• Journal of environmental and Sanitary engineering
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• v.12 no.3
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• pp.31-39
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• 1997

The seasonal and spatial changes in dissolved organic carbon(DOC) in Lake Kasumigaura, a shallow and eutrophic lake, were analyzed from October 1992 to October 1995. The proportion of T-DOC was classified by labile(L-DOC) and refractory DOC(R-DOC) on the basis of long-term incubation, fractionated the molecular weight of T-DOC by ultrafiltration. The porewater DOC were measured at sedimental surface of the central basin in order to evaluate the DOC released from the sediment. The proportion of L-DOC and R-DOC were accounted for about 15% and 85% of T-DOC in the central basin, respectively. The molecular weight(MW) distribution occupied some 60% of the low and medium MW. The horizontal variation of T-DOC concentrations trended to higher in the central basin than in the inlet of influent rivers, because of contribution by autochthonous organic carbon loading. The seasonal variation of T-DOC showed to higher summer than winter in the inlet of influent, but at the central basin it fluctuated little seasonally. During the high increase of porewater DOC in 1994 evaluated the high release possibility from the sediment surface (10cm). The present study suggests that autochthonous organic carbon loading must be controlled for improving the water quality of the eutrophic lakes.

• Food Science and Biotechnology
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• v.16 no.6
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• pp.902-909
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• 2007

Granular maize starch was treated with Thermus scotoductus 4-${\alpha}$-glucanotransferase (${\alpha}$-GTase), and its physicochemical properties were determined. The gelatinization and pasting temperatures of ${\alpha}$-GTase-modified starch were decreased by higher enzyme concentrations. ${\alpha}$-GTase treatment lowered the peak, setback, and [mal viscosity of the starch. At a higher level of enzyme treatment, the melting peak of the amylose-lipid complex was undetectable on the DSC thermogram. Also, ${\alpha}$-GTase-modified starch showed a slower retrogradation rate. The enzyme treatment changed the dynamic rheological properties of the starch, leading to decreases in its elastic (G') and viscous (G") moduli. ${\alpha}$-GTase-modified starch showed more liquid-like characteristics, whereas normal maize starch was more elastic and solid-like. Gel permeation chromatography of modified starch showed that amylose was degraded, and a low molecular-weight fraction with $M_w$ of $1.1{\times}10^5$ was produced. Branch chain-length (BCL) distribution of modified starch showed increases in BCL (DP>20), which could result from the glucans degraded from amylose molecules transferred to the branch chains of amylopectin by inter-/intra-molecular transglycosylation of ${\alpha}$-GTase. These new physicochemical functionalities of the modified starch produced by ${\alpha}$-GTase treatment are applicable to starch-based products in various industries.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.347-358
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• 2014

본 논문에서는 양자 역학적 분자 동역학(Quantum Mechanical/Molecular Mechanical-Molecular Dynamics, QM/MM-MD)을 통해 수용액에 녹아 있는 Potassium Thiocyanate의 dynamics를 연구했다. Umbrella sampling technique을 활용하여 association/dissociation에 해당하는 Free energy surface를 구했다. 두 개의 Free energy minimum이 녹아 있는 두 이온의 center of mass 사이의 거리가 $4{\AA}$일 때와 $5{\sim}6{\AA}$ 부근일 때 나타났으며 $4{\AA}$일 때 더 안정 했다. 본 논문에서는 $4{\AA}$일 때를 Contact Ion Pair(CIP) $6{\AA}$일 때를 Dissociation Ion Pair(DlP)라고 칭했다. 이 minimum들이 무엇인 지를 밝혀 내기 위해 추가 연구를 수행하였다. Free energy 상에서 가장 안정 할 때(CIP) solute인 Potassium thiocyanate의 구조를 살펴 봤더니 Potassium ion은 Thiocyanate ion의 Sulfur보다 Nitrogen side를 선호하였다. 그 원인을 알아보기 위해 salvation shell의 구조를 Radial distribution function을 통해 살펴 봤더니 물 분자가 Nitrogen보다 Sulfur와 더 강한 상호작용을 하고 있었다. 그로 인해 Potassium ion이 Nitrogen을 선호한단 결과가 나온 것이다. 한편, 두 번째 minimum은 물 분자가 Potassium 이온과 Thiocyanate 이온 사이에 flexible하게 bridging을 하는 구조였다. 또한 단순 양자 계산을 통해서도 비슷한 구조를 얻을 수 있었다. 그러나 QM 계산은 0K에서 수행하는 것이기 때문에 엔트로피 효과가 없는 계산이지만 본 연구는 온도 300K로 실제 용매와 가깝게 수행함으로써 고정되어 있는 구조가 아니라 엔트로피와 엔탈피가 균형적으로 존재하는 실제 용액 속에서의 구조를 처음으로 보여주는 것이다.

• Food Science and Biotechnology
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• v.18 no.1
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• pp.157-161
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• 2009

Resveratrol-loaded poly($\varepsilon$-caprolactone) (PCL) nanoparticles were prepared by oil in water (O/W) emulsion solvent evaporation method. The morphology of the nanoparticles was evaluated using atomic force microscope (AFM), in which well-shaped and rigid nanoparticles were prepared. The mean particle size of nanoparticles prepared using only dichloromethane (DCM) ($523.5{\pm}36.7\;nm$) was larger than that prepared with a mixture of DCM and either ethanol (EtOH) ($494.5{\pm}29.2\;nm$) or acetone ($493.5{\pm}6.9\;nm$). The encapsulation efficiency of nanoparticles prepared only with DCM as dispersed phase ($78.3{\pm}7.7%$) was the highest of those prepared with solvent mixtures. An increase in the molecular weight of PCL led to an increase in encapsulation efficiency (from $78.3{\pm}7.7$ to $91.4{\pm}3.2%$). Pluronic F-127 produced the smallest mean size ($523.5{\pm}36.7\;nm$) with the narrowest particle size distribution. These results show that dispersed phase, molecular weight of wall materials, emulsion stabilizer could be important factors to affect the properties of nanoparticles.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.178-187
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• 1993

Degradation of the starch-polyethylene composite film by an activated sludge treatment and a soil burial test was examined. The treated films had deformed structures which were resulted from the removal of starch during the treatments. The added auto-oxidant caused the degradation of the polyethylene matrices and the crosslinking reactions after the oxidation of polyethylene chains as well. As a result of soil burial test, the degradation reaction of the composite film containing corn oil as an auto-oxidant was, however, prevalent : number- and weight-average molecular weight of polyethylene decreased, while the molecular weight distribution increased.

• Journal of Species Research
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• v.9 no.3
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• pp.210-217
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• 2020

Microseira wollei (Farlow ex Gomont) G.B.McGregor and Sendall ex Kennis, a mat-forming filamentous harmful cyanobacterium, has historically been found in the United States. Microseira wollei produces neurotoxins and hepatotoxins which affect declining water quality. In the present research, we report of unrecorded M. wollei with morphology, TEM anatomy, molecular phylogeny on the Korean population. Based on 16S rRNA gene sequences, Korean population were different by 0.02% (2 bp) to the Japanese population, 1.2-1.3% to the Australian population, and 2.5-3.7% to the United States populations. nifH gene sequences were 8.4-8.7% different to Australian ones and 3.5-3.8% to other population, however molecular phylogenetic analysis of M. wollei living in Korea revealed monophyly with the geographical populations of U.S.A., Australia, and other geographical populations. Since the mat of M. wollei has been reported to be maintained for several years in other countries, it is necessary further investigate the seasonal and regional distribution of this species in Korea.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.236-242
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• 2014

Isospecific propylene polymerization behavior of meta- and para-Lewis base (E) functionalized unbridged zirconocenes ($[1-(E_n-Ph)-3,4-Me_2C_5H_2]_2ZrCl_2$, E = $NMe_2$, OMe; n = 1 or 2) was investigated under bulk conditions. Catalytic activity of the zirconocenes, and molecular weight and isotacticity of polypropylenes are found to be dependent on the position and number of the Lewis base functional groups in the zirconocenes. All the crude polypropylenes possess a broad molecular weight distribution and multi-melting transitions, indicating an involvement of multi-catalytic active species in the polymerization. The highest [mmmm] value of an isotactic portion of the polypropylenes reached 89%, which is higher than that (85%) from the well-known $C_2$-symmetric EBIZr (rac-$Et(Ind)_2ZrCl_2$) catalyst. These results support that the in situ generated, rigid rac-like cation-anion pair through the Lewis acid-base interactions between the functional groups of zirconocenes and methylaluminoxane anion is effective in the formation of isotactic polypropylene under bulk propylene polymerization conditions.

• The Korean Journal of Zoology
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• v.38 no.2
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• pp.167-176
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• 1995

Glucose-regulated proteins (grp's), srp94 3nd grp78/BiP, are a group of stress proteins which are highly synthesized in cells exposed to a variety of stressful agents including tunicamycin 3nd Ca2+ ionophore. Grp78/BiP is hon to function as a molecular chaperone which regulates the folding and assembly of secretory or membrane proteins, but the biological function of grp941 remains to be elucidated. In this study, we have examined the intracellular distribution of grV's and the function of srp94. Grp's are resident in the endoplasmic reticulum (ERI 3nd a specific sequence (Lys-Asp-Glu-Leu) at their C-terminus is known to be responsible for their retention within the ER. However, it has been unclear whether upon disturbance of cellular Caa+ homeostasis by the Ca2+ ionophore, grp94 is retained within the ER or secreted into the medium. In this study, we showed that in the presence of C3a+ ionophore, grp94 and gif78/BiP are present in the cells, mainly within the ER. We have also investigated whether grp94 might function as a molecular chaperone. Here we showed that in the immunoglobulin (Ig)-secreting hvbridom3 cells, grp94 transientlY interacts with fully glycosylated Is heavy chain, suggesting that grpg94 may be involved in facilitating the folding and assembly of Ig heavy chains.

• Journal of the Korean Applied Science and Technology
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• v.25 no.1
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• pp.1-14
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• 2008

To prepare weather-resistant modified silane acrylic resin coatings for an architectural purpose, tetrapolymers were synthesized by radical polymerization. 3-Methacryloxypropyltrimethoxysilane (MPTS) as a silicone monomer and n-butyl acrylate, methyl methacrylate, and n-butyl methacrylate as acrylic monomers were used. The composition of monomers was adjusted to fix the glass transition temperature of acrylic polymer for $20^{\circ}C$. The composition of MPTS in the synthesized polymer were varied from 10 wt% to 30 wt%. On the basis of synthesized resin amber paints were prepared and their physical properties and effects on weatherability were examined. The presence of MPTS in modified silane acrylic resins generally resulted in low molecular weight and broad molecular weight distribution, and also lowered the viscosity of the copolymers. The coated films prepared from these resins showed good and balanced properties in general. Adhesion to the substrate was outstanding in particular. Weatherability tests were carried out in three different types such as outdoor exposure, QUV, and SWO. The test results showed that the modified silane acrylic resins containing 30 wt% of MPTS had superior weathering properties.

• Journal of the Korean Ceramic Society
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• v.44 no.6 s.301
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• pp.319-324
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• 2007

The structural properties of $SiO_2$ liquid at finite temperatures have been investigated by molecular dynamics (MD) simulations utilizing the Tersoff interatomic potential. During cooling process, the $SiO_2$ liquid structure quenched with a cooling rate of $1.0{\times}10^{11}K/sec$ shows the traditional properties observed in the experiments. The coordination defects of system decrease with decreasing temperature up to 17%. The $SiO_2$ glass quenched up to 1600 K contains defects consisting of the fivefold coordination of Si, and the threefold coordination of O atoms. The calculated diffusion coefficients which are calculated by monitoring. the mean-square displacement of atoms drop to almost zero below 3000 K ($<10^{-6}\;cm^2/sec$) but has a fluctuations at low temperature. The structure properties of $SiO_2$ liquid shows a significant dependence on the temperature during cooling process. Bond-angle distribution at around $120^{\circ}$ originate from the O and Si atoms consisting of the over-coordinated O atoms.