Bayesian model comparison for compartmental models with applications in positron emission tomography

We develop strategies for Bayesian modelling as well as model comparison, averaging and selection for compartmental models with particular emphasis on those that occur in the analysis of positron emission tomography (PET) data. Both modelling and computational issues are considered. Biophysically inspired informative priors are developed for the problem at hand, and by comparison with default vague priors it is shown that the proposed modelling is not overly sensitive to prior specification. It is also shown that an additive normal error structure does not describe measured PET data well, despite being very widely used, and that within a simple Bayesian framework simultaneous parameter estimation and model comparison can be performed with a more general noise model. The proposed approach is compared with standard techniques using both simulated and real data. In addition to good, robust estimation performance, the proposed technique provides, automatically, a characterisation of the uncertainty in the resulting estimates which can be considerable in applications such as PET

Optical read-out techniques for the control of test-masses in gravitational wave observatories

This thesis discusses the development of optical read-out techniques, including a simple shadow sensor and a more elaborate compact homodyne interferometer, known as EUCLID. Both of these sensors could be utilised as part of a seismic isolation and suspension system of a ground-based gravitational wave observatory, such as Advanced LIGO. As part of the University of Birmingham’s commitment to the upgrade of the Advanced LIGO, it was responsible for providing a large quantity of sensor and actuator units. This required the development and qualification of the shadow sensor, through to production and testing. While characterising production units, an excess noise issue was uncovered and eventually mitigated; demonstrating that even for a ‘simple’ shadow sensor, ensuring a large quantity of units meet the target sensitivity requirement of 300 pm/rt-Hz at 1 Hz, is not a trivial exercise. Over the duration of this research, I played a key role in the design and fabrication of a novel compact interferometer. The objective of this work was to demonstrate that the interferometric technique offers a significant improvement over the existing shadow sensors and could easily be deployed in current, or future, generations of gravitational wave observatories. Encouraging sensitivities of approximately 50 pm/rt-Hz at 1 Hz, over operating ranges of approximately 6 mm have been achieved, whilst maintaining around 1 degree of mirror tilt immunity. In addition, this design overcomes many of the drawbacks traditionally associated with interferometers

Dynamic filtering of static dipoles in magnetoencephalography

We consider the problem of estimating neural activity from measurements of the magnetic fields recorded by magnetoencephalography. We exploit the temporal structure of the problem and model the neural current as a collection of evolving current dipoles, which appear and disappear, but whose locations are constant throughout their lifetime. This fully reflects the physiological interpretation of the model. In order to conduct inference under this proposed model, it was necessary to develop an algorithm based around state-of-the-art sequential Monte Carlo methods employing carefully designed importance distributions. Previous work employed a bootstrap filter and an artificial dynamic structure where dipoles performed a random walk in space, yielding nonphysical artefacts in the reconstructions; such artefacts are not observed when using the proposed model. The algorithm is validated with simulated data, in which it provided an average localisation error which is approximately half that of the bootstrap filter. An application to complex real data derived from a somatosensory experiment is presented. Assessment of model fit via marginal likelihood showed a clear preference for the proposed model and the associated reconstructions show better localisation

Complex amplitude phase motion in Dalitz plot heavy meson three body decay

We propose a method to determine the phase motion of a complex amplitude in three body heavy meson decays. We show that the phase variation of a complex amplitude can be directly revealed through the interference observed in the Dalitz Plot region where it crosses with a well established resonant state. This method could be applied to the decays \d3pi and $D^+\to K^-\pi^+\pi^+$, to determine whether the low mass states $\sigma$ and $\kappa$, suggested by E791, have phase motions compatible with resonances.Comment: To appear in Physics Letters

Strong Decays of Strange Quarkonia

In this paper we evaluate strong decay amplitudes and partial widths of strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give numerical results for all energetically allowed open-flavor two-body decay modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and 1F multiplets, comprising strong decays of a total of 43 resonances into 525 two-body modes, with 891 numerically evaluated amplitudes. This set of resonances includes all strange qqbar states with allowed strong decays expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical results for all amplitudes present in each decay mode. We also discuss the status of the associated experimental candidates, and note which states and decay modes would be especially interesting for future experimental study at hadronic, e+e- and photoproduction facilities. These results should also be useful in distinguishing conventional quark model mesons from exotica such as glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table

Discovery of palladium, antimony, tellurium, iodine, and xenon isotopes

Currently, thirty-eight palladium, thirty-eight antimony, thirty-nine tellurium, thirty-eight iodine, and forty xenon isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.Comment: to be published in At. Data Nucl. Data Table

A vulnerability approach to irregular migration and modern slavery in Australia

It is widely recognised that migrants and irregular migrants are at risk of modern slavery and slavery-like practices worldwide. As migrants and irregular migrants make their way across state borders, or reach their destination countries, they have been victim to practices such as forced labour, exploitation, wage theft, torture and inhuman treatment and sexual servitude, among other practices. Australia is no exception, with just under 300 cases of modern slavery reported to the Australian Federal Police between 2021 and 2022. Although Australia has acted to stop slavery and slavery-like practices, it has focused on a law enforcement response, ignoring the role that laws and policies play in contributing to modern slavery in Australia. This article adopts a vulnerability approach to modern slavery, examining how legal, policy, institutional and structural factors within Australia contribute to exacerbating the vulnerability of migrants and irregular migrants to modern slavery and slavery-like practices. Utilising a vulnerability framework not only moves beyond the law enforcement approaches taken by the Australian government, but sheds important light on the need for policy, legal and institutional reform to effectively combat modern slavery in Australia and ensure there is redress and justice for its victims