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| 12. |
- Dahlqvist, Peter
(författare)
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Late Ordovician-Early Silurian facies development and stratigraphy of Jämtland, central Sweden
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is based on studies of Lower Palaeozoic sedimentary successions within the central Scandinavian Caledonides. These deposits have been transported by considerable nappe displacement (several kilometres), and are today relatively isolated from the nearest coeval outcrops (Dalarna 250 km, Oslo Region 350 km). As a consequence, and due to the previously limited biostratigraphical control the investigated area have received little attention the last decades. Therefore, a detailed investigation, using several untried geological tools was performed. During the study it became clear that the strata reflected substantial changes in depositional environment and complexity in lateral facies relationship during the Late Ordovician?Early Silurian. This was a time characterised by global environmental changes such as glacio-eustasy and climate change, in particular during the end-Ordovician (Hirnantian) glaciation. Facies and sequence stratigraphical analysis of two key units (the Ede Quartzite and the Kyrkås Quartzite) and their preceding and succeeding units resulted in reinterpretations and refinement of the stratigraphy. The new data implied that the successions could be linked to known Hirnantian sea-level fluctuations. This correlation was subsequently supported, and our understanding of the timing of changes was improved, by biostratigraphical evidence (conodonts, graptolites, and brachiopods). This revealed a ca 5 myr stratigraphical gap, within the Ede Quartzite, spanning the Ordovician?Silurian boundary. It is concluded that the interaction of allocyclic changes (sea level and climate) were the overriding controls on deposition during the Late Ordovician?Early Silurian in the Jämtland basin. The contrasting sedimentary architecture of the Ede Quartzite to the west and the partly coeval Kyrkås Quartzite to the east remained enigmatic. Provenance studies (radiometric dating of zircons) tentatively indicate different dominating source areas, but further studies are needed to solve their relationship.
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| 13. |
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| 14. |
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| 15. |
- Dahlqvist, Peter, et al.
(författare)
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The lowermost Silurian of Jamtland, central Sweden: conodont biostratigraphy, correlation and biofacies
- 2005
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Ingår i: Transactions of the Royal Society of Edinburgh. Earth Sciences. - 0263-5933. ; 96:1, s. 1-19
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Forskningsöversikt (refereegranskat)abstract
- The Late Ordovician-Early Silurian succession in Jamtland includes the marine Kogsta Siltstone, which is unconformably overlain by the shallow-water Ede Quartzite that grades into the open-marine Berge Limestone. A Hirnantia shelly fauna dates the uppermost Kogsta Siltstone as Hirnantian, and shelly fossils indicate an Aeronian age for the Berge Limestone. Biostratigraphically highly diagnostic conodonts of the early-middle Aeronian Pranognathus tenuis Zone provide the first firm date of the Upper Ede Quartzite and the lowermost Berge Limestone. The Lower Ede Quartzite has not yielded fossils, but sedimentological data suggest it to be of Hirnantian age and reflect the glacio-eustatic low-stand. The contact between the Lower and Upper Ede Quartzite, here taken to be the Ordovician-Silurian boundary, appears to be an unconformity associated with a stratigraphic gap that at least includes the Rhuddanian Stage. The biostratigraphically important conodonts Pranognathus tenuis, Kockelella? manitoulinensis, and Pranognathus siluricus are recorded from Sweden for the first time, and these and other conodonts are used for correlations with coeval units in Europe and North America. In a regional review of Aeronian conodont faunas, three intergrading, apparently depth-related, conodont biofacies are recognised, the Jamtland conodonts representing the one characteristic of the shallowest water.
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| 16. |
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| 17. |
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| 18. |
- Engström, Susanne, 1962-
(författare)
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Fysiken spelar roll! : Undervisning om hållbara energisystem, fokus på gymnasiekursen fysik A
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis will present the result from one main investigation (step 1) and two follow-up studies (step 2 and 3). The main study consists of an interpreting, iterative analysis of statements made by ‘experts’ on contents of education gathered from a questionnaire, which result in a subject-specific content for physics education on sustainable energy systems (SES) presented as a category system. The categories from Step 1 are used as means for analysis in step 2 and 3, which involve the study of educational material and one classroom analysis. The results show that the content of physics for upper secondary, in order for students to reach insight, should comprise certain physical concepts and relations not only in “limited contexts” but also in relation to greater contextual connections, in which problematisation and insight in solutions for the future is necessary. These parts should have a similar weight according to the statements of the experts. This is not to be found in either the typical educational material (textbooks) or in one studied classroom teaching example.
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| 19. |
- Friman, O., et al.
(författare)
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A General Method for Correction of Intensity Inhomogeniety in Two Point Dixon Imaging
- 2008
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Ingår i: Proceedings of the International Society for Magnetic Resonance in Medicine annual meeting (ISMRM'08). - : International Society for Magnetic Resonance in Medicine.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Two point Dixon imaging can be used for quantitative fat estimation. However, field inhomogeneities pose a problem that needs to be corrected for before quantitative measurements can be obtained. We present a general framework for field inhomogeneitiy correction by fitting a set of smooth 3D spatial basis functions to voxels with high fat content. By choosing the number of basis functions, the smoothness constraint of the field can be controlled. The method is evaluated by measuring the FWHM of the fat peak in histograms for different number of basis functions. It is also compared to a previous method with good results.
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| 20. |
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