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Nonlinear and Quantum Optics Near Nanoparticles

Nonlinear and Quantum Optics Near Nanoparticles

Date: December 2015
Creator: Dhayal, Suman
Description: We study the behavior of electric fields in and around dielectric and metal nanoparticles, and prepare the ground for their applications to a variety of systems viz. photovoltaics, imaging and detection techniques, and molecular spectroscopy. We exploit the property of nanoparticles being able to focus the radiation field into small regions and study some of the interesting nonlinear, and quantum coherence and interference phenomena near them. The traditional approach to study the nonlinear light-matter interactions involves the use of the slowly varying amplitude approximation (SVAA) as it simplifies the theoretical analysis. However, SVVA cannot be used for systems which are of the order of the wavelength of the light. We use the exact solutions of the Maxwell's equations to obtain the fields created due to metal and dielectric nanoparticles, and study nonlinear and quantum optical phenomena near these nanoparticles. We begin with the theoretical description of the electromagnetic fields created due to the nonlinear wavemixing process, namely, second-order nonlinearity in an nonlinear sphere. The phase-matching condition has been revisited in such particles and we found that it is not satisfied in the sphere. We have suggested a way to obtain optimal conditions for any type and size of material medium. ...
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Self-definition and College Adaptation in Students From the Ronald E Mcnair Postbaccalaureate Achievement Program

Self-definition and College Adaptation in Students From the Ronald E Mcnair Postbaccalaureate Achievement Program

Date: December 2015
Creator: Vance, Jeffrey Michael
Description: While a great deal of psychological research is conducted on college students, less has been done on their adaptation to college. These young adults, as they develop ego identity and differentiate themselves from parents and families, must adjust to the social and academic environment of college. Psychosocial adjustment predicts college retention better than academic predictors do. First generation college students face greater than typical challenges adapting to college. The Ronald E. McNair Post-Baccalaureate Achievement Program exists to aid first generation, lower income undergraduate student who wish to pursue a doctoral degree. Self-definition scored from thematic apperceptive technique stories reflects an individual’s relative freedom from social role constraint. This study examined the role of self-definition and familial understanding and acceptance in this population as predictors of successful adaptation to college. While neither was found to be a significant predictor, family understanding and acceptance was found to be a more defining characteristic of this sample than was self-definition. This suggests that when social support is sufficient, individuals do not need to rely on self-definition.
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Accurate Energetics Across the Periodic Table Via Quantum Chemistry

Accurate Energetics Across the Periodic Table Via Quantum Chemistry

Date: December 2015
Creator: Peterson, Charles Campbell
Description: Greater understanding and accurate predictions of structural, thermochemical, and spectroscopic properties of chemical compounds is critical for the advancements of not only basic science, but also in applications needed for the growth and health of the U.S. economy. This dissertation includes new ab initio composite approaches to predict accurate energetics of lanthanide-containing compounds including relativistic effects, and optimization of parameters for semi-empirical methods for transition metals. Studies of properties and energetics of chemical compounds through various computational methods are also the focus of this research, including the C-O bond cleavage of dimethyl ether by transition metal ions, the study of thermochemical and structural properties of small silicon containing compounds with the Multi-Reference correlation consistent Composite Approach, the development of a composite method for heavy element systems, spectroscopic of compounds containing noble gases and metals (ArxZn and ArxAg+ where x = 1, 2), and the effects due to Basis Set Superposition Error (BSSE) on these van der Waals complexes.
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An Initial Study of Binary and Ternary Ti-based Alloys Manufactured Using Laser Engineered Net Shaping (Lenstm)

An Initial Study of Binary and Ternary Ti-based Alloys Manufactured Using Laser Engineered Net Shaping (Lenstm)

Date: December 2015
Creator: Gray, Alyn M.
Description: In this study an initial assessment of the composition – microstructure – property relationships in binary and ternary Ti – based systems are made possible using LENSTM technology. Laser Engineering Net Shaping (LENSTM), a rapid prototyping, directed laser deposition methodology of additive manufacturing (AM) was used to create bulk homogenous specimens that are compositionally graded. Compositionally graded specimens were made possible by incorporating elemental blends of powder during the LENSTM process. While there have been numerous studies assessing the influence of common elements (e.g., V, Mo, Al, and Cr) on the resulting microstructure in titanium alloys, other elements have been neglected. A systematic study of the Ti – Fe – Al ternary system based upon varying compositions of the eutectoid former, Fe with Al to stabilize the a and b phases respectively has also been neglected. This research effort focuses on exploiting the LENSTM process by rapidly assessing the composition – microstructure – property relationships in a combinatorial approach for the Ti – W, Ti – Fe, and Ti – Fe – Al systems. Compositionally graded specimens of Ti – xW (0<x<40wt.%(14.79at.%)), Ti – xFe (0<x<35wt.%(36.37at.%)), and Ti – xFe – yAl (0<x<40wt.%(36.37at.%)), y=5,10, 15wt.%) have been heat treated to ...
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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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Parameter Estimation of Microwave Filters

Parameter Estimation of Microwave Filters

Access: Use of this item is restricted to the UNT Community.
Date: December 2015
Creator: Sun, Shuo
Description: The focus of this thesis is on developing theories and techniques to extract lossy microwave filter parameters from data. In the literature, the Cauchy methods have been used to extract filters’ characteristic polynomials from measured scattering parameters. These methods are described and some examples are constructed to test their performance. The results suggest that the Cauchy method does not work well when the Q factors representing the loss of filters are not even. Based on some prototype filters and the relationship between Q factors and the loss, we conduct preliminary studies on alternative representations of the characteristic polynomials. The parameters in these new models are extracted using the Levenberg–Marquardt algorithm to accurately estimate characteristic polynomials and the loss information.
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The Forty-fifth Illinois Volunteer Infantry Regiment: the Washburne Lead Mine Regiment in the Civil War

The Forty-fifth Illinois Volunteer Infantry Regiment: the Washburne Lead Mine Regiment in the Civil War

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Date: December 2015
Creator: Mack, Thomas B.
Description: Of the roughly 3,500 volunteer regiments and batteries organized by the Union army during the American Civil War, only a small fraction has been studied in any scholarly depth. Among those not yet examined by historians was one that typified the western armies commanded by the two greatest Federal generals, Ulysses S. Grant and William T. Sherman. The Forty-fifth Illinois Volunteer Infantry was at Fort Donelson and Shiloh with Grant in 1862, with Grant and Sherman during the long Vicksburg campaign of 1862 and 1863, and with Sherman in the Meridian, Atlanta, Savannah, and Carolinas campaigns in the second half of the war. These Illinois men fought in several of the most important engagements in the western theater of the war and, in the spring of 1865, were present when the last important Confederate army in the east surrendered. The Forty-fifth was also well connected in western politics. Its unofficial name was the “Washburne Lead Mine Regiment,” in honor of U.S Representative Elihu B. Washburne, who used his contacts and influences to arm the regiment with the best weapons and equipment available early in the war. (The Lead Mine designation referred to the mining industry in northern Illinois.) In addition, ...
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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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