1,721,328 research outputs found
Screening Polarimetric SAR Data via Geometric Barycenters for Covariance Symmetry Classification
Full text linkThis letter proposes a robust framework for polarimetric covariance symmetries classification in Synthetic Aperture Radar (SAR) images applying a pre-screening on the data looks before they are used to perform inferences. More specifically, the devised method improves the performance of a previous work based on the exploitation of the special structures assumed by the covariance/coherence matrix when symmetric scattering mechanisms dominate the polarimetric returns. To do this, the algorithm selects first the most homogeneous data through the cancellation of those sharing the highest Generalized Inner Product (GIP) values computed with the use of the geometric barycenters. Then, the procedure based on Model Order Selection (MOS) developed in the homogeneous case is applied on the filtered data. The conducted tests show the potentiality of the proposed method in correctly classifying the observed scene of L-band real-recorded SAR data with respect to its standard counterpart
Insulin glargine in enteric tube feeding.
No full textDiabetes Res Clin Pract. 2007 Nov;78(2):298-9. Epub 2007 May 3.
Insulin glargine in enteric tube feeding.
Marchetti G, Tesauro M, Di Daniele N, Bollea MR, Lauro R, Bertoli A.
Insulin glargine, a long-acting insulin analogue, was
introduced to provide effective basal insulin replacement
with once-daily dosing. An insulin regimen with
insulin glargine allows optimal glucose control with a
lower risk of hypoglycaemia compared with neutral
protaminated hagedorn insulin in Type 2 diabetes [1,2].
Recently, insulin glargine has been proposed for
patients on continuous enteral artificial nutrition [3,4].
We report an 18-month follow-up of a patient treated
with basal insulin glargine during continuous enteral
nutrition and thereafter during intermittent enteral
nutrition without evidence of hypoglycaemic events
Geophysical characterization of the Krafla volcanic area from seismic tomography and attenuation
No full textExploration and exploitation of natural resources, such as geothermal energy, require a proper
understanding of the physical properties of the upper crust, where they are mostly allocated.
Indeed, the transition from brittle to ductile deformation (BDT), occurring at these depths, marks a
progressive change in crustal rheology and a reduction in the rock’s permeability. Therefore, the
characterization of underground conditions is crucial for planning explorative studies in
geothermal systems. It has been recently demonstrated that the analysis of the propagation of
seismic waves provides information on physical rocks’ behavior and an alternative assessment of
the BDT depth [1]. In particular, the decay of the amplitude of the seismic waves (i.e. seismic
attenuation), which is usually described by a “quality factor” Q, depends on the seismic frequency,
temperature, water content, and grain size of the rocks. Depending on the seismic scale, it could
be used as an indicator of subsurface heterogeneities.
In this study, we investigate the seismic velocity and attenuation sensitivity to the crustal
heterogeneities in areas affected by young tectonics and hot thermal conditions. To this aim, we
implement a Q seismic tomography in the volcanic system of Krafla. The volcanos of age 0.5–1.8
Myr extend over an area of 21 km by 17 km and are characterized by faults and fissures, which
allow water to penetrate and circulate at shallow depths [2] easily. In these geothermal fields, the
temperatures, in a range of 400-600 °C at a depth < 5 km [3], make the BDT depth close to the
surface.
We apply the method that solves Qp perturbations, using a combination of a spectral decay
technique to retrieve the attenuation operator (t*) and tomographic inversion [4]. The distribution
of seismic wave velocities is obtained from a 3D tomographic inversion, using 1453 earthquakes
detected from a local seismic network (2009-2012) [2]. Qp inversion is performed with the
simul2014 algorithm [5], while a linearized technique solves a nonlinear problem that uses a
damped least-squares inversion for model perturbations.
We obtain a map of Qp variations for the first 4 km, which we jointly interpret with the seismic
wave velocities [2]. In this way, we can discriminate between anomalies related to temperatures
and compositional heterogeneities. We also test the possibility to detect the BDT depth on the
base of the reduction of the Qp, related to hot temperatures/melt conditions. The obtained results
will contribute to understanding the dynamics of the tectonic features and help plan explorative
studies of high enthalpy geothermal systems, adding constraints to the correlation between
viscous rocks’ deformation and their seismic attenuation
Adaptive Detection of Targets on the Sea Surface based upon Range-Compressed SAR Data
No full textThis paper addresses adaptive detection of possibly-extended
targets on the sea surface based upon range-compressed SAR
data. The detection problem has been re-cast in the context
of space-time adaptive processing and an adaptive detector,
capable to operate in uncertain scenarios, has been
proposed. The proposed detector takes advantage of signature
diversity, namely of the fact that possible useful signals
from different range cells span a vector space whose dimension
is greater than one. The performance assessment shows
that it can be a viable means to cope with realistic scenario
An overview of the velocity and attenuation distribution in the Krafla volcanic system
No full textNatural resources, such as geothermal energy, are usually allocated in the uppermost part of
the crust. The exploration and exploitation of these resources rely on a proper understanding
of the rock’s physical and rheological properties. For instance, the reduction in the rock’s
permeability with depth depends on the progressive porosity decrease, due to the lithostatic
pressure increase and the transition from brittle to ductile deformation (BDT), related to the
rising temperature. Therefore, the characterization of underground conditions is crucial for
planning explorative studies in geothermal systems. One way to retrieve subsurface
information is through the analysis of the propagation of seismic waves, which provides
information on physical rocks’ behavior and an alternative assessment of the BDT depth [1].
In particular, the decay of the amplitude of the seismic waves (i.e. seismic attenuation),
usually described by a “quality factor”, depends on the seismic frequency, temperature, water
content, and grain size of the rocks. Depending on the seismic scale, it could be used as an
indicator of subsurface heterogeneities.
In this study, we investigate the seismic velocity and attenuation sensitivity to the crustal
heterogeneities in the volcanic system of Krafla, an area affected by young tectonics and hot
thermal conditions. To this aim, we implement a Q seismic tomography, using as input a
published seismic tomography model [2] and estimate the seismic quality factors of basalt
rocks sampled in the Krafla area. To retrieve the QP perturbations, we implement a method
consisting of a combination of a spectral decay technique to derive the attenuation operator
(t∗) and seismic tomographic inversion [3]. The distribution of seismic wave velocities is
obtained from a 3D tomographic inversion, using 1453 earthquakes detected from a local
seismic network (2009-2012) [2]. QP inversion is performed with the simul2014 algorithm
[3], while a linearized technique solves a nonlinear problem that uses a damped least-squares
inversion for model perturbations. We obtain a map of QP variations for the first 4 km, which
we jointly interpret with the seismic wave velocities [2]. In this way, we can discriminate
between temperature anomalies and compositional heterogeneities. We also test the
possibility to detect the BDT depth on the base of the reduction of the QP , related to hot
temperatures/melt conditions. In order to estimate the seismic quality factors at the laboratory
scale, we first develop a numerical method to extract seismic attenuation information from
ultrasonic signals in the frequency domain (Spectral Ratio Method). The technique is
implemented and tested on suitable synthetic attenuated models [4]. The aim of this test is to
assess the reliability and robustness of the method in diverse signal noise conditions and
absorption levels. Additionally, the test helps identify the frequency ranges satisfying the
assumption of constant seismic quality factor and assess the influence of the windowing
effect on providing an accurate seismic quality factor. Subsequently, the method is applied to
real ultrasonic waves acquired in the basalts during the execution of a hydrostatic test. The
results help constrain the QP variations previously obtained.
This study will contribute to understanding the dynamics of the tectonic features and help
plan explorative investigations of high enthalpy geothermal systems, adding constraints to the
correlation between viscous rocks’ deformation and their seismic attenuation
il padel
No full textLa disciplina del “padel”, nata in Messico negli anni 70, sta riscuotendo anche in Italia una sempre più ampia popolarità; nel mondo ci sono oltre 6 milioni di giocatori e dall’aprile 2008 questa attività è stata riconosciuta dal CONI ed inserita nella Federazione Italiana Tennis.
Il padel è un gioco divertente al quale possono partecipare persone di diversa età, sesso, condizioni tecniche e fisiche.
Con la pubblicazione di questo lavoro, la Redazione si augura di fornire ai lettori un utile spunto di approfondimento e riflessione su questa interessante e moderna disciplina sportiva
Seismic tomography and attenuation models for the geophysical characterization of the Krafla volcanic area.
No full textThe characterization of the underground structures is crucial for planning explorative studies in
geothermal systems. As recently demonstrated, analysis of the propagation of seismic waves
provides information on physical rocks’ behavior and alternative assessments of the brittle-ductile
transition (BDT) depth [1]. In particular, the decay of the amplitude of the seismic waves (i.e. seismic
attenuation), which is usually described by a “quality factor” Q, depending on the seismic scale,
could be used as indicator of the subsurface heterogeneities.
In this study, we investigate the sensitivity of the seismic velocity and attenuation to the crustal
heterogeneities, by implementing a Q seismic tomography of the Krafla volcanic system, an area
affected by young tectonics and hot thermal conditions.
The applied method solves for Qp perturbations, using a combination of a spectral decay technique
to retrieve the attenuation operator (t*) and tomographic inversion [2]. The distribution of seismic
wave velocities is obtained from a 3D tomographic inversion, using 1453 earthquakes detected from
a local seismic network (2009-2012) [2,3].
The obtained Qp variations up to a depth of 4 km is interpreted together with the seismic wave
velocity values [3]. The joint interpretation helps discriminate between anomalies related to
temperatures and compositional heterogeneities, defining the main structures of the area. We also
try to define the BDT depth, on the base of the strong reduction of the Qp, related to hot
temperatures/melt conditions
Revisiting the geodynamics of the Middle East region from an integrated geophysical perspective
Full text linkA long-standing question in geodynamics is whether mantle flow is driven by the plate motion alone, or mantle upwelling makes a significant contribution to it. Subducting slabs and lateral variations of the continental lithosphere can further influence the asthenospheric flow and control its direction. The Middle East region (MER) is a complex continental setting where different processes such as rifting, break-up, plate collision, and tectonic escape kinematically interact with each other. In this context, the role that lithospheric structure, mantle flow, and active upwellings may play is debated. Tomographic images provide a snapshot of the current thermal conditions of a region and seismic anisotropy can also help resolve mantle convection. Here, we synthesize shear-wave splitting observations together with up-to-date tomography models of the mantle structure beneath the MER and other geophysical data. Low-velocity anomalies are seen at asthenospheric depths beneath W Arabia, NW Iran, and Anatolia, suggesting a spreading zone of warm mantle. Two deep low-velocity bodies in Afar and Levant –interpreted as hot mantle plumes– are the sources of this shallower mantle flow. Where low velocities are imaged, we observe predominantly NE–SW oriented anisotropy, anomalously high topography, and abundant basaltic volcanism. The integrated analysis suggests that a horizontal component associated with active upwelling is present in the upper-mantle flow field. The large-scale circulation flow fed by the Afar and Levant Plumes, aided by the subduction-induced forces, facilitates the lateral motion of the Anatolian microplate and affects the dynamic evolution of the Zagros orogen. The proposed scenario demonstrates that the interplay between plate-tectonic events and mantle dynamics controls the kinematics of the region and can explain the general patterns of deformation observed at the surface
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