Search results for "COMPOSITION CHIMIQUE"
showing 4 items of 4 documents
Interaspecific chemical variability and highlighting of chemotypes of leaf essential oils from Ravensara aromatica Sonnerat, a tree endemic to Madaga…
2006
Ravensara aromatica Sonnerat is a tree endemic to Madagascar. The essential oil extracted from the leaves is used in aromatherapy. Previous chemical studies have generated some confusion with regard to the chemical composition of this essential oil. In order to eliminate this uncertainty, we undertook a systematic evaluation of the chemical composition of essential oils from leaves of this species. The study focused on 28 individual samples formally identified as R. aromatica. The essential oils were obtained by hydrodistillation and analysed by GC and GC–MS. It was possible to distinguish four groups of trees through principal components analysis and agglomerative hierarchical clustering a…
Magnesium silicate hydrate (M-S-H) characterization : temperature, calcium, aluminium and alkali
2017
The various options to store radioactive wastes in deep geological strata considered in France or Switzerland include the use of large volumes of cementitious materials for infrastructure in contact with argillaceous rocks. So-called low-pH binders were developed to minimize disruption to the surrounding rock by the alkaline plume. Studies conducted on the interaction zone between concrete and clay systematically highlighted the formation of magnesium silicate phases including magnesium silicate hydrate (M-S-H) at the interfaces, which can presently be modeled only partially due to incomplete thermodynamic data. The purpose of this study was to characterize these phases in temperature, alum…
Mise en évidence de corps d'origine cosmique probable au sein de la formation de Carnot (République Centrafricaine)
1992
Resume Deux etudes realisees independamment l'une de l'autre, ont permis de mettre en evidence, au sein de la Formation de Carnot, formation fluviatile mesozoique, d'une part des spherules magnetiques recuperees dans les residus d'un forage (zone de Boyali), d'autre part une anomalie magnetique tres localisee (sur 270 metres de long) traduisant la presence d'un corps decametrique a forte magnetisation remanente (zone de Gambondo). Ces deux elements magnetiques ont une origine cosmique probable. Ils correspondent a des micrometeorites et a une meteorite ayant atteint l'ouest de la Republique Centrafricaine entre l'Albien et le Maastrichtien.
Typology of exogenous organic matters based on chemical and biochemical composition to predict potential nitrogen mineralization
2010
Our aim was to develop a typology predicting potential N availability of exogenous organic matters (EOMs) in soil based on their chemical characteristics. A database of 273 EOMs was constructed including analytical data of biochemical fractionation, organic C and N, and results of N mineralization during incubation of soil–EOM mixtures in controlled conditions. Multiple factor analysis and hierarchical classification were performed to gather EOMs with similar composition and N mineralization behavior. A typology was then defined using composition criteria to predict potential N mineralization. Six classes of EOM potential N mineralization in soil were defined, from high potential N minerali…