130,775 research outputs found
In Field Application of an Innovative Sensor for Monitoring Road and Runway Surfaces
No full textWater and ice detection over road and runway surfaces is important to improve traffic safety and to reduce maintenance costs. An innovative low cost capacitive sensor was endowed with an algorithm based on the time derivative of the measured capacitance to indicate the transitions between dry, wet, or icy state of road and runway surfaces. The sensor was investigated theoretically and validated with experiments on field
Crystal structure and revision of the chemical formula of georgiadesite, Pb4(AsO3)Cl4(OH)
No full textThe crystal structure of the rare secondary lead mineral georgiadesite has been solved from single-crystal X-ray diffraction data (R = 0.071). The structure can be visualized in terms of alternating puckered (100) layers of [Pbφ6] octahedra and [Pbφ8] bicapped trigonal prisms (φ = generic anion). Lead also occurs in irregular, lopsided polyhedra. This structural study shows unambiguously that arsenic occurs as As3+ and not as As5+. The chemical formula of georgiadesite has therefore been revised, on structural grounds, to Pb4(AsO3)Cl4(OH)
Crystal structure refinement of mendipite, Pb3O2Cl2
No full textThe crystal structure of mendipite from the Mendip Hills (UK) was refined in the space group Pnma, using single-crystal X-ray diffraction data, to R-F = 0.078. The refined unit cell parameters are a = 11.905(2), b = 5.817(1), c = 9.542(2) Angstrom, Z = 4. The structure corresponds to that of synthetic Pb3O2Cl2, and differs from the previously proposed model for natural mendipite. In mendipite three independent and irregular [Pb phi (6)] and [Pb phi (7)] polyhedra (phi = generic anion) occur. Cation-anion distances are spread over a wide range, due to the lone-pair effect of Pb2+, resulting in (4+2) and (4+3) coordinations for the lead atoms. In the structure of mendipite, columnar arrangement of lead-centered polyhedra is realized, and columns alternate with structural voids
Crystal structures of two iron-containing minerals: sturmanite and biraite-(Ce) (a new mineral)
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D. S. Avalle, "Cultura e lingua francese delle origini nella 'Passion' di Clermont-Ferrand
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