Stokes theory of thin-film rupture

The structure of the flow induced by the van der Waals destabilization of a non-wetting liquid film placed on a solid substrate is unraveled by means of theory and numerical simulations of the Stokes equations. Our analysis reveals that lubrication theory, which yields $h_{\text{min}} \propto \tau^{1/5}$ where $h_{\text{min}}$ is the minimum film thickness and $\tau$ is the time until breakup, cannot be used to describe the local flow close to rupture. Instead, the slender lubrication solution is shown to experience a crossover to a universal self-similar solution of the Stokes equations that yields $h_{\text{min}} \propto \tau^{1/3}$, with an opening angle of $37^{\circ}$ off the solid.Comment: 12 pages, 7 figure

OLOF WESSBERG (Q.D.D.G) KAREN MOGENSEN (Q.D.D.G.) “LOS PADRES DE LA RESERVA NATURAL ABSOLUTA CABO BLANCO”

En mayo de 1955 llegó a Costa Rica, procedente de Suecia, el matrimonio formado por Olof Wessberg –un oficial retirado del ejército sueco- y Karen Mogensen, su esposa danesa, con la idea de cultivar frutas y tener colmenas en una finca de 40 ha que habían adquirido en Montezuma y en la cual luego restauraron el bosque. Esa finca constituye actualmente la Reserva Natural Absoluta Nicolás Wessberg, de 63 ha. En algún momento, luego de instalarse en su finca, Olof fue a visitar el área de Cabo Blanco y según relató su esposa Karen, vio “… qué linda era esa montaña, montaña virgen todavía; volvió diciendo que todavía había bosque virgen allá y que había visto una gran manada de pizotes, pero que si iban a cortar ese bosque también, ¿a dónde iban a ir todos esos animales?” (Hilje et al., 2002)

Economic valuation of environmental services of the ecological reserve Mache Chindul, Ecuador climate regulation

Environmental services are all those benefits that a population obtains from ecosystems. Ecological book, as part of terrestrial ecosystems, offer important environmental services, including the protection of draining basins, biodiversity conservation, and carbon retention in the soil. Other functions are to collect water for the aquiferous systems, which affects its own quality, by filtering, absorbing and retaining some polluting agents, which are prevented from going to the reservoirs. They also contribute to regulating temperature and moisture, which improves air quality, all of which are factors related to quality of life. In this research the importance of the identification and economic valuation of the environmental services of an ecological reserve is highlighted as an instrument for conservation and sustainable use of ecosystems. Throughout this study, the impact of the Mache-Chindul ecological reserve is analyzed in relation to climate regulation, based on the current scenario of climate change. To conduct an economical valuation is only possible if there is an adequate understanding of the role that natural resources and biological biodiversity play from a socio-economical perspective

Diffusion-flame flickering as a hydrodynamic global mode

The present study employs a linear global stability analysis to investigate buoyancy-induced flickering of axisymmetric laminar jet diffusion flames as a hydrodynamic global mode. The instability-driving interactions of the buoyancy force with the density differences induced by the chemical heat release are described in the infinitely fast reaction limit for unity Lewis numbers of the reactants. The analysis determines the critical conditions at the onset of the linear global instability as well as the Strouhal number of the associated oscillations in terms of the governing parameters of the problem. Marginal instability boundaries are delineated in the Froude number/Reynolds number plane for different fuel jet dilutions. The results of the global stability analysis are compared with direct numerical simulations of time-dependent axisymmetric jet flames and also with results of a local spatio-temporal stability analysis.Norbert Peters pointed out the need for the present analysis in his seminal paper with John Buckmaster published thirty years ago (Buckmaster & Peters 1986). It is with great sorrow that we received the news of his passing last year. This paper is devoted to his memory in gratitude for his many outstanding contributions to Combustion Science. The constructive comments of one anonymous referee have led to substantial improvements of the paper and are gratefully acknowledged. This work was supported by the Spanish MCINN through project no. CSD2010-00010 and by the Spanish MINECO through project no. DPI2014-59292-C3-1-P

Estudio de la adecuación del bagazo de cerveza en alimentación animal. II. Experiencia de digestibilidad en cerdos de dietas conteniendo bagazo o soja

The digestibility of two semisynthetic diets with the same nitrogen and caloric content has been studled in pigs, the only source of protein being a fine fraction of dried brewers' grain or soya flour. This was done to establísh the digestive efficiency of this new protein concentrate compared to soya. Using direct method the digestibility has been studied in castrated male pigs weighing 26.7 Kg at the beginning of the experiments. The results obtained indicate a higher digestive utilization of all the nutrients studied in the diet containing soya. It was found that the digestibilíty coefficient of protein was 86.7% for this diet, and 60,8% for the diet containing the fine fraction of brewers' grain, a difference believed to be due to the excessive heating to which this subproduct was submittect during dessication.Se ha estudiado en cerdos la digestibilidad de dos dietas semisintéticas isonitrogenadas e isccalóricas llevando como única fuente de proteína fracción fina del bagazo de cerveza desecado o harina de soja, con el fin de conocer la eficacia digestiva de este nuevo concentrado protéico frente a la soja. Se ha estudiado la digestibilidad por el mtéodo directo en cerdos machos castrados de 26,7 kg al comienzo de las experiencias. Los resultados obtenidos nos muestran una mayor utilización digestiva de todos los nutrientes investigados en la dieta que tiene soja, encontrando un coeficiente de digestibilidad de la proteina de 86,7% para esta dieta, y de 60,8% para la dieta que contiene la fracción fina del bagazo, diferencia que creemos se debe al excesivo calentamiento al que se ha sometido este subproducto durante su desecación