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The Descriptive Paleontology and Applied Ichthyoarchaeology of the Ponsipa Fauna (open access)

The Descriptive Paleontology and Applied Ichthyoarchaeology of the Ponsipa Fauna

The archaeology of the Northern Rio Grande region of New Mexico has recently received an increased amount scholarly attention. In particular, understanding past trends in demographics, agricultural productivity, violence, and social networks have been primary goals of archaeological research. Understanding patterns in animal exploitation has, however, received far less attention due to a small yet growing regional zooarchaeological database. Through the identification of animal remains from a site called Ponsipa (occupied ca. A.D. 1300 to 1600), this thesis adds one large dataset to this growing database. In addition, this thesis expands on the pre-impoundment distribution of an endangered native freshwater fish species in the state of New Mexico called the blue sucker (Cycleptus elongatus). The blue sucker is a unique fish that is currently experiencing range reduction across all of its known North American distribution due to anthropogenic habitat fragmentation and degradation. Skeletal remains that were identified from Ponsipa represent the farthest known northern record of its occurrence in the state of New Mexico and highlight the extent of range restriction of the species in the area. The data concerning the historical biogeography of the blue sucker from Ponsipa have implications for the effective conservation and restoration of blue sucker …
Date: May 2015
Creator: Dombrosky, Jonathan
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Design of Multi Band Microwave Devices Using Coupled Line Transmission Lines (open access)

Design of Multi Band Microwave Devices Using Coupled Line Transmission Lines

Multi band technology helps in getting multiple operating frequencies using a single microwave device. This thesis presents the design of dual and tri band microwave devices using coupled transmission line structures. Chapter 2 presents the design of a novel dual band transmission line structure using coupled lines. In chapter 3, Design of a dual band branch line coupler and a dual band Wilkinson power divider are proposed using the novel dual band transmission line structure presented in the previous chapter. In chapter 4, Design of a tri band transmission line structure by extending the dual band structure is presented. The Conclusion and future work are presented in chapter 5.
Date: May 2015
Creator: Katakam, Sri
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Distributed Frameworks Towards Building an Open Data Architecture (open access)

Distributed Frameworks Towards Building an Open Data Architecture

Data is everywhere. The current Technological advancements in Digital, Social media and the ease at which the availability of different application services to interact with variety of systems are causing to generate tremendous volumes of data. Due to such varied services, Data format is now not restricted to only structure type like text but can generate unstructured content like social media data, videos and images etc. The generated Data is of no use unless been stored and analyzed to derive some Value. Traditional Database systems comes with limitations on the type of data format schema, access rates and storage sizes etc. Hadoop is an Apache open source distributed framework that support storing huge datasets of different formatted data reliably on its file system named Hadoop File System (HDFS) and to process the data stored on HDFS using MapReduce programming model. This thesis study is about building a Data Architecture using Hadoop and its related open source distributed frameworks to support a Data flow pipeline on a low commodity hardware. The Data flow components are, sourcing data, storage management on HDFS and data access layer. This study also discuss about a use case to utilize the architecture components. Sqoop, a framework …
Date: May 2015
Creator: Venumuddala, Ramu Reddy
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Dual-Band Quarter Wavelength and Half Wavelength Microstrip Transmission Line Design (open access)

Dual-Band Quarter Wavelength and Half Wavelength Microstrip Transmission Line Design

The thesis represents the design for dual-band quarter wavelength and half wavelength microstrip transmission line. Chapter 2 proposed the design of a novel dual-band asymmetric pi-shaped short-circuited quarter wavelength microstrip transmission line working at frequencies 1GHz and 1.55 GHz for 50Ω transmission line and at frequencies 1GHz and 1.43GHz for 60Ω transmission line. Chapter 3 proposed the design of a novel dual-band quarter wavelength microstrip transmission line with asymmetrically allocated open stubs and short-circuited stubs working at frequencies 1GHz and 1.32GHz. Chapter 4 proposed the design of dual-band pi-shaped open stub half wavelength microstrip transmission line working at frequencies 1GHz and 2.07GHz. Numerical simulations are performed both in HyperLynx 3D EM and in circuit simulator ADS for all of the proposed designs to measure the return loss (S11) and insertion loss (S12) in dB and phase response for S12 in degree.
Date: May 2015
Creator: Imran, Md Asheque
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Effect of Friction-stir Processing on the Wear Behavior of Titanium (Ti-1Al-8V-5Fe) and Stainless Steel (A-286) Alloys (open access)

Effect of Friction-stir Processing on the Wear Behavior of Titanium (Ti-1Al-8V-5Fe) and Stainless Steel (A-286) Alloys

The effect of friction stir processing (FSP) on the mechanical wear behavior was investigated for Ti-1Al-8V-5Fe (Ti-185) and stainless steel (Incoloy® A-286) alloys. The Ti-185 and A-286 alloys were tested in different processing conditions, including as rolled (AR), AR+FSP, and AR+FSP+aged. A high frequency reciprocating rig was used to simulate fretting-type wear of these alloys at room temperature. The Vickers micro-hardness and wear rates were calculated and compared for each processing condition. It was determined that along with increasing hardness in the stir zones, FSP resulted in improved wear resistance for both alloys. Specifically, wear rates in the stir zones were reduced to lowest values of 1.6 x 10-5 and 5.8 x 10-7 mm3/N·m for the AR+FSP+aged Ti-185 and A-286 alloys, respectively, despite lower hardness for A-286 alloy. Mechanistic studies were conducted to determine the reason behind these improvements in wear resistance and the effect of FSP on the microstructural evolution during wear. For the Ti-185 alloy, x-ray diffraction revealed that there was a phase transformation from β-Ti (AR+FSP) to α-Ti (AR+FSP+aged). This phase decomposition resulted in the harder and stiffer Ti phase responsible for lowering of wear rate in Ti-185. While x-ray diffraction confirmed the A-286 alloy retains its …
Date: May 2015
Creator: Tinubu, Olusegun Olukunle
Object Type: Thesis or Dissertation
System: The UNT Digital Library
The Effects of a Psychosocial Environment on College Women’s Exercise Regulations and Social Physique Anxiety (open access)

The Effects of a Psychosocial Environment on College Women’s Exercise Regulations and Social Physique Anxiety

A positive psychosocial intervention comprised of high autonomy support, task-involvement, and caring was implemented in physical activity classes to examine its effects on college women’s basic psychological needs (i.e. autonomy, competence, relatedness), exercise regulations (i.e. external, introjected, identified, integrated, intrinsic) and social physique anxiety (SPA). We hypothesized that at the end of the semester, participants in the intervention group (N = 73) would report greater need satisfaction, more self-determined regulations and less SPA than participants in the non-intervention group (N = 60). At T1 and T2, both the intervention and non-intervention participants reported “agreeing” with experiencing an autonomy supportive, task-involving, and caring environment. Furthermore, both groups at T1 and T2 reported moderate SPA. No significant group differences were found at T1. At T2, significant group differences were observed in the intervention and non-intervention groups’ report of external regulation and intrinsic regulation. The results suggests that group exercise instructors are capable of creating a positive psychosocial environment to enhance students’ intrinsic motivation.
Date: May 2015
Creator: Alvarez, Ana
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Estimation of Air Emissions During Production Phase from Active Oil and Gas Wells in the Barnett Shale Basin: 2010-2013 (open access)

Estimation of Air Emissions During Production Phase from Active Oil and Gas Wells in the Barnett Shale Basin: 2010-2013

The Barnett shale basin, the largest onshore gas field in the state of Texas, mainly produces natural gas. The basin’s oil and gas productions have dramatically increased over the past two decades with the enhancement via shale fracturing (fracking) technology. However, recent studies suggest that air emissions from shale fracking have significantly contributed to the growing air pollution problem in North Texas. In this study, air emissions from the Barnett shale basin during the production phase of the oil and gas activities (once the product is collected from the wells) are quantified. Oil and gas production data were acquired from the Texas Railroad Commission for the baseline years of 2010 through 2013. Methodology from prior studies on shale basins approved by the Texas Commission on Environmental Quality was employed in this study and the emission inventories from the production phase sources were quantified. Accordingly, the counties with the most gas operations in the basin, Tarrant, Johnson, Denton and Wise, were found to be the highest emitters of air pollutants. Tarrant County was responsible for the highest emitted NOx (42,566 tons) and CO (17,698 tons) in the basin, while Montague County released the maximum VOC emissions (87,601 tons) during the study …
Date: May 2015
Creator: Dohde, Farhan A.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
An Evaluation of Matrix Training Approaches for Teaching Compound Labels to Toddlers (open access)

An Evaluation of Matrix Training Approaches for Teaching Compound Labels to Toddlers

Matrix training techniques arrange instruction for stimulus relations that facilitate emergent responding to novel stimulus arrangements, which is a phenomenon known as recombinative generalization. The current study compared two common matrix training approaches, an overlapping (OV) design and a non-overlapping (NOV) design, with respect to arranging relations targeted for training. Two, typically-developing toddlers were taught compound action-object labels in either an OV or NOV matrix training design. Results suggest that an OV matrix design facilitates recombinative generalization more effectively than a NOV design.
Date: May 2015
Creator: Wilshire, Tayla C.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
An Evaluation of Reinforcement Effects of Preferred Items During Discrete-Trial Instruction (open access)

An Evaluation of Reinforcement Effects of Preferred Items During Discrete-Trial Instruction

This study compared the relative reinforcing efficacy of high-preferred and low-preferred stimuli, as determined by two types of preference assessments, on acquisition rates in three children diagnosed with an Autism Spectrum Disorder (ASD). The study also evaluated the indirect effects of preference on students’ stereotypy and problem behavior during instructional periods. Participants were presented with a task and provided high or low-preferred stimuli contingent upon correct responding. Results showed that acquisition occurred more rapidly in the highly preferred condition for some participants. Higher rates of problem behavior occurred in the low preferred condition for all participants. These results highlight the importance of utilizing preference assessment procedures to identify and deliver high-preferred items in skill acquisition procedures for individuals with ASD.
Date: May 2015
Creator: Rorer, Lynette
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Forward Genetic Characterization of Medicago truncatula Tnt1 Insertion Mutants Defective in Nodule Development and Symbiotic Nitrogen Fixation (open access)

Forward Genetic Characterization of Medicago truncatula Tnt1 Insertion Mutants Defective in Nodule Development and Symbiotic Nitrogen Fixation

Legumes are unique plants because they form special structures “nodules”, via symbiotic relationships with rhizobial bacteria present in the soil. Once rhizobia mature inside nodules, they fix atmospheric nitrogen providing a source of bioavailable nitrogen to the plant. To discover novel genetic components involved in the legume-rhizobia symbiosis by using forward genetic screening, we have isolated Medicago truncatula Tnt1 insertion mutants in the R108 ecotype, which are defective in nodule development and symbiotic nitrogen fixation in response to Sinorhizobium meliloti. Out of three mutants NF11044, NF11217 and NF8324, one of the mutants showed brown nodules and Fix- phenotype that is defective in symbiotic nitrogen fixation. The other two mutants showed white nodules and Fix- phenotype, also indicator of defects in symbiotic nitrogen fixation. To identify the underlying mutation causing the phenotype, we have developed molecular genetic markers by obtaining genomic sequences flanking the Tnt1 insertions by TAIL-PCR and Illumina sequencing. To carry out co-segregation analysis, back-crossed BC1F2 segregating populations were obtained. These are being phenotyped, genotyped and analyzed for co-segregation of the phenotype with the Tnt1 genetic markers. Back-crossing also has the effect of reducing the Tnt1 insertions, which are not linked to the nodulation defective phenotypes. Out of the …
Date: May 2015
Creator: Kadel, Khem L.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Gracias a La Nacionalización De Los Hidrocarburos: a Critical Analysis of Bolivia’s Transition to Compressed Natural Gas (open access)

Gracias a La Nacionalización De Los Hidrocarburos: a Critical Analysis of Bolivia’s Transition to Compressed Natural Gas

This paper critically analyzes the implementation of compressed natural gas and the ways in which it creates discourse in urban Bolivia. The rapidly developing nation is keen on making ubiquitous use of compressed natural gas a reality by issuing subsidies, citing increased mobility, savings, and environmental stewardship as the primary motives. Currently, eight out of every 10 public vehicles in Bolivia are powered by compressed natural gas. Through semi-structured interviews, questionnaires and secondary data collection, this paper elucidates the transitional process of building a natural gas-based transport network through discursive governance. This work draws on the critical discourse analysis literature to dissect disaggregated modal preference data, government documents, and news articles collected in Santa Cruz, Latin America's second fastest growing city. Moreover, this paper identifies and examines the ways in which the counter-discourse impacts the transformation of the country’s energy matrix. Results show that Bolivian automobile owners are reluctant to convert their automobiles, despite reduced transportation costs, stating that minimal compressed natural gas infrastructure exists outside of urban areas, and the conversion damages their vehicles’ motor. Additionally, the research reveals that automobile owners are currently the main beneficiaries, though respondents who do not posses an automobile speak more favorably of …
Date: May 2015
Creator: McCollum, Jerl Levi
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Grand Canyons: Authoritative Knowledge and Patient-Provider Connection (open access)

Grand Canyons: Authoritative Knowledge and Patient-Provider Connection

In 2011, African Americans in Tarrant County, Texas experienced an infant mortality rate of 14.3 per 1,000 live births. The leading cause of infant mortality in Tarrant County is prematurity and maternal nutritional status. Both maternal under-nutrition and over-nutrition are known risk factors for premature birth. Improving maternal nutrition, by reducing rates of gestational diabetes and preeclampsia, and by increasing consumption of essential prenatal vitamins and nutrients, is a road to decreasing preterm birth in African Americans. This qualitative study, based on both anthropology and public health theory, of the nutrition behavior of a group of African American expectant mothers and the experience of their health care providers and co-facilitators had a goal to provide a foundation for future development of nutrition behavior research and education for this specific population. The main finding of this study was the substantial gap of lived experience and education between the patients and their providers and co-facilitators, which hinders delivery of care and the patients’ acquiescence to nutrition recommendations. The discrepancies between the authoritative knowledge of the providers and the bodily knowledge of expectant mothers were responsible for the ineffectiveness of nutrition recommendations.
Date: May 2015
Creator: Fowler, Rebecca (Public health researcher)
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Ideal Learning Spaces: the Student Perspective (open access)

Ideal Learning Spaces: the Student Perspective

Classrooms, libraries, student unions, and university campuses shape students’ learning experiences. These physical learning spaces set the stage for college student engagement and academic performance. Most of the research about the role of physical spaces in learning lacks the student perspective. The goal of this study was to offer a student-centered vision of ideal learning spaces. Students are the learners for whom learning spaces are designed, and this thesis examines the way students of one summer class at Oklahoma Baptist University conceptualized and interacted with their learning spaces. Data collection included surveys of the students, a focus group with members of the class, participant observation in the classroom, and interviews with students and the professor. Students viewed physical spaces as the backdrop for human action and chose spaces that supported their learning styles and goals. Students described supportive spaces as warm, purposefully crafted spaces, and full of other people who were seriously pursuing the same goals. This thesis explores the ways students conceptualized and interacted with learning spaces as a network of support for their learning and provides recommendations for the design of learning spaces that facilitate this support.
Date: May 2015
Creator: Sidler, Elizabeth D.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
The Influence of Psychological Momentum on Basketball Shooting Performance (open access)

The Influence of Psychological Momentum on Basketball Shooting Performance

The purpose of this research was to examine the influence of fictitious scoring updates on psychological momentum (PM) and athletic performance in a competitive basketball setting. The participants included in this study were 50 male undergraduate students who reported having played basketball previously and qualified by being able to make more than 24% (12 out of 50) of their 3-point shots in a pre-trial session. Participants were told that they were competing in a 50 shot, 3-point shooting competition against another individual, equal in ability. After every 10 shots, participants were given a fabricated score update and answered four questions used to measure PM. Results showed that the fictitious score updates significantly (p < .01) influenced participants’ PM scores, where those who were told they led had higher PM scores than those who were told they trailed. As for shooting performance, no significant differences (p = .76) were found between positive and negative PM states for participants who reported experiencing both during the competition. Together, these findings suggest that manufactured score updates can influence PM, but resultant performance differences may not exist. Results of this study lend support to the notion that PM is experienced by athletes. However, when examining …
Date: May 2015
Creator: Harris, Connor
Object Type: Thesis or Dissertation
System: The UNT Digital Library
The Intervention of Human Modifications on Plant and Tree Species in the Landscape of the LBJ National Grasslands (open access)

The Intervention of Human Modifications on Plant and Tree Species in the Landscape of the LBJ National Grasslands

An analysis utilizing both ArcGIS and ethnographic interviews from private land owners and environmental professionals examined how man-made landscape changes affected plant and tree species in the LBJ National Grasslands in Wise County, Texas north of Decatur. From the late 1800s to the Dust Bowl Era the land was used for crop production and cattle grazing resulting in erosion and loss of soil nutrients. The research indicated by 2001 that cattle grazing and population increase resulted in land disturbance within the administrative boundary of the national grasslands. Participants expressed concern over the population increase and expansion of 5 to 10 acre ranchettes for cattle grazing common in modern times. Recommendations for the future included utilizing and expanding the resources already existing with environmental professionals to continue controlling erosion.
Date: May 2015
Creator: Lang, Brett M.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Let the Punishment Fit the Crime: an Overview of the Historical Approach to Probation in the State of Texas (open access)

Let the Punishment Fit the Crime: an Overview of the Historical Approach to Probation in the State of Texas

Adult probation evolved in the United States as a result of the suspended sentence concept. As a result of a lack of follow through when an individual obtained a suspended sentence, there was no “checks and balances” to monitor whether an individual completed the guidelines set forth. As time progressed, it became apparent a more cohesive and monitored system was needed. Thus, an energetic and motivated individual, John Augustus, started the concept of probation by taking it upon himself to assist in the rehabilitative process of individuals charged with criminal behavior. Subsequent to his death, the concept of probation was embraced by his advocates who lobbied legislatively in order to enact probation laws that would oversee the success of probationers. It wasn’t until the 1950’s that the counties in the state of Texas took it upon themselves to enact their own system of monitoring of probationers. Over time the states have guided their probation concepts from evidence based research. Juvenile probation in the United States didn’t gain a solid foundation until the end of the 19th century with the development of the first juvenile court in Illinois. It took this country time to understand that juveniles were different than adults …
Date: May 2015
Creator: Reichstein, Sheldon Philip
Object Type: Thesis or Dissertation
System: The UNT Digital Library
The Light of Dark-Age Athens: Factors in the Survival of Athens after the Fall of Mycenaean Civilization (open access)

The Light of Dark-Age Athens: Factors in the Survival of Athens after the Fall of Mycenaean Civilization

When looking at Dark Age Greece, one of the most important sites to consider is Athens. The Dark Age was a transitional period between the fall of Mycenaean Greece of the Bronze Age, and Archaic Greece of the Iron Age. This period is called the Dark Age because the palaces that ruled the Mycenaean age collapsed, and with them fell civilization in mainland Greece. Writing, fine art, massive architecture, trade, and luxury goods disappear from mainland Greece. But Athens survived the fall of the Mycenaeans. In order to understand the reason why Athens survived one must look at what the causes of the fall of the Mycenaeans were. Theories range from raiders and invasion, to natural disasters, such as earthquakes, droughts, and plagues. One must also examine Greece itself. The landscape and climate of Greece have a large impact on the settlement of the Greeks. The land of Greece also affects what Greek communities were able to do economically, whether a city would be rich or poor. It is because Athens is located in Attica that it survived. Attica had the poorest soil in the Mycenaean world, and was the poorest of the major cities, therefore, when looking at the …
Date: May 2015
Creator: Golightly, Paul
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Loading Mode Dependent Effective Properties of Octet-truss Lattice Structures Using 3D-Printing (open access)

Loading Mode Dependent Effective Properties of Octet-truss Lattice Structures Using 3D-Printing

Cellular materials, often called lattice materials, are increasingly receiving attention for their ultralight structures with high specific strength, excellent impact absorption, acoustic insulation, heat dissipation media and compact heat exchangers. In alignment with emerging additive manufacturing (AM) technology, realization of the structural applications of the lattice materials appears to be becoming faster. Considering the direction dependent material properties of the products with AM, by directionally dependent printing resolution, effective moduli of lattice structures appear to be directionally dependent. In this paper, a constitutive model of a lattice structure, which is an octet-truss with a base material having an orthotropic material property considering AM is developed. In a case study, polyjet based 3D printing material having an orthotropic property with a 9% difference in the principal direction provides difference in the axial and shear moduli in the octet-truss by 2.3 and 4.6%. Experimental validation for the effective properties of a 3D printed octet-truss is done for uniaxial tension and compression test. The theoretical value based on the micro-buckling of truss member are used to estimate the failure strength. Modulus value appears a little overestimate compared with the experiment. Finite element (FE) simulations for uniaxial compression and tension of octet-truss lattice materials …
Date: May 2015
Creator: Challapalli, Adithya
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Marital Status and Racial/Ethnic Differences in Health Outcomes (open access)

Marital Status and Racial/Ethnic Differences in Health Outcomes

Substantial evidence demonstrates that marriage is associated with better health outcomes and lower mortality risk. Some evidence suggests that there are gender and race/ethnicity differences between the marriage-health benefits association. However, previous studies on marriage and health have mainly focused on non-Hispanic White-Black differences. Limited information is available regarding the roles of Hispanics. The present study examined marital status, gender, and the differences between non-Hispanic Whites, non-Hispanic Blacks, and Hispanics, in health outcomes. A retrospective cohort analysis of 24,119 Hispanic, NH White, and NH Black adults admitted to a large hospital was conducted. A total of 16,661 patients identified as either married or single was included in the final analyses. Consistent with the broader literature, marriage was associated with beneficial hospital utilization outcomes. With respect to differences in these benefits, results suggest that married patients, Hispanic patients, and women, were less likely to experience in-hospital mortality. Similar effects were observed in aggregated length of stay with married Hispanic women hospitalized nearly 2 days less than their single counterparts (6.83 days and 8.66 days, respectively). These findings support existing literature that marriage is associated with health benefits, add to the emerging research of a Hispanic survival advantage, and broaden the understanding …
Date: May 2015
Creator: Villarreal, Cesar
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Master Recital - 2015-05-01 - Jesús "Chucho" Insuasty, double bass

Access: Use of this item is restricted to the UNT Community
Recital presented at the UNT College of Music Recital Hall in partial fulfillment of the Master of Music (MM) degree.
Date: May 1, 2015
Creator: Insuasty, Jesús
Object Type: Sound
System: The UNT Digital Library
"Miss Kathy" (open access)

"Miss Kathy"

Miss Kathy is a documentary film that tells the story of Kathy Griffin-Grinan, a lead recovery coach for prostitution and human trafficking with the Harris County Sheriff’s Office. Her non-profit organization —We’ve Been There, Done That – works in conjunction with law-enforcement to offer the survivors of prostitution a chance at rehabilitation. With endless enthusiasm, she mentors survivors as they struggle to escape a destructive lifestyle. This film also explores the relationship between human trafficking and prostitution, while addressing issues of victimization and exploitation.
Date: May 2015
Creator: Alexander, Jeffrey, 1982-
Object Type: Thesis or Dissertation
System: The UNT Digital Library
A Multimodal Investigation of Renewal of Human Avoidance, Perceived Threat, and Emotion (open access)

A Multimodal Investigation of Renewal of Human Avoidance, Perceived Threat, and Emotion

Many people who receive exposure-based treatments for anxiety disorders exhibit a return of fear and avoidance which is often referred to as renewal or relapse. Human and nonhuman research on fear conditioning and renewal has been instrumental in helping understand relapse in anxiety disorders. The purpose of this investigation was to examine renewal of human avoidance and assess whether avoidance may aid in sustaining renewal of fear responses. We adopted a multimodal measurement approach consisting of an approach-avoidance task along with ratings of perceived threat and fear and measures of skin-conductance, a widely used physiological measure of fear. A traditional, single-subject research design was used with six healthy adults. All tasks employed a discrete trial procedure. Experimental conditions included Pavlovian fear conditioning in which increased probability of money loss was paired with a “threat” meter in Context A and later followed extinction in Context B. Fear and avoidance increased to higher threat levels in Context A but not Context B. Renewal testing involved presenting the threat meter on a return to Context A to determine if it evoked fear and avoidance (i.e., relapse). As predicted, renewal testing in Context A showed that increased threat was associated with increased avoidance, ratings …
Date: May 2015
Creator: Ludlum, Madonna L.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Nanohybrids Based on Solid and Foam Polyurethanes (open access)

Nanohybrids Based on Solid and Foam Polyurethanes

Polymer nanocomposites are a going part of Materials Science and Engineering. These new composite materials exhibit dimensional and thermal stability of inorganic materials and toughness and dielectric properties of polymers. Development of nanocomposites become an important approach to create high-performance composite materials. In this study silica, fly ash, silica nanotubes and carbon black particles have been added to modify polyurethane foam and thermoplastic polyurethanes. It has been found that the addition of silica can diminish the size of foam bubbles, resulting in an increased stiffness of the material, increase of the compressive strength, and greater resistance to deformation. However, the uniformity of bubbles is reduced, resulting in increased friction of the material. Fly ash added to the foam can make bubbles smaller and improve uniformity of cells. Therefore, the material stiffness and compressive strength, resistance to deformation, and has little impact on the dynamic friction of the material. Adding nanotubes make bubble size unequal, and the arrangement of the bubble uneven, resulting in decreased strength of the material, while the friction increases. After the addition of carbon black to the polyurethane foam, due to the special surface structure of the carbon black, the foam generates more bubbles during the foaming …
Date: May 2015
Creator: Bo, Chong
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Neurotoxicity of the Industrial Solvent 4-Methylcyclohexanemethanol: Involvement of the GABA Receptor (open access)

Neurotoxicity of the Industrial Solvent 4-Methylcyclohexanemethanol: Involvement of the GABA Receptor

A recent chemical spill of 4-Methylcyclohexanemethanol (4-MCHM) in West Virginia left 300,000 people without water. Officials claimed that this compound is not lethally toxic, but potentially harmful if swallowed or inhaled, and can cause eye and skin irritation. Sittig's Handbook of Toxic and Hazardous Chemical Carcinogens reports high exposures from skin contact or inhalation may cause damage to the heart, liver, kidneys, and lungs, and may result in death. However, no quantitative data seem to exist and no references can be found on neurotoxicity. We have investigated the neurotoxicity of 4-MCHM using mammalian nerve cell networks grown on microelectrode arrays. Network spontaneous activity from multiple units (range 48 – 120 per network) were used as the primary readout. Individual units were followed based on spike waveforms digitized at 40 kHz (Plexon MNAP system). Dose response curves show the effective inhibitory concentration at 50 percent decrease (EC50) to average 27.4 microM SD±6.17. However, in the presence of 40 microM bicuculline, a competitive GABAA antagonist, the EC50 shifts to 70.63uM SD ±4.3; implying that early, low concentration exposures to 4-MCHM involve GABA activation. Initial activity loss occurs without active unit loss (defined as 10 or more template threshold crossing per min), indicating …
Date: May 2015
Creator: Gibson, Jason (Jason Robert)
Object Type: Thesis or Dissertation
System: The UNT Digital Library