Solución del problema elastohidrodinámico de contacto lineal

Se presenta un nuevo método para resolver en forma simultánea las ecuaciones que gobiernan los problemas elastohidrodinámicos. Este método está basado en la técnica de elementos finitos, el método de Newton y el procedimiento de continuación de primer orden para seguir en forma eficiente el camino de solución a lo largo del parámetro de continuación. El método es aplicado al problema de contacto lineal resuelto originalmente por Dowson y Higginson; la posición desconocida de la frontera de salida de flujoPeer Reviewe

Estudio del desplazamiento de una interfase líquido-gas usando el método de elementos finitos. Caso plano y axisimétrico

En este trabajo se emplea el método de elementos finitos combinado con una adecuada parametrización de la superficie libre para analizar el desplazamiento en estado estacionario de una burbuja en un líquido contenido inicialmente entre dos placas planas paralelas o en un tubo capilar de paredes rectas. Los valores obtenidos para variables, tales como el espesor de la película formada entre la burbuja y la pared del tubo, coinciden muy bien con los resultados experimentales y teóricos de la bibliografía. La técnica permite obtener soluciones en un rango muy amplio del número Capilar que incluye y extiende el rango analizado previamente en la literatura. Los resultados muestran un tipo de recirculación de flujo que no había sido descrito previamente.Peer Reviewe

Estudio del desplazamiento de una interfase líquido-gas usando el método de elementos finitos. Caso plano y axisimétrico

En este trabajo se emplea el método de elementos finitos combinado con una adecuada parametrización de la superficie libre para analizar el desplazamiento en estado estacionario de una burbuja en un líquido contenido inicialmente entre dos placas planas paralelas o en un tubo capilar de paredes rectas. Los valores obtenidos para variables, tales como el espesor de la película formada entre la burbuja y la pared del tubo, coinciden muy bien con los resultados experimentales y teóricos de la bibliografía. La técnica permite obtener soluciones en un rango muy amplio del número Capilar que incluye y extiende el rango analizado previamente en la literatura. Los resultados muestran un tipo de recirculación de flujo que no había sido descrito previamente.Peer Reviewe

Photoexcitation of the P4480 state induces a secondary photocycle that potentially desensitizes channelrhodopsin-2

Channelrhodopsins (ChRs) are light-gated cation channels. In spite of their wide use to activate neurons with light, the photocurrents of ChRs rapidly decay in intensity under both continuous illumination and fast trains of light pulses, broadly referred to as desensitization. This undesirable phenomenon has been explained by two interconnected photocycles, each of them containing a nonconductive dark state (D1 and D2) and a conductive state (O1 and O2). While the D1 and O1 states correspond to the dark-state and P3520 intermediate of the primary all-trans photocycle of ChR2, the molecular identity of D2 and O2 remains unclear. We show that P4480, the last intermediate of the all-trans photocycle, is photoactive. Its photocycle, characterized by time-resolved UV/vis spectroscopy, contains a red-shifted intermediate, I3530. Our results indicate that the D2 and O2 states correspond to the P4480 and I3530 intermediates, connecting desensitization of ChR2 with the photochemical properties of the P4480 intermediate

Online financial and demographic education for workers: experimental evidence from an Italian pension fund

This study experimentally tests a low-cost, Internet-based, online literacy intervention program implemented with the largest employer-based pension fund in Italy. This program, called Financial Education and Planning for a Long Life included: 1) an online instructional video on financial, and demographic, (survival) literacy; 2) an experimental design to evaluate the impact of the online videoprogram on financial and demographic literacy, as well as and on short-term behavioral changes in behavior; and 3) a follow-up to assess the impact of the intervention program on subsequent choices of available investment lines in the Italian pension fund. Finlife was designed as a low-cost and, scalable approach aimed at increasing financial and demographic survival literacy, which is consistent with a ‘nudge’ philosophy. Based on the findings, Finlife significantly increased the financial and demographic survival literacy of the participants, and “nudged” them to actively pursue more information and becoming more active in financial decisions

pH-sensitive vibrational probe reveals a cytoplasmic protonated cluster in bacteriorhodopsin

Infrared spectroscopy has been used in the past to probe the dynamics of internal proton transfer reactions taking place during the functional mechanism of proteins but has remained mostly silent to protonation changes in the aqueous medium. Here, by selectively monitoring vibrational changes of buffer molecules with a temporal resolution of 6 µs, we have traced proton release and uptake events in the light-driven proton-pump bacteriorhodopsin and correlate these to other molecular processes within the protein. We demonstrate that two distinct chemical entities contribute to the temporal evolution and spectral shape of the continuum band, an unusually broad band extending from 2,300 to well below 1,700 cm−1. The first contribution corresponds to deprotonation of the proton release complex (PRC), a complex in the extracellular domain of bacteriorhodopsin where an excess proton is shared by a cluster of internal water molecules and/or ionic E194/E204 carboxylic groups. We assign the second component of the continuum band to the proton uptake complex, a cluster with an excess proton reminiscent to the PRC but located in the cytoplasmic domain and possibly stabilized by D38. Our findings refine the current interpretation of the continuum band and call for a reevaluation of the last proton transfer steps in bacteriorhodopsin

Liquid film drag out in the presence of molecular forces

From a practical as well as a conceptual point of view, one of the most interesting problems of physicochemical hydrodynamics is the drag out of a liquid film by a moving solid out of a pool of liquid. The basic problem, sometimes denoted the Landau-Levich problem [L. Landau and B. Levich, “Dragging of a liquid by amoving plate,” Acta Physicochim. USSR 17, 42–54 (1942)], involves an interesting blend of capillary and viscous forces plus a matching of the static solution for capillary rise with a numerical solution of the film evolution equation, neglecting gravity, on the downstream region of the flow field. The original solution describes experimental data for a wide range of Capillary numbers but fails to match results for large and very small Capillary numbers. Molecular level forces are introduced to create an augmented version of the film evolution equation to show the effect of van derWaals forces at the lower range of Capillary numbers. A closed form solution for static capillary rise, including molecular forces, was matched with a numerical solution of the augmented film evolution equation in the dynamic meniscus region. Molecular forces do not sensibly modify the static capillary rise region, since film thicknesses are larger than the range of influence of van der Waals forces, but are determinant in shaping the downstream dynamic meniscus of the very thin liquid films. As expected, a quantitatively different level of disjoining pressure for different values of molecular constants remains in the very thin liquid film far downstream. Computational results for a wide range of Capillary numbers and Hamaker constants show a clear transition towards a region where the film thickness becomes independent of the coating speed.Fil: Schmidhalter, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); ArgentinaFil: Cerro, R. L.. University of Alabama in Huntsville; Estados UnidosFil: Giavedoni, Maria Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); ArgentinaFil: Saita, Fernando Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentin

Phylogenetic Analysis of Cellulolytic Enzyme Genes from Representative Lineages of Termites and a Related Cockroach

The relationship between xylophagous termites and the protists resident in their hindguts is a textbook example of symbiosis. The essential steps of lignocellulose degradation handled by these protists allow the host termites to thrive on a wood diet. There has never been a comprehensive analysis of lignocellulose degradation by protists, however, as it has proven difficult to establish these symbionts in pure culture. The trends in lignocellulose degradation during the evolution of the host lineage are also largely unknown. To clarify these points without any cultivation technique, we performed meta-expressed sequence tag (EST) analysis of cDNA libraries originating from symbiotic protistan communities in four termite species and a wood-feeding cockroach. Our results reveal the establishment of a degradation system with multiple enzymes at the ancestral stage of termite-protistan symbiosis, especially GHF5 and 7. According to our phylogenetic analyses, the enzymes comprising the protistan lignocellulose degradation system are coded not only by genes innate to the protists, but also genes acquired by the protists via lateral transfer from bacteria. This gives us a fresh perspective from which to understand the evolutionary dynamics of symbiosis