Raisonnements en électricité et en hydrodynamique

Les raisonnements des étudiants en électricité sont connus. Dans cet article nous les rappelons et les comparons avec ceux que les étudiants utilisent à propos des circuits hydrauliques. Nous montrons qu'ils sont qualitativement semblables mais quantitativement très différents à cause d'une dépendance par rapport au contenu. Nos conclusions portent sur l'usage de l'analogie hydraulique. Nous formulons aussi l'hypothèse selon laquelle ces "raisonnements naturels" peuvent être hiérarchisés et constituent un passage obligé dans l'apprentissage des sciences

Early antibody response in healthcare professionals after two doses of SARS-CoV-2 mRNA vaccine (BNT162b2)

Data on the immune response after two doses of BNT162b2 are so far limited. Previously infected individuals were excluded from pivotal clinical trials and the optimal dose regimen in this population has not been clearly studied. The CRO-VAX HCP study aims at investigate the early antibody response in a population of healthcare professionals having received two doses of the BNT162b2 mRNA COVID-19 vaccine. The CRO-VAX HCP study is a multicenter, prospective, interventional study conducted in several sites in Belgium. The study included 231 healthcare professional volunteers who received the two-dose regimen of the BNT162b2 mRNA COVID-19 vaccine. Of these, 73 were previously infected by SARS-CoV-2 and 158 were uninfected and seronegative. In the first group, blood samples were collected at baseline and after 2, 4, 7, 10, 14, 21, and 28 days. In the second group, samples were obtained at baseline and after 14 and 28 days. Antibodies against the SARS-CoV-2 nucleocapsid and the receptor binding domain of the S1 subunit of the spike protein were measured in all individuals at different time points. In uninfected individuals, 95.5% (95% CI 91.0-98.2%) developed anti-spike antibodies after 14 days and a 24.9-fold rise (95% CI 21.4-28.9%) in antibody titer was observed after the second dose. In previously infected individuals, peak antibody response was reached after 7 days (i.e. 6,347 U/mL) and the second dose did not lead to significantly higher antibody titers (i.e. 8,856 to 11,911 U/mL). Antibody titers were higher in previously infected individuals. This study supports the concept that a single dose of BNT162b2 would be sufficient in previously infected individuals

Prégnance de l'explication électrostatique dans la construction du concept de circuit électrique : points de vue historique et didactique

Dans cet article on étudie la construction du concept de circuit électrique du double point de vue historique et psychogénétique. Dans les deux cas, on montre que la connaissance préalable d'électrostatique constitue un cadre de référence déformant pour la construction du concept de circuit électrique. On met en évidence un processus de réinvestissement électrostatique qui consiste à focaliser son attention sur les pôles du générateur où se trouvent accumulées, même en circuit fermé, des charges constituant l'élément essentiel d'analyse du circuit

Student's learning paths observation in basic electricity

Une démarche d'ingénierie didactique relative à l'enseignement de l'électricité en classe de seconde (grade 10) en France a permis d'observer des étapes de son apprentissage par les élèves. Des analyses préalables nous ont conduits à tester quatre hypothèses reposant sur la maîtrise des prérequis, une approche énergétique préalable du circuit électrique, une démarche qualitative et une introduction indépendante des concepts. Leur mise en oeuvre, d'abord dans la classe du chercheur, puis dans d'autres classes, enfin dans d'autres académies ont permis de découvrir : - des aides à l'apprentissage, comme la maîtrise des prérequis ou l'approche qualitative, facilitées par des classes plutôt homogènes et des espaces de remédiation ; - des chemins d'apprentissage du concept d'intensité électrique ; - des difficultés non résolues comme le passage au formalisme ; - l'élaboration par ces élèves d'un savoir d'une nature différente

Peri-infection titers of neutralizing and binding antibodies as a predictor of COVID-19 breakthrough infections in vaccinated healthcare professionals:importance of the timing

The BNT162b2 messenger RNA vaccine is highly effective in reducing COVID-19 infection, hospitalization and death. However, many subjects developed a breakthrough infection despite a full vaccination scheme. Since the waned efficacy of mRNA vaccines is correlated with the decrease of antibodies occurring over time, we aimed at evaluating whether lower levels of antibodies were associated with an increased risk of breakthrough infection in a cohort of breakthrough subjects that received three vaccine doses. Total binding antibodies against the RBD of the S1 subunit (Roche Diagnostics, Machelen, Belgium) and neutralizing antibodies using the Omicron B.1.1.529 variant pseudovirus were measured. Based on individual kinetic curves, the antibody titer of each subject was interpolated just before the breakthrough infection and compared to a matched-control group that did not develop a breakthrough infection. Lower levels of total binding and neutralizing antibodies were observed compared to the control group (6.900 [95% CI; 5.101-9.470] vs. 11.395 BAU/mL [8.627-15.050] [p=0.0301] and 26.6 [18.0-39.3] vs. 59.5 dilution titer [32.3-110] [p=0.0042], respectively). The difference between breakthrough and control subjects was mostly observed for neutralizing antibodies before three months after the homologous booster administration (46.5 [18.2-119] vs. 381 [285-509] [p=0.0156]). Considering the measurement of total binding antibodies before 3 months, there was no significant difference (p=0.4375). In conclusion, our results showed that subjects that developed a breakthrough infection had lower levels of neutralizing and total binding antibodies compared to controls. The difference was mostly noticeable considering neutralizing antibodies, especially for infections occurring before 3 months after the booster administration

Opioid-free versus opioid-based anesthesia in pancreatic surgery

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Correction to : Opioid-free versus opioid-based anesthesia in pancreatic surgery

Peer reviewedPublisher PD