HAL-Polytechnique

    Branch crack development from the flank of a fatigue crack propagating in mode II

    No full text
    International audienc

    Anticipating the fate and impact of organic environmental contaminants: A new approach applied to the pharmaceutical furosemide

    No full text
    International audienceThe presence of trace levels of organic contaminants in the environment is currently an environmental concern. When these contaminants are subjected to environmental transformations, environmental transformation products (ETPs) are obtained, whose structures often remain unknown. The absence of information concerning these new compounds makes them unavailable and consequently makes their environmental detection as well as their (eco)toxicological study impossible. This report describes a multidisciplinary approach that seeks to both anticipate the fate and evaluate the impact of organic environmental contaminants.Our approach consists of three steps. First, isolated and fully characterized transformation products (TPs) of the parent molecule are obtained. In the second step, the parent molecule is subjected to environmentally relevant transformations to identify plausible ETPs. The detection of previously characterized TPs allows the concomitant identification of plausible ETPs. The third step is devoted to the toxicological evaluation of the identified plausible ETPs.Such an approach has recently been applied to furosemide and has allowed the identification of its main TPs. This report now seeks to identify and evaluate toxicologically plausible ETPs of this drug, which is also known as an environmental contaminant

    Stabilization for an ensemble of half-spin systems

    No full text
    International audienceFeedback stabilization of an ensemble of non interacting half spins described by Bloch equations is considered. This system may be seen as a prototype for infinite dimensional systems with continuous spectrum. We propose an explicit feedback law that stabilizes asymptotically the system around a uniform state of spin +1/2 or -1/2. The proof of the convergence is done locally around the equilibrium in the H^1 topology. This local convergence is shown to be a weak asymptotic convergence for the H^1 topology and thus a strong convergence for the C^0 topology. The proof relies on an adaptation of the LaSalle invariance principle to infinite dimensional systems. Numerical simulations illustrate the efficiency of these feedback laws, even for initial conditions far from the equilibriu

    Testing aluminium alloy from quasi-static to dynamic strain rates with a modified split Hopkinson bar method.

    No full text
    An aluminum alloy was tested at quasi-static to dynamic strain rates (from 10-1 to 5 103 s-1), using a single measuring device, a modified Split Hopkinson Bar. A wave separation technique [Bussac & al., 2002] based on the maximum likelihood method was applied to process the strain and velocity measurements recorded at various points on each bar. With this method, which takes the wave dispersion into account, it is possible to compute the stress, strain, displacement and velocity at any point on the bar. Since the measurement time is unlimited, the maximum strain measured in a given specimen no longer decreases with the strain rate, as occurs with the classical Split Hopkinson Bar method

    Colour centre production in yttria-stabilized zirconia by swift charged particle irradiations

    No full text
    International audienceWe have studied the colour centre production by swift electron and heavy ion irradiations of yttria-stabilized zirconia (YSZ), i.e. ZrO2:Y with 9.5 mol% Y2O3. For this purpose, we performed irradiations of - or -oriented YSZ single crystals with 2.5 MeV electrons, 145 MeV C-13, 180 MeV S-32, 200 MeV Ni-58, 230 MeV Br-79, 120 MeV I-127, 200 MeV I-127, 200 MeV Au-197, and 2.6 GeV U-238 ions. X-band electron paramagnetic resonance (EPR) and UV-visible optical absorption measurements were used to monitor the point defect formation. The EPR line saturations were measured between 6 and 150 K, in order to obtain the spin-lattice relaxation time (T-1). Electron and ion beams produce the same two colour centres: (i) the first one is identified as an F+-type Centre (singly ionized oxygen vacancy) with an axial (100) symmetry, a small g-factor anisotropy (g(perpendicular to) = 1.972 and g(parallel to) = 1.996) and long T-1 values, (ii) the second one is similar to the well known T-centre (Zr3+, in a trigonal oxygen environment) with an axial (I 11) symmetry and a large g-factor anisotropy (g(perpendicular to) = 1.855 and g(parallel to) = 1.986), which is also produced by photon irradiations. A broad optical absorption band centred at a wavelength near 500 nm is observed with an absorption coefficient proportional to the Volume density of the F+-type centre deduced from the room temperature EPR spectra. Since no change of this band occurs between 10 and 300 K, it indicates that the electron-phonon coupling of this colour centre must be strong, in agreement with an F+-type centre. Owing to the axial (100) symmetry and lack of hyperfine structure of the EPR lines of this defect, it is suggested that the first coordination shell must contain one native oxygen vacancy. The plots of the volume density of this centre versus fluence are on the whole rescaled as functions of the number of displacements per atom induced by elastic collision

    Modulation of the Pyrococcus abyssi NucS endonuclease activity by replication clamp at functional and structural levels

    No full text
    International audiencePyrococcus abyssi NucS is the founding member of a new family of structure-specific DNA endonucleases that interact with the replication clamp proliferating cell nuclear antigen (PCNA). Using a combination of small angle x-ray scattering and surface plasmon resonance analyses, we demonstrate the formation of a stable complex in solution, in which one molecule of the PabNucS homodimer binds to the outside surface of the PabPCNA homotrimer. Using fluorescent labels, PCNA is shown to increase the binding affinity of NucS toward single-strand/double-strand junctions on 5′ and 3′ flaps, as well as to modulate the cleavage specificity on the branched DNA structures. Our results indicate that the presence of a single major contact between the PabNucS and PabPCNA proteins, together with the complex-induced DNA bending, facilitate conformational flexibility required for specific cleavage at the single-strand/double-strand DNA junction. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc

    Computing with D-algebraic power series

    No full text
    International audienc

    A local model for the trianguline variety and applications

    No full text
    International audienceWe describe the completed local rings of the trianguline variety at certainpoints of integral weights in terms of completed local rings of algebraicvarieties related to Grothendieck's simultaneous resolution of singularities.We derive several local consequences at these points for the triangulinevariety: local irreducibility, description of all local companion points in thecrystalline case, combinatorial description of the completed local rings of thefiber over the weight map, etc. Combined with the patched Hecke eigenvariety(under the usual Taylor-Wiles assumptions), these results in turn have severalglobal consequences: classicality of crystalline strictly dominant points onglobal Hecke eigenvarieties, existence of all expected companion constituentsin the completed cohomology, existence of singularities on global Heckeeigenvarieties
    HAL-Polytechniqueis based in FR
    Access Repository Dashboard
    Do you manage HAL-Polytechnique? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! CORE Repository Dashboard!