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6 March 2008
Michelle Oyen is spearheading an Engineering for Life Sciences Week here in the Department.
Engineering for the Life Sciences is a major initiative in the Department and key to the Department's strategy which seeks to address major global challenges. There is a growing need for a more integrated approach to the understanding of biological systems, providing many opportunities for the application of engineering to clinical and life sciences. Engineering for the Life Sciences is a rapidly growing field encompassing the use of engineering tools to solve problems in medicine and biology as well as new quantitative approaches to biological systems based on engineering principles.
The week of events will include:
Bioengineering Lab Open House
Wednesday 12th March 2008, 16:00-18:00, Inglis Mezzanine
Members of the Department, both staff and students, will have the opportunity to get a walk-through of the new bioengineering facility. New pieces of equipment inside the lab will be labelled. These include new microscopes, an FTIR system for doing chemical analysis, cell culture equipment, a mechanical testing system optimized for soft tissues and compliant materials, and a working "wet lab" for general biological use. Many of these capabilities are unique to the Department, and represent different capabilities than have ever been here before.
Markus J. Buehler
Fracture mechanics of biological protein materials: Robustness, strength and adaptability
(part of the Engineering for the Life Sciences Seminars series)
Markus J. Buehler (Massachusetts Institute of Technology)
Thursday 13th March 2008, 16:00-17:00, Baker Building, Lecture Room 6
Proteins constitute critical building blocks of life, forming biological materials such as hair, bone, skin, spider silk or cells, which play an important role in providing key mechanical functions in biological systems. The fundamental deformation and fracture mechanisms of biological protein materials remain largely unknown, partly due to a lack of understanding of how individual protein building blocks respond to mechanical load and how they participate in the function of the overall biological system. However, such understanding is vital to advance models of diseases, the understanding of biological processes such as mechanotransduction, or the development of biomimetic materials. Recent theoretical and computational progress provides us with the first insight into such mechanisms and clarifies how biology 'works' at the ultimate, molecular scale, and how this relates with macroscopic phenomena such as cell mechanics or tissue behavior, across multiple hierarchical scales. Here we review how molecular dynamics (MD) simulations implemented on ultra-large computing facilities, combined with statistical theories, is used to develop predictive models of the deformation and fracture behavior of protein materials. This approach explicitly considers the hierarchical architecture of proteins, including the details of their chemical bonding, capable of accurately predicting their unfolding behavior and thereby providing a rigorous structure-property relationship. We exemplify the approach in the analysis of the deformation mechanisms of beta-sheets and alpha-helices, two prominent protein motifs that form the basis of many protein materials, including spider silk and intermediate filaments. Spider silk is a protein material that can reach the strength of steel cables, despite the predominant weak hydrogen bonding. Intermediate filaments are an important class of structural proteins responsible for the mechanical integrity of eukaryotic cells, which, if flawed, can cause serious diseases such as the rapid aging disease progeria or muscle dystrophy. For both examples, our studies elucidate intriguing material concepts that enable them to balance strength, energy dissipation and robustness by selecting nanopatterned, hierarchical features. We present an analysis that reveals that the utilization of such hierarchical features in protein materials is vital to synthesize materials that combine seemingly incompatible material properties such as strength and robustness, self-adaptation and adaptability, by overcoming the physical limitations of conventional material design. We discuss the general implications of our work for the science of multi-scale interactions and how this knowledge can be utilized to develop de novo biomimetic materials based on a bottom-up structural design.
A Methodology to Study Morphological Changes in Sclerotic Arteries, and Related Biomechanical Modelling and Simulation (part of the Engineering Department Mechanics Colloquia Research Seminars series)
Gerhard Holzapfel (Graz University of Technology Institute for Biomechanics)
Friday 14 March 2008, 14:30-15:30, Baker Building, Lecture Room 6
The assessment of morphologic changes in sclerotic arteries during interventional procedures such as balloon angioplasty is an issue of highest clinical importance. A MR -based methodology is presented to allow 3D morphomechanical modeling of the artery, the plaque and the lumen at different stages of angioplasty by using multi-spectral images. Using generalized gradient vector flow active contours a segmentation process is used to generate NURBS -based geometric models of an individual artery at different balloon pressures. In the studied arteries an increase in lumen cross-sectional areas after angioplasty was observed. Dissection between the inner and middle arterial layers and reduction of the lipid pool are the primary mechanisms of dilatation. Physical and finite element models which are able to trace the dissection during angioplasty are presented. The arterial wall is described as an anisotropic, heterogeneous, highly deformable, nearly incompressible solid, whereas tissue failure is captured by strong discontinuity kinematics and cohesive zone models. Numerical implementation is based on the partition of unity FEM and the interface element method. The later is used to link meshes of the different tissue components. The predicted numerical results indicate that dissections develop between the inner and middle arterial layers at the fibrous cap location with the smallest thickness, and that dissections cause localized mechanical trauma, which prevents the main portion of sclerotic arteries from high stress, and hence from continuous tissue damage.
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