Repetitive tetramers of the DNA sequence 5'-CAAT-3' are present in several loci associated with lipooligosaccharide (LOS) phase variation in Haemophilus influenzae type b (Hib). In an attempt to identify H. somnus phase-variable LOS genes, the presence of CAAT repeats within the H. somnus 738 genome was confirmed using a (CAAT)7 probe. A 3.9 kb EcoRI fragment that reacted with the probe was cloned and sequenced. Sequence analysis confirmed the presence of 31 CAAT repeats downstream of two potential start codons, and indicated that small or large proteins would be encoded depending on the number of CAAT repeats. The larger gene products showed 46% amino acid homology to Lex2b from Hib, which influences LOS phase variation in that species. In H. somnus, this gene was named lob1 (lipooligosaccharide biosynthesis gene). Sequence analysis showed that randomly selected colonies most frequently contained 33 CAAT repeats in lob1, corresponding to a 294 amino acid product. Colonies selected for negative reactivity to mAb 5F5 were significantly more likely to have different numbers of CAAT repeats in lob1 than randomly selected colonies. The presence of lob1 in trans altered the LOS profile of a non-phase variable strain of H. somnus, and caused increased levels of reactivity to polyclonal antisera made to purified LOS from strain 738. Based on the ability of this gene to alter the LOS profile of a non-phase varying strain and the correlation of changes in CAAT repeats with mAb 5F5 reactivity, lob1 appears to be involved in LOS biosynthesis and phase variation. / Master of Science

Yes / There is a significant lack of geomagnetic field strength (archaeointensity) measurements for many archaeological time periods in the United Kingdom (UK). This not only makes past geomagnetic secular variation difficult to model but also limits the development of archaeointensity dating. This paper presents the first archaeointensity study on UK Neolithic material. In this study, twenty-five sherds of Neolithic Grooved Ware pottery from the Ness of Brodgar, Orkney, UK, some with direct radiocarbon dates, were subjected to a full archaeomagnetic investigation with the aim of increasing the amount of archaeointensity data for the UK. Both thermal Thellier and microwave palaeointensity experiments were used to determine which technique would be most suitable for British Neolithic pottery. Three successful archaeointensity results between 35 and 40μT were obtained using thermal Thellier method, which is consistent with the limited data available within a 15° radius and geomagnetic field model predictions from the same time. We separated the results into four different types with an intention of explaining the behaviours that determine the likelihood of achieving an acceptable archaeointensity estimate. The feasibility of obtaining geomagnetic field strength information during the UK Neolithic from ceramics has been demonstrated and the results provide a solid basis for improving our knowledge of geomagnetic secular variation during archaeological time in Britain. / The Andy Jagger Fund, University of Bradford, for supporting the stay at the University of Liverpool and Crafoord Grant, Sweden, No. 20160763. The radiocarbon dates were funded by AHRC NF/2017/2/7.

La duplication de gènes est l’un des plus importants mécanismes évolutifs pour la génération de diversité fonctionelle. Lorsqu’un gène est dupliqué, la nouvelle copie partage toutes ses fonctions avec la copie ancestrale car elles encodent pour des protéines identiques. Donc, les deux protéines, appelées paralogues, auront le même réseau d’interactions physiques protéine-protéine. Cependant, dans le cas de la duplication des gènes qui codent des protéines qui interagissent avec elles-mêmes (homomères), la nouvelle protéine interagira aussi avec la copie ancestrale, ce qui introduit une nouvelle interaction (heteromère) (Kaltenegger and Ober, 2015; Pereira-Leal et al., 2007). Puisque ces interactions peuvent avoir des différents motifs de rétention et de fonction (Ashenberg et al., 2011; Baker et al., 2013; Boncoeur et al., 2012; Bridgham et al., 2008), il est important de mieux comprendre comment ces états sont atteints et quelles forces évolutives les favorisent. Dans ce memoire, je cible ces questions avec des simulations in silico de l’évolution des protéines suite à la duplication de gènes en travaillant avec des structures crystallographiques de haute qualité, provenant de la Protein Data Bank (Berman et al., 2000; Dey et al., 2018). Les simulations montrent que les sous-unités et interfaces partagées entraînent une forte corrélation entre les trajectoires évolutives de ces complexes. Ainsi, les simulations prédisent que la préservation de seulement les deux homomères ou seulement l’hétéromère ne devrait pas être fréquente. Toutefois, la simulation qui applique la sélection seulement sur un homomère montre que l’homomère neutre est destabilisé plus rapidement que l’hétéromère neutre. Nous avons comparé ces prédictions avec des résultats expérimentaux du réseau d’interactions protéine-protéine de la levure. Comme suggéré par les simulations, les patrons d’interactions les plus fréquents ont été la formation des trois complexes (deux homomères et un hétéromère) ou la formation de seulement un homomère. Les patrons correspondants à deux homomères sans hétéromères ou un hétéromère sans homomères sont rares. Nos résultats démontrent l’extension de l’hétéromérisation entre paralogues dans le réseau d’interactions physiques protéine-protéine de la levure, les mécanismes sous-jacents et ses implications. / Gene duplication is one of the most important evolutionary mechanisms for the generation of functional diversity. When a gene is duplicated, the new copy shares all of the ancestral copy’s functions because they encode identical proteins. Therefore, the two proteins, called paralogs, will have the same protein-protein interaction network. However, in the case of the duplication of genes encoding proteins that self-interact (homomers), the new protein will also interact with the ancestral copy, introducing a novel interaction (heteromer) (Kaltenegger and Ober, 2015; Pereira-Leal et al., 2007). As these interactions can have different retention and functional patterns (Ashenberg et al., 2011; Baker et al., 2013; Boncoeur et al., 2012; Bridgham et al., 2008), it is important to understand better how these states are reached and what evolutionary forces favor each of them. In this thesis, I approach these questions by means of in silico simulations of protein evolution after gene duplication by working with high-quality crystal structures from the Protein Data Bank (Berman et al., 2000; Dey et al., 2018). The simulations show that the shared subunits and interfaces lead to these complexes having highly correlated evolutionary trajectories. Thus, the simulations predict that the preservation of only the two homomers or only the heteromer is not likely to happen often. Nevertheless, simulating evolution with selection on only one homomer shows that the neutral homomer is destabilized faster than the neutral heteromer. We compared these predictions against experimental results from the yeast protein-protein interaction network. As suggested by the simulations, the most abundant interaction patterns were either the formation of all three complexes (two homomers and one heteromer) or the formation of only one homomer, with motifs corresponding to two homomers without a heteromer or a heteromer without homomers being rare. Our results highlight the extent of heteromerization between paralogs in the yeast protein-protein interaction network, the underlying mechanisms, and its implications

Swedish students are showing a continuous deterioration of knowledge about the concept of mathematical place-value and by looking at a closer analysis, made by the TIMSS, it was made even more visible that the concept of place-value, which is associated with our positional system, is very central to students' understanding of the number concept. The PISA - report further demonstrates that it is possible to discern the deteriorating knowledge of students' perceptions of digits’ place-values in calculations of standard algorithms. The study is carried out because I want to explore as well as contribute to the research on the opportunities students are given to understand the positional system. The study aims to create knowledge on students' opportunity to understand the positional system in the sixth grade. The questions the study seeks to answer are the following:  What are the different patterns of variation the students meet during the lesson about the positional system?  Which are the critical aspects that can be discerned when listening to the students' descriptions of the positional system? To get answers to these questions, and thus fulfill the purpose of the study, different teachings have been observed and students have been interviewed. The theory of this work is variation theory. This theory was chosen because it makes it possible to understand many different ways to treat a selected subject of matter as well as to relate it to students' opportunities to learn. Results of the study show that students encounter several different parts of the pattern of variation in the teaching about the positional system, including contrast, generalization and separation. By taking in the students' descriptions of the positional system, three critical aspects could be discerned. These were the place-value together with the significance of zero in multi-digit numbers, numbers properties and lastly number sence. The conclusion is that students have different opportunities to develop an understanding of the positional system in the sixth grade. The possibilities are different depending on which critical aspects that are distinguished by the students in the education of the positional system. / Svenska elever visar kontinuerligt försämrade kunskaper kring begreppet platsvärde och vid en noggrannare granskning av TIMSS (Skolverket, 2012) synliggjordes att begreppet platsvärde, som är förknippat med vårt positionssystem, är ett centralt begrepp för elevers förståelse av talbegrepp. PISA rapporten (Skolverket, 2013) påvisar ytterligare att det går att urskilja försämrade kunskaper om elevers uppfattningar om siffrors platsvärden vid beräkningar av standardalgoritmer. Studien genomfördes för att undersöka och bidra till forskningen om vilka möjligheter elever ges till att förstå positionssystemet. Studien syftar till att bilda kunskap om elevers möjligheter att förstå positionssystemet i årskurs 6. De frågeställningar studien syftar till att besvara är:  Vilka variationsmönster möter elever i undervisning om positionssystemet?  Vilka kritiska aspekter kan urskiljas vid elevers beskrivningar av positionssystemet? För att få svar på frågeställningarna och därmed uppfylla syftet med studien har undervisning observerats och elever intervjuats. I studien finns inslag av variationsteorin. Teorin valdes för att göra det möjligt att förstå hur olika sätt att behandla ett valt ämnesinnehåll relaterar till elevers möjligheter att lära. Studiens resultat visar att elever möter olika variationsmönster i undervisning om positionssystemet, däribland kontrast, generalisering och separation. Vid elevers beskrivningar av positionssystemet kunde det urskiljas tre kritiska aspekter, positionens värde och nollans betydelse i ett flersiffrigt tal, talens egenskaper och talsortsuppfattning. Slutsatsen är att elever har olika möjligheter att utveckla förståelse för positionssystemet i årskurs 6. Möjligheterna ser olika ut beroende på vilka kritiska aspekter eleverna urskilt i undervisning om positionssystemet.

Studiens syfte är att bilda kunskap om elevers förståelse av likhetstecknet och hur undervisning om likhetstecknet i årskurs 3 kan varieras för att bli så effektiv som möjligt. Syftet ska besvaras genom frågeställningarna: vilka variationsmönster som de studerade eleverna kan möta och vilka kritiska aspekter som elever kan identifiera. Kritiska aspekter är det som elever behöver identifiera för att förstå det som ska läras. Variationsmönster innebär att det som är kritiskt i undervisningen ska varieras för att synliggöras. Studien har sin ansats i variationsteorin, där variationsmönster och kritiska aspekter är centrala begrepp. En lektion observerades i årskurs 3 och sex elever valdes ut och intervjuades om likhetstecknet. Resultatet av studien visar att eleverna mötte sex kritiska aspekter i undervisningen. I varje kritisk aspekt mötte eleverna ett eller flera variationsmönster. Studien visar också att alla de intervjuade eleverna har en relationell och instrumentell förståelse av likhetstecknet. Eleverna har förståelse av en kritisk aspekt, som den observerade lektionen inte hade berört, nämligen att alla tal måste ingå i en uppgift för att lösningen ska vara korrekt. Fyra av sex elever har förståelse av den kritiska aspekten att det ska vara ekvivalens i en kedja av likheter. Resultatet visar också att elevernas förståelse av likhetstecknet inte är beroende av att de möter variationsmönster i undervisningen, men att de möter de kritiska aspekterna på något sätt. / The aim of the study is to explore the understanding of the equal sign and how the teaching about the equal sign among third grade students can be varied to be as effective as possible.  The aim will be answered trough the questions: what patterns of variation can the studied students meet and what critical aspects have the students identified. Patterns of variation means that what is critical in the teaching should be varied to become visible. Critical aspects is what students need to identify to understand what should be learned. The foundation of the study is the Variation Theory, where patterns of variation and critical aspects are central concepts. The observations were accomplished during a third grade lesson and six students were selected for interviews about the equal sign. The result of the study shows that the students met six critical aspects during the lesson. For every critical aspect there were one or several patterns of variation that was exposed to the students. The result also states that the students who were interviewed have a relational and instrumental understanding of the equal sign. The students also have understanding of a critical aspect that they did not meet in the observed lesson, namely that all numbers have to enter in a task. Four out of six students have understanding of the critical aspect that there should be equivalence in a chain of similarities. The result also show that the students understanding of the equal sign is not dependent of that they meet patterns of variation in the teaching, but that they meet the critical aspects somehow.

Problemlösning genomsyrar hela läroplanen och är en viktig del av matematik-undervisningen i skolan (Skolverket, 2011a). Att lösa problem kommer naturligt för barn och det är lärarens uppgift att ta vara på den förmågan och hjälpa elever att bli effektiva problemlösare. Förmågan att lösa problem är en viktig kunskap som varje elev har fördel av att kunna (Lester, 1996). Studiens syfte är att undersöka variationen av problemlösnings-strategier som elever använder samt undersöka hur eleverna resonerar när de löser ett problem. 39 elever från två olika skolor i England och Sverige fick lösa ett matematiskt problem och sedan intervjuades 12 av dem med olika lösningsstrategier. Resultatet visade att eleverna använde sig av fyra olika kategorier av lösningsstrategier. De olika kategorierna var: lösningsstrategi genom addition, lösningsstrategi genom addition och subtraktion, lösningsstrategi genom att gissa och resonera, och lösningsstrategi genom att söka mönster. Det fanns även en grupp elever som inte hade någon utläsbar lösningsstrategi. Slutsatsen av studien är att elever behöver explicit undervisning i problemlösning för att till fullo kunna behärska den. / Problemlösning genomsyrar hela läroplanen och är en viktig del av matematik-undervisningen i skolan (Skolverket, 2011a). Att lösa problem kommer naturligt för barn och det är lärarens uppgift att ta vara på den förmågan och hjälpa elever att bli effektiva problemlösare. Förmågan att lösa problem är en viktig kunskap som varje elev har fördel av att kunna (Lester, 1996). Studiens syfte är att undersöka variationen av problemlösnings-strategier som elever använder samt undersöka hur eleverna resonerar när de löser ett problem. 39 elever från två olika skolor i England och Sverige fick lösa ett matematiskt problem och sedan intervjuades 12 av dem med olika lösningsstrategier. Resultatet visade att eleverna använde sig av fyra olika kategorier av lösningsstrategier. De olika kategorierna var: lösningsstrategi genom addition, lösningsstrategi genom addition och subtraktion, lösningsstrategi genom att gissa och resonera, och lösningsstrategi genom att söka mönster. Det fanns även en grupp elever som inte hade någon utläsbar lösningsstrategi. Slutsatsen av studien är att elever behöver explicit undervisning i problemlösning för att till fullo kunna behärska den. Problem solving permeates the Swedish national curriculum and it is an important part of mathematics education (Skolverket, 2011a). To solve problems comes naturally to children and it is the teacher’s task to harvest this ability and help pupils to be effective problem solvers. The ability to solve problems is an important knowledge and if known provides an advantage in life (Lester, 1996). The purpose of this study is to investigate the variation of problem solving strategies that pupil use and to investigate their mathematical reasoning while solving a mathematical problem. 39 pupils from two different schools in England and Sweden got to solve a mathematical problem and then 12 of them, which had different solution strategies, were selected for an interview. The result showed that the pupils used four categories or solving strategies. The categories were: finding a solution though addition, finding a solution though both addition and subtraction, finding a solution though guessing and reasoning and finding a solution though seeking patterns. There was also one group of pupils who did not have a distinguishable solution strategy. The conclusion of this study is that pupils need explicit teaching about problem solving to be able to fully master it.

Dissertation (PhD)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Within arthropods, inter-individual and inter-population variation is generally poorly explored for physiological parameters. Such physiological variability is important, as it can provide insight into the capacity for evolutionary adaptation and how animals may cope with anthropogenic climate change. Insect vectors of human and animal diseases, such as tsetse flies (Diptera, Glossinidae) which carry trypanosomes, are of particular interest. Predictions of tsetse fly (Glossina spp.) range expansion, possibly paralleled by increased disease occurrence, have been made under future climate scenarios. Moreover, since there are generally strong relationships between abiotic variables (e.g. temperature and moisture availability), population dynamics, distribution and abundance, determining the physiological mechanisms influencing such relationships has utility for predictive modelling of spatial and temporal changes in tsetse fly distributions. I investigated physiological variation among individuals and populations, focusing mainly on Glossina spp. but using other arthropods to address certain issues. Specifically, I show the following: i) metabolic rate is repeatable (intra-class correlation coefficient) within individuals, and may be influenced by several factors such as age, gender, body mass and pregnancy; ii) while metabolic rate is repeatable within individuals, it remains unaltered with acclimation to laboratory conditions from field collection; iii) within a population, metabolic rate-temperature relationships are surprisingly invariant among physiological states such as age, gender, feeding status, pregnancy and temperature acclimation; iv) the magnitude of the effect of temperature acclimation differs among traits, in that upper thermal tolerances respond less than lower thermal tolerances, while metabolic rate responds to heat but not to cold. Water loss rate is relatively unresponsive to either treatment; v) plasticity can account for most inter-population variation in physiological traits related to climatic stress resistance (e.g. thermotolerances and desiccation rates) in the natural environment; vi) adult physiological performance responds differently to developmental and adult acclimation, such that marked traitspecific variation occurs, and combinations of both developmental and adult plasticity can result in further alteration of adult performance. These results have implications for the evolution of stress resistance to abiotic factors in these and other arthropods. I conclude by discussing the potential physiological patterns linking population dynamics and abiotic factors, with particular reference to tsetse flies. / AFRIKAANSE OPSOMMING: Binne arthropoda, is tussen-individu en tussen-bevolking variasie in die algemeen sleg bestudeer vir fisiologiese parameters. Hierdie fisiologiese variasie is belangrik want dit kan insig gee in die mate van evolusionêre aanpassing en hoe diere antropogenies klimaatsverandering kan hanteer. Dit is veral belangrik in die geval van insekte wat mens- en diersiektes kan dra, soos tsetse vlieë (Diptera, Glossinidae) wat trypanosome oordra. In die geval van tsetse vlieë (Glossina spp.) is voorspellings vir verhoogde verspreiding, en gevolglik verhoogde siekte voorkoms, gemaak onder toekomstige voorkoms klimaat senario’s. Verder, aangesien daar in die algemeen sterk verwantskappe tussen abiotiese parameters (bv. temperatuur en water beskikbaarheid), bevolkingsdynamika, verspreiding en voorkoms is, is die bepaling van die fisiologiese meganisme, wat ‘n invloed het op hierdie verwantskappe, nuttig vir die voorspelling van tsetse oor spasie en tyd. Hier, met hoofsaaklik die gebruik van Glossina spp., maar ook ander arthropoda wanneer dit nodig is, word navorsing wat fisiologiese variasie tussen individue en bevolkings aanspreel voorgelê. Spesifiek, word dit gewys dat i) metaboliese tempo is herhaalbaar (intra-klas korrelasie koeffisient) binne individue, alhowel metaboliese tempo kan beinvloed word deur faktore soos ouderdom, geslag, liggaamsmassa en swangerskap, ii) terwyl metaboliese tempo binne individue herhaalbaar is, verander dit nie met akklimasie na laboratorium toestande vanaf versameling in die veld, iii) binne ‘n bevolking metaboliese tempo-temperatuur verwantskappe is verbasend eenders tussen fisiologiese toestande soos ouderdom, geslag, voeding staat, swangerskap en temperatuur akklimasie, iv) die grootte van die effek van temperatuur akklimasie verskil tussen eienskappe, en die boonste termiese limiete reageer minder as laer termiese limiete, terwyl metaboliese tempo reageer op hitte maar nie koue nie, en waterverlies tempo is relatief terughoudend tot enige temperatuur toestand, v) buigbaarheid kan die meeste van inter-bevolkingsvariasie in fisiologiese eienskappe van klimaatstres weerstandsvermoë (termiese toleransie en uitdrogingstempo) in die natuurlike omgewing verklaar, vi) volwasse fisiologiese prestasie reageer verskillend op ontwikkelende en volwasse akklimasie, soveel dat eienskap-spesifieke variasie kan voorkom, en ‘n kombinasie van beide ontwikkelende en volwasse buigbaarheid ‘n verskillende volwasse prestasie tot gevolg kan hê. Hierdie resultate het implikasies vir die evolusie van weerstandsvermoë tot abiotiese faktore in hierdie en ander arthropoda. Hierdie tesis word afgesluit met ‘n bespreeking van die moontlikke fisiologiese patrone wat bevolkingsdinamika en abiotiese faktore kan verbind, met ‘n fokus op tsetse vlieë.

published_or_final_version / abstract / English / Doctoral / Doctor of Philosophy

On a depuis longtemps fait le constat de nombreuses variantes grammaticales en français (la négation avec et sans ne, SV(O) vs. la dislocation à gauche, etc.), les unes étant valorisées et les autres stigmatisées. Dans ce travail, on défend l'idée que l'on a affaire à une situation de diglossie. Cela suppose que les locuteurs intériorisent deux grammaires : l'une, le français démotique, est acquise " sur les genoux de la mère " et l'autre, le français classique tardif, est acquise à l'école et à travers les institutions qui exigent son emploi. On place cette problématique dans un cadre qui requiert l'étude des productions spontanées, l'abandon de l'opposition oral-écrit et de son caractère explicatif, et une transcription phonologique des données. À travers l'étude du nombre, de la négation, et des alternatives à SV(O), on montre l'intérêt descriptif et typologique de décrire deux grammaires. Chaque grammaire ainsi décrite est plus consistante. Enfin, une étude de corpus observe un locuteur diglosse, qui n'active bien qu'une grammaire à la fois : il mélange par exemple la dislocation à gauche avec la négation sans ne, mais jamais avec la négation avec ne.

The purpose of this study is to investigate how the teaching of mathematics is reflected in the students' understanding of the concept of the subtraction. The empirical data is based on observations in the classroom and student interviews. The understanding of the concept of the subtraction is shown through vocabulary and choice of examples and representations. The study used both qualitative methods and quantitative reports. The data is represented by one school and one classroom in grade three.  The theoretical framework is based on Liping Mas Subject Matter Knowledge and the variation theory of Marton and Booth and the relationship between these frameworks and concepts of variation, concretization, aids, subtraction and types of subtraction.  The results show that the impact of education is that subtraction is understood as the invers of addition. Complement and add to, is the type of strategy most frequently used, followed closely by the strategy remove and count down. The strategy compare is the least used. The observations in the classrooms shows several aspects and variations of the concept of the subtraction. Although the number line, and various forms of representation used in teaching has shown small effects of these aids in the students' own counting. The conclusions that can be drawn is that more and other metaphors and tools are needed in education to deepen students' understanding of the concept of the subtraction. They also need to be connected in the teaching. The language and the mathematical ideas discussed plays a critical role in the pupils’ acquisition of understanding.