• Elastomers and Composites
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• v.59 no.1
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• pp.8-16
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• 2024

As regulations on greenhouse gas emission have strengthened globally, the demand for improved fuel efficiency in automobiles continues to rise. In response, the tire industry is actively conducting research to improve fuel efficiency by enhancing tire performance. In this study, silica-filled epoxidized natural rubber (ENR)/butadiene rubber (BR) blend compounds were manufactured according to ENR types and silica contents, and their physical properties and vulcanizate structure were evaluated. ENR-50, which has a higher epoxide content than ENR-25, exhibited stronger filler-rubber interaction, resulting in superior abrasion resistance. In addition, because of its high glass transition temperature (T_g), the wet grip performance of ENR-50 improved, even though the rolling resistance increased. Increasing the amount of silica had little effect on the abrasion resistance due to the increase in filler-rubber interaction and decrease in toughness. In addition, ENR-50 exhibited better wet grip performance; however, the rolling resistance increased. The results indicated that truck bus radial (TBR) tire tread compounds can be designed by applying ENR-50 to improve wear resistance and wet grip performance. In addition, by applying ENR-25 and reducing the silica contents improve fuel efficiency.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.135-142
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• 1999

The effects of 1 wt.% N-benzylpyrazinium hexafluoroantimonate (BPH) as a thermal latent initiator and blend compositions composed of 0, 5, 10, 20 and 40 wt.% of phenol-novolac resin to epoxy resin were investigated in terms of cure kinetics, thermal stabilities and rheological properties. Thermal latent properties of BPH were measured from the conversion as a function of reaction temperature on a dynamic DSC. This cationic BPH system turned out to be an effective thermal latent initiator in the epoxy-phenol curing system. And the increase of phenol-novolac resin concentration led to the decrease in the latent temperature and to the increase of cure activation energy ($E_a$) of the blend system. The thermal stability and activation energy ($E_t$) for decomposition, gel-time and activation energy ($E_c$) for cross-linking from rheometer increased within the composition range of 20~40 wt.% of phenol-novolac resin. This implies that the three-dimensional cross-linking may take place among hydroxyl group within phenol resin, epoxide ring within epoxy resin and BPH.

• Bulletin of the Korean Chemical Society
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• v.24 no.4
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• pp.413-420
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• 2003

A gas chromatography/mass spectrometric assay method was developed for the simultaneous determination of neutral and bacis twenty-five disruptors $(ED_S)$ in frog and fish. Afther homogenization and sonication of 5 g of sample, purification was achieves in one step with a solid phase extraction procedure using silica gelflorisl. Eluton was performed with 50mL of acetone : n-hexane (1 : 9) solution. The eluate was concentrated to approximately 10uL and dissolves with 100 uL of hexane and analyzed by GC-MS (SIM). The peaks had good chromatographic properties and the extraction of these compounds from sample also gave relatively high recoveries with small variatoins. Detection limits were 0.1 ng/g for 4-nitrotoluene, benzophenone, hexachlorobenzene, atrazine, malathion, o,p-DDT, o,p-DDT and permethrin, and 0.2 ng/g for heptachlor epoxide, γ-chlordane, α-chlordane, p,p'-DDE, p,p'-DDD, cypermethrin and fenvalerate, and 0.3 ng/g for trifluralin, metribuzin, alachlor, dieldrin and p,p'-DDT, and 0.5 ng/g for heptachlor, aldrin and parathion, and 0.7 ng/g for endrin, and 0.8 ng/g for nitrofen. The recoveries were between 33 and 109%. The method was used to analyze twenty-five frogs and forty-six fishes fishes samples caught from various regions in Korea. Benzophenone was detected at concentration of up to 17.2 ng/g in frog or fish. Heptachlor, aldrin, γ-chlordane, p,p'-DDE, p,p'-DDD, endrin and o,p-DDD were detected at concentrations of 0.7-12.5 ng/g in frog or fish. Also significant leveles of dieldrin (up to 22.5 ng/g) were observed. The developed method may be valuable to be used to the national monitoring project of EDS in biota samples.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.132-137
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• 2015

BEA-zeolite was modified by alkaline solution to introduce mesoporosity in the crystals and the homogeneous chiral Co(III) salen was immobilized in the mesopores. The dinuclear chiral Co(salen)-$GaCl_3$ catalyst immobilized on mesoporous BEA-zeolite showed high activity for the regioselective ring opening of terminal epoxides by carboxylic acids. Various chiral monoester derivatives could be synthesized with moderate enantioselectivity (47~69 ee%) from racemic epoxides through above reaction. When the chiral (S)-ECH was used as a reactant, it was efficiently resolved by carboxylic acid with a high enantioselectivity in the presence of heterogenized chiral salen catalyst, and the ring opened product afforded optically pure monoester epoxide (R)-GB (up to 98 ee%) through the ring closing in the basic solution by elimination of HCl. The heterogeneous catalyst could be fabricated easily, and the catalytic activity was retained for several times reuse without any further regeneration step.

• Korean Journal of Environmental Agriculture
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• v.1 no.2
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• pp.83-88
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• 1982

Residues of some organochlorine pesticides $({\alpha}-BHC,\; {\gamma}-BHC,$ heptachlor, aldrin, heptachlor epoxide, dieldrin, p,p'-DDD, p,p'-DDT) in the cultivating soils (53 samples) were evaluated in the suburbs of Gwangju-City, Jeollanam-Do. Results obtained are summarized as follows. 1) Seven organochlorine pesticides were detected in more than 60% of the sample soils except dieldrin. In particular, ${\alpha}-BHC$ was detected in almost all soil samples and residue level of p,p'-DDT was higher than that of the others. 2) Detection frequencies and residue levels of up-land soil were higher than those of paddy soil. 3) There was no difference in the organochlorine residue levels between land-readjusted paddy soil and natural paddy soil.

• Journal of Physiology & Pathology in Korean Medicine
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• v.17 no.6
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• pp.1448-1452
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• 2003

The water extract of Scutellariae radix was treated to rat and the primary culture of hepatocytes, and the expressions of several glutathione S-transferase (GST) isozymes and the activity of GST Yc1/2 were investigated by Western blot and by the use of HPLC. The results were obtained as follows: The water extract of Scutellariae radix did not induce the expressions of cytosolic GST Ya and GST Yp in rat livers. But, the extract increased the expression of cytosolic GST Yc1/2 to 2-4 fold higher than control. The expression of GST Yc1/2 in the primary culture of rat hepatocytes was induced by the water extract of Scutellariae radix in a dose-dependent manner, reaching 21-fold over control with 50 ㎍/㎖ treatment. The induction of the expression of GST Yc1/2 in rat livers increased the formation of AFB₁-glutathione conjugate from AFB₁-8,9-epoxide which was made in the metabolism of AFB₁.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.5
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• pp.756-762
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• 2006

The objective of this study was to define the effects of various cooking and re-heating methods (pan roasting, steaming, oven grilling and micro-waving) on the cholesterol and formation of cholesterol oxidation products in beef loin during storage at $4^{\circ}C$. Raw samples showed lower total cholesterol content than cooked products sampled during storage for 6 d. The following cholesterol oxidation products (COPs) were separated by gas chromatography: $7{\beta}$-hydroxy cholesterol, $20{\alpha}$-hydroxy cholesterol, 25-hydroxy cholesterol, cholestane-$3{\beta}$, $5{\alpha}$, $6{\beta}$ triol (triol), ${\alpha}$-epoxide and 7-ketocholesterol. Total amounts of COPs/cholesterol at 0 d were 0.74, 0.63, 0.76, 1.23 and 0.83% for the raw sample, pan roasting, steaming, oven grilling and micro waving methods, respectively. After 6 d storage almost of the samples had higher content of total COPs than at 0 and 3 d; the lowest (0.55%) COPs was found in the steaming cooking and re-heating method. The highest (5.96%) of COPs was found in the pan roasting cooking and re-heating method after 6 d storage. In conclusion, the concentration of total cholesterol and cholesterol oxidation of beef loin were increased as a consequence of cooking and re-heating methods. Steaming and micro-waving methods showed the lowest of cholesterol oxidation products under refrigerated storage for 6 d. However, each cooking and re-heating method had its own distinctive cooking effects.

• The Korean Journal of Pesticide Science
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• v.9 no.2
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• pp.181-184
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• 2005

The heterocyclic PPO inhibitor compounds have been studied due to their potent herbicidal effects without toxic to human and animals. We have designed and synthesized 4,5,6,7-tetrahydroindazole, maleimide, and tetrahydrophthalimide compounds carrying diverse epoxide substituents at 5- position of the phenyl group. Their herbicidal activities were evaluated under submerged paddy conditions. These results showed that 4,5,6,7-tetrahydroindazole compounds gave potent herbicidal activities especially to ECHOR, MOOVA, and CYPSE at a relatively low rate of 16 g/ha and improved tolerance on rice compared to S-275 as a standard herbicide in this experiment.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.603-608
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• 2005

The molded macroporous poly (glycidyl methacrylate-co-ethylene glycol dimethacrylate) rods produced by a facile molding process were polymerized in situ within a tubular mold, chromatographic column ($4.6{\times}100mm$) by free radical polymerization. It was complemented by epoxy derivatized monolithic column and chemical modification of the epoxide groups with the sulphuric acid. By variation of the polymerization conditions, such as the ratio of the monomers, the porogen (pore generating material), and the temperature, the pore size could be varied, so the retention time of the samples may be adjusted. For the mixture of caffeine and tryptophan in the prepared monolithic column, the influences of polymerization material compositions to the efficiency, selectivity, and resolution of the monolithic column were investigated.

• Composites Research
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• v.17 no.6
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• pp.37-43
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• 2004

To determine the effect of chain length and chemical structure of linear amine curing agents on thermal and mechanical properties, a standard bifunctional linear DGEBF epoxy resin was cured with EDA and HMDA having amine group at the both ends of main chain in a stoichiometrically equivalent ratio in condition of preliminary and post cure. From this work, the effect of linear amine curing agents on the thermal and mechanical properties is significantly influenced by numbers of carbon atoms of main chain. In contrast, the results show that the DCEBF/EDA system having two carbons had higher values in the thermal stability, density, shrinkage (%), grass transition temperature, tensile modulus and strength, flexural modulus and strength than the DGEBF/HMDA system having six carbons, whereas the DGEBF/EDA cure system had relatively low values in maximum ekothermic temperature, maximum conversion of epoxide, thermal expansion coefficient than the DGEBF/HDMA cure system. These findings indicate that the packing capability (rigid property) in the EDA structure affects the thermal and mechanical properties predominantly. It shows that flexural fracture properties have a close relation to flexural modulus and strength.