• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.632-637
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• 2017

The vehicle lubricant occupies upto 35% in a total lubricant market and engine oil occupies upto 77% in the vehicle lubricant market in Korea. A suitable quality management of the circulating engine oil is necessary for driver and engine protection. But, KS and synthetic engine oil products (involved over 30% synthetic oil) are exempt to any quality management under Petroleum and Alternative Fuel Business Act. It is also known that synthetic oils such as PAO (poly alpha olefin) have excellent properties and performance like anti-wear, varnish control and oxidation stability than those of mineral oils. For this reason, PAO has been used for an engine oil, rotary screw and reciprocating compressor in addition to heavy duty and other extreme service applications. In this study, our research group analyzed the chromatogram pattern for the mineral oil, PAO and mineral oil involved a typical ratio of PAO using SIMDIST (simulated distillation). In the SIMDIST chromatogram, the mineral oil showed a broad peak, while PAO showed a sharp typical peak. Also the oil with a large viscosity grade exhibited a long retention time due to the heavy molecular weight and high boiling point. In particular, the blended mineral oil with 20% PAO sample showed a distinctly different pattern compared to that of using the conventional mineral oil. For monitoring PAO contents in distributing engine oils, we analyzed the SIMDIST for 27 kinds of engine oils which were popularly sold in Korea. The analytic results indicate that all kinds of engine oils showed that PAO contents were below 20% in engine oil products. Moreover, the PAO titled product was found to have a small amount of PAO. Thus, we conclude that the related laws for the proper quality management of synthetic oils are needed to be established.

• Journal of Sericultural and Entomological Science
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• v.41 no.1
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• pp.41-47
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• 1999

Silk fibroin dissolved in highly concentrated calcium chloride and ethanol mixture aqueous solution turned into gel under suitable conditions. Preparation conditions and properties of gel were investigated as a function of parameters such as pH of solution, fibroin concentration, glycerol concentration and molecular weight. When pH of silk fibroin aqueous solution was near the isoelectronic point(pH 3.9~4.0), gelation occurred rapidly and strength of gel was stonger than that of pH-unadjusted due to electrostatic repulsion decrease between silk fibroin macromolecules. As concentration of silk fibroin and glycerol was higher, gelation occurred more rapid. FT Infra-red spectra of freeze-dried fibroin gel showed that gelation was derived by intermolecular anti-parallel ${\beta}$-sheet structure formation. In addition to, it was found that white-precipitate occurred instead of gelation when aqueous silk fibroin was treated by enzyme(flavouzyme), however, after flavouzyme-treated silk fibroin aqueous solution was centrifugated gelation occurred instantly. The results of differential scanning thermal analysis and infra-red spectroscopy showed that thermal stability and crystallinity of enzyme-hydrolyzed fibroin are superior to those of unhydrolyzed fibroin.

• Journal of the Korean Applied Science and Technology
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• v.29 no.1
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• pp.108-115
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• 2012

Archaeological waterlogged woods found under the sea, in lakes, or in swamp environments are generally weak and fragile. If waterlogged wood materials were taken out of the water and left without modification, they would collapse and lose their original dimensions completely. Conservation is performed to replace the water with chemical agents and to give dimensional stabilization and durability. EDTA and PEG are the most commonly used in the preservation of wood. pH control-precipitation method is used for recovery of EDTA from waste fluid of archeological waterlogged wood conservation treatment. The black substance is eliminated from wood as Fe-EDTA complex are formed and EDTA is separated and precipitated from Fe-EDTA complexes at pH 2.68 or less. The result of analysis of the precipitated products and the commercial EDTA by FT-IR and FE-SEM showed that precipitated product by pH adjusted was not a type of Fe-EDTA complex, but pure EDTA. Waste fluid produced in PEG treatment shows the black color and has an offensive odor by organic matter extracted from wood. Color of waste fluid is decolored with oxidation reaction by peroxy hydrate. In FT-IR and SEM-EDX of PEG after freeze-drying process, no significant change of functional groups induced from oxidation is observed, and any metal ion does not exist in the solid PEG specimen. The molecular weight of PEG is measured using GPC and viscometry. Properties of PEG before and after preservation treatment, and after oxidation with $H_2O_2$ were not changed. Consequently, the peroxidation with $H_2O_2$ is a reasonable and simple method to decolor the used PEG solution.

• The Korean Journal of Mycology
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• v.24 no.4 s.79
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• pp.310-321
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• 1996

Five strains AF027, AF069, AF2001, AF2011 and SD02 of Pseudomonas cepacia were isolated from soil, and the antifungal cyclic lipopeptides(CLP) i.e, CLP027A, CLP069A, Cepacidine A, CLP2011A and CLP02A were produced from each strains, respectively. Nitrogen and carbon sources in media were proved to be important factors for the production of CLP and among them, polypeptone-S, glucose and fructose were the most effective. It appeared that compounds CLP027A and CLP069A were identical with Cepacidine A and Xylocandine A, respectively. contain aspartic acid as amino acid component, are differentiated from Xylocandine A containing asparagine. Although molecular weight, amino acid composition and UV spectrum of CLP2011A and CLP02A are same with those of Cepacidine A, it is postulated that these compounds are not identical with Cepacidine A when the antifungal spectra and antifungal activity were compared to those of Cepacidine A.

• Polymer(Korea)
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• v.25 no.1
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• pp.71-77
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• 2001

Unsaturated polyester(UP) resin is one of the major thermosetting resins. It is very useful as the matrix resin of the composite material because of its low viscosity. The polymer resin, however, has several drawbacks; The volume shrinkage occurs during the crosslinking reaction of the UP resin with styrene monomer and the resulting polymer is weak to the alkali and also brittle. The mechanical properties of UP resin can be improved by blending various materials. In this study, polyurethane(PU) was used as a modifier in order to enhance the toughness of the UP resin. The goal of the research is to study the effect of the polyol molecular weight as a PU soft segment and the PU contents on the toughness of PU-modified UP resins. UP/PU polymer network may occur through the reaction between isocyanate group in the methyldiisocyanate(MDI) and hydroxyl group in the UP molecules. The maximum toughness value was shown at 2 wt% of the PU content. This effect results from the incorporation of the PU segment into the UP resin.

• Polymer(Korea)
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• v.24 no.6
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• pp.737-743
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• 2000

Polyquinonediimines (PQDI) which have stable structure on heat and contains mono-azobenzene in the side chain were synthesized by means of condensation polymerization under TiCl$_4$. The synthesized monomers and polymers were identified by FT-IR, $^1$H-NMR, and elementary analysis. Especially, PQDI was comfirmed by the double-bonding peak of >C=N appeared near 1625 $cm^{-1}$ / by means of FT-IR spectrum. PQDI containing mono-azobenzene group in both side chains wat not soluble in non-polar solvents at all but partially soluble in the polar solvents having small dielectric constant, and dissolved in the strong acid such as sulfuric acid and $CH_3$SO$_3$H. Molecular weight distribution of PQDI measured by GPC showed 1.74. It was confirmed through X-ray diffraction analysis that the polymer was partially crystalline at the low angle region, but amorphous after heat treatment at 1$25^{\circ}C$. The glass transition temperature (T$_{g}$ ) of synthesized polymer was measured as 1$25^{\circ}C$ by differential scanning calorimetry. The SHG value for $\chi$$^{(2)}$ after poling at 1$25^{\circ}C$ was 8.6 pm/V (λ=1.542 ${\mu}{\textrm}{m}$). The SHG value slowly decreased with time from the start but appeared temporal stability after 100 hours.

• Journal of the Korean Chemical Society
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• v.43 no.5
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• pp.578-588
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• 1999

The purpose of this study is to develope the more effective chemistry teaching strategy through analyzing the demanded cognitive levels of contents in high school chemistry I textbooks and the cognitive levels of students who learn these textbooks. For this purpose, the levets of cognitive development stages of 821 second grade students of high schools in Seoul City were anaIyzed using the GALT short version test. The demanded cognitive levels of understanding the contents of chemistry I textbooks in high school were analyzed using the curriculum analysis taxonomy developed by CSMS (Concept in Secondaly Mathematics and Science) program of the Great Britain. The resuIts showed that the proportion of students in the concrete operational stage, the transition stage, and the formal operational stage was l0.7%, 43.0% and 46.3%, respectively. The demanded levels of textbook contents were mostly the early formal operational stages. The concepts demanded the level of the late formal operational stage were 'atomic and molecular weight', 'stoichiometry of chemical reaction', and 'periodic properties of elements'. The results will be helpful for teachers in knowing what concepts are difficult for students to understand and in planning strategies for teaching those concepts. To demonstrate the application of the results obtained in this study, an example of developing teaching strategy which includes the adjustment of cognitive level of contents was shown.

• Korean Journal of Environmental Biology
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• v.25 no.4
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• pp.289-296
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• 2007

Di-(ethyhexyl) phthalate (DEHP), commonly used as a plasticizer for manufacturing flexible vinyl products, has been the topic of extensive research, especially concerning endocrine disrupting properties. Metallothionein (MT) is a low molecular weight (6,000$\sim$7,000 Da), cysteine-rich (22$\sim$23%), metal-binding protein and is known to be induced by extrinsic factors such as chemical agents and stresses. Some of the known function of MT include detoxification of heavy metals and alkylating agents and neutralization of free radicals. Nonetheless, the definitive physiological function of MT are still unknown. This study was carried out to investigate the effects of DEHP on the ultrastructural changes and the expression of MT of the rat liver. The rats were orally intubated with either corn oil (experimental control) or 0.5 mg, 1.5 mg and 4.5 mg DEHP kg$^{-1}$ day$^{-1}$ in 0.5 mL of corn oil for 15 days before sacrificing and sampling. DEHP induced mild ultrastrctural changes of some cell organelles such as rough endoplasmic reticulum, mitochondria, lysosomes and peroxisomes in the rat liver treated with DEHP. In the respect of immunogold labelling and Western blotting, MT expression of the liver tissue was up-regulated by DEHP. In conclusion, DEHP has effects on the ultrastructures and hepatic function for MT expression in rat.

• Korean journal of food and cookery science
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• v.3 no.1
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• pp.47-53
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• 1987

The physicochemical properties of kidney bean crude and refined starch were investigated. The results were as follows : Amylose content of refined starch was 77%. Blue values of crude and refined starch were 0.375 and 0.410, respectively. Ferricyanide numbers of crude and refined starch were 1.00 and 1.94, respectively, and alkalinumbers of crude and refined starch were 8.67 and 6.90, respectively. Amylose had molecular weight of 18067 and degree of polymerization was 112. Amylopectin had degree of branching of 3.7 per 100 glucose units and glucose units of 27 per segment of amylopectin. Water binding capacities of crude and refined starch were 202.1% and 169.4%, respectively. Both swelling powers of crude and refined starch were increased rapidly from $70^{\circ}C$ to $90^{\circ}C$ and their curves showed a single-stage pattern. The optical transmittance of 0.2% crude starch suspension was increased rapidly from $80^{\circ}C$ to $83^{\circ}C$ and that of 0.2% refined starch suspension was increased rapidly from $77^{\circ}C$ to $83^{\circ}C$. Brabender hot-paste viscosities of crude and refined starch at 6% and 8% concentation (solid basis) showed the similar amylogram patterns of c type with no peak vircosity.

• Parasites, Hosts and Diseases
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• v.35 no.1
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• pp.55-62
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• 1997

The molecular weight 30 kDa membrane protein of Toxoplusma Sondii (Toxoplasma 30 kDa) apparently conserved in most strains of T. gondii and sera of infected hosts. The present study aimed to elucidate Toxoplasmc 30 kDa as a useful diagnotic antigen for serodiagnisis of toxoplasmosis by ELISA and for induction of protective immunity. Murine spleen cells immunized with the membrane antigen of T. gondii were fused with mouse Sp2/0-Ag 14 myeloma cells. Out of 8 clones selected, five were IgG2b, the others belonged to IgG 1 and IgG2a. The 30 kDa antigen was distributed mainly on the surface membrane of tachyzoites by indirect fluorescence method. Murine peritoneal macrophages which were activated by 30 kDa antigen produced more amounts of NO2 compared with crude antigen-treated group, however there were no significant differences in toxoplamacidal activity between the two groups. Higher specificity of Toxoplosma 30 kDa antigen was recognized for serodiagnosis of toxoplasmosis than the crude antigen. From these results, ToxopLasmo 30 kDa antigen enhances the cytotoxic effect of macrophages as well as a more reliable means for the serodiagnosis of toxoplasmosis by ELISA. Key words: Toxoplosma gondii, 30 kDa antigen (p30), mouse, serodiagnosis, macrophage, cytotoxicity.