| 1. |
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| 2. |
- Jana, Somnath, et al.
(författare)
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Atom-specific magnon driven ultrafast spin dynamics in Fe1-xNix alloys
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- By employing element specific ultrafast spectroscopy in Fe1-xNix alloys alloys, we find a composition dependent effect in the demagnetization that we relate to changes in electron-magnon scattering. In all six measured alloys of different composition, the demagnetization of Ni compared to Fe exhibits a delay, an effect which we find is inherent in alloys but not in elemental Fe and Ni. Using a model based on electron-magnon scattering, we extract a spin-wave stiffness from all alloys that show excellent agreement with values obtained from other techniques. The result establishes the atom-specific sd-exchange induced magnon generation as an underlying mechanism during ultrafast demagnetization in Fe1-xNix alloys
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| 3. |
- Jana, Somnath, et al.
(författare)
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Atom-specific magnon-driven ultrafast spin dynamics in Fe1-xNix alloys
- 2023
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 107:18
-
Tidskriftsartikel (refereegranskat)abstract
- By employing element-specific spectroscopy in the ultrafast time scale in Fe1-xNix alloys, we find a composition-dependent effect in the demagnetization that we relate to electron-magnon scattering and changes in the spin-wave stiffness. In all six measured alloys of different composition, the demagnetization of Ni compared to Fe exhibits a delay, an effect which we find is inherent in alloys but not in elemental Fe and Ni. Using a model based on electron-magnon scattering, we extract a spin-wave stiffness from all alloys that show excellent agreement with values obtained from other techniques.
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| 4. |
- Arnell, Matilda, 1987-
(författare)
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Distribution patterns of fleshy-fruited woody plants at local and regional scales
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fleshy-fruited woody plants share a long history with humans, providing us with food and wood material. Because of this relation, we have actively moved some of these plants across landscapes and continents. In Sweden, these species are often found in open and semi-open habitats such as forest edges, their fruits are most often dispersed by birds and their flowers are, with some exceptions, pollinated by insects. In this thesis my overall aim was to map and analyse distribution patterns of fleshy-fruited woody plants in Sweden to expand our knowledge on the mechanisms governing their distributions. First, I mapped a population of the early flowering, fleshy-fruited shrub Daphne mezereum (common mezeron, tibast) and surveyed the reproduction and fruit removal of all individuals (chapter I). My main aim was to investigate to what extent reproduction and fruit removal was affected by local distribution patterns. Secondly, I mapped local distribution patterns of fleshy-fruited woody species and analysed spatial associations between life stages and species (chapter II). My main aim was to relate these spatial associations to predictions of how bird dispersal would shape the local distribution patterns and the hypothesis that birds create ‘wild orchards’. Thirdly, I digitized historical maps and surveyed fleshy-fruited woody species along transects across landscapes (chapter III). My aim was to examine the hypothesis that these species accumulate in open and semi open habitats created by human land use. Fourthly, I estimated range filling of woody plants in Sweden at a 1 km2 resolution (chapter IV). My aim was to compare these estimates among species with different dispersal systems to understand the effect of dispersal on the occupancy of woody species at regional scales.I found the distribution patterns of these species to be affected by past and present land use, supporting the hypothesis that these plants accumulate in open habitats. Occurrences of species in this guild in todays’ forest are positively related to past human land use (chapter III) and the density of D. mezereum increases with decreasing distances to forest edges (chapter I). This accumulation may in part be explained by the positive effect of forest edges on reproduction and fruit removal (chapter I). I further found local distribution patterns of this guild and the individual species to be aggregated (chapter I and II), and spatial associations between saplings and reproductive individuals to support the ‘orchard’ hypothesis (chapter II). The aggregated pattern of fruit-bearing individuals was positively related to fruit removal whereas aggregated flowering individuals was negatively related to fruit set (chapter I). On the regional scale, I found these species to occupy climatically suitable areas, or fill their potential ranges, to a less extent that wind dispersed trees and shrubs (chapter IV), which may indicate dispersal limitation.In conclusion, the behaviour of birds and humans have shaped, and still shape the current distribution of fleshy-fruited trees and shrubs in Sweden, resulting in accumulation in open habitats and locally aggregated distribution patterns. Changing land-use practices and potential mismatches between fruit maturation and bird dispersal with a changing climate may thus result in even lower chances of these species to fill their potential ranges, due to habitat losses and dispersal limitations at local and regional scales.
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| 5. |
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| 6. |
- Arnell, Matilda, 1987-, et al.
(författare)
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Reproductive success, fruit removal and local distribution patterns in the early-flowering shrub Daphne mezereum
- 2023
-
Ingår i: Nordic Journal of Botany. - 0107-055X .- 1756-1051. ; :10
-
Tidskriftsartikel (refereegranskat)abstract
- In insect-pollinated, bird-dispersed plants, both investment in reproduction and reproductive success involve interactions between plants and their pollinators and dispersers. The outcome of these plant–animal interactions may be affected by the number of flowers and fruits, as well as by the plants' local environment and by spatial associations among plants. In this study we mapped the spatial distribution of individuals in a population of the early flowering, fleshy-fruited shrub Daphne mezereum, in a forest in boreo-nemoral Sweden. For all mapped individuals we collected data on numbers of flowers and fruits and fruit removal, for three consecutive years. We analysed spatial associations among individuals, and the effects on reproductive performance and fruit removal of plant height, numbers of flowers and fruits, distance to forest edge, and neighbouring flower and fruit density. Our results show that the density of D. mezereum increases with increasing proximity to forest edge. The number of flowers produced, as well as fruit set and fruit removal, show the same positive relationship with increasing proximity to forest edges. We further show that individuals are aggregated up to distances of about 10 m. The flower production of neighbouring conspecific individuals within 10 m is negatively related to fruit set whereas the fruit production of neighbours is positively related to fruit removal. Our main conclusion is that the spatial distribution of D. mezereum affects reproductive success and fruit removal, which in turn has the potential to feed back to the spatial distribution pattern. Combining studies of reproduction with spatial analyses is important to advance our understanding of the dynamics of plant populations.
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| 7. |
- Eriksson, Emelie, 1987-
(författare)
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Patterns of corporate visual selfrepresentation in accounting narratives
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation deals with firms’ visual and pre-visual self-representations in accounting narratives. Self-representations are those descriptions about the company that firms include in accounting narratives to convey the current standings and their identity. External stakeholders increasingly expect non-numerical information about firms to be disclosed, and accounting narratives are a key medium for firms to account for their activities and maintain legitimacy as social actors. The question of which reporting conventions exist for legitimating selfrepresentations, especially from a visual perspective, remains unexplored. The purpose of this study is therefore to explore the empirical phenomenon of self-representations in accounting narratives in relation to legitimation rhetoric.The study is based on three research papers dealing with different patterns of self-representations in accounting-related narratives, including corporate reporting and business model diagrams. The examples are viewed through the theoretical lenses of semiotics and institutional theory, particularly legitimation theory. The study combines visual methods (visual content analysis and visual taxonomy) with other methods (interviews, text analysis) to conceptualize and exemplify what is meant by self-representations in accounting narratives. The study finds that there may be multiple parallel pre-visual self-representations at play to influence representations of the self, that visual self-representations are becoming more common in accounting narratives, and that several rhetorical strategies for legitimation are observable in these representations. By showing how diagrams can serve a legitimating purpose in accounting narratives, it is argued that diagrams should be considered on par with graphs and photographs as visual rhetorical devices in accounting narratives, and that they could be used as key communicative elements in the accounting process.Second, based on the longitudinal and comparative examples of self-representations, it is suggested that self-representations increasingly refer to abstract rather than concrete referents. This change is discussed in terms of the increasingly digital and service-based knowledge economy, where material referents give way to “amaterial” values. The contribution of this study is to describe selfrepresentations through several empirical examples, and to thereby increase awareness among practitioners and researchers of how visuals serve as communicative resources with legitimating functions in accounting narratives. Four concepts are proposed as tools for explaining the observed developments, and for improving visual literacy with regard to accounting narratives: inclusive perspective on accounting narratives, amateriality, self-representation, and diagrams.
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| 8. |
- Eriksson, Johan, 1987, et al.
(författare)
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An atom probe tomography study of the chemistry of radiation-induced dislocation loops in Zircaloy-2 exposed to boiling water reactor operation
- 2021
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 550
-
Tidskriftsartikel (refereegranskat)abstract
- This study is complementary to previous atom probe tomography (APT) studies of irradiation effects in the zirconium alloy Zircaloy-2. Using APT in voltage pulse mode, a difference in morphology was observed between clusters of Fe and Ni and clusters of Fe and Cr in Zircaloy-2 exposed to a high fast neutron fluence in a commercial boiling water reactor. The Fe–Ni clusters were disc-shaped with a diameter of 5–15 nm, whereas the Fe–Cr clusters were spheroidal with a diameter of approximately 5 nm. Both types of clusters appeared to be located at irradiation-induced -type dislocation loops aligned in layers normal to the -direction. The concentration of Fe was higher in the Fe–Cr clusters than in the Fe–Ni clusters. The dilute Fe–Ni clusters, which seem to be segregation of Fe and Ni inside the loops, had formed on all three families of first-order prismatic planes with some deviation from perfect -axis alignment. The Fe–Cr clusters might be very small precipitates with a nucleation associated with the loops.
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| 9. |
- Eriksson, Johan, 1987
(författare)
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Atom probe tomography of Zircaloy-2 exposed to boiling water reactor operation
- 2021
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Zirconium alloys are used as cladding tubes for the fuel in nuclear reactors. In boiling water reactors (BWRs), the alloy Zircaloy-2, which contains the alloying elements Sn, Fe, Cr, Ni, and O, is commonly used. In this thesis, results from atom probe tomography studies of Zircaloy-2 exposed to three and nine annual cycles of BWR operation are presented. The alloying elements were observed to be redistributed after reactor exposure. Clusters of Fe and Cr or Fe and Ni were observed at expected positions of radiation-induced type dislocation loops. Regions containing mainly Fe–Cr clusters were much more common than regions containing mainly Fe–Ni clusters. The Fe–Cr clusters appeared dense and spheroidal, whereas the Fe–Ni clusters appeared dilute and disc-shaped. The Fe–Ni discs occupied planes that correspond to all three families of first-order prismatic planes but with deviation from perfect axis alignment. Many grain boundaries were observed, and there were large grain-to-grain variations in cluster number density and cluster composition. Regarding cluster number density, there was on average no difference between three cycles and nine cycles. After nine cycles the clusters were on average larger and contained more Cr. Sn was observed to cluster in regions where there were no Fe–Cr or Fe–Ni clusters. Enrichment of Sn and Fe and small amounts of Cr and Ni was observed at grain boundaries. After nine cycles, but not after three cycles, enrichment of Sn, Fe, and Ni at ring-shaped features interpreted to be radiation-induced component loops was observed. Hydrogen was observed to be preferentially located outside a partially dissolved Zr(Fe,Cr)2 second phase particle that also contained Ni and Si. The present work demonstrates that the well-known dislocation loops have a chemistry, in the form of clusters of different types and shapes, that might substantially affect mechanisms degrading the cladding tubes, e.g. irradiation growth, corrosion, and hydrogen pickup.
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| 10. |
- Eriksson, Johan, 1987
(författare)
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Evolution of microstructure and nanoscale chemistry of Zircaloy-2-type alloys during nuclear reactor operation
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Zirconium alloys are used as fuel cladding tubes in nuclear reactors. During reactor operation, these alloys are degraded by corrosion, hydrogen pickup (HPU), and radiation-induced growth, processes influenced by the alloying elements. The alloy Zircaloy-2, which contains Sn, Fe, Cr, Ni, and O as alloying elements, is commonly used in boiling water reactors (BWRs). This thesis deals with atom probe tomography (APT) investigations of Zircaloy-2 and a similar model alloy, Alloy 2, before and after up to nine years of BWR operation. Alloy 2 contains more Fe and Cr and exhibits lower corrosion and HPU. Less than 10 wt ppm each of Fe, Cr, and Ni was observed in the matrix of as-produced Zircaloy-2 and Alloy 2 of commercial heat treatment, a consequence of very low solubility and formation of second phase particles (SPPs). After reactor exposure, these elements were found in nanoscale clusters that were located at radiation-induced ⟨a⟩-type dislocation loops. The amount of Fe, Cr, and Ni in clusters increased with increasing fluence. There were two main types of clusters, spheroidal Fe–Cr clusters and disc-shaped Fe–Ni clusters. On average there were no large differences in clusters before and after acceleration in degradation, only small increases in cluster number density, cluster size, and cluster Cr content. ⟨c⟩-component loops decorated with Sn, Fe, and Ni were observed after but not before acceleration in degradation. Sn formed a network-like structure. No differences in cluster and matrix chemistry between Zircaloy-2 and Alloy 2 were observed after reactor exposure, indicating that the improved properties of Alloy 2 are related to additional Fe and Cr being located in SPPs. It was possible to analyse the materials using voltage-pulsed APT. Voltage pulsing was needed to reliably determine Fe–Ni cluster composition and shape. Fe–Cr clusters were observed also using laser-pulsed APT. Focused-ion-beam (FIB) preparation of APT specimens at room temperature resulted in phase transformation from α-Zr to γ-hydride, whereas cryo-FIB preparation did not. The average number of ions detected before specimen fracture was higher for γ-hydride specimens. There were no significant differences in clustering of Fe, Cr, and Ni between α-Zr and γ-hydride specimens.
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| 11. |
- Eriksson, Johan, 1987, et al.
(författare)
-
Nanoscale chemistry of Zircaloy-2 exposed to three and nine annual cycles of boiling water reactor operation — an atom probe tomography study
- 2022
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 561
-
Tidskriftsartikel (refereegranskat)abstract
- Atom probe tomography was used in this work to study the metal close to the metal/oxide interface in the zirconium alloy Zircaloy-2 exposed to three and nine annual cycles of operation in a commercial boiling water reactor. The two exposure times correspond to before and after the onset of acceleration in corrosion, hydrogen pickup, and growth. The alloying elements Sn, Fe, Cr, and Ni were observed to be redistributed after exposure. After both three and nine cycles, clusters containing Fe and Cr and typically of a spheroidal shape with an approximate diameter of 5 nm were observed to be located in layers presumed to be layers of -loops. On average, the cluster number density was slightly higher after nine cycles, with larger and more Cr-rich clusters. However, there were large grain-to-grain variations, which were larger than the differences between the two exposure times. Ni was only occasionally observed in the clusters. Sn was observed to be slightly enriched in the Fe–Cr clusters, but the Sn concentration was higher between than inside the layers of clusters. After nine cycles, clusters of Sn were detected in regions that were depleted of Fe and Cr. Enrichment of Sn, Fe, and Ni at features that appeared to be -component loops was observed after nine cycles, whereas no such features were observed after three cycles. Enrichment of Sn and Fe, and small amounts of Cr and Ni, was observed at grain boundaries after both exposure times. After three cycles, a partially dissolved second phase particle of Zr(Fe,Cr)2 type that contained about ten times more Cr than Fe was observed.
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| 12. |
- Eriksson, Johan, 1987, et al.
(författare)
-
Solute Concentrations in the Matrix of Zirconium Alloys Studied by Atom Probe Tomography
- 2023
-
Ingår i: ASTM Special Technical Publication. - 0066-0558. ; STP1645, s. 149-172
-
Konferensbidrag (refereegranskat)abstract
- This work indicates that the matrix content of the alloying elements iron, chromium, and nickel in as-produced commercial Zircaloy-2-type materials is lower than what has been indicated by many previous studies. Atom probe tomography in voltage pulse mode was used to study the matrix content of solutes in Zircaloy-2 of type LK3/L and a similar model alloy, called Alloy 2, of the same heat treatment. Both alloys were analyzed in the as-produced state and after reactor exposure. In the as-produced materials, the concentrations of iron, chromium, and nickel were all below the detection limits of around 10 wt. ppm. After reactor exposure, these alloying elements were observed to reside in clusters at loops, and the matrix content (including clusters) of iron had increased to about 1,200 wt. ppm in the fueled region of the rod and to about half that value in the plenum region. The chromium content in the fueled region was approximately 100 wt. ppm, and the nickel content was approximately 200 wt. ppm. In the plenum region, the content of these elements was lower. However, due to an uneven distribution of clusters, there was a wide scatter in the measured concentrations in the irradiated materials. Additionally, the matrix concentrations of solute elements in (nonirradiated) Zircaloy-2 were investigated for a series of samples subjected to a annealing at 770◦C followed by cooling at different rates. From these measurements, the solubilities at 770◦C were estimated to be around 65 wt. ppm for chromium, at least 37 wt. ppm for iron, and below 9 wt. ppm for nickel. Slow cooling resulted in virtually no iron, chromium, or nickel in the matrix. The concentration of aluminum in the matrix was observed to be between 10 and 20 wt. ppm for all a-annealed samples and for the as-produced materials of commercial heat treatment.
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| 13. |
- Lage, Sandra, 1987-, et al.
(författare)
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BMAA in shellfish from two Portuguese transitional water bodies suggests the marine dinoflagellate Gymnodinium catenatum as a potential BMAA source
- 2014
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Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 152, s. 131-138
-
Tidskriftsartikel (refereegranskat)abstract
- The neurotoxin -N-methylamino-l-alanine (BMAA) and its putative role in multiple neurodegenera-tive diseases have been intensely studied since 2005 when the toxin was discovered to be producedby worldwide-distributed cyanobacterial species inhabiting terrestrial, marine, brackish, and freshwaterecosystems. Recently, BMAA production was also associated with one eukaryotic group, namely, diatoms,raising questions about its production by other phytoplanktonic groups. To test for BMAA bioavailabilityin ecosystems where abundant phytoplanktonic blooms regularly occur, samples of filter-feeding shell-fish were collected in two Portuguese transitional water bodies. BMAA content in cockles (Cerastodermaedule) collected weekly between September and November 2009 from Ria de Aveiro and at least once amonth from May to November from Ria Formosa, fluctuated from 0.079 ± 0.055 to 0.354 ± 0.066 g/g DWand from below the limit of detection to 0.434 ± 0.110 g/g DW, respectively. Simultaneously to BMAAoccurrence in cockles, paralytic shellfish toxins were detected in shellfish as a result of Gymnodiniumcatenatum blooms indicating a possible link between this marine dinoflagellate and BMAA production.Moreover, considerable high BMAA levels, 0.457 ± 0.186 g/g DW, were then determined in a laboratorygrown culture of G. catenatum. This work reveals for the first time the presence of BMAA in shellfishfrom Atlantic transitional water bodies and consubstantiate evidences of G. catenatum as one of the mainsources of BMAA in these ecosystems.
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| 14. |
- Malik, Rameez Saeed, 1987-, et al.
(författare)
-
Ultrafast dynamics in Fe65Co35 alloys: Effect of Re doping
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Annan publikation (populärvet., debatt m.m.)abstract
- Soft magnetic FeCo alloys are of great interest due to their potential spintronics applications. The magnetic damping parameter plays a vital role in the performance of these spintronics devices. The Gilbert damping parameter increase in these alloys with doping of 5d elements. Here, we have investigated the effect of Re doping on the element-specific magnetization dynamics of Ru/Fe65Co35/Ru thin films using the time-resolved magneto-optical Kerr effect. When varying the concentration of Re from 0 to 12.6 %, no change of the demagnetization time constant is observed. However, a gradual change of the remagnetization time is observed with the increase of Re concentration. This remagnetization dynamics can be related to the Gilbert damping parameter of these films. An interesting time-resolved dynamics at the Ru-edge is observed. A significant increase (40%) of the asymmetry signal is observed for the undoped sample and drops down with the Re doping. This effect is possibly a super diffusive spin current going from the magnetic layer to the non magnetic capping layer.
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| 15. |
- Malik, Rameez Saeed, 1987-, et al.
(författare)
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Ultrafast magnetization dynamics in half-metallic Co2FeAl Heusler alloy
-
Annan publikation (populärvet., debatt m.m.)abstract
- We report on optically induced, ultrafast magnetization dynamics in the Heusler alloy Co2FeAl,probed by time-resolved magneto-optical Kerr effect. Experimental results are compared to resultsfrom electronic structure theory and atomistic spin-dynamics simulations. Experimentally, we findthat the demagnetization time (τM) in films of Co2FeAl is almost independent of varying structuralorder, and that it is similar to that in elemental 3d ferromagnets. In contrast, the slower processof magnetization recovery, specified byτR, is found to occur on picosecond time scales, and isdemonstrated to correlate strongly with the Gilbert damping parameter (α). Our results showthat Co2FeAl is unique, in that it is the first material that clearly demonstrates the importance ofthe damping parameter in the remagnetization process. Based on these results we argue that for Co2FeAl the remagnetization process is dominated by magnon dynamics, something which mighthave general applicabilit
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| 16. |
- Malik, Rameez Saeed, 1987-, et al.
(författare)
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Ultrafast magnetization dynamics in magnetically frustrated NiFe2O4 ferrimagnet
-
Annan publikation (populärvet., debatt m.m.)abstract
- NiFe2O4 shows complex dynamics between its elements after an ultrashort laser pulse excitation. The reflectivity shows oscillations, indicating either a reordering of the charge distribution several picoseconds after absorption of the laser pulse or a coherent phonon mode with a frequency of 0.5 THz. Also, the magnetic asymmetry exhibits oscillations that cannot be attributed to transverse magnetic excitations (magnons) but correspond to longitudinal excitations. The demagnetization shows different behavior depending on the excitation photon energy, for energies close to the band gap (1.55 eV) oscillations in the asymmetry are prominent, while for higher energies (3.1 eV) the demagnetization becomes dominant and the oscillations vanish. A fast demagnetization is observed when using 3.1 eV compared to 1.55 eV, while the electronic response remains similar, which indicates that the fast demagnetization dynamics is driven by holes created deeper in the valence band while the dynamics of electrons excited to d-states in the conduction band provides a smaller contribution to the demagnetization.The oscillations in the asymmetry can be a consequence of the competing exchange interactions that are antiferromagnetic between all three sublattices, but where a ferromagnetic alignment between octahedral Ni and octahedral Fe is the ground state.
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| 17. |
- Malik, Rameez Saeed, 1987-, et al.
(författare)
-
Ultrafast magnetization dynamics in the half-metallic Heusler alloy Co2FeAl
- 2021
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 104:10
-
Tidskriftsartikel (refereegranskat)abstract
- We report on optically induced, ultrafast magnetization dynamics in the Heusler alloy Co2FeAl, probed by time-resolved magneto-optical Kerr effect. Experimental results are compared to results from electronic structure theory and atomistic spin-dynamics simulations. Experimentally, we find that the demagnetization time (tau(M)) in films of Co2FeAl is almost independent of varying structural order, and that it is similar to that in elemental 3d ferromagnets. In contrast, the slower process of magnetization recovery, specified by tau(R), is found to occur on picosecond time scales, and is demonstrated to correlate strongly with the Gilbert damping parameter (alpha). Based on these results we argue that for Co2FeAl the remagnetization process is dominated by magnon dynamics, something which might have general applicability.
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| 18. |
- Mayweg, David, 1986, et al.
(författare)
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Focused Ion Beam induced hydride formation does not affect Fe, Ni, Cr-clusters in irradiated Zircaloy-2
- 2023
-
Ingår i: Journal of Nuclear Materials. - 0022-3115. ; 581
-
Tidskriftsartikel (refereegranskat)abstract
- Room temperature focused ion beam (FIB) milling is known to potentially promote the formation of hydrides in zirconium and its alloys. We used atom probe tomography (APT) to determine the composition of irradiated and as-produced Zircaloy-2 fuel cladding. We consistently found ∼ 50 at% hydrogen in all room temperature FIB-milled specimens run in voltage pulsing APT measurements. Crystallographic analysis of APT data however showed slightly better agreement with δ-hydride (ZrH2, FCC, ∼ 60–66.7 at% H) than γ-hydride (ZrH, FCT, ∼ 50 at% H). Electron energy loos spectroscopy (EELS) measurements prior to APT analyses confirmed the presence of δ-hydride. Hence, APT gives a systematic underestimation of hydrogen for Zr-hydride. Milling at cryogenic temperatures was found to not cause such hydride formation. However, we did not find significant differences in the clusters formed by segregation of the alloying elements Fe, Cr and Ni to irradiation induced a-loops whether the material was identified as α-Zr or hydride. Therefore, analyzing irradiation-induced redistribution of alloying elements in Zr fuel cladding using APT does not rely on FIB preparation at cryogenic temperatures. However, in conjunction with voltage pulsing APT cryo-FIB can be worthwhile if one aims at investigating hydrogen distribution or hydrides.
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| 19. |
- Mayweg, David, 1986, et al.
(författare)
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Formation of pure zirconium islands inside c-component loops in high-burnup fuel cladding
- 2024
-
Ingår i: Journal of Nuclear Materials. - 0022-3115. ; 597
-
Tidskriftsartikel (refereegranskat)abstract
- High-burnup Zr-based nuclear fuel claddings exhibit accelerated irradiation growth, corrosion and hydrogen pick-up, all correlated with the emergence of c-component dislocation loops. We made use of sub-nm-resolution atom probe tomography to characterize the nanoscale chemistry of c-loops in fuel cladding from boiling water reactor operation. We found segregation of Fe, Ni and Sn to dislocation lines and depletion of Sn and O inside the loops, resulting in nearly pure Zr islands. We also observed nucleation of suboxide inside one c-loop, pointing to a possible mechanism of accelerated in-reactor corrosion. Such Zr-islands might also promote hydride precipitation and associated degradation.
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| 20. |
- Naesström, Matilda, 1987-
(författare)
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Deep brain stimulation in obsessive-compulsive disorder
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Deep brain stimulation (DBS) is under investigation for severe obsessive-compulsive disorder (OCD) resistant to other therapies. As a crucial part of the anxiety circuit in the brain, the bed nucleus of stria terminalis (BNST) has been proposed as a target for DBS in OCD. However, the mechanism of action of BNST DBS in OCD is not yet fully understood. In our studies, the aim was to evaluate the effect and side effects of DBS in the BNST in severe OCD, to investigate which anatomical areas are being affected by the stimulation and what could be the potential mechanism of action of DBS in this target. We also explored the knowledge and concerns regarding DBS in OCD among psychiatrists, psychotherapists and patients suffering from the disorder. We investigate clinical outcomes and safety of DBS in the BNST in a series of 11 participants with severe therapy-refractory OCD. The primary outcome was a change in the Yale-Brown Obsessive-Compulsive Scale (YBOCS) scores one year after surgery. Using image and stimulation parameter data from the study above, we investigate through participant-specific simulation of the electric field, which anatomical areas are affected by the electric field, and if this can be related to the clinical results. Six of the participants were evaluated with symptom provocation fMRI pre-operatively and in DBS ON and OFF conditions. A web-based study surveyed psychiatrists, patients, and cognitive-behavioural therapists regarding previous knowledge of DBS, source of knowledge, attitudes, and concerns towards the therapy.At baseline, the mean±SD YBOCS score was 33±3.0. One year after DBS, mean±SD YBOCS score was 20±4.8 (38% improvement (range 10- 60%) p <0.01). Of the 11 participants, six were considered responders (decrease in YBOCS ≥35%) and four partial responders (decrease in YBOCS 25-34%). Surgical adverse events included one case of skin infection leading to reimplantation. The most common transient stimulation-related side-effects were anxiety and insomnia. The individual electric stimulation fields by stimulation in the BNST were similar at the 12 and 24-months follow up, involving mainly the anterior limb of the internal capsule (ALIC), genu of the internal capsule, BNST, fornix, anteromedial globus pallidus externa (GPe) and the anterior commissure. A statistically significant correlation (p < 0.05) between clinical effect measured by the YBOCS and simulation was found at the 12-month follow-up in the ventral ALIC and anteromedial GPe. A significant decrease in anxiety-related brain activity in the pre-supplementary motor area (pre-SMA) and the anterior insula was seen in 3/6 participants, with a comparable reduction (below significance level) in the other three participants. Results from the survey found that the primary source of information was from scientific sources among psychiatrists and psychotherapists. The patients' primary source of information was the media. Common concerns among the groups included complications from surgery, anaesthesia, stimulation side effects, and the novelty of the treatment. Specific concerns for the groups included; personality changes mentioned by patients and psychotherapists and ethical concerns among psychiatrists.BNST DBS is a promising therapy in severe therapy-refractory OCD. Our results are in line with previous publications regarding effect and safety profiles. We hypothesise that possible mechanisms of BNST DBS in OCD could be modulation of anxiety-related activity in the pre-SMA and anterior insula, two regions that play an important role in the pathophysiology of OCD. Many of the targets under investigation for OCD are in anatomical proximity, and as seen in our study, offtarget effects overlap. Therefore, DBS in the region of ALIC, NA, and BNST may perhaps be considered to be stimulation of the same target. DBS challenges in obsessive-compulsive disorder consist of source and quality of information, potential long-term adverse effects and eligibility. A broad research agenda is needed for studies as we advance in this field.
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| 21. |
- Natesan, Elanghovan, 1989, et al.
(författare)
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Effect of Strain Rate on the Deformation Behaviour of A356-T7 Cast Aluminium Alloys at Elevated Temperatures
- 2020
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 10:9, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Internal combustion engine downsizing and powertrain electrification trends in recent years have led to higher thermal loads on the cylinder head materials with an increased number of engine start–stop thermal load cycles. This requires designing cylinder heads that are resilient against thermomechanical fatigue damage. To reduce the developmental costs, reliable numerical models for use in computer-aided design approaches are required. Thus, a comprehensive understanding of the material deformation behaviour under loads mimicking in-service conditions is desired to make better engineering decisions. This study examines the effect of strain rate on the cyclic deformation behaviour of the A356-T7 + 0.5% Cu aluminium alloy commonly used in modern internal combustion engine cylinder heads. Samples extracted from the valve bridge areas of the cylinder heads are tested in strain-controlled fatigue tests. Samples are tested at strain rates of 1% s−1 and 10% s−1 at room temperature, 150 and 200 °C. The material exhibits increased isotropic hardening and softening rates and an increased number of cycles to failure at 10% s−1. The strain rate has a dramatic influence on the mean stress development at room temperature. The role of silicon particles in the fracture mechanism is investigated using electron microscopy techniques.
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- Vryonidis, Efstathios, 1989-, et al.
(författare)
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Pathways to Identify Electrophiles In Vivo Using Hemoglobin Adducts : Hydroxypropanoic Acid Valine Adduct and Its Possible Precursors
- 2022
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Ingår i: Chemical Research in Toxicology. - : American Chemical Society (ACS). - 0893-228X .- 1520-5010. ; 35:12, s. 2227-2240
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Tidskriftsartikel (refereegranskat)abstract
- Analytical methods and tools for the characterization of the human exposome by untargeted mass spectrometry approaches are advancing rapidly. Adductomics methods have been developed for untargeted screening of short-lived electrophiles, in the form of adducts to proteins or DNA, in vivo. The identification of an adduct and its precursor electrophile in the blood is more complex than that of stable chemicals. The present work aims to illustrate procedures for the identification of an adduct to N-terminal valine in hemoglobin detected with adductomics, and pathways for the tracing of its precursor and possible exposure sources. Identification of the adduct proceeded via preparation and characterization of standards of adduct analytes. Possible precursor(s) and exposure sources were investigated by measurements in blood of adduct formation by precursors in vitro and adduct levels in vivo. The adduct was identified as hydroxypropanoic acid valine (HPA-Val) by verification with a synthesized reference. The HPA-Val was measured together with other adducts (from acrylamide, glycidamide, glycidol, and acrylic acid) in human blood (n = 51, schoolchildren). The HPA-Val levels ranged between 6 and 76 pmol/g hemoglobin. The analysis of reference samples from humans and rodents showed that the HPA-Val adduct was observed in all studied samples. No correlation of the HPA-Val level with the other studied adducts was observed in humans, nor was an increase in tobacco smokers observed. A small increase was observed in rodents exposed to glycidol. The formation of the HPA-Val adduct upon incubation of blood with glycidic acid (an epoxide) was shown. The relatively high adduct levels observed in vivo in relation to the measured reactivity of the epoxide, and the fact that the epoxide is not described as naturally occurring, suggest that glycidic acid is not the only precursor of the HPA-Val adduct identified in vivo. Another endogenous electrophile is suspected to contribute to the in vivo HPA-Val adduct level.
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