Now showing items 3083-3102 of 3321

• #### Toward an optimal solver for the obstacle problem

An optimal algorithm for solving a problem with m degrees of freedom is one that computes a solution in O (m) time. In this paper, we discuss a class of optimal algorithms for the numerical solution of PDEs called multigrid methods. We go on to examine numerical solvers for the obstacle problem, a constrained PDE, with the goal of demonstrating optimality. We discuss two known algorithms, the so-called reduced space method (RSP) [BM03] and the multigrid-based projected full-approximation scheme (PFAS) [BC83]. We compare the performance of PFAS and RSP on a few example problems, finding numerical evidence of optimality or near-optimality for PFAS.
• #### Toward Arctic transitions and sustainability: modeling risks and resilience across scales of governance

The Arctic region has been the subject of international attention in recent years. The magnitude of impacts from global climate change, land-use change, and speculations about economic development and accessible polar shipping lanes have intensified this focus. As a result, the potential to manage complex ecological, social and political relationships in the context of changes, risks and opportunities is the focus of a large and growing body of research. This dissertation contributes to the expanding scholarship on managing Arctic social-ecological systems for resilience by answering the question: What conditions improve cross-scale learning and resilience in nested social-ecological systems experiencing rapid changes? Using the framework of social-ecological systems and the drivers of change that can transform fundamental relationships within, three studies profile the spatial and temporal dimensions of learning and risk perceptions that impact nested social systems. The first study presents a spatial and temporal analysis of scale- and level-specific processes that impact learning from risks. It draws on four cases to underscore the need for a plurality of risk assumptions in learning for resilience, and sums up essential resources needed to support key decision points for increasing resilience. Two additional studies present research conducted with northern Alaska communities and resource managers. In these studies, I analyzed the extent to which perceptions of risks scale horizontally (between same-level jurisdictions), and vertically (between levels in a dominant jurisdictional structure). These examples illustrate the need for innovative institutions to enhance cross-scale learning, and to balance global drivers of change with local socioeconomic, cultural, and ecological interests. Based on findings of the dissertation research I propose recommendations to optimize the tools and processes of complex decision making under uncertainty.
• #### Toward computer generated folk music using recurrent neural networks

In this paper, we compare the effectiveness of two different types of Recurrent Neural Networks, fully connected and Long Short Term Memory, for modeling music compositions. We compare both the categorical accuracies of these models as well as the quality of generated compositions, and find that the model based on Long Short Term Memory is more effective in both cases. We find that the fully connected model is not capable of generating non repeating note sequences longer than a few measures, and that the Long Short Term Memory model can do significantly better in some cases.
• #### A toxicity assessment of total dissolved solid ions in mine effluent using two common bioassays: the 22-hour MicroTox assay and a S. carpricornutum growth assay

This research evaluated two microassays and a synthetic TDS standard to measure the effects of elevated TDS from mine effluent on biota of freshwater systems. Field samples from Red Dog and Fort Knox mines were tested on Selenastrum capricornutum and the MicroTox assay, and compared to the synthetic standard. Results indicate that the synthetic TDS standard is a poor representation of produced waters with similar total TDS concentrations. Additionally, no correlation was found between the toxicological responses of the two assays. Principle component analysis found the MicroTox assay to be most sensitive to cadmium and chloride. At concentrations present in the field samples, there does not appear to be a relationship between toxicity and TDS as measured on these assays.
• #### The toxicity of creosote treated wood to pacific herring (Clupea pallasi) embryos and characterization of polycyclic aromatic hydrocarbons near creosoted pilings in Juneau, Alaska

These studies documented creosote toxicity to developing Pacific herring (Clupea pallasi) embryos at low microgram per liter concentrations and determined that detrimental concentrations of polycyclic aromatic hydrocarbons (PAHs) near creosoted pilings exist. Creosote total PAH concentrations of 7 μg/L resulted in skeletal defects and ineffective swimming in hatched larvae and represent a lowest observed effect concentration (LOEC) for Pacific herring embryos not previously defined. In the field, PAHs consistent with creosote were elevated at distances up to a meter from creosoted pilings in some cases. Concentrations likely sufficient to induce teratogenic effects were found directly on creosoted pilings and within ten centimeters of pilings. Cumulatively, these studies provide useful and needed data on the interactions between Pacific herring embryos and creosoted pilings in the nearshore environment.
• #### Toxicodistribution of mercury and selenium in pinnipeds of Alaska

This study is divided into two major parts (chapters) in order to better understand mercury (Hg) and selenium (Se) tissue distribution in pinnipeds. The first part of the study focuses on determining total mercury ([THg]) and selenium ([TSe]) concentrations (mass and molar based) among cardiac and renal tissues of ice seals (focus on bearded seals, Erignathus barbatus) as compared to the more traditionally analyzed tissues (e.g. liver, skeletal muscle). Determining Hg distribution within these tissues is essential in establishing sampling methods for biomonitoring, histopathology and biochemistry of Hg. Age was determined to be an important driver of [THg] and Se:Hg molar ratios in heart and kidney. In bearded seals [THg] varied by heart region and therefore future studies should use consistent sampling methods in order to determine and compare [THg]. Despite the differences in seal kidney structure when compared to many terrestrial mammals, the kidney cortex was the main accumulation site for Hg within the kidney of bearded seals and requires consideration in sampling designs. Se:Hg molar ratios greater than 1 in all tissues can be considered a baseline for normal Se concentrations under relatively low [THg]. The second part of the study focuses on THg and TSe distribution in Steller sea lion (Eumetopias jubatus) pup tissues in addition to THg tissular and body burdens. Hair had the highest [THg] in all 5 Steller sea lion pups as compared to other tissue compartments. Since these pups were 1-2 months of age, the hair (lanugo) sampled was a good indicator of Hg exposure via maternal placental transfer (in utero) and potentially a good indicator of individual THg tissue burdens. The percent of total Hg body burden for many organs in Steller sea lion pups was similar to that found in Pacific harbor seals. The Se:Hg molar ratios were between 1 and 50 in all tissues of 4 of the 5 pups while the pup with the highest [THg] in all tissues, had Se: Hg molar ratios of 0.7 or less in 9 of 14 tissues indicating that this animal may have limited Se-dependent protection related to Hg toxicosis.
• #### Toxins And Toxicity Of Protogonyaulax From The Northeast Pacific

Dinoflagellates of the genus Protogonyaulax contain a group of substances that can be lethal to many creatures, including man, and may accumulate at many points in the food web. The substances are most familiar as paralytic shellfish poison (PSP), which occurs sporadically in bivalves. The present study was undertaken because previous work left in doubt both the origin and chemical nature of the toxins along the Alaskan coast. To investigate the problem, dinoflagellates were isolated from locations along the Pacific coast ranging from San Francisco to Dutch Harbor. Most isolates were obtained by incubating subtidal sediments to germinate resting cysts. Toxic isolates were obtained from most locations sampled. On the basis of morphology, all toxic isolates fell within the genus Protogonyaulax. The growth and toxicity of one clone (PI07) was studied under a variety of culture conditions. Toxicity was greatly suppressed under the conditions traditionally employed for culturing Protogonyaulax, suggesting that the toxicity of cells in nature may in general be higher than has been recognized. Chemical studies of the toxins extracted from Protogonyaulax revealed that the six toxins previously known (saxitoxin, its N-1-hydroxyl and 11-hydroxysulfate derivatives) are generally accompanied by somewhat larger amounts of their 21-sulfo derivatives. These have likely not been recognized in past studies due to their greatly reduced toxicity, facile hydrolysis, and altered chromatographic properties. The toxin composition of several isolates was determined and indicates that toxin composition is a conservative property of each clone and that there are regional populations of Protogonyaulax with uniform toxin composition, but that toxin composition differs substantially among regions. This pattern of variation, coupled with the great differences in the properties of the toxins, indicates that the nature of PSP will similarly vary from one region to another but will be uniform within each.
• #### Toxins and toxicity of Protogonyaulax from the Northeast Pacific

Dinoflagellates of the genus Protogonyaulax contain a group of substances that can be lethal to many creatures, including man, and may accumulate at many points in the food web. The substances are most familiar as paralytic shellfish poison (PSP), which occurs sporadically in bivalves. The present study was undertaken because previous work left in doubt both the origin and chemical nature of the toxins along the Alaskan coast. To investigate the problem, dinoflagellates were isolated from locations along the Pacific coast ranging from San Francisco to Dutch Harbor. Most isolates were obtained by incubating subtidal sediments to germinate resting cysts. Toxic isolates were obtained from most locations sampled. On the basis of morphology, all toxic isolates fell within the genus Protogonyaulax. The growth and toxicity of one clone (PI07) was studied under a variety of culture conditions. Toxicity was greatly suppressed under the conditions traditionally employed for culturing Protogonyaulax, suggesting that the toxicity of cells in nature may in general be higher than has been recognized. Chemical studies of the toxins extracted from Protogonyaulax revealed that the six toxins previously known (saxitoxin, its N-1-hydroxyl and 11-hydroxysulfate derivatives) are generally accompanied by somewhat larger amounts of their 21-sulfo derivatives. These have likely not been recognized in past studies due to their greatly reduced toxicity, facile hydrolysis, and altered chromatographic properties. The toxin composition of several isolates was determined and indicates that toxin composition is a conservative property of each clone and that there are regional populations of Protogonyaulax with uniform toxin composition, but that toxin composition differs substantially among regions. This pattern of variation, coupled with the great differences in the properties of the toxins, indicates that the nature of PSP will similarly vary from one region to another but will be uniform within each.
• #### The trace formulas for a half-line Schrodinger operator with long-range potentials

The present work deals with trace formulas for a half-line Schrödinger operator with long-range potentials. These formulas relate the potential with some scattering data. We generalize some relevant results by Buslaev; Faddeev; Gesztesy, Holden, Simon, and others to the case of square integrable potentials. The relation between the number of the trace formulas and the number of integrable derivatives of the potential is also given.
• #### Trace metals in Arctic fast ice

Trace metals in the marine environment are found in trace amounts, but are important tracers of oceanographic processes, and bioactive trace metals can impact ocean biogeochemistry through their nutrient or toxic influence of microbial populations. Sea ice is an intrinsic feature of the Arctic Ocean that likely plays a key role in the cycling of trace metals, given that this substrate can concentrate, alter, and transport these elements. Warming conditions in the Arctic have decreased sea ice cover over the past decades and the loss of sea ice threatens to drastically change the Arctic ecosystem, but the implications are not entirely understood. The scarcity of studies on Arctic sea ice entrained trace metals is due in part to the lack of commercially available sampling equipment capable of collecting sea ice without introducing contamination, and in part to the logistic and economic difficulties in accessing remote Arctic sea ice sites. Natural heterogeneity related to large sediment loads incorporated in uneven patches across Arctic fast ice poses a challenge when designing observational studies of trace metals in sea ice. The scope of this thesis is on the study of trace metals in Alaskan Beaufort Sea fast ice environment. The study includes snow, sea ice and seawater under the ice. Analysis of dissolved (Mn, Fe, Cu and Zn) and particulate (Al, Mn, Fe, Cu and Zn) phases was carried out from 50 ice cores collected with a trace metal clean ice corer developed at the University of Alaska Fairbanks. The results of this study indicated that the ice corer developed at UAF was able to collect uncontaminated samples. Highly variable and elevated concentrations of particulate (> 0.2 μm) trace elements were observed due to the notable variability in the amount of sediment incorporated within ice cores, but surprisingly dissolved (< 0.2 μm) metal concentrations were relatively low and consistent. The observed low dissolved metal concentrations, along with low bulk salinity and low percent leachable particulate trace metal fractions, suggest that desalination removed reactive metals from the ice matrix prior to sampling. Spatial variability of dissolved and particulate trace metals was statistically analyzed and indicated generally negligible variability on the meter scale, but significant variability on the kilometer scale, for both size classes. These results emphasize that future studies of trace metals in sea ice should include temporal and spatial considerations.
• #### Trace mineral reserves for reproduction and development in muskoxen

In muskoxen (Ovibos moschatus), trace minerals required for reproduction and development are unknown. I described use of copper in pregnant muskoxen and concurrent accumulation of copper in fetuses. Utilization of copper was examined in neonates during early development and importance of milk as a source of copper was assessed. Additionally, I examined the effect of maternal copper supplementation during gestation on copper reserves acquired in-utero, and during lactation on mineral status of milk. During gestation, the fetus must acquire reserves of copper adequate to support early neonatal development because milk is a poor source of copper. The transition from milk to a forage-based diet may compromise immune function, growth, and survival of young as reserves established in-utero are likely depleted by that time. Maternal supplementation of copper during gestation and lactation provided little benefit to young, neither increasing mineral reserves in the fetus nor mineral content of milk. Nonetheless, supplementation during gestation may offset maternal costs.
• #### Tracing Amino Acid Metabolism Of Harbor Seals (Phoca Vitulina) Using Stable Isotope Techniques

Compound specific isotope techniques were used to trace amino acid metabolism in captive harbor seals (Phoca vitulina) through a two-year controlled feeding trial with either Pacific herring (Clupea pallasi ) or walleye pollock (Theragra chalcogramma). Techniques were developed for measuring carbon and nitrogen isotope ratios of individual amino acids. Carbon and nitrogen trophic enrichments in serum of captive harbor seals varied with the two fish diets, which might have resulted from the changes in metabolic pathway due to the differing dietary protein intake between herring and pollock. Data on serum free amino acid compositions also showed, from a different perspective, that changes in seal metabolism occurred in response to these different feeding regimes. Carbon and nitrogen isotopic composition of individual amino acids varied much more within an organism than across trophic levels, reflecting the distinct amino acid biosynthetic pathways. The similar patterns in relative amino acid carbon isotopic composition at different trophic levels indicated a conservative transfer of delta13C from primary producers to top predators. Nitrogen trophic enrichments in different amino acids were not uniform, depending upon the extent to which a given amino acid was transaminated or deaminated, with several essential amino acids showing lesser variations than most non-essential and branched-chain amino acids. The differences in amino acid isotope ratios among phocids from the North Pacific or Atlantic and their counterparts from the Antarctic reflected the geographic variations in isotopic composition of phytoplankton. The striking similarities in relative amino acid isotopic composition among phocids from the three distinct geographic locations indicated that phytoplankton worldwide had similar biosynthetic pathways during initial amino acid biosynthesis. This has important implications for using individual amino acid isotope ratios in studies of modern and prehistoric marine organisms. Amino acid metabolic pathways governed the varying patterns of 15N enrichments following 15N-labeled amino acid tracer infusions. Tracer experiments further confirmed that phenylalanine, threonine, lysine and probably histidine may be useful as relatively conservative natural biomarkers. This study provided new insight into mechanisms of isotopic trophic dynamics in food web studies and improved our understanding of seal protein metabolism.
• #### Tracing sea ice algae into various benthic feeding types on the Chukchi Sea shelf

Climate change in the Arctic is expected to have drastic effects on marine primary production sources by shifting ice-associated primary production to an overall greater contribution from pelagic primary production. This shift could influence the timing, amount, and quality of algal material reaching the benthos. We determined the contribution of sea ice particulate organic matter (iPOM) to benthic-feeding invertebrates by examining concentrations and stable carbon isotope values (expressed as δ¹³C values) of three FAs prominent in diatoms: 16:4(n-1), 16:1(n-7) and 20:5(n-3). Our underlying assumption was that diatoms make up the majority in sea ice algal communities compared with phytoplankton communities. According to the FA concentrations, subsurface deposit feeders consumed the most iPOM and suspension feeders the least. Conversely, there were little differences in δ¹³C values of FAs between deposit and suspension feeders, but the higher δ¹³C values of 16:1(n-7) in omnivores indicated greater consumption of iPOM. We suggest that omnivores accumulate the ice algal FA biomarker from their benthic prey, which in turn may feed on ice algae from a deposited sediment pool. The dissimilar results between FA concentrations and isotope values suggest that the FAs used here may not be sufficiently source-specific and that other unaccounted for production sources, such as bacteria, may also contribute to the FA pool. We propose that FA isotope values are a more indicative biomarker than FA concentrations, but there is a further need for more specific ice algal biomarkers to resolve the question of ice algal contributions to the Arctic benthic food web.
• #### Tracing The Movement And Storage Of Magma In The Crust Through Seismology: Examples From Alaska And Western Mexico

Four studies are presented that examine magma movement and storage in the crust using seismology at three different volcanoes: Fourpeaked volcano in the Cook Inlet region of Alaska, Paricutin volcano in the Michoacan-Guanajato volcanic field in western Mexico, and Colima volcano at the western edge of the Trans-Mexican Volcanic Belt. In 2006, Fourpeaked volcano, Alaska, had a widely-observed phreatic eruption. A modest seismic network was installed in stages following the unrest. The eruption was followed by several months of sustained seismicity punctuated by vigorous swarms and SO2 emissions exceeding a thousand tons/day. Based on the history of Fourpeaked, and observations during and after the phreatic eruption, it is proposed that the activity was caused by a modest injection of new magma beneath the volcano. Also presented are a series of studies from western Mexico, an area of high seismic and volcanic activity. A description of the creation of an automatically generated regional catalog of seismic activity is presented, along with a comparison with existing seismicity studies of the area. From this catalog, a swarm of earthquakes near Parfcutin in May-June 2006 was discovered. This swarm demonstrated a steady upward migration in depth with time. Focal mechanisms during the first part of the swarm reflect the increased stress caused by dike inflation. In early June, the stress orientation changed and became more consistent with the inflation of a horizontal sill-like structure. At Colima volcano, a P-wave tomographic inversion using arrivals from 299 regional earthquakes is presented. The results of the inversion show two distinct low-velocity zones. One is in the upper 10 km under the volcano and may be caused by a magma chamber-type structure. The second anomaly, with peak values of 2.5% slower velocities, was imaged in the crust southeast of the volcano at depths of 15-30 km. This body may be due to partial melt and increased temperatures from a second, deeper area of magma storage.
• #### Tracking carbon sources through an Arctic marine food web: insights from fatty acids and their carbon stable isotopes

Marine production across the Bering-Chukchi continental shelf is influenced by seasonal sea ice dynamics and climatic conditions. Of particular importance is variability in the magnitude and timing of annual phytoplankton production in the water column and in sea ice, and effects of such variability on food web composition and productivity. Of primary concern is the long-term effect of the projected loss of Arctic sea ice on ecosystem productivity and stability, and the fate of upper trophic level species. I examined a portion of the Bering-Chukchi Sea food web by analyzing the fatty acid composition and stable carbon isotope ratios of individual fatty acids in particulate organic matter from sea ice and the water column. These techniques were used to make inferences about diets of three species of zooplankton (Themisto libellula, Calanus marshallae/glacialis, Thysanoessa raschii) sampled during a recent climatically cold, relatively heavy sea ice period in the Bering Sea. I also analyzed fatty acids of four species of ice-associated seals--ringed (Pusa/Phoca hispida), bearded (Erignathus barbatus), spotted (Phoca largha), and ribbon seals (Histriophoca fasciata)--sampled during the same relatively cold period (2007-2010) as well as a preceding warm (2002-2005), relatively low sea ice period in the Bering Sea. Particulate organic matter from sea ice and the water column had different fatty acid characteristics, most likely stemming from differences in algal composition. My results also showed that in the Bering Sea cold period, the amphipod T. libellula was predominately carnivorous, and the copepod C. marshallae/glacialis and euphausiid T. raschii were primarily herbivorous, but displayed some degree of omnivory. Across all years (2002-2010), fatty acid composition of ice seals showed clear evidence of resource partitioning among them, and little niche separation between spotted and ribbon seals, which is consistent with previous studies. The fatty acid composition of primarily pelagic feeding adult ringed seals and predominantly benthic feeding adult bearded seals did not differ between the recent warm (2002-2005) and cold (2007-2010) periods in the Bering Sea, suggesting that their diets and possibly food web structures were not affected by these large multiyear environmental fluctuations. Notably however, the stable carbon isotope ratios of individual fatty acids of bearded seals from the Bering Sea cold period were higher than those from the warm period, which suggests that their prey base in the Bering Sea was receiving more input from particulate organic matter from sea ice than the water column during those years. By using the stable carbon isotope ratios of individual fatty acids of particulate organic matter from sea ice and the water column in a series of stable isotope mixing models, I estimated the proportional contribution of fatty acids from sea ice particulate organic matter in T. libellula, C. marshallae/glacialis, and T. raschii collected in 2009 and 2010 as 36-72%, 27-63%, and 39-71%, respectively. Using a similar set of mixing models, I estimated that adult bearded seals had the highest level of fatty acids from sea ice particulate organic matter (62-80%), followed by spotted seals (51-62%), and then ringed seals (21-60%) in 2009 and 2010. Although estimates could not be made for ribbon seals due to lack of samples in 2009 and 2010, their stable carbon isotope ratios of individual fatty acids from 2003 were very similar to those of spotted seals suggesting that the proportional contribution of fatty acids from sea ice particulate organic matter to ribbons seals was similar to that of spotted seals. Assuming that seals sourced their sympagic fatty acids from the Bering Sea, these results suggest that sympagic production is currently an important contributor to food webs supporting both benthic and pelagic upper trophic level species in years with heavy ice cover in the Bering Sea. Thus, the question is raised--with the projected continuing loss of seasonal sea ice in the Arctic, will organic matter input from sympagic production also decline, and will it be compensated for by pelagic production to balance both pelagic and benthic carbon and energy budgets?
• #### Traditional ecological knowledge of stem concepts in informal and place-based western educational systems: lessons from the North Slope, Alaska

Upon regaining the right to direct education at the local level, the North Slope Borough (NSB) of Alaska incorporated Iñupiat educational philosophies into the educational system. The NSB in partnership with the University of Alaska Fairbanks established Iḷisaġvik College, the only tribal college in Alaska. Iḷisaġvik College seeks to broaden science, technology, engineering, and mathematical education on the North Slope. Incorporation of place-based and informal lessons with traditional ecological knowledge engages students in education. Iḷisaġvik hosted a 2-week climate change program from 2012 -- 2015 for high school and middle school students that examined climate science and the effects of a warming climate on the local environment from a multitude of perspectives from scientists, Iñupiat Elders, and instructor-led field trips. Pre-assessments and post-assessments using the Student Assessment of Learning Gains tool measured students' interests and conceptual understanding. Students developed and enhanced their understanding of science concepts and, at the end of the program, could articulate the impact of climatic changes on their local environment. Similarly, methods to incorporate Indigenous knowledge into research practices have been achieved, such as incorporating field trips and discussion with Elders on the importance of animal migration, whale feeding patterns, and the significance of sea-ice conditions, which are important community concerns.
• #### Traditional food security and diet quality in Alaska Native women

Commutators between the transfer and Steenrod squares have been investigated by several authors. Let X be a finite simplicial complex and $\tau$ be a regular involution on X. If $\tau$ has no fixed point, then the commutator is trivial by certain results in generalized cohomology theory. For involutions with possible fixed points, the commutator was first expressed by Bott as $\Delta\sp*$Sq$\sp{\rm i}$ + Sq$\sp{\rm i}\Delta\sp* = \mu$Sq$\sp{\rm i-1}\Delta\sp*.$ Here $\Delta\sp*$ is the transfer map and $\mu$ denotes the connecting morphism of the Smith sequence. Another formula, closely related to the one above, was given by Kubelka and gives the commutator in terms of the cohomology class restricted to the fixed point set and certain characteristic classes arising from the double cover of the complement to the fixed point set. In this thesis, I prove the generalization of the formulas above for sheaf cohomology. As one of the consequences, due to the powerful nature of sheaf theory we gain the results without serious restrictions on the space: X is required to be paracompact, Hausdorff. In Chapter 1, I review the standard sheaf-theoretical constructions for both the transfer and the Steenrod powers based on Bredon's results. I state and prove a few technical lemmas on Smith sequences that are necessary in my setting. In Chapter 2, I state and prove the analogue of Bott's formula for paracompact Hausdorff spaces. In Chapter 3, we derive a generalization of Kubelka's formula for spaces as above.