206 research outputs found
Ansiedade Social na Infância e Pré-Adolescência: A versão portuguesa da SASC-R
[resumo][abstract
Ansiedade Social na Infância e Pré-Adolescência: Adaptação para o Português de Portugal da SASC-R
A Escala de Ansiedade Social para Crianças (forma revista) - SASC-R destina-se a avaliar as experiências de ansiedade social e de evitamento das crianças e pré-adolescentes no contexto das relações com os pares. Neste estudo, pretende-se validar para a população portuguesa a SASC-R, utilizando a estrutura proposta pelos autores da escala original, através da análise fatorial confirmatória (AFC). Procedemos à aplicação da SASC-R numa amostra de 486 crianças entre os 9 e os 15 anos. Os resultados indicam que a escala replica os fatores da versão original, possui boa consistência interna e uma validade de constructo bastante satisfatória. Este estudo sugere que a SASC-R é uma escala útil na avaliação da ansiedade social em crianças.The Social Anxiety Scale for Children (revised form) - SASC-R evaluates the experience of social anxiety and avoidance felt by children and pre-adolescents in the context of relationship with their peers. This study aims to validate the Portuguese version of the SASC-R by confirmatory factor analysis using the structure proposed by the authors of the original scale. In a survey donewith 486 children between the ages of nine and 15 years, the results show that the scale reproduces the original factors, has a good internal consistency and a quite satisfactory construct validity. This study suggests that the SASC-R is a useful scale on the evaluation of social anxiety among children
A preocupação com o excesso de peso dos filhos enquanto determinante das atitudes de controlo alimentar maternas
[resumo][abstract
Cluster Masses Accounting for Structure along the Line of Sight
Weak gravitational lensing of background galaxies by foreground clusters
offers an excellent opportunity to measure cluster masses directly without
using gas as a probe. One source of noise which seems difficult to avoid is
large scale structure along the line of sight. Here I show that, by using
standard map-making techniques, one can minimize the deleterious effects of
this noise. The resulting uncertainties on cluster masses are significantly
smaller than when large scale structure is not properly accounted for, although
still larger than if it was absent altogether.Comment: 5 pages, 5 figure
Ising Spins on Thin Graphs
The Ising model on ``thin'' graphs (standard Feynman diagrams) displays
several interesting properties. For ferromagnetic couplings there is a mean
field phase transition at the corresponding Bethe lattice transition point. For
antiferromagnetic couplings the replica trick gives some evidence for a spin
glass phase. In this paper we investigate both the ferromagnetic and
antiferromagnetic models with the aid of simulations. We confirm the Bethe
lattice values of the critical points for the ferromagnetic model on
and graphs and examine the putative spin glass phase in the
antiferromagnetic model by looking at the overlap between replicas in a
quenched ensemble of graphs. We also compare the Ising results with those for
higher state Potts models and Ising models on ``fat'' graphs, such as those
used in 2D gravity simulations.Comment: LaTeX 13 pages + 9 postscript figures, COLO-HEP-340,
LPTHE-Orsay-94-6
Glassy dynamics in granular compaction: sand on random graphs
We discuss the use of a ferromagnetic spin model on a random graph to model
granular compaction. A multi-spin interaction is used to capture the
competition between local and global satisfaction of constraints characteristic
for geometric frustration. We define an athermal dynamics designed to model
repeated taps of a given strength. Amplitude cycling and the effect of
permanently constraining a subset of the spins at a given amplitude is
discussed. Finally we check the validity of Edwards' hypothesis for the
athermal tapping dynamics.Comment: 13 pages Revtex, minor changes, to appear in PR
Zero temperature phases of the frustrated J1-J2 antiferromagnetic spin-1/2 Heisenberg model on a simple cubic lattice
At zero temperature magnetic phases of the quantum spin-1/2 Heisenberg
antiferromagnet on a simple cubic lattice with competing first and second
neighbor exchanges (J1 and J2) is investigated using the non-linear spin wave
theory. We find existence of two phases: a two sublattice Neel phase for small
J2 (AF), and a collinear antiferromagnetic phase at large J2 (CAF). We obtain
the sublattice magnetizations and ground state energies for the two phases and
find that there exists a first order phase transition from the AF-phase to the
CAF-phase at the critical transition point, pc = 0.28. Our results for the
value of pc are in excellent agreement with results from Monte-Carlo
simulations and variational spin wave theory. We also show that the quartic 1/S
corrections due spin-wave interactions enhance the sublattice magnetization in
both the phases which causes the intermediate paramagnetic phase predicted from
linear spin wave theory to disappear.Comment: 19 pages, 4 figures, Fig. 1b modified, Appendix B text modifie
Perturbation evolution with a non-minimally coupled scalar field
We recently proposed a simple dilaton-derived quintessence model in which the
scalar field was non-minimally coupled to cold dark matter, but not to
`visible' matter. Such couplings can be attributed to the dilaton in the low
energy limit of string theory, beyond tree level. In this paper we discuss the
implications of such a model on structure formation, looking at its impact on
matter perturbations and CMB anisotropies. We find that the model only deviates
from CDM and minimally coupled theories at late times, and is well
fitted to current observational data. The signature left by the coupling, when
it breaks degeneracy at late times, presents a valuable opportunity to
constrain non-minimal couplings given the wealth of new observational data
promised in the near future.Comment: Version appearing in Physical Review D. 10 pages, 9 figs. Comparison
with SN1a and projected MAP results, and appendix adde
CMB-Cluster Lensing
Clusters of galaxies are powerful cosmological probes, particularly if their
masses can be determined. One possibility for mass determination is to study
the cosmic microwave background (CMB) on small angular scales and observe
deviations from a pure gradient due to lensing of massive clusters. I show
that, neglecting contamination, this technique has the power to determine
cluster masses very accurately, in agreement with estimates by Seljak and
Zaldarriaga (1999). However, the intrinsic small scale structure of the CMB
significantly degrades this power. The resulting mass constraints are useless
unless one imposes a prior on the concentration parameter c. With even a modest
prior on c, an ambitious CMB experiment (0.5' resolution and 1 microK per
pixel) could determine masses of high redshift (z>0.5) clusters with ~ 30%
accuracy.Comment: 17 pages, 10 figure
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