2,491 research outputs found
A new method to suppress the bias in polarized intensity
Computing polarised intensities from noisy data in Stokes U and Q suffers
from a positive bias that should be suppressed. To develop a correction method
that, when applied to maps, should provide a distribution of polarised
intensity that closely follows the signal from the source. We propose a new
method to suppress the bias by estimating the polarisation angle of the source
signal in a noisy environment with help of a modified median filter. We then
determine the polarised intensity, including the noise, by projection of the
observed values of Stokes U and Q onto the direction of this polarisation
angle. We show that our new method represents the true signal very well. If the
noise distribution in the maps of U and Q is Gaussian, then in the corrected
map of polarised intensity it is also Gaussian. Smoothing to larger Gaussian
beamsizes, to improve the signal-to-noise ratio, can be done directly with our
method in the map of the polarised intensity. Our method also works in case of
non-Gaussian noise distributions. The maps of the corrected polarised
intensities and polarisation angles are reliable even in regions with weak
signals and provide integrated flux densities and degrees of polarisation
without the cumulative effect of the bias, which especially affects faint
sources. Features at low intensity levels like 'depolarisation canals' are
smoother than in the maps using the previous methods, which has broader
implications, for example on the interpretation of interstellar turbulence.Comment: accepted for publication in Astronomy & Astrophysic
The NOD3 software package: A graphical user interface-supported reduction package for single-dish radio continuum and polarisation observations
The venerable NOD2 data reduction software package for single-dish radio
continuum observations, developed for use at the 100-m Effelsberg radio
telescope, has been successfully applied over many decades. Modern computing
facilities call for a new design.
We aim to develop an interactive software tool with a graphical user
interface (GUI) for the reduction of single-dish radio continuum maps. Special
effort is given on the reduction of distortions along the scanning direction
(scanning effects) by combining maps scanned in orthogonal directions or dual-
or multiple-horn observations that need to be processed in a restoration
procedure. The package should also process polarisation data and offer the
possibility to include special tasks written by the individual user.
Based on the ideas of the NOD2 package we developed NOD3, which includes all
necessary tasks from the raw maps to the final maps in total intensity and
linear polarisation. Furthermore, plot routines and several methods for map
analysis are available. The NOD3 package is written in Python which allows to
extend the package by additional tasks. The required data format for the input
maps is FITS.
NOD3 is a sophisticated tool to process and analyse maps from single-dish
observations that are affected by 'scanning effects' due to clouds, receiver
instabilities, or radio-frequency interference (RFI). The 'basket-weaving' tool
combines orthogonally scanned maps to a final map that is almost free of
scanning effects. The new restoration tool for dual-beam observations reduces
the noise by a factor of about two compared to the NOD2 version. Combining
single-dish with interferometer data in the map plane ensures the full recovery
of the total flux density.Comment: 8 pages, 10 figures, Accepted for publication in A&
Neuroinflammation, Microglia and Implications for Anti-Inflammatory Treatment in Alzheimer's Disease
Neuroinflammation has been implicated in the pathology of Alzheimer's disease (AD) for decades. Still it has not been fully understood when and how inflammation arises in the course of AD. Whether inflammation is an underling cause or a resulting condition in AD remains unresolved. Mounting evidence indicates that microglial activation contributes to neuronal damage in neurodegenerative diseases. However, also beneficial aspects of microglial activation have been identified. The purpose of this review is to highlight new insights into the detrimental and beneficial role of neuroinflammation in AD. It is our intention to focus on newer controversies in the field of microglia activation. Precisely, we want to shed light on whether neuroinflammation is associated to brain tissue damage and functional impairment or is there also a damage limiting activity. In regard to this, we discuss the limitations and the advantages of anti-inflammatory treatment options and identify what future implications might result from this underling neuroinflammation for AD therapy
Soft Dynamic Time Warping for Multi-Pitch Estimation and Beyond
Many tasks in music information retrieval (MIR) involve weakly aligned data,
where exact temporal correspondences are unknown. The connectionist temporal
classification (CTC) loss is a standard technique to learn feature
representations based on weakly aligned training data. However, CTC is limited
to discrete-valued target sequences and can be difficult to extend to
multi-label problems. In this article, we show how soft dynamic time warping
(SoftDTW), a differentiable variant of classical DTW, can be used as an
alternative to CTC. Using multi-pitch estimation as an example scenario, we
show that SoftDTW yields results on par with a state-of-the-art multi-label
extension of CTC. In addition to being more elegant in terms of its algorithmic
formulation, SoftDTW naturally extends to real-valued target sequences.Comment: Accepted at ICASSP 202
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