Flux across the membrane

Examination of equation 12 shows that water separation rate increases with the Water Permeabihty Constant Unfortunately, the salt flux across the membrane also does, resulting in a more salty product. An approximation for this salt flow is... 

Ca may activate phospholipase A2 and cause production of lyso-lipids and fatty acids. In addition, ionic fluxes across the membrane occur, leading to pH changes and membrane depolarization. It is not clear how these other responses are initiated, but there may be direct G-protein links to effector systems such as phospholipase A2 or ionic channels. 

The basic flux across the membranes may be related to that across a thin film [83]. Pick s First Law of Diffusion indicates that the total flux of diffusant across a homogeneous membrane, /, is proportional to the concentration gradient of the diffusant ... 

Assuming that the exiting hydrogen atoms are oxidized sufficiently fast, the concentration of absorbed hydrogen direcdy beneath the exit surface may be taken as zero. Using Faraday s law, the steady-state hydrogen flux across the membrane is described by the steady-state hydrogen permeation current ... 

These K" " measurements have monitored net K" " flux across the membrane. The above data can be more easily interpreted if... 

The CPC present in the aqueous phase is distributed between the aqueous and organic phases at the SLM-liquid interface. By maintaining low Cl ion concentration in the feed phase and high Cl ion concentration in the stripping phase, the distribution ratio of CPC (P ion form) at the aqueous feed-SLM interface can be made much higher than that at the aqueous strip-SLM interface. Under this condition, the steady-sate overall CPC flux across the membrane can be obtained from Pick s distribution law applied to aqueous diffusion film as well as the membrane itself and from interfacial reaction kinetics which describe the interfacial flux. 

The question hits the big unknown in explaining the cation permselectivity of the neutral carrier systems mentioned in my report. In the solvent polymeric membranes we studied, the contribution of anions to the electrical current (anion transport number) is usually negligible if hydrophilic anions (e.g., Cl ) are involved. In the presence of lipophilic anions (e.g., SCN ) there exists some contribution of anions to the total ion flux across the membrane [see Anal. Chem., 48, 1031 (1976)]. The reasons for such a behavior may be ... 

Membrane transporters are excipients that enhance permeability of a drug across the gastrointestinal (GI) epithelium by increasing the flux across the membrane. As illustrated in Figure 3, the enhancement could occur as a result of receptor-mediated... 

This expression, which reflects the entropy increase resulting from distributing the molecules more randomly between the two solutions, holds for both free and facilitated diffusion. If [Cj] > [C2], AG, 2 is negative and molecules diffuse spontaneously from solution 1 to solution 2. Net flux across the membrane ceases when [Cj] = [C2] and AG, 2 is zero. 

The solvent flux across the membrane / is proportional to the applied force, which is equal to the applied pressure reduced by the osmotic pressure All as (Belter et al., p. 255,1988),... 

The decrease of the solution volume is equal to the membrane area A times the solvent flux across the membrane f. 

This development, of course, says nothing about the metal ion flux across the membrane under non-equilibrium conditions this is described by Fick s law. At steady state, the flux jMRn, in mol/cm2 s, of metal complex MR, across the liquid membrane is given by... 

This finding depends on different factors and, as previously described, was partially solved by enhancing the turbulent flow on the membrane surface. In this way, the deposition of the substrate and the catalyst was limited, avoiding the concentration polarization phenomenon that also affects the water flux across the membrane. This aspect is currently under study and some preliminary results obtained in a study on the Gemfibrozil degradation in the described PMR are reported in Table 15.4. 

Simkiss, K., and Taylor, M.G. (1989) Metal fluxes across the membranes of aquatic organisms. Rev. Aquat. Sci. 1, 173-188. 

The initiation of an electrogenic process causes an adjustment of the passive ionic fluxes across the membrane. In particular, the net charge actively brought in is soon electrically compensated by appropriate passive movements of that ion and other ions into or out of the cell. The actual electrical potential difference across the membrane then results from the diffusion potential caused by these new passive fluxes plus a steady-state contribution from the electrogenic process involving the active transport of various charged species. We can represent the electrical potential difference generated by the active transport of species/, atj, by... 

As the membrane pore dimensions decrease, for example, due to pore blockage, or the mean free path of the molecules increase, the permeating particles tend to collide more with the pore walls than among themselves, then the Knudsen flow regime is established. In this case the expression for the permeation flux across the membrane is given by [83] ... 

In brain research, microdialysis sampling employing a miniaturized dialysis unit (probe) containing a dialysis membrane of a few millimeters length has become popular. The probe is implanted into the tissue or organ of the test animal and is infused with an isotonic solution (typically at 0.5-25 L/min). A steady-state osmotic flux across the membrane removes molecules with a mass below the cutoff of the membrane from the extracellular matrix. Microdialysis yields relatively clean samples of volumes in the range 20-100 jU-L. However, the recovery of neuropeptides can be as low as 0.5-15%, leading to a low neuropeptide concentration in the samples [5,6]. 

Under most common DMFC operation conditions, the oxygen reduction process is under interfacial kinetics control and the methanol oxidation process is determined by the methanol flux across the membrane,. /crossover, (Eqs 59-61). The increase in cathode overpotential is therefore be given by... 

A.23.3 (a) (1) the partial permeability of the membrane to charged species, (2) the uniformity of charge distribution across the membrane, (3) the net equality of charge flux across the membrane, (4) tire applicability of the Donnan equilibrium for each ionic species to which the membrane is permeable enough to permit free distribution across the membrane, and, (5) the absence of an electrogenic pump and its resultant driving force. 

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