Il primo OBS/H italiano per il monitoraggio e lo studio di faglie e vulcani sottomarini

L’Istituto Nazionale di Geofisica e Vulcanologia (INGV) ha testato con successo, nel luglio 2006, il primo Ocean Bottom Seismometer with Hydrophone (OBS/H) italiano (Fig. 1). Lo strumento, interamente progettato e realizzato all’Osservatorio di Gibilmanna del Centro Nazionale Terremoti, dopo aver superato i test in laboratorio, in camera iperbarica a 600 bar ed in mare a 3412 m di profondità, è stato deposto per 9 giorni (12-21/07/’06) sulla spianata sommitale del vulcano sottomarino Marsili a 790 m di profondità (Fig. 2) ed ha registrato 835 eventi tra cui un telesisma, 8 eventi regionali e circa 800 eventi vulcanici

Il primo OBS/H italiano per il monitoraggio e lo studio di faglie e vulcani sottomarini

L’Istituto Nazionale di Geofisica e Vulcanologia (INGV) ha testato con successo, nel luglio 2006, il primo Ocean Bottom Seismometer with Hydrophone (OBS/H) italiano (Fig. 1). Lo strumento, interamente progettato e realizzato all’Osservatorio di Gibilmanna del Centro Nazionale Terremoti, dopo aver superato i test in laboratorio, in camera iperbarica a 600 bar ed in mare a 3412 m di profondità, è stato deposto per 9 giorni (12-21/07/’06) sulla spianata sommitale del vulcano sottomarino Marsili a 790 m di profondità (Fig. 2) ed ha registrato 835 eventi tra cui un telesisma, 8 eventi regionali e circa 800 eventi vulcanici.La realizzazione dell’OBS/H si colloca nell’ambito dei progetti finanziati dalla convenzione tra l’INGV e il Dipartimento Nazionale della Protezione Civile (DPC), che ha avuto come obiettivo la costituzione di un primo pool strumentale, costituito da 7 OBS/H, da impiegare come rete mobile sottomarina in occasione di forti eventi sismici che dovessero interessare le coste e i mari italiani. Tale progetto si inquadra in uno scenario di ben più ampio respiro che vedrà nei prossimi anni l’estensione a mare della rete sismica nazionale, obiettivo strategico inserito nel piano triennale dell’INGV che porterà entro il 2008 alla realizzazione della prima stazione italiana real-time collegata a terra via radio, che verrà posizionata a circa 30 miglia a sud-est di Ustica, luogo in cui è stato localizzato il terremoto di Palermo del 6 settembre 2002. Il prototipo di OBS/H utilizzato nel test sul Marsili è stato equipaggiato con un sensore sismico Trillium 40s della Nanometrics ed un idrofono OAS E-2PD con banda di risposta piatta tra 0 e 5 kHz. I segnali emessi da questi strumenti sono stati registrati da un digitalizzatore a 21 bit a basso consumo (Geolon MLS della SEND) che ha acquisito i dati ad una frequenza di campionamento di 200 campioni al secondo, per sfruttare il più possibile l’ampia banda di risposta dell’idrofono, al fine di mettere in evidenza l’attività idrotermale del vulcano. Il sensore sismico è posto all’interno di una bentosfera di 17 pollici (sfera di vetro certificata per operazioni sino a 6000 m di profondità), installato su una base autolivellante controllata elettronicamente. Il digitalizzatore e le batterie sono poste all’interno di un contenitore in ERGAL 7075. Per il recupero dello strumento a fine esperimento, è stato utilizzato uno sganciatore acustico IXSEA AR816S-MR opportunamente modificato dal personale dell’osservatorio di Gibilmanna per attivare, una volta ricevuto il segnale di “release”, un sistema di sgancio elettrolitico (burn-wire). Per deposizioni di lungo periodo, sino ad uno o due anni in relazione al tipo di sismometro a bordo, l’OBS/H sarà dotato della strumentazione indicata nella Tab. 1 Attualmente è in fase di progettazione un’evoluzione dello strumento che mira a dotarlo di un digitalizzatore a 24 bit, di un sistema di comunicazione basato su modem acustico e di un PC industriale con processore ARM grazie al quale, nell’eventualità di interventi della rete mobile sottomarina, sarà possibile estrarre tracce degli eventi verificatisi per una più accurata localizzazione dell’epicentro senza che si renda necessario il recupero dello strumento. Inoltre, mediante l’implementazione di algoritmi di trigger, sarà possibile l’utilizzo dell’OBS/H all’interno di un sistema di allerta tsunami in comunicazione con una boa di superficie collegata al centro di controllo via satellite

Characterization of iodine particles with Volatilization-Humidification Tandem Differential Mobility Analyser (VH-TDMA), Raman and SEM techniques

Particles formed upon photo-oxidation of CH2I2 and particles of I2O5 and HIO3 have been studied using a Volatilisation and Humidification Tandem Differential Mobility Analyser (VH-TDMA) system. Volatilization and hygroscopic behaviour have been investigated as function of temperature (from 25 to 400 degrees Celsius), humidity (RH from 80 to 98%), initial aerosol sizes (from 27 to 100 nm mobility diameter) and in nitrogen or air as the sheath gasses. The volatility behaviour of particles formed upon photo-oxidation of CH2I2 is more similar to that of HIO3 particles in a filtered sheath air than in nitrogen, with the particle shrinkage occurring at 190 degrees Celsius and accompanied by hygroscopic growth. Despite its high solubility, HIO3 was found not to be hygroscopic at room temperature with no significant growth displayed until the thermodenuder temperature reached 200 degrees Celsius or above when the particles have transformed into I2O5. Diiodopentaoxide (I2O5) particles exhibit relatively low hygroscopic growth factors of 1.2-2 in the humidity range investigated. Scanning Electron Microscopy (SEM) of particles formed upon photo-oxidation of CH2I2 shows that their primary elemental components were iodine and oxygen in a stoichiometric ratio of approximately 1:2 with 10% error. Both Raman spectra and SEM show poor crystallinity for all the aerosols produced

Observing Brownian motion in vibration-fluidized granular matter

At the beginning of last century, Gerlach and Lehrer observed the rotational Brownian motion of a very fine wire immersed in an equilibrium environment, a gas. This simple experiment eventually permitted the full development of one of the most important ideas of equilibrium statistical mechanics: the very complicated many-particle problem of a large number of molecules colliding with the wire, can be represented by two macroscopic parameters only, namely viscosity and the temperature. Can this idea, mathematically developed in the so-called Langevin model and the fluctuation-dissipation theorem be used to describe systems that are far from equilibrium? Here we address the question and reproduce the Gerlach and Lehrer experiment in an archetype non-equilibrium system, by immersing a sensitive torsion oscillator in a granular system of millimetre-size grains, fluidized by strong external vibrations. The vibro-fluidized granular medium is a driven environment, with continuous injection and dissipation of energy, and the immersed oscillator can be seen as analogous to an elastically bound Brownian particle. We show, by measuring the noise and the susceptibility, that the experiment can be treated, in first approximation, with the same formalism as in the equilibrium case, giving experimental access to a ''granular viscosity'' and an ''effective temperature'', however anisotropic and inhomogeneous, and yielding the surprising result that the vibro-fluidized granular matter behaves as a ''thermal'' bath satisfying a fluctuation-dissipation relation

Analytically unramified one-dimensional semilocal rings and their value semigroups

AbstractIn a one-dimensional local ring R with finite integral closure each nonzerodivisor has a value in Nd, where d is the number of maximal ideals in the integral closure. The set of values constitutes a semigroup, the value semigroup of R. We investigate the connection between the value semigroup and the ring. There is a particularly close connection for some classes of rings, e.g. Gorenstein rings, Arf rings, and rings of small multiplicity. In many respects, the Arf rings and the Gorenstein rings turn out to be opposite extremes. We give applications to overrings, intersection numbers, and multiplicity sequences in the blow-up sequences studied by Lipman

First long time OBS campaign in the Ionian Sea

The INGV started its interest to extend the seismic monitoring network to the sea in 1995 with GEOSTAR (Geophysical and Oceanographic Station for Abyssal Research) project, coming out with the realization of the first multidisclipinary observatory for deep-sea monitoring [Favali et al. 2002]. At the end of 2004, the National Earthquake Center (CNT) of INGV decided to provide a pool of Ocean Bottom Seismometers to be employed as a submarine mobile network and to study submarine faults and volcanoes. This was possible thanks to an agreement between the INGV and the Italian National Civil Protection Department (DPC). On July 2006, the Gibilmanna OBS Lab, tested the first OBS prototype for nine days on the flat top of the Marsili submarine volcano [D’Anna et al. 2007] and in early 2007 other seven OBS’s were ready to be deployed on the seafloor. In May 2007, within the European project NERIES (activity NA6), the Gibilmanna OBS Lab of the INGV has deployed three Broad Band Ocean Bottom Seismometers (BBOBS) in the southern Ionian Sea at 3500-4000 meters of depth. This area has been chosen during the NERIES – “NA6-BBOBS net” meeting in Rome, on the 11th of September 2006 because at first, there are at the moment few seismological data [Scrocca et al., 2003] to construct a reliable model for the Ionian lithosphere and also the rate and features of the seismicity in the area between the Hyblean-Malta fault system and the accretionary prism of the Calabrian Arc are largely unknown [Catalano et al. 2002]. The Ionian Sea is indeed one of the most seismically active area in the Mediterranean region with several destructive earthquakes sometimes followed by tsunamis [Tinti et al. 2004]. The seismicity occurring in the Ionian basin is characterized by large location uncertainties due to the lack of seafloor seismic stations. In 2002, the quality of the seismic sensing and the location of earthquakes have been improved by the deployment of the real-time submarine observatory SN-1, about 25 km offshore Eastern Sicily [Sgroi et al, 2007]. However, the SN-1 location only allows to characterize the seismicity in the area offshore the eastern Sicily. Two of the three OBS’s were successfully recovered on the 2nd of February 2008; the last one was recovered on the 15th of March 2008 and another OBS was deployed on the same location to accomplish the continuous long-term seismic monitoring task (until May 2010) as planned in NERIES project

Rheology, Morphology and Thermal Properties of a PLA/PHB/Clay Blend Nanocomposite: The Influence of Process Parameters

The effect of process parameters on the final properties of a poly-lactic acid (PLA) and polyhydroxybutyrate (PHB) polymer blend filled with nanoclays was evaluated. To this aim, the nanofilled blend was processed in a co-rotating twin screw extruder, considering three different screw profiles and different values of the screw rotation speed, and the thermal and thermo-mechanical properties of the so-obtained materials were investigated. Furthermore, XRD analyses, SEM observations and rheological characterization were exploited to infer the coupled effect of the process parameters and nanoclay presence on the microstructure of the filled blend. Preliminary thermodynamic calculations allowed predicting the preferential localization of the nanoclay in the interfacial region between the polymeric phases. The relaxation mechanism of the particles of the dispersed phase in nanofilled blend processed, by rheological measurements, is not fully completed due to an interaction between polymer ad filler in the interfacial region with a consequent modification of the blend morphology and, specifically, a development of an enhanced microstructure. Therefore, by varying the screw configuration, particularly the presence of backflow and distribution elements in the screw profile, high shear stresses are induced during the processing able to allow a better interaction between polymers and clay. This finding also occurs in the thermo-mechanical properties of material, as an improvement of storage modulus up to 20% in filled blend processed with a specific screw profile. Otherwise, the microstructure of filled blend processed with different screw speed is similar, according to the other characterizations where no remarkable alterations of materials were detected

Il nuovo OBS/H dell’INGV

In 2005, thanks to the 3-year agreement between Dipartimento Nazionale della Protezione Civile (DPC) and Istituto Nazionale di Geofisica e Vulcanologia (INGV) - Centro Nazionale Terremoti (CNT), the project of the first Italian “Ocean Bottom Seismometer with Hydrophone” (OBS/H) for long-term deployment was developed at the OBS Lab of the Gibilmanna Observatory (Sicily). The drawing of the instrument started in January 2005 and, after 18 months, the prototype was ready for test in laboratory, in shallow and deep water. Afterwards, the first OBS/H was tested during an oceanographic campaign on the Marsili submarine volcano, from the 10th to the 21st of July 2006.More than 1000 events of several kinds were recorded: 817 VTB (Volcano Tectonic events, B-type), 159 HF (High Frequency events), 53 SDE (Short Duration Event), 8 regional events localized by INGV land network, 10 not localized events, 1 teleseismic event an 2 rockfall events. The INGV OBS/H are equipped with: - Nanometrics Trillium 120p seismometers (theoretical flat response between 120s and 175 Hz) installed in a 17 inches glass sphere on a Nautilus gimbal for the leveling or Guralp CMG40T-OBS (flat response between 60s and 100 Hz); - Cox-Webb Differential Pressure Gauge (bandwidth 500s-2Hz) or OAS E-2PD hydrophone (0-5kHz); - 21 bits, 4 channels SEND Geolon-MLS digitizer with sampling frequency up to 200 Hz

A kinetic study of the basic hydrolysis of 2-phenylethyl nitrite in the presence of borate buffer and β-cyclodextrin

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