• Economic and Environmental Geology
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• v.50 no.3
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• pp.215-224
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• 2017

Arsenic (As) is known to be the most toxic element and frequently detected in groundwater environment. Inorganic As exists as arsenite [As(III)] and arsenate [As(V)] in reduced and oxidized environments, respectively. It has been reported that the toxicity of arsenite is much higher than that of arsenate and furthermore arsenite shows relatively higher mobility in aqueous environments. For this reason, there have been numerous researches on the process for oxidation of arsenite to arsenate to reduce the toxicity of arsenic. In particular, photooxidation has been considered to be simple, economical, and efficient to attain such goal. This study was conducted to evaluate the applicability of naturally-occurring goethite as a photocatalyst to substitute for $TiO_2$ which has been mostly used in the photooxidation processes so far. In addition, the effects of several factors on the overall performance of arsenite photocatalytic oxidation process were evaluated. The results show that the efficiency of the process was affected by total concentration of dissolved cations rather than by the kind of those cations and also the relatively higher pH conditions seemed to be more favorable to the process. In the case of coexistence of arsenite and arsenate, the removal tendency by adsorption onto goethite appeared to be different between arsenite and arsenate due to their different affinities with goethite, but any effect on the photocatalytic oxidation of arsenite was not observed. In terms of effect of humic acid on the process, it is likely that the higher concentration of humic acid reduced the overall performance of the arsenite photocatalytic oxidation as a result of competing interaction of activated oxygen species, such as hydroxyl and superoxide radicals, with arsenite and humic acid. In addition, it is revealed that the injection of oxygen gas improved the process because oxygen contributes to arsenite oxidation as an electron acceptor. Based on the results of the study, consequently, the photocatalytic oxidation of aqueous arsenite using goethite seems to be greatly feasible with the optimization of process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3437-3443
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• 2013

The polymer insulators have been extensively used as an alternate material of ceramic insulators. However, when they are used in practical conditions, there are many problems of decreasing performance and shortening lifetime due to the exposures of degradation factors applied from the outdoor situations. Accordingly, the analysis of polymer degradations has been getting influential too late as one of important subjects for improvements of safety and reliability. Heat, water treatments are arbitrary simulated for finding out the initiations and processes of surface degradation on the polymer surface. Especially, this study is focused on the chemical changes properties. From the analysis of hydrophilic and hydrophobic molecular structures, final modeling of surface degradation is accomplished. We checked the contact angle depending on heat and moisturized accelerated degradation and ran an XPS analysis to check the mechanism change of the surface of the PCB polymer composite. The surface that had a tendency to attract moisture showed a decrease in the contact angle and generated a large amount of carboxyl($-COO^*$) radicals. The hydrophobized surface showed an increase in the contact angle and had a stable chemical composition constituted of the breakaway of oxygen radicals and the formation of double bond by carburization.

• Journal of Life Science
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• v.30 no.9
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• pp.763-771
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• 2020

Korean ginseng (Panax ginseng) generally has a good safety profile and contains many bioactive substances, such as ginsenosides or panaxosides. Korean red ginseng might help to stabilize the sympathetic nervous system and improve cognition in individuals. Soft red ginseng is produced by new processing technology. This study focused on investigating whether soft red ginseng produced under the new processing technology reduces or improves the existing antioxidant effects. No significant difference in 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) scavenging activity was found between soft red ginseng and ready-made red ginseng (p<0.05). Soft red ginseng extract showed higher 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and hydroxyl radical (OH) scavenging activity than other ginseng extracts. OH scavenging activity was significantly different across three groups (raw ginseng, soft red ginseng, and red ginseng sap) (p<0.05). Nitric oxide (NO) scavenging activity was also significantly different among raw ginseng, soft red ginseng, and purchased red ginseng liquid products (p<0.05). Many calcium crystals appeared on the electron microscope in soft red ginseng. Magnesium and potassium showed no significant difference between soft red ginseng and hard red ginseng. The extract of soft red ginseng scavenged different free radicals efficiently due to the presence of DPPH and OH and may help treat free radical-induced diseases.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.3
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• pp.233-241
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• 2012

Photodynamic therapy (PDT) is a technique that involves the activation of photosensitizer by light in the presence of tissue oxygen, resulting in the production of reactive radicals capable of inducing cell death. The aim of this study was to evaluate the effect of PDT on Streptococcus mutans in planktonic conditions, previously treated with different photosensitive concentrations of erythrosine, using halogen and LED curing unit as a light source. And we compared the effects of PDT on six strains of S. mutans isolated from oral cavity and reference strain. As a result, S. mutans was susceptible to the combination of hand held photopolymerizer (HHP) and erythrosine. The higher concentration of erythrosine in the presence of light irradiation induced greater effects in reduction of viability of S. mutans. Isolated S. mutans showed a significant reduction in bacterial counts of the groups submitted to PDT compared to the control groups. And they appeared to be similar or slightly lower antimicrobial effect compared with reference strain. However, the difference was not significant (p < 0.05). In conclusion, PDT using erythrosine as a photosensitizing agent and HHP as a light source could be an efficient option for diseases caused by S. mutans.

• Journal of the Korean Applied Science and Technology
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• v.34 no.3
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• pp.536-544
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• 2017

This study was carried out to find out the physiological activity effect of Sicyos angulatus L. extract which is known as an ecosystem disturbance plant and confirm the availability as a functional cosmetic material. Total polyphenol and flavonoid contents were measured, and DPPH radical scavenging, intracellular ROS, and its inhibitory effect on the expression Nitric oxide of and COX-2 were evaluated. The content of polyphenol and flavonoid was found to be 3.079 mg(CA)/100g and 72 mg(Q)/100g of Sicyos angulatus L. extract and antioxidant activity through high radical scavenging activity was confirmed. ~Significant cytotoxicity was not observed up to a concentration of $100{\mu}g/mL$ in RAW 264.7 cells and HDF cells and concentration-dependent inhibition of ROS production in HDF cells, inhibition of high NO production and inhibition of COX-2 protein expression in RAW 264.7 cells were confirmed. Through these results, we found the possibility of use as a functional cosmetic material with excellent antioxidant effect and antioxidant and anti-inflammatory effects through inhibition of intracellular ROS generation, inhibition of NO generation, and inhibition of COX-2 protein expression.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.633-642
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• 2018

The purpose of this study was to assess the antioxidant, anti-inflammatory and preservative effects of Water Chestnut from 70% ethanol extracts. The toxicity of extracts from Water Chestnut investigated using the RAW 264.7 cell showed higher than 90% of cell survival rate. The total content of polyphenol ethanol extract was $353.1{\pm}5.6mg/g$, while the total content of flavonoid was $26.2{\pm}1.4mg/g$. With a concentration level of $1{\sim}1000 ({\mu}g/m{\ell})$ ethanol extract of Water Chestnut the range of removal of 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radicals was $17.0{\pm}2.8%{\sim}88.6{\pm}0.6%$ respectively and the range of removal of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals was also $2.3{\pm}0.8%{\sim}93.9{\pm}0.2%$ respectively. There were decreases in reactive oxygen species(ROS) generations ethanol extracts of Water Chestnut 1, 10, $100({\mu}g/m{\ell})$ and significance decrease at $100{\mu}g/m{\ell}$ (p<.01). As a result of measuring the Nitric Oxide(NO) generation amount of Water Chestnut extract 1, 10, $100({\mu}g/m{\ell})$ concentration exhibited significant (p<.001, p<.01) decreases. For the anti-bacterial features using a paper disk and the preservative features using petri film, no significance was found and therefore water chestnut extracts had not anti-bacterial or preservative features.

• Asian Journal of Turfgrass Science
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• v.25 no.1
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• pp.17-21
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• 2011

Korean bennudagrass collections showed diverse genetic variations in their morphology, growth habit, and cytological aspects. Chromosome number and nuclear DNA content of the bennudagrasses indicated a ploidy level ranging from triploid (2n=3x) to hexaploid (2n=6x). In this study, we investigated the different responses of antioxidant enzymes (superoxide dismutase, catalase, peroxidase, ascorbate peroxidase) and cell membrane stability of those bennudagrass cytotypes to lower temperature and shorter day length, which meets a dormant induction in Korea. All the antioxidant enzymes were found to be higher during dormant stage, while the heme-containing catalase which converts hydrogen peroxide ($H_2O_2$) to water and oxygen molecules was activated before dormant initiation in the three cytotypes except for hexaploid bennudagrass. The triploid and tetraploid which exhibited relatively finer leaves and a rapid establishment speed were found to show increased activities of superoxide dismutase and peroxidase enzyme. The malondialdehyde(MDA) which is a product of lipid peroxidation in the cell membrane damaged by the hydroxyl radical was increased in all cytotypes as temperature declined, and tri- and tetraploids which had more protective antioxidant enzymes demonstrated a significantly lower MDA production. Similarly electrolyte leakage was higher in penta- and hexaploidy, seemingly more damage to cell membrane when low temperature was implemented. Results indicated that antioxidant responses of different cytotypes were genetically specific, which needs to be investigated the relevance with the low temperature tolerance in the bermudagrass further at the molecular level.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.33 no.1 s.60
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• pp.53-60
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• 2007

(6R)-5,6,7,8-tetrahydrobiopterin ($6-BH_4$) cofactor is essential for various process, and is present in probably every cell or tissue of higher organism. $6-BH_4$ is required lot various enzyme activities, and for less defined functions at the cellular level. And it is well known about the antioxidant effects as a non-protein compound. Recently, scientists proposed another roles for $6-BH_4$ in melanogenesis. $6-BH_4$ is a well known tyrosinase inhibitor. In this study, we found that methyl-$BH_4$ and $6-BH_4$ have antioxidant activities and inhibitory activity for melanin synthesis. These pterin compounds were not toxic in HaCaT and B16F10 cells and showed scavenging activity against DPPH radicals. We also showed that pterin compounds decreased protein levels of tyrosinase and TRP-1. In a clinical test, pterin compounds showed the significant skin whiteining effect after treatment for 3 weeks. Furthermore pterin compounds significantly suppressed the UVB-induced expression of $PGE_2$ and IL-6 genes induced UVB In HaCaT and inhibited UVB-induced melanogenesis in B16F10 cells. These results showed the effect of pterin compounds as a cosmeceutical ingredient.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.395-402
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• 1997

The $SiO_2$ films were prepared by ECR(electron cyclotron resonance) plasma diffusion method, Deal-Grove model and Wolters-Zegers-van Duynhoven model were used to estimate the oxidation rate which was correlated with surface morphology for different orientation of Si(100) and Si(111). It was seen the $SiO_2$ thickness increased linearly with initial oxidation time. But oxidation rate slightly decrease with oxidation time. It was also shown that the oxidation process was controlled by the diffusion of the reactive species through the oxide layer rather than by the reaction rate at the oxide interface. The similar time dependency has been observed for thermal and plasma oxidation of silicon. From D-G model and W-Z model, the oxidation rate of Si(111) was 1.13 times greater than Si(100) because Si(111) had higher diffusion and reaction rate, these models more closely fits the experimental data. The $SiO_2$ surface roughness was found to be uniform at experimental conditions without etching although oxidation rate was increased, and to be nonuniform due to etching at experimental condition with higher microwave power and closer substrate distance.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.433-437
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• 2013

Electrical discharge plasma created in a multi-channel porous ceramic membrane-supported catalyst was applied to the decomposition of a volatile organic compound (VOC). For the purpose of improving the oxidation capability, the ceramic membrane used as a low-pressure drop catalyst support was loaded with zinc oxide photocatalyst by the incipient wetness impregnation method. Alternating current-driven discharge plasma was created inside the porous ceramic membrane to produce reactive species such as radicals, ozone, ions and excited molecules available for the decomposition of VOC. As the voltage supplied to the reactor increased, the plasma discharge gradually propagated in the radial direction, creating an uniform plasma in the entire ceramic membrane above a certain voltage. Ethylene was used as a model VOC. The ethylene decomposition efficiency was examined with experimental variables such as the specific energy density, inlet ethylene concentration and zinc oxide loading. When compared at the identical energy density, the decomposition efficiency obtained with the zinc oxide-loaded ceramic membrane was substantially higher than that of the bare membrane case. Both nitrogen and oxygen played an important role in initiating the decomposition of ethylene. The rate of the decomposition is governed by the quantity of reactive species generated by the plasma, and a strong dependence of the decomposition efficiency on the initial concentration was observed.