The thesis addresses the influence of compressible effects on the stability of deflagration waves. Due to the quasi-isobaric nature of slow flames, compressible effects in laminar flames are usually neglected. Nevertheless, turbulent deflagrations may propagate at substantially higher speeds, suggesting that compressible effects may play a role in their dynamics. In the present thesis, the stability of diffusion-dominated high-speed deflagrations is addressed. The deflagration is studied in the thickened regime, hence addressing the long wavelength limit of these deflagrations. The deflagrations are modelled by the compressible reactive Navier-Stokes equations with a single-step Arrhenius reaction model. The 2D stability of the steady traveling-wave solution is studied by direct simulation. It is found that, as the flame compressibility becomes significant, not only does the growth rates of the cellular profile of the deflagration waves increase, but the traditional correlation of the burning velocity and the flame surface area become far less strong. Significant compression regions form in front of the nonlinear flames. These compression regions have been found to increase the growth rates by increasing the temperature of the unburned gas in front of the flames, as well as convecting the flame forward. The results show that the flame propagation velocity in references to the unburned gas was significantly faster than the burning velocity. The vorticity was given consideration, as the compressibility of flame increase one can expect the baroclinic source to be of greater significance. The vorticity was show to, in effect, increase as compressibility increases while unexpectedly having a stabilizing direction of rotation on the cellular structure of the flames.

A estabilidade do tronco é geralmente desafiada nas sessões do método Pilates. A compreensão da estabilidade/instabilidade, desafiada pela alteração de molas e dependente do nível de treinamento dos executantes, possui grande impacto no controle do tronco. Após uma revisão sistemática foi possível verificar que a principal técnica biomecânica empregada para compreender a estabilidade do tronco é a modelagem. Sendo assim, o objetivo deste estudo foi desenvolver e avaliar um modelo biomecânico para quantificar e comparar a estabilidade do tronco em dois diferentes níveis de praticantes de Pilates e em dois diferentes níveis de intensidade do exercício long stretch front do Pilates. O exercício long stretch front, criado para utilizar o powerhouse e desafiar a estabilidade do tronco, é executado no aparelho reformer na posição de prancha e consiste na extensão de ombros. O movimento foi modelado como um sistema massa-mola sendo a rigidez (K) o parâmetro de estabilidade do tronco. Como dados de entrada foram utilizadas informações cinemáticas, de câmeras infra-vermelho, cinéticas, de células de carga acopladas ao equipamento reformer, e informações antropométricas extraídas da literatura. Foram avaliados 15 praticantes avançados de Pilates e 15 iniciantes. Os indivíduos mais experientes foram mais estáveis durante o exercício do que iniciantes, F(1,28)=7,965; η2=0,22; p=0,009. A execução dos exercícios com duas molas apresentou menor rigidez do que com uma única mola, F(1,28)=67,891; η2=0,71; p<0,001. Não houve interação entre os fatores, F(1,28)=0,587; η2=0,02; p=0,450. Quando os grupos foram comparados separadamente para cada um dos níveis de dificuldade, os mais experientes (K = 272 ± 27 Nm/rad) apresentaram maior rigidez que os iniciantes (K = 171 ± 42 Nm/rad) com uma única mola, e também com o uso de duas molas, com K = 196 ± 17 Nm/rad para os executantes experientes e K = 108 ± 21 Nm/rad para os executantes iniciantes. Conclui-se que o modelo proposto, utilizando o coeficiente de rigidez, foi capaz de quantificar a estabilidade durante o exercício longh stretch front do Pilates. O modelo também identificou as diferenças entre indivíduos mais ou menos experientes, bem como quando o exercício é executado com uma ou com duas molas. / Trunk stability is usually challenged during Pilates method ’sessions. The stability/instability, generated by altering springs or by the practitioner’s experience level during a Pilates exercise, has great impact in trunk control. Following a systematic review, it was observed that modelling is the main biomechanical technique applied for understanding trunk stability. Hence, this study aimed to develop and evaluate a biomechanical model for quantifying and compare trunk stability in two different Pilates practitioners levels and two different intensities of the exercise during Pilates’ long stretch front exercise. The long stretch front exercise, created for using the powerhouse and challenging trunk stability, is performed in the reformer apparatus, keeping the trunk in the plunk position while shoulder extension is performed. The movement was modelled as a spring-mass system using stiffness (K) as the parameter to express trunk stability. Model input consisted of kinematics data, obtained from infrared cameras images, kinetic data, from load cells attached to the reformer equipment, and anthropometric data, obtained from literature. Fifteen experienced and 15 beginner Pilates practitioners, who performed ten repetitions of the exercise in two difficulty levels, with one and two springs, were evaluated. Experienced subjects were more stable during the exercise when compared to beginners F(1.28)=7.965; η2=0.22; p=0.009. The exercise performed using two springs presented a lower rigidity level when compared to one spring F(1.28)=67.891; η2=0.71; p<0.001. There was no interaction between the factors , F(1.28)=0.587; η2=0.02; p=0.450. When groups were compared separately for each difficulty level, experienced (K=272 ± 27 Nm.rad-1) presented higher rigidity than beginners (K=171 ± 42 Nm.rad-1) using one spring, and also using two springs with K=196 ± 17 Nm.rad-1 for experienced performers and K=108 ± 21 Nm.rad-1 for beginners. Concludes that the proposed model is capable of quantifying stability during the Pilates long stretch front exercise using rigidity coefficient. In addition model identifies differences between more or less experienced subjects, as well as when the exercise is performed using one or two springs.

In order to equally segregate their genetic material into daughter cells during mitosis, it is essential that chromosomes undergo major restructuring to facilitate compaction. However, the process of transforming diffuse, entangled interphase chromatin into discrete, highly organised chromosomal structures is extremely complex, and currently not completely understood. The complexes involved in chromatin compaction and sister chromatid decatenation in preparation for mitosis include condensins I and II. Mutations in condensin subunits have been identified in human tumours, reflecting the importance of accurate cell division in the prevention of aneuploidy and tumour formation. Most mutations described in TCGA (The Cancer Genome Atlas) and COSMIC (Catalogue of Somatic Mutations in Cancer) are missense, and therefore likely to only partially affect condensin function. Most functional genetic studies of condensin, however, have used loss of function systems, which typically cause severe chromosome segregation defects and cell death. Mice carrying global hypomorphic mutations within the kleisin subunit of the condensin II complex develop T cell lymphomas. The Caph2nes/nes mouse model is therefore a good system for understanding how condensin dysfunction can influence tumourigenesis. However, little is known about which cellular processes are affected in mutant cells before transformation. I therefore set out to use the Caph2nes/nes mouse model to study the consequences of the condensin II deficiency on cell cycle regulation in several different hematopoietic lineages. The Caph2nes/nes mice are viable and fertile, with no obvious abnormalities other than the thymus, which is drastically reduced in size. Previous studies reported greater than a hundred-fold reduction in the number of CD4+ CD8+ thymocytes. I set out to understand why the alteration of a ubiquitously expressed protein which functions in a fundamental cellular process would result in such a cell-type specific block in development. To achieve this, I investigated the possibility that condensin II is involved in interphase processes as well as in mitosis. In addition, I studied the aspects of T cell development that may make this lineage particularly vulnerable to condensin II deficiency. Finally, I carried out a preliminary investigation into the biochemical properties of the condensin complexes. During my PhD., I found strong evidence to suggest that the Caph2nes/nes T cell-specific phenotype arises due to abnormal cell division. However, I was unable to find any evidence to support the hypothesis that the phenotype is a consequence of abnormal interphase processes. Upon systematic analysis of several stages of hematopoietic differentiation, I found that at a specific stage of T cell development, the mutation results in an increased proportion of cells with abnormal ploidy, followed by a drastic reduction in cell numbers. Erythroid cells revealed a similar increase in the frequency of hyperdiploid cells, but no reduction in cell numbers. B cells and hematopoietic precursors did not reveal an increase in hyperdiploidy, or a reduction in cell numbers in wildtype relative to mutant. Subsequently, I found preliminary evidence to suggest that the T cell-specificity may be due to more rapid progression of CD4+ CD8+ T cells from S phase to M phase, relative to other hematopoietic stages. Finally, a preliminary investigation into the biochemical properties of the condensin complex revealed apparent imbalances in the expression of condensin subunits in T, B and erythroid cells. The sedimentation profile of CAP-H2 from whole-thymus extract did not exclude the possibility that condensin subunits might be forming heavier-weight complexes with non-SMC proteins. Further work must be carried out to determine whether this sedimentation pattern is unique to T cells.

Geophysical granular flows, such as snow avalanches, pyroclastic density currents, mudslides and debris flows, can be extremely hazardous to local populations, and understanding their complex behaviour remains an important challenge. This project aims to provide insight into these events by exploring different aspects in isolation, using a combination of mathematical theory, numerical simulations and small-scale experiments. Firstly, the effect of lateral confinement is examined by studying granular material moving in an inclined chute. This can have applications to natural releases flowing down confined valleys or conduits, and the relative simplicity of the geometry also provides a useful test case for new theoretical models. One such model is the recent depth-averaged μ(I)-rheology, which, because of the viscous terms introduced into the depth-averaged momentum balance, may be described as an intermediate approach between full constitutive laws and classical shallow-water-type equations for dense granular flows. Here, a generalisation of the new system to two spatial dimensions is described, and the resulting viscous equations are able to capture the cross-slope curvature of the downslope velocity profiles in steady uniform chute flows. This may be regarded as major progress compared to traditional hyperbolic models, which only admit constant velocity solutions. Particle size-segregation in geophysical granular flows is then investigated, which can cause important feedback on the overall bulk properties as it can lead to the development of regions with different frictional properties. A particularly striking example is segregation-induced 'finger' formation, where large particles are segregated to the flow surface and sheared to form a resistive coarse-rich front, which is unstable and spontaneously breaks down into a series of lobate structures. These travel both faster and further than one might anticipate. To model such segregation-mobility feedback effects, the depth-averaged μ(I)-rheology is extended to bidisperse flows by coupling with a depth-integrated model for size-segregation. The system of equations remains mathematically well-posed and is able to qualitatively capture finger formation, with the newly-introduced viscous terms controlling the characteristics of the leveed channels that develop. A more subtle segregation effect is studied in bidisperse roll waves, which form as small irregularities merge and coarsen as they move downslope, eventually growing into destructive large amplitude pulses. Experimental measurements show lateral, as well as vertical, segregation profiles, with the coarser grains accumulating at the fastest moving wave crests. The disturbances that form in mixtures with higher proportions of large particles grow more slowly, leading to smaller amplitude waves that travel at slower speeds, and the new coupled model predicts qualitatively similar behaviour. Finally, the influence of complex topography is investigated. A smooth two-dimensional bump is placed across the width of a chute, which, depending on the initial conditions, can lead to the formation of an airborne jet or granular shock at steady state. A simple depth-averaged model in a curvilinear coordinate system following the topography accurately captures both regimes, and represents a significant improvement on using an aligned Cartesian approach.

Este trabalho aborda o estudo da instabilidade lateral das vigas pré-moldadas durante o regime de serviço e durante a fase transitória. Na fase de serviço inclui os casos de apoios indeformáveis e deformáveis à torção. Para a fase transitória, o cálculo da carga crítica é desenvolvido para as diversas disposições dos cabos de içamento. O estudo do equilíbrio no espaço é realizado a partir da resolução das equações diferenciais regentes da instabilidade elástica. A resolução do sistema diferencial composto pelas equações acopladas da flexão lateral e da torção é realizada por vários métodos, incluindo o desenvolvimento e automatização do método numérico de Runge-Kutta, para algumas seções típicas. Apresentam-se ainda os procedimentos empíricos encontrados na literatura técnica, baseados em ensaios experimentais, para o cálculo dos fatores de segurança. Os resultados dos exemplos numéricos mostram que as situações de serviço não são, em geral críticas, ao contrário da fase transitória. Os exemplos mostram ainda que a suspensão com balanços é uma forma de diminuir os problemas de instabilidade lateral desta fase. / This work deals with the lateral stability of precast beams on service and during intermediate phase - handling and transportation. At service phase it is considered rigid and semi-rigid connections with torsion deformation. At handling phase, the critical load is evaluated for several positions of lifting cables. The study of the equilibrium conditions is done with the solution of the differential equation of elastic instability problem. The solution of flexural and torsional coupled equation is gotten by use of some methods, including the one developed and authomatized from the application of Runge-Kutta method, for certain sections. Empirical procedures are presented based on experimental tests, found in technical papers to compute fators of safety. The results of numerical examples show that the service situations are not generally critical, unlike the intermediate situations. The results show also that a possible way to avoid this problem is with the use of lifting points with a distance from the ends.

The primary aim of this thesis is to investigate the transition between different flow regimes in porous media. The complete transition spectrum of single-phase flow, from creeping flow to inertial, unsteady laminar, and turbulent flow regimes, was examined in sphere packings. Further understanding of the fundamental fluid dynamics was derived based on the pore-scale flow visualisation using magnetic resonance velocimetry (MRV). Spiral imaging was selected as the ultrafast imaging protocol to probe the transient phenomena, and the acquisition was further accelerated by combining subsampling and compressed sensing reconstruction. In a random sphere packing column with column-to-diameter ratio of 3.44, the inertial effect and the onset of unsteady regime were examined with respect to the principal flow characteristics: the inertial core/channeling, backflow, and helical vortices. Helical vortices have been observed experimentally in a random packing for the first time, and the analogy between the swirling flow and helical vortices provides insight into the design and operation of packed bed reactors. Another new observation is that the transition to the unsteady regime is a highly heterogeneous process, where the evolution of the flow instability depends on the pore geometry. Moreover, pixelwise validation was achieved between the experimental and simulation results on three-dimensional velocity fields in the inertial regime; this is enabled by an image-based meshing pipeline, which reproduces the geometry of the random packing in MRV for the numerical simulation. The unsteady regimes were further investigated using a regular sphere packing, the simple cubic packing (SCP). The spectral analysis, in both the random and regular packing, revealed a route to chaos from the steady to periodic, quasi-periodic, and chaotic dynamics, which was only predicted numerically before. During the transition to turbulence, the coherent structures were extracted using proper orthogonal decomposition (POD), which yields a coherent picture regarding the turbulent dynamics, when combined with the skewness, flatness, and quadrant analysis. Furthermore, it was found that the macroscopic properties converged at lower Reynolds number than the microscopic features. In conclusion, the opportunity to measure flow fields at high spatial and temporal resolution will play an increasingly significant role in the advancement of fundamental fluid dynamics. In this thesis, MRV is used, which is particularly advantageous for non-invasive measurements in opaque systems. This thesis provides the experimental and analysis toolkits for such studies and has demonstrated the contribution to characterising and understanding different flow regimes in porous media.

With 50,310 related deaths this year, colorectal cancer (CRC) has emerged as the second largest cause of cancer related deaths among Americans. While 70 million Americans are considered at-risk of developing CRC, it is highly curable if detected early. Cohesin proteins, which hold sister chromatids together during replication, have emerged as a potential biomarker in multiple cancer lines. Because of their probable role in DNA replication, DNA repair, chromatin nano-architecture, and gene expression, this paper assessed whether cohesion proteins could be used as a potential biomarker for colorectal cancer risk stratification. While cohesin protein mutations have been reported in different cancers and involved in chromosomal instability, its role in early cancer formation has yet to be observed. Using immunohistochemical and Quantitative Real Time PCR analysis, this thesis assessed the protein and RNA expression levels of cohesin proteins SA-1, NIPBL, and SMC3 from human biopsies at different stages and locations of colorectal cancer development. The results showed that SA-1, a structural cohesion subunit, was significantly (p<0.01) down regulated in cancerous compared to normal tissue. The SA-1 protein was also down regulated in the involved mucosa adjacent to CRC polyps. The cohesion loading protein, NIPBL, was also significantly (p<0.01) under expressed in cancerous versus normal tissue. The RNA expression analysis of rectal mucosa showed that SMC3 and SA-1 was over expressed two fold in patients harboring hyperplastic and adenomous polyps, giving evidence that cohesin proteins are differentially expressed throughout the field of carcinogenesis. Our results demonstrate for the first time that cohesion dysregulation is an early event in human colorectal cancer development and may serve as an important biomarker of field carcinogenesis.

This thesis consists of eight studies that cover topics in the increasingly influential field of futures- commodities, macroeconomic volatility and financial development. Chapter 2 considers the case of Argentina and provides a first thorough examination of the timing of the Argentine debacle. By applying a group of econometric tests for structural breaks on a range of GDP growth series over a period from 1886 to 2003 we conclude that there are two key dates in Argentina's economic history (1918 and 1948) that need to be inspected closely in order to further our understanding of the Argentine debacle. Chapters 3 and 4 investigated the time-varying link between financial development and economic growth. By employing the logistic smooth transition framework to annual data for Brazil covering the period 1890-2003 we found that financial development has a mixed (either positive or negative) time- varying effect on growth, which depends on trade openness thresholds. We also find a positive impact of trade openness on growth while a mainly negative one for the various political instability measures. Chapter 5 studied the convergence properties of inflation rates among the countries of the European Monetary Union over the period 1980-2013. By applying recently developed panel unit root/stationarity tests overall we are able to accept the stationarity hypothesis. Similarly, results from the univariate testing procedure indicated a mixed evidence in favour of convergence. Hence next we employ a clustering algorithm in the context of multivariate stationarity tests and we statistically detect three absolute convergence clubs in the pre-euro period, which consist of early accession countries. We also detect two separate clusters of early accession countries in the post-1997 period. For the rest of the countries/cases we find evidence of divergent behaviour. For robustness check we additionally employ a pairwise convergence Bayesian framework, which broadly confirms our findings. Finally, we show that in the presence of volatility spillovers and structural breaks time-varying persistence will be transmitted from the conditional variance to the conditional mean. Chapter 6 focuses on the negative consequences that the five years of austerity (2010-2014) imposed on the Greek economy and the society in general. To achieve that goal we summarize the views of three renowned economists, namely Paul De Grauwe, Paul Krugman and Joseph Stiglitz on the eurozone crisis as well as the Greek case. In support of their claims we provide solid evidence of the dramatic effects that the restrictive policies had on Greece. Chapter 7 analyzes the properties of inflation rates and their volatilities among five European countries over a period 1960-2003. Unlike to previous studies we investigate whether or not the infl ation rate and its volatility of each individual country displayed time-varying characteristics. By applying various power ARCH processes with structural breaks and with or without in-mean effects the results indicated that the conditional means, variances as well as the in-mean effect displayed time-varying behaviour. We also show that for France, Italy and Netherlands the in-mean effect is positive, whereas that of Austria and Denmark is negative. Chapter 8 examines the stochastic properties of different commodity time series during the recent fi nancial and EU sovereign debt crisis (1997-2013). By employing the Bai-Perron method we detect five breaks for each of the commodity returns (both in the mean and in the variance). The majority of the breaks are closely associated with the two aforementioned crises. Having obtained the breaks we estimated the power ARCH models for each commodity allowing the conditional means and variances to switch across the breakpoints. The results indicate overall that there is a time-varying behaviour of the conditional mean and variance parameters in the case of grains, energies and softs. In contrast, metals and soya complex show time-varying characteristics only in the conditional variance. Finally, conducting a forecasting analysis using spectral techniques (in both mapped and unmapped data) we find that the prices of corn remained almost stable while for wheat, heating oil, wti and orange juice the prices decreased further, though slightly. In the case of natural gas, coffee and sugar overall the prices experienced significant defl ationary pressures. As far as the prices of oats, platinum, rbob, cocoa, soybean, soymeal and soyoil is concerned, they showed an upward trend. Chapter 9 examines the effect of health and military expenditures, trade openness and political instability on output growth. By employing a pooled generalised least squares method for 19 NATO countries from 1993 to 2010 we fi nd that there is a negative impact of health and military expenditures, and political instability on economic growth whereas that of trade openness is positive.

Over the past few decades various models of different formats have been developed to correctly evaluate and predict the strength of materials. However, these models are limited in certain environmental conditions in implementing the effect of material's thickness into their models. As such an there was a need to consider the basics of mechanical engineering and to try and define the trend, thickness has upon the behaviour of materials with respect to environmental conditions. The work consisted of a representation of tensile testing testing of common engineering alloys across a wide range of temperature, strain rate and thickness. Acquisition of high strain rate data and extended strain data (split-hopkinson, bulge forming and plane strain compression). A review of existing graphical techniques and limited applications using strength reduction factors, as well as applying the accepted empirical formulae, Johnson-Cook, Armstrong-Zerrili, Ramberg-Osgood and Hollomon. Later, recognising a need for a new approach as with a universal (quartic) polynomial fit to all plastic flow curves in which coefficients are T, ε̇ and t̄ dependant. Adoptation of a common numerical procedure for strain intercept ε0 and cut-off instability co-ordinates (σi, εi)- each as the solution to the roots of a quartic. Therefore, a proposal of the flow curve tables allowing interpolation and extrapolation, a numerical representation of any previous "Atlas of Curves". Subsequently, leading to reconstruction of the full stress-strain curve with the addition of elastic strain calculated from the modulus applicable to the specific test condition by further testing of these data from literature; both improving the existing and producing new empirical and simulation based models to analyse the materials, which will be subjected to dynamic loading as well as temperature and strain rates variations. The main objective of the work, was involved in creating a polynomial fit to describe the three physical conditions in terms of coefficients and to verify the findings in a FEA package, ABAQUS. A new process in reading the stress-strain data. By means of such development an instability study of strain limits based on Considére criteria was developed which illustrated the ways to prolong the instability limit. A secondary study of this work relates to creating a bridge between the micro-structure and macro-structure of the tested materials. A series of correlations and trends were developed to further signify the shift in micro-structural restructuring, whilst the material is under load. Another important aspect of the work consists, of carrying out an analytical study on Ramberg-Osgood equation. Ramberg-Osgood equation has been at the forefront of many engineering advancement. However it can yet be improved and reformatted by means of defining a set value for its variable constants. As such a fix ƞt value based on a best-fit approach was developed which was analytically tested.

The two-phase flow displacement of a viscous fluid by a less viscous one in a confined environment leads to a viscous fingering instability commonly encountered in natural systems, for example, in flows through porous media or pulmonary airways. The classical study of viscous fingering has been conducted in rectangular channels of high aspect ratio (large channel width/height), known as Hele-Shaw channels where a unique, steady symmetric, semi-infinite bubble (finger) emerges. In this Journal Format thesis, the propagation of semi-infinite (open) and finite (closed) air bubbles is considered in Hele-Shaw channels where thin, axially-uniform occlusions are introduced. This configuration is known to generate symmetric, asymmetric and oscillatory modes with complex interactions and rich behaviour. Numerical results of finger propagation using a depth-averaged model in these constricted channels are found to be in quantitative agreement with experimental results once the aspect ratio reaches a value of $\alpha\geq40$ and capillary numbers below $Ca\leq 0.012$. The same evolution of the bifurcation scenario between multiple modes is found, however, it occurs for decreasing values of occlusion height as the value of aspect ratio is increased that the system exhibits sensitivity to small but finite depth-variations. The numerical simulations reveal multiple-tipped unstable symmetric solutions which interact with the single symmetric mode at vanishing occlusion heights resulting in stabilisation of the asymmetric and oscillatory modes. Moreover, deviations from the single symmetric mode are predicted when depth-variations of order of the roughness of the channel walls ($\sim 1$ $\mu$m) are introduced for larger aspect ratios of $\alpha\geq 155$. The propagation of finite bubbles is studied in a channel with constant aspect ratio of $\alpha=30$ and where the height of the occlusion, termed rail, is $1/40$ of the channel height. For bubble diameters of the order of the rail width, a tongue-shaped stability boundary for symmetric (on-rail) propagation is encountered so that for flow rates marginally larger than a critical value, a narrow band of bubble sizes can propagate (stably) over the rail while bubbles of other sizes segregate to the side of the rail. The numerical depth-averaged model is adapted for bubble propagation and captures in qualitative agreement the experimental observations. Time-dependent calculations are additionally performed, showing that on-rail bubble propagation is the result of a non-trivial dynamical interaction between capillary and viscous forces.