• Implications for strain accommodation in an oblique subduction zone: new paleomagnetic and geologic data from the central Aleutian arc, Alaska

      Krutikov, Lena (2006-12)
      Oblique subduction results in partitioning of strain into arc-normal and arc-parallel components, and a complex pattern of upper plate deformation. Although partitioning of strain is observed in areas of oblique subduction around the world, the kinematics of strain accommodation are poorly understood. This is particularly true in the Aleutian arc because of a paucity of geologic and geophysical data. In the Aleutian arc, models previously proposed for forearc deformation have been characterized by clockwise rotation and westward translation of discrete tectonic blocks. This study utilizes two separate datasets to help constrain these mechanisms. The first step utilizes new high-resolution multibeam sonar data that provides a first detailed look at deformational structures on the seafloor. The second step is to examine the validity of paleomagnetic data previously collected from the arc, by re-measuring samples with improved methods. The multibeam sonar data reveal dense deformational patterns on the seafloor that suggest considerable diffuse strain between block boundaries. Remeasured paleomagnetic samples produce results that are similar to previous findings, but with reduced error bars and improved resolution. Younger rocks indicate little rotation, while samples from Amchtika Island indicate greater rotation than expected.
    • An improved method of ice nucleus measurement

      Shih, Chi-Fan G. (1982-09)
      Ice nuclei, which initiate the ice nucleation process at a higher temperature than the homogeneous nucleation temperature, are essential for the initiation of the ice phase in clouds. Unfortunately, no standard method has been established for the measurement of ice nucleus concentration. The filter technique is a promising candidate if the tendency for ice nucleus concentrations to decreases as the volume sampled increases can be explained. For this study, an improved ventilation method for the development of exposed filters was developed and tested. The results were compared with results obtained in a static diffusion chamber. The volume effect was observed to be less with the new dynamic system. Further work needs to be done to find the optimum flow rate in order to reduce the vapor depletion problem to a minimum. The ratio of total counts of dynamic and static system appears to be a promising evaluation index.
    • Improved Modeling Of Turbulent Transport: From Noise In Transport Models To The Parareal Algorithm Applied To Full Turbulence Codes

      Samaddar, Debasmita; Newman, David (2010)
      Turbulence and turbulent transport are ubiquitous in nature and are of fundamental importance in everything from the spread of pollution to confinement in fusion plasmas. In order to study this, turbulence models need to be as realistic as possible and one must also be able to evolve the turbulence and the profiles of the quantities of interest on transport (long) time scales. Improving turbulence simulations by the introduction of new techniques forms the basis of this research. One part of this work involved improving the performance of a 1D transport model by the addition of noise. On a more fundamental level, studying long time dynamics for turbulence simulations is very difficult even with the fastest computers available now or in the near future. To help overcome this difficulty, a new way of simulating turbulence has been presented, namely parallelizing in time. Time parallelization of a fully developed turbulent system is a new application. Parallelizing the space domain to computationally solve partial differential equations has been extensively used and is one of the most common forms of parallelization. In contrast, the Parareal Algorithm parallelizes the time domain and has been found to significantly reduce the computational wall time in many simpler systems. Despite its success in other less complex problems, it has not yet been successfully applied to a turbulent system (to the best of our knowledge). If efficiently applied, this algorithm will allow study of the turbulent transport dynamics on transport time scales - something that has heretofore been very difficult. In this work, the results of applying the Parareal Algorithm to simulations of drift wave turbulence in slab geometry in which the relative dominance of the polarization and E x B nonlinearities are tuned artificially, are presented. These turbulent systems are in many ways similar to neutral fluid turbulence models, so success of the Parareal scheme in them expands the prospect of a broader range of application to many other turbulent problems. This thesis also presents the results of a modification to the algorithm. A model to study and predict the parameters governing the convergence of the scheme is also explored.
    • An in vitro analysis of neuronal survival in response to hormones and photoperiod in the HVc of the songbird Junco hyemalis

      Humphries, Catherine Martin (2003-12)
      The ability of songbirds to sing is essential for their survival, proper reproductive behavior, and territorial establishment. Male and female juvenile passerine songbirds learn their song through the formation of a song template in their earliest days of life, first by listening to their parents, and then followed by auditory feedback against their own templates to crystallize their individual songs. However, in most passerine species, only the adult males actually sing on a seasonal basis with little to no singing during winter, followed by a phase of song production in the spring in correlation with increased plasma testosterone concentration and extended photoperiods. While the production of new neurons in the song system of adult males is continuous throughout the year, a counterbalancing turnover of these neurons must exist until the spring, when a three- to four-fold decrease in dying HVc (hyperstriatum pars ventralis caudale or higher vocal center) neurons in males initiates song production. We hypothesized that testosterone, under the influence of increased photoperiod, attenuates the rate of programmed cell death (apoptosis) of newly generated neurons migrating into the HVc song nucleus in the wild arctic songbird Junco hyemalis. Using an organotypic culture system, we examined the effect of testosterone and [beta]-estradiol on the degree of apoptosis in the HVc obtained from photo stimulated and non-photo stimulated male and female juncos. We employed a TUNEL assay and BrdU-labeling to detect and quantify apoptosis. We found that hormonal treatment with testosterone, and [beta]-estradiol in photostimulated birds only, extends the lifespan of cells within the HVc compared to controls, as shown by BrdU labeling, and decreasing apoptosis, as shown by TUNEL assay.
    • In-Situ monitoring of sea ice dielectric properties and implications for the tracking of seasonal evolution of microstructure

      O'Sadnick, Megan; Eicken, Hajo; Truffer, Martin; Pettit, Erin (2015-08)
      The microstructure of sea ice evolves throughout the seasonal cycle, from ice formation in the fall through melt in the summer. Observations of this seasonal evolution and its effect on the interaction between sea ice and the surrounding environment face fundamental challenges, however. Any removal of ice cores to obtain data on ice properties results in the loss of brine and alterations of microstructure. The remoteness of field sites also limits observations. Methods to monitor sea ice microstructure continuously and non-destructively are therefore being explored. This thesis examines the potential for the electric properties of sea ice, highly sensitive to the brine distribution within the ice, to serve as a proxy for microstructure and hence other ice transport properties. Throughout the Spring of 2013 and 2014, measurements of low frequency complex dielectric permittivity in the range of 10 Hz to 95 kHz were made in landfast ice off the coast of Barrow, Alaska. Temperature and salinity measurements and ice samples were collected for ice microstructure characterization. Results reveal a significant correlation between measurements of complex dielectric permittivity, brine volume fraction, and microstructural characteristics including pore volume and connectivity. The influence of temperature and salinity variations and further explanation of the relationships between ice properties, microstructural characteristics, and dielectric behavior are explored through multivariate analysis of the combined data set. The findings are discussed in terms of future research directions and promising approaches for in-situ ice property monitoring based on dielectric measurements.
    • Increases And Fluctuations In Thermal Activity At Mount Wrangell, Alaska (Volcano, Glacier)

      Motyka, Roman John (1983)
      The objectives of this study were to document and interpret changes in thermal activity at two of three craters located on the rim of the ice-filled summit caldera of Mount Wrangell, an active glacier-clad shield volcano in south-central Alaska. The technique of "glacier calorimetry" was developed, through which changes in the volume of glacier ice in the craters and caldera were measured and related to changes in heat flow. Chemical analyses of gases and acid-thermal waters provided information on the underlying heat source. In 1965, thermal activity began increasing at both the North and West Craters. During the ensuing years, heat flow increased significantly at the North Crater, although in a highly fluctuating manner, while gradually declining at the West Crater. Pulses in heat flow at the North Crater occurred in 1966-68 and 1972-74, with both pulses followed by a four-year decline in activity. Increases in heat flow began again in 1978-79 and have continued unabated through the summer of 1983. Over 80 percent of the 4.4 x 10('7)m('3) ice volume within the crater in 1966 was melted by 1982, and the meltwaters have drained or evaporated from the crater. The subsequent rapid development of numerous fumaroles, the large dry-gas proportion of SO(,2) (27 percent), and the inferred presence of gaseous HCl indicate that a shallow degassing magma body is the source of heat driving the thermal system. Seismically induced fracturing above the magma body is hypothesized to explain the initial increases in thermal activity. The resulting massive influx of meltwaters into the subsurface is suggested as the cause of the fluctuations in heat flow. The continued increase in activity since 1979 suggests that the volume of meltwater being generated is no longer sufficient to quench the heat source beneath the crater.
    • Induction of heat shock proteins in cold- adapted and coldacclimated Fishes

      Teigen, Laura Elizabeth; O'Brien, Kristin; Taylor, Barbara; Podlutsky, Andrej (2014-05)
      I examined the effects of oxidative stress and changes in temperature on heat shock protein (Hsp) levels in cold-adapted and cold-acclimated fishes. Adaptation of Antarctic notothenioids to cold temperature is correlated with high levels of Hsps, thought to minimize cold-induced protein denaturation. Hsp70 levels were measured in red- and white-blooded Antarctic notothenioid fishes exposed to their critical thermal maximum (CTMax), 4°C warm acclimated, and notothenioids from different latitudes. I determined the effect of cold acclimation on Hsp levels and the role of sirtuins in regulating Hsp expression and changes in metabolism in threespine stickleback, Gasterosteus aculeatus, cold-acclimated to 8°C. Levels of Hsps do not increase in Antarctic notothenioids exposed to their CTMax, and warm acclimation reduced levels of Hsp70. Hsp70 levels were higher in Antarctic notothenioids compared to a temperate notothenioid and higher in white-blooded notothenioids compared to red-blooded notothenioids, despite higher oxidative stress levels in red-blooded fish, suggesting Hsp70 does not mitigate oxidative stress. Cold acclimation of stickleback resulted in tissue-specific increases in some Hsps and sirtuins. My research indicates that cold acclimation increases Hsp levels, and moderate increases in temperature reduce Hsp levels in cold-adapted fishes. Together, these data lend support to the hypothesis that cold denatures proteins.
    • Infection rates, parasitemia levels, and genetic diversity of hematozoa in New World waterfowl

      Smith, Matthew M.; Lindberg, Mark; McCracken, Kevin; Winker, Kevin; Pearce, John (2014-12)
      Blood parasites can limit the productivity of birds and increase the vulnerability of isolated and naïve populations to extinction. I examined 804 blood samples collected from 11 species of South American waterfowl to assess infection by Haemoproteus, Plasmodium and/or Leucocytozoon parasites. In addition, I strove to develop a new molecular tool to quickly and accurately determine relative parasitemia rates of Leucocytozoon parasites in avian blood. I used samples collected from waterfowl in interior Alaska (n = 105) to develop and optimize a real-time, quantitative PCR methodology using TaqMan fluorogenic probes. Molecular screening produced an apparent prevalence rate of 3.1% for hematozoa infections in South American waterfowl samples, and analysis of hematozoa mitochondrial DNA produced 12 distinct hematozoa haplotypes, four of which were identical to hematozoa lineages previously found infecting waterfowl in North America. Phylogenetic analyses of hematozoa DNA revealed close relationships between parasite lineages infecting waterfowl on both continents. Our qPCR assay showed high levels of sensitivity (91%) and specificity (100%) in detecting Leucocytozoon DNA from host blood when compared to results from a well-used nested-PCR protocol. Additionally, statistical results of a linear regression supported correlation between relative parasitemia estimates from our qPCR assay and greater numbers of parasites observed on blood smears (R2 = 0.67, P = 0.003).
    • Inflammatory stress in the cerebellum: implications for nutritional intervention in alcohol-mediated CNS damage

      Hogan, Mary Barile (2012-05)
      Presently there are no effective disease-modifying treatments to combat neurodegeneration among chronic alcoholics. Alcohol abuse imparts a sustained presence of oxidative stressors, including pro-inflammatory cytokine TNFα, in the brain. A persistent presence of TNFα leads to an accumulation of reactive oxygen species, which promotes oxidative damage, subsequent neurodegeneration, and ultimately permanent cognitive changes in afflicted individuals. Our laboratory has demonstrated the potency of ursolic acid, isolated from Alaskan blueberries, to abolish TNFα mediated neurotoxicity in human neuroblastoma cells. Our current study investigated the neuroinflammatory effects of ethanol and TNFα on dissociated neurons and glia cells cultured from embryonic chicks while quantitatively evaluating the preventive and therapeutic effectiveness of blueberry extracts. We compared both CNS and PNS neurons to examine correlations to clinically indicated neurodegeneration. Our results clearly revealed a particular sensitivity of cerebellar neurons to oxidative stress; however, supplementation with blueberry extracts rescued neuronal health by up-regulating antioxidant defenses, suppressing TNFα secretion, blunting lipid peroxidation, restoring cytoskeleton organization, modulating lipid rafts and altering the lipid environment of ion channels. Implementation of blueberries into the diet may offer an inexpensive and safe means to improve quality of life and reduce future health care costs associated with alcohol abuse and neurodegenerative disease.
    • The influence of climate and tectonics on topography in the Hayes Range and its foothills

      Vance, Gabrielle; Wallace, Wesley; Nadin, Elisabeth; Beget, James (2013-12)
      Complex feedback exists among climate, tectonics, and glacial erosion in the creation of topography: climate influences glaciation; tectonics and glacial erosion modify topography; topography influences climate. The objectives of this study are to determine elevation distribution in the Hayes Range area of the central Alaska Range and to identify evidence for structural or erosional controls. I have used geospatial information systems (GIS) software to map mean elevation, calculate geomorphic indices from a digital elevation model (DEM), and characterize climatic, tectonic, and topographic patterns. Deformation, elevation, and erosion all increase southward within the range. In the northern part of the range, Quaternary doubly plunging anticlines and thrust faults uplift and deform a relict landscape. Despite the dominance of fluvial erosion, these elliptical topographic highs are tectonically controlled. Similar larger elliptical topographic highs are present farther into the range to the south, but Quaternary structures are more difficult to identify because of greater glaciation and erosion. The study area is one of high mean elevation, summits, slope, and relief. Topography in the Hayes Range exceeds what would be expected if glacial erosion kept pace with rock uplift. A young antiform in the Hayes Range can account for the rapid rock uplift needed.
    • The influence of mechanical stratigraphy on the development of detachment folds and associated mesoscopic structures: an example from the Lisburne group carbonates, northeastern Brooks Range, Alaska

      Hayes, Michael Robert (2004-08)
      The mechanical properties of individual stratigraphic layers in a multi-layer sequence of sedimentary rock influence the deformational response before, during, and after fold development. To demonstrate this, the mechanical character of stratigraphic layers and mesoscopic deformational structures within individual stratigraphic layers were documented in two well-exposed outcrop-scale detachment folds in the Lisburne Group carbonates, northeastern Brooks Range, Alaska. Fold geometry and fold-related mesoscopic structures indicate that flexural slip and flexural flow are the operative fold mechanisms until a critical interlimb angle of 90° is reached, after which homogenous flattening occurs. Changes in bed thicknesses due to homogenous flattening alter the overall fold geometry. Lithostratigraphic unit boundaries do not always coincide with mechanical unit boundaries. Thin shale layers lower the bedding interface strength and commonly form flexural slip horizons that define mechanical unit boundaries. As fold shortening progresses, slip horizon spacing is interpreted to decrease, causing mechanical unit thickness to decrease. Newly forming mechanical boundaries alter the conditions of deformation, which change the overall fold dynamics. Surveyed fracture sets reveal the influence of lithology, mechanical unit thickness, anisotropy, and structural position on fracture distribution within individual mechanical units. Fracture densities vary from set to set and unit to unit due to structural and stratigraphic controls within these folds.
    • Influence of permafrost extent on photochemical reactivity, functional group composition, and geochemical cycling of a subarctic discontinuous permafrost Alaskan watershed

      Gagné, Kristin R.; Guerard, Jennifer J.; Simpson, William; Trainor, Thomas P.; Jones, Jeremy (2020-05)
      Sub-Arctic Alaskan boreal forests are currently extremely susceptible to permafrost thaw caused by increases in atmospheric temperatures in the region. Upon thaw, permafrost soil organic matter can leach out organic matter, nitrogen, and metals. It is important to observe the effects the leaching of permafrost may have on photoreactivity, functional group composition, and metal introduction. Photoproduced reactive oxygen species may affect metal fate and transport through mechanisms such as the photo-Fenton reaction. Functional group analysis allows for differences in natural organic matter source and ability to complex metals throughout a watershed. Additionally, permafrost soils may have the ability to leach in metals through lateral flow of surface waters as observed in other studies. These metals could then complex to organic matter and alter the geochemical cycling within the watershed. Organic matter is a nutrient source, and metals (e.g., As) may increase the toxicity of surface waters through the thaw of permafrost. The influx of sequestered organic matter and metals to surface waters has the potential to drastically alter ecosystem processes. This study observes how permafrost leaching affects water composition, including its overall photoreactivity and functional group composition. The data obtained was then used to observe and deduce conclusions on how permafrost thaw influences surface water photoreactivity and functional group composition. Finally, trace metal analysis was conducted on a whole watershed scale over three years to observe how permafrost influences the geochemical composition of three main thermokarst surface waters with varying degrees of permafrost degradation. Overall, permafrost was determined to be heterogeneous and highly photoreactive both inter- and intra- watershed. Additionally, the functional group composition of surface waters influenced by permafrost thaw was different between summer and winter, indicating that winter is an important period to sample. Due to this change in functional group composition, the photoreactivity of winter samples was higher than summer with regard to the production of reactive oxygen species. Metal concentrations also increased during the winter for lakes identified to be undergoing active permafrost thaw. Finally, this case study found that metal concentration data combined with optical indices provided important information for resolving the possible extent of permafrost beneath thermokarst lakes.
    • The influence of phenocrysts in silicic magma degassing

      deGraffenried, Rebecca; Larsen, Jessica; Freymueller, Jeffrey; Izbekov, Pavel (2017-08)
      Understanding the degassing process in magma is an important goal because of the first-order control it exerts on determining eruption style. Degassing in high viscosity magmas is of particular interest since these magmas tend to erupt explosively. However, the role of phenocrysts in the degassing process is still poorly constrained, though recent data indicate that the presence of phenocrysts should promote permeability development at lower porosities than in crystal-free magmas. This study specifically examined the effect of phenocrysts in a rhyolitic magma, but the results can also be applied to crystal-rich intermediate magmas that have rhyolitic matrix melts. Isothermal decompression experiments were conducted using powdered rhyolite (76 wt. % SiO2) and seeded with corundum (Al2O3) crystals to approximate magmas with 20 and 40 vol. % phenocrysts. Experiments were saturated at 900˚C and 110 MPa then continuously decompressed to final pressures between 75 and 15 MPa. Percolation threshold was determined by measuring permeability on a benchtop permeameter and measuring porosity from reflected light images. Additionally, vesicle structure was assessed by measuring pore throat radii from back-scattered electron images and plotting bubble size distributions. Finally, degassing state was checked by measuring dissolved water contents in the glass with Fourier Transform Infrared (FTIR) spectroscopy analyses. The addition of at least 20 vol. % phenocrysts resulted in a decrease in percolation threshold from 70-80 vol. % porosity in crystal-free rhyolites to 55 vol. % porosity. Bubble size distribution patterns indicate that coalescence was more widespread as final pressure decreased and crystal content increased. Minimum pore throat radii in the 40 vol. % phenocryst series were larger than in the 20 vol.% phenocryst and crystal-free series. The dissolved water measurements indicate that these experiments degassed in equilibrium even at the fast decompression rate of 0.25 MPa/s. Calculations of the magnitude of outgassing from the decreased percolation threshold and timescales of pressure dissipation indicate that the presence of phenocrysts plays a role in the effusive-explosive cyclicity of Vulcanian-style eruptions.
    • Insights into deep structure and evolution of Alaska based on a decade of observations of shear wave splitting and mantle flow

      Bellesiles, Anna K. (2011-05)
      This thesis covers shear wave splitting results from a decade of temporary networks deployed throughout Alaska. The analysis and interpretation of data from the MOOS (Multidiscipline Observations Of Subduction) and ARCTIC (Alaska Receiving Cross Transect for the Inner Core) PASSCAL (Program for Array Seismic Studies of the Continental Lithosphere) deployments, combined with the previously published BEAAR (Broadband Experiment Across the Alaska Range) results provide anisotropy and flow observations across the state. In south central Alaska, a region dominated by the subduction of the Pacific plate under the North American plate, fast directions are dominantly in the direction of convergence (NNW-SSE), or trench-normal. This is either due to entrained flow below the subducting portion of the Yakutat block, or anisotropy within the block itself. Farther north above the mantle wedge the shear wave splitting results are dominated by fast directions along the strike of the subducting slab (NE-SW), due to along strike flow within the mantle wedge. North of the mantle wedge, fast directions transition into a more NNE to SSW orientation which is the Brooks Range and North slope are in the direction of absolute plate motion.
    • Inter-individual variation in gene expression in torpid and interbout euthermic Arctic ground squirrels

      Burman, Adlai Max (2006-12)
      Alaskan Arctic ground squirrels, Spermophilus paryii, hibernate about seven months per year. During two-week torpor periods, respiration, circulation, metabolism, and catabolism are dramatically decreased, except for brief periods of interbout euthermia. These divergent hibernation states provide a particularly compelling model for variance-based studies of global gene expression. A guiding hypothesis in this Thesis is that Arctic ground squirrels exit interbout euthermia and enter torpor with an invariant metabolic scaffolding of various metabolites that are erected to serve as a ready metabalome for the challenges of the next brief return to euthermia. To develop this hypothesis further, I performed an exploratory data analysis of high-density mouse cDNA micro arrays cross-hybridized with Arctic ground squirrel mRNA to measure transcriptomes in brown adipose, skeletal muscle, and liver tissues. The results revealed that variation in transcript expression profiles were tissue specific and may reflect the degree to which tissues are active during hibernation. These results are encouraging. They justify a more thorough evaluation of the utility of using global variation in transcript expression patterns. In combination with a priori biological knowledge, these patterns will guide future studies into more detailed analyses of hibernation-state dependent and functionally relevant transcripts.
    • The interaction of Io and the Jovian magnetic field: Io's Alfven wings and particle acceleration

      Dols, Vincent (2001-08)
      Conditions for the formation of an electric field along the field lines of Jupiter crossing the satellite Io are investigated by examining the properties of Io's Alfven wave. A three-dimensional self-consistent MHD model, using a simplified magnetosphere description, illustrates the formation of this electric field and of Io's related auroral emission in the Jovian ionosphere. The Alfven wing properties between Io and Jupiter are studied with a one-dimensional MHD model and a realistic magnetosphere. Any change in the Io/Jupiter system affects the structure of the Alfven wing and likely affects the structure of Io's auroral emissions. This emission is likely structured in multi-spots and the angle between the first spot and the instantaneous projection of Io is less than 3°. In the limited context of the 1D approximation, the acceleration mechanism is expected close to Jupiter.
    • Interaction of two tributary glacier branches and implications for surge behavior

      Knowles, Christopher P.; Truffer, Martin; Larsen, Chris; Newman, David; Wackerbauer, Renate (2018-05)
      A glacier surge is a dynamic phenomenon where the glacier after a long period of quiescence, increases its velocities by up to two orders of magnitude. These surges tend to have complex interactions with tributaries, yet the role of these tributary interactions towards glacier surging has yet to be fully investigated. In this work we construct a synthetic glacier with an adjustable tributary intersection angle to study tributary interaction with the trunk glacier. The geometry we choose is loosely based on the main trunk and tributary interaction of Black Rapids Glacier, AK, USA, which last surged in 1936-1937. We investigate surface elevations, medial moraine locations, and erosive power at the bed of the glacier in response to our adjustable domain and relative flux. A nonlinear relationship between tributary flux and surface elevations is found that indicates flow restrictions can occur with geometries like Black Rapids Glacier. These flow restrictions cause increased ice thicknesses up-glacier which can lead to surges via increased stresses.
    • Intermittent hypercapnia induces long-lasting ventilatory plasticity to enhance CO₂ responsiveness to overcome dysfunction

      Mosher, Bryan Patrick; Harris, Michael B.; Taylor, Barbara E.; Hueffer, Karsten; Edmonds, Brian W. (2014-05)
      The ability of the brain to detect (central CO₂ chemosensitivity) and respond to (central CO₂ chemoresponsiveness) changes in tissue CO₂/pH, is a homeostatic process essential for mammalian life. Dysfunction of the serotonin (5-HT) mechanisms compromises ventilator CO₂ chemosensitivity/responsiveness and may enhance vulnerability to pathologies such as the Sudden Infant Death Syndrome (SIDS). The laboratory of Dr. Michael Harris has shown medullary raphe' contributions to central chemosensitivity involving both 5-HT- and y-aminobutyric acid (GABA)-mediated mechanisms. I tested the hypothesis that postnatal exposure to mild intermittent hypercapnia (IHc) induces respiratory plasticity, due in part to strengthening of bicuculline- and saclofen-sensitive mechanisms (GABAA and GABAB receptor antagonists respectively). Rats were exposed to IHc-pretreatment (8 cycles of 5 % CO₂) for 5 days beginning at postnatal day 12 (P12). I subsequently assessed CO₂ responsiveness using an in situ perfused brainstem preparation. Hypercapnic responses were determined with and without pharmacological manipulation. In addition, IHc-pretreatment effectiveness was tested for its ability to overcome dysfunction in the CO₂ responsiveness induced by a dietary tryptophan restriction. This dysfunctional CO₂ responsiveness has been suggested to arise from a chronic, partial 5-HT reduction imparted by the dietary restriction. Results show IHc-pretreatment induced plasticity sufficient for CO₂ responsiveness despite removal of otherwise critical ketanserin-sensitive mechanisms. CO₂ responsiveness following IHc-pretreatment was absent if ketanserin was combined with bicuculline and saclofen, indicating that the plasticity was dependent upon bicuculline- and saclofen-sensitive mechanisms. IHc-induced plasticity was also capable of overcoming the ventilatory defects associated with maternal dietary restriction. Duration of IHc-induced plasticity was also investigated and found to last far into life (up to P65). Furthermore, I performed experiments to investigate if IHc-induced plasticity was more robust at a specific developmental period. No such critical period was identified as IHc-pretreatment induced robust respiratory plasticity when administered at all developmental periods tested (P12-16, P21-25 and P36-40). I propose that IHc-induced plasticity may be able to reduce the severity of reflex dysfunctions underlying pathologies such as SIDS.
    • Interpretation of radarsat SAR scenes of Sagwon Alaska, to establish temporal, spatial and physical active layer behavior

      Lovick, Joseph Thomas (2003-05)
      Radarsat SAR images of the Kuparuk Basin in North Alaska can be used to describe the timing and characteristics of the seasonal freeze-thaw cycle and the spatial distribution of two types of Arctic Tundra. The freezing of the ground surface; decreases backscatter brightness by 3dB allowing the date of freeze-up and thaw to be established. Using Empirical Orthogonal Functions on amplitude images allows the subtle change in the brightness (during winter) of different tundra types to be enhanced, which provides a technique for discriminating between areas of Moist Acidic Tundra and Moist Non-acidic Tundra. The sand to clay ratio affects the backscatter properties of frozen soil and is inferred to cause this brightness difference. Coherence images show the dynamic nature of Arctic tundra, and low coherence limits the applicability of interferometric techniques to describe active layer heave, however, preliminary results show promise in the application of a differential interferometric technique.
    • Intrinsic Markers In Avian Populations: Explorations In Stable Isotopes, Contaminants, And Genetics

      Rocque, Deborah Anne; Winker, Kevin; Duffy, Lawrence K.; Ben-David, Merav; Barry, Ronald P. (2003)
      This research outlines the diversity of questions that intrinsic markers have the potential to answer and demonstrates some of these marker's limitations and successes. To test the working hypothesis that feathers grown on different continents have significantly different stable isotope ratios in commonly used markers, I analyzed stable isotopes in two generations of feathers from three species of birds that breed at high latitudes and winter on different continents. As expected, significant differences in stable isotope ratios were detected between summer- and winter-grown feathers in both plover species (Pluvialis fulva and P. domininca). However, no differences were found between the two groups of winter-grown plover feathers, despite being grown on different continents. Similarly, no differences were detected in isotope values between summer- and winter-grown feathers in northern wheatears (Oenanthe oenanthe). Large variances in isotope ratios limited the percentage of feathers correctly assigned to their origins to 41%. Atmospheric transport has been identified as the source of pollutants in several arctic ecosystems and has the potential to severely impact high-latitude populations. To determine whether long-range atmospheric transport, point sources, or migratory prey were sources of contaminants in the North Pacific, birds from two trophic levels were sampled across the longitudinal transect of the Aleutian Archipelago. Carbon isotope ratios differed among islands, thereby linking birds to island food webs and ruling out contaminant transfer through migratory prey. Patterns in some PCB congeners indicated local point sources, but significant west-to-east declines in contaminant concentrations for the majority of detected organochlorines provided evidence of long-range transport. Linking individuals to source populations using intrinsic markers has only been successful at broad scales. To determine whether increased resolution among populations could be achieved by merging multiple intrinsic marker classes, a new analytical procedure was developed. Discrete and continuous markers were combined to evaluate a Bayesian method of assignment across marker classes. For three datasets, two real and one simulated, the percentage of individuals assigned to correct source populations increased with the addition of markers and marker classes. In all cases, the maximum number of individuals was correctly assigned when all marker classes were combined.