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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
341

Composição isotópica de Pb-Sr e Nd da mineralização de ouro do depósito Córrego do Sítio, Quadrilátero Ferrífero (MG): implicações na modelagem conceitual / Composition isotópica of Pb-Sr and Nd of the mineralization of gold of the deposit stream of the small farm, Quadrilateral Ferrífero (M.G.): implications in the conceptual modeling

Marta Edith Velásquez David 22 September 2006 (has links)
O Quadrilátero Ferrífero (MG) é uma importante unidade geotectônica do Cráton do São Francisco que alberga jazidas de ferro e ouro hospedadas na seqüência greenstone belt Rio das Velhas e cuja evolução geodinâmica esteve regida por vários eventos tectonometamórficos. Depósitos de ouro gerados por fluidos epitermais e remobilizações orogênicas proterozóicas se associam intimamente com camadas bandas de ferro e raramente disseminados em metapelitos no topo do greenstone. Nas mineralizações é comum uma paragênese que cristalizou mediante diversos processos e em distintos estágios com predomínio de sulfetos de ferro. Em geral os minérios possuem forte controle estrutural por dobras, falhas e cisalhamentos transcorrentes, desenvolvidos durante vários eventos deformacionais de diversa índole e estreita relação com processos de alteração hidrotermal como sericitização, carbonatação, cloritização, entre outros de menor incidência. O depósito de ouro Córrego do Sítio hospeda-se na seqüência silisiclástica de origem turbidítica metamorfisada em fácies xisto verde denominada Associação de Litofácies Ressedimentada que faz parte do Grupo Nova Lima, se apresenta disseminado em metapelitos e em veios de quartzo com carbonato. A mineralização que acompanha o ouro cristalizou em vários estágios principais nos que predominaram (i) pirita + pirrotita, (ii) arsenopirita + pirrotita + pirita com texturas finas e orientadas, (iii) arsenopirita com pirrotita e sulfosais em veios de quartzo, (iv) pirita grossa pervasiva em todas as rochas hospedeiras. O estudo da composição isotópica Pb, Sr e Nd, permitiu identificar que as fontes dos fluidos mineralizantes foram as rochas hospedeiras, que na evolução policíclica da mineralização participaram eventos metamórficos e hidrotermais a 2.2, 2.0 Ga. e sobreimpostos a ~600 Ma. os quais induziram os processos de circulação hidrotermal na área de estudo. Mediante comparativa com outros depósitos da região, sugere-se que os metais formadores do minério depositaram-se em Córrego do Sítio à idade de 2.2 Ga. originados a partir da BIF tipo São Bento e remobilizados por fluidos através de falhas inversas. Análises geocronológicas U-Pb (SHRIMP) e K-Ar embora não decisivos em quanto à determinação da idade da mineralização, revelaram a idade de ~2.7 Ga. como o limite temporal para a deposição das rochas hospedeiras. No contexto geológico aplicado se estabelece a potencialidade para a prospecção aurífera que apresentam as rochas metapelíticas do topo do Greenstone Belt Rio das Velas associadas a camadas bandadas de ferro com ouro, e que os alvos mais relevantes seriam zonas com falhas inversas e cisalhamentos transcorrentes. / The Quadrilátero Ferrífero is an important geotectonic unit of the São Francisco Craton that host iron and gold deposits within the vulcanosedimentary rocks of the greenstone belt Rio das Velhas. The geodynamic evolution of this greenstone includes several tectonometamorphic events. Gold deposits were formed by epithermal fluids, remobilized during the Proterozoic orogenic processes, are associated whit the banded iron formations and are sporadically disseminate in metapelitic rocks within the top of the greenstone sequence. In the ores is common the crystallization of iron sulfide minerals during diverse stages. Gold deposits have an important structural control by folds, reverse faults and strike-slip shearing zones, and are commons several hydrothermal alteration processes like sericitization, chloritization and carbonate usually related to the deformation. The Córrego do Sítio gold deposit is hosted in turbiditic siliciclastic rocks that are metamorphosed in the greenschist facies. The gold is associated with the iron sulfide arsenopyrite and pyrite, which are disseminated in metapelitic rocks and quartz-carbonate veins. The mineralization includes vary stages of crystallization, (1) pyrite and pyrrotite (2) arsenopyrite, pyrrotite and fine pyrite, (3) arsenopyrite whit pyrrotite and sulphosalts in quartz vein, and (4) pervasive pyrite. An integrated Pb, Sr e Nd, isotopic study of the Córrego do Sítio deposit allowed to identify that sources of the mineralizing fluids was the host rocks, that in the policiclic evolution the gold mineralizaton had participation events of metamorphism and hidrothermalism to age 2.2, 2.0 and 0.6 Ga. respectively the wich induced the hydrothermal circulation processes in the study area. The isotopic character of this deposit and its comparison with similar ones, suggest that the gold and its metals associated it is deposited in Córrego do Sítio to age 2.2 Ga. and that metals were derived from the banded iron formations, and remobilized by hidrothermal fluids across reverse faults. Although U-Pb (SHRIMP) and K-Ar geochronologic data were not conclusive to constrain the age of the mineralization, they provide to age ~2.7 Ga. that a good limit for the sedimentation of the host rock. It is suggest that there is a potential for gold prospection within the metapellitic rocks associated with banded iron formation of the Greenstone Rio das Velhas, and that the more relevant targets include areas with inverse and strike-slip fault.
342

Study of the coherent effects in rubidium atomic vapor under bi-chromatic laser radiation / Etude des effets cohérents dans la vapeur de rubidium atomique sous irradiation laser bi-chromatique

Mirzoyan, Rafayel 04 June 2013 (has links)
L’effet de la transparence induite électromagnétiquement est observée à l’aidede cellules nanométriques et de cellules micrométriques. La résonance EIT avec de bons paramètres (fort contraste et faible largeur du signal à mi-hauteur) est obtenue dans des cellules étroites. L' éclatement de la résonance EIT dans un champ magnétique est observé pour les raies D1 du 85Rb et 87Rb. Nous présentons un modèle théorique qui explique la dépendance du déplacement en fréquence des composantes de la résonance EIT en fonction de l’intensité du champ magnétique. Les résultats théoriques et expérimentaux sont comparés et démontrent un bon accord.Pour la première fois une résonance de type N est obtenue dans une micro-cellule. Nous obtenons de bons paramètres (fort contraste et faible largeur du signal à mi-hauteur) dela résonance N à l’aide d’une micro-cellule. Cela nous permet d’observer le comportement d’une résonance N dans un champ magnétique. L’éclatement de la résonance N dans unchamp magnétique est observé pour les raies D1 du 85Rb et 87Rb. Nous présentons les calculs théoriques qui expliquent la dépendance du déplacement en fréquence des composantes dela résonance N en fonction de l’intensité du champ magnétique. Les résultats théoriques et expérimentaux sont comparés et démontrent un bon accord. Le comportement de la résonance N en régime hyperfin Paschen-Back est présenté et expliqué. Enfin une comparaison des résonances EIT et N est faite / The effect of electromagnetically induced transparency is observed, using nanocelland microcell. The EIT-resonance with good parameters (high contrast and small FWHM) is obtained in thick cells. The EIT-resonance splitting in magnetic field is observed for the cases of D1-line of 85Rb and 85Rb. The theoretical model, explaining the EIT-resonance components frequency shift dependence on magnetic field strength is presented. The theoretical and experimental results are compared and good agreement is shown. Also the EIT-resonance behavior in hyperfine Paschen-Back regime is presented and explained. For the first time the N-type resonance in microcell is observed. Good parameters of theN-type resonance in microcell are obtained. It allows us to observe the N-type resonance behavior in magnetic field. The N-resonance splitting in magnetic field is observed for the cases of 85Rb and 85Rb. The theoretical calculations of the N-resonance components frequency shift dependence on magnetic field is presented. The theoretical and experimental results are compared and good agreement is shown. Also the N-resonance behavior in hyperfine Paschen-Back regime is presented and explained. Simultaneous observation of N- and EIT-resonance is shown. Comparison of EIT- and N-resonance is made
343

Vulnérabilité des ressources en eau souterraine : origines de la salinité en domaine karstique côtier et de la contamination après-mine en métaux lourds. Approche par multitracage géochimique / Groundwater resources vulnerability : origins of salinity in coastal karst groundwater, contamination by heavy metals in post closure mine : multiple tracers, geochemical approach

Khaska, Mahmoud 03 December 2013 (has links)
La premier thématique a pour objectifs :1) de tracer l’origine de la salinité des eaux des aquifères karstiques en milieu côtier méditerranéen,2) de quantifier les proportions de mélange entre les eaux salées et les eaux karstiques,3) de discriminer les traceurs géochimiques pour identifier et modéliser les processus de salinisation d’aquifères karstiques côtiers. La seconde thématique a pour objectifs:1) d’établir les [As] d’origine naturelle des eaux de surface et des eaux souterraines, 2) de quantifier le niveau de contamination en arsenic de ces eaux et sa variabilité spatio-temporelle 3) de tracer l’origine naturelle ou anthropique de la pollution en As à l’aide d’outils isotopiques adaptés. les origines de la salinité identifié inclue i) des venues d’eaux profondes salées ii) des venues profondes d’eau salées remontant vers la surface par une faille majeure normale. Le 36Cl/Cl a permis d’identifier l’origine profonde des eaux salées et une recharge d’eau météorique infiltrée lors de la période des essais thermonucléaires. La modélisation PHREEQC permet de différentier le mélange avec une eau profonde salée de celui avec une eau de mer actuelle. Le 87Sr/86Sr montre un comportement conservatif pour tracer l’origine des eaux salées dans les aquifères karstiques. Les traceurs Cs, Rb, Li et B permettent de différentier les trois origines identifiées de la salinité. Les données acquises sur la contamination en As soulignent une augmentation nette et pérenne des [As] à partir des anciens sites de traitement minier réhabilités. Les rapports 87Sr/86Sr et δ18O et δ2H se révèlent dans ce cas un traceur très discriminant de l’origine naturelle ou anthropique de l’arsenic. / The first theme has for objectives: 1) to trace the origin of the salinity of the waters of the karst aquifers in coastal environment mediterraneen,2) to quantify the mixing proportions between salt waters and the waters karstiques,3) to discriminate the geochemical tracers to identify and model the process of salinization of aquifers coastal karst. The second theme has for objectives:1) to establish the [hast] of natural origin of surface waters and groundwater, 2) to quantify the level of contamination by arsenic in these waters and its spatial and temporal variability 3) to trace the natural or anthropogenic origin of pollution in hast to the aid of isotopic tools adapted. the origins of the salinity identified include i) of came from deep waters salted ii) of come deep water salted dating back toward the surface by a major flaw normal. The 36Cl/Cl has allowed us to identify the origin of deep saline waters and a recharge of meteoric water infiltrated during the period of thermonuclear tests. The PHREEQC modeling used to differentiate between the mixture with a deep water of salt that one with a sea water current. The 87SR/ 86Sr shows a conservative behavior for tracing the origin of saline waters in karst aquifers. The plotters Cs, Rb, Li and B allows to differentiate the three origins identified of salinity. The data acquired on the contamination in hast underline a net increase and perennial of [hast] from the ancient sites of mining processing rehabilitated. The reports 87SR/ 86Sr and δ18O and δ2H will reveal in this case a chartplotter very discriminant of natural or anthropogenic origin of arsenic.
344

The implications of large-scale irrigated bioenergy plantations for future water use and water stress

Stenzel, Fabian 06 October 2021 (has links)
Diese Arbeit ist die erste systematische Analyse des globalen Bewässerungsbedarfs für die Bioenergieproduktion des 21. Jahrhundert. In der aktuellen Literatur finden sich diesbezüglich Prognosen von 128,4–9000 km3 yr−1. Die Zahlen hängen stark von den gewählten Parametern und Annahmen sowie den angewandten Methoden und Modellen ab. In systematischen Simulationen für die wichtigsten Parameter mit dem globalen Vegetationsmodell LPJmL, ergeben sich zwei mögliche Pfade um die Erwärmung auf 1.5°C zu begrenzen. Entweder müssten hocheffiziente Bioenergiesysteme entwickelt werden oder es müsste eine unbegrenzte Plantagenfläche bewässert werden dürfen, ohne dabei den Wasserbedarf der Ökosysteme zu berücksichtigen. Letzteres führt zu einem Interessenkonflikt, bei dem die Biomasseproduktion zur Klimarettung auf der einen Seite und der Schutz von Ökosystemen auf der anderen Seite stehen. Ein weiteres Dilemma wird sichtbar, wenn man den Wasserstress, der sich aus der zusätzlichen Bewässerung ergäbe, mit dem in einer durch ungebremsten Klimawandel um 3°C erwärmten Welt ohne Bioenergie vergleicht: In beiden Szenarien könnte (im Vergleich zu heute) der Wasserstress bis zum Ende des 21. Jahrhunderts stark steigen. Tatsächlich ergäbe sich im Bioenergie-Szenario aber sogar potenziell mehr Wasserstress als im Klimawandel-Szenario. Nachhaltiges Wassermanagement als Kombination aus Wasserentnahmebeschränkungen gemäß den Anforderungen von Flussökosystemen und verbessertem Wassermanagement auf agrarischen Nutzflächen hätte das Potenzial, diesen zusätzlichen Wasserstress zu begrenzen, wäre jedoch auf globaler Ebene schwierig zu etablieren. Diese Arbeit bestätigt, dass Bioenergieplantagen neben den Negativemissionen, die sie liefern sollen, auch zu unerwünschten Nebenwirkungen in anderen Dimensionen des Erdsystems führen könnten. / This thesis provides a first systematic assessment of 21st century global irrigation water demands for bioenergy production, for which the current body of literature projects a range of 128.4–9000 km3 yr−1. The numbers strongly depend on the parameters and assumptions chosen as well as methodologies and models applied. Systematic simulations for the identified key parameters in the dynamic global vegetation model LPJmL yield that even with optimal bioenergy plantation locations, 1.5°C can only be reached in scenarios with highly efficient bioenergy systems or strong irrigation expansion without withdrawal limitations. As a result of the large irrigation requirements, a conflict of interest arises between producing sufficient biomass and protecting environmental flows. A further dilemma is delineated by a comparison of the water stress resulting from the additional irrigation needed to limit climate change and the water stress in a 3°C warmer world without bioenergy. In both scenarios, the global area and the number of people experiencing water stress would increase severely by the end of the 21st century. The bioenergy scenario shows even higher water stress than the case of unmitigated climate change. Sustainable water management, as a combination of water withdrawal restrictions according to environmental flow requirements and improved on-field water management, has the potential to limit this additional water stress. But it would be a challenge to establish such strategies on a global scale. This work confirms that in order to provide large amounts of negative emissions, BECCS might lead to undesired deterioration of our environment and impacts for humanity. It further highlights the dilemma of rising water stress regardless whether climate change or climate change mitigation via irrigated bioenergy become a reality.
345

Study of the coherent effects in rubidium atomic vapor under bi-chromatic laser radiation

Mirzoyan, Rafayel 04 June 2013 (has links) (PDF)
The effect of electromagnetically induced transparency is observed, using nanocelland microcell. The EIT-resonance with good parameters (high contrast and small FWHM) is obtained in thick cells. The EIT-resonance splitting in magnetic field is observed for the cases of D1-line of 85Rb and 85Rb. The theoretical model, explaining the EIT-resonance components frequency shift dependence on magnetic field strength is presented. The theoretical and experimental results are compared and good agreement is shown. Also the EIT-resonance behavior in hyperfine Paschen-Back regime is presented and explained. For the first time the N-type resonance in microcell is observed. Good parameters of theN-type resonance in microcell are obtained. It allows us to observe the N-type resonance behavior in magnetic field. The N-resonance splitting in magnetic field is observed for the cases of 85Rb and 85Rb. The theoretical calculations of the N-resonance components frequency shift dependence on magnetic field is presented. The theoretical and experimental results are compared and good agreement is shown. Also the N-resonance behavior in hyperfine Paschen-Back regime is presented and explained. Simultaneous observation of N- and EIT-resonance is shown. Comparison of EIT- and N-resonance is made
346

Úloha nádorového supresoru PML v odpovědi na poškození DNA a buněčné senescenci po genotoxickém stresu / Role of the tumour suppressor PML in DNA damage response and cellular senescence after genotoxic stress

Knoblochová, Lucie January 2015 (has links)
The promyelocytic leukemia protein (PML) is a tumour suppressor. It has been reported that PML interaction with the p53 protein is involved in the activation of cell cycle checkpoints and, when persistent, may lead to the premature onset of cellular senescence. Cellular senescence is a state of permanent cell growth arrest that is associated with characteristic morphological and metabolic changes and persistent DNA damage signalling. Importantly, PML nuclear bodies coassociate with persistent DNA damage foci in senescent cells; however, the role of this interaction is still obscure. My goal was to characterize the role of PML in DNA damage response (DDR) and the induction of premature cellular senescence after genotoxic stress, namely X-radiation, using both siRNA-mediated PML knock down (PML KD) and complete PML knock out (PML KO) in human cells. The dynamics of DNA damage foci, levels of various proteins involved in DDR, and proliferation rate were measured in both PML KD and KO cells. No significant changes in the formation of DNA damage foci, activated DDR (p53 and Chk2), activated p21CIP1/WAF1 cyclin-dependent kinase inhibitor, senescent morphology, and SA-β-galactosidase activity in PML KO cells were observed. However, PML KO cells displayed higher levels of retinoblastoma protein (Rb) and...
347

Estabilização de lasers de diodo para utilização em espectroscopia atômica. / Stabilization of diode lasers for use in atomic spectroscopy.

Tuboy, Aparecida Marika 13 July 1990 (has links)
Um dos primeiros requisitos para utilização de lasers de diodo em espectroscopia é sua estabilização térmica. Neste trabalho desenvolvemos um sistema de controle de temperatura para laser de diodo que permite estabilização melhor que 0.01&#176C. O controle é feito através de um sistema sensor e um elemento Peltier como atuador. Lasers somente estabilizados em temperatura (estabilização primária) foram utilizados para realização de espectroscopia de vapores atômicos de Rb e Cs. / One of the first requisites for utilization of diode lasers in spectroscopy is its thermal stabilization. In this work, we develop a diode laser temperature controlling system, which yields stabilization better than 0.01&#176C. The controlling is obtained by means of a sensor system and a Peltier element as actuator. Lasers stabilized in temperature only (primary stabilizations) were utilized in the spectroscopy of atomic vapors of Rb and Cs.
348

SSD RB - sistema de suporte a decisão proposto para a gestão quali-quantitativa dos processos de outorga e cobrança pelo uso da água. / Decision Support System to help with the implementation of water quality and quantity management mechanisms such as the analysis of authorization of water uses (permits) and water charging.

Rodrigues, Roberta Baptista 10 May 2005 (has links)
O presente trabalho apresenta-se como um marco inovador na área de gestão de recursos hídricos, já que o mesmo consegue inserir aspectos de qualidade da água para os processos de outorga e cobrança pelo uso da água, de forma articulada a todos os instrumentos da Política Nacional de Recursos Hídricos (Lei 9.433 de 1997), possibilitando a efetiva aplicação da Política e da Resolução n° 48, de 21 de março de 2005, que estabelece critérios gerais para a cobrança pelo uso dos recursos hídricos. Traz também para a Política um novo conceito, o de Justiça Hídrica, ou seja, quem capta água com qualidade superior paga mais do que quem capta água com qualidade inferior, assim como, quem mais polui e prejudica os usuários de jusante, mais paga. Neste trabalho, a variável de decisão do sistema é o volume outorgado e o estudo leva em consideração a capacidade de autodepuração, o enquadramento em classes de uso, o regime de vazão do corpo hídrico, a qualidade da água captada e os prejuízos, em termos de qualidade da água, ocasionados pelos usuários-poluidores aos usuários de jusante. A ferramenta de auxílio aqui oferecida é um Sistema de Suporte a Decisão (SSD), denominado RB, que apresenta: um módulo Interface, um módulo Modelos, constituído pelo modelo de outorga e cobrança pelo uso da água RM1 e pelo modelo de qualidade das águas QUAL2E e, por fim, um módulo Dados, que representa os dados de entrada e saída do sistema. O SSD RB foi aplicado à bacia do rio Jundiaí, afluente do rio Tietê, localizado no Estado de São Paulo. Na aplicação do SSD RB, foi realizada uma análise comparativa para a variação de cenários relativa a Classes de Uso do corpo hídrico, vazões de referência e diferentes valores de cobrança que podem ser utilizados. A aplicação do SSD RB reflete a necessidade de uma articulação sistemática entre os instrumentos da Política Nacional de Recursos Hídricos, apoiada na diretriz de gestão integrada de recursos hídricos, ou seja, existe um único corpo de trabalho (a gestão de recursos hídricos) cujos membros (instrumentos de gestão) só ganham sentido quanto articulados entre si com um mesmo objetivo: a garantia de água de boa qualidade com a quantidade necessária à atual e às futuras gerações. / The main objective of this study is to develop a set of tools to help with the implementation of water management mechanisms such as the analysis of authorization of water uses (permits) and water charging. An integrated analysis of both water quality and quantity is needed and the decision process must also take into account watershed plans and the designated uses of the water. In this study, the decision variable is the volume of water authorized in each permit. The tool developed in this study is a Decision Support System named RB, based on the QUAL2E model and an water permit and charging simulation system named RM1. The RB system was tested in the Jundiaí watershed, a tributary of the Tietê river located in the State of São Paulo. In this case study, several scenarios with different classification of water bodies, reference flows and water values were tested. The application of the system shows that water management tools must be applied in an integrated manner, mainly to reflect both aspects of water quality and quantity. Water management tools are to be articulated so that the main objective of supplying water with good quality and in an adequate amount is sustainable in the long run.
349

Landschaftsmaße

Kappler, Olaf 10 June 2015 (has links)
Schon seit langer Zeit, besonders intensiv jedoch in den letzten Jahrzehnten werden Ausschnitte der Geosphäre hinsichtlich ihrer geometrischen Eigenschaften verglichen und bewertet. Dafür wurden empirisch viele verschiedene Landschaftsmaße gefunden, die diese geometrischen Eigenschaften auf unterschiedlichste Weise in mehreren Ebenen abbilden. Für die unterste Ebene, d.h. für die direkte Bewertung von individuellen, relativ homogenen Landschaftselementen, wird in dieser Arbeit eine Theorie vorgestellt. Ausgehend von der inhaltlichen Zielstellung der vorliegenden Arbeit wird ein System redundanzfreier Grundmaße theoretisch hergeleitet. Dieses System wird hinsichtlich der mathematischen Eigenschaften untersucht und sowohl mit normierten, abstrakten Objekten als auch anhand von realen Beispieldaten veranschaulicht. Unter Verwendung dieser Grundmaße können dann Landschaftselemente über statistische Verfahren klassifiziert oder komplexere Landschaftsmaße mit gewünschten Eigenschaften je nach praktischer Anforderung konstruiert werden. Die Zusammenhänge von bereits bekannten Landschaftsmaßen und diesen Grundmaßen sowie die Vorgehensweise bei der Ableitung neuer, anwendungsspezifischer, komplexer Landschaftsmaße aus den Grundmaßen werden in dieser Arbeit vorgestellt. / For a long time, but especially during the last decades parts of the geosphere were compared and valued using their geometrical properties. Therefore many different landscape measures were found empirically which map these geometrical qualities into several levels in a variety of ways. In this paper there will be presented a theory which deals with the basic level i.e. with these measures which evaluate individual relative homogeneous landscape elements. Based on the objective of this paper a system of redundance-free basic measures will be deduced theoretically. This system will be studied in regard to its mathematical properties and will be illustrated by using standardized abstract objects and real example data. Landscape elements can be classified using statistical procedures or complex landscape measures with practically requested properties can be constructed by using these basic measures. The relations between well-known landscape measures and these basic measures are shown. The procedure of deduction of new application-specific complex landscape measures from the basic measures are introduced in this paper.
350

Complex network analysis of extreme rainfall in South America

Boers, Niklas 01 June 2015 (has links)
Basierend auf der Theorie von Netzwerken wird ein allgemeines Rahmenwerk entwickelt, um kollektive Synchronisationsphänome von Extremereignissen in komplexen Systemen zu studieren. Die Methode vergleicht die Variabilität der einzelnen Teile des Systems auf Grundlage von Beobachtungszeitreihen mit dem Ziel, emergente Synchronisationsmuster von Extremereignissen auf makroskopischer Ebene aufzudecken. Zu diesem Zweck werden die einzelnen Zeitreihen eines interaktiven Systems mit den Knoten eines Netzwerks identifiziert und die Abhängigkeiten zwischen diesen durch die Kanten des Netzwerks dargestellt. Die komplexe interne Synchronisationsstruktur des Systems wird so in Form der Netzwerktopologie mathematisch zugänglich gemacht und kann durch die Einführung geeigneter Netzwerkmaße analysiert werden. Die Methode wird im Folgenden auf räumlich und zeitlich hochaufgelöste Regendaten aus Satellitenmessungen angewendet, um die kollektive Dynamik extremer Regenereignisse in Südamerika zu untersuchen. Diese Anwendung verfolgt drei Ziele: Erstens wird gezeigt, wie die hier entwickelte Methode zur klimatologischen Analyse verwendet werden kann. Zweitens können Quellen und Senken von Extremereignissen durch die Einführung des Konzeptes der Netzwerkdivergenz identifiziert werden. Dies erlaubt es, die gerichteten Netzwerkpfade, entlang derer Extremereignisse synchronisieren, nachzuverfolgen. Auf dieser Grundlage wird eine statistische Regel gewonnen, die beträchtliche Anteile der extremen Regenereignisse in den Zentralanden vorhersagt. Drittens werden die bis dahin entwickelten Methoden und gewonnenen Einsichten dazu verwendet, die Darstellung extre- mer Regenereignisse in verschiedenen Datensätzen zu vergleichen. Insbesondere wird in diesem Kontext die Implementierung solcher Ereignisse in drei gängigen Klimamodellen evaluiert. / Based on the theory of networks, a general framework is developed to study collective synchronization phenomena of extreme events in complex systems. The method relies on observational time series encoding the variability of the single parts of the system, and is intended to reveal emerging patterns of extreme event synchronization on the macroscopic level. For this purpose, the time series obtained from an interactive system under consideration are identified with network nodes, and the possibly delayed and non-linear interdependence of extreme events in different time series is represented by network links connecting the nodes. In this way, the complex internal synchronization structure of the system becomes accessible in terms of the topology of the network, which can be analyzed by introducing suitable network measures. The methodology is applied to satellite-derived rainfall time series of high spatiotemporal resolution in order to investigate the collective dynamics of extreme rainfall events in South America. The purpose of this application is threefold: First, it is shown how the methodology can be used for climatic analysis by revealing climatological mechanism from the spatial patterns exhibited by different network measures. Second, by introducing the concept of network divergence, sink and source regions of extreme events can be identified, allowing to track their directed synchronization pathways through the network. A simple statistical forecast rule is derived on this basis, predicting substantial fractions of extreme rainfall events in the Central Andes. Third, the methodology and the insights developed in the first two steps are used to evaluate the dynamical representation of extreme events in different datasets, and in particular their dynamical implementation in three state of the art climate models.

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