Quelques résultats relatifs aux connaissances disciplinaires de professeurs stagiaires dans des situations simulées d’évaluation de productions d’élèves en mathématiques

Dans cet article, nous étudions l’activité de dix-huit enseignants stagiaires – professeurs des écoles et professeurs de mathématiques – accomplissant des tâches d’évaluation de productions d’élèves en mathématiques. La recherche s’inscrit dans une double orientation didactique : didactique professionnelle et didactique des mathématiques. Le dispositif de recherche, organisé autour d’un « simulateur », permet de ménager des conditions expérimentales analogues pour tous les professeurs. L’identification et la catégorisation des connaissances mobilisées par les enseignants lors de l’accomplissement des tâches d’évaluation servent d’appui à une analyse comparative de leur activité. Les résultats obtenus montrent que les connaissances disciplinaires jouent un rôle essentiel dans la réalisation des tâches que nous leur proposons.This article examines how students’ productions in mathematics are evaluated by eighteen student teachers/practicum, both schoolteachers and math teachers. There are two pedagogical objectives: professional didactics and mathematical didactics. The research design, organized around a “simulator”, allows the authors to arrange analogous experimental conditions for all subjects. The identification and categorization of knowledge that is used by the teachers during their evaluations is then used to support a comparative analysis of their activity. The results show that disciplinary knowledge plays an essential role in the accomplishment of the tasks proposed.En el presente artículo, estudiamos la actividad de diez y ocho docentes en práctica – maestros de las escuelas y maestros de matemáticas – llevando a cabo tareas de evaluación de producciones de alumnos en matemáticas. La investigación se inscribe en una doble orientación didáctica: didáctica profesional y didáctica de las matemáticas. El dispositivo de investigación, organizado alrededor de un «simulador», posibilita la habilitación de condiciones experimentales análogas para todos los maestros. La identificación y la categorización de los conocimientos movilizados por los docentes al momento de cumplir con tareas de evaluación sirven de apoyo a un análisis comparativo de su actividad. Los resultados conseguidos muestran que los conocimientos disciplinarios juegan un papel esencial en la realización de las tareas que les proponemos

Évaluation de la lecture au CP : mise en œuvre d’une approche multiple

Dans cet article, nous présentons un dispositif d’évaluation de la lecture en fin de CP (cours préparatoire) dont l’élaboration repose sur la prise en compte de deux dimensions du savoir-lire, le décodage-identification et la compréhension. Nous analysons la validité des épreuves qui le composent en référence à des modèles du décodage et de l’identification de mots ainsi que de la compréhension de texte. Le dispositif est testé, en passation individuelle, auprès de soixante-huit élèves de CP. Nous montrons par des analyses quantitatives et qualitatives des données l'intérêt d’une approche combinant plusieurs épreuves, dont deux consacrées à la compréhension autonome d'un texte écrit, pour évaluer en lecture des élèves et pour identifier différents types d’élèves en difficulté.In this paper we present an evaluation method to assess the level of reading of end of first-grade children (cours préparatoire), which takes into account two reading skills dimensions: decoding-identifying and understanding. The validity of the method is analyzed through both word decoding/identifying models and text understanding models. On the basis of quantitative and qualitative data analyses of the tests passed by sixty-eight first grade children, we show the interest of an evaluation method that combines several tests, including two for autonomous understanding of a written text, in order to assess children reading skills and to identify the different types of difficulties they can encounter

A low δ7Li lower crustal component: Evidence from an alkalic intraplate volcanic series (Chaîne des Puys, French Massif Central)

International audienceThe intraplate volcanic suite of the Chaîne des Puys (French Massif Central) shows a complete petrologic range, from alkali basalts to trachytes. The significant variations of trace elements and radiogenic isotopes along the series strongly support the occurrence of crustal assimilation associated with fractional crystallization (AFC). The least contaminated basalts are clearly related to a HIMU-type reservoir (206Pb/204Pb > 19.6; 87Sr/86Sr + 4). The behavior of radiogenic isotopes suggests that the most likely crustal contaminants are meta-sediments located in the lower crust. The Li isotopic compositions of the lavas range from high δ7Li (> + 7‰) in basalts to lighter values in more evolved lavas (down to δ7Li ≈ 0‰). The mantle component, expressed in the least evolved lavas, has a heavy Li isotopic signature, in good agreement with previous δ7Li measurements of OIB lavas with HIMU affinities. The evolution of Li isotopic compositions throughout the volcanic series is in agreement with the AFC model suggested by the Sr–Nd–Pb isotopic systems. Although the behavior of Li isotopes during assimilation processes is currently poorly constrained, our calculations suggest that at least a portion of the lower crust beneath the Chaîne des Puys is characterized by a light Li isotopic composition (δ7Li < − 5‰)

188: Prevalence of early repolarization in congenital long QT syndrome A combination of early and delayed repolarization

Introductionearly repolarization (ER) in Brugada or short QT syndrome is common and has been associated to a less favourable outcome. Even if apparently paradoxical, ER can also be seen in long QT (LQT) but prevalence and correlations to other variables are unknown.Methods12 lead ECG of 37 LQT pts (19 men, 39±21 yo) and 80 matched controls were reviewed. LQT pts were selected by a positive genetic testing (n=27) or by showing abnormal T wave and long QT interval (n=10) either spontaneously or during epinephrin infusion. ER was defined by >1mm J point elevation in the inferior or lateral leads with notch or slurring pattern. Presence of ER was correlated to the clinical and ECG characteristics and results genetic analysis.ResultsQT was 409±53 msec in pts and 372±24 in controls (p<0.0001) (QTc 476±52 vs 392±26 msec, p<0.0001). Two LQT pts presented with resuscitated sudden death and 4 with syncope at the time of diagnosis.14/37 LQT pts (38%) had ER compared to 17/80 (21%) controls (p=0.05).ER was more frequent in men (12/19, 63%) compared to women (2/18, 11%) (p=0.001) but was not correlated to age. Pts with ER had slower heart rate (63±10 vs 75±18 bpm, p=0.02).ER was not correlated to symptoms or cardiac events (no ER in the 2 pts with SD and in 2/4 pts with syncope).QT were longer in pts with ER (450±68 vs 397±54 msec in V2, p=0.01) but there was no correlations between ER and corrected QT intervals.ER was more often seen in pts with or without mutations although non significantly (8/27 vs 6/10, p=0.09), but there was a trend toward more frequent ER in case of HeRG mutations (6/12) than KCNQ1 or KCNJ2 mutations (2/11 and 0/4) (p=0.09).ConclusionER is very common in LQT pts and is related to the gender and to the heart rate but not to the corrected QT duration. ER does not seem to be correlated to cardiac events in this series but may be linked to some gene mutations. Further studies are needed for demonstrating additional mutations/ variants or the existence of an early transient voltage gradient due to altered kinetics in muted potassium channels with loss of function

The size of plume heterogeneities constrained by Marquesas isotopic stripes

International audienceThe scale and geometry of chemical and isotopic heterogeneities in the source of plumes have important scientific implications on the nature, composition and origin of plumes and on the dynamics of mantle mixing over time. Here, we address these issues through the study of Marquesas Islands, one of the Archipelagoes in Polynesia. We present new Sr, Nd, Pb, Hf isotopes as well as trace element data on lavas from several Marquesas Islands and demonstrate that this archipelago consists of two adjacent and distinct rows of islands with significantly different isotopic compositions. For the entire 5.5 Ma construction period, the northern islands, hereafter called the Ua Huka group, has had systematically higher 87Sr/86Sr and lower 206Pb/204Pb ratios than the southern Fatu Hiva group at any given 143Nd/144Nd value. The shape and curvature of mixing arrays preclude the ambient depleted MORB mantle as one of the mixing end-members. We believe therefore that the entire isotopic heterogeneity originates in the plume itself. We suggest that the two Marquesas isotopic stripes originate from partial melting of two adjacent filaments contained in small plumes or "plumelets" that came from a large dome structure located deep in the mantle under Polynesia. Low-degree partial melting under Marquesas and other "weak" Polynesian hot spot chains (Pitcairn-Gambier, Austral-Cook, Society) sample small areas of the dome and preserve source heterogeneities. In contrast, more productive hot spots build up large islands such as Big Island in Hawaii or Réunion Island, and the higher degrees of melting blur the isotopic variability of the plume source

La nécropole du haut Moyen Âge du « Clos II » à Buchères (Aube)

Dans le cadre d’une fouille préventive, réalisée en 2009, une nécropole du haut Moyen Âge a été mise au jour à Buchères (Aube). Cent trente-neuf structures funéraires y ont été dénombrées. L’étude typo-chronologique du mobilier ainsi que les datations radiocarbone permettent de dater l’utilisation de cette nécropole entre la fin du VIe et le tout début du XIe siècle. Le mobilier funéraire exhumé témoigne de la pratique de l’inhumation habillée et du dépôt d’objets dans les sépultures.As part of a rescue archaeology operation carried out in 2009, a medieval graveyard was discovered in Buchères (Aube). One hundred and thirty nine graves were excavated. The typo-chronological study of the funeral deposit and the radiocarbon dating of the skeletons date this site from the end of the VIth to the early beginning of the XIth century. The funeral deposit proves that both dressed burials and artefact deposits were practiced (Nous remercions le Dr. John Sills (Oxford Institute for Archæology) pour sa révision du résumé).Im Rahmen einerPräventivgrabung wurde 2009 in Buchères (Département Aube) eine frühmittelalterliche Nekropole mit 139 Gräbern freigelegt. Die typologische und chronologische Untersuchung der Grabbeigaben und die Radiokarbondaten lassen eine Nutzung dieser Nekropole zwischen dem Ende des 6. und den ersten Jahren des 11. Jahrhunderts erkennen. Die Grabausstattung zeugt von der Sitte die Toten bekleidet beizusetzen und ihnen Beigaben mitzugeben

Mercury and methylmercury concentrations in high altitude lakes and fish (Arctic charr) from the French Alps related to watershed characteristics

International audienceTotal mercury (THg) andmethylmercury (MeHg) concentrations were measured in the muscle of Arctic charr (Salvelinus alpinus) and in the water column of 4 lakes that are located in the French Alps. Watershed characteristics were determined (6 coverage classes) for each lake in order to evaluate the influence of watershed composition on mercury and methylmercury concentrations in fish muscle and in the water column. THg and MeHg concentrations in surface water were relatively low and similar among lakes and watershed characteristics play a major role in determining water column Hg and MeHg levels. THg muscle concentrations for fish with either a standardized length of 220 mm, a standardized age of 5 years or for individualuals did not exceed the 0.5 mg kg−1 fish consumption advisory limit established for Hg by the World Health Organization (WHO, 1990). These relatively low THg concentrations can be explained by watershed characteristics, which lead to short Hg residence time in the water column, and also by the short trophic chain that is characteristic of mountain lakes. Growth rate did not seem to influence THg concentrations in fish muscles of these lakes and we observed no relationship between fish Hg concentrations and altitude. This study shows that in the French Alps, high altitude lakes have relatively low THg and MeHg concentrations in both the water column and in Arctic charr populations. Therefore, Hg does not appear to present a danger for local populations and the fishermen of these lakes

Cantaloupe line CZW-30 containing coat protein genes of cucumber mosaic virus, zucchini yellow mosaic virus, and watermelon mosaic virus-2 is resistant to these three viruses in the field

Cantaloupe line CZW-30 containing coat protein gene constructs of cucumber mosaic cucumovirus (CMV), zucchini yellow mosaic potyvirus (ZYMV), and watermelon mosaic virus 2 potyvirus (WMV-2) was investigated in the field over two consecutive years for resistance to infections by CMV, ZYMV, and/or WMV-2. Resistance was evaluated under high disease pressure achieved by mechanical inoculations and/or natural challenge inoculations by indigenous aphid vectors. Across five different trials, homozygous plants were highly resistant in that they never developed systemic symptoms as did the nontransformed plants but showed few symptomatic leaves confined close to the vine tips. Hemizygous plants exhibited a significant delay (2-3 weeks) in the onset of disease compared to control plants but had systemic symptoms 9-10 weeks after transplanting to the field. Importantly, ELISA data revealed that transgenic plants reduced the incidence of mixed infections. Only 8% of the homozygous and 33% of the hemizygous plants were infected by two or three viruses while 99% of the nontransformed plants were mixed infected. This performance is of epidemiological significance. In addition, control plants were severely stunted (44% reduction in shoot length) and had poor fruit yield (62% loss) compared to transgenic plants, and most of their fruits (60%) were unmarketable. Remarkably, hemizygous plants yielded 7.4 times more marketable fruits than control plants, thus suggesting a potential commercial performance. This is the first report on extensive field trials designed to assess the resistance to mixed infection by CMV, ZYMV, and WMV-2, and to evaluate the yield of commercial quality cantaloupes that are genetically engineere

Le début du ive s. av. J.-C. dans l’espace culturel sénonais : les habitats de Bois d’Echalas à Ville-Saint-Jacques et de Beauchamp à Varennes-sur-Seine (Seine-et-Marne) dans le contexte de l’interfluve Seine-Yonne

L’étude de deux habitats du début du ive s. av. J.-C. installés à proximité de la confluence Seine-Yonne permet de définir le faciès mobilier de cette partie du Bassin parisien au cours de La Tène B1a, notamment grâce à l’association d’un important cortège de céramiques locales et importées et d’un mobilier métallique significatif. L’analyse des structures de conservation et du mobilier conduit à établir une hiérarchie des établissements. Celui de Ville-Saint-Jacques, Bois d’Echalas, occupe une place prééminente dans le système social mis en place dans la région considérée, alors que celui de Varennes-sur-Seine, Beauchamp, se révèle d’un niveau inférieur. Au-delà de la comparaison entre les deux sites, c’est une lecture socio-économique de l’organisation territoriale qui est proposée.The study of two settlements of the beginning of the 4th century BC near the confluence of the Seine and the Yonne enables us to define the movable culture of this part of the Paris basin during La Tène B1a, notably because of the association of an important series of local and imported ceramics and significant metal articles. The analysis of the structures of conservation and of furniture lead to the establishment of a hierachy of settlements. That of Ville-Saint-Jacques, Bois d’Echalas, occupied a prominent place in the social system set up in the region in question, whereas that of Varennes-sur-Seine, Beauchamp, proved to be of a lower level. Beyond the comparison between the two sites, what is presented is a socio-economic lecture on territorial organisation

Le début du ive s. av. J.-C. dans l’espace culturel sénonais : les habitats de Bois d’Echalas à Ville-Saint-Jacques et de Beauchamp à Varennes-sur-Seine (Seine-et-Marne) dans le contexte de l’interfluve Seine-Yonne

L’étude de deux habitats du début du ive s. av. J.-C. installés à proximité de la confluence Seine-Yonne permet de définir le faciès mobilier de cette partie du Bassin parisien au cours de La Tène B1a, notamment grâce à l’association d’un important cortège de céramiques locales et importées et d’un mobilier métallique significatif. L’analyse des structures de conservation et du mobilier conduit à établir une hiérarchie des établissements. Celui de Ville-Saint-Jacques, Bois d’Echalas, occupe une place prééminente dans le système social mis en place dans la région considérée, alors que celui de Varennes-sur-Seine, Beauchamp, se révèle d’un niveau inférieur. Au-delà de la comparaison entre les deux sites, c’est une lecture socio-économique de l’organisation territoriale qui est proposée.The study of two settlements of the beginning of the 4th century BC near the confluence of the Seine and the Yonne enables us to define the movable culture of this part of the Paris basin during La Tène B1a, notably because of the association of an important series of local and imported ceramics and significant metal articles. The analysis of the structures of conservation and of furniture lead to the establishment of a hierachy of settlements. That of Ville-Saint-Jacques, Bois d’Echalas, occupied a prominent place in the social system set up in the region in question, whereas that of Varennes-sur-Seine, Beauchamp, proved to be of a lower level. Beyond the comparison between the two sites, what is presented is a socio-economic lecture on territorial organisation