The influence of the strain rate and heat treatment on the occurrence of plastic instabilities in extruded AlSi1MgMn (6082) and cold rolled AlMg4.5Mn0.4 (5182) alloys was studied. The samples were uniaxially loaded at various strain rates and at room temperature (RT). The results are discussed using concurrent acoustic emission (AE) monitoring during mechanical testing and the AE parameters are correlated to the microstructure and to the stress-time curves. All samples exhibited the Portevin-Le Châtelier (PLC) effect of different types, dependently on the heat treatment and the applied strain rate. The occurrence of the PLC effect is manifested by burst AE signals with high amplitudes. Statistical analysis of the AE signals has shown the power-law probability distribution.

The dissertation consists of three chapters on econometric methods related to parameter instability, forecasting and long memory. The first chapter introduces a new frequentist-based approach to forecast time series in the presence of in and out-of-sample breaks in the parameters. We model the parameters as random level shift (RLS) processes and introduce two features to make the changes in parameters forecastable. The first models the probability of shifts according to some covariates. The second incorporates a built-in mean reversion mechanism to the time path of the parameters. Our model can be cast into a non-linear non-Gaussian state-space framework. We use particle filtering and Monte Carlo expectation maximization algorithms to construct the estimates. We compare the forecasting performance with several alternative methods for different series. In all cases, our method allows substantial gains in forecasting accuracy. The second chapter extends the RLS model of Lu and Perron (2010) for the volatility of asset prices. The extensions are in two directions: a) we specify a time-varying probability of shifts as a function of large negative lagged returns; b) we incorporate a mean reverting mechanism so that the sign and magnitude of the jump component change according to the deviations of past jumps from their long run mean. We estimate the model using daily data on four major stock market indices. Compared to competing models, the modified RLS model yields the smallest mean square forecast errors overall. The third chapter proposes a method of inference about the mean or slope of a time trend that is robust to the unknown order of fractional integration of the errors. Our tests have the standard asymptotic normal distribution irrespective of the value of the long-memory parameter. Our procedure is based on using quasi-differences of the data and regressors based on a consistent estimate of the long-memory parameter obtained from the residuals of a least-squares regression. We use the exact local-Whittle estimator proposed by Shimotsu (2010). Simulation results show that our procedure delivers tests with good finite sample size and power, including cases with strong short-term correlations.

Childhood sexual abuse (CSA) is a stressful life experience with lasting/far-reaching health and psychopathological consequences. Our laboratory recently identified a significantly increased frequency of acquired chromosomal anomalies (assessed using the cytokinesis-blocked micronucleus assay) in adult female twins exposed to CSA when compared to their unexposed co-twin. The primary aim of this study was to evaluate potential mechanism(s) underlying the observed increases in levels of micronuclei in an expanded group of 90 female identical twins (61 CSA+ females and 29 CSA- females [including a total of 27 MZ co-twin pairs]) using fluorescence in situ hybridization (FISH) methodologies, with PNA probes specific for the centromeric and telomeric regions of all chromosomes coupled with the standard CBMN assay, we were able to characterize the chromosomal contents of MN and, thus, gain insight into the mechanisms underlying MN formation. By scoring 100 MN per study participant for the number of centromeric signal(s) and/or telomeric signal(s) present, we categorized the MN as harboring either: (1) terminal fragments (only a telomeric signal); (2) acentric interstitial fragments (no telomeric or centromeric signal); (3) centric interstitial fragments (only a centromeric signal); or (4) an intact chromosome(s) or chromatid(s). We identified elevated frequencies of intact chromosome-derived MN in CSA+ women as compared to CSA- women (P=0.014), implicating chromosome loss as a mechanism potentially underlying the increased frequencies of MN identified in adult females with a history of CSA. MN containing fragmented chromosomes were also observed in all of the study participants evaluated; however MN containing terminal fragments and MN containing acentric interstitial fragments were seen less frequently in CSA+ women compared to CSA- women. This study represents the first time that the chromosomal contents of MN have been evaluated in individuals in the context of a psychosocial factor. As chromosomal loss and breakage contributes to the development of age-related health problems, these observations provide important insight into the biological mechanisms that may underlie the latent morbidity and psychopathology associated with childhood adversity. Future studies aimed at understanding the biological impact of early-life trauma could determine if the observed increase in acquired chromosomal abnormalities results in detectable somatic clonal mosaicism. This knowledge could ultimately be used to develop screening tools to identify individuals “at risk” for negative health outcomes in adulthood.

Through the study's analysis with background to theories and previous research, it turns out that financial instability is hidden in boom and economic stability. Where causes are speculation, optimism, risk-taking and credit expansion. Minsky (1982a) pointed out, among other things, that high debt ratio increases the risk of financial instability, which is an effect of the lavish lending, partly as a result of global financing. The purpose of this study is to investigate whether there was a state of financial instability prior to Sweden's crises, focusing on Sweden's three most recent crises: the financial crisis of 1990, the IT bubble of 2000 and the financial crisis of 2008. The study illustrates how Minsky's financial instability hypothesis that "stability breeds instability" also can explain the emergence of Swedish crises. The result shows that there is a clear link between increased debt before crises. / Genom studiens analys med bakgrund till teorier och tidigare forskning visar det sig att finansiell instabilitet döljer sig i högkonjunktur och ekonomisk stabilitet. Där orsaker som ligger till grund är spekulation, optimism, risktagning och kreditexpansion. Minsky (1982a) pekade bland annat på att hög skuldkvot ökar risken för finansiell instabilitet, något som är en effekt av den frikostiga kreditgivningen, bland annat som en följd av den globala finansieringen. Syftet med denna studie är att undersöka om där funnits ett tillstånd av finansiell instabilitet innan Sveriges kriser, med fokus på Sveriges tre senaste kriser: finanskrisen 1990, it-bubblan 2000 och finanskrisen 2008. Studien åskådliggör hur Minskys finansiella instabilitetshypotes om att "stability breeds instability" även kan förklara uppkomsten av svenska kriser. Resultatet visar på att det finns ett tydligt samband mellan ökad skuldsättning innan kriser.

Sedimenting suspensions exist in a varity of natural phenomena and industrial applications. It is already observed in experiments that the dilute fibre suspensions experience a hydrodynamics instability under gravity at low Reynolds numbers. Initially well-mixed suspensions become inhomogeneous and anisotropic due to this instability.The main goal of this work is to understand the instability in a dilute fibre suspension by means of an Eulerian approach which is based on the Navier-Stokes equations coupled to Fokker-Planck equation for the PDF of fibres.Using a linear stability analysis, we show that inertia and hydrodynamic translational diffusion damp perturbations at long wavelengths and short wavelengths, respectively, leading to a wavenumber selection. For small, but finite Reynolds number of the fluid bulk motion, the most unstable wavenumber is a finite value which increases with Reynolds number, and where the diffusion narrows the range of unstable wavenumbers. With periodic boundary conditions, numerical simulations of the full non-linear evolution in time of a normal mode perturbation show that the induced flow may either die or saturate on a finite amplitude. The character of this long time behaviour is dictated by the wavenumber and the presence or absence of the translational and rotational diffusivities.In a simulation domain confined by vertical walls, a series of alternating structures of risers and streamers emerge continuously from the walls until they meet in the middle of the domain. For moderate times, this agrees qualitatively with experimental and theoretical results. Moreover, our simulation in a vessel of infinite height obtained an increasing wavelength evolution due to the congregation of the streamers or risers. In the end, there is constantly only one streamer left, and it drifts randomly to one side of the container until the evolution reaches a steady state. It is also found that the perturbations added to the initial conditions can induce more high density regions whose sizes and velocities are strongly linked to the initial perturbations of the number density or the flow field. In addition, the maximum number of streamers increases with Reynolds number, volume fraction and channel width. / QC 20120625

Ankle sprains are among the most common injuries for participants in running and jumping sports. Following an initial sprain injury, many (30-40%) will develop chronic ankle instability (CAI), characterized by a perception of instability and repeated sprain injuries. Quasi-static test methods indicate poor postural stability and joint position sense (JPS) as associated motor control deficits. Little research, though, has investigated ankle motor control under dynamic (simulated sport) or fatigue conditions. To better understand factors contributing to the increased sprain rate in adults with CAI, three studies were completed investigating the roles of running speed, fatigue, and ankle bracing on motor control in adults with CAI. First, two groups with and without ankle instability performed dynamic athletic maneuvers at each of two running speeds. Joint kinematics and kinetics were measured to identify differences in motor control strategies. Participants also completed two quasi-static tests (JPS and single leg drop landings). The level of correspondence between quasi-static and dynamic test methods was of particular interest. A second study compared fatigue development and fatigue adaptations when executing single leg drop landings. Strength loss and ratings of perceived exertion measured fatigue development, and joint kinematics, kinetics, and muscle activation quantified drop landing performance. A final study examined whether ankle braces, a common treatment for ankle sprains, retained their effectiveness when an athlete was fatigued. JPS and ankle stiffness were measured before and after a fatigue protocol while using each of three brace conditions. Overall, results indicated that adults with CAI exhibit distinct adaptations to changes in speed and to fatigue that may increase their risk for ankle reinjury. Specific changes, however, depended on the particular activity being performed. Single leg drop landing kinematics may be a good representation of kinematics during dynamic athletic performance. Neither test brace improved JPS following fatigue, but each may be effective in providing mechanical stiffness compared to an unbraced condition. The effectiveness of a particular test brace, however, may be gender-specific. Future work should focus on identifying the benefits of different braces under broader conditions to help inform brace selection. / Ph. D.

Placering i familjehem är en vanlig insats när barn och unga inte bedöms kunna få sina behov tillgodosedda i sin ursprungsfamilj och utgör i Sverige majoriteten av placeringar i samhällsvård. Instabilitet i denna typ av placeringar är vanligt förekommande då många familjehemsplaceringar avbryts och kännetecknas av en brist på kontinuitet. Syftet med denna litteraturstudie var att utforska barn och ungas upplevelser av instabilitet i familjehem, samt deras upplevelser av inflytande och delaktighet i instabiliteten. Detta gjordes utifrån frågeställningarna Hur upplever barnet/den unge instabiliteten? och Hur uppfattar barnet/den unge sin egen delaktighet och sitt inflytande i perioder av instabilitet i placeringen?. De studier som inkluderades bearbetades genom tematisk syntes och ett antal analytiska teman användes för att förstå empirin. Resultatet visade att många barn och unga upplever instabilitet som en oundviklig del av att vara i samhällets vård. Instabiliteten upplevs som emotionellt påfrestande och får negativa konsekvenser för måendet även i vuxen ålder. En del av påfrestningen i instabiliteten är att inte få tillräckligt med information från vuxna samt att inte bli hörd. Upprepad instabilitet kan också bidra till svårigheter att bygga stabila och långvariga relationer. Att uppleva instabilitet i familjehemsvården kan dock föra med sig vissa färdigheter, lärdomar och erfarenheter som är till nytta i vuxenlivet. / Foster care placement is a common arrangement when children and youth are unable to have their needs met in their family of origin, making up a majority of social care placements in Sweden. Instability in such placements is common due to many foster care placements being interrupted and characterized by a lack of continuity. The aim of this literature review was exploring children and youth’s experiences of instability in foster care, as well as the experiences of influence and participation in the instability. This was done through the following questions: How does the child/youth experience the instability? and How does the child/youth perceive their own participation and influence during times of instability in foster care placement?. The studies included was processed through a thematic synthesis, and a number of analytical themes was used to understand the empirical data. The results showed that many children and youth experience instability as an unavoidable part of being in social care. Instability is experienced as being emotionally taxing and leads to negative consequences for the individual’s well-being, even in adulthood. Part of the emotional taxation during instability comes from the lack of information provided by adults, as well as feeling unheard. Repeated instability in foster care can however contribute to some skills, lessons and experiences that are beneficial in adulthood.

Context: Individuals with chronic ankle instability (CAI) rely more on visual information during postural control due to impaired proprioceptive function. The increased reliance on visual information may increase the risk of injury when their vision is limited during complex sports activities. Stroboscopic glasses may help elicit sensory reweighting during postural control. Therefore, we assumed that the glasses would induce and train CAI patients to reweight sensory information for the somatosensory system during dynamic balance training. Purpose: (1) to identify the effects of the 4-week dynamic balance training on the reliance of visual information during postural control in patients with CAI and (2) to compare the effects of the 4-week dynamic balance with and without stroboscopic glasses on postural control in patients with CAI. Methods: This study was a randomized controlled trial. Twenty-eight CAI patients were equally assigned to one of 2 groups: a strobe group (6 males and 8 females) or a control group (8 males and 6 females). The 4-week dynamic balance training consisted of multiple single-legged exercises. The strobe group wore stroboscopic glasses during the training, but the control group did not. The main outcome measures included the following: self-reported function measures, static postural control (center of posture (COP)-based measures), and dynamic postural control including the Dynamic Postural Stability Index (DPSI), and the Star Excursion Balance Test (SEBT). There were 3 visual conditions in the static postural control (eyes-open (EO), strobe vision (SV), and eyes-closed (EC)), and 2 conditions in the dynamic postural control (EO and SV). Two-way randomized block ANOVAs were used to assess changes in postural control in each group and condition by using pretest-posttest mean differences. Results: The strobe group showed a higher difference in COP velocity in medial-lateral direction (VelML) and vertical stability index (VSI) under the SV condition compared with the control group (p = .005 and .004, respectively). In addition, the strobe group had significant decreases in VelML, DPSI, and VSI at the posttest compared with the pretest (p = .0001, .01, and .005, respectively). Conclusion: The 4-week dynamic balance training with stroboscopic glasses appeared to be effective in improving postural control and altering visual reliance in patients with CAI.

The effect of different vertical support stiffness of a frame railway bridge is investigated in this study. Due to the dynamic loads of the high speed trains that run over the railway bridges, the response of these structures is far from the static effects. The frame bridge chosen for this study is the Rössjö bridge, located on the Bothnia Line, the first high speed railway built in Sweden. Using a theoretical model of this bridge, the eigenfrequencies of the structure and the vertical accelerations of the deck are evaluated. Not only different vertical support stiffness, but also different trains and train speeds are studied. Finally, some real in-situ measurements are compared with the results from the theoretical model.

The natural resource curse is a widely debated phenomenon usually proposing a connection between large extractive resource wealth and substandard economic performance. This paper concerns the connection between large extractive resource wealth and the potential for its effects on long term political stability. Using Venezuela as a case study, this paper delves into the political history of Venezuela, plagued by endemic political instability, and attempts to test the political aspect of the resource curse, analysing history with a focus on the oil industry. The conclusion is that there is a clear connection between oil price volatility and political instability, but only evident starting in the latter half of the 20th -century. Further research into specific regimes, eras, as well as comparative analyses between Venezuela and other states is required to provide additional answers in regard to specific causes for political instability in the early 20th -century and the pre-oil period.