82 research outputs found
PKS B1545-321: Bow shocks of a relativistic jet?
Sensitive, high resolution images of the double-double radio galaxy PKS
B1545-321 reveal detailed structure, which we interpret in the light of
previous work on the interaction of restarted jets with pre-existing relict
cocoons. We have also examined the spectral and polarization properties of the
source, the color distribution in the optical host and the environment of this
galaxy in order to understand its physical evolution. We propose that the
restarted jets generate narrow bow shocks and that the inner lobes are a
mixture of cocoon plasma reaccelerated at the bow shock and new jet material
reaccelerated at the termination shock. The dynamics of the restarted jets
implies that their hot spots advance at mildly relativistic speeds with
external Mach numbers of at least 5. The existence of supersonic hot spot Mach
numbers and bright inner lobes is the result of entrainment causing a reduction
in the sound speed of the pre-existing cocoon. The interruption to jet activity
in PKS B1545-321 has been brief - lasting less than a few percent of the
lifetime of the giant radio source. The host
galaxy is located at the boundary of a large scale filamentary structure, and
shows blue patches in color distribution indicative of a recent merger, which
may have triggered the Mpc-scale radio galaxy.Comment: 26 pages including 1 table and 16 figures. To appear in MNRA
Double-double radio galaxies: further insights into the formation of the radio structures
Double-double radio galaxies (DDRGs) offer a unique opportunity for us to
study multiple episodes of jet activity in large-scale radio sources. We use
radio data from the Very Large Array and the literature to model two DDRGs,
B1450+333 and B1834+620, in terms of their dynamical evolution. We find that
the standard Fanaroff-Riley II model is able to explain the properties of the
two outer lobes of each source, whereby the lobes are formed by ram-pressure
balance of a shock at the end of the jet with the surrounding medium. The inner
pairs of lobes, however, are not well-described by the standard model. Instead
we interpret the inner lobes as arising from the emission of relativistic
electrons within the outer lobes, which are compressed and re-accelerated by
the bow-shock in front of the restarted jets and within the outer lobes. The
predicted rapid progression of the inner lobes through the outer lobes requires
the eventual development of a hotspot at the edge of the outer lobe, causing
the DDRG ultimately to resemble a standard Fanaroff-Riley II radio galaxy. This
may suggest that DDRGs are a brief, yet normal, phase of the evolution of
large-scale radio galaxies.Comment: Accepted for publication in MNRAS. 17 pages; 15 figures, 2 of which
are in colou
A study of the environments of large radio galaxies using SDSS
The distributions of galaxies in the environments of 16 large radio sources
have been examined using the Sloan Digital Sky Survey. In the giant radio
galaxy J1552+2005 (3C326) which has the highest arm-length ratio, the shorter
arm is found to interact with a group of galaxies which forms part of a
filamentary structure. Although most large sources occur in regions of low
galaxy density, the shorter arm is brighter in most cases suggesting
asymmetries in the intergalactic medium which may not be apparent in the
distribution of galaxies. In two cases with strong and variable cores,
J0313+4120 and J1147+3501, the large flux density asymmetries are possibly also
caused by the effects of relativistic motion.Comment: Accepted for publication in MNRA
Association of statin pretreatment with collateral circulation and final infarct volume in acute ischemic stroke patients: A meta-analysis
Statin pretreatment (SP) is associated with improved outcomes in acute ischemic stroke (AIS) patients. Collateral circulation status and final infarct volume (FIV) are independent predictors of functional outcome in AIS.info:eu-repo/semantics/publishedVersio
Endovascular Treatment for Anterior Circulation Large-Vessel Occlusion Ischemic Stroke with Low ASPECTS: a Systematic Review and Meta-Analysis
Background: Endovascular treatment (EVT) for acute ischemic stroke (AIS) patients presenting with Alberta Stroke Program Early CT Score (ASPECTS) 0-5 has not yet proven safe and effective by clinical trials.
Objectives: The aim of the study was to assess whether EVT in AIS patients presenting with low ASPECTS is beneficial.
Design: Systematic review and meta-analysis of available studies in accordance with the PRISMA statement.
Data sources and methods: We have searched MEDLINE, the Cochrane Central Register of Controlled Trials, and reference lists of articles published until 28 May 2022 with the aim to calculate (1) modified Rankin scale (mRS) score 0-3 at 3 months, (2) mRS score 0-2 at 3 months, (3) symptomatic intracranial hemorrhage (sICH), and (3) mortality at 3 months.
Results: Overall, 24 eligible studies were included in the meta-analysis, comprising a total of 2539 AIS patients with ASPECTS 0-5 treated with EVT. The pooled proportion of EVT-treated patients achieving mRS 0-3 at 3 months was calculated at 38.4%. The pooled proportion of EVT-treated patients achieving mRS 0-2 at 3 months was 25.7%. Regarding safety outcomes, sICH occurred in 12.8% of patients. The 3-month pooled mortality was 30%. In pairwise meta-analysis, patients treated with EVT had a higher likelihood of achieving mRS 0-3 at 3 months compared with patients treated with best medical therapy (BMT, OR: 2.41). sICH occurred more frequently in EVT-treated patients compared with the BMT-treated patients (OR: 2.30). Mortality at 3 months was not different between the two treatment groups (OR: 0.71).
Conclusion: EVT may be beneficial for AIS patients with low baseline ASPECTS despite an increased risk for sICH. Further data from randomized-controlled clinical trials are needed to elucidate the role of EVT in this subgroup of AIS patients.
Registration: The protocol has been registered in the International Prospective Register of Ongoing Systematic Reviews PROSPERO; Registration Number: CRD42022334417.info:eu-repo/semantics/publishedVersio
On the relationship between a giant radio galaxy MSH 05-22 and the ambient large-scale galaxy structure
We present a comparison of the properties of a giant radio galaxy and the
ambient intergalactic medium, whose properties are inferred from the
large-scale distribution in galaxies. The double lobes of the radio galaxy MSH
05-22 are giant--1.8 Mpc projected linear size--and interacting with the
environment outside the interstellar medium and coronal halo associated with
the host galaxy. The radio lobes appear to be relicts and the double structure
is asymmetric. We have examined the large-scale structure in the galaxy
distribution surrounding the radio source. The host galaxy of MSH 05-22 is
associated with a small group that lies close to the boundary of sheet-like and
filamentary density enhancements, and adjacent to a void. Assuming that the
galaxies trace gas, the asymmetries in the radio morphology in this case study
appear related to the anisotropy in the medium. However, the observed
overdensities and structure formation models for the heating of the
intergalactic medium (IGM) suggest a density-temperature product for the IGM
environment that is an order of magnitude below that expected from the
properties of the radio source. The discordance suggests that even sources like
MSH 05-22, which are observed in the relatively low-density IGM environment
associated with the filamentary large-scale structure and have multiple
signatures of being relicts, may be overpressured and evolving towards an
equilibrium relaxed state with the ambient IGM. Alternately, it is speculated
that astrophysical feedback originating in galaxy overdensities observed 1-2
Mpc to the N and NE of MSH 05-22 might be the mechanism for the heating of the
ambient IGM gas.Comment: 27 pages including 1 table and 13 figures. To appear in Ap
An unbiased sample of bright southern Compact Steep Spectrum and Gigahertz Peaked Spectrum Sources
Compact Steep Spectrum (CSS) and Gigahertz Peaked Spectrum (GPS) sources are
classes of compact, powerful, extragalactic objects. These sources are thought
to be the earliest stages in the evolution of radio galaxies, capturing the
ignition (or, in some cases, re-ignition) of the AGN. As well as serving as
probes of the early stages of large-scale radio sources, these sources are
good, stable, amplitude calibrators for radio telescopes. We present an
unbiased flux density limited (>1.5 Jy at 2.7 GHz) catalogue of these objects
in the Southern Hemisphere, including tabulated data, radio spectra, and where
available, optical images and measurements. The catalogue contains 26 sources,
consisting of 2 new candidate and 15 known CSS sources, and 9 known GPS
sources. We present new Australia Telescope Compact Array (ATCA) data on ten of
these 26 sources, and data on a further 42 sources which were excluded from our
final sample. This bright sample will serve as a reference sample for
comparison with subsequent faint (mJy level) samples of CSS and GPS candidates
currently being compiled.Comment: Accepted by MNRAS. 13 figures and 10 tables. The full version of
Table 8 will be available online after publication by MNRAS. Boldface
commands remove
Predictors of NOAC versus VKA use for stroke prevention in patients with newly diagnosed atrial fibrillation: Results from GARFIELD-AF.
INTRODUCTION: A principal aim of the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) was to document changes in treatment practice for patients with newly diagnosed atrial fibrillation during an era when non-vitamin K antagonist oral anticoagulants (NOACs) were becoming more widely adopted. In these analyses, the key factors which determined the choice between NOACs and vitamin K antagonists (VKAs) are explored. METHODS: Logistic least absolute shrinkage and selection operator regression determined predictors of NOAC and VKA use. Data were collected from 24,137 patients who were initiated on AC ± antiplatelet (AP) therapy (NOAC [51.4%] or VKA [48.6%]) between April 2013 and August 2016. RESULTS: The most significant predictors of AC therapy were country, enrolment year, care setting at diagnosis, AF type, concomitant AP, and kidney disease. Patients enrolled in emergency care or in the outpatient setting were more likely to receive a NOAC than those enrolled in hospital (OR 1.16 [95% CI: 1.04-1.30], OR: 1.15 [95% CI: 1.05-1.25], respectively). NOAC prescribing seemed to be favored in lower-risk groups, namely, patients with paroxysmal AF, normotensive patients, and those with moderate alcohol consumption, but also the elderly and patients with acute coronary syndrome. By contrast, VKAs were preferentially used in patients with permanent AF, moderate to severe kidney disease, heart failure, vascular disease, and diabetes and with concomitant AP. CONCLUSION: GARFIELD-AF data highlight marked heterogeneity in stroke prevention strategies globally. Physicians are adopting an individualized approach to stroke prevention where NOACs are favored in patients with a lower stroke risk but also in the elderly and patients with acute coronary syndrome
Safety of intravenous thrombolysis for acute ischemic stroke in specific conditions
Introduction: Intravenous administration of tissue-type plasminogen activator (IV-tPA) remains the only approved therapy that may reverse neurological deficit in patients with acute ischemic stroke (AIS). During the past 20 years, accumulating real-word experience have provided additional information regarding its safety and efficacy in various clinical settings that were originally considered as contraindications for systemic thrombolysis.Areas covered: In this narrative review, we address the safety of intravenous thrombolysis (IVT) in specific conditions: dissection of the aortic arch of extracranial and intracranial arteries, concomitant presence of unruptured intracranial aneurysms, arteriovenous malformations and dural fistulas, co-existing brain tumors as well as in conditions mimicking AIS. The review systematically evaluates the safety of off-label use of IVT and summarizes data from case reports of uncommon complications of systemic thrombolysis administration in the setting of acute cerebral ischemia.Expert opinion: The present narrative review summarizing 20 years of clinical experience with IVT for AIS highlights that many of the current guidelines and protocols should be adjusted to accommodate recent data from registries and real-world experience underscoring the safety of IVT in numerous conditions of AIS that were originally considered as relative or absolute contraindications for administration of IV-tPA. © 2015 Informa UK, Ltd
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