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A COMPUTED TOMOGRAPHY-BASED MODEL OF THE INFANT HIP ANATOMY FOR DYNAMIC FINITE ELEMENT ANALYSIS OF HIP DYSPLASIA BIOMECHANICS
Title
A COMPUTED TOMOGRAPHY-BASED MODEL OF THE INFANT HIP ANATOMY FOR DYNAMIC FINITE ELEMENT ANALYSIS OF HIP DYSPLASIA BIOMECHANICS.
Creator
Snethen, Kyle, Kassab, Alain, University of Central Florida
Abstract / Description
Newborns diagnosed with hip dysplasia face severe consequences when treatments fail. The Pavlik harness presents the most common worldwide treatment for correcting this medical hip abnormality in newborns, but becomes increasingly ineffective as subluxation increases. A dynamic finite element analysis on the hip joint would yield results that could provide insight to physicians as to how the Pavlik harness could be optimized to increase its success rate and develop patient-specific treatment...
Show moreNewborns diagnosed with hip dysplasia face severe consequences when treatments fail. The Pavlik harness presents the most common worldwide treatment for correcting this medical hip abnormality in newborns, but becomes increasingly ineffective as subluxation increases. A dynamic finite element analysis on the hip joint would yield results that could provide insight to physicians as to how the Pavlik harness could be optimized to increase its success rate and develop patient-specific treatment plans. The study completes the first step in such an analysis by generating a three-dimensional model of an infant hip joint directly derived from computed tomography imaging in order to accurately represent the anatomical locations of muscle origins and insertions points as well as the unique cartilaginous characteristics of a neonate hip and femur. Such models will further enhance findings on the biomechanics of hip dysplasia that resulted from a preliminary study using computer-aided design to recreate the hip joint. In addition to the models, the orientation of the psoas tendon in a dysplastic hip through full range abduction and flexion was analyzed using a cadaveric dissection. It was determined that the psoas tendon was not an obstruction to reduction when the hip was in flexion so long as the tendon was not adherent to the hip capsule, and therefore can be disregarded in a finite element analysis or dynamic simulation that introduces flexion. The work of this thesis will lay the foundation for complex finite element analyses regarding the biomechanics of hip dysplasia in neonates as well as other hip abnormalities relevant to early child development.
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Date Issued
2013
Identifier
CFH0004423, ucf:45144
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004423
Probing the Effects of Substrate Stiffness on Astrocytes Mechanics
Title
Probing the Effects of Substrate Stiffness on Astrocytes Mechanics.
Creator
Bizanti, Ariege, Steward, Robert, Samsam, Mohtashem, Huang, Helen, University of Central Florida
Abstract / Description
Astrocytes are among the most functionally diverse population of cells in the central nervous system (CNS) as they are essential to many important neurological functions including maintaining brain homeostasis, regulating the blood brain barrier, and preventing build-up of toxic substances within the brain, for example. Astrocyte importance to brain physiology and pathology has inspired a host of studies focused on understanding astrocyte behavior primarily from a biological and chemical...
Show moreAstrocytes are among the most functionally diverse population of cells in the central nervous system (CNS) as they are essential to many important neurological functions including maintaining brain homeostasis, regulating the blood brain barrier, and preventing build-up of toxic substances within the brain, for example. Astrocyte importance to brain physiology and pathology has inspired a host of studies focused on understanding astrocyte behavior primarily from a biological and chemical perspective. However, a clear understanding of astrocyte dysfunction and their link to disease has been hampered by a lack of knowledge of astrocyte behavior from a biomechanical perspective. Furthermore, astrocytes (and all cells) can sense and respond to their external biomechanical environment via the extracellular matrix and various other biomechanical cues.One such biomechanical cue, substrate stiffness changes within the brain under certain pathologies, which subsequently leads to changes in the biomechanical behavior of the cell. For example, increased tissue stiffness is a hallmark of brain tumors that subsequently alters astrocyte biomechanical behavior. Therefore, to gain a better understanding of this process we cultured astrocytes on stiffnesses that mimicked that of the normal brain, meningioma, and glioma and investigated astrocyte biomechanical behavior by measuring cell-substrate tractions and cell-cell intercellular stresses utilizing traction force microscopy and monolayer stress microscopy, respectively. Our findings showed an increase in traction forces, average normal intercellular stress, maximum shear intercellular stress, and strain energy proportional to increased substrate stiffness. A substrate stiffness of 4 kPa showed 2.1 fold increase in rms tractions, 1.8 fold increase in maximum shear stress, 2.6 fold increase in average normal stress, and 1.6 fold increase in strain energy. While 11 kPa showed a 4.6 fold increase in rms tractions, 6.6 fold increase in maximum shear stress, 5.2 fold increase in average normal stress, and 2.3 fold increase in strain energy. Cell velocity, on the other hand, showed a decreasing trend with increasing stiffness. This study demonstrates for the first time that astrocytes can bear intercellular stresses and that astrocyte intercellular stresses and traction can be modified using substrate stiffness. We believe this study will be of great importance to brain pathology, specifically as it relates to treatment methods for brain tumors.
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Date Issued
2018
Identifier
CFE0007312, ucf:52126
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007312
Energy Expenditure and Stability During Self-Paced Walking on Different Slopes
Title
Energy Expenditure and Stability During Self-Paced Walking on Different Slopes.
Creator
Raffaelli, Alanna, Huang, Helen, Fu, Qiushi, Kassab, Alain, University of Central Florida
Abstract / Description
Metabolic power and cost of transport (COT) are common quantifiers for effort when performing tasks including walking and running. Most studies focus on using a range of normal walking speeds over level ground or varied slopes. However, these studies use fixed-speed conditions. Fatigue, stability, metabolic expenditure, heart rate, and many other factors contribute to normal walking speed varying over time. This study aimed to show that allowing a subject to walk with a self-paced speed...
Show moreMetabolic power and cost of transport (COT) are common quantifiers for effort when performing tasks including walking and running. Most studies focus on using a range of normal walking speeds over level ground or varied slopes. However, these studies use fixed-speed conditions. Fatigue, stability, metabolic expenditure, heart rate, and many other factors contribute to normal walking speed varying over time. This study aimed to show that allowing a subject to walk with a self-paced speed should correlate to a minimum COT at a given slope. This study also aimed to determine if a preferred slope exists based on minimizing metabolic expenditure or maximizing stability. In this study, subjects walked at four different speed conditions including three fixed speeds (0.75 m/s, 1.0 m/s, 1.25 m/s) and their self-paced speed at five different slopes (-6(&)deg;, -3(&)deg;, 0(&)deg;, 3(&)deg;, 6(&)deg;) while metabolic energy expenditure and motion were recorded. The minimum COT occurred at a 3(&)deg; decline. At this slope, some subjects preferred to walk at a faster speed compared to level ground, whereas other subjects walked with a slower speed compared to level ground. Thus, there was a greater range of self-paced speeds, from 0.745 m/s-2.045 m/s. In comparison, at a 6(&)deg; incline, the range of self-paced speeds was much smaller, from 0.767 m/s-1.434 m/s. The variance among self-paced speeds and slope conditions between subjects suggests that COT, alone, does not explain walking decisions; stability might play a greater role than initially believed. These results provide greater insight into why humans choose to walk at a certain speed over a range of slopes and terrains.
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Date Issued
2019
Identifier
CFE0007515, ucf:52629
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007515
AN INVESTIGATION OF THE EVOLUTION OF THE MINIMALIST SHOETHROUGH A REVIEW OF RESEARCH LITERATURE
Title
AN INVESTIGATION OF THE EVOLUTION OF THE MINIMALIST SHOETHROUGH A REVIEW OF RESEARCH LITERATURE.
Creator
Sommarvong, Samantha, Fisher, Thomas, University of Central Florida
Abstract / Description
As an investigation of the evolution of the minimalist shoes, the purpose of this thesis was to examine popularity trends of the rise and fall of the minimalist movement. By evaluating the history and research behind the designs of the minimalist shoes, this thesis viewed the peak in popularity when minimalist shoes first made their debut. Initially, footwear sales skyrocketed upon its introduction. Its popularity grew due the prospective effects of improving athletic performance and the...
Show moreAs an investigation of the evolution of the minimalist shoes, the purpose of this thesis was to examine popularity trends of the rise and fall of the minimalist movement. By evaluating the history and research behind the designs of the minimalist shoes, this thesis viewed the peak in popularity when minimalist shoes first made their debut. Initially, footwear sales skyrocketed upon its introduction. Its popularity grew due the prospective effects of improving athletic performance and the possibility of decreasing the prevalence of running-related injuries. To understand the sales trends of the footwear industry, various shoe examples from the different categories of footwear padding were also examined. Hence, after learning more about each type of footwear, it is crucial to understand how to transition safely and without injury. Injury prevalence has been suggested to be associated with the change in biomechanics involved with changing a runner's footwear. Through the review of research literature on the subject, 33 sources of peer-reviewed studies, found via Google Scholar or EBSCOHost using select key word searches, were taken into account. After reviewing the results and conclusions, a common finding suggest that more research is needed to come to clear consensus. There is not enough evidence to suggest that the use of minimalist shoes either lowered the risk of injury or improved performance. Hence, the decline of minimalist movement may have been due to the unfulfilled benefits that were proposed. After consumers did not reap the benefits of transitioning to minimalist shoes, sales trends continued to fall.
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Date Issued
2015
Identifier
CFH0004905, ucf:45495
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004905
Mechanism of Hip Dysplasia and Identification of the Least Energy Path for its Treatment by using the Principle of Stationary Potential Energy
Title
Mechanism of Hip Dysplasia and Identification of the Least Energy Path for its Treatment by using the Principle of Stationary Potential Energy.
Creator
Zwawi, Mohammed abdulwahab m, Moslehy, Faissal, Kassab, Alain, Mansy, Hansen, Divo, Eduardo, University of Central Florida
Abstract / Description
Developmental dysplasia of the hip (DDH) is a common newborn condition where the femoral head is not located in its natural position in the acetabulum (hip socket). Several treatment methods are being implemented worldwide to treat this abnormal condition. One of the most effective methods of treatment is the use of Pavlik Harness, which directs the femoral head toward the natural position inside the acetabulum. This dissertation presents a developed method for identifying the least energy...
Show moreDevelopmental dysplasia of the hip (DDH) is a common newborn condition where the femoral head is not located in its natural position in the acetabulum (hip socket). Several treatment methods are being implemented worldwide to treat this abnormal condition. One of the most effective methods of treatment is the use of Pavlik Harness, which directs the femoral head toward the natural position inside the acetabulum. This dissertation presents a developed method for identifying the least energy path that the femoral head would follow during reduction. This is achieved by utilizing a validated computational biomechanical model that allows the determination of the potential energy, and then implementing the principle of stationary potential energy. The potential energy stems from strain energy stored in the muscles and gravitational potential energy of four rigid-body components of lower limb bones. Five muscles are identified and modeled because of their effect on DDH reduction. Clinical observations indicate that reduction with the Pavlik Harness occurs passively in deep sleep under the combined effects of gravity and the constraints of the Pavlik Harness.A non-linear constitutive equation, describing the passive muscle response, is used in the potential energy computation. Different DDH abnormalities with various flexion, abduction, and hip rotation angles are considered, and least energy paths are identified. Several constraints, such as geometry and harness configuration, are considered to closely simulate real cases of DDH. Results confirm the clinical observations of two different pathways for closed reduction. The path of least energy closely approximated the modified Hoffman-Daimler method. Release of the pectineus muscle favored a more direct pathway over the posterior rim of the acetabulum. The direct path over the posterior rim of the acetabulum requires more energy. This model supports the observation that Grade IV dislocations may require manual reduction by the direct path. However, the indirect path requires less energy and may be an alternative to direct manual reduction of Grade IV infantile hip dislocations. Of great importance, as a result of this work, identifying the minimum energy path that the femoral head would travel would provide a non-surgical tool that effectively aids the surgeon in treating DDH.?
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Date Issued
2015
Identifier
CFE0006022, ucf:51000
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006022
Treatment-Specific Approaches for Analysis and Control of Left Ventricular Assist Devices
Title
Treatment-Specific Approaches for Analysis and Control of Left Ventricular Assist Devices.
Creator
Farag Allah, George, Simaan, Marwan, Qu, Zhihua, Haralambous, Michael, Kassab, Alain, Divo, Eduardo, University of Central Florida
Abstract / Description
A Left Ventricular Assist Device (LVAD) is a mechanical pump that helps patients with heart failure conditions. This rotary pump works in parallel to the ailing heart and provides an alternative path for blood flow from the weak left ventricle to the aorta. The LVAD is controlled by the power supplied to the pump motor. An increase in the pump motor power increases the pump speed and the pump flow. The LVAD is typically controlled at a fixed setting of pump power. This basically means that...
Show moreA Left Ventricular Assist Device (LVAD) is a mechanical pump that helps patients with heart failure conditions. This rotary pump works in parallel to the ailing heart and provides an alternative path for blood flow from the weak left ventricle to the aorta. The LVAD is controlled by the power supplied to the pump motor. An increase in the pump motor power increases the pump speed and the pump flow. The LVAD is typically controlled at a fixed setting of pump power. This basically means that the controller does not react to any change in the activity level of the patient. An important engineering challenge is to develop an LVAD feedback controller that can automatically adjusts its pump motor power so that the resulting pump flow matches the physiological demand of the patient. To this end, the development of a mathematical model that can be used to accurately simulate the interaction between the cardiovascular system of the patient and the LVAD is essential for the controller design. The use of such a dynamic model helps engineers and physicians in testing their theories, assessing the effectiveness of prescribed treatments, and understanding in depth the characteristics of this coupled bio-mechanical system.The first contribution of this dissertation is the development of a pump power-based model for the cardiovascular-LVAD system. Previously, the mathematical models in the literature assume availability of the pump speed as an independent control variable. In reality, however, the device is controlled by pump motor power which, in turn, produces the rotational pump speed. The nonlinear relationship between the supplied power and the speed is derived, and interesting observations about the pump speed signal are documented.The second contribution is the development of a feedback controller for patients using an LVAD as either a destination therapy or a bridge to transplant device. The main objective of designing this controller is to provide a physiological demand of the patient equivalent of that of a healthy individual. Since the device is implanted for a long period of time, this objective is chosen to allow the patient to live a life as close to normal as possible.The third contribution is an analysis of the aortic valve dynamics under the support of an LVAD. The aortic valve may experiences a permanent closure when the LVAD pump power is increased too much. The permanent closure of the aortic valve can be very harmful to the patients using the device as a bridge to recovery treatments. The analysis illustrates the various changes in the hemodynamic variables of the patient as a result of aortic valve closing. The results establish the relationship between the activity level and the heart failure severity with respect to the duration of the aortic valve opening.
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Date Issued
2014
Identifier
CFE0005491, ucf:50354
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005491
"TECHNIQUE ARMS THE IMAGINATION" DEVELOPING AN ACTING THEORY BEST SUITED FOR MOTION CAPTURE PERFORMANCE AND THE CREATION OF A VIRTUAL CHARACTER
Title
"TECHNIQUE ARMS THE IMAGINATION" DEVELOPING AN ACTING THEORY BEST SUITED FOR MOTION CAPTURE PERFORMANCE AND THE CREATION OF A VIRTUAL CHARACTER.
Creator
Rogers, Brendan, Niess, Christopher, University of Central Florida
Abstract / Description
"The untrained body, like the sculptor's marble, can express nothing but its own limitations" (Lust 70). As acting styles have changed through the years, corresponding schools of thought have arisen to prepare performers for their unique challenges. Perhaps the goal of producing a "gripping performance," one in which the audience is truly invested, has remained the same since the time of Thespis. How one arrives at this desired result, however, has varied greatly through the ages. Techniques,...
Show more"The untrained body, like the sculptor's marble, can express nothing but its own limitations" (Lust 70). As acting styles have changed through the years, corresponding schools of thought have arisen to prepare performers for their unique challenges. Perhaps the goal of producing a "gripping performance," one in which the audience is truly invested, has remained the same since the time of Thespis. How one arrives at this desired result, however, has varied greatly through the ages. Techniques, not surprisingly, tend to build on previous theories, beliefs and practices. Etienne Decroux's corporeal mime technique builds on the teachings of Jacques Copeau, but as a result, takes the art form into a radically new direction. Vsevolod Meyerhold studied with Stanislavski, learning his inside-out approach to performance, and, with biomechanics, creates a performance technique that turns Stanislavski's approach on its head. The point is not that these theorists developed something that undermines the previous work, but that they built their theories from knowledge of older techniques. In essence, these theorists learned from the past to prepare for the future. Advancements in film technology have dramatically changed both the nature of film, and performance, itself. Computer-generated characters and environments are becoming more commonplace in film due to the flexibility they provide in composing shots, and the relatively low price tag that comes with them. Technology still can't replace the subtlety that comes from a human performance, so currently, actors find themselves in the unique position of having one foot in the real world and the other foot in the virtual world. The motion-capture process, or moCap, is the best example of this unique relationship. By placing sensors at key joints on an actor's body, their performance can be tracked by a computer and then directly applied to a computer-generated model (Hooks 30). In a sense, it's digital puppetry. Because only the movements are being recorded and not the actor's physical appearance, performers can play parts that are not necessarily their physical type or even their own species. Director Peter Jackson cast Andy Serkis to play a forty-foot-tall ape in the 2005 remake of King Kong, and thanks to the motion-capture process, the result is a perfect blend of live acting and computer-generated graphics. The relatively low cost and flexibility of this process has made it available, not just to filmmakers in Hollywood, but also to the independent market. I am currently directing a feature length film that utilizes both computergenerated backgrounds and virtual characters accomplished through the motion-capture process. This production has been in the works since I started graduate school. As I learn more and more about specific acting techniques in class, I am always looking for something that I could apply specifically to motion-capture performance. Currently there is little research on the topic and certainly, there's no specific acting theory that applies to this medium. In this paper I hope to formulate an acting technique that is tailored for the field of motion-capture performance, building upon theories of the past. Further study in this technique will better prepare future performers in this field, as well as provide insights for directors new to the medium. The following three techniques in particular, each with their emphasis on an outside-in approach to acting, will provide the basis for this theory: Meyerhold's biomechanics; Decroux's corporeal mime; and Edward Gordon Craig's uber-marionette concept. I will provide detailed sections on each one of these approaches, discussing the theoretical sides of each, as well as specific exercises students in these schools are asked to perform. Next, I will provide a detailed section on the motion-capture process, discussing how it works and the challenges it presents to performers. Finally I will apply each one of the three theories to the motion-capture process, finding points where the theories apply and also where they fall short. By choosing specifically what applies to the moCap process from each one of the techniques, we will be left with a new theory that specifically relates to virtual performance. This will not only serve as an invaluable guide to both future performers and directors entering the field of motion capture, but will hopefully be the beginnings of an acting theory that can bring performance education programs into the 21st century. Working in the virtual realm requires a performer to use his imagination, but having training and knowledge in theories of the past will mean the imagination is not the only thing actors have to work with.
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Date Issued
2011
Identifier
CFE0003975, ucf:48679
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003975
Inverse-Consistent Determination of Young's Modulus of Human Lung
Title
Inverse-Consistent Determination of Young's Modulus of Human Lung.
Creator
Seyfi Noferest, Behnaz, Ilegbusi, Olusegun, Santhanam, Anand, Kassab, Alain, Moslehy, Faissal, University of Central Florida
Abstract / Description
Human lung undergoes respiration-induced deformation due to sequential inhalation and exhalation. Accurate determination of lung deformation is crucial for tumor localization and targeted radiotherapy in patients with lung cancer. Numerical modeling of human lung dynamics based on underlying physics and physiology enables simulation and virtual visualization of lung deformation. Dynamical modeling is numerically complicated by the lack of information on lung elastic behavior, structural...
Show moreHuman lung undergoes respiration-induced deformation due to sequential inhalation and exhalation. Accurate determination of lung deformation is crucial for tumor localization and targeted radiotherapy in patients with lung cancer. Numerical modeling of human lung dynamics based on underlying physics and physiology enables simulation and virtual visualization of lung deformation. Dynamical modeling is numerically complicated by the lack of information on lung elastic behavior, structural heterogeneity as well as boundary constrains. This study integrates physics-based modeling and image-based data acquisition to develop the patient-specific biomechanical model and consequently establish the first consistent Young's modulus (YM) of human lung. This dissertation has four major components: (i) develop biomechanical model for computation of the flow and deformation characteristics that can utilize subject-specific, spatially-dependent lung material property; (ii) develop a fusion algorithm to integrate deformation results from a deformable image registration (DIR) and physics-based modeling using the theory of Tikhonov regularization; (iii) utilize fusion algorithm to establish unique and consistent patient specific Young's modulus and; (iv) validate biomechanical model utilizing established patient-specific elastic property with imaging dataThe simulation is performed on three dimensional lung geometry reconstructed from four-dimensional computed tomography (4DCT) dataset of human subjects. The heterogeneous Young's modulus is estimated from a linear elastic deformation model with the same lung geometry and 4D lung DIR. The biomechanical model adequately predicts the spatio-temporal lung deformation, consistent with data obtained from imaging. The accuracy of the numerical solution is enhanced through fusion with the imaging data beyond the classical comparison of the two sets of data. Finally, the fused displacement results are used to establish unique and consistent patient-specific elastic property of the lung.
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Date Issued
2015
Identifier
CFE0006391, ucf:51512
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006391
Biomechanical Models of Human Upper and Tracheal Airway Functionality
Title
Biomechanical Models of Human Upper and Tracheal Airway Functionality.
Creator
Kuruppumullage, Don Nadun, Ilegbusi, Olusegun, Kassab, Alain, Moslehy, Faissal, Santhanam, Anand, Mansy, Hansen, Hoffman Ruddy, Bari, University of Central Florida
Abstract / Description
The respiratory tract, in other words, the airway, is the primary airflow path for several physiological activities such as coughing, breathing, and sneezing. Diseases can impact airway functionality through various means including cancer of the head and neck, Neurological disorders such as Parkinson's disease, and sleep disorders and all of which are considered in this study. In this dissertation, numerical modeling techniques were used to simulate three distinct airway diseases: a weak...
Show moreThe respiratory tract, in other words, the airway, is the primary airflow path for several physiological activities such as coughing, breathing, and sneezing. Diseases can impact airway functionality through various means including cancer of the head and neck, Neurological disorders such as Parkinson's disease, and sleep disorders and all of which are considered in this study. In this dissertation, numerical modeling techniques were used to simulate three distinct airway diseases: a weak cough leading to aspiration, upper airway patency in obstructive sleep apnea, and tongue cancer in swallow disorders. The work described in this dissertation, therefore, divided into three biomechanical models, of which fluid and particulate dynamics model of cough is the first. Cough is an airway protective mechanism, which results from a coordinated series of respiratory, laryngeal, and pharyngeal muscle activity. Patients with diminished upper airway protection often exhibit cough impairment resulting in aspiration pneumonia. Computational Fluid Dynamics (CFD) technique was used to simulate airflow and penetrant behavior in the airway geometry reconstructed from Computed Tomography (CT) images acquired from participants. The second study describes Obstructive Sleep Apnea (OSA) and the effects of dilator muscular activation on the human retro-lingual airway in OSA. Computations were performed for the inspiration stage of the breathing cycle, utilizing a fluid-structure interaction (FSI) method to couple structural deformation with airflow dynamics. The spatiotemporal deformation of the structures surrounding the airway wall was predicted and found to be in general agreement with observed changes in luminal opening and the distribution of airflow from upright to supine posture. The third study describes the effects of cancer of the tongue base on tongue motion during swallow. A three-dimensional biomechanical model was developed and used to calculate the spatiotemporal deformation of the tongue under a sequence of movements which simulate the oral stage of swallow.
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Date Issued
2018
Identifier
CFE0007034, ucf:51986
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007034