We analyze how the impact of a change in the sovereign debt-to-GDP ratio on economic growth depends on the level of debt, the stress level on the financial market and the membership in a monetary union. A dynamic growth model is put forward demonstrating that debt affects macroeconomic activity in a non-linear manner due to amplifications from the financial sector. Employing dynamic country-specific and dynamic panel threshold regression methods, we study the non-linear relation between the growth rate and the debt-to-GDP ratio using quarterly data for sixteen industrialized countries for the period 1981Q1-2013Q2. We find that the debt-to-GDP ratio has impaired economic growth primarily during times of high financial stress and only for countries of the European Monetary Union and not for the stand-alone countries in our sample. A high debt-to-GDP ratio by itself does not seem to necessarily negatively affect growth if financial markets are calm. (authors' abstract)

<p>The advances in three related areas of state-space modeling, sequential Bayesian learning, and decision analysis are addressed, with the statistical challenges of scalability and associated dynamic sparsity. The key theme that ties the three areas is Bayesian model emulation: solving challenging analysis/computational problems using creative model emulators. This idea defines theoretical and applied advances in non-linear, non-Gaussian state-space modeling, dynamic sparsity, decision analysis and statistical computation, across linked contexts of multivariate time series and dynamic networks studies. Examples and applications in financial time series and portfolio analysis, macroeconomics and internet studies from computational advertising demonstrate the utility of the core methodological innovations.</p><p>Chapter 1 summarizes the three areas/problems and the key idea of emulating in those areas. Chapter 2 discusses the sequential analysis of latent threshold models with use of emulating models that allows for analytical filtering to enhance the efficiency of posterior sampling. Chapter 3 examines the emulator model in decision analysis, or the synthetic model, that is equivalent to the loss function in the original minimization problem, and shows its performance in the context of sequential portfolio optimization. Chapter 4 describes the method for modeling the steaming data of counts observed on a large network that relies on emulating the whole, dependent network model by independent, conjugate sub-models customized to each set of flow. Chapter 5 reviews those advances and makes the concluding remarks.</p> / Dissertation

Accelerator driven transmutation systems could be a solution to the problem with long-lived nuclear waste and opening the way to thorium fuel cycle. Due to intensive neutron source based on spallation reaction are these systems very litle dependent on the arrangement of the core and fuel quality. These systems can transmute the spent fuel, eventually 232Th or 238U without affecting maintenance of fission reaction. Additionally subcritical blanket ensures high safety. For these systems it is necessary to know the cross sections of reactions of fast neutrons produced in the spallation reaction with different materials. This data is necessary not only for the selection of appropriate construction materials, but also for creation of programs simulating accelerator driven transmutation systems. This thesis is focused on the experimental determination of cross sections of reactions 89Y(n,2n)88Y and 89Y(n,3n)87Y with neutron energies from 17,6 to 33,6 MeV. Yttrium is analyzed for its (n,xn) threshold reactions, which makes it appropriet activation detector for study of the neutron fields in model configurations of accelerator driven transmutation systems. The obtained cross sections are unique, in that so far there are no experimental data for used neutron energies.

Members of the European Parliament are chosen according to 28 different election systems. The European Union determines only few basic rules, which are concretised by member states in their law systems. Diploma thesis "Election system of European Parliament" deals with similarities and differences between these regulations in order to show inequality of European elections. In the second part of this thesis the author compares a partial aspect of the election system, election threshold in Germany and in the Czech Republic. While the Federal Constitutional Court of Germany invalidated firstly the five-percent-threshold and then even the three-percent-threshold because of its contradiction to Basic Law, the Czech Constitutional Court confirmed it as constitutional afterwards. Both courts judicated that it is a violation of election equality but in the opinion of the Czech one fragmentation of the Parliament would hinder its work with such intensity that election threshold preventing from this fragmentation is justifiable. The judgements are compared and their argumentations analysed if reasonable. This thesis comes to the conclusion, that considered the current state and predictable development election threshold has its justification. Powered by TCPDF (www.tcpdf.org)

Title: Large claims modeling Author: Barbora Zuzáková Department: Department of Probability and Mathematical Statistics Supervisor: RNDr. Michal Pešta, Ph.D. Abstract: This thesis discusses a statistical modeling approach based on the extreme value theory to describe the behaviour of large claims of an insurance portfolio. We focus on threshold models which analyze exceedances of a high threshold. This approach has gained in popularity in recent years, as compared with the much older methods based directly on the extreme value distributions. The method is illustated using the group medical claims database recorded over the periods 1997, 1998 and 1999 maintained by the Society of Actuaries. We aim to demonstrate that the proposed model outperforms classical parametric distri- butions and thus enables to estimate high quantiles or the probable maximum loss more precisely. Keywords: threshold models, generalized Pareto distribution, large claims. 1

Doctor of Philosophy / Department of Electrical and Computer Engineering / Caterina Scoglio / Vector-borne diseases not only cause devastating economic losses, they also significantly impact human health in terms of morbidity and mortality. From an economical and humane point of view, mitigation and control of vector-borne diseases are essential. Studying dynamics of vector-borne disease transmission is a challenging task because vector-borne diseases show complex dynamics impacted by a wide range of ecological factors. Understanding these factors is important for the development of mitigation and control strategies. Mathematical models have been commonly used to translate assumptions concerning biological (medical, demographical, behavioral, immunological) aspects into mathematics, linking biological processes of transmission and dynamics of infection at population level. Mathematical analysis translates results back into biology. Classical deterministic epidemic models do not consider spatial variation, assuming space is homogeneous. Spatial spread of vector-borne diseases observed many times highlights the necessity of incorporating spatial dynamics into mathematical models. Heterogeneous demography, geography, and ecology in various regions may result in different epidemiological characteristics. Network approach is commonly used to study spatial evolution of communicable diseases transmitted among connected populations. In this dissertation, the spread of vector-borne diseases in time and space, is studied to understand factors that contribute to disease evolution. Network-based models have been developed to capture different features of disease transmission in various environments. Network nodes represent geographical locations, and the weights represent the level of contact between regional pairings. Two competent vector populations, Aedes mosquitoes and Culex mosquitoes, and two host populations, cattle and humans were considered. The deterministic model was applied to the 2010 Rift Valley fever outbreak in three provinces of South Africa. Trends and timing of the outbreak in animals and humans were reproduced. The deterministic model with stochastic parameters was applied to hypothetical Rift Valley fever outbreak on a large network in Texas, the United States. The role of starting location and size of initial infection in Rift Valley fever virus spread were studied under various scenarios on a large-scale network. The reproduction number, defined as the number of secondary infections produced by one infected individual in a completely susceptible population, is typically considered an epidemic threshold of determining whether a disease can persist in a population. Extinction thresholds for corresponding Continuous-time Markov chain model is used to predict whether a disease can perish in a stochastic setting. The network level reproduction number for diseases vertically and horizontally transmitted among multiple species on heterogeneous networks was derived to predict whether a disease can invade the whole system in a deterministic setting. The complexity of computing the reproduction number is reduced because the expression of the reproduction number is the spectral radius of a matrix whose size is smaller than the original next generation matrix. The expression of the reproduction number may have a wide range of applications to many vector-borne diseases. Reproduction numbers can vary from below one to above one or from above one to below one by changing movement rates in different scenarios. The observations provide guidelines on executing movement bans in case of an epidemic. To compute the extinction threshold, corresponding Markov chain process is approximated near disease free equilibrium. The extinction threshold for Continuous-time Markov chain model was analytically connected to the reproduction number under some assumptions. Numerical simulation results agree with analytical results without assumptions, proposing a mathematical problem of proving the existence of the relationships in general. The distance of the extinction threshold were shown to be closer to one than the reproduction number. Consistent trends of probability of extinction varying with disease parameters observed through numerical simulations provide novel insights into disease mitigation, control, and elimination.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Caterina Maria Scoglio / We have analytically discovered the existence of two global epidemic invasion thresholds in a directed meta-population network model of the United States cattle industry. The first threshold describes the outbreak of disease first within the core of the livestock system while the second threshold describes the invasion of the epidemic into a second class of locations where the disease would pose a risk for contamination of meat production. Both thresholds have been verified through extensive numerical simulations. We have further derived the relationship between the pair of thresholds and discovered a unique dependence on the network topology through the fractional compositions and the in-degree distributions of the transit and sink nodes. We then addressed a major challenge for epidemiologists and their efforts to model disease outbreaks in cattle. There is a critical shortfall in the availability of large-scale livestock movement data for the United States. We meet this challenge by developing a method to estimate cattle movement parameters from publicly available data. Across 10 Central States of the US, we formulated a large, convex optimization problem to predict the cattle movement parameters which, having minimal assumptions, provide the best fit to the US Department of Agriculture's Census database and follow constraints defined by scientists and cattle experts. Our estimated parameters can produce distributions of cattle shipments by head which compare well with shipment distributions also provided by the US Department of Agriculture. This dissertation concludes with a brief incorporation of the analytic models and the parameter estimation. We approximated the critical movement rates defined by the global invasion thresholds and compared them with the average estimated cattle movement rates to find a significant opportunity for epidemics to spread through US cattle populations.

In Chapter 1, I hypothesize that there is a differential response by agents to changes in sovereign credit or default risk in both quiet (low default risk) and turbulent markets (high default risk). These market conditions create two different states of the market (world) or regimes. Investors and policy makers respond differently in the two regimes but the response in the turbulent market condition is amplified as policy makers attempt to smoothen the fluctuations and uncertainty while investors rebalance their portfolios in an attempt to hedge against downside risk of wealth loss. In the two regimes, the short run and long run dynamic relationships between any two cointegrated assets may change. To capture this phenomenon, this study tests for nonlinearities that may characterize the regimes, how cointegration relationships, short term dynamic interaction and price discovery (speed of adjustment to new information between two assets) may change in alternative regimes. To this end, I employ threshold cointegration, threshold vector error correction model (TVECM) asymmetrical return spillover modeling for sovereign credit default swaps (CDS), bonds and equity markets of seventeen emerging markets from four geographical regions. I find that there is non-linear cointegration and momentum in long-run adjustment process in 43/51 spreads analyzed. All countries analyzed have at least 2/6 possible regime specific asymmetric price discovery process. The study also finds evidence in support of asset substitution hypothesis and news-based hypothesis of financial contagions in sovereign CDS, bond and equity markets. The findings have important implications for asset allocation and portfolio rebalancing decisions by investors, policy intervention in financial markets, risk management and regime specific short and/or long term dynamic interactions among assets held in a portfolio as well as nonlinear speed of adjustment to new information. In chapter 2, I hypothesize that financial intermediaries can be categorized into bank-based institutions (BBIs) and market-based institutions (MBIs). MBIs and BBIs are under different regulatory agencies. Traditionally, only BBIs, regulated by the Fed, are used as conduits of transmitting liquidity and monetary policy into real economy and financial markets yet MBIs also play important role in providing liquidity and stability in financial markets. I use two tools of monetary policy (Federal fund rate and monetary aggregate) under two monetary policy regimes to investigate the impact of monetary policy under each regime on the liquidity of MBIs and BBIs. I investigate whether MBIs be used as conduits of transmitting monetary policy and liquidity in the market and if they should, under what economic and financial conditions (Regimes) should they be used. Moreover, what monetary policy tool is more effective for MBIs relative to BBIs under different regimes? Using Threshold vector auto-regressions and regime specific impulse response functions, I find that liquidity of BBIs and MBIs respond differently to different monetary policy tools under different regimes. Moreover, monetary policies are uncertain and vary over time. The Fed cannot continue to ignore MBIs in formulating and implementing monetary policy. Moreover, monetary aggregate policy is more effective when used on MBIs during contractionary monetary policy intervention (economic downturn) while Federal fund rate is more effective when used on BBIs under expansionary monetary policy.

Between the actualized built spaces that the artist moves around and through on a daily basis and the more abstract systems we invent to represent these structures sits the illusion of space and structure found in his drawings and paintings. Constant turnover within the built environment offers not only content, but rich analogy for his artistic practice. The artist’s endeavors in the studio in many ways echo the genesis, evolution and possibility he observes in the transitioning city around him. In the actual making of the work, he gleans from traditional methods of drawing and painting, from the architectural lexicon, from experiments with new materials, from the effects of time and decay and from building processes themselves.

Notre travail de thèse avait pour buts d’explorer les mécanismes de contrôle de la fonction respiratoire au cours de l’exercice incrémentiel maximal mais également de corréler les évènements biochimiques associés à l’exercice progressif aux modifications de l’électromyogramme des muscles participant à l’effort. Les résultats de nos trois études ont montré : 1) que la baisse de PO2, intervenant pendant les premiers paliers d’un exercice incrémentiel maximal, était bien dépendante d’une défaillance de la commande centrale de la réponse ventilatoire. 2) que le pattern ventilatoire durant la période située entre le seuil ventilatoire (VTh) et le 2ème seuil (RCP) lors d’un exercice incrémentiel, pouvait évoluer selon deux modalités différentes, l’une caractérisée essentiellement par une augmentation de VT (un tiers des sujets) et l’autre déterminée majoritairement par une augmentation de FR. L’hypothèse d’une différence interindividuelle du gain du réflexe de Hering-Breuer peut être évoquée pour expliquer ces différents modes ventilatoires pendant l’exercice ; 3) qu’il est mesuré une augmentation de la concentration plasmatique de l’IMA (marqueur du stress oxydatif), corrélée à la consommation de RAA (antioxydant endogène), durant la phase la plus intense de l’exercice incrémentiel. L’adaptation de la commande motrice via le mécanisme d’épargne musculaire (« muscle wisdom ») n’intervient que chez les sujets qui développent un stress oxydatif. Ainsi, la variabilité interindividuelle mesurée dans l’amplitude du stress oxydatif, à niveau d’exercice comparable, affecte la capacité des sujets à lutter contre la fatigue musculaire. / The aim of our PhD work was to explore, in healthy humans, the control mechanisms of the respiratory function during a maximal incremental exercise and also to correlate the changes in the motor control of working muscles to the changes in exercise-induced blood signals. The results of our three studies showed:1) The occurrence of a PO2 fall during the first steps of the incremental exercise, associated with a modest PCO2 increase, strongly suggests a non-adaptation of the central command to the oxygen demand and CO2 washout;2) Two opposite changes in the ventilatory pattern were observed between the ventilatory threshold (VTh) and the respiratory compensation point (RCP); one third of the subjects tends to recruit predominantly VT and the others the breathing frequency. The hypothesis of an inter-individual difference in the strength of the Hering-Breuer reflex seems to be the more consistent explanation. 3) The plasma concentration of IMA, a marker of the oxidative stress, increased at the highest levels of incremental exercise and was correlated to the consumption of endogenous antioxidant (RAA). Because we observed that the adaptive motor response to cycling (leftward shift of the EMG spectrum) closely depends on the importance of the oxidative stress response, we hypothesized that all the healthy subjects do not have the same chances to be protected against muscle fatigue.