• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.664-671
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• 1998

Poly pyrrole polymer(ppy) has an excellent electrical conductivity and can be easily polymerized on anode to give various morophology according to doped anion on electroactive sites. To improve the properties of brittleness, ageing and hydrophobisity, poly furan polymer(pfu) having a high initiation potential was anodically implanted in this porous ppy film matrix to get the Pt/ppy/pfu(x)type of polymer composite electrode. Cyclic voltammetry and electrochemical impedance methods were used to these electrode, where $PF_6^-,\; BF_4^-$, and $ClO_4^-$ ions were employed as dopants. The composition of the pfu(x) at the electrode was changed from 0 to 1.10, but the range was useful only at 0.1 to 0.2 as the redox electrode. The polymer composite electrode doped with $PF_6^-$ was better in charge transfer resistance by a factor of 40 times and in double layer capacitance by a factor of 20 times than others. The charge transfer in the polymer film of the electrode was influenced on frequency change and equivalent circuit of this electrode had Warburg impedance including mass transfer.

• Preventive Nutrition and Food Science
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• v.6 no.1
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• pp.43-50
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• 2001

The effects of cardiac ischemia-reperfusion and $\beta$-adrenergic stimulation on metabolic function and energetics were investigated in Lan gendorff-perfused spontaneously hypertensive rat (SHR) hearts. Sarcoplasmic reticulum {TEX}$Ca^{2+}${/TEX}-dependent ATPase and cardiac lactate dehydrogenase (LDH) are additionally studied. The perfusion medium (1.0 mM {TEX}$Ca^{2+}${/TEX}) contained 5 mM glucose(+5 U/L insulin) and 2 mM pyruvate as substrates. Global ischemia was induced by reducing perfusion pressure of 100 to 40 cm {TEX}$H_{2}${/TEX}O, followed by 20 min reperfusin. Isoproterenol (ISO, 1$\mu$M) was infused for 10 min. Coronary vascular resistance and myocardial oxygen consumption ({TEX}$MVO_{2}${/TEX}) of SHR were increased in parallel with enhanced venous lactate during ischemia and reperfusion compared to those of Sprague Dawley (SD) hearts. Although ischemia-induced increase in venous lactate and combined adenosine plus inosine was abolished, coronary vasodilation produced in SD during reperfusion. In SHR, depressed reactive hyperemia was associated with a fall in cardiac ATP and CrP/Pi ratio and a rise in intracellular lactate/Pyruvate ratio. On the other hand, ISO produced coronary functional hyperemia and an increase in {TEX}$MVO_{2}${/TEX}. However, these responses were less than those in SHR hearts. The ATPase activity of SHR was attenuated in free {TEX}$Ca^{2+}${/TEX} concentrations used under basal condition and with ISO compared to that of SD. Venous lactate output and cardiac LDH activity were augmented in SHR as influenced by ISO. These results demonstrate that coronary reactive and functional hyperemia was dpressed in SHR, which cold be explained by alterations in the cytosolic phosphorylation potential and the cytosolic redox state manipulated by LDH, and by abnormal free calcium handling.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.435-436
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• 2008

Dye-sensitized Solar Cells(DSSCs) which convert incident sun light into electricity were expected to overcome global warming and depletion of fossil fuels. And it is one of study that is lately getting into the spotlight because manufacturing method is more simple and inexpensive than existing silicon solar cells. In this respect, DSSCs are in the limelight as the next generation solar cells. DSSCs are generally composed of a dye-modified $TiO_2$ photoelectrode, a Pt counter electrode, and an electrolytes containing a redox couple$(I^-/I_3^-)$. Among these elements, pt electrode were prepared by applying electric potential to FTO substrate in the $H_2PtCl_6$ solution. In this study, we report the solar cell efficiency depending on $PtCl_4$ concentration change. $PtCl_4$ concentration was 1mM, 5mM, 10mM, and 20mM, and adhered on FTO glass substrate by sintering process. When applied each $PtCl_4$ counter electrode on DSSC, the best efficiency was found at 10mM of $PtCl_4$ concentration. The catalyst promotes the movement of electron from the counter electrode to the electrolyte the higher the molarity, the better the efficiency. However, in case of 20mM, it is estimated that over-deposited $PtCl_4$ tends to restrict the movement of electron due to its bundle formation.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.11-16
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• 2009

Composite electrodes for redox supercapacitor were prepared potentiodynamically by the deposition of $RuO_2$ and the co-deposition of Ru-Co mixed oxide on the surface of single-walled carbon nanotube. Electrode of Ru-Co mixed oxide, in which Ru(13.13 wt%) and Co(2.89 wt%) were deposited on the carbon nanotube, exhibited a similar specific capacitance(${\sim}620\;F\;g^{-1}$) with $RuO_2$ electrode at a low potential scan rate($10\;mV\;s^{-1}$), but showed a superior one ($570\;F\;g^{-1}$) at a high scan rate($500\;mV\;s^{-1}$) than that of $RuO_2$($475\;F\;g^{-1}$). Such increase in the specific capacitance at high scan rate by the co-deposition of Ru and Co species was due to the structural support of Co species to provide the electronic conduction through Ru species.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.04a
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• pp.18-25
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• 2001

A new wood-degrading fungus Trichophyton rubrum LKY-7 secretes a high level of laccase in a glucose-peptone liquid medium. The production of laccase by the fungus was barely induced by 2,5-xylidine. The laccase has been purified to homogeneity through three chromatography steps in an overall yield of 40%. The molecular mass of the purified laccase was about 65 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified laccase had the distinct blue color and had basic spectroscopic features of a typical blue laccase: two absorption maxima at 278 and 610 nm and a shoulder at 338 nm. The N-terminus of the laccase has been sequenced, revealing high homology to laccases from wood-degrading white-rot fungi such as Ceriporiopsis subvermispora. The enzyme had a "low" redox potential (0.5 V vs normal hydrogen electrode), yet it was one of the most active laccases in oxidizing a series of representative substrates/mediators. Compared with other fungal laccases, the laccase has a very low Km value with ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid] as a substrate and a very high Km value with violuric acid as a substrate. The laccase has the isoelectric point of 4.0. The laccase had very acidic optimal pH values (pH 3-4) while it was more stable at neutral pH than at acidic pH. The laccase oxidized hydroquinone faster than catechol and pyrogallol. The oxidation of tyrosine by the laccase was not detectable under the reaction conditions. The laccase was strongly inhibited by sodium azide and sodium fluoride. fluoride.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.208-209
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• 2011

In this work, we developed self-assembled monolayers (SAMs) of alkanethiols on gold that can release amine groups, when an electrical potential was applied to the gold. The strategy was based on the introduction of the electroactive carbamate group, which underwent the two-electron oxidation with simultaneous release of the amine molecules, to alkanethiols. The synthesis of the designed thiol compounds was achieved by coupling isocyanate-containing compound with hydroquinone. The electroactive thiols were mixed with hydroxyl-containing alkanethiol [$HS(CH_2)_{11}OH$] to form mixed monolayers, and cyclic votammetry was used for the characterization of the release. The mixed SAMs showed a first oxidation peak at +540 mV (versus Ag/AgCl reference electrode), demonstrating irreversible conversion from carbamate to hydroqinone with simultaneous release of the amine groups. The second and third cycles showed typical reversible redox reaction of hydroquinone and quione: the oxidation and reduction occurred at +290 mV and -110 mV, respectively. The measurement of ToF-SIMS further indicates that electrochemical-assisted chemical reaction successfully released amine groups. This new SAM-based electrochemistry would be applicable for direct release of biologically active molecules that contain amine groups.

• Korean Journal of Environmental Biology
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• v.17 no.2
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• pp.183-190
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• 1999

The bioleaching of heavy metals from fly ash was performed by Thiobacillus thiooxidans MET isolated from the enrichment culture of an anaerobically digested sludge. The effect of solid concentrations on the efficiency of metal leaching was studied in shaken flasks. In the range of solid concentrations 20 g.L­$^1$to 100 g.L­$^1$T. thiooxidans MET oxidized S$^{0}$ to sulfate without any lag period. The final pH of slurry solution was decreased to below pH 1, and the final oxide-redox potential (ORP) was increased to over 420 mV in the solid concentrations below 100 g.L­$^1$. However, the initial lag period of 4 to 8 days was required to obtain the pH reduction and ORP increase of the slurry solutions in the range of solid concentrations 150 g.L­$^1$to 300 g.L­$^1$. The sulfur oxidation rate of T. thiooxidans MET in 20~100 g.L­$^1$solid concentrations was 0.70~0.75 g-S.L­$^1$ㆍ d­$^1$, but its sulfur oxidation activity was remarkably inhibited with increasing solid concentration over 150 g.L­$^1$. Increasing fly ash solids concentration in the range of solids concentration 20 g.L­$^1$ to 200 g.L­$^1$decreased the removal efficiency of Zn, Cu, Mn, Cr and Pb. The solubilization of heavy metals from fly ash was strongly correlated with the pH value of slurry solution. When the pH of slurry solution was reduced to 3, the solubilization process of Zn, Cu and Mn started, and their solubilization efficiency of Zn, Cu and Mn was progressively increased below pH 2. However, the solubilization process of Cr and Pb started at pH 2.5 and 2.0, respectively.

• Nuclear Engineering and Technology
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• v.42 no.5
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• pp.552-561
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• 2010

This study investigates the solubility of neptunium (Np) in the deep natural groundwater of the Korea Atomic Energy Research Institute Underground Research Tunnel (KURT). According to a Pourbaix diagram (pH-$E_h$ diagram) that was calculated using the geochemical modeling program PHREEQC 2.0, the redox potential and the carbonate ion concentration both control the solubility of neptunium. The carbonate effect becomes pronounced when the total carbonate concentration is higher than $1.5\;{\times}\;10^{-2}$ M at $E_h$ = -200 mV and the pH value is 10. Given the assumption that the solubility-limiting stable solid phase is $Np(OH)_4(am)$ under the reducing condition relevant to KURT, the soluble neptunium concentrations were in the range of $1\;{\times}\;10^{-9}$ M to $3\;{\times}\;10^{-9}$ M under natural groundwater conditions. However, the solubility of neptunium, which was calculated with the formation constants of neptunium complexes selected in an OECD-NEA TDB review, strongly deviates from the value measured in natural groundwater. Thus, it is highly recommended that a prediction of neptunium solubility is based on the formation constants of ternary Np(IV) hydroxo-carbonato complexes, even though the presence of those complexes is deficient in terms of the characterization of neptunium species. Based on a comparison of the measurements and calculations of geochemical modeling, the formation constants for the "upper limit" of the Np(IV) hydroxo-carbonato complexes, namely $Np(OH)_y(CO_3)_z^{4-y-2z}$, were appraised as follows: log $K^{\circ}_{122}\;=\;-3.0{\pm}0.5$ for $Np(OH)_2(CO_3)_2^{2-}$, log $K^{\circ}_{131}\;=\;-5.0{\pm}0.5$ for $Np(OH)_3(CO_3)^-$, and log $K^{\circ}_{141}\;=\;-6.0{\pm}0.5$ for $Np(OH)_4(CO_3)^{2-}$.

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.298-305
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• 2016

The development of non-precious metal based electrocatalysts is highly desired for the oxygen reduction reaction (ORR) as alternates to noble metal based ORR electrocatalysts. Herein, we report mononulcear copper(II) complex $[CuLbpy]ClO_4$ (L=4-[(2-hydroxyphenylimino)methyl]benzoic acid) containing poly(allylamine.HCl) polymer (PAlACuLbpy) as an electrocatalyst for oxygen reduction reaction (ORR). PAlACuLbpy was mixed with poly(acrylic acid) and tetraethylortho silicate to prepare a composite and then deposited on the screen printed electrode surface. The modified electrode (PAlACuLbpy/PCE) is highly stable and showed a quasi-reversible redox behavior with $E_{1/2}=-0.2V$ vs. Ag/AgCl(3 M KCl) in 0.1 M phosphate buffer at pH 7 under argon atmosphere. PAlACuLbpy/PCE exhibited a remarkable ORR activity with an onset potential of -0.1 V vs Ag/AgCl in 0.1 M PB (pH 7) in the presence of oxygen. The kinetics for ORR was studied by rotating disk voltammetry in neutral aqueous medium and the results indicated that the number of electrons involving in the ORR is four and the conversion products are water and hydrogen peroxide.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.5
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• pp.564-571
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• 2016

As the amount of rice straw collected increases, green manure crops are used to provide the needed organic matter. However, as green manure crops generate methane in the process of decomposition, we tested with different tillage depths in order to reduce the emission. The atmosphere temperature of the chamber was $25{\sim}40^{\circ}C$ during the examination of methane and soil temperature was $2{\sim}10^{\circ}C$ lower than air temperature. The redox potential (Eh) of the soil drastically fell right before irrigated transplanting and showed -300~-400 mV during the cultivating period of rice (7~106 days after transplant). When hairy vetch was incorporated to soil and the field was not irrigated, the generation of methane did not occur from 12 to 4 days before transplanting rice and started after irrigation. Regarding the pattern of methane generation during the cultivation of rice, methane was generated 7 days after transplanting, reached the pinnacle at by 63~74 days after transplanting, rapidly decreased after 86~94 days past transplanting and stopped after 106 days past transplanting. When tested by different soil types, methane emission gradually increased in loam and clay loam during early transplant, whereas it sharply increased in sandy loam. The total amount of methane emitted was highest in sandy loam, followed by loam and clay loam. In all three soil types, methane emission significantly reduced when tillage depth was 20 cm compared to 10 cm. The rice growths and yield were not affected by tillage depth. Therefore, reduction of methane emission could be achieved when application hairy vetch to the soil with tillage depth of 20 cm in paddy soil.