| 1. |
- Franke, A., et al.
(författare)
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Status and trends of circumpolar peregrine falcon and gyrfalcon populations
- 2020
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 49:3, s. 762-783
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Tidskriftsartikel (refereegranskat)abstract
- The peregrine falcon (Falco peregrinus) and the gyrfalcon (Falco rusticolus) are top avian predators of Arctic ecosystems. Although existing monitoring efforts are well established for both species, collaboration of activities among Arctic scientists actively involved in research of large falcons in the Nearctic and Palearctic has been poorly coordinated. Here we provide the first overview of Arctic falcon monitoring sites, present trends for long-term occupancy and productivity, and summarize information describing abundance, distribution, phenology, and health of the two species. We summarize data for 24 falcon monitoring sites across the Arctic, and identify gaps in coverage for eastern Russia, the Arctic Archipelago of Canada, and East Greenland. Our results indicate that peregrine falcon and gyrfalcon populations are generally stable, and assuming that these patterns hold beyond the temporal and spatial extents of the monitoring sites, it is reasonable to suggest that breeding populations at broader scales are similarly stable. We have highlighted several challenges that preclude direct comparisons of Focal Ecosystem Components (FEC) attributes among monitoring sites, and we acknowledge that methodological problems cannot be corrected retrospectively, but could be accounted for in future monitoring. Despite these drawbacks, ample opportunity exists to establish a coordinated monitoring program for Arctic-nesting raptor species that supports CBMP goals.
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| 2. |
- Ehrich, Dorothee, et al.
(författare)
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Documenting lemming population change in the Arctic : Can we detect trends?
- 2020
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 49:3, s. 786-800
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Tidskriftsartikel (refereegranskat)abstract
- Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective.
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| 3. |
- Marković, Igor, et al.
(författare)
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Electronically driven spin-reorientation transition of the correlated polar metal Ca3Ru2O7
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 117:27, s. 15524-15529
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Tidskriftsartikel (refereegranskat)abstract
- The interplay between spin-orbit coupling and structural inversion symmetry breaking in solids has generated much interest due to the nontrivial spin and magnetic textures which can result. Such studies are typically focused on systems where large atomic number elements lead to strong spin-orbit coupling, in turn rendering electronic correlations weak. In contrast, here we investigate the temperature-dependent electronic structure of Ca3Ru2O7, a 4d oxide metal for which both correlations and spin-orbit coupling are pronounced and in which octahedral tilts and rotations combine to mediate both global and local inversion symmetry-breaking polar distortions. Our angle-resolved photoemission measurements reveal the destruction of a large hole-like Fermi surface upon cooling through a coupled structural and spinreorientation transition at 48 K, accompanied by a sudden onset of quasiparticle coherence. We demonstrate how these result from band hybridization mediated by a hidden Rashba-type spin- orbit coupling. This is enabled by the bulk structural distortions and unlocked when the spin reorients perpendicular to the local symmetry-breaking potential at the Ru sites. We argue that the electronic energy gain associated with the band hybridization is actually the key driver for the phase transition, reflecting a delicate interplay between spin-orbit coupling and strong electronic correlations and revealing a route to control magnetic ordering in solids.
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| 4. |
- Romanovski, V. , I, et al.
(författare)
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Features of Cu - Ni nanoparticle synthesis : Experiment and computer simulation
- 2020
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Ingår i: PHYSICAL AND CHEMICAL ASPECTS OF THE STUDY OF CLUSTERS NANOSTRUCTURES AND NANOMATERIALS. - : Tver State University. - 2226-4442 .- 2658-4360. ; :12, s. 293-309
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Tidskriftsartikel (refereegranskat)abstract
- Combination of experiment and computer simulation made it possible to study the features of the process of Cu -Ni nanoparticle synthesis. Nanoparticles are synthesized by the method of exothermic combustion in solutions. The X-ray phase analysis of the obtained materials showed that all samples are pure bimetallic nanopowders with a distorted cubic crystal structure of each metal. The Monte-Carlo method in the temperature range from 300 to 600 K established regularities of the neck formation for two cases of the initial location of copper and nickel nanoparticles: direct contact and relative displacement by 0,2 nm. The possibility of close integration of crystal structures as a Cu and Ni nanoparticles interaction result is shown.
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| 5. |
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