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Design, Construction, and Application of an Electrostatic Quadrupole Doublet for Heavy Ion Nuclear Microprobe Research (open access)

Design, Construction, and Application of an Electrostatic Quadrupole Doublet for Heavy Ion Nuclear Microprobe Research

A nuclear microprobe, typically consisting of 2 - 4 quadrupole magnetic lenses and apertures serving as objective and a collimating divergence slits, focuses MeV ions to approximately 1 x 1 μm for modification and analysis of materials. Although far less utilized, electrostatic quadrupole fields similarly afford strong focusing of ions and have the added benefit of doing so independent of ion mass. Instead, electrostatic quadrupole focusing exhibits energy dependence on focusing ions. A heavy ion microprobe could extend the spatial resolution of conventional microprobe techniques to masses untenable by quadrupole magnetic fields. An electrostatic quadrupole doublet focusing system has been designed and constructed using several non-conventional methods and materials for a wide range of microprobe applications. The system was modeled using the software package "Propagate Rays and Aberrations by Matrices" which quantifies system specific parameters such as demagnification and intrinsic aberrations. Direct experimental verification was obtained for several of the parameters associated with the system. Details of the project and with specific applications of the system are presented.
Date: December 2017
Creator: Manuel, Jack Elliot
System: The UNT Digital Library
Children with Emotional and Behavioral Disorders in Saudi Arabia: A Preliminary Prevalence Screening (open access)

Children with Emotional and Behavioral Disorders in Saudi Arabia: A Preliminary Prevalence Screening

Education in Saudi Arabia, including the education of children with special needs, is developing rapidly. However, children with emotional and behavioral disorders are neither consistently identified nor adequately served in Saudi Arabia although they are recognized as a distinct category of children who require special education services. The goal of this study was to examine the prevalence of emotional and behavioral disorders among children in Saudi Arabia to assess the need for intervention services to help those children reach their potential. The current research identified the types of behaviors that are most evident in the study sample. Also, the relationship between demographics and emotional and behavioral disorders is studied to identify possible predictors of disruptive forms of behavior. Parents of children aged 4-17 years in Saudi Arabia were surveyed using the Strengths and Difficulties Questionnaire. The findings of the study suggest that children with emotional and behavioral disorders in Saudi Arabia may account for 20% of the population of children between the ages of 4 and 17. The findings also revealed that over 20% of children in Saudi Arabia have difficulties in peer relationship and lack the necessary prosocial behaviors. The parent reporting, child gender, child education type, the geographical …
Date: December 2017
Creator: Maajeeny, Hassan
System: The UNT Digital Library
Homologs of Mammalian Lysosomal Lipase in Arabidopsis and Their Roles in Lipid Droplet Dynamics (open access)

Homologs of Mammalian Lysosomal Lipase in Arabidopsis and Their Roles in Lipid Droplet Dynamics

Lipid droplets (LDs) are organelles with many functions in cells and numerous protein interactors facilitate their biogenesis, maintenance, and turnover. The mammalian lipase responsible for LD turnover during lipophagy, LipA, has two candidate homologs in Arabidopsis: MPL1 and LIP1. One or both of these plant homologs may function in a similar manner to mammalian LipA, providing an LD breakdown pathway. To test this hypothesis, wild type (WT) Arabidopsis plants, MPL1 over-expressing (OE) mutants, and T-DNA insertion mutants of MPL1 (mpl1) and LIP1 (lip1) were examined for LD phenotypes in normal conditions and in environments where LD numbers are known to fluctuate. Plants to be imaged by confocal microscopy were exposed to heat stress and wounding to increase LD accumulation, senescence was induced in leaves to deplete lipids, and LDs were imaged throughout the day/night period to observe their diurnal regulation. The mutation of both MPL1 and LIP1 lead to an increase in LDs within the leaf mesophyll cells, although the spatial distribution of the LDs differed between the two mutants. mpl1 mutants had disrupted diurnal regulation of their LDs, but lip1 mutants did not. Alternately, lip1 mutants retained LDs during dark-induced senescence, and mpl1 mutants did not. Together these results …
Date: December 2017
Creator: McClinchie, Elizabeth A
System: The UNT Digital Library
"A Kind of Ghost" (open access)

"A Kind of Ghost"

A mosaic of past and present, mother and daughter, body and spirit: A Kind of Ghost inhabits memory and imagined spaces, haunting and begging to be remembered.
Date: December 2017
Creator: Pilcher, Lauren
System: The UNT Digital Library
Cattle Capitalists: The XIT Empire in Texas and Montana (open access)

Cattle Capitalists: The XIT Empire in Texas and Montana

The Texas Constitution of 1876 set aside three million acres of Texas public land in exchange for construction of the monumental red granite Capitol that continues to house Texas state government today. The Capitol project and the land went to an Illinois syndicate led by men influential in business and politics. Austin's statehouse is a recognizable symbol of Texas around the world. So too, the massive Panhandle tract given in exchange -- what became the "fabulous" XIT Ranch -- has come to, for many, symbolize Texas and its role in the nineteenth century cattle boom. After finding sales prospects for the land, known as the Capitol Reservation, weak at the time, backed by British capital, the Illinois group, often called the Capitol Syndicate, turned their efforts to cattle ranching to satisfy investors until demand for the land increased. The operation included a satellite ranch in Montana to which two-year-old steers from Texas were sent for fattening, often "over the trail" on a route increasingly blocked by people and settlement. Rather than a study focused on ranching operations on the ground -- the roundups, the cattle drives, the cowboys -- this instead uncovers the business and political side of the Syndicate's …
Date: December 2017
Creator: Miller, Michael M.
System: The UNT Digital Library
Niche Expansion of an Invasive Predator (Neovison vison), Prey Response, and Facilitative Interactions with Other Invasive Mammals at the Southern End of the Americas: Conservation Challenges and Potential Solutions (open access)

Niche Expansion of an Invasive Predator (Neovison vison), Prey Response, and Facilitative Interactions with Other Invasive Mammals at the Southern End of the Americas: Conservation Challenges and Potential Solutions

The Cape Horn Biosphere Reserve is located at the southern tip of South America. This large archipelago is considered one of the last pristine areas left on the world. Despite it being an unpopulated area with most of the native forest cover intact, it has not been exempt from biological invasions, one of the major drivers of biodiversity loss. Three species that naturally interact in their native range in North America – American beavers (Castor canadensis), muskrats (Ondatra zibethicus), and American mink (Neovison vison) – were independently introduced in this remote region. In my dissertation, I investigated (i) the hypothesis of niche expansion in the invasive mink population on Navarino Island towards terrestrial habitats; (ii) potential mink impact on breeding success of forest-bird populations; (iii) habitat selection of small-rodent species and their perception on the mink's novel predation risk; and (iv) the dynamics of multiple-species invasions under the hypothesis of an invasional meltdown. Additionally, I worked within the framework of environmental philosophy. I provide an example of combining ecological and cultural dimensions within the International Long-Term Ecological Research network to disentangle the ethical dilemmas that surround the management of invasive species. I finally proposed a management plan based on the …
Date: December 2017
Creator: Crego, Ramiro Daniel
System: The UNT Digital Library
Surface Degradation Behavior of Bulk Metallic Glasses and High Entropy Alloys (open access)

Surface Degradation Behavior of Bulk Metallic Glasses and High Entropy Alloys

In this study, the surface degradation behavior was studied for typical examples from bulk metallic glasses (BMGs), metallic glass composites (MGCs) and high entropy alloys (HEAs) alloy systems that are of scientific and commercial interest. The corrosion and wear behavior of two Zr-based bulk metallic glasses, Zr41.2Cu12.5Ni10Ti13.8Be22.5 and Zr57Cu15.4Ni12.6Al10Nb5, were evaluated in as-cast and thermally relaxed states. Significant improvement in corrosion rate, wear behavior, and friction coefficient was seen for both the alloys after thermal relaxation. Fully amorphous structure was retained with thermal relaxation below the glass transition temperature. This improvement in surface properties was explained by annihilation of free volume, the atomic scale defects in amorphous metals resulting from kinetic freezing. Recently developed MGCs, with in situ crystalline ductile phase, demonstrate a combination of mechanical properties and fracture behavior unseen in known structural metals. The composites showed higher wear rates but lower coefficient of friction compared to monolithic amorphous glasses. No tribolayer formation was seen for the composites in sharp contrast to that of the monolithic metallic glasses. Corrosion was evaluated by open circuit potential (OCP) analysis and potentiodynamic polarization. Site-specific corrosion behavior was studied by scanning vibration electrode technique (SVET) to identify formation of galvanic couples. Scanning kelvin …
Date: December 2017
Creator: Ayyagari, Venkata A
System: The UNT Digital Library
OPNET Based Design and Performance Evaluation of ZigBee Networks (open access)

OPNET Based Design and Performance Evaluation of ZigBee Networks

ZigBee is a substandard of IEEE 802.15 family that is specially designed to take care of factors such as power, data rate and area that primarily affect network performance. This has controlling and monitoring capability, which finds potential applications in different sectors. ZigBee allows the concept of hybrid networks and mobility. A comprehensive analysis of ZigBee networks was carried out by constructing and simulating the networks to evaluate the performance in terms of throughput, delay, network load, and packets dropped. This research is aimed at evaluating the effect of network topology on the system performance. A careful review of simulation platforms brought the conclusion of using OPNET Modeler which has the required frame work. Different network topologies of simple and hybrid were built and simulated. Throughout the simulations, the best-case scenarios were drawn to the conclusion by the graphical analysis of parameters of evaluation. Mobile networks were constructed and simulated to investigate the effect of mobility on communication.
Date: December 2017
Creator: Nurubhashu, Mabusubhan Vali
System: The UNT Digital Library
Psychopathy in Male and Female Offenders: Validating the CAPP-IRS and Investigating the Impact of Gender Role Conformity (open access)

Psychopathy in Male and Female Offenders: Validating the CAPP-IRS and Investigating the Impact of Gender Role Conformity

Recent conceptualizations of psychopathy are moving toward more inclusive, purely trait-based models. However, researchers continue to heavily rely on assessments of psychopathy that include categorical behavioral elements. The newly developed Comprehensive Assessment of Psychopathic Personality – Institutional Rating Scale appears to be a promising interview-based measure of psychopathy, but research on its reliability and validity is in its infancy. As a second issue, the vast majority of research on psychopathy, particularly in offender populations, is conducted with male participants. Nonetheless, the growing body of literature involving incarcerated females suggests gender differences in the prevalence and manifestation of psychopathic traits. Reasons for these differences are unclear, but some have proposed socialized gender roles as a contributing factor. With a sample of 52 female 49 male offenders recruited from a large, metropolitan jail, this dissertation evaluated the construct validity of the CAPP-IRS and examined the effect of gender role conformity on the manifestation of psychopathic traits. Results indicated that a three-factor model of psychopathy represented by antagonistic interpersonal relations, restricted emotions, and disinhibited behavior best fit the data. Findings further suggested convergent and discriminant validity for the CAPP-IRS. Additionally, masculine and feminine gender role conformity differentially related to psychopathy, but generally accounted …
Date: December 2017
Creator: Carter, Rachel Marjann
System: The UNT Digital Library
Postmodern Multiplicities in Three Original Works (open access)

Postmodern Multiplicities in Three Original Works

My recent compositions are situated within a postmodern theoretical framework. The heterogeneity of materials and hybridity of musical formation in these works are interpreted and contextualized within a personal reading of postmodern theories. The critical essay traces my aesthetics through a historical investigation into the definition of musical postmodernism. Through extensive citation and analysis of the writings of Julius T. Fraser, Italo Calvino, and Richard Rorty, the essay aims to provide a theoretical context for the interpretation of the musical examples. The creative documentation contains three newly-composed musical works: Piano Trio from Opus 3/c, Opus 6 for Violin, and Opus 7 for Piccolo. The works' postmodern features include creative approaches to the fragmentation of musical time into separate levels, historical allusions, and the exploration of multiplicity.
Date: December 2017
Creator: Bejo, Ermir
System: The UNT Digital Library
Emergent Functionality and Controllability in Beamforming System (open access)

Emergent Functionality and Controllability in Beamforming System

This dissertation presents beamforming designs. Using novel techniques and methods, the performance of the beamforming is improved on dual-band, tri-band, flexible function, tunable function in THz, and dynamic controllability on incident wave.
Date: December 2017
Creator: Ren, Han
System: The UNT Digital Library
Facets of Positive Affect and Risk for Bipolar Disorder: Role of the Behavioral Activation System (open access)

Facets of Positive Affect and Risk for Bipolar Disorder: Role of the Behavioral Activation System

Bipolar disorder is characterized by disruptions in mood and affect that occur not only during mood episodes, but during euthymic periods as well. At the same time, sensitivity of the behavioral activation system (BAS) has been implicated in the disorder and is a risk marker for it. Less clear is the relationship between BAS sensitivity and positive affect, particularly lower level facets of positive affect. The aim of the present study was to examine the relationship between positive affect and vulnerability for mania as assessed using BAS sensitivity. Specifically, the link between daily levels and fluctuations of positive affect and baseline BAS sensitivity was examined. Following the hierarchical model of affect, this study also assessed the relationship between BAS sensitivity and the distinct facets of positive affect. Finally, this study examined whether BAS sensitivity moderates associations between daily rewards and positive affect. Undergraduates (N = 265) from a large university in the South were recruited to complete measures of BAS sensitivity, affect, and mood symptoms at baseline. Using ecological momentary assessment (EMA), participants completed daily surveys assessing affect and engagement with rewarding situations. An exploratory factory analysis revealed a four factor structure of positive affect, consisting of Serenity, Joviality, Attentiveness, …
Date: December 2017
Creator: Dornbach-Bender, Allison
System: The UNT Digital Library
P-type Doping of Pulsed Laser Deposited WS2 with Nb (open access)

P-type Doping of Pulsed Laser Deposited WS2 with Nb

Layered transition metal dichalcogenides (TMDs) are potentially ideal semiconducting materials due to their in-plane carrier transport and tunable bandgaps, which are favorable properties for electrical and optoelectronic applications. However, the ability to make p-n junctions is the foundation of semiconductor devices, and therefore the ability to achieve reproducible p- and n-type doping in TMD semiconducting materials is critical. In this work, p-type substitutional doping of pulsed laser deposited WS2 films with niobium is reported. The synthesis technique of the PLD target with dopant incorporation which also ensures host material stoichiometry is presented. Hall electrical measurements confirmed stable p-type conductivity of the grown films. Structural characterization revealed that there was no segregation phase of niobium in the fabricated films and x-ray phtoelectron spectroscopy (xps) characterization suggest that the p-type doping is due to Nb4+ which results in p-type behavior. Stable hole concentrations as high as 10E21(cm-3) were achieved. The target fabrication and thin film deposition technique reported here can be used for substitutional doping of other 2D materials to obtain stable doping for device applications.
Date: December 2017
Creator: Egede, Eforma Justin
System: The UNT Digital Library
Analysis and Performance of a Cyber-Human System and Protocols for Geographically Separated Collaborators (open access)

Analysis and Performance of a Cyber-Human System and Protocols for Geographically Separated Collaborators

This dissertation provides an innovative mechanism to collaborate two geographically separated people on a physical task and a novel method to measure Complexity Index (CI) and calculate Minimal Complexity Index (MCI) of a collaboration protocol. The protocol is represented as a structure, and the information content of it is measured in bits to understand the complex nature of the protocol. Using the complexity metrics, one can analyze the performance of a collaborative system and a collaboration protocol. Security and privacy of the consumers are vital while seeking remote help; this dissertation also provides a novel authorization framework for dynamic access control of resources on an input-constrained appliance used for completing the physical task. Using the innovative Collaborative Appliance for REmote-help (CARE) and with the support of a remotely located expert, fifty-nine subjects with minimal or no prior mechanical knowledge are able to elevate a car for replacing a tire in an average time of six minutes and 53 seconds and with an average protocol complexity of 171.6 bits. Moreover, thirty subjects with minimal or no prior plumbing knowledge are able to change the cartridge of a faucet in an average time of ten minutes and with an average protocol complexity …
Date: December 2017
Creator: Jonnada, Srikanth
System: The UNT Digital Library
Xenotopia: Death and Displacement in the Landscape of Nineteenth-Century American Authorship (open access)

Xenotopia: Death and Displacement in the Landscape of Nineteenth-Century American Authorship

This dissertation is an examination of the interiority of American authorship from 1815–1866, an era of political, social, and economic instability in the United States. Without a well-defined historical narrative or an established literary lineage, writers drew upon death and the American landscape as tropes of unity and identification in an effort to define the nation and its literary future. Instead of representing nationalism or collectivism, however, the authors in this study drew on landscapes and death to mediate the crises of authorial displacement through what I term "xenotopia," strange places wherein a venerated American landscape has been disrupted or defamiliarized and inscribed with death or mourning. As opposed to the idealized settings of utopia or the environmental degradation of dystopia, which reflect the positive or negative social currents of a writer's milieu, xenotopia record the contingencies and potential problems that have not yet played out in a nation in the process of self-definition. Beyond this, however, xenotopia register as an assertion of agency and literary definition, a way to record each writer's individual and psychological experience of authorship while answering the call for a new definition of American literature in an indeterminate and undefined space.
Date: December 2017
Creator: Lewis, Darcy Hudelson
System: The UNT Digital Library
Historical Memory and Ethics in Spanish Narrative (open access)

Historical Memory and Ethics in Spanish Narrative

This study traces the current status of Spanish ethics as seen through the optics of historical memory. Starting from the Spanish Civil War in 1936, the thesis relates contemporary themes to their proposed origin throughout three additional distinctive eras of the 20th and 21st century in Spain: 1982-1996 (Socialist Spain), 1997-2010 (Post-modern Spain), and 2011-present (current Spain). Spanish narratives ranging from Los Abel by Matute, La magnitud de la tragedia by Monzó, "Fidelidad" of Ha dejado de llover by Barba and Las fosas de Franco by Silva are contextualized through their ethical architecture, in accordance with their socio-political context, and relationship to past historical traumas. This work proposes that the themes of anticlericalism, the pursuit of social equality, anti bureaucracy, and political distrust are trends culminating from Kohlberg's third level of morality. The thesis aims to be an exposition and legitimization of different ethical schemas that might otherwise be polarized as wrong and inferior by others.
Date: December 2017
Creator: Wilson, Rachelle
System: The UNT Digital Library
Economic Resilience, Disasters, and Green Jobs:  An Institutional Collective Action Framework (open access)

Economic Resilience, Disasters, and Green Jobs: An Institutional Collective Action Framework

This dissertation is about economic resilience of local governments to natural disasters. Specifically, the dissertation investigates resilience on regional level. Moreover, the dissertation also investigates growth in the green job sector in local governments. The findings indicate that local governments working with each other helps green job creation. In addition, the dissertation finds that green jobs, following disasters, experience three percent growth. This dissertation is important because it investigates the relationship between climate- related disasters and green jobs, which is an area that is under-investigated.
Date: December 2017
Creator: Ismayilov, Orkhan M.
System: The UNT Digital Library
The Aesthetics of Sin: Beauty and Depravity in Early Modern English Literature (open access)

The Aesthetics of Sin: Beauty and Depravity in Early Modern English Literature

This dissertation argues that early modern writers such as William Shakespeare, Thomas Middleton, George Herbert, John Milton, and Andrew Marvell played a critical role in the transition from the Neoplatonic philosophy of beauty to Enlightenment aesthetics. I demonstrate how the Protestant Reformation, with its special emphasis on the depravity of human nature, prompted writers to critique models of aesthetic judgment and experience that depended on high faith in human goodness and rationality. These writers in turn used their literary works to popularize skepticism about the human mind's ability to perceive and appreciate beauty accurately. In doing so, early modern writers helped create an intellectual culture in which aesthetics would emerge as a distinct branch of philosophy.
Date: December 2017
Creator: Jeffrey, Anthony Cole
System: The UNT Digital Library
Civil Liberties and National Unity: Reaction to the Sedition Act in the Southern States, 1798 (open access)

Civil Liberties and National Unity: Reaction to the Sedition Act in the Southern States, 1798

The traditional narrative of political party development in the United States of America during the latter half of the 1790s ascribes the decline in popularity of the Federalist Party in the Election of 1800 to that party's passage of controversial legislation, specifically the Sedition Act of 1798, prior to the election. Between the passage of the Sedition Act and the Election of 1800, however, the midterm elections of 1798-1799 transpired and resulted in a significant increase in Federalist popularity in four states – North Carolina, South Carolina, Georgia, and Virginia. This study seeks to ascertain why these four states increased their support for the Federalist Party in 1798-1799, despite the passage of the Sedition Act by the Federalist Party. By examining newspapers and election results, this study analyzes the reaction of these four states to the passage of the Sedition Act and finds that generally, these states did not react strongly against the Sedition Act in the immediate aftermath of its passage. Instead, all four states urged national unity and emphasized the need to support the national government because the United States faced the threat of war with France. This study employs a state-by-state formula to determine each state's individual …
Date: December 2017
Creator: Robinson, Sarah Elizabeth
System: The UNT Digital Library
It's All Coming Back to You: 1980s Retro Film Culture and the Masculinity of Cult (open access)

It's All Coming Back to You: 1980s Retro Film Culture and the Masculinity of Cult

The 1980s is a formative decade in American history. America sought to reestablish itself as a global power and to reassert the dominant ideology of white, patriarchal capitalism. Likewise, media producers in the 1980s sought to reassert the dominance of the white, male, muscled body in filmic representations. The identity politics of the 1980s and the depictions of the white, muscled body once prominent in the 1980s have been the site of conservative nostalgia for a young, male-dominated, cult audience that is a subset of a larger cultural trend known as retro film culture. This thesis provides historical context behind the populist 1980s B-action films from Cannon Group, Inc that celebrate violent masculinity in filmic representations with white, male action heroes. Equally important is the revival of VHS collecting and how this 1980s-inspired subculture reinforces white, patriarchal capitalism through the cult films they valorize and their capitalistic trading practices despite their claims of oppositionality against mainstream taste and Hollywood films. Lastly, this thesis reveals how a new cycle of contemporary films primarily produced outside of Hollywood reasserts and celebrates the dominance of the white, male, muscled body in filmic representations despite a postmodern and hyperconscious exterior. Overall, I argue how …
Date: August 2017
Creator: Collins, Ryan William
System: The UNT Digital Library
Two-Phase Spray Cooling with HFC-134a and HFO-1234yf for Thermal Management of Automotive Power Electronics using Practical Enhanced Surfaces (open access)

Two-Phase Spray Cooling with HFC-134a and HFO-1234yf for Thermal Management of Automotive Power Electronics using Practical Enhanced Surfaces

The objective of this research was to investigate the performance of two-phase spray cooling with HFC-134a and HFO-1234yf refrigerants using practical enhanced heat transfer surfaces. Results of the study were expected to provide a quantitative spray cooling performance comparison with working fluids representing the current and next-generation mobile air conditioning refrigerants, and demonstrate the feasibility of this approach as an alternative active cooling technology for the thermal management of high heat flux power electronics (i.e., IGBTs) in electric-drive vehicles. Potential benefits of two-phase spray cooling include achieving more efficient and reliable operation, as well as compact and lightweight system design that would lead to cost reduction. The experimental work involved testing of four different enhanced boiling surfaces in comparison to a plain reference surface, using a commercial pressure-atomizing spray nozzle at a range of liquid flow rates for each refrigerant to determine the spray cooling performance with respect to heat transfer coefficient (HTC) and critical heat flux (CHF). The heater surfaces were prepared using dual-stage electroplating, brush coating, sanding, and particle blasting, all featuring "practical" room temperature processes that do not require specialized equipment. Based on the obtained results, HFC-134a provided a better heat transfer performance through higher HTC and …
Date: August 2017
Creator: Altalidi, Sulaiman Saleh
System: The UNT Digital Library
Crystallographic Complex Reflection Groups and the Braid Conjecture (open access)

Crystallographic Complex Reflection Groups and the Braid Conjecture

Crystallographic complex reflection groups are generated by reflections about affine hyperplanes in complex space and stabilize a full rank lattice. These analogs of affine Weyl groups have infinite order and were classified by V.L. Popov in 1982. The classical Braid theorem (first established by E. Artin and E. Brieskorn) asserts that the Artin group of a reflection group (finite or affine Weyl) gives the fundamental group of regular orbits. In other words, the fundamental group of the space with reflecting hyperplanes removed has a presentation mimicking that of the Coxeter presentation; one need only remove relations giving generators finite order. N.V Dung used a semi-cell construction to prove the Braid theorem for affine Weyl groups. Malle conjectured that the Braid theorem holds for all crystallographic complex reflection groups after constructing Coxeter-like reflection presentations. We show how to extend Dung's ideas to crystallographic complex reflection groups and then extend the Braid theorem to some groups in the infinite family [G(r,p,n)]. The proof requires a new classification of crystallographic groups in the infinite family that fail the Steinberg theorem.
Date: August 2017
Creator: Puente, Philip C
System: The UNT Digital Library
Reproduction and Metabolic Responses to Acute and Chronic Hypoxia in Ovoviviparous Blaberid Cockroaches, with a Focus on Blaptica dubia (open access)

Reproduction and Metabolic Responses to Acute and Chronic Hypoxia in Ovoviviparous Blaberid Cockroaches, with a Focus on Blaptica dubia

The major components of the tracheal system of insects are an extension of the exoskeleton, and the size of the exoskeleton is fixed in the adult stage, so any increase in metabolic demand that may accompany reproduction must be met by a relatively unaltered tracheal system that the female set in place at ecdysis, when entering adulthood. Acute hypoxia tends to elicit an increase in ventilation in insects, and here, I observe increased interburst VCO2 release, and a tendency towards a more continuous gas exchange pattern being preferred over discontinuous gas exchange when Blaptica dubia and Eublaberus posticus are exposed to a descending regime of hypoxia. Additionally, higher temperatures appear to increase sensitivity to hypoxia in these species, an expected result because both species, like most ectothermic animals, display a Q10 effect, increasing metabolic rates as temperature increases. The reproductive mode of B. dubia is considered to be lecithotrophic pseudoviviparity (or type A ovoviviparity), and by the time the embryos are born, they have more than doubles in volume from the time of oviposition. This gain is apparent in the wet mass of the embryo, with no change occurring in dry mass. The egg mass that can be attributed to …
Date: August 2017
Creator: Mallery, Christopher Sean
System: The UNT Digital Library
How Attitudes towards Statistics Courses and the Field of Statistics Predicts Statistics Anxiety among Undergraduate Social Science Majors: A Validation of the Statistical Anxiety Scale (open access)

How Attitudes towards Statistics Courses and the Field of Statistics Predicts Statistics Anxiety among Undergraduate Social Science Majors: A Validation of the Statistical Anxiety Scale

The aim of this study was to validate an instrument that can be used by instructors or social scientist who are interested in evaluating statistics anxiety. The psychometric properties of the English version of the Statistical Anxiety Scale (SAS) was examined through a confirmatory factor analysis of scores from a sample of 323 undergraduate social science majors enrolled in colleges and universities in the United States. In previous studies, the psychometric properties of the Spanish and Italian versions of the SAS were validated; however, the English version of the SAS had never been assessed. Inconsistent with previous studies, scores on the English version of the SAS did not produce psychometrically acceptable values of validity. However, the results of this study suggested the potential value of a revised two-factor model SAS to measure statistics anxiety. Additionally, the Attitudes Towards Statistics (ATS) scale was used to examine the convergent and discriminant validities of the two-factor SAS. As expected, the correlation between the two factors of the SAS and the two factors of the ATS uncovered a moderately negative correlation between examination anxiety and attitudes towards the course. Additionally, the results of a structural regression model of attitudes towards statistics as a predictor …
Date: August 2017
Creator: Obryant, Monique J
System: The UNT Digital Library