Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Meeus B) "

Sökning: WFRF:(Meeus B)

  • Resultat 11-18 av 18
  • Föregående 1[2]
Sortera/gruppera träfflistan
  • Liseau, René, 1949, et al. (författare)
  • Resolving the cold debris disc around a planet-hosting star. PACS photometric imaging observations of q1 Eridani (HD 10647, HR 506)
  • 2010
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 518:Article Number: L132
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. About two dozen exo-solar debris systems have been spatially resolved. These debris discs commonly display a variety of structural features such as clumps, rings, belts, excentric distributions and spiral patterns. In most cases, these features are believed to be formed, shaped and maintained by the dynamical influence of planets orbiting the host stars. In very few cases has the presence of the dynamically important planet(s) been inferred from direct observation. Aims. The solar-type star q(1) Eri is known to be surrounded by debris, extended on scales of less than or similar to 30 ''. The star is also known to host at least one planet, albeit on an orbit far too small to make it responsible for structures at distances of tens to hundreds of AU. The aim of the present investigation is twofold: to determine the optical and material properties of the debris and to infer the spatial distribution of the dust, which may hint at the presence of additional planets. Methods. The Photodetector Array Camera and Spectrometer (PACS) aboard the Herschel Space Observatory allows imaging observations in the far infrared at unprecedented resolution, i.e. at better than 6 '' to 12 '' over the wavelength range of 60 mu m to 210 mu m. Together with the results from ground-based observations, these spatially resolved data can be modelled to determine the nature of the debris and its evolution more reliably than what would be possible from unresolved data alone. Results. For the first time has the q(1) Eri disc been resolved at far infrared wavelengths. The PACS observations at 70 mu m, 100 mu m and 160 mu m reveal an oval image showing a disc-like structure in all bands, the size of which increases with wavelength. Assuming a circular shape yields the inclination of its equatorial plane with respect to that of the sky, i > 53 degrees. The results of image de-convolution indicate that i likely is larger than 63 degrees, where 90 degrees corresponds to an edge-on disc. Conclusions. The observed emission is thermal and optically thin. The resolved data are consistent with debris at temperatures below 30 K at radii larger than 120 AU. From image de-convolution, we find that q(1) Eri is surrounded by an about 40 AU wide ring at the radial distance of similar to 85 AU. This is the first real Edgeworth-Kuiper Belt analogue ever observed.
  • Marshall, J. P., et al. (författare)
  • A Herschel resolved far-infrared dust ring around HD 207129
  • 2011
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 529
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Dusty debris discs around main sequence stars are thought to be the result of continuous collisional grinding of planetesimals in the system. The majority of these systems are unresolved and analysis of the dust properties is limited by the lack of information regarding the dust location. Aims. The Herschel DUNES key program is observing 133 nearby, Sun-like stars (
  • Eiroa, C., et al. (författare)
  • Exocomet signatures around the A-shell star φ Leonis?
  • 2016
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361. ; 594
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an intensive monitoring of high-resolution spectra of the Ca ii K line in the A7IV shell star φ Leo at very short (minutes, hours), short (night to night), and medium (weeks, months) timescales. The spectra show remarkable variable absorptions on timescales of hours, days, and months. The characteristics of these sporadic events are very similar to most that are observed toward the debris disk host star β Pic, which are commonly interpreted as signs of the evaporation of solid, comet-like bodies grazing or falling onto the star. Therefore, our results suggest the presence of solid bodies around φ Leo. To our knowledge, with the exception of β Pic, our monitoring has the best time resolution at the mentioned timescales for a star with events attributed to exocomets. Assuming the cometary scenario and considering the timescales of our monitoring, our results indicate that φ Leo presents the richest environment with comet-like events known to date, second only to β Pic.
  • Pinto, P. B., et al. (författare)
  • Do Parental Pain Knowledge, Catastrophizing, and Hypervigilance Improve Following Pain Neuroscience Education in Healthy Children?
  • 2021
  • Ingår i: Children. - 2227-9067. ; 8:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Pediatric chronic pain is a challenging problem for children and their families, although it is still under-recognized and under-treated. The aim of this study was to investigate whether a pain neuroscience education program for children (PNE4Kids) delivered to healthy children aged 8 to 12 years old and attended by their parents would result in improved parental knowledge about pain neurophysiology, decreased parental pain catastrophizing about their own pain and their children's, decreased parental pain vigilance and awareness, and decreased fear of pain in children. Twenty-seven healthy child-parent dyads received a 45 min PNE4Kids session. Demographic data were collected, and the Neurophysiology of Pain Questionnaire (NPQ), Fear of Pain Questionnaire-Parent Proxy Report (FOPQ-P), Pain Catastrophizing Scale (PCS), Pain Catastrophizing Scale for Parents (PCS-P), and the Pain Vigilance and Awareness Questionnaire (PVAQ) were completed by the parents before and after the PNE4Kids session. Twenty-six dyads completed study participation. In response to the PNE4Kids session, significant short-term (1 week) improvements were shown in the NPQ (p < 0.001) and the FOPQ-P (p = 0.002). Parents' level of pain knowledge and children's fear of pain, reported by their parents, improved after a 45 min PNE4Kids session. Thus, PNE4Kids should likewise be further investigated in healthy child-parent dyads as it might be useful to target parental and children's pain cognitions at a young age.
  • Rebollido, I., et al. (författare)
  • Exocomets: A spectroscopic survey
  • 2020
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 639
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. While exoplanets are now routinely detected, the detection of small bodies in extrasolar systems remains challenging. Since the discovery of sporadic events, which are interpreted to be exocomets (falling evaporating bodies) around β Pic in the early 1980s, only ∼20 stars have been reported to host exocomet-like events. Aims. We aim to expand the sample of known exocomet-host stars, as well as to monitor the hot-gas environment around stars with previously known exocometary activity. Methods. We have obtained high-resolution optical spectra of a heterogeneous sample of 117 main-sequence stars in the spectral type range from B8 to G8. The data were collected in 14 observing campaigns over the course of two years from both hemispheres. We analysed the Ca » II K&H and Na » I D lines in order to search for non-photospheric absorptions that originated in the circumstellar environment and for variable events that could be caused by the outgassing of exocomet-like bodies. Results. We detected non-photospheric absorptions towards 50% of the sample, thus attributing a circumstellar origin to half of the detections (i.e. 26% of the sample). Hot circumstellar gas was detected in the metallic lines inspected via narrow stable absorptions and/or variable blue- and red-shifted absorption events. Such variable events were found in 18 stars in the Ca » II and/or Na » I lines; six of them are reported in the context of this work for the first time. In some cases, the variations we report in the Ca » II K line are similar to those observed in β Pic. While we do not find a significant trend in the age or location of the stars, we do find that the probability of finding CS gas in stars with larger v sin i is higher. We also find a weak trend with the presence of near-infrared excess and with anomalous (λ Boo-like) abundances, but this would require confirmation by expanding the sample.
  • Rebollido, I., et al. (författare)
  • The co-existence of hot and cold gas in debris discs
  • 2018
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 614
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Debris discs have often been described as gas-poor discs as the gas-to-dust ratio is expected to be considerably lower than in primordial, protoplanetary discs. However, recent observations have confirmed the presence of a non-negligible amount of cold gas in the circumstellar (CS) debris discs around young main-sequence stars. This cold gas has been suggested to be related to the outgassing of planetesimals and cometary-like objects. Aims. The goal of this paper is to investigate the presence of hot gas in the immediate surroundings of the cold-gas-bearing debris-disc central stars. Methods. High-resolution optical spectra of all currently known cold-gas-bearing debris-disc systems, with the exception of β Pic and Fomalhaut, have been obtained from La Palma (Spain), La Silla (Chile), and La Luz (Mexico) observatories. To verify the presence of hot gas around the sample of stars, we have analysed the Ca II H&K and the Na I D lines searching for non-photospheric absorptions of CS origin, usually attributed to cometary-like activity. Results. Narrow, stable Ca II and/or Na I absorption features have been detected superimposed to the photospheric lines in 10 out of the 15 observed cold-gas-bearing debris-disc stars. Features are found at the radial velocity of the stars, or slightly blue- or red-shifted, and/or at the velocity of the local interstellar medium (ISM). Some stars also present transient variable events or absorptions extended towards red wavelengths (red wings). These are the first detections of such Ca II features in 7 out of the 15 observed stars. Although an ISM origin cannot categorically be excluded, the results suggest that the stable and variable absorptions arise from relatively hot gas located in the CS close-in environment of the stars. This hot gas is detected in at least ~80%, of edge-on cold-gas-bearing debris discs, while in only ~10% of the discs seen close to face-on. We interpret this result as a geometrical effect, and suggest that the non-detection of hot gas absorptions in some face-on systems is due to the disc inclination and likely not to the absence of the hot-gas component. This gas is likely released in physical processes related in some way to the evaporation of exocomets, evaporation of dust grains, or grain-grain collisions close to the central star.
  • Sadd, Ben M., et al. (författare)
  • The genomes of two key bumblebee species with primitive eusocial organization
  • 2015
  • Ingår i: Genome Biology. - 1465-6906 .- 1474-760X. ; 16:76
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats.RESULTS: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits.CONCLUSIONS: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation.
  • Van Looveren, E., et al. (författare)
  • The Association between Sleep and Chronic Spinal Pain: A Systematic Review from the Last Decade
  • 2021
  • Ingår i: Journal of Clinical Medicine. - 2077-0383. ; 10:17
  • Tidskriftsartikel (refereegranskat)abstract
    • Chronic spinal pain, including both neck and low back pain, is a common disabling disorder in which sleep problems are frequently reported as a comorbidity. The complex processes of both sleep and chronic pain seem to have overlapping mechanisms, which may explain their often established bidirectional relationship. This systematic review aims to investigate the assumed association between sleep and chronic spinal pain by providing an overview of the literature from the last decade. Eligible studies were obtained by searching four databases (PubMed, Embase, Web of Science, and PsycARTICLES). Articles were found relevant if they included a human adult population and investigated the possible association between sleep parameters and chronic spinal pain. Only studies published after January 2009 were included, as this review aimed to provide an update of a previous literature overview on this topic. The quality of the studies was assessed by risk of bias and level of evidence. A total of twenty-seven studies (6 cohort, 5 case-control, and 16 cross-sectional studies) were included in this systematic review. The methodological quality of these studies was low to moderate. The majority of studies reported weak to moderate evidence for an association between sleep parameters and chronic spinal pain, with more severe pain accompanied by more disturbed sleep. Addressing frequently reported sleep problems in chronic spinal pain patients therefore appears to be a necessary complement to pain management to achieve optimal treatment outcomes.
Skapa referenser, mejla, bekava och länka
  • Resultat 11-18 av 18
  • Föregående 1[2]

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy