• YAKHAK HOEJI
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• v.52 no.1
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• pp.67-72
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• 2008

The use of doxorubicin, which is one of the most effective anticancer agents, is often limited by occurrence of acquired resistance in tumor cells. GSH has been shown to be involved in the development of this drug resistance. Transcription factor Nrf2 governs the expression of GSH synthesizing glutamylcysteine ligase (GCL), as well as multiple phase 2 detoxifying enzymes. Here we show that Nrf2 is one of factors determining doxorubicin sensitivity. Nrf2-deficient fibroblasts (murine embryonic fibroblasts, MEF) were more susceptible to doxorubicin mediated cell death than wild-type cells. Doxorubicin treatment elevated levels of Nrf2-regulated genes including NAD(P)H: quinone oxidoreductase (Nqo1) and GCL in wild-type fibroblasts, while no induction was observed in Nrf2-deficient cells. Doxorubicin resistance in human ovarian SK-OV cells was reversed by treatment with L-buthionine-sulfoxamine (BSO), which is depleting intracellular GSH. Finally, transfection of SK-OV cells with Nrf2 siRNA resulted in exacerbated cytotoxicity following doxorubicin treatment compared to scrambled RNA control. These results indicate that the Nrf2 pathway, which plays a protective role in normal cells, can be a potential target to control cancer cell resistance to anticancer agents.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.295-304
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• 2010

Performance of a landfill liner is evaluated based on leakage rate and mass flux. In this study, the recently utilized double composite liner system, which consists of a geomembrane (GM), a geosynthetic clay liner (GCL), a GM, and a compacted clay layer (61 or 91.5 cm) is compared with other popular composite liners including the single GCL system, the Subtitle D liner system, and the Wisconsin NR500 liner system. The leakage rate through circular and long defects in the GM of the landfill liners is analyzed using numerical models. For the mass flux criterion, the analyses of inorganic contaminant transport through defects in the GM component of liner systems and diffusion of organic compounds through intact landfill liners are conducted using three- and one-dimensional numerical models, respectively. Cadmium and toluene are used in the analyses as a typical inorganic and organic substance, respectively, which will be chemical species encountered during landfill operation. The comparison shows that the double composite liner systems are superior to the other liner systems according to the performance-based evaluation.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1961-1971
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• 2006

A soft recovery system (SRS) is a device that stops a high speed projectile without damaging the projectile. The SRS is necessary to verify the shock resistant requirements of microelectronics and electro-optic sensors in smart munitions, where the projectiles experience over 20,000 g acceleration inside the barrel. In this study, a computer code for the performance evaluation of a SRS based on ballistic compression decelerator concept has been developed. It consists of a time accurate compressible one-dimensional Euler code with use of deforming grid and a projectile motion analysis code. The Euler code employs Roe's approximate Riemann solver with a total variation diminishing (TVD) method. A fully implicit dual time stepping method is used to advance the solution in time. In addition, the geometric conservation law (GCL) is applied to predict the solutions accurately on the deforming mesh. The equation of motion for the projectile is solved with the four-stage Runge-Kutta time integration method. A small scale SRS to catch a 20 mm bullet fired at 500 m/s within 1,600 g-limit has been designed with the proposed method.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.245-254
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• 2009

Efficiency of landfill liners system is usually evaluated based on leakage rate and mass flux. In this study, composite liner systems including the GCL(geosynthetic clay liner) composite liner, the Subtitle D liner, the Wisconsin NR500 liner, and the recently utilized double composite liner, which is a combination of the GCL composite liner and Subtitle D-type liner, have been examined. The leakage rate through circular and long defects in the geomembrane (GM) of the liner system was analyzed with the aids of analytical and numerical methods. For the mass flux criterion, contaminant transport through defects in the GM of landfill liners can be evaluated based on the calculated leakage rates. The diffusion rate of volatile organic compounds through intact landfill liners was evaluated by performing a one-dimensional numerical model. Cadmium and toluene were adoptted in the analyses as typical inorganic and organic substances, respectively, which will be chemical species encountered during landfill operation. The performance-based evaluation indicates that the double composite liner systems are superior to the other types of liner.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.321-328
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• 2002

Various geosynthetics used as liners or the Protection layers are installed in the solid waste landfill. The interface shear strength between geosynthetics installed at the slope of the landfill is a very important variable for the safe design of bottom and cover systems in the solid waste landfill. The interface shear strengths between (1) Geomembrane(GM)/Geotexile(GT) and (2) Geomembrane(GM)/Geosynthetic Clay Liner(GCL) were estimated by a large direct shear test in this study and were evaluated by the Mohr-Coulomb failure criterion. Especially, this research is focused on the effect of water which exists between geosynthetics because interfaces become easily wet or hydrated by rain, leachate and groundwater beneath liners. The strength reduction at large displacement and the effects of the magnitude of normal stresses and GCL hydration methods also investigated. The test results showed that the interface shear strength and shear behavior varied depending upon the magnitude of normal stresses, water at the interface, and hydration methods. Summary of secant friction angles, which could be used as reference values at a site where similar geosynthetics are installed, together with normal stress and hydration condition are presented.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.391-396
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• 2015

Purpose: The objective of this study was to investigate the visual system of the greater horseshoe bat (Rhinolophus ferrumequinum) by location analysis of some major neurotransmitters glutamate, ${\gamma}$-aminobutyric acid (GABA), acetylcholine, and their receptors, and $m{\ddot{u}}ller$ glial cells in retina. Methods: Standard immunocytochemical techniques were used after vibratome section of retinal tissues of adult greater horseshoe bat for this study. Immnoreactions in immunofluorescence images were analyzed using confocal microscope. Results: Anti-glutamate-immunoreactive neurons were mainly localized in the ganglion cell layer (GCL). The majority of anti-GABA-immunoreactive cells distributed in the inner nuclear layer (INL), and GABAA receptors were localized in the inner plexiform layer (IPL). Anti-choline acetyltransferase-immuoreactive cholinergic neurons were mainly located in the INL and GCL, and most of nicotinic acetylcholine receptors were localized in the IPL. The $m{\ddot{u}}ller$ cells in the retina of the greater horseshoe bat stretched theirs range from the GCL to outer nuclear layer (ONL). Conclusions: This study revealed that the retinas of the greater horseshoe bats contain the same major neurotransmitters and receptors, and glial cell in visually functional mammalian retinas. The present results may suggest that the greater horseshoe bats have the functional retinas for visual analysis through the organized retinal neural circuits.

• Applied Microscopy
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• v.28 no.4
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• pp.425-434
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• 1998

This study was designed to investigate the microglial reactions to the neurodegenerative changes in the cat retina. All experiments were performed using adult cats of both sex, weighing $2,500g\sim3,500g$. 5,7-DHT $(100{\mu}g)$ dissolved in 0.1% ascorbic acid was injected into the vitreous body. All injections were performed in one-side eye; the other side served as the control, which was injected only with 0.1% ascorbic acid. Cats were sacrificed at 1, 3, 7, 14 and 21 days after intravitreal injection of 5,7-DHT For light microscopy, retinae were fixed with 4% paraformaldehyde and processed using NDPase histochemistry. Same retinae were fixed with 1% para(formaldehyde-2.5% glutaraldehyde and processed for electron microscopy. NDPase-positive microglial cells were mainly distributed in the inner plexiform layer of the retina, and characterized by a small somata with a few slender processes, which were also extended in the ganglion cell layer (GCL) and inner nuclear layer (INL). The intensity of the microglia stained for NDPase was abruptly increased at 7 day as compared with that of the control, and thereafter continuously sustained until 21 day, the last experimental group in this study. Under the electron microscopical observation, microglial cells in the control group exhibited elongate nucleus with perinuclear chromatin condensation, and the perikaryon was scanty. However, a few hypertrophic glial cells were frequently found at 3 days after the drug injection. By 7 day, most microglial cells directed toward the degenerated neurons in the GCL, and the number of microglial cells was slightly increased as compared with the former group. At the 14 day, most microglial cells wrapped the degenerated cells in the GCL, and a few cells showed phagocytotic features. By 21 day, most microglial cells were engaged in phagocytotic activity, and their cytoplasm was filled with the phagorytosed material. Based on the results, 5,7-DHT may act as a specific neurotoxin to the cat retina, and microglial reactions to the neuronal death are already induced in early experimental stage. These results indicate that the microglial cells in the cat retina show characteristic features as a protective effect of neural tissue.

• Journal of the Korean Geosynthetics Society
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• v.1 no.1
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• pp.43-51
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• 2002

In this study, free swell index of betonite was examined in several regeants; distilled water, leachate, seawater and 3% NaCl solution. Free swell index values of bontonite to be added Poly(acrlylic acid), PYA(Polyvinyl Alcohol) or SCMC (Sodium Carboxymethyl Cellulose) were evaluated and compared. From this, it was confirmed that hydraulic conductivities of GCL in seawater were examined and the hydraulic conductivities of GCL in seawater were compared to those in distilled water. The average values of free swell indices of bentonite were decreased in order of distilled water>leachate>seawater. It was shown that no significant differences were occurred for free swell index between seawater and 3% NaCl solution. For bentonite to be added PVA, the other reagents except distilled water didn't affect increase of swelling. Swelling properties of bentonite to be added SCMC were improved except 3% NaCl solution.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.393-400
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• 2003

지오멤브레인(geomembrane)과 다른 토목섬유, 즉 지오텍스타일 또는 GCL, 사이의 interface 전단거동을 특성화하는 strain-softening 모델을 개발하였다. 본 연구에 제안된 모델은 일차적으로 smooth 지오멤브레인과 textured 지오멤브레인을 대상으로 실시한 직접전단 시험결과를 대상으로 구축되었다. 시험을 통해 측정된 변위-전단응력의 관계는 strain-softening 현상를 고려하기 위해서 최대점이 발생하는 위치를 기준으로, pre-peak과 post-peak 영역으로 나누어 분석을 실시하였다. 실험결과를 토대로 구축된 모델식은 원 자료와의 비교를 통해 본 모델의 유효성을 검증하였다. 비교 결과 높은 연직 응력에서 약간의 차이를 보이긴 하지만, 대체적으로 실험 결과와 구축된 모델을 이용한 역계산의 값이 좋은 일치를 보임을 확인할 수 있었다. 특별히 연직응력이 낮은 단계에서는 높은 일치를 보였는데, 이를 통해 제안된 식이 매립지의 최종 cover와 같이 상재 연직하중이 작은 경우에 지오멤브레인이 포함된 interface의 전단 거동에 대한 합리적인 구성 방정식이 될 수 있음을 확인할 수 있었다.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.34-37
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• 2009

Deforming mesh should be used when bodies are deforming or moving relative to each other due to the presence of aerodynamic forces and moments. Also, the flow solver for such a flow problem should satisfy the geometric conservation law to ensure the accuracy of the solutions. In this paper, a RANS(Reynolds Averaged Navier-Stokes) solver including automatic mesh capability using TFI(Transfinite Interpolation) method and GCL is developed and applied to flows induced by oscillating wings with given frequencies. The computations are performed both on deforming meshes and on rigid meshes. The computational results are compared with experimental data, which shows a good agreement.