Purpose: Currently there are attempts to slow myopia progression by manipulating peripheral refractive error. This study proposed to establish the distribution of peripheral refractive errors in hyperopic, emmetropic and myopic children and to test the hypothesis that relative peripheral hyperopia is a risk factor in the onset and progression of myopia. Methods: Refraction was measured under non-cycloplegic conditions, at 0°, 10° (superior, inferior, temporal and nasal retina) and 30° (temporal and nasal retina), at distance and near. Central spherical equivalent refractive error (SER) was used to classify the eyes as myopic (≤ −0.75 D), emmetropic (−0.75 < SER < +0.75 D) or hyperopic (≥ +0.75 D). Relative peripheral refraction was calculated as the difference between the central (i.e. foveal) and peripheral refractive measurements. At baseline, measurements were taken from 554 children and in a subset of 300 of these same children at the follow-up visit. The time interval between initial and follow-up measurement was 9.71 ± 0.87 months. Results: Results were analysed on 528 participants (10.21 ±0.94 years old) at baseline and 286 longitudinally. At baseline, myopic children (n=61) had relative peripheral hyperopia at all eccentricities at distance and near, except at 10°-superior retina where relative peripheral myopia was observed at near. Hyperopic eyes displayed relative peripheral myopia at all eccentricities, at distance and near. The emmetropes showed a shift from relative peripheral myopia at distance to relative peripheral hyperopia at near at all eccentricities, except at 10°-superior retina, where the relative peripheral myopia was maintained at near. In the longitudinal data analysis, myopes who became more myopic did not show greater relative peripheral hyperopia at baseline compared with myopic sub-groups whose central refraction remained stable. Conclusions: The peripheral refractive profile differences between different refractive groups that are reported in other studies have been confirmed in this study. Relative peripheral hyperopia is not found to be a significant risk factor in the onset or progression of myopia in children.

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The aim of the present work is to experimentally study the dynamics of the formation of a fiber network formed from the filtration of a fiber suspension. This is relevant for all industrial applications (e.g. papermaking, productions of composite material, etc.) where a suspension of fibers has to flow through narrow gaps, and the quality of the product depends on the distribution of mass and orientation of the fibers. To study the dynamics of network formation, we developed an experimental setup where the filtration of a fiber suspension through a semi-permeable screen can be studied. In the setup, both the fluid and the solid phase can be visualized. The focus of the present thesis is to study the fluid flow generated during the filtration. Index of refraction matching, image processing and particle image velocimetry have been used to measure the velocity field in the proximity of the resulting fiber network. Experiments with varying fiber length and filtration velocity have been performed. The disturbances generated by the screen and the forming network was found to be confined in a region (boundary region), whose extension varies with time: first, after the formation of the first fiber layers, the extent of the boundary region increases; at later times, the boundary region is thinner. The extent appears to be correlated to the gap size either of the screen (at very early times) or of the fiber network, but independent of the filtration velocity. Fluctuations on a scale larger than a fiber length are also observed during the filtration process. These fluctuations are found to be correlated to the nondimensional number Se that relates the sedimentation velocity of a fiber to the filtration velocity. The governing non-dimensional parameters are derived from the equations. The parameters are used to relate the experimental observations to the dewatering process in papermaking. / QC 20101103

No / A small-scale flow cell has been developed and used for small-angle neutron scattering (SANS) investigations of polymer melts in Poiseuille flow through a 4:1 contraction. The cell enables the investigation of polymer melt flow subject to a volumetric flow rate of up to 6 cm3 s-1, at pressures up to 10 MPa, temperatures up to 230°C, and a melt viscosity up to 65000 Pas. The cell has recirculating flow path and a relatively small capacity (circa 200 g of polymer) so that polymers with novel and well-defined molecular architectures may be investigated. The details of its construction and operation are described. When two walls of the cell are composed of zero order birefringent sapphire, both small-angle neutron scattering and birefringence studies can be undertaken in the same cell providing a link between macroscopic and molecular level descriptions of the influence of melt flow. Both birefringence and the first melt flow SANS data for a monodisperse, linear polystyrene are presented. These demonstrate the capability and potential of the apparatus to provide data which provide a crucial test for molecular theories of the rheology of entangled polymer melts. However, the use of sapphire windows limits the maximum flow rate that can be used and higher flows necessitated an all aluminum flow cell to cope with the higher pressures developed in flow. Clear evidence of a stretching of the molecule in the direction of the melt flow and a contraction perpendicular to the flow direction has been provided

Yes / A new simplified approach is proposed to evaluate the vertical refractivity profile within the lowest 1 km of atmosphere from the analysis of surface refractivity, Ns, in areas where upper air data are not available. Upper-air measurements from the nearest available radiosonde location with similar surface profile to these sites are utilized. The profiles of Ns and refractivity extrapolated to sea level, No, obtained from surface meteorological data using both fixed stations and radiosonde are investigated and compared. Vertical refractivity gradient, ΔN, is evaluated at three atmospheric layer heights within the first kilometer above the ground in addition to propagation parameters relevant to each atmospheric layer. At six sites, different approaches are compared for the analysis of three important parameters; namely effective earth radius factor, k, anomalous propagation probability parameter, β0, and point refractivity gradient at 65 m not exceeded for 1% of time, dN1. The k-factor parameter is investigated using a new weighted average approach of ΔN at 65 m, 100 m and 1 km layers above the ground. The results are compared with the latest ITU maps and tables for the same area.

Although the petroleum industry has imaged reflections from the sides of salt domes, steeply dipping structures have not been imaged as reflectors outside of sedimentary basins; to do so requires appropriate data acquisition, prestack depth migration, and an excellent seismic velocity model. Poststack time migrated seismic images, normal moveout velocity analysis, well logs, and other geologic information are used to build the velocity model. In regions of interest outside of sedimentary basins, such as major strike-slip faults, seismic reflectivity is often sparse and little is known of detailed subsurface geology. Alternate methods of velocity model construction must be used. First arrival (refraction and turning ray) traveltime tomography is proposed to construct the preliminary velocity model for steep-dip prestack depth migration in settings with little a priori subsurface information. A densely spaced synthetic seismic data set with long-offset recording, modeled after a real survey across the San Andreas Fault, was constructed using a finite-difference algorithm. First arrival traveltimes were picked from the data and a velocity model was constructed using tomography. The velocity model was used to perform a Kirchhoff prestack depth migration of the synthetic shot gathers. The subsurface structure was sufficiently reconstructed that the velocity model could be refined through migration velocity analysis. A series of tomography tests was used to determine the spatial resolution limits of the velocity model. Isolated erroneous anomalies with sizes near the resolution limits were added to the velocity model derived from tomography and used as input for migration. This pessimistic test provided an adequate image and identifiable arrivals in migrated common image gathers, allowing the velocity model to be improved through migration moveout analysis. Data acquisition requirements for tomography include long recording offsets and times, larger sources, and dense spacings, very similar to the requirements for steep-dip reflection imaging. / Master of Science

Near surface structures across the Brevard fault zone are studied using the refraction and reflection arrivals recovered from the Appalachian Ultradeep Core Hole (ADCOH) regional seismic Line 1. In using refracted arrivals, a new processing approach is introduced that translates refracted first arrivals from multifold seismic data into a refraction stack of two-way delay time sections. Reprocessing of reflected arrivals has improved shallow reflectors and allowed better imaging of the Brevard fault zone. Following processing of refraction and reflection arrivals independently, both data sets are combined into a <u>composite stack</u> section. The composite stack section displays one bright refractor interpreted as the boundary between the weathered layer and high velocity crystalline rocks. This refractor is continuous in the Inner Piedmont with occasional vertical offsets. The continuity of the refractor diminishes across the Brevard fault zone. In the eastern Blue Ridge, the refractor is discontinuous with high angle truncations. On the composite stack section, the Brevard fault zone can be traced from the surface to 6 km (2 s) where it appears to splay from the Blue Ridge thrust. Different from previous interpretations, the Brevard fault zone is imaged as having both an upper and a lower boundary surface as well as a group of reflectors within the zone. This reflection package initially thickens to 2 km at 3 km depth, then thins as it reaches the Blue Ridge master decollement. The Blue Ridge thrust is as shallow as 1.5 km (0.5 s) at the northwest end of the Line l. A deeper decollement is interpreted below the Blue Ridge thrust. The depth of this deeper thrust is 3 km (1 s) at the northwest end of the line, and also joins to the Blue Ridge thrust at 6 km depth making the structures below the Brevard fault zone more complex than previously published. / Master of Science

After being theorized by Veselago in 1967, recent developments in metamaterials over the last two decades have allowed scientists and researchers to physically demonstrate that artificial composite media can be engineered to exhibit exotic material properties, such as negative refractive index, by exploiting features in arrays of sub-wavelength unit inclusions. These unconventional electromagnetic properties are realized through the coupling of the microscopic unit inclusions, which govern the macroscopic properties of the structure. After demonstrating that a periodic array of capacitively-loaded loop (CLL) inclusions paired with continuous wire results in negative refraction, this study performs numerical simulations to characterize random metamaterial structures. These structures consist of CLLs that are randomized in both position and orientation. In addition, this thesis introduces an innovative antenna enhancing structure consisting of capacitively-loaded loop (CLL) metamaterial elements loaded radially around a standard dipole antenna at an electrically small distance. As a result of this innovative arrangement, the dipole antenna is easily transformed into a directive mechanically scanned antenna with high realized gain. The desired directivity and gain can be tuned based on the number of radial CLL fins placed around the dipole. Interactions between the antenna and metamaterial elements result in significant enhancement of the maximum radiated field amplitude and front-to-back ratio. This innovative CLL-loaded dipole antenna is compared to the conventional Yagi-Uda antenna. The structures presented in this thesis are modeled using full-wave simulation, and one antenna structure is experimentally verified as a proof-of-concept. / Master of Science