27,291 research outputs found
Velocity measurements for a solar active region fan loop from Hinode/EIS observations
The velocity pattern of a fan loop structure within a solar active region
over the temperature range 0.15-1.5 MK is derived using data from the EUV
Imaging Spectrometer (EIS) on board the Hinode satellite. The loop is aligned
towards the observer's line-of-sight and shows downflows (redshifts) of around
15 km/s up to a temperature of 0.8 MK, but for temperatures of 1.0 MK and above
the measured velocity shifts are consistent with no net flow. This velocity
result applies over a projected spatial distance of 9 Mm and demonstrates that
the cooler, redshifted plasma is physically disconnected from the hotter,
stationary plasma. A scenario in which the fan loops consist of at least two
groups of "strands" - one cooler and downflowing, the other hotter and
stationary -- is suggested. The cooler strands may represent a later
evolutionary stage of the hotter strands. A density diagnostic of Mg VII was
used to show that the electron density at around 0.8 MK falls from 3.2 x 10^9
cm^-3 at the loop base, to 5.0 x 10^8 cm^-3 at a projected height of 15 Mm. A
filling factor of 0.2 is found at temperatures close to the formation
temperature of Mg VII (0.8 MK), confirming that the cooler, downflowing plasma
occupies only a fraction of the apparent loop volume. The fan loop is rooted
within a so-called "outflow region" that displays low intensity and blueshifts
of up to 25 km/s in Fe XII 195.12 A (formed at 1.5 MK), in contrast to the
loop's redshifts of 15 km/s at 0.8 MK. A new technique for obtaining an
absolute wavelength calibration for the EIS instrument is presented and an
instrumental effect, possibly related to a distorted point spread function,
that affects velocity measurements is identified.Comment: 42 pages, 15 figures, submitted to Ap
Dynamic and Stagnating Plasma Flow Leading to Magnetic Flux Tube Collimation
Highly collimated, plasma-filled magnetic flux tubes are frequently observed
on galactic, stellar and laboratory scales. We propose that a single, universal
magnetohydrodynamic pumping process explains why such collimated, plasma-filled
magnetic flux tubes are ubiquitous. Experimental evidence from carefully
diagnosed laboratory simulations of astrophysical jets confirms this assertion
and is reported here. The magnetohydrodynamic process pumps plasma into a
magnetic flux tube and the stagnation of the resulting flow causes this flux
tube to become collimated.Comment: to be published in PRL; color figures on electronic versio
The Cool ISM in Elliptical Galaxies. II. Gas Content in the Volume - Limited Sample and Results from the Combined Elliptical and Lenticular Surveys
We report new observations of atomic and molecular gas in a volume limited
sample of elliptical galaxies. Combining the elliptical sample with an earlier
and similar lenticular one, we show that cool gas detection rates are very
similar among low luminosity E and SO galaxies but are much higher among
luminous S0s. Using the combined sample we revisit the correlation between cool
gas mass and blue luminosity which emerged from our lenticular survey, finding
strong support for previous claims that the molecular gas in ellipticals and
lenticulars has different origins. Unexpectedly, however, and contrary to
earlier claims, the same is not true for atomic gas. We speculate that both the
AGN feedback and merger paradigms might offer explanations for differences in
detection rates, and might also point towards an understanding of why the two
gas phases could follow different evolutionary paths in Es and S0s. Finally we
present a new and puzzling discovery concerning the global mix of atomic and
molecular gas in early type galaxies. Atomic gas comprises a greater fraction
of the cool ISM in more gas rich galaxies, a trend which can be plausibly
explained. The puzzle is that galaxies tend to cluster around
molecular-to-atomic gas mass ratios near either 0.05 or 0.5.Comment: 37 pages, including 4 tables and 12 figures. Accepted for publication
in the Astrophysical Journa
A 5 item version of the Compliance Questionnaire for Rheumatology (CQR5) successfully identifies low adherence to DMARDs
© 2013 Hughes et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedTaking DMARDs as prescribed is an essential part of self-management for patients with Rheumatoid Arthritis. To date, the Compliance Questionnaire for Rheumatology (CQR) is the only self-report adherence measure created specifically for and validated in rheumatic diseases. However, the factor structure of the CQR has not been reported and it can be considered lengthy at 19 items. The aim of this study was to test the factor structure of the CQR and reduce the number of items whilst retaining robust explanation of non-adherence to DMARDs. Such a reduction would increase the clinical utility of the scale, to identify patients with sub-optimal adherence to DMARDs in the clinic as well as for research purposes.Peer reviewe
Simulations of Metal Enrichment in Galaxy Clusters by AGN Outflows
We assess the importance of AGN outflows with respect to the metal enrichment
of the intracluster medium (ICM) in galaxy clusters. We use combined N-body and
hydrodynamic simulations, along with a semi-numerical galaxy formation and
evolution model. Using assumptions based on observations, we attribute outflows
of metal-rich gas initiated by AGN activity to a certain fraction of our model
galaxies. The gas is added to the model ICM, where the evolution of the
metallicity distribution is calculated by the hydrodynamic simulations. For the
parameters describing the AGN content of clusters and their outflow properties,
we use the observationally most favorable values. We find that AGNs have the
potential to contribute significantly to the metal content of the ICM or even
explain the complete abundance, which is typically ~0.5 Z_sun in core regions.
Furthermore, the metals end up being inhomogeneously distributed, in accordance
with observations.Comment: 7 pages, 6 figures, accepted for publication in A&
GREAT: the SOFIA high-frequency heterodyne instrument
We describe the design and construction of GREAT, the German REceiver for
Astronomy at Terahertz frequencies operated on the Stratospheric Observatory
for Infrared Astronomy (SOFIA). GREAT is a modular dual-color heterodyne
instrument for highresolution far-infrared (FIR) spectroscopy. Selected for
SOFIA's Early Science demonstration, the instrument has successfully performed
three Short and more than a dozen Basic Science flights since first light was
recorded on its April 1, 2011 commissioning flight.
We report on the in-flight performance and operation of the receiver that -
in various flight configurations, with three different detector channels -
observed in several science-defined frequency windows between 1.25 and 2.5 THz.
The receiver optics was verified to be diffraction-limited as designed, with
nominal efficiencies; receiver sensitivities are state-of-the-art, with
excellent system stability. The modular design allows for the continuous
integration of latest technologies; we briefly discuss additional channels
under development and ongoing improvements for Cycle 1 observations.
GREAT is a principal investigator instrument, developed by a consortium of
four German research institutes, available to the SOFIA users on a
collaborative basis
Structure and Magnetic Fields in the Precessing Jet System SS 433 II. Intrinsic Brightness of the Jets
Deep Very Large Array imaging of the binary X-ray source SS 433, sometimes
classified as a microquasar, has been used to study the intrinsic brightness
distribution and evolution of its radio jets. The intrinsic brightness of the
jets as a function of age at emission of the jet material tau is recovered by
removal of the Doppler boosting and projection effects. We find that
intrinsically the two jets are remarkably similar when compared for equal tau,
and that they are best described by Doppler boosting of the form D^{2+alpha},
as expected for continuous jets. The intrinsic brightnesses of the jets as
functions of age behave in complex ways. In the age range 60 < tau < 150 days,
the jet decays are best represented by exponential functions of tau, but linear
or power law functions are not statistically excluded. This is followed by a
region out to tau ~ 250 days during which the intrinsic brightness is
essentially constant. At later times the jet decay can be fit roughly as
exponential or power law functions of tau.Comment: 30 Pages, 11 Figures, Submitted to Ap
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