8,056 research outputs found
Maser Source Finding Methods in HOPS
The {\bf H}{\bf O} Southern Galactic {\bf P}lane {\bf S}urvey (HOPS) has
observed 100 square degrees of the Galactic plane, using the Mopra radio
telescope to search for emission from multiple spectral lines in the 12\,mm
band (19.5\,--\,27.5\,GHz). Perhaps the most important of these spectral lines
is the 22.2\,GHz water maser transition. We describe the methods used to
identify water maser candidates and subsequent confirmation of the sources. Our
methods involve a simple determination of likely candidates by searching peak
emission maps, utilising the intrinsic nature of water maser emission -
spatially unresolved and spectrally narrow-lined. We estimate completeness
limits and compare our method with results from the {\sc Duchamp} source
finder. We find that the two methods perform similarly. We conclude that the
similarity in performance is due to the intrinsic limitation of the noise
characteristics of the data. The advantages of our method are that it is
slightly more efficient in eliminating spurious detections and is simple to
implement. The disadvantage is that it is a manual method of finding sources
and so is not practical on datasets much larger than HOPS, or for datasets with
extended emission that needs to be characterised. We outline a two-stage method
for the most efficient means of finding masers, using {\sc Duchamp}.Comment: 8 pages, 1 table, 4 figures. Accepted for publication in PASA special
issue on Source Finding & Visualisatio
Broadband, radio spectro-polarimetric study of 100 radiative-mode and jet-mode AGN
We present the results from a broadband (1 to 3 GHz), spectro-polarimetry
study of the integrated emission from 100 extragalactic radio sources with the
ATCA, selected to be highly linearly polarized at 1.4 GHz. We use a general
purpose, polarization model-fitting procedure that describes the Faraday
rotation measure (RM) and intrinsic polarization structure of up to three
distinct polarized emission regions or 'RM components' of a source. Overall,
37%/52%/11% of sources are best fit by one/two/three RM components. However,
these fractions are dependent on the signal-to-noise ratio (S/N) in
polarization (more RM components more likely at higher S/N). In general, our
analysis shows that sources with high integrated degrees of polarization at 1.4
GHz have low Faraday depolarization, are typically dominated by a single RM
component, have a steep spectral index, and a high intrinsic degree of
polarization. After classifying our sample into radiative-mode and jet-mode
AGN, we find no significant difference between the Faraday rotation or Faraday
depolarization properties of jet-mode and radiative-mode AGN. However, there is
a statistically significant difference in the intrinsic degree of polarization
between the two types, with the jet-mode sources having more intrinsically
ordered magnetic field structures than the radiative-mode sources. We also find
a preferred perpendicular orientation of the intrinsic magnetic field structure
of jet-mode AGN with respect to the jet direction, while no clear preference is
found for the radiative-mode sources.Comment: 29 pages (including Appendix), 28 figures, 7 tables. Accepted for
publication in MNRA
Endothelial HO-1 induction by model TG-rich lipoproteins is regulated through a NOX4-Nrf2 pathway
Circulating levels of chylomicron remnants (CMRs) increase postprandially and their composition directly reflects dietary lipid intake. These TG-rich lipoproteins likely contribute to the development of endothelial dysfunction, albeit via unknown mechanisms. Here, we investigated how the FA composition of CMRs influences their actions on human aortic endothelial cells (HAECs) by comparing the effects of model CMRs—artificial TG-rich CMR-like particles (A-CRLPs)—containing TGs extracted from fish, DHA-rich algal, corn, or palm oils. HAECs responded with distinct transcriptional programs according to A-CRLP TG content and oxidation status, with genes involved in antioxidant defense and cytoprotection most prominently affected by n-3 PUFA-containing A-CRLPs. These particles were significantly more efficacious inducers of heme oxygenase-1 (HO-1) than n-6 PUFA corn or saturated FA-rich palm CRLPs. Mechanistically, HO-1 induction by all CRLPs requires NADPH oxidase 4, with PUFA-containing particles additionally dependent upon mitochondrial reactive oxygen species. Activation of both p38 MAPK and PPARβ/δ culminates in increased nuclear factor erythroid 2-related factor 2 (Nrf2) expression/nuclear translocation and HO-1 induction. These studies define new molecular pathways coupling endothelial cell activation by model CMRs with adaptive regulation of Nrf2-dependent HO-1 expression and may represent key mechanisms through which dietary FAs differentially impact progression of endothelial dysfunction
High-fat meals rich in EPA plus DHA compared with DHA only have differential effects on postprandial lipemia and plasma 8-isoprostane F-2 alpha concentrations relative to a control high-oleic acid meal: a randomized controlled trial
Background: Eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) supplementation has beneficial cardiovascular effects, but postprandial influences of these individual fatty acids are unclear. Objectives: The primary objective was to determine the vascular effects of EPA + DHA compared with DHA only during postprandial lipemia relative to control high–oleic acid meals; the secondary objective was to characterize the effects of linoleic acid–enriched high-fat meals relative to the control meal. Design: We conducted a randomized, controlled, double-blind crossover trial of 4 high-fat (75-g) meals containing 1) high–oleic acid sunflower oil (HOS; control), 2) HOS + fish oil (FO; 5 g EPA and DHA), 3) HOS + algal oil (AO; 5 g DHA), and 4) high–linoleic acid sunflower oil (HLS) in 16 healthy men (aged 35–70 y) with higher than optimal fasting triacylglycerol concentrations (mean ± SD triacylglycerol, 1.9 ± 0.5 mmol/L). Results: Elevations in triacylglycerol concentration relative to baseline were slightly reduced after FO and HLS compared with the HOS control (P < 0.05). The characteristic decrease from baseline in plasma nonesterified fatty acids after a mixed meal was inhibited after AO (Δ 0–3 h, P < 0.05). HLS increased the augmentation index compared with the other test meals (P < 0.05), although the digital volume pulse–reflection index was not significantly different. Plasma 8-isoprostane F(2α) analysis revealed opposing effects of FO (increased) and AO (reduced) compared with the control (P < 0.05). No differences in nitric oxide metabolites were observed. Conclusions: These data show differential postprandial 8-isoprostane F(2α) responses to high-fat meals containing EPA + DHA–rich fish oil compared with DHA-rich AO, but these differences were not associated with consistent effects on postprandial vascular function or lipemia. More detailed analyses of polyunsaturated fatty acid–derived lipid mediators are required to determine possible divergent functional effects of single meals rich in either DHA or EPA. This trial was registered at clinicaltrials.gov as NCT01618071
Interacting Large-Scale Magnetic Fields and Ionised Gas in the W50/SS433 System
The W50/SS433 system is an unusual Galactic outflow-driven object of
debatable origin. We have used the Australia Telescope Compact Array (ATCA) to
observe a new 198 pointing mosaic, covering , and
present the highest-sensitivity full-Stokes data of W50 to date using
wide-field, wide-band imaging over a 2 GHz bandwidth centred at 2.1 GHz. We
also present a complementary H mosaic created using the Isaac Newton
Telescope Photometric H Survey of the Northern Galactic Plane (IPHAS).
The magnetic structure of W50 is found to be consistent with the prevailing
hypothesis that the nebula is a reanimated shell-like supernova remnant (SNR),
that has been re-energised by the jets from SS433. We observe strong
depolarization effects that correlate with diffuse H emission, likely
due to spatially-varying Faraday rotation measure (RM) fluctuations of
to 61 rad m on scales to 6 pc. We also report the discovery of
numerous, faint, H filaments that are unambiguously associated with the
central region of W50. These thin filaments are suggestive of a SNR's shock
emission, and almost all have a radio counterpart. Furthermore, an RM-gradient
is detected across the central region of W50, which we interpret as a loop
magnetic field with a symmetry axis offset by to the
east-west jet-alignment axis, and implying that the evolutionary processes of
both the jets and the SNR must be coupled. A separate RM-gradient is associated
with the termination shock in the Eastern ear, which we interpret as a
ring-like field located where the shock of the jet interacts with the
circumstellar medium. Future optical observations will be able to use the new
H filaments to probe the kinematics of the shell of W50, potentially
allowing for a definitive experiment on W50's formation history.Comment: Submitted to MNRA
National Evaluation of the Capacity Building Programme in English Local Government: Evaluation of the National Programmes: Annex 2: Evaluation of the National Programmes
The report is one of a series of outputs from the national evaluation of the CBP, being undertaken by a team of researchers at the Policy Research Institute (PRI) at Leeds Metropolitan University and the Cities Research Unit at the University of West of England. The Capacity Building Programme for local government was launched in 2003 as a joint Department for Communities and Local Government (DCLG) / Local Government Association (LGA) initiative to support capacity building and improvement activities within local authorities in England. The evaluation of the Capacity Building Programme has been underway since late 2004. A scoping phase was conducted until May 2005, including a short evaluation of the Pilot Programmes. The main phase of the evaluation commenced in September 2005 and encompassed four main phases (see Section 1.3: p10)
A radio-polarisation and rotation measure study of the Gum Nebula and its environment
The Gum Nebula is 36 degree wide shell-like emission nebula at a distance of
only 450 pc. It has been hypothesised to be an old supernova remnant, fossil
HII region, wind-blown bubble, or combination of multiple objects. Here we
investigate the magneto-ionic properties of the nebula using data from recent
surveys: radio-continuum data from the NRAO VLA and S-band Parkes All Sky
Surveys, and H-alpha data from the Southern H-Alpha Sky Survey Atlas. We model
the upper part of the nebula as a spherical shell of ionised gas expanding into
the ambient medium. We perform a maximum-likelihood Markov chain Monte-Carlo
fit to the NVSS rotation measure data, using the H-halpha data to constrain
average electron density in the shell . Assuming a latitudinal background
gradient in RM we find , angular radius
, shell thickness
, ambient magnetic field strength
and warm gas filling factor
. We constrain the local, small-scale (~260 pc)
pitch-angle of the ordered Galactic magnetic field to
, which represents a significant
deviation from the median field orientation on kiloparsec scales
(~-7.2). The moderate compression factor X=6.0\,^{+5.1}_{-2.5} at
the edge of the H-alpha shell implies that the 'old supernova remnant' origin
is unlikely. Our results support a model of the nebula as a HII region around a
wind-blown bubble. Analysis of depolarisation in 2.3 GHz S-PASS data is
consistent with this hypothesis and our best-fitting values agree well with
previous studies of interstellar bubbles.Comment: 33 pages, 16 figures. Accepted by The Astrophysical Journa
63 Use of tigecycline to treat difficult respiratory pathogens in cystic fibrosis – early experiences
S-band Polarization All Sky Survey (S-PASS): survey description and maps
We present the S-Band Polarization All Sky Survey (S-PASS), a survey of
polarized radio emission over the southern sky at Dec~ taken with
the Parkes radio telescope at 2.3~GHz. The main aim was to observe at a
frequency high enough to avoid strong depolarization at intermediate Galactic
latitudes (still present at 1.4 GHz) to study Galactic magnetism, but low
enough to retain ample Signal-to-Noise ratio (S/N) at high latitudes for
extragalactic and cosmological science. We developed a new scanning strategy
based on long azimuth scans, and a corresponding map-making procedure to make
recovery of the overall mean signal of Stokes and possible, a
long-standing problem with polarization observations. We describe the scanning
strategy, map-making procedure, and validation tests. The overall mean signal
is recovered with a precision better than 0.5\%. The maps have a mean
sensitivity of 0.81 mK on beam--size scales and show clear polarized signals,
typically to within a few degrees of the Galactic plane, with ample S/N
everywhere (the typical signal in low emission regions is 13 mK, and 98.6\% of
the pixels have S/N ). The largest depolarization areas are in the inner
Galaxy, associated with the Sagittarius Arm. We have also computed a Rotation
Measure map combining S-PASS with archival data from the WMAP and Planck
experiments. A Stokes map has been generated, with a sensitivity limited to
the confusion level of 9 mK.Comment: Accepted for publication on MNRAS. Maps are available for download at
the website indicated in the manuscrip
Luminescence Spectra of Quantum Dots in Microcavities. I. Bosons
We provide a unified theory of luminescence spectra of coupled light-matter
systems realized with semiconductor heterostructures in microcavities,
encompassing: i) the spontaneous emission case, where the system decays from a
prepared (typically pure) initial state, and ii) luminescence in the presence
of a continuous, incoherent pump. While the former case has been amply
discussed in the literature (albeit mainly for the case of resonance), no
consideration has been given to the influence of the incoherent pump. We show
how, by provoking a self-consistent quantum state, the pump considerably alters
the emission spectra, even at vanishing intensities. The main outcome of our
analysis is to unambiguously identify strong-coupling in situations where it
appears in disguise or only seems to appear. Here, we consider bosonic matter
fields, in which case fully analytical solutions can be obtained. This
describes the case of quantum wells or large quantum dots, or the limit of low
excitation where the average populations remain much smaller than one
- …