1 - 17 of 17
rss atomLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
  • Public defence: 2019-10-24 10:00 De Geersalen, Stockolm
    Aldama Campino, Aitor
    Stockholm University, Faculty of Science, Department of Meteorology .
    Atmospheric and oceanic circulation from a thermodynamic perspective2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The climate system is continuously transporting and exchanging heat, freshwater, carbon and other tracers in different spatio-temporal scales. Therefore, analysing the system from a thermodynamic or biogeochemical framework is highly convenient. In this thesis the interaction between the ocean and the atmospheric circulation is analysed using thermodynamical and biogeochemical coordinates. Due to the dimensionality of the climate system stream functions are used to reduce this complexity and facilitate the understanding of the different processes that take place. The first half of this thesis, focuses on the interaction between the atmospheric and the ocean circulation from a thermodynamic perspective. We introduce the hydrothermohaline stream function which combines the atmospheric circulation in humidity-potential temperature (hydrothermal) space and the ocean circulation in salinity-temperature coordinates (thermohaline). A scale factor of 7.1 is proposed to link humidity and salinity coordinates. Future scenarios are showing an increase of humidity in the atmosphere due to the increase of temperatures which results in a widening of the hydrothermal stream function along the humidity coordinate. In a similar way, the ocean circulation in the thermohaline space expands along the salinity coordinate. The link between salinity and humidity changes is strongest at net evaporation regions where the gain of water vapour in the atmosphere results in a salinification in the ocean. In addition, the ocean circulation in latitude-carbon space is investigated. By doing so, we are able to distinguish the roles of different water masses and circulation pathways for ocean carbon. We find that the surface waters in the subtropical gyres are the main drivers of the meridional carbon transport in the ocean. By separating the carbon in its different constituents we show that the carbon transported by the majority of the water masses is a result of the solubility pump. The contribution of the biological pump is predominant in the deep Pacific Ocean. The effects of the Mediterranean Overflow Waters on the North Atlantic are discussed in the final part of the thesis.

  • Public defence: 2019-10-25 10:00 William-Olssonsalen, Geovetenskapens hus, Stockholm
    Ödalen, Malin
    Stockholm University, Faculty of Science, Department of Meteorology .
    Model analysis of ocean carbon storage and transport across climate states2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The ocean carbon cycle plays a fundamental role in the Earth’s climate system, on decadal to multi-millennial timescales. Of the carbon held in the ocean, the atmosphere, and the terrestrial biosphere combined, more than 90% resides in the ocean. Carbon enters the surface ocean through air-sea gas exchange and from terrestrial sources. It is transported to the deep ocean with the ocean circulation and through the so-called biological pump, where carbon is taken up in the surface ocean by photosynthetic organisms that fall down and decompose at depth. This thesis contributes to the understanding of the processes involved in ocean carbon storage and transport. It examines how these processes respond to model perturbations, and how this response influences our attempts to simulate glacial-interglacial fluctuations in atmospheric carbon dioxide (CO2).

    The thesis investigates the response of the simulated ocean carbon storage, and distribution of the isotopic tracer δ13C, to changes in physical and biological parameters. In the included studies, we use observational as well as proxy records of oceanic properties to evaluate our model simulations. In addition, we use a climate model to interpret proxy evidence of glacial-interglacial changes in ocean δ13C. By using a separation framework, we identify the origin of the carbon in the model ocean, and attribute observed changes to the processes involved.

    The results indicate a strong link between ocean carbon storage and the strength of the global ocean overturning circulation. Stronger circulation leads to less carbon storage through a weakening of the biological pump, and through reduced solubility due to an increase in global ocean average temperature.

    In simulations of glacial climate, we find that biological adaptability to the surrounding nutrient conditions, through a flexible carbon-to-phosphorus ratio (C/P) in ocean photosynthesis, increases the ocean carbon storage compared to simulations where fixed C/P is applied. The biological flexibility improves the model’s ability to reproduce glacial atmospheric CO2. In line with previous research, we find freshwater input to the North Atlantic to be an important factor for reproducing glacial proxy records. The ensemble of simulations that achieve a good representation of glacial-interglacial δ13C indicates a deglacial whole-ocean change in δ13C of 0.28 ± 0.06‰.

    The thesis underlines the importance of the initial state, and the choice of model parameterisations, for the outcome of model ensemble, and intercomparison studies. Finally, it proposes a new method for estimation of ocean carbon transport, and attribution of this transport to different water masses and carbon system processes.

  • Public defence: 2019-10-25 10:00 Ahlmannsalen, Geovetenskapens hus, Stockholm
    Aguirre Vidal, Gladis
    Stockholm University, Faculty of Social Sciences, Department of Social Anthropology.
    Mobilising care: Ecuadorian families and transnational lives between Ecuador and Spain2019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis focuses on the dynamics of care in the transnational lives of Ecuadorian migrant women in Spain. It is concerned with the various forms of care that take shape and are sustained in the workplace, between friends, and among family members in Ecuador and Spain. Ultimately, it sheds light on how care is mobilised to sustain ideals of solidarity at work as well as togetherness in transnational life. The thesis is set against the background of the economic and political crisis in Ecuador of the late 1990s and early 2000s, which resulted not only in the dollarization of the economy and the removal of the country’s president, but in a dramatic shift of traditional male migration from the southern highlands to the United States, to a new wave of largely middle class female migration to Western Europe, especially Spain. Women from across the country left their children, spouses and elderly parents behind to work in domestic and care jobs abroad. In Ecuador, this disturbed the dominant cultural imaginary of the co-habitating and united family, centred on the presence of the woman as mother and wife. In light of this, the thesis engages with women’s dilemmas in giving and receiving care during years of absence, the role of family members, friends and domestic workers in this process, and the development of long-term goals focused on remittances, reunification, return, and the ultimate goal of creating a better future. Most generally, while challenging a series of dichotomies between love and money, home and work, gift and commodity—which have structured academic discussions concerning the feminization of international migration—the thesis describes the intimate relationship between women’s participation in the gift economy and a global labour market through the lens of care relationships.

  • Public defence: 2019-10-25 14:00 Nordenskiöldsalen, Geovetenskapens hus, Stockholm
    Darougheh, Saman
    Stockholm University, Faculty of Social Sciences, Department of Economics. Stockholm University, Faculty of Social Sciences, Institute for International Economic Studies.
    Search and Mismatch2019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    I define occupations that are employed in more industries as “broader” occupations. I study the implications of occupation-level broadness for mismatch of unemployed and vacancies across occupations and industries. In the cross-section, workers in broader occupations are better insured against industry-level shocks and less at risk of being mismatched. Using geographical variation in occupation-level broadness, I show that during the Great Recession, unemployed workers from broader occupations had higher job-finding rates and smaller increases in unemployment than those previously employed in more specialized occupations. I contrast these cross-sectional results to the aggregate implications of mismatch. To that end, I build a model where the resulting mismatch of an industry-level shock depends on how specialized the affected occupations are. The model extends the Lucas (1974) island setting with frictional intra-island labor markets and frictional inter-island mobility. Workers in broader occupations are insured against industry-level productivity shocks because they can stay in their occupation but work in other unaffected industries. When individuals from broad occupations move to other industries, they propagate the shock to more workers. This strong general equilibrium mechanism offsets the direct effect. The results indicate that recessions which cause more mismatch lead to larger unemployment risk for workers in specialized occupations, but do not cause larger fluctuations of the aggregate unemployment rate.   

    I develop a model of the consumer good market where the individual’s search decision is consistent with balanced-growth preferences. Here, optimal search is independent of income but increases with the time endowment. I characterize the potentially multiple equilibria and test whether the model can replicate differences in observed shopping behavior across employed and unemployed individuals. Using the American Time Use Survey, I show that unemployed individuals have an almost 50 % larger time endowment available for leisure and shopping. Meanwhile, they only spend 18 % more time shopping than the employed. In the calibrated model, however, unemployed households will spend around twice as much time shopping as employed households. I argue that consumer-goods search models are not yet ready for business cycle analysis, and discuss ways of reconciling the model with the data.   

    We study the impact of worker protection in an environment with heterogeneous match productivity and a constrained wage setting. Firms can either employ costly screening to determine the match quality, or hire workers out of their applicant pool at random, learn about the match quality, and disengage from bad matches. Thus, layoff protections intervene with a firm’s ability to screen matches. In our calibration, a policy that prevents layoffs reduces unemployment and increases consumption in the new steady state. However, the economy becomes more susceptible to productivity shocks. Two additional channels transmit productivity shocks when layoffs are regulated. First, the value of hiring at random is more volatile when separating bad matches is no longer an option. Second, additional screening in recessions worsens the composition of the unemployed pool. Consequently, recessions will be long lasting and hiring is lower even after the TFP shock has receded. We conclude that economies potentially have a higher average output under layoff regulations, but that this comes at the cost of higher volatility and jobless recoveries.

  • Public defence: 2019-10-28 10:00 David Magnussonsalen (U31), Stockholm
    Zakirova Engstrand, Rano
    Stockholm University, Faculty of Social Sciences, Department of Special Education.
    Families of young children with autism spectrum disorder in Sweden: The role of culture and intergenerational support2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Children with autism spectrum disorder (ASD) have shown high variability in learning outcomes in response to evidence-based interventions, suggesting a need for individualization of intervention programmes for each child and his/her family. To explain this variability and develop effective intervention strategies research suggested focusing on identification of important contextual factors that might influence the effectiveness of a specific intervention for each child such as family cultural characteristics and characteristics of service settings and systems. The overarching aim of the thesis was to identify and describe proximal and distal environmental factors and processes affecting implementation and provision of interventions and services for young children with ASD and their families within the context of the Swedish support system. Two theoretical models guided the research project: Bronfenbrenner’s bioecological model of human development and Wachs’s multiple-influences model of individual variability. The specific objectives addressed using a mixture of qualitative and quantitative methods were: (i) to investigate the scope of reporting ethnicity and other cultural factors in research publications by Swedish scholars involved in empirical research in ASD in children and youth (Study 1); (ii) to explore perceptions of autism, beliefs about its causes, and treatment preferences expressed by parents of children with ASD from culturally, ethnically and linguistically diverse backgrounds (Study 2), and (iii) to explore grandparents’ perceived needs in relation to having a young grandchild with ASD (Study 3).

    The results of data triangulation across the three studies showed that within the context of the Swedish support system, three proximal environmental factors were associated with identification of ASD in young children and families’ use of services and interventions before and after the child was diagnosed with ASD. These were parents’ belief systems (including perceptions about child’s autism, help-seeking behaviours, and treatment preferences); the role of preschool teachers, and the role of other service providers, such as healthcare professionals. Data triangulation singled out seven groups of distal environmental factors: beliefs of extended family; family cultural, ethnic and linguistic background; family socio-economic characteristics (occupation and education level); Swedish formal support system enacted through various legislative acts; international laws and regulations; information sources (mass media and social media), and conceptualization and clinical definition of ASD (as reflected in DSM and ICD classifications). Findings also highlight the importance of taking into consideration of role of ASD researchers as an additional distal environmental factor affecting implementation of interventions and services for culturally and linguistically diverse children with ASD and their families.

    The results of the studies provide insights into understanding of families’ belief systems about ASD causes, treatment preferences, and needs that are essential for planning and provision of family-level early interventions for children with ASD in the cultural context of Sweden. Implications for practice and future research are discussed. 

  • Public defence: 2019-10-28 13:00 FP41, hus 1, AlbaNova universitetscentrum, Stockholm
    de Andrés Prada, Roberto
    Stockholm University, Faculty of Science, Department of Physics. Physics Department and Fribourg Center for Nanomaterials (FriMat), University of Fribourg, Switzerland.
    Pulsed laser deposition and nanofabrication of mesoscopic devices based on cuprates and manganites2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis explores the growth, the nano-fabrication and the study of the magneto-transport properties of Superconductor/Ferromagnet/Superconductor (SFS) structures from complex oxides such as the high Tc superconducting cuprate YBa2Cu3O7 (YBCO) and the ferromagnetic manganites La2/3Ca1/3MnO3 and La2/3Sr1/3MnO3 (LCMO and LSMO), deposited with the pulsed laser deposition (PLD) technique.The present work has been possible thanks to the collaboration between the “Magnetism and Superconductivity” Group at the University of Fribourg, in Switzerland, and the “Experimentell Kondenserade Materiens Fysik” Group at Stockholm University, in Sweden.

    Earlier, the two research groups in Fribourg and Stockholm had studied SFS structures from YBCO/LaMnO3/YBCO multilayers with 20 nm thick ferromagnetic and insulating LaMnO3 barriers, and obtained signs of an unconventional spin-triplet current across these structures. This finding motivated the present thesis work with a focus on two main aspects.

    Firstly, to explore other candidate materials suitable as barriers and optimise their growth conditions as to maintain a large ferromagnetic moment and thus a high spin polarisation of the charge carriers. Secondly, to study what happens when the thickness of the ferromagnetic and insulating LaMnO3 barrier is reduced well below 20 nm to enable larger supercurrents.

    It has been shown for a series of YBCO/LCMO multilayers that the ferromagnetic moment of LCMO depends critically on the PLD growth conditions as well as on the thickness and even structural details of the YBCO layer on which they are grown. Furthermore, a protocol has been established to grow heterostructures with strongly ferromagnetic manganite layers embedded in thick YBCO layers by optimising the PLD growth conditions and by substituting the bottom YBCO layer with a Co and Ca substituted version of YBCO that has a tetragonal structure (tYBCO) instead of the orthorhombic one of plain YBCO.

    Devices suitable for perpendicular magneto-transport measurements have been nano-fabricated from YBCO/manganite/YBCO multilayers with ~10 nm thick LCMO and LSMO layers as the F barriers. While no clear indications of a spin-triplet component of the superconducting order parameter have been obtained yet, a negative and hysteretic magneto-resistance has been observed that is indicative of a strong ferromagnetic order in the thin manganite barrier. The latter suggests a potential memory functionality of such structures that could be exploited in future spintronic memory devices.

    Moreover, devices have been fabricated on SFS structures with a reduced thickness of the LaMnO3 barrier of 10 nm and 5 nm. These samples were grown prior to the beginning of this PhD work using non optimised growth conditions, and it was found that the ferromagnetic properties of these LaMnO3 barriers are strongly deteriorated. It remains to be seen whether the ferromagnetic order of such thin LaMnO3 layers can be also recovered by using the optimised growth conditions as for LSMO and LCMO.

  • Public defence: 2019-10-30 09:00 David Magnussonsalen (U31), Stockholm
    Eklund, Rasmus
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Electrophysiological correlates of consciousness2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    How does the brain enable us to experience seeing or hearing a stimulus? If a stimulus is repeatedly presented at the awareness threshold, subjects will report that they are aware of the stimulus on half of the presentations. Electroencephalography (EEG) can be used to non-invasively record neural activity as event-related potentials (ERPs). The contrastive analysis of neural activity to trials rated as aware minus neural activity to trials rated as unaware reveals the neural correlates of consciousness (NCC). Research on the NCC in vision has resulted in two ERPs: an early negative difference wave (visual awareness negativity, VAN) and a subsequent late positivity (LP). Visual awareness may be reflected by one or both of these ERPs. However, the contrastive analysis (aware minus unaware) may not isolate the NCC because it arguably compares aware processing with a combination of unaware processing and no processing. In support, previous research that tried to isolate a comparison between aware processing and unaware processing found that LP was the only NCC. However, subsequent replications suggested VAN and LP as NCC. Because of these mixed results, we followed up on these studies in Study I with a preregistered design that manipulated stimulus size. Results showed VAN and LP as NCC. The findings provide evidence for VAN as an early NCC.

    Another main goal of this thesis was to investigate auditory awareness. In Study II, an auditory threshold task was used, and the contrastive analysis revealed an early negative difference wave (auditory awareness negativity, AAN) and LP. These ERPs are comparable to VAN and LP in vision. Because post-perceptual processes related to responding may confound the NCC in contrastive analysis, no-response tasks can be used to isolate awareness-related activity. In vision, a previous study in which the manual response requirement was manipulated showed effects on LP but not on VAN. In Study III, we used a similar task with auditory stimuli at the awareness threshold. Results suggested that AAN and LP are unaffected by the response manipulation. However, the present no-response task may not be optimal for removing post-perceptual processing because subjects need to reflect on their experience even if they do not need to respond manually. Additional analyses that attempted source localization of the AAN suggested that it is generated in auditory cortex.

    From a theoretical perspective, one view of these results is that VAN and AAN reflect local recurrent processing and that this is the neural signature of awareness, whereas LP reflects global recurrent processing that enables reporting. Other views suggest that VAN and AAN merely reflect preconscious processes, whereas LP and global recurrent processing reflect consciousness. The studies described in this thesis do not support one theory over the other but provide robust evidence for early neural correlates of visual and auditory awareness.

  • Public defence: 2019-11-01 10:00 CCK lecture hall, building R8, Solna
    Sandström, Helena
    Stockholm University, Faculty of Science, Department of Physics.
    Contouring & planning variability in stereotactic radiosurgery: How to assess and address the weakest link in stereotactic radiosurgery?2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of stereotactic radiosurgery (SRS) employing one or a few fractions of high doses of radiation has continuously increased due to the technical development in dose delivery and morphological and functional imaging. As the target volume in SRS is usually defined without margins, the treatment success critically depends on accurate definition and contouring of the target volume and organs at risk (OARs) which are commonly situated in the proximity of the target making their precise delineation particularly important in order to limit possible normal tissue complications. Subsequent treatment planning is reliant on these volumes, which makes the accurate contouring a requisite to high quality treatments. 

    The purpose of this work was to evaluate the current degree of variability for target and OAR contouring and to establish methods for analysing multi-observer data regarding structure delineation variability. Furthermore, this was set in a broader picture including the importance of contouring studies, the clinical implications of contouring errors and the possible mitigation of the variability in contouring by robust treatment planning.

    A multi-centre target and OAR contouring study was initiated. Four complex and six common cases to be treated with SRS were selected and subsequently distributed to centres around the world performing Gamma Knife® radiosurgery for delineation and treatment planning. The resulting treatment plans and the corresponding delineated structures were collected and analysed.

    Results showed a very high variability in contouring for the four complex radiosurgery targets. Similar results indicating high variability in delineating the common targets and OARs were also reported. This emphasised the need of continuous work towards consistent and standardized SRS treatments. Consequently, the results of the OAR analysis were incorporated in an effort to standardize stereotactic radiosurgery (SRS). Variations in treatment planning were as well analysed for several of the indications included in the initial study on contour delineation and the results showed a high variability in planned doses including several plans presenting large volumes of the brain receiving a higher dose than 12 Gy, indicating an elevated risk of normal tissue complications.

    The results of the contouring work were, as a last step of this thesis, used as input for a robust treatment planning approach considering the variability in target delineation. The very preliminary results indicate the feasibility of the probabilistic approach and the potential of robust treatment planning to account for uncertainties in target extent and location.

  • Public defence: 2019-11-06 14:00 Gröjersalen, hus 3, Kräftriket, Stockholm
    Dahlström, Petter
    Stockholm University, Faculty of Social Sciences, Stockholm Business School.
    New Insights on Computerized Trading: Implications of Frequently Revised Trading Decisions2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Computerized trading may be viewed as an aspect of modernization of financial markets. This dissertation contains four articles that in different ways examine to what extent the modernization influences the economics of the markets.

    Article 1 investigates transaction costs for large orders which are split up by execution algorithms to be executed in smaller pieces.  I find that the costs associated with not being able to execute all pieces are substantial. These costs can be lowered by speeding up the trading pace but at the expense of higher costs for the successfully executed pieces.

    Article 2 investigates the strategies trading firms pursue in particular cases, known as toxic arbitrage opportunities. We find that trading firms, that otherwise behave as market makers, morph into liquidity takers as toxic arbitrage opportunities emerge. In contrast to common belief, market makers are net beneficiaries of toxic arbitrage, and this finding puts into question whether the amount of toxic arbitrage leads to wider bid-ask spreads.

    Article 3 investigates the information content of limit orders in an alternative way by studying the price impact implied by the depth in the limit order book. I find that the price impact estimates are slightly lower relative to those from a structural vector auto regressive model, but slightly higher compared to those from a price impact regression. Thus, the limit order book implied price impact estimates match those from benchmark models, and this finding contradicts earlier research.

    Article 4 investigates the economic rationale behind limit order cancellations. We put forth a model that explains the frequent limit order cancellations seen in today’s markets, and we test its predictions using a unique data set from Nasdaq. Our results points towards that frequent order cancellations is a benign feature of modern market making, as opposed to different types of manipulative behavior.

  • Public defence: 2019-11-08 10:00 Magnélisalen, Kemiska övningslaboratoriet, Stockholm
    Vilhjálmsdóttir, Jóhanna
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Choreography of a proton pump: Studies of charge-transfer reactions in cytochrome c oxidase2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the last step of cellular respiration, electrons from metabolites are transferred to molecular oxygen, mediated by the enzyme complexes of the respiratory chain. Some of these enzyme complexes couple these redox reactions to formation of an electrochemical proton gradient across the cell membrane. The proton gradient is used e.g. by ATP synthase to drive synthesis of ATP. 

    The terminal enzyme complex in the respiratory chain, cytochrome c oxidase (CytcO), catalyses reduction of O2 to water. In this process it contributes to maintaining the electrochemical proton gradient by two separate mechanisms: (i) by uptake of electrons and protons from the opposite sides of the membrane (for O2 reduction to water). (ii) by proton pumping across the membrane. Protons used in the O2 reduction, as well as protons that are pumped, are taken up through two different proton-uptake pathways, the D and the K pathways. In addition, a third proton-transfer pathway has been suggested for the mitochondrial CytcOs, namely the H pathway. So far, the molecular mechanism by which CytcO pumps protons has not been determined. 

    In this work we have studied proton- and electron-transfer reactions in aa3-type CytcOs, with the aim of understanding the functional design of the proton-pumping machinery in CytcO. First, we studied structural variants of CytcO from the bacterium Rhodobacter (R.) sphaeroides, where an amino-acid at position 425, previously shown to undergo redox-induced conformational changes, was substituted. The results point to a link between redox-induced structural changes and intramolecular proton-transfer rates through the D pathway. Second, we studied the electron distribution in the “activated” oxidized (OH) state of CytcO, by using an electrostatic complex of CytcO and cytochrome c. We also investigated electron-transfer reactions linked to proton pumping in structural variants of CytcO from R. sphaeroides and the yeast Saccharomyces (S.) cerevisiae, with mutations in the proposed D and H proton-uptake pathways. The data indicate that the S. cerevisiae mitochondrial CytcO uses the D pathway for proton uptake and pumping as the R. sphaeroides CytcO. Lastly, we studied reactions linked to proton uptake and pumping in structural variants of CytcO from R. sphaeroides with alterations in both proton-uptake pathways. The data elucidated the mechanism of proton transfer and gating in CytcO.

  • Public defence: 2019-11-08 10:00 Vivi Täckholmsalen (Q-salen), NPQ-huset, Stockholm
    Silao, Fitz Gerald S.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    The Role of Proline Catabolism in Candida albicans Pathogenesis2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Candida albicans is an opportunistic fungal pathogen that has evolved in close association with human hosts. Pathogenicity is linked to an array of virulence characteristics expressed in response to environmental cues and that reflect the requirement to take up and metabolize nutrients available in the host. Metabolism generates the energy to support the bioenergetic demands of infectious growth, including the ability to reversibly switch morphologies from yeast to filamentous hyphal forms. Amino acids are among the most versatile nutrients available in the hosts as they can serve as both carbon and nitrogen sources, be transformed to key metabolic intermediates, or utilized to modulate extracellular pH via deamination forming ammonia. Of the proteinogenic amino acids, proline is unique in having a secondary amine covalently locked within an imine ring. Accumulating evidence implicates proline catabolism as being critical in the pathogenesis of many human diseases, ranging from bacterial and parasitic infections to cancer progression. This work focuses on the role of proline catabolism on C. albicans  pathogenesis.

    Paper I describes how proline induces filamentous growth in C. albicans. Hyphal growth is induced by an increase in intracellular ATP, a positive regulator of the Ras1/cAMP/PKA pathway. Proline is a direct substrate for ATP production, its catabolism in the mitochondria by proline oxidase (Put1) and Δ1-pyrroline-5-carboxylate (P5C) dehydrogenase (Put2) leads to the generation of FADH2 and NADH, respectively. Arginine and ornithine induce filamentous growth due to being catabolized to proline. Strikingly, mitochondrial proline catabolism is essential for hyphal growth and escape from macrophages.

    Paper II documents that proline catabolism is an important regulator of reactive oxygen species (ROS) homeostasis in C. albicans. When cells depend on proline as an energy source, the activities of the two catabolic enzymes Put1 and Put2 must operate in synchrony; perturbation of these highly regulated catabolic steps exerts deleterious effects on growth. Cells lacking PUT2 exhibit increased sensitivity to exogenous proline. This sensitivity is linked to ROS generation, likely due to the accumulation of the toxic intermediate P5C. Consistently, a put2-/- mutant is avirulent in Drosophila and in a 3D skin infection model, and hypovirulent in neutrophils and a systemic murine infection model.

    Paper III shows that the enzymatic step directly downstream of Put2, the deamination of glutamate to α-ketoglutarate catalyzed by glutamate dehydrogenase (Gdh2), releases the ammonia responsible for the alkalization of the extracellular environment when C. albicans  cells grow in the presence of amino acids. Cells lacking GDH2 do not alkalinize the medium. Alkalization is thought to induce hyphal growth in cells engulfed by macrophages. Surprisingly, filamentous growth of gdh2-/- cells is not impaired in filament-inducing media, or importantly, in situ in the phagosome of primary murine macrophages. Thus, alkalization is not a requisite for filamentous growth within macrophages.

    The results demonstrate that under physiologically relevant host conditions, proline catabolism is important for C. albicans pathogenesis. Further studies are warranted to determine the applicability of this pathway as a potential target for therapeutic approaches aimed at combating this major fungal pathogen.

  • Public defence: 2019-11-08 13:00 Lilla hörsalen, Naturhistoriska riksmuseet, Stockholm
    Larsson, Eric
    Stockholm University, Faculty of Social Sciences, Department of Education.
    Innerstadsgymnasierna: En studie av tre elitpräglade gymnasieskolor i Stockholm och deras positionering på utbildningsmarknaden2019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    During the early 1990s Sweden underwent extensive educational reforms. Vouchers, freedom of choice, establishment of so-called “free-schools” together with far-reaching decentralization took the place of a highly centralized educational system, with few private schools and a very low degree of differentiation. A stated intention of these reforms was that freedom of choice as well as a greater number of educational options would level the playing field. It was believed that existing regulations hampered socially disadvantaged students and, by extension, opportunities for social and geographical mobility. Educational marketization has advanced and intensified since the 1990s, particularly in metropolitan areas and medium-sized cities. This is evident both in the increasing number of schools and in students commuting to inner city schools, and additionally in the continuous development of marketing strategies. Consequently, marketization has become an institutionalized part of Swedish education, and students and schools must equally adjust to the prevailing competitive conditions. Much of the research in the field has focused on the effects and extension of marketization and how free-schools and school choice affect socially vulnerable areas. However, instead of focusing on schools in socially vulnerable areas, I am interested in the schools at the top of the hierarchy and the elite segment of upper secondary schools in Stockholm. More precisely, the focus of this dissertation has been on how three sought-after and prestigious upper secondary schools position themselves in the educational market, but also how they are affected by and adjust to it. A further aim has been to analyse students’ educational strategies and the socialization processes that arise in their encounter with the schools as institutions. 

    This thesis has been guided by a theoretically inspired ethnography. The ethnographical data were primarily collected during a single academic year and within three separate elite upper secondary schools. The data set consists of observations in classrooms and other school-related spaces (meeting rooms, corridors etc.), interviews and data from official statistics. It also contains a wide array of documents, web sites, school magazines, anniversary books and photographs.  

    Using a Bourdieusian perspective, the analysis shows how both schools and students deploy strategies to cope with and adapt to the hierarchies and struggles of the contemporary educational market. The schools rely on accumulated institutionalized assets such as history, alumni, transfers to prestigious universities and their geographical locations. At the same time, they also need to provide an up-to-date educational setting to stay ahead, and moreover, to be able to collaborate and compete with the other elite schools. The analysis also illustrates why students choose these socially and academically selective schools and how they adjust to the school environment. It is illuminated that these schools are more than formal educational settings, they are places where students negotiate, debate, explore and develop soft skills. Nevertheless, they are also competitive school environments and while some students thrive, others struggle. This becomes apparent when they encounter and act in relation to the different social, symbolic and academic boundaries that exist in each school.

  • Public defence: 2019-11-15 10:00 William-Olssonsalen, Geovetenskapens hus, Stockholm
    Ul Hassan, Mahmood
    Stockholm University, Faculty of Social Sciences, Department of Statistics.
    Achievement tests and optimal design for pretesting of questions2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Achievement tests are used to measure the students' proficiency in a particular knowledge. Computerized achievement tests (e.g. GRE and SAT) are usually based on questions available in an item bank to measure the proficiency of students. An item bank is a large collection of items with known characteristics (e.g. difficulty). Item banks are continuously updated and revised with new items in place of obsolete, overexposed or flawed items over time. This thesis is devoted to updating and maintaining the item bank with high-quality questions and better estimations of item parameters (item calibration). 

    The thesis contains four manuscripts. One paper investigates the impact of student ability dimensionality on the estimated parameters and the other three deal with item calibration.

    In the first paper, we investigate how the ability dimensionality influences the estimates of the item-parameters. By a case and simulation study, we found that a multidimensional model better discriminates among the students.

    The second paper describes a method for optimal item calibration by efficiently selecting the examinees based on their ability levels. We develop an algorithm which selects intervals for the students' ability levels for optimal calibration of the items. We also develop an equivalence theorem for item calibration to verify the optimal design.  

    The algorithm developed in Paper II becomes complicated with the increase of number of calibrated items. So, in Paper III we develop a new exchange algorithm based on the equivalence theorem developed in Paper II.

    Finally, the fourth paper generalizes the exchange algorithm described in Paper III by assuming that the students have multidimensional abilities to answer the questions.

  • Public defence: 2019-11-15 10:00 Magnélisalen, Kemiska övningslaboratoriet, Stockholm
    Srinivas, Vivek
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    To metal, or not to metal: Diverse mechanisms of O2-activation and radical storage in the ferritin superfamily2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Proteins in the Ferritin-like superfamily are characterized by a four alpha-helical structural motif. These proteins are distributed across all three kingdoms of life and perform a wide range of functions. Several members in this protein superfamily can activate dioxygen using a di-metal active site coordinated by four carboxylate and two histidine amino acid residues. The resulting diverse set of dioxygen activated intermediates is used in nature to perform complex redox chemical reaction in cells. The R2 subunit of class I Ribonucleotide reductase and soluble Methane monooxygenase are the most well-characterized groups of proteins in this superfamily. Upon oxygen (or reduced-oxygen) activation of the di-metal site, the R2 subunit can generate a catalytic radical required for the conversion of ribonucleotides to deoxyribonucleotides, while soluble Methane monooxygenase can oxidize methane to methanol in an alternative form of carbon assimilation.

    The work presented in this thesis aims to better understand metal selectivity, working and the regulation of substrate specificity in various proteins of the Ferritin-like superfamily, and the development of a novel method to study radiation-sensitive intermediates. The papers discussed in this thesis present crystallographic and spectroscopic studies of several Ferritin-like superfamily proteins.

    In paper I, the assembly mechanisms of the heterodinuclear manganese-iron cofactor in a class Ic R2 protein and an R2-like ligand-binding oxidase are compared. Paper II presents the discovery of a novel radical-generating subunit subclass of Ribonucleotide reductase in Mollicutes, including mycoplasma pathogens, that breaks the paradigm of metal requirement for radical translocation and catalysis. This new subclass, denoted class Ie, is shown to instead use an unprecedented modified tyrosine DOPA residue in its four-helix bundle for radical translocation and storage. Paper III presents a new X-ray free-electron laser sample delivery system that combines acoustic droplet ejection with a drop-on-tape setup, allowing simultaneous multimodal X-ray diffraction and X-ray emission data collection. This setup is also shown to support photochemical and chemical activation of catalysis in crystals, allowing the study of radiation-sensitive transient reaction intermediates. We used this setup in paper IV to solve the first radiation damage-free crystallographic structures of the soluble methane monooxygenase hydroxylase and its regulatory subunit complex from Methylosinus trichosporium OB3b. The high-resolution crystal structures of the complex, in both di-ferrous and di-ferric oxidation states, illustrate the structural reorganization in the hydroxylase subunit upon binding to the regulatory subunit.

    These results illustrate the functional range and flexibility in the Ferritin-like protein superfamily. Including the distinctive metal discrimination in heterodinuclear metalloproteins, influencing substrate specificity in sMMO, and using a novel metal-free DOPA radical to catalyze ribonucleotide reduction in the class Ie R2 subclass. Experiments using the novel ADE-DOT setup also showed promising progress towards determining the highly sought-after structures of di-metal oxygen activated intermediates such as X and Q in subclass Ia R2 and sMMO, respectively.

  • Public defence: 2019-11-15 10:00 De Geersalen, Geovetenskapens hus, Stockholm
    H. Britton, Thérèse
    Stockholm University, Faculty of Humanities, Department of Humanities and Social Sciences Education.
    Att möta det levda: Möjligheter och hinder för förståelse av levd religion i en studiebesöksorienterad religionskunskapsundervisning2019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The general aim of this study is to develop knowledge about how field visit-oriented religious teaching can contribute to students’ understanding of lived religion, in terms of inner diversity, religious practice and experiential dimensions. Previous research about Religious education (RE) shows that the Swedish non-confessional school subject “Religion” mainly deals with history, dogmas and concepts. Few students are concerned with the subject-matter itself in RE. "Secular" students talk about religion as something old-fashioned that concerns "the others". On the other hand, students who identify themselves religiously do not recognize what is being taught in school about their own tradition, since they miss perspectives concerning religion as part of everyday life, i.e., lived religion. A growing interest in individuals’ lived religion has also been identified in the field of religious studies. These circumstances related to field of RE serve as motivational ground for the present doctoral thesis.

    This thesis investigates designed RE-teaching in lower secondary school (year nine). The teaching design draws on findings reported in the licentiate thesis (Britton 2014).  Three theoretical approaches are used and integrated in a theoretical framework. The approaches applied to define and operationalize students’ understanding of lived religion are selected parts of Michail Bachtin's (1997) dialogue theory, Robert Jackson's (2002) interpretive approach of Religious education, and Meredith McGuire's (2008) religion sociology theories about lived religion.

    The empirical data were produced from selected parts of an enacted teaching design about Buddhism, including a field visit to a Tibetan-Buddhist congregation. The data consist of grade nine students' oral and written utterances from a lesson sequence, including lesson recordings, student journals, lesson exercises, assignments, group discussions and an examination. In addition, follow-up interviews were conducted with students, the teacher and the temple representative. Data were analysed using the integrated theoretical-analytical framework, in order to provide knowledge about what opportunities and obstacles in religious teaching that contribute to students’ understandings of lived religion.

    Three main results emerged. First, students' personal perspectives and values ​​of religion in general, and of the religious tradition studied (Buddhism) in particular, are important parts of students' understanding of lived religion. From students’ responses, some perspectives that interfered with their understanding of lived (Buddhist) religion were identified: student understandings that touch upon the links between individual freedom and religion; the relation between belief and religious practice and experiences; and ‘Western Buddhism’ in relation to Buddhism outside the West. Second, three didactical tools were constructed, aiming to develop RE teaching to further facilitate students’ understanding of lived religion: individual perspective, a diversity model and self-reflection. Didactical questions about representation, safe space and self-reflexivity came up. Third, there is support for arguing that lived religion as a perspective in the Swedish school subject of religion can be a goal as well as means to create a more inclusive religious education.

  • Public defence: 2019-11-15 13:00 Lilla Hörsalen, Naturhistoriska riksmuseet, Stockholm
    Jønland Højsgaard, Trine
    Stockholm University, Faculty of Social Sciences, Department of Education.
    Reframed Identity: Red Cross nurses' identity formation between 1945 and 19772019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The overall aim is to explore the construction of nurse identity at the Red Cross Nursing School (RCNS) in Sweden, between 1945 and 1977, when nursing became part of the system of higher education in Sweden. Occupational identity is understood as a construct both of social learning and of a self-image. The empirical data consist of documents from the Red Cross Archive concerning the training of nurses and of interviews with nurses trained during the studied period. A hermeneutical interpretative method has been used. The result showed that the period studied was divided into two different phases. The first phase between 1945 and the end of the 1960s, is called the post war phase. The following phase, from the 1960s until 1977, is called the reform friendly phase. RCNS was in the post war phase a kind of total institution, based on a particular belonging to a very special and highly respected social community, reinforced by the student nurses being dressed in the same uniform and living under the same strong authority in a quite homogeneous group. The training was an introduction to a life-long membership in the total Red Cross Nurse community. This community was in the reform friendly phase challenged by diverse external changes in society. Within a period of approximately ten years, much came to be questioned, and many previously important customs and habits were abandoned. The total community started to dilute, and the lives of students changed gradually passing to a social arrangement where they slept, lived and worked in different places with different people under different authorities. The total community was impossible to modernise, built as it was on pre-modern values and hierarchies. This led to a breakdown of the traditional Red Cross nurse identity based on honour, where they were first of all Red Cross sisters. While the uniform occupational identity was challenged, more and more nurses combined family and work. This meant that their self-identities became more multidimensional. The key to our understanding of the Red Cross nursing education and the shift that took place in the late 1960s is thus to be found in the transformation of the internal collective, where nurses no longer lived and 2 learnt the traditional Red Cross codes of honour and conduct. Gradually, nurse training was integrated into higher education. This was a major reframing of the occupational identity formation, from specially selected Red Cross nurse students being trained into a total community of experienced Red Cross nurses, to an academic education of professional nurses.

  • Public defence: 2019-11-15 13:00 Nordenskiöldsalen, Stockholm
    Nystrand von Unge, Elin
    Stockholm University, Faculty of Humanities, Department of Ethnology, History of Religions and Gender Studies.
    Samla samtid: Insamlingspraktiker och temporalitet på kulturhistoriska museer i Sverige2019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis is a study of contemporary collecting practices at museums of cultural history in Sweden. The study takes off from two questions: How is this practice of collecting understood at museums of cultural history today, and how are these modes of collecting effected when museums explicitly collect the “present” rather than the “past”? The aim is to examine how the present day has been collected, what modes of ordering were activated, as well as what relational effects contemporary collecting has had on the knowledge-building processes within the practice.

    The overall theoretical framework of the study primarily stands on sociologist John Law’s understanding of actor network theory. The actor network model is used as a theoretical tool to understand how agency and processes of knowledge production work. In addition, theoretical concepts from memory studies, as well as theories on knowledge building processes, are applied.The empirical material is collected through a combination of interviews and participant observations. Furthermore, archival studies were executed at the Nordiska museet archive.

    Through four chapters, the modes of ordering the Time, the Collectors, the Objects, and the Ideas are examined. The material analysed shows that the cultural historical “hinterland” that shaped the modern museum have had lasting effects on museum-collecting at large, but also on contemporary collecting practices. However, the reversed is also true: Contemporary collecting often acts as an important tool to make the self-evident position of traditional collecting visible. As the act of collecting activates fundamental ethical and moral questions concerning time, place, and social conditions, the practice has had constant effects on museum work in general. Therefore, without an active and conscious collecting, the content of museum work is in risk of stagnating. It is not only through exhibitions and outreach work that museums should have a contemporary societal awareness, but the collecting practices also deserve a mental presence in public space. Stating this, a continued expansive collecting at museums of cultural history is a necessity, by which the general museum-work is pushed forward and expanded. To collect and record expressions of the same contemporary perspectives is here seen as an active way of dealing with the blinding effects of being in the present.