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

Driving offences and risk of subsequent crash in novice drivers: the DRIVE cohort study 12-year follow-up

Background Penalties are a key component to improve road user safety, but previous studies suggested that they might not be successful in reducing crashing in offending drivers. However, these studies were not able to consider important crash risk factors in the analysis that might confound the results. Using data from a large prospective cohort study of young drivers in New South Wales, Australia, we explored if novice drivers with driving offences have a higher rates of car crash and if these differences are explained by established crash risk factors. Methods We used data from a 2003/2004 Australian survey of young drivers, linked to police reported offence and crash data, hospital data and deaths data up to 2016. We used Poisson regression models adjusted for confounders to estimate the association between driving offences during 2003–2006 with car crash during 2007–2016. Results The study cohort comprised 20 781 young drivers of whom 7860 drivers (37.8%) had at least one driving offence and 2487 (12.0%) were involved in at least one crash. After adjusting for confounders in the regression model, drivers with three or more driving offences had 2.25 (95% CI 1.98 to 2.57), 2.87 (95% CI 1.60 to 5.17) and 3.28 (95% CI 2.28 to 4.72) times higher rates of any crash, crashes that resulted in hospital admission or death and single vehicle crashes compared with drivers with no driving offences. Conclusion Measures that successfully mitigate the underlying risk factors for both, crashes and offences, have the potential to improve road safety

Risky youth to risky adults: Sustained increased risk of crash in the DRIVE study 13 years on.

The objective of this study was to investigate if drivers who exhibit risky driving behaviours during youth (aged 17-24 years) have an increased risk of car crash up to 13 years later. We used data from the DRIVE study, a 2003/04 survey of 20,806 young novice drivers in New South Wales, Australia. The data were linked with police crash, hospital and deaths data up to 2016. We analysed differences in crash associated with 13 items of risky driving behaviours using negative binominal regression models adjusted for driver demographics, driving exposure and known crash risk factors. The items were summarised in one index and grouped into quintiles for the analysis. After adjusting for confounding, drivers of the third (RR 1.16, 95% CI 1.05-1.30), fourth (RR1.22, 95% CI1.09-1.36) and fifth quintile (RR 1.36, 95% CI 1.21-1.53) had higher crash rates compared to the lowest risk-takers. Drivers with the highest scores on the risky driving measure had higher rates of crash related hospital admission or death (RR 1.92, 95% CI 1.13-3.27), crashes in wet conditions (RR 1.35,95% CI 1.05-1.73), crashes in darkness (RR 1.55, 95% CI 1.25-1.93) and head-on crashes (RR 2.14, 95% CI 1.07-4.28), compared with drivers with the lowest scores. Novice adolescent drivers who reported high levels of risky driving when they first obtained a driver licence remained at increased risk of crash well into adulthood. Measures that successfully reduce early risky driving, have the potential to substantially reduce road crashes and transport related injuries and deaths over the lifespan

Optimization of Material Contrast for Efficient FIB‐SEM Tomography of Solid Oxide Fuel Cells

Focused ion beam (FIB) – scanning electron microscopy (SEM) serial sectioning tomography has become an important tool for three‐dimensional microstructure reconstruction of solid oxide fuel cells (SOFC) to obtain an understanding of fabrication‐related effects and SOFC performance. By sequential FIB milling and SEM imaging a stack of cross‐section images across all functional SOFC layers was generated covering a large volume of 3.5·10$^{4}$ μm$^{3}$. One crucial step is image segmentation where regions with different image intensities are assigned to different material phases within the SOFC. To analyze all relevant SOFC materials, it was up to now mandatory to acquire several images by scanning the same region with different imaging parameters because sufficient material contrast could otherwise not be achieved. In this work we obtained high‐contast SEM images from a single scan to reconstract all functional SOFC layers consisting of a Ni/Y$_{2}$O$_{3}$‐doped ZrO$_{2}$ (YDZ) cermet anode, YDZ electrolyte and (La,Sr)MnO$_{3}$/YDZ cathode. This was possible by using different, simultaneous read‐out detectors installed in a state‐of‐the‐art scanning electron microscope. In addition, we used a deterministic approach for the optimization of imaging parameters by employing Monte Carlo simulations rather than trial‐and‐error tests. We also studied the effect of detection geometry, detecting angle range and detector type

Nature and Functionality of La0.58_{0.58}Sr0.4_{0.4}Co0.2_{0.2}Fe0.8_{0.8}O3−δ_{3-δ} / Gd0.2_{0.2}Ce0.8_{0.8}O2−δ_{2-δ} / Y0.16_{0.16}Zr0.84_{0.84}O2−δ_{2-δ} Interfaces in SOFCs

Interdiffusion phenomena and secondary phase formation at the interface La0.58Sr0.4Co0.2Fe0.8O3-δ (LSCF) / Gd0.2Ce0.8O2-δ (GDC) / Y0.16Zr0.84O2-δ (YSZ) are correlated to linear and non-linear losses in symmetrical and full SOFC cells. FIB/SEM (focussed ion beam / scanning electron microscopy) tomography is applied for determining the local distribution of the primary phases LSCF, GDC, and YSZ and elemental analysis via STEM/EDXS (scanning transmission electron microscopy / energy dispersive X-ray spectroscopy) provides information on the secondary phase SrZrO3 (SZO) and the interdiffusion between GDC and YSZ (ID). This reveals the effect of GDC co-sintering temperature (varied from 1100°C to 1400°C), alongside the sintering of LSCF at 1080°C, on these multi-layered microstructures. Electrochemical impedance spectra on symmetrical cells show that the polarization resistance (ASRcat) of the cathode/electrolyte interface is pronouncedly affected by three orders of magnitude, changing the overall power density of anode supported SOFC single cells at 0.8V by as much as a factor of 20. In conclusion, the chemical composition of the ID has a tremendous impact on the electrochemical efficiency of the investigated LSCF/GDC/YSZ interface, and processing parameters of anode supported cells with LSCF cathode have to be carefully chosen for individual SOFC cell concepts

Are there sex differences in crash and crash-related injury between men and women? A 13-year cohort study of young drivers in Australia

BackgroundYoung men have long been known to be disproportionately impacted by road crash and crash-related injury compared to young women and older drivers. However, there is limited insight into how sex differences in crash and crash-related injury changes over time as men and women get older and gain more driving experience. To explore sex differences in crash and crash-related injury, we undertook a sex disaggregated analysis in a large longitudinal cohort of over 20,000 young drivers in New South Wales, Australia, for up to 13 years after they first attained their independent car driver licence.MethodsDRIVE Study survey data from 2003-04 were linked with police, hospital and deaths data up to 2016. Sex differences were analysed using cumulative incidence curves investigating time to first crash and in negative binominal regression models adjusted for driver demographics and crash risk factors.ResultsAfter adjusting for demographics and driving exposure, compared with women, men had 1.25 (95% CI 1.18-1.33), 2.07 (1.75-2.45), 1.28 (95% CI 1.13-1.46), 1.32 (95% CI 1.17-1.50) and 1.59 (95% CI 1.43-1.78) times higher rates of any crash, single vehicle crash, crash on streets with a speed limit of 80 km/h or above, crash in wet conditions and crash in the dark, respectively. By contrast, men were less likely to be involved in crashes that resulted in hospitalisation compared to women 0.73 (95% CI 0.55-0.96).ConclusionsYoung men are at increased risk of crash, and this risk persists as they get older and gain more driving experience. Despite lower risk of crash, women are at higher risk of crash related injury requiring hospitalisation. These differences in men's and women's risk of crash and injury signal the need for better understanding of how sex and/or gender may contribute to risk of crash and injury across the life-course

Peripheral sensory neuropathy is associated with altered postocclusive reactive hyperemia in the diabetic foot

Objective: This study examined whether the presence of peripheral sensory neuropathy or cardiac autonomic deficits is associated with postocclusive reactive hyperemia (reflective of microvascular function) in the diabetic foot. Research design and methods: 99 participants with type 2 diabetes were recruited into this crosssectional study. The presence of peripheral sensory neuropathy was determined with standard clinical tests and cardiac autonomic function was assessed with heart rate variation testing. Postocclusive reactive hyperemia was measured with laser Doppler in the hallux. Multiple hierarchical regression was performed to examine relationships between neuropathy and the peak perfusion following occlusion and the time to reach this peak. Results: Peripheral sensory neuropathy predicted 22% of the variance in time to peak following occlusion (p<0.05), being associated with a slower time to peak but was not associated with the magnitude of the peak. Heart rate variation was not associated with the postocclusive reactive hyperemia response. Conclusions: This study found an association between the presence of peripheral sensory neuropathy in people with diabetes and altered microvascular reactivity in the lower limb

Cognitive behavioral therapy, singly and combined with medication, for persistent insomnia : a randomized controlled trial

Context: Cognitive behavioral therapy (CBT) and hypnotic medications are efficacious for short-term treatment of insomnia, but few patients achieve complete remission with any single treatment. It is unclear whether combined or maintenance therapies would enhance outcome. Objectives: To evaluate the added value of medication over CBT alone for acute treatment of insomnia and the effects of maintenance therapies on long-term outcome. Design, Setting, and Patients: Prospective, randomized controlled trial involving 2-stage therapy for 160 adults with persistent insomnia treated at a university hospital sleep center in Canada between January 2002 and April 2005. Interventions: Participants received CBT alone or CBT plus 10 mg/d (taken at bedtime) ofzolpidemforaninitial6-weektherapy,followedbyextended6-monththerapy.Patients initially treated with CBT attended monthly maintenance CBT for 6 months or received no additional treatment and those initially treated with combined therapy (CBT plus 10 mg/d of zolpidem) continued with CBT plus intermittent use of zolpidem or CBT only. Main Outcome Measures: Sleep onset latency, time awake after sleep onset, total sleep time, and sleep efficiency derived from daily diaries (primary outcomes); treatment response and remission rates derived from the Insomnia Severity Index (secondary outcomes). Results: Cognitive behavioral therapy used singly or in combination with zolpidem produced significant improvements in sleep latency, time awake after sleep onset, and sleep efficiency during initial therapy (all P .001); a larger increase of sleep time was obtained with the combined approach (P=.04). Both CBT alone and CBT plus zolpidem produced similar rates of treatment responders (60% [45/75] vs 61% [45/74], respectively; P=.84) and treatment remissions (39% [29/75] vs 44% [33/74], respectively; P=.52) with the 6-week acute treatment, but combined therapy produced a higher remission rate compared with CBT alone during the 6-month extended therapy phase and the 6-month follow-up period (56% [43/74 and 32/59] vs 43% [34/75 and 28/68]; P=.05). The best long-term outcome was obtained with patients treated with combined therapy initially, followed by CBT alone, as evidenced by higher remission rates at the 6-month follow-up compared with patients who continued to take zolpidem during extended therapy (68% [20/30] vs 42% [12/29]; P=.04). Conclusion: In patients with persistent insomnia, the addition of medication to CBT produced added benefits during acute therapy, but long-term outcome was optimized when medication is discontinued during maintenance CBT