• Polymer(Korea)
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• v.26 no.1
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• pp.9-17
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• 2002

The free radical bulk copolymerizations of perfluoroalkylethyl acrylate(FA) containing perfluoro group ($CF_3(CF_2)_nCH_2CH_2$-; n=5, 7, 9, 11) with styrene were conducted at $60^{\circ}C$ using AIBN as an initiator. Reactivity ratios($r_1$, $r_2$) were determined from monomer feed compositions and the NMR spectroscopically measured copolymer compositions using Kelen-Tudos method. The structures of copolymers were characterized with FT-IR and $^1H-NMR$ analysis. Their thermal properties investigated with DSC and TGA were decreased with increasing the content of fluorinated acrylate in the copolymer. Their surface free energies were calculated with measuring contact angles of the copolymers and PMMA blends with a small amount of them.

• Journal of the Korean Chemical Society
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• v.19 no.1
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• pp.53-64
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• 1975

The polymerization of methyl methacrylate initiated by cobalt(II) chloride in tetrahydrofuran has been studied. The conversion was increased liearly with polymerization time at initial stage of 6${\sim}$7% conversion and then the rate of polymerization was slightly reduced, and after that the autoacceleration was observed. The rate of polymerization was increased with the concentration of cobalt(Ⅱ) chloride, but at the concentration of cobalt(II) chloride higher than $3.4{\times}10^{-4}$ mole/l the rate of polymerization was decreased. The rate of polymerization was dependent on the 1.38 power of the concentration of methyl methacrylate. The effect of the radical inhibitor DPPH was observed and the inhibition time was increased with the concentration of DPPH. The apparent overall activation energy was calculated to be 13.2 kcal/mole. In the copolymerization of methyl methacrylate ($M_1$) and styrene ($M_2$), the monomer reactivity ratio was found to be $r_1$ = 2.35, $r_2$ = 0.78. From the above results. the initiation mechanism of polymerization was discussed and it was considered that the polymerization proceeds mainly via diradical mechaism.

• Journal of the Society of Disaster Information
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• v.9 no.3
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• pp.324-331
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• 2013

Epoxy asphalt concrete is used to reduce dead load and to increase durability on long-span steel bridge overlay. The strength development properties of epoxy asphalt concrete are affected by time and temperature because epoxy asphalt is two-phase reactive materials. The strength development of epoxy asphalt concrete should be predicted precisely to decide traffic opening time. Based on this background in mind, the prediction model for traffic opening time for epoxy asphalt pavement was proposed in this research. The developed model using nonlinear curve fitting revealed R2 value of 0.943 while the R2 value of the existing model using chemical kinetics was 0.806. An improved precise prediction result is to be obtained when the prediction model uses accurate temperature data of pavement.

• Polymer(Korea)
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• v.35 no.6
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• pp.526-530
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• 2011

Furan-2,5-dicarboxylic acid (FDCA) was synthesized by $KMnO_4$ oxidation of 2,5-dihydroxymethylfuran(DHMF) derived from biomass. Polyesters were synthesized by esterification and polycondensation of FDCA with various diols(ethane-1,2-diol, propane-1,3-diol, butane-1,4-diol, hexane-1,6-diol, decane-1,10-diol). The composition of polyesters was characterized by using $^1H$ NMR. Thermal properties of the polyesters were characterized by DSC and TGA. Intrinsic viscosities(IV) of the polyesters were measured to be 0.78~1.2 dL/g comparable with IV of commercial poly(ethylene terephthalate)(PET). As the chain lengths of diols increased, Young's modulus and strength decreased and elongation-to-break generally increased. Young's modulus and strength of the polyesters were measured to be 3551 MPa and 103 MPa, respectively, comparable with commercial PET.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.22 no.2
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• pp.65-70
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• 1977

The effects of regional climatic factors on wheat quality were discussed. The most important climatic factor on wheat quality during the ripening period of wheat was air temperature during the ripening period of wheat. The protein content and sedimentation value were higher in northern parts of Korea compared to southern parts in Korea. The varietal effects of ripening temperature on protein content and sedimentation value of wheat were varied in nine tested varieties.

• Microbiology and Biotechnology Letters
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• v.15 no.2
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• pp.122-128
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• 1987

Lipases from Candida rogosa and Rhizopus arrhizus were immobilized by entrapment with photo-crosslinkable resin prepolymer for the study of fat splitting and interesterification in isooctane-two phase system. Dioctylsulfosuccinate was selected as the most suitable surfactant during the immobilization. Lipase entrapped with hydrophobic photo-crosslinkable resin prepolymer(ENTP-3000) exhibited the highest activity, whereas lipase entrapped with hydrophilic gel(ENT-4000) was more stable in organic solvent. As the degree of hydrophobicity of the immobilization matrix was increased, Vm(app) of the lipase entrapped was increased, but Km(app) was approximately constant. While the optimum pH of the lipases entrapped on hydrophilic gel (ENT-4000) were around pH 7.0 for Candida lipase and Rhizopus lipase, the reaction rate of the lipases entrapped on hydrophobic gel were less dependent on pH variations for short reaction time. However, for longer reaction time, the lipnses from C. rugosa and R. arrhizus entrapped on hydrophobic gel yielded maximum rate at pH 6.0 and 6.5, respectively, Entrapment method endowed the lipase with thermal stability.

• KSBB Journal
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• v.15 no.6
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• pp.630-634
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• 2000

Chiral epoxides are useful chiral synthons in organic synthesis, and various biological methods have been investigated for their production. In this work, the enantioselective resolution of racemic styrene oxide was investigated using Aspergillus niger sp. for the production of optically pure (S)-styrene oxide. The enantioselectivity and initial hydrolysis rates of the racemic substrate were highly dependent of the pH, temperature, and the volume ratio of cosolvent. Experimental sets of pH, temperature, and the volume ratio of cosolvent were investigated using a central composite experimental design, and reaction conditions were optimized by response surface analysis. The optimal conditions of pH, temperature, and the volume ratio of cosolvent were determined to be 7.78, $28.32^{\circ}C$, and 2.4%(v/v), respectively, and optically pure (S)-styrene oxide (>99% ee) was obtained at 35% yield using this microbial enantioselective hydrolysis reaction.

• The Korean Journal of Nuclear Medicine Technology
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• v.22 no.1
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• pp.51-54
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• 2018

Purpose $^{18}F-THK5351$ is the newly developed PET probe for tau imaging in alzheimer's disease. The purpose of study was to establish the automated production of $^{18}F-THK5351$ on a commercial module. Materials and Methods Two different approaches were evaluated for the synthesis of $^{18}F-THK5351$. The first approach (method I) included the nucleophilic $^{18}F$-fluorination of the tosylate precursor, subsequently followed by pre-HPLC purification of crude reaction mixture with SPE cartridge. In the second approach (method II), the crude reaction mixture was directly introduced to a semi-preparative HPLC without SPE purification. The radiosynthesis of $^{18}F-THK5351$ was performed on a commercial GE $TRACERlab^{TM}$ $FX-_{FN}$ module. Quality control of $^{18}F-THK5351$ was carried out to meet the criteria guidelined in USP for PET radiopharmaceuticals. Results The overall radiochemical yield of method I was $23.8{\pm}1.9%$ (n=4) as the decay-corrected yield (end of synthesis, EOS) and the total synthesis time was $75{\pm}3min$. The radiochemical yield of method II was $31.9{\pm}6.7%$ (decay-corrected, n=10) and the total preparation time was $70{\pm}2min$. The radiochemical purity was>98%. Conclusion This study shows that method II provides higher radiochemical yield and shorter production time compared to the pre-SPE purification described in method I. The $^{18}F-THK5351$ synthesis by method II will be ideal for routine clinical application, considering short physical half-life of fluorine-18 ($t_{1/2}=110min$).

• Korean Journal of Food Science and Technology
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• v.29 no.2
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• pp.309-313
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• 1997

Maillard reaction products (MRPs) added into a culture and the resultant bacterial growth were investigated using response surface methodology. The coefficients of determination $(R^{2})$ of response surface regression equations for bacteria were 0.9544 and 0.9578 in Bacillus subtilis and Bacillus natto, respectively. The MRPs produced at higher reaction temperature and for longer reaction time showed greater antimicrobial effect for Bacillus subtilis. Especially, the MRPs produced at temperature above $150^{\circ}C$ for 8 to 12 hrs showed the strongest antimicrobial effect. The MRPs produced at lower reaction temperature and for shorter reaction time showed greater microbial growth effect for Bacillus natto, but those produced at the reaction temperature higher than $160^{\circ}C$ showed the greatest antimicrobial effect. In the ridge analysis, the growth of Bacillus subtilis was the most significantly inhibited in the presence of MRPs prepared at $159.10^{\circ}C$ and pH 12.21 for 9.67 hrs, and the growth of Bacillus natto was the most significantly inhibited in the presence of MRPs prepared at $169.94^{\circ}C$ and pH 9.66 for 9.22 hrs.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.1
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• pp.43-50
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• 2012

The safety of cosmetics or cosmetic ingredients on human skin is generally evaluated by visual assessment but some early subtle skin changes may not be noticed by the naked eyes. Thus, the present study was conducted to detect skin reactions induced by mildly irritating cosmetic ingredients by using a laser Doppler perfusion imager (LDPI) method that measures blood flow, a $Vapometer^{(R)}$ that measure strans epidermal water loss (TEWL), and a spectrophotometer that measures the skin color as the erythema values ($a^*$). Visual assessment showed that all tested oils and humectants except propylene glycol belong to the low skin irritation ranges (grades 0+ to 2.9+) while all tested surfactants and propylene glycol belong to the moderate-to strong-skin irritation ranges (grades 3+ to 5+). Among three instrumental methods, TEWL assessment appeared to be more sensitive than spectrophotometric or LDPI method and suitable for the detection of subtle skin response invisible to the naked eye (grades 0+ to 2.9+). Skin reactions of grade 3+ to 5+ could be detected by all three instrumental methods. In conclusion, the current study suggested that the sub-clinical skin reactions due to mild irritants contained in cosmetics can be best assessed by TEWL measurements.