Browsing by Author "Murr, Ashley"

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    Acoustic Observations of Zooplankton Migration in Lake Superior
    (2023-07) Murr, Ashley
    The diel vertical migration (DVM) of aquatic organisms in marine environments is commonly studied using acoustic instruments because of their ability to sample with high spatial and temporal resolution for extended periods of time. The practice of using acoustic instruments in the Laurentian Great Lakes, however, is not as widespread. This research presents six years of Acoustic Doppler Current Profiler (ADCP) backscatter data from a site in Lake Superior to demonstrate that ADCPs can increase the resolution and robustness of data pertaining to the vertical migration of freshwater organisms, presumably zooplankton. We observed migratory behavior with sub-hour sampling over the course of entire seasons, including transitional seasons and the winter. The data distinctly reveals a diurnal signal consistent with DVM. In addition, with the high resolution of the data, we observe lunar and seasonal variation in the diurnal signal. We employ a simplified method using the change in measured intensity to isolate the diurnal signal, allowing us to compare data regardless of instrument modification, backscatter calibration, and range correction. We do not estimate abundance, biomass, population distribution, or species identification, instead we offer general observations on DVM patterns over days, months, and years to supplement standard biological sampling methods.
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    A Feasibility Investigation of Glass Pozzolans in Marine Concrete
    (2018) Murr, Ashley
    Marine concrete can be especially susceptible to chemical and physical deterioration, including corrosion of the reinforcement steel. For this reason, pozzolans such as fly ash, blast furnace slag, and silica fume, are commonly used to reduce corrosion in concrete subjected to marine environments by decreasing the permeability of the concrete matrix. The permeability of a concrete matrix is commonly used to indicate the susceptibility of a concrete to the corrosion of the steel reinforcement due to its effects on initial corrosion and subsequent corrosion. The water/cementitious materials (w/cm) ratio, binder type, curing conditions, and compaction factors can impact the level of permeability. A lower w/cm ratio can reduce the permeability, as does the addition of pozzolans. Ground glass is currently under intense scrutiny for its potential as a pozzolan in portland cement concrete, as it differs from other pozzolans due to its high alkali content. This research considers the potential for ground glass use as a pozzolan in marine concrete applications by investigating concrete mixtures with partial ground glass replacement. In order to determine whether ground glass reduces the permeability and therefore, chloride ion penetration, in marine concrete, a measurement of the electrical resistivity will be conducted.