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Coming dissertations at TekNat

  • Adsorption of dissolved organic matter in aquatic ecosystems : Effects on composition and reactivity

    Author: Marloes M. Groeneveld
    Publication date: 2020-11-25 10:11

    Inland waters receive organic matter from terrestrial ecosystems and in situ production. In transit from land to the ocean, dissolved organic carbon (DOC) may be mineralised to inorganic forms (CO2 and CH4) by microbial degradation and photodegradation. It may also transition from dissolved into particulate phase, and be transferred to the sediment and buried. One way in which this can happen is by adsorption of dissolved organic matter (DOM) to mineral particles. This process is rarely studied in inland waters, since suspended particles are often in short supply. However, there are scenarios under which high particle concentrations occur, and in those cases, adsorption may have a substantial effect on DOM composition and reactivity. The overall aim of this thesis was to investigate the potential for DOM adsorption to inorganic particles and the resulting effect on DOM composition, as well as its biological reactivity. Three studies within this thesis focus on different types of surfaces waters in the boreal landscape of Sweden, and one study focuses on coastal moorland streams in the United Kingdom. Adsorption experiments were conducted under controlled laboratory conditions...

  • Exploring Diversity in the Midbrain Dopamine System with Emphasis on the Ventral Tegmental Area

    Author: Bianca Vlcek
    Publication date: 2020-11-25 08:22

    Midbrain dopamine neurons of the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) are important for motor, cognitive and limbic functions through substantial projections to forebrain structures. Dysfunction of the midbrain dopamine system is associated with several disorders, including Parkinson´s disease (PD) and substance use disorder. PD is characterized by the loss of dopaminergic neurons leading to severe motor dysfunction and by the brain distribution of aggregated α-Synuclein protein. Mutations in the α-Synuclein gene (SNCA) have been associated with PD.

    The overall aim of this thesis was to increase the understanding of anatomical and histological features of dopamine neurons by identifying and characterizing gene expression differences between dopamine neurons, primarily those located within VTA but also the SNc. This knowledge should help towards increased understanding of the roles exerted by different dopamine neurons in behavior during healthy conditions and in disease. For this purpose, unbiased microarray analysis was first performed to identify genes that are differentially expressed in the VTA and SNc. Identified genes, e.g....

  • Regularity Properties of Oscillatory Integral Operators on Function Spaces

    Author: Anders Israelsson
    Publication date: 2020-11-24 10:00

    We establish regularity results for a variety of oscillatory integral operators, some of which introduced for the first time in this thesis, in general function spaces such as Besov-Lipschitz and Triebel-Lizorkin spaces. These estimates yield new local and global regularity results for evolutionary partial differential equations.

  • Identification of SLiMs: Mapping and characterizing motif-based protein interactions

    Author: Muhammad Ali
    Publication date: 2020-11-20 10:17

    During the last twenty years it has become evident that about 35-40% of amino acids in the proteome are in regions that have evolved to remain unstructured. These intrinsically disordered regions contain short linear motifs (SLiMs), which serve as docking sites for protein-protein interactions. SLiMs often mediate low-to-medium affinity interactions that are transient in their nature. The characteristics of SLiM-based interactions make them difficult to be captured using conventional approaches like affinity-purification coupled to mass spectrometry or yeast-two-hybrid. We therefore used and developed a dedicated method for large-scale screening of SLiM-based interactions termed proteomic peptide phage display (ProP-PD).

    Using ProP-PD, We identified large sets of ligands, for the binding pocket of shank1 PDZ domain, containing C-terminal or internal binding motifs and established the consensus motifs to be xTxL/F-COOH and xTxFx respectively. We further validated interactions using biophysical affinity determinations and pulldown experiments. Using X-ray crystallization, we uncovered that shank1 PDZ binds to internal xTxFx motifs using a binding mode similar to that for C-...

  • The Powers of Perturbation Theory : Loops and Gauge Invariance in Particle Physics

    Author: Johan Löfgren
    Publication date: 2020-11-20 10:10

    The Standard Model is the best particle physics theory we have, but there are still phenomena that it cannot explain. In this thesis I have worked on two different projects that connect to two of the biggest unsolved questions of the Standard Model.

    From observations of neutrino oscillations we know that at least one of the neutrinos has to be massive. But the neutrinos of the Standard Model are massless. The first paper in the thesis investigates a simple extension of the Standard Model that realizes a fifth force as a U(1) gauge group. In such models, extra care has to be taken to not introduce inconsistencies known as anomalies. It turns out that the simplest way to avoid these problems is to introduce three right-handed neutrinos. Such models can then incorporate neutrino masses in a convenient way. In the second paper we have investigated a twist on this model that does not have neutrino masses, but which makes other interesting models possible—such as a model with gauged lepton number.

    The observed asymmetry between matter and antimatter cannot be explained by the Standard Model. One of the more popular of the possible explanations is known as electroweak...

  • Machine Behavior Development and Analysis using Reinforcement Learning

    Author: Yuan Gao
    Publication date: 2020-11-20 09:45

    We are approaching a future where robots and humans will co-exist and co-adapt. To understand how can a robot co-adapt with humans, we need to understand and develop efficient algorithms suitable for our interactive purposes. Not only it can help us to advance the field of robotics but also it can help us to understand ourselves. A subject Machine Behavior, proposed by Iyad Rahwan in a recent Science article, studies algorithms and the social environments in which algorithms operate. What this paper's view tells us is that, when we would like to study any artificial robot we create, like natural science, a two-step method based on logical positivism should be applied. That is, we need to, on one hand, provide a complicated theory based on logical deduction, and on another hand, empirically setup experiments to conduct.

    Reinforcement learning (RL) is a computational model that helps us to build a theory to explain the interactive process. Integrated with neural networks and statistics, the current RL is able to obtain a reliable learning representation and adapt over interactive processes. It might be one of the first times that we are able to use a theoretical framework...

  • Genomics of Arbuscular Mycorrhizal Fungi : Expanding knowledge, one assembly at a time

    Author: Merce Montoliu-Nerin
    Publication date: 2020-11-20 09:21

    Most life forms that inhabit Earth today are still unknown or are difficult to study. Accessing their DNA can give us information of their biology, ecology, and evolution, even when unculturable. The research here presented focused on method development for genomic research of non-model organisms. Paper I and II contributed to a comprehensive expansion of the genomic data available in arbuscular mycorrhizal (AM) fungi, an essential group of plant symbionts. While paper III and IV focused on the analysis of the generated genomic data. Paper I presents the development of a workflow that allows for DNA sequencing and assembling of AM fungal genomes, from as little as one single spore, by sorting and individually amplifying and sequencing nuclei. In paper II, the novel workflow was utilized to expand genomic data on AM fungi, by generating de novo genome assemblies from 22 different taxa. The evolutionary relationships within the group was also explored. In paper III possible genetic differences between nuclei of individual AM fungal organisms was examined, following the...

  • The Evolutionary Significance of Cambrian Ecdysozoan Trace Fossils

    Author: Giannis Kesidis
    Publication date: 2020-11-19 09:49

    The origin of most of the animal phyla is tied to the Cambrian explosion, a rapid diversification event that took place from about 540 million years ago. This diversification is coupled with a great number of concurrent metazoan body plan innovations such as the development of the coelom, antagonistic muscles and a through-gut. While the body fossil record and molecular clocks document this apparent diversification, albeit with somewhat divergent results, there exists a third much more accurate record for the timing of life’s journey: the trace fossil record. The ecdysozoan trace fossil record first appears in the terminal Ediacaran and extends into the Cambrian. It exhibits a similar pattern of diversification to the body fossil record, pointing to a rapid ethological expansion through this interval. Here, I investigate particular ethologies of early Cambrian ecdysozoan trace fossils and frame the corresponding trace fossil morphologies in an evolutionary context. The first part of the thesis includes observations on the Cambrian representatives of the ichnogenera Cruziana and Rusophycus. I identify the links between the two morphologies and suggest that some...

  • Dynamic and quasi-stationary electrochromic response of amorphous tungsten oxide thin films : In situ combined electrochemical and optical measurements during lithium intercalation

    Author: Edgar Alonso Rojas González
    Publication date: 2020-11-17 10:28

    Electrochromic (EC) materials can adjust their optical properties, reversibly, by means of an external electrical stimulus. They have relevant technological applications; for example, energy-efficient smart windows, which can adapt dynamically—according to the given environmental conditions—to control the heat and visible light fluxes between the interior and exterior of a building. EC applications are currently available on the market. However, there are still questions concerning the fundamental processes responsible for the EC effects.

    This thesis focuses on EC inorganic oxide materials in the thin film form; particularly, amorphous tungsten oxide. In this case, the electrochromism is induced by the intercalation of small ions (such as lithium ions) into the material and the insertion of electrons from an external circuit due to charge neutrality requirements within the film. These electrons are the ones causing the optical changes. This work centers its attention to the quasi-equilibrium and dynamic EC processes. They were studied by in situ simultaneous electrochemical and optical measurements at different conditions—that is, for a wide range of...

  • Engineered temporary networks : Effects of control and temporality on inter-organizational interaction

    Author: Carl Kronlid
    Publication date: 2020-11-12 14:24

    The world is facing a growing threat of antibiotic resistance. The development of new antibiotics is of utmost importance; otherwise, we go back to the pre-antibiotic era where common infections become life-threatening. Despite this need for new antibiotics, a market failure is hampering its development. To mitigate this market failure, policy makers have initiated inter-organizational R&D projects for antibiotic development. These projects involve different actors, are intentionally created, and have clearly defined objectives, as well as duration, for developing new antibiotics. These initiatives can be seen as engineered temporary networks. Engineered temporary networks need to be managed in order to avoid the risk of not reaching the network objectives. Managing these networks is a matter of formally controlling the interaction among the organizations involved in the networks, making sure that the network proceeds toward its objectives. 

    The aim of this thesis is to understand the effects of formal control mechanisms used to engineer a temporary network on inter-organizational interaction, with a special focus on temporality. The thesis uses a case study...