• Journal of Ecology and Environment
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• v.41 no.9
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• pp.235-245
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• 2017

Background: Loading of excess nutrient via bioremediation of polluted sediment to overlying water could trigger anoxia and eutrophication in coastal area. The aim of this research was to understand the changes of overlying water features such as dissolved oxygen (DO); pH; oxidation reduction potential (ORP); $chlorophyll-{\alpha}$ ($Chl-{\alpha}$); and nitrogen nutrients ammonia ($N-NH_4{^+}$), nitrate ($N-NO_3{^-}$), and nitrite ($N-NO_2^-$) when the sediment was not treated (control) and treated by calcium peroxide for 5 weeks. Methods: The water samples were analyzed for measuring physical and chemical properties along with the sediment analyzed by polymerase chain reaction (PCR) including denaturing gradient gel electrophoresis (DGGE) for identifying the phylogenetic affiliation of microbial communities. Results: Results showed that due to the addition of calcium peroxide in sediment, the overlying water exposed the rise of dissolve oxygen, pH, and ORP than control. Among the nitrogen nutrients, ammonia inhibition was higher in calcium peroxide treatment than control but in case of nitrate inhibition, it was reversed than control. $Chlorophyll-{\alpha}$ was declined in treatment column water by 30% where it was 20% in control column water. Actibacter and Salegentibacter group were detectable in the calcium-peroxide-treated sediment; in contrary, no detectable community ware found in control sediment. Both phylogenetic groups are closely related to marine microflora. Conclusions: This study emphasizes the importance of calcium peroxide as an oxygen release material. Interaction with peroxide proved to be enhancing the formation of microbial community that are beneficial for biodegradation and spontaneity of nutrient attenuation into overlying water.

• Journal of Environmental Health Sciences
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• v.36 no.3
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• pp.236-246
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• 2010

In preparative anti-corrosive coating experiments, polyaniline was obtained by reacting an oxidizing agent with the monomer aniline. Further, the primer coating was prepared using a variety of widely-used materials such as urethane resin. For the top coating, epoxy resin and acrylic urethane resin were used. Characteristics of the coatings were assessed according to KS and ASTM specifications, and the structure of the polyaniline was characterized using FT-IR and TGA. For analysis of anti-corrosive properties in salt-spray experiments, measurements of the oxidation state of iron and surface atomic analysis were conducted using XPS and SEM-EDX. Unlike general anti-corrosive coatings which exhibit anti-corrosive effects only as a primer coating, the anti-corrosive coatings using polyaniline as the anti-corrosive pigment showed a marked synergistic effect with the top coatings. In other words, the top coatings not only produce a fine view effect, but also increase, through interaction with the primer coatings, the resistance to diffusion of corrosive factors from the external environment. It was also found that, unlike the heavy metal oxide-forming layer of the passive barrier alone, the polyaniline anti-corrosive pigment oxidized iron at the interface with the iron substrate to form a passive barrier in the oxidic layer, and itself formed a potential barrier layer with anti-corrosive factors from the external environment. Although the passive layer was damaged, the damaged area did not become completely oxidized iron; on the contrary, it showed a tendency to reduction. This can be interpreted such that a passive layer is formed again on the damaged area, and that at the same time there is a tendency to self-healing.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.167-173
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• 2013

A series of highly efficient red phosphorescent heteroleptic iridium(III) complexes 1-6 containing two cyclometalating 2-(2,4-substitued phenyl)quinoxaline ligands and one chromophoric ancillary ligand were synthesized: (pqx)$_2Ir$(mprz) (1), (dmpqx)$_2Ir$(mprz) (2), (dfpqx)$_2Ir$(mprz) (3), (pqx)$_2Ir$(prz) (4), (dmpqx)$_2Ir$(prz) (5), (dfpqx)$_2Ir$(prz) (6), where pqx = 2-phenylquinoxaline, dfpqx = 2-(2,4-diflourophenyl)quinoxaline, dmpqx = 2-(2,4-dimethoxyphenyl)quinoxaline, prz = 2-pyrazinecarboxylate and mprz = 5-methyl-2-pyrazinecarboxylate. The absorption, emission, electrochemical and thermal properties of the complexes were evaluated for potential applications to organic light-emitting diodes (OLEDs). The structure of complex 2 was also determined by single-crystal X-ray diffraction analysis. Complex 2 exhibited distorted octahedral geometry around the iridium metal ion, for which 2-(2,4-dimethoxyphenyl)quinoxaline N atoms and C atoms of orthometalated phenyl groups are located at the mutual trans and cis-positions, respectively. The emission spectra of the complexes are governed largely by the nature of the cyclometalating ligand, and the phosphorescent peak wavelengths can be tuned from 588 to 630 nm with high quantum efficiencies of 0.64 to 0.86. Cyclic voltammetry revealed irreversible metal-centered oxidation with potentials in the range of 1.16 to 1.89 V as well as two quasi-reversible reduction waves with potentials ranging from -0.94 to -1.54 V due to the sequential addition of two electrons to the more electron-accepting heterocyclic portion of two distinctive cyclometalated C^N ligands.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.99-102
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• 2004

Display process has adopted RCA clean, being applied to large area and coped with environmental issue for last ten years. However, the approaching concept of ozonized, hydrogenised, or electrolyzed water cleaning technologies is within RCA clean paradigm. In this work, only electrolyzed anode water was applied to clean particles and organics as well as metals based on Pourbaix concept, and as a test vehicle, MgO particles were introduced to prove the new concept. The electrolyzed anode water is very oxidative with high oxidation reduction potential(ORP) and low in pH of more than 900mV and 3.1, respectively. MgO particles were immerged in the anode water and its weight losses due to dissolution were measured with time. Weight losses were in the ranges of 100 to 500 micrograms in 250m1 anode waters depending on their ORP and pH. Therefore it was concluded that the cleaning radicals in the anode water was at least in the range of 1 to 5E20 ea per 250 ml anode water equivalent to IE18 ea/cm3. Hence it can be assumed that the anode water be applied to display cleaning since 1E10 to IE15 ea/cm3 ranges of contaminants are being treated. In addition, it was observed that anode water does not develop micro-roughness on hydrophobic surface while it does on the native silicon oxide.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.4
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• pp.379-392
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• 2010

In these days, constructed wetlands are applied in Korea for various purposes ; post-treatment of effluent in wastewater treatment, management of stormwater and restoration of aquatic ecosystems. However, the removal mechanisms for water pollutant in constructed wetlands are not clearly understood because they are affected by climate, influent characteristics and local constraints. Therefore, this paper is focused on the process that the pollutant, especially nitrogen and phosphorus, of the wetland is removed by. In this study, the main nitrogen removal is performed by nitrification/denitrification mechanism in the rhizosphere of constructed wetlands. And the majority of the phosphorus is removed by adsorption on the substrate of wetland. However the fate of phosphorus in wetlands can be diverse depending on the Oxidation Reduction Potential(ORP), adsorption/desorption, precipitation/dissolution, microbial effect, etc.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.4
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• pp.86-96
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• 1998

In this study, an intermittently aerated activated sludge process, modified process from conventional activated sludge process, was developed to treat high strength swine wastewater, which has been blamed as major pollutant for stream pollution. Therefore, the optimum cycle for oxic and anoxic period, SRT, and OLR were studied as design parameters. The effects of different time interval for oxic and anoxic period on nitrification and denitrification were examined by operating two reactors with 60/60min and 60/90min as oxic/anoxic period. Although the reactor with 60/60min showed complete denitrification of $NO_x-N$ generated during oxic period, the reactor with 60/90min showed incomplete nitrification due to the inactivity of nitrifier by accumulated $NH_3-N$ toxicity during anoxic period. Therefore, it is recommended to operate same interval for oxic and anoxic period. In order to determine the optimum cycle for oxic/anoxic period, four different reactors with 30/30, 60/60, 90/90 and 120/120min were examined. The reactor operation with 90/90min was optimum to get the most stable results in this study. However, the optimum cycle for oxic and anoxic period should be changed with characteristics of influent wastewater and operating conditions. According to lie operation results of three reactors with SRT of 15, 20 and 30days. The reactor with 2Odays SRT showed best removal efficiency of T-N. The optimum OLR would be $2.5Kg\;COD/m^3/day$ which showed the most stable nitrification and denitrification. Since characteristics of influent wastewater in the real system has a severe fluctuation, so it is very difficult to determine each interval for oxic and anoxic period. Therefore, ORP curves, describing the change of oxidation/reduction potential in reactor, can be used as a control parameter for automatic control of oxic and anoxic period. In other words, bending point (Nitrate Knee) of ORP curve during anoxic period could be used as a starting point of oxic period.

• Bulletin of the Korean Chemical Society
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• v.21 no.6
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• pp.588-594
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• 2000

Structural changes of an iron phthalocyanine (FePC) monolayer induced by adsorption and externally applied potential on high area carbon surface have been investigated in situ by iron K-edge X-ray absorption fine structure (XAFS) in 0.5 M $H_2S0_4.$ Fine structures shown in the X-ray absorption near edge structure (XANES) for microcrystalline FePC decreased upon adsorption and further diminished under electrochemical conditions. Fe(II)PC(-2) showed a 1s ${\rightarrow}$ 4p transition as poorly resolved shoulder to the main absorption edge rather than a distinct peak and a weak 1s ${\rightarrow}$ 3d transition. The absorption edge position measured at half maximum was shifted from 7121.8 eV for Fe(lI)PC(-2) to 7124.8 eV for $[Fe(III)PC(-2)]^+$ as well as the 1s ${\rightarrow}$ 3d pre-edge peak being slightly enhanced. However, essentially no absorption edge shift was observed by the 1-electron reduction of Fe(Il)PC(-2), indicating that the species formed is $[Fe(II)PC(-3)]^-$. Structural parameters were obtained by analyzing extended X-ray absorption fine structure (EXAFS) oscillations with theoretical phases and amplitudes calculated from FEFF 6.01 using multiple-scattering theory. When applied to the powder FePC, the average iron-to-phthalocyanine nitrogen distance, d(Fe-$N_p$) and the coordination number were found to be 1.933 $\AA$ and 3.2, respectively, and these values are the same, within experimental error, as those reported ( $1.927\AA$ and 4). Virtually no structural changes were found upon adsorption except for the increased Debye-Wailer factor of $0.005\AA^2$ from $0.003\AA^2.$ Oxidation of Fe(II)PC(-2) to $[Fe(III)PC(-2)]^+$ yielded an increased d(Fe-Np) (1 $.98\AA)$ and Debye-Wailer factor $(0.005\AA^2).$ The formation of $[Fe(II)PC(-3)]^-$, however, produced a shorter d(Fe-$N_p$) of $1.91\AA$ the same as that of crystalline FePC within experimental error, and about the same DebyeWaller $factor(0.006\AA^2)$.

• Bulletin of the Korean Chemical Society
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• v.14 no.2
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• pp.195-200
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• 1993

The neutral, reduced, and oxidized 2,2-trans isomers of $Rh_2(ap)_4$ (ap=2-anilinopyridinate) were investigated with respect to dioxygen binding in $CH_2Cl_2$ containing 0.1 M tetrabutyl-ammonium perchlorate. $Rh_2(ap)_4$ binds dioxygen in nonaqueous media and forms a $Rh^{II}Rh^{III}$ superoxide complex, $Rh_2(ap)_4(O_2)$. This neutral species was isolated and is characterized by UV-visible and IR spectroscopy, mass spectrometry and cyclic voltammetry. It can be reduced by one electron at $E_{1/2}$ = -0.45 V vs. SCE in $CH_2Cl_2$ and gives ${[Rh_2(ap)_4(O_2)]}^-$ as demonstrated by the ESR spectrum of a frozen solution taken after controlled potential reduction. The superoxide ion in ${[Rh_2(ap)_4(O_2)]}^-$ is axially bound to one of the two rhodium ions, both of which are in a +2 oxidation state. $Rh_2(ap)_4(O_2)$ can also be stepwise oxidized in two one-electron transfer steps at $E_{1/2}$ = 0.21 V and 0.85 V vs. SCE in $CH_2Cl_2$ and gives ${[Rh_2(ap)_4(O_2)]}^+$ followed by ${[Rh_2(ap)_4(O_2)]}^{2+}$. ESR spectra demonstrate that the singly oxidized complex is best described as ${[Rh^{II}Rh^{III}(ap)_4(O_2)]}^+$ where the odd electron is delocalized on both of the two rhodium ions and the axial ligand is molecular oxygen.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.14-22
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• 2022

To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst were synthesized. The reduced TiO₂ nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO₂ photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti⁴⁺ ions on TiO₂ surface were converted to Ti³⁺ ion. The formation of Ti³⁺ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO₂ nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO₂ band gap energy induced by formation of Ti³⁺ species on TiO₂, and by improvement of the charge transfer reaction.

• Journal of Microbiology and Biotechnology
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• v.31 no.7
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• pp.990-998
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• 2021

Melanin is a natural skin pigment produced by specialized cells called melanocytes via a multistage biochemical pathway known as melanogenesis, involving the oxidation and polymerization of tyrosine. Melanogenesis is initiated upon exposure to ultraviolet (UV) radiation, causing the skin to darken, which protects skin cells from UVB radiation damage. However, the abnormal accumulation of melanin may lead to the development of certain skin diseases, including skin cancer. In this study, the antioxidant and antimelanogenic activities of the cell-free supernatant (CFS) of twenty strains were evaluated. Based on the results of 60% 2,2-diphenyl-1-picrylhydrazyl scavenging activity, 21% 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) scavenging capacity, and a 50% ascorbic acid equivalent ferric reducing antioxidant power value, Limosilactobacillus fermentum JNU532 was selected as the strain with the highest antioxidant potential. No cytotoxicity was observed in cells treated with the CFS of L. fermentum JNU532. Tyrosinase activity was reduced by 16.7% in CFS-treated B16F10 cells (but not in the cell-free system), with >23.2% reduction in melanin content upon treatment with the L. fermentum JNU532-derived CFS. The inhibitory effect of the L. fermentum JNU532-derived CFS on B16F10 cell melanogenesis pathways was investigated using quantitative reverse transcription polymerase chain reaction and western blotting. The inhibitory effects of the L. fermentum JNU532-derived CFS were mediated by inhibiting the transcription of TYR, TRP-1, TRP-2, and MITF and the protein expression of TYR, TRP-1, TRP-2, and MITF. Therefore, L. fermentum JNU532 may be considered a potentially useful, natural depigmentation agent.