800 research outputs found
More insights into bar quenching. Multi-wavelength analysis of four barred galaxies
The underlying nature of the process of star formation quenching in the
central regions of barred disc galaxies that is due to the action of stellar
bar is not fully understood. We present a multi-wavelength study of four barred
galaxies using the archival data from optical, ultraviolet, infrared, CO, and
HI imaging data on star formation progression and stellar and gas distribution
to better understand the process of bar quenching. We found that for three
galaxies, the region between the nuclear or central sub-kiloparsec region and
the end of the bar (bar region) is devoid of neutral and molecular hydrogen.
While the detected neutral hydrogen is very negligible, we note that molecular
hydrogen is present abundantly in the nuclear or central sub-kiloparsec regions
of all four galaxies. The bar co-rotation radius is also devoid of recent star
formation for three out of four galaxies. One galaxy shows significant
molecular hydrogen along the bar, which might mean that the gas is still being
funnelled to the centre by the action of the stellar bar. Significant star
formation is also present along the bar co-rotation radius of this galaxy. The
study presented here supports a scenario in which gas redistribution as a
result of the action of stellar bar clears the bar region of fuel for further
star formation and eventually leads to star formation quenching in the bar
region.Comment: Accepted for publication in A&A. Continuation on the letter paper
(arXiv:1812.04178) to appear in main journa
GASP XVIII: Star formation quenching due to AGN feedback in the central region of a jellyfish galaxy
We report evidence for star formation quenching in the central 8.6 kpc region
of the jellyfish galaxy JO201 which hosts an active galactic nucleus, while
undergoing strong ram pressure stripping. The ultraviolet imaging data of the
galaxy disk reveal a region with reduced flux around the center of the galaxy
and a horse shoe shaped region with enhanced flux in the outer disk. The
characterization of the ionization regions based on emission line diagnostic
diagrams shows that the region of reduced flux seen in the ultraviolet is
within the AGN-dominated area. The CO J map of the galaxy disk reveals
a cavity in the central region. The image of the galaxy disk at redder
wavelengths (9050-9250 \overset{\lower.5em\circ}{\mathrm{A}}) reveals the
presence of a stellar bar. The star formation rate map of the galaxy disk shows
that the star formation suppression in the cavity occurred in the last few
10 yr. We present several lines of evidence supporting the scenario that
suppression of star formation in the central region of the disk is most likely
due to the feedback from the AGN. The observations reported here make JO201 a
unique case of AGN feedback and environmental effects suppressing star
formation in a spiral galaxy.Comment: Author's accepted manuscrip
Dissecting star-formation in the "Atoms-for-Peace" galaxy: Ultra-Violet Imaging Telescope observations of the post-merger galaxy NGC7252
The tidal tails of post-merger galaxies exhibit ongoing star formation far
from their disks. The study of such systems can be useful for our understanding
of gas condensation in diverse environments. The ongoing star formation in the
tidal tails of post-merger galaxies can be directly studied from ultraviolet
(UV) imaging observations. The post merger galaxy NGC7252 ("Atoms-for-Peace"
galaxy) is observed with the Astrosat UV imaging telescope (UVIT) in broadband
NUV and FUV filters to isolate the star forming regions in the tidal tails and
study the spatial variation in star formation rates. Based on ultraviolet
imaging observations, we discuss star formation regions of ages 200 Myrs in
the tidal tails. We measure star formation rates in these regions and in the
main body of the galaxy. The integrated star formation rate of NGC7252 (i.e.,
that in the galaxy and tidal tails combined) without correcting for extinction
is found to be 0.81 0.01 M/yr. We show that the integrated star
formation rate can change by an order of magnitude if the extinction correction
used in star formation rates derived from other proxies are taken into
consideration. The star formation rates in the associated tidal dwarf galaxies
(NGC7252E, SFR=0.02 M/yr and NGC7252NW, SFR=0.03 M/yr) are
typical of dwarf galaxies in the local Universe. The spatial resolution of the
UV images reveals a gradient in star formation within the tidal dwarf galaxy.
The star formation rates show a dependence on the distance from the centre of
the galaxy. This can be due to the different initial conditions responsible for
the triggering of star formation in the gas reservoir that was expelled during
the recent merger in NGC7252.Comment: Accepted for publication in Astronomy & Astrophysic
Ultra-Violet Imaging Telescope Observations of the Star-Forming Ring in NGC7252: Evidence of Possible AGN Feedback Suppressing Central Star Formation
Some post-merger galaxies are known to undergo a starburst phase that quickly
depletes the gas reservoir and turns it into a red-sequence galaxy, though the
details are still unclear. Here we explore the pattern of recent star formation
in the central region of the post-merger galaxy NGC7252 using high resolution
UV images from the UVIT on ASTROSAT. The UVIT images with 1.2 and 1.4 arcsec
resolution in the FUV and NUV are used to construct a FUV-NUV colour map of the
central region. The FUV-NUV pixel colour map for this canonical post-merger
galaxy reveals a blue circumnuclear ring of diameter 10 " (3.2 kpc) with
bluer patches located over the ring. Based on a comparison to single stellar
population models, we show that the ring is comprised of stellar populations
with ages 300 Myr, with embedded star-forming clumps of younger age
( 150Myr). The suppressed star formation in the central region, along
with the recent finding of a large amount of ionised gas, leads us to speculate
that this ring may be connected to past feedback from a central super-massive
black hole that has ionised the hydrogen gas in the central 4"
1.3 kpc.Comment: Accepted for publication in Astronomy & Astrophysics Letter
Ultraviolet imaging observations of three jellyfish galaxies: Star formation suppression in the centre and ongoing star formation in stripped tails
Spiral galaxies undergo strong ram-pressure effects when they fall into the
galaxy cluster potential. As a consequence, their gas is stripped to form
extended tails within which star formation can happen, giving them the typical
jellyfish appearance. The ultraviolet imaging observations of jellyfish
galaxies provide an opportunity to understand ongoing star formation in the
stripped tails. We report the ultraviolet observations of the jellyfish
galaxies JW39, JO60, JO194 and compare with observations in optical continuum
and . We detect knots of star formation in the disk and
tails of the galaxies and find that their UV and H flux are well
correlated. The optical emission line ratio maps of these galaxies are used to
identify for every region the emission mechanism, due to either star formation,
LINER or a mix of the two phenomena. The star-forming regions in the emission
line maps match very well with the regions having significant UV flux. The
central regions of two galaxies (JW39, JO194) show a reduction in UV flux which
coincides with composite or LINER regions in the emission line maps. The
galaxies studied here demonstrate significant star formation in the stripped
tails, suppressed star formation in the central regions and present a possible
case of accelerated quenching happening in jellyfish galaxies.Comment: Accepted for publication in MNRA
Reduction of missed appointments at an urban primary care clinic: a randomised controlled study
<p>Abstract</p> <p>Background</p> <p>Missed appointments are known to interfere with appropriate care and to misspend medical and administrative resources. The aim of this study was to test the effectiveness of a sequential intervention reminding patients of their upcoming appointment and to identify the profile of patients missing their appointments.</p> <p>Methods</p> <p>We conducted a randomised controlled study in an urban primary care clinic at the Geneva University Hospitals serving a majority of vulnerable patients. All patients booked in a primary care or HIV clinic at the Geneva University Hospitals were sent a reminder 48 hrs prior to their appointment according to the following sequential intervention: 1. Phone call (fixed or mobile) reminder; 2. If no phone response: a Short Message Service (SMS) reminder; 3. If no available mobile phone number: a postal reminder. The rate of missed appointment, the cost of the intervention, and the profile of patients missing their appointment were recorded.</p> <p>Results</p> <p>2123 patients were included: 1052 in the intervention group, 1071 in the control group. Only 61.7% patients had a mobile phone recorded at the clinic. The sequential intervention significantly reduced the rate of missed appointments: 11.4% (n = 122) in the control group and 7.8% (n = 82) in the intervention group (p < 0.005), and allowed to reallocate 28% of cancelled appointments. It also proved to be cost effective in providing a total net benefit of 1846. - EUR/3 months. A satisfaction survey conducted with 241 patients showed that 93% of them were not bothered by the reminders and 78% considered them to be useful. By multivariate analysis, the following characteristics were significant predictors of missed appointments: younger age (OR per additional decade 0.82; CI 0.71-0.94), male gender (OR 1.72; CI 1.18-2.50), follow-up appointment >1year (OR 2.2; CI: 1.15-4.2), substance abuse (2.09, CI 1.21-3.61), and being an asylum seeker (OR 2.73: CI 1.22-6.09).</p> <p>Conclusion</p> <p>A practical reminder system can significantly increase patient attendance at medical outpatient clinics. An intervention focused on specific patient characteristics could further increase the effectiveness of appointment reminders.</p
Parasite fate and involvement of infected cells in the induction of CD4+ and CD8+ T cell responses to Toxoplasma gondii
During infection with the intracellular parasite Toxoplasma gondii, the presentation of parasite-derived antigens to CD4+ and CD8+ T cells is essential for long-term resistance to this pathogen. Fundamental questions remain regarding the roles of phagocytosis and active invasion in the events that lead to the processing and presentation of parasite antigens. To understand the most proximal events in this process, an attenuated non-replicating strain of T. gondii (the cpsII strain) was combined with a cytometry-based approach to distinguish active invasion from phagocytic uptake. In vivo studies revealed that T. gondii disproportionately infected dendritic cells and macrophages, and that infected dendritic cells and macrophages displayed an activated phenotype characterized by enhanced levels of CD86 compared to cells that had phagocytosed the parasite, thus suggesting a role for these cells in priming naĂŻve T cells. Indeed, dendritic cells were required for optimal CD4+ and CD8+ T cell responses, and the phagocytosis of heat-killed or invasion-blocked parasites was not sufficient to induce T cell responses. Rather, the selective transfer of cpsII-infected dendritic cells or macrophages (but not those that had phagocytosed the parasite) to naĂŻve mice potently induced CD4+ and CD8+ T cell responses, and conferred protection against challenge with virulent T. gondii. Collectively, these results point toward a critical role for actively infected host cells in initiating T. gondii-specific CD4+ and CD8+ T cell responses
One-year clinical outcome of patients with nonvalvular atrial fibrillation: Insights from KERALA-AF registry.
BackgroundWe report patient characteristics, treatment pattern and one-year clinical outcome of nonvalvular atrial fibrillation (NVAF) from Kerala, India. This cohort forms part of Kerala Atrial Fibrillation (KERALA-AF) registry which is an ongoing large prospective study.MethodsKERALA-AF registry collected data of adults with previously or newly diagnosed atrial fibrillation (AF) during April 2016 to April 2017. A total of 3421 patients were recruited from 53 hospitals across Kerala state. We analysed one-year follow-up outcome of 2507 patients with NVAF.ResultsMean age at recruitment was 67.2 years (range 18-98) and 54.8% were males. Main co-morbidities were hypertension (61.2%), hyperlipidaemia (46.2%) and diabetes mellitus (37.2%). Major co-existing diseases were chronic kidney disease (42.1%), coronary artery disease (41.6%), and chronic heart failure (26.4%). Mean CHA2DS2-VASc score was 3.18 (SD ± 1.7) and HAS-BLED score, 1.84 (SD ± 1.3). At baseline, use of oral anticoagulants (OAC) was 38.6% and antiplatelets 32.7%. On one-month follow-up use of OAC increased to 65.8% and antiplatelets to 48.3%. One-year all-cause mortality was 16.48 and hospitalization 20.65 per 100 person years. The main causes of death were cardiovascular (75.0%), stroke (13.1%) and others (11.9%). The major causes of hospitalizations were acute coronary syndrome (35.0%), followed by arrhythmia (29.5%) and heart failure (8.4%).ConclusionsDespite high risk profile of patients in this registry, use of OAC was suboptimal, whereas antiplatelets were used in nearly half of patients. A relatively high rate of annual mortality and hospitalization was observed in patients with NVAF in Kerala AF Registry
- âŠ