| 1. |
- Buntgen, U., et al.
(författare)
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Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the 14C content in 484 individual tree rings formed in the periods 770–780 and 990–1000 CE. Distinct 14C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved 14C measurements are needed.
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| 2. |
- Frankenberg, Sofia J., et al.
(författare)
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Bidirectional collaborations in an intervention randomized controlled trial performed in the Swedish early childhood education context
- 2019
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Ingår i: Journal of Cognition and Development. - : Informa UK Limited. - 1524-8372 .- 1532-7647. ; 20:2, s. 182-202
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Tidskriftsartikel (refereegranskat)abstract
- Within the field of developmental science, there is a general agreement of the need to work together across academic disciplinary boundaries in order to advance the understandings of how to optimize child development and learning. However, experience also shows that such collaborations may be challenging. This paper reports on the experiences of bidirectional collaboration between researchers in a multidisciplinary research team and between researchers and stakeholders, in the first randomized controlled trial in Swedish preschool. The objective of the trial was to investigate the effects of two pedagogical learning strategies evaluating language, communication, attention, executive functions and early math. The interdisciplinary team includes researchers from early childhood education, linguistics, developmental psychology and cognitive neuro science. Educational researchers and theorists within the field of early childhood education in Sweden have during the last two decades mainly undertaken small-scale qualitative praxis-oriented and participative research. There is a widespread skepticism with regards to some of the core principles in controlled intervention methodologies, including a strong resistance towards individual testing of children. Consequently unanticipated disagreements and conflicts arose within the research team, as RCT methodology requires the measurement of effects pre and post the intervention. The aim of this article is to discuss the conditions for bidirectional collaboration both between researchers and stakeholders and between researchers in the research team. The findings illustrate strategies and negotiations that emerged in order to address ontological and epistemological controversies and disagreements. These include (a) the negotiation of research ethics, (b) making divergences visible and learning from each other, (c) using a multi-epistemological and methodological approach as a complement to the RCT design and (d) the negotiation of research problems that are shared between educators and researchers.
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