Thermodynamic, thermoelectric, and magnetic properties of FeSb2: A combined first-principles and experimental study

We analyze the thermodynamic, magnetic, and transport properties of the narrow band-gap semiconductor FeSb2 using density functional theory calculations corroborated by nuclear inelastic spectroscopy and ultrasound experiments. The vibrational properties (phonon spectrum density of states, heat capacity) and elastic constants are computed through response function calculations and are in good agreements with the measurements. The electron-phonon coupling effects are also studied. The estimations of linewidth broadening due to electron-phonon coupling along the high-symmetry directions in the first Brillouin zone are given. The linewidth broadening reaches the largest value for Fe optical modes in the vicinity of the X[0.5,0,0] point. The broadening, when compared to those obtained at the other symmetry points, differs by up to two orders of magnitude. From the Boltzmann theory applied to our electronic band structure, we investigate the electrical transport properties. It is found that a purely electronic structure description is incompatible with the record value of the Seebeck coefficient experimentally observed at T approximate to 12 K. The diamagnetic to paramagnetic crossover at a temperature around 100 K is also described from the calculation of the magnetic susceptibility, and results compare well with experiment

A numerical modeling study of the Southern Senegal upwelling shelf: Circulation and upwelling source waters

The regional ocean circulation along the Southern Senegal shelf is studied using a numerical model for varying forcing fields during the upwelling season (November-May). The main objective is to study the shelf circulation of the marine environment in the Southern Senegal Upwelling Shelf (SSUS), the Lagrangian pathways by which waters are transported to the surface in the upwelling tongue and the fate of these waters. Model results are compared with hydrographic measurements during UPSEN2-ECOAO survey and satellite images datasets. The upwelling source waters and also the warm nearshore waters are analyzed, from a Lagrangian point of view, by computing the paths of particles that are passively advected by the regional ocean model velocity field (ROMS). It was found that the model is capable of representing the main characteristics of the SSUS whose Sea Surface Temperature (SST) patterns and their variability have an important similarities but the assessment of the current simulated by the model is less obvious because of the few available observations. The present results suggest that high frequency of wind has a strong influence over the mesoscale patterns of the cross-shore circulation in association with local topography and the presence of the Cape Verde peninsula. These cross-shore circulations are dominated by an onshore flow around 14.5°N and an offshore flow around 14.1°N. The onshore flow is in agreement with the previous eulerian studies regarding the coastal divergence of the surface flow (upwelling) that was strongly localized within a few tens of kilometers south of the Cape Verde in the Hann Bight. Lagrangian experiments show also very clearly that coastal warm waters are upwelling waters that were advected from Hann Bight and underwent a strong warming by the heat flux from the atmosphere to the ocean in a shallow area (∼10 m); therefore, easy to warm up. All numerical solutions have shown a tendency of upwelling particles remaining on the shelf for more than a month. These results may explain the enrichment of water in the SSUS and suggest the need to consider the whole shelf as a retention area

Potential of Sahelian native shrub materials to suppress the spiral nematode Helicotylenchus dihystera

Pearl millet (Pennisetum glaucum) is a drought -tolerant cereal commonly grown for grain and fodder in arid areas throughout the world. Senegalese millet fields are infested with Helicotylenchus. The native evergreen woody shrub Pihostigma retic ulatumi s widely distributed in sub-Saharan Africa. Its coppiced residues are used by small farmers as mulch in crop fields. The shrub's nematicidal effect on the spiral nematode Hehmohdenchus dihystera was evaluated in a pearl millet pot experiment. The abundance of nematodes decreased by 64% after application of either leaf powder or a pulverized mixing of leaves and stems, suggesting the use of aboveground materials of P reficulatum as a potential nematicide. The results show promise for use of a local resotu're. by subsistence farmers in the Sahel. Further research is needed on application to fully develop this approach as a biopesticide

LaAu2 and CeAu2 surface intermetallic compounds grown by high-temperature deposition on Au(111)

We report on the crystal structure and electronic bands of LaAu2 and CeAu2 surface intermetallic compounds grown by high-temperature deposition on Au(111). By scanning-tunneling microscopy we study the formation of different alloy phases as a function of growth temperature and lanthanide coverage. We determine the specific growth conditions to achieve monolayers and bilayers of LaAu2 and CeAu2 with high crystalline quality. Due to lattice mismatch with the underlying Au substrate, both LaAu2 and CeAu2 exhibit long-range moire ́ patterns, which can serve as templates for further nanostructure growth. By angle-resolved photoemission we map the two-dimensional band structure of these surface alloys, discussing the nature of the different spectral features in the light of first-principles calculations