173 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
Inorganic Carbon Accumulation Stimulates Linear Electron Flow to Artificial Electron Acceptors of Photosystem I in Air-Grown Cells of the Cyanobacterium Synechococcus UTEX 625
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
Photosynthetic Nitrite Reduction as Influenced by the Internal Inorganic Carbon Pool in Air-Grown Cells of Synechococcus UTEX 625
The inner jet of radio galaxy NGC 315 as observed with Chandra and the VLA
We present Chandra X-ray results for the jet, nucleus, and gaseous atmosphere
of NGC 315, a nearby radio galaxy whose jet kinematics are known through deep
radio mapping. Diffuse X-ray synchrotron emission is detected from the jet out
to 30 arcsec from the nucleus, through regions both of fast bulk flow and
deceleration. The X-ray to radio flux ratio drops considerably where the flow
decelerates, but the X-ray and radio emissions show similar transverse extents
throughout, requiring distributed particle acceleration to maintain the supply
of X-ray-emitting electrons. A remarkable knotty filament within the jet is
seen in both the radio and X-ray, contributing roughly 10 per cent of the
diffuse emission along its extent at both wavelengths. No completely
satisfactory explanation for the filament is found, though its oscillatory
appearance, roughly aligned magnetic field, and requirements for particle
acceleration, suggest that it is a magnetic strand within a shear layer between
fast inner and slower outer flow.Comment: Accepted for publication in the MNRAS. 13 pages,14 figures (some in
colour
Analysing the Transverse Structure of the Relativistic Jets of AGN
This paper describes a method of fitting total intensity and polarization profiles in VLBI images of astrophysical jets to profiles predicted by a theoretical model. As an example, the method is used to fit profiles of the jet in the Active Galactic Nucleus Mrk501 with profiles predicted by a model in which a cylindrical jet of synchrotron plasma is threaded by a magnetic field with helical and disordered components. This fitting yields model Stokes Q profiles that agree with the observed profiles to within the 1-2 \sigma uncertainties; the I model and observed profiles are overall not in such good agreement, with the model I profiles being generally more symmetrical than the observed profiles. Consistent fitting results are obtained for profiles derived from 6cm VLBI images at two distances from the core, and also for profiles obtained for different wavelengths at a single location in the VLBI jet. The most striking success of the model is its ability to reproduce the spine-sheath polarization structure observed across the jet. Using the derived viewing angle in the jet rest frame, \delta' approximately 83 degrees, together with a superluminal speed reported in the literature, \beta apparent = 3.3, yields a solution for the viewing angle and velocity of the jet in the observer's frame \delta degrees and \beta approximately 0.96. Although these results for Mrk501 must be considered tentative, the combined analysis of polarization profiles and apparent component speeds holds promise as a means of further elucidating the magnetic field structures and other parameters of parsec-scale AGN jets
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
A review of carbon offset strategies with seaweed aquaculture – feasibility, current knowledge, and suggestions for future research. The Scottish Association for Marine Science, Oban, UK. Report prepared for the Scottish Government
In September 2022, a group of international collaborators
gathered from six European countries (hereby referred to
as the ‘working group’) to take part in a workshop at the
Scottish Association for Marine Science (SAMS), Oban.
The workshop was funded as part of Marine Scotland’s Blue Carbon International Policy Challenge (BCIPC). The main aim of the workshop was to produce a document outlining the potential for carbon offset by macroalgal aquaculture. The discussions held at the workshop focused on various concepts and hypotheses surrounding carbon drawdown by seaweed aquaculture and the potential for mitigation of atmospheric CO2. The key points of these discussions have been compiled into a policy brief which aims to highlight important areas for future research, uncertainties and challenges faced by the industry, policy makers and other stakeholders
Accrual and drop out in a primary prevention randomised controlled trial: qualitative study
<p>Abstract</p> <p>Background</p> <p>Recruitment and retention of participants are critical to the success of a randomised controlled trial. Gaining the views of potential trial participants who decline to enter a trial and of trial participants who stop the trial treatment is important and can help to improve study processes. Limited research on these issues has been conducted on healthy individuals recruited for prevention trials in the community.</p> <p>Methods</p> <p>Semi-structured interviews with people who were eligible but had declined to participate in the Aspirin for Asymptomatic Atherosclerosis (AAA) trial (N = 11), and AAA trial participants who had stopped taking the trial medication (N = 11). A focus group with further participants who had stopped taking the trial medication (N = 6). (Total participants N = 28).</p> <p>Results</p> <p>Explanations for declining to participate could be divided into two groups: the first group were characterised by a lack of necessity to participate and a tendency to prioritise other largely mundane problems. The second group's concern was with a high level of perceived risk from participating.</p> <p>Explanations for stopping trial medication fell into four categories: side effects attributed to the trial medication; starting on aspirin or medication contraindicating to aspirin; experiencing an outcome event, and changing one's mind.</p> <p>Conclusions</p> <p>These results indicate that when planning trials (especially in preventive medicine) particular attention should be given to designing appropriate recruitment materials and processes that fully inform potential recruits of the risks and benefits of participation.</p> <p>Trial registration</p> <p>ISRCTN66587262</p
An argument against the focus on Community Resilience in Public Health
Background - It has been suggested that Public Health professionals focus on community resilience in tackling chronic problems, such as poverty and deprivation; is this approach useful?
Discussion - Resilience is always i) of something ii) to something iii) to an endpoint, as in i) a rubber ball, ii) to a blunt force, iii) to its original shape. “Community resilience” might be: of a neighbourhood, to a flu pandemic, with the endpoint, to return to normality. In these two examples, the endpoint is as-you-were. This is unsuitable for some examples of resilience. A child that is resilient to an abusive upbringing has an endpoint of living a happy life despite that upbringing: this is an as-you-should-be endpoint. Similarly, a chronically deprived community cannot have the endpoint of returning to chronic deprivation: so what is its endpoint? Roughly, it is an as-you-should-be endpoint: to provide an environment for
inhabitants to live well. Thus resilient communities will be those that do this in the face of challenges. How can they be identified?
One method uses statistical outliers, neighbourhoods that do better than would be expected on a range of outcomes given a range of stressors. This method tells us that a neighbourhood is resilient but not why it is. In response, a number of researchers have attributed characteristics to resilient communities; however, these generally fail to distinguish characteristics of a good community from those of a resilient one. Making this distinction is difficult and we have not seen it successfully done; more importantly, it is arguably unnecessary.
There already exist approaches in Public Health to assessing and developing communities faced with chronic problems, typically tied to notions such as Social Capital. Communityresilience to chronic problems, if it makes sense at all, is likely to be a property that emerges from the various assets in a community such as human capital, built capital and natural capital.
Summary - Public Health professionals working with deprived neighbourhoods would be better to focus on what neighbourhoods have or could develop as social capital for living well, rather than on the vague and tangential notion of community resilience.</p
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