• Natural Attenuation Of Chlorinated Solvents In Subarctic Ground Water

      Richmond, Sharon Alice (2001)
      Little is known about natural attenuation of chlorinated solvents in subarctic ground water. This study aimed to better understand the biogeochemistry and microbiology associated with naturally occurring processes of contaminant removal at two hydrologically diverse sites near Fairbanks, Alaska. Six Mile Village, located several km north of the Tanana River, is hydrologically stable, experiencing minor fluctuations in ground-water levels. Fort Wainwright is located adjacent to the Chena River and is hydrologically dynamic, experiencing seasonal flow reversals and substantial fluctuations in water-table elevations. By comparing data collected seasonally and with data collected at the two sites, I determined how ground-water/surface-water interactions affected in situ redox conditions and, hence, natural attenuation processes. A portion of the aquifer at Fort Wainwright was undergoing active treatment so I was also able to compare differences in chlorinated solvent transformations in treated and untreated ground water. Although ground water at Fort Wainwright was generally more oxidized than ground water at Six Mile Village, hydrogen concentrations at both sites were almost uniformly within ranges suggestive of iron or manganese reduction. However, aquifer sediments in the Tanana/Chena Alluvium are composed of mafic (containing reduced iron and manganese) minerals; suspended ferric iron appeared to result from oxidation of ferrous iron as ground water rose through the unsaturated zone. Sulfate concentrations were substantial and dissolved sulfide in most samples suggested that sulfate reduction might have been an important process. Calculated in situ Gibbs free energies for iron and sulfate reduction were energetically favorable at both sites; given other geochemical data, it seems likely these two processes co-occurred. Although methane was present in most samples, methanogenesis from H2 /CO2 was generally not energetically feasible at either site. Methane likely diffused from underlying permafrost or peat. The presence of less chlorinated intermediates of solvent degradation suggested that biological reductive dechlorination occurred, providing further support that sulfate-reducing conditions existed. However, low rates of microbial activity, incomplete degradation and persistence of contaminants imply that biologically mediated mechanisms did not likely represent an important contribution to natural attenuation of contaminants at either site where dilution appeared to be a major attenuation mechanism.
    • Natural compounds isolated from wild Alaska bog blueberries intervene with molecular targets of neuroinflammation

      Gustafson, Sally Jane (2010-05)
      NADPH Oxidase (NOX) has emerged as a key mediator of inflammatory processes that are prevalent in acute and chronic pathologies of the nervous system, cardiovascular system, and the immune system. Activation of NOX results in the formation of superoxide, a specific type of reactive oxygen species (ROS). Excessive accumulation of superoxide causes severe oxidative stress and ultimately, progressive cellular damage and degeneration. Despite the implications of NOX in a multitude of pathologies, pharmaceutical interventions against this molecular target remain non-existent. A diet rich in fruits and vegetables has immense health benefits beyond the high content of antioxidant compounds. Dietary intake of blueberries improves age related cognitive deficits and alleviates inflammatory damage as shown through human trials and animal studies. These findings imply that blueberries harbor specific inhibitors against molecular targets implicated in neuronal inflammation. Our investigations unveil natural compounds present in wild Alaska bog blueberries that potently inhibit NOX activity, reduce oxidative stress, and protect neuronal health in a cellular model of neuroinflammation. These studies illuminate nutrition-guided strategies as potential therapies for the prevention and intervention of neurodegeneration and cognitive decline associated with aging and with disease.
    • Natural fracture character and distribution adjacent to the Nenana basin, central Alaska

      Rizzo, Alec J.; Hanks, Catherine; McCarthy, Paul; Nadin, Elisabeth (2015-08)
      The NE-trending Nenana basin is a Cenozoic-aged basin located in central Alaska between the Denali and Tintina fault systems. The narrow, deep basin is a current exploration target for oil and gas resources in Interior Alaska. Natural fractures were analyzed to further understand larger structural features such as faults and folds related to the structural evolution of the Nenana basin and surrounding areas. Fracture sets were measured and described on the margin of the basin at four field locations: the Fairbanks area, along the Parks Highway between Fairbanks and Nenana, and in outcrop around the Nenana and Healy areas. In addition to measuring fracture sets in outcrop and collecting oriented samples, statistical and thin section analyses were used to further analyze fracture characteristics. Calcite twin thermometry and apatite fission track analysis were used to constrain the timing and thermal evolution of the field area. Based on the orientations of observed map-scale faults, folds, and fracture sets, I divided the four field locations into two structural domains. Domain I is characterized by NE-striking faults and associated active seismicity while Domain II is dominated by E-W striking folds and faults related to the late Cenozoic development of the Northern Foothills fold-and-thrust belt. I interpret that fracture sets in Domain I are related to the evolution of high angle faulting between the Nenana basin and the Fairbanks area during Cenozoic time. In Domain II, I interpret fracture sets are related to the evolution of the fold-and-thrust belt north of the Alaska Range. By combining fracture characteristics and apatite fission track analyses I provide constraints for the timing and shear sense of larger structural features related to the opening history of the Nenana basin. Furthermore, I propose that the evolution of the Nenana basin took place in three distinct tectonic phases during the Cenozoic. The three phases represent the transition from a pure extensional setting in the Late Paleocene to oblique-extensional faulting from the Late Miocene to present day.
    • Natural fracturing in carbonate rocks as a function of lithology and structural position in a detachment fold: examples from the northeastern Brooks Range, Alaska

      Brinton, Joseph S. (2002-08)
      Fractures in detachment folded Mississippian-Pennsylvania Lisburne Group carbonates provide insight into the distribution and character of natural fractures as a function of folding and lithology. Data from five detachment folds suggest that hinges show a higher fracture density than limbs. This study also suggests that the amount of shortening does not play a significant role in determining fracture density or uniformity of fracture orientation. A mechanical classification based on lithologic homogeneity reflects natural fracture distribution as a function of lithology more accurately than conventional lithologic classifications. Two main fracture sets were observed, a N-S set, perpendicular to fold axes, and an E-W set, parallel to fold axes. Statistical analyses suggest that E-W fracturing occurred before and during folding and that N-S fracturing occurred both before and after folding.
    • NCPA propagation code users manual

      Winkelman, Andrew T.; Szuberla, Curt A.; Fee, David E.; Olson, John V. (2015-12)
      This manual was written for University of Alaska Fairbanks infrasound group to assist researchers in using the National Center for Physical Acoustics (NCPA) code suite to further investigate observed infrasonic phenomena. The NCPA code suite is designed to simulate various aspects of infrasound propagation through a model atmosphere. This suite was developed and tested by the University of Mississippi National Center for Physical Acoustics infrasound group. Included are raytrace routines to initially establish signal paths, both single frequency and broadband modal routines to calculate pressure fields and transmission losses, and a parabolic method to calculate pressure fields and transmission losses in model atmospheres.
    • Neotectonic framework of the north-central Alaska Range foothills

      Bemis, Sean Patrick (2004-12)
      The northern foothills of the Alaska Range form a northward-convex salient at the apex of this orogen and the Denali fault. Despite the proximity of the northern foothills to the Denali fault and several historic large-magnitude earthquakes, the tectonic framework of this region has not been well-studied. A distinct pattern of east-trending folds and faults exists in both the bedrock and the geomorphic features. To assess the active structures of the region, I interpreted previous geologic mapping, developed cross-sections across the foothills belt, analyzed topographic and stream profiles, mapped the sequence of Quaternary fluvial terraces, and performed GPS transects across several terrace treads. A northward topographic slope across the northern foothills corresponding with the pattern of faulting and folding suggests the presence of an orogenic wedge overlying a south-dipping basal detachment. Mapping and GPS transects show evidence for progressive deformation of the terraces. Geomorphic analyses suggest deformation and differential uplift over the entire foothills belt. These results indicate that the northern foothills are an active fold-and-thrust belt and are prograding northward into the Tanana Basin. Tectonic activity of these structures suggests that this region represents a potential seismic hazard for nearby military facilities and important transportation corridors.
    • The neotectonics, uplift, and accommodation of deformation of the Talkeetna mountains, south-central Alaska

      Mixon, Demi C.; Hanks, Catherine; Nadin, Elisabeth; Beget, James (2016-08)
      South-central Alaska is home to many tectonic structures and mountain ranges that have experienced active uplift and deformation within the past 5 to 10 Ma. The Talkeetna Mountains are located above the area of flat-slab subduction of the Yakutat microplate. I hypothesize that the Talkeetna Mountains have been uplifted as a result of this underlying flat-slab subduction and that areas of the Talkeetna Mountains are neotectonically active. The Talkeetna Mountains are deforming heterogeneously across four different structural domains defined by differences in geomorphic patterns, seismicity, dominant fault types, and the orientation of horizontal maximum stress (SHmax). A strain partitioning structure divides the northern and southern domains, and is observed by a change in SHmax orientation from E-W in southern domains to NW-SE in the northern domain. The strain partition is accommodated by a crustal break along the Talkeetna thrust fault, which is expressed at the surface as a wide zone of deformation. Apatite fission-track analysis suggests two distinct periods of uplift: one dated from 45 to 30 Ma and another from approximately 10 Ma to present, with uplift rates of 0.14 mm/yr and 0.24 mm/yr, respectively. The first phase of uplift coincides with a time of significant plate reorganization in the north Pacific which resulted in translation of terranes northwestward. The second phase of uplift correlates with Neogene accretion of the Yakutat microplate. I propose that the majority of Neogene deformation and uplift in the Talkeetna Mountains is due to farfield deformation in the upper plate above the subducting slab. Variations in both composition of the crust and depth to the downgoing slab resulted in strain partitioning and northwest-directed compression in the northern Talkeetna Mountains and northwest compression and warping in the southern Talkeetna Mountains.
    • Nest -Building Behavior In House Mice (Mus Musculus), A Potential Model Of Obsessive -Compulsive Disorder In Humans

      Greene-Schloesser, Dana M.; Bult-Ito, Abel (2007)
      OCD (obsessive-compulsive disorder) is a chronic and debilitating psychiatric condition characterized by intrusive and persistent thoughts (obsessions) and repetitive behaviors (compulsions) that become ritualistic in an attempt to escape the obsessions. Currently there is a paucity of animal models with robust and spontaneous (non-drug or non-behaviorally induced) compulsive-like behaviors. This study is aimed at validating a novel robust and spontaneous genetic mouse model of OCD. The compulsive-like nest-building behavior in mice selected for high levels of nest-building behavior (BIG) has good face validity, with a behavioral phenotype that resembles hoarding behavior characteristic of OCD. In addition, male and female BIG mice displayed compulsivelike digging behavior relative to mice selected for low levels of nest-building behavior (SMALL), as assessed by the marble-burying test. Both chronic oral fluoxetine and clomipramine treatment reduced compulsive-like nest-building behavior in male BIG mice. Furthermore, chronic oral fluoxetine administration decreased nest-building behavior of BIG mice in a dose-dependent manner, while desipramine, an antidepressant not effective for treating OCD, did not significantly alter this behavior. The administration of fluoxetine did not cause a decrease in general locomotor behavior. These findings suggest that the nest-building phenotype has predictive validity. In addition, chronic oral fluoxetine treatment reduced compulsive-like digging behavior in male and female BIG mice as compared to SMALL mice. Gender effects were also found in treatment response. Clomipramine did not reduce nest-building in female BIG mice in a dose-dependent manner, which is consistent with previous studies. These data are in contrast to previous studies using BIG male mice which had a significant decrease in nest-building behavior with oral clomipramine. These results are consistent with studies on humans, which have found gender differences in the treatment effects of antidepressants. Additional construct validity is implicated by the results of targeted serotonergic lesions of the raphe nuclei in male BIG mice, which reduced repetitive nest-building behavior. More research is necessary to confirm the appropriateness of this model for human OCD; however, this model is promising based on the data that support good face, predictive and construct validity.
    • Nest and attribute data for 24 Hooded Cranes (Grus monacha) and control plots from field surveys in Northeast China 1993-2010

      Huettmann, Falk (Yu Guo, S. Jiao and colleagues, 2013-05-31)
      This dataset conists of 24 nests and their environmental attributes for the Hooded Crane (Grus monarcha, taxonomic serial number TSN 176186, Avibase ID38F36091DBC85095) in China. It is a legacy dataset, presents the best available information, and covers 9 years of survey work (time window 1993-2010). The Hooded Crane is a vulnerable (VU) species according to the IUCN Red list. The estimated world population of this species is just 10,160 individuals, of which more than 8,000 winter in Izumi, Japan. The Hooded Crane breeds in landscapes of Eastern Russia and Northeastern China. It generally nests in forest swamps, mostly within the permafrost zone. This data set can be used for nest preference studies and is available as an Open Office, ASCII or MS Excel format data sheet. The following environmental attributes have been collected for nests as well as for 81 control plots: elevation (in Meters), aspect (in Degrees), slope position (in degrees), distance to the nearest tree (Meters), distance to the nearest road (meters), distance to the nearest human settlement (Meters), distance to the nearest feeding site (Meters), distance to the nearest skidding road (Meters), water surface area around the nest (Square Meters), average water depth around the nest (Centimeter), canopy coverage (Percent), shrub coverage (Percent), grass coverage (Percent). number of trees (Count).
    • Nest and duckling survival of scaup at Minto Flats, Alaska

      Walker, Johann (2004-05)
      To address the hypothesis that declines in recruitment were related to recent declines in abundance of lesser and greater scaup, I estimated variation in nest and duckling survival of these species at Minto Flats, Alaska (64°50'N, 148°50'W) during 2002-2003. I included nest survival data from two previous studies conducted during 1989-1993 in my analysis. Daily Survival Rate (DSR) of nests was variable within and among years and among habitats. Estimated nest survival of scaup ranged from 0.02 (95% CI: 0.00 to 0.06) in 1992 to 0.61 (95% CI: 0.50 to 0.74) in 1993. Predation was the primary apparent cause of nest failure, and flooding of nests was an important secondary influence. DSR of ducklings varied between years and increased with age of the ducklings and body condition of the brood female. Duckling survival to 30 days was: 0.24 (95% CI: 0.16 to 0.36) in 2002 and 0.03 (95% CI: 0.00 to 0.19) in 2003. I conclude that high temporal variability in production of scaup at Minto Flats was likely related to annual variation in the risks of predation and flooding and indicated that intermittent years of high production could be particularly influential to this population.
    • Neural control of singing in the dark-eyed junco (Junco hyemalis)

      Gulledge, Cynthia Corbitt (1997)
      This dissertation includes several discrete projects addressing various aspects of the neural control of singing in the Dark-eyed Junco (Junco hyemalis), a migratory songbird. I collected the birds from a local wild population during the breeding season and migration. Chapter 2 addresses the role of testosterone in controlling volumes of the brain regions that control song learning and song production (vocal control regions, VCRs), which grow and shrink seasonally and are correlated with changes in singing behavior. I found that: the role testosterone plays may depend on the age of the bird and the brain region in question. Expanding on that study, I investigated the independent roles of testosterone and photoperiod in the control of VCR volumes in adolescent male juncos (Chapter 3). In seasonally breeding species, circulating androgens increase with increasing photoperiod, so increases in VCR volumes in the spring had been thought to be a result of photoperiod-induced increases in testosterone. Experimental separation of photoperiod and testosterone revealed that long photoperiod alone can have stimulatory effects on VCR growth, despite low testosterone levels. In fact, in adolescent male juncos, lengthening photoperiod may play a greater role in determining VCR volumes than testosterone does, again suggesting that the role of testosterone in the vocal control system may change with age. Other neurochemicals besides testosterone are present in the vocal control system; Chapter 4 describes the first description of opioid peptide receptor localization and density measurement in the vocal control system of adult male songbirds. I expanded that study to include nonsinging female and juvenile juncos (Chapter 5). The results of the expanded study indicate that opioids may modulate development of the vocal control system between adolescence and adulthood, as well as auditory processing throughout life.
    • Neural Network Approach To Classification Of Infrasound Signals

      Lee, Dong-Chang; Szuberla, Curt (2010)
      As part of the International Monitoring Systems of the Preparatory Commissions for the Comprehensive Nuclear Test-Ban Treaty Organization, the Infrasound Group at the University of Alaska Fairbanks maintains and operates two infrasound stations to monitor global nuclear activity. In addition, the group specializes in detecting and classifying the man-made and naturally produced signals recorded at both stations by computing various characterization parameters (e.g. mean of the cross correlation maxima, trace velocity, direction of arrival, and planarity values) using the in-house developed weighted least-squares algorithm. Classifying commonly observed low-frequency (0.015--0.1 Hz) signals at out stations, namely mountain associated waves and high trace-velocity signals, using traditional approach (e.g. analysis of power spectral density) presents a problem. Such signals can be separated statistically by setting a window to the trace-velocity estimate for each signal types, and the feasibility of such technique is demonstrated by displaying and comparing various summary plots (e.g. universal, seasonal and azimuthal variations) produced by analyzing infrasound data (2004--2007) from the Fairbanks and Antarctic arrays. Such plots with the availability of magnetic activity information (from the College International Geophysical Observatory located at Fairbanks, Alaska) leads to possible physical sources of the two signal types. Throughout this thesis a newly developed robust algorithm (sum of squares of variance ratios) with improved detection quality (under low signal to noise ratios) over two well-known detection algorithms (mean of the cross correlation maxima and Fisher Statistics) are investigated for its efficacy as a new detector. A neural network is examined for its ability to automatically classify the two signals described above against clutter (spurious signals with common characteristics). Four identical perceptron networks are trained and validated (with >92% classification rates) using eight independent datasets; each dataset consists of three-element (each element being a characterization parameter) feature vectors. The validated networks are tested against an expert, Prof. Charles R. Wilson, who has been studying those signals for decades. From the graphical comparisons, we conclude that such networks are excellent candidate for substituting the expert. Advantages to such networks include robustness and resistance to errors and the bias of a human operator.
    • Neuroplasticity And Neurotoxicology: Central Breathing Control Following Developmental Nicotine Or Ethanol Exposure

      Brundage, Cord M.; Taylor, Barbara (2010)
      Nicotine or ethanol exposure early in development are both risk factors for Sudden Infant Death Syndrome (SIDS). I tested the hypothesis that both nicotine and ethanol may be linked to SIDS by impairing central breathing control responses to low oxygen (hypoxia) and high carbon dioxide (hypercapnia) stressors. Experiments were conducted in bullfrog tadpoles, a model system for respiratory neurotoxicology research. I addressed three specific aims: to characterize the effect of chronic ethanol on central responses to hypercapnia and hypoxia, to characterize the effect of chronic nicotine on central hypoxic responses, and to determine the persistence of hypercapnic impairments following 10-wk exposure to either nicotine or ethanol. 10-wk nicotine exposure resulted in neuroplastic changes that eliminated the central hypoxic responses of early but not late metamorphic tadpoles. Thus, central responses to both hypoxia and hypercapnia were impaired following nicotine exposure. The attenuated central hypercapnic response of nicotine-exposed tadpoles persisted for 1 - 3 wk. Following 10-wk chronic ethanol exposure central responses to hypercapnia and hypoxia were lost regardless of the developmental timing of exposure. Impairments in central hypercapnic responses persisted for 3 - 6 wk after ethanol exposure ended. The recovery of central hypercapnic responses in nicotine- and ethanol-exposed tadpoles may be an example of recuperative neuroplasticity resulting in either a reinstatement of network components and functions or an accommodation to deleterious nicotine- and ethanol-evoked neuroplastic changes. Collectively these data suggest that both nicotine and ethanol may target adaptive and compensatory mechanisms in central breathing control. The teratogen-induced impairments were developmentally dependent in the case of nicotine, and they persisted longer following ethanol exposure. The overall result of exposure to either neuroteratogen was an inability to respond to central breathing stressors, supporting the possible link to SIDS.
    • Neuroprotection in hippocampal slices from the hibernating species Arctic ground squirrel, Spermophilus parryii

      Ross, Austin Pfeiffer (2005-08)
      Stroke is the third leading cause of death in the U.S. and the leading cause of adult onset disability worldwide. Despite tremendous efforts to find therapeutics, only one currently approved treatment for stroke exists which is indicated for use in less than 5% of stroke victims. During a stroke, the brain experiences oxygen and nutrient deprivation due to lack of blood flow (i.e., ischemia) and tissue destruction ensues. Hibernating Arctic ground squirrels (AGS), Spermophilus parryii, are able to survive profound decreases in blood flow and cerebral perfusion during torpor, and return of blood flow (i.e., reperfusion) during intermittent euthermic periods without neurological damage. Hibernating species are a natural model of tolerance to insults, such as ischemia, that would be injurious to non-hibernating species, and are a novel model for investigating much needed therapeutics for pathologies such as stroke. Tolerance to traumatic brain injury demonstrated in hibernating AGS in vivo could be due to tissue properties, circulating factors or hypothermia. To investigate mechanisms of tolerance in brain of hibernating animals, the current project established a chronic culture system for hippocampal slices from AGS at 37°C. By using this in vitro approach, tissue properties of AGS brain could be assessed without effects of circulating factors or the protective nature of hypothermia. This project determined whether an intrinsic tissue tolerance to oxygen and nutrient deprivation, an in vitro model of ischemia-reperfusion, persists in chronic AGS slice culture and addressed associated mechanisms. Here, for the first time, slices from hibernating AGS were shown to possess a persistent tolerance to oxygen and nutrient deprivation. Thus, intrinsic tissue properties in hippocampus of hibernating AGS confer tolerance to oxygen and nutrient deprivation in addition to hypothermia. Evidence in the literature supports that neuroprotective factors are present in serum and tissue of hibernating animals, and here a preliminary investigation suggests that factors in AGS serum may play a role in protection in brain of hibernating AGS. Finally, a model is proposed that incorporates these findings, which suggests that mimicking properties of tissue and serum from hibernating animals in non-hibernating species may yield success in developing efficacious stroke therapeutics.
    • Neuroprotection in the hibernating brain: tissue trauma and glutamate studied by microdialysis

      Zhou, Fang (2001-08)
      Hibernation, a natural model of tolerance to 'cerebral ischemia', represents a state of pronounced fluctuation in cerebral blood flow where no brain damage occurs. This study systematically investigates the brain tissue response of hibernating and euthermic arctic ground squirrels to CNS trauma, modeled by insertion of microdialysis probes. The effect of glutamate, an excitatory amino acid neurotransmitter, on the cellular response and the origin of the significant amount of gltuamate were determined by quantitative microdialysis study. The present results indicate in euthermic brain tissue a typical inflammatory tissue response evidenced by the presence of activated microglia and astrocytes and the oxidative stress response. However, this response was profoundly suppressed in hibernating animals. Importantly, the progressive increase in [glu]dia is not necessarily associated with the enhanced tissue response observed in euthermic animals and could be avoided by using sterile microdialysis technique, which suggests a microbial origin of glutamate.
    • New 3-d video methods reveal novel territorial drift-feeding behaviors that help explain environmental correlates of Chena River chinook salmon productivity

      Neuswanger, Jason; Rosenberger, Amanda E.; Evenson, Matthew J.; Adkinson, Milo D.; Bradford, Michael J. (2014-08)
      Chinook salmon (Oncorhynchus tshawytscha) are critical to subsistence and commerce in the Yukon River basin, but several recent years of low abundance have forced devastating fishery closures and raised urgent questions about causes of the decline. The Chena River subpopulation in interior Alaska has experienced a decline similar to that of the broader population. To evaluate possible factors affecting Chena River Chinook salmon productivity, I analyzed both population data and the behavior of individual fish during the summer they spend as fry drift feeding in the river. Using a stereo pair of high definition video cameras, I recorded the fine-scale behavior of schools of juvenile Chinook salmon associated with woody debris along the margins of the Chena River. I developed a software program called VidSync that recorded 3-D measurements with sub-millimeter accuracy and provided a streamlined workflow for the measurement of several thousand 3-D points of behavioral data (Chapter 1). Juvenile Chinook salmon spent 91% of their foraging attempts investigating and rejecting debris rather than capturing prey, which affects their energy intake rate and makes foraging attempt rate an unreliable indicator of foraging success (Chapter 2). Even though Chinook salmon were schooling, some were highly territorial within their 3-D school configurations, and many others maintained exclusive space-use behaviors consistent with the population regulatory effects of territoriality observed in other salmonids (Chapter 3). Finally, a twenty-year population time series from the Chena River and neighboring Salcha River contained evidence for negative density dependence and a strong negative effect of sustained high summer stream discharge on productivity (Chapter 4). The observed territoriality may explain the population's density dependence, and the effect of debris on foraging efficiency represents one of many potential mechanisms behind the negative effect of high stream discharge. In combination, these findings contribute to a statistically and mechanistically plausible explanation for the recent decline in Chena River Chinook salmon. If they are, in fact, major causes of the decline (other causes cannot be ruled out), then we can be tentatively hopeful that the population may be experiencing a natural lull in abundance from which a recovery is possible.
    • New algorithms for the compilation of glacier inventories

      Kienholz, Christian; Hock, Regine; Arendt, Anthony; Meyer, Franz (2013-12)
      Glacier inventories are used for many applications in glaciology, however, their manual compilation is time-consuming. Here, we present two new algorithms for the automatic compilation of glacier inventories. The first approach is based on hydrological modeling tools and separates glacier complexes into individual glaciers, requiring a digital elevation model (DEM) and glacier complex outlines as input. Its application to > 60,000 km² of ice in Alaska (~98% success rate) and southern Arctic Canada (~97% success rate) indicates the method is robust if DEMs and glacier complex outlines of good quality are available. The second algorithm relies on glacier outlines and a DEM and derives centerlines in a three-step 'cost grid -- least cost route' procedure. First, termini and heads are determined for every glacier. Second, centerlines are derived by determining the least cost route on a previously determined cost grid. Third, the centerlines are split into branches, followed by the attribution of a branch order. Application to > 21,000 Alaska glaciers shows that ~5.5% of the glacier heads and ~3.5% of the termini require manual correction. With corrected heads and termini, ~1.5% of the actual derived centerlines need edits. Comparison with alternative approaches reveals that the centerlines vary significantly depending on the algorithm used.
    • A new elasmosaurid (Sauropterygia: plesiosauria) from the Bearpaw Formation (late Cretaceous, Maastrichtian) of Montana and the evolution of neck length in elasmosauridae

      Serratos, Danielle J.; Druckenmiller, Patrick; McCarthy, Paul; Fowell, Sarah (2015-08)
      Plesiosauria is a diverse clade of marine reptiles that have been studied since the early 19th century. However, phylogenetic relationships within the group have been contentious due to limited taxon sampling and a misunderstanding of how ontogeny, interspecific and intraspecific variation affect character states. This is particularly true for elasmosaurids, a clade of long-necked plesiosaurians known from the Cretaceous. In 2010, a new, nearly complete skeleton, MOR 3072, was collected from the Late Cretaceous (Campanian-Maastrichtian) Bearpaw Shale of northeast Montana, and it provides morphological information rarely observed within Elasmosauridae. MOR 3072 consists of a complete skull, the anterior 23 cervical vertebrae, a partial dorsal and caudal vertebral column, incomplete pectoral and pelvic girdles, elements of both fore- and hindlimbs, ribs, and gastralia. Here, I present a detailed description of the specimen and conduct the most complete phylogenetic analysis of Elasmosauridae to date. A new taxon is recognized on the basis of the following suite of autapomorphies and unique character combinations: a chordate bilobed external naris, a squared-off posteroventral margin of maxilla, the presence of a maxilla-squamosal contact, a deep anteroposterior-oriented cleft in the articular posterior to the glenoid, a reduced number of cervical vertebrae, proximal caudal vertebrae that are wider than dorsoventrally tall, and small facets for forelimb and hindlimb preaxial accessory ossicles. A phylogenetic analysis places MOR 3072 as the sister taxon to the long-necked, Western Interior elasmosaurids Hydralmosaurus serpentinus + Styxosaurus snowii. Being early Maastrichtian in age, MOR 3072 is the stratigraphically youngest elasmosaurid yet known from the Western Interior Seaway. It is also one of the smallest adult elasmosaurids ever recovered (4.5-5 m) and exhibits a reduced neck length due to a reduction in both the number of cervical vertebrae and centrum length, which is convergent with another clade of Maastrichtian elasmosaurids, Aristonectinae.
    • New instrumentation for the detection of sulfur dioxide in the remote atmosphere

      Nicks, Dennis Keith, Jr.; Benner, Richard (1999)
      Sulfur gases are an important chemical component of the atmosphere. Gaseous sulfur compounds effect the acidity of rainwater and are important precursors to aerosol particles which affect public health, climate and visibility of scenic vistas such as the Grand Canyon. Sulfate aerosols are also known to participate in ozone catalysis in the stratosphere. A vast majority of the gaseous sulfur cycling through the atmosphere will exist as sulfur dioxide (SO2) at some time during its atmospheric lifetime. Since SO 2 is a primary component of the atmospheric sulfur cycle, quality measurements of this gas are important to understanding the cycling of sulfur through the atmosphere. The mixing ratio of SO2 in the atmosphere can be as low as a few 10's of parts-per-trillion by volume (pptv) in unpolluted areas and as high as 100's of parts-per-billion by volume (ppbv) near industrial centers. Obtaining SO2 measurements with mixing ratios that can differ by 105 in magnitude is a difficult task, especially for mixing ratios less than a few hundred pptv. The Diffusion Denuder/Sulfur Chemiluminescence Detector (DD/SCD) was developed further and tested in a rigorously blind comparison under controlled laboratory conditions. The DD/SCD exhibited excellent sensitivity and little-to-no interference from other trace gases. The DD/SCD performance was comparable to that of other state-of-the-art instruments developed for measuring SO 2 in the remote atmosphere. The Continuous SO2 Detector was developed to overcome the limitation of long sampling times (4 to 90 minutes) inherent in the DD/SCD and other state-of-the-art techniques. The Continuous SO2 Detector (CSD) was developed based on the design of the DD/SCD, but has been optimized for sensitive, high-time resolved measurements of SO2 in air. Sensitive, high-time resolved measurements would be beneficial for studying atmospheric SO2 over large geographical areas from a moving sampling platform such as an aircraft. The current prototype of the CSD is capable of measuring SO2 at mixing ratios of less than 100 pptv on the order of seconds. The DD/SCD, CSD and an automated, computer controlled dynamic dilution system described in this thesis represent a suite of instruments for the measurement of SO2 in the remote atmosphere.
    • A new model for the substorm growth phase

      Hsieh, Min-Shiu; 謝旻秀; Otto, Antonius; Bristow, William; Ng, Chung-Sang; Zhang, Hui (2014-08)
      The physics of geomagnetic substorms has been under debate for a long time. In particular, the formation of a thin current sheet (CS) is a central unresolved problem because it provides the magnetotail conditions for the expansion phase onset. This dissertation presents a new CS thinning mechanism based on midnight magnetic flux depletion (MFD), which is caused by sunward convection to balance dayside reconnection during periods of southward interplanetary magnetic field. The results demonstrate that MFD is a highly efficient mechanism to generate a very thin CS in the near-Earth tail. This study also examines CS formation under the influence of adiabatic lobe compression in combination with MFD and proposes a double-current sheet evolution at distinct locations in the near-Earth region and mid-tail region. The results suggest that substorm expansion onset is associated only with near-Earth onset of magnetic reconnection, while mid-tail reconnection causes bursty bulk flows. In addition, this dissertation investigates the changes of the auroral morphology associated with the magnetotail evolution. An ionospheric map is constructed based on Tsyganenko 96 magnetic field model corrected by magnetic flux conservation. By employing MFD, the mapping results such as the equatorward expansion of the open/closed field boundary, the convergent motion of strong field-aligned currents, and the location of electron and ion isotropy boundaries are consistent with typical ionospheric observations. These results demonstrate that MFD is the first model that can consistently explain and predict the typical magnetotail and ionospheric evolution during the substorm growth phase and shed light on the physics of the growth phase aurora.