University of Cagliari

About: University of Cagliari is a education organization based out in Cagliari, Italy. It is known for research contribution in the topics: Population & Dopamine. The organization has 11029 authors who have published 29046 publications receiving 771023 citations. The organization is also known as: Università degli Studi di Cagliari & Universita degli Studi di Cagliari.

Measurements of the S-wave fraction in B 0 → K + π − μ + μ − decays and the B 0 → K ∗ (892) 0 μ + μ − differential branching fraction

Abstract: A measurement of the differential branching fraction of the decay B0→K∗(892)0μ+μ− is presented together with a determination of the S-wave fraction of the K+π− system in the decay B0→K+π−μ+μ−. The analysis is based on pp-collision data corresponding to an integrated luminosity of 3\,fb−1 collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, q2. Precise theoretical predictions for the differential branching fraction of B0→K∗(892)0μ+μ− decays are available for the q2 region 1.1

A Cenozoic-style scenario for the end-Ordovician glaciation.

Abstract: The end-Ordovician was an enigmatic interval in the Phanerozoic, known for massive glaciation potentially at elevated CO 2 levels, biogeochemical cycle disruptions recorded as large isotope anomalies and a devastating extinction event. Ice-sheet volumes claimed to be twice those of the Last Glacial Maximum paradoxically coincided with oceans as warm as today. Here we argue that some of these remarkable claims arise from undersampling of incomplete geological sections that led to apparent temporal correlations within the relatively coarse resolution capability of Palaeozoic biochronostratigraphy. We examine exceptionally complete sedimentary records from two, low and high, palaeolatitude settings. Their correlation framework reveals a Cenozoic-style scenario including three main glacial cycles and higher-order phenomena. This necessitates revision of mechanisms for the end-Ordovician events, as the first extinction is tied to an early phase of melting, not to initial cooling, and the largest d 13 C excursion occurs during final deglaciation, not at the glacial apex.

Cationic distribution and spin canting in CoFe2O4 nanoparticles.

Abstract: CoFe(2)O(4) nanoparticles ( D(NPD) ~6 nm), prepared by a thermal decomposition technique, have been investigated through the combined use of dc magnetization measurements, neutron diffraction, and (57)Fe Mossbauer spectrometry under high applied magnetic field. Despite the small particle size, the value of saturation magnetization at 300 K (M(s) = 70 A m(2) kg(-1)) and at 5 K (M(s) = 100 A m(2) kg(-1)) are rather close to the bulk values, making the samples prepared with this method attractive for biomedical applications. Neutron diffraction measurements indicate the typical ferrimagnetic structure of the ferrites, showing an inversion degree (γ(NPD) = 0.74) that is in very good agreement with cationic distribution established from low temperature (10 K) Mossbauer measurements in high magnetic field (γ(moss) = 0.76). In addition, the in-field Mossbauer spectrum shows the presence of a non-collinear spin structure in both A and B sublattices. The results allow us to explain the high value of saturation magnetization and provide a better insight into the complex interplay between cationic distribution and magnetic disorder in ferrimagnetic nanoparticles.

Electronic structure of divalent hexaborides

Abstract: Recent experiments suggest that divalent hexaborides like SrB6 and CaB6, traditionally considered small-gap semiconductors, can actually be semimetals. We calculate the structural and electronic properties of SrB6, CaB6 and of ferromagnetic EuB6, using the full-potential linearized augmented plane wave (FLAPW) method, within the local (spin) density approximation. The lattice constants and internal parameters are in very good agreement with the measured ones. Because of a small band overlap at the X point, all the materials are semimetals. The calculated Hall coefficient for SrB6 changes sign around zero doping, and has the freeelectron value for doping beyond ≈ 1.5%. The plasma frequency has a minimum at zero doping. We interpret the high-temperature transport properties of SrB6 and CaB6 in terms of a thermal gap deduced from the shape of the density of states around the Fermi energy. We also calculate the imaginary part of the dielectric function for SrB6, which can be compared to recent experiments.