1,588 research outputs found
Ab-initio and Critical behaviors of the perovskite CaMnO for solar cell applications
In this work, we used the density functional calculation (DFT) implemented in
the Quantum Espresso software, using the approximations (GGA, GGA+U) to
illustrate the electronic and magnetic properties of the perovskite CaMnO.
It has been found that the CaMnO perovskite is stable in the G-AFM phase.
When expecting the total and partial DOSs, a strong contribution of the d-Mn
states has been outlined. The Coulomb correction U and the site exchange
interaction J have been implemented and then we compared the two approximations
GGA and GGA+U. It is found that the GGA+U method leads to more accurate results
since this correction takes into account the bonding effects between different
atoms. To complete this study we performed the simulations under Monte Carlo
code based on the Metropolis algorithm. In fact, we have simulated the physical
quantities: magnetization, susceptibility, and specific heat of the studied
CaMnO material as a function of temperature
Dislocation structures and the role of grain boundaries in cyclically deformed Ni micropillars
Transmission electron microscopy and finite element-based dislocation simulations were combined to study the development of dislocation microstructures after cyclic deformation of single crystal and bicrystal Ni micropillars oriented for multi-slip. A direct correlation between large accumulation of plastic strain and the presence of dislocation cell walls in the single crystal micropillars was observed, while the presence of the grain boundary hampered the formation of wall-like structures in agreement with a smaller accumulated plastic strain. Automated crystallographic orientation and nanostrain mapping using transmission electron microscopy revealed the presence of lattice heterogeneities associated to the cell walls including long range elastic strain fields. By combining the nanostrain mapping with an inverse modelling approach, information about dislocation density, line orientation and Burgers vector direction was derived, which is not accessible otherwise in such dense dislocation structures. Simulations showed that the image forces associated with the grain boundary in this specific bicrystal configuration have only a minor influence on dislocation behavior. Thus, the reduced occurrence of âmatureâ cell walls in the bicrystal can be attributed to the available volume, which is too small to accommodate cell structures
Suivi épidémiologique des avortements de petits ruminants dans les zones pastorales du Maroc
Le prĂ©sent travail fait partie dâun programme de suivi Ă©pidĂ©miologique des avortements chez les petits ruminants au Maroc. Il expose les rĂ©sultats prĂ©liminaires sur trois campagnes agricoles des foyers dâavortement dans quatre rĂ©gions pastorales. Les rĂ©sultats rĂ©vĂšlent des taux dâavortement entre 7 et 27% selon les rĂ©gions et les annĂ©es. Le taux dâavortement global est plus Ă©levĂ© chez les caprins (19%) que chez les ovins (10,6%) avec une frĂ©quence Ă©levĂ©e en Ă©levage sylvo-pastoral. Les analyses sĂ©rologiques montrent que la chlamydophilose, seule ou associĂ©e Ă dâautres infections, a Ă©tĂ© trouvĂ©e dans 28,6% des troupeaux enquĂȘtĂ©s, suivie de la toxoplasmose et la fiĂšvre Q. La salmonellose Ă Salmonella abortus ovis a Ă©tĂ© trouvĂ©e dans 4,7% des troupeaux ovins. Une proportion dâenviron 50% des avortements reste inexpliquĂ©e. Les plantes toxiques seraient probablement Ă lâorigine dâune partie de ces avortements. Bien que les infections abortives soient largement associĂ©es aux avortements, des investigations Ă©pidĂ©miologiques sont en cours pour lâĂ©tude des contraintes liĂ©es Ă la surveillance et au diagnostic des avortements en zones pastorales. Ceci devrait permettre dâamĂ©liorer la qualitĂ© des prĂ©lĂšvements pour diagnostic, dĂ©terminer prĂ©cisĂ©ment la part respective des avortements infectieux et non infectieux et vĂ©rifier lâhypothĂšse de lâassociation des plantes toxiques aux avortements
The endemic Chamaecytisus albidus is nodulated by symbiovar genistearum of Bradyrhizobium in the Moroccan Maamora Forest
Out of 54 isolates from root nodules of the Moroccan-endemic Chamaecytisus albidus plants growing in soils from the Maamora cork oak forest, 44 isolates formed nodules when used to infect their original host plant. A phenotypic analysis showed the metabolic diversity of the strains that used different carbohydrates and amino acids as sole carbon and nitrogen sources. The isolates grew on media with pH values ranging from 6 to 8. However, they did not tolerate high temperatures or drought and they did not grow on media with salt concentrations higher than 85 mM. REP-PCR fingerprinting grouped the strains into 12 clusters, of which representative strains were selected for ARDRA and rrs analyses. The rrs gene sequence analysis indicated that all 12 strains were members of the genus Bradyrhizobium and their phylogeny showed that they were grouped into two different clusters. Two strains from each group were selected for multilocus sequence analysis (MLSA) using atpD, recA, gyrB and glnII housekeeping genes. The inferred phylogenetic trees confirmed that the strains clustered into two divergent clusters. Strains CM55 and CM57 were affiliated to the B. canariense/B. lupini group, whereas strains CM61 and CM64 were regrouped within the B. cytisi/B. rifense lineage. The analysis of the nodC symbiotic gene affiliated the strains to the symbiovar genistearum. The strains were also able to nodulate Retama monosperma, Lupinus luteus and Cytisus monspessulanus, but not Phaseolus vulgaris or Glycine max. Inoculation tests with C. albidus showed that some strains could be exploited as efficient inocula that could be used to improve plant growth in the Maamora forest.The authors want to thank all the people who contributed to theachievement of this study. Financial support was obtained fromââAcadĂ©mie Hassan II des Sciences et Techniquesâ (Morocco). MrOmar Bouhnik received a grant from the Hassan II Academy of Science and Technology. The authors also thank the Ministerio de EconomĂa, Industria y Competitividad (Spain) for the granting ofthe ERDF-cofinanced project AGL2017â85676R
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