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 Collection: UNT Theses and Dissertations
Effect of Alloy Composition, Free Volume and Glass Formability on the Corrosion Behavior of Bulk Metallic Glasses

Effect of Alloy Composition, Free Volume and Glass Formability on the Corrosion Behavior of Bulk Metallic Glasses

Date: December 2015
Creator: Ayyagari, Venkata Aditya
Description: Bulk metallic glasses (BMGs) have received significant research interest due to their completely amorphous structure which results in unique structural and functional properties. Absence of grain boundaries and secondary phases in BMGs results in high corrosion resistance in many different environments. Understanding and tailoring the corrosion behavior can be significant for various structural applications in bulk form as well as coatings. In this study, the corrosion behavior of several Zr-based and Fe-Co based BMGs was evaluated to understand the effect of chemistry as well as quenched in free volume on corrosion behavior and mechanisms. Presence of Nb in Zr-based alloys was found to significantly improve corrosion resistance due to the formation of a stable passive oxide. Relaxed glasses showed lower rates compared to the as-cast alloys. This was attributed to lowering of chemical potential from the reduced fraction of free volume. Potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) techniques helped in quantifying the corrosion rate and polarization resistance. The effect of alloy composition was quantified by extensive surface analysis using Raman spectroscopy, energy dispersive x-ray spectroscopy and auger spectroscopy. Pitting intensity was higher in the as-cast glasses than the relaxed glasses. The electrochemical behavior of a Zr-Ti-Cu-Ni-Be bulk metallic glass ...
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A High-fat Meal Alters Post-prandial Mrna Expression of Sirt1, Sirt4, and Sirt6

A High-fat Meal Alters Post-prandial Mrna Expression of Sirt1, Sirt4, and Sirt6

Date: December 2015
Creator: Best Sampson, Jill Nicole
Description: Sirtuins (SIRT) regulate the transcription of various genes involved in the development of diet-induced obesity and chronic disease; however, it is unknown how they change acutely following a high-fat meal. The purpose of this study was to determine the effect of a high-fat meal (65% kcals/d; 85% fat recommendation), on SIRT1-7 mRNA expression in blood leukocytes at 1, 3, and 5-h post-prandial. Men and women (N=24) reported to the lab following an overnight fast (>12H). Total RNA was isolated and reverse transcribed prior to using a Taqman qPCR technique with 18S rRNA as a normalizer to determine SIRT1-7 mRNA expression. An additional aliquot of serum was used to measure triglycerides. Data was analyzed using a RM ANOVA with P<0.05. Triglycerides (P<0.001; 124%) peaked at 3-h. SIRT 1 (P=0.004; 70%), and SIRT 6 (P=0.017; 53%) decreased expression at 3-h. SIRT4 (P=0.024) peaked at 5H relative to baseline (70%) and 3-h (68%). To our knowledge, this is the first study to report that consumption of a high-fat meal transiently alters SIRT mRNA expression consistent in a pattern that mirrors changes in serum triglycerides. Decrease in expression of SIRT1 and SIRT6 combined with an increased SIRT4 would be consistent with an increase in ...
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Parent-adolescent Attachment, Bullying and Victimization, and Mental Health Outcomes

Parent-adolescent Attachment, Bullying and Victimization, and Mental Health Outcomes

Date: December 2015
Creator: Guinn, Megan D.
Description: Traditional and cyber bullying have been identified as universal problematic issues facing adolescents, and research is needed to understand correlates associated with these phenomena. Structural equation modeling analyses examined associations between attachment to parents, traditional and cyber bullying or victimization, and mental health outcomes among 257 high school students (Average age 15.9 years). Key patterns emerged, including associations between maternal attachment and mental health outcomes; victimization and mental health concerns; and bullying and victimization in both traditional and cyber contexts. The role of attachment to mothers and fathers varied by context. Findings extend the literature by identifying risk factors in adolescence associated with bullying and victimization, as well as suggesting appropriate prevention and intervention strategies to increase adolescent well-being.
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Deformation Micro-mechanisms of Simple and Complex Concentrated Fcc Alloys

Deformation Micro-mechanisms of Simple and Complex Concentrated Fcc Alloys

Date: December 2015
Creator: Komarasamy, Mageshwari
Description: The principal objective of this work was to elucidate the effect of microstructural features on the intrinsic dislocation mechanisms in two FCC alloys. First alloy Al0.1CoCrFeNi was from a new class of material known as complex concentrated alloys, particularly high entropy alloys (HEA). The second was a conventional Al-Mg-Sc alloy in ultrafine-grained (UFG) condition. In the case of HEA, the lattice possess significant lattice strain due to the atomic size variation and cohesive energy differences. Moreover, both the lattice friction stress and the Peierls barrier height are significantly larger than the conventional FCC metals and alloys. The experimental evidences, so far, provide a distinctive identity to the nature and motion of dislocations in FCC HEA as compared to the conventional FCC metals and alloys. Hence, the thermally activated dislocation mechanisms and kinetics in HEA has been studied in detail. To achieve the aim of examining the dislocation kinetics, transient tests, both strain rate jump tests and stress relaxation tests, were conducted. Anomalous behavior in dislocation kinetics was observed. Surprisingly, a large rate sensitivity of the flow stress and low activation volume of dislocations were observed, which are unparalleled as compared to conventional CG FCC metals and alloys. The observed trend ...
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Let Her Be Shorn: 1 Corinthians 11 and Female Head Shaving in Antiquity

Let Her Be Shorn: 1 Corinthians 11 and Female Head Shaving in Antiquity

Date: December 2015
Creator: Montier, Curtis E.
Description: In 1 Corinthians 11:3-15, Paul writes that if a woman is to be so immodest as to wear her hair uncovered while praying or prophesying in a Christian assembly she might as well shave her head. Paul instructs the Corinthians that it is “one and the same” for a woman to have her head shaved and for her to unveil her hair. There is a large body of works cataloging the modesty standards in Hellenistic Greece but Paul’s reference to head-shaving remains obscure. This thesis looks to find the best explanation of Paul’s instructions. Research in this topic began as an investigation of a popular modern view. It can be found in conversation or a simple Google search, that women in Ancient Greece with their head shaved were prostitutes. Beyond being prostitutes, they were probably temple prostitutes. The evidence does not bear this out as there is no artwork depicting prostitutes, or indeed any women, with their heads shaved. Instead prostitutes are shown in Greek erotic art with both long and short hair, some with and some without head coverings. Literary sources do offer several different examples of women who had their hair cut off. There are examples of women ...
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Messiaen’s Musical Language: Technique and Theological Symbolism in Les Corps Glorieux, “Combat De La Mort Et De La Vie”

Messiaen’s Musical Language: Technique and Theological Symbolism in Les Corps Glorieux, “Combat De La Mort Et De La Vie”

Date: December 2015
Creator: Dellosa, Lerie Grace
Description: One of the most important ways to understand Olivier Messiaen’s musical language is through the lens of the theological ideas that many of his works convey. He considers expressing his Christian faith to be the primary purpose in his music. Through his idiosyncratic technique, Messiaen gives power and life to his religious music that he combines with his interest in literature, musical analysis, poetic imagery and symbolism, his love for theatre, and his compositional and organ abilities. The abundant studies of Messiaen’s works deal with the intricacies of his musical language, yet most of these studies barely discuss his theological ideas. Nevertheless, technical analysis of his music poses immense challenges, especially in the domains of melody and harmony. Although my approach is unconventional and do not follow any existing system, I base my technical and theological analyses mainly from Messiaen's technique, his commentaries and his references to the Scriptures. The “Combat de la mort et de la vie” is the heart of Les Corps glorieux in both technical and theological aspects. It is an intricate musical artwork where Messiaen demonstrates his melodic and harmonic developments using his idiosyncratic language, and through symbolism portrays the most complex of all drama according ...
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The Effect of Post-exercise Ethanol Consumption on the Acute Hormonal Response to Heavy Resistance Exercise in Women

The Effect of Post-exercise Ethanol Consumption on the Acute Hormonal Response to Heavy Resistance Exercise in Women

Date: December 2015
Creator: Budnar, Jr., Ronald G.
Description: The purpose of this study was to examine the hormonal response to acute ethanol ingestion following a bout of heavy resistance exercise in women. Eight resistance trained women completed two identical acute heavy resistance exercise tasks (AHRET). From 10-20 minutes post-AHRET, participants consumed either a grain ethanol or a placebo beverage. Blood was collected before (PRE) and immediately after the AHRET (IP) and then every 20 minutes for five hours. Blood collected after beverage ingestion was pooled into 3 batches (phases: 20-40 minutes, 60-120 minutes, and 140-300 minutes post-exercise) and analyzed for serum total testosterone (TT), free testosterone (FT), insulin-like growth factor-I (IGF-I), human growth hormone (GH), cortisol (COR), and estradiol (E2) concentrations. Circulating concentrations of TT were significantly greater at P20-40 than at PRE, P60-120, and P140-300. Circulating concentrations of FT were significantly greater at P20-40 than at all other times. Circulating concentrations of GH were significantly greater at IP than at PRE, P60-120, and P140-300. Circulating concentrations of COR were significantly greater at P20-40 than at all other times. Additionally, COR concentrations at P140-300 were significantly lower than at all other times. Circulating concentrations of IGF-1 were significantly greater at P20-40 than at P60-120 and P140-300. Circulating concentrations ...
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Characterization of Ti-6al-4v Produced Via Electron Beam Additive Manufacturing

Characterization of Ti-6al-4v Produced Via Electron Beam Additive Manufacturing

Date: December 2015
Creator: Hayes, Brian J.
Description: In recent years, additive manufacturing (AM) has become an increasingly promising method used for the production of structural metallic components. There are a number of reasons why AM methods are attractive, including the ability to produce complex geometries into a near-net shape and the rapid transition from design to production. Ti-6Al-4V is a titanium alloy frequently used in the aerospace industry which is receiving considerable attention as a good candidate for processing via electron beam additive manufacturing (EBAM). The Sciaky EBAM method combines a high-powered electron beam, weld-wire feedstock, and a large build chamber, enabling the production of large structural components. In order to gain wide acceptance of EBAM of Ti-6Al-4V as a viable manufacturing method, it is important to understand broadly the microstructural features that are present in large-scale depositions, including specifically: the morphology, distribution and texture of the phases present. To achieve such an understanding, stereological methods were used to populate a database quantifying key microstructural features in Ti-6Al-4V including volume fraction of phases, a lath width, colony scale factor, and volume fraction of basket weave type microstructure. Microstructural features unique to AM, such as elongated grains and banded structures, were also characterized. Hardness and tensile testing were ...
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Culturally Proficient Leadership:  Teacher Perceptions of Elementary School Principals in Urban, Title I Schools

Culturally Proficient Leadership: Teacher Perceptions of Elementary School Principals in Urban, Title I Schools

Date: December 2015
Creator: Hendrix, Royond P.
Description: This study examined elementary teachers’ perceptions of their principal’s level of cultural proficiency. Practices for Developing a Culturally Competent School Environment, a survey Camille Smith and adapted by Dr. Mack T. Hines, was completed from a sample size of 119 teachers. The survey contained 35 items, including six constructs: valuing diversity, assessing the culture, managing the dynamics of difference, institutionalizing cultural knowledge and resources, adapting to diversity and inclusiveness. Teachers rated their principal using a Likert scale which consisted of 1 = never uses, 2 = rarely uses, 3 = sometimes uses, 4 = frequently uses, and 5 = always uses. Teachers of various races, ages and years with their principal participated in this study. The study reveals that these variables do not make a statistically significant difference in the teachers’ perception of how proficient they are in valuing diversity, a assessing his/her own culture and institutionalizing cultural knowledge. This quantitative study reveals the variances of statistical significance of teacher demographics: age, gender, years served under current principal and accountability rating of the school. Cultural proficiency is important to the development and maintenance of the necessary relationships among students, teachers, principals and the school community.
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Exploring Student Learning on a Short-term, Faculty-led Study Abroad Course Through a Student Development Lens

Exploring Student Learning on a Short-term, Faculty-led Study Abroad Course Through a Student Development Lens

Date: December 2015
Creator: Garcia, Hope F.
Description: Embarking on a study abroad experience is thought to be a transformational experience for students, and previous researchers have tended to find that the potential benefits of study abroad experiences, including greater conceptual and behavioral intercultural competence, are greater with longer periods abroad. The purpose of this study was to create an intentional learning experience for students who embarked on a short-term study abroad in rural areas of China and to apply faculty intervention of a student development approach to student learning to create a high-impact learning environment for students centered on a service-learning project. This qualitative study gathered primary data from students and instructors during the course through a collection of observation and field notes, student journals, pre- and post-construct tests, and final presentation. Follow-up interviews were conducted 10 months after course completion. Six students participated in this course and study who were from a variety of disciplines and classifications. Five students were female; one was male. Four students were undergraduates; two were graduate students. Student ethnicities included three Caucasians and African American, along with two international students from Mexico and Iran. Key outcomes of this study were that when short-term study abroad faculty members applied creative interventions, students ...
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