• Korean Journal of Food Science and Technology
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• v.45 no.2
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• pp.137-141
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• 2013

Flavonoids have various biological activities; however, their cellular uptake mechanism is beginning to be understood only recently. This review focuses on cellular flavonoids transport mechanisms in both plants and animals. In plants, flavonoids exist in various cellular compartments, providing a specialized transport system. Newly synthesized flavonoids can be transported from the endoplasmic reticulum to the vacuoles or extracellular space via cellular trafficking pathway. Among membrane transporters, ATP binding cassette, multidrug and toxic extrusion, bilitranslocase homologue transporters play roles in both the influx and efflux of cellular flavonoids across the cell membrane. In recent years, extensive researches have provided a better understanding on the cellular flavonoid transport in mammalian cells. Bilitranslocase transports flavonoids in various tissues, including the liver, intestine and kidneys. However, other transport mechanisms are largely unknown and thus, further investigation should provide detailed mechanisms, which can potentially lead to an improved bioavailability and cellular function of flavonoids in humans.

• Applied Microscopy
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• v.19 no.2
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• pp.119-137
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• 1989

It has been shown in this and earlier investigation that the turtle bladder mucosa has three main cell types on their mucosal surface. They are the granular cells, ${\alpha}$ CA cells, and ${\beta}$ CA cells. The three major transport mechanisms that occurs in the turtle bladder are sodium reabsorption, proton secretion, and bicarbonate secretion. In the present work the trans-port mechanisms by bladder epithelial cells of freshwater turtle, Pseudemys scripta, are summarized as follows. 1. The granular cells play an important role in sodium transport, while the ${\alpha}$ and ${\beta}$ CA cells do not appear to play a determining role in sodium transport. 2. It appears that the active sodium transport in the granular cells occurs in two-step process, implying that first, sodium diffuses into the cells, followed by an energy-dependent efflux step, which is catalyzed by the ouabain-sensitive Na-K ATPase. 3. The ${\alpha}$ type of CA cells are responsible for the proton secretion using the proton pump on the apical plasma membrane, while the ${\beta}$ type of CA cells are believed to be responsible for bicarbonate secretion. 4. When looked at under freeze-fracture electron microscopy, the apical plasma membrane of ${\alpha}$ cells have a characteristic population of rod-shaped intramembranous particles which are believed to be components of the proton pumps. Conversely, ${\beta}$ type of CA cells show rod-shaped particles in their basolateral plasma membranes, which is consistent with the proton absorptive, bicarbonate secretory mechanism. 5. In the turtle bladder, the ${\alpha}$ and ${\beta}$ type of cells are believed to be both responsible for proton transport, but in opposite directions.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.27-27
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• 2011

For the design of real applicable molecular devices, current-voltage properties through molecular nanostructures such as metal-molecule-metal junctions (molecular junctions) have been studied extensively. In thiolate monolayers on the gold electrode, the chemical bonding of sulfur to gold and the van der Waals interactions between the alkyl chains of neighboring molecules are important factors in the formation of well-defined monolayers and in the control of the electron transport rate. Charge transport through the molecular junctions depends significantly on the energy levels of molecules relative to the Fermi levels of the contacts and the electronic structure of the molecule. It is important to understand the interfacial electron transport in accordance with the increased film thickness of alkyl chains that are known as an insulating layer, but are required for molecular device fabrication. Thiol-tethered RuII terpyridine complexes were synthesized for a voltage-driven molecular switch and used to understand the switch-on mechanism of the molecular switches of single metal complexes in the solid-state molecular junction in a vacuum. Electrochemical voltammetry and current-voltage (I-V) characteristics are measured to elucidate electron transport processes in the bistable conducting states of single molecular junctions of a molecular switch, Ru(II) terpyridine complexes. (1) On the basis of the Ru-centered electrochemical reaction data, the electron transport rate increases in the mixed self-assembled monolayer (SAM) of Ru(II) terpyridine complexes, indicating strong electronic coupling between the redox center and the substrate, along the molecules. (2) In a low-conducting state before switch-on, I-V characteristics are fitted to a direct tunneling model, and the estimated tunneling decay constant across the Ru(II) terpyridine complex is found to be smaller than that of alkanethiol. (3) The threshold voltages for the switch-on from low- to high-conducting states are identical, corresponding to the electron affinity of the molecules. (4) A high-conducting state after switch-on remains in the reverse voltage sweep, and a linear relationship of the current to the voltage is obtained. These results reveal electron transport paths via the redox centers of the Ru(II) terpyridine complexes, a molecular switch.

• Economic and Environmental Geology
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• v.29 no.6
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• pp.713-724
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• 1996

The time-series resident solute concentrations, monitored at two field plots using the automated 144-channel TDR system by Kim (this issue), are used to investigate the dominant transport mechanism at field scale. Two models, based on contradictory assumptions for describing the solute transport in the vadose zone, are fitted to the measured mean breakthrough curves (BTCs): the deterministic one-dimensional convection-dispersion model (CDE) and the stochastic-convective lognormal transfer function model (CLT). In addition, moment analysis has been performed using the probability density functions (pdfs) of the travel time of resident concentration. Results of moment analysis have shown that the first and second time moments of resident pdf are larger than those of flux pdf. Based on the time moments, expressed in function of model parameters, variance and dispersion of resident solute travel times are derived. The relationship between variance or dispersion of solute travel time and depth has been found to be identical for both the time-series flux and resident concentrations. Based on these relationships, the two models have been tested. However, due to the significant variations of transport properties across depth, the test has led to unreliable results. Consequently, the model performance has been evaluated based on predictability of the time-series resident BTCs at other depths after calibration at the first depth. The evaluation of model predictability has resulted in a clear conclusion that for both experimental sites the CLT model gives more accurate prediction than the CDE model. This suggests that solute transport at natural field soils is more likely governed by a stream tube model concept with correlated flow than a complete mixing model. Poor prediction of CDE model is attributed to the underestimation of solute spreading and thus resulting in an overprediction of peak concentration.

• Animal cells and systems
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• v.1 no.2
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• pp.341-344
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• 1997

Receptor-mediated endocytosis has been suggested for a stage-specific transport mechanism of vitellogenin into the oocytes of a sabellid poly chaete, Pseudopotamilla occelata. Membrane proteins of oocytes of three size classes, including small (30-70 $\mu\textrm{m}$ in diameter), intermediate (70-140 $\mu\textrm{m}$ in diameter) and large (180-200 $\mu\textrm{m}$ in diameter), showed a atage-specific variation. Coelomic fluid proteins (CP), ass$\mu\textrm{m}$ed to be vitellogenin, consists of several proteins, which showed quite a different pattern from that of yolk proteins. Incorporation of $^{125}I$-CP into the oocytes of the intermediate size class almost linearly increases with time, showing a contrast to the pattern of the large size class, in which the incorporation is low and approaches a plateau, suggesting the vitellogenin transports by a regulated process only in the intermediate size class. Vitellogenin receptor proteins were identified to be 60 kDa and 68 kDa only in the intermediate size class by a ligand blotting test.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1679-1683
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• 2013

Intergrowth perovskite type complex oxides $La_{0.8}Ln_{0.2}Sr_2MnCrO_{7-{\delta}}$ (Ln=La, Nd, Gd, and Dy) have been synthesized by sol-gel method. Rietveld profile analysis shows that the phases crystallize with tetragonal unit cell in the space group I4/mmm. The unit cell parameters a and c decrease with decreasing effective ionic radius of the lanthanide ion. The magnetic studies suggest that the ferromagnetic interactions are dominant due to $Mn^{3+}$-O-$Mn^{4+}$ and $Mn^{3+}$-O-$Cr^{3+}$ double exchange interactions. Both Weiss constant (${\theta}$) and Curie temperature ($T_C$) increase with decreasing ionic radius of lanthanide ion. It was found that the transport mechanism is dominated by Mott's variable range hopping (VRH) model with an increase of Mott localization energy.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.6
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• pp.43-53
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• 2014

Supporting handover functionality in V2I communication environments is important to provide higher quality service to users on the road. Wireless Access in Vehicular Environments(WAVE) standards define some features that devices can communicate with each other more efficiently in vehicular environments but they do not include handover function for providing effective V2I services. In this paper, we introduce a handover scheme in WAVE system and show the performance result of proposed scheme.

• Journal of Korean Society of Transportation
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• v.9 no.2
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• pp.57-74
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• 1991

Deregulation privatization regionalism and globalization are the specific examples of the recent trends in the world air transport market. As encouraged by the international trends and the domestic policy of promoting market mechanism Korean has been driving a two-airline policy since 1989. But due to the absence of experience and philosophy about the airline co-mpetition both Korean government and the two airlines have been criticized for failing to set fair-competition rules and for struggling to secure air service rights regardless of national interest. Therefore this study shows the costs and benefits of a two-airline policy in a small count-ry reviews the empirical studies about the cost structure of American and Canadian airlines and analyzes the economic consequences of allocating air service rights between two airlines. The policy recommendations are (1) removing government restrictions and expanding ai-rport facilities to develop the domestic market (2) retaining the two-airline policy in the in-ternational market (3) increasing traffic density rather than expanding network for the small airline (4) improving comparative advantage through a global alliance and a technological innovation for the big airline and (5) building an official committee for co-ordinating the two airlines' interests.

• Journal of Environmental Science International
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• v.6 no.6
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• pp.589-594
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• 1997

A total of 24 surface sediment samples collected from coastal region and fronting of sea cliff on Cape Cod In southeastern Massachusetts, were analyzed to Investigate the sediment transport mechanism. According to the result of grainsize analysis, the overall trend of g.k size decreases from the north(Wood End Beach) to the south(Nauset Light Beachy. The coarser materials tend to be deposited at the foreshore than at the backshore. Especially gavel content(%) Is very high in northern beaches. The lavel fraction tended to concentrate at the toe of the beach. In addition to gravel. the beach and nearshore bar also tended to be deposite of very coarse sand and the Inner fraction accumulate in the offshore bar, Grainsize analyses of sediment Indicates that the coarsest sands Including gravel accumulate In the beach and nearshore bar, the finer fraction winnowed out by wave action to be deposited In the offshore bar. The beach and nearshore bar sands and gavel are subsequently transported laterally by the wave-driven longshore drift, and finally they come to rest in the distal end of Provincetown Hook. The faller offshore sands are trnasported laterally to the south by net southward-directed longshore current.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1447-1456
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• 2000

Simulated experiments of high pressure melt ejection(HPME) are performed to measure the released fraction of corium simulant from the French type PWR cavity. The experiments are carried out on a 1/20th linear scaled model of the Ulchin 1&2 cavity. Water or woods metal and nitrogen is used as simulant of molten corium and steam, respectively. Experimental parameters are water mass, annulus area and breach size. It is shown that only breach size effects is very important while the mass and the annulus area do not affect the released fraction. It is found that the liquid film transport is much more dominant mechanism than the entrainment droplet transport, especially in linear scale down simulated HPME experiment.