An improved atomistic simulation based mixed-mode cohesive zone law considering non-planar crack growth

AbstractA novel and improved atomistic simulation based cohesive zone law characterizing interfacial debonding is developed which explicitly accounts for the non-planarity of the crack propagation. Group of atoms in the simulation constituting cohesive zones which are used to obtain local stress and crack opening displacement data are determined dynamically during the non-planar crack growth as they cannot be determined apriori. The methodology is used to study the debonding of Σ5 (210)/[001] symmetric tilt grain boundary interface in a Cu bicrystal under several mixed mode loading conditions. Simulations show that such bicrystalline specimen exhibits three types of energy dissipative mechanisms – shear coupled GB migration (SCM) away from the crack-tips, change in spacial orientation of GB structural units rendering highly disordered grain boundary near the crack tips and brittle intergranular fracture. Which combination of these three deformation mechanism will be active influencing the degree of non-planarity of the crack propagation at various stages of loading depends on the loading mode-mixity. As the ratio of shear component of the loading parallel to the GB plane and normal to the tilt axis with respect to the normal loading increases (thereby increasing the mode-mixity), overall strain-to-failure also increases and SCM tends to become the dominant deformation mechanism. Through this framework, analytical functional forms and parameters describing cohesive laws for both normal and shear traction as a function of the mode-mixity of the loading and crack opening displacement are predicted

Removal Efficiency of Lipid-regulating Drug Clofibric Acid from the Aquatic Environment by Calcined Anionic Clay ZnAl-CO3

Clofibric acid (CA) is widely used as regulator of lipid levels in blood; it is considered one of the residual drugs that have a high persistence in the aquatic environment. After wastewater treatment, only a small amount of CA can be removed. The aim of this work was to investigate the reduction of CA in contaminated wastewater using calcined anionic clay ZnAl-CO3, which was chosen for its higher adsorption capacity, recyclability, and non-regeneration of sludge. The maximum retention amount, Qm, exceeded 2220 mg g–1, and the value of DH° suggested a physical process. The removal rate achieved 90 %, and the remaining quantity was widely below the tolerance thresholds. Retention was achieved by hydrogen bonds and electrostatic interactions between the adsorbate molecules. Recycling tests clearly suggested that this material is recyclable, promising, and very effective compared to other adsorbents. This retention contributes to the attenuation of persistent lipid regulator. This work is licensed under a Creative Commons Attribution 4.0 International License

Synthesis and characterization of Mn/Ce-Doped TiO2: Investigation of structural and optical properties

The improvement of the optical properties of Titanium dioxide by doping with transition metals and rare earth ions is one of the most studies carried out by researchers. In this paper the TiO2: 0.01 Mn2+ x Ce3+ (x= 0; 1; 2 and 5 mol%) was synthesized by co-precipitation way. The structural and morphological properties were defined using X-ray diffraction, Fourier Transformation Total Infrared Reflection (FTIR), Raman Spectroscopy and Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX).The optical properties have been studied by UV-Visible spectroscopy. The co-doping with Ce3+ affects the lattice parameters of TiO2 and decreases the optical gap energy Eg which improve the absorption capability in the UV-Visible region. The results are discussed

Water reuse after removing a textile dye methyl orange using a recyclable hydrotalcite material

Hydrotalcite type material based on zinc, aluminum and carbonates was synthesized by coprecipitation method and its derived calcined at 500°C (CHT) was used to remove the textile dye methyl orange (MO). This adsorbent has a great potential for removing pollutants from aqueous solutions without generating sludge. Adsorption was performed in batch experiments. A rapid process of retention confirmed by kinetics reflects a high affinity between CHT material and MO dye. The adsorption isotherms follow the Langmuir model (L type). The results of several techniques suggest the intercalation of the pollutant between the hydrotacite sheets reconstructed from mixed oxides with a gallery of 2.35 nm. The retention capacity reaches 2500 mg/g with a removal rate of 100% for an optimum mass ratio MO/CHT of 0.3. After the recycling studies the material CHT justify its recyclability and confirms its efficiency for eliminating such pollutant

Rapid analysis of fluoxetine and its metabolite in plasma by LC-MS with column-switching approach

Abstract.: A rapid and sensitive method was developed for the simultaneous determination of fluoxetine and its primary metabolite, norfluoxetine, in plasma. It was based on a column-switching approach with a precolumn packed with large size particles coupled with a liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS). After a simple centrifugation, plasma samples were directly injected onto the precolumn. The endogenous material was excluded thanks to a high flow rate while analytes were retained by hydrophobic interactions. Afterwards, the target compounds were eluted in back flush mode to an octadecyl analytical column and detected by ESI-MS. The overall analysis time per sample, from plasma sample preparation to data acquisition, was achieved in less than 4min. Method performances were evaluated. The method showed good linearity in the range of 25-1000ngmL−1 with a determination coefficient higher than 0.99. Limits of quantification were estimated at 25ngmL−1 for fluoxetine and norfluoxetine. Moreover, method precision was better than 6% in the studied concentration range. These results demonstrated that the method could be used to quantify target compounds. Finally, the developed assay proved to be suitable for the simultaneous analysis of fluoxetine and its metabolite in real plasma sample

LES OUTILS D’EVALUATION DE LA PERFORMANCE INDIVIDUELLE : QUELLE QUALITE ET QUELLE OBJECTIVITÉ DANS LE SECTEUR PUBLIQUE

Indépendamment de la forme exacte que prend la pratique d’évaluation des compétences et des performances, il importe de s’assurer de la qualité du processus mis en place. En effet, la pratique d’évaluation constitue souvent la base sur laquelle repose en partie l’évolution de carrière des personnes ou encore le système de rémunération de l’organisation. Etant donné ces implications délicates pour les salariés, on comprend dès lors l’utilité d’analyser (et d’éventuellement améliorer) la qualité des pratiques d’évaluation en organisation et particulièrement en administration publique. L’objectif du présent article est de sensibiliser les acteurs locaux aux défaillances du système d’évaluation et de notation de la fonction publique au Maroc. Après avoir effectué une analyse du système en vigueur, notre objectif est de proposer des mesures correctives s’éloignant au maximum de l’arbitraire, et ce ; en se basant sur des indicateurs d’évaluation précis et objectifs destinés à réduire autant que possible les erreurs d'appréciation lors de l’octroi de la note.  Ce travail résulte d’une motivation personnelle de vouloir instaurer un système d’évaluation plus objectif en vue de procéder au futur à une évaluation équitable et juste de la performance des fonctionnaires de l’administration publique

Multi-technique characterisation of MOVPE-grown GaAs on Si

The heterogeneous integration of III-V materials on a Si CMOS platform offers tremendous prospects for future high speed and low power logic applications. That said this integration generates immense scientific and technological challenges. In this work multi-technique characterisation is used to investigate properties of GaAs layers grown by Metal-Organic Vapour Phase Epitaxy (MOVPE) on Si substrates - (100) with 4⁰ offset towards - under various growth conditions. This being a crucial first step towards the production of III-V template layers with a relatively lower density of defects for selective epitaxial overgrowth of device quality material. The optical and structural properties of heteroepitaxial GaAs are first investigated by micro-Raman spectroscopy and photoluminescence and reflectance measurements. High-resolution X-ray diffraction (HR-XRD) is used to investigate structural properties. Advanced XRD techniques, including double-axis diffraction and X-ray crystallographic mapping are used to evaluate degrees of relaxation and distribution of the grain orientations in the epilayers, respectively. Results obtained from the different methodologies are compared in an attempt to understand growth kinetics of the materials system. The GaAs overlayer grown with annealing at 735⁰C following As predeposition at 500⁰C shows the best crystallinity. Close inspection confirms the growth of epitaxial GaAs preferentially oriented along (100) embedded in a highly-textured polycrystalline structure