Secondary Rayleigh-Taylor type Instabilities in the Reconnection Exhaust Jet as a Mechanism for Supra-Arcade Downflows

Supra-arcade downflows (hereafter referred to as SADs) are low-emission, elongated, finger-like features usually observed in active-region coronae above post-eruption flare arcades. Observations exhibit downward moving SADs intertwined with bright upward moving spikes. Whereas SADs are dark voids, spikes are brighter, denser structures. Although SADs have been observed for decades, the mechanism of formation of SADs remains an open issue. In our three-dimensional resistive magnetohydrodynamic simulations, we demonstrate that secondary Rayleigh-Taylor type instabilities develop in the downstream region of a reconnecting current sheet. The instability results in the formation of low-density coherent structures that resemble SADs, and high-density structures that appear to be spike-like. Comparison between the simulation results and observations suggests that secondary Rayleigh-Taylor type instabilities in the exhaust of reconnecting current sheets provide a plausible mechanism for observed SADs and spikes

Identification of genetic factors underpinning phenotypic heterogeneity in Huntington's disease and other neurodegenerative disorders

Neurodegenerative diseases including Huntington’s disease (HD), the spinocerebellar ataxias and C9orf72 associated Amyotrophic Lateral Sclerosis / Frontotemporal dementia (ALS/FTD) do not present and progress in the same way in all patients. Instead there is phenotypic variability in age at onset, progression and symptoms. Understanding this variability is not only clinically valuable, but identification of the genetic factors underpinning this variability has the potential to highlight genes and pathways which may be amenable to therapeutic manipulation, hence help find drugs for these devastating and currently incurable diseases. Identification of genetic modifiers of neurodegenerative diseases is the overarching aim of this thesis. To identify genetic variants which modify disease progression it is first necessary to have a detailed characterization of the disease and its trajectory over time. In this thesis clinical data from the TRACK-HD studies, for which I collected data as a clinical fellow, was used to study disease progression over time in HD, and give subjects a progression score for subsequent analysis. In this thesis I show blood transcriptomic signatures of HD status and stage which parallel HD brain and overlap with Alzheimer’s disease brain. Using the Huntington’s disease progression score in a genome wide association study, both a locus on chromosome 5 tagging MSH3, and DNA handling pathways more broadly, are shown to modify HD progression: these results are explored. Transcriptomic signatures associated with HD progression rate are also investigated. In this thesis I show that DNA repair variants also modify age at onset in spinocerebellar ataxias (1, 2, 3, 6, 7 and 17), which are, like HD, caused by triplet repeat expansions, suggesting a common mechanism. Extending this thesis’ examination of the relationship between phenotype and genotype I show that the C9orf72 expansion, normally associated with ALS/FTD, is also the commonest cause of HD phenocopy presentations

Cross-national gender differences in the socioeconomic factors associated with smoking in Australia, the United States of America and South Korea

Objectives: We compared rates of smoking among those aged 45 years and older in Australia, the United States of America and South Korea, and examined cross-national gender differences in key socioeconomic differentials in smoking. Methods: We conducted weighted analyses on cross-sectional data from nationally representative surveys conducted in 2006. Results: Current smoking was more prevalent for males than females in all countries; the gender difference was largest in Korea. Being unpartnered increased the likelihood of smoking in all countries, while greater wealth reduced it. In Korea these effects interacted with gender; both indicators showed larger differentials among women than men. Lower educational attainment increased the likelihood of smoking for all groups except Korean women, among whom high school educated women were less likely to smoke than the tertiary educated. Conclusions: Our findings support a cultural interpretation of gender differences in smoking: in countries with low gender empowerment, gender differences in smoking are greater. With increasing divorce and female tertiary education rates in nations like Korea, we highlight the need for health promotion messages targeted towards older and more educated women

Correlates of subjective health across the aging lifespan: understanding self-rated health in the oldest old

OBJECTIVES: To examine the determinants of self-rated health (SRH) in different age groups of older adults, including the oldest-old. METHODS: Variables assessing physical health, difficulty with self-care, depressive symptoms and cognitive impairment were pooled and harmonised from three Australian longitudinal studies of ageing (n=5,222). The association of these with SRH was examined in older adults aged 60-64 years, 65-74 years, 75-84 years and 85 years and older. RESULTS: SRH was not associated with cognitive impairment or difficulty with self-care in the oldest-old, and its association with physical health was diminished compared with younger groups. Depression showed a significant relationship in all age groups, conferring an approximately fourfold increase in the likelihood of poorer SRH. DISCUSSION: As old age progresses, self-reports of poor health become most closely related to psychological symptoms. This explains some of the paradoxes of past literature and offers important insights for health professionals working with the oldest-old.National Health and Medical Research Council (NHMRC); Australian Research Council Centre of Excellence in Population Ageing Research (CEPAR

Alcohol use and depression from middle age to the oldest old: Gender is more important than age

Background: Alcohol use disorders are associated with other mental health disorders in young adults, but there are few data on alcohol use and mental health outcomes in older adults, particularly the oldest old. This study examines the relationship between alcohol consumption and depressive symptoms. Methods: Data were collected from the Dynamic Analyses to Optimise Ageing (DYNOPTA) project, which has pooled nine Australian longitudinal studies. Alcohol consumption was classified using standard drinks (10 g alcohol)/day as: abstinent, low risk (2–≤4) and short-term risk (>4). Probable depression was classified from harmonized scores on various standard instruments (e.g. Centre for Epidemiological Studies Depression scale). Results: Overall, 39,104 (86%) participants contributed data. Alcohol classification at baseline showed 7,526 abstinent, 28,112 low risk, 2,271 long-term risk, and 1,195 short-term risk participants. Age ranged from 45 to 103 year (median 60). Using generalized estimating equations (GEE), there were significant gender by alcohol and gender by age interactions, so the analysis was split by gender. Among males, the abstinent and short-term risk groups had increased likelihood of depression: in females the abstinent, long- and short-term risk groups had increased odds of depression. Increased odds of depression was also associated with former and current smoking, younger age-group, not being partnered, leaving school before age 15 and increasing levels of health-impaired walking, dressing, or bathing. Conclusion: The impact of alcohol use differs by gender, nevertheless those using higher levels of alcohol or who smoke should be screened for depression and may benefit from interventions

Engaged queer scholarship: Probing a new paradigm of knowledge creation

This article features a reflexive iteration of engaged scholarship regarding the Queer Liberation Theory Project, a community-based research study with the social justice group Queer Ontario, which involves academics, activists, and artists, a number of whom are cross affiliated. We explore the tensions and challenges involved in developing and creating knowledge via an engaged scholarship process that must respect the historical philosophical perspectives of a social movement as well as today’s academic theories. This article addresses the challenges of developing new knowledge (a theory) that counters a powerful, neoliberal, mainstream segment of today’s lesbian, gay, bisexual, and transgender (LGBT) movements, with implications for society at large. The layered issues associated with engaged scholarship are disentangled, including vulnerability to neoliberalism, navigating competing perspectives, and how academics/activists/artists both understand and engage in knowledge creation

Forward Modelling of a Brightening Observed by AIA

A comprehensive understanding of the different transient events is necessary for any eventual solution of the coronal heating problem. We present a cold loop whose heating caused a short-lived small-scale brightening that was observed by AIA. The loop was simulated using an adaptive hydrodynamic radiation code that considers the ions to be in a state of non-equilibrium. Forward modelling was used to create synthetic AIA intensity plots, which were tested against the observational data to confirm the simulated properties of the event. The hydrodynamic properties of the loop were determined. We found that the energy released by the heating event is within the canonical energy range of a nanoflare

Genetic modifiers of repeat expansion disorders

Repeat expansion disorders (REDs) are monogenic diseases caused by a sequence of repetitive DNA expanding above a pathogenic threshold. A common feature of the REDs is a strong genotype-phenotype correlation in which a major determinant of age at onset (AAO) and disease progression is the length of the inherited repeat tract. Over a disease-gene carrier's life, the length of the repeat can expand in somatic cells, through the process of somatic expansion which is hypothesised to drive disease progression. Despite being monogenic, individual REDs are phenotypically variable, and exploring what genetic modifying factors drive this phenotypic variability has illuminated key pathogenic mechanisms that are common to this group of diseases. Disease phenotypes are affected by the cognate gene in which the expansion is found, the location of the repeat sequence in coding or non-coding regions and by the presence of repeat sequence interruptions. Human genetic data, mouse models and in vitro models have implicated the disease-modifying effect of DNA repair pathways via the mechanisms of somatic mutation of the repeat tract. As such, developing an understanding of these pathways in the context of expanded repeats could lead to future disease-modifying therapies for REDs

The Queer Liberation Theory Project

Community partners who also serve as researchers and academics are in a unique position to do engaged scholarship. With the QLT project, researchers have both challenged homo-normative LGBT stances, and engaged wider audiences in the conversation.York’s Knowledge Mobilization Unit provides services and funding for faculty, graduate students, and community organizations seeking to maximize the impact of academic research and expertise on public policy, social programming, and professional practice. It is supported by SSHRC and CIHR grants, and by the Office of the Vice-President Research & Innovation. [email protected] www.researchimpact.c