• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.504-508
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• 2003

In this study, development of papain which is extremely stable to negative ionic environment was made by directed molecular evolution. The screening method to confirm papain activity was designed using anionic material and skim milk agar plate for obtaining stable modified papain. Most stable modified papain P38-10 was obtained, which shows activity 10-15 times higher compared to wild type papain in anionic environment.

• Journal of Environmental Science International
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• v.15 no.6
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• pp.593-600
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• 2006

SIS triblock copolymers, one of the major raw materials of oil gelling agent, were synthesized by living anionic polymerization and the resultant copolymers formed with various shapes and sizes were used to examine their oil gelling capacities. Coupling method was adapted to form final triblock products from diblock living polymers. Prior to polymerization, the impurities in monomers and solvents were throughly removed by killing technique. We experimentally investigated the effects of operating parameters of synthesis and forming of SIS triblock copolymers on oil gelling capacity. The photocatalytic decomposition of SIS triblock copolymer under ultraviolet circumstance was also investigated and it is found that the addition of P-25 enhances the photocatalytic decomposition.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.143-146
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• 2004

Natural zeolites have exhibited high sorption capacity for inorganic cations including heavy metals and ammonium. Moreover, they were proven to be effective for environmental applications such as permeable barriers for controlling the spread of cation-contaminated groundwater. However zeolites have little or no affinity for anionic species like chromium, as they possess a net negative structural charge. To achieve the simultaneous sorption for anionic contaminants, surfactant-modified zeolite (SMZ) has been employed as the possible sorbents. Current study focuses on simultaneous removal of heavy metals having different ionic form in aqueous solution, cadmium (C $d^{2+}$) and chromium (Cr $O_{4}$$^{2-}$), using newly developed materials, ZanF. ZanF, a potential alternative to SMZ, was derived from zeolite modified by Fe(II) chloride followed by reduction with sodium borohydride. Batch experiments were performed to estimate the removal efficiency of ZanF at different conditions. Under different pH ranging from 2 to 6, removal efficiency was investigated. And C $d^{2+}$ removal efficiency was estimated by varying background concentration of Cr $O_{4}$$^{2-}$, and vice versa. With the test results, ZanF was expected to be a possible reactive materials alternative to SMZ in permeable reactive barriers (PRBs) for treating the contaminated groundwater with cationic and anionic heavy metals.als.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.1
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• pp.59-66
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• 2013

Fillers have been used for printing paper to improve printability, sheet formation and optical properties and to reduce production costs by replacing expensive wood pulps. However, an increased filler content will decrease paper strength because filler particles interfere with fiber-fiber bonding. In order to increase filler content without sacrificing too much paper strength in high filler content papers, the surface of precipitated calcium carbonate (PCC) has been modified by adsorbing anionic polyacrylamide and cationic starch in series. The adsorbed polymer layers would enhance interactions between the filler surface and the fiber surface, improving internal bonding. It was found that the modified PCC increased paper strength at a given filler content compared to the coventional method. Negligible differences in optical properties and formation of paper, filler and fines retention and drainage on the wire section were observed between the modified and the conventional PCC. However, the decreased bulk of paper was observed when the modified PCC was used.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.24.2-24.2
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• 2011

Ru is used as a bottom electrode capacitor in dynamic random access memories (DRAMs) and ferroelectric random access memories (FRAMs). The surface of the Ru needs to be planarized which is usually done by chemical mechanical polishing (CMP). Ru CMP process requires chemical slurry consisting of abrasive particles and oxidizer. A slurry containing NaIO4 and alumina particles is already proposed for Ru CMP process. However, the stability of the slurry is critical in the CMP process since if the particles in the slurry get agglomerated it would leave scratches on the surface being planarized. Thus, in the present work, the stability behavior of the slurry using a suitable anionic polyelectrolyte is investigated. The parameters such as slurry pH, polyelectrolyte concentration, adsorption time and the sequence of addition of chemicals are optimized. The results show that the slurry is stable for longer time at an optimized condition. The polishing behavior of the Ru using the optimized slurry is also investigated.

• Economic and Environmental Geology
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• v.32 no.3
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• pp.307-315
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• 1999

Four organic polymers were mixed with mothmorillonite. Two cationic polymers a hi로 molecular weight polyacrylamide (494C) and a low molecular weight polymer (587C).Two anionic polymers include a high molecular weight polymer (aerotil). Each clay supension series were allowed to stand for 24 hours and were centrifuged, and the clay plugs were washed and dried. The dried samples investigated by XRD, IR and CEC measurement. The suspended clay containing anionic polymers was not flocculated at any concentratuons of polymer. But the suspendions containing two cationic polymers were rapidly flocculated at almost all concentrations. the d(001) spacings of Na-montmorillonite after being with cationic polymer 587C show about 15$\AA$ suggesting the polymers may have entered the interlayer spaces. The polymer 494C-treated sample produced double peaks of about 12 and 15$\AA$ in XRD. It indicates that the high molecular weight polymer. And cationic polymer 494C may be adsorbed mainy on the outside surface of clay, and some polymers may peretrate into olny interlayers in the margin of montmorillonite particles because of its high molecular weught. CEC of polumer 587-treated sample was reduecd mmarkedly suggesting polymer blocks CEC sites. The d(001) spacings of Ca-montmorillonite after being treated with cationic polymers show about 15$\AA$ suggesting that the interlayer spaces have not been expanded. In the experiment using a dilute Ca-bearing solution, the suspended caly containinf anionic polymers was flocculated. The results indicate that the flocculation behavior of montmorillonite-polymer supension depends on not only polymer properties such as concentration, electric charge and molecular weight but also compositions of solvent.

• Journal of Nutrition and Health
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• v.30 no.6
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• pp.658-668
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• 1997

Path of a small hydrophobic molecule through the aqueous cytoplasma is not linear. Partition may favor membrane binding by several orders of magnitude : thus significant membrane association will markedly decrease the cytosolic transport rate. The presence of high concentration of soluble binding proteins for these hydrophobic molecules would compete with membrane association and thereby increase transport rate. For long chain fatty acid molecules, a family of cytosolic binding proteins collectively known as the fatty acid binding proteins(FABP), are thought to act as intracellular transport proteins. This paper examines the mechanism of transfer of fluorescent antyroyloxy-labeled fatty acids(AOFA) from purified FABPs to phosholipid membranes. With the exception of the liver FABP, AOFA is transferred from FABP by collisional interaction of the protein with a acceptor membrane. The rate of transfer increased markedly when membranes contain anionic phospholipids. This suggests that positively charged residues on the surface of the FABP may interact with the membranes. Neutralization of the surface lysine residues of adipocyte FABP decreased fatty acid transfer rate, and transfer was found to proceed via aqueous diffusion rather than collisional interaction. Site specific mutagenesis has further shown that the helix-turn-helix domain of the FABP is critical for interaction with anionic acceptor membranes. Thus cytosolic FABP may function in intracellular transport of fatty acid to decrease their membranes association as well as to target fatty acid to specific subcellular sites of utilization.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.3
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• pp.21-28
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• 2003

It is essential to use base papers having proper surface characteristics in coating operation for improving coated paper quality and coater runnability. To fulfill these purposes surface sizing of coating base stock with anionic oxidized starch is commonly practiced. It is suggested that use of cationic starch for surface sizing rather than conventional oxidized starch will improve coated paper quality since cationic starch penetrates less into paper structure because of its strong electrostatic interaction with anionically charged paper surface. Strong interaction of cationic surface sizing starch with anionic coating color is expected to promote rapid immobilization of the coating color and improve coating holdout and optical property. The immediate objective of this study was to examine the influence of surface sizing starches on the properties of coated papers. Structural characteristics of the coatings formed on the substrate surface sized with cationic and anionic starches were examined. To enhance the efficiency of cationic surface sizing starch on coated paper properties, strongly charged cationic polymers were added to the surface sizing starch and its effect on coated paper properties was evaluated. Results showed that opacity and light scattering coefficient of coated paper were higher when base paper surface sized with cationic starch was used. Addition of less than 1% of cationic poly-DADMAC to the cationic surface sizing starch improved the opacity of coated paper significantly.

• Journal of the Korean Chemical Society
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• v.26 no.3
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• pp.179-187
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• 1982

The copolymerization of N-acryloylpyrrolidone and acrylonitrile was performed in N,N'-dimethylformamide at 50$^{\circ}$C and monomer reactivity ratio was obtained by using IR working curve and Fineman and Ross equation. ($r_1$ = 0.43, $r_2$ = 1.56) It is found that resulting copolymer is good polymeric initiator for anionic graft copolymerization of 2-pyrrolidone. Graft copolymers with polybutylamide (nylon-4) grafts onto poly(NAP-Co-AN) backbone were synthesized and the various effects on the graft copolymerization of 2-pyrrolidone were examined. The rate constants ($K_p$) of graft anionic polymerization at 40 and 50$^{\circ}$C were 2.82${\times}$10 and 2.93${\times}$10(l/mole, min), respectively.

• Composites Research
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• v.32 no.6
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• pp.375-381
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• 2019

Multiwalled carbon nanotubes (MWCNTs) are covalently functionalized with isocyanates by directly reacting commercial hydroxyl functionalized MWCNTs with excess 4,4'-methylenebis (phenyl isocyanate) (MDI) and hexamethylene diiosocyanate (HDI). HDI-modified MWCNTs results in a higher surface isocyanate density than MDI-modified MWCNTs. Anionic ring-opening polymerization of ε-caprolactam is conducted using a sodium caprolactam initiator in combination with a di-functional hexamethylene-1,6-dicarbamoylcaprolactam activator in the presence of isocyanate functionalized MWCNTs. This polymerization proceeds in a highly efficient manner at relatively low reaction temperature (150℃) and short reaction times (10 min). During the polymerization, the isocyanate functionalized MWCNTs act not only as reinforcing fillers but also as second activators. Nanocomposites with HDI modified MWCNTs exhibit higher reinforcement and faster isothermal crystallization than MDI modified MWCNTs. The results show that PA6 chains grow more effectively from HDI modified MWCNT surface than from MDI modified MWCNT surface, resulting in stronger interaction between PA6 and MWCNTs.