A computational fluid dynamic study on the filtering mechanics in suspension feeding marine invertebrates

Les suspensivores ont la tâche importante de séparer les particules de l'eau. Bien qu'une grande gamme de morphologies existe pour les structures d'alimentation, elles sont pratiquement toutes constituées de rangées de cylindres qui interagissent avec leur environnement fluide. Le mécanisme de capture des particules utilisé dépend des contraintes morphologiques, des besoins énergétiques et des conditions d'écoulement. Comme nos objectifs étaient de comprendre ces relations, nous avons eu recours à des études de comparaison pour interpréter les tendances en nature et pour comprendre les conditions qui provoquent de nouveaux fonctionnements. Nous avons utilisé la dynamique des fluides numérique (computational fluid dynamics, CFD) pour créer des expériences contrôlées et pour simplifier les analyses. Notre première étude démontre que les coûts énergétiques associés au pompage dans les espaces petits sont élevés. De plus, le CFD suggère que les fentes branchiales des ptérobranches sont des structures rudimentaires, d'un ancêtre plus grande. Ce dernier point confirme l'hypothèse qu'un ver se nourrit par filtration tel que l'ancêtre des deuterostomes. Notre deuxième étude détermine la gamme du nombre de Reynolds number critique où la performance d'un filtre de balane change. Quand le Re est très bas, les différences morphologiques n'ont pas un grand effet sur le fonctionnement. Cependant, une pagaie devient une passoire lorsque le Re se trouve entre 1 et 3,5. Le CFD s’est dévoilé être un outil très utile qui a permis d’obtenir des détails sur les microfluides. Ces études montrent comment la morphologie et les dynamiques des fluides interagissent avec la mécanisme de capture ou de structures utilisées, ainsi que comment des petits changements de taille, de forme, ou de vitesse d'écoulement peuvent conduire à un nouveau fonctionnement.Suspension feeders have the important task of separating particles from the liquid medium surrounding them. Although a wide range of morphologies exist for feeding structures, essentially all consist of arrays of cylinders interacting with their fluid environment. The particle capture mechanism employed depends on morphological constraints, energy requirements, and flow conditions, therefore our objectives were to understand these relationships through comparison studies to interpret trends in nature and to understand the conditions in which novel functioning arises. Our studies used computational fluid dynamics (CFD) to create controlled experiments and to simplify analyses. The first study demonstrates the unfeasibly high energetic costs of pumping in small and medium pharynx sizes of hemichordates, implying the gill pores of pterobranchs are likely vestigial structures from a larger ancestor. This last point further supports the hypothesis of an acorn worm as the ancestor to all deuterostomes. Our second study determined the critical Reynolds number (Re) range where barnacle filters transition from a paddle to a sieve. At very low Re, morphological differences have no major effect on functioning and filters behave as paddles, however, at Re 1 - 3.5, these differences dictate when a paddle becomes a sieve. CFD proved to be a very useful tool for simplifying studies and providing detailed microfluidics. These studies demonstrate how morphology and fluid dynamics interact to dictate the capture mechanisms or appendages employed and how simple changes in size, shape, or flow speed can lead to novel functioning

The 1985-86 NASA space/gravitational biology accomplishments

Individual Technical summaries of research projects of NASA's Space/Gravitational Biology Program are presented. This Program is concerned with using the unique characteristics of the space environment, particularly microgravity, as a tool to advance knowledge in the biological sciences; understanding how gravity has shaped and affected life on Earth; and understanding how the space environment affects both plant and animal species. The summaries for each project include a description of the research, a listing of the accomplishments, an explanation of the significance of the accomplishments, and a list of publications

Comportement mécanique des roches et dynamique de la lithosphère: Des données de terrain aux modèles numériques

non renseignéCe mémoire dresse le bilan de mes activités de recherche depuis ma thèse de 3ème cycle. Il s’agit làd’une tentative de synthèse des travaux effectués à Rennes pendant 2 ans de post-doctorat (2007-2008), à Zürich durant 1 an (en 2008-2009), puis à Rennes depuis mon recrutement en septembre 2009en tant que maître de conférences

Genetic gold : the post-human homunculus in alchemical and visual texts

The phenomenon of the homunculus as an aspect of creating life in the laboratory is a documented attribute of Western premodern and medieval Arabic alchemy. Early alchemical texts can be seen to reveal the archetypes and myths present in the contemporary practice of creating life in the laboratory. Current genetics research endeavours to create ever-more complex genetic chimeras using human DNA and the creation of such creatures can be seen to constitute a return to the homunculus mythology. The extent to which this creature, this genetic homunculus, manifests in contemporary society is revealed in popular visual culture and the arts to be a prominent feature of the contemporary psyche. Ontological means of negotiation of a genetically engineered being falls to arguments of natural versus artificial in terms of post-humanism. The homunculus is shown to be impossible to arbitrate in terms of a transcendent mythology in this sense and the provided examples from visual culture reveal that this marvel is, as a result, myriad in teleological outcomes. CopyrightDissertation (MA)--University of Pretoria, 2009.Visual Artsunrestricte

Women Framing Hair: Serial Strategies in Contemporary Art

This thesis explores the complex and enigmatic motif of hair in the work of five contemporary women artists, Chrystl Rijkeboer, Alice Maher, Annegret Soltau, Kathy Prendergast and Ellen Gallagher, from the late 1970s to the present. The purpose of the research is to investigate why hair is such a productive and resonant site of meaning, how it is suggestive of and responds to serial strategies, and why it appears to be of particular significance to women who are artists. I explore the implications of hair as an embodied material, as well as its role as a haptic metaphor of the life cycle. I also discuss some of the divergent histories of hair as a rich marker of identity in cultural discourses of beauty, myth and femininity, and as a symbol of status and power. What might be seen as a darker, more liminal side of hair as a site of excess and body waste, and its ability to represent trauma and 'wounding', are also explored. As I argue, through its somatic connections hair can be positioned both of, and yet abjected from, the living body. Informed by a range of theoretical approaches, this research has drawn on Julia Kristeva's theorizations of the abject, Hélène Cixous's notion of écriture feminine, and a Deleuzian consideration of difference. A major concern is the different artists' strategies and negotiations with notions of seriality, which enable rich and compelling possibilities for writing the female body in imaginative and fluid ways. This, together with gender issues, identity and the body - specifically the head - and memory as a marker of biography, are key themes throughout the thesis. In combination with its historiography, the medium of hair and its simulacra in art practice are seen to have the potential to challenge and subvert conceptions of feminine identity and some of the bastions of traditional painting and sculpture

Imagining Earth: Concepts of Wholeness in Cultural Constructions of Our Home Planet

While concepts of Earth have a rich tradition, more recent examples show a distinct quality: Though ideas of wholeness might still be related to mythical, religious, or utopian visions of the past, "Earth" itself has become available as a whole. This raises several questions: How are the notions of one Earth or our Planet imagined and distributed? What is the role of cultural imagination and practices of signification in the imagination of "the Earth"? Which theoretical models can be used or need to be developed to describe processes of imagining Planet Earth? This collection invites a wide range of perspectives from different fields of the Humanities to explore the means of imagining Earth

Integrated design approach for responsive solar-shadings in double skin facades in hot arid climate

Ph. D. Thesis.To deliver climate adaptive architecture, current trends in architecture are directed towards dynamic and responsive building skins. ‘Responsive building skin’ is used to describe the ability of building envelopes to adapt in real time in response to external environmental conditions. Recent attention has focused on ‘soft robotics’ approach which uses soft and/or extensible materials to deform with muscle‐like actuation, mimicking biological systems. Material embedded actuation can autonomously alter shading systems’ morphology stimulated by external environmental conditions. Passively thermally‐activated shading systems offer responsive actuation by solar‐radiation and stratified hot air in a double skin façade (DSF) without recourse to energy consuming systems. This research identifies the intersection between bio‐inspiration, folding principles and smart materials to integrate the underlying mechanisms in responsive solar‐shading systems and assesses their environmental performance. The thesis proposes an interdisciplinary mixed methodology linking hands‐on experimentation with environmental performance simulation of responsive building skins. ‘Practice‐led approach’ is used to explore the design potential of responsive systems using smart materials. ‘Computational Fluid Dynamics’ (CFD) numerical methods are used to measure the impact of responsive solar‐shading systems on multiple environmental factors in a DSF cavity. This helps the design decisions, selection and customisation of smart materials. Hands‐on experimentation is used to explore various prototypes, leading to the selection of a folded prototype, to be simulated for environmental performance. Solar‐shading systems are tested within a DSF, in an hot arid climate. Flat and folded solar‐shading devices are installed in a DSF cavity with three aperture sizes (30%, 50% & 70%) to represent the responsive system states. Point‐in‐time simulations are carried at 9:00 am, 12:00 pm and 15:00 pm in peak summer and winter day. The developed analytical design framework presents different design parameters for responsive solar‐shading systems to guide decision‐making in research of climate actuated smart shading systems. Keywords: Responsive skins, Adaptive facades, Soft robotics, Bio‐inspiration, Origami, Deployable structures, Actuation, Smart materials, Shape memory alloys, Double skin facades, Energy efficiency, Digital simulation, CFD Modelling

Imagining Earth

While concepts of Earth have a rich tradition, more recent examples show a distinct quality: Though ideas of wholeness might still be related to mythical, religious, or utopian visions of the past, ''Earth'' itself has become available as a whole. This raises several questions: How are the notions of one Earth or our Planet imagined and distributed? What is the role of cultural imagination and practices of signification in the imagination of ''the Earth''? Which theoretical models can be used or need to be developed to describe processes of imagining Planet Earth? This collection invites a wide range of perspectives from different fields of the Humanities to explore the means of imagining Earth