| 1. |
- Hamaus, N., et al.
(författare)
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Euclid : Forecasts from redshift-space distortions and the Alcock-Paczynski test with cosmic voids
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658
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Tidskriftsartikel (refereegranskat)abstract
- Euclid is poised to survey galaxies across a cosmological volume of unprecedented size, providing observations of more than a billion objects distributed over a third of the full sky. Approximately 20 million of these galaxies will have their spectroscopy available, allowing us to map the three-dimensional large-scale structure of the Universe in great detail. This paper investigates prospects for the detection of cosmic voids therein and the unique benefit they provide for cosmological studies. In particular, we study the imprints of dynamic (redshift-space) and geometric (Alcock-Paczynski) distortions of average void shapes and their constraining power on the growth of structure and cosmological distance ratios. To this end, we made use of the Flagship mock catalog, a state-of-the-art simulation of the data expected to be observed with Euclid. We arranged the data into four adjacent redshift bins, each of which contains about 11000 voids and we estimated the stacked void-galaxy cross-correlation function in every bin. Fitting a linear-theory model to the data, we obtained constraints on f/b and DMH, where f is the linear growth rate of density fluctuations, b the galaxy bias, D-M the comoving angular diameter distance, and H the Hubble rate. In addition, we marginalized over two nuisance parameters included in our model to account for unknown systematic effects in the analysis. With this approach, Euclid will be able to reach a relative precision of about 4% on measurements of f/b and 0.5% on DMH in each redshift bin. Better modeling or calibration of the nuisance parameters may further increase this precision to 1% and 0.4%, respectively. Our results show that the exploitation of cosmic voids in Euclid will provide competitive constraints on cosmology even as a stand-alone probe. For example, the equation-of-state parameter, w, for dark energy will be measured with a precision of about 10%, consistent with previous more approximate forecasts.
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| 2. |
- Jahnke, T., et al.
(författare)
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Inner-Shell-Ionization-Induced Femtosecond Structural Dynamics of Water Molecules Imaged at an X-Ray Free-Electron Laser
- 2021
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Ingår i: Physical Review X. - : American Physical Society. - 2160-3308. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- The ultrafast structural dynamics of water following inner-shell ionization is a crucial issue in high-energy radiation chemistry. We have exposed isolated water molecules to a short x-ray pulse from a free-electron laser and detected momenta of all produced ions in coincidence. By combining experimental results and theoretical modeling, we can image dissociation dynamics of individual molecules in unprecedented detail. We reveal significant molecular structural dynamics in H2O2+, such as asymmetric deformation and bond-angle opening, leading to two-body or three-body fragmentation on a timescale of a few femtoseconds. We thus reconstruct several snapshots of structural dynamics at different time intervals, which highlight dynamical patterns that are relevant as initiating steps of subsequent radiation-damage processes.
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| 3. |
- Contarini, S., et al.
(författare)
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Euclid : cosmological forecasts from the void size function
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 667
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Tidskriftsartikel (refereegranskat)abstract
- The Euclid mission - with its spectroscopic galaxy survey covering a sky area over 15 000 deg(2) in the redshift range 0.9 < z < 1.8 - will provide a sample of tens of thousands of cosmic voids. This paper thoroughly explores for the first time the constraining power of the void size function on the properties of dark energy (DE) from a survey mock catalogue, the official Euclid Flagship simulation. We identified voids in the Flagship light-cone, which closely matches the features of the upcoming Euclid spectroscopic data set. We modelled the void size function considering a state-of-the art methodology: we relied on the volume-conserving (Vdn) model, a modification of the popular Sheth & van de Weygaert model for void number counts, extended by means of a linear function of the large-scale galaxy bias. We found an excellent agreement between model predictions and measured mock void number counts. We computed updated forecasts for the Euclid mission on DE from the void size function and provided reliable void number estimates to serve as a basis for further forecasts of cosmological applications using voids. We analysed two different cosmological models for DE: the first described by a constant DE equation of state parameter, w, and the second by a dynamic equation of state with coefficients w(0) and w(a). We forecast 1 sigma errors on w lower than 10% and we estimated an expected figure of merit (FoM) for the dynamical DE scenario FoM(w0,wa) = 17 when considering only the neutrino mass as additional free parameter of the model. The analysis is based on conservative assumptions to ensure full robustness, and is a pathfinder for future enhancements of the technique. Our results showcase the impressive constraining power of the void size function from the Euclid spectroscopic sample, both as a stand-alone probe, and to be combined with other Euclid cosmological probes.
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| 4. |
- Pöntinen, M., et al.
(författare)
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Euclid: Identification of asteroid streaks in simulated images using deep learning
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 679
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Tidskriftsartikel (refereegranskat)abstract
- The material composition of asteroids is an essential piece of knowledge in the quest to understand the formation and evolution of the Solar System. Visual to near-infrared spectra or multiband photometry is required to constrain the material composition of asteroids, but we currently have such data, especially in the near-infrared wavelengths, for only a limited number of asteroids. This is a significant limitation considering the complex orbital structures of the asteroid populations. Up to 150 000 asteroids will be visible in the images of the upcoming ESA Euclid space telescope, and the instruments of Euclid will offer multiband visual to near-infrared photometry and slitless near-infrared spectra of these objects. Most of the asteroids will appear as streaks in the images. Due to the large number of images and asteroids, automated detection methods are needed. A non-machine-learning approach based on the Streak Det software was previously tested, but the results were not optimal for short and/or faint streaks. We set out to improve the capability to detect asteroid streaks in Euclid images by using deep learning. We built, trained, and tested a three-step machine-learning pipeline with simulated Euclid images. First, a convolutional neural network (CNN) detected streaks and their coordinates in full images, aiming to maximize the completeness (recall) of detections. Then, a recurrent neural network (RNN) merged snippets of long streaks detected in several parts by the CNN. Lastly, gradient-boosted trees (XGBoost) linked detected streaks between different Euclid exposures to reduce the number of false positives and improve the purity (precision) of the sample. The deep-learning pipeline surpasses the completeness and reaches a similar level of purity of a non-machine-learning pipeline based on the StreakDet software. Additionally, the deep-learning pipeline can detect asteroids 0.25–0.5 magnitudes fainter than StreakDet. The deep-learning pipeline could result in a 50% increase in the number of detected asteroids compared to the StreakDet software. There is still scope for further refinement, particularly in improving the accuracy of streak coordinates and enhancing the completeness of the final stage of the pipeline, which involves linking detections across multiple exposures.
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| 5. |
- Guillemin, R., et al.
(författare)
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Isotope effects in dynamics of water isotopologues induced by core ionization at an x-ray free-electron laser
- 2023
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Ingår i: STRUCTURAL DYNAMICS-US. - 2329-7778. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- Dynamical response of water exposed to x-rays is of utmost importance in a wealth of science areas. We exposed isolated water isotopologues to short x-ray pulses from a free-electron laser and detected momenta of all produced ions in coincidence. By combining experimental results and theoretical modeling, we identify significant structural dynamics with characteristic isotope effects in H2O2+, D2O2+, and HDO2+, such as asymmetric bond elongation and bond-angle opening, leading to two-body or three-body fragmentation on a timescale of a few femtoseconds. A method to disentangle the sequences of events taking place upon the consecutive absorption of two x-ray photons is described. The obtained deep look into structural properties and dynamics of dissociating water isotopologues provides essential insights into the underlying mechanisms.
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| 6. |
- Billman, Maja, et al.
(författare)
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Small carbon stocks in sediments of Baltic Sea eelgrass meadows
- 2023
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Ingår i: Frontiers in Marine Science. - 2296-7745. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Seagrass meadows act as an effective carbon sink and store carbon in the sediments for substantial periods of time. The drivers of carbon sequestration are complex, and global and regional estimates of carbon stocks have large uncertainties. Here, we report new carbon stock estimates from 14 sites along the Swedish coast and compile existing literature to estimate the magnitude of carbon stocks of Zostera marina (eelgrass) meadows in the Baltic Sea. Eelgrass meadows in the Baltic Sea have considerably lower carbon content and lower stocks (0.25 ± 0.21% DW, 635 ± 321 g C m-2) than in the Kattegat-Skagerrak region (3.25 ± 2.78% DW, 3457 ± 3382 g C m-2) and the average for temperate regions in general (1.4 ± 0.4% DW, 2721 ± 989 g C m-2). Unfavorable growing conditions for eelgrass in the Baltic Sea often lead to meadows occurring in areas of high hydrodynamics, preventing significant carbon accumulation. Stable isotopes revealed that the dominating source of organic carbon in the meadows was planktonic, further highlighting that Baltic Sea eelgrass meadows are not major carbon reservoirs in comparison to unvegetated sediments and other seagrass areas. The results also highlight that environmental conditions drive intraspecific variation of carbon sequestration on large spatial scales. Overall, the carbon stocks and sequestration potential in eelgrass meadows of the Baltic Sea are small compared to other temperate regions.
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| 7. |
- Ernits, Heiti, 1979
(författare)
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Ledarskap i mellanrummen – fallstudie av gränsgångare och gränspraktiker ienkomplex samverkansmiljö
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gränsöverskridande samarbete, samverkan och tidsbegränsade arbetssätt är på modet. Stadsplanering, samhällsstyrning, välfärdsproduktion och tackling av samhälleliga utmaningar sker allt mer i projektform och inkluderar en blandning av offentliga verksamheter, privata aktörer och intressenter. Så kallad gränsöverskridande organisering sker över olika typer av professionella, organisatoriska, geografiska och institutionella gränser. Denna trend har även inneburit ett ökat intresse för gränsgångare och olika typer av gränspraktiker som enligt studier spelar en allt viktigare roll i gränsöverskridande samverkansmiljöer. Denna studie söker svar på hur en gränsgångarpraktik kommer till uttryck i en samverkansmiljö, vilka problem som uppstår och på vilket sätt praktiken eventuellt bidrar till samverkan. Studien har fokuserat på projektet Kraftsamling Sjöbo som har pågått sedan december 2017. I Kraftsamlingen deltar offentliga verksamheter, civilsamhället, myndigheter, föreningar, akademin, forskningsinstitut och invånare. Syftet är en hållbar omställning av en stadsdel. För det första visar studien att det krävdes en omfattande arbetsinsats för att åstadkomma ett fungerande samarbete över gränser. Det gränsöverskridande samarbetet försvårades delvis på grund av skillnader i kultur, intressen, värderingar och organisatoriska förutsättningar. För det andra visar studien att projektledarrollen förändrades och arbetet med Kraftsamlingen visade sig kräva omfattande gränsöverskridande interaktion, facilitering och ständigt pågående problemlösning. Gränsgångaren trädde in i en ledarskapsroll när situationer krävde det och arbetade aktivt för att skapa strukturella förutsättningar för att åstadkomma fungerande samarbete, baserat på Kraftsamlingens mission och värden. Gränsgångarpraktiken visade sig vara komplex och mångfacetterad. Gränsgångaren kopplade exempelvis samman aktörer, byggde sociala nätverk, mobiliserade resurser, försökte påverka rådande tanke- och arbetssätt, förflyttade information över gränser, agerade som översättare mellan professionella gemenskaper, löste uppblossande konflikter, skapade nya organisatoriska strukturer, försökte skapa engagemang och drev på för kollektiv handling. Gränsgångaren försökte etablera en gemensam samverkanskultur och arbetade aktivt med de sociala sammanhangen i organisationen. För det tredje indikerar studien att den här typen av gränsöverskridande ledarskapspraktik spelar en viktig roll i gränsöverskridande samverkansmiljöer där en mångfald av aktörer som har olika förutsättningar och intressen deltar. Studien illustrerar även de utmaningar som ett projektbaserat arbetssätt kan innebära när gränser korsas och när frågorna som hanteras är komplexa och sammansatta. Studiens resultat kan också omsättas till ett antal praktiska rekommendationer. För det första bör synen på projektledarskapet i komplexa samverkansprojekt nyanseras och utvidgas. För det andra bör gränsgångarroller och det informella ledarskapet synliggöras och uppvärderas i samverkansmiljöer. För det tredje bör de specifika kompetenserna och det nödvändiga sociala hantverket synliggöras och inkluderas i rekryteringsarbetet hos organisationer.
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| 8. |
- Jahnke, Marlene, et al.
(författare)
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Biophysical models of dispersal contribute to seascape genetic analyses
- 2022
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 377
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Tidskriftsartikel (refereegranskat)abstract
- Dispersal is generally difficult to directly observe. Instead, dispersal is often inferred from genetic markers and biophysical modelling where a correspon- dence indicates that dispersal routes and barriers explain a significant part of population genetic differentiation. Biophysical models are used for wind- driven dispersal in terrestrial environments and for propagules drifting with ocean currents in the sea. In the ocean, such seascape genetic or seascape genomic studies provide promising tools in applied sciences, as actions within management and conservation rely on an understanding of population structure, genetic diversity and presence of local adaptations, all dependent on dispersal within the metapopulation. Here, we surveyed 87 studies that combine population genetics and biophysical models of dis- persal. Our aim was to understand if biophysical dispersal models can generally explain genetic differentiation. Our analysis shows that genetic differentiation and lack of genetic differentiation can often be explained by dispersal, but the realism of the biophysical model, as well as local geomor- phology and species biology also play a role. The review supports the use of a combination of both methods, and we discuss our findings in terms of recommendations for future studies and pinpoint areas where further development is necessary, particularly on how to compare both approaches. This article is part of the theme issue ‘Species’ ranges in the face of changing environments (part I)’.
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| 9. |
- Jahnke, Marlene, et al.
(författare)
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Integrating genetics, biophysical, and demographic insights identifies critical sites for seagrass conservation
- 2020
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Ingår i: Ecological Applications. - : Wiley. - 1051-0761 .- 1939-5582. ; 30:6
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Tidskriftsartikel (refereegranskat)abstract
- The eelgrass Zostera marina is an important foundation species of coastal areas in the Northern Hemisphere, but is continuing to decline, despite management actions. The development of new management tools is therefore urgent in order to prioritize limited resources for protecting meadows most vulnerable to local extinctions and identifying most valuable present and historic meadows to protect and restore, respectively. We assessed 377 eelgrass meadows along the complex coastlines of two fjord regions on the Swedish west coast-one is currently healthy and the other is substantially degraded. Shoot dispersal for all meadows was assessed with Lagrangian biophysical modeling (scale: 100-1,000 m) and used for barrier analysis and clustering; a subset (n = 22) was also assessed with population genetic methods (20 microsatellites) including diversity, structure, and network connectivity. Both approaches were in very good agreement, resulting in seven subpopulation groupings or management units (MUs). The MUs correspond to a spatial scale appropriate for coastal management of "waterbodies" used in the European Water Framework Directive. Adding demographic modeling based on the genetic and biophysical data as a third approach, we are able to assess past, present, and future metapopulation dynamics to identify especially vulnerable and valuable meadows. In a further application, we show how the biophysical approach, using eigenvalue perturbation theory (EPT) and distribution records from the 1980s, can be used to identify lost meadows where restoration would best benefit the present metapopulation. The combination of methods, presented here as a toolbox, allows the assessment of different temporal and spatial scales at the same time, as well as ranking of specific meadows according to key genetic, demographic and ecological metrics. It could be applied to any species or region, and we exemplify its versatility as a management guide for eelgrass along the Swedish west coast.
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| 10. |
- Jahnke, Marlene, et al.
(författare)
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Seascape genomics identify adaptive barriers correlated to tidal amplitude in the shore crab Carcinus maenas
- 2022
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 31:7, s. 1980-94
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Tidskriftsartikel (refereegranskat)abstract
- Most marine invertebrates disperse during a planktonic larval stage that may drift for weeks with ocean currents. A challenge for larvae of coastal species is to return to coastal nursery habitats. Shore crab (Carcinus maenas L.) larvae are known to show tidal rhythmicity in vertical migration in tidal areas and circadian rhythmicity in micro-tidal areas, which seems to increase successful coastal settlement. We studied genome-wide differentiation based on 24,000 SNPs of 12 native populations of shore crab sampled from a large tidal amplitude gradient from macro-tidal (ca. 8 m) to micro-tidal (ca. 0.2 m). Dispersal and recruitment success of larvae was assessed with a Lagrangian biophysical model, which showed a strong effect of larval behavior on long-term connectivity, and dispersal barriers that partly coincided with different tidal environments. The genetic population structure showed a subdivision of the samples into three clusters, which represent micro-, meso- and macro-tidal areas. The genetic differentiation was mostly driven by 0.5% outlier loci, which showed strong allelic clines located at the limits between the three tidal areas. Demographic modelling suggested that the two genetic barriers have different origins. Differential gene expression of two clock genes (cyc and pdp1) further highlighted phenotypic differences among genetic clusters that are potentially linked to the differences in larval behaviour. Taken together, our seascape genomic study suggest that tidal regime acts as a strong selection force on shore crab population structure, consistent with larval behaviour affecting dispersal and recruitment success.
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