Feshbach-type resonances for two-particle scattering in graphene

Two-particle scattering in graphene is a multichannel problem, where the energies of the identical or opposite-helicity channels lie in disjoint energy segments. Due to the absence of Galilean invariance, these segments depend on the total momentum $Q$. The dispersion relations for the two opposite-helicity scattering channels are analogous to those of two one-dimensional tight-binding lattices with opposite dispersion relations, which are known to easily bind states at their edges. When an $s$-wave separable interaction potential is assumed, those bound states reveal themselves as three Feshbach resonances in the identical-helicity channel. In the limit $Q \rightarrow 0$, one of the resonances survives and the opposite-helicity scattering amplitudes vanish.Comment: 8 pages, 2 figure

Una nueva especie del género Yuriria Jordan & Evermann, 1896 (Actinopterygii, Cyprinidae) de la cuenca del río Ameca en la Mesa Central Mexicana

A new cyprinid species is described based on morfometric, meristic and genetic characters. The new species identified, Yuriria amatlana sp. nov., inhabits the high Ameca Basin in the central plateau of Mexico. This Mexican minnow differs from Yuriria alta and Yuriria chapalae in terms of the following characters: (50-52) 53-54 pored lateralline scales; 10 upper transverse-line scales, 5-6 lower transverse-line scales and 8-10 gill rakers. Body coloration is light yellowish-brown. Compared to Yuriria alta and Yuriria chapalae, the new species has a less conspicuous dark grey band running from the start of the dorsal fin to the head. Cytochrome b gene sequences differ from those of Yuriria alta and Yuriria chapalae in terms of 29 fixed nucleotide positions (molecular autopomorphies). Calculated genetic divergences for the cytochrome b gene were: `DHKY = 3.8 (3.2-4.4%) between Yuriria amatlana sp. nov. and Y. alta; `DHKY = 5 (4.8-5.2%) between Y. amatlana sp. nov and Y. chapalae; and `DHKY = 2.6 (2.1-3.3%) between Y. chapalae and Y. alta.Se describe una nueva especie, Yuriria amatlana sp. nov., en base a caracteres morfométricos, merísticos y genéticos. La nueva especie proviene de la parte alta de la cuenca del río Ameca en la Meseta Central de México. Esta especie se diferencia de Yuriria alta y Yuriria chapalae por una combinación de los siguientes caracteres: (50-52) 53-54 escamas en una serie longitudinal, 10 escamas en una serie transversal por encima de la línea lateral y 5-6 escamas por debajo de la línea lateral y 8-10 branquiespinas. El color del cuerpo es amarillo-marrón claro. La nueva especie tiene una banda gris oscura menos marcada en el cuerpo desde el comienzo de la aleta dorsal hacia la cabeza con respecto a Yuriria alta y Yuriria chapalae. La nueva especie se diferencia de Yuriria alta y Yuriria chapalae en 29 posiciones nucleotídicas fijadas (autopomorfias moleculares) para el citocromo b. La divergencia genética entre Yuriria alta y Yuriria amatlana sp. nov. para el citocromo b fue de `DHKY = 3.8 (3.2-4.4%); entre Y. amatlana sp. nov. y Y. chapalae fue `DHKY = 5 (4.8-5.2%) y entre Y. chapalae y Y. alta fue `DHKY = 2.6 (2.1-3.3%)

Theory of capillary-induced interactions beyond the superposition approximation

Within a general theoretical framework we study the effective, deformation-induced interaction between two colloidal particles trapped at a fluid interface in the regime of small deformations. In many studies, this interaction has been computed with the ansatz that the actual interface configuration for the pair is given by the linear superposition of the interface deformations around the single particles. Here we assess the validity of this approach and compute the leading term of the effective interaction for large interparticle separation beyond this so-called superposition approximation. As an application, we consider the experimentally relevant case of interface deformations owing to the electrostatic field emanating from charged colloidal particles. In mechanical isolation, i.e., if the net force acting on the total system consisting of the particles plus the interface vanishes, the superposition approximation is actually invalid. The effective capillary interaction is governed by contributions beyond this approximation and turns out to be attractive. For sufficiently small surface charges on the colloids, such that linearization is strictly valid, and at asymptotically large separations, the effective interaction does not overcome the direct electrostatic repulsion between the colloidal particles.Comment: Minor typos correcte

Documentation of model components EXPAMOD and CAPRI

ISBN no.: 978-90-8585-129-