Déformations covariantes sur les orbites polarisées d''un groupe de Lie

We prove the existence of covariant star-products on the orbits of the coadjoint representation of a Lie group which admits polarisations.     

Enumeration of multi-colored rooted maps

We present a study of n-colored rooted maps in orientable and locally orientable surfaces. As far as we know, no work on these maps has yet been published. We give a system of n functional equations satisfied by n-colored orientable rooted maps regardless of genus and with respect to edges and vertices. We exhibit the solution of this system as a vector where each component has a continued fraction form and we deduce a new equation generalizing the Dyck equation for rooted planar trees. Similar results are shown for n-colored rooted maps in locally orientable surfaces.     

Lowering of the Populations of Excited Hydrogen and Helium Atoms in Plasmas Irradiated by a Laser Beam

The populations of excited hydrogen and helium atoms in non-L.T.E. plasmas have been calculated for two different physical situations, namely (i) no external radiation field present, and (ii) strong superposed radiation originating from a CO₂, Ruby or Argon Ion Laser. The radiation field intervenes in the collisional-radiative model via two new terms: Photoionization and stimulated recombination induced by the Laser radiation field. The solutions of the rate equations yield a lowering of the populations when a plasma is irradiated by a Laser beam. The lowering is different for cold recombining and hot diffusion-dominated plasmas. At high radiation densities a saturation effect occurs, since the photoionization rate becomes equal to the rate of stimulated recombination. Measurements of the populations of excited H and He atoms in a glow discharge irradiated by a CO₂ Laser beam of power density 10⁵ W/cm² are in broad agreement with the theoretical predictions.     

Insertion of CS2 and CSe2 into metal—amido bonds. Mono- versus bi-dentate dithiocarbamates formed by reactions of CS2 + NHR2 with {CpMo(CO)n}2 (M  Fe, n  2; m  Mo, n  3)

The reaction of Cp₂Fe₂(CO)₄ with NHEt₂ and CS₂ gives the monodentate dithiocarbamate CpFe(CO)₂-η¹-SC(S)NEt₂ (Ia), whereas the same reaction with CP₂Mo₂(CO)₆ gives the chelate CPMo(CO)₂-η₂-S₂CNEt₂ (II). New complexes of amines CpFe(CO)₂(NHR₂)⁺PF₆- (III, R  Me, Et, SiMe₃) have been synthesized by treating CpFe(CO)₂Cl with NHR₂. They do not react with CS₂ and give only [CpFe(CO)₂]₂ upon refluxing with bases such as t-BuOK or NEt(i-Pr)₂, but concerted CS₂ insertion in the presence of a base immediately gives I at 20°C. This clean route is used to synthesize the monodentate diselenocarbamate CpFe(CO)₂-η¹-SeC(Se)NMe₂ (IV) by reaction of CSe₂ with III (R  Me) in the presence of t-BuOK. Whereas the known reaction of CpFe(CO)₂Cl with Na⁺S₂CNMe₂^? gives Ib (R  Me), the analogous reaction of C₅Me₅Me(CO)₂Br gives specifically the thermally stable chelate C₅Me₅Fe(CO)-η²-S₂CNMe₂ (Vb′).     

Preparation of amphiphilic polyisobutylenes-b-polyethylenamines by mannich reaction. III. Synthesis of polyisobutylenes-b-polyethylenamines

Copolymers associating α-phenololigoisobutylene and triethylenetetramine blocks in the same chain are prepared by reacting aqueous formaldehyde with α-phenololigoisobutylene and triethylenetetramine. When para-formaldehyde is used instead of monomeric formaldehyde, the reaction does not take place, contrary to what is observed when low molecular weight models are used instead of oligomers. The ability of these copolymers to disperse sludges in motor oil was evaluated by the “spot-test” method. When oil does not contain water, the efficiency of the copolymers is comparable to that of commercial compounds. When oil contains water (1% w) the efficiency of the dispersive agent is drastically reduced. We show that this is due to the presence of phenol group. © 1993 John Wiley & Sons, Inc.     

Homogeneous metathesis of functionalised acetylenes

The first examples of functionalised acetylenes metathesis are described :(1) using molybdenum carbonyl-phenol complexes gave the expected tolane (2) and disubstituted acetylene (3).