3,250 research outputs found
A Markov Chain Monte Carlo approach to the study of massive black hole binary systems with LISA
The Laser Interferometer Space Antenna (LISA) will produce a data stream
containing a vast number of overlapping sources: from strong signals generated
by the coalescence of massive black hole binary systems to much weaker
radiation form sub-stellar mass compact binaries and extreme-mass ratio
inspirals. It has been argued that the observation of weak signals could be
hampered by the presence of loud ones and that they first need to be removed to
allow such observations. Here we consider a different approach in which sources
are studied simultaneously within the framework of Bayesian inference. We
investigate the simplified case in which the LISA data stream contains
radiation from a massive black hole binary system superimposed over a (weaker)
quasi-monochromatic waveform generated by a white dwarf binary. We derive the
posterior probability density function of the model parameters using an
automatic Reversible Jump Markov Chain Monte Carlo algorithm (RJMCMC). We show
that the information about the sources and noise are retrieved at the expected
level of accuracy without the need of removing the stronger signal. Our
analysis suggests that this approach is worth pursuing further and should be
considered for the actual analysis of the LISA data.Comment: submitted to cqg as GWDAW-10 conference proceedings, 10 pages, 4
figures, some changes to plots and numerical detail
LISA Response Function and Parameter Estimation
We investigate the response function of LISA and consider the adequacy of its
commonly used approximation in the high-frequency range of the observational
band. We concentrate on monochromatic binary systems, such as white dwarf
binaries. We find that above a few mHz the approxmation starts becoming
increasingly inaccurate. The transfer function introduces additional amplitude
and phase modulations in the measured signal that influence parameter estmation
and, if not properly accounted for, lead to losses of signal-to-noise ratio.Comment: 4 pages, 2 figures, amaldi 5 conference proceeding
Conceptualising the employment value proposition: the role of the extended marketing mix
In Australia, as elsewhere in the Western world, firms are faced with the challenge of recruiting, retaining and motivating quality human resources from increasingly competitive labour markets. One response to this challenge has manifest in firms attempting to position themselves as ‘Employers of Choice’ (EOC) in their relevant industries. In order to contribute to that ongoing debate, this paper explores the application of a key element in marketing theory – the ‘extended marketing-mix’ concept – to the management of the employment relationship
The Effect of the LISA Response Function on Observations of Monochromatic Sources
The Laser Interferometer Space Antenna (LISA) is expected to provide the
largest observational sample of binary systems of faint sub-solar mass compact
objects, in particular white-dwarfs, whose radiation is monochromatic over most
of the LISA observational window. Current astrophysical estimates suggest that
the instrument will be able to resolve about 10000 such systems, with a large
fraction of them at frequencies above 3 mHz, where the wavelength of
gravitational waves becomes comparable to or shorter than the LISA arm-length.
This affects the structure of the so-called LISA transfer function which cannot
be treated as constant in this frequency range: it introduces characteristic
phase and amplitude modulations that depend on the source location in the sky
and the emission frequency. Here we investigate the effect of the LISA transfer
function on detection and parameter estimation for monochromatic sources. For
signal detection we show that filters constructed by approximating the transfer
function as a constant (long wavelength approximation) introduce a negligible
loss of signal-to-noise ratio -- the fitting factor always exceeds 0.97 -- for
f below 10mHz, therefore in a frequency range where one would actually expect
the approximation to fail. For parameter estimation, we conclude that in the
range 3mHz to 30mHz the errors associated with parameter measurements differ
from about 5% up to a factor of 10 (depending on the actual source parameters
and emission frequency) with respect to those computed using the long
wavelength approximation.Comment: replacement version with typos correcte
Selection of an internet content filtering solution using the analytic hierarchy process
This talk describes the selection of an Internet Content Filtering solution suitable for the specific requirements of the Waikato Institute of Technology (Wintec). Product data was collected from a variety of sources including: vendor product datasheets, industry benchmark tests, the experiences of other institutions and the academic literature. The available solutions were compared using the Analytic Hierarchy Process (Saaty 1980), a multicriteria decision support tool, using the above data and priority weightings determined for each criterion
Care of elderly patients: a prospective audit of the prevalence of hypotension and the use of BIS intraoperatively in 25 hospitals in London
BACKGROUND: Anaesthesia is frequently complicated by intraoperative hypotension (IOH) in the elderly, and this is associated with adverse outcome. The definition of IOH is controversial, and although management guidelines for IOH in the elderly exist, the frequency of IOH and typical clinically applied treatment thresholds are largely unknown in the UK. METHODS: We audited frequency of intraoperative blood pressure against national guidelines in elderly patients undergoing surgery. Depth of anaesthesia (DOA) monitoring was also audited due to the association between low DOA values and IOH with increased mortality (as part of "double" and "triple low" phenomena) and because it is a suggested management strategy to reduce IOH. RESULTS: Twenty-five hospitals submitted data on 481 patients. Hypotension varied depending on the definition, but affected 400 patients (83.3Â %) using the AAGBI standard. Furthermore, 2.9, 13.5, and 24.6Â % had mean arterial blood pressures <50, <60, and <70Â mmHg for 20Â min, respectively, and 136 (28.4Â %) had systolic blood pressure decrease by 20Â % for 20Â min. DOA monitors were used for 45 (9.4Â %) patients. CONCLUSIONS: IOH is common and use of DOA monitors is less than implied by guidelines. Improved management of IOH may be a simple intervention with real potential to reduce morbidity in this vulnerable group
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