• Stochastic reconstruction of snow microstructure from x-ray microtomography images

      Yuan, Hongyan (2007-08)
      The three-dimensional (3D) high-resolution digitized snow microstructure (pixel size 6 micron) was obtained by X-ray microtomography. The experimental result was verified by measuring the density of the snow sample. Statistical characteristics (porosity, local porosity, two-point correlation function) were extracted from cross-sectional images. The one-level-cut Gaussian random field model was used to stochastically reconstruct snow microstructure from X-ray microtomography images. Efficient computer programs were developed in MATLAB for the whole stochastic reconstruction procedure, including the numerical inversion of the correlation function and the generation of 3D large-scale Gaussian random fields by 3D inverse fast Fourier transform. The quality of the reconstruction was assessed by comparing the two-point correlation function and cross-sectional images.
    • Stock Structure And Environmental Effects On Year Class Formation And Population Trends Of Pacific Herring, Clupea Pallasi, In Prince William Sound, Alaska

      Brown, Evelyn Dale; Norcross, Brenda L. (2003)
      Fluctuating forage fish populations trigger large ecosystem responses in the North Pacific. A representative species, Pacific herring, Clupea pallasi, was chosen to model environmental effects on population fluctuations and recruitment with a case example in Prince William Sound (PWS), Alaska. A unique approach was used to (1) develop a spatially-explicit, life history-based conceptual stock model, (2) quantify population level effects of climatic trends, and (3) model key environmental factors affecting recruitment. Framed as a simulation model, the stock model was compartmentalized by life-history stages based on shared habitats and environmental forcing. Initial model conditions impacting year-class formation were adult size-at-age, spawn timing, location and spawner density, and conditions during egg incubation, all impacting a two-stage larval mortality rate. Larval survival probably dictates the extremes in year-class strength. Age1 abundance should reflect recruitment levels 2--3 yrs later, unless a predator pit exists. A metapopulation structure was proposed with at least two local population groupings with spatial complexity required to maintain stock levels. Herring abundance correlated with long-term climate trends supporting hypotheses of bottom up environmental forcing. Adult growth was oscillatory over a 13 yr period in phase with zooplankton production and climatic trends. Spawn timing occurred progressively earlier over the last 30 yr period with a concurrent regional spawn allocation shift and decrease in recruits per spawner. Incorporating local stock structure and local environmental variables into nonlinear herring recruitment models improved explanatory power over traditional models. Best-fit variables were eastern PWS SST, salinity, SST variance, and salinity variance from spring to fall. Eight critical life stage periods were defined based on the season and lag of the best-fitting varibles. Examining other variables in these critical periods led to defining potential key processes affecting year class formation. Allocation of spawn and age-3 recruits to metapopulation regions also impacted recruitment to PWS as a whole and these results supported the metapopulation theory. The results led to formulation of a new theory, entitled "opposing response", explaining the mechanism producing the observed pattern of alternating strong and week year class strengths in northern Pacific herring.
    • Stock structure and environmental effects on year class formation and population trends of Pacific herring, Clupea pallasi, in Prince William Sound, Alaska

      Brown, Evelyn D. (2003-12)
      Fluctuating forage fish populations trigger large ecosystem responses in the North Pacific. A representative species, Pacific herring, Clupea pallasi, was chosen to model environmental effects on population fluctuations and recruitment with a case example in Prince William Sound (PWS), Alaska. A unique approach was used to 1) develop a spatially-explicit, life history-based conceptual stock model, 2) quantify population level effects of climatic trends, and 3) model key environmental factors affecting recruitment. Framed as a simulation model, the stock model was compartmentalized by life-history stages based on shared habitats and environmental forcing. Initial model conditions impacting year-class formation were adult size-at-age, spawn timing, location and spawner density, and conditions during egg incubation, all impacting a two-stage larval mortality rate. Larval survival probably dictates the extremes in year-class strength. Age-1 abundance should reflect recruitment levels 2-3 yrs later, unless a predator pit exists. A metapopulation structure was proposed with at least two local population groupings with spatial complexity required to maintain stock levels. Herring abundance correlated with long-term climate trends supporting hypotheses of bottom up environmental forcing. Adult growth was oscillatory over a 13 yr period in phase with zooplankton production and climatic trends. Spawn timing occurred progressively earlier over the last 30 yr period with a concurrent regional spawn allocation shift and decrease in recruits per spawner. Incorporating local stock structure and local environmental variables into nonlinear herring recruitment models improved explanatory power over traditional models. Best-fit variables were eastern PWS SST, salinity, SST variance, and salinity variance from spring to fall. Eight critical life stage periods were defined based on the season and lag of the best-fitting varibles. Examining other variables in these critical periods led to defining potential key processes affecting year class formation. Allocation of spawn and age-3 recruits to metapopulation regions also impacted recruitment to PWS as a whole and these results supported the metapopulation theory. The results led to formulation of a new theory, entitled 'opposing response', explaining the mechanism producing the observed pattern of alternating strong and week year class strengths in northern Pacific herring.
    • Stopover ecology of semipalmated sandpipers (Calidris pusilla) at coastal deltas of the Beaufort Sea, Alaska

      Churchwell, Roy Thomas; Powell, Abby; Gens, Rudiger; Dunton, Kenneth; Blanchard, Arny; Hundertmark, Kris; Hollmen, Tuula (2015-12)
      Avian migration is one of the wonders of the natural world. Stored fats are the main source of nutrients and fuel for avian migration and it is assumed the fat deposition at stopover sites is a critical component of a successful migration. Stopover sites are crucial in the successful migration of many birds, but particularly for arctic-breeding shorebirds that migrate long distances from breeding to wintering grounds. Despite the importance of stopover sites, it is often difficult to determine the importance of these sites to migrating shorebirds. I investigated three aspects of stopover ecology of Semipalmated Sandpipers (Calidris pusilla) foraging at coastal deltas on the Beaufort Sea coast, Alaska. First, I quantified the spatial and temporal distribution and abundance of the benthic macroinvertebrate community living within the mudflats. I found that there were two ecological groups of macroinvertebrates using river deltas, one originated in terrestrial freshwater habitats and most importantly could withstand freezing in delta sediments over the winter, and the other originated from the marine environment, could not withstand freezing and had to migrate to intertidal habitats each summer from deeper water areas that did not freeze over the winter. Stable isotope analysis allowed me to describe the origin of carbon consumed by invertebrates in intertidal habitats. I predicted freshwater invertebrates would consume terrestrial carbon, and marine invertebrates would consume marine carbon, but I found that both groups utilized the same carbon, which was a mixture of terrestrial and marine sources. My second research question determined the importance of delta foraging habitat for fall migrating Semipalmated Sandpipers. I mapped the temporal distribution and abundance of birds and quantified this relationship to invertebrate distribution and abundance. I researched fattening rates of shorebirds by measuring triglycerides in the blood of shorebirds I captured. I hypothesized that triglyceride levels would be correlated with invertebrate abundance and related to habitat quality; however, I found no relationship. Next, I determined shorebird dependence on marine invertebrates using the stable isotope signature of invertebrates and shorebird plasma. I found that shorebird abundance was associated with invertebrate abundance, and that shorebirds did feed almost exclusively on invertebrates from the mudflats later in the season. I did not find a significant difference in habitat quality among the deltas, although more birds were counted at the Jago Delta than at the other two deltas. Finally, I researched the question of how change in water levels due to lunar tides and storm surge events impacted the availability of foraging habitat. I assessed the phenology of Semipalmated Sandpiper migration and how this related to the availability of forage based on abundance, distribution, and accessibility of macroinvertebrates. There was a significant decline in the calories available for forage when there was a lunar tide and when there was a storm surge event. The most foraging habitat was available late in the migration period, while the peak in Semipalmated Sandpiper migration was early in the period. Late in the season there is also a greater chance of a storm surge event occurring due to the lack of sea ice during that period. In summary, I found Beaufort Sea deltas were more diverse than I expected both in macroinvertebrate community and in how shorebirds use the available foraging habitat. After completing this research I feel this habitat is critical to Semipalmated Sandpiper migration; however, there is a real risk of extensive change to these deltas due to future warming with negative consequences for shorebirds.
    • Stories Find You: Narratives Of Place In A Central Yup'ik Community

      Cusack-Mcveigh, Holly M.; Morrow, Phyllis (2004)
      Yup'ik narratives of place make powerful statements about the health or illness of the world. Such stories illustrate how the land itself is responsive to human thought and action. The land, in essence, is a being among beings, and a particularly powerful and sensitive one. The sentient world responds to joy as well as to sorrow. This is an essential aspect of place in southwestern Alaska. In Hooper Bay, stories confer both personal and political power, allowing people to instruct others about dangerous situations, and indirectly make statements about events that are otherwise unspoken for fear of "making bad things worse." Narrative discourse of place empowers people who have experienced a history of domination and control. Man-made places, like the land, are also barometers of change. Stories allow people to speak about unspeakable tragedies that reflect the tensions of their relationships with outsiders. Other stories define and exclude those outsiders, such as missionaries and teachers, who are particularly associated with the institutions that represent domination. I argue, then, that for Yupiit in Hooper Bay, stories are not simply symbolic expressions but are active in social life. As Elsie Mather says, "Storytelling is part of the action of living" (Morrow and Schneider 1995:33).
    • The story of E. Lyman Graves: a dispassionate exploration of a hard luck Harry who also happened to be my grandpa

      Uzzell, Gwen S. (Wendy); Farmer, Daryl; Cole, Terrance; Brightwell, Gerri (2014-12)
      This story follows the life of E. Lyman Graves for a quarter of a century and connects his personal story to social change during that time. At the very beginning of the 1930's LymanGraves had a pioneering vision and he yearned to seek his personal fate in the frontier of the Territory of Alaska. This time period reflects the pressures on Lyman related to The Great Depression, World War II, and federal influence in the economics of individuals in the Territory of Alaska. Lyman wrote a two page timeline as a retrospective of his life around 1955, titled "Twenty-five Years of Progress", and defined his efforts as "success" or "failure." Through the use of family story, personal, historical and public document research, this work is an exploration of Lyman's challenges. Authorial reflection as Lyman's granddaughter reveals understanding that is acquired through this process. Through the use of Lyman's personal story the reader will have a new understanding of how an individual is influenced not just by their own decisions, but also by events outside of their ability to control.
    • Strategies for applying active seismic subglacial till characterization methods to valley glaciers

      Zechman, Jenna M.; Truffer, Martin; Larsen, Christopher F.; Coakley, Bernard J.; Amundson, Jason M. (2017-05)
      Subglacial materials play an important role in glacier dynamics. High pore-pressure, high porosity (dilatant) tills can contribute to high basal motion rates by deforming. Amplitude Variation with Angle (AVA) analysis of seismic reflection data uses the relationship between basal reflectivity and reflection incidence angle to characterize the subglacial material. This technique can distinguish between dilatant tills and less-porous, non-deforming (dewatered) tills due to their distinctive reflectivity curves. However, noise from crevasses and glacier geometry effects can complicate reflectivity calculations, which require a source amplitude derived from the bed reflection multiple. We use a forward model to produce synthetic seismic records, including datasets with and without visible bed reflection multiples. The synthetic data are used to test source amplitude inversion and crossing angle analysis, which are amplitude analysis techniques that do not require absolute reflectivity calculations. We and that these alternative methods can distinguish subglacial till types, as long as reflections from crevasses do not obscure the bed reflection. The forward model can be used as a planning tool for seismic surveys on glaciers, as it can predict AVA success or failure based on crevasse geometries from remote sensing data and glacier bed geometry from radar or from a worst-case-scenario assumption of glacier bed shape. Applying lessons from the forward model, we perform AVA on a seismic dataset collected from Taku Glacier in Southeast Alaska in March 2016. Taku Glacier is a valley glacier thought to overlay thick sediment deposits. It has been the subject of numerous studies focusing on its ice-sediment interactions. Our analysis indicates that Taku Glacier overlies unconsolidated tills with porosity values greater than 33 %, though because of uncertainties due to the lack of a bed reflection multiple, it is possible that the tills are not dilatant.
    • Strategies for Chinese international students to overcome the challenges of studying in the United States

      Chen, Yuerong; Simpson, Joni; McMorrow, Samantha; Renes, Susan L. (2015)
      Using current research and literature, this project discusses the challenges that Chinese international students may have while they experience cultural adjustment in the United States. In addition, this project also examines strategies for Chinese international students to smooth the cultural transition during their stay in the United States. There is research about Chinese immigrants' cultural transition and international students' transitional periods. However, there is a very limited amount of research specifically on Chinese international students' cultural adjustment in the United States. Educating the Chinese international students, educators and counselors in international institutions about the challenges of cultural transition and the strategies to overcome the challenges may potentially help these students when they arrive in the United States. The application of this project is a presentation to international office personnel, counselors who work at university counseling centers and faculty members who have a large population of Chinese international students in their classrooms. The project also offers recommendations for any professionals who work to help Chinese international students to succeed in their study in a new educational system and a new culture.
    • Stratigraphic variation across a Middle Devonian to Mississippian rift-basin margin and implications for subsequent fold and thrust geometry, northeastern Brooks Range, Alaska

      Anderson, Arlene Verona; Wallce, Wesley K.; Coney, Peter J.; Crowder, R. Keith; Mull, C. G.; Watts, Keith F. (1993)
      A stratigraphic record from the eastern Brooks Range, Alaska, is interpreted to represent erosion and deposition of syn-rift and post-rift terrigenous clastic rocks across a Middle Devonian - Mississippian rift-basin margin. Middle Devonian - Mississippian terrigenous clastic rocks unconformably overlie complexly deformed Romanzof chert and constrain the age of latest mid-Paleozoic contractional deformation to pre-Middle Devonian time. The succession forms an abruptly southward-thickening basin-margin wedge characterized by abrupt facies changes, local evidence of active tectonism, multiple unconformities merging northward toward the basin margin, locally derived clastic deposits. The oldest deposits of this wedge are Middle - Upper(?) Devonian shallow-marine to alluvial-fan deposits (Ulungarat formation). Algal limestone with intercalated terrigenous clastic deposits and plant fossils (Mangaqtaaq formation) locally overlies the Ulungarat formation. The Ulungarat and Mangaqtaaq formations are interpreted to record syn-rift deposition. Coastal-plain to marine deposits of transgressive Kayak Shale overlie and intertongue with retrogradational Kekiktuk Conglomerate, recording coastal retreat and drowning of low-energy paleoshoreline. Deposits of the retrogradational Kekiktuk fluvial system thin and fine upward and to the north, reflecting depositional onlap of the basin-margin high. Kekiktuk Conglomerate and Kayak Shale are interpreted to overlie the post-rift unconformity and record the beginning of thermal subsidence. This stratigraphic succession provides a spatial and genetic link between structurally separated, stratigraphically distinct rocks of the Endicott Group. Thick, allochthonous rocks to the south record progradation and eventual retrogradation of a basin-filling wedge, whereas thin, autochthonous rocks to the north record transgressive overlap of the basin-margin sediment source area. The structural boundary between the north-central and northeastern Brooks Range coincides with the mid-Paleozoic rift-basin margin. North-vergent duplexes beneath the Kayak Shale consist of horses in the Middle Devonian-Mississippian clastic wedge to the south and thicker horses in pre-Middle Devonian rocks to the north. Above the Kayak Shale, north-vergent thrust-truncated folds are succeeded northward by detachment folds. These structural characteristics reflect the combined influence of abrupt lateral changes in stratigraphy across the rift-basin margin and stratigraphically controlled vertical variations in structural behavior.
    • Stratigraphy, major oxide geochemistry, and ⁴⁰Ar/³⁹Ar geochronology of a tephra section near Tok, Alaska

      Schaefer, Janet (2002-12)
      Stratigraphy, major oxide geochemistry, and ⁴⁰Ar/³⁹Ar geochronology are used to describe a tephra section near Tok, Alaska, north ofthe Wrangell volcanic field. This tephra section contains seven type II tephras and two type I tephras. Hornblende in a tephra near the base of the section was dated at 627.5 +/- 47.7 ka using the ⁴⁰Ar/³⁹Ar method of single-step total laser fusion. This hornblende-rich tephra is here named the Tetlin Tephra. The age and composition of the Tetlin Tephra indicates that it is likely the product of an explosive phase of activity of Mount Drum volcano, where petrologically similar domes were emplaced 650 to 400 ka. Two widespread tephras, the Old Crow Tephra and the Sheep Creek Tephra are also found at this site. The documentation of these tephras combined with the lithologic descriptions provide valuable information for interpretation of the Pleistocene history of this part of interior Alaska.
    • Stratigraphy, structure, and origin of the Mendeleev Ridge from bathymetry, controlled source seismic, and gravity observations

      Dove, Dayton W. (2007-05)
      Multi-channel-seismic (MCS), seismic refraction, and gravity data collected over the Mendeleev Ridge have been processed and interpreted to describe the crustal style of the ridge, as well as the structural and depositional history. These results provide constraints on the origin of the ridge, and the tectonic evolution of the Amerasian Basin. MCS images reveal two primary sediment sequences separated by an unconformity that persists across the entire Mendeleev Ridge. The basement and lower sediment sequence exhibit pervasive normal faulting and the regional unconformity is interpreted to mark the end of extensional deformation. Modeling of the seismic refraction data reveals an upper crustal velocity structure consistent with either a volcanic rifted continental margin, or an oceanic plateau. Gravity anomalies collected along the MCS lines can be reproduced with models containing bathymetry, sediment and basement horizons, and a crust of 2.86 g/cm³. This result is consistent with homogeneous, mafic crust. Comparing the velocity and density structures of the Mendeleev Ridge to the Alpha Ridge suggests they are contiguous and share a common geologic origin. Three tectonic models are presented for the origin of the Alpha Mendeleev Ridge (AMR) that satisfy constraints set by this and previous studies.
    • Straying, stress, and potential for reproductive interactions between hatchery-produced and wild chum salmon (Oncorhynchus keta) in Southeast Alaska

      McConnell, Casey John; Westley, Peter; McPhee, Megan; Atkinson, Shannon; Oxman, Dion (2017-12)
      Approximately 1.5 billion juvenile hatchery-produced Pacific salmon (Oncorhynchus spp.) are currently released each year into Alaskan waters with goals of enhancing important fisheries and minimizing detrimental impacts on wild stocks. As the abundance of hatchery-produced salmon has increased, so have concerns about hatchery-origin strays entering wild systems and interactions with wild individuals on the spawning grounds. The influx of non-native strays and their associated fitness-related traits can reduce the resilience and productivity of recipient wild stocks, and is likely to be most deleterious when disparities in population sizes and heritable phenotypic characteristics between wild and hatchery fish exist. Thus, understanding the ecological and life-history mechanisms that regulate gene flow between hatchery and wild populations is crucial for conservation and management strategies in areas where hatchery enhancement is common. Currently, the ecology of strays on the spawning grounds and proximate physiological factors associated with straying (e.g., stress) are not well known. In this thesis I examine, 1) differences and similarities in several fitness-related phenotypic traits between naturally produced (presumably wild local individuals) and stray hatchery-produced chum salmon (Oncorhynchus keta) that died on the spawning grounds of Sawmill Creek, a small watershed near Juneau, Alaska, and 2) physiological differences in cortisol concentrations and the frequency of crystalline (vaterite) structure of otoliths between straying and correctly homing salmon. Hatchery-strays comprised 51.4% of the adult chum salmon that returned to Sawmill Creek during the 2015 spawning season. Hatchery males and females returned approximately seven days later, were consistently smaller (10% for males, 6% for females) in length, and younger on average than their naturally-produced counterparts. Additionally, hatchery-produced females lived fewer days on the spawning grounds during the spawning season, and retained a higher proportion of their eggs than did naturally produced females. To explore the potential role of stress on straying, I compared cortisol samples and frequency of vaterite formation in otoliths among groups of hatchery-produced fish that homed to the hatchery, hatchery-produced fish that strayed to Sawmill Creek, and naturally produced chum salmon that presumably homed to Sawmill Creek. No significant differences in cortisol concentration were found among any groups, though differences between the sexes were detected. Males of all groups had significantly lower cortisol concentrations than did females. No differences in frequency of vaterite occurrence were found between hatchery-stray and hatchery-home groups, though both hatchery groups were higher than naturally produced groups, which is consistent with findings of other studies. Thermal marking while at the hatchery during early development was not associated with vaterite formation, and no difference in frequency of vaterite formation was observed among groups of varying mark intensities. Overall, these results revealed there was ample opportunity for reproductive interactions between stray hatchery-produced and naturally produced chum salmon in Sawmill Creek during the 2015 spawning season, and consistent differences in phenotypic traits suggests the potential for gene flow to alter population-level phenotypic variation. However, despite the potential for gene flow, these results also reveal potential barriers to introgression and indicate that at least some of the presumed locally adapted traits of the natural stock remain intact. It remains unknown what the characteristics of the wild stock were prior to regional hatchery production and the extent to which the traits of this population are reflections of genetic differences between the hatchery and wild groups or phenotypic plasticity. To the extent these results are generalizable, observed differences in fitness-related traits between naturally produced and stray hatchery-produced fish may underlie the reduced reproductive success often reported in the literature. There were no differences in cortisol concentrations and frequency of vaterite occurrence between hatchery chum salmon that strayed and those that homed correctly, and the frequency of vaterite occurrence of hatchery chum salmon did not change as thermal mark intensity increased, which suggests that thermal marking may not directly alter homing ability of adults or development of juveniles, at least via otolith formation. Despite not having an effect on straying, the consistent findings of higher frequency of vaterite occurrence in hatchery-produced fish compared to naturally produced counterparts highlight the need for future work to uncover the causal underlying mechanisms and implications of vaterite on survival of the 1.5 billion salmon released each year in Alaskan waters.
    • Strengthening cultural identity through Iļisaġvik College's Iñupiaq studies program: reconstruction and the Iñupiaq studies framework

      Aamodt, Jerica S.; Ramos, Judith D.; Stern, Charlene B.; Kaplan, Lawrence D. (2019-05)
      This program proposal is for the Iñupiaq Studies Program at Iḷisaġvik College. Iḷisaġvik College is located in Utqiaġvik, the northernmost village on the North Slope of Alaska. This proposal is intended to guide the future restructuring of the Iñupiaq Studies Program. The project was informed by interviews conducted with seventeen key individuals as well as the Iñupiaq Learning Framework created by the North Slope Borough School District. The proposal includes a mission, words of wisdom for the Iñupiaq Studies Framework, revised Iñupiaq Studies program outcomes, course descriptions, certificate and degree proposals, study plans, a sample course syllabus, and a sample course origination form.
    • Strengths-based analysis of student success in online courses

      Gering, Carol; Sheppard, Dani'; Morotti, Allan; Adams, Barbara; Renes, Susan (2017-08)
      The purpose of this research was to increase understanding of post-secondary student success in online courses by evaluating a contextually rich combination of personal, circumstantial, and course variables. A strengths-based perspective framed the investigation. Mixed-method data were collected and analyzed sequentially in three phases: two phases of quantitative collection and analysis were followed by qualitative interviews and comprehensive analysis. The study first used logistic regression to analyze existing data on more than 27,000 student enrollments, spanning a time period of four academic years. The second phase of research enhanced the modeling focused on a subset of the total population; students from a single semester were invited to complete an assessment of non-cognitive attributes and personal perceptions. Between the two phases, 28 discreet variables were analyzed. Results suggest that different combinations of variables may be effective in predicting success among students with varying levels of educational experience. This research produced preliminary predictive models for student success at each level of class standing. The study concluded with qualitative interviews designed to explain quantitative results more fully. Aligned with a strengths-based perspective, 12 successful students were asked to elaborate on factors impacting their success. Themes that emerged from the interviews were congruent with quantitative findings, providing practical examples of student and instructor actions that contribute to online student success.
    • Stress and surface deformation due to earthquakes and volcanoes in Alaska

      Lu, Zhong; Wyss, Max; Carsey, Frank D.; Christensen, Douglas H.; McNutt, Stephen R.; Palpan, Hans (1996)
      A new method has been developed to investigate stress homogeneity along plate boundaries based on the cumulative misfit between the theoretical and observed slip directions on fault planes of individual earthquake focal mechanisms, calculated using assumed stress tensors. This method allows identification of volumes with uniform stress directions, suitable for inversion for stress orientations, with a minimum of computing time. The method also affords an alternative estimate of the significance of differences in stress directions. Applying this method in the Aleutians, we found that the Aleutian plate boundary is segmented based on the observations that the misfits are relatively constant within segments of uniform stress orientation but that they change abruptly at segment boundaries. The segmentation boundaries correspond to fracture zones, boundaries of asperities and ends of aftershock zones of great earthquakes. Applying this method in the Alaska Wadati-Benioff Zone (WBZ), we depict the stress field at two different scales. The stress directions measured by large earthquakes (Ms ~ 5) are homogeneous, with extension down dip and greatest compression along strike. The unusual orientation of the greatest principal stress is attributed to the bend of the slab under central Alaska, which generates compressive stresses along strike. The stress directions measured by small earthquakes $\rm(M\sb{L}\sim3),$ reveal a great deal of heterogeneity as a function of depth and along strike, although they show a trend that confirms the overall stress field derived from the large events. We propose that the ratio of the dimensions of the stress field (sensed by earthquakes) to the rupture dimensions is about 20 to 50. Using ERS-1 Synthetic Aperture Radar (SAR) interferometry, we have constructed high resolution topographic maps, and detected several centimeters of uplift that accumulated during two years (1993-1995) at two neighboring volcanoes in Alaska's Katmai National Park: New Trident vent and Novarupta Dome. From the uplift gradient we estimate the depth of the pressure source, presumably a magma body or hydrothermal system, under New Trident volcano to be 2 km. These are the first observations of volcanic deformation in this area and will be helpful to characterize the volcano's structure and behavior.
    • Stress physiology in breeding seabirds: coping with a variable food supply

      Shultz, Michael T. (2007-05)
      Recent life-history models predict that long-lived seabirds, breeding in variable food environments, should exhibit flexible reproductive effort. However, these models assume that food availability fluctuates unpredictably and birds are unable to match reproductive output perfectly to food abundance. However, the degree to which predictable changes in food availability versus stochastic ones influence reproductive performance of seabirds is unknown. In this study we examined the role of food abundance prior to egg-laying versus food abundance during chick rearing for determining reproductive output of two species of high latitude nesting seabird; the Black-legged Kittiwake (Rissa tridactyla) and Common Murre (Uria aalge). We also examined the role of stress hormones in facilitating flexible reproductive effort. Here we demonstrate for the first time that initial reproductive performance (e.g., number of eggs laid, timing of egg-laying) is related to food abundance prior to egg-laying and not to anticipated food abundance during chick-rearing. We also demonstrate that stress hormones facilitate flexible reproductive effort-the failure of adults to increase stress hormone concentrations in response to an acute food shortage resulted in physiological and reproductive costs. Taken together, these results demonstrate that increases in stress hormone concentration are an adaptive response to breeding under variable foraging conditions.
    • Stress reduction support for new teachers in rural Alaska

      Wray, Tapiana; Renes, Susan L.; Topkok, Sean A.; Morton, James (2018-05)
      Teachers experience many different facets of stress that directly affect attrition and burnout in the profession. While the research on teacher retention and attrition in Arctic Alaska is limited, that does not diminish the impact felt by the students, the community, and the state. Teacher attrition and retention is a multidimensional issue that could benefit from an intervention created on behalf of administrators, communities, and the teachers themselves. This paper presents one approach to address teacher retention: teachers and administrators incorporating stress reduction techniques into their lives have been proven successful in reducing teacher stress to mitigate teacher burnout.
    • Stress-corrosion cracking susceptibility of polystyrene/TiO₂ nanocomposite coated thin-sheet aluminum alloy 2024-T3 with 3.5% NaCl

      Baart, Brian V.; Chen, Cheng-fu; Ahn, Il Sang; Zhang, Lei (2020-05)
      This thesis reports an investigation into the performance of nanocomposite coatings, which consist of titanium dioxide nanoparticles within a polystyrene matrix, on the resistance to stress-corrosion cracking (SCC). The coatings are applied to compact tension specimens subject to conditions that promote failure by (SCC). It has been well documented in the literature that high-strength aluminum alloys such as 2024- T3 are prone to SCC when exposed to chloride media and sufficient levels of stress. The use of polymerbased nanocomposite coatings to protect aluminum alloy 2024-T3 has recently been shown to exhibit anticorrosion properties, which has been motivation for further study. The performance of such coatings on SCC is thus investigated here, using a fracture mechanics approach with compact tension specimens. The specimens are subject to a slow strain rate test using a constant displacement rate of 1.25 nm/s while exposed to periodically supplied 3.5% wt. sodium chloride solution. Measurements of load and crackmouth opening displacement data are recorded from the specimen throughout the test and used to characterize the response of the material to the applied mechanical loading in a corrosive environment. Results from the methods used herein showed a quantitative influence derived from the test results for several criteria of interest such as maximum load, time-to-failure, and fracture toughness. In total, four different coatings were applied; three with different titanium dioxide nanoparticle aspect ratios, and one without any titanium dioxide nanoparticles present in the polystyrene matrix. Characterization of the results showed that the shape of the titanium dioxide nanoparticle is a dominant factor that influences the susceptibility of aluminum alloy 2024-T3 to SCC.
    • Structural geology of the Big Bend anticline, Brooks Range foothills, Alaska

      Sanders, Cheryl M.; Wallace, Wesley; Prakash, Anupma; Hanks, Catherine (2014-12)
      Big Bend anticline is near the northern edge of the Brooks Range foothills of northern Alaska. The structure of the foothills is a low-taper triangle zone or passive-roof duplex within Brooks Range foreland basin deposits. The dominant structures are detachment folds locally cut by thrust faults and Big Bend anticline is one of these. This research combines detailed surface mapping (1:25,000) with interpretation of aerial photos and satellite imagery of the Big Bend anticline and seismic reflection data from the Umiat anticline to reconstruct its surface and subsurface geometry. The research area surrounds the Big Bend of the Chandler River and covers approximately 10 km². The mechanical stratigraphy of the area consists of the competent Nanushuk sandstones between two incompetent units-the overlying Seabee and underlying Torok shales. The structure of the area consists of an east-trending anticline with a hinge that branches westward into two open, broad anticlines and an intervening syncline. A forethrust near the southern hinge and a backthrust near the northern hinge have broken through the anticline west of the branch point. Subsurface data of Umiat anticline combined with surface projected cross sections from the study area provide an analog of the subsurface structure in the Big Bend area. These cross sections show gentle anticlines separated by flat bottomed synclines in competent Nanushuk Formation sandstone. The anticlines overly Torok Formation thickened by north vergent folds and thrust faults above a detachment zone. Collectively, these structures form a low-taper triangle zone. Cross section restoration suggests more shortening in the Torok duplex than in the overlying folds and breakthrough faults. Results of this research provide an analog for other anticlines in the region that are currently the focus of oil and gas exploration.