Electron Beams with Orbital Angular Momentum

Electron vortex beams are beams of freely propagating electrons that possess orbital angular momentum. Recently predicted and experimentally verified, electron vortices are hoped to lead to new developments in several areas, in particular electron microscopy, as well as other areas as diverse as spintronics and quantum information. This thesis introduces and examines key concepts relating to electron vortices, and as an introduction, the major developments relating to electron vortices over the past few years are outlined and discussed. The Bessel beam is derived as a suitable solution to the Schrodinger equation for an electron beam carrying orbital angular momentum. The linear and orbital angular momenta of such a beam are discussed alongside the use of electron vortices in manipulation of nanoparticles. Being a charged particle the electron vortex carries electromagnetic fields; the magnetic field is found to have an axial component, unique to the vortex beam. Coupling between the spin and orbital angular momentum of the electron propagating within its own field is found to be negligible in typical electron microscope contexts. Electron vortices are found to have a similar form as the more widely known optical vortices, but key differences between electrons and photons lead to fundamentally different behaviour in many circumstances. The main differences between electron and optical vortices are outlined throughout this thesis. Interactions between the electron and optical vortices and matter, in the form of a hydrogenic atom, are considered. In contrast to the optical vortex, interactions between atomic matter and the electron vortex are found to lead to transfer of orbital angular momentum, opening the possibility of using electron vortices in the electron microscope to probe magnetism at nano- or atomic-scales. The premise and requirements of such experiments are discussed

Quantised orbital angular momentum transfer and magnetic dichroism in the interaction of electron vortices with matter

Following the very recent experimental realisation of electron vortices, we consider their interaction with matter, in particular the transfer of orbital angular momentum in the context of electron energy loss spectroscopy, and the recently observed dichroism in thin film magnetised iron samples. We show here that orbital angular momentum exchange does indeed occur between electron vortices and the internal electronic-type motion, as well as center of mass motion of atoms in the electric dipole approximation. This contrasts with the case of optical vortices where such transfer only occurs in transitions involving multipoles higher than the dipole. The physical basis of the observed dichroism is explained

Considerations for the development of agility during childhood and adolescence

Despite being recognized as an essential component of sports performance, agility development in youths is largely under-researched. this article reviews the evidence examining the effects of growth, maturation and training on both change of direction speed and cognitive processing in children and adolescents, and how combined, these factors may influence agility. training guidelines are provided to help strength and conditioning coaches prescribe agility training for youths at different stages of maturation, in a safe and effective manner

Worlds of events: deduction with partial knowledge about causality

Interactions between internet users are mediated by their devices and the common support infrastructure in data centres. Keeping track of causality amongst actions that take place in this distributed system is key to provide a seamless interaction where effects follow causes. Tracking causality in large scale interactions is difficult due to the cost of keeping large quantities of metadata; even more challenging when dealing with resource-limited devices. In this paper, we focus on keeping partial knowledge on causality and address deduction from that knowledge.We provide the first proof-theoretic causality modelling for distributed partial knowledge. We prove computability and consistency results. We also prove that the partial knowledge gives rise to a weaker model than classical causality. We provide rules for offline deduction about causality and refute some related folklore. We define two notions of forward and backward bisimilarity between devices, using which we prove two important results. Namely, no matter the order of addition/ removal, two devices deduce similarly about causality so long as: (1) the same causal information is fed to both. (2) they start bisimilar and erase the same causal information. Thanks to our establishment of forward and backward bisimilarity, respectively, proofs of the latter two results work by simple induction on length.-This work was partially funded by the SyncFree project in the European Seventh Framework Programme under Grant Agreement 609551 and by the Erasmus Mundus Joint Doctorate Programme under Grant Agreement 2012-0030. Our special thanks to the SyncFree peers for their prolific comments on the early versions of this work. We would like to also thank the anonymous referees for their constructive discussion over the ICE forum.info:eu-repo/semantics/publishedVersio

A systematic review of the neural correlates of sexual minority stress: towards an intersectional minority mosaic framework with implications for a future research agenda

Background: Systemic oppression, particularly towards sexual minorities, continues to be deeply rooted in the bedrock of many societies globally. Experiences with minority stressors (e.g. discrimination, hate-crimes, internalized homonegativity, rejection sensitivity, and microaggressions or everyday indignities) have been consistently linked to adverse mental health outcomes. Elucidating the neural adaptations associated with minority stress exposure will be critical for furthering our understanding of how sexual minorities become disproportionately affected by mental health burdens. Following PRISMA-guidelines, we systematically reviewed published neuroimaging studies that compared neural dynamics among sexual minority and heterosexual populations, aggregating information pertaining to any measurement of minority stress and relevant clinical phenomena. Results: Only 1 of 13 studies eligible for inclusion examined minority stress directly, where all other studies focused on investigating the neurobiological basis of sexual orientation. In our narrative synthesis, we highlight important themes that suggest minority stress exposure may be associated with decreased activation and functional connectivity within the default-mode network (related to the sense-of-self and social cognition), and summarize preliminary evidence related to aberrant neural dynamics within the salience network (involved in threat detection and fear processing) and the central executive network (involved in executive functioning and emotion regulation). Importantly, this parallels neural adaptations commonly observed among individuals with posttraumatic stress disorder (PTSD) in the aftermath of trauma and supports the inclusion of insidious forms of trauma related to minority stress within models of PTSD. Conclusions: Taken together, minority stress may have several shared neuropsychological pathways with PTSD and stress-related disorders. Here, we outline a detailed research agenda that provides an overview of literature linking sexual minority stress to PTSD and insidious trauma, moral affect (including shame and guilt), and mental health risk/resiliency, in addition to racial, ethnic, and gender related minority stress. Finally, we propose a novel minority mosaic framework designed to inform future directions of minority stress neuroimaging research from an intersectional lens

Post-Traumatic Stress Symptoms in Long-Term Non-Hodgkin's Lymphoma Survivors: Does Time Heal?

Little is known about the trajectory of post-traumatic stress disorder (PTSD) symptoms in cancer survivors, despite the fact that such knowledge can guide treatment. Therefore, this study examined changes in PTSD symptoms among long-term survivors of non-Hodgkin's lymphoma (NHL) and identified demographic, clinical, and psychosocial predictors and correlates of PTSD symptomatology

Quality of Life Among Long-Term Survivors of Non-Hodgkin Lymphoma: A Follow-Up Study

Little is known about change in quality of life (QOL) among long-term cancer survivors. We examined change over time in QOL among long-term survivors of non-Hodgkin lymphoma and identified demographic, clinical, and psychosocial risk factors for poor outcomes

The impact and perception of England’s web-based heart age test of cardiovascular disease risk: A mixed-methods study

Background: It is well documented that individuals struggle to understand cardiovascular disease percentage risk scores which led to the development of heart age as a means of communicating risk. Developed for clinical use, its application in raising public awareness of heart health as part of a self-directed digital test has not been considered before. Objectives: To understand who accesses England’s heart age test and its effect on user perception, knowledge and understanding of CVD risk, future behaviour intentions and potential engagement with primary care services. Methods: There were three sources of data: 1. Routinely gathered data on all those accessing the heart age test (Feb 2015-Jun 2020); 2. Online survey, distributed January-March 2021; 3. Interviews with a sub-sample of survey respondents (February-March 2021). Data were used to describe the test user population, explore knowledge and understanding of CVD risk, confidence in interpreting CVD risk and control of CVD risk, and the effect on future behaviour intentions and potential engagement with primary care. Interviews were analysed using reflexive thematic analysis. Results: Between Feb 2015 and Jun 2020, the heart age test was completed almost 5 million times, with more completions by males (54.8%), those aged 50-59 years (27.2%), from a White ethnic background (81%), and those living in the least deprived 20% of areas (14.4%). The study concluded with 819 survey responses and 33 semi-structured interviews. Participants suggested they understood the meaning of a higher estimated heart age and self-reported at least some improvements to understanding and confidence in understanding and control of CVD risk. Negative emotional responses were provoked among users when estimated heart age did not equate to their prior risk perceptions. The limited information needed to complete it or the production of a result when physiological risk factor information was missing (i.e., blood pressure, cholesterol) led some users to question the credibility of the test. Yet, most suggested they would or had already recommended the test to others, would use it again in the future, would be more likely to take up the offer of a NHS Health Check, and self-reported that they had made or intended to make changes to their health behaviour or felt encouraged to continue to make changes to their health behaviour. Conclusions: England’s web-based heart age test has engaged large numbers of people on their heart health. Improvements to England’s heart age test, noted in this paper, may enhance user satisfaction and prevent confusion. Future work to understand the longer-term benefit of the test on behavioural outcomes is warranted

Wonder, education, and human flourishing:Theoretical, empirical, and practical perspectives

The premise that underlies this volume is that there are strong interconnections between wonder, education and human flourishing. And more specifically, that wonder can make a significant difference to how well one’s education progresses and how well one’s life goes. The contributors to this volume – both senior, well-known and beginning researchers and students of wonder – variously explore aspects of these connections from philosophical, empirical, theoretical and practical perspectives. The three chapters that comprise Part I of the book are devoted to the importance of wonder for education and for human flourishing. Part II contains four chapters offering conceptual analyses of wonder and perspectives from developmental psychology and philosophy (Spinoza, Wittgenstein, philosophy of religion). The seven chapters that form Part III contain a wealth of ideas and educational strategies to promote wonder in education and teacher education. This volume not only underlines and articulates the importance of wonder in education and in life but also offers fresh perspectives, allowing us to look with renewed wonder at wonder itself