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  • Public defence: 2019-02-22 09:30 P216. NPQ-huset, Stockholm
    Caputo, Andrea
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Genomic and morphological diversity of marine planktonic diatom-diazotroph associations: a continuum of integration and diversification through geological time2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Symbioses between eukaryotes and nitrogen (N2)-fixing cyanobacteria (or diazotrophs) are quite common in the plankton community. A few genera of diatoms (Bacillariophyceae) such as Rhizosolenia, Hemiaulus and Chaetoceros are well known to form symbioses with the heterocystous diazotrophic cyanobacteria Richelia intracellularis and Calothrix rhizosoleniae. The latter are also called diatom-diazotroph associations, or DDAs. Up to now, the prokaryotic partners have been morphologically and genetically characterized, and the phylogenetic reconstruction of the well conserved nifH gene (encodes for the nitrogenase enzyme) placed the symbionts in 3 clusters based on their host-specificity, i.e. het-1 (Rhizosolenia-R. intracellularis), het-2 (Hemiaulus-R. intracellularis), and het-3 (Chaetoceros-C- rhizosoleniae). Conversely, the diatom-hosts, major representative of the phytoplankton community and crucial contributors to the carbon (C) biogeochemical cycle, have been understudied.

    The first aim of this thesis was to genetically and morphologically characterize the diatom-hosts, and to reconstruct the evolutionary background of the partnerships and the symbiont integration in the host. The molecular-clock analysis reconstruction showed the ancient appearance of the DDAs, and the traits characterizing the ancestors. In addition, diatom-hosts bearing internal symbionts (with more eroded draft genomes) appeared earlier than diatom-hosts with external symbionts. Finally a blast survey highlighted a broader distribution of the DDAs than expected.

    The second aim of this thesis was to compare genetic and physiological characteristics of the DDAs symbionts with the other eukaryote-diazotroph symbiosis, i.e. prymnesiophyte-UCYN-A (or Candidatus Atelocyanobacterium thalassa). The genome comparison highlighted more genes for transporters in het-3 (external symbiont) and in the UCYN-A based symbiosis, suggesting that symbiont location might be relevant also for metabolic exchanges and interactions with the host and/or environment. Moreover, a summary of methodological biases that brought to an underestimation of the DDAs is reported.

    The third aim of this thesis was to determine the distribution of the DDAs in the South Pacific Ocean using a quantitative polymerase chain reaction (qPCR) approach and to outline the environmental drivers of such distribution. Among the het-groups, het-1 was the most abundant/detected and co-occurred with the other 2 symbiotic strains, all responding similarly to the influence of abiotic factors, such as temperature and salinity (positive and negative correlation, respectively). Globally, Trichodesmium dominated the qPCR detections, followed by UCYN-B. UCYN-A phylotypes (A-1, A-2) were detected without their proposed hosts, for which new oligonucleotides were designed. The latter suggested a facultative symbiosis. Finally, microscopy observations of the het-groups highlighted a discrepancy with the qPCR counts (i.e. the former were several order of magnitudes lower), leading to the idea of developing a new approach to quantify the DDAs.  

    The fourth aim of this thesis was to develop highly specific in situ hybridization assays (CARD-FISH) to determine the presence of alternative life-stages and/or free-living partners. The new assays were applied to samples collected in the South China Sea and compared with abundance estimates from qPCR assays for the 3 symbiotic strains. Free-living cells were indeed detected along the transect, mainly at deeper depths. Free-living symbionts had two morphotypes: trichomes and single-cells. The latter were interpreted as temporary life-stages. Consistent co-occurrence of the 3 het-groups was also found in the SCS and application of a SEM model predicted positive interactions between the het groups. We interpreted the positive interaction as absence of intra-specific competition, and consistent with the previous study, temperature and salinity were predicted as major drivers of the DDAs distribution.

  • Public defence: 2019-02-22 10:00 Vivi Täckholmsalen (Q-salen), NPQ-huset, Stockholm
    A. Manneh, Ilana
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education.
    Supporting Learning and Teaching of Chemistry in the Undergraduate Classroom2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is agreement in research about the need to find better ways of teaching chemistry to enhance students’ understanding. This thesis aims to contribute to the understanding of how we better support teaching and learning of undergraduate chemistry to make it meaningful and intelligible for students from the outset. The thesis is concerned with examining the interactions between student, specific content and teacher in the undergraduate chemistry classroom; that is, the processes making up the three relations of the didactic triangle. The data consists of observations of students and tutors during problem-solving activities in an introductory chemistry course and interviews with graduate students.

    Systematic analyses of the different interactions between the student, the chemistry content, and the tutor are made using the analytical tool of practical epistemology analysis. The main findings of the thesis include detailed insights into how undergraduate chemistry students deal with newly encountered content together with didactic models and concrete suggestions for improved teaching and for supporting continuity and progression in the undergraduate chemistry classroom. Specifically, I show how students deal with the chemistry content through a complex interaction of knowledge, experiences, and purposes on different levels invoked by both students and tutors as they interact with each other. Whether these interactions have a positive or negative effect on students’ learning depends on the nature of knowledge, experiences and purposes that were invoked. Moreover, the tutor sometimes invoked other purposes than the ones related to the task at hand for connecting the activity to the subject matter in general. These purposes were not always made continuous with the activity which resulting in confusion among students. The results from these analyses were used for producing hypotheses and models that could support continuity and progression during the activity. The suggested models aim to make the content more manageable and meaningful to students, enabling connections to other experiences and purposes, and helping teachers and tutors to analyze and reflect on their teaching. Moreover, a purpose- and activity-based progression is suggested that gives attention to purposes in chemistry education other than providing explanations of chemical phenomena. The aim of this ‘progression in action’ is to engage students in activities were they can see the meaning of chemical concepts and ideas through their use to accomplish different chemical tasks. A general conclusion is that detailed knowledge about the processes of teaching and learning is important for providing adequate support to both undergraduate students and university teachers in the chemistry classroom.

  • Public defence: 2019-02-22 10:00 William-Olssonsalen, Geovetenskapens hus, Stockholm
    Leiva, Alejandro
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Three Faces of Diversity Rhetoric: Managerialization, marketing and ambiguity2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the past decades, the language of diversity management has spread from the US to many parts of the world, including Sweden, where it emerged in the mid 1990’s. Consisting of three papers, this thesis contributes to the field of critical diversity studies by examining the multifaceted character of diversity rhetoric among Swedish diversity consultants. A central point of debate in previous research has been the relationship between, on one hand, diversity management rhetoric, and on the other hand, equal opportunities and antidiscrimination law. Scholars suggest that Scandinavian and Swedish “diversity” are strongly associated with ideals of equality, antidiscrimination and corporate social responsibility. This thesis gives nuance to this picture by focusing on the views of consultants.

    Paper 1 tries to answer this question: Do Swedish diversity consultants managerialize antidiscrimination law? Research on the US and the UK asserts a conflict between legal equality and the instrumental rhetoric of diversity management. However, studies on continental Europe and Scandinavia tend to posit diversity rhetoric as linked to ethnicity and tempered by legal and social equality. Building on interviews with diversity consultants, this paper shows that their diversity constructions conform to the managerialization thesis. 

    Paper 2 argues that diversity’s three common rhetorical moves—its broad scope, its business case, and its dissociation from legal frames—are more open to interpretation than typically portrayed in the critical diversity research. While scholars tend to interpret this rhetoric as managerial dilution of legal and equality ideals, findings indicate that consultants may use the same rhetorical moves to incorporate an equality logic and extend legal ideas beyond the limits of the law. These interpretative discrepancies are conceptualized as ambiguity—i.e., the same rhetorical moves may support more than one interpretation.

    Paper 3 examines the ongoing institutional work of diversity consultants as they rhetorically try to build a business case for “ethnic marketing” in Sweden. Extant literature suggests that ethnic marketing relies on making differences between “them” (ethnic minority consumers) and “us” (majority consumers). This paper asserts that while making differences is crucial when creating “ethnic” consumers (“different from us”), another rhetorical strategy, “making similarities,” is used to construct already otherized people as “consumers” (“similar to us”). Further, findings show that Sweden’s lack of official statistics on ethnicity and general reluctance towards highlighting ethnicity may function as institutional obstacles that hamper the legitimacy and spread of ethnic marketing.

  • Public defence: 2019-02-22 13:30 Vivi Täckholmsalen (Q-salen), Stockholm
    Neethiraj, Ramprasad
    Stockholm University, Faculty of Science, Department of Zoology.
    Advances in studying the role of genetic divergence and recombination in adaptation in non-model species2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Understanding the role of genetic divergence and recombination in adaptation is crucial to understanding the evolutionary potential of species since they can directly affect the levels of genetic variation present within populations or species. Genetic variation in the functional parts of the genome such as exons or regulatory regions is the raw material for evolution, because natural selection can only operate on phenotypic variation already present in the population. When natural selection acts on a phenotype, it usually results in reduction in the levels of genetic variation at the causal loci, and the surrounding linked loci, due to recombination dynamics (i.e. linkage); the degree to which natural selection influences the genetic differentiation in the linked regions depends on the local recombination rates.

    Studies investigating the role of genetic divergence and recombination are common in model species such as Drosophila melanogaster. Only recently have genomic tools allowed us to start investigating their role in shaping genetic variation in non-model species. This thesis adds to the growing research in that domain. In this thesis, I have asked a diverse set of questions to understand the role of genetic divergence and recombination in adaptation in non-model species, with a focus on Lepidoptera.

    First, how do we identify causal genetic variation causing adaptive phenotypes? This question is fundamental to evolutionary biology and addressing it requires a well-assembled genome, the generation of which is a cost, labor, and time intensive task. In paper I, I present a tool, MESPA, that stitches together exonic sequences in fragmented assemblies to produce high-quality gene models. These high-quality gene models can be used by researchers in the downstream analyses, providing genomic insights for a fraction of cost of a high quality genome. 

    Second, what does the pattern of recombination rate look like in chromosomes that lack centromeres (i.e.holocentric chromosomes)? In paper II, I compare the recombination landscape and the patterns of nucleotide diversity in three Lepidotera with holocentric chromosomes, Pieris napi, Bombyx mandarina, and Bombyx mori, with a monocentric species. Our results show that on average these three Lepidoptera have high rates of recombination across the vast majority of their genome. Our results also suggest that given similar effective population sizes, these species are likely to harbor more genetic diversity compared to monocentric species, which has important evolutionary consequences for these species.

    Third, what is the potential for parallelism at the genetic level in convergent melanic phenotypes? In paper III, I investigated the genetic basis of the female-limited melanic phenotype in the green-veined white (Pieris napi) butterfly, and found a 20kb region, approximately 50kb from the gene cortex, associated with this trait. This gene has been implicated in melanic phenotypes in other Lepidoptera that diverged from Pieris approximately 100my, indicating very high predictability for this trait.

    Finally, what is the role of cis-regulatory variation in local adaptation? In paper IV, I analyzed the relationship between allele specific expression (ASE) and genetic divergence (FST) in the F1 hybrids of Pieris napi napi and Pieris napi adalwinda. I show that intersecting results from ASE with FST is a powerful approach to identify genes involved in local adaptation.

  • Public defence: 2019-02-25 10:00 FA31, Stockholm
    Morå, Knut Dundas
    Stockholm University, Faculty of Science, Department of Physics. OKC.
    Statistical Modelling and Inference for XENON1T2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A great number of astrophysical observations suggests that of the matter in our universe, only a sixth is made up of known matter. The rest, named dark matter, has not been successfully identified. This thesis presents the analysis and statistical inference that was used by the XENON1T collaboration to conduct a search for a particular dark matter candidate; weakly interacting massive particles (WIMPs).

     

    XENON1T is a dual-phase time projection chamber that can detect particles scattering in a 2 tonne target of liquid xenon with deposited recoil energies above ~3 keV. This is low enough to observe the elastic recoil between a WIMP and a xenon nucleus for WIMP masses >5 GeV c-2.

    The results presented in this thesis use 278.8 days of data, with an analysis mass of 1.3 tonne.

     

    XENON1T uses models for backgrounds and signals within this volume to construct a combined likelihood for two science data-taking periods as well as calibration data-sets. Fits to simulated data-sets were used to calibrate and validate the confidence interval construction. In addition, analysis choices were evaluated both to optimize the discovery power and expected sensitivity of the search, and to improve the robustness of the analysis.

     

    No significant excess was observed in the search for a spin-independent WIMP-nucleon interaction for any WIMP masses between 6  GeV c-2 and 104 GeV c-2 for the 1 ton-year exposure. This analysis produced the strongest constraint on the spin-independent WIMP-nucleon cross-section so far, with a minimum of 4.1 10-47 cm2  for a 30 GeV c-2 WIMP.

  • Public defence: 2019-02-26 09:00 Room FA32, AlbaNova University Center, Stockholm
    Campanini, Donato
    Stockholm University, Faculty of Science, Department of Physics.
    Thermodynamic characterization of superconducting and magnetic materials using nanocalorimetry2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Measurement of specific heat is a powerful technique for the investigation of novel materials. Superconducting and magnetic systems, in particular, can be thoroughly characterized by studying their electronic contribution to the specific heat. To investigate their behavior in magnetic fields, single crystals need to be used, since the magnetic properties are dependent on the crystalline orientation. Crystal quality is often enhanced when sizes are reduced down to below the 100 μm scale, which is lower than the limit of conventional calorimeters. Nanocalorimetry allows to detect the weak electronic signature in the specific heat for such small samples with a preserved combination of high resolution and good accuracy. This is achieved by miniaturizing the device using microsystems technology and by a proper optimization of the measurement conditions.

    In this thesis, a nanocalorimeter designed for the study of samples with masses from sub-μg  to 100 μg in the temperature range 1-350 K is used for studying three different systems, yielding insights into their physical properties.

    In the magnetocaloric compound Fe2P a deep thermodynamic understanding of the first-order magnetic phase transition at the Curie temperature TC ≈ 217 K is lacking. The nanocalorimeter is used to map the magnetic phase diagram for fields applied parallel and perpendicular to the easy axis of magnetization. Two different phase diagrams are obtained depending on the applied field orientation. The first-order magnetic phase transition is characterized by specific and latent heat, providing a textbook example of thermodynamic properties around such a transition. The results are complemented with a combined nanocalorimetry - x-ray diffraction study and by magnetization measurements.

    The iron-based high-temperature superconductor BaFe2(As1-xPx)2 shows several anomalous physical properties which have been associated to the presence of a quantum critical point. High-resolution specific heat measurements are an important piece of the puzzle in understanding the behavior of this material. The specific heat is measured as a function of phosphorus doping x in the superoptimally substituted range and several superconducting parameters are extracted. An evolution from a single-gap to a two-gap is seen with doping, as well as a decrease of the London penetration depth close to optimum doping, without signs of divergence.

    The superconducting properties are as well investigated in the metastable β phase of gallium. β-Ga is obtained in-situ from the stable α-Ga by increasing the temperature about 10 K above the melting point. This novel method to produce β-Ga allows more reproducible and reliable measurements in comparison to traditional methods. A thorough thermodynamic characterization of the metastable phase is obtained, giving insights into the conditions for a strongly enhanced superconductivity in β-Ga in comparison to α-Ga. β-Ga is found to be a strong-coupling superconductor, with a 2.55 higher density of states at the Fermi energy in comparison to α-Ga.

    These measurements demonstrate how several problems in condensed matter physics can be addressed through nanocalorimetry, which allows mapping various phase diagrams and obtaining fundamental thermodynamic properties on high-quality samples in magnetic fields.

     

  • Public defence: 2019-02-28 10:00 Nordenskiöldsalen, Geovetenskapens hus, Stockholm
    Zguna, Nadezda
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Mass-spectrometry based survey of BMAA sources, distribution and transfer2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    β-methylaminoalanine (BMAA) is a neurotoxic non-protein amino acid first isolated from cycad seeds in 1967. It is believed to be connected to neurodegenerative diseases such as Parkinson’s, Alzheimer’s and amyotrophic lateral sclerosis (ALS) and is a ubiquitous compound produced by cyanobacteria, diatoms and dinoflagellates. Consequently, elucidating natural production, distribution and routes for human exposure of BMAA are of particular importance. However, the natural function of BMAA and its mechanisms of toxicity have not been fully established yet. The contradictory results about BMAA presence in cyanobacterial cultures and food webs have been reported by different scientific groups, which required the development of more sensitive and reliable analytical methods. 

    This thesis is focused on the analytical chemistry dimension of BMAA research: covering both new method development and novel applications. New analytical methods for BMAA detection and quantification were developed, focusing on improving sensitivity, since BMAA is normally found in natural samples at low concentrations. In Paper I, a new derivatization technique was implemented, which increased sensitivity and selectivity in the analysis of BMAA and its isomers. Subsequently, this developed method was applied to determine the presence of BMAA in fat and oil matrices in Paper II, which is a step towards discovering BMAA forms other than the documented free and protein-bound BMAA species. In Paper III, a method for separation and quantification of L- and D-BMAA stereoisomers in complex biological matrix was developed and applied to determine the enantiomeric composition of BMAA in cycad seed. Studying environmental distribution of BMAA is important to evaluate potential exposure routes and health risks for humans. Part of the work was devoted to broaden assessment on environmental occurrence of BMAA by applying existing robust methodology to new samples, such as commercial seafood in Paper IV and Baltic Sea biota in Paper V. Some of the “overlooked” aspects in the existing BMAA literature (i.e., BMAA chiral analysis, possible BMAA presence in dietary oil supplements and defined food webs) were successfully addressed. 

    Overall, the thesis presents important analytical developments, which can help to further elucidate sources, distribution and transfer of BMAA.

  • Public defence: 2019-03-01 10:00 Vivi Täckholmsalen (Q-salen), NPQ-huset, Stockholm
    Luijten, Ineke H. N.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Modulators of UCP1-dependent thermogenesis: Glucocorticoids, diet and novel research models2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The activation and recruitment of brown adipose tissue (BAT) thermogenesis has been put forward as a promising strategy to reduce the disease burden of obesity and obesity-related diseases. Heat production by BAT can be attributed to the tissue-specific mitochondrial uncoupling protein 1 (UCP1). Upon activation, UCP1 uncouples substrate oxidation from ATP production, thereby dissipating energy solely as heat and thus facilitating the ‘wasting’ of energy. To date, cold exposure is the strongest known BAT activator. However, to harness the energy wasting potential of BAT as a weight-reducing agent, the search for alternative factors that alter the activation or recruitment state of BAT is ongoing. The goal of this thesis is to obtain a better understanding of compounds and processes that modulate UCP1-dependent thermogenesis. 

    We investigate glucocorticoids for their potential to alter the UCP1-dependent thermogenic capacity of mice. We provide the novel insight that glucocorticoid supplementation reduces total BAT UCP1 protein levels, but only in mice housed at thermoneutrality. This reduction occurs at the transcriptional level by direct binding of the liganded glucocorticoid receptor to Ucp1regulatory regions. We also demonstrate that the glucocorticoid-induced reduction in BAT thermogenesis does not contribute to the development of glucocorticoid-induced obesity.

    Further, we show that high-fat diet- and cafeteria diet-feeding induces the activation and recruitment of BAT UCP1 protein in the obesity-resistant 129S mouse strain. We demonstrate the importance of this diet-induced modulation of BAT thermogenic capacity by reporting an increased metabolic efficiency in UCP1-ablated mice compared to wild-type mice. 

    We finally present two novel models that can be used for the identification of novel modulators of BAT thermogenesis, namely a brown adipocyte clonal cell line derived from adult human BAT, and a UCP1-luciferase reporter mouse which facilitates real-time tracking of endogenous Ucp1expression. Using these models, we identify the genes Mtus1and Kcnk3, and the compound WWL113, as novel modulators of UCP1-dependent thermogenesis. 

  • Public defence: 2019-03-01 10:00 JMK-salen, Garnisonen, Stockholm
    Skillen, Sara
    Stockholm University, Faculty of Humanities, Department of Media Studies.
    'Dior without Dior': Tradition and Succession in a Paris Couture House, 1957-20152019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This study explores how the French luxury fashion house, Dior has mobilised its power over a 70 year period through the constructed persona of the designer, who functions as a figurehead, together with the brand’s heritage. It investigates how the house of Dior reinvented itself after the death of its founder in 1957 through the charismatic succession of a series of designers; Yves Saint Laurent, Marc Bohan, Gianfranco Ferré, John Galliano, and finishes in 2015 with the departure of Raf Simons. The house of Dior understood from its earliest days that the image it projected of the designer was of the utmost importance to the success of the business. In the case of Dior ‘the couturier’ and Dior ‘the brand’, these two distinct entities have merged within the mythology that was constructed around the founder, so that the very fabric of Christian Dior’s own life and upbringing has become part of the brand’s vocabulary. My analysis of materials such as print media texts and images, journalist’s archives, press releases, fashion show invitations, press packs, exhibition catalogues, and life writing, highlights the use of a textual, as well as a visual vocabulary, in the construction and strengthening of Dior’s heritage.

    Pierre Bourdieu highlighted how the artist is unique and irreplaceable, whereas in the fashion field, the name of the designer as well as their products and business can live on long after their death. This research identifies how the symbolic production of the designer is achieved, through various institutions of consecration within the field of fashion, which is complicit in the idea of collective belief. In order to promote the brand globally, the public personae of the designers who followed Christian Dior were strategically constructed, legitimated and assimilated into the existing Dior identity myth through ritual acts such as catwalk shows, award ceremonies, documentaries and museum exhibitions, which also reinforced the status of the house, enabling it to continue in the Dior tradition. Dior’s history can therefore be read as a kind of palimpsest which has been inscribed, erased and overwritten with each new era, creating layers of visual and textual memories which reinforce the stylistic codes and heritage of the house. My investigation aims to bring a new perspective to discussions surrounding the importance of a ‘name’ designer as figurehead for a luxury fashion brand, the importance of heritage to a fashion house, as well as a new understanding of how fashion histories are written.

    The full text will be freely available from 2020-02-06 09:00
  • Public defence: 2019-03-08 10:00 Nordenskiöldsalen, Geovetenskapens Hus, Stockholm
    Andersson, Linus
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Essays on Family Dynamics: Partnering, Fertility and Divorce in Sweden2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Diversity in household and family structures poses interesting questions for scientific inquiry. What accounts for patterns of reproduction, partnering, household formation and household dissolution? This dissertation investigates facets of this question in the context of modern Sweden from a longitudinal and individual level perspective. It consists of three empirical studies using data from administrative registers and panel survey data. The first study begins with noting a rapid expansion in online education and analyzes whether this development leads to higher fertility in student populations. The second study asks whether individuals’ predispositions towards divorce change after exposure to the experience of parenthood, union formation and union dissolution. The third study builds on the literature on assortative mating and investigates what drives underlying preferences for this behavior. 

  • Public defence: 2019-03-11 13:00 L50, NOD-huset, Stockholm
    Bahati, Bernard
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Technology-enhanced formative assessment in higher education: An intervention design of scaffolding student self-regulated learning2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    As online learning is increasingly adopted in higher education institutions, many instructors are faced with the challenges of devising and implementing effective pedagogical practices that advance student learning. One of the challenges points to the design and development of assessment activities that truly inform the teaching and learning process. Despite the fact that both formative and summative assessment are important in teaching and learning, summative assessment has been dominating instructional processes in higher education at the expense of formative assessment. In higher education, in many countries including Rwanda, efforts that are made to practice formative assessment are hampered by a variety of factors that lead to ill-practices. Using technology-enhanced instructional interventions, this study attempted to address these factors. The study aimed at developing technology-enhanced instructional interventions to support student-based formative assessment that promote self-regulated learning. Additionally, this study proposes the design guidelines for the development of such instructional interventions. The study was guided by the following general research question: What are the characteristics of technology-enhanced formative assessment activities that promote student self-regulated learning? This research question was addressed using three specific research questions: (1) How do lecturers and students understand and practice formative assessment and feedback? (2) How can technology-enhanced formative assessment activities help student develop self-regulated learning skills? (3) What design guidelines should be followed in order to develop technology-enhanced formative assessment activities that promote student self-regulated learning? This study used Educational Design Research approach. Technology-enhanced instructional interventions were formatively developed, iteratively tested and evaluated in order to help students develop their self-regulated learning skills. Based on the findings of this study, three improved formative e-assessment packages are proposed as a practical research contribution: online knowledge survey, online peer-scaffolding through student-generated questions and peer-responses, and electronic reflective journals. In addition, based on the findings, this dissertation suggests a set of design guidelines and lessons learned in order to inform other educational practitioners who would like to develop technology-enhanced formative assessment activities that promote student-regulated learning.

  • Public defence: 2019-03-12 10:00 Magnélisalen, Kemiska övningslaboratoriet, Stockholm
    Margarita, Cristiana
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantio- and Regioselective Iridium-Catalyzed Hydrogenation of Olefins: From Development to Total Synthesis2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis concerns the iridium-catalyzed asymmetric hydrogenation of cyclic olefins and allylic alcohols for the preparation of useful chiral intermediates with various substitution patterns. The strategy provides stereocontrol for both non-functionalized as well as functionalized substrates and aims to be implemented in the stereoselective preparation of chiral building blocks having more than one stereocenter. The first part (Chapter 2) is focused on the asymmetric hydrogenation of 1,4-cyclohexadienes bearing a number of different functionalities. The development of a novel set of imidazole-based Ir-N,P catalyst enabled the efficient and enantioselective hydrogenation of prochiral substrates. In addition, the challenging regioselective mono-hydrogenation of only one of the two trisubstituted double bonds of the diene was accomplished.

    The sequential preparation of chiral cyclic allylsilanes by means of iridium-catalyzed asymmetric hydrogenation and their employment in the Hosomi-Sakurai reaction was also studied (Chapter 3). Several patterns of alkyl substitution on the prochiral olefins were evaluated and the hydrogenation afforded the allylsilanes in high conversions and excellent enantiomeric excesses. These chiral silanes were then used in the TiCl4-promoted allylation of aldehydes, which took place with high diastereoselectivity.

    In Chapter 4, the kinetic resolution of allylic alcohols via asymmetric hydrogenation is described. High selectivity was observed for a broad range of substrates using a combination of an Ir-N,P catalyst and K2CO3 under mild reaction conditions. This highly efficient process is complementary to our previously reported asymmetric hydrogenation/DKR protocol. The final part (Chapter 5) covers the application of Ir-catalyzed hydrogenations as key steps in total synthesis. A sequential strategy involving enantio- and regioselective hydrogenations was successfully employed in the synthesis of the natural sesquiterpene (-)-Juvabione. In the following project, two allylic alcohols were hydrogenated to prepare chiral intermediates for a convergent formal synthesis of the renin inhibitor Aliskiren. 

  • Public defence: 2019-03-13 13:00 FB52, AlbaNova universitetscentrum, Stockholm
    Chiappo, Andrea
    Stockholm University, Faculty of Science, Department of Physics.
    Dark matter signal normalisation for dwarf spheroidal galaxies: A frequentist analysis of stellar kinematics for indirect Dark Matter searches2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Indirect detection strategies of Dark Matter (DM) entail searching for signals of DM annihilation or decay, typically in the form of excess positrons or high-energy photons above the astrophysical background, originating from (inferred) DM-rich environments. Due to their characteristics, dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are considered very promising targets for indirect particle DM identification. To compare model predictions with the observed fluxes of product particles, most analyses of astrophysical data - which are generally performed via frequentist statistics - rely on estimating the abundance of DM by calculating the so-called J-factor. This quantity is usually inferred from the kinematic properties of the stellar population of a dSph, performing a Jeans analysis by means of Bayesian techniques. Previous works have, therefore, combined different statistical methods when analysing astrophysical data from dSphs. This thesis describes the development of a new, fully frequentist approach for constructing the profile likelihood curve for J-factors of dSphs, which can be implemented in indirect DM searches. This method improves upon previous ones by producing data-driven expressions of the likelihood of J, thereby allowing a statistically consistent treatment of the astroparticle and astrometric data from dSphs. Using kinematic data from twenty one satellites of the Milky Way, we derive estimates of their maximum likelihood J-factor and its confidence intervals. The analyses are performed in two different frameworks: the standard scenario of a collisionless DM candidate and the possibility of a self-interacting DM species. In the former case, the obtained J-factors and their uncertainties are consistent with previous, Bayesian-derived values. In the latter, we present prior-less estimates for the Sommerfeld enhanced J-factor of dSphs. In agreement with earlier studies, we find J to be overestimated by several orders of magnitude when DM is allowed is attractively self-interact. In both cases we provide the profile likelihood curves obtained. This technique is validated on a publicly available simulation suite, released by Gaia Challenge, by evaluating its coverage and bias. The results of these tests indicate that the method possesses good statistical properties. Lastly, we discuss the implications of these findings for DM searches, together with future improvements and extensions of this technique.

  • Public defence: 2019-03-15 13:00 Vivi Täckholmsalen (Q-salen), NPQ-huset, Stockholm
    Eggertsen, Linda
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Identification and implications of fish nurseries in tropical and subtropical seascapes2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Many species of reef fish reside in specific nursery habitats as juveniles. Seagrass meadows, and mangroves are examples of well-recognized nursery habitats, but only recently canopy-forming seaweeds have been found to provide important habitats for some fish species in the tropics. Availability of nurseries can have effects on the abundance and spatial distribution of adult fish, which is why it is important to recognize key nursery habitats for proper management. Information on reef fish nurseries is largely lacking in the South Western Atlantic (SWA), while information in the Western Indian Ocean (WIO) and elsewhere is more extensive. However, more information on the  consequences of nursery availability on adult fish populations is needed. This thesis studies nursery habitat use of reef fish on tropical and subtropical reefs in the SWA and in seagrass and reef systems in the WIO. The hypothesis that seagrass and canopy-forming macroalgae meadows function as a nursery habitat for reef fish is tested in the SWA. The aim of this thesis is also to understand distribution patterns of fish arising from the arrangement of the seascape, using a seascape ecology approach, linking patterns to non-reef nursery habitat use (mangroves and seagrass systems). Results showed that spatial and temporal patterns of juvenile reef fish abundance were weak on rocky, subtropical reefs in the SWA (Paper I), while there was a stronger preference for certain habitats on SWA tropical biogenic reefs, especially seaweed beds dominated by Sargassum (Paper II). The widely accepted paradigm that seagrass meadows function as nursery habitats for reef fish was not supported by the results from the study site in the tropical SWA (Paper II). This may be related to habitat availability in the seascape. In the SWA, seagrass meadows are spatially small, fragmented and less complex, compared to in the WIO, where they display high structural complexity and cover large areas. At the WIO study site (Bazaruto Archipelago), the juvenile fish assemblage in the seagrass meadows encompassed a number of reef fish species from a range of trophic groups and families, as well as resident seagrass species (Paper III). Key variables and extent of spatial scales that structure ontogenetic migrations were identified in both seagrass and reef habitats. Fish distribution patterns in the seagrass seascape was strongly influenced by seascape configuration and distance to adjacent habitats, highlighting that not all seagrass meadows are equally productive as nursery habitats. Variables important for distribution patterns of fish were identified, which in most cases were species-specific, and related to life history and functional traits of species. Effects of two small protected areas on the fish assemblage was also linked to geographical placement of reserves in the seascape. Likewise, the adult fish community composition on the reefs was found to be structured by the spatial arrangement of nursery habitats in the seascape, and presence of stretches of sand acting as isolating barriers (Paper IV). Nursery fish species were less abundant on reefs far from nurseries, resulting in differences in community and functional group composition along distance gradients in the seascape. Depending on functional traits of the nursery fish assemblage, seagrass and mangroves can enhance certain ecological functions on reefs. Both community structure and ecosystem functioning may therefore change depending on nursery habitat availability, highlighting the need to adopt a holistic seascape approach in management.

  • Public defence: 2019-03-15 13:00 sal FB52, AlbaNova universitetscentrum, Stockholm
    Asensio Torres, Ruben
    Stockholm University, Faculty of Science, Department of Astronomy.
    High-contrast imaging of low-mass companions and debris disks2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The search for exoplanets, i.e., planets orbiting other stars than the Sun, is a relatively new research field, but has already established itself as one of the most prolific and intriguing areas of astronomy. By now we are in a situation where the focus is not only on finding companions to stars, but also on characterising their atmospheres and physical properties, which overall allows us to put our Solar System into context. In the near future, these efforts could potentially lead to the first confirmation of a life-bearing planet besides the Earth. 

    The great majority of these exoplanet studies have been carried out indirectly, where the presence and characterisation of the companions are inferred solely from the observation of the host star. In the last decade, however, high-contrast direct imaging has been continuously developed to get rid of the starlight and reveal the existence of low-mass companions. Although this technique is currently limited to giant planets orbiting at large separations, it is able to directly detect the light emitted or scattered off the planet’s atmosphere at high signal to noise, which makes it the most promising planet-hunting method to characterise new worlds. Moreover, its capability to image faint objects close to the parent star allows for not only the detection of planetary-mass companions, but also low-mass stars, brown dwarfs, and circumstellar disks where planet formation takes place. This opens up a broad range of science cases where direct observations can be used to understand planet formation, atmospheric physics and stellar evolution.      

    In this PhD thesis I provide an up-to-date introduction to the basis of the direct imaging technique, and explain the star and planet formation mechanisms. Three publications are attached to this introduction, each of them dealing with distinct science cases that can be  assessed with high-contrast observations. In Paper I we resolve and model the aftermath of star formation, the so-called debris disk phase analogue to the asteroid and Kuiper belts in our Solar System, around the HD 32297 star with Subaru/HiCIAO.  We reveal an edge-on disk and find the first indications of a double-ring scenario. We also present the first polarimetric study of this system, constraining the properties of the dust around the star.  In Paper II we focus on the planetary-mass regime, and conduct the first direct imaging survey searching for circumbinary planets orbiting tight binary systems (SPOTS: Search for Planets Orbiting Two Stars). We present the results of the observations of 62 targets with VLT/NaCo and VLT/SPHERE, and perform a statistical analysis on the findings, placing constraints on the population of giant planets and brown dwarfs on wide orbits. Finally, in Paper III we resolve a triple stellar system with the newly-commissioned SCExAO/CHARIS integral field spectrograph. Taking advantage of the coeval nature of the system and the different range of masses involved, we use the data to reaffirm a previously suggested isochronal age discrepancy between the low- and the intermediate-mass population of stars.