El fondo de reserva de la seguridad social

El objetivo del presente trabajo es analizar y explicar el funcionamiento del Fondo de Reserva de la seguridad social. Para ello se describen tanto los precedentes directos como indirectos de dicho fondo para posteriormente proceder a explicar la normativa jurídica referente al fondo, los criterios de inversión y materialización de los activos de dicho fondo y evolución de diferentes aspectos cuantitativos del Fondo. Esto nos permitirá enmarcarlo dentro de un conjunto de Fondos de Reserva Europeos para poder apreciar las diferentes formas de gestionar dichos Fondos, los cuales se erigen de vital importancia para la sostenibilidad del sistema de la seguridad social. Por último, se llevará a cabo una sencilla estimación partiendo de unas hipótesis realistas que nos permitirá conocer hasta cuando dará de si el Fondo de Reserva en caso de seguir recurriendo a este como se ha venido haciendo en los últimos años.

Forma vs. función en tipología prehistórica: el caso de las bramaderas óseas magdalenienses

Este trabajo ha sido realizado en el marco del Grupo de Investigación Consolidado GIC 07/21-IT.288.07.

Can environmental constraints determine random patterns of plant species co-occurrence?

Plant community ecologists use the null model approach to infer assembly processes from observed patterns of species co-occurrence. In about a third of published studies, the null hypothesis of random assembly cannot be rejected. When this occurs, plant ecologists interpret that the observed random pattern is not environmentally constrained - but probably generated by stochastic processes. The null model approach (using the C-score and the discrepancy index) was used to test for random assembly under two simulation algorithms. Logistic regression, distance-based redundancy analysis, and constrained ordination were used to test for environmental determinism (species segregation along environmental gradients or turnover and species aggregation). This article introduces an environmentally determined community of alpine hydrophytes that presents itself as randomly assembled. The pathway through which the random pattern arises in this community is suggested to be as follows: Two simultaneous environmental processes, one leading to species aggregation and the other leading to species segregation, concurrently generate the observed pattern, which results to be neither aggregated nor segregated - but random. A simulation study supports this suggestion. Although apparently simple, the null model approach seems to assume that a single ecological factor prevails or that if several factors decisively influence the community, then they all exert their influence in the same direction, generating either aggregation or segregation. As these assumptions are unlikely to hold in most cases and assembly processes cannot be inferred from random patterns, we would like to propose plant ecologists to investigate specifically the ecological processes responsible for observed random patterns, instead of trying to infer processes from patterns

Hartle's model within the general theory of perturbatiye matchings: the change in mass

Hartle's model provides the most widely used analytic framework to describe isolated compact bodies rotating slowly in equilibrium up to second order in perturbations in the context of General Relativity. Apart from some explicit assumptions, there are some implicit, like the "continuity" of the functions in the perturbed metric across the surface of the body. In this work we sketch the basics for the analysis of the second order problem using the modern theory of perturbed matchings. In particular, the result we present is that when the energy density of the fluid in the static configuration does not vanish at the boundary, one of the functions of the second order perturbation in the setting of the original work by Hartle is not continuous. This discrepancy affects the calculation of the change in mass of the rotating star with respect to the static configuration needed to keep the central energy density unchanged.