Anomalous interactions in confined charge-stabilized colloid

Charge-stabilized colloidal spheres dispersed in weak 1:1 electrolytes are supposed to repel each other. Consequently, experimental evidence for anomalous long-ranged like-charged attractions induced by geometric confinement inspired a burst of activity. This has largely subsided because of nagging doubts regarding the experiments' reliability and interpretation. We describe a new class of thermodynamically self-consistent colloidal interaction measurements that confirm the appearance of pairwise attractions among colloidal spheres confined by one or two bounding walls. In addition to supporting previous claims for this as-yet unexplained effect, these measurements also cast new light on its mechanism.Comment: 8 pages, 5 figures, RevTeX4. Conference proceedings for CODEF-04, Colloidal Dispersions in External Fields, March 29 - April 1, 200

Período apropriado para a substituição de copa do cajueiro anão precoce ou para a enxertia direta no campo.

O estudo tem o objetivo de apresentar uma alternativa para formacão de pomares de cajueiro anão precoce, em razão da grande dificuldade de disponibilidade de mudas enxertadas a época própria para plantio.bitstream/CNPAT-2010/11938/1/Pa-044.pd

Like-charge attraction through hydrodynamic interaction

We demonstrate that the attractive interaction measured between like-charged colloidal spheres near a wall can be accounted for by a nonequilibrium hydrodynamic effect. We present both analytical results and Brownian dynamics simulations which quantitatively capture the one-wall experiments of Larsen and Grier (Nature 385, p. 230, 1997).Comment: 10 pages, 4 figure

Avaliação da semeadura direta, do plantio de porta-enxertos e de mudas do cajueiro anão precoce para enxertia no campo ou substituição de copa.

Entre as dificuldades do estabelecimento de pomares de cajueiro anao precoce, desejaveis em epocas proprias para o plantio, o transporte e o consequente alto custo que acarreta, uma vez que nem sempre os produtores dispoem de infra estrutura suficientemente adequada para a sua producao.bitstream/CNPAT-2010/5374/1/Ct-029.pd

Comment on "Long-range electrostatic interactions between like-charged colloids: Steric and confinement effects"

In a recent study [Phys. Rev. E 60, 6530 (1999)], Trizac and Raimbault showed that the effective pair interaction between like charged colloids immersed in a cylindrically confined electrolyte remains repulsive even when the size of the micro-ions or the finite longitudinal extension of the confining cylinder are taken into account. Contrary to their claim, we argue that the case of finite longitudinal confinement doesn't always generate repulsive interactions and to illustrate this point we also provide a simple example.Comment: 3 pages, 1 figure. Accepted for publication in Phys. Rev. E 200

Structure of Polyelectrolytes in Poor Solvent

We present simulations on charged polymers in poor solvent. First we investigate in detail the dilute concentration range with and without imposed extension constraints. The resulting necklace polymer conformations are analyzed in detail. We find strong fluctuations in the number of pearls and their sizes leading only to small signatures in the form factor and the force-extension relation. The scaling of the peak in the structure factor with the monomer density shows a pertinent different behavior from good solvent chains.Comment: 7 pages, 5 figures. submitted to EP

On the nature of long-range contributions to pair interactions between charged colloids in two dimensions

We perform a detailed analysis of solutions of the inverse problem applied to experimentally measured two-dimensional radial distribution functions for highly charged latex dispersions. The experiments are carried out at high colloidal densities and under low-salt conditions. At the highest studied densities, the extracted effective pair potentials contain long-range attractive part. At the same time, we find that for the best distribution functions available the range of stability of the solutions is limited by the nearest neighbour distance between the colloidal particles. Moreover, the measured pair distribution functions can be explained by purely repulsive pair potentials contained in the stable part of the solution.Comment: 6 pages, 5 figure

Medios de comunicación y derecho a la información en Jalisco 2013

En el primer apartado, dedicado al sistema de medios en general, se presentan tres artículos: “Nuevos medios de comunicación en Jalisco”, “c7 ¿medio público o vocero del gobierno?” y “Réquiem por un ombudsman”. El segundo apartado está dedicado al tema de la libertad de expresión; se presentan aquí dos textos: “La vulnerabilidad en un ambiente de cambio. Los ataques a los medios de comunicación en Jalisco durante el año” y “Violaciones a la libertad de expresión de periodistas y trabajadores de medios en Jalisco, 1995-2013”. En el apartado “Derecho a la información, comunicación y política” se ofrecen cuatro textos de índole muy diversa: “La estrategia de comunicación del Gobierno del Estado”, “Diálogos públicos: la discusión de una nueva ley de transparencia para Jalisco”, “Cuando un niño desaparece, el peor enemigo es el tiempo…”, sobre la alerta Amber, y “2013: un año marcado por despidos en diversos periódicos de Guadalajara”. En la sección “Los que se fueron” se presenta la semblanza de Felipe Vicencio. Y en el apartado de “La investigación del observatorio de medios” se comparten los resultados de un trabajo sobre los columnistas de opinión jaliscienses que escriben en la prensa local.ITESO, A.C