• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.319-322
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• 2009

Gel polymer electrolytes were prepared by immersing a porous poly(vinylidene fluoride-co-hexafluoropropylene) membrane in an electrolyte solution containing small amounts of polymerizable additive (3,4-ethylenedioxythiophene, thiophene, biphenyl). The organic additives were electrochemically oxidized to form conductive polymer films on the electrode at high potential. With the gel polymer electrolytes containing different organic additive, lithium-ion polymer cells composed of carbon anode and LiCo$O_2$ cathode were assembled and their cycling performances were evaluated. Adding small amounts of thiophene or 3,4-ethylenedioxythiophene to the gel polymer electrolyte was found to reduce the charge transfer resistance in the cell and it thus exhibited less capacity fading and better high rate performance.

• Journal of Electrochemical Science and Technology
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• v.15 no.2
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• pp.314-320
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• 2024

Lithium dendrite formation is one of the most significant problems with lithium metal batteries. The lithium dendrite reduces the lithium metal batteries' cycling life and safety. To apply consistent external pressure to a lithium metal pouch cell, we design a press jig in this study. External pressure creates dense lithium morphology by preventing lithium dendrite formation. After 300 cycles at 1 C, the cells with the external pressure perform far better than the cells without it, with a cycling retention of 97.8%. The formation of stable lithium metal is made possible by external pressure, which also enhances safety and cyclability.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.317-340
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• 1993

This study was designed 1) to compare the distributions of periapical inflammatory cells and 2) to identify lymphocytes and compare the lymphocyte distribution with T lymphocyte subpopulation and then 3) to examine the distribution of cycling cell in human dental periapical lesions. From each of the twenty-five human dental periapical lesions observed one small portion was fixed, embeded in paraffin, sectioned serially and stained with HE. The periapical inflammatory cells were counted to obtain the relative concentration of lymphocyte, plasma cell, macrophage and neutrophil. The large part of each lesion was analysed using Flow cytometer and monoclonal antibodies to obtain the relative concentration of T lymphocyte, B lymphocyte, T'helper cell and T suppressor/cytotoxic cell. In addition to that, seven human dental periapical lesions were examined with DNA analysis to observe the distribution of cycling cell. Following results were obtained: 1. 24 cases of the 32 periapical lesions examined were diagnosed as periapical granuloma and the remaining 8 cases as periapical cyst. Lymphocytes comprised 42.1% of total inflammatory cells in periapical granuloma and 41.8% in periapical cyst. Corresponding percentages for macrophages were 33.8% and 30.3%; for plasma cells, 15.9% and 19.0%; for neutrophils, 8.2% and 8.8%. 2. All of the periapical lesions examined had T lymphocyte, B lymphocyte, T helper cell, T suppressor/cytotoxic cell. And in all cases, T lymphocytes were observed predominantly more than B lymphocytes. 3. In 2 cases of the control group only T lymphocytes were found, and in the remaining 2 cases T lymphocytes were observed predominantly. 4. T helper cells were observed predominantly more than T suppressor/cytotoxic cells in all cases of perapical granulomas. 5. T suppressor/cytotoxic cells were observed predominantly more than T helper cells in 4 cases of periapical cysts (total 5 cases were examined) and only in one case T helper cells were more than T suppressor/cytotoxic cells. 6. In control group, T helper cells were predominant in 2 cases and T helper cells were equivalent to T suppressor/cytotoxic cells in one case. In remaining one case T suppressor/cytotoxic cells were predominant. 7. As the result of DNA analysis, the average proliferating indices of the various groups examined were measured as follows: in the control group 5.45%, in periapical granuloma 6.64%, in periapical cyst 10.1%. The highest index was observed in periapical cyst.

• Journal of Electrochemical Science and Technology
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• v.14 no.4
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• pp.361-368
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• 2023

In lithium-sulfur (Li-S) batteries, encapsulation of sulfur in activated carbon (AC) materials is a promising strategy for preventing the dissolution of lithium polysulfide into electrolytes and enhancing cycle life, because instead of solid-liquid-solid reactions, quasi-solid-state (QSS) reactions occur in the AC micropores. While a high weight fraction of sulfur in S/AC composites is essential for achieving a high energy density of Li-S cells, the deterioration mechanisms under such conditions are still unclear. In this study, we report the deterioration mechanisms during charge-discharge cycling when the discharge products overflow from the AC. Analysis using scanning electron microscopy and energy-dispersive X-ray spectrometry confirms that the sulfur in the S/AC composites migrates outside the AC as cycling progresses, and it is barely present in the AC after 20 cycles, which corresponds to the capacity decay of the cell. Impedance analysis clearly shows that the electrical resistance of the S/AC composite and the charge-transfer resistance of QSS reactions significantly increase as a result of sulfur migration. On the other hand, the charge-discharge cycling performance under limited-capacity conditions, where the discharge products are encapsulated inside the AC, is extremely stable. These results reveal the degradation mechanism of a Li-S cell with micro-porous carbon and provide crucial insights into the design of a S/AC composite cathode and its operating conditions needed to achieve stable cycling performance.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.266-275
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• 2018

Herein, a novel operating life (OL) test method was evaluated with 200 mAh pouch-type lithium-ion batteries. By combining the calendar life (CL) test with intermediate pulse power cycling, more realistic life prediction was possible, which encompassed real operation of batteries accompanying with thermal acceleration. Larger capacity decrease and resistance increase of pouch cell were observed in the OL test, which was well explained using the SEI film growth model. After dissemble of pouch cell, capacity loss and resistance increase mostly occurred within anode, reflecting that SEI film growth on anode surface was highly attributable to cell degradation.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.1
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• pp.82-89
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• 2006

The redox behaviors of anode-supported flat tube for solid oxide fuel cell has been studied. The mass change of the extruded NiO/YSZ anode flat tube during redox cycling was examined by thermogravimetric analysis(TGA). The result of TGA was shown a rapidly mass change in the range of $455\;-\;670^{\circ}C$ and the reoxidation of the NiO/YSZ anode was almost completed at $750^{\circ}C$. The starting temperature of reoxidation and the maximum temperature of oxidation rate decreased with increasing the reoxidation cycle, which is attributed to the increased porosity caused by volume change. Bending strengths of the NiO/YSZ anode after redox cycling were 96 - 80 MPa and the bending strength decreased slightly with increasing the redox cycle. On the other hand, the bending strength of the NiO/YSZ anode with electrolyte showed 130 MPa after first redox cycling but decreased rapidly with increasing the redox cycle. From the results of the bending test and the microstructure observation, we conclude that the crack initiation of the electrolyte-coated NiO/YSZ anode was induced easily at interface of electrolyte/anode tube and propagated cross the electrolyte.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.2
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• pp.79-90
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• 1997

Extensive work has been done on investigating the inner cell pressure characteristics of sealed type Ni-MH battery in which Zr-Ti-Mn-V-Ni alloy is used as anode. The inner cell pressure of this type Ni-MH battery much more increases with the charge/discharge cycling than that of the other type Ni-MH battery where commercialized $AB_5$ type alloy is used as anode. The increase of inner cell pressure in the sealed type Ni/MH battery using Zr-Ti-Mn-V-Ni alloy system is mainly due to the accumulation of oxygen gas during charge/discharge cycling. The accumulation of oxygen gas arises mainly due to the low rate of oxygen recombination on the MH electrode surface during charge/discharge cycling. The difference of oxygen recombination rate between $AB_5$ type electrode and Zr-Ti-Mn-V-Ni electrode is caused by the difference of electrode reaction surface area resulting from different particle size after their activation and the difference of surface catalytic activity for oxygen recombination reaction, respectively. After EIS analysis, it is identified that the surface catalytic activity affects much more dominantly on the oxygen recombination reaction than the reaction surface area does. In order to suppress the inner cell pressure of Ni-MH battery where Zr-Ti-Mn-V-Ni is used as anode, it is suggested that the surface catalytic activity for oxygen recombination should be improved.

• 한국전기화학회:학술대회논문집
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• 2003.10a
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• pp.21-21
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• 2003

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.2
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• pp.685-689
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• 2013

Objective: To study the effects of down-regulation of HDAC6 expression on proliferation, cell cycling and migration of esophageal squamous cell carcinoma (ESCC) cells and related molecular mechanisms. Methods: ESCC cell line EC9706 cells were randomly divided into untreated (with no transfection), control siRNA (transfected with control siRNA) and HDAC6 siRNA (transfected with HDAC6 small interfering RNA) groups. Effects of HDAC6 siRNA interference on expression of HDAC6 mRNA and protein in EC9706 cells were investigated by semi-quantitative RT-PCR, Western blotting and immunocytochemistry methods. Effects of down-regulation of HDAC6 expression on cell proliferation, cell cycle, and cell migration were studied using a CCK-8 kit, flow cytometry and Boyden chambers, respectively. Changes of mRNA and protein expression levels of cell cycle related factor (p21) and cell migration related factor (E-cadherin) were investigated by semi-quantitative RT-PCR and Western blotting methods. Results: After transfection of HDAC6 siRNA, the expression of HDAC6 mRNA and protein in EC9706 cells was significantly downregulated. In the HDAC6 siRNA group, cell proliferation was markedly inhibited, the percentage of cells in G0/G1 phase evidently increased and the percentage of cells in S phase decreased, and the number of migrating cells significantly and obviously decreased. The mRNA and protein expression levels of p21 and E-cadherin in the HDAC6 siRNA group were significantly higher than those in the untreated group and the control siRNA group, respectively. Conclusions: HDAC6 siRNA can effectively downregulate the expression of HDAC6 mRNA and protein in EC9706 cells. Down-regulation of HDAC6 expression can obviously inhibit cell proliferation, arrest cell cycling in the G0/G1 phase and reduce cell migration. The latter two functions may be closely related with the elevation of mRNA and protein expression of p21 and E-cadherin.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.445-449
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• 2012

The activation process of the membrane-electrode assembly (MEA) is important for the mass production of the polymer electrolyte membrane fuel cell. The conventional activation process for the MEA requires excessive time and hydrogen gas and it might become the barrier for the commercialization of the fuel cell. The conventional activation process is based on hydrolysis of ion conducting membrane. In the study, we suggest the cyclic voltammetry (CV) technique as an on-line activation process and the CV activation process consists of two steps : 1) the humidification of the polymer electrolyte membrane and the electrode with 100% RH humidified nitrogen ($N_{2}$) gas, and 2) the removal step of the oxide layer on the surface of the Pt catalyst with CV cycling. The cycling reduces the activation time of the MEA by 2.5 h and use of hydrogen gas by 1/4.