33 research outputs found
Systematic performance of the ASKAP Fast Radio Burst search algorithm
Detecting fast radio bursts (FRBs) requires software pipelines to search for
dispersed single pulses of emission in radio telescope data. In order to enable
an unbiased estimation of the underlying FRB population, it is important to
understand the algorithm efficiency with respect to the search parameter space
and thus the survey completeness. The Fast Real-time Engine for Dedispersing
Amplitudes (FREDDA) search pipeline is a single pulse detection pipeline
designed to identify radio pulses over a large range of dispersion measures
(DM) with low latency. It is used on the Australian Square Kilometre Array
Pathfinder (ASKAP) for the Commensal Real-time ASKAP Fast Transients (CRAFT)
project . We utilise simulated single pulses in the low- and high-frequency
observation bands of ASKAP to analyse the performance of the pipeline and infer
the underlying FRB population. The simulation explores the Signal-to-Noise
Ratio (S/N) recovery as a function of DM and the temporal duration of FRB
pulses in comparison to injected values. The effects of intra-channel
broadening caused by dispersion are also carefully studied in this work using
control datasets. Our results show that for Gaussian-like single pulses, of the injected signal is recovered by pipelines such as FREDDA at DM <
3000 using standard boxcar filters compared to an ideal
incoherent dedispersion match filter. Further calculations with sensitivity
implies at least of FRBs in a Euclidean universe at target
sensitivity will be missed by FREDDA and HEIMDALL, another common pipeline, in
ideal radio environments at 1.1 GHz.Comment: 11 pages 13 figures. Accepted for MNRAS; Data and simulation code
available onlin
Limits on Absorption from a 332-MHz survey for Fast Radio Bursts
Fast Radio Bursts (FRBs) are bright, extragalactic radio pulses whose origins
are still unknown. Until recently, most FRBs have been detected at frequencies
greater than 1 GHz with a few exceptions at 800 MHz. The recent discoveries of
FRBs at 400 MHz from the Canadian Hydrogen Intensity Mapping Experiment (CHIME)
telescope has opened up possibilities for new insights about the progenitors
while many other low frequency surveys in the past have failed to find any
FRBs. Here, we present results from a FRB survey recently conducted at the
Jodrell Bank Observatory at 332 MHz with the 76-m Lovell telescope for a total
of 58 days. We did not detect any FRBs in the survey and report a 90 upper
limit of 5500 FRBs per day per sky for a Euclidean Universe above a fluence
threshold of 46 Jy ms. We discuss the possibility of absorption as the main
cause of non-detections in low frequency (< 800 MHz) searches and invoke
different absorption models to explain the same. We find that Induced Compton
Scattering alone cannot account for absorption of radio emission and that our
simulations favour a combination of Induced Compton Scattering and Free-Free
Absorption to explain the non-detections. For a free-free absorption scenario,
our constraints on the electron density are consistent with those expected in
the post-shock region of the ionized ejecta in Super-Luminous SuperNovae
(SLSNe).Comment: 12 pages, 9 Figures, 2 Tables, Second revision submitted to MNRA
Probing the extragalactic fast transient sky at minute timescales with DECam
Searches for optical transients are usually performed with a cadence of days
to weeks, optimised for supernova discovery. The optical fast transient sky is
still largely unexplored, with only a few surveys to date having placed
meaningful constraints on the detection of extragalactic transients evolving at
sub-hour timescales. Here, we present the results of deep searches for dim,
minute-timescale extragalactic fast transients using the Dark Energy Camera, a
core facility of our all-wavelength and all-messenger Deeper, Wider, Faster
programme. We used continuous 20s exposures to systematically probe timescales
down to 1.17 minutes at magnitude limits (AB), detecting hundreds of
transient and variable sources. Nine candidates passed our strict criteria on
duration and non-stellarity, all of which could be classified as flare stars
based on deep multi-band imaging. Searches for fast radio burst and gamma-ray
counterparts during simultaneous multi-facility observations yielded no
counterparts to the optical transients. Also, no long-term variability was
detected with pre-imaging and follow-up observations using the SkyMapper
optical telescope. We place upper limits for minute-timescale fast optical
transient rates for a range of depths and timescales. Finally, we demonstrate
that optical -band light curve behaviour alone cannot discriminate between
confirmed extragalactic fast transients such as prompt GRB flashes and Galactic
stellar flares.Comment: Published in MNRA
Detection of a glitch in the pulsar J1709-4429
We report the detection of a glitch event in the pulsar J17094429 (also
known as B170644) during regular monitoring observations with the Molonglo
Observatory Synthesis Telescope (UTMOST). The glitch was found during timing
operations, in which we regularly observe over 400 pulsars with up to daily
cadence, while commensally searching for Rotating Radio Transients, pulsars,
and FRBs. With a fractional size of ,
the glitch reported here is by far the smallest known for this pulsar,
attesting to the efficacy of glitch searches with high cadence using UTMOST.Comment: 3 pages, 1 figur
A Clinician\u27s Guide to Next Generation Imaging in Patients With Advanced Prostate Cancer (RADAR III).
PURPOSE: The advanced prostate cancer therapeutic landscape has changed dramatically in the last several years, resulting in improved overall survival of patients with castration naïve and castration resistant disease. The evolution and development of novel next generation imaging techniques will affect diagnostic and therapeutic decision making. Clinicians must navigate when and which next generation imaging techniques to use and how to adjust treatment strategies based on the results, often in the absence of correlative therapeutic data. Therefore, guidance is needed based on best available information and current clinical experience.
MATERIALS AND METHODS: The RADAR (Radiographic Assessments for Detection of Advanced Recurrence) III Group convened to offer guidance on the use of next generation imaging to stage prostate cancer based on available data and clinical experience. The group also discussed the potential impact of next generation imaging on treatment options based on earlier detection of disease.
RESULTS: The group unanimously agreed that progression to metastatic disease is a seminal event for patient treatment. Next generation imaging techniques are able to detect previously undetectable metastases, which could redefine the phases of prostate cancer progression. Thus, earlier systemic or locally directed treatment may positively alter patient outcomes.
CONCLUSIONS: The RADAR III Group recommends next generation imaging techniques in select patients in whom disease progression is suspected based on laboratory (biomarker) values, comorbidities and symptoms. Currently 18F-fluciclovine and 68Ga prostate specific membrane antigen positron emission tomography/computerized tomography are the next generation imaging agents with a favorable combination of availability, specificity and sensitivity. There is ongoing research of additional next generation imaging technologies, which may offer improved diagnostic accuracy and therapeutic options. As next generation imaging techniques evolve and presumably result in improved global accessibility, clinician ability to detect micrometastases may be enhanced for decision making and patient outcomes
The Location of Young Pulsar PSR J0837-2454: Galactic Halo or Local Supernova Remnant?
We present the discovery and timing of the young (age ∼28.6 kyr) pulsar PSR J0837-2454. Based on its high latitude (b = 9°8) and dispersion measure (DM = 143 pc cm-3), the pulsar appears to be at a z-height of >1 kpc above the Galactic plane, but near the edge of our Galaxy. This is many times the observed scale height of the canonical pulsar population, which suggests this pulsar may have been born far out of the plane. If accurate, the young age and high z-height imply that this is the first pulsar known to be born from a runaway O/B star. In follow-up imaging with the Australia Telescope Compact Array (ATCA), we detect the pulsar with a flux density S1400 = 0.18 ± 0.05 mJy. We do not detect an obvious supernova remnant around the pulsar in our ATCA data, but we detect a colocated, low-surface-brightness region of ∼1°5 extent in archival Galactic and Extragalactic All-sky MWA Survey data. We also detect colocated Hα emission from the Southern Hα Sky Survey Atlas. Distance estimates based on these two detections come out to ∼0.9 kpc and ∼0.2 kpc, respectively, both of which are much smaller than the distance predicted by the NE2001 model (6.3 kpc) and YMW model (>25 kpc) and place the pulsar much closer to the plane of the Galaxy. If the pulsar/remnant association holds, this result also highlights the inherent difficulty in the classification of transients as "Galactic" (pulsar) or "extragalactic" (fast radio burst) toward the Galactic anticenter based solely on the modeled Galactic electron contribution to a detection
A Simultaneous Dual-site Technosignature Search Using International LOFAR Stations
The Search for Extraterrestrial Intelligence aims to find evidence of
technosignatures, which can point toward the possible existence of
technologically advanced extraterrestrial life. Radio signals similar to those
engineered on Earth may be transmitted by other civilizations, motivating
technosignature searches across the entire radio spectrum. In this endeavor,
the low-frequency radio band has remained largely unexplored; with prior radio
searches primarily above 1 GHz. In this survey at 110-190 MHz, observations of
1,631,198 targets from TESS and Gaia are reported. Observations took place
simultaneously with two international stations (noninterferometric) of the Low
Frequency Array in Ireland and Sweden. We can reject the presence of any
Doppler drifting narrowband transmissions in the barycentric frame of
reference, with equivalent isotropic radiated power of 10 17 W, for 0.4 million
(or 1.3 million) stellar systems at 110 (or 190) MHz. This work demonstrates
the effectiveness of using multisite simultaneous observations for rejecting
anthropogenic signals in the search for technosignatures.Comment: 15 Pages, 16 Figures, 2 Machine Readable Table
A Gaussian-processes approach to fitting for time-variable spherical solar wind in pulsar timing data
Propagation effects are one of the main sources of noise in high-precision pulsar timing. For pulsars below an ecliptic latitude of 5°, the ionized plasma in the solar wind can introduce dispersive delays of order 100 µs around solar conjunction at an observing frequency of 300 MHz. A common approach to mitigate this assumes a spherical solar wind with a time-constant amplitude. However, this has been shown to be insufficient to describe the solar wind. We present a linear, Gaussian-process piecewise Bayesian approach to fit a spherical solar wind of time-variable amplitude, which has been implemented in the pulsar software RUN_ENTERPRISE. Through simulations, we find that the current EPTA+InPTA data combination is not sensitive to such variations; however, solar wind variations will become important in the near future with the addition of new InPTA data and data collected with the low-frequency LOFAR telescope. We also compare our results for different high-precision timing data sets (EPTA+InPTA, PPTA, and LOFAR) of 3 ms pulsars (J0030+0451, J1022+1001, J2145−0450), and find that the solar-wind amplitudes are generally consistent for any individual pulsar, but they can vary from pulsar to pulsar. Finally, we compare our results with those of an independent method on the same LOFAR data of the three millisecond pulsars. We find that differences between the results of the two methods can be mainly attributed to the modelling of dispersion variations in the interstellar medium, rather than the solar wind modelling
Gene therapy for carcinoma of the breast: Pro-apoptotic gene therapy
The dysregulation of apoptosis contributes in a variety of ways to the malignant phenotype. It is increasingly recognized that the alteration of pro-apoptotic and anti-apoptotic molecules determines not only escape from mechanisms that control cell cycle and DNA damage, but also endows the cancer cells with the capacity to survive in the presence of a metabolically adverse milieu, to resist the attack of the immune system, to locally invade and survive despite a lack of tissue anchorage, and to evade the otherwise lethal insults induced by drugs and radiotherapy. A multitude of apoptosis mediators has been identified in the past decade, and the roles of several of them in breast cancer have been delineated by studying the clinical correlates of pathologically documented abnormalities. Using this information, attempts are being made to correct the fundamental anomalies at the genetic level. Fundamental to this end are the design of more efficient and selective gene transfer systems, and the employment of complex interventions that are tailored to breast cancer and that are aimed concomitantly towards different components of the redundant regulatory pathways. The combination of such genetic modifications is most likely to be effective when combined with conventional treatments, thus robustly activating several pro-apoptotic pathways