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- Villforth, C., et al.
(författare)
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Variability and stability in blazar jets on time-scales of years : optical polarization monitoring of OJ 287 in 2005-2009
- 2010
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 402:3, s. 2087-2111
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Tidskriftsartikel (refereegranskat)abstract
- OJ 287 is a BL Lac object at redshift z = 0.306 that has shown double-peaked bursts at regular intervals of similar to 12 yr during the last similar to 40 yr. We analyse optical photopolarimetric monitoring data from 2005 to 2009, during which the latest double-peaked outburst occurred. The aim of this study is twofold: firstly, we aim to analyse variability patterns and statistical properties of the optical polarization light curve. We find a strong preferred position angle in optical polarization. The preferred position angle can be explained by separating the jet emission into two components: an optical polarization core and chaotic jet emission. The optical polarization core is stable on time-scales of years and can be explained as emission from an underlying quiescent jet component. The chaotic jet emission sometimes exhibits a circular movement in the Stokes plane. We find six such events, all on the time-scales of 10-20 d. We interpret these events as a shock front moving forwards and backwards in the jet, swiping through a helical magnetic field. Secondly, we use our data to assess different binary black hole models proposed to explain the regularly appearing double-peaked bursts in OJ 287. We compose a list of requirements a model has to fulfil to explain the mysterious behaviour observed in OJ 287. The list includes not only characteristics of the light curve but also other properties of OJ 287, such as the black hole mass and restrictions on accretion flow properties. We rate all existing models using this list and conclude that none of the models is able to explain all observations. We discuss possible new explanations and propose a new approach to understanding OJ 287. We suggest that both the double-peaked bursts and the evolution of the optical polarization position angle could be explained as a sign of resonant accretion of magnetic field lines, a 'magnetic breathing' of the disc.
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| 2. |
- Debeffe, L., et al.
(författare)
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Short- and long-term repeatability of docility in the roe deer: sex and age matter
- 2015
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 109, s. 53-63
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Tidskriftsartikel (refereegranskat)abstract
- Behavioural consistency is a key assumption when evaluating how between-individual differences in behaviour influence life history tactics. Hence, understanding how and why variation in behavioural repeatability occurs is crucial. While analyses of behavioural repeatability are common, few studies of wild populations have investigated variation in repeatability in relation to individual status (e.g. sex, age, condition) and over different timescales. Here, we aimed to fill this gap by assessing within-population variation in the repeatability of docility, as assessed by the individual’s response to human handling, in a free-ranging population of European roe deer, Capreolus capreolus. Docility was an equally repeatable behaviour at both short- and long-term timescales, suggesting that this behavioural trait is stable across time. Repeatability did not differ markedly between age and sex categories but tended to be higher in juvenile males than in juvenile females. Finally, contrary to expectation, individual variation in the repeatability of docility was not correlated with individual body mass. Further studies are required to assess the life history consequences of the individual variation in docility we report here.
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| 9. |
- Maselli, Bianca S., et al.
(författare)
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Comparative mutagenic activity of atmospheric particulate matter from limeira, stockholm, and kyoto
- 2019
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Ingår i: Environmental and Molecular Mutagenesis. - : Wiley. - 0893-6692 .- 1098-2280. ; 60:7, s. 607-616
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric particulate matter (PM) organic fractions from urban centers are frequently mutagenic for the Salmonella/microsome assay. This mutagenicity is related to both primary and secondary pollutants, and meteorological conditions have great influence on the secondary pollutant's formation. Our objective was to compare the mutagenicity of atmospheric total suspended particulates (TSP) from three cities with marked different meteorological conditions and TSP concentrations: Limeira (Brazil) with 99.0 mu g/m(3), Stockholm (Sweden) with 6.2 mu g/m(3), and Kyoto (Japan) with 28.0 mu g/m(3). For comparison, we used the same batch of filters, sample extraction method, and Salmonella/microsome testing protocol with 11 strains of Salmonella with and without metabolic activation. Samples were collected during winter and pooled into one single extract representing each city. All samples were mutagenic for all tested strains, except for TA102. Based on the strain's selectivity, nitroarenes, polycyclic aromatic hydrocarbons, and aromatic amines play a predominant role in the mutagenicity of these samples. The mutagenic potencies expressed by mass of extracted organic material (EOM; revertants/mu g EOM) were similar (similar to twofold difference) among the cities, despite differences in meteorological conditions and pollution sources. In contrast, the mutagenic potencies expressed by air volume (rev/m(3)) varied similar to 20-fold, with Limeira > Kyoto approximate to Stockholm. These results are the first systematic assessment of air mutagenicity from cities on three continents using the same protocols. The results confirm that the mutagenic potency expressed by EOM mass is similar regardless of continent of origin, whereas the mutagenic potency expressed by air volume can vary by orders of magnitude. Environ. Mol. Mutagen. 2019.
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| 10. |
- Meiland, FJ M., et al.
(författare)
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COGKNOW : helping people with mild dementia navigate their day
- 2007
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Konferensbidrag (refereegranskat)abstract
- Dementia is a progressive, chronic disease affecting 5% of all persons above 65 and over 40% of people over 90. The aim of the COGKNOW project is to achieve a breakthrough with research that addresses the needs of those with dementia, particularly those with mild dementia living in the community. This entails cognitive reinforcement in four main areas: helping people to remember, helping to maintain social contact, helping with performing daily life and recreational activities and finally enhance feelings of safety. Based on a sound foundation of needs reported in dementia literature, workshops and individual interviews have been carried out with dementia sufferers and their carers in three European countries. A ranked analysis of information from workshops and interviews, and the state of the art of successful ICT solutions will be the basis for formulating the functionalities of the technical solution and for the development of a cognitive prosthetic device with associated services for people with mild dementia. The research and evaluation will be conducted from human factors, technology, and business perspectives in three phases of one year each. In this paper we discuss the design of the COGKNOW project, the first results of the user needs inquiry workshops and the ICT solutions the COGKNOW project will focus on in the first year.
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