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- Pedro J. Romero, Carlos E. Ortíz, Carmelo Melitto
- The Journal of Membrane Biology
- 1990

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)

- Argimiro Arratia, Carlos E. Ortiz
- LATIN
- 2004

We present a probability logic (essentially a first order language extended with quantifiers that count the fraction of elements in a model that satisfy a first order formula) which, on the one hand, captures uniform circuit classes such as AC and TC over arithmetic models, namely, finite structures with linear order and arithmetic relations, and, on the… (More)

- Argimiro Arratia, Carlos E. Ortiz
- J. Log. Comput.
- 2006

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)

- Argimiro Arratia, Carlos E. Ortiz
- Electronic Colloquium on Computational Complexity
- 2006

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)

- Pedro J. Romero, Carlos E. Ortiz
- The Journal of Membrane Biology
- 1988

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)

- Argimiro Arratia, Carlos E. Ortiz
- LATIN
- 2006

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)

- Argimiro Arratia, Carlos E. Ortiz
- WoLLIC
- 2013

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)

- Carlos E. Ortiz
- 2008

We prove a Model Existence Theorem for a fully infinitary logic LA for metric structures. This result is based on a generalization of the notions of approximate formulas and approximate truth in normed structures introduced by Henson ([7]) and studied in different forms by Anderson ([1]) and Fajardo and Keisler ([2]). This theorem extends Henson’s… (More)

- Argimiro Arratia, Carlos E. Ortiz
- Logic Journal of the IGPL
- 2009

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)