Investigation of mechanosynthesized Fe50Ni40Al10 powders

International audienc

The formation mechanism of mechanically alloyed Fe–20at% Al powder

International audienc

Genotypic and symbiotic diversity of Rhizobium populations associated with cultivated lentil and pea in sub-humid and semi-arid regions of Eastern Algeria

The genetic structure of rhizobia nodulating pea and lentil in Algeria, Northern Africa was determined. A total of 237 isolates were obtained from root nodules collected on lentil (Lens culinaris), proteaginous and forage pea (Pisum sativum) growing in two eco-climatic zones, sub-humid and semi-arid, in Eastern Algeria. They were characterised by PCR-restriction fragment length polymorphism (RFLP) of the 16S-23S rRNA intergenic region (IGS), and the nodD-F symbiotic region. The combination of these haplotypes allowed the isolates to be clustered into 26 distinct genotypes, and all isolates were classified as Rhizobium leguminosarum. Symbiotic marker variation (nodD-F) was low but with the predominance of one nod haplotype (g), which had been recovered previously at a high frequency in Europe. Sequence analysis of the IGS further confirmed its high variability in the studied strains. An AMOVA analysis showed highly significant differentiation in the IGS haplotype distribution between populations from both eco-climatic zones. This differentiation was reflected by differences in dominant genotype frequencies. Conversely, no host plant effect was detected. The nodD gene sequence-based phylogeny suggested that symbiotic gene diversity in pea and lentil nodulating rhizobial populations in Algeria was low compared to that reported elsewhere in the world

DC and high-frequency conductivity of CuInSe2 bulk crystals

International audienceBulk crystals of CuInSe2 (CIS) were grown by vacuum fusion technique with specific proportions of Cu, In and Se. The studied samples, cut from the central part of the ingots, were first characterised by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The conductivity of the crystals was investigated by using a contactless technique based on hyper-frequency microwave. The method consisted in measurements made in a rectangular resonance cavity at 9192 MHz. Conductivity has been also measured by conventional Van der Paw method and the values obtained, varied in the range [3.10-3-7.10-3]Ω-1cm-1, didn't show significant discrepancies between the two techniques

Bacterial capacities to mineralize phytate increase in the rhizosphere of nodulated common bean (Phaseolus vulgaris) under P deficiency

Phytate (a form of Inositol phosphate), which is one of the most abundant sources of organic phosphorus (Po) in soils, needs to be mineralized by microbial phosphatases to become available for plants. Phytases are the most active phosphatases for the dephosphorylation of phytate but the ecology of the phytate mineralising bacteria (PMB) remains poorly understood. The aim of this work was to determine if PMB represent an important component of the rhizosphere of legumes and if their density and their activities depend upon the soil-P availability. In this work the density, activity and phylogenetic affiliation of the PMB were characterized in the nodulated rhizosphere of a legume (Phaseolus vulgaris) grown in two soils with contrasting Low-P or P-sufficient content Screened on solid medium, the density of PMB was higher in the rhizosphere of common bean than in the bulk soil only when plants were cultured on the low-P soil. In liquid culture, half of the rhizosphere isolates were able to use phytate as the sole P source and to release free inorganic P in the medium at rates much higher when bacterial strains were isolated from low-P than from P-sufficient soil. Enzymatic activity confirmed the ability of these rhizosphere isolates to mineralize phytate. Whatever the soil P level, the PMB belonged to the same genera Pseudomonas, Pantoae, Enterobacter and Salmonella, but not Bacillus. Our work demonstrates that low soil P availability increases both PMB density in the rhizosphere compared to the bulk soil and the activities of PMB populations through different growth patterns

DC and high-frequency conductivity of CuInSe2 bulk crystals

International audienceBulk crystals of CuInSe2 (CIS) were grown by vacuum fusion technique with specific proportions of Cu, In and Se. The studied samples, cut from the central part of the ingots, were first characterised by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The conductivity of the crystals was investigated by using a contactless technique based on hyper-frequency microwave. The method consisted in measurements made in a rectangular resonance cavity at 9192 MHz. Conductivity has been also measured by conventional Van der Paw method and the values obtained, varied in the range [3.10-3-7.10-3]Ω-1cm-1, didn't show significant discrepancies between the two techniques