A time-stepping dynamically-consistent spherical-shell dynamo code

A pseudo-spectral dynamo code, developed as a computational laboratory, is described. The magnetic, heat and Boussinesq Navier-Stokes equations, with inertia, non-linear advection, buoyancy with asymmetric gravity, Coriolis, viscous and Lorentz forces, are solved numerically in a rotating conducting fluid shell. The convection is thermally driven by prescribed boundary temperatures. The equations are discretised using toroidal-poloidal fields, Chebychev collocation in radius and spherical harmonic expansion in angles. Derivatives are performed spectrally. Products are evaluated in physical space for efficiency. Fields are transformed between physical and spectral spaces by fast Fourier and Gauss-Legendre methods. Linear terms are time-stepped implicitly and product terms explicitly using an Adams predictor/corrector. Results are presented for two benchmark models

Morning quiet-time ionospheric current reversal at mid to high latitudes

The records of an array of magnetometers set up across the Australian mainland are examined. In addition to a well-defined current whorl corresponding to the ionospheric <i>S<sub>q</sub></i> current system, another system of eastward flowing currents is often found in the early morning. The system is most easily identified at observatories poleward of the focus of the <i>S<sub>q</sub></i> system, where a morning reversal from eastward to westward currents can be seen. The time of the reversal is usually later, sometimes up to 12h local noon, in June (Southern Winter) than in other seasons. There is some evidence of a similar current system at other longitudes and in the Northern Hemisphere. An important outcome of the study is that it enables identification of which features of a daily variation of the northward magnetic field Δ<i>X</i> relate to an <i>S<sub>q</sub></i> current whorl and which must be attributed to some other current system

Magnetohydrodynamic activity inside a sphere

We present a computational method to solve the magnetohydrodynamic equations in spherical geometry. The technique is fully nonlinear and wholly spectral, and uses an expansion basis that is adapted to the geometry: Chandrasekhar-Kendall vector eigenfunctions of the curl. The resulting lower spatial resolution is somewhat offset by being able to build all the boundary conditions into each of the orthogonal expansion functions and by the disappearance of any difficulties caused by singularities at the center of the sphere. The results reported here are for mechanically and magnetically isolated spheres, although different boundary conditions could be studied by adapting the same method. The intent is to be able to study the nonlinear dynamical evolution of those aspects that are peculiar to the spherical geometry at only moderate Reynolds numbers. The code is parallelized, and will preserve to high accuracy the ideal magnetohydrodynamic (MHD) invariants of the system (global energy, magnetic helicity, cross helicity). Examples of results for selective decay and mechanically-driven dynamo simulations are discussed. In the dynamo cases, spontaneous flips of the dipole orientation are observed.Comment: 15 pages, 19 figures. Improved figures, in press in Physics of Fluid

A vector spherical harmonic spectral code for linearised magnetohydrodynamics

Linearised rotating magnetohydrodynamic stability code for the steady axisymmetric basic states of an electrically conducting fluid sphere is described. The code generates compact hybrid angular spectral forms of the magnetic induction, heat and Boussinesq Navier-Stokes equations, using toroidal and poloidal representations of the perturbation vector fields, and vector or scalar spherical harmonic expansions of all fields. The momentum equation may include inertial, Coriolis, buoyancy, viscous and magnetic Lorentz forces. Three subroutines evaluate the spectral interactions of products. There are only six radial functions, which are discretised using uniform second-order finite differences. The resulting large scale complex non-hermitian generalised eigen- and critical-value problems are solved using inverse and Newton-Raphson iteration methods, respectively. Test results are presented for several models

Revitalising audit and feedback to improve patient care

Healthcare systems face challenges in tackling variations in patient care and outcomes. Audit and feedback aim to improve patient care by reviewing clinical performance against explicit standards and directing action towards areas not meeting those standards. It is a widely used foundational component of quality improvement, included in around 60 national clinical audit programmes in the United Kingdom. Ironically, there is currently a gap between what audit and feedback can achieve and what they actually deliver, whether led locally or nationally. Several national audits have been successful in driving improvement and reducing variations in care, such as for stroke and lung cancer, but progress is also slower than hoped for in other aspects of care (table 1). Audit and feedback have a chequered past.6 Clinicians might feel threatened rather than supported by top-down feedback and rightly question whether rewards outweigh efforts invested in poorly designed audit. Healthcare organisations have limited resources to support and act on audit and feedback. Dysfunctional clinical and managerial relationships undermine effective responses to feedback, particularly when it is not clearly part of an integrated approach to quality assurance and improvement. Unsurprisingly, the full potential of audit and feedback has not been realised

Evidence Synthesis for Complex Interventions Using Meta-Regression Models

This study was funded by the Canadian Institutes of Health Research (grants FDN-143269 and FRN-123345) and a research fellowship held by K.J.K. (Frederick Banting and Charles Best Canada Graduate Scholarship GSD-134936). N.M.I. holds a Canada Research Chair (Tier 2) in Implementation of Evidence Based Practice and a Clinician Scientist Award from the Department of Family and Community Medicine at the University of Toronto (Toronto, Ontario, Canada). J.M.G. held a Canada Research Chair in Health Knowledge Transfer and Uptake during the time of the study’s conduct and was supported by a Foundation Grant from the Canadian Institutes of Health Research. D.M. was supported by a University of Ottawa Research Chair during the time of study conduct.Peer reviewedPublisher PD

Electron Emission from Ferroelectric/Antiferroelectric Cathodes Excited by Short High-Voltage Pulses

Un-prepoled Lead Zirconate Titanate Lanthanum doped-PLZT ferroelectric cathodes have emitted intense current pulses under the action of a high voltage pulse of typically 8 kV/cm for PLZT of 8/65/35 composition and 25 kV/cm for PLZT of 4/95/5 composition. In the experiments described in this paper, the exciting electric field applied to the sample is directed from the rear surface towards the emitting surface. The resulting emission is due to an initial field emission from the metal of the grid deposited over the emitting surface with the consequent plasma formation and the switching of ferroelectric domains. These electrons may be emitted directly form the crystal or from the plasma. This emission requires the material in ferroelectric phase. In fact, PLZT cathodes of the 8/65/35 type, that is with high Titanium content, showing ferroelectric-paraelectric phase sequence, emit at room temperature, while PLZT cathodes of the 4/95/5 type, that is with low Titanium content, having antiferro-ferro-paraelectric phase sequence, emit strongly at a temperature higher than 130°C

The Sydney Triage to Admission Risk Tool (START) to predict Emergency Department Disposition: A derivation and internal validation study using retrospective state-wide data from New South Wales, Australia.

BACKGROUND: Disposition decisions are critical to the functioning of Emergency Departments. The objectives of the present study were to derive and internally validate a prediction model for inpatient admission from the Emergency Department to assist with triage, patient flow and clinical decision making. METHODS: This was a retrospective analysis of State-wide Emergency Department data in New South Wales, Australia. Adult patients (age ≥ 16 years) were included if they presented to a Level five or six (tertiary level) Emergency Department in New South Wales, Australia between 2013 and 2014. The outcome of interest was in-patient admission from the Emergency Department. This included all admissions to short stay and medical assessment units and being transferred out to another hospital. Analyses were performed using logistic regression. Discrimination was assessed using area under curve and derived risk scores were plotted to assess calibration. RESULTS: 1,721,294 presentations from twenty three Level five or six hospitals were analysed. Of these 49.38% were male and the mean (sd) age was 49.85 years (22.13). Level 6 hospitals accounted for 47.70% of cases and 40.74% of cases were classified as an in-patient admission based on their mode of separation. The final multivariable model including age, arrival by ambulance, triage category, previous admission and presenting problem had an AUC of 0.82 (95% CI 0.81, 0.82). CONCLUSION: By deriving and internally validating a risk score model to predict the need for in-patient admission based on basic demographic and triage characteristics, patient flow in ED, clinical decision making and overall quality of care may be improved. Further studies are now required to establish clinical effectiveness of this risk score model

Vulnerability to fatal drowning among the population in Southern Bangladesh: Findings from a cross-sectional household survey

© 2019 Author(s). Objectives This study aimed to determine the fatal drowning burden and associated risk factors in Southern Bangladesh. Settings The survey was conducted in 39 subdistricts of all 6 districts of the Barisal division, Southern Bangladesh. Participants All residents (for a minimum 6 months prior to survey) of the Barisal division, Southern Bangladesh. Intervention/methods A cross-sectional, divisionally representative household survey was conducted in all six districts of the Barisal division between September 2016 and February 2017, covering a population of 386 016. Data were collected by face-to-face interview with adult respondents using handheld electronic tablets. International Classification of Diseases (ICD)-v. 10 (ICD-10) Chapter XX: External causes of morbidity and mortality codes for drowning, W65-W74, X36-X39, V90, V92, X71 or X92, were used as the operational definition of a drowning event. Results The overall fatal drowning rate in Barisal was 37.9/100 000 population per year (95% CI 31.8 to 43.9). The highest fatal drowning rate was observed among children aged 1-4 years (262.2/100 000/year). Mortality rates among males (48.2/100 000/year) exceeded that for females (27.9/100 000/year). A higher rate of fatal drowning was found in rural (38.9/100 000/year) compared with urban areas (29.3/100 000/year). The results of the multivariable logistic regression identified that the factors significantly associated with fatal drowning were being male (OR 1.7, 95% CI 1.2 to 2.3), aged 1-4 years (OR 3.0, 95% CI 1.4 to 6.4) and residing in a household with four or more children (four or more children OR 1.8, 95% CI 1.1 to 2.9; and five or more children OR 2.1, 95% CI 1.2 to 3.7). Conclusion Drowning is a public health problem, especially for children, in the Barisal division of Southern Bangladesh. Male gender, children 1-4 years of age and residing in a household with four or more children were associated with increased risk of fatal drowning events. The Barisal division demands urgent interventions targeted at high-risk groups identified in the survey