Search

65 pages; International audience; Résumé Ce travail étudie les riches faunes d'ammonites du Pliensbachien et de la base du Toarcien dans la localité très fossilifère de la carrière de la Roche Blain (Calvados). Une cinquantaine d'espèces pliensbachiennes, récoltées dans une douzaine de niveaux distincts sont toutes décrites et illustrées. Leur préservation est parfois remarquable. Des structures fragiles comme les péristomes ou les mégastries sont assez souvent préservées. A l'exception de deux spécimens d'affinités téthysiennes (Arieticeras cf. amalthei (Oppel, 1853) et Dactylioceras (Eodactylites) sp.), les ammonites récoltées à la Roche Blain se rattachent toutes, sans ambiguïté, aux faunes d'affinités nord-ouest européennes, largement dominantes à l'époque dans le Bassin anglo-normand. Les peuplements d'ammonites du Pliensbachien de la Roche Blain sont remarquablement diversifiés. La présence de deux espèces nouvelles (Acanthopleuroceras gauthieri nov. sp. Dommergues & Meister et Catriceras (?) rioulti nov. sp. Dommergues & Meister) est particulièrement remarquable. Les faunes d'affinités nord-ouest européennes sont bien connues et il est surprenant de découvrir deux formes notoirement nouvelles dans un seul gisement du nord-ouest de l'Europe en général, et du Bassin anglo-parisien en particulier. Il existe aussi au sein des faunes récoltées à la Roche Blain un nombre important de spécimens relativement bien conservés mais difficiles à attribuer sans réserve à un genre et/ou à une espèce connue. Ces nombreuses formes difficiles à classer, et souvent laissées en nomenclature ouverte, renforcent l'originalité des faunes trouvées à la Roche Blain. L'explication de cette exceptionnelle diversité faunique est sans doute à rechercher dans le contexte paléogéographique pliensbachien des Campagnes de Caen et de Falaise formées d'écueils, de hauts-fonds, de sillons et de cuvettes plus ou moins profonds qui devaient offrir une très riche mosaïque de biotopes. Cette région de seuil proche de la bordure orientale du Massif armoricain était directement ouverte sur des zones moins agitées (plus profondes?) et/ou plus subsidentes du Bassin anglo-parisien. Des échanges fauniques faciles devaient exister tant avec les bassins de la Manche occidentale (e.g. Dorset) qu'avec le Bassin de Paris, mais aucun argument paléobiogéographique ne permet actuellement de privilégier l'une ou l'autre de ces sources de peuplement.

International audience; Organically modified montmorillonites obtained by cation exchange from the same natural layered silicate were studied. The surface properties of the pristine and a series of organically modified clays were determined by inverse gas chromatography and the water adsorption mechanisms were studied by a gravimetric technique coupled with a microcalorimeter. A significant increase of the specific surface area, a decrease of the water adsorption, and a decrease of the dispersive component of the surface energy were observed when the sodium cations of the natural montmorillonite were exchanged for a quaternary ammonium. Slighter differences in surface properties were observed, on the other hand, between the different types of organically modified montmorillonites. Indeed, similar dispersive components of the surface energy were determined on the organoclays. Nevertheless, the specific surface area increased in the range 48-80 m2/g with increasing d-spacing values and the presence of specific'groups attached to the quaternary ammonium, such as phenyl rings or hydroxyl groups, led to some specific behaviors, i.e., a more pronounced base character and a higher water adsorption at high activity, respectively. Differences in interlayer cation chain organization, denoted as crystallinity, were also observed as a function of the nature of the chains borne by the quaternary ammonium. In a later step, polyethylene-based nanocomposites were prepared with those organically modified montmorillonites. The clay dispersion and the barrier properties of the nanocomposites were discussed as a function of the montmorillonite characteristics and of the matrix/montmorillonite interactions expected from surface energy characterization.

The aim of this article was to study the physiopathology of tumoral uptake of 111In-pentetreotide using factorial analysis of dynamic series (FADS) and to assess the usefulness of this analysis in somatostatin receptor scintigraphy.Forty-one patients were included, 24 women and 17 men. After intravenous injection of 111 MBq 111In-pentetreotide, dynamic image acquisition (68 images of 30 s) began in front of the suspected tumoral site: thoracic in 10 patients with medullary carcinoma of the thyroid and 2 patients with bronchogenic carcinoid, and abdominal in 12 cases of midgut carcinoid and 17 cases of other gastroenteropancreatic neuroendocrine tumors. FADS was performed with FAMIS software. Static images were obtained 4 h and 24 h later. For every patient, surgery and/or clinical follow-up (4 y) was used to classify results as true (T) or false (F) positive (P) or negative (N) and to evaluate both the sensitivity of static images and the usefulness of FADS.Of the 14 cases of carcinoid tumor, 5 patients were TN; 9 patients were TP with static images but only 8 were TP with FADS (a bronchogenic carcinoid of 6 mm was missed). Of the 17 cases of gastroenteropancreatic neuroendocrine tumor, static images were TP in 9 patients, and FADS were TP in 5 of these patients (and 4 FN). Static images and FADS were FN in 4 patients and TN in 3 patients, and in the 2 last patients static images were FP, but FADS were TN. Of the 10 cases of medullary carcinoma of the thyroid, static images and FADS were TN in 1 patient, static images were TP in 3 patients and FADS were TP in 2 of these patients (and 1 FN). In the six last cases, static images were FN, but FADS were FN in 3 patients and TP in 3 patients, showing an infiltrate.FADS demonstrates that tumoral kinetics are similar to those of the spleen. FADS can show a diffuse tumoral uptake corresponding to tumoral infiltrate in medullary carcinoma of the thyroid or in hepatic miliaria, whereas static images were normal or doubtful.