Browsing by Author "von Fischer, Joseph C., committee member"
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Item Open Access Candidate reservoir underlying re-emergent plague outbreaks(Colorado State University. Libraries, 2019) Markman, David W., author; Antolin, Michael F., advisor; von Fischer, Joseph C., committee member; Gage, Kenneth L., committee member; Bowen, Richard A., committee memberTo view the abstract, please see the full text of the document.Item Open Access Facies patterns and depositional environments of the Peltura scarabaeoides trilobite biozone sediments, Upper Cambrian Alum Shale Formation, southern Sweden(Colorado State University. Libraries, 2012) Newby, Warren, author; Egenhoff, Sven O., advisor; Hannah, Judith L., committee member; von Fischer, Joseph C., committee memberThe Upper Cambrian-age Peltura Scarabaeoides Biozone represents 2.2m - 5.94m of the Alum Shale in Västergötland, southern Sweden. The Alum Shale succession has historically been characterized as an accumulation of dark, organic-rich "monotonous" mudstones deposited in an anoxic and tranquil setting. However, the results of this study indicate the contrary and will place the Alum Shale alongside many other high-TOC mudstones that document abundance of benthic life and advective sediment transport. Description of continuous thin sections at the microscopic-scale enabled the subdivision of the Peltura scarabaeoides Biozone into four carbonate and three siliciclastic facies. The entire biozone represents an overall shallowing trend that can be sub-divided into eight medium-scale shallowing-upward cycles consisting of intercalated carbonates and siliciclastic mudstones. These medium-scale cycles can further be sub-divided into numerous small-scale shallowing- and deepening-upward siliciclastic mudstone cycles. Time estimates suggest that long eccentricity explains the eight medium-scale cycles whereas the driver of the small-scale cycles remains unclear. Along a shelf transect, the proximal sections contain high energy shell debris and pack- to grainstones that grade into carbonate wackestone and mudstones; the distal sections are composed of dark organic-rich shales. All siliciclastic mudstone facies are characterized by abundant bioturbation, with more proximal types being horizontal and larger, and distal ones multidirectional and smaller. All facies also show signs of bed load transport in the form of irregular laminae or ripple structures. Several millimeter-thick slump units are present in the succession, indicating active tectonic movements in the area. The Peltura scarabaeoides Biozone therefore exemplarily shows that early in the Phanerozoic the deep shelf environment was already colonized by a variety of organisms burrowing millimeters into the soft substrate. Silt transported from the shoreline by currents reached even the most distal parts of this shelf. Therefore, the Cambrian deep shelves must have already presented an environment similar to later Paleozoic examples with probably dysoxic to oxic, not anoxic conditions controlling the accumulation of high-TOC sediments.Item Open Access Patterns of association in a co-introduced insect herbivore and parasitoid wasp(Colorado State University. Libraries, 2017) Bowker, Cheryl Lindsay, author; Ode, Paul J., advisor; Black, William C., IV, committee member; Bjostad, Louis, committee member; Bowers, Deane, committee member; von Fischer, Joseph C., committee memberSpecies within trophic networks that experience a range expansion can lead to populations of coevolved species re-associating in some areas, not associating in others, or creating novel associations with native species at one or more trophic level(s). Although most studies have focused predominantly on coevolved interactions between pairs of species, a growing number of studies investigate interactions within a broader community context across geographically widespread areas. By tracing the invasion routes of co-introduced species that share a close evolutionary history in their native range, I address the relative importance of long-term historical associations versus ecological fitting in community assembly. In the context of invasion ecology, ecological fitting refers to the process whereby exotic species form novel associations with native species that lack a shared coevolutionary relationship. In Chapter 1 of my dissertation, I review the literature that has taken a population ecology approach to understanding community assembly of introduced coevolved species. Collectively, these studies suggest that multiple factors ranging from local adaptation and ecological fitting are important in shaping multi-species associations in the introduced range and can occur simultaneously in one system. For example, coevolution can be an important factor in the re-association of many exotic plant-herbivore species, but ecological fitting also readily occurs as evidenced by the prevalence of native species host switching to exotics, and vice-versa. For the remainder of my dissertation, I used molecular methods to determine the invasion routes of the herbivorous parsnip webworm (Depressaria pastinacella; Lepidoptera: Depressariidae), and its primary parasitoid, Copidosoma sosares (Hymenoptera: Encyrtidae) to address the importance of shared population history and ecological fitting in shaping species interactions in introduced ranges. The coevolved reciprocal interaction between wild parsnip, parsnip webworm, and C. sosares has been well documented. Throughout its native range in Europe and much of its introduced range in North America, the parsnip webworm attacks wild parsnip (Pastinaca sativa; Apiaceae). Wild parsnips produce furanocoumarins, allelochemicals that are broadly biocidal because they intercalate DNA and interfere with transcription. Selection for chemically-based resistance occurs in plant populations by increasing concentrations of three furanocoumarins: xanthotoxin, bergapten, and sphondin. Genetic variation also exists in webworm populations in the rate at which these furanocoumarins are metabolized indicating that plant chemistry can act as a selective force on insect physiology. The wild parsnip was introduced to the United States (U.S.) as a food crop in the 17th century, where it escaped cultivation and spread throughout the U.S. By the 1860s, parsnip webworm was accidentally introduced to the U.S. and has re-associated with its coevolved wild parsnip plant, and formed novel associations with cow parsnip (Heracleum maximum; Apiaceae), a plant native to the U.S. Copidosoma sosares is also found in the U.S., but its arrival date is unclear. Copidosoma sosares attacks webworms on both wild parsnip and cow parsnip, but its distribution is patchy compared to parsnip webworms; with rare exception, C. sosares populations are restricted to the western U.S. In Chapter 2, I used a mitochondrial molecular marker to determine: 1) the source population(s) of U.S. and New Zealand parsnip webworms, and 2) whether parsnip webworm populations in the U.S. or Europe are locally adapted to the host plant species they attack. I found that parsnip webworms experienced a genetic bottleneck during introduction to the U.S. and New Zealand. U.S. parsnip webworm populations were founded by a single (or a few) population(s) of parsnip webworms from the British Isles. British Isles populations of parsnip webworm are themselves genetically isolated from continental European parsnip webworm populations. The introduction pattern of webworms stands in contrast to that of its host plant, wild parsnip, in the introduced ranges of the U.S. and New Zealand. The acquisition of the non-coevolved cow parsnip by webworms in the U.S has led to genetic divergence from webworms feeding on their coevolved plant species. In contrast, European webworm populations are not restricted to the host plant species on which they feed. In Chapter 3, I describe the development of novel microsatellite markers for tracing the routes of C. sosares within the introduced range of the U.S. Thirty-four candidate loci were identified, 12 of which were ultimately chosen for detailed screening. Seven of the 12 loci were polymorphic, but only 5 of the 7 were successfully amplified across samples and ranges. Of these 5 polymorphic loci, there were 3 - 9 alleles per locus. Inbreeding coefficients and the null allele frequency ranged from -0.04 to 0.74 and 0 to 0.73, respectively. After Bonferroni correction, only one locus (Csos 4) significantly deviated from Hardy-Weinberg Equilibrium (HWE, P < 0.05) across all populations sampled. When the data were partitioned by location (European and U.S. populations), loci Csos 2, Csos 3, and Csos 4 in European populations conformed to HWE (P > 0.05), whereas loci Csos 1, Csos 2, and Csos 3 in the U.S. conformed to HWE (P>0.05). No pairs of loci demonstrated linkage disequilibrium, neither across all populations, nor when the data was partitioned into European and U.S populations (P > 0.05). These results indicate the developed microsatellite markers for C. sosares are well suited for use as genetic markers for elucidating the population structure of C. sosares. In Chapter 4, I used the microsatellite markers developed in Chapter 3 and an additional mitochondrial marker to test three hypotheses: 1) C. sosares populations in the U.S. came from the same European location as their webworm hosts in Europe (Host-Pursuit Hypothesis), 2) once in the U.S., C. sosares followed a similar host plant switch onto cow parsnip as parsnip webworms (Continued Host-Pursuit Hypothesis), and 3) C. sosares populations will have limited geneflow between sites that are geographically farther apart, and differ in elevation (isolation by distance and elevation). The molecular data indicate the Netherlands and several other European sites served as sources for U.S. C. sosares populations, following the predictions from the Host-Shift Hypothesis. European C. sosares populations from hogweed have directly established on U.S. cow parsnip, and U.S. C. sosares populations on wild parsnip have host plant switched to cow parsnip. However, C. sosares geneflow is not restricted to either host plant species in the U.S., contrary to our findings with U.S. webworms. Overall, the factors that can influence the establishment of an herbivore (i.e., host plant species, concentrations of plant toxins) in an introduced area, may not be important for its primary parasitoid.Item Open Access Phase-based analysis to determine first order decay rates for a bioreactor landfill(Colorado State University. Libraries, 2017) Nwaokorie, Kelechi J., author; Bareither, Christopher A., advisor; Sharvelle, Sybil E., advisor; von Fischer, Joseph C., committee memberIn recent years, the goal of municipal solid waste (MSW) landfill management has transitioned from waste sequestration to waste stabilization. A bioreactor landfill is an MSW landfill operated with a deliberate goal to achieve waste stabilization via in situ organic waste decomposition. Enhanced landfill gas (LFG) generation that results from moisture addition to increase the rate of anaerobic biodegradation can have different consequences on landfill operations. Additionally, landfills commonly are constructed and filled in phases (i.e., delineated areas of the landfill where waste is placed) that are operated with different moisture enhancement strategies. Thus, there is a need to simulate and predict LFG generation in a bioreactor landfill on a phase-specific basis to more accurately assess waste decomposition and progression of organic waste stabilization. In this study, site-wide and phase-specific LFG modeling was conducted for a bioreactor landfill. A phase-specific LFG modeling approach was developed and used to assess six separate phases of the landfill. This approach included a temporal estimate of waste disposal and separation of LFG collection data for the six phases. Landfill gas collection in each phase was used to compute methane collection based on gas composition analyses and used to estimate methane generation based on two considerations of collection efficiency: constant collection efficiency of 85% and temporally varying collection efficiency. Methane generation was predicted using the U.S. EPA LandGEM. Model simulations were compared with adjusted methane collection data to optimize the first-order decay rate (k), which was the primary variable used to assess waste decomposition and stabilization. First-order decay rates were optimized for site-wide and phase-specific analyses that considered (i) monthly versus annual averaging techniques for LFG data, (ii) collection efficiencies, and (iii) LFG collected only in the gas wells versus LFG collected in gas wells and perforated pipes in leachate collection and recirculation systems. The recommended gas modeling approach is to use monthly average LFG flow rates, a constant collection efficiency of 85%, and LFG collected from gas wells and leachate collection / recirculation systems. The optimized k for the site-wide analysis was 0.078 1/yr, whereas the default k for conventional MSW landfills with no moisture enhancement is 0.04 1/yr. Thus, the site-wide k supports enhanced organic waste biodegradation and stabilization. The optimized ks for the phase-specific analyses ranged between 0.025 and 0.13 1/yr, which suggest that although the overall site was operating at an enhanced rate of waste decomposition, the rate varied between landfill phases. Moisture addition via leachate recirculation and liquid waste addition was implemented at the landfill for the five more recent phases. The k values for these five phases increased with increasing liquid addition per waste mass whereby the optimized k values increased from the driest phase, Phase 3 & 4 (0.037 1/yr), to the wettest phase, Phase 6 (0.127 1/yr). The LFG modeling and findings from this study can assist with developing moisture enhancement strategies for bioreactor landfills and assessing LFG collection data to support claims of enhanced waste decomposition and stabilization.Item Open Access Plasma modification of metal oxides and textiles: tailoring surface properties for improved gas sensor and protective clothing applications(Colorado State University. Libraries, 2021) Hiyoto, Kimberly A. M., author; Fisher, Ellen R., advisor; Menoni, Carmen S., committee member; Rappe, Anthony K., committee member; von Fischer, Joseph C., committee memberThis dissertation focuses on utilizing inductively coupled plasma processing to modify various materials for applications in gas sensing and protective clothing. By relating changes in the plasma gas-phase during treatment, resulting material characteristics, and application-based performance, insights into how these materials work can be gained. Ultimately, this knowledge allows for a targeted approach to optimizing the material's surface properties for a specific behavior. The first part of this work concentrates on the plasma modification of semiconducting metal oxides (SMO) to create gas sensors that are more responsive to a target gas at lower operating temperatures. First, SnO2 nanoparticles (NP) supported by a traditional substrate (ZrO2 wafer) were treated with a CO or CO2 plasma as a function of applied plasma power (P). X-ray photoelectron spectroscopy (XPS) analysis of the NP after plasma exposure demonstrates that the CO plasma deposits an amorphous carbon film, whereas the CO2 plasma results in the etching of the SnO2 lattice. Optical emission spectroscopy (OES) studies were used to identify key excited-state species in the plasma gas-phase to explain the depositing and etching nature of these two systems. Gas sensing performance studies demonstrate that the deposition of a film on the SnO2 blocked analyte-sensor interactions, resulting in a negative effect on the response of the sensor. The CO2 plasma treated sensors, however, displayed an increased response to benzene and CO at lower operating temperatures when compared to the untreated (UT) material. The adaptation of the SnO2 sensor and plasma treatments to be compatible with a paper-based sensor (PGS) provided positive indicators for future studies. Indeed, an Ar/O2 plasma was used to treat SnO2 NP PGS at P = 15 – 60 W. Similar to the CO2 plasma, this system has also been shown to etch the SnO2 lattice resulting in improved device performance. The PGS treated at 15 and 60 W showed an increased response to ethanol and CO at operating temperatures ≤50 °C. These studies indicate that the selectivity of the sensor can be tuned with plasma P. Additionally, these sensors showed some response and recovery behavior to ethanol, indicating that these devices are robust enough to be used multiple times. Preliminary work expanding the SMO used to make these PGS is also included to demonstrate the applicability of this device fabrication and plasma modification methods for other materials and SMO morphologies. These gas sensor studies highlight the importance of understanding the relationship between surface properties and device performance. By obtaining a better understanding of the gas detection process, a targeted approach to fabricating improved gas sensors can be established. The final section of this work examines the effect of fabric hydrophobicity on NP attachment and resuspension. These studies employed C3F8 and H2O(v) plasmas to treat four common lab coat materials. XPS and water contact angle goniometry confirm that the C3F8 plasma treatment increases the hydrophobicity of the fabrics and the H2O(v) plasma increases the wettability of most materials. Hydrophobic recovery studies of the H2O(v) treated samples suggest that there are minimal aging effects on the Tyvek® and 100% cotton fabrics, but further work is needed to optimize the plasma parameters for the 80/20 polyester/cotton and 100% polypropylene samples. The attachment and release behavior of Al2O3 NP, carbon black, and carbon nanotubes with the UT and treated materials are also discussed. Ideally, personal protective clothing should either repel (preventing initial NP attachment and fabric contamination) or hold on to (limiting the potential for secondary exposure from contaminated clothes) NP. In general, it is thought that the tightness of the fabric weave is the only factor that influences NP attachment and resuspension. Scanning electron microscopy images of the contaminated and shaken fabrics reveal that the surface chemistry of the material cannot be excluded as the attachment and release of the nanomaterials differed between the C3F8, H2O(v), and UT fabrics. Through these studies, fabric characteristics that influence the interaction with nanomaterials are explored and can be used to inform better safety recommendations when working with these materials.Item Open Access Sequence stratigraphic distribution of coal-bearing rocks from the Mesaverde Group in the easternmost Atlantic Rim of the Washakie Basin, Wyoming(Colorado State University. Libraries, 2010) Dereume, Jeffrey Michael, author; Egenhoff, Sven O., advisor; Harry, Dennis L., committee member; von Fischer, Joseph C., committee memberCoals occur in various levels of the siliciclastic Campanian upper Mesaverde Group in the Atlantic Rim area, Washakie Basin, south central Wyoming. This unit consists of continental, delta, and offshore facies showing several orders of internal cyclic architecture. At least five large-scale cycles form the upper part of the Mesaverde Group, internally arranged in stacks of up to five medium-scale cycles that are in turn subdivided into a maximum of five small-scale cycles. These cycles reflect million-year to Milankovitch-type sea-level fluctuations causing trans- and regression of varying magnitude, within an overall transgressive regime. Coals developed preferentially in paralic and lower coastal plain environments in the Atlantic Rim in relative proximity to a nearby delta. The position closest to the shoreline was occupied by coal-rich mudstones reflecting siliciclastic input from the delta and the sea during floods. Both coals and coal-rich siliciclastic mudstones occur during all stages of a sea-level curve. While previous models suggested a preferential accumulation of coals during early transgressions, a peak in coal frequency characterizes early regressive sediments within the Mesaverde Group in the Atlantic Rim. This is believed to be the result of a heightened water table during early regressions promoting anoxic swamp and marsh environments, and frequent flooding of floodplains forming an ideal setting for accumulation of organic matter. The lateral continuity of Mesaverde coals is also positively influenced by development within paralic settings. Many of the most correlative coal seams in the Atlantic Rim occur within close stratigraphic proximity and/or lateral to marine deposits. Integrating a sequence stratigraphic framework into the upper Mesaverde Group significantly enhances prediction patterns of coaly rocks by constraining their stratigraphic and lateral distributions. Clay- and silt-bearing organic-rich mudstones mark the transition from continental to marine facies, while pure coals only occur at a distance from the shoreline. The overall transgressive nature of the upper part of the Mesaverde Group reveals a highly diachronous facies distribution within the Washakie Basin. A significantly thicker coal-bearing interval characterizes the southern part, while successions further north show abundant mudstones, representing an overall earlier transition to marine conditions.