120 research outputs found
Promotion of physical activity in rural, remote and northern settings: a Canadian call to action
Introduction: The lack of policy, practice and research action on physical activity and features of the physical (built and natural) environments in rural, remote and northern settings is a significant threat to population health equity in Canada. This paper presents a synthesis of current evidence on the promotion of physical activity in non-urban settings, outcomes from a national priority-setting meeting, and a preliminary call to action to support the implementation and success of population-level initiatives targeting physical activity in non-urban settings.
Methods: We conducted a “synopses of syntheses” scoping review to explore current evidence on physical activity promotion in rural, remote, northern and natural settings. Next, we facilitated a collaborative priority-setting conference with 28 Canadian experts from policy, research and practice arenas to develop a set of priorities on physical activity in rural, remote and northern communities. These priorities informed the development of a preliminary Canadian call to action.
Results: We identified a limited number of reviews that focused on physical activity and the built environment in rural, remote and northern communities. At the priority-setting conference, participants representing rural, remote and northern settings identified top priorities for policy, practice and research action to begin to address the gaps and issues noted in the literature. These priorities include self-identifying priorities at the community level; compiling experiences; establishing consistency in research definitions and methods; and developing mentorship opportunities.
Conclusion: Coordinated action across policy, practice and research domains will be essential to the success of the recommendations presented in this call to action
Cosmological Imprint of an Energy Component with General Equation of State
We examine the possibility that a significant component of the energy density
of the universe has an equation-of-state different from that of matter,
radiation or cosmological constant (). An example is a cosmic scalar
field evolving in a potential, but our treatment is more general. Including
this component alters cosmic evolution in a way that fits current observations
well. Unlike , it evolves dynamically and develops fluctuations,
leaving a distinctive imprint on the microwave background anisotropy and mass
power spectrum.Comment: revised version, with added references, to appear in Phys. Rev. Lett.
(4 pages Latex, 2 postscript figures
Observationally Determining the Properties of Dark Matter
Determining the properties of the dark components of the universe remains one
of the outstanding challenges in cosmology. We explore how upcoming CMB
anisotropy measurements, galaxy power spectrum data, and supernova (SN)
distance measurements can observationally constrain their gravitational
properties with minimal assumptions on the theoretical side. SN observations
currently suggest the existence of dark matter with an exotic equation of state
p/rho < -1/3 that accelerates the expansion of the universe. When combined with
CMB anisotropy measurements, SN or galaxy survey data can in principle
determine the equation of state and density of this component separately,
regardless of their value, as long as the universe is spatially flat. Combining
these pairs creates a sharp consistency check. If p/rho > -1/2, then the
clustering behavior (sound speed) of the dark component can be determined so as
to test the scalar-field ``quintessence'' hypothesis. If the exotic matter
turns out instead to be simply a cosmological constant (p/rho = -1), the
combination of CMB and galaxy survey data should provide a significant
detection of the remaining dark matter, the neutrino background radiation
(NBR). The gross effect of its density or temperature on the expansion rate is
ill-constrained as it is can be mimicked by a change in the matter density.
However, anisotropies of the NBR break this degeneracy and should be detectable
by upcoming experiments.Comment: 16 pages, 10 figures, RevTeX, submitted to PR
The Imprint of Gravitational Waves in Models Dominated by a Dynamical Cosmic Scalar Field
An alternative to the standard cold dark matter model has been recently
proposed in which a significant fraction of the energy density of the universe
is due to a dynamical scalar field () whose effective equation-of-state
differs from that of matter, radiation or cosmological constant (). In
this paper, we determine how the Q-component modifies the primordial inflation
gravitational wave (tensor metric) contribution to the cosmic microwave
background anisotropy and, thereby, one of the key tests of inflation.Comment: 15 pages, 14 figures, revtex, submitted to Phys. Rev.
Resolving the Cosmological Missing Energy Problem
Some form of missing energy may account for the difference between the
observed cosmic matter density and the critical density. Two leading candidates
are a cosmological constant and quintessence (a time-varying, inhomogenous
component with negative pressure). We show that an ideal, full-sky cosmic
background anisotropy experiment may not be able to distinguish the two, even
when non-linear effects due to gravitational lensing are included. Due to this
ambiguity, microwave background experiments alone may not determine the matter
density or Hubble constant very precisely. We further show that degeneracy may
remain even after considering classical cosmological tests and measurements of
large scale structure.Comment: 6 pages, Latex, 4 postscript figures; revised analysis to include
gravitational lensin
The Structure of Structure Formation Theories
We study the general structure of models for structure formation, with
applications to the reverse engineering of the model from observations. Through
a careful accounting of the degrees of freedom in covariant gravitational
instability theory, we show that the evolution of structure is completely
specified by the stress history of the dark sector. The study of smooth,
entropic, sonic, scalar anisotropic, vector anisotropic, and tensor anisotropic
stresses reveals the origin, robustness, and uniqueness of specific model
phenomenology. We construct useful and illustrative analytic solutions that
cover cases with multiple species of differing equations of state relevant to
the current generation of models, especially those with effectively smooth
components. We present a simple case study of models with phenomenologies
similar to that of a LambdaCDM model to highlight reverse-engineering issues. A
critical-density universe dominated by a single type of dark matter with the
appropriate stress history can mimic a LambdaCDM model exactly.Comment: 31 pages, 18 figures, RevTeX, submitted to Phys. Rev.
Multiple Merging Events in the Double Cluster A3128/A3125
Multi-fiber spectroscopy has been obtained for 335 galaxies in the field of
the double cluster A3128/A3125, using the 2dF multi-fiber positioner on the
AAT. A total of 532 objects in the double cluster now have known redshifts. We
have also obtained a 20 ks Chandra ACIS-I image of A3128 and radio imaging with
the MOST and the ATCA. The spatial-kinematic distribution of redshifts in the
field of A3128/A3125, when combined with the Chandra image of A3128, reveals a
variety of substructures present in the galaxy distribution and in the hot ICM.
The most striking large-scale feature in the galaxy distribution is an
underpopulated redshift zone ~4000 km/s on either side of the cluster velocity
at ~17500 km/s. We attribute this depletion zone to the effect of the extensive
Horologium-Reticulum Supercluster (HRS), within which A3128/A3125 is embedded.
In addition, numerous smaller groups of galaxies are identified, particularly
in the underpopulated region within +-4000 km/s of the cluster redshift. Due to
the large gravitational influence of the HRS, these groups arrive at A3128 with
a very high (hypersonic) infall velocity. Two of these groups appear as
elongated filaments in position-velocity diagrams, indicating that they are
tidally distended groups which have been disrupted after a close passage
through A3128. We have identified a primary NE-SW merger axis connecting A3128
with A3125, along which the filaments are also oriented. In addition, the
Chandra image reveals that the X-ray emission is split into two components,
each with very small core radii, that are separated by ~1 Mpc along the NE-SW
axis. We propose that the complex X-ray morphology is likely the result of the
hypersonic infall of a relatively small group into A3128. The group produces a
major disruption in the ICM due to its high infall velocity.Comment: 52 pages, 27 figures, accepted for publication in the Astronomical
Journal. A more easily down-loaded version with full resolution figures is
available at http://www.physics.unc.edu/~jim/a3128/LANL
UBVRI Light Curves of 44 Type Ia Supernovae
We present UBVRI photometry of 44 type-Ia supernovae (SN Ia) observed from
1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The
data set comprises 2190 observations and is the largest homogeneously observed
and reduced sample of SN Ia to date, nearly doubling the number of
well-observed, nearby SN Ia with published multicolor CCD light curves. The
large sample of U-band photometry is a unique addition, with important
connections to SN Ia observed at high redshift. The decline rate of SN Ia
U-band light curves correlates well with the decline rate in other bands, as
does the U-B color at maximum light. However, the U-band peak magnitudes show
an increased dispersion relative to other bands even after accounting for
extinction and decline rate, amounting to an additional ~40% intrinsic scatter
compared to B-band.Comment: 84 authors, 71 pages, 51 tables, 10 figures. Accepted for publication
in the Astronomical Journal. Version with high-res figures and electronic
data at http://astron.berkeley.edu/~saurabh/cfa2snIa
CMB-S4 Science Book, First Edition
This book lays out the scientific goals to be addressed by the
next-generation ground-based cosmic microwave background experiment, CMB-S4,
envisioned to consist of dedicated telescopes at the South Pole, the high
Chilean Atacama plateau and possibly a northern hemisphere site, all equipped
with new superconducting cameras. CMB-S4 will dramatically advance cosmological
studies by crossing critical thresholds in the search for the B-mode
polarization signature of primordial gravitational waves, in the determination
of the number and masses of the neutrinos, in the search for evidence of new
light relics, in constraining the nature of dark energy, and in testing general
relativity on large scales
Estimating population parameters of longsnout seahorses, Hippocampus reidi (Teleostei: Syngnathidae) through mark-recapture
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