‘Knock on nanocellulose’: Approaching the laminar burning velocity of powder-air flames

International audienc

Nanocellulose explosions: influence of the agglomeration and turbulence on the combustion rate-limiting step and flame propagation

Dust explosion risk assessment is relatively well established for micron-sized particles and requires the determination of key safety parameters representing the ignition sensitivity and explosion severity of the dust. When considering nanoparticles, the particle size distribution (PSD) is more likely to vary during the injection process, due to both the agglomeration phenomenon inherent to strong interactions and the fragmentation phenomenon due to flow shear stresses. As a consequence, safety parameters and their determination methods can differ significantly from micro to nanopowders. A peculiar attention has then to be given to the cloud characteristics (PSD, turbulence), more precisely at the exact moment of ignition. This work focuses on nanocellulose and aims at evaluating the influence of the agglomeration phenomenon and flow turbulence on the dust combustion. Flame propagation tests were performed to evaluate the unstretched burning velocity and explosions tests were carried out to estimate the combustion mechanisms involved

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed