Crisis de naturaleza y justicia en las sociedades de riesgo

Los niesgos ambientales en las sociedades actuales son un tópico de amplío debate, que derivan de la consideración de los problemas incluidos en el cambio global que se manifiestan a nivel biosférico como por ejemplo el aumento de los gases efecto invernadero, la disminución del ozono estratosférico, o el incremento de nutrientes y contaminantes en los océanos y a nivel local a través de cambios a pequeña escala en distintos lugares del planeta pero que sumados, también constituyen un cambio global, como los cambios en los usos de la tierra, la fragmentación de los ambientes, la pérdida de biodiversidad, las invasiones biológicas, o el incremento de los procesos de desertificación. Estos riesgos constituyen la crisis de la naturaleza, que compromete la supervivencia de todos los seres vivos, incluida nuestra especie

Spin-glass behaviour on random lattices

The ground-state phase diagram of an Ising spin-glass model on a random graph with an arbitrary fraction $w$ of ferromagnetic interactions is analysed in the presence of an external field. Using the replica method, and performing an analysis of stability of the replica-symmetric solution, it is shown that $w=1/2$, correponding to an unbiased spin glass, is a singular point in the phase diagram, separating a region with a spin-glass phase ($w<1/2$) from a region with spin-glass, ferromagnetic, mixed, and paramagnetic phases ($w>1/2$)

Processamento de umbu-cajá, variedade suprema, na forma de geleia dietética e convencional.

A umbu-cajazeira (Spondias sp.), pertencente à família Anarcadiaceae, é nativa das regiões semiáridas do Nordeste e encontra-se difundida principalmente entre os estados do Rio Grande do Norte, Ceará, Piauí, Pernambuco e Bahia (CARVALHO et al., 2008; NARAIN et al., 2007). Seus frutos apresentam pH que varia entre 2,4 a 3,0 e sabor ácido acentuado, que dificulta o seu consumo in natura (CARVALHO et al., 2008).bitstream/item/55928/1/CircularTecnica-102-1.pd

Isochronous island bifurcations driven by resonant magnetic perturbations in Tokamaks

Recent evidences show that heteroclinic bifurcations in magnetic islands may be caused by the amplitude variation of resonant magnetic perturbations in tokamaks. To investigate the onset of these bifurcations, we consider a large aspect ratio tokamak with an ergodic limiter composed of two pairs of rings that create external primary perturbations with two sets of wave numbers. An individual pair produces hyperbolic and elliptic periodic points, and its associated islands, that are consistent with the Poincar\'e-Birkhoff fixed point theorem. However, for two pairs producing external perturbations resonant on the same rational surface, we show that different configurations of isochronous island chains may appear on phase space according to the amplitude of the electric currents in each pair of the ergodic limiter. When one of the electric currents increases, isochronous bifurcations take place and new islands are created with the same winding number as the preceding islands. We present examples of bifurcation sequences displaying (a) direct transitions from the island chain configuration generated by one of the pairs to the configuration produced by the other pair, and (b) transitions with intermediate configurations produced by the limiter pairs coupling. Furthermore, we identify shearless bifurcations inside some isochronous islands, originating nonmonotonic local winding number profiles with associated shearless invariant curves