Cause and Amelioration of MRI-Induced Heating Through Medical Implant Lead Wires

The RF fields present in magnetic resonance imaging (MRI) scanners can induce hazardous heating in patients wearing medical implants. The inherent design and locale of deep brain stimulators (DBS) and spinal cord stimulators (SCS) make them particularly susceptible. We apply antenna concepts and use electromagnetic (EM) simulation to explain the phenomenon and anticipate its sensitivity to lead wire length. We anticipate that a DC resistance of less than 50 Ω/m and an RF impedance of more than 1:23kΩ/m would be required for a safe electrode for SCS use. We investigate the possibility of manipulating wire conductivity and diameter in order to use the skin depth effect to achieve a safe electrode. The effect of the thickness and permittivity of insulation surrounding the wires is explored

Impulse TDR and its application to measurement of antennas

The traditional stimulus signal used in a time-domain reflectometer (TDR) is a voltage step. We propose an alternative technique, whereby an impulse generator is employed in place of the step generator in a TDR. The advantage conferred by “impulse TDR” is that more energy is available at higher frequencies than with conventional step TDR, and so a higher bandwidth and signal-to-noise ratio (SNR) is achieved. The theoretical result is compared with measurement

Measurement of antennas and microwave components using time-domain reflectometry of a voltage impulse

Band-pass microwave systems such as ultra-wideband antennas are traditionally characterized in the frequency-domain through a vector network analyzer in an anechoic chamber. A recent study proved antennas could be accurately measured in the time-domain using a step-function time-domain reflectometer (TDR), without the need for an anechoic chamber. We propose a new advance in the TDR characterization method. An impulse generator is employed in place of the step generator in a TDR set-up. The advantage conferred by this change is that more energy is available beyond a given frequency than with a step, and so a higher signal-to-noise ratio is achieved. The theoretical result is compared with measurement

Women in Polish Cinema

The title of Ewa Mazierska and Elżbieta Ostrowska's Women in Polish Cinema designates an area of film studies doubly neglected. In the field of Polish cinema studies, itself marginal territory, there has been scant attention paid to gender issues. The authors lay much of the blame for this at the feet of Polish film scholars themselves, resistant to gender studies out of an all too symptomatic hostility towards feminism as an alien, "corrupting Western influence". Attempting significantly to redress this situation, the authors establish a twofold purpose: to assess the representations of women onscreen and to reassess the place within Polish cinema of women behind the camera. Their analysis mediated by a strong sense of national specificity, Mazierska and Ostrowska reveal the range of historical, political and religious factors that have determined (indeed sometimes over-determined) constructions of femininity in Polish culture and film...

Stereoelectronic effects on the binding of neutral Lewis bases to CdSe nanocrystals

Using P-31 nuclear magnetic resonance (NMR) spectroscopy, we monitor the competition between tri-nbutylphosphine (Bu3P) and various amine and phosphine ligands for the surface of chloride terminated CdSe nanocrystals. Distinct P-31 NMR signals for free and bound phosphine ligands allow the surface ligand coverage to be measured in phosphine solution. Ligands with a small steric profile achieve higher surface coverages (Bu3P = 0.5 nm(-2), Me2P-n-octyl = 2.0 nm(-2), NH2Bu = >3 nm(-2)) and have greater relative binding affinity for the nanocrystal (binding affinity: Me3P > Me2P -n-octyl similar to Me2P -n-octadecyl > Et3P > Bu3P). Among phosphines, only Bu 3 P and Me2P-n-octyl support a colloidal dispersion, allowing a relative surface binding affinity (K-rel) to be estimated in that case (K-rel = 3.1). The affinity of the amine ligands is measured by the extent to which they displace Bu3P from the nanocrystals (K-rel: H2NBu similar to N-n-butylimidazole > 4-ethylpyridine > Bu3P similar to HNBu2 > Me2NBu > Bu3N). The affinity for the CdSe surface is greatest among soft, basic donors and depends on the number of each ligand that bind. Sterically unencumbered ligands such as imidazole, pyridine, and n-alkylamines can therefore outcompete stronger donors such as alkylphosphines. The influence of repulsive interactions between ligands on the binding affinity is a consequence of the high atom density of binary semiconductor surfaces. The observed behavior is distinct from the self-assembly of straight-chain surfactants on gold and silver where the ligands are commensurate with the underlying lattice and attractive interactions between aliphatic chains strengthen the binding

Doctor of Philosophy

dissertationThe nonsense-mediated mRNA decay (NMD) pathway functions as a quality control mechanism and a feature of post-transcriptional gene regulation. NMD degrades mRNAs containing premature termination codons (PTCs) to prevent the production of potentially harmful truncated proteins, and it also destroys many error-free endogenous mRNAs to limit the expression of these genes. NMD is critical for viability in most complex organisms, highlighting the importance of this pathway; however, it is unknown which of the two NMD functions is the feature essential for viability. Understanding how NMD recognizes and degrades targets may provide insight to uncover the requirement of this pathway for viability, but the molecular mechanisms of NMD target recognition and destruction also remain unclear. Work presented in this dissertation describes genetic analysis in Drosophila to reveal the feature of the NMD pathway that is critical for viability, and refines the model describing the mechanism of NMD target degradation. We screened a collection of heterozygous deficiencies for suppression of the incomplete lethality of a hypomorphic allele of the core NMD factor Upf2. This screen identified three autosomal regions that partially suppress Upf2 mutant lethality when deleted. The endogenous NMD target Gadd45 is located within one suppressing region, and we found that elimination of Gadd45 restores viability to multiple null NMD mutants. Mekk1, a factor that acts downstream of Gadd45, resides in another suppressing region, and loss of Mekk1 also restores viability to NMD mutants. The third suppressing region contains ! ! iv! Arc2, and we found that Arc2 and the closely related Arc1 may also contribute to the lethality of Drosophila lacking NMD activity. In addition, this dissertation describes the first genetic analysis of Drosophila Smg5 mutants, and determines that Smg5 is a critical NMD factor required for viability and all NMD function. Further analysis of the first characterization of double mutants for multiple NMD factors reveals there are multiple mechanisms for NMD target degradation. These findings provide a new foundation for understanding the crucial NMD gene regulatory function and reshape the model of the NMD pathway

Bayesian Uncertainty Analysis and Decision Support for Complex Models of Physical Systems with Application to Production Optimisation of Subsurface Energy Resources

Important decision making problems are increasingly addressed using computer models for complex real world systems. However, there are major limitations to their direct use including: their complex structure; large numbers of inputs and outputs; the presence of many sources of uncertainty; which is further compounded by their long evaluation times. Bayesian methodology for the analysis of computer models has been extensively developed to perform inference for the physical systems. In this thesis, the Bayesian uncertainty analysis methodology is extended to provide robust decision support under uncertainty. Bayesian emulators are employed as a fast and efficient statistical approximation for computer models. We establish a hierarchical Bayesian emulation framework that exploits known constrained simulator behaviour in constituents of the decision support utility function. In addition, novel Bayesian emulation methodology is developed for computer models with structured partial discontinuities. We advance the crucial uncertainty quantification methodology to perform a robust decision analysis developing a technique to assess and remove linear transformations of the utility function induced by sources of uncertainty to which conclusions are invariant, as well as incorporating structural model discrepancy and decision implementation error. These are encompassed within a novel iterative decision support procedure which acknowledges utility function uncertainty resulting from the separation of the analysts and final decision makers to deliver a robust class of decisions, along with any additional information, for further consideration. The complete toolkit is successfully demonstrated via an application to the problem of optimal petroleum field development, including an international and commercially important benchmark challenge

Popular Theology from Popular Scientists: Assessing the Legacy of Eddington and Jeans as Apologists

This thesis asserts and demonstrates that the current historical evaluation of the significance of Arthur Eddington and James Jeans is inadequate. Not only has their importance in the years between the two World Wars been forgotten, but their transitional role in the science and religion debate post-Darwin is now largely unrecognised. Both had a major influence on subsequent popular apologists and Eddington in particular influenced post war academic theologians as diverse as Thomas Torrance and Eric Mascall. It is generally accepted that the apologetic writings of Eddington and Jeans were widely read and were adept at conveying their message. They have, however, been increasingly ignored by historians and theologians. This thesis argues that their work post-Darwin on the new physics of the early twentieth century was significant in steering the science and religion dialogue in the United Kingdom away from the more conflict-based approaches such as the beginnings of creationism in the United States. Further their deployment of metaphor, ability to engage in dialogue with the public through the press and the new technology of the wireless were innovative and left a legacy for apologetics and the science and religion dialogue. By an examination of three key texts, a new account is given of the authors’ importance and of the reactions of contemporary theologians, philosophers and scientists. Their work brought the latest science to bear on important areas of traditional theological debate in an accessible way and to a good apologetic end. The role of intuition and ‘seeking’ in relation to Eddington’s writing shows a fresh Quaker-influenced approach to apologetics and the science and religion debate. The widely-accepted role of Susan Stebbing in the post-war decline of Eddington and Jeans is examined and dismissed as simplistic. A new analysis of the reasons for their decline and neglect is made. Jeans and Eddington remind us that the importance of general cultural trends and contemporary events in the science and religion debate is often overlooked. The history of the reception of their apologetic work and the pattern of their continuing significance illustrate the connectedness of theology with current events

Soul-blindness, police orders and Black Lives Matter: Wittgenstein, Cavell, and Rancière

What does it mean to see someone as human, as a member of humankind? What kind of call for justice is it to demand that a group be seen as human beings? This article explores a fundamental kind of injustice: one of perception and how we respond to our perceptions. Drawing on Cavell, Wittgenstein and Rancière we elucidate “soul blindness” as a distinct and basic form of injustice. Rancière’s police orders and Cavell’s soul blindness are mutually constitutive; the undoing of police orders entails a politics of soul dawning. Soul dawning entails acknowledging the humanity of others without erasing difference. In the concluding section we consider white obliviousness to the Black Lives Matters (BLM) movement as a case of soul blindness. Part of the political import of BLM is its capacity to illustrate how practices of soul blindness in the U.S. constitute whiteness in a racialized police order