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Learning stationary time series using Gaussian processes with nonparametric kernels
Gaussian process deconvolution
Let us consider the deconvolution problem, that is, to recover a latent
source from the observations of a
convolution process , where is an additive noise,
the observations in might have missing parts with respect to ,
and the filter could be unknown. We propose a novel strategy to address
this task when is a continuous-time signal: we adopt a Gaussian process
(GP) prior on the source , which allows for closed-form Bayesian
nonparametric deconvolution. We first analyse the direct model to establish the
conditions under which the model is well defined. Then, we turn to the inverse
problem, where we study i) some necessary conditions under which Bayesian
deconvolution is feasible, and ii) to which extent the filter can be learnt
from data or approximated for the blind deconvolution case. The proposed
approach, termed Gaussian process deconvolution (GPDC) is compared to other
deconvolution methods conceptually, via illustrative examples, and using
real-world datasets.Comment: Accepted at Proceedings of the Royal Society
Microwave Phase Detection at the Level of rad
We report on a noise measurement system with the highest spectral resolution
ever achieved in the microwave domain. It is capable of detecting the phase
fluctuations of amplitude of at Fourier
frequencies above few . Such precision allows the study of intrinsic
fluctuations in various microwave components and materials, as well as precise
tests of fundamental physics. Employing this system we discovered a previously
unknown phenomenon of down-conversion of pump oscillator phase noise into the
low-frequency voltage fluctuations.Comment: Accepted for publication in Review of Scientific Instrument
Sustained reentry in a 3d regionally ischemic human heart. A simulation study
In this work, we have studied the vulnerable window and propagation patterns in a human heart during acute ischemia. A 3-D biventricular model of a human heart with realistic heterogeneity and fiber orientations has been considered. The ischemic region was located in the anterior left ventricular wall mimicking the occlusion of the circumflex artery. The electrical activity of the tissue was modeled with the monodomain model along with a modified version of the ten Tusscher 2006 ionic model. The model predicts the generation of sustained re-entrant activity in the form of a rotor around the ischemic zone. Patterns in the form of figure-of-eight were also observed within the vulnerable window. The re-entrant activity originates in the endocardial surface and propagates transmurally towards the epicardium
Maser Oscillation in a Whispering-Gallery-Mode Microwave Resonator
We report the first observation of above-threshold maser oscillation in a
whispering-gallery(WG)-mode resonator, whose quasi-transverse-magnetic, 17th
azimuthal-order WG mode, at a frequency of approx. 12.038 GHz, with a loaded Q
of several hundred million, is supported on a cylinder of mono-crystalline
sapphire. An electron spin resonance (ESR) associated with Fe3+ ions, that are
substitutively included within the sapphire at a concentration of a few parts
per billion, coincides in frequency with that of the (considerably narrower) WG
mode. By applying a c.w. `pump' to the resonator at a frequency of approx.
31.34 GHz, with no applied d.c. magnetic field, the WG (`signal') mode is
energized through a three-level maser scheme. Preliminary measurements
demonstrate a frequency stability (Allan deviation) of a few times 1e-14 for
sampling intervals up to 100 s.Comment: REVTeX v.4, 3 pages, with a separate .bbl file and 3 .eps figure
Ventilator-associated Pneumonia After Elective Cardiac Surgery Caused by Pneumocystis Jirovecii
Ventilator-associated pneumonia is a severe complication among patients undergoing cardiac
surgery. Although hospital-acquired bacterial pathogens, often multidrug resistant, are the most
frequent cause, non-bacterial atypical and opportunistic agents traditionally associated with
immunocompromise are increasingly recognized. We describe ventilator-associated pneumonia
due to Pneumocystis jirovecii in the absence of traditional risk factors for Pneumocystis
pneumonia in a patient after cardiac surgery
Improved Constraints on Isotropic Shift and Anisotropies of the Speed of Light using Rotating Cryogenic Sapphire Oscillators
We demonstrate that Michelson-Morley tests, which detect direction-dependent
anisotropies in the speed of light, can also be used to place limits upon
isotropic deviations of the vacuum speed of light from , as described by the
photon sector Standard Model Extension (SME) parameter . A
shift in the speed of light that is isotropic in one inertial frame implies
anisotropic shifts in others. Using observer Lorentz covariance, we derive the
time-dependent variations in the relative resonance frequencies of a pair of
electromagnetic resonators that would be generated by such a shift in the rest
frame of the Sun. A new analysis of a recent experimental test of relativity
using this result constrains with a precision of
. This represents the first constraint on
by a Michelson-Morley experiment and the first analysis
of a single experiment to simultaneously set limits on all nine
non-birefringent terms in the photon sector of the SME
No habitat selection during spring migration at a meso-scale range across mosaic landscapes: A case study with the woodcock (Scolopax rusticola)
Success of migration in birds in part depends on habitat selection. Overall, it is still poorly known whether there is habitat selection amongst landbird migrants moving across landscapes. Europe is chiefly covered by agro-forestry mosaic landscapes, so migratory species associated to either agricultural landscapes or woodland habitats should theoretically find suitable stopover sites along migration. During migration from wintering to breeding quarters, woodcocks (Scolopax rusticola) tagged with PTT satellite-tracking transmitters were used to test for the hypothesis that migrants associated to agro-forest habitats have no habitat selection during migration, at a meso-scale level. Using a GIS platform we extracted at a meso-scale range habitat cover at stopover localities. Results obtained from comparisons of soil covers between points randomly selected and true stopover localities sites revealed, as expected, the species may not select for particular habitats at a mesoscale range, because the habitat (or habitats) required by the species can be found virtually everywhere on their migration route. However, those birds stopping over in places richer in cropland or mosaic habitats including both cropland and forest and with proportionally less closed forest stayed for longer than in areas with lower surfaces of cropland and mosaic and more closed forest. This suggests that areas rich in cropland or mosaic habitat were optimal
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