282 research outputs found
Assessing the Energetics of Spinning Binary Black Hole Systems
In this work we study the dynamics of spinning binary black hole systems in
the strong field regime. For this purpose we extract from numerical relativity
simulations the binding energy, specific orbital angular momentum, and
gauge-invariant orbital frequency. The goal of our work is threefold: First, we
extract the individual spin contributions to the binding energy, in particular
the spin-orbit, spin-spin, and cubic-in-spin terms. Second, we compare our
results with predictions from waveform models and find that while
post-Newtonian approximants are not capable of representing the dynamics during
the last few orbits before merger, there is good agreement between our data and
effective-one-body approximants as well as the numerical relativity surrogate
models. Finally, we present phenomenological representations for the binding
energy for non-spinning systems with mass ratios up to and for the
spin-orbit interaction for mass ratios up to obtaining accuracies of
and , respectively
Rumor Has It...
A curious graduate takes it upon herself to investigate four tales that have become part of campus lore -- and determine what\u27s fact and what\u27s fiction
Self-Portraits and Gravity Bodies
Self-portraiture allows for the rapid fruition of ideas. An analysis of the work of Francesca Woodman and Ana Mendieta shows how the artistâs body can be variably used in photography. David Wojnarowiczâs memoir establishes a connection between gravity and the human condition. My practice has been informed by this connection
Springbrook: Challenges in developing a long-term, rainforest wireless sensor network
We describe the design, development and learnings from the first phase of a rainforest ecological sensor network at Springbrook - part of a World Heritage precinct in South East Queensland. This first phase is part of a major initiative to develop the capability to provide reliable, long-term monitoring of rainforest ecosystems. We focus in particular on our analysis around energy and communication challenges which need to be solved to allow for reliable, long-term deployments in these types of environments
A luminosity distribution for kilonovae based on short gamma-ray burst afterglows
The combined detection of a gravitational-wave signal, kilonova, and short
gamma-ray burst (sGRB) from GW170817 marked a scientific breakthrough in the
field of multi-messenger astronomy. But even before GW170817, there have been a
number of sGRBs with possible associated kilonova detections. In this work, we
re-examine these "historical" sGRB afterglows with a combination of
state-of-the-art afterglow and kilonova models. This allows us to include
optical/near-infrared synchrotron emission produced by the sGRB as well as
ultraviolet/optical/near-infrared emission powered by the radioactive decay of
-process elements (i.e., the kilonova). Fitting the lightcurves, we derive
the velocity and the mass distribution as well as the composition of the
ejected material. The posteriors on kilonova parameters obtained from the fit
were turned into distributions for the peak magnitude of the kilonova emission
in different bands and the time at which this peak occurs. From the sGRB with
an associated kilonova, we found that the peak magnitude in H bands falls in
the range [-16.2, -13.1] ( of confidence) and occurs within after the sGRB prompt emission. In g band instead we obtain a peak
magnitude in range [-16.8, -12.3] occurring within the first after
the sGRB prompt. From the luminosity distributions of GW170817/AT2017gfo,
kilonova candidates GRB130603B, GRB050709 and GRB060614 (with the possible
inclusion of GRB150101B) and the upper limits from all the other sGRBs not
associated with any kilonova detection we obtain for the first time a kilonova
luminosity function in different bands.Comment: Published in MNRAS, 24 pages, 14 figure
Prioritising children and young people with disability in research about domestic and family violence : Methodological, ethical and pragmatic reflections
Purpose
The perspectives of children and young people with disability who experience domestic and family violence are under-researched, impeding the development of approaches that meet their needs. Knowledge gaps stem from the layered discursive positioning of disability, childhood/youth, or domestic and family violence in addition to the methodological, ethical and pragmatic complexity of research needed to understand their priorities and be attuned to their lived experience. This article explores methodological, ethical and practical challenges to centring their voices in research about domestic and family violence.
Method
A conceptual framework of feminist disability theory and intersectionality informed our co-designed research, across three phases: (1) quantitative large-scale data linkage and case file analysis; (2) qualitative research with children and young people, their families and service providers and (3) stakeholder engagement workshops.
Results
We reflect on how our research was able to prioritise the contextual agency of children and young people with disability, ways it could not, and other constraints.
Conclusion
Children and young people with disability experiencing domestic and family violence hold an expert and unique vantage point on what happens to them. Amplifying their priorities for directing policy and organisational change requires more of researchers in terms of methods, but also more flexibility in how projects are funded to enable creativity and innovation. We call for collective attention to frameworks for supported decision-making and child ethics to progress inclusive research which recognises the importance of participation for children and young people with disability
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LADTAP-PROB: A PROBABILISTIC MODEL TO ASSESS RADIOLOGICAL CONSEQUENCES FROM LIQUID RADIOACTIVE RELEASES
The potential radiological consequences to humans resulting from aqueous releases at the Savannah River Site (SRS) have usually been assessed using the computer code LADTAP or deterministic variations of this code. The advancement of LADTAP over the years included LADTAP II (a computer program that still resides on the mainframe at SRS) [1], LADTAP XL{copyright} (Microsoft Excel{reg_sign} Spreadsheet) [2], and other versions specific to SRS areas such as [3]. The spreadsheet variations of LADTAP contain two worksheets: LADTAP and IRRIDOSE. The LADTAP worksheet estimates dose for environmental pathways including ingestion of water and fish and external exposure resulting from recreational activities. IRRIDOSE estimates potential dose to individuals from irrigation of food crops with contaminated water. A new version of this deterministic methodology, LADTAP-PROB, was developed at Savannah River National Laboratory (SRNL) to (1) consider the complete range of the model parameter values (not just maximum or mean values), (2) determine the influences of parameter uncertainties within the LADTAP methodology, to perform a sensitivity analysis of all model parameters (to identify the input parameters to which model results are most sensitive), and (3) probabilistically assess radiological consequences from contaminated water. This study presents the methodology applied in LADTAP-PROB
Screen Time Weight-loss Intervention Targeting Children at Home (SWITCH): process evaluation of a randomised controlled trial intervention
Abstract
Background
The Screen Time Weight-loss Intervention Targeting Children at Home (SWITCH) trial tested a family intervention to reduce screen-based sedentary behaviour in overweight children. The trial found no significant effect of the intervention on childrenâs screen-based sedentary behaviour. To explore these null findings, we conducted a pre-planned process evaluation, focussing on intervention delivery and uptake.
Methods
SWITCH was a randomised controlled trial of a 6-month family intervention to reduce screen time in overweight children aged 9â12 years (nâ=â251). Community workers met with each childâs primary caregiver to deliver the intervention content. Community workers underwent standard training and were monitored once by a member of the research team to assess intervention delivery. The primary caregiver implemented the intervention with their child, and self-reported intervention use at 3 and 6Â months. An exploratory analysis determined whether child outcomes at 6Â months varied by primary caregiver use of the intervention.
Results
Monitoring indicated that community workers delivered all core intervention components to primary caregivers. However, two thirds of primary caregivers reported using any intervention component âsometimesâ or less frequently at both time points, suggesting that intervention uptake was poor. Additionally, analyses indicated no effect of primary caregiver intervention use on child outcomes at 6Â months, suggesting the intervention itself lacked efficacy.
Conclusions
Poor uptake, and the efficacy of the intervention itself, may have played a role in the null findings of the SWITCH trial on health behaviour and body composition.
Trial registration
The trial was registered in the Australian and New Zealand Clinical Trials Registry (no.
ACTRN12611000164998
); registration date: 10/02/2011
Screen Time Weight-loss Intervention Targeting Children at Home (SWITCH): process evaluation of a randomised controlled trial intervention
Abstract
Background
The Screen Time Weight-loss Intervention Targeting Children at Home (SWITCH) trial tested a family intervention to reduce screen-based sedentary behaviour in overweight children. The trial found no significant effect of the intervention on childrenâs screen-based sedentary behaviour. To explore these null findings, we conducted a pre-planned process evaluation, focussing on intervention delivery and uptake.
Methods
SWITCH was a randomised controlled trial of a 6-month family intervention to reduce screen time in overweight children aged 9â12 years (nâ=â251). Community workers met with each childâs primary caregiver to deliver the intervention content. Community workers underwent standard training and were monitored once by a member of the research team to assess intervention delivery. The primary caregiver implemented the intervention with their child, and self-reported intervention use at 3 and 6Â months. An exploratory analysis determined whether child outcomes at 6Â months varied by primary caregiver use of the intervention.
Results
Monitoring indicated that community workers delivered all core intervention components to primary caregivers. However, two thirds of primary caregivers reported using any intervention component âsometimesâ or less frequently at both time points, suggesting that intervention uptake was poor. Additionally, analyses indicated no effect of primary caregiver intervention use on child outcomes at 6Â months, suggesting the intervention itself lacked efficacy.
Conclusions
Poor uptake, and the efficacy of the intervention itself, may have played a role in the null findings of the SWITCH trial on health behaviour and body composition.
Trial registration
The trial was registered in the Australian and New Zealand Clinical Trials Registry (no.
ACTRN12611000164998
); registration date: 10/02/2011
Standardizing kilonovae and their use as standard candles to measure the Hubble constant
The detection of GW170817 is revolutionizing many areas of astrophysics with the joint observation of gravitational waves and electromagnetic emissions. These multimessenger events provide a new approach to determine the Hubble constant, thus, they are a promising candidate for mitigating the tension between measurements of type-Ia supernovae via the local distance ladder and the cosmic microwave background. In addition to the "standard siren"provided by the gravitational-wave measurement, the kilonova itself has characteristics that allow one to improve existing measurements or to perform yet another, independent measurement of the Hubble constant without gravitational-wave information. Here, we employ standardization techniques borrowed from the type-Ia community and apply them to kilonovae, not using any information from the gravitational-wave signal. We use two versions of this technique, one derived from direct observables measured from the light curve, and the other based on inferred ejecta parameters, e.g., mass, velocity, and composition, for two different models. These lead to Hubble constant measurements of H0=109-35+49 km s-1 Mpc-1 for the measured analysis, and H0=85-17+22 km s-1 Mpc-1 and H0=79-15+23 km s-1 Mpc-1 for the inferred analyses. This measurement has error bars within âź2 to the gravitational-wave measurements (H0=74-8+16 km s-1 Mpc-1), showing its promise as an independent constraint on H0
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