Développement et analyse d'un modèle poroélastique et composite du cartilage

Introduction, états des connaissances et objectifs -- Composition du cartillage -- Structure et organisation dans le cartillage -- Les différents types de tests existants -- Les propriétés mécaniques du cartilage -- Les modèles existants -- Propriétés mécaniques quantitatives -- Développement et analyse du modèle analytique composite nonhomogène en compression non confinée -- Hypothèses prises en compte pour l'élaboration du modèle -- Développement et validation du modèle analytique et analyse du cartilage en compression non confinée (Article1) -- Développement du modèle éléments finis -- Élaboration du modèle par éléments finis en compression non confinée -- Propriétés de matériaux

Experimental validation of a new biphasic model of the contact mechanics of the porcine hip

Hip models that incorporate the biphasic behaviour of articular cartilage can improve understanding of the joint function, pathology of joint degeneration and effect of potential interventions. The aim of this study was to develop a specimen-specific biphasic finite element model of a porcine acetabulum incorporating a biphasic representation of the articular cartilage and to validate the model predictions against direct experimental measurements of the contact area in the same specimen. Additionally, the effect of using a different tension-compression behaviour for the solid phase of the articular cartilage was investigated. The model represented different radial clearances and load magnitudes. The comparison of the finite element predictions and the experimental measurement showed good agreement in the location, size and shape of the contact area, and a similar trend in the relationship between contact area and load was observed. There was, however, a deviation of over 30% in the magnitude of the contact area, which might be due to experimental limitations or to simplifications in the material constitutive relationships used. In comparison with the isotropic solid phase model, the tension-compression solid phase model had better agreement with the experimental observations. The findings provide some confidence that the new biphasic methodology for modelling the cartilage is able to predict the contact mechanics of the hip joint. The validation provides a foundation for future subject-specific studies of the human hip using a biphasic cartilage model

Biphasic investigation of contact mechanics in natural human hips during activities

The aim of this study was to determine the cartilage contact mechanics and the associated fluid pressurisation of the hip joint under eight daily activities, using a three-dimensional finite element hip model with biphasic cartilage layers and generic geometries. Loads with spatial and temporal variations were applied over time and the time-dependent performance of the hip cartilage during walking was also evaluated. It was found that the fluid support ratio was over 90% during the majority of the cycles for all the eight activities. A reduced fluid support ratio was observed for the time at which the contact region slid towards the interior edge of the acetabular cartilage, but these occurred when the absolute level of the peak contact stress was minimal. Over 10 cycles of gait, the peak contact stress and peak fluid pressure remained constant, but a faster process of fluid exudation was observed for the interior edge region of the acetabular cartilage. The results demonstrate the excellent function of the hip cartilage within which the solid matrix is prevented from high levels of stress during activities owing to the load shared by fluid pressurisation. The findings are important in gaining a better understanding of the hip function during daily activities, as well as the pathology of hip degeneration and potential for future interventions. They provide a basis for future subject-specific biphasic investigations of hip performance during activities

A rheological network model for the continuum anisotropic and viscoelastic behavior of soft tissue

The mechanical behavior of soft tissue demonstrates a number of complex features including nonlinearity, anisotropy, viscoelasticity, and growth. Characteristic features of the time-dependent and anisotropic behavior are related to the properties of various components of the tissue such as fibrous collagen and elastin networks, large proteins and sugars attached to these networks, and interstitial fluid. Attempts to model the elastic behavior of these tissues based on assumptions about the behavior of the underlying constituents have been reasonably successful, but the essential addition of viscoelasticity to these models has been met with varying success. Here, a new rheological network model is proposed using, as its basis, an orthotropic hyperelastic constitutive model for fibrous tissue and a viscoelastic reptation model for soft materials. The resulting model has been incorporated into numerical and computational models, and is shown to capture the mechanical behavior of soft tissue in various modes of deformation including uniaxial and biaxial tension and simple shear.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47943/1/10237_2004_Article_49.pd

Poetics of the encounter in Katherine Mansfield’s short stories

S’intégrant dans une époque moderne souvent définie par la déstabilisation des institutions et du rapport intersubjectif, les nouvelles de Katherine Mansfield présentent de nombreux exemples d’échecs intersubjectifs. Il s’agit donc d’effectuer un retour aux sources de la relation pour trouver les formes et modes de rencontre possibles et interroger leur potentiel fondateur. Telle que l’envisage Mansfield, la rencontre en tant que problématique de l’altérité – trouvée en soi ou en l’autre – s’organise selon trois espaces, symboliques ou réels : dans l’espace intime et intersubjectif, la rencontre déploie des enjeux ontologiques et existentiels ; dans l’espace géographique, elle invite à adopter une perspective qui interroge la place du politique dans les mouvements coloniaux et internationaux ; dans l’espace artistique, les déclinaisons infinies de la rencontre laissent envisager la possibilité d’une poétique originale façonnée par la convergence des arts, des genres et styles. La poétique de la rencontre se manifeste dans une logique qui n’est pas aristotélicienne au sens strict et où la création artistique est en jeu.Modernity has been defined as a destabilizing time for both the institution and the subject. Katherine Mansfield’s short stories fit in this definition as they provide many examples of inter-subjective failure. It is thus fundamental to go back to the origins of the relationship in order to uncover the various types and modes of encounter and to interrogate their constructive potential. The encounter as Mansfield conceives of it addresses the question of otherness within three different spaces. The encounter displays ontological and existential stakes in the intimate space; it invites the reader to displace the critical perspective on colonial and global movements from the political to the cultural in the geographic space; and it unveils its countless variants in an artistic space, thus generating an original poetics shaped by the convergence of arts, genres, and styles. The poetics of the encounter manifests itself according to a definition that goes beyond the Aristotelian frame. What is at stake is artistic creation itself

Poétique de la rencontre dans les nouvelles de Katherine Mansfield

S intégrant dans une époque moderne souvent définie par la déstabilisation des institutions et du rapport intersubjectif, les nouvelles de Katherine Mansfield présentent de nombreux exemples d échecs intersubjectifs. Il s agit donc d effectuer un retour aux sources de la relation pour trouver les formes et modes de rencontre possibles et interroger leur potentiel fondateur. Telle que l envisage Mansfield, la rencontre en tant que problématique de l altérité trouvée en soi ou en l autre s organise selon trois espaces, symboliques ou réels : dans l espace intime et intersubjectif, la rencontre déploie des enjeux ontologiques et existentiels ; dans l espace géographique, elle invite à adopter une perspective qui interroge la place du politique dans les mouvements coloniaux et internationaux ; dans l espace artistique, les déclinaisons infinies de la rencontre laissent envisager la possibilité d une poétique originale façonnée par la convergence des arts, des genres et styles. La poétique de la rencontre se manifeste dans une logique qui n est pas aristotélicienne au sens strict et où la création artistique est en jeu.Modernity has been defined as a destabilizing time for both the institution and the subject. Katherine Mansfield s short stories fit in this definition as they provide many examples of inter-subjective failure. It is thus fundamental to go back to the origins of the relationship in order to uncover the various types and modes of encounter and to interrogate their constructive potential. The encounter as Mansfield conceives of it addresses the question of otherness within three different spaces. The encounter displays ontological and existential stakes in the intimate space; it invites the reader to displace the critical perspective on colonial and global movements from the political to the cultural in the geographic space; and it unveils its countless variants in an artistic space, thus generating an original poetics shaped by the convergence of arts, genres, and styles. The poetics of the encounter manifests itself according to a definition that goes beyond the Aristotelian frame. What is at stake is artistic creation itself.NANTERRE-PARIS10-Bib. élec. (920509901) / SudocSudocFranceF

Simultaneous magnetic resonance imaging and consolidation measurement of articular cartilage

Magnetic resonance imaging (MRI) offers the opportunity to study biological tissues and processes in a non-disruptive manner. The technique shows promise for the study of the load-bearing performance (consolidation) of articular cartilage and changes in articular cartilage accompanying osteoarthritis. Consolidation of articular cartilage involves the recording of two transient characteristics: the change over time of strain and the hydrostatic excess pore pressure (HEPP). MRI study of cartilage consolidation under mechanical load is limited by difficulties in measuring the HEPP in the presence of the strong magnetic fields associated with the MRI technique. Here we describe the use of MRI to image and characterize bovine articular cartilage deforming under load in an MRI compatible consolidometer while monitoring pressure with a Fabry-Perot interferometer-based fiber-optic pressure transducer