K+ to pi-mu+mu+ and doubly-charged Higgs

The rate for the lepton-number-violating decay K+ to pi- mu+mu+ is calculated in a model which incorporates doubly-charged Higgs bosons. We find that for reasonable values of the parameters the decay branching ratio may be as large as 2E-16. Although this is a discouragingly small number, it is of the same order of magnitude as the rate mediated by massive Majorana neutrinos.Comment: 8 pages, RevTex, Figure1 is P

Exact Solution of a Electron System Combining Two Different t-J Models

A new strongly correlated electron model is presented. This is formed by two types of sites: one where double occupancy is forbidden, as in the t-J model, and the other where double occupancy is allowed but vacancy is not allowed, as an inverse t-J model. The Hamiltonian shows nearest and next-to-nearest neighbour interactions and it is solved by means of a modified algebraic nested Bethe Ansatz. The number of sites where vacancy is not allowed, may be treated as a new parameter if the model is looked at as a t-J model with impurities. The ground and excited states are described in the thermodynamic limit.Comment: Some corrections and references added. To be published in J. Phys.

Formation of Flavanol-aldehyde Adducts in Barrel-aged White Wine - Possible Contribution of These Products to Colour

[EN] This paper describes the formation and diversity of new compounds resulting from the polymerisation of furanic and phenolic flavanol-aldehydes with HPLC¿DAD and LC¿ES/MS analysis. Polymerisation, resulting from nucleophilic reactions, formed dimers, trimers, soluble and insoluble polymers. Reactions in hydroalcoholic solution with pure aldehydes (phenolic and furanic) and flavanols (catechin) were studied. The study was repeated with different aldehydes in white wine. This research focused particularly on the colour properties of the released products and their potential impact on the colour of white wine. Some products were purified and isolated; these were mainly catechinfurfuraldehyde, catechin-methyl-5-furfuraldehyde, catechin-hydroxymethyl-furfuraldehyde, catechin-vanillin, and catechin-syringaldehyde dimers. The most powerful coloured products resulted from furanic aldehydes. Over the course of the experiment, the reaction produced dimers, trimers and oligomers. After 50 to 60 days, the colour of the solution was mainly due to soluble polymeric forms. In addition, the role of SO2 , generally used during vinification and ageing, was studied. The influence of SO2 on the kinetics of the reaction was limited.Vivas, N.; Nonier, MFB.; Absalon, C.; Lizama Abad, V.; Jamet, F.; De Gaulejac, NV.; Vitry, C.... (2008). Formation of Flavanol-aldehyde Adducts in Barrel-aged White Wine - Possible Contribution of These Products to Colour. South African journal of enology and viticulture. 29(2):98-108. http://hdl.handle.net/10251/105310S9810829

Formation of Flavanol-aldehyde Adducts in Barrel-aged White Wine – Possible Contribution of These Products to Colour

This paper describes the formation and diversity of new compounds resulting from the polymerisation of furanic andphenolic flavanol-aldehydes with HPLC‑DAD and LC‑ES/MS analysis. Polymerisation, resulting from nucleophilicreactions, formed dimers, trimers, soluble and insoluble polymers. Reactions in hydroalcoholic solution with purealdehydes (phenolic and furanic) and flavanols (catechin) were studied. The study was repeated with differentaldehydes in white wine. This research focused particularly on the colour properties of the released products and theirpotential impact on the colour of white wine. Some products were purified and isolated; these were mainly catechinfurfuraldehyde,catechin-methyl-5-furfuraldehyde, catechin-hydroxymethyl-furfuraldehyde,catechin-vanillin, andcatechin-syringaldehyde dimers. The most powerful coloured products resulted from furanic aldehydes. Over thecourse of the experiment, the reaction produced dimers, trimers and oligomers. After 50 to 60 days, the colour of thesolution was mainly due to soluble polymeric forms. In addition, the role of SO2, generally used during vinificationand ageing, was studied. The influence of SO2 on the kinetics of the reaction was limited

Reaction-diffusion and reaction-subdiffusion equations on arbitrarily evolving domains

Reaction-diffusion equations are widely used as the governing evolution equations for modeling many physical, chemical, and biological processes. Here we derive reaction-diffusion equations to model transport with reactions on a one-dimensional domain that is evolving. The model equations, which have been derived from generalized continuous time random walks, can incorporate complexities such as subdiffusive transport and inhomogeneous domain stretching and shrinking. A method for constructing analytic expressions for short time moments of the position of the particles is developed and moments calculated from this approach are shown to compare favourably with results from random walk simulations and numerical integration of the reaction transport equation. The results show the important role played by the initial condition. In particular, it strongly affects the time dependence of the moments in the short time regime by introducing additional drift and diffusion terms. We also discuss how our reaction transport equation could be applied to study the spreading of a population on an evolving interface.Comment: 38 pages, 10 figure

Algebraic Bethe Ansatz for Integrable Extended Hubbard Models Arising from Supersymmetric Group Solutions

Integrable extended Hubbard models arising from symmetric group solutions are examined in the framework of the graded Quantum Inverse Scattering Method. The Bethe ansatz equations for all these models are derived by using the algebraic Bethe ansatz method.Comment: 15 pages, RevTex, No figures, to be published in J. Phys.

Los ostrácodos como trazadores ambientales en medios contaminados: el río Odiel (SO España)

In this paper, ostracods are used as tracers of the environmental changes observed in the lower estuary of the Odiel River during the last decades. These microorganisms have a differential behaviour according to the sedimentary environment studied (ebb-end channels, distributaries, main channels). In the ebb-end channels draining the salt marsh bodies, the subaerial exposure is the main factor controlling the evolution of the ostracod assemblages. In the deeper distributaries and the main channel, the acid wastes derived from two industrial concentrations cause the disappearance of these microcrustaceans between 1966 and 1985. In the distributaries, a recovery was observed in the present-day sediments, whereas no individuals were collected in the main channel. The ostracod carapace is a good indicator of water pollution. Percentages of SO3, FeO and CuO are higher in the valves belonging to the pre-industrial (before 1966) and industrial periods. These components may be derived from the industrial wastes, with a latter tidal redistribution along the estuary.En este trabajo, los ostrácodos son usados como trazadores de los cambios ambientales detectados en el estuario bajo del río Odiel durante las últimas décadas. Estos microorganismos tienen un comportamiento diferencial dependiendo del medio sedimentario estudiado (canales finalizadores, distribuidores, principales). En los canales finalizadores, la exposición subaérea es el principal factor que controla la evolución de las asociaciones de ostrácodos. En los distributarios más profundos y en el canal principal, los desechos ácidos procedentes de dos concentraciones industriales causaron la desaparición de estos microcrustáceos entre 1966 y 1985. En los distributarios, se ha apreciado una parcial recuperación en los sedimentos actuales, en tanto que los primeros centímetros del canal principal no contenían valvas o caparazones de ostrácodos. El caparazón de los ostrácodos es un buen indicador de la contaminación del agua. Los porcentajes de SO3, FeO y CuO son mayores en las valvas obtenidas en sedimentos depositados durante el período pre-industrial (antes de 1965) e industrial. Estos componentes podrían proceder de los efluentes industriales, con una redistribución mareal posterior a lo largo del estuario

Transmission of light through periodic arrays of square holes: From a metallic wire mesh to an array of tiny holes

J. Bravo-Abad, L. Martín-Moreno, F. J. García-Vidal, Euan Hendry, and J. Gómez Rivas, Physical Review B, Vol. 76, article 241102(R) (2007). "Copyright © 2007 by the American Physical Society."A complete landscape is presented of the electromagnetic coupling between square holes forming a two-dimensional periodic array in a metallic film. By combining both experimental and theoretical results along with a first-principles Fano model, we study the crossover between the physics of metallic wire meshes (when holes occupy most of the unit cell) and the phenomenon of extraordinary optical transmission, which appears when the size of the holes is very small in comparison with the period of the array

Morphologic and bioerosive features from an old marine highstand: the Cabililla archaeological shelter, Benzú, Ceuta

The micro-morphologic and bioerosive features, analyzed in the Benzú shelter (Ceuta), allow us to deduce an erosion marine surface elaborated onto dolomite triassic substrate. The Entobia-Gastrochaenolites Ichnoassociation and Entobia ichnofacies denote high energy coastal or shallow marine environment with low sedimentation rates. Two phases are differentiated in the evolution of these bioerosive structures: the first one defined by great borings of Gastrochaenolites, and the second recorded by bioerosive activity of Entobia and truncation of both, the previous borings and the cliff surface