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  • 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.