Nuclear multifragmentation within the framework of different statistical ensembles

The sensitivity of the Statistical Multifragmentation Model to the underlying statistical assumptions is investigated. We concentrate on its micro-canonical, canonical, and isobaric formulations. As far as average values are concerned, our results reveal that all the ensembles make very similar predictions, as long as the relevant macroscopic variables (such as temperature, excitation energy and breakup volume) are the same in all statistical ensembles. It also turns out that the multiplicity dependence of the breakup volume in the micro-canonical version of the model mimics a system at (approximately) constant pressure, at least in the plateau region of the caloric curve. However, in contrast to average values, our results suggest that the distributions of physical observables are quite sensitive to the statistical assumptions. This finding may help deciding which hypothesis corresponds to the best picture for the freeze-out stageComment: 20 pages, 7 figure

Chaos in one-dimensional lattices under intense laser fields

A model is investigated where a monochromatic, spatially homogeneous laser field interacts with an electron in a one-dimensional periodic lattice. The classical Hamiltonian is presented and the technique of stroboscopic maps is used to study the dynamical behavior of the model. The electron motion is found to be completely regular only for small field amplitudes, developing a larger chaotic region as the amplitude increases. The quantum counterpart of the classical Hamiltonian is derived. Exact numerical diagonalizations show the existence of universal, random-matrix fluctuations in the electronic energy bands dressed by the laser field. A detailed analysis of the classical phase space is compatible with the statistical spectral analysis of the quantum model. The application of this model to describe transport and optical absorption in semiconductor superlattices submitted to intense infrared laser radiation is proposed.Comment: 9 pages, RevTex 3.0, EPSF (6 figures), to appear in Europhys. J.

Modeling electrodialysis and a photochemical process for their integration in saline wastewater treatment.

Oxidation processes can be used to treat industrial wastewater containing non-biodegradable organic compounds. However, the presence of dissolved salts may inhibit or retard the treatment process. In this study, wastewater desalination by electrodialysis (ED) associated with an advanced oxidation process (photo-Fenton) was applied to an aqueous NaCl solution containing phenol. The influence of process variables on the demineralization factor was investigated for ED in pilot scale and a correlation was obtained between the phenol, salt and water fluxes with the driving force. The oxidation process was investigated in a laboratory batch reactor and a model based on artificial neural networks was developed by fitting the experimental data describing the reaction rate as a function of the input variables. With the experimental parameters of both processes, a dynamic model was developed for ED and a continuous model, using a plug flow reactor approach, for the oxidation process. Finally, the hybrid model simulation could validate different scenarios of the integrated system and can be used for process optimization

Geometric combinatorial algebras: cyclohedron and simplex

In this paper we report on results of our investigation into the algebraic structure supported by the combinatorial geometry of the cyclohedron. Our new graded algebra structures lie between two well known Hopf algebras: the Malvenuto-Reutenauer algebra of permutations and the Loday-Ronco algebra of binary trees. Connecting algebra maps arise from a new generalization of the Tonks projection from the permutohedron to the associahedron, which we discover via the viewpoint of the graph associahedra of Carr and Devadoss. At the same time that viewpoint allows exciting geometrical insights into the multiplicative structure of the algebras involved. Extending the Tonks projection also reveals a new graded algebra structure on the simplices. Finally this latter is extended to a new graded Hopf algebra (one-sided) with basis all the faces of the simplices.Comment: 23 figures, new expanded section about Hopf algebra of simplices, with journal correction

Tres nuevas especies del género Geocharis Ehlers, 1883 de Portugal (Coleoptera, Carabidae)

Three endogean carabid species (Coleoptera: Carabidae, Anillini) from Portugal, Geocharis fermini n. sp., Geocharis bivari n. sp. and Geocharis quartaui n. sp. are described. The work provides diagnostic characters of these species, and in particular, the structure of male genitalia. Affinities with closely related species are discussed and ecological data are also included. Faunistic notes on Geocharis olisipensis (Schatzmayr, 1937) and a key for the identification of the species occurring in Portugal north of the Tajo River are also given.Se describen tres nuevas especies de carábidos Anillini endogeos (Coleoptera: Carabidae) de Portugal: Geocharis fermini n. sp., Geocharis bivari n. sp. y Geocharis quartaui n. sp. Se destacan los caracteres que las definen y, en particular, la estructura de la genitalia masculina. Se discute la afinidad con las especies más relacionadas y además se aportan datos ecológicos. También se aportan datos faunísticos sobre Geocharis olisipensis (Schatzmayr, 1937). Por último se incluye una clave de las especies conocidas en Portugal al norte del Río Tajo

Dos nuevas especies del género Typhlocharis Dieck, 1869 de Portugal y notas sobre especies relacionadas (Coleoptera, Carabidae)

The present study describes two endogean carabid species of Typhlocharis Dieck, Typhlocharis rochapitei n. sp. and Typhlocharis crespoi n. sp., belonging to the T. diecki species group and to the T. outereloi species group, respectively. The work provides diagnostic characters and in particular, the structure of male genitalia. Affinities to putative relatives and keys for the identification of the diecki (all species) and outereloi (Portugal) species groups are also given.Se describen dos nuevas especies de carábidos Anillini endogeos (Coleoptera: Carabidae) de Portugal, Typhlocharis rochapitei n. sp. y Typhlocharis crespoi n. sp., pertencientes a los grupos diecki y outereloi, respectivamente. Se destacan los caracteres que las definen y, en particular, la estructura de la genitalia masculina. Se discute la afinidad con las especies más relacionadas y además se aportan datos ecológicos. Por último, se incluyen claves de todas las especies conocidas del grupo diecki y de las especies del grupo outereloi conocidas en Portugal