Influence de la teneur de nickel sur le comportement tribologique et électrochimique de l’alliage TiNi.

Parmi les matériaux métalliques, les alliages de TiNi sont employés principalement pour des applications biomédicales et/ou dentaires dues à leur meilleure compatibilité mécanique avec les tissus, leur module de Young proche de celui de l’os et une résistance élevée à la corrosion dans les fluides du corps et une bonne biocompatibilité. Pour cette raison, le comportement à la corrosion et à l’usure de l’alliage TiNi avec des teneurs en Ni varie de 40 à 60% en poids, ont été étudiés afin de vérifier l’effet du Ni sur la biocompatibilité de cet alliage pour des applications dentaires

Microscopy of bacterial translocation during small bowel obstruction and ischemia in vivo – a new animal model

BACKGROUND: Existing animal models provide only indirect information about the pathogenesis of infections caused by indigenous gastrointestinal microflora and the kinetics of bacterial translocation. The aim of this study was to develop a novel animal model to assess bacterial translocation and intestinal barrier function in vivo. METHODS: In anaesthetized male Wistar rats, 0.5 ml of a suspension of green fluorescent protein-transfected E. coli was administered by intraluminal injection in a model of small bowel obstruction. Animals were randomly subjected to non-ischemic or ischemic bowel obstruction. Ischemia was induced by selective clamping of the terminal mesenteric vessels feeding the obstructed bowel loop. Time intervals necessary for translocation of E. coli into the submucosal stroma and the muscularis propria was assessed using intravital microscopy. RESULTS: Bacterial translocation into the submucosa and muscularis propria took a mean of 36 ± 8 min and 80 ± 10 min, respectively, in small bowel obstruction. Intestinal ischemia significantly accelerated bacterial translocation into the submucosa (11 ± 5 min, p < 0.0001) and muscularis (66 ± 7 min; p = 0.004). Green fluorescent protein-transfected E. coli were visible in frozen sections of small bowel, mesentery, liver and spleen taken two hours after E. coli administration. CONCLUSIONS: Intravital microscopy of fluorescent bacteria is a novel approach to study bacterial translocation in vivo. We have applied this technique to define minimal bacterial transit time as a functional parameter of intestinal barrier function

Performances evaluation of binary concrete designed with silica fume and metakaolin

The use of various pozzolanic and cementitious materials not only has an environmental and economic impact, by the reduction of Portland cement clinker production, but also could significantly improve the strength and durability performances of concrete. Silica fume (SF) is a well-known and largely used pozzolanic material due to numerous improvements that could provide to concrete while metakaolin (MK) even with quite similar performance is still less popular in concrete industry. The present study investigates and compares the key mechanical properties and durability performances of binary concrete mixes designed with different replacement levels of SF and MK varying from 5% to 25% of Portland cement (PC). The results indicate that using both SF and MK in a partial substitution of PC could significantly improve strengths and durability performances of blended cement concrete mixes in comparison with the control PC-concrete. Meanwhile, SF-concrete seems to perform better than MK-concrete with regards to strength development and resistance to freezing-thawing while MK-concrete has exhibited a better performance with regard to carbonation and chloride ions ingress. Furthermore, although economical assessment showed an increase in the cost of concrete made with SF/MK due to the fact that SF/MK are more expensive than PC, environmental assessment revealed that significant reduction of the embodied CO 2 (ECO 2 ) is generated when using MK, and especially SF as a partial substitution of PC. Designing a binary SF and MK concretes may help towards producing clean and environmentally friendly concrete material