Giant optical birefringence of semiconductor nanowire metamaterials

Semiconductor nanowires exhibit large polarization anisotropy for the absorption and emission of light, making them ideal building blocks for novel photonic metamaterials. Here, we demonstrate that a high density of aligned nanowires exhibits giant optical birefringence, a collective phenomenon observable uniquely for collections of wires. The nanowire material was grown on gallium phosphide (GaP) (111) in the form of vertically standing GaP nanowires. We obtain the largest optical birefringence to date, with a difference between the in-plane and out-of-plane refractive indices of 0.80 and a relative birefringence of 43%. These values exceed by a factor of 75 the natural birefringence of quartz and a by more than a factor of two the highest values reported so far in other artificial materials. By exploiting the specific crystallographic growth directions of the nanowires on the substrate, we further demonstrate full control over the orientation of the optical birefringence effect in the metamaterial.Comment: 10 pages, 4 figure

Volcanic Risk System (SRV): ASI Pilot Project to Support The Monitoring of Volcanic Risk In Italy by Means of EO Data

The ASI-SRV(Sistema Rischio Vulcanico) project started at the beginning of the 2007 is funded by the Italian Space Agency (ASI) in the frame of the National Space Plan 2003-2005 under the Earth Observations section for natural risks management. Coordinated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), which is responsible at national level for the volcanic monitoring, the project has as main objective to develop a pre-operative system based on EO data and ground measurements integration to support the volcanic risk monitoring of the Italian Civil Protection Department. The project philosophy is to implement specific modules which allow to process, store and visualize through Web GIS tools EO derived parameters considering three activity phases: 1) knowledge and prevention; 2) crisis; 3) post crisis. In order to combine effectively the EO data and the ground networks measurements the system will implement a multi-parametric analysis tool, which represents and unique tool to analyze contemporaneously a large data set of data in “near real time”. The SRV project will be tested his operational capabilities on three Italian Volcanoes: Etna,Vesuvio and Campi Flegrei

Coulomb effects in tunneling through a quantum dot stack

Tunneling through two vertically coupled quantum dots is studied by means of a Pauli master equation model. The observation of double peaks in the current-voltage characteristic in a recent experiment is analyzed in terms of the tunnel coupling between the quantum dots and the coupling to the contacts. Different regimes for the emitter chemical potential indicating different peak scenarios in the tunneling current are discussed in detail. We show by comparison with a density matrix approach that the interplay of coherent and incoherent effects in the stationary current can be fully described by this approach.Comment: 6 pages, 6 figure

Volcanic Risk System (SRV): ASI Pilot Project to Support The Monitoring of Volcanic Risk In Italy by Means of EO Data

The ASI-SRV(Sistema Rischio Vulcanico) project started at the beginning of the 2007 is funded by the Italian Space Agency (ASI) in the frame of the National Space Plan 2003-2005 under the Earth Observations section for natural risks management. Coordinated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), which is responsible at national level for the volcanic monitoring, the project has as main objective to develop a pre-operative system based on EO data and ground measurements integration to support the volcanic risk monitoring of the Italian Civil Protection Department. The project philosophy is to implement specific modules which allow to process, store and visualize through Web GIS tools EO derived parameters considering three activity phases: 1) knowledge and prevention; 2) crisis; 3) post crisis. In order to combine effectively the EO data and the ground networks measurements the system will implement a multi-parametric analysis tool, which represents and unique tool to analyze contemporaneously a large data set of data in “near real time”. The SRV project will be tested his operational capabilities on three Italian Volcanoes: Etna,Vesuvio and Campi Flegrei.I.N.G.V. - O.V. SEZIONE DI NAPOLI I.R.E.A. - C.N.R. E.S.A. A.S.I.PublishedNapoli1.10. TTC - Telerilevamentoope

Volcanic Risk System (SRV): ASI Pilot Project to Support The Monitoring of Volcanic Risk In Italy by Means of EO Data

The ASI-SRV(Sistema Rischio Vulcanico) project started at the beginning of the 2007 is funded by the Italian Space Agency (ASI) in the frame of the National Space Plan 2003-2005 under the Earth Observations section for natural risks management. Coordinated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), which is responsible at national level for the volcanic monitoring, the project has as main objective to develop a pre-operative system based on EO data and ground measurements integration to support the volcanic risk monitoring of the Italian Civil Protection Department. The project philosophy is to implement specific modules which allow to process, store and visualize through Web GIS tools EO derived parameters considering three activity phases: 1) knowledge and prevention; 2) crisis; 3) post crisis. In order to combine effectively the EO data and the ground networks measurements the system will implement a multi-parametric analysis tool, which represents and unique tool to analyze contemporaneously a large data set of data in “near real time”. The SRV project will be tested his operational capabilities on three Italian Volcanoes: Etna,Vesuvio and Campi Flegrei

Recent deformation at Campi Flegrei caldera (Italy) detected by DinSar and leveling techniques

The Campi Flegrei caldera, a volcanic and densely populated area located to the west of Napoli (Italy), was characterized by rapid ground deformation during 1970-72 and 1982-84, for a total amount of 3.5 m in the city of Pozzuoli. Since 1985 a slow deflation was active, with episodic microcrises of uplifts. A new and consistent uplift event is now going on, beginning in November 2004, as revealed by spatial and terrestrial geodetic techniques. In particular, we adopt almost all the available ENVISAT ASAR data acquired from both ascending and descending orbits during 2002-2006, to generate mean deformation velocity maps and time series with spatial resolution of about 100 m. The maps are computed following the Small BAseline Subset (SBAS) approach (Berardino et al., 2002), that implements an appropriate combination of differential interferograms generated from SAR data pairs (60 SAR images for this work). In addition to satellite observations, we show data from the high precision levelling network of the INGV-Osservatorio Vesuviano, consisting in about 320 benchmarks. Levelling measurements are regularly carried out on both the whole network and along the coast line; in case of a bradyseismic crisis, the temporal sampling is strongly increased. Both DInSAR and levelling data evidence the maximum value of the vertical displacement near the city of Pozzuoli. We model the observed deformation by means of 3D pressurized point-source and extended source, performing inversions to constrain their shape and location. The resulting sources are also compared with that inverted for the 1982-84 unrest.UnpublishedWienope

Monitoring of Land Subsidence in Ravenna Municipality Using Integrated SAR - GPS Techniques: Description and First Results

The Emilia Romagna Region (N-E Italy) and in particular the Adriatic Sea coastline of Ravenna, is affected by a noticeable subsidence that started in the 1950s, when the exploitation of on and off-shore methane reservoirs began, along with the pumping of groundwater for industrial uses. In such area the current subsidence rate, even if lower than in the past, reaches the -2 cm/y. Over the years, local Authorities have monitored this phenomenon with different techniques: spirit levelling, GPS surveys and, more recently, Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques, confirming the critical situation of land subsidence risk. In this work, we present the comparison between the results obtained with DInSAR and GPS techniques applied to the study of the land subsidence in the Ravenna territory. With regard to the DInSAR, the Small Baseline Subset (SBAS) and the Coherent Pixel Technique (CPT) techniques have been used. Different SAR datasets have been exploited: ERS-1/2, ENVISAT, TerraSAR-X and Sentinel-1. Some GPS campaigns have been also carried out in a subsidence prone area. 3D vertices have been selected very close to existing persistent scatterers in order to link the GPS measurement results to the SAR ones. GPS data were processed into the International reference system and the comparisons between the coordinates, for the first 6 months of the monitoring, provided results with the same trend of the DInSAR data, even if inside the precision of the method

Barriers and facilitators to adherence to group exercise in institutionalized older people living with dementia: a systematic review

Objectives Research suggests targeted exercise is important for people living with dementia, especially those living in residential care. The aim of this review was to collect and synthesize evidence on the known barriers and facilitators to adherence to group exercise of institutionalized older people living with dementia. Methods We searched all available electronic databases. Additionally, we searched trial registries (clinicaltrial.gov, and WHO ICTRP) for ongoing studies. We searched for and included papers from January 1990 until September 2017 in any language. We included randomized, non-randomized trials. Studies were not eligible if participants were either healthy older people or people suffering from dementia but not living in an institution. Studies were also excluded if they were not focused on barriers and facilitators to adherence to group exercise. Results Using narrative analysis, we identified the following themes for barriers: bio-medical reasons and mental wellbeing and physical ability, relationships dynamics, and socioeconomic reasons. The facilitators were grouped under the following thematic frames: bio-medical benefits and benefits related to physical ability, feelings and emotions and confidence improvements, therapist and group relationships dynamics and activity related reasons. Conclusions We conclude that institutionalized older people living with dementia, even those who are physically frail, incontinent and/or have mild dementia can demonstrate certain level of exercise adherence, and therefore can respond positively to exercise programs. Tailored, individually-adjusted and supported physical activity, led by a knowledgeable, engaging and well communicating therapist/facilitator improves the adherence to group exercise interventions of institutionalized older people living with dementia

Recent deformation at Campi Flegrei caldera (Italy) detected by DinSar and leveling techniques

The Campi Flegrei caldera, a volcanic and densely populated area located to the west of Napoli (Italy), was characterized by rapid ground deformation during 1970-72 and 1982-84, for a total amount of 3.5 m in the city of Pozzuoli. Since 1985 a slow deflation was active, with episodic microcrises of uplifts. A new and consistent uplift event is now going on, beginning in November 2004, as revealed by spatial and terrestrial geodetic techniques. In particular, we adopt almost all the available ENVISAT ASAR data acquired from both ascending and descending orbits during 2002-2006, to generate mean deformation velocity maps and time series with spatial resolution of about 100 m. The maps are computed following the Small BAseline Subset (SBAS) approach (Berardino et al., 2002), that implements an appropriate combination of differential interferograms generated from SAR data pairs (60 SAR images for this work). In addition to satellite observations, we show data from the high precision levelling network of the INGV-Osservatorio Vesuviano, consisting in about 320 benchmarks. Levelling measurements are regularly carried out on both the whole network and along the coast line; in case of a bradyseismic crisis, the temporal sampling is strongly increased. Both DInSAR and levelling data evidence the maximum value of the vertical displacement near the city of Pozzuoli. We model the observed deformation by means of 3D pressurized point-source and extended source, performing inversions to constrain their shape and location. The resulting sources are also compared with that inverted for the 1982-84 unrest

Single quantum dot nanowire LEDs

We report reproducible fabrication of InP-InAsP nanowire light emitting diodes in which electron-hole recombination is restricted to a quantum-dot-sized InAsP section. The nanowire geometry naturally self-aligns the quantum dot with the n-InP and p-InP ends of the wire, making these devices promising candidates for electrically-driven quantum optics experiments. We have investigated the operation of these nano-LEDs with a consistent series of experiments at room temperature and at 10 K, demonstrating the potential of this system for single photon applications