Physical Sciences and Mathematics Commons^™

Estimating Permeability From The Grain-Size Distributions Of Natural Sediment, Lawrence Mastera

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Permeability, k, can be estimated using the Kozeny-Carman equation, given a grain-size distribution with any number of grain-size categories and the porosity of a sediment. A recursive method was developed to calculate the effective grain-size parameter, d, for sediment mixtures with more than three grain sizes. The method was tested on four sediment models of sand, gravelly sand, sandy gravel, and open-framework gravel created from grain-size distributions. The k estimated from the recursive method were consistent with physical measurements of k.

Ab Initio Simulations Of Hydrogen And Lithium Adsorption On Silicene, Tim H. Osborn

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The energies and temperature-dependent dynamics of hydrogen and lithium chemisorption on a silicon nanosheet, called silicene, were studied using density functional theory and molecular-dynamics (MD) simulations. Silicene has a buckled honeycomb structure, and has been fabricated as suspended monolayer sheets and nanoribbons in recent experiments. We calculated the adsorption energies of hydrogen and lithium on silicene for different adsorption ratios between 3.1% and 100%. The studies will clarify the characteristics of these novel and promising nanomaterials, and pave the way for their applications.

For Hydrogen, the adsorption energy had a maximum of 3.01 eV/H for complete hydrogenation, and decreased by …

Dimethylmercury Production In Freshwater Sediments, David C. Kelly

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Dimethylmercury (DMHg) has been examined almost exclusively in marine environments to date, plays an uncertain role in the global cycling of Hg, and is produced by a currently unknown mechanism in natural systems. We examined DMHg production in microcosms containing 100 cm3 of freshwater sediment sampled from 3 wetlands and a lake near Dayton, Ohio. DMHg was produced from all sediments analyzed, and found that production is increased significantly by the addition of inorganic Hg from ~0.1pM to ~10pM, its production is unaffected by autoclaving the sediment, and organic carbon additions had no discernible effect on production. Its total concentrations …

Crustacean Endocrine Disruption Through A Pathway Involving Nuclear Receptors, Cyclic Nucleotides And Calcium Transporters, Laxminath Tumburu

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Endocrine disruption is a complex phenomenon in the sense that endocrine disrupting chemicals (EDCs) are known to act via multiple modes of action, but the mechanisms of actions are poorly understood. In crustaceans, calcium (Ca²⁺) apart from its role as a second messenger, is also a major constituent of the calcified exoskeleton which undergoes a periodic mineralization/demineralization process known as the molting cycle. Molt cycle is under the control of steroid hormones, ecdysteroids. EDCs disrupt this molting process via their interference with receptor-mediated ecdysteroid signaling. However, the hormonal regulation of Ca²⁺ flux in crustacean molting is poorly …

Transport Through Georeservoirs: Spatial Entropy In Hydraulic Properties, And Temporal Entropy In Residence Time Distributions, Lumeng Huang

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The general principle of maximum entropy can be used to guide the construction of flow and transport models parameters when are uncertain. The principle states that the model which maximizes the entropy should be chosen so that the full multiplicity or uncertainty is represented in the model outcomes.

In models for flow and transport through georeservoirs, the principle would commonly be applicable to the uncertainty in the model outcome for the time of travel through the system, in order to represent the full range of multiplicity in the distribution of residence times. Importantly, the model which maximizes the entropy in …

Sulfur-Tolerant Catalyst For The Solid Oxide Fuel Cell, Bozeman Joe Frank Iii

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JP-8 fuel is easily accessible, transportable, and has hydrogen content essential to solid oxide fuel cell (SOFC) operation. However, this syngas has sulfur content which results in a poisonous hydrogen sulfide that degrades electrochemical activity and causes complete SOFC failure in some cases. The goal is to synthesize and verify a cost-effective, catalyst supported on cerium oxide that either stabilizes ionic conductivity in the presence of hydrogen sulfide and/or is highly sulfur-resistant. After thorough computational analysis, it was concluded that the platinum-copper skin catalyst was the most cost-effective, sulfur-resistant catalyst. Experimental synthesis of copper, platinum, and platinum-copper skin catalysts supported …

How The Growth Of The Frampton Fold Affected The Growth Of The Green Knoll Diapir, John A. Zinck

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The growth of structural features formed by the movement of the Louann Salt within the study area follows a fold-first model (Rowan et al., 2000), in which the formation of the Frampton Fold predates the formation of the Green Knoll Diapir. The Frampton Fold was formed during two growth episodes driven by movement of the Louann Salt within the study area. The folding and faulting resulting from these growth episodes created a conduit through which the autochthonous Louann Salt was extruded to the sea floor during the Pliocene. Following a depositional episode consisting of the early sequences of the Mississippi …

Estimating Evapotranspiration Using Remote Sensing: A Hybrid Approach Between Modis Derived Enhanced Vegetation Index, Bowen Ratio System, And Ground Based Micro-Meteorological Data, Sumantra Chatterjee

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We investigated water loss by evapotranspiration (ET) from the Palo Verde Irrigation District (PVID) and the Cibola National Wildlife Refuge (CNWR) in southern California bordering the Colorado River collaborating with the United States Bureau of Reclamation (U.S.B.R.). We developed an empirical model to estimate ET for the entire PVID using satellite derived MODIS enhanced vegetation index (EVI), and ground based measurements of solar radiation and vapor pressure. We compared our predictions with U.S.B.R. estimates through statistical cross validation and showed they agree with an error less than 8%. We tested the same model for an alfalfa field inside PVID to …

Reservoir Analysis Of The Clinton Interval In Stark And Summit Counties, Ohio, Dominick Andrew Wytovich

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The characteristics of a sandstone reservoir of Silurian age (the "Clinton interval") were analyzed using 382 geophysical well logs from the Dominion Gas storage field located in Stark and Summit Counties, Ohio. These sandstones have long been identified by the informal drillers' terms, White, Red, and Stray Clinton. Gamma ray logs were used to analyze the distribution of net stand thickness and its relation to initial production through the construction of isopach and net sand isolith maps. I constructed eight cross sections to identify and correlate the tops of three prominent sandstones and two marine flooding surfaces to evaluate reservoir …

Functional Identification Of Microorganisms That Transform Mercury In Marine Sediments, Lisa Romas

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Monomethylmercury (MMHg) is the toxic form of mercury (Hg) that biomagnifies in food webs, and human exposure to MMHg occurs predominantly via consumption of fish. The primary source of MMHg to the marine environment is thought to be in situ sedimentary production by benthic microorganisms, namely sulfate-reducing bacteria (SRB). I collected sediments from the continental shelf (stations 2 and 6) and slope (station 9) of the NW Atlantic Ocean, and amended them with various inhibitor and promoter solutions to target specific functional groups capable of Hg transformations. I also added stable enriched Hg isotopes to quantify gross Hg methylation and …

Mercury Speciation In Temperate Tree Foliage, Melissa Danielle Tabatchnick

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Cycling of mercury (Hg) and monomethylmercury (MMHg) in forest ecosystems can affect exposures of terrestrial and aquatic wildlife within the watershed. Litterfall has been posited to be a major source of MMHg and total Hg to the forest floor; however, the origin of MMHg associated with tree foliage is largely unknown. I tested the hypothesis that leaf MMHg would be controlled by root uptake and thereby proportional to levels in soil. Fresh leaves and associated soil samples were sampled from nine tree species (deciduous and coniferous) at 30 locations spanning a 1145 km2 area in southwest Ohio, a region presumed …

Trace Metal Fluxes In Southwest Ohio Watersheds, Avani Naik

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Land-use and watershed characteristics affect the cycling and transport of trace metals in rivers. I investigated the influence of different land uses and water physicochemistry on loadings, partitioning, and speciation of Hg, Zn, Cr, Ni, V, Cd, Cu, and Pb in three contrasting watersheds near the Dayton, Ohio metropolitan area over a 13-month period; Wolf Creek (urban/residential), Holes Creek (urban/residential), and Little Miami River (agricultural). Metal concentrations were related positively to discharge in each stream. Dissolved organic ligands appear to influence trace-metal partitioning between filtered and particle phases, however, particle-associated metals were dominant in each site. Total Hg concentrations and …

Biodegradation Of Groundwater Pollutants (Chlorinated Hydrocarbons) In Vegetated Wetlands: Role Of Aerobic Microbes Naturally Associated With Roots Of Common Plants, Christina Lynn Powell

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Chlorinated aliphatic hydrocarbons (CAHs) are often found as groundwater contaminants because of past industrial activities and disposal practices. CAHs pose a threat to human health and thus, create a need to find both natural and engineered processes that can remove these chlorinated compounds from the environment. Natural attenuation by oxidative biodegradation is especially important because it can allow for mineralization to carbon dioxide, a nontoxic end-product. The goal of this research was to evaluate the potential oxidative biodegradation of CAHs by microorganisms that are naturally associated with wetland plant roots. The research was divided into field work and laboratory batch …

Fabrication Of Zinc Oxide Thin Films For Renewable Energy And Sensor Applications, Theresa Y. Hill

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Progress in commercializing renewable energy technologies is being advanced by developments in Zinc Oxide material science. The photovoltaic cell, for example, generates electricity by receiving solar energy into the cell, generating electrons, and simultaneously transporting electrical charge out of the cell. Metals are capable of removing electrical charge but block transmission of sunshine. Glass and plastics are capable of transmitting sunshine but block the removal of electrical charge. Therefore an exterior layer that is both optically transparent and electrically conductive is desirable. Transparent conductive oxides (TCOs) are the ideal material for such applications since they are capable of both functions. …

Conversion Of Carbon Dioxide And Hydrogen Into Methane In Bench-Scale Microcosms And Packed Column Reactors, Brian Alexander Congiu

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Escalating energy demands, rising costs, and increasing awareness of the environmental impacts of current energy sources have created an immediate need for sustainable, alternative energy resources and innovative fuel technologies. It is believed that a potential carbon-neutral fuel source can be generated through the microbial production of methane gas by methanogenic archaea. Carbon dioxide captured from the atmosphere and renewable production of hydrogen can be used to support these microorganisms for the large-scale production of methane. Bench-scale investigations involving 160 mL serum bottle batch experiments and two 11L packed-column reactors were conducted to evaluate the feasibility and efficiency of microbial …