Bruniquel – Grotte

Rappels En 2015, une seconde opération programmée a été menée dans la grotte de Bruniquel qui, rappelons-le, a été découverte en 1990 par un spéléologue, B. Kowalczelski (société spéléo-archéologique de Caussade, SSAC). Après expertise de la cavité et de son potentiel paléontologique et archéologique par F. Rouzaud qui confirma l’existence – loin de l’entrée – d’étranges structures agencées avec des concrétions, deux autorisations ont été délivrées en 1992 et 1993 au nom de l’un d’entre nous ..

Comparative static curing versus dynamic curing on tablet coating structures

International audienceCuring is generally required to stabilize film coating from aqueous polymer dispersion. This post-coating drying step is traditionally carried out in static conditions, requiring the transfer of solid dosage forms to an oven. But, curing operation performed directly inside the coating equipment stands for an attractive industrial application. Recently, the use of various advanced physico-chemical characterization techniques i.e., X-ray micro-computed tomography, vibrational spectroscopies (near infrared and Raman) and X-ray microdiffraction, allowed new insights into the film-coating structures of dynamically cured tablets. Dynamic curing end-point was efficiently determined after 4 h. The aim of the present work was to elucidate the influence of curing conditions on film-coating structures. Results demonstrated that 24 h of static curing and 4 h of dynamic curing, both performed at 60 degrees C and ambient relative humidity, led to similar coating layers in terms of drug release properties, porosity, water content, structural rearrangement of polymer chains and crystalline distribution. Furthermore, X-ray microdiffraction measurements pointed out different crystalline coating compositions depending on sample storage time. An aging mechanism might have occur during storage, resulting in the crystallization and the upward migration of cetyl alcohol, coupled to the downward migration of crystalline sodium lauryl sulfate within the coating layer. Interestingly, this new study clearly provided further knowledge into film-coating structures after a curing step and confirmed that curing operation could be performed in dynamic conditions

Comprehensive study of dynamic curing effect on tablet coating structure

International audienceThe dissolution method is still widely used to determine curing end-points to ensure long-term stability of film coatings. Nevertheless, the process of curing has not yet been fully investigated. For the first time, joint techniques were used to elucidate the mechanisms of dynamic curing over time from ethylcellulose (Aquacoat (R))-based coated tablets. X-ray micro-computed tomography (X mu CT), Near Infrared (NIR), and Raman spectroscopies as well as X-ray microdiffraction were employed as non-destructive techniques to perform direct measurements on tablets. All techniques indicated that after a dynamic curing period of 4 h, reproducible drug release can be achieved and no changes in the microstructure of the coating were any longer detected. X mu CT analysis highlighted the reduced internal porosity, while both NIR and Raman measurements showed that spectral information remained unaltered after further curing. X-ray microdiffraction revealed densification of the coating layer with a decrease in the overall coating thickness of about 10 pm as a result of curing. In addition, coating heterogeneity attributed to cetyl alcohol was observed from microscopic images and Raman analysis. This observation was confirmed by X-ray microdiffraction that showed that crystalline cetyl alcohol melted and spread over the coating surface with curing. Prior to curing, X-ray microdiffraction also revealed the existence of two coating zones differing in crystalline cetyl alcohol and sodium lauryl sulfate concentrations which could be explained by migration of these constituents within the coating layer. Therefore, the use of non-destructive techniques allowed new insights into tablet coating structures and provided precise determination of the curing end-point compared to traditional dissolution testing. This thorough study may open up new possibilities for process and formulation control

Les chancis des peintures de chevalet : étude des traitements de restauration actuels et proposition d’une alternative innovante

Les chancis de vernis et de couches picturales des peintures de chevalet à l’huile sont des altérations récurrentes induites principalement par l’humidité. L’article expose un état de l’art sur la restauration des peintures chancies à partir de substances transparentes filmogènes ou de solvants sous forme vapeur ou liquide. Pour les chancis de vernis, l’analyse par nanotomographie à contraste de phase de prélèvements restaurés selon des pratiques actuelles (application d’un solvant suivi d’un vernissage) démontre leur manque d’efficacité et surtout de durabilité. Trouver une solution pérenne constitue un enjeu de taille pour la restauration et la conservation des œuvres chancies. L’emploi du perfluoropolyéther développé dans le cadre de ce projet a été testé sur des échantillons modèles. Les analyses par spectrocolorimétrie et microtomographie X en absorption mettent en évidence son efficacité et sa réversibilité à l’échelle macroscopique et microscopique.The blanching of the varnish and paint layers in easel paintings executed in oils is a recurrent alteration mainly caused by humidity. This paper is a review of the restoration of blanched paintings using transparent film-forming substances or liquid or vaporous solvents. For the blanched varnish layers, analysis by phase-contrast nanotomography of samples restored by current practices (application of a solvent followed by varnishing) showed their ineffectiveness and, above all, their lack of durability. Finding a long-standing solution represents a serious challenge for the restoration and conservation of blanched paintings. The use of perfluoropolyether (PFPE), developed in the course of this investigation, was tested on selected samples. Spectrocolorimetry and X-ray microtomography demonstrated its effectiveness and reversibility on a macroscopic and microscopic scale

Cadre climatique et environnemental des acheuléens de la grotte du Lazaret, à Nice. Données paléontologiques, biogéochimiques et radiométriques établies sur les faunes de vertébrés et d’invertébrés

L’évolution climatique et environnementale enregistrée dans la grotte du Lazaret a été établie à partir de l’étude des faunes des vertébrés (mammifères, amphibiens, reptiles) et des mollusques marins, et placée dans le cadre chronologique du Quaternaire. Les faunes de vertébrés permettent d’attribuer les dépôts archéologiques (complexe C) à la dernière période glaciaire du Pléistocène moyen (OIS 6). Leurs exigences écologiques mettent en évidence une certaine variété de paysages continentaux et un climat plus frais et plus humide que l’actuel climat méditerranéen. L’étude 18O‰ des mollusques marins d’origine anthropique a montré que lors du dépôt de ces formations continentales, la température de la Méditerranée était globalement plus froide que celle de la mer actuelle et surtout des mers transgressives des stades isotopiques 7 et 5e enregistrées dans le site et à proximité. La présence de littorines nordiques (L. fabalis et L. saxatilis) dans les ensembles stratigraphiques C II sup. et surtout C III, confirme ce refroidissement amorcé au stade 6,4, amplifié au stade 6,2 avec un petit adoucissement lors du dépôt de l’unité archéostratigraphique UA25 (stade 6,3). La méthode ESR/U-Th combinée appliquée à l’émail dentaire de cerfs confirme l’attribution de l’ensemble stratigraphique C II supérieur au stade isotopique 6 de l’oxygène. Les résultats sont compatibles avec les repères chronologiques sous et sus-jacents au complexe stratigraphique C, que constituent d’une part, le niveau marin B inférieur dont l’âge maximal est de 238 ka et d’autre part, le plancher stalagmitique supérieur E qui se serait formé au cours des stades isotopiques 5, 4 et 3 d’après les datations U-Th.The palaeoclimatic and palaeoenvironmental evolution recorded within of the sedimentary sequence from the prehistoric cave of Lazaret has been established from the faunal studies carried out on large mammals, rodents, he rpetofauna and molluscs, as part of a well defined cultural and chronological framework. The fauna of the vertebrates shows that the archaeological deposits (Complex C) date from the last glacial period of the Middle Pleistocene (OIS 6). The fauna is representative of varied environments and of cooler and especially more humid conditions than the present Mediterranean climate. Relative proportions of species show clearly a cooling period towards the summit of the deposit. The 18O‰ study performed on small marine gastropods of an anthropogenic origin, has shown that at the time of continental formations, the temperature of the Mediterranean was globally colder than that of the present sea and especially that of transgressive phases at stages 7 and 5e recorded on site and in surrounding areas. The presence of Nordic littorinids (L. fabalis and L.  saxatilis) in the stratigraphic ensembles C II superior and especially C III, confirms this cooling initiated at stage 6.4, intensified at stage 6.2, with a mild warming up at the time of the deposit of the stratigraphical unit UA 25 (stage 6.3). The ESR/U-Th combined method applied to the tooth enamel of deer from archaeological levels of the stratigraphical ensemble C II superior of the excavations performed at the entrance and centre of the cave, allows us to consider the archaeological levels contemporary to OIS 6. The results are compatible with the chronological landmark adjacent below and above stratigraphical Complex C, which constitute, on the one hand, the marine level B inferior, whose age is more recent than 238 ka and on the other hand, the stalagmitic floor superior E which would have been formed during isotopic stages 5, 4 and 3 according to the U-Th dating

Supercontinuum generation in silicon waveguides relying on wave-breaking

Four-wave-mixing processes enabled during optical wave-breaking (OWB) are exploited in this paper for supercontinuum generation. Unlike conventional approaches based on OWB, phase-matching is achieved here for these nonlinear interactions, and, consequently, new frequency production becomes more efficient. We take advantage of this kind of pulse propagation to obtain numerically a coherent octave-spanning mid-infrared supercontinuum generation in a silicon waveguide pumping at telecom wavelengths in the normal dispersion regime. This scheme shows a feasible path to overcome limits imposed by two-photon absorption on spectral broadening in silicon waveguide