Showing papers by "University of Grenoble published in 1981"

Gravitational convection from instantaneous sources on inclined boundaries

Abstract: Two-dimensional buoyant clouds moving along inclined boundaries under a gravitational force are investigated theoretically and experimentally. It is found that the ‘thermal theory’ gives a good description of the flow in the slope angle range 5° [lsim ] θ ≤ 90°. In this range the spatial growth rates of the cloud height and length are constant for a given slope angle and show a linear dependence on θ. For a cloud released with zero initial velocity the front velocity Uf first increases and then decreases, with the characteristic time of acceleration predicted by theory. In the decelerating state Uf/(g0′Q0/xf)½ is 2·6 ± 0·2 at θ ≃ 15°, and then reduces uniformly with increasing θ to a value of 1·5 ≃ 0·2 at 90° (where g0′Q0 is the released buoyancy and xf is the front position measured from a virtual origin). The shape of the cloud is well approximated by a half-ellipse. The variation of the ratio of the principal axes of the half-ellipse with slope angle is identical with that of the head of an inclined starting plume (Britter & Linden 1980). However, the cloud has a greater growth rate than the head of a starting plume.

An Equivalence Between Relational Database Dependencies and a Fragment of Propositional Logic

Abstract: It is known that there is an eqmvalence between functional dependencies m a relatmonal database and a certain fragment of proposmonal logic Thins eqmvalence is extended to include both functional and multivalued dependencmes. Thus, for each dependency there is a corresponding statement m proposmonal logic. It ms then shown that a dependency (funcuonal or multivalued) is a consequence of a set of dependencies ff and only ff the corresponding proposiuonal statement ~s a consequence of the corresponding set of proposmonal statements. Examples are given to show that these techniques are valuable mn provmdmg much shorter proofs of theorems about dependencies than have been obtained by more tradmonal means It is shown that this eqmvalence cannot be extended to include either join dependencies or embedded multmvalued dependencies.

Nonparametric estimation of the drift coefficient in the diffusion equation

Abstract: A class of nonparametric estimators of the drift coefficient in the Ito diffusion equation, and the related estimators of the nonlinear regression function of a Markov sequence is considered. The estimates are shown to be weakly consistent and asymptotically normal, and estimates at different location points are shown to be asymptotically independent. A study of the asymptotic bias of the estimates is also included.

Seismic evidence of a crustal overthrust in the Western Alps

Abstract: Seismic data provided by the ALP75 experiment in the northwestern part of the Alpine Arc has been re-evaluated using ray-tracing techniques in a laterally inhomogeneous medium, thus improving a previous interpretation. The structure of the crust definitely appears to be different in the Northern Subalpine Chains where it is layered with an ESE mean dip of 30° and in the inner part of the Alpine Are where no clear stratification can be derived from the available data.

Differential Nucleolar Staining Affinity with a Modified Papanicolaou Staining Procedure

Abstract: A modified Papanicolaou staining procedure using diluted Harris' hematoxylin with potassium alum is described. Nucleolar staining varies from blue to bright red. This technique has been applied to mammary tumor cell lines in vitro under several conditions of hormonal stimulation known to induce protein synthesis and cell differentiation. Blue nucleoli are observed in control resting cells, while bright red nucleoli are seen after hormonal stimulation.

Asymptotic Inference for Markov Random Fields on ℤd

Abstract: The purpose of this paper is to generalize results of D.K. PICKARD [1,2,3] on asymptotic inference for the Ising model. Using properties of Gibbs measures on ℤd, we give the canonical exponential structure in which we can study the estimation problem, in the case of vertical sampling. This exponential structure depends on the range of the interaction potential of the underlying Markov random field; we construct, therefore, a test to measure this range: this test is based on the markovian character of the associated Gibbs measure; next we present the properties and the asymptotic laws of the estimators and we compare horizontal to vertical sampling [4]. Certain properties depend on the criticality of the interaction potential [5,6]: consequently, we construct a test of criticality for the interaction potential. Finally, we set the problem of estimation in a random Ising model.

Découverte de coulées pyroclastiques sous-marines dans la zone de l’Iran Central — Mécanisme de mise en place

Abstract: L’etude des coulees pyroclastiques sousmarines decouvertes en Iran revet un double interet. Tout d’abord, un interet regional car elles permettent d’expliquerpro parte l’origine des debris de verre argilises largement repandus dans les series sedimentaires eocenes de la zone de l’Iran Central, que les anciens auteurs appelaient tufs verts, boues tuffitiques ou, le plus souvent, series vertes. Un interet plus general ensuite car, contrairement au volcanisme basaltique, le volcanisme sous-marin acide est encore tres peu connu. Le dynamisme que nous proposons implique qu’a partir d’une lave acide sous-marine, fortement vesiculee et a phenocristaux automorphes, l’expansion des gaz engendre un facies vitroclastique a echardes, tandis que les phenocristaux sont fragmentes. L’ensemble forme un ecoulement gravitaire, riche en ponces, echardes, cristaux brises et gaz, de plus en plus turbulent vers l’aval et capable d’arracher au fond marin des lambeaux de sediments. Il evolue par la suite a la maniere d’un courant de turbidite.

Approche pluridisciplinaire des problemes poses par un glissement de terrain sur faible pente

Abstract: LA PRESENTE NOTE EMANE D'UN GROUPE DE TRAVAIL PLURIDISCIPLINAIRE QUI S'EST CONSTITUE A L'UNIVERSITE DE GRENOBLE POUR ABORDER SOUS TOUS LEURS ASPECTS LES PROBLEMES, FREQUENTS DANS LA REGION, POSES PAR LA STABILITE DES TALUS NATURELS. ELLE CONCERNE LE CAS D'UN GLISSEMENT DE TERRAIN SUR FAIBLE PENTE DANS DES ARGILES VARVEES DU TRIEVES (SUD DE GRENOBLE - ISERE). APRES LES ANALYSES GEOLOGIQUES ET MECANIQUES DU PHENOMENE, ON ENVISAGE LES SOLUTIONS POSSIBLES POUR LA RESTAURATION DU TERRAIN. CELLES-CI TIENNENT COMPTE DU FAIT QUE L'INTERET ECONOMIQUE DE LA ZONE DESTABILISEE, POURTANT VASTE (9 HA), EST FAIBLE. (A)

Relaxation nucléaire dans le fluorure de benzyle : III — Influence du solvant sur la barrière de rotation interne dans le fluorure de benzyle en solution par relaxation du deutérium

Abstract: Nous avons mesure la barriere de rotation Interne du groupe benzylique du fluorure de benzyle perdeutere, en solution autour de la liaison carbone aromatique-carbone benzylique a partir des temps de relaxation du deuterium traites selon la methode de Woessner. Cette barriere vaut 11,3 kJ mol— 1 dans le compose per hydrogene, 7,6 dans l'acetone et 10,7 dans le methanol. Les variations des temps de relaxation quadripolaire en fonction de la fraction molaire du solute, les valeurs du coefficient de microviscosite caracterisant le mouvement d'ensemble et les valeurs de la barriere suggerent que le fluorure de benzyle perdeutere est peu solvate dans l’acetone, engage dans une interaction au moins binaire avec le fluorure de benzyle per hydrogene, et est solvate par liaison hydrogene dans le methanol.

19F and 1H NMR of aldimines of fluoroamino acids with pyridoxal‐5′‐phosphate

Abstract: 1H and 19F NMR spectra were obtained for six Schiff bases (aldimines) formed by pyridoxal-5′-phosphate (PLP) with four fluorinated or their two parent non-fluorinated α-amino acids (phenylalanine and α-aminobutyric acid). pKA Values were derived from 1H and 19F titration curves. The imine nitrogen of the aldimines is very basic (∼13) and sensitive to the electron withdrawing effect of fluorine. The pyridine nitrogen is less basic in the aldimines (∼7) than in PLP (8.12) and is less sensitive to the electron withdrawing effect of the fluorine than is the imine nitrogen. The phosphate group has a pK in the same range (∼6) and the chemical shifts of some nuclei are sensitive to both pK values. Protonation of the aldimine causes the 1H signal to shift downfield at the methyl protons of the pyridine ring and at the aldehydic proton of the aldimine for the high pK value (except for the aldimines prepared from the β-fluorophenylalanine), but upfield at the aromatic proton and at the aldehydic proton of the aldimine for the low pK. Protonation of the aldimine causes the 19F signal of an aryl fluorine to shift downfield but gives an upfield shift at a β-fluorine. These data are related to the highly conjugated electronic structure of the Schiff bases.

Perméabilité des géotextiles et perméamètres

Abstract: Effectuer une mesure realiste de la permeabilite des geotextiles est moins aise qu'il n'y parait au premier abord.

Introduction to Real Quasianalytic Classes and Continuation Problems

Abstract: In this paper we point out some similar properties between analytic functions and elements of quasianalytic classes and give some examples. It seems to us that quasianalytic classes may be a means to give a sense to the continuation of an analytic function on a path through its natural boundary.