460 research outputs found
Power Spectrum Estimation from Peculiar Velocity Catalogues
The peculiar velocities of galaxies are an inherently valuable cosmological
probe, providing an unbiased estimate of the distribution of matter on scales
much larger than the depth of the survey. Much research interest has been
motivated by the high dipole moment of our local peculiar velocity field, which
suggests a large scale excess in the matter power spectrum, and can appear to
be in some tension with the LCDM model. We use a composite catalogue of 4,537
peculiar velocity measurements with a characteristic depth of 33 h-1 Mpc to
estimate the matter power spectrum. We compare the constraints with this
method, directly studying the full peculiar velocity catalogue, to results from
Macaulay et al. (2011), studying minimum variance moments of the velocity
field, as calculated by Watkins, Feldman & Hudson (2009) and Feldman, Watkins &
Hudson (2010). We find good agreement with the LCDM model on scales of k > 0.01
h Mpc-1. We find an excess of power on scales of k < 0.01 h Mpc-1, although
with a 1 sigma uncertainty which includes the LCDM model. We find that the
uncertainty in the excess at these scales is larger than an alternative result
studying only moments of the velocity field, which is due to the minimum
variance weights used to calculate the moments. At small scales, we are able to
clearly discriminate between linear and nonlinear clustering in simulated
peculiar velocity catalogues, and find some evidence (although less clear) for
linear clustering in the real peculiar velocity data.Comment: 10 pages, 13 figures, updated to match version accepted by MNRA
Challenges to the provision of diabetes care in first nations communities: results from a national survey of healthcare providers in Canada
<p>Abstract</p> <p>Background</p> <p>Aboriginal peoples globally, and First Nations peoples in Canada particularly, suffer from high rates of type 2 diabetes and related complications compared with the general population. Research into the unique barriers faced by healthcare providers working in on-reserve First Nations communities is essential for developing effective quality improvement strategies.</p> <p>Methods</p> <p>In Phase I of this two-phased study, semi-structured interviews and focus groups were held with 24 healthcare providers in the Sioux Lookout Zone in north-western Ontario. A follow-up survey was conducted in Phase II as part of a larger project, the Canadian First Nations Diabetes Clinical Management and Epidemiologic (CIRCLE) study. The survey was completed with 244 healthcare providers in 19 First Nations communities in 7 Canadian provinces, representing three isolation levels (isolated, semi-isolated, non-isolated). Interviews, focus groups and survey questions all related to barriers to providing optimal diabetes care in First Nations communities.</p> <p>Results</p> <p>the key factors emerging from interviews and focus group discussions were at the patient, provider, and systemic level. Survey results indicated that, across three isolation levels, healthcare providers' perceived patient factors as having the largest impact on diabetes care. However, physicians and nurses were more likely to rank patient factors as having a large impact on care than community health representatives (CHRs) and physicians were significantly less likely to rank patient-provider communication as having a large impact than CHRs.</p> <p>Conclusions</p> <p>Addressing patient factors was considered the highest impact strategy for improving diabetes care. While this may reflect "patient blaming," it also suggests that self-management strategies may be well-suited for this context. Program planning should focus on training programs for CHRs, who provide a unique link between patients and clinical services. Research incorporating patient perspectives is needed to complete this picture and inform quality improvement initiatives.</p
Resolving the ancestry of Austronesian-speaking populations
There are two very different interpretations of the prehistory of Island Southeast Asia (ISEA), with genetic evidence invoked in support of both. The “out-of-Taiwan” model proposes a major Late Holocene expansion of Neolithic Austronesian speakers from Taiwan. An alternative, proposing that Late Glacial/postglacial sea-level rises triggered largely autochthonous dispersals, accounts for some otherwise enigmatic genetic patterns, but fails to explain the Austronesian language dispersal. Combining mitochondrial DNA (mtDNA), Y-chromosome and genome-wide data, we performed the most comprehensive analysis of the region to date, obtaining highly consistent results across all three systems and allowing us to reconcile the models. We infer a primarily common ancestry for Taiwan/ISEA populations established before the Neolithic, but also detected clear signals of two minor Late Holocene migrations, probably representing Neolithic input from both Mainland Southeast Asia and South China, via Taiwan. This latter may therefore have mediated the Austronesian language dispersal, implying small-scale migration and language shift rather than large-scale expansion
Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow
We review modeling of astrocyte ion dynamics with a specific focus on the
implications of so-called spatial potassium buffering, where excess potassium
in the extracellular space (ECS) is transported away to prevent pathological
neural spiking. The recently introduced Kirchoff-Nernst-Planck (KNP) scheme for
modeling ion dynamics in astrocytes (and brain tissue in general) is outlined
and used to study such spatial buffering. We next describe how the ion dynamics
of astrocytes may regulate microscopic liquid flow by osmotic effects and how
such microscopic flow can be linked to whole-brain macroscopic flow. We thus
include the key elements in a putative multiscale theory with astrocytes
linking neural activity on a microscopic scale to macroscopic fluid flow.Comment: 27 pages, 7 figure
Cooperation, Norms, and Revolutions: A Unified Game-Theoretical Approach
Cooperation is of utmost importance to society as a whole, but is often
challenged by individual self-interests. While game theory has studied this
problem extensively, there is little work on interactions within and across
groups with different preferences or beliefs. Yet, people from different social
or cultural backgrounds often meet and interact. This can yield conflict, since
behavior that is considered cooperative by one population might be perceived as
non-cooperative from the viewpoint of another.
To understand the dynamics and outcome of the competitive interactions within
and between groups, we study game-dynamical replicator equations for multiple
populations with incompatible interests and different power (be this due to
different population sizes, material resources, social capital, or other
factors). These equations allow us to address various important questions: For
example, can cooperation in the prisoner's dilemma be promoted, when two
interacting groups have different preferences? Under what conditions can costly
punishment, or other mechanisms, foster the evolution of norms? When does
cooperation fail, leading to antagonistic behavior, conflict, or even
revolutions? And what incentives are needed to reach peaceful agreements
between groups with conflicting interests?
Our detailed quantitative analysis reveals a large variety of interesting
results, which are relevant for society, law and economics, and have
implications for the evolution of language and culture as well
Detected fluctuations in SDSS LRG magnitudes: Bulk flow signature or systematic?
In this paper we search for a signature of a large scale bulk flow by looking
for fluctuations in the magnitudes of distant LRGs. We take a sample of LRGs
from the Sloan Digital Sky Survey with redshifts of z>0.08 over a contiguous
area of sky. Neighboring LRG magnitudes are averaged together to find the
fluctuation in magnitudes as a function of R.A.. The result is a fluctuation of
a few percent in flux across roughly 100 degrees. The source of this
fluctuation could be from a large scale bulk flow or a systematic in our
treatment of the data set, or the data set itself. A bulk flow model is fitted
to the observed fluctuation, and the three bulk flow parameters, its direction
and magnitude: alpha_b, delta_b, v_b are constrained. We find that the bulk
flow direction is consistent with the direction found by other authors, with
alpha_b 180, delta_b -50. The bulk flow magnitude however was found to be
anomalously large with v_b>4000km/s. The LRG angular selection function cannot
be sufficiently taken into account in our analysis with the available data, and
may be the source of either the anomalous magnitude of the bulk flow signal, or
possibly the entire fluctuation. However, the fluctuation indicates a bulk flow
direction very close to those found using other data sets and analyses. Further
investigation with upcoming data is required to confirm this detection.Comment: 10 pages, 7 figures, 1 table. V2: citations added to the introduction
and a paragraph to the discussion. V3: Accepted by MNRAS. 1 figure,
additional clarifications, discussion and references adde
Work-In-Progress & Lessons Learned Lessons Learned in Using Community-Based Participatory Research to Build a National Diabetes Collaborative in Canada
The Red Sea, Coastal Landscapes, and Hominin Dispersals
This chapter provides a critical assessment of environment, landscape and resources in the Red Sea region over the past five million years in relation to archaeological evidence of hominin settlement, and of current hypotheses about the role of the region as a pathway or obstacle to population dispersals between Africa and Asia and the possible significance of coastal colonization. The discussion assesses the impact of factors such as topography and the distribution of resources on land and on the seacoast, taking account of geographical variation and changes in geology, sea levels and palaeoclimate. The merits of northern and southern routes of movement at either end of the Red Sea are compared. All the evidence indicates that there has been no land connection at the southern end since the beginning of the Pliocene period, but that short sea crossings would have been possible at lowest sea-level stands with little or no technical aids. More important than the possibilities of crossing the southern channel is the nature of the resources available in the adjacent coastal zones. There were many climatic episodes wetter than today, and during these periods water draining from the Arabian escarpment provided productive conditions for large mammals and human populations in coastal regions and eastwards into the desert. During drier episodes the coastal region would have provided important refugia both in upland areas and on the emerged shelves exposed by lowered sea level, especially in the southern sector and on both sides of the Red Sea. Marine resources may have offered an added advantage in coastal areas, but evidence for their exploitation is very limited, and their role has been over-exaggerated in hypotheses of coastal colonization
Austro-Asiatic Tribes of Northeast India Provide Hitherto Missing Genetic Link between South and Southeast Asia
Northeast India, the only region which currently forms a land bridge between the Indian subcontinent and Southeast Asia, has been proposed as an important corridor for the initial peopling of East Asia. Given that the Austro-Asiatic linguistic family is considered to be the oldest and spoken by certain tribes in India, Northeast India and entire Southeast Asia, we expect that populations of this family from Northeast India should provide the signatures of genetic link between Indian and Southeast Asian populations. In order to test this hypothesis, we analyzed mtDNA and Y-Chromosome SNP and STR data of the eight groups of the Austro-Asiatic Khasi from Northeast India and the neighboring Garo and compared with that of other relevant Asian populations. The results suggest that the Austro-Asiatic Khasi tribes of Northeast India represent a genetic continuity between the populations of South and Southeast Asia, thereby advocating that northeast India could have been a major corridor for the movement of populations from India to East/Southeast Asia
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