1,822 research outputs found
Perceptions of physiotherapists towards research: a mixed methods study
OBJECTIVES: To explore the perceptions of physiotherapists towards the use of and participation in research.
DESIGN: Concurrent mixed methods research, combining in-depth interviews with three questionnaires (demographics, Edmonton Research Orientation Survey, visual analogue scales for confidence and motivation to participate in research).
SETTING: One physiotherapy department in a rehabilitation hospital, consisting of seven specialised areas.
PARTICIPANTS: Twenty-five subjects {four men and 21 women, mean age 38 [standard deviation (SD) 11] years} who had been registered as a physiotherapist for a mean period of 15 (SD 10) years participated in this study. They were registered with the New Zealand Board of Physiotherapy, held a current practising certificate, and were working as a physiotherapist or physiotherapy/allied health manager at the hospital.
MAIN OUTCOME MEASURE: The primary outcome measure was in-depth interviews and the secondary outcome measures were the three questionnaires.
RESULTS: Physiotherapists were generally positive towards research, but struggled with the concept of research, the available literature and the time to commit to research. Individual confidence and orientation towards research seemed to influence how these barriers were perceived.
CONCLUSION: This study showed that physiotherapists struggle to implement research in their daily practice and become involved in research. Changing physiotherapists' conceptions of research, making it more accessible and providing dedicated research time could facilitate increased involvement in the physiotherapy profession
Bayesian model selection for testing the no-hair theorem with black hole ringdowns
General relativity predicts that a black hole that results from the merger of
two compact stars (either black holes or neutron stars) is initially highly
deformed but soon settles down to a quiescent state by emitting a superposition
of quasi-normal modes (QNMs). The QNMs are damped sinusoids with characteristic
frequencies and decay times that depend only on the mass and spin of the black
hole and no other parameter - a statement of the no-hair theorem. In this paper
we have examined the extent to which QNMs could be used to test the no-hair
theorem with future ground- and space-based gravitational-wave detectors. We
model departures from general relativity (GR) by introducing extra parameters
which change the mode frequencies or decay times from their general
relativistic values. With the aid of numerical simulations and Bayesian model
selection, we assess the extent to which the presence of such a parameter could
be inferred, and its value estimated. We find that it is harder to decipher the
departure of decay times from their GR value than it is with the mode
frequencies. Einstein Telescope (ET, a third generation ground-based detector)
could detect departures of <1% in the frequency of the dominant QNM mode of a
500 Msun black hole, out to a maximum range of 4 Gpc. In contrast, the New
Gravitational Observatory (NGO, an ESA space mission to detect gravitational
waves) can detect departures of ~ 0.1% in a 10^8 Msun black hole to a
luminosity distance of 30 Gpc (z = 3.5).Comment: 9 pages, 5 figure
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
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
Testing the no-hair theorem with black hole ringdowns using TIGER
The Einstein Telescope (ET), a proposed third-generation gravitational wave
observatory, would enable tests of the no-hair theorem by looking at the
characteristic frequencies and damping times of black hole ringdown signals. In
previous work it was shown that with a single black hole
at distance Gpc (or redshift ), deviations of a few
percent in the frequencies and damping times of dominant and sub-dominant modes
would be within the range of detectability. Given that such sources may be
relatively rare, it is of interest to see how well the no-hair theorem can be
tested with events at much larger distances and with smaller signal-to-noise
ratios, thus accessing a far bigger volume of space and a larger number of
sources. We employ a model selection scheme called TIGER (Test Infrastructure
for GEneral Relativity), which was originally developed to test general
relativity with weak binary coalescence signals that will be seen in
second-generation detectors such as Advanced LIGO and Advanced Virgo. TIGER is
well-suited for the regime of low signal-to-noise ratio, and information from a
population of sources can be combined so as to arrive at a stronger test. By
performing a range of simulations using the expected noise power spectral
density of Einstein Telescope, we show that with TIGER, similar deviations from
the no-hair theorem as considered in previous work will be detectable with
great confidence using sources distributed uniformly in
co-moving volume out to 50 Gpc ().Comment: 11 pages, 20 figures. Matches version in PR
Negative Quasi-Probability as a Resource for Quantum Computation
A central problem in quantum information is to determine the minimal physical
resources that are required for quantum computational speedup and, in
particular, for fault-tolerant quantum computation. We establish a remarkable
connection between the potential for quantum speed-up and the onset of negative
values in a distinguished quasi-probability representation, a discrete analog
of the Wigner function for quantum systems of odd dimension. This connection
allows us to resolve an open question on the existence of bound states for
magic-state distillation: we prove that there exist mixed states outside the
convex hull of stabilizer states that cannot be distilled to non-stabilizer
target states using stabilizer operations. We also provide an efficient
simulation protocol for Clifford circuits that extends to a large class of
mixed states, including bound universal states.Comment: 15 pages v4: This is a major revision. In particular, we have added a
new section detailing an explicit extension of the Gottesman-Knill simulation
protocol to deal with positively represented states and measurement (even
when these are non-stabilizer). This paper also includes significant
elaboration on the two main results of the previous versio
Power scalable TEM(oo) CW Nd: YAG laser with thermal lens compensation
We present finite-element analyzes and experimental results to validate our approach for building high-power single-mode Nd:YAG lasers. We show that the thermooptical and thermomechanical properties of a slab laser can be controlled. This is essential for the use of the proposed unstable resonator. We include demonstration of an efficient subscale laser operating at 20 W TEM00.D. Mudge, M. Ostermeyer, P. J. Veitch, J. Munch, B. Middlemiss, D. J. Ottaway and M. W. Hamilto
Compensation of Strong Thermal Lensing in High Optical Power Cavities
In an experiment to simulate the conditions in high optical power advanced
gravitational wave detectors such as Advanced LIGO, we show that strong thermal
lenses form in accordance with predictions and that they can be compensated
using an intra-cavity compensation plate heated on its cylindrical surface. We
show that high finesse ~1400 can be achieved in cavities with internal
compensation plates, and that the cavity mode structure can be maintained by
thermal compensation. It is also shown that the measurements allow a direct
measurement of substrate optical absorption in the test mass and the
compensation plate.Comment: 8 page
Scaling Observation Error for Optimal Assimilation of CCI SST Data into a Regional HYCOM EnOI System
South Africa currently possesses no operational ocean forecasting system for the purpose of predicting ocean state variables including temperature,salinity and velocity. Substantial initial efforts towards this goal have been made and resulted in a system using a regional Hybrid Coordinate Ocean Model (HYCOM) along with the Ensemble Optimal Interpolation (EnOI)assimilation scheme. Assimilating only sea surface temperature (SST) observations from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) product into the system resulted in a degraded forecast. Aiming to address this, Climate Change Initiative (CCI) SSTs are assimilated into the system in an effort to improve the forecast skill. Observation errors in the assimilated product are used in the EnOI to determine whether more confidence should be placed in the model or observations in producing the analysis, but overconfidence in observations can shock the model and result in failure. To tweak the impact of the assimilation, a scaling factor is applied in the assimilation code. A scaling factor of 25 was found to produce a favourable result with lowest mean root mean square error (RMSE;1.098C) between the model and observations over time. Postulating the error to be overconfident, a floor value is introduced in order to set a minimum value for the observation error thereby reducing confidence in the observations. These experiments fared less favourably with a floor value of 0.5 and a scaling factor of 15 producing the best mean RMSE (1.118C)
The effects of LIGO detector noise on a 15-dimensional Markov-chain Monte-Carlo analysis of gravitational-wave signals
Gravitational-wave signals from inspirals of binary compact objects (black
holes and neutron stars) are primary targets of the ongoing searches by
ground-based gravitational-wave (GW) interferometers (LIGO, Virgo, and
GEO-600). We present parameter-estimation results from our Markov-chain
Monte-Carlo code SPINspiral on signals from binaries with precessing spins. Two
data sets are created by injecting simulated GW signals into either synthetic
Gaussian noise or into LIGO detector data. We compute the 15-dimensional
probability-density functions (PDFs) for both data sets, as well as for a data
set containing LIGO data with a known, loud artefact ("glitch"). We show that
the analysis of the signal in detector noise yields accuracies similar to those
obtained using simulated Gaussian noise. We also find that while the Markov
chains from the glitch do not converge, the PDFs would look consistent with a
GW signal present in the data. While our parameter-estimation results are
encouraging, further investigations into how to differentiate an actual GW
signal from noise are necessary.Comment: 11 pages, 2 figures, NRDA09 proceeding
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