The influence of surface roughness on the adhesive interactions and phase behavior of suspensions of calcite nanoparticles

We investigate the impact of nanoparticle roughness on the phase behaviour of suspensions in models of calcium carbonate nanoparticles. We use a Derjaguin approach that incorporates roughness effects and interactions between the nanoparticles modelled with a combination of DLVO forces and hydration forces, derived using experimental data and atomistic molecular dynamics simulations, respectively. Roughness effects, such as atomic steps or terraces appearing in mineral surfaces result in very different effective inter-nanoparticle potentials. Using stochastic Langevin Dynamics computer simulations and the effective interparticle interactions we demonstrate that relatively small changes in the roughness of the particles modify significantly the stability of the suspensions. We propose that the sensitivity of the phase behavior to the roughness is connected to the short length scale of the adhesive attraction arising from the ordering of water layers confined between calcite surfaces. Particles with smooth surfaces feature strong adhesive forces, and form gel fractal structures, while small surface roughness, of the order of atomic steps in mineral faces, stabilize the suspension. We believe that our work helps to rationalize the contrasting experimental results that have been obtained recently using nanoparticles or extended surfaces, which provide support for the existence of adhesive or repulsive interactions, respectively. We further use our model to analyze the synergistic effects of roughness, pH and ion concentration on the phase behavior of suspensions, connecting with recent experiments using calcium carbonate nanoparticles

Reconstrucción de las redes sociales : el caso de las FARC, el ELN y las ACCU-AUC

Se explora una estrategia para analizar los comunicados de las FARC, el ELN y las ACCU-AUC. Ella se basa en la mínima estructura gramatical: Sujeto-Acción-Objeto. A partir de ella se reconstruye una red de relaciones a la que le son aplicadas algunas de las medidas del Análisis de Redes Sociales. Se identifican varios mecanismos relacionados con estas propiedades estructurales: a) definir para cada actor su propio conjunto de relaciones; b) la parte es distinta al todo; c) Temas en los que se hace énfasis sirven para ubicar cerca un conjunto de nodos.It is explored a strategy to analyze the press releases made by the FARC, the ELN, and the ACCU-AUC. It is based on the minimal grammatical structure: Subject- Action - Object. Using this grammatical triplet, the network of connections are built up; and then, some of the Social Network Analysis tools are applied to it. Some mechanisms related with these structural properties are identified: a) To define for each actor a distinctive set of relationships; b) the part is different from the whole; c) the emphasized topics do the work of putting near a set of nodes

The impact of the interfacial Kapitza resistance on colloidal thermophoresis

Thermal gradients impart a force on colloidal particles pushing the colloids towards cold or hot regions, a phenomenon called thermophoresis. Existing theories describe thermophoresis by considering the local perturbation of the thermal field around the colloid. While these approaches incorporate interfacial surface free energies, they have consistently ignored the impact of the Kapitza resistance associated with the colloid-solvent interface. We propose a theoretical approach to include interfacial Kapitza resistance effects, and we test the new equations using non-equilibrium molecular dynamics simulations. We demonstrate that the Kapitza resistance influences the local thermal field around a colloid, modifying the Soret coefficient. We conclude that interfacial thermal conductance effects must be included to describe thermophoresis.Comment: Main paper/: 6 pages, 4 figures; Supplementary: 6 pages, 6 figure

Las universidades y la planificación de la investigación y la innovación: los retos éticos en el nuevo siglo

Últimamente la investigación en las universidades se ha visto envuelta en una serie de cambios tecnológicos, políticos y sociales: en este campo entran a jugar la bibliometría y la geopolítica, entre otros aspectos. Esto obliga a repensar cuál es la función de la universidad ante los retos actuales de la investigación, pero también a trascender el estado de la reflexión y proponer agendas políticas, usos y aplicaciones de la investigación, teniendo en cuenta todo un trasfondo ético. Se propone un enfoque de la investigación hacia la responsabilidad social, basado en el diálogo entre actores y la conciencia simultánea de los contextos global y local. El gran reto es crear un código de ética de investigación, que se aplique a las verdaderas necesidades contemporáneas, pero que también sugiera elementos de medición de las consecuencias de los avances científicos y técnicos

Nanocátalysts for oxygen removal from biomass derived biofuel

The use of bio-energy as a renewable alternative to fossil fuels is nowadays attracting more and more attention. Bio-fuel from biomass seems to be a potential energy substitute for fossil fuels since it is a renewable resource that could contribute to sustainable development and global environmental preservation and it appears to have significant economic potential. Liquid fuels can be obtained from fast pyrolysis of lignocellulosic biomass, where fast pyrolysis is a promising route because the process takes place at moderate temperatures, in absence of air and with a short hot vapor residence time. However, these liquid fuels have poor quality due to their low volatility, high viscosity, low heating value, a high oxygen content and poor chemical stability. This high oxygen is due to the presence of oxygen-containing compounds such as alcohols, aldehydes, ketones, furans and phenols. In this sense, catalytic hydrodeoxygenation (HDO) is one the most efficient processes to remove oxygen from these liquid fuels. In this context, the catalyst design is of upmost importance to achieve a high degree of deoxygenation, and bifunctional catalysts are required to achieve high degrees of activity. Noble metal and non-noble metal based catalysts will be evaluated in HDO of model molecules in order to get further insight about the important role of the active phase. Transition metal phosphides have shown excellent catalytic performances due to their good hydrogen transfer properties that diminishes the amount of metal exposed, avoiding, as much as possible, the deactivation, and modifies the electronic density of the catalyst leading to solids that favors the HDO. In addition these phosphides show bifunctional catalytic properties (metallic sites for hydrogenation and acid sites for cracking, methyl transfer reaction, dehydration and isomerization).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Palabras de una vida decorosa

Manual de tolerancia. Héctor Abad Gómez. Editorial Universidad de Antioquia, Editorial Planeta, Medellín, Bogotá, 2007, 155 págs

Inovações sociais na educação

  This paper addresses current debates around the concept of innovation, social innovation, and their emergence in the context of education through the tension between conscious purpose and nature proposed by Bateson (1998, p. 457). This way, we are able to clarify the sense, meaning, and application of the idea of social innovations in education. This concept is used for social innovations associated  with formal education, but also with popular and communitarian education. It explores the link with the field of innovation studies, and with de-colonial, praxeologic, and studies about other pedagogies. This allows us to identify the challenges that researching and teaching on social innovations in education entail.  En este escrito se da cuenta de los debates alrededor de los conceptos de innovación e innovación social, y su emergencia en el ámbito educativo a partir de la tensión entre propósito consciente y naturaleza, propuestos por Bateson (1998, p. 457). De modo que se logra precisar el sentido, significado y aplicación del concepto de innovaciones sociales en educación. Concepto que se usa tanto para innovaciones sociales relacionadas con la educación formal, como con la educación popular y comunitaria. Se explora su relación con el ámbito de los estudios sobre innovación, así como con los decoloniales, la praxeología y las pedagogías otras. Lo que permite precisar los retos que confrontan la investigación y la docencia en innovaciones sociales en educación.Este artigo aborda os debates atuais sobre o conceito de inovação, inovação social, e seu surgimento no contexto da educação através da tensão entre propósito consciente e natureza proposto por Bateson (1998, p. 47) Assim, é possível especificar o sentido, significado e aplicação do conceito de inovação social na educação. Conceito usado para inovações sociais relacionadas à educação formal, bem como à educação popular e comunitária. É explorada sua relação com o campo de estudos sobre inovação, bem como com descoloniais, praxeologia e outras pedagogias. O que permite especificar os desafios que a pesquisa e o ensino enfrentam nas inovações sociais na educação

Una novela pachuca

Open the window para que la mosca fly. Jaime Espinal. Ediciones B, Bogotá, 2007, 246 págs

De Pueblos, Ciudades Y Metrópolis: Urbanitas Y Urbanismos

Eneste ensayo se buscadar cuentade los procesos de cambiosociocultural de pueblos y ciudades a partir de mi propia experiencia como urbanita migrante, pues comoseñala Manuel Delgado1serurbanita esserhabitantedel espacio público, en múltiples viajes, en cruces inesperados, en los que se construye ese modo de ser urbano que no se puede reducir a la ciudad, a sus múltiplesdispositivos, es más expresiónde esa características emergentes del modo de habitarla en tanto ciudadanos y urbanitas. La experiencia que se recorre es la vivenciatranscurrida del pueblo (La Mesa) alaciudadmoderna (Medellín,Bogotá),ensusmúltiples ¡dasy vueltas

Una novela pachuca

Open the window para que la mosca fly. Jaime Espinal. Ediciones B, Bogotá, 2007, 246 págs