Keratinolytic activity of Streptomyces strain BA7, a new isolate from Turkey

A wild type Streptomyces strain BA7 which was isolated from soil, showed a high keratinolytic activity when cultured on native feather medium. Optimum keratinolytic activity was observed at 50°C and pH 8.5 when using fluid supernatant obtained from aerated culture of this organism. The keratinolytic activity was completely stable (100%) between 30 and 60°C. The molecular weight of crude enzyme was estimated by SDS-PAGE about 44000 Da. The degradation of intact feathers by Streptomyces sp. BA7 keratinase was obtained after 24 h of incubation at 50°C. Keratinolytic activity was partially inhibited by 1,10-phenanthroline, but slightly inhibited by CaCl2, ZnCl2, and SDS. In addition keratinolytic activity was enhanced by DMSO, EDTA, Triton-X 100 and sodium sulphite. Streptomyces strain BA7 could be a useful in biotechnology in therms of valorization of keratin-containing wastes or in the leather industry

Dynamical modeling of bi-layer Aluminium adhesive tape for laser shock applications

International audienceThe presented work covers the response of Aluminium tape (Al tape) under high strain rate of deformation (order of ) using laser shock. High power laser (J) with a short pulse duration (ns) is used to create laser shock within the water confinement regime on two Al tape configurations in order to apply low and high pressure (order of MPa and GPa). Al tape has been modeled using Johnson-Cook (J-C) material model for the Al layer, and Steinberg–Cochran–Guinan (SCG) material model (elastic with pressure dependence) for the adhesive layer, both material models are coupled with Grüneisen equation of state. The Al tape model has been validated by comparing the simulated Back Face Velocity (BFV) of the target with the measured one by the Velocity Interferometer System for Any Reflector (VISAR). In addition, the validated material model is used to conduct the sensitivity studies about the transmitted pressure depending on the acoustical impedance of the target and adhesive thickness. Moreover, location and magnitude of maximum tensile stress within the target are calculated in function of the adhesive thickness of the Al tape. Finally, it has been proved that using one laser beam configuration, maximum tensile zone could appears close to the front face by increasing the adhesive thickness

Modeling of multi-edge effects in the case of laser shock loadings applied on thin foils: Application for material characterization of aluminum alloys

This article presents the study of the shock wave propagation through aluminum alloys (pure aluminum and aluminum 2024-T3) produced by laser plasma using experimental and numerical tests. Water confinement regime interaction, pulse duration (7.2 ns), and power density (1-5 GW / cm 2) range correspond to laser shock peening process configuration and parameters. To that scope, we simulate the shock wave propagation using non-linear explicit code LS-DYNA, which we validate with experimental results. Thereupon, we present a descriptive analysis that links separately the material model and loading conditions to the dynamic response of aluminum alloys under high strain rate laser shock by coupling the Johnson-Cook (J-C) material model with the Grüneisen equation of state (MAT_015 and EOS_GRUNEISEN accordingly). In addition, we make use of stress propagation into target thickness to analyze the origin of different points on the Back Face Velocity (BFV) profile during shock propagation. Finally, we provide evidence that 2D compressive effects do not depend only on the focal spot size or target thickness such as the edge effects but also on power density and material initial yield strength