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 Degree Level: Master's
 Collection: UNT Theses and Dissertations
Ab Initio and Density Functional Investigation of the Conformer Manifold of Melatonin and a Proposal for a Simple Dft-based Diagnostic for Nondynamical Correlation

Ab Initio and Density Functional Investigation of the Conformer Manifold of Melatonin and a Proposal for a Simple Dft-based Diagnostic for Nondynamical Correlation

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Date: August 2013
Creator: Fogueri, Uma
Description: In this work we address two problems in computational chemistry relevant to biomolecular modeling. In the first project, we consider the conformer space of melatonin as a a representative example of “real-life” flexible biomolecules. Geometries for all 52 unique conformers are optimized using spin-component scaled MP2, and then relative energies are obtained at the CCSD (T) level near the complete basis set limit. These are then used to validate a variety of DFT methods with and without empirical dispersion corrections, as well as some lower-level ab initio methods. Basis set convergence is found to be relatively slow due to internal C-H…O and C-H…N contacts. Absent dispersion corrections, many DFT functionals will transpose the two lowest conformers. Dispersion corrections resolve the problem for most functionals. Double hybrids yield particularly good performance, as does MP2.5. In the second project, we propose a simple DFT-based diagnostic for nondynamical correlation effects. Aλ= (1-TAE [ΧλC]/TAE[XC])/λ where TAE is the total atomization energy, XC the “pure” DFT exchange-correlation functional, and ΧλC the corresponding hybrid with 100λ% HF-type exchange. The diagnostic is a good predictor for sensitivity of energetics to the level of theory, unlike most of the wavefunction-based diagnostics. For GGA functionals, Aλ values approaching unity ...
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The Academic Steroid: Nonmedical Use of Prescription Stimulants at a North Texas University

The Academic Steroid: Nonmedical Use of Prescription Stimulants at a North Texas University

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Date: December 2014
Creator: Pennington, Cody W.
Description: The goal of this study was to determine the extent, motivations, and justifications of nonmedical prescription stimulant use among the population at a large public university in the North Texas region. Participants consisted of 526 undergraduate students enrolled at the studied university during the spring and summer 2014 semesters. The findings of the study suggest that the nonmedical use by students was higher than the findings in much of the current literature, but was within the parameters established in the literature. The primary motivation for nonmedical use was academic in nature and was justified by moderation of nonmedical use to strategic academic times.
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Accelerated Corrosion Test with Operation Simulation of All-Aluminum Microchannel Heat Exchangers

Accelerated Corrosion Test with Operation Simulation of All-Aluminum Microchannel Heat Exchangers

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Date: May 2016
Creator: Vaughan, Haydn
Description: The HVAC&R industry is looking to transition from copper-aluminum heat exchangers to all-aluminum microchannel technology. The want for the transition stemmed from seeing the performance improvement of all-aluminum microchannel radiators in the automotive industry. Applications differ between the two industries; therefore, applying this technology for HVAC&R use must be validated. Research towards operating modes of an all-aluminum heat exchanger in a defined corrosive environment will provide the industry with a better understanding of heat exchanger design and heat exchanger material selection. The worth in this is preventing overdesign and producing more efficient heat exchangers. Furthermore, ASHRAE members and the corrosion community will find value in a defined corrosion system and corrosion test procedure. The information gained through past research has progressed assessment of material performance; however, the methods improperly simulate and expedite natural weathering. The most common method being used is the ASTM (American Society of Testing Materials) Sea Water Acetic Acid Test. The research discussed in this paper was focused on improving a standard corrosion system by implementing system modifications to simulate heat exchanger operation while performing a modified wet-dry cyclic test (e.g. ASTM G85 Annex 5). The goal is to produce results that are more representative of natural ...
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Accuracy of Self-Reported Height, Weight, and Calculated BMI and Resulting FITNESSGRAM® Healthy Fitness Zone Classification

Accuracy of Self-Reported Height, Weight, and Calculated BMI and Resulting FITNESSGRAM® Healthy Fitness Zone Classification

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Date: May 2006
Creator: Rowell, Chelsie Joyce
Description: The determination of adiposity in adolescents is often assessed with calculations of body mass indices (BMI). Researchers often obtain these measurements from self-reported (SR) values. The purpose of this study was to determine the accuracy of SR height, weight, and calculated BMI (from height and weight). SR and actual measured (ME) BMI values were compared with standards from the FITNESSGRAM® Healthy Fitness Zone (HFZ) classifications. SR height and calculated BMI were found to be accurate while SR weight was, on average, underreported by 4.77 lbs. Because of these errors in SR height and weight, accuracy of classification into the FITNESSGRAM® HFZ was compromised. Consequently, it is important that researchers ascertain actual values of height and weight when measuring adolescents rather than use those from self-reports.
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Accuracy Variations in Human Facial Identification Based on Time of Exposure.

Accuracy Variations in Human Facial Identification Based on Time of Exposure.

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Date: December 2006
Creator: Cowle, Kenneth M.
Description: This study examined the relationship between time of exposure to the human face and accurate subsequent photo line-up identification. A volunteer group of 124 undergraduate students was divided into three approximately equal sized subgroups. The three groups were then exposed to a video or a portion of a video depicting a theft. Exposure times ranged from two minutes to 30 seconds. The subjects were then given a questionnaire and shown a photo line-up of the mock perpetrator and five foils. Subjects were asked to identify the perpetrator and mark that identification on the questionnaire. Results of the experiment indicated that the longer a subject was exposed the greater the possibility of an accurate identification.
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Acute Effects of the Antibiotic Streptomycin on Neural Network Activity and Pharmacological Responses

Acute Effects of the Antibiotic Streptomycin on Neural Network Activity and Pharmacological Responses

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Date: December 2014
Creator: Zeng, Wei Rong
Description: The purpose of this study is to find out that if antibiotic streptomycin decreases neuronal network activity or affects the pharmacological responses. The experiments in this study were conducted via MEA (multi-electrode array) technology which records neuronal activity from devices that have multiple small electrodes, serve as neural interfaces connecting neurons to electronic circuitry. The result of this study shows that streptomycin lowered the spike production of neuronal network, and also, sensitization was seen when neuronal network pre-exposed to streptomycin.
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Adhesion and Surface Energy Profiles of Large-area Atomic Layers of Two-dimensional MoS2 on Rigid Substrates by Facile Methods

Adhesion and Surface Energy Profiles of Large-area Atomic Layers of Two-dimensional MoS2 on Rigid Substrates by Facile Methods

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Date: May 2016
Creator: Wu, Min
Description: Two-dimensional (2D) transition metal dichalcogenides (TMDs) show great potential for the future electronics, optoelectronics and energy applications. But, the studies unveiling their interactions with the host substrates are sparse and limits their practical use for real device applications. We report the facile nano-scratch method to determine the adhesion energy of the wafer scale MoS2 atomic layers attached to the SiO2/Si and sapphire substrates. The practical adhesion energy of monolayer MoS2 on the SiO2/Si substrate is 7.78 J/m2. The practical adhesion energy was found to be an increasing function of the MoS2 thickness. Unlike SiO2/Si substrates, MoS2 films grown on the sapphire possess higher bonding energy, which is attributed to the defect-free growth and less number of grain boundaries, as well as less stress and strain stored at the interface owing to the similarity of Thermal Expansion Coefficient (TEC) between MoS2 films and sapphire substrate. Furthermore, we calculated the surface free energy of 2D MoS2 by the facile contact angle measurements and Neumann model fitting. A surface free energy ~85.3 mJ/m2 in few layers thick MoS2 manifests the hydrophilic nature of 2D MoS2. The high surface energy of MoS2 helps explain the good bonding strength at MoS2/substrate interface. This simple adhesion ...
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Adolescent Insomnia as a Predictor of Early Adulthood Outcomes

Adolescent Insomnia as a Predictor of Early Adulthood Outcomes

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Date: December 2006
Creator: Roane, Brandy Michelle
Description: Recent research found insomnia is a risk factor for psychiatric disorders in adults. To see if the same would be true in adolescents, the current study re-analyzed data from a national longitudinal study collected by ADDHealth that evaluated health behaviors in 4552 adolescents (mean age 14.9 years [SD 1.7]) at baseline and again 7-8 years later (n = 3489) during young adulthood. Insomnia was reported by 9.2% of the adolescents. Cross-sectionally, adolescent insomnia was associated with alcohol, cannabis, non-cannabis drugs, and tobacco use, and depression after controlling for gender and ethnicity. Prospectively, adolescent insomnia was a significant risk factor for depression diagnosis, suicidal ideation, and the use of depression and stress prescription medications in young adulthood after controlling for gender, ethnicity, and significant baseline variable. In addition, a trend was noted for suicidal attempts.
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An Analysis of Major American Riots: Issues in Riots and Riot Control

An Analysis of Major American Riots: Issues in Riots and Riot Control

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Date: August 2001
Creator: Cinoglu, Huseyin
Description: By conducting sound research to understand the concepts surrounding rioting and efficient riot response tactics, professionals, especially whose main job is to ensure the tranquility in the society, will be better prepared to deal with all kinds of civil movements. The purpose of this study, consequently, is to meet the growing need for educational materials in this area and to provide riot response case studies, which demonstrate the numerous administrative challenges faced by law enforcement decision makers. In this study, seven major riots from throughout the United States are discussed including the Hay Market Riot of 1886, the Watts Riot of 1965, and Los Angeles Riots of 1992. Each riot case is studied in five different and independent stages: the setting and pre-disturbance situation, basic causes of the event, the disturbance situation, the response to the riot, and the aftermath of the incident. The study of all of these stages is intended to help police administrators acquire a general perspective on collective violence, and help them prevent future occurrences in their jurisdictions. In this thesis a special reference is given to the deficiencies of American riot policing and some recommendations were formed accordingly. Therefore, the study concludes with a list ...
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An Analysis of Motivational Cues in Virtual Environments.

An Analysis of Motivational Cues in Virtual Environments.

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Date: December 2003
Creator: Voruganti, Lavanya
Description: Guiding navigation in virtual environments (VEs) is a challenging task. A key issue in the navigation of a virtual environment is to be able to strike a balance between the user's need to explore the environment freely and the designer's need to ensure that the user experiences all the important events in the VE. This thesis reports on a study aimed at comparing the effectiveness of various navigation cues that are used to motivate users towards a specific target location. The results of this study indicate some significant differences in how users responded to the various cues.
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An Analysis of the Composition Process of Bartók's Eight Improvisations on Hungarian Peasant Songs, Op. 20

An Analysis of the Composition Process of Bartók's Eight Improvisations on Hungarian Peasant Songs, Op. 20

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Date: May 2000
Creator: Kochbeck, Olivia M.
Description: This is a study of Bartók's compositional process as it relates to the Improvisations, Op. 20. The study, which focuses on the analysis of the draft manuscript 50PS1, compares the draft and other relevant sources with the final composition. Bartók's framework for the entire Improvisations is based on a compositional strategy of pairing individual improvisations combined with systematic revision of the draft copy by the introduction of tritones as tonal equivalents and movement by fifths from semitones, to achieve structural coherence in the individual improvisations. The tonic-dominant relationship is used to rearrange the individual improvisations in the draft and tritones as tonal equivalents are used to propel the movement between the improvisations to produce a coherent whole.
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Anchor Nodes Placement for Effective Passive Localization

Anchor Nodes Placement for Effective Passive Localization

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Date: August 2010
Creator: Pasupathy, Karthikeyan
Description: Wireless sensor networks are composed of sensor nodes, which can monitor an environment and observe events of interest. These networks are applied in various fields including but not limited to environmental, industrial and habitat monitoring. In many applications, the exact location of the sensor nodes is unknown after deployment. Localization is a process used to find sensor node's positional coordinates, which is vital information. The localization is generally assisted by anchor nodes that are also sensor nodes but with known locations. Anchor nodes generally are expensive and need to be optimally placed for effective localization. Passive localization is one of the localization techniques where the sensor nodes silently listen to the global events like thunder sounds, seismic waves, lighting, etc. According to previous studies, the ideal location to place anchor nodes was on the perimeter of the sensor network. This may not be the case in passive localization, since the function of anchor nodes here is different than the anchor nodes used in other localization systems. I do extensive studies on positioning anchor nodes for effective localization. Several simulations are run in dense and sparse networks for proper positioning of anchor nodes. I show that, for effective passive localization, the ...
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'...and one of time.': A Composition for Full Orchestra with Narration

'...and one of time.': A Composition for Full Orchestra with Narration

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Date: December 1999
Creator: Rinker, John Thomas
Description: ‘...and one of time.' is a reinterpretation of a small musical moment from Philip Glass' opera, Einstein on the Beach, centered around the phrase "Berne, Switzerland 1905." This reinterpretation is realized through the use of several different compositional techniques including spectral composition, micropolyphony and dodecaphony, as well as the application of extra-musical models developed by Alan Lightman, John Gardner, Italo Calvino and Albert Einstein.
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“The Angular Degrees of Freedom” and Other Stories

“The Angular Degrees of Freedom” and Other Stories

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Date: December 2014
Creator: Feagin, Aprell McQueeney
Description: The preface, " Performing Brain Surgery: The Problematic Nature of Endings in Short Fiction," deals with the many and varied difficulties short story writers encounter when attempting to craft endings. Beginning with Raymond Carver and Flannery O’Connor and moving to my own work, I discuss some of the obscure criteria used to designate a successful ending, as well as the more concrete idea of the ending as a unifying element. Five short stories make up the remainder of this thesis: "In-between Girls," "Crocodile Man," "Surprising Things, Sometimes Amusing," "Good Jewelry," and "The Angular Degrees of Freedom."
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Animals That Die

Animals That Die

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Date: December 2006
Creator: Campbell, Susan Maxwell
Description: The thesis has two parts. Part I is a critical essay entitled "Lessons Under the Amfalula." Part II is the collection of poems entitled "Animals That Die."
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The Apologist Tradition: A Transitional Period in Southern Proslavery Thought, 1831-1845

The Apologist Tradition: A Transitional Period in Southern Proslavery Thought, 1831-1845

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Date: December 2000
Creator: Austin, Clara
Description: Early antebellum defenders of slavery acknowledged that slavery created problems for southern society. They contended, however, that slave society was better and more natural than other forms of social organization. Thomas R. Dew, William Harper, and James Henry Hammond each expressed a social philosophy in which slavery had a crucial role in preserving social order. They argued from the basis of social organicism, the idea that society should have an elite that controlled the masses. For all three men, slavery represented a system of order that helped balance the dangers of democracy. Significantly, however, all three men recognized that the slave system was not perfect, and despite their defense of slavery, argued that it was a human institution and therefore corruptible.
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The Application of a Health Service Utilization Model to a Low Income, Ethnically Diverse Sample of Women

The Application of a Health Service Utilization Model to a Low Income, Ethnically Diverse Sample of Women

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Date: August 2000
Creator: Keenan, Lisa A.
Description: A model for health care utilization was applied to a sample of low income women. Demographic Predisposing, Psychosocial Predisposing, Illness Level, and Enabling indicators were examined separately for African American (n = 266), Anglo American (n = 200), and Mexican American (n = 210) women. Structural Equation Modeling revealed that for African American and Anglo American women, Illness Level, the only significant path to Utilization, had a mediating effect on Psychosocial Predisposing indicators. The model for Mexican Americans was the most complex with Enabling indicators affecting Illness Level and Utilization. Psychosocial Predisposing indicators were mediated by Illness Level and Enabling indicators which both directly affected Utilization. Implications of the results for future research are addressed.
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Application of Cyclic Polarization of Aluminum 3003 Used in All-aluminum Microchannel Heat Exchangers

Application of Cyclic Polarization of Aluminum 3003 Used in All-aluminum Microchannel Heat Exchangers

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Date: May 2015
Creator: Barnes, Javier
Description: All-aluminum microchannel heat exchangers are designed to significantly reduce refrigerant charge requirements, weight, reduced brazed joints, and decreased potential for leakage by increasing reliability. Al 3003 alloy is corrosion resistant and can be formed, welded, and brazed but the issue with all-aluminum heat exchangers is localized corrosion (pitting) in corrosive environments. Currently, there is no universally accepted corrosion test that all coil manufacturers use to characterize their products. Electrochemical testing method of cyclic polarization was employed in this investigation and relevant parameters including electrolyte corrosive agent and its concentration, electrolyte pH, and applied potential scan rate was varied to find an optimal set of parameters. Results of cyclic polarization of Al 3003 in electrolytes containing various concentrations of NaCl were compared with those of the tests in Sea Water Acidified Accelerated Test (SWAAT) electrolyte and it is shown the SWAAT electrolyte (4.2% sea salt acidified to pH of 2.9) is by far stronger (in terms of corrosivity) than typical 3.5% NaCl solution used in most corrosion testing. Corrosion rates (g/m2yr) of Al 3003 measured in this investigation were comparable to those provided by ISO 9223 standard corresponding to C1 through CX categories. Duration of cyclic polarization test is much shorter ...
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Application of Thermomechanical Characterization Techniques to Bismuth Telluride Based Thermoelectric Materials

Application of Thermomechanical Characterization Techniques to Bismuth Telluride Based Thermoelectric Materials

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Date: August 2002
Creator: White, John B.
Description: The thermoelectric properties of bismuth telluride based thermoelectric (TE) materials are well-characterized, but comparatively little has been published on the thermomechanical properties. In this paper, dynamic mechanical analysis (DMA) and differential scanning calorimetry data for bismuth telluride based TE materials is presented. The TE materials' tan delta values, indicative of viscoelastic energy dissipation modes, approached that of glassy or crystalline polymers, were greater than ten times the tan delta of structural metals, and reflected the anisotropic nature of TE materials. DMA thermal scans showed changes in mechanical properties versus temperature with clear hysteresis effects. These results showed that the application of DMA techniques are useful for evaluation of thermophysical and thermomechanical properties of these TE materials.
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Art Criticism and the Gendering of Lee Bontecou's Art, ca. 1959 - 1964

Art Criticism and the Gendering of Lee Bontecou's Art, ca. 1959 - 1964

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Date: December 2005
Creator: Estrada-Berg, Victoria
Description: This thesis identifies and analyzes gendering in the art writing devoted to Lee Bontecou's metal and canvas sculptures made from the 1959 - 1964. Through a careful reading of reviews and articles written about Bontecou's constructions, this thesis reconstructs the context of the art world in the United States at mid-century and investigates how cultural expectations regarding gender directed the reception of Bontecou's art, beginning in 1959 and continuing through mid-1960s. Incorporating a description of the contemporaneous cultural context with description of the constructions and an analysis of examples of primary writing, the thesis chronologically follows the evolution of a tendency in art writing to associate gender-specific motivation and interpretation to one recurring feature of Bontecou's works.
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Asserting Identity in Wagner's Shadow: The Case of Engelbert Humperdinck's  Königskinder (1897)

Asserting Identity in Wagner's Shadow: The Case of Engelbert Humperdinck's Königskinder (1897)

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Date: August 2004
Creator: Kinnett, Forest Randolph
Description: Engelbert Humperdinck (1854-1921), who was considered a Wagnerian due to to his past work in Bayreuth and the Wagnerian traits of his Hänsel und Gretel, seems to have believed that to define himself as a composer, he had to engage somehow with that designation, whether through orthodox Wagner imitation or an assertion of his independence from Wagner's musical legacy. The latter kind of engagement can be seen in Humperdinck's Königskinder (1897), in which he developed a new kind of declamatory notation within the context of melodrama, thus fulfilling Wagnerian ideals as well as progressing beyond them. The effectiveness of Humperdinck's effort is seen in the ensuing critical reception, in which the realities of being heard as a Wagnerian composer are clarified.
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Assessing Optimal Sibling Training Conditions: An Empirical Approach.

Assessing Optimal Sibling Training Conditions: An Empirical Approach.

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Date: August 2005
Creator: Merker, Stephanie K.
Description: The purpose of the study was to investigate the effects of play materials on the interactions between a child with autism and her sibling. Three conditions were assessed: open choice, materials chosen by the child with autism, and materials chosen by the typically developing sibling. Within each activity, measures of social interactions were assessed. Results of the assessment showed that more interactions occurred with a material chosen by the child with autism. After sibling training (targeting specific teaching skills), social interactions remained highest in the condition with materials chosen by the child with autism. The results are discussed in terms of a material assessment to optimize sibling training conditions and the importance of sibling relationships.
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Assessing the Potential Effects of Climate Variability on Reservoir Water Volume in North-Central Texas Using GIS and Models: A Case Study of Ray Roberts Lake.

Assessing the Potential Effects of Climate Variability on Reservoir Water Volume in North-Central Texas Using GIS and Models: A Case Study of Ray Roberts Lake.

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Date: December 2005
Creator: Osei-Adjei, Peter
Description: Assessing the impact of climate variability on water resources is one of the difficult tasks in planning the future growth of North-Central Texas. This study defined twelve extreme climate scenarios. Data from each scenario was input to a hydrological model (HEC-HMS) to calculate watershed runoff to Lake Ray Roberts. Model parameters are determined using Geographic Information System (GIS). The water balance was calculated for current and future water demand and resulting change in the volume and level of this reservoir. The results indicate certain climate scenarios decrease in volume. Thus, local governments should plan alternative water management strategies during droughts.
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Automated Defense Against Worm Propagation.

Automated Defense Against Worm Propagation.

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Date: December 2005
Creator: Patwardhan, Sudeep
Description: Worms have caused significant destruction over the last few years. Network security elements such as firewalls, IDS, etc have been ineffective against worms. Some worms are so fast that a manual intervention is not possible. This brings in the need for a stronger security architecture which can automatically react to stop worm propagation. The method has to be signature independent so that it can stop new worms. In this thesis, an automated defense system (ADS) is developed to automate defense against worms and contain the worm to a level where manual intervention is possible. This is accomplished with a two level architecture with feedback at each level. The inner loop is based on control system theory and uses the properties of PID (proportional, integral and differential controller). The outer loop works at the network level and stops the worm to reach its spread saturation point. In our lab setup, we verified that with only inner loop active the worm was delayed, and with both loops active we were able to restrict the propagation to 10% of the targeted hosts. One concern for deployment of a worm containment mechanism was degradation of throughput for legitimate traffic. We found that with proper ...
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