Mécanisme de réduction de l'ion molybdo-11 tungstique: (MoW11O40H2)6−

The reduction of the molybdotungstate ion: (MoW₁₁O₄₀H₂)^6? has been studied by polarographic, linear sweep voltammetric and spectrophotometric methods. Reduced products corresponding to 1, 2, 6, 10, 12 and 14 electrons per molecule of molybdotungstate have been prepared by electrolysis: some of their chemical and electrochemical properties (stability as a function of pH, disproportionation reactions) are described.     

Efficient synthesis of 8-substituted pyrazolo[1,5-a]-1,3,5-triazines by regioselective acylation

An efficient two-step synthesis of 8-acylated pyrazolo[1,5-a]-1,3,5-triazines has been accomplished. The key strategic elements of this novel synthetic approach involve the use of the N-methyl-N-phenylamino activating group, which was easily obtained in high yield by treatment of the pyrazolotriazin-4-one with phosphorus oxychloride and dimethylaniline through high pressure reaction coupled with a regioselective acylation at position 8 followed by the subsequent displacement of the N-methyl-N-phenylamino group upon treatment with various amines.     

Une nouvelle preparation du fluoroacetylene - sa reaction avec les organometalliques. Synthese d'alcynes et d'enynes divers

FCCH has been prepared from 1,1-difluoroethylene at low temperature. Its reaction with various organometallics opens a way to acetylenes bearing tertiary alkyl-, vinyl-, aryl- or heteroaryl groups directly α to the unsaturation.     

Manganese in the water supply of the town of Beaucaire: origins and solutions

Changes in domestic water supply appearance and quality linked with increasing manganese amount and iron at a lesser degree, having been found by the inhabitants of Beaucaire (Rh?ne Valley), a study was made by chemists, hydrogeologists and biologists to detect the origin. The problem is not specific to this town and can frequently be found in the Sa?ne and Rh?ne valleys. The results show that we have to deal with an aquifer with semi-captive groundwater whose supply is double: the Rh?ne and calcareous mountain masses. The low-oxygen waters are enriched, by dissolution from gravel, with manganese and iron which are preferentially fixed on porous and cracked surface elements. The conditions for manganese liberation are connected with the presence of organic matters, bacteria (capable to reduce the manganic compounds) and anaerobiosis. The supply does not seem to be the only cause in the low-oxygen contents; the action of heterotrophic microorganism using organic matter and consuming oxygen, at the groundwater periphery, must be taken into account. Thus the central part of the groundwater system is a reducing environment which allows the modification of the bacterial metabolism towards a ferric and manganic compounds reduction process. The result is the transformation of insoluble manganic and ferric compounds into manganous and ferrous compounds which are liberated into the groundwater.     

Effect of metals on herbicides-alpha-synuclein association: a possible factor in neurodegenerative disease studied by capillary electrophoresis

The aggregation of alpha-synuclein in the dopaminergic neurons of the substantia nigra is a critical step in the Parkinson's disease (PD). The etiology of the disease is unknown but recent epidemiological and experimental studies have renewed interest in the hypothesis that environmental factors, especially herbicides and metals, have a role on the pathogenesis of PD. For the first time, the association constants of alpha-synuclein with five herbicides have been calculated using a capillary electrophoresis (CE) method. In addition, the effect of a number of metals on this binding has been investigated. It appears that the herbicides preferentially bind to a partially folded intermediate conformation of alpha-synuclein induced by manganese, aluminium, cadmium, copper and zinc. Then, metal increases the synuclein-herbicide association. However, this study shows contrasting actions with the antibiotic rifampicin and magnesium addition leading to a decrease of the alpha-synuclein-herbicide interaction even if other metals are present in the bulk solvent. Considering epidemiological studies, all these results suggest an underlying molecular basis for PD and related body diseases.     

Frequency stabilization of quantum-cascade lasers by use of optical cavities

We report a heterodyne beat with a linewidth of 5.6+/-0.6 Hz between two cavity-stabilized quantum-cascade lasers operating at 8.5 microm . We also present a technique for measuring this beat that avoids the need for extreme isolation of the optical cavities from the environment, that of employing a third servo loop with low bandwidth to force one cavity to track the slow drifts and low-frequency fluctuations of the other. Although it is not fully independent, this technique greatly facilitates heterodyne beat measurements for evaluating the performance of cavity-locked lasers above the bandwidth of the third loop.