• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.211-216
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• 2012

Wet chemical etching of stainless steel foil by aqueous ferric chloride solution was investigated in this study. Effects of various process parameters (e.g. etchant agitation rate, etchant temperature, $Fe^{3+}$ ion concentration, free HCl concentration, specific gravity, etc.) on the etch rate was first studied, and it was found that the etch rate of AK (aluminum-killed) steel, chromium metal and stainless steel (STS430J1L alloy) follows the pseudo-first order reaction equation. When the fatigue ratio of etchant was kept under 16%, sludge was not formed in the solution, and the etched surface showed smooth roughness. The etch rate decreases as Baume of etchant increases, but the effect of free HCl concentration on the etch rate turned out to be minimal. Experimental data were compared with the calculated results from modeled equation, showing very good agreement.

• Journal of Life Science
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• v.7 no.2
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• pp.119-126
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• 1997

Phytase(myo-inositol hexkisphosphate phosphohydrolase ; EC 3.1.3.8) was purified from the mucoas of rat intestinal. The molecular weight of enzyme was determined to be 160kDa by sephacryl S-200 gel filtration. Analysis of the purified enzyme o SDS-polyacrylamide gel electrophoresis(SDS-PAGE) showen that it was composed of two different subunits and the molecular weight of its subunit was found to be 70kDa and 90kDa respectively, indicating that this enzyme is hetrodimer. The enzyme activities were activated in the presence of $ MgCl_{2}$, but inhibited by $ZnCl_{2}$, $MnCl_{2}$, and EDTA. The substrates tested, phytase showed the highest affinity for the enzyme at the physiological ph. The Km value for phytic acid(inositol-hexakisphosphate)was 0.31 mM at pH 7.4. rat intestinal mucosa phytase seems to play an important in the metabolism of inositol.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.802-807
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• 1996

Second-order rate constants have been measured spectrophotometrically for the reactions of aryl benzoates (X-C6H4CO2C6H4-Y) with EtO-, Z-C6H4O- and Z-C6H4C(Me)=NO- in absolute ethanol at 25.0 ℃. All the reactions have been performed in the presence of excess 18-crown-6 ether in order to eliminate the catalytic effect shown by alkali metal ion. A good Hammett correlation has been obtained with a large ρ- value (-1.96) when σ- (Z) constant was used for the reaction of p-nitrophenyl benzoate (PNPB) with Z-C6H4O-. Surprisingly, the one for the reaction of PNPB with Z-C6H4C(Me)=NO- gives a small but definitely positive ρ- value (＋0.09). However, for reactions of C6H5CO2C6H4-Y with EtO-, correlation of log k with σ- (Y) constant gives very poor Hammett correlation. A significantly improved linearity has been obtained when σ0 (Y) constant was used, indicating that the leaving group departure is little advanced at the TS of the RDS. For reactions of X-C6H4CO2C6H4-4-NO2 with EtO-, C6H5O- and C6H5C(Me)=NO-, correlations of log k with σ (X) constants for all the three nucleophile systems give good linearity with large positive ρ values, e.g. 2.95, 2.81 and 3.06 for EtO-, C6H5O- and C6H5C(Me)=NO-, respectively. The large ρ values clearly suggest that the present reaction proceeds via a stepwise mechanism in which the formation of the addition intermediate is the RDS.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.262-270
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• 2019

Ferronickel slag, which is an industrial byproduct, is activated by mechanochemical reaction as a nonferrous metal and can be used as an admixture. Therefore, ferronickel slag is used as a substitute resource of admixture. In this study, to evaluate the effect of mixed of ferronickel slag powder and admixture, a mortar using a mixture of ferronickel slag powder, quicklime, gypsum and calcium chloride was fabricated by vibrated and rolled manufacturing method. Strength were evaluated by flexural and compressive strength tests, and durability was evaluated by performing chlorine ion penetration resistance and chemical resistance test. When the substitution ratio of ferronickel slag powder is constant, it is considered that the mixed use of quicklime, gypsum and calcium chloride as admixtures increases the performance.

• Analytical Science and Technology
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• v.19 no.4
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• pp.285-289
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• 2006

In this study, the effect of an acidic treatment on granular activated carbon (GAC) and activated carbon fibers (ACF) was investigated for a $Pb^{2+}$ and $Ni^{2+}$ ion adsorption. 1.0 M nitric acid solution was used as the acid solution for the surface treatment. Surface properties of the GAC and ACF were characterized by the pH, elemental analysis and pHpzc (pH of the point of zero charge). Their specific surface area and the pore structure were also evaluated by the nitrogen adsorption data at 77K. As a result, the acidic treatment led to an increase of the oxygen-containing functional groups. Furthermore, the adsorption capacity of the acid-treated GAC and ACF was improved in the order of acidic-ACF > untreated-ACF > acidic-GAC > untreated-GAC, though the decrease in specific surface area induced by a pore blocking of the functional groups was observed.

• Journal of the Korean Electrochemical Society
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• v.20 no.2
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• pp.27-33
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• 2017

Conventional lithium ion batteries suffer from notorious safety issues caused by inevitable lithium dendrite formation and proliferation during over/fast charging processes. The lithium dendrites or mechanical damage on the separator induce internal short circuit in LiB that generates extensive amount of heat within contacted electrode surfaces through the separator. During this heat generation, conventional polyolefin separators shrinks dramatically, and increasing short circuit pathway, that causes the battery to explode. To overcome this serious issue, ceramic coated separators are developed in commercial LiB to enhance thermal and mechanical stability. In this paper, various size(IL = 488.5 nm, I = 538.7 nm, S = 810.3 nm, D = 1533.3 nm) of $Al_2O_3$ particles are coated using styrene-butadiene rubber(SBR) / carboxymethyl cellulose(CMC) binder on PE separator to investigate its thermal stability and electrochemical effect on LiB coin cell with NCM cathode and Li metal anode.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.292-297
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• 2005

$LiMO_{2}(M=Co,Ni)$ samples were synthesized with $Li_{2}CO_{3},\;Co_{3}O_{4}$, and NiO by the solid-state reaction method. In the case of $LiCoO_{2}$, at low temperature$(T=400^{\circ}C)$ spinel structure was synthesized and the obtained spinel phase was transformed to layered phase at high temperature$(T\ge600^{\circ}C)$. The phase transition behaviors of $LiCoO_{2}$ were investigated with various heating temperature and time. The rate of transition was directly proportional to the concentrations of reactant, and activation energy of reaction was around 6.76 kcal/mol. When CoO(rock salt structure) was used as a starting material instead of $Co_{3}O_{4}$(spinel structure), layered structure of $LiCoO_{2}$ was obtained at low temperature. In the case of $LiNiO_{2}$ the transition from layered structure to rock salt structure occurred easily by disordering/ordering reaction, but did not occur in $LiCoO_{2}$. The difference in metal ion radii in $LiCoO_{2}$ and $LiNiO_{2}$ results in different behaviors of phase transitions.

• Microbiology and Biotechnology Letters
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• v.34 no.1
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• pp.28-34
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• 2006

A native extracellular acid phosphatase, phytase (EC 3.1.3.8), from Bacillus coagulans IDCC 1201 (commercially known as Lactobacillus sporogenes) used as probiotics, was characterized. Though some strains of B. coagulans have been evaluated with regard to several health-promoting effects, it has not been reported to produce phytase. Partially purified phytase front the strain IDCC 1201 had a pH optimum of 4.0 and a temperature optimum of $50^{\circ}C$, respectively. The requirement for divalent cations was studied and cobalt ion remarkably increased the enzyme activity. The removal of metal ions from the enzyme by EDTA decreased activity below 50%. The enzyme activity depleted restored when the assay was performed in the presence of $Co^{2+}$. Also, $Co^{2+}$ is the most active stimulator and has unique activation effect at high temperature. The phytase was specific for sodium phytate and p-nitrophenylphosphate, which is different from other known Bacilli phytases. The putative amino acid sequences of the phytase from B. coagulans IDCC 1201 were very similar to that of the phytase from B. subtilis strain 168. Based on these data, we concluded that the phytase from B. coagulans IDCC 1201 is a $Co^{2+}$-dependent acid phosphatase. Therefore, the strain B. coagulans IDCC 1201 is thought to be a valuable addititive for livestocks as well as a beneficial probiotics for human.

• Journal of the Korean Chemical Society
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• v.33 no.4
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• pp.366-370
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• 1989

A new macrocyclic ligand 1,15,18-triaza-3,4;12,13-dibenzo-5,8,11-cycloeicosane (NdienOdien$H_4$ = $N_3O_3$) has been synthesized and identified by element analysis, NMR and IR spectrophotometry. Stepwise protonation constants of ligand are determined by potentiometry in 95% methanol solution(I = 0.1 mol $dm^{-3}$, $Me_4$NCl). log $K_1$;log $K_2$;log $K_3$ = 9.1;8.1;3.6.The kinetics of the acid-promoted dissociation reactions of complex cations of nickel(II) and copper(III) with NdienOdien and NdienOen macrocyclic ligands having, respectively, 17 and 20 ring members, have been studied spectrophotometrically in HCl$O_4$ NaCl$O_4$ aqueous solutions. From the temperature effect on kinetic constant ($k_{obs}$), the parameters of activation(${\Delta}H^{\neq}$, ${\Delta}S^{\neq}$) of dissociation reaction for $ML^{2+}$ with $H^+$ ion have been determined. We have proposed the possible mechanism of the reaction from the data obtained.

• Korean Journal of Microbiology
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• v.34 no.4
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• pp.225-230
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• 1998

This study was carried out to investigate the effect of cadmium ion on activities of cadmium-adapted malate dehydrogenase (adapted-MDH), which is defined to be an enzyme obtained from an extreme cadmium-tolerant yeast Hansenula anomaul B-7 grown in medium containing 1 mM cadmium ion. Cadmium-nonadapted malate dehydrogenase (nonadapted-MDH), which is defined to be enzyme expressed in the cells grown in $Cd^{2+}$ -free medium was also characterized by the same manner. Activities of the adapted-MDH and the nonadapted-MDH were strongly induced to 450% and to 150% in comparision with the control examined with 1 mM $Cd^{2+}$, respectively. The adapted-MDH activity was stimulated to 147%, 150%, and 135% compared with the control analyzed with 1 mM $Zn^{2+}$, 1 mM $Mn^{2+}$, and 1 mM $Ca^{2+}$, respectively and to 925%, and 250% compared with the control analyzed in the presence of 2 mM $Cd^{2+}$, and 2.5 mM $Zn^{2+}$, respectively. Km values of the adapted-MDH and the nonadapted-MDH were calculated to be the same 6.9 mM for L-malate, respectively. The Km value of the nonadapted-MDH was not changed by $Cd^{2+}$ while Vmax of the nonadapted-MDH was increased by $Cd^{2+}$. In contrast, both the Km and the Vmax values of the adapted-MDH were changed by $Cd^{2+}$.