215 research outputs found
Modifications of thick-target model: re-acceleration of electron beams by static and stochastic electric fields
We study two modifications of the collisional thick-target model (CTTM) based
on the global and local re-acceleration of non-thermal electrons by static and
stochastic electric fields during their transport from the coronal acceleration
site to the thick-target region in the chromosphere. We concentrate on a
comparison of the non-thermal electron distribution functions, chromospheric
energy deposits, and HXR spectra obtained for both considered modifications
with the CTTM itself. The results were obtained using a relativistic
test-particle approach. We simulated the transport of non-thermal electrons
with a power-law spectrum including the influence of scattering, energy losses,
magnetic mirroring, and also the effects of the electric fields corresponding
to both modifications of the CTTM. We show that both modifications of the CTTM
change the outcome of the chromospheric bombardment in several aspects. The
modifications lead to an increase in chromospheric energy deposit, change of
its spatial distribution, and a substantial increase in the corresponding HXR
spectrum intensity.Comment: 15 pages, 14 figures, 3 tables, to be published in Astronomy and
Astrophysic
The High-redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey: Investigating the Role of Environment on Bent Radio AGNs Using LOFAR
© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Bent radio active galactic nucleus (AGN) morphology depends on the density of the surrounding gas. However, bent sources are found inside and outside clusters, raising the question of how environment impacts bent AGN morphology. We analyze new LOw-Frequency Array the LOFAR Two-metre Sky Survey (LoTSS) Data Release II observations of 20 bent AGNs in clusters and 15 not in clusters from the high-z Clusters Occupied by Bent Radio AGN (COBRA) survey (0.35 1.2 Mpc) or bent AGNs in weaker groups rather than the field.Peer reviewe
Response of optical hydrogen lines to beam heating: I. Electron beams
We investigate the role of non-thermal electrons in the formation regions of
Halpha, Hbeta, and Hgamma lines in order to unfold their influence on the
formation of these lines. We concentrate on pulse-beam heating varying on a
subsecond timescale. Furthermore, we theoretically explore possibility that a
new diagnostic tool exists indicating the presence of non-thermal electrons in
the flaring chromosphere based on observations of optical hydrogen lines. To
model the evolution of the flaring atmosphere and the time-dependent hydrogen
excitation and ionisation, we used a 1-D radiative hydrodynamic code combined
with a test-particle code that simulates the propagation, scattering, and
thermalisation of a power-law electron beam in order to obtain the flare
heating and the non-thermal collisional rates due to the interaction of the
beam with the hydrogen atoms. All calculated models have shown a
time-correlated response of the modelled Balmer line intensities on a subsecond
timescale, with a subsecond timelag behind the beam flux. Depending on the beam
parameters, both line centres and wings can show pronounced intensity
variations. The non-thermal collisional rates generally result in an increased
emission from a secondary region formed in the chromosphere.Comment: 13 pages, 11 figures, accepted to Astronomy and Astrophysic
Spiral valve parasites of blue and common thresher sharks as indicators of shark feeding behaviour and ecology
Open Access via the Jisc Wiley agreement Acknowledgements This work would not have been possible without the assistance and samples provided by the National Marine Fisheries Service (NMFS) Southwest Region Fishery Observer Program and the participating drift gillnet fishermen. A. Arevalo, E. Reed, H. Colley, J. Williams, J. Tamez and K. Tran assisted with spiral valve dissections and parasite sorting in the lab. D. Losey helped with library research. D. Sweetnam, A. Yau, A. Thompson, M. Craig, S. Stohs, G. DiNardo provided constructive critiques that helped improve the manuscript. This research was supported by the National Oceanographic Atmospheric Administration (NOAA).Peer reviewedPublisher PD
A scoping review of the implications of adult obesity in the delivery and acceptance of dental care.
Background Due to the increasing prevalence of obesity within the general population it is presumed that the prevalence of overweight and obese adults accessing dental services will also increase. For this reason dentists need to be aware of implications of managing such patients.Methods A scoping review was carried out. Both Medline via OVID and Scopus databases were searched along with grey literature databases and the websites of key organizations. Inclusion and exclusion criteria were established. The data were collected on a purpose-made data collection form and analysed descriptively.Results The review identified 28 relevant published articles and two relevant items of grey literature. Following review of this literature three themes relating to adult obesity in the delivery and acceptance of dental care emerged; clinical, service delivery and patient implications. The majority of the papers focused on the clinical implications.Conclusion On the topic of adult obesity and dental care, the majority of published and grey literature focuses on the clinical implications. Further research is needed on both the patients' perspectives of being overweight or obese and the delivery and acceptance of dental care and the service delivery implications
Where the wild things are: galaxy evolution and radio source properties in the High-z COBRA survey
Galaxie
The effect of tightly-bound water molecules on scaffold diversity in computer-aided de novo ligand design of CDK2 inhibitors
We have determined the effects that tightly bound water molecules have on the de novo design of cyclin-dependent kinase-2 (CDK2) ligands. In particular, we have analyzed the impact of a specific structural water molecule on the chemical diversity and binding mode of ligands generated through a de novo structure-based ligand generation method in the binding site of CDK2. The tightly bound water molecule modifies the size and shape of the binding site and we have found that it also imposed constraints on the observed binding modes of the generated ligands. This in turn had the indirect effect of reducing the chemical diversity of the underlying molecular scaffolds that were able to bind to the enzyme satisfactorily
Registro semiautomático entre imagens infravermelhas e RGB coletadas por um par de câmaras digitais
A utilização de imagens adquiridas por sensores CCDs de médio formato, em plataformas aéreas, é uma alternativa para a redução de custos de projetos de aerolevantamento. Porém, a utilização de sensores que captem somente a banda do visível (RGB) restringe algumas aplicações, tornando-se relevante integrar um sensor adicional que capte o infravermelho próximo (IR). No mercado há várias soluções para a aquisição simultânea de várias bandas espectrais. Uma alternativa que possibilita uma redução nos custos de integração é coletar as bandas RGB com uma câmara e a infravermelha com uma segunda câmara. É necessário, então, registrar as imagens, o que implica em determinar um conjunto de pontos ou feições correspondentes, calcular uma função de mapeamento polinomial e reamostrar uma das imagens. Um dos problemas mais críticos é a determinação de correspondência entre as imagens, devido às diferenças radiométricas entre as imagens. Neste trabalho são utilizadas técnicas de detecção de pontos de interesse e é proposta uma função de correspondência usando as diferenças nas magnitudes e direções dos gradientes de intensidade entre as imagens RGB e IR. Foram realizados vários experimentos com a técnica proposta, indicando que é possível utilizar esta técnica obtendo-se erros residuais inferiores a 1,5 pixel
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