• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.137-140
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• 2011

The aminolysis reactions of phenyl N-benzyl thiocarbamate with benzylamines in acetonitrile at $50.0^{\circ}C$ are investigated. The reactions are first order in both the amine and the substrate. Under amine excess, pseudo-first coefficient ($k_{obs}$) are obtained, plot of $k_{obs}$ vs free amine concentration are linear. The signs of ${\rho}_{XZ}$ (< 0) are consistent with concerted mechanism. Moreover, the variations of $\rho_X$ and $\rho_Z$ with respect to the sustituent in the substrate and large ${\rho}_{XZ}$ value indicate that the reactions proceed concerted mechanism. The normal kinetic isotope effects ($k_H/k_D$ = 1.3 ~ 1.5) involving deuterated benzylamine nucleophiles suggest a hydrogen-bonded, four-centered-type transition state. The activation parameters, ${\Delta}H^\ddagger$ and ${\Delta}S^\ddagger$, are consistent with this transition state structure.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.382-388
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• 1987

Kinetics studies on the reaction system of $[Ni(H_2O)_6]^{2+}+4CN^-{\rightleftharpoons}[Ni(CN)_4]^{2-}$ have been carried out in 0.005% gelatin solution at $25^{\circ}C$ by means of conductometry. The fifth-order kinetics were observed in the formation rate of $[Ni(CN)_4]^{2-}$ from the reaction of [Ni(H$_2O)_6]^{2+}$ and [CN]$^-$. The reaction was found first order in $[Ni(H_2O)_6]^{2+}$ and fourth order in [CN]$^-$. ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ were obtained the values of 5.15kcal/mole and -35.07 e.u., respectively. We have proposed the possible mechanism from the data obtained.

• Journal of the Korean Applied Science and Technology
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• v.10 no.2
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• pp.65-72
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• 1993

The kinetics of the addition of thiourea to cinnamenylisophorone derivatives(X : H, p-Br, $p-CH_3$ $m-CH_3$, $p-OCH_3$) was investigated using ultraviolet spectrophotometry in 20%(v/v) dioxane-$H_2O$ at $25^{\circ}C$. A rate equation which can be applied over wide pH range(pH $1.0{\sim}13.0$) was obtained. In order to investigate the substituent effects of cinnamenylisophorone derivatives. Hammett constant was plotted. As the result, the rate of uncleophilic addition of thiourea to cinnamenylisophorone derivatives was facilitated by electron donating group. It was found that addition of neutral thiourea which was not dissociated at the pH $1.0{\sim}9.0$ was proceeded, the reaction was proceeded by addition of dissociated anion of thiourea above the pH 10.0. On the basis of this kinetic study, the reaction mechanism of nucleophilic addition of thiourea was investigated.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1539-1542
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• 2011

The aminolysis of O-methyl S-aryl thiocarbonates with benzylamines are studied in acetonitrile at -45.0$^{\circ}C$. The ${\beta}_X$(${\beta}_{nuc}$) values are in the range 0.62-0.80 with a negative cross-interaction constant, ${\rho}_{XZ}$ = -0.42, which are interpreted to indicate a concerted mechanism. The kinetic isotope effects involving deuterated benzylamine nucleophiles ($XC_6H_4CH_2ND_2$) are large, $k_H/k_D$ = 1.29-1.75, suggesting that the N-H(D) bond is partially broken in the transition state by forming a hydrogen-bonded four-center cyclic structure. The concerted mechanism is enforced by the strong push provided by the MeO group which enhances the nucleofugalities of both benzylamine and arenethiolate from the putative zwitterionic tetrahedral intermediate.

• Journal of Environmental Science International
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• v.4 no.4
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• pp.367-377
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• 1995

The study of flocculation kinetics is of fundamental interest in the field of water treatment, because rational study of the factors affecting the coagulation process should be based on the rate of particle growth. The effect of sulfate on flocculation kinetics were examined using ferric nitrate as a coagulant to coagulate kaolin clay in water under several experimental conditions. Both the particle size distribution data obtained from the AIA and the on-line measurement of turbidity fluctuation by the PDA were used to measure flocculation kinetics. Results show that sulfate ion added to the kaolin suspension played an important role in the flocculation process, not only improving flocculation kinetics at more acidic pH levels but also changing surface charge of particles. The kinetics of flocculation were improved mainly by the enhanced rate and extent of Fe(III) precipitation attributed to the addition of sulfate, and thereby, better interparticle collision frequency, but little by the charge reductions resulting from the sulfate addition. The increase in sulfate concentration beyond $3\times10^{-4}M (up to 2\times10^{-3}M)$ did not induce further improvement in flocculation kinetics, although the higher concentrations of sulfate ion substantially increased the negative ZP value of particles. Key Words : Flocculation Kinetics, Fe(III) Coagulant, Sulfate ion, Turbidity Fluctuation.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.4
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• pp.2343-2347
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• 2013

Objective: This investigation aimed to determine effects of celecoxib on the cell cycle kinetics of the gastric cancer cell line MGC803 and the mechanisms involved by assessing expression of cytochrome C and caspase-9 at the protein level. Methods: Cell proliferation of MGC803 was determined by MTT assay after treatment with celecoxib. Apoptosis was assessed using fluorescence staining and cell cycle kinetics by flow cytometry. Western blotting was used to detect the expression of caspase-9 protein and of cytochrome C protein in cell cytosol and mitochondria. Results: Celecoxib was able to restrain proliferation and induce apoptosis in a dose- and time-dependent manner, inducing G0/G1 cell cycle arrest, release of cytochrome C into the cytosol, and cleavage of pro-caspase-9 into its active form. Conclusion: Celecoxib can induce apoptosis in MGC803 cells through a mechanism involving cell cycle arrest, mitochondrial cytochrome C release and caspase activation.

• Journal of Environmental Science International
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• v.22 no.10
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• pp.1327-1335
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• 2013

Na-A zeolite (Z-Cl) was synthesized from coal fly ash, which is a byproduct of coal combustion for the generation of electricity. The adsorption of $Cu^{2+}$ and $Zn^{2+}ions$ onto Z-C1 was investigated via batch tests over a range of temperatures (303.15 to 323.15 K). The resultant experimental equilibrium data were compared to theoretical values calculated using model equations. With these results, the kinetics and equilibrium parameters of adsorption were calculated using Lagergren and Langmuir-Freundlich models. The adsorption kinetics revealed that the pseudo second-order kinetic mechanism is predominant. The maximum adsorption capacity ($q_{max}$) values were 139.0-197.9 mg $Zn^{2+}$/g and 75.0-105.1 mg $Cu^{2+}/g$. Calculation of the thermodynamic properties revealed that the absorption reactions for both $Cu^{2+}$ and $Zn^{2+}$ were spontaneous and endothermic. Collectively, these results suggest that the synthesized zeolite, Z-C1, can potentially be used as an adsorbent for metal ion recovery during the treatment of industrial wastewater at high temperatures.

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.946-951
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• 2005

Biodegradation of the endocrine-disrupting chemical di-n-butyl phthalate (DBP) was investigated using a bacterium, Pseudomonas fluorescens B-1, isolated from mangrove sediment. The effects of temperature, pH, salinity, and oxygen availability on DBP degradation were studied. Degradation of DBP was monitored by solid-phase extraction using reversed-phase HPLC and UV detection. The major metabolites of DBP degradation were identified as mono-n-butyl phthalate and phthalic acid by gas chromatography-mass spectrometry (GC-MS) and a pathway of degradation was proposed. Degradation by P. fluorescens B-1 conformed to first-order kinetics. Degradation of DBP was also tested in seawater by inoculating P. fluorescens B-1, and complete degradation of an initial concentration of $100{\mu}g/l$ was achieved in 144 h. These results suggest that DBP is readily degraded by bacteria in natural environments.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.410-417
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• 2009

Carbon dioxide was absorbed into GMA solution in a stirred flat cell using mesoporous catalyst Imidazole-CP-MS41, which was synthesized by CP-MCM41 with imidazole. Experiments were carried out at a batch-type absorber with different conditions, varying reaction temperature, concentration of GMA, solvent but maintaining 50 rpm of agitation speed and 2 g of catalyst. Absorption rate of $CO_2$ was used to obtain the kinetics based on the film theory using zwitterion mechanism with 2 elementary reaction and the kinetics were correlated with the solubility parameter of the solvents.

• Applied Biological Chemistry
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• v.40 no.1
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• pp.53-57
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• 1997

The rate of hydrolysis of insecticidal 1-(6-chloro-3-pyridylmethyl) -2-nitro-iminoimidazolidine (common name; imidacloprid) have been investigated in 15%(v/v) aqueous dioxane at $45^{\circ}C$. From the kinetics and non-kinetics data such as pH-effect, solvent effect(m=0.04, n=0.30 IT m<${\Delta}H^{\neq}=16.14kcal{\cdot}mol^{-1}\;&\;{\Delta}S^{\neq}=-0.03e.u.$), rate equation ($k_{obs.}=4.56{\times}10^{-3}[OH^-]$) and analysis of hydrolysis product, 1-(6-chloro-3-pyridylmethyl-2)-imidazolidinon, the hydrolysis mechanism of imidacloprid is proposed that the specific base catalyzed hydrolysis($K_{OH^-}$) through nucleophilic addition-elimination ($Ad_N-E$) mechanism proceed via intermediate, 1-(6-chloro-3- pyridylmethyl)-2-hydroxy-2-imidazolidinylisonitraminate (I) and ${\beta}$-3-(6-chloro-3-pyridylmethyl)aminoethyl-1-nitrourea(III). And the half-life(t1/2) of hydrolytic degradation at pH 8.0 and $45^{\circ}C$ was about 4.5 months.