374 research outputs found
Phase rigidity breaking in open Aharonov-Bohm ring coupled to a cantilever
The conductance and the transmittance phase shifts of a two-terminal
Aharonov-Bohm (AB) ring are analyzed in the presence of mechanical
displacements due to coupling to an external can- tilever. We show that phase
rigidity is broken, even in the linear response regime, by means of inelastic
scattering due to phonons. Our device provides a way of observing continuous
variation of the transmission phase through a two-terminal
nano-electro-mechanical system (NEMS). We also propose measurements of phase
shifts as a way to determine the strength of the electron-phonon coupling in
NEMS.Comment: 7 pages, 8 figure
Effects of fission-fragment damage on vortex dimensionality in silver-sheathed Bi2Sr2Ca2Cu3Ox tapes
We report on the vortex dimensionality of uranium-doped Ag/Bi2223 tapes, before and after irradiation to a thermal-neutron fluence. The effective activation energies, as a function of current density and applied field, were calculated from dynamic magnetization relaxation measurements. A dimensional crossover from a three-dimensional (3D) elastic creep regime to a 2D plastic creep was observed in the nonirradiated tape at an applied magnetic field ”0Hcr[approximate]0.37 T, with an associated change in the flux hop velocity and temperature dependence. After the introduction of the fission-fragment damage by irradiation, a shift in the crossover to ”0Hcr[approximate]0.65 T was observed. These results indicate an enhancement of the c-axis vortex coherence by the introduced splayed columnar defects, explaining the greater pinning efficiency of the uranium-fission method in Bi2223 rather than the less anisotropic Y123. Conflicting results obtained for the irradiated tape in the absence of any temperature scaling of the activation energies demonstrate the importance of the inclusion of scaling in the magnetization relaxation analysis
Measuring GNSS ionospheric total electron content at Concordia, and application to L-band radiometers
In the framework of the project BIS - Bipolar Ionospheric Scintillation and Total Electron Content Monitoring, the ISACCO-DMC0 and ISACCO-DMC1 permanent monitoring stations were installed in 2008.
The principal scope of the stations is to measure the ionospheric total electron content (TEC) and to monitor the ionospheric scintillations, using high-sampling-frequency global positioning system (GPS) ionospheric scintillation and TEC monitor (GISTM) receivers. The disturbances that
the ionosphere can induce on the electromagnetic signals emitted by the
Global Navigation Satellite System constellations are due to the presence
of electron density anomalies in the ionosphere, which are particularly frequent
at high latitudes, where the upper atmosphere is highly sensitive to
perturbations coming from outer space. With the development of present and future low-frequency space-borne microwave missions (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active
Passive missions), there is an increasing need to estimate the effects of the ionosphere on the propagation of electromagnetic waves that affects
satellite measurements. As an example, how the TEC data collected at Concordia station are useful for the calibration of the European Space Agency SMOS data within the framework of an experiment promoted by the European Space Agency (known as DOMEX) will be discussed.
The present report shows the ability of the GISTM station to monitor ionospheric scintillation and TEC, which indicates that only the use of continuous GPS measurements can provide accurate information on TEC
variability, which is necessary for continuous calibration of satellite data
Synergic use of botulinum toxin injection and radial extracorporeal shockwave therapy in multiple sclerosis spasticity
Background and aim: In Multiple Sclerosis (MS) spasticity worsens the patientâs quality of life. Botulinum NeuroToxin TypeA (BoNT-A) is extensively used in focal spasticity, frequently combined with physical therapies. Radial extracorporeal shock waves (rESW) were already used in association with BoNTA. Considering that loss of efficacy and adverse events are determinants of BoNT-A treatment interruption, this study aimed to evaluate the possibility to prolong BoNT-Aâs effect by using rESW in MS focal spasticity. Methods: Sixteen MS patients with spasticity of triceps surae muscles were first subjected to BoNT-A therapy and, four months later, to 4 sections of rESWT. Patients were evaluated before, 30, 90 days after the end of the treatments, by using Modified Ashworth Scale (MAS), Modified Tardieu Scale (MTS), and kinematic analysis of passive and active ankle ROM. Results: BoNT-A determined a significant reduction of spasticity evaluated by MAS with a reduction of positive effects after 4months (p<0.05); MTS highlighted the efficacy only 90 days after injection (p<0.05). rESWT decreased MAS values at the end and 30 days later the treatment (p<0.01); MTS values showed instead a prolonged effect (p<0.01). BoNT-A determined a gain of passive and active ankle ROM, persisting along with treatment and peaking the maximum value after rESWT (p<0.05). Conclusions: rESWT can prolong BoNT-A effect inducing a significant reduction of spasticity and improvement in passive and active ankle ROM in MS patients. The use of rESWT following BoNT-A injection is useful to avoid some limitations and to prolong the therapeutic effects of BoNT-A therapy. (www.actabiomedica.it)
Monitoring of a methane-seeping pockmark by cabled benthic observatory (Patras Gulf, Greece)
A new seafloor observatory, the gas monitoring
module (GMM), has been developed for continuous and
long-term measurements of methane and hydrogen sulphide
concentrations in seawater, integrated with temperature (T),
pressure (P) and conductivity data at the seafloor. GMM
was deployed in April 2004 within an active gas-bearing
pockmark in the Gulf of Patras (Greece), at a water depth of
42 m. Through a submarine cable linked to an onshore
station, it was possible to remotely check, via direct phone
connection, GMM functioning and to receive data in nearreal
time. Recordings were carried out in two consecutive
campaigns over the periods AprilâJuly 2004, and September
2004âJanuary 2005, amounting to a combined dataset
of ca. 6.5 months. This represents the first long-term
monitoring ever done on gas leakage from pockmarks by
means of CH4+H2S+T+P sensors. The results show
frequent T and P drops associated with gas peaks, more
than 60 events in 6.5 months, likely due to intermittent,
pulsation-like seepage. Decreases in temperature in the
order of 0.1â1°C (up to 1.7°C) below an ambient T of ca.
17°C (annual average) were associated with short-lived
pulses (10â60 min) of increased CH4+H2S concentrations.
This seepage âpulsationâ can either be an active process
driven by pressure build-up in the pockmark sediments, or a
passive fluid release due to hydrostatic pressure drops
induced by bottom currents cascading into the pockmark
depression. Redundancy and comparison of data from
different sensors were fundamental to interpret subtle proxy
signals of temperature and pressure which would not be
understood using only one sensor.Published297-302JCR Journalreserve
NEMO-SN1 (Western Ionian Sea, off Eastern Sicily): A Cabled Abyssal Observatory with Tsunami Early Warning Capability
The NEMO-SN1 (NEutrino Mediterranean Observatory - Submarine
Network 1) seafloor observatory is located in the central
Mediterranean, Western Ionian Sea, off Eastern Sicily Island (Southern
Italy) at 2100 m water depth, 25 km from the harbour of the city of
Catania. It is a prototype of cabled deep-sea multiparameter
observatory, and the first operating with real-time data transmission in
Europe since 2005. NEMO-SN1 is also the first-established node of
EMSO (European Multidisciplinary Seafloor Observatory,
http://emso-eu.org), one of the European large-scale research
infrastructures. EMSO will address long-term monitoring of
environmental processes related to marine ecosystems, climate change
and geo-hazards. NEMO-SN1 will perform geophysical and
environmental long-term monitoring by acquiring seismological,
geomagnetic, gravimetric, accelerometric, physico-oceanographic,
hydro-acoustic, bio-acoustic measurements to study earthquake and
tsunami generation, and to characterize ambient noise which includes
marine mammal sounds, and environmental and anthropogenic sources.
NEMO-SN1 is also equipped with a prototype tsunami detector, based
on the simultaneous measurement of the seismic and bottom pressure
signals and a new high performance tsunami detection algorithm.
NEMO-SN1 will be a permanent tsunami early warning node in
Western Ionian Sea, an area where very destructive earthquakes have
occurred in the past, some of them tsunamigenic (e.g., 1693, M=7.5;
1908, M=7.4).
Another important feature of NEMO-SN1 is the installation of a low
frequency-high sensibility hydrophone and two (scalar and vector,
respectively) magnetometers. The objective is to improve the tsunami
detection capability of SN1 through the recognition of tsunami-induced
hydro-acoustic and electro-magnetic precursors.SubmittedRhodes, Greece3A. Ambiente Marinorestricte
Growth of Ordered Iron Oxide Nanowires for Photo-electrochemical Water Oxidation
This work reports the synthesis of ordered and vertically aligned iron oxide nanowires for photo-electrochemical (PEC) water oxidation. The nanowires exhibited promising PEC activity for water oxidation with saturated photocurrents of âŒ0.8 mA cm-2 at 1.23 V vs RHE. Various factors inevitably affect their photochemical activity such as crystallinity, morphology, compositional gradient, and surface states. They were studied with HRTEM, EELS, and Raman shift techniques. The nanowires had complex compositional and morphological structures at nano and atomic scales. The nanowires annealed at 350 °C had an outer shell dominated by Fe3+ cations, while the core had mixed oxidation states of iron cations (+2 and +3). In contrast, nanowires annealed at 450 °C are fully oxidized with Fe3+ cations only and were found to be more active. At the same time, we observed anisotropic compositional gradients of nickel cations inside the iron oxide, originating from the nickel support film. Our work shows that the methodology used can affect the composition of the surface and near surface of the grown nanowires. It therefore points out the importance of a detailed analysis, in order to obtain a realistic structure-activity relationship in photo-electrocatalysis
Measuring GNSS ionospheric total electron content at Concordia, and application to L-band radiometers
<p>In the framework of the project BIS - Bipolar Ionospheric Scintillation and Total Electron Content Monitoring, the ISACCO-DMC0 and ISACCO-DMC1 permanent monitoring stations were installed in 2008. The principal scope of the stations is to measure the ionospheric total electron content (TEC) and to monitor the ionospheric scintillations, using high-sampling-frequency global positioning system (GPS) ionospheric scintillation and TEC monitor (GISTM) receivers. The disturbances that the ionosphere can induce on the electromagnetic signals emitted by the Global Navigation Satellite System constellations are due to the presence of electron density anomalies in the ionosphere, which are particularly frequent at high latitudes, where the upper atmosphere is highly sensitive to perturbations coming from outer space. With the development of present and future low-frequency space-borne microwave missions (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active Passive missions), there is an increasing need to estimate the effects of the ionosphere on the propagation of electromagnetic waves that affects satellite measurements. As an example, how the TEC data collected at Concordia station are useful for the calibration of the European Space Agency SMOS data within the framework of an experiment promoted by the European Space Agency (known as DOMEX) will be discussed. The present report shows the ability of the GISTM station to monitor ionospheric scintillation and TEC, which indicates that only the use of continuous GPS measurements can provide accurate information on TEC variability, which is necessary for continuous calibration of satellite data.</p
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
GEMS (Gamma Energy Marine Spectrometer) is a prototype of an autonomous radioactivity sensor for underwater measurements, developed in the framework for a development of a submarine telescope for neutrino detection (KM3NeT Design Study Project). The spectrometer is highly sensitive to gamma rays produced by 40K decays but it can detect other natural (e.g., 238U,232Th) and anthropogenic radio-nuclides (e.g., 137Cs). GEMS was firstly tested and calibrated in the laboratory using known sources and it was successfully deployed for a long-term (6 months) monitoring at a depth of 3200 m in the Ionian Sea (Capo Passero, offshore Eastern Sicily). The instrument recorded data for the whole deployment period within the expected specifications. This monitoring provided, for the first time, a continuous time-series of radioactivity in deep-sea.In press4.5. Studi sul degassamento naturale e sui gas petroliferiJCR Journalope
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