UNT Theses and Dissertations - 403 Matching Results

Search Results

Note: All results matching your query require you to be a member of the UNT Community (you must be on campus or login with university credentials for access).

Drive Level Dependence of Advanced Piezoelectric Resonators

Description: Resonators are one of the most important parts of electronic products. They provide a stable reference frequency to ensure the operation of these products. Recently, the electronic products have the trend of miniaturization, which rendered the size reduction of the resonators as well [1]. Better design of the resonators relies on a better understanding of the crystals' nonlinear behavior [2]. The nonlinearities affect the quality factor and acoustic behavior of MEMS (Micro-Electro-Mechanical-System) and nano-structured resonators and filters [3]. Among these nonlinear effects, Drivel Level Dependence (DLD), which describes the instability of the resonator frequency due to voltage level and/or power density, is an urgent problem for miniaturized resonators [2]. Langasite and GaPO4 are new promising piezoelectric material. Resonators made from these new materials have superior performance such as good frequency-temperature characteristics, and low acoustic loss [2]. In this thesis, experimental measurements of drive level dependence of langasite resonators with different configurations (plano-plano, single bevel, and double bevel) are reported. The drive level dependence of GaPO4 resonators are reported as well for the purpose of comparison. The results show that the resonator configuration affects the DLD of the langasite resonator. Experiments for DLD at elevated temperature are also performed, and it was found that the temperature also affects the DLD of the langasite resonator.
Date: August 2012
Creator: Xie, Yuan
Partner: UNT Libraries

A Driver, Vehicle and Road Safety System Using Smartphones

Description: As vehicle manufacturers continue to increase their emphasis on safety with advanced driver assistance systems (ADAS), I propose a ubiquitous device that is able to analyze and advise on safety conditions. Mobile smartphones are increasing in popularity among younger generations with an estimated 64% of 25-34 year olds already using one in their daily lives. with over 10 million car accidents reported in the United States each year, car manufacturers have shifted their focus of a passive approach (airbags) to more active by adding features associated with ADAS (lane departure warnings). However, vehicles manufactured with these sensors are not economically priced while older vehicles might only have passive safety features. Given its accessibility and portability, I target a mobile smartphone as a device to compliment ADAS that can bring a driver assist to any vehicle without regards for any on-vehicle communication system requirements. I use the 3-axis accelerometer of multiple Android based smartphone to record and analyze various safety factors which can influence a driver while operating a vehicle. These influences with respect to the driver, vehicle and road are lane change maneuvers, vehicular comfort and road conditions. Each factor could potentially be hazardous to the health of the driver, neighboring public, and automobile and is therefore analyzed thoroughly achieving 85.60% and 89.89% classification accuracy for identifying road anomalies and lane changes, respectively. Effective use of this data can educate a potentially dangerous driver on how to operate a vehicle safely and efficiently. with real time analysis and auditory alerts of these factors, I hope to increase a driver's overall awareness to maximize safety.
Date: May 2012
Creator: Gozick, Brandon
Partner: UNT Libraries

Early College High School: Hispanic Students’ Perceptions and Experiences From a Texas Campus

Description: Early college high school (ECHS) is a dual enrollment program that allows high school students to earn college credits while in high school. ECHS was developed with the intention of attracting students to pursue a 4-year college degree, especially students who might not attend college without intervention. The program targets students from low-income families, students who have low academic achievement, and students from minority groups including Hispanics, African Americans, and Native Americans. The purpose of this study was to explore the perceptions and opinions of Hispanic students about their experiences in an ECHS, and to better understand how their ECHS experiences affected motivation to engage in academics. The expectancy theory and college-going culture provided the theoretical framework for this case study. Semi-structured interviews captured the experiences of the participants. The study focused on 10 Hispanic students, 5 seniors and 5 juniors, enrolled at an ECHS located on a community college campus in Texas. The study found that students with higher motivation to work at high school and college courses had several reasons for choosing to attend ECHS. The reasons included a chance to earn a high school diploma and associate’s degree simultaneously, free college tuition, and an accelerated program to get through college. The students also identified rewarding outcomes for completing college. Those outcomes included satisfying career, personal satisfaction, ability to provide for their family and making their family proud as the first high school graduate and college attendee. One student had a lower motivation to work at high school and college work. He chose to attend ECHS to seek more freedom than a traditional high school. He was not certain about graduating from high school and doubtful about college graduation. This study contributes to the ECHS literature by providing details on students’ experiences at an ECHS. Using the qualitative ...
Date: May 2012
Creator: Brenner, Rose K.
Partner: UNT Libraries

Early Literacy of Young Children in New Immigrant and Native Families in Taiwan: Educational and Socio-political Implications

Description: Because of shifting demographics, the Taiwanese government opened the country to immigrants from Southeast Asia. Foreign-born brides of Taiwanese men have contributed significantly to this trend of new immigration, inspiring fears that their children, inadequately prepared for the literacy requirements of early education, might negatively impact the educational system and society. to better understand the socio-political implications of this cultural shift, the researcher gathered data from one hundred and twenty immigrant and native families with first graders in six major cities in Taiwan. Purposes of this research are to: (a) investigate to what extent, if any parenting style is impacted by differences in immigration status between native Taiwanese and Southeast Asian immigrant mothers, (b) examine to what extent, if any maternal parenting styles relate to children’s early literacy, and (c) determine to what extent, if any maternal parenting styles along with the children’s and familial characteristics associate with children’s early literacy. the study found that (a) immigrant mothers are statistically lower on authoritative and higher on permissive parenting style than native mothers; (b) immigrant mothers’ participation in integration programs does not relate to maternal parenting styles or children’s literacy performances; (c) children from immigrant families are significantly lower than their peers from native families on receptive vocabulary and phonological awareness; (d) children from higher income families perform better on receptive vocabulary than their lower income peers; (e) children whose mothers are senior high school graduates achieve significantly better on literacy skills than others. Furthermore, children of mothers with higher education perform better on receptive vocabulary than those whose mothers have lower education levels; (f) there was little relationship between children’s literacy development and the three maternal parenting styles; (g) age and gender are the most significant predictors of children’s literacy development. the limited influence of parenting styles on childhood literacy ...
Date: May 2012
Creator: Wang, Hui-Fen
Partner: UNT Libraries

Ecological Forms of Life: Wittgenstein and Ecolinguistics

Description: The present philosophical literature on philosopher Ludwig Wittgenstein tends to either stagnate by focusing upon issues particular to Wittgenstein's philosophy or expand the boundaries of Wittgenstein's thought to shed light onto other areas of study. One area that has largely been ignored is the realm of environmental philosophy. I prepare the way for a solution to this by first arguing that Wittgenstein's later philosophy of language shows 'proto-ecolinguistic' concerns, sharing much in common with the ecolinguistic thought of both Peter Mühlhäusler and Luisa Maffi. This reading, as well as the work of Mühlhäusler and Maffi, is a starting point for an opposition to a common trend in much of contemporary linguistics of adhering to a linguistic paradigm of universalizing linguistic atomism that gives an impoverished account of language. This impoverished account is argued to have potential environmental and ecological consequences which the universalizing atomistic paradigm is ill-equipped to address.
Date: December 2012
Creator: Sarratt, Nicholas M.
Partner: UNT Libraries

Ecological Significance and Underlying Mechanisms of Body Size Differentiation in White-tailed Deer

Description: Body size varies according to nutritional availability, which is of ecological and evolutionary relevance. The purpose of this study is to test the hypothesis that differences in adult body size are realized by increasing juvenile growth rate for white-tailed deer (Odocoileus virginianus). Harvest records are used to construct growth rate estimates by empirical nonlinear curve fitting. Results are compared to those of previous models that include additional parameters. The rate of growth increases during the study period. Models that estimate multiple parameters may not work with harvest data in which estimates of these parameters are prone to error, which renders estimates from complex models too variable to detect inter-annual changes in growth rate that this simpler model captures
Date: May 2012
Creator: Barr, Brannon
Partner: UNT Libraries

Ecology and Recolonization of Benthic Macroinvertebrates in a Groundwater-dependent Stream in North Central Texas During a Supra-seasonal Drought

Description: Extreme climatic events such as droughts are known to eliminate aquatic biota and alter community structure and function. Perennial headwater springs provide important drought refugia to benthic macroinvertebrates and an important source of colonists via drift or aerial adults to intermittent streams post-drought. During a supra-seasonal drought in North-central Texas summer and fall 2006, benthic macroinvertebrates from persistent groundwater-dependent macrohabitats of varying hydrological connectivity and riparian shading were studied: perennial riffles, connected pools, shaded disconnected pools, and full sun disconnected pools. Riffles were a distinct habitat with significantly higher taxa richness, proportion of lotic taxa, diversity and evenness than other macrohabitats. Macrohabitats were found to be important refugia for 106 benthic macroinvertebrates and 4 microcrustacean taxa. Throughout the extreme drought, perennially flowing habitats were refugia to 19 taxa (17.9% total taxa) not collected in disconnected pools. Shaded disconnected pools contained lotic taxa not previously known to be able to complete their lifecycles in lentic habitats, emphasizing the importance of groundwater effluent and shading. With the resumption of flow at a downstream intermittent site of Ash Creek in mid-October 2006, an annual recolonization study was conducted comparing the perennial headwaters’ benthic macroinvertebrate taxa richness, densities and community ecology with the downstream intermittent site. The headwaters supported higher mean taxa richness than the intermittent site over the duration of the study (ANOVA P < 0.001). However, the unexpected result of overall decreasing taxa richness at the perennial headwater site from August 2006 to April 2008 appears to reflect lag effects of the supra-seasonal drought combined with effects of multiple spates of 2007, which are factors confounding the point of recovery for taxa richness. Recovery of taxa richness at the intermittent site took 9 months compared to 1 to 2 months reported in other arid and semi-arid streams in the United States recovering ...
Date: May 2012
Creator: Burk, Rosemary A.
Partner: UNT Libraries

Educational Performance: Texas Open Enrollment Charter High Schools Compared to Traditional Public High Schools

Description: The study examined mathematics and English student achievement, attendance rates, dropout rates, and expenditures per pupil for Texas high school students in both open-enrollment charter schools and traditional public high schools for the 2009–2010 school year. All data were assembled using archived information found at the Texas Education Agency (TEA). This information included the TEA report entitled Texas Open Enrollment Charter Schools Evaluation; TEA Snapshot Yearly Report; and Academic Excellence Indicator System (AEIS) data files. Microsoft Excel (Version 2010) was used to randomly select traditional public high schools categorized as Title 1 and non-Title 1 for comparison with Title 1 and non-Title 1 open-enrollment charter high schools. The IBM Statistical Package for the Social Sciences (SPSS) (IBM Statistics Version 20) was used for a one-way analysis of variance (ANOVA) conducted between one independent variable (charter or traditional school) and five dependent variables (mathematics exit-level TAKS scores, English exit-level TAKS scores, attendance rates, dropout rates, and expenditures per pupil). Traditional public high school students had higher or better average mean values than charter schools for mathematics exit-level TAKS scores, English exit-level TAKS scores, attendance rates, dropout rates, and expenditures per pupil. The ANOVA found that four of the five dependent variables were statistically significant at the 0.05 confidence level for the independent variable of school type, whether charter or traditional school. There was no significant difference found between the schools for attendance rates. Effect size calculations, using the eta-squared method, confirmed the comparisons with significant differences.
Date: December 2012
Creator: Jackson, Nokomis “Butch,” Jr.
Partner: UNT Libraries

Effect of Age on Likelihood to Test for Hiv

Description: HIV/AIDS can affect individuals of any age. Efforts to educate those considered to be most at-risk, based on the age at which the most individuals are infected, are ongoing and public. Less work and mainstream education outreach, however, is being directed at an older population, who can be more likely to contract HIV, is more susceptible to the effects of HIV, and more likely to develop AIDS, than younger persons. Guided by the Health Belief Model theory, research was conducted to determine what, if any, relationship existed between age of an individual and the possibility that an HIV test will be sought. Factors of gender, education, ethnicity and marital status were included in analyses. the research indicated that as age increased, likelihood for getting an HIV test decreased. Overall, most individuals had not been tested for HIV. the implications of an aged and aging population with HIV include a need for coordinated service delivery, increased education and outreach.
Date: May 2012
Creator: Dreyer, Katherine
Partner: UNT Libraries

The Effect of Naturalistic Behavior Strategies on the Quality of Social Interactions for Children with Autism

Description: Autism is primarily a social disorder and deficits in social?orienting may be responsible for the failure of children with autism to initiate critical social behaviors. The purpose of this research was to improve the quality of social interactions of children with autism by implementing naturalistic behavior strategies intervention utilizing a multiple baseline design across four participants. Naturalistic behavior strategies comprised a comprehensive package of integrated components including: (a) intervention in the child’s natural environment; (b) child-initiated play activities ; (c) prompts to emit language; (d) shaping for all vocal approximations and (e) delivery of natural reinforcement with embedded social interactions to maintain learned behavior. In addition to intervention, generalization of child behaviors was assessed across untrained parents and/or caregivers in the same environment. Results indicated the effectiveness of naturalistic teaching strategies package in increasing (a) the frequency of vocal mands for all children, (b) the number of times that children initiated social engagement during manding, and (c) intervals of nonverbal dyadic orienting. These skills generalized across two untrained caregivers in the same clinical setting without any training from the interventionist. Two parents required training during the generalization phase in order for their child’s behaviors to maintain at levels demonstrated during the intervention phase. Implications for future research and clinical practice are discussed.
Date: August 2012
Creator: Nichols, Susan Marie
Partner: UNT Libraries

Effect of Resistance Training on Cytokines in Hiv+ Men with Chemical Dependence

Description: Human immunodeficiency virus (HIV) and substance abuse (drug and/or alcohol) independently impair the immune system; importantly, the combination of HIV infection and substance abuse might produce more than an additive effect on this system. Tumor necrosis factor-alpha (TNF-?) and Interferon gamma (IFN?) are pro-inflammatory cytokines involved in differentiation of Th0 cells into Th1 cells. Interleukin 4 (IL-4) and Interleukin 10 (IL-10) are anti-inflammatory cytokine involved in differentiation of Th0 cells to Th2 cells. Unbalanced Th1 and Th2 cells can lead to immune suppression. Thus, changes in these cytokines could have important implications for people infected with HIV (HIV+). Resistance training can counteract muscle wasting, improve strength, and improve muscle mass. The purpose of this study was to examine the effect of resistance training on resting concentrations of circulating TNF-?, IFN-?, IL-4, and IL-10. Sixteen men (42 ± 11 years, 180.4 ± 9.1 cm, 89.2 ± 20.7 kg) infected with HIV and enrolled in an intensive 60-day in-patient substance addiction/abuse treatment program were recruited shortly after admission to the treatment facility. Participants were assigned to one of two groups using randomization: supervised resistance exercise 3 times per week using a progressive and non-linear periodized program (Exercise) or no exercise training (Non-Exercise) for six weeks. Before (Pre) and after (Post) the 6-week period, resting and fasted blood samples were obtained and analyzed for serum TNF-?, IFN-?, IL-4, and IL-10 concentrations using a high-sensitivity ELISA. TNF-? did not change following the 6-week period for Exercise (Pre: 4.8 ± 2.7 pg·ml-1; Post: 4.6 ± 2.4 pg·ml-1) or Non-Exercise (Pre: 3.0 ± 1.3 pg·ml-1; Post: 2.7 ± 0.8 pg·ml-1). IFN-?, IL-4, and IL-10 concentrations were below detectable limits. No adverse effects of the intervention were reported. A six-week resistance training program does not elicit changes in circulating TNF-? concentrations in men infected with HIV and ...
Date: May 2012
Creator: Curtis, John Harper
Partner: UNT Libraries

The Effect of Three Compositional Structures on the Compositional and Instructional Self-efficacy of Pre-service Music Teachers

Description: The purpose of this study was two-fold: 1) to compare the effects of three different composition tasks with varying degrees of structure on pre-service music teachers’ creative self-efficacy as composers and their instructional self-efficacy as pedagogues of composition; and 2) to describe through pre-service music teachers’ talk perceptions of composition and their experiences completing the three composition tasks. Participants (N = 29) were music education majors from three different sized universities in the northern-central region of the United States. At the beginning of the study, the participants answered a researcher-design self-efficacy questionnaire that measured (a) their self-efficacy as composers and (b) their self-efficacy as teachers of composition. Next, they composed three compositions of various task structures (unstructured, poem, and rhythm). Immediately after completing each task they again completed the self-efficacy questionnaire. Statistically significant mean differences between the pre-task administration of the measuring instrument and all three composition tasks were found for the pre-service teachers’ compositional self-efficacy. Statistically significant mean differences were also found between the unstructured task and the rhythm task, but not between the rhythm and poem tasks or the unstructured and poem tasks. For the pre-service teachers’ self-efficacy as pedagogues of composition question, the results were also statistically significant between the pre-task administration of the measuring instrument and all three composition tasks. Statistically significant mean differences were also found between the unstructured task and the rhythm task as well as the poem and rhythm tasks, but not between the unstructured and poem tasks. Additional data were gathered through semi-structured one-on-one interviews. Through their talk the pre-service music teachers commented that they enjoyed the overall composition process. This experience also seemed to challenge the participants’ assumptions about composition and appeared to make creative experiences more tenable and relevant to their future classroom experiences. The results of this study suggest ...
Date: August 2012
Creator: Hauser, Christian Vernon
Partner: UNT Libraries

The Effects of a Group Parent-coaching Package on the Behavior of Children with Autism and Their Parents

Description: Support for parents is an important part of treatment programs for children diagnosed with autism. Parent training programs have generally focused on prescribed goals in one-on-one training settings with measures directly related to the goals. Of interest here are the few studies that included collaborative goals, expanded measures, and group training. Benefits of such approaches include the establishment of natural communities of reinforcement and better understanding of the breadth of effects. The purpose of this study was to determine if a group coaching approach would be effective in changing a large range of parent and child skills. This experiment involved group sessions (presentations, discussion, video sharing, and problem solving) and three individual in-vivo coaching sessions. The intervention took place over the course of four weeks. Direct measures included a parent skills checklist and child target behaviors. Results indicated an overall improvement on most measures that maintained or improved at follow-up.
Date: December 2012
Creator: Vaughn, Brittany M. L.
Partner: UNT Libraries

Effects of a Self-care Intervention for Counselors on Compassion Fatigue and Compassion Satisfaction

Description: This study investigated the impact of a psychoeducational and experiential structured counselor self-care curriculum, developed by Drs. Charles and Kathleen Figley, on compassion fatigue and the prevention of professional impairment as measured by the Professional Quality of Life (ProQOL), Version 5. Volunteer licensed professional counselors, supervisors, and interns from four children's advocacy centers in Texas were assigned to treatment group (n = 21; 20 females, 1 male; mean age 34.4 years) or waitlist control group (n = 21; 19 females, 2 males; mean age 34.6 years). Participating counselors identified themselves ethnically as 64% Caucasian, 26% Hispanic, 7% African-American, and 2% Native-American. Employing a quasi-experimental design, three reliability-corrected analysis of covariance (ANCOVA) were utilized to analyze the data with an alpha level of .05 to assess statistical significance and partial eta squared to assess effect size. With pre-test scores as the covariate, results revealed in the experimental group a statistically significant reduction with large treatment effect for burnout (p = .01; partial ?2 = .15), a statistically nonsignificant reduction with a medium effect for secondary traumatic stress (p = .18; partial ?2 = .05), and a statistically nonsignificant increase with a medium effect for compassion satisfaction (p = .06; partial ?2= .09). Findings supported the use of this curriculum to train counselors on self-care as required of professional counselors by the American Counseling Association code of ethics and listed as a necessary skill in the standards of the Council for Accreditation of Counseling and Related Educational Programs.
Date: December 2012
Creator: Koehler, Christine Marie Guthrie
Partner: UNT Libraries

Effects of Dissipation on Propagation of Surface Electromagnetic and Acoustic Waves

Description: With the recent emergence of the field of metamaterials, the study of subwavelength propagation of plane waves and the dissipation of their energy either in the form of Joule losses in the case of electomagnetic waves or in the form of viscous dissipation in the case of acoustic waves in different interfaced media assumes great importance. with this motivation, I have worked on problems in two different areas, viz., plasmonics and surface acoustics. the first part (chapters 2 & 3) of the dissertation deals with the emerging field of plasmonics. Researchers have come up with various designs in an efort to fabricate efficient plasmonic waveguides capable of guiding plasmonic signals. However, the inherent dissipation in the form of Joule losses limits efficient usage of surface plasmon signal. a dielectric-metal-¬dielectric planar structure is one of the most practical plasmonic structures that can serve as an efficient waveguide to guide electromagnetic waves along the metal-dielectric boundary. I present here a theoretical study of propagation of surface plasmons along a symmetric dielectric-metal-dielectric structure and show how proper orientation of the optical axis of the anisotropic substrate enhances the propagation length. an equation for propagation length is derived in a wide range of frequencies. I also show how the frequency of coupled surface plasmons can be modulated by changing the thickness of the metal film. I propose a Kronig-Penny model for the plasmonic crystal, which in the long wavelength limit, may serve as a homogeneous dielectric substrate with high anisotropy which do not exist for natural optical crystals. in the second part (chapters 4 & 5) of the dissertation, I discuss an interesting effect of extraordinary absorption of acoustic energy due to resonant excitation of Rayleigh waves in a narrow water channel clad between two metal plates. Starting from the elastic properties of the ...
Date: May 2012
Creator: Nagaraj, Nagaraj
Partner: UNT Libraries

The Effects of Increasing Rates of Reinforcement Through an Alternative Fluent Behavior on the Acquisition and Extinction of Behavior in Dogs

Description: The purpose of the present study was to experimentally investigate the effects of interspersing the opportunity to perform a fluent behavior during the acquisition of a new behavior. The experimenter trained left and right paw movements in domestic canines using a multiple treatment design. One paw movement was trained with a typical shaping procedure while the other was trained with an opportunity to perform a fluent behavior, touching the dog’s nose to a plastic disc, following each successive approximation in the shaping procedure. Two extinction phases were implemented during the experiment. The results showed that higher rates of reinforcement were achieved primarily following changes in criteria for reinforcement for the behavior in acquisition. There were no effects on rate of acquisition of the behavior, but adding an alternative fluent behavior may have slowed the differentiation between the reinforced behavior and alternative behaviors for one dog. The behavior trained with the addition of an alternative fluent behavior extinguished more quickly than in the control condition and extinguished at similar rates to the opposite leg movement. This suggests that the technique of offering an alternative fluent behavior may facilitate the chaining of the opposite behavior with the behavior targeted for reinforcement.
Date: August 2012
Creator: Coulter, Laura E.
Partner: UNT Libraries

Effects of Layer Double Hydroxide Nanoclays on the Toxicity of Copper to Daphnia Magna

Description: Nanoparticles may affect secondary pollutants such as copper. Layer Double Hydroxides (LDH) are synthetically produced nanoparticles that adsorb copper via cation exchange. Pretreatment of copper test solutions with LDH nanoparticles followed by filtration removal of LDH nanoparticles demonstrated the smallest LDH aggregates removed the most copper toxicity. This was due to increased surface area for cation exchange relative to larger particle aggregates. Co-exposure tests of copper chloride and clay were run to determine if smaller clay particles increased copper uptake by D. magna. Coexposure treatments had lower LC50 values compared to the filtration tests, likely as a result of additive toxicity. LDH nanoclays do reduce copper toxicity in Daphnia magna and may serve as a remediation tool.
Date: May 2012
Creator: Blake, Deanne Renee
Partner: UNT Libraries

Effects of Minimum Quantity Lubrication (Mql) on Tool Life in Drilling Aisi 1018 Steel

Description: It has been reported that minimum quantity lubrication (MQL) provides better tool life compared to flood cooling under some drilling conditions. In this study, I evaluate the performance of uncoated HSS twist drill when machining AISI 1018 steel using a newly developed lubricant designed for MQL (EQO-Kut 718 by QualiChem Inc.). A randomized factorial design was used in the experiment. The results show that a tool life of 1110 holes with a corresponding flank wear of 0.058 mm was realized.
Date: August 2012
Creator: Maru, Tejas
Partner: UNT Libraries

Effects of Peripheral Nerve Injury on the Cells of the Dorsal Root Ganglion: a Role for Primary Cilia

Description: Primary cilia are ubiquitous sensory organelles found on most cell types including cells of the dorsal root ganglia (DRG). The DRG are groups of peripheral neurons that relay sensory information from the periphery to the CNS. Other cell types in the DRG include a type of glial cell, the satellite glial cells (SGCs). The SGCs surround the DRG neurons and, with the neurons, form functional sensory units. Currently are no reports describing the numbers of DRG cells that have cilia. We found that 26% of the SGCs had primary cilia. The incidence of cilia on neurons varied with neuron size, a property that roughly correlates with physiological characteristics. We found that 29% of the small, 16% of the medium and 5% of the large neurons had primary cilia. Primary cilia have been shown to have a role in cell proliferation in a variety of cell types. In some of the cells the cilia mediate the proliferative effects of Sonic hedgehog (Shh). In the CNS, Shh signaling through primary cilia affects proliferation during development as well as following injury, but no studies have looked at this function in the PNS. The SGCs and neurons of the DRG undergo complex changes following peripheral nerve injury such as axotomy. One marked change seen after axotomy is SGC proliferation and at later stages, neuronal death. We found that following axotomy there is a significant increase in the percentage of SGCs with primary cilia. We also found a significant increase in the percentage of medium-sized neurons with primary cilia. In other experiments we tested the idea that Shh plays a role in SGC proliferation. When Shh signaling was blocked following axotomy we found decreased proliferation of SGCs. This is the first report of a change in the percentage of cells with cilia following injury in ...
Date: December 2012
Creator: Smith, Sarah K.
Partner: UNT Libraries

The Effects of Price and Durability on Individual Discounting Functions When Purchasing Hypothetical Goods in a Simulated Internet Store

Description: Online shopping has rapidly expanded in the last decade. Online shopping necessarily imposes delays on all transactions. Behavior analysis has long studied the effects of delay on choice. Additionally, a number of researchers are beginning to study consumer behavior using a behavior-analytic approach. The current study attempted to extend research focusing on consumer behavior in online contexts. The experimenters attempted to evaluate whether goods acquire functional properties and whether these properties influence consumer choice. The researchers were specifically interested in studying acquisition costs and durability and in simulating a natural online shopping environment. Results from the current study extend the findings showing that delay and price influence choice. The data from the current study provide mixed evidence for control by item durability.
Date: August 2012
Creator: Gesick, Jeffrey Glen
Partner: UNT Libraries

The Effects of Textual Fluency on the Rate of Acquisition and Application of Intraverbal Relations

Description: Intraverbal behavior governs core elements of academic and intellectual behavior. These intraverbal relations can be explicitly taught when an individual is prompted to provide an appropriate response with pictures, text, or other stimuli following a verbal stimulus. It is possible that a focus on fluency of the target repertoires may lead to more conclusive data. the current study assessed the effects of precision teaching based instruction for component textual repertoires on the acquisition of intraverbal relations. Specifically, this study compared the effectiveness of two textual prompting procedures (with and without fluency-based instruction) on the acquisition and application of intraverbal relations using time-delay and a carefully controlled set of intraverbal stimuli. Results indicate that the use of textual prompts and an errorless time-delay transfer of stimulus control procedure were effective strategies for teaching intraverbal responses regardless of the inclusion of fluency-based instruction.
Date: May 2012
Creator: Shrontz, Rachael E.
Partner: UNT Libraries

Electrochemical Depostion of Bismuth on Ruthenium and Ruthenium Oxide Surfaces

Description: Cyclic voltammetry experiments were performed to compare the electrodeposition characteristics of bismuth on ruthenium. Two types of electrodes were used for comparison: a Ru shot electrode (polycrystalline) and a thin film of radio-frequency sputtered Ru on a Ti/Si(100) support. Experiments were performed in 1mM Bi(NO3)3/0.5M H2SO4 with switching potentials between -0.25 and 0.55V (vs. KCl sat. Ag/AgCl) and a 20mV/s scan rate. Grazing incidence x-ray diffraction (GIXRD) determined the freshly prepared thin film electrode was hexagonally close-packed. After thermally oxidizing at 600°C for 20 minutes, the thin film adopts the tetragonal structure consistent with RuO2. a hydrated oxide film (RuOx?(H2O)y) was made by holding 1.3V on the surface of the film in H2SO4 for 60 seconds and was determined to be amorphous. Underpotential deposition of Bi was observed on the metallic surfaces and the electrochemically oxidized surface; it was not observed on the thermal oxide.
Date: May 2012
Creator: Taylor, Daniel M.
Partner: UNT Libraries

Electrostatic Effects in III-V Semiconductor Based Metal-optical Nanostructures

Description: The modification of the band edge or emission energy of semiconductor quantum well light emitters due to image charge induced phenomenon is an emerging field of study. This effect observed in quantum well light emitters is critical for all metal-optics based light emitters including plasmonics, or nanometallic electrode based light emitters. This dissertation presents, for the first time, a systematic study of the image charge effect on semiconductor–metal systems. the necessity of introducing the image charge interactions is demonstrated by experiments and mathematical methods for semiconductor-metal image charge interactions are introduced and developed.
Date: May 2012
Creator: Gryczynski, Karol Grzegorz
Partner: UNT Libraries

Electrostatic Mechanism of Emission Enhancement in Hybrid Metal-semiconductor Light-emitting Heterostructures

Description: III-V nitrides have been put to use in a variety of applications including laser diodes for modern DVD devices and for solid-state white lighting. Plasmonics has come to the foreground over the past decade as a means for increasing the internal quantum efficiency (IQE) of devices through resonant interaction with surface plasmons which exist at metal/dielectric interfaces. Increases in emission intensity of an order of magnitude have been previously reported using silver thin-films on InGaN/GaN MQWs. the dependence on resonant interaction between the plasmons and the light emitter limits the applications of plasmonics for light emission. This dissertation presents a new non-resonant mechanism based on electrostatic interaction of carriers with induced image charges in a nearby metallic nanoparticle. Enhancement similar in strength to that of plasmonics is observed, without the restrictions imposed upon resonant interactions. in this work we demonstrate several key features of this new interaction, including intensity-dependent saturation, increase in the radiative recombination lifetime, and strongly inhomogeneous light emission. We also present a model for the interaction based on the aforementioned image charge interactions. Also discussed are results of work done in the course of this research resulting in the development of a novel technique for strain measurement in light-emitting structures. This technique makes use of a spectral fitting model to extract information about electron-phonon interactions in the sample which can then be related to strain using theoretical modeling.
Date: May 2012
Creator: Llopis, Antonio
Partner: UNT Libraries