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Implementation of polarization diversity pulse-pair technique using airborne W-band radar
This work describes the implementation of polarization diversity on the National Research Council Canada W-band Doppler radar and presents the first-ever airborne Doppler measurements derived via polarization diversity pulse-pair processing. The polarization diversity pulse-pair measurements are interleaved with standard pulse-pair measurements with staggered pulse repetition frequency, this allows a better understanding of the strengths and drawbacks of polarization diversity, a methodology that has been recently proposed for wind-focused Doppler radar space missions. Polarization diversity has the clear advantage of making possible Doppler observations of very fast decorrelating media (as expected when deploying Doppler radars on fast-moving satellites) and of widening the Nyquist interval, thus enabling the observation of very high Doppler velocities (up to more than 100 m s−1 in the present work). Crosstalk between the two polarizations, mainly caused by depolarization at backscattering, deteriorated the quality of the observations by introducing ghost echoes in the power signals and by increasing the noise level in the Doppler measurements. In the different cases analyzed during the field campaigns, the regions affected by crosstalk were generally associated with highly depolarized surface returns and depolarization of backscatter from hydrometeors located at short ranges from the aircraft. The variance of the Doppler velocity estimates can be well predicted from theory and were also estimated directly from the observed correlation between the H-polarized and V-polarized successive pulses. The study represents a key milestone towards the implementation of polarization diversity in Doppler space-borne radars
The effect of tides on the Sculptor dwarf spheroidal galaxy
Dwarf spheroidal galaxies (dSphs) appear to be some of the most dark matter
dominated objects in the Universe. Their dynamical masses are commonly derived
using the kinematics of stars under the assumption of equilibrium. However,
these objects are satellites of massive galaxies (e.g.\ the Milky Way) and thus
can be influenced by their tidal fields. We investigate the implication of the
assumption of equilibrium focusing on the Sculptor dSph by means of ad-hoc
-body simulations tuned to reproduce the observed properties of Sculptor
following the evolution along some observationally motivated orbits in the
Milky Way gravitational field. For this purpose, we used state-of-the-art
spectroscopic and photometric samples of Sculptor's stars. We found that the
stellar component of the simulated object is not directly influenced by the
tidal field, while the mass of the more diffuse DM halo is
stripped. We conclude that, considering the most recent estimate of the
Sculptor proper motion, the system is not affected by the tides and the stellar
kinematics represents a robust tracer of the internal dynamics. In the
simulations that match the observed properties of Sculptor, the present-day
dark-to-luminous mass ratio is within the stellar half-light radius
( kpc) and within the maximum radius of the analysed dataset
( kpc).Comment: 19 pages, 10 figures, accepted for publication in MNRAS. V3: updated
after editor comments See our playlist for simulation videos:
https://av.tib.eu/series/633/supplemental+videos+of+the+paper+the+effect+of+tides+on+the+sculptor+dwarf+spheroidal+galax
Constraints on the active tectonics of the Friuli/NW Slovenia area from CGPS measurements and three-dimensional kinematic modeling
We use site velocities from continuous GPS (CGPS) observations and kinematic
modeling to investigate the active tectonics of the Friuli/NW Slovenia area. Data from 42
CGPS stations around the Adriatic indicate an oblique collision, with southern Friuli
moving NNW toward northern Friuli at the relative speed of 1.6 to 2.2 mm/a. We
investigate the active tectonics using 3DMove, a three-dimensional kinematic model tool.
The model consists of one indenter-shaped fault plane that approximates the Adriatic
plate boundary. Using the ‘‘fault-parallel flow’’ deformation algorithm, we move the
hanging wall along the fault plane in the direction indicated by the GPS velocities. The
resulting strain field is used for structural interpretation. We identify a pattern of
coincident strain maxima and high vorticity that correlates well with groups of
hypocenters of major earthquakes (including their aftershocks) and indicates the
orientation of secondary, active faults. The pattern reveals structures both parallel and
perpendicular to the strike of the primary fault. In the eastern sector, which shows more
complex tectonics, these two sets of faults probably form an interacting strike-slip
system
Activated Tryptophan-Kynurenine metabolic system in the human brain is associated with learned fear
Fear is widely recognized as a defensive emotion that has developed as a consequence
of its adaptive function in protecting the entire animal kingdom from danger, ensuring
the survival (Bouton, 2002; Milad and Quirk, 2002). Although fear associated with specific
stimuli is an innate emotion (e.g., a loud noise triggering fear in infants, fear of potential
predators), it can also be acquired rapidly and permanently to enable an appropriate and
adaptive response to new or unpredictable environmental situations (LeDoux, 2000; Beckers
et al., 2013)
Keeping watch over Colombia’s slumbering volcanoes
The Volcanological and Seismological Observatories of Manizales, Pasto and Popayan (Colombian Geological Survey) monitor and study the active volcanoes of Colombia using seismological, geodetic, geochemical and other techniques. Since 2009, permanent GNSS stations have been installed to complement classical geodetic measurements (e.g., tilt, EDM). At the moment, there are a total of 20 GNSS stations installed at Nevado del Ruiz, Cerro MachÃn, Puracé and Galeras volcanoes.
Nevado del Ruiz has remained the most dynamic of the active Colombian volcanoes since its tragic eruption of 13 November 1985. The most significant deformation occurred between 2007 and 2012, when inflation, associated with magma migration and several small to moderate explosive eruptions in 2012 (VEI less or equal to 3), was observed.
Galeras has experienced more than 25 moderate Vulcanian eruptions (VEI less or equal to 3) since 1989. In particular, the deformation network detected significant signals associated with magma migration and the extrusion of lava domes in 1991, 2005, 2008 and 2012.
Puracé volcano has been the site of more than 10 minor eruptive episodes (VEI=2) in the past century, most recently in 1977. Monitoring of this volcano started in 1994. Unrest at Puracé since that time has been characterized by significant increases in seismic activity but with little or no deformation.
We employ GAMIT/GLOBK to process GPS data from the monitoring network with support from the Volcano Disaster Assistance Program (U.S. Geological Survey). Additionally, differential processing is carried out using the commercial package Trimble 4D Control. Preliminary results for 2012 show no significant deformation at Puracé and Galeras volcanoes. On the other hand, the time series from Nevado del Ruiz shows a minor inflation (2-4 cm/yr) associated with the eruptive activity of 2012
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