145 research outputs found
Developing young people's sense of self and place through sport
Previous research has recognized positive health implications, both physical and mental, as an outcome of participation in leisure pursuits. They provide opportunities for self-expression and stress reduction, as well as an environment in which people can socialize. Leisure activities, specifically sport activities, can play a significant role in young people's identity development. This paper explores the leisure activities in which young people in Adelaide, Australia participate. It examines the role of leisure activities in terms of young people's identity and feelings towards their hometown. This study consisted of semi-structured focus groups conducted with 24 senior high school students, followed by a survey resulting in 226 useable responses. Respondents were aged between 16 and 18 years of age. From the range of activities identified and explored, the results revealed sports activities to have the greatest impact on young people's lives. The results demonstrated that frequency of participation has a significant effect on young people's involvement levels and how they identify with the activity
On the Sunyaev-Zel'dovich effect from dark matter annihilation or decay in galaxy clusters
We revisit the prospects for detecting the Sunyaev Zel'dovich (SZ) effect
induced by dark matter (DM) annihilation or decay. We show that with standard
(or even extreme) assumptions for DM properties, the optical depth associated
with relativistic electrons injected from DM annihilation or decay is much
smaller than that associated with thermal electrons, when averaged over the
angular resolution of current and future experiments. For example, we find:
(depending on the assumptions) for \mchi
= 1 GeV and a density profile for a template cluster
located at 50 Mpc and observed within an angular resolution of , compared
to . This, together with a full spectral
analysis, enables us to demonstrate that, for a template cluster with generic
properties, the SZ effect due to DM annihilation or decay is far below the
sensitivity of the Planck satellite. This is at variance with previous claims
regarding heavier annihilating DM particles. Should DM be made of lighter
particles, the current constraints from 511 keV observations on the
annihilation cross section or decay rate still prevent a detectable SZ effect.
Finally, we show that spatial diffusion sets a core of a few kpc in the
electron distribution, even for very cuspy DM profiles, such that improving the
angular resolution of the instrument, e.g. with ALMA, does not necessarily
improve the detection potential. We provide useful analytical formulae
parameterized in terms of the DM mass, decay rate or annihilation cross section
and DM halo features, that allow quick estimates of the SZ effect induced by
any given candidate and any DM halo profile.Comment: 27 p, 6 figs, additional section on spatial diffusion effects.
Accepted for publication in JCA
Reionization by active sources and its effects on the cosmic microwave background
We investigate the possible effects of reionization by active sources on the
cosmic microwave background. We concentrate on the sources themselves as the
origin of reionization, rather than early object formation, introducing an
extra period of heating motivated by the active character of the perturbations.
Using reasonable parameters, this leads to four possibilities depending on the
time and duration of the energy input: delayed last scattering, double last
scattering, shifted last scattering and total reionization. We show that these
possibilities are only very weakly constrained by the limits on spectral
distortions from the COBE FIRAS measurements. We illustrate the effects of
these reionization possibilities on the angular power spectrum of temperature
anisotropies and polarization for simple passive isocurvature models and simple
coherent sources, observing the difference between passive and active models.
Finally, we comment on the implications of this work for more realistic active
sources, such as causal white noise and topological defect models. We show for
these models that non-standard ionization histories can shift the peak in the
CMB power to larger angular scales.Comment: 21 pages LaTeX with 11 eps figures; replaced with final version
accepted for publication in Phys. Rev.
Gravitational field around a time-like current-carrying screwed cosmic string in scalar-tensor theories
In this paper we obtain the space-time generated by a time-like
current-carrying superconducting screwed cosmic string(TCSCS). This
gravitational field is obtained in a modified scalar-tensor theory in the sense
that torsion is taken into account. We show that this solution is comptible
with a torsion field generated by the scalar field . The analysis of
gravitational effects of a TCSCS shows up that the torsion effects that appear
in the physical frame of Jordan-Fierz can be described in a geometric form
given by contorsion term plus a symmetric part which contains the scalar
gradient. As an important application of this solution, we consider the linear
perturbation method developed by Zel'dovich, investigate the accretion of cold
dark matter due to the formation of wakes when a TCSCS moves with speed and
discuss the role played by torsion. Our results are compared with those
obtained for cosmic strings in the framework of scalar-tensor theories without
taking torsion into account.Comment: 21 pages, no figures, Revised Version, presented at the "XXIV-
Encontro Nacional de Fisica de Particulas e Campos ", Caxambu, MG, Brazil, to
appear in Phys. Rev.
Topological Defects and CMB anisotropies : Are the predictions reliable ?
We consider a network of topological defects which can partly decay into
neutrinos, photons, baryons, or Cold Dark Matter. We find that the degree-scale
amplitude of the cosmic microwave background (CMB) anisotropies as well as the
shape of the matter power spectrum can be considerably modified when such a
decay is taken into account. We conclude that present predictions concerning
structure formation by defects might be unreliable.Comment: 14 pages, accepted for publication in PR
The Behavioral Roots of Information Systems Security:Exploring Key Factors Related to Unethical IT Use
Unethical information technology (IT) use, related to activities such as hacking, software piracy, phishing, and spoofing, has become a major security concern for individuals, organizations, and society in terms of the threat to information systems (IS) security. While there is a growing body of work on this phenomenon, we notice several gaps, limitations, and inconsistencies in the literature. In order to further understand this complex phenomenon and reconcile past findings, we conduct an exploratory study to uncover the nomological network of key constructs salient to this phenomenon, and the nature of their interrelationships. Using a scenario-based study of young adult participants, and both linear and nonlinear analyses, we uncover key nuances of this phenomenon of unethical IT use. We find that unethical IT use is a complex phenomenon, often characterized by nonlinear and idiosyncratic relationships between the constructs that capture it. Overall, ethical beliefs held by the individuals, along with economic, social, and technological considerations are found to be relevant to this phenomenon. In terms of practical implications, these results suggest that multiple interventions at various levels may be required to combat this growing threat to IS security
Broad-scale patterns of body size in squamate reptiles of Europe and North America
Aim To document geographical interspecific patterns of body size of European and North American squamate reptile assemblages and explore the relationship between body size patterns and environmental gradients. Location North America and western Europe. Methods We processed distribution maps for native species of squamate reptiles to document interspecific spatial variation of body size at a grain size of 110 x 110 km. We also examined seven environmental variables linked to four hypotheses possibly influencing body size gradients. We used simple and multiple regression, evaluated using information theory, to identify the set of models best supported by the data. Results Europe is characterized by clear latitudinal trends in body size, whereas geographical variation in body size in North America is complex. There is a consistent association of mean body size with measures of ambient energy in both regions, although lizards increase in size northwards whereas snakes show the opposite pattern. Our best models accounted for almost 60% of the variation in body size of lizards and snakes within Europe, but the proportions of variance explained in North America were less than 20%. Main conclusions Although body size influences the energy balance of thermoregulating ectotherms, inconsistent biogeographical patterns and contrasting associations with energy in lizards and snakes suggest that no single mechanism can explain variation of reptile body size in the northern temperate zone
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