• Journal of the Korean Electrochemical Society
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• v.8 no.4
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• pp.177-180
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• 2005

A series of inorganic-organic hybrid membranes were prepared with a systematic variation of titanium dioxide nano particles content. Their liquid uptake, methanol permeability and proton conductivity as a function of inorganic oxide content were investigated. The results obtained show that the inorganic oxide network decreases the proton conductivity and liquid uptake. It is also found that increase in inorganic oxide content leads to decrease of methanol permeability. In terms of the morphology, membranes are homogeneous and exhibit a good adhesion between inorganic domains and the polymer matrix. The properties of the composite membranes are compared with the standard nafion membrane.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.25-29
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• 2012

Agriculture activities account for 58% of total anthropogenic emissions of nitrous oxide ($N_2O$) with global warming potential of 298 times as compared to carbon dioxide ($CO_2$) on molecule to molecule basis. Quantifying $N_2O$ from managed soil is essential to develop national inventories of greenhouse gas (GHG) emissions. The objective of the study was to compare $N_2O$ emission from livestock compost applied arable land with that for fertilizer treatment. The study was conducted for two years by cultivating Chinese cabbage (Brassica campestris L.) in Chuncheon, Gangwon-do. Accumulated $N_2O$ emission during cultivation of Chinese cabbage after applying livestock compost was slightly greater than that for chemical fertilizer. Slightly greater $N_2O$ emission factor for livestock compost was observed than that for chemical fertilizer possibly due to lump application of livestock compost before crop cultivation compared with split application of chemical fertilizers and enhanced denitrification activity through increased carbon availability by organic matter in livestock compost.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.226-234
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• 2002

A systematic study of the role of transfer films on friction properties was performed with various temperatures in the brake system. An NAO friction material specimens containing 9 ingredients were tested using a pad-on-disk type friction tester A new method of measuring the transfer film thickness was developed by considering the electrical resistance of the transfer film using a 4-point probe technique. The properties of transfer film such as surface morphology and film distribution vaied according to the relative amount of graphite and magnesium oxide. By using SEM, it was possible to obtain information about the chemical composition of the transfer film. Results showed that there detected a threshold value of the relative amount of a two active materials to maintain a certiain thickness of a transfer film. Results also showed that formation of friction layer generated on the friction surface was strongly affected by chemical action of two ingredients during sliding due to chemical reaction of solid lubricants at different interface temperature. The results suggested that no apparent relationship between transfer film thickness and the average friction coefficient was founded and friction characteristics were affected more by the property of the solid lubricant and abrasive in the material.

• Bulletin of the Korean Chemical Society
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• v.26 no.9
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• pp.1354-1358
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• 2005

Nano- and microstructured indium nitride crystals were synthesized by the reaction of indium oxide ($In_2O_3$) powder and its pellet with ammonia in the temperature range 580-700 ${^{\circ}C}$. The degree of nitridation of $In_2O_3$ to InN was very sensitive to the nitridation temperature. The formation of zero- to three-dimensional structured InN crystals demonstrated that $In_2O_3$ is nitridated to InN via two dominant parallel routes (solid ($In_2O_3$)-to-solid (InN) and gas ($In_2O$)-to-solid (InN)). The growth of InN crystals with such various morphologies was explained by the vapor-solid (VS) mechanism where the degree of supersaturation of In vapor determines the growth morphology and the vapor was mainly by the reaction of $In_2O$ with ammonia and partially by sublimation of solid InN. The pellet method was proven to be useful to obtain homogeneous InN nanowires.

• Journal of the Korean Electrochemical Society
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• v.20 no.1
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• pp.1-6
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• 2017

This study investigated the effect of surface pretreatment, which removes native Cu oxides on Cu seed layer, on subsequent Cu electro-/electroless deposition in Cu interconnection. The native Cu oxides were removed by using citric acid-based solution frequently used in Cu chemical mechanical polishing process and the selective Cu oxide removal was successfully achieved by controlling the solution composition. The characterization of electro-/electrolessly deposited Cu films after the oxide removal was then performed in terms of film resistivity, surface roughness, etc. It was observed that the lowest film resistivity and surface roughness were obtained from the substrate whose native Cu oxides were selectively removed.

• Biomedical Science Letters
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• v.24 no.1
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• pp.50-54
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• 2018

N-nitroso-N-methylurea (NMU) and N-nitroso-N-ethylurea (NEU), direct alkylating chemical mutagens and carcinogens, are shown to be the upregulators of cellular $NF-{\kappa}B$, regulating various genes that mediate tumorigenesis and carcinogenesis. Nitric oxide (NO), a toxic reactive radical gas, has been known to induce programmed cell death or apoptosis in various cells. Therefore, the assessment of NO production was examined to elucidate the possible contribution of NO release to the chemical carcinogenic potency of NMU and NEU in human skin cells. NMU and NEU did not alter the NO production, but they caused a significant downregulation of the NO generation on lipopolysaccharide (LPS)-induced NO production at concentrations ranging from $2{\sim}5{\mu}M$. The degree of downregulation of NO by NMU and NEU decreased up to 15% and 20%, respectively, compared to the control. These results demonstrate that the LPS-inducible keratinocytes NO synthase is involved in modulating carcinogenic potency by NMU and NEU, and the regulation of the cellular $NF-{\kappa}B$ activity by NMU and NEU is negatively correlated with the level of LPS-induced NO production in human skin cells. The findings of this study suggest the hypothesis that NMU and NEU-induced carcinogenesis may be associated with the downregulation of NO production, and the inducible NO may play an important role in NMU and NEU-induced carcinogenicity in human epidermal keratinocytes.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.1979-1984
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• 2014

We have developed an efficient method to generate highly active Pd and PdO nanoparticles (NPs) dispersed on graphene and graphene oxide (GO) by an impregnation method combined with thermal treatments in $H_2$ and $O_2$ gas flows, respectively. The Pd NPs supported on graphene (Pd/G) and the PdO NPs supported on GO (PdO/GO) demonstrated excellent carbon-carbon cross-coupling reactions under a solvent-free, environmentally-friendly condition. The morphological and chemical structures of PdO/GO and Pd/G were fully characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). We found that the remarkable reactivity of the Pd/G and PdO/GO catalysts toward the cross-coupling reaction is attributed to the high degree of dispersion of the Pd and PdO NPs while the oxidative states of Pd and the oxygen functionalities of graphene oxide are not critical for their catalytic performance.

• Journal of the Korean institute of surface engineering
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• v.35 no.6
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• pp.383-390
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• 2002

To investigate behaviors of Ti and O elements and microstructures of anodic titanium oxide films, the films were prepared by anodizing pure titanium in $H_2$S $O_4$, $H_3$P $O_4$, and $H_2O$$_2$ mixed solution at 180V. The microstructures and chemical states of the elements were analyzed using SEM, X-ray mapping, AFM, XRD, XPS (depth profile). The films formed on a titanium substrate showed porous layers which were composed of pore and wall, And with increasing anodizing time a hexagonal shape of cell structures were dominant and solace roughness increased. From the XRD result the structure of the Ti $O_2$ layer was anatase type of crystal on the whole. In the XPS spectra it was found that Ti and O were chemically binded in forms of Ti $O_2$, TiOH, $Ti_2$ $O_3$ at Ti 2p, and Ti $O_2$, $Ti_2$ $O_3$, $P_2$ $O_{5}$, S $O_4^{2-}$ at O ls respectively. Concentration of Ti $O_2$ decreased as the depth increased from the surface of the oxide film towards the substrate, but to the contrary concentrations of TiOH and $Ti_2$ $O_3$ increased.d.

• Current Photovoltaic Research
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• v.1 no.2
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• pp.97-102
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• 2013

Aluminum-doped zinc oxide (AZO) thin films were prepared by dc magnetron sputtering at room temperature and the effect of heat treatment on the structural, electrical and optical properties of the films were examined. As the annealing temperature and time increased, the resistivity decreased and the transmittance improved. All AZO films had c-axis oriented (002) plane of ZnO, regardless of the annealing process employed. As the annealing temperature and time increased, the crystallinity of AZO thin films increased due to the formation of a new ZnO phase in which Al was substituted for Zn. However, at the high annealing temperature of $400^{\circ}C$, the resistivity of the films increased via separation of Zn and Al from ZnO phase due to their low melting points. X-ray diffraction, field emission scanning electron micrograph and Hall effect measurement confirmed the formation of uniformly distributed new grains of ZnO substituted with Al. The variation of Al contents in AZO films was shown to be the primary factor for the changes in resistivity and carrier concentration of the films.

• Korean Journal of Pharmacognosy
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• v.49 no.1
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• pp.1-6
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• 2018

Six compounds, eupatilin (1), dammaradienyl acetate (2), glutinol acetate (3), $3{\beta}-acetoxyoleanan-12-one$ (4), taraxasterol (5) and quercetin-3,4'-dimethyl ether (6) were isolated from the aerial parts of Artemisia absinthium. The chemical structures of compounds 1-6 were determined by the basis of physico-chemical properties and spectroscopic methods such as 1D and 2D NMR. Among them, compounds 2-5 were isolated from this plant for the first time. The inhibitory effects of these isolated compounds against nitric oxide (NO) production in LPS-induced RAW264.7 cells or BV2 microglia were also examined. Among the tested compounds, compound 1, eupatilin, inhibited the production of NO in LPS-induced RAW264.7 cells and BV2 microglia, respectively.