Surface effects on the statistics of the local density of states in metallic nanoparticles: manifestation on the NMR spectra

In metallic nanoparticles, shifts in the ionization energy of surface atoms with respect to bulk atoms can lead to surface bands. Within a simple Tight Binding model we find that the projection of the electronic density of states on these sites presents two overlapping structures. One of them is characterized by the level spacing coming from bulk states and the other arises from the surface states. In very small particles, this contributes to an over-broadening of the NMR absorption spectra, determined by the Knight shift distribution of magnetic nuclei. We compare our calculated Knight shifts with experiments on aluminum nanoparticles, and show that the deviation of the scaling law as a function of temperature and particle size can be explained in terms of surface states.Comment: 1 tar.gz fil

Populations réfugiées : de l'exil au retour

L'Etat somalien n'existe plus depuis 1991. La coalition qui avait contraint Siyaad Barre à fuir, s'est rompue : l'ex-Somaliland a proclamé son indépendance tandis que le Sud demeure déchiré entre seigneurs de la guerre. Pourtant, la Somalie est sans doute l'Etat-nation le plus homogène d'Afrique sub-saharienne. Marqués par l'élevage nomade et la division en clans, les Somali sont-ils condamnés à ne jamais former un Etat ? En dépit de leur tradition, ancienne, de mobilité et de migrations, ils ont fondé, sur leur territoire actuel, des cités-Etats, des émirats et des sultanats. (Résumé d'auteur

Higgs boson production via vector-like top-partner decays: diphoton or multilepton plus multijets channels at the LHC

We first build a minimal model of vector-like quarks where the dominant Higgs boson production process at LHC -- the gluon fusion -- can be significantly suppressed, being motivated by the recent stringent constraints from the search for direct Higgs production over a wide Higgs mass range. Within this model, compatible with the present experimental constraints on direct Higgs searches, we demonstrate that the Higgs ($h$) production via a heavy vector-like top-partner ($t_2$) decay, $pp \to t_2 \bar t_2$, $t_2\to t h$, allows to discover a Higgs boson at the LHC and measure its mass, through the decay channels $h\to \gamma\gamma$ or $h\to ZZ$. We also comment on the recent hint in LHC data from a possible $\sim 125$ GeV Higgs scalar, in the presence of heavy vector-like top quarks.Comment: 14 pages, 8 figure

Application of large area SiPMs for the readout of a plastic scintillator based timing detector

In this study an array of eight 6 mm x 6 mm area SiPMs was coupled to the end of a long plastic scintillator counter which was exposed to a 2.5 GeV/c muon beam at the CERN PS. Timing characteristics of bars with dimensions 150 cm x 6 cm x 1 cm and 120 cm x 11 cm x 2.5 cm have been studied. An 8-channel SiPM anode readout ASIC (MUSIC R1) based on a novel low input impedance current conveyor has been used to read out and amplify SiPMs independently and sum the signals at the end. Prospects for applications in large-scale particle physics detectors with timing resolution below 100 ps are provided in light of the results

Application of large area SiPMs for the readout of a plastic scintillator based timing detector

In this study an array of eight 6 mm x 6 mm area SiPMs was coupled to the end of a long plastic scintillator counter which was exposed to a 2.5 GeV/c muon beam at the CERN PS. Timing characteristics of bars with dimensions 150 cm x 6 cm x 1 cm and 120 cm x 11 cm x 2.5 cm have been studied. An 8-channel SiPM anode readout ASIC (MUSIC R1) based on a novel low input impedance current conveyor has been used to read out and amplify SiPMs independently and sum the signals at the end. Prospects for applications in large-scale particle physics detectors with timing resolution below 100 ps are provided in light of the results

320g Ionization-Heat Cryogenic Detector for Dark Matter Search in the EDELWEISS Experiment

The EDELWEISS experiment used in 2001 a 320g heat-and-ionization cryogenic Ge detector operated in a low-background environment in the Laboratoire Souterrain de Modane for direct WIMP detection. This detector presents an increase of more than 4 times the mass of previous detectors. Calibrations of this detector are used to determine its energy resolution and fiducial volume, and to optimize the detector design for the 1kg phase of the EDELWEISS-I experiment. Analysis of the calibrations and characteristics of a first series of 320g-detectors are presented.Comment: 4 pages, 3 figure

A Case of Urogenital Human Schistosomiasis from a Non-endemic Area

© 2015 Calvo-Cano et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article