1,721,498 research outputs found
The Cold Waters in the Port of Genoa (NW Mediterranean Sea) during the Marine Heatwave in Summer 2022
No full textExtreme weather phenomena have become more frequent and intense in recent decades in the context of climate change, and these include heat waves that affect both the atmosphere and seawater masses. In 2022, a summer marine heatwave (MHW) affected the entire Mediterranean Sea, and temperatures up to 5 °C above seasonal mean were reached in the Ligurian Sea in the NW part of the Mediterranean basin. In this scenario, the waters of the Port of Genoa (at the northern apex of the Ligurian Sea) distinguished themselves by maintaining lower temperatures than those of the open sea (a maximum gradient of −6.1 °C on 9 August 2022) after the passage of a fast-moving storm. In this study, the weather and sea parameters of the period (June–December 2022) are analysed to determine the phenomenon that caused the drop in temperatures in the water masses of the Port of Genoa. The sudden cooling of the water masses inside the port was caused by a heavy rainfall event in early August. Moreover, the isolation of the port water masses due to the weak dynamics of the period kept them stationary and locked inside the port. Seawater temperatures inside the port slowly rose again after the event, remaining cooler than outside temperatures throughout August (−0.3 °C on 31 August), reaching and exceeding outside temperatures on 3 September (26.4 °C), and remaining warmer until 3 November 2022 (21.5 °C)
Baseline on rare earth elements in the marine sediments of a Mediterranean commercial port as environmental tracers and their relationships with inorganic contaminants
No full textThe Port of Genoa (north-western Mediterranean Sea) receives sediments from two different catchment areas
(Bisagno and Polcevera torrents). The aim of the work is to evaluate if Rare Earth Elements (REEs) could be used to identify the two sedimentary inputs and to unravel the origin of inorganic contaminants in an anthropised basin. REE results constitute a baseline for this port. The main REE-bearing minerals are phosphates and zircon. As, Cd, Hg, Pb, and Sn concentrate in the sediments closer to the Bisagno Torrent mouth, and the correlation with Ca and Light-REEs suggests their plausible geological origin. Co, Mn, and Ni maxima lie in the sediments closer to the Polcevera Torrent. Their correlation with Middle-REEs and Mg suggest that ophiolitic rocks could explain their presence. Cr, Cu, V, and Zn do not show a clear correlation with REEs, and their origin probably is a combination of natural and anthropogenic sources
Use of microseismic data to monitor significant sea wave heights in support of marine weather forecasting and coastal protection
No full textThe focus of the Ph.D. project was the implementation of a network for monitoring significant sea wave heights (Hs) along the Ligurian coasts (north-western Mediterranean Sea), in order to provide near-real time data to weather forecasters and sea users (vessel captains, pilots, Coast Guard, Port Authorities and yachtsmen). The project was divided into a part dedicated to the use of microseismic data, interfaced with data derived from modelling hindcasts and from the wave buoy of Capo Mele, for the determination of Hs, and a part dedicated to the Interreg Italy-France Maritime 2014-2020 SINAPSI "Assistance to navigation for safe access to ports” Project, which involves the installation of instruments for measuring weather and sea parameters along the coasts of the Ligurian Sea.
The first phase of the Ph.D. project involved the study and updating of a mathematical procedure for the estimation of Hs from the microseismic data recorded by the network of seismic stations along the Ligurian arch. The procedure exploited the existing relationship between sea wave heights and microseismic signal and included the use of hindcast data to calibration steps and data from the Capo Mele wave buoy to verify the reliability of the estimated Hs data. In October 2018, an extreme sea storm hit the Ligurian coast with waves characterised by Hs greater than 6 m; these wave heights were not matched by an equivalent energy in the microseismic signal, which therefore led to an underestimation of the Hs estimated by the procedure. It was therefore necessary to investigate the extreme event of 2018, which led to the evidence of a lack in the energy of the microseismic signal and the need for a data compensation, which was possible thanks to the use of weather data (wind speed and atmospheric pressure) that were included in an additional element to the estimation procedure. The second phase of the Ph.D. project therefore involved verifying the reliability of the data estimated by the procedure, which led to the evidence of a generic underestimation of Hs. This led to the study of a first modification of the procedure and to the consequent monitoring of its validity on a large time scale. The monitoring of the reliability of the estimated data will be continued after the end of the Ph.D., as well as the updating/refinement of the procedure.
The Ph.D. project involved the participation in the SINAPSI Project, which started in April 2019, in all its components, from the management to the implementation of the monitoring network, also including the communication and dissemination of the project activities to the stakeholders.
The Ph.D. has achieved the improvement of the Hs estimation procedure. The research activities will continue beyond the Ph.D. natural end to implement the results with data from a radar antenna system that will be installed in the Genoa area in the framework of the SINAPSI Project
THE NEPHELOID BOTTOM LAYER AND THE DYNAMICS OF THE WATER MASSES AT THE SHELF-BREAK OF THE WESTERN ROSS SEA
No full textIn the austral summers of 2000/2001 and 2002/2003 the Italian CLIMA Project carried out two oceanographic cruises along the northwestern margin of the Ross Sea, where the Antarctic Bottom Water forms. Here there is an interaction between the water masses on the sea floor of the outer shelf and slope with a consequent evolution of benthic nepheloid layers and an increase in total particulate matter. We observed three different situations:(a)the presence of triads (bottom structures characterized by a concomitant jump in turbidity, temperature, and salinity data) and high re- suspension phenomena related to the presence of the Circumpolar Deep Water and its mixing with cold, salty shelf waters associated with gravity currents;(b)the absence of triads with highre-suspension, implying that when the gravity currents are no longer active the benthic nepheloid layer may persist until the suspended particles settle to the seafloor, suggesting that the turbidity data can be used to study recent gravity current events;and(c) the absence of turbidity and sediment e-suspension phenomena supports the theory that as teady situation had been re-established and the current interaction no longer occurred or had finished some time before
Environmental pollution in river and marine sediments: the case of Gromolo Torrent (Liguria, Italy)
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Six MeV proton acceleration from plasma generated by high-intensity laser using advanced thin polyethylene targets
No full textProton acceleration can be induced by non-equilibrium plasma developed by high-intensity laser pulses, at 1016 W/cm2, irradiating different types of thin polyethylene targets. The process of proton acceleration and directive yield emission was investigated, optimizing the laser parameters, the irradiation conditions, and the target properties. The use of 600 J pulse energy, a laser focalization inducing self-focusing effects and advanced targets with embedded nanoparticles and optimal thicknesses, has permitted to accelerate forward protons up to the energies of about 6 MeV and amount of the order of 1015 H+/pulse. High proton energy is obtained using thin foils enriched with gold nanoparticles, whereas high proton yield is obtained using targets with a thickness of about 10 μm. The plasma diagnostics using SiC semiconductor detectors in time-of-flight configuration was fundamental to monitor the optimal conditions to improve the plasma processes concerning the ion acceleration and the X-ray and relativistic electron emission
Tantalum ion acceleration in laser-generated plasma and dependence on the pulse duration
No full textThe laser irradiation of tantalum targets is presented for different pulsed laser intensities ranging from 1010 up to about 1018 W/cm2 and pulse durations from 9 ns up to 40 fs. The results show that the produced non-equilibrium plasma accelerates Ta ions in the backward direction from values of the order of keV up to values of about 5 MeV. In thin foils, the forward plasma, developed behind the target along the direction of incoming laser, at intensities of about 1016 W/cm2 and 300 ps pulse duration, accelerates Ta ions at energies of the order of 4.6 MeV and produces charge states up to about 40+. For fs lasers at intensities of the order of 1018 W/cm2, only proton acceleration occurs up to 2.1 MeV while no Ta ions are accelerated, due to the reduced duration of the electric field and to the too high inertial mass of the Ta ions
Protons and carbon ions acceleration in the target-normal-sheath-acceleration regime using low-contrast fs laser and metal-graphene targets
Full text linkfs pulsed lasers at an intensity of the order of 1018 W/cm2, with a contrast of 10−5, were employed to irradiate thin foils to study the target-normal-sheath-acceleration (TNSA) regime. The forward ion acceleration was investigated using 1/11 μm thickness foils composed of a metallic sheet on which a thin reduced graphene oxide film with 10 nm thickness was deposited by single or both faces. The forward-accelerated ions were detected using SiC semiconductors connected in time-of-flight configuration. The use of intense and long pre-pulse generating the low contrast does not permit to accelerate protons above 1 MeV because it produces a pre-plasma destroying the foil, and the successive main laser pulse interacts with the expanding plasma and not with the overdense solid surface. Experimental results demonstrated that the maximum proton energies of about 700 keV and of 4.2 MeV carbon ions and higher were obtained under the condition of the optimal acceleration procedure. The measurements of ion energy and charge states confirm that the acceleration per charge state is measurable from the proton energy, confirming the Coulomb–Boltzmann-shifted theoretical model. However, heavy ions cannot be accelerated due to their mass and low velocity, which does not permit them to be subjected to the fast and high developed electric field driving the light-ion acceleration. The ion acceleration can be optimized based on the laser focal positioning and on the foil thickness, composition, and structure, as it will be presented and discussed
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