<p>Computational fluid dynamic (CFD) models of aortic blood flow have developed over the past decade from rigid one dimensional models to three dimensional models that include wall flexibility. Although anatomically correct, these models have been significantly idealized as compared to their physiologic in vivo conditions. This thesis investigates the effect of addition of four dimensional MRI inlet flow, motion of the heart at the aortic inlet and addition of wall elasticity coupled with tissue backing support. Results show that the addition of MRI inlet data and aortic inlet motion of the heart significantly change flow in the aorta and should be included in future aortic CFD simulations.</p> / Master of Applied Science (MASc)

Mechanical conditioning has been shown to promote tissue formation in a wide variety of tissue engineering efforts. However the underlying mechanisms by which external mechanical stimuli regulate cells and tissues are not known. This is particularly relevant in the area of heart valve tissue engineering (HVTE) owing to the intense hemodynamic environments that surround native valves. Some studies suggest that oscillatory shear stress (OSS) caused by steady flow and scaffold flexure play a critical role in engineered tissue formation derived from bone marrow derived stem cells (BMSCs). In addition, scaffold flexure may enhance nutrient (e.g. oxygen, glucose) transport. In this study, we computationally quantified the i) magnitude of fluid-induced shear stresses; ii) the extent of temporal fluid oscillations in the flow field using the oscillatory shear index (OSI) parameter, and iii) glucose and oxygen mass transport profiles. Noting that sample cyclic flexure induces a high degree of oscillatory shear stress (OSS), we incorporated moving boundary computational fluid dynamic simulations of samples housed within a bioreactor to consider the effects of: 1) no flow, no flexure (control group), 2) steady flow-alone, 3) cyclic flexure-alone and 4) combined steady flow and cyclic flexure environments. We also coupled a diffusion and convention mass transport equation to the simulated system. We found that the coexistence of both OSS and appreciable shear stress magnitudes, described by the newly introduced parameter OSI-t , explained the high levels of engineered collagen previously observed from combining cyclic flexure and steady flow states. On the other hand, each of these metrics on its own showed no association. This finding suggests that cyclic flexure and steady flow synergistically promote engineered heart valve tissue production via OSS, so long as the oscillations are accompanied by a critical magnitude of shear stress. In addition, our simulations showed that mass transport of glucose and oxygen is enhanced by sample movement at low sample porosities, but did not play a role in highly porous scaffolds. Preliminary in-house in vitro experiments showed that cell proliferation and phenotype is enhanced in OSI-t environments.

Master of Science / Department of Clinical Sciences / James D. Lillich / Objective - To compare the biomechanical characteristics of the currently recommended (CR) technique and a less invasive (LI) surgical approach for arthrodesis of the proximal interphalangeal joint (PIPJ). Additionally, to describe a technique for cartilage removal and disruption of the subchondral bone. Study design - Randomized paired limb design for biomechanical comparison. Cartilage removal and subchondral bone disruption was accomplished using an orthopedic drill bit. Sample Population – 76 cadaver limbs. Methods - Cadaver PIPJs were drilled using a 3.5mm, 4.5mm or 5.5mm drill bit. Articular surfaces were digitally photographed and analyzed. Other paired PIPJs were arthrodesed using either the CR or the LI surgical technique. Implants consisted of a 3-hole DCP and two 5.5mm transarticular screws. Constructs were tested to failure in dorso-palmar/plantar and latero-medial in single cycle 3-point bending. The maximum load and yield load was measured and composite stiffness was calculated and statistically compared. Results - The LI technique had significantly greater mean yield load (11.3 ± 2.8 kN vs. 7.68 ± 1.1 kN, P=0.008) and mean maximum load (13.5 ± 3.1 kN vs. 10.1 ± 1.94 kN, P= 0.02) under latero-medial bending. Under dorso-palmar/plantar bending there was no statistical difference between the surgical approaches (P=0.5). The 4.5mm drill bit removed 42% ± 7.3 of the cartilage and disrupted subchondral bone. The LI technique had a decreased surgical time (19 ± 3 min.) when compared with the CR (31 ± 3 min.) technique. Conclusion – The LI technique results in a stronger composite as measured in 3-point bending, loaded to failure. Clinical Relevance – The LI surgical technique may be considered for clinical cases requiring arthrodesis of the PIPJ as there is no reduction in composite strength.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Optical motion capture (Mocap) systems measure 3D human kinematics accurately and at high sample rates. One of the limitations of these systems is that they can only be used indoors. However, advances in inertial sensing have led to the development of inertial Mocap technology (IMCT). IMCT measures kinematics using inertial measurement units (IMUs) attached to a subject's body without the need for external sensors. It is thus completely portable which opens up new horizons for clinical Mocap. This study evaluates the use of IMCT for improving road cycling kinematics. Ten male sub-elite cyclists were recorded with an IMCT system for one minute while cycling at 2, 3.5 and 5.5 W.kg-1 on a stretch of road and on a stationary trainer. A benchmark test was also done where cycling kinematics was measured simultaneously with the IMCT and a gold-standard Vicon optical system. The first goal was to assess the feasibility of conducting field measurements of cycling kinematics. Magnetic analysis results showed that the IMUs near the pedals and handlebars experienced significant magnetic interference (up to 50% deviation in intensity) from ferrous materials in the road bicycles, causing significant errors in kinematic measurement. Therefore, it was found that the IMCT cannot measure accurate full-body kinematics with the subject on a road bicycle. However, the results of the benchmark test with the Vicon showed that the IMCT can still measure accurate hip (root mean square error (RMSE) < 1°), knee (RMSE < 3.5°) and ankle (RMSE < 3°) flexion using its Kinematic Coupling algorithm. The second goal was to determine whether there is a significant difference between road cycling kinematics captured on the road and in a laboratory. The outdoor flexion results were significantly different to the indoor results, especially for minimum flexion (P < 0.05 for all joints). Changes in rider kinematics between high and low power were also found to have significantly more variability on the road (R2 = 0.36, 0.61, 0.08) than on the trainer (R2 = 0.93, 0.89, 0.56) for the hip, knee and ankle joints respectively. These results bring into question the ecological validity of laboratory cycling. Lastly, applications of IMCT for optimizing cycling performance were to be identified. Several aspects of kinematic analysis and performance optimization using the IMCT were evaluated. It was determined that IMCT is most suited for use as a dynamic bicycle fitting tool for analysis of biomechanical efficiency, bilateral asymmetry and prevention of overuse injuries. Recommendations for future work include the elimination of the magnetic interference and integration of the IMCT data with kinetic measurements to develop an outdoor dynamic fitting protocol. / AFRIKAANSE OPSOMMING: Optiese bewegingswaarnemingstelsels (BWS) meet drie-dimensionele menslike kinematika met hoë akkuraatheid en teen hoë monstertempo's. Een van die nadele van BWS is dat hulle slegs binnenshuis gebruik kan word. Onlangse ontwikkelings in sensor tegnologie het egter gelei na die beskikbaarheid van traagheids-BWS-tegnologie (TBT). TBT gebruik traagheidsmetingseenhede (TMEs) wat aan 'n persoon se liggaam aangeheg kan word om die kinematika te verkry sonder enige eksterne sensore. TBT is dus volkome draagbaar, wat nuwe geleenthede skep vir kliniese bewingsanalises. Hierdie projek evalueer die gebruik van TBT vir die verbetering van fietsry kinematika. Tien kompeterende fietsryers (manlik) was getoets met 'n TBT terwyl hulle teen 2, 3.5 and 5.5 W.kg-1 gery het op 'n pad, en op 'n stilstaande oefenfietsraam. 'n Maatstaftoets was ook uitgevoer waar fietsry-kinematika gelyktydig met die TBT en die Vicon optiese BWS opgeneem was. Die eerste doel van die navorsing was om die moontlikheid te ondersoek of fietsryer kinematika op die pad gemeet kan word. Die resultate toon dat die ferro-magnetiese materiale wat in meeste padfietse voorkom, 'n beduidende magnetiese steuring (tot 50% afwyking in intensiteit) op die TMEs naby die pedale en handvatsels veroorsaak, wat lei tot aansienlike foute in die kinematiese metings. Gevolglik was dit gevind dat die TBT nie volle-liggaam kinematika op 'n fiets kan meet nie. Nogtans, het die resultate van die Vicon maatstaftoets bewys dat die TBT nog steeds akkurate heup (wortel van die gemiddelde kwadraad fout (WGKF) < 1°), knie (WGKF < 4°) en enkel (WGKF < 3°) fleksie kan meet met die “Kinematiese Koppeling” algoritme. Die tweede doel was om te bepaal of daar 'n beduidende verskil tussen die laboratorium en pad fietsry-kinematika is. Die buitelug fleksie data het beduidend verskil van die binnenshuise resultate, veral vir minimum fleksie (P < 0.05 vir alle gewrigte). Veranderinge in fietsryer kinematika tussen hoë en lae krag het ook beduidend meer variasie op die pad (R2 = 0.36, 0.61, 0.08) as op die oefenfietsraam (R2 = 0.93, 0.89, 0.56) vir die heup, knie en enkel gewrigte, onderskeidelik, gehad. Hierdie resultate bevraagteken die ekologiese geldigheid van kinematiese toetse op fietsryers in 'n laboratorium. 'n Laaste doel was om die toepassings van TBT vir die optimering van fietsry kinematika te ondersoek. 'n Verskeidenheid aspekte van die analise en verbetering van fietsry kinematika met die TBT word bespreek. Die gevolgtrekking is dat TBT geskik is vir gebruik as 'n dinamiese instrument vir die analise van biomeganiese doetreffendheid, bilaterale asimmetrie en die voorkoming van beserings. Aanbevelings vir toekomstige werk, sluit in die uitskakeling van die magnetiese inmenging, asook die integrasie van die TBT data met kinetiese metings.

OBJECTIVE:Vascular smooth muscle cell (VSMC) hypertrophy and proliferation occur in response to strain-induced local and systemic inflammatory cytokines and growth factors which may contribute to hypertension, atherosclerosis, and restenosis. We hypothesize VSMC strain, modeling normotensive arterial pressure waveforms in vitro, results in attenuated proliferative and increased hypertrophic responses 48 hrs post-strain.METHODS:Using Flexcell Bioflex Systems we determined the morphological, hyperplastic and hypertrophic responses of non-strained and biomechanically strained cultured rat A7R5 VSMC. We measured secretion of nitric oxide, key cytokine/growth factors and intracellular mediators involved in VSMC proliferation via fluorescence spectroscopy and protein microarrays. We also investigated the potential roles of VEGF on VSMC strain-induced proliferation.RESULTS:Protein microarrays revealed significant increases in VEGF secretion in response to 18 hours mechanical strain, a result that ELISA data corroborated. Apoptosis-inducing nitric oxide (NO) levels also increased 43% 48 hrs post-strain. Non-strained cells incubated with exogenous VEGF did not reproduce the antimitogenic effect. However, anti-VEGF reversed the antimitogenic effect of mechanical strain. Antibody microarrays of strained VSMC lysates revealed MEK1, MEK2, phospo-MEK1T385, T291, T298, phospho-Erk1/2T202+Y204/T185+T187, and PKC isoforms expression were universally increased, suggesting a proliferative/inflammatory signaling state. Conversely, VSMC strain decreased expression levels of Cdk1, Cdk2, Cdk4, and Cdk6 by 25-50% suggesting a partially inhibited proliferative signaling cascade.CONCLUSIONS:Subjecting VSMC to cyclic biomechanical strain in vitro promotes cell hypertrophy while attenuating cellular proliferation. We also report an upregulation of MEK and ERK activation suggestive of a proliferative phenotype. Hhowever, the proliferative response appears to be aborogated by enhanced antimitogenic cytokine VEGF, NO secretion and downregulation of Cdk expression. Although exogenous VEGF alone is not sufficient to promote the quiescent VSMC phenotype, we provide evidence suggesting that strain is a necessary component to induce VSMC response to the antimitogenic effects of VEGF. Taken together these data indicate that VEGF plays a critical role in mechanical strain-induced VSMC proliferation and vessel wall remodeling. Whether VEGF and/or NO inhibit signaling distal to Erk 1/2 is currently under investigation.

Composition is a process of applied research. In a portfolio of eight original pieces, the technical and aesthetic components of this process are investigated from the perspective of several theoretical precepts which both inform and underpin its creative strategy. Drawing on theories of intertextuality, composition is collocated within a broad current of thought in which ideas and material from pre-existing ‘texts’ across a variety of disciplines are utilised and explored to create new compositional ‘texts’. This procedure is tested from several, key perspectives, characterised variously as: (i) problem-seeking, (ii) serendipitous, (iii) transgressive, and (iv) transcriptive. The first of these draws on John Dewey’s notions of art as a form of creative problematisation. In the second, techniques are developed in which performance flexibility is balanced against structural exactitude, aided by a series of parametric tables that outline a range of variables across the different elements of musical sound. As a transgressive process, compositional procedure is informed by Viktor Shklovsky’s theory of aesthetic defamiliarisation. Finally, as a form of transcription, the research draws on Ferruccio Busoni’s observations about notation and its key transmutational role in manipulating and recasting musical ideas. By adopting an eclectic attitude towards materials and techniques, a compositional strategy is formulated which offers an alternative to the assumption that advancement in the field is inevitably shaped by an ineluctable, dialectical process. A polyvalent approach and direct interaction with materials, it is argued, are the important creative ingredients which present valuable and meaningful developments in compositional language, form and technique.

Background: The multiplicities of factors, which may contribute to injury from sporting activity, and the complexity of the relations among them, indicate that identifying causal mechanisms poses a challenge to epidemiologists. The identification of risk factors associated with the effect of the injury on subsequent participation may be as important in understanding how to reduce the burden of injuries on sports participants, as identifying factors associated with the injury incidence rate. Aim: The aim of this study was to develop a biomechanical, antbropometrical, physical, motor and injury epidemiology profile for elite U/19 rugby players. Design: A prospective cohort study. Subiects: In this study 77 elite rugby players were used during the first testing episode (October 2005). These players had just completed their school career and were selected to form part of the Rugby Institute of the University of North West. The U/19 first team members were (n = 31) tested again in July 2006. Two different profiles were established. Method: Once approval had been granted by both the players and by the Rugby Institute of the North West University, the players were submitted to a test battery. Anthropometric, Physical and Motor tests were done at the beginning of the season and the players re-tested at the end of the season. A Biomechanical and Postural Evaluation was done once-off at the beginning of the season. The necessary steps were taken to address existing shortcomings identified in the test subjects. After the results had been analysed, individual programmes were formulated, explained and implemented. The aim was to minimize the possible risk areas indicated by screening. Results: The results were statistically processed, recorded and compared with previous literature studies, according to both the total group and the different player positions - these are the tight five, the loose forwards, the halfbacks and the backs. The Anthropometrical, Physical and Motor testings showed a low or nil practical significant difference for the total group after a season of professional training and coaching, with slight differences between the player groups. The Biomechanical and Postural Evaluation proved the group to be dynamically overloaded with poor regional stability and musculature as far as the upper and lower limbs were concerned, with asymmetry and weak core stability of the spinal and pelvic region. A total of 184 injuries were reported over the season, with the lower limbs (58%) and upper limbs (23%) as the most commonly injured body parts; and sprains (22%) and strains (17%) the type of injury which occurred most often. The tight five (32%) had the highest injury rate, with the flanker (13%) the least injured player position. Conclusion: A profile for elite U/19 rugby players has been determined. This profile can be implemented in conjunction with similar findings in existing literature for future guidelines by coaches and the management to select a better team, to ensure a higher quality of performance and to prevent injuries. / Thesis (M.Ed.)--North-West University, Potchefstroom Campus, 2007.

Heart failure (HF) is one of the leading causes of death and impacts millions of people throughout the world. Recently, injectable hydrogels have been developed as a potential new therapy to treat myocardium infarction (MI). This dissertation is focused on two main topics: 1) to gain a better understanding the transmural contractility in the healthy left ventricle (LV) wall and 2) investigate the efficacy of the hydrogel injection treatment on LV wall stress and function. The results indicate that a non-uniform distribution of myocardial contractility in the LV wall provide a better representation of normal LV function. The other important study explored the influence altering the stiffness of the biomaterial hydrogel injections. These results show that a larger volume and higher stiffness injection reduce myofiber stress the most and maintaining the wall thickness during loading. The computational approach developed in this dissertation could be used in the future to evaluate the optimal properties of the hydrogel. The last study used a combination of MRI, catheterization, finite element (FE) modeling to investigate the effects of hydrogel injection on borderzone (BZ) contractility after MI. The results indicate that the treatment with hydrogel injection significantly improved BZ function and reduce LV remodeling, via altered MI properties. Additionally, the wall thickness in the infarct and BZ regions were significantly higher in the treated case. Conclusion: hydrogel injection could be a valuable clinical therapy for treating MI.

The blood flow through the Bidirectional Glenn shunt (BGS) and modified Blalock-Taussig shunt (mBTS) to the pulmonary arteries (PAs) was analyzed using Computational Fluid Dynamics. This study consisted of the steady and pulsatile cases. In case one, the results of blood flow through the BGS for the Newtonian and non-Newtonian viscosity models were compared. Case two focused on having an additional pulsatile blood flow through the mBTS using the non-Newtonian Carreau viscosity model. The geometries were created based on the angiograms. In case one, boundary conditions to be specified at the inlets were obtained from the flow rate measurements via Doppler flow studies in children and young adults. The averaged velocities were obtained from these flow rates and specified as parabolic velocity profiles at the inlets. The average PA pressures were obtained from the catheterization data and specified at the branches of the PA outlets. In case two, boundary conditions at the same inlets were constant during the cardiac cycle. The pulsatile PA and aortic pressure tracings obtained from the catheterization data were specified at the outlets and mBTS inlet, respectively. A comparison is made between the first and second case results.

<p>During the last six million years, humans shifted from a primarily arboreal lifestyle to a habitually bipedal, terrestrial lifestyle. Australopithecus had a significant bipedal component to its locomotion; whether suspensory and climbing behavior were also important has remained unclear. Morphological features of the forelimb have been linked to locomotor differences among primates, but the interpretation of human fossils has remained problematic.</p><p>This dissertation examined the total morphological pattern of the forelimb, specifically the functional integration of the musculature and joint systems. This approach employed both geometric morphometrics and a biomechanical modeling approach to studying how and how well the forelimb morphology of living suspensory and quadrupedal primates, as well as humans and fossil hominins, accommodate climbing and suspensory locomotion. Data collected with a microscribe 3-D digitizer on the scapula, humerus, radius, and ulna of Australopithecus sediba, Australopithecus afarensis, and Homo erectus were compared to a sample of Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus, Hylobates lar, and Macaca fuscicularis.</p><p>The hominin upper limb is a rich mosaic of primitive and derived traits. The blade of Australopithecus sediba, although appearing most similar to extant orangutans, is in fact functionally most similar to chimpanzees. The overall morphology of the australopith elbow joint appears most similar to Pan, as does the elbow joint of Homo erectus, suggesting that the modern human configuration happened more recently than 1.5 million years ago. </p><p>Au. afarensis and Au. sediba share important similarities, but are clearly distinct species. While their overall elbow joint shape is strikingly similar, the articular surface is not identical. Au. afarensis is more similar in this respect to Pan and Homo, while Au. sediba is more similar to extant taxa that spend substantially more time engaging in vertical climbing and suspensory behavior.</p><p>The results from this study support previous interpretations that not all australopiths across time were employing the same locomotor repertoire. While this study does not present unambiguous conclusions regarding early hominin arboreal locomotion, this study suggests that the morphology of the upper limb is varied, and caution must be taken when interpreting single skeletal elements in the hominin fossil record.</p> / Dissertation