Showing papers by "Pierre-and-Marie-Curie University published in 1979"

Elemental and Sr isotope variations in basic lavas from Iceland and the surrounding ocean floor

Abstract: Major and trace element data are used to establish the nature and extent of spatial and temporal chemical variations in basalts erupted in the Iceland region of the North Atlantic Ocean. The ocean floor samples are those recovered by legs 38 and 49 of the Deep Sea Drilling Project. Within each of the active zones on Iceland there are small scale variations in the light rare earth elements and ratios such as K/Y: several central complexes and their associated fissure swarms erupt basalts with values of K/Y distinct from those erupted at adjacent centres; also basalts showing a wide range of immobile trace element ratios occur together within single vertical sections and ocean floor drill holes. Although such variations can be explained in terms of the magmatic processes operating on Iceland they make extrapolations from single basalt samples to mantle sources underlying the outcrop of the sample highly tenuous.

Inhibition and nickel electrocrystallization

Abstract: The electrocrystallization of Ni is known to be a highly inhibited process. This work gives some conclusions about the nature of the major inhibiting species. All of these species are formed in the catholyte because of the hydrogen codeposition. Depending on plating conditions, mainly pH and current density of metallic deposition, we observe a predominancy of a definite inhibitor which selectively promotes one mode of growth and leads to a deposit exhibiting definite structural properties. A careful structural investigation of Ni deposits obtained from a Watts solution, thanks to both X-ray diffractometry and electron-microscope techniques, leads us to distinguish a free mode of growth, which is characterized by [100] oriented deposits, from several inhibited modes such as 〈110〉, [210], 〈211〉 and 〈111〉. The two latter are stabilized by Ni(OH)2 while the two former are respectively due to atomic and molecular forms of adsorbed hydrogen.

Deafferentation hypersensitivity in the rat after dorsal rhizotomy: a possible animal model of chronic pain.

Abstract: Unilateral dorsal rhizotomies were done at the cervicothoracic and lumbosacral spinal cord levels in rats. In preliminary experiments dermatome maps were determined for the roots to be sectioned. The behavior of 37 rats was observed for many months after the rhizotomies. The rats with the dorsal roots sectioned in the cervicothoracic spinal cord exhibited the following behavior: at the border of the skin adjacent to the zone of deafferentation, the rat scratched vigorously and progressively denuded the skin; self-mutilation of varying degrees occurred in the deafferented limb. In some animals scratching occurred in the contralateral skin dermatome opposite to the partially deafferented zone. The rats with the dorsal roots sectioned at the lumbosacral level exhibited hypersensitivity to cutaneous stimulation but there was no scratching or self-mutilation. These results are discussed in the light of previous similar research.

E vs k--> and Inverse Lifetime of Cu(110)

Abstract: We present a very accurate determination of the valence bands of copper along $\ensuremath{\Gamma}\mathrm{KX}$. This is obtained with high-resolution angle-resolved photoemission spectroscopy, using synchrotron radiation in the $15l~\ensuremath{\hbar}\ensuremath{\omega}l~100$ eV photon energy range. In addition the data yield inverse lifetime measurements for the $3d$ hole at the top and the bottom of the $d$ band which have a value much smaller ( 50 and 250 meV) than recently reported.

Estimate of symbiotically fixed nitrogen in field grown soybeans using variations in15N Natural abundance

Abstract: The use of variations in natural abundance of15N between nitrogen fixing and non nitrogen fixing soybeans was investigated for quantitative estimate of symbiotic nitrogen fixation

Étude ultrasonore des phénomènes critiques dans les gels

Abstract: 2014 We have measured the ultrasonic velocity and attenuation in an acrylic gel. We have deduced the elastic constant and the frictional coefficient from the results obtained from the gel and those obtained from the pure solvent (H2O). We have observed a critical behaviour of these parameters. LE JOURNAL DE PHYSIQUE -LETTRES TOME 40, 1 er JANVIER 1979, Classification Physics Abstracts 61.40K 43.35 Un gel est constitue d’un reseau de polymere reticule en immersion dans un fluide. Récemment quelques experiences de diffusion de lumiere [1], [2], [3], [4], ont ete entreprises pour mettre en evidence les fluctuations de concentration du reseau de polymere. Tanaka et al. [5] ont observe une divergence critique de 1’intensite de la lumiere diffusée dans un gel polyacrylamide. L’intensité et le temps de correlation augmentaient quand la temperature decroissait ; et une divergence apparaissait a une certaine temperature Tg. Ces resultats s’expliquent en considerant les phenomenes critiques lies a la separation de phases d’un melange binaire, compose dans le cas d’un gel du fluide et du reseau polymérique; c’est-a-dire, un retrecissement du reseau dans le fluide ambiant quand on s’approche de la temperature de transition. Le but de cette lettre est de presenter les mesures liees a la propagation d’une onde ultrasonore longitudinale traversant un gel en fonction de la temperature afin d’en deduire les parametres propres au gel (constante elastique du reseau, coefficient de friction entre le reseau et le fluide ambiant) et d’étudier ces phenomenes aux voisinages de Ts (temperature spinodale) [6]. 1. Theorie. Pour simplifier le calcul, nous n’allons considerer que la propagation d’une onde longitudinale dans un gel. On appelle r le deplacement du reseau, s celui du fluide, pr, Er et Ps, ES leur densite et leur module longitudinal respectifs. On obtient le systeme d’equations couplees suivant [1], [7], [8] : c est la concentration du polymere, f le coefficient de friction entre le reseau et le fluide, 11 et ~ les coefficients de viscosite du fluide respectivement de cisaillement et de volume. La resolution du systeme d’equations (1) aboutit a l’equation de dispersion suivante : en considerant Er ES et cv flcp 2. Dans le cas ou la partie imaginaire du vecteur d’onde est petite devant sa partie reelle, on obtient pour la vitesse dans le gel : Av représente la variation de la vitesse dans le gel. Quant a 1’attenuation, elle comporte deux termes dus : l’un a la viscosite du fluide, I’autre a l’interaction entre le reseau et le solvant. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyslet:019790040010500 L-6 JOURNAL DE PHYSIQUE LETTRES 2. Methode expérimentale. Nous avons utilise un systeme a impulsions ultrasonores classique. Les transducteurs ultrasonores employes sont des barreaux de quartz de coupe X en forme de clou. Le gel non encore reticule est place entre les deux quartz separes par des cales de 2 mm a 100 ~ qui en définissent 1’epaisseur (les frequences variant de 100 MHz a 200 MHz). La mesure de 1’intensite du faisceau ultrasonore transmis en fonction de la temperature donne la variation de 1’attenuation, tandis que celle de la phase permet d’accéder a la variation de la vitesse de phase. Ces quartz sont places dans un four dont la temperature est regulee a + 0,02 ~C; celui-ci est mis dans un dewar dont la temperature peut varier de I’ambiante a 100 °C. Une methode impedometrique en ondes longitudinales [9] nous a permis de determiner les vitesses du son dans 1’eau et dans du gel en valeur absolue. Nous utilisons un gel acrylique immcrge dans 1’eau. Pour l’obtenir d’une maniere reproductible, nous commençons par preparer une solution mere (30 g d’acrylamide, 0,8 g bis-acrylamide pour 100 ml d’H20). Pour 10 ml de gel, nous ajoutons successivement 3,33 ml de solution mere, 0,330 ml d’une solution de sulfate d’ammonium (1 g/100 ml) et 5 ~1 de tetramethyl-ethylene-diamine (TEMED). Le gel commence a reticuler quelques minutes apres le melange. Les experiences sont faites 24 heures plus tard. 3. Résultats experimentaux. Nous nous sommes interesses au comportement critique du gel au voisinage de sa temperature spinodale Ts [6]. Nous avons vu précédemment que les mesures ultrasonores permettent de determiner les parametres caracteristiques du gel (Er, f). Nous avons mesure la variation de la vitesse de phase dans le gel Ov/v a 194 MHz et 560 MHz. On observe sur la figure 1 que w/v decroit quand la temperature decroit, mais un net changement de pente apparait aux environs de 10 °C. La mesure impedometrique nous donne une valeur de la vitesse dans le gel de 1 450 + 50 m/s a 20 °C. Fig. 1. Variation de vitesse dans le gel en fonction de la temperature. [Temperature dependence of velocity in the gel.] Sur la figure 2 nous avons porte l’attenuation du gel moins celle de 1’eau en fonction de la temperature (a 162 MHz). On voit clairement que (Xg~ 2013 C(eau diverge quand on s’approche de la transition. Fig. 2. Dif’erence entre 1’attenuation dans le gel et celle dans 1’eau en fonction de la temperature. [Temperature dependence of the difference between attenuation in the gel and water.] En fait il y a une incertitude sur la valeur de T~. Dans 1’eau pure, la temperature de solidification depend du volume de 1’eau [10]. Pour un volume ayant la forme d’un cylindre d’une section de 3 mm et d’epaisseur de 1 mm, nous pouvons retarder la solidification jusqu’a 17 °C et meme jusqu’a 26 °C pour une epaisseur de quelques microns [11]. Pour des volumes equivalents, la temperature de solidification du gel varie de 15 °C a 2013 18 °C. Nous avons donc pris Ts = 18 °C. 4. Interpretation des resultats. Tanaka et al. [5] ont calcule le module elastique longitudinal a partir de la pression osmotique en tenant compte de 1’&nergie elastique et de celle de melange en utilisant les resultats de Flory. Ils ont trouve que D’autre part, Kawasaki [12] a calcule la fonction de correlation des fluctuations de concentration dans les melanges binaires par une methode de couplage de modes. Tanaka [6] a recemment applique ce calcul a celui de la separation de phase dans un gel en considerant les fluctuations de concentrations du réseau polymerique. La valeur de la constante de diffusion est donnée par 1’expression suivante avec ~ longueur de correlation des fluctuations de concentration, q viscosite de cisaillement du fluide, et celle de l’intensité de la lumiere diffusee :

Self-Diffusion in the Two-Dimensional, Classical Electron Gas

Abstract: Molecular-dynamics simulations of the two-dimensional, classical electron gas yield indications for the existence of a self-diffusion constant, in contrast to the case of shortrange interactions. The velocity autocorrelation function exhibits marked oscillations in the strong-coupling regime. In order to avoid the Ewald summations of the Coulomb interactions in a periodic system, the electrons are confined on a spherical surface.

Basaltic pillars in collapsed lava-pools on the deep ocean floor

Abstract: Observations of peculiar volcanic objects, made by a submersible on the deep sea floor at a depth of about 2,600 m at and near the axis of the East Pacific Rise during the CYAMEX expedition as part of the RITA Project1 are presented here. Two basic types of flow forms were observed within the crestal area of the East Pacific Rise: pillow flows and fluid lavas, the latter sometimes overlying massive flows. The East Pacific Rise at 21° N comprises an axial, unfaulted extrusion zone bordered by an extension zone characterised by faulting2,3. Pillow flows occupy the innermost or extrusion zone and constitute small elongated volcanic highs. Fluid lavas tend to occur at the edge of the adjacent extension zone in bathymetric lows controlled by normal faults or steep primary slopes of constructional highs. In the 50 × 200 m lows which border the extrusion zone the fluid lava is smooth and lobate surfaces which represent the upper surface of the flow are locally collapsed and reveal the internal structure of the fluid lavas. Where the roof collapse is extensive, layered columnar features are visible and volcanic layering can be seen against the flank of the bordering volcanic highs (Figs 1–3). Similar features have been reported from the Galapagos Rift4. The diameter of the approximately cylindrical pillars ranges from 0.5 to 2 m. Some pillars are made of multiple coalescent cylinders. The tops of the pillars are glassy, funnel-shaped and always widening upwards. The pillars were presumed to be hollow from several observations of gashes or openings in the vertical walls of the pillars. This was demonstrated during dive CY 78–19 to the south where a small pillar was toppled by CYANA and subsequent examination revealed a circular canal along the axis of the pillar. The outer surface of the pillars is marked by centimetre-thick glassy, subhorizontal ledges extending several centimetres from the outer vertical surface of the pillars (Figs 2–4). The ledges are spaced every 2–5 cm and show small lava stalactites hanging on the under-side of the ledges. Examination of large layered fragments of pillars recovered by CYANA demonstrated that the layering is only a surface feature as it does not extend through the basaltic mass of the pillars. The apparent layering is due to glass ledges adhering to a vertical basaltic pipe. In some rare instances the pillar outer surface showed no ledges and instead a smooth surface corrugated with vertical grooves. Some pillars are inclined or slightly curved; others get narrower towards the base. The pillars are almost totally aphyric and have the same bulk composition as other lava types recovered in the axial zone of the East Pacific Rise at 21° N (ref. 5).

Equations de Schrödinger non linéaires en dimension deux

Abstract: This paper is devoted to the study of some non linear Schrodinger equations in two dimensions, arising in non linear optics; in particular, it is concerned with solutions to the Cauchy problem. The problem of global existence and regularity of the solutions, the asymptotic behaviour of global solutions, and the blow-up of non global solutions are studied.

The chromaffin and chromaffin-like cells in the autonomic nervous system.

Abstract: Publisher Summary This chapter discusses the chromaffin and chromaffin-like (CCL) cells in the autonomic nervous system. It has been known for a long time that there were clusters of chromaffin cells scattered along and within the nerves and ganglia of the autonomic nervous system when new interest in these cells was aroused about 1960 because they could represent a structural basis for explanation of special features of the synaptic transmission in the sympathetic ganglia. They were considered chromaffin cells, as their shape and fluorescence was identical to those of the adrenomedullary cells. There is a striking diversity in the shape and connections, and probably in the functions, of CCL cells located within the autonomic nervous system or in close association with it. The present state of research is still far from covering all the vertebrate groups equally, and the variety of the situations already described suggests that a more extensive analysis will again reveal new models.

Direct Resolution of Enantiomers in Column Liquid Chromatography

Abstract: Important progress has been performed during the ten past years, in the direct resolution (without derivatization) of enantiomers by column liquid chromatography. Generally chiral packings proceeding from natural or synthetic optically active polymers are used. Complete resolutions of hole families of chiral solutes is obtained in systems involving a steric locking interaction (charge transfer between aromatic substituents, crown ether cavity, crowded complexes with metal ions). For analytical purposes an other proraising way is the use of a classical packing and a chiral mobile phase.

The spectra of unresolved split normal mode multiplets

Abstract: Summary A seismic spectrum corresponding to an isolated multiplet nSl or nTl on a spherical earth is characterized fully by three parameters: an amplitude, a peak or central frequency and a half-width. The amplitude depends on the mechanism of the seismic source; it may be complex for single-station spectra, but it is real and positive for spectral stacks. The central frequency is the degenerate eigenfrequency of the multiplet, and the half-width is a measure of the decay rate due to the Earth's anelasticity. On an aspherical earth, the multiplet nSl or nTl is split into 2l+ 1 nearly degenerate singlets. In general this splitting cannot be resolved. If the apparent amplitude, central frequency and half-width of an unresolved multiplet are measured on an aspherical earth, and subsequently interpreted as if the Earth were spherical, there may be a bias introduced by the splitting. Perturbation theory is used here, correct to zeroth order in the eigenfunctions and first order in the eigenfrequencies, to investigate this bias. Correct to this order, single-station amplitudes, and therefore source mechanism determinations, are unaffected by asphericity. Measurements of Q made on spectral stacks are always biased toward low Q. The limiting case n≪l and s≪l, where s is the maximum significant degree in the spherical harmonic expansion of the asphericity, is examined in particular detail. Single-station spectra appear in this limit to consist of a single line broadened by attenuation alone; Q measurements made on these spectra, prior to stacking, are therefore unbiased. A travelling wave decomposition is considered in order to compare the results of normal mode perturbation theory in this limit with those obtained by applying the theory of geometrical optics to the equivalent surface waves. At the level of truncation considered in this paper, perturbation theory predicts that surface waves will propagate on an aspherical earth at a uniform velocity. This discrepancy with geometrical optics is attributed to the neglect of eigenfunction perturbations.

An analysis of a mixed finite element method for the Navier-Stokes equations

Abstract: A simple mixed finite element method is developed to solve the steady state, incompressible Navier-Stokes equations in a neighborhood of an isolated--but not necessarily unique--solution Convergence is established under very mild restrictions on the triangulation, and, when the solution is sufficiently smooth, optimal error bounds are obtained

The Corpora Allata of Insects

Abstract: Publisher Summary This chapter discusses the corpora allata of insects Insect corpora allata or corps allates are endocrine glands which were previously called “paired posterior visceral ganglia,” “ganglia allata,” or “corpora incertae,” owing to their being confused with the sympathetic cerebral structures constituting the stomatogastric system The endocrine activity of the corpora allata and the mode of action of the different forms of juvenile hormone (JH) are well known and retain a central position in entomological research They are concerned with morphogenesis, activation of follicular cells and sexual-accessory glands, control of polymorphism, general physiology, and behavior Research has been carried out on juvenoids, growth regulators, and juvenile hormone mimetics with specific short-range action affecting insects which are economically important In small insects the corpora allata contain a limited number of cells and growth depends exclusively on cytoplasmic and nuclear hypertrophy which may or may not be associated with endopolyploidy