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        검색결과 170

        61.
        2013.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Quantitative analyses of naturally occurring methanol were performed for the alcoholic beverages commonly consumed in Jecheon, Chungbuk province, South Korea. The headspace analysis method was optimized for the low and high alcoholic beverages. The external standard method was applied due to the overlapping of 2-propanol and 2-butanol (the internal standard candidates) with target sample matrix peaks. The target samples were selected based on the retail sales amounts of alcoholic beverages in the largest retailer food-mart chain, Jecheon, Chungbuk province, South Korea. There was no sample containing methanol over 0.5 ㎎/㎖, the Korean maximum level of methanol in alcoholic beverages (1.0 ㎎/㎖ for fruit originated liquor etc). The total exposure amount of methanol via alcoholic beverages was estimated based on the daily alcohol consumption of 40 g. The hazard indices calculated by methanol RfD 0.5 ㎎/㎏ bw day (US EPA) and ADI 20 ㎎/㎏ bw day (proposed by Lachenmeier etc.) were 0.301 and 0.008, respectively. As with the hazard index, aggregate exposures below a HI of 1.0 will likely not result in adverse noncancer health effects over a lifetime of exposure. Then the methanol exposure via the alcoholic liquours might not hazard to Jecheon citizen.
        4,000원
        62.
        2012.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Methanol as a carbon source in chemical vapor deposition (CVD) graphene has an advantage over methane and hydrogen in that we can avoid optimizing an etching reagent condition. Since methanol itself can easily decompose into hydrocarbon and water (an etching reagent) at high temperatures [1], the pressure and the temperature of methanol are the only parameters we have to handle. In this study, synthetic conditions for highly crystalline and large area graphene have been optimized by adjusting pressure and temperature; the effect of each parameter was analyzed systematically by Raman, scanning electron microscope, transmission electron microscope, atomic force microscope, four-point-probe measurement, and UV-Vis. Defect density of graphene, represented by D/G ratio in Raman, decreased with increasing temperature and decreasing pressure; it negatively affected electrical conductivity. From our process and various analyses, methanol CVD growth for graphene has been found to be a safe, cheap, easy, and simple method to produce high quality, large area, and continuous graphene films.
        4,000원
        63.
        2012.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Oxidative stress has been reported to be one of causes of neuritis. This study examined antioxidative activities of methanol extracts of six amphibian species known to be medicinal animals (Rana catesbeiana, R. coreana, R. rugosa, R. dybowskii, R. nigromaculata, and Hyla japonica) and investigated their effects of inhibiting nitric oxide (NO) production and cytotoxicity on the murine macrophage RAW264.7 cells. As inflammation is closely associated with reactive oxygen species, assays on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, xanthine oxidase inhibitory activity, superoxide anion radical scavenging activity and NO scavenging activity of the extracts of the six species were performed to investigate their antioxidative activity. The results obtained were as follows; All extracts showed antioxidative activity, and the activity of R. dybowskii was the highest in comparison among those. Anti-inflammatory effects of the extracts were also examined, the five extracts except that of R. rugosa did not show cytotoxicity for RAW264.7 cells at the maximal concentration (1,000 μg mL-1). Selectivity index, meaning NO scavenging activity compared to cytotoxicity, showed the highest level in the extract of R. dybowskii. These results will be very useful basic data for future studies on prevention and treatment of human diseases to understand the biological roles of amphibian extracts throughout the antioxidative or anti-inflammatory pathways.
        4,000원
        64.
        2012.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Two types of Pt nanoparticle electrocatalysts were composited on Pt nanowires by a combination of an electrospinning method and an impregnation method with NaBH4 as a reducing agent. The structural properties and electrocatalytic activities for methanol electro-oxidation in direct methanol fuel cells were investigated by means of scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. In particular, SEM, HRTEM, XRD, and XPS results indicate that the metallic Pt nanoparticles with polycrystalline property are uniformly decorated on the electro-spun Pt nanowires. In order to investigate the catalytic activity of the Pt nanoparticles decorated on the electro-spun Pt nanowires, two types of 20 wt% Pt nanoparticles and 40 wt% Pt nanoparticles decorated on the electro-spun Pt nanowires were fabricated. In addition, for comparison, single Pt nanowires were fabricated via an electrospinning method without an impregnation method. As a result, the cyclic voltammetry and chronoamperometry results demonstrate that the electrode containing 40 wt% Pt nanoparticles exhibits the best catalytic activity for methanol electro-oxidation and the highest electrochemical stability among the single Pt nanowires, the 20 wt% Pt nanoparticles decorated with Pt nanowires, and the 40 wt% Pt nanoparticles decorated with Pt nanowires studied for use in direct methanol fuel cells.
        4,000원
        65.
        2012.06 구독 인증기관·개인회원 무료
        This study was conducted to investigate the physiological activities of the water and ethanol extracts from three strains of Hypsizygus marmoreus. Largely, anti-hypertensive, anti-inflammatory, anti-diabetic, anti-tumorigenic activities were carried out. In addition, β-glucan contents were also measured. Mangadak 2 ho has the 36%(w/w) β-glucan contents, it is highest value of all strains. And it also showed highest inhibitory activities of angiotensin converting enzyme. GONJI No.6 highly inhibited releasing of nitric oxide from Raw 264.7. Anti-diabetic activity, the Hypsizygus marmoreus(from Japan) showed highest inhibitory activity on amyloglucosidase. MTT assay was performed on the anti-tumorigenic test. The cancer cell were used to HeLa, A549. repectively.
        68.
        2011.11 구독 인증기관·개인회원 무료
        This study was conducted to investigate the physiological activities of the water and methanol extracts from Auricularia auricula-judae(black and brown) and Auricularia polytricha. Largely, anti-oxidant, anti-tumorigenic, anti-inflammatory, anti-diabetic activities were carried out. DPPH scavenging activity was performed on the anti-oxidant test. MTT assay and nitrite scavenging acitivity were performed on the anti-tumorigenic test. The cancer cell were used to HeLa, A549, HT-29 and MCF-7 and normal cell was used as control. lastly, in the anti-inflammatory and anti-diabetic activities, NO assay and α-amyloglucosidase inhibition were performed, repectively.
        71.
        2011.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구에서는 뛰어난 전도도와 물리적 강도를 가지는 그라핀의 고른 분산성을 얻기 위하여 두 가지 다른 방법으로 그라핀을 개질시켰다. 그리고 SPAES/그라핀 복합막은 각기 다른 함량을 첨가하여 제조되었으며 그라핀의 제조방법과 첨가된 그라핀의 함량에 따른 성능을 비교하였다. 복합막의 모폴로지는 SEM을 이용하여 관찰하였으며 개질된 그라핀의 화학적 구조는 FT-IR과 TGA를 사용하여 분석되었다. 그라핀의 함량변화가 0.5~3.0 wt% 일 때 복합막의 이온전도도와 메탄올 투과도를 측정하였으며 80℃, 100% 가습상태에서 SPAES/그라핀 복합막의 이온전도도(0.216 S/cm)는 순수한 SPAES 전해질 막보다 높은 이온전도도(0.098 S/cm)를 나타내었으며 그라핀의 함량이 1.5 wt%까지 증가될 때 메탄올 투과도는 감소되었다.
        4,000원
        72.
        2011.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Pt nanoparticle catalysts incorporated on RuO2 nanowire support were successfully synthesized and their electrochemical properties, such as methanol electro-oxidation and electrochemically active surface (EAS) area, were demonstrated for direct methanol fuel cells (DMFCs). After fabricating RuO2 nanowire support via an electrospinning method, two different types of incorporated Pt nanoparticle electrocatalysts were prepared using a precipitation method via the reaction with NaBH4 as a reducing agent. One electrocatalyst was 20 wt% Pt/RuO2, and the other was 40 wt% Pt/RuO2. The structural and electrochemical properties of the Pt nanoparticle electrocatalysts incorporated on electrospun RuO2 nanowire support were investigated using a bright field transmission electron microscopy (bright field TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. The bright field TEM, XRD, and XPS results indicate that Pt nanoparticle electrocatalysts with sizes of approximately 2-4 nm were well incorporated on the electrospun RuO2 nanowire support with a diameter of approximately 50 nm. The cyclic voltammetry results showed that the Pt nanoparticle catalysts incorporated on the electrospun RuO2 nanowire support give superior catalytic activity in the methanol electro-oxidation and a higher electrochemically active surface (EAS) area when compared with the electrospun Pt nanowire electrocatalysts without the RuO2 nanowire support. Therefore, the Pt nanoparticle catalysts incorporated on the electrospun RuO2 nanowire support could be a promising electrode for direct methanol fuel cells (DMFCs).
        4,000원
        73.
        2011.05 구독 인증기관·개인회원 무료
        Antioxidant activities of Hericium erinaceum was in vestigated in subfractions of methanol extract such as hexane, chloroform, ethylacetate, butanol and water subfractions. Chlorofrom fraction exhibited the highest antioxidant activity and showed the highest level of total phenolic contents. The level of total phenolics may be correlated with the antioxidant activities of the subfractions. Therefore, the phenolic compound in the chloroform subfractions exhibiting high antioxidant acticity was identified by mass spectrometry using LC-MS/MS. In addition, hot water extract of this mushroom were tested for antimutagenic activity by Ames Salmonellaassay.Thisextractshowed inhibitiory effect on the mutagenesis induced in Salmonella typhimurium strain TA100 and TA98 by the directly actingmutagen 4-nitroquinoline-1-oxide(0.15μg/plate) and sodium azide (0.5μg/plate). The extract also inhibited mutagenesis induced in Salmonella typhimurium strain TA100 and TA98 by the indirectly actingmutagen 2-aminoanthracen(2μg/plate) at 5000μg/plate and 200 μg/plate, respectively.
        74.
        2011.05 구독 인증기관·개인회원 무료
        To find an alternative for synthetic pesticides, methanol extract from plant samples were tested for their insecticidal activity against insect. The extract of Asiasarum sieboldii had strongly insecticidal activity against Plutella xylostella. Roots of A. sieboldii were extracted with methanol, and the concentrated extract was partitioned with n-hexane, ethylacetate, n-buthanol and H2O. The highest activity was shown in the hexane fraction. Activity-guided fractionation led to the isolation of two amides from hexane fration through the repeated silica gel column chromatographic separations. From the interpretation of spectropic data including NMR, MS, IR, the chemical structures of compounds were determined as dodeca-2E,4E,8Z,10Z-tetraenoic acid isobutylamide and dodeca-2E,4E,8Z, 10E-tetraenoic acid isobutylamide. These compounds showed insecticidal activity on P. xylostella by 96.7% at 100ppm. The liquid formulation controlled on cabbage effectively. The extract and compounds from A. sieboldii showed insecticidal activity against Nilaparvata lugens. As a naturally occurring pesticide, A. sieboldii could be useful as a new botanic insecticide.
        76.
        2011.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 시험은 무궁화과에 속하는 초본 식물인 Kenaf (Hibiscus cannabinus L.)를 경상대학교 시험농장 에서 2010년 6월 1일 파종하여 같은 해 11월 18일 수확하여 건조 한 후, 꽃 (HCME-F)과 잎 (HCME-L)에서 추출한 메탄올 추출물을 이용하여, 세포 독성 시험 및 주요 병원균에 대한 항균효과를 규명하였다. 항균효과에 사용된 균주는 가축에서 피부 질환, 유방염 및 소화기질병을 유발하는 그람양성 균인 St. aureus 와 Str. epidermidis, 그람음성균인 S. typhimurium 과 E. coli 균을 공시균주로 사용하였다. 추출물의 안전성을 평가하기 위해 두 추출물 HCME-F과 HCME-L을 0, 25, 50, 100 및 200 ㎍/ml 농도로 첨가한 배지에서 RAW 264.7 세포와 24시간 반응 후 세포 독성을 측정해 본 결과, 세포 독성이 인정되지 않았으며, 항균효과 시험결과 그람양성균인 St. aureus와 Str. epidermidis 균에 대하여 1, 50 및 100 ㎍/ml의 추출물 농도 및 반응시간 경과에 따라 항균 효과가 증가되었으나, 그람음 성균인 S. typhimurium 과 E. coli 에서는 항균효과가 인정되지 않았다. 종합적으로 Kenaf의 꽃과 잎 에서 추출한 메탄올 추출물이 세포에 대한 안전성이 입증되었고, 가축과 사람의 피부 질환 및 유방염의 대표적 그람양성균인 St. aureus와 Str. epidermidis 균에 대한 항균효과를 보여, Kenaf의 꽃과 잎을 이용한 선택적 그람양성균 치료제 및 사료첨가제 개발이 가능할 것으로 판단된다.
        4,000원
        77.
        2011.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Nanosized Pt, Pt-Ru and Pt-CeO2 electrocatalysts supported on acid-treated carbon nanotube (CNT) were synthesized by microwave-assisted heating of polyol process using H2Cl6Pt·6H2O, RuCl3, CeCl3 precursors, respectively, and were characterized by XRD and TEM. And then the electrochemical activity of methanol oxidation for catalyst/CNT nanocomposite electrodes was investigated. The microwave assisted polyol process produced the nano-sized crystalline catalysts particles on CNT. The size of Pt supported on CNT was 7~12 nm but it decreased to 3~5 nm in which 10wt% sodium acetate was added as a stabilizer during the polyol process. This fine Pt catalyst particles resulted in a higher current density for Pt/CNT electrode. It was also found that 10 nm size of PtRu alloys were formed by polyol process and the onset potential decreased with Ru addition. Cyclic voltammetry analysis revealed that the Pt75Ru25/CNT electrode had the highest electrochemical activity owing to a higher ratio of the forward to reverse anodic peak current. And the chronoamperemetry test showed that Pt75Ru25 catalyst had a good catalyst stability. The activity of Pt was also found to be improved with the addition of CeO2.
        4,000원
        78.
        2010.05 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Sn doped In2O3 (ITO) and ITO/Cu/ITO (ICI) multilayer films were prepared on glass substrates with a reactive radiofrequency (RF) magnetron sputter without intentional substrate heating, and then the influence of the Cu interlayer on themethanol gas sensitivity of the ICI films were considered. Although both ITO and ICI film sensors had the same thicknessof 100nm, the ICI sensors had a sandwich structure of ITO 50nm/Cu 5nm/ITO 45nm. The ICI films showed a ten timeshigher carrier density than that of the pure ITO films. However, the Cu interlayer may also have caused the decrement of carriermobility because the interfaces between the ITO and Cu interlayer acted as a barrier to carrier movement. Although the ICIfilms had two times a lower mobility than that of the pure ITO films, the ICI films had a higher conductivity of 3.6·10-4Ωcmdue to a higher carrier density. The changes in the sensitivity of the film sensors caused by methanol gas ranging from 50 to500ppm were measured at room temperature. The ICI sensors showed a higher gas sensitivity than that of the ITO single layersensors. Finally, it can be concluded that the ICI film sensors have the potential to be used as improved methanol gas sensors.
        3,000원
        80.
        2010.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 차세대 에너지원으로 주목 받고 있는 직접메탄올연료전지(Direct Methanol Fuel Cell, DMFC)에 대해 mutiscale 기법을 사용하여 DMFC의 MEA부분에 대한 상세 모델링 및 전산모사를 통한 이론적 고찰을 시도하였다. 본 연구에서 이용한 multiscale 모델링 방법은 공정시스템 공학의 kinetic 중심의 모델링 방법과 전산유체역학(Computational Fluid Dynamics, CFD)의 유동중심의 모델링 방법을 유기적으로 결합하여 모사 중간에 필요한 데이터 교환을 함으로써 정확한 모델링 및 전산모사 결과를 얻었다. CFD 모델링으로 유체 이동현상을 3차원으로 해석하였고, 동시에 복잡한 비선형 대수방정식으로 표현되는 반응속도, 전기화학반응을 DAE (Differential & Algebraic Equation) solver로 계산하였다. 모델은 메탄올의 산화반응과 산소의 환원반응을 중심으로 MEA (Membrane Electorde Assembly)부분에서 물리화학적, 전기적 현상 현상을 규명하고, 반응 메커니즘을 구성하였다. MEA 모델은 3차원 공간에서 변위를 가지는 3차원 모델로 구성하였으며, 정상상태 및 등온공정의 조건하에 수립되었다. 이를 통해 channel을 포함한 MEA 부분에서 발생되는 물리적, 화학적, 전기적 현상을 정확히 예측 할 수 있다. 본 연구를 통해 수행된 결과는 DMFC의 실험계획 및 운전조건을 도출함에 있어 매우 유용한 역할을 할 수 있을 것으로 사료되며, 추가적인 연구를 통해 DMFC의 상용화에 크게 이바지 할 수 있을 것으로 사료된다.
        4,200원
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