The focus of this study is on the Foundation Phase mathematical and pedagogical knowledge construction. This study is about how two lecturers and a number of final year B.Ed. Foundation Phase student teachers construct Foundation Phase mathematical and pedagogical knowledge during the initial teacher education programme. The initial B.Ed. Foundation Phase teacher education provides student teachers with different mathematical knowledge for teaching. A Foundation Phase mathematics pedagogical knowledge construction framework was utilised to generate and analyse data. The Foundation Phase mathematics pedagogical knowledge construction framework is developed with the assumption that the integrated learning knowledge and the process of pedagogical reasoning action is a continuous process. Furthermore, it is assumed that student teachers’ active participation in their learning and paddling through the pedagogical reasoning action process, leads to the construction of Foundation Phase mathematical pedagogical knowledge. The study utilised a qualitative case study design to investigate how two initial teacher education programmes construct Foundation Phase mathematical pedagogical knowledge in their programme to prepare student teachers to teach Foundation Phase mathematics. Data were collected from Foundation Phase mathematics lecturers through semi-structured interviews, focus group interviews with final year Foundation Phase student teachers as well as document analysis from the institutions to achieve triangulation. Data analysis and findings were based on themes and categories that emerged. The findings suggest that Foundation Phase mathematical and pedagogical knowledge construction is an interconnected and continuous process that includes different types of knowledge and pedagogical reasoning. / Dissertation (MEd)--University of Pretoria, 2014. / tm2015 / Educational Psychology / MEd / Unrestricted

Zellen sind in der Lage, gleichzeitig ganz unterschiedliche biochemische Prozesse zu bewältigen. Dies gelingt ihnen durch eine Einteilung ihres Inneren in Kompartiemente, sogennante Organellen, die die jeweils geeignete biochemische Umgebung für die unterschiedlichen Aufgaben schaffen. Bei membranumschlossenen Kompartimenten ist leicht vorstellbar, dass sie eine andere biochemische Zusammensetzung als ihre Umgebung haben können. Jedoch existieren auch Organelle ohne Membran die durch eine flüssig-flüssig Phasenseparation entstehen. Manche dieser Kompartiemente haben die Fähigkeit, RNA zu binden und Proteinkomplexe auszubilden, während andere auf die Veränderungen innerhalb der Zelle, wie z.B. die Veränderung des pH-Werts und der damit Verbunden Änderung ihres Protonierungszustands, reagieren können. Um diese Prozesse theoretisch analysieren zu können, entwickeln wir zunächst ein allgemeingültiges, thermodynamisches Gerüst, um Systeme zu untersuchen, die im chemischen Gleichgewicht flüssig-flüssig hasensepariert vorliegen können. Dies erlaubt, basierend auf den Erhaltungsgrößen, im chemischen Gleichgewicht thermodynamisch konjungierten Variablen zu identifizieren, welche aus den erhaltenen Komponenten und den zugehörigen chemischen Potentialen bestehen. Mithilfe des obig erwähnten Gerüsts können wir den Einfluss des pH-Wertes auf die flüssig-flüssig Phasenseparation in einem minimalen Modell untersuchen. Dies beschreibt die makromolekulare Phasenseparation, kontrolliert durch Protonierungs- und Deprotonierungreaktionen, welche wiederum vom pH-Wert abhängig sind. Unsere Untersuchung der pH-Abhängigkeit der Phasenseparation kommt zu folgenden Ergebnissen: Erstens liegt die größte Region von Phasenseparation im Phasendiagramm typischerweise im Bereich des isoelektrischen Punkts. Zweitens zeigt das Modell eine Fähigkeit der erneuten Mischung auf. Drittens ist die Topologie des Phasendiagrams von der dominantesten Interaktion bestimmt. Unser Modell stimmt mit experimentellen Beobachtungen zur Phasenseparation von intrinsisch ungeordneten, Proteinen, deren Struktur sich pH abhängig verändern, überein. Das Modell ist außerdem konsistent mit Beobachtungen von Phasenseparation von Proteinen im Zytosol von Hefezellen, die entsteht, wenn der intrazellulare pH-Wert in die Nähe des isoelektrischen Punkt dieser Proteine gebracht wird. Des Weiteren geht diese Arbeit auf den physikalischen Mechanismus ein, mit dem flüssigkeitsähnliche Organellen, sog. P granules, im Organismus Caenorhabditis elegans positioniert werden. Um dieses Phänomen zu analysieren, stellen wir zunächst experimentelle Beobachtungen vor, die zeigen, dass PGL-3, eine Hauptkomponente der P granules, flüssigkeitsähnliche Tropfen bildet, deren Zusammensetzung von RNA moduliert werden kann. Darüber hinaus zeigen wir Daten, die großen Unterschiede zwischen der RNA-Bindungsaffinität von Proteinen wie Mex-5, die für die Positionierung der P granules relevant sind, und solchen, die P granules bilden, wie PGL-3, zeigen. Dies deutet darauf hin, dass eine Konkurrenz zwischen den Bestandteilen der P Granula und MEX-5 um die zur Bindung zur Verfügung stehende RNA besteht, die die Kondensation und Auflösung von P Granula räumlich kontrollieren könnte. Auf diesen experimentellen Befunden aufbauend führen wir ein minimalles Modell ein, in dem wir die Phasenseparation von PGL-3 an Bindungsreaktionen der MEX-5 Proteine und RNA koppeln. Um die experimentellen Beobachtungen beschreiben zu können, muss die Neigung des PGL-3 Proteins zur Phasenseparation zunehmen, wenn es Komplexe mit RNA bildet. Dies unterstützt die Idee, dass MEX-5 diese Phasenseparation unterdrückt, indem es die Anzahl an möglichen RNA-Bindungspartner für PGL-3 herabsetzt und damit die weitere Entstehung derartiger Protein-RNA-Komplexe erschwert. Dieser einfache Mechanismus scheint die Hauptursache dafür zu sein, dass P granules auf der posterioren Seite des Caenorhabditis elegans Embryos zu finden sind. / One of the main features of cells is their incredible ability to control biochemical processes in space and time. They do so by organizing their interior in sub-compartments called organelles, each of them with a different biochemical environment that allows them to perform specific tasks in the cell. It is sometimes believed that these compartments need a membrane in order to have a stable biochemical environment and regulat their compositions. However, there are some organelles which lack a membrane and seem to form and organize via liquid-liquid phase separation. Some of the components that form these membraneless organelles have the ability to bind to RNA and form complexes, while some others react to changes in the intracellular environment such as pH variations, which in turn affects their protonation state. In order to study these processes from a theoretical perspective, we develop a generic thermodynamic framework to study systems exhibiting liquid-liquid phase separation at chemical equilibrium. This framework, based on the use of conservation laws in chemical reactions, allow us to identify thermodynamic conjugate variables at chemical equilibrium, which are given by a set of conserved quantities and the corresponding conjugate chemical potentials. Within the aforementioned framework, we introduce a minimal model to study the effect of pH on liquid-liquid phase separation. Our model explains macromolecular phase separation controlled by protonation and deprotonation reactions, which are tuned by the pH of the system. We study the phase behavior of the system as a function of pH. Our main findings are: Firstly, the broadest region of phase separation is typically found at the isoelectric point. Secondly, the system exhibits reentrant behavior. Thirdly, that the dominating interaction in the system determines the topology of the phase diagrams. Our model is in agreement with experimental observations of in vitro protein phase separation of pH-responsive intrinsically disordered proteins, as well as with observations of protein phase separation exhibited by many cytosolic proteins when the intracellular pH in yeast cells is brought close to the isoelectric point of such proteins. Moreover, this work analyses the physical mechanism behind the positioning of liquid-like organelles in the {\it{Caenorhabditis elegans}} organism known as P granules. In order to study this phenomenon, we first present firm experimental evidence showing that PGL-3 protein, a key component of P granules, forms liquid-like drops whose assembly can be modulated by RNA. We then present data showing that the RNA-binding affinity differs significantly between proteins relevant for the positioning of P granules, such as MEX-5 and the proteins forming the P granules, like the aforementioned PGL-3. This points to a possible mechanism of RNA-binding competition between P granule constituents and MEX-5 in order to spatially control the condensation and dissolution of P granules. Based on the experimental evidence, we propose a minimal model in which we couple phase separation of PGL-3 to a set of binding reactions involving the MEX-5 protein and RNA. We find that in order to explain the experimental data, the tendency for phase separation of the PGL-3 protein increases with the formation of complexes of PGL-3 bound to RNA. This therefore supports the idea that MEX-5 inhibits this protein phase separation by depleting the RNA available for PGL-3 to form such complexes. This simple mechanism is at the core of how P granules localize to the posterior side of the Caenorhabditis elegans embryo.

La fibrillation auriculaire affecte un nombre grandissant d’individus chaque année et peut mener à de graves complications telles qu’un accident vasculaire cérébral. Une approche thérapeutique est la thermo- ou cryoablation par cathéter de zones tissulaires essentielles au maintien des épisodes de fibrillation. Une des cibles proposées pour l’ablation est le centre des rotors qui maintiennent l’arythmie en créant des réentrées stables. Ces rotors sont détectés à partir de signaux de cartographie électrique ou optique ou dans des simulations à l’aide du concept de singularité de phase (SP). L’analyse de ces SP donne une description de la dynamique de la fibrillation. Le suivi dans le temps (tracking) des SP a une importance critique pour calculer la durée de vie des rotors et leur stabilité. L’objectif du projet est donc d’améliorer les algorithmes de détection et de suivi des SP. Nous avons développé des modèles de tissus cardiaques 2D avec des hétérogénéités dynamiques (variations battement à battement), ionique (conductance des canaux potassiques), et structurelles (fibrose). Des épisodes de fibrillation ont été simulés dans ces modèles. Le script développé permet de suivre avec précision les SP de l’ensemble de simulations. La performance de cet algorithme varie en fonction de la complexité de la dynamique étudiée et du pas de temps utilisé pour faire le suivi. Une correction a posteriori et une simplification à partir d’un facteur de seuillage (τps = 15ms) permettent de mettre en évidence les rotors permanents avec une longue durée de vie. Cet algorithme permettra donc de faciliter les analyses de dynamique de fibrillation auriculaire en contexte de simulation sous la forme de feuillet tissulaire 2D. La méthode utilisée est aussi généralisable aux modèles 3-dimensionnels. / Atrial fibrillation affects a growing number of individuals each year. These patients are subject to severe complication such as AVCs if a treatment is not applied to their condition. One possible therapeutic approach is catheter ablation of the problematic tissue with heat or cold. This method targets fibrillation sources known as rotors. To allow for a more efficient and personalizable treatment, detection of such rotors is done through electrical or optical signal cartography. The resulting map of membrane potentials can then be used to find the center of the target rotors: phase singularities (PS). PS analysis allows a deeper understanding of AF dynamics. Moreover, tracking these reentries is essential for the evaluation of PS lifespan. The sources with longer the lifespans can be identified as stable and kept as possible candidates for ablative therapy. The projects objective is to improve PS detection and tracking algorithms We have developed 2D atrium models with dynamic (beat-to-beat variation), ionic (potassium channel conductance) and structural (fibrosis) heterogeneities. Episodes of atrial fibrillation were simulated for each model. The developed method allows for precise PS tracking for the simulated cases of AF. The error rate of the method is dependent of the temporal resolution and the complexity of the fibrillation dynamics. By applying a post-processing correction method and a threshold to the lower lifespan values ( ps = 15ms) it is possible to highlight longer lasting rotors that could be considered permanent when the temporal resolution is sufficiently low (dt = 0.1ms). The result of the following project allows for easier AF dynamics analysis for simulated 2D sheet cases. The method is theoretically applicable to 3D cases if the algorithm is adapted to such models.

Digitalization is changing most organizations and businesses in order to increase efficiency and improve safety. Within healthcare, different departments have specialized needs and therefore a myriad of different systems have been created, which has compromised interoperability. openEHR is a potential solution to this issue. It facilitates standardization of both data and clinical models which provides interoperability. This paper discusses the task of evaluating a new formbuilder based on openEHR, and the process of developing in this formbuilder. The perspectives of onboarding and information infrastructure are used in order to give insight into the challenges of such a new system. An autoethnographic method was conducted, which found three themes in the data: the formbuilder’s maturity, the uncertainties regarding the task and what sources of knowledge were used to complete the task. In the analysis, it was found that the formbuilder was in a deficiency of functionality, that the task’s objectives were often modified due to uncertainty and also the role of knowledge sources such as documentation and mentors was highlighted. In the discussion, a challenge found was having to gain users without functionality, but still provide enough functionality to show the formbuilder’s potential. A relationship between openEHR and the formbuilder was found, where the formbuilder has a potential to contribute with a positive network effect as new products adopt openEHR standards and gain users to their coherent solutions. The paper concludes that the onboarding process is resource-intense and it is important to facilitate learning as efficiently as possible in order to gain users. In the scope of the task, both onboarding and information infrastructure gave answers about the challenges of a system in a bootstrap phase, and worked well together in order to evaluate the formbuilder. / Digitaliseringen påverkar de flesta organisationer att öka sin effektivitet och förbättra dess säkerhet. Inom sjukvården har olika avdelningar specialiserade behov och därav har mängder av olika system skapats, vilket i sin tur påverkat deras interoperabilitet. openEHR är en potentiell lösning på det problemet. Det främjar standardisering av både data och kliniska modeller vilket leder till interoperabilitet. Denna uppsats diskuterar uppgiften av att utvärdera en ny formulärbyggare baserad på openEHR och processen av att utveckla inom formulärbyggaren. Onboarding och informations infrastruktur är två koncept som används för att ge insikter i utmaningarna som ett sådant system befinner sig i. En autoetnografisk metod användes, där tre teman identifierades i datan: formulärbyggarens mognad, osäkerheten kring uppgiften och kunskapskällorna som användes för att sluföra uppgiften. I analysen upptäcktes att formulärbyggaren saknade funktionalitet, att uppgiften ofta blev omskriven på grund av oklarheter och även kunskapskällor som dokumentation och mentorers roll belystes. I diskussionen påvisades att en utmaning var att få fler användare utan funktionalitet, men fortfarande ha tillräckligt för att påvisa systemets potential. En relation mellan openEHR och formulärbyggaren upptäcktes, där formulärbyggaren har en potential att bidra med positiva nätverkseffekter när nya produkter antar openEHR standarden och genererar användare till deras sammanhängande lösningar. Uppsatsen konstaterar att onboarding kräver mycket resurser och att det därför är viktigt att främja lärande så effektivt som möjligt för att locka användare. Inom ramen av uppgiften gav både onboarding och information infrastruktur svar om utmaningarna för ett nytt system i bootstrap fasen, och dessa koncept fungerade bra för att tillsammans utvärdera formulärbyggaren.

The random fluctuations of signal phase of an oscillator limit the precision of time and frequency measurements. The noise and long-term stability of the system’s oscillator or clock is of major importance in applications such as optical and wireless communications, high-speed digital electronics, radar, and astronomy. The Optoelectronic Oscillator (OE Oscillator), a new class of time delay oscillator with promise as a low-phase noise source of microwave carriers, was introduced by Steve Yao and Lute Malek in 1996. The OE Oscillator combines into a closed loop an RF photonic link and an RF chain. The RF photonic link consists of a laser, electro-optic modulator, optical fibre delay line, and a photo-receiver that together provide an RF delay. An RF chain consists of one or more amplifiers and a RF resonator that together provide the sustaining amplification and the frequency selectivity necessary for single mode oscillation of the loop. The low loss of optical fibres enables the attainment of delays that correspond to optical fibre lengths of several kilometers. It is the long delay, unattainable in an all electronic implementations that is responsible for the superior phase noise performance of an OE Oscillator. In this thesis the fundamental principles of operation of an OE Oscillator are described and the principal sources of in-loop phase fluctuations that are responsible for phase-noise identified. This lays the ground for an exposition of the mechanism that describes the perturbation of a time delay oscillator by injection into the loop of a carrier that is detuned in frequency from the natural frequency of the oscillator. For sufficiently small detuning the oscillator can become phase locked to the injected carrier. The model presented in the thesis generalises the traditional Yao-Maleki and Leeson model to include all the important features that describe the injection locking dynamics of an OE Oscillator. In particular the common assumptions of single mode oscillation and weak injection are removed. This is important to correctly predict the effect of injection locking on the spurious peaks in the phase noise spectrum corresponding to the side-modes of a time delay oscillator. Simulation results are presented in order to validate the dynamics of the oscillator under injection and analytic results on the lock-in range and phase noise spectrum. A 10 GHz OE Oscillator with a single 5km delay line is used as an example in the simulation illustration.

Nous avons étudié des méthodes de volumes finis pour la simulation numérique d'un flux impliquant deux phases incompressibles ou deux phases générales compressibles en déséquilibre mécanique. Les principales difficultés du régime où il y a une apparition de phase ou une disparition de phase est la singularité de la vitesse. Nous montrons que l'utilisation du l'entropie correction améliorer beaucoup ces problèmes. Enfin, nous simulons certains tests numériques importants pour vérifier les méthodes numériques, telles que la séparation de phase par gravité ou un canal bouillant. / We investigated some finite volume methods for the numerical simulation of a flow involving two incompressible phases or general two compressible phases in mechanical disequilibrium. The main difficulties of the regime where there is either a phase appearance or a phase disappearance is the singularity of the velocity. We show that using the entropy fix will much improve these problems. Finally, we perfom some important numerical tests to verify the numerical methods, such as a phase separation by gravity or a boiling channel.

No description available.

The rapid growth in additive manufacturing technologies have brought various optimization techniques and methodologies to improve each phase that needs to be integrated and analyzed on system level to optimize the system performance. The challenges and limitations of each phase affect the system when integrated as a whole - creating a complex manufacturing environment that needs to be critically examined and managed. To have a better management of complex, emergent, and uncertain manufacturing system from design to recycling phase, a new way of thinking based on more holistic approach is necessary. In this paper, the system of systems paradigm (SoS) is introduced to treat additive manufacturing system as a whole and to present some SoS approaches that are based on holistic thinking. This paper provides a conceptual knowledge of SoS approach using systems principles, laws and approach emphasizing the characteristics and attributes of complex manufacturing system to the AM domain.

No description available.

<p> This dissertation is concerned with establishing the conditions under which planar phase interfaces are morphologically unstable during phase transformations in isothermal ternary systems. First, linear perturbation methods are employed in a detailed treatment of precipitatematrix interface stability for dilute ternary systems. Following this, the stability of the planar interface in a two-phase ternary diffusion couple is examined with the aid of perturbation theory. An experimental investigation into the stability of <alpha>-<beta> phase interfaces in the Cu-Zn-Ni system at 775°C is described. The results of this experimental study are shown to be in good agreement with the earlier theoretical predictions. </p> / Thesis / Doctor of Philosophy (PhD)