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1,529 Matching Results
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Effect of Engineered Surfaces on Valve Performance
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Performance of air operated valves is a major maintenance concern in process industries. Anecdotal information indicates that reliability of some high maintenance valves has been improved by using an ion deposition process to achieve engineered surfaces on selected components. This project compared friction for various surface treatments of selected valve components. Results indicate valve performance may be slightly more consistent when an engineered surface is applied in the valve packing area; however surface treatment in this area does not appear to have a dominant affect on reducing valve friction. Results indicate a linear relation between stem friction and torque applied to packing flange nuts, and even after a valve is in service, controlled packing adjustments can be made without significantly changing valve stroke time.
Date:
December 2000
Creator:
Pope, Larry G.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Southwest Retort, Volume 56, Number 4, December 2003
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 2003
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Southwest Retort, Volume 61, Number 4, December 2008
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 2008
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Southwest Retort, Volume 55, Number 4, December 2002
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 2002
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Southwest Retort, Volume 57, Number 4, December 2004
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 2004
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Southwest Retort, Volume 53, Number 4, December 2000
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 2000
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Southwest Retort, Volume 60, Number 4, December 2007
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 2007
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Southwest Retort, Volume 58, Number 4, December 2005
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 2005
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Southwest Retort, Volume 62, Number 4, December 2009
This publication of the Dallas-Fort Worth Section of the American Chemical Society includes information about research, prominent scientist, organizational business, and various other stories of interest to the community.
Date:
December 2009
Creator:
American Chemical Society. Dallas/Fort Worth Section.
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library
Parenting Stress: A Comparison of Mothers and Fathers of Disabled and Non-Disabled Children
This study compared perceived levels of parenting stress between mothers and fathers of children with Attention-Deficit Hyperactivity Disorder (ADHD), children with developmental disabilities, and normally developing children. The relationship of certain demographic variables, such as Socio-economic Status (SES), number of children, years married, parent age, and child age, as well as social support with parenting stress was also examined for mothers and fathers of these three groups. Identification of factors related to parenting stress in fathers was of particular importance for this study, as fathers are often an underrepresented group within parenting research. Identifying effective methods for predicting high levels of parenting stress is important, as stress has been linked to psychological well-being, potential for abuse, and a greater likelihood of poor adjustment for both parent and child. Results from the present study comparing reported stress levels between groups of parents were supportive of previous studies indicating that parents of children with ADHD and developmentally disabilities experience significantly greater parenting stress, specifically with respect to child characteristics. Significant gender differences were also found between mothers and fathers in terms of parent characteristics related to stress. Fathers reported greater stress in the areas of attachment, while mothers reported more parent role …
Date:
December 2000
Creator:
Walker, Alexis Philbin
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Texas Annexation and the Presidential Election of 1844 in the Richmond, Virginia, and New Orleans, Louisiana, Newspaper
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This thesis examines the issue of Texas annexation from the viewpoints of two southern cities: Richmond, Virginia, and New Orleans, Louisiana. It looks primarily at four major newspapers, two in each city: the Richmond Enquirer and the Richmond Whig; and the New Orleans Times-Picayune and the New Orleans Whig. These four newspapers were examined thoroughly from January 1844 to July 1845. In addition to the above newspapers, the Congressional Globe and national voting patterns on Texas annexation were examined. Analysis of the editorial articles in the above newspapers offers the best possibility of understanding public sentiment toward Texas annexation and the presidential election of 1844. The evidence examined in this study indicates that Texas annexation became a decisive issue in the presidential election of 1844. It also shows that, although the press and elements within both Democratic and Whig parties were aware that the slavery question was intricately linked to the Texas annexation issue, slavery and sectional politics were not the primary factors influencing annexation. Ultimately, fundamental concerns regarding western expansion in general, especially for the Whigs, and political party loyalty proved the decisive factors in the presidential election of 1844 and Texas annexation. The evidence gathered in this study …
Date:
December 2001
Creator:
Short, Steven W.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Characterizaton of Triethoxyfluorosilane and Tetraethoxysilane Based Aerogels
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Use of this item is restricted to the UNT Community
Aerogels are highly porous, low dielectric constant (low k) materials being considered by the semiconductor industry as an interlayer dielectric. Low k materials are needed to overcome capacitance problems that limit device feature sizes. Precursors triethoxyfluorosilane (TEFS) and tetraethoxysilane (TEOS) were used to prepare bulk aerogels. Samples were prepared by sol-gel methods, and then carbon dioxide supercritically-dried. Effects of varying the water to precursor ratio were studied with respect to aerogel properties and microstructure. Methods of analysis for this study include FTIR-ATR, TEM, RBS, EDS, SEM, dielectric constant determination by impedance and surface area by gas adsorption. Si-F bonds were determined to be present in both acid- and base-catalyzed TEFS as well as HF-catalyzed TEOS. Fluorine promotes a fractal network microstructure as opposed to a particle-like microstructure. Surface area and dielectric constant were determined to increase slightly with increases in the water to precursor ratio.
Date:
December 2001
Creator:
Roepsch, Jodi Ann
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A meta-analysis of service learning research in middle and high schools.
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Use of this item is restricted to the UNT Community
This study examines the relationship between service learning innovations and improved academics, self-concept, and social or personal growth in middle and high school students. Meta-Analysis is employed to arrive at effect-size estimates for each construct. A historical overview of service learning is presented and a detailed description of the study selection process is provided. The data revealed a moderate relationship between service learning participation and academics, self-concept and social or personal growth in middle and high school students. The findings are presented, and some appropriate conclusions are drawn. A discussion of the implications of these findings and recommendations for future research are also provided.
Date:
December 2001
Creator:
White, Amy E.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Immediate and subsequent effects of fixed-time food presentations on automatically maintained mouthing.
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Use of this item is restricted to the UNT Community
Several studies have demonstrated that fixed-time (FT) schedules of stimulus delivery can function to reduce a variety of behaviors. The purpose of this study was to evaluate the immediate and subsequent effects of FT food deliveries on mouthing. In Phase 1, a preference assessment showed that caramel popcorn, chocolate cookies and pretzels were highly preferred food items. Thus, providing the basis for use of food items during treatment. In Phase 2, a functional analysis showed that mouthing was a nonsocially maintained problem behavior. Phase 3 demonstrated the use of FT schedules of food deliveries as treatment for nonsocially maintained mouthing. Results indicated that FT schedules of food significantly reduced mouthing. In addition, levels of mouthing observed during post-FT observations were reliably lower than pre-FT observations. Treatment effects, operative mechanisms responsible for the treatment effects and the experimental arrangement used to investigate varying FT schedules are discussed.
Date:
December 2001
Creator:
Simmons, Jason N.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Microwave Cavity Test for Superconductivity
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Use of this item is restricted to the UNT Community
The first part of this paper describes the Meissner effect in superconductors which serves as the most definitive evidence for superconductivity. It is shown that the microwave perturbation technique may be used to demonstrate this effect. By measuring the changes of resonant frequency and inverse quality factor Q of a microwave cavity with a small volume of sample loading, the Meissner effect can be shown by using the Slater perturbation equation. The experimental system is described with details and the basic principle of each component discussed. The second part of this work describes the technique employed to do the actual measurements. The experiments were conducted on samples of Gallium Arsenide (GaAs) and lead zirconate titanate (PZT) to look for the possible high temperature superconductivity properties. Results of these experiments are presented and discussed. Conclusion and suggestions to future exploration are made.
Date:
December 2001
Creator:
Tang, Shan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Teacher Practice, Curriculum, and Children's Moral Development in Buddhist Temple Preschools in Thailand
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Use of this item is restricted to the UNT Community
This study investigated what constitutes a moral development program in Buddhist temple preschools in Thailand. The researcher employed three qualitative methods: structured, in-depth interviews, observations of teachers' instruction, and document analysis of curriculum guides. Four Buddhist temple preschools were selected as the sites. Participants for interview included three abbots and one head nun, four principals, and twelve teachers. Participants for observations included four teachers of third year classes in each preschool. The study concentrated on four research questions: (a) what are the elements of the character education curriculum? (b) How do teachers teach moral development concepts and skills? (c) What are the teachers' perceptions of the moral development of third year preschoolers? (d) How do teachers assess their pupils' moral development? Key findings for the research questions were: character education was not a subject in the National Preschool Curriculum which was implemented in the Buddhist temple preschools. Core morality was integrated into every topic. The moral behaviors emphasized in the curriculum and the lesson plans included discipline, mindfulness, kindness, helpfulness, patience, honesty, respect, thriftiness, and politeness. The Buddhist concept of the process of moral development includes character education and meditation. The preschoolers were trained to pay respect to teachers and …
Date:
December 2001
Creator:
Phisalaphong, Rathdow
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Topological uniqueness results for the special linear and other classical Lie Algebras.
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Use of this item is restricted to the UNT Community
Suppose L is a complete separable metric topological group (ring, field, etc.). L is topologically unique if the Polish topology on L is uniquely determined by its underlying algebraic structure. More specifically, L is topologically unique if an algebraic isomorphism of L with any other complete separable metric topological group (ring, field, etc.) induces a topological isomorphism. A local field is a locally compact topological field with non-discrete topology. The only local fields (up to isomorphism) are the real, complex, and p-adic numbers, finite extensions of the p-adic numbers, and fields of formal power series over finite fields. We establish the topological uniqueness of the special linear Lie algebras over local fields other than the complex numbers (for which this result is not true) in the context of complete separable metric Lie rings. Along the way the topological uniqueness of all local fields other than the field of complex numbers is established, which is derived as a corollary to more general principles which can be applied to a larger class of topological fields. Lastly, also in the context of complete separable metric Lie rings, the topological uniqueness of the special linear Lie algebra over the real division algebra of quaternions, …
Date:
December 2001
Creator:
Rees, Michael K.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Comparative Morphology of Sensilla Styloconica on the Proboscis of North American Nymphalidae and Other Selected Taxa: Systematic and Ecological Considerations.
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Sensilla styloconica on the proboscis of 107 species of North American and tropical butterflies were comparatively studied using the scanning electron microscope. Focus was on 76 species of North American Nymphalidae representing 45 genera and 11 subfamilies. Nomenclature for generalized and specific types of nymphalid sensilla is proposed. Written descriptions and micrographs are presented for each species studied. Morphological features were generally consistent for all or most species within genera and sometimes within subfamilies, with specified exceptions. Statistical analysis revealed significant differences for six of eight variables tested between two distinct feeding guilds of North American Nymphalidae. Average number, density, extent of proboscis coverage with sensilla, their total length, and shoulder spine length were all significantly greater in the non-nectar feeding guild than in nectar feeders, and may indicate adaptation for greater efficiency in feeding on flat surfaces. The greater frequency of apical shoulder spines in non-nectar feeders may represent adaptation for protection of sensory pegs from mechanical abrasion during feeding, or for anchoring the flexible proboscis tip to the surface. Correlation analysis revealed 9 out of 28 positive correlations in nectar feeders and 5 out of 28 in non-nectar feeders. Results of preliminary cladistic analysis were not considered to …
Date:
December 2001
Creator:
Petr, Daniel
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A Novel Phytoestrogen that Acts as an Agonist for Human Estrogen Receptors.
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Use of this item is restricted to the UNT Community
Estrogen is the natural agonist of the estrogen receptor (ER). However, certain plant-derived compounds or phytoestrogens have been identified that mimic estrogens and act as agonists and/or antagonists of ERs, depending on subtype and target tissue. Understanding how phytoestrogens interact with ERs, and therefore effect the estrogenic response, may prove beneficial in hormone replacement therapy and in the prevention and treatment of hormone-related diseases. Using Thin Layer Chromatography, gas chromatography/mass spectrometry (GC/MS), and proton nuclear nagnetic resonance (HNMR), I identified 4-ethoxymethylphenol (4EM) found in Maclura pomifera. While most phytoestrogens are heterocyclic compounds, 4EM is a simple phenol that acts as an agonist of ER-alpha and -beta in HeLa and MCF-7 cells. To study the effect of 4EM on ER-alpha and -beta activity, I performed transient transfection assays and showed that 4EM activates ER dependent gene transcription in a dose dependent manner in both ER subtypes. Further, 4EM- mediated transcription in ER-alpha, like estrogen, was enhance in the presense of co-activators, SRC-1 (steroid receptor coactivator-1), CBP (CREB binding proteins), and E6-AP (E6-associated protein) and inhibited by trans-4- hydroxytamoxifen (4HT). I found that 4EM was specific for ER and did not activate transcription of the progesterone receptor in HeLa cells.
Date:
December 2001
Creator:
Pearce, Virginia
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Parsing Records from TSLAC ARIS Database into XML: Notes (Work Area B.2 - B.4)
Report for an Institute of Museum and Library Sciences (IMLS) Grant Partner Uplift Project. The report describes parsing records from the Texas State Library and Archives Commission (TSLAC) Archives and Information Services (ARIS) database into XML files, creating XML schemas, and mapping elements to simple Dublin core schema.
Date:
December 15, 2006
Creator:
Plumer, Danielle; Phillips, Mark Edward & Polyakov, Serhiy
Object Type:
Paper
System:
The UNT Digital Library
Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines
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The second order rate constants for nucleophilic substitution by methoxide of (Z)- and (E)-O-methylbenzohydroximoyl fluorides [C6H4C(F)=NOCH3] with various substituents on the phenyl ring [p-OCH3 (1h, 2h), p-CH3 (1g, 2g), p-Cl (1f, 2f), p-H (1e, 2e), (3,5)-bis-CF3 (1i, 2i)] in 90:10 DMSO:MeOH have been measured. A Hammett plot of these rate constants vs σ values gave positive ρ values of 2.95 (Z isomer) and 3.29 (E isomer). Comparison of these rates with methoxide substitution rates for Omethylbenzohydroximoyl bromide [C6H4C(Br)=NOCH3] and Omethylbenzohydroximoyl chloride [C6H4C(Cl)=NOCH3] reveal an element effect for the Z isomers of Br:Cl:F(1e) = 2.21:1.00:79.7 and for the E isomers of Cl:F(2e) = 1.00:18.3. With the p-OCH3-imidoyl halides the following element effects are found: Br:Cl:F(1h) = 2.78:1.00:73.1 for the Z isomer and Br:Cl:F(2h) = 1.97:1.00:12.1 for the E isomer. Measurement of activation parameters revealed ∆S≠ = -17 eu for 1e and ∆S≠ = -9.9 eu for 2e. Ab initio calculations (HF/6-31+G*, MP2/6-31+G*//HF/6-31+G*, B3LYP/6- 31+G*//HF/6-31+G*, HF-SCIPCM/6-31+G*//HF/6-31+G*) were performed to define the reaction surface. These calculations demonstrate a relatively large barrier for nucleophilic attack in relation to halogen loss and support the experimental findings that this reaction proceeds by an addition-elimination mechanism (AN# + DN). The imidoyl fluorides have been used to synthesize …
Date:
December 2001
Creator:
Dolliver, Debra D.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Mineral-filled polypropylene: Improvement of scratch resistance
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Use of this item is restricted to the UNT Community
A potential alternative to acrylonitrile-butadiene-styrene (ABS) and polycarbonate+ABS (PC+ABS), pigmented mineral-filled polypropylene (PP) finds an opening in automotive interior components such as instrument panels, knee bolsters, consoles, etc. Because of the lack of surface aesthetics, pigmented mineral-filled PP is experiencing a limitation to its acceptance in many applications. This study focuses on exploring various mineral fillers and additives in polypropylene to provide a material with enhanced scratch resistance. Several physical properties including Rockwell and Shore D hardness are investigated, and it is determined that Filler W improves scratch resistance. It is also determined that Filler T-filled-PP has poor scratch resistance even with the addition of a lubricant.
Date:
December 2001
Creator:
Khatib, Jamal F.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The preparation and characterization of thermo-sensitive colored hydrogel film and surfactant-free porous polystyrene three-dimensional network.
Polymer hydrogel films change their properties in response to environmental change. This remarkable phenomenon results in many potential applications of polymer hydrogel films. In this thesis colored thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel film was prepared by firstly synthesizing polymer latex and secondarily crosslinking the nanoparticles and casting the polymers onto glass. The shape-memory effect has been observed when changing the environmental temperature. The temperature-dependent of turbidity of polymer hydrogel film was measured by HP UVVisible spectrophotometer. This intelligent hydrogel might be used in chemomechanical systems and separation devices as well as sensors. Polymer adsorption plays an important role in many products and processes. In this thesis, surfactant-free three-dimensional polystyrene (PS) nanoparticle network has been prepared. The infrared spectroscopy and solubility experiment are performed to prove the crosslinking mechanism, also the BET method was used to measure the adsorption and desorption of polystyrene network. The BET constant (C) is calculated (C=6.32). The chemically bonded polymer nanoparticle network might have potential applications as catalyst or used for chromatographic columns.
Date:
December 2001
Creator:
Zhou, Bo
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Music preferences, music and non-music media use, and leisure involvement of Hong Kong adolescents.
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Use of this item is restricted to the UNT Community
The study sought to determine the relationships of preference responses to grade, gender, familiarity, musical training, peers'/parents' listening habits, music media use, and listening contexts. Grade six through nine Hong Kong students (N = 310) completed the audio preference test followed by verbal responses to training, peers'/parents' preferences, leisure/music media involvement, and listening context. Results indicated: The preferred genres, in descending order, were Western pop/rock, Cantopop/rock, Western classical; the disliked genres were jazz, Chinese, and non- Western/non-Chinese. Preference correlated strongly with genre familiarity. Pop genres were the most familiar to all adolescents. The students' preference toward Western pop/rock and Cantopop/rock associated with several listening contexts: solitary listening, having great freedom to choose one's desired music for listening, listening to music in one's room, and listening to music as background activity. The adolescents expressed that their leisure activities were spent with their family and friends. However, they made it clear that music listening was a personal activity that very likely was listened to alone. On all listening occasions, the girls exhibited a more positive response than the boys did. With four to five hours daily leisure time, the adolescents watched TV for three to four hours while spending less than two …
Date:
December 2001
Creator:
Hui, Viny Wan-Fong
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library