1,653 research outputs found
A fully-coherent all-sky search for gravitational-waves from compact binary coalescences
We introduce a fully-coherent method for searching for gravitational wave
signals generated by the merger of black hole and/or neutron star binaries.
This extends the coherent analysis previously developed and used for targeted
gravitational wave searches to an all-sky, all-time search. We apply the search
to one month of data taken during the fifth science run of the LIGO detectors.
We demonstrate an increase in sensitivity of 25% over the coincidence search,
which is commensurate with expectations. Finally, we discuss prospects for
implementing and running a coherent search for gravitational wave signals from
binary coalescence in the advanced gravitational wave detector data.Comment: 17 pages, 12 figure
Improved source localization with LIGO India
A global network of advanced gravitational wave interferometric detectors is
under construction. These detectors will offer an order of magnitude
improvement in sensitivity over the initial detectors and will usher in the era
of gravitational wave astronomy. In this paper, we evaluate the benefits of
relocating one of the advanced LIGO detectors to India.Comment: 7 pages, 3 figures, accepted for publication in proceedings of
ICGC2011 conference. Localization figures update
Improved methods for detecting gravitational waves associated with short gamma-ray bursts
In the era of second generation ground-based gravitational wave detectors,
short gamma-ray bursts (GRBs) will be among the most promising astrophysical
events for joint electromagnetic and gravitational wave observation. A targeted
search for gravitational wave compact binary merger signals in coincidence with
short GRBs was developed and used to analyze data from the first generation
LIGO and Virgo instruments. In this paper, we present improvements to this
search that enhance our ability to detect gravitational wave counterparts to
short GRBs. Specifically, we introduce an improved method for estimating the
gravitational wave background to obtain the event significance required to make
detections; implement a method of tiling extended sky regions, as required when
searching for signals associated to poorly localized GRBs from Fermi Gamma-ray
Burst Monitor or the InterPlanetary Network; and incorporate astrophysical
knowledge about the beaming of GRB emission to restrict the search parameter
space. We describe the implementation of these enhancements and demonstrate how
they improve the ability to observe binary merger gravitational wave signals
associated with short GRBs.Comment: 13 pages, 6 figure
A coherent triggered search for single spin compact binary coalescences in gravitational wave data
In this paper we present a method for conducting a coherent search for single
spin compact binary coalescences in gravitational wave data and compare this
search to the existing coincidence method for single spin searches. We propose
a method to characterize the regions of the parameter space where the single
spin search, both coincident and coherent, will increase detection efficiency
over the existing non-precessing search. We also show example results of the
coherent search on a stretch of data from LIGO's fourth science run but note
that a set of signal based vetoes will be needed before this search can be run
to try to make detections.Comment: 14 pages, 4 figure
Horizon energy and angular momentum from a Hamiltonian perspective
Classical black holes and event horizons are highly non-local objects,
defined in terms of the causal past of future null infinity. Alternative,
(quasi)local definitions are often used in mathematical, quantum, and numerical
relativity. These include apparent, trapping, isolated, and dynamical horizons,
all of which are closely associated to two-surfaces of zero outward null
expansion. In this paper we show that three-surfaces which can be foliated with
such two-surfaces are suitable boundaries in both a quasilocal action and a
phase space formulation of general relativity. The resulting formalism provides
expressions for the quasilocal energy and angular momentum associated with the
horizon. The values of the energy and angular momentum are in agreement with
those derived from the isolated and dynamical horizon frameworks.Comment: 39 pages, 3 figures, Final Version : content essentially unchanged
but many small improvements made in response to referees, a few references
adde
Networks of gravitational wave detectors and three figures of merit
This paper develops a general framework for studying the effectiveness of
networks of interferometric gravitational wave detectors and then uses it to
show that enlarging the existing LIGO-VIRGO network with one or more planned or
proposed detectors in Japan (LCGT), Australia, and India brings major benefits,
including much larger detection rate increases than previously thought... I
show that there is a universal probability distribution function (pdf) for
detected SNR values, which implies that the most likely SNR value of the first
detected event will be 1.26 times the search threshold. For binary systems, I
also derive the universal pdf for detected values of the orbital inclination,
taking into account the Malmquist bias; this implies that the number of
gamma-ray bursts associated with detected binary coalescences should be 3.4
times larger than expected from just the beaming fraction of the gamma burst.
Using network antenna patterns, I propose three figures of merit that
characterize the relative performance of different networks... Adding {\em any}
new site to the planned LIGO-VIRGO network can dramatically increase, by
factors of 2 to 4, the detected event rate by allowing coherent data analysis
to reduce the spurious instrumental coincident background. Moving one of the
LIGO detectors to Australia additionally improves direction-finding by a factor
of 4 or more. Adding LCGT to the original LIGO-VIRGO network not only improves
direction-finding but will further increase the detection rate over the
extra-site gain by factors of almost 2, partly by improving the network duty
cycle... Enlarged advanced networks could look forward to detecting three to
four hundred neutron star binary coalescences per year.Comment: 38 pages, 7 figures, 2 tables. Accepted for publication in Classical
and Quantum Gravit
Evaluating âenhancing pragmatic language skills for young children with social communication impairmentsâ (E-PLAYS): protocol for a feasibility randomised controlled trial study
Background: A number of children experience difficulties with social communication and this has long-term deleterious effects on their mental health, social development and education. The proposal presented in this article describes a feasibility study for a trial to test an intervention (âE-PLAYSâ) aimed at supporting children with social communication impairments. E-PLAYS harnesses technology in the form of a novel computer game in order to develop collaborative and communication skills. Preliminary studies by the authors show that when E-PLAYS was administered by the research team, children with social communication impairments showed improvements on communication test scores and on observed collaborative behaviours. The study described here is a pragmatic trial to test the application of E-PLAYS delivered by NHS speech and language therapists together with schools.
Methods: This protocol outlines a two-arm feasibility cluster-randomised controlled trial of the E-PLAYS intervention with treatment as usual control arm, with randomisation at the level of the speech and language therapist. The aim of this study is to ascertain whether it will be feasible to progress to running a full-scale definitive trial to test the effectiveness of E-PLAYS in an NHS setting. Data relating to recruitment and retention, the appropriateness of outcomes and the acceptability of E-PLAYS to participants will be collected.
Speech and language therapists will select suitable children (ages 4â7 years old) from their caseloads and deliver either the E-PLAYS intervention (experimental group) or treatment as usual (control group). Assessments will include blinded language measures and observations, non-blinded teacher-reported measures of peer relations and classroom behaviour and parent-reported use of resources and quality of life. There will also be a qualitative process evaluation.
Discussion: The findings of this study will inform the decision as to whether to progress to a full-scale definitive randomised controlled trial to test the effectiveness of E-PLAYS when delivered by speech and language therapists and teaching assistants within schools. The use of technology in game form is a novel approach in an area where there are currently few available interventions
A blind hierarchical coherent search for gravitational-wave signals from coalescing compact binaries in a network of interferometric detectors
We describe a hierarchical data analysis pipeline for coherently searching
for gravitational wave (GW) signals from non-spinning compact binary
coalescences (CBCs) in the data of multiple earth-based detectors. It assumes
no prior information on the sky position of the source or the time of
occurrence of its transient signals and, hence, is termed "blind". The pipeline
computes the coherent network search statistic that is optimal in stationary,
Gaussian noise, and allows for the computation of a suite of alternative
statistics and signal-based discriminators that can improve its performance in
real data. Unlike the coincident multi-detector search statistics employed so
far, the coherent statistics are different in the sense that they check for the
consistency of the signal amplitudes and phases in the different detectors with
their different orientations and with the signal arrival times in them. The
first stage of the hierarchical pipeline constructs coincidences of triggers
from the multiple interferometers, by requiring their proximity in time and
component masses. The second stage follows up on these coincident triggers by
computing the coherent statistics. The performance of the hierarchical coherent
pipeline on Gaussian data is shown to be better than the pipeline with just the
first (coincidence) stage.Comment: 12 pages, 3 figures, accepted for publication in Classical and
Quantum Gravit
The EVerT2 (Effective Verruca Treatments) trial : a randomised controlled trial of needling versus nonsurgical debridement for the treatment of plantar verrucae
Background:
Verrucae are a common foot skin pathology which can in some cases persist for many years. Plantar verrucae can be unsightly and painful. There are a range of treatment options including needling.
Objectives:
The EVerT2 trial aimed to evaluate the clinical and cost effectiveness of the needling procedure for the treatment of plantar verrucae, relative to callus debridement.
Methods:
This single centre randomised controlled trial recruited 60 participants (aged 18 years and over with a plantar verruca). Participants were randomised 1:1 to the intervention group (needling) or the control group (debridement of the overlying callus). The primary outcome was clearance of the index verruca at 12 weeks after randomisation. Secondary outcomes include recurrence of the verruca; clearance of all verrucae; number of verrucae; size of the index verruca; pain; and participant satisfaction at 12 and 24 weeks. A cost-effectiveness analysis was carried out from the NHS perspective over 12 weeks.
Results:
Sixty eligible patients were randomised (needling group n=29, 48.3%; debridement group n=31, 51.7%) and 53 were included in the primary analysis (needling n=28, 96.6%; debridement n=25, 80.7%). Clearance of the index verruca occurred in 8 (15.1%) participants (needling n=4, 14.3%; debridement n=4, 16.0%, p=0.86). The needling intervention costs were on average ÂŁ14.33 (95% CI 5.32 to 23.35) more per patient than debridement.
Conclusions:
There is no evidence that the needling technique is more clinically or cost effective than callus debridement. The results show a significant improvement in pain outcomes after needling compared to the debridement treatment alone.
Trial registration number: Current Controlled Trials ISRCTN1642944
Magnetic levitation stabilized by streaming fluid flows
We demonstrate that the ubiquitous laboratory magnetic stirrer provides a simple passive method of magnetic levitation, in which the so-called âfleaâ levitates indefinitely. We study the onset of levitation and quantify the fleaâs motion (a combination of vertical oscillation, spinning and âwagglingâ), finding excellent agreement with a mechanical analytical model. The waggling motion drives recirculating flow, producing a centripetal reaction force that stabilized the flea. Our findings have implications for the locomotion of artificial swimmers and the development of bidirectional microfluidic pumps, and they provide an alternative to sophisticated commercial levitators
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