• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.139-145
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• 2005

Artificial neural networks (ANNs), for a first time, were successfully developed for the modeling and prediction of solvent effects on rate constant of [2+2] cycloaddition reaction of diethyl azodicarboxylate with ethyl vinyl ether in various solvents with diverse chemical structures using quantitative structure-activity relationship. The most positive charge of hydrogen atom (q$^+$), dipole moment ($\mu$), the Hildebrand solubility parameter (${\delta}_H^2$) and total charges in molecule (q$_t$) are inputs and output of ANN is log k$_2$ . For evaluation of the predictive power of the generated ANN, the optimized network with 68 various solvents as training set was used to predict log k$_2$ of the reaction in 16 solvents in the prediction set. The results obtained using ANN was compared with the experimental values as well as with those obtained using multi-parameter linear regression (MLR) model and showed superiority of the ANN model over the regression model. Mean square error (MSE) of 0.0806 for the prediction set by MLR model should be compared with the value of 0.0275 for ANN model. These improvements are due to the fact that the reaction rate constant shows non-linear correlations with the descriptors.

• 대한화학회지
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• 제40권6호
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• pp.415-419
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• 1996

수소결합, 유전효과 그리고 입체효과는 케톤의 카르보닐 신축진동을 결정하는 요인이 된다. 케톤의 카르보닐 신축진동은 다양한 용매에서 케톤의 농도변화에 영향을 받는다. 비극성용매에서 카르보닐 신축진동은 케톤의 부피%가 증가함에 따라 낮은 파수로 이동하고 극성용매에서는 높은 파수로 이동한다. 용매 아세토니트릴에서 카르보닐 신축진동은 dimethyl ketone을 제외하고 케톤의 부피%가 증가함에 따라 높은 파수로 이동한다. 용매의 극성이 증가할수록 카르보닐 신축진동은 낮은 파수로 이동하고 혼합용매 $CHCI_3CCI_4$에서 부피%가 증가할수록 낮은 파수로 이동한다.

• Bulletin of the Korean Chemical Society
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• 제18권10호
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• pp.1090-1093
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• 1997

The solvent effects on the isotropic NMR shifts in conformationally rigid ligands such as quinuclidine, pyridine, and 4-aminopyridine coordinated to the paramagnetic polyoxometalate, [SiW11CoⅡO39]6- (SiW11Co), are reported. For these complexes the ligand exchange is slow on the NMR time scale and pure 1H NMR signals have been observed at room temperature. The signals for the SiW11Co complexes are shifted upfield whe dimethyl sulfoxide-d6 (DMSO) is added to a D2O solution. The isotropic shifts are separated into contact and pseudocontact contributions by assuming that the contact shifts are proportional to the isotropic shifts of the same ligands coordinated to [SiW11NiⅡO39]6-. It is shown that both the contact and pseudocontact shifts decrease (the absolute values of the pseudocontact shifts increase), when D2O is replaced by DMSO. It is suggested that D2O, a strong hydrogen bond donor, withdraws electron density from [SiW11CoⅡO39]6-, increasing the acidity of the cobalt ion toward the axial ligand. When D2O is replaced by DMSO, the acidity of the cobalt ion in SiW11Co decreases, weakening the Co-N bond. Then both the contact and pseudocontact shifts are expected to decrease in agreement with the observed solvent effects.

• 한국식품과학회지
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• 제29권6호
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• pp.1222-1227
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• 1997

본 연구는 기존의 HPLC방법과는 달리 고정상과 이동상이 모두 액상으로 구성되어 분리하고자 하는 물질의 활성을 상실하지 않고 비교적 높은 순도로 분리, 정제할 수 있는 HSCCC 방법을 이용하여 인체에 유효한 약리작용을 나타내는 생리활성 물질을 분리하기 위한 기초 연구로써 수행 하였다. HSCCC의 운용변수에 따른 분리 효율을 알아보기 위하여 용매시스템의 물리화학적 특성이 생리활성 물질의 분리에 미치는 영향을 알아보기 위하여 용매시스템의 pH, KCl의 농도 및 극성에 따라 분리효율에 미치는 영향을 알아보았다. 용매시스템의 pH가 2.0에서 10.0으로 증가할수록 컬럼내 고정상의 유지율은 각각 73.8%에서 68.9%로 감소하는 경향을 나타내었다. 용매시스템의 상하층부 사이의 계면장력은 계속증가 하여 pH 8.0에서 최대로 증가한 후에 pH 10.0에서 감소하였다. 용매시스템의 pH에 따른 ginkgo flavonoid 표준품의 분획계수는 pH가 증가함에 따라 증가하였으며 특히 quercetin의 경우 pH 10.0에서 크게 증가하여 용매시스템의 pH를 적절히 조절하여 분리하고자 하는 물질의 분획계수를 쉽게 조절할 수 있음을 알 수 있었다. 용매시스템의 염농도가 HSCCC의 분리효율에 미치는 영향을 알아본 결과 KCl의 농도에 따른 컬럼내 고정상 유지율 변화 및 용매시스템의 계면장력에는 크게 영향을 미치지 않았다. 은행잎 flavonoid 표준품에 대한 분칙계수는 KCl의 농도가 변화함에 따라서 약간의 변화를 나타내었다. 용매시스템의 극성에 따른 분획계수의 변화는 blending solvent인 methanol 함량의 증가로 인하여 용매시스템의 극성 차이가 감소함에 따라 상하층부에 대한 물질의 친화성 차이가 감소하여 분획계수 값이 1에 근접하는 경향을 나타내었다.

• 한국수소및신에너지학회논문집
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• 제25권3호
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• pp.305-310
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• 2014

This study examined the morphological changes in lithium surface immersed in 1mol $dm^{-3}$ (M) $LiPF_6 $ dissolved in propylene carbonate (PC) containing different 1,2-dimethoxyethane (DME) concentrations as a co-solvent. A passivation film was formed on the surface of lithium metal by electrolyte decomposition. The passivation film formation reactions were significantly affected by the amount of co-solvent, DME, in electrolyte solution. A stable film was obtained from the 1 M $LiPF_6 $ / PC:DME (67:33) solution in which lithium electrode showed good electrochemical performances. Atomic force microscope (AFM) and electrochemical impedance spectroscopy (EIS) results revealed that there were no direct correlations between changes in the surface morphology of lithium metal and the resistance behavior of its passivation film.

• 생명과학회지
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• 제5권4호
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• pp.155-161
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• 1995

The effects of substrate concentration, enzyme concentration, reaction temperature, and water content were investigated in intramolecular esterification. This study used cyclohexane as organic solvent, power lipase as enzyme, and benzyl alcohol and octanoic acid as substrate. The initial reaction rate was found to be proportional to enzyme concentration; followed Michaelis-Menten equation for octanoic acid; and was inhibited by benzyl alcohol . The observed initial reaction rate first increased, then decreased with increasing reaction temperature, giving rise to the maximum rate at 20$\circ$. The drop in the reaction rate at higher temperature was to partition equilibrium change of substrate between organic solvent and hydration layer of enzyme molecule in addition to the deactivation by enzyme denaturation. Water layer surrounding enzyme molecule seemed to activate in organic solvent and the realistic reaction was done in the water layer. In the enzymatic reaction in organic solvent, the initial reaction rate was influenced by partition quilibrium of substrate, so the optimum condition of substrate concentration, enzyme concentration, reaction temperature, and water content would give a good design tool.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.307-307
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• 2006

The reduction behavior of silver ions to silver nanoparticles is an important research topic in polymer/silver salt complex membranes for facilitated olefin transport, because it has a significant effect on the long-term stability of membrane performance. In this study, the effects of solvent on the formation of silver nanoparticles and long-term membrane performance in polymer/silver salt complex membrane were investigated. This effect was assessed for the complexes of poly(N-vinyl pyrrolidone) $(PVP)/AgBF_{4}$ with the use of ionic liquid (IL), acetonitrile (ACN) and water as a solvent. Membrane performance test shows that long-term stability is strongly dependent on the kind of solvent and arranged: IL > ACN >> water.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2002년도 춘계 국제 학술대회
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• pp.1.1-2
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• 2002

Ultimate objective of industrial hygiene is the prevention of health impairment that may result from exposure to chemicals at workplaces. This implies the definition of permissible levels of exposure, that is, levels that according to the present status of knowledge are estimated to cause no adverse health effects during the lifetime of the workers, and the regular assessment of the possible health risk associated with exposure by comparing the current or the integrated exposure with the permissible exposure limits. Workers in solvent thinner-using occupation environment might be highly exposed to VOCs(volatile organic compounds) because solvent thinner has been used extensively such as painting, spraying, degreasing, coating and so on in Korea. The purpose of this study was to recognize, evaluate and propose the alternative control the VOCs from solvent thinner-using workplace.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2488-2492
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• 2010

A method is described for the determination of the Po nuclides in a water sample. After the Po nuclides were purified from interfering elements in a water sample using a manganese dioxide precipitation followed by a solvent extraction method, the Po nuclides were deposited onto the silver plate. A large volume of the water sample was effectively pretreated with manganese dioxide precipitation method. To determine the optimum conditions for plating Po, the effects of the pH, volume, temperature and time on the Po deposition were investigated in hydrochloric acid solution. The investigated determination method of Po nuclides with solvent extraction was applied to a tap water sample.

• Archives of Pharmacal Research
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• 제23권4호
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• pp.385-390
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• 2000

To demonstrate the effect of formulation conditions on the controlled release of protein from poly(lactide-co-glycolide) (PLGA) microspheres for use as a parenteral drug carrier, ovalbumin (OVA) microspheres were prepared using the W/O/W multiple emulsion solvent evaporation and extraction method. Methylene chloride or ethyl acetate was applied as an organic phase and poly(vinyl alcohol) as a secondary emulsion stabilizer. Low loading efficiencies of less than 20％ were observed and the in vitro release of OVA showed a burst effect in all batches of different microspheres, followed by a gradual release over the next 6 weeks. Formulation processes affected the size and morphology, drug content, and the controlled release of OVA from PLGA microspheres.