The Lower Ordovician El Paso Group is a >400-m-thick carbonate succession exposed in the Franklin Mountains, El Paso, Texas. The El Paso Group contains multiple breccias related to collapsed-paleocave systems. These breccias have been documented as having formed during the top-Lower Ordovician Sauk depositional supersequence lowstand. Evidence presented in this study suggests that cave formation may have been as much as 350 million years younger and related to Laramide oblique right lateral compression. Regardless of the timing of formation, the breccias mapped in this study are of collapsed paleocave origin based on breccia clast organization and matrix content. Speleogenetic models are compared against observations of breccia distribution by direct field observations and mapping on sub-meter airborne light detection and ranging or lidar data. Point vectors were defined for every point within study area to highlight subtle changes in outcrop erosional profile for mapping geological features directly on the lidar point cloud. In addition, spectral data from airborne photography and hyperspectral image analysis were used assist in geological contact definition. A digital outcrop model was constructed from 3D geologic mapping results from which spatial statistic were extracted and used to reconstruct collapsed paleocave breccia bodies. The resultant breccia geometries were compared against laser-scanned modern cave dimensions, from Devil's Sinkhole, Rocksprings, Texas, and used in analysis of conceptual models for cave formation. The breccias of the southern Franklin Mountains follow linear trends that closely match Riedel shear fracture patterns predicted from right-lateral oblique compression. Stress orientations that match right-lateral oblique compression in the Phanerozoic of the El Paso region are related to the Laramide orogeny. The relationship of observed structures and the orientation of collapse breccias may indicate that southern Franklin Mountain breccia bodies are the result of a solution-enhanced tectonic karst system. / text

Bacteriophage Mu exhibits low specificity for the 5 bp sequence it selects as its transposition target, but shows regional biases in its insertion choices. For example, Mu prefers AT-rich DNA in vitro, exhibits a 1000-fold bias in target preference within the E. coli chromosome, and avoids targets carrying Mu end sequences. The Mu transposase is responsible for recognition of the 5 bp target consensus, but depends on the accessory protein MuB for efficient target capture. MuB preferentially binds to AT-rich DNA, explaining this particular regional preference. We have uncovered opposing roles for MuB in target capture and integration. We show while MuB-bound AT-rich DNA is favored for integration, the bound DNA itself is refractory, and that transposition occurs adjacent to, but not within the bound region. We show that this property of MuB is likely responsible for immunity of Mu from self-integration, since MuB was found to be strongly bound within the Mu genome. Genome-wide analysis of MuB binding on the E. coli chromosome showed that Mu target preference is positively related to MuB binding profile, and that MuB binding is insulated by the nucleoid-associated protein Fis but not by transcription events. Since Fis binding to the chromosome responds to the frequency of A-tracts, a chromosome domain structure signal, Mu transposition must also respond to chromosome domain signals. Work in this dissertation has provided a new understanding of how MuB influences and controls Mu target choice, and of reciprocal interactions between a bacterial chromosome and a transposable element. / text

Consider the reality that the traditional college curriculum works against community college students -- think of the implications. It is no secret that community college students are the most disadvantaged in higher education, and their chances of succeeding in college are slim. Scholars have pondered this situation for years. Alas, consider if the problem is the structure of the curriculum itself. Specifically, research indicates that community college students tend to be field dependent and the traditional curriculum works against this type of student because it does not provide the type of community support these students require. One way the needs of these students could be met is through learning communities, which are conscious curricular structures that link two or more courses. This curricular tactic offers a way to fulfill the cognitive needs of community college students and enables them to succeed. To determine whether learning communities are an appropriate curricular tactic, the methodology of Interactive Qualitative Analysis (IQA) was used to understand the experiences of field-dependent students. Through focus groups and individual interviews, this method helped to crystallize these common experiences and provide a voice for them. The results substantiated that learning communities provide the peer support, faculty interaction, academic involvement and collaborative learning environment field-dependent students need to succeed. Curricular tactics like learning communities can be utilized to meet the needs of community college students. Rather than employing the traditional curriculum, which works against community college students, curriculum needs to be tailored into applied models like learning communities, which work for them. / text

In the context of critical development communication, the processes are discussed centering two key constructs including 'power' and 'dialogic praxis' in the analytical frame for this research. In addition, theories and practices of immigrant media and social movements provide constructive perspectives discussing characteristics forms of collective actions for immigrant communities (local-global, transnational, and heterogeneous; roles of immigrant media (movement resource and cultural resource) in a host society. However, we are less informed about communication processes for migrant agents to construct migrant social movement. Much less is discussed about communication processes and their implications of media communications of immigrant media. Thus, to bridge the theoretical and practical gaps, this dissertation research attempt to contextualize communication processes of an immigrant media, MWTV, engaged in the migrant social movement in order to explore how relatively powerless migrant agents develop alternative forms and ways of praxis for social change through their media communications. Throughout two field research, this particular research could identify a 'asymmetric power structure' formed through the relations between diverse social agencies related to the processes for social changes for the immigrant communities in Korea, which induce 'the mediated praxis' shaping 'asymmetric solidarity,' 'objectification of the migrant agents,' and 'assimilation of movement culture.' Then, the immigrant media, MWTV have been developed to 'remediate' existing dominant forms and ways of social changes constitutive of 'dialogic praxis' of the foreign agents. Thus, media communication of immigrant media is viewed as conscious collective actions to 'remediate mediated praxis' for social and cultural change in a host society rather than mere symbolic resources for social or cultural reorientation. It means that the flexible, collaborator, and reflective communication structure of MWTV are deliberately reconstructed not as 'conditions' but as 'consequences' of critical reflection on mediated praxis. / text

Terrorism has been an international threat to high occupancy civilian structures, government buildings, and military installations for many years. Statistical data from past terrorist attacks show that transportation infrastructure has been widely targeted, and a bombing of an ordinary highway bridge is a realistic scenario. Recent threats to bridges in the U.S. confirm this concern and have caught the attention of the bridge engineering community. Given that many ordinary highway bridges in the United States support critical emergency evacuation routes, military transportation plans, and vital economic corridors, the loss of a key bridge could result in severe national security, economic, and socioeconomic consequences. Therefore, in this research, a simplified procedure is developed to predict blast loads on bridge columns, and an understanding of the mechanisms that cause damage and ultimately failure of blast-loaded reinforced concrete bridge columns is advanced. To that end, computational fluid dynamics models are constructed and validated using experimental data. These numerical models are used to characterize the structural loads experienced by square and circular bridge columns subjected to blast loads, which is followed by the formulation of a simplified load prediction procedure. Additionally, nonlinear, three-dimensional, dynamic finite element models of blast-loaded reinforced concrete bridge columns are developed and validated using qualitative and quantitative data from recent experimental tests. The results of these analyses illustrate the fact that circular columns cannot be assumed to experience less base shear demand than a square column simply because they experience less net resultant impulse. Furthermore, the column response models developed in this research are used to identify and explain the mechanisms that lead to the spalling of side cover concrete off blast-loaded reinforced concrete members observed in recent experimental tests. Therefore, the results of this research advance the understanding of the structural loads on and the resulting response of reinforced concrete bridge columns subjected to blast loads, and as such these contributions to the structural engineering community enhance the security of the U.S. transportation infrastructure. / text

RNA recognition motifs (RRMs) are a ubiquitous class of proteins which bind RNA in a sequence-specific fashion, often with high affinity. The mechanisms through which this single protein domain recognizes diverse RNA sequences is not fully understood. High-resolution three-dimensional structures are particularly important in understanding the structural features required for RNA recognition and binding. This work presents the structure of an expanded RRM domain from the Drosophila melanogaster Bruno protein. The Bruno protein is involved in establishing proper body patterning during development. This is accomplished through the translational repression of several mRNAs, in particular, the oskar mRNA. Previous work has identified an expanded RRM domain within the Bruno protein. This RRM requires an additional forty amino acids prior to the start of the canonical RRM domain for high affinity RNA binding. The protein was found to contain a canonical RRM domain comprised of four anti-parallel [beta] strands and two [alpha] helices. The RRM is preceded by a ten amino acid loop that interacts with [alpha]₁ and [beta]₂, while the remaining amino acids are flexible in solution. Interestingly, the deletion of these residues does not alter the fold or stability of the RRM domain. Thus, these additional residues must be involved in RNA binding, as they are not required for structure. From these studies, the Bruno RRM represents a new example of protein features required for recognition and high affinity binding of RNA. / text

When a writer, usually a woman, uses fairy tales as a veil through which to narrate a story of her life, I call this practice asymptotic autobiography. In mathematics, the asymptote is a straight line that a curve approaches increasingly closely, but never actually touches. I define “asymptotic autobiography” as a term for discussing any personal narrative that deliberately employs fiction in order to tell truth. In this inquiry, I examine the use of fairy tale language in giving voice to women writers’ autobiographical representations, using Zelda Fitzgerald’s novel and letters as the focus for my analysis. My research and critical analysis will examine how Save Me the Waltz, which Zelda Fitzgerald wrote while she was a psychiatric patient in the Phipps Clinic, uses fairy tales to provide a mapping of the many performances that autobiographical selfhood entails. By experimenting with open-ended fairy tale conventions instead of being limited by clinical truths, and by contextualizing her personal history in the realm of the imaginary, Fitzgerald removes her story from the psychiatric ward and places it safely in legend. The first three chapters of this dissertation show how, in sequence, the autobiographical self becomes free through the use of fairy tales in three stages: once the autobiographer has worked to separate herself from being bound by illness or clinical reality (Chapter One), she is free to make the decision of which self or selves she wishes to narrate and perform (Chapter Two); only once she has established her sense of self can the autobiographer then locate her plot, her map, and her narrative (Chapter Three). In Chapter Four, I offer an example of asymptotic autobiography in the form of a one-person play script that I wrote and performed about Zelda Fitzgerald’s life and hospitalization, using as a frame the fairy tale “The Swan Maiden.” This hybrid essay-performance combines the play script itself with personal writing of my own in which I describe the difficulties I had approaching and performing the rich material of Zelda’s life. / text

Nuclear magnetic resonance force microscopy (NMRFM) is a technique that combines aspects of scanning probe microscopy (SPM) and nuclear magnetic resonance (NMR) to obtain 3 dimensional nanoscale spatial resolution and perform spectroscopy. We describe the components of a helium-3 NMRFM probe and studies of ammonium sulfate ((NH₄)₂SO₄) and magnesium diboride (MgB₂). For our room temperature (NH₄)₂SO₄ studies we were able to perform a 1-D scan and perform nutation and spin echo experiments. In our 77 K MgB₂ we demonstrate a 1-D scan of a 30 micron powder sample. In addition, we describe magnetic measurements of the possible dilute semiconductors Mn[subscript x]Sc[subscript 1-x]N and Fe₀.₁Sc₀.₉N. / text

Conjugated polymers are widely used and rapidly developed in practical polymer-based light-emitting electronic devices. Understanding the electrochemical reaction of conjugated polymer has become essential in the design and operation of devices such as electrochemical light-emitting diodes. In particular, we have studied the dynamics and kinetics of oxidation/reduction behavior of conjugated polymer single-molecules and nanoparticles in order to obtain the molecular level properties of deeply trapped holes in organic semiconductor devices. Theoretical calculations suggest the penetration of ions and solvent molecules effectively stabilizes the injected charges, which allows homogeneous charge distribution and further hole injection. The formation and decay of deep traps have been explored by changing the charging rate and duration. We found that the laser excitation significantly promotes the untrapping of deep holes. Electrogenerated chemiluminescence of single nanoparticles has been investigated to unravel the effects due to particle heterogeneity, which are masked in bulk electrochemical studies of nanoparticles. Bigger particles showed more intense light and longer duration time than smaller ones. Co-reactant, tripropylamine can facilitate the formation of electrogenerated chemiluminescence as well as alleviate the polymer oxidation and following irreversible electrochemical reaction. Electrochemically generated light waves from the conjugated polymer thin films have been visualized to obtain microscopic level understanding on the complex reaction mechanism. Electrochemical reaction occurs at local defects and propagates isotropically over macroscopic distances with a sharp wave front. The initially injected holes (oxidized polymers) drag counter-ions into the film, thereby induce a phase-transition-like swelling that enhances transport of ions and solvent and move forward the double layer and corresponding propagation of the wave. / text

Two of the principal phenomena observed and exploited in the field of spintronics are giant magnetoresistance (GMR) and spin transfer torque (STT). With GMR, the resistance of a magnetic multilayer is affected by the relative orientation of its magnetic layers due to (electron) spin dependent scattering. For the STT effect, a spin-polarized electric current is used to alter the magnetic state of a ferromagnet. Together, GMR and STT are at the foundation of numerous technologies, and they hold promise for many more applications. To achieve the high current densities (~10¹² A/m²) that are necessary to observe STT effects, point contacts – constricted electrical pathways (~1–100 nm in diameter) between conducting materials – are often used because of their small cross-sectional areas. In this sense, we have explored STT in bilayer magnetic nanopillars, where an electric current was used to induce precession of a ferromagnetic layer. This precessional state was detected as an increase in resistance of the device, akin to GMR. Temperature dependent measurements of the onset of precession shed light on the activation mechanism, but raised further questions about its detailed theory. Point contacts can also be used as local sources or detectors of electrons. In this context, we have observed transverse electron focusing (TEF) in a single crystal of bismuth. TEF is a k-selective technique for studying electron scattering from within materials. Using lithographically fabricated point contacts, we have studied the temperature dependence of the relaxation time for ballistic electrons from 4.2 to 100 K. These measurements indicated a transition between electron-electron dominated scattering at low temperatures and electron-phonon scattering as the Debye temperature was approached. We present preliminary work toward a TEF experiment to measure spin dependent scattering from a non-magnet/magnet interface. We also investigated spin wave propagation in thin, magnetic waveguide structures. At the boundary between the waveguide and continuous magnetic film, spin wave rays were found to radiate into the film, or to reflect and form standing waves in the waveguide. A circular defect in the waveguide was observed to cause diffraction of spin waves, generating an interference pattern of higher modes of oscillation. / text