Critical behavior in nonequilibrium phase transitions

The nonequilibrium phase transitions occurring in a fast-ionic-conductor model and in a reaction-diffusion Ising model are studied by Monte Carlo finite-size scaling to reveal nonclassical critical behavior; our results are compared with those in related models.

Critical behavior of a water monolayer under hydrophobic confinement

The properties of water can have a strong dependence on the confinement. Here, we consider a water monolayer nanoconfined between hydrophobic parallel walls under conditions that prevent its crystallization. We investigate, by simulations of a many-body coarse-grained water model, how the properties of the liquid are affected by the confinement. We show, by studying the response functions and the correlation length and by performing finite-size scaling of the appropriate order parameter, that at low temperature the monolayer undergoes a liquid-liquid phase transition ending in a critical point in the universality class of the two-dimensional (2D) Ising model. Surprisingly, by reducing the linear size L of the walls, keeping the walls separation h constant, we find a 2D-3D crossover for the universality class of the liquid-liquid critical point for L/h=~50, i.e. for a monolayer thickness that is small compared to its extension. This result is drastically different from what is reported for simple liquids, where the crossover occurs for , and is consistent with experimental results and atomistic simulations. We shed light on these findings showing that they are a consequence of the strong cooperativity and the low coordination number of the hydrogen bond network that characterizes water.

Description of diffusive and propagative behavior on fractals

The known properties of diffusion on fractals are reviewed in order to give a general outlook of these dynamic processes. After that, we propose a description developed in the context of the intrinsic metric of fractals, which leads us to a differential equation able to describe diffusion in real fractals in the asymptotic regime. We show that our approach has a stronger physical justification than previous works on this field. The most important result we present is the introduction of a dependence on time and space for the conductivity in fractals, which is deduced by scaling arguments and supported by computer simulations. Finally, the diffusion equation is used to introduce the possibility of reaction-diffusion processes on fractals and analyze their properties. Specifically, an analytic expression for the speed of the corresponding travelling fronts, which can be of great interest for application purposes, is derived

La escala de análisis: un tema central en didáctica de la geografía = The scale of analysis a central didactic theme in Geography

Geographical scale is not merely a technical question. The learning of geographical scale goes beyond geometricunderstanding; it implies the etymological comprehension of the concept, the recognition of the importance of scale in theelaboration of the geographical discourse. It implies placing oneself in the centre of the teaching and learning of Geographyand asking oneself, what scale? Why this scale? What progression of scales? The answer to these questions puts in doubtthe scientific discourse that is presently taught in schools especially on the scale of analysis, the sequencing of studiedspaces and the false dichotomy local and global

Otra mirada al tema del cambio de escala: los nuevos espacios de comercio, ocio y turismo = Another look at the theme of the change of scale: new spaces in commerce, leisure and tourism

The technological advances and new organisation of the economy together with a change in ideas in consumer habits andlifestyle that have happened in the last 25 years have placed us in a new state of capitalism. The spatial translation of thisnew state has been immediate and implies among other changes the overcoming of the concept of scale. Commercialspaces and those of leisure and tourism offer us an unbeatable opportunity of exemplifying these changes because they arethe most effected by the new postmodern tendencies