Barrier breakdown in a multiple quantum well structure

We explore a regime of unipolar electronic transport in a multiple quantum well structure with very large current discontinuities - up to five orders of magnitude. Magneto-transport experiments reveal different transport regimes. Quantum well impact ionization shifts the structure from a resistive down state, where the current flows through inter-well quantum tunneling, to a highly conductive up state. In the latter regime, the current leaks through a barrier suddenly broken down because of an efficient ionization of the first quantum well.Comment: 16 pages, 5 figure

The NWCSAF/GEO software package for the MSG/IODC satellite service

Póster presentado en: EUMETSAT Meteorological Satellite Conference celebrada del 2 al 6 de Octubre de 2017 en Roma

Use of NWCSAF NWC/GEO Software Package with MSG, HIMAWARI-8/9 and GOES-13/16 Satellites

Ponencias presentadas en: Joint EUMETSAT/AMS/NOAA Conference 2019 celebrada en Boston del 30 de septiembre al 4 de octubre de 2019

The nowcasting SAF products and services: recent improvements in the new SW packages PPS v2018 and GEO v2018 and future plans

Presentación realizada en la 3rd European Nowcasting Conference, celebrada en la sede central de AEMET en Madrid del 24 al 26 de abril de 2019

Alleanze e parentele Le “affinità elettive” nella storiografia sulla Sicilia antica. Atti del Convegno internazionale Palermo 14-15 aprile 2010

Nel 1966, parlando della Sicilia, Fernand Braudel la definiva un “continente in miniatura”, assegnandole già quelle caratteristiche di microcosmo che ne hanno fatto, nel corso dei secoli, un laboratorio privilegiato d’indagine sulle dinamiche d’interazione tra le civiltà antiche. Per la sua posizione, centrale e facilmente accessibile dal mare, per le sue dimensioni, per la fertilità del suo territorio, l’isola diventò presto crocevia di uomini, terreno d’incontro e di scontro tra città ma anche tra ethne di origine diversa. Se, da un lato è vero che le vicende della Sicilia possono leggersi attraverso i momenti di conflitto e di cesura che, di volta in volta, la attraversarono; dall’altro, altrettanto paradigmatici sono quei fenomeni di convergenza e di “associazione” che ne segnarono la storia. La chiave delle alleanze e delle parentele costituisce dunque una lente, come un’altra, attraverso cui rileggere la storiografia antica e moderna sull’isola: il modo in cui forme di aggregazioni reali o fittizie si autorappresentarono o vennero rappresentate dagli storici antichi e dalle riletture dei moderni

Kinship diplomacy between Sicily and Rome

"The phenomenon of kinship diplomacy, if not perfectly defined, is nonetheless widely understood and extensively studied. The presence of kinship diplomacy in the political interactions between Rome and other Mediterranean states has in turn received specific treatment. At the same time, the extent of kinship claims in the island of Sicily and the associated claims about origines made by many of the communities on the island have also been studied in very considerable detail. In other words, this paper does not intend to cover new ground – indeed, the individual case studies upon which I shall focus have themselves been the objects of considerable attention. However, it is fair to state that the several instances of kinship diplomacy which can be documented between Sicilian communities and Rome have so far not been considered as an ensemble (although individually often considered in relation to one or more of the other instances). In itself, that would not necessarily be sufficient reason to justify a fresh study. The further argument that the Sicilian cases deserve to be better known, not least because they present a number of unusual features, could likewise be dismissed as special pleading. A more serious argument however remains, and this is that consideration of the Sicilian cases in their own right, and as a group, strongly suggests a more diverse and earlier use of the phenomenon of kinship diplomacy, in relation to Rome, than is commonly accepted." (From the Introduction

Observations of the Ushant front displacements with MSG/SEVIRI derived sea surface temperature data

International audienceHourly Sea Surface Temperature (SST) fields derived from the Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) onboard Meteosat Second Generation (MSG) are frequently used in studies of the diurnal cycle of the ocean. In this article, we focus on high frequency SST variability induced by tidal currents in the Iroise Sea, west of Brittany (France). This region is known for its strong tidal currents that are responsible in summer for the generation of an intense thermal front, the Ushant front. We use hourly MSG/SEVIRI derived SST to compute the displacements of this front. In the northern part of the front, at 48.75°N, we show that the longitudinal displacements of the front on subdiurnal time scales can be explained by the Lagrangian advection induced by surface currents.We also present maps of surface currents computed from hourly SEVIRI derived SST data using the Maximum Cross Correlation (MCC) method. Comparison of SEVIRI derived velocities with velocities obtained with high frequency (HF) radar measurements and a hindcast numerical simulation (Mercator Ocean) gives encouraging results in the northern part of the Ushant front, near the Ushant Island. Within that region, the mean bias of the SEVIRI velocities was below 0.12 m·s− 1, with the standard deviation ranging from 0.26 m·s− 1 during moderate tides to 0.49 m·s− 1 during spring tides. Further offshore, where the surface thermal structures are weaker and the SST more homogeneous, currents derived using the MCC method were overestimated by 0.3 m·s− 1 and showed larger error standard deviations

Combining model and geostationary satellite data to reconstruct hourly \{SST\} field over the Mediterranean Sea

Abstract This work focuses on the reconstruction of Sea Surface Temperature (SST) diurnal cycle through combination of numerical model analyses and geostationary satellite measurements. The approach takes advantage of geostationary satellite observations as the diurnal signal source to produce gap-free optimally interpolated (OI) hourly \{SST\} fields using model analyses as first-guess. The resulting \{SST\} anomaly field (satellite-model) is free, or nearly free, of any diurnal cycle, thus allowing one to interpolate \{SST\} anomalies using satellite data acquired at different times of the day. The method is applied to reconstruct the hourly Mediterranean \{SST\} field during summer 2011 using \{SEVIRI\} data and Mediterranean Forecasting System analyses. A synthetic cloud reconstruction experiment demonstrated that the \{OI\} \{SST\} method is able to reconstruct an unbiased \{SST\} field with a RMS = 0.16 °C with respect to \{SEVIRI\} observations. The \{OI\} interpolation estimate, the model first guess and the \{SEVIRI\} data are evaluated using drifter and mooring measurements. Special attention is devoted to the analysis of diurnal warming (DW) events that are particularly frequent in the Mediterranean Sea. The model reproduces quite well the Mediterranean \{SST\} diurnal cycle, except for the \{DW\} events. Due to the thickness of the model surface layer, the amplitude of the model diurnal cycle is often less intense than the corresponding \{SEVIRI\} and drifter observations. The Diurnal \{OI\} \{SST\} (DOISST) field, resulting from the blending of model and \{SEVIRI\} data via optimal interpolation, reproduces well the diurnal cycle including extreme \{DW\} events. The evaluation of \{DOISST\} products against drifter measurements results in a mean bias of − 0.07 °C and a \{RMS\} of 0.56 °C over interpolated pixels. These values are very close to the corresponding statistical parameters estimated from \{SEVIRI\} data (bias = − 0.16 °C, RMS = 0.47 °C). Results also confirm that part of the mean bias between temperature measured by moorings at 1 m depth and the satellite observations can be ascribed to the different nature of the measurements (bulk versus skin)

Simulation of African dust properties and radiative effects during the 2015 SHADOW campaign in Senegal

International audienc

Characterizing the regional contribution to PM10 pollution over northern France using two complementary approaches: Chemistry transport and trajectory-based receptor models

International audienc