10,119 research outputs found
Turning the information-sharing dial: efficient inference from different data sources
A fundamental aspect of statistics is the integration of data from different
sources. Classically, Fisher and others were focused on how to integrate
homogeneous (or only mildly heterogeneous) sets of data. More recently, as data
is becoming more accessible, the question of if data sets from different
sources should be integrated is becoming more relevant. The current literature
treats this as a question with only two answers: integrate or don't. Here we
take a different approach, motivated by information-sharing principles coming
from the shrinkage estimation literature. In particular, we deviate from the
do/don't perspective and propose a dial parameter that controls the extent to
which two data sources are integrated. How far this dial parameter should be
turned is shown to depend, for example, on the informativeness of the different
data sources as measured by Fisher information. In the context of generalized
linear models, this more nuanced data integration framework leads to relatively
simple parameter estimates and valid tests/confidence intervals. Moreover, we
demonstrate both theoretically and empirically that setting the dial parameter
according to our recommendation leads to more efficient estimation compared to
other binary data integration schemes.Comment: 35 pages, 8 figures, 4 table
Rapid Surface Lowering of Benito Glacier, Northern Patagonian Icefield
The Patagonian Icefields, which straddle the Andes below 46?S, are one of the most sensitive ice masses to climate change. However, recent mass loss from the icefields, along with its spatial and temporal variability, is not well constrained. Here we determine surface elevation changes of Benito Glacier, a 163 km2 outlet glacier draining the western flank of the North Patagonian Icefield, using a combination of field and satellite-derived elevation data acquired between 1973 and 2017. Our results demonstrate that, just below the equilibrium line, the glacier dramatically thinned by 139 m in the past 44 years, equivalent to a mean rate of 3.2 ? 0.2 m a-1. However, surface lowering was temporally variable, characterized by a hiatus between 2000 and 2013, and a subsequent increase up to 7.7 ? 3.0 m a-1 between 2013 and 2017. Analysis of Benito Glacier?s flow regime throughout the period indicates that the observed surface lowering was caused by negative surface mass balance, rather than dynamic thinning. The high rate of surface lowering observed over the past half a decade highlights the extreme sensitivity of mid-latitude glaciers to recent atmospheric forcingpublishersversionPeer reviewe
Acceptability and Feasibility of Virtual Reality to Promote Health Literacy in Primary Care from the Health Professional’s view: A Qualitative Study
ObjectiveThe development of health literacy is important in the management of chronic pain and virtual reality may be an effective medium for its development. This study aims to understand the usability and acceptability of a virtual reality-based pain education system for the facilitation of health literacy.MethodsSemi-structured interviews were conducted with health professionals who had used a VR-based pain education system within their clinical practice, to explore perceptions of feasibility. Data collection and analyses were informed by the Unified Theory of Acceptance and Use of Technology and the Integrated Model of Health Literacy.ResultsFrom 10 participants, the VR-based system was considered feasible in providing immersive experiential learning which addressed patient understanding and health-related communication.ConclusionVR appears to be perceived as an acceptable and feasible technology to support the development of health literacy in people with chronic pain. Its largest perceived benefit was its capacity to provide an immersive and entertaining alternative to conventional methods of pain education.Practice ImplicationsVirtual reality is considered as a feasible method of facilitating patient understanding and health-related communication related to chronic pain. Feasibility of such a tool relies clinically on time available, social expectations of VR, and the role of immersive and experiential learning within the management of chronic pain
Plausibility functions and exact frequentist inference
In the frequentist program, inferential methods with exact control on error
rates are a primary focus. The standard approach, however, is to rely on
asymptotic approximations, which may not be suitable. This paper presents a
general framework for the construction of exact frequentist procedures based on
plausibility functions. It is shown that the plausibility function-based tests
and confidence regions have the desired frequentist properties in finite
samples---no large-sample justification needed. An extension of the proposed
method is also given for problems involving nuisance parameters. Examples
demonstrate that the plausibility function-based method is both exact and
efficient in a wide variety of problems.Comment: 21 pages, 5 figures, 3 table
A galaxy as the source of a Civ absorption system close to the epoch of reionization
We find a bright (L_{UV}=2.5 L*_{z=6}) Lyman alpha emitter at redshift
z=5.719 at a projected distance of 79 physical kpc from a strong triply ionized
carbon (Civ) absorption system at redshift z=5.7238 previously reported in the
spectrum of the z_{em} = 6.309 QSO SDSS J1030+0524. This is the highest
redshift galaxy-absorber pair detected to-date, supporting the idea that
galaxy-wide outflows were already in place at the end of the epoch of
reionization. The proximity of this object makes it the most likely source of
metals, consistent with models of outflows at lower redshift where significant
observational evidence relates metal absorption systems with galaxies hosting
outflows.
In a typical outflow scenario, a wind of 200 km/s, active since the universe
was only 0.6 Gyr old (z ~8.4), could eject metals out to 79 kpc at z=5.719.
Although the origin of metals in the intergalactic medium (IGM) is still under
debate, our results are consistent with predictions from cosmological
simulations which reproduce the evolution of the cosmic density of Civ, from z
~ 6 to the present day based on outflow-driven enrichment of the IGM.
We also report two more Lyman alpha emitters in this field, at z=5.973\pm
0.002 and z=5.676\pm 0.002 respectively, the former confirming the original
identification by Stiavelli et al. Our results suggest that the colour cut
typically used to identify i-dropouts (i_{775}-z_{850}>1.3) misses a
non-negligible fraction of blue galaxies with faint UV continuum at z \geq 5.7.Comment: Accepted for publication in MNRAS, 9 pages, 3 figures, 1 tabl
Barchan-Parabolic Dune Pattern Transition From Vegetation Stability Threshold
Many dune fields exhibit a downwind transition from forward-pointing barchan dunes to stabilized, backward-pointing parabolic dunes, accompanied by an increase in vegetation. A recent model predicts this pattern transition occurs when dune surface erosion/deposition rates decrease below a threshold of half the vegetation growth rate. We provide a direct test using a unique data set of repeat topographic surveys across White Sands Dune Field and find strong quantitative support for the model threshold. We also show the threshold hypothesis applied to a barchan dune results naturally in its curvature inversion, as the point of threshold crossing progresses from the horns to the crest. This simple, general threshold framework can be an extremely useful tool for predicting the response of dune landscapes to changes in wind speed, sediment supply, or vegetation growth rate. Near the threshold, a small environmental change could result in a drastic change in dune pattern and activity
The HI Content of Local Late-Type Galaxies
We present a solid relationship between the neutral hydrogen (HI) disk mass
and the stellar disk mass of late-type galaxies in the local universe. This
relationship is derived by comparing the stellar disk mass function from the
Sloan Digital Sky Survey and the HI mass function from the HI Parkes All Sky
Survey (HIPASS). We find that the HI mass in late-type galaxies tightly
correlates with the stellar mass over three orders of magnitude in stellar disk
mass. We cross-check our result with that obtained from a sample of HIPASS
objects for which the stellar mass has been obtained by inner kinematics. In
addition, we derive the HI versus halo mass relationship and the dependence of
all the baryonic components in spirals on the host halo mass. These
relationships bear the imprint of the processes ruling galaxy formation, and
highlight the inefficiency of galaxies both in forming stars and in retaining
their pristine HI gas.Comment: 6 pages, 5 figures. Match to the published version. References
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