Damage law identification of a quasi brittle ceramic from a bending test using Digital Image Correlation

Although ceramics are generally considered to be elastic brittle solids, some of them are quasi brittle. These ceramics show a non-linear mechanical behaviour resulting most of the time in a difference between their tensile and compressive stress–strain laws. The characterization of their fracture strengths might be biased if linear elastic formulae are used to analyze classical tests like bending tests. Based on Digital Image Correlation (DIC), an efficient technique to measure full field displacements, a methodology is proposed to characterize and model materials with dissymmetric behaviours between tension and compression. Applying specific basis functions for DIC displacement decompositions for bending, compressive and tensile tests, a stress–strain model and its damage law are identified and then validated for aluminium titanate, a damageable micro-cracked ceramic at room temperature. This identification method using DIC can obviously be applied to other quasi brittle materials.     

Rheological and high gelling properties of mango (Mangifera indica) and ambarella (Spondias cytherea) peel pectins

Ambarella and mango peels are good sources of pectins (15–20%), with high degree of methylation (60–78%) and high molar masses. Ambarella and mango ( Améliorée and Mango varieties) peel pectins were extracted using HCl or oxalic acid/ammonium oxalate (OAAO). Purified pectins were analysed for their flow behaviour and phase diagrams were established at pH 3 as sucrose vs. pectin concentration. The gelation kinetics and mechanical spectra of these pectin gels were studied and compared to those of commercial citrus (lime) pectins. At a concentration of 1% (w/v), all pectic solutions had a shear thinning behaviour but at 0.6% (w/v), only OAAO-extracted pectins exhibited such behaviour. Phase diagrams showed that at pH 3, gelation of OAAO mango extracted pectins was possible at low polymer concentration (0.2%; w/w) for a sucrose concentration of 60% (w/w). OAAO-extracted pectins exhibited a higher gelling ability than HCl-extracted ones. Sucrose (45–50%) and pectin (0.2–0.6%) concentration had a deep impact on the gel strength. Our results enable to conclude that the OAAO extraction from mango and ambarella peels allowed the recovery of pectins that exhibit high gelling properties.     

Experimental study of the stacking sequence effect on polymer/composite multi-layers submitted to thermomechanical cyclic loadings

Fast filling of hydrogen pressure tank leads to thermomechanical stresses in vessel structure. In this paper, the aim is to study the thermomechanical behaviour of the material used in the vessel structure. Flat coupons made of the same constituents as the hydrogen tank materials and with different stacking sequences have been tested under quasi-static tensile tests and fatigue. Three types of fatigue tests have been performed in order to understand damage mechanisms due to interactions between thermal and mechanical stresses: thermomechanical fatigue, 1 Hz mechanical fatigue and mechanical fatigue with a constant stress level stage. Damage development has been followed by acoustic emission and microscopic observations. Results show that, whatever the applied loading, there is a significant influence of the stacking sequence of the composite part. Moreover, the comparison of the material response to the different types of fatigue has revealed the harmful role of coupled temperature/mechanical cyclic stresses.     

Quantum dot encapsulation in viral capsids

Incorporation of CdSe/ZnS semiconductor quantum dots (QDs) into viral particles provides a new paradigm for the design of intracellular microscopic probes and vectors. Several strategies for the incorporation of QDs into viral capsids were explored; those functionalized with poly(ethylene glycol) (PEG) can be self-assembled into viral particles with minimal release of photoreaction products and enhanced stability against prolonged irradiation.     

Influence of operating parameters on chromic ions removal from aqueous solution by liquid membranes

This paper presents the possibility of using liquid membranes as a separation and concentration technique to facilitate the recovery of Cr(VI) from water. Chromium(VI) being highly carcinogenic and mutagenic, it is necessary for risk assessment to remove and concentrate it in order to re-use it instead of reducing Cr(VI) to Cr(III). A separation scheme has been designed, using liquid membranes and rotating disk modules as contactors. Separation and enrichment can be simultaneously achieved in the same apparatus. Four operation parameters are considered : rotating disks speed, flow rate of chromium solution, initial chromium concentration and membrane volume. Experiments are performed in continuous mode. Estimation of the mass transfer coefficients is performed using macroscopic mass balances.     

Social Identity, Group Processes, and Performance in Synchronous Computer-Mediated Communication.

This study examined group processes in a synchronous context and their effects on performance, assuming that these processes would be strongly dependent on the salience of social identity. It was predicted that the mere categorization of students into an online group and comparison with other groups, 2 basic conditions related to social identity, would enhance group identification, interaction patterns, and group performance in a relatively complex academic task. As predicted, the categorization manipulation enhanced group identification and increased task- and morale-building communication. It was not related to performance. These findings invite a more thorough examination of the impact of social identity on the building of a sense of online community at the early stage of a learning process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cationic RuII Cyclopentadienyl Complexes with Antifungal Activity against Several Candida Species

Fungal infections, including those caused by antifungal-resistant Candida, are a very challenging health problem worldwide. Whereas different ruthenium complexes were previously studied for their anti-Candida potential, Ru-cyclopentadienyl complexes were overlooked. Here, we report an antifungal activity assessment of three Ru-cyclopentadienyl complexes with some insights into their potential mode of action. Among these complexes, only the cationic species [Ru-ACN]⁺ and [Ru-ATZ]⁺ displayed a significant antifungal activity against different Candida strains, notably against the ones that did not respond to one of the most currently used antifungal drugs fluconazole (FCZ). However, no apparent activity was observed for the neutral species, Ru−Cl, thus indicating the important role of the cationic backbone of these complexes in their biological activity. We suggest that reactive oxygen species (ROS) generation might be involved in the mechanism of action of these complexes as, unlike neutral Ru−Cl, [Ru-ACN]⁺ and [Ru-ATZ]⁺ could generate intracellular concentration-dependent ROS. We also observed a correlation between the ruthenium cellular uptake, ROS generation and fungal growth inhibitory activity of the compounds. Furthermore, docking simulations showed that the CYP51 enzyme can form more energetically favorable complexes with [Ru-ATZ]⁺ than fluconazole (FCZ); this suggests that CYP51 inhibition could also be considered as a potential mode of action.     

Safety assessment of dairy microorganisms: the Lactococcus genus

The Lactococcus genus includes 5 species. Lactococcus lactis subsp. lactis is the most common in dairy product but L. garviae has been also isolated. Their biotope is animal skin and plants. Owing to its biochemical characteristics, strains of L. lactis are widely used in dairy fermented products processing. Cases of human infections due to lactococci are very seldom reported even if Lactococcus garviae can be involved in fish diseases. Then L. lactis can be considered as safe and it is most commonly considered as Generally Recognized as Safe.