396 research outputs found
Winds as the origin of radio emission in radio-quiet extremely red quasars
Most active galactic nuclei (AGNs) are radio-quiet, and the origin of their
radio emission is not well-understood. One hypothesis is that this radio
emission is a by-product of quasar-driven winds. In this paper, we present the
radio properties of 108 extremely red quasars (ERQs) at . ERQs are among
the most luminous quasars ( erg/s) in the Universe,
with signatures of extreme ( km/s) outflows in their
[OIII]5007 \AA\ emission, making them the best subjects to seek the
connection between radio and outflow activity. All ERQs but one are unresolved
in the radio on kpc scales, and the median radio luminosity of ERQs
is erg/s, in the radio-quiet regime, but
one to two orders of magnitude higher than that of other quasar samples. The
radio spectra are steep, with a mean spectral index . In addition, ERQs neatly follow the extrapolation of the low-redshift
correlation between radio luminosity and the velocity dispersion of
[OIII]-emitting ionized gas. Uncollimated winds, with a power of one per cent
of the bolometric luminosity, can account for all these observations. Such
winds would interact with and shock the gas around the quasar and in the host
galaxy, resulting in acceleration of relativistic particles and the consequent
synchrotron emission observed in the radio. Our observations support the
picture in which ERQs are signposts of extremely powerful episodes of quasar
feedback, and quasar-driven winds as a contributor of the radio emission in the
intermediate regime of radio luminosity erg/s.Comment: accepted by MNRA
Labours of Love: A Conversation on Art, Gender, and Social Reproduction
Taking the form of a discussion among an art historian, a curator and an artist, the article explores the assumption that it is love, rather than material gain, that motivates art and cultural workers. Addressing the internalisation of the ideology that one loves one's labour, the interlocutors consider the gendered and class conditions of work in the cultural and academic sectors. Reading ‘theory’ against ‘practice’, they reflect on their own work experiences and upbringings, their curatorial research, and their readings of feminist and Marxist theories of artistic and feminised labour. The discussion considers how the precarious conditions of cultural labour today divide and isolate workers, immersing them in antagonism and competition, and how reflections within feminist art history and theory have possibly downplayed the ongoing (rather than historical) importance of class as well as reproductive labour. Highlighting the dangers of over-identifying with work, the three contributors consider the potential of dis-identifying from work roles and from institutional conventions as one strategy that can potentially challenge the exploitation of the self as well as others. The article concludes with a consideration of how ‘labours of love’ might be collectively revalued and prioritised
The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines
Quasar emission lines are often shifted from the systemic velocity due to
various dynamical and radiative processes in the line-emitting region. The
level of these velocity shifts depends both on the line species and on quasar
properties. We study velocity shifts for the line peaks of various narrow and
broad quasar emission lines relative to systemic using a sample of 849 quasars
from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The
coadded (from 32 epochs) spectra of individual quasars have sufficient
signal-to-noise ratio (SNR) to measure stellar absorption lines to provide
reliable systemic velocity estimates, as well as weak narrow emission lines.
The sample also covers a large dynamic range in quasar luminosity (~2 dex),
allowing us to explore potential luminosity dependence of the velocity shifts.
We derive average line peak velocity shifts as a function of quasar luminosity
for different lines, and quantify their intrinsic scatter. We further quantify
how well the peak velocity can be measured for various lines as a function of
continuum SNR, and demonstrate there is no systematic bias in the line peak
measurements when the spectral quality is degraded to as low as SNR~3 per SDSS
pixel. Based on the observed line shifts, we provide empirical guidelines on
redshift estimation from [OII]3728, [OIII]5008, [NeV]3426, MgII, CIII],
HeII1640, broad Hbeta, CIV, and SiIV, which are calibrated to provide unbiased
systemic redshifts in the mean, but with increasing intrinsic uncertainties of
46, 56, 119, 205, 233, 242, 400, 415, and 477 km/s, in addition to the
measurement uncertainties. These more realistic redshift uncertainties are
generally much larger than the formal uncertainties reported by the redshift
pipelines for spectroscopic quasar surveys, and demonstrate the infeasibility
of measuring quasar redshifts to better than ~200 km/s with only broad lines.Comment: matched to the published version; minor changes and conclusions
unchange
Short-term serotonergic but not noradrenergic antidepressant administration reduces attentional vigilance to threat in healthy volunteers
Anxiety is associated with threat-related biases in information processing such as heightened attentional vigilance to potential threat. Such biases are an important focus of psychological treatments for anxiety disorders. Selective serotonin reuptake inhibitors (SSRIs) are effective in the treatment of a range of anxiety disorders. The aim of this study was to assess the effect of an SSRI on the processing of threat in healthy volunteers. A selective noradrenergic reuptake inhibitor (SNRI), which is not generally used in the treatment of anxiety, was used as a contrast to assess the specificity of SSRI effects on threat processing. Forty-two healthy volunteers were randomly assigned to 7 d double-blind intervention with the SSRI citalopram (20 mg/d), the SNRI reboxetine (8 mg/d), or placebo. On the final day, attentional and interpretative bias to threat was assessed using the attentional probe and the homograph primed lexical decision tasks. Citalopram reduced attentional vigilance towards fearful faces but did not affect the interpretation of ambiguous homographs as threatening. Reboxetine had no significant effect on either of these measures. Citalopram reduces attentional orienting to threatening stimuli, which is potentially relevant to its clinical use in the treatment of anxiety disorders. This finding supports a growing literature suggesting that an important mechanism through which pharmacological agents may exert their effects on mood is by reversing the cognitive biases that characterize the disorders that they treat. Future studies are needed to clarify the neural mechanisms through which these effects on threat processing are mediated
Patient flow within UK emergency departments: a systematic review of the use of computer simulation modelling methods
Background: Overcrowding in the emergency department (ED) is common in the UK as in other countries worldwide. Computer simulation is one approach used for understanding the causes of ED overcrowding and assessing the likely impact of changes to the delivery of emergency care. However, little is known about the usefulness of computer simulation for analysis of ED patient flow. We undertook a systematic review to investigate the different computer simulation methods and their contribution for analysis of patient flow within EDs in the UK. Methods: We searched eight bibliographic databases (MEDLINE; EMBASE; COCHRANE; WEB OF SCIENCE; CINAHL; INSPEC; MATHSCINET; and ACM DIGITAL LIBRARY) from date of inception until 31 March 2016. Studies were included if they used a computer simulation method to capture patient progression within the ED of an established UK NHS hospital. Studies were summarised in terms of simulation method, key assumptions, input and output data, conclusions drawn, and implementation of results. Results: Twenty one studies met the inclusion criteria. Of these, 19 used discrete event simulation and 2 used system dynamics models. The purpose of many of these studies (n=16; 76%) centred on service redesign. Seven studies (33%) provided no details about the ED being investigated. Most studies (n=18; 86%) used specific hospital models of ED patient flow. Overall, the reporting of underlying modelling assumptions was poor. Nineteen studies (90%) considered patient waiting or throughput times as the key outcome measure. Twelve studies (57%) reported some involvement of stakeholders in the simulation study. However, only 3 studies (14%) reported on the implementation of changes supported by the simulation. Conclusions: We found that computer simulation can provide a means to pre-test changes to ED care delivery before implementation in a safe and efficient manner. However, there are some methodological, data, stakeholder, implementation, and reporting issues, which must be addressed by future studies
Biases in Virial Black Hole Masses: An SDSS Perspective
We compile black hole (BH) masses for quasars in the redshift
range included in the Fifth Data Release of the
Sloan Digital Sky Survey (SDSS), using virial BH mass estimators based on the
\hbeta, \MgII, and \CIV emission lines. We find that: (1) within our sample,
the widths of the three lines follow log-normal distributions, with means and
dispersions that do not depend strongly on luminosity or redshift;(2) the
\MgII- and \hbeta-estimated BH masses are consistent with one another; and (3)
the \CIV BH mass estimator may be more severely affected by a disk wind
component than the \MgII and \hbeta estimators, giving a positive bias in mass
correlated with the \CIV-\MgII blueshift. Most SDSS quasars have virial BH
masses in the range . There is a clear upper mass limit of
for active BHs at , decreasing at lower
redshifts. Making the reasonable assumptions that the underlying BH mass
distribution decreases with mass and that the Eddington ratio distribution at
fixed BH mass has non-zero width, we show that the measured virial BH mass
distribution and Eddington ratio distribution are subject to Malmquist bias. A
radio quasar subsample (with ) has mean virial BH
mass larger by dex than the whole sample. A broad absorption line
(BAL) quasar subsample (with ) has identical virial
mass distribution as the nonBAL sample, with no mean offset. (Abridged)Comment: Updated virial mass measurements; improved presentation of the MC
simulation; added new discussion sections; conclusions unchanged. The full
table1 is available at
http://www.astro.princeton.edu/~yshen/BH_mass/datafile1.txt.tar.g
Variations in policies for accessing elective musculoskeletal procedures in the English National Health Service:A documentary analysis
OBJECTIVE: The overall aim of this study was to investigate how commissioning policies for accessing clinical procedures compare in the context of the English National Health Service. Our primary objective was to compare policy wording and categorise any variations identified. Our secondary objective was to explore how any points of variation relate to national guidance. METHODS: This study entailed documentary analysis of commissioning policies that stipulated criteria for accessing eight elective musculoskeletal procedures. For each procedure, we retrieved policies held by regions with higher and lower rates of clinical activity relative to the national average. Policies were subjected to content and thematic analysis, using constant comparison techniques. Matrices and descriptive reports were used to compare themes across policies for each procedure and derive categories of variation that arose across two or more procedures. National guidance relating to each procedure were identified and scrutinised, to explore whether these provided context for explaining the policy variations. RESULTS: Thirty-five policy documents held by 14 geographic regions were included in the analysis. Policies either focused on a single procedure/treatment or covered several procedures/treatments in an all-encompassing document. All policies stipulated criteria that needed to be fulfilled prior to accessing treatment, but there were inconsistences in the evidence cited. Policies varied in recurring ways, with respect to specification of non-surgical treatments and management, requirements around time spent using non-surgical approaches, diagnostic requirements, requirements around symptom severity and disease progression, and use of language, in the form of terms and phrases (‘threshold modifiers’) which could open up or restrict access to care. National guidance was identified for seven of the procedures, but this guidance did not specify criteria for accessing the procedures in question, making direct comparisons with regional policies difficult. CONCLUSIONS: This, to our knowledge, is the first study to identify recurring ways in which policies for accessing treatment can vary within a single-payer system with universal coverage. The findings raise questions around whether formulation of commissioning policies should receive more central support to promote greater consistency – especially where evidence is uncertain, variable or lacking
Quantitative myocardial inflammation assessed using a novel USPIO-Magnetic Resonance Imaging acquisition and analysis protocol
Markers of cardiac dysfunction in cognitive impairment and dementia
Markers of cardiac dysfunction such as amino terminal pro-brain natriuretic peptide (NTpro-BNP) and high sensitivity cardiac troponin T (hs-cTnT) may be associated with dementia. However, limited data exist on their association with either pre-dementia stages, that is, cognitive impairment no dementia (CIND), or the burden of cerebrovascular diseases (CeVD). We therefore, examined the association of these biomarkers of cardiac dysfunction with CeVD in both CIND and dementia. A case–control study, with cases recruited from memory clinics and controls from memory clinics and community. All subjects underwent collection of blood samples, neuropsychological assessment, and neuroimaging. Subjects were classified as CIND and dementia based on clinical criteria whilst significant CeVD was defined as the presence of cortical infarcts and/or more than 2 lacunes and/or confluent white matter lesions in two regions of brain on Age-Related White Matter Changes Scale. We included a total of 35 controls (mean age: 65.9 years), 78 CIND (mean age: 70.2 years) and 80 cases with dementia (mean age: 75.6 years). Plasma concentrations of hs-cTnT were associated significantly with CeVD in both CIND (odds ratios [OR]: 9.05; 95% confidence interval [CI]: 1.64–49.79) and dementia (OR: 16.89; 95%CI: 2.02–142.67). In addition, NTpro-BNP was associated with dementia with CeVD (OR: 7.74; 95%CI: 1.23–48.58). These associations were independent of other vascular risk factors. In this study, we showed that plasma NTproBNP and hs-cTnT are associated with dementia and CIND, only when accompanied by presence of CeVD
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