New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation

(abridged) The heating mechanism at high densities during M dwarf flares is poorly understood. Spectra of M dwarf flares in the optical and near-ultraviolet wavelength regimes have revealed three continuum components during the impulsive phase: 1) an energetically dominant blackbody component with a color temperature of T $\sim$ 10,000 K in the blue-optical, 2) a smaller amount of Balmer continuum emission in the near-ultraviolet at lambda $<$ 3646 Angstroms and 3) an apparent pseudo-continuum of blended high-order Balmer lines. These properties are not reproduced by models that employ a typical "solar-type" flare heating level in nonthermal electrons, and therefore our understanding of these spectra is limited to a phenomenological interpretation. We present a new 1D radiative-hydrodynamic model of an M dwarf flare from precipitating nonthermal electrons with a large energy flux of $10^{13}$ erg cm$^{-2}$ s$^{-1}$. The simulation produces bright continuum emission from a dense, hot chromospheric condensation. For the first time, the observed color temperature and Balmer jump ratio are produced self-consistently in a radiative-hydrodynamic flare model. We find that a T $\sim$ 10,000 K blackbody-like continuum component and a small Balmer jump ratio result from optically thick Balmer and Paschen recombination radiation, and thus the properties of the flux spectrum are caused by blue light escaping over a larger physical depth range compared to red and near-ultraviolet light. To model the near-ultraviolet pseudo-continuum previously attributed to overlapping Balmer lines, we include the extra Balmer continuum opacity from Landau-Zener transitions that result from merged, high order energy levels of hydrogen in a dense, partially ionized atmosphere. This reveals a new diagnostic of ambient charge density in the densest regions of the atmosphere that are heated during dMe and solar flares.Comment: 50 pages, 2 tables, 13 figures. Accepted for publication in the Solar Physics Topical Issue, "Solar and Stellar Flares". Version 2 (June 22, 2015): updated to include comments by Guest Editor. The final publication is available at Springer via http://dx.doi.org/10.1007/s11207-015-0708-

Atomic X-ray Spectroscopy of Accreting Black Holes

Current astrophysical research suggests that the most persistently luminous objects in the Universe are powered by the flow of matter through accretion disks onto black holes. Accretion disk systems are observed to emit copious radiation across the electromagnetic spectrum, each energy band providing access to rather distinct regimes of physical conditions and geometric scale. X-ray emission probes the innermost regions of the accretion disk, where relativistic effects prevail. While this has been known for decades, it also has been acknowledged that inferring physical conditions in the relativistic regime from the behavior of the X-ray continuum is problematic and not satisfactorily constraining. With the discovery in the 1990s of iron X-ray lines bearing signatures of relativistic distortion came the hope that such emission would more firmly constrain models of disk accretion near black holes, as well as provide observational criteria by which to test general relativity in the strong field limit. Here we provide an introduction to this phenomenon. While the presentation is intended to be primarily tutorial in nature, we aim also to acquaint the reader with trends in current research. To achieve these ends, we present the basic applications of general relativity that pertain to X-ray spectroscopic observations of black hole accretion disk systems, focusing on the Schwarzschild and Kerr solutions to the Einstein field equations. To this we add treatments of the fundamental concepts associated with the theoretical and modeling aspects of accretion disks, as well as relevant topics from observational and theoretical X-ray spectroscopy.Comment: 63 pages, 21 figures, Einstein Centennial Review Article, Canadian Journal of Physics, in pres

Encapsulating peritoneal sclerosis: incidence, predictors, and outcomes

Encapsulating peritoneal sclerosis is a complication of peritoneal dialysis characterized by persistent, intermittent, or recurrent adhesive bowel obstruction. Here we examined the incidence, predictors, and outcomes of encapsulating peritoneal sclerosis (peritoneal fibrosis) by multivariate logistic regression in incident peritoneal dialysis patients in Australia and New Zealand. Matched case–control analysis compared the survival of patients with controls equivalent for age, gender, diabetes, and time on peritoneal dialysis. Of 7618 patients measured over a 13-year period, encapsulating peritoneal sclerosis was diagnosed in 33, giving an incidence rate of 1.8/1000 patient-years. The respective cumulative incidences of peritoneal sclerosis at 3, 5, and 8 years were 0.3, 0.8, and 3.9%. This condition was independently predicted by younger age and the duration of peritoneal dialysis, but not the rate of peritonitis. Twenty-six patients were diagnosed while still on peritoneal dialysis. Median survival following diagnosis was 4 years and not statistically different from that of 132 matched controls. Of the 18 patients who died, only 7 were attributed directly to peritoneal sclerosis. Our study shows that encapsulating peritoneal sclerosis is a rare condition, predicted by younger age and the duration of peritoneal dialysis. The risk of death is relatively low and not appreciably different from that of competing risks for mortality in matched dialysis control patients.David W. Johnson, Yeoungjee Cho, Brian E.R. Livingston, Carmel M. Hawley, Stephen P. McDonald, Fiona G. Brown, Johan B. Rosman, Kym M. Bannister and Kathryn J. Wiggin

Representações da relação entre exercício físico e saúde por pacientes fibromiálgicos Representations of the relationship between physical exercise and health for patients with fibromyalgia

Fibromialgia (FM) é uma síndrome caracterizada por dor músculo esquelética crônica generalizada, fadiga, distúrbio do sono e sintomas associados. Preocupação com o controle da síndrome justifica-se por sua crescente prevalência e pelo impacto negativo na qualidade de vida dos afetados. Das opções de tratamento não-medicamentoso, o exercício físico (EF) é elemento terapêutico relevante. Há preocupação como o impacto da síndrome e sua terapêutica sobre a saúde, aqui entendida como um conjunto de dimensões - física, emocional, social, espiritual, intelectual e profissional - de uma pessoa. O objetivo do estudo foi identificar a percepção de pacientes com FM sobre a relação entre EF e saúde. Utilizou-se o referencial teórico-metodológico das Representações Sociais numa amostra de 22 mulheres de um projeto multidisciplinar: Educação Física, Nutrição, Medicina e Psicologia. A análise dos dados foi realizada a partir do conteúdo transcrito das gravações de entrevista semiestruturada e interpretação de ilustrações feitas pelas pacientes. Houve melhora na dimensão física, demonstrada pelo alívio da dor nas falas; houve também melhora na dimensão emocional, evidenciada pela melhora da autoestima indicada nas ilustrações. Com base na teoria utilizada, as pacientes reconhecem a relação positiva entre EF e saúde.<br>The fibromyalgia syndrome (FMS) is characterized by widespread chronic musculoskeletal pain, fatigue, disturbed sleep and associated symptoms. Its increasing prevalence and life quality impairment of patients justify researches for its control. Physical exercise (PE) is a relevant therapeutic tool among nonpharmachologic treatments options. It is important to mind the impact of FMS and different therapeutics on health, here understood as a set of dimensions: physical, emotional, social, spiritual, intellectual and professional. This study aimed to identify FMS patients' perception of relationship between PE and health. It used the theoretical methodological reference of Social Representation to study 22 women of a multidisciplinary project: Physical Education, Nutrition, Medicine and Psychology. Data analysis considered transcription of recorded semi-structured interview, and interpretation of patients' illustrations. There were improvements in physical dimension evidenced by pain relief. Positive effects were also observed in emotional dimension, evidenced by self-esteem improvement, which appeared in the pictures. Based on the theory adopted, it was possible to identify that patients recognize a positive relationship between PE and health