POTENTIOMETRIC and LASER FLASH PHOTOLYSIS STUDIES OF THE pH DEPENDENCE OF HYDROGEN PEROXIDE PRODUCTION BY THE SEMICARBAZIDE/LUMIFLAVIN/OXYGEN PHOTOSYSTEM

The effect of pH on hydrogen peroxide photoproduction by the semicarbazide/lumiflavin/ oxygen system has been investigated by using the potentiometric and laser flash photolysis techniques. Kinetic analysis of (a) primary and secondary reactions involved in the photoreduction of lumiflavin and (b) lumiflavin reoxidation by oxygen have been carried out at varying pH values, drastic differences being observed in the pH dependence of both types of reactions. The reaction mechanism appears to proceed by semicarbazide-quenching (reductive type) of the light-excited lumiflavin in its triplet state followed, depending on pH, either by reoxidation of the so formed flavosemiquinone by molecular oxygen or by flavosemiquinone disproportionation into oxidized and fully reduced lumiflavin.     

Structure of Lorentzian tori with a killing vector field

All Lorentzian tori with a non-discrete group of isometries are characterized and explicitly obtained. They can lie into three cases: (a) flat, (b) conformally flat but non-flat, and (c) geodesically incomplete. A detailed study of many of their properties (including results on the logical dependence of the three kinds of causal completeness, on geodesic connectedness and on prescribed curvature) is carried out. The incomplete case is specially analyzed, and several known examples and results in the literature are generalized from a unified point of view.

     

Life span of solutions of a weakly coupled parabolic system

We consider the Cauchy problem for the weakly coupled parabolic system ∂ _t w _λ−Δ w _λ = F(w _λ) in R ^N , where λ > 0, w _λ = (u _λ, v _λ), F(w _λ) = (v _λ ^p , u _λ ^q ) for some p, q ≥ 1, pq > 1, and w_l(0) = (lj₁, l^\fracq+1p+1j₂)w_{\lambda}(0) = ({\lambda}{\varphi}_1, {\lambda}^{\frac{q+1}{p+1}}{\varphi}_2), for some nonnegative functions φ₁, φ₂ ?\in C ₀(R ^N ). If (p, q) is sub-critical or either φ₁ or φ₂ has slow decay at ∞, w _λ blows up for all λ > 0. Under these conditions, we study the blowup of w _λ for λ small.     

The obstacle problem for nonlinear elliptic equations with variable growth and L1-data

The aim of this paper is twofold: to prove, for L ¹-data, the existence and uniqueness of an entropy solution to the obstacle problem for nonlinear elliptic equations with variable growth, and to show some convergence and stability properties of the corresponding coincidence set. The latter follow from extending the Lewy-Stampacchia inequalities to the general framework of L ¹.     

On causality and closed geodesics of compact Lorentzian manifolds and static spacetimes

Some results related to the causality of compact Lorentzian manifolds are proven: (1) any compact Lorentzian manifold which admits a timelike conformal vector field is totally vicious, and (2) a compact Lorentzian manifold covered regularly by a globally hyperbolic spacetime admits a timelike closed geodesic, if some natural topological assumptions (fulfilled, for example, if one of the conjugacy classes of deck transformations containing a closed timelike curve is finite) hold. As a consequence, any compact Lorentzian manifold conformal to a static spacetime is geodesically connected by causal geodesics, and admits a timelike closed geodesic.     

Local realistic photon model compatible with Malus' law for experiments testing Bell's inequalities

A local realistic model is proposed that agrees approximately with quantum mechanics in the predictions about experiments testing Bell's inequalities by measuring polarization correlations of photon pairs emitted in atomic cascades. No free parameters exist, except polarizer efficiencies, which may be measured independently using Malu's law.     

The Information Interpretation and the Conceptual Problems of Quantum Mechanics

It has been traditionally considered that Quantum Mechanics has two conceptual kinds of problems, namely, those related with local-realism and the so-called measurement problem. That is, the uniqueness of the result when we make a measurement. With the development of what is called generically Quantum Information Theory, a new form of the Copenhagen interpretation of the formalism has taken shape.⁽¹⁾ In this paper, we will analyse if this information interpretation is able to clarify these old problems. Although this interpretation seems to be the most promising approach we have, we have reached the conclusion that the answer cannot be given in a positive and clear way yet.