Carlos E. Ortiz

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The effects of cAMP, ATP and GTP on the Ca2+-dependent K+ channel of fresh (1–2 days) or cold-stored (28–36 days) human red cells were studied using atomic absorption flame photometry of Ca2+-EGTA loaded ghosts which had been resealed to monovalent cations in dextran solutions. When high-K+ ghosts were incubated in an isotonic Na+ medium, the rate constant(More)
We present a second order logic of proportional quantifiers, SOLP, which is essentially a first order language extended with quantifiers that act upon second order variables of a given arity r, and count the fraction of elements in a subset of r–tuples of a model that satisfy a formula. Our logic is capable of expressing proportional versions of different(More)
We formulate a formal syntax of approximate formulas for the logic with counting quantifiers, SOLP, studied by us in [1], where we showed the following facts: (i) In the presence of a built–in (linear) order, SOLP can describe NP–complete problems and fragments of it capture classes like P andNL; (ii) weakening the ordering relation to an almost order (in(More)
A systematic study was made of the action of 4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonic acid (SITS) and 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS) on active Ca2+ transport of human erythrocytes. Pumping activity was estimated in inside-out vesicles (IOV's) by means of Ca2+-selective electrodes or use of tracer45Ca2+. The stilbenes(More)
We present a second order logic of proportional quantifiers, SOLP, which is essentially a first order language extended with quantifiers that act upon second order variables of a given arity r, and count the fraction of elements in a subset of r–tuples of a model that satisfy a formula. Our logic is capable of expressing proportional versions of different(More)
The first order logic Ring(0,+, ∗, <) for finite residue class rings with order is presented, and extensions of this logic with generalized quantifiers are given. It is shown that this logic and its extensions capture DLOGTIME-uniform circuit complexity classes ranging from AC to TC. Separability results are obtained for the hierarchy of these logics when(More)
This paper presents a syntax of approximate formulae suited for the logic with counting quantifiers SOLP. This logic was formalised by us in [1] where, among other properties, we showed the following facts: (i) In the presence of a built–in (linear) order, SOLP can describe NP–complete problems and some of its fragments capture the classes P and NL; (ii)(More)