Systematic challenges for future gravitational wave measurements of precessing binary black holes

The properties of precessing, coalescing binary black holes are presently inferred through comparison with two approximate models of compact binary coalescence. In this work we show these two models often disagree substantially when binaries have modestly large spins ($a\gtrsim 0.4$) and modest mass ratios ($q\gtrsim 2$). We demonstrate these disagreements using standard figures of merit and the parameters inferred for recent detections of binary black holes. By comparing to numerical relativity, we confirm these disagreements reflect systematic errors. We provide concrete examples to demonstrate that these systematic errors can significantly impact inferences about astrophysically significant binary parameters. For the immediate future, parameter inference for binary black holes should be performed with multiple models (including numerical relativity), and carefully validated by performing inference under controlled circumstances with similar synthetic events.Comment: 12 pages, 9 figure

Safety in numbers: Does perceived safety mediate associations between the neighborhood social environment and physical activity among women living in disadvantaged neighborhoods?

The aim of this study is to examine associations between the neighborhood social environment and leisure-time physical activity (LTPA)(1) and walking among women, and whether these associations are mediated by perceived personal safety

Carers\u27 preferences for the delivery of therapy services for people with disability in rural Australia: Evidence from a discrete choice experiment

Background: The implementation of the Australian National Disability Insurance Scheme (NDIS) is expected to generate a responsive, person-centred system that will empower people with disability to choose the services and support they receive. However little attention has been paid to examine how users of the NDIS will choose and spend their individual budgets. This study aimed to determine quantitatively the relative importance that carers of people with a disability living in rural Australia place on different therapy service delivery characteristics. Methods: A stated preference discrete choice experiment (DCE) was incorporated into a survey of carers of people with disability living in rural Australia. Carers chose between therapy delivery services differing in attributes such as travel time to receive therapy, sector providing the service (i.e. Government, not-for-profit, private), out-of-pocket costs, person who delivers the therapy (therapist or other staff) and waiting time. Results: A total of 133 carers completed the DCE. The majority of respondents cared for a child with a disability (84%), the average age of the person they cared for was 17 years (SD 14.25). Participants expressed strong preferences for a short waiting time (0-3 months) to receive therapy services; services delivered by a therapist, no out of pocket cost and travelling up to 4 hours to receive a therapy session (p Conclusion: Carers of people with a disability in rural Australia exhibited strongest preferences for short waiting times (0-3 months). Therapy services that are delivered by therapy assistants or support workers will require careful introduction to achieve uptake and acceptability

Factors affecting retention of allied health professionals working with people with disability in rural New South Wales, Australia: discrete choice experiment questionnaire development

Objective: This paper describes the development of a discrete choice experiment (DCE) questionnaire to identify the factors (attributes) that allied health professionals (AHPs) working with people with disability identify as important to encouraging them to remain practising in rural areas. Methods: Focus groups and semi-structured interviews were conducted with 97 purposively selected service providers working with people with disability in rural New South Wales, Australia. Focus groups and interviews were digitally recorded, transcribed, and analysed using a modified grounded theory approach involving thematic analysis and constant comparison. Results: Six attributes that may influence AHPs working with people with disability in rural areas to continue to do so were inductively identified: travel arrangements, work flexibility, professional support, professional development, remuneration, and autonomy of practice. The qualitative research information was combined with a policy review to define these retention factors and ensure that they are amenable to policy changes. Conclusion: The use of various qualitative research methods allowed the development of a policy-relevant DCE questionnaire that was grounded in the experience of the target population (AHPs)

Organised drives will control foxes

Until 1916, there were no foxes known to exist in Western Australia. One was reported as having been seen at Esperance in that year and there are records of a fox being shot at Sandstone in 1917. Within a few years of the first recordings, foxes had spread almost throughout the State, and although bonuses have been paid on over 893,000 fox scalps during the past 30 years, we still have a large and thriving fox population which takes a heavy annual toll of young lambs and poultry besides contributing to insect damage of crops and pastures by the destruction of insectivorous birds

Should I stay or should I go? Exploring the job preferences of allied health professionals working with people with disability in rural Australia

Introduction: The uneven distribution of allied health professionals (AHPs) in rural and remote Australia and other countries is well documented. In Australia, like elsewhere, service delivery to rural and remote communities is complicated because relatively small numbers of clients are dispersed over large geographic areas. This uneven distribution of AHPs impacts significantly on the provision of services particularly in areas of special need such as mental health, aged care and disability services. Objective: This study aimed to determine the relative importance that AHPs (physiotherapists, occupational therapists, speech pathologists and psychologists – “therapists”) living in a rural area of Australia and working with people with disability, place on different job characteristics and how these may affect their retention. Methods: A cross-sectional survey was conducted using an online questionnaire distributed to AHPs working with people with disability in a rural area of Australia over a 3-month period. Information was sought about various aspects of the AHPs’ current job, and their workforce preferences were explored using a best–worst scaling discrete choice experiment (BWSDCE). Conditional logistic and latent class regression models were used to determine AHPs’ relative preferences for six different job attributes. Results: One hundred ninety-nine AHPs completed the survey; response rate was 51 %. Of those, 165 completed the BWSDCE task. For this group of AHPs, “high autonomy of practice” is the most valued attribute level, followed by “travel BWSDCE arrangements: one or less nights away per month”, “travel arrangements: two or three nights away per month” and “adequate access to professional development”. On the other hand, the least valued attribute levels were “travel arrangements: four or more nights per month”, “limited autonomy of practice” and “minimal access to professional development”. Except for “some job flexibility”, all other attributes had a statistical influence on AHPs’ job preference. Preferences differed according to age, marital status and having dependent children. Conclusions: This study allowed the identification of factors that contribute to AHPs’ employment decisions about staying and working in a rural area. This information can improve job designs in rural areas to increase retention

A Bayesian approach to the follow-up of candidate gravitational wave signals

Ground-based gravitational wave laser interferometers (LIGO, GEO-600, Virgo and Tama-300) have now reached high sensitivity and duty cycle. We present a Bayesian evidence-based approach to the search for gravitational waves, in particular aimed at the followup of candidate events generated by the analysis pipeline. We introduce and demonstrate an efficient method to compute the evidence and odds ratio between different models, and illustrate this approach using the specific case of the gravitational wave signal generated during the inspiral phase of binary systems, modelled at the leading quadrupole Newtonian order, in synthetic noise. We show that the method is effective in detecting signals at the detection threshold and it is robust against (some types of) instrumental artefacts. The computational efficiency of this method makes it scalable to the analysis of all the triggers generated by the analysis pipelines to search for coalescing binaries in surveys with ground-based interferometers, and to a whole variety of signal waveforms, characterised by a larger number of parameters.Comment: 9 page

Studying stellar binary systems with the Laser Interferometer Space Antenna using Delayed Rejection Markov chain Monte Carlo methods

Bayesian analysis of LISA data sets based on Markov chain Monte Carlo methods has been shown to be a challenging problem, in part due to the complicated structure of the likelihood function consisting of several isolated local maxima that dramatically reduces the efficiency of the sampling techniques. Here we introduce a new fully Markovian algorithm, a Delayed Rejection Metropolis-Hastings Markov chain Monte Carlo method, to efficiently explore these kind of structures and we demonstrate its performance on selected LISA data sets containing a known number of stellar-mass binary signals embedded in Gaussian stationary noise.Comment: 12 pages, 4 figures, accepted in CQG (GWDAW-13 proceedings

Bayesian coherent analysis of in-spiral gravitational wave signals with a detector network

The present operation of the ground-based network of gravitational-wave laser interferometers in "enhanced" configuration brings the search for gravitational waves into a regime where detection is highly plausible. The development of techniques that allow us to discriminate a signal of astrophysical origin from instrumental artefacts in the interferometer data and to extract the full range of information are some of the primary goals of the current work. Here we report the details of a Bayesian approach to the problem of inference for gravitational wave observations using a network of instruments, for the computation of the Bayes factor between two hypotheses and the evaluation of the marginalised posterior density functions of the unknown model parameters. The numerical algorithm to tackle the notoriously difficult problem of the evaluation of large multi-dimensional integrals is based on a technique known as Nested Sampling, which provides an attractive alternative to more traditional Markov-chain Monte Carlo (MCMC) methods. We discuss the details of the implementation of this algorithm and its performance against a Gaussian model of the background noise, considering the specific case of the signal produced by the in-spiral of binary systems of black holes and/or neutron stars, although the method is completely general and can be applied to other classes of sources. We also demonstrate the utility of this approach by introducing a new coherence test to distinguish between the presence of a coherent signal of astrophysical origin in the data of multiple instruments and the presence of incoherent accidental artefacts, and the effects on the estimation of the source parameters as a function of the number of instruments in the network.Comment: 22 page

Feedback control of thermal lensing in a high optical power cavity

This paper reports automatic compensation of strong thermal lensing in a suspended 80 m optical cavity with sapphire test mass mirrors. Variation of the transmitted beam spot size is used to obtain an error signal to control the heating power applied to the cylindrical surface of an intracavity compensation plate. The negative thermal lens created in the compensation plate compensates the positive thermal lens in the sapphire test mass, which was caused by the absorption of the high intracavity optical power. The results show that feedback control is feasible to compensate the strong thermal lensing expected to occur in advanced laser interferometric gravitational wave detectors. Compensation allows the cavity resonance to be maintained at the fundamental mode, but the long thermal time constant for thermal lensing control in fused silica could cause difficulties with the control of parametric instabilities.This research was supported by the Australian Research Council and the Department of Education, Science and Training and by the U.S. National Science Foundation, through LIGO participation in the HOPF