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| 2. |
- Johansson, Åke, et al.
(författare)
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A geochronological review of magmatism along the external margin of Columbia and in the Grenville-age orogens forming the core of Rodinia
- 2022
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268 .- 1872-7433. ; 371, s. 1-43
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Tidskriftsartikel (refereegranskat)abstract
- A total of 4344 magmatic U-Pb ages in the range 2300 to 800 Ma have been compiled from the Great Proterozoic Accretionary Orogen along the margin of the Columbia / Nuna supercontinent and from the subsequent Grenvillian collisional orogens forming the core of Rodinia. The age data are derived from Laurentia (North America and Greenland, n = 1212), Baltica (NE Europe, n = 1922), Amazonia (central South America, n = 625), Kalahari (southern Africa and Dronning Maud Land in East Antarctica, n = 386), and western Australia (n = 199). Laurentia, Baltica, and Amazonia (and possibly other cratons) most likely formed a ca. 10 000-km-long external active continental margin of Columbia from its assembly at ca. 1800 Ma until its dispersal at ca. 1260 Ma, after which all cratons studied were involved in the Rodinia-forming Grenvillian orogeny. However, the magmatic record is not smooth and even but highly irregular, with marked peaks and troughs, both for individual cratons and the combined data set. Magmatic peaks typically range in duration from a few tens of million years up to around hundred million years, with intervening troughs of comparable length. Some magmatic peaks are observed on multiple cratons, either by coincidence or because of paleogeographic proximity and common tectonic setting, while others are not. The best overall correlation, 0.617, is observed between Baltica and Amazonia, consistent with (but not definitive proof of) their being close neighbours in a SAMBA-like configuration at least in Columbia, and perhaps having shared the same peri-Columbian subduction system for a considerable time. Correlation factors between Laurentia and Baltica, or Laurentia and Amazonia, are below 0.14. Comparison between the Grenville Province in northeastern Laurentia and the Sveconorwegian Province in southwestern Fennoscandia (Baltica) shows some striking similarities, especially in the Mesoproterozoic, but also exhibits differences in the timing of events, especially during the final Grenville-Sveconorwegian collision, when the Sveconorwegian evolution seems to lag behind by some tens of million years. Between the other cratons, the evolution before and during the final Grenvillian collision is also largely diachronous. After 900 Ma, magmatic activity had ceased in all areas investigated, attesting to the position of most of them within the stable interior of Rodinia.
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- Bergemann, Maria, et al.
(författare)
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The Gaia-ESO Survey : Hydrogen lines in red giants directly trace stellar mass
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 594
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Tidskriftsartikel (refereegranskat)abstract
- Red giant stars are perhaps the most important type of stars for Galactic and extra-galactic archaeology: they are luminous, occur in all stellar populations, and their surface temperatures allow precise abundance determinations for many different chemical elements. Yet, the full star formation and enrichment history of a galaxy can be traced directly only if two key observables can be determined for large stellar samples: age and chemical composition. While spectroscopy is a powerful method to analyse the detailed abundances of stars, stellar ages are the missing link in the chain, since they are not a direct observable. However, spectroscopy should be able to estimate stellar masses, which for red giants directly infer ages provided their chemical composition is known. Here we establish a new empirical relation between the shape of the hydrogen line in the observed spectra of red giants and stellar mass determined from asteroseismology. The relation allows determining stellar masses and ages with an accuracy of 10-15%. The method can be used with confidence for stars in the following range of stellar parameters: 4000 < T-eff < 5000 K, 0.5 < log g < 3.5, -2.0 < [ Fe/H] < 0.3, and luminosities log L/L-Sun < 2.5. Our analysis provides observational evidence that the H-alpha spectral characteristics of red giant stars are tightly correlated with their mass and therefore their age. We also show that the method samples well all stellar populations with ages above 1 Gyr. Targeting bright giants, the method allows obtaining simultaneous age and chemical abundance information far deeper than would be possible with asteroseismology, extending the possible survey volume to remote regions of the Milky Way and even to neighbouring galaxies such as Andromeda or the Magellanic Clouds even with current instrumentation, such as the VLT and Keck facilities.
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| 4. |
- Evers, Arne, et al.
(författare)
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Testing Practices and Attitudes Toward Tests and Testing : An International Survey
- 2017
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Ingår i: International Journal of Testing. - : ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD. - 1530-5058 .- 1532-7574. ; 17:2, s. 158-190
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Tidskriftsartikel (refereegranskat)abstract
- On behalf of the International Test Commission and the European Federation of Psychologists' Associations a world-wide survey on the opinions of professional psychologists on testing practices was carried out. The main objective of this study was to collect data for a better understanding of the state of psychological testing worldwide. These data could guide the actions and measures taken by ITC, EFPA, and other stakeholders. A questionnaire was administered to 20,467 professional psychologists from 29 countries. Five scales were constructed relating to: concern over incorrect test use, regulations on tests and testing, internet and computerized testing, appreciation of tests, and knowledge and training relating to test use. Equivalence across countries was evaluated using the alignment method, four scales demonstrated acceptable levels of invariance. Multilevel analysis was used to determine how scores were related to age, gender, and specialization, as well as how scores varied between countries. Although the results show a high appreciation of tests in general, the appreciation of internet and computerized testing is much lower. These scales show low variability over countries, whereas differences between countries on the other reported scales are much greater. This implies the need for some overarching improvements as well as country-specific actions.
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