227 research outputs found

    Spectral Line Depth Variability in Radial Velocity Spectra

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    Stellar active regions, including spots and faculae, can create radial velocity (RV) signals that interfere with the detection and mass measurements of low mass exoplanets. In doing so, these active regions affect each spectral line differently, but the origin of these differences is not fully understood. Here we explore how spectral line variability correlated with S-index (Ca H & K emission) is related to the atomic properties of each spectral line. Next we develop a simple analytic stellar atmosphere model that can account for the largest sources of line variability with S-index. Then we apply this model to HARPS spectra of {\alpha} Cen B to explain Fe I line depth changes in terms of a disk-averaged temperature difference between active and quiet regions on the visible hemisphere of the star. This work helps establish a physical basis for understanding how stellar activity manifests differently in each spectral line, and may help future work mitigating the impact of stellar activity on exoplanet RV surveys.Comment: 13 pages, 7 figures, submitted to The Astrophysical Journal, August 202

    Kempsey, New South Wales : How social and political divisions in Kempsey’s early history impacted the town’s economic and environmental development to 1865, and its ongoing susceptibility to disaster

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    This study addresses the question: how did social and political divisions influence the
 economic and environmental development of Kempsey during the colonial period up
 to 1865? Primary documents including personal letters, journals, memoirs, political
 and governmental papers, along with a range of colonial newspapers have been
 studied and interpreted to form a social historical solution to the question. Due to the
 range of sources available for this investigation, a variation of methodologies has been
 employed, with particular emphasis on an empirical qualitative analysis. In addition to
 considering existing non-scholarly thematic histories of the Macleay Valley, this
 thesis draws existing scholarly investigations together and builds upon them, looking
 into the interdependence between society and environment, politics and geographical
 developments, culture and social movements to piece together the story of Kempsey
 and uncover the key events which have led to long lasting impacts on the town. No
 other scholarly study of this kind has been undertaken to bring the entire complex and
 multifaceted story of Kempsey’s early years into one scholarly investigation.
 Implications for this study highlight the important factor that powerful social and
 political divisions in a community have when important decisions about town
 planning, environmental protection, and issues of social justice need to be addressed.
 These divisions can lead to catastrophic outcomes that could impact generations to
 follow, as shown in the tumultuous history of Kempsey, New South Wales

    Investigating the Role of Hypothalamic Tumor Involvement in Sleep and Cognitive Outcomes Among Children Treated for Craniopharyngioma

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    Objective: Despite excellent survival prognosis, children treated for craniopharyngioma experience significant morbidity. We examined the role of hypothalamic involvement (HI) in excessive daytime sleepiness (EDS) and attention regulation in children enrolled on a Phase II trial of limited surgery and proton therapy. Methods: Participants completed a sleep evaluation (N = 62) and a continuous performance test (CPT) during functional magnetic resonance imaging (fMRI; n = 29) prior to proton therapy. Results: EDS was identified in 76% of the patients and was significantly related to increased HI extent (p = .04). There was no relationship between CPT performance during fMRI and HI or EDS. Visual examination of group composite fMRI images revealed greater spatial extent of activation in frontal cortical regions in patients with EDS, consistent with a compensatory activation hypothesis. Conclusion: Routine screening for sleep problems during therapy is indicated for children with craniopharyngioma, to optimize the timing of interventions and reduce long-term morbidity

    Paracetamol reduces influenza-induced immunopathology in a mouse model of infection without compromising virus clearance or the generation of protective immunity

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    Background: Seasonal influenza A infection affects a significant cohort of the global population annually, resulting in considerable morbidity and mortality. Therapeutic strategies are of limited efficacy, and during a pandemic outbreak would only be available to a minority of the global population. Over-the-counter medicines are routinely taken by individuals suffering from influenza, but few studies have been conducted to determine their effectiveness in reducing pulmonary immunopathology or the influence they exert upon the generation of protective immunity. Methods: A mouse model of influenza infection was utilised to assess the efficacy of paracetamol (acetaminophen) in reducing influenza-induced pathology and to examine whether paracetamol affects generation of protective immunity. Results: Administration (intraperitoneal) of paracetamol significantly decreased the infiltration of inflammatory cells into the airway spaces, reduced pulmonary immunopathology associated with acute infection and improved the overall lung function of mice, without adversely affecting the induction of virus-specific adaptive responses. Mice treated with paracetamol exhibited an ability to resist a second infection with heterologous virus comparable with that of untreated mice. Conclusions: Our results demonstrate that paracetamol dramatically reduces the morbidity associated with influenza but does not compromise the development of adaptive immune responses. Overall, these data support the utility of paracetamol for reducing the clinical symptoms associated with influenza virus infection
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