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Bacterial Challenge in Lumbricus Terrestris: A Terrestrial Invertebrate Immunotoxicity Model.

Description: A bacterial challenge assay was developed utilizing the earthworm, Lumbricus terrestris, in order to assess potential immunotoxic effects from exposure to specific polychlorinated biphenyl congeners. Earthworms were inoculated with Aeromonous hydrophila, establishing a 10-day LD50. In vitro assays for effects of PCBs on phagocytosis agreed with mammalian studies, demonstrating potent suppression of phagocytosis by the non-coplanar PCB congener 138 and no suppression by the coplanar congener 126. However, when the effects of the two PCB congeners were evaluated for suppression of resistance to a whole animal infection challenge assay, coplanar PCB 126 decreased the ability of L. terrestris to withstand infection while non-coplanar PCB 138 did not.
Date: May 2007
Creator: McDonald, Jennifer C.
Partner: UNT Libraries
open access

The use of democratic institutions as a strategy to legitimize authoritarian rule.

Description: Numerous authoritarian states use institutions usually associated with democratic regimes like a constitution, elections, and a legislature. This seems to be counterintuitive. Authoritarian regimes should rather shrink away from democratic institutions. Elections can be won by the opposition and legislatures can make decisions against the interests of the ruler. So, why do autocratic regimes install institutions which limit their power and threaten their survival in office? Assuming actors behave rationally, one should expect authoritarian rulers only to introduce procedures working in their favor. This study looks at the effect of institutions in authoritarian regimes. The findings suggest that legislatures significantly lower the chances of regime breakdown in the long run. However, particularly in election years, authoritarian regimes are facing a higher likelihood of failure.
Date: May 2007
Creator: Michalik, Susanne
Partner: UNT Libraries
open access

Diffusion of Slow Electrons in Gases

Description: The properties of electrons in a gas and an external electric field, e.g., agitation velocity, free path, energy lost per collision, and collision cross sections, were determined for electrons of energy less than 2 ev in a large number of gases. The computations were made from previously measured values for Townsend's energy factor or the ratio of electron agitation energy to molecule thermal energy. Results are presented for hydrogen, nitrogen, carbon dioxide, methane, ethylene, cyclopropane, and argon. (D.L.C.)
Date: October 24, 1961
Creator: Forester, D. W. & Cochran, L. W.
Partner: UNT Libraries Government Documents Department
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A Study of the Kinetic and Mechanical Properties of a Stabilized Beta Phase Plutonium Alloy

Description: The elements Sn, Mg, Ti, Zr, Hf, Si, Cd, and U were alloyed with plutonium to determine their effect on stabilization of the beta phase. Zirconium was found to be the ' most effective. Kinetic studies were conducted on Pu-Zr alloys having 0.24, 0.65, and 1.7 at.% Zr contents. The beta to alpha transformation in the Pu-Zr alloys was somewhat similar to that in unalloyed plutonium. The main difference being that time, temperature, transformation curves of the alloys were shifted to the right as the zirconium concentration increased. It was determined that the amount of beta phase retained at room temperature increased as the zirconium concentration increased. The minimum amount of Zr needed to stabilize the beta phase of plutonium at room temperature was determined to be 2.0 at.%. A 2.4 at.% Zr addition stabilized the beta phase of plutonium at atmospheric pressure from room temperature to 265 deg C. During mechanical property testing it was determined that the stabilized beta Pu-2.4 at.% Zr alloy was brittle from room temperature to 230 deg C. Both tensile and compression strengths of the beta stabilized alloy were greater than the unalloyed beta phase of plutonium. A brittle-ductile transition was noted between 130 and 180 deg C on the Pu-0.65 at.% Zr alloy. Age hardening studies were conducted at room temperature with a Pu -2.4 at.% Zr alloy. A slight aging effect was noted due to the precipitation of an intermetallic compound. Compression tests on the Pu-2.4 at.% Zr alloy indicated that below 80 deg C the stabilized beta phase started to transform to alpha phase during the application of compressive loads. (auth)
Date: January 1, 1962
Creator: Taylor, J. M.
Partner: UNT Libraries Government Documents Department
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The Geologic and Archaeological History of the Dickie Carr Site 41PR26

Description: This thesis is an analysis and synthesis of the geologic and archaeological history of the Dickie Carr site, 41PR26, on Mill Creek in north central Texas. Included are analyses of the stratigraphy, sedimentary environments, and soils of the locality. A regional comparison is made with respect to the Late Quaternary geology of the upper Trinity River basin, Texas to interpret the geologic data. Two stratigraphic units were identified that record the Pleistocene-Holocene transition. The buried lower unit is comprised of terrace, floodplain, and channel deposits with extensive pedogenesis. The unit is Late Pleistocene in age and contains the remains of Mammuthus columbi. The upper stratigraphic unit is comprised of terrace and floodplain sediments with well-expressed pedogenesis. The unit is Early Holocene in age with Late Paleoindian and Late Archaic occupations. The archaeological components are compared and contrasted with documented sites from the Elm and East Forks of the Trinity River. The occupations are examined in a geoarchaeological context. The Late Paleoindian occupation is post-depositional and located in terrace deposits. The Late Archaic occupation is syndepositional and located in floodplain deposits.
Date: May 2007
Creator: Byers, Johnny A.
Partner: UNT Libraries
open access

Applying Cognitive Load Theory to the Design of Online Learning.

Description: The purpose of the study was to investigate the application of cognitive load theory to the design of online instruction. Students in three different courses (N = 146) were measured on both learning performance and perceptions of mental effort to see if there were any statistically significant differences. The study utilized a quasi-experimental posttest-only control group design contrasting modified and unmodified instructional lessons. Both groups were given a posttest to measure knowledge gained from the lesson (cognitive domain of learning) and perceptions of mental effort involved. Independent samples t-tests were used to compare the mean performance scores of the treatment groups (i.e. the sections using redesigned materials) versus the control groups for all three courses. Cohen's d was also computed to determine effect size. Mental effort scores were similarly compared for each group on the overall cognitive load score, for a total of six data points in the study. Of the four hypotheses examined, three (H1, H2, H4) found no statistically significant difference between the experimental and control groups. Negative significance was found between the experimental and control group on the effect of modality (H3). On measures of cognitive load, no statistically significant differences were found.
Date: May 2007
Creator: Burkes, Kate M. Erland
Partner: UNT Libraries
open access

The Representation of Hispanic Females in Gifted and Talented and Advanced Placement Programs in a Selected North-Central Texas Public High School

Description: Analysis of a particular north-central Texas public high school revealed a strong representation of Hispanic females in advanced academic programs, i.e., AP and GT in proportion to their representation in the overall student population. Research seems to indicate that a progressive approach to academic-potential identification; culturally effective mentoring, traditional Hispanic values, and newly emerging personal and social characteristics all seem to be contributing factors. This study seems to indicate that a new type of Hispanic female is emerging who is more assertive academically, more visible in the classroom, and less marriage-and-family oriented as might be believed by teachers, society, their peers, and perhaps even their parents.
Date: May 2007
Creator: Brown, Monty
Partner: UNT Libraries
open access

Determining Properties of Synaptic Structure in a Neural Network through Spike Train Analysis

Description: A "complex" system typically has a relatively large number of dynamically interacting components and tends to exhibit emergent behavior that cannot be explained by analyzing each component separately. A biological neural network is one example of such a system. A multi-agent model of such a network is developed to study the relationships between a network's structure and its spike train output. Using this model, inferences are made about the synaptic structure of networks through cluster analysis of spike train summary statistics A complexity measure for the network structure is also presented which has a one-to-one correspondence with the standard time series complexity measure sample entropy.
Date: May 2007
Creator: Brooks, Evan
Partner: UNT Libraries
open access

An examination of the effects of accuracy+rate versus accuracy+observing response training methods on matching-to-sample performance.

Description: The relative efficacy of training procedures emphasizing accuracy versus those which add a rate criterion is a topic of debate. The desired learning outcome is fluent responding, assessed by measures of retention, endurance, stability, and application. The current study examined the effects of these two procedures on fluency outcomes using a matching-to-sample paradigm to train participants to match English to Japanese characters. An explicit FR-3 observing response was added to an accuracy-only condition to assess the extent to which it may facilitate learning. Total time spent responding in practice drills in accuracy-only conditions was yoked to total time spent in drills achieving rate aims in accuracy+rate (AR) conditions. One participant clearly demonstrated superior fluency outcomes after AR training while another displayed superior endurance and stability outcomes after such training. The remaining two participants did not demonstrate significantly different fluency outcomes across conditions.
Date: May 2007
Creator: Anderson, Jesse
Partner: UNT Libraries
open access

A Contravention of Established Principles of Interspecific Allometric Metabolic Scaling in Developing Silkworms, Bombyx Mori.

Description: Established interspecific metabolic allometric relationships do not adequately describe the complexity and variable physiological states of developing animals. Consequently, intraspecific allometric relationships of oxygen consumption and carbon dioxide production as a function of body mass; the respiratory quotient; the function of the silk cocoon; and body composition were investigated for each distinct developmental stage of the silkworm, Bombyx mori. Whole animal O2 consumption in Bombyx ranged from 0.00064 + 0.000047 ml O2 .hr-1 at larval instar I to 0.77 + 0.06 ml O2 .hr-1 in pre-pupal, falling to 0.21+ 0.01 ml O2 .hr-1 in the pupae. Those instars having a significant relationship between O2 consumption as a function of body mass, the slope of the line relating O2 consumption to body mass varied between 0.99 and 1.02, while across all instars the slope was 0.82. Developmental allometry should be presented for individual developmental stages because the individual allometric exponents of the stages can be significantly different from the overall allometric exponent throughout development and in some cases, the overall allometric exponent can be a statistical artifact. The first larval instar of Bombyx mori has the lowest cross sectional area of high metabolic tissue of the midgut (27%) and had one of the highest percentages of some metabolically inert tissues (i.e. lipid, 7.5%). Body composition of the first instar does not support the idea that smaller mass animals having the highest O2 consumption are composed of a greater percentage of metabolically active organs when compared to larger animals. However, this developmental stage has the highest percentage of the mitochondrial marker cytochrome oxidase, which correlates well with the high O2 consumption rate of the smaller mass. Therefore, established interspecific principles should not be assumed to function as valid models for intraspecific developmental relationships of metabolism as a function of body mass. Developmental …
Date: May 2007
Creator: Blossman-Myer, Bonnie
Partner: UNT Libraries
open access

Establishing genetic and physiological baselines for the black-tailed prairie dog (Cynomys ludovicianus).

Description: The black-tailed prairie dog (Cynomys ludovicianus) has experienced dramatic declines over much of its historical range due to habitat loss, plague, poisonings, and shootings. Many populations now occur as isolated genetic relicts. A multiple locus genetic profile was obtained using microsatellite analyses of six polymorphic nucleotide repeats from 319 black-tailed prairie dogs collected from 16 colonies throughout the state of Texas. This assessment revealed that existing populations have sufficient variation at all six loci to verify the usefulness of this approach as a primary genetic tool in conservation and preservation. The data reveals regional-dependent frequency patterns as well as support for founder/bottleneck effects for several of the 16 sites. Although the prairie dog population in Texas as a whole may appear genetically diverse, considerable genetic divergence has already occurred among the subpopulations (FST = 0.164). Isolation by distance is supported by genic differentiation analysis (P < 0.001) and pairwise correlation analysis between genetic distance and geographic distance (P < 0.001). Prairie dogs from six (COC, LUBA, LUBC, LUBD, LUBE, and TAR) of the original 16 sites have been relocated or exterminated, or were in the process of being relocated. Results indicated the following colonies (COT, DAL, HOW, and HUD) are of sufficient size and possess ample genetic diversity to be characterized as candidate foundation populations for future preservation efforts. The proximity of small colonies (< 20 hectares) such as HEMB, LUBB, and PEC, to other colonies should be examined to determine if they are isolated or part of a metapopulation. Colonies (HAR, HEMA, and SCH) with low genetic diversity would be ideal candidates for supplementation. Alternatively, these colonies could be relocated or blended with other similar but genetically distinct colonies. Baselines for healthy, pet prairie dog hematology and blood chemistries were also established. Results signify that data gathered from pet …
Date: May 2007
Creator: Biggs, Cindy Dawn
Partner: UNT Libraries
open access

Study of Substituted Benzenesulfonate-Containing Layered Double Hydroxides and Investigation of the Hexamethylenetetramine Route of LDH Synthesis

Description: Benzenesulfonates, para-substituted with amine, chloride and methyl groups were successfully incorporated into layered double hydroxides of two different compositions, 2:1 Mg-Al LDH and 2:1 Zn-Al LDH. These parent materials were also doped with small amounts of nickel and the differences in the two systems were studied. The hexamethylenetetramine route of layered double hydroxide synthesis was investigated to verify if the mechanism is indeed homogeneous. This included attempting preparation of 2:1 Mg-Al LDH, 2:1 Zn-Al LDH and 2:1 Zn-Cr LDH with two different concentrations of hexamethylenetetramine. The analytical data of the products suggest that the homogeneous precipitation may not be the true mechanism of reaction involved in LDH synthesis by this method.
Date: May 2007
Creator: Ambadapadi, Sriram
Partner: UNT Libraries
open access

Comparison of Bare Root vs. Potted Plants, Species Selection, and Caging Types for Restoration of a Prairie Wetland, and Quantitative Analysis and Descriptive Survey of Plant Communities and Associations at Lewisville Lake Environmental Learning Area (LLELA), Lewisville, TX

Description: Lewisville Lake Environmental Learning Area (LLELA) is an 809-hectare property in Denton County, TX. A study of the vegetation community identified 466 species in 104 families, with 25% of the species from only two families, Asteraceae and Poaceae. The property demonstrates the characteristics of an early successional community, dominated by weedy species. Prairie communities are dominated by Johnson grass and ragweed, with climax tall grass prairie communities only in areas that have been planted with native grass seed. Forest communities are similarly in an early successional stage, dominated by the hackberry-elm-ash alliance, with small remnants of native Cross Timbers found in isolated patches. Species richness and diversity were highest in the forests and lowest in the wetlands; evenness, though not different across ecosystems, demonstrated a strong seasonal component. The species list was compared with previously reported lists for Denton County, and 256 species identified had not been previously reported for the county. A wetland restoration study was conducted to determine if there was a difference in survival and growth between potted transplants with intact root systems and bare-root transplants. Two different mesh sizes were used for protection, and the success of the different caging was evaluated. Of eight species, only four survived through the second growing season. There was no significant difference in the success of the propagule types for Sagittaria latifolia. The treatments planted with intact root systems showed significantly higher growth and reproduction than the bare-root treatments for Eleocharis quadrangulata, Heteranthera dubia, and Vallisneria americana. There was no survival recorded in the coarse mesh cages, likely due to the presence of crayfish that are able to get through the coarser mesh and feed on the transplants.
Date: May 2007
Creator: Buckallew, Robin R.
Partner: UNT Libraries
open access

Theory of ordering transformations in metals and minerals

Description: This dissertation presents an investigation of ordering in FCC based systems using the pair potential approximation in the ground state and mean field limits. The theoretical approach is used to explain the occurrence of observed equilibrium phases and characteristics of thermodynamic instabilities, in particular, spinodal ordering and decomposition. It is shown that the stability of non-integer domain sizes in long period superstructures such as Al{sub 3}Ti and Ag{sub 3}Mg may result from the tendency of a system to reduce the number of non-dominant ordering waves, thus producing domain sizes that have rational fraction form n/m. This conclusion is used to explain the domain size stability with respect to variations in temperature and electron concentration. The cation ordering in the precipitate phases in calcite and dolomite is analyzed by analogy with ordering in FCC based metals. The ordered phases in calcite and dolomite are shown to be consistent with pair potential minima at {l brace}100{r brace} and {l brace}1/2, 1/2, 1/2{r brace} positions in reciprocal space respectively. 32 refs., 6 figs.
Date: July 1, 1991
Creator: Lindsey, Timothy Francis
Partner: UNT Libraries Government Documents Department
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Perceptions of importance of diagnostic competencies among educational diagnosticians.

Description: This research was two-fold in its purpose: the first purpose being to assess the perceived relevance of the current state competency standards adopted in Texas by the State Board for Educator Certification (SBEC) as they apply to the work of the educational diagnostician and the second being to examine the diagnostician's perceived ability of training institutions to prepare professionals for the field of special education evaluation. This study examined the perceptions of educational diagnosticians (N = 432) through the use of a survey instrument. Specifically the survey instrument was designed to assess diagnosticians' perceptions of importance of the SBEC competencies to special education evaluation in general, and to their practice in particular; the frequency with which they use the competencies; and their degree of training to meet the demands of the competencies through their preparatory program. Results indicate variability with regard to the perceived importance of the competencies and the degree of preparation to meet the demands of the competencies in practice.
Date: May 2007
Creator: Cavin, Lisa Lyle
Partner: UNT Libraries
open access

Around the Fibonacci Numeration System

Description: Let 1, 2, 3, 5, 8, … denote the Fibonacci sequence beginning with 1 and 2, and then setting each subsequent number to the sum of the two previous ones. Every positive integer n can be expressed as a sum of distinct Fibonacci numbers in one or more ways. Setting R(n) to be the number of ways n can be written as a sum of distinct Fibonacci numbers, we exhibit certain regularity properties of R(n), one of which is connected to the Euler φ-function. In addition, using a theorem of Fine and Wilf, we give a formula for R(n) in terms of binomial coefficients modulo two.
Date: May 2007
Creator: Edson, Marcia Ruth
Partner: UNT Libraries
open access

Interest Differentiation and Profile Elevation: Investigating Correlates of Depression, Confidence, and Vocational Identity

Description: Using a correlational design, this study examined relationships among and between differentiation, profile elevation, gender and educational level (predictors) and depression, confidence, and vocational identity (criterion). Clients presenting for counseling services (n = 90) with a career concern at a large, metropolitan university were included in the study. Six assumptions were examined using three single hierarchical regression analyses to reveal relationships among and between variables. Two research assumptions were confirmed at the .05 level of significance. Bivariate correlations were computed to examine the structure coefficients. Beta weights and structure coefficients were examined to determine the relative contribution of the predictors in the regression model. Results indicated that differentiation, profile elevation, gender and educational level did not predict significant variance in depression and vocational identity. However, differentiation, profile elevation, and educational level did significantly predict confidence (p< .0001).
Date: May 2007
Creator: Davis, Greta Ann
Partner: UNT Libraries
open access

Lining Up

Description: A creative, multi-genre collection that includes three personal essays (non-fiction) and two short stories (fiction). The pieces in this collection primarily focus on the themes of loneliness and waiting. It includes pieces dealing with homosexual relationships, friendships and heterosexual relationships. Collection includes the essays "The Line," "Why We Don't Talk about Christmas," and "Boys Who Kiss Back," and includes the short stories "I Am Allowed to Say Faggot" and "Dear Boy."
Date: May 2007
Creator: Davis, Allegra
Partner: UNT Libraries
open access

An Analysis of Changes in Perceptions of Certified Athletic Trainers from 1996 to 2006 on the Women in Athletic Training Survey

Description: This study investigates how perceptions vary in athletic trainers regarding issues pertaining to women in the profession. Subjects included 1500 male and 1500 female certified athletic trainers who responded to 44 demographic and perceptions survey items used to determine whether perceptions were different based on the respondent's gender. Results were compared to a previously disseminated survey in 1996 to also determine if perceptions had changed from 10 years earlier. Results regarding the presentation of awards and the attainment of leadership positions in the organization were also compared to actual data collected. The data suggested that males perceptions had not changed, but females' perceptions had changed, in that females perceived that opportunities had improved. Data regarding the number of females who had ascended to leadership positions or had received awards did not support these perceptions, however, and female athletic trainers continue to struggle to obtain equality in both of these areas. Additionally, homosocial reproduction continues to influence the decreased number of women who are hired into various jobs, or advance into leadership positions, maintaining patriarchy in the athletics arena and in the athletic training organizations. Results suggested that because athletic training has been dominated by men since its inception, patriarchy continues to influence the lack of ascension of women into leadership positions and awards recognition. Many women are choosing to leave the profession due to the gender role pressure that they can not sustain a career in athletic training and raise a family. Men's professional sports continue to reject the concept of hiring women to serve as athletic trainers with their athletes, which also continues to preserve a patriarchal environment.
Date: May 2007
Creator: Dieringer, Katherine I.
Partner: UNT Libraries
open access

Latino success stories in higher education: A qualitative study of recent graduates from a health science center.

Description: This study used qualitative research, particularly life history analysis, to determine the personal pathways of success for Latino students who chose to enter a health science center for graduate study and who graduated. By giving voice to individual success stories of Latino students, some of the influences on the life pathways of these graduates were determined. For the purposes of this study, success was defined as graduation from a health science center with either a doctor of philosophy, doctor of public health or doctor of osteopathic medicine degree. Four research subjects agreed to participate in this study from a possible 11 students from the graduating class of 2004-2005 at this health science center. Data were gathered through multiple in-depth interviews of the students themselves over a period of no more than one month for each participant. Data were analyzed using the mind mapping technique and Padilla's unfolding matrix. Findings indicate that each participant traveled a different pathway to achieve educational success although similarities did exist across participants. The influences of family background, cultural background, educational background and personal perceptions and goals did affect the pathways of these four Latino graduates. While three of four participants indicated that family was the most important influence on their academic success, all participants related the importance of family to their success, although their definitions of family seemed to vary and included the concepts of education, culture, and personal perceptions and goals. The concepts of family support of education and a culture of education within the family unit emerged as similar themes among study participants. Other similarities among participants were a high academic self-concept, a strong internal locus of control, the ability to create academic community, and a positive view of potentially negative situations. Individual themes emerged from the narratives within each category for each …
Date: May 2007
Creator: Colley, Kay Lynne
Partner: UNT Libraries
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