanism for catalytic of autoxidation core@anti-oxidation shell in PEMFCs is suggested.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.33 no.1 s.60
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• pp.41-45
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• 2007

Recently plant extracts have obtained increased attention because of their health-related beneficial aspects. In this study, we evaluated anti-oxidation, whitening and anti-wrinkle of four different extracts obtained from Rubus coreanus (ethanol extracts of unripe, ripe fruits, leaves/stems, and roots). The ethanol extract of unripe fruits of Rubus coreanus generally showed stronger whitening and the anti-wrinkle activities than other extracts of Rubus coreanus. As a results, we knew that the ethanol extract of unripe Rubus coreanus fruit had mote possibility as a whitening and anti-wrinkle ingredient for skin care products.

• Journal of the Korean Society of Food Culture
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• v.34 no.5
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• pp.645-650
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• 2019

Skin plays important roles in protecting the internal organs from the chemical-biological risk factors and ultraviolet light. Exposure to the chemical and biological stimuli has a detrimental effect on skin's structure and physiological regulation. Therefore, much attention has been paid to natural products that show biological activities such as anti-oxidation, anti-aging and anti-bacterial activities. In this study, we investigated the skin-related biological activities of Oenothera lamarckiana aerial part extract. The extract contained 229.35 mg TAE (tannic acid equivalents)/g total polyphenolic compounds and the extract showed relative high antioxidant activity ($SC_{50}$ value: $8.52{\mu}g/mL$). The $IC_{50}$ value against tyrosinase and elastase were 307.94 and $181.51{\mu}g/mL$, respectively. This suggested that O. lamarckiana can be applied to whiten skin and slow the aging of skin. O. lamarckiana extract showed a growth inhibitory effect on Staphylococcu epidermidis (minimum inhibitory concentration: $250{\mu}g/mL$). Interestingly, O. lamarckiana extract showed no inhibitory effect on Pseudomonas aeruginosa on the paper disc assay. Yet the extract inhibited the growth of Pseudomonas aeruginosa on the broth dilution assay in a dose-dependent manners. Taken together, O. lamarckiana could have good potential for development as an additive in the cosmetic industry.

• YAKHAK HOEJI
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• v.50 no.1
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• pp.47-51
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• 2006

The roots of Dipsacus asper are used in traditional Chinese medicine as an analgesic, enhancement of liver activity, an anti-inflammatory agent and the treatment of fractures. In order to investigate the antioxidative activity, Dipsaci Radix was extracted with MeOH and fractionated with $CHCl_3$, EtOAc, BuOH and water. MeOH ex. and its solvent fractions were determined on the free radical scavenging activity by DPPH method and antioxidative activity on low density lipoprotein oxidation. The EtOAc and BuOH fractions showed antioxidative activities and from their fractions, two compounds were isolated and identified as hederagenin 3-O-${alpha}$-L-arabino pyranoside (compound 1) and O-${\alpha}$-L-arabinopyranosyl hed-eragenin 28-O-${\beta}$-D-glucopyranosyl ($1{\to}6$)-${\beta}$-D-glucopyranosyl ester (compound 2). Saponin glycoside, compound I showed anti-oxidative activity.

• Journal of Physiology & Pathology in Korean Medicine
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• v.25 no.3
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• pp.528-532
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• 2011

This study was designed to investigate the collagen metabolism and tyrosinase activity of Meretrix extracts (ME). The effect of ME on type I procollagen production and collagenase activity in human normal fibroblasts HS68 after UVB (312 nm) irradiation was measured by ELISA method. The tyrosinase activity after treatment of ME was measured as well. Type I procollagen production was recovered by ME in UVB damaged HS68 cells. The increased collagenase activity after UVB damage was significantly recovered by ME. The tyrosinase activity and L-DOPA oxidation were significantly reduced as well. However, the effects on tyrosinase activity and L-DOPA oxidation were not powerful enough to be used as whitening agents. ME showed the anti-wrinkle effects and some whitening effects in vitro. These results suggest that ME may be a useful drug as an anti-wrinkle treatments.

• Journal of the Korean Chemical Society
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• v.19 no.1
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• pp.50-52
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• 1975

The oxidation stability of samples prepared by blending samples reported previously with diesel oil and diesel oil with additives(alkyl benzene and phenolic type of materials), was tested to study the mechanism of thermal oxidation stability of the regenerated lubricating oils. It was found that the improvement of thermal oxidation stability of such oils was caused by the formation of aromatic compounds, especially phenolic type of organic materials.

• KSBB Journal
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• v.31 no.1
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• pp.14-19
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• 2016

To investigate the effect of peanut sprout extract on skin care, we measured anti-oxidant activity and whitening action. As a result of measuring DPPH radical scavenging activity to examine independent anti-oxidation of peanut sprout extract, there was strongly scavenging activity. Fluorescent material DCF-DA was used to measure hydrogen peroxide created in RAW 264.7 cells, and all concentration dependently decreased ROS production. As a result of measuring nitric oxide to examine anti-inflammation of peanut sprout extract, there was strongly inhibited nitric oxide production in RAW 264.7 cells. Tyrosinase activation was found to inhibited dose-dependant. Melanin production was also prevented dose-dependant. Therefore, it is expected to be used effectively in development of functional cosmetic materials.

• Journal of the Korean Chemical Society
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• v.67 no.2
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• pp.145-149
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• 2023

Talipariti hamabo is a plant growing around salt marshes in the Lava Coast region of Jeju Island, Korea. In this study, the extract of T. hamabo leaves was investigated for the anti-inflammatory, anti-oxidative and anti-bacterial activities and their active constituents were identified. In the anti-inflammatory tests using lipopolysaccharide-stimulated RAW264.7 cells, the ethyl acetate (EtOAc) fraction inhibited the nitric oxide production without causing cell toxicity. Moreover, the EtOAc fraction reduced pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-6) as well as prostaglandin E₂. In the anti-oxidative studies with DPPH and ABTS⁺ radicals, potent scavenging activities were observed in the EtOAc and n-butanol fractions. Upon the anti-bacterial tests using Staphylococcus epidermidis, EtOAc and n-butanol fractions exhibited good activities. Through the phytochemical studies on EtOAc fraction, three components were isolated by repeated column chromatography; oleic acid (1), p-hydroxyphenethyl-trans-ferulate (2), nicotiflorine (3). Based on these results, the extract of T. hamabo leaves can be developed as natural resources for cosmetic applications.