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Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification (open access)

Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification

The research program reported here is focused on critical issues that represent conspicuous gaps in current understanding of rapid solidification, limiting our ability to predict and control microstructural evolution (i.e. morphological dynamics and microsegregation) at high undercooling, where conditions depart significantly from local equilibrium. More specifically, through careful application of phase-field modeling, using appropriate thin-interface and anti-trapping corrections and addressing important details such as transient effects and a velocity-dependent (i.e. adaptive) numerics, the current analysis provides a reasonable simulation-based picture of non-equilibrium solute partitioning and the corresponding oscillatory dynamics associated with single-phase rapid solidification and show that this method is a suitable means for a self-consistent simulation of transient behavior and operating point selection under rapid growth conditions. Moving beyond the limitations of conventional theoretical/analytical treatments of non-equilibrium solute partitioning, these results serve to substantiate recent experimental findings and analytical treatments for single-phase rapid solidification. The departure from the equilibrium solid concentration at the solid-liquid interface was often observed during rapid solidification, and the energetic associated non-equilibrium solute partitioning has been treated in detail, providing possible ranges of interface concentrations for a given growth condition. Use of these treatments for analytical description of specific single-phase dendritic and cellular operating point …
Date: August 15, 2011
Creator: Choi, Jeong
System: The UNT Digital Library
Measurement and Interpretation of Moments of the Combined Hadronic Mass and Energy Spectrum in Inclusive Semileptonic B-Meson Decays (open access)

Measurement and Interpretation of Moments of the Combined Hadronic Mass and Energy Spectrum in Inclusive Semileptonic B-Meson Decays

This thesis presents first measurements of moments of the hadronic n{sub X}{sup 2} distribution measured in inclusive semileptonic decays of B mesons to final states containing a charm quark, B {yields} X{sub c}{ell}{nu}. The variable n{sub X}{sup 2} is a combination of the invariant mass of the charmed meson m{sub X}, its energy in the B-meson rest-frame E{sub X;BRF}, and a constant {tilde {Lambda}} = 0.65 GeV, n{sub X}{sup 2} = m{sub X}{sup 2}c{sup 4}-2{tilde {Lambda}}E{sub X,BRF} + {tilde {Lambda}}{sup 2}. The moments <n{sub X}{sup k}> with k = 2,4,6 are measured as proposed by theory to constrain assumptions made in the theoretical description of inclusive observables in semileptonic B-meson decays. This description uses Heavy Quark Expansion (HQE), an effective QCD combined with an Operator Product Expansion. The measurement is based on a sample of 231.6 million e{sup +}e{sup -} {yields} {Upsilon}(4S) {yields} B{bar B} events recorded with the BABAR experiment at the PEP-II e{sup +}e{sup -}-storage rings at SLAC. We reconstruct the semileptonic decay by identifying a charged lepton in events tagged by a fully reconstructed hadronic decay of the second B meson. Correction procedures are derived from Monte Carlo simulations to ensure an unbiased measurement of the moments …
Date: August 12, 2011
Creator: Klose, Verena
System: The UNT Digital Library
Search for the Standard Model Higgs Boson at D$\O$ in the Final State with Two $\tau$'s and Two Jets (open access)

Search for the Standard Model Higgs Boson at D$\O$ in the Final State with Two $\tau$'s and Two Jets

The Standard Model (SM) is a very successful description of particle physics, and its predictions have stood up to a multitude of precision experimental tests. But one of the central elements of the SM, the Higgs mechanism, has yet to be verified. The Higgs mechanism (and the associated Higgs Boson) generates electroweak symmetry breaking and consequently allows for W and Z bosons and fermions to be massive. This thesis presents a search for the SM Higgs boson at the D0 experiment using the Tevatron particle accelerator at Fermilab in the final state {tau}{tau} + jet jet with 4.3 fb{sup -1} of data. This final state is sensitive to the Higgs production mechanisms gluon-gluon fusion and vector-boson fusion, and to the Higgs produced in association with a W or Z, for Higgs masses from 100 to 200 GeV. We see no evidence for the Higgs boson, but by itself our search does not rule out the SM Higgs. When this analysis is combined with other searches at the Tevatron the Higgs can be ruled out at a 95% confidence level for the mass range from 156 to 177 GeV.
Date: August 1, 2011
Creator: Tschann-Grimm, Kathryn
System: The UNT Digital Library
Indirectly detected chemical shift correlation NMR spectroscopy in solids under fast magic angle spinning (open access)

Indirectly detected chemical shift correlation NMR spectroscopy in solids under fast magic angle spinning

The development of fast magic angle spinning (MAS) opened up an opportunity for the indirect detection of insensitive low-{gamma} nuclei (e.g., {sup 13}C and {sup 15}N) via the sensitive high-{gamma} nuclei (e.g., {sup 1}H and {sup 19}F) in solid-state NMR, with advanced sensitivity and resolution. In this thesis, new methodology utilizing fast MAS is presented, including through-bond indirectly detected heteronuclear correlation (HETCOR) spectroscopy, which is assisted by multiple RF pulse sequences for {sup 1}H-{sup 1}H homonuclear decoupling. Also presented is a simple new strategy for optimization of {sup 1}H-{sup 1}H homonuclear decoupling. As applications, various classes of materials, such as catalytic nanoscale materials, biomolecules, and organic complexes, are studied by combining indirect detection and other one-dimensional (1D) and two-dimensional (2D) NMR techniques. Indirectly detected through-bond HETCOR spectroscopy utilizing refocused INEPT (INEPTR) mixing was developed under fast MAS (Chapter 2). The time performance of this approach in {sup 1}H detected 2D {sup 1}H{l_brace}{sup 13}C{r_brace} spectra was significantly improved, by a factor of almost 10, compared to the traditional {sup 13}C detected experiments, as demonstrated by measuring naturally abundant organic-inorganic mesoporous hybrid materials. The through-bond scheme was demonstrated as a new analytical tool, which provides complementary structural information in solid-state systems in …
Date: August 15, 2011
Creator: Mao, Kanmi
System: The UNT Digital Library
Instrumentation and Beam Dynamics Study of Advanced Electron-Photon Facility in Indiana University (open access)

Instrumentation and Beam Dynamics Study of Advanced Electron-Photon Facility in Indiana University

The Advanced eLectron-PHoton fAcility (ALPHA) is a compact electron accelerator under construction and being commissioned at the Indiana University Center for Exploration of Energy and Matter (CEEM). In this thesis, we have studied the refurbished Cooler Injector Synchrotron (CIS) RF cavity using both the transmission line model and SUPERFISH simulation. Both low power and high power RF measurements have been carried out to characterize the cavity. Considering the performance limit of ferrite, we have designed a new ferrite loaded, co-axial quarter wave like cavity with similar structure but a more suitable ferrite material. We have also designed a traveling wave stripline kicker for fast extraction by POISSON and Microwave Studio. The strips geometry is trimmed to maximize the uniformity of the kicking field and match the impedance of the power cables. The time response simulation shows the kicker is fast enough for machine operation. The pulsed power supply requirement has also been specified. For the beam diagnosis in the longitudinal direction, we use a wideband Wall Gap Monitor (WGM) served in CIS. With proper shielding and amplification to get good WGM signal, we have characterized the injected and extracted beam signal in single pass commissioning, and also verified the debunching …
Date: August 1, 2011
Creator: Luo, Tianhuan
System: The UNT Digital Library
Equilibrium Speciation of Select Lanthanides in the Presence of Acidic Ligands in Homo- and Heterogeneous Solutions (open access)

Equilibrium Speciation of Select Lanthanides in the Presence of Acidic Ligands in Homo- and Heterogeneous Solutions

This dissertation explores lanthanide speciation in liquid solution systems related to separation schemes involving the acidic ligands: bis(2-ethylhexyl) phosphoric acid (HDEHP), lactate, and 8-hydroxyquinoline. Equilibrium speciation of neodymium (Nd3+), sodium (Na+), HDEHP, water, and lactate in the TALSPEAK liquid-liquid extraction system was explored under varied Nd3+ loading of HDEHP in the organic phase and through extraction from aqueous HCl and lactate media. System speciation was probed through vapor pressure osmometry, visible and Fourier Transform Infrared (FTIR) spectroscopy, 22Na and 13C labeled lactate radiotracer distribution measurements, Karl Fischer titrations, and equilibrium pH measurements. Distribution of Nd3+, Na+, lactate, and equilibrium pH were modeled using the SXLSQI software to obtain logKNd and logKNa extraction constants under selected conditions. Results showed that high Nd3+ loading of the HDEHP led to Nd3+ speciation that departs from the ion exchange mechanism and includes formation of highly aggregated, polynuclear [NdLactate(DEHP)2]x; (with x > 1). By substituting lanthanum (La3+) for Nd3+ in this system, NMR scoping experiments using 23Na, 31P nuclei and 13C labeled lactate were performed. Results indicated that this technique is sensitive to changes in system speciation, and that further experiments are warranted. In a homogeneous system representing the TALSPEAK aqueous phase, Lactate protonation behavior …
Date: August 11, 2011
Creator: Robinson, Troy A.
System: The UNT Digital Library
Improving the phase stability and oxidation resistance of B-NiAl (open access)

Improving the phase stability and oxidation resistance of B-NiAl

High temperature alloys are essential to many industries that require a stable material to perform in harsh oxidative environments. Many of these alloys are suited for specific applications such as jet engine turbine blades where most other materials would either melt or oxidize and crumble (1). These alloys must have a high melting temperature, excellent oxidation resistance, good creep resistance, and decent fracture toughness to be successfully used in such environments. The discovery of Ni based superalloys in the 1940s revolutionized the high temperature alloy industry and there has been continued development of these alloys since their advent (2). These materials are capable of operating in oxidative environments in the presence of combustion gases, water vapor and at temperatures around 1050 C. Demands for increased f uel efficiency, however, has highlighted the need for materials that can be used under similar atmospheres and at temperatures in excess of 1200 C. The current Ni based superalloys are restricted to lower temperatures due to the presence of a number of low melting phases that result in softening of the alloys above 1000 C. Therefore, recent research has been aimed at exploring and developing newer alloy systems that can meet the escalating requirements. …
Date: August 15, 2011
Creator: Brammer, Travis
System: The UNT Digital Library
Search for the Standard Model Higgs boson produced in association with a W Boson in the isolated-track charged-lepton channel using the Collider Detector at Fermilab (open access)

Search for the Standard Model Higgs boson produced in association with a W Boson in the isolated-track charged-lepton channel using the Collider Detector at Fermilab

The Higgs boson is the only elementary particle predicted by the Standard Model (SM) that has not yet been observed experimentally. If it exists, it explains the spontaneous electroweak symmetry breaking and the origin of mass for gauge bosons and fermions. We test the validity of the SM by performing a search for the associated production of a Higgs boson and a W boson in the channel where the Higgs boson decays to a bottom-antibottom quark pair and the W boson decays to a charged lepton and a neutrino (the WH channel). We study a dataset of proton-antiproton collisions at a centre-of-mass energy {radical}s = 1.96 TeV provided by the Tevatron accelerator, corresponding to an integrated luminosity of 5.7 fb{sup -1}, and recorded using the Collider Detector at Fermilab (CDF).We select events consistent with the signature of exactly one charged lepton (electron or muon), missing transverse energy due to the undetected neutrino (MET) and two collimated streams of particles (jets), at least one of which is required to be identified as originating from a bottom quark. We improve the discrimination of Higgs signal from backgrounds through the use of an artificial neural network. Using a Bayesian statistical inference approach, we …
Date: August 1, 2011
Creator: Buzatu, Adrian
System: The UNT Digital Library
Campbell penetration depth in Fe-based superconductors (open access)

Campbell penetration depth in Fe-based superconductors

A 'true' critical current density, j{sub c}, as opposite to commonly measured relaxed persistent (Bean) current, j{sub B}, was extracted from the Campbell penetration depth, {lambda}{sub c}(T,H) measured in single crystals of LiFeAs, and optimally electron-doped Ba(Fe{sub 0.954}Ni{sub 0.046}){sub 2}As{sub 2} (FeNi122). In LiFeAs, the effective pinning potential is nonparabolic, which follows from the magnetic field - dependent Labusch parameter {alpha}. At the equilibrium (upon field - cooling), {alpha}(H) is non-monotonic, but it is monotonic at a finite gradient of the vortex density. This behavior leads to a faster magnetic relaxation at the lower fields and provides a natural dynamic explanation for the fishtail (second peak) effect. We also find the evidence for strong pinning at the lower fields.The inferred field dependence of the pinning potential is consistent with the evolution from strong pinning, through collective pinning, and eventually to a disordered vortex lattice. The value of j{sub c}(2 K) {approx_equal} 1.22 x 10{sup 6} A/cm{sup 2} provide an upper estimate of the current carrying capability of LiFeAs. Overall, vortex behavior of almost isotropic, fully-gapped LiFeAs is very similar to highly anisotropic d-wave cuprate superconductors, the similarity that requires further studies in order to understand unconventional superconductivity in cuprates and …
Date: August 15, 2011
Creator: Prommapan, Plegchart
System: The UNT Digital Library
Theory of spin-fluctuation induced superconductivity in iron-based superconductors (open access)

Theory of spin-fluctuation induced superconductivity in iron-based superconductors

In this dissertation we focus on the investigation of the pairing mechanism in the recently discovered high-temperature superconductor, iron pnictides. Due to the proximity to magnetic instability of the system, we considered short-range spin fluctuations as the major mediating source to induce superconductivity. Our calculation supports the magnetic fluctuations as a strong candidate that drives Cooper-pair formation in this material. We find the corresponding order parameter to be of the so-called ss-wave type and show its evolution with temperature as well as the capability of supporting high transition temperature up to several tens of Kelvin. On the other hand, our itinerant model calculation shows pronounced spin correlation at the observed antiferromagnetic ordering wave vector, indicating the underlying electronic structure in favor of antiferromagnetic state. Therefore, the electronic degrees of freedom could participate both in the magnetic and in the superconducting properties. Our work shows that the interplay between magnetism and superconductivity plays an important role to the understanding of the rich physics in this material. The magnetic-excitation spectrum carries important information on the nature of magnetism and the characteristics of superconductivity. We analyze the spin excitation spectrum in the normal and superconducting states of iron pnictides in the magnetic scenario. …
Date: August 15, 2011
Creator: Zhang, Junhua
System: The UNT Digital Library
Helicity Asymmetry Measurement for pi^0 Photoproduction with FROST (open access)

Helicity Asymmetry Measurement for pi^0 Photoproduction with FROST

This thesis reports on the first helicity asymmetry measurement for single neutral pion photoproduction using the CLAS detector in Hall B at the Thomas Jefferson National Accelerator Facility (JLab). This measurement used longitudinally polarized protons and circularly polarized photons at energies between 350 MeV and 2400 MeV. The experimental results are compared to three available model calculations.
Date: August 1, 2011
Creator: Iwamoto, Hideko
System: The UNT Digital Library
The Use of Evidence-based Practices in the Provision of Social Skills Training for Students with Autism Spectrum Disorders: a National Survey of School Psychologists' Training, Attitudes, and Practices (open access)

The Use of Evidence-based Practices in the Provision of Social Skills Training for Students with Autism Spectrum Disorders: a National Survey of School Psychologists' Training, Attitudes, and Practices

The purpose of this exploratory study was to examine school psychologists' use of evidence- based practices (EBP), in general, and more specifically in the area of social skills training (SST) for students with autism spectrum disorders (ASD). Study participants, consisting of 498 school psychologists from across the nation, participated in an online survey that gathered information about their training, attitudes, and practices. The frequency with which specific EBP practices for social skills training for students with ASD was examined, as was prediction of use of these practices. Multiple-regression analyses revealed multiple independent variables that were predictors for overall use of EBP. Results indicated that over half of the participants provide SST for students with ASD. Although the majority of participants indicated that their graduate program included at least one course with information about ASD and EBP practices, in general, nearly half indicated that their coursework did not include any courses that directly addressed social skills training for students with ASD. Confirmatory factor analysis (CFA) was used to determine the extent to which the data fit the factor model. Participants' perception of the importance placed on EBP by their school district, scores on the openness subscale of the Evidence Based Practices …
Date: August 2011
Creator: Austin, Jennifer E.
System: The UNT Digital Library
Booty Calls, Rage, and Racialized/sexualized Subjects: Tmz's Coverage of Rihanna and Chris Brown (open access)

Booty Calls, Rage, and Racialized/sexualized Subjects: Tmz's Coverage of Rihanna and Chris Brown

Internet-based celebrity gossip blog site, TMZ, is a growing cultural force. Employing critical rhetorical analytics, the author examines the TMZ coverage of Chris Brown's assault on his then-girlfriend, Rihanna. This project explicates TMZ's enthymematic invocation of dominant cultural ideologies surrounding race, sex, and domestic violence. Chapter 1 demonstrates the theoretical importance of both celebrities and gossip blogs, signaling the ideological importance of each. Chapter 2 critiques TMZ's reliance on historic myths regarding sex and race in their reporting on this case. Chapter 3 analyzes TMZ's humorous and affective strategies that bolster broader investments in colorblind ideologies. Chapter 4 concludes by examining the interplay of formal rhetorical elements that inform the project's findings. This research reveals that TMZ utilizes affective, enthymematic strategies that camouflage broader racist and sexist ideological impulses that perpetuate domestic violence myths.
Date: August 2011
Creator: Sabino, Lauren
System: The UNT Digital Library
Rehlet Iraqi (An Iraqi Journey) (open access)

Rehlet Iraqi (An Iraqi Journey)

Rehlet Iraqi was created to depict an Iraqi refugee family’s struggle after fleeing war-torn Iraq. Their struggle is highlighted with hope and high expectations for a better life within the United States. This film emphasizes the toll that emigration has on the life of a family before and after their arrival to Grand Rapids, Michigan.
Date: August 2011
Creator: Wahbeh, Fadi
System: The UNT Digital Library
The “Dallas Way” in the Gayborhood: The Creation of a Lesbian, Gay, Bisexual, and Transgender Community in Dallas, Texas, 1965-1986 (open access)

The “Dallas Way” in the Gayborhood: The Creation of a Lesbian, Gay, Bisexual, and Transgender Community in Dallas, Texas, 1965-1986

This thesis describes the creation of the gay and lesbian community in Dallas, the fourth largest metropolitan area in the United States. Employing more than seventy-five sources, this work chronicles the important contributions the gay men and lesbians of Dallas have made in the struggle for gay civil rights. This thesis adds to the studies of gay and lesbian history by focusing on a region of the United States that has been underrepresented, the South. In addition, this work addresses the conflicts that arise within the community between men and women.
Date: August 2011
Creator: Wisely, Karen S.
System: The UNT Digital Library
Interfacial Electrochemistry of Copper and Spectro-Electrochemical Characterization of Oxygen Reduction Reaction (open access)

Interfacial Electrochemistry of Copper and Spectro-Electrochemical Characterization of Oxygen Reduction Reaction

The first part of this dissertation highlights the contents of the electrochemical characterization of Cu and its electroplating on Ru-based substrates. The growth of Ru native oxide does diminish the efficiency of Cu plating on Ru surface. However, the electrochemical formed irreversible Ru hydrate dioxide (RuOxHy) shows better coverage of Cu UPD. The conductive Ru oxides are directly plateable liner materials as potential diffusion barriers for the IC fabrication. The part II of this dissertation demonstrates the development of a new rapid corrosion screening methodology for effective characterization Cu bimetallic corrosion in CMP and post-CMP environments. The corrosion inhibitors and antioxidants were studied in this dissertation. In part III, a new SEC methodology was developed to study the ORR catalysts. This novel SEC cell can offer cheap, rapid optical screening results, which helps the efficient development of a better ORR catalyst. Also, the SEC method is capable for identifying the poisoning of electrocatalysts. Our data show that the RuOxHy processes several outstanding properties of ORR such as high tolerance of sulfation, high kinetic current limitation and low percentage of hydrogen peroxide.
Date: August 2011
Creator: Yu, Kyle Kai-Hung
System: The UNT Digital Library
Assessment and Treatment of Multiple Topographies of Self-injury Maintained by Separate Reinforcement Contingencies (open access)

Assessment and Treatment of Multiple Topographies of Self-injury Maintained by Separate Reinforcement Contingencies

Functional analysis procedures were used to assess and treat multiple topographies of self-injurious behavior exhibited by an individual. An experimental functional analysis indicated that one topography, hand biting, appeared to be maintained by social positive reinforcement in the form of delivery of tangible items. The analysis also provided evidence that a second form of self-injury, skin picking, was automatically reinforced. To treat positively reinforced hand biting, access to a preferred tangible was arranged contingent on the omission of biting for a prespecified time interval. Hand biting was nearly eliminated, and low rates were maintained as the schedule of reinforcement was thinned to 10 min. Competing stimulus assessments identified that magazines effectively suppressed all occurrences of skin picking; therefore, noncontingent access to magazines was implemented. Using a combination of multielement and multiple baseline designs, we were able to demonstrate that the two topographies of self-injury were maintained by independent reinforcement contingencies and that interventions corresponding to each topography and function effectively treated both behaviors.
Date: August 2011
Creator: Pace, Amy
System: The UNT Digital Library
Molecular Structure Analyses of Asymmetric Hydrocarbon Liquid Compounds in the Gas Phase Using Chirped-pulse Fourier Transform Microwave Spectroscopy: Acyl Chlorides and Perfluorinated Acyl Chlorides (open access)

Molecular Structure Analyses of Asymmetric Hydrocarbon Liquid Compounds in the Gas Phase Using Chirped-pulse Fourier Transform Microwave Spectroscopy: Acyl Chlorides and Perfluorinated Acyl Chlorides

Examinations of the effects of (a.) alkyl carbon chain length and (b.) perfluorination of acyl chlorides; propionyl chloride, butyryl chloride, valeroyl chloride, and perfluorinated acyl chlorides; perfluoropropionyl chloride and perfluorobutyryl chloride, are reported and compared using CP-FTMW spectroscopy. All of these molecules are already published in various journals except for valeroyl chloride. The chapters are organized by molecule alkyl chain length and include some background theory. Conformational stability, internal rotation, helicity, and ionic character of the C-Cl bond via the nuclear electric quadrupole coupling constant (χzz) are analyzed. Results show syn, syn-anti/syn-gauche, and syn-anti-anti/syn-gauche-anti stable conformations. Internal rotation was only seen in propionyl chloride. Helicity was not observed. (χzz) was observed to be inert to alkyl chain length, ~ 60 MHz and ~ 65 MHz for the nonfluorinated and fluorinated acyl chlorides. Partial fluorination and varying functional groups are recommended.
Date: August 2011
Creator: Powoski, Robert A.
System: The UNT Digital Library
The Martial Arts of Medieval Europe (open access)

The Martial Arts of Medieval Europe

During the late Middle Ages and into the Renaissance, fighting books—Fechtbücher—were produced in northern Italy, among the German states, in Burgundy, and on the Iberian peninsula. Long dismissed by fencing historians as “rough and untutored,” and largely unknown to military historians, these enigmatic treatises offer important insights into the cultural realities for all three orders in medieval society: those who fought, those who prayed, and those who labored. The intent of this dissertation is to demonstrate, contrary to the view of fencing historians, that the medieval works were systematic and logical approaches to personal defense rooted in optimizing available technology and regulating the appropriate use of the skills and technology through the lens of chivalric conduct. I argue further that these approaches were principle-based, that they built on Aristotelian conceptions of arte, and that by both contemporary and modern usage, they were martial arts. Finally, I argue that the existence of these martial arts lends important insights into the world-view across the spectrum of Medieval and early Renaissance society, but particularly with the tactical understanding held by professional combatants, the knights and men-at-arms. Three treatises are analyzed in detail. These include the anonymous RA I.33 Latin manuscript in the Royal …
Date: August 2011
Creator: Price, Brian R.
System: The UNT Digital Library
Stable Book-Tax Differences, Prior Earnings and Earnings Persistence (open access)

Stable Book-Tax Differences, Prior Earnings and Earnings Persistence

This study resolves divergent prior findings relating book-tax differences to future earnings, determines whether prior literature has missed relationships between different types of book-tax differences and pre-tax and/or after-tax income, and investigates prior earnings as a factor contributing to the observed relationships. As past research has found that some firms have large book-tax differences over several years, this study separates these firms with large stable book-tax differences from others with large book-tax differences (non-stable) when investigating the link between large book-tax differences and future earnings. Finally, this study investigates whether the relationship between book-tax differences and future earnings reflects information about prior earnings and finds that prior earnings growth explains much of the lower persistence found for firms with large book-tax differences.
Date: August 2011
Creator: Racca, Joshua C.
System: The UNT Digital Library
Mythic Archaeologies: The Impact of Visual Culture on the Art and Identity of Four Hopi Artists (open access)

Mythic Archaeologies: The Impact of Visual Culture on the Art and Identity of Four Hopi Artists

This qualitative critical ethnography examines how visual culture impacted the identity and art of four Hopi artists. Sources of data included a personal journal, artists’ interviews, group discussion, art work interpretations, and historical research of Hopi art, visual culture, and issues of native identity. In particular, my analysis focused on issues of power / knowledge relationships, identity construction, and the artist as co-constructor of culture through personal narratives. Implications for art education centered on the concept of storytelling through mythic archaeology situated in identities of past, present, and future.
Date: August 2011
Creator: Santos, Lori J.
System: The UNT Digital Library
High-Precision Micropipette Thermal Sensor for Measurement of Thermal Conductivity of Carbon Nanotubes Thin Film (open access)

High-Precision Micropipette Thermal Sensor for Measurement of Thermal Conductivity of Carbon Nanotubes Thin Film

The thesis describes novel glass micropipette thermal sensor fabricated in cost-effective manner and thermal conductivity measurement of carbon nanotubes (CNT) thin film using the developed sensor. Various micrometer-sized sensors, which range from 2 µm to 30 µm, were produced and tested. The capability of the sensor in measuring thermal fluctuation at micro level with an estimated resolution of ±0.002oC is demonstrated. The sensitivity of sensors was recorded from 3.34 to 8.86 µV/oC, which is independent of tip size and dependent on the coating of Nickel. The detailed experimental setup for thermal conductivity measurement of CNT film is discussed and 73.418 W/moC was determined as the thermal conductivity of the CNT film at room temperature.
Date: August 2011
Creator: Shrestha, Ramesh
System: The UNT Digital Library
Early Predictors of Early Freshman Year Attrition in Female Hispanic Students (open access)

Early Predictors of Early Freshman Year Attrition in Female Hispanic Students

The Texas Hispanic population is projected to grow to 18.8 million, almost tripling its number within the state, in only 30 years. This rapid growth is a concern for Texas higher education because this group has traditionally been under-represented in colleges and universities. Also, according to national, state, and local data, Hispanic students are retained at a lower rate than are other ethnic groups. Because of lower retention rates for Hispanic students and because the majority of Hispanic college students are female, an increasing number of Hispanic women are heads of households. Studying the attrition rates of Hispanic females could provide a better understanding of how the state can improve both the participation and retention rates of this population. This study utilized descriptive statistics and regression analysis to identify the correlations between and among the dependent variable of attrition and independent variables derived from (1) pre-college survey responses measuring college expectations and (2) early-first semester survey responses measuring actual college experience. Institutional data were used to confirm enrollment status at the beginning of the second semester. The sample of the study was all female, full-time, first-time-in college student survey respondents attending a public 4-year institution in Texas. This number included …
Date: August 2011
Creator: Speed, Heather Faye
System: The UNT Digital Library
Psychopathy and Antisocial Personality Disorder: Gender Differences in Empathy and Alexithymia (open access)

Psychopathy and Antisocial Personality Disorder: Gender Differences in Empathy and Alexithymia

Traditional conceptualizations of psychopathy highlight the importance of affective features of the syndrome in perpetuating social deviance. However, little research has directly investigated the callousness that psychopathic offenders display toward society and their victims. The current study investigated the roles of empathy and alexithymia in psychopathy among male and female incarcerated offenders, particularly in distinguishing psychopathy from antisocial personality disorder. Gender differences were also investigated. Regarding empathy, as predicted, group differences were largest between psychopathic and non-psychopathic offenders; no reliable differences emerged between psychopathic and APD-only offenders. In contrast, alexithymia robustly distinguished between offenders with prominent psychopathic traits, those with only APD, and those with neither condition. Psychopathic females unexpectedly exhibited slightly higher levels of alexithymia than their male counterparts, while empathic deficits were relatively consistent across genders. These findings are discussed in terms of improving assessment methods for the accurate identification and treatment of offenders with prominent psychopathic features.
Date: August 2011
Creator: Rogstad, Jill E.
System: The UNT Digital Library