• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2822-2827
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• 2008

Among the main components of PEM fuel cell, the functions of GDL are to transport reactants from the channel to the catalyst and remove reaction products from the catalyst and transport heat from the catalyst to the channels in the flow filed plate. Permeability of GDL is known to make it possible to enhance the gas transport through GDL, devoting to get better performance. In this paper, three dimensional numerical simulation of the fuel cell by the permeability of GDL is presented by using a FLUENT modified to include the electrochemical behavior. Results show that as permeability is higher than $10^{-12}m^2$, gradients of temperature distribution, oxygen molar concentration and current density distribution in MEA were decreased. Although heat generation was increased as high permeability, MEA's temperature was lower than the low permeability of GDL. This seems because that convection was higher affects in mass and heat transfer process than diffusion as permeability of GDL is increases.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.134-136
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• 2005

Homogenization method is adopted to predict the permeability tenor for glass fiber plain woven fabrics. Calculating the permeability tensor numerically is an encouraging task because the permeability tensor is a key parameter in resin transfer molding (RTM). Based on multi-scale approach of the homogenization method, the permeability for the micro-unit cell within fiber tow is computed and compared with that obtained from flow analysis for the same micro-unit cell. It is found that they are in good agreement. In order to calculate the permeability tensor of macro-unit cell for the plain woven fabrics, the Stokes and Brinkman equations which describe inter-tow and intra-tow flow respectively are employed as governing equations. The effective permeabilities homogenized by considering intra-tow flow are compared with those obtained experimentally. Control volume finite element method (CVFEM) is used as a numerical method. It is shown that the asymptotic expansion homogenization method is an attractive method to predict the effective permeability for heterogeneous media.

• The Korean Journal of Physiology and Pharmacology
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• 제10권4호
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• pp.207-212
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• 2006

Mitochondrial permeability transition has been shown to be involved in neuronal cell death. Mitochondrial monoamine oxidase (MAO)-B is considered to play a part in the progress of nigrostriatal cell death. The present study examined the effect of MAO inhibitors against the toxicity of 1-methyl-4-phenylpyridinium $(MPP^+)$ in relation to the mitochondrial permeability transition. Chlorgyline (a selective inhibitor of MAO-A), deprenyl (a selective inhibitor of MAO-B) and tranylcypromine (nonselective inhibitor of MAO) all prevented cell viability loss, cytochrome c release, caspase-3 activation, formation of reactive oxygen species and depletion of GSH in differentiated PC12 cells treated with $500\;{\mu}M$$MPP^+$. The MAO inhibitors at $10\;{\mu}M$ revealed a maximal inhibitory effect and beyond this concentration the inhibitory effect declined. On the basis of concentration, the inhibitory potency was tranylcypromine, deprenyl and chlorgyline order. The results suggest that chlorgyline, deprenyl and tranylcypromine attenuate the toxicity of $MPP^+$ against PC12 cells by suppressing the mitochondrial permeability transition that seems to be mediated by oxidative stress.

• Biomolecules & Therapeutics
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• 제12권1호
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• pp.9-18
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• 2004

Opening of the mitochondrial permeability transition pore has been recognized to be involved in cell death. The present study investigated the effect of ${\beta}$-carbolines (harmaline and harmalol) and deprenyl on the dopamine-induced change in the mitochondrial membrane permeability and cell death in differentiated PC12 cells. Cell death due to 250 4{\mu}$M dopamine was inhibited by caspase inhibitors (z-IETD.fmk, z-LEHD.fmk and z-DQMD.fmk) and antioxidants (N-acetylcysteine, ascorbate, superoxide dismutase, catalase and carboxy-PTIO). ${\beta}$-Carbolines prevented the dopamine-induced cell death in PCl2 cells, while deprenyl did not inhibit cell death. ${\beta}$-Carbolines decreased the condensation and fragmentation of nuclei caused by dopamine in PC12 cells. ${\beta}$-Carbolines inhibited the decrease in mitochondrial transmembrane potential, cytochrome c release, formation of reactive oxygen species and depletion of GSH caused by dopamine in PC12 cells, whereas deprenyl did not decrease dopamine-induced mitochondrial damage. ${\beta}$-Carbolines, deprenyl and antioxidants depressed the formation of nitric oxide and melanin in dopamine-treated PC12 cells. The results suggest that cell death due to dopamine PC12 cells is mediated by caspase-8, -9 and -3. Unlike deprenyl, ${\beta}$-carbolines may attenuate the dopamineinduced cell death in PC12 cells by suppressing change in the mitochondrial membrane permeability through inhibition of the toxic action of reactive oxygen and nitrogen species.

• Natural Product Sciences
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• 제20권1호
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• pp.1-6
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• 2014

P-glycoprotein (P-gp) is a permeability glycoprotein also known as multidrug resistance protein 1 (MDR1). P-gp is an ATP-binding cassette (ABC) transporter that pumps various types of drugs out of cells. These transporters reduce the intracellular concentrations of drugs and disturb drug absorption. The Caco-2 cell permeability assay system is an effective in vitro system that predicts the intestinal absorption of drugs and the functions of enzymes and transporters. Rhodamine-123 (R-123) and digoxin are well-known P-gp substrates that have been used to determine the function of P-gp. Efflux of P-gp substrates by P-gp has been routinely evaluated. To date, a number of herbal medicines have been tested with Caco-2 cell permeability assay system to assess bioavailability. There are growing efforts to find phytochemicals that potentially regulate P-gp function. The Caco-2 cell permeability assay system is a primary strategy to search for candidates of P-gp inhibitors. In this mini review, we have summarized the P-gp modulation by herbal extracts, decoctions or single components from natural products using Caco-2 cell permeability assays. Many natural products are known to regulate P-gp and herbal medicines could be used in combination with conventional drugs to enhance bioavailability.

• Journal of Microbiology and Biotechnology
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• 제32권1호
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• pp.37-45
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• 2022

The fungal cell wall and membrane are the principal targets of antifungals. Herein, we report that myricetin exerts antifungal activity against Candida albicans by damaging the cell wall integrity and notably enhancing the membrane permeability. In the presence of sorbitol, an osmotic protectant, the minimum inhibitory concentration (MIC) of myricetin against C. albicans increased from 20 to 40 and 80 ㎍/ml in 24 and 72 h, respectively, demonstrating that myricetin disturbs the cell wall integrity of C. albicans. Fluorescence microscopic images showed the presence of propidium iodide-stained C. albicans cells, indicating the myricetin-induced initial damage of the cell membrane. The effects of myricetin on the membrane permeability of C. albicans cells were assessed using crystal violet-uptake and intracellular material-leakage assays. The percentage uptakes of crystal violet for myricetin-treated C. albicans cells at 1×, 2×, and 4× the MIC of myricetin were 36.5, 60.6, and 79.4%, respectively, while those for DMSO-treated C. albicans cells were 28.2, 28.9, and 29.7%, respectively. Additionally, myricetin-treated C. albicans cells showed notable DNA and protein leakage, compared with the DMSO-treated controls. Furthermore, treatment of C. albicans cells with 1× the MIC of myricetin showed a 17.2 and 28.0% reduction in the binding of the lipophilic probes diphenylhexatriene and Nile red, respectively, indicating that myricetin alters the lipid components or order in the C. albicans cell membrane, leading to increased membrane permeability. Therefore, these data will provide insights into the pharmacological worth of myricetin as a prospective antifungal for treating C. albicans infections.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.181-183
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• 2002

The accurate permeability for preform is critical to model and design the impregnation of fluid resin in the composite manufacturing process. In this study, the in-plane and transverse permeability for a woven fabric are predicted numerically through the coupled flow model which combines microscopic with macroscopic flow. The microscopic and macroscopic flow which are flows within the micro-unit and macro-unit cell, respectively, are calculated by using 3-D CVFEM(control volume finite element method). To avoid checker-board pressure field and improve the efficiency on numerical computation, A new interpolation function for velocity is proposed on the basis of analytic solutions. The permeability of plain woven fabric is measured through unidirectional flow experiment and compared with the permeability calculated numerically. Based on the good agreement of the results, the relationships between the permeability and the structures of preform such as the fiber volume fraction and stacking effect can be understood. The reverse and the simple stacking are taken in account. Unlike past literatures, this study is based on more realistic unit cell and the improved prediction of permeability can be achieved. It is observed that in-plane flow is more dominant than transverse flow in the real flow through preform and the stacking effect of multi-layered preform is negligible. Consequently, the proposed coupled flow model can be applied to modeling of real composite materials processing.

• Geomechanics and Engineering
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• 제21권2호
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• pp.103-109
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• 2020

The inflow rate is of interest in the design of underground structures such as tunnels and buried pipes below the groundwater table. Soil permeability governing the inflow rate significantly affects the hydro-geological behavior of soils but is difficult to estimate due to its wide range of distribution, nonlinearity and anisotropy. Volume changes induced by stress can cause nonlinear stress-strain behavior, resulting in corresponding permeability changes. In this paper, the nonlinearity and anisotropy of permeability are investigated by conducting Rowe cell tests, and a nonlinear permeability model considering anisotropy was proposed. Model modification and parameter evaluation for field application were also addressed. Significance of nonlinear permeability was illustrated by carrying out numerical analysis of a tunnel. It is highlighted that the effect of nonlinear permeability is significant in soils of which volume change is considerable, and particularly appears in the short-term flow behavior.

• 한국지반환경공학회 논문집
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• 제4권3호
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• pp.5-17
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• 2003

수직 및 수평방향 압밀시험을 수행할 수 있도록 제작된 Rowe cell을 사용하여 재성형된 포항 이암풍화토의 수직 및 수평방향의 압밀과 투수특성을 살펴보았고, 그 결과를 Oedometer 시험결과와 비교분석 하였다. 간접투수계수는 9가지의 압밀계수 산정법에 의해 구하여진 압밀계수로부터 산정하였다. 수직배수인 경우 ${\sqrt{t}}$ 법과 hyperbolic 방법에 의한 간접투수계수가 비교적 직접투수계수와 잘 일치하였고, 수평배수의 경우는 전반적으로 모든 방법에서 과대평가되는 경향이 나타났다. 수직 및 수평방향 직접투수계수에 의한 이암풍화토의 투수에 대한 이방성 효과를 검토한 결과 모든 압밀하중에서 평균 약 13정도의 이방성을 보였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권3호
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• pp.147-150
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• 2004

Permeabilization is known to overcome cell membrane barriers of whole cell biocatalysts. The use of organic solvents is advantageous in terms of cost, simplicity, and efficiency. In this study, Ochrobactrum anthropi SY509 was permeabilized with various organic solvents. Treatment with organic solvents resulted in lower permeability barriers due to falling out lipids of the cell membrane. Therefore, permeabilized cells showed higher enzyme activity with no cell viability. Among various organic solvents, 0.5% (v/v) chloroform was selected as the most efficient permeabilizing reagent. Changes in the cell membrane structure were observe d and the residual amounts of phospholipids of the cell membrane were measured to investigate the mechanism of the improved permeability.