475 research outputs found
Depressive Symptoms and Amygdala Volume in Elderly with Cerebral Small Vessel Disease: The RUN DMC Study
Introduction. Late onset depressive symptoms (LODSs) frequently occur in elderly with cerebral small vessel disease (SVD). SVD cannot fully explain LODS; a contributing factor could be amygdala volume. We investigated the relation between amygdala volume and LODS, independent of SVD in 503 participants with symptomatic cerebral SVD. Methods. Patients underwent FLAIR and T1 scanning. Depressive symptoms were assessed with structured questionnaires; amygdala and WML were manually segmented. The relation between amygdala volume and LODS/EODS was investigated and adjusted for age, sex, intracranial volume, and SVD. Results. Patients with LODS had a significantly lower left amygdala volume than those without (P = 0.02), independent of SVD. Each decrease of total amygdala volume (by mL) was related to an increased risk of LODS (OR = 1.77; 95% CI 1.02â3.08; P = 0.04).
Conclusion. Lower left amygdala volume is associated with LODS, independent of SVD. This may suggest differential mechanisms, in which individuals with a small amygdala might be vulnerable to develop LODS
Patterns of Care of Cancers and Radiotherapy in Ethiopia
PURPOSE: Radiotherapy (RT) is an essential component of cancer treatment. There is a lack of RT services in sub-Saharan Africa as well as limited knowledge regar
Optimized Trigger for Ultra-High-Energy Cosmic-Ray and Neutrino Observations with the Low Frequency Radio Array
When an ultra-high energy neutrino or cosmic ray strikes the Lunar surface a
radio-frequency pulse is emitted. We plan to use the LOFAR radio telescope to
detect these pulses. In this work we propose an efficient trigger
implementation for LOFAR optimized for the observation of short radio pulses.Comment: Submitted to Nuclear Instruments and Methods in Physics Research
Section
Continuum source catalog for the first APERTIF data release
The first data release of Apertif survey contains 3074 radio continuum images
covering a thousand square degrees of the sky. The observations were performed
during August 2019 to July 2020. The continuum images were produced at a
central frequency 1355 MHz with the bandwidth of 150 MHz and angular
resolution reaching 10". In this work we introduce and apply a new method to
obtain a primary beam model using a machine learning approach, Gaussian process
regression. The primary beam models obtained with this method are published
along with the data products for the first Apertif data release. We apply the
method to the continuum images, mosaic them and extract the source catalog. The
catalog contains 249672 radio sources many of which are detected for the first
time at these frequencies. We cross-match the coordinates with the NVSS,
LOFAR/DR1/value-added and LOFAR/DR2 catalogs resulting in 44523, 22825 and
152824 common sources respectively. The first sample provides a unique
opportunity to detect long term transient sources which have significantly
changed their flux density for the last 25 years. The second and the third ones
combined together provide information about spectral properties of the sources
as well as the redshift estimates.Comment: 12 pages, 9 figures; accepted for publication in A&
Characterising the Apertif primary beam response
Context. Phased Array Feeds (PAFs) are multi element receivers in the focal
plane of a telescope that make it possible to form simultaneously multiple
beams on the sky by combining the complex gains of the individual antenna
elements. Recently the Westerbork Synthesis Radio Telescope (WSRT) was upgraded
with PAF receivers and carried out several observing programs including two
imaging surveys and a time domain survey. The Apertif imaging surveys use a
configuration, where 40 partially overlapping compound beams (CBs) are
simultaneously formed on the sky and arranged in an approximately rectangular
shape. Aims. This manuscript aims to characterise the response of the 40
Apertif CBs to create frequency-resolved, I, XX and YY polarization empirical
beam shapes. The measured CB maps can be used for image deconvolution, primary
beam correction and mosaicing of Apertif imaging data. Methods. We use drift
scan measurements to measure the response of each of the 40 CBs of Apertif. We
derive beam maps for all individual beams in I, XX and YY polarisation in 10 or
18 frequency bins over the same bandwidth as the Apertif imaging surveys. We
sample the main lobe of the beams and the side lobes up to a radius of 0.6
degrees from the beam centres. In addition, we derive beam maps for each
individual WSRT dish as well. Results. We present the frequency and time
dependence of the beam shapes and sizes. We compare the compound beam shapes
derived with the drift scan method to beam shapes derived with an independent
method using a Gaussian Process Regression comparison between the Apertif
continuum images and the NRAO VLA Sky Survey (NVSS) catalogue. We find a good
agreement between the beam shapes derived with the two independent methods.Comment: Accepted for publication by A&A, 14 pages, 15 figure
Characterising the Apertif primary beam response
Context. Phased array feeds (PAFs) are multi-element receivers in the focal plane of a telescope that make it possible to simultaneously form multiple beams on the sky by combining the complex gains of the individual antenna elements. Recently, the Westerbork Synthesis Radio Telescope (WSRT) was upgraded with PAF receivers to carry out several observing programs, including two imaging surveys and a time-domain survey. The Apertif imaging surveys use a configuration of 40 partially overlapping compound beams (CBs) simultaneously formed on the sky and arranged in an approximately rectangular shape. Aims. This work is aimed at characterising the response of the 40 Apertif CBs to create frequency-resolved I, XX, and YY polarization empirical beam shapes. The measured CB maps can be used for the image deconvolution, primary beam correction, and mosaicking processes of Apertif imaging data. Methods. We used drift scan measurements to measure the response of each of the 40 Apertif CBs. We derived beam maps for all individual beams in I, XX, and YY polarisation in 10 or 18 frequency bins over the same bandwidth as the Apertif imaging surveys. We sampled the main lobe of the beams and the side lobes up to a radius of 0.6 degrees from the beam centres. In addition, we derived beam maps for each individual WSRT dish. Results. We present the frequency and time dependence of the beam shapes and sizes. We compared the compound beam shapes derived with the drift scan method to beam shapes derived with an independent method using a Gaussian Process Regression comparison between the Apertif continuum images and the NRAO VLA Sky Survey (NVSS) catalogue. We find a good agreement between the beam shapes derived with the two independent methods
The LOFAR LBA Sky Survey II. First data release
The Low Frequency Array (LOFAR) is the only existing radio interferometer
able to observe at ultra-low frequencies (<100 MHz) with high resolution (<15")
and high sensitivity (<1 mJy/beam). To exploit these capabilities, the LOFAR
Surveys Key Science Project is using the LOFAR Low Band Antenna (LBA) to carry
out a sensitive wide-area survey at 41-66 MHz named the LOFAR LBA Sky Survey
(LoLSS). LoLSS is covering the whole northern sky above declination 24 deg with
a resolution of 15" and a sensitivity of 1-2 mJy/beam (1 sigma) depending on
declination, field properties, and observing conditions. Here we present the
first data release. An automated pipeline was used to reduce the 95 fields
included in this data release. The data reduction procedures developed for this
project have general application and are currently being used to process LOFAR
LBA interferometric observations. Compared to the preliminary release,
direction-dependent errors have been corrected for during the calibration
process. This results in a typical sensitivity of 1.55 mJy/beam at the target
resolution of 15". The first data release of the LOFAR LBA Sky Survey covers
650 sqdeg in the HETDEX spring field. The resultant data products released to
the community include mosaic images (I and V Stokes) of the region, and a
catalogue of 42463 detected sources and related Gaussian components used to
describe sources' morphologies. Separate catalogues for 6 in-band frequencies
are also released. The first data release of LoLSS shows that, despite the
influences of the ionosphere, LOFAR can conduct large-scale surveys in the
frequency window 42-66 MHz with unprecedentedly high sensitivity and
resolution. The data can be used to derive unique information on the
low-frequency spectral properties of many thousands of sources with a wide
range of applications in extragalactic and galactic astronomy.Comment: 20 pages, 22 figures, images and catalogues available at
https://www.lofar-surveys.org/lolss.htm
Neuroinflammation, Mast Cells, and Glia: Dangerous Liaisons
The perspective of neuroinflammation as an epiphenomenon following neuron damage is being replaced by the awareness of glia and their importance in neural functions and disorders. Systemic inflammation generates signals that communicate with the brain and leads to changes in metabolism and behavior, with microglia assuming a pro-inflammatory phenotype. Identification of potential peripheral-to-central cellular links is thus a critical step in designing effective therapeutics. Mast cells may fulfill such a role. These resident immune cells are found close to and within peripheral nerves and in brain parenchyma/meninges, where they exercise a key role in orchestrating the inflammatory process from initiation through chronic activation. Mast cells and glia engage in crosstalk that contributes to accelerate disease progression; such interactions become exaggerated with aging and increased cell sensitivity to stress. Emerging evidence for oligodendrocytes, independent of myelin and support of axonal integrity, points to their having strong immune functions, innate immune receptor expression, and production/response to chemokines and cytokines that modulate immune responses in the central nervous system while engaging in crosstalk with microglia and astrocytes. In this review, we summarize the findings related to our understanding of the biology and cellular signaling mechanisms of neuroinflammation, with emphasis on mast cell-glia interactions
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