• Trace mineral reserves for reproduction and development in muskoxen

      Rombach, Emmajean Pearl (2001-12)
      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 The Movement And Storage Of Magma In The Crust Through Seismology: Examples From Alaska And Western Mexico

      Gardine, Matthew D.; West, Michael (2010)
      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.
    • Traditional ecological knowledge of stem concepts in informal and place-based western educational systems: lessons from the North Slope, Alaska

      Nicholas-Figueroa, Linda; Duffy, Lawrence K.; Barnhardt, Ray; Dunlap, Kriya; Middlecamp, Kathy (2017-05)
      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

      Walch, Amanda; Bersamin, Andrea; Johnson, Rhonda; Loring, Philip; Lopez, Ellen (2016-08)
      This dissertation addresses the need for a better understanding of traditional foods, food security, and diet quality and how they collectively influence health of low income Alaska Native women receiving the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). The ultimate aims are to understand the beliefs and behaviors regarding traditional foods in low income Alaska Native women in Anchorage receiving WIC assistance and examine whether these foods moderate the relationship between food security and diet quality. Food security is a growing public health concern in Alaska, especially among Alaska Native people living in urban areas. I begin the dissertation by conducting a literature review on traditional food security research in Alaska, examining research that has been conducted in the past decades. The review yielded a total of 28 articles for the systematic review, where traditional food security was categorized into three main types of research: those that quantified traditional food intake (n=19), those that quantified food security (n=2), and qualitative articles that addressed at least one pillar of food security (n=8). The three categories were used to evaluate how traditional foods relate to the pillars of food security in Alaska and determine future research needs. I estimated the intake of traditional food among urban Alaska Native women receiving WIC assistance and examined the associations between participants’ practices, attitudes, and beliefs of traditional foods. Results indicate that participants are mixed on their opinion of the economic value of traditional foods and the healthfulness of traditional foods over store bought foods. Linear regression analysis shows that participants who ate more traditional foods are more likely to have traveled to a rural Alaska Native community in the past year (p=.001) and have a preference for traditional foods over store bought foods (p=.001). Finally I estimated diet quality and food security of Alaska Native women receiving WIC assistance who are living in an urban community in order to understand how intake of traditional foods affects these estimates. Results indicate the average intake of traditional foods is 3.7% of total calories and participants’ diet quality was lower than the national average, with a 48 on the Health Eating Index (HEI). Multivariate regression analysis with significance at P<= .05 indicates that participants with increasing traditional food intake are positively associated with higher diet quality scores. An increase of 10% of traditional foods yielded an increase of 7.3 points on the HEI. Increased education and advocacy of traditional food intake for this population can help increase overall nutrition and long-term health status. Based on the collective findings from the research I recommend the following measures: 1) ensure that nutrition education in food and nutrition assistance programs to be culturally relevant and address the barriers associated with access and availability of traditional foods in urban areas, 2) use the data to inform intervention programs to improve dietary adequacy in this high-risk population, and 3) modify the list of foods acceptable for purchase through the WIC program to promote diet quality and aid in chronic disease prevention in the Alaska Native population.
    • Transient spatiotemporal chaos in a diffusively and synaptically coupled Morris-Lecar neuronal network

      Lafranceschina, Jacopo; Wackerbauer, Renate; Newman, David E.; Szuberla, Curt A. L. (2014-05)
      Transient spatiotemporal chaos was reported in models for chemical reactions and in experiments for turbulence in shear flow. This study shows that transient spatiotemporal chaos also exists in a diffusively coupled Morris-Lecar (ML) neuronal network, with a collapse to either a global rest state or to a state of pulse propagation. Adding synaptic coupling to this network reduces the average lifetime of spatiotemporal chaos for small to intermediate coupling strengths and almost all numbers of synapses. For large coupling strengths, close to the threshold of excitation, the average lifetime increases beyond the value for only diffusive coupling, and the collapse to the rest state dominates over the collapse to a traveling pulse state. The regime of spatiotemporal chaos is characterized by a slightly increasing Lyapunov exponent and degree of phase coherence as the number of synaptic links increases. In contrast to the diffusive network, the pulse solution must not be asymptotic in the presence of synapses. The fact that chaos could be transient in higher dimensional systems, such as the one being explored in this study, point to its presence in every day life. Transient spatiotemporal chaos in a network of coupled neurons and the associated chaotic saddle provide a possibility for switching between metastable states observed in information processing and brain function. Such transient dynamics have been observed experimentally by Mazor, when stimulating projection neurons in the locust antennal lobe with different odors.
    • Transient spatiotemporal chaos in a Morris-Lecar neuronal ring network collapses to either the rest state or a traveling pulse

      Keplinger, Keegan (2012-12)
      Transient spatiotemporal dynamics exists in an electrically coupled Morris-Lecar neuronal ring network, a theoretical model of an axo-axonic gap junction network. The lifetime of spatiotemporal chaos was found to grow exponentially with network size. Transient dynamics regularly collapses from a chaotic state to either the resting potential or a traveling pulse, indicating the existence of a chaotic saddle. For special conditions, a chaotic attractor can arise in the Morris-Lecar network to which transient chaos can collapse. The short-term outcome of a Morris-Lecar ring network is determined as a function of perturbation configuration. Perturbing small clusters of nearby neurons in the network consistently induced chaos on a resting network. Perturbation on a chaotic network can induce collapse in the network, but transient chaos becomes more resistant to collapse by perturbation when greater external current is applied.
    • Transient spatiotemporal chaos on complex networks

      Rawoot, Safia (2004-12)
      Some of today's most important questions regard complex dynamical systems with many interacting components. Network models provide a means to gain insight into such systems. This thesis focuses on a network model based upon the Gray-Scott cubic autocatalytic reaction-diffusion system that manifests transient spatiotemporal chaos. Motivated by recent studies on the small-world topology discovered by Watts and Strogatz, the network's original regular ring topology was modified by the addition of a few irregular connections. The effects of these added connections on the system's transience as well on the dynamics local to the added connections were examined. It was found that the addition of a single connection can significantly effect the transient time of spatiotemporal chaos and that the addition of two connections can transform the system's spatiotemporal chaos from transient to asymptotic. These findings suggest that small modifications to a network's topology can greatly affect its behavior.
    • Transport And Formation Processes For Fine Airborne Ash From Three Recent Volcanic Eruptions In Alaska: Implications For Detection Methods And Tracking Models

      Rinkleff, Peter G.; Cahill, Catherine F.; Dehn, Jonathan; Dean, Kenneson G.; Beget, James E. (2012)
      Airborne fine volcanic ash was collected during the eruptions of Augustine Volcano in 2006, Pavlof Volcano in 2007, and Redoubt Volcano in 2009 using Davis Rotating Unit for Measurement (DRUM) cascade impactors to observe atmospheric processes acting on ash as an atmospheric particle. During the Redoubt eruption, samples were also collected by Beta Attenuation Mass (BAM-1020) and Environmental Beta Attenuation Mass (EBAM) monitors. BAM-1020s and EBAMs provided real-time mass concentration data; DRUM samplers provided samples for post-eruptive analysis. DRUM samples were retrospectively analyzed for time-resolved mass concentration and chemistry. EBAM and BAM-1020s reported near real-time, time-resolved mass concentrations. Scanning Electron Microscopy with Energy Dispersive Spectroscopy was conducted to determine particle size, shape, and composition. Image processing methods were developed to determine particle size distributions and shape factors. Ash occurred as single grains, ash aggregates, and hybrid aggregates. Ash aggregates occurred in plumes from pyroclastic flows and were found in a discrete aerodynamic size range (2.5-1.15 microm). Hybrid ash was common in all samples and likely formed when downward mixing ash mingled with upward mixing sea salt and non-sea salt sulfate. The mass concentration of sulfate did not vary systematically with ash which indicated that the source of sulfate was not necessarily volcanic. Ash size distributions were log-normal. Size distribution plots of ash collected from the same plume at different transport distances showed that longer atmospheric residence times allowed for more aggregation to occur which led to larger but fewer particles in the plume the longer it was transported. Ash transport and dispersion models forecasted ash fall over a broad area, but ash fall was only observed in areas unaffected by topographic barriers. PM10 (particulates &le; 10 microm in aerodynamic diameter or OA) ash was detected closer to the volcano when no PM2.5 (particulates &le; 2.5 microm O A) ash was observed. Further downwind, PM2.5 ash was collected which indicated that the settling rates of PM10 and PM2.5 influenced their removal rates. Diurnal variations in ash mass concentrations were controlled by air masses rising due to solar heating which transported ash from the sampling site, or descending due to radiative cooling which brought ash to the sampling site. Respirable (PM2.5) ash was collected when there were no satellite ash detections which underscored the importance of ash transport and dispersion models for forecasting the presence of ash when mass concentrations are below satellite detection limits.
    • The transport of aerosols into Denali National Park and Preserve

      Wallace, Ashley N. (2012-05)
      Denali National Park and Preserve (DNPP) is a federally protected Class I visibility area in Alaska. The Regional Haze Rule in the U.S. Clean Air Act requires the visibility in all Class I areas to be 'pristine.' According to the EPA DNPP does not have `pristine' air. Therefore, the Alaska Department of Environmental Conservation conducted a 15-month study of particulate matter smaller than 2.5 micrometers (PM2.5) from March, 2008 through June, 2009 to identify the aerosol sources in DNPP. DRUM aerosol impactors collected aerosols at four sites (DNPP Headquarters, Trapper Creek, McGrath, and Lake Minchumina) around DNPP. The aerosol data underwent a series of analyses including: a seasonal analysis of elemental composition, an analysis of potential source regions as identified by the HYbrid Single-Particle Lagrangian Integrated Trajectory ectory (HYSPLIT) model, and Chemical Mass Balance (CMB) analyses to identify specific aerosol sources. These analyses show that the predominant sources of aerosols impacting DNPP during winter and spring lie outside of Alaska and during summer and fall are from outside and local sources. Outside sources include deserts in China and industry in Russia. Because many of the aerosols impacting DNPP are produced internationally, the visibility in DNPP cannot be restored without international collaboration.
    • The treatment of missing data on placement tools for predicting success in college algebra at the University of Alaska

      Crawford, Alyssa (2014-05)
      This project investigated the statistical significance of baccalaureate student placement tools such as tests scores and completion of a developmental course on predicting success in a college level algebra course at the University of Alaska (UA). Students included in the study had attempted Math 107 at UA for the first time between fiscal years 2007 and 2012. The student placement information had a high percentage of missing data. A simulation study was conducted to choose the best missing data method between complete case deletion, and multiple imputation for the student data. After the missing data methods were applied, a logistic regression with fitted with explanatory variables consisting of tests scores, developmental course grade, age (category) of scores and grade, and interactions. The relevant tests were SAT math, ACT math, AccuPlacer college level math, and the relevant developmental course was Devm /Math 105. The response variable was success in passing Math 107 with grade of C or above on the first attempt. The simulation study showed that under a high percentage of missing data and correlation, multiple imputation implemented by the R package Multivariate Imputation by Chained Equations (MICE) produced the least biased estimators and better confidence interval coverage compared to complete cases deletion when data are missing at random (MAR) and missing not at random (MNAR). Results from multiple imputation method on the student data showed that Devm /Math 105 grade was a significant predictor of passing Math 107. The age of Devm /Math 105, age of tests, and test scores were not significant predictors of student success in Math 107. Future studies may consider modeling with ALEKS scores, and high school math course information.
    • Tribological Comparison of Materials

      Shi, Bing; Duffy, Lawrence K.; Kuhn, Thomas B.; Liang, Hong; Rekow, Dianne (2004-12)
      Approximately 600,000 total joint replacement surgeries are performed each year in the United States. Current artificial joint implants are mainly metal-on-plastic. The synthetic biomaterials undergo degradation through fatigue and corrosive wear from load-bearing and the aqueous ionic environment of the human body. Deposits o f inorganic salts can scratch weight-bearing surfaces, making artificial joints stiff and awkward. The excessive wear debris from polyethylene leads to osteolysis and potential loosening of the prosthesis. The lifetime for well-designed artificial joints is at most 10 to 15 years. A patient can usually have two total joint replacements during her/his lifetime. Durability is limited by the body’s reaction to wear debris of the artificial joints. Wear of the artificial joints should be reduced. A focus of this thesis is the tribological performance of bearing materials for Total Replacement Artificial Joints (TRAJ). An additional focus is the scaffolds for cell growth from both a tissue engineering and tribological perspective. The tribological properties of materials including Diam ond-like Carbon (DLC) coated materials were tested for TRAJ implants. The DLC coatings are chemically inert, impervious to acid and saline media, and are mechanically hard. Carbon-based materials are highly biocompatible. A new alternative to total joints implantation is tissue engineering. Tissue engineering is the replacement of living tissue with tissue that is designed and constructed to meet the needs of the individual patient. Cells were cultured onto the artificial materials, including metals, ceramics, and polymers, and the frictional properties of these materials were investigated to develop a synthetic alternative to orthopedic transplants. Results showed that DLC coated materials had low friction and wear, which are desirable tribological properties for artificial joint material. Cells grew on some of the artificial matrix materials, depending on the surface chemistry, wettability, morphology, microstructure etc. The dry, lubricated, and cell culture friction tests showed that bovine serum albumin solution and culture media performed as lubricants. Frictional properties varied. Glass and TR-2 (PET, polyethylene terephthalate) showed good cell culture results and low friction. Both are suitable materials, both as artificial joint implant coatings and as substrates for preparing total joint implants via tissue engineering.
    • Trichodectes canis, an invasive ectoparasite of Alaskan wolves: detection methods, current distribution, and ecological correlates of spread

      Woldstad, Theresa M. (2010-05)
      Trichodectes canis, (Ischnocera: Trichodectidae), was first documented on Alaska gray wolves (Canis lupis) in 1981. Two hypotheses may explain why T. canis was not observed in Alaska until the 1980s. Symptomatic wolves could be predisposed to pediculosis, whereas mild infestations outside the observed infestation region are undetected by visual inspection. A second possible explanation is that T. canis is an invasive ectoparasite, and Alaska wolves outside the infestation region do not harbor lice. We examined wolf hides from December 2003 to February 2009, to investigate potential sampling locations, determine T. canis current distribution within Alaska, and investigate potential ecological correlates of spread. We determined that the caudal region of the wolf possessed the highest mean proportion of T. canis and we detected all cases of mild pediculosis. Lice were documented on wolves in a contiguous distribution from Southcentral Alaska to immediately north of the Alaska Range, (estimated area 174,000 km²). Occult infestations were not detected outside of the current infestation zone. That pattern of occurrence suggests that T. canis is a novel parasite within Alaska. Ecological correlates positively associated with T. canis presence include wolf densities greater than eight wolves/1000 km² and mean annual January temperatures warmer than -19°C.
    • Trophic dynamics in a changing Arctic: interactions between ptarmigan and willows in Northern Alaska

      Christie, Katie; Ruess, Roger; Lindberg, Mark; Mulder, Christa; Schmutz, Joel (2014-12)
      Shrubs have been expanding in the Arctic over the past century, with important consequences for ecosystem functioning, plant community composition, and wildlife habitat. Herbivores have the capacity to strongly moderate the growth and biomass of shrubs, and therefore need to be considered when attempting to understand and project future changes to Arctic ecosystems. Ptarmigan (Lagopus lagopus, L. muta) are common and widespread in many tundra regions, and feed on shrubs throughout their life cycle. Ptarmigan are likely to be an important herbivore in northern Alaska where shrub expansion is rapidly occurring; however, little is known about their spatial and temporal distribution in the Arctic, or the effect of their browsing on shrubs. This dissertation provides novel information on ptarmigan population ecology and herbivory in northern Alaska. Ptarmigan occupancy in northeastern Alaska increased from March through May, lending support to the idea that they undergo a spring migration from southern wintering grounds to breeding grounds north of the Brooks Range. Ptarmigan distributions were strongly linked to the presence of shrubs; occupancy was greatest in dense patches of riparian willows that grew tall enough to exceed snow depth. The frequency and intensity of ptarmigan browsing in feltleaf willow (Salix alaxensis) stands in northeastern and northwestern Alaska was high, such that ptarmigan browsed 82-89% of willows and removed 30-39% of buds. Browsed willow branches produced fewer catkins than un-browsed branches, but doubled the volume of current annual growth produced the following summer. These longer, larger-diameter shoots bore 40-60% more buds than shoots on unbrowsed branches. The removal of distal buds stimulated dormant buds at the base of the branch to produce shoots, resulting in a "broomed" architecture. Despite their tendency to produce longer shoots when browsed, highly broomed willows with a history of browsing were shorter than un-broomed willows. Broomed willows were more likely to be re-browsed by ptarmigan. Moose browsing was not as prevalent (17-44% of willows browsed) as ptarmigan browsing and resulted in reduced catkin production and increased shoot volume. Simulated ptarmigan browsing of feltleaf willows caused a similar response to that observed in the wild. Browsed willows produced fewer catkins and more buds per shoot, although buds were smaller than on un-browsed willows. Browsing altered the architecture and bud production of willows such that the biomass of easily accessible buds (within 50 cm of snow level) was greater (129 ± 30 mg) on browsed willows than un-browsed willows (113 ± 50 mg). Browsing did not affect nitrogen concentrations, but slightly reduced carbon concentrations and protein precipitation capacity (tannins) in buds produced the following winter. In a feeding preference study, when broomed and un-broomed willow branches were placed in the snow at equal heights, wild ptarmigan showed no preference for either type but obtained more buds from broomed willows. A synthesis of original and published research showed that browsing by vertebrate herbivores in the Arctic is not uniform, and that certain shrubs (such as willows) are more heavily browsed than others (such as evergreen ericoids, resin birches, and Siberian alder (Alnus viridis fruticosa)). These differences in preference translate to variation in the degree to which herbivores regulate Arctic shrub growth and community structure. As shrubs expand in the Arctic, unpalatable, fast-growing species such as alder may have an advantage over more palatable species such as willows. Collectively, this research fills critical gaps in our knowledge of ptarmigan population ecology in Alaska, provides novel insights into how ptarmigan regulate their food source for their own benefit, and enhances our understanding of how herbivores influence shrub expansion in the Arctic.
    • Trophic dynamics of boreal lakes in a changing northern landscape: impacts of lake drying and forest fires

      Lewis, Tyler L.; Lindberg, Mark; Schmutz, Joel; Larsen, Amy; Jones, Jeremy; Heglund, Patricia (2015-05)
      The abundant lakes of northern latitudes are the primary breeding grounds for many waterbird species. In recent decades, temperatures in the north have increased by twice the global average. This substantial warming has caused lake drying and increased wildfires, both of which may impact waterbird habitats. Fires release nutrients locked in terrestrial resources, making them available for transport to lakes, while lake drying concentrates nutrients and other solutes into smaller water volumes. Increased nutrients may fundamentally alter ecosystem processes of lakes by changing the timing and abundance of phytoplankton blooms, which in turn affects the abundance of aquatic invertebrates - the primary food source for breeding waterbirds and their broods. I examined effects of forest fires and lake drying on ecosystems of Subarctic boreal lakes in the Yukon Flats, Alaska, documenting changes to (1) aquatic nutrient and chlorophyll concentrations, (2) aquatic invertebrate densities, and (3) abundance and occupancy of waterbirds. Nutrient, chlorophyll, and invertebrate levels were largely unaffected by a recent forest fire. This ecosystem stability transferred upward to waterbirds, as brood abundance was also unaffected by the fire. On drying lakes, nitrogen and phosphorus concentrations increased >200% and >100%, respectively, from the 1980s to present. At the same time, concentrations of 4 major ions increased, including increases of >500% for chloride and >100% for sodium. Nonetheless, chlorophyll levels, aquatic invertebrate abundance, and occupancy of waterbird broods were largely unaffected by these chemical changes on drying lakes. Overall, ecosystems of Yukon Flats were largely resilient to short-term effects of forest fires and rising chemical concentrations associated with lake drying. Moreover, this resilience spanned multiple trophic levels, from phytoplankton to aquatic invertebrates to waterbirds.
    • Trophic pathways supporting Arctic Grayling in a small stream on the Arctic Coastal Plain, Alaska

      McFarland, Jason John; Wipfli, Mark S.; Ruess, Roger; Arp, Chris D. (2015-05)
      Arctic Grayling (Thymallus arcticus) are widely distributed on the Arctic Coastal Plain (ACP) of Alaska, and are one of the few upper level consumers in streams, but the trophic pathways and food resources supporting these fish are unknown. Grayling migrate each summer into small beaded streams, which are common across the landscape on the ACP, and appear to be crucial foraging grounds for these and other fishes. I investigated prey resources supporting different size classes of grayling in a beaded stream, Crea Creek, where petroleum development is being planned. The specific objectives were to measure terrestrial prey subsidies entering the stream, quantify prey ingested by Arctic Grayling and Ninespine Stickleback (Pungitius pungitius), determine if riparian plant species affect the quantity of terrestrial invertebrates ingested by grayling, and determine if prey size and type ingested were a function of predator size. Results indicated that small grayling (< 15 cm fork length (FL)) consumed mostly aquatic invertebrates (caddisflies, midges, and blackflies) early in the summer, and increasing quantities of terrestrial invertebrates (wasps, beetles, and spiders) later in summer, while larger fish (> 15 cm FL) foraged most heavily on stickleback. Riparian plant species influenced the quantity of terrestrial invertebrates entering the stream, however these differences were not reflected in fish diets. This study showed that grayling can be both highly insectivorous and piscivorous, depending upon fish size class, and that both aquatic and terrestrial invertebrates, and especially stickleback, are the main prey of grayling. These results highlight the importance of beaded streams as summer foraging habitats for grayling. Understanding prey flow dynamics in these poorly studied aquatic habitats, prior to further petroleum development and simultaneous climate change, establishes essential baseline information to interpret if and how these freshwater ecosystems may respond to a changing Arctic environment.
    • Trophic pathways supporting juvenile chinook and coho salmon in the glacial Susitna River, Alaska: patterns of freshwater, terrestrial, and marine resource use across a seasonally dynamic habitat mosaic

      Rine, Kristin M.; Wipfli, Mark S.; Jones, Jeremy B.; Stricker, Craig A. (2015-12)
      In large, seasonally dynamic and spatially complex watersheds, the availability and relative importance of various food resources for stream fishes can be expected to vary substantially. While numerous studies have attempted to uncover the trophic linkages that support stream salmonids, much of these efforts have occurred at small scales that disregard variability of food resources inherent in lotic systems. This study aimed to determine large-scale patterns in the contributions of freshwater, terrestrial, and marine-derived food resources to juvenile Chinook and Coho salmon (Oncorhynchus tshawytscha and O. kisutch) in the large, glacially influenced Susitna River, Alaska. I quantified diet patterns both spatially, across different macrohabitat types positioned along a 169-km segment of the river corridor, and temporally, from June to October, using stable isotope and stomach content analyses. To further resolve energy pathways from basal carbon sources to juvenile salmon, I determined the relative roles of terrestrial organic matter and freshwater periphyton food sources to aquatic benthic invertebrate diets. The latter analysis showed that invertebrate consumers were more reliant on freshwater periphyton than on terrestrial organic matter. Bayesian stable isotope mixing models indicated that juvenile salmon in the middle Susitna River were, in turn, largely supported by freshwater invertebrate prey regardless of spatial and temporal context. The relative contribution of marine-derived prey (salmon eggs) to juvenile salmon diets was greatest in the fall within tributary mouth and off-channel macrohabitats during both years of the study. Terrestrial invertebrate prey contributions were generally greatest during mid-summer within all macrohabitat types sampled, however this pattern varied across years. No upstream to downstream diet pattern was apparent from the data. These results underscore the importance of freshwater energy pathways for sustaining juvenile Chinook and Coho salmon in the Susitna River and provide further spatial and temporal context for the importance of pulsed marine and terrestrial prey subsidies. As Pacific salmon stocks continue to decline, management and mitigation efforts should operate on knowledge gained from studies that encompass the largescale spatial and temporal variability inherent in riverine landscapes.
    • Trophic relationships in an Arctic marine foodweb and implications for trace element dynamics

      Dehn, Larissa-A (2005-08)
      Tissues of subsistence-harvested Arctic marine and terrestrial mammals and potential prey species were analyzed for isotopes of carbon and nitrogen and selected trace elements describing contaminant pathways in the food web. Feeding habits of ice seals were characterized using stable isotopes and gastric contents analysis. Bearded seals (Erignathus barbatus) relied on the benthic food chain. Zooplankton and fishes were significant prey for ringed seals (Phoca hispida), while fishes were the principal prey in spotted seals (Phoca largha). Gastric prey composition and isotope ratios varied with age and sex. Effects of age, trophic level, and prey prevalence on trace element concentrations in seal tissues were investigated. Most trace elements differed significantly in phocid tissues. Bearded seals had the highest cadmium (Cd) concentrations and spotted seals the lowest. This indicates a connection of Cd with invertebrate prey, while mercury (Hg), in particular the proportion of organic to total Hg (THg), accumulated in the piscivorous food web. Silver (Ag) showed possible association to benthic feeding habits. Altered trace element accumulation patterns were observed in compromised seals. Stable isotopes illustrated belugas (Delphinapterus leucas) occupied a higher trophic level than bowheads (Balaena mysticetus) and gray whales (Eschrichtius robustus). Trace element concentrations also differed significantly among these cetaceans. Observed relationships with age or length in species analyzed were complex and nonlinear rather than previously reported continuous bioaccumulation with age. Cd was similar in belugas and bowheads but lowest in gray whales. THg was highest in belugas and near detection limit in mysticetes, supporting the connection of Hg with fish and Cd with invertebrates. The hepatic selenium (Se ):THg ratio exceeded the frequently described equimolarity in all species. Se:THg molar ratios and tissue concentrations of zinc (Zn) may show promise as indicators of immune status and animal health. Polar bears (Ursus maritimus) feed on the highest trophic level, though Cd concentrations were either similar to, or significantly lower than those in belugas or ice seals. Conversely, THg increased significantly from seal to bear. Generally, trace elements in Alaska-harvested animals were lower than for other Arctic regions, and trace metal magnification in the Arctic food web was not significant.
    • Tsunami runup in U and V shaped bays

      Garayshin, Viacheslav Valer'evich; Гарайшин, Вячеслав Валерьевич; Rybkin, Alexei; Rhodes, John; Nicolsky, Dmitry (2013-08)
      Tsunami runup can be effectively modeled using the shallow water wave equations. In 1958 Carrier and Greenspan in their work "Water waves of finite amplitude on a sloping beach" used this system to model tsunami runup on a uniformly sloping plane beach. They linearized this problem using a hodograph type transformation and obtained the Klein-Gordon equation which could be explicitly solved by using the Fourier-Bessel transform. In 2011, Efim Pelinovsky and Ira Didenkulova in their work "Runup of Tsunami Waves in U-Shaped Bays" used a similar hodograph type transformation and linearized the tsunami problem for a sloping bay with parabolic cross-section. They solved the linear system by using the D'Alembert formula. This method was generalized to sloping bays with cross-sections parameterized by power functions. However, an explicit solution was obtained only for the case of a bay with a quadratic cross-section. In this paper we will show that the Klein-Gordon equation can be solved by a spectral method for any inclined bathymetry with power function for any positive power. The result can be used to estimate tsunami runup in such bays with minimal numerical computations. This fact is very important because in many cases our numerical model can be substituted for fullscale numerical models which are computationally expensive, and time consuming, and not feasible to investigate tsunami behavior in the Alaskan coastal zone, due to the low population density in this area
    • Two- and three-dimensional study of the Kelvin-Helmholtz instability, magnetic reconnection and their mutual interaction at the magnetospheric boundary

      Chen, Qinxue; Otto, Antonius; Watkins, Brenton; Sentman, Davis; Smith, Roger (1997)
      Magnetic reconnection and the Kelvin-Helmholtz (KH) instability regulate the transport of magnetic flux, plasma, momentum and energy from the solar wind into the magnetosphere. In this thesis, I use two-dimensional and three-dimensional MHD simulations to investigate the KH instability, magnetic reconnection, and their relationship. Two basic flow and magnetic field configurations are distinguished at the Earth's magnetopause: (1) configurations where the difference in plasma velocity between the two sides of the boundary $\Delta$v (velocity shear) is parallel to the difference of the magnetic field $\Delta$b (magnetic shear), and (2) configurations where the velocity shear is perpendicular to the magnetic shear. For configuration (1), either magnetic reconnection is modified by the shear flow, or the KH instability is modified by the magnetic shear and resistivity. The evolution of the basic configuration (2) requires three dimensions. In this case, both processes can operate simultaneously in different planes. If the KH instability grows faster initially, it can wrap up the current layer and thereby initiate a very fast and turbulent reconnection process. The resulting magnetic turbulence can provide the first explanation of often very turbulent structures of the magnetopause current layer. For the first time, it is quantitatively confirmed that the KH instability operates at the magnetospheric boundary at low latitudes.
    • Two-dimensional Bernstein-Greene-Kruskal modes in a magnetized plasma with kinetic effects from electrons and ions

      Tang, Han; Chung-Sang, Ng; Delamere, Peter; Newman, David (2020-05)
      Electrostatic structures are observed in various of space environments including the auroral acceleration region, the solar wind region and the magnetosphere. The Bernstein-Greene-Kruskal (BGK) mode, one of the non-linear solutions to the Vlasov-Poisson system, is a potential explanation to these phenomena. Specifically, two dimensional (2D) BGK modes can be constructed through solving the Vlasov-Poisson-Ampère system with the assumption of a uniform ion background. This thesis discusses the existence and features of the 2D BGK modes with kinetic effects from both electrons and ions. Specifically, we construct electron or ion BGK modes with finite temperature ratio between ions and electrons. More general cases, the electron-ion 2D BGK mode with the participation of both non-Boltzmann electron and ion distributions are constructed and analyzed as well.