Artykuły w czasopismach: „Transport Process and Kinetics”

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Aydiner, C., M. Kobya i I. Koyuncu. "Coupled transport of cyanide ions through liquid membranes". Water Science and Technology 41, nr 10-11 (1.05.2000): 125–33. http://dx.doi.org/10.2166/wst.2000.0624.

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In this study, the transport kinetics of coupled transport of cyanide ions through liquid membrane (trichloromethane) containing tetraoctylammonium chloride as a carrier was examined at different temperatures. The kinetics of cyanide transport could be analyzed in the formalism of two consecutive irreversible first order reactions. The influence of the temperature on the kinetic parameters (k1d, k2m, k2a, Rmmax, tmax, Jdmax, Jamax) has been established. For maximum membrane entrance and exit fluxes, Jdmax and Jamax, the activation energies were found from the slopes of the two linear relationships: 9.02 kcal/mol and 11.20 kcal/mol, respectively. The values of the found activation energy indicate that in the first step the transport process of cyanide ions through liquid membrane is difussional controlled, whereas in the second step it is most probably controlled by species diffusion and the rate of the reversible chemical reaction.

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Albasri, Sawsan Abd Muslim Mohammed, i Husna Salim Wahab. "Removal of Acetaminophen Residues from Wastewater by Bulk Liquid Membrane Process". Iraqi Journal of Chemical and Petroleum Engineering 21, nr 4 (30.12.2020): 1–9. http://dx.doi.org/10.31699/ijcpe.2020.4.1.

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The removal of Anit-Inflammatory drugs, namely; Acetaminophen (ACTP), from wastewater by bulk liquid membrane (BLM) process using Aliquat 336 (QCl) as a carrier was investigated. The effects of several parameters on the extraction efficiency were studied in this research, such as the initial feed phase concentration (10-50) ppm of ACTP, stripping phase (NaCl) concentration (0.3,0.5,0.7 M), temperature (30-50oC), the volume ratio of feed phase to membrane phase (200-400ml/80ml), agitation speed of the feed phase (75-125 rpm), membrane stirring speed (0, 100, 150 rpm), carrier concentration (1, 5, 9 wt%), the pH of feed (2, 4, 6, 8, 10), and solvent type (CCl4 and n-Heptane). The study shows that high extraction efficiency for ACTP of about 97% was achieved by a bulk liquid membrane at 50 ppm initial concentration of feed; stirring speed of feed phase 130 rpm; stirring speed of membrane phase 100rpm; 0.5 M NaCl concentration; carrier concentration 1wt%; volume ratio of 200ml feed:80ml membrane; feed pH of ACTP is 6, and 50˚C. The transport kinetics was evaluated using a kinetic model with two consecutive first-order irreversible reactions. The kinetics of (ACTP) transport by bulk liquid membrane was investigated at the best experimental conditions. The activation energy values of the extraction and stripping processes were 1.733 and 1.826 kJ.mol−1. The activation energy confirms that the transport process from solutions is controlled by diffusion.

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Nikolic, Natasa, M. V. Nikolic, S. M. Radic-Ristic i Momcilo Ristic. "Sintering as a process of transport of activated volume". Science of Sintering 34, nr 1 (2002): 53–56. http://dx.doi.org/10.2298/sos0201053n.

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Starting with the fact that sintering is the consequence of the process of transport of activated volume, it has been shown how the kinetics of the sintering process can be defined. The activated volume was in principle defined as a parameter which describes a system?s deffectivity on an atomic level.

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Van Vaerenbergh, S., i J. C. Legros. "Kinetics of the Soret effect: Transient in the transport process". Physical Review A 41, nr 12 (1.06.1990): 6727–31. http://dx.doi.org/10.1103/physreva.41.6727.

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Riechers, Birte, Florine Maes, Elias Akoury, Benoît Semin, Philipp Gruner i Jean-Christophe Baret. "Surfactant adsorption kinetics in microfluidics". Proceedings of the National Academy of Sciences 113, nr 41 (29.09.2016): 11465–70. http://dx.doi.org/10.1073/pnas.1604307113.

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Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than 90% to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning—here through ion exchange—unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore–surfactant interactions.

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Seleznev, E., V. Bereznev i I. Chernova. "PARTIAL NEUTRON TRANSPORT EQUATIONS". PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES: NUCLEAR AND REACTOR CONSTANTS 2019, nr 3 (26.09.2019): 143–52. http://dx.doi.org/10.55176/2414-1038-2019-3-143-152.

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To analyze the spatial kinetics of the reactor, a system of equations for the spatial kinetics of the reactor, consisting of two equations, is usually used. One of them describes the behavior of the neutron flux density, and the second describes the behavior of the precursors of delayed neutrons. In this case, the density of the neutron flux includes the flux density prompt neutrons, appearing directly upon fission of the nucleus, and delayed neutrons that appear in the decay of some fission fragments. This system of equations is called classical. This paper considers the possibility of representing the neutron flux density in a nonstationary process by individual equations for prompt and delayed neutrons and presents the initial results of modeling the nonstationary process for dumping a control rod in a fast medium-power reactor. A system of equations describing such a behavior of the neutron field in a reactor is called a system of partial equations.

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Nikolic, M. V., Nebojsa Labus i Momcilo Ristic. "A phenomenological analysis of sintering kinetics from the viewpoint of activated volume". Science of Sintering 37, nr 1 (2005): 19–25. http://dx.doi.org/10.2298/sos0501019n.

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The sintering kinetics of real systems has been viewed as a process of transport of activated volume. Activated volume is a parameter that can be used to describe mass transport during the sintering process. It defines the movement of point defects and dislocations during the sintering process. A phenomenological equation has been defined using this parameter, which can be applied to analyze kinetics of the sintering process. It has been applied to analyze the sintering process of several disperse systems. Values obtained for parameters of the equation have also been analyzed.

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Westholm, Daniel E., David R. Salo, Kevin J. Viken, Jon N. Rumbley i Grant W. Anderson. "The Blood-Brain Barrier Thyroxine Transporter Organic Anion-Transporting Polypeptide 1c1 Displays Atypical Transport Kinetics". Endocrinology 150, nr 11 (9.10.2009): 5153–62. http://dx.doi.org/10.1210/en.2009-0769.

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Organic anion-transporting polypeptide (Oatp) 1c1 is a high-affinity T4 transporter expressed in brain barrier cells. Oatp1c1 transports a variety of additional ligands including the conjugated sterol estradiol 17β-glucuronide (E217βG). Intriguingly, published data suggest that E217βG inhibition of Oatp1c1-mediated T4 transport exhibits characteristics suggestive of atypical transport kinetics. To determine whether Oatp1c1 exhibits atypical transport kinetics, we first performed detailed T4 and E217βG uptake assays using Oatp1c1 stably transfected HEK293 cells and a wide range of T4 and E217βG concentrations (100 pm to 300 nm and 27 nm to 200 μm, respectively). Eadie-Hofstee plots derived from these detailed T4 and E217βG uptake experiments display a biphasic profile consistent with atypical transport kinetics. These data along with T4 and E217βG cis-inhibition dose-response measurements revealed shared high- and low-affinity Oatp1c1 binding sites for T4 and E217βG. T4 and E217βG recognized these Oatp1c1 binding sites with opposite preferences. In addition, sterols glucuronidated in the 17 or 21 position, exhibited preferential substrate-dependent inhibition of Oatp1c1 transport, inhibiting Oatp1c1-mediated E217βG transport more strongly than T4 transport. Together these data reveal that Oatp1c1-dependent substrate transport is a complex process involving substrate interaction with multiple binding sites and competition for binding with a variety of other substrates. A thorough understanding of atypical Oatp1c1 transport processes and substrate-dependent inhibition will allow better prediction of endo- and xenobiotic interactions with the Oatp transporter.

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Jange, Camila G., Carl R. Wassgren i Kingsly Ambrose. "The Significance of Tablet Internal Structure on Disintegration and Dissolution of Immediate-Release Formulas: A Review". Powders 2, nr 1 (17.02.2023): 99–123. http://dx.doi.org/10.3390/powders2010008.

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The internal microstructure of a tablet, such as pore geometry, formulation properties, and compact strength, impacts the tablet’s disintegration kinetics. Ideally, one could design the microstructure to control dissolution onset and therapeutical performance of immediate-release formulas; however, manufacturing tablets with a desired microstructure can be challenging due to the interplay between formulation and process parameters. Direct quantification of tablet microstructure can provide a framework for optimizing composition and process parameters based on a Quality-by-Design approach. This article reviews the importance of tablet microstructure design and liquid transport kinetics to help optimize the release and dissolution profiles of immediate-release products. Additionally, the formulation and process parameters influencing the tablet microstructure and liquid transport kinetics are discussed.

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Serban, Ecaterina Anca, Ioana Diaconu, Elena Ruse, Georgiana Ileana Badea, Adriana Cuciureanu i Gheorghe Nechifor. "Evaluation of Kinetic Parameters at the Transport of Indole-3-acetic Acid Through Bulk Liquid Membranes". Revista de Chimie 68, nr 5 (15.06.2017): 903–7. http://dx.doi.org/10.37358/rc.17.5.5577.

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Indole-3-acetic acid is a growth phytohormone considered the most important representative of auxin class. This paper presents the assessment of some kinetic parameters in the process of transport of indole-3-acetic acid taking into consideration the kinetic model of consecutive irreversible first order reactions. It was pursued the influence upon the process of parameters such as: feed phase concentration, stripping phase concentration in the presence of two type carriers: tributyl phosphate (TBP) and trioctylphosphine oxide (TOPO). Depending on these transport parameters were calculated kinetics parameters such as: pseudo-first-order apparent membrane entrance and exit rate constants, the maximum flux at the entrance and exit out of the membrane. The highest values of the transport flux is obtained in the presence of carrier trioctylphosphine oxide (TOPO) at the concentration in the feed phase of 10-4 mol/L indole-3-acetic acid and a concentration of 10--2mol/L NaOH in the stripping phase.

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León, Gerardo, Elisa Gómez, Beatriz Miguel, Asunción María Hidalgo, María Gómez, María Dolores Murcia i María Amelia Guzmán. "Feasibility of Adsorption Kinetic Models to Study Carrier-Mediated Transport of Heavy Metal Ions in Emulsion Liquid Membranes". Membranes 12, nr 1 (3.01.2022): 66. http://dx.doi.org/10.3390/membranes12010066.

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Emulsion liquid membranes have been successfully used for the removal of different types of organic and inorganic pollutants by means of carrier-mediated transport mechanisms. However, the models that describe the kinetics and transport of such mechanisms are very complex due to the high number of model parameters. Starting from an analysis of the similarity between the elemental mechanisms of carrier-mediated transport in liquid membranes and of transport in adsorption processes, this paper presents an experimental analysis of the possibility of applying kinetic and mechanistic models developed for adsorption to carrier-mediated transport in emulsion liquid membranes. We study the removal of a target species, in this case, Cu(II), by emulsion liquid membranes containing membrane phase solutions of benzoylacetone (carrier agent), Span 80 (emulsifying agent) and kerosene (diluent), and hydrochloric acid as a stripping agent in the product phase. The experimental results fit the pseudo-second-order adsorption kinetic model, showing good relationships between the experimental and model parameters. Although both Cu(II) diffusion through the feed/membrane interface boundary layer and complex Cu-benzoylacetone diffusion through the membrane phase controls Cu(II) transport, it is the former step that mainly controls the transport process.

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De Prisco, Giuseppe, i Xiaowen Shan. "Mass Transport/Diffusion and Surface Reaction Process with Lattice Boltzmann". Communications in Computational Physics 9, nr 5 (maj 2011): 1362–74. http://dx.doi.org/10.4208/cicp.021009.241210s.

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AbstractMulti-component flow with chemical reactions is a common problem in different industrial applications: the mixing chamber of a reaction injection molding (RIM) machine; the dynamics of diesel soot particles interacting with a porous-ceramic particulate filter; reactive transport in porous media; bio-chemical processes involving enzyme-catalyzed kinetics. In all these cases, mass diffusion/convection and wall or volume chemical interactions among components play an important role. In the present paper we underline the importance of diffusion/convection/reaction mechanisms in bio-chemical processes using the Lattice Boltzmann (LB) technique. The bio-application where we studied diffusion/convection/reaction mechanisms is the quorum-sensing pathway for the bio-synthesis of the AI-2, a molecule that allows the bacteria to launch a coordinated attack on a host immune system (see [9,10] for more details of the bio-application). The overall goal is to create a micro-device to screen potential drugs that inhibit AI-2 bio-synthesis. The Michaelis-Menten saturation kinetic model is implemented at the reactive surface and the results are shown in terms of two dimensionless numbers: Damkohler (Da) and Peclet (Pe) number. For high Pe number a small conversion of reactants into products is obtained at the reactive surface, but the overall flux of products is high; moreover, a fast saturation of the conversion of reactants to products is obtained for high Da numbers. The trade-off for setting the Pe and Da numbers depends on the specific application and the technologies used in the micro-device (e.g., sensitivity of the detector, cost of reactants).

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Berg, S., i C. Nender. "Modeling of Mass Transport and Gas Kinetics of the Reactive Sputtering Process". Le Journal de Physique IV 05, nr C5 (czerwiec 1995): C5–45—C5–54. http://dx.doi.org/10.1051/jphyscol:1995502.

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Journal, Baghdad Science. "Kinetic Model for Solute Diffusion in Liquid Membrane Systems". Baghdad Science Journal 13, nr 2 (5.06.2016): 48–57. http://dx.doi.org/10.21123/bsj.13.2.48-57.

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In this study, a mathematical model for the kinetics of solute transport in liquid membrane systems (LMSs) has been formulated. This model merged the mechanisms of consecutive and reversible processes with a “semi-derived” diffusion expression, resulting in equations that describe solute concentrations in the three sections (donor, acceptor and membrane). These equations have been refined into linear forms, which are satisfying in the special conditions for simplification obtaining the important kinetic constants of the process experimentally.

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Wang, Huannan, Dandan Yan, Huan Zeng i Jiajie He. "Using corncob-based biochar to intercept BTEX in stormwater filtration systems". Water Science and Technology 82, nr 9 (23.09.2020): 1858–67. http://dx.doi.org/10.2166/wst.2020.463.

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Abstract A biochar material made from corncobs was tested for its capability in BTEX adsorption/interception in stormwater filtration systems. Batch experiments were conducted to examine the adsorption kinetics, adsorption isotherms, and adsorption thermodynamics of BTEX onto this biochar. The feasibility of applying this biochar in stormwater filtration was studied by dynamic transport experiments and model simulations. The result showed that this biochar can adsorb BTEX and the adsorption is a thermodynamically spontaneous, and endothermic process. The BTEX adsorption kinetic experiment and adsorption retarded BTEX transport experiment indicated that the BTEX adsorption kinetics can be changed by the driving force between the BTEX concentrations and the active adsorption site as well as the contact time between BTEX and the biochar. In terms of applying this biochar in stormwater filtration, the Monte Carlo uncertainty analysis indicated that the BTEX interception is sensitive to the hydraulic conductivity of the biochar filter and the adsorption kinetics of the biochar material. Although this corncob-made biochar demonstrated effective pollutant adsorption capability, the biochar adsorption capability should be utilized to retain the pollutant long enough for biodegradation to take effect for ultimate pollutant attenuation.

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Basuki, Rahmat, Bambang Rusdiarso, Sri Juari Santosa i Dwi Siswanta. "The Dependency of Kinetic Parameters as a Function of Initial Solute Concentration: New Insight from Adsorption of Dye and Heavy Metals onto Humic-Like Modified Adsorbents". Bulletin of Chemical Reaction Engineering & Catalysis 16, nr 4 (12.08.2021): 773–95. http://dx.doi.org/10.9767/bcrec.16.4.11816.773-795.

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Kinetics parameters are the essential issue in the design of water treatment systems for pollutants uptake. Though numerous studies have identified the boundary conditions that exert influence on the kinetics parameters, the influence of the dynamic initial solute concentration (C0) to the kinetic parameters generated from fitting kinetics model to experimental data has not been investigated thoroughly. This study revealed a change in the kinetics parameter value due to changes in the adsorption mechanism as an effect of dynamic C0. It was observed that at higher C0 the adsorbed solute at equilibrium (qe) increases and it takes longer time to reach equilibrium. As a result, the kinetics rate constant (k) calculated from adsorption reaction model (Lagergren, Ho, Santosa, and RBS) was decreased. In general, Ho model exhibit higher correlation coefficient value (R2) among the other model at low C0. At high C0, Ho’s R2 tend to decrease while the Lagergren and RBS’s R2 was increased. The amendment mechanism from external mass transport to intra-particle diffusion as a rate limiting step was evidenced by Boyd and Weber-Morris kinetics model. Further, the physicochemical properties of the adsorbent used in this work: chitin and Fe3O4 modified horse dung humic acid (HDHA-Fe3O4 and HDHA-Ch, respectively) with the solute: Pb(II), Methylene Blue (MB), and Ni(II) was deeply discussed in this paper. The outcomes of this work are of prime significance for effective and optimum design for pollutant uptake by adsorption equipment. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

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Leitner, Jindřich, Petr Voňka, Josef Stejskal, Přemysl Klíma i Rudolf Hladina. "Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method". Collection of Czechoslovak Chemical Communications 56, nr 10 (1991): 2020–29. http://dx.doi.org/10.1135/cccc19912020.

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The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

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Chafer, M., S. Perez i A. Chiralt. "Kinetics of Solute Gain and Water Loss During Osmotic Dehydration of Orange Slices". Food Science and Technology International 9, nr 6 (grudzień 2003): 389–96. http://dx.doi.org/10.1177/1082013203040545.

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The effect of the osmotic solution (sucrose and dextrose syrups) on the kinetics and process yield was evaluated on osmotic dehydration of orange (Valencia Late var.). Processes were carried out at 30 C, using 35, 45, 55 and 65 Brix solutions and by applying a vacuum pulse (100 mbar for 10 min) at the beginning of the process. Kinetics of sugar gain-water loss and mass changes were analysed by separately considering peel and pulp fractions of orange slices. Mass transport properties of orange slices in osmotic treatments were different for pulp and peel fractions due to the different contributions of the mechanisms involved. Faster water and solute transport were observed in the peel impregnated with the osmotic solution. Sugar gain in sucrose solutions was enhanced in comparison with dextrose treatments, whereas diffusional water loss was faster in samples treated with dextrose. These effects made the process yield higher for sucrose treatments. An increase in the osmotic solution concentration implied higher mass transport rates, but did not notably affect process yield.

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Ono, Uchikoshi, Hayashi, Kitagawa, Yeh, Yamaguchi i Tanabe. "A Heterothermic Kinetic Model of Hydrogen Absorption in Metals with Subsurface Transport". Metals 9, nr 10 (22.10.2019): 1131. http://dx.doi.org/10.3390/met9101131.

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A versatile numerical model for hydrogen absorption into metals was developed. Our model addresses the kinetics of surface adsorption, subsurface transport (which plays an important role for metals with active surfaces), and bulk diffusion processes. This model can allow researchers to perform simulations for various conditions, such as different material species, dimensions, structures, and operating conditions. Furthermore, our calculation scheme reflects the relationship between the temperature changes in metals caused by the heat of adsorption and absorption and the temperature-dependent kinetic parameters for simulation precision purposes. We demonstrated the numerical fitting of the experimental data for various Pd temperatures and sizes, with a single set of kinetic parameters, to determine the unknown kinetic constants. Using the developed model and determined kinetic constants, the transitions of the rate-determining steps on the conditions of metal-hydrogen systems are systematically analyzed. Conventionally, the temperature change of metals during hydrogen adsorption and absorption has not been a favorable phenomenon because it can cause errors when numerically estimating the hydrogen absorption rates. However, by our calculation scheme, the experimental data obtained under temperature changing conditions can be positively used for parameter fitting to efficiently and accurately determine the kinetic constants of the absorption process, even from a small number of experimental runs. In addition, we defined an effectiveness factor as the ratio between the actual absorption rate and the virtually calculated non-bulk-diffusion-controlled rate, to evaluate the quantitative influence of each individual transport process on the overall absorption process. Our model and calculation scheme may be a useful tool for designing high-performance hydrogen storage systems.

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Zarifi, Mojdeh, Bjørn Kvamme i Tatiana Kuznetsova. "Modeling Heat Transport in Systems of Hydrate-Filled Sediments Using Residual Thermodynamics and Classical Nucleation Theory". Applied Sciences 11, nr 9 (30.04.2021): 4124. http://dx.doi.org/10.3390/app11094124.

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As in any other phase transition, hydrate phase transition kinetics involves an implicit coupling of phase transition thermodynamic control and the associated dynamics of mass and heat transport. This work provides a brief overview of certain selected hydrate film growth models with an emphasis on analyzing the hydrate phase transition dynamics. Our analysis is based on the fundamental properties of hydrate and hydrate/liquid water interfaces derived from molecular modeling. We demonstrate that hydrate phase transitions involving water-dominated phases are characterized by heat transport several orders of magnitude faster than mass transport, strongly suggesting that any hydrate phase transition kinetic models based on heat transport will be entirely incorrect as far as thermodynamics is concerned. We therefore propose that theoretical studies focusing on hydrate nucleation and growth should be based on concepts that incorporate all the relevant transport properties. We also illustrate this point using the example of a fairly simplistic kinetic model, that of classical nucleation theory (CNT), modified to incorporate new models for mass transport across water/hydrate interfaces. A novel and consistent model suitable for the calculation of enthalpies is also discussed and appropriate calculations for pure components and relevant mixtures of carbon dioxide, methane, and nitrogen are demonstrated. This residual thermodynamic model for hydrate is consistent with the free energy model for hydrate and ensures that our revised CNT model is thermodynamically harmonious.

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CHIEN, L. H., A. SERGEEV, N. VAGIDOV i V. MITIN. "HOT-ELECTRON TRANSPORT IN QUANTUM-DOT PHOTODETECTORS". International Journal of High Speed Electronics and Systems 18, nr 04 (grudzień 2008): 1013–22. http://dx.doi.org/10.1142/s0129156408005965.

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Employing Monte-Carlo simulations we investigate effects of an electric field on electron kinetics and transport in quantum-dot structures with potential barriers created around dots via intentional or unintentional doping. Results of our simulations demonstrate that the photoelectron capture is substantially enhanced in strong electric fields and this process has an exponential character. Detailed analysis shows that effects of the electric field on electron capture in the structures with barriers are not sensitive to the redistribution of electrons between valleys and these effects are not related to an increase of drift velocity. Most data find adequate explanation in the model of hot-electron transport in the potential relief of quantum dots. Electron kinetics controllable by potential barriers and an electric field may provide significant improvements in the photoconductive gain, detectivity, and responsivity of photodetectors.

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Cvetkovic, Vladimir, i Gedeon Dagan. "Transport of kinetically sorbing solute by steady random velocity in heterogeneous porous formations". Journal of Fluid Mechanics 265 (25.04.1994): 189–215. http://dx.doi.org/10.1017/s0022112094000807.

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A Lagrangian framework is used for analysing reactive solute transport by a steady random velocity field, which is associated with flow through a heterogeneous porous formation. The reaction considered is kinetically controlled sorption–desorption. Transport is quantified by the expected values of spatial and temporal moments that are derived as functions of the non-reactive moments and a distribution function which characterizes sorption kinetics. Thus the results of this study generalize the previously obtained results for transport of non-reactive solutes in heterogeneous formations (Dagan 1984; Dagan et al. 1992). The results are illustrated for first-order linear sorption reactions. The general effect of sorption is to retard the solute movement. For short time, the transport process coincides with a non-reactive case, whereas for large time sorption is in equilibrium and solute is simply retarded by a factor R = 1+Kd, where Kd is the partitioning coefficient. Within these limits, the interaction between the heterogeniety and kinetics yields characteristic nonlinearities in the first three spatial moments. Asymmetry in the spatial solute distribution is a typical kinetic effect. Critical parameters that control sorptive transport asymptotically are the ratio εr between a typical reaction length and the longitudinal effective (non-reactive) dispersivity, and Kd. The asymptotic effective dispersivity for equilibrium conditions is derived as a function of parameters εr and Kd. A qualitative agreement with field data is illustrated for the zero- and first-order spatial moments.

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Gherman, Timea, Violeta Popescu, Rahela Carpa, Georgiana Luminita Gavril, Maria Rapa i Elena Emilia Oprescu. "Salvia Officinalis Essential Oil Loaded Gelatin Hydrogel as Potential Antibacterial Wound Dressing Materials". Revista de Chimie 69, nr 2 (15.03.2018): 410–14. http://dx.doi.org/10.37358/rc.18.2.6118.

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Salvia officinalis essential oil loaded gelatin hydrogels with improved antibacterial activity and enhanced stability was prepared by microwave-assisted polymerization method. FT-IR spectra indicated no chemical interaction between the hydrogel matrix and the essential oil functional groups. According to the swelling studies, enhanced stability in all pH media was obtained. Studying two kinetic models: Fickian transport and Schott second order kinetic model, it was demonstrated that the swelling process of the prepared hydrogels occurs after a second order kinetics. Antibacterial activity, investigated by the agar diffusion method, regarding S. aureus and E. coli is comparable to that of silver nanoparticles and twice more efficient compared to cinnamon essential oil.

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Seval, Kadir, Canan Onac, Ahmet Kaya i Abdullah Akdogan. "Separation of Boron from Geothermal Waters with Membrane System". Membranes 11, nr 4 (16.04.2021): 291. http://dx.doi.org/10.3390/membranes11040291.

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This study presents the separation and recovery of boron from geothermal waters with a polymeric membrane system and suggests a transport mechanism. The optimum relative parameters of the transport were examined. The recovery value of boron was 60.46% by using polymeric membrane system from prepared aquatic solution to the acceptor phase. The membrane’s capacity and selectivity of the transport process were examined. Kinetics values were calculated for each transport parameter. The optimum kinetic values were 1.4785 × 10−6 (s−1), 7.3273 × 10−8 (m/s), 13.5691 × 10−8 (mol/m2.s), 5.8174 × 10−12 (m2/s) for constant rate, permeability coefficient, flux, and diffusion coefficient, respectively. Boron was transported selectively and successfully from geothermal waters in the presence of other metal cations with 59.85% recovery value. This study indicates the application of real samples in polymeric membrane systems, which are very practical, economic, and easy to use for large-scale applications. The chemical and physical properties of polymer inclusion membranes (PIMs) offer the opportunity to be specially designed for specific applications.

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Sarmento, Sandra M., i José T. G. Miranda. "Kinetics of the atrazine degradation process using H2O2-UVC". Water Science and Technology 69, nr 11 (24.03.2014): 2279–86. http://dx.doi.org/10.2166/wst.2014.158.

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This work is concerned with the intrinsic reaction kinetic of the degradation of atrazine (ATZ) using H2O2-UVC. Experimental runs were carried out in annular photoreactor. The initial concentration of ATZ was 2.2 × 10−2 mol m−3 while the H2O2-ATZ molar ratio range was 0–578 mol H2O2 mol−1 ATZ. The ATZ molecules are decomposed by means of free-radical attack (95.2%) and direct photolysis (4.8%). There is an optimal H2O2/ATZ molar ratio (ROP = 347 H2O2 mol−1 ATZ) which maximizes the initial degradation rate and conversion at 300 s at 83% and 77%, respectively. The process is economically feasible as the values of the energy requirement, energy and H2O2 costs at ROP are 0.14 KWh m−3 order−1, US$0.02 kWh−1 m−3 and US$1.0 m−3, respectively. The kinetic model proposed is based on Lea's reaction scheme for the H2O2 direct photolysis, the hypothesis that unknown ATZ sub-products that absorb UVC radiation are generated, and the local volumetric rate of photon absorption. The radiation transport equation was solved and the linear spherical source emission model was used to represent the lamp emission. Intrinsic reaction kinetic parameters were estimated and the model was validated. The model predicted the data in a range of 90 to 98%.

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Biedlingmaier, Susanne, i Ahlert Schmidt. "Sulfate Transport in Normal and S-Deprived Chlorella fusca". Zeitschrift für Naturforschung C 44, nr 5-6 (1.06.1989): 495–503. http://dx.doi.org/10.1515/znc-1989-5-625.

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Abstract Sulfate uptake into the unicellular green alga Chlorella fusca Shihira et Krauss strain 211-8 b was described as a pH-, temperature-and energy-dependent process. Transport followed triphasic kinetics with Km-values of 1.3 x 10-5, 3.9 x 10-5 and 2.8 x 10-4M. The Hill plot showed coefficients of 1.0 for each uptake isotherm. Sulfate uptake was substantially inhibited by chromate, selenate, sulfite, thiosulfate and tetrathionate. Cysteine and other mercaptides diminished sulfate transport, whereas methionine was not inhibitory. Uptake was sensitive towards inhibitors of photosynthesis and respiration and towards SH-group reagents. Sulfate uptake could be strongly enhanced by polyvalent cations, apparently via reduction of the surface potential. Sulfate uptake in S-deprived algae was markedly different from constitutive sulfate uptake. Time kinetics was not linear but showed an initial rapid phase. Uptake was neither multiphasic nor conformed to simple Michaelis-Menten kinetics. Sulfate uptake was hardly affected by pH and temperature in the suboptimal range. The Arrhenius plot was biphasic with a discontinuity at 38 °C.

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Fijał-Kirejczyk, Izabela M., Massimo Rogante, Jacek J. Milczarek, Joanna Żołądek-Nowak, Zdzisław Jurkowski, Jan Żołądek i Dariusz Rusinek. "Studies on water transport in quasi two-dimensional porous systems using neutron radiography". Nukleonika 67, nr 1 (5.12.2021): 3–9. http://dx.doi.org/10.2478/nuka-2021-0034.

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Abstract The spontaneous wetting and drying of flat porous samples of linen, cotton and synthetic textiles were studied using dynamic neutron radiography (DNR). The progress of the wetting process of the media was delineated from the obtained neutron dynamical radiography images. The results of the investigation reveal a non-classical behaviour of kinetics of wicking of these materials. The character of the wetting kinetics is discussed in terms of the fractal character of the tortuosity of fabric capillaries.

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Shevtsova, O. N., i V. K. Shevtsova. "Mathematical Simulation of Transport Kinetics of Tumor-Imaging Radiopharmaceutical99mTc-MIBI". Computational and Mathematical Methods in Medicine 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/2414878.

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The proposed model describes in a quality way the process of tumor-imaging radiopharmaceuticalTc99m-MIBI distribution with taking into account radiopharmaceutical accumulation, elimination, and radioactive decay. The dependencies of concentration versus the time are analyzed. The model can be easily tested by the concentration data of the radioactive pharmaceuticals in the blood measured at early time point and late time point of the scanning, and the obtained data can be used for determination of the washout rate coefficient which is one of the existing oncology diagnostics methods.

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Hernández-Hernández, M., W. F. Cruz-Mendez, C. Gonzalez-Rivera i M. A. Ramírez-Argáez. "Mathematical modeling of aluminum degassing by the impeller injector technique validated by a physical modeling". MRS Proceedings 1611 (2014): 49–54. http://dx.doi.org/10.1557/opl.2014.757.

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ABSTRACTA mathematical model is developed to describe deoxidation of water in a physical model of a batch aluminum degassing reactor equipped with the rotor-injector technique, assuming that deoxidation kinetics of water is similar to dehydrogenization of liquid aluminum. Degassing kinetics is described by using mass transport and mass balance principles by assuming that degassing kinetics can be characterized by a mass transfer coefficient, which depends on the process variables. The transport coefficient and the average bubble diameter are estimated with correlations reported in the literature for similar gas-injection systems. The water physical model helped to validate the mathematical model and to perform a process analysis by varying: 1) Gas flow rate (20 and 40 l/min); and 2) Impeller’s angular velocity (290 and 573 rpm). Results from the model agree well with measurements of deoxidation kinetics at low impeller rotating speeds. At high rotating speeds the model is still valid but less reliable because it does not take into account the formation of the vortex at the free surface. Nevertheless, the model provides predictions of the influence of every operating parameter and it can be used as a good approximation for real systems.

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Lebedev, Artem, Daria Lovskaya i Natalia Menshutina. "Experimental Investigation and CFD Modeling of Supercritical Adsorption Process". Polymers 12, nr 9 (29.08.2020): 1957. http://dx.doi.org/10.3390/polym12091957.

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The kinetics of the supercritical adsorption process was experimentally studied by the example of ”ibuprofen-silica aerogel” composition obtainment at various parameters: Pressure 120–200 bar and temperature 40–60 °C. Computational Fluid Dynamics (CFD) model of the supercritical adsorption process in a high-pressure apparatus based on the provisions of continuum mechanics is proposed. Using supercritical adsorption process kinetics experimental data, the dependences of the effective diffusion coefficient of active substance in the aerogel, and the maximum amount of the adsorbed active substance into the aerogel on temperature and pressure are revealed. Adequacy of the proposed model is confirmed. The proposed mathematical model allows predicting the behavior of system (fields of velocity, temperature, pressure, composition, density, etc.) at each point of the studied medium. It makes possible to predict mass transport rate of the active substance inside the porous body depending on the geometry of the apparatus, structure of flow, temperature, and pressure.

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Petraitienė, Akvilė. "The Modeling of Nitrogen Mass Transport in CoCr Alloys". Rural Sustainability Research 36, nr 331 (1.12.2016): 19–26. http://dx.doi.org/10.1515/plua-2016-0010.

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Abstract The kinetics of plasma nitriding of CoCr alloy below temperatures of nitrides formation and mechanisms of nitrogen penetration are analyzed by proposed kinetic modeling in this article. Proposed nitrogen diffusion model is based on the trapping – detrapping (TD) model and developed taking into account the effect of the concentration dependent diffusivity of nitrogen, nitrogen adsorption on the surface of alloy and surface swelling process. The model indicates the influence of chromium atoms to nitrogen atoms diffusivity. The model consists of time and depth dependent diffusion, which is described by a partial differential equation, and it is solved by using Crank – Nicolson finite difference method. By fitting of experimental nitrogen depth profiles, it is shown that nitrogen diffusion coefficient varies with nitrogen concentration according to Einstein-Smoluchowski relation. Nitrogen depth profiles in plasma nitrided medical grade CoCr alloy (ISO 5831 – 12) at T = 400 °C for 1, 4 and 20 hours calculated on the basis of this model are in good agreement with experimental nitrogen profiles. Furthermore, the swelling process is showed and analyzed, derived the dependency of swelling rate on nitriding duration – the swelling rate is inversely proportional to the square root of nitriding duration. The obtained diffusion coefficient value and the swelling process rates satisfy the experimental data form Ref. The derived model explains physical processes during plasma nitriding and allows obtaining nitrogen depth profiles for any requisite nitriding duration.

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32

Marcus, Leanne, Julia Plumeri, Gary M. Baker i Jon S. Miller. "A teacher-developed inquiry model to teach the molecular basis of hyperbolic kinetics in biological membrane transport". Advances in Physiology Education 37, nr 2 (czerwiec 2013): 165–75. http://dx.doi.org/10.1152/advan.00010.2013.

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A previously published classroom teaching method for helping students visualize and understand Michaelis-Menten kinetics ( 19 ) was used as an anticipatory set with high school and middle school science teachers in an Illinois Math and Science Partnership Program. As part of the activity, the teachers were asked to collect data by replicating the method and to analyze and report the data. All concluded that the rate data they had collected were hyperbolic. As part of a guided inquiry plan, teachers were then prompted to reexamine the method and evaluate its efficacy as a teaching strategy for developing specific kinetic concepts. After further data collection and analysis, the teachers discovered that their data trends were not, in fact, hyperbolic, which led to several teacher-developed revisions aimed at obtaining a true hyperbolic outcome. This article outlines the inquiry process that led to these revisions and illustrates their alignment with several key concepts, such as rapid equilibrium kinetics. Instructional decisions were necessary at several key points, and these are discussed.

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33

Saravanakumar, R., P. Pirabaharan i L. Rajendran. "Transport and kinetics in an electroenzymatic process incurred in PPO-based rotating disk bioelectrodes". Journal of Electroanalytical Chemistry 913 (maj 2022): 116293. http://dx.doi.org/10.1016/j.jelechem.2022.116293.

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Lozano, Gustavo A., Jose M. Bellosta von Colbe, Thomas Klassen i Martin Dornheim. "Transport phenomena versus intrinsic kinetics: Hydrogen sorption limiting sub-process in metal hydride beds". International Journal of Hydrogen Energy 39, nr 33 (listopad 2014): 18952–57. http://dx.doi.org/10.1016/j.ijhydene.2014.09.035.

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Lee, Jai Sung, W. K. You i B. H. Cha. "Hierarchical Structured Nanomaterial Fabricated by Nanopowder Process: Nanopowder Agglomerate Sintering". Materials Science Forum 638-642 (styczeń 2010): 93–97. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.93.

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The key concept of nanopowder agglomerate sintering (NAS) process is based on the optimization of structure design and full density processing of nanopowder into nanostructured micro-components. The kinetics of NAS process is characteristic of being controlled by material transport through hierarchical interface structures of nanopowder agglomerates. Through optimal design of those hierarchical interfaces such as nano grain boundary and agglomerate boundary, thus, full density nanopowder materials can be fabricated by pressureless sintering. In this paper we overview recent studies on the role of hierarchical interfaces for processing of full density nanopowder materials.

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36

Pecha, M. Brennan, Kristiina Iisa, Michael Griffin, Calvin Mukarakate, Richard French, Bruce Adkins, Vivek S. Bharadwaj i in. "Ex situ upgrading of pyrolysis vapors over PtTiO2: extraction of apparent kinetics via hierarchical transport modeling". Reaction Chemistry & Engineering 6, nr 1 (2021): 125–37. http://dx.doi.org/10.1039/d0re00339e.

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37

Dochain, D., S. N. Agathos i P. Vanrolleghem. "Asymptotic observers as a tool for modelling process dynamics". Water Science and Technology 36, nr 5 (1.09.1997): 259–68. http://dx.doi.org/10.2166/wst.1997.0212.

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This paper deals with the dynamical modelling of processes with a special emphasis on wastewater treatment. Dynamical process modelling is usually derived from mass balance considerations and results in models which contain two types of terms representing the hydrodynamics and transport dynamics, and the conversion due to the involved (bio)chemical reactions involved, respectively. The conversion terms are indeed generally speaking the products of two terms: a yield coefficient and a reaction rate (strictly speaking, the kinetics). The latter usually concentrates a predominant part of the model uncertainty. The bioprocess model building exercise is usually global in the sense that it concerns all the terms involved in the model. In addition to the inherent bioprocess modelling difficulties (model complexity, data scarcity), this makes the interpretation of the model identification results difficult if not questionable. In this paper it is suggested how to use asymptotic observers to model and validate reaction schemes independently of the reaction kinetics. The results will be illustrated with two wastewater treatment processes: an activated sludge process and a detoxification reactor.

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38

Persson, R., i R. F. Pettersson. "Formation and intracellular transport of a heterodimeric viral spike protein complex." Journal of Cell Biology 112, nr 2 (15.01.1991): 257–66. http://dx.doi.org/10.1083/jcb.112.2.257.

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We have analyzed the heterodimerization and intracellular transport from the ER to the Golgi complex (GC) of two membrane glycoproteins of a bunyavirus (Uukuniemi virus) that matures by a budding process in the GC. The glycoproteins G1 and G2, which form the viral spikes, are cotranslationally cleaved in the ER from a 110,000-D precursor. Newly synthesized G1 was transported to the GC and incorporated into virus particles about 30-45 min faster than newly synthesized G2. Analysis of the kinetics of intrachain disulfide bond formation showed that G1 acquired its mature form within 10 min, while completion of disulfide bond formation of G2 required a considerably longer time (up to 60 min). During the maturation process, G2 was transiently associated with the IgG heavy chain binding protein for a longer time than G1. Protein disulfide isomerase also coprecipitated with antibodies against G1 and G2. In virus particles, G1 and G2 were present exclusively as heterodimers. Immunoprecipitation with monoclonal antibodies showed that heterodimerization occurred rapidly, probably in the ER, between newly made G1 and mature, dimerization competent G2. Taken together, our results show that these two viral glycoproteins have different maturation kinetics in the ER. We conclude that the apparent different kinetics of ER to GC transport of G1 and G2 is due to the different rates by which these proteins fold and become competent to enter into heterodimeric complexes prior to exit from the ER.

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39

Reshkin, S. J., i G. A. Ahearn. "Intestinal glycyl-L-phenylalanine and L-phenylalanine transport in a euryhaline teleost". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 260, nr 3 (1.03.1991): R563—R569. http://dx.doi.org/10.1152/ajpregu.1991.260.3.r563.

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The transport mechanisms for the dipeptide glycyl-L-phenylalanine (Gly-Phe) and L-phenylalanine (Phe) were characterized in fish intestinal brush-border membrane vesicles (BBMV). Gly-Phe was rapidly hydrolyzed only intravesicularly with almost total hydrolysis occurring even at 10 s. Dipeptide uptake was not stimulated by an inward gradient of Na, K, or H. Phe uptake was stimulated by an inward gradient of either Na or K but displayed an overshoot phenomenon only in the presence of an Na gradient. Kinetic analysis of the effect of substrate concentration on transport rate revealed that transport of both Gly-Phe and Phe occurred by a saturable process conforming to Michaelis-Menten kinetics. The Km for Gly-Phe was 9.8 +/- 3.5 mM, whereas that for Phe in the presence of Na or K, respectively, was 0.74 +/- 0.13 and 1.1 +/- 0.37 mM. Maximum uptake for Gly-Phe and for Phe in the presence of Na and K was 5.1, 0.9, and 0.4 nmol.mg and protein-1.5 s-1, respectively. Gly-Phe and Phe transport displayed different patterns of inhibition by dipeptides and amino acids. These results suggest that Gly-Phe and Phe are transported via different mechanisms, with Gly-Phe being hydrolyzed during a carrier-mediated, cation-independent process and Phe being transferred via a Na+ cotransport process similar to that described in mammals. During conditions of high luminal dipeptide concentrations, the Gly-Phe pathway may make a significant contribution to total Phe uptake.

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40

Shtyka, Olga, Łukasz Przybysz, Mariola Błaszczyk i Jerzy P. Sęk. "Analysis of process of emulsions transport in hydrophilic/oleophilic granular porous media driven by capillary force". Technical Sciences 2, nr 21 (22.03.2018): 85–101. http://dx.doi.org/10.31648/ts.2719.

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The research focuses on the issues concerning a process of multiphase liquids transport in granular porous media driven by the capillary pressure. The current publication is meant to introduce the results of experimental research conducted to evaluate the kinetics of the imbibition and emulsions behavior inside the porous structures. Moreover, the influence of the dispersed phase concentration and granular media structure on the mentioned process was considered. The medium imbibition with emulsifier-stabilized emulsions composed of oil as the dispersed phase in concentrations of 10 vol%, 30 vol%, and 50 vol%, was investigated. The porous media consisted of oleophilic/hydrophilic beads with a fraction of 200–300 and 600–800 μm. The experimental results provided that the emulsions imbibition in such media depended stronger on its structure compare to single-phase liquids. The increase of the dispersed phase concentration caused an insignificant mass decreasing of the imbibed emulsions and height of its penetration in a sorptive medium. The concentrations of the imbibed dispersions exceeded their initial values, but reduced with permeants front raise in the granular structures that can be defined as the influential factor for wicking process kinetics.

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41

Wilson, David J. "Modeling of Ion-Exchange Column Operation. II. Mass Transport Kinetics". Separation Science and Technology 21, nr 10 (grudzień 1986): 991–1008. http://dx.doi.org/10.1080/01496398608058392.

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Muhmood, Luckman, Anna Semykina, Masanori Iwase i Seshadri Seetharaman. "Some Novel Studies of Thermodynamics, Kinetics and Transport Phenomena in Slags". High Temperature Materials and Processes 31, nr 4-5 (30.10.2012): 351–58. http://dx.doi.org/10.1515/htmp-2012-0067.

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AbstractThe following paper revolves around the research work conducted in collaboration during Professor Iwase's brief visits to the Materials Process Science Division at Royal Institute of Technology, Stockholm. The paper focuses on the thermodynamic aspects of CaO–FeO–SiO2 and CaO–FeO–SiO2–MnO slag oxidation in air and sulfur transport through CaO–Al2O3–SiO2 slag. Thermodynamics of slag oxidation in air opens potential new areas in terms of focus on effective recovery of iron oxide from slag. The slag transport studies are of fundamental nature and focuses on a novel technique to calculate the diffusion of species through slag by analyzing its corresponding concentration in the metal phase.

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43

Mashkina, Elena, Alan M. Bond i Alexandr N. Simonov. "Limitations in Electrochemical Determination of Mass-Transport Parameters: Implications for Quantification of Electrode Kinetics Using Data Optimisation Methods". Australian Journal of Chemistry 70, nr 9 (2017): 990. http://dx.doi.org/10.1071/ch17241.

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Voltammetric quantification of the electrode kinetics for the quasi-reversible reaction requires detailed experiment–theory comparisons. Ideally, predicted data derived from the theoretical model are fitted to the experimental data by adjusting the reversible potential (E0), heterogeneous electron transfer rate constant at E0 (k0), and charge transfer coefficient α, with mass-transport and other parameters exactly known. However, parameters relevant to mass transport that include electrode area (A), diffusion coefficient (D), and concentration (c), are usually subject to some uncertainty. Herein, we examine the consequences of having different combinations of errors present in A, D, and c in the estimation of E0, k0, and α on the basis of the a.c. (alternating current) voltammetric experiment–theory comparisons facilitated by the use of a computer-assisted parameter optimisation algorithm. In most cases, experimentally reasonable errors (<10 %) in the mass-transport parameters do not introduce significant errors in recovered E0, k0, and α values. However, a pernicious situation may emerge when a slight overestimation of A, D or c is included in the model and results in erroneous identification of a reversible redox process as a quasi-reversible one with a report of apparently quantifiable kinetic parameters k0 and α.

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44

Medvedev, N., A. E. Volkov, R. Rymzhanov, F. Akhmetov, S. Gorbunov, R. Voronkov i P. Babaev. "Frontiers, challenges, and solutions in modeling of swift heavy ion effects in materials". Journal of Applied Physics 133, nr 10 (14.03.2023): 100701. http://dx.doi.org/10.1063/5.0128774.

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Since a few breakthroughs in the fundamental understanding of the effects of swift heavy ions (SHIs) decelerating in the electronic stopping regime in the matter have been achieved in the last decade, it motivated us to review the state-of-the-art approaches in the modeling of SHI effects. The SHI track kinetics occurs via several well-separated stages and spans many orders of magnitude in time: from attoseconds in ion-impact ionization depositing an extreme amount of energy in a target to femtoseconds of electron transport and hole cascades, to picoseconds of lattice excitation and response, to nanoseconds of atomic relaxation, and even longer times of the final macroscopic reaction. Each stage requires its own approaches for quantitative description. We discuss that understanding the links between the stages makes it possible to describe the entire track kinetics within a hybrid multiscale model without fitting procedures. The review focuses on the underlying physical mechanisms of each process, the dominant effects they produce, and the limitations of the existing approaches, as well as various numerical techniques implementing these models. It provides an overview of the ab initio-based modeling of the evolution of the electronic properties, Monte Carlo simulations of nonequilibrium electronic transport, molecular dynamics modeling of atomic reaction including phase transformations and damage on the surface and in the bulk, kinetic Mote Carlo of atomic defect kinetics, and finite-difference methods of track interaction with chemical solvents describing etching kinetics. We outline the modern methods that couple these approaches into multiscale and combined multidisciplinary models and point to their bottlenecks, strengths, and weaknesses. The analysis is accompanied by examples of important results, improving the understanding of track formation in various materials. Summarizing the most recent advances in the field of the track formation process, the review delivers a comprehensive picture and detailed understanding of the phenomenon. Important future directions of research and model development are also outlined.

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45

Qian, Y., E. Tiffany-Castiglioni i E. D. Harris. "Copper transport and kinetics in cultured C6 rat glioma cells". American Journal of Physiology-Cell Physiology 269, nr 4 (1.10.1995): C892—C898. http://dx.doi.org/10.1152/ajpcell.1995.269.4.c892.

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C6 rat glioma cells accumulate and efflux 67Cu. Both processes showed saturation kinetics with increasing 67Cu concentration. The Michaelis constant (Km) for uptake was 0.63 +/- 0.14 microM; maximum velocity (Vmax) was 3.29 +/- 0.57 pmol Cu.mg protein-1.min-1. The Km for efflux was 0.15 +/- 0.06 microM; Vmax was 1.08 +/- 0.71 pmol Cu.mg protein-1.min-1. p-Chloromercuribenzoate (p-CMB) totally blocked 67Cu efflux but had no effect on Km or Vmax of uptake. Total 67Cu in the cell after 50 min was partitioned equally between particulate and soluble fractions. p-CMB-treated cells accumulated more 67Cu, but < 10% was bound to the particulate (membrane) fraction. Pb also increased 67Cu accumulation without affecting Km and Vmax of 67Cu uptake. These data suggest that carriers for import and export of Cu in C6 cells are distinct or operate in two different cellular environments. Efflux is a sulfhydryl-dependent process subject to inhibition by Pb. The data are consistent with a P-type ATPase in the efflux of Cu from cells and the potential for Pb to inhibit the efflux mechanism.

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46

Shchepakin, Denis, Leonid Kalachev i Michael Kavanaugh. "Modeling of excitatory amino acid transporters and clearance of synaptic cleft on millisecond time scale". Mathematical Modelling of Natural Phenomena 14, nr 4 (2019): 407. http://dx.doi.org/10.1051/mmnp/2019020.

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Excitatory Amino Acid Transporters (EAATs) operate over wide time scales in the brain. They maintain low ambient concentrations of the primary excitatory amino acid neurotransmitter glutamate, but they also seem to play a significant role in clearing glutamate from the synaptic cleft in the millisecond time-scale process of chemical communication that occurs between neurons. The detailed kinetic mechanisms underlying glutamate uptake and clearance remain incompletely understood. In this work we used a combination of methods to model EAAT kinetics and gain insight into the impact of transport on glutamate dynamics in a general sense. We derive reliable estimates of the turnover rates of the three major EAAT subtypes expressed in the mammalian cerebral cortex. Previous studies have provided transporter kinetic estimates that vary over an order of magnitude. The values obtained in this study are consistent with estimates that suggest the unitary transporter rates are approximately 20-fold slower than the time course of glutamate in the synapse. A combined diffusion/transport model provides a possible mechanism for the apparent discrepancy.

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47

Bizi, Mohamed, i Fatima-Ezzahra EL Bachra. "Transport of Carbamazepine, Ciprofloxacin and Sulfamethoxazole in Activated Carbon: Solubility and Relationships between Structure and Diffusional Parameters". Molecules 26, nr 23 (2.12.2021): 7318. http://dx.doi.org/10.3390/molecules26237318.

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The transport of carbamazepine, ciprofloxacin and sulfamethoxazole in the different pores of activated carbon in an aqueous solution is a dynamic process that is entirely dependent on the intrinsic parameters of these molecules and of the adsorbent. The macroscopic processes that take place are analyzed by interfacial diffusion and reaction models. Modeling of the experimental kinetic curves obtained following batch treatment of each solute at 2 µg/L in tap water showed (i) that the transport and sorption rates were controlled by external diffusion and intraparticle diffusion and (ii) that the effective diffusion coefficient for each solute, with the surface and pore diffusion coefficients, were linked by a linear relationship. A statistical analysis of the experimental data established correlations between the diffusional parameters and some geometrical parameters of these three molecules. Given the major discontinuities observed in the adsorption kinetics, the modeling of the experimental data required the use of traditional kinetic models, as well as a new kinetic model composed of the pseudo first or second order model and a sigmoidal expression. The predictions of this model were excellent. The solubility of each molecule below 60 °C was formulated by an empirical expression.

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Gardner, HG, i PL Kaye. "Characterization of glucose transport in preimplantation mouse embryos". Reproduction, Fertility and Development 7, nr 1 (1995): 41. http://dx.doi.org/10.1071/rd9950041.

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Membrane transport of glucose divorced from metabolism, was analysed in 2-cell embryos, morulae and blastocysts in the preimplantation mouse. A non-metabolizable radiolabelled analogue, 3,0 methyl D-glucose (3OMG) was used, and glucose was used as well in morulae and blastocysts; incubation times were < or = 5 min. Uptake occurred by combination of a non-saturable process, resistant to cytochalasin-B, and a facilitated process exhibiting classic Michaelis-Menten kinetics. The rate constant for the non-saturable component increased from 1.22 +/- 0.12 pL embryo-1 min-1 in 2-cell embryos to 2.08 +/- 0.44 pL embryo-1 min-1 in blastocysts, determined using 3OMG. The Km values of the saturable component for 3OMG at 22 degrees C were relatively constant at about 6.5 mM in 2-cell embryos, morulae and blastocysts. At 37 degrees C, the Km increased from 6 mM in 2-cell embryos to 17 mM in blastocysts. Vmax increased about five-fold during development from the 2-cell stage to the morula stage and about three-fold during development to the blastocyst. The Km values for glucose in morulae and blastocysts were constant at about 1.3 mM at 37 degrees C. Uptake of 3OMG in blastocysts was inhibited by glucose and stimulated by incubation in glucose-free medium. There was no kinetic evidence for the participation of multiple saturable components in uptake by blastocysts or morulae. This supports the observation that the glucose transporter GLUT2, which is first expressed at the 8-cell stage to supplement GLUT1 expressed in the oocyte, does not contribute to the uptake of environmental glucose and is, therefore, probably restricted in expression to abcoelic membrane areas of the trophectoderm. Together with the known values of glucose in uterine fluid, the kinetic data indicate that most glucose enters the trophectoderm by this GLUT1 at a rate which directly reflects the external glucose concentrations. The activity increased on a cellular basis as development proceeded, suggesting increased activity to meet the increasing metabolic requirements of the blastocyst for glucose.

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Zhao, Ying, Qiang Xue i Lei Liu. "A Coupling Kinetics Model for Pollutant Release and Transport in the Process of Landfill Settlement". International Journal of Environmental Research and Public Health 9, nr 10 (27.09.2012): 3437–53. http://dx.doi.org/10.3390/ijerph9103437.

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Dandy, David S., i Michael E. Coltrin. "A simplified analytical model of diamond growth in direct current arcjet reactors". Journal of Materials Research 10, nr 8 (sierpień 1995): 1993–2010. http://dx.doi.org/10.1557/jmr.1995.1993.

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A simplified model of a direct current arcjet-assisted diamond chemical vapor deposition reactor is presented. The model is based upon detailed theoretical analysis of the transport and chemical processes occurring during diamond deposition, and is formulated to yield closed-form solutions for diamond growth rate, defect density, and heat flux to the substrate. In a direct current arcjet reactor there is a natural division of the physical system into four characteristic domains: plasma torch, free stream, boundary layer, and surface, leading to the development of simplified thermodynamic, transport, and chemical kinetic models for each of the four regions. The models for these four regions are linked to form a single unified model. For a relatively wide range of reactor operating conditions, this simplified model yields results that are in good quantitative agreement with stagnation flow models containing detailed multicomponent transport and chemical kinetics. However, in contrast to the detailed reactor models, the model presented here executes in near real-time on a computer of modest size, and can therefore be readily incorporated into process control models or global dynamic loop simulations.

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