• 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.
    • Nesting biology of the spectacled eider Somatera fischeri (Brandt) on the Yukon-Kuskokwim Delta, Alaska

      Dau, Christian P. (1974-05)
      Nesting biology of the Spectacled Eider Somateria fischeri (Brandt) on the Yukon-Kuskokwim Delta, Alaska, was studied in 1972 and 1973. These data are compared with data from 1969, 1970, and 1971 (Eisenhauer et al. 1971, Eisenhauer and Frazer 1972, and Mickelson 1973). Paired, the birds arrived mostly from the north within a 3-4 day period in mid-May. Before 7 June, 80 percent of the nests were initiated. Located on islands, shorelines and peninsulas, most nests were within 7 feet of water. Rate of egg laying was 1/day (mean clutch size 4.5 eggs). Incubation lasted 24 days. Hatching took place from 20 June to 10 July (nesting success range 35 percent to 83 percent). Timing of nest site availability appears to dictate clutch size and reproductive success. Ducklings are raised on shallow freshwater ponds within 1.5 miles of their nest site.
    • Nesting ecology of ducks in interior Alaska

      Petrula, Michael J. (1994-09)
      This study represents one of the first intensive efforts to locate and monitor duck nests in interior Alaska. We located 263, 409 and 450 nests of 12 duck species on Minto Flats in 1989, 1990 and 1991,respectively. We conclude that habitat for breeding waterfowl cannot be considered stable in interior Alaska. Flooding reduced the availability of meadows which precluded ducks from nesting in high-water years despite their presence during the Breeding Pair Survey. Differences in the length of the breeding season and differential response to photoperiod between sub-Arctic and prairie nesting ducks suggest the potential for genetic differences between populations. Similar clutch sizes between high and mid-latitudes, however, suggest that ducks are able to compensate for the additional energetic costs associated with breeding at high latitudes. Flooding of meadow habitat and low nest success resulting from predation probably limit overall duck production on Minto Flats.
    • Nesting ecology of migratory golden eagles (Aquila chrysaetos) in Denali National Park, Alaska

      McIntyre, Carol L. (1995-12)
      Between 1988 and 1993 I measured occupancy of nesting territories and reproduction of golden eagles (Aquila chrysaetos) in Denali National Park, Alaska. I collected data occupancy of nesting territories and three reproductive variables (pairs nesting, pairs producing fledglings, and fledgling production) at 74 nesting territories using three aerial surveys each year. During my study, annual fledgling production varied nearly threefold, from 20 fledglings in 1992 to 58 fledglings in 1989. Although rates of nesting territory occupancy did not vary significantly among years (yj = 8.21, d.f. = 5, P = 0.114), I noted significant variation in the proportion of pairs laying eggs (X2 = 33.12, d.f. = 5, P < 0.001) and the proportion of pairs fledging young (X2 = 16.03, d.f. = 5, P = 0.007) among years. Decreases in pairs laying eggs were correlated with decreases in average daily numbers of snowshoe hare (Lepus americanus) and willow ptarmigan (Lagopus lagopus) observed in the study area (rs = 0.83, P = 0.04).
    • Networks of change: extending Alaska-based communication networks to meet the challenges of the anthropocene

      Hum, Richard E.; Taylor, Karen; Chapin, F. Stuart, III; Koskey, Michael; Brower, Pearl Kiyawn Nageak; Carlson, Cameron (2017-08)
      The Anthropocene is a contested term. As I conceptualize it throughout this dissertation, the Anthropocene is defined by an increased coupling of social and environmental systems at the global scale such that the by-products of human processes dominate the global stratigraphic record. Additionally, I connect the term to a worldview that sees this increased coupling as an existential threat to humanity's ability to sustain life on the planet. Awareness that the planet-wide scale of this coupling is fundamentally a new element in earth history is implicit in both understandings. How individuals and communities are impacted by this change varies greatly depending on a host of locally specific cross-scale factors. The range of scales (physical and social) that must be negotiated to manage these impacts places novel demands on the communication networks that shape human agency. Concern for how these demands are being met, and whose interests are being served in doing so, are the primary motivation for my research. My work is grounded in the communication-oriented theoretical traditions of media ecology and the more recent social-ecological system conceptualizations promoted in the study of resilience. I combine these ideas through a mixed methodology of digital ethnography and social network analysis to explore the communication dynamics of four Alaska-based social-ecological systems. The first two examples capture communication networks that formed in response to singular, rapid change environmental events (a coastal storm and river flood). The latter two map communication networks that have formed in response to more diffuse, slower acting environmental changes (a regional webinar series and an international arctic change conference). In each example, individuals or organizations enter and exit the mapped network(s) as they engage in the issue and specific communication channel being observed. Under these parameters a cyclic pattern of network expansion and contraction is identified. Expansion events are heavily influenced by established relationships retained during previous contraction periods. Many organizational outreach efforts are focused on triggering and participating in expansion events, however my observations highlight the role of legacy networks in system change. I suggest that for organizations interested in fostering sustainable socialecological relationships in the Anthropocene, strategic intervention may best be accomplished through careful consideration of how communicative relationships are maintained immediately following and in between expansion events. In the final sections of my dissertation I present a process template to support organizations interested in doing so. I include a complete set of learning activities to facilitate organizational use as well as examples of how the Alaska Native Knowledge Network is currently applying the process to meet their unique organizational needs.
    • 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.
    • Neural-Network Modeling Of Placer Ore Grade Spatial Variability

      Ke, Jinchuan; Bandopadhyay, Sukumar (2002)
      Traditional geostatistical methods have been used in ore reserve estimation for decades. Research in the last two decades or so has added a number of other statistical methodologies for ore reserve estimation procedures. Recent advances in neural networks have provided a new approach to solve this problem. This thesis is focused on the Neural-network modeling for the estimation of placer ore reserve. Due to the spatial variability, multiple dimensional inputs and very noisy drill hole sample data from the selected region, it requires that the neural-network be organized in a multiple-layers to handle the non-linearity and hidden slabs for smoothing the predicted results. Various neural-network architectures are investigated and the Back-propagation is selected for modeling the ore reserve estimation problem. Sensitivity analysis is performed for the following parameters: the type of neural-network architecture, number of hidden layers and hidden neurons, type of activation functions, learning rate and momentum factors, input pattern schedule, weight updated, and so on. The influences of these parameters on the predicted output are analyzed in details and the optimal parameters are determined. To investigate the accuracy and promise of neural network modeling as a tool for ore reserve estimation, the ore grade and tonnage of Neural-network output is compared with those estimated by geostatistical methods under various cut-off grades. In addition, the overall performance is also validated by the analysis of R-squared (R2), Root-Mean-Squared (RMS), and the comparison between predicted values and 'actual' values. As the final part of this study, the optimized Neural Network was used to estimate the distribution of placer gold grade and volume of gold resource in offshore Nome. The predicted results for all the mining blocks in the lease area are validated by checking the values of RMS, R2, and Scatter plots. The estimated gold grades are also presented as contour maps for visualization.
    • Neuroendocrine control of song in the dark-eyed junco (Junco hyemalis)

      Dloniak, Stephanie Marie (2000-08)
      This dissertation includes three discrete projects addressing various aspects of the neuroendocrine control of song in the Dark-eyed Junco (Junco hyemalis), a migratory songbird. Specifically, the roles of testosterone, photoperiodic condition, opioids, and age were investigated with respect to song production and neural plasticity in the regions of the brain that control song (vocal control regions, VCRs)." The author "found that, in males photoperiodic condition and testosterone interact to regulate seasonal VCR volume plasticity, whereas testosterone alone controls song production. The opioid system is probably not involved in VCR plasticity or song production, but is indicated to play a role in song learning or auditory processing. Finally, VCR volumes and song production do not differ with age in photostimulated adult male juncos.
    • 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.
    • A new affordability indicator for rural Alaskan water utilities

      Johnson, Barbara A. L.; Little, Joseph M.; Baek, Jungho; Kennedy, Camilla; Wright, Christopher (2016-12)
      The Alaska Department of Environmental Conservation (DEC) administers funding for the construction of new water utilities in rural parts of the state. Funding allocation is partially based on whether the recipient community can cover the annual operation, maintenance, repair, equipment and capital replacement costs of the utility. Currently, the DEC deems a project affordable if the annual costs account for 5% or less of the community's median household income (MHI). In rural Alaska MHI is an inaccurate affordability indicator. This is partially because MHI fails to reflect the cost burden experienced by below median income households, it is a static snapshot of income, it does not account for living costs, nor does it account for the demographic composition of a community or the distribution of income. An alternative indicator was developed. The new indicator is composed of a Residential Indicator (RI) and a Financial Capability Index (FCI). RI is obtained by dividing the community's annual user fee by each income quintile value. FCI is composed of socioeconomic indicators chosen for their ability to detail the situation in rural Alaska. The FCI value is obtained by calculating the average of score assigned to the indicators based on pre-established thresholds. The new indicator was found to be more accurate than the MHI indicator. The new indicator was retroactively applied to Akiachak and found to more accurately assess affordability. The new indicator was also used to assess the current situation in communities with water utilities. The MHI indicator was found to have underestimated the price burden of user fees in numerous communities, and to have overestimated the burden in one community.
    • 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.
    • New microfabrication method for prototyping integrated microfluidic modules with SR-3000 and polydimethylsiloxane (PDMS)

      Gerlach, Thomas Frederick (2012-08)
      This thesis presents the first work on the fabrication of microfluidic modules with SR-3000 Rayzist photoresist paper and polydimethylsiloxane (PDMS). Chapter 1 of the thesis is on the analysis of elemental composition of SR-3000. By using the X-Ray Fluorescence spectrometer we found the SR-3000 sheet is enriched with silicon, the key element for forming covalent bonding to PDMS. Chapters 2, 3,and 4 of the thesis is focused on the characterization of both the hydrophilicity of the plasma-treated SR-3000 surface and the bonding strength between SR-3000 and PDMS. Unfiltered air was used as the process gas for plasma-assisted bonding of SR-3000 to PDMS. Pressure rupture tests were conducted to measure the strength at the bonding interface, which can be as high as 57.7 psi, strong enough to hold the fluid pressure for typical microfluidics applications. The hydrophilicity of SR-3000 is mainly governed by the plasma treatment time. Chapter 5 demonstrates how to use the developed microfabrication method to prototype microfluidic modules for typical microfluidic applications, which include manipulation of laminar flow, mixing of miscible fluids, and production of oil droplets in a stream of water flow.