States

Scaling supernova hydrodynamics to the laboratory (open access)

Scaling supernova hydrodynamics to the laboratory

Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane et al., Astrophys. J.478, L75 (1997) The Nova laser is used to shock two-layer targets, producing Richtmyer-Meshkov (RM) and Rayleigh-Taylor (RT) instabilities at the interfaces between the layers, analogous to instabilities seen at the interfaces of SN 1987A. Because the hydrodynamics in the laser experiments at intermediate times (3-40 ns) and in SN 1987A at intermediate times (5 s-10{sup 4} s) are well described by the Euler equations, the hydrodynamics scale between the two regimes. The experiments are modeled using the hydrodynamics codes HYADES and CALE, and the supernova code PROMETHEUS, thus serving as a benchmark for PROMETHEUS. Results of the experiments and simulations are presented. Analysis of the spike and bubble velocities in the experiment using potential flow theory and a modified Ott thin shell theory is presented. A numerical study of 2D vs. 3D differences in instability growth at the O-He and He-H interface of SN 1987A, and the design for analogous laser experiments …
Date: June 1, 1999
Creator: Kane, J.O.
System: The UNT Digital Library
An Evaluation of Unsaturated Flow Models in an Arid Climate (open access)

An Evaluation of Unsaturated Flow Models in an Arid Climate

The objective of this study was to evaluate the effectiveness of two unsaturated flow models in arid regions. The area selected for the study was the Area 5 Radioactive Waste Management Site (RWMS) at the Nevada Test Site in Nye County, Nevada. The two models selected for this evaluation were HYDRUS-1D [Simunek et al., 1998] and the SHAW model [Flerchinger and Saxton, 1989]. Approximately 5 years of soil-water and atmospheric data collected from an instrumented weighing lysimeter site near the RWMS were used for building the models with actual initial and boundary conditions representative of the site. Physical processes affecting the site and model performance were explored. Model performance was based on a detailed sensitivity analysis and ultimately on storage comparisons. During the process of developing descriptive model input, procedures for converting hydraulic parameters for each model were explored. In addition, the compilation of atmospheric data collected at the site became a useful tool for developing predictive functions for future studies. The final model results were used to evaluate the capacities of the HYDRUS and SHAW models for predicting soil-moisture movement and variable surface phenomena for bare soil conditions in the arid vadose zone. The development of calibrated models along …
Date: December 1, 1999
Creator: Dixon, J.
System: The UNT Digital Library
The Effects of Music Training on Electroencephalographic Coherence of Preschool Children (open access)

The Effects of Music Training on Electroencephalographic Coherence of Preschool Children

The purpose of this study was to examine the effects of music training on electroencephalographic (EEG) coherence of preschool children. EEG coherence is a measurement of brain wave activity that reflects anatomical and neurophysiological parameters and functional connectivity between areas of the brain. Participants were 4- to 6-year-old children divided into two groups: one received music training for 20 minutes twice a week for 10 weeks while the other group served as controls. Nineteen channels of EEG data were collected from each child pre- and post-training. Data were collected from three conditions: eyes-open resting, listening to music, and performing the Object Assembly subtest of the Weschler Preschool and Primary Scale of Intelligence - Revised (1989). The hypothesis was that the music training group would show increased EEG coherence as compared to controls. The EEG data was reduced into seven bandwidths and analyzed separately for each condition. Multiple ANCOVAs were used to factor out pre-test variability and to maximize connectivity changes between the two groups. The dependent measures were the post-QEEG electrode pairs and the covariates were the pre-QEEG electrode pairs. Results indicated the eyes-open and listening to music conditions showed more significant changes between the groups than the Object Assembly …
Date: August 1999
Creator: DeBeus, Roger J. (Roger John)
System: The UNT Digital Library
Development and Validation of the Checklist for Differential Diagnosis of Attentional Problems (open access)

Development and Validation of the Checklist for Differential Diagnosis of Attentional Problems

The current study discussed the development and validation of the Checklist for Differential Diagnosis of Attentional Problems (CDDAP), a tool for use with adults seeking diagnosis and treatment of an Attention Deficit Hyperactivity Disorder. Normative data are provided on three subject groups (ADHD adults, controls, and adults with other psychiatric disorders). Convergent validity was established with the SCL-90, and criterion validity established through comparing scaled scores with final diagnoses. Overall, this measure was accurate at differentiating adults with ADHD from controls and adults with other psychiatric disorders. Results indicated that the CDDAP was also able to identify other psychiatric disorders with 71 to 92% accuracy, depending on the disorder.
Date: May 1999
Creator: Taylor, Cindy J.
System: The UNT Digital Library

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

Access: Use of this item is restricted to the UNT Community
‘...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.
Date: December 1999
Creator: Rinker, John Thomas
System: The UNT Digital Library
A Model of Salespeople's Training Attitudes and Related Outcomes (open access)

A Model of Salespeople's Training Attitudes and Related Outcomes

Today many selling organizations are reexamining and revising their philosophy for managing salespeople because of increase costs of hiring and maintaining a sales force. More than everm management is looking for ways to assist salespeople in becoming more productive and effective faster. One avenue for enhancing salespersons' performance is through improved sales training practices. improved sales training practices should help salespeople view training, and how sales training transcends to the job environment. Considering the need for greater understanding concerning salespeople's perceptions of sales training and assuming the influence of those perceptions on job performance and other outcomes, this study develops and executes an analysis of several proposed relationships among personal characteristics, job related characteristics, perceived training needs, sales training variables, and related outcomes. The program of research identifies and evaluates salespeople's attitudes toward sales training and specifies influences of those training perceptions on salesperson' behaviors and general attitudes. As well, a relationship between salespeople's transfer of training materials, their use, and individual performance are evaluated.
Date: August 1999
Creator: Wilson, Phillip H.
System: The UNT Digital Library
The Effects of a Brain-based Learning Strategy, Mind Mapping, on Achievement of Adults in a Training Environment with Considerations to Learning Styles and Brain Hemisphericity (open access)

The Effects of a Brain-based Learning Strategy, Mind Mapping, on Achievement of Adults in a Training Environment with Considerations to Learning Styles and Brain Hemisphericity

This study examined the effectiveness of Mind Mapping (a diagram of the structure of ideas in an associative manner, using graphics, color and key words) as a note-taking device in a training course in a large, high-tech corporation, as compared to traditional note-taking. The population for this study consisted of personnel employed by a major high-tech firm, that had voluntarily registered for a Mind Mapping training class. The effect of Mind Mapping was measured by the pre-test and post-test of the control and experimental groups.
Date: May 1999
Creator: Williams, Marian H. (Marian Haile)
System: The UNT Digital Library
A Comparative Analysis of Intensive Individual Play Therapy and Intensive Sibling Group Play Therapy with Child Witnesses of Domestic Violence (open access)

A Comparative Analysis of Intensive Individual Play Therapy and Intensive Sibling Group Play Therapy with Child Witnesses of Domestic Violence

This study was designed to determine the effectiveness of intensive sibling group play therapy in: (a) improving the self-concept of child witnesses of domestic violence; (b) reducing internalizing behavior problems, such as withdrawal, somatic complaints, anxiety and depression, of child witnesses of domestic violence; (c) reducing externalizing behavior problems, such as aggression and delinquency, of child witnesses of domestic violence; and (d) reducing overall behavior problems of child witnesses of domestic violence. A second objective of this study was to compare the effectiveness of intensive sibling group play therapy and intensive individual play therapy on the above identified dimensions.
Date: May 1999
Creator: Tyndall-Lind, Ashley
System: The UNT Digital Library
Scientific Considerations of Olestra as a Fat Substitute (open access)

Scientific Considerations of Olestra as a Fat Substitute

Olestra is, a sucrose polyester, a noncaloric fat substitute, made from sucrose and several fatty acid esters. It has been approved by the FDA as a food additive used in preparing low-fat deep-frying foods such as savory snacks. Available literature on olestra was evaluated that had both positive and negative connotations. Clinical trials in numerous species of animals including humans were conducted to determine if olestra would affect the utilization and absorption of macro- and micronutrients; the effects of olestra on growth, reproduction, or its toxicity were also examined. The roles of olestra as a fat substitute, how it could effect on humans and the environment, and the potential impacts from its use in large amounts were assessed. Olestra can be removed from the environment by aerobic bacteria and fungi which may be isolated from activated sludge and soils.
Date: December 1999
Creator: Rattagool, Kullakan
System: The UNT Digital Library
The Effects of Brief Exposure to Non Traditional Media Messages on Female Body Image (open access)

The Effects of Brief Exposure to Non Traditional Media Messages on Female Body Image

Body image may be defined as the perception or attitude one has regarding the appearance of his or her body. Body image concerns are not only central to the diagnostic criteria of eating disorders, but also create distress for nonclinical populations. Females (n = 167) from three universities participated in a study by completing the Eating Disorder Inventory - 2 (Garner, 1991) and the Figure Rating Scale (Stunkard, Sorenson, & Schulsinger, 1983); watching a video; and then completing the instruments again. Subjects in the treatment group (n = 89) viewed a video designed to increase awareness of unrealistic body sizes and shapes seen in the media (Kilbourne, 1995). Subjects in the comparison group (n = 77) viewed a video unrelated to female body image.
Date: August 1999
Creator: Garber, Carla F.
System: The UNT Digital Library
Online Student Services in American Higher Education: Contemporary Issues and Future Implications (open access)

Online Student Services in American Higher Education: Contemporary Issues and Future Implications

This study examined the way in which the top 100 "most wired" colleges and universities provide online student services. Named by a national publication in May 1998, these colleges and universities were chosen because of their technological infrastructure, courses offered online, public computers on campus, and online student services, among other aspects.
Date: May 1999
Creator: McRae, Mary Suzanne
System: The UNT Digital Library
Stochastic Characterization of Cast Metal Microstructure (open access)

Stochastic Characterization of Cast Metal Microstructure

The major goal of this work is to provide a means to characterize the final structure of a metal that has solidified from a melt. The thermally controlled solidification of a binary alloy, nucleated at isolated sites, is described by the evolution of a probability distribution function (PDF). The relevant equation required for propagating the PDF is developed with variables for grain size and distance to nearest neighbor. The phenomena of nucleation, growth, and impingement of the grains are discussed, and used as the basis for developing rate equations that evolve the PDF. The complementary equations describing global heat and solute transfer are discussed, and coupled with the microstructure evolution equations for grain growth and PDF evolution. The full set of equations is solved numerically and results are compared with experimental data for the plutonium 1 weight percent gallium system. The three principal results of this work are: (1) The formulation of transient evolution equations for the PDF description of nucleation, growth, and impingement of a distribution of grain sizes and locations; (2) Solution of the equations to give a correlation for final average grain size as a function of material parameters, nucleation site density, and cooling rate; and (3) …
Date: June 1, 1999
Creator: Steinzig, M.
System: The UNT Digital Library
Large eddy simulation of Rayleigh-Taylor instability using the arbitrary Lagrangian-Eulerian method (open access)

Large eddy simulation of Rayleigh-Taylor instability using the arbitrary Lagrangian-Eulerian method

This research addresses the application of a large eddy simulation (LES) to Arbitrary Lagrangian Eulerian (ALE) simulations of Rayleigh-Taylor instability. First, ALE simulations of simplified Rayleigh-Taylor instability are studied. The advantages of ALE over Eulerian simulations are shown. Next, the behavior of the LES is examined in a more complicated ALE simulation of Rayleigh-Taylor instability. The effects of eddy viscosity and stochastic backscatter are examined. The LES is also coupled with ALE to increase grid resolution in areas where it is needed. Finally, the methods studied above are applied to two sets of experimental simulations. In these simulations, ALE allows the mesh to follow expanding experimental targets, while LES can be used to mimic the effect of unresolved instability modes.
Date: December 1, 1999
Creator: Darlington, R
System: The UNT Digital Library
Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants (open access)

Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants

Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO{sub 2} were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO{sub 2}, large photoelectrocatalytic effect for the reduction of CO{sub 2} was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO{sub 2} in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.
Date: November 8, 1999
Creator: Zheng, Junwei
System: The UNT Digital Library
Preliminary studies on identification of inorganic species in complex mixtures by electrospray mass spectrometry in the counter ion mode (open access)

Preliminary studies on identification of inorganic species in complex mixtures by electrospray mass spectrometry in the counter ion mode

Suppression of mass spectral peaks due to matrix problem is a major hurdle to overcome during identification work. So far, preliminary studies have been done in investigating solutions containing various percentages of nitric and hydrochloric acid. Since other anions would also be present in real samples, also needed to be examined is how the extent of suppression of metal complexes by Cl{sup {minus}} compares with suppression by other anions such as PO{sub 4}{sup 3{minus}} or SO{sub 4}{sup 2{minus}}. If suppression of other anions is as severe as that of the chloride ion, then it would be virtually impossible to analyze unknown samples containing large amount of such anions by direct infusion electrospray mass spectrometry. It seems like a separation step is needed to separate these matrix anions from the metal complexes prior to putting the solution through the electrospray. However, separation of inorganic complexes can be difficult and has not been studied thoroughly as LC separation of bioorganic compounds. Both zinc and copper chloro complexes have been observed to be more tolerant to higher amount of chloride ion present in a solution compared to the group I and II metal chloro complexes. Other transition metals including the lanthanide complexes need …
Date: November 8, 1999
Creator: Mollah, Sahana
System: The UNT Digital Library
An Analysis of Program Options for Gifted Middle School Students (open access)

An Analysis of Program Options for Gifted Middle School Students

The purpose of this study was to compare three different types of programming options for identified gifted and talented middle school students.
Date: May 1999
Creator: Curry, Brenda Lierin
System: The UNT Digital Library
Asleep in the Arms of God (open access)

Asleep in the Arms of God

A work of creative fiction in the form of a short novel, Asleep in the Arms of God is a limited-omniscient and omniscient narrative describing the experiences of a man named Wafer Roberts, born in Jack County, Texas, in 1900. The novel spans the years from 1900 to 1925, and moves from the Keechi Valley of North Texas, to Fort Worth and then France during World War One, and back again to the Keechi Valley. The dissertation opens with a preface, which examines the form of the novel, and regional and other aspects of this particular work, especially as they relate to the postmodern concern with fragmentation and conditional identity. Wafer confronts in the novel aspects of his own questionable history, which echo the larger concern with exploitative practices including racism, patriarchy, overplanting and overgrazing, and pollution, which contribute to and climax in the postmodern fragmentation. The novel attempts to make a critique of the exploitative rage of Western civilization.
Date: December 1999
Creator: Clay, Kevin M.
System: The UNT Digital Library
Information Seeking in a Virtual Learning Environment (open access)

Information Seeking in a Virtual Learning Environment

Duplicating a time series study done by Kuhlthau and associates in 1989, this study examines the applicability of the Information Search Process (ISP) Model in the context of a virtual learning environment. This study confirms that students given an information seeking task in a virtual learning environment do exhibit the stages indicated by the ISP Model. The six-phase ISP Model is shown to be valid for describing the different stages of cognitive, affective, and physical tasks individuals progress through when facing a situation where they must search for information to complete an academic task in a virtual learning environment. The findings in this study further indicate there is no relationship between the amount of computer experience subjects possess and demonstrating the patterns of thoughts, feelings, and actions described by the ISP Model. The study demonstrates the ISP Model to be independent of the original physical library environments where the model was developed. An attempt is made to represent the ISP model in a slightly different manner that provides more of the sense of motion and interaction among the components of thoughts, feelings, and action than is currently provided for in the model. The study suggests that the development of non-self-reporting …
Date: August 1999
Creator: Byron, Suzanne M.
System: The UNT Digital Library

Peer Education: Building Community Through Playback Theatre Action Methods

Access: Use of this item is restricted to the UNT Community
The primary purpose of this study was to use some of the action methods of playback theatre to facilitate the acquisition of knowledge through the experience of building community. The impact of action methods on group dynamics and the relationship among methods, individual perceptions, and the acquisition of knowledge were analyzed. The researcher suggested that playback theatre action methods provided a climate in which groups can improve the quality of their interactions. The Hill Interaction Matrix (HIM) formed the basis for the study's analysis of interactions. Since the researcher concluded there were significantly more interactions coded in the "power quadrant" after training, the researcher assumed that playback theatre action methods are a catalyst for keeping the focus on persons in the group, encouraging risk-taking behaviors, and producing constructive feedback between members. Based on session summaries, individual interviews, and an analysis of the Group Environment Scale (GES), the training group became more cohesive, became more expressive, promoted independence, encouraged self-discovery, and adapted in innovative ways. The experience of an interconnected community created a space where positive growth could occur. The researcher concluded that the process of community building is intricately connected with a person's ability to make meaning out of experiences. …
Date: August 1999
Creator: Kintigh, Monica R.
System: The UNT Digital Library
Monitoring Watershed Health in the Upper Trinity River Basin, North Central Texas (open access)

Monitoring Watershed Health in the Upper Trinity River Basin, North Central Texas

This study conducts watershed analysis using biological and geo-spatial techniques. Incorporating landscape features with biological attributes has been shown to be an effective method of monitoring environmental quality within watersheds. In situ biomonitoring using the Asiatic Clam, Corbicula fluminea, habitat suitability, and water quality data were evaluated for their potential to describe ecological conditions in agricultural and urban areas within the Upper Trinity River watershed. These data were analyzed with GIS to identify effects of land use on ecological conditions. C. fluminea downstream of point source effluents was effective detecting in-stream toxicity. Ambient toxicity appears to have improved in the Trinity, although urban influences limit aspects of aquatic life. No association between habitat quality and land use was identified.
Date: May 1999
Creator: Csekitz, Jill Diane
System: The UNT Digital Library

Hospitality Students' Attitudes and Behavioral Intentions toward Learning and Using Computer Technology

Access: Use of this item is restricted to the UNT Community
Following Ajzen/Fishbein's 1980 Theory of Reasoned Action, influences of hospitality students' external variables (age, gender, university classification, and work experience) on computer attitudes, and relationships between computer attitudes and intentions to learn and use computers were tested. A sample of 412 hospitality students completed two measurements: Loyd/Gressard's 1984 Computer Attitude Scale, and Behavioral Intentions to Learn and Use Computers. Males and females had positive computer attitudes. Graduates had more positive computer attitudes. No interaction effect existed between gender and classification. No relationships existed between age and work experience on computer attitudes. Computer attitudes positively correlated with intentions to learn and use computers. Results supported the Theory of Reasoned Action. External variables partially influence attitudes and attitudes influence intentions.
Date: December 1999
Creator: Chuvessiriporn, Suttichai
System: The UNT Digital Library

Animals-as-Trope in the Selected Fiction of Zora Neale Hurston, Alice Walker, and Toni Morrison

Access: Use of this item is restricted to the UNT Community
In this dissertation, I show how 20th century African-American women writers such as Zora Neale Hurston, Alice Walker, and Toni Morrison utilize animals-as-trope in order to illustrate the writers' humanity and literary vision. In the texts that I have selected, I have found that animals-as-trope functions in two important ways: the first function of animal as trope is a pragmatic one, which serves to express the humanity of African Americans; and the second function of animal tropes in African-American women's fiction is relational and expresses these writers' "ethic of caring" that stems from their folk and womanist world view. Found primarily in slave narratives and in domestic fiction of the 19th and early 20th centuries, pragmatic animal metaphors and/or similes provide direct analogies between the treatment of African-Americans and animals. Here, these writers often engage in rhetoric that challenges pro-slavery apologists, who attempted to disprove the humanity of African-Americans by portraying them as animals fit to be enslaved. Animals, therefore, become the metaphor of both the abolitionist and the slavery apologist for all that is not human. The second function of animals-as-trope in the fiction of African-American women writers goes beyond the pragmatic goal of proving African-Americans's common humanity, even …
Date: August 1999
Creator: Erickson, Stacy M.
System: The UNT Digital Library
The Role of Individuation Processes in the Launching of Children into Adulthood (open access)

The Role of Individuation Processes in the Launching of Children into Adulthood

The purpose of this study was to examine the extent to which levels of individuation and separation in adulthood would predict adjustment to the empty nest transition. Two-hundred and twenty-seven adults (M age = 48) who had experienced the empty nest within the last year completed a battery of scales assessing individuation from family of origin, spouse, and children as well as measures of adjustment, role strain, coping, and sex role attitudes. MANOVAS and hierarchical regression analyses suggested that levels of individuation from one's family of origin, spouse, and children differentially affect one's adjustment to, and coping with, the experience of launching of the youngest child from the home. Empty nest parents who are less differentiated from their own parents, from their spouses, and from their children reported a more negative impact of the empty nest in terms of more overall stress and role strain, more negative mood, and less life satisfaction than did empty nest parents who were more differentiated with regard to parents, spouse, and children. Results regarding the impact of individuation on empty nest adjustment regarding sex role attitudes were less clear cut, and may reflect cohort differences in work role opportunities for women and a parallel …
Date: August 1999
Creator: Hobdy, Juli
System: The UNT Digital Library

Structural Analysis of the TOL pDK1 xylGFJQK Region and Partial Characterization of the xylF and xylG Gene Products

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TOL plasmids encode enzymes responsible for utilization of toluene and related aromatic compounds by Pseudomonas putida, ultimately converting them to central metabolic intermediates. The nucleotide sequence for the 5.6 kb xylGFJQK region of the pDK1 TOL meta operon was determined. DNA sequence analysis revealed the presence of five open reading frames corresponding to xylG (1458 bp), xylF (846 bp), xylJ (783 bp), xylQ (936 bp) and xylK (1047 bp), encoding predicted protein products of 51.6, 31.3, 27.8, 32.8, and 36.6 kDa in size, respectively. The average G+C content of the xylLTEGFJQK region was 65.7%, somewhat higher than the 58.9% seen in the immediately upstream xylXYZ region and substantially more than the 50% G+C content reported for the upper TOL operon of this plasmid. Homology comparisons were made with genes and proteins of related catabolic plasmids. The dmpCDEFG and pWWO xylGFJQK regions exhibit consistently high levels of nucleotide and amino acid homology to pDK1 xylGFJQK throughout the entire region. In contrast, although the nucleotide sequence homology of the Acinetobacter atdCDE region to xylGFJ is high, the homology of atdFG to xylQK is markedly less. Such radical changes in homology between corresponding regions of different operons, combined with variable base and codon …
Date: December 1999
Creator: Poulter, Melinda D.
System: The UNT Digital Library