http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 주제어 : 반응성-선택성 (검색결과 6 건)
-
알코올-물 혼합용매계에서 4-치환된 벤질 유도체의 반응성-선택성에 대한 반응속도 모델
For solvolyses of various benzyl substrates in ethanol-water (EW) and methanol-water (MW) mixtures, product selectivities (S) are reported for chlorides at 75 ˚C defined as follows using molar concentrations: S = ([ether product]/[alcohol product]) x ([water]/[alcohol solvent]). The results support earlier evidence that solvolyses of 4-nitrobenzyl substrates are S_(N)2 processes, which are not susceptible to mechanistic changes over the whole range of solvents from water to alcohol. S values at 25 and/or 45 ˚C in EW and MW, and additional kinetic data including kinetic solvent isotope effects (KSIE) are reported for solvolyses of 4-nitrobenzyl mesylate and tosylate. A kinetic model, explaining both rates and product, is proposed; a general medium effect due to solvent polarity is combined in one parameter with solvent effects on the nucleophilicity of the water and alcohol molecules acting as nucleophiles in S_(N)2 reactions. According to this model, as alcohol is added to water the rate of reaction decreases due to a decrease in solvent polarity, but the nucleophilicity of water increases relative to alcohol. The availability of experimental rate and product data over the whole range of solvent compositions from alcohol to water, reveals limitations of alternative approaches using activities.
-
-
-
-
이재웅 Graduate School, Yonsei University 2024 국내석사
In this study, we report on the highly stable and sensitive hydrogen sensing properties of the Bimetallic Catalyst Hydrogen Sensor using PdAg-coated SnO2 nanorod arrays and post heat treatment has been investigated. In contemporary society, means of transportation using fossil fuels have problems in terms of environmental contamination, fuel capacity limits or energy conversion efficiency. To solve these problems, various types of renewable energies have been studied, but hydrogen gas (H2) is the center of attention as one of the most promising alternative energy. However, Hydrogen gas has the disadvantage of exploding at concentrations above 4% in the atmosphere. Therefore, a hydrogen sensor capable of precise and fast detection is required to Hydrogen Fuel Cell Vehicle (HFCV). In this study, the PdAg-coated SnO2 nanorods (PdAg-SnO2 NRs) were fabricated by glancing angle deposition (GLAD) method and post heat treatment. Metal-oxide semiconductor (MOS)-based sensors using Palladium catalyst are one of the promising candidates because of low detection limit and high response. However, due to the α-β phase transition of Pd, the performance decreases and the concentration discrimination power disappears above a certain concentration. These proeprties suggest that the usage of a single catalyst, Pd, shows the limits of the hydrogen concentration discrimination. In order to obtain a fast response time and reliable hydrogen concentration distinction, the bimetallic catalyst PdAg was adopted to form a capped morphology on the nanorods through interfacial diffusion while forming a sequential layered morphology. The resistance after hydrogen reaction (Rg) of PdAg coated-SnO2 NRs showed a fast response and good stability also in terms of long-term stability and repeatability test. In addition, it can be driven sufficiently at an operating temperature of 80 ℃ or more, the optimum temperature for operation at low temperatures is 80 ℃. In conclusion, the PdAg-SnO2 NRs hydrogen sensor showed excellent concentration distinction for 1 ppm – 4 % H2 and fast response (~2 s) for 1 % H2 with an optimal operating temperature of 80 ℃. This study will suggest a direction for improving hydrogen gas sensing through catalyst reforming or alloying, making it possible to apply it to applications that require actual wide range of hydrogen concentration measurement. 본 논문에서는 팔라듐 실버가 코팅된 산화주석 나노막대 어레이를 이용한 이종금속 촉매 수소 센서의 매우 안정적이고 민감한 수소 감지 특성과 열처리 후의 수소 감지 특성을 연구된다. 현대 사회에서 화석 연료를 사용하는 운송 수단은 환경 오염, 연료 저장량 한계 또는 에너지 변환 효율 측면에서 문제가 있다. 이러한 문제를 해결하기 위해 다양한 종류의 재생에너지가 연구되고 있는데, 그 중 수소가스가 가장 유망한 대체에너지로 주목받고 있다. 하지만 수소 가스는 대기 중 4 % 이상의 농도에서 폭발하는 단점이 존재해 수소연료전지차의 경우 정밀하고 빠른 감지가 가능한 수소 센서가 필요하다. 본 연구에서는 경사각 증착법을 통해 팔라듐 실버가 코팅된 산화주석 나노막대 (Pd/Ag/Pd-SnO2 NRs)를 제작하고 후열처리 공정을 통해 제작한다. 팔라듐 촉매를 사용하는 금속 산화물 반도체(MOS) 기반 센서는 검출 한계가 낮고 반응성이 높아 유망한 후보 중하나이다. 그러나 팔라듐의 α – β 상전이로 인해 일정 농도 이상에서는 성능이 저하되고 농도 구분력이 사라지는 단점이 있다. 이러한 특성은 단일 촉매인 팔라듐을 사용하는 것이 수소 농도 판별의 한계를 보여준다는 것을 시사한다. 빠른 반응 속도와 신뢰성 있는 수소 농도 구분을 위해 이종금속 촉매인 팔라듐 실버를 채택하여 계면 확산을 통해 나노막대에 캡 형상을 형성하면서 순차적으로 층상 구조를 형성하는 방법을 사용했다. 팔라듐 실버가 코팅된 산화주석 나노막대의 수소 반응 후 저항(Rg)은 장기 안정성 및 반복성 테스트에서도 빠른 반응과 우수한 안정성을 보인다. 또한 80 도 이상의 작동 온도에서도 충분히 구동이 가능하며, 저온에서 구동하기 위한 최적 온도는 80 도이다. 결론적으로, 팔라듐 실버 산화주석 나노막대 수소 센서는 0.1 – 4 % 수소 농도에서도 우수한 농도 구분 능력을 보이며, 1 % 수소 농도에서는 1.5 초 이내의 빠른 응답을 보이며, 최적 작동 온도는 80 도로 나타났다. 이 연구는 촉매 개질이나 합금화를 통해 수소 가스 센싱을 개선할 수 있는 방향을 제시하여 실제 고농도 수소 측정이 필요한 응용 분야에 적용할 수 있을 것으로 기대된다.
-
in silico Prediction of Regioselectivity in Cytochrome P450 Mediated Metabolism
Cytochrome P450s are involved in the metabolism of a wide variety of xenobiotic chemicals. Early prediction of metabolites of xenobiotic compounds is crucial for cost efficient drug discovery and development. We developed a new combined model, MLite, for the prediction of regioselectivity in cytochrome P450 3A4, 2C9, and 2D6 mediated metabolism. In the model, the ensemble catalyticphore-based docking method was implemented for the accessibility prediction and the reactivity estimation method and ATDL descriptor were used for the reactivity prediction.Diverse CYP2C9, 2D6, and 3A4 substrates were used in the prediction of regioselectivity, aliphatic hydroxylation, N-dealkylation, O-dealkylation, aromatic hydroxylation, and electron transfer reaction. The metabolic reaction informations were collected for 296 CYP3A4 substrates, 98 CYP2C9 substrates and 129 CYP2D6 substrates from public literatures. All data were divided as training set and validation set for the ensemble catalyticphore-based docking method. MLite predicted correctly about 74.7%, 96.0%, and 85.3% of the first three sites in the ranking list on the validation set of CYP3A4, CYP2C9, and CYP2D6, respectively. This predictability is comparable with that of another combined model, MetaSite, and recently published QSAR model proposed by Sheridan et al. MLite also offer information about binding configurations of substrate-enzyme complex. This may be useful in drug modification by the structure-based drug design.
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
