Now showing items 21-40 of 8536

    • Engineering education professional development for teachers in the Delta Greely School District

      Dougherty, Jennifer; Kaden, Ute; Thorsen, Denise; Larson, Angela (2019-12)
      Over the last two decades engineering has become a new focus in many science curricula, in part due to the emphasis on STEM (science, technology, engineering, and math) education. Most teachers lack training or education in engineering and are not adequately prepared to implement effective engineering education. This research identifies the needs and constraints of one district, the Delta Greely School District (DGSD), in Delta Junction, AK (approximately 750 students district-wide). Surveys were distributed to fifty teachers and five administrators to gather information on attitudes and beliefs surrounding engineering education. Focus groups were conducted with teachers and administrators to better understand the needs of the teachers and the district as well as the perceived obstacles that currently limit engineering education in the classroom. The results were used to create recommendations for professional development to improve and increase engineering education in the district's K-5 classrooms. The final recommendations focus on a professional development plan and professional development delivery modes. Results of the study support two levels of professional development: one introductory level for teachers unfamiliar or not comfortable with engineering education and one for teachers who are comfortable with the subject and would like to improve their teaching. It was also determined that specific teaching resources (i.e., lesson plans and curricular material) should be part of professional development, and that professional development solution should be designed to complement the specific district-provided resources and curricula.
    • The role of tundra vegetation in the Arctic water cycle

      Clark, Jason A.; Tape, Ken; Schnabel, William; Euskirchen, Eugénie; Ruess, Roger (2019-12)
      Vegetation plays many roles in Arctic ecosystems, and the role of vegetation in linking the terrestrial system to the atmosphere through evapotranspiration is likely important. Through the acquisition and use of water, vegetation cycles water back to the atmosphere and modifies the local environment. Evapotranspiration is the collective term used to describe the transfer of water from vascular plants (transpiration) and non-vascular plants and surfaces (evaporation) to the atmosphere. Evapotranspiration is known to return large portions of the annual precipitation back to the atmosphere, and it is thus a major component of the terrestrial Arctic hydrologic budget. However, the relative contributions of dominant Arctic vegetation types to total evapotranspiration is unknown. This dissertation addresses the role of vegetation in the tundra water cycle in three chapters: (1) woody shrub stem water content and storage, (2) woody shrub transpiration, and (3) partitioning ecosystem evapotranspiration into major vegetation components. In Chapter 1 I present a method to continuously monitor Arctic shrub water content. The water content of three species (Salix alaxensis, Salix pulchra, Betula nana) was measured over two years to quantify seasonal patterns of stem water content. I found that spring uptake of snowmelt water and stem water storage was minimal relative to the precipitation and evapotranspiration water fluxes. In Chapter 2, I focused on water fluxes by measuring shrub transpiration at two contrasting sites in the arctic tundra of northern Alaska to provide a fundamental understanding of water and energy fluxes. The two sites contrasted moist acidic shrub tundra with a riparian tall shrub community having greater shrub density and biomass. The much greater total shrub transpiration at the riparian site reflected the 12-fold difference in leaf area between the sites. I developed a statistical model using vapor pressure deficit, net radiation, and leaf area, which explained >80% of the variation in hourly shrub transpiration. Transpiration was approximately 10% of summer evapotranspiration in the tundra shrub community and a possible majority of summer evapotranspiration in the riparian shrub community. At the tundra shrub site, the other plant species in that watershed apparently accounted for a much larger proportion of evapotranspiration than the measured shrubs. In Chapter 3, I therefore measured partitioned evapotranspiration from dominant vegetation types in a small Arctic watershed. I used weighing micro-lysimeters to isolate evapotranspiration contributions from moss, sedge tussocks, and mixed vascular plant assemblages. I found that mosses and sedge tussocks are the major constituents of overall evapotranspiration, with the mixed vascular plants making up a minor component. The potential shrub transpiration contribution to overall evapotranspiration covers a huge range and depends on leaf area. Predicted increases in shrub abundance and biomass due to climate change are likely to alter components of the Arctic hydrologic budget. The thermal and hydraulic properties of the moss and organic layer regulate energy fluxes, permafrost stability, and future hydrologic function in the Arctic tundra. Shifts in the composition and cover of mosses and vascular plants will not only alter tundra evapotranspiration dynamics, but will also affect the significant role that mosses, their thick organic layers, and vascular plants play in the thermodynamics of Arctic soils and in the resilience of permafrost.
    • Effects of target properties on the formation of lunar impact craters in the simple-to-complex transition

      Chandnani, Mitali; Herrick, Robert; Kramer, Georgiana; Larsen, Jessica; Dehn, Jonathan (2019-12)
      The transition from simple to complex crater morphology in impact craters with increase in crater size has been modelled and observed in planetary bodies across the Solar System. The transition diameter depends upon the strength and gravity of the planetary body. On the Moon, this transition takes place over a diameter range of several kilometers. This range spans a diversity of crater morphologies including simple, transitional and complex craters. The diameter range of 15 20 km falls within the lunar simple-to-complex transition. All other impactor properties held constant, the 15-20 km range corresponds to a factor of three in the magnitude of impact kinetic energy. I conducted detailed geologic investigation of 244 well-preserved craters in this diameter range to elucidate the root causes of morphological variations. I used panchromatic data for observing crater and surface morphology, Digital Elevation Models (DEMs) for evaluating crater morphometry and topographic variation of pre-impact terrain, near-infrared (NIR) bands for determining the composition of crater cavity and surrounding terrain, thermal infrared bands for examining rock abundance, and Synthetic Aperture Radar (SAR) data for detecting impact melt deposits. The results of my investigation indicate that the morphological differences are primarily governed by target properties. Simple craters are confined to the highlands, and the mare are more abundant in complex craters. The mare are composed of solidified basaltic lava flows interlayered with regolith. The layering creates vertical strength heterogeneities that drive the destabilization of the transient cavity and its collapse, causing the transition to complex craters at smaller diameters in the mare. The non-layered highlands are more vertically homogeneous in strength and therefore favor simple crater formation. Eight atypically deep simple craters were identified in the highlands near the mare highlands boundaries, the most porous terrains on the lunar surface. After detailed examination of these craters in comparison to their normal-depth counterparts, I conclude that part of the energy from impact on porous target was spent in target compaction. The higher the porosity of the target, the deeper the crater and greater its volume, due to increased compaction. That only some of the craters in the high porosity terrains are deep suggests that those craters are on locally extreme-high porosity patches. However, an unusual impactor property, such as a high velocity impact, a high density impactor, or a near-vertical impact may also be a contributor. The simple craters in the highlands were observed to be located on flat or gradually sloping surfaces or degraded rims and terraces of pre-existing craters. Most craters with localized slumps superpose sharp topographic breaks such as well-developed rims and terraces of pre-existing craters. However, the topographic settings of 35% of the craters with localized slumps appeared to be similar to that of the simple craters. More detailed topographic study of the pre-impact terrains of these two morphologies revealed that the pre-impact terrains of 35% of the craters with localized slumps are gradually sloping or have subtle topographic breaks. Both sharp and subtle breaks are characterized with similar sloping directions as the adjacent craters' walls, which led to over steepening of the transient cavity walls around this part of the rim and their collapse, thereby causing the accumulation of localized slumped material. Several simple craters were also identified to have formed on pre-impact topographic breaks. However, the simple craters' walls that superpose these breaks were observed to be sloping in directions opposite to that of the breaks. So the ejecta around these walls was deposited along the break slopes, and thus syn-impact mass wasting occurred external (and not internal) to the crater cavity.
    • Foliage and winter woody browse quality of an important Salix browse species: effects of presence of alder-derived nitrogen and winter browsing by Alaskan moose (Alces alces gigas)

      Burrows, Justin; Kielland, Knut; Wagner, Diane; Ruess, Roger (2019-12)
      In this study, I examined the relationship between soil nitrogen and winter browsing by moose on the physical and chemical characteristics of Salix alaxensis; specifically stem production, leaf nutritional quality, and stem nutritional quality of tissues produced the following growing season. I measured stem biomass production the 2013 growing season and offtake during the 2013-2014 winter browsing season at 16 sites on the Tanana River floodplain near Fairbanks, Alaska. I revisited the sites the following summer and autumn to assess regrowth and to collect soil, foliage, and stem samples. Browsing intensity and total soil nitrogen were similar in sites with and without alder, a nitrogen-fixing shrub. Soil nitrogen and browsing intensity were not consistently related to changes in stem or leaf quality, although there were significant relationships in some subsets. Soil nitrogen and browsing intensity also did not have consistent relationships with stem regrowth the following growing season. These results indicate that S. alaxensis growing in this system are able to recover from a naturally broad range of browsing utilization, including very high levels of offtake, and continue to produce nutritious leaves and stems.
    • Developing sociolinguistic awareness through a digital lexicon project in a fifth grade classroom in rural Alaska

      Boynton, Julia F.; Martelle, Wendy; Siekmann, Sabine; Patterson, Leslie (2019-12)
      This teacher action research examines how teachers can build student awareness of language variations in order to help students make meaning during the learning process thus bridging the gap between home discourse and school discourse. In this study students built a digital lexicon using a class generated list of Village English terms that are present in Aniak, Alaska. The purpose of this study was to build students' sociolinguistic awareness through explicit instruction and the Aniak Digital Lexicon project. The findings showed that providing students with explicit instruction helped develop students during their meaning making process and students were able to differentiate between Village English and Standard Academic English. The findings in this research study can be used to inform educators interested in teaching students about language variations and in particular learning about their own dialectal variation of English.
    • Tua'll (and then) I used math to tell a story: Using think alouds to enhance agency and problem solving in an indigenous high school mathematics class

      Boyd, Jennifer Ayaginaar; Patterson, Leslie; Martelle, Wendy; Siekmann, Sabine (2019-12)
      This paper examines action research in a high school math classroom with a focus on student discourse and agency. Students' use of language to explain their problem-solving processes was documented and analyzed. Specifically, the focus was on variations in student language and how the teacher responded to students during the problem-solving process. The following questions guided the analysis of what happened in the classroom: 1) How do my students talk about their math process? 2) How do I mediate their problem solving? One of the teacher researcher's earliest realizations was that she interfered in students' opportunities to problem solve on their own. Additionally, the students' explanations of their "problem-solving process" included more narration than justification or explanation of the process. On reflection, the teacher researcher decided to return to the research process to look further into these interactions while students were problem-solving. The second phase of research focused on student agency and how teachers can mediate for their students. Over a four-week period, the teacher researcher looked at the influences of multiple levels of assistance while each student was talking through his or her problem-solving process. Data sources include field notes, student artifacts, videos of student think aloud videos, and transcriptions of group work from the teacher researcher's classroom. The findings provide detailed insights into how these high school students approach math problems and how they describe and explain their problem-solving processes. The teacher researcher explores implications for teacher actions, insights into how students work together, and observations of students discussing their problem solving. Specifically, the teacher researcher noticed a need for language focus in mathematics instruction. In addition, teachers should problem solve with their students, rather than for their students; and allow students to mediate with each other to develop student agency.
    • Response of major modes of eastern Arctic Ocean variability to climate change

      Baumann, Till M.; Polyakov, Igor V.; Bhatt, Uma S.; Walsh, John E.; Weingartner, Thomas J. (2019-12)
      The Arctic Ocean plays a central role in ongoing climate change, with sea ice loss being the most prominent indicator. Recent observations showed that Atlantic inflows play an increasingly important role in the demise of sea ice. This encroaching atlantification of the eastern Arctic Ocean impacts the mean state and the variability of hydrography and current dynamics throughout the basin. Among the most energetic modes of variability are the seasonal cycle and high frequency semidiurnal (∼12-hourly) dynamics in the tidal and inertial frequency band. Limited observations indicated a substantial increase of both, hydrographic seasonal cycles as well as semidiurnal current dynamics in the eastern Arctic over the last decade. Using a uniquely comprehensive data set from an array of six moorings deployed across the eastern Eurasian Basin (EB) continental slope along the 125°E meridian between 2013 and 2015 within the NABOS project, we assess the state of hydrographic seasonal cycles in the eastern EB. Results show a complex pattern of seasonality with a remarkably strong (∆T=1.4°C), deep reaching (∼600 m) temperature signal over the continental slope and large-scale seasonal displacements of isopycnal interfaces. Seasonally changing background conditions are also the main source of variability of semidiurnal frequency band currents: During winter, vigorous baroclinic tidal currents whose amplitudes by far exceed predictions follow the vertical evolution of the pycnocline. During summer, extensive open-water periods additionally lead to strong wind-driven inertial currents in the upper ocean, routinely exceeding 30 cm/s far offshore in the deep basin. In order to obtain an Arctic-wide perspective on the impact of baroclinic tidal currents, a pan-Arctic tidal current atlas has been developed that synthesizes all available observations from the last 20 years. This atlas allows for in-depth studies of regional baroclinic tidal current variability as well as for validation of ocean and climate models, an essential step towards more accurate projections of the future Arctic Ocean state. Our findings from the eastern EB region already indicate a new, more dynamic state of the eastern Arctic Ocean with direct implications for the ecosystem and further sea-ice reduction.
    • Ecological interactions among important groundfishes in the Gulf of Alaska

      Barnes, Cheryl L.; Beaudrea, Anne H.; Dorn, Martin W.; Holsman, Kirstin K.; Hunsicker, Mary E.; Mueter, Franz J. (2019-12)
      Complex ecological interactions such as predation and competition play an important role in shaping the structure and function of marine communities. In fact, these processes can have greater impacts than those related to fishing. We assessed ecological interactions among economically important fishes in the Gulf of Alaska - a large marine ecosystem that has recently undergone considerable shifts in community composition. Specifically, we developed an index of predation for Walleye Pollock (Gadus chalcogrammus) to examine spatiotemporal changes in consumption, quantify portfolio effects, and better understand diversity-stability relationships within the demersal food web. We also evaluated the potential for competition between two important pollock predators, Arrowtooth Flounder (Atheresthes stomias) and Pacific Halibut (Hippoglossus stenolepis). We found highly variable predation intensity on Gulf of Alaska pollock. The combination of a single dominant predator and synchronous consumption dynamics indicated strong top-down control in the region. Spatial heterogeneity, however, may offset trophic instability at the basin scale. Assessments of resource partitioning provided little indication for competition between Arrowtooth Flounder and Pacific Halibut of similar lengths. Morphological differences between the two flatfish predators prompted an exploration into whether our conclusions about resource partitioning were dependent upon the size metric used. From this study, we found a relatively early onset of piscivory for Arrowtooth Flounder. Relationships between predator size and prey size also suggested gape limitation among Pacific Halibut sampled. Trophic niche separation was more pronounced for fishes with larger gapes, indicating greater potential for competition among smaller Arrowtooth Flounder and Pacific Halibut in Southeast Alaska. Reexamining basin-scale relationships between spatial and dietary overlap according to gape size would further elucidate the effects an increasing Arrowtooth Flounder population has had on changes in Pacific Halibut size-at-age. Results from this dissertation improve our understanding about the impacts of complex ecological interactions on population and community dynamics, and how those interactions may change in time, space, and under different environmental conditions.
    • Laboratory and Field Evaluation of Modified Asphalt Binders and Mixes for Alaskan Pavements

      Liu, Jenny; Liu, Jun (2019-08)
      In order to properly characterize modified asphalt binders and mixes for Alaskan pavements, this study evaluated properties of 13 asphalt binders typically used in Alaska from three different suppliers, and 10 hot mix asphalt (HMA) mixtures which were either produced in the lab or collected from existing paving projects in Alaska. Various binder and mixture engineering properties were determined, including true high binder grades, complex modulus (G*), and phase angle (δ) at high performance temperatures, multiple stress creep recovery rate and compliance, bending beam rheometer stiffness and m-value, Glover-Rowe parameter, ΔT, rheological index, and crossover frequency for binders, and rut depth, critical strain energy release rate (Jc), Indirect tensile (IDT) creep stiffness and strength for mixtures. Binder cracking temperatures were determined using asphalt binder cracking device. Mixture cracking temperatures were determined with IDT creep compliance and strength data. It was found that rutting and cracking resistances of the mixtures with highly modified binders were better than the mixture with unmodified asphalt binder (PG 52-28). Future recommendations for highly modified asphalt binders applications and research were provided based on laboratory testing results and field survey evaluation.
    • Alaska Map of Distance to Infrastructure

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The Alaska map of distance to infrastructure is a raster image file that includes Euclidean distance value from the Alaska infrastructure. The map is prepared at 60 m spatial resolution using vector map of the Alaska infrastructure. The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Map of Distance to Main Roads

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The Alaska map of distance to main roads is a raster image file that includes Euclidean distance value from the Alaska main roads. The map is prepared at 60 m spatial resolution using vector map of the Alaska main roads. The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Map of Distance to Towns

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The Alaska map of distance to towns is a raster image file that includes Euclidean distance value from the Alaska towns and cities. The map is prepared at 60 m spatial resolution using vector map of the Alaska towns and cities. The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Map of Distance to Drainage Network

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The Alaska map of distance to drainage network is a raster image file that includes Euclidean distance value from the Alaska drainage network with more ephemeral water channels. The map is prepared at 60 m spatial resolution using vector map of the Alaska drainage network. The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Map of Distance to Lakes and Rivers

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The Alaska map of distance to lakes and rivers is a raster image file that includes Euclidean distance value from the Alaska lakes and rivers with more permanently standing or flowing water. The map is prepared at 60 m spatial resolution using vector map of the Alaska lakes and rivers. The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Map of Distance to Coastline

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The distance to coastline map of Alaska is a raster image file that includes Euclidean distance value from the Alaska coastline. The map is prepared at 60 m spatial resolution using vector map of the Alaska coastline. The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Aspect Map

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The aspect map is a raster image file that includes aspect value at 60 m spatial resolution derived from the Alaskan Digital Elevation Model (DEM). The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Slope Map

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The slope map is a raster image file that includes slope value at 60 m spatial resolution derived from the Alaskan Digital Elevation Model (DEM). The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Digital Elevation Model (DEM)

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2019)
      The Digital Elevation Model (DEM) is a raster image file that includes elevation value at 60 m spatial resolution. The geographic projection is NAD 1983 Alaska Albers.
    • Alaska Mean Monthly Temperature in 2010

      Zabihi, Khodabakhsh; Huettmann, Falk; Young, Brian (2010)
      The folder includes 2010 average monthly temperature across the state of Alaska as a raster image file. The spatial resolution is 60 m and the geographic projection is NAD 1983 Alaska Albers.