Dissertations / Theses on the topic 'Modelli formativi'

L’obiettivo della ricerca è quello di comprendere come si trasformano i processi formativi all’interno di quelli che oggi sono definiti come ecosistemi formativi. Il focus principale della ricerca riguarda la trasformazione dei modelli di formazione basati sul criterio della domanda-offerta a modelli più ibridi e negoziali e di knowledge management. La definizione degli oggetti della formazione, dei bisogni formativi e delle risposte formative messe in campo dalle organizzazioni si configurano sempre più come processi distribuiti basati sul principio della gestione condivisa delle sfide organizzative e del sapere piuttosto che su logiche lineari: definizione degli obiettivi, scelta dei metodi e valutazione finale. La ricerca si inserisce all’interno della tradizione di studi sulla sociomaterialità, utilizzando come cornice teorica la Teoria dell’attività storico-culturale (Engëstrom, 1987;1999; 2001; Fenwick, 2008; 2010; 2011). La ricerca muove da una analisi della letteratura sviluppando nella seconda parte dell’elaborato un’indagine empirica. Per discutere e comprendere le potenzialità e i limiti degli ecosistemi della formazione sono state studiate le Academy aziendali, in quanto esperienze in cui da anni si sono sedimentate esperienze innovative di gestione della formazione basate sulla collaborazione tra sistemi formali e non formali di formazione. La ricerca empirica qualitativa (Creswell, 2012; Silverman, 2008) ha utilizzato lo studio di caso (Creswell, 2012) analizzando in particolare una Academy aziendale di una organizzazione italiana medio-grande leader nel settore ICT. Il piano della ricerca ha previsto l’esplorazione delle pratiche di formazione all’interno dell’Academy attraverso un’analisi documentale e l’utilizzo di interviste semi-strutturate. Nelle riflessioni finali si discuterà alla luce dell’analisi condotta di tre aspetti principali: a) la natura emergente dei bisogni formativi e il loro sviluppo e riconoscimento come evento socialmente costruito, dipendente dal contesto storico- culturale in cui esso viene generato (Fabbri, 2021); b) la spinta degli ecosistemi a ripensare gli oggetti della formazione in chiave sistemica. Se è accertato che i modelli formativi sono spinti a configurarsi certamente come azioni per rispondere ai bisogni di innovazione strumentali e ai cambiamenti tecnologici o professionali delle persone, è altrettanto interessante vedere come questi modelli sembrano evolversi anche per rispondere a esigenze nuove: creare network, aumentare la reputazione organizzativa, produrre un sapere che possa essere riconosciuto come utile anche dagli stakeholders territoriali, unire lo sviluppo professionale alle strategie aziendali, generare conoscenza partendo dal coinvolgimento delle persone e delle comunità che abitano le organizzazioni; c) la transizione da bisogni formativi di natura professionale a quelli personali.<br>The aim of the research is to understand how training processes are being transformed within what are now defined as training ecosystems. The main focus of the research concerns the transformation of training models based on the demand-supply criterion to more hybrid, negotiated and knowledge management models. The definition of training objects, training needs and the training responses put in place by organisations are increasingly taking shape as distributed processes based on the principle of shared management of organisational challenges and knowledge rather than on linear logics: definition of objectives, choice of methods, final evaluation. The research is part of the tradition of sociomateriality studies, using cultural-historical activity theory as a theoretical framework (Engëstrom, 1987; 1999; 2001; Fenwick, 2008; 2010; 2011). The research starts from a literature analysis and develops an empirical investigation in the second part of the paper. In order to discuss and understand the potential and limits of training ecosystems, corporate academies were studied as experiences in which innovative training management experiences based on the collaboration between formal and non-formal training systems have been settled for years. Qualitative empirical research (Creswell, 2012; Silverman, 2008) used the case study (Creswell, 2012) analysing in particular a corporate Academy of a medium- large Italian organisation leader in the ICT sector. The research plan involved the exploration of training practices within the Academy through a documentary analysis and the use of semi-structured interviews. In the final reflections, three main aspects will be discussed in the light of the analysis conducted: a) the emergent nature of training needs and their development and recognition as a socially constructed event, dependent on the historical-cultural context in which it is generated (Fabbri, 2021); b) the drive of ecosystems to rethink the objects of training in a systemic key. If it is ascertained that training models are certainly driven to configure themselves as actions to respond to instrumental innovation needs and to people's technological or professional changes, it is equally interesting to see how these models also seem to evolve to respond to new needs: to create networks, to increase organisational reputation, to produce knowledge that can also be recognised as useful by territorial stakeholders, to unite professional development with corporate strategies, to generate knowledge starting from the involvement of people and the communities that inhabit organisations; c) The transition from professional to personal training needs.

This study is concerned with the mathematical modelling of the formation and subsequent evolution of sand dunes, both beneath rivers (fluvial) and in deserts (Aeolian). Dunes are observed in the environment in many different shapes and sizes; we begin by discussing qualitatively how and why the different forms exist. The most important aspect of a successful model is the relationship between the bed shape and the shear stress that the flow exerts on the bed. We first discuss a simple model for this stress applied to fluvial dunes, which is able to predict dune-like structures, but does not predict the instability of a flat bed which we would hope to find. We therefore go on to look at improved models for the shear stress based on theories of turbulent flow and asymptotic methods, using assumptions of either a constant eddy viscosity or a mixing length model for turbulence. Using these forms for the shear stress, along with sediment transport laws, we obtain partial integrodifferential equations for the evolution of the bed, and we study these numerically using spectral methods. One important feature of dunes which is not taken into account by the above models is that of the slip face - a region of constant slope on the downwind side of the dune. When a slip face is present, there is a discontinuity in the slope of the bed, and hence it is clear that flow separation will occur. Previous studies have modelled separated flow by heuristically describing the boundary of the separated region with a cubic or quintic polynomial which joins smoothly to the bed at each end. We recreate this polynomial form for the wake profile and demonstrate a method for including it into an evolution system for dunes. The resulting solutions show an isolated steady-state dune which propagates downstream. From the asymptotic framework developed earlier with a mixing length model for turbulence, we are able, using techniques of complex analysis, to model the shape of the wake region from a purely theoretical basis, rather than the heuristic one used previously. We obtain a Riemann-Hilbert problem for the wake profile, which can be solved using well-known techniques. We then use this method to calculate numerically the wake profile corresponding to a number of dune profiles. Further, we are able to find an exact solution to the wake profile problem in the case of a sinusoidally shaped dune with a slip face. Having found a method to calculate the shear stress exerted on the dune from the bed profile in the case of separated flow, we then use this improved estimate of the shear stress in an evolution system as before. In order to do this efficiently, we consider an alternative method for calculating the wake profile based on the spectral method used for solving the evolution system. We find that this system permits solutions describing an isolated dune with a slip face which propagates downstream without changing shape. All of the models described above are implemented in two spatial dimensions; the wind is assumed to blow in one direction only, and the dunes are assumed to be uniform in a direction perpendicular to the wind flow. While this is adequate to explain the behaviour of transverse dunes, other dune shapes such as linear dunes, barchans, and star dunes are by nature three-dimensional, so in order to study the behaviour of such dunes, the extension of the models to three dimensions is essential. While most of the governing equations generalize easily, it is less obvious how to extend the model for separated flow, due to its reliance on complex variables. We implement some three-dimensional evolution models, and discuss the possibility of modelling three-dimensional flow separation.

De konstnärliga högre utbildningarna med bild- och forminriktning har till övervägande del en studentsammansättning med kulturellt kapital1 hemifrån. För att hårdra betyder det att elever med litet ekonomisk, socialt eller kulturellt kapital inte söker estetiskt gymnasieprogram eller blir studenter på förberedande konstnärlig utbildning.Här ges en bild av hur villkoren ser ut på fältet och hur rekrytering till högre konstnärlig utbildning går till. Utbildningsanordnarna som intervjuas i undersökningen konstaterar den rådande sociala snedrekryteringen i Stockholm.En utbyggd användning av portfolio inom gymnasieskolan skulle kunna fungera som modell för att bryta den sociala snedrekryteringen. Portfoliomodellen ger elever och studenter utrymme att träna sig i självvärdering genom samlande och reflektion av egna alster. Att kunna värdera sig själv ger perspektiv och utvecklingsmöjligheter i förståelsen av sig själv som en del av ett större sammanhang, en helhet, en kultur. Genom de kriterier som innefattas av konstruktionen av portfolion, ges utmaning i att se nya möjligheter i sina framtida yrkes- och utbildningsval.<br>The education at an advanced level of Fine Arts is dominated by students with a cultural capital from their heritage2 In strong words this will mean that students with small economic, social or cultural capital won´t apply for aesthetic high schools or even become students in art schools.This degree thesis gives a picture of how the conditions look like in reality and how the recruitment to higher artistic education is conducted. The education organisers that were interviewed in the survey established that there is a prevailing social imbalance in Stockholm.A larger use of the portfolio in high-schools could stand as a model in order to break the prevailing social imbalance. The portfolio model gives each person the space, through collecting and reflection of their own material, to find and train in self evaluation. To be able to evaluate your own person it will give perspectives on his or hers development opportunities in the understanding of itself as a part of a bigger contexts, a whole, a culture. Through the criteria that are included of the structure of the portfolio, is given a challenge in seeing new possibilities in his or her future trade's - and educational choices.

The work presented in this thesis is primarily concerned with modelling the formation of secondary organic aerosols (SOAs). SOAs cannot easily be measured with direct analytical chemical methods; indirect methods like applying organic carbon to elemental carbon ratios and utilising computer models have been employed to provide an estimate of the SOA mass concentrations in ambient air. The five models presented in this work were either developed or assessed using environmental chamber data. Chamber experiments were undertaken using initial isoprene concentrations in the range of 22 ppb to 343 ppb, with the reactive organic carbon (ROC) to NOx ratios in the range of 2.0 to about 18. Chamber experiments were also performed for the a-pinene / NOx system with initial a-pinene concentrations ranging from 79 ppb to 225 ppb, with ROC/NOx ratios varying from 5.5 to about 41. All of the experiments were performed without the addition of propene or seed aerosol. Background aerosol levels were very low for the experiments presented in the thesis and so homogeneous nucleation processes were considered to occur in the chamber in addition to absorption and oligomerisation formation processes. Initial nucleation events resulting from the photooxidation of isoprene could be detected once the aerosol diameter was greater than 12 nm. In the a-pinene system,new particles formed via homogeneous nucleation processes were detectable in the 100-200nm diameter range. The models presented range in complexity from the near explicit Master Chemical Mechanism to an empirical model whose key feature is its simplicity. The mechanistic model provides an insight into the SOA formation pathways and the influence of varying the initial experimental conditions and the duration of photooxidation on the simulated SOA composition. The aim of the empirical model is to simulate the SOA mass concentration produced during a chamber experiment. The development of the model is intentionally simple so that it can be applied to any hydrocarbon and has been applied successfully to isoprene and a-pinene chamber experiments. In this way, the empirical model is presented as an alternative approach to predicting the temporal variation in SOA mass concentrations. An analysis of the partitioning absorption models developed by Odum et al. (1996) and Hoffmann et al. (1997) has informed the development of the SOA module which has been coupled to a 3D atmospheric model. Embodied within the SOA module is the gas / aerosol partitioning theory which includes the model proposed initially by Pankow et al. (1994) and by Odum et al. (1996).

Nella letteratura pedagogica contemporanea, il lavoro rappresenta una delle dimensioni maggiormente attraversate dai venti impetuosi del cambiamento: la discontinuità, la frammentazione, l’ibridazione, si configurano quali nuovi condizionamenti sociali e culturali che coinvolgono la stessa natura umana e il suo potenziale conoscitivo, influenzando in positivo o in negativo, il modo di pensare una pedagogia del lavoro tesa a progettare il futuro del soggetto-persona contemporaneo. In questo senso, appare chiara l’esigenza pedagogica di aprire la scuola alla vita concreta, di fare del lavoro manuale uno strumento per lo sviluppo integrale e integrato della persona. Pertanto, prende forma la nuova frontiera dell’alternanza formativa volta ad accompagnare il giovane studente nel percorso di ricerca vocazionale e professionale.<br>Contemporary pedagogical reflection can make assist in interpreting the connection between scholastic and working contexts. Its principal contribution is to underline reasons for the primacy of the person over the logic of profit, and also to promote the rediscovery of work as a typically human activity with value, functional to the achievement of a person s life goals. Hence the idea of a curriculum based on the alternation between school and the world, with reference to the spirit of initiative and entrepreneurship, and contributing to the integral formation of the person.

Under atmospheric blocking conditions, the normal passage of storms is interrupted by a region of high-pressure which remains lodged at the end of the storm tracks for periods of a week or more, causing the jet to split and the storms forced to pass around to the north and south, causing anomalous weather conditions over this high-pressure region. Being able to predict when these events occur, how long they will persist, and their eventual decay would be of value to improve weather prediction. This work looks at a simplified idealisation of this situation, with a view to improve understanding of any precursors to such events occurring and their subsequent behaviour. A 2-layer, <I>β</I>-plane, quasi-geostrophic channel model is used to examine the interactions between an upper-layer jet and high-frequency eddies supplied from a wavemaker in the lower layer. For certain initial jets, a dipole similar to an atmospheric block is formed, which remains stable to large-amplitude. By adding a shear to the upper-layer jet, a low-frequency vacillation cycle is induced, whereby the high-frequencies excite a split in the jet, which breaks down due to instability. This instability is demonstrated using a local instability analysis technique, and is also reflected in energy diagnostics. The role of the high-frequency eddies through the various phases of the cycle is also examined. A spherical-geometry model is also used with an aim to help bridge the gap between this highly-simplified model and the real atmosphere. These results suggest that the meridional shear in the upper-level atmospheric jetstream may determine whether blocking would develop, persist or breakdown. The structure of the upper-level jet could be controlled by seasonal variations or large-scale teleconnection patterns.

Remarkable progress has been made over the last few decades in furthering our understanding of the growth of cosmic structure. Nonetheless, there remains a great deal of uncertainty regarding the precise details of the complex baryonic physics that regulate galaxy formation. Any theory of star formation in galaxies must encompass the radiative cooling of gas into dark matter haloes, the formation of a turbulent, multiphase interstellar medium (ISM), the efficiency with which molecular gas is able to collapse into cores and ultimately stars, and the subsequent interaction of those stars with the gas through ionizing radiation, winds and supernova (SN) explosions. Given the highly non-linear nature of the problem, numerical simulations provide an invaluable tool with which to study galaxy formation. Yet, even with contemporary computational resources, the inherently large dynamical range of spatial scales that must be tackled makes the development of such models extremely challenging, inevitably leading to the adoption of `subgrid' approximations at some scale. In this thesis, I explore new methods of incorporating the physics of star formation and stellar feedback into high resolution hydrodynamic simulations of galaxies. I first describe a new implementation of star formation and SN feedback that I have developed for the state-of-the-art moving mesh code Arepo. I carry out a detailed study into various classes of subgrid SN feedback schemes commonly adopted in the literature, including injections of thermal and/or kinetic energy, two parametrizations of delayed cooling feedback and a 'mechanical' feedback scheme that injects the appropriate amount of momentum depending on the relevant scale of the SN remnant (SNR) resolved. All schemes make use of individually time-resolved SN events. Adopting isolated disk galaxy setups at different resolutions, with the highest resolution runs reasonably resolving the Sedov-Taylor phase of the SNR, I demonstrate that the mechanical scheme is the only physically well-posed method of those examined, is efficient at suppressing star formation, agrees well with the Kennicutt-Schmidt relation and leads to converged star formation rates and galaxy morphologies with increasing resolution without fine tuning any parameters. However, I find that it is difficult to produce outflows with high enough mass loading factors at all but the highest resolution. I discuss the various possible solutions to this effect, including improved modelling of star formation. Moving on to a more self-consistent setup, I carry out a suite of cosmological zoom-in simulations of low mass haloes at very high resolution, performed to z = 4, to investigate the ability of SN feedback models to produce realistic galaxies. The haloes are selected in a variety of environments, ranging from voids to crowded locations. In the majority of cases, SN feedback alone has little impact at early times even in low mass haloes ($\sim10^{10}\,\mathrm{M_\odot}$ at z = 0). This appears to be due largely to the build up of very dense gas prior to SN events, suggesting that other mechanisms (such as other stellar feedback processes) are required to regulate ISM properties before SNe occur. The effectiveness of the feedback also appears to be strongly dependent on the merger history of the halo. Finally, I describe a new scheme to drive turbulence in isolated galaxy setups. The turbulent structure of the ISM very likely regulates star formation efficiencies on small scales, as well as affecting the clustering of SNe. The large range of potential drivers of ISM turbulence are not fully understood and are, in any case, unlikely to arise ab initio in a whole galaxy simulation. I therefore neglect these details and adopt a highly idealised approach, artificially driving turbulence to produce an ISM structure of my choice. This enables me to study the effects of a given level of ISM turbulence on global galaxy properties, such as the fragmentation scale of the disk and the impact on SN feedback efficiencies. I demonstrate this technique in the context of simulations of isolated dwarfs, finding that moderate levels of turbulent driving in combination with SN feedback can produce a steady-state of star formation rates and global galaxy properties, rather than the extremely violent SN feedback that is produced by a rapidly fragmenting disk.

Nella letteratura pedagogica contemporanea, il lavoro rappresenta una delle dimensioni maggiormente attraversate dai venti impetuosi del cambiamento: la discontinuità, la frammentazione, l ibridazione, si configurano quali nuovi condizionamenti sociali e culturali che coinvolgono la stessa natura umana e il suo potenziale conoscitivo, influenzando in positivo o in negativo, il modo di pensare una pedagogia del lavoro tesa a progettare il futuro del soggetto-persona contemporaneo. In questo senso, appare chiara l esigenza pedagogica di aprire la scuola alla vita concreta, di fare del lavoro manuale uno strumento per lo sviluppo integrale e integrato della persona. Pertanto, prende forma la nuova frontiera dell alternanza formativa volta ad accompagnare il giovane studente nel percorso di ricerca vocazionale e professionale.

The accumulation of surface meltwater on ice shelves can lead to the formation of melt lakes. Melt lakes have been implicated in crevasse propagation and ice shelf collapse; the Larsen B ice shelf on the Antarctic Peninsula was observed to have a large amount of melt lakes present on its surface just before its collapse in 2002. Such collapse can affect ocean circulation and temperature, and cause a loss of habitat. Additionally, it can cause a loss of the buttressing effect that ice shelves can have on their tributary glaciers, thus allowing the glaciers to accelerate, contributing to sea level rise. We present results of a 1-D mathematical model of surface melt on an idealised ice shelf. The model incorporates a calculation of the surface energy balance of an ice shelf, heat transfer through the upper ice shelf, the production and percolation of meltwater into the firn, the formation of ice lenses in the firn and the formation, development and refreezing of surface melt lakes on the ice shelf. The melt lake model is applied to the Larsen C Ice Shelf, located on the Antarctic Peninsula, where melt lakes have been observed. The Antarctic Peninsula has warmed several times the global average over the last century and Larsen C has been suggested as a candidate for becoming fully saturated with meltwater by the end of the current century. When forced with automatic weather station data from Larsen C, our model produces surface melting, meltwater accumulation, melt lake development and refreezing consistent with current observations. We examine the sensitivity of lake formation to uncertain parameters, and provide evidence of the importance of processes such as the lateral transport of meltwater (and thus ice shelf topography) to the formation of surface lakes, a process without which lakes were not found to form. Furthermore, we investigate the impact on melt lakes and the surface energy balance of possible future atmospheric conditions.

The bone remodelling process, performed by the Bone Multicellular Unit (BMU) is a key multi-hierarchically regulated process, which provides and supports various functionality of bone tissue. It is also plays a critical role in bone disorders, as well as bone tissue healing following damage. Improved modelling of bone turnover processes could play a significant role in helping to understand the underlying cause of bone disorders and thus develop more effective treatment methods. Moreover, despite extensive research in the field of bone tissue engineering, bonescaffold development is still very empirical. The development of improved methods of modelling the bone remodelling process should help to develop new implant designs which encourage rapid osteointegration. There are a number of limitations with respect to previous research in the field of mathematical modelling of the bone remodelling process, including the absence of an osteocyte loop of regulation. It is within this context that this research presented in this thesis utilises a range of modelling methods to develop a framework for bone remodelling which can be used to improve treatment methods for bone disorders. The study concentrated on dynamic and steady state variables that in perspective can be used as constraints for optimisation problem considering bone remodelling or tissue remodelling with the help of the grafts/scaffolds.The cellular and combined allosteric-regulation approaches to modelling of bone turnover, based on the osteocyte loop of regulation, have been studied. Both approaches have been studied different within wide range of rate parameters. The approach to the model validation has been considered, including a statistical approach and parameter reduction approach. From a validation perspective the cellular class of modes is preferable since it has fewer parameters to validate. The optimal control framework for regulation of remodelling has been studied. Future work in to improve the models and their application to bone scaffold design applications have been considered. The study illustrates the complexity of formalisation of the metabolic processes and the relations between hierarchical subsystems in hard tissue where a relatively small number of cells are active. Different types/modes of behaviour have been found in the study: relaxational, periodical and chaotic modes. All of these types of behaviour can be found, in bone tissue. However, a chaotic or periodic modes are ones of the hardest to verify although a number of periodical phenomena have been observed empirically in bone and skeletal development. Implementation of the allosteric loop into cellular model damps other types of behaviour/modes. In this sense it improves the robustness, predictability and control of the system. The developed models represent a first step in a hierarchical model of bone tissue (system versus local effects). The limited autonomy of any organ or tissue implies differentiation on a regulatory level as well as physiological functions and metabolic differences. Implementation into the cellular phenomenological model of allosteric-like loop of regulation has been performed. The results show that the robustness of regulation can be inherited from the phenomenological model. An attempt to correlate the main bone disorders with different modes of behaviour has been undertaken using Paget’s disorder in bone, osteoporosis and some more general skeleton disorders which lead to periodical changes in bone mass, reported by some authors. However, additional studies are needed to make this hypothesis significant. The study has revealed a few interesting techniques. When studying a multidimensional phenomenon, as a bone tissue is, the visualisation and data reduction is important for analysis and interpretation of results. In the study two novel technical methods have been proposed. The first is the graphical matrix method to visualise/project the multidimensional phase space of variables into diagonal matrix of regular combination of two-dimensional graphs. This significantly simplifies the analysis and, in principle, makes it possible to visualise the phase space higher than three-dimensional. The second important technical development is the application of the Monte-Carlo method in combination with the regression method to study the character and stability of the equilibrium points of a dynamic system. The advantage of this method is that it enables the most influential parameters that affect the character and stability of the equilibrium point to be identified from a large number of the rate parameters/constants of the dynamic system. This makes the interpretation of parameters and conceptual verification of the model much easier.

Hydrate formation in oil and gas pipelines can be troublesome and often, without a proper remediation, the formation of hydrates can lead to a pipe blockage. As hydrate formation is a non-isothermal process, the modelling of the thermodynamic behaviour of the phases within the flow is proposed. A single energy equation has been formulated and verified with parametric analyses. A new hydrate kinetics routine, based on a two-step hydrate formation mechanism, in an oil-dominated flow is proposed. The first step involves the mass transfer of gas from the free gas phase into the oil (gas dissolution rate) and the second step is the mass transfer of the dissolved gas into the water (gas consumption rate). Suitable models in the form of transport equations for each mechanism, together with appropriate closure relations to account for the agglomeration of hydrate particles and hydrate slurry viscosity, are formulated. Both the energy equation and the hydrate kinetics routine were integrated into an existing in-house research code, TRIOMPH (Transient Implicit One-Dimensional Multiphase). The model was tested and validated against two flow loop experiments, and has shown good agreement. Advancement over the only other existing model in predicting hydrate formation in the heavily slugged hypothetical pipe, has also been shown, giving the current model versatility in simulating both slug and non-slug cases.

Acentrosomal microtubules are not bound to a microtubule organising centre yet are still able to form ordered arrays. Two clear examples of this behaviour are the acentrosomal apico-basal (side wall) array in epithelial cells and the parallel organisation of plant cortical microtubules. This research investigates their formation through mathematical modelling and Monte Carlo simulations with the software programs developed ourselves. In epithelial cells there is a generally accepted `release and capture' hypothesis for the transfer of centrosomal microtubules onto the side wall array. We use a combination of mathematical and Monte Carlo simulation models to perform the first modelling of this hypothesis. We find that a tubulin concentration dependent dynamic instability is not a good�fit to this hypothesis but that a reduced centrosomal nucleation rate in response to an increased number of side wall microtubules makes the hypothesis work in biologically reasonable conditions. We propose that the loss of nucleation rate is a result of ninein being transferred from the centrosome to the side wall. We show OpenCL to be a useful tool in building a simulation program for parameter searches. We use a Monte Carlo simulation model to investigate how the collision induced catastrophe (CIC) probability affects the formation of the ordered array of cortical plant microtubules. We find that with entrainment an ordered array stops forming once the CIC drops below 0.5. We�find that the severing action of katanin is able to restore order at CIC probabilities below 0.5 but the speed at which crossovers must be severed becomes unfeasibly fast as the CIC decreases. This implies that at very low CICs observed in nature (�0.1), katanin may be necessary but not suffi�cient to create the ordered array. We also provide a customisable and intuitive cortical microtubule simulation software to aid in further research.

The transformation from a single cell to the adult form is one of the remarkable wonders of nature. However, the fundamental mechanisms and interactions involved in this metamorphic change still remain elusive. Due to the complexity of the process, researchers have attempted to exploit simpler systems and, in particular, have focussed on the emergence of varied and spectacular patterns in nature. A number of mathematical models have been proposed to study this problem with one of the most well studied and prominent being the novel concept provided by A.M. Turing in 1952. Turing's simple yet elegant idea consisted of a system of interacting chemicals that reacted and di used such that, under certain conditions, spatial patterns can arise from near homogeneity. However, the implicit assumption that cells respond to respective chemical levels, di erentiating accordingly, is an oversimpli cation and may not capture the true extent of the biology. Here, we propose mathematical models that explicitly introduce cell dynamics into pattern formation mechanisms. The models presented are formulated based on Turing's classical mechanism and are used to gain insight into the signi cance and impact that cells may have in biological phenomena. The rst part of this work considers cell di erentiation and incorporates two conceptually di erent cell commitment processes: asymmetric precursor di erentiation and precursor speci cation. A variety of possible feedback mechanisms are considered with the results of direct activator upregulation suggesting a relaxation of the two species Turing Instability requirement of long range inhibition, short range activation. Moreover, the results also suggest that the type of feedback mechanism should be considered to explain observed biological results. In a separate model, cell signalling is investigated using a discrete mathematical model that is derived from Turing's classical continuous framework. Within this, two types of cell signalling are considered, namely autocrine and juxtacrine signalling, with both showing the attainability of a variety of wavelength patterns that are illustrated and explainable through individual cell activity levels of receptor, ligand and inhibitor. Together with the full system, a reduced two species system is investigated that permits a direct comparison to the classical activator-inhibitor model and the results produce pattern formation in systems considering both one and two di usible species together with an autocrine and/or juxtacrine signalling mechanism. Formulating the model in this way shows a greater applicability to biology with fundamental cell signalling and the interactions involved in Turing type patterning described using clear and concise variables.

Biofilms are matrix-producing communities of bacterial cells that adhere to surfaces and adopt a multicellular lifestyle. As the predominant life-form of bacteria (estimates suggest that 99% of all bacteria exist in biofilm communities), biofilms play a crucial role in the Earth’s ecosystems, where their existence is known to contribute both beneficial and detrimental effects. One of the defining characteristics of biofilms is heterogeneity in their structure. Indeed, it is commonly observed that biofilms of certain species of bacteria grown under certain conditions can display an unusual wrinkled structure, the pattern of which can vary at different locations throughout the biofilm. It is known that the type of wrinkle morphology displayed can be partially attributed to the expression of particular genes, which also have an effect on the mechanical properties observed in biofilms. Although the functions of wrinkles in biofilms, and the mechanisms controlling their formation, are not fully understood, it is believed that the presence of wrinkles enhances antimicrobial resistance (a property often associated with biofilms). In this thesis we investigate cellular processes and mechanical mechanisms that may contribute to biofilm wrinkle formation. Some emphasis is directed towards the development of wrinkling patterns in biofilms of the Bacillus subtilis bacterium. Particular focus on the role of cell death in initiating pattern formation is explored through the analysis and numerical simulations of mathematical models. In addition we investigate whether classical mathematical tools and techniques that were originally designed to be applied to non-biological structures, and which take into account the mechanical properties of materials, can be implemented and used to explain biofilm wrinkling patterns. Using a mixture of mathematical modelling, analysis and numerical simulations, we conclude that a model description that incorporates the interplay between both biological and mechanical effects may be a useful tool for gaining a better understanding of the biofilm wrinkling process, and thus in the future, may enhance our knowledge of how these complex communities function.

Understanding of basin-scale crater formation is limited; only a few examples of basin-scale craters exist and these are difficult to access. The approach adopted in this research was to numerically model basin-scale impacts with the aim of understanding the basin-forming process and basin structure. Research was divided into: (1) investigating early stage formation processes (impactor survivability), (2) investigating later stage formation processes (excavation and modification) and basin structure, and (3) constraining an impact scenario for the largest lunar crater, the South Pole-Aitken Basin. Various impact parameters were investigated, quantifying their effect on the basin-forming process. Simulations showed impactor survivability, the fraction of impactor remaining solid during the impact process, greatly increased if the impactor was prolate in shape (vertical length > horizontal length) rather than spherical. Low (≲15 km/s) impact velocities and low impact angles (≲30 ) also noticeably increased survivability. Lunar basin-scale simulations removed a significant volume of crustal material during impact, producing thinner post-impact crustal layers than those suggested by gravity-derived basin data. Most simulations formed large, predominantly mantle, melt pools; inclusion of a steep target thermal gradient and high internal temperatures greatly influenced melt volume production. Differences in crustal thickness between simulations and gravity-derived data could be accounted for by differentiation of the voluminous impact-generated melt pools, predicted by the simulations, into new crustal layers. Assuming differentiation occurs, simulation results were used to predict features such as transient crater size for a suite of lunar basins and tentatively suggest lunar thermal conditions during the basin-forming epoch. Additional simulations concerned the formation of the South Pole-Aitken Basin. By constraining simulation results to geochemical and gravity-derived basin data, a best-fit impact scenario for the South Pole-Aitken Basin was found.

Soot emission from hydrocarbon fuel combustion is a major source of particulate pollution. The increasingly stringent regulations on emissions have necessitated the developments of soot models to aid designs of combustion devices with cleaner performance. Such models will also make valuable contributions in designing and optimising processes that produce beneficial carbonaceous particulates, e.g. carbon black plants and processes requiring enhanced soot-induced radiation. The present work aims to develop a detailed soot model and implements the model in the sparse multiple mapping conditioning (MMC) - large eddy simulation (LES) framework to form a predictive tool for soot evolution in turbulent flames. The thesis consists of two major parts presenting soot evolution without and with turbulence, respectively. In the first part, the fundamental physics of soot evolution processes is presented, followed by a review of soot formation modelling that focuses on the sectional methods. The current work uses a sectional soot kinetics scheme that approximates solutions to the population balanced equations by lumped species and replaces individual growth/oxidation models by a sequence of equivalent physicochemical reactions with Arrhenius-like rate expression. The soot kinetics is a reduced version derived from a multisectional soot mechanism (Sirignano et al., Energy & Fuels 27, 2013). In this work, a novel generalised model describing the interaction potential well depth between soot particles of any size and composition is proposed for a thermal rebound based coagulation model to account for the probability of combining electrically neutral entities, i.e. nucleation, condensation and coagulation. The coagulation model is then simplified into Arrhenius expression so that the gas and soot kinetics can be integrated into a fully coupled system. The model is tested by comparisons to the experimental data of a series of ethylene burner stabilised stagnation (BSS) premixed flames and a methane laminar coflow diffusion flame, and the sensitivity to model parameters is investigated. Overall, the simulation results show good agreement with the experimental measurement, but strong sensitivity to the parameter λ that accounts for void fractions of soot particles is observed. In the second part, the turbulence and combustion models are reviewed. The focus is placed on the LES and MMC methods and the closure strategies in the methods. As the source terms of a lumped species reflecting different evolution processes are represented by a chemical source term in the sectional soot kinetics model, the filtered transport equation of lumped species can be straightforwardly closed by a joint filtered density function (FDF) of gas-phase species and lumped species. This work employs the sparse generalised MMC-LES, a stochastic FDF type method but uses much fewer notional particles (usually fewer than the number of LES cells) than the traditional FDF method. Combined with the code developments with some emphasis on computational load balancing models, the coupled turbulence-chemistry-soot model is shown to provide detailed soot evolution solutions, such as particle size distribution (PSD), with reasonable computational costs. The model is examined by comparison to the experimental data of the Delft Adelaide flame. Although discrepancies exist, the numerical predictions on soot volume fraction and intermittency are in reasonable accuracy. Detailed investigations on the probability density functions of the soot volume fraction show that the model captures the key features of soot formation but predicts significantly more soot in the range between 0.1 ppb and 6.4 ppb than the experimental measurements. Lastly, the predicted soot PSDs are presented. The results suggest that the PSDs in the turbulent flame simulation are in mixed unimodal and bimodal distributions.

Thesis (Ph.D.)--Texas A&M University, 2003.<br>"Major Subject: Aerospace Engineering" Title from author supplied metadata (record created on Jul. 18, 2005.) Vita. Abstract. Includes bibliographical references.

At present, the best model for the Universe as a whole is given by the so called ``Hot Big Bang'', which describes an expanding universe in which the density and temperature of matter and radiation are followed in time. The value of the parameters characterizing the observed universe is summarized by the concordance $\Lambda$CDM model, where CDM stands for Cold Dark Matter (the main matter component), and $\Lambda$ is the cosmological constant (some kind of unknown energy, with an anti-gravitational effect). According to this model, the universe is spatially flat (i.e. the density parameter $\Omega$ equals one), and 75\% of its energy balance is assigned to dark energy, about 20\% to dark matter and about 5\% to ordinary (baryonic) matter; the expansion speed assumes a value $H_{0}=70.5$ Km/s/Mpc (the Hubble parameter). The present dissertation focuses on the distribution of dark matter into virialized structures, called dark matter haloes. According to structure formation theory, cosmic structures originates from the amplification of quantum fluctuations during an early stage of accelerated expansion (cosmic inflation); these perturbations grow by self-gravity until they collapse and originate virialized structures. In the linear regime (when fluctuations are small), this process is well understood by the Jeans' theory. The non linear regime is much harder to describe; erlier attempts assumed a simple spherical simmetry, where the collapse is driven only by the internal density (e.g. Peebles, 1980); more recently (White \& Silk 1979; Bond \& Myers 1996) this hypothesis has been relaxed, and a more complex model was proposed in which proto-structures are described by triaxial ellipsoids, governed by their internal density and shape. Using the results coming from the dynamical analysis of the spherical collapse, and exploiting the statistical ``excursion sets formalism'', it is possible to obtain analytical information about the mass distribution of dark matter haloes. In this approach, for each particle in the universe, the trajectory describing the density evolution of a sphere of matter built around that particle is modeled as a random walk as a function of the mass $M$ within that sphere. When a trajectory crosses some pre-defined threshold, one assumes that a virialized structure of mass $M$ has formed. By considering all the particles in the universe one obtains analytical forms for the global mass function, and for the progenitor and descendant mass functions. From these it is possible to calculate other quantities, like the (instantaneous and integrated) rates of creation and destruction of dark matter haloes. In the 1990's the ellipsoidal collapse was first tried in order to find a better match with numerical simulations. However, partly due to the analytical complexity of the model, until now one can still not find in the literature analytical forms for e.g. the descendant and merger rate distributions (see Table \ref{tab:scec}). The main goal of this work is to provide such expressions for a number of statistics related to the mass distributions of dark matter haloes, striving to obtain simple and accurate formulas. In order to do so, we start from the statistical considerations by Sheth, Mo e Tormen (2001), who introduced the dynamical effects of the ellipsoidal collapse into the excursion sets formalism just by modifying the shape of the density threshold. Sheth and Tormen (2002) further suggested an new expression for the ellipsoidal global mass function, using a Taylor expansion series for the barrier: this expression allows one to also derive analytical formulas for the conditional mass functions. We obtain a set of models changing the order of this Taylor expansion, and considering the normalization of the distribution as a free parameter; we then compare these equations with the results of the cosmological simulation Gif2 (Gao et al. 2004) and, in some cases, with the Millennium Simulation (Springel et al. 2005). For the global and conditional mass functions the match between models and simulations is estimated using a $\chi ^2$-method. For the merger rates we compare the results qualitatively, whereas for the creation rates we only derived analytical results. We especially focus on the cases providing the simplest analytical expressions: the zero-order and the infinite-orders Taylor series. In the last part of the dissertation we propose a new statistical method that can overcome two inconvenients of $\chi ^2$-methods: (i) data binning and (ii) neglect of field particles (dust) in simulations. Concerning point (i), different bin-sizes can lead to small differences in the $\chi ^2$-results. As for point (ii), particles that are not bound to haloes are usually considered only for computing the normalization. By using a maximum likelihood analysis we can treat unbinned data, as well as take into account dust in the determination of the best parameters of the mass function. Our tests are performed by comparing a two-parameter mass function with results of Monte Carlo simulations. Our work naturally settles within the systematic search of analytical expressions associated to the ellipsoidal collapse of dark matter haloes. Since haloes are thought to be the sites where baryons can condense and form stars, galaxies and other luminous objects, the expression we derive can be used for a number of applications, ranging from unveiling the nature of dark matter through self-annihilation, to the understanding of the mechanisms leading to galaxy formation. Furthermore, the description of galaxy evolution requires knowledge on the hosting haloes: semi-analytical models of galaxy formation depend on the global mass function of the dark matter haloes, and the corrisponding merger-trees are based on the progenitor mass functions. The rates of creation and destruction are useful to compute the abundances of objects like Active Galactic Nuclei (AGNs) and Super Massive Black Holes (SMBHs). Many other examples can be found in the literature for the use of dark matter distributions in studies of galaxy formation. The structure of the dissertation is as follows: {\bf Chapters 1} justifies the need of dark matter. In {\bf Chapters 2} we present the concordance cosmological model, its geometry and thermal history. We also introduce the linear and non-linear models for the formation of dark matter haloes. {\bf Chapter 3} describes the excursion sets approach in the framework of the spherical collapse. The extension of this method to the ellipsoidal collapse is given in {\bf Chapter 4}, where the firsts analytical results are derived. In {\bf Chapter 5} we compare our analytical predictions to a number of results from numerical simulations. {\bf Chapter 6} is devoted to the new maximum likelihood tests with unbinned data and dust particles. We finally draw our {\bf Conclusions}, followed by one {\bf Appendix} where the numerical simulations are described.<br>La miglior descrizione dell'Universo, di cui si dispone al momento, è il modello del ``Big Bang Caldo'', che contempla un universo in espansione nel quale viene seguita l'evoluzione temporale della densità e della temperatura della materia e della radiazione. I parametri che caratterizzano l'Universo osservato sono riassunti in un modello chiamato $\Lambda$CDM di concordanza: CDM sta per Cold Dark Matter (la componente dominante della materia), e $\Lambda$ è la costante cosmologica (una sorta di energia oscura, con effetto anti-gravitazionale). Secondo questo modello, l'universo è spazialmente piatto (cioè il parametro di densità $\Omega$ è uguale a uno), e il $75\%$ del suo bilancio energetico è assegnato all'energia oscura, circa il $20\%$ alla materia oscura e circa il $5\%$ alla materia ordinaria (barioni); la velocità dell'espansione assume il valore $70.5$ Km/s/Mpc (parametro di Hubble). Questa tesi si sofferma sulla distribuzione della materia oscura in strutture virializzate, chiamate aloni di materia oscura. Secondo la teoria di formazione delle strutture, le strutture cosmiche hanno origine dall'amplificazione di fluttuazione quantistiche durante un periodo iniziale di espansione accelerata (inflazione cosmica); queste perturbazioni crescono per effetto dell'autogravità fino al collasso, creando delle strutture virializzate. Durante il regime lineare (quando le fluttuazioni sono piccole), questo processo è ben descritto dalla teoria di Jeans. Il regime non lineare è molto più difficile da descrivere; i primi tentativi assumono una simmetria sferica, per la quale il collasso è descritto solo dalla densità interna (es. Peebles, 1980); più recentemente (White \& Silk 1979; Bond \& Myers 1996) questa ipotesi è stata rilassata, ed è stato proposto un modello più complesso nel quale le protostrutture sono descritte da ellissoidi triassiali, regolati dalla loro densità interna e dalla loro forma. Utilizzando i risultati ottenuti dall'analisi dinamica del collasso sferico e sfruttando il formalismo statistico degli ``excursion set'', è possibile ottenere informazioni analitiche in merito alla distribuzione di massa degli aloni di materia oscura. In questo approccio, per ogni particella nell'universo, la traiettoria che descrive l'evoluzione della densità della sfera di materia costruita attorno a quella particella viene modellata come un cammino browniano come funzione della massa $M$ all'interno della sfera. Quando una traiettoria interseca una pre-definita soglia, si assume che venga a formarsi una struttura virializzata di massa $M$. Considerando tutte le particelle dell'universo, si ottengono forme analitiche per la funzione di massa globale, e per le funzioni di massa dei progenitori e dei figli. Da queste, è possibile calcolare altre quantità, come i tassi di creazione e distruzione (istantanei e integrati). Negli anni '90, il collasso ellissoidale è stato utilizzato per trovare un miglior accordo con le simulazioni numeriche. Tuttavia, in parte a causa della complessità analitica del modello, fino ad ora non è stato ancora possibile trovare in letteratura forme analitiche per esempio per la funzione dei figli o per i tassi di distruzione (vedi Tabella \ref{tab:scec}). l'obiettivo principale di questo lavoro è di fornire tali espressioni per una serie di funzioni legate alle distribuzione di massa degli aloni di materia oscura, aspirando ad ottenere delle formule semplici ed accurate. Per farlo, siamo partiti dalle considerazioni statistiche di Sheth, Mo e Tormen (2001) che introducono gli effetti dinamici del collasso ellissoidale nel formalismo excursion sets, modificando la forma della soglia di densità. Sheth e Tormen (2002), inoltre, propongono una nuova espressione per la funzione di massa globale ellissoidale, usando uno sviluppo in serie di Taylor per la barriera: questa espressione permette di derivare forme analitiche anche per le funzioni di massa condizionali. Abbiamo ottenuto un set di modelli cambiando l'ordine di questo sviluppo di Taylo, e considerando la normalizzazione delle distribuzioni come un parametro libero; abbiamo poi confrontato queste equazioni con i risultati della simulazione cosmologica Gif2 (Gao et al. 2004) e, in alcuni casi, con la Millennium Simulation (Springel et al. 2005). Per le funzioni di massa globale e condizionali, l'accordo tra modelli e simulazioni è stimato usando un metodo $\chi ^2$. Per i merger rates abbiamo confronti qualitativi, mentre per i tassi di creazione abbiamo derivato le sole equazioni analitiche. Ci siamo soffermati specialmente sui casi che forniscono le espressioni analiticamente più semplici: le serie di Taylor con zero ordini e con infiniti ordini. Nell'ultima parte della tesi, proponiamo un nuovo metodo statistico che può scartare gli inconvenienti dei metodi $\chi ^2$: (i) la divisione in intervalli dei dati e (ii) il trascurare le particelle di campo (polvere) delle simulazioni. Per quanto riguarda il punto (i), differenti ampiezze degli internalli di massa possono portare a piccole differenze nei risultati del $\chi^2$. Il punto (ii) si riferisce al fatto che le particelle che non sono legate in aloni sono di solito considerate solo per il calcolo della normalizzazione. Usando un'analisi di massima verosimiglianza, possiamo trattare dati non raggruppati in intervalli e considerare la polvere nella determinazione dei parametri migliori per la funzione di massa. I nostri tests sono condotti confrontando una funzione di massa a due parametri con i risultati di simulazioni Monte Carlo. Il nostro lavoro si inserisce naturalmente nella ricerca sistematica delle espressioni analitiche associate al collasso ellissoidale degli aloni di materia oscura. Poichè si pensa che gli aloni siano i siti ove i barioni possono concentrarsi e formare stelle, galassie ed altri oggetti luminosi, le espressioni che otteniamo possono essere usate in varie applicazioni, dallo svelare la natura della materia oscura attraverso l'auto annichilazione, fino alla comprensione dei meccanismi che portano alla formazione galattica. Inoltre, la descrizione dell'evoluzione galattica richiede la conoscenza dell'alone correlato: i modelli semi-analitici di formazione galattica dipendono dalla funzione di massa globale degli aloni di materia oscura, e i corrispondenti merger-trees sono basati sulle funzioni di massa dei progenitori. I tassi di creazione e distruzione sono utili per calcolare le abbondanze di oggetti come Nuclei Galattici Attivi (AGN) e Buchi Neri Super Massicci (SMBH). Altri esempi dell'utilizzo delle distribuzioni della materia oscura in studi di formazione galattica si possono trovare copiosi in letteratura.\\ L'elaborato si articola in questo modo: il {\bf Capitoli 1} giustifica la necessità della materia oscura. Nel {\bf Capitolo 2} presentiamo il modello cosmologico di concordanza, la sua geometria e la storia termica. Inoltre, introduciamo i modelli, lineare e non lineare, di formazione degli aloni di materia oscura. Il {\bf Capitolo 3} descrive l'approccio degli excursion sets nel contesto del collasso sferico. L'estensione di questo metodo al collasso ellissoidale è proposto nel {\bf Capitolo 4}, ove vengono esposti i primi risultati analitici. Nel {\bf Capitolo 5} confrontiamo le nostre predizioni analitiche con i risultati di due simulazioni numeriche. Il {\bf Capitolo 6} è dedicato all'esposizione dei test di un nuovo metodo di massima verosimiglianza con l'utilizzo di dati non raggruppati in intervalli e con le particelle di polvere. Infine tracciamo le nostre {\bf Conclusioni}, seguite da un'{\bf Appendice} ove sono descritte le simulazioni numeriche.

To date, bacterial resistance to antibiotics is an increasing problem and there is a growing appreciation that biofilm formation is a significant contributor to antibiotic resistance. This has led to .increased research on ways to reduce/control biofilm formation. One such target is bacterial cell-cell communication that allows bacteria to coordinate gene expression, and that has been shown to be involved in biofilm formation and production of virulence factors. By interfering with this communication system it should be possible to control gene expression and thus inhibit production of virulence factors as well as the formation of biofilms. However, these processes are multi-factorial, which make it a very complicated task to experimentally identify key parameters that subsequently could guide the development of cell-cell communication strategies to control bacterial virulence and biofilm formation. However, by using mathematical modelling, it is possible to study complex processes and to identify those parameters that are most important for these processes. The focus of this thesis was to develop mathematical models of bacterial cell-cell communication systems and biofilm formation to identify key parameters that could subsequently guide the development of cell-cell communication strategies to control bacterial virulence and biofilm formation. It was found that the cell-cell communication system in the model bacterium Pseudomonas aeruginosa works by hysteretic switching between two stable steady states, reflecting low and high rates of signal production, respectively. It was also shown that this bacterium uses different regulators to adjust the cell density required for switching the system on or off. Moreover, it was also demonstrated that signal antagonists have the capacity to switch the system from an induced state to the lower, uninduced state. However, it was also shown that this blocking behaviour is extremely dependent on the properties of the AHL antagonists, since even very small differences could greatly affect the outcome. Finally, accumulation of damage was predicted to be the main cause of cell death during the formation of biofilms. In addition, a strong relationship between nutrient availability and damage accumulation (and consequently cell death) was also found.

One of the most important contributions to flavour compounds in beer is that associated with the activity of yeast. A kinetic model that quantitatively predicts the influence of changing process parameters on yeast metabolism and the production of flavour compounds would be invaluable. However a review of the literature has revealed that there is an absence of good quantitative data on which to build a model. The literature uses a wide variety of yeast strains and undefined fermentation media. There is also very little quantitative analysis of flavour formation and the models that have been published have little physiological relevance. The aim of the present study was to develop a kinetic model that would describe the production of the higher alcohols, isoamylalcohol and isobutanol, by the yeast N.C.Y.C 1681 within a brewery fermentation system. H.P.L.C., G.C. and enzyme assay analytical methods were developed that allowed the determination of concentrations of pertinent medium components during a fermentation. Amino acid concentrations were determined using Pico-tag (P.I.T.C.) pre-column derivatisation chemistry. Beer volatile components were analysed using G.C. head space analytical procedures. Yeast growth was studied in experimental defined media and in the complex wort medium. The vessels of the study were stirred tank fermenters, tall tubes and brewery cylindroconicals. Higher alcohol production is intimately linked with the yeast populations amino acid metabolism. Thus the influence of medium nitrogen content was investigated in relation to catabolic and anabolic production of higher alcohols.

Since Lick indices were introduced in 1994, they have been used as a source of observational data against which computer models of galaxy evolution have been compared. However, as this thesis demonstrates, observed Lick indices lead to mathematical ill-conditioning: small variations in observations can lead to very large differences in population synthesis models attempting to recreate the observed values. As such, limited reliance should be placed on any results currently or historically in the literature purporting to give the star formation history of a galaxy, or group of galaxies, where this is deduced from Lick observations taken from a single instrument, without separate verification from at least one other source. Within these limitations, this thesis also constrains the star formation histories of 21 nearby elliptical galaxies, finding that they formed 13.26 +0.09 -0.06 Gyrs ago, that all mergers are dry, and that galactic winds are formed from AGN activity (rather than being supernovae-driven). This thesis also finds evidence to support the established galaxy-formation theory of “downsizing”. An existing galactic model from the literature is examined and evaluated, and the reasons for it being unable to establish star formation histories of individual galaxies are ascertained. A brand-new model is designed, developed, tested and used with two separate data sets, corroborated for 10 galaxies by data from a third source, and compared to results from a Single Stellar Population model from the literature, to model the star formation histories of nearby elliptical galaxies.

In this Thesis I present simulation- and theory-based studies of pattern formation and growth in collections of micro-organisms, in particular bacterial colonies. The aim of these studies is to introduce simple models of the 'micro-scale' behaviour of bacterial cells in order to study the emergent behaviour of large collections of them. To do this, computer simulations and theoretical techniques from statistical physics, and in particular non-equilibrium statistical physics, were used, as the systems under study are far from thermodynamic equilibrium, in common with most biological systems. Since the elements making up these sytems - the micro-organisms - are active, constantly transducing energy from their environment in order to move and grow, they can be viewed as `active matter' systems. First, I describe my work on a generalization of an archetypal model of active matter - the Vicsek model of flocking behaviour - in which the speed of motion of active particles depends on the local density of particles. Such an interaction had previously been shown to be responsible for some forms of pattern formation in bacterial colonies grown on agar plates in the laboratory. Simulations and theory demonstrated a variety of pattern formation in this system, and these results may be relevant to explaining behaviour observed in experiments done on collections of molecular motors and actin fibres. I then go on to describe work on modelling pattern formation and growth in bacterial biofilms - dense colonies of cells growing on top of solid surfaces. I introduce a simple simulation model for the growth of non-motile cells on a flat surface, whereby they move only by growing and pushing on each other as they grow. Such colonies have previously been observed experimentally to demonstrate a transition from round to 'branched' colonies, with a pattern similar to diffusion-limited aggregation. From these simulations and analytical modelling, a theory of the growth of such colonies is developed which is quite different from previous theories. For example, I find that the colony cannot grow at a constant speed if the cells are not compressible. Finally, I present some results on genetic drift and evolution in growing bacterial colonies. Genetic drift is greatly enhanced in colonies which are expanding in space, as only a few individuals at the edge of the population are able to pass on their genes onto their progeny. The individual-based simulations of biofilms described above are used to analyse which factors - such as the shape of the colony, the thickness of the growing layer of cells, and the interactions between the cells - affect the rate of genetic drift and the probability of fixation of beneficial mutations. This has implications, for example, for the evolution of antibiotic resistance in such colonies.

Orographic Rossby waves are the main mechanism by which the jet streams meander aroundthe Earth and have possibly far-reaching impacts on weather and climate (chapter 1). Hence,they are of particular importance to study and this project should serve as a starting point inwhat to consider when trying to model these waves. For example, we have to account forpressure gradients, Coriolis effect, orography, potential vorticity conservation and also Earth’scurvature at this scale. These are covered in detail in ch. 2 and adapted to the Shallow WaterEquations. In addition, some entry-level numerical techniques for solving these equations arepresented throughout ch. 2.4 and then implemented for the global-scale Shallow WaterEquations with conserved potential vorticity in ch. 3. The model is validated to work for typicalshallow water flows in a bath tub and passes common tests like the Gaussian curve test (ch.4.1). However, when considering atmospheric flows (ch. 4.2) it becomes evident that ourmodel, as well as our numerical methods are lacking and cannot reproduce Rossby waves ina stable manner. Hence, a heavily modified version of Hogan’s model (Hogan, n.d) isemployed with a simplified numerical scheme. With these corrections, orographic Rossbywaves appear to naturally form at appropriate locations. However, they do not fully exhibit theexpected behaviours discussed in ch. 2.2. Even Hogan’s model appears to have severelimitations as waves propagate in the wrong direction. Hence, this study is not complete andwarrants further development in order to be useful.<br>Orografiska Rossby-vågor är den huvudsakliga mekanismen genom vilken jetströmmarnaslingrar runt jorden och kan ha en omfattande inverkan på väder och klimat (kapitel 1). Därförär de av särskild betydelse att studera och detta projekt bör fungera som en utgångspunkt förvad man måste överväga när man försöker modellera dessa vågor. Till exempel så måste vi tahänsyn till tryckgradienter, Coriolis-effekten, orografi, potentiell vorticitetsbevarande och ävenjordens krökning på denna skala. Dessa beskrivs i detalj i kap. 2 och anpassas tillrörelseekvationerna för grunt vatten (Saint-Venant-ekvationerna). Därefter presenteras någranumeriska tekniker på grundläggande nivå för att lösa dessa ekvationer i kap. 2.4, varvid desedan implementeras för de globala Saint-Venant-ekvationerna med bevarad potentiellvorticitet i kap 3. Modellen är validerad för typiska grunda vattenflöden i ett badkar ochpasserar vanliga numeriska tester så som Gauss-kurvtestet (kap. 4.1) och bore-testet. Mennär vi överväger atmosfäriska flöden (kap. 4.2) blir det tydligt att våra modeller och numeriskametoder är primitiva och inte kan reproducera Rossby-vågor på ett stabilt sätt. Därmed,modifierar vi Hogans modell (Hogan, n.d) för att passa vår modell vilket resulterar orografiskaRossby-vågor. Dock så är dessa förskjutna och stämmer inte riktigt överens med teorin i kap.2.2. Även Hogans modell visar sig ha allvarliga begränsningar då vågorna propagerar i felriktning. Därmed är denna studie ej komplett och kräver ytterligare utveckling för att varaanvändbar.

Orientador: Prof. Dr. Marat Rafikov<br>Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Mecânica, 2017.<br>O presente trabalho trata do controle de multiplos robos moveis enquanto mantem uma formação, atraves do uso do metodo de controle State-Dependent Riccati Equation. Seis robos com chassi diferencial são utilizados em um esquema onde um é considerado o lider e os outros cinco são considerados seguidores. Alterando parametros de formação, este trabalho busca obter cinco formações diferentes: Triangular, Echelon, Linha, Coluna e Quadrangular. Um painel de controle foi criado e simulações foram feitas utilizando o software LabVIEW, demonstrando o sucesso da aplicação do metodo de controle no problema de rastreamento de robos moveis em formação. Este trabalho tambem propõe estrategias anti-colisão para prevenir choques tanto com obstaculos quanto com outros robos. Um algoritmo é criado e implementado com sucesso para evitar colisões.

During fracture healing, many complex and cryptic interactions occur between cells and bio-chemical molecules to bring about repair of damaged bone. In this thesis two mathematical models were developed, concerning the cellular differentiation of osteoblasts (bone forming cells) and the mineralisation of new bone tissue, allowing new insights into these processes. These models were mathematically analysed and simulated numerically, yielding results consistent with experimental data and highlighting the underlying pattern formation structure in these aspects of fracture healing.

The objective of this study is to examine the thermo-mechanical evolution of the Yorkshire(Cleveland), Sole Pit and East Midland Basins, Southern North Sea using theoretical models of basin formation(subsidence) and basin destruction(inversion).Subsidence occurs in response to a driving tectonic force and is amplified by the input of sediments, which impart a load on the Uthosphere. The form of subsidence varies depending on the degree of crustal and sub-crustal involvement. In order to isolate this driving tectonic subsidence the loading effect of the sediments is removed by backstripping. Intrinsic to the accurate modelling of basin formation using this method are firstly, the presence of a complete sedimentary sequence representing the maximum load on the basement and secondly, a normal and representative compaction trend. Subsidence in the Yorkshire, Sole Pit and East Midland Basins was terminated in the late Cretaceous-early Tertiary by inversion. This inversion is demonstrated to have been controlled by pre-existing structures and accommodated differentially within the Yorkshire and Sole Pit Basins in the form of basement uplift and shortening. A significant proportion of the sediments was removed by this uplift. This is quantified by studying compaction trends and is used to reconstruct the basin configuration prior to inversion to facilitate modelling of basin formation. The patterns of subsidence appear to conform well to those predicted by a model of simple lithospheric stretching with a rapid initial subsidence followed by more gentle thermal and flexural subsidence. Superimposed on this background subsidence are discrete events which appear to be related to periods of active faulting or increases in regional loading(eustatic). Subsidence, like inversion, occurs differentially within the fault bounded margins of the Yorkshire and Sole Pit Basins. The relationship between faults at different crustal levels is complicated by stress partitioning by Permo-Triassic salt horizons, yet it does appear that reactivation of Carboniferous and older structures has influenced the geological evolution of these basins.