249 research outputs found
Multifrequency observations of the jets in the radio galaxy NGC 315
We present images of the jets in the nearby radio galaxy NGC 315 made with
the VLA at five frequencies between 1.365 and 5 GHz with resolutions between
1.5 and 45 arcsec FWHM. Within 15 arcsec of the nucleus, the spectral index of
the jets is 0.61. Further from the nucleus, the spectrum is flatter, with
significant transverse structure. Between 15 and 70 arcsec from the nucleus,
the spectral index varies from 0.55 on-axis to 0.44 at the edge. This spectral
structure suggests a change of dominant particle acceleration mechanism with
distance from the nucleus and the transverse gradient may be associated with
shear in the jet velocity field. Further from the nucleus, the spectral index
has a constant value of 0.47. We derive the distribution of Faraday rotation
over the inner +/-400 arcsec of the radio source and show that it has three
components: a constant term, a linear gradient (both probably due to our
Galaxy) and residual fluctuations at the level of 1 - 2 rad/m^2. These residual
fluctuations are smaller in the brighter (approaching) jet, consistent with the
idea that they are produced by magnetic fields in a halo of hot plasma that
surrounds the radio source. We model this halo, deriving a core radius of
approximately 225 arcsec and constraining its central density and
magnetic-field strength. We also image the apparent magnetic-field structure
over the first +/-200 arcsec from the nucleus.Comment: 20 pages, 17 figures, accepted for publication in MNRAS. Minor
corrections to match published version, including a short note on emission
from the background galaxy FGC011
The Entrainment-Limited Evolution of FR II Sources: Maximum Sizes and A Possible Connection to FR Is
We construct a simple theoretical model to investigate how entrainment
gradually erodes high-speed FR II jets. This process is described by embedding
a mixing-layer model developed originally to describe FR I objects in a
self-similar model for the lobe structure of classical FR II sources. Following
the classical FR II models, we assume that the lobe is dominated by the
particles injected from the central jet. The entrainment produces a boundary
shear layer which acts at the interface between the dense central jet and the
less denser surrounding lobe, and the associated erosion of the jet places
interesting limits on the maximum size of FR II sources. The model shows that
this limit depends mainly on the initial bulk velocity of the relativistic jet
triggered. The bulk velocities of FR IIs suggested by our model are in good
agreement with that obtained from direct pc-scale observations on ordinary
radio galaxies and quasars. Finally, we discuss how FR IIs may evolve into FR
Is upon reaching their maximum, entrainment-limited sizes.Comment: 9 pages, 5 figures, accepted for publication in MNRA
A relativistic model of the radio jets in NGC 315
We apply our intrinsically symmetrical, decelerating relativistic jet model
to deep VLA imaging of the inner 140 arcsec of the giant low-luminosity radio
galaxy NGC 315. An optimized model accurately fits the data in both total
intensity and linear polarization. We infer that the velocity, emissivity and
field structure in NGC 315 are very similar to those of the other
low-luminosity sources we have modelled, but that all of the physical scales
are larger by a factor of about 5. We derive an inclination to the line of
sight of 38 degrees for the jets. Where they first brighten, their on-axis
velocity is approximately v/c = 0.9. They decelerate to v/c = 0.4 between 8 and
18 kpc from the nucleus and the velocity thereafter remains constant. The speed
at the edge of the jet is roughly 0.6 of the on-axis value where it is best
constrained, but the transverse velocity profile may deviate systematically
from the Gaussian form we assume. The proper emissivity profile is split into
three power-law regions separated by shorter transition zones. In the first of
these, at 3 kpc (the flaring point) the jets expand rapidly at constant
emissivity, leading to a large increase in the observed brightness on the
approaching side. At 10 kpc, the emissivity drops abruptly by a factor of 2.
Where the jets are well resolved their rest-frame emission is
centre-brightened. The magnetic field is modelled as random on small scales but
anisotropic and we rule out a globally ordered helical configuration. To a
first approximation, the field evolves from a mixture of longitudinal and
toroidal components to predominantly toroidal, but it also shows variations in
structure along and across the jets, with a significant radial component in
places. Simple adiabatic models fail to fit the emissivity variations.Comment: 20 pages, 17 figures, MNRAS (in press
Safety and contagion in acute psychiatric wards: How the milieu is implicated in the occurrence of clustered safety incidents.
In psychiatry, clustered safety incidents are often attributed to behavioural contagion. Drawing on
Kindermann and Skinner’s conceptual work in our analysis of staff accounts, we explored whether
clustered safety incidents could be attributable to contagion and the role played by staff and the
psychiatric milieu (as a physical, cultural, and therapeutic space). Our analysis suggests that
whether the clustered incidents identified by staff are attributable to contagion depends on how
broadly the “incident” is defined, with clear implications for the over or under identification of
contagion. We also identified the role of staff and the milieu in what was often perceived as
contagion. We argue that the pursuit of safety by creating a predictable milieu may paradoxically
contribute to this clustering of safety incidents and staffs’ perception of them as contagious via the
mechanisms of risk amplification, involuntary convergence (increased exposure to safety incidents),
and depletion of the milieu’s therapeutic potential
Clinical efficacy of omalizumab in chronic spontaneous urticaria is associated with a reduction of FcεRI-positive cells in the skin
Background. Treatment with omalizumab, a humanized recombinant monoclonal
anti-IgE antibody, results in clinical efficacy in patients with Chronic
Spontaneous Urticaria (CSU). The mechanism of action of omalizumab in CSU has
not been elucidated in detail. Objectives. To determine the effects of
omalizumab on levels of high affinity IgE receptor-positive (FcεRI+) and IgE-
positive (IgE+) dermal cells and blood basophils. Treatment efficacy and
safety were also assessed. Study design. In a double-blind study, CSU patients
aged 18‑75 years were randomized to receive 300 mg omalizumab (n=20) or
placebo (n=10) subcutaneously every 4 weeks for 12 weeks. Changes in disease
activity were assessed by use of the weekly Urticaria Activity Score (UAS7).
Circulating IgE levels, basophil numbers and levels of expression of FcεRI+
and IgE+ cells in the skin and in blood basophils were determined. Results.
Patients receiving omalizumab showed a significantly greater decrease in UAS7
compared with patients receiving placebo. At Week 12 the mean difference in
UAS7 between treatment groups was -14.82 (p=0.0027), consistent with previous
studies. Total IgE levels in serum were increased after omalizumab treatment
and remained elevated up to Week 12. Free IgE levels decreased after
omalizumab treatment. Mean levels of FcεRI+ skin cells in patients treated
with omalizumab 300 mg were decreased at Week 12 compared with baseline in the
dermis of both non-lesional and lesional skin, reaching levels comparable with
those seen in healthy volunteers (HVs). There were no statistically
significant changes in mean FcɛRI+ cell levels in the placebo group. Similar
results were seen for changes in IgE+ cells, although the changes were not
statistically significant. The level of peripheral blood basophils increased
immediately after treatment start and returned to Baseline values after the
follow-up period. The levels of FcεRI and IgE expression on peripheral blood
basophils were rapidly reduced by omalizumab treatment up to Week 12.
Conclusions. Treatment with omalizumab resulted in rapid clinical benefits in
patients with CSU. Treatment with omalizumab was associated with reduction in
FcɛRI+ and IgE+ basophils and intradermal cells
Carer involvement in compulsory out-patient psychiatric care in England
Background: There is an expectation in current heath care policy that family carers are involved in service delivery. This is also the case with compulsory outpatient mental health care, Community Treatment Orders (CTOs) that were introduced in England in 2008. No study has systematically investigated family involvement through the CTO process.
Method: We conducted qualitative interviews with 24 family carers to ascertain their views and experiences of involvement in CTOs. The transcripts were subjected to thematic analysis that incorporated both deductive and inductive elements.
Results: We found significant variation in both the type and extent of family carer involvement throughout the CTO process (initiation, recall to hospital, renewal, tribunal hearings, discharge). Some were satisfied with their level of involvement while others felt (at least partly) excluded or that they wanted to be more involved. Some wanted less involvement than what they had. From the interviews we identified key factors shaping carers' involvement. These included: perceptions of patient preference; concern over the relationship to the patient; carers’ knowledge of the CTO and of the potential for carer involvement; access to and relationships with health professionals; issues of patient confidentiality; opportunities for private discussions, and; health professionals limiting involvement. These factors show that health professionals have many opportunities to facilitate, or hinder, carer involvement. The various roles attributed to carers, such ‘proxy’ for patient decision, ‘gatekeeper’ to services, ‘mother’ or ‘expert carer’, however, conflict with one another and make the overall role unclear.
Conclusions: There is a need for clarification of the expectations of carers in individual care situations, for carers to be equipped with the information they need to in order to be involved, and for services to find flexible and innovative ways of ensuring continuous, open communication. The introduction of CTOs in England has not been successful in its ambition for carer involvement
Patient information leaflets (PILs) for UK randomised controlled trials : a feasibility study exploring whether they contain information to support decision making about trial participation
Peer reviewedPublisher PD
The HST survey of the B2 sample of radio galaxies: detection of two optical jets
We present HST observations of previously undetected optical jets in the
low-luminosity radio galaxies B2 0755+37 and B2 1553+24. We show that there is
accurate spatial coincidence between optical and radio emission, implying that
the former is likely to be synchrotron radiation. The physical properties of
the jets are similar to those known previously: their radio-optical spectral
indices are ~0.7 and in B2 0755+37, the spectrum steepens between optical and
X-ray wavelengths. Our results support the hypothesis that optical emission is
detectable from jets orientated within ~20 degrees of the line of sight for the
B2 sample.Comment: Accepted for publication in A&A, 6 pages, 4 figure
Understanding psychiatric institutionalization: a conceptual review
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 cited
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