| 1. |
- Vestergren, Johan, 1968-
(author)
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Analysis and speciation of organic phosphorus in environmental matrices : Development of methods to improve 31P NMR analysis
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Phosphorus (P) is an essential element for life on our planet. It is central in numerous biochemical processes in terrestrial and aqueous ecosystems including food production; and it is the primary growth-limiting nutrient in some of the world’s biomes. The main source of P for use as agricultural fertilizer is mining of non-renewable mineral phosphate. In terrestrial ecosystems the main source is soil P, where the largest fraction is organic P, composed of many species with widely differing properties. This fraction controls the utilization of P by plants and microorganisms and influences ecosystem development and productivity. However, there is only scarce knowledge about the molecular composition of the organic P pool, about the processes controlling its bioavailability, and about its changes as soils develop. Therefore, the aim of this thesis was to develop robust solution- and solid-state 31P nuclear magnetic resonance spectroscopy (NMR) methods to provide molecular information about speciation of the organic P pool, and to study its dynamics in boreal and tropical soils. By studying humus soils of a groundwater recharge/discharge productivity gradient in a Fennoscandian boreal forest by solution- and solid-state NMR, it was found that P speciation changed with productivity. In particular, the level of orthophosphate diesters decreased with increasing productivity while mono-esters such as inositol phosphates increased. Because the use of solution NMR on conventional NaOH/EDTA extracts of soils was limited due to severe line broadening caused by the presence of paramagnetic metal ions, a new extraction method was developed and validated. Based on the removal of these paramagnetic impurities by sulfide precipitation, a dramatic decrease in NMR linewidths was obtained, allowing for the first time to apply modern multi-dimensional solution NMR techniques to soil extracts. Identification of individual soil P-species, and tracking changes in the organic P pools during soil development provided information for connecting P-speciation to bioavailability and ecosystem properties. Using this NMR approach we studied the transformation of organic P in humus soils along a chronosequence (7800 years) in Northern Sweden. While total P varied little, the composition of the soil P pool changed particularly among young sites, where also the largest shift in the composition of the plant community and of soil microorganisms was observed. Very old soils, such as found Africa, are thought to strongly adsorb P, limiting plant productivity. I used NMR to study the effect of scattered agroforestry trees on P speciation in two semi-arid tropical woodlands with different soil mineralogy (Burkina Faso). While the total P concentration was low, under the tree canopies higher amounts of P and higher diversity of P-species were found, presumably reflecting higher microbial activity.
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| 2. |
- Bodin, Hristina, 1977-
(author)
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Wastewater treatment in constructed wetlands : Effects of vegetation, hydraulics and data analysis methods
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Degradation of water resources has become one of the most pressing global concerns currently facing mankind. Constructed Wetlands (CWs) represent a concept to combat deterioration of water resources by acting as buffers between wastewater and receiving water bodies. Still, constructing wetlands for the sole purpose of wastewater treatment is a challenging task. To contribute to this research area, the fundamental question raised in this doctorate thesis was: how do factors such as vegetation and residing water movements (hydraulics) influence wastewater treatment in CWs? Also, effects of different data analysis methods for results of CW hydraulics and wastewater treatment were investigated. Research was focused on phosphorus (P), ammonium-nitrogen (NH4+-N) and solids (TSS) in wastewater and o n P in macrophyte biomass. Studies were performed in pilot-scale free water surface (FWS) CW systems in Kenya (Chemelil) and Sweden (Halmstad) and as computer simulations.Results from the Chemelil CWs demonstrated that meeting effluent concentration standards simultaneously for all water quality parameters in one CW was difficult. Vegetation harvest, and thus nutrient uptake by young growing macrophytes, was important for maintaining low effluents of NH4+-N and P, especially during dry seasons. On the other hand, mature and dense vegetation growing for at least 4 months secured meeting TSS standards. Phosphorus in above-ground green biomass accounted for almost 1/3 of the total P mass removal, demonstrating high potential for P removal through macrophyte harvest in CWs. Also, results suggested that harvest should be species-specific to achieve high P removal by macrophytes and overall acceptable wastewater treatment in CWs. Still, different methods to estimate evapotranspiration (ET) from the Chemelil CWs showed that water balance calculations greatly impacted estimations of wastewater treatment results.Hydraulic tracer studies performed in the Chemelil and Halmstad CWs showed that mature and dense emergent vegetation in CWs could reduce effective treatment volumes (e-values), which emphasized the importance of regulating this type of vegetation. Also, it was shown that hydraulic tracer studies with lithium chloride performed in CWs with dense emergent vegetation had problems with low tracer recoveries. This problem could be reduced by promoting the distribution of incoming tracer solution into the CW using a barrier near the CW inlet pipe. Computer simulation results showed that the choice of tracer data analysis method greatly influenced quantifications of CW hydraulics and pollutant removal. The e-value could be 50% higher and the pollutant removal 13% higher depending upon used method. Moreover, unrealistic evalues (above 100%) in published literature could to some extent be explained by tracer data analysis method. Hence, to obtain more reliable hydraulic data and wastewater treatment results from CWs, more attention should be paid to the choice of tracer data analysis method.
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| 3. |
- Brodtkorb, Thor-Henrik, 1976-
(author)
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Cost-effectiveness analysis of health technologies when evidence is scarce
- 2010
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Doctoral thesis (other academic/artistic)abstract
- Given the increasing pressures on health care budgets, economic evaluation is used in many countries to assist decision-making regarding the optimal use of competing health care technologies. Although the standard methods of estimating cost-effectiveness underpinning these decisions have gained widespread acceptance, concerns have been raised that many technologies would not be considered for funding, due to scarcity of evidence. However, as long as the amount and quality of evidence used for the analysis are properly characterized, scarce evidence per se should not be seen as a hindrance to perform cost-effectiveness analyses. Characterizing uncertainty appropriately, though, may pose a challenge even when there is a large body of evidence available, and even more so when evidence is scarce. The aims of this thesis are to apply a methodological framework of cost-effectiveness analysis and explore methods for characterising uncertainty when evidence is scarce. Three case studies associated with limited evidence provide economic evaluations on current decision problems, investigate the feasibility of using the framework, and explore methods for characterizing uncertainty when evidence is scarce.The results of the case studies showed that, given current information, providing transfemoral amputees with C-Leg and Airsonett Airshower to patients with perennial allergic asthma could be considered cost-effective whereas screening for hyperthrophic cardiomyopathy among young athletes is unlikely to be cost-effective. In the cases of C-Leg and Airsonett Airshower conducting further research is likely to be cost-effective. The case studies indicate that it is feasible to apply methods of cost-effectiveness in health care for technologies not commonly evaluated due to lack of evidence. The analysis showed that failing to account for individual experts’ might have a substantial effect on the interpretation of the results of cost-effectiveness analysis. Formal expert elicitation is a promising method of characterizing uncertainty when evidence is missing, and thus enable cost-effectiveness and value of further research to be appropriately estimated in such situations.In conclusion, this thesis shows that scarcity of evidence should not preclude the use of cost-effectiveness analysis. On the contrary, in such cases it is probably more important than ever to use a framework that enable us to define key parameters for a decision problem and identify available evidence in order to determine cost-effectiveness given current information and provide guidance on further data collection.
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| 4. |
- Jonsson, Sofi, 1984-
(author)
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Unraveling the importance of solid and adsorbed phase mercury speciation for methylmercury formation, evasion and bioaccumulation
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Monomethylmercury, MeHg, is formed under anoxic conditions in waters, sediments and soils and then bioaccumulated and biomagnified in aquatic food webs, negatively effecting both human and wildlife health. It is generally accepted that precipitation of mercury, Hg, and adsorption of Hg to e.g. organic matter and mineral surfaces are important processes limiting the reactivity of Hg mobilized in the environment by natural and anthropogenic activities. However, knowledge concerning the role of different solid and adsorbed chemical forms of Hg for MeHg formation, evasion and bioaccumulation is missing. Such information is vital for the understanding of environmental processes controlling MeHg formation and bioaccumulation, as well as for predicting how changes in e.g. loading rates of atmospheric Hg and the outcome of climate change scenarios and anthropogenic land use could alter Hg concentrations in biota.In this thesis, a novel experimental approach, using isotopically enriched solid and adsorbed phases of inorganic Hg, HgII, as tracers, was developed. Using this approach, we successfully determined rates of MeHg formation from solid and adsorbed Hg species in sediment slurries and in mesocosm systems under conditions closely resembling those in field. We conclude that the solid/adsorbed phase speciation of HgII is a major controlling factor for MeHg net formation rates. Microcosm experiments revealed that newly formed MeHg was a major contributor to the evasion of MeHg from the water‒sediment system, emphasizing the importance of MeHg formation rate, rather than MeHg concentration, in the sediment for this process. From mesocosm systems, we provide experimental evidence, as well as quantitate data, for that terrestrial and atmospheric sources of HgII and MeHg are more available for methylation and bioaccumulation processes than HgII and MeHg stored and formed in sediments. This suggests that the contribution from terrestrial and atmospheric sources to the accumulation of Hg in fish may have been underestimated. As a consequence, in regions where climate change is expected to further increase land runoff, terrestrial MeHg sources may have even higher negative effects on biota than previously thought. Data and concepts presented in this thesis lay the basis for unprecedented in-depth modeling of processes in the Hg biogeochemical cycle that will improve our understanding and the predicting power on how aquatic ecosystems may respond to environmental changes or differences in loading rates for atmospheric Hg.
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| 5. |
- Nelson, Hanna, 1976-
(author)
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Modelling precipitation and surface complexation reactions in systems with Goethite, Cu(II) and Oxyanions Containing As(V) or P(V)
- 2012
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Doctoral thesis (other academic/artistic)abstract
- The aqueous solubility of oxyanion (e.g. phosphates and arsenates), and thereby their mobility, bioavailability (phosphates) and toxicity (arsenates), in soils and sediments is dependent upon their chemical speciation. In complex, multicomponent systems, equilibrium modelling can be a useful tool to predict chemical speciation. When establishing a model, it is essential to understand the interactions between all the components not only in solution but also on mineral surfaces at a molecular level. By applying surface complexation models processes at mineral surfaces can be accounted for. This thesis is a summary of four papers and focuses on surface complexation of the oxyanions arsenate, phosphate and monomethyl phosphate adsorbed onto the surface of goethite (α-FeOOH). Furthermore, adsorption and precipitation of copper(II) arsenates from aqueous solutions has been studied. Solid copper(II) arsenates obtained in precipitation experiments were characterised and five different solid phases with different Cu(II) to As(V) ratio, as well as proton and Na +content, were identified; Cu5Na(HAsO4)(AsO4)3(s), Cu5Na2(AsO4)4(s), Cu3(AsO4)2(s), Cu3(AsO4)(OH)3(s) and Cu2(AsO4)(OH)(s). The adsorption of arsenate and copper(II) to the goethite surface, could not be predicted by only applying the combined model from the two binary systems, arsenate-goethite and copper(II)-goethite. Instead, two ternary copper-arsenate-goethite surface complexes were added. In one of the surface complexes arsenate is bound to goethite surface via a copper(II) ion coordinating to surface hydroxyl groups and in the other surface complex, copper(II) is coordinating arsenate bound to the goethite surface. Surface complexation models, in agreement with macroscopic data and detailed spectroscopic results, were designed for monomethyl phosphate, phosphate and arsenate adsorbed to goethite. The models contain monodentate inner sphere surface complexes stabilized by hydrogen bonding to neighbouring surface sites. The charge distribution of the complexes was assigned according to Pauling’s valence bond theory. The monomethyl phosphate model consists of three singly protonated surface isomers, only differentiated by the location of the proton . In the case of phosphate and arsenate, six surface complexes, including two pair-wise surface isomers, are suggested to form; ≡FeOAsO 32.5-; (≡FeOAsO3; ≡Fe3OH)2-;(≡FeOAsO3H; ≡Fe3O)2-; (≡FeOAsO3H; ≡Fe3OH)1-; (≡FeOAsO3H2; ≡Fe3O)1- and ≡FeOAsO3H20.5-. A combination of structural information from spectroscopic measurements and quantitative data from spectroscopy, potentiometry and adsorption experiments provides a better understanding of the complexity of the coordination chemistry of particle surfaces and forms the basis for equilibrium models with high physical/chemical relevance.
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| 6. |
- Persson Slumpi, Thomas, 1973-
(author)
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Making the Systemically Desirable Culturally Feasible : Towards the Integration of Gender-Knowledge into Informatics Study Programs
- 2011
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Doctoral thesis (other academic/artistic)abstract
- This dissertation scrutinizes the problem domain of gender-knowledge integration into Swedish higher education study programs in informatics. This integration has been expressed as desirable by for example the Swedish government, individual universities and university colleges and the student union alike. In Swedish informatics study programs however, gender-knowledge seems to have been integrated to a limited extent and there is a dearth of research in this area as well. This indicates that gender-knowledge has so far only to a limited extent been recognized as important for Swedish informatics study programs. The purposes of this research is to 1) increase the insight of managers and developers of informatics study programs into the potential of gender-knowledge to enrich informatics as a subject; and to 2) inspire commitment and provide a means for the design of informatics study programs in which gender-knowledge is integrated. The overarching research question for this project is: What are the crucial challenges for a successful integration of gender-knowledge into Swedish informatics study programs? To address the overarching research question, several studies have been conducted through scrutinizing documents like articles, reports, evaluations and syllabuses, as well as listening to the accounts of experiences of the gender-knowledge integration process communicated by lecturers, PhD students and study program coordinators following a hermeneutic research approach. The results of these studies indicate that the process of integrating gender-knowledge is challenging and that there is a need of support for getting the process up and running. For this, a guide that identifies different important questions to be addressed related to challenge categories like knowledge, organization, pedagogical, and resistance has been developed. The knowledge challenge seems to be particularly challenging hence special attention is paid to the development of a basic theoretical gender-knowledge base that, along with some concrete examples on how the basic theoretical gender-knowledge base, could be integrated into areas of concern for informatics study programs. The different types of support suggested above should be considered food for thought and perhaps pointers of where to start looking. After all, only the local informatics community can integrate gender-knowledge into a study program in an enriching way thus making the systemically desirable culturally feasible.
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| 7. |
- Ask, Per, 1978-
(author)
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Invasion of top and intermediate consumers in a size structured fish community
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- In this thesis I have investigated the effects of invading top and intermediate consumers in a size-structured fish community, using a combination of field studies, a lake invasion experiment and smaller scale pond and aquaria experiments. The lake invasion experiment was based on introductions of an intermediate consumer, ninespine stickleback (Pungitius pungitius L.), in to allopatric populations of an omnivorous top predator, Arctic char (Salvelinus alpinus L.). The invasion experiment was performed in two tundra lakes and in two birch forest lakes to investigate the effect of climate on the invasion success. I found that the effect of sticklebacks on char was size dependent. Small char suffered reduced growth from resource competition with sticklebacks whereas the maximum size of adult char increased from the addition of a larger prey resource, stickleback. The negative effect of sticklebacks on the growth of small char suggests that sticklebacks may be a better resource competitor than char, which was also supported by the pond and aquaria experiments. The pond experiments also suggested that char were more efficient cannibals than interspecific predators on sticklebacks. Cannibalism in char may limit the recruitment of char and decrease both their predatory and competitive effect on coexisting species and thereby also promote the coexistence of char and sticklebacks. The successful invasion by sticklebacks and their subsequent increases in density suggest that the absence of sticklebacks in char lakes in this region is not caused by biotic interactions with char. Instead, it may be suggested that co-occurrence of sticklebacks and char in the region is limited by dispersal. The char – stickleback system resembles an intraguild predation system with char as the top consumer and stickleback as the intermediate consumer. The effects of the stickleback invasion is also contrasted with a field study of a northern pike (Esox lucius L.) invasion into a system with coexisting char and stickleback, where pike can be viewed as the top consumer and char as the intermediate consumer both feeding on sticklebacks. In this case pike excluded char. The identity of the invading species and the relative strength of the predatory and competitive interactions in the two contrasting systems are discussed in relation to coexistence in intraguild predation systems. I found that the identity of the invading species is of crucial importance for the response at the ecosystem level, and that the inherent size dependency of competitive and predatory interactions in fish communities is important for attaining a mechanistical understanding of the effects of invasive species in lake ecosystems.
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| 8. |
- Markkanen, Peter, 1964-
(author)
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"Tekniken utan en lärare är ingenting" : En studie om användande av teknik i geometriundervisning
- 2014
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Licentiate thesis (other academic/artistic)abstract
- Målet med denna avhandling är att bidra med kunskap om hur digital teknik kan bidra till att utveckla matematikundervisning. I studien riktades intresset mot undervisning i tredimensionell geometri som skedde med stöd av interaktiva skrivtavlor. Syftet varatt studera hur läraren utnyttjar tekniken för att skapa matematiska situationer vilka kan möjliggöra lärande. Studien har en etnografisk inriktning där forskaren under fem veckor följdeen lärares teknikunderstödda undervisning i en klass i årskurs 9. Det empiriska materialet samlades in genom videounderstödd observation, intervju med läraren, fokusgruppsintervjuer med elever samt elevtester. Detta materialanalyserades med fokus på desätt på vilka läraren utnyttjar tekniken för att lyfta fram och arbetamed det matematiska innehållet. Resultatet visar att läraren utnyttjar flertalet strategier som tekniken erbjuder för att representera det matematiska innehållet och med teknikens hjälp växla mellan olika representationsformer, t.ex. genom att bearbeta, flytta och klona geometriska figurer. Läraren är överlag positiv till användande av teknik i matematikundervisningen, och de fördelar med tekniken som hon lyfter fram är att den hjälper och understödjerhenne utifrån de behov som uppstår i undervisningen och ger henne fler verktyg att belysa sådant som en del elever kan ha svårt att få syn på. Resultatet visar även att det fordras mycket arbete av läraren att sätta sig in i teknikens möjligheter och anpassa dessa till den egna undervisningen. Även eleverna är positiva till undervisning som sker med stöd av teknik då de menar att det hjälper dem att skapa sig en förståelse för tredimensionell geometri. Detta stärks av resultaten på det uppföljandetest som genomfördes efter arbetsområdet vilket visar att eleverna på ett påtagligt sätt utvecklat sin förståelse för geometriska begrepp.
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| 9. |
- Olsson, Rickard, 1969-
(author)
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Surface reactions on mineral particles controlling the hydrolysis of glucose phosphates
- 2011
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Doctoral thesis (other academic/artistic)abstract
- Phosphorus (P) is an essential nutrient. A significant amount of soil P may be in the form of organophosphates. Due to the size of these compounds, hydrolysis is often required before P can be assimilated by organisms. Hydrolysis may be mediated by mineral surfaces, or catalyzed by extra cellular enzymes. Since both organophosphates and enzymes have a strong affinity for environmental particles, a study of the hydrolysis of organophosphates must focus on reactions at the water/particle interface. This thesis is a summary of four papers, discussing the adsorption, desorption, and abiotic and enzymatic hydrolysis of glucose-1-phosphate (G1P) and glucose-6-phosphate (G6P) in aqueous goethite suspensions. A new technique for simultaneous infrared and potentiometric titrations (SIPT) allowed in-situ measurements of the interfacial reactions. It was found that glucose phosphates form pH-dependent inner sphere complexes on goethite, which coordinate in a monodentate fashion, and are stabilized by hydrogen bonding. Desorption involves a change in speciation of the surface complexes, illustrating the difficulty in determining desorption rates for individual complexes. The surface mediated hydrolysis is primarily base catalyzed for G1P, and acid catalyzed for G6P. The difference is partly due to electronic factors, and partly to differences in glucose group/goethite interactions. Considerably more extensive is the hydrolysis catalyzed by an acid phosphatase (AcPase). The rate of the enzymatic hydrolysis are strongly dependent on the glucose phosphate surface coverage, showing that surface properties affect the adsorption mode of enzymes, and thus their catalytic activity. In solution, AcPase showed a greater specificity towards G6P, but this specificity was partly lost after adsorption onto goethite.
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| 10. |
- Palisaitis, Justinas
(author)
-
Electron Energy Loss Spectroscopy of III-Nitride Semiconductors
- 2011
-
Licentiate thesis (other academic/artistic)abstract
- This Licentiate Thesis covers experimental and theoretical investigations of the bulk plasmon response to different compositions and strain states of group III-nitride materials. Investigated materials were grown using magnetron sputtering epitaxy and metal organic chemical vapour deposition and studied by Rutherford backscattering spectrometry, X-ray diffraction, electron microscopy and electron energy loss spectroscopy (EELS).It is shown that low-loss EELS is a powerful method for a fast compositional determination in AlxIn1-xN system. The bulk plasmon energy of the investigated material system follows a linear relation with respect to lattice parameter and composition in unstrained layers.Furthermore, the effect of strain on the bulk plasmon peak position has been investigated by using low-loss EELS in group III-nitrides. We experimentally determine the AlN bulk plasmon peak shift of 0.156 eV per 1% volume change. The AlN peak shift was corroborated by full potential calculations (Wein2k), which reveal that the bulk plasmon peak position of III-nitrides varies near linearly with unit cell volume variations.Finally, self-assembled ternary Al1-xInxN nanorod arrays with variable In concentration have been realized onto c-plane sapphire substrates by ultra-high-vacuum magnetron sputtering epitaxy with Ti0.21Zr0.79N or VN seed layer assistance. The nanorods exhibit hexagonal cross-sections with preferential growth along the Al1-xInxN c-axis. A coaxial rod structure with higher In concentration in the core was observed by scanning transmission electron microscopy in combination with low-loss EELS.
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