Comparison of max-plus automata and joint spectral radius of tropical matrices

Weighted automata over the max-plus semiring S are closely related to finitely generated semigroups of matrices over S. In this paper, we use results in automata theory to study two quantities associated with sets of matrices: the joint spectral radius and the ultimate rank. We prove that these two quantities are not computable over the tropical semiring, i.e. there is no algorithm that takes as input a finite set of matrices M and provides as output the joint spectral radius (resp. the ultimate rank) of M. On the other hand, we prove that the joint spectral radius is nevertheless approximable and we exhibit restricted cases in which the joint spectral radius and the ultimate rank are computable. To reach this aim, we study the problem of comparing functions computed by weighted automata over the tropical semiring. This problem is known to be undecidable and we prove that it remains undecidable in some specific subclasses of automata

Wattrelos – Ferme Malvache

Date de l'opération : 1991 (SU) Inventeur(s) : Guillon P La fouille a été menée avec l’aide de M. l’abbé Tieghem sur la ferme Malvache que devait faire disparaître la route départementale 700 (CD 700). Un relevé d’architecture et photographique, avec l’étude des plans cadastraux, a permis de suivre l’évolution de cette ferme depuis 1820. Les deux sondages effectués dans la cour proche des fondations de l’ancienne habitation attestent une occupation certaine dès le XVe s. Le premier, en nive..

Role of phosphoinositide 3-kinase in the autophagic death of serum-deprived PC12 cells

The death of serum-deprived undifferentiated PC12 cells shows both autophagic and apoptotic features. Since it is still controversial whether the autophagy is instrumental in the cell death or a mere epiphenomenon, we tested the effects of inhibiting the autophagy by a variety of phosphoinositide 3-kinase inhibitors, and provided evidence that the autophagy, or a related trafficking event, is indeed instrumental in the cell death. Furthermore, by comparing the effects of PI3-K inhibition and caspase-inhibition on autophagic and apoptotic cellular events, we showed that in this case the autophagic and apoptotic mechanisms mediate cell death by parallel pathways and do not act in serie

Coherent acoustic vibration of metal nanoshells

Using time-resolved pump-probe spectroscopy we have performed the first investigation of the vibrational modes of gold nanoshells. The fundamental isotropic mode launched by a femtosecond pump pulse manifests itself in a pronounced time-domain modulation of the differential transmission probed at the frequency of nanoshell surface plasmon resonance. The modulation amplitude is significantly stronger and the period is longer than in a gold nanoparticle of the same overall size, in agreement with theoretical calculations. This distinct acoustical signature of nanoshells provides a new and efficient method for identifying these versatile nanostructures and for studying their mechanical and structural properties.Comment: 5 pages, 3 figure

Barometric pumping of a fractured porous medium

International audienceBarometric pumping plays a crucial role in the release of trace gases from fractured porous media to the atmosphere, and it requires a rigorous and complete modeling in order to go beyond the approximate schemes available in the literature. Therefore, a coupled set of convection and convection-diffusion equations for a slightly compressible fluid in unsteady conditions should be solved. The numerical methodology is presented, and it is applied to conditions close to the ones of the Roselend Natural Laboratory (France). The precision of the code is assessed and the mechanism of barometric pumping is explained. The usual schematization by simple vertical fractures is shown to be only qualitative. Finally, barometric pumping is shown to be efficient in a narrow range of parameter values; its efficiency is a decreasing function of the matrix porosity and of the fracture density

Isolement d'une souche de virus de la maladie de Carré à propriétés biologiques particulières

Reculard Pierre, Guillon J.-C. Isolement d’une souche de virus de la maladie de Carré à propriétés biologiques particulières. In: Bulletin de l'Académie Vétérinaire de France tome 120 n°10, 1967. pp. 507-511

Syndrome érythrémique chez le chat

Groulade Paul, Guillon J. C. Syndrome érythrémique chez le chat. In: Bulletin de l'Académie Vétérinaire de France tome 119 n°3, 1966. pp. 127-131

Toxoplasmose à localisation biliaire et pancréatique chez le chien

Groulade Paul, Guillon J.-C. Toxoplasmose à localisation biliaire et pancréatique chez le chien. In: Bulletin de l'Académie Vétérinaire de France tome 120 n°5, 1967. pp. 221-225