University of Geneva

About: University of Geneva is a education organization based out in Geneva, Switzerland. It is known for research contribution in the topics: Population & Galaxy. The organization has 26887 authors who have published 65265 publications receiving 2931373 citations. The organization is also known as: Geneva University & Universite de Geneve.

Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes

Abstract: Gaia Data Release 1 (Gaia DR1) contains astrometric results for more than 1 billion stars brighter than magnitude 20.7 based on observations collected by the Gaia satellite during the first 14 months of its operational phase. We give a brief overview of the astrometric content of the data release and of the model assumptions, data processing, and validation of the results. For stars in common with the Hipparcos and Tycho-2 catalogues, complete astrometric single-star solutions are obtained by incorporating positional information from the earlier catalogues. For other stars only their positions are obtained by neglecting their proper motions and parallaxes. The results are validated by an analysis of the residuals, through special validation runs, and by comparison with external data. Results. For about two million of the brighter stars (down to magnitude ~11.5) we obtain positions, parallaxes, and proper motions to Hipparcos-type precision or better. For these stars, systematic errors depending e.g. on position and colour are at a level of 0.3 milliarcsecond (mas). For the remaining stars we obtain positions at epoch J2015.0 accurate to ~10 mas. Positions and proper motions are given in a reference frame that is aligned with the International Celestial Reference Frame (ICRF) to better than 0.1 mas at epoch J2015.0, and non-rotating with respect to ICRF to within 0.03 mas/yr. The Hipparcos reference frame is found to rotate with respect to the Gaia DR1 frame at a rate of 0.24 mas/yr. Based on less than a quarter of the nominal mission length and on very provisional and incomplete calibrations, the quality and completeness of the astrometric data in Gaia DR1 are far from what is expected for the final mission products. The results nevertheless represent a huge improvement in the available fundamental stellar data and practical definition of the optical reference frame.

Detecting psychological distress in cancer patients: validity of the Italian version of the Hospital Anxiety and Depression Scale

Abstract: The psychometric properties of the Italian version of the Hospital Anxiety and Depression Scale and its utility as a screening instrument for anxiety and depression in a non-psychiatric setting were evaluated. The questionnaire was administered twice to 197 breast cancer patients randomised in a phase III adjuvant clinical trial: before the start of chemotherapy and at the first follow-up visit. The presence of psychiatric disorders was evaluated at the follow-up visit using the Structured Clinical Interview for DSM-III-R in 132 patients. Factor analyses identified two strictly correlated factors. Crohnbach's alpha for the anxiety and depression scales ranged between 0.80 and 0.85. At follow-up, 50 patients (38%) were assigned a current DSM-III-R diagnosis, in most cases adjustment disorders (24%) or major depressive disorder (10%). Receiver operating characteristics (ROC) analysis was used to test the discriminant validity for both anxiety and depressive disorders. The comparison of the areas under the curve (AUC) between the two scales did not show any difference in identifying either anxiety (P=0.855) or depressive disorders (P=0.357). The 14-item total scale showed a high internal consistency (alpha=0.89 and 0.88) and a high discriminating power for all the psychiatric disorders (AUC=0.89; 95% CI=0.83–0.94). The cut-off point that maximised sensitivity (84%) and specificity (79%) was 10. These results suggest that the total score is a valid measure of emotional distress, so that the Italian version of HADS can be used as a screening questionnaire for psychiatric disorders. The use of the two subscales as a 'case identifier' or as an outcome measure should be considered with caution.

The euro's trade effects

Abstract: This paper reviews and reassesses the methodology and principal findings of the "Rose effect," i.e., the trade effects of currency union, looking at both EMU and non-EMU currency unions. The consensus estimate suggests that the euro has already boosted intra-euro area trade by five to ten percent. The paper discusses a gamut of models that might explain the Rose effect in Europe and suggests a series of empirical test that could help identify the economic mechanisms involved.

Thermoelectric transport in disordered metals without quasiparticles: The Sachdev-Ye-Kitaev models and holography

Abstract: We compute the thermodynamic properties of the Sachdev-Ye-Kitaev (SYK) models of fermions with a conserved fermion number Q. We extend a previously proposed Schwarzian effective action to include a phase field, and this describes the low-temperature energy and Q fluctuations. We obtain higher-dimensional generalizations of the SYK models which display disordered metallic states without quasiparticle excitations, and we deduce their thermoelectric transport coefficients. We also examine the corresponding properties of Einstein-Maxwell-axion theories on black brane geometries which interpolate from either AdS4 or AdS5 to an AdS2×R2 or AdS2×R3 near-horizon geometry. These provide holographic descriptions of nonquasiparticle metallic states without momentum conservation. We find a precise match between low-temperature transport and thermodynamics of the SYK and holographic models. In both models, the Seebeck transport coefficient is exactly equal to the Q derivative of the entropy. For the SYK models, quantum chaos, as characterized by the butterfly velocity and the Lyapunov rate, universally determines the thermal diffusivity, but not the charge diffusivity.

Domain Wall Creep in Epitaxial Ferroelectric P b ( Z r 0.2 T i 0.8 ) O 3 Thin Films

Abstract: Ferroelectric switching and nanoscale domain dynamics were investigated using atomic force microscopy on monocrystalline $\mathrm{P}\mathrm{b}\mathrm{(}\mathrm{Z}{\mathrm{r}}_{\mathrm{0.2}}\mathrm{T}{\mathrm{i}}_{\mathrm{0.8}}\mathrm{)}{\mathrm{O}}_{\mathrm{3}}$ thin films. Measurements of domain size versus writing time reveal a two-step domain growth mechanism, in which initial nucleation is followed by radial domain wall motion perpendicular to the polarization direction. The electric field dependence of the domain wall velocity demonstrates that domain wall motion in ferroelectric thin films is a creep process, with the critical exponent $\ensuremath{\mu}$ close to 1. The dimensionality of the films suggests that disorder is at the origin of the observed creep behavior.