• Journal of the Korean institute of surface engineering
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• v.32 no.1
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• pp.67-77
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• 1999

The Ni base superalloy Mar-M247 substrate was aluminized or aluminized after boronizing by the pack cementation under Ar atmosphere. The hot corrosion resistance and after-heat-treatment effect of aluminized specimens were studied by the cyclic hot corrosion test in $Na_2SO_4$-NaCl molten salt. XRD analysis showed that the $Ni_2Al_3$ phase was formed between the coated layer and substrate below 1273K but the NiAl phase above 1273K. The peak of the NiAl phase was developed after heat treatment. Corrosion test showed that corrosion resistance of the specimen with the NiAl phase was better than that with the $Ni_2Al_3$ phase. Corrosion resistance could be improved by heat treatment to form ductile NiAl phase, where cracks were not formed by thermal shock on coating layer. Moreover, it appeared that heat treatment played a role to improve corrosion resistance of Al diffusion coating above 1273K. The existence of boron in the Al diffusion coating layer obstructed outwared diffusion of Cr from the substrate, and it influenced on corrosion resistance of the coating layer by weakening adherence of the oxide scale.

• Journal of the Korean Applied Science and Technology
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• v.27 no.3
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• pp.378-384
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• 2010

Regenerated cellulose was prepared from Buckeye wood pulp V60 via dissolution in N-methylmorpholin N-oxide (NMMO) solvent system. The effect of antioxidants such as, n-propylgallate (PG), tris(nonylphenyl) phosphite (TRIS), ethylenediamine tetraacetic acid disodium salt (EDTA), and magnesium sulfate on the properties of regenerated cellulose was studied using X-ray diffraction, copper index calculation, and viscometry. Only addition of more than 0.01% of PG into NMMO solvent was effective to avoid the reduction of the degree of polymerization(DP) of regenerated cellulose during dissolution at $110^{\circ}C$. However, the early stage(within 0.5h of dissolution process) degradation of cellulose was not prevented eventhough up to 0.5% PG was appled to hot NMMO system. In addition, to recover the expensive NMMO after cellulose regenerating process, the washing filtrate was studied using simple techniques, such as refractive index, pH, and conductivity measurements. Through conductivity measurement result, 4-time of washing was enough to remove the NMMO completely from regenerated cellulose.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.2
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• pp.271-278
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• 2021

In this study, a chlorination technique for recycling Li₂ZrO₃, a reaction product of ZrO₂-assisted rinsing process, was investigated to minimize the generation of secondary radioactive pyroprocessing waste. It was found that the reaction temperature was a key parameter that determined the reaction rate and maximum conversion ratio. In the temperature range of 400-600℃, an increase in the reaction temperature resulted in a profound increase in the reaction rate. Hence, according to the experimental results, a reaction temperature of at least 450℃ was proposed to ensure a Li₂ZrO₃ conversion ratio that exceeded 80% within 8 h of the reaction time. The activation energy was found to be 102 ± 2 kJ·mol^-1·K^-1 between 450 and 500℃. The formation of LiCl and ZrO₂ as reaction products was confirmed by X-ray diffraction analysis. The experimental results obtained at various total flow rates revealed that the overall reaction rate depends on the Cl₂ mass transfer rate in the experimental condition. The results of this study prove that the chlorination technique provides a solution to minimize the amount of radioactive waste generated during the ZrO₂-assisted rinsing process.

• Journal of Animal Science and Technology
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• v.63 no.5
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• pp.955-976
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• 2021

The aim of this study was to investigate the effects of dietary sodium nitrite and meat on human health. Sodium nitrite in processed meat is known to be one of the main precursors of carcinogens, such as N-nitroso compounds. However, we previously found that processed meat is not the primary source of sodium nitrite; nitrate or the conversion of nitrate in vegetables are contribute to generate more than 70% Sodium nitrite or nitrate containing compounds in body. Although the heavy consumption of meat is likely to cause various diseases, meat intake is not the only cause of colorectal cancer. Our review indicates that sodium nitrite derived from foods and endogenous nitric oxide may exhibit positive effects on human health, such as preventing cardiovascular disease or improving reproductive function. Therefore, further epidemiological studies considering various factors, such as cigarette consumption, alcohol consumption, stress index, salt intake, and genetic factors, are required to reliably elucidate the effects of dietary sodium nitrite and meat on the incidence of diseases, such as colorectal cancer.

• 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.

• Korean Journal of Materials Research
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• v.32 no.2
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• pp.80-84
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• 2022

Copper nanoparticles (CuNPs) are considered of great importance due to their high catalytic and antimicrobial activities. This study focuses on the preparation and characterization of CuNPs, and on their antibacterial/antifungal activities. A copper salt (copper sulfate pentahydrate) as precursor, starch as stabilizing agent, and ascorbic acid as reducing agent were used to fabricate CuNPs. The resulting product was characterized via different techniques such as X-ray diffractrometry (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Scanning electron microscopy (SEM) to confirm its characteristic properties. Employing the Scherrer formula, the mean crystallite sizes of copper (Cu) and cuprous oxide (Cu₂O) nanocrystals were found to be 29.21 and 25.33 nm, respectively, as measured from the main X-ray diffraction peaks. The functional groups present in the resulting CuNPs were confirmed by FTIR. In addition, the engineered CuNPs showed antibacterial and antifungal activity against tested pathogenic bacterial and fungal strains.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2021.04a
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• pp.55-55
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• 2021

Hibiscus hamabo is a deciduous shrub that grows around salt marshes and is considered a semi-mangrove plant found in Asia. There are no studies on the biological activity of H. hamabo except for studies on the anthocyanin content. We investigated the anti-inflammatory effects of H. hamabo extract (HHE) on lipopolysaccharide (LPS)-induced RAW 264.7 cells. As nuclear factor-kappa B (NF-kB) induced by LPS moves into the nucleus, inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and inflammatory cytokines are promoted and the inflammatory reaction begins. The nitric oxide (NO) production decreased by the treatment of HHE. Moreover, mRNA levels of inflammation-related cytokines, such as tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β, were significantly suppressed by HHE. Similarly, the expressions of iNOS and COX-2 were also decreased. The phosphorylation of p65, a subunit of NF-κB, was suppressed by HHE. As a result, HHE can be used as an effective natural material for the anti-inflammatory agent.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.6
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• pp.833-840
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• 2023

In this study, the antioxidant and anti-skin aging properties of the Korean marine algae Ishige foliacea were investigated. Solvent extracts from I. foliacea were prepared with 70% ethanol, 80% methanol, and water. The extraction yields of various solvent extracts ranged from 9.55% to 35.12%. In terms of antioxidant activity, the ethanol extract showed the highest ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) radical scavenging activity, nitrite oxide scavenging activity, reducing power, and FRAP (ferric reducing antioxidant power). Regarding anti-skin aging activity, evaluation of the skin whitening and anti-wrinkle activities revealed that the methanol, water, and ethanol extracts possessed the highest tyrosinase (IC₅₀=0.98 mg/mL), elastase (IC₅₀=0.15 mg/mL), and collagenase (IC₅₀=0.06 mg/mL) inhibitory activities, respectively. These results suggest that I. foliacea holds potential as an antioxidant and anti-skin aging substance in food and cosmetic materials.

• Polymer(Korea)
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• v.39 no.1
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• pp.88-98
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• 2015

4-Amino-N-hexadecylbenzamide-graphene sheets (AHB-GSs), used in the preparation of the polyimide (PI) nanocomposite films, were synthesized by mixing a dispersion of graphite oxide with a solution of the ammonium salt of AHB. The atomic force microscope image of functionalized-GS on mica and a profile plot revealed the average thickness of AHB-GS to be ~3.21 nm. PI films were synthesized by reacting 4,4'-biphthalic anhydride and bis(4-aminophenyl) sulfide. PI nanocomposite films containing various contents of AHB-GS over the range of 0-10 wt% were synthesized using the solution intercalation method. The PI nanocomposite films under different thermal imidization temperatures, 250 and $350^{\circ}C$, were examined. The graphenes, for the most part, were well dispersed in the polymer matrix despite some agglomeration. However, micrometer-scale particles were not detected. The average thickness of the particles was <10 nm, as revealed from the transmission electron microscope images. Only a small amount of AHB-GS was required to improve the gas barrier, and electrical conductivity. In contrast, the glass transition and initial decomposition temperatures of the PI hybrid films continued to decrease with increasing content of AHB-GS up to 10 wt%. In general, the properties of the PI hybrid films heat treated at $350^{\circ}C$ were better than those of films heat treated at $250^{\circ}C$.

• The Korea Journal of Herbology
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• v.22 no.3
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• pp.117-125
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• 2007

Objective : Lonicera japonica (Caprifoliaceae) has long been used for treatment of infectious diseases in oriental countries. The aim of this study was to investigative the effect by which the aqueous extract from flower of L. japonica (LJFAE) inhibited the lipopolysaccharide (LPS)-induced inflammatory mediators in murine macrophages, RAW 264.7 cells Methods : The dried flowers of L. japonica were extracted with distilled water at $100^{\circ}C$ for 7 h. The extract was filtered through 0.45 ${\mu}m$ filter, freeze-dried. The dried extract was dissolved in Hank's balanced salt solution (HBSS) and filtered through 0.22 ${\mu}m$ filter before use. Accumulated nitrite, an oxidative product of nitric oxide (NO), was measured in the culture medium by the Griess reaction. The levels of prostaglandin E2 (PGE2), tumor necrosis factor-$\alpha$ (TNF-$\alpha$), interleukin-1$\beta$ (IL-1$\beta$), and IL-6 production, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression were measured by enzyme-linked immunosorbent assay and Western blot analysis. Results: LJFAE (10-400 ${\mu}g$/ml) per se had no cytotoxic effect in unstimulated macrophages, but LJFAE concentration-dependently reduced NO, PGE2, TNF-, IL-l, and IL-6 production and COX-2 activity caused by stimulation of LPS. The levels of iNOS and COX-2 protein expressions were markedly suppressed by the treatment with LJFAE in a concentration dependent manner. Conclusions : These results suggest that LJFAE suppress the NO and PGE2production in macrophages by inhibiting iNOS and COX-2 expression and these properties may contribute to the anti-inflammatory activity of Lonicera japonica.