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  • Disputas: 2018-10-22 09:00 L70, Kista
    Saqr, Mohammed
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Using Learning Analytics to Understand and Support Collaborative Learning2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Learning analytics (LA) is a rapidly evolving research discipline that uses insights generated from data analysis to support learners and optimize both the learning process and learning environment. LA is driven by the availability of massive data records regarding learners, the revolutionary development of big data methods, cheaper and faster hardware, and the successful implementation of analytics in other domains. The prime objective of this thesis is to investigate the potential of learning analytics in understanding learning patterns and learners’ behavior in collaborative learning environments with the premise of improving teaching and learning. More specifically, the research questions comprise: How can learning analytics and social network analysis (SNA) reliably predict students’ performance using contextual, theory-based indicators, and how can social network analysis be used to analyze online collaborative learning, guide a data-driven intervention, and evaluate it. The research methods followed a structured process of data collection, preparation, exploration, and analysis. Students’ data were collected from the online learning management system using custom plugins and database queries. Data from different sources were assembled and verified, and corrupted records were eliminated. Descriptive statistics and visualizations were performed to summarize the data, plot variables’ distributions, and detect interesting patterns. Exploratory statistical analysis was conducted to explore trends and potential predictors, and to guide the selection of analysis methods. Using insights from these steps, different statistical and machine learning methods were applied to analyze the data. The results indicate that a reasonable number of underachieving students could be predicted early using self-regulation, engagement, and collaborative learning indicators. Visualizing collaborative learning interactions using SNA offered an easy-to-interpret overview of the status of collaboration, and mapped the roles played by teachers and students. SNA-based monitoring helped improve collaborative learning through a data-driven intervention. The combination of SNA visualization and mathematical analysis of students’ position, connectedness, and role in collaboration was found to help predict students’ performance with reasonable accuracy. The early prediction of performance offers a clear opportunity for the implementation of effective remedial strategies and facilitates improvements in learning. Furthermore, using SNA to monitor and improve collaborative learning could contribute to better learning and teaching.

  • Disputas: 2018-10-22 13:00 sal 14, hus 5, Kräftriket, Stockholm
    Balletti, Gabriele
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Classifications, volume bounds and universal Ehrhart inequalities of lattice polytopes2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this PhD thesis we study relations among invariants of lattice polytopes. Particular emphasis is placed on bounds for the volume of lattice polytopes with interior points, and inequalities for the coefficients of their Ehrhart delta polynomials. The major tools used for this investigation are explicit classifications and computer-assisted proofs.

    In the first paper we give an upper bound on the volume of a polytope which is dual to a d-dimensional lattice polytope with exactly one interior lattice point, in each dimension d. This bound, expressed in terms of the Sylvester sequence, is sharp, and is achieved by the dual to a particular reflexive simplex. Our result implies a sharp upper bound on the volume of a d-dimensional reflexive polytope.

    In the second paper we classify the three-dimensional lattice polytopes with two lattice points in their strict interior. Up to unimodular equivalence there are 22 673 449 such polytopes. This classification allows us to verify, for this case only, the sharp conjectural upper bound for the volume of a lattice polytope with interior points, and provides strong evidence for more general new inequalities on the coefficients of the Ehrhart delta polynomial in dimension three.

    In the third paper we prove the existence of inequalities for the coefficients of the Ehrhart delta polynomial of a lattice polytope P which do not depend on the degree or dimension of P. This proves that the space of all Ehrhart delta polynomials of lattice polytopes have coordinate-projections whose images do not fully cover the codomain. This is done by extending Scott's inequality to lattice polytopes whose Ehrhart delta polynomial has vanishing cubic coefficient.

    In the fourth paper we associate to any digraph D a simplex P whose vertices are given as the rows of the Laplacian of D, generalizing a work of Braun and Meyer. We show how basic properties of P can be read from D, for example the normalized volume of P equals the complexity of D, and P contains the origin in its relative interior if and only if D is strongly connected. We extend Braun and Meyer's study of cycles, by characterizing properties such as being Gorenstein and IDP. This is used to produce interesting examples of reflexive polytopes with non-unimodal Ehrhart delta vectors.

    In the fifth paper we describe an algorithm for an explicit enumeration of all equivalence classes of lattice polytopes, once dimension and volume are fixed. The algorithm is then implemented to create a database of small lattice polytopes up to dimension six. The resulting database is then compared with existing ones, used to understand the combinatorics of small smooth polytopes, and to give conjectural inequalities for coefficients of Ehrhart delta polynomials in dimension three. The frequency of some of the most important properties of lattice polytopes can be explicitly studied, and interesting minimal examples are extracted and discussed.

  • Disputas: 2018-10-24 10:00 Magnélisalen, Stockholm
    Lin, Junzhong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Synthesis, characterization and applications of hierarchical porous inorganic materials: a multi-dimensional approach2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Zeolites are a type of microporous crystalline materials that have been widely used in industrial applications including separation, adsorption, and catalysis. However, great limitations on diffusion through these materials can arise due to the small pores present in mircoporous frameworks, and this can impact catalytic reactions in particular. The synthesis of hierarchical zeolites has solved the diffusion problem. In this thesis, various hierarchically porous materials have been synthesized and tested as catalysts.

    In the first part of this thesis, a titanium-containing hierarchically porous silicate material has been constructed from double-four-ring (D4R) units as building blocks.

    In the second part of this thesis, hierarchical MWW zeolites were synthesized by swelling and pillaring of a lamellar MWW zeolitic precursor (MCM-22) using D4R building units. The synthesis procedure has been carefully studied by various characterization methods, such as PXRD, TEM, N2 adsorption–desorption etc.

    In the last part of this thesis, MFI zeolites with controllable hierarchical pore systems have been prepared. Firstly, hierarchical ZSM-5 and TS-1 with open pores were generated using a temperature programmed dissolution–recrystallization post-synthesis treatment and tested as catalysts for benzyl alcohol self-etherification and cyclohexanone ammoximation. Secondly, single-crystalline hierarchical shell-like ZSM-5 has been synthesized via a dissolution–recrystallization post-treatment of mesoporous ZSM-5. The post-treatment increased the catalytic activity of the ZSM-5 zeolite for the aldol condensation of bulky substrates.

  • Disputas: 2018-10-25 13:00 Magnélisalen, Kemiska övningslaboratoriet, Stockholm
    Gordeyeva, Korneliya
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Design, processing and properties of lightweight foams from cellulose nanofibers2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Foams are applied in many areas including thermal insulation of buildings, flotation devices, packaging, filters for water purification, CO2 sorbents and for biomedical devices. Today, the market is dominated by foams produced from synthetic, non-renewable polymers, which raises serious concerns for the sustainable and ecological development of our society. This thesis will demonstrate how lightweight foams based on nanocellulose can be processed and how the properties in both the wet and dry state can be optimized.

    Lightweight and highly porous foams were successfully prepared using a commercially available surface-active polyoxamer, Pluronic P123TM, cellulose nanofibers (CNFs), and soluble CaCO3 nanoparticles. The stability of wet and dry composite foams was significantly improved by delayed aggregation of the CNF matrix by gluconic acid-triggered dissolution of the CaCO3 nanoparticles, which generated a strong and dense CNF network in the foam walls. Drying the Ca2+-reinforced foam at 60 °C resulted in moderate shrinkage but the overall microstructure and pore/foam bubble size distribution were preserved after drying. The elastic modulus of Ca2+-reinforced composite foams with a density of 9 – 15 kg/m3 was significantly higher than fossil-based polyurethane foams.

    Lightweight hybrid foams have been prepared from aqueous dispersions of a surface-active aminosilane (AS) and CNF for a pH range of 10.4 – 10.8. Evaporative drying at a mild temperature (60 °C) resulted in dry foams with low densities (25 – 50 kg/m3) and high porosities (96 – 99%). The evaporation of water catalyzed the condensation of the AS to form low-molecular linear polymers, which contributed to the increase in the stiffness and strength of the CNF-containing foam lamella.

    Strong wet foams suitable for 3D printing were produced using methylcellulose (MC), CNFs and montmorillonite clay (MMT) as a filler and tannic acid and glyoxal as cross-linkers. The air-water interface of the foams was stabilized by the co-adsorption of MC, CNF and MMT. Complexation of the polysaccharides with tannic acid improved the foam stability and the viscoelastic properties of the wet foam for direct ink writing of robust cellular architectures. Glyoxal improved the water resistance and stiffened the lightweight material that had been dried at ambient pressure and elevated temperatures with minimum shrinkage. The highly porous foams displayed a specific Young’s modulus and yield strength that outperformed other bio-based foams and commercially available expanded polystyrene.

    Unidirectional freezing, freeze-casting, of nanocellulose dispersions produced cellular foams with high alignment of the rod-like nanoparticles in the freezing direction. Quantification of the alignment with X-ray diffraction showed high orientation of CNF and short and stiff cellulose nanocrystals (CNC).

  • Disputas: 2018-10-26 10:00 David Magnussonsalen (U31), Stockholm
    Cornell Kärnekull, Stina
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen.
    Auditory and Olfactory Abilities in Blind and Sighted Individuals: More Similarities than Differences2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Blind individuals face various challenges in everyday life because of the lack of visual input. However, since they need to rely on the non-visual senses for everyday tasks, for instance, when navigating the environment, the question has been raised as to whether perceptual and cognitive abilities in these senses may be enhanced. This question has mainly been addressed for auditory and tactile abilities, whereas there is considerably less research into the chemical senses, such as olfaction. However, to determine whether blindness has general effects, different senses and types of tasks should be studied, preferably in one and the same study. Therefore, throughout this thesis, analogous auditory and olfactory tasks that varied in cognitive complexity were studied. In Study I, absolute thresholds, discrimination, identification, episodic recognition (i.e., after a short retention interval), metacognition, and self-reported imagery ability were assessed in early blind, late blind, and sighted participants. The only objective measure on which the blind and sighted clearly differed was the auditory episodic recognition task. The fact that early blind but not late blind participants displayed better memory than the sighted suggested that the onset age of blindness may be important for whether this ability becomes enhanced following blindness. Furthermore, the early blind participants rated their auditory imagery ability higher than the sighted, whereas both early and late blind participants rated their olfactory imagery ability higher than the sighted. In Study II, the participants from Study I were followed up after more than a year and retested on auditory and olfactory episodic recognition and identification. This time, the early blind displayed no advantage over the sighted, suggesting that the influence of blindness on auditory memory may be modulated by the length of the retention interval. Moreover, in line with Study I, identification of sounds and odors was similar in the three groups. In Study III, early blind and sighted participants were examined for potential differences in autobiographical memory as evoked by sounds and odors, respectively. Blindness did not influence the reminiscence bumps (i.e., memory peaks in certain age intervals) or have any clear impact on the number of retrieved sound- or odor-evoked memories. Taken together, the present findings indicate that blindness has no general influence across tasks or sensory modalities. Rather, specific auditory abilities, such as episodic memory, may be enhanced in blind individuals, although such effects may depend on both the onset age of blindness and the length of the retention interval. In conclusion, for most perceptual and cognitive abilities examined, performance seemed unaffected by blindness.

     

  • Disputas: 2018-10-26 10:00 hörsal 11 hus F, Stockholm
    Lundquist, Elin
    Stockholms universitet, Humanistiska fakulteten, Institutionen för etnologi, religionshistoria och genusvetenskap.
    Flyktiga möten: Fågelskådning, epistemisk gemenskap och icke-mänsklig karisma2018Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis investigates birdwatching and focuses on the knowledges, skills and ideas that are obtained and acknowledged among birdwatchers. The aim is to explore how these ways of relating to birds are constituted. Birdwatching is considered as an epistemic practice, which produce and maintain knowledge. Thus, the human participants of these practices are regarded as members of an epistemic community. The overall theoretical framework is based on a material-semiotic perspective: the epistemic community, is viewed as not only made up of human beings, but of a variety of human and nonhuman actors – birds, technologies and landscapes – which altogether co-produce the practices. To investigate how habitual ways of relating to birds are established, the geographer Jamie Lorimer’s theoretical model of non-human charisma is applied to the analysis. The joint ways of relating to and engaging with birds are interpreted in terms of “affective logics” that characterize the epistemic community.

    The study is based on a multi-sited ethnographic fieldwork which took place at different birdwatching spots in Sweden; at birdwatching fairs and on websites where birdwatchers discuss and share information about birds. Furthermore the study is based on interviews with birdwatchers. The methodological approach during the fieldwork as well as in analyzing the research material, is to “follow the object”, or more precisely to follow how birds are acknowledged in these different settings. 

    The ways of relating to birds are interpreted as embodied skills and “knowledge by familiarity” with different species and landscapes. One central affective logic is the “joy of recognition” which motivates birdwatchers to learn how to identify birds in the field.The main method for gathering information in order to make claims about the objects of knowledge, i.e. the birds, within the epistemic community is through these embodied skills.The analysis shows that claims, based on these observations, are undergoing a number of validation processes. This creates a certain type of observer that must be prepared to get their claims reviewed. The methods for establishing claims are however challenged when new technologies, such as DNA-techniques and digital tools, are put to use in the identification processes.

    The analysis also shows that while all wild birds are potentially interesting as objects of knowledge within the community, not every bird is attended to with the same kind of interest and enthusiasm. Birdwatchers are more devoted to some species of birds, than others, in relation to the spatial and temporal circumstances of the encounters, and in relation to the birdwatcher’s previous experiences of similar encounters. A central theme that characterizes the practices is a negotiation of approximating the birds without disturbing them. This is made possible by the use of various technological extensions, such as binoculars and hides. However the analysis also shows that some of the, rather new, digital tools are acknowledged as potentially causing intrusive behavior.

  • Disputas: 2018-10-26 13:00 B25, Giessen
    Vuletic, Snezana
    Stockholms universitet, Humanistiska fakulteten, Engelska institutionen.
    From Colonial Disruption to Diasporic Entanglements: Narrations of Igbo Identities in the Novels of Chinua Achebe, Chimamanda Ngozi Adichie and Chris Abani2018Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    With a general interest in Igbo identities, this study critically explores a set of questions which relate to the production, evolution and potential of ‘Igboness’ in literary fiction. The study approaches these questions while relying on two premises. First, it understands ‘Igbo identity’ as a highly transformative and heterogeneous category that exists in the plural. Secondly, it defines narratives as significant elements in (re)shaping and illuminating the meaning of Igbo identities. Therefore, the author of this study approaches Igbo identity as a construct created in narrative discourse and contends that to consider the question of what Igbo identity means is almost inevitably to consider what it means to write Igbo identity. While narrative construction of Igbo identities can be investigated in a wide range of texts, the present study limits its focus to Nigerian Anglophone novelistic writing and the select novels by Chinua Achebe, Chimamanda Ngozi Adichie and Chris Abani.

    The overarching goal in the study is to bring narratologically informed readings to postcolonial literary studies, in a way which illuminates the dynamic between narrative form, socio-historical context and ideological content. Reading literary representations of Igbo identities from a postcolonial narratological perspective has a two-fold potential. First, it helps to understand how notions of Igbo identity result from the ways in which narrative forms reflect and refract the influences from the embedding contexts, on the one hand, and how they actively shape ideologies of the text, on the other. Secondly, the exploration of the relation between postcolonial poetics and the sociocultural, and thus the ideological in the text helps to bridge the gap between narratology and postcolonial literary criticism, in a way which provides evidence for narrative forms as variables sensitive to cultural and historical difference. While meeting these two aims, the study defines a notion of postcolonial poetics as poetics that brings together structures of narrative and an acute historical sensibility, and thus seeks to overcome the schism between reading African novels either as sociological accounts with little use of fictionalisation or as purely decorative and apolitical forms.

    To achieve the above stated goals, the study focuses on Chinua Achebe’s Things Fall Apart (1958), No Longer at Ease (1960) and Arrow of God (1964); Chimamanda Ngozi Adichie’s Half of a Yellow Sun (2006) and Americanah (2013); and Chris Abani’s GraceLand (2004) and The Virgin of Flames (2007). The literary analyses in this study thus range from the explorations of early postcolonial literary responses to colonial Orientalist discourses in the form of positive nativism; contemporary representations of Igbo identities as responses to a sense of ambiguity about the nation and an increasing imperative to question totalising discourses on tradition in post-independence Nigeria; to contemporary novels that examine Igbo identities from a transnational angle, in a way that destabilises colonial discourses of exotic and knowable African as well as early postcolonial discourses of reliable African identity. The analyses of these novels ultimately show how formal presentation of Igbo identities in fiction has never been far removed from wider questions of inequality in representation, social inclusion and exclusion, and domination and resistance.

  • Disputas: 2018-10-26 13:00 Hörsal 7 hus D, Stockholm
    Sivertsson, Fredrik
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Kriminologiska institutionen.
    Criminal Careers in the Long Run: Patterns and Predictions of Criminal Convictions across Age, Time, and Gender2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Why is it that a small proportion of the population accounts for the majority of crime? This question has stimulated a great deal of theoretical and methodological controversy in criminology. In essence, the debate is rooted in different theoretical underpinnings of continuity and change in crime, and the extent to which it is possible to foresee a life of crime by zeroing in on at-risk juvenile offenders. The current thesis explores four contentious empirical issues that may move this debate forward: the long-term predictability of persistent offending in adulthood on the basis of childhood risk factors (Study I); the magnitude of adult-onset offending (Study II); the predictive value of gender for criminal recidivism (Study III); and the association between birth cohort membership and criminal career parameters (Study IV). All four studies employ longitudinal Swedish administrative data, based on cohorts of individuals born between the early 1940s and the mid-1980s, and followed on the basis of detailed conviction data. The thesis also utilizes qualitative life-history narratives with former at-risk juvenile delinquents. The results suggest that theories aiming to explain crime beyond the transition to adulthood should incorporate factors presumed to cause within-individual change, even among high-risk juvenile offenders. Although childhood cumulative risk, including a wide range of individual, family, school, and peer measures, were clearly associated with adult crime, they had limited value for predicting those persistent offenders who eventually ended up in the tail of the crime distribution. Furthermore, although gender is generally one of the main demographic predictors of criminal convictions, the results indicate that it is important to include females for the purpose of understanding continuity and change in adulthood. This is in part because adult-onset offending is more prevalent within the female offending population than within the male offending population and in part because the risk for criminal recidivism among female offenders becomes increasingly similar to that found among male offenders as convictions accumulate over the life span. Finally, the results suggest that the typical criminal career has undergone significant changes both within and across gender groups during the period since the mid-1970s, a period which has witnessed a historical decline in the aggregate conviction rate in Sweden. Taking this into consideration, the employment and extensive analysis of longitudinal multiple cohort data ought to provide a basis for furthering our knowledge on the inherent complexity of crime trends, while at the same time also locating the study of criminal careers in its historical context.

  • Disputas: 2018-10-27 10:00 Auditoriet, Stockholm
    Brinch, Rebecca
    Stockholms universitet, Humanistiska fakulteten, Institutionen för kultur och estetik.
    Att växa sidledes: Tematik, barnsyn och konstnärlig gestaltning i Suzanne Ostens scenkonst för unga2018Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The aim of this thesis is to highlight and discuss the artistic force, potential and significance of performing arts for children and young audiences through the example of the work by Suzanne Osten. The focus of this research is on themes, notions of the child and artistic expressions and strategies. The dissertation discusses both the aesthetic and the political aspects of Osten’s theatre for young audiences and takes an interdisciplinary approach, combining theatre and performance studies and childhood studies. A fundamental assumption is that childhood is not a fixed or stable phase that manifests itself in one particular way for all children during all times. Another assumption is that theatre is more than what is visually apparent on stage. What is staged does not take place inside a vacuum, but is closely connected to the surrounding society and culture. To study theatre for young audiences as a cultural expression is therefore, to a great extent, also about analysing notions of the child.

    Five performances have been selected, all for young audiences: Paddakvariet (The Toad Aquarium, 1988, for ages 10 and over), Delfinen (The Dolphin, 1992, for ages 3 and over), Irinias nya liv (Irina’s New Life, 1996, for ages 9 and over), Flickan, mamman och soporna (The Girl, the Mother and the rubbish, 1998, for ages 7 and over), and Lammungarnas fest (The Baa-lambs Holiday, 2014, for ages 13 and over). A model for performance analysis has been constructed, based on hermeneutics and semiotics, complemented by three key theoretical concepts. Firstly focalization, as used by theatre scholar Maaike Bleeker, in order to understand the interaction between the spectator and the visions produced by the apparatus of performance. The reasoning of theatre scholar Gay McAuley about space in performance is used to examine how space is utilized and retained in the performances, while the notion of utopian performative by theatre scholar Jill Dolan provides tools to discuss how moments of ‘feeling utopia’ are a significant part of the selected works which raises questions of the transformative and affective power of theatre. In order to contextualize and historicise the analyses, the response of the performances is also taken into account drawing mainly on theatre reviews.

    As a whole the analyses show Osten’s theatre for young audiences as an ongoing research project problematizing the situation and position of children in society, as well as the view of art for children. Ostens performances for young audiences exhibit and make possible notions of a child outside of the norm in late 20th and early 21st century childhood discourses both within research and society as a whole. Osten’s theatre and artistry are identified as growing sideways, developing in unexpected directions while disrupting ideas about childhood and adulthood, and also what can be viewed as theatre for children and theatre for adults. The dissertation states that Osten’s theatre for young audiences can be seen as pioneering, not only in the field of children’s theatre, but also for the development and renewal of Swedish theatre in general.

  • Disputas: 2018-10-29 13:00 Magnélisalen, Kemiska övningslaboratoriet, Stockholm
    Björnerbäck, Fredrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Sustainable porous organic materials: Synthesis, sorption properties and characterization2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The resources available to us humans, including metals, minerals, biomass, air, water, and anything else on the planet, are being used at an increasing rate. This anthropogenic use of resources both depletes the resources and has negative impacts on other resources, e.g. the biosphere. Thus, developing (more) sustainable chemical and industrial processes are of the utmost importance for the well-being of the creatures of Earth and for the long-term sustainability of human society.

    This thesis focuses on organic porous materials, and more specifically their synthesis and characterization. Porous materials are, for example, used in detergents, water treatment, bio gas upgrading, carbon dioxide capture, as catalysts, in sensors, and in various biological applications. The application of porous materials can contribute to the drive towards a more sustainable society. However, porous materials are typically not sustainable themselves. Thus, there is a need to develop more sustainable porous materials. The synthesis and characterization of three different groups of porous organic materials are described in this thesis.

    In pulp- and paper manufacturing, lignin is separated from desirable products and is typically combusted for heat. In one section of this thesis, lignin was used to produce bio-oil for potential use in fuels and chemicals. However, the bio-oil process produced a solid by-product. The by-product was used to synthesize and study activated carbons with very high porosities and magnetic properties, a combination of properties that may prove to be useful in applications.

    Sugar is known to produce solid and unwanted compounds through reactions with acids. It is shown here that it is possible to produce highly microporous humins, i.e. organic porous materials with a large amount of small pores, using sulphuric acid and a range of saccharides and bio-based polymers. This work supports that solid by-products in a wide range of biomass conversion processes can be of high value, both economically and as replacements for less sustainable alternatives.

    The biosphere contains vast amounts of molecules with aromatic structures. The last section of this thesis shows how such aromatic molecules can be used to produce highly porous materials through Friedel-Crafts type chemistry using sulfolane as a solvent and iron chloride as a catalyst. This synthesis strategy produces high-performance materials, improves upon the sustainability of traditional Friedel-Crafts chemistry, and makes use of typically underutilized and abundant bio-based molecules.

  • Disputas: 2018-10-29 13:00 L30 Nodhuset, Kista
    Andrenucci, Andrea
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Using Language Technology to Mediate Medical Information on Health Portals: User Studies and Experiments2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The World Wide Web has revolutionized our lifestyle, our economies and services within health care. Health care services are no longer provided only at specialist centers and at scheduled hours, but also through online tools that give health care consumers access to medical information, health records, medical counselling and peer support. Such tools and applications are generally available on larger web sites or gateways called health portals. A large majority of online medical information consumers are laypeople (i.e. non experts) who appreciate the possibility to submit their information needs in their own native language. The information retrieval process where information requests from users and retrieved documents/answers are in different languages is called cross-language information retrieval (CLIR). 

    Mental health is one of the medical areas where some online applications have been successfully deployed in order to help people by providing in-depth medical information, counseling and advice. Despite the fact that online health portals are considered priority e-health tools for improving mental health, there are no formal knowledge instruments such as knowledge patterns that explicitly support the development of online health portals in the field of psychology/psychotherapy. 

    The goal of this research is to produce and evaluate a set of knowledge patterns, for the development and implementation of cross-lingual online health portals aimed at information seekers without medical expertise in the domain of psychology and psychotherapy. The knowledge patterns synthetize results of three research foundations: 1) User studies of portal interaction, based on interviews and observations about how users experience health information online and personalized search 2) Knowledge integration of existing language technology approaches, and 3) Experiments with language technology applications, in the field of cross-lingual information retrieval/question-answering. The target groups of this research are developers, researchers and health care providers, i.e. people who are responsible for mediating medical information on online health portals for users without medical expertise. 

    The chosen research framework is design science, i.e. the science that focuses on the study, development and evaluation of artefacts (objects that help people solve a practical problem). Typical examples of artefacts in IT are algorithms, software solutions and databases, but also objects such as processes or knowledge patterns. The developed and evaluated artefact in this research is a set of knowledge patterns for online health portal development. 

    The developed artefact contains fourteen knowledge patterns covering the three research foundations. Formative (structured workshops) and summative (online survey) evaluation of the artefact indicate that the knowledge patterns are useful, relevant and adoptable to a large extent, they also provide further directions for development of online mental health portals. Developing portals with multilingual support and tailored interfaces has the potential of helping larger groups of citizens to access relevant medical information.

  • Disputas: 2018-11-02 10:00 Magnélisalen Kemiska övningslaboratoriet, Stockholm
    Lehto, Tõnis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik. Stockholm University.
    Characterization of nucleic acid delivery with fatty acid modified cell-penetrating peptide nanoparticle formulations2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Recent advances with techniques used for manipulating gene expression have brought us to an era where various gene therapeutic approaches are becoming common therapeutic tools for many previously incurable diseases. The main factor impeding the wider translation of gene therapy is that the active pharmaceutical ingredients used for interfering with gene expression are based on nucleic acids and synthetic oligonucleotides and such molecules do not readily reach their intracellular targets due to their physicochemical properties and therefore they require delivery vectors to cross the cell membrane. 

    Cell-penetrating peptides (CPPs) is one such class of delivery vectors that comprise excellent potential for transporting bioactive cargo molecules across cellular membranes, both in vitro and in vivo conditions. CPPs have shown to be very versatile carriers for various types of bioactive cargo, including different nucleic acids such as plasmids (pDNA), splice-correcting oligonucleotides (SCOs), small interfering RNAs (siRNA) and mRNA, or peptides and proteins or even small molecules.

    This thesis focuses on characterizing the delivery of various nucleic acids-based molecules with a variety of novel fatty acid modified CPPs. In order to achieve this we utilize the ability of a family of CPPs called PepFects to non-covalently formulate nucleic acids into nanoparticles. More particularly the aim of the thesis is to find and characterize the key parameters of these peptide/nucleic nanoparticles that would improve their potential applicability as a drug formulation and delivery system for future gene therapies.

    By simultaneously characterizing the role of N-terminal fatty acid modification and the peptide/nucleic acid ratio in the nanoparticles we were able to show in Papers I and II that increasing the hydrophobicity and reducing unbound free fraction of the peptide improves delivery efficiency and decreases toxicity of these nanoparticles both in vitro and in vivo.

    Based on the findings from Paper I regarding the ability of these amphiphilic peptides to self-associate into supramolecular structures we went deeper in Paper III to study the formation, composition and live cell association of these peptide/nucleic acid complexes at single molecule sensitivity.

    And finally in Paper IV we enhanced the specificity of these nanoparticles towards in vivo xenograft tumors by incorporating the capacity to be specifically activated in the tumor microenvironment.

    Conclusively, these findings contribute to the field with identifying and characterizing some of the key factors in developing efficient and safe peptide-based delivery vectors for gene modulating therapeutics.

  • Disputas: 2018-11-02 13:00 David Magnussonsalen (U31), Stockholm
    Gonzalez, Nichel
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen.
    Interest to Reinvest: Individuals’ use of numerical information for investment decisions2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The general aim of this thesis is to contribute to the understanding of how numerical information, such as asset values and interest rates, influences inexperienced investors in their investment decisions. In relation to this, I have investigated the participants’ own understanding of what information they rely on for their own decisions. I have also investigated how their willingness to wait for greater rewards is related to their investment decisions. Importantly, I have distinguished between average behavior (group behavior) and individual behavior in an attempt to better describe how different information is important for different individual investors.

    On the group level the only reliable predictor of investment size was whether there was a gain or a loss during the period before the investment. However, how large the gain or loss was had no, or very limited, influence on investment size. When looking at each investor’s individual decisions, it was revealed that a substantial number of participants actually did rely on information other than only the gain/loss information, for example, the interest rates of forecasted developments of the different investment prospects. Furthermore, a substantial number of participants relied heavily on one of the cues; at least 50% of their investments were explained by the cue relied upon.

    Interestingly, very few participants’ investments were influenced by their own judgments of future asset outcomes. Furthermore, the participants’ willingness to invest in funds with guaranteed gains was used as a proxy for time preference (willingness to wait for greater rewards instead of accepting lesser rewards in the present). Time preference was relevant for investments but it did not relate to judged asset outcomes. This indicates that people may be more influenced by their future-oriented preferences rather than by their future-oriented beliefs (judgments).

    To conclude, these findings suggest that people use a preference-driven simplified strategy for investments and that these strategies differ substantially between individuals. This corroborates the idea about heuristic thinking, meaning that people simplify their decisions in a way that can deviate from normative value-maximizing behavior. For practical application, it is important to note the variety of strategies among individuals. This variety suggests that there is no “one size fits all” solution regarding instructions that can be given to inexperienced investors. The participants’ very limited insight into what information they relied upon is reason for researchers and advisors to understand the individuality in strategies in greater depth.

  • Disputas: 2018-11-02 13:00 Vivi Täckholmssalen (Q-salen), NPQ-huset, Stockholm
    Liao, Sifang
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    The role of insulin signaling during development, reproductive diapause and aging in Drosophila Melanogaster2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The insulin/insulin-like growth factor signaling pathway exists from invertebrates to vertebrates and it can regulate various biological processes, including development, metabolism, stress resistance and lifespan. In Drosophila, eight insulin-like peptides (DILP1-8) have been found. The specific function of each DILP is not fully known, especially for DILP1. In paper I, we found that dilp1 is specifically expressed in the brain insulin producing cells (IPCs), and it is mainly expressed from early pupa until few days of adult life, which correspond to non-feeding stages. The expression of dilp1 can last for at least 9 weeks of adult life when newborn virgin flies are induced to enter reproductive diapause. In addition, we found that the expression of dilp1 is under regulation by other dilps. Also larva-derived fat body, short neuropeptide F (sNPF) and juvenile hormone can affect dilp1 expression. We found that mutation of dilp1 affects female reproduction and starvation resistance. In paper II, we found that reproductive diapause can extend Drosophila life span, and at the same time ameliorate behavioral senescence, including negative geotaxis, activity rhythms and exploratory walking. Age-related changes in neuromuscular junction (NMJ) in abdominal muscle cannot be found in diapause-induced aging flies. The levels of several neuromodulators in the brain, including pigment dispersion factor (PDF), tyrosine hydroxylase (TH) and short neuropeptide F (sNPF), decreased significantly in normally aging flies, but less so in diapausing flies. In paper III, we show that mutation of dilp1 leads to a reduced organismal bodyweight, whereas overexpression increases it during the nonfeeding pupal stage. Overexpression of dilp1 additionally increases body size of flies, but reduces stores of larval-derived energy. This results in decreased starvation tolerance and increased feeding in newborn flies. In paper IV, we found that dilp1 expression is needed to extend lifespan in dilp2 mutant flies. Single dilp1 mutation has no effect on female lifespan, whereas transgene expression of dilp1 in flies with dilp1-dilp2 double mutant genetic background increased the lifespan. Furthermore, dilp1 and dilp2 interact to control circulating sugar, starvation resistance in a redundant or synergistic way.

  • Disputas: 2018-11-09 09:00 CCK Lecture Hall, Stockholm
    Henry, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Interlaced proton grid therapy: development of an innovative radiation treatment technique2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Spatially fractionated radiotherapy, also known as grid therapy (GRID), has been used for more than a century to try to treat several kinds of lesions. Yet, the grid technique remains a relatively unknown and uncommon treatment modality nowadays. Spatially fractionated beams, instead of conventional homogeneous fields, have been used to exploit the experimental finding that normal tissue can tolerate higher doses when smaller tissue volumes are irradiated. This increase in tolerance with reducing beam size is known as the dose-volume effect. Despite the fact that targets were given inhomogeneous dose distribution, sometimes with some volumes receiving close to no dose, good results in the form of shrinking of bulky tumors have been observed in palliative treatments. The biological processes responsible for this effect are still under discussion, with several possible causes. However, numerous experiments on mice, rats and pigs have confirmed the existence of such effect, which in turn motivates the present development of grid therapy.While mainly photons have been used in grid therapy, proton and ion grid therapies are also emerging as potential alternatives. In this work, an innovative form of grid therapy was proposed. Grids of proton beamlets were interlaced over a target volume with the intention of achieving two main objectives: (1) to keep the grid pattern (made of adjacent high and low doses) from the skin up to the vicinity of the target while (2) delivering nearly homogeneous dose to the target volume. This interlaced proton grid therapy was explored with the use of different beam sizes, from conventional sizes deliverable at modern proton facilities, down to millimeter sized beams. Other considerations that would prevent its clinical use, such as the variable relative biological effectiveness of protons or the use of cone beam computed tomography, were also evaluated. The overall aim was to assess if, and how, such treatment modality could be applied clinically, from a physics and dosimetry point of view. While it presented several theoretical advantages, its potential issues of concern and limitations were also evaluated.

  • Disputas: 2018-11-09 10:00 De Geersalen, Geovetenskapens hus, Stockholm
    Thiessen, Fiona Karen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    The evolution of lunar breccias: U-Pb geochronology of Ca-phosphates and zircon using Secondary Ion Mass Spectrometry2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Planetary bodies in our Solar System, including the Moon, were exposed to an intense asteroid bombardment between ~4.5-3.8 Ga, shaping their surfaces and leaving visible “footprints” in the form of large impact basins. The end of this period (~4.0-3.85 Ga), might have been marked by a cataclysmic increase in impacts, the so-called Late Heavy Bombardment (LHB), although this remains highly contentious. Since destructive processes, such as tectonics or erosion, have destroyed ancient (> 3.0 Ga) impact structures on Earth, studies of the early Solar System are mainly restricted to lunar samples, because impact structures are much better preserved on the Moon.

    In this thesis, we have therefore analysed impact breccias from three Apollo landing sites (Apollo 12, 14, and 17) with the overall aim to gain a better understanding of the lunar impact history. This endeavour included comprehensive textural and petrological analyses of the breccias and grains of interest (i.e. Ca-phosphates and zircon), as well as obtaining precise U-Pb Secondary Ion Mass Spectrometry (SIMS) ages. The U-Pb ages of Ca-phosphates obtained are consistent with the age of the Imbrium impact at ~3925 Ma, whereas an older age of ~3930 Ma yielded by Ca-phosphates in an Apollo 17 breccia might be linked to the formation of the Serenitatis basin. Furthermore, an impact event at ~3940 Ma was identified in zircon grains in Apollo 14 breccias, which is in agreement with older Ca-phosphate ages yielded in a previous study. The identification of three possible impact events within ~15 myr has important implications for the lunar bombardment history.

    However, there is a possibility that partial Pb loss from older grains during a relatively late event (e.g. Imbrium) might result in apparently older ages in Ca-phosphates. Incomplete resetting of the U-Pb system was recorded in zircon grains in an Apollo 12 breccia, leading to meaningless U-Pb ages which cannot be interpreted unambiguously as either magmatic or as impact events. Nevertheless, the U-Pb ages of several zircon grains occurring in lithic clasts in Apollo 14 breccias can plausibly be linked to magmatic activity, exhibiting several magmatic events between ~4286 Ma and ~4146 Ma. The data obtained in this thesis, together with previously published zircon and Ca-phosphate data, indicate several spikes in the magmatic and impact history during the first ~600 myr of lunar history. This study highlights the importance of combining high-precision age determination with thorough petrological and textural analyses in order to exclude meaningless ages and to interpret the impact and magmatic history of the Moon. 

     

  • Disputas: 2018-11-13 13:00 sal E306, Arrheniuslaboratorierna, Stockholm
    Martins, António
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för molekylär biovetenskap, Wenner-Grens institut.
    The cell biology and catalytic properties of the nutrient-induced signaling endoprotease Ssy52018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Cells continuously sense and respond to changes in the presence, quality and quantity of external and internal nutrients. Specific signaling proteases have been identified based on their roles in processing or destruction of distinct sets of downstream effector proteins in response to environmental cues. The Saccharomyces cerevisiae Ssy5 signaling endoprotease has a key role in regulating central metabolism, cellular aging, and morphological transitions important for growth and survival. Ssy5 is a core component of the Ssy1–Ptr3-Ssy5 (SPS) sensor, which enables yeast cells to respond to extracellular amino acids and induce their uptake. Ssy5 cleaves transcription factors Stp1 and Stp2, permitting their translocation to the nucleus where they enhance the expression of amino acid permease genes. This thesis focuses on Ssy5, its biogenesis and catalytic properties (paper I), the spatial determinants underlying Ssy5 function in SPS-sensor context (paper II) and substrate cleavage (paper III).

    Ssy5 is comprised of pro- and catalytic-(Cat)-domains. The Cat-domain possesses characteristic hallmarks of a serine protease; however, serine protease-specific inhibitors have limited effect, confounding its classification. In paper I we unambiguously show that Ssy5 is a serine protease, define the precise sites of cleavage in Stp1 and Stp2, and describe the sequence specific requirements of their cleavage. The uniquely large prodomain (381 amino acids) has two essential functions. Initially, it is required in cis for the maturation of the Cat-domain, helping to overcome a folding barrier that is reflected in the high stability of the Cat-domain. Subsequent to attaining enzymatic competence, Ssy5 undergoes an autolytic cleavage event. The domains remain associated and the prodomain functions to fetter the proteolytic activity of the Cat-domain.

    The plasma membrane (PM) localization of Ssy1 has recently been questioned in a report that postulated that Ssy1 is a component of the endoplasmic reticulum (ER) and contributes to the formation of ER-PM junctions. In paper II, using mutational and subcellular fractionation experiments we critically examined this notion that is inconsistent with the current understanding of Ssy5 activation, i.e., the unfettering of the Cat-domain occurs in strict association with Ssy1 at the PM. The data show that Ssy1 is indeed a PM protein, and importantly, Ssy5-activation occurs independent of ER-PM junctions. A di-acidic ER exit motif was identified that is critical for proper PM localization and function of Ssy1. In paper III, we report that the Cat-domain is post-translationally modified in a manner dependent on Ptr3 and the PM casein kinase I (Yck1/2), consistent with Ssy5 activation occurring at the PM. Strikingly, the activated Cat-domain is capable of properly cleaving Stp1 fused to an ER membrane protein. The amino acid-induced cleavage of this artificial membrane-bound substrate occurs in a Δtether strain (ist2Δ scs2Δ scs22Δ tcb1Δ tcb2Δ tcb3Δ) lacking ER-PM junctions. These findings indicate that the activated Cat-domain can bind and functionally interact with substrates distant from the PM. Finally, we show that the Cat-domain is degraded faster in amino acid-induced cells. These findings provide novel insights into the SPS-sensing pathway and demonstrate for the first time that the resetting of the SPS-sensing system correlates with Cat-domain degradation.