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

Stability of Concentrated Solution of Vancomycin Hydrochloride in Syringes for Intensive Care Units

Abstract Background Vancomycin is increasingly administrated by continuous infusion. But the treatment of patient in intensive care need restricted volume to prevent fluid overload. The aim of the study was to evaluate the physical and chemical stability of solutions of a high concentration of vancomycin hydrochloride in 5 % glucose or 0.9 % NaCl. Methods Eight syringes of 50 mL, containing 41.66 mg/mL of vancomycin hydrochloride four syringes in 5 % glucose and four in 0.9 % NaCl were prepared and stored at ambient temperature during 48 h. Immediately after preparation and during 48 h, vancomycin hydrochloride concentrations were measured by a high-performance liquid chromatography (HPLC). Spectrophotometric absorbance at different wavelengths, pH measurement and microscopic observations were also performed. Results All solutions were physico-chemically stable during the whole period storage at ambient temperature: no color change, turbidity, precipitation or opacity, no significant pH variations or optic densities were observed in the solutions. Any crystals were seen by microscopic analysis. Solutions are considered chemically stable as the lower limit of the 95 % unilateral confidence interval on the mean remained above 90 % of the initial concentration for at least 48 h. Conclusions Solutions of vancomycin hydrochloride 41.66 mg/mL in syringe of 5 % glucose or 0.9 % NaCl are physically and chemically stable for at least 48 h when stored in syringes at ambient temperature. </jats:sec

Dégradation du malathion formulé sur attapulgite et kaolin. 2. Conséquence d'un traitement thermique des matières de charge

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Mise en évidence de chemins d'apprentissage des élèves lors d'une ingénierie didactique d'électrocinétique

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Management of congenital and posttraumatic splenic cysts in children.

Splenic cysts are rarely observed in young patients. We report three cases of splenic cysts. The management and the surgical procedure, if needed, are discussed. If the splenic cyst is symptomatic or if its size reaches a diameter of 4-6cm, it requires surgical management. This treatment would be performed by laparoscopic approach and is intended to spare splenic tissue as much as possible. A prophylactic anti-pneumococcal vaccination is recommended before surgical treatment.Case ReportsJournal Articleinfo:eu-repo/semantics/publishe

Study of follitropin receptors in testis using a homologous system. Binding of porcine follitropin to plasma membranes from immature porcine testis and correlation with adenylate cyclase stimulation.

The properties of follitropin receptors in immature porcine testis were determined using highly purified porcine follitropin. 1. The characteristics of follitropin binding to a subcellular fraction rich in plasma membranes were studied using a 125I-labelled follitropin with high specific activity (75-100 Ci/g) and high binding activity. The binding is dependent on time, temperature and pH. It is specific to follitropin as demonstrated by the very low binding activity of the follitropin alpha and beta subunits and of the other glycoprotein hormones. Scatchard analysis of binding data indicated an equilibrium association constant of 2 x 10(10) M-1 and a concentration of high affinity binding sites of 500 fmol/mg membrane proteins. 2. A sensitive radio-ligand receptor assay was developed. Fifty percent inhibition of binding was obtained with as little as 2 ng of porcine follitropin. Ovine and bovine follitropins and pregnant mare serum gonadotropin gave binding inhibition curves parallel to that given by porcine follitropin. With equine and human follitropin, significantly different slopes were recorded. 3. Kinetics of dissociation of labelled follitropin from its testis receptors showed the presence of at least two compartments with fast and slow dissociation rate constants. The ratio between the sizes of the slow and fast compartments appeared dependent upon preincubation time. 4. A temporal correlation was observed between binding of follitropin to testis receptors and activation of membrane bound adenylate cyclase