Explosions in Electrical Control Boxes as a Potential “Nested Bang-Box” Mechanism for Severe Vapour Cloud Explosions

The ignition source for Buncefield, the United Kingdom’s most severe recent vapour cloud explosion (VCE) was potentially electrical control boxes situated inside a pump house immersed in the vapour cloud. There are other reports of confined or bang box ignition sources for other VCEs, such as Port Hudson and Jaipur where it is proposed these ignition sources were responsible for transition to detonation (DDT). There has, however, been relatively little previous research into this type of ignition mechanism and its effect on the explosion severity. Commercially available electrical control boxes measuring 600 mm high, 400 mm wide and 250 mm deep were used to explore the pressure development, venting processes and flame characteristics of stoichiometric propane/air explosions using cling film, aluminium foil and the supplied doors as vent coverings. In this work the boxes were empty of their usual contents in order to establish a baseline for the effect of the internal congestion of the boxes. It was found that, in these empty-box tests the overpressure was dominated by the bursting pressure of the ventcovering and the external explosion, although clearly presenting significant ignition source to a potential surrounding flammable cloud, it produced no significant overpressure. The door produced a flat petal shaped flame that differed drastically from the rolling vortex bubble flame shape traditionally associated with vented explosions

Experimental investigation of potential confined ignition sources for vapour cloud explosions

Electrical control boxes are prolific on high vapour cloud hazard sites, and in the case of the Buncefield explosion the ignition source was inside such a box that was sited in an emergency pump house building. There has, however, been relatively little previous research into this type of ignition mechanism and its effect on the explosion severity. Commercially available electrical control boxes measuring 600 mm high, 400 mm wide and 250 mm deep were used to explore the pressure development, venting processes and flame characteristics of stoichiometric propane/air explosions using aluminium foil and the supplied doors as vent coverings. In this work, the boxes were empty of their usual contents in order to establish a baseline for the effect of the internal congestion of the boxes. It was found that, in these empty-box tests, the door produced a flat petal shaped flame, which differed drastically from the mushroom flame shape, associated rolling vortex bubble venting traditionally observed with large orifice vented explosions

General dental practices with and without a dental therapist: a survey of appointment activities and patient satisfaction with their care.

Introduction Policy changes regarding the role of Dental Hygienist-Therapists (DTs) have been implemented in recent years with a view to promoting delivery of oral health-care through a more preventive-focused, team work approach. Aims To explore i) treatments led by dentists and DTs, and ii) patients' satisfaction with the care they received. Materials and methods Six case-studies of general dental practices in Wales, UK: three with, and three without a DT. For each participant, a patient-satisfaction questionnaire and a staff-member-completed appointment record form were completed. We sought to recruit 150 patients seeing a dentist and 100 patients seeing a DT, per case-study practice. Results 1,224 patients were recruited in total (314 DT and 910 dentist appointments). Preventive work accounted for nearly half of all treatments. Dentists, in practices with a DT, undertook significantly less preventive and restorative work, and significantly more extractions and advanced treatment (p <0.005, χ² = 15.352). Patient satisfaction and confidence in dentists' or DTs' ability was uniformly high (97% and 99% each group respectively). Conclusion Practices with DTs provided a more preventive-focused approach to oral health-care delivery; dentists in these practices performed more complex work. Positive patient satisfaction and confidence in practitioners' ability suggest patient acceptability of a preventive model

Temporally resolved laser induced plasma diagnostics of single crystal silicon - Effects of ambient pressure

Laser-Induced Breakdown Spectroscopy of silicon was performed using a nanosecond pulsed frequency doubled Nd:YAG (532 nm) laser. The temporal evolution of the laser ablation plumes in air at atmospheric pressure and at an ambient pressure of ∼10−5 mbar is presented. Electron densities were determined from the Stark broadening of the Si (I) 288.16 nm emission line. Electron densities in the range of 6.91×1017 to 1.29×1019 cm−3 at atmospheric pressure and 1.68×1017 to 3.02×1019 cm−3 under vacuum were observed. Electron excitation temperatures were obtained from the line to continuum ratios and yielded temperatures in the range 7600–18,200 K at atmospheric pressure, and 8020–18,200 K under vacuum. The plasma morphology is also characterized with respect to time in both pressure regimes

Tackling the challenge of the impact of continuing education: An evidence synthesis charting a global, cross-professional shift away from counting hours

Introduction: Health professionals worldwide are required to maintain their knowledge and skills through continuing education. However, there is limited evidence that the accumulation of hours of educational activity enhances practice. The aim of this study was to review evidence of the impact of continuing professional development (CPD), best educational practice and new models of CPD requirements. Methods: We conducted a rapid evidence synthesis, reviewing literature and websites on continuing education for healthcare and non-healthcare professionals. Results: We extracted data from 184 publications. Evidence of changed practice and improved patient care is uncommon in studies of CPD. What evidence there is suggests that activities are more likely to have impact if a combination of methods is used and if they are aligned with learning needs. Impact is also affected by the learner and their work environment. In terms of CPD requirements, we identified three models: input-based; outcomes-based and mixed models. We found a clear shift from quantitative, time-serving, input-models to outcomes-focused models which emphasise the identification of learning needs, selection of educational activity relevant to practice and reflection on practice improvement. Across a range of professions, recently updated CPD regulations no longer require registrants to accumulate CPD hours/points/credits. Conclusion: Outcomes-based models support registrants’ engagement in relevant, meaningful CPD which holds greater potential to positively impact on practice and strengthen patient safety. In funding this study, the UK General Dental Council exemplifies its commitment to reviewing its CPD requirments. © 2020 John Wiley &amp; Sons A/S. Published by John Wiley &amp; Sons Lt