• Title/Summary/Keyword: Counter-transport

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Pharmacokinetic Modeling and Simulation of the Carrier-Mediated Hepatic Transport of Organic Anions (음이온계 약물의 간수송과정에 있어서 담체매개 수송의 약물동력학적 모델링 및 시뮬레이션)

  • 이준섭;강민희;김묘경;이명구;정석재;심창구;정연복
    • YAKHAK HOEJI
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    • v.47 no.2
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    • pp.110-119
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    • 2003
  • The purpose of the present study was to kinetically investigate the carrier-mediated uptake in the hepatic transport of organic anions, and to simulate the ″in vivo counter-transport″ phenomena, using kinetic model which was developed in this study. The condition that the mobility of carrier-ligand complex is greater than that of free carrier is not essential for the occurrence of ″counter-transport″ phenomenon. To examine the inhibitory effects on the initial uptake of a ligand by the liver, it is necessary to judge whether the true counter-transport mechanism (trans-stimulation) is working or not. The initial plasma disappearance curves of a organic anion were then kinetically analyzed based on a flow model, in which the ligand is eliminated only from the peripheral compartment (liver compartment). Moreover, ″in vive counter-transport″ phenomena were simulated based on the perfusion model which incorporated the carrier-mediated transport and the saturable intracellular binding. The ″in vivo counter-transport″ phenomena in the hepatic transport of a organic anion were well demonstrated by incorporating the carrier-mediated process. However, the ″in vivo counter-transport″ phenomena may be also explained by the enhancement of back diffusion due to the displacement of intracellular binding. In conclusion, one should be more cautious in interpreting data obtained from so-called ″in vivo counter-transport″ experiments.

Pharmacokinetic Modelling and Simulation of the Counter-transport in the Hepatic Transport of Organic Anions (음이온계 약물의 간수송과정에 있어서 대향수송의 약물동력학적 모델링 및 시뮬레이션)

  • Song, Suk-Gil;Lee, Jun-Seup;Chung, Youn-Bok
    • YAKHAK HOEJI
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    • v.49 no.4
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    • pp.275-283
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    • 2005
  • The purpose of the present study was to kinetically investigate the carrier-mediated uptake in the hepatic transport of organic anions, and to simulate the 'in vivo counter-transport' phenomena, using kinetic model which was developed in this study. The condition that the mobility of carrier-ligand complex is greater than that of free carrier is not essential for the occurrence of 'counter-transport' phenomenon. To examine the inhibitory effects on the initial uptake of organic anions by the liver, it is necessary to judge whether the true counter-transport mechanism (trans-stimulation) is working or not. Effects of bromophenol blue (BPB) or bromosulfophthalein (BSP) on the plasma disappearance curves of a 1-anilino-8-naphthalene sulfonate (ANS) were then kinetically analyzed based on a flow model, in which the ligand is eliminated only from the peripheral compartment (liver compartment). Moreover, 'in vivo counter-transport' phenomena were simulated based on the perfusion model which incorporated the carrier-mediated transport and the saturable intracellular binding. The 'in vivo counter-transport' phenomena in the hepatic transport of a organic anions were well demonstrated by incorporating the carrier-mediated process. However, the 'in vivo counter-transport' phenomena may be also explained by the enhancement of back diffusion due to the displacement of intracellular binding. In conclusion, one should be more cautious in interpreting data obtained from so-called 'in vivo counter-transport' experiments.

Kinetic Analysis of the Counter-transport Phenomenon in the Hepatic Transport of Organic Anionic Drugs (유기 음이온계 약물의 간수송과정에 있어서 대향수송현상에 관한 속도론적 연구)

  • Chung, Youn-Bok;Han, Kun;No, Jung-Ryul
    • Journal of Pharmaceutical Investigation
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    • v.22 no.4
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    • pp.289-300
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    • 1992
  • The counter-transport phenomena in the hepatic transport of 1-anilino-8-naphthalene sulfonate (ANS) were kinetically investigated by analyzing the plasma disappearance-time profiles and the transport into the isolated hepatocytes. In vivo "counter transport phenomena" were simulated based on the perfusion model which incorporated the carrier-mediated transport and the saturable intracellular binding. The condition that the mobility of carrier-ligand complex is greater than that of free carrier is not essential for the occurrence of counter-transport phenomenon. To examine the inhibitory effects on the initial uptake of a ligand by the liver, it is necessary to judge whether the true counter-transport mechanism (trans-stimulation) is working or not. The initial plasma disappearance curves of ANS were then kinetically analyzed based on a two-compartment model, in which the ligand is eliminated only from the peripheral compartment (liver compartment). No effects on the initial plasma disappearance rates of ANS were observed after preloading of bromophenol blue (BPB) or rose bengal (RB) in the liver. Inhibitory effect of BPB or RB on the initial uptake (or efflux) rates of ANS by the isolated hepatocytes were not observed, suggesting that the true counter transport mechanism is not working. In conclusion, checking the preloading effects of transstimulation on the initial uptake of a ligand by the liver could be a useful criterion for carrier cycling and common use of the same carrier between two ligands. However, one cannot exclude those possibilities even if the preloading effects cannot be observed.

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Three Dimensional Computational Study on Performance and Transport Characteristics of PEMFC by Flow Direction (유동방향 변화에 따른 고분자 전해질 연료전지의 성능 및 전달특성에 대한 3차원 수치해석적 연구)

  • Lee, Pil-Hyong;Han, Sang-Seok;Hwang, Sang-Soon
    • Journal of the Korean Electrochemical Society
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    • v.11 no.1
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    • pp.51-58
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    • 2008
  • Many researches for effects of different flow configurations on performance of Proton Exchange Membrane Fuel Cell have extensively been done but the effects of flow direction at the same flow channel shape should be considered for optimal operation of fuel cell as well. In this paper a numerical computational methode for simulating entire reactive flow fields including anode and cathode flow has been developed and the effects of different flow direction at parallel flow was studied. Pressure drop along the flow channel and density distribution of reactant and products and water transport, ion conductivity across the membrane and I-V performance are compared in terms of flow directions(co-flow or counter-flow) using above numerical simulation method. The results show that the performance under counter-flow condition is superior to that under co-flow condition due to higher reactant and water transport resulting to higher ion conductivity of membrane.

Transport of Phenol in Waste Water Through Liquid Surfactant Membrane (폐수중 액체막에 의한 페놀의 이동)

  • 우인성;김병석;김윤선
    • Journal of the Korean Society of Safety
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    • v.5 no.3
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    • pp.39-43
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    • 1990
  • The transport of phenol from waste water through the liquid surfactant membrane containing Aliquat 336 as a carrier was analyzed by a theoretical model. Extraction experiments was carried out to investigate the effect of process parameters, such as mixing intensity, concentration of sodium hydroxide in internal aqueous solution, and counter anions, and initial phenol concentration in waste water at $25^{\circ}C$. It was found that transport rate of phenol increased with increasing pH differents. The transport rate of phenol in waste water was influenced by counter anions.

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Effect of Counter-doping Thickness on Double-gate MOSFET Characteristics

  • George, James T.;Joseph, Saji;Mathew, Vincent
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.10 no.2
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    • pp.130-133
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    • 2010
  • This paper presents a study of the influence of variation of counter doping thickness on short channel effect in symmetric double-gate (DG) nano MOSFETs. Short channel effects are estimated from the computed values of current-voltage (I-V) characteristics. Two dimensional Quantum transport equations and Poisson equations are used to compute DG MOSFET characteristics. We found that the transconductance ($g_m$) and the drain conductance ($g_d$) increase with an increase in p-type counter-doping thickness ($T_c$). Very high value of transconductance ($g_m=38\;mS/{\mu}m$) is observed at 2.2 nm channel thickness. We have established that the threshold voltage of DG MOSFETs can be tuned by selecting the thickness of counter-doping in such device.

Research on Safety-related Communication of Railway Automatic Block Between Railway Stations System

  • Yun, Pei-Yan;Guo, Jin
    • International Journal of Railway
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    • v.2 no.3
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    • pp.127-130
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    • 2009
  • The system improves the safety and efficiency of railway transport, combining the advanced axle-counter with single-track semiautomatic block. Using computer, to accomplish relay-based semiautomatic block logic operation and axle-counter to check section status, it will further increase the performance of railway transport. Safety-related communication is one of the important topics in railway signal system. By referring to relevant safety-related communication standards, to research on safety-related communication of Micro-computer automatic block between Railway Stations System, the thesis introduces the basic requirements, concept model, codes, and the process, etc.

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Separation and Concentration of L-Phenylalanine using a Supported Liquid Membrane

  • Jeong Woo Choi;Kyu
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.3 no.1
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    • pp.24-31
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    • 1998
  • The separation and concentration of L-phenylalanine (L-Phe) using a supported liquid membrane (SLM) is investigated. A cation complex agent, di-2-ethylhexyl phosphoric acid (D2EHPA), is used as a carrier in the SLM with n-Heptane as a solvent. The reaction order and equilibrium constant in the formation reaction of L-phe-carrier complex are obtained from the extraction experiment. A mathematical model for a carrier mediated counter transport process is proposed to estimate the diffusion coefficient of L-phe-carrier complexly in the liquid membrant. Permeation experiments of L-phe using a SLM are performed under various operating conditions and optimum conditions for the transport of L-phe are obtained. Concentration of L-phe in the strip phase against its concentration is observed. Transport rate of glucose through liquid membrane is less than that of L-phe in the competitive transport of L-phe and glucose. And the existence of glucose reduced the transport rate of L-phe. The performance of separation with continuous strip phase is increased due to the dilution effect in the strip phase.

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Effect of Valine on facilitated O1e1in Transport Membranes (올레핀 촉진수송 분리막의 성능향상을 위한 Valine의 효과)

  • Yong Soo Kang;Sang Wook Kang;Jong Hak Kim;Jongok Won;Kookheon Char
    • Membrane Journal
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    • v.13 no.2
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    • pp.125-129
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    • 2003
  • A remarkable separation performance of olefin/paraffin mixtures has been observed through facilitated olefin transport membranes consisting of silver ions dissolved in polymer matrices. In this research, valine, an amino acid, was introduced in poly (2-ethyl-2-oxazoline) (POZ)/$AgBF_4$ membranes to increase the separation performance. FT-IR spectra show that the cationic sites ($-NH_3^+$) of valine interact with the counter anion of the silver salt, resulting in the enhanced activity of the silver ions and consequently improved separation perfornance. Therefore, the $POZ/AgBF_4$ membranes containing valines exhibit the higher permeance as well as the higher selectivity of propylene/propane than those without valine.

Dynamic Behaviors of a Single Vortex in Counter Non-reacting and Reacting Flow Field (대향류 반응 및 비반응 유동장에서의 단일 와동의 동적 거동)

  • Yoo, Byung-Hun;Oh, Chang-Bo;Hwang, Chul-Hong;Lee, Chang-Eon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.9
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    • pp.1262-1272
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    • 2003
  • A two-dimensional direct numerical simulation is performed to investigate the dynamic behaviors of a single vortex in counter reacting and non-reacting flow field. A predictor-corrector-type numerical scheme with a low Mach number approximation is used in this simulation. A 16-step augmented reduced mechanism is adopted to treat the chemical reaction. The budget of the vorticity transport equation is examined to reveal a mechanism leading to the formation, destruction and transport of a single vortex according to the direction of vortex generation in reacting and non-reacting flows. The results show that air-side vortex has more larger strength than that of fuel-side vortex in both non-reacting and reacting flows. In reacting flow, the vortex is more dissipated than that in non-reacting flow as the vortex approach the flame. The total circulation in reacting flow, however, is larger than that in non-reacting flow because the convection transport of vorticity becomes much large by the increased velocity near the flame region. It is also found that the stretching and the convection terms mainly generate vorticity in non-reacting and reacting flows. The baroclinic torque term generates vorticity, while the viscous and the volumetric expansion terms attenuate vorticity in reacting flow. Furthermore, the contribution of volumetric expansion term on total circulation for air-side vortex is much larger than that of fuel-side vortex. It is also estimated that the difference of total circulation near stagnation plane according to the direction of vortex generation mainly attributes to the convection term.