SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Hutchings J.) "

Sökning: WFRF:(Hutchings J.)

  • Resultat 1-10 av 27
  • [1]23Nästa
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Tidskriftsartikel (refereegranskat)
  •  
2.
  • Tidskriftsartikel (refereegranskat)
  •  
3.
  • Tidskriftsartikel (refereegranskat)
  •  
4.
  • Tidskriftsartikel (refereegranskat)
  •  
5.
  • Edelson, R. A., et al. (författare)
  • Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
  • 1996
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
  • Tidskriftsartikel (refereegranskat)abstract
    • For pt.III see ibid., vol.470, no.1, p.349-63 (1996). Combines data from the three preceding papers in order to analyze the multi wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA=6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Aring. These data do not probe extreme ultraviolet (1200 Aring to 0.1 keV) or hard X-ray (250 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of lsim0.15 day between 1275 Aring and the other ultraviolet bands, lsim0.3 day between 1275 Aring and 1.5 keV, and lsim1 day between 1275 and 5125 Aring. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (ales-2.5)
  •  
6.
  • Crenshaw, D. M., et al. (författare)
  • Multiwavelength observations of short-timescale variability in NGC 4151. I. Ultraviolet observations
  • 1996
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 470:1, s. 322-335335
  • Tidskriftsartikel (refereegranskat)abstract
    • Presents the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every ~70 minutes, and during 4 hr periods for 4 days prior to and 5 days after the continuous-monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 to 2688 Aring went through four significant and well-defined ldquoeventsrdquo of duration 2-3 days during the continuous-monitoring period. The authors find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of ~0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip) and do not correlate well with continuum light curves over the short duration of the campaign, because the timescale for continuum variations is apparently smaller than the response times of the emission lines
  •  
7.
  •  
8.
  •  
9.
  • Knutsen, H., et al. (författare)
  • Stable coexistence of genetically divergent Atlantic cod ecotypes at multiple spatial scales
  • 2018
  • Ingår i: Evolutionary Applications. - 1752-4571. ; 11:9, s. 1527-1539
  • Tidskriftsartikel (refereegranskat)abstract
    • Coexistence in the same habitat of closely related yet genetically different populations is a phenomenon that challenges our understanding of local population structure and adaptation. Identifying the underlying mechanisms for such coexistence can yield new insight into adaptive evolution, diversification and the potential for organisms to adapt and persist in response to a changing environment. Recent studies have documented cryptic, sympatric populations of Atlantic cod (Gadus morhua) in coastal areas. We analysed genetic origin of 6,483 individual cod sampled annually over 14 years from 125 locations along the Norwegian Skagerrak coast and document stable coexistence of two genetically divergent Atlantic cod ecotypes throughout the study area and study period. A "fjord" ecotype dominated in numbers deep inside fjords while a "North Sea" ecotype was the only type found in offshore North Sea. Both ecotypes coexisted in similar proportions throughout coastal habitats at all spatial scales. The size-at-age of the North Sea ecotype on average exceeded that of the fjord ecotype by 20% in length and 80% in weight across all habitats. Different growth and size among individuals of the two types might be one of several ecologically significant variables that allow for stable coexistence of closely related populations within the same habitat. Management plans, biodiversity initiatives and other mitigation strategies that do not account for the mixture of species ecotypes are unlikely to meet objectives related to the sustainability of fish and fisheries.
  •  
10.
  • Nygren, Arne, 1971, et al. (författare)
  • A mega-cryptic species complex hidden among one of the most common annelids in the North East Atlantic
  • 2018
  • Ingår i: PLoS ONE. - 1932-6203. ; 13:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate mitochondrial (COI, 16S rDNA) and nuclear (ITS2, 28S rDNA) genetic structure of North East Atlantic lineages of Terebellides, a genus of sedentary annelids mainly inhabiting continental shelf and slope sediments. We demonstrate the presence of more than 25 species of which only seven are formally described. Species boundaries are determined with molecular data using a broad range of analytical methods. Many of the new species are common and wide spread, and the majority of the species are found in sympatry with several other species in the complex. Being one of the most regularly encountered annelid taxa in the North East Atlantic, it is more likely to find an undescribed species of Terebellides than a described one.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 27
  • [1]23Nästa
 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy