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- Title
- ANALYTICAL AND NUMERICAL SOLUTIONS OF DIFFERENTIALEQUATIONS ARISING IN FLUID FLOW AND HEAT TRANSFER PROBLEMS.
- Creator
-
Sweet, Erik, Vajravelu, Kuppalapalle, University of Central Florida
- Abstract / Description
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The solutions of nonlinear ordinary or partial differential equations are important in the study of fluid flow and heat transfer. In this thesis we apply the Homotopy Analysis Method (HAM) and obtain solutions for several fluid flow and heat transfer problems. In chapter 1, a brief introduction to the history of homotopies and embeddings, along with some examples, are given. The application of homotopies and an introduction to the solutions procedure of differential equations (used in the...
Show moreThe solutions of nonlinear ordinary or partial differential equations are important in the study of fluid flow and heat transfer. In this thesis we apply the Homotopy Analysis Method (HAM) and obtain solutions for several fluid flow and heat transfer problems. In chapter 1, a brief introduction to the history of homotopies and embeddings, along with some examples, are given. The application of homotopies and an introduction to the solutions procedure of differential equations (used in the thesis) are provided. In the chapters that follow, we apply HAM to a variety of problems to highlight its use and versatility in solving a range of nonlinear problems arising in fluid flow. In chapter 2, a viscous fluid flow problem is considered to illustrate the application of HAM. In chapter 3, we explore the solution of a non-Newtonian fluid flow and provide a proof for the existence of solutions. In addition, chapter 3 sheds light on the versatility and the ease of the application of the Homotopy Analysis Method, and its capability in handling non-linearity (of rational powers). In chapter 4, we apply HAM to the case in which the fluid is flowing along stretching surfaces by taking into the effects of "slip" and suction or injection at the surface. In chapter 5 we apply HAM to a Magneto-hydrodynamic fluid (MHD) flow in two dimensions. Here we allow for the fluid to flow between two plates which are allowed to move together or apart. Also, by considering the effects of suction or injection at the surface, we investigate the effects of changes in the fluid density on the velocity field. Furthermore, the effect of the magnetic field is considered. Chapter 6 deals with MHD fluid flow over a sphere. This problem gave us the first opportunity to apply HAM to a coupled system of nonlinear differential equations. In chapter 7, we study the fluid flow between two infinite stretching disks. Here we solve a fourth order nonlinear ordinary differential equation. In chapter 8, we apply HAM to a nonlinear system of coupled partial differential equations known as the Drinfeld Sokolov equations and bring out the effects of the physical parameters on the traveling wave solutions. Finally, in chapter 9, we present prospects for future work.
Show less - Date Issued
- 2009
- Identifier
- CFE0002889, ucf:48017
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002889
- Title
- Analytical solutions to nonlinear differential equations arising in physical problems.
- Creator
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Baxter, Mathew, Vajravelu, Kuppalapalle, Li, Xin, Mohapatra, Ram, Shuai, Zhisheng, Kassab, Alain, University of Central Florida
- Abstract / Description
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Nonlinear partial differential equations are difficult to solve, with many of the approximate solutions in the literature being numerical in nature. In this work, we apply the Homotopy Analysis Method to give approximate analytical solutions to nonlinear ordinary and partial differential equations. The main goal is to apply different linear operators, which can be chosen, to solve nonlinear problems. In the first three chapters, we study ordinary differential equations (ODEs) with one or two...
Show moreNonlinear partial differential equations are difficult to solve, with many of the approximate solutions in the literature being numerical in nature. In this work, we apply the Homotopy Analysis Method to give approximate analytical solutions to nonlinear ordinary and partial differential equations. The main goal is to apply different linear operators, which can be chosen, to solve nonlinear problems. In the first three chapters, we study ordinary differential equations (ODEs) with one or two linear operators. As we progress, we apply the method to partial differential equations (PDEs) and use several linear operators. The results are all purely analytical, meaning these are approximate solutions that we can evaluate at points and take their derivatives.Another main focus is error analysis, where we test how good our approximations are. The method will always produce approximations, but we use residual errors on the domain of the problem to find a measure of error.In the last two chapters, we apply similarity transforms to PDEs to transform them into ODEs. We then use the Homotopy Analysis Method on one, but are able to find exact solutions to both equations.
Show less - Date Issued
- 2014
- Identifier
- CFE0005303, ucf:50527
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005303
- Title
- Dynamical Invariants and the Fluid Impulse in Plasma Models.
- Creator
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Michalak, Martin, Shivamoggi, Bhimsen, Mohapatra, Ram, Brennan, Joseph, Eastes, Richard, University of Central Florida
- Abstract / Description
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Much progress has been made in understanding of plasmas through the use of the MHD equations and newer models such as Hall MHD and electron MHD. As with most equations of fluid behavior, these equations are nonlinear, and no general solutions can be found. The use of invariant structures allows limited predictions of fluid behavior without requiring a full solution of the underlying equations. The use of gauge transformation can allow the creation of new invariants, while differential...
Show moreMuch progress has been made in understanding of plasmas through the use of the MHD equations and newer models such as Hall MHD and electron MHD. As with most equations of fluid behavior, these equations are nonlinear, and no general solutions can be found. The use of invariant structures allows limited predictions of fluid behavior without requiring a full solution of the underlying equations. The use of gauge transformation can allow the creation of new invariants, while differential geometry offers useful tools for constructing additional invariants from those that are already known. Using these techniques, new geometric, integral and topological invariants are constructed for Hall and electron MHD models. Both compressible and incompressible models are considered, where applicable. An application of topological invariants to magnetic reconnection is provided. Finally, a particular geometric invariant, which can be interpreted as the fluid impulse density, is studied in greater detail, its nature and invariance in plasma models is demonstrated, and its behavior is predicted in particular geometries under different models.
Show less - Date Issued
- 2013
- Identifier
- CFE0005382, ucf:50442
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005382
- Title
- GENETIC DIFFERENTIATION AMONG FLORIDA POPULATIONS OF DIADEMA ANTILLARUM.
- Creator
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Chandler, Luke M, Hoffman, Eric, University of Central Florida
- Abstract / Description
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This project used molecular genetic markers (microsatellites) to determine the amount of genetic diversity within populations and whether significant differentiation exists among Florida populations of the long-spined sea urchin, Diadema antillarum. Specifically, this project aimed to (1) compare genetic diversity of D. antillarum from six populations in south Florida ranging from Biscayne Bay, the Florida Keys, and Dry Tortugas, and (2) determine whether two broodstock populations of D....
Show moreThis project used molecular genetic markers (microsatellites) to determine the amount of genetic diversity within populations and whether significant differentiation exists among Florida populations of the long-spined sea urchin, Diadema antillarum. Specifically, this project aimed to (1) compare genetic diversity of D. antillarum from six populations in south Florida ranging from Biscayne Bay, the Florida Keys, and Dry Tortugas, and (2) determine whether two broodstock populations of D. antillarum contain variation indicative of native Florida populations. Together, these questions can address whether broodstock populations contain the genetic variation necessary to meet the Florida Fish and Wildlife Conservation Commission�s (FWC�s) genetic policies for reintroduction throughout south Florida. Global FST among native populations was 0.0004 with a highest pairwise FST of 0.0025 between the Upper Keys and the area west of Key West, showing an overall trend of little natural differentiation between populations. Global FST for all populations inclusive of the broodstock samples was 0.0019 with a highest pairwise FST between a native population and broodstock of 0.0066 between Dry Tortuga and Mote�s broodstock, indicating little differentiation resulting from captive breeding. Average allelic richness and heterozygosity ranged from 22.6�24.4 and 0.937�0.956, respectively, for each population. Two-way ANOVAs comparing genetic diversity between native and broodstock populations showed no statistical difference in allelic richness (F= 3.892, p= 0.0535) or heterozygosity (F=1.43, p=0.237). The computer program STRUCTURE estimated the most likely number of genetic clusters to be k=1, inclusive of broodstock populations, further indicating a lack of differentiation either among native populations or between native and broodstock populations. These data suggest that captive-bred individuals of D. antillarum could be used for reintroduction as part of a plan to re-establish healthy urchin populations throughout the Florida Keys.
Show less - Date Issued
- 2016
- Identifier
- CFH2000044, ucf:45558
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000044
- Title
- Modeling Network Worm Outbreaks.
- Creator
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Foley, Evan, Shuai, Zhisheng, Kaup, David, Nevai, A, University of Central Florida
- Abstract / Description
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Due to their convenience, computers have become a standard in society and therefore, need the utmost care. It is convenient and useful to model the behavior of digital virus outbreaks that occur, globally or locally. Compartmental models will be used to analyze the mannerisms and behaviors of computer malware. This paper will focus on a computer worm, a type of malware, spread within a business network. A mathematical model is proposed consisting of four compartments labeled as Susceptible,...
Show moreDue to their convenience, computers have become a standard in society and therefore, need the utmost care. It is convenient and useful to model the behavior of digital virus outbreaks that occur, globally or locally. Compartmental models will be used to analyze the mannerisms and behaviors of computer malware. This paper will focus on a computer worm, a type of malware, spread within a business network. A mathematical model is proposed consisting of four compartments labeled as Susceptible, Infectious, Treatment, and Antidotal. We shall show that allocating resources into treating infectious computers leads to a reduced peak of infections across the infection period, while pouring resources into treating susceptible computers decreases the total amount of infections throughout the infection period. This is assuming both methods are receiving resources without loss. This result reveals an interesting notion of balance between protecting computers and removing computers from infections, ultimately depending on the business executives' goals and/or preferences.
Show less - Date Issued
- 2015
- Identifier
- CFE0005948, ucf:50816
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005948
- Title
- BMP-7 Inhibits p38 and JNK Pathways and Increases M2 Macrophage Differentiation to Reduce Atherosclerosis in Apolipoprotein E-/- Mice.
- Creator
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Shoulders, Heidi, Singla, Dinender, Cheng, Zixi, Naser, Saleh, University of Central Florida
- Abstract / Description
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We have previously shown that treating atherosclerosis with bone morphogenetic protein-7 (BMP-7) affects the presence of macrophage subtypes in vitro, however it remains unknown whether BMP-7 treatment affects development and progression of atherosclerosis in vivo at an early and mid-stage of the disease. We therefore performed a Day 5 (D5) and Day 28 (D28) study to examine BMP-7's potential to affect monocyte differentiation. Atherosclerotic plaque formation was developed using our standard...
Show moreWe have previously shown that treating atherosclerosis with bone morphogenetic protein-7 (BMP-7) affects the presence of macrophage subtypes in vitro, however it remains unknown whether BMP-7 treatment affects development and progression of atherosclerosis in vivo at an early and mid-stage of the disease. We therefore performed a Day 5 (D5) and Day 28 (D28) study to examine BMP-7's potential to affect monocyte differentiation. Atherosclerotic plaque formation was developed using our standard method and ApoE-/- mice were sacrificed at D5 and D28 post-surgery. Treatment animals received intravenous injections of BMP-7 at 200(&)#181;g/kg of bodyweight. Hematoxylin and Eosin morphological stain shows that BMP-7 is capable of significantly reducing plaque accumulation at D28 post-surgery vs. PLCA group, p(<)0.05. At D5, plaque formation was reduced but not significant. Immunohistochemistry staining was performed to determine BMP-7's effect on monocytes (CD14), inflammatory M1 (iNOS) and anti-inflammatory M2 (CD206, Arginase-1) macrophages. Immunohistochemistry results show BMP-7 administration reduced pro-inflammatory monocytes and M1 macrophages at D5 and D28 compared to PLCA animals; however, monocytes were not statistically lower at D28. The anti-inflammatory M2 macrophage population was significantly less in PLCA animals compared to SHAM animals at D5 and D28. There was no significant difference in M2 macrophages between PLCA and PLCA + BMP7 animals at D5, however, by D28, PLCA + BMP7 animals showed a significant increase in M2 macrophages compared to PLCA animals. Western blot analysis confirms a significant increase in pro-survival kinase ERK and a significant reduction in pro-inflammatory kinases p38 and JNK in BMP-7 treated mice (D5 and D28, p(<)0.05). ELISA showed a significant reduction in pro-inflammatory cytokines IL-6, MCP-1, and TNF-? (D5 and D28, p(<)0.05) and a significant increase in anti-inflammatory cytokine IL-10 in BMP-7 treated mice (D5 and D28, p(<)0.05). In summary, our data indicate BMP-7 treatment induces monocyte to M2 macrophage differentiation, increases anti-inflammatory cytokine levels (IL-1ra and IL-10), and improves blow flow velocity (D5 and D28, p(<)0.05) compared to untreated animals. The mechanisms of monocyte to M2 macrophage differentiation appear to be mediated by the p38, JNK, and ERK pathways. This study suggests BMP-7 is capable of reducing inflammation and slowing progression of atherosclerosis at both an early and mid-stage of the disease.
Show less - Date Issued
- 2016
- Identifier
- CFE0006504, ucf:51388
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006504
- Title
- Character Evolution and Microbial Community Structure in a Host-associated Grasshopper.
- Creator
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Raszick, Tyler, Song, Hojun, Fedorka, Kenneth, Hoffman, Eric, University of Central Florida
- Abstract / Description
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The spotted bird grasshopper, Schistocerca lineata Scudder (Orthoptera: Acrididae), is a widely distributed species found throughout most of the continental United States and southern Canada. This species is known to be highly variable in morphology, with many distinct ecotypes across its native range. These ecotypes display high levels of association with type-specific host plants. Understanding the evolutionary relationships among different ecotypes is crucial groundwork for studying the...
Show moreThe spotted bird grasshopper, Schistocerca lineata Scudder (Orthoptera: Acrididae), is a widely distributed species found throughout most of the continental United States and southern Canada. This species is known to be highly variable in morphology, with many distinct ecotypes across its native range. These ecotypes display high levels of association with type-specific host plants. Understanding the evolutionary relationships among different ecotypes is crucial groundwork for studying the process of ecological differentiation. I examine four ecotypes from morphological and phylogeographic perspectives, and look for evidence of distinct evolutionary lineages within the species. I also begin to explore the potential role of the microbial community of these grasshoppers in ecological divergence by using 454 pyrosequencing to see if the microbial community structure reflects the ecology of the grasshoppers. I find support for a distinct aposematic lineage when approaching the data from a phylogeographic perspective and also find that this ecotype tends to harbor a unique bacterial community, different from that of a single other ecotype.
Show less - Date Issued
- 2014
- Identifier
- CFE0005540, ucf:50316
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005540
- Title
- STUDIES ON THE NOVEL FUNCTION OF AMYLOID PRECURSOR PROTEIN IN GLIAL DIFFERENTIATION OF NEURAL STEM CELLS.
- Creator
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Kwak, Young-Don, Sugaya, Kiminobu, University of Central Florida
- Abstract / Description
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Although amyloid beta (A beta) deposition has been a hallmark of Alzheimer's disease (AD), the physiological function of amyloid precursor protein (APP) is not clear. Our results suggested that high concentration of APP induces glial differentiation while physiological level of APP promotes migration and differentiation of neural stem cell (HNSC). HNSCs were mainly differentiated into astrocytes when they are transplanted into APP transgenic mouse brain or treated with a high...
Show moreAlthough amyloid beta (A beta) deposition has been a hallmark of Alzheimer's disease (AD), the physiological function of amyloid precursor protein (APP) is not clear. Our results suggested that high concentration of APP induces glial differentiation while physiological level of APP promotes migration and differentiation of neural stem cell (HNSC). HNSCs were mainly differentiated into astrocytes when they are transplanted into APP transgenic mouse brain or treated with a high concentration of secreted-type APP (sAPP) in culture. Staurosporine (STS) induced a distinctive astrocytic morphology in NT-2/D1 neural progenitor cells with expressions of APP and astrocyte-specific markers, glial fibrillary acidic protein (GFAP), aspartate transporter, and glutamate transporter-1. Expression of APP is correlated with GFAP expression in both mRNA and protein level in this experiment. Inhibition of APP expression by RNA interference (RNAi) or treatment with MEK1 inhibitor (PD098059), which reduces APP expression by suppressing ERK phosphorylation, abolished GFAP expression. These results indicate that STS induces glial differentiation of neuronal progenitor cells by increasing APP levels through activation of ERK pathway. We also found that APP-induced glial differentiation of neural progenitor NT-2/D1 cells is mediated by activation of IL-6/gp130 and notch signaling pathway. Treatment of APP activated IL-6/gp130 signal pathway via protein-protein interaction between APP and gp130 and it increased the gene expressions of CNTF, gp130 and JAK1, and phosphorylation of STAT3 while gene silencing of CNTF, JAK1 or STAT3 by RNAi, or treatment the cells with antibodies recognizing gp130 suppressed GFAP expression, indicating these molecules are crucial for APP-induced glial differentiation. Thus treatment of sAPP may promote glial differentiation of neural progenitor cells by activation of IL-6/gp130 signaling cascade. Treatment of sAPP increased the generation of notch intracellular domain as well as gene expression of Hes1 but did not change expression levels of notch or its ligands. We also found protein-protein interaction of APP and notch using immunoprecipitation suggesting that glial differentiation of NT-2/D1 cells is mediated by the physical interaction between APP and notch. N-terminal domain of APP (1-205 a.a.) alone can bind to notch and activate these signaling cascade in NT-2/D1 cells. Thus, APP may induce glial differentiation through activation of IL-6/gp130 and notch signal cascade by binding with its N-terminal domain. Taken together, our results suggest that APP regulates neural stem cell (NSC) differentiation through IL-6/gp130 and notch signaling pathway. Furthermore, the activation of both glial differentiation mechanisms may be necessary to potentiate APP-induced glial differentiation of NSC. Altered APP metabolism in Down syndrome and Alzheimer's disease may accelerate premature glial differentiation of NSCs, resulting in gliosis found in these diseases. Although it is not clear that how adult neurogenesis contributes to maintain normal brain function, destruction of neuroreplacement mechanism by NSCs may pose a problem. We may also have to consider effect of APP on the stem cell therapy for these diseases, since HNSCs may not properly differentiate into neurons under these pathological conditions.
Show less - Date Issued
- 2006
- Identifier
- CFE0001375, ucf:46980
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001375
- Title
- A NUMERICAL ANALYSIS APPROACH FOR ESTIMATING THE MINIMUM TRAVELING WAVE SPEED FOR AN AUTOCATALYTIC REACTION.
- Creator
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Blanken, Erika, Qi, Yuan-wei, University of Central Florida
- Abstract / Description
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This thesis studies the traveling wavefront created by the autocatalytic cubic chemical reaction A + 2B → 3B involving two chemical species A and B, where A is the reactant and B is the auto-catalyst. The diffusion coefficients for A and B are given by and . These coefficients differ as a result of the chemical species having different size and/or weight. Theoretical results show there exist bounds, and , depending on , where for speeds , a traveling wave solution exists, while for speeds , a...
Show moreThis thesis studies the traveling wavefront created by the autocatalytic cubic chemical reaction A + 2B → 3B involving two chemical species A and B, where A is the reactant and B is the auto-catalyst. The diffusion coefficients for A and B are given by and . These coefficients differ as a result of the chemical species having different size and/or weight. Theoretical results show there exist bounds, and , depending on , where for speeds , a traveling wave solution exists, while for speeds , a solution does not exist. Moreover, if , and are similar to one another and in the order of when it is small. On the other hand, when there exists a minimum speed vmin, such that there is a traveling wave solution if the speed v > vmin. The determination of vmin is very important in determining the dynamics of general solutions. To fill in the gap of the theoretical study, we use numerical methods to determine vmin for various cases. The numerical algorithm used is the fourth-order Runge-Kutta method (RK4).
Show less - Date Issued
- 2008
- Identifier
- CFE0002061, ucf:47571
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002061
- Title
- AN EXAMINATION OF THE EFFECTIVENESS OF THE ADOMIAN DECOMPOSITION METHOD IN FLUID DYNAMIC APPLICATIONS.
- Creator
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Holmquist, Sonia, Mohapatra, Ram, University of Central Florida
- Abstract / Description
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Since its introduction in the 1980's, the Adomian Decomposition Method (ADM) has proven to be an efficient and reliable method for solving many types of problems. Originally developed to solve nonlinear functional equations, the ADM has since been used for a wide range of equation types (like boundary value problems, integral equations, equations arising in flow of incompressible and compressible fluids etc...). This work is devoted to an evaluation of the effectiveness of this method...
Show moreSince its introduction in the 1980's, the Adomian Decomposition Method (ADM) has proven to be an efficient and reliable method for solving many types of problems. Originally developed to solve nonlinear functional equations, the ADM has since been used for a wide range of equation types (like boundary value problems, integral equations, equations arising in flow of incompressible and compressible fluids etc...). This work is devoted to an evaluation of the effectiveness of this method when used for fluid dynamic applications. In particular, the ADM has been applied to the Blasius equation, the Falkner-Skan equation, and the Orr-Sommerfeld equation. This study is divided into five Chapters and an Appendix. The first chapter is devoted to an introduction of the Adomian Decomposition method (ADM) with simple illustrations. The Second Chapter is devoted to the application of the ADM to generalized Blasius Equation and our result is compared to other published results when the parameter values are appropriately set. Chapter 3 presents the solution generated for the Falkner-Skan equation. Finally, the Orr-Sommerfeld equation is dealt with in the fourth Chapter. Chapter 5 is devoted to the findings and recommendations based on this study. The Appendix contains details of the solutions considered as well as an alternate solution for the generalized Blasius Equation using Bender's delta-perturbation method.
Show less - Date Issued
- 2007
- Identifier
- CFE0001735, ucf:47318
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001735
- Title
- MCP-1 AND APP INVOLVEMENT IN GLIAL DIFFERENTIATION AND MIGRATION OF NEUROPROGENITOR CELLS.
- Creator
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Vrotsos, Emmanuel, Sugaya, Kiminobu, University of Central Florida
- Abstract / Description
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Neuroprogenitor cells are an important resource because of their potential to replace damaged cells in the brain caused by trauma and disease. It is of great importance to better understand which factors influence the differentiation and migration of these cells. Previously it has been reported that neuroprogenitor cells undergoing apoptotic stress have increased levels of Amyloid precursor protein (APP) and increased APP expression results in glial differentiation. APP activity was also...
Show moreNeuroprogenitor cells are an important resource because of their potential to replace damaged cells in the brain caused by trauma and disease. It is of great importance to better understand which factors influence the differentiation and migration of these cells. Previously it has been reported that neuroprogenitor cells undergoing apoptotic stress have increased levels of Amyloid precursor protein (APP) and increased APP expression results in glial differentiation. APP activity was also shown to be required for staurosporine induced glial differentiation of neuroprogenitor cells. Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that is expressed during inflammatory. The binding of MCP-1 to its chemokine receptor induces expression of novel transcription factor MCP-1 induced protein (MCPIP). MCPIP expression subsequently leads to cell death. Previous studies have shown that pro apoptotic factors have the ability to induce neural differentiation. Therefore, we investigated if MCPIP expression leads to differentiation of NT2 neuroprogenitor cells. Results showed that MCPIP expression increased glial fibrillary acid protein expression and also caused distinct morphological changes, both indicative of glial differentiation. Similar results were observed with MCP-1 treatment. Interestingly, APP expression decreased in response to MCPIP. Instead, we found APP activity regulates expression of both MCP-1 and MCPIP. Furthermore, inhibition of either p38 MAPK or JAK signaling pathways significantly reduced APP's effect on MCP-1 and MCPIP. These data demonstrate the role APP has in glial differentiation of NT2 cells through MCP-1/MCPIP signaling. It is possible that increased APP expression after CNS injury could play a ii role in MCP-1 production, possibly promoting astrocyte activation at injured site. We next investigated the effect that MCP-1 has on NT2 cell migration. Studies have shown that when neuroprogenitor cells are transplanted into the brain they migrate towards damaged areas, suggesting that these areas express factors that recruit migrating cells. Generally, after neuronal injury there is a neuroinflammatory response that results in increased chemokine production. We demonstrate that MCP-1 significantly induces the migration of NT2 neuroprogenitor cells. Activation of intracellular cyclic adenosine monophosphate (cAMP) or protein kinase C with forskolin and phorbol 12-myristate 13-acetate (PMA), respectively, was able to completely abolish the MCP-1 induced migration. Contrarily, neither extracellular signal-regulated kinase or p38 mitogen activated protein kinase was required for NT2 cells to respond to MCP-1. Interestingly, APP's ability to activate MCP-1 expression was shown to play a role in NT2 cell migration. We showed that NT2 cells expressing APP were capable of inducing migration of other neuroprogenitor cells. Utilizing a MCP-1 neutralizing antibody we discovered that APP induced migration was not caused solely by increased MCP-1 production. Interestingly, APP increased expression of several C-C chemokines: MCP-1, Regulated upon Activation, Normal T-cell Expressed, and Secreted (RANTES), and macrophage inflammatory protein alpha (MIP-1 alpha). This demonstrates the unique role APP has in regulating chemokine production, which directly affects cell migration. Taken together, this study provides us with a greater understanding of the mechanisms involved in both glial differentiation and migration of NT2 neuroprogenitor cells.
Show less - Date Issued
- 2009
- Identifier
- CFE0002517, ucf:47661
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002517
- Title
- THE EFFECTS OF DIFFERENTIAL ITEM FUNCTIONING ON PREDICTIVE BIAS.
- Creator
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Bryant, Damon, Stone-Romero, Eugene, University of Central Florida
- Abstract / Description
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The purpose of this research was to investigate the relation between measurement bias at the item level (differential item functioning, dif) and predictive bias at the test score level. Dif was defined as a difference in the probability of getting a test item correct for examinees with the same ability but from different subgroups. Predictive bias was defined as a difference in subgroup regression intercepts and/or slopes in predicting a criterion. Data were simulated by computer. Two...
Show moreThe purpose of this research was to investigate the relation between measurement bias at the item level (differential item functioning, dif) and predictive bias at the test score level. Dif was defined as a difference in the probability of getting a test item correct for examinees with the same ability but from different subgroups. Predictive bias was defined as a difference in subgroup regression intercepts and/or slopes in predicting a criterion. Data were simulated by computer. Two hypothetical subgroups (a reference group and a focal group) were used. The predictor was a composite score on a dimensionally complex test with 60 items. Sample size (35, 70, and 105 per group), validity coefficient (.3 or .5), and the mean difference on the predictor (0, .33, .66, and 1 standard deviation, sd) and the criterion (0 and .35 sd) were manipulated. The percentage of items showing dif (0%, 15%, and 30%) and the effect size of dif (small = .3, medium = .6, and large = .9) were also manipulated. Each of the 432 conditions in the 3 x 2 x 4 x 2 x 3 x 3 design was replicated 500 times. For each replication, a predictive bias analysis was conducted, and the detection of predictive bias against each subgroup was the dependent variable. The percentage of dif and the effect size of dif were hypothesized to influence the detection of predictive bias; hypotheses were also advanced about the influence of sample size and mean subgroup differences on the predictor and criterion. Results indicated that dif was not related to the probability of detecting predictive bias against any subgroup. Results were inconsistent with the notion that measurement bias and predictive bias are mutually supportive, i.e., the presence (or absence) of one type of bias is evidence in support of the presence (or absence) of the other type of bias. Sample size and mean differences on the predictor/criterion had direct and indirect effects on the probability of detecting predictive bias against both reference and focal groups. Implications for future research are discussed.
Show less - Date Issued
- 2004
- Identifier
- CFE0000157, ucf:46160
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000157
- Title
- SOLITARY WAVE FAMILIES IN TWO NON-INTEGRABLE MODELS USING REVERSIBLE SYSTEMS THEORY.
- Creator
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Leto, Jonathan, Choudhury, S. Roy, University of Central Florida
- Abstract / Description
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In this thesis, we apply a recently developed technique to comprehensively categorize all possible families of solitary wave solutions in two models of topical interest. The models considered are: a) the Generalized Pochhammer-Chree Equations, which govern the propagation of longitudinal waves in elastic rods, and b) a generalized microstructure PDE. Limited analytic results exist for the occurrence of one family of solitary wave solutions for each of these equations. Since, as mentioned...
Show moreIn this thesis, we apply a recently developed technique to comprehensively categorize all possible families of solitary wave solutions in two models of topical interest. The models considered are: a) the Generalized Pochhammer-Chree Equations, which govern the propagation of longitudinal waves in elastic rods, and b) a generalized microstructure PDE. Limited analytic results exist for the occurrence of one family of solitary wave solutions for each of these equations. Since, as mentioned above, solitary wave solutions often play a central role in the long-time evolution of an initial disturbance, we consider such solutions of both models here (via the normal form approach) within the framework of reversible systems theory. Besides confirming the existence of the known family of solitary waves for each model, we find a continuum of delocalized solitary waves (or homoclinics to small-amplitude periodic orbits). On isolated curves in the relevant parameter region, the delocalized waves reduce to genuine embedded solitons. For the microstructure equation, the new family of solutions occur in regions of parameter space distinct from the known solitary wave solutions and are thus entirely new. Directions for future work, including the dynamics of each family of solitary waves using exponential asymptotics techniques, are also mentioned.
Show less - Date Issued
- 2008
- Identifier
- CFE0002151, ucf:47930
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002151
- Title
- THE EXPRESSION OF MAKORIN1 RING FINGER PROTEIN, AN E3 UBIQUITIN LIGASE FOR TELOMERASE REVERSE TRANSCRIPTASE, IS INDUCED WITH DIFFERENTIATION THERAPY IN LEUKEMIA.
- Creator
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Salvatico, Jose, Muller, Mark, University of Central Florida
- Abstract / Description
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Telomeres are important structural and functional components of chromosomes, serving to provide stability and enabling full replication of the chromosomes. However, a shortening of the telomeres occurs with each cell division that can be fixed by a polymerase activity provided by telomerase, preventing this loss which would otherwise eventually lead to chromosome end-to-end fusions, senescence and cell death. The telomerase activity is present in stem cells and germ line cells, but absent or...
Show moreTelomeres are important structural and functional components of chromosomes, serving to provide stability and enabling full replication of the chromosomes. However, a shortening of the telomeres occurs with each cell division that can be fixed by a polymerase activity provided by telomerase, preventing this loss which would otherwise eventually lead to chromosome end-to-end fusions, senescence and cell death. The telomerase activity is present in stem cells and germ line cells, but absent or barely noticeable in adult somatic cells. However, in approximately 80-90% of transformed somatic cells the telomerase activity is recovered, resulting in a "telomerase positive phenotype". This phenotype has been a prime target in cancer research, and recently a novel mechanism for regulating telomerase levels has been uncovered. Makorin 1 RING finger protein (MKRN1) was found to be an E3 ubiquitin ligase for hTERT, the rate-limiting catalytic component of telomerase, leading to the ubiqutin-mediated 26s proteasomal degradation of hTERT and reduced telomerase activity. So, MKRN1 plays a role in telomere homeostasis. In this study we looked at the expression of MKRN1 in numerous tumor cell lines (Hela, HCT116, HL60) and the normal diploid fibroblasts (WI-38). In the latter cell line, basal levels of MKRN1 were found to increase 6-fold when the cells were serum starved and arrested in G1/G0. In contrast, the cancer cell lines expressed MKRN1 at low levels or undetectable. This would indicate that MKRN1 is up-regulated in resting or G1 arrested cells.In one cell line the promyelocytic leukemia, HL-60, showed no protein levels of MKRN1. This cell line is able to be terminally differentiated upon ATRA treatment, when cells are arrested at G1. In this model system of cellular differentiation hTERT mRNA levels and telomerase activity decrease drastically and quickly. We hypothesized that the differentiation of HL-60 induced by ATRA would be accompanied by an increase in MKRN1 levels. MKRN1 mRNA and protein levels were strongly up-regulated during the ATRA-mediated differentiation of HL-60 cells. Although, a decrease in hTERT mRNA is a contributor to telomerase inhibition during cellular differentiation; our data indicate that the up-regulation of MKRN1 ensures the effective removal of residual telomerase activity by the ubiquitin-mediated degradation pathway at the proteasome.
Show less - Date Issued
- 2009
- Identifier
- CFE0002879, ucf:48032
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002879
- Title
- Assessment of Staphylococcus aureus Genetics: Clinical versus Community Epidemiology.
- Creator
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Lawrance, Matthew, Parkinson, Christopher, Savage, Anna, Cole, Alexander, University of Central Florida
- Abstract / Description
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Staphylococcus aureus has an historical relationship with anthropogenic environments, particularly hospitals, where infection characteristics differ from community-acquired disease. This has promoted a designation of strains as healthcare or community associated. Despite this affiliation, genetic approaches have failed to support these groupings. In order to establish the genetic relationship between S. aureus from differing anthropogenic environments, I have analyzed the relatedness between...
Show moreStaphylococcus aureus has an historical relationship with anthropogenic environments, particularly hospitals, where infection characteristics differ from community-acquired disease. This has promoted a designation of strains as healthcare or community associated. Despite this affiliation, genetic approaches have failed to support these groupings. In order to establish the genetic relationship between S. aureus from differing anthropogenic environments, I have analyzed the relatedness between three cohorts of S. aureus: nasal carriage isolates from community participants, infectious isolates from hospitals, and a cohort from an uninvestigated environment, an ambulatory clinic. Multilocus Sequence Typing (MLST) and Staphylococcus aureus protein a (spa) repeat regions were analyzed and the genetic relationships between cohorts at these sites were determined. I found high similarity in recovered sequences within and between all cohorts, with cohorts sharing 100% sequence identity across some samples. Phylogenetic reconstruction of the combined datasets indicate panmixia, with samples of all origins belonging to shared genetic lineages. Additional clustering algorithms supported this pattern. The findings of this study indicate that there is strong genetic similarity between both infectious strains and nasal carriage strains and between isolates from all cohorts. This research has implications for healthcare, as it demonstrates that S. aureus from differing environments are genetically similar (often identical), cautioning against delineating strains into nasal carriage or infectious based on origin. This research also informs the study of S. aureus evolution (-) strengthening the conclusion that differentiation at stably selected markers in lineages within differing 'healthcare habitats' is insufficient to explain observed phenotypic differences, and alternative explanations must be explored.
Show less - Date Issued
- 2016
- Identifier
- CFE0006534, ucf:51369
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006534
- Title
- The Ethos of Humor in Technical Communication.
- Creator
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Roberts, David, Applen, John, Dombrowski, Paul, Flammia, Madelyn, University of Central Florida
- Abstract / Description
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Within the realm of technical communication, humor has often been regarded as an unnecessary or risky rhetorical device that can negatively impact the credibility of a document. While many other professional fields, such as medicine, computer technology fields, or business have used humor, and humor continues to crop up in (")user as producer(") documentation, technical writing continues to approach humor cautiously and with little theoretical guidance. In order to fully understand how humor...
Show moreWithin the realm of technical communication, humor has often been regarded as an unnecessary or risky rhetorical device that can negatively impact the credibility of a document. While many other professional fields, such as medicine, computer technology fields, or business have used humor, and humor continues to crop up in (")user as producer(") documentation, technical writing continues to approach humor cautiously and with little theoretical guidance. In order to fully understand how humor functions, it is important to understand the main theories of humor: superiority, relief, and incongruity. It is also important to understand how humor functions, by looking at Meyer's four functions of humor: identification, clarification, enforcement, and differentiation. Some primary and secondary manuals have successfully used a rhetorical strategy incorporating humor. Google uses a persona and situated ethos that projects a sense of fun and humor, and incorporates some humor into their documentation. The (")(")For Dummies(")(") series is well known and recognized for the situated ethos of providing fun, entertaining direction, while individual authors choose a specific invented ethos for each book written. The three theories of humor and four functions of humor can be applied to humor used in Google and (")(")For Dummies(")("). This demonstration better highlights how humor operates and functions in communication, and can provide technical communicators with a tool to use when considering the application of humor in documentation. The application further highlights the need for greater understanding of how humor affects the credibility and success of documentation.
Show less - Date Issued
- 2013
- Identifier
- CFE0004920, ucf:49629
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004920
- Title
- Differential Games for Multi-Agent Systems under Distributed Information.
- Creator
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Lin, Wei, Qu, Zhihua, Simaan, Marwan, Haralambous, Michael, Das, Tuhin, Yong, Jiongmin, University of Central Florida
- Abstract / Description
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In this dissertation, we consider differential games for multi-agent systems under distributed information where every agent is only able to acquire information about the others according to a directed information graph of local communication/sensor networks. Such games arise naturally from many applications including mobile robot coordination, power system optimization, multi-player pursuit-evasion games, etc. Since the admissible strategy of each agent has to conform to the information...
Show moreIn this dissertation, we consider differential games for multi-agent systems under distributed information where every agent is only able to acquire information about the others according to a directed information graph of local communication/sensor networks. Such games arise naturally from many applications including mobile robot coordination, power system optimization, multi-player pursuit-evasion games, etc. Since the admissible strategy of each agent has to conform to the information graph constraint, the conventional game strategy design approaches based upon Riccati equation(s) are not applicable because all the agents are required to have the information of the entire system. Accordingly, the game strategy design under distributed information is commonly known to be challenging. Toward this end, we propose novel open-loop and feedback game strategy design approaches for Nash equilibrium and noninferior solutions with a focus on linear quadratic differential games. For the open-loop design, approximate Nash/noninferior game strategies are proposed by integrating distributed state estimation into the open-loop global-information Nash/noninferior strategies such that, without global information, the distributed game strategies can be made arbitrarily close to and asymptotically converge over time to the global-information strategies. For the feedback design, we propose the best achievable performance indices based approach under which the distributed strategies form a Nash equilibrium or noninferior solution with respect to a set of performance indices that are the closest to the original indices. This approach overcomes two issues in the classical optimal output feedback approach: the simultaneous optimization and initial state dependence. The proposed open-loop and feedback design approaches are applied to an unmanned aerial vehicle formation control problem and a multi-pursuer single-evader differential game problem, respectively. Simulation results of several scenarios are presented for illustration.
Show less - Date Issued
- 2013
- Identifier
- CFE0005025, ucf:49991
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005025
- Title
- Influence of Chitosan-Alginate Scaffold Stiffness on Bone Marrow Stromal Cell Differentiation.
- Creator
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Arias Ponce, Isabel, Florczyk, Stephen, Fang, Jiyu, Khaled, Annette, Leon, Lorraine, University of Central Florida
- Abstract / Description
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Tissue grafts are the gold standard for replacing large volume tissue defects. Yet, they present several risks, including infection, low functional outcomes, and reduced graft integrity. Tissue engineering (TE) combines cells and biomaterial scaffolds to foster tissue growth and remodeling. Bone marrow stromal cells (BMSCs) have been shown to respond to the stiffness of their microenvironment, resulting in differentiation into different lineages. 3D porous chitosan-alginate (CA) scaffolds...
Show moreTissue grafts are the gold standard for replacing large volume tissue defects. Yet, they present several risks, including infection, low functional outcomes, and reduced graft integrity. Tissue engineering (TE) combines cells and biomaterial scaffolds to foster tissue growth and remodeling. Bone marrow stromal cells (BMSCs) have been shown to respond to the stiffness of their microenvironment, resulting in differentiation into different lineages. 3D porous chitosan-alginate (CA) scaffolds have been previously demonstrated for bone TE with osteoblasts and BMSCs; however, only a single scaffold composition (4 wt%) was studied. Three CA scaffold compositions (2, 4, 6 wt% CA) were produced. Scanning electron microscopy images were obtained to determine average pore sizes for 2, 4, and 6 wt% CA scaffolds, which were 233, 208, and 146 ?m. Compression testing was performed on CA scaffolds in dry and wet conditions, where higher concentrations yielded higher stiffnesses ranging from 0.22 to 5.34 kPa and 21.1 to 47.3 Pa, respectively. Fourier transform infrared spectroscopy performed on the CA scaffolds confirmed polyelectrolyte complex formation for all compositions. Human BMSCs from three donors were seeded on CA scaffolds, cultured in growth media for 14 days, then cultured in adipogenic or osteogenic differentiation media for 28 days to promote differentiation. Our hypothesis was that scaffold stiffness would influence BMSC differentiation, with softer scaffolds promoting adipogenesis and stiffer scaffolds promoting osteogenesis. BMSCs formed multicellular spheroids in all CA scaffold concentrations, while the 2 wt% CA scaffolds had smaller spheroids compared to the 4 wt% and 6 wt% CA scaffolds. Osteogenic and adipogenic differentiation were evaluated with Alizarin Red and Oil Red O staining, respectively. While positive staining was observed in all scaffold compositions, more robust differentiation was expected, thereby disproving our hypothesis. The polysaccharide composition of the CA scaffolds likely contributed to the spheroid formation and limited differentiation.
Show less - Date Issued
- 2018
- Identifier
- CFE0007389, ucf:52061
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007389
- Title
- MATHEMATICAL MODELS OF MOSQUITO POPULATIONS.
- Creator
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Reed, Hanna, Shuai, Zhisheng, University of Central Florida
- Abstract / Description
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The intent of this thesis is to develop ordinary differential equation models to better understand the mosquito population. We first develop a framework model, where we determine the condition under which a natural mosquito population can persist in the environment. Wolbachia is a bacterium which limits the replication of viruses inside the mosquito which it infects. As a result, infecting a mosquito population with Wolbachia can decrease the transmission of viral mosquito-borne diseases,...
Show moreThe intent of this thesis is to develop ordinary differential equation models to better understand the mosquito population. We first develop a framework model, where we determine the condition under which a natural mosquito population can persist in the environment. Wolbachia is a bacterium which limits the replication of viruses inside the mosquito which it infects. As a result, infecting a mosquito population with Wolbachia can decrease the transmission of viral mosquito-borne diseases, such as dengue. We develop another ODE model to investigate the invasion of Wolbachia in a mosquito population. In a biologically feasible situation, we determine three coexisting equilibria: a stable Wolbachia-free equilibrium, an unstable coexistence equilibrium, and a complete invasion equilibrium. We establish the conditions under which a population of Wolbachia infected mosquitoes may persist in the environment via the next generation number and determine when a natural mosquito population may experience a complete invasion of Wolbachia.
Show less - Date Issued
- 2018
- Identifier
- CFH2000299, ucf:45845
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000299
- Title
- THE ROLE OF STRESS IN THE DIFFERENTIAL DIAGNOSIS OF APRAXIA OF SPEECH AND APHASIA.
- Creator
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Ferranti, Jennifer G, Troche, Joshua, Bislick-Wilson, Lauren, University of Central Florida
- Abstract / Description
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The intent of this thesis is to explore and develop the quantification of AOS features, particularly the deficits of prosodic elements, lexical stress and duration. This study investigated whether PVI can be used as a sensitive tool for the differential diagnosis of AOS. Specifically, we sought to determine whether analysis of vowel length of stressed and unstressed syllables is helpful in differentiating between individuals with AOS and aphasia versus aphasia alone. Significant differences...
Show moreThe intent of this thesis is to explore and develop the quantification of AOS features, particularly the deficits of prosodic elements, lexical stress and duration. This study investigated whether PVI can be used as a sensitive tool for the differential diagnosis of AOS. Specifically, we sought to determine whether analysis of vowel length of stressed and unstressed syllables is helpful in differentiating between individuals with AOS and aphasia versus aphasia alone. Significant differences support the hypothesis that PVI, analyzed from vowel length, is uniquely affected in AOS. This yields reason for further research in prosodic deficits in differential diagnosis, as well as application of this theory for a speech-language pathologist.
Show less - Date Issued
- 2018
- Identifier
- CFH2000388, ucf:45746
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000388
