717 research outputs found
Can Meso-Level Simulation Increase Medical Students' Confidence in recognising and Responding to Clinical Deterioration in Adult Hospital Patients?
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Preordering saddle-point systems for sparse LDLT factorization without pivoting
This paper focuses on efficiently solving large sparse symmetric indefinite systems of linear equations in saddleâpoint form using a fillâreducing ordering technique with a direct solver. Row and column permutations partition the saddleâpoint matrix into a block structure constituting a priori pivots of order 1 and 2. The partitioned matrix is compressed by treating each nonzero block as a single entry, and a fillâreducing ordering is applied to the corresponding compressed graph. It is shown that, provided the saddleâpoint matrix satisfies certain criteria, a block LDLT factorization can be computed using the resulting pivot sequence without modification. Numerical results for a range of problems from practical applications using a modern sparse direct solver are presented to illustrate the effectiveness of the approach
Long term improvements in activities of daily living in patients with hemispatial neglect
No abstract available
Towards fully covariant machine learning
Any representation of data involves arbitrary investigator choices. Because
those choices are external to the data-generating process, each choice leads to
an exact symmetry, corresponding to the group of transformations that takes one
possible representation to another. These are the passive symmetries; they
include coordinate freedom, gauge symmetry, and units covariance, all of which
have led to important results in physics. In machine learning, the most visible
passive symmetry is the relabeling or permutation symmetry of graphs. Our goal
is to understand the implications for machine learning of the many passive
symmetries in play. We discuss dos and don'ts for machine learning practice if
passive symmetries are to be respected. We discuss links to causal modeling,
and argue that the implementation of passive symmetries is particularly
valuable when the goal of the learning problem is to generalize out of sample.
This paper is conceptual: It translates among the languages of physics,
mathematics, and machine-learning. We believe that consideration and
implementation of passive symmetries might help machine learning in the same
ways that it transformed physics in the twentieth century.Comment: substantial revision from v1; submitted to TML
The influence of topography on steady currents and internal waves,
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1971.Bibliography: leaves 134-136.by Nelson G. Hogg.Ph.D
Polarized Radio Sources: A Study of Luminosity, Redshift and Infrared Colors
The Dominion Radio Astrophysical Observatory Deep Field polarization study
has been matched with the Spitzer Wide-Area Infrared Extragalactic survey of
the European Large Area Infrared Space Observatory Survey North 1 field. We
have used VLA observations with a total intensity rms of 87 microJy beam^-1 to
match SWIRE counterparts to the radio sources. Infrared color analysis of our
radio sample shows that the majority of polarized sources are elliptical
galaxies with an embedded active galactic nucleus. Using available redshift
catalogs, we found 429 radio sources of which 69 are polarized with redshifts
in the range of 0.04 < z <3.2. We find no correlation between redshift and
percentage polarization for our sample. However, for polarized radio sources,
we find a weak correlation between increasing percentage polarization and
decreasing luminosity.Comment: 35 pages, 12 figures, accepted for publication in The Astrophysical
Journa
Decline of an Ecotone Forest: 50 Years of Demography in the Southern Boreal Forest
Variation in tree recruitment, mortality, and growth can alter forest community composition and structure. Because tree recruitment and mortality events are generally infrequent, longâtime scales are needed to confirm trends in forests. We performed a 50âyr demographic census of a forest plot located on the southern edge of the Canadian boreal forest, a region currently experiencing forest dieâback in response to direct and indirect effects of recent severe droughts. Here, we show that over the last 30 yr biomass, basal area, growth, and recruitment have decreased along with a precipitous rise in mortality across the dominant tree species. The stand experienced periods of drought in combination with multiple outbreaks of forest tent caterpillar (Malacosoma disstria) and bark beetles. These insect disturbances interacted to increase mortality rates within the stand and decrease stand density. The interaction of endogenous and exogenous factors may shift forests in this region onto novel successional trajectories with the possibility of changes in regional vegetation type
Preparing Red-Green-Blue (RGB) Images from CCD Data
We present a new, and we believe arguably correct, algorithm for producing
Red-Green-Blue (RBG) composites from 3-band astronomical images. Our method
ensures that an object with a specified astronomical color (e.g. g-r and r-i)
has a unique color in the RGB image, as opposed to the burnt-out white stars to
which we are accustomed. A natural consequence of this is that we can use the
same colors to code color-magnitude diagrams, providing a natural `index' to
our images. We also introduce the use of an asinh stretch, which allows us to
show faint objects while simultaneously preserving the structure of brighter
objects in the field, such as the spiral arms of large galaxies. We believe
that, in addition to their aesthetic value, our images convey far more
information than do the traditional ones, and provide examples from Sloan
Digital Sky Survey (SDSS) imaging, the Hubble Deep Field (HDF), and Chandra to
support our claims. More examples are available at
http://www.astro.princeton.edu/~rhl/PrettyPicture
Sex-specific prenatal stress effects on the rat reproductive axis and adrenal gland
Social stress during pregnancy has profound effects on offspring physiology. This study examined whether an ethologically relevant social stress during late pregnancy in rats alters the reproductive axis and adrenal gland structure in post-pubertal male and female offspring. Prenatally stressed (PNS) pregnant rats (n=9) were exposed to an unfamiliar lactating rat for 10 min/day from day 16 to 20 of pregnancy inclusive, whereas control pregnant rats (n=9) remained in their home cages. Gonads, adrenal glands and blood samples were obtained from one female and one male from each litter at 11 to 12-weeks of age. Anogenital distance was measured. There was no treatment effect on body, adrenal or gonad weight at 11â12 weeks. PNS did not affect the number of primordial, secondary or tertiary ovarian follicles, numbers of corpora lutea or ovarian FSH receptor expression. There was an indication that PNS females had more primary follicles and greater ovarian aromatase expression compared with control females (both P=0.09). PNS males had longer anogenital distances (0.01Âą0.0 cm/g vs 0.008Âą0.00 cm/g; P=0.007) and higher plasma FSH concentrations (0.05 ng/mL vs 0.006 ng/mL; s.e.d.=0.023; P=0.043) compared with control males. There were no treatment effects on the number of Sertoli cells or seminiferous tubules, seminiferous tubule area, plasma testosterone concentration or testis expression of aromatase, FSH receptor or androgen receptor. PNS did not affect adrenal size. These data suggest that the developing male reproductive axis is more sensitive to maternal stress and that PNS may enhance aspects of male reproductive development
Improved delivery of cardiovascular care (IDOCC) through outreach facilitation: study protocol and implementation details of a cluster randomized controlled trial in primary care
Abstract
Background
There is a need to find innovative approaches for translating best practices for chronic disease care into daily primary care practice routines. Primary care plays a crucial role in the prevention and management of cardiovascular disease. There is, however, a substantive care gap, and many challenges exist in implementing evidence-based care. The Improved Delivery of Cardiovascular Care (IDOCC) project is a pragmatic trial designed to improve the delivery of evidence-based care for the prevention and management of cardiovascular disease in primary care practices using practice outreach facilitation.
Methods
The IDOCC project is a stepped-wedge cluster randomized control trial in which Practice Outreach Facilitators work with primary care practices to improve cardiovascular disease prevention and management for patients at highest risk. Primary care practices in a large health region in Eastern Ontario, Canada, were eligible to participate. The intervention consists of regular monthly meetings with the Practice Outreach Facilitator over a one- to two-year period. Starting with audit and feedback, consensus building, and goal setting, the practices are supported in changing practice behavior by incorporating chronic care model elements. These elements include (a) evidence-based decision support for providers, (b) delivery system redesign for practices, (c) enhanced self-management support tools provided to practices to help them engage patients, and (d) increased community resource linkages for practices to enhance referral of patients. The primary outcome is a composite score measured at the level of the patient to represent each practice's adherence to evidence-based guidelines for cardiovascular care. Qualitative analysis of the Practice Outreach Facilitators' written narratives of their ongoing practice interactions will be done. These textual analyses will add further insight into understanding critical factors impacting project implementation.
Discussion
This pragmatic, stepped-wedge randomized controlled trial with both quantitative and process evaluations demonstrates innovative methods of implementing large-scale quality improvement and evidence-based approaches to care delivery. This is the first Canadian study to examine the impact of a large-scale multifaceted cardiovascular quality-improvement program in primary care. It is anticipated that through the evaluation of IDOCC, we will demonstrate an effective, practical, and sustainable means of improving the cardiovascular health of patients across Canada.
Trial Registration
ClinicalTrials.gov: NCT0057480
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