2005 MU dissertations - Freely available online
Permanent URI for this collection
The items in this collection are dissertations that are available to the general public. Click on one of the browse buttons above for a complete listing of the works.
Browse
Recent Submissions
Item Pressure dependence of the luminescence and Raman modes in polyfluorene(University of Missouri--Columbia, 2005) Martin, Christopher M., 1973-; Chandrasekhar, Holalkere R.I present a study of the optical properties of poly-para-phenylene and three different side-chain substituted polyfluorene polymers. I present an analysis of the Raman spectra under hydrostatic pressures for three oligo(para-phenylene) materials (p-terphenyl, 3P; p-quaterphenyl, 4P; and p-hexaphenyl, 6P) under hydrostatic pressure up to 80 kbar, with a focus on the 15-25 kbar region where the molecules are known to be forced into a more planar state. I present studies of the photoluminescence (PL) and Raman modes of polyfluorene (PF2/6) under hydrostatic pressures of 0-120 kbar at room temperature. The distinct PL with associated vibronics observed at atmospheric pressure blue shifts and changes dramatically around 20 kbar, above this pressure a broad peak at about 2.3 eV, associated with the keto defect, begins to dominate the PL. Raman modes observed are the 1417 cm-1 mode from the C-C stretch within the monomer, the 1342 cm-1 and 1290 cm-1 modes from phenyl rings connecting the monomer units, and the 1600 cm-1 modes from the intra-ring C-C stretch. All Raman modes analyzed shift to higher energies with pressure. Some of the phonon lines exhibit an antiresonance effect at higher pressures that is indicative of a high electron phonon interaction between the Raman phonons and the (real) PL transitions.Item Teacher perceived impact of technology on elementary classrooms and teaching(University of Missouri--Columbia, 2005) Crane, Connie M., 1967-; Cockrell, Dan; Valentine, JerryIssues surrounding technology integration are varied. Over the last decade, the presence of technology in elementary classrooms has increased; however, research indicates that many teachers are not utilizing these resources effectively. Although research supports the notion that technology in the classroom has an influence on student learning, research also points to the teacher as an important lynch pin in technology integration in the curriculum (Mandell, Sorge, & Russell, 2002). The purpose of this study was to investigate how technology is used and integrated into the elementary curriculum and to explore the influence of technology on student success. The study focused primarily on the teachers' knowledge and skill levels in using and integrating technology into the curriculum and on professional development opportunities in the area of technology use and integration provided to teachers. Using a mixed method comparative design, data were generated from teacher surveys and focus group and individual interviews. Data from the survey questionnaire were analyzed using descriptive statistics. A t-test was used to determine if there was a significant difference between the groups of teachers, including those from a non-technology school and those from a technology school who teach in non-technology and technology classrooms. Focus group and individual interview data were analyzed in order to identify patterns and topics of belief, values, and practices related to the teachers' classroom technology use. The two schools in this study were an elementary school (technology school) that has an intensive technology program (eMINTS) and another elementary school (nontechnology school) that does not have an intensive technology program. The following subgroups of teachers from the schools were included in the study: a) teachers in grades K-3 of both schools b) teachers in the non-technology school grades 1-3 and Non-eMINTS teachers in the technology school K-6 c) teachers in the non-technology school grades 1-3 and teachers in the eMINTS program grades 3-6 d) teachers in the technology school grades 3-6 that were eMINTS teachers and teachers in the same school grades K-6 that were not eMINTS teachers. The findings revealed significant differences between teachers' perceptions of their roles and responsibilities for integrating technology, the influence of technology on student success, and the type of professional development activities conducted. With the eMINTS grades 3-6 versus Non-eMINTS grades K-6 analysis at the technology school, there was a significant difference in beliefs and reality of the teachers. Non-eMINTS teachers perceived greater external pressure to use and integrate technology in the classroom; whereas, the eMINTS teachers in grades 3-6 identified a greater ideology about, competence level in, and resources available for technology. Differences in perceptions about professional development were also found. Qualitative findings for this study revealed three primary themes that appear to be essential to understanding the use and integration of technology in elementary classrooms and the influence of technology on student success. Those primary themes include: (1) barriers to technology integration; (2) importance of technology training; and (3) learning environment.Item Mechanical properties of complex biological systems using AFM-based force spectroscopy(University of Missouri--Columbia, 2005) Graham, John Stephen, 1965-; White, HenryAn atomic force microscope (AFM) was designed and built to study the mechanical properties of small collagen fibrils and the plasma membrane of living cells. Collagen is a major component of bone, skin and connective tissues, and is abundant in the extracellular matrix (ECM). Because of its abundance, an understanding of how disease affects collagen mechanics is crucial in disease prevention efforts. Two levels of type I collagen structure were investigated, subfibrils (on the order of 1 [mu] m in length) and longer fibrils. Comparisons were made between measurements of wild-type (wt) collagen and collagen from the mouse model of osteogenesis imperfecta (OI). Significant differences between OI and wt collagen were observed, primarily that intermolecular bonds in OI collagen fibrils are weaker than in wt, or not ruptured, as in the case of OI subfibrils. As cells interact with collagen in the ECM, the mechanical properties of the plasma membrane are also of great interest. Membrane tethers were extracted from living cells under varied conditions in order to assess the contributions of membrane-associated macromolecules such as the actin cytoskeleton and the glycocalyx, as well as intracellular signaling processes triggered by thapsigargin. Tether extraction force was found to be sensitive to all of these altered conditions, suggesting that tether extraction may be used to monitor various cellular processes.Item Transport, network, and data link layer protocol designs to improve geo-stationary Earth orbit satellite data set transmission performance(University of Missouri--Columbia, 2005) Wiedemeier, Paul Douglas, 1968-; Tyrer, Harry W.Geo-stationary earth orbit (CEO) satellites are wireless transmission media that provide near-earth Internet and Intranet data communication, but are limited to low Megabits per second transmission rates and small messages. They can provide communication infrastructure to rural earth locales, are not affected by terrorist events and natural disasters that render terrestrial channels unusable, and can replace terrestrial communication infrastructure. In this thesis, we present new designs for a transport layer data transmission protocol, a network layer routing strategy, and a data-link layer medium access control strategy. Through simulation, we show that our designs permit earth stations to transmit large data sets at high transmission rates over GEO satellites in less time than the Transmission Control Protocol variant Reno and frequency division multiplexing. Our designs can be used by organizations that wish to transmit large data sets quickly over CEO satellites that exhibit large bandwidth delay products and large bit error rates.Item P2Y[subscript 2] nucleotide receptor up-regulation and function in submandibular gland epithelium(University of Missouri--Columbia, 2005) Schrader-Ratchford, Ann Marie; Weisman, Gary A.; Lim, Robert W.Sjögren's syndrome (SS) is an autoimmune disease that specifically targets exocrine glands, including salivary glands, and results in an impairment of secretory function. P2Y₂ nucleotide receptors for extracellular ATP and UTP are up-regulated in response to stress or injury in a variety of tissues including submandibular glands (SMGs). Therefore, our objective was to assess whether P2Y₂ receptor expression is up-regulated in SMGs of the NOD.B10 mouse model of SS, and to determine the function of P2Y₂Rs in salivary gland tissue. Our data indicate that P2Y₂Rs are up-regulated in SMGs of the NOD.B10 mice, and this up-regulation increases as the disease progresses. Moreover, data obtained using a human submandibular gland cell line, demonstrate that P2Y₂Rs activate a signaling pathway leading to gene transcription via at least two distinct mechanisms. These findings suggest that regulation of P2Y₂Rs is likely to be an important therapeutic target for various diseases.