Non-ideal magnetohydrodynamics versus turbulence – I. Which is the dominant process in protostellar disc formation?

Funding: European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013 grant agreement no. 339248); University of St Andrews (JW). National Aeronautics and Space Administration (NASA) through grant NN17AK90G and from the National Science Foundation (NSF) through grants no 1517488 and PHY-1748958 (BTL).Non-ideal magnetohydrodynamics (MHD) is the dominant process. We investigate the effect of magnetic fields (ideal and non-ideal) and turbulence (sub- and transsonic) on the formation of circumstellar discs that form nearly simultaneously with the formation of the protostar. This is done by modelling the gravitational collapse of a 1 M☉ gas cloud that is threaded with a magnetic field and imposed with both rotational and turbulent velocities. We investigate magnetic fields that are parallel/antiparallel and perpendicular to the rotation axis, two rotation rates, and four Mach numbers. Disc formation occurs preferentially in the models that include non-ideal MHD where the magnetic field is antiparallel or perpendicular to the rotation axis. This is independent of the initial rotation rate and level of turbulence, suggesting that subsonic turbulence plays a minimal role in influencing the formation of discs. Aside from first core outflows that are influenced by the initial level of turbulence, non-ideal MHD processes are more important than turbulent processes during the formation of discs around low-mass stars.Publisher PDFPeer reviewe

Non-ideal magnetohydrodynamics versus turbulence II : which is the dominant process in stellar core formation?

Funding: JW acknowledges support from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007- 2013 grant agreement no. 339248), and from the University of St Andrews. BTL acknowledges the support of the National Aeronautics and Space Administration (NASA) through grant NN17AK90G and from the National Science Foundation (NSF) through grants no. 1517488 and PHY-1748958.Non-ideal magnetohydrodynamics (MHD) is the dominant process. We investigate the effect of magnetic fields (ideal and non-ideal) and turbulence (sub- and transsonic) on the formation of protostars by following the gravitational collapse of 1 M☉ gas clouds through the first hydrostatic core to stellar densities. The clouds are imposed with both rotational and turbulent velocities, and are threaded with a magnetic field that is parallel/antiparallel or perpendicular to the rotation axis; we investigate two rotation rates and four Mach numbers. The initial radius and mass of the stellar core are only weakly dependent on the initial parameters. In the models that include ideal MHD, the magnetic field strength implanted in the protostar at birth is much higher than observed, independent of the initial level of turbulence; only non-ideal MHD can reduce this strength to near or below the observed levels. This suggests that not only is ideal MHD an incomplete picture of star formation, but that the magnetic fields in low mass stars are implanted later in life by a dynamo process. Non-ideal MHD suppresses magnetically launched stellar core outflows, but turbulence permits thermally launched outflows to form a few years after stellar core formation.Publisher PDFPeer reviewe

Primary group size, social support, gender and future mental health status in a prospective study of people living in private households throughout Great Britain

Background. Structural characteristics of social networks such as primary group size have received less attention than measures of perceived social support. Previous research suggests that associations between social network size and later common mental disorder status may differ according to sex and initial mental state. Method. Adults participating in the 2000 British National Household Survey of psychiatric morbidity were randomly selected for follow-up 18 months later. The revised Clinical Interview Schedule (CIS-R) and the Interview Measure of Social Relations (IMSR) were administered at baseline and follow-up. Primary group size was defined as the total number of close relatives and friends. A four-level scale of common mental disorder was modelled with ordinal logistic regression, based on weighted data (n=2413). Findings. After adjusting for confounders, a primary group size of three or less at time 1 predicted worse mental health at time 2. This effect was greatest in men who were initially non-cases at baseline (averaged odds 4.5) and in women who were initially cases at baseline (average odds 2.9). Primary group size at time 2 was significantly predicted by level of common mental disorder at time 1 in women but not in men. Thus, confounding by baseline disorder does not explain risk of developing poor mental health in socially isolated men. Conclusion. This study replicates the strong effects of primary group size on future mental health that emerge when men and women are studied separately and when subjects are categorized according to baseline mental health status

Roof-snow behavior and ice-dam prevention in residential housing

20 pages; includes photographs, maps and drawings. This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

Frailty in Indigenous populations: A scoping review

Background: Indigenous populations experience high rates of age-related illness when compared to their non-Indigenous counterparts. Frailty is a challenging expression of aging and an important public health priority. The purpose of this review was to map what the existing literature reports around frailty in Indigenous populations and to highlight the current gaps in frailty research within the Indigenous landscape. Method: Scoping review of English language original research articles focusing on frailty within Indigenous adult populations in settler colonial countries (Australia, Canada, New Zealand and USA). Ten electronic databases and eight relevant institutional websites were searched from inception to October 2020. Results: Nine articles met our inclusion criteria, finding this population having a higher prevalence of frailty and frailty occurring at younger ages when compared to their non-Indigenous counterparts, but two did not use a formal frailty tool. Females presented with higher levels of frailty. No culturally specific frailty tool was identified, and the included articles did not assess strategies or interventions to manage or prevent frailty in Indigenous peoples. Conclusions: There was little definitive evidence of the true frailty prevalence, approaches to frailty screening and of potential points of intervention to manage or prevent the onset of frailty. Improvements in the quality of evidence are urgently needed, along with further research to determine the factors contributing to higher rates of frailty within Indigenous populations. Incorporation of Indigenous views of frailty, and instruments and programs that are led and designed by Indigenous communities, are crucial to address this public health priority

Preventing ice-dams on Minnesota homes

1 online resource (PDF, 2 pages)This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu