Modélisation théorique d'écoulements pulses de fluides non newtoniens en conduites viscoélastiques poreuses et anisotropes

A theoretical study concerning the pulsatile flow of an inelastic fluid through anisotropic porous viscoelastic pipes is presented. The objective is to investigate the effects of porosity, conicity in pause, anisotropy and viscoelasticity of pipe wall material for a generalized Casson fluid. An implicit difference method is used to solve the equations, and to determine the axial and radial velocity profiles, the pressure, the flow rate and the flow rate filtration distributions, the transverse rotation and the wall axial and radial displacement. This study, considered as a step in the modelling of flow in blood vessels, may also contribute to other important fields such as water desalination or gel filtration.     

Numération et taille des bactéries planctoniques au moyen de l'analyse d'images couplée à l'épifluorescence

The interest of the image analysis procedure is the time-saving in automated planktonic bacterial counting and sizing, with the possibility of manual visual field control at all times. Bacterial biomass (in number and volume) and bacterial projected area histograms were determined with a microcomputer. Performance limits of image-analysed epifluorescence microscopy were: camera sensitivity, considering the very low fluorescence levels on stained bacteria; pixel-μm conversion factor, and the impossibility of the apparatus distinguishing between bacteria and fluorescent small particles. This method is not of interest for counting sediment bacteria.     

Contribution à l'étude des méthodes de dosages électrotitrimétriques

The author establishes a general equation for the polarisation curve of an oxidation-reduction system taking into account the kinetics of reactions and concentration polarisation, and shows how it can be applied to the interpretation of titration curves obtained by the dead-stop end-point method of Foulk and Bawden and by the derivative method of Reilley, Cooke and Furman.     

Dosages en analyse minérale par extraction à l'aide de cations colorés : Dosages par extraction à l'aide de colorants basiques c. dosage de traces de phosphate par la safranine

An extraction method is described for the determination of traces of phosphate in the form of phosphomolybdate, in which safranine is used as complexing agent.     

Calcul de flammes turbulentes non prémélangées à l'aide d'une approche probabiliste et d'une cinétique chimique réduite

The emergence of methods allowing the simplification of detailed chemical kinetics enables detailed modeling of turbulent diffusion flames. One of these methods, the “Intrinsic Law-Dimensional Manifolds” (ILDM) method and its application to the computation of turbulent reactive flows are described here. A CFD solver and a Monte-Carlo code solving the transport equation of the scalar joint pdf are coupled and two jet-flames stabilized by a pilot flame are calculated. It is shown that this coupled, solver leads to a good prediction of the partial extinction of the flame as well as to a correct estimation of the main variables describing the flame. © 1999 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS     

Pont électrolytique et électrode de référence pour titrages potentiométriques

A salt bridge and a reference electrode for potentiometric titrations are described.     

Linéarisation et homogénéisation en viscoélasticité

Constitutive equations for non-linear viscoelastic materials are expressed first using a causal operator which relates a response function to any loading history. The corresponding tangent linear equations are then defined through the Fréchet derivative of this operator. This definition is used to propose a step-by-step treatment in view of the derivation of the overall behaviour of non-linear non-ageing viscoelastic heterogeneous materials.     

Méthode indépendante des propriétés locales pour le calcul des indices de rétention en Chromatographie en phase gazeuse à température programmée

Retention indices of some phthalates, separated by temperature-programmed gas chromatography, computed using B-spline interpolations are more consistent with the scheme of this retention parameter. In applying this technique to a mixture of reference n-alkanes, which two successive members do not defer of more than four carbon atoms, it is possible to recover classical retention indices.     

Etude de la fluorescence du 9,9′-bianthryl en solutions liquides et en milieux polymériques rigides à la température ambiante

The fluorescence of 9,9′-bianthryl (9,9′BA) is very sensitive to the polarity of the solvent. This molecule exibits an intramolecular charge transfer state in polar medium. The study of the fluorescence of 9,9′BA, in liquid solutions, shows a strong dependency of the Stokes shift versus the dipole moment m of the aprotic lowly viscous solvent. Moreover, this compound exhibits in polyvinylacohol (PVA) an original anomalous behaviour.     

Géométrie de l'intermittence en turbulence développée

A geometrical interpretation of intermittency in fully developed turbulence is realized through an hierarchy of fractal structures Ω_p of dimensions Δ_p linked each other by the relations Ω_{p + 1} − Ω_p (i.e. Δ_{p + 1} < Δ_p) and γ = (Δ_{p + 1} − Δ_∞)/(Δ_p − Δ_∞) with γ = ((1 + 3/√8)^1/3 + (1 − 3/√8)^1/3)³ and Δ_∞ = 1 and Δ_∞ = 1. This is obtained by the introduction of an entropy jump, defined at the scale r, ΔS_p(r) = (Δ_{p + 1} − Δ_p) ln (r/r₀) characterizing the order level of each sub-structure Ω_p and verifying a linear relation ΔS_p(r) = γ ΔS_{p − 1}(r).     

Fonctionnalisations régio et stéréospécifiques successives en méta et en ortho des η6-arènetricarbonylchrome

The η⁶-1-methoxy-2,3-dimethylbenzenetricarbonylchrome and the η⁶-1-dimethylamino-2,3-dimethylbenzenetricarbonylchrome are chemically functional on the methyl group 3 first; the methyl group 2, which is less reactive, is functional later. The η⁶-1-dimethylamino-5,6,7,8-tetrahydronaphthalenetricarbonylchrome is difunctional on positions 5 then 8 using two different electrophiles.     

Résolution du problème à deux électrons en mécanique quantique par détermination directe des orbitales naturelles

Résumé La fonction d'onde et l'énergie de l'état fondamental de l'atome d'hélium et des ions isoélectroniques sont calculées selon un procédé proposé antérieurement [10]. Les équations intégrodifférentielles relatives aux orbitales naturelles (NO) sont résolues approximativement dans une représentation matricielle utilisant les fonctions complètes de Laguerre comme base, ainsi qu'avec de simples approximations analytiques des NO. On réussit à tenir compte de 95% environ de l'énergie de corrélation. La convergence du développement naturel est telle que les NO dont le nombre quantique principal est plus petit ou égal à 4 sont les seules à apporter une contribution appreciable à l'énergie. Les contributions de l'énergie cinétique et des énergies potentielles, d'attraction nucléaire et de répulsion interélectronique à l'énergie de corrélation sont examinées. Une certaine simplification du potentiel de corrélation aboutit à une justification du principe des intégrales interélectroniques réduites.

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The wave function and the energy of the ground state of the helium atom and the corresponding isoelectronic ions are calculated by a procedure recently proposed by the author [10]. The integro-differential equations of the natural orbitals (NO) are resolved approximatively in a matrix representation using the complete Laguerre functions as its basis as well as in a simple analytical approximation for the NO. The natural expansion converges so rapidly that only those NO whose principal quantum number is 4 or less contribute significantly to the energy. This method succeeds in accounting for some 95% of the correlation energy. The kinetic, potential and interelectronic energy contributions to the correlation energy have been examined separately. By simplifying the correlation potential in a certain manner the principle of reduced electron interaction integrals is justified.

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Zusammenfassung Die Wellenfunktion und die Energie des Grundzustandes des Heliumatoms und der mit ihm isoelektronischen Ionen wird gemäß einer vom Verfasser vorgeschlagenen Methode [10] berechnet. Dazu löst man die Integrodifferentialgleichungen für die natürlichen Einelektronenfunktionen (NO) näherungsweise in einer Matrixdarstellung unter Benutzung der vollständigen Laguerre-Funktionen als Basis. In dieser Näherung erfaßt man etwa 95% der Korrelationsenergie. Die natürliche Entwicklung konvergiert so gut, daß nur die NO mit der Hauptquantenzahl kleiner oder gleich 4 wesentlich zur Energie beitragen. Die Anteile der kinetischen Energie, der potentiellen Einelektronenenergie und der Elektronenwechselwirkungsenergie an der Korrelationsenergie werden untersucht. Ausgehend von einer bestimmten Näherung für das Korrelationspotential läßt sich die Methode der reduzierten Wechselwirkungsintegrale rechtfertigen.

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L'auteur a bénéficié d'une bourse de recherches de l'OTAN qui lui a été accordée par l'intermédiaire de «Deutscher Akademischer Austauschdienst». M. Gaston Berthier, Maitre de recherches au CNRS a pris un grand intérêt à ce travail et y a beaucoup contribué. Qu'il soit remercié cordialement.     

Les systemes binaires cobalt-gallium et nickel-gallium-étude comparée

The binary systems CoGa and NiGa have been reexamined in detail by DTA, X-ray diffraction, micrography and X-ray microprobe analysis. The two phase diagrams are quite different. CoGa gives only two intermediate phases, CoGa (from 25 to 64,5 at.% Ga) and CoGa₃ over a very narrow range, whereas for NiGa six intermetallic phases are present with incongruent melting, NiGa₃, Ni₅Ga₃, Ni₃Ga₂, Ni₃Ga₄, Ni₂Ga₃ and NiGa₄ and one (NiGa) with congruent melting, the only one similar to CoGa with respect to its CsCl structure and melting point (1215 °C). The possible reasons for such large differences in the two systems are discussed.