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        검색결과 10

        1.
        2014.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Au 정광으로부터 Au Ag의 용출율을 향상시키기 위하여 기계적-화학적 활성화와 티오요소-티오시안산염 혼합용액을 적용하였다. 기계적-화학적 활성화를 이루기 위하여 정광 시료를 건식으로 그리고 습식으로 미분쇄하였다. 입도분포 분석과 XRD 분석 결과, 평균 입도 크기와 결정크기는 정광 시료보다 건식-시료에서 그리고 건식-시료보다 습식-시료에서 더 작게 나타났다. SEM과 XRD 분석 결과 기계적-화학적 활성화에 의해서 습식-시료에서 비정질화 현상이 관찰되었다. Au Ag에 대한 용출실험을 티오요소 용액, 티오시안산염 용액 그리고 티오요소-티오시안산염 혼합 용액으로 각각 수행하였다. Au Ag 용출율은 정광 시료보다 건식-시료에서 그리고 건식-시료보다 습식-시료에서 더 높게 나타났다. Au Ag는 티오요소 용액에서 보다 티오시안산염 용액에서 그리고 티오시안산염 용액에서보다 티오요소-티오시안산염 혼합 용액에서 더 높게 용출되었다. 습식-시료와 티오요소-티오시안산염 혼합 용액을 적용할 때 Au Ag가 99% 이상으로 용출되었다.
        4,200원
        2.
        2012.06 구독 인증기관 무료, 개인회원 유료
        It has been documented that SPA0355 exerts anti-inflammatory effects via the inhibition of nuclear factor¬kappaB activation. In present study, we investigated the inhibitory effects of SPA0355 on periodontitis in an animal model. Periodontitis was induced by ligation of the cervix of the 1st molar in the left mandible in rats. After ligature, the rats were randomly divided into four groups and topically applied with SPA0355 (0.5, 1, and 2%) or the vehicle alone once daily for 10 days. Body weight and food intake were measured daily throughout the experimental period. At day 10 post-ligature, the infiltration of inflammatory cells and distance of the cementoenamel junction (CEJ) to the alveolar bone crest (ABC) in the distal area of ligatured tooth were estimated histopathologically. No changes in body weight or food intake were found between the control and SPA0355 groups. The degree of inflammation was decreased in all three SPA0355 application groups. A decrease CEJ-ABC distance was observed in the 0.5% and 1% SPA0355 groups. These results indicate that SPA0355 inhibits the infiltration of inflammatory cells and alveolar bone resorption and suggests its potential as a therapeutic agent for periodontitis.
        4,000원
        4.
        1997.05 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Furfurylidene acetophenone derivatives were synthesis, it was measured that nucleophilic addition made use of UV at a wide pH 1.0~13.0 range in 30% dioxane-H2O solution, 25℃. On the basis of general base catalysis, substitutent effect, confirmation of nucleophilic addition products, it was measured the reaction rate of furfurylidene acetophenone derivatives for the pH change. It may be concluded that a part was unrelated to pH and another part was in proportion to concentration of hydroxide ion: Above pH 10.0. sulfide anion adds to the double bond (Michael type addition), a part having no concern with pH, addition reaction to double bond is initiated by addition of neutral thiourea molecule. From the result of measurement the reaction rate, nucleophilic addition of furfurylidene acetophenone derivatives confirmed to the irreversible first order. Through measurement the substituent effect. It found that reaction rate was accelerated by electron attracting group. On the basis of these findings, nucleophilic addition of thiourea for the furfurylidene acetophenone derivative was proposed a fitting mechanisms.
        4,000원
        5.
        1995.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Benzoyl styrene derivatives were synthesized by Claisen-Schmidt condensation. It was measured that nucleophilic addition of thiourea for benzoyl styrene made use of ultraviolet spectrophotometery at a wide pH 1.0~13.0 range in 5% dioxane-H2O at 40℃. On the basis of general base catalysis, substitutent effect, and confirmation of addtion reaction product, the nucleophilic addtion kinetics of thiourea for benzoylstyrene derivatives were measured by pH change. It maybe concluded that a part was unrelated to pH and another part was in proportion to concentration of hydroxide ion : Above pH 10.0. It was in propotion to concentration of hydroxide ion, a part having no concern with pH was added to the neutral thiourea molecule. From the results of measurement the reaction rate and there findings, nucleophilic addition of thiourea to benzoylstyrene derivative was proposed a fitting mechanism.
        4,000원
        6.
        1993.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The kinetics of the addition of thiourea to cinnamenylisophorone derivatives(X : H, p-Br, p-CH3 m-CH3, p-OCH3) was investigated using ultraviolet spectrophotometry in 20%(v/v) dioxane-H2O at 25℃. A rate equation which can be applied over wide pH range(pH 1.0~13.0) was obtained. In order to investigate the substituent effects of cinnamenylisophorone derivatives. Hammett constant was plotted. As the result, the rate of uncleophilic addition of thiourea to cinnamenylisophorone derivatives was facilitated by electron donating group. It was found that addition of neutral thiourea which was not dissociated at the pH 1.0~9.0 was proceeded, the reaction was proceeded by addition of dissociated anion of thiourea above the pH 10.0. On the basis of this kinetic study, the reaction mechanism of nucleophilic addition of thiourea was investigated.
        4,000원
        7.
        1991.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The kinetics of the addition of 1-benzylindole-3-(p-substituted) acetophenone derivatives was investigated by ultraviolet spectrophotometery in 30% dioxane -H2O at 25℃. A rate equation which can be applied over wide pH range was obtained. The Substituent effects on 1-benzylindole-3-(p-substituted) acetophenone derivatives were studied, and addition were facilitated by electron attracting groups. On the base of the rate equation, substituent effect, and general base effect the plausible addition mechanism was proposed : Below pH 3.0, only neutral thiourea molecule was added to the carbon-carbon double bond, and in the range of pH 0.0~14.0, netural thiourea molecule and thiourea anion competitively attacted the double bond. By contrast, above pH 10.0, the reaction was dependent upon only the addition of thiourea anion.
        4,000원
        8.
        1991.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The rate constants for the addition reaction of thiourea to nitrone derivatives were determind at various pH and reaction rate equation which could be applied over a wide pH were obtained. The substituent effects and general base catalysis for the addition of thiourea to nitrone derivatives were observed. On the basis of these findings, a plausible reaction mechanism for the nucleophilic addition of thiourea to nitrone was proposed.
        4,000원
        9.
        1990.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Synthesizing octylphosphate(OTP) from phosphorus pentoxide with n-octyl alcohol, octylphosphatethiourea(OTPU) was prepared from OTP with thiourea. After flame retardant finishing OTPU to acrylic fabrics, nylon taffeta and tetron taffeta, the physical properties, such as tear strength and flame retardancy were measured. As the results of the measurement, OTPU was found to be a good flame retardant having softness using to synthetic fibers.
        4,000원
        10.
        2013.03 KCI 등재 서비스 종료(열람 제한)
        티오요소를 사용하여 삼조광업 정광으로부터 은을 친환경적으로 용출시키고자 하였다. 삼조광산의 광석은 황철석, 황동석, 방연석, 유비철석, 섬아연석 등과 같은 광석광물들로 구성되어 있다. 티오요소 용출실험에는 750℃에서 소성시킨 소성정광을 사용하였다. 다양한 실험조건으로 용출실험을 수행한 결과, 본 실험 조건 중 가장 높은 은 용출율이 나타나는 조건은 티오요소 농도 0.8 g일 때, 황산 제2철 0.425 g일 때, 그리고 용출온도 60℃일 때였다. 광액농도 10%일 때 은 용출율 91.5%를 얻었다. 그러나 고체 잔유물에 대해서 XRD 분석을 수행한 결과, 은 용출율이 가장 높은 고체 잔유물들에서 황철석, 방연석, 적철석 등이 나타났다. 이러한 결과로 미루어 볼 때 고체 잔유물에 포함된 은은 회수하지 못하고 소실될 것으로 예상된다.