Numerical analysis of the fluid-structure interaction in a membrane pump

In this research, the fluid-structure interaction in a recently developed membrane pump is analysed. The governing equations for the laminar flow and for the deformation of the membrane are solved with two separate codes, which are coupled with the quasi-Newton technique with an approximation for the inverse of the Jacobian from a least-squares model. After the description of the model and the solution techniques, a detailed analysis of the flow field, the deformation of the structure and the stress in the membrane is presented. An energetic analysis of the pump is performed, and the pump's efficiency is calculated

Numerical modelling of the fluid-structure interaction in complex vascular geometries

A complex network of vessels is responsible for the transportation of blood throughout the body and back to the heart. Fluid mechanics and solid mechanics play a fundamental role in this transport phenomenon and are particularly suited for computer simulations. The latter may contribute to a better comprehension of the physiological processes and mechanisms leading to cardiovascular diseases, which are currently the leading cause of death in the western world. In case these computational models include patient-specific geometries and/or the interaction between the blood flow and the arterial wall, they become challenging to develop and to solve, increasing both the operator time and the computational time. This is especially true when the domain of interest involves vascular pathologies such as a local narrowing (stenosis) or a local dilatation (aneurysm) of the arterial wall. To overcome these issues of high operator times and high computational times when addressing the bio(fluid)mechanics of complex geometries, this PhD thesis focuses on the development of computational strategies which improve the generation and the accuracy of image-based, fluid-structure interaction (FSI) models. First, a robust procedure is introduced for the generation of hexahedral grids, which allows for local grid refinements and automation. Secondly, a straightforward algorithm is developed to obtain the prestress which is implicitly present in the arterial wall of a – by the blood pressure – loaded geometry at the moment of medical image acquisition. Both techniques are validated, applied to relevant cases, and finally integrated into a fluid-structure interaction model of an abdominal mouse aorta, based on in vivo measurements

Synthesis and biological activity of α-galactosyl ceramide KRN7000 and galactosyl (α1→2) galactosyl ceramide

We herein report a faster and less cumbersome synthesis of the biologically attractive, α-galactosyl ceramide (α-GalCer), known as KRN7000, and its analogues. More importantly, the use of a silicon tethered intramolecular glycosylation reaction gave easy access to the diglycosyl ceramide Gal(α1→2)GalCer, which has been shown to require uptake and processing to the biologically active α-GalCer derivative

Inverse modelling of image-based patient-specific blood vessels : zero-pressure geometry and in vivo stress incorporation

In vivo visualization of cardiovascular structures is possible using medical images. However, one has to realize that the resulting 3D geometries correspond to in vivo conditions. This entails an internal stress state to be present in the in vivo measured geometry of e.g. a blood vessel due to the presence of the blood pressure. In order to correct for this in vivo stress, this paper presents an inverse method to restore the original zero-pressure geometry of a structure, and to recover the in vivo stress field of the final, loaded structure. The proposed backward displacement method is able to solve the inverse problem iteratively using fixed point iterations, but can be significantly accelerated by a quasi-Newton technique in which a least-squares model is used to approximate the inverse of the Jacobian. The here proposed backward displacement method allows for a straightforward implementation of the algorithm in combination with existing structural solvers, even if the structural solver is a black box, as only an update of the coordinates of the mesh needs to be performed

Perceptions and perspectives on effective student representation

Students have been increasingly involved in university governance since the late 1960s. Since that time there have been competing paradigms about how students are seen, whether as consumers, service-users, stakeholders, democratic participants or as partners. Each of these paradigms has been used to justify increased involvement of students but with quite different expectations of how and why they are involving students. This study explores the factors of what makes effective student involvement in university governance. Student involvement in university governance has been widely researched but in most cases student involvement is considered in relation to one, or possibly two, of these paradigms but not all of them. This study identifies key gaps in the literature around the important role of university staff as gatekeepers; the extent to which committee structures consider how they engage students including how they address power differentials; as well as considering the perceptions of the effectiveness of the representatives themselves and the activities that they undertake. The study argues that the way in which students are seen in relation to key paradigms identified in the literature review impacts on how effective the processes are seen to be. The study is based primarily on perceptions of key stakeholders gathered through a national survey of university quality managers and students’ union course-rep co-ordinators. The study contributes to knowledge by conceptualising a theoretical framework within which to consider effective student involvement in university governance. The study develops a new theoretical framework on effective student involvement in university governance placing the key factors of effective student representatives, staff engagement and university committees within Ashraf and Kadir’s (2012) effectiveness model. This is then situated within a wider set of paradigms that emerge from the literature which highlighted the impact of how students are seen