Life Sciences Commons^™

Accurate Determination And Application Of Local Strain For Studying Tissues With Gradients In Mechanical Properties, John Boyle

McKelvey School of Engineering Theses & Dissertations

Determination of the mechanical behavior of materials requires an understanding of deformation during loading. While this is traditionally accomplished in engineering by examining a force displacement curve for a whole sample, these techniques implicitly ignore local geometric complexities and local material inhomogeneities commonly found in biologic tissues. Techniques such as normalized cross correlation have been classically applied to address this issue and resolve deformation at the local level; however, these techniques have proven unreliable when deformations become large, if the sample undergoes a rotation, and/or if strain fields become incompatible (e.g. at or near failure).

Presented here is a toolbox …

Characterizing Anisotropy In Fibrous Soft Materials By Mr Elastography Of Slow And Fast Shear Waves, John Larson Schmidt

McKelvey School of Engineering Theses & Dissertations

The general objective of this work was to develop experimental methods based on magnetic resonance elastography (MRE) to characterize fibrous soft materials. Mathematical models of tissue biomechanics capable of predicting injury, such as traumatic brain injury (TBI), are of great interest and potential. However, the accuracy of predictions from such models depends on accuracy of the underlying material parameters. This dissertation describes work toward three aims. First, experimental methods were designed to characterize fibrous materials based on a transversely isotropic material model. Second, these methods are applied to characterize the anisotropic properties of white matter brain tissue ex vivo. Third, …

Mechanics Of The Developing Brain: From Smooth-Walled Tube To The Folded Cortex, Kara Ellspermann Garcia

McKelvey School of Engineering Theses & Dissertations

Over the course of human development, the brain undergoes dramatic physical changes to achieve its final, convoluted shape. However, the forces underlying every cinch, bulge, and fold remain poorly understood. This doctoral research focuses on the mechanical processes responsible for early (embryonic) and late (preterm) brain development.

First, we examine early brain development in the chicken embryo, which is similar to human at these stages. Research has primarily focused on molecular signals to describe morphogenesis, but mechanical analysis can also provide important insights. Using a combination of experiments and finite element modeling, we find that actomyosin contraction is responsible for …

Mechanobiology Of Epithelial Clusters In Ecms Of Diverse Mechanical Properties, Samila Nasrollahi

McKelvey School of Engineering Theses & Dissertations

Cell clusters reside in complex extracellular matrices (ECMs) of varying mechanical properties. Epithelial cells sense and translate the mechanical cues presented by the surrounding ECM into biochemical signals through a process called ‘mechanotransduction’, which controls fundamental aspects of disease and development. During the course of metastasis, mechanical changes in the tumor microenvironment can lead to declustering of epithelial cells through a process called epithelial-to-mesenchymal transition (EMT). Throughout different steps of metastasis, escaped epithelial clusters encounter heterogeneous tissues of varying mechanical properties that ultimately influence their behavior in distant locations within the body. This dissertation investigates the mechanobiology of epithelial clusters …

Vrshape: A Virtual Reality Tool For Shaping Movement Compensation, Matthew Hale Foreman

Arts & Sciences Electronic Theses and Dissertations

The majority of persons living with chronic stroke experience some form of upper extremity motor impairment that affects their functional movement, performance of meaningful activities, and participation in the flow of daily life. Stroke survivors often compensate for these impairments by adapting their movement patterns to incorporate additional degrees of freedom at new joints and body segments. One of the most common compensatory movements is the recruitment of excessive trunk flexion when reaching with the affected upper extremity. Long-term use of these compensations may lead to suboptimal motor recovery and chronic pain or injury due to overuse. Rehabilitation focuses on …

Examining The Lumbar Movement Pattern During Functional Activities In People With Low Back Pain, Andrej Vincent Marich

Arts & Sciences Electronic Theses and Dissertations

Low back pain (LBP) is a highly prevalent condition that is often characterized by persistent pain and limitations in the performance of daily functional activities. The repeated use of altered movement patterns during the performance of daily functional activities is proposed to contribute to the development and course of LBP. Specifically, in the case of LBP, the proposed alteration of movement is one in which the lumbar spine moves more readily than other joints that can contribute to the movement. This altered movement pattern is proposed to contribute to accumulation of localized tissue stress, micro- and macro-trauma of lumbar spine …