Actions moyennables et fonctions harmoniquesAmeanable actions and harmonic functions

We prove that the action of a countable discrete group on a locally compact invariant space of minimal harmonic functions is ameanable. To cite this article: P. Biane, E. Germain, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 355–358.     

On the Lamb vector and the hydrodynamic charge

This work is an attempt to test the concept of the hydrodynamic charge (analogous to the electric charge in electromagnetism) in the simple case of a coherent structure such as the Burgers vortex. We provide experimental measurements of both the so-called Lamb vector and its divergence (the charge) by two-dimensional particles images velocimetry. In addition, we perform a Helmholtz–Hodge decomposition of the Lamb vector in order to explore its topological features. We compare the charge with the well-known Q-criterion in order to assess its interest in detecting and characterizing coherent structure. Usefulness of this concept in studies of vortex dynamics is demonstrated.

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Mechanistic studies of the O2-dependent aliphatic carbon-carbon bond cleavage reaction of a nickel enolate complex

The mononuclear nickel(II) enolate complex [(6-Ph(2)TPA)Ni(PhC(O)C(OH)C(O)Ph]ClO(4) (I) was the first reactive model complex for the enzyme/substrate (ES) adduct in nickel(II)-containing acireductone dioxygenases (ARDs) to be reported. In this contribution, the mechanism of its O(2)-dependent aliphatic carbon-carbon bond cleavage reactivity was further investigated. Stopped-flow kinetic studies revealed that the reaction of I with O(2) is second-order overall and is ～80 times slower at 25 °C than the reaction involving the enolate salt [Me(4)N][PhC(O)C(OH)C(O)Ph]. Computational studies of the reaction of the anion [PhC(O)C(OH)C(O)Ph](-) with O(2) support a hydroperoxide mechanism wherein the first step is a redox process that results in the formation of 1,3-diphenylpropanetrione and HOO(-). Independent experiments indicate that the reaction between 1,3-diphenylpropanetrione and HOO(-) results in oxidative aliphatic carbon-carbon bond cleavage and the formation of benzoic acid, benzoate, and CO:CO(2) (～12:1). Experiments in the presence of a nickel(II) complex gave a similar product distribution, albeit benzil [PhC(O)C(O)Ph] is also formed, and the CO:CO(2) ratio is ～1.5:1. The results for the nickel(II)-containing reaction match those found for the reaction of I with O(2) and provide support for a trione/HOO(-) pathway for aliphatic carbon-carbon bond cleavage. Overall, I is a reasonable structural model for the ES adduct formed in the active site of Ni(II)ARD. However, the presence of phenyl appendages at both C(1) and C(3) in the [PhC(O)C(OH)C(O)Ph](-) anion results in a reaction pathway for O(2)-dependent aliphatic carbon-carbon bond cleavage (via a trione intermediate) that differs from that accessible to C(1)-H acireductone species. This study, as the first detailed investigation of the O(2) reactivity of a nickel(II) enolate complex of relevance to Ni(II)ARD, provides insight toward understanding the chemical factors involved in the O(2) reactivity of metal acireductone species.     

Analogues méso-hétérocycliques du dihydro-9,10 anthracène. XII — Sur quelques indoles dérivés de la dibenzo-p-dioxine

2-Aminodibenzo-p-dioxine undergoes facile condensation with different ω-bromoketones to give 2-aroylmethylaminodibenzo-p-dioxines, which undergo Möhlau-Bischler cyclisation under certain conditions. Some indolo[5,6-b] [1,4]benzodioxine were prepared by this method and their biochemical effect on the zoxazolamine hydroxylase in rats was studied.     

Synthèses d'indoles par cyclisation réductrice. II Nouvelle mélhode de synthèse des indole carboxamides-3, donnant accés aux dérivés de la gramine

A new synthetic method for 3-indolecarboxamides, in two steps from 2-halogenonitrobenzenes, is reported. These benzene derivatives, reacting with sodium salts of cyanoacetamides in N,N-dimethylformamide, give 2-(2-nitrophenyl)cyanoacetamides. Catalytic hydrogenation of the nitro derivatives, at 80°, leads directly to 3-indolecarboxamides. Reduction of the amides by lithium aluminium hydride gives finally 3-aminomethylindoles (gramine and its derivatives), so obtained by a new synthetic route.     

Etude de la dispersion du technetium-99 sur les côtes françaises de la manche à l'aide de deux indicateurs biologiques:Fucus sp. etPatella sp.

Determination of⁹⁹Tc in two biological indicators,Fucus sp. andPatella sp., of the French coast of the Channel showed that this radionuclide found in small amounts, was dispersed eastwards from the La Hague reprocessing fuel plant. However,⁹⁹Tc trace amounts were also detected in the river Seine bay and in the bay of Mont St. Michel, which confirms the great mobility of this element.