Effect of Grain Refinement on Jerky Flow in an Al-Mg-Sc Alloy

International audienceThe influence of microstructure on the manifestations of the Portevin-Le Chatelier (PLC) effect was studied in an Al-Mg-Sc alloy with unrecrystallized, partially recrystallized, and fully recrystallized grain structures. It was found that the extensive grain refinement promotes plastic instability: the temperature-strain rate domain of the PLC effect becomes wider and the critical strain for the onset of serrations decreases. Besides, the amplitude of regular stress serrations observed at room temperature and an intermediate strain rate increases several times, indicating a strong increase of the contribution of solute solution hardening to the overall strength. Moreover, the grain refinement affects the usual sequence of the characteristic types of stress serrations, which characterize the dynamical mechanisms governing a highly heterogeneous unstable plastic flow. Finally, it reduces the strain localization and surface roughness and diminishes the difference between the surface markings detected in the necked area and in the region of uniform elongation

Urticaria exacerbations and adverse reactions in patients with chronic urticaria receiving COVID-19 vaccination : results of the UCARE COVAC-CU study

Background: Concern about disease exacerbations and fear of reactions after coronavirus disease 2019 (COVID-19) vaccinations are common in chronic urticaria (CU) patients and may lead to vaccine hesitancy. Objective: We assessed the frequency and risk factors of CU exacerbation and adverse reactions in CU patients after COVID-19 vaccination. Methods: COVAC-CU is an international multicenter study of Urticaria Centers of Reference and Excellence (UCAREs) that retrospectively evaluated the effects of COVID-19 vaccination in CU patients aged ≥18 years and vaccinated with ≥1 dose of any COVID-19 vaccine. We evaluated CU exacerbations and severe allergic reactions as well as other adverse events associated with COVID-19 vaccinations and their association with various CU parameters. Results: Across 2769 COVID-19–vaccinated CU patients, most (90%) received at least 2 COVID-19 vaccine doses, and most patients received CU treatment and had well-controlled disease. The rate of COVID-19 vaccination–induced CU exacerbation was 9%. Of 223 patients with CU exacerbation after the first dose, 53.4% experienced recurrence of CU exacerbation after the second dose. CU exacerbation most often started <48 hours after vaccination (59.2%), lasted for a few weeks or less (70%), and was treated mainly with antihistamines (70.3%). Factors that increased the risk for COVID-19 vaccination–induced CU exacerbation included female sex, disease duration shorter than 24 months, having chronic spontaneous versus inducible urticaria, receipt of adenovirus viral vector vaccine, having nonsteroidal anti-inflammatory drug/aspirin intolerance, and having concerns about getting vaccinated; receiving omalizumab treatment and Latino/Hispanic ethnicity lowered the risk. First-dose vaccine–related adverse effects, most commonly local reactions, fever, fatigue, and muscle pain, were reported by 43.5% of CU patients. Seven patients reported severe allergic reactions. Conclusions: COVID-19 vaccination leads to disease exacerbation in only a small number of CU patients and is generally well tolerated