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Undergraduate Research Opportunities Program

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Office of Undergraduate Education

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Now showing 1 - 10 of 75

The influence of rocker profile footwear on rollover during walking

(Georgia Institute of Technology, 2014-05-05) Oludare, Simisola O.

Rocker profiles are one of the most commonly prescribed footwear modifications provided to individuals with impaired rollover. Impaired rollover is caused due to loss of neuromuscular function (i.e. stoke) or orthotic ankle constraint. When rollover is impaired, continued forward progression is interrupted and walking gait becomes less efficient (i.e. increased energy expenditure). Rocker profile footwear modifications are designed to mimic the functions of the anatomical ankle-foot rockers and provide its users with a smooth and efficient rollover. However, while there is theory governing the design of a rocker profile and subjective descriptions of rocker profile function, the extent to which a rocker profile footwear provides rollover has not yet been quantified. The aim of this study was to quantify effective and ineffective rollover and test whether our rocker profile provides effective rollover. We hypothesized that healthy subjects (n=4) walking with orthotic ankle constraint and the rocker profile (STOP) would have no change in rollover and energy expenditure outputs compared to walking with orthotic ankle free and rocker profile (FREE); but that healthy subjects (n=4) walking in STOP would have a change in rollover and energy expenditure outputs compared to walking with orthotic ankle constraint and no rocker profile (STOP-NR). To test this hypothesis, rollover was quantified as stance phase duration, cadence and radius of curvature and energy expenditure was quantified as heart rate and rating of perceived exertion. In addition to these outputs, we analyzed the ground reaction forces and duration of stance in early, middle and late stance period to determine the effects of the rocker profile footwear components. Through the rollover and energy expenditure outputs of the STOP, FREE and STOP-NR conditions, we quantified effective rollover as 0.29 (0.01) radius of curvature with a heart rate of 110.5(6.7) bpm and ineffective rollover as 0.69(0.12) radius of curvature with a heart rate of 131.5 (8.1) bpm. By creating this scale, we were able to determine that our rocker profile provided effective rollover (0.34[0.04] radius of curvature with a heart rate of 111.3[8.3] bpm). However, a future study with a greater sample size is needed to confirm these results.
Metro-Atlanta Parents' Roles in Technology Education and Their Advantages

(Georgia Institute of Technology, 2014-05-05) Reid, Cecili

In this study, 15 interviews with parents from low-income areas were evaluated to understand the roles these parents fulfilled in their child’s technology education. Of the 15 parents initially interviewed, three parents were contacted and interviewed within a year after an education and computer workshop to understand if this intervention impacted their roles. From the initial interviews, the parents stated that they have not aided in the development of their child’s technology education. However, parents did indicate they were involved in various other aspects of their children’s education and they express interest in being more involved. Although the parents participation in the workshop did not drastically alter their roles in their children’s education, the workshop is a starting point for how to further involve parents in the technology education of their children. Expanding the role of parents in low-income areas could prove pivotal in the field of computer science education to both increase interest in computing and to help prepare students better for future course work in computing.
State Space Partitions of Stochastic Chaotic Maps

(Georgia Institute of Technology, 2014-05-05) Heninger, Jeffrey M.

The finest resolution that can be achieved in any real chaotic system is limited by the presence of noise. This noise can be used to define neighborhoods of the deterministic periodic orbits using the local eigenfunctions of the Fokker-Planck operator and its adjoint. We extend the work of D. Lippolis to include hyperbolic periodic orbits. The dynamics along the stable and unstable directions are separated. The neighborhoods on the stable and unstable manifolds can be defined in the same way as the neighborhoods for entirely stable or entirely unstable orbits. The neighborhoods are then returned to the original coordinates. The Fokker-Planck evolution can be described as a finite Markov transition graph between these neighborhoods. Its spectral determinant is used to calculate the time averages of observables. We apply this technique to calculate long time observables of the Lozi map.
Improvements to the bioartificial pancreas: characterizing an encapsulation material and studying the effects of hypoxia on islet functions

(Georgia Institute of Technology, 2014-05-05) Le, Thuy

Diabetes is a metabolic disease in which a person has high blood sugar resulting from one of two ways: the pancreas not producing enough insulin to maintain normal blood sugar levels or insulin resistance. It is a major health problem that affects approximately 23.6 million people in the United States, 27% of which (about 6.4 million people) have become insulin-dependent. Without proper regulation, deviations from normoglycemia increases risk for heart disease, kidney failure, blindness, and nerve damage. To further understand how to improve bioartificial pancreas development, this thesis focuses on two aims: 1) characterizing PEGylated beads by stability and insulin diffusivity in order to refine the encapsulation material and 2) determining the effects of oxygen availability on the function of encapsulated adult porcine and neonatal porcince islets. For the first aim, the paper hypothesizes that PEGylating, or covalently binding poly(ethylene glycol) [PEG], the AP hydrogels will help reduce the fibrotic adhesion due to the steric hindrance effects of the PEG compound. In order to prevent fibrotic overgrowth, the PEG layer must be stable. However, to achieve the main goal of the bioartificial pancreas, the PEG layer should not affect the insulin diffusivity compared with AP capsules. The second aim studied the effects of oxygen availability on encapsulated islets to enhance our understanding of the functions of islets under hypoxic conditions. This experiment will look at total protein content as a relationship to protein synthesis, the ratio of insulin secretion to intracellular insulin content, and metabolic activity of encapsulated cells exposed to different oxygen levels.
Review study on left atrial appendage occlusion and current implant devices

(Georgia Institute of Technology, 2014-05-05) Moon, Young Suk

Stroke and heart-related diseases are one of the leading causes of deaths in United States. There are many factors that may cause stroke, and left atrial appendage coagulation is one of them. Left atrial appendage coagulation is a coagulation of blood inside the left atrial appendage caused by atrial fibrillation, not rhythmical contraction of your heart muscle. For left atrial appendage, not like other heart defects, anti-coagulant currently is only solution to solve this problem. There isn’t any implant device solution specific for left atrial appendage occlusion. However, there are some devices that are currently going through FDA approval process. These are Watchman and Lariat. According to interviews performed with cardiac specialists throughout Atlanta, they are emphasizing three major factors. They are stability, customizability, and full occlusion. Limitations of Watchman and Lariat are customizability and full occlusion. To satisfy all three factors and to improve from Lariat and Watchman, Flow Medical has come up with innovative left atrial appendage occlusion balloon.
Thin, flexible PDMS microfluidic pump actuated by compressive and bending force

(Georgia Institute of Technology, 2014-05-02) Han, Hyungtak

Microfluidic pumps have many possible applications in the field of medine. This thesis will discuss the design and fabrication of thin PDMS microfluidic pumps that are actuated by mechanical forces resulting from compression and bending motion. The thin PDMS pumps were fabricated using replica molding and laser machining using standard PDMS mixtures to create flexible pumps. Pumps of different sizes and aspect ratios were fabricated to study the effects of geometry on the flow rate performance and the actuation force. Flow experiments were conducted to test the performance of the thin PDMS pumps. Flow rates range from 18.2 - 35.2 µL per compression and 1.8 - 11.9 µL per bend. Results indicate possible approaches to designing an efficient, simple-to-use, and electricity-free microfluidic pump.
Green route to green energy: C-H activation of diflourinated benzothiadiazole as a dye creation for dye-sensitized solar cells

(Georgia Institute of Technology, 2014-05-02) Rojas, Anthony Jose

Controlling sensitizer structures and synthetic routes for synthesis of dyes on a nanocrystaline TiO2 surface is important for facilitating charge transfer, limiting charge recombination, and reducing costs in organic solar cells. We successfully developed and employed C-H activation methods for 5,6-difluoro-2,1,3-benzothiadiazole to synthesize a dye, limiting the route to subsequent steps and reducing waste. Additionally, we substituted the commonly used π-bridge, thiophene, for a more aggregating-preventative cyclopentadithiophene with 2 hexyl groups flanking out of the conjugated plane to construct a novel D−A−π−A-featuring dye, AR-II-13. The dye had of several beneficial characteristics: (i) extended absorption bands to dyes of similar construct effectively decrease the HOMO-LUMO band gap; (ii) the elaborate structure efficiently limits the recombination of electrons in TiO2 and electrolyte. The dye-sensitized solar cell device created using AR-II-13 exhibited promising power conversion efficiency of up to 6.6 +/- 0.1%, based on preliminary findings, with a short-circuit current density (Jsc) of 12.7 mA cm−2, an open-circuit voltage (Voc) of 0.73 V, and a fill factor (FF) of 0.712 under AM 1.5 illumination (100 mW cm−2). The combination of each donor/acceptor moiety to the difluorinated benzothiadiazole bridge using C-H activation demonstrated the success possible in these types of reactions by producing high yields, even on unsymmetrical dyes. The successful C-H activation implementation on this type of molecule towards creating a functional unit is especially intriguing as it reduces waste and cost of materials.
Chronically elevating spontaneous activity in cultured neuronal networks results in distint homeostatic changes

(Georgia Institute of Technology, 2014-05-02) Law, Rachel Candace

During the first few weeks in vitro, cultured neuronal networks exhibit spontaneous bursts of action potentials, even in the absence of external input [10]. Pharmacological intervention, as well as electrical stimulation provide a direct means for chronically elevating this spontaneous network activity and allow the study of homeostatic plasticity [3, 8]. In this study, embryonic day 18 rat cortical neurons were dissociated and grown on multi-electrode arrays (MEAs). During the third week in vitro, activity was chronically increased for 24 hours by disinhibiting the network using a GABA_A receptor antagonist, or by electrically stimulating the network using the MEA. Spiking activity was continuously recorded through the MEA before, during, and after each perturbation, and the frequency of spontaneous population bursts was obtained to give insight on how the overall network was affected. Chronic pharmacological blockade of GABA_A receptors increased culture burst frequency and after washing out the drug, a significant homeostatic reduction in bursting was observed. Meanwhile, the same increase in elevated burst frequency was attempted using distributed electrical stimulation. Although electrical stimulation did not increase activity in every trial, of the cultures that did experience elevated bursting, a surprisingly distinct homeostatic effect was seen. When compared to drug treated cultures that had similar increases in burst frequency, there was a significant difference in bursting immediately following treatment ending. These experiments may help improve our knowledge of clinical interventions where neural tissue is subject to chronic electrical stimulation, as well as identify the consequences of these therapeutic approaches.
Leg, vertical, and joint stiffness levels in rear-foot and fore-foot strike landings

(Georgia Institute of Technology, 2014-05-02) Gainer, Allison Nichol

Bouncing gait, specifically hopping, running, and jumping, involves a complex combination of legs, joints, muscles, and nerves coordinated to perform simple biomechanical tasks. The findings associated with spring-mass modeling of bouncing gait suggest that hopping and running humans maintain center of mass (CoM) motions by adjusting vertical leg stiffness. Overall, lower extremity stiffness increases with the demands of the activity such as increased hopping frequency, hopping or jumping height, and running speed, which are all associated with increased stiffness. The increase in leg, vertical, and joint stiffness occurs because as more physical demands are imparted on the body, greater resistance to movement is needed to produce controlled movements. Studies comparing fore-foot strike (FFS) and rear-foot strike (RFS) patterns in running and hopping have shown converse results regarding the contribution of knee and ankle joint stiffness levels in preserving total leg stiffness. It is known that fore-foot strike runners generate smaller collision forces than rear-foot strike runners. However, an understanding of how joint stiffness levels differ when in a fore-foot strike pattern compared to a rear-foot strike patterns is unknown. Moreover, it is unclear how leg, vertical, and joint stiffness are affected when humans run at increasing speeds with both a fore-foot and rear-foot strike pattern. Investigations that assess the relationship between strike patterns and changes in velocity are needed in order to clarify joint contributions to changes in performance tasks. We completed a study on vertical hopping, fore-foot strike running, and rear-foot strike running to determine how ankle and knee joint stiffness values vary across different performance tasks. Throughout the study, leg stiffness remained constant (P>0.05) and vertical stiffness increased as the step frequency increased (P<0.05). During the fore-foot strike running trials, there were greater increases in ankle joint stiffness in comparison to knee joint stiffness. This suggests that the knee joint was stiffer than the ankle joint throughout the fore-foot strike running performance. In contrast, there was a greater increase in knee joint stiffness than ankle joint stiffness throughout the rear-foot strike performance, which implies that the ankle joint was stiffer than the knee joint. The changes in joint stiffness levels across the two strike patterns could be attributed to the small decrease in knee excursion and increase in ankle excursion in the fore-foot strike pattern compared to the rear-foot strike pattern. Understanding how these joint-level responses to differentiating in tasks influence the stability of leg stiffness may aid robotic, lower limb prosthetic, and even running shoe design.
Viability of a novel stretchable microelectrode array for epimysial implantation

(Georgia Institute of Technology, 2014-05-02) Cheek, Ashton Leigh

Stretchable microelectrode arrays (sMEAs) have been identified for use as neuroprosthetics to treat paralysis. Previous research has focused on assessment of electrical viability and biocompatibility of a novel sMEA device design. However, the mechanical functionality of the device, when implanted epimysially, has yet to be characterized. The device consists of stainless steel arrowhead-shaped electrodes with barbs to promote adhesion to the surface of muscle. A polydimethylsiloxane (PDMS) substrate is used to promote conformation to the muscle surface and stretching of the device alongside muscle movement. Silver PDMS traces are used as stretchable circuits for the device. The adhesive ability of the device, the effect of the device on muscle contraction, and the tensile strain v. resistance relationship of the stretchable traces are assessed. The ninth electrode design is found to be the best design for adhesion of the device epimysially amongst eleven other electrode designs. Epimysial implantation of the device on cat gastrocnemius is not found to significantly affect muscle contraction. The silver PDMS traces are found to fail at 90% strains on average and resistance increases with strain. Stretching cycles of 50% strain are found to consistently increase the base resistance of traces.