| 11. |
- Mertins, H. -Ch., et al.
(författare)
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Giant magneto-optical Faraday effect of graphene on Co in the soft x-ray range
- 2018
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 98:6
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Tidskriftsartikel (refereegranskat)abstract
- Using polarization analysis of linearly polarized synchrotron radiation we demonstrate the existence of a giant magneto-optical Faraday effect at the carbon 1s edge of single-layer graphene on Co, reaching Faraday rotation angles of 2.9 x 10(5)deg/mm. This value is of the order of those observed at the Co 3p and 2p edges. Using element-selective magnetic hysteresis curves we find that graphene on Co exhibits ferromagnetic order. The magnetism in graphene is found to be carried by and be strongly enhanced by aligned n orbitals of carbon atoms. It is induced by hybridization with the Co 3d(z)2 orbitals while carbon a bonds show negligible magnetism due to insignificant hybridization with Co. From additional x-ray magnetic circular dichroism and transversal magneto-optical Kerr effect spectra a magnetic moment of 0.14 mu(B) is estimated for graphene. From Faraday spectra the complete set of x-ray magneto-optical constants of graphene has been deduced which allows for future modeling of magneto-optical devices based on graphene. The strong magnetism in graphene results from hybridization of carbon p(z) and metal 3d orbitals. Atoms of the graphene sublattice A, placed on top of Co, lead to strongest hybridization with Co 3d(z)( )(2)orbitals. Carbon atoms of sublattice B, and those of rotated graphene domains without Co atoms beneath, hybridize with each other and with 3d(xy) and 3d(yz) orbitals of neighboring Co atoms forming tilted p(z) bonds. We show that the related reduction of A-B symmetry leads to a splitting of the spin-polarized density of conduction-band states which is responsible for the strong magneto-optical Faraday effect.
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| 12. |
- Suturin, S. M., et al.
(författare)
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Role of gallium diffusion in the formation of a magnetically dead layer at the Y3Fe5O12/Gd3Ga5O12 epitaxial interface
- 2018
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Ingår i: PHYSICAL REVIEW MATERIALS. - : AMER PHYSICAL SOC. - 2475-9953. ; 2:10
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Tidskriftsartikel (refereegranskat)abstract
- We have clarified the origin of a magnetically dead interface layer formed in yttrium iron garnet (YIG) films grown at above 700 degrees C onto a gadolinium gallium garnet (GGG) substrate by means of laser molecular beam epitaxy. The diffusion-assisted formation of a Ga-rich region at the YIG/GGG interface is demonstrated by means of composition depth profiling performed by x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and x-ray and neutron reflectometry. Our finding is in sharp contrast to the earlier expressed assumption that Gd acts as a migrant element in the YIG/GGG system. We further correlate the presence of a Ga-rich transition layer with considerable quenching of ferromagnetic resonance and spin wave propagation in thin YIG films. Finally, we clarify the origin of the enigmatic low-density overlayer that is often observed in neutron and x-ray reflectometry studies of the YIG/GGG epitaxial system.
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| 13. |
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| 14. |
- Rheubottom, Sarah, I, et al.
(författare)
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Hiding in the background : community-level patterns in invertebrate herbivory across the tundra biome
- 2019
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Ingår i: Polar Biology. - : Springer. - 0722-4060 .- 1432-2056. ; 42:10, s. 1881-1897
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Tidskriftsartikel (refereegranskat)abstract
- Invertebrate herbivores depend on external temperature for growth and metabolism. Continued warming in tundra ecosystems is proposed to result in increased invertebrate herbivory. However, empirical data about how current levels of invertebrate herbivory vary across the Arctic is limited and generally restricted to a single host plant or a small group of species, so predicting future change remains challenging. We investigated large-scale patterns of invertebrate herbivory across the tundra biome at the community level and explored how these patterns are related to long-term climatic conditions and year-of-sampling weather, habitat characteristics, and aboveground biomass production. Utilizing a standardized protocol, we collected samples from 92 plots nested within 20 tundra sites during summer 2015. We estimated the community-weighted biomass lost based on the total leaf area consumed by invertebrates for the most common plant species within each plot. Overall, invertebrate herbivory was prevalent at low intensities across the tundra, with estimates averaging 0.94% and ranging between 0.02 and 5.69% of plant biomass. Our results suggest that mid-summer temperature influences the intensity of invertebrate herbivory at the community level, consistent with the hypothesis that climate warming should increase plant losses to invertebrates in the tundra. However, most of the observed variation in herbivory was associated with other site level characteristics, indicating that other local ecological factors also play an important role. More details about the local drivers of invertebrate herbivory are necessary to predict the consequences for rapidly changing tundra ecosystems.
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| 15. |
- Sirkiä, Päivi M., et al.
(författare)
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Fecundity selection does not vary along a large geographical cline of trait means in a passerine bird
- 2015
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066. ; 114:4, s. 808-827
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Tidskriftsartikel (refereegranskat)abstract
- Local environmental and ecological conditions are commonly expected to result in local adaptation, although there are few examples of variation in phenotypic selection across continent-wide spatial scales. We collected standardized data on selection with respect to the highly variable plumage coloration of pied flycatcher (Ficedula hypoleucaPall.) males from 17 populations across the species' breeding range. The observed selection on multiple male coloration traits via the annual number of fledged young was generally relatively weak. The main aim of the present study, however, was to examine whether the current directional selection estimates are associated with distance to the sympatric area with the collared flycatcher (Ficedula albicollisTemminck), a sister species with which the pied flycatcher is showing character displacement. This pattern was expected because plumage traits in male pied flycatchers are changing with the distance to these areas of sympatry. However, we did not find such a pattern in current selection on coloration. There were no associations between current directional selection on ornamentation and latitude or longitude either. Interestingly, current selection on coloration traits was not associated with the observed mean plumage traits of the populations. Thus, there do not appear to be geographical gradients in current directional fecundity selection on male plumage ornamentation. The results of the present study do not support the idea that constant patterns in directional fecundity selection would play a major role in the maintenance of coloration among populations in this species. By contrast, the tendency for relatively weak mosaic-like variation in selection among populations could reflect just a snapshot of temporally variable, potentially environment-dependent, selection, as suggested by other studies in this system. Such fine-grained variable selection coupled with gene flow could maintain extensive phenotypic variation across populations.(c) 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 808-827.
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| 16. |
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| 17. |
- Agarwal, Girish, et al.
(författare)
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Light, the universe and everything-12 Herculean tasks for quantum cowboys and black diamond skiers
- 2018
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 65:11, s. 1261-1308
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Tidskriftsartikel (refereegranskat)abstract
- The Winter Colloquium on the Physics of Quantum Electronics (PQE) has been a seminal force in quantum optics and related areas since 1971. It is rather mind-boggling to recognize how the concepts presented at these conferences have transformed scientific understanding and human society. In January 2017, the participants of PQE were asked to consider the equally important prospects for the future, and to formulate a set of questions representing some of the greatest aspirations in this broad field. The result is this multi-authored paper, in which many of the world's leading experts address the following fundamental questions: (1) What is the future of gravitational wave astronomy? (2) Are there new quantum phases of matter away from equilibrium that can be found and exploited - such as the time crystal? (3) Quantum theory in uncharted territory: What can we learn? (4) What are the ultimate limits for laser photon energies? (5) What are the ultimate limits to temporal, spatial and optical resolution? (6) What novel roles will atoms play in technology? (7) What applications lie ahead for nitrogen-vacancy centres in diamond? (8) What is the future of quantum coherence, squeezing and entanglement for enhanced super-resolution and sensing? (9) How can we solve (some of) humanity's biggest problems through new quantum technologies? (10) What new understanding of materials and biological molecules will result from their dynamical characterization with free-electron lasers? (11) What new technologies and fundamental discoveries might quantum optics achieve by the end of this century? (12) What novel topological structures can be created and employed in quantum optics?
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| 18. |
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| 19. |
- Elmhagen, Bodil, et al.
(författare)
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Homage to Hersteinsson and Macdonald : climate warming and resource subsidies cause red fox range expansion and Arctic fox decline
- 2017
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Ingår i: Polar Research. - : Norwegian Polar Institute. - 0800-0395 .- 1751-8369. ; 36:suppl. 1
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Forskningsöversikt (refereegranskat)abstract
- Climate change can have a marked effect on the distribution and abundance of some species, as well as their interspecific interactions. In 1992, before ecological effects of anthropogenic climate change had developed into a topical research field, Hersteinsson and Macdonald published a seminal paper hypothesizing that the northern distribution limit of the red fox (Vulpes vulpes) is determined by food availability and ultimately climate, while the southern distribution limit of the Arctic fox (Vulpes lagopus) is determined by interspecific competition with the larger red fox. This hypothesis has inspired extensive research in several parts of the circumpolar distribution range of the Arctic fox. Over the past 25 years, it was shown that red foxes can exclude Arctic foxes from dens, space and food resources, and that red foxes kill and sometimes consume Arctic foxes. When the red fox increases to ecologically effective densities, it can cause Arctic fox decline, extirpation and range contraction, while conservation actions involving red fox culling can lead to Arctic fox recovery. Red fox advance in productive tundra, concurrent with Arctic fox retreat from this habitat, support the original hypothesis that climate warming will alter the geographical ranges of the species. However, recent studies show that anthropogenic subsidies also drive red fox advance, allowing red fox establishment north of its climate-imposed distribution limit. We conclude that synergies between anthropogenic subsidies and climate warming will speed up Arctic ecosystem change, allowing mobile species to establish and thrive in human-provided refugia, with potential spill-over effects in surrounding ecosystems.
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| 20. |
- Fretland, Asmund Avdem, et al.
(författare)
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Inflammatory Response After Laparoscopic Versus Open Resection of Colorectal Liver Metastases : Data From the Oslo-CoMet Trial.
- 2015
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Ingår i: Medicine. - 0025-7974 .- 1536-5964. ; 94:42, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Laparoscopic and open liver resection have not been compared in randomized trials. The aim of the current study was to compare the inflammatory response after laparoscopic and open resection of colorectal liver metastases (CLM) in a randomized controlled trial.This was a predefined exploratory substudy within the Oslo CoMet-study. Forty-five patients with CLM were randomized to laparoscopic (n = 23) or open (n = 22) resection. Ethylenediaminetetraacetic acid-plasma samples were collected preoperatively and at defined time points during and after surgery and snap frozen at -80 C. A total of 25 markers were examined using luminex and enzyme-linked immunosorbent assay techniques: high-mobility box group 1(HMGB-1), cell-free DNA (cfDNA), cytokines, and terminal C5b-9 complement complex complement activation.Eight inflammatory markers increased significantly from baseline: HMGB-1, cfDNA, interleukin (IL)-6, C-reactive protein, macrophage inflammatory protein -1β, monocyte chemotactic protein -1, IL-10, and terminal C5b-9 complement complex. Peak levels were reached at the end of or shortly after surgery. Five markers, HMGB-1, cfDNA, IL-6, C-reactive protein, and macrophage inflammatory protein -1β, showed significantly higher levels in the open surgery group compared with the laparoscopic surgery group.Laparoscopic resection of CLM reduced the inflammatory response compared with open resection. The lower level of HMGB-1 is interesting because of the known association with oncogenesis.
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