Membrane transfer kinetics

Bioconcentration of lipophilic organic contaminants may be influenced by physicochemical properties, such as molecular configuration or steric properties that influence biotransformation and membrane transfer kinetics, and biological factors, such as the partitioning between storage lipids and structural lipids 17. 

Brederode ME, Jones MR, Van Grondelle R (1997) Primary electron transfer kinetics in membrane-bound Rhodobacter sphaeroides reaction centers a global and target analysis. 

Rathbone MJ (1991a) Human buccal absorption. I. A method for estimating the transfer kinetics of drugs across the human buccal membrane. Int J Pharm 69 103-108... 

Jonsson, J.A., P. Lovkvist, G. Audunsson, and G. Nilve. 1993. Mass transfer kinetics for analytical enrichment and sample preparation using supported liquid membranes in a flow system with stagnant acceptor liquid. Anal. Chim. Acta 111 9-24. 

Micelles and microemulsions have been explored as membrane mimetic systems since they possess charged microscopic interfaces which act as barriers to the charge recombination process (Fendler et al., 1980 Hurst et al., 1983). Namely, the influence of the location of the sensitizer on photoinduced electron transfer kinetics and on charge separation between photolytic products in reversed micelles has been studied (Pileni etal., 1985). 

In the polarization curve, three parts can be observed kinetic, ohmic, and mass transfer. In the kinetic part, the cell voltage drop is due to the charge-transfer kinetics, i.e., the 02 reduction and H2 oxidation rate at the electrode surface, which is dominated by the kinetic I-rj equation (Equation 1.37). In the ohmic part, the cell voltage drop is mainly due to the internal resistance of the fuel cell, including electrolyte membrane resistance, catalyst layer resistance, and contact resistance. In the mass transfer part, the voltage drop is due to the transfer speed of H2 and 02 to the electrode surface. 

A high electroosmotic flow through the stationary-phase particles may be created when the appropriate conditions are provided. This pore flow has important consequences for the chromatographic efficiency that may be obtained in CEC. From plate height theories on (pressure-driven) techniques such as perfusion and membrane chromatography, it is known that perfusive transport may strongly enhance the stationary-phase mass transfer kinetics [30-34], It is emphasised... 

Van Stokkum, I. H. M., Beekman, L. M. P., Jones, M. R., Van Brederode, M. E., and Van Grondelle, R., 1997, Primary electron transfer kinetics in membrane-bound Rhodobacter sphaeroides reaction centers A global and target analysis. Biochemistry, 36 11360n 11368. 

Despite this last observation, for this type of simulation and modelling research, two main means of evolution remain the first consists in enlarging the library with new and newly coded models for unit operations or apparatuses (such as the unit processes mentioned above multiphase reactors, membrane processes, etc.) the second is specified by the sophistication of the models developed for the apparatus that characterizes the unit operations. With respect to this second means, we can develop a hierarchy dividing into three levels. The first level corresponds to connectionist models of equilibrium (frequently used in the past). The second level involves the models of transport phenomena with heat and mass transfer kinetics given by approximate solutions. And finally, in the third level, the real transport phenomena the flow, heat and mass transport are correctly described. In... 

Park [74] studied the efficiency of the ELM with non-Newtonian hquids in the removal of Zn, Pb, Ni and Cd from a simulated industrial wastewater using the Taylor-vortex column. The author adapted the shrinking core mathematical model of Liu and Liu [86] for quantitative description of the mass-transfer kinetics of the process [74]. The LM was prepared by the dissolution of 5 g dm of polyisobutylene in Soltrol 220 (see above). After complete dissolution of the polymer, the membrane phase... 

The ion transfer kinetics of a particular membrane at a given ion strength depend on several parameters, including the dimension and mobility of the solnte, which define the speed constant. These variables explain the differences in migration observed when different ions are treated with varions membranes (Audinos, 1983). 

The voltammetry for the ion transfer at the interface of two immiscible electrolyte solutions, VITIES, is expected to offer much information available for analyzing the ion transfer at the aqueous/membrane interface [14,15], if the organic solution is regarded as the membrane. Transfer energies of ions at the aqueous/membrane interface and amounts of ions transferred can be evaluated precisely by VITIES. The kinetics of the ion transfer and the interfacial adsorption can also be investigated by this method. The present authors measured the relations between the membrane potential and the membrane current (the... 

Kramer, G.F.H., S.Th. Bouwer, R.W. van Gemert, J.T.P. Derksen, and F.P. Cuperus, En-z)Tnatic PeroxycarboxyUc Acid Formation in a Hollow-Fibre Membrane Reactor Kinetics and Mass Transfer, Catalysis Today 22 537-547 (1994). 

At the macroscopic scale, the full competition of reactant diffusion, electron and proton migration, and charge transfer kinetics unfolds. The water balance further complicates this interplay. Moreover, performance is subject to operation conditions and complex boundary conditions at interfaces to membrane and gas diffusion layer. A vast list of structural characteristics steers this interplay, including thickness, composition, pore size distributions, and wetting properties of pores. 

However, because of its far red shifted emission maximum (approximately 1030 nm) until recently it was not possible to measure its fluorescence kinetics on a picosecond time scale. We have investigated the energy transfer kinetics of whole cells, chromatophore membranes, photoreceptor units (quantasomes) and reaction centers in a dark adapted state and in the presence of different redox agents, using single photon timing fluorescence techniques. 

Mutant M21 lacks LH2 and contains the core antenna LHl, together with the reaction centre. From an energy transfer point of view this mutant could be expected to behave similary to membranes of Rhodospirilium rubrum, which has only one major antenna complex LHl, containing a minor Bchl896 component (1). The energy transfer kinetics shows... 

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