Dissertations / Theses: 'Biomedical fluid mechanics'

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Kumar, Krishna Nandan. "Acoustic Studies on Nanodroplets, Microbubbles and Liposomes." Thesis, The George Washington University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10639706.

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Microbubbles and droplets are nanometer to micron size biocompatible particles which are primarily used for drug delivery and contrast imaging. Our aim is to broaden the use of microbubbles from contrast imaging to other applications such as measuring blood pressure. The other goal is to develop in situ contrast agents (phase shift droplets) which can be used for applications such as cancer tumor imaging. Therefore, the focus is on developing and validating the concept using experimental and theoretical methods. Below is an overview of each of the projects performed on droplets and microbubbles.

Phase shift droplets vaporizable by acoustic stimulation offer many advantages over microbubbles as contrast agents due to their higher stability and possibility of smaller sizes. In this study, the acoustic droplet vaporization (ADV) threshold of a suspension of PFP droplets (400-3000nm) was acoustically measured as a function of the excitation frequency by examining the scattered signals, fundamental, sub- and second-harmonic. This work presents the experimental methodology to determine ADV threshold. The threshold increases with frequency: 1.25 MPa at 2.25 MHz, 2.0 MPa at 5 MHz and 2.5 MPa at 10 MHz. The scattered response from droplets was also found to match well with that of independently prepared lipid-coated microbubble suspension in magnitude as well as trends above the threshold value. Additionally, we have employed classical nucleation theory (CNT) to investigate the ADV, specifically the threshold value of the peak negative pressure required for vaporization. The theoretical analysis predicts that the ADV threshold increases with increasing surface tension of the droplet core and frequency of excitation, while it decreases with increasing temperature and droplet size. The predictions are in qualitative agreement with experimental observations.

A technique to measure the ambient pressure using microbubbles was developed. Here we are presenting the results of an in vitro study aimed at developing an ultrasound-aided noninvasive pressure estimation technique using contrast agents--Definity®, a lipid coated microbubble, and an experimental PLA (Poly lactic acid) microbubbles. Scattered responses from these bubbles have been measured in vitro as a function of ambient pressure using a 3.5 MHz acoustic excitation of varying amplitude. At an acoustic pressure of 670 kPa, Definity^® microbubbles showed a linear decrease in subharmonic signal with increasing ambient pressure, registering a 12dB reduction at an overpressure of 120 mm Hg. Ultrasound contrast microbubbles experience widely varying ambient blood pressure in different organs, which can also change due to diseases. Pressure change can alter the material properties of the encapsulation of these microbubbles. Here the characteristic rheological parameters of contrast agent Definity and Targestar are determined by varying the ambient pressure (in a physiologically relevant range 0-200 mmHg). Four different interfacial rheological models are used to characterize the microbubbles. Both the contrast agents show an increase in their interfacial dilatational viscosity and interfacial dilatational elasticity with ambient pressure.

It has been well established that liposomes prepared following a careful multi-step procedure can be made echogenic. Our group as well as others experimentally demonstrated that freeze-drying in the presence of mannitol is a crucial component to ensure echogenicity. Here, we showed that freeze-dried aqueous solutions of excipients such as mannitol, meso-erythritol, glycine, and glucose that assume a crystalline state, when dispersed in water creates bubbles and are echogenic even without any lipids. We also present an explanation for the bubble generation process because of dissolution of mannitol.

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Langeard, Olivier. "Numerical study of a Navier-Stokes flow through a fibrous porous medium." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15944.

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Yousefi, Koupaei Atieh. "Biomechanical Interaction Between Fluid Flow and Biomaterials: Applications in Cardiovascular and Ocular Biomechanics." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595335168435434.

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Kadel, Saurav. "Computational Assessment of Aortic Valve Function and Mechanics under Hypertension." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1594243694736478.

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Nasar, Abouzied. "Eulerian and Lagrangian smoothed particle hydrodynamics as models for the interaction of fluids and flexible structures in biomedical flows." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/eulerian-and-lagrangian-smoothed-particle-hydrodynamics-as-models-for-the-interaction-of-fluids-and-flexible-structures-in-biomedical-flows(507cd0db-0116-4258-81f2-8d242e8984fa).html.

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Fluid-structure interaction (FSI), occurrent in many areas of engineering and in the natural world, has been the subject of much research using a wide range of modelling strategies. However, problems with high levels of structural deformation are difficult to resolve and this is particularly the case for biomedical flows. A Lagrangian flow model coupled with a robust model for nonlinear structural mechanics seems a natural candidate since large distortion of the computational geometry is expected. Smoothed particle Hydrodynamics (SPH) has been widely applied for nonlinear interface modelling and this approach is investigated here. Biomedical applications often involve thin flexible structures and a consistent approach for modelling the interaction of fluids with such structures is also required. The Lagrangian weakly compressible SPH method is investigated in its recent delta-SPH form utilising inter-particle density fluxes to improve stability. Particle shifting is also used to maintain particle distributions sufficiently close to uniform to enable stable computation. The use of artificial viscosity is avoided since it introduces unphysical dissipation. First, solid boundary conditions are studied using a channel flow test. Results show that when the particle distribution is allowed to evolve naturally instabilities are observed and deviations are noted from the expected order of accuracy. A parallel development in the SPH group at Manchester has considered SPH in Eulerian form (for different applications). The Eulerian form is applied to the channel flow test resulting in improved accuracy and stability due to the maintenance of a uniform particle distribution. A higher-order accurate boundary model is developed and applied for the Eulerian SPH tests and third-order convergence is achieved. The well documented case of flow past a thin plate is then considered. The immersed boundary method (IBM) is now a natural candidate for the solid boundary. Again, it quickly becomes apparent that the Lagrangian SPH form has limitations in terms of numerical noise arising from anisotropic particle distributions. This corrupts the predicted flow structures for moderate Reynolds numbers (O(102)). Eulerian weakly compressible SPH is applied to the problem with the IBM and is found to give accurate and convergent results without any numerical stability problems (given the time step limitation defined by the Courant condition). Modelling highly flexible structures using the discrete element model is investigated where granular structures are represented as bonded particles. A novel vector-based form (the V-Model) is identified as an attractive approach and developed further for application to solid structures. This is shown to give accurate results for quasi-static and dynamic structural deformation tests. The V-model is applied to the decay of structural vibration in a still fluid modelled using Eulerian SPH with no artificial stabilising techniques. Again, results are in good agreement with predictions of other numerical models. A more demanding case representative of pulsatile flow through a deep leg vein valve is also modelled using the same form of Eulerian SPH. The results are free of numerical noise and complex FSI features are captured such as vortex shedding and non-linear structural deflection. Reasonable agreement is achieved with direct in-vivo observations despite the simplified two-dimensional numerical geometry. A robust, accurate and convergent method has thus been developed, at present for laminar two-dimensional low Reynolds number flows but this may be generalised. In summary a novel robust and convergent FSI model has been established based on Eulerian SPH coupled to the V-Model for large structural deformation. While these developments are in two dimensions the method is readily extendible to three-dimensional, laminar and turbulent flows for a wide range of applications in engineering and the natural world.

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Shrestha, Liza. "CFD study on effect of branch sizes in human coronary artery." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/885.

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Atherosclerosis is a term coined to describe a state in which arterial wall thickens due to the accumulation of fatty materials like cholesterol. Though not completely understood, it is believed to occur due to the accumulation of macrophage white blood cells and promoted by low density lipoprotein. Increase in accumulation of plaque leads to enlargement of arteries as arterial wall tries to remodel itself. But eventually the plaque ruptures, letting out its inner content to blood stream. The ruptured plaque clots and heals and shrinks down as well but leaves behind stenosis - narrowing of cross section. Depending on the degree of stenosis blood supply from the artery to its respective organ could decrease and even get blocked completely. Frequently, as the vulnerable plaques rupture, thrombus formed as such could flow through bloodstream towards smaller vessels and block them, leading to a sudden death of tissues fed by that vessel. If the plaques do not rupture and artery gets enlarged to a great extent then it results in an aneurysm. Such blockage of coronary arteries in heart can lead to myocardial infarction - heart attack, in carotid arteries in brain can lead to what is called a stroke, in peripheral arteries in legs can lead to ulcers, gangrene (death of tissue) and hence loss of leg, in renal arteries can lead to kidney malfunction. The most disturbing fact about atherosclerosis is the inability to detect the disease in preliminary stages. As stated by Miller (2001), most of the times coronary artery disease (CAD) gets diagnosed only after 50-75 percent occlusion of arteries.

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Copploe, Antonio. "Bioengineered Three-dimensional Lung Airway Models to Study Exogenous Surfactant Delivery." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1505482360585247.

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Benmadda, El Mostafa. "Etude de l'ecoulement pulse d'un fluide incompressible dans une conduite elastique : application a la circulation arterielle." Poitiers, 1987. http://www.theses.fr/1987POIT2267.

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Kaul, Himanshu. "A multi-paradigm modelling framework for simulating biocomplexity." Thesis, University of Oxford, 2013. https://ora.ox.ac.uk/objects/uuid:a3e6913d-b4c1-49fd-88fb-7e7155de2e2f.

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The following thesis presents a computational framework that can capture inherently non-linear and emergent biocomplex phenomena. The main motivation behind the investigations undertaken was the absence of a suitable platform that can simulate, both the continuous features as well as the discrete, interaction-based dynamics of a given biological system, or in short, dynamic reciprocity. In order to determine the most powerful approach to achieve this, the efficacy of two modelling paradigms, transport phenomena as well as agent-based, was evaluated and eventually combined. Computational Fluid Dynamics (CFD) was utilised to investigate optimal boundary conditions, in terms of meeting cellular glucose consumption requirements and exposure to physiologically relevant shear fields, that would support mesenchymal stem cell growth in a 3-dimensional culture maintained in a commercially available bioreactor. In addition to validating the default bioreactor configuration and operational parameter ranges as suitable towards sustaining stem cell growth, the investigation underscored the effectiveness of CFD as a design tool. However, due to the homogeneity assumption, an untenable assumption for most biological systems, CFD often encounters difficulties in simulating the interaction-reliant evolution of cellular systems. Therefore, the efficacy of the agent-based approach was evaluated by simulating a morphogenetic event: development of in vitro osteogenic nodule. The novel model replicated most aspects observed in vitro, which included: spatial arrangement of relevant players inside the nodule, interaction-based development of the osteogenic nodules, and the dependence of nodule growth on its size. The model was subsequently applied to interrogate the various competing hypotheses on this process and identify the one that best captures transformation of osteoblasts into osteocytes, a subject of great conjecture. The results from this investigation annulled one of the competing hypotheses, which purported the slow-down in the rate of matrix deposition by certain osteoblasts, and also suggested the acquisition of polarity to be a non-random event. The agent-based model, however, due to being inherently computationally expensive, cannot be recommended to model bulk phenomena. Therefore, the two approaches were integrated to create a modelling platform that was utilised to capture dynamic reciprocity in a bioreactor. As a part of this investigation, an amended definition of dynamic reciprocity and its computational analogue, dynamic assimilation, were proposed. The multi-paradigm platform was validated by conducting melanoma chemotaxis under foetal bovine serum gradient. Due to its CFD and agent-based modalities, the platform can be employed as both a design optimisation as well as hypothesis testing tool.

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Smith, Amy. "Multi-scale modelling of blood flow in the coronary microcirculation." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:e6f576a2-75d9-4778-a640-a1e8551141a6.

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The importance of coronary microcirculatory perfusion is highlighted by the severe impact of microvascular diseases such as diabetes and hypertension on heart function. Recently, highly-detailed three-dimensional (3D) data on ex vivo coronary microvascular structure have become available. However, hemodynamic information in individual myocardial capillaries cannot yet be obtained using current in vivo imaging techniques. In this thesis, a novel data-driven modelling framework is developed to predict tissue-scale flow properties from discrete anatomical data, which can in future be used to aid interpretation of coarse-scale perfusion imaging data in healthy and diseased states. Mathematical models are parametrised by the 3D anatomical data set of Lee (2009) from the rat myocardium, and tested using flow measurements in two-dimensional rat mesentery networks. Firstly, algorithmic and statistical tools are developed to separate branching arterioles and venules from mesh-like capillaries, and then to extract geometrical properties of the 3D capillary network. The multi-scale asymptotic homogenisation approach of Shipley and Chapman (2010) is adapted to derive a continuum model of coronary capillary fluid transport incorporating a non-Newtonian viscosity term. Tissue-scale flow is captured by Darcy's Law whose coefficient, the permeability tensor, transmits the volume-averaged capillary-scale flow variations to the tissue-scale equation. This anisotropic permeability tensor is explicitly calculated by solving the capillary-scale fluid mechanics problem on synthetic, stochastically-generated periodic networks parametrised by the geometrical data statistics, and a thorough sensitivity analysis is conducted. Permeability variations across the myocardium are computed by parametrising synthetic networks with transmurally-dependent data statistics, enabling the hypothesis that subendocardial permeability is much higher in diastole to compensate for severely-reduced systolic blood flow to be tested. The continuum Darcy flow model is parametrised by purely structural information to provide tissue-scale perfusion metrics, with the hypothesis that this model is less sensitive and more reliably parametrised than an alternative, estimated discrete network flow solution.

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McCormick, Matthew. "Ventricular function under LVAD support." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:0d49ba30-b508-4c69-9ba6-b398d4338c01.

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This thesis presents a finite element methodology for simulating fluid–solid interactions in the left ventricle (LV) under LVAD support. The developed model was utilised to study the passive and active characteristics of ventricular function in anatomically accurate LV geometries constructed from normal and patient image data. A non–conforming ALE Navier–Stokes/finite–elasticity fluid–solid coupling system formed the core of the numerical scheme, onto which several novel numerical additions were made. These included a fictitious domain (FD) Lagrange multiplier method to capture the interactions between immersed rigid bodies and encasing elastic solids (required for the LVAD cannula), as well as modifications to the Newton–Raphson/line search algorithm (which provided a 2 to 10 fold reduction in simulation time). Additional developments involved methods for extending the model to ventricular simulations. This required the creation of coupling methods, for both fluid and solid problems, to enable the integration of a lumped parameter representation of the systemic and pulmonary circulatory networks; the implementation and tuning of models of passive and active myocardial behaviour; as well as the testing of appropriate element types for coupling non–conforming fluid– solid finite element models under high interface tractions (finding that curvilinear spatial interpolations of the fluid geometry perform best). The behaviour of the resulting numerical scheme was investigated in a series of canonical test problems and found to be convergent and stable. The FD convergence studies also found that discontinuous pressure elements were better at capturing pressure gradients across FD boundaries. The ventricular simulations focused firstly on studying the passive diastolic behaviour of the LV both with and without LVAD support. Substantially different vortical flow features were observed when LVAD outflow was included. Additionally, a study of LVAD cannula lengths, using a particle tracking algorithm to determine recirculation rates of blood within the LV, found that shorter cannulas improved the recirculation of blood from the LV apex. Incorporating myocardial contraction, the model was extended to simulate the full cardiac cycle, converging on a repeating pressure–volume loop over 2 heart beats. Studies on the normal LV geometry found that LVAD implementation restricts the recirculation of early diastolic inflow, and that fluid–solid coupled models introduce greater heterogeneity of myocardial work than was observed in equivalent solid only models. A patient study was undertaken using a myocardial geometry constructed using image data from an LVAD implant recipient. A series of different LVAD flow regimes were tested. It was found that the opening of the aortic valve had a homogenising effect on the spatial variation of work, indicating that the synchronisation of LVAD outflow with the cardiac cycle is more important if the valve remains shut. Additionally, increasing LVAD outflow during systole and decreasing it during diastole led to improved mixing of blood in the ventricular cavity – compared with either the inverse, or holding outflow constant. Validation of these findings has the potential to impact the treatment protocols of LVAD patients.

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Chambers, Andrea Marie. "Stressed and Strung Out: The Development and Testing of an In Vivo Like Bench-top Bioreactor for the Observation of Cells Under Shear Stress." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1438218205.

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Louison, Charles Davidson. "A biomedical device business plan for Medicraften Devices Inc. to develop a fluid medication dispenser." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36730.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (leaf 32).
This thesis surrounds an analysis to understand what it would take for a company to successfully launch a prescription fluid dispensing device. This device would in theory be able to dispense medication at any time daily in correspondence to a patient's prescription. This thesis does not surround the actual development of a prototype, but gives a clear background into its technology. Other areas of research in this report include potential alliances and acquisitions of this company. This report gives a background into the target market, how the market will benefit from this device, and who the potential competitors of this device could be. Also explored are a potential advisory board for this company and how staff will be organized. Although the people on the advisory board and company's staff do exist, they are not actually involved in the conception of the thesis' device. This thesis uses techniques learned in management, engineering, and biomedical enterprise courses at MIT to give a real world case of how an effective biomedical device company can be formed and effectively managed.
by Charles Davidson Louison.
S.B.

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Ranga, Adrian. "Fluid-structure interaction in the aortic valve : implications for surgery and prosthesis design." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83925.

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The aortic valve is a complex and dynamic structure, which, with age, degenerative disease, or genetic abnormality, can become pathological and cease to function as in its natural state. A particularly prevailing disease of the aortic valve occurs when the valve becomes abnormally dilated, and regurgitation, or backflow of blood occurs. When this condition becomes severe and is accompanied by debilitating clinical manifestations, the standard procedure has been to replace the entire aortic root and valve with a composite valve graft incorporating either a mechanical or a bioprosthetic valve, during a type of surgery known as the Bentall procedure. However, both of these options have significant drawbacks for the patient, and for cases in which only the aortic root wall is dilated but the leaflets are still intact, novel surgical reconstruction techniques known as "valve-sparing procedures" have been adopted in recent years. The main idea is to excise only the dilated part of the wall, suturing a synthetic graft conduit in its place and thereby leaving the leaflets intact. A number of variants have been proposed, with a vigorous debate in the surgical community as to which is preferable in restoring valve dynamics and hemodynamics, thus leading to a more durable repair and a more favorable outcome for the patient. The objective of this work is to develop numerical simulation techniques to simulate the behavior of the normal aortic valve, and to quantify the effect that these various procedures, as compared to the benchmark native aortic valve. Various types of computational methods have been developed in the past to study the aortic valve, with an increasing level of sophistication as computational resources have evolved. Most of these studies have been structural finite element analyses, where the valve structures have been loaded with uniform distributed pressure loads in order to simulate the effect of blood. Recent efforts have focused

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Hosseinipour, Milad. "Design and Development of an Intra-Ventricular Assistive Device For End Stage Congestive Heart Failure Patients: Conceptual Design." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372726495.

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Doyle, Matthew G. "Simulation of blood flow in a ventricular assist device with fluid-structure interaction effects." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26630.

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Numerical simulations combining solid and fluid models and fluid-structure interaction effects were performed for a diaphragm-type ventricular assist device (VAD). These simulations include an open loop configuration, in which the VAD inlet and outlet tubes are open to the surroundings, and a closed loop configuration, in which the VAD is connected to an idealized model of the circulatory system. Comparisons have been made between the open loop case and previous experimental and numerical results for a similar VAD designed by a group at Brunel University. Differences between the two models can be partially accounted for by differences in flow forcing. Even with these differences, this comparison validates this method as a tool for the design and optimization of VADs. For the closed loop case, results were limited by the required use of a slightly compressible fluid model. Further relaxation of this requirement is needed to fully explore closed loop simulations.

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Shaffer, Nicholas. "Magnetic Resonance Image-Based Hydrodynamic Analysis of Cerebrospinal Fluid Motion in Type I Chiari Malformation." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1417545898.

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Van, der Merwe Schalk Willem. "A MEMS based valveless micropump for biomedical applications." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4230.

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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The valveless micropump holds great potential for the biomedical community in applications such as drug delivery systems, blood glucose monitoring and many others. It is also a critical component in many a lab-on-a-chip device, which in turn promises to improve our treatment and diagnosis capabilities for diseases such as diabetes, tuberculosis, and HIV/AIDS. The valveless micropump has attracted attention from researchers on the grounds of its simple design, easy manufacturability and sensitive fluid handling characteristics, which are all important in biomedical applications. The pump consists of a pump chamber with a diffuser and nozzle on opposing sides of the pump chamber. The flow into the diffuser and nozzle is induced by an oscillating piezoelectric disc located on top of the pump chamber. The nozzle and diffuser rectify the flow in one direction, due to different pressure loss coefficients. The design process however is complex. In this study, we investigate the characteristics of a diffuser / nozzle based micropump using detailed computational fluid dynamic (CFD) analyses. Significant parameters are derived using the Buckingham-Pi theorem. In part based on this, the respective shapes of the diffuser and of the nozzle of the micropump are selected for numerical investigation. Hence the influence of the selected parameters on the flow rate of the micropump is studied using three-dimensional transient CFD analyses. Velocity profiles from the CFD simulations are also compared to the Jeffery-Hamel solution for flow in a wedge shaped channel. Significant similarities exist between the data and the predicted Jeffery-Hamel velocity profiles near the exit of the diffuser. Three different diffuser geometries were simulated at three frequencies. The flow rate and direction of flow are shown to be highly sensitive to inlet and outlet diffuser shapes, with the absolute flow rate varying by as much as 200% for the geometrical perturbations studied. Entrance losses at both the diffuser inlet and nozzle inlet appear to dominate the flow resistance at extremely laminar flow conditions with the average Reynolds number of Reave ≈ 500.
AFRIKAANSE OPSOMMING: Die kleplosemikropomp hou groot potensiaal in vir die biomediese gemeenskap in toepassings soos medisyne dosering sisteme, bloed glukose monitering en baie ander. Dit is ook ’n kritiese komponent in “lab-on-chip” sisteme, wat beloof om die behandeling en diagnose van siektes soos suikersiekte, tuberkulose enMIV/VIGS te verbeter. Die kleplose mikropomp het tot dusver die aandag van navorsers geniet as gevolg van sy eenvoudige ontwerp, maklike vervaardiging en sensitiewe vloeistof hantering. Hierdie kenmerke is krities inmenige biomediese toepassings. Die pomp bestaan uit ’n pompkamer met ’n diffusor en ’n mondstuk aan teenoorstaande kante van die pompkamer. Vloei in die diffusor en mondstuk in word geinduseer deur ’n ossillerende piëso-elektiese skyf wat bo-op die pompkamer geleë is. Weens verskillende druk verlies koëffisinëte van die diffusor en diemondstuk word die vloei in een rigting gerig. Die ontwerp-proses is egter kompleks. In hierdie studie word die eienskappe van die diffusor /mondstuk ondersoek deur gebruik temaak van gedetailleerde numeriese vloei-dinamiese analises. Belangrike parameters word afgelei deur gebruik te maak van die Buckingham-Pi teorema. Gedeeltelik gebaseer hierop word die onderskeidelike vorms van die diffusor en die mondstuk van die mikropomp geselekteer vir numeriese ondersoek. Gevlolglik word die invloed van die geselekteerde parameters op die vloei tempo van diemikropomp ondersoek deur gebruik temaak van drie-dimensionele tyd afhanklike numeriese vloei-dinamiese analises. Snelheids profiele van hierdie simulasiesword vergelykmet die Jeffrey-Hamel oplossing vir die vloei in ’n wigvormige kanaal. Daar is oorwegende ooreenkomstighede tussen hierdie data en die voorspelde Jeffrey-Hamel snelheids profiele veral by die uitgang van die diffusor. Drie verskillende diffusor vorms is by drie frekwensies gesimuleer. Daar is bewys dat die vloei tempo en vloeirigting baie sensitief is vir inlaat- en uitlaat diffusor vorms en dat die absolute vloei tempo kan varieermet soveel as 200%vir die geometriese versteuringswat ondersoek is. Inlaat verliese by beide die diffusor inlaat en die mondstuk inlaat, blyk om die vloei weerstand te domineer waar die vloei uiters laminêr ismet ’n gemiddelde Reynolds getal van Regem ≈ 500

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Heidari, Pahlavian Soroush. "Non-Invasive Assessment of Cerebrospinal Fluid and Brain Tissue Biomechanics using MRI and Computational Modeling." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1522060187703491.

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Ridzon, Matthew C. "Quantifying Cerebellar Movement With Fluid-Structure Interaction Simulations." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1590752448366714.

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Cudjoe, Edward. "Tribocorrosion Behavior of Metallic Implants: A Comparative Study of CoCrMo and Ti6Al4V in Simulated Synovial Fluids." Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu156634015910627.

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THYAGARAJ, SURAJ. "In Vitro Investigation Of Cerebrospinal Fluid Dynamics In Chiari Malformation By 4D Phase Contrast MRI." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462548992.

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Sethaput, Thunyaseth. "Mathematical Model for Hemodynamic and Intracranial Windkessel Mechanism." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1363149368.

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Takaddus, Ahmed Tasnub. "Numerical Investigations of Unobstructed and Obstructed Human Ureter Peristalsis." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1516150297659937.

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Shupe, Andrew C. "Convective Flow Patterns of a Three Generation Bifurcation Model." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353035707.

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Torkaman, Saeed. "Experimental and Computational Study of Intraglottal Pressures in a Three-Dimensional Model with a Non-Rectangular Glottal Shape." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302011788.

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Celestin, Carey Jr. "Computational Fluid Dynamics Applied to the Analysis of Blood Flow Through Central Aortic to Pulmonary Artery Shunts." ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/1972.

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This research utilizes CFD to analyze blood flow through pathways representative of central shunts, commonly used as part of the Fontan procedure to treat cyanotic heart disease. In the first part of this research, a parametric study of steady, Newtonian blood flow through parabolic pathways was performed to demonstrate the effect that flow pathway curvature has on wall shear stress distribution and flow energy losses. In the second part, blood flow through two shunts obtained via biplane angiograms is simulated. Pressure boundary conditions were obtained via catheterization. Results showed that wall shear stresses were of sufficient magnitude to initiate platelet activation, a precursor for thrombus formation. Steady results utilizing time-averaged boundary conditions showed excellent agreement with the time-averaged results obtained from pulsatile simulations. For the points of interest in this research, namely wall shear stress distribution and flow energy loss, the Newtonian viscosity model was found to yield acceptable results.

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Chen, Xiaodong. "Fluid-Structure Interaction Modeling of Epithelial Cell Deformation during Microbubble Flows in Compliant Airways." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1332208862.

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McElroy, Mark Allen. "A Procedure for Generating Finite Element Models (FEM) of Abdominal Aortic Aneurysms with Fluid Boundary Conditions Derived from Magnetic Resonance Imaging (MRI) Velocimetry." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1284670607.

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Sheer, Francis Joseph. "Multi-Scale Computational Modeling of Fluid-Structure Interactions and Adhesion Dynamics in the Upper Respiratory System." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316287639.

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IBRAHIMY, ALAADDIN. "Computational Methodology to Estimate Resistance to Cerebrospinal Fluid Motion in the Spinal Canal for Chiari Patients with Specific and Nonspecific Symptoms." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1574449883152461.

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Yun, Brian Min. "Simulations of pulsatile flow through bileaflet mechanical heart valves using a suspension flow model: to assess blood damage." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/53378.

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Defective or diseased native valves have been replaced by bileaflet mechanical heart valves (BMHVs) for many years. However, severe complications still exist, and thus blood damage that occurs in BMHV flows must be well understood. The aim of this research is to numerically study platelet damage that occurs in BMHV flows. The numerical suspension flow method combines lattice-Boltzmann fluid modeling with the external boundary force method. This method is validated as a general suspension flow solver, and then validated against experimental BMHV flow data. Blood damage is evaluated for a physiologic adult case of BMHV flow and then for BMHVs with pediatric sizing and flow conditions. Simulations reveal intricate, small-scale BMHV flow features, and the presence of turbulence in BMHV flow. The results suggest a shift from previous evaluations of instantaneous flow to the determination of long-term flow recirculation regions when assessing thromboembolic potential. Sharp geometries that may induce these recirculation regions should be avoided in device design. Simulations for predictive assessment of pediatric sized valves show increased platelet damage values for potential pediatric valves. However, damage values do not exceed platelet activation thresholds, and highly damaged platelets are found far from the valve. Thus, the increased damage associated with resized valves is not such that pediatric valve development should be hindered. This method can also be used as a generic tool for future evaluation of novel prosthetic devices or cardiovascular flow problems.

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Rahman, Roussel. "Analysis and Sensitivity Study of Zero-Dimensional Modeling of Human Blood Circulation Network." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1494769445938849.

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Liu, Janet. "Design of a Novel Tissue Culture System to Subject Aortic Tissue to Multidirectional Bicuspid Aortic Valve Wall Shear Stress." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1527077368757049.

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Rifai, Bassel. "Cavitation-enhanced delivery of therapeutics to solid tumors." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:374b2ee1-0711-4994-8434-bf90358d9e47.

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Poor drug penetration through tumor tissue has emerged as a fundamental obstacle to cancer therapy. The solid tumor microenvironment presents several physiological abnormalities which reduce the uptake of intravenously administered therapeutics, including leaky, irregularly spaced blood vessels, and a pressure gradient which resists transport of therapeutics from the bloodstream into the tumor. Because of these factors, a systemically administered anti-cancer agent is unlikely to reach 100% of cancer cells at therapeutic dosages, which is the efficacy required for curative treatment. The goal of this project is to use high-intensity focused ultrasound (HIFU) to enhance drug delivery via phenomena associated with acoustic cavitation. ‘Cavitation’ is the formation, oscillation, and collapse of bubbles in a sound field, and can be broadly divided into two types: ‘inertial’ and ‘stable’. Inertial cavitation involves violent bubble collapse and is associated with phenomena such as heating, fluid jetting, and broadband noise emission. Stable cavitation occurs at lower pressure amplitudes, and can generate liquid microstreaming in the bubble vicinity. It is the combination of fluid jetting and microstreaming which it is attempted to explore, control, and apply to the drug delivery problem in solid tumors. First, the potential for cavitation to enhance the convective transport of a model therapeutic into obstructed vasculature in a cell-free in vitro tumor model is evaluated. Transport is quantified using post-treatment image analysis of the distribution of a dye-labeled macromolecule, while cavitation activity is quantified by analyzing passively recorded acoustic emissions. The introduction of exogenous cavitation nuclei into the acoustic field is found to dramatically enhance both cavitation activity and convective transport. The strong correlation between inertial cavitation activity and drug delivery in this study suggested both a mechanism of action and the clinical potential for non-invasive treatment monitoring. Next, a flexible and efficient method to simulate numerically the microstreaming fields instigated by cavitating microbubbles is developed. The technique is applied to the problem of quantifying convective transport of a scalar quantity in the vicinity of acoustically cavitating microbubbles of various initial radii subject to a range of sonication parameters, yielding insight regarding treatment parameter choice. Finally, in vitro and in vivo models are used to explore the effect of HIFU on delivery and expression of a biologically active adenovirus. The role of cavitation in improving the distribution of adenovirus in porous media is established, as well as the critical role of certain sonication parameters in sustaining cavitation activity in vivo. It is shown that following intratumoral or intravenous co-injection of ultrasound contrast agents and adenovirus, both the distribution and expression of viral transgenes are enhanced in the presence of inertial cavitation. This ultrasound-based drug delivery system has the potential to be applied in conjunction with a broad range of macromolecular therapeutics to augment their bioavailability for cancer treatment. In order to reach this objective, further developmental work is recommended, directed towards improving therapeutic transducer design, using transducer arrays for treatment monitoring and mapping, and continuing the development of functionalized monodisperse cavitation nuclei.

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Wright, Darrel W. "Pressure losses experienced by liquid flow through straight PDMS microchannels of varying diameters." Honors in the Major Thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1527.

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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.
Bachelors
Engineering and Computer Science
Mechanical Engineering

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Lind, Anne-Li. "Biomarkers for Better Understanding of the Pathophysiology and Treatment of Chronic Pain : Investigations of Human Biofluids." Doctoral thesis, Uppsala universitet, Anestesiologi och intensivvård, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326180.

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Chronic pain affects 20 % of the global population, causes suffering, is difficult to treat, and constitutes a large economic burden for society. So far, the characterization of molecular mechanisms of chronic pain-like behaviors in animal models has not translated into effective treatments. In this thesis, consisting of five studies, pain patient biofluids were analyzed with modern proteomic methods to identify biomarker candidates that can be used to improve our understanding of the pathophysiology chronic pain and lead to more effective treatments. Paper I is a proof of concept study, where a multiplex solid phase-proximity ligation assay (SP-PLA) was applied to cerebrospinal fluid (CSF) for the first time. CSF reference protein levels and four biomarker candidates for ALS were presented. The investigated proteins were not altered by spinal cord stimulation (SCS) treatment for neuropathic pain. In Paper II, patient CSF was explored by dimethyl and label-free mass spectrometric (MS) proteomic methods. Twelve proteins, known for their roles in neuroprotection, nociceptive signaling, immune regulation, and synaptic plasticity, were identified to be associated with SCS treatment of neuropathic pain. In Paper III, proximity extension assay (PEA) was used to analyze levels of 92 proteins in serum from patients one year after painful disc herniation. Patients with residual pain had significantly higher serum levels of 41 inflammatory proteins. In Paper IV, levels of 55 proteins were analyzed by a 100-plex antibody suspension bead array (ASBA) in CSF samples from two neuropathic pain patient cohorts, one cohort of fibromyalgia patients and two control cohorts. CSF protein profiles consisting of levels of apolipoprotein C1, ectonucleotide pyrophosphatase/phosphodiesterase family member 2, angiotensinogen, prostaglandin-H2 D-isomerase, neurexin-1, superoxide dismutases 1 and 3 were found to be associated with neuropathic pain and fibromyalgia. In Paper V, higher CSF levels of five chemokines and LAPTGF-beta-1were detected in two patient cohorts with neuropathic pain compared with healthy controls. In conclusion, we demonstrate that combining MS proteomic and multiplex antibody-based methods for analysis of patient biofluid samples is a viable approach for discovery of biomarker candidates for the pathophysiology and treatment of chronic pain. Several biomarker candidates possibly reflecting systemic inflammation, lipid metabolism, and neuroinflammation in different pain conditions were identified for further investigation.
Uppsala Berzelii Technology Centre for Neurodiagnostics

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38

Nanna, W. L. Bryan. "Arterial fluid mechanics computations with the stabilized space-time fluid-structure interaction techniques." Thesis, 2007. http://hdl.handle.net/1911/20565.

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The stabilized space-time fluid-structure interaction (SSTFSI) techniques developed by the Team for Advanced Flow Simulation and Modeling (T☆AFSM) are applied to the field of arterial fluid mechanics through the FSI modeling of a cerebral artery with a small, saccular aneurysm. All arterial structures are modeled with membrane elements, which are geometrically nonlinear. FSI computations of cardio-vascular systems presently interest the scientific community as such types of analysis provide a non-invasive means of analyzing a patient's condition and risk for aneurysm rupture, a potentially life-threatening condition. Test computations for varying arterial wall thickness and blood pressure are presented for this cerebral aneurysm, with the arterial geometries of the computations closely approximating patient-specific image-based data. Results show the T☆AFSM's ability to handle complex and realistic FSI simulations while demonstrating the capability and utility of FSI simulations in the field of cardiovascular fluid mechanics.

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Cragin, Timothy L. "Stabilized space-time fluid-structure interaction techniques with the continuum element." Thesis, 2007. http://hdl.handle.net/1911/20497.

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We present the methods used to add continuum element functionality to the structure side of our Fluid-Structure Interaction (FSI) solver. The FSI solver, already capable of handling the interaction between membrane structure elements and fluid elements, can now accurately simulate fully 3D structure models as well. A few simple test calculations are presented in order to verify the proper implementation of these changes. Then we aim to establish the effectiveness of these methods by modeling blood flow through a cerebral sacular aneurysm. These computations are performed with three different structural models: linearly-elastic, hyperelastic (Mooney-Rivlin), and Neo-Hookean. Futhermore, each structure model is tested with two different pressure profiles and two different aneurysm thicknesses. Finally, we suggest a procedural change for further investigation: instead of assuming image-based geometry corresponds to zero blood pressure, use that image-based geometry to estimate the zero-pressure arterial geometry.

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Haque, Sara Salim. "Applications of Nanoparticle Image Velocimetry in Nanofluids." 2011. http://trace.tennessee.edu/utk_gradthes/974.

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Particle Image Velocimetry (PIV) is an optical technique used for the visualization of fluid flow. PIV can be combined with other techniques to enhance the analysis of fluid flow. A novel far-field plasmonic resonance enhanced nanoparticle-seeded Particle Image Velocimetry (nPIV) has been demonstrated to measure the velocity in a micro channel. Chemically synthesized silver nanoparticles have been used to seed the flow. By using Discrete Dipole Approximation (DDA), plasmonic resonance enhanced light scattering has been calculated for spherical silver nanoparticles with diameters ranging from 15 nm to 200 nm in two media: water and air. The diffraction-limited plasmonic resonance enhanced images of silver nanoparticles at different diameters have been recorded. By using standard PIV techniques, the velocity within the micro channel has been determined from the images collected. The plasmonic resonance effects of nanoparticles from different media as compared to metal nanoparticles are also examined. Localized Surface Plasmon Resonance (LSPR) effects by naturally occurring Chinese yam particles are observed and quantified. Chinese yam particles are found by an atomic force microscope and a high-speed optical dark-field microscope. The particles with diameters greater than 200 nm are found to contribute most to UV-Vis absorption. LSPR effects of silver nanoparticles by the Chinese yam particles lead to the red shift of the extinction peaks of the silver nanoparticles. The wavelength shifts are quantitatively predicted based on DDA of the LSPR effects, which are sensitive to the local dielectric constant changed by the Chinese yam particles. This finding may open a new avenue to detect the biological sub-micron particles or virus in solution. PIV gives a new perspective on fluid flow that is otherwise difficult to see. An application of PIV studying the flagella movement of Giardia Lamblis trophozoites is examined. Standard PIV techniques are employed using a combination of high-contrast CytoViva ® imaging system to capture the images at high speeds and the Insight 3G software to measure the speed and direction of fluid motion generated by the microscale flagella. The PIV images illustrate how the flagella of the Giardia interact with each other and how they move in their environment.

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Μανόπουλος, Χρήστος. "Πειραματικός και θεωρητικός προσδιορισμός "περισταλτικών αντλιών αίματος"." Thesis, 1999. http://nemertes.lis.upatras.gr/jspui/handle/10889/3174.

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Joly, Florian. "Numerical Insights for AAA Growth Understanding and Predicting: Morphological and Hemodynamic Risk Assessment Features and Transient Coherent Structures Uncovering." Thèse, 2019. http://hdl.handle.net/1866/22597.

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Shajahan, T. K. "Studies Of Spiral Turbulence And Its Control In Models Of Cardiac Tissue." Thesis, 2008. http://hdl.handle.net/2005/759.

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There is a growing consensus that life-threatening cardiac arrhythmias like ventricular tachycardia (VT) or ventricular fibrillation (VF) arise because of the formation of spiral waves of electrical activation in cardiac tissue; unbroken spiral waves are associated with VT and broken ones with VF. Several experimental studies have shown that inhomogeneities in cardiac tissue can have dramatic effects on such spiral waves. In this thesis we try to understand these experimental results by carrying out detailed and systematic studies of the interaction of spiral waves with different types of inhomogeneities in mathematical models for cardiac tissue. In Chapter 1 we begin with a general introduction to cardiac arrhythmias, the cardiac conduction system, and the connection between electrical activation waves in cardiac tissue and cardiac arrhythmias. As we have noted above, VT and VF are believed to be associated with spiral waves of electrical activation on cardiac tissue; such spiral waves form because cardiac tissue is an excitable medium. Thus we give an overview of excitable media, in which sub-threshold perturbations decay but super-threshold perturbations lead to an action potential that consists of a rapid stage of depolarization of cardiac cells followed by a slow phase of repolarization. During this repolarization phase the cells are refractory. We then give an overview of earlier studies of the effects of inhomogeneities in cardiac tissue; and we end with a brief description of the principal problems we study here. Chapter 2 describes the models we use in our work. We start with a general introduction to the cable equation and then discuss the Hodgkin-Huxley-formalism for the transport of ions across a cell membrane through voltage-gated ion channels. We then describe in detail the three models that we use for cardiac tissue, which are, in order of increasing complexity, the Panfilov model, the Luo Rudy Phase I (LRI) model, and the reduced Priebe Beuckelmann (RPB)model. We then give the numerical schemes we use for solving these model equations and the initial conditions that lead to the formation of spiral waves. For all these models we give representative results from our simulations and compare the states with spiral turbulence. In Chapter 3 we investigate the effects of conduction inhomogeneities (obstacles) in the three models introduced in Chapter 2. We outline first the experimental results that have provided the motivation for our study. We then discuss how we introduce obstacles in our simulations of the Panffilov, LRI, and RPB models for cardiac tissue. Next we present the results of our numerical studies of the effects, on spiral-wave dynamics, of the sizes, shapes, and positions of the obstacles. Our Principal result is that spiral-wave dynamics in these models depends sensitively on the position of the obstacle. We find, in particular, that, merely by changing the position of a conduction inhomogeneity, we may convert spiral turbulence (the analogue in our models of VF) to a single rotating spiral (the analogue of VT) anchored to the obstacle or vice versa; even more exciting is the possibility that, at the boundary between these two types of behaviour, we find a quiescent state Q with no spiral waves. Thus our study obtains all the possible qualitative behaviours found in experiments, namely, (1) VF might persist even in the presence of an obstacle, (2) it might be suppressed partially and become VT, or (3) it might be eliminated completely. In Chapter 4 we extend our work on conduction inhomogeneities (Chapter 3) to ionic inhomogeneities. Unlike conduction inhomogeneities, ionic inhomogeneities allow the conduction of activation waves. We find, nevertheless, that they too can lead to the anchoring of spiral waves or even the complete elimination of spiral-wave turbulence. Since spiral waves can enter the region in which there is an ionic inhomogeneity, their behaviours in the presence of such an inhomogeneity are richer than those with conduction inhomogeneities. We find, in particular, that a single spiral wave anchored at an ionic inhomogeneity can show temporal evolution that may be periodic, quasiperiodic, or even chaotic. In the last case the spiral wave shows a chaotic pattern inside the ionic inhomogeneity and a regular one outside it. Defibrillation is the control of arrhythmias such as VF. Most often defibrillation is effected electrically by administering a shock, either externally or via an internally implanted defibrillator. The development of low-amplitude defibrillation schemes, which minimise the deleterious effects of the applied shock, is a major challenge in the treatment of cardiac arrhythmias. Numerical studies of models for cardiac tissue provide us with convenient means of studying the elimination of spiral-wave turbulence by the application of external electrical stimuli; this is the numerical analogue of defibrillation. Over the years some low-amplitude defibrillation schemes have been suggested on the basis of such numerical studies. In Chapter 5 we discuss two such schemes that have been shown to suppress spiral-wave turbulence in two-dimensional models for cardiac tissue and also scroll-wave turbulence in three-dimensional models. One of these schemes uses local electrical pacing, typically in the centre of the simulation domain; the other applies the external electrical stimuli over a mesh. We study the efficacy of these schemes in the presence of conduction inhomogeneities. We find, in particular, that the local-pacing scheme, though effective in a homogeneous simulation domain, fails to control spiral turbulence in the presence of an obstacle and, indeed, might even facilitate spiral-wave break up. By contrast, the second scheme, which uses a mesh, succeeds in eliminating spiral-wave turbulence even in the presence of an obstacle. We end with some concluding remarks about the possible experimental implications of our study in Chapter 6.

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Mengistu, Meron. "The effects of fluid shear stress on micro-mechanical properties and mechanotransduction events in endothelial cells." 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3314475.

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"Numerical studies of fluid-structure interactions in biomechanical systems." Tulane University, 2007.

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Modelling of biological flows has received growing attention in the last years. The fluid dynamics in the heart cavities and the fluid tissue interaction present several modelling difficulties and their understanding is still far from being satisfactory. Therefore, an innovative numerical model basis for the complex hemodynamics in biomechanical systems is developed. This method, named Immersed Finite Element Method is based on different numerical methods previously derived by gathering all their merits and eliminating their shortcomings. A new algorithm, that follows the principle of the physical virtual method, is implemented to ensure the rigidity at fluid-rigid solid interface. Detailed derivation of the method is presented. Biomechanical systems are then modelized starting from the simulations of blood flow in arteries with the aim of validating the method at physiologic conditions and capturing relevant hemodynamic parameters prone to atherosclerosis. The results lead to a better understanding of atherosclerosis. Finally, the left atrium function in sinus and abnormal rhythm is studied. The aim of this study is to understand the importance of the left atrial appendage in the development of strokes in those suffering from atrial fibrillation. Using IFEM, a solution is obtained at physiologic Reynolds numbers by applying pulmonary venous inflow and appropriate constitutive equations to closely mimic the overall behavior of the myocardium muscle. Hemodynamic parameters and velocity fields are investigated and the influence of the presence of the left atrial appendage is discussed. This model leads to a better understanding of the flow in the left atrial appendage and zones that seem to be particularly favorable to thrombus formation are identified
acase@tulane.edu

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46

(11205849), Patrick A. Giolando. "Mathematical and Computational Modeling in Biomedical Engineering." Thesis, 2021.

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Mathematical and computational modeling allow for the rationalization of complex phenomenon observed in our reality. Through the careful selection of assumptions, the intractable task of simulating reality can be reduced to the simulation of a practical system whose behavior can be replicated. The development of computational models allow for the full comprehension of the defined system, and the model itself can be used to evaluate the results of thousands of simulate experiments to aid in the rational design process.

Biomedical engineering is the application of engineering principles to the field of medicine and biology. This discipline is composed of numerous diverse subdisciplines that span from genetic engineering to biomechanics. Each of these subdisciplines is concerned with its own complex and seemingly chaotic systems, whose behavior is difficult to characterize. The development and application of computational modeling to rationalize these systems is often necessary in this field and will be the focus of this thesis.

This thesis is centered on the development and application of mathematical and computational modeling in three diverse systems in biomedical engineering. First, computational modeling is employed to investigate the behavior of key proteins in the post-synapse centered around learning and memory. Second, computational modeling is utilized to characterize the drug release rate from implantable drug delivery depots, and produce a tool to aid in the tailoring of the release rate. Finally, computational modeling is utilized to understand the motion of particles through an inertial focusing microfluidics chip and optimize the size selective capture efficiency.

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Yum, Kyungsuk. "Interfacing nanomaterials with fluids and living biological systems /." 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3363123.

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Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2009.
Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3757. Adviser: Min-Feng Yu. Includes bibliographical references (leaves 93-110). Available on microfilm from Pro Quest Information and Learning.

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Lightstone, Noam S. "Design of a Bioreactor to Mimic Hemodynamic Shear Stresses on Endothelial Cells in Microfluidic Systems." Thesis, 2014. http://hdl.handle.net/1807/65572.

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The mechanisms behind cardiovascular disease (CVD) initiation and progression are not fully elucidated. It is hypothesized that blood flow patterns regulate endothelial cell (EC) function to affect the progression of CVDs. A system that subjects ECs to physiologically-relevant shear stress waveforms within microfluidic devices has not yet been demonstrated, despite the advantages associated with the use of these devices. In this work, a bioreactor was designed to fulfill this need. Waveforms from regions commonly affected by CVDs including were derived. Pump motion and fluid flow profiles were validated by actuator motion tracking, particle image velocimetry, and flowmeters. While several relevant waveforms were successfully replicated, physiological waveforms could not be produced at physiological frequencies owing to actuator velocity and accuracy limitations, as well as dampening effects in the system. Overall, this work lays the foundation for designing a system that provides insight into the role of shear stress in CVD pathogenesis.

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Furse, Alexander. "Development of a Low Cost Swing-phase Control Mechanism." Thesis, 2010. http://hdl.handle.net/1807/25587.

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Seven above-knee amputees were fitted with a low-cost prosthetic knee and different low-cost swing-phase setups were clinically assessed. Clinical testing included the 20-meter walk tests utilizing a mobile computer setup connected to a potentiometer and accelerometer mounted on the prosthetic limb. As hypothesized, incorporating friction and a spring system resulted in improved gait function. Of the two spring systems evaluated, the dual spring system performed better than the single spring system resulting in increased walking velocity with decreased maximum flexion and terminal impact. The dual spring system resulted in lower terminal impact because the deactivation of the stiff spring and activation of the less stiff spring during the last 25 degrees of swing-phase before extension allows the shank to decelerate and hit the bumper at a lower velocity. The swing-phase control mechanisms evaluated have the potential to improve prosthetic function and are ideal for use in low-cost and peadiatric prostheses.

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Xie, Xueying. "Modeling viscoelastic free surface and interfacial flows, with applications to the deformation of droplets and blood cells." Thesis, 2006. http://hdl.handle.net/1911/18995.

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This thesis models viscoelastic free surface and interfacial flows. Capillarity and viscoelasticity are important in many interesting problems, e.g. the deformation of droplets and blood cells, coating flows of polymer solutions, and blood flow in arteries and capillaries. The study of the combined effects of capillarity and viscoelasticity is still in its infancy due to complex physics combined with the numerical difficulties in three-dimension. This thesis extends to three-dimensional flows from the previous studies focused on two-dimensional problem. Modeling viscoelastic free surface flows presents several challenges which include modeling the liquid viscoelasticity, locating free surface boundaries, and implementing large-scale computations. Conformation tensor models are used to model the fluid viscoelasticity because they balance generality, realistic physics, and computational cost. A new, convenient open-flow boundary condition is developed for the transport equation of the conformation tensor. The domain deformation method is used to locate both two- and three-dimensional free surfaces and interfaces by treating the mesh as an elastic pseudo-solid. In addition, an isochoric domain deformation method is developed to conserve domain volumes for certain free surface flows where the volume of a liquid domain is prescribed, such as a cell deforming in shear flow. The equations for solving viscoelastic free surface flows are discretized by the finite element method. The non-linear discretized equations are solved by Newton's method and the resulting large set of linear algebraic equations is solved by parallel GMRES preconditioned by a new sparse approximate inverse preconditioner (SPAI). The parallel solver together with SPAI is scalable in a wide range of capillary and Weissenberg numbers; tests on benchmark viscoelastic free surface flows show that problems with millions of unknowns can be tackled on Linux clusters. The development of viscoelastic free surface flow modeling and isochoric domain deformation method is applied to model cell (viscoelastic drop) deformation.

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Dissertations / Theses on the topic 'Biomedical fluid mechanics'

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