The dissertation first investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Several initially balanced and localized jets induced by vortex dipoles are examined here. Within these dipoles, inertia-gravity waves with intrinsic frequencies 1-2 times the Coriolis parameter are simulated in the jet exit region. The ray tracing analysis reveals strong variation of wave characteristics along ray paths. The dependence of wave amplitude on the Rossby number is examined through experiments in which the two vortices are initially separated by a large distance but subsequently approach each other and form a vortex dipole with an associated amplifying localized jet. The amplitude of stationary gravity waves in the simulations with a 90-km grid spacing increases nearly linearly with the square of the Rossby number but significantly more rapidly when smaller grid spacing is used. To further address the source mechanism of the gravity waves within the vortex dipole, a linear numerical framework is developed based on the framework proposed by Plougonven and Zhang (2007). Using the nonlinearly balanced fields as the basic state and driven by three types of large scale forcing, the vorticity, divergence and thermodynamic forcing, this linear model is utilized to obtain linear wave responses. The wave packets in the linear responses compare reasonably well with the MM5 simulated gravity waves. It is suggested that the vorticity forcing is the leading contribution to both gravity waves in the jet exit region and the ascent/descent feature in the jet core. This linear model is also adopted to study inertia-gravity waves in the vicinity of a baroclinic jet during the life cycle of an idealized baroclinic wave. It is found that the thermodynamic forcing and the vorticity forcing are equally important to the gravity waves in the low stratosphere, but the divergence forcing is again playing a lesser role. Two groups of wave packets are present in the linear responses; their sources appear to locate either near the surface front or near the middle/upper tropospheric jet.

Carnegie Ridge is a prominent bathymetric feature of the Gal??pagos Volcanic Province originated from the interaction of the Gal??pagos Hot Spot and the Cocos - Nazca Spreading Center. Our present knowledge regarding its crustal structure is limited to ridge transects along which wide-angle refraction seismic experiments have been conducted. In this study, the long-wavelength crustal structure of Carnegie Ridge between ~81?? W and 89?? W was determined by employing 2-D forward gravity modeling as the primary analytical technique. Model structures were built by assuming Airy isostasy and crustal layers of constant density. The geometry and density structure of the thickened oceanic crust beneath the ridge was constrained based on available seismic velocity models. Except for regions near the Ecuador Trench, the gravity modeling solution along the different transects examined in this study accounted adequately for the observed gravity anomaly field over the ridge. Crustal overthickening mainly accommodated in oceanic layer 3 and the asymmetry of the crustal root geometry characterize the estimated long-wavelength crustal structure. The asymmetry on eastern Carnegie Ridge is thought to be related to a ridge-related rifting whereas the origin and nature of that estimated on western Carnegie Ridge remain uncertain. Crustal volume fluxes were calculated at Carnegie Ridge and the Gal??pagos Archipelago, and at Cocos Ridge in order to explain the along-axis variations of the estimated crustal thickness. Along-axis crustal thickness variations on eastern Carnegie Ridge, and the formation of its bathymetric saddle were found to be related to the decline in the total volume output of the Gal??pagos Hot Spot. According to my results, this decay started soon after the spreading center shifted to the south of the hotspot (i.e., ~15 Ma) and continued for ~4.5 m.y. Since ~10 Ma the volume output of the GHS started to increase again, giving rise to the formation of western Carnegie Ridge and the Gal??pagos Archipelago. This increase continued until ~2 Ma, when the hotspot intensity started a new decrease that continues until the present time.

Thesis (M. Sc.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on Jan. 15, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Physics, University of Alberta. Includes bibliographical references.

Thesis (M. Sc.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on Jan. 21, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Applied Mathematics, Department of Mathematical and Statistical Sciences. Includes bibliographical references.

Thesis (M.S. in Bio. E.)--School of Mechanical Engineering, Georgia Institute of Technology, 2004. Directed by Hanjoong Jo. / Includes bibliographical references (leaves 46-58).

The 2008 Wenchuan Ms 8.0 earthquake resulted in huge casualty and heavy strike to the local economy. Consequently, Chengdu Plain, with dense population and short distance to the highly active Longmen Shan fault zone needs an evaluation of the risk of earthquake as soon as possible. As part of a big project, we conducted mapping of gravity anomaly of Chengdu Plain in order to locate the possible buried fault zones beneath the Chengdu Plain. In this project a total of 640 km2 area was surveyed, and 230 relative gravity data have been collected along six profiles with each extending to about 70 km across the plain area. 140 more spots were measured around the city area in order to have a more precise delineation of geological structures beneath the city region. The Bouguer gravity anomaly has been calculated to delineate the large-scale anomaly trend on the surface. Data analyses presented that a coincidence between the sedimentation thickness and the residual gravity anomaly. The minimum residual anomalies suggested locations where depo-centers used to located (Pengzhou-Chongzhou, across Xinsheng County). The long-wave trend of Bouguer anomaly which reflects the deeply buried Moho discontinuity presented a northwest dipping trend of this density boundary underneath the plain region. / published_or_final_version / Earth Sciences / Master / Master of Philosophy

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All organisms have been subjected to and have evolved with the ubiquitous force of gravity, and most exhibit the ability to sense and respond to this stimulus. To simplify an investigation of the molecular components of a cell's gravity response, this dissertation employs the single-celled spores of the fern Ceratopteris richardii. These spores have a polar calcium flux that is determined by the gravity vector, but an understanding of what the molecular components driving this flux are and how they influence subsequent developmental processes is lacking. Of the possible molecular components, available literature pointed to Ca²⁺-ATPase transporters as an obvious key participant and so they were selected as the main molecule of investigation. Our results describe the first cloned Ca²⁺-ATPase from C. richardii, CrACA1. CrACA1 has high similarity to known plant Ca²⁺-ATPases, specifically plasma membrane (PM) Ca²⁺-ATPases from Arabidopsis, and exhibits in vivo Ca²⁺-ATPase activity. An improved method for the statistical analysis and presentation of qualitative RT-PCR data was employed. The RNA, as well as the protein, of CrACA1 is present during the polarity fixation window which supported the need for further analyses of the role of Ca²⁺-ATPases. Our results showing that Ca²⁺-ATPase inhibitors significantly alter the gravity-directed calcium flux of spores are consistent with previous work but offer valuable new insights. The spore PM Ca²⁺-ATPases have large impacts on the calcium flux and rhizoid growth but no appreciable impact on polar axis alignment. The results on endomembrane-type Ca²⁺-ATPases make it clear that this class of pumps has major roles in both axis alignment and tip growth; rhizoid growth is inhibited but alignment to the gravity vector is improved. The updated model for gravity perception responses in C. richardii spores places a strong emphasis on calcium channels and Ca²⁺-ATPases working in concert to result in a bottom-localized calcium pool to align the polar axis with hints of store-operated calcium mobilization. The work presented represents an increase in our knowledge of one way a single cell can respond to the force of gravity, offering testable hypotheses to further refine gravity perception models incorporating calcium localization. / text

Corpus Christi Bay in Texas is a wind driven system, and under most conditions winds over the bay mix the water column vertically. However, seasonal, episodic, bottom-water hypoxia has been observed in the bay in conjunction with vertical salinity stratification. This stratification may be caused by dense gravity currents entering the bay. Understanding and modeling the mechanisms that result in stratification in Corpus Christi Bay may help predict hypoxia, and for this reason that is the focus of this dissertation. An evaluation of existing gravity current modeling techniques shows that most currently available models are designed to capture either phenomena local to a gravity current, such as gravity current entrainment and spreading, or larger scale phenomena such as wind mixing and large-scale circulation, but not both. Because gravity current mixing in Corpus Christi Bay is enhanced by wind-induced turbulence, both local gravity current physics and wind mixing effects are critical elements governing gravity current propagation in Corpus Christi Bay. As existing models do not represent gravity current entrainment and wind mixing together, this dissertation develops a coupled model system that accounts explicitly for turbulent wind mixing of a bottom-boundary layer, in addition to representing other local features of dense gravity current propagation such as entrainment and spreading. The coupled model system consists of a 2D depth-averaged hydrodynamic model that calculates gravity current mixing and spreading, coupled with a 3D hydrodynamic model whose domain includes a lighter ambient fluid surrounding the gravity current. The coupled models have flexible boundary conditions that allow fluid exchange to represent mixing from both gravity current entrainment and wind mixing. The coupled model system’s development, verification and application in Corpus Christi Bay advances understanding of gravity current mechanisms, and contributes to our scientific understanding of hypoxia in Corpus Christi Bay. This modeling technique has the flexibility to be applied to other density-stratified systems that are shallow and potentially wind-driven, such as shallow desalination brine disposal sites. / text

published_or_final_version / toc / Applied Geosciences / Master / Master of Science