8 research outputs found
Nouvelles observations dans le dépocentre volcano-sédimentaire carbonifère du Massif du Tazekka, Moyen-Atlas, Maroc : implications sur l'évolution géodynamique de la chaîne Hercynienne
A análise integrada das estruturas tectónicas e das fácies do Complexo Vulcano Sedimentar do Maciço de Tazekka sugere que
este, à escala da grande bacia carbonífera de ante país da Meseta Oriental marroquina, corresponde a um depocentro ou sub bacia
em compressão controlada pela propagação, para NW, de dobras de amortecimento do cavalgamento de Hajra Sbaa el Caid. As
sequências tectono sedimentares, detrito conglomeráticas e/ou tufíticas, estão associadas a um magmatismo extrusivo com
basaltos, andesitos, dacitos, riodacitos e riólitos homogéneos ou piroclásticos com blocos re sedimentados. Estes vulcanitos
correspondem a uma sequência sub alcalina equivalente. As sequências calco alcalinas orogénicas características de ambientes de
subducção.
Estes resultados, assim como a comparação das idades de contracção regional na Meseta marroquina, permitem integrar o Maciço
de Tazekka num contexto de wedge top deepzone dum sistema de bacias de ante país flexural, em compressão comandada pela
progressão de duas sequências de cavalgamentos prógrados, de NW, desde o Fameno Tournaisiano ao Viseano sup. Terminal
Westfaliano inf., da Meseta Oriental para a Meseta Ocidental, em Marrocos setentrional
Copper (I) SNS Pincer Complexes: Impact of Ligand Design and Solvent Coordination on Conformer Interconversion from Spectroscopic and Computational Studies
The syntheses and detailed characterizations (X-ray crystallography, NMR spectroscopy, cyclic voltammetry, infrared spectroscopy, electrospray mass spectrometry, and elemental analyses) of two new Cu(I) pincer complexes are reported. The pincer ligand coordinates through one nitrogen and two sulfur donor atoms and is based on bis-imidazole or bis-triazole precursors. These tridentate SNS ligands incorporate pyridine and thione-substituted imidazole or triazole functionalities with connecting methylene units that provide flexibility to the ligand backbone and enable high bite-angle binding. Variable temperature 1H NMR analysis of these complexes and of a similar zinc(II) SNS system shows that all are fluxional in solution and permits the determination of ΔGexp‡ and ΔSexp‡. DFT calculations are used to model the fluxionality of these complexes and indicate that a coordinating solvent molecule can promote hemilability of the SNS ligand by lowering the energy barrier involved in the partial rotation of the methylene units
Contaminated agricultural soils: Trace-elements speciation, their phytoavailability and their uptake by flax plants
Flax seeds are used in animal food because of their high content in Omega 3. A number of trace-elements
(TEs) - essential as micronutrients, however toxic at supraoptimal concentrations - can accumulate in this plant at
quantities incompatible with their introduction in food chain. In order to control this risk and evaluate the uptake of
TEs, it is necessary to assess the contents of various species of TEs in soils and plants (each organ and total
contents). We were mainly interested in evaluating the availability of Cd, Cu, Ni, Pb and Zn in soils on which flax
were grown. Two situations have been compared: the first corresponds to fields into which some sewage sludge
were brought in agronomie doses and the second corresponds to plots of land irrigated by waste water over a 100
years period. We are currently performing TEs extractions from soils and plants using different methods : the data of
sequential and total extractions (assisted by microwaves) are presented. We have studied two flax varieties in four
stages of culture (sowing, stage 10cm. tlowering, maturation). The content, speciation of TEs in soils as well as their
transfer in flax seeds are discussed