Resonant Soft X-ray Scattering from Complex Magnetic Structures

This thesis lays out a number of investigations into different magnetic systems governed by short- and long-range magnetic interactions. We take advantage of the sensitivity of soft x-rays to magnetism and the polarisation dependence of magnetic x-ray scattering to investigate these systems. Full polarisation analysis is a highly sensitive technique which can be utilised to refine small deviations in magnetic structures. We present work on improving the efficiency of these measurements, finding efficiencies of up to 75\% in the measurement method by rotating the incident light angle with the polarisation analyser fixed at the peak of intensity. Full polarisation analysis has been applied to the study of magnetism in the heavy fermion system CeRu$_2$Al$_{10}$. Although this system has a relatively simple magnetic structure it is highly unstable to doping and has an anomalously high transition temperature. Magnetic scattering was observed at the cerium $M$-edges and the polarisation dependence of the scattering is only consistent with a non-collinear magnetic structure. Least squares fitting of the non-collinear structure revealed a small spin canting of the magnetic structure towards the $a$-axis. This canting requires a symmetry lowering of the space group from $Cmcm$ to the subgroup $Pmnm$ to allow for the Dzyaloshinskii-Moriya interaction. Full polarisation analysis as well as neutron powder and single crystal measurements have been undertaken on the multiferroic skyrmion system Cu$_2$OSeO$_3$. Measurements were taken in the helical, conical, skyrmion, and ferrimagnetic regions. The (1, 0, 0) reflection at the Cu $L$-edge was found to be due to the anisotropy of the tensor of x-ray susceptibility (ATS). The satellite reflections around the ATS peak were observed not to display the polarisation dependence expected for a helix. The polarisation dependence observed is not consistent with a non-collinear structure and can be fitted with a long spin density wave with the moment pointing along the scattering vector. This structure would be expected to produce stepped features in the magnetisation measurements which are not observed. This long spin density wave structure is also not consistent with previous Lorentz transmission electron microscopy measurements. Neutron scattering measurements confirm the three up one down magnetic structure in the ferrimagnetic phase. However, the magnetic intensity at the $(1, 0, 0)$ position in the helical phase indicates a change in the magnetic structure Rietveld refinement fitting with a reduced ferrimagnetic structure where one of the $4a$ site copper moments is coupled antiferromagnetically to the $12b$ and remaining $4a$ site moments. Finally, the magnetic properties of thin films have been investigated using absorption techniques and x-ray magnetic circular dichroism. Manganese oxide monolayers and bilayers have been grown in different charge environments provided by heterostructuring with SrTiO$_3$ and LaAlO$_3$, with the aim of controlling the magnetic properties of the manganese \textit{via} charge transfer. It was found that the magnetic properties of the manganese is strongly linked to the capping layer used. This is due to different effects introduced by the growth of the different capping layers; LaAlO$_3$ introducing strong ion intermixing, and SrTiO$_3$ introducing oxygen vacancies. Both capping layers displayed superparamagnetic temperature and field dependent properties with small clusters (around 4) of strongly interacting manganese ions. The strongly interacting manganese ions are separated by either the ion intermixing or oxygen vacancies. Both capping layers displayed superparamagnetic temperature and field dependent properties. Superparamagnetism is usually only observed in nanoparticles. The elimination of the magnetic interactions required for nanoparticle-like properties to be possible are due to a combination of ion intermixing and oxygen vacancies

Refining the Reasonable Apprehension of Bias Test: Providing Judges Better Tools for Addressing Judicial Disqualification

Despite a considerable amount of litigation concerning judicial impartiality, the Canadian reasonable apprehension of bias test for judicial disqualification has remained fundamentally unaltered and is well accepted in the jurisprudence. Unfortunately, the application of the test continues to generate difficulties for judges who need to use it to make decisions in marginal cases. Based on previously published doctrinal and empirical research, the goal in the present contribution is to suggest modifications to the test that will better explain the existing jurisprudence and make it easier for judges to understand when recusal is or is not necessary in marginal cases. The authors consider first the advantages of the existing test and suggest that in order to be useful, any refinement to the test must, to the greatest extent possible, preserve those advantages. Second, the authors explain why inconsistent application of the test in marginal cases is a concern. Third, they analyze the ways in which the existing test, and the jurisprudence explaining and applying it, are problematic. Fourth, the authors propose a modification to the reasonable apprehension of bias test that is designed to address these shortcomings while preserving the key advantages of the existing test

High temperature reliability of power module substrates

The thermal cycling reliability of candidate copper and aluminium power substrates has been assessed for use at temperatures exceeding 300°C peak using a combination of thermal cycling, nanoindentation and finite element modelling to understand the relative stresses and evolution of the mechanical properties. The results include the relative cycling lifetimes up to 350°C, demonstrating almost an order of magnitude higher lifetime for active metal brazed Al / AlN substrates over Cu / Si3N4, but four times more severe roughening and cracking of the Ni-P plating's on the Al / AlN (DBA) substrates. The nonlinear finite element modelling illustrated that the yield strength of the metal and the thickness of the ceramic are the main stress controlling factors, but comparisons with the cycling lifetime results demonstrated that the fracture toughness (resistance) of the ceramic is the over-riding controlling factor for the overall passive thermal cycling lifetimes. In order to achieve the highest substrate lifetime for the highly stressed high temperature thermal cycled applications, the optimum solution appears to be annealed copper, brazed on to a thicker than normal or higher fracture toughness Si3N4 ceramic

Glory in optical backscattering from air bubbles

Observations of light backscattered from air bubbles in a viscous liquid demonstrate an enhancement due to axial focusing. A physical-optics approximation for the cross-polarized scattering correctly describes the spacing of regular features observed. The non-cross polarized scattering is not adequately described by a single class of rays

Long-term effects of mild traumatic brain injury on cognitive performance

Although a proportion of individuals report chronic cognitive difficulties after mild traumatic brain injury (mTBI), results from behavioral testing have been inconsistent. In fact, the variability inherent to the mTBI population may be masking subtle cognitive deficits. We hypothesized that this variability could be reduced by accounting for post-concussion syndrome (PCS) in the sample. Thirty-six participants with mTBI (>1 year post-injury) and 36 non-head injured controls performed information processing speed (Paced Visual Serial Addition Task, PVSAT) and working memory (n-Back) tasks. Both groups were split by PCS diagnosis (4 groups, all n = 18), with categorization of controls based on symptom report. Participants with mTBI and persistent PCS had significantly greater error rates on both the n-Back and PVSAT, at every difficulty level except 0-Back (used as a test of performance validity). There was no difference between any of the other groups. Therefore, a cognitive deficit can be observed in mTBI participants, even 1 year after injury. Correlations between cognitive performance and symptoms were only observed for mTBI participants, with worse performance correlating with lower sleep quality, in addition to a medium effect size association (falling short of statistical significance) with higher PCS symptoms, post-traumatic stress disorder (PTSD), and anxiety. These results suggest that the reduction in cognitive performance is not due to greater symptom report itself, but is associated to some extent with the initial injury. Furthermore, the results validate the utility of our participant grouping, and demonstrate its potential to reduce the variability observed in previous studies

Feasibility and Design Studies: Camplain Valley Sanitary Landfill

Guidebook for field trips in Vermont: 64th annual meeting October 13, 14, 15, 1972 Burlington, Vermont: Trip EG-

Internal auditory canal metastasis mimicking a vestibular schwannoma at presentation - a case report and review of the literature.

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Metastasis to the internal auditory canal from breast carcinoma is extremely rare and difficult to diagnose. It radiologically mimics vestibular schwannoma and can occur as a first manifestation of systemic relapse after a long disease-free interval in patients previously treated for early breast cancer. The diagnosis is usually made retrospectively and the optimal management of such metastasis following complete resection remains undefined

Facebook is not a silver bullet for teachers' professional development : Anatomy of an eight-year-old social-media community

Online communities and social-network sites are used to deliver professional-development services for teachers. Professional development should help teachers to reflect on their practice and improve in helping them to guide students' growth. Peer and community models, such as coaching and sharing knowledge in network and knowledge communities, have been proposed. Recently these practices have been taken into use in social media services, such as Facebook. Although earlier research has examined teachers' online communities, we move beyond understanding individuals motivations and examine community-level dynamics. Understanding these dynamics is important to understand the interaction between teachers, resources and the platform in use and resulting professional development. To understand the evolution of an informal and self-organised Facebook teachers' group, containing nearly 20,000 teachers, its eight years of activity was analysed by employing a mixed-methods research design; data science and participatory observation. Analysis gives account of both the evolution of participants' engagement and activity, and the evolution of content and its relevance for teachers' professional development. The results suggest that managers of professional development need to consider how to facilitate participation in order to focus on pedagogically motivated use of information technology, for system developers to consider how to assist recruitment of members and sustain their activity, and for all stakeholders to acknowledge that a peer-organised online professional development community requires significant effort. Furthermore, we suggest that instead of addressing large groups like these as communities, scholars and practitioners should instead see them as personal learning networks and think about how to establish smaller and more manageable groups as communities.Peer reviewe