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  • Disputas: 2019-12-13 09:15 Newton, Växjö
    Ivanenko, Yevhen
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Optimization and Physical Bounds for Passive and Non-passive Systems2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Physical bounds in electromagnetic field theory have been of interest for more than a decade. Considering electromagnetic structures from the system theory perspective, as systems satisfying linearity, time-invariance, causality and passivity, it is possible to characterize their transfer functions via Herglotz functions. Herglotz functions are useful in modeling of passive systems with applications in mathematical physics, engineering, and modeling of wave phenomena in materials and scattering. Physical bounds on passive systems can be derived in the form of sum rules, which are based on low- and high-frequency asymptotics of the corresponding Herglotz functions. These bounds provide an insight into factors limiting the performance of a given system, as well as the knowledge about possibilities to improve a desired system from a design point of view. However, the asymptotics of the Herglotz functions do not always exist for a given system, and thus a new method for determination of physical bounds is required. In Papers I–II of this thesis, a rigorous mathematical framework for a convex optimization approach based on general weighted Lp-norms, 1≤p≤∞, is introduced. The developed framework is used to approximate a desired system response, and to determine an optimal performance in realization of a system satisfying the target requirement. The approximation is carried out using Herglotz functions, B-splines, and convex optimization. 

    Papers III–IV of this thesis concern modeling and determination of optimal performance bounds for causal, but not passive systems. To model them, a new class of functions, the quasi-Herglotz functions, is introduced. The new functions are defined as differences of two Herglotz functions and preserve the majority of the properties of Herglotz functions useful for the mathematical framework based on convex optimization. We consider modeling of gain media with desired properties as a causal system, which can be active over certain frequencies or  frequency intervals.  Here, sum rules can also be used under certain assumptions.

    In Papers V–VII of this thesis, the optical theorem for scatterers immersed in lossy media is revisited. Two versions of the optical theorem are derived: one based on internal equivalent currents and the other based on external fields in terms of a T-matrix formalism, respectively. The theorems are exploited to derive fundamental bounds on absorption by using elementary optimization techniques. The theory has a potential impact in applications where the surrounding losses cannot be neglected, e.g., in medicine, plasmonic photothermal therapy, radio frequency absorption of gold nanoparticle suspensions, etc.  In addition to this, a new method for detection of electrophoretic resonances in a material with Drude-type of dispersion, which is placed in a straight waveguide, is proposed.

  • Disputas: 2019-12-17 13:15 Homeros, Växjö
    Engström, Robin
    Linnéuniversitetet, Fakulteten för konst och humaniora (FKH), Institutionen för språk (SPR).
    The Scottish Independence Referendum in Text, Image and Thought2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In 2014, a referendum was held in Scotland in order to decide the country’s constitutional future. The referendum was the climax of years of campaigning that gave rise to a rich body of political discourse. This compilation thesis attempts to show how an independent Scotland was discursively constructed, and how these constructions impacted on Scottish identity. The thesis consists of four original research papers which employ a number of complementary approaches in order to analyse a rich and diverse data set.

    The first article examines how the Scottish government looked at small European states in order to construct a vision of a future independent Scotland. This was achieved by discursively constructing small states as economically successful and democratically progressive and then by emphasizing Scotland’s role as a small country.

    The second article analyses the many new metaphorical personifications of Scotland, notably as a woman, that appeared during the campaign. The article finds that traditional, gendered metaphors were largely reworked in order to function in a modern political context.

    The third article maps the central topics and the ideological morphology of discourses on Scottish independence produced by the Scottish National Party and the intellectual and artistic movement National Collective. Unlike previous research, the results of the analysis suggest that these organizations as complementary but labels the former politically nationalist and the latter culturally nationalist.

    The fourth article analyses image tweets published by the official Yes and No campaigns in order to ascertain how the two campaigns legitimated their own standpoints and how they delegitimated their opponents online. The analysis finds that the Yes campaign balanced between promoting its own visions whilst criticizing their opponents, in contrast to the No campaign which almost entirely focused on delegitimating its opponents, thus failing to offer alternative visions.

    Collectively, the thesis paints a picture of a diverse independence movement with different aims and different rationales for advocating independence. Besides making a contribution to the literature on nationalism in general and Scottish nationalism in particular, the thesis further integrates the fields of political theory and discourse studies.

  • Disputas: 2019-12-18 09:30 Fregatten Ma117 campus Kalmar, Kalmar
    Osbeck, Christofer
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Exploring gene expression responses of marine bacteria to environmental factors2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Bacterioplankton are abundant in marine ecosystems, where they as “masters of transformation” of dissolved organic matter (DOM) are important for energy fluxes and biogeochemical cycles. However, the performance of bacteria in a changing marine environment influenced by anthropogenic activities is poorly understood. In this thesis, I did experiments with model bacteria and natural assemblages of bacteria, using microbiology methods combined with modern molecular tools, to investigate responses of marine bacteria to changes in environmental conditions like ocean acidification, organic pollution and organic matter released by phytoplankton. Experiments with a model gammaproteobacterium demonstrated that bacteria in stationary phase showed little responses to organic pollutants, whereas pollutants caused decreased bacterial growth and had a broad physiological impact on actively growing bacteria (as deduced from gene expression analysis). In an experiment with two distantly related marine model bacteria, we identified several important bacterial mechanisms, such as uptake of macromolecules and phosphonates, by which bacteria respond when exposed to DOM produced by photosynthetic dinoflagellates. Using natural bacterial communities in a Baltic Sea mesocosm experiment with the addition of river water from a forested or an agriculture influenced catchment area, we showed important interactions between river water type and the development of phytoplankton blooms that caused different bacterial gene expression activities. In the fourth set of experiments, marine bacterial communities were subjected to elevated CO2, to mimic ocean acidification, under high and low nutrient conditions in a mesocosm study. We found increased bacterial gene expression activity focused on maintaining pH homeostasis, but only under low nutrient conditions, indicating that bacteria focus on cell maintenance instead of growth when challenged by lowered pH. Finally, in a computational analysis, we compared genomes from yet uncultivated prokaryotes by two different strategies: metagenome assembled and single amplified genomes. Importantly, the analysis showed that both methods selected abundant taxa and generated nearly identical sequences in overlapping regions. To conclude, this thesis presents discoveries that will help form a better understanding of marine bacterial responses to present and future anthropogenic disturbances of marine ecosystems.