Dissertations / Theses on the topic 'Instability'
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Trouvé, Arnaud. "Instabilités hydrodynamiques et instabilités de combustion de flammes turbulentes prémélangées." Châtenay-Malabry, Ecole centrale de Paris, 1989. http://www.theses.fr/1989ECAP0097.
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Etude des modes de combustion instable observes sur une maquette de statoréacteur ou l'instabilité est le résultat d'interactions complexes entre la dynamique de l'écoulement dans la zone de réaction, les processus de dégagement de chaleur et le comportement acoustique du système confine. Etude des modes hydrodynamiques au cours d'un régime de combustion stable
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Gryfe, Robert. "Colorectal cancer microsatellite instability." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ59033.pdf.
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Strefford, Jon C. "P53 and chromosome instability." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639125.
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This research project utilised methodologies from the fields of genetic toxicology and cytogenetic to accurately assess chromosome damage in p53-modified cell lines. Three primary diploid fibroblast cell lines were used; a control cell exhibited wild-type p53 characteristics, a mutant p53 cell line with a codon 143val-ala mutation, and a near null cell line containing transcripts for the E6 onco-fragments from the human papillomavirus type 16. These cell lines were characterised cytogenetically, and treated with genotoxic compounds so that the degree of chromosome damage could be assessed and correlated to p53 functional status. The mutant p53 plasmid induced significantly higher levels of spontaneous damage and premature centromeric division. After G1 and G2 chemical treatment, the E6 cell lines exhibited a significantly higher frequency of chromosome breakage, supporting the previous observations that p53 monitors these stages of the cell cycle. Chromosome painting and centromeric FISH for chromosome 1, 7 and 17 showed a shift towards abnormalities of chromosome 17 in the p53-modified cell lines. Post-treatment with a spindle poison, chromosome loss and non-disjunction were elevated in the p53 modified cell lines, implicating p53 as a monitoring protein in proper spindle formation. Treatment with Diazepam, showed ambiguous results, but suggested a limited role of p53 during centriole formation. This study demonstrated several p53-dependent monitoring capacities throughout cell cycle progression, several of which were novel observations. Premature centromeric division showed a clear correlation with changes in p53 functional status.
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Foreman, S. J. "Baroclinic instability and blocking." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354071.
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Wood, R. A. "Instability of oceanic fronts." Thesis, University of Exeter, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381309.
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Williamson, David. "Haemoglobin mutation and instability." Thesis, Open University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315297.
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Jomah, Adel M. "Instability in switching systems." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322593.
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BUFFONI, SALETE SOUZA DE OLIVEIRA. "PARAMETRIC INSTABILITY OF COLUMNS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2132@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORUNIVERSIDADE FEDERAL DO PARÁ
O presente trabalho tem por objetivo desenvolver uma formulação e certas estratégias que permitam a análise da perda de estabilidade de colunas esbeltas submetidas a carregamento axial periódico, fenômeno este conhecido como ressonância paramétrica. Uma excitação é dita paramétrica quando aparece nas equações de movimento do sistema na forma de coeficientes variáveis com o tempo - geralmente periódicos - e não como uma não homogeneidade. A coluna é descrita pela formulação clássica de Navier. O presente trabalho trata a coluna considerando-se um e três graus de liberdade com ou sem não-linearidades. As equações de movimento são obtidas utilizando-se o princípio de Hamilton através do método de Ritz. A equação linear (equação de Mathieu) e a equação de Duffing com pequeno amortecimento, são resolvidas de forma aproximada pelo método das múltiplas escalas, revelando a possibilidade de instabilização da posição de equilíbrio em diversas regiões do espaço definido pelos parâmetros de controle. A mesma conclusão é mostrada utilizando-se procedimentos computacionais para a resolução dos sistemas de equações lineares e nãolineares, com ou sem imperfeição geométrica inicial, podendo-se obter assim, a resposta do sistema, planos fase, seções de Poincaré e diagramas de bifurcação. Mostra-se a partir dos resultados numéricos, que a coluna submetida a cargas axiais harmônicas, pode tanto apresentar soluções com o mesmo período da força excitadora, quanto oscilações subarmônicas e superarmônicas de diversas ordens, além de movimentos caóticos.
The main aim of the present work is to develop a formulation and some strategies for the instability analysis of slender columns under an axial harmonic force this phenomenon is known as parametric ressonance. An excitation is said to be parametric if it appears as timedependent - often periodic - coefficients in the equations governing the motion of the system,and not as an inhomogeneous term.The column is described by Navier classical formulation. The present work consider the column with one or three degrees of freedom with or without nonlinearities. The equations governing the motion are obtained by the Ritz method.The linear equation (Mathieu equation) and the Duffing equation with small damping are solved in an approximate way using multiple scales techniques, revealing the possibility of destabilizing the static equilibrium position in certain regions of the control space. A similar conclusion is obtained by employing numerical methods for the solution of linear and nonlinear equation systems with or without initial geometrical imperfections.This enables one to obtain time response, phase space, projections Poincaré sections and bifurcation diagrams. These numerical results show that the column with nonlinearities and loaded by a periodic longitudinal force can present various solutions with the same period as the forcing and subharmonic e superharmonic oscillations, as well as chaotic motions.
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Hou, Hang-sheng. "Cavitation instability in solids." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13697.
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Miller, Ronald Lindsay. "Topics in shear instability." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/54962.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990.Includes bibliographical references.
by Ronald Lindsay Miller.
Viscous destabilization of stratified shear flow -- Organization of rainfall by an unstable jet aloft.
Ph.D.
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Andreoni, Federica. "SSB and genetic instability." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3993.
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Genome stability has great importance in maintaining cell viability and optimal functionality of cellular processes. Loss of genome stability can lead to cell death in the simplest organisms and to deregulation of the cell proliferation machinery in higher organisms, potentially causing cancer or morbid states. The Single Stranded DNA Binding (SSB) protein of Escherichia coli is an essential protein that binds and stabilises ssDNA stretches. Its role is particularly crucial during DNA replication, recombination and repair processes and it has therefore been predicted to play a prominent role in the maintenance of genome stability. The role of SSB in genome instability was investigated using an E. coli strain in which, the expression of the ssb gene was placed under the control of the arabinose promoter. The level of SSB protein present in the cell could therefore be tuned by varying the arabinose concentration in the medium. A wide characterisation of the behaviour of the strain at low SSB level was carried out. Viability and growth tests showed that a threshold level of protein is required to allow normal growth. Microscopy analyses were carried out to follow cell division, nucleoid morphology and SOS response activation. Cells grown at low SSB level, showed a phenotype consistent with impaired cell division and altered nucleoid morphology. The SOS response was activated at low SSB levels and cell elongation was detected. Lowering the arabinose concentration in solid medium allowed the selection of suppressor strains that could form colonies under the new conditions. Sequencing of the entire genome of one such suppressor strain was carried out revealing a possible candidate for the phenotype change. The stability of a 105bp and of a 246bp DNA imperfect palindromes and the stability of CAG·CTG trinucleotide repeat arrays, inserted in the E. coli chromosome, were investigated in correlation to the SSB cellular level. Lowering the SSB level in cells grown on solid medium, increased the instability of the 105bp palindrome presumably by increasing the number of slippage events. On the other hand, SSB overexpression did not have an effect on the stability of the 246bp palindrome. The stability of a leading strand (CAG)75 repeat array was highly increased by overexpressing SSB, while the same effect was not observed for a leading strand (CTG)137 repeat array. Furthermore, excess SSB caused a change in the deletion size distribution profile for the leading strand (CAG)75 strain, lowering the bias towards big deletions. This is consistent with SSB being able to preferentially impede the formation of big DNA hairpins. Also, SbcCD nuclease was shown to have an effect on the deletion size distribution profile of the leading strand (CTG)137 strain. The lack of SbcCD led to a slight reduction of the number of big deletions.
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Lai, Chi-hsuan. "Neutrino electron plasma instability /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Pieri, Alexandre. "Turbulence barocline : effets couplés de rotation, stratification et cisaillement." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00781602.
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La finalité de cette thèse est de fournir une meilleure compréhension de la turbulence homogène anisotrope soumise à un forçage barocline. À cette fin, nous utilisons une approche numérique pseudo-spectrale basée sur la transformation de Rogallo. L'utilisation d'un tel algorithme nous permet de considérer une asymétrie des fonctions de probabilité en faveur des évènements négatifs est observée. Le lien entre la distribution de vorticité potentielle et celle d'un scalaire passif est également étudié. Il est montré qu'à faible nombre de Richardson, c'est le mode vortex (à vorticité potentielle nulle) qui contient les plus importantes fuctuations de scalaire. Un écoulement homogène dans les trois directions de l'espace. Plusieurs simulations numériques directes (DNS) sont effectuées dans un contexte assez proche des écoulements géophysiques que l'on retrouve entre autre dans la stratosphère, où un gradient constant de vitesse zonale vient se coupler à un gradient constant de densité dans un repère tournant. Les résultats obtenus s'articulent autour de quatre axes principaux. Tout d'abord, une étude linéaire à temps fini est présentée en vue de compléter les résultats existants sur la dynamique linéaire asymptotique. La solution linéaire est décomposée en une partie 'onde' (qui se propage) et une partie dite 'vortex'(stationnaire). L'étude analytique est complétée par un modèle synthétique de turbulence (Kinematic Simulation ou KS) basé sur la théorie de la distorsion rapide(RDT). Nous montrons qu'une distribution initiale non nulle de vorticité potentielle linéarisée peut conduire à d'importantes croissances transitoires. Ce résultat pourrait s'étendre à des modélisations du climat ou météorologique, où la distribution initiale de vorticité potentielle semble avoir autant d'importance que la distribution initiale de température ou de vitesse. Ensuite, nous consacrons une partie de notre étude à l'analyse paramétrique et à la stabilité de l'écoulement. Plusieurs DNS sont effectuées pour différents taux de rotation et stratification. Le diagramme de stabilité obtenu montre que pour de faibles taux de rotation, la limite de stabilité est identique à celle connue des écoulements sans rotation. À plus faible nombre de Rossby -- lorsque la baroclinicité devient importante -- la limite linéaire de stabilité Ri = 1 relative à l'instabilité symétrique est confirmée. La coexistance de l'instabilité barocline avec l'instabilité symétrique est également clarifiée. Une analyse énergétique détaillée mène à la conclusion suivante : la stratification doit être suffisamment importante (Ri ' 1) pour que l'instabilité barocline soit dominante i.e. que la conversion d'énergie potentielle soit la source principale d'énergie cinétique turbulente. Dans le cas contraire, l'instabilité symétrique -- qui tire son énergie de l'énergie cinétique de l'écoulement moyen et non de son énergie potentielle -- domine la dynamique de l'écoulement. Le troisième axe d'étude concerne la turbulence à proprement parler. En conséquence de l'ajustement géostrophique, le vent thermique force la turbulence d'une manière naturelle, en opposition à d'autres méthodes de forçage stochastique. L'émergence de structures dans le contexte barocline est approfondie. Des statistiques Euleriennes sont présentées afin de fournir une caractérisation fine de l'anisotropie de l'écoulement. Enfin, nous étendons notre étude à la caractérisation de la vorticité potentielle turbulente. Les fonctions de probabilité de la vorticité potentielle d'Ertel montrent que des anomalies sont présentes dans les configurations instables. En particulier, une asymétrie des fonctions de probabilité en faveur des évènements négatifs est observée. Le lien entre la distribution de vorticité potentielle et celle d'un scalaire passif est également étudié. Il est montré qu'à faible nombre de Richardson, c'est le mode vortex (à vorticité potentielle nulle) qui contient les plus importantes fuctuations de scalaire.
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Wang, Chen. "Novel software tool for microsatellite instability classification and landscape of microsatellite instability in osteosarcoma." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1554829925088174.
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Schaefer, Rodrigo Gonçalves. "Global instability in Hamiltonian systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/620741.
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In Chapters 1 and 2 of this thesis, we prove that for any non-trivial perturbation depending on any two independent harmonics of a pendulum and a rotor there is global instability. The proof is based on the geometrical method and relies on the concrete computation of several scattering maps. A complete description of the different kinds of scattering maps takes place.
We separate the proof of the general system in two cases. The first one is studied in Chapter 1. There, a proof is given for the simplest perturbation function. Besides, we find out some very special diffusion orbits, called "highways", and we give estimates of the time of diffusion for these orbits. The second case is considered in Chapter 2, and the proof of diffusion is completed. In Chapter 2, the existence of piecewise smooth global scattering maps is also provided.
In Chapter 3, we consider a similar Hamiltonian with 3 degrees of freedom. We prove the diffusion using a combination of scattering maps and inner dynamics with concrete diffusion paths.We also compare the results obtained in this case with the results in Chapter 1.
Closing the thesis, we comment some open problems remained of the study that we have done along the three previous Chapters.Als Capítols 1 i 2 d'aquesta tesi es prova que per a una pertorbació no trivial depenent de dos harmònics qualsevol d'un pèndol i un rotor, hi ha inestabilitat global. La demostració es basa en el mètode geomètric i s'ha elaborat a través de computació concreta de diversos scattering maps. Es realitza una descripció completa dels diferents tipus de scattering map. La demostració del sistema general es divideix en dos casos. El primer és estudiat al Capítol 1, on es presenta una demostració per la funció de pertorbació més simple. A més a més, s'han observat algunes òrbites de difusió molt especials, anomenades "highways", i s'ha pogut fer estimacions sobre el temps de difusió d'aquestes òrbites. El segon cas és tractat al Capítol 2, en el que es completa la demostració de l'existència de difusió. Al Capítol 2, també s'estableix l'existència de "piecewise smooth global scattering maps". Al Capítol 3, es considera un Hamiltonià similar amb 3 graus de llibertat. S'ha provat la difusió utilitzant una combinació d'scattering maps i dinàmica interna amb camins de difusió concrets. Finalment, es comparen els resultats obtinguts en aquest cas amb els obtinguts al Capítol 1. Per a acabar, es comenten alguns problemes pertanyents a l'àmbit de la tesi, que seria interessant estudiar en futurs treballs
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Kreider, Rose M. "Interracial marriage and marital instability." Click to view the dissertation via Digital dissertation consortium, 1999.
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Ross, Julius. "Instability of polarised algebraic varieties." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/1250.
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By analogy with the definition for sheaves, we define the slope of a polarised algebraic variety and of each of its subschemes. This gives a notion of slope stability, which we show is a necessary condition for K-stability. We also give the modifications needed to get a necessary condition for asymptotic Chow stability. We then give various calculations of slope and concrete examples. These examples have been chosen to be of interest to the conjectured correspondence between K-stability and the existence of K¨ahler metrics of constant scalar curvature. In particular we get new examples of polarised manifolds that do not admit such metrics.
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Kim, Han Soo. "Aerodynamic instability of inclined cables." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/8976.
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A series of wind tunnel tests was conducted to investigate the existence of the galloping instability of inclined dry cables and also to identify the influence of some parameters on it. These parameters are the structural damping and cable surface roughness, which may have significant impact on the vibration characteristics. The test results showed both the divergent type of galloping instability and the limited amplitude high wind speed vortex shedding excitation. Galloping instability was observed in only one case. Parametric study shows that the vortex shedding oscillation can be easily suppressed with an increase of the structural damping. It was also shown that the instability criterion indicated by earlier research was too conservative compared to the results obtained from the present study.
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Murray, John. "Instability in the human genome." Thesis, University of Leicester, 1998. http://hdl.handle.net/2381/30309.
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The DNA flanking hypervariable minisatellite MS32 was sequenced and searched for polymorphisms. The polymorphisms found were used in recombination analysis by A.J. Jefferys which described the recombination hotspot immediately flanking MS32, and responsible for the polarity of mutation observed within the repeat array. It became apparent that gene conversion and crossover processes at the locus were probably initiated in the same manner. Comparative analysis of the sequence flanking MS32, MS31 and CEB1 revealed all were situated in an environment rich in dispersed repeats and other repetitive DNA. Other minisatellites are not clustered near MS32, probably reflecting its interstitial location. Evidence suggested the existence of two diverged genes flanking CEB1. No candidates for a conserved sequence element acting as a cis-acting mutation initiator were found. No unusual conserved secondary DNA structures were found. No apparent association between base composition and hypervariability was found. Double-stand breaks which might play a role as recombination intermediates were detectable in DNA prepared from human testis tissue, but the possibility that they were artifacts could not be eliminated. Gel shift assays identified a complex, partly double-strand specific binding activity with preference for sequence including the OIG/C polymorphism which is associated with variations in the mutation rate at the minisatellite MS32; but it proved extremely difficult to purify for further analysis.
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Coleman, Mark Giles. "Genomic instability in colorectal carcinoma." Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/29371.
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Microsatellite instability (MSI) in colorectal tumours is demonstrated by PCR amplification of several different microsatellite loci. Minisatellites, which are repeats of longer sequences also found throughout the genome, may also be affected by tumorigenesis. Certain minisatellite alleles contain 2 types of similar repeat unit that are randomly interspersed. The interspersion pattern can be analysed by mapping variant repeat units along an amplified allele, minisatellite variant repeat unit mapping PCR (MVR-PCR). We have applied microsatellite analysis with ten markers and MVR-PCR for locus D7S21 to 33 cases of colorectal neoplasia, 27 sporadic and 6 from patients suspected of having hereditary non-polyposis colorectal cancer (HNPCC). Of the 27 sporadic cases, 3 were MSI-high on microsatellite analysis and one MSI-low. Features such as band loss on PCR product amplification suggesting instability were seen with MVR-PCR only for the MSI-high cases. Four of the HNPCC patients had mismatch repair (MMR) gene mutations proven by sequencing (hMLHl and hMSH2). All 4 had DNA instability by MVR-PCR, but only two of these had MSI (one high, one low). The other two were negative to mutation analysis. One was from an Amsterdam criteria positive kindred but did not demonstrate instability by any technique. The other had features strongly suggestive of HNPCC and was unstable by both microsatellite analysis (MSI-high) and by MVR-PCR. MVR-PCR detects DNA instability in MSI-high sporadic tumours and in those associated with HNPCC where MSI is observed. Further, in some MMR mutation positive cases MSI was not seen but instability was observed by MVR-PCR. MVR-PCR may be a valuable adjunct to the detection of MMR deficiency in colorectal tumours and it may allow new insights into the nature of DNA instability in this situation.
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Salmeron, Raquel. "Magnetorotational Instability in Protostellar Discs." Physics, 2005. http://hdl.handle.net/2123/919.
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Doctor of PhilosophyWe investigate the linear growth and vertical structure of the magnetorotational instability (MRI) in weakly ionised, stratified accretion discs. The magnetic field is initially vertical and perturbations have vertical wavevectors only. Solutions are obtained at representative radial locations from the central protostar for different choices of the initial magnetic field strength, sources of ionisation, disc structure and configuration of the conductivity tensor. The MRI is active over a wide range of magnetic field strengths and fluid conditions in low conductivity discs. For the minimum-mass solar nebula model, incorporating cosmic ray and x-ray ionisation and assuming that charges are carried by ions and electrons only, perturbations grow at 1 AU for B < 8G. For a significant subset of these strengths (200mG < B < 5 G), the growth rate is of order the ideal MHD rate (0.75 Omega). Hall conductivity modifies the structure and growth rate of global unstable modes at 1 AU for all magnetic field strengths that support MRI. As a result, at this radius, modes obtained with a full conductivity tensor grow faster and are active over a more extended cross-section of the disc, than perturbations in the ambipolar diffusion limit. For relatively strong fields (e.g. B > 200 mG), ambipolar diffusion alters the envelope shapes of the unstable modes, which peak at an intermediate height, instead of being mostly flat as modes in the Hall limit are in this region of parameter space. Similarly, when cosmic rays are assumed to be excluded from the disc by the winds emitted by the magnetically active protostar, unstable modes grow at this radius for B < 2 G. For strong fields, perturbations exhibit a kink at the height where x-ray ionisation becomes active. Finally, for R = 5 AU (10 AU), unstable modes exist for B < 800 mG (B < 250 mG) and the maximum growth rate is close to the ideal-MHD rate for 20 mG < B < 500 mG (2 mG < B < 50 mG). Similarly, perturbations incorporating Hall conductivity have a higher wavenumber and grow faster than solutions in the ambipolar diffusion limit for B < 100 mG (B < 10 mG). Unstable modes grow even at the midplane for B > 100 mG (B ~ 1 mG), but for weaker fields, a small dead region exists. When a population of 0.1 um grains is assumed to be present, perturbations grow at 10 AU for B < 10 mG. We estimate that the figure for R = 1 AU would be of order 400 mG. We conclude that, despite the low magnetic coupling, the magnetic field is dynamically important for a large range of fluid conditions and field strengths in protostellar discs. An example of such magnetic activity is the generation of MRI unstable modes, which are supported at 1 AU for field strengths up to a few gauss. Hall diffusion largely determines the structure and growth rate of these perturbations for all studied radii. At radii of order 1 AU, in particular, it is crucial to incorporate the full conductivity tensor in the analysis of this instability, and more generally, in studies of the dynamics of astrophysical discs.
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Rebentisch, Eric. "Preliminary Observations on Program Instability." Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/7331.
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This white paper reports emerging findings at the end of Phase I of the Lean Aircraft Initiative in the Policy focus group area. Specifically, it provides details about research on program instability. Its objective is to discuss high-level findings detailing: 1) the relative contribution of different factors to a program’s overall instability; 2) the cost impact of program instability on acquisition programs; and 3) some strategies recommended by program managers for overcoming and/or mitigating the negative effects of program instability on their programs. Because this report comes as this research is underway, this is not meant to be a definitive document on the subject. Rather, is it anticipated that this research may potentially produce a number of reports on program instability-related topics. The government managers of military acquisition programs rated annual budget or production rate changes, changes in requirements, and technical difficulties as the three top contributors, respectively, to program instability. When asked to partition actual variance in their program’s planned cost and schedule to each of these factors, it was found that the combined effects of unplanned budget and requirement changes accounted for 5.2% annual cost growth and 20% total program schedule slip. At a rate of approximately 5% annual cost growth from these factors, it is easy to see that even conservative estimates of the cost benefits to be gained from acquisition reforms and process improvements can quickly be eclipsed by the added cost associated with program instability. Program management practices involving the integration of stakeholders from throughout the value chain into the decision making process were rated the most effective at avoiding program instability. The use of advanced information technologies was rated the most effective at mitigating the negative impact of program instability.
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Valkhoff, Nienke Jeltje Marjoke. "Stabilization by competing instability mechanisms." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2006. http://dare.uva.nl/document/37776.
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Brown, Cathleen N. Guskiewicz Kevin M. "Factors contributing to ankle instability." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,272.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Interdisciplinary Human Movement Science (School of Medicine)." Discipline: Human Movement Science; Department/School: Medicine.
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Spotton, Brenda L. (Brenda Lynn). "A study of financial instability." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41138.
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This study is a theoretical and historical study of the combined issues of destabilizing speculation and financial crises. First, we critically examine the orthodox mathematical theory of a speculative bubble. This model, we determine, is inadequate for the empirical purposes of identifying and fully explaining a bubble. Next, we examine the 19th-century British Classical view of the mania-crisis phenomenon and compare it with some of the leading early 20th-century views. We find that the 20th-century writers maintained a distinctly Classical view of the issues and that this view is fundamentally different from the orthodox mathematical theory. We also find that the Classical theory, though richer than the mathematical theory, inadequately explains the phenomenon. We then turn to a comparative history of selected mania-crisis episodes. From a detailed analysis of these episodes, we establish those stylized facts which characterize unstable periods of financial activity. We complete the study with a new perspective on financial instability.
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Mitmaker, Elliot. "Microsatellite instability in thyroid neoplasia." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101730.
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Micro satellite instability (MSI) is a form of genomic instability that has recently been implicated in the pathogenesis of thyroid cancer. The purpose of this study is to further define the distribution of microsatellite instability in both normal and neoplastic thyroid follicular epithelium.Using laser capture microdissection, cells from both normal and tumor tissue were individually collected. PCR amplification of the DNA was then performed using six dinucleotide and two mononucleotide microsatellite markers.
Forty benign and malignant thyroid tumors were compared with their adjacent normal thyroid follicular tissue and were analyzed for MSI. 9/14 papillary thyroid carcinomas and 10/16 of follicular thyroid carcinomas demonstrated MSI at >30--40% of loci tested. For benign follicular adenomas, 9/10 demonstrated microsatellite stability or low-frequency MSI.
Microsatellite instability appears to play a role in thyroid pathogenesis as evidenced by the high frequency of MSI in malignant thyroid neoplasms. In addition our study showed a significant difference in MSI frequency between follicular adenomas and follicular carcinomas. More importantly, the technique of laser capture microdissection allows for more accurate selection of benign, malignant and normal DNA.
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Gregory, Michael Peter Robert. "Farm income inequality and instability." Thesis, Imperial College London, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338982.
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Kandil, Mohamed Abdelhadi. "On rotor internal damping instability." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421790.
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Sethia, Krishna Kumar. "The pathophysiology of detrusor instability." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235958.
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Erwin, Patrick Seumas. "Palaeomagnetic investigations of volcano instability." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249474.
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Bhattacharya, S. "Pile instability during earthquake liquefaction." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596628.
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A theory of pile failure, based on buckling instability is proposed in this thesis. The main postulate of this theory is that if piles are too slender they require lateral support from the surrounding soil if they are to avoid buckling instability. During earthquake-induced liquefaction, the soil surrounding the pile loses effective confining stress and can no longer offer sufficient support to the pile. A slender pile may then buckle sideways in the direction of least elastic bending stiffness pushing aside the initially liquefied soil, and eventually rupturing under the increased bending moment and shear force. Lateral loading due to slope movement, inertia or out-of-straightness increases lateral deflections, which in turn induces plasticity in the pile and reduces the buckling load, promoting more rapid collapse. These lateral loads are, however, secondary to the basic requirements that piles in liquefiable soil must be checked against Euler's buckling. This theory has been formulated based on a study of fifteen case histories of pile foundation performance and verified using dynamic centrifuge tests. Analytical studies also support this theory of pile failure. A hypothesis of post-buckling pile-soil interaction is also developed to fit the centrifuge test data. Centrifuge tests were designed in level ground to avoid the effects of lateral spreading and the main aim was to study the effect of axial load as soil liquefies. The failure mode observed in the tests was very similar to those observed in the field in laterally spreading soil. It is concluded in this thesis that it is not necessary to invoke lateral spreading of the soil to cause a pile to collapse. The pile may even collapse before lateral spreading starts. The key parameter identified to distinguish whether the pile pushes the soil (buckling) or the soil pushes the pile (lateral spreading) is the slenderness ratio of the pile in the liquefiable region. The critical value of this parameter is approximately 50. In summary, it has been shown that the current codes of practice for pile design omit considerations necessary to avoid buckling in event of soil liquefaction. These codes are inadequate and buckling needs to be addressed. It has been identified that many of the structures designed based on the current codes of practice may be unsafe and may need retrofitting. Therefore, a design method is proposed taking into consideration the buckling effect.
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Nguyen, Giang Huong. "Cancer, aging and genome instability." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600238.
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Bloom syndrome is a rare autosomal recessive disease caused by loss of function mutations in the BLM gene and characterized by telangiectatic erythema, proportionaJ dwarfism, immune deficiency, infertility, type II diabetes, and a predisposition to many types of cancer. It is unclear how germline mutations in BLM that encodes a helicase protein lead to the highly tissueMspecific changes and disease states associated with BS. In addition, previous works have demonstrated the various roles of BLM in DNA replication and repairs; however, there is currently no mechanism to acutely disable BLM function in cells in order to identify synthetic lethality with other DNA repair factors in an effort to determine how the pathological features of BS might driven by the loss of a single helicase alone. This work aims to develop the fist selective and patent BLM inhibitor that could be used to characterize the role of BLM in gene and rnicroRNA expression as well as the dual effects ofBLM and other DNA damage response proteins such as NIP45. 8
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Gore, Whitney L. "AFFECTIVE INSTABILITY ACROSS DIAGNOSTIC MODELS." UKnowledge, 2015. http://uknowledge.uky.edu/psychology_etds/76.
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The National Institute of Mental Health’s (NIMH) Research Domain Criteria (RDoC; Insel et al., 2010; Sanislow et al., 2010) were established in an effort to explore underlying dimensions that cut across many existing disorders as well as to provide an alternative to the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5; APA, 2013). The present dissertation aimed to study one major component of the RDoC model, negative valence, as compared to other models hypothesized to be closely related, as well as its relationship to a key component of psychopathology, affective instability. Participants were adult community residents (N=90) currently in mental health treatment. Participants received self-report measures of RDoC negative valence, five-factor model (FFM) neuroticism, and DSM-5 Section 3 negative affectivity, along with measures of affective instability, borderline personality disorder, and social-occupational impairment. Through this investigation, a better understanding and potential expansion of this new model of diagnosis for clinicians and researchers is provided. In particular, it is suggested that RDoC negative valence is commensurate with FFM neuroticism and DSM-5 negative affectivity, and it would be beneficial if it was expanded to include affective instability.
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Dixon, Richard Stuart. "Diagnostic studies of symmetric instability." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270255.
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Elliott, Simon S. "Numerical studies of baroclinic instability." Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:eb0c26fe-b0f0-4f2b-aa3b-00428cdd2a57.
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This thesis describes two studies of baroclinic instability in a rotating fluid annulus subject to differential heating. The first part is concerned with the development of a time dependent axisymmetric numerical model. The model was formulated using the control volume finite element method and was designed to be as flexible as possible both in terms of the range of problems to be studied and the techniques used to study them. Details of these techniques are presented together with a discussion of their limitations and possible refinements and extensions which could be made. The second part of this thesis describes a numerical study of unstable normal mode perturbations which can develop on a prescribed mean state. The growth rate and structure of these modes are examined for various background states and the relevance of these results to laboratory measurements is discussed. Evidence is presented to suggest the possible presence of hitherto unobserved baroclinic weak waves in an internally heated annulus system.
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Grimshaw, P. N. "Quantitative assessment of knee instability." Thesis, University of Salford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234593.
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Lucey, Anthony Denis. "Hydroelastic instability of flexible surfaces." Thesis, University of Exeter, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235966.
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Khumbah, Fidelis Morfaw. "Instability of three-dimensional frameworks." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315305.
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Gajo, Alessandro. "Instability phenomena in sand samples." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399938.
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Andriotis, Andreas. "Fracture instability in nuclear graphite." Thesis, University of Bristol, 2018. http://hdl.handle.net/1983/8f4c72b9-6a8a-4c69-8ded-5425f847a148.
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This dissertation considers the fracture instability of nuclear graphite, specifically of isotropic Gilsocarbon, grade IM1-24, which acts as a structural component and neutron moderator within reactors. The presence of cracks within this graphite informs its behaviour and necessitates a study of fracture properties and instability. Amongst the factors studied, a major finding was that the size effect was the most prevalent. Two aspects of instability were also examined: the crack driving force or energy release rate and the fracture resistance or the incremental work of fracture. The conditions between the extremes of load control and displacement control affecting the energy release rate were studied, based on the compliance of the surrounding components or additional elastic material, generally known as elastic follow-up. The effects of elastic follow-up and specimen geometry on fracture instability was investigated in an idealised model. Two sets of experiments were presented to quantify the effect and to validate the idealised benchmark study. No measurable differences were exhibited at the equivalent degrees of elastic follow-up achieved in the experimental work. Additionally, the effects of load multiaxiality on the fracture of graphite were investigated. Despite the influence of load multiaxiality on fracture stress of graphite, there was little effect in post-peak fracture behaviour indicating the lack of influence on fracture stability. Moreover, to evaluate fracture resistance, this work investigated the crack growth resistance curves, KR and R. To produce these curves, a considerable number of experiments of cyclic load and unload, with crack propagation, is presented. Different sized compact tension specimens were tested, to investigate the size effect typically exhibited in quasi-brittle materials which describes the fracture behaviour of IM1-24. The rising KR and R-curve behaviour observed in all sizes, especially in the more distinct initial fracture stages of KR, can be attributed to the formation of a bridging zone in the wake of the propagating crack. A mismatch between the scaling of the fracture process zone and the specimens was also exhibited, evident from the considerable differences in apparent toughness KQ as well as the linear elastic contributions to the work of fracture. The results indicated that the fracture stability of IM1-24 graphite is only marginally affected by elastic follow-up, whilst size effect is a more prominent contributor.
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Wu, Xuesong. "Nonlinear instability of Stokes-layers." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/59202.
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The Stokes-layer generated by a sinusoidally oscillating flat plate in an infinite fluid is an important prototype of unsteady flows, and is known to be susceptible to high-frequency instability. According to linear theory (Tromans, 1977; Cowley, 1987), small disturbances can grow exponentially over part of a period and become neutral at some time. The present study considers nonlinear effects on the instability under a high-Reynolds-number assumption, i.e. R ^ 1. It is shown that in the vicinity of the neutral time, the small disturbances evolve from a linear stage to a nonlinear stage due to enhanced nonlinear interactions inside the critical layers - the neighbourhood of a level at which the phase velocity of the disturbance is equal to the basic flow velocity. Specifically, we have studied the evolution of a two-dimensional wave, a pair of oblique waves and a resonant triad of waves. The temporal-spatial modulation of near-planar waves is also considered. For a two-dimensional disturbance, it is shown that the evolution is controlled by nonlinear eff'ects once the linear growth rate has decreased from order one to 0(6?), where e is the magnitude of the disturbance. The amplitude equation turns out to be an integro-differential one of Hickernell type (Hickernell 1984). We study the amplitude equation by series-extension and numerical methods. For the inviscid case, i.e. e >> the solutions always develop a finite-time singularity. When viscosity is included, i.e. e ~ R~^, it is found that (a) viscosity generally delays the finite-time singularity, and (b) if viscosity is sufficiently large the singularity can be completely eliminated, with the result that the wave evolves to an equilibrium state, confirming the findings of Goldstein Sz Leib (1989). In particular, for the present problem it is found that for disturbances with wavenumbers in the range [0.6, 1.3], a finite-time singularity always occurs, no matter how large the scaled viscosity parameter is. If e < C i.e. the disturbance is relatively small, the amplitude equation can be reduced to a classical Stuart-Landau equation by taking a limit of the integro-differential equation. The stability of the equilibria is also studied. For the case where the disturbance consists of a pair of oblique waves, the non-linear evolution stage comes at a much earlier time, namely when linear growth rate is ), and it then evolves over a much faster time scale 0(e~3), as in Goldstein & Choi (1989). Mathematically this is due to a pole type of singularity in the outer solution for the streamwise and spanwise velocities, which is much stronger than the branch-point singularity associated with Uyy{yc) ^ 0. We show that for the disturbances with order-one spanwise wavenumbers, the amplitude equation is the same as that of Goldstein & Choi(1989), although Uyy{yc) = 0 in their case. However, we point out that when three-dimensionality is relatively weak, the fact that Uyy{yc) 7^ 0 in our problem does bring in a difference. Moreover, we obtain an amplitude equation for the case when viscosity effects are important in the leading order equations of the critical layers, thus extend the analysis of Goldstein & Choi (1989). At least under the inviscid hmit, the solution of the amplitude equation can develop a finite-time singularity, corresponding to the finite-distance singularity of Goldstein & Choi (1989). In addition, it is noted that the nonlinear interaction of waves can generate strong vortices of the same magnitude as the waves. We suggest that these vortices may be identified as those observed in experiments, and may have relevance to the streaky structure in a turbulent boundary layer. For the case when three waves form a resonant-triad, we show that when the amplitude of the planar and the obhque waves are C)(c3) and 0(e) respectively, a mutual interaction takes place and the disturbances are governed by a coupled integro-differential equation system. These amplitude equations are significantly different from those of Raetz (1959), Craik (1971), Smith & Stewart (1987) in two important aspects. Firstly the local growth rate depends on the the whole history of the evolution, unlike a conventional resonant triad, where the local growth rate depends only on the instantaneous amplitudes of the disturbances (see Goldstein & Lee, 1990). Secondly the back reaction of the obhque waves on the 2-D wave is accounted for by two cubic terms and one quartic term rather than by one quadratic term. The amplitudes of the two-dimensional and the three-dimensional waves can exhibit a finite-time singularity, the structure for which is proposed. The evolution equations obtained in our study are shown to be valid until the magnitude of the disturbance becomes order one; thus they provide a full description of the development of resonant-triad waves from their linear small amplitude stage towards the fully-nonhnear order-one-amplitude stage. For the temporal-spatial modulation case, i.e. the case when the amplitude of the disturbance is a slowly-varying function of spanwise position as well as of time, it is shown that the development of the disturbance is controlled by critical-layer nonlinearity when its linear growth rate decreases to 0(es). Nonlinear interactions influence the evolution by producing a streamwise vortex and cross-flow distortion. The modulation equation turns out to be an integro-payimZ-differential one contain-ing hi story-dependent nonlinear terms. A novel feature of the amplitude equation is that the derivatives with respect to space, including the highest derivative, appear in the nonlinear terms. These terms are associated with three-dimensionality, and hence represent vortex stretching and tilting effects. The possible properties of the amplitude equation are discussed. It is shown that a localized singularity may occur in a finite time. This provides a possible explanation for the focusing of streamwise vorticity and the formation of streaks. The finite-time singularity, which can occurs in all the four cases studied, suggests that explosive growth is induced by critical-layer nonlinear effects. Hence an initially small disturbance is further amplified by nonlinear effects; moreover this nonlinear growth can prevent the disturbance evolving into an equilibrium state as implied by linear theory. We suggest that this nonlinear blow-up of high-frequency disturbances is related to the bursting phenomena observed in experiments, and can lead to transition to turbulence.
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Dodgson, Emily. "Thermoconvective instability in porous media." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547618.
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This thesis investigates three problems relating to thermoconvective stability in porous media. These are (i) the stability of an inclined boundary layer flow to vortex type instability, (ii) front propagation in the Darcy-B´enard problem and (iii) the onset of Prantdl-Darcy convection in a horizontal porous layer subject to a horizontal pressure gradient. The nonlinear, elliptic governing equations for the inclined boundary layer flow are discretised using finite differences and solved using an implicit, MultiGrid Full Approximation Scheme. In addition to the basic steady state three configurations are examined: (i) unforced disturbances, (ii) global forced disturbances, and (iii) leading edge forced disturbances. The unforced inclined boundary layer is shown to be convectively unstable to vortex-type instabilities. The forced vortex system is found to produce critical distances in good agreement with parabolic simulations. The speed of propagation and the pattern formed behind a propagating front in the Darcy-B´enard problem are examined using weakly nonlinear analysis and through numerical solution of the fully nonlinear governing equations for both two and three dimensional flows. The unifying theory of Ebert and van Saarloos (Ebert and van Saarloos (1998)) for pulled fronts is found to describe the behaviour well in two dimensions, but the situation in three dimensions is more complex with combinations of transverse and longitudinal rolls occurring. A linear perturbation analysis of the onset of Prandtl-Darcy convection in a horizontal porous layer subject to a horizontal pressure gradient indicates that the flow becomes more stable as the underlying flow increases, and that the wavelength of the most dangerous disturbances also increases with the strength of the underlying flow. Asymptotic analyses for small and large underlying flow and large Prandtl number are carried out and results compared to those of the linear perturbation analysis.
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Akl, Sherif Adel. "Wellbore instability mechanisms in clays." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/64569.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2011."February 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 331-341).
This dissertation investigates the stability of wellbores drilled in Ko-consolidated clays using non-linear finite element method (FEM) and effective stress soil models to characterize the behavior of clay and unconsolidated shale formations. Two constitutive models are used: Modified Cam Clay (MCC; Roscoe and Burland, 1968), and MIT-E3 (Whittle and Kavvadas, 1994). These soil models are incorporated in the commercial finite element program ABAQUS TM through user material subroutines (Hashash, 1992). The wellbores are modeled by a quasi-3D finite element model to approximate the far field stresses and plane strain boundary conditions. The constitutive models are calibrated to the behavior of Resedimented Boston Blue Clay (RBBC), an analog shale material which is Ko-consolidated to stress levels ranging from 0.15MPa to 10.0 MPa. The thesis comprises three major parts. Part one analyzes the short-term wellbore instability during drilling in low permeability formations. The part focuses on the relationship between the mud pressure inside the wellbore and the undrained shear deformations within the formations. The analyses predict critical mud pressure values necessary to maintain wellbore stability at different deviation angles and stress histories. The MIT-E3 model predicted higher deformations at reference mud pressure and estimated higher values of mud pressures than the underbalanced limit to prevent failure in highly deviated wellbores in NC clays. The second part validates the numerical analyses by comparing model predictions to results of an extensive program of model borehole tests. The lab experiments are performed on high pressure Thick- Walled Cylinder (TWC devices) using RBBC as analog testing material (Abdulhadi, 2009). The MIT-E3 predictions demonstrated a very good match with results from the experiments. The results from the analyses illustrated the effect of the device boundary conditions on specimen behavior and validated approximate analytical methods for interpreting TWC results. Part three studies the effects of consolidation on long-term wellbore stability. Non-linear coupled consolidation analyses are performed to simulate the post-drilling, time-dependent deformations and pore pressures around the wellbore. The analyses consider two different boundary conditions on seepage at the cavity. The analyses show that consolidation generates extensive volumetric strains around the wellbore and cavity deformations can aggravate stability conditions in highly deviated wellbores.
by Sherif Adel Akl.
Ph.D.
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Tivey, Hannah S. E. "Physiological responses to genomic instability." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54394/.
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Abnormalities in the cellular senescence programme may contribute to premature ageing and cancer predisposition. Primary human cells have a limited proliferative capacity, entering a state of irreversible growth arrest/senescence arising from telomere attrition (replicative senescence). Stress-induced premature senescence (SIPS) can additionally limit cellular lifespan and there are several human genomic instability (Gl) disorders—cancer-prone/premature ageing syndromes—in which SIPS may prematurely limit cellular lifespan. The hypothesis is that increased Gl is a critical factor in limiting the lifespan of somatic cells by activating common pathways leading to SIPS. This study examines the extent to which Gl cells present restraints on cellular proliferation with a focus on the degree to which they share similar properties—not least a common dependence on the p38 mitogen-activated protein kinase (MAPK) mediated stress response pathway. The study utilised a panel of normal (N) and a Gl panel of fibroblasts comprising: Rothmund Thomson syndrome (RTS), Bloom syndrome (BS), Cockayne syndrome A (CSA), Hutchinson-Gilford Progeria syndrome (HGPS), Nijmegen Breakage syndrome (NBS), Werner syndrome (WS), Seckel syndrome (SS), Dyskeratosis Congenita (DKC) and Ligase 4 syndrome (LIG4). The study revealed a commonality of response to p38 inhibitors—increased clonogenicity and lifespan—for normal and Gl syndrome cells, suggesting that all cells undergo some degree of p38-mediated proliferation restraint/SIPS. A degree of inter-strain heterogeneity for reduced replicative potential and/or altered morphology was apparent for both normal and Gl syndrome primary fibroblasts. This study revealed truncated lifespans for LIG4, SS, HGPS, BS, RTS, DKC and NBS cells. GM18366(SS) and GM07166(NBS) cell strains show an altered morphology and increased p38 inhibitor responses suggesting elevated SIPS operation. Growth and DNA damage studies using a newly created bank of hTert-immortalised cell strains AG16409(N), AG18371(RTS), GM02548(BS), GM07166(NBS), GM01856(CSA), AG11498(HGPS) and GM17523(LIG4) showed that Gl syndrome cells, alleviated from the stress of telomere attrition, remain susceptible to SIPS. Of these RTS cells were hTert-immortalised for the first time, showing that senescence in these strains is telomere-dependent. Cell cycle analysis revealed a common p38- associated mechanism that limits retention in cycle. The specific p38 inhibitor BIRB796 was found to increase clonogenic potential of both normal and Gl syndrome cells. The findings suggest that both RTS and WS cells show a higher proportion of cells that are non-dividing. Furthermore, the study suggests that WS cells have an altered cell cycle transit time that is reduced by BIRB796 treatment. Overall, the study highlights successful single cell analysis approaches for testing the impact of p38 inhibitors by teasing out the nature of cellular heterogeneity arising from different sources for specific cell strains. These findings support and expand previous evidence that WS cells undergo higher levels of SIPS compared to normal cells and provide new evidence that RTS cells may also show an increased propensity for SIPS.
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Blakey, Caroline. "Anterior instability of the hip." Thesis, St George's, University of London, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676894.
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The evolution of humans to an upright stance has led to a change in the postural relationship between the human pelvis and the lower limb. However, despite the uncovering of the femoral head anteriorly, the bipedal hip remains inherently stable due to its bony anatomy and strong ligamentous support. Deviation from normal osseous anatomy results in a loss of constraint to dynamic movement with pathological translation of the femoral head (1,2). A similar scenario is expected with compromise of the surrounding soft tissue structures. A presentation of nine clinical cases describes the condition thought to result from compromise of the anterior hip ligaments. A triad of clinical signs are described. To investigate the patho-mechanical mechanism in these patients, a magnetic resonance imaging (MR.I) study of symptomatic hips was performed. Although increased joint , translation was not demonstrated in this study, distinctive appearances of the iliofemoral ligament were identified. Results of a cadaveric study then go on to demonstrate the stabilizing roles of the anterior capsular ligaments. With damage to the anterior capsule, increased translation of the femoral head was seen not only throughout movement range, but specifically correlated with the functional positions of the iliofemoral and pubofemoral ligaments. The concept of instability of the hip due to soft tissue laxity is postulated to result in progressive damage to the labrum and chondral surfaces as the femur abuts the acetabular rim during extra-physiological motion. Chronic capsular injury may destabilise previously asymptomatic hips with subsequent development of pain in young, active patients. Knowledge of the function of the capsule and its reinforcements is critical if hip surgeons are to manage these patients appropriately and understand the implications of capsular compromise on long-term function.
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Tajik, Mohammad. "Banking instability : causes and remedies." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/10667.
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The recent U.S. subprime mortgage crisis rapidly spread throughout the world and put the global financial system under extraordinary pressure. The main implication of the recent crisis is that complex banking regulations failed to adequately identify and limit riskiness of banking systems at both domestic and international levels. In spite of a large empirical literature on the causes and remedies of the recent crisis, there remains substantial uncertainty on (i) how risk measuring models performed during crisis, (ii) how systematic factors such as house prices affected the financial system, and (iii) how effectively government policy responses resolved the financial crisis. This thesis seeks to narrow this gap in the literature by offering three empirical essays. The first essay investigates the performance of alternative parametric VaR models in forecasting riskiness of international equity portfolios. Notably, alternative univariate VaR models are compared to multivariate conditional volatility models with special focus given to conditional correlation models. Conditional correlation models include the constant conditional correlation (CCC), dynamic conditional correlation (DCC), and asymmetric DCC (ADCC) models. Various criteria are then applied for backtesting VaR models and to evaluate their one-day-ahead forecasting ability in a wide range of countries and during different global financial conditions. It is found that most VaR models have satisfactory performance with small number of violations during pre-crisis period. However, the number of violations, mean deviation of violations, and maximum deviation of violations dramatically increase during crisis period. Furthermore, portfolio models incur lower number of violations compared to univariate models while DCC and ADCC models perform better than CCC models during crisis period. From risk management perspective, most single index models fail to pass Basel criteria for internal VaR models during crisis period, whereas empirical evidence on the choice between CCC, DCC, and ADCC models is mixed. The recent crisis also raised serious concerns about factors that can systematically destabilise the whole banking system. In particular, the collapse of house prices in the United States triggered the recent subprime mortgage crisis, which was associated with a sharp increase in the number of nonperforming loans and bank failures. This in turn demonstrates the key role that house prices play in systematically undermining the whole banking system. The second essay investigates the determinants of nonperforming loans (NPL) with a special focus on house price fluctuations as a key systematic factor. Using a panel of U.S. banking institutions from 1999 to 2012, the analysis is carried out across different loan categories, different types of banks, and different bank size. It is found that house price fluctuations have a significant impact on the evolution of nonperforming loans, while the magnitude of their impact varies across loan categories, institution types, and between large and small banks. Also, the impact of house price fluctuations on nonperforming loans is more pronounced during crisis period. The last essay of this thesis investigates the effectiveness of the U.S. government strategy to combat the crisis. As a comprehensive response to the recent financial crisis, the US government created the Troubled Asset Relief Program (TARP). The Capital Purchase Program (CPP) was launched as an initial program under the TARP. The CPP was designed to purchase preferred stocks or equity warrants from viable financial institutions. Using a large panel of the U.S. commercial banks over the period 2007Q1 to 2012Q4, survival analysis is used to investigate the impact of TARP funds on the likelihood of survival in the recipient banks. It is found that larger recipient banks are more likely to avoid regulatory closure, while receiving capital assistance does not effectively help banks to avoid technical failure. This implies that governmental capital assistance serves larger banks much better than their smaller counterparts. In addition, TARP recipients are more likely to be acquired, regardless of their size and financial health. In summary, the empirical findings reveal that capital infusions do not enhance the survival likelihood of the recipient banking institutions.
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Kordesch, Wendy E. C. "Middle Eocene greenhouse climate instability." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/402327/.
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Understanding warm climate states is increasingly important as projections of anthropogenic climate change indicate atmospheric carbon dioxide concentrations in the coming century not previously seen on Earth for tens of millions of years. The Eocene (~56-34 Ma) is a critical period in the long-term Cenozoic climate evolution, encompassing the transition from widespread greenhouse warmth and high atmospheric carbon dioxide levels pervasive during the early Eocene to an icehouse world with major Antarctic ice sheets and cooler temperatures. Increasingly, it has become apparent that global climate during this transition was not gradual; the middle Eocene is characterized by significant short-term climate variability with recent findings including both transient warming and cooling events. However, the timing, and nature of many of the climate fluctuations during this interval are poorly constrained. To this end, this thesis aims to better characterize the long-term background trends and investigate the nature of short-term transient perturbations during the greenhouse climate of the middle Eocene. In Chapter 2, new nine million year long benthic foraminiferal stable isotope records (~46 to 38 Ma) generated from recently drilled equatorial Pacific sediments with excellent age control are presented. These are the first records to document that the seven enigmatic equatorial Pacific Carbon Accumulation Events (CAEs) are not associated with transient global cooling and/or glaciation events, as previously hypothesized. Further, new carbonate accumulation records in Chapter 3 provide the first robust evidence for the presence of CAEs 3 and 4 in the Atlantic basin. Together, these findings constrain the feasibility of potential CAE forcing mechanisms and imply that there are only two viable mechanisms; (1) solute flux from continental weathering, and (2) increased organic carbon burial from marine assemblage changes. A new compilation (including new and published records) of carbonate accumulation records from a paleodepth transect (2-4 km) in the Atlantic and Pacific basins provides the first multi-basin look at deep-sea carbonate burial at high temporal resolution across the Middle Eocene Climatic Optimum global warming event (~40 Ma). New CCD and lysocline interpretations reveal for the first time that multiple rapid fluctuations (< 100 kyrs) and extreme lysocline shoaling (reaching > 2 km water depth) are superimposed on long-term trends. This finding implies multiple pulses of carbon input to the ocean–atmosphere system during the MECO and provides critical time constraints to potential forcing mechanisms, which have so far remained elusive. In the final Chapter 4, new lithological and geochemical data from the Atlantic and Pacific Basins are presented which reveal the global nature of the transient ‘C19r event’ (~41.5 Ma) and confirm that the event meets the criteria to be defined as a ‘hyperthermal’. Further, analyses of the stable isotope datasets suggests that the C19r event was not exceptional and is one (albeit the most extreme) of a large number of transient ‘warming’ events throughout the middle Eocene, adding to the growing body of data implying that hyperthermal occurrence is pervasive outside of the very warm late Paleocene and early Eocene.
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Gadgil, Rujuta Yashodhan. "Instability at Trinucleotide Repeat DNAs." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1472231204.
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Santos, Tapia Celia. "Understanding chromosomal instability-induced senescence." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/671915.
Full textAbstract:
Aneuploidy, defined as a chromosome number that deviates from a multiple of the haploid set, is a common feature in human cancer, and around 70% of human solid tumours are aneuploid. The resulting metabolic imbalance is proposed to play a fundamental role in the compromised fitness of these cells and lead to malignant transformation by causing proteotoxic stress and affecting cell cycle proliferation and growth. However, most of the molecular pathways and cellular behaviours underlying aneuploid-induced tumorigenesis remain uncharacterized. Drosophila larval epidermal primordia have proved useful model systems to demonstrate the contribution of aneuploidy-induced metabolic stress to tumour growth. By depleting different Spindle Assembly Checkpoint (SAC) genes in the epithelial cells, we induce chromosomal instability and generate aneuploidy. When prevented from undergoing programmed cell death (PCD), these cells give rise to a neoplasic overgrowth. Here we propose that CIN-induced aneuploidy in epithelial cells activates low levels of the c-Jun N-terminal kinase (JNK) and the DNA damage response (DDR). This induces a G1 stall that prevents the accumulation of damage. However, when due to CIN these cells become highly aneuploid, they delaminate from the epithelium and acquire a senescent behaviour. This senescent behaviour is dependent on high levels of JNK and DDR signalling, and induce the secretion of wide variety of factors - also known as the senescence-associated secretory phenotype (SASP) -, and a permanent G2 arrest, among other senescent features. In addition, we have identified two target effectors, Fizzy-related and String, that are miss-regulated and could act downstream JNK and the DDR to induce the G2 arrest. Finally, we were able to explore two different ways to target CIN-aneuploid cells based on their basal levels of replicative stress: genetic (CycE/Dap overexpression) and chemical (Hydroxyurea), which significantly affect tissue growth and impair tumour progression.La aneuploidía, que se define como un número de cromosomas diferente al haploide, es una característica muy común en cáncer ya que se encuentra en alrededor de 68% de los tumores sólidos. Esta resulta en un desequilibrio metabólico que compromete la función celular induciendo estrés proteotóxico y afectando el crecimiento celular, dando lugar a así a una transformación maligna de estas células. Sin embargo, muchos de los mecanismos moleculares detrás de esta transformación generada por la aneuploidía son aún desconocidos. En este trabajo, usamos el epitelio del ala de Drosophila como tejido modelo para demostrar la contribución de la aneuploidía al crecimiento tumoral. Mediante la inhibición de genes del checkpoint del huso mitótico, inducimos inestabilidad cromosómica y aneuploidía que, tras bloquear la muerte celular, da lugar a un sobrecrecimiento tumoral. Cuando las células no tienen aún altos niveles de aneuploidía, activan bajos niveles de la quinasa c-Jun N-terminal (JNK) y activan la respuesta a daño en el DNA (DDR). Esto induce un arresto temporal en G1 que previene la acumulación de más daño. Sin embargo, debido a la inestabilidad cromosómica, estas células continúan proliferando y acumulan altos niveles de aneuploidía, delaminan del epitelio y adquieren un comportamiento senescente. Este depende de la activación de altos niveles de JNK y la DDR y tiene como consecuencia la secreción de distintos factores (SASP) y un arresto permanente en G2, entre otras características senescentes. Además, hemos podido identificar dos factores involucrados en el arresto, Tribbles and String, que podrían actuar en respuesta a JNK y a la DDR para hacer efectivo el arresto en G2. Finalmente, exploramos dos maneras distintas de afectar los tumores CIN aprovechando que sufren daño en el DNA: genéticamente (mediante la sobre-expresión de CycE/Dap) y químicamente (mediante el tratamiento con hidroxiurea), afectando ambas el crecimiento del tejido e inhibiendo la progresión tumoral.
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Ismael, Mohanad. "Market imperfections and macroeconomic instability." Thesis, Evry-Val d'Essonne, 2011. http://www.theses.fr/2011EVRY0011/document.
Full textAbstract:
Dans cette thèse, on étudie l’effet de l’imperfection de marché sur la stabilité macroéconomique dans le modèle standard de Ramsey et celui de OLG. pour effectuer cette objective, on utilise la méthode de l’analyse de dynamique local lancé par Grandmont, Pintus et De Vilder (1998). les imperfections qu’on utilise sont les externalités en consommation, imperfection dans le marche de crédit, la présence de taxe progressive sur le revenu salariel et l’existence de coût de transaction associé avec l’accumulation de capitalIn this thesis, we study the effect of market imperfection on macroeconomic stability in the standard Ramsey model and that of the Olg. In order to achieve this objective, we use the local analysis method pioneered by Grandmont, Pintus and De Vilder (1998). The imperfections used in this thesis are the consumption externalities, credit market imperfections, progressive labor-income taxation policy and the presence of transaction costs associated with capital accumulations