Textural controls on induced polarization and permeability in granular media

The spatial resolution visualized with hydrological models and the conceptualized images of subsurface hydrological processes often exceed resolution of the data collected with classical instrumentation at the field scale. In recent years it was possible to increasingly diminish the inherent gap to information from point like field data through the application of hydrogeophysical methods at field-scale. With regards to all common geophysical exploration techniques, electric and electromagnetic methods have arguably to greatest sensitivity to hydrologically relevant parameters. Of particular interest in this context are induced polarisation (IP) measurements, which essentially constrain the capacity of a probed subsurface region to store an electrical charge. In the absence of metallic conductors the IP- response is largely driven by current conduction along the grain surfaces. This offers the perspective to link such measurements to the characteristics of the solid-fluid-interface and thus, at least in unconsolidated sediments, should allow for first-order estimates of the permeability structure.¦While the IP-effect is well explored through laboratory experiments and in part verified through field data for clay-rich environments, the applicability of IP-based characterizations to clay-poor aquifers is not clear. For example, polarization mechanisms like membrane polarization are not applicable in the rather wide pore-systems of clay free sands, and the direct transposition of Schwarz' theory relating polarization of spheres to the relaxation mechanism of polarized cells to complex natural sediments yields ambiguous results.¦In order to improve our understanding of the structural origins of IP-signals in such environments as well as their correlation with pertinent hydrological parameters, various laboratory measurements have been conducted. We consider saturated quartz samples with a grain size spectrum varying from fine sand to fine gravel, that is grain diameters between 0,09 and 5,6 mm, as well as corresponding pertinent mixtures which can be regarded as proxies for widespread alluvial deposits. The pore space characteristics are altered by changing (i) the grain size spectra, (ii) the degree of compaction, and (iii) the level of sorting. We then examined how these changes affect the SIP response, the hydraulic conductivity, and the specific surface area of the considered samples, while keeping any electrochemical variability during the measurements as small as possible. The results do not follow simple assumptions on relationships to single parameters such as grain size. It was found that the complexity of natural occurring media is not yet sufficiently represented when modelling IP. At the same time simple correlation to permeability was found to be strong and consistent. Hence, adaptations with the aim of better representing the geo-structure of natural porous media were applied to the simplified model space used in Schwarz' IP-effect-theory. The resulting semi- empiric relationship was found to more accurately predict the IP-effect and its relation to the parameters grain size and permeability. If combined with recent findings about the effect of pore fluid electrochemistry together with advanced complex resistivity tomography, these results will allow us to picture diverse aspects of the subsurface with relative certainty. Within the framework of single measurement campaigns, hydrologiste can than collect data with information about the geo-structure and geo-chemistry of the subsurface. However, additional research efforts will be necessary to further improve the understanding of the physical origins of IP-effect and minimize the potential for false interpretations.¦-¦Dans l'étude des processus et caractéristiques hydrologiques des subsurfaces, la résolution spatiale donnée par les modèles hydrologiques dépasse souvent la résolution des données du terrain récoltées avec des méthodes classiques d'hydrologie. Récemment il est possible de réduire de plus en plus cet divergence spatiale entre modèles numériques et données du terrain par l'utilisation de méthodes géophysiques, notamment celles géoélectriques. Parmi les méthodes électriques, la polarisation provoquée (PP) permet de représenter la capacité des roches poreuses et des sols à stocker une charge électrique. En l'absence des métaux dans le sous-sol, cet effet est largement influencé par des caractéristiques de surface des matériaux. En conséquence les mesures PP offrent une information des interfaces entre solides et fluides dans les matériaux poreux que nous pouvons lier à la perméabilité également dirigée par ces mêmes paramètres. L'effet de la polarisation provoquée à été étudié dans différentes études de laboratoire, ainsi que sur le terrain. A cause d'une faible capacité de polarisation des matériaux sableux, comparé aux argiles, leur caractérisation par l'effet-PP reste difficile a interpréter d'une manière cohérente pour les environnements hétérogènes.¦Pour améliorer les connaissances sur l'importance de la structure du sous-sol sableux envers l'effet PP et des paramètres hydrologiques, nous avons fait des mesures de laboratoire variées. En détail, nous avons considéré des échantillons sableux de quartz avec des distributions de taille de grain entre sables fins et graviers fins, en diamètre cela fait entre 0,09 et 5,6 mm. Les caractéristiques de l'espace poreux sont changées en modifiant (i) la distribution de taille des grains, (ii) le degré de compaction, et (iii) le niveau d'hétérogénéité dans la distribution de taille de grains. En suite nous étudions comment ces changements influencent l'effet-PP, la perméabilité et la surface spécifique des échantillons. Les paramètres électrochimiques sont gardés à un minimum pendant les mesures. Les résultats ne montrent pas de relation simple entre les paramètres pétro-physiques comme par exemples la taille des grains. La complexité des media naturels n'est pas encore suffisamment représenté par les modèles des processus PP. Néanmoins, la simple corrélation entre effet PP et perméabilité est fort et consistant. En conséquence la théorie de Schwarz sur l'effet-PP a été adapté de manière semi-empirique pour mieux pouvoir estimer la relation entre les résultats de l'effet-PP et les paramètres taille de graines et perméabilité. Nos résultats concernant l'influence de la texture des matériaux et celles de l'effet de l'électrochimie des fluides dans les pores, permettront de visualiser des divers aspects du sous-sol. Avec des telles mesures géo-électriques, les hydrologues peuvent collectionner des données contenant des informations sur la structure et la chimie des fluides des sous-sols. Néanmoins, plus de recherches sur les origines physiques de l'effet-PP sont nécessaires afin de minimiser le risque potentiel d'une mauvaise interprétation des données.

Le renouveau des antagonistes de l'atdostérone [The revived interest in aldosterone antagonists]

Aldosterone plays a pivotal role in sodium and water homeostasis, in particular in patients with heart failure or high blood pressure. These medications, when used on top of a standard therapy, improve the outcome of patients with heart failure and are also effective in lowering blood pressure of hypertensive patients. The major risk associated with the use of these antagonists is hyperkalemia, which can be prevented in avoiding their prescription in patients with impaired renal function. Eplerenone has the advantage, compared with spironolactone, to be better tolerated in terms of "hormonal" adverse effects.

Effective corporate governance : experimental evidence on international auditors'judgments and the contribution of financial accounting education

1 Summary This dissertation deals with two major aspects of corporate governance that grew in importance during the last years: the internal audit function and financial accounting education. In three essays, I contribute to research on these topics which are embedded in the broader corporate governance literature. The first two essays consist of experimental investigations of internal auditors' judgments. They deal with two research issues for which accounting research lacks evidence: The effectiveness of internal controls and the potentially conflicting role of the internal audit function between management and the audit committee. The findings of the first two essays contribute to the literature on internal auditors' judgment and the role of the internal audit function as a major cornerstone of corporate governance. The third essay theoretically examines a broader issue but also relates to the overall research question of this dissertation: What contributes to effective corporate governance? This last essay takes the perspective that the root for quality corporate governance is appropriate financial accounting education. r develop a public interest approach to accounting education that contributes to the literature on adequate accounting education with respect to corporate governance and accounting harmonization. The increasing importance of both the internal audit function and accounting education for corporate governance can be explained by the same recent fundamental changes that still affect accounting research and practice. First, the Sarbanes-Oxley Act of 2002 (SOX, 2002) and the 8th EU Directive (EU, 2006) have led to a bigger role for the internal audit function in corporate governance. Their implications regarding the implementation of audit committees and their oversight over internal controls are extensive. As a consequence, the internal audit function has become increasingly important for corporate governance and serves a new master (i.e. the audit committee) within the company in addition to management. Second, the SOX (2002) and the 8th EU Directive introduced additional internal control mechanisms that are expected to contribute to the reliability of financial information. As a consequence, the internal audit function is expected to contribute to a greater extent to the reliability of financial statements. Therefore, effective internal control mechanisms that strengthen objective judgments and independence become important. This is especially true when external- auditors rely on the work of internal auditors in the context of the International Standard on Auditing (ISA) 610 and the equivalent US Statement on Auditing Standards (SAS) 65 (see IFAC, 2009 and AICPA, 1990). Third, the harmonization of international reporting standards is increasingly promoted by means of a principles-based approach. It is the leading approach since a study of the SEC (2003) that was required by the SOX (2002) in section 108(d) was in favor of this approach. As a result, the Financial Accounting Standards Board (FASB) and the International Accounting Standards Board (IASB) commit themselves to the development of compatible accounting standards based on a principles-based approach. Moreover, since the Norwalk Agreement of 2002, the two standard setters have developed exposure drafts for a common conceptual framework that will be the basis for accounting harmonization. The new .framework will be in favor of fair value measurement and accounting for real-world economic phenomena. These changes in terms of standard setting lead to a trend towards more professional judgment in the accounting process. They affect internal and external auditors, accountants, and managers in general. As a consequence, a new competency set for preparers and users of financial statements is required. The basil for this new competency set is adequate accounting education (Schipper, 2003). These three issues which affect corporate governance are the initial point of this dissertation and constitute its motivation. Two broad questions motivated a scientific examination in three essays: 1) What are major aspects to be examined regarding the new role of the internal audit function? 2) How should major changes in standard setting affect financial accounting education? The first question became apparent due to two published literature reviews by Gramling et al. (2004) and Cohen, Krishnamoorthy & Wright (2004). These studies raise various questions for future research that are still relevant and which motivate the first two essays of my dissertation. In the first essay, I focus on the role of the internal audit function as one cornerstone of corporate governance and its potentially conflicting role of serving both management and the audit committee (IIA, 2003). In an experimental study, I provide evidence on the challenges for internal auditors in their role as servant for two masters -the audit committee and management -and how this influences internal auditors' judgment (Gramling et al. 2004; Cohen, Krishnamoorthy & Wright, 2004). I ask if there is an expectation gap between what internal auditors should provide for corporate governance in theory compared to what internal auditors are able to provide in practice. In particular, I focus on the effect of serving two masters on the internal auditor's independence. I argue that independence is hardly achievable if the internal audit function serves two masters with conflicting priorities. The second essay provides evidence on the effectiveness of accountability as an internal control mechanism. In general, internal control mechanisms based on accountability were enforced by the SOX (2002) and the 8th EU Directive. Subsequently, many companies introduced sub-certification processes that should contribute to an objective judgment process. Thus, these mechanisms are important to strengthen the reliability of financial statements. Based on a need for evidence on the effectiveness of internal control mechanisms (Brennan & Solomon, 2008; Gramling et al. 2004; Cohen, Krishnamoorthy & Wright, 2004; Solomon & Trotman, 2003), I designed an experiment to examine the joint effect of accountability and obedience pressure in an internal audit setting. I argue that obedience pressure potentially can lead to a negative influence on accountants' objectivity (e.g. DeZoort & Lord, 1997) whereas accountability can mitigate this negative effect. My second main research question - How should major changes in standard setting affect financial accounting education? - is investigated in the third essay. It is motivated by the observation during my PhD that many conferences deal with the topic of accounting education but very little is published about what needs to be done. Moreover, the Endings in the first two essays of this thesis and their literature review suggest that financial accounting education can contribute significantly to quality corporate governance as argued elsewhere (Schipper, 2003; Boyce, 2004; Ghoshal, 2005). In the third essay of this thesis, I therefore focus on approaches to financial accounting education that account for the changes in standard setting and also contribute to corporate governance and accounting harmonization. I argue that the competency set that is required in practice changes due to major changes in standard setting. As the major contribution of the third article, I develop a public interest approach for financial accounting education. The major findings of this dissertation can be summarized as follows. The first essay provides evidence to an important research question raised by Gramling et al. (2004, p. 240): "If the audit committee and management have different visions for the corporate governance role of the IAF, which vision will dominate?" According to the results of the first essay, internal auditors do follow the priorities of either management or the audit committee based on the guidance provided by the Chief Audit executive. The study's results question whether the independence of the internal audit function is actually achievable. My findings contribute to research on internal auditors' judgment and the internal audit function's independence in the broader frame of corporate governance. The results are also important for practice because independence is a major justification for a positive contribution of the internal audit function to corporate governance. The major findings of the second essay indicate that the duty to sign work results - a means of holding people accountable -mitigates the negative effect of obedience pressure on reliability. Hence, I found evidence that control .mechanisms relying on certifications may enhance the reliability of financial information. These findings contribute to the literature on the effectiveness of internal control mechanisms. They are also important in the light of sub-certification processes that resulted from the Sarbanes-Oxley Act and the 8th EU Directive. The third essay contributes to the literature by developing a measurement framework that accounts for the consequences of major trends in standard setting. Moreovér, it shows how these trends affect the required .competency set of people dealing with accounting issues. Based on this work, my main contribution is the development of a public interest approach for the design of adequate financial accounting curricula. 2 Serving two masters: Experimental evidence on the independence of internal auditors Abstract Twenty nine internal auditors participated in a study that examines the independence of internal auditors in their potentially competing roles of serving two masters: the audit committee and management. Our main hypothesis suggests that internal auditors' independence is not achievable in an institutional setting in which internal auditors are accountable to two different parties with potentially differing priorities. We test our hypothesis in an experiment in which the treatment consisted of two different instructions of the Chief audit executive; one stressing the priority of management (cost reduction) and one stressing the priority of the audit committee (effectiveness). Internal auditors had to evaluate internal controls and their inherent costs of different processes which varied in their degree of task complexity. Our main results indicate that internal auditors' evaluation of the processes is significantly different when task complexity is high. Our findings suggest that internal auditors do follow the priorities of either management or the audit committee depending on the instructions of a superior internal auditor. The study's results question whether the independence of the internal audit function is actually achievable. With our findings, we contribute to research on internal auditors' judgment and the internal audit function's independence in the frame of corporate governance.

Analysis of a finite volume method for a cross-diffusion model in population dynamics

The main goal of this paper is to propose a convergent finite volume method for a reactionâeuro"diffusion system with cross-diffusion. First, we sketch an existence proof for a class of cross-diffusion systems. Then the standard two-point finite volume fluxes are used in combination with a nonlinear positivity-preserving approximation of the cross-diffusion coefficients. Existence and uniqueness of the approximate solution are addressed, and it is also shown that the scheme converges to the corresponding weak solution for the studied model. Furthermore, we provide a stability analysis to study pattern-formation phenomena, and we perform two-dimensional numerical examples which exhibit formation of nonuniform spatial patterns. From the simulations it is also found that experimental rates of convergence are slightly below second order. The convergence proof uses two ingredients of interest for various applications, namely the discrete Sobolev embedding inequalities with general boundary conditions and a space-time $L^1$ compactness argument that mimics the compactness lemma due to Kruzhkov. The proofs of these results are given in the Appendix.

The business model ontology a proposition in a design science approach

The goal of this dissertation is to find and provide the basis for a managerial tool that allows a firm to easily express its business logic. The methodological basis for this work is design science, where the researcher builds an artifact to solve a specific problem. In this case the aim is to provide an ontology that makes it possible to explicit a firm's business model. In other words, the proposed artifact helps a firm to formally describe its value proposition, its customers, the relationship with them, the necessary intra- and inter-firm infrastructure and its profit model. Such an ontology is relevant because until now there is no model that expresses a company's global business logic from a pure business point of view. Previous models essentially take an organizational or process perspective or cover only parts of a firm's business logic. The four main pillars of the ontology, which are inspired by management science and enterprise- and processmodeling, are product, customer interface, infrastructure and finance. The ontology is validated by case studies, a panel of experts and managers. The dissertation also provides a software prototype to capture a company's business model in an information system. The last part of the thesis consists of a demonstration of the value of the ontology in business strategy and Information Systems (IS) alignment. Structure of this thesis: The dissertation is structured in nine parts: Chapter 1 presents the motivations of this research, the research methodology with which the goals shall be achieved and why this dissertation present a contribution to research. Chapter 2 investigates the origins, the term and the concept of business models. It defines what is meant by business models in this dissertation and how they are situated in the context of the firm. In addition this chapter outlines the possible uses of the business model concept. Chapter 3 gives an overview of the research done in the field of business models and enterprise ontologies. Chapter 4 introduces the major contribution of this dissertation: the business model ontology. In this part of the thesis the elements, attributes and relationships of the ontology are explained and described in detail. Chapter 5 presents a case study of the Montreux Jazz Festival which's business model was captured by applying the structure and concepts of the ontology. In fact, it gives an impression of how a business model description based on the ontology looks like. Chapter 6 shows an instantiation of the ontology into a prototype tool: the Business Model Modelling Language BM2L. This is an XML-based description language that allows to capture and describe the business model of a firm and has a large potential for further applications. Chapter 7 is about the evaluation of the business model ontology. The evaluation builds on literature review, a set of interviews with practitioners and case studies. Chapter 8 gives an outlook on possible future research and applications of the business model ontology. The main areas of interest are alignment of business and information technology IT/information systems IS and business model comparison. Finally, chapter 9 presents some conclusions.

Phytochemical investigation of plants used in African traditional medicine: "Dioscorea sylvatica" (Dioscoreaceae), "Urginea altissima" (Liliaceae), "Jamesbrittenia fodina" and "Jamesbrittenia elegantissima" (Scrophulariaceae)

Les plantes médicinales représentent la seule source de médicaments pour près de 90 % de la population de certains pays d?Afrique. Le savoir-faire des guérisseurs traditionnels, d?une valeur inestimable, représente un point de départ pour l?investigation pharmacologique et phytochimique de ces médicaments naturels. Dans le cadre de ce travail, nous nous sommes dans un premier temps intéressés à valider l?utilisation en médecine traditionnelle de deux plantes, Diuscorea sylvatica (Dioscoreaceae) et Urginea altissima (Liliaceae), qui produisent, lorsqu?elles sont frottées sur la peau, une inflammation et des démangeaisons. Ces réactions cutanées ont pu être expliquées, au moins en partie, par la présence d?aiguilles acérées d?oxalate de calcium dans les organes souterrains. Ces microtraumatismes répétés de l?épiderme risquent de provoquer, lors d?une utilisation prolongée, des lésions granulomateuses. L?histamine n?a pas été détectée, mais d?autres substances pourraient être impliquées dans le processus inflammatoire. La seconde partie de ce travail a consisté en la détection, l?isolement et la caractérisation de nouveaux composés naturels présentant un intérêt thérapeutique potentiel. 70 extraits provenant de 28 plantes supérieures du Zimbabwe ont été soumis à un criblage chimique et biologique. Les extraits méthanoliques des parties aériennes de Jamesbrittenia fodina et J. elegantissima (Scrophulariaceae) ont été sélectionnés sur la base de leurs nombreuses activités. Le fractionnement guidé par l?activité de J. fudina a permis l?isolement des saponines A et B, responsables des activités antifongique, antibactérienne et molluscicide de l?extrait. De plus, les deux saponines ont montré une activité équivalente en tant qu?inhibiteurs de l?acétylcholinestérase, propriété encore non décrite pour cette classe de composés. Une analyse LC/uv/MS de l?extrait a permis d?attribuer l?activité antiradicalaire au verbascoside, un dérivé du phenylpropane; cette analyse a de plus montré la présence d?une série de dérivés de l?acide cinnamique, dont l?isolement a été entrepris. Deux problèmes d?instabilité sont apparus, empêchant l?isolement des composés par des méthodes chromatographiques de pointe, en dépit de très bonnes conditions de séparations. Des analyses LC/?H-NMR combinées à des analyses RMN classiques des mélanges ont permis d?attribuer ces instabilités d?une part à une isomérisation cis/trans induite par la lumière, et d?autre part à une transacylation du groupe cinnamoyl sur une unité de sucre. Ceci a permis l?identification de 12 esters cinnamiques d?iridoïdes, dont 8 nouveaux produits naturels. Ces dérivés présentent un intérêt thérapeutique, car des composés similaires ont montré des propriétés anti-inflammatoires significatives dans différents modèles in vivo. Deux flavanones ont aussi été isolées de l?extrait. Cette classe de composés n?a jamais été rapportée chez un membre des Scrophulariaceae. Une analyse LC/UV/MS comparative des extraits polaires des deux espèces, J. fodina et J. elegantissima, a été effectuée pour détecter la présence éventuelle de compos.és communs. Les saponines A et B et le verbascoside ont été identifiés dans l?extrait de J. elegantissima. Trois flavonoïdes ont de plus été isolés de ce dernier par CPC et HPLC semi-préparative.<br/><br/>In certain African countries, medicinal plants represent the unique source of to 90% of the population. The knowledge of traditional healers represents a basis for the pharmacological and phytochemical investigation of these natural medicines. This work first focused on the validation of use of two plants frequently employed in traditional medicine, Dioscorea sylvatica (Dioscoreaceae) and Urginea altissimu (Liliaceae), which produce mild inflammation and itching when rubbed on the skin. These cutaneous reactions were shown to be due, at least in part, to the presence of sharp needles of calcium oxalate, implying the risk of granulomatous lesions following a long term use. Histamine was not detected, but other compounds could be involved in the inflammatory process. The second part of this work consisted of the detection, isolation and characterisation of new natural compounds of potential therapeutic interest from African plants. Seventy extracts obtained from 28 higher plants of Zimbabwe were submitted to a chemical and biological screening. The methanol extracts of the whole plants of Jamesbrittenia fodina and J. elegantissima (Scrophulariaceae) were selected for their various activities. An activity-guided fractionation of J. fodina led to the isolation of the saponins A and B, responsible for the antifungal, antibacterial and molluscicidal properties. Both saponins were equally active as inhibitors of acetylcholinesterase, a property that has, to our knowledge, never been described for this class of compounds. A LC/UV/MS analysis of the extract allowed the identification of verbascoside as the product with radical scavenging activity, and indicated the presence of a series of potentially interesting cinnamic acid derivatives. Two types of instability problems occurred in the course of their isolation, as some compounds could not be separated despite very good chromatographic conditions. LC/'H-NMR analyses combined with in-mixture NMR analyses enabled the attribution of the cause of the instability in one case to a cidtrans light-induced isomerisation, and in the other case to a transacylation of the cinnamoyl moiety on a sugar residue. These problems of instability have not been the object of previous studies. 12 cinnamic iridoid esters could be characterised, 8 of these being new natural compounds. Several similar substances have displayed significant anti-inflammatory properties in different in vivo models, suggesting a therapeutic interest for these new derivatives. Two flavanones were isolated from the same extract. This class of compound has not been previously reported from species of the Scrophulariaceae family. A comparative LCAJVNS study of the polar extracts of the two species J. elegantissima and J. fodina was performed in order to detect possible common compounds. Saponins A and B and verbascoside were thus identified in .J. elegantissima. Moreover, three supplementary flavonoids were isolated from J. elegantissima..

Three essays on the determinants of output, inflation and interest rates

Résumé: Output, inflation and interest rates are key macroeconomic variables, in particular for monetary policy. In modern macroeconomic models they are driven by random shocks which feed through the economy in various ways. Models differ in the nature of shocks and their transmission mechanisms. This is the common theme underlying the three essays of this thesis. Each essay takes a different perspective on the subject: First, the thesis shows empirically how different shocks lead to different behavior of interest rates over the business cycle. For commonly analyzed shocks (technology and monetary policy errors), the patterns square with standard models. The big unknown are sources of inflation persistence. Then the thesis presents a theory of monetary policy, when the central bank can better observe structural shocks than the public. The public will then seek to infer the bank's extra knowledge from its policy actions and expectation management becomes a key factor of optimal policy. In a simple New Keynesian model, monetary policy becomes more concerned with inflation persistence than otherwise. Finally, the thesis points to the huge uncertainties involved in estimating the responses to structural shocks with permanent effects.

GIS and geodatabases application to global scale plate tectonics modelling

Les reconstructions palinspastiques fournissent le cadre idéal à de nombreuses études géologiques, géographiques, océanographique ou climatiques. En tant qu?historiens de la terre, les "reconstructeurs" essayent d?en déchiffrer le passé. Depuis qu?ils savent que les continents bougent, les géologues essayent de retracer leur évolution à travers les âges. Si l?idée originale de Wegener était révolutionnaire au début du siècle passé, nous savons depuis le début des années « soixante » que les continents ne "dérivent" pas sans but au milieu des océans mais sont inclus dans un sur-ensemble associant croûte « continentale » et « océanique »: les plaques tectoniques. Malheureusement, pour des raisons historiques aussi bien que techniques, cette idée ne reçoit toujours pas l'écho suffisant parmi la communauté des reconstructeurs. Néanmoins, nous sommes intimement convaincus qu?en appliquant certaines méthodes et certains principes il est possible d?échapper à l?approche "Wégenerienne" traditionnelle pour enfin tendre vers la tectonique des plaques. Le but principal du présent travail est d?exposer, avec tous les détails nécessaires, nos outils et méthodes. Partant des données paléomagnétiques et paléogéographiques classiquement utilisées pour les reconstructions, nous avons développé une nouvelle méthodologie replaçant les plaques tectoniques et leur cinématique au coeur du problème. En utilisant des assemblages continentaux (aussi appelés "assemblées clés") comme des points d?ancrage répartis sur toute la durée de notre étude (allant de l?Eocène jusqu?au Cambrien), nous développons des scénarios géodynamiques permettant de passer de l?une à l?autre en allant du passé vers le présent. Entre deux étapes, les plaques lithosphériques sont peu à peu reconstruites en additionnant/ supprimant les matériels océaniques (symbolisés par des isochrones synthétiques) aux continents. Excepté lors des collisions, les plaques sont bougées comme des entités propres et rigides. A travers les âges, les seuls éléments évoluant sont les limites de plaques. Elles sont préservées aux cours du temps et suivent une évolution géodynamique consistante tout en formant toujours un réseau interconnecté à travers l?espace. Cette approche appelée "limites de plaques dynamiques" intègre de multiples facteurs parmi lesquels la flottabilité des plaques, les taux d'accrétions aux rides, les courbes de subsidence, les données stratigraphiques et paléobiogéographiques aussi bien que les évènements tectoniques et magmatiques majeurs. Cette méthode offre ainsi un bon contrôle sur la cinématique des plaques et fournit de sévères contraintes au modèle. Cette approche "multi-source" nécessite une organisation et une gestion des données efficaces. Avant le début de cette étude, les masses de données nécessaires était devenues un obstacle difficilement surmontable. Les SIG (Systèmes d?Information Géographiques) et les géo-databases sont des outils informatiques spécialement dédiés à la gestion, au stockage et à l?analyse des données spatialement référencées et de leurs attributs. Grâce au développement dans ArcGIS de la base de données PaleoDyn nous avons pu convertir cette masse de données discontinues en informations géodynamiques précieuses et facilement accessibles pour la création des reconstructions. Dans le même temps, grâce à des outils spécialement développés, nous avons, tout à la fois, facilité le travail de reconstruction (tâches automatisées) et amélioré le modèle en développant fortement le contrôle cinématique par la création de modèles de vitesses des plaques. Sur la base des 340 terranes nouvellement définis, nous avons ainsi développé un set de 35 reconstructions auxquelles est toujours associé un modèle de vitesse. Grâce à cet ensemble de données unique, nous pouvons maintenant aborder des problématiques majeurs de la géologie moderne telles que l?étude des variations du niveau marin et des changements climatiques. Nous avons commencé par aborder un autre problème majeur (et non définitivement élucidé!) de la tectonique moderne: les mécanismes contrôlant les mouvements des plaques. Nous avons pu observer que, tout au long de l?histoire de la terre, les pôles de rotation des plaques (décrivant les mouvements des plaques à la surface de la terre) tendent à se répartir le long d'une bande allant du Pacifique Nord au Nord de l'Amérique du Sud, l'Atlantique Central, l'Afrique du Nord, l'Asie Centrale jusqu'au Japon. Fondamentalement, cette répartition signifie que les plaques ont tendance à fuir ce plan médian. En l'absence d'un biais méthodologique que nous n'aurions pas identifié, nous avons interprété ce phénomène comme reflétant l'influence séculaire de la Lune sur le mouvement des plaques. La Lune sur le mouvement des plaques. Le domaine océanique est la clé de voute de notre modèle. Nous avons attaché un intérêt tout particulier à le reconstruire avec beaucoup de détails. Dans ce modèle, la croûte océanique est préservée d?une reconstruction à l?autre. Le matériel crustal y est symbolisé sous la forme d?isochrones synthétiques dont nous connaissons les âges. Nous avons également reconstruit les marges (actives ou passives), les rides médio-océaniques et les subductions intra-océaniques. En utilisant ce set de données très détaillé, nous avons pu développer des modèles bathymétriques 3-D unique offrant une précision bien supérieure aux précédents.<br/><br/>Palinspastic reconstructions offer an ideal framework for geological, geographical, oceanographic and climatology studies. As historians of the Earth, "reconstructers" try to decipher the past. Since they know that continents are moving, geologists a trying to retrieve the continents distributions through ages. If Wegener?s view of continent motions was revolutionary at the beginning of the 20th century, we know, since the Early 1960?s that continents are not drifting without goal in the oceanic realm but are included in a larger set including, all at once, the oceanic and the continental crust: the tectonic plates. Unfortunately, mainly due to technical and historical issues, this idea seems not to receive a sufficient echo among our particularly concerned community. However, we are intimately convinced that, by applying specific methods and principles we can escape the traditional "Wegenerian" point of view to, at last, reach real plate tectonics. This is the main aim of this study to defend this point of view by exposing, with all necessary details, our methods and tools. Starting with the paleomagnetic and paleogeographic data classically used in reconstruction studies, we developed a modern methodology placing the plates and their kinematics at the centre of the issue. Using assemblies of continents (referred as "key assemblies") as anchors distributed all along the scope of our study (ranging from Eocene time to Cambrian time) we develop geodynamic scenarios leading from one to the next, from the past to the present. In between, lithospheric plates are progressively reconstructed by adding/removing oceanic material (symbolized by synthetic isochrones) to major continents. Except during collisions, plates are moved as single rigid entities. The only evolving elements are the plate boundaries which are preserved and follow a consistent geodynamical evolution through time and form an interconnected network through space. This "dynamic plate boundaries" approach integrates plate buoyancy factors, oceans spreading rates, subsidence patterns, stratigraphic and paleobiogeographic data, as well as major tectonic and magmatic events. It offers a good control on plate kinematics and provides severe constraints for the model. This multi-sources approach requires an efficient data management. Prior to this study, the critical mass of necessary data became a sorely surmountable obstacle. GIS and geodatabases are modern informatics tools of specifically devoted to store, analyze and manage data and associated attributes spatially referenced on the Earth. By developing the PaleoDyn database in ArcGIS software we converted the mass of scattered data offered by the geological records into valuable geodynamical information easily accessible for reconstructions creation. In the same time, by programming specific tools we, all at once, facilitated the reconstruction work (tasks automation) and enhanced the model (by highly increasing the kinematic control of plate motions thanks to plate velocity models). Based on the 340 terranes properly defined, we developed a revised set of 35 reconstructions associated to their own velocity models. Using this unique dataset we are now able to tackle major issues of the geology (such as the global sea-level variations and climate changes). We started by studying one of the major unsolved issues of the modern plate tectonics: the driving mechanism of plate motions. We observed that, all along the Earth?s history, plates rotation poles (describing plate motions across the Earth?s surface) tend to follow a slight linear distribution along a band going from the Northern Pacific through Northern South-America, Central Atlantic, Northern Africa, Central Asia up to Japan. Basically, it sighifies that plates tend to escape this median plan. In the absence of a non-identified methodological bias, we interpreted it as the potential secular influence ot the Moon on plate motions. The oceanic realms are the cornerstone of our model and we attached a particular interest to reconstruct them with many details. In this model, the oceanic crust is preserved from one reconstruction to the next. The crustal material is symbolised by the synthetic isochrons from which we know the ages. We also reconstruct the margins (active or passive), ridges and intra-oceanic subductions. Using this detailed oceanic dataset, we developed unique 3-D bathymetric models offering a better precision than all the previously existing ones.