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Brechemin Piano Series December 6, 2012
No full textConcert ProgramBrechemin Piano Series December 6, 201
Manganese Exposure Estimation and its Association with Blood Manganese
No full textThesis (Master's)--University of Washington, 2012Despite evidence of adverse health effects resulting from exposure to welding fume and in particular to manganese (Mn), biomarkers of exposure are poorly understood and have not been thoroughly evaluated in a longitudinal design. This study evaluates the relationship between well-characterized inhaled Mn exposure and whole blood Mn concentrations. A cohort of 34 apprentice welders was observed for three academic quarters during which subjects were exposed to welding fume. Personal airborne exposures to Mn and total particulate mass were measured five times each quarter and blood samples were taken twice on four days in each quarter for each subject. Individual characteristics with the potential to influence the relationship between air and biomarker concentrations, including type of welding and respirator use, were assessed in all subjects via questionnaire. Using these data, a mixed effects predictive model was developed to quantitatively estimate air Mn exposures on non-sampling days, allowing for both fixed and random effects. Air exposure results demonstrated that different welding types were significantly associated with air Mn exposure. The relationship between air exposure levels and predicted exposures were correlated to whole blood Mn levels using robust linear regression. No significant association was found between air exposure and blood Mn when compared across day. A statistically significant association was found between estimated quarterly air Mn exposure and cross-quarter blood Mn. This positive relationship indicated a loose association between increasing exposure and increasing difference in blood Mn levels. However, the overall results of this study indicate that blood Mn does not seem to be an effective short-term biomarker of exposure as analyzed. More data and a different time structure for analysis could lead towards a better understanding of blood Mn's association with air Mn exposure
Experimental and Analytical Study of Mode II Interlaminar Failure of Bolted and Bonded Composite Structures
No full textThesis (Master's)--University of Washington, 2012The capability of a fastener to arrest and stabilize pure Mode II interlaminar failure in composite structures has been investigated both experimentally and analytically. A novel pure Mode II three-beam axially loaded specimen was designed specifically for the study. Test specimens were manufactured with [(0/45/90/-45)3]S quasi-isotropic carbon fiber composite laminates for each beam. Teflon inserts were installed as initial cracks, and several variations of plies and bonding techniques were used at the crack interface. Testing showed that crack initiation loads depended on the plies at the crack interface and the bonding technique used. The fracture toughness of the bond in several configurations resulted in the crack initiation loads being higher that the load at which filled-hole tension failure of the laminates occurred; in such cases the full arrestment capability of the fasteners was not able to be captured, but post failure C-scans showed that the presence of a fastener did provide more crack arrestment than without a fastener. However, the testing of other specimens with lower fracture toughness of crack interface bonds displayed the capability of the fastener to arrest and stabilize a crack before filled-hole tension failure. An analytical model and solution were developed to simulate crack growth in the three-beam specimen. The analytical solution was verified using FEM, and showed very good agreement of the results. The analytical model was used to determine the critical Mode II strain energy release rate, GIIC, of each specimen configuration. Also, the analytical model was used to perform a series of parametric analysis of the three-beam specimen to study the effect that changing specimen parameters, such as laminate layup and thickness, had on the crack propagation behavior of the specimen. It was advised that the analytical model be used to aid in the design of alternate specimen configurations for further study
Effects of water source and mixing on phytoplankton dynamics within a tidally influenced system
No full textPhytoplankters are primary producers and an important energy source within pelagic nearshore habitats. The growth of these organisms is affected by riverine-oceanic interactions. A measurable interaction over 24 hours is the density difference between these water sources, where less-dense riverine water is warmer and has lower salinity. Ebb currents enhance the advection of riverine output, placing it on top of the oceanic water and creating stratification. Primary production increased during stratification periods, but reduced when transitioning between a flood and ebb current. Visual analysis of phytoplankton community composition also highlighted increases in the population during high ebb and flood current rates. The large increase in Skeletonema population during this study suggested that the movement or growth of certain phytoplankton genera are affected by these water source interactions. This study concludes that since changes happen within the water column over a short period of time, an entire tidal exchange must be monitored before any conclusions can be made about the water column or its occupants
THE TALE OF TWO TIDEPOOLS: EXAMINING CARBONATE CHEMISTRY IN THE INTERTIDAL
No full textTidepools are a prominent feature of the intertidal zone, housing a great diversity of both
macroalgae and mobile animal components. Tidepool organisms are exposed to wide variations
in temperature, salinity, and pH over the course of the low tide. As of yet, very few studies have
quantified the changes in carbonate chemistry in tidepools. The objective of this study was to
quantify the changes in carbonate chemistry in tidepools over the course of three consecutive low
tides and to determine if biological additions would alter the degree of change in carbonate
parameters occurring over the course of the low tide. The carbonate chemistry in the tidepools
we surveyed underwent drastic changes over the course of the low tide. With increasing
isolation time, the total alkalinity and dissolved inorganic carbon decreased, and the pH
increased. However, no signal from the addition of Ulva sp. or Mytilus trossulus was detected
in this study
