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To characterize the stated practices of qualified Canadian physicians toward tracheostomy for pediatric prolonged mechanical ventilation and whether subspecialty and comorbid conditions impact attitudes toward tracheostomy.Cross sectional web-based survey.Pediatric intensivists, neonatologists, respirologists, and otolaryngology-head and neck surgeons practicing at 16 tertiary academic Canadian pediatric hospitals.Respondents answered a survey based on three cases (Case 1: neonate with bronchopulmonary dysplasia; Cases 2 and 3: children 1 and 10 years old with pediatric acute respiratory distress syndrome, respectively) including a series of alterations in relevant clinical variables.We compared respondents' likelihood of recommending tracheostomy at 3 weeks of mechanical ventilation and evaluated the effects of various clinical changes on physician willingness to recommend tracheostomy and their impact on preferred timing (≤ 3 wk or3 wk of mechanical ventilation). Response rate was 165 of 396 (42%). Of those respondents who indicated they had the expertise, 47 of 121 (38.8%), 23 of 93 (24.7%), and 40 of 87 (46.0%) would recommend tracheostomy at less than or equal to 3 weeks of mechanical ventilation for cases 1, 2, and 3, respectively (p0.05 Case 2 vs 3). Upper airway obstruction was associated with increased willingness to recommend earlier tracheostomy. Life-limiting condition, severe neurologic injury, unrepaired congenital heart disease, multiple organ system failure, and noninvasive ventilation were associated with a decreased willingness to recommend tracheostomy.This survey provides insight in to the stated practice patterns of Canadian physicians who care for children requiring prolonged mechanical ventilation. Physicians remain reluctant to recommend tracheostomy for children requiring prolonged mechanical ventilation due to lung disease alone at 3 weeks of mechanical ventilation. Prospective studies characterizing actual physician practice toward tracheostomy for pediatric prolonged mechanical ventilation and evaluating the impact of tracheostomy timing on clinically important outcomes are needed as the next step toward harmonizing care delivery for such patients.

Providing a reliable hot surface ignition system (glow plug, GP) for natural gas-direct injection engines is challenging. This paper presents experimental results of aging all-ceramic Si3N4-based GPs in an engine, continuing previously published results on electric and gas burner rigs. The microstructural modifications of the ceramic heater, leading to degradation and ultimately to failure, are effected by four synergistic mechanisms: electrical, chemical, mechanical, and thermal. GP lifetime in engine follows the general Arrhenius law, with activation energy of 5.2 eV, (vs 9.1 V on burner rig and 13.8 eV on electric rig, as reported previously), suggesting additional factors contributing to GP failure in the engine.

In the development of advanced natural gas and hydrogen direct injection combustion engines, a challenge is providing reliable hot-surface (glow plug, GP) ignition systems; most promising are GPs with silicon nitride-based heaters. This paper presents experimental results of accelerated degradation tests of the GPs on natural gas-burning rig, continuing previously published results on GP degradation in air. Degradation, ultimately leading to GP failure, occurs through the synergistic effects of electric field and chemical reactions in the combustion environment. The resulting microstructural modifications of the ceramic heater, studied by SEM/EDS, are a combination of sintering additive ions migration and surface oxidation.

All-ceramic glow plugs (GP) based on sintered-silicon nitride are evaluated as hot surface ignition systems for natural gas and hydrogen direct injection combustion engines. This paper presents experimental results of the accelerated degradation tests of the GPs in air, wherein GP is heated solely by dc electricity. The complex degradation process has been linked mostly to the redistribution of the sintering additives in Si3N4/Yb2O3 system under an influence of dc electric field and temperatures over 1300°C, as experienced by GP in-service. Ytterbium ions migration varies with time, temperature, and voltage. The microstructural damage was studied primarily by SEM microscopy.

Details of the Infra-Cambrian Polarisbreen Series are given, arising partly out of observations made since they were defined in outline by the authors in 1956. The Polarisbreen Series includes the distinctive Polarisbreen Tillite Formation, which correlated with the neighbouring Sveanor Formation of Nordaustlandet and with other tillites in Vestspitsbergen. They are regarded as a product of the great infra-Cambrian ice age and are correlated with world-wide tillite horizons of this age.

Continuation of a description of the Hecla Hoek strata in Ny Friesland, giving the results of Cambridge expeditions to Spitsbergen; deals with the upper middle Hecla Hoek rocks of late Precambrian age. The succession consists of the lower and upper Grusdievbreen limestones, comprising ten unnamed members, and the Akademikerbreen series, comprising four formations of limestones, dolomites, conglomerates, and oolites. The wide variety of lithology and color provides the means for reliable correlations.