Counterion density profiles at charged flexible membranes

Counterion distributions at charged soft membranes are studied using perturbative analytical and simulation methods in both weak coupling (mean-field or Poisson-Boltzmann) and strong coupling limits. The softer the membrane, the more smeared out the counterion density profile becomes and counterions pentrate through the mean-membrane surface location, in agreement with anomalous scattering results. Membrane-charge repulsion leads to a short-scale roughening of the membrane.Comment: 4 pages, 4 figure

The Odonatoptera of the Late Permian Lodève Basin (Insecta)

El descubrimiento de una numerosa y variada fauna de Odonatoptera en el Pérmico Superior rojo de la cuenca de Lodève pone en cuestión la hipótesis de un paleoclima seco a muy seco para este yacimiento. Sugiere la presencia de masas de agua más o menos permanentes, rodeadas por una importante diversidad de medios terrestres. El descubrimiento de grandes a muy grandes ejemplares de Meganeuridae contradice la existencia de una relación directa entre la disminución de la talla de cuerpo y de las alas de los insectos durante el Pérmico Superior, y el decrecimiento de la tasa de oxígeno atmosférico en esta época

One-dimensional metallic behavior of the stripe phase in La2−x_{2-x}Srx_xCuO4_4

Using an exact diagonalization method within the dynamical mean-field theory we study stripe phases in the two-dimensional Hubbard model. We find a crossover at doping $\delta\simeq 0.05$ from diagonal stripes to vertical site-centered stripes with populated domain walls, stable in a broad range of doping, $0.05<\delta<0.17$. The calculated chemical potential shift $\propto -\delta^2$ and the doping dependence of the magnetic incommensurability are in quantitative agreement with the experimental results for doped La$_{2-x}$Sr$_x$CuO$_4$. The electronic structure shows one-dimensional metallic behavior along the domain walls, and explains the suppression of spectral weight along the Brillouin zone diagonal.Comment: 4 pages, 4 figure