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A Ilani

Publications and source records attributed to A Ilani.

26 records · Page 2Linked to original sources
PubMed1973

Relation between the dielectric constant of hydrophobic cation exchange membrane and membrane permeability to counterions.

Filters made of cellulose acetate-nitrate when saturated with organic solvents and interposed between aqueous solutions form membranes which behave like cation exchangers. The diffusion coefficients of counterions in such membranes are strongly dependent upon the dielectric constant of the saturating solvent. The results obtained suggest that a linear relationship between the log of the cation's diffusion coefficient (or membrane conductance) and the reciprocal value of the dielectric constant of the saturating solvent exists. There is also a good correlation between the relative membrane permeability to organic cations and the solubility of the cations in the pure solvent phase. These studies indicate that there are two routes for cation movement through the membrane: (a) the bulk hydrophobic phase and (b) continuous narrow aqueous channels.

Cations, Monovalent↗
PubMed1973

Model hydrophobic ion exchange membrane.

Two models of hydrophobic ion exchange membranes were examined theoretically with regard to the characteristics of cellulose acetate-nitrate membranes saturated with hydrophobic solvents. The first model, consisting of fixed negative sites dispersed in a homogeneous medium of low dielectric constant, was shown to be invalid for the experimental membranes. The second model, consisting of fixed negative sites in an aqueous channel surrounded by a medium of low dielectric constant, explains many properties of the cellulose acetate-nitrate hydrophobic membranes and was analyzed in some detail. Organic cations can enter the membranes through the hydrophobic phase as well as through the aqueous channels. The mechanism of counterion movement in such a model is assumed to consist of exchange of vacancies and or double-occupied sites positions. The presence of the medium of low dielectric constant around the aqueous channel increases the "self"-energy of the ions in the channel and the electrostatic interaction between a fixed site and a counterion in the membrane. Both these factors can account for the marked dependence of ion mobility in the aqueous channels on the dielectric constant of the surrounding medium. The model predicts membrane preference for monovalent counterions over divalent ones.

Capillary Action↗
PubMed1968

Frequency-dependent capacitance of hydrophobic membranes containing fixed negative charges.

Filters containing fixed negative charges were saturated with hydrophobic solvent and interposed between aqueous solutions. The capacitance of such membranes was measured in the frequency range of 0.05-30 kc. The capacitance increased with decrease in frequency. The frequency dependence of the capacitance was sensitive to nature of the cation present and to salt concentration in the aqueous solution. It is suggested that variation of membrane resistivity in the space charge region of the membrane is responsible for this phenomenon. Possible effects of the potential and counterion concentration profiles at the membrane-water interface are discussed.

Electrophysiology↗
PubMed1966

Interaction between cations in hydrophobic solvent-saturated filters containing fixed negative charges.

Previous investigations have shown that Millipore filters bearing fixed negatively charged sites saturated with organic solvents behaved like cation exchangers. In this study the mobilities of some cations in bromobenzene-saturated filters were determined at various membrane compositions. Appreciable interaction between counterions in the membrane was demonstrated; e.g., Na(+) was about four times more mobile in a Na(+) membrane than in a K(+) one. The qualitative nature of the interaction could be summarized as follows: the bringing together of rapid and slow counterions in the membrane made the fast ion faster and the slow ion slower. Possible mechanisms for such an interaction are discussed. A quantitative estimation of K and Na mobilities and selectivity factors at various K-Na fractions in the membrane was made. The above parameters were used to compute the potential difference in a K-Na bi-ionic cell. The calculated bi-ionic potential was found to agree reasonably well with the measured value.

Benzene↗
PubMedDate not supplied

Phosphate load as the evolutionary driving force for the development of a high filtration rate based excretory organ: a hypothesis.

It is proposed that the nutritional load of phosphate is the primary factor that led to the development of an excretory organ that is based on a high filtration rate of the extracellular fluid. This hypothesis is based on the following arguments: 1) phosphate and potassium impose the highest average nutritional load rates defined as the ratio between the average ion content in foods that satisfies the energy demands of the body per unit time and the respective ionic plasma concentration. Due to the much higher intracellular than extracellular potassium concentration it is argued that a secretory based excretory organ would be more useful for disposal of potassium. 2) Magnesium and calcium nutritional load rates are lower than that of phosphate; in addition the disposal of magnesium should have been dealt with preferably by secretion due to its slightly higher intracellular concentration. The nutritional load rate of calcium is tempered by the inherently low absorption capacity of the intestinal mucosa. 3) In aglomerular teleost fishes the phosphate plasma concentration is significantly elevated vis a vis the mammals and other marine fishes, in comparison to only slight differences in calcium, magnesium and potassium levels. It is suggested that the seemingly peculiar and costly way in which sodium excretion is accomplished in the kidney represents the outcome of the solution to the phosphate nutritional load.

Animal Nutritional Physiological Phenomena↗