• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.819-824
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• 2016

The accelerated thermal aging of CSPE (chlorosulfonated polyethylene) was carried out for 33.64 and 67.27 days at 110[$^{\circ}C$], equivalent to 40 and 80 years of aging at 50[$^{\circ}C$], respectively. These samples were referred to as CSPE-0y, CSPE-40y and CSPE-80y, respectively. As the accelerated thermally aged years of the CSPE increase, the insulation resistance[$\Omega$] at 20[Hz], 500[Hz], and 2[KHz], and the percent elongation [%EL] of the CSPE decrease. However, the dissipation factor($tan{\delta}$) at 20[Hz], 500[Hz], and 2[KHz], the apparent density[$g/cm^3$], the glass transition temperature and the melting temperature of the CSPE were increased. The period of time that the voltage has to be applied until electric breakdown of the CSPE-0y is longer than that of the CSPE-40y, and the CSPE-80y, but the dielectric strength of the CSPE-80y is lower than that of the CSPE-0y and the CSPE-40y. The differential temperatures after the AC and DC voltages are applied to CSPE-0y, CSPE-40y and CSPE-80y are 0.026~0.028[$^{\circ}C$], 0.030~0.042[$^{\circ}C$], 0.018~0.045[$^{\circ}C$], respectively. The variations of temperature for the AC voltage are higher than those for the DC voltage when an AC voltage is applied to CSPE-0y, CSPE-40y and CSPE-80y. It is found that the dielectric loss owing to the dissipation factor[$tan{\delta}$] is related to the electric dipole conduction current. It is ascertained that the ionic (electron or hole) leakage current is increased by the separation of the branch chain of CSPE polymer from the main chain of the polyethylene as a result of thermal stress due to accelerated thermal aging as well as by conducting ions such as $Na^+$, $Cl^-$, $Mg^{2+}$, $SO_4^{2-}$, $Ca^{2+}$ and $K^+$ after seawater soaking.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.915-922
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• 2017

The study on the thermal and oil resistance rubber composite, 2016. [6] predicted the lifetime of Fluorocarbon Rubber by accelerating aging at high temperature ($150^{\circ}C$, $175^{\circ}C$, $200^{\circ}C$). general rubber products are likely to exhibit different properties depending on the degradation factors such as temperature, humidity, ozone, light, emulsion, mechanical and electrical stress. To solve these problems, We compared the rate of change about tensile strength, elongation rate, volume change rate, weight change rate, thickness change rate, thermal conductivity in low temperature promoting aging on the basis of predictive lifetime of high temperature promoting aging. As a result of the review, the required life expectancy was satisfied, but there was a slight difference in the rate of change between the high-temperature promoted aging life result and the low temperature promoted aging life result. The cause was a reduction in "tensile strength / elongation" and an increase in "volume / weight / thickness" caused by the main chain decomposition of fluorine rubber due to aging at high temperature promoting aging. However, the low temperature promoting aging was caused by the curing reaction of fluorine rubber at $80^{\circ}C$. The tensile strength / elongation and volume / weight / thickness changes were small.

• Journal of Microbiology and Biotechnology
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• v.28 no.9
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• pp.1527-1535
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• 2018

Bacterial strain BAS23 was isolated from rice field soil and identified as Bacillus amyloliquefaciens. Based on dual culture method results, the bacterium BAS23 exhibited potent in vitro inhibitory activity on mycelial growth against a broad range of dirty panicle fungal pathogens of rice (Curvularia lunata, Fusarium semitectum and Helminthosporium oryzae). Cell-free culture of BAS23 displayed a significant effect on germ tube elongation and mycelial growth. The highest dry weight reduction (%) values of C. lunata, H. oryzae and F. semitectum were 92.7%, 75.7%, and 68.9%, respectively. Analysis of electrospray ionization-mass spectrometry (ESI-MS) and $^1H$ nuclear magnetic resonance (NMR) spectroscopy revealed that the lipopeptides were iturin A with a C14 side chain (C14 iturinic acid), and a C15 side chain (C15 iturinic acid), which were produced by BAS23 when it was cultured in nutrient broth (NB) for 72 h at $30^{\circ}C$. BAS23, the efficient antagonistic bacterium, also possessed in vitro multiple traits for plant growth promotion and improved rice seedling growth. The results indicated that BAS23 represents a useful option either for biocontrol or as a plant growth-promoting agent.

• Journal of Life Science
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• v.14 no.4
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• pp.644-649
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• 2004

During plant development, active gibberellins (GAs) control many aspects of plant growth and development including seed germination, stem elongation, flower induction, anther development and seed growth. To understand the biosynthesis and functional role of active GAs in high plants, this study investigated GA 3$\beta$-hydroxylase gene en-coding $GA_1$ and$GA_4$ catalizing last step in GA biosynthetic pathway. The antisense GA 3$\beta$-hydroxylase gene was inserted into expression vector, pIG121-Hm. Calli derived from mature seeds of rice (Oryza satiiva L. cv. Donjinbyeo) were co-cultivated with Agrohacterium tumefaciens EHA101 earring a pIG121-Hm containing hygromycin resistance ($Hyg^r$) and antisense GA 3$\beta$-hydroxylase gene. Seventeen transgenic plants obtained inhibiting GA 3$\beta$-hydroxylase. Transgenic plants had shorter plant height more than that of the Dongjinbyeo. Stable integration of antisense GA 3$\beta$-hydroxylase gene was confirmed by polymerase chain reaction of genomic DNA isolated from the leaf organs of the $T_o$ generation.

• Fibers and Polymers
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• v.4 no.3
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• pp.114-118
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• 2003

The prepolymer and the final polyurethane (PU) block copolymer were synthesized by reacting 4,4-methylene bis(phenylisocyanate) with poly(tetramethylene glycol) and the prepolymer with 1,4-butanediol as a chain extender, respectively, to investigate the relation between phase separation and it's resulting properties. According to FT-IR data, the phase separation of hard and soft segments in the prepolymer and the PU block copolymer grew bigger by increasing the hard segment content, and the PU showed more dominant phase separation than the prepolymer. The heat of fusion due to soft segments decreased in both the prepolymer and the PU by increasing the hard segment content, whereas the heat of fusion due to hard segments increased in the PU did not appear in the prepolymers. The breaking stress and modulus of the prepolymer increased by increasing the hard segment content, and the elongation at break decreased gradually, and the PU showed the highest breaking stress and modulus at 58% hard segment content. However, the best shape recovery of the PU was obtained at 47% hard segment content due to the existence of proper interaction among the hard segments for shape memory effect. Consequently, the mechanical properties and shape memory effect of the PU were influenced by the degree of phase separation, depending on the incorporation of chain extender as well as the hard segment content.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.673-679
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• 2011

Bimodal high-density polyethylenes with different comonomer type and content were synthesized by polymerization of ethylene using Ziegler-Natta catalyst. Their structure and properties were studied using GPC, NMR, DSC and tensile test. It was found that ethylene/1-hexene copolymer exhibits higher tensile strength and elongation at break than that of ethylene/1-butylene copolymer with similar comonomer content. The molecular weight decreases as the comonomer content of the polymer increases. Short chain branching affects the crystallinity and thus the morphology and consequently the mechanical properties of the corresponding bimodal high-density polyethylenes. After SSA treated, the multiple endothermic peaks were observed. Multiple endothermic peaks are mainly attributed to the heterogeneity of ethylene sequence length and lamellar thickness. The difference of broadness index indicates that SCB distribution of polyethylene containing higher comonomer content has improved uniformity.

• Korean Journal of Environmental Biology
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• v.27 no.4
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• pp.391-396
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• 2009

The biological effects of carcinogenic polycyclic aromatic hydrocarbons (cPAHs) including benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DBA), benzo[a]anthracene (BaA), benzo[b] fluoranthene (BbF), benzo[k]fluoranthene (BkF), and indeno[1,2,3-c, d]pyrene (InP) on transcriptomic changes were determined in the liver of Oryzias latipes. Differentially expressed genes (DEGs) by binary exposure to cPAHs (BaP+BaA, BaP+BbF, BaP+BkF, BaP+DbA, BaP+InP) were screened by annealing control primers-based polymerase chain reaction followed by sequence analysis and BLAST searching. The results showed that four DEGs were commonly expressed by cPAHs and they were identified as ribosomal protein S4, coagulation factor II, elongation factor 1 beta, and a predicted protein similar to human immunodeficiency virus type I enhancer binding protein 3. This finding suggests that binary exposure to cPAHs interferes protein synthesis required for fundamental liver functions in fish.

• Microbiology and Biotechnology Letters
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• v.46 no.2
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• pp.91-101
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• 2018

The aim of this study was to transfer the 18.5 kb gene clusters coding for 17 genes from Lactobacillus rhamnosus to Lactococcus lactis subsp. cremoris MG1363 in order to determine the effect of host on exopolysaccharide (EPS) production and to provide a model for studying the phosphorylation of proteins which are proposed to be involved in EPS polymerization. Lactobacillus rhamnosus RW-9595M and ATCC 9595 have 99% identical operons coding for EPS biosynthesis, produced different amounts of EPS (543 vs 108 mg/l). L. lactis subsp. cremoris MG1363 transformed with the operons from RW-9595M and ATCC 9595 respectively, produced 326 and 302 mg/l EPS in M17 containing 0.5% glucose. The tyrosine protein kinase transmembrane modulator (Wzd) was proposed to participate in regulating chain elongation of EPS polymers by interacting with the tyrosine protein kinase Wze. While Wzd was found in phosphorylated form in the presence of the phosphorylated kinase (Wze), no phosphorylated proteins were detected when all nine tyrosines of Wzd were mutated to phenylalanine. Lactococcus lactis subsp. cremoris could produce higher amounts of EPS than other EPS-producing lactococci when expressing genes from L. rhamnosus. Phosphorylated Wzd was essential for the phosphorylation of Wze when expressed in vivo.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.823-827
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• 2003

Streptomyces venezuelae ATCC 15439 is notable in its ability to produce two distinct groups of macrolactones. It has been reported that the generation of two macrolactone structures results from alternative expression of pikromycin (Pik) polyketide synthase (PKS). It was previously reported that the hybrid pikromycin-tylosin PKS can also produce two different macrolactones but its mechanistic basis remains unclear. In order to address this question, a series of site-directed mutagenesis of tentative alternative ribosome binding site and translation start codons in tylGV were performed. The results suggest that macrolactone ring size is not determined by the alternative expression of TylGV but through other mechanism(s) involving direct interaction between the PikAIII and TE domain or skipping of the final chain elongation step. This provides new insight into the mechanism of macrolactone ring size determination in hybrid PKS as well as an opportunity to develop novel termination activities for combinatorial biosynthesis.