• Molecules and Cells
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• v.39 no.1
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• pp.6-19
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• 2016

Redox signalling comprises the biology of molecular signal transduction mediated by reactive oxygen (or nitrogen) species. By specific and reversible oxidation of redoxsensitive cysteines, many biological processes sense and respond to signals from the intracellular redox environment. Redox signals are therefore important regulators of cellular homeostasis. Recently, it has become apparent that the cellular redox state oscillates in vivo and in vitro, with a period of about one day (circadian). Circadian timekeeping allows cells and organisms to adapt their biology to resonate with the 24-hour cycle of day/night. The importance of this innate biological timekeeping is illustrated by the association of clock disruption with the early onset of several diseases (e.g. type II diabetes, stroke and several forms of cancer). Circadian regulation of cellular redox balance suggests potentially two distinct roles for redox signalling in relation to the cellular clock: one where it is regulated by the clock, and one where it regulates the clock. Here, we introduce the concepts of redox signalling and cellular timekeeping, and then critically appraise the evidence for the reciprocal regulation between cellular redox state and the circadian clock. We conclude there is a substantial body of evidence supporting circadian regulation of cellular redox state, but that it would be premature to conclude that the converse is also true. We therefore propose some approaches that might yield more insight into redox control of cellular timekeeping.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.426-432
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• 2011

The oxidation behavior of CVD ${\beta}$-SiC was investigated for Very High Temperature Gas-Cooled Reactor (VHTR) applications. This study focused on the surface analysis of the oxidized CVD ${\beta}$-SiC to observe the effect of impurity gases on active/passive oxidation. Oxidation test was carried out at $950^{\circ}C$ in the impurity-controlled helium environment that contained $H_2$, $H_2O$, CO, and $CH_4$ in order to simulate VHTR coolant chemistry. For 250 h of exposure to the helium, weight changes were barely measurable when $H_2O$ in the bulk gas was carefully controlled between 0.02 and 0.1 Pa. Surface morphology also did not change based on AFM observation. However, XPS analysis results indicated that a very small amount of $SiO_2$ was formed by the reaction of SiC with $H_2O$ at the initial stage of oxidation when $H_2O$ partial pressure in the CVD ${\beta}$-SiC surface placed on the passive oxidation region. As the oxidation progressed, $H_2O$ consumed and its partial pressure in the surface decreased to the active/passive oxidation transition region. At the steady state, more oxidation did not observable up to 250 h of exposure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.511-517
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• 2002

The complex 1 $([Cp*Fe(CO)_2]_2-(\mu-CH=CH-CH=CH))$ which have butadiene as a bridge were synthesized from $Cp*(CO)_2FeK$ and cis-3,4-dichlorocyclobutene. The derivatives of complex 1 where one or two carbonyl groups are replaced by phosphine ligands have been prepared by photochemical substitution. The new derivatives $([Cp*Fe(L)_2]_2-(\mu-CH=CH-CH=CH))$ where L = $(Ph_2PCH_2CH_2PPh_2)$ and $([Cp*Fe(CO)(L)]_2-(\mu-CH=CH-CH=CH))$ where L : $PPh_3$ have been characterized from $^^1H-$, $^^13C-$,$^^31P-NMR$ and elemental analysis. Obtained complexes have been studied in electrochemical experiment and UV/VIS-near-IR. The mixed-valence radical cation forms of complex 2, 3 species were found to be delocalized as the Class III. Based on the separation of the waves ($\triangle E$ : 0.470 ~ 0.605 V), the efficiency of electronic communication between two metal centers of cation species leading to stabilization relative to neutral species. The phosphine-substitute complexes (2, 3) displays two reversible oxidation waves and oxidation state of metal centers-dependent color change, electrochromism, was observed from yellow to orange and deep blue in methylene chloride.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.2
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• pp.103-108
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• 2007

The absorption spectra of Pu in stock solution were measured using a UV-Vis-NIR spectrophotometer after dissolving $PuO_2\;with\;HNO_3$, HF and $HClO_4$. The spectroscopic characteristics of Pu (III, IV, VI) in acidic, neutral and alkali media were investigated. Also, the intensities and position of major peaks for Pu(VI) were observed with increasing acidic and alkali concentration. The variation of oxidation states of Pu(VI) with an adding reducing reactant was investigated in HCl and NaOH medium.

• Environmental Engineering Research
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• v.25 no.2
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• pp.186-196
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• 2020

Pillared clays with Zr and Fe/Cu/Zr polycations have been prepared from natural clays found in large deposits of Kazakhstan and assessed as catalysts for the catalytic wet peroxide oxidation (CWPO), using 4-nitrophenol (4-NP) as model compound. The performance of the catalysts was followed by measuring the concentration of 4-NP, H₂O₂ and the total organic carbon (TOC), considering C_4-NP = 5 g L^-1, $C_{H_2O_2}$ = 17.8 g L^-1, C_cat = 2.5 g L^-1, initial pH = 3.0 and T = 50℃. At those selected conditions, the pillared clays showed higher activity than natural clays in the CWPO of 4-NP. The conversion of the model pollutant was complete when Fe/Cu/Zr-PILCs were used, with the TOC removal reaching 78.4% after 24 h with the best Fe/Cu/Zr-PILC. The H₂O₂, 4-NP and TOC time-evolution was well described by a kinetic model based on TOC lumps in three blocks, considering the initial TOC (corresponding to 4-NP), the production of oxidizable intermediates and the formation of refractory products.

• Journal of Korean Vacuum Science & Technology
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• v.5 no.2
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• pp.47-51
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• 2001

To obtain high remnant polarization and good crystalinity of ferroelectric thin films in non-volatile memory devices, the high temperature treatment in oxygen ambient is inevitable. Severe problems that occur in this process are oxygen diffusion into substrate, oxidation of electrode and buffer layer, degradation of microstructure and so on. We made ruthenium dioxide thin film by reactive sputtering with oxygen and argon mixture atmosphere. Comparing quantitatively the core-level spectra of Ru and RuO$_2$ obtained by x-ray photoelectron spectroscopy(XPS), we found that chemical state of RuO$_2$ is very stable and of good resistance to oxygen diffusion and oxidation of adjacent layers. It opens the use of RuO$_2$ thin film as a multifunctional layer of good conducting electrode and resistive barrier for the diffusion and the oxidation. We also suggest a correct understanding of Ru 3d core-level spectrum for RuO$_2$ based on the scheme of final state screening and charge transfer satellites.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.309-316
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• 2011

Molybdenum is the most abundant fission product since its fission yield is equivalent to that of xenon, and it has a very special role in the chemistry of nuclear fuel because it influences the oxygen potential of $UO_2$ fuel. In this study, the distribution of molybdenum in spent $UO_2$ fuel specimens with 33.3, 41.0 and 57.6 GWd/tU burnup was measured by a LA-ICP-MS system and the reproducibility of the measured data was obtained. The Mo distribution was almost constant along the radius of a fuel except an increase at the periphery of the fuel. It showed a drop in reproducibility with relatively high deviation of measured values for the highest burnup fuel. To explain this, the state of molybdenum in a $UO_2$ matrix and its effect on the oxidation behavior of $UO_2$ were investigated. The low reproducibility was explained by the segregation of molybdenum, and the inhibition of oxidation by the molybdenum was also observed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1220-1221
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• 2006

[ $LiMn_2O_4$ ] powders for lithium ion batteries were synthesized from two separate raw material pairs of LiOH/MnO and $LiOH/MnO_2$. The powders prepared at 780 and $850^{\circ}C$ and their difference of electrochemical properties were investigated. Both powders calcined at 780 and $850^{\circ}C$ were composed of a single-phase spinel structure but those treated at $850^{\circ}C$ showed a lower intensity ratio of $I_{311}$ to $I_{400}$, a slightly larger lattice parameter, and an increased discharge capacity by 10% under $3.0{\sim}4.3V$ voltage range. The XPS study on the oxidation states of manganese repealed that powders made from LiOH/MnO had less $Mn^{3+}$ ion and gave better battery performances than those from $LiOH/MnO_2$.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.5
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• pp.485-500
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• 2016

We examined acidity state of inorganic aerosol and oxidation state of organic aerosol by High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) at Baengnyeong Super site from Jan 2012 to Dec 2013. Additionally, we carried out the analysis for the aerosol component group of organic matter ($C_xH_y$, $C_xH_yO_1$, $C_xH_yO_z$, $C_xH_yO_zN_p$) and elemental composition to calculate H/C, O/C, N/C, OM/OC and identify the oxidation state. The aerosol chemical composition in this study is dominated by sulfate ($SO_4{^{2-}}$), nitrate ($NO_3{^-}$) plays a smaller role in aerosol acidity. Ammonium ($NH_4{^+}$) was found in a formation of $(NH_4)_3H(SO_4)_2$. However, the binding formations of $NH_4NO_3$ and $NH_4Cl$ increase in the winter. $C_xH_yO_1$ indicating the oxidized state of $PM_{1.0}$ has the highest ratio of 41% while $C_xH_y$ indicating the non-oxidized state has a lower ratio of 36%, meaning that the oxidation level of $PM_{1.0}$ in Baengnyeong Island is high. The ratio between H/C and O/C was 1.33 and 0.78 respectively, showing the characteristic of LV-OOA (Low volatility-Oxygenated Organic Aerosol). Acidic and oxidized aerosols sampled during this field study were largely anthropogenic in origin from Chinese continent and photochemically aged.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.220.2-220.2
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• 2011

Biodiesel and biodiesel blend fuel are receiving increasing attention as alternative fuels for diesel engines without substantial modifications. Biodiesel fuels and blending have been widely studied and applied in diesel engine because of biodiesel's lower sulfur, lower aromatic hydrocarbon and higher oxygen content. Biodiesels have the potential to be oxidized in different condition. It has reported that oxidation deterioration of biodiesel is different in the condition of storage and oxidation causes chemical property change of methyl esters. Sunlight intensity, temperature, material of container and contact surface with oxygen are key dominant factors accelerating oxidation deterioration. In this study, we chose temperature among key oxidation conditions and metal container filled with biodiesel was heated at about $110^{\circ}C$ for 10 days in order to accelerate oxidation deterioration. To better understand the effect of biodiesel blends on emission, steady state tests were conducted on a heavy duty diesel engine. The engine was fueled with Ultra Low Sulphur Diesel(ULSD), a blend of 10% and 20%(BD10, BD20) on volumetric basis, equipped with a common rail direct injection system and turbocharger, lives up to the requirements of EURO 3. The experimental results show that the blend fuel of normal biodiesel with BD10 and BD20 increased NOx. The result of PM was similar to diesel fuel on BD10, but the result of PM on BD20 was increased about 63% more than its of diesel. The blend fuel of Oxidation biodiesel with BD10 and BD20 increased NOx as the results of normal biodiesel. But PM was all increased on BD10 and BD20. Especially THC was extremely increased when test fuel contains biodiesel about 140% more than its of diesel. Through this study, we knew that oxidation deterioration of biodiesel affects emission of diesel engine.