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Practical application of SrCo0.8Fe0.2O3-–δ(SCF) perovskite oxide for oxygen separation is hindered by poor stability. Here, we developed new KxSr1–xCo0.8Fe0.2O3–δ membrane material by optimizing K+ doping in A-site of prototypical SCF. The partial substitution of Sr2+ with K+ can lead to the enhanced mechanical strength and intermediate-temperature oxygen permeation stability. It is found that the doping content of K+ should be lower than 20% because the excessive doping of K+ in A-site of SrCo0.8Fe0.2O3–δcan destroy their cubic perovskite structure. While x ≥ 0.2, some diffraction peaks different from cubic perovskite can be evidenced by X-ray diffraction and their oxygen permeation flux also decreases rapidly. Among the fabricated membranes, K0.1Sr0.9Co0.8Fe0.2O3–δexhibits the highest oxygen permeation flux (1.5 cm3 min−1 cm−2 at 950°C) under an air/He gradient. More important is that K0.1Sr0.9Co0.8Fe0.2O3–δ displays a stable oxygen permeation performance during over 120 h permeation operation at 750°C.

Practical application of SrCo0.8Fe0.2O3-–δ(SCF) perovskite oxide for oxygen separation is hindered by poor stability. Here, we developed new KxSr1–xCo0.8Fe0.2O3–δ membrane material by optimizing K+ doping in A-site of prototypical SCF. The partial substitution of Sr2+ with K+ can lead to the enhanced mechanical strength and intermediate-temperature oxygen permeation stability. It is found that the doping content of K+ should be lower than 20% because the excessive doping of K+ in A-site of SrCo0.8Fe0.2O3–δcan destroy their cubic perovskite structure. While x ≥ 0.2, some diffraction peaks different from cubic perovskite can be evidenced by X-ray diffraction and their oxygen permeation flux also decreases rapidly. Among the fabricated membranes, K0.1Sr0.9Co0.8Fe0.2O3–δexhibits the highest oxygen permeation flux (1.5 cm3 min−1 cm−2 at 950°C) under an air/He gradient. More important is that K0.1Sr0.9Co0.8Fe0.2O3–δ displays a stable oxygen permeation performance during over 120 h permeation operation at 750°C. [ABSTRACT FROM AUTHOR]

The ionic components of the pacemaker current are quantitatively analysed in sheep cardiac Purkinje fibres by simultaneous measurements of the intracellular Na activity ( a) and the membrane current under voltage clamp. The pacemaker current is operationally defined as the Cs inhibited membrane current ( I) in Ba containing media at clamp potentials negative to −60 mV. At these potentials solutions containing CsCl (0.2-5 mM) shift the holding membrane current into the outward direction and simultaneously decrease a. The Cs effects on membrane current and a display a similar voltage dependence. A Cs inhibited Na influx contributes to I. The ratio I/(Cs inhibited Na influx in electrical units) is <1 at membrane potentials positive to the potassium equilibrium potential E and >1 at potentials negative to E. The ratio is close to 1 at E suggesting Na ions to be the only carriers of the current at E whereas K ions contribute to I at potentials different from E. The effects of Cs on the Cs inhibited Na influx and I show a very similar dose dependence. The effect is half maximum at ∼0.2 mM CsCl (in 21.6 mM K; clamp potential: −85 mV). An increase of the external K concentration augments I and the Cs inhibited Ca influx. Na and K ions carrying I probably cross the membrane via an identical channel. The permeability of the channel for K is about 10-20 times larger than for Na. The I reversal potential of a fibre bathed in a medium containing 5.4 mM K is estimated to be −50 to −60 mV. [ABSTRACT FROM AUTHOR]

NMR and potentiometric methods revealed at least two types of interactions of Na and K ions with κ-carrageenan, viz., Coulombic interaction with polysaccharide sulfate groups, and a coordination one, leading, in the case of the Na ions, to formation of nonstoichiometric complexes. The absence of any correlation between the coordination binding density of the cations and their promoting effect on gelation process was demonstrated. [ABSTRACT FROM AUTHOR]

Rat C glioma cells were cultured for 4 days in MEM medium supplemented with 10% bovine serum and Na,K-ATPase activity was determined in homogenates of harvested cells. Approximately 50% of enzyme activity was attained at 1.5 mM K and the maximum (2.76±0.13 μmol Pi/h/mg protein) at 5 mM K. The specific activity of Na,K-ATPase was not influenced by freezing the homogenates or cell suspensions before the enzyme assay. Ten minutes' exposure of glioma cells to 10 or 10 M noradrenaline (NA) remained without any effect on NA,K-ATPase activity. Neither did the presence of NA in the incubation medium, during the enzyme assay, influence the enzyme activity. The nonresponsiveness of Na,K-ATPase of C glioma cells to NA is consistent with the assumption that α(+) form of the enzyme may be preferentially sensitive to noradrenaline. Na,K-ATPase was inhibited in a dose-dependent manner by vanadate and 50% inhibition was achieved at 2×10 M concentration. In spite of the fact that Na,K-ATPase of glioma cells was not responsive to NA, the latter could at least partially reverse vanadate-induced inhibition of the enzyme. Although the present results concern transformed glial cells, they suggest the possibility that inhibition of glial Na,K-ATPase may contribute to the previously reported inhibition by vanadate of Na,K-ATPase of the whole brain tissue. [ABSTRACT FROM AUTHOR]

The effect of high NaCl concentrations on accumulation of biomass and change in content of sodium and potassium ions in 17 accessions of nine species of Aegilops L. is studied. Three salt-tolerant accessions ( Ae. tauschii k-677 and 674 and Ae. cylindrica k-676) containing the D genome and having a high K/Na ratio are identified. [ABSTRACT FROM AUTHOR]