• Journal of Life Science
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• v.24 no.2
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• pp.128-136
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• 2014

Alginates are linear acidic polysaccharides composed with (1-4)-linked ${\alpha}$-L-guluronic acid and ${\beta}$-Dmannuronic acid. Alginate can be degraded by diverse alginate lyases, which cleave the alginate using a ${\beta}$-elimination reaction and produce unsaturated uronate oligomers. A gene for a polyMG-specific alginate lyase possessing a novel structure was previously identified and cloned from Stenotrophomonas maltophilia KJ-2. Homology modeling of KJ-2 polyMG-specific alginate lyase showed it belongs to the PL6 family, whereas three Azotobacter vinelandii polyMG lyases belong to the PL7 family of polysaccharide lyases. From $^1H$-NMR spectra data, KJ-2 polyMG lyase preferably degraded the M-${\beta}$(1-4)-G glycosidic bond than the G-${\alpha}$(1-4)-M glycosidic bond. Seventeen mutants were made by site-directed mutagenesis, and alginate lyase activity was analyzed. Lys220Ala, Arg241Ala, Arg241Lys, and Arg265Ala lost alginate lyase activity completely. Arg155Ala, Gly303Glu, and Tyr304Phe also lost the activity by 60.7-80.1%. These results show that Arg155, Lys220, Arg241, Arg265, Gly303, and Tyr304 are important residues for catalytic activity and substrate binding.

• Polymer(Korea)
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• v.33 no.6
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• pp.602-607
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• 2009

A polyurethane (PU) surface enabling in vivo endothelialization via endothelial progenitor cell (EPC) capture was prepared for cardiovascular applications. To introduce CD34 monoclonal antibody (mAb) inducing EPC adhesion onto a surface, poly (poly (ethylene glycol) acrylate-co-butyl methacrylate) and poly (PEGA-co-BMA) were synthesized and then coated on a surface of PU, followed by immobilizing CD34 mAb. $^1H$-NMR analysis demonstrated that poly(PEGA-co-BMA) copolymers with a desired composition were synthesized. Poly(PEGA-co-BMA)-coated PU was much more effective for the immobilization of CD34 mAb, comparing with PEG-grafted PU prepared in our previous study, as demonstrated by that surface density and activity of CD34 mAb increased over 32 times. Physico-chemical properties of modified PU surfaces were characterized by X-ray photoelectron spectroscopy (XPS), water contact angle, and atomic force microscopy (AFM). The results demonstrated that the poly(PEGA-co-BMA) coating was effective for CD34 mAb immobilization and feasible for applying to cardiovascular biomaterials.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.2002-2007
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• 1999

In this paper, the n-channel poly-Si thin-film transistors (poly-Si TFT's) formed by solid phase crystallization (SPC) on glass were investigated by measuring the electrical properties of poly-Si films, such as I-V characteristics, mobility, leakage current, threshold voltage, and subthreshold slope. It is done to decide to be applied on TFT-LCD with large-size and high density. In n-channel poly-Si TFT with 2, 10, 25$\mu\textrm{m}$ of channel length, the field effect mobilities are 111, 126 and 125 $\textrm{cm}^2$/V-s and leakage currents are 0.6, 0.1, and 0.02 pA/$\mu\textrm{m}$, respectively. Low threshold voltage and subthreshold slope, and good ON-OFF ratio are shown, as well. Thus, the poly-Si TFT’s used by SPC are expected to be applied on TFT-LCD with large-size and high density, which can integrate display panel and peripheral circuit on a large glass substrate.

• Journal of the Korean Chemical Society
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• v.37 no.2
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• pp.249-254
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• 1993

N-p-nitrophenyl poly(m-phenylene isophthalamide) was obtained from treatment of poly(m-phenylene isophthalamide) with sodium hydride in dimethyl sulfoxide followed by the addition of 1-fluoro-4-nitrobenzene in 43 wt% yield. Its inherent viscosity was 0.606 g/cm${\cdot}$sec determined from a solution of 0.125 g of the above polymer dissolved in 25 ml of 98% sulfuric acid at $30^{\circ}C.$ In order to synthesize poly(m-phenylene isophthalamide), 1,3-phenylenediamine is allowed to react with isophthaloyl chloride in chloroform in the presence of triethylamine and added triethylamine hydrochloride. The value of inherent viscosity is 0.560 g/cm${\cdot}$sec measured at the same condition. The substitution ratio of N-p-nitrophenyl poly(m-phenylene isophthalamide) was to be 16.7∼47.0% by using the $^1H-NMR$ integration. When the higher inherent viscosity of poly(m-phenylene isophthalamide) was used, lower substitution ratio would be calculated.

• Polymer(Korea)
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• v.35 no.5
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• pp.438-443
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• 2011

In order to enhance water permeability through the improvement of fouling phenomena and wettability of hydrophobic porous membranes, various adsorption materials, i.e., poly(vinyl amine), poly (styrene sulfonic acid), poly(vinyl sulfonic acid), and poly(acrylamide-co-acrylic acid) were adsorbed onto the surface of polyethylene (PE) porous membrane. The concentration of adsorption solutions, adsorption time, the sort of salts and their ionic strength were varied, and the pure water permeability of their resulting adsorbed membranes was measured. In general, water permeability increased with an initial increase in the concentration of adsorption solution, adsorption time, and ionic strength and then decreased with a further increase. The pure water permeability of 375 $L/m^2h$(LMH), 35% enhancement, was obtained at a condition of poly(vinyl sulfonic acid) 1000 ppm, $Mg(NO_3)_2$ ionic strength(IS) 0.1, and adsorption time 150 sec, while the 50% (411 LMH) and 35% (374 LMH) enhancements were obtained at conditions of poly(styrene sulfonic acid) 1000 ppm, adsorption time 60 sec, and NaCl IS 0.1 and 0.2, respectively.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.314-317
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• 2000

In order to analyze the characteristics of complicated TFT-LCD (Thin Film Transistor-Liquid Crystal Display) circuits, it is indispensible to use simulation programs. In this study, we present a systematic method of extracting the input parameters of poly-Si TFT for Spice simulation. This method is applied to two different types of poly-Si TFTs fabricated in our group with good results. Among the Spice simulators, Pspice has the graphic user interface feature making the composition of complicated circuits easier. We added successfully a poly-Si TFT model on the Pspice simulator, which would contribute to efficient simulations of poly-Si TFT-LCD pixels and arrays.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.261-264
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• 2007

In this study, the consolidation and casting processes of fine Si powders, by-products of making high purity Poly-Si rods in the current method, were systematically investigated for use as economical solar-grade feedstock. Morphology, size, and contamination type of the poly-Si fine powders were inspected by combined analysis of SEM, particle size analyzer, and FT-IR. Poly-Si powder compacts were tried to fabricate by a consolidation process without a binding agent and then their density ratio and strength were evaluated. Finally, the electrical resistivity of the specimens prepared by an electromagnetic casting method was examined for purity assessment.

• Korea-Australia Rheology Journal
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• v.17 no.2
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• pp.71-77
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• 2005

We investigated thermal, rheological, morphological and mechanical properties of a binary blend of poly(lactic acid) (PLA) and poly(butylene succinate adipate) (PBSA). The blends were extruded and their molded properties were examined. DSC thermograms of blends indicated that the thermal properties of PLA did not change noticeably with the amount of PBSA, but thermogravimetric analysis showed that thermal stability of the blends was lower than that of pure PLA and PBSA. Immiscibility was checked with thermal data. The rheological properties of the blends changed remarkably with composition. The tensile strength and modulus of blends decreased with PBSA content. Interestingly, however, the impact strength of PLA/PBSA (80/20) blend was seriously increased higher than the rule of mixture. Morphology of the blends showed a typical sea and island structure of immiscible blend. The effect of the blend composition on the biodegradation was also investigated. In the early stage of the degradation test, the highest rate was observed for the blend containing $80wt\%$ PBSA.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.123-124
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• 2000

Three types of conjugated polymer, poly(DFPZ-AV), poly(MEHPV-PV) and poly(BFMP12-BPV), were obtained by Honer-Emmons condensation using potassium tert-butoxide from the synthesized monomers in anhydrous tetrahydrofurane. The Honer-Emmons reaction was found to be a useful synthetic method for the preparing a wide range of EL polymers. The EL devices using poly(DFPZ-AV), poly(MEHPV-PV) and poly(BFMP12-BPV) as light emitting layer gave red, green and blue emission, respectively, which were in close chromaticity with the CIE 1931 NTSC standard.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.686-697
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• 2003

A new colloidal silver (Ag) system is present in which a fine colloidal Ag is in situ deposited onto functionalized porous poly (ethylene glycol dimethacrylate) (poly (EGDMA)) microspheres. The effectiveness of Ag deposition was investigated considering the surface characteristics of poly (EGDMA) microspheres. The result reported in this study illustrates that the control of surface area and surface functionality (in this study, a hydroxyl group) of poly (EGDMA) microspheres is an important factor that determines practically the degree of deposition of colloidal Ag. The x-ray analysis showed that Ag nanoparticles were dispersed evenly inner and outer surfaces and had a face center cubic (fee) phase. In the preservative efficacy test, the Ag-containing poly (EGDMA) microspheres had a powerful anti-bacterial activity, showing a high potential for a new preservative in cosmetic industry.