179 research outputs found
Localization Using Convolutional Neural Networks
With the increased accessibility to powerful GPUs, ability to develop machine learning algorithms has increased significantly. Coupled with open source deep learning frameworks, average users are now able to experiment with convolutional neural networks (CNNs) to solve novel problems. This project sought to train a CNN capable of classifying between various locations within a building. A single continuous video was taken while standing at each desired location so that every class in the neural network was represented by a single video. Each location was given a number to be used for classification and the video was subsequently titled locX. These videos were converted to frames to train several well known CNNs using fine-tuning. Once the CNNs were trained, their performance on test sets of photos were observed
A Fast Radio Burst in a Compact Galaxy Group at ~1
FRB 20220610A is a high-redshift Fast Radio Burst (FRB) that has not been
observed to repeat. Here, we present rest-frame UV and optical observations of the field of FRB 20220610A. The imaging
reveals seven extended sources, one of which we identify as the most likely
host galaxy with a spectroscopic redshift of =1.017. We spectroscopically
confirm at least three additional sources to be at the same redshift, and
identify the system as a compact galaxy group with possible signs of
interaction among group members. We determine the host of FRB 20220610A to be a
star-forming galaxy with stellar mass of ,
mass-weighted age of ~Gyr, and star formation rate (integrated over
the last 100 Myr) of ~M~yr. These host properties
are commensurate with the star-forming field galaxy population at z~1 and trace
their properties analogously to the population of low- FRB hosts. Based on
estimates of the total stellar mass of the galaxy group, we calculate a
fiducial contribution to the observed Dispersion Measure (DM) from the
intragroup medium of (rest-frame). This
leaves a significant excess of (in the
observer frame), with additional sources of DM possibly originating from the
circumburst environment, host galaxy interstellar medium, and/or foreground
structures along the line of sight. Given the low occurrence rates of galaxies
in compact groups, the discovery of an FRB in such a group demonstrates a rare
and novel environment in which FRBs can occur.Comment: 24 pages, 8 figures, 2 tables, submitte
An X-ray Census of Fast Radio Burst Host Galaxies: Constraints on AGN and X-ray Counterparts
We present the first X-ray census of fast radio burst (FRB) host galaxies to
conduct the deepest search for AGN and X-ray counterparts to date. Our sample
includes seven well-localized FRBs with unambiguous host associations and
existing deep Chandra observations, including two events for which we present
new observations. We find evidence for AGN in two FRB host galaxies based on
the presence of X-ray emission coincident with their centers, including the
detection of a luminous ()
X-ray source at the nucleus of FRB20190608B's host, for which we infer an SMBH
mass of and an Eddington ratio , characteristic of geometrically thin disks in
Seyfert galaxies. We also report nebular emission line fluxes for 24 highly
secure FRB hosts (including 10 hosts for the first time), and assess their
placement on a BPT diagram, finding that FRB hosts trace the underlying galaxy
population. We further find that the hosts of repeating FRBs are not confined
to the star-forming locus, contrary to previous findings. Finally, we place
constraints on associated X-ray counterparts to FRBs in the context of
ultraluminous X-ray sources (ULXs), and find that existing X-ray limits for
FRBs rule out ULXs brighter than .
Leveraging the CHIME/FRB catalog and existing ULX catalogs, we search for
spatially coincident ULX-FRB pairs. We identify two ULX in the galaxy NGC 2633
that are spatially coincident with the repeating FRB20180908B and for which the
DM-inferred redshift is comparable to the distance of the galaxy, assuming a
contribution of .Comment: 15 pages, 5 figures; submitted to Ap
Host Galaxy Properties and Offset Distributions of Fast Radio Bursts: Implications for Their Progenitors
We present observations and detailed characterizations of five new host galaxies of fast radio bursts (FRBs) discovered with the Australian Square Kilometre Array Pathfinder (ASKAP) and localized to ≾ 1". Combining these galaxies with FRB hosts from the literature, we introduce criteria based on the probability of chance coincidence to define a subsample of 10 highly confident associations (at z = 0.03–0.52), 3 of which correspond to known repeating FRBs. Overall, the FRB-host galaxies exhibit a broad, continuous range of color (M_u − M_r = 0.9–2.0), stellar mass (M_★ = 10⁸ − 6 × 10¹⁰ M_⊙), and star formation rate (SFR = 0.05–10 M_⊙ yr⁻¹) spanning the full parameter space occupied by z 99% c.l.). We measure a median offset of 3.3 kpc from the FRB to the estimated center of the host galaxies and compare the host-burst offset distribution and other properties with the distributions of long- and short-duration gamma-ray bursts (LGRBs and SGRBs), core-collapse supernovae (CC-SNe), and SNe Ia. This analysis rules out galaxies hosting LGRBs (faint, star-forming galaxies) as common hosts for FRBs (>95% c.l.). Other transient channels (SGRBs, CC-, and SNe Ia) have host-galaxy properties and offsets consistent with the FRB distributions. All of the data and derived quantities are made publicly available on a dedicated website and repository
Host Galaxy Properties and Offset Distributions of Fast Radio Bursts: Implications for their Progenitors
We present observations and detailed characterizations of five new host
galaxies of fast radio bursts (FRBs) discovered with the Australian Square
Kilometre Array Pathfinder (ASKAP) and localized to . Combining
these galaxies with FRB hosts from the literature, we introduce criteria based
on the probability of chance coincidence to define a sub-sample of 10
highly-confident associations (at ), three of which correspond to
known repeating FRBs. Overall, the FRB host galaxies exhibit a broad,
continuous range of color (), stellar mass (), and star-formation rate () spanning the full parameter space
occupied by galaxies. However, they do not track the color-magnitude,
SFR-, nor BPT diagrams of field galaxies surveyed at similar
redshifts. There is an excess of "green valley" galaxies and an excess of
emission-line ratios indicative of a harder radiation field than that generated
by star-formation alone. From the observed stellar mass distribution, we rule
out the hypothesis that FRBs strictly track stellar mass in galaxies (
c.l.). We measure a median offset of 3.3 kpc from the FRB to the estimated
center of the host galaxies and compare the host-burst offset distribution and
other properties with the distributions of long- and short-duration gamma-ray
bursts (LGRBs and SGRBs), core-collapse supernovae (CC-SNe), and Type Ia SNe.
This analysis rules out galaxies hosting LGRBs (faint, star-forming galaxies)
as common hosts for FRBs ( c.l.). Other transient channels (SGRBs, CC-
and Type Ia SNe) have host galaxy properties and offsets consistent with the
FRB distributions. All of the data and derived quantities are made publicly
available on a dedicated website and repository.Comment: Accepted for publication in ApJ. All data are publicly available at
https://frbhosts.org and https://github.com/FRBs/FRB. Version 2 of manuscript
includes updated FRB uncertainty estimate
A non-repeating fast radio burst in a dwarf host galaxy
We present the discovery of as-of-yet non-repeating Fast Radio Burst (FRB),
FRB 20210117A, with the Australian Square Kilometer Array Pathfinder (ASKAP) as
a part of the Commensal Real-time ASKAP Fast Transients (CRAFT) Survey. The
sub-arcsecond localization of the burst led to the identification of its host
galaxy at a . This redshift is much lower than what would be
expected for a source dispersion measure (DM) of 729 pc cm, given
typical contributions from the intergalactic medium and the host galaxy.
Optical observations reveal the host to be a dwarf galaxy with little on-going
star formation, very different to the dwarf host galaxies of known repeating
FRBs 20121102A, and 20190520B. We find an excess DM contribution from the host
and attribute it to the FRB's local environment. We do not find any radio
emission from the FRB site or host galaxy. The low magnetized environment and
lack of a persistent radio source (PRS) indicate that the FRB source is older
than those found in other dwarf host galaxies, and establish the diversity of
FRB sources in dwarf galaxy environments. We find our observations to be fully
consistent with the hypernebula model, where the FRB is powered by
accretion-jet from a hyper-accreting black hole. Finally, our high-time
resolution analysis reveals burst characteristics similar to those seen in
repeating FRBs. We encourage follow-up observations of FRB 20210117A to
establish any repeating nature.Comment: 15 pages, 9 figures, 2 Table
The effectiveness of dietary approaches to stop hypertension (DASH) counselling on estimated 10-year cardiovascular risk among patients with newly diagnosed grade 1 hypertension : a randomised clinical trial
The Dietary Approaches to Stop Hypertension (DASH) has been shown to lower blood pressure in the West. However, the real-life impact of DASH on reducing cardiovascular (CV) risk in routine clinical setting has not been studied.
Methods
A parallel-group, open-labelled, physician-blinded, randomised controlled trial was conducted in January–June 2013 and followed up for 6- and 12-months in primary care settings in Hong Kong. Patients newly diagnosed with grade 1 hypertension (aged 40–70 years) who had no concomitant medical conditions requiring dietary modifications were consecutively recruited. Subjects were randomised to standard education (usual care) (n = 275), or usual care plus dietitian-delivered DASH-based dietary counselling in a single one-to-one session (intervention) (n = 281). Primary outcomes were the changes in estimated 10-year CV risk.
Results
Outcome data were available for 504 (90.6%) and 485 (87.2%) patients at 6 and 12 months, respectively. There was no difference in the reduction of 10-year CV risk between the two groups at 6 months (−0.13%, 95% confidence interval [95% CI] −0.50% to 0.23%, p = 0.477) and 12 months (−0.08%, 95% CI −0.33% to 0.18%, p = 0.568). Multivariate regression analyses showed that male subjects, younger patients, current smokers, subjects with lower educational level, and those who dined out for main meals for ≥4 times in a typical week were significantly associated with no improvements in CV risk.
Conclusions
The findings may not support automatic referral of newly diagnosed grade 1 hypertensive patients for further one-to-one dietitian counselling on top of primary care physician's usual care. Patients with those risk factors identified should receive more clinical attention to reduce their CV risk
Comparative effectiveness of dipeptidyl peptidase-4 (DPP-4) inhibitors and human glucagon-like peptide-1 (GLP-1) analogue as add-on therapies to sulphonylurea among diabetes patients in the Asia-Pacific region: a systematic review
The prevalence of diabetes mellitus is rising globally, and it induces a substantial public health burden to the healthcare systems. Its optimal control is one of the most significant challenges faced by physicians and policy-makers. Whereas some of the established oral hypoglycaemic drug classes like biguanide, sulphonylureas, thiazolidinediones have been extensively used, the newer agents like dipeptidyl peptidase-4 (DPP-4) inhibitors and the human glucagon-like peptide-1 (GLP-1) analogues have recently emerged as suitable options due to their similar efficacy and favorable side effect profiles. These agents are widely recognized alternatives to the traditional oral hypoglycaemic agents or insulin, especially in conditions where they are contraindicated or unacceptable to patients. Many studies which evaluated their clinical effects, either alone or as add-on agents, were conducted in Western countries. There exist few reviews on their effectiveness in the Asia-Pacific region. The purpose of this systematic review is to address the comparative effectiveness of these new classes of medications as add-on therapies to sulphonylurea drugs among diabetic patients in the Asia-Pacific countries. We conducted a thorough literature search of the MEDLINE and EMBASE from the inception of these databases to August 2013, supplemented by an additional manual search using reference lists from research studies, meta-analyses and review articles as retrieved by the electronic databases. A total of nine randomized controlled trials were identified and described in this article. It was found that DPP-4 inhibitors and GLP-1 analogues were in general effective as add-on therapies to existing sulphonylurea therapies, achieving HbA1c reductions by a magnitude of 0.59–0.90% and 0.77–1.62%, respectively. Few adverse events including hypoglycaemic attacks were reported. Therefore, these two new drug classes represent novel therapies with great potential to be major therapeutic options. Future larger-scale research should be conducted among other Asia-Pacific region to evaluate their efficacy in other ethnic groups
Mapping Obscured Star Formation in the Host Galaxy of FRB 20201124A
We present high-resolution 1.5--6 GHz Karl G. Jansky Very Large Array (VLA)
and () optical and infrared
observations of the extremely active repeating fast radio burst (FRB)
FRB20201124A and its barred spiral host galaxy. We constrain the location
and morphology of star formation in the host and search for a persistent radio
source (PRS) coincident with FRB20201124A. We resolve the morphology of the
radio emission across all frequency bands and measure a star formation rate SFR
yr, a factor of larger than
optically-inferred SFRs, demonstrating dust-obscured star formation throughout
the host. Compared to a sample of all known FRB hosts with radio emission, the
host of FRB20201124A has the most significant obscured star formation.
While observations show the FRB to be offset from the bar or spiral
arms, the radio emission extends to the FRB location. We propose that the FRB
progenitor could have formed (e.g., a magnetar central
engine born from the explosion of a massive star). It is still plausible,
although less likely, that the progenitor of FRB20201124A migrated from the
central bar of the host, e.g., via a runaway massive star. We further place a
limit on the luminosity of a putative PRS at the FRB position of $L_{\rm 6.0 \
GHz}\lesssim\times10^{27}^{-1}^{-1}\gtrsim 10^{5}$
yr in each model, respectively.Comment: 21 pages, 6 figures, 3 tables, Submitte
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