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• 1. [Article] Investigation of the Relationship Between Abdominal Aortic Aneurysm Rupture and Mechanical Stress

  The factors that cause abdominal aortic aneurysm rupture were investigated. Included in this study were aneurysm volume, thrombus thickness, lumen area, thrombus area, the average stress acting on the ...

  Citation × Citation Citation Abstract Copy Title: Investigation of the Relationship Between Abdominal Aortic Aneurysm Rupture and Mechanical Stress Author: Agalzoff, Nicholas The factors that cause abdominal aortic aneurysm rupture were investigated. Included in this study were aneurysm volume, thrombus thickness, lumen area, thrombus area, the average stress acting on the aorta, and the maximum stress on the aorta. The geometric values were obtained by tracing a series of computerized axial tomography (CT) scans for each patient to obtain a series of cross sections of the lumen and the thrombus. The cross sections were then put through a program that found a best fit surface for both the lumen and the thrombus. These meshes were analyzed to obtain the geometric information. The stress data were calculated by using the meshes to make an ADINA file programmed with average human values for outlet pressure, flow rate of blood, and load pressure. This resulted in a model of each patient’s aorta with the stress values included. A binomial logistic regression analysis revealed that none of the parameters investigated here were able to predict a rupture with a high degree of confidence (p<0.05). Title: Investigation of the Relationship Between Abdominal Aortic Aneurysm Rupture and Mechanical Stress Author: Agalzoff, Nicholas The factors that cause abdominal aortic aneurysm rupture were investigated. Included in this study were aneurysm volume, thrombus thickness, lumen area, thrombus area, the average stress acting on the aorta, and the maximum stress on the aorta. The geometric values were obtained by tracing a series of computerized axial tomography (CT) scans for each patient to obtain a series of cross sections of the lumen and the thrombus. The cross sections were then put through a program that found a best fit surface for both the lumen and the thrombus. These meshes were analyzed to obtain the geometric information. The stress data were calculated by using the meshes to make an ADINA file programmed with average human values for outlet pressure, flow rate of blood, and load pressure. This resulted in a model of each patient’s aorta with the stress values included. A binomial logistic regression analysis revealed that none of the parameters investigated here were able to predict a rupture with a high degree of confidence (p<0.05). Close

• 2. [Article] Simulating the global distribution of nitrogen isotopes in the ocean

  We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth system climate model designed for millennial timescale simulations. The model includes ...

  Citation × Citation Citation Abstract Copy Title: Simulating the global distribution of nitrogen isotopes in the ocean Author: Somes, Christopher J., Lehmann, Moritz F., Bourbonnais, Annie, Eby, Michael, Schmittner, Andreas, Altabet, Mark A., Galbraith, Eric D., Mix, Alan C., Montoya, Joseph P., Letelier, Ricardo M. We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth system climate model designed for millennial timescale simulations. The model includes prognostic tracers for the two stable nitrogen isotopes, 14N and 15N, in the nitrate (NO3−), phytoplankton, zooplankton, and detritus variables of the marine ecosystem model. The isotope effects of algal NO3− uptake, nitrogen fixation, water column denitrification, and zooplankton excretion are considered as well as the removal of NO3− by sedimentary denitrification. A global database of δ15NO3− observations is compiled from previous studies and compared to the model results on a regional basis where sufficient observations exist. The model is able to qualitatively and quantitatively reproduce many of the observed patterns such as high subsurface values in water column denitrification zones and the meridional and vertical gradients in the Southern Ocean. The observed pronounced subsurface minimum in the Atlantic is underestimated by the model presumably owing to too little simulated nitrogen fixation there. Sensitivity experiments reveal that algal NO3− uptake, nitrogen fixation, and water column denitrification have the strongest effects on the simulated distribution of nitrogen isotopes, whereas the effect from zooplankton excretion is weaker. Both water column and sedimentary denitrification also have important indirect effects on the nitrogen isotope distribution by reducing the fixed nitrogen inventory, which creates an ecological niche for nitrogen fixers and, thus, stimulates additional N2 fixation in the model. Important model deficiencies are identified, and strategies for future improvement and possibilities for model application are outlined. Title: Simulating the global distribution of nitrogen isotopes in the ocean Author: Somes, Christopher J., Lehmann, Moritz F., Bourbonnais, Annie, Eby, Michael, Schmittner, Andreas, Altabet, Mark A., Galbraith, Eric D., Mix, Alan C., Montoya, Joseph P., Letelier, Ricardo M. We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth system climate model designed for millennial timescale simulations. The model includes prognostic tracers for the two stable nitrogen isotopes, 14N and 15N, in the nitrate (NO3−), phytoplankton, zooplankton, and detritus variables of the marine ecosystem model. The isotope effects of algal NO3− uptake, nitrogen fixation, water column denitrification, and zooplankton excretion are considered as well as the removal of NO3− by sedimentary denitrification. A global database of δ15NO3− observations is compiled from previous studies and compared to the model results on a regional basis where sufficient observations exist. The model is able to qualitatively and quantitatively reproduce many of the observed patterns such as high subsurface values in water column denitrification zones and the meridional and vertical gradients in the Southern Ocean. The observed pronounced subsurface minimum in the Atlantic is underestimated by the model presumably owing to too little simulated nitrogen fixation there. Sensitivity experiments reveal that algal NO3− uptake, nitrogen fixation, and water column denitrification have the strongest effects on the simulated distribution of nitrogen isotopes, whereas the effect from zooplankton excretion is weaker. Both water column and sedimentary denitrification also have important indirect effects on the nitrogen isotope distribution by reducing the fixed nitrogen inventory, which creates an ecological niche for nitrogen fixers and, thus, stimulates additional N2 fixation in the model. Important model deficiencies are identified, and strategies for future improvement and possibilities for model application are outlined. Close

• 3. [Article] Traffic and greenhouse gas modeling in future land use development scenarios of Skagit County

  Energy use and greenhouse gas emissions are on the forefront of planning policy in the world today. In the U.S., the transportation sector accounts for 50 percent of greenhouse gas (GHG) emissions, the ...

  Citation × Citation Citation Abstract Copy Title: Traffic and greenhouse gas modeling in future land use development scenarios of Skagit County Author: Mooney, Abraham A. Energy use and greenhouse gas emissions are on the forefront of planning policy in the world today. In the U.S., the transportation sector accounts for 50 percent of greenhouse gas (GHG) emissions, the most of any single sector. State and local levels of government have been very proactive in the mitigation of GHG, with Washington State as one of the leaders. Two state laws passed in 2008 mandate a reduction in GHG and vehicle miles traveled (VMT), a primary metric in measuring traffic. This research focuses on Skagit County, Washington, as we attempt to model and quantify both GHG and VMT as they are affected by land use development. This research relies heavily on the Envision software platform as it was used a project involving an agent based model of alternative future landscapes. The project provided spatial population and employment data in the context of various future development scenarios such as the compact development of the Ecosystem Scenario where the goal was 90% growth within urban growth areas. On the other extreme was the Development Scenario where up to 40% of the growth was allowed in remote and non-incorporated areas. A majority of the research of this thesis document is devoted to the development of a traffic model structured around the commute of 17 population centers to job centers within Skagit County. The population centers are defined by traffic area zones, or TAZ, that encompass the entire county. The model is unique in traffic modeling literature for its small number of population and destination centers. The countywide accuracy of the model is exemplary at -0.87% standard error relative to current Highway Performance Monitoring System VMT data, although it should be understood that this result has not been repeated by applying the same methodology to other counties. Given that buildings energy use is second to the transportation sector as the largest single contributor to GHG emissions, a residential building model was created, in which parcel level population densities characterize high and low density building development. Defined as Apartments and Houses, respectively, within the text, energy use values were assigned to each from climate-specific data of the Residential Energy Consumption Survey national data set. Thus, as population and employment grow in various development scenarios of the Envision-Skagit 2060 project, the GHG generation from buildings and vehicles is calculated for comparison. The compact development of the Ecosystem Scenario generated the least amount of GHG in both models. Only a 5.9% difference was found in GHGs generated from the building model in the two extreme growth scenarios (Ecosystem and Development). In the traffic model, a 19% difference was found in the VMT of the same two scenarios. Compact, near job center development creates more of an impact on GHG inventory in the transportation sector at approximately twice the GHG impact of compact buildings. Comparing our results to Washington State law mandated reductions for both VMT and GHGs, we find that neither will be met in the transportation or building sectors. When a applying the Energy Information Association’s most efficient vehicle fuel efficiency scenario where all vehicles are projected to average 59.6 mpg we find that even the best combination of scenarios (Ecosystem land-use and 59.3 mpg vehicle efficiency) results in GHGs that are 1.8 times larger than those permissible by the law as applied to year 2050. Our results assume the same 'standard of living' as today applied to home appliances, heating/cooling, and vehicle use. The traffic model assumes all commuters continue to use all modes of transit in the same fractions as today: 77.4% use single occupancy vehicles, 12.6% use high occupancy vehicles, 1.0% mass transit, 4.6% walk or bike, and 4.4% work at home in Skagit County. Although increased use of mass transportation was not modeled in this research, it may be the only option given our findings, with regards to the Washington State reduction requirements. In any case, our most important result is a novel approach to traffic modeling that requires only spatial knowedge of population and employment in order to predict traffic and quantify GHG emissions as they change with urban form. Title: Traffic and greenhouse gas modeling in future land use development scenarios of Skagit County Author: Mooney, Abraham A. Energy use and greenhouse gas emissions are on the forefront of planning policy in the world today. In the U.S., the transportation sector accounts for 50 percent of greenhouse gas (GHG) emissions, the most of any single sector. State and local levels of government have been very proactive in the mitigation of GHG, with Washington State as one of the leaders. Two state laws passed in 2008 mandate a reduction in GHG and vehicle miles traveled (VMT), a primary metric in measuring traffic. This research focuses on Skagit County, Washington, as we attempt to model and quantify both GHG and VMT as they are affected by land use development. This research relies heavily on the Envision software platform as it was used a project involving an agent based model of alternative future landscapes. The project provided spatial population and employment data in the context of various future development scenarios such as the compact development of the Ecosystem Scenario where the goal was 90% growth within urban growth areas. On the other extreme was the Development Scenario where up to 40% of the growth was allowed in remote and non-incorporated areas. A majority of the research of this thesis document is devoted to the development of a traffic model structured around the commute of 17 population centers to job centers within Skagit County. The population centers are defined by traffic area zones, or TAZ, that encompass the entire county. The model is unique in traffic modeling literature for its small number of population and destination centers. The countywide accuracy of the model is exemplary at -0.87% standard error relative to current Highway Performance Monitoring System VMT data, although it should be understood that this result has not been repeated by applying the same methodology to other counties. Given that buildings energy use is second to the transportation sector as the largest single contributor to GHG emissions, a residential building model was created, in which parcel level population densities characterize high and low density building development. Defined as Apartments and Houses, respectively, within the text, energy use values were assigned to each from climate-specific data of the Residential Energy Consumption Survey national data set. Thus, as population and employment grow in various development scenarios of the Envision-Skagit 2060 project, the GHG generation from buildings and vehicles is calculated for comparison. The compact development of the Ecosystem Scenario generated the least amount of GHG in both models. Only a 5.9% difference was found in GHGs generated from the building model in the two extreme growth scenarios (Ecosystem and Development). In the traffic model, a 19% difference was found in the VMT of the same two scenarios. Compact, near job center development creates more of an impact on GHG inventory in the transportation sector at approximately twice the GHG impact of compact buildings. Comparing our results to Washington State law mandated reductions for both VMT and GHGs, we find that neither will be met in the transportation or building sectors. When a applying the Energy Information Association’s most efficient vehicle fuel efficiency scenario where all vehicles are projected to average 59.6 mpg we find that even the best combination of scenarios (Ecosystem land-use and 59.3 mpg vehicle efficiency) results in GHGs that are 1.8 times larger than those permissible by the law as applied to year 2050. Our results assume the same 'standard of living' as today applied to home appliances, heating/cooling, and vehicle use. The traffic model assumes all commuters continue to use all modes of transit in the same fractions as today: 77.4% use single occupancy vehicles, 12.6% use high occupancy vehicles, 1.0% mass transit, 4.6% walk or bike, and 4.4% work at home in Skagit County. Although increased use of mass transportation was not modeled in this research, it may be the only option given our findings, with regards to the Washington State reduction requirements. In any case, our most important result is a novel approach to traffic modeling that requires only spatial knowedge of population and employment in order to predict traffic and quantify GHG emissions as they change with urban form. Close

• 4. [Article] Nitrogen isotopes in a global ocean biogeochemical model : constraints on the coupling between denitrification and nitrogen fixation

  We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes ...

  Citation × Citation Citation Abstract Copy Title: Nitrogen isotopes in a global ocean biogeochemical model : constraints on the coupling between denitrification and nitrogen fixation Author: Somes, Christopher J. We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes prognostic tracers for the stable nitrogen isotopes, ¹⁴N and ¹⁵N, in the nitrate (NO₃ˉ), phytoplankton, zooplankton, and detritus variables of the marine ecosystem model. The isotope effects of algal NO₃ˉ assimilation, water column denitrification, and zooplankton excretion are considered as well as the input of newly fixed nitrogen by diazotrophs. A global database of δ¹⁵NO₃ˉ observations is compiled from previous studies and compared to the model results on a regional basis where sufficient observations exist. The model is able to qualitatively and quantitatively reproduce the observed patterns such as high subsurface values in denitrification zones, the meridional and vertical gradients in the Southern Ocean, and the meridional gradient in the Central Equatorial Pacific. The observed subsurface minimum in the Atlantic is underestimated presumably owing to too little nitrogen fixation there. Sensitivity experiments show that algal NO₃ˉ assimilation, nitrogen fixation and water column denitrification have strong effects on the simulated distribution of nitrogen isotopes, whereas the effect from zooplankton excretion is weaker. Both water column and sedimentary denitrification also have important indirect effects on the nitrogen isotopes distribution by reducing the fixed nitrogen inventory, which creates an ecological niche for diazotrophs and stimulates additional nitrogen fixation. Water column denitrification has a strong but rather localized effect on the nitrogen isotope distribution in model versions without iron limitation of diazotrophy, in which a tight coupling of nitrogen fixation exists. However, including iron limitation of diazotrophy inhibits a tight coupling between water column denitrification and nitrogen fixation in the Eastern Pacific and shifts the main location of nitrogen fixation from the Eastern Tropical Pacific to the Western Tropical Pacific, which results in a better agreement with N' = NO₃ˉ−16PO₄³ˉ and δ¹⁵NO₃ˉ observations. Thus, our model results suggest that iron limitation of diazotrophy can modulate the feedback between denitrification and nitrogen fixation in the ocean. We speculate that a feedback response time on the centennial to millennial time scale may exist between denitrification and nitrogen fixation, producing imbalances in the global oceanic fixed nitrogen cycle, which may well have contributed to past changes of atmospheric CO₂ via the biological pump. Title: Nitrogen isotopes in a global ocean biogeochemical model : constraints on the coupling between denitrification and nitrogen fixation Author: Somes, Christopher J. We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes prognostic tracers for the stable nitrogen isotopes, ¹⁴N and ¹⁵N, in the nitrate (NO₃ˉ), phytoplankton, zooplankton, and detritus variables of the marine ecosystem model. The isotope effects of algal NO₃ˉ assimilation, water column denitrification, and zooplankton excretion are considered as well as the input of newly fixed nitrogen by diazotrophs. A global database of δ¹⁵NO₃ˉ observations is compiled from previous studies and compared to the model results on a regional basis where sufficient observations exist. The model is able to qualitatively and quantitatively reproduce the observed patterns such as high subsurface values in denitrification zones, the meridional and vertical gradients in the Southern Ocean, and the meridional gradient in the Central Equatorial Pacific. The observed subsurface minimum in the Atlantic is underestimated presumably owing to too little nitrogen fixation there. Sensitivity experiments show that algal NO₃ˉ assimilation, nitrogen fixation and water column denitrification have strong effects on the simulated distribution of nitrogen isotopes, whereas the effect from zooplankton excretion is weaker. Both water column and sedimentary denitrification also have important indirect effects on the nitrogen isotopes distribution by reducing the fixed nitrogen inventory, which creates an ecological niche for diazotrophs and stimulates additional nitrogen fixation. Water column denitrification has a strong but rather localized effect on the nitrogen isotope distribution in model versions without iron limitation of diazotrophy, in which a tight coupling of nitrogen fixation exists. However, including iron limitation of diazotrophy inhibits a tight coupling between water column denitrification and nitrogen fixation in the Eastern Pacific and shifts the main location of nitrogen fixation from the Eastern Tropical Pacific to the Western Tropical Pacific, which results in a better agreement with N' = NO₃ˉ−16PO₄³ˉ and δ¹⁵NO₃ˉ observations. Thus, our model results suggest that iron limitation of diazotrophy can modulate the feedback between denitrification and nitrogen fixation in the ocean. We speculate that a feedback response time on the centennial to millennial time scale may exist between denitrification and nitrogen fixation, producing imbalances in the global oceanic fixed nitrogen cycle, which may well have contributed to past changes of atmospheric CO₂ via the biological pump. Close