121 research outputs found
A case study of random field models applied to thin-walled composite cylinders in finite element analysis
The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing
The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV
solar telescope on board ESA's Project for Onboard Autonomy 2 (PROBA2) mission
launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm
and provides images of the low solar corona over a 54x54 arcmin field-of-view
with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is
designed to monitor all space-weather-relevant events and features in the low
solar corona. Given the limited resources of the PROBA2 microsatellite, the
SWAP telescope is designed with various innovative technologies, including an
off-axis optical design and a CMOS-APS detector. This article provides
reference documentation for users of the SWAP image data.Comment: 26 pages, 9 figures, 1 movi
Dynamics of solar coronal loops II. Catastrophic cooling and high-speed downflows
This work addresses the problem of plasma condensation and ``catastrophic
cooling'' in solar coronal loops. We have carried out numerical calculations of
coronal loops and find several classes of time-dependent solutions (static,
periodic, irregular), depending on the spatial distribution of a temporally
constant energy deposition in the loop. Dynamic loops exhibit recurrent plasma
condensations, accompanied by high-speed downflows and transient brightenings
of transition region lines, in good agreement with features observed with
TRACE. Furthermore, these results also offer an explanation for the recent EIT
observations of De Groof et al. (2004) of moving bright blobs in large coronal
loops. In contrast to earlier models, we suggest that the process of
catastrophic cooling is not initiated by a drastic decrease of the total loop
heating but rather results from a loss of equilibrium at the loop apex as a
natural consequence of heating concentrated at the footpoints of the loop, but
constant in time.Comment: 13 pages, 15 figure
Neural Correlates of Behavioural Olfactory Sensitivity Changes Seasonally in European Starlings
Possibly due to the small size of the olfactory bulb (OB) as compared to rodents, it was generally believed that songbirds lack a well-developed sense of smell. This belief was recently revised by several studies showing that various bird species, including passerines, use olfaction in many respects of life. During courtship and nest building, male European starlings (Sturnus vulgaris) incorporate aromatic herbs that are rich in volatile compounds (e.g., milfoil, Achillea millefolium) into the nests and they use olfactory cues to identify these plants. Interestingly, European starlings show seasonal differences in their ability to respond to odour cues: odour sensitivity peaks during nest-building in the spring, but is almost non-existent during the non-breeding season.This study used repeated in vivo Manganese-enhanced MRI to quantify for the first time possible seasonal changes in the anatomy and activity of the OB in starling brains. We demonstrated that the OB of the starling exhibits a functional seasonal plasticity of certain plant odour specificity and that the OB is only able to detect milfoil odour during the breeding season. Volumetric analysis showed that this seasonal change in activity is not linked to a change in OB volume. By subsequently experimentally elevating testosterone (T) in half of the males during the non-breeding season we showed that the OB volume was increased compared to controls.By investigating the neural substrate of seasonal olfactory sensitivity changes we show that the starlings' OB loses its ability during the non-breeding season to detect a natural odour of a plant preferred as green nest material by male starlings. We found that testosterone, applied during the non-breeding season, does not restore the discriminatory ability of the OB but has an influence on its size
Resonant Absorption of Axisymmetric Modes in Twisted Magnetic Flux Tubes
It has been shown recently that magnetic twist and axisymmetric MHD modes are ubiquitous in the solar atmosphere, and therefore the study of resonant absorption for these modes has become a pressing issue because it can have important consequences for heating magnetic flux tubes in the solar atmosphere and the observed damping. In this investigation, for the first time, we calculate the damping rate for axisymmetric MHD waves in weakly twisted magnetic flux tubes. Our aim is to investigate the impact of resonant damping of these modes for solar atmospheric conditions. This analytical study is based on an idealized configuration of a straight magnetic flux tube with a weak magnetic twist inside as well as outside the tube. By implementing the conservation laws derived by Sakurai et al. and the analytic solutions for weakly twisted flux tubes obtained recently by Giagkiozis et al. we derive a dispersion relation for resonantly damped axisymmetric modes in the spectrum of the Alfvén continuum. We also obtain an insightful analytical expression for the damping rate in the long wavelength limit. Furthermore, it is shown that both the longitudinal magnetic field and the density, which are allowed to vary continuously in the inhomogeneous layer, have a significant impact on the damping time. Given the conditions in the solar atmosphere, resonantly damped axisymmetric modes are highly likely to be ubiquitous and play an important role in energy dissipation. We also suggest that, given the character of these waves, it is likely that they have already been observed in the guise of Alfvén waves
Using the unmet obstetric needs indicator to map inequities in life-saving obstetric interventions at the local health care system in Kenya
A virtual appliance as proxy pipeline for the Solar Orbiter/Metis coronagraph
Metis is the coronagraph on board Solar Orbiter, the ESA mission devoted to the study of the Sun that will be launched in October 2018. Metis is designed to perform imaging of the solar corona in the UV at 121.6 nm and in the visible range where it will accomplish polarimetry studies thanks to a variable retarder plate. Due to mission constraints, the telemetry downlink on the spacecraft will be limited and data will be downloaded with delays that could reach, in the worst case, several months. In order to have a quick overview on the ongoing operations and to check the safety of the 10 instruments on board, a high-priority downlink channel has been foreseen to download a restricted amount of data. These so-called Low Latency Data will be downloaded daily and, since they could trigger possible actions, they have to be quickly processed on ground as soon as they are delivered. To do so, a proper processing pipeline has to be developed by each instrument. This tool will then be integrated in a single system at the ESA Science Operation Center that will receive the downloaded data by the Mission Operation Center. This paper will provide a brief overview of the on board processing and data produced by Metis and it will describe the proxy-pipeline currently under development to deal with the Metis low-latency data
On Solving the Coronal Heating Problem
This article assesses the current state of understanding of coronal heating,
outlines the key elements of a comprehensive strategy for solving the problem,
and warns of obstacles that must be overcome along the way.Comment: Accepted by Solar Physics; Published by Solar Physic
Host switching pathogens, infectious outbreaks and zoonosis: A Marie Skłodowska-Curie innovative training network (HONOURs)
The increase of the human population is accompanied by growing numbers of livestock to feed this population, as well as by an increase of human invasion into natural habitats of wild animals. As a result, both animals and humans are becoming progressively vulnerable to infections with known (zoonotic) pathogens, but are also increasingly exposed to novel viruses. Global trade as well as climate changes can contribute to pathogen transmission, e.g. through import of infected vectors or expansion of habitats for arthropod vectors such as mosquitoes and midges. Infectious disease outbreaks, especially those by novel viruses, are generally unexpected, and therefore we should be prepared with tools and abilities for immediate action, including the identification of the causative agent, the evaluation of its pathogenic potential for animals and humans, and the fast development of diagnostic assays to allow contact tracing and quarantine measures. HONOURs is a Marie Skłodowska-Curie Actions Innovative Training Network (MSCA-ITN), teaching 15 talented young researchers to become “preparedness-experts”. HONOURs, initiated in April 2017, involves 11 laboratories from 6 different European countries, all at the forefront of novel virus investigations and characterizations. The network includes surveillance experts in both the veterinary and the human health sector, who have developed and utilize highly sensitive virus discovery techniques, e.g. next generation sequencing based genomics and universal primers based PCR, to allow identification and characterization of novel viruses. Production of pure viral proteins, providing high-resolution structures, aids in the design of novel, fast and easy-to-use diagnostics. Organotypic in vitro cell cultures systems (e.g. pseudostratified human airway epithelia) provide tools for virus replication, if needed via a reverse genetics platform, and the production of virus stocks permits inoculation in animal models to examine disease, evaluate candidate vaccines, and fulfilment of the Koch's postulates. Scientists of the various institutes will provide training in the HONOURs network through specialized courses and workshops, combined with challenging research projects. The final aim of the network is to deliver 15 expert scientists, ready to act in case of the emergence of an epidemic
Solar Physics in the 2020s: DKIST, Parker Solar Probe, and Solar Orbiter as a Multi-Messenger Constellation
The National Science Foundation (NSF) Daniel K. Inouye Solar Telescope (DKIST) has started operations at the summit of Haleakalā (Hawai'i). DKIST joins the nominal science phases of the NASA and ESA Parker Solar Probe and Solar Orbiter encounter missions. By combining in-situ measurements of the near-Sun plasma environment and detailed remote observations of multiple layers of the Sun, the three observatories form an unprecedented multi-messenger constellation to study the magnetic connectivity in the solar system. This work outlines the synergistic science that this multi-messenger suite enables
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