686 research outputs found
Patients with Diabetes and Significant Epicardial Coronary Artery Disease have Increased Systolic Left Ventricular Apical Rotation and Rotation Rate at Rest
Objective
The purpose of this study was to determine whether resting myocardial deformation and rotation may be altered in diabetic patients with significant epicardial coronary artery disease (CAD) with normal left ventricular ejection fraction.
Design
A prospective observational study.
Setting
Diagnosis of epicardial CAD in patients with diabetes.
Patients and Methods
Eighty-four patients with diabetes suspected of epicardial CAD scheduled for cardiac catheterization had a resting echocardiogram performed prior to their procedure. Echocardiographic measurements were compared between patients with and without significant epicardial CAD as determined by cardiac catheterization.
Main Outcome Measures
Measurement of longitudinal strain, strain rate, apical rotation, and rotation rate, using speckle tracking echocardiography.
Results
Eighty-four patients were studied, 39 (46.4%) of whom had significant epicardial CAD. Global peak systolic apical rotation was significantly increased (14.9 ± 5.1 vs. 11.0 ± 4.8 degrees, P < 0.001) in patients with epicardial CAD along with faster peak systolic apical rotation rate (90.4 ± 29 vs. 68.1 ± 22.2 degrees/sec, P < 0.001). These findings were further confirmed through multivariate logistic regression analysis (global peak systolic apical rotation OR = 1.17, P = 0.004 and peak systolic apical rotation rate OR = 1.05, P < 0.001).
Conclusions
Patients with diabetes with significant epicardial CAD and normal LVEF exhibit an increase in peak systolic apical counterclockwise rotation and rotation rate detected by echocardiography, suggesting that significant epicardial CAD and its associated myocardial effects in patients with diabetes may be detected noninvasively at rest
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Experimental design for three interrelated marine ice sheet and ocean model intercomparison projects: MISMIP v. 3 (MISMIP +), ISOMIP v. 2 (ISOMIP +) and MISOMIP v. 1 (MISOMIP1)
Coupled ice sheet–ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of marine ice sheets and tidewater glaciers, from process studies to future projections of ice mass loss and sea level rise. The Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP) is a community effort aimed at designing and coordinating a series of model intercomparison projects (MIPs) for model evaluation in idealized setups, model verification based on observations, and future projections for key regions of the West Antarctic Ice Sheet (WAIS).
Here we describe computational experiments constituting three interrelated MIPs for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities. These consist of ice sheet experiments under the Marine Ice Sheet MIP third phase (MISMIP+), ocean experiments under the Ice Shelf-Ocean MIP second phase (ISOMIP+) and coupled ice sheet–ocean experiments under the MISOMIP first phase (MISOMIP1). All three MIPs use a shared domain with idealized bedrock topography and forcing, allowing the coupled simulations (MISOMIP1) to be compared directly to the individual component simulations (MISMIP+ and ISOMIP+). The experiments, which have qualitative similarities to Pine Island Glacier Ice Shelf and the adjacent region of the Amundsen Sea, are designed to explore the effects of changes in ocean conditions, specifically the temperature at depth, on basal melting and ice dynamics. In future work, differences between model results will form the basis for the evaluation of the participating models
The non‐local impacts of Antarctic subglacial runoff
Little is known about Antarctic subglacial hydrology, but based on modeling, theory and indirect observations it is thought that subglacial runoff enhances submarine melt locally through buoyancy effects. However, no studies to date have examined effects of runoff on sea ice and oceanography on the continental shelf. Here we use modeled and observational estimates of runoff to force a regional model of the Amundsen Sea Embayment. We find that runoff enhances melt locally (i.e. within the ice-shelf cavity), increasing melt at Thwaites ice shelf by up to 15 Gt/a given estimates of steady runoff, and up to 25 Gt/a if runoff is episodic as remote sensing measurements suggest. However runoff also has smaller non-local effects on melt through freshwater influence on flow and stratification. We further find that runoff reduces summer sea-ice volume over the continental shelf (by up to 10% with steady runoff but over 30% with episodic runoff). Furthermore runoff is much more effective at reducing sea ice than an equivalent volume of ice-shelf meltwater — due in part to the latent heat loss associated with submarine melting. Results suggest that runoff may play an important role in continental shelf dynamics, despite runoff flux being small relative to ice-shelf melting — and that runoff-driven melt and circulation may be an important process missing from regional Antarctic ocean models
A new era of wide-field submillimetre imaging: on-sky performance of SCUBA-2
SCUBA-2 is the largest submillimetre wide-field bolometric camera ever built.
This 43 square arc-minute field-of-view instrument operates at two wavelengths
(850 and 450 microns) and has been installed on the James Clerk Maxwell
Telescope on Mauna Kea, Hawaii. SCUBA-2 has been successfully commissioned and
operational for general science since October 2011. This paper presents an
overview of the on-sky performance of the instrument during and since
commissioning in mid-2011. The on-sky noise characteristics and NEPs of the 450
and 850 micron arrays, with average yields of approximately 3400 bolometers at
each wavelength, will be shown. The observing modes of the instrument and the
on-sky calibration techniques are described. The culmination of these efforts
has resulted in a scientifically powerful mapping camera with sensitivities
that allow a square degree of sky to be mapped to 10 mJy/beam rms at 850 micron
in 2 hours and 60 mJy/beam rms at 450 micron in 5 hours in the best weather.Comment: 18 pages, 15 figures.SPIE Conference series 8452, Millimetre,
Submillimetre and Far-infrared Detectors and Instrumentation for Astronomy VI
201
The HST Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant
Since the launch of the Hubble Space Telescope nine years ago, Cepheid
distances to 25 galaxies have been determined for the purpose of calibrating
secondary distance indicators. A variety of these can now be calibrated, and
the accompanying papers by Sakai, Kelson, Ferrarese, and Gibson employ the full
set of 25 galaxies to consider the Tully-Fisher relation, the fundamental plane
of elliptical galaxies, Type Ia supernovae, and surface brightness
fluctuations.
When calibrated with Cepheid distances, each of these methods yields a
measurement of the Hubble constant and a corresponding measurement uncertainty.
We combine these measurements in this paper, together with a model of the
velocity field, to yield the best available estimate of the value of H_0 within
the range of these secondary distance indicators and its uncertainty.
The result is H_0 = 71 +/- 6 km/sec/Mpc. The largest contributor to the
uncertainty of this 67% confidence level result is the distance of the Large
Magellanic Cloud, which has been assumed to be 50 +/- 3 kpc
A Wide-Field Study of the z~0.8 Cluster RX J0152.7-1357: the Role of Environment in the Formation of the Red-Sequence
[ABRIDGED] We present the first results from the largest spectroscopic survey
to date of an intermediate redshift galaxy cluster, the z=0.834 cluster RX
J0152.7-1357. We use the colors of galaxies, assembled from a D~12 Mpc region
centered on the cluster, to investigate the properties of the red-sequence as a
function of density and clustercentric radius. Our wide-field multi-slit survey
with a low-dispersion prism in the IMACS spectrograph at Magellan allowed us to
identify 475 new members of the cluster and its surrounding large scale
structure with a redshift accuracy of dz/(1+z)~1% and a contamination rate of
~2% for galaxies with i<23.75 mag. We combine these new members with the 279
previously known spectroscopic members to give a total of 754 galaxies from
which we obtain a mass-limited sample of 300 galaxies with stellar masses
M>4x10^{10} M_sun. We find that the red galaxy fraction is 93+/-3% in the two
merging cores of the cluster and declines to a level of 64+/-3% at projected
clustercentric radii R>~3 Mpc. At these large projected distances, the
correlation between clustercentric radius and local density is nonexistent.
This allows an assessment of the influence of the local environment on galaxy
evolution, as opposed to mechanisms that operate on cluster scales. Even beyond
R>3 Mpc we find an increasing fraction of red galaxies with increasing local
density. The red fraction at the highest local densities in two groups at R>3
Mpc matches the red fraction found in the two cores. Strikingly, galaxies at
intermediate densities at R>3 Mpc, that are not group members, also show signs
of an enhanced red fraction. Our results point to such intermediate density
regions and the groups in the outskirts of the cluster, as sites where the
local environment influences the transition of galaxies onto the red-sequence.Comment: 15 pages, 10 figures, 1 table, accepted for publication in ApJ,
expanded introduction and additional references adde
The HST Key Project on the Extragalactic Distance Scale. XXII. The Discovery of Cepheids in NGC 1326-A
We report on the detection of Cepheids and the first distance measurement to
the spiral galaxy NGC 1326-A, a member of the Fornax cluster of galaxies. We
have employed data obtained with the Wide Field and Planetary Camera 2 on board
the Hubble Space Telescope. Over a 49 day interval, a total of twelve V-band
(F555W) and eight I-band (F814W) epochs of observation were obtained. Two
photometric reduction packages, ALLFRAME and DoPHOT, have been employed to
obtain photometry measures from the three Wide Field CCDs. Variability analysis
yields a total of 17 Cepheids in common with both photometry datasets, with
periods ranging between 10 and 50 days. Of these 14 Cepheids with high-quality
lightcurves are used to fit the V and I period-luminosity relations and derive
apparent distance moduli, assuming a Large Magellanic Cloud distance modulus
(m-M) (LMC) = 18.50 +- 0.10 mag and color excess E(B-V) = 0.10 mag. Assuming
A(V)/E(V-I) = 2.45, the DoPHOT data yield a true distance modulus to NGC 1326-A
of (m-M)_0 = 31.36 +- 0.17 (random) +- 0.13 (systematic) mag, corresponding to
a distance of 18.7 \pm 1.5 (random) \pm 1.2 (systematic) Mpc. The derived
distance to NGC 1326-A is in good agreement with the distance derived
previously to NGC 1365, another spiral galaxy member of the Fornax cluster.
However the distances to both galaxies are significantly lower than to NGC
1425, a third Cepheid calibrator in the outer parts of the cluster.Comment: 33 pages A gzipped tar file containing 12 figures can be obtained
from http://www.ipac.caltech.edu/H0kp/n1326a/n1326a.htm
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