2,603 research outputs found
Classifying the unknown: discovering novel gravitational-wave detector glitches using similarity learning
The observation of gravitational waves from compact binary coalescences by
LIGO and Virgo has begun a new era in astronomy. A critical challenge in making
detections is determining whether loud transient features in the data are
caused by gravitational waves or by instrumental or environmental sources. The
citizen-science project \emph{Gravity Spy} has been demonstrated as an
efficient infrastructure for classifying known types of noise transients
(glitches) through a combination of data analysis performed by both citizen
volunteers and machine learning. We present the next iteration of this project,
using similarity indices to empower citizen scientists to create large data
sets of unknown transients, which can then be used to facilitate supervised
machine-learning characterization. This new evolution aims to alleviate a
persistent challenge that plagues both citizen-science and instrumental
detector work: the ability to build large samples of relatively rare events.
Using two families of transient noise that appeared unexpectedly during LIGO's
second observing run (O2), we demonstrate the impact that the similarity
indices could have had on finding these new glitch types in the Gravity Spy
program
Identification of long-duration noise transients in LIGO and Virgo
The LIGO and Virgo detectors are sensitive to a variety of noise sources,
such as instrumental artifacts and environmental disturbances. The Stochastic
Transient Analysis Multi-detector Pipeline (STAMP) has been developed to search
for long-duration (t1s) gravitational-wave (GW) signals. This pipeline
can also be used to identify environmental noise transients. Here we present an
algorithm to determine when long-duration noise sources couple into the
interferometers, as well as identify what these noise sources are. We analyze
the cross-power between a GW strain channel and an environmental sensor, using
pattern recognition tools to identify statistically significant structure in
cross-power time-frequency maps. We identify interferometer noise from
airplanes, helicopters, thunderstorms and other sources. Examples from LIGO's
sixth science run, S6, and Virgo's third scientific run, VSR3, are presented.Comment: 10 pages, 7 figures, Gravitational-wave Physics & Astronomy Worksho
Multimessenger Universe with Gravitational Waves from Binaries
Future GW detector networks and EM observatories will provide a unique
opportunity to observe the most luminous events in the Universe involving
matter in extreme environs. They will address some of the key questions in
physics and astronomy: formation and evolution of compact binaries, sites of
formation of heavy elements and the physics of jets.Comment: 11 pages, two tables, White Paper submitted to the Astro-2020 (2020
Astronomy and Astrophysics Decadal Survey) by GWIC-3G Science Case Team
(GWIC: Gravitational-Wave International Committee
Supplement: Going the Distance: Mapping Host Galaxies of LIGO and Virgo Sources in Three Dimensions Using Local Cosmography and Targeted Follow-up
This is a supplement to the Letter of Singer et al.
(https://arxiv.org/abs/1603.07333), in which we demonstrated a rapid algorithm
for obtaining joint 3D estimates of sky location and luminosity distance from
observations of binary neutron star mergers with Advanced LIGO and Virgo. We
argued that combining the reconstructed volumes with positions and redshifts of
possible host galaxies can provide large-aperture but small field of view
instruments with a manageable list of targets to search for optical or infrared
emission. In this Supplement, we document the new HEALPix-based file format for
3D localizations of gravitational-wave transients. We include Python sample
code to show the reader how to perform simple manipulations of the 3D sky maps
and extract ranked lists of likely host galaxies. Finally, we include
mathematical details of the rapid volume reconstruction algorithm.Comment: For associated data release, see
http://asd.gsfc.nasa.gov/Leo.Singer/going-the-distanc
Methods for Reducing False Alarms in Searches for Compact Binary Coalescences in LIGO Data
The LIGO detectors are sensitive to a variety of noise transients of
non-astrophysical origin. Instrumental glitches and environmental disturbances
increase the false alarm rate in the searches for gravitational waves. Using
times already identified when the interferometers produced data of questionable
quality, or when the channels that monitor the interferometer indicated
non-stationarity, we have developed techniques to safely and effectively veto
false triggers from the compact binary coalescences (CBCs) search pipeline
Rural/Nonrural Differences in Colorectal Cancer Incidence in the United States, 1998--2001
BACKGROUND. Few studies of colorectal cancer incidence by rural, suburban, and metropolitan residence have been published.
METHODS. The authors examined colorectal cancer incidence among men and women in U.S. counties classified as rural, suburban, and metropolitan for the period 1998–2001. They examined rural/suburban/metropolitan differences in incidence by age, race, Hispanic ethnicity, stage at diagnosis, histology, and percentage of the total county population below the poverty level, using data from the CDC’s National Program of Cancer Registries, the NCI’s Surveillance, Epidemiology, and End Results Program, and the 2000 U.S. Census.
RESULTS. A total of 495,770 newly diagnosed or incident cases of colorectal cancer were included in this analysis (249,919 among men and 245,851 among women). Over the period 1998–2001, the colorectal cancer incidence rates among men tended to be lower among those who resided in rural areas, for each of the subgroups examined, with the exception of Asians and Pacific Islanders and those living in more affluent counties. Among women aged 75 years and older, the colorectal cancer incidence rates tended to be lower among rural than metropolitan or suburban residents, though the differences were slight. In multivariate analysis, the incidence of colorectal cancer was higher in metropolitan, suburban, and rural areas for blacks than that for whites (incidence rate ratios [RR] = 1.12, 1.07, and 1.06, respectively, all P \u3c 0.015).
CONCLUSIONS. This study suggests that black men who reside in metropolitan areas have a higher risk of colorectal cancer than black men who reside in rural areas. This finding suggests the need for diverse approaches for reducing colorectal cancer when targeting rural compared with metropolitan areas
Expression of Protease-Activated Receptor 1 and 2 and Anti-Tubulogenic Activity of Protease-Activated Receptor 1 in Human Endothelial Colony-Forming Cells
Endothelial colony-forming cells (ECFCs) are obtained from the culture of human peripheral blood mononuclear cell (hPBMNC) fractions and are characterised by high proliferative and pro-vasculogenic potential, which makes them of great interest for cell therapy. Here, we describe the detection of protease-activated receptor (PAR) 1 and 2 amongst the surface proteins expressed in ECFCs. Both receptors are functionally coupled to extracellular signal-regulated kinase (ERK) 1 and 2, which become activated and phosphorylated in response to selective PAR1- or PAR2-activating peptides. Specific stimulation of PAR1, but not PAR2, significantly inhibits capillary-like tube formation by ECFCs in vitro, suggesting that tubulogenesis is negatively regulated by proteases able to stimulate PAR1 (e.g. thrombin). The activation of ERKs is not involved in the regulation of tubulogenesis in vitro, as suggested by use of the MEK inhibitor PD98059 and by the fact that PAR2 stimulation activates ERKs without affecting capillary tube formation. Both qPCR and immunoblotting showed a significant downregulation of vascular endothelial growth factor 2 (VEGFR2) in response to PAR1 stimulation. Moreover, the addition of VEGF (50–100 ng/ml) but not basic Fibroblast Growth Factor (FGF) (25–100 ng/ml) rescued tube formation by ECFCs treated with PAR1-activating peptide. Therefore, we propose that reduction of VEGF responsiveness resulting from down-regulation of VEGFR2 is underlying the anti-tubulogenic effect of PAR1 activation. Although the role of PAR2 remains elusive, this study sheds new light on the regulation of the vasculogenic activity of ECFCs and suggests a potential link between adult vasculogenesis and the coagulation cascade
Transit timing variation and transmission spectroscopy analyses of the hot Neptune GJ3470b
GJ3470b is a hot Neptune exoplanet orbiting an M dwarf and the first sub-Jovian planet to exhibit Rayleigh scattering. We present transit timing variation (TTV) and transmission spectroscopy analyses of multiwavelength optical photometry from 2.4-m and 0.5-m telescopes at the Thai National Observatory, and the 0.6-m PROMPT-8 telescope in Chile. Our TTV analysis allows us to place an upper mass limit for a second planet in the system. The presence of a hot Jupiter with a period of less than 10 d or a planet with an orbital period between 2.5 and 4.0 d are excluded. Combined optical and near-infrared transmission spectroscopy favour an H/He-dominated haze (mean molecular weight 1.08 ± 0.20) with high particle abundance at high altitude. We also argue that previous near-infrared data favour the presence of methane in the atmosphere of GJ3470b
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