Avaliação de factores determinantes na alteração do uso do solo para o Sul de Portugal

O objectivo deste estudo consistiu em analisar os cenários e modelos climáticos em função de um conjunto de factores de modo a determinar a probabilidade de ocorrência das duas principais classes de uso do solo previstas para um determinado ano

Gravitational Repulsion in an Expanding Ball of Dust

In general relativity, there is a velocity dependent term in the gravitational acceleration of a test particle for an observer at infinity. Depending on the direction of motion and the speed, that term can be repulsive. We show that this is also the case in the Parametrized Post-Newtonian (PPN) formalism. We compute the magnitude of that repulsive term for an expanding sphere of dust observed at infinity, and find that it could mimic the effect of a cosmological constant. The time evolution of such an expanding ball of dust for an observer at infinity is calculated, and compared with the standard $\Lambda$CDM model. We find that the so-called coincidence problem does not exist for such a model as the energy density attributed to the expansion is always of the same order as the matter energy density.Comment: 8 pages, 2 figures. Accepted for publication in Class. Quantum Gra

A viable relativistic scalar theory of gravitation

We build a self-consistent relativistic scalar theory of gravitation on a flat Minkowski spacetime from a general field Lagrangian. It is shown that, for parameters that satisfy the Equivalence Principle, this theory predicts the same outcome as general relativity for every classical solar-system test. This theory also admits gravitational waves that propagate at the speed of light, and the gravitational radiation energy loss in a binary system is shown to be very similar to the GR prediction. We then analyze the strong gravity regime of the theory for a spherically symmetric configuration and find that there is an effective "singularity" near the Schwarzschild radius. The main goal of this work is to show that, contrary to what is commonly believed, there are relativistic scalar theories of gravitation defined on a Minkowski spacetime that are not ruled out by the classical solar system tests of general relativity.Comment: 15 pages, 4 figures. Accepted for publication in Classical and Quantum Gravit

Can self-esteem mediate the association between social support and different levelsof physical activity in adolescents?

The aim was to analyze the mediation role of self-esteem in the interaction between social support from the best friend, friends, and parents, and physical activity (PA). Participants were N=444 adolescents of both genders (male= 205), aged between 12-18 years (M= 16.02; SD= 1.57). Structural equation modeling, serial mediation and multigroup analysis were used to test the proposed hypothesis. Self-reported instruments were used to collect both PA social support and self-esteem. Self-esteem partially mediates the interaction between different social supports and vigorous PA, independently of adolescent sex. Interestingly, self-esteem fully mediated the interaction between parents’ social support and vigorous PA in female adolescents. In contrast, self-esteem revealed no mediation in the interaction between social support and light and moderate PA. In conclusion, self-esteem mediates the relationship between social support and vigorous PA, the strength of mediation is higher in girls than in boys, in both genders, the mediation is higher when the social support has come from parents.info:eu-repo/semantics/publishedVersio

Socio-cultural and somatic factors associated with children’s motor competence

The purpose of this study was to assess the effect of somatic and socio-cultural factors on children’s motor competence (MC). MC was assessed through the standing long jump (SLJ), distance throw of a tennis ball (TTB), and 20 m dash (20 m) in 181 children (84 girls) with a mean age of 6.10(0.47) years. The effect of socio-economic status, house/living space, educational practices, the child’s interaction with peers and siblings, and the sum of five skinfolds (SS) were analysed via structural equation modelling (SEM) in each motor skill. The SEM models displayed a good fit to the data. In addition, standardized direct effects are significant on different outcome variables, except for brotherhood relationship (BR) and peer relationship in TTB, and 20 m dash and BR in standing long jump (SLJ). SS are negatively related to all motor skills.This research was funded Portuguese Foundation for Science and Technology, I.P., grant number UID04045/2020.info:eu-repo/semantics/publishedVersio

Can self-esteem mediate the association between social support and different levels of physical activity in adolescents?

The aim was to analyze the mediation role of self-esteem in the interaction between social support from the best friend, friends, and parents, and physical activity (PA). Participants were N=444 adolescents of both genders (male= 205), aged between 12-18 years (M= 16.02; SD= 1.57). Structural equation modeling, serial mediation and multigroup analysis were used to test the proposed hypothesis. Self-reported instruments were used to collect both PA social support and self-esteem. Self-esteem mediates partially the interaction between different social supports and vigorous PA, independently of adolescent sex. Interestingly, self-esteem was fully mediating the interaction between parents’ social support and vigorous PA in female adolescents. In contrast, self-esteem revealed no mediation in the interaction between social support and light and moderate PA. In conclusion, self-esteem mediates the relationship between social support and vigorous PA, the strength of mediation is higher in girls than in boys, in both genders the mediation is higher when the social support has come from parents