Dissertations / Theses on the topic 'Heterogeneity of regimes'

As a unique habitat that encompasses steep environmental gradients, it is important to evaluate threats posed to the intertidal zone by rapid climate change. It is thought that intertidal ectotherms are living close to their physiological limit; therefore slight changes in temperature could result in high levels of mortality. Past studies on intertidal species measured thermal tolerance under constant temperatures, neglecting to consider the impacts of natural variation in field temperatures. I conducted a study on the barnacle, Balanus glandula, to assess if a variable thermal environment would alter thermal tolerance. Barnacles were acclimated in an intertidal mesocosm to either daily cold (maximum 20.4◦C), daily warm (maximum 26.5◦C), or variable (two days cold, two days warm) low-tide temperatures. I measured each barnacle’s critical thermal maximum (CTmax) by increasing air temperature 6◦C/hour and identifying the point at which the barnacle ceased to function. Barnacles exposed to any warm temperatures demonstrated an increased thermal tolerance, suggesting that this population of barnacles is capable of shifting their thermal maximum. Furthermore, acclimation to thermal heterogeneity raised thermal maximum, reinforcing the need for future thermal tolerance studies to incorporate biologically-relevant thermal regimes in laboratory experiments. These results demonstrate that B. glandula in the field are well-adapted for increasing air temperatures.

Nach dem Zusammenbruch der Sowjetunion stellte der Aufbau eines unabhängigen Staates und einer unabhängigen Nation eine große Herausforderung für die Regierenden der fünfzehn ehemaligen Sowjetrepubliken dar Zwanzig Jahre später, pendelt der Typus, der aus jenen Prozessen hervorgegangenen politischen Regime, zwischen Demokratie und Autokratie. Diese Dissertation konzentriert sich auf die Grauzone zwischen diesen beiden Idealtypen, d.h. auf ‚hybride Regime‘, verstanden als Staaten, die nachweislich freie und faire Wahlen einerseits mit einem autokratischen Regierungsstil andererseits kombinieren. Unter den ehemaligen Sowjetrepubliken sind dies Georgien, Moldawien und die Ukraine. Die zentrale Frage der Arbeit lautet, welche Faktoren die Funktionstüchtigkeit dieser Regime gewährleistet. Es zeigt sich, dass die drei genannten Länder ethnisch stark heterogen sind relative arme Volkswirtschaften mit sehr schwachem Wachstum sind. Es wird argumentiert, dass es diese beiden Strukturmerkmale sind, die das Handeln der heimischen Eliten wesentlich determinieren und die, zusammen mit den durch internationale Geldgeber gesetzten Anreizen, die Dauerhaftigkeit dieser hybriden Regime bedingen. Dagegen steht die politische Polarisierung im Kern des Erklärungsmodells dieser Dissertation. Im Detail sieht das Erklärungsmodell vor, dass sie diesen Einfluss vermittelt durch das Moment der politischen Polarisierung ausüben. Ethnische Spaltungen spiegeln sich in polarisierten politischen Gruppierungen wieder und sind dadurch für einen hochgradig kompetitiven Charakter von Wahlen verantwortlich. Die heimischen Eliten betonen ethnische Antagonismen in ihren Wahlkämpfen und auch die internationalen Geldgeber schüren eine bereits latent konfliktreiche Atmosphäre. Dieses Verhaltensschema sichert den Fortbestand der hybriden Regime in Moldawien und der Ukraine. Die Abwesenheit von Polarisierung, die auf einer leicht entflammbaren Fragen basiert, resultiert in einem Mangel an Kompetitivität.
In the aftermath of the breakdown of the Soviet Union, the leadership in the fifteen former republics found themselves challenged by complex processes of independent state- and nation-building. Twenty years later, the political regimes that emerged vary from democracies to autocracies. This dissertation focuses on the grey zone in between the pure types. Conceptualizing hybrid regimes as the ones that combine holding of free and fair, recognized elections, and autocratic governance, it asks the question of what keeps the former viable. This research singles out Georgia, Moldova and Ukraine as the countries with hybrid regimes. It shows that the three are highly ethnically heterogeneous and have relatively poor, very low-growing economies. This dissertation argues that these structural conditions are responsible for the actions of the domestic elites, which together with the incentives that the international donors provide the domestic elites with make hybrid regimes permanent. The political polarization is at the core of the explanatory account this dissertation presents. Ethnic divisions, reflected in political polarization are responsible for emergence of regimes with competitive elections. The elites emphasize the divisive issues in their campaigning, while the donors support the already thriving competitive environment. This keeps competitive hybrid regimes in Moldova and Ukraine viable. Absence of polarization based on easily inflammable issues results in the lack of competitiveness. However, an absence of divisiveness produces orientation on one vector of donors (the West). The stimulation of reform and praise for achievement in governance that the donors provide keep the non-competitive hybrid regime in Georgia afloat.

Antimicrobial resistance is a serious and imminent threat to human health, though its rise may be controlled with improved stewardship strategies that limit the emergence and spread of resistant strains. Motivated by theoretical models from population genetics and ecology, my M.Sc. experimentally evaluates how varying drug availability in either time or space impacts the prevalence of resistance in a population. By experimentally evolving Pseudomonas aeruginosa under different antibiotic selection regimes in vitro, I show that spatial, but not temporal, drug free refuges delay the fixation of resistance by promoting the coexistence of sensitive and resistant genotypes. Second, I establish that this polymorphism is underlain by a trade-off between resistance and growth rate in the absence of antibiotic that underpins the maintenance of diversity through negative frequency dependent selection. Third, I demonstrate that spatially varied drug selection cannot prevent the fixation of resistance because continued selection leads to the evolution of resistant types that pay smaller costs of resistance and gradually displace sensitive strains. These results provide insight into the fate of diversity under long-term selection and highlight the value of incorporating the principles of evolutionary ecology into antimicrobial resistance stewardship.

This dissertation is a cross-national investigation of the relationship between cultural heterogeneity and regimes' respect for basic human rights. The quantitative human rights literature has not yet addressed the question of whether high levels of cultural diversity are beneficial or harmful. My research addresses this gap. I address the debate between those who argue that diversity is negatively related to basic human rights protection and those who argue it is likely to improve respect for these rights. Ultimately, I propose that regimes in diverse countries will be less likely to provide an adequate level of subsistence (otherwise known as basic human needs) and security rights (also known as integrity of the person rights) to their citizens than regimes in more homogeneous countries. Using a data set of 106 non-OECD countries for the years 1983 and 1993, I employ bivariate, linear multivariate regression, and causal modeling techniques to test whether higher levels of ethnolinguistic and religious diversity are associated with less regime respect for subsistence and security rights. The analysis reveals that higher levels of cultural diversity do appear to lead to lower respect for subsistence rights. However, counter to the hypothesized relationship, high levels of diversity appear to be compatible with high levels of respect for security rights.

Water resources in hard rock terrain are difficult to characterize due to heterogeneity and anisotropy in the fracture network, low porosities and limited recharge volumes available during the summer season. Three methods were developed and evaluated in order to assist in water supply planning. A groundwater resources potential index was estimated using multivariate statistics, where physical and geological variables were classified using Analysis of Variance and Fisher's Least Significant Difference tests according to their effect on hydraulic properties. Principal component analysis was used to assign weights to the different classed variables. Classes and weights were used to produce an index referred to as groundwater resources potential (GRP), which correlated significantly with well data. Nearly 80% of the wells with less than median specific capacity values also had GRP values at those locations of zero or lower. Non-stationary variance was observed in specific capacity sub-samples taken from the Geological Survey of Sweden's well archive, despite homogeneous geology and topography. Spatial statistical analyses showed that spatial correlations were weak in well archive samples, implying that regional approximations based on sparse point data are highly error prone. Kinematic porosity estimated using superficial fracture measurements correlated significantly with well archive data. However, low correlation coefficients indicated that well data is likely not a suitable method for predicting water supply characteristics. This approach is an efficient method which shows promise in preliminary estimations of groundwater storage in heterogenic terrains. A groundwater balance model which describes seasonal groundwater storage changes was created in order to better approximate the groundwater situation often found in Swedish urbanized and semi-urbanized hard rock terrains. The model was based on a water budget approach at the pixel scale, and allows for approximation of well extraction which is not uniformly distributed in space. The model showed that in specific regions groundwater extraction may lead to severe decreases in groundwater level, where these impacts may not otherwise be expected. Dry season modelling with 10% increased evapotranspiration showed that in several areas groundwater reservoir depletion may be influenced by more than 50%.

QC 20140331

This paper analyses the role of the spatial structure of migrant networks in the location decision of migrants to the European Union at the regional level. Using a random parameters logit specification, a significant positive effect of migrant networks in neighbouring regions on migrants' location decisions is found. Although this spatial spillover effect is smaller than the effect of networks in the host regions, omitting to control for this spatial dependence results in a 40% overestimation of the effect of regional migrant networks on the location decision of newly arriving migrants.

The present thesis explores the internationalisation of firms in relation to regionsector characteristics. We focus on outward investment by German firms and classify the heterogeneity across firms, regions and sectors, as well as foreign destinations. The thesis is structured in 5 chapters: a general introduction, followed by 3 empirical chapters and a final conclusion. In the introductory chapter we provide a general conceptual framework and selective review of the literature. Our starting point is that internationalisation is heterogenous across firms as it requires ownership advantages. However, the source of these is less explored and we discuss how regional factors such as the proximity to MNEs can influence foreign expansions. Conceptually we rely on spillover and competition effects and put forward that MNEs can act as catalysts for internationalising domestic firms. Chapter 2 analyses the propensity of German firms to be active as outward investors, exploring and qualifying the heterogeneity across firms, regions and sectors. We find that different forms of proximity matter for the intensive and extensive margins of outward investment by German firms. First, region-sector co-location with MNEs is more important than regional co-location. This lends support to the notion of technological proximity as a facilitator of spillovers. Second, the association between region-sector proximity and the propensity of firms to invest abroad is larger at finer spatial scales. This hints to the tacitness of some knowledge and information about internationalisation processes, as these types of effects and externalities mainly arise between spatially proximate firms. Third, region-sector proximity is shown to matter most when the firm and the proximate MNE are both German-owned. It highlights a potential role of cultural proximity and regional embeddedness for positive externalities or feedback loops to occur. Chapter 3 enquires how destination-specific ties available in the home region in Germany can be leveraged by the internationalising firm when making location decisions abroad. We provide empirical evidence on this by using data on inward and outward investment linkages and migrant networks between a German region and foreign destination. Our findings also reveal that those matter more for likely first-time investors, while within business group experience is not shown to play a role. Using a mixed logit model we further highlight significant heterogeneity across firms in their directionality of outward investments. Larger firms are found to be able to expand to more distant foreign destinations while smaller firms mainly choose European locations. Chapter 4 turns our focus to whole sectors and compares their domestic and global geography. To do so we use detailed geocoded data on the global locations of German manufacturing firms. We reveal that also at the global level there is considerable heterogeneity in the spatial pattern across sectors. The concentration ’intensity’ is also generally higher than at the domestic level and the level of technology in a sector plays a key role for its pattern. While at the domestic level high-tech sectors are found to be the most concentrated, at the global level it is rather low and medium-low tech sectors. At the same time, firms in medium-high tech sectors are the least concentrated in both. As they are often referred to as the ’backbone’ of the German economy, we see potential implications for territorial cohesion and regional disparities.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
In this study, we sampled two anuran communities in two physiographic regions of the Pampa biome, Serra do Sudeste and Depressão Central, were made monthly campaigns during the period between September 2011 and August 2012 where there were registered 25 species of frogs. Scinax granulatus, Physalaemus gracilis e Pseudis minuta were the most abundant species in the Serra do Sudeste, while Dendropsophus minutus, D. sanborni and Scinax squalirostris were the most abundant of the Depressão Central. We recorded 15 species of frogs in the larval stage and four reproductive modes classified as generalists. Ordination analysis showed a segregation among the two physiographic regions, related to anurofauna with a difference of 65% between them. The influence of environmental descriptors and physicochemical variables of water in the structure of the two communities showed that the set of variables, pH, number of extracts of emergent vegetation and temperature were important in structuring the community of Depressão Central, as dissolved oxygen, electrical conductivity number of extracts of emergent vegetation, hydroperiod and percentage of vegetation cover were important factors structuring the community of Serra do Sudeste. However the abundance and richness of the Serra do Sudeste community showed no significant relation with the variables tested and the distance between the puddles did not influence the structure of both communities.
Neste estudo, foram amostradas duas comunidades de anuros em duas regiões fisiográficas do bioma Pampa, a Serra do Sudeste e a Depressão Central, nestas, foram realizadas campanhas mensais durante o período de setembro de 2011 a agosto de 2012 onde foram registradas 25 espécies de anuros. Scinax granulatus, Physalaemus gracilis e Pseudis minuta foram as espécies mais abundantes na Serra do Sudeste, enquanto Dendropsophus minutus, D. sanborni e Scinax squalirostris foram as mais abundantes da Depressão Central. Foram registrados 15 espécies de anuros em estágio larval e quatro modos reprodutivos generalistas. A análise de ordenação mostrou uma segregação quanto a anurofauna das duas regiões fisiográficas e uma diferença de 65% entre elas. A influência dos descritores ambientais e das variáveis físico-químicas da água na estrutura das duas comunidades mostrou que o conjunto de variáveis, pH, número de extratos de vegetação emergente e temperatura foram importantes na estruturação da comunidade da Depressão Central, já o oxigênio dissolvido, condutividade elétrica número de extratos de vegetação emergente, hidroperíodo e porcentagem de cobertura vegetal foram importantes estruturadores da comunidade da Serra do Sudeste. A abundância e a riqueza de anuros da Serra do Sudeste não apresentou relação significativa com as variáveis testadas e a distância entre as poças não influenciou na estrutura das mesmas.

Cette thèse s’intéresse à l’option de création d’une union monétaire entre les trois pays du Maghreb, àsavoir l’Algérie, le Maroc et la Tunisie. Elle essaye de répondre aux interrogations suivantes : quelles sont lescaractéristiques des régimes monétaires des pays du Maghreb et comment leurs choix sont-ils justifiés ? Les structures et lesinstitutions de ces pays les rendent-ils éligibles à une union monétaire ? Quelles conséquences macroéconomiques ces payspourront-ils supporter s’ils décident de créer cette union ? Existe-t-il des régimes monétaires alternatifs plus appropriés leursfacilitant in fine la transition vers l’étape ultime de l’intégration monétaire ?Afin de répondre à ces questions, nous avons opté pour la présentation de quatre chapitres. Nous avons décritdans un premier chapitre les fondements théoriques de l’intégration monétaire à travers l’étude de la théorie desZones Monétaires Optimales (ZMO), ses développements, ses lacunes, ses prolongements et ses applicationsempiriques. Nous avons tenté dans un deuxième chapitre de spécifier les mécanismes structurels et institutionnelssusceptibles de garantir la viabilité du processus d’intégration monétaire et de faire recours à quelques expérienceshistoriques. Nous avons essayé dans un troisième chapitre de décrire les régimes monétaires pratiqués par lespays du Maghreb et d’expliquer l’origine de leur hétérogénéité avant d’expliciter les possibilités de création d’uneZMO en présence de cette hétérogénéité. Enfin, nous avons cherché dans un quatrième chapitre à évaluer lesconséquences de la création d’une union monétaire entre les trois pays. Nous avons aussi proposé les régimesmonétaires envisageables qui leur permettent in fine une transition réussie vers cette union monétaire.Nos principaux résultats montrent que la création d’une union monétaire -et son corollaire la mise en place d’unerègle monétaire commune- n’est pas bénéfique, surtout pour l’Algérie du fait que la variabilité de l’inflation et del’activité est beaucoup plus importante qu’au Maroc ou en Tunisie. D’autre part, il a été convenu quel’harmonisation des cibles d’inflation dans le cadre d’un taux de change quasi-flexible ou l’instauration simultanéed’une caisse d’émission pourraient être des régimes monétaires appropriés permettant à ces trois pays unetransition réussie vers l’unification monétaire
This thesis focuses on the option of the launching of a monetary union across three Maghreb Countries, notablyAlgeria, Morocco and Tunisia. It tries to answer the following questions: What are the characteristics of monetaryregimes in the Maghreb Countries and what are the underlying factors for their choices? Do the countries’ structures andinstitutions constitute a favourable environment for the creation of a monetary union between these countries? What would bethe macroeconomic consequences for these countries if they decided to create a monetary union? Are there any alternativemonetary regimes which would enable them to move toward the final steps of monetary integration in a more appropriate way?In order to answer these questions, we opted for a presentation of four chapters. In a first chapter, we describedthe theoretical foundations of monetary integration through the study of Optimum Currency Area Theory (OCA),their theoretical developments, their drawbacks, their extensions and their empirical applications. We tried in asecond chapter to present the structural and institutional mechanisms that insure the viability of the monetaryintegration process and to recourse to some historical experiences. We attempted in a third chapter to describe themonetary regimes currently in use in the Maghreb Countries and to explain the origin of their heterogeneity beforeanalyzing the possibility of setting up an OCA in this context of heterogeneity. Finally, in a fourth chapter, weassessed the consequences of the creation of a monetary union across the three countries. We also suggest possiblemonetary regimes which, in fine, might allow these countries to successfully move toward monetary union.Our main results show that the creation of a monetary union –and its corollary the implementation of a commonmonetary rule- is not beneficial, especially for Algeria where the variability of inflation and activity is moreimportant than in Morocco and Tunisia. On the other hand, we came to the conclusion that the harmonization ofinflation targets within a quasi-flexible exchange rate or the simultaneous setting up of a currency board in thesecountries could represent an appropriate monetary regime which would allow a safe move to monetary union

Диссертация на соискание ученой степени доктора технических наук по специальности 05.13.03 – системы и процессы управления. – Харьковский национальный технический университет сельського хозяйства имени Петра Василенка. – Харьков, 2015. Диссертация посвящена решению проблемы поддержки принятия решений и оценки их эффективности в системе управления качеством процесса распределения электрической энергии при неоднородных режимах работы в условиях неопределенности. Проведенный анализ литературных источников показал, что в системах управления распределением электрической энергии (СУРЭ) имеют место неоднородные режимы вследствие несимметрии и несинусоидальности токов и напряжений, обусловленные неравномерным распределением электроприемников между фазами и наличием электроприемников с нелинейными вольт-амперными характеристиками, что в свою очередь негативно сказывается на работе электрооборудования объектов электроснабжения и сроке его службы, а также приводит к увеличению дополнительных потерь электрической энергии. Исследована работа СУРЭ в условиях неоднородности режимов вследствие несимметрии и несинусоидальности напряжения. Разработан метод оценки качества электрической энергии в СУРЭ с однофазными нагрузками, который позволяет определять уровни напряжений у потребителей и потери при любой ее конфигурации, несиметрии токов и напряжений. Разработан метод определения потерь электрической энергии в СУРЭ при неоднородных режимах вследствие несимметрии напряжений, который позволяет производить вычисления по величинам напряжений в начале и в конце линии и ее средним электрическим параметрам. Разработан комплекс технических средств, которые позволяют выполнять как мониторинг, так и осуществлять корректирующее воздействие на параметры неоднородных режимов СУРЭ и показатели качества электрической энергии, а также снижать дополнительные потери от неоднородных режимов.
Dissertation for scientific degree of doctor of technical sciences on specialty 05.13.03 – management of systems and processes. – Kharkiv Petro Vasylenko National Technical University of Agriculture. – Kharkiv, 2015. The thesis is devoted to the problem solving of decision-making supporting and valuing their effectiveness in the system of quality management process of distribution of electric power in heterogeneous modes under uncertainty. It was developed valuation methods heterogeneous operating mode of SOED, taking into account unsymmetric with stochastic or deterministic nature, in order to raise the effectiveness of process control of electrical energy distribution. With the purpose of identification of heterogeneous regimes as result of non-sinusoidal voltage distortion in SOED a method based on the wavelet analysis and neural network developed and it allows you to recognize a distorted image signal voltage. It was investigated that wavelet Paul can provide various voltage distortion and gain frequency components and their positions at the time axis simultaneously.It was worked out a method for decision support with a equal distribution of SOED using genetic algorithms, which allows you select the Pareto-optimal solutions in terms of reduction of losses and the quantitative re-strapping. Also, it was developed the method of decision-making in SOED by equal distribution of electro-based neural network that uses voltage average of distribution at the maximum loading per the season, thus reducing the additional losses of electricity.In order to assess the quality of the control system functioning of electricity distribution quality in terms of uncertainty it was developed the method, which evaluates a fuzzy extent accordance to standards and quality indicators to track change of electricity quality even if the major parameters do not exceed permissible values.

Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.13.03 – системи та процеси керування. – Харківський національний технічний університет сільського господарства імені Петра Василенка. – Харків, 2015. Дисертацію присвячено вирішенню проблеми підтримки прийняття рішень і оцінки їх ефективності в системі керування якістю процесу розподілу електричної енергії при неоднорідних режимах роботи в умовах невизначеності. Для підвищення ефективності керування процесом розподілу електричної енергії розроблено методи оцінки неоднорідних режимів роботи СКРЕ з урахуванням несиметрії, що носить стохастичний або детермінований характер. З метою ідентифікації неоднорідних режимів внаслідок несинусоїдальних спотворень напруги в СКРЕ розроблено метод, що базується на використанні вейвлет-аналізу та нейронної мережі, і дозволяє розпізнати образ спотвореного сигналу напруги. Досліджено, що вейвлет Paul дозволяє виділити різні спотворення напруги та отримати частотні компоненти і їх положення на часовій осі одночасно. Розроблено метод підтримки прийняття рішення з рівномірного розподілу електроприймачів в СКРЕ з використанням генетичних алгоритмів, який дозволяє вибрати Парето-оптимальні рішення за рівнем зниження втрат і кількості перекомутацій. Також розроблено метод прийняття рішень в СКРЕ по рівномірному розподілу електроприймачів на базі нейронної мережі, який використовує математичні сподівання струмів в максимум навантаження за сезон, що дозволяє знизити додаткові втрати електричної енергії. З метою оцінки функціонування системи керування якості процесу розподілу електричної енергії в умовах невизначеності розроблено метод, який в нечіткому вигляді оцінює ступінь відповідності показників якості нормам та дозволяє відслідковувати зміну якості електричної енергії навіть, якщо основні показники не виходять за межі допустимих значень.
Dissertation for scientific degree of doctor of technical sciences on specialty 05.13.03 – management of systems and processes. – Kharkiv Petro Vasylenko National Technical University of Agriculture. – Kharkiv, 2015. The thesis is devoted to the problem solving of decision-making supporting and valuing their effectiveness in the system of quality management process of distribution of electric power in heterogeneous modes under uncertainty. It was developed valuation methods heterogeneous operating mode of SOED, taking into account unsymmetric with stochastic or deterministic nature, in order to raise the effectiveness of process control of electrical energy distribution. With the purpose of identification of heterogeneous regimes as result of non-sinusoidal voltage distortion in SOED a method based on the wavelet analysis and neural network developed and it allows you to recognize a distorted image signal voltage. It was investigated that wavelet Paul can provide various voltage distortion and gain frequency components and their positions at the time axis simultaneously.It was worked out a method for decision support with a equal distribution of SOED using genetic algorithms, which allows you select the Pareto-optimal solutions in terms of reduction of losses and the quantitative re-strapping. Also, it was developed the method of decision-making in SOED by equal distribution of electro-based neural network that uses voltage average of distribution at the maximum loading per the season, thus reducing the additional losses of electricity.In order to assess the quality of the control system functioning of electricity distribution quality in terms of uncertainty it was developed the method, which evaluates a fuzzy extent accordance to standards and quality indicators to track change of electricity quality even if the major parameters do not exceed permissible values.

Big Data on cities and regions bring new opportunities and challenges to data analysts and city planners. On the one side, they hold great promise to combine increasingly detailed data for each citizen with critical infrastructures to plan, govern and manage cities and regions, improve their sustainability, optimize processes and maximize the provision of public and private services. On the other side, the massive sample size and high-dimensionality of Big Data and their geo-temporal character introduce unique computational and statistical challenges. This chapter provides overviews on the salient characteristics of Big Data and how these features impact on paradigm change of data management and analysis, and also on the computing environment.
Series: Working Papers in Regional Science

Pine sandhill are integral pyrogenic communities in the southeastern United States. Though once widespread, habitat destruction, fire suppression and fragmentation have reduced the population to nearly 3%. It is important to learn as much as possible about these unique areas in order to implement best management practices to conserve and restore the existing populations of these communities. Fire is central to the maintenance of pine sandhill communities and two conceptual hypothesis regarding burn frequency have come to light in maintaining the unique species composition and richness of these areas. The first is the Intermediate Disturbance Hypothesis which suggests that intermediate fire regime maintains species diversity. The second is the Most Frequent Fire Hypothesis suggests that these areas should be burned as frequently as fuels allow. We used species area curves and species area relationships to answer the following questions about a pine sandhill community in the burn plot area of the University of South Florida Ecological Research Area (ERA). What are the patterns of species richness and how do they change with spatial scale? What are the factors contributing to the heterogeneity of this area and how much are they contributing? Do similarly burned areas have similar species composition? Do our results shed some light on the Intermediate Disturbance Hypothesis or Most Frequent Fire Hypothesis? We found that physical distance contributed more to species compositional and spatial patterns than burn regime or elevation, whose effects were small. On this particular scale, the results did not support either the Intermediate Disturbance Hypothesis or Most Frequent Fire Hypothesis, as acquisition rates of species in all burn regimes were quite similar. There was no obvious pattern of increased species richness with frequent or intermediate burning. Our results suggest a need for a dynamic plan for the conservation, preservation and management of pine sandhill communities. One must consider as many factors as possible when managing these lands, as every sandhill is unique. More research should be conducted on these ecologically sensitive and diminished areas in order to formulate best management practices to conserve, protect and restore pine sandhill in the southeastern United States.

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Estudos abrangendo aspectos da ecologia populacional de plantas fornecem informações importantes sobre os processos de regeneração, ocorrência de perturbações e os meios pelos quais as espécies exploram seus ambientes. Estudos dessa natureza em Florestas de Restinga, feições marcantes no litoral brasileiro, ainda são escassos. Assim, no presente trabalho foram investigados alguns aspectos da ecologia populacional de Calophyllum brasiliense Cambess. (Clusiaceae), uma espécie de ampla ocorrência em ambienteis sujeitos à inundação nas florestas Neotropicais, em 0,5 ha de Floresta de Restinga, localizada no Parque Estadual da Serra do Mar, Núcleo Picinguaba, Ubatuba, SP. Foi realizada uma análise temporal da estrutura de tamanho e do padrão de distribuição espacial da população, visando compreender como a heterogeneidade ambiental, relacionada às variações na microtopografia (mosaico de regiões sobre e entre cordões arenosos), na abertura do dossel da floresta e nas condições de drenagem do solo, afeta os parâmetros da estrutura populacional analisados. Observou-se que a população apresenta estrutura com predomínio de indivíduos nas menores classes de tamanho e distribuição agregada em todas as classes (plântulas, jovens, imaturos e adultos). A saturação hídrica do solo e as diferenças na microtopografia dos cordões arenosos influenciaram o padrão encontrado e afetaram os parâmetros demográficos, entretanto, não foram encontradas correlações entre a abertura de dossel e os parâmetros analisados. Além disso, a análise da estrutura de tamanho em subclasses de altura revelou ausência de indivíduos com alturas entre três e 15 metros, o que pode ser um indicativo de que apesar da população apresentar representantes em todas as classes de tamanho, o acesso dos indivíduos à classe reprodutiva está comprometido...
Studies concerning plant population ecology provide important information about status of regeneration, occurrence of disturbances and the means by which the species exploit the environment. Studies like these, in the “Restingas” forests, striking features in the Brazilian coast, are still scarce. Therefore, we investigated some aspects of population ecology of Calophyllum brasiliense Cambess. (Clusiaceae), in 0.5 ha of the Restinga Forest, in the “Parque Estadual da Serra do Mar”, “Núcleo Picinguaba”, Municipality of Ubatuba, São Paulo State. We performed a temporal analysis of size structure and spatial pattern, to understand how the environmental heterogeneity, such as microtopography variations, light availability and soil drainage conditions can affect the population structure. Population structure presented dominance of individuals in lower size classes as well as aggregated distribution. These patterns result of both drainage and microtopography conditions, however, no correlations were found between canopy openness and the parameters analyzed. In addition, the size structure analysis, performed into different height classes, showed no individuals with heights between 3 and 15 m, which can suggest that the access to reproductive class seems to be compromised, even though there were individuals within all size classes. It was also observed a high frequency of herbivory damage; however, such damage did not contribute to increase the mortality rate of the population. In general, it could be concluded that environmental heterogeneity has a major influence on the size structure and spatial distribution, mainly in smaller size classes, and that the population seems to have trouble reaching the reproductive stage, which can lead, as a long term, to its disappearance in the area.

Dans cette thèse, nous nous intéressons aux questions de l’hétérogénéité inobservée et des solutions en coin dans les modèles de choix d’assolements. Pour répondre à ces questions, nous nous appuyons sur un modèle de choix de production multicultures avec choix d’assolement de forme NMNL, dont nous proposons des extensions. Ces extensions conduisent à des problèmes spécifiques d’estimation, auxquels nous apportons des solutions. La question de l’hétérogénéité inobservée est traitée en considérant une spécification à paramètres aléatoires. Ceci nous permet de tenir compte des effets de l’hétérogénéité inobservée sur l’ensemble des paramètres du modèle. Nous montrons que les versions stochastiques de l’algorithme EM sont particulièrement adaptées pour estimer ce type de modèle.Nos résultats d’estimation et de simulation montrent que les agriculteurs réagissent de façon hétérogène aux incitations économiques et que ne pas tenir compte de cette hétérogénéité peut conduire à des effets simulés de politiques publique biaisés.Pour tenir compte des solutions en coin dans les choix d’assolement, nous proposons une modélisation basée sur les modèles à changement de régime endogène avec coûts fixes associés aux régimes. Contrairement aux approches basées sur des systèmes de régression censurées, notre modèle est cohérent d’un point de vue micro-économique. Nos résultats montrent que les coûts fixes associés aux régimes jouent un rôle important dans le choix des agriculteurs de produire ou non certaines cultures et qu’ils constituent, à court terme, un déterminant important des c
In this thesis, we are interested in questions of unobserved heterogeneity and corner solutions in acreage choice models. To answer these questions, we rely on a NMNL acreage share multi-crop models, of which we propose extensions. These extensions lead to specific estimation problems, to which we provide solutions.The question of unobserved heterogeneity is dealt with by considering a random parameter specification. This allows us to take into account the effects of the unobserved heterogeneity on all the parameters of the model. We show that the stochastic versions of the EM algorithm are particularly suitable for estimating this type of modelOur estimation and simulation results show that farmers react heterogeneously to economic incentives and that ignoring this heterogeneity can lead to biased simulated effects of public policies.In order to take account of the corner solutions in acreage choices, we propose modelling based on endogenous regime switching models with regime fixed costs. Unlike approaches based on censored regression systems, our model is “fully” consistent from a micro-economic viewpoint. Our results show that the regime fixed costs play an important role in farmers’ choice to produce or not some crops and they are, in the short term, an important determinant of acreage choices

Doutoramento em Bioquímica
Os polissacarídeos são os componentes maioritários dos grãos de café verde e torrado e da bebida de café. Os mais abundantes são as galactomananas, seguindo-se as arabinogalactanas. Durante o processo de torra, as galactomananas e arabinogalactanas sofrem modificações estruturais, as quais estão longe de estar completamente elucidadas devido à sua diversidade e à complexidade estrutural dos compostos formados. Durante o processo de torra, as galactomananas e arabinogalactanas reagem com proteínas, ácidos clorogénicos e sacarose, originando compostos castanhos de alto peso molecular contendo nitrogénio, designados de melanoidinas. As melanoidinas do café apresentam diversas atividades biológicas e efeitos benéficos para a saúde. No entanto, a sua estrutura exata e os mecanismos envolvidos na sua formação permanecem desconhecidos, bem como a relação estrutura-atividade biológica. A utilização de sistemas modelo e a análise por espectrometria de massa permitem obter uma visão global e, simultaneamente, detalhada das modificações estruturais nos polissacarídeos do café promovidas pela torra, contribuindo para a elucidação das estruturas e mecanismos de formação das melanoidinas. Com base nesta tese, oligossacarídeos estruturalmente relacionados com a cadeia principal das galactomananas, (β1→4)-Dmanotriose (Man3), e as cadeias laterais das arabinogalactanas, (α1→5)-Larabinotriose (Ara3), isoladamente ou em misturas com ácido 5-Ocafeoilquínico (5-CQA), o ácido clorogénico mais abundante nos grãos de café verde, e péptidos compostos por tirosina e leucina, usados como modelos das proteínas, foram sujeitos a tratamento térmico a seco, mimetizando o processo de torra. A oxidação induzida por radicais hidroxilo (HO•) foi também estudada, uma vez que estes radicais parecem estar envolvidos na modificação dos polissacarídeos durante a torra. A identificação das modificações estruturais induzidas por tratamento térmico e oxidativo dos compostos modelo foi feita por estratégias analíticas baseadas principalmente em espectrometria de massa, mas também em cromatografia líquida. A cromatografia de gás foi usada na análise de açúcares neutros e ligações glicosídicas. Para validar as conclusões obtidas com os compostos modelo, foram também analisadas amostras de polissacarídeos do café obtidas a partir de resíduo de café e café instantâneo. Os resultados obtidos a partir dos oligossacarídeos modelo quando submetidos a tratamento térmico (seco), assim como à oxidação induzida por HO• (em solução), indicam a ocorrência de despolimerização, o que está de acordo com estudos anteriores que reportam a despolimerização das galactomananas e arabinogalactanas do café durante a torra. Foram ainda identificados outros compostos resultantes da quebra do anel de açúcares formados durante o tratamento térmico e oxidativo da Ara3. Por outro lado, o tratamento térmico a seco dos oligossacarídeos modelo (individualmente ou quando misturados) promoveu a formação de oligossacarídeos com um maior grau de polimerização, e também polissacarídeos com novos tipos de ligações glicosídicas, evidenciando a ocorrência de polimerização através reações de transglicosilação não enzimática induzidas por tratamento térmico a seco. As reações de transglicosilação induzidas por tratamento térmico a seco podem ocorrer entre resíduos de açúcares provenientes da mesma origem, mas também de origens diferentes com formação de estruturas híbridas, contendo arabinose e manose como observado nos casos dos compostos modelo usados. Os resultados obtidos a partir de amostras do resíduo de café e de café instantâneo sugerem a presença de polissacarídeos híbridos nestas amostras de café processado, corroborando a ocorrência de transglicosilação durante o processo de torra. Além disso, o estudo de misturas contendo diferentes proporções de cada oligossacarídeo modelo, mimetizando regiões do grão de café com composição distinta em polissacarídeos, sujeitos a diferentes períodos de tratamento térmico, permitiu inferir que diferentes estruturas híbridas e não híbridas podem ser formadas a partir das arabinogalactanas e galactomananas, dependendo da sua distribuição nas paredes celulares do grão e das condições de torra. Estes resultados podem explicar a heterogeneidade de estruturas de melanoidinas formadas durante a torra do café. Os resultados obtidos a partir de misturas modelo contendo um oligossacarídeo (Ara3 ou Man3) e 5-CQA sujeitas a tratamento térmico a seco, assim como de amostras provenientes do resíduo de café, mostraram a formação de compostos híbridos compostos por moléculas de CQA ligadas covalentemente a um número variável de resíduos de açúcar. Além disso, os resultados obtidos a partir da mistura contendo Man3 e 5-CQA mostraram que o CQA atua como catalisador das reações de transglicosilação. Por outro lado, nas misturas modelo contendo um péptido, mesmo contendo também 5-CQA e sujeitas ao mesmo tratamento, observou-se uma diminuição na extensão das reações transglicosilação. Este resultado pode explicar a baixa extensão das reações de transglicosilação não enzimáticas durante a torra nas regiões do grão de café mais ricas em proteínas, apesar dos polissacarídeos serem os componentes maioritários dos grãos de café. A diminuição das reações de transglicosilação na presença de péptidos/proteínas pode dever-se ao facto de os resíduos de açúcares redutores reagirem preferencialmente com os grupos amina de péptidos/proteínas por reação de Maillard, diminuindo o número de resíduos de açúcares redutores disponíveis para as reações de transglicosilação. Além dos compostos já descritos, uma diversidade de outros compostos foram formados a partir dos sistemas modelo, nomeadamente derivados de desidratação formados durante o tratamento térmico a seco. Em conclusão, a tipificação das modificações estruturais promovidas pela torra nos polissacarídeos do café abre o caminho para a compreensão dos mecanismos de formação das melanoidinas e da relação estrutura-atividade destes compostos.
Polysaccharides are the major components of green and roasted coffee beans, and coffee brew. The most abundant ones are galactomannans, followed by arabinogalactans. During the roasting process, galactomannans and arabinogalactans undergo structural modifications that are far to be completely elucidated due to their diversity and complexity of the compounds formed. During the roasting process, galactomannans and arabinogalactans react with proteins, chlorogenic acids, and sucrose, originating high molecular weight brown compounds containing nitrogen, known as melanoidins. Several biological activities and beneficial health effects have been attributed to coffee melanoidins. However, their exact structures and the mechanisms involved in their formation remain unknown, as well as the structure-biological activity relationship. The use of model systems and mass spectrometry analysis allow to obtain an overall view and, simultaneously, detailed, of the structural modifications in coffee polysaccharides promoted by roasting, contributing to the elucidation of the structures and formation mechanisms of melanoidins. Based on this thesis, oligosaccharides structurally related to the backbone of galactomannans, (β1→4)-D-mannotriose, and the side chains of arabinogalactans, (α1→5)-Larabinotriose, alone or in mixtures with 5-O-caffeoylquinic acid, the most abundant chlorogenic acid in green coffee beans, and dipeptides composed by tyrosine and leucine, used as models of proteins, were submitted to dry thermal treatments, mimicking the coffee roasting process. The oxidation induced by hydroxyl radicals (HO•) was also studied, since these radicals seem to be involved in the modification of the polysaccharides during roasting. The identification of the structural modifications induced by thermal and oxidative treatment of the model compounds was performed mostly by mass spectrometry-based analytical strategies, but also using liquid chromatography. Gas chromatography was used in the analysis of neutral sugars and glycosidic linkages. To validate the conclusions achieved with the model compounds, coffee polysaccharide samples obtained from spent coffee grounds and instant coffee were also analysed. The results obtained from the model oligosaccharides when submitted to thermal treatment (dry) or oxidation induced by HO• (in solution) indicate the occurrence of depolymerization, which is in line with previous studies reporting the depolymerization of coffee galactomannans and arabinogalactans during roasting. Compounds resulting from sugar ring cleavage were also formed during thermal treatment and oxidative treatment of Ara3. On the other hand, the dry thermal treatment of the model oligosaccharides (alone or when mixed) promoted the formation of oligosaccharides with a higher degree of polymerization, and also polysaccharides with new type of glycosidic linkages, evidencing the occurrence of polymerization via non-enzymatic transglycosylation reactions induced by dry thermal treatment. The transglycosylation reactions induced by dry thermal treatment can occur between sugar residues from the same origin, but also of different origins, with formation of hybrid structures, containing arabinose and mannose in the case of the model compounds used. The results obtained from spent coffee grounds and instant coffee samples suggest the presence of hybrid polysaccharides in these processed coffee samples, corroborating the occurrence of transglycosylation during the roasting process. Furthermore, the study of mixtures containing different proportions of each model oligosaccharide, mimicking coffee bean regions with distinct polysaccharide composition, subjected to different periods of thermal treatment, allowed to infer that different hybrid and non-hybrid structures may be formed from arabinogalactans and galactomannans, depending on their distribution in the bean cell walls and on roasting conditions. These results may explain the heterogeneity of melanoidins structures formed during coffee roasting. The results obtained from model mixtures containing an oligosaccharide (Ara3 or Man3) and 5-CQA and subjected to dry thermal treatment, as well as samples derived from spent coffee grounds, showed the formation of hybrid compounds composed by CQA molecules covalently linked to a variable number of sugar residues. Moreover, the results obtained from the mixture containing Man3 and 5-CQA showed that CQA acts as catalyst of transglycosylation reactions. On the other hand, in the model mixtures containing a peptide, even if containing 5-CQA and subjected to the same treatment, it was observed a decrease in the extent of transglycosylation reactions. This outcome can explain the low extent of non-enzymatic transglycosylation reactions during roasting in coffee bean regions enriched in proteins, although polysaccharides are the major components of the coffee beans. The decrease of transglycosylation reactions in the presence of peptides/proteins can be related with the preferential reactivity of reducing residues with the amino groups of peptides/proteins by Maillard reaction, decreasing the number of reducing residues available to be directly involved in the transglycosylation reactions. In addition to the compounds already described, a diversity of other compounds were formed from model systems, namely dehydrated derivatives formed during dry thermal treatment. In conclusion, the identification of the structural modifications in coffee polysaccharides promoted by roasting pave the way to the understanding of the mechanisms of formation of melanoidins and structure-activity relationship of these compounds.

碩士
國立交通大學
經營管理研究所
105
It becomes more difficult for researcher to analyze data from internet or company due to data increases dramatically. Therefore, when researcher intends to find the causal relationship from the database to study or decide, the traditional experiment needs to be modified. Fortunately, DID approximation provides a way to solve this problem. When the analysis is made, we should choose independent variable and dependent variable based on theory to avoid tautology mistake. In addition, the individual heterogeneity is also a very important parameter for research results. However, the individual experience of subject may influence his/her attitude in the studying process, and further affect the behavior he/she presents in the study. Once it happens, the truth may be hidden beyond the individual characteristics or thinking and the correct attribution cannot be obtained.

Commodities are known to exhibit a cyclical behavior. The present work studies the dynamics of commodities regimes and their portfolio diversification properties. Using an extension of the regime-switching model, we find that the twelve commodities studied can be clustered into four classes with different regime dynamics. This demonstrates that commodities are far from having a homogenous asset class behavior. The existence of two regimes is transversal to the assets studied. One regime marked by a high volatility and the other by a low volatility. In both regimes, most of the commodities exhibit returns which are not statistically different from the stock market. The exceptions are Crude Oil-Brent and Natural Gas during the low volatility regime. The analysis of regime synchronization between the assets studied shows that our stock market proxy has a low synchronization with the commodities. This suggests a potential diversification value from adding commodities to an equity portfolio. Constructing the portfolio efficient frontier with the assets studied for each regime of our stock market proxy, we find that commodities have diversification value when added to an equity portfolio in both regimes. The benefits of diversifying into commodities are particularly strong in the stock market bear regime.
As commodities são conhecidas por exibir um comportamento cíclico. O presente trabalho estuda a dinâmica dos regimes das commodities e as suas propriedades de diversificação da carteira. Utilizando uma extensão do modelo de mudança de regime, observamos que as doze commodities estudadas podem ser agrupadas em quatro classes com diferentes dinâmicas de regime. Este resultado demonstra que as commodities se encontram longe de apresentar um comportamento homogéneo enquanto classe de ativos. A existência de dois regimes é transversal aos ativos estudados. Um dos regimes é marcado por uma alta volatilidade e o outro por uma baixa volatilidade. Em ambos os regimes, a maior parte das commodities estudadas apresenta retornos que não são estatisticamente diferentes dos apresentados pelo mercado de acções. As exceções são o Crude Oil-Brent e o Gás Natural no regime de baixa volatilidade. A análise da sincronização de regimes entre os ativos estudados mostra que a nossa proxy do mercado de ações apresenta uma baixa sincronização com as commodities. Este resultado sugere a existência de um potencial valor de diversificação resultante da adição de commodities a uma carteira de ações. Da construção da fronteira eficiente de portfolio com os ativos estudados para cada um dos regimes da nossa proxy do mercado acionista, verificamos que as commodities têm valor de diversificação quando adicionadas a uma carteira de ações em ambos os regimes. Este valor de diversificação é particularmente evidente no regime de contração do mercado acionista.

abstract: Broadband dielectric spectroscopy is a powerful technique for understanding the dynamics in supercooled liquids. It generates information about the timescale of the orientational motions of molecular dipoles within the liquid. However, dynamics of liquids measured in the non-linear response regime has recently become an area of significant interest, because additional information can be obtained compared with linear response measurements. The first part of this thesis describes nonlinear dielectric relaxation experiments performed on various molecular glass forming-liquids, with an emphasis on the response at high frequencies (excess wing). A significant nonlinear dielectric effect (NDE) was found to persist in these modes, and the magnitude of this NDE traces the temperature dependence of the activation energy. A time resolved measurement technique monitoring the dielectric loss revealed that for the steady state NDE to develop it would take a very large number of high amplitude alternating current (ac) field cycles. High frequency modes were found to be ‘slaved’ to the average structural relaxation time, contrary to the standard picture of heterogeneity. Nonlinear measurements were also performed on the Johari-Goldstein β-relaxation process. High ac fields were found to modify the amplitudes of these secondary modes. The nonlinear features of this secondary process are reminiscent of those found for the excess wing regime, suggesting that these two contributions to dynamics have common origins. The second part of this thesis describes the nonlinear effects observed from the application of high direct current (dc) bias fields superposed with a small amplitude sinusoidal ac field. For several molecular glass formers, the application of a dc field was found to slow down the system via reduction in configurational entropy (Adam-Gibbs relation). Time resolved measurements indicated that the rise of the non-linear effect is slower than its decay, as observed in the electro-optical Kerr effect. A model was discussed which quantitatively captures the observed magnitudes and time dependencies of the NDE. Asymmetry in these rise and decay times was demonstrated as a consequence of the quadratic field dependence of the entropy change. It was demonstrated that the high bias field modifies the polarization response to the field, even including the zero field limit.
Dissertation/Thesis
Doctoral Dissertation Chemistry 2016

In the central Alps permafrost can be expected above 2300 m a.s.l., at altitudes where mean annual air temperatures are below -1 °C. Isolated permafrost occurrences can be detected in north-exposed talus slopes, far below the timberline, where mean annual air temperatures are positive. Driving factors are assumed to be a low income of solar radiation, a thick organic layer with high insulation capacities as well as the thermally induced chimney effect. Aim of this study is to achieve a deeper understanding of the factors determining the site-specific thermal regime, as well as the spatially limited and temporally highly variable permafrost occurrences in vegetated talus slopes. Three supercooled talus slopes in the Swiss Alps were chosen for investigation. Substantially different characteristics were a central criterion in the selection of study sites. Located in the Upper Engadin, climatic conditions, altitude as well as dimensions of the talus slopes are comparable for the study sites Val Bever and Val Susauna; major differences are rooted in the nature of talus substrate and in humus- and vegetation distribution. Characteristics of the Brüeltobel site, located in the Appenzeller Alps, diverge with regard to climatic conditions, altitude and dimensions of the talus slope; humus- and vegetation compositions are comparable to the Val Susauna site. Confirmation and characterisation of ground ice is accomplished by the application of electrical resistivity and seismic refraction tomography. The estimation of the spatial permafrost distribution is based on quasi-3D resistivity imaging. For the confirmation of permafrost and the analysis of its temporal variability electrical resistivity monitoring arrays were constructed and installed at all study sites, to allow year-round measurements. In addition to resistivity monitoring, the – up to now – first seismic refraction tomography winter monitoring was conducted at the Val Susauna to analyse the permafrost evolution during the winter half-year. Investigations of the ground thermal regime were based on the analysis of temperature logger data. Besides recording air- and ground surface temperatures, focus was set on the temperature evolution in vents and in the organic layer. To analyse the relationship between permafrost distribution on the one hand and humus- and vegetation distribution on the other hand, an extensive mapping of humus characteristics and vegetation composition was conducted at Val Susauna. The existence of permafrost could be proven at all study sites. Spatially, permafrost bodies show a narrow transition to neighbouring, unfrozen areas. As observed at Val Susauna, the permafrost distribution strongly correlates with areas with exceptionally thick organic layer, high percentages of mosses and lichens in the undergrowth and dwarf grown trees. The temporal variability of permafrost has proven to be exceptionally high, with the magnitude of seasonal variations distinctly exceeding intra-annual changes. Thereby, the winter season is characterised by a significant supercooling. During snowmelt a growth in volumetric ice content is induced by refreezing of percolating meltwater on the supercooled talus. The results confirmed the fundamental influence of the chimney effect on the existence and temporal variability of permafrost in talus slopes. Divergences in the effectiveness of the thermal regime were detected between the study sites. These are based on differences in the nature of talus material, humus characteristics and vegetation composition. During summer, the organic material is usually dry at the daytime, inducing a high insulation capability and a protection of the subsurface against high atmospheric temperatures. Bouldery talus slopes typically show an organic layer that is fragmented by large boulders, which induces a strongly reduced insulation capability and allows an efficient heat exchange by convective airflow and percolating precipitation water. In the winter half-year, the thermal conductivity of the organic layer increases massively under moist or frozen conditions, allowing an efficient, conductive cooling of the talus material. The convective cooling in bouldery talus slopes affects an earlier onset and a higher magnitude of supercooling than under consistent humus conditions. Here, conductive heat flow is dominant and the cooling in autumn is buffered by a prolonged zero curtain. The snow cover has proven to be incapable of prohibiting an efficient supercooling of the talus slope in winter, almost independent from thickness
In den zentralen Alpen kann oberhalb einer Höhe von 2300 m ü NN, bei mittleren Jährlichen Lufttemperaturen von weniger als -1 °C mit Permafrost gerechnet werden. Isolierte Permafrostvorkommen können jedoch in nordexponierten Hangschutthalden bei positiven Jahresmitteltemperaturen bis weit unterhalb der Waldgrenze gefunden werden. Ziel dieser Arbeit ist es ein tieferes Verständnis des Faktorenkomplexes zu erreichen, der das standortspezifische, kleinräumige thermale Regime bedingt und damit die räumlich begrenzten, zeitlich hochvariablen Permafrostvorkommen in Hangschutthalden unterhalb der Waldgrenze steuert und ermöglicht. Drei unterkühlte Hangschutthalden in den Schweizer Alpen wurden zur Untersuchung ausgewählt. Bei der Auswahl wurde im Speziellen auf fundamentale Unterschiede der Standortfaktoren Wert gelegt. Im Unterengadin gelegen sind die klimatischen Bedingungen, Höhenlage sowie die Dimensionen der Hangschutthalden an den Standorten Val Bever und Val Susauna vergleichbar; Eigenschaften des Hangschuttes, Charakteristik der organischen Auflage sowie der Vegetation unterscheiden sich. Der in den Appenzeller Alpen gelegenen Standort Brüeltobel unterscheidet sich in Bezug auf die klimatischen Bedingungen, der Höhenlage und der Ausmaße der Hangschutthalde deutlich, zeigt jedoch eine zum Val Susauna ähnliche Humus- und Vegetationscharakteristik. Der Nachweis und die Charakterisierung von Untergrundeis basiert auf der Kombination von elektrischer Widerstandstomographie und seismischer Refraktionstomographie. Zur Detektion der räumlichen Verbreitung von Untergrundeis wurden diese Methoden durch quasi-3D Widerstandstomographie ergänzt. Zum Nachweis von Permafrost und zur Analyse seiner zeitlichen Variabilität wurden Monitoringauslagen konstruiert und an den Standorten fest installiert. Widerstandsmessungen wurden ganzjährig durchgeführt. In Ergänzung zu dem Widerstandsmonitoring wurde im Val Susauna erstmalig seismische Refraktionstomographie zum Monitoring der Permafrostentwicklung im Winter durchgeführt. Die Analyse des thermalen Regimes basiert auf der Analyse von Temperaturlogger Daten. Dabei wurden neben Luft- und Bodentemperaturen vor allem die Temperaturentwicklung in den Schloten sowie in der Humusauflage berücksichtigt. Zur Untersuchung des Zusammenhangs der Permafrostverbreitung mit der Humus- und Vegetationscharakteristik wurde im Val Susauna eine Kartierung der Humuseigenschaften sowie der Vegetationszusammensetzung durchgeführt. An allen untersuchten Standorten konnte Permafrost nachgewiesen werden. Räumlich sind die Permafrostkörper sehr scharf von benachbarten Hangbereichen abgegrenzt. Am Standort Val Susauna konnte ein hoher räumlicher Zusammenhang zwischen der Permafrostverbreitung und Bereichen mit besonders mächtiger Humusauflage, einem hohen Anteil an Moosen und Flechten im Unterwuchs sowie einem ausgeprägtem Zwergwuchs nachgewiesen werden. Die zeitliche Variabilität des Permafrost hat sich an allen Standorten als außergewöhnlich hoch herausgestellt. Dabei übersteigt die Magnitude der saisonalen Variabilität die mehrjährigen Veränderungen deutlich. Das Winterhalbjahr zeigt sich durch eine effiziente Unterkühlung geprägt. Die Schneeschmelze im Frühling steht in Verbindung mit einem deutlichen Eiszuwachs, der durch ein wiedergefrieren des versickernden Schmelzwassers an dem unterkühlten Hangschutt verursacht wird. Die Ergebnisse haben den fundamentalen Einfluss des Chimney Effekt auf die Existenz und zeitliche Variabilität von Permafrost in Hangschutthalden bestätigt. Unterschiede in der Wirkungsweise des thermalen Regimes konnten herausgestellt werden, die in erster Linie auf die unterschiedliche Ausprägung der Humusauflage, Charakteristik des Hangschutts, und die Vegetationszusammensetzung zurückzuführen sind. Während des Sommers ermöglicht die sehr geringe thermische Leitfähigkeit der im oberflächennahen Bereich meist recht trockenen organischen Auflage eine ausgeprägte Isolation des Untergrundes gegenüber hohen Außentemperaturen. Die in grobblockigen Hangschutthalden zu findende ungleichmäßige, von Blockmaterial fragmentierte organische Auflage zeigt eine deutlich geringere Isolationsfähigkeit und ermöglicht einen effektiven, Wärmeaustausch durch Konvektion und perkolierendes Niederschlagswasser. Im Winterhalbjahr steigt die thermische Leitfähigkeit des organischen Materials unter durchfeuchteten sowie gefrorenen Bedingungen massiv an und ermöglicht eine effiziente Auskühlung der Hangschutts. Die Unterkühlung in grobblockigen Hangschutthalden zeigt aufgrund des auch im Winter ausgeprägten konvektiven Wärmeflusses eine höhere Magnitude und ein früheres Einsetzen als bei homogenen Humusauflagen, wo konduktiver Wärmefluss dominiert und eine Auskühlung im Herbst durch eine ausgeprägte zero-curtain Periode gepuffert wird. Der Einfluss der Schneedecke auf das thermale Regime ist insgesamt gering; ihre Isolationsfähigkeit ist, annähernd unabhängig von der Schneemächtigkeit, stark reduziert

Cette thèse est une collection de trois articles en macroéconomie et finances publiques. Elle développe des modèles d'Equilibre Général Dynamique et Stochastique pour analyser les implications macroéconomiques des politiques d'imposition des entreprises en présence de marchés financiers imparfaits. Le premier chapitre analyse les mécanismes de transmission à l'économie, des effets d'un ré-échelonnement de l'impôt sur le profit des entreprises. Dans une économie constituée d'un gouvernement, d'une firme représentative et d'un ménage représentatif, j'élabore un théorème de l'équivalence ricardienne avec l'impôt sur le profit des entreprises. Plus particulièrement, j'établis que si les marchés financiers sont parfaits, un ré-échelonnement de l'impôt sur le profit des entreprises qui ne change pas la valeur présente de l'impôt total auquel l'entreprise est assujettie sur toute sa durée de vie n'a aucun effet réel sur l'économie si l'état utilise un impôt forfaitaire. Ensuite, en présence de marchés financiers imparfaits, je montre qu'une une baisse temporaire de l'impôt forfaitaire sur le profit des entreprises stimule l'investissement parce qu'il réduit temporairement le coût marginal de l'investissement. Enfin, mes résultats indiquent que si l'impôt est proportionnel au profit des entreprises, l'anticipation de taxes élevées dans le futur réduit le rendement espéré de l'investissement et atténue la stimulation de l'investissement engendrée par la réduction d'impôt. Le deuxième chapitre est écrit en collaboration avec Rui Castro. Dans cet article, nous avons quantifié les effets sur les décisions individuelles d'investis-sement et de production des entreprises ainsi que sur les agrégats macroéconomiques, d'une baisse temporaire de l'impôt sur le profit des entreprises en présence de marchés financiers imparfaits. Dans un modèle où les entreprises sont sujettes à des chocs de productivité idiosyncratiques, nous avons d'abord établi que le rationnement de crédit affecte plus les petites (jeunes) entreprises que les grandes entreprises. Pour des entreprises de même taille, les entreprises les plus productives sont celles qui souffrent le plus du manque de liquidité résultant des imperfections du marché financier. Ensuite, nous montré que pour une baisse de 1 dollar du revenu de l'impôt, l'investissement et la production augmentent respectivement de 26 et 3,5 centimes. L'effet cumulatif indique une augmentation de l'investissement et de la production agrégés respectivement de 4,6 et 7,2 centimes. Au niveau individuel, nos résultats indiquent que la politique stimule l'investissement des petites entreprises, initialement en manque de liquidité, alors qu'elle réduit l'investissement des grandes entreprises, initialement non contraintes. Le troisième chapitre est consacré à l'analyse des effets de la réforme de l'imposition des revenus d'entreprise proposée par le Trésor américain en 1992. La proposition de réforme recommande l'élimination des impôts sur les dividendes et les gains en capital et l'imposition d'une seule taxe sur le revenu des entreprises. Pour ce faire, j'ai eu recours à un modèle dynamique stochastique d'équilibre général avec marchés financiers imparfaits dans lequel les entreprises sont sujettes à des chocs idiosyncratiques de productivité. Les résultats indiquent que l'abolition des impôts sur les dividendes et les gains en capital réduisent les distorsions dans les choix d'investissement des entreprises, stimule l'investissement et entraîne une meilleure allocation du capital. Mais pour être financièrement soutenable, la réforme nécessite un relèvement du taux de l'impôt sur le profit des entreprises de 34\% à 42\%. Cette hausse du taux d'imposition décourage l'accumulation du capital. En somme, la réforme engendre une baisse de l'accumulation du capital et de la production respectivement de 8\% et 1\%. Néanmoins, elle améliore l'allocation du capital de 20\%, engendrant des gains de productivité de 1.41\% et une modeste augmentation du bien être des consommateurs.
This thesis is a collection of three papers in macroeconomics and public finance. It develops Dynamic Stochastic General Equilibrium Models with a special focus on financial frictions to analyze the effects of changes in corporate tax policy on firm level and macroeconomic aggregates. Chapter 1 develops a dynamic general equilibrium model with a representative firm to assess the short-run effects of changes in the timing of corporate profit taxes. First, it extends the Ricardian equivalence result to an environment with production and establishes that a temporary corporate profit tax cut financed by future tax-increase has no real effect when the tax is lump sum and capital markets are perfect. Second, I assess how strong the ricardian forces are in the presence of financing frictions. I find that when equity issuance is costly, and when the firm faces a lower bound on dividend payments, a temporary tax cut reduces temporary the marginal cost of investment and implies positive marginal propensity of investment. Third, I analyze how do the intertemporal substitution effects of tax cuts interact with the stimulative effects when tax is not lump-sum. The results show that when tax is proportional to corporate profit, the expectations of high future tax rates reduce the expected marginal return on investment and mitigate the stimulative effects of tax cuts. The net investment response depends on the relative strength of each effect. Chapter 2 is co-authored with Rui Castro. In this paper, we quantify how effective temporary corporate tax cuts are in stimulating investment and output via relaxation of financing frictions. In fact, policymakers often rely on temporary corporate tax cuts in order to provide incentives for business investment in recession times. A common motivation is that such policies help relax financing frictions, which might bind more during recessions. We assess whether this mechanism is effective. In an industry equilibrium model where some firms are financially constrained, marginal propensities to invest are high. We consider a transitory corporate tax cut, funded by public debt. By increasing current cash flows, corporate tax cuts are effective at stimulating current investment. On impact, aggregate investment increases by 26 cents per dollar of tax stimulus, and aggregate output by 3.5 cents. The stimulative output effects are long-lived, extending past the period the policy is reversed, leading to a cumulative effect multiplier on output of 7.2 cents. A major factor preventing larger effects is that this policy tends to significantly crowd out investment among the larger, unconstrained firms. Chapter 3 studies the effects of the 1992's U.S. Treasury Department proposal of a Comprehensive Business Income Tax (CBIT) reform. According to the U.S. tax code, dividend and capital gain are taxed at the firm level and further taxed when distributed to shareholders. This double taxation may reduce the overall return on investment and induce inefficient capital allocation. Therefore, tax reforms have been at the center of numerous debates among economists and policymakers. As part of this debate, the U.S. Department of Treasury proposed in 1992 to abolish dividend and capital gain taxes, and to use a Comprehensive Business Income Tax (CBIT) to levy tax on corporate income. In this paper, I use an industry equilibrium model where firms are subject to financing frictions, and idiosyncratic productivity and entry/exit shocks to assess the long run effects of the CBIT. I find that the elimination of the capital gain and dividend taxes is not self financing. More precisely, the corporate profit tax rate should be increased from 34\% to 42\% to keep the reform revenue-neutral. Overall, the results show that the CBIT reform reduces capital accumulation and output by 8\% and 1\%, respectively. However, it improves capital allocation by 20\%, resulting in an increase in aggregate productivity by 1.41\% and in a modest welfare gain.