• Korea-Australia Rheology Journal
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• v.15 no.3
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• pp.151-156
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• 2003

In this research, experimental studies were performed to examine the rheological behavior of equimolar solutions of cetylpyridinium chloride (CPyCl) and sodium salicylate (NaSal) solutions with concentration. The surfactant solutions were prepared by dissolving 2 mM/2 mM - 80 mM/80 mM of surfactant/counterion in double-distilled water. It has been observed that the zero shear viscosity shows abrupt changes at two critical values of C^*$ and C^{**}$. These changes are caused by the switching of relaxation mechanism with concentration of CPyCl/NaSal solutions at those concentrations. The wall slip velocities of dilute and semidilute CPyCl/NaSal solutions show a dramatic increase with shear rate where the shear viscosity exhibits shear thickening behavior for dilute solutions and shear thinning behavior for semi-dilute solutions, respectively. Considering that the dramatic increase in wall slip velocity should be related to the formation of shear-induced structure (SIS) in the surfactant solution, the shear thickening behavior of semi-dilute solutions is caused by elastic instability unlike the case of dilute solutions.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1277-1281
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• 2011

Making use of chitosan (CS) and ethylenediaminetetraacetic acid (EDTA) as a reaction system, CS-EDTA nanoparticles were synthesized through a facile counterion complex coacervation method. $Ag^+$ could enter porous CS nanoparticles synthesized with this method, allowing Ag nanoparticles within chitosan nanoparticles were synthesized by reducing silver nitrate with chitosan. Because of the noncovalent interaction between CS and EDTA, the EDTA could be easily removed via dialysis against water, and pure core/shell-type Ag/CS nanoparticles could be obtained. The nanoparticles showed higher antibacterial activity toward E. coli than the active precursor Ag nanoparticles and CS.

• Polymer(Korea)
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• v.25 no.6
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• pp.826-832
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• 2001

In this study, PPy/gold/mylar type electroactive bi-layer actuator was prepared by the electrochemical polymerization of pyrrole onto the gold/mylar film and the actuation characteristics were studied using bending beam method. Conducting polymer-based actuators undergo volumetric changes due to the movement of dopant ions into the film during the electrical oxidation process. The bilayer films exhibited different actuation characteristics depending on dopant ion size. It was observed that the relatively small dopant ion (i.e. toluene sulfonate) moved into the PPy film at oxidized state, so volume expanded to result in bending motion. In case of the film having large dopant ion (i.e. dodecylbenzenesulfonate), volume expansion was observed at reduced state. This is due to the incorporation of $Na^+$ counterion with water molecules, while the large dopant ion was fixed in the film due to the limited mobility during tile redox process.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1527-1532
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• 2007

Lysine produced during microbial fermentation is usually recovered by an ion-exchange process, in which lysine is first converted to the cationic form (by lowering the pH to less than 2.0 with sulfuric acid) and then fed to a cationexchange column containing an exchanger that has a sulfone group with a weak counterion such as NH;. Ammonia water with a pH above 11 is then supplied to the column to displace the purified lysine from the column and allow its recovery. To enhance the adsorption capacity and for a possible reduction in chemical consumption, monovalent lysine fed at pH 4 was investigated in comparison with conventional divalent lysine fed at pH 1.5. The adsorption capacity increased by more than 70% on a mass basis using pH 4 feeding compared with pH 1.5 feeding. Lysine adsorbed at pH 4 started to elute earlier than that adsorbed at pH 1.5 when ammonia water was used as the eluant solution, and the extent of early elution became more notable at lower concentrations of ammonia. Moreover, the elution of monovalent lysine fed at pH 4 displayed a stiffer front boundary and higher peak concentration. However, when the ammonium concentration was greater than 2.0 N, complete saturation of the bed was delayed during adsorption and the percent recovery yield from elution was lowered., both drawbacks that were considered inevitable features originating from the increased adsorption of monovalent lysine.

• The Korean Journal of Food & Health Convergence
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• v.5 no.4
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• pp.13-17
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• 2019

Amiodarone hydrochloride is an antiarrhythmic agent which has low aqueous solubility and presents bioavailability problem. These properties are a challenge for the pharmaceutical industry. Inclusion of lipophilic compound in the hydrophobic core of micelles, i.e. self-assembled structures based on surfactants in aqueous solution, is one way of increasing the solubility. Intravenous formulation of amiodarone hydrochloride with polysorbate 80 as a detergent and benzyl alcohol as a co-solvent is used in medical practice. This paper aimed to study the effect of polysorbate 80 and benzyl alcohol on the water solubility of amiodarone hydrochloride. Formation of mixed micelles consisting of nonionic surfactant polysorbate 80 and cationic amiodarone with chloride counterion was investigated by fluorescence spectroscopy. Benzyl alcohol was found to decrease the stability of the mixed micelles and lead to crystallization of amiodarone hydrochloride. The greatest amounts of crystals formed at 4℃ for 30 days in the model drug solutions with polysorbate 80 concentrations of 100.1 mg/mL and 97.9 mg/mL. A change of the polysorbate 80 concentration and avoidance the use of benzyl alcohol are recommended to improve the stability of the parenteral dosage form. These results can open new perspectives in the optimization of amiodarone intravenous formulations.

• Fisheries and Aquatic Sciences
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• v.10 no.1
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• pp.8-15
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• 2007

Rhodopsin, a dim-light receptor, is a model system for the study of G protein-coupled receptors that transduce extracellular signals into cells. To study the molecular mechanisms of visual systems in fish, the rod opsin gene of olive flounder Paralichthys olivaceus was characterized. The full-length P. olivaceus opsin gene was obtained by PCR amplification of genomic DNA, as well as cDNA synthesis. A comparison of clones obtained from both methods indicated that the olive flounder rod opsin gene lacks introns. Sequence analysis of the opsin gene indicated that it contains a 1,056-bp open reading frame encoding 352 amino acids. The deduced amino acid sequence contains features of typical rod opsins, such as sites for Schiff's base formation (K296) and its counterion (E113), disulfide formation (C110 and C187), and palmitoylation (C322 and C323). An opsin sequence alignment showed the highest similarity between P. olivaceus and Solea solea (95.1%), followed by Hippoglossus hippoglossus (94.5%). An opsin phylogenetic tree revealed a close relationship between olive flounder and teleost rod opsins.

• Journal of the Korean Applied Science and Technology
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• v.25 no.1
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• pp.65-72
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• 2008

The ion exchangers supported on silica gel containing primary, secondary, or tertiary amine groups show a behaviour that is weakly acidic, while the quaternary salts are strongly acidic. These properties change according to the hydrophilicities of the modifier functional groups. Ammonium salt derivatives supported on silica gel were prepared from silica modified with 3-Aminopropyltriethoxysiliane and N-3-(Trimethoxysilyl)propylehtylene diamine. The preparation and the ion exchange properties of two systems were discussed. Two systems have different hydrophilicities and contain ammonium chloride derivatives of 3-amminopropyltriethoxysilane and N-3-(triehtoxysilyl)propyl ethylene diamine supported on silica gel, $SA^+/Cl^-$ and $SA^+/Cl^-$, respectively. The high affinity to perchlorate ion presented by the $SA^+/Cl^-$ through the equilibrium studies of ion exchange led us to its application as an ion selective electrode for the perchlorate ion. The determination of the perchlorate ion in the presence of other anions and in complexes is very difficult. Few analytical methods are available and most of them are indirect. Both materials showed potential use as an ion exchanger; they are thermically stable, achieve equilibrium rapidly in the presence of suitable exchanger ions, and are easily recovered.

• Polymer(Korea)
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• v.36 no.4
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• pp.519-524
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• 2012

Capacitance measurements of the polymer light-emitting diodes (PLEDs) with conjugated polyelectrolyte (CPE) electron transporting layers (ETLs) provide important information of device physics for understanding the function of CPEs as ETLs, together with current density-voltage-luminescence measurements. We investigated the counterion-dependent capacitance behaviors that present a highly negative or positive capacitance at the low frequency, and suggested different carrier injection mechanisms. Capacitance model study reveals that the electron injection mechanism can be described either by the dipole alignment scheme or by electronic charge carrier accumulation at the cathode/ETL/emission layer interfaces.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.477-483
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• 2006

Ionic liquids in the form of organic salts are being widely used as new solvent media. In this paper three positional isomers, o-amino benzoic acid, m-amino benzoic acid, and p-amino benzoic acids were separated with four different ionic liquids as mobile phase additives using high performance liquid chromatography (HPLC). The following ionic liquids were used: 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][$BF_{4}$]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIm][$BF_{4}$]), 1-ethyl-3-methylimidazolium methylsulfate ([EMIm][MS]), and 1-octyl-3-methylimidazolium methylsulfate ([OMIm][MS]). The effects of the alkyl group length on the imidazolium ring and its counterion, and the concentrations of the ionic liquids on the retention factors and resolutions of amino benzoic acid isomers were tested. The results of the separations with ionic liquids as the eluents were better than those without ionic liquids. Excellent separations of the three isomers were achieved using 2.0-8.0 mM/L [OMIm][MS] and 1.0-8.0 mM/L [EMIm][MS] as the eluent modifiers.

• Journal of Photoscience
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• v.9 no.2
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• pp.311-313
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• 2002

X-ray structures of pharaonis phoborhodopsin (ppR) show the different direction of the side chain of Arg72 from that of the corresponding residue (Arg82) of bacteriorhodopsin, BR. For BR, this residue is considered to play an important role in the proton pumping. In order to investigate the role of Arg72 in ppR, we constructed Arg72 mutants of R72A, R72K and R72Q, and measured the photocycle and proton pumping activities. The pH-titration curves on the absorption maximum of the mutants were shifted to alkaline in comparison of that of the wild-type. This may imply the increase of pKa of D75, suggesting the presence of the (probably electric) interaction between D75 and Arg72. Rate constants of the M-decay were 3-7 times faster than that of the wild-type, and the time for the completion of the photocycling was also reduced. Using Sn0$_2$ electrode, the rate of transmembrane proton transport was measured upon illumination. The photo-induced proton pumping activities were estimated after the corrections that are the percentages of the associated form of D75 (which has no pumping activity) and the photocycling rates. R72A and R72Q showed the reduced activity while R72K did not reduce the activity.