• Korean Journal of Food Science and Technology
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• v.34 no.3
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• pp.361-364
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• 2002

This study was performed to establish a simple and accurate method for the determination of oxygen that is a processing aid in various beverage. The quantitative determination of dissolved oxygen (DO) contents in 30 cases of samples were performed by traditional titration method and polarography. As a result of the study, the analysis of DO contents in fruit-extract beverages containing oxygen by titration method was time consuming and large sample volumes were needed. Besides, serious interferences with compounds such as hydroxylamine and nitric oxide were observed, leading to false response. Although the polarography is easily affected by $H_2S$, proteins, and various organic compounds, it is a simple and practical method that provides inexpensive and relatively rapid analysis. The polarography is best suited to the routine determination of DO in a large number of samples and it is expected that the polarography can directly be applied to the quality control of the beverages containing added oxygen. The analysis results of DO contents in various fruit-extract beverages with oxygen and without oxygen were as follows: 23.10 ppm to 32.60 ppm for various frutis extract beverages with oxygen, 0.70 pp to 2.54 ppm for mixed beverages without oxygen, 7.63 ppm to 8.28 ppm for drinking water.

• Korean Journal of Materials Research
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• v.15 no.4
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• pp.240-245
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• 2005

An oxygen free copper was severely deformed by accumulative roll-bonding (ARB) process for improvement of its mechanical properties. Two copper sheets 1 m thick, 30 mm wide and 300 m long are first degreased and wire-brushed for sound bonding. The sheets are then stacked to each other, and roll-bonded by about $50\%$ reduction rolling without lubrication at ambient temperature. The bonded sheet is then cut to the two pieces of same dimensions and the same procedure was repeated to the sheets up to eight cycles $(\varepsilon-6.4)$. TEM observation revealed that ultrafine grains were developed after the third cycle, and their size was slightly increased at higher cycles. Tensile strength of the copper increased with the strain at low strain levels, but it hardly increased from 3 cycles $(\varepsilon>2.4)$ due to occurrence of dynamic recovery, even if the imposed strain increased.

• Journal of the Korean institute of surface engineering
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• v.37 no.2
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• pp.110-118
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• 2004

The corrosion of pure titanium (CP- Ti Grade 2) and titanium alloy (Ti6Al4V ELI) were studied under various conditions of simulated body fluids. The static immersion test and the electrochemical test were performed in accordance with ISO 10271 : 2001. For the electrochemical test, the open circuit potential was monitored as a function of time, and the cyclic polarization curve was recorded. The corrosion resistance was evaluated from the values of corrosion potential, passivation current density, breakdown potential, and the shape of hysteresis etc. The effects of alloy type, surface condition, temperature, oxygen, and constituents in the fluids such as acid, chloride were estimated. Both specimens had extremely low dissolution rate in the static immersion test. They showed strong passivation characteristics in the electrochemical test. They maintained negligible current density throughout the wide anodic potential range. The passive layer was not broken up to 2.0 V (vs. SCE). The hysteresis and the shift of passivation potential toward the anodic direction was observed during the reversed scan. The passivation process appeared to be accelerated by oxygen in air or that dissolved in the fluids. The passivation also proceeded without oxygen by the reaction of constituents in the fluids. Acid or chloride in the fluids, specially later weakened the passive layer, and then induced higher passivation current density and less shift of passivation potential in the reversed scan. CP-Ti Grade 2 was more reactive than Ti6Al4V ELI in the fluids containing acid or chloride, but thicker layer produced on its surface provided higher corrosion resistance.

• BMB Reports
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• v.31 no.6
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• pp.572-577
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• 1998

A soluble protein from Saccharomyces cerevisiae provides protection against a thiol-containing oxidation system but not against an oxidation system without thiol. This 25-kDa protein acts as a peroxidase but requires the NADPH-dependent thioredoxin system or a thiol-containing intermediate, and was thus named thioredoxin peroxidase. The protective role of thioredoxin peroxidase against ionizing radiation, which generates reactive oxygen species harmful tocellular function, was investigated in wild-type and mutant yeast strains in which the tsa gene encoding thioredoxin peroxidase was disrupted by homologous recombination. Upon exposure to ionizing radiation, there was a distinct difference between these two strains in regard to viability and the level of protein carbonyl content, which is the indicative marker of oxidative damage to protein. Activities of other antioxidant enzymes, such as catalase, superoxide dismutase, glucose-6-phosphate dehydrogenase, and glutathione reductase were increased at 200-600 Gy of irradiation in wild-type cells. However, the activities of antioxidant enzymes were not significantly changed by ionizing radiation in thioredoxin peroxidase-deficient mutant cells. These results suggest that thioredoxin peroxidase acts as an antioxidant enzyme in cellular defense against ionizing radiation through the removal of reactive oxygen species as well as in the protection of antioxidant enzymes.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.622-629
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• 2015

Cu circuits were successfully fabricated on flexible PET(polyethylene terephthalate) substrates using wettability difference and electroless plating without an etching process. The wettability of Cu plating solution on PET was controlled by oxygen plasma treatment and $SiO_x$-DLC(silicon oxide containing diamond like carbon) coating by HMDSO(hexamethyldisiloxane) plasma. With an increase of the height of the nanostructures on the PET surface with the oxygen plasma treatment time, the wettability difference between the hydrophilicity and hydrophobicity increased, which allowed the etchless formation of a Cu pattern with high peel strength by selective Cu plating. When the height of the nanostructure was more than 1400 nm (60 min oxygen plasma treatment), the reduction of the critical impalement pressure with the decreasing density of the nanostructure caused the precipitation of copper in the hydrophobic region.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.108-116
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• 2002

The diesel engine is one of the most effective transport options available in all sizes and covering a wide range of applications. But, many researchers developing the diesel engine are facing tough challenges in view of the increasingly lower emissions standards. Thus, this study will explore the possible fuel additive technology to further reduce the emissions from the IDI diesel engine. The purpose of this study is to investigate the effects of oxygenated fuels on the exhaust emissions and to attain a better trade-off relation between smoke and NOx in four cylinder diesel engine. Experiments were conducted with oxygenated fuels as an effective way to improve the combustion efficiency. Some of oxygenated fuel(Diglyme and DEE) were added to the conventional diesel fuel which had no an oxygen content. Also, EGR was adopted for reducing NOx without any strong adverse effects on other exhaust emissions. This study concluded that exhaust emissions in diesel engine could be reduced by adding the oxygenated fuels which had lower boiling point, and the combustion efficiency was also improved as the oxygen content in fuel increased.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1577-1582
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• 2010

A 20 wt % Pt/C is fabricated and characterized for use as the cathode catalyst in a polymer electrolyte membrane fuel cell (PEMFC). By using the polyol method, the fabrication process is optimized by modifying the carbon addition sequence and precursor mixing conditions. The crystallographic structure, particle size, dispersion, and activity toward oxygen reduction of the as-prepared catalysts are compared with those of commercial Pt/C catalysts. The most effective catalyst is obtained by ultrasonic treatment of ethylene glycol-carbon mixture and immediate mixing of this mixture with a Pt precursor at the beginning of the synthesis. The catalyst exhibits very uniform particle size distribution without agglomeration. The mass activities of the as-prepared catalyst are 13.4 mA/$mg_{Pt}$ and 51.0 mA/$mg_{Pt}$ at 0.9 V and 0.85 V, respectively, which are about 1.7 times higher than those of commercial catalysts.

• Journal of the East Asian Society of Dietary Life
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• v.5 no.3
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• pp.215-221
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• 1995

This study was undertaken to investigate the effect of Taraxacum herba extract on the hepatic xanthine oxidase activity as a oxygen free radical generating enzyme in vitro and in vivo. It was observed that partial purified hepatic xanthine oxidase (type O) activity was strongly inhibited by the addition of Taraxacum herba n-butanol extract in vitro. The Km value of xanthine oxidase without affecting the Vmax value for xanthine was significantly increased by the addition of ta-dase (type O) activity was significantly inhibited by the treatment of Taraxacum gerba n-butanol ex-tract for 5days(over 40mg/kg, i.p), whereas, xanthine oxidase (type D) activity was not changed by the injection of Taracacum herba n-butanol extract. Meanwhile, liver weight / body weight(%), serum alanine aminotransferase activity and hepatic lipid peroxide content in Taraxacum herba n-buta-nol extract-treated rat were not changed. These findings led us to conclude that Taraxacum herba n-butanol extract may regulate the hepatic xanthine oxidase type O activity to prevent toxic effect of oxidative stress by the oxygen free radicals.

• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.77-84
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• 2010

Annealing characteristics of an oxygen free copper (OFC) processed by differential speed rolling (DSR) were investigated in detail. An OFC sample with a thickness of hum was rolled to 35% reduction at ambient temperature without lubrication, varying the differential speed ratio from 1.0:1 to 2.2:1, and then annealed for 0.5h at various temperatures from 100 to $400^{\circ}C$. Different recrystallization behavior was observed depending on the differential speed ratio, especially in the case of annealing at $200^{\circ}C$ Complete recrystallization occurred in the specimens annealed at temperatures above $250^{\circ}C$ regardless of the differential ratios. The hardness distribution in the thickness direction of the rolled OFC sheets varied depending on the differential speed ratios. These annealing characteristics were explained by the magnitude of shear strain introduced during rolling.

• Journal of Korean society of Dental Hygiene
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• v.21 no.5
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• pp.545-553
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• 2021

Objectives: This study aimed to investigate the cytotoxicity of Nexus RMGIC, an indirect restorative cement, on cell survival rate and reactive oxygen species (ROS) production in periodontal stem cells (PDSCs). Methods: PDSCs were incubated with serially diluted Nexus RMGIC eluates with and without the addition of N-acetyl-cysteine (NAC). Cell survival was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The ROS generation was determined by measuring the fluorescence intensity for 2',7'-dichlorofluorescin diacetate. Results: Nexus RMGIC exposure decreased cell proliferation and cell survival rate in a dose-dependent manner (1:8, 1:4, 1:2, 1:1) in PDSCs. The cytotoxicity of Nexus RMGIC was inhibited by treatment with 10-mM NAC. In addition, the production of ROS was detected by immunofluorescence after PDSCs were exposed to Nexus RMGIC. However, ROS generation was significantly suppressed in the NAC pretreatment compared with the Nexus RMGIC group. Conclusions: Nexus RMGIC increased the cytotoxicity and ROS generation. ROS was involved in Nexus RMGIC-induced cell toxicity.