La problématique traitée. Cette étude est dédiée à l’institution de la résolution unilatérale, c’est-à-dire, à la situation quand le contrat est anéanti par la déclaration unilatérale du créancier émise à la suite de l’inexécution importante d’une obligation contractuelle par le débiteur. Cette étude concerne principalement la résolution unilatérale légale comme elle a été consacrée dans l’article 1552 du Code civil roumain et les particularités de la résolution unilatérale conventionnelle. La distinction entre la résolution judiciaire et la résolution unilatérale a comme fondement la manière de laquelle la résolution opère. Ainsi, tandis que la résolution judiciaire est disposée par le juge, la résolution unilatérale est déclarée par la partie en droit. En conséquence, à l’exception de la manière dont la résolution opère, la résolution judiciaire et celle unilatérale ont le même régime juridique. Pour ces raisons la recherche exhaustive de ce sujet a supposé une analyse des éléments communs de la résolution. De plus, en vue de la manière de la rédaction et de la position des articles qui la concerne, ainsi comme des avantages offerts par cette manière d’opérer, la résolution unilatérale est prévue comme le moyen général d’anéantissement du contrat pour l’inexécution des obligations. En conséquence, dans le contexte du Nouveau Code civil roumain, pour traiter le sujet de la résolution unilatérale, une analyse complète du régime juridique de la résolution s’impose. Bien qu’en apparence, les résolutions du Nouveau Code civil roumain concernant la résolution n’apportent pas de modifications en substance par rapport au régime juridique de l’ancien Code civil roumain inspirée par le Code civil français, une analyse systématique des dispositions regardant l’exécution des obligations contractuelles mènent à une autre solution. Pour ce motif, on a choisi de commencer cette étude par la présentation des considérations générales en ce qui concerne la résolution (la Ière Partie), cela ayant comme finalité l’essai d’identifier les traits caractéristiques de cette institution, sa nature juridique et son fondement. A la suite, on a opté d’examiner les conditions pour que le droit à la résolution, les particularités de la résolution et de la résiliation unilatérale conventionnelle (la IIème Partie) et les effets de la résolution et de la résiliation (la IIIe Partie) [...] / The object. This study is dedicated to the unilateral termination of the contract in the situation when the contract is destroyed by the unilateral declaration issued by the creditor as a result of the significant breach of a contractual obligation by the debtor. This study mainly concerns the unilateral and legal termination of contract for breach as it was enshrined in Article 1552 of the Romanian Civil Code and also the case of the conventional unilateral resolution. The distinction between judicial termination of contract for breach and unilateral resolution of contract for breach is based on how the termination operates. Thus, while judicial termination of contract for breach is declared by the judge, the unilateral termination of contract for breach is declared by the party entitled. Excepting this distinction, the judicial termination of contract for breach and the unilateral one have the same legal regime. For these reasons this analyses focuses on the common elements of the termination of contract for breach. Furthermore, we believe that in this new legal frame the unilateral termination of contract for breach is intended as a general means of destruction of a contract for breach. This is the reason why in order to address the issue of unilateral termination of contract for breach we appreciated that a comprehensive analysis of the legal regime of the termination of contract for breach is required […]

Le rôle du collicule inférieur dans les divers processus auditif demeure à ce jour méconnu chez l’humain. À l’aide d’évaluations comportementales et électrophysiologiques, le but des études consiste à examiner l’intégrité fonctionnelle du système nerveux auditif chez une personne ayant une lésion unilatérale du collicule inférieur. Les résultats de ces études suggèrent que le collicule inférieur n’est pas impliqué dans la détection de sons purs, la reconnaissance de la parole dans le silence et l’interaction binaurale. Cependant, ces données suggèrent que le collicule inférieur est impliqué dans la reconnaissance de mots dans le bruit présentés monauralement, la discrimination de la fréquence, la reconnaissance de la durée, la séparation binaurale, l’intégration binaurale, la localisation de sources sonores et, finalement, l’intégration multisensorielle de la parole. / The role of the inferior colliculus in human auditory processing is still poorly understood. We report the results obtained from a 12-year-old boy who suffered a very circumscribed lesion at the level of the right inferior colliculus without additional neurological damage. The child underwent an extensive battery of psychophysical and electrophysiological tests. Results revealed that tonal detection thresholds, speech recognition in the absence of competing auditory input and performance on binaural interaction tasks were unimpaired. However, the pattern of results suggests that auditory functions such as the recognition of low-redundancy speech presented monaurally, frequency discrimination, the recognition of tone-duration patterns, binaural separation, binaural integration, sound-source localization in space as well as mutlisensory integration depend on the integrity of the bilateral auditory pathways at the level of the inferior colliculus.

Perceptual rivalry refers to visual phenomena that are characterised by alternations between different percepts, despite an unchanging sensory input. Two common types of perceptual rivalry are (i) reversible figures — two-dimensional stable images that when viewed, are perceived to switch between different interpretations, and (ii) binocular rivalry — the alternations in image dominance resulting from the presentation of conflicting stimuli, one to each eye. Several investigators have suggested that these rivalling phenomena are mediated by similar neural mechanisms. Such a view, however, has not only been inadequately substantiated, but has also yet to be assessed in the context of a directly testable neurophysiological model. Miller and Pettigrew have proposed a novel, high-level interhemispheric switch (IHS) explanatory model of binocular rivalry. This model conceptualises the perceptual alternations as being mediated by alternations between one hemisphere’s selected image and the other hemisphere’s selected (rival) image. To assess their hypothesis, caloric vestibular stimulation (CVS) was used. CVS is a simple, inexpensive, and non-invasive brain stimulation technique that unilaterally activates high-level attentional areas. In accordance with the IHS model, CVS was found to significantly affect predominance (the duration that one image is perceived relative to the other, within a given viewing period) during conventional binocular rivalry with horizontal/vertical gratings and with orthogonal oblique gratings. The present thesis therefore aims, through the use of CVS, to extend this IHS model of binocular rivalry to reversible-figure alternations and propose a general IHS model of perceptual rivalry. Chapter 1 provides a detailed literature review of the field within the context of comparing both perceptual rivalries. In Chapter 2, investigations are presented on two different reversible figures — the perspective-reversing Necker cube and the figure–ground reversing Rubin’s vase–faces illusion. In these experiments, CVS was found to significantly change observers’ predominance compared to their baseline predominance. These results demonstrate that interhemispheric switching also mediates the alternations of these visual phenomena, in addition to binocular rivalry, thereby extending the IHS model to one of perceptual rivalry in general. Moreover, the findings are interpreted in a cognitive neuroscience context, including a novel proposal of a forebrain framework for the IHS model. Chapter 3 presents CVS experiments that address the issue of percept–to–hemisphere selection and the reproducibility of CVS effects, following Miller’s initial work on two types of conventional binocular rivalry. In planned analyses, significant predominance changes were not found in horizontal/vertical rivalry, oblique rivalry and Necker-cube rivalry. In post-hoc analyses that accounted for study-design differences between Miller’s original experiments and the present experiment, CVS was again not shown to induce significant predominance changes in any of the rivalry types. Assessment of directional predominance changes following CVS appeared to suggest an arbitrary selection of percept–to–hemisphere in all rivalry types, although no firm conclusions could be drawn from the obtained data on this issue. Nevertheless, the experiments further extend upon Miller’s earlier work by examining the inter- and intra-individual reproducibility of CVS-induced effects on predominance. Such reproducibility was found to be low and potential reasons for this are discussed. The experiments in Chapter 4 examine a type of binocular rivalry in which dichoptic presentation of Díaz-Caneja stimuli yields rivalry among four different stable images: half-field rivalry between the images presented to the eyes, and coherence rivalry in which aspects of each eye’s presented image are perceptually regrouped into rivalling coherent images. Each of these rivalries was found to occur for about half the given viewing time. Furthermore, CVS significantly shifted the predominance of perceived coherent images (coherence rivalry) but not half-field images (eye rivalry). This finding suggests that coherence rivalry (like conventional rivalry according to previous experiments) is mediated by interhemispheric switching at a high level, while eye rivalry is mediated by intrahemispheric mechanisms, most likely at a low level. In addition, it is proposed that Díaz-Caneja stimuli induce ‘meta-rivalry’ whereby these discrete high- and low-level competitive processes themselves rival for visual consciousness. The current thesis thus presents a novel meta-rivalry model of multistable binocular rivalry. It also presents the first direct evidence that interhemispheric switching mediates reversible-figure alternations, thereby supporting a generalised IHS model of perceptual rivalry. It is argued that both models provide a parsimonious exploratory framework within which specific predictions can be made and readily tested. Finally, the findings of all experiments in the current thesis are summarised.

Perceptual rivalry refers to visual phenomena that are characterised by alternations between different percepts, despite an unchanging sensory input. Two common types of perceptual rivalry are (i) reversible figures — two-dimensional stable images that when viewed, are perceived to switch between different interpretations, and (ii) binocular rivalry — the alternations in image dominance resulting from the presentation of conflicting stimuli, one to each eye. Several investigators have suggested that these rivalling phenomena are mediated by similar neural mechanisms. Such a view, however, has not only been inadequately substantiated, but has also yet to be assessed in the context of a directly testable neurophysiological model. Miller and Pettigrew have proposed a novel, high-level interhemispheric switch (IHS) explanatory model of binocular rivalry. This model conceptualises the perceptual alternations as being mediated by alternations between one hemisphere’s selected image and the other hemisphere’s selected (rival) image. To assess their hypothesis, caloric vestibular stimulation (CVS) was used. CVS is a simple, inexpensive, and non-invasive brain stimulation technique that unilaterally activates high-level attentional areas. In accordance with the IHS model, CVS was found to significantly affect predominance (the duration that one image is perceived relative to the other, within a given viewing period) during conventional binocular rivalry with horizontal/vertical gratings and with orthogonal oblique gratings. The present thesis therefore aims, through the use of CVS, to extend this IHS model of binocular rivalry to reversible-figure alternations and propose a general IHS model of perceptual rivalry. Chapter 1 provides a detailed literature review of the field within the context of comparing both perceptual rivalries. In Chapter 2, investigations are presented on two different reversible figures — the perspective-reversing Necker cube and the figure–ground reversing Rubin’s vase–faces illusion. In these experiments, CVS was found to significantly change observers’ predominance compared to their baseline predominance. These results demonstrate that interhemispheric switching also mediates the alternations of these visual phenomena, in addition to binocular rivalry, thereby extending the IHS model to one of perceptual rivalry in general. Moreover, the findings are interpreted in a cognitive neuroscience context, including a novel proposal of a forebrain framework for the IHS model. Chapter 3 presents CVS experiments that address the issue of percept–to–hemisphere selection and the reproducibility of CVS effects, following Miller’s initial work on two types of conventional binocular rivalry. In planned analyses, significant predominance changes were not found in horizontal/vertical rivalry, oblique rivalry and Necker-cube rivalry. In post-hoc analyses that accounted for study-design differences between Miller’s original experiments and the present experiment, CVS was again not shown to induce significant predominance changes in any of the rivalry types. Assessment of directional predominance changes following CVS appeared to suggest an arbitrary selection of percept–to–hemisphere in all rivalry types, although no firm conclusions could be drawn from the obtained data on this issue. Nevertheless, the experiments further extend upon Miller’s earlier work by examining the inter- and intra-individual reproducibility of CVS-induced effects on predominance. Such reproducibility was found to be low and potential reasons for this are discussed. The experiments in Chapter 4 examine a type of binocular rivalry in which dichoptic presentation of Díaz-Caneja stimuli yields rivalry among four different stable images: half-field rivalry between the images presented to the eyes, and coherence rivalry in which aspects of each eye’s presented image are perceptually regrouped into rivalling coherent images. Each of these rivalries was found to occur for about half the given viewing time. Furthermore, CVS significantly shifted the predominance of perceived coherent images (coherence rivalry) but not half-field images (eye rivalry). This finding suggests that coherence rivalry (like conventional rivalry according to previous experiments) is mediated by interhemispheric switching at a high level, while eye rivalry is mediated by intrahemispheric mechanisms, most likely at a low level. In addition, it is proposed that Díaz-Caneja stimuli induce ‘meta-rivalry’ whereby these discrete high- and low-level competitive processes themselves rival for visual consciousness. The current thesis thus presents a novel meta-rivalry model of multistable binocular rivalry. It also presents the first direct evidence that interhemispheric switching mediates reversible-figure alternations, thereby supporting a generalised IHS model of perceptual rivalry. It is argued that both models provide a parsimonious exploratory framework within which specific predictions can be made and readily tested. Finally, the findings of all experiments in the current thesis are summarised.

Au début du nouveau millénaire, aujourd’hui même, nous entendons sans cesse de part en part des clameurs sur la lutte entre les philosophies et entre la science et la philosophie, et des nouvelles de la fin de la philosophie au pireC’est pourquoi nous devons rechercher une Science radicale et universelle sans hiérarchie, ni primauté sur les autres. Or, dans les philosophies de la Différence contemporaines, l’autorité de la Différe(a)nce comme l’invariant philosophique s’installe subrepticement dans l’immanence qui retombe dans la transcendance métaphysique. Le cercle vicieux de la dualité transcendante y continue au nom du retour éternel, de la répétition, du chiasme du logos, et puis du Vide. Il semble que l’errance de la pensée contemporaine nous ramène à l’absurdité aporétique. En occurrence, Laruelle F. nous démontre une pensée du Milieu apaisant la dépression et le tourbillonnement de la pensée contemporaine. La non-philosophie dont le Milieu immanental parvient à la Science générique plus universelle comme avant-première. Du coup, cette Science générique forgée de la non-philosophie est sobre, mais libre à la force de l’immanence de l’Un ou/et de la Vision-en-Un. Par ailleurs, par les recherches et les expérimentations de la pensée du Milieu en Asie : le Vide (空性 Gongxing, śūnyatā) dans la théorie de Chungguan (中觀 Madhyamaka) comme la Vision-en-Milieu de Nāgārjuna, le Zhenru (眞如 tathatā) de Weishi (唯識 vijñāna–mātráta) comme l’Un et la Vision-en-UN, et puis le Yixin ermen (一心二門) comme la Dualité unilatérale dans Daichengqixin lun, nous pensons plus profondément au Milieu immanent et transcendantal comme Milieu-en-Un. Si bien que nous pouvons atteindre une Science du Milieu rigoureuse en vertu de la rencontre de la Science générique et des pensées du Milieu en Asie. Par conséquent, nous pratiquerons la Science du Milieu universelle à travers la Détermination de l’Homme en-dernière-instance ou de l’Homme-en-personne. La Détermination-en-dernière-instance consiste dans le Milieu-en-Un, la Dualité unilatérale de la Vision-en-Milieu et de la Vision-en-Un, ou de la Vision-en-Milieu-en-Un. / As the new millennium dawns, there is a growing debate about the conflict between philosophies and between science and philosophy, and even about the end of philosophy itself. For this reason, we must seek out a radical and universal science that does not claim hierarchical importance or primacy over the others. Yet in the contemporary philosophies of Difference, the overriding importance of Difference as the philosophical invariant finds its place in the theory of immanence and, in juxtaposition, metaphysical transcendence. The vicious circle of the transcendent duality persists here in the name of the eternal recurrence, repetition, the chiasmus of the logos, and Emptiness. It would appear that the meanderings of contemporary thinking about these matters is leading us towards aporetic absurdity. In this regard, F. Laruelle demonstrates one thought of the Middle, which alleviates the depression and chaos of contemporary thinking. (Non-) philosophy, such as the immanental Middle, manages to make Generic science more universal as an avant-première. Generic science carved out from non-philosophy is sober, but free from the power of immanence of One or immanence of the Vision-in-One. Besides, through the research and experimentation of the thinking of the Middle in Asia – Emptiness (空性 Gongxing, śūnyatā) in the theory of Chungguan (中觀 Madhyamaka), the Vision-in-Middle of Nāgārjuna, Zhenru (眞如 tathatā) of Weishi (唯識 vijñāna–mātráta), such as the One or the Vision-in-One, Yixin ermen (一心二門) and the Unilateral Duality in Daichengqixin lun – we now consider more clearly the immanent and transcendental Middle as the Middle-in-One. This enables us to attain a rigorous science of the Middle thanks to the coming together of Generic Science and the thinking of the Middle in Asia. As a result, we will be able to practice the universal Science of the Middle through the Determination of the man in-the-last-instance or the Man-in-person. The Determination-in-the-last-instance takes on board the notions of the Middle-in-One, the Unilateral Duality of the Vision-in-Middle and of the Vision-in-One, or of the Vision-in-Middle-in-One.

L’évolution contemporaine du droit privé des contrats est marquée par la multiplication des hypothèses dans lesquelles l’une ou l’autre des parties dispose de la possibilité d’agir seule sur le contenu ou le sort d’un contrat définitivement formé. Par exemple, depuis 1995, il est admis que l’une des parties à un contrat-cadre puisse seule fixer le prix. De même, en cas de manquement grave de l’une des parties, l’autre peut, à ses risques et périls, procéder à la résolution du contrat. Ces deux types de prérogatives contractuelles appartiennent à une catégorie plus large que la doctrine désigne couramment sous le nom de « pouvoirs contractuels ». Or, les pouvoirs contractuels viennent perturber les règles traditionnelles du droit privé des contrats à deux égards. D’une part, les pouvoirs contractuels introduisent une logique unilatéraliste, synonyme d’inégalité, dans le contrat qui répond traditionnellement à une logique consensualiste synonyme d’égalité. D’autre part, le mécanisme des pouvoirs contractuels implique une redéfinition de la place du juge dans le contentieux contractuel puisque ce dernier ne devra plus nécessairement être saisi pour trancher les litiges entre les parties relatifs à l’exécution du contrat. Celui-ci sera saisi postérieurement à la modification des effets du contrat décidée unilatéralement, et ce, par la partie qui entend en contester la régularité. Consacrer une étude aux pouvoirs contractuels suppose donc de chercher à identifier plus précisément ce mécanisme qui vient introduire dans le contrat une logique de pouvoir qui n’est pas la sienne, puis, de tenter de définir les contours de l’intervention du juge. / The contemporary evolution of the private law of contracts is marked by the multiplication of the hypotheses in which one or other of the parties has the possibility of acting alone on the content or fate of a definitively formed contract. For example, since 1995, it has been accepted that one of the parties to a framework contract can only fix the price. Similarly, in the event of a serious breach by one of the parties, the other party may, at his own risk, proceed to the termination of the contract. These two types of contractual prerogatives belong to a broader category that the doctrine commonly refers to as "contractual powers". However, contractual powers disrupt the traditional rules of private contract law in two respects. On one hand, contractual powers introduce a unilateralist logic, synonymous with inequality, in the contract that traditionally responds to a consensualist logic synonymous with equality. On the other hand, the mechanism of contractual powers implies a redefinition of the judge's place in contractual disputes since the latter will no longer necessarily be seized to settle disputes between the parties relating to the performance of the contract. It will be seized after the modification of the effects of the contract decided unilaterally, and this, by the party who intends to contest the regularity. To devote a study to the contractual powers therefore presupposes seeking to identify more precisely this mechanism that introduces into the contract a logic of power that is not its own, and then attempts to define the contours of the judge's intervention.

Let us have a boundary value problem for the fourth order homogeneous linear ordinary differential equation with constant coefficients, four zero boundary conditions and one additional unilateral condition in the interior of the domain. We prove the existence of a sequence of non-trivial solutions for three types of boundary conditions.

The present work studies instantaneous motion of smooth planar and spatial objects in unilateral point contacts. The traditional first-order instantaneous kinematic analysis is found insufficient to explain many common physical scenarios. The present work looks beyond the velocity state of motion for a comprehensive understanding through higher-order kinematic analysis of the above system. The methodology proposed herein is a Euclidean space approach to second-order motion space analysis of objects in point contacts. The geometries of the objects are approximated up to second-order in the differential vicinity of the point of contact; meaning, up to curvature at the point of contact. The instantaneous motion is approximated up to second-order kinematics, i.e., up to acceleration state. The basic approach consists of impressing an instantaneous motion upon one object while holding the other fixed which is in a single point contact initially, and observing for one of the following three states: penetration, separation, and persistence of contact between the two objects. These three states are characterized by the interference between the geometries of the objects. Penetration and separation of two curves for rotation about points on the plane is geometrically studied based on the relative configuration of the osculating circles at the point of contact. It is shown that the plane is partitioned into four regions of rotation centers. Partitioning of the plane into motion space regions at a contact provided a geometrical framework compose the motion space for multiple contacts. The applications include second-order form-closure (SFC) and synthesis of kinematic pairs. To explore the consequence of a generic motion, an analytical scheme is formulated using the screw theoretic concepts of twist and twist-derivative. It is shown that the characteristics of second-order motions at a single contact depends only upon the geometric kinematic properties of the motion; meaning, the motion characteristics are time-independent. The geometric conditions for the second-order motion that will be admissible or restrained at a contact are not available in the existing literature on \second-order mobility". The classical Euler-Savary equation for enveloping curves is found to represent the condition which is both necessary and sufficient for the second-order roll-slide motion. An elegant generalized geometric characterization of second-order motions is derived. This is made use for deriving condition of immobilization of, planar mechanisms with up to 2-degrees-of-freedom (d.o.f.), with a single point contact. Illustrative examples of four-bar and 2R-mechanisms are presented. Rapid prototyped model of the four-bar mechanism is fabricated and the SFC theory is verified satisfactorily. Through a novel use of Meusnier's theorem, rotational motion characteristics of planar curves in a point contact is used to determine the patterns and distribution of admissible axes of rotation in space for two surfaces in a single point contact. In the generalized analytical method of motion space analysis, the surfaces are locally represented in Monge's form up to second-order terms and motion is represented using twist and twist-derivative. An analytical framework for the second-order motion space analysis of surfaces with multiple contacts has been developed. Using this procedure, pairs of objects are analyzed for SFC and equivalent lower kinematic pair freedom. Revolute and planar joints with two contacts, prismatic joint with three contacts, SFC of regular concave spherical tetrahedron and regular tetrahedron with four contacts are demonstrated. Although conventional first-order studies demand seven contact points for form-closure, within the context of second-order motion, the present study established that, under special geometric conditions relative immobilization of two smooth objects can be enabled with much fewer contacts. Conditions for immobilization using three and two smooth contacts have been derived. Using contact kinematics equations based on higher-order reciprocity, an instantaneous spatial higher pair to lower pair substitute-connection which is kinematically equivalent up to acceleration analysis for two smooth surfaces in persistent point contact is derived. An illustrative example of a three-link direct-contact mechanism is presented.

Propagation des fissures microscopiques, est représentée par des variables d’endommagement. L’évolution de la variable d’endommagement est généralement formulée sur la base d’observations expérimentales. De nombreux modèles phénoménologiques d’endommagement ont été proposés dans la littérature. L’objet de cette thèse est de développer une nouvelle procédure pour obtenir des lois d’évolution macroscopique d’endommagement,dans lesquelles l’évolution de l’endommagement est entièrement déduite de l’analyse de la microstructure. Nous utilisons une homogénéisation basée sur des développements asymptotiques pour décrire le comportement global à partir de la description explicite d’un volume élémentaire microfissuré.Nous considérons d’une part un critère quasi-fragile (indépendant du temps) puis un critère sous-critique(dépendant du temps) pour décrire la propagation des microfissures. De plus, le frottement entre les lèvres des microfissures est pris en compte. Une analyse énergétique est proposée, conduisant à une loi d’évolution d’endommagement qui intègre une dégradation de la rigidité, un adoucissement du comportement du matériau, des effets de taille et d’unilatéralité, mettant en avant un comportement différent à la rupture en contact avec et sans frottement. L’information sur les micro-fissures est contenue dans les coefficients homogénéisés et dans la loi d’évolution de l’endommagement. Les coefficients homogénéisés décrivent la réponse globale en présence de micro-fissures (éventuellement statiques), tels qu’ils sont calculées avec la(quasi-) solution microscopique statique. La loi d’endommagement contient l’information sur l’évolution des micro-fissures, résultant de l’équilibre énergétique dans le temps pendant la propagation microscopique.La loi homogénéisée est formulée en incrément de contrainte. Les coefficients homogénéisés sont calculées numériquement pour des longueurs de fissures et des orientations différentes. Cela permet la construction complète des lois macroscopiques. Une première analyse concerne le comportement local macroscopique, pour des trajets de chargement complexes, afin de comprendre le comportement prédit par le modèle à deux échelles et l’influence des paramètres micro structuraux, comme par exemple le coefficient de frottement. Ensuite, la mise en œuvre en éléments finis des équations macroscopiques est effectuée et des simulations pour différents essais de compression sont réalisées. Les résultats des simulations numériques sont comparés avec les résultats expérimentaux obtenus en utilisant un nouvel appareil triaxial récemment mis au point au Laboratoire 3SR à Grenoble (France). / In continuum damage models, the degradation of the elastic moduli, as the results of microscopic crackgrowth, is represented through damage variables. The evolution of damage variable is generally postulatedbased on the results of the experimental observations. Many such phenomenological damage modelshave been proposed in the literature. The purpose of this contribution is to develop a new procedurein order to obtain macroscopic damage evolution laws, in which the damage evolution is completelydeduced from micro-structural analysis. We use homogenization based on two-scale asymptotic developmentsto describe the overall behaviour starting from explicit description of elementary volumes withmicro-cracks. We consider quasi-brittle (time independent) and sub-critical (time dependent) criteria formicro-cracks propagation. Additionally, frictional contact is assumed on the crack faces. An appropriatemicro-mechanical energy analysis is proposed, leading to a damage evolution law that incorporates stiffnessdegradation, material softening, size effect, and unilaterality, different fracture behaviour in contactwithout and with friction. The information about micro-cracks is contained in the homogenized coefficientsand in the damage evolution law. The homogenized coefficients describe the overall response inthe presence of (possibly static) micro-cracks, as they are computed with the (quasi-) static microscopicsolution. The damage law contains the information about the evolution of micro-cracks, as a result ofthe energy balance in time during the microscopic propagation. The homogenized law is obtained in therate form. Effective coefficients are numerically computed for different crack lengths and orientations.This allows for the complete construction of the macroscopic laws. A first analysis concerns the localmacroscopic behaviour, for complex loading paths, in order to understand the behaviour predicted bythe two-scale model and the influence of micro structural parameters, like for example friction coefficient.Next, the FEM implementation of the macroscopic equations is performed and simulations for variouscompression tests are conducted. The results of the numerical simulations are compared with the experimentalresults obtained using a new true-triaxial apparatus recently developed at the Laboratory 3SRin Grenoble (France).

Made available in DSpace on 2014-12-17T14:13:56Z (GMT). No. of bitstreams: 1 CarlosAAG.pdf: 323369 bytes, checksum: 093c86d6d5662ee9fb5d64b4afd66037 (MD5) Previous issue date: 2004-02-19 / The objective of this study is to estimate the prevalence of Ocular Toxocariasis, Diffuse Unilateral Subacute Neuroretinitis (DUSN), Toxoplasma gondii infection and Ocular Toxoplasmosis in a student population in Natal-RN/Brazil and relate it to demographic, epidemiologic and socio-economic risk factors. The incidence of DUSN was observed in patients at the Federal University of Rio Grande do Norte Ophthalmology Service and the Prontoclinica de Olhos Ophthalmology clinic in Natal. In cases where a worm was found in the subretinal space, the result of treatment with photocoagulation using Green Laser (Eye Light ALCON) was evaluated in relation to final visual result. The sample was randomly selected among the schools of the four districts of Natal, according to the type of institution (public or private), its level (elementary or secondary), and study period (morning, afternoon or evening). The school population was studied from March to May, 2001. Initially, the students answered a questionnaire to evaluate demographic, epidemiologic and socio-economic risk factors. Afterwards, the following procedures were carried out: blood samples were taken for Toxoplasmosis (IgG, IgM) serology, hemogram, ophthalmological examination, consisting of clinical history, measurement of visual acuity, refraction under cycloplegia, biomicroscopy of the anterior segment and annexa, funduscopy and examination of extrinsic motility. The prevalence of Toxocariasis was 0.2% or 2 per one thousand students. The sample was insufficient to estimate the prevalence of DUSN. Seventy patients with DUSN diagnosis were examined from January, 2001 to January, 2003. A live worm was found in the subretinal space of all four patients in the acute phase, and these were treated with laser photocoagulation. After follow-up (average = 11.5 months), visual acuity improved in three eyes and remained unaltered in one eye. Worms were found in 22 of the 66 patients in the chronic phase, and these also were treated with laser photocoagulation. After a follow-up period of 13.1 months, on average, visual acuity improved in two of the patients, remained unchanged in 19 and worsened in one. The comparison of visual result before and after treatment was not statistically significant (p = 0.302). The diagnosis of DUSN in the acute phase, followed by prompt localization and destruction of the worm by photocoagulation, can improve the patient s vision. However, destruction of the worm by laser photocoagulation in eyes with DUSN in the chronic phase does not improve visual acuity. Seroprevalence for IgG was 46% (Confidence Interval CI 95%-42.9-49.2%) and for IgM it was 1.4% (CI 95% = 0.8-2.4%). The prevalence of ocular lesion was 1.15% (CI 95% = 0.6 - 2.0%). Socio-economic conditions were determinants in the prevalence of Systemic and Ocular Toxoplasmosis in the bivaried analysis and confirmed in the multivaried analysis (mother s scholarity illiterate/ OR = 2.9 and p < 0.001). The T. gondii infection prevalence, although high, was less than that found in studies performed in the South and Southeast of Brazil and that of Ocular Toxoplasmosis was completely discrepant, varying from 5 to 17 times less. Although important epidemiological variables such as owning a cat, drinking unfiltered water, and coming into contact with rivers or lakes showed an association in the preliminary analysis, they lost their influence when included in the logistic model. Future studies are scheduled to begin in March, 2004, in collaboration with other Brazilian and American universities in an attempt to discover the reason for these findings, as well as identifying the different strains of Toxoplasma gondii, and studying the sources of water utilized by the population of Natal Brazil / Esta pesquisa teve como objetivo, estimar a preval?ncia da Toxocar?ase Ocular, Neuroretininte Sub-aguda Difusa Unilateral (DUSN), Infec??o pelo Toxoplasma gondii e Toxoplasmose Ocular na popula??o de escolares de Natal-RN/Brasil e relacion?-la aos fatores de risco demogr?ficos, epidemiol?gicos e socioecon?micos. Estudar a incid?ncia de DUSN em pacientes atendidos no Servi?o de Oftalmologia da Universidade Federal do Rio Grande do Norte e Prontoclinica de Olhos, em Natal, bem como, avaliar, nos casos em que foi encontrada larva no espa?o sub-retiniano, o resultado do tratamento com fotocoagula??o utilizando o Laser Verde (Eye Light ALCON) em rela??o ao resultado visual. A amostra foi selecionada aleatoriamente e distribu?da nas escolas dos quatro distritos da cidade de Natal de acordo com a natureza da institui??o (p?blica ou privada), seu n?vel (fundamental ou m?dio) e turno em que o escolar estudava (matutino, vespertino ou noturno). A popula??o de escolares foi estudada no per?odo de mar?o a maio de 2001. Inicialmente, responderam a um question?rio para avalia??o de fatores de risco demogr?fico, epidemiol?gico e socioecon?mico. Depois foram feitos os seguintes procedimentos: coleta de sangue para realiza??o de sorologia para Toxoplasmose (IgG, IgM), hemograma, exame oftalmol?gico constando de hist?ria cl?nica, medida da acuidade visual, refra??o sob cicloplegia, biomicroscopia do segmento anterior e anexos, fundoscopia e exame da motilidade extr?nseca. A preval?ncia de Toxocar?ase foi de 0,2% ou 2 por mil escolares. A amostra n?o foi suficiente para estimar a preval?ncia de DUSN. Foram examinados 70 pacientes com diagn?stico de DUSN, no per?odo de janeiro de 2001 a janeiro de 2003. Foi encontrada larva viva no espa?o sub-retiniano de todos os quatro que se encontravam na fase aguda, e tratados com fotocoagula??o a laser. Ap?s acompanhamento dos pacientes (m?dia = 11,5 meses), a acuidade visual melhorou em tr?s olhos e permaneceu inalterada em um olho. Dos 66 pacientes na fase cr?nica, foi encontrada larva em 22 deles e tratados com fotocoagula??o a laser. Ap?s acompanhamento por um per?odo de 13,1 meses em m?dia, a acuidade visual melhorou em dois, permaneceu a inicial em 19 e diminuiu em um paciente. A compara??o do resultado visual antes e ap?s o tratamento, n?o foi estatisticamente significante (p = 0,302). O diagn?stico de DUSN na fase aguda, seguida por pronta localiza??o e destrui??o da larva por fotocoagula??o, pode melhorar a vis?o dos pacientes. No entanto, a destrui??o da larva por fotocoagula??o a laser em olhos com DUSN, na fase cr?nica, n?o melhora a acuidade visual. A soropreval?ncia para IgG foi de 46% (Intervalo de Confian?a -IC 95% - 42,9-49,2%) e para IgM foi 1,4% (IC 95% = 0,8-2,4%). A preval?ncia de les?o ocular foi 1,15% (IC 95% = 0,6 2,0%). As condi??es socioecon?micas foram determinantes na preval?ncia da Infec??o pelo T. gondii e Toxoplasmose Ocular na an?lise bivariada e confirmada na an?lise multivariada (escolaridade da m?e n?o alfabetizada/OR = 2,9 e p< 0,001). A preval?ncia de Toxoplasmose Sist?mica, embora elevada, foi menor do que a encontrada em estudos realizados no Sul e Sudeste do Brasil e, a da Toxoplasmose Ocular foi totalmente discrepante, variando de 5 a 17 vezes menos. Embora importantes vari?veis epidemiol?gicas, tais como possuir gato, beber ?gua n?o filtrada, ter contato com lagoas ou rios, tenham mostrado associa??o na an?lise preliminar, perderam sua influ?ncia quando inclu?das no modelo log?stico. Estudos futuros j? est?o planejados para ter inicio em mar?o pr?ximo, em colabora??o com outras Universidades do Brasil e dos Estados Unidos com a finalidade de encontrar a raz?o destes achados, bem como, identificar diferentes tipos de cepas do Toxoplasma gondii, e estudar as fontes de ?gua utilizadas pela popula??o de Natal-RN