Denna kvalitativa studie syftar till att undersöka lågstadielärares perspektiv på utomhusundervisning inom de naturorienterande ämnena samt dess påverkan på elevers lärande och känslomässiga band till naturen. Mot bakgrund av minskad utomhusvistelse bland barn och unga, vilket även kan påverka deras känslomässiga band till naturen, skolprestationer samt engagemang för natur och miljö, betonas skolans viktiga roll i att vända denna nedåttrend, eftersom eleverna spenderar en betydande del av sin uppväxt i skolan. Genom semistrukturerade intervjuer och en ramfaktorteoretisk utgångspunkt, visar studien att lärarna anser att elever behöver möjlighet att vistas i naturen för att skapa ett band till den, vilket även främjar ett djupare lärande. Denna studie synliggör även att lärare med erfarenhet av utomhusundervisning även upplever den som främjande för elevers lärande och känslomässiga band till naturen, eftersom de får större möjligheter att förstå naturen på ett konkret sätt. Dock indikerar studien att lärarnas egen inställning till naturen utgör den största begränsande faktorn för utomhusundervisning. Detta visar att skolledningens insatser är centrala för att stödja lärare genom exempelvis fortbildning för att de sedan ska kunna skapa möjligheter för eleverna att bygga upp positiva relationer till naturen redan i årskurs F-3.

Vårt arbete fokuserar på undervisningsmaterial och identifikation av de faktorer som påverkar valen av dessa, särskilt för årskurserna 4 - 6. Vi har analyserat användningen av undervisningsmaterial inom naturvetenskap ute på skolor för elever i årskurs 4–6. Genom detta har vi kartlagt vilka material som för närvarande används och identifierat viktiga faktorer som påverkar valet av dessa i undervisningen. En betydande del av studien fokuserade på att samla data om de specifika läromedel som lärare och skolor har gjort. Genom intervjuer fick vi en bild av vilka resurser som används för att undervisa i naturvetenskap i dessa årskurser. Detta innefattade läroböcker, digitala plattformar, experimentmaterial, utflykter och andra undervisningsresurser. Resultaten från undersökningen visar på att det är vissa läromedel som tycks vara vanligt förekommande och att dessa anpassas utifrån skolmiljön och olika pedagogiska behov. Digitala resurser tycks bli alltmer betydelsefulla och flera skolor har övergått till att integrera teknologi för att förbättra inlärningsupplevelsen. När det gäller faktorer som påverkar valen av materialet framkom det att lärarnas kompetens och pedagogiska metoder spelar en avgörande roll. Lärarnas bedömning av materialets lämplighet för elevernas nivå, engagemang och intresse var centrala överväganden. Dessutom påverkades valen av läromedel utifrån faktorer som tillgänglighet, kostnad och överensstämmelse med läroplanen.

Syftet med studien var att med en kvalitativ forskningsansats undersöka lärares upplevda möjligheter och utmaningar med programmeringsundervisningen i teknik ur ett ramfaktorteoretiskt perspektiv. Detta har undersökts med hjälp av semistrukturerade intervjuer med fem lärare. Tidigare forskning har visat att lärare haft bristande ämneskunskaper, låg självkänsla och saknat tid för att implementera programmering i teknikundervisningen, något även denna studies resultat har visat.  Ramfaktorteorin har använts som teoretiskt ramverk för att synliggöra vilka faktorer lärare upplever som utmanande och möjliggörande i samband med programmeringsundervisningen i teknik. Studien har genomförts med avsikten att kunna formulera insikter kring vilka ramfaktorer som kan påverka denna undervisning. Resultatet visar att lärares inre ramar som ämneskunskaper och självförtroende har en stark påverkan på vilka möjligheter som finns för undervisningen i programmering och att det är utmanande att bedriva programmeringsundervisning utan skolans stöd. De yttre ramarna som skolans förhållningssätt och stöd samt tid upplevs utmanande på olika sätt utifrån de självupplevda inre ramarna.

The ability of cells to move through their environment and spread on surfaces is fundamental to a host of biological processes; including wound healing, growth and immune surveillance. Controlling cell motion has wide-ranging potential for medical applications; including prevention of cancer metastasis and improved colonisation of clinical implants. The relevance of the topic coupled with the naturally arising interplay of biomechanical and biochemical mechanisms that control cell motility make it an exciting problem for mathematical modellers. Two-phase flow models have been widely used in the literature to model cell motility; however, little is known about the mathematical properties of this framework. The majority of this thesis is dedicated to improving our understanding of the two-phase flow framework. We first present the simplest biologically plausible two-phase model for a cell crawling on a flat surface. Stability analyses and a numerical study reveal a number of features relevant to modelling cell motility. That these features are present in such a stripped-down two-phase flow model is notable. We then proceed to investigate how these features are altered in a series of generalisations to the minimal model. We consider the effect of membrane-regulated polymerization of the cell's actin network, the effect of describing the network as viscoelastic, and the effect of explicitly modelling myosin, which drives contraction of the actin network. Validation of hydrodynamical models for cell crawling and spreading requires data on cell shape. The latter part of the thesis develops an image processing routine for extracting the three-dimensional shape of cells settling on a flat surface from confocal microscopy data. Models for cell and droplet settling available in the literature are reviewed and we demonstrate how these could be compared to our cell data. Finally, we summarise the key results and highlight directions for future work.

Our bodies contain a vast number and diversity of microbes. These microbes interact, and these interactions can define how microbes affect us. Microbial ecology and evolution, therefore, are important for both microbiology and human health. However, our understanding of microbial communities remains limited. There is a need for theory that dissects the complexity and identifies the key factors and processes affecting microbial groups. Here I develop realistic computer simulations and population models of microbial communities. My first project seeks to explain microbial communication (quorum sensing) and argues that quorum sensing is a way to infer when competing genotypes are no longer a threat. The second project proposes an evolutionary explanation for another major microbial trait: adhesion. I argue that adhesion is a weapon allowing cells to compete within microbial groups and push competitors out, particularly when growing on a host epithelium. The third project moves from microbes to the host and asks whether a host can control which microbes grow and persist inside it. I develop a model of the human gut epithelium and show that the gut architecture amplifies the ability of hosts to select helpful microbes over harmful ones using nutrient secretion. In addition to selecting particular microbial strains, a host will also benefit from stable symbiotic communities that behave in a predictable manner. But what determines whether host-associated communities are ecologically stable? My final project uses ecological network theory to show that ecological stability is likely to be a problem for gut communities that are diverse and contain species that cooperate with each other. However, I argue that the host should function as an ecosystem engineer that increases ecological stability by weakening the strong dependence of cooperating species upon one another. While host-associated communities are complex ecological systems, my thesis identifies key factors that affect their form and function.

Determining the dynamics and parameter values that drive tumor growth is of great interest to mathematical modelers, experimentalists and practitioners alike. We provide a basis on which to estimate the growth dynamics of ten different tumors by fitting growth parameters to at least five sets of published experimental data per type of tumor. These timescale tumor growth data are also used to determine which of the most common tumor growth models (exponential, power law, logistic, Gompertz, or von Bertalanffy) provides the best fit for each type of tumor. In order to compute the best-fit parameters, we implemented a hybrid local-global least squares minimization algorithm based on a combination of Nelder-Mead simplex direct search and Monte Carlo Markov Chain methods.

Ecosystems are often made up of interactions between large numbers of species. They are considered complex systems because the behaviour of the system as a whole is not always obvious from the properties of the individual parts. A complex system can be represented by a network: a set of interconnected objects. In the case of ecological networks and food webs, the objects are species and the connections are interactions between species. Many complex systems are dynamic and exhibit intricate time series. Time series analysis has been developed to understand a wide range of natural phenomena. This thesis deals with the structure, dynamics, and robustness of ecological networks, the spatial dynamics of fluctuations in a social system, and the analysis of cardiac time series. Biodiversity on Earth is decreasing largely due to human-induced causes. My work looks at the effect of anthropogenic change on ecological networks. In Chapter Two, I investigate predator adaptation on food-web robustness following species extinctions. I identify a new theoretical category of species that may buffer ecosystems against environmental change. In Chapter Three, I study changes in parasitoid-host (consumer-resource) interaction frequencies between complex and simple environments. I show that the feeding preferences of parasitoid species actively change in response to habitat modification. Ecological networks are embedded in spatially-heterogeneous landscapes. In Chapter Four, I assess the role of geography on population fluctuations in an analogous social system. I demonstrate that fluctuations in the number of venture capital firms registered in cities in the United States of America are consistent with spatial and temporal contagion. Understanding how physiological signals vary through time is of interest to medical practitioners. In Chapter Five, I present a technique for quickly quantifying disorder in high frequency event series. Applying the algorithm to patient cardiac time series provides a rapid way to detect the onset of heart arrhythmia. Increasingly, answers to scientific questions lie at the intersection of traditional disciplines. This thesis applies techniques developed in physics and mathematics to problems in ecology and medicine.

Colorectal cancer (CRC) is one of the most prevalent and deadly forms of cancer. Its high mortality rate is associated with difficulties in early detection, which is crucial to survival. The onset of CRC is marked by macroscopic changes in intestinal tissue, originating from a deviation in the healthy cell dynamics of glands known as the crypts of Lieberkuhn. It is believed that accumulated genetic alterations confer on mutated cells the ability to persist in the crypts, which can lead to the formation of a benign tumour through localised proliferation. Stress on the crypt walls can lead to buckling, or crypt fission, and the further spread of mutant cells. Elucidating the initial perturbations in crypt dynamics is not possible experimentally, but such investigations could be made using a predictive, computational model. This thesis proposes a new discrete crypt model, which focuses on the interaction between cell- and tissue-level behaviour, while incorporating key subcellular components. The model contains a novel description of the role of the surrounding tissue and musculature, which allows the shape of the crypt to evolve and deform. A two-dimensional (2D) cross-sectional geometry is considered. Simulation results reveal how the shape of the crypt base may contribute mechanically to the asymmetric division events typically associated with the stem cells in this region. The model predicts that epithelial cell migration may arise due to feedback between cell loss at the crypt collar and density-dependent cell division, an hypothesis which can be investigated in a wet lab. Further, in silico experiments illustrate how this framework can be used to investigate the spread of mutations, and conclude that a reduction in cell migration is key to confer persistence on mutant cell populations. A three-dimensional (3D) model is proposed to remove the spatial restrictions imposed on cell migration in 2D, and preliminary simulation results agree with the hypotheses generated in 2D. Computational limitations that currently restrict extension to a realistic 3D geometry are discussed. These models enable investigation of the role that mechanical forces play in regulating tissue homeostasis, and make a significant contribution to the theoretical study of the onset of crypt deformation under pre-cancerous conditions.

Metapopulation ecology has developed to explain the population dynamics that occur in spatially structured landscapes. In this study, I combined an empirical laboratory approach, using metapopulation microcosms of Callosobruchus maculatus and its endospecific parasitoid Anisopteromalus calandrae, with mathematical population models in order to investigate several fundamental metapopulation processes. Population dynamics in these systems can be studied at two scales; the local patch-wise scale and the regional metapopulation scale. Here I demonstrate that in both homogeneous and heterogeneous landscapes knowledge of local scale demographic processes is necessary in order to understand regional metapopulation dynamics. The differences in the rate and net direction of dispersal between patches as a result of the permeability of the matrix in homogeneous systems and density-dependent dispersal in heterogeneous systems were also explored. Metapopulation dynamics rely on a balance between local extinctions and recolonisations. Therefore, increasing local mortality rates is likely to be detrimental to the persistence of the system. Here, the impact of several common harvesting strategies on the persistence of a host-parasitoid metapopulation was examined. Contrary to expectation I discovered that harvesting in these systems increased both local and regional population sizes. The increased population size as a result of increased mortality was explained in terms of a hydra effect, where harvesting relaxed density-dependence acting on local host populations. The results presented in this thesis are relevant for the monitoring, management and conservation of natural metapopulations and the development of sustainable harvesting strategies in structured landscapes.

Successful T cell activation depends on the recognition of antigenic peptides in the context of a Major Histocompatibility Complex molecule (pMHC) by the T cell antigen receptor (TCR), together with additional signals from co-stimulatory receptors such as CD28. Despite their importance, a thorough understanding of how TCR-pMHC binding properties relate to T cell functional responses remains unclear. In addition, there are no consensuses to the exact mechanism leading to CD28 receptor triggering. Activation of CD28 is dependent on the phosphorylation of key tyrosine residues within its cytoplasmic domain by Src family kinases. Just like the TCRs, CD28 receptors are susceptible to perturbations of the local kinase: phosphatase ratio. The K-S model postulates that upon ligand engagement, large RPTPs such as CD45 are segregated from the area of close contact, resulting in increased relative kinase concentration and CD28 receptor triggering. This hypothesis was tested in chapter 3, where elongated forms of CD80 were examined for their ability to costimulate primary T cells. CD28 costimulation was indeed diminished and there was reduced CD45 segregation from the elongated CD80 molecules. Additionally, CD28 habouring key Y170F tyrosine mutations were less susceptible to CD28 signal abrogation by elongated CD80 molecules. Interestingly, elongated CD80 molecules remained much less effective in mediating costimulation even when pMHC molecules were also elongated, suggesting that TCR-pMHC and CD28-CD80 size matching is not critical for costimulation. Despite the well-documented MHC-restriction requirement for TCR recognition, the relative energetic contributions of peptide versus MHC in TCR-pMHC interactions remain elusive. To address this question, the energetic footprints of four TCRs (1G4, JM22, A6 and G10) to HLA-A2 were determined via systematic alanine scanning mutagenesis on the HLA-A2 heavy chain in chapter 4. By targeting exclusive TCR contacting residues on the MHC, we conservatively estimate the contribution of MHCs for the four TCRs to range from 15% to over 70%. Several models have been formulated in an attempt to relate TCR-pMHC binding properties to T cell activation. Validity of the models was tested in chapter 5 using a supra-physiological TCR. By mutating key residues within the cognate pMHC, we generated a panel of TCR-pMHC with affinities that varies up to 105-fold. These reagents were used to stimulate Jurkat and primary T cells transduced with the supra-physiological TCR. Results in the Jurkat T cell system demonstrated the presence of an optimal off-rate (k_off) for TCR-pMHC interaction at low concentrations of pMHC concentration. The results argue against affinity models and the basic kinetic proofreading model for T cell activation.