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TESTING THE PENINSULA EFFECT: DOES IT AFFECT FRESHWATER CRUSTACEANS INHABITING EPHEMERAL WETLANDS ON FLORIDA'S RIDGES?
Title
TESTING THE PENINSULA EFFECT: DOES IT AFFECT FRESHWATER CRUSTACEANS INHABITING EPHEMERAL WETLANDS ON FLORIDA'S RIDGES?.
Creator
Rinne, Debra, Jenkins, David, University of Central Florida
Abstract / Description
The peninsula effect is a pattern of diversity wherein species richness decreases along a peninsula from base to tip and is attributed to three mechanisms: historical processes, habitat gradients, and immigration-extinction equilibrium. Numerous studies have reported conflicting results involving the existence, cause, and validity of the peninsula effect in part because they did not account for effects of history or habitat on species richness patterns and because most previous research...
Show moreThe peninsula effect is a pattern of diversity wherein species richness decreases along a peninsula from base to tip and is attributed to three mechanisms: historical processes, habitat gradients, and immigration-extinction equilibrium. Numerous studies have reported conflicting results involving the existence, cause, and validity of the peninsula effect in part because they did not account for effects of history or habitat on species richness patterns and because most previous research focused on organisms that actively disperse, which could confound results with behavioral habitat selection. Florida poses an excellent opportunity to study the peninsula effect because of its geological history and its unique ridges have similar histories (e.g. age, elevation, and sediment). Habitat changes down the peninsula, from a warm temperate climate in the north to a subtropical climate in the south. I studied freshwater crustaceans in isolated wetlands because crustaceans are diverse and disperse passively among these discrete habitats. My study design and statistical analyses controlled for two of the three mechanisms (habitat and history) that may generate a peninsula effect to better test for the third hypothesis (immigration-extinction equilibrium) on the Florida peninsula. Thirty-one wetlands were sampled for crustaceans monthly from November 2004 through April 2005, or until a site dried. Human disturbance was minimized by choosing isolated, ephemeral wetlands located within state reserves, parks, and forests located on four major ridges: Trail, Brooksville, Mount Dora and Lake Wales. I measured several environmental variables to assess habitat variation among sites. Limnological parameters included temperature, pH, dissolved oxygen, conductivity, chlorophyll á, pheophytin, total nitrogen, total phosphorus, and total hardness. Other habitat variables included surface area, distance to nearest water body, fish presence or absence, hydroperiod, total transmitted light and canopy openness. Crustacean species were identified to the lowest practical taxonomic level (typically species) and recorded as present or absent. A total of 53 different crustaceans were identified, including 41 cladocerans, 10 copepods, and 2 ostracods. In a multiple regression, environmental variables and sampling effort accounted for 57% of the variation in species richness. Regression of remaining variation (residuals) against latitude, which measures position along the peninsula, was not statistically significant. The same pattern was obtained when the sequence of regressions was reversed. Therefore, the peninsula effect does affect the species richness of freshwater crustaceans inhabiting ephemeral wetlands on Florida's ridges. Instead, variation in species richness was determined mainly by habitat differences, particularly the complex interaction of phosphorus levels, isolation, fish presence or absence, and hydroperiod. This study may serve as a model for more thorough analyses of mechanisms (history, habitat, and immigration-extinction) of a peninsula effect in other taxa.
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Date Issued
2006
Identifier
CFE0001034, ucf:46809
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001034
How Much is Enough? Trauma Recall and the Exposure Therapy Process
Title
How Much is Enough? Trauma Recall and the Exposure Therapy Process.
Creator
Morrison, Krystal, Beidel, Deborah, Bowers, Clint, Bohil, Corey, University of Central Florida
Abstract / Description
Prevailing theoretical models of posttraumatic stress disorder (PTSD) as well as exposure therapy (EXP) methodology suggest that recall of a trauma is crucial to altering the conditioned fear response associated with PTSD (Benito (&) Walther, 2015; Craske et al., 2008; Foa (&) Kozak, 1986). However, it is unclear whether limited recall of the event impacts the EXP process and treatment outcomes. This study examined whether incomplete trauma recall affected pre-treatment PTSD severity, Initial...
Show morePrevailing theoretical models of posttraumatic stress disorder (PTSD) as well as exposure therapy (EXP) methodology suggest that recall of a trauma is crucial to altering the conditioned fear response associated with PTSD (Benito (&) Walther, 2015; Craske et al., 2008; Foa (&) Kozak, 1986). However, it is unclear whether limited recall of the event impacts the EXP process and treatment outcomes. This study examined whether incomplete trauma recall affected pre-treatment PTSD severity, Initial Fear Activation (IFA), Overall Fear Activation (OFA), Within-Session Habituation (WSH), Between-Session Habituation (BSH; overall extinction), average length of EXP sessions, number of EXP sessions, and post-treatment PTSD severity, in 166 veterans of Operation Enduring Freedom, Operation Iraqi Freedom, and Operation New Dawn, who completed EXP treatment. Contrary to predicted outcomes, the extent of recall did not attenuate veterans' participation in EXP as measured by IFA, OFA, WSH and BSH. Furthermore, less recall did not result in more severe pre-treatment PTSD, longer EXP sessions, more EXP sessions, or attenuated treatment response, as measured by the Clinician-Administered PTSD Scale for DSM-IV (CAPS; Weathers, Ruscio, (&) Keane, 1999) and PTSD Checklist Military Version (PCL-M; Weathers, Huska, (&) Keane, 1991) at pre- and post-treatment. This suggests that veterans who are unable to recall aspects of their traumatic experience can engage successfully and benefit equally from EXP akin to veterans who experience less difficulty recalling trauma details. This research is the first to examine trauma recall in the context of the EXP process and contributes to the current body of literature that aims to address the question: For whom do treatments work?
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Date Issued
2018
Identifier
CFE0007347, ucf:52116
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007347
MECHANISMS OF LEAN FLAME EXTINCTION
Title
MECHANISMS OF LEAN FLAME EXTINCTION.
Creator
Lasky, Ian M, Ahmed, Kareem, University of Central Florida
Abstract / Description
Lean flame blowout is investigated experimentally within a high-speed combustor to analyze the temporal extinction dynamics of turbulent premixed bluff body stabilized flames. The lean blowout process is induced through fuel flow reduction and captured temporally using simultaneous high-speed particle imaging velocimetry (PIV) and CH* chemiluminescence. The evolution of the flame structure, flow field, and the resulting strain rate along the flame are analyzed throughout extinction to...
Show moreLean flame blowout is investigated experimentally within a high-speed combustor to analyze the temporal extinction dynamics of turbulent premixed bluff body stabilized flames. The lean blowout process is induced through fuel flow reduction and captured temporally using simultaneous high-speed particle imaging velocimetry (PIV) and CH* chemiluminescence. The evolution of the flame structure, flow field, and the resulting strain rate along the flame are analyzed throughout extinction to distinguish the physical mechanisms of blowout. Flame-vortex dynamics are found to be the main driving mechanism of flame extinction; namely, a reduction of flame-generated vorticity coupled with an increase of downstream shear layer vorticity. The vorticity dynamics are linked to hydrodynamic instabilities that vary as a function of the decreasing equivalence ratio. Frequency analysis is performed to characterize the dynamical changes of the hydrodynamic instability modes during flame extinction. Additionally, various bluff body inflow velocity regimes are investigated to further characterize the extinction instability modes. Both equivalence ratio and flow-driven instabilities are captured through a universal definition of the Strouhal number for the reacting bluff body flow. Finally, a Karlovitz number-based criterion is developed to consistently predict the onset of global extinction for different inflow velocity regimes.
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Date Issued
2018
Identifier
CFH2000369, ucf:45710
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH2000369
Mechanisms of Flame Extinction for Bluff Body Stabilized Flames with Influences of Pressure Gradient Tailoring
Title
Mechanisms of Flame Extinction for Bluff Body Stabilized Flames with Influences of Pressure Gradient Tailoring.
Creator
Morales, Anthony, Ahmed, Kareem, Bhattacharya, Samik, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description
Flame extinction continues to hinder the performance of combustion technologies used in propulsion systems and power generating turbomachinery. Within these applications, there is a crucial need to improve energy output while minimizing harmful environmental impacts. Lean combustion helps attain these goals by minimizing fuel costs and reducing NOx emissions. However, operating at lean conditions increases the likelihood of flame extinction; the flame becomes more susceptible to hydrodynamic...
Show moreFlame extinction continues to hinder the performance of combustion technologies used in propulsion systems and power generating turbomachinery. Within these applications, there is a crucial need to improve energy output while minimizing harmful environmental impacts. Lean combustion helps attain these goals by minimizing fuel costs and reducing NOx emissions. However, operating at lean conditions increases the likelihood of flame extinction; the flame becomes more susceptible to hydrodynamic instabilities which can induce global blowout and termination of the combustion process. The work in this thesis is focused on identifying the mechanisms of flame extinction and controlling these mechanisms via pressure gradient tailoring. This is accomplished within a premixed blow-down combustion facility utilizing a bluff body flame stabilizer where flame extinction is induced by removing the flow of fuel into the reactant mixture. CH* chemiluminescence imaging and high-speed particle imaging velocimetry (PIV) are used to determine the flame boundary and resolve the reacting flow field, respectively. The mechanisms of flame extinction are attributed to the changing vorticity dynamics within the flow field as the equivalence ratio is reduced, which will directly influence the strain rate experienced by the flame. To influence these vorticity dynamics, the test section walls are manipulated to alter the downstream pressure gradients. It is determined that increasing the magnitude of the downstream pressure gradient increases the growth of the strain rate and vorticity experienced by the flame.
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Date Issued
2018
Identifier
CFE0007229, ucf:52240
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007229
(UN)NATURAL BODIES, ENDANGERED SPECIES, AND EMBODIED OTHERS IN MARGARET ATWOOD'S ORYX AND CRAKE
Title
(UN)NATURAL BODIES, ENDANGERED SPECIES, AND EMBODIED OTHERS IN MARGARET ATWOOD'S ORYX AND CRAKE.
Creator
Galbreath, Marcy, Murphy, Patrick, University of Central Florida
Abstract / Description
The developing knowledge of life sciences is at the crux of Margaret Atwood's Oryx and Crake as she examines human promise gone awry in a near-future dystopia. This thesis examines aspects of posthumanism, ecocriticism, and feminism in the novel's scientific, cultural, and environmental projections. Through the trope of extinction, Atwood's text foregrounds the effects of human exceptionalism and instrumentalism in relation to the natural world, and engenders an analysis of human...
Show moreThe developing knowledge of life sciences is at the crux of Margaret Atwood's Oryx and Crake as she examines human promise gone awry in a near-future dystopia. This thesis examines aspects of posthumanism, ecocriticism, and feminism in the novel's scientific, cultural, and environmental projections. Through the trope of extinction, Atwood's text foregrounds the effects of human exceptionalism and instrumentalism in relation to the natural world, and engenders an analysis of human identity through its biological and cultural aspects. Extinction thus serves as a metaphor for both human development and human excesses, redefining the idea of human within the context of vulnerable species. Oryx and Crake reveals humanity's organic connections with non-human others through interspecies gene-splicing and the ensuing hybridity. In this perspective, Atwood's text provides a dialogue on humankind's alienation from the natural world and synchronic connections to the animal other, and poses timely questions for twenty-first century consumerism, globalism, and humanist approaches to nature. The loss of balance provoked by the apocalyptic situation in Oryx and Crake challenges commonplace attitudes toward beneficial progress. This imbalance signals the need for a new narrative: A consilient reimagining of humanity's role on earth as an integrated organism rather than an intellectual singularity.
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Date Issued
2010
Identifier
CFE0003227, ucf:48552
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003227