Monte Carlo simulations of equilibrium selectivity of Na channels with a DEKA locus are performed over a range of radius R and protein dielectric coefficient epsilon(p). Selectivity arises from the balance of electrostatic forces and steric repulsion by excluded volume of ions and side chains of the channel protein in the highly concentrated and charged (approximately 30 M) selectivity filter r...

-The conditions under which an exchanger phase will behave as an ideal mixture are established from thermodynamic principles. It is shown that, if a stoichiometric cation-exchange reaction is reversible, the exchanger phase will exhibit ideal behavior if the Vanselow selectivity coefficient is independent of the exchanger composition. This criterion is applied to some recently published data fo...

The behaviour of a system comprising two competitive autocatalytic processes, A ] B] 2B, and A] C] 2C, rate \ k1a6 b 6 where and represent the concentrations of the various species, is considered. In a well-stirred batch reactor, the rate \ 2 a6 c6 , a6 , b 6 c6 Ðnal equilibrium composition always corresponds to a mixture of the two product species B and C, with their respective equilibrium con...

Results from a numerical study examining micro-macro relations linking local geometry parameters to sound absorption properties are presented. For an hexagonal structure of solid fibers, the porosity , the thermal characteristic length ’, the static viscous permeability k0, the tortuosity , the viscous characteristic length , and the sound absorption coefficient are computed. Numerical solution...

A theory is presented that describes the matched potential method (MPM) for the determination of the potentiometric selectivity coefficients (KA,Bpot) of ion-selective electrodes for two ions with any charge. This MPM theory is based on electrical diffuse layers on both the membrane and the aqueous side of the interface, and is therefore independent of the Nicolsky-Eisenman equation. Instead, t...

We investigate the effects of the relative dielectric coefficient on ionic flows in open ion channels, using mathematical analysis of reasonably general Poisson-Nernst-Planck type models that can include the finite sizes of ions. The value of the relative dielectric coefficient is of course a crucial parameter for ionic behavior in general. Using the powerful theory of singularly perturbed prob...

studies by the us salinity laboratory, using gapon rule, led to the value of 0.01475 (mmol l-1)-0.5for the modified gapon selectivity coefficient (k'g). nevertheless, the results of subsequent research reveled that k'g isn’t constant and could take on a wide range of values depending on soil properties. the aim of this study was to determine the relationship between exchangeable sodiu...

A PVC membrane Cr(III) ion selective electrode has been constructed using 2H-1,4-benzothioazine-2,3(4H)dione dioxime (BTD) as membrane carrier. The influence of membrane composition on the electroderesponse was studied. The electrode exhibits a Nernstian response over a Cr(III) concentration range of 1.0 x10 6 to 1.0>< 10-1 M (r = 0.99) with a slope of 19.5 ± 0.5 mV per decade of concentration,...

A magnesium ion-selective liquid membrane electrode based on a synthetic neutral carrier is presented. The selectivity for Mg2+ over Na+, K+, and H+ is sufficient for assays in the physiological range, but a chemometric correction of approximately 10% is still necessary for the Ca2+ interference. We optimized the membrane composition especially with respect to selectivity and accuracy by perfor...