• Carbon letters
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• v.16 no.3
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• pp.198-202
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• 2015

Carbon-supported Pt catalyst systems containing defect adsorption sites on the anode of direct methanol fuel cells were investigated, to elucidate the mechanisms of H₂ dissociation and carbon monoxide (CO) poisoning. Density functional theory calculations were carried out to determine the effect of defect sites located neighboring to or distant from the Pt catalyst on H₂ and CO adsorption properties, based on electronic properties such as adsorption energy and electronic band gap. Interestingly, the presence of neighboring defect sites led to a reduction of H₂ dissociation and CO poisoning due to atomic Pt filling the defect sites. At distant sites, H₂ dissociation was active on Pt, but CO filled the defect sites to form carbon π-π bonds, thus enhancing the oxidation of the carbon surface. It should be noted that defect sites can cause CO poisoning, thereby deactivating the anode gradually.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.513-515
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• 2005

• Archives of Pharmacal Research
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• v.28 no.10
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• pp.1156-1160
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• 2005

An iridoid glycoside, oldenlandoside III (5) was isolated from the n-butanol fraction of methanol extracts of the aerial parts of Oldenlandia diffusa Roxb. along with six others previously characterized iridoid glycosides; geniposidic acid (1), scandoside (2), feretoside (3), 10-O-ben-zoylscandoside methyl ester (4), asperulosidic acid (6) and deacetylasperulosidic acid (7). Compounds 1, 2, and 7 inhibited LDL-oxidation, and showed $63.3{\pm}2.0,\;62.2{\pm}1.6,\;and\;63.8{\pm}1.5\%$ inhibition, respectively, at a concentration of 20 ${\mu}g/mL$.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2098-2105
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• 2016

Massive reserves of methane ($CH_4$) remain unexplored as a feedstock for the production of liquid fuels and chemicals, mainly because of the lack of economically suitable and sustainable strategies for selective oxidation of $CH_4$ to methanol. The present study demonstrates the bioconversion of $CH_4$ to methanol mediated by Type I methanotrophs, such as Methylomicrobium album and Methylomicrobium alcaliphilum. Furthermore, immobilization of a Type II methanotroph, Methylosinus sporium, was carried out using different encapsulation methods, employing sodium-alginate (Na-alginate) and silica gel. The encapsulated cells demonstrated higher stability for methanol production. The optimal pH, temperature, and agitation rate were determined to be pH 7.0, $30^{\circ}C$, and 175 rpm, respectively, using inoculum (1.5 mg of dry cell mass/ml) and 20% of $CH_4$ as a feed. Under these conditions, maximum methanol production (3.43 and 3.73 mM) by the encapsulated cells was recorded. Even after six cycles of reuse, the Na-alginate and silica gel encapsulated cells retained 61.8% and 51.6% of their initial efficiency for methanol production, respectively, in comparison with the efficiency of 11.5% observed in the case of free cells. These results suggest that encapsulation of methanotrophs is a promising approach to improve the stability of methanol production.

• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.65-69
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• 2001

The potential change, and the crossover of alcohol in a liquid-feed solid polymer electrolyte fuel cell operating at atmosphere and room temperature was investigated. Alcohol crossover was generated from all the alcohol by using the fuel. The single-cell property of direct methanol fuel cell was higher than that of other alcohol species as $31mW/cm^2$ at 0.23 V at 4.5M of methanol.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.44-50
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• 2006

Contents of phenolic compounds in peel, flesh, and core of three Asian pear cultivars, Hosui, Niitaka, and Chuwhangbae, were determined at different stages of maturity. Antioxidant properties of methanol extracts of peels at various fruit maturity stages were also evaluated. Total phenolic content decreased with maturity. Arbutin, chlorogenic acid, and epicatechin were major phenolic compounds in young fruits. Catechin, 4-hydroxymethyl benzoic acid, and caffeic acid were detected in peel and core of immature and mature pears. 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activities of methanol extracts were 16.30 and $15.73\;{\mu}g$ in peel of immature Hosui and Chuwhangbae pears, respectively, and $11.59\;{\mu}g$ in mature Niitaka pears, which was significantly higher than those of other maturity stage in the same cultivar. Inhibitory activities on lipid oxidation of methanol extracts of three cultivars at all maturity stages were similar to that of ${\alpha}$-tocopherol.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.727-731
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• 2008

Mesoporous Pt-Au alloy films were successfully fabricated on ITO-coated glass by electrodeposition method using tri-blockcopolymer (P123) as a templating agent. The electrolyte consisted of 10 mM hydrogen hexachloroplatinate ($H_2PtCl_6$), 10 mM hydrogen tetrachloroaurate ($HAuCl_4$), and proper amount of P123. For comparison, control samples were electrodeposited without $HAuCl_4$ and P123. Film composition was determined by EDS(Energy Dispersive X-ray Spectroscopy), and the mesoporous structure was confirmed by TEM(Transmission Electron Microscopy). SEM(Scanning Electron Microscopy) was utilized to examine surface morphology, and it was observed that the addition of P123 affected the particle growth, resulting in the significant change of surface morphology. Methanol oxidation and CO oxidation were carried out to investigate electrocatalytic activities of synthesized samples. It was observed that the catalytic activity was strongly dependent on the film compositions. Compared with nonporous electrode prepared without P123 templating, mesoporous films prepared with P123 templating showed much higher catalytic activities and stability for both methanol oxidation and CO oxidation. These enhanced electrocatalytic activities were due to the high surface area and facilitated charge transfer of mesoporous films.

• Journal of Soil and Groundwater Environment
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• v.26 no.1
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• pp.45-53
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• 2021

The removal of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution by coupled electro-oxidation and Fe(II) activated persulfate oxidation process was investigated. The electrochemical oxidation was performed using carbon sheet electrode and persulfate using Fe(II) ion as an activator. The oxidation efficiency was investigated by varying current density (2 - 10 mA/㎠), electrolyte (Na2SO4) concentration (10 - 100 mM), persulfate concentration (5 - 20 mM), and Fe(II) concentration (10 - 20 mM). The 2,4-D removal efficiency was in the order of Fe(II) activated persulfate-assisted electrochemical oxidation (Fe(II)/PS/ECO, 91%) > persulfate-electrochemical oxidation (PS/ECO, 51%) > electro-oxidation (EO, 36%). The persulfate can be activated by electron transfer in PS/ECO system, however, the addition of Fe(II) as an activator enhanced 2,4-D degradation in the Fe(II)/PS/ECO system. The 2,4-D removal efficiency was not affected by the initial pHs (3 - 9). The presence of anions (Cl- and HCO3-) inhibited the 2,4-D removal in Fe(II)/PS/ECO system due to scavenging of sulfate radical. Scavenger experiment using tert-butyl alcohol (TBA) and methanol (MeOH) confirmed that although both sulfate (SO4•-) and hydroxyl (•OH) radicals existed in Fe(II)/PS/ECO system, hydroxyl radical (SO4•-) was the predominant radical.

• The Korea Journal of Herbology
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• v.30 no.4
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• pp.89-94
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• 2015

Objectives : It had been reported that herbal medicines containing polyphenol and flavonoid have been shown to be associated with decreased the cause of aging and variety of disease such as reactive nitrogen species and reactive oxygen species in several recent studies. Salviae miltiorrhizae Radix, origined fromSalvia miltiorrhizaBGE., is one of popular traditional herbal medicines that is commonly used by traditional medicine practitioners. To this date, Salviae miltiorrhizae Radix has more than 2000-year history of mature application. This study was conducted to investigate whether the Salviae miltiorrhizae Radix methanol extract has an inhibitory effect association with oxidation or inflammation.Methods : Cytotoxic activity of Salviae miltiorrhizae Radix methanol extract on RAW264.7 cells was evaluated by using 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide solution. Nitric oxide production was measured using griess reagent system. Western blot analysis and measurement for changes of protein expression, nitric oxide synthase and cyclooxygenase-2, also performed.Results : The medicinal plant, Salviae miltiorrhizae Radix, does not impair the cell viability in tested concentration (25-100 μg/ml). SMR showed anti-oxiative effectsin vitroby decreasing electron donating ability, and also showed anti-inflammatory effects suppressing NO and COX-2 expressin in LPS induced RAW264.7 activation. SMR inhibited the generation of intracellular ROS production as dose dependant manner.Conclusions : These results indicate that Salviae miltiorrhizae Radix methanol extract has an anti-inflammatory activities via anti-oxidative effects, and the anti-inflammatory effect was presentedd as dose dependant manner.

• Korean Journal of Materials Research
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• v.30 no.1
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• pp.14-21
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• 2020

Carbon supports for dispersed platinum (Pt) electrocatalysts in direct methanol fuel cells (DMFCs) are being continuously developed to improve electrochemical performance and catalyst stability. However, carbon supports still require solutions to reduce costs and improve catalyst efficiency. In this study, we prepare well-dispersed Pt electrocatalysts by introducing titanium dioxide (TiO₂) into biomass based nitrogen-doped carbon supports. In order to obtain optimized electrochemical performance, different amounts of TiO₂ component are controlled by three types (Pt/TNC-2 wt%, Pt/TNC-4 wt%, and Pt/TNC-6 wt%). Especially, the anodic current density of Pt/TNC-4 wt% is 707.0 mA g^-1_pt, which is about 1.65 times higher than that of commercial Pt/C (429.1 mA g^-1_pt); Pt/TNC-4wt% also exhibits excellent catalytic stability, with a retention rate of 91 %. This novel support provides electrochemical performance improvement including several advantages of improved anodic current density and catalyst stability due to the well-dispersed Pt nanoparticles on the support by the introduction of TiO₂ component and nitrogen doping in carbon. Therefore, Pt/TNC-4 wt% may be electrocatalyst a promising catalyst as an anode for high-performance DMFCs.