6,069 research outputs found
The near-infrared morphology of ultraluminous infrared galaxies
Near-infrared images at 1.25 μm, 1.65 μm, and 2.2 μm have been obtained of nine galaxies from the IRAS Bright Galaxy Sample with infrared luminosities L_(IR) ≥ 10^(12) L_☉. Two of the 2.2 μm images reveal previously undetected double nuclei, increasing the number of close double nuclei known for this sample from two to four. For three of these four sources, the colors of both nuclei are substantially different from those of normal spiral galaxies, indicating that the high activity state in high-luminosity mergers tends to occur in both nuclei. Three sources show 2.2 μm emission that is more centrally concentrated than the emission at 1.3 μm, a result that can be explained as the effects of dust emission and/or extinction or, alternatively, as the result of direct emission at 2.2 μm from the accretion disk of a central active galactic nucleus. Implications of these results for the model that galaxy collisions lead to quasar formation are briefly discussed. Finally, from the frequency and separation of the double nucleus sources, the lifetime of the ultraluminous phase of galaxies is estimated to be ~ 4 x 10^8 yr
The ArgoNeuT Detector in the NuMI Low-Energy beam line at Fermilab
The ArgoNeuT liquid argon time projection chamber has collected thousands of
neutrino and antineutrino events during an extended run period in the NuMI
beam-line at Fermilab. This paper focuses on the main aspects of the detector
layout and related technical features, including the cryogenic equipment, time
projection chamber, read-out electronics, and off-line data treatment. The
detector commissioning phase, physics run, and first neutrino event displays
are also reported. The characterization of the main working parameters of the
detector during data-taking, the ionization electron drift velocity and
lifetime in liquid argon, as obtained from through-going muon data complete the
present report.Comment: 43 pages, 27 figures, 5 tables - update referenc
How the weather affects the pain of citizen scientists using a smartphone app
Patients with chronic pain commonly believe their pain is related to the weather. Scientific evidence to support their beliefs is inconclusive, in part due to difficulties in getting a large dataset of patients frequently recording their pain symptoms during a variety of weather conditions. Smartphones allow the opportunity to collect data to overcome these difficulties. Our study Cloudy with a Chance of Pain analysed daily data from 2658 patients collected over a 15-month period. The analysis demonstrated significant yet modest relationships between pain and relative humidity, pressure and wind speed, with correlations remaining even when accounting for mood and physical activity. This research highlights how citizen-science experiments can collect large datasets on real-world populations to address long-standing health questions. These results will act as a starting point for a future system for patients to better manage their health through pain forecasts
Effects of noise on convergent game learning dynamics
We study stochastic effects on the lagging anchor dynamics, a reinforcement
learning algorithm used to learn successful strategies in iterated games, which
is known to converge to Nash points in the absence of noise. The dynamics is
stochastic when players only have limited information about their opponents'
strategic propensities. The effects of this noise are studied analytically in
the case where it is small but finite, and we show that the statistics and
correlation properties of fluctuations can be computed to a high accuracy. We
find that the system can exhibit quasicycles, driven by intrinsic noise. If
players are asymmetric and use different parameters for their learning, a net
payoff advantage can be achieved due to these stochastic oscillations around
the deterministic equilibrium.Comment: 17 pages, 8 figure
Validity and reliability of a novel 3D scanner for assessment of the shape and volume of amputees’ residual limb models
Objective assessment methods to monitor residual limb volume following lower-limb amputation are required to enhance practitioner-led prosthetic fitting. Computer aided systems, including 3D scanners, present numerous advantages and the recent Artec Eva scanner, based on laser free technology, could potentially be an effective solution for monitoring residual limb volumes.
The aim of this study was to assess the validity and reliability of the Artec Eva scanner (practical measurement) against a high precision laser 3D scanner (criterion measurement) for the determination of residual limb model shape and volume. Three observers completed three repeat assessments of ten residual limb models, using both the scanners. Validity of the Artec Eva scanner was assessed (mean percentage error <2%) and Bland-Altman statistics were adopted to assess the agreement between the two scanners. Intra and inter-rater reliability (repeatability coefficient <5%) of the Artec Eva scanner was calculated for measuring indices of residual limb model volume and shape (i.e. residual limb cross sectional areas and perimeters). Residual limb model volumes ranged from 885 to 4399 ml. Mean percentage error of the Artec Eva scanner (validity) was 1.4% of the criterion volumes. Correlation coefficients between the Artec Eva and the Romer determined variables were higher than 0.9. Volume intra-rater and inter-rater reliability coefficients were 0.5% and 0.7%, respectively. Shape percentage maximal error was 2% at the distal end of the residual limb, with intra-rater reliability coefficients presenting the lowest errors (0.2%), both for cross sectional areas and perimeters of the residual limb models.
The Artec Eva scanner is a valid and reliable method for assessing residual limb model shapes and volumes. While the method needs to be tested on human residual limbs and the results compared with the current system used in clinical practice, it has the potential to quantify shape and volume fluctuations with greater resolution
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The XMM-Newton Wide field survey in the COSMOS field: redshift evolution of AGN bias and subdominant role of mergers in triggering moderate luminosity AGN at redshift up to 2.2
We present a study of the redshift evolution of the projected correlation
function of 593 X-ray selected AGN with I_AB<23 and spectroscopic redshifts
z<4, extracted from the 0.5-2 keV X-ray mosaic of the 2.13 deg^2 XMM-COSMOS
survey. We introduce a method to estimate the average bias of the AGN sample
and the mass of AGN hosting halos, solving the sample variance using the halo
model and taking into account the growth of the structure over time. We find
evidence of a redshift evolution of the bias factor for the total population of
XMM-COSMOS AGN from b(z=0.92)=2.30 +/- 0.11 to b(z=1.94)=4.37 +/- 0.27 with an
average mass of the hosting DM halos logM [h^-1 M_sun] ~ 13.12 +/- 0.12 that
remains constant at all z < 2. Splitting our sample into broad optical lines
AGN (BL), AGN without broad optical lines (NL) and X-ray unobscured and
obscured AGN, we observe an increase of the bias with redshift in the range
z=0.7-2.25 and z=0.6-1.5 which corresponds to a constant halo mass logM [h^-1
M_sun] ~ 13.28 +/- 0.07 and logM [h^-1 M_sun] ~ 13.00 +/- 0.06 for BL /X-ray
unobscured AGN and NL/X-ray obscured AGN, respectively. The theoretical models
which assume a quasar phase triggered by major mergers can not reproduce the
high bias factors and DM halo masses found for X-ray selected BL AGN with L_BOL
~ 2e45 erg s^-1. Our work extends up to z ~ 2.2 the z <= 1 statement that, for
moderate luminosity X-ray selected BL AGN, the contribution from major mergers
is outnumbered by other processes, possibly secular such as tidal disruptions
or disk instabilities.Comment: 16 emulateapj pages, 18 figures and 3 tables. Accepted for the
publication in The Astrophysical Journa
Measurement of the Ds Lifetime
We report the results of a precise measurement of the Ds meson lifetime based
on 1662 +/- 56 fully reconstructed Ds -> phi pi decays, from the charm
hadroproduction experiment E791 at Fermilab. Using an unbinned maximum
likelihood fit, we measure the Ds lifetime to be 0.518 +/- 0.014 +/- 0.007 ps.
The ratio of the measured Ds lifetime to the world average D0 lifetime is 1.25
+/- 0.04. This result differs from unity by six standard deviations, indicating
significantly different lifetimes for the Ds and the D0.Comment: 12 pages, 3 figures, 2 table. LaTe
The status of GEO 600
The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode
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