Showing papers by "University of Grenoble published in 1985"

Ergodicité et fonctions propres du laplacien

Abstract: Nous donnons la preuve d'une generalisation d'un resultat recent de S. Zelditch concernant la repartition asymptotique des fonctions propres du laplacien sur une variete compacte dont le flot geodesique est ergodique.

Synergism of Cellulases from Trichoderma reesei in the Degradation of Cellulose

Abstract: The action of cellobiohydrolases I and II (CBHI and CBHII) and endoglucanases I and II (EGI and EGII) purified from Tri-choderma reesei was evaluated against various substrates. CBHI degraded the β-D-glucan from barley in a typical endo pattern. With cellulose substrates, the synergism between CBHI and endoglucanase I or II depended on the structural and ultrastructural features of the substrate. This effect, unrelated to endo-exo cooperation, was found with substrates of intermediate crystallinity whereas weak or no synergism was recorded with cellulose microcrystals or the soluble carboxy-methyl cellulose derivative. Synergistic degradation of cellulose was also recorded with mixtures of CBHI and CBHII. On the other hand, synergism between endoglucanases and CBHII followed the pattern expected for an endo-exo cooperation. These results presented support evidence for multiple types of cooperation between the cellulolytic enzymes.

The traveling salesman problem on a graph and some related integer polyhedra

Abstract: Given a graphG = (N, E) and a length functionl: E → ℝ, the Graphical Traveling Salesman Problem is that of finding a minimum length cycle goingat least once through each node ofG. This formulation has advantages over the traditional formulation where each node must be visited exactly once. We give some facet inducing inequalities of the convex hull of the solutions to that problem. In particular, the so-called comb inequalities of Grotschel and Padberg are generalized. Some related integer polyhedra are also investigated. Finally, an efficient algorithm is given whenG is a series-parallel graph.

Attached cavitation and the boundary layer: experimental investigation and numerical treatment

Abstract: Attached cavitation on a wall with continuous curvature is investigated on the basis of experiments carried out on various bodies (circular and elliptic cylinders, NACA 16 012 foil). Visualization of the boundary layer by dye injection at the leading edge shows that a strong interaction exists between attached cavitation and the boundary layer. In particular, it is shown that the cavity does not detach from the body at the minimum pressure point, but behind a laminar separation, even in largely developed cavitating flow. A detachment criterion which takes into account this link between attached cavitation and boundary layer is proposed. It consists of connecting a cavitating potential-flow calculation and a boundary-layer calculation. Among all the theoretically possible detachment points, the actual detachment point is chosen to be the one for which the complete calculation predicts a laminar separation just upstream. This criterion, applied to the NACA foil, leads to a prediction which is in good agreement with experimental results.

Automated translation at Grenoble University

Abstract: The authors thank Dr. Slocum for the opportunity to present the work on machine translation at Grenoble. The plan he has proposed for the contributions to this special issue was certainly a very good starting point, as a common frame to present various systems around the world. It is, however, inevitable that we could not completely fit into it, so that we have sometimes taken some liberty for which we hope to be excused.

Diffusion of a passive scalar in two-dimensional turbulence

Abstract: We study the spectral statistics of the fluctuations of a passive scalar convected by a two-dimensional homogeneous isotropic turbulence using the eddy-damped quasinormal Markovian (EDQNM) theory, and – in certain cases – the near-equivalent test-field model (TFM). For zero correlation between scalar and vorticity fields it is known that these closures lead to inertial–convective ranges following respectively a k−1 law in the enstrophy-cascade range and a k−5/3 law in the inverse-energy-cascade range. We show that the scalar cascade in the latter range is direct, and is characterized by a positive eddy diffusivity. For forced flows in which correlation between vorticity and scalar forcing is prescribed, the k−5/3 range is replaced by a k1/3 range if the correlation is perfect, and for imperfect correlation we describe an analysis that bridges the ranges k1/3, k−1.We also examine the infrared (k → 0) behaviour of the energy and scalar spectra. Statistically steady injection of energy and scalar variance at a wavenumber kI produces an energy spectrum E(k) ∼ k3, and a scalar spectrum E0(k) ∼ k. In the unforced case, for any initial conditions, the energy spectrum develops a k3 range for k less than the wavenumber characteristic of the energy-containing eddies and a k−3 range for larger k. This allows a demonstration – via closure – that this energy-bearing wavenumber decreases as t−1 and the enstrophy as t−2 (modulo logarithmic corrections), as predicted by Batchelor (1969). Finally we show the scalar-fluctuation variance decays as the enstrophy, if the enstrophy spectrum is considered as a passive scalar. If not, the decay exponent is proportional to the ratio of the characteristic eddy-damping rates of the velocity and scalar third-order moments.

Two-Point Closure Used for a Sub-Grid Scale Model in Large Eddy Simulations

Abstract: A statistical two-point closure — the Eddy Damped Quasi Normal Markovian (EDQNM) — approximation is used to model the sub-grid scales (SGS) in a large-eddy simulation (LES) of three-dimensional homogeneous turbulence. First, eddy viscosities and diffusivities are derived from the hypothesis of a k −5/3 energy spectrum to parameterize the small scales of velocity and passive scalar fields: in that case, the LES yields fairly good k −5/3 inertial spectra up to the cutoff wavenumber. Then, a complete coupling between the LES in the large scales and the EDQNM calculation of the small scales is developed. Finally, the numerical simulation of large eddies is assessed from the standpoint of predictability studies.

RM3Ga2 Compounds (R ≡ rare earth, M ≡ Co, Ni): A new structural series

Abstract: X-ray diffraction on single crystals was used to establish the crystal structure of YCo 3 Ga 2 and YNi 3 Ga 2 . This hexagonal structure belongs to the P 6/ mmm space group. RCo 3 Ga 2 compounds with R ≡ La — Er and RNi 3 Ga 2 with R ≡ La — Tm crystallize with the same structure which is closely related to the hexagonal CaCu 5 -type structure.

Sur les Images Directes deD-Modules

Abstract: Let\(Y\xrightarrow{f}X\) be a morphism of compact analytic manifolds, and M a right coherentDY-module admitting a good filtration; if V⊂T*Y denotes the characteristic variety of M, one can define [M]V as the class of gr M in some suitable Grothendieck group of sheaves with support in V. Let\(T*Y\xleftarrow{F}Y\mathop { \times T*X\xrightarrow{{\bar f}}T*X}\limits_X \) be the morphisms naturally defined by f. A result of Kashiwara says that, for all i, the characteristic variety of ∫fiM is contained in\(W = \bar fF^{ - 1} V\). Here we prove the following K-theoretic version of this result:\(\sum {( - 1)^i [\int_f^i {M]} _W } = \bar f_* F*[M]_V \).

On the definitions of attractors

Abstract: We introduce the notion of attractor and present its historical evolution. Then we show that previous definitions are too stringent. We present two equivalent definitions of attractors, show that in this case strange attractors are indeed attractors and give some properties.

In vitro transcription initiation of the spinach chloroplast 16S rRNA gene at two tandem promoters

Abstract: Two potential prokaryotic promoters, P1 and P2, are characterized 164 and 114 bp upstream of the spinach chloroplast 16S rRNA gene. The strengths of these promoters, calculated according to an homology score established for E. coli RNA-polymerase, are identical. Experiments performed with a Taq I-DNA fragment, containing 16 bp of the 16S rDNA and 243 bp upstream of the gene, give evidence that in vitro, E. coli RNA-polymerase starts transcription at these two promoters. These results are based on both the size of the transcripts and their nucleotide sequences. A possible regulation by differential control of these dual promoters is suggested. S1 mapping with RNAs extracted either from green or from etiolated spinach plants, indicates that, at these two steps of plastid development, transcription in vivo starts at P1. Surprisingly only P2 appears to be conserved in the homologous sequences reported for maize, mustard and Spirodela.

Actinide solids 5f dependence of physical properties

Abstract: This chapter is an introduction to the main concepts underlying the present unterstanding of the physical properties of actinide solids.

The surgical treatment of cholesteatoma in children

Abstract: Between 1966 and 1981, 141 cholesteatomas were operated upon in children who were 3-15 years old. Radical mastoidectomy was performed in 5 cases. Open cavity tympanoplasty was done in 3 cases. Intact canal wall technique was performed in 99 cases, with a planned second stage in 83 cases (all cholesteatoma cases since 1973). ICWT avoids a large cavity in a well pneumatized mastoid and the second stage controls residual cholesteatomas which were more frequent in children (50%) than in adults (22%). Because of multiple or large residual cholesteatomas, a third stage was performed in 3 cases. Because of a large mesotympanum and/or attic residual cholesteatoma, a transformation of ICWT to an obliteration technique was performed in 4 cases. Retraction pockets were found after the first stage in 12 cases and a transformation of ICWT to an obliteration technique was done in 8 cases at the second stage. Late retraction pockets were found after 5 years in 20% after 2 stages and in 25% after one stage. If a retraction pocket is observed at the second stage, transformation of ICWT to an obliteration technique must be performed. Obliteration technique was performed in 34 cases. A second stage was planned in 26 cases only if the mesotympanum was to be dissected raw. Hearing results were better with an intact stapes (56% of air-bone gap less than or equal to 20 dB).

Magnetic properties of actinide solids

Abstract: The various magnetic properties observed in actinide solids are largely determined by the degree the unsaturated 5 f shells retain an atomic localized character or lose it in an itinerant mode. Hence the investigation of magnetism (and of related properties such as low temperature electrical resistivity) has played a central role in understanding bonding in actinide solids. Between clear cut cases of “localization” or “itineracy” intermediate situations are observed (leading for instance to spin fluctuating behaviour) which have made actinide magnetic research a rich but also controversial field.

Physical boson basis states in the boson expansion theories.

Abstract: The use of physical boson basis states is stressed for the calculations in the boson space The explicit form of physical boson basis states in terms of bosons is derived for the nonunitary boson mapping of Dyson The ambiguity in the normalization introduced due to the use of bi-orthonormal basis states is satisfactorily resolved, resulting in a Hermitian matrix This Hermitian matrix is found to coincide with the Hamiltonian matrix in the fermion space The model cases where the use of a boson basis is justified are shown to be consistent with our view of using physical boson basis states

The Physical and Chemical Structure of Circumstellar Envelopes

Abstract: The physical and chemical structure of massive circumstellar envelopes is reviewed in relation with infrared and millimeter observations, with a particular emphasis on the carbon-rich shell IRC+ 10216. The spatial distribution of the physical parameters (temperature, density, velocity field, mass-loss, ionization, etc.) and their relations are discussed. The different chemical processes responsible for the observed molecular abundances are examined: freezing-out of chemical equilibrium, radical and ion reactions, grain processes, photochemistry, etc.

Spinach chloroplast genes coding for three ribosomal proteins

Abstract: A pBR322 recombinant plasmid containing the spinach chloroplast DNA fragment SalI-5 has been used for coupled transcription-translation. Translational products of 19, 16 and 12x103 daltons give a positive immunoreaction with mixed antibodies against 30S and 50S spinach chloroplast ribosomal proteins. Three translational products co-migrate with basic chloroplast ribosomal proteins separated by two-dimensional electrophoresis. It is concluded that at least three ribosomal proteins are encoded by the SalI-5 DNA fragment, probably CS-S19, CS-L24 and CS-L25.

Prevention of recurrences in frequently relapsing herpes labialis with thymopentin a randomized double-blind placebo-controlled multicenter study

Abstract: The present randomized, placebo-controlled double-blind multicenter study included a population of 36 subjects with frequent recurrences (at least once a month) of herpes labialis. Most of the patients had failed to respond adequately to previous treatment with other therapeutic tools, including acyclovir. Either 50 mg of thymopentin or of placebo was administered 3 times a week, by the subcutaneous route, for 6 weeks. Subsequently, the patients were observed for nearly 6 months on the average. The results achieved with thymopentin for the individual parameters were significantly superior to those obtained with placebo; thus significant improvement was seen in patients on thymopentin in the duration of the longest symptomfree period (prolonged from 2.1 weeks to 20.9 weeks, p = 0.000), in the number of relapses (reduced from 1.6 to 0.4 episodes/month, p = 0.001), and in the total duration of herpes symptoms per month (shortened from 2.0 to 0.3 weeks, p = 0.000). Placebo treatment also resulted in considerable improvement (p < 0.05 or 0.01), but was significantly inferior to the improvement obtained with thymopentin. The longest symptomfree period in the placebo group was prolonged from 2.4 to 11.2 weeks. The number of relapses per month was reduced from 1.4 to 0.8, and the total duration of herpes symptoms per month from 2 to 0.9 weeks. The results of intergroup analyses, in which the observed parameters and the improvement achieved in either group were compared, significantly favored thymopentin treatment. The effect of thymopentin was in all but one parameters superior to that of placebo and highly significant (p < 0.01).

Factitivity, presupposition and the relativised predicate in Krio

Abstract: After a brief review of the literature on factivity and presupposition, the paper examines a case of asymmetry in the interpretation of a construction known as the relativised predicate (RP). Whenever the main verb of the sentence with RP is me?k (= 'make'), the sentence may be interpreted in two ways, including one with "the fact that". However, if the matrix verb is other than me?k, there is only one interpretation possible-without "the fact that". It is concluded that the dual interpretation is possible because the relative particle (which is also a complementizer linked to factive verbs) associates with the factive me?k.