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- Title
- CHANGING TRADITIONS: EXAMINING THE FACTORS THAT DETERMINE THE PROBABILITY OF BIDDING TO HOST THE OLYMPIC GAMES OVER TIME.
- Creator
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Dickens, Jessie R, Hofler, Richard, University of Central Florida
- Abstract / Description
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In September 2017, the International Olympic Committee (IOC) announced that, for the first time in its history, it would award the hosting of two different Olympic Games at the same time, giving the 2024 and 2028 Summer Olympic Games to Paris and Los Angeles respectively. As a result, the question is raised as to why the IOC broke tradition in its host city selection process. The break of tradition is presumably due to a lack of candidates to host the 2028 Summer Olympics. With prior host...
Show moreIn September 2017, the International Olympic Committee (IOC) announced that, for the first time in its history, it would award the hosting of two different Olympic Games at the same time, giving the 2024 and 2028 Summer Olympic Games to Paris and Los Angeles respectively. As a result, the question is raised as to why the IOC broke tradition in its host city selection process. The break of tradition is presumably due to a lack of candidates to host the 2028 Summer Olympics. With prior host cities reporting astronomical costs and high debt balances associated with hosting, many cities have retracted their bids or have refused to submit candidature bids altogether. The Olympics are one of the largest, most economically impactful mega-events in modern culture. While hosting does provide a nation with the opportunity to show off its infrastructure and culture before millions of people worldwide, the costs to host the event have steadily risen as the Olympics have become a larger and larger spectacle. This study uses a logistic regression model to determine the relative factors that determine a city's willingness to bid and uses the results to draw conclusions as to why the willingness to host has fluctuated across time. The results show a definite change in the probabilities of a potential city bidding to host the Olympic Games across time and also provide insight into the factors that determine these changes in probabilities. By determining these conclusions, this study hopes to provide insight into ways that hosting the Olympics can become accessible to all prospective host cities so that there is increased competition in the host city selection process.
Show less - Date Issued
- 2018
- Identifier
- CFH2000293, ucf:45727
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000293
- Title
- ATP-Induced Disassembly of CDTB/CDTC Heterodimer of Cytolethal Distending Toxin.
- Creator
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Huhn, George, Teter, Kenneth, Cole, Alexander, Jewett, Mollie, University of Central Florida
- Abstract / Description
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Cytolethal distending toxin (CDT) is a virulence factor produced by many Gram-negative bacteria, including Haemophilus ducreyi. This fastidious pathogen is the causative agent of genital cancroid. CDT is a heterotrimeric toxin with an AB2 structure consisting of a cell-binding (")B(") domain (CdtA + CdtC) and a catalytic (")A(") domain (CdtB) that has DNase activity. This toxin assembles in the bacterial periplasm that lacks ATP and is secreted into the extracellular environment. After cell...
Show moreCytolethal distending toxin (CDT) is a virulence factor produced by many Gram-negative bacteria, including Haemophilus ducreyi. This fastidious pathogen is the causative agent of genital cancroid. CDT is a heterotrimeric toxin with an AB2 structure consisting of a cell-binding (")B(") domain (CdtA + CdtC) and a catalytic (")A(") domain (CdtB) that has DNase activity. This toxin assembles in the bacterial periplasm that lacks ATP and is secreted into the extracellular environment. After cell binding, CDT is internalized by endocytosis and travels through the endosomes and Golgi before arriving in the endoplasmic reticulum (ER). CdtA is lost from the holotoxin before reaching the Golgi, and CdtB separates from CdtC in the ER. CdtB is then transported into the nucleus, inducing cell cycle arrest and apoptosis. Using disassembly of the AB5 pertussis toxin as a model, we explore that ATP, which is present in the ER lumen but not in the endosomes or Golgi, will cause dissociation of the CdtB/CdtC heterodimer. We have cloned and purified the three individual subunits of the H. ducreyi CDT. When combined, the subunits form a lethal holotoxin. Examining the individual toxin subunits, only CdtB binds with ATP but does not function as an ATPase. CdtB's binding to ATP also does not cause global changes to its secondary structure. After isolating the CdtB/CdtC heterodimer, we have shown the addition of ATP causes CdtC to dissociate from CdtB. The work presented in this Thesis provides a molecular basis for why the CdtB/CdtC heterodimer disassembles after reaching the ER and confirms the novel two-stage disassembly mechanism for CDT, a first in the AB toxin field.
Show less - Date Issued
- 2019
- Identifier
- CFE0007657, ucf:52488
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007657
- Title
- Host and Bacterial Determinants of Staphylococcus aureus Nasal Colonization in Humans.
- Creator
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Muthukrishnan, Gowrishankar, Cole, Alexander, Moore, Sean, Self, William, Parkinson, Christopher, University of Central Florida
- Abstract / Description
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Staphylococcus aureus (SA), an opportunistic pathogen colonizing the anterior nares in approximately 30% of the human population, causes severe hospital-associated and community-acquired infections. SA nasal carriage plays a critical role in the pathogenesis of staphylococcal infections and SA eradication from the nares has proven to be effective in reducing endogenous infections. To understand SA nasal colonization and its relation with consequent disease, assessment of nasal carriage...
Show moreStaphylococcus aureus (SA), an opportunistic pathogen colonizing the anterior nares in approximately 30% of the human population, causes severe hospital-associated and community-acquired infections. SA nasal carriage plays a critical role in the pathogenesis of staphylococcal infections and SA eradication from the nares has proven to be effective in reducing endogenous infections. To understand SA nasal colonization and its relation with consequent disease, assessment of nasal carriage dynamics among a diverse population and determining factors responsible for SA nasal carriage have become major imperatives.Here, we report on an extensive longitudinal monitoring of SA nasal carriage in 109 healthy individuals over a period of up to three years to assess nasal carriage dynamics. Phylogenetic analyses of SA housekeeping genes and hypervariable virulence genes revealed that not only were SA strains colonizing intermittent and persistent nasal carriers genetically similar, but no preferential colonization of specific SA strains in these carriers was observed over time. These results indicated that other non-SA factors could be involved in determining specific carriage states. Therefore, to elucidate host responses during SA nasal carriage, we performed human SA nasal recolonization in a subset of SA nasal carriers within our cohort. In these studies, SA colonization levels were determined, and nasal secretions were collected and analyzed for host immune factors responsible for SA nasal carriage. Interestingly, we observed that stimulation of host immune responses lead to clearance of SA while sustained SA colonization was observed in hosts that did not mount a response during carriage. Further, analysis of nasal secretions from hosts revealed that proinflammatory cytokines and chemokines were significantly induced during SA nasal clearance suggesting that innate immune effectors influence carriage.SA utilizes a repertoire of surface and secreted proteins to evade host immune response and successfully colonize the nose. Analysis of the most abundant immunoevasive proteins in the exoproteome of SA nasal carrier strains revealed that expression levels of Staphylococcal protein A (SPA) produced by SA nasal carrier strains in vitro corresponded to the level of persistence of SA in the human nose. To determine if SPA is involved in modulating the host's response to SA colonization, a subset of participants in our cohort was nasally recolonized with equal concentrations of both wild-type (WT) and spa-disrupted (?spa) autologous strains of SA. Interestingly, ?spa strains were eliminated from the nares significantly faster than WT when the host mounted an immune response, suggesting that the immunoevasive role of SPA is a determinant of carriage persistence. Collectively, this report augments our understanding of SA nasal carriage dynamics, in addition to identifying important host and microbial determinants that influence SA nasal colonization in humans. Better understanding of this phenomenon can lead to improved preventative strategies to thwart carriage-associated SA infections.
Show less - Date Issued
- 2014
- Identifier
- CFE0005673, ucf:50173
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005673
- Title
- Role of host immune response and bacterial autolysin Atl in human nasal colonization by Staphylococcus aureus.
- Creator
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Paramanandam, Vanathy, Cole, Alexander, Naser, Saleh, Self, William, University of Central Florida
- Abstract / Description
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Staphylococcus aureus (SA) is a major human pathogen that colonizes the anterior nares in 30% of the human population. Though nasal carriage of SA is a known risk factor for the subsequent spread of SA infections, the dynamics of SA nasal colonization is poorly understood. Our research focuses on understanding the host and bacterial factors that might contribute to the human nasal colonization by SA. In an attempt to elucidate the host response to SA, we performed an autologous human in vivo...
Show moreStaphylococcus aureus (SA) is a major human pathogen that colonizes the anterior nares in 30% of the human population. Though nasal carriage of SA is a known risk factor for the subsequent spread of SA infections, the dynamics of SA nasal colonization is poorly understood. Our research focuses on understanding the host and bacterial factors that might contribute to the human nasal colonization by SA. In an attempt to elucidate the host response to SA, we performed an autologous human in vivo nasal colonization study, which showed decreased survival rates of SA in hosts who elicited a robust immune response. We also identified a significant correlation between SA nasal colonization and the expression of host proinflammatory, chemotactic and growth factors.Additionally, we functionally disrupted a major autolysin, atl a surface expressed bacterial protein that plays multiple roles in cell separation, adhesion and biofilm formation of SA. Microscopic analysis of the ?atl strains showed phenotypic differences, including cell clumping and cluster formation due to defective cell separation, which confirmed the functional loss of atl. Subsequent analysis of the ?atl and wild-type strains revealed that there was no significant difference in their ability to adhere to human nasal epithelial cells (hNEC) in an ex vivo hNEC model. Similarly, our competitive in vivo human nasal colonization study, in which equal colony-forming units of each wild-type and ?atl SA strain were inoculated in the anterior nares of donors, showed similar survival rates between wild-type and ?atl. These results suggest that Atl might not be directly involved in the adherence and colonization of SA to the anterior nares. Furthermore, our study suggests that host factors might play a predominant role in determining SA colonization to human anterior nares.
Show less - Date Issued
- 2013
- Identifier
- CFE0005393, ucf:50463
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005393
- Title
- Characterization of Novel Borrelia burgdorferi Transcripts Expressed during Tick and Mammalian Infection.
- Creator
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Adams, Philip, Jewett, Mollie, Rohde, Kyle, Moore, Sean, Fernandez-Valle, Cristina, University of Central Florida
- Abstract / Description
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The purpose of this dissertation is to characterize the transcriptome of Borrelia (Borreliella) burgdorferi to discover novel transcripts, important for pathogenesis. As a spirochete and the etiological agent of Lyme disease, the foremost vector-borne bacterial infection in the world, B. burgdorferi fulfills a distinctive niche among bacterial pathogens. Persisting in the disparate environments of a tick vector and mammalian reservoirs, it is absolutely dependent on its hosts for transmission...
Show moreThe purpose of this dissertation is to characterize the transcriptome of Borrelia (Borreliella) burgdorferi to discover novel transcripts, important for pathogenesis. As a spirochete and the etiological agent of Lyme disease, the foremost vector-borne bacterial infection in the world, B. burgdorferi fulfills a distinctive niche among bacterial pathogens. Persisting in the disparate environments of a tick vector and mammalian reservoirs, it is absolutely dependent on its hosts for transmission and nutrient acquisition. B. burgdorferi harbors a complex fragmented genome which is largely linear, unlike that of most prokaryotes, lacks an array of classically described metabolic genes, and contains an unusually large percentage of unique genomic sequences specific to Borrelia (Borreliella) species. To date, few regulatory mechanisms have been identified which contribute to the ability of the spirochete to sense and respond to its environment. Efforts to use global transcript analysis to elucidate the molecular mechanisms of B. burgdorferi host adaptation have proven challenging due to the low numbers of the pathogen present during infection. Previously, our laboratory successfully developed an in vivo expression technology based approach for B. burgdorferi (BbIVET) to identify spirochete promoter sequences that are active during a murine infection. This screen identified 233 unique putative promoters which mapped to locations across the entire genome. These putative infection-active B. burgdorferi promoters were not only located at the 5' end of annotated open reading frames (ORFs), but also mapped to unannotated locations antisense, intergenic, and intragenic to ORFs. Given the limited characterization of the B. burgdorferi transcriptome, this dissertation applies an RNA sequencing approach (5'RNA-seq) to globally annotate the transcriptional start sites (TSSs) and 5' processed ends of the spirochete's RNA during in vitro cultivation. This resulted in the discovery of numerous novel internal, intergenic, and antisense transcripts. Synergistic analysis combining Northern blotting techniques, alignments of these transcripts to BbIVET proposed promoters, and interrogation of promoter activity via in vivo live imaging of mice, confirmed the expression of a variety of RNAs during laboratory culture and mammalian infection. Further, as a means to improve quantitation of the expression of these transcripts, a new methodology was developed and applied to measure B. burgdorferi promoter activity during tick-pathogen interactions, in a strand specific manner. Finally, because the Lyme disease spirochete harbors many unclassified and unique genomic sequences, the mammalian infection-expressed gene bb0562, identified through BbIVET and 5'RNA-seq, was selected for targeted deletion and evaluation throughout B. burgdorferi's infectious cycle. This demonstrated that gene bb0562 encodes a membrane associated protein, whose presence is critical for establishing murine infection through the bite of an infected tick. In sum, this work contributes significant insight into the transcriptome of B. burgdorferi, provides an innovative approach for the analysis of RNA transcripts at the tick-pathogen interface, and identifies a novel gene critical for Lyme disease pathogenesis.
Show less - Date Issued
- 2017
- Identifier
- CFE0006707, ucf:51915
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006707
- Title
- Determinants of Satisfaction and EWOM in Collaborative Consumption and the Sharing Economy: Timeshare Stays Versus Peer-to-Peer Accommodations.
- Creator
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Redditt, Jennifer, Fyall, Alan, Gregory, Amy, Ro, Heejung, Orlowski, Marissa, Altinay, Levent, University of Central Florida
- Abstract / Description
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Considered a disrupter in the lodging industry, sharing economy accommodations have become an emergent field in hospitality literature. While this literature predominantly addresses peer-to-peer accommodations such as Airbnb, it has not considered timeshares, one of the sharing economy pioneers. However, consumer behavior literature has integrated timeshares into the sharing economy due to the shared resource of accommodations between consumers. This study examined the determinants of...
Show moreConsidered a disrupter in the lodging industry, sharing economy accommodations have become an emergent field in hospitality literature. While this literature predominantly addresses peer-to-peer accommodations such as Airbnb, it has not considered timeshares, one of the sharing economy pioneers. However, consumer behavior literature has integrated timeshares into the sharing economy due to the shared resource of accommodations between consumers. This study examined the determinants of Satisfaction (Amenities, Community Belonging, Economic Benefits, Trust, and Vacation Counselor/Host) for consumers of two different types of sharing economy lodging products, timeshares and peer-to-peer accommodations, and their electronic word-of-mouth (eWOM) behavior. Considered a critical travel information source, eWOM has been attributed to affecting purchase decisions in hospitality literature. Current research has revealed a gap in peer-to-peer accommodation studies related to eWOM. This study extended eWOM research by exploring the role of Satisfaction as a mediator between the determinants and eWOM. In addition, accommodation type (timeshare vs. peer-to-peer accommodation) was investigated as a moderator to the relationship between the determinants and Satisfaction, and to the relationship between Satisfaction and eWOM. The study employed the two-step approach of confirmatory factor analysis (CFA) and structural equation modelling (SEM). The results indicated that Amenities, Community Belonging, Economic Benefits, Trust, and Vacation Counselor/Host had a positive impact on sharing economy lodging Satisfaction. Amenities, Economic Benefits, and Trust demonstrated an indirect effect on eWOM behavior through sharing economy lodging satisfaction. The model also revealed that Community Belonging had a direct effect on eWOM. Multiple group SEM revealed that accommodation type moderated the effect of Community Belonging's impact on sharing economy lodging Satisfaction, as well as the effect of sharing economy lodging Satisfaction on eWOM behavior. Satisfaction did not mediate any relationships for peer-to-peer accommodations. This study extends eWOM literature and provides competitive advantage insights between two sharing economy accommodation types.
Show less - Date Issued
- 2019
- Identifier
- CFE0007854, ucf:52785
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007854
- Title
- High performance liquid crystal devices for augmented reality and virtual reality.
- Creator
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Talukder, Md Javed Rouf, Wu, Shintson, Moharam, Jim, Amezcua Correa, Rodrigo, Dong, Yajie, University of Central Florida
- Abstract / Description
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See-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time...
Show moreSee-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time enable low duty ratio operation, which plays a key role for suppressing image blurs. A dimmer placed in front of AR display helps to control the incident background light, which in turn improves the image contrast. In this dissertation, we have focused three crucial display metrics: high luminance, fast motion picture response time (MPRT) and high ambient contrast ratio.We report a fringe-field switching liquid crystal display, abbreviated as d-FFS LCD, by using a low viscosity material and new diamond-shape electrode configuration. Our proposed device shows high transmittance, fast motion picture response time, low operation voltage, wide viewing angle, and indistinguishable color shift and gamma shift. We also investigate the rubbing angle effects on transmittance and response time. When rubbing angle is 0 degree, the virtual wall effect is strong, resulting in fast response time but compromised transmittance. When rubbing angle is greater than 1.2 degree, the virtual walls disappear, as a result, the transmittance increases dramatically, but the tradeoff is in slower response time. We also demonstrate a photo-responsive guest-host liquid crystal (LC) dimmer to enhance the ambient contrast ratio in augmented reality displays. The LC composition consists of photo-stable chiral agent, photosensitive azobenzene, and dichroic dye in a nematic host with negative dielectric anisotropy. In this device, transmittance changes from bright state to dark state by exposing a low intensity UV or blue light. Reversal process can be carried out by red light or thermal effect. Such a polarizer-free photo-activated dimmer can also be used for wide range of applications, such as diffractive photonic devices, portable information system, vehicular head-up displays, and smart window for energy saving purpose. A dual-stimuli polarizer-free dye-doped liquid crystal (LC) device is demonstrated as a dimmer. Upon UV/blue light exposure, the LC directors and dye molecules turn from initially vertical alignment (high transmittance state) to twisted fingerprint structure (low transmittance state). The reversal process is accelerated by combining a longitudinal electric field to unwind the LC directors from twisted fingerprint to homeotropic state, and a red light to transform the cis azobenzene back to trans. Such an electric-field-assisted reversal time can be reduced from ~10s to a few milliseconds, depending on the applied voltage. Considering power consumption, low manufacturing cost, and large fabrication tolerance, this device can be used as a smart dimmer to enhance the ambient contrast ratio for augmented reality displays.
Show less - Date Issued
- 2019
- Identifier
- CFE0007731, ucf:52425
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007731