• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.6
• /
• pp.396-404
• /
• 2011

An investigation on the removals of PAH-quinone compounds, which are commonly produced from the biological and/or chemical treatments of PAH-contaminated soils, from the aqueous phase via birnessite (${\delta}-MnO_2$)-mediated oxidative transformation is described. It was demonstrated that acenaphthenequinone (APQ), p-PAH quinone can be removed via birnessite-mediated oxidative-coupling reactions, and anthraquinone (AQ) and 1,4-naphthoquinone (1,4-NPQ), o-PAH quinones were efficiently removed by birnessite-mediated cross-coupling reactions in the presence of catechol (CAT) as a reactive mediator. The removals of PAH-quinone compounds followed pseudo-first-order reactions, and the rate constant (k, $hr^{-1}$) for the removals of 1,4-NPQ under the experiment conditions (1,4-NPQ = 10 mg/L, CAT = 50 mg/L, ${\delta}-MnO_2$ = 1.0 g/L, pH 5, Reaction time = 6~96 hr) was 0.0426, which was about 4 times lower than that of APQ (0.173). With the observed pseudo-first order rate constants with respect to birnessite loadings under the same experimental conditions, the surface-normalized specific rate constant, $K_{surf}$, for 1,4-NPQ was determined to be $8.5{\times}10^{-4}L/m^2{\cdot}hr$. The analysis of the kinetic data with respect to birnessite loading indicated that the cross-coupling reactions of 1,4-NPQ consist of two different reaction steps over time and the results have also been discussed in terms of the reaction mechanisms.

• Carbon letters
• /
• v.7 no.2
• /
• pp.87-96
• /
• 2006

This paper describes the physical properties of filled Nylon6 composites resin with nano-sized carbon black particle and graphite nanofibers prepared by melt extrusion method. In improving adhesions between resin and fillers, the surface of the carbon filler materials were chemically modified by thermo-oxidative treatments and followed by treatments of silane coupling agent. Crystallization temperature and rate of crystallization increased with increases in filler concentration which would act as nuclei for crystallization. The silane treatments on the filler materials showed effect of reduction in crystallization temperature, possibly from enhancement in wetting property of the surface of the filler materials. Percolation transition phenomenon at which the volume resistivity was sharply decreased was observed above 9 wt% of carbon black and above 6 wt% of graphite nanofiber. The graphite nanofibers contributed to more effectively in an increase in electrical conductivity than carbon black did, on the other hand, the silane coupling agent negatively affected to the electrical conductivity due to the insulating property of the silane. Positive temperature coefficient (PTC) phenomenon, was observed as usual in other composites, that is, temperature increase results conductivity increase. The dispersity of the fillers were excellently approached by melt extrusion of co-rotational twin screw type and it could be illustrated by X-ray diffraction and SEM.

• Proceedings of the Korean Biophysical Society Conference
• /
• 2003.06a
• /
• pp.19-19
• /
• 2003

We have developed a cardiac cell model (Kyoto Model) for the sinoatrial node and ventricle, which is composed of a common set of kinetic equations of membrane ionic currents, Ca$\^$2+/dynamics of sarcoplasmic reticulum and contractile protein. To expand this model by including metabolic pathways, the intracellular ATP metabolism, which is pivotal in cardiac excitation - contraction coupling, was incorporated. ATP consumption by the sarcolemmal Na$\^$+/ pump and the Ca pump in the sarcoplasmic reticulum were calculated with stoichiometry of 3Na:2K:1ATP and 2Ca:1ATP, respectively. ATP consumption by contraction was estimated according to experimental data. Dependence of contraction on ATP and inorganic phosphate was modeled, based on data of skinned cardiac fiber. in production by mitochondrial oxidative phosphorylation was modified from Korzeniewski '||'&'||' Zoladz (2001), and creatine kinase and adenylate kinase reactions were incorporated. ATP dependence of ATP-sensitive K channel and L type Ca channel were also included.

• Journal of Soil and Groundwater Environment
• /
• v.14 no.1
• /
• pp.44-50
• /
• 2009

The occurrence of endocrine disrupting compounds (EDCs), chemicals that interfere with human hormone system, are increasing in the freshwater, waste water and subsurface as well. In this study, we determined the reactivity of three EDCs in the presence of birnessite. In aqueous phase, bisphenol A, 2,4-dichlorophenol and 17${\beta}$-estradiol, which possesses phenoxy-OH, were very rapidly transformed by birnessite: up to 99% of initial concentrations (50 mg/L for bisphenol A, 100mg/L for 2,4-dichlorophenol, and 1.5mg/L for 17${\beta}$-estradiol) were destroyed within 60 minutes. Especially, bisphenol A was the most reactive chemical, disappearing by 99% in a few minutes. The reaction occurred on the surface of birnessite, showing a linear increase of first-order kinetic constants with the increase of the surface area of birnessite. In soil slurry phase, the reactivity of birnessiteto EDCs was faster than in aqueous phase probably due to the cross coupling reaction of phenoxy radicals with soil organic matter. Considering the rapid transformation of the EDCs in the both phases, this oxidative cross coupling reaction mediated by birnessite would be an effective solution for the remediation of EDCs in environmental media, especially in soil.

• Environmental Engineering Research
• /
• v.11 no.4
• /
• pp.217-231
• /
• 2006

The gas-phase formation of polychlorinated naphthalenes (PCNs) and dibenzofurans (PCDFs) was experimentally investigated by slow combustion of the three chlorophenols (CPs): 2-chlorophenol (2-CP), 3-chlorophenol (3-CP) and 4-chlorophenol (4-CP), in a laminar flow reactor over the range of 550 to $750^{\circ}C$ under oxidative condition. Contrary to the a priori hypothesis, different distributions of PCN isomers were produced from each CP. To explain the distributions of polychlorinated dibenzofuran (PCDF) and PCN congeners, a pathway is proposed that builds on published mechanisms of PCDF formation from chlorinated phenols and naphthalene formation from dihydrofulvalene. This pathway involves phenoxy radical coupling at unsubstituted ortho-carbon sites followed by CO elimination to produce dichloro-9, 10-dihydrofulvalene intermediates. Naphthalene products are formed by loss of H and/or Cl atoms and rearrangement. The degree of chlorination of naphthalene and dibenzofuran products decreased as temperature increased, and, on average, the naphthalene congeners were less chlorinated than the dibenzofuran congeners. PCDF isomers were found to be weakly dependent to temperature, suggesting that phenoxy radical coupling is a low activation energy process. Different PCN isomers, on the other hand, are formed by alternative fusion routes from the same phenoxy radical coupling intermediate. PCN isomer distributions were found to be more temperature sensitive, with selectivity to particular isomers decreasing with increasing temperature.

• Fibers and Polymers
• /
• v.1 no.1
• /
• pp.25-31
• /
• 2000

Poly(3-hexyl thiophene)(P3HT) and poly(3-dodecyl thiophene)(P3DT) were polymerized by oxidative coupling with ferric chloride. The P3HT light-emitting device emitted red light and it could be observable in the ordinary indoor light. The device had the turn-on electric field of about 3$\times$$10^7$ V/m. The maximum electroluminescene (EL) intensity was obtained when the thickness of polymer layer was about 130 nm in IT0/P3HT/Al device. The maximum external quantum yield was 0.002%. The maximum luminance was 21 cd/$m^2$. The EL intensity decreases with increasing the crystallinity of the polymer layer. By using the oriented poly(3-alkyl thiophene)(PAT) layer as an electroluminescent layer in the ITO/polymer/Al light-emitting devices, the polarized EL light emission was observed. The EL intensity ratio of parallel to perpendicular direction to the stretch direction for P3HT was about 1.40.

• Proceedings of the Korean Fiber Society Conference
• /
• 1987.06b
• /
• pp.12-12
• /
• 1987

To improve the fibrillation phenomenon and processibili to of poly(p-phenyleneterephthalamide) (PPD-T) , a P/E copolyamide was prepared by introducing 4,4'-ethylene dianiline (EDA) into rigid chain backbone. The effects of semi-flexible segment on the liquid crystalline properties were investigated. The EDA, used as a comonomer, was prepared by catalylitic reduction of p,p'-dinitrophenyl , obtained by oxidative coupling of p,p'-dinitrotoluene. Various high molecular weight PIE copolyamides were prepared by low temperature solution polycondensation of terephthaloyl chloride (TPC) with various mixtures of p-phenylene diamine (PPD) and EOA. The PfE copolyamides were completely dissolved in 100% svlfuric acid, and the phase transition of P/E copolyamide-sulfuric acid systems was examined in teams of concentration and temperature. Over the chemical compositions, PIE=911, 812, and 713, solutions of anisotropic single phase were acquired. In particular, the two mixing ratios, 911 and 812, gave a good anisotropic spinning dope.

• Macromolecular Research
• /
• v.17 no.9
• /
• pp.714-717
• /
• 2009

Hole transport copolymers consisting of 3,4-ethylenedioxythiophene (EDOT) and N-4-butylphenyl-N,N-diphenylamine (BTPA) were synthesized by oxidative coupling reaction using $FeCl_3$ as an oxidant. These copolymers showed good solubility and their thin films showed sufficient morphological stability. The copolymers showed an absorption maximum around 320 nm. Copolymers had an oxidation peak at approximately $1.03{\sim}1.14V$ versus the Ag/AgCl electrode. The hole mobility increased with increasing portion of the EDOT unit. The hole mobility of the copolymer containing 57% of the EDOT unit showed the highest mobility of $3{\times}10^{-5}cm^2/V{\cdot}s$.

• Bulletin of the Korean Chemical Society
• /
• v.10 no.6
• /
• pp.568-572
• /
• 1989

Terphenyl dialdehyde 6 was obtained in 17.4% overall yield through oxidative coupling, methylation, and bisformylation reactions starting from p-cresol, and then coupled intermolecularly using McMurry reaction to give 22-membered macrocylic host 7 in 14.4% yield. In crystal structure host 7 has $C2_v$ symmetry with cis-cis configuration of two double bonds. Four methoxy groups adjacent to double bonds and the other two methoxy groups are directed opposite side, forming a cavity which can nest a guest. The cavity is filled by two inward-turned methyl groups out of four methoxy groups adjacent to double bonds. The kinetically controlled reaction mechanism leading to cis product was proposed. The cation binding properties of 7 were obtained using picrate extraction experiment from $D_2O\; into\; CDCl_3\; at\; 25^{\circ}C$. All the spherical cations (from $Li^+ to NH4^+)$ are complexed with free energies of $7.3{\pm}0.3$ kcal/mol.

• The Korean Journal of Pesticide Science
• /
• v.7 no.1
• /
• pp.45-50
• /
• 2003

This study was conducted to understand the role of oxidative enzyme cytochrome $P_{450}$ in the bioactivation of benfuracarb and to know metabolites of benfuracarb by cytochrome $P_{450}$. The bimolecular imhibition rate constant $(k_i)$ of benfuracarb on acetylcholinesterase (AChE) was as low as $1.1{\times}10^3\;M^{-1}\;min^{-1}$, suggesting that benfuracarb should be activated for its toxic action. The potency of benfuracarb on AChE in the oxidase system (cytochrome $P_{450}$ + NADPH) in vitro was 10-fold higher than that of control (cytochrome $P_{450}$). Such a similar result was also found in the oxidase + PBO system. In vivo the $I_{50}$ of benfuracarb was 22.7mg $kg^{-1}$, but pie-treatment of piperonyl butoxide (PBO) reduced the $I_{50}$ by >100mg $kg^{-1}$. This result suggests that cytochrome $P_{450}$ was involved in the activation of benfuracarb. Using microsomal oxidase system, metabolites of benfuracarb were elucidated. Fifty-eight percent of benfuracarb was converted to carbofuran, a major toxic metabolite, in the oxidase system, while only less than two percent of benfuracarb was converted to carbofuran in the oxidase + PBO system. These results also suggest that cytochrome $P_{450}$ was involved in the activation of benfuracarb. Overall results indicate that cytochrome $P_{450}$ could be involved in the bioactivation of benfuracarb to carbofuran.