• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.79-86
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• 2009

With the substantial increase of the size of structure, the management of excavation becomes more difficult. Therefore, massive collapses which are related to retaining wall recently increase. However, since the study on measuring and monitoring the pre-stressing force of anchor is insufficient, behavior of anchor may not be predicted and monitored appropriately by the existing strain gauge and load cell type monitoring system. FBG Sensor, which is smaller than strain gauge and has better durability and does not have a noise from electromagnetic waves, is adapted to measure the strain and pre-stressing force of 7-wire strand, so called smart tendon. A series of pullout tests were performed to verify the feasibility of smart tendon and find out the load transfer mechanism around the steel wire tendon fixed to rock with grout. Distribution of measured strains and estimated shear stresses are compared with those predicted by theoretical solutions. It was found that developed smart tendon can be used effectively for measuring strain of 7-wire strand anchor and theoretical solutions underestimate the magnitude of shear stress and load transfer depth.

• Journal of Chest Surgery
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• v.37 no.6
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• pp.482-491
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• 2004

Background: The xenogenic or allogenic valves after in Vitro repopulation with autologous cells or in vivo repo-pulation after acellularization treatment to remove the antigenicity could used as an alternative to synthetic polymer scaffold. In the present study, we evaluated the process of repopulation by recipient cell to the acellu-larized xenograft treated with NaCl-SDS solution and grafted in the right ventricular outflow tract. Material and Method: Porcine pulmonary valved conduit were treated with. NaCl-SDS solution to make the grafts acellularized and implanted in the right ventricular outflow tract of the goats under cardiopulmonary bypass. After evaluating the functions of pulmonary valves by echocardiography, goats were sacrificed at 1 week, 1 month, 3 months, 6 months, and 12 months after implantation, respectively. After retrieving the implanted valved conduits, histopathologic examination with Hematoxylin-Eosin, Masson' trichrome staining and immunohistochemical staining was performed. Result: Among the six goats, which had been implanted with acellularized pulmonary valved conduits, five survived the expected time period. Echocardiographic examinations for pulmonary valves revealed good function except mild regurgitation and stenosis. Microscopic analysis of the leaflets showed progressive cellular in-growth, composed of fibroblasts, myofibroblasts, and endothelial cells, into the acellularized leaflets over time. Severe inflammatory respon-se was detected in early phase, though it gradually decreased afterwards. The extracellular matrices were regenerated by repopulated cells on the recellularized portion of the acellularized leaflet. Conclusion: The acellularized xenogenic pulmonary valved conuits were repopulated with fibroblasts, myofibroblasts, and endothelial cells of the recipient and extracellullar matrices were regenerated by repopulted cells 12 months after the implantation. The functional integrity of pulmonary valves was well preserved. This study showed that the acellularized porcine xenogenic valved conduits could be used as an ideal valve prosthesis with long term durability.

• Journal of Chest Surgery
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• v.37 no.4
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• pp.297-306
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• 2004

Current artificial heart valves have several disadvantages, such as thromboembolism, limited durability, infection, and inability to grow. The solution to these problems would be to develop a tissue-engineered heart valves containing autologous cells. The aim of this study was to optimize the protocol to obtain a porcine acellular matrix and seed goat autologous endothelial cells on it, and to evaluate the biological responses of xenograft and xeno-autograft heart valves in goats. Material and Method: Fresh porcine pulmonic valves were treated with one method among 3 representative decellularization protocols (Triton-X, freeze-thawing, and NaCl-SDS). Goat venous endothelial cells were isolated and seeded onto the acellularized xenograft leaflets. Microscopic examinations were done to select the most effective method of decellularizing xenogeneic cells and seeding autologous endothelial cells. Two pulmonic valve leaflets of. 6 goats were replaced by acellularized porcine leaflets with or without seeding autologous endothelial cells while on cardiopulmonary bypass. Goats were sacrificed electively at 6 hours, 1 day, 1 week, 1 month, 3 months, and 6. months after operation. Morphologic examinations were done to see the biological responses of replaced valve leaflets. Result: The microscopic examinations showed that porcine cells were almost completely removed in the leaflets treated with NaCl-SDS. The seeded endothelial cells were more evenly preserved in NaCl-SDS treatment. All 6 goats survived the operation without complications. The xeno- autografts and xenografts showed the appearance, the remodeling process, and the cellular functions of myofibroblasts, 1 day, 1 month, and 3 months after operation, respectively. They were compatible with the native pulmonary leaflet (control group) except for the increased cellularity at 6 months. The xenografts revealed the new endothelial cell lining at that time. Conclusion: Treatment with NaCl-SDS was most effective in obtaining decellularized xenografts and facilitate seeding autologous endothelial cells. The xenografts and xeno-autografts were repopulated with myofibroblasts and endothelial cells in situ serially. Both of grafts served as a matrix for a tissue engineered heart valve and developed into autologous tissue for 6 months.

• Membrane Journal
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• v.27 no.4
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• pp.344-349
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• 2017

Alkaline fuel cells using polymer electrolyte membranes are expected to replace proton exchange membrane fuel cells, which have similar system configurations. In particular, in alkaline fuel cells, a low-cost non-platinium catalyst can be used. In this study, to fabricate high performance and high durability anion exchange membranes for alkaline fuel cell systems, two kinds of supports, polybenzoxazole and polyethylene supports, were impregnated with Fumion FAA ionomer, by which we tried to fabricate the support-impregnated membrane which has higher mechanical strength and higher ion conductivity than the Fumion series. Finally, the Pore-filling membranes were successfully fabricated and ionic conductivity and mechanical properties were different depending on the properties of the supports. In the pore-filling membranes with Fumion ionomer on the PE support, excellent mechanical properties were obtained, but ionic conductivity decreased. On the other hand, when the PBO support was impregnated with Fumion ionomer, high ionic conductivity was shown after impregnation due to high basicity of PBO, but the mechanical strength was relatively low as compared with Fumion-PE membrane. As a result, it was concluded that it is necessary to consider the characteristics of the support according to the operating conditions of the alkaline fuel cell during the preparation of the pore-filling membranes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.1-7
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• 2017

Cobalt silicide was used as a counter electrode in order to confirm its reliability in dye-sensitized solar cell (DSSC) devices. 100 nm-Co/300 nm-Si/quartz was formed by an evaporator and cobalt silicide was formed by vacuum heat treatment at $700^{\circ}C$ for 60 min to form approximately 350 nm-CoSi. This process was followed by etching in $80^{\circ}C$-30% $H_2SO_4$ to remove the cobalt residue on the cobalt silicide surface. Also, for the comparison against Pt, we prepared a 100 nm-Pt/glass counter electrode. Cobalt silicide was used for the counter electrode in order to confirm its reliability in DSSC devices and maintained for 0, 168, 336, 504, 672, and 840 hours at $80^{\circ}C$. The photovoltaic properties of the DSSCs employing cobalt silicide were confirmed by using a simulator and potentiostat. Cyclic-voltammetry, field emission scanning electron microscopy, focused ion beam scanning electron microscopy, and energy dispersive spectrometry analyses were used to confirm the catalytic activity, microstructure, and composition, respectively. The energy conversion efficiency (ECE) as a function of time and ECE of the DSSC with Pt and CoSi counter electrodes were maintained for 504 hours. However, after 672 hours, the ECEs decreased to a half of their initial values. The results of the catalytic activity analysis showed that the catalytic activities of the Pt and CoSi counter electrodes decreased to 64% and 57% of their initial values, respectively(after 840 hours). The microstructure analysis showed that the CoSi layer improved the durability in the electrolyte, but because the stress concentrates on the contact surface between the lower quartz substrate and the CoSi layer, cracks are formed locally and flaking occurs. Thus, deterioration occurs due to the residual stress built up during the silicidation of the CoSi counter electrode, so it is necessary to take measures against these residual stresses, in order to ensure the reliability of the electrode.

• Journal of Chest Surgery
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• v.41 no.1
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• pp.12-24
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• 2008

Background: It is currently thought that tissue valve degeneration is related to an animal's immune response, which is mainly due to cell surface ${\alpha}$-Gal epitopes. Cell surface ${\alpha}$-Gal epitopes are known to be degraded by the enzyme called green coffee bean ${\alpha}$-Galactosidase. It is also well known that ${\alpha}$-Gal epitopes are immunologically stained by Griffonia Simplicifolia isolectin type B4. We know that many commercially available tissue valves are made of aortic valves and pericardial tissue of pig. So, we investigated whether ${\alpha}$-Gal epitopes of the aortic valve and pericardial tissue of a pig can be removed by green coffee bean ${\alpha}$-Galactosidase, and we did so by comparing immunologic staining of the tissues before and after the enzyme treatment. Material and method: After treating fresh porcine aortic valve and pericardial tissue with green coffee bean ${\alpha}$-Galactosidase at concentrations of 0.5 unit/mL, 1.0 unit/mL, 2.0 unit/mL, respectively, under the condition of pH 6.5, temperature. $4^{\circ}C$ and 24 hours of incubation, each sample was stained with Griffonia Simplicifolia isolectin type B4 immunpfluorescent labeling. We then examined whether the ${\alpha}$-Gal epitopes were reduced or abolished in each consecutive. concentration of green coffee bean ${\alpha}$-Galactosidase by comparing the degree of the Griffonia Simplicifolia isolectin B4 staining in each sample. Result: In the pig aortic valve tissue, a 1.0 unit/mL concentration of green coffee bean ${\alpha}$-Galactosidase at pH 6.5, $4^{\circ}C$ and reaction for 24 hours was enough for complete removal of ${\alpha}$-Gal epitopes from the cell sur face on the immunostaining with Griffonia Simplicifolia isolectin B4. On the other hand, more ${\alpha}$-Gal epitopes were present in the pig pericardial tissue on Griffonia Simplicifolia isolectin B4 staining before the enzyme treatment, and 1.0 unit/mL of galactosidase was not sufficient for complete removal of ${\alpha}$-Gal from the tissue. 2.0 units/mL of green coffee bean ${\alpha}$-Galactosidase was needed to completely remove the ${\alpha}$-Gal epitopes from the pericardial tissue on immunostaining. Conclusion: The ${\alpha}$-Gal epitopes of the pig's aortic valve and pericardial tissue were successfully stained with Griffonia Simplicifolia isolectin B4. We could remove nearly all the ${\alpha}$-Gal epitopes using green coffee bean ${\alpha}$-Galactosidase at the concentration of 1.0 unit/mL in the aortic valve. Of pig, and 2.0 unit/mL was need to nearly completely remove all the ${\alpha}$-Gal epitopes in the pericardial tissue of pig under the condition of pH 6.5, $4^{\circ}C$ and 24 hours of reaction time. In the near future, removal of ${\alpha}$-Gal epitapes in the pig's aortic valve and pericardial tissue will become a powerful tool for the improvement of the tissue valve durability. It needs to be determined if ${\alpha}$-galactosidase treated pig tissue is immune to human anti-Gal antibody or anit-Gal mooclonal antibodies.

• Journal of Chest Surgery
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• v.39 no.7 s.264
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• pp.527-533
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• 2006

Background: A retrospective study was conducted to analyze the results of St. Jude Medical mitral valve replacement at the Chonbuk National University Hospital since the initial implant in May 1984. Material and Method: Between May of 1984 and December of 1996, 95 patients underwent MVR with the St. Jude Medical mechanical valve prosthesis at Department of Medical Science of Chonbuk National University Hospital and follow-up ended in May of 2004. Result: Age ranged from 19 to 69 years. Follow-up (mean${\pm}$standard deviation) averaged $10.6{\pm}4.2\;year$. Thirty-day operative mortality was 4.2% (4/95). Nine late deaths have occurred and actuarial survival was $90.5{\pm}3.0%,\;87.9{\pm}3.4%\;and\;83.2{\pm}4.6%$ at 5, 10 and 20 years, respectively. Probability of freedom from valve-rotated death was $95.5{\pm}2.1%,\;94.3{\pm}2.4%\;and\;91.0{\pm}3.9%$ at 5, 10 and 20 years, respectively. Seven patients have sustained thromboembolic events (1,05%/patient-year). Fifteen patients had anticoagulation related hemorrhage (3.56%/patient-year). There was no structural valve deterioration. Probability of freedom from all complications was $82.0{\pm}3.9%,\;71.3{\pm}4.8%\;and\;42.4{\pm}10.5%$ at 5, 10 and 20 years, respectively. Conclusion: We confirm the effective and excellent durability of the St. Jude Medical prosthesis in the mitral position with a low event rate at long-term follow-up. It also demonstrates the commonly encountered practical difficulty of adjusting the anti-coagulation protocol in patients with prosthetic mitral valves.