No description available.

No description available.

No description available.

Since 2000, there has been a marked decline in the number of harbour seals in some regions around Britain; one possible contributing cause is competition for prey with sympatric grey seals. To explore one important aspect of this interaction, in this thesis the diet of harbour seals is estimated using analysis of hard prey remains recovered from faeces and compared with equivalent results for grey seals. To estimate coefficients to account for partial and complete digestion of hard prey remains, 100 whole prey feeding trials were conducted with six harbour seals and 18 prey species. Differences were found among prey species and between harbour and grey seals highlighting the importance of applying predator- and prey-specific digestion correction factors when reconstructing diet. In a comprehensive exploration of the diet of harbour seals around Britain, sandeel and flatfish dominated in the North Sea and large gadoids dominated on the Scottish west coast with seasonal pulses of pelagic prey. Variation in diet was linked to regional and seasonal differences in prey distribution and abundance. Sex-specific variation in harbour seal diet was examined in four regions. The main difference detected was in The Wash, where female diet quality was significantly higher than males in winter, which appeared to be driven by greater consumption of pelagic prey by female seals associated with seasonal energetic requirements of their annual life cycle. Comparison of the diet of harbour and grey seals revealed regional differences in diet composition, diversity and quality between the two species. However, there was no consistent pattern in this variation in relation to regional variation in harbour and grey seals population trajectories and no clear evidence for interspecific competition for prey. Future work should focus on an integrated investigation of prey abundance and distribution, and seal diet and foraging behaviour/distribution.

This thesis presents the results of high supply (up to 84 bar) pressure testing of hole-pattern annular gas seals performed at the Texas A & M Turbomachinery Laboratory in College Station, TX. The test variables were chosen to determine the influence of pressure ratio, rotor speed, and negative preswirl on seal performance. Preswirl signifies the circumferential fluid flow entering a seal, and negative preswirl indicates a fluid swirl in the direction opposite of rotor rotation. Changes in pressure ratio had only small effects on most rotordynamic coefficients. Cross-coupled stiffness showed slightly different profiles through the mid-range of excitation frequencies. Pressure ratio showed some influence on direct and cross-coupled damping at low excitation frequencies. Rotor speed significantly affected both cross-coupled stiffness and cross-coupled damping. As rotor speed increased, the magnitude of cross-coupled rotordynamic coefficients increased due to the positive fluid swirl induced by rotor rotation. For the low rotor speed, negative inlet preswirl was able to overpower the positive rotor induced fluid rotation, producing a negative cross-coupled stiffness. This outcome showed that, for hole-pattern seals, positive fluid swirl does indeed produce positive cross-coupled stiffness coefficients and negative fluid swirl produces negative cross-coupled stiffness coefficients. The addition of negative preswirl greatly reduced cross-coupled rotordynamic coefficients, while direct rotordynamic terms were unaffected. Cross-over frequency signifies the excitation frequency where effective damping transitions from a negative value to a positive value with increasing excitation frequency. Peak effective damping was increased by 50 percent and cross-over frequency reduced by 50 percent for high-negative preswirl versus zero preswirl results. This led to the conclusion that a reverse swirl could greatly enhance the stability of hole-pattern balance piston seals. A two-control-volume model that uses the ideal gas law at constant temperature (ISOT) was used to predict rotordynamic coefficients and leakage. This model predicted direct rotordynamic coefficients well, but greatly under predicted cross-coupled rotordynamic coefficients especially at high negative preswirls. The model predicted seal leakage well at low pressure ratios, but showed increasing error as the pressure ratio was increased. These results showed that the prediction model could not adequately estimate cross-coupled rotordynamic coefficients for a hole-pattern seal with negative inlet preswirl and requires modification to do so.

The effects of habitat features on the distribution of ringed seals (Phoca hispada) in the fast ice of Barrow Strait were examined between March and June 1984 to 1986. Breathing hole density in thirty-two, 2-4 km$ sp2$ study plots provided an index of seal abundance. Densities of seal holes were determined using a combination of trained dogs to locate the subnivean breathing holes and removal sampling. / Birth lairs were not seen before 4 April, but the incidence of these structures increased as the season progressed. Structures maintained by male seals were evident in late March, but were not found after mid-May. In 1984, densities of seal holes were correlated with ice thickness. In 1985, no relationship was detected between seal hole density and habitat. In 1986, the highest densities of subnivean structures including birth lairs, were associated with deep snow conditions located in areas of late consolidating ice. No relationship was identified between the density of male structures and any habitat variables. / The mean reproductive rate for females $>$7 years old was 0.64. Between March and June for adult males lost 204 g per day with 72% of this weight being lost from blubber. Pregnant females lost 467 g per day with 68% of the loss occurring from the blubber. In adult seals no differences in body condition were detected between sexes or between years, but juveniles collected in 1986 were in significantly better condition than juveniles collected in 1984 and 1985.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 71-77).

vii, 55 leaves : ill. ; 28 cm Typescript. (Another copy on microfilm is located in Archives) Thesis (M.S.)--University of Oregon Includes vita and abstract Bibliography: leaves 52-56 University of Oregon theses, Dept. of Biology, M.S., 1981

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 84-90). Description: xiv, 90 leaves : ill. ; 29 cm.

The interface between a reservoir and a caprock is generally considered a flow boundary where capillary trapping at the base of the caprock and low permeability of the seal resists the upward migration of fluids. Joints and faults may act as mechanisms for seal bypass, allowing fluids to escape from the reservoir. The injection and storage of carbon dioxide (CO2) in subsurface porous sandstone with effective top seals is a proposed method for reducing the amount of anthropogenic CO2 in the atmosphere in the system of carbon capture utilization and storage (CCUS). Uplift and erosion of the San Rafael Swell in south-central Utah has exposed the Jurassic Navajo Sandstone and Carmel Formation reservoir-seal pair that is analogous to potential CO2 injection targets. The outcrops show evidence of seal failure through mesoscopic opening-mode fractures and faults in the caprock. We focus on three sites of different structural position with exposures of the reservoir-seal pair that were analyzed for fracture characteristics. Deformation-band faults, joints, and joint clusters are present in the Navajo Sandstone and deformation-band faults are present in the Page Sandstone where faulting has occurred. The structures in the reservoir lithologies penetrate the interface and transition into opening-mode fractures in the caprock. The fractures in the caprock show evidence of seal failure which include multiple mineralization events and bleaching, likely from reducing fluids within the fractures. Seal failure is most likely where fracture density is highest. Fracture density data acquired from scan-line measurements shows that fracture density is highest in fracture clusters, in the syncline hinge where curvature is highest, and near faults. The fracture distributions are related to the structural settings in which transmissive fractures have predictable orientations. The opening-mode fractures and faults of the study may compromise the seal integrity of the caprock and are undetectable using traditional seismic techniques. Mesoscopic subseismic seal-compromising features may allow CO2 to leak though the caprock slowly, which could be significant over the thousands of years necessary for CCUS to be feasible.