• Journal of the Korean Ceramic Society
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• v.45 no.2
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• pp.99-104
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• 2008

Zeta potential, sedimentation bulk density and rheology in the dispersion system have been studied in terms of solid loading (40-55 vol%), and types of additives. Ammonium polymethacrylate, glycerol, ethoxylated acetylenic diol, and polyvinyl alcohol have been used as the dispersant, cryo-protectant, surfactant, and binder, respectively. Sedimentation density greatly increased upon adding dispersant; the effect was more pronounced with ionic alumina suspension compared with covalent silicon carbide. With further addition of cryo-protectant and surfactant to dispersant, the sedimentation density increased somewhat. The suspension viscosity generally behaviored in an opposite manner to the sedimentation density, i.e., high sedimentation gave low high-shear viscosity, indicative of low order structure formation in the suspended particles. Shear rate rheology in shear rate of $2-300\;sec^{-1}$ showed a shear thinning and its onset began at similar shear rate (${\sim}100\;sce^{-1}$), regardless of solid loading.

• Journal of Life Science
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• v.12 no.5
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• pp.584-588
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• 2002

Asymmetric enantioselective resolution system using epoxide hydrolase activity of Aspergillus niger LK was developed and operated for the production of optically pure styrene oxide. Two-phase hollow-fiber reactor system was employed for the enhanced solubility of racemic styrene oxide in organic phase and protection of epoxide hydrolase activity in aqueous phase. For the removal of phenyl-1,2-ethandiol, the inhibitor of epoxide hydrolase, cascade hollow-fiber reactor system was also developed. Chiral (S)-styrene oxide (39 mM in dodecane) could be asymmetrically resolved with high enantiopurity (> 99% ee) using these reactor system.

• Elastomers and Composites
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• v.31 no.2
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• pp.104-110
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• 1996

The polyurethane was synthesized by the reaction of polycaprolactone diol(Mw 2000), 4,4'-diphenylmethane diisocyanate and 1,4-butanediol as the chain extender. Also, the modified polyurethane polymers based on liquid polybutadiene as a part of soft segment and dimethylolpropionic acid as a chain extender, giving polyurethane with various polarity, were synthesized. The thermal, mechanical, adhesion properties and water contact angles of the polyurethanes were examined. From the result of the water contact angle, the polarity of the acid modified PU containing 6% acid content was unchanged but mechanical and adhesion properties were improved. The water contact angles on polybutadiene modified PU films were increased with increasing polybutadiene content. The mechanical properties of the polybutadiene modified PU were higher than that of acid modified PU. However, the mechanical properties were reduced as polybutadiene content increased. The result is presumably due to phase separation between hard segment and soft segment. The peel strength of the polyurethane introduced with 5wt% polybutadiene was improved about 150% than that of unmodified PU. The same as the mechanical properties, the more polybutadiene was introduced, the lower peel strength was obtained.

• Natural Product Sciences
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• v.26 no.2
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• pp.151-157
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• 2020

Extensive column chromatography separation of the MeOH extract from the aerial parts of Phyllanthus urinaria afforded seventeen compounds (1 - 17). The structures of the compounds were elucidated by physicochemical and spectroscopic methods to be 5'-β-D-glucopyranosyloxyjasmonic butyl ester (1), (+)-cucurbic acid (2), dendranthemoside B (3), boscialin 4'-O-β-D-glucoside (4), 4,5-dihydroblumenol A (5), (6R,9R)-megastigman-4-ene-9,13-diol (6), (3S,5R,6S,9R)-3,6-dihydroxy-5,6-dihydro-β-ionol (7), (6S,9R)-roseoside (8), mallophenol B (9), icariside B₅ (10), corchoinoside B (11), canangaionoside (12), 5,6-epoxy-3-hydroxy-7-megastigmen-9-one (13), icariside B₂ (14), (7E)-2β,3β-dihydroxy-megastigm-7-en-9-one (15), betulalbuside A (16), and loliolide (17). The compounds 1, and 3 - 16 were isolated for the first time from this plant. The absolute stereochemistry of compound 1 was newly determined. The isolated compounds were tested for cytotoxic activity against four human tumor cell lines in vitro using a Sulforhodamin B bioassay, but all the compounds showed weak cytotoxic activities.

• Journal of Environmental Health Sciences
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• v.28 no.2
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• pp.41-49
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• 2002

Resource recovery and recycling of materials and products including polyurethanes are viewed as a necessity in today's society. The problems of recycling polyurethane wastes has major technological, economic and ecological significance because polyurethane itself is relatively expensive and its disposal by burning is also costly. In general, the recycling methods for polyurethane could be classified as mechanical, chemical and physical. In the chemical recycling method, there ate hydrolysis, glycolysis, pyrolysis and aminolysis. This study was carried out glycolysis using new method such as sonication and catalyzed reaction. There are kinds of recycled polyols were produced by current method(glycolysis) but, this study were with catalyzed reaction and sonication as decomposers and the chemical properties were analyzed. The reaction results in the formation of polyester urethane diols and then the OH value which is determined by the quantity of diol used for the glycolysis conditions. The glycolysis rates by sonication and catalyzed reaction for the various glycols, increased as: PPG

• Environmental Mutagens and Carcinogens
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• v.25 no.3
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• pp.104-109
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• 2005

[ $7{\beta}$ ]-Hydroxycholesterol (cholest-5-ene-3, 7-diol, $7{\beta}$-OHC) showed the cytotoxicity on human cervical carcinoma cells (HeLa), $10{\mu}M$ of 50% inhibitory concentration. We evaluated $7{\beta}$-OHC as the possibility of radiation sensitizer. The combination effect of $7{\beta}-OHC\;and\;{\gamma}$-irradiation was measured using colony forming assay and flow cytometer with propidium iodide and $DiOC_6$ stained cells, respectively. The combined treatment of $7{\beta}-OHC\;and\;{\gamma}$-irradiation did not show significant enhancing effects on HeLa cells.

• Membrane and Water Treatment
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• v.8 no.1
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• pp.19-34
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• 2017

Boron exists in dilute concentrations in sea water, ground water and waste waters. Reactive liquid extraction can be used for removing boron to make the treated water suitable for drinking and irrigation, with its final concentration less than 0.5 ppm. The results of equilibrium experiments are reported on the removal of boron using 2-butyl-2-ethyl-1, 3-propanediol (BEPD as a nonionic carrier) in sunflower oil, a non-traditional solvent. The results of removal of boron from aqueous solutions in the concentration range 0.5-20 ppm are presented. It is shown that this new liquid membrane system, is able to remove boron from ground waters at their natural pH of 6-8 (without any chemical addition for pH adjustments). The removal efficiency is good when the process is upgraded to a hollow-fibre membrane contactor and approximately 45% boron can be removed in a single-stage contact. There are additional advantages of this new approach that includes reduced operational health and safety and environmental issues. The results reported here provide guidelines to the development of boron removal process using renewable, biodegradable, safe and cheap solvent system such as sunflower oil.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.317-327
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• 2009

In this study DMT(Dimethylterephthalate), NDC(Dimethyl-2, 6-Naphthalene Dicarboxylate) were used to synthesize polyester polyol which shows enhanced storage stability, improved flame retardancy, and good compressive strength. If DMT and NDC react respectively with DEG(Diethylene Glycol) which is kind of linear diol, the obtained polyester polyols tend to crystallize easily after the reaction. In case of DMT, PA(Phthalic Anhydride) which has asymmetric structure was introduced to retard the crystallization. In case of NDC, DPG(Dipropylene Glycol) which has an methyl side chain was introduced to prevent the crystallization. It was found that to introduce DPG was much more effective method to prevent the crystallization than PA. NDC and DMT were reacted together with DPG for various compositions of NDC:DMT(8:2, 6:4, 4:6 mol ratio). The obtained NDC-DMT-DPG based polyester polyol showed improved flame retardancy, and good compressive strength with increasing the content of NDC.

• Macromolecular Research
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• v.13 no.3
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• pp.212-217
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• 2005

The pyrolysis kinetics of polyurethanes synthesized from polycaprolactone diol (PCL) and diisocyanate (HDI, $H_{12}MDI$) using catalysts such as dibutyltin dilaurate (DBTDL) were studied by a thermogravimetric (TG) technique, which involved heating the sample at the rates of 10, 20 and $30^{\circ}C$/min. The effect of the kind of diisocyanate and the hard segment contents on the activation energy and reaction order were examined at conversions ranging from 1 to $100\%$. The activation energies at first increased slowly with increasing conversion. Also, differential scanning calorimetry (DSC) was used to investigate the structural differences in each polyurethane. DSC can reveal the melting behavior, in terms of the glass transition temperature ($T_g$), which is known to vary as a function of the stoichiometry and processing conditions.

• Korean Journal of Organic Agriculture
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• v.28 no.1
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• pp.95-108
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• 2020

To develop an environment-friendly fungicide for controlling tomato wilt diseases, antifungal active substance was isolated Rheum australe D. Don roots against Fusarium oxysporum f. sp. lycopersici, a pathogen of tomato wilt, in this study. Methanol extract obtained from Rheum australe roots was successively fractionated with hexane, chloroform, ethyl acetate, butanol and water. The ethyl acetate fraction, which showed the highest antifungal activity, was separated by column chromatography, and 60 subfractions were obtained. The 60 subfractions were anlayzed for antifungal activities by bioassay. The active compound was identified as 5-[(E)-2- (3-hydroxy-4-methoxyphenyl)ethenyl]benzene-1,3-diol (rhapontigenin) by NMR and GC-MS analysis. As a result of testing antifungal activity of rhapontigenin against Fusarium oxysporum, EC₅₀ of rhapontigenin was showed strong antifungal activity at 7.48 mg/L. Therefore, this study showed that the Rheum australe roots extract can be a potential candidate which is a environment-friendly fungicide against Fusarium oxysporum.