| 1. |
- Lindgren, Johan, et al.
(författare)
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Molecular composition and ultrastructure of Jurassic paravian feathers
- 2015
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Feathers are amongst the most complex epidermal structures known, and they have a well-documented evolutionary trajectory across non-avian dinosaurs and basal birds. Moreover, melanosome-like microbodies preserved in association with fossil plumage have been used to reconstruct original colour, behaviour and physiology. However, these putative ancient melanosomes might alternatively represent microorganismal residues, a conflicting interpretation compounded by a lack of unambiguous chemical data. We therefore used sensitive molecular imaging, supported by multiple independent analytical tests, to demonstrate that the filamentous epidermal appendages in a new specimen of the Jurassic paravian Anchiornis comprise remnant eumelanosomes and fibril-like microstructures, preserved as endogenous eumelanin and authigenic calcium phosphate. These results provide novel insights into the early evolution of feathers at the sub-cellular level, and unequivocally determine that melanosomes can be preserved in fossil feathers.
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| 2. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 3. |
- Adman, Per, et al.
(författare)
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171 forskare: ”Vi vuxna bör också klimatprotestera”
- 2019
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Ingår i: Dagens nyheter (DN debatt). - Stockholm. - 1101-2447.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- DN DEBATT 26/9. Vuxna bör följa uppmaningen från ungdomarna i Fridays for future-rörelsen och protestera eftersom det politiska ledarskapet är otillräckligt. Omfattande och långvariga påtryckningar från hela samhället behövs för att få de politiskt ansvariga att utöva det ledarskap som klimatkrisen kräver, skriver 171 forskare i samhällsvetenskap och humaniora.
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| 4. |
- Gren, Johan, et al.
(författare)
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Dental histology of mosasaurs and a marine crocodylian from the Campanian (Upper Cretaceous) of southern Sweden: incremental growth lines and dentine formation rates
- 2014
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Ingår i: Geological Magazine. - 0016-7568. ; 151:1, s. 134-143
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Tidskriftsartikel (refereegranskat)abstract
- Mosasaurs are an extinct group of secondarily adapted aquatic lizards that became the dominant marine tetrapods in the Late Cretaceous oceans. They continuously shed and replaced their teeth in order to maintain a functional dentition at all times; however, the process of tooth development in mosasaurs is still incompletely known. Based on incremental line width measurements and growth line counts, we assess dentine formation rates in three mosasaur taxa (Dollosaurus, cf. Platecarpus and Tylosaurus) and one genus of marine crocodylian (Aigialosuchus), all from the lower Campanian (Upper Cretaceous) of southernmost Sweden. Two sets of periodic dentinal markings characterized by concentric, alternating opaque and transparent laminae are recognized: one set comprising thin bands situated 6-34 m apart (depending on taxon), which is superimposed onto a second set of coarser bands where spaces vary between 102 and 275 m. Assuming that the finer striations represent daily increments (i.e. lines of von Ebner), it is estimated that the deposition of dentine at the sectioned level of the tooth-crowns took 342 (cf. Platecarpus), 426 (Dollosaurus), 487 (Tylosaurus) and 259 (Aigialosuchus) days, respectively. The coarser bands contain between 11 and 13 thin striations each, and are thus considered to be homologous to similar periodic dentinal markings in extant vertebrates, i.e. Andresen lines. Prolonged tooth development times in large-toothed taxa, such as Tylosaurus, presumably increased the risk of long-term incapacity to capture prey after dental trauma, an evolutionary trade-off which may have been compensated for by allometric modifications of the teeth.
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| 5. |
- Gren, Johan, et al.
(författare)
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Molecular and microstructural inventory of an isolated fossil bird feather from the Eocene Fur Formation of Denmark
- 2017
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Ingår i: Palaeontology. - : Blackwell Publishing. - 0031-0239 .- 1475-4983. ; 60:1, s. 73-90
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Tidskriftsartikel (refereegranskat)abstract
- An isolated, yet virtually intact contour feather (FUM-1980) from the lower Eocene Fur Formation of Denmark was analysed using multiple imaging and molecular techniques, including field emission gun scanning electron microscopy (FEG-SEM), X-ray absorption spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Additionally, synchrotron radiation X-ray tomographic microscopy (SRXTM) was employed in order to produce a digital reconstruction of the fossil. Under FEG-SEM, the proximal, plumulaceous part of the feather revealed masses of ovoid microstructures, about 1.7 μm long and 0.5 μm wide. Microbodies in the distal, pennaceous portion were substantially smaller (averaging 0.9 × 0.2 μm), highly elongate, and more densely packed. Generally, the microbodies in both the plumulaceous and pennaceous segments were aligned along the barbs and located within shallow depressions on the exposed surfaces. Biomarkers consistent with animal eumelanins were co-localized with the microstructures, to suggest that they represent remnant eumelanosomes (i.e. eumelanin-housing cellular organelles). Additionally, ToF-SIMS analysis revealed the presence of sulfur-containing organics – potentially indicative of pheomelanins – associated with eumelanin-like compounds. However, since there was no correlation between melanosome morphology and sulfur content, we conclude these molecular structures derive from diagenetically incorporated sulfur rather than pheomelanin. Melanosomes corresponding roughly in both size and morphology with those in the proximal part of FUM-1980 are known from contour feathers of extant parrots (Psittaciformes), an avian clade that has previously been reported from the Fur Formation.
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| 6. |
- Lindgren, Johan, et al.
(författare)
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Biochemistry and adaptive colouration of an exceptionally preserved juvenile fossil sea turtle
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- The holotype (MHM-K2) of the Eocene cheloniine Tasbacka danica is arguably one of the best preserved juvenile fossil sea turtles on record. Notwithstanding compactional flattening, the specimen is virtually intact, comprising a fully articulated skeleton exposed in dorsal view. MHM-K2 also preserves, with great fidelity, soft tissue traces visible as a sharply delineated carbon film around the bones and marginal scutes along the edge of the carapace. Here we show that the extraordinary preservation of the type of T. danica goes beyond gross morphology to include ultrastructural details and labile molecular components of the once-living animal. Haemoglobin-derived compounds, eumelanic pigments and proteinaceous materials retaining the immunological characteristics of sauropsid-specific β-keratin and tropomyosin were detected in tissues containing remnant melanosomes and decayed keratin plates. The preserved organics represent condensed remains of the cornified epidermis and, likely also, deeper anatomical features, and provide direct chemical evidence that adaptive melanism - a biological means used by extant sea turtle hatchlings to elevate metabolic and growth rates - had evolved 54 million years ago. © 2017 The Author(s).
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| 7. |
- Lindgren, Johan, et al.
(författare)
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Interpreting melanin-based coloration through deep time : A critical Review
- 2015
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : Royal Society of London. - 0962-8452 .- 1471-2954. ; 282:1813
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Forskningsöversikt (refereegranskat)abstract
- Colour, derived primarily from melanin and/or carotenoid pigments, is integral to many aspects of behaviour in living vertebrates, including social signalling, sexual display and crypsis. Thus, identifying biochromes in extinct animals can shed light on the acquisition and evolution of these biological traits. Both eumelanin and melanin-containing cellular organelles (melanosomes) are preserved in fossils, but recognizing traces of ancient melanin-based coloration is fraught with interpretative ambiguity, especially when observations are based on morphological evidence alone. Assigning microbodies (or, more often reported, their ‘mouldic impressions’) as melanosome traces without adequately excluding a bacterial origin is also problematic because microbes are pervasive and intimately involved in organismal degradation. Additionally, some forms synthesize melanin. In this review, we survey both vertebrate and microbial melanization, and explore the conflicts influencing assessment of microbodies preserved in association with ancient animal soft tissues.We discuss the types of data used to interpret fossil melanosomes and evaluate whether these are sufficient for definitive diagnosis. Finally, we outline an integrated morphological and geochemical approach for detecting endogenous pigment remains and associated microstructures in multimillion-year-old fossils.
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| 8. |
- Lindgren, Johan, et al.
(författare)
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Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles.
- 2014
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 506:7489, s. 484-484
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Tidskriftsartikel (refereegranskat)abstract
- Throughout the animal kingdom, adaptive colouration serves critical functions ranging from inconspicuous camouflage to ostentatious sexual display, and can provide important information about the environment and biology of a particular organism. The most ubiquitous and abundant pigment, melanin, also has a diverse range of non-visual roles, including thermoregulation in ectotherms. However, little is known about the functional evolution of this important biochrome through deep time, owing to our limited ability to unambiguously identify traces of it in the fossil record. Here we present direct chemical evidence of pigmentation in fossilized skin, from three distantly related marine reptiles: a leatherback turtle, a mosasaur and an ichthyosaur. We demonstrate that dark traces of soft tissue in these fossils are dominated by molecularly preserved eumelanin, in intimate association with fossilized melanosomes. In addition, we suggest that contrary to the countershading of many pelagic animals, at least some ichthyosaurs were uniformly dark-coloured in life. Our analyses expand current knowledge of pigmentation in fossil integument beyond that of feathers, allowing for the reconstruction of colour over much greater ranges of extinct taxa and anatomy. In turn, our results provide evidence of convergent melanism in three disparate lineages of secondarily aquatic tetrapods. Based on extant marine analogues, we propose that the benefits of thermoregulation and/or crypsis are likely to have contributed to this melanisation, with the former having implications for the ability of each group to exploit cold environments.
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| 9. |
- Alonso Aller, Elisa, et al.
(författare)
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Single and joint effects of regional- and local-scale variables on tropical seagrass fish assemblages
- 2014
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 161:10, s. 2395-2405
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Tidskriftsartikel (refereegranskat)abstract
- Seagrass beds are highly important for tropical ecosystems by supporting abundant and diverse fish assemblages that form the basis for artisanal fisheries. Although a number of local- and regional-scale variables are known to influence the abundance, diversity and assemblage structure of seagrass-associated fish assemblages, few studies have evaluated the relative and joint (interacting) influences of variables, especially those acting at different scales. Here, we examined the relative importance of local- and regional-scale factors structuring seagrass-associated fish assemblages, using a field survey in six seagrass (Thalassodendron ciliatum) areas around Unguja Island (Zanzibar, Tanzania). Fish density and assemblage structure were mostly affected by two regional-scale variables; distance to coral reefs, which positively affected fish density, and level of human development, which negatively affected fish density. On the local scale, seagrass biomass had a positive (but weaker) influence on fish density. However, the positive effect of seagrass biomass decreased with increasing level of human development. In summary, our results highlight the importance of assessing how multiple local and regional variables, alone and together, influence fish communities, in order to improve management of seagrass ecosystems and their services.
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| 10. |
- Andersson, C A Morgan, 1965, et al.
(författare)
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Bygglov Göteborg 2017.
- 2022
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- I boken finns samlat beviljade bygglov för flerbostadshus i Göteborg 2017. Författarna analyserar i boken projekten och delat in dem i typer, antal och storlekar. Här beskrivs också tendenser som identifierats i byggloven, exempelvis nya kökstyper som korridorköket och entréköket. Men även planlösningsproblematik med lägenheter där alla sovrum vetter ut mot loftgång och lägenheter med stor andel kommunikationsyta. Boken lyfter också fram de goda exemplen, föredömen, som finns i materialet. Syftet med sammanställningen är att initiera en diskussion om vad som byggs, vilka lägenhetsstorlekar, vilka typer, var i staden nya bostäder byggs, vem som bygger, vilka arkitekter som ritar och vilka arkitekturkvaliteter som framgår av planlösningarna.
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| 11. |
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| 12. |
- Andersson, Erik, et al.
(författare)
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Reconnecting Cities to the Biosphere : Stewardship of Green Infrastructure and Urban Ecosystem Services
- 2014
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Ingår i: Ambio. - : Springer. - 0044-7447 .- 1654-7209. ; 43:4, s. 445-453
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Tidskriftsartikel (refereegranskat)abstract
- Within-city green infrastructure can offer opportunities and new contexts for people to become stewards of ecosystem services. We analyze cities as social-ecological systems, synthesize the literature, and provide examples from more than 15 years of research in the Stockholm urban region, Sweden. The social-ecological approach spans from investigating ecosystem properties to the social frameworks and personal values that drive and shape human interactions with nature. Key findings demonstrate that urban ecosystem services are generated by social-ecological systems and that local stewards are critically important. However, land-use planning and management seldom account for their role in the generation of urban ecosystem services. While the small scale patchwork of land uses in cities stimulates intense interactions across borders much focus is still on individual patches. The results highlight the importance and complexity of stewardship of urban biodiversity and ecosystem services and of the planning and governance of urban green infrastructure.
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| 13. |
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| 14. |
- Bahaloo, Hassan, et al.
(författare)
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Capillary Bridge in Contact with Ice Particles Can Be Related to the Thin Liquid Film on Ice
- 2024
-
Ingår i: Journal of cold regions engineering. - : American Society of Civil Engineers (ASCE). - 0887-381X .- 1943-5495. ; 38:1
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate the presence of a capillary bridge in the contact between an ice particle and a smooth aluminum surface at a relative humidity of approximately 50% and temperatures below the melting point. We conduct the experiments in a freezer with a controlled temperature and consider the mechanical instability of the bridge upon separation of the ice particle from the aluminum surface at a constant speed. We observe that a liquid bridge forms, and this formation becomes more pronounced as the temperature approaches the melting point. We also show that the separation distance is proportional to the cube root of the volume of the bridge. We hypothesize that the volume of the liquid bridge can be used to provide a rough estimate of the thickness of the liquid layer on the ice particle since in the absence of other driving mechanisms, some of the liquid on the surface must have been pulled to the bridge area. We show that the estimated value lies within the range previously reported in the literature. With these assumptions, the estimated thickness of the liquid layer decreases from nearly 56 nm at T = −1.7°C to 0.2 nm at T = −12.7°C. The dependence can be approximated with a power law, proportional to (TM − T)−β, where β < 2.6 and TM is the melting temperature. We further observe that for a rough surface, the capillary bridge formation in the considered experimental conditions vanishes.
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| 15. |
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| 16. |
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| 17. |
- Bahaloohoreh, Hassan, 1983-, et al.
(författare)
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Ice sintering: Dependence of sintering force on temperature, load, duration, and particle size
- 2022
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 131:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present experiments along with an approximate, semi-analytic, close-form solution to predict ice sintering force as a function of temperature, contact load, contact duration, and particle size during the primary stage of sintering. The ice sintering force increases nearly linear with increasing contact load but nonlinear with both contact duration and particle size in the form of a power law. The exponent of the power law for size dependence is around the value predicted by general sintering theory. The temperature dependence of the sintering force is also nonlinear and follows the Arrhenius equation. At temperatures closer to the melting point, a liquid bridge is observed upon the separation of the contacted ice particles. We also find that the ratio of ultimate tensile strength of ice to the axial stress concentration factor in tension is an important factor in determining the sintering force, and a value of nearly 1.1 MPa can best catch the sintering force of ice in different conditions. We find that the activation energy is around 41.4KJ/mol41.4KJ/mol, which is close to the previously reported data. Also, our results suggest that smaller particles are “stickier” than larger particles. Moreover, during the formation of the ice particles, cavitation and surface cracking is observed which can be one of the sources for the variations observed in the measured ice sintering force.
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| 18. |
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| 19. |
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| 20. |
- Barthel, Stephan, 1968-
(författare)
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Nytt miljonprogram unik chans att lösa flera frågor
- 2016
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Ingår i: Dagens Nyheter. - Stockholm. - 1101-2447. ; :25-apr
-
Annan publikation (populärvet., debatt m.m.)abstract
- Dolt värde av enorma mått. Ett nytt miljonprogram kan förskräcka, men kan vara just vad Sverige behöver. Men vi ska inte upprepa misstagen från förra gången. Istället måste politierna nu ta fasta på denna unika chans at ta itu med vår tids stora utmaningar som integration, tillväxt och hållbarhet.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Colding, Johan, et al.
(författare)
-
Frontiers in Social-Ecological Urbanism
- 2022
-
Ingår i: Land. - : MDPI AG. - 2073-445X. ; 11:6
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes a new approach in urban ecological design, referred to as social- ecological urbanism (SEU). It draws from research in resilience thinking and space syntax in the analysis of relationships between urban processes and urban form at the microlevel of cities, where social and ecological services are directly experienced by urban dwellers. The paper elaborates on three types of media for urban designers to intervene in urban systems, including urban form, institutions, and discourse, that together function as a significant enabler of urban change. The paper ends by presenting four future research frontiers with a potential to advance the field of social-ecological urbanism: (1) urban density and critical biodiversity thresholds, (2) human and non-human movement in urban space, (3) the retrofitting of urban design, and (4) reversing the trend of urban ecological illiteracy through affordance designs that connect people with nature and with each other.
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| 25. |
- Colding, Johan, 1958-, et al.
(författare)
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Frontiers in Social-Ecological Urbanism
- 2022
-
Ingår i: Land. - : MDPI AG. - 2073-445X. ; 11:6, s. 929-
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes a new approach in urban ecological design, referred to as social- ecological urbanism (SEU). It draws from research in resilience thinking and space syntax in the analysis of relationships between urban processes and urban form at the microlevel of cities, where social and ecological services are directly experienced by urban dwellers. The paper elaborates on three types of media for urban designers to intervene in urban systems, including urban form, institutions, and discourse, that together function as a significant enabler of urban change. The paper ends by presenting four future research frontiers with a potential to advance the field of social-ecological urbanism: (1) urban density and critical biodiversity thresholds, (2) human and non-human movement in urban space, (3) the retrofitting of urban design, and (4) reversing the trend of urban ecological illiteracy through affordance designs that connect people with nature and with each other.
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| 26. |
- Colding, Johan, et al.
(författare)
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The Incremental Demise of Urban Green Spaces
- 2020
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Ingår i: Land. - : MDPI AG. - 2073-445X. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- More precise explanations are needed to better understand why public green spaces are diminishing in cities, leading to the loss of ecosystem services that humans receive from natural systems. This paper is devoted to the incremental change of green spaces-a fate that is largely undetectable by urban residents. The paper elucidates a set of drivers resulting in the subtle loss of urban green spaces and elaborates on the consequences of this for resilience planning of ecosystem services. Incremental changes of greenspace trigger baseline shifts, where each generation of humans tends to take the current condition of an ecosystem as the normal state, disregarding its previous states. Even well-intended political land-use decisions, such as current privatization schemes, can cumulatively result in undesirable societal outcomes, leading to a gradual loss of opportunities for nature experience. Alfred E. Kahn referred to such decision making as 'the tyranny of small decisions.' This is mirrored in urban planning as problems that are dealt with in an ad hoc manner with no officially formulated vision for long-term spatial planning. Urban common property systems could provide interim solutions for local governments to survive periods of fiscal shortfalls. Transfer of proprietor rights to civil society groups can enhance the resilience of ecosystem services in cities.
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| 27. |
- Egegård, Colin Hultgren, et al.
(författare)
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Climate Proofing Cities by Navigating Nature-Based Solutions in a Multi-Scale, Social–Ecological Urban Planning Context: A Case Study of Flood Protection in the City of Gothenburg, Sweden
- 2024
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Ingår i: Land. - : MDPI. - 2073-445X. ; 13:2
-
Tidskriftsartikel (refereegranskat)abstract
- Due to unsustainable land management and climate change, floods have become more frequent and severe over the past few decades and the problem is exacerbated in urban environments. In the context of climate-proofing cities, the importance of nature-based solutions (NBSs), obtaining relevant outcomes in the form of ecosystem services, has been highlighted. Although the role of ecosystem services in building resilience against negative climate change effects is widely recognized and there is an identified need to better integrate ecosystem services into urban planning and design, this has proven difficult to operationalize. A critical limitation is that modeling is a time-consuming and costly exercise. The purpose is to roughly estimate the ecosystem service of water run-off mitigation through simplified, cost-effective, and user-friendly modelling at three nested biophysical scales, under four climate change scenarios. Using the Swedish city of Gothenburg as an example, we propose an approach for navigating NBS-oriented flooding adaptation strategies, by quantifying the ecosystem service of water run-off mitigation at three nested biophysical scales, under four climate change scenarios, hence, proposing an approach for how to navigate nature-based solutions in a multi-scale, social–ecological urban planning context against present and future flooding events. Our findings validate the effectiveness of employing an ecosystem service approach to better comprehend the significant climate change issue of flooding through user-friendly and cost-efficient modeling.
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| 28. |
- Einarsson, Elisabeth, et al.
(författare)
-
X-ray microtomography and 3D visualization of a plesiosaur propodial (Reptilia: Sauropterygia) from the Late Cretaceous of southern Sweden provides insights in bone histology, bone microstructures, and bone growth.
- 2023
-
Konferensbidrag (refereegranskat)abstract
- Polycotylid and elasmosaurid plesiosaurs inhabited the Kristianstad Basin during Late Cretaceous (uppermost lower Campanian Belemnellocamax mammillatuszone) around 80 million years ago. The setting represents one of the most famous Mesozoic fossil sites in Scandinavia. The Kristianstad Basin fossils are generally fragmentary and isolated due to high-energy environments in a protected shallow inner shelf bay with limited mixing from other water bodies.This study includes an isolated plesiosaurian propodial (R2008) from Ivö Klack, currently housed in the Natural History Museum of Stockholm. As preserved, the propodial measures 109 mm in length, 38 mm in width at the proximal shaft and 68 mm in the distal expanded part. A foramen is visible on the posterior surface of the shaft.We used X-ray microtomography to investigate inner bone structure and bone histology of the specimen. The method is non-destructive and provides a prime alternative to conventional thin sections. In addition to visualization through arbitrary 2D slicing of the 3D volume, image analysis was used to digitally segment hollow vascular canals. The internal vascular network and the foramen of the external surface were then visualized in 3D.Virtual longitudinal sections of R2008 display cancellous bone in a fan-like shape, emerging from the medullary cavity at the center of the specimen. The cancellous bone is surrounded by denser compact bone, in turn displaying a series of at least 10 lines of arrested growth (LAGs).Vascular canals are traceable throughout the cancellous bone, with a few large vessels at the center, branching into a multitude of smaller vessels at both the proximal and distal ends of the propodial. Our 3D model of the vascular canals provides a detailed overview of the nutrient distribution network, giving insight into the pattern of bone growth.We found that the method is valuable for highlighting features such as LAGs in compact bone, the contacts between compact and cancellous bone, and the network of vascular canals, while avoiding destructive sectioning of the sample. Use of this methodology is recommended as an alternative for exploring bone histology of fossil specimens where the integrity of the sample needs to be preserved.
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| 29. |
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| 30. |
- Engelmann, Marc, et al.
(författare)
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Hunters' trade-off in valuation of different game animals in Sweden
- 2018
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Ingår i: Forest Policy and Economics. - : Elsevier BV. - 1389-9341 .- 1872-7050. ; 92, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- Vehicle accidents and damage to farm and forest land by ungulates have been documented in several studies, which call for regulation of population size according to their damages. These species may also create value for hunters in terms of recreational and other values. However, in Sweden and many other countries hunters have access to multiple game species, which needs to be considered when comparing eventual costs and values of different game. In this study we estimated hunters' trade-offs in valuation of the four main game animals in Sweden, moose, roe deer, wild boar and small game, by regarding them as different attributes of hunting. To this end, a discrete choice experiment framework was used to elicit hunters' trade-offs between the different game animals. Estimates with a mixed logit model showed significant differences in valuations of the game animals. Average annual marginal willingness to pay (WTP) for hunting moose was SEK 1878/animal (SEK 8.44 = 1 USD in 2015), which was approximately four-fold and six-fold the corresponding WTP for roe deer and wild boar, respectively.
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| 31. |
- Engelmann, Marc, et al.
(författare)
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Hunting value of wild boar in Sweden: a choice experiment
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this study is to estimate hunters’ valuation of wild boar in Sweden. However, hunters have access to hunt, not only wild boar, but also other game such as moose and roe deer. Therefore, wild boar is regarded as an attribute of hunting together with other game, which includes moose, roe deer, and small game. A discrete choice experiment framework is used to elicit hunters’ trade-offs between wild boar, moose, roe deer and small game. Estimates with a mixed logit model showed that the average annual willingness to pay (WTP) for a wild boar is approximately SEK 330/animal, which corresponds to 1/8 of the average WTP for a moose and ¼ of that for a roe deer. The range in WTP is determined by the activity of the hunters, as measured by number of hunting days per year, the least active gives the lowest WTP (SEK 113) and the most active the highest WTP (SEK 529). This can be a result of the specific challenges when hunting the wild boars, which are active in night time and equipped with excellent hearing and smell. Hunters that are farmers also give a relatively low WTP (SEK 134), which can be explained by the damages on crops created by the animal
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| 32. |
- Gren, Daniel, 1994, et al.
(författare)
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Fatigue Crack Characteristics in Gradient Predeformed Pearlitic Steel under Multiaxial Loading
- 2024
-
Ingår i: Advanced Engineering Materials. - 1527-2648 .- 1438-1656. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Rolling contact fatigue of railway rails not only severely deforms the surface material near the rail head, but also induces an anisotropy in the mechanical behavior due to work hardening and alignment of the microstructure along the shear direction. Cracks typically initiate in this region and propagate along the aligned microstructure. The fatigue behavior of rails is evaluated under uniaxial loading in the undeformed material state. However, this is not representative of the contact loading condition and material performance after years of service. Herein, the nonproportional multiaxial fatigue of as-received and biaxially predeformed pearlitic rail steel R260 is investigated. Four material states are investigated, corresponding to the microstructure found at different depths from the severely deformed surface material at the rail head. A starting notch is machined by electrical discharge machining to control crack initiation and allow for comparable surface crack propagation measurements. The crack path is found to be strongly influenced by the degree of predeformation while the early surface crack propagation rate is found to be similar for all material states.
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| 33. |
- Gren, Daniel, 1994, et al.
(författare)
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Fatigue Crack Propagation on Uniaxial Loading of Biaxially Predeformed Pearlitic Rail Steel
- 2023
-
Ingår i: Metals. - 2075-4701. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- Rolling contact fatigue loading causes the surface material in the top of the rail to severely deform. The microstructure aligns along the shear direction and the mechanical behavior in terms of plastic flow becomes anisotropic. Cracks are initiated in the severely deformed surface region and propagates along the direction of microstructure flow lines. However, the effect of large shear deformation on fatigue crack growth is not yet well understood. In this study, uniaxial fatigue crack propagation of undeformed and biaxially predeformed pearlitic rail steel R260 has been investigated. The material was predeformed to different deformation states using combined axial compression and shear deformation, corresponding to material found at different depths in the severely deformed surface layer of rails. Fatigue crack propagation rate was dependent on the material state and influenced by both work hardening and microstructural anisotropy. It was found that predeformed material exhibited lower crack growth rates than undeformed material under this loading condition. The influence of predeformation on the crack growth direction was limited.
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| 34. |
- Gren, Johan
(författare)
-
Molecular, micro- and ultrastructural investigations of labile tissues in deep time
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis comprises investigations of microstructures and molecular remains, preserved in a variety of fossil specimens. The results are presented in six papers, collectively aiming to thoroughly examine fossil traces of such remains by employing a combination of both established and relatively new analytical methods. The main questions asked are: What can we learn about the biology, ecology and behaviour of ancient organisms by studying these fossilised remnants, and what methods are best suited to accomplish this?The work presented herein has been conducted through a series of case studies performed on fossils representing an array of taxa, collected from different geological ages and settings. Methods applied include light and electron microscopy, computed tomography, and molecular analyses, such as time-of-flight secondary ion mass spectrometry, IR microspectroscopy and X-ray absorption spectroscopy. Microscopic analysis and histology of teeth from Mesozoic marine reptiles allowed calculations of dentine formation and tooth replacement rates. My findings include evidence that while teeth of larger mosasaur taxa took longer time to develop, their dentine formation rates were more rapid, relative to that of smaller species.In other fossils, microscopic investigations of eye, skin and feather remnants revealed aggregations of micrometre-sized, sub-rounded to elongate structures. Because similar microbodies have previously been described alternatively as relict melanosomes (i.e. pigment-containing, eukaryotic cellular organelles) and lithified bacteria, my co-authors and I performed chemical and molecular analyses in order to explore the affinity of these structures. To ascertain the chemical identity of our fossil samples, corresponding analyses were carried out also on molecularly similar compounds, including modern eumelanin, as controls. My studies show chemical evidence of animal eumelanin in close association with the microbodies, advocating the melanosome interpretation for the analysed specimens.Beyond the results reported in the included papers, this thesis provides a short review of melanin formation in vertebrate eyes and integument, as well as in fungi and bacteria which also produce this type of pigment. An overview of the various methods applied is presented and followed by a discussion about possible outcomes and pitfalls when studying fossil microstructures and molecular palaeontology. Whereas remnant melanosomes could potentially provide new insight into a multitude of biological and ecological aspects of ancient life, there is still no straight-forward approach to determine the affinity of ‘melanosome-like’ microstructures found in fossils. Therefore, a thorough investigation of such remains, including chemical analyses, should be applied in each study – at least until a consensus has been reached regarding the minimum amount of criteria to be used for a confident recognition.
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| 35. |
- Gren, Åsa, et al.
(författare)
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How smart is smart growth? : Examining the environmental validation behind city compaction
- 2019
-
Ingår i: Ambio. - : Springer Netherlands. - 0044-7447 .- 1654-7209. ; 48:6, s. 580-589
-
Forskningsöversikt (refereegranskat)abstract
- Smart growth (SG) is widely adopted by planners and policy makers as an environmentally friendly way of building cities. In this paper, we analyze the environmental validity of the SG-approach based on a review of the scientific literature. We found a lack of proof of environmental gains, in combination with a great inconsistency in the measurements of different SG attributes. We found that a surprisingly limited number of studies have actually examined the environmental rationales behind SG, with 34% of those studies displaying negative environmental outcomes of SG. Based on the insights from the review, we propose that research within this context must first be founded in more advanced and consistent knowledge of geographic and spatial analyses. Second, it needs to a greater degree be based on a system's understanding of urban processes. Third, it needs to aim at making cities more resilient, e.g., against climate-change effects.
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| 36. |
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| 37. |
- Malmborg, Vilhelm, et al.
(författare)
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Relating aerosol mass spectra to composition and nanostructure of soot particles
- 2019
-
Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 142, s. 535-546
-
Tidskriftsartikel (refereegranskat)abstract
- The composition and carbon nanostructure of soot are important parameters influencing health and climate effects, and the efficacy of soot mitigation technologies. We used laser-vaporization, electron-ionization aerosol mass spectrometry (or SP-AMS) to systematically investigate relationships between aerosol mass spectra, carbon nanostructure (HRTEM), and composition (thermal-optical carbon analysis) for soot with varying physicochemical properties. SP-AMS refractory black carbon concentrations (based on C≤5+ clusters) were correlated to elemental carbon (r = 0.98, p < 10−8) and equivalent black carbon (aethalometer) concentrations. The SP-AMS large carbon (C≥6+, midcarbons and fullerene carbons) fraction was inversely correlated to fringe length (r = −0.97, p = 0.028) and linearly correlated to the fraction of refractory organic carbon that partially pyrolize during heating (r = 0.89, p < 10−4). This refractory organic carbon material was incompletely detected with conventional aerosol mass spectrometry (flash vaporization at 600 °C). This suggests that (SP-AMS) refractory carbon cluster analysis provides insight to chemical bonding and nanostructures in refractory carbon materials, lowcarbons (C≤5+) indicate mature soot and large carbons indicate refractory organic carbon and amorphous nanostructures related to C5-components. These results have implications for assessments of soot particle mixing state and brown carbon absorption in the atmosphere and enable novel, on-line analysis of engineered carbon nanomaterials and soot characteristics relevant for climate and health.
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| 38. |
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| 39. |
- Meyer, Knut Andreas, 1990, et al.
(författare)
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A method for in-field railhead crack detection using digital image correlation
- 2022
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Ingår i: International Journal of Rail Transportation. - : Informa UK Limited. - 2324-8386 .- 2324-8378. ; 10:6, s. 675-694
-
Tidskriftsartikel (refereegranskat)abstract
- Railway infrastructure managers must decide when and how to maintain rails. However, they often have insufficient information about railhead cracks. Therefore, we propose a new method for rail crack detection using a train-mounted digital image correlation (DIC) camera system. The measurement train's weight cause rail bending, allowing the DIC to measure strain concentrations caused by surface-breaking cracks. In this study, we evaluate the method under laboratory conditions. The detected cracks correlate to the actual crack network in the analysed rail field sample. Furthermore, finite element simulations show the method's high sensitivity to crack depths. Existing methods, such as ultra-sonic and eddy-current, produce damage severity indications. The proposed method complements these techniques by providing a discrete description of the surface-breaking cracks and their depth. This information enables infrastructure managers to optimize rail maintenance. Additionally, such detailed measurements can be valuable for research in railhead damage evolution.
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| 40. |
- Shahim, Pashtun, 1984, et al.
(författare)
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Neurochemical Aftermath of Repetitive Mild Traumatic Brain Injury
- 2016
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Ingår i: JAMA Neurology. - : American Medical Association (AMA). - 2168-6149 .- 2168-6157. ; 73:11, s. 1308-1315
-
Tidskriftsartikel (refereegranskat)abstract
- Importance:Evidence is accumulating that repeated mild traumatic brain injury (mTBI) incidents can lead to persistent, long-term debilitating symptoms and in some cases a progressive neurodegenerative condition referred to as chronic traumatic encephalopathy. However, to our knowledge, there are no objective tools to examine to which degree persistent symptoms after mTBI are caused by neuronal injury.Objective:To determine whether persistent symptoms after mTBI are associated with brain injury as evaluated by cerebrospinal fluid biochemical markers for axonal damage and other aspects of central nervous system injury.Design, Settings, and Participants:A multicenter cross-sectional study involving professional Swedish ice hockey players who have had repeated mTBI, had postconcussion symptoms for more than 3 months, and fulfilled the criteria for postconcussion syndrome (PCS) according to the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) matched with neurologically healthy control individuals. The participants were enrolled between January 2014 and February 2016. The players were also assessed with Rivermead Post Concussion Symptoms Questionnaire and magnetic resonance imaging.Main Outcomes and Measures:Neurofilament light protein, total tau, glial fibrillary acidic protein, amyloid β, phosphorylated tau, and neurogranin concentrations in cerebrospinal fluid.Results:A total of 31 participants (16 men with PCS; median age, 31 years; range, 22-53 years; and 15 control individuals [11 men and 4 women]; median age, 25 years; range, 21-35 years) were assessed. Of 16 players with PCS, 9 had PCS symptoms for more than 1 year, while the remaining 7 returned to play within a year. Neurofilament light proteins were significantly increased in players with PCS for more than 1 year (median, 410 pg/mL; range, 230-1440 pg/mL) compared with players whose PCS resolved within 1 year (median, 210 pg/mL; range, 140-460 pg/mL) as well as control individuals (median 238 pg/mL, range 128-526 pg/mL; P = .04 and P = .02, respectively). Furthermore, neurofilament light protein concentrations correlated with Rivermead Post Concussion Symptoms Questionnaire scores and lifetime concussion events (ρ = 0.58, P = .02 and ρ = 0.52, P = .04, respectively). Overall, players with PCS had significantly lower cerebrospinal fluid amyloid-β levels compared with control individuals (median, 1094 pg/mL; range, 845-1305 pg/mL; P = .05).Conclusions and Relevance:Increased cerebrospinal fluid neurofilament light proteins and reduced amyloid β were observed in patients with PCS, suggestive of axonal white matter injury and amyloid deposition. Measurement of these biomarkers may be an objective tool to assess the degree of central nervous system injury in individuals with PCS and to distinguish individuals who are at risk of developing chronic traumatic encephalopathy.
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| 41. |
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| 42. |
- Taylor, Gavin J., et al.
(författare)
-
Exploring the visual world of fossilized and modern fungus gnat eyes (Diptera: Keroplatidae) with X-ray microtomography
- 2020
-
Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 17:163
-
Tidskriftsartikel (refereegranskat)abstract
- Animal eyes typically possess specialized regions for guiding different behavioural tasks within their specific visual habitat. These specializations, and evolutionary changes to them, can be crucial for understanding an animal's ecology. Here, we explore how the visual systems of some of the smallest flying insects, fungus gnats, have adapted to different types of forest habitat over time (approx. 30 Myr to today). Unravelling how behavioural, environmental and phylogenetic factors influence the evolution of visual specializations is difficult, however, because standard quantitative techniques often require fresh tissue and/or provide data in eye-centric coordinates that prevent reliable comparisons between species with different eye morphologies. Here, we quantify the visual world of three gnats from different time periods and habitats using X-ray microtomography to create high-resolution three-dimensional models of the compound eyes of specimens in different preservation states-fossilized in amber, dried or stored in ethanol. We present a method for analysing the geometric details of individual corneal facets and for estimating and comparing the sensitivity, spatial resolution and field of view of species across geographical space and evolutionary time. Our results indicate that, despite their miniature size, fungus gnats do have variations in visual properties across their eyes. We also find some indication that these visual specializations vary across species and may represent adaptations to their different forest habitats. Overall, the findings demonstrate how such investigations can be used to study the evolution of visual specializations-and sensory ecology in general-across a range of insect taxa from different geographical locations and across time.
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| 43. |
- Thuvander, Liane, 1970, et al.
(författare)
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Potentials and Challenges for Integrating PV in Roof Renovation of Multi-residential Houses—A Questionnaire Survey
- 2019
-
Ingår i: Cold Climate HVAC 2018. - Cham : Springer International Publishing. - 9783030006624 ; , s. 231-241
-
Konferensbidrag (refereegranskat)abstract
- A questionnaire survey investigates the conditions for future roof renovations, driving forces and incentives as well as barriers to install roof mounted or roof integrated photovoltaics (PV) among Swedish owners and managers of multi-residential buildings. Respondents were identified through a database hosted by the Swedish Energy Agency holding information about all projects that received subsidies for installation of PV between 2009 and 2016. The final sample comprised 77 organizations and the response rate was 36%. The questionnaire covers general information about the responding companies’ property portfolios; roof renovations in general; routines, motives, and driving forces for installation of roof PV; and planned roof renovations. Results show that the main cause for conducting roof renovations is end of life-time and improvement of energy efficiency. The initiative to install PV is mostly taken by the board of a Housing Association, the management team, or the board of a company. Standard PV modules mounted onto the roof is the predominant choice. Better profitability is needed to encourage more PV installations, for example, through higher subsidy levels and long-term security of the value of produced electricity. None of respondents asks for more appealing design of PV products, better internal organization, or improved knowledge about operation and management of the PV plant.
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| 44. |
- Thuvander, Liane, 1970, et al.
(författare)
-
Solceller i samband med takrenovering på flerbostadshus – En litteratur- och enkätstudie
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport redovisar en undersökning av möjligheten att installera solceller i samband med takrenoveringar i flerbostadshus. Undersökning har genomförts i form av en enkätstudie med följande frågeställning i fokus: Vilka motiv, drivkrafter och hinder finns det för att installera solceller på tak i flerfamiljshus såsom de uppfattas av förvaltare och ägare av flerfamiljshus? Enkäten riktade sig till svenska bostadsföretag och bostadsrättsföreningar som förvaltar flerbostadshus och som har fått solcellsstöd från Energimyndigheten. För att sätta frågeställningen i en större kontext, har studien kompletterats med en kunskapsöversikt inom området beslutsprocesser och arkitek-tonisk integration av solceller. Energimyndighetens databas användes både för att identifiera företag och föreningar som skulle ingå i vår studie samt för att ta fram statistik kring projektens geografiska spridning, typ av ägare och olika hustyper. Enkäten skickades till 77 potentiella respondenter. Svarsfrekvensen blev 36 procent. Frågeområden som ingick i studien var: allmän information om företagets bostads-bestånd; genomförda takrenoveringar; genomförda solcellsinstallationer inklusive rutiner, motiv och drivkrafter; planerade takrenoveringar; samt generella reflektioner och bakgrundsinformation. Anledningen till att ett tak läggs om eller en större takrenovering genomförs är, inte helt oväntat, främst på grund av att takets livslängd närmar sig sitt slut. I några fall är även energieffektivisering en utlösande faktor. De vanligaste procedurerna i samband med takrenoveringar är att installera solceller eller lägga om tak utan ändringar. Påbyggnad av en ny våning, inredning av vind, samt prefab-lösningar är bland de åtgärder som genomförs minst. På frågan om vilka typer av takrelaterade åtgärder som genomförts de senaste fem åren, så är det sett från antalet svarande vanligast att respondenterna har installerat solceller och renoverat tak vid samma tillfälle men nästan lika många har installerat solceller på befintligt tak utan att renovera tak och något färre har renoverat tak utan att installera solceller. Anledningarna till att man inte installerar solceller i samband med takrenovering är övervägande ekonomiska, till exempel dålig lönsamhet och höga investeringskostnader, följd av olämplig utformning av taket, ogynnsamma väderstreck och osäkerhet kring det framtida värdet av den producerade elen. Ingen anger brist på lämpliga produkter eller osäkerhet kring drift och förvaltning som orsak till att avstå installation. I bostadsrättsföreningar tas initiativet till att installera solceller främst av styrelsen, i vissa fall av förvaltaren av bostadsrättsföreningen, de boende, en anlitad arkitekt eller entreprenör. I bostadsföretag med hyresrätter är det främst före-tagsledningen som tar initiativet eller anställda inom företag såsom driftpersonal, teknisk chef eller energi- och VVS samordnare. De vanligaste motiven för att installera solceller är att spara energi och att öka sin grad av självförsörjande tillsammans med att det uppfattas som en effektiv miljöåtgärd. Även tillgång till bidrag är viktig. Det är också de främsta motiven bland bostadsrättsföreningar för installation av solceller. För hyresrätter är de främsta motiven marknadsföring av företagets miljöprofil, spara energi, följa företagets miljöpolicy och att det anses vara en effektiv miljöåtgärd. När det gäller lärdomar från att genomföra takrenoveringar med solceller, anger de allra flesta att de är nöjda med projektet. Endast ett fåtal uppger att de skulle gjort någon större ändring eller att de stött på problem. På frågan om vad som krävs för att andelen takomläggningar med solcellsinstallationer ska öka, så dominerar även här ekonomiska faktorer. Högre lönsamhet, mer bidrag och större säkerhet över tid vad gäller kostnader och intäkter hamnar överst. Bostadsrättsföreningar efterlyser även tydligare skatte-regler, företag som erbjuder helhetslösningar, och teknisk utveckling av solcells-produkterna. Ingen av de svarande företag eller föreningar anser att det behövs mer estetiskt tilltalande solcellsprodukter, bättre organisation inom företaget, eller förbätt-ringar av drift och förvaltning av solcellsanläggningarna. Prefabricerade takelement med integrerade solceller, ett koncept där platta och låglutande tak kompletteras med ett nytt sadeltak av prefabricerade takelement med en takbeläggning av solceller, verkar inte vara av större intresse för respondenterna. När det gäller metoder för att kunna hantera tidsvisa överskott av solel för att motverka negativa ekonomiska resultat så vill de flesta införa ett gemensamt el-abonnemang för hela byggnaden så att elen kan användas i lägenheterna och genom att installera batterier som lagrar överskottsel från dagen till kvällen. Utmaningen är att stimulera solcellstänket bland alla bostadsförvaltare och se lång-siktiga vinster med att samordna takrenovering med installation av solceller, inte minst i miljonprogrammets flerbostadshus där det finn stort renoveringsbehov. Huvud-motiven för att installera solceller är energibesparing, självförsörjning och att det är en effektiv miljöåtgärd. Motiven skiljer sig något mellan bostadsrätter och hyresrätter där hyresrätter har ett större inslag av miljöprofilering som till exempel marknadsföring och miljöpolicy. Ekonomi och regelverk är viktiga aspekter, både som drivkraft och hinder. Statligt bidrag är ett incitament som bör finnas även framöver för att stimulerar utvecklingen av en större marknad för solceller. En ökad efterfråga är dock inte enbart beroende av kostnaderna utan även av en efterfrågan från beställare och arkitekten. Här behövs det dokumenterad kunskap och estetiskt tilltalande byggda exempel. Påbyggnad och prefab-element är i dagsläget av begränsat intresse, men det kan vara att intressant att utveckla som ett alternativ. För en bättre förståelse av takrenoveringarna och potentialerna för integration av solceller i flerbostadshus behöver framtida forskning fokusera på renoveringsprocessen generellt, större empiriskt material, och resonemang bakom beslutsfattandet som inte bara omfattar bostadsförvaltare utan även andra intressenter såsom arkitekter och andra konsulter samt stadsplanerare. Det är också viktigt att ta hänsyn till olika upplåtelseformer, dvs. skillnader mellan hyresrätter och bostadsrätter.
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| 45. |
- Thuvander, Liane, 1970, et al.
(författare)
-
Takrenovering med solceller – en enkätstudie
- 2018
-
Ingår i: Bygg & teknik. - 0281-658X. ; , s. 15-18
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Hur resonerar fastighetsägare kring solcellsinstallation i samband med en takrenovering? Vad krävs för att öka installationstakten av solcell er och varför väljs solceller ofta bort under byggprocessens gång? I en mindre enkätstudie riktad till bostadsföretag och bostadsrättsföreningar som har fått solcellsstöd undersökte vi drivkrafter, incitament och hinder till att sätta solceller på flerbostadshusens tak i samband med en renovering. Studien är ett delprojekt i det nyligen avslutade E2B2 projektet ”Miljontak – Takrenovering med solceller”, en genomförbarhetsstudie som utgår från miljonprogrammets stora energieffektiviseringsutmaning med särskilt fokus på tak.
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| 46. |
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| 47. |
- Öhman, Johan, 1991-, et al.
(författare)
-
Experimental investigation of face mask filtration in the 15–150 μm range for stationary flows
- 2022
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 131:4
-
Tidskriftsartikel (refereegranskat)abstract
- The effectiveness of face masks for preventing airborne transmission has been debated heavily during the COVID-19 pandemic. This paper investigates the filtration efficiency for four different face mask materials, two professional and two homemade, for different airflow conditions using model experiments and artificially generated water droplets. The size range chosen represents particles with the largest volume that can be suspended in air. The particles are detected using double pulsed interferometric particle imaging, from which it is possible to estimate the positions, velocity, and size of individual particles. It is found that all the tested face masks are efficient in preventing particles from transmission through the mask material. In the presence of leakage, particles larger than approximately 100?m are completely removed from the air stream. The filtration efficiency decreases with the decreasing particle size to approximately 80% for 15?m particles. The size dependency in the leakage is mainly due to the momentum of the larger particles. The results show that even simple face mask materials with leakage prevent a large portion of the emitted particles in the 15–150 ?m range.
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| 48. |
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| 49. |
- Öhman, Johan, 1991-, et al.
(författare)
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Polarization-resolved dual-view holographic system for 3D inspection of scattering particles
- 2019
-
Ingår i: Applied Optics. - : The Optical Society. - 1559-128X .- 2155-3165. ; 58:34, s. G31-G40
-
Tidskriftsartikel (refereegranskat)abstract
- A novel dual-view polarization-resolved pulsed holographic system for particle measurements is presented. Both dual-view configuration and polarization-resolved registration are well suited for particle holography. Dual-view registration improves the accuracy in the detection of 3D position and velocities, and polarization-resolved registration provides polarization information about individual particles. The necessary calibrations are presented, and aberrations are compensated for by mapping the positions in the two views to positions in a global coordinate system. The system is demonstrated on a sample consisting of 7 μm spherical polystyrene particles dissolved in water in a cuvette. The system is tested with different polarizations of the illumination. It is found that the dual view improves the accuracy significantly in particle tracking. It is also found that by having polarization-resolved holograms, it is possible to separate naturally occurring sub-micrometer particles from the larger, 7 μm seeding particles.
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| 50. |
- Öhman, Johan, 1991-, et al.
(författare)
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Polarization Resolved Dual-View Holographic System for Investigation of Microparticles
- 2019
-
Ingår i: Proceedings Digital Holography and Three-Dimensional Imaging 2019. - : Optical Society of America.
-
Konferensbidrag (refereegranskat)abstract
- A dual-view polarization resolved digital-holographic system is presented. The necessary calibration for both polarization and spatial coordinates are outlined. As an example the system is is used to track spherical microparticles in a cuvette.
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