Une caméra dans le cours de mathématiques : pour quoi faire?

International audienceNous nous interrogeons sur la pertinence des pratiques mises en place par les enseignants lors de l'intégration des nouvelles technologies dans leur classe. Pour cela, nous avons observé un professeur de mathématiques qui utilisait dans ses cours une caméra reliée à un vidéo-projecteur au cours d'une activité de recherche mettant en oeuvre des constructions géométriques. Nous avons cherché quel était l'impact de l'utilisation de cet outil sur ses pratiques et celles de ses élèves, notamment en ce qui concernait la prise en compte des productions de la classe, l'apprentissage des « savoir-faire transparents » et la constitution d'une mémoire didactique commune. A travers l'étude de ce cas particulier, nous avons pu observer les intérêts mais également entrevoir certains des effets pervers que pouvait entraîner l'intégration cette nouvelle technologie dans la classe. Mots clés : nouvelles technologies, genèse instrumentale, prise en compte des productions d'élèves, savoirs transparents, mémoire didactique. Abstract: The purpose of this article is to examine teachers' practices when using new technologies in their classrooms. With this objective in mind, we observed a mathematics teacher who used a camera linked to a video projector during a research activity with geometric constructions, and we sought to determine the impact of this choice on his practices and those of his students. We observed that the use of this tool enabled a better integration of pupils' work as part of the lesson. We also noticed the teaching of some essential but tacit practices as well as the reactivation of didactic memory. However, we also detected some negative effects on the learning and teaching process due to the use of this tool

Purification of thonningianins A and B and four further derivatives from Thonningia sanguinea by one‐ and two‐dimensional centrifugal partition chromatography

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Evolution of product phase assemblages during thermal decomposition of muscovite under strong disequilibrium conditions

http://www.minsocam.org/MSA/AmMin/TOC/Abstracts/2006_Abstracts/FM06_Abstracts/Devineau_p413_06.pdfWe investigated the thermal decomposition of muscovite in natural granite powders heated to 1175°C for durations from 5 min to 68 h, at 1 bar, paying special attention to the early stages of decomposition. This study shows that muscovite is completely transformed after 5 min. Muscovite pseudomorphs consist of glass, mullite, and Al-rich oxides. For short durations (5 and 40 min), the Al-rich phase was identiÞ ed by XRD, electron diffraction, and TEM microanalysis as γ-Al2O3 containing 4.8 wt% FeO (total Fe), probably a few weight percents of MgO, and possibly up to 10 wt% SiO2. Faint superstructure spots and diffuse streaks observed in electron-diffraction patterns suggest vacancy or trace elements ordering in the γ-Al2O3 defect spinel structure. γ-Al2O3 displays an unexpected acicular morphology, elongated along three directions at 120° in the basal (001)musc planes and parallel to lateral faces of the former muscovite. Mullite forms rods elongated in the basal (001)musc planes along a direction at 90° from one set of γ-Al2O3 needles. The γ-Al2O3 structure appears to be a metastable phase that is replaced by corundum for longer durations

Design of a refueling tanker delivering liquid hydrogen

A refueling tanker that could deliver 155,000 lb of liquid hydrogen to a hypersonic tanker in 15 min was designed. A flying boom system was chosen to fit strict delivery criteria. Tank design and material specification were also addressed. To assure the flow required, it was important to cancel the pressure drop phenomenon. Geometry, aerodynamics, weight considerations, propulsion, stability, and performance for the tanker were also considered. Finally, the cost of developing three prototypes was estimated

Chronic pneumonia with Pseudomonas aeruginosa and impaired alveolar fluid clearance

BACKGROUND: While the functional consequences of acute pulmonary infections are widely documented, few studies focused on chronic pneumonia. We evaluated the consequences of chronic Pseudomonas lung infection on alveolar function. METHODS: P. aeruginosa, included in agar beads, was instilled intratracheally in Sprague Dawley rats. Analysis was performed from day 2 to 21, a control group received only sterile agar beads. Alveolar-capillary barrier permeability, lung liquid clearance (LLC) and distal alveolar fluid clearance (DAFC) were measured using a vascular ((131)I-Albumin) and an alveolar tracer ((125)I-Albumin). RESULTS: The increase in permeability and LLC peaked on the second day, to return to baseline on the fifth. DAFC increased independently of TNF-α or endogenous catecholamine production. Despite the persistence of the pathogen within the alveoli, DAFC returned to baseline on the 5(th )day. Stimulation with terbutaline failed to increase DAFC. Eradication of the pathogen with ceftazidime did not restore DAFC response. CONCLUSIONS: From these results, we observe an adequate initial alveolar response to increased permeability with an increase of DAFC. However, DAFC increase does not persist after the 5(th )day and remains unresponsive to stimulation. This impairment of DAFC may partly explain the higher susceptibility of chronically infected patients to subsequent lung injury

A dietary supplementation with leucine and antioxidants is capable to accelerate muscle mass recovery after immobilization in adult rats

Prolonged inactivity induces muscle loss due to an activation of proteolysis and decreased protein synthesis; the latter is also involved in the recovery of muscle mass. The aim of the present work was to explore the evolution of muscle mass and protein metabolism during immobilization and recovery and assess the effect of a nutritional strategy for counteracting muscle loss and facilitating recovery. Adult rats (6-8 months) were subjected to unilateral hindlimb casting for 8 days (10-18) and then permitted to recover for 10 to 40 days (R10-R40). They were fed a Control or Experimental diet supplemented with antioxidants/polyphenols (AOX) (10 to 18), AOX and leucine (AOX + LEU) (18 to R15) and LEU alone (R15 to R40). Muscle mass, absolute protein synthesis rate and proteasome activities were measured in gastrocnemius muscle in casted and non-casted legs in post prandial (PP) and post absorptive (PA) states at each time point. Immobilized gastrocnemius protein content was similarly reduced (-37%) in both diets compared to the non-casted leg. Muscle mass recovery was accelerated by the AOX and LEU supplementation (+6% AOX+LEU vs. Control, P<0.05 at R40) due to a higher protein synthesis both in PA and PP states (+23% and 31% respectively, Experimental vs. Control diets, P<0.05, R40) without difference in trypsin-and chymotrypsin-like activities between diets. Thus, this nutritional supplementation accelerated the recovery of muscle mass via a stimulation of protein synthesis throughout the entire day (in the PP and PA states) and could be a promising strategy to be tested during recovery from bed rest in humans

Effects of monoclonal anti-PcrV antibody on Pseudomonas aeruginosa-induced acute lung injury in a rat model

BACKGROUND: The effects of the murine monoclonal anti-PcrV antibody Mab166 on acute lung injury induced by Pseudomonas aeruginosa were analyzed in a rat model. METHODS: Lung injury was induced by the instillation of P. aeruginosa strain PA103 directly into the left lungs of anesthetized rats. One hour after the bacterial instillation, rabbit polyclonal anti-PcrV IgG, murine monoclonal anti-PcrV IgG Mab166 or Mab166 Fab-fragments were administered intratracheally directly into the lungs. The degree of alveolar epithelial injury, amount of lung edema, decrease in oxygenation and extent of lung inflammation by histology were evaluated as independent parameters of acute lung injury. RESULTS: These parameters improved in rats that had received intratracheal instillation of either rabbit polyclonal anti-PcrV IgG, murine monoclonal anti-PcrV IgG Mab166 or Mab166 Fab-fragments in comparison with the control group. CONCLUSION: Mab166 and its Fab fragments have potential as adjuvant therapy for acute lung injury due to P. aeruginosa pneumonia