Connection between type B (or C) and F factorizations and construction of algebras

In a recent paper (Del Sol Mesa A and Quesne C 2000 J. Phys. A: Math. Gen. 33 4059), we started a systematic study of the connections among different factorization types, suggested by Infeld and Hull, and of their consequences for the construction of algebras. We devised a general procedure for constructing satellite algebras for all the Hamiltonians admitting a type E factorization by using the relationship between type A and E factorizations. Here we complete our analysis by showing that for Hamiltonians admitting a type F factorization, a similar method, starting from either type B or type C ones, leads to other types of algebras. We therefore conclude that the existence of satellite algebras is a characteristic property of type E factorizable Hamiltonians. Our results are illustrated with the detailed discussion of the Coulomb problem.Comment: minor changes, 1 additional reference, final form to be published in JP

Sobre la validez del modelo difusional en la determinación de los parámetros de transporte eléctrico de compuestos semiconductores

In this work we have studied the variable range hopping as a predominant electronic transport mechanism for semiconductor materials used as absorbent layer in photovoltaic devices. Dark conductivity measurements were carried out from 120 to 420 K in Si, Cu3BiS3, SnS, Cu2ZnSnSe4, and CuInGaSe2 thin lms. In the low-temperature range, variational range hopping was established for all samples. Using classical equations from the percolation theory and the difusional model, the density of states near the Fermi level (NF), as well as the hopping parameters (W-activation energy and R hopping range) were calculated. A correlation between both models allowed us to evaluate the validity of the difusional model in semiconductor compounds

Ecología, arquitectura y rehabilitación: necesidad de soluciones integradas

Los edificios son en buena medida responsables de la insostenibilidad del sistema productivo. En España, una importante labor para la disminución del impacto ambiental de la edificación radica en la adaptación del parque edificatorio existente a las nuevas exigencias. Sin embargo, la profesión del arquitecto tiene arraigados unos cánones de la buena Arquitectura que no contemplan el criterio de la sostenibilidad y la rehabilitación con criterios ecológicos, representando una minoría los arquitectos que sí se han embarcado en este compromiso. En este trabajo estudiamos los aspectos ecológicos en la normativa española y europea de edificios, que representa las preocupaciones de la sociedad, así como en los premios de Arquitectura, que representan la mirada del arquitecto. Con ello, buscamos demostrar la divergencia entre dos mundos, frente a la que proponemos la necesidad de soluciones integradas de rehabilitación que ponen en valor los aspectos ecológicos y arquitectónicos de la edificación

Some Advances in the Circuit Modeling of Extraordinary Optical Transmission

The phenomenon of extraordinary optical transmission (EOT) through electrically small holes perforated on opaque metal screens has been a hot topic in the optics community for more than one decade. This experimentally observed frequency-selective enhanced transmission of electromagnetic power through holes, for which classical Bethe\'s theory predicts very poor transmission, later attracted the attention of engineers working on microwave engineering or applied electromagnetics. Extraordinary transmission was first linked to the plasma-like behavior of metals at optical frequencies. However, the primary role played by the periodicity of the distribution of holes was soon made evident, in such a way that extraordinary transmission was disconnected from the particular behavior of metals at optical frequencies. Indeed, the same phenomenon has been observed in the microwave and millimeter wave regime, for instance. Nowadays, the most commonly accepted theory explains EOT in terms of the interaction of the impinging plane wave with the surface plasmon-polariton-Bloch waves (SPP-Bloch) supported by the periodically perforated plate. The authors of this paper have recently proposed an alternative model whose details will be briefly summarized here. A parametric study of the predictions of the model and some new potential extensions will be reported to provide additional insight