• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.4
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• pp.313-320
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• 2017

A spectroelectrochemical method has been applied to investigate the electrochemical behaviors and identify the kinds of samarium ions dissolved in high temperature molten LiCl-KCl eutectic. An optically transparent electrode (OTE) fabricated with a tungsten gauze as a working electrode has been used to conduct cyclic voltammetry and potential step chronoabsorptometry. Based on the reversibility of the redox reaction of $Sm^{3+}/Sm^{2+}$, which was determined from the cyclic voltammograms, the formal potential and the diffusion coefficient were calculated to be -1.99 V vs. $Cl_2/Cl^-$ and $2.53{\times}10^{-6}cm^2{\cdot}s^{-1}$, respectively. From the chronoabsorptometry results at the applied potential of -1.5 V vs. Ag/AgCl (1wt%), the characteristic peaks of absorption for samarium ions were determined to be 408.08 nm for $Sm^{3+}$ and 545.62 nm for $Sm^{2+}$. Potential step chronoabsorptometry was conducted using the anodic and the cathodic peak potentials from the voltammograms. Absorbance analysis at 545.63 nm shows that the diffusion coefficient of $Sm^{3+}$ is $2.15{\times}10^{-6}cm^2{\cdot}s^{-1}$, which is comparable to the value determined by cyclic voltammetry at the same temperature.

• Korean Journal of Microbiology
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• v.48 no.2
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• pp.156-162
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• 2012

A mannitol dehydrogenase (StMDH) gene was cloned from Salmonella typhimurium LT2 (KCTC 2421) and overexpressed in Escherichia coli. It has a 1,467 bp open reading frame encoding 488 amino acids with deduced molecular mass of 54 kDa, which shares approximately 36% of amino acid identity with known long-chain dehydrogenase/reductatse (LDR) family enzymes. The recombinant StMDH showed the highest activity at $30^{\circ}C$, and pH 5.0 and 10.0 for D-fructose reduction and D-mannitol oxidation, respectively. On the contrary, it has no activity on glucose, galactose, xylose, and arabinose. StMDH can catalyze the oxidative/reductive reactions between D-fructose and D-mannitol only in the presence of $NAD^+$/NADH as coenzymes. These results indicate that StMDH is a typical $NAD^+$/NADH-dependent mannitol dehydrogenase (E.C. 1.1.1.67).

• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.172-178
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• 2014

In this work, we describe an electrochemical immunosensor for simple, fast and quantitative detection of a urinary hippuric acid (HA). Urinary HA, of molecular weight 180 DA, is one of the major metabolites and biological indicators in toluene-exposed humans. Simple and ubiquitous monitoring of exposure to toluene is very important in occupational health care. We propose the electrochemical immunoassay based on the dopamine-antigen conjugate for detecting hippuric acid. Our electrochemical immunoassay system employs a conjugate of dopamine (DA) as an electrochemical active molecule and hippuric acid (HA) as an antigen. As an electrochemical aspect, dopamine (DA) containing two hydroxyl group can show excellent redox signal. Also, dopamine-tethered hippuric acid (DA-HA) shows the reversible redox signal in the immunoassay. The competition between HA and DA-HA generated electric signals proportional to HA concentration. The electrochemical immunoassay was performed with DA-HA on the screen printed carbon electrodes (SPCEs), and then applies the mixture antigen (HA) and HA-antibody. The electrical signals were proportional to HA in the range of 0.010~2.500 mg/mL which is enough range to be used for the point-of-care.

• Korean Journal of Microbiology
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• v.52 no.1
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• pp.1-9
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• 2016

A unique Schizosaccharomyces pombe $TrxR^+$ gene encoding thioredoxin reductase (TrxR) was found to be positively regulated by stress-inducing agents through the stress-responsive transcription factor Pap1. In the present study, the protective roles of S. pombe TrxR were evaluated using the TrxR-overexpressing recombinant plasmid pHSM10. In the presence of hydrogen peroxide ($H_2O_2$) and superoxide anion-generating menadione (MD), S. pombe TrxR increased cellular growth and the total glutathione (GSH) level, while it reduced levels of intracellular reactive oxygen species (ROS). The nitric oxide (NO) levels of the TrxR-overexpressing cells, in the presence of $H_2O_2$ and MD, were maintained to be similar to those of the corresponding non-treated cells. Although S. pombe TrxR was able to scavenge NO generated by sodium nitroprusside (SNP), it had no significant modulating effects on cellular growth, ROS levels, or the total GSH level of SNP-exposed yeast cells, compared with the differences in those of the two non-treated cell cultures. TrxR increased the cellular growth and total GSH level, which were diminished by nitrogen starvation. It also scavenged ROS and NO produced during nitrogen starvation. Taken together, the S. pombe TrxR protects against oxidative, nitrosative, and nutritional stresses.

• Journal of the Mineralogical Society of Korea
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• v.26 no.2
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• pp.129-138
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• 2013

River bank filtration has been considered as a promising alternative water management scheme, in which groundwater is extracted from an aquifer near a river after infiltration of the river water into the aquifer, thereby improving and maintaining the quality of water recovered. Iron (Fe) associated with sediment in contact with groundwater and infiltrating surface water is an important factor in determining the quality of water recovered from the pumping wells in river bank filtration. This study reports the results of Fe speciation in the aquifer sediment samples collected from different depths at the river bank filtration site in Changwon, studied using four different chemical extraction methods, namely, ferrozine, oxalate, HCl, and DCB methods. Overall, the results show that Fe(II) as well as the total Fe content decreases with depth down to ~20 m and then increases further below. This trend is consistent with the redox characteristics suggested by visual observation. The silt/clay size fraction (${\phi}$ < 62.5 ${\mu}M$) has up to 2~10 times more Fe compared with the sand size fraction (62.5 ${\mu}M$ < ${\phi}$ < 2 mm), depending on the extraction method. Of the four extraction methods, DCB solution extracted the most Fe from the sediment samples. The amounts of Fe extracted by the different extraction methods can be a good indicator of the redox conditions along the depth of the aquifer.

• Journal of the Korean Chemical Society
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• v.47 no.2
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• pp.121-126
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• 2003

Tris(2-cyclohexylaminoethyl)amine (L) was synthesized by the Schiff base condensation reaction of tris(2-aminoethyl)amine with cyclohexanone, followed by reduction. The thermodynamic characteristics, mole ratio and formation constant of [Zn(II)-L] complex were measured by the cyclic voltammetry and isothermal titration. In the case of Zn(II), well-defined cathodic and anodic peak were obtained at -1.02V and -0.48V vs Ag/AgCl , respectively. For the [Zn(II)-L] complex, both peaks were obtained at -1.19V and -0.45V vs Ag/AgCl, respectively. In addition, the peak height gradually increases as the scan rate increases, suggesting that the currents obtained were diffusion - controlled. The mole ratio and stability constant of the complex measured cyclic voltammerty were 1:1 and logK$_f$= 5.8, respectively. And the mole ratio and stability constant of the complexe calculated by isothermal titration method was 1:1 and logK =5.4, respectively. ${\Delta}$H, ${\Delta}$G and T${\Delta}$S for the complex formation were -53.0 kJ/mol, -31.1 kJ/mol, and -21.9 J/K at 25 ${\circ}$C, respectively.

• Journal of Ginseng Research
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• v.24 no.4
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• pp.176-182
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• 2000

The effects of red ginseng component (water extracts, alcohol extracts, lipophilic extracts, total saponins, panaxadiol and panaxatriol) administration on glutathione (GSH) and lipid peroxidation levels in mice were investigated. 20~25 g ICR mice which were pretreated with water extracts (50 mg/kg), alcohol extracts (50 mg/kg), lipophilic extracts (50 mg/kg), total saponins (50 mg/kg), panaxadiol (50 mg/kg) and panaxatriol (50 mg/kg) for 15 days. The ability of red ginseng component to protect against oxidative damage to the mouse liver was examined by determining the level of lipid peroxidation (MDA), glutathione, and the activities of glutathione peroxidase (GPX). The GSH level was raised by all the ginseng component, but the GSSG level was lowered ]argely by all the ginseng component. The ratio of GSSG/total GSH was decreased because the level of GSSG was decreased more than that of GSH. Finally, the lipid peroxidation (MDA) level was the lowest in lipophilic extracts and panaxadiol nest. In conclusion, the order of effectiveness of anti-oxidants was to be lipophilic extracts>panaxadiol>total saponins.

• Clean Technology
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• v.18 no.4
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• pp.446-450
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• 2012

Strong alkaline electrolyzed water which is produced in cathode by electrolyzing the solution where electrolytes (NaCl, $K_2CO_3$ etc.) are added in diaphragm electrolytic cell, is eco-friendly and has cleaning effects. So, it is viewed as a substitution of chemical cleaner. In addition, strong alkaline electrolyzed water is being used by some Japanese automobile and precision parts manufacturing industries. When strong alkaline electrolyzed water is produced by using diaphragm electrolytic cell, it is necessarily produced at the anode side. Since strong acidic electrolyzed water produced is discarded when its utilization cannot be found, production efficiency of electrolyzed water is consequently decreased. Also, there is a weakness electrolytic efficiency is decreasing due to the pollution of diaphragm. In order to overcome this, non-diaphragm all-in-one electrolytic cell integrated with electrode reaction chamber and dilution chamber was applied. Strong alkaline electrolyzed water was produced for different composition of electrolytes, and their properties and characteristics were identified. In comparing the properties between strong alkaline electrolyzed water produced in diaphragm electrolytic cell and that produced in all-in-one electrolytic cell, the differences in ORP and chlorine concentration were found. In emulsification test to confirm surface-active capability, similar results were obtained and strong alkaline electrolyzed water produced in non-diaphragm all-in-one electrolytic cell was identified to be useable as a cleaner like strong alkaline electrolyzed water produced in diaphragm electrolytic cell. Strong alkaline electrolyzed water produced in non-diaphragm all-in-one electrolytic cell is thought to have sterilizing power because it has active chlorine which is different from strong alkaline electrolyzed water produced in diaphragm electrolytic cell.

• Resources Recycling
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• v.31 no.4
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• pp.26-33
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• 2022

Owing to the demand for lithium-ion batteries, the recovery of valuable metals from waste lithium-ion batteries is required in future. A pyrometallurgical treatment is appropriate for recycling a large number of waste lithium-ion batteries, but Li loss to slag and dust present a significant challenge. This research investigated carbonation roasting and water leaching behaviors in Li-ion batteries by graphite addition to recover Li from the NCM-based cathode materials of waste Li-ion batteries. When 10 wt% of graphite was added, CO and CO₂ gases were emitted with a rapid weight reduction at apporoximately 850 K, when heated in Ar and CO₂ atmosphere. After the rapid weight reduction, NCM was decomposed and reduced to metal oxides and pure metals. In the carbonation roasting of black powder (NCM+graphite), O₂ is generated via the decomposition of NCM, and an oxides, such as Li₂O and NiO were were also generated. Subsequently, Li₂O reacts with CO₂ to generate Li₂CO₃, and a part of NiO was reduced by graphite to produce metal Ni. In addition, up to 94.5 % Li₂CO₃ with ~99.95 % purity was recovered via water leaching after carbonation roasting.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.411.2-411.2
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• 2016

직접 메탄올 연료전지 (DMFCs)는 친환경적이고 낮은 작동 온도로 인한 빠른 구동, 높은 에너지 밀도 등 다양한 장점을 가지고 있어 차세대 에너지 변환소자로 많은 관심을 받고 있다. 직접 메탄올 연료전지는 메탄올을 연료로 사용하며, 메탄올이 보유하고 있는 화학적 에너지를 전기 에너지로 변환하는 장치로써 음극에서는 백금 촉매로 인한 메탄올 산화반응, 양극에서는 환원 반응이 일어나며 전기화학적 구동을 하게 된다. 하지만 일산화탄소 피독으로 인한 촉매 활성 저하, 메탄올의 cross over, 백금 촉매 사용으로 인한 고비용 등의 문제점을 가지고 있다. 따라서 많은 연구자들이 백금 사용량을 줄이고 백금 촉매를 고르게 분포하기 위해 값이 저렴하고 넓은 비표면적을 갖는 탄소계 (graphite, graphene, carbon nanotube, carbon nanofiber 등) 지지체 재료를 도입하고 있다. 이 중 탄소나노섬유 (carbon nanofibers, CNFs)는 우수한 전기전도도와 열적/화학적 안정성을 가지고 있으며, 특히 넓은 비표면적을 가지고 있어 백금 촉매의 지지체로서 많은 연구가 진행되고 있다[1]. 따라서 우리는 전기방사법을 활용하여 넓은 비표면적을 보유하는 다공성 탄소나노섬유를 성공적으로 합성하였다. 또한, 이를 백금 촉매의 지지체로 도입하여 직접 메탄올 연료전지를 위한 다공성 탄소나노섬유에 담지된 고분산성 백금 촉매를 제조하였다. 제조한 다공성 탄소나노섬유의 형상 및 구조 분석은 주사전자 현미경 (field-emission scanning electron microscopy)와 투과전자 현미경 (transmission electron microscopy)를 이용하여 분석하였고, 결정구조와 화학적 결합상태는 X-선 회절분석 (X-ray diffraction) 및 X-선 광전자 분광법 (X-ray photoelectron spectroscopy)를 이용하여 규명하였다. 전기화학적 특성은 순환 전압 전류법 (cyclic voltammetry)를 이용하였다. 이러한 실험 결과들을 바탕으로 다공성 탄소나노섬유에 담지된 고분산성 백금 촉매의 자세한 특성을 본 학회에서 다루도록 하겠다.