Chromium (II) chloride : a new reagent for cross-aldol reactions

The proposed cross aldolization of α-bromoketones with aldehydes in presence of Chromium (II) chloride is an excellent stereospecific reaction. One exception to the stereospecific orientation is reported.     

Stabilité élastique des structures unidimensionnelles

In this paper, we consider the problem of stability of one-dimensional structures and give a general formulation by means of the energy method. We propose then a numerical method of deriving the critical rate requiring eigenvalues of a sequence of small matrices rather than of a big one.

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Cet article est le résumé d'une thèse présentée à l'Ecole Polytechnique de l'Université de Lausanne [17]. Je tiens à exprimer ma vive gratitude au ProfesseurCh. Blanc, directeur de l'Institut de Mathématiques Appliquées, dont les conseils et encouragements m'ont été très précieux.     

Perhydro dioxazepines-1,5,3 : Methode generale de synthese

Perhydrodioxazepines-1,5,3 are obtained by reacting a primary amine with a 1,2-diol and paraformaldehyde.     

Proprietes magnetiques et electriques de la phase Ca2MnO4−xFx

The magnetic properties of the antiferromagnetic Ca₂MnO_4?x solid solution (0?x?0,30) are essentially characterized by a weak ferromagnetism with a maximum value for x = 0,20. Spin canting results from the competition between the antiferromagnetic super-exchange couplings and the double exchange ferromagnetic interactions due to the presence of manganese in oxidation states + III and + IV. It seems independent of the site of fluorine in the framework. The variation of Weiss constant and ordering temperature withx is also discussed. Electrical conductivity results from a hopping mechanism between Mn³⁺ and Mn⁴⁺ ions. The electrical conductivity presents a maximum when x = 0.10, corresponding to an activation energy minimum.     

Atlas-based segmentation of pathological MR brain images using a model of lesion growth

We propose a method for brain atlas deformation in the presence of large space-occupying tumors, based on an a priori model of lesion growth that assumes radial expansion of the lesion from its starting point. Our approach involves three steps. First, an affine registration brings the atlas and the patient into global correspondence. Then, the seeding of a synthetic tumor into the brain atlas provides a template for the lesion. The last step is the deformation of the seeded atlas, combining a method derived from optical flow principles and a model of lesion growth. Results show that a good registration is performed and that the method can be applied to automatic segmentation of structures and substructures in brains with gross deformation, with important medical applications in neurosurgery, radiosurgery, and radiotherapy.