| 1. |
- Andersson, Rassmus
(författare)
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Discovering new ground in ion transport: Exploring coordination effects in polymer electrolytes : – From method development to battery implementation
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The exponentially increasing demand for portable and stationary energy storage devices is pushing the development of lithium-ion batteries (LIBs). This requires safer and more sustainable electrolytes where solid polymer electrolytes (SPEs) are a viable alternative to the flammable liquid electrolytes used nowadays. However, SPEs are characterized by poor ionic conductivity compared to their liquid equivalents, preventing large-scale implementation. Furthermore, to meet the increasing production rate of batteries, alternative battery chemistries based on more abundant resources than Li are explored. To address these matters, a fundamental understanding of ion transport in SPEs for a range of relevant cations is vital in the development process.In the thesis, the ion transport is explored on a fundamental level for Li+ in addition to cations “beyond Li” such as Na+, K+ and Mg2+ in polyether-, polyester- and polycarbonate-based SPEs, where the core encompasses the connection between the ion coordination strength and the transference number (T+). New methods to investigate these properties have been developed especially targeting these more challenging cations. To study the ion coordination strength, two qualitative and one quantitative methods based on NMR and FTIR, are presented. In addition, eNMR and EIS have been combined to determine T+.Regardless of the cation investigated, the strongest coordination was observed for polyethylene oxide, stemming from its chelating effect on the cations. In contrast, poly(trimethylene carbonate) exhibited the weakest coordination, while poly(ε-caprolactone) fell in between. A direct correlation between the coordination strength and the T+ was also recognized, where strong interactions are accompanied by low T+ and vice versa. Moreover, the divalent Mg2+ displayed particularly interesting transport characteristics, where the [MgTFSI]+ speciation appears to be a large contributor to the net Mg mobility. Lastly, the outcome of incorporating an ion-conducting polymer as the soft segment in polyurethanes is that the transport mechanism of the pure SPE remains. In combination with sustained long-term cycling in lithium metal batteries, the polyurethanes illustrate opportunities for new designs by adjusting the soft segments. Similarly, the properties of poly(1-oxoheptamethylene) can be controlled by tuning its saturation degree, which is crucial for the ion conduction and mechanical properties in lithium metal batteries, since it highly affects the crystallinity and the crosslinking of the systems.In summary, this thesis contributes toward the understanding of ion transport in systems belonging to “next-generation” batteries, where SPEs for lithium-metal batteries as well as for cations “beyond Li” are considered to play an important part.
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| 2. |
- Andriantsaralaza, Miora, 1996-
(författare)
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Mass Loss of Evolved Stars : Improving Mass-Loss Rates and Distances
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the final stages of their lives, low to intermediate-mass stars enter the Asymptotic Giant Branch (AGB) phase, where they experience significant mass loss through dusty stellar winds. This mass loss is pivotal, not only for the chemical enrichment of the interstellar medium, setting the stage for new stars and planets to form, but also in dictating the evolution and the ultimate fate of the stars themselves. The study of mass loss in AGB stars is therefore of paramount importance. Analyses of emission from CO gas in these outflows allow for the determination of mass-loss rates, as CO serves as a primary tracer for the molecular gas in the circumstellar envelopes of AGB stars. However, one of the main uncertainties in mass loss estimations arises from the assumptions on the size of the CO envelope. This uncertainty can be removed using interferometry, which allows for direct measurements of the spatial extent of the CO emission. Using the compact array of the Atacama Large Millimeter/submillimeter Array (ALMA), we measured the extent and investigated the degree of sphericity of the CO-emitting regions around 69 AGB stars in the DEATHSTAR programme. Of those, 27 are presented in this thesis.Another significant source of uncertainty in mass-loss rate estimates lies in the distance, a fundamental parameter which has been notoriously difficult to accurately determine for AGB stars, especially when relying on optical parallaxes like those from Gaia. To tackle this, we conducted a comparative analysis between Gaia DR3 parallaxes and the more robust parallaxes obtained from high-resolution interferometric observations of maser emissions. This approach enabled us to provide reliable distance estimates for a sample of 200 AGB stars, including the DEATHSTAR sample, offering a valuable resource for the AGB scientific community. Using the newly calculated distances and updated CO envelope size measurements, we performed radiative transfer modelling to derive the mass-loss rates of a sample of 27 carbon-rich AGB stars. The spatial information provided by ALMA observations acted as strong constraints for our models, ensuring a more accurate representation of flux contributions from various spatial scales.By providing the measurement of CO envelope sizes, improving the distance determination to AGB stars, and presenting improved mass-loss rates, this thesis provides new insights into the complex nature of AGB stars and their mass loss.
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| 3. |
- Ben-Shahar, Maor
(författare)
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Color-Kinematics Duality and Gravitational Waves
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent developments in theoretical physics have led to new insights for gauge theory and gravity scattering amplitudes.The color-kinematics duality, in particular, describes an intriguing set of identities obeyed by the kinematic numerators of gauge-theory scattering amplitudes, mirroring the Jacobi identity of the color factors. The kinematic Jacobi identities suggest the existence of some unknown kinematic algebra underlying the gauge-theory Feynman rules. However, as of yet, there is no complete Lagrangian construction of duality-satisfying numerators, nor an off-shell realization of a kinematic algebra even for pure Yang-Mills gauge theory. This thesis presents substantial progress on these open problems, first through a Lagrangian whose Feynman rules compute duality-satisfying numerators in the NMHV sector of Yang-Mills theory. In addition, Chern-Simons gauge theory is shown to obey the color-kinematics duality completely off shell, giving rise to a kinematic algebra of volume preserving diffeomorphisms. Similar structures are also identified in the pure-spinor description of super Yang-Mills theory.The recent detection of gravitational waves by the LIGO/Virgo/KAGRA collaboration, as well as anticipated improvement in sensitivity of future detectors, call for improved precision of the theoretical predictions for binary merger events. Analytical computations involving gravitating and rotating compact objects require both increased classical loop orders in the gravitational coupling as well as the incorporation of spin effects, which have important contributions to the dynamics. For this purpose, an extension of the worldline quantum field theory is presented, based on the effective worldline action of a classical spinning compact object. The formalism is used to compute tree and one-loop amplitudes up to fourth order in spin, and coefficients in the effective worldline action are fixed such that it reproduces known Kerr observables from black hole perturbation theory.
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| 4. |
- Blyth, Samuel, 1988-
(författare)
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Casting for Knowledge and Landing Understanding : Exploring the management of Swedish recreational fisheries as social-ecological systems
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The successful management of recreational fisheries must balance ecological, and social goals; select from and implement a range of management tools; operate under often complex governance structures; and contend with diverse human stakeholders’ expectations, desires, and actual behaviour in response to management activities. This complexity also means that there are many knowledge and research gaps regarding the information needed to meet the requirements of specific fisheries. This thesis explores Swedish recreational fisheries as social-ecological systems to help close these gaps, and improve their future management.The sea trout (Salmo trutta) fishery around the island of Gotland provides context for investigating the human and ecological dimensions of catch-and-release (C&R), and stock level connections between angler expectations, catches, and spawning returns. This case study first identifies key motivations to retain or release sea trout of legal size, and factors anglers think are important for successful C&R. Then determines which angler-related, fish-related, or environmental factors impact stress levels and injuries for sea trout. Further, it identifies the potential for small changes in anglers harvest preferences to significantly impact mortality rates for an important segment of the spawning population. Taken together these outcomes identify knowledge and behavioural gaps that influence the successful application of C&R in this fishery, and that could affect the achievement of fishery management goals.Several opportunities to improve the transfer of information between stakeholder groups in Swedish recreational fisheries are illuminated through an assessment of how best practices for C&R are communicated to anglers, and an evaluation of potential biases generated when collecting data through angler surveys. Communication from freshwater fishery managers to fishing license buyers is deficient in the quality and quantity of information on best practices for C&R. In addition, this is notably poorer for certain fisheries and target species that have very high rates of C&R. In the opposite direction, the collection of information from anglers is also challenging, as common sampling techniques and the grouping of survey responses in recreational fisheries can introduce significant biases that impact how data can be interpreted. These include psychological dimensions of fishing experiences that connect angler motivations and behaviours to fishery management structures.This thesis contributes to the knowledge and discussion about sustainably managing recreational fisheries, but the methods to apply this information to existing governance structures and induce positive behavioural change in diverse populations of anglers require further development.
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| 5. |
- Bylin, Johan
(författare)
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The interaction of hydrogen with metallic glass
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Combining theoretical ab initio calculations with high-purity thin film sample synthesis and in situ measurements is a compelling way to bridge the gap in our understanding concerning hydrogen in metallic glasses, which is the primary work of this dissertation thesis. The main emphasis has been on how hydrogen affects the structure of metallic glasses, and how those changes influence not only the electronic properties of the amorphous metals but also their thermal stability. The real-space correlations in the form of the pair distribution functions in thin metallic films have primarily only been accessible through synchrotron radiation. An effective methodological procedure using laboratory-based x-ray sources is here brought forth, which, for the first time, can produce accessible and accurate pair distribution functions from thin films down to a thickness of 80 nm. The underpinning mechanisms behind the hydrogen-induced volume expansion of metallic glasses in the form of the dipole force tensor and an elastic hydrogen-hydrogen interaction were examined using in situ neutron reflectometry and first-principles calculations of expanding V80Zr20 amorphous structures. The dipole force tensor was concluded to be similar in magnitude to a mole-fraction-weighted sum of the ones found in hydrogen-contained vanadium and zirconium crystals, and the theoretical calculations demonstrated that it and the interaction energy varies with hydrogen concentration. The electronic structure of the metallic glass V80Zr20 was determined via hard x-ray photoemission spectrometry and confirmed by first-principles calculations to be modified by the presence of hydrogen, in which a collection of s-d hybridized states 7 eV below the Fermi level was formed. The changes closer to the Fermi level, together with the volume expansion, were via experiments and ab initio calculations established to cause a parabolic change in resistance and a strong wavelength dependence on the optical transmission. The thermal stability of amorphous VxZr1-x metals, investigated via ab initio calculations of the thermodynamic driving force towards crystallization, was found to affirm the observed hydrogen-induced enhancement in thermal stability.
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| 6. |
- Cangemi, Lucile
(författare)
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From Quantum to Classical Scattering of Kerr Black Holes : A construction of massive higher-spin scattering amplitudes and their classical limits.
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gravitational scattering processes involving black holes as asymptotic states can provide insight into the classical dynamics of binary black hole systems. The observed gravitational waves emitted during mergers need to be compared to high-precision theoretical predictions. By modelling black holes as massive point particles in an effective quantum field theory, one can take advantage of the advanced computational tools originally designed for collider physics. For Schwarzschild black holes the natural objects to study are scattering amplitudes involving massive scalar fields with interactions mediated by gravitons. The classical physics is extracted by considering limits of the kinematics.Extending this effective description to rotating Kerr black holes introduces subtleties. To leading order in the post-Minkowskian perturbation scheme, there now exists candidate three-point scattering amplitudes for massive higher-spin particles that in the classical limit reproduce the Kerr metric. For small quantum spins, these are given by familiar theories of interacting massive fields which have a well-behaved massless limit. These theories are sufficient to capture the first few spin-multipole orders for the classical observables; however, to capture more orders one is required to use input from higher-spin theories. The three-point higher-spin amplitudes were originally introduced without reference to an underlying Lagrangian description. Lagrangians for interacting higher-spin fields are notoriously complicated as they necessarily describe composite fields in an effective higher-derivative theory.This thesis explores the underlying higher-spin effective theories suitable for describing rotating black holes, and proposes a new spin-s family of Compton scattering amplitudes. We present two complementary constructions for consistent interacting higher-spin Lagrangians: the first relies on massive higher-spin gauge symmetry to remove unwanted states, and the second one manifests the correct degrees of freedom using a chiral field framework. A significant portion of the thesis discusses how to extract classical physics from quantum amplitudes, focusing on consistent treatments of the spin degrees of freedom. The resulting quantum and classical Compton amplitudes are built to be consistent with perturbations of the Kerr metric, through a combination of constraints from higher-spin considerations and classical analysis. In addition to the black-hole amplitudes, we study the scattering of higher-spin fields in a gauge theory referred to as root-Kerr. The three point amplitudes of this gauge theory are closely related to the Kerr ones, such that it provides an instructive model for both higher-spin consistency and classical analysis. Another toy model discussed is the scattering of higher-spin superstring states on the leading Regge trajectory.
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| 7. |
- Cediel-Ulloa, Andrea, 1989-
(författare)
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Novel Endpoints To Unravel Developmental Neurotoxicity : From DNA methylation responses to methylmercury to the in vitro identification of endocrine disruptors
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The developing brain is especially sensitive to environmental stressors due to its dependence on the precise spatiotemporal regulation of multiple signals, and the long time period required for its formation. Some chemicals can interfere with molecular and cellular processes driving brain development, including epigenetic processes such as DNA methylation. Hence, identification of DNA methylation changes induced by chemical exposure may serve as early molecular markers for developmental neurotoxicity (DNT). Chemicals known as endocrine disruptors (EDCs) can produce adverse effects due to their capability to alter the endocrine system. Since brain development is highly dependent on endocrine signals, the potential adverse effects of EDCs on brain development needs to be addressed. Detection of DNT in the regulatory context has been based on in vivo testing, however, the financial costs and time intensive characteristics of these methods have resulted in a limited assessment of the DNT hazard of chemicals. In addition, in order to regulate EDCs, it is paramount to demonstrate that their adverse effects are a product of disruption of endocrine signals. Yet, at the moment, there are no approved methods which address both an endocrine mode of action and adverse neurodevelopmental outcomes. This doctoral thesis had two main aims: Firstly, to identify epigenetic changes, at the level of DNA methylation, underlying DNT induced by exposure to methylmercury (MeHg); and secondly, to develop new approach methods (NAMs) for the detection of DNT induced by endocrine disruption. Epigenetic effects were studied both in epidemiological data and experimentally in vitro. Associations between prenatal MeHg exposure and DNA methylation of GRIN2B and NR3C1 were found in children. In vitro validation of DNA methylation changes found in epigenome-wide association studies of populations exposed to MeHg, uncovered the potential involvement of the Mediator Complex Subunit 31 (MED31) in MeHg DNT. To contribute to the endocrine disruption (ED)-induced DNT field, the applicability of an in vitro model composed of murine neural progenitor cells (the C17.2 cell-line) was evaluated. We found that C17.2 neural differentiation and morphology were sensitive to retinoic acid (RAR), retinoic X (RXR), peroxisome proliferator-activated β/δ (PPARβ/δ), and glucocorticoid (GR) agonism. Furthermore, two out of 25 tested EDCs decreased neurite outgrowth and branching in the C17.2 system. These effects were recovered by co-exposure of the chemicals with antagonists of RAR, RXR, or PPARβ/δ, indicating that their DNT effect is mediated by hormonal disruption. Altogether, this thesis contributed to the development of new methodologies and endpoints for the assessment of DNT induced by MeHg and EDCs.
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| 8. |
- De Tarafder, Arindam
(författare)
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Adaptive Evolution of the Bacterial Translation Machinery
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The process of protein synthesis via translation is of paramount importance for the existence of life on Earth. The bacterial translation machinery has embraced more than 3.5 billion years of molecular evolution to adapt and function efficiently under the provided physiological conditions. This thesis dwells on the intricacies of the adaptive evolution, which the massively complex translation machinery has undergone to function optimally in diverse conditions and habitats. In Paper I, we used elongation factor Tu (EF-Tu) as a model system to follow the evolution of ribosome specificity in translation factors. For that, we have biochemically characterized two sequence-reconstructed ancestral EF-Tu variants for their specificities towards two unrelated extant bacterial ribosomes, mesophilic Escherichia coli and thermophilic Thermus thermophilus. Our fast kinetics-based biochemical analysis hints at the ‘generalist’ ancestry of modern EF-Tu proteins. In Paper II, we have reconstituted an in vitro translation system of the psychrotolerant bacteria Pseudoalteromonas haloplanktis to quantitatively characterize the steps of translation elongation. Our results demonstrate similar kinetics of peptide bond formation in psychrotolerant P. haloplanktis and mesophilic E. coli. In contrast, P. haloplanktis ribosome exhibits much slower rates of EF-G-catalyzed tRNA translocation than E. coli. Comparison and swapping of the EF-Gs and tRNAs between the two in vitro translation systems indicate that the slow translocation is likely an inherent property of the P. haloplanktis ribosome. Furthermore, our results demonstrate the varied extent of antibiotic inhibition on the P. haloplanktis minimal translation system, particularly when targeting processes related to translocation and peptide bond formation, compared to E. coli. In Paper III, we used ribosomes from bacterial species of diverse habitats to show that the ribosomes in vitro can maintain their catalytic activity beyond the survival temperature cutoff of the native host. Moreover, our results indicate that the thermostability of essential translation factors, EF-Tu and EF-G, dictates the upper limit of reaction temperature for translation elongation. Finally, we demonstrate that ribosomes from a psychrophile, mesophile, and thermophile can function in a vast temperature range of 10-70 °C, provided the translation factors remain structurally and functionally stable. Our results highlight the thermal versatility of the ribosome and reiterate the early emergence of a thermostable ribosomal core in the primordial RNA world.The outcome of this thesis will unveil some of the intricate mechanisms underlying the evolution of bacterial translation machinery. This knowledge may open up new research avenues regarding the emergence and diversification of bacteria and the development of new therapeutic strategies.
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| 9. |
- Dimitriadi, Christina
(författare)
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Double Higgs τrouble : Searches for Higgs boson pairs in the ATLAS experiment and their interpretations
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the discovery of the Higgs boson by the ATLAS and CMS experiments at the Large Hadron Collider (LHC), extensive measurements of its properties have confirmed the predictions of the Standard Model (SM). However, the Higgs boson self-coupling, which is related to the shape of the Higgs potential, still remains loosely constrained experimentally. Searches for the production of Higgs boson pairs (HH) are of great interest, especially for measuring the Higgs boson self-coupling. While the SM predicts a very small event rate for this process, modifications of the Higgs boson self-coupling or new couplings introduced in effective field theories (EFTs) can lead to enhancements of the HH cross-section. This thesis focuses on searches for, and interpretations of, non-resonant Higgs boson pair production in the final state with two b-quarks and two τ-leptons using 140 fb-1 of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded by the ATLAS experiment. This final state offers a sizeable branching ratio and moderate background rates, making it one of the most appealing search channels for HH production. No statistically significant signal excess is found above the expected background, therefore upper limits are set on the HH signal strength. The search yields an observed (expected) upper limit of 5.9 (3.3) times the SM cross-section prediction at 95% confidence level. In turn, the ratio of the Higgs boson self-coupling to its SM value, κλ, is constrained to an observed (expected) 95% confidence interval of [-3.1, 9.0] ([-2.5, 9.3]). The results are also interpreted within two distinct EFT frameworks, the Higgs EFT (HEFT) and Standard Model EFT (SMEFT), through constraints on the respective Wilson coefficients and upper limits on the HH cross-section for seven HEFT shape benchmarks with representative features in the HH invariant mass spectrum. Looking forward, the sensitivity of the search is explored at the High-Luminosity LHC by extrapolating the results to 14 TeV and 3000 fb-1. The projected signal significance assuming SM kinematics reaches 2.8σ, while κλ is expected to be constrained to the 2σ confidence interval [-0.3, 7.4].
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| 10. |
- Edelbroek, Bart
(författare)
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Function and Evolution of Small Regulatory RNAs and their Associated Proteins : A Journey from Genome to Proteome
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organisms throughout the tree of life have evolved distinct ways to regulate gene expression. Some of these processes involve non-coding RNAs (ncRNAs), which are not translated but functional nonetheless. These ncRNAs are of utmost importance, with dysregulation of some causing severe developmental effects or even being lethal.In order to get a better fundamental understanding of gene regulation, and the ncRNAs that evolved to regulate gene expression, we study this in Amoebozoa. Members of this taxon vary greatly in lifestyle and organismal complexity. Some are strictly unicellular, free-living, whereas others, such as the social amoeba Dictyostelium discoideum can transition between unicellular and multicellular lifestyles. D. discoideum features a variety of small ncRNAs. Among these are the microRNAs. microRNAs have mostly been studied in plants and animals, where they are believed to have evolved convergently, and hypothesized to have played a role when these taxa evolved multicellular lifestyles. At what point the D. discoideum microRNAs evolved, how they function, and if they are involved in its multicellular lifestyle are fundamental questions addressed in this thesis. Here, we studied the evolution and function of microRNAs in a broad set of species belonging to Amoebozoa. We could identify microRNAs in all studied amoebae, and concluded that they are probably not involved in the evolution of multicellularity. To in detail investigate the evolution of microRNAs, we performed comparative genomics using D. discoideum and the close relative Dictyostelium firmibasis. For this, we sequenced, assembled and annotated the genome of the latter. At this point, our findings suggest that the microRNAs evolved several times in Amoebozoa, although we cannot rule out if they have a deep evolutionary history.The Class I RNAs are another type of ncRNAs. These, on the other hand, are only present in the social amoebae. They are hypothesized to regulate the transition from unicellular to multicellular in these species, potentially in a post-transcriptional manner. In order to investigate this, it is essential to understand to what extent the proteome and transcriptome correlate. Hence, we performed paired transcriptomics and proteomics in a time-series during multicellular development. By including a strain in which a specific Class I RNA is knocked out, we have initiated studies of its role during the transition to multicellularity.In conclusion, we were able to answer broad evolutionary and functional questions about gene regulation and ncRNAs by studying Amoebozoa from genome to proteome.
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