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Importance and Spatial Distribution of Phytophthora Ramorum Host Species in a Coast Redwood Forest (open access)

Importance and Spatial Distribution of Phytophthora Ramorum Host Species in a Coast Redwood Forest

Phytophthora ramorum, an exotic forest pathogen known as ‘sudden oak death’ (SOD), has received considerable attention in recent years because of its effects on vegetation structure, composition, and fire disturbance regimes in western U.S. coastal forests. This research examines differences in the importance (e.g., density, dominance, and frequency) and distribution of five host species of P. ramorum–– Umbellularia californica (California bay laurel), Quercus agrifolia (coast live oak), Pseudotsuga menziesii (Douglas fir), Sequoia sempervirens (Coast redwood), and Arbutus menziesii (Madrone)––in Soquel, California. A stratified random sampling design was used to select 66 plots surrounding a managed forest edge in Soquel Demonstration State Forest. Vegetation measurements were conducted in summer 2013. In each plot, all trees ≥3 cm diameter at breast height (DBH) were identified to species, counted, and DBH, height, and canopy position measured. Leaf area index (LAI) of bay laurel was measured to quantify the amount of leaves available for pathogen dispersal with a LiCOR 2200 Plant Canopy Analyzer. In addition, morning (9:00 am) and afternoon (1:00 pm) photosynthetically active radiation (PAR) were quantified using a quantum light sensor. This paper examines the influence of environmental variables, including distance to edge, aspect, slope, and light availability on host species spatial …
Date: May 2014
Creator: Gray, Alicia E.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
How Cooperative Systems Respond to External Forces (open access)

How Cooperative Systems Respond to External Forces

Cooperative interactions permeate through nature, bringing about emergent behavior and complexity. Using a simple cooperative model, I illustrate the mean field dynamics that occur at the critical point of a second order phase transition in the framework of Langevin equations. Through this formalism I discuss the response, both linear and nonlinear, to external forces. Emphasis is placed on how information is transferred from one individual to another in order to facilitate the collective response of the cooperative network to a localized perturbation. The results are relevant to a wide variety of systems, ranging from nematic liquid crystals, to flocks and swarms, social groups, and neural networks.
Date: May 2014
Creator: Svenkeson, Adam
Object Type: Thesis or Dissertation
System: The UNT Digital Library
From Development of Semi-empirical Atomistic Potentials to Applications of Correlation Consistent Basis Sets (open access)

From Development of Semi-empirical Atomistic Potentials to Applications of Correlation Consistent Basis Sets

The development of the semi-empirical atomistic potential called the embedded atom method (EAM) has allowed for the efficient modeling of solid-state environments, at a lower computational cost than afforded by density functional theory (DFT). This offers the capability of EAM to model the energetics of solid-state phases of varying coordination, including defects, such as vacancies and self-interstitials. This dissertation highlights the development and application of two EAMs: a Ti potential constructed with the multi-state modified embedded atom method (MS-MEAM), and a Ni potential constructed with the fragment Hamiltonian (FH) method. Both potentials exhibit flexibility in the description of different solid-states phases and applications. This dissertation also outlines two applications of DFT. First, a study of structure and stability for solid-state forms of NixCy (in which x and y are integers) is investigated using plane-wave DFT. A ground state phase for Ni2C is elucidated and compared to known and hypothesized forms of NixCy. Also, a set of correlation consistent basis sets, previously constructed using the B3LYP and BLYP density functionals, are studied. They are compared to the well-known to the correlation consistent basis sets that were constructed with higher-level ab initio methodologies through computations of enthalpies of formation and combustion enthalpies. …
Date: May 2014
Creator: Gibson, Joshua S.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Gualterio Armando's 34 Canciones Hispanoamericanas Para Canto Y Piano: a Comprehensive Edition and an Analytical Study of the Work’s Thematic Unity, Chromaticism, and Use of Musical Quotations (open access)

Gualterio Armando's 34 Canciones Hispanoamericanas Para Canto Y Piano: a Comprehensive Edition and an Analytical Study of the Work’s Thematic Unity, Chromaticism, and Use of Musical Quotations

During the 1930s, German-born music critic and composer Gualterio Armando (1887-1973), formerly known as Walter Dahms, set to music thirty-four poems by some of the most important Hispano-American poets from the latter part of the nineteenth and first half of the twentieth century. In these songs, Armando tries to capture the spirit and idiosyncrasy of Hispano-American cultures while incorporating his own musical aesthetics. Armando’s 34 Canciones Hispanoamericanas para Canto y Piano (34 Hispano-American songs for voice and piano) display an original sound and style full of rhythms, shapes, colors, and textures found in the music of various Hispanic cultures. Nevertheless, the essence of these songs is deeply rooted in nineteenth-century German musical traditions. This eclecticism results in unique works that developed and evolved as reflections of their creator’s musical psyche. This dissertation presents an analytical study of selected songs from the 34 Canciones. The study focuses on three compositional aspects: unity within song cycles, chromaticism, and the use of pre-existing musical material. Since only one of the 34 Canciones has ever been published, this document also includes a complete edition of the thirty-four songs. Additionally, a significant part of the research incorporates a biographical sketch of the composer.
Date: May 2014
Creator: Pérez Torres, René
Object Type: Thesis or Dissertation
System: The UNT Digital Library
IAPP e-Monitor, Volume 1, Number 9, May 2011 (open access)

IAPP e-Monitor, Volume 1, Number 9, May 2011

Monthly newsletter of the International Association of Panoramic Photographers discussing news and events, organizational updates, and articles on topics of interest to members, along with photographs and advertising.
Date: May 2011
Creator: International Association of Panoramic Photographers
Object Type: Journal/Magazine/Newsletter
System: The UNT Digital Library
International Association of Panoramic Photographers e-Monitor, Volume 3, Number 9, May 2013 (open access)

International Association of Panoramic Photographers e-Monitor, Volume 3, Number 9, May 2013

Monthly newsletter of the International Association of Panoramic Photographers discussing news and events, organizational updates, and articles on topics of interest to members, along with photographs and advertising.
Date: May 2013
Creator: International Association of Panoramic Photographers
Object Type: Journal/Magazine/Newsletter
System: The UNT Digital Library

Mapping the Southwest Project: Putting the Region's Maps Online

This poster discusses the Mapping the Southwest Project, involving putting our region's maps online. The poster includes background information on the project, the project plan, workflow and equipment, and the impacts and lessons learned.
Date: May 7, 2013
Creator: Alemneh, Daniel Gelaw; Jones, Jerrell; Hartman, Cathy Nelson; Phillips, Mark Edward; Hodges, Ann; Huseman, Ben et al.
Object Type: Poster
System: The UNT Digital Library

Cold-Formed Steel Member Connections Using BAC Screw Fasteners

Access: Use of this item is restricted to the UNT Community
In this project, the main research objective is intend to seek criteria for evaluating the capacity of BAC screw fasteners with mixed configuration of waterproof seal washer, sealer tape and different pre-drill holes to determine shear and tension strength values for the screws used in cold-formed steel connections. The thesis presents the design methods and test program conducted to investigate the behavior and strength of the screw connections in shear and tension test. Test results were compared with AISI design provisions to determine if new design equations will be developed for those screws used in BAC cooling tower applications. LRFD resistance factors and ASD safety factors were investigated to the proposed design equations.
Date: May 2019
Creator: Li, Xun
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Topology and Lattice-Based Structural Design Optimization for Additively Manufactured Medical Implants (open access)

Topology and Lattice-Based Structural Design Optimization for Additively Manufactured Medical Implants

Topology-based optimization techniques and lattice structures are powerful ways to accomplish lightweight components with enhanced mechanical performance. Recent developments in additive manufacturing (AM) have led the way to extraordinary opportunities in realizing complex designs that are derived from topology and lattice-based structural optimization. The main aim of this work is to give a contribution, in the integration between structural optimization techniques and AM, by proposing a setup of a proper methodology for rapid development of optimized medical implants addressing oseeointegration and minimization of stress shielding related problems. The validity of the proposed methodology for a proof of concept was demonstrated in two real-world case studies: a tibia intramedullary implant and a shoulder hemi prosthetics for two bone cancer patients. The optimization was achieved using topology optimization and replacement of solid volumes by lattice structures. Samples of three lattice unit cell configurations were designed, fabricated, mechanically tested, and compared to select the most proper configuration for the shoulder hemi prosthesis. Weight reductions of 30% and 15% were achieved from the optimization of the initial design of the tibia intramedullary implant and the shoulder hemiprosthesis respectively compared to initial designs. Prototypes were fabricated using selective laser melting (SLM) and direct light processing …
Date: May 2019
Creator: Peto, Marinela
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Smartphones and Tablets: Patterns of Usage among College Student Populations (open access)

Smartphones and Tablets: Patterns of Usage among College Student Populations

This study offers insight into students' use and desire to use mobile devices for educational purposes. I examined college students' mobile device usage on the basis of demographic factors including sex, age, ethnicity, class standing, mode of delivery, and socioeconomic status. This study also investigated factors that affect students' likelihood to use mobile devices for academic pursuits. I utilized data from the EDUCAUSE Center for Analysis and Research's (ECAR) 2015 Student Technology Survey. Of the 10,000 undergraduate respondents, 56% were female, 70% were between the ages of 18-24, 73% attended college full time and the breakdown of ethnicity included 59% Caucasian, 16% Hispanic, 13% African American, 8% Asian and 1% Native American. The results indicated that traditional aged students reportedly used smartphones more frequently, whereas non-traditional aged students reportedly used tablets more. Students most frequently reported using their devices in class to connect to the learning material. Institutional technology infrastructure and support were strong factors impacting students' use of smartphones. Results of this research can assist higher education faculty and administrators in devising comprehensive training and technology plans to support and encourage students' use of mobile devices for educational purposes.
Date: May 2017
Creator: Phillips, Ann (Higher education researcher)
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Public Research Universities as Gendered Organizations: Institutional Rewards and the Faculty Salary Gap (open access)

Public Research Universities as Gendered Organizations: Institutional Rewards and the Faculty Salary Gap

Gendered organizational conditions create the context for persisting differences between men and women in the workplace. Within, higher education, this manifests as a salary gap between male and female faculty members. The academic capitalistic policy environment creates the conditions for increasing competition for external funding, especially in the areas of research and science and engineering. The change in the academic climate may sustain or intensify the gendering of universities as organizations. Universities with the highest level of research activity were chosen for this study and formed the 130 public institution sample. This study used fixed effects panel regression analysis to explore the relationship between the faculty gender salary gap and institutional emphasis on research as well as science and engineering. In addition, the relationship between institutional emphasis and the faculty gender salary gap was explored over time with the inclusion of a time trend and temporal interaction terms. Results showed that the higher the percentage of female faculty members, the greater the faculty gender salary gap for assistant professors. In addition, science and engineering emphasis over time had a significant impact on the professor salary gap with a decreasing effect both at the mean and one standard deviation above the …
Date: May 2017
Creator: Johnson, Jessica Ann (Higher education researcher)
Object Type: Thesis or Dissertation
System: The UNT Digital Library