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Sökning: WFRF:(Ahnesjö Jonas)

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  • Hargeby, Anders, et al. (författare)
  • Habitat-specific pigmentation in a freshwater isopod : Adaptive evolution over a small spatiotemporal scale
  • 2004
  • Ingår i: Evolution. - 0014-3820 .- 1558-5646. ; 58:1, s. 81-94
  • Tidskriftsartikel (refereegranskat)abstract
    • <p><strong data-auto="strong_text">Pigmentation</strong> in the <strong data-auto="strong_text">freshwater</strong> <strong data-auto="strong_text">isopod</strong> Asellus aquaticus (Crustacea) differed between <strong data-auto="strong_text">habitats</strong> in two Swedish lakes. In both lakes, <strong data-auto="strong_text">isopods</strong> had lighter <strong data-auto="strong_text">pigmentation</strong> in stands of submerged vegetation, consisting of stoneworts (Chara spp.), than in nearby stands of reed (Phragmites australis). Experimental crossings of light and dark <strong data-auto="strong_text">isopods</strong> in a common environment showed that <strong data-auto="strong_text">pigmentation</strong> had a genetic basis and that genetic variance was additive. Environmental effects of diet or chromatophore adjustment to the background had minor influence on <strong data-auto="strong_text">pigmentation</strong>, as shown by laboratory rearing of <strong data-auto="strong_text">isopods</strong> on stonewort or reed substrates, as well as analyses of stable isotope ratios for <strong data-auto="strong_text">isopods</strong> collected in the field. In both study lakes, the average phenotype became lighter with time (across generations) in recently established stonewort stands. Taken together, these results indicate that altered phenotype <strong data-auto="strong_text">pigmentation</strong> result from evolutionary responses to local differences in natural selection. Based on the assumption of two generations per year, the evolutionary rate of change in <strong data-auto="strong_text">pigmentation</strong>was 0.08 standard deviations per generation (haldanes) <strong data-auto="strong_text">over</strong> 20 generations in one lake and 0.22 haldanes <strong data-auto="strong_text">over</strong> two generations in the other lake. This genetic change occurred during an episode of population growth in a novel <strong data-auto="strong_text">habitat</strong>, a situation known to promote <strong data-auto="strong_text">adaptive</strong> <strong data-auto="strong_text">evolution</strong>. In addition, stonewort stands constitute large and persistent patches, characteristics that tend to preserve local adaptations produced by natural selection. Results from studies on selective forces behind the <strong data-auto="strong_text">adaptive</strong>divergence suggest that selective predation from visually oriented predators is a possible selective agent. We found no indications of phenotype-<strong data-auto="strong_text">specific</strong>movements between <strong data-auto="strong_text">habitats</strong>. Mating within stonewort stands was random with respect to <strong data-auto="strong_text">pigmentation</strong>, but on a whole-lake <strong data-auto="strong_text">scale</strong> it is likely that mating is assortative, as a result of local differences in phenotype distribution.</p>
  • Ahnesjö, Jonas, 1969-, et al. (författare)
  • Effects on white blood cells in senior citizens during post exercise recovery in three different environments (indoors, simulated outdoors and outdoors)
  • 2016
  • Ingår i: HERO.
  • Konferensbidrag (refereegranskat)abstract
    • <p>Introduction</p><p>Natural environments are known to promote health and may also provide extraordinary conditions for post exercise recovery (Kuo 2015). In the project Health Effects of Recreation Outdoors (HERO) we explore the hypothesis that post exercise recovery in natural environments may be reflected in white blood cell counts (WBC). In our study 50 seniors (age &gt;65 years) performed moderate physical activity (20 min) followed by passive recovery (2h) in three different environments (indoors, simulated outdoors and “true” outdoors).</p><p>Method</p><p>The experimental setup was a randomized cross-over design, thus all test persons did all treatments in a randomized order. We sampled white blood cells (WBC-diff), which were used to detect and quantify inflammatory response.</p><p>Results</p><p>Our early findings provide some support for the hypothesis that environment may impose differences in recovery effectiveness. White blood cell count (WBC-diff) appears to differ between the treatments and there is a significant interaction between sampling time and recovery environment in the monocytes, suggesting that the monocyte numbers differ, not only between sampling times but also between environments. In addition, WBC also show that some of the test persons develop leukocytosis during exercise and that white blood cell levels decrease rapidly immediately post exercise to levels significantly lower than base line values.</p><p>Discussion</p><p>Our results suggest that moderate physical activity in senior citizens may result in acute leukocytosis (see e.g. Sand et. al. 2013) and that recovery effectiveness (e.g in monocyte response) may be dependent upon environmental factors. The clinical importance of our results are not fully understood but there has been suggested an “open window” immediately post exercise in which infection risk may be elevated (Pedersen &amp; Toft 2000) and it is possible that recovery out of doors may reduce this risk.</p><p>References</p><p>Sand, K., L, Flatebo, K., Andersen, M., B., Maghazachi, A., A. (2013) World J Exp Med 20; 3(1): 11-20</p><p>Pedersen, B., K. &amp; Toft, A., D. (2000) Br J Sports Med 34:246–251</p><p>Kuo, M. (2015) Frontiers in Psychology 6:1-8</p>
  • Ahnesjö, Jonas, 1969-, et al. (författare)
  • Recreational fishing in an educational intervention context promotes awareness and knowledge about nature in schoolchildren
  • 2013
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • <p>Outdoor activities may be intuitively associated with interest for nature and environmental concern. However, most scientific studies suggest that no such correlation exists. In this quantitative study we have used a questionnaire and explored the hypothesis that a one day educational intervention may be a successful tool in increasing environmental awareness, interest for nature and interest for recreational fishing. We present evidence suggesting that educational interventions in which young people are exposed to natural environments in a recreational fishing context have positive effects on interest for nature and recreational fishing, knowledge about nature and environmental awareness. Our findings also reveal that frequency of nature visits does not correlate with self estimated interest for nature.  We also show that the observed effects of the educational intervention “Klassdraget” appear to be larger for the girls which are, by tradition, less interested in recreational fishing as compared to boys.</p>
  • Andersson, Jonas, 1975- (författare)
  • Ion recombination in liquid ionization chambers development of an experimental method to quantify general recombination
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • <p>An experimental method (the two-dose-rate method) for the correction of general recombination losses in liquid ionization chambers has been developed and employed in experiments with different liquids and radiation qualities. The method is based on a disassociation of initial and general recombination, since an ionized liquid is simultaneously affected by both of these processes.</p><p>The two-dose-rate method has been compared to an existing method for general recombination correction for liquid ionization chambers, and has been found to be the most robust method presently available.</p><p>The soundness of modelling general recombination in liquids on existing theory for gases has been evaluated, and experiments indicate that the process of general recombination is similar in a gas and a liquid. It is thus reasonable to employ theory for gases in the two-dose-rate method to achieve experimental corrections for general recombination in liquids. There are uncertainties in the disassociation of initial and general recombination in the two-dose-rate method for low applied voltages, where initial recombination has been found to cause deviating results for different liquids and radiation qualities.</p><p>Sensitivity to ambient electric fields has been identified in the microLion liquid ionization chamber (PTW, Germany). Experimental data may thus be perturbed if measurements are conducted in the presence of ambient electric fields, and the sensitivity has been found to increase with an increase in the applied voltage. This can prove to be experimentally limiting since general recombination may be too severe for accurate corrections if the applied voltage is low.</p>
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