Structure of the southern Senegalo-Mauritanian basin, West Africa, from geoelectrical studies

L'interprétation des données magnétotelluriques (MT) a permis de mettre en évidence les caractéristiques électriques, l'épaisseur et la structure de la partie sud du bassin sénégalo-mauritanien. L'utilisation de données de forages a fourni un modèle simplifié des unités géo-électriques du bassin qui montre des sédiments de faible résistivité, saturés d'eau et non consolidés (Résumé d'auteur

Geologic sections across the onshore Senegal - Mauritania basin derived from geoelectric studies

La structure géoélectrique régionale du bassin sédimentaire du Sénégal-Mauritanie a été déterminée au moyen de modèles magnétotelluriques à deux dimensions établis sur trois lignes transversales. Un modèle schématique de la structure sédimentaire générale du Sénégal a été élaboré à partir des enseignements fournis par les coupes géoélectriques couplés avec les données lithologiques et électriques des puits de forage. L'étude suggère que le bassin est formé d'un pli monoclinal ouvert, incliné vers l'ouest, dans lequel la structure est contrôlée par les failles du socle orientées nord-sud offrant un style structural en escalier

New Circularly Polarized Matrix Antenna For Space Applications

International audiencethis paper presents a new electromagnetic approach of matrix antenna, specialized for circularly polarized space applications. The design of the proposed antenna matrix is based on small pixels which generate circular polarization field. The concept of the pixels is well demonstrated as a patent and verified for the use in antenna arrays. The design will be used for several space applications with directive and wide angle beams. Index Terms—antenna array, axial ratio, beam forming, Isoflux, Electromagnetic band gap material EBG, Frequency selective surface FSS

Unit-cell for dual-circular polarisation reflectarrays

International audience—A new unit-cell composed of two layers for dual-CP reflectarrays is proposed for the first time with the unique capability to reflect independently and simultaneously the two incident circular polarisations at the same frequency. The experimental results demonstrate that this unit-cell exhibits a 3.8% bandwidth around 8.4 GHz for a phase resolution better than 1.92 bits in LHCP and in RHCP. As a first step towards a reflectarray in dual-CP, this innovative unit-cell is studied in an array configuration. To increase the value of the maximum incidence angle up to 30°, a matching dielectric layer is placed over the cell

Is adhesion superficial? Silicon wafers as a model system to study van der Waals interactions

Adhesion is a key issue for researchers of various fields, it is therefore of uppermost importance to understand the parameters that are involved. Commonly, only surface parameters are employed to determine the adhesive forces between materials. Yet, van der Waals forces act not only between atoms in the vicinity of the surface, but also between atoms in the bulk material. In this review, we describe the principles of van der Waals interactions and outline experimental and theoretical studies investigating the influence of the subsurface material on adhesion. In addition, we present a collection of data indicating that silicon wafers with native oxide layers are a good model substrate to study van der Waals interactions with coated materials

Pitt on a Pedestal: Sculpture and Slavery in Late-Eighteenth-Century Charleston

On July 5, 1770, South Carolina raised its first public sculpture. Representing the English statesman William Pitt the Elder in the mode of a classical orator, the marble statue stood on a pedestal at the intersection of Meeting and Broad Streets, in Charleston’s historic Civic Square. This essay reconstructs the significance of its location and its competing meanings within the colonial slave city. It examines how the statue functioned to reflect the racial politics of elite Charlestonians while illuminating the cultures of surveillance, discipline, and display that linked black and white bodies. At the symbolic center of the urban landscape, the figure of Pitt exposed the implicated nature of neoclassical sculpture and transatlantic slavery

Biogeochemical spatio-temporal transformation of copper in <i>Aspergillus niger</i> colonies grown on malachite with different inorganic nitrogen sources

This work elucidates spatio-temporal aspects of the biogeochemical transformation of copper mobilized from malachite (Cu2 (CO3 )(OH)2 ) and bioaccumulated within Aspergillus niger colonies when grown on different inorganic nitrogen sources. It was shown that the use of either ammonium or nitrate determined how copper was distributed within the colony and its microenvironment and the copper oxidation state and succession of copper coordinating ligands within the biomass. Nitrate-grown colonies yielded ∼1.7× more biomass, bioaccumulated ∼7× less copper, excreted ∼1.9× more oxalate and produced ∼1.75× less water-soluble copper in the medium in contrast to ammonium-grown colonies. Microfocus X-ray absorption spectroscopy (XAS) revealed that as the mycelium matured, bioaccumulated copper was transformed from less stable and more toxic Cu(I) into less toxic Cu(II) which was coordinated predominantly by phosphate/malate ligands. With time, a shift to oxalate coordination of bioaccumulated copper occurred in the central older region of ammonium-grown colonies. This article is protected by copyright. All rights reserved.</p

Islamic Relief Organizations: Between 'Islamism' and 'Humanitarianism'

The predominant conception of international aid remains anchored in a dualistic vision of the world: a 'North' considered wealthy and developed comes to the rescue of a poor and under-developed 'South'. The 'civilizing' missions that justified 19th-century imperialism were substituted by themes - such as 'third world-ism' and development aid - of the second half of the 20th century. After the Biafra war, defence of fundamental human rights begins to justify claims to the 'right to intervene' as practised by nongovernmental organizations, such as Doctors without Borders, setting the tone for what humanitarian action should be