| 1. |
- André, Hampus, 1989
(författare)
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Assessing Mineral Resource Scarcity in a Circular Economy Context
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to humanity’s dependence on metal resources there are growing concerns regarding impacts related to their potential scarcity, both for current and future generations. The vision of a more circular economy suggests that extending the functional use of metals through measures aiming for resource-efficiency (RE) such as increasing technical lifetime, repairing and recycling could reduce mineral resource scarcity. However, evidence of this is limited. In addition, there is limited understanding regarding on what principles metals can be prioritized when assessing mineral resource scarcity. The aim of this thesis is to provide knowledge on mineral resource scarcity impacts of RE measures applied to metal-diverse products and on which conditions they depend. This is achieved by: 1) studying RE measures from a life cycle perspective; 2) comparing principles of prioritization between metals on which mineral resource scarcity impacts are assessed and 3) analysing how such principles (of prioritization) can affect conclusions regarding RE measures applied to metal-diverse products. The research is conducted through case studies, syntheses of literature and method development within the methodologies of life cycle assessment, material flow analysis and criticality assessment. Results indicate that effects of RE measures depend on a number of product characteristics and real-world conditions. RE measures can both increase and decrease mineral resource scarcity impacts compared to business as usual and effects vary greatly between metals. RE measures based on use extension e.g. reuse of laptops, repair of smartphones, and increasing technical lifetimes of LED lighting, have been indicated to reduce impacts through two principal features: use extension, and, increased functional recycling. However, there are risks of increasing mineral resource scarcity impacts if RE measures require additional metal use, product use extensions are short and if functional recycling is lacking. For example, repair of smartphones risks to increase the use of metals in commonly replaced components such as screens. Because of the varying effects on different metals, implementation of RE measures requires prioritizing some metals over others. The principles of prioritization give diverging results, and, are sometimes unclear and methodologically inconsistent. The thesis clarifies how they relate to concepts such as depletion, criticality, rarity and scarcity. Further it suggests that, although mineral resources are fundamentally stock resources, they can pose stock, fund and flow problems. Distinguishing between these different problems in distinct methodologies is conducive to purposive and complementary assessment by resolving methodological inconsistencies and providing accurate terminology. In the long term, scarcity is most purposively addressed by focusing on depletion of ecospheric stocks. Accordingly, the Crustal Scarcity Indicator is proposed to assess potential long term scarcity in life cycle assessment, alongside other environmental impacts. In the near term, potential scarcity for nations, industries and companies, as commonly assessed in criticality assessment, is most purposively addressed by focusing on technospheric circumstances, such as geopolitics, which can disrupt technospheric resource flows. In medium term, secondary resources in technospheric funds could be relevant, especially, with the advent of a more circular economy. Altogether, it is recommended that implementation of RE measures to metal-diverse products are based on analysis of product characteristics and real-world conditions and that effects of RE measures are assessed by methodologies which distinguish between mineral resource flows, funds and stocks so that well-informed prioritizations between metals can be made.
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| 2. |
- Axelsson Linkowski, Weronika
(författare)
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Managing mountains, past and present conditions for traditional summer farming and Sami reindeer husbandry in northern Scandinavia
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Traditional land use and conditions for maintenance of biodiversity are often interlinked. When land use changes and ecosystems change as a result, there is a risk to loose both the traditional ecological knowledge and the biodiversity connected to this land use. This thesis focuses on traditional land use, summer farming and Sami reindeer husbandry, in the mountain areas of northern Scandinavia (mainly Sweden), in a historical and contemporary perspective. The overall aim is to contribute to the understanding of the conditions for the traditional land use in the Scandinavian (mainly Swedish) mountains, using the concepts of traditional ecological knowledge (TEK) and a historical-ecological perspective. Both summer farming and reindeer husbandry are under strong external pressure and face large challenges today. Some of these challenges are shared and some differ between the two types of northern pastoralism. Scandinavian summer farmers experience that different views on their land use from different authorities affect them negatively. The increasing populations of large carnivores also worry the summer farmers. Recent depredation rates are in fact of the same level as historically (around 1900). Interviews showed that traditional knowledge about protective measures had eroded during years without carnivores, but also that farming practices have changed recently and that new knowledge developed. Sami plant use has been studied historically, but information about Sami plant management of Angelica archangelica was not documented. We argue that Sami ecological knowledge should be used to ensure sustainable harvest methods. Today traditional reindeer husbandry faces severe problems due to the reduction of winter grazing land by different encroachments, most importantly from modern forestry. The negative effects are even larger since increasingly difficult winter conditions create a need for a wider range of good grazing areas. Traditional knowledge is essential in the herders´ daily work, but the usability of the knowledge is severely constrained by recent changes. In the future planning of an ecologically and socially sustainable mountain management it is necessary to work with traditional land users and integrate their traditional knowledge.
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| 3. |
- Cascone, Claudia
(författare)
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Optical sensors in drinking water production : Towards automated process control in relation to natural organic matter
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Access to safe and clean drinking water is a basic human right (A/RES/64/292). In Sweden, large drinking water treatment plants use mainly surface water as water source. The long-term trend of increasing natural organic matter (NOM) in boreal and north European surface waters negatively affects the overall performance of the treatment processes. To address this issue, sensors are increasingly used as a tool for real-time analysis of water quality providing early warning of potential contamination and decision support for process control.In this thesis, absorbance- and fluorescence-based sensors were used to estimate dissolved organic matter (DOM) concentrations in two Swedish rivers prior to managed aquifer recharge (MAR) and their accuracy was compared (Paper I and IV). The possibility of coupling a coagulation treatment with MAR was explored at laboratory-scale. Two pilot-scale experiments using granular activated carbon filtration were carried out to optimise DOM removal (Paper II). A recent method for molecular DOM analysis was tested to investigate the effect of ozone on low molecular weight compounds. An open-source Python toolbox called “AbspectroscoPY” was developed to pre-process the large amount of absorbance-based sensor data and compute a range of spectral metrics from the time-series data. This allowed a preliminary identification of variability in the spectrophotometric profiles of treated water as a step forward toward automated early warning systems (Paper III). An algorithm for turbidity compensation of the raw absorbance spectra was added (Paper IV). This thesis contributes to an increased knowledge on NOM removal in water treatment using high frequency sensor data from optical sensors.
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| 4. |
- Hellervik, Alexander, 1978
(författare)
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Networks of urban interaction - Growth and centrality in the complex geography of urban activity
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- How cities and regions grow and decline depend on technological, social and economic factors. Understanding the interplay of these forces is central in research efforts aiming to improve urban and transport planning. The purpose of this thesis is to explore how mathematical modelling and computer simulation can contribute to these efforts and a central aim is to achieve practically useful models with retained conceptual simplicity as well as correspondence to important empirical patterns. The approach combines a spatially fine-grained representation of land, with processes of urban interaction based on the theory of complex networks. Urban activity at a location is modelled as the sum of all economic interactions stemming from that location. The potentials for interactions and activity are deduced mainly from spatial constraints, such as transport networks and land use regulations. Concepts that are studied include urban growth, accessibility and urban agglomeration. For model validation, an extensive data set on Swedish land taxation values is used. These values are based on actual sales prices and rent levels and can thus be considered as reasonable proxies for urban economic activity. Comparisons are made between empirical data and model outcomes, both with regard to probability distributions and geographical distributions. The empirical probability distribution of land values is found to be well approximated by a power law, strengthening the case for modelling the system as a complex network based on a process of multiplicative growth. By combining these principles with spatial interaction mediated by a transport network, the preferential centrality model is formulated. The activity predictions generated by this model reproduces empirical geographical patterns of land values. The presented models provide explanatory links between the structure of transportation networks and the geographical distributions of urban economic activity. This makes them attractive as starting points for the further step of creating practically useful planning applications. For example, the models could be used to assess how specific transport infrastructure improvements influence urban expansion.
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| 5. |
- Miller, Andrea
(författare)
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The role of rodents in the transmission of Echinococcus multilocularis and other tapeworms in a low endemic area
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Echinococcus multilocularis is zoonotic tapeworm in the Taeniidae family with a two part lifecycle involving a canid definitive host and a rodent intermediate host. The work of this thesis followed the first identification E. multilocularis in Sweden in 2011 in a red fox (Vulpes vulpes). The main purpose was to describe the importance of the rodents for E. multilocularis transmission in Sweden. Echinococcus multilocularis was identified in both the water vole (Arvicola amphibius) and the field vole (Microtus agrestis), but not the bank vole (Myodes glareolus) or mice (Apodemus spp). As the number of E. multilocularis positive rodents was low (n=9), the examination of other taeniid parasites was used to investigate overall parasite transmission patterns. Rodents caught in field habitat (field voles and water voles) were ten times more likely to be parasitized than rodents caught in forest habitat (bank voles and mice). These results provide further support for the importance of field- and water voles found in field habitat for cestode transmission. Still, these rodent species differ from the most common rodent intermediate hosts in central Europe, and metacestode development within these species may be limited. Thus, the presence of E. multilocularis in Sweden could be constrained by the lack of an ideal intermediate host. The distribution E. multilocularis was found to be highly aggregated with localized areas of high parasite egg contamination. Despite an extremely low national prevalence, multiple positive rodents and feces were identified in areas with known and unknown E. multilocularis status. This success is credited to the targeted sampling strategy, which was designed to focus collection efforts in areas where risk for parasite presence was estimated to be highest. This sampling strategy could be used as a basis for future risk-based sampling to detect E. multilocularis in areas where parasite prevalence is low or unknown.
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| 6. |
- Nikoleris, Lina
(författare)
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The estrogen receptor in fish and effects of synthetic estrogens in the environment - Ecological and evolutionary perspectives and societal awareness
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Synthetic hormones are a group of pharmaceuticals used for various human and animal treatments. However, consumption and disposal of these substances have also given rise to negative effects and environmental problems for organisms in the wild which is why these substances have been classified as estrogenic endocrine-disrupting chemicals (EDCs). Studies on the estrogen receptors (ers) and their genes are of particular interest when investigating emerging negative effects from estrogenic EDC contaminants. In vertebrates, the ers are well conserved between organisms and regulate activation and deactivation involved for example in growth, reproduction and development in both males and females. The initial aims of my research presented in this thesis were to show how the duplicated er genes in vertebrates, by studying fish and salmonid species in particular, are distributed, activated or disrupted by both ecological and pharmaceutical challenges. I have worked with three different fish species: Atlantic salmon (Salmo salar); brown trout (Salmo trutta); and roach (Rutilus rutilus) sampled from natural populations in the wild. I show that there is a complex interaction between estrogens and its receptors, depending on which tissues and life stages are investigated. I have also identified multiple ers in salmonids, which could affect their sensitivity to EDC exposure. In the framework of how 17α-ethinylestradiol (EE2) affects fish and the environment we linked exposure of EE2 to changes in behavior and gene expression and as such the consequences it might have for the structure and function of an ecosystem. Because of the recent focus on technical solutions for the removal of pharmaceutical EDCs in the environment a complementary aim was to investigate whether increased knowledge regarding the disposal and usage of EDCs, so called upstream work, could lower use of and prescriptions for the human female contraception EE2. For this I assessed the societal awareness among the main prescribers and decision makers in Sweden on the negative effects release of EE2 has on the environment. I show that providing nurse midwives with more knowledge and information about the negative consequences synthetic hormones have on ecosystems could lead to changes in their consultations practices and their prescriptions of EE2. This, in combination with updated recommendations regarding norms and practice for safe contraceptive care from authorities, could in the future help lower EE2 residues in the environment in the future. To conclude, this thesis identifies key factors for understanding how EDCs affect organisms. I show that ers vary in expression between both life stages and between tissues and that this should be considered when estimating risks for organisms after EDC exposure. This thesis also opens up a new and hitherto unappreciated field in the work surrounding the upstream knowledge and EDCs.
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| 7. |
- Stenvall, Anna
(författare)
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The Importance of Dosimetry and Radiobiology in Nuclear Medicine : Quantitative methods and modelling
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nuclear medicine uses radioactive pharmaceuticals for diagnostic or therapeutic purposes. The ionizing radiation emitted from the radiopharmaceutical is partially absorbed within the patient's body and internal dosimetry is the method to estimate the absorbed dose to a tumour or risk organ. This is of special importance in radiopharmaceutical therapy (RPT), where particle-emitting radionuclides are utilized for their therapeutic effect. A better understanding of where and to what extent the radiation energy is deposited, i.e. dosimetry, in combination with a better understanding of the irradiation-induced biological processes in tissues and tumours, i.e., radiobiology, is the foundation to establish an absorbed dose-effect relationship. This thesis comprises quantitative methods and modelling within dosimetry and radiobiology, with a special focus on quantitative methods for activity concentration, absorbed dose calculation and quantification of biological effects after nuclear medicine exposures. Nonuniformity of activity distribution and the biological effect of internal irradiation is considered in Paper I and Paper II. When a radiopharmaceutical primarily localizes within specific tissue substructures of an organ, the average absorbed dose to the whole organ may become insufficient for dosimetric analysis. Hence, the nonuniformities of the distribution of activity need to be considered and absorbed dose calculations to part of an organ, cellular, or a sub-cellular structure may be a better predictor of the therapy outcome or normal tissue toxicity. In Paper I, a small-scale anatomical dosimetry model of the liver tissue structure addressed the issue of activity nonuniformity. Monte Carlo simulations were performed to simulate the particle transport from various substructure sources within the organ model for some clinically available radionuclides. The model enabled comparison between the average absorbed dose to the entire organ and the local absorbed dose close to the source region, which for particle emitting radionuclides differed significantly. To address the resulting biological effect after internal irradiation, an ex vivo method using the γH2AX surrogate marker to visualize and quantify DNA double-strand breaks in in vivo-irradiated tissues was developed. The method was demonstrated to be useful for γH2AX-foci quantification in both the fast proliferating, radiosensitive testis tissue and the slow proliferating and more radioresistant liver tissue. Image-based activity quantification and absorbed dose estimation are considered in Paper III and Paper IV, using somatostatin receptor targeting agents for both diagnostic and therapeutic applications for neuroendocrine tumours. In Paper III, the quantitative accuracy of pre-therapeutic 111In-Octreoscan® SPECT/CT and [68Ga]Ga-DOTA-TATE PET/CT images was investigated due to the change in clinical method to use PET- instead of SPECT-imaging. Further, the quantitative relationship between the theragnostic pair of DOTA-TATE was investigated in Paper IV. The relationship between activity uptakes observed at [68Ga]Ga-DOTA-TATE PET imaging and absorbed doses at subsequent [177Lu]Lu-DOTA-TATE therapy was studied. The study demonstrated that on a group level, a higher tumour uptake measured from pretherapeutic PET images is associated with higher absorbed doses in subsequent therapy with [177Lu]Lu-DOTA-TATE. However, on the individual level, there are limitations of using the 68Ga PET as a predictor for therapy absorbed dose.
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| 8. |
- Wang, Jiatang
(författare)
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Analysis of Deformation of Gas Diffusion Layers and the Impact on Performance of PEM Fuel Cells
- 2017. - Jiatang Wang
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Proton exchange membrane (PEM) fuel cells have been promoted due to significant breakthroughs in various aspects and increasing public interests. The porous features of the gas diffusion layer (GDL) and the necessary assembly processes generate localized pressure forces on the channel/shoulder structure of the bi-polar plates (BPP). As a consequence, the assembly pressure acting on a single cell and a fuel cell stack has important influence on the geometric deformation of the GDL resulting in a change in porosity, permeability, and the resistance for heat and charge transfer in PEM fuel cells. It is expected that the cell performance is also affected by these physical parameters. To optimize the cell performance, it is necessary to consider the assembly effects, which is conducted by a numerical method in this work. The effect of the GDL porosity change caused by various compression ratios is investigated by a three-dimensional (3D) PEM fuel cell model based on the finite volume method (FVM). The model was validated and further applied to predict the transport phenomena including heat, mass and charges, as well as the effects on the cell performance. The simulation results show that a high compression ratio on the GDL leads to lower porosity, which is favorable for the heat removal from the cell. However, the compression has contradictory effects on the mass transfer and finally deteriorates the cell performance. To predict the GDL deformation and associated effects on the geometric parameters as well as porosity, mass transport properties and the cell performance, both the finite element method (FEM) and the FVM are applied, respectively. A non-homogeneous deformation, porosity, oxygen diffusion coefficient and the electric resistance of the GDL have been observed across the fuel cell in the in-plane direction. The obtained non-homogeneous physical parameters of the deformed GDL are applied for further computational fluid dynamics (CFD) analysis. The CFD results reveal that a higher assembly pressure decreases the porosity, GDL thickness, gas flow channel cross-sectional areas, oxygen diffusion coefficient, oxygen concentration and cell performance. It is found that, the reduction of the GDL porosity is a dominating factor that decreases the cell performance compared with the decreased gas channel flow area and GDL thickness in the assembly condition. A sufficient GDL thickness is required to ensure transfer of the fresh gas to the reaction sites far away from the channel. As the entire electric resistance is considered, the optimized cell performance is obtained if the cell is operating below 1 MPa assembly pressure. It is found from a newly developed electric resistance model that both through-plane resistance of a cell and the interfacial resistance between the GDL and BPP for electrons decrease with higher assembly pressures. Comparing with a zero-compressed cell, the cell operating at an assembly pressure above 2 MPa creates a new contact area between the GDL and BPP at the vertical interface. Therefore, the corner of a BPP close to the channel becomes the dominating zones for electron transfer. Finally, it is suggested that the assembly pressure should be considered properly in designing and manufacturing of PEM fuel cells.Popular science summaryProton exchange membrane (PEM) fuel cell is one of the promising fuel cells in conversion of chemical energy to electric energy with a relative high efficiency. It is widely known that the PEM fuel cell has nearly-zero pollutants if it is fueled by hydrogen. People can use the sustainable electric power without any noise in home usage, transportation and commutation facilities and so on. The current interest of this device is to replace combustion engines to release the environmental problems like CO2 emissions. A PEM fuel cell involves several technologies. Many achievements have been reached in the past decades. However, the cost and stability are two main limitations preventing wide use of PEM fuel cells. In various research and development fields, such as materials, design and manufacturing, some breakthroughs have been made in improving the cell performance. Even though large efforts have been paid in experiments, the closed-space and small-scale of the cell device make it hard to investigate. Therefore, numerical methods have become very popular and presented efficient ways to investigate the transport phenomena and optimizing the cell performance.The assembly process of a single cell or a cell stack is a necessary step to prevent gas leakage and decrease the contact resistance between the various layers. The porous carbon fibers in the gas diffusion layer (GDL) are touching the channel/shoulder structure of the bi-polar plates (BPP). As a consequence, the physical properties of the GDL, such as dimensions, porosity, mass transfer resistance, and interfacial resistances for heat and electrons will be changed. These factors may result in unexpected or decreased cell performance.In this work, the commercial software ANSYS and the newly developed open source code OpenFOAM (“Open Source Field Operation and Manipulation”) are applied to study the important assembly processes. The model in ANSYS predicts the GDL deformation behavior. Then the deformed GDL and the corresponding yield properties are implemented in the PEM fuel cell model to study the effects of the assembly pressure on the transport phenomena and cell performance. To optimize the cell performance, the electric resistance in the deformed bulk of a cell and the interfacial resistance between the GDL and BPP are considered. All the parameters are expressed as a function of the assembly pressure. To investigate the porosity effects independently, different porosities of the GDL caused by various assumed compression ratios are applied as initial conditions for the PEM fuel cell model. In the study of porosity effects, the GDL deformation and the electric resistance variations are neglected. Then the model is further extended to include real deformation of the GDL and the electron transfer effects, respectively. By evaluating several topics, the cell performance is optimized in terms of assembly pressures or compression ratios. Guidelines for design and manufacturing of PEM fuel cells can be set up based on this thesis.
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| 9. |
- Willskytt, Siri, 1989
(författare)
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Resource efficient products in a circular economy – The case of consumables. From environmental and resource assessment to design guidelines
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The circular economy (CE) is a concept to challenge the unsustainable production, consumption, and waste management of products, through the recirculation of resources and products through various means while reducing environmental impact. Within this concept, many measures are recommended for reducing environmental impact and resource use. However, to ensure and verify whether a measure is leading to its intended outcome, environmental and resource assessment is necessary. This thesis aims to investigate which measures are resource efficient and identify for which products different measures are suitable and under what circumstances they lead to their intended outcomes. Based on this, design methods are developed to enable the design of more resource-efficient products. Finally, this thesis aims to investigate more specifically the measures that are suitable for consumable products, as these products have not been examined thoroughly in the circular economy literature as durable products. The aims of this research were met by investigating which resource-efficiency measures exist and are applicable to products with different characteristics. This was done through life cycle assessment studies of specific consumable products. Further, a synthesis study was carried out in which lifecycle-based assessment studies of different products and measures were analysed. This research concludes that depending on a product’s characteristics, some measures are more relevant than others. In addition, the analysis shows that many measures lead to trade-offs between different types of environmental impacts and resources uses, as well as between different life cycle phases. For these findings to be practically useful, they were subsequently translated into design guidelines expressed as a design tool. Finally, a literature review was conducted of general product design guidelines in the CE and ecodesign literature to compile and analyse to what extent the design guidelines are applicable to different types of consumables. Among other factors, this review shows that, on average, less than half of the recommendations found in the general product design guidelines are possible to apply to consumables. Further, the CE literature was found to provide fewer relevant design considerations than the ecodesign literature. This work also identifies what aspects make product-types specific design guidelines transferable to other consumables.
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| 10. |
- Andersson, Johanna, 1972-
(författare)
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Barns teckningar som utgångspunkt i det naturvetenskapliga samtalet
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Barns föreställningar utgör en viktig del i deras begreppsbildning inom naturvetenskap vilket betonas inom konstruktivismen. I denna avhandling utgör en socialkonstruktivistisk syn på lärande det teoretiska ramverket. Det övergripande syftet med avhandlingen är att i samtal med barn i åldrarna 4–13 år och med utgångspunkt i deras teckningar, utveckla kunskap om de föreställningar de ger uttryck för inom fyra naturvetenskapliga områden: värme, blandning, människokroppen och vad som är levande/inte levande. Två forskningsfrågor behandlas i avhandlingen: Vilka föreställningar ger barn uttryck för i teckningar och i samtal om naturvetenskapliga fenomen? Vilka metodologiska förutsättningar och utmaningar finns det när det gäller att använda teckningar som utgångspunkt och som meningsskapande redskap för att fånga barns föreställningar? En multimodal metod bestående av teckningar, samtal och barnens aktivitet användes vid datainsamlingen, vilket är i linje med ett socialsemiotiskt perspektiv.Avhandlingen består av fyra studier. Resultatet i de två första studierna visar att barns föreställningar om blandningar var något mer utvecklade än vad som visats i tidigare studier, medan deras föreställningar gällande värme överensstämde med vad som tidigare rapporterats.Den tredje studien visar att barnen känner till fler organ i människokroppen och visar, till skillnad från vad som framkommit i tidigare forskning, förmåga att rita kopplingar mellan organen. I den fjärde studien talar en majoritet av barnen om död som en motsats till liv och några ritade att det som inte lever tidigare har levt. Barn som är medvetna om mikroskopiska objekt klassificerar dem som levande. Förklaringarna visar på en inkonsekvens i barnens resonemang om växter lever eller inte.Metodologiskt framkom att barns föreställningar med fördel fångas genom deras egna teckningar tillsammans med deras förklaringar av dessa. Teckningarna fungerar även som hjälpmedel för att föra fram och delge olika resonemang. I avhandlingen diskuteras barns lösningar på rittekninska problem som de mötte vid sidan av den naturvetenskapliga uppgiften. I studien om människokroppen handlar dessa problem om svårigheten i att överföra den tredimensionella människokroppen till två dimensioner. En annan svårighet var att kroppens organ, skelett, muskler och vävnader ligger ovanpå varandra. Där använde barnen strategin att rita röntgenbilder för att visa det som ligger dolt. Barn i olika åldrar löste ofta dessa rittekniska problem på ett mycket kreativt sätt i kombination med deras muntliga/skriftliga kommentarer. Förutom teckningarnas betydelse diskuteras skillnaden mellan kontextualiserade och dekontextualiserade uppgifter. De olika områdena som studerats i avhandlingens artiklar befinner sig på olika abstraktionsnivåer vilket påverkar barnens föreställningar och hur detta uttrycks in bilder. Naturvetenskap innefattar olika dimensioner där det handlar om att både lära sig strukturell och processuell kunskap. Den multimodala metoden gav barnen hjälp med att samla, strukturera och uttrycka sina tankar
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