Thesis (D. Min.)--Abilene Christian University, 1994. / Includes abstract. Includes bibliographical references (leaves 229-234).

Researchers at Brigham Young University (BYU) have developed an optical biosensor that can quickly analyze a sample to detect any type of nucleic acid based organism, such as viruses or bacteria. The biosensor's reliability over time is compromised due to water absorbing into the SiO2 waveguides of the chip. It was hypothesized that keeping the thin-film stress of the waveguides close to zero would slow or stop water absorption from occurring. Completion of this thin-film study relied upon a new plasma enhanced chemical vapor deposition (PECVD) machine and a new 3-D optical profilometer, both of which were installed in the BYU cleanroom. The new PECVD machine was much more capable than previous machines at controlling deposition parameters and was a critical component in accurately controlling the intrinsic stress of deposited films. The 3-D optical profilometer provided us a way to accurately measure the intrinsic stress of the films. Rib waveguides made from different stressed SiO2 films were fabricated over anti-resonant reflecting optical waveguide (ARROW) layers. The wafers were baked out, cleaved, and their initial throughputs recorded. All waveguides were placed in a humid environment and were removed periodically to check their optical throughput. The resulting measurements were normalized to the highest measured throughput to determine how throughput was changing over time. Rib waveguides with the lowest stressed SiO2 had the slowest rate of throughput change, dropping to 50% of the original throughput after 40 days in the humid environment. The +50 MPa stressed waveguides performed next best, dropping to 20% of the original throughput after 40 days. The +100 MPA stressed waveguides dropped to 20% throughput after 16 days while the -50 MPa stressed wafers dropped to 20% optical throughput after 7 days. Keeping the stress of the film as low as possible helped reduce the rate of water absorption, but did not eliminate it completely. A method involving the use of high index difference buried channel waveguides is shown to be effective at stopping the effects of water absorption in our waveguides.

The accurate prediction of warm-season convective systems, and the heavy rainfall and severe weather associated with them, remains a challenge for numerical weather prediction models. This study looks at one such circumstance in which back-building convection forms perpendicular to, and above the cold pool region behind strong bow echoes. We refer to this phenomenon as a "bow and arrow" because, on radar imagery, the two convective lines resemble an archer's bow and arrow. The "arrow" can extend over hundreds of kilometers and can cause damage from high winds, hail and flooding. Events of this nature pose a particular challenge to forecast because they require an accurate forecast of the earlier convection and the effects of that convection on the environment. In this study, radar and surface observations of four events are presented to identify common environmental conditions prior to the development of the back-building convection. Additionally, simulations of three cases using the Weather Research and Forecasting (WRF) model are analyzed in an attempt to understand the mechanisms responsible for initiating and maintaining the convective line. Due to coarse resolution, observational analyses are only useful for inspection of the synoptic-scale. Model output from numerical simulations is utilized to examine the mesoscale in the vicinity of the convective arrow. Several environmental characteristics are evident in each of the studied cases. Strong southwesterly flow (inducing warm air advection and gradual isentropic lifting), in addition to directional and speed convergence into the convective arrow region possibly contribute to convection initiation. Horizontal wind speed shear and increased wind speed in the area surrounding the arrow may be associated with the linear orientation of the arrow. It seems as though when these ingredients are combined with thermodynamic instability, there is a greater possibility of formation and maintenance of a convective arrow behind a bow echo.

In most terahertz (THz) systems, the propagation of THz signals relies on metal or dielectric waveguides which suffer from high conductivity losses caused by the skin effect or dielectric losses resulted from the material absorption. Due to this reason, we propose and demonstrate a simple low-loss air-core tube strucutre for THz waveguiding. The simulation method we utilized is the finite-difference frequency-domain (FDFD) method with the perfectly matched layers (PMLs). The modal indices and propagation losses of the guided core modes on the THz tube waveguide are successfully obtained. The simulation results show that the guiding mechanism of the hollow tube waveguide is based on the antiresonant reflecting optical waveguide (ARROW) model. We also utilize a Fabry-Perot resonantor model to find out the resonance frequencies of the dielectric layer, which match well with the results of the FDFD method. By varying the core size, it is observed that the propagation losses are reduced when the core size is increased. The propagation losses can be reduced from 10-3 cm-1 (0.0043 dB/cm) to 10-4 cm-1 (4.34¡Ñ10-4 dB/cm). In addition, we can use the thin dielectric layer to provide a broad transmission band with £Gf = 0.13THz. We also propose a novel tube THz waveguide sensor. The influence of the thickness and material of the dielectric layer 2 are investigated. We can observe that the shift of the propagation loss peak is inversely proportional to the thickness of dielectric layer 2, which can be used as a thickness sensor with the sensing sensitivity being 0.125 GHz/£gm. On the other hand, the index of the dielectric layer 2 and the position of the propagation loss peak are in an exponential relationship. These properties of the tube waveguide can be applied in the dielectric-film sensing.

This thesis analyzes the direction of time problem in the framework of philosophy of science. The radiation arrow, Newtonian arrow, thermodynamic arrow and quantum mechanical arrow have been studied in detail. The importance of the structure of space-time concerning direction of time is emphasized.

Thesis (M.S.)--University of North Texas, May, 2009. / Title from title page display. Includes bibliographical references.

Thesis (D. Min.)--Gordon-Conwell Theological Seminary, 2006. / Abstract and vita. Includes bibliographical references (leaves 152-156).

Thesis (M.A. in anthropology)--Washington State University, May 2010. / Title from PDF title page (viewed on Apr. 30, 2010). "Department of Anthropology ." Includes bibliographical references (p. 144-156).

Thesis (D. Min.)--Gordon-Conwell Theological Seminary, 2006. / Abstract and vita. Includes bibliographical references (leaves 152-156).

The role of warfare in Maya society is much debated, but it seems to have been widespread during the Late Postclassic (A.D. 1250-1519) and Protohistoric (A.D. 1519-1696) periods. This study investigates the manner in which the Maya engaged in warfare during these centuries by reviewing archaeological data on Maya warfare and Spanish accounts of their contacts with the Maya of central Petén, Guatemala. The bow and arrow, which were not used during the Classic period, are "area weapons" that can be used at a distance, and appear to have changed the character and tactics of warfare in the Postclassic period and in Maya defensive interactions with the Spaniards. Eighty small projectile points from the sites of Zacpetén and Ixlú were analyzed. These triangular points, believed to have tipped arrows, were made of chert and obsidian and varied particularly in the placement and number of notches, in the shape of their bases, and in the amount of retouch. Notching and basal variation do not clearly relate to differing ethno-political units in the central Petén Postclassic, to functional areas of the sites, or to ballistic performance. Variations in amount of retouch may indicate that the points were made quickly.