Physical and mechanical behaviour of a roller compacted concrete reinforced with polypropylene fiber

In order to study the behaviour of a roller compacted concrete (RCC) reinforced with polypropylene fiber, six types of RCC were made with different content of fibers (0, 0.5, 1, 1.5, 2 and 2.5 Kg/m3). The physical parameters are the density, the workability, the shrinkage and the water absorption. For the mechanical parameters; the performances such as the compressive strength and the tensile strength (3 point bending and splitting) has been studied. The results show that the RCC reinforced with fibers present the better performances in terms of strength and physical behaviour. The results obtained show the positive effect of the polypropylene fiber addition on the mechanical strength, which increases about 23% for the mixture with 1 Kg/m3. For the physical properties, there is a decrease in the density and workability and an improvement in the water absorption proportional with the addition of polypropylene fiber. In addition, we conclude the positive effect of polypropylene fiber on the kinetics and development of the shrinkage. In this study, the best physical and mechanical performance was being observed in the mixture with 1 Kg/m3 of polypropylene.Keywords: Roller compacted concrete, polypropylene fiber, workability, mechanical strength, shrinkag

The Triassic-Liassic volcanic sequence and rift evolution in the Saharan Atlas basins (Algeria). Eastward vanishing of the Central Atlantic magmatic province

We investigate the Triassic-Liassic sequence in ten diapirs from the Saharan Atlas (Algeria). Based on detailed mapping, two episodes are identified. The first one consists of a volcano-sedimentary sequence in which three volcanic units were identified (lower, intermediate and upper units). They are interlayered and sometimes imbricated with siliciclastic to evaporitic levels which record syn-sedimentary tectonics. This sequence was deposited in a lagoonal-continental environment and is assigned to the Triassic magmatic rifting stage. The second episode, lacking lava flows (post magmatic rifting stage), consists of carbonate levels deposited in a lagoonal to marine environment during the Rhaetian-Hettangian. The volcanic units consist of several thin basaltic flows, each 0.5 to 1m thick, with a total thickness of 10–15m. The basalts are low-Ti continental tholeiites, displaying enrichment in large ion lithophile elements and light rare earth elements [(La/Yb)n= 2.5-6] with a negative Nb anomaly. Upwards decrease of light-rare-earth-elements enrichment (e.g. La/Yb) is modelled through increasing melting rate of a spinel-bearing lherzolite source from the lower (6–10wt.%) to the upper (15–20wt.%) unit. The lava flows from the Saharan Atlas share the same geochemical characteristics and evolution as those from the Moroccan Atlas assigned to the Central Atlantic magmatic province. They represent the easternmost witness of this large igneous province so far known

Removal of zinc and cadmium ions from contaminated soils with rhamnolipid biosurfactant produced by Pseudomonas aeruginosa S7PS5

A soil treatment process using froth flotation technique involving anionic biosurfactant (rhamnolipids) using Sodium sulfide was studied. The supernatant produced by the strain Pseudomonas aeruginosa S7PS5 was tested for biosurfactants production, HPLC analysis showed the presence of L-rhamnosyl- β- hydroxydecanoyl- β-hydroxydecanoate (RL1) and L-rhamnosyl L-rhamnosyl- β-hydroxydecanoyl-β- hydroxydecanoate (RL2). The influence of the collector (rhamnolipid), pulp pH, a chemical activation step (sulfidization) and process time on metal removal efficiency has been investigated to recover Zn and Cd ions from a contaminated soil. An effective CMC of 35 mg/L was obtained. A perfect Zn and Cd removal efficiency was made at pH = 12 and 4 mg/g of Na2S during the first 5 min of soil washing process, then a longer flotation time ( > 5 min) caused mechanical entrainment of Zn and Cd.Keywords: Biosurfactants, flotation, Pseudomonas aeruginosa, rhamnolipids, soil washin

The synthesis of TiO2 thin film by Chemical Bath Deposition (CBD) method

Titanium oxide (TiO2) films have several advantages for applications in solar cells and very commonly used as a photo-catalyst for degradation of environmental pollutants. In this study, TiO2 films were synthesized using, a simple, less expensive, low temperature and convenient for large area deposition method, a chemical bath deposition (CBD) and their structural and optical properties were examined at various calcinations temperatures. The X-ray diffraction (XRD) technique shows the presence of the picks characteristic of anatase phase after annealing our films at 500°C, 600°C and rutile phase appears after heat treatment at 700°C. The surface morphology of the deposited films was characterized by the FEG scanning electronic microscopy (FEGSEM) and atomic force microscopy (AFM). Energy dispersive X-ray spectroscopy (EDS) analysis was used to determine the chemical composition of the prepared films. The UV-Vis-NIR spectroscopy shows that the film exhibits a transmission around 60%. The indirect band gap of the deposited films was between 2.88 and 3.22 eV

NUMERICAL SIMULATION OF PHOTOCURRENT IN A SOLAR CELL BASED AMORPHOUS SILICON

We propose in this work, a method of simulation based on the resolution of the equations of continuities for homostructures of silicon-based solar, and used a method of calculation the photocurrent delivered by the silicon solar cell applying the equations of continuities and the currents by analogy to the phenomena of loads transport according to the model of an homojunction n-a-Si:H/p-a-Si:H. We used Matlab software to simulate and optimize the layers thicknesses to achieve the maximum photocurrent generated under AM1.5 solar spectrum. The optimization of donor layer thickness shows clearly that the best results are obtained with the finest structures.  We worked out a numerical model based on the resolution of the equations of continuities who gave the results in good agreement with literature and which allowed, moreover a better control of the performances of the cells based on silicon, for their improvement

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