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Earth Sciences

Wright State University

2009

Articles 1 - 7 of 7

Full-Text Articles in Physical Sciences and Mathematics

Multiproxy Lake Sediment Records At The Northern And Southern Boundaries Of The Aspen Parkland Region Of Manitoba, Canada, Rebecca Teed, Charles Umbanhower, Philip Camill Sep 2009

Multiproxy Lake Sediment Records At The Northern And Southern Boundaries Of The Aspen Parkland Region Of Manitoba, Canada, Rebecca Teed, Charles Umbanhower, Philip Camill

Earth and Environmental Sciences Faculty Publications

Aspen parkland in central Canada may change substantially with increased warming and aridity as prairies replace forests, fire return intervals decrease and lake levels decline. We examined the relationships among vegetation, climate, fire and lake-ecosystem properties using lake sediment cores from the current northern and southern boundaries of the aspen parkland in southwestern Manitoba. We analyzed pollen, charcoal, sediment magnetics, biogenic silica, phosphorus, grain size and LOI, and dated the cores using 210Pb and 14C (AMS, calibrated). The Jones Lake record, from the southern edge of the parkland, began considerably earlier (~11 000 cal. BP) than the Mallard …

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Strain Waves, Earthquakes, Slow Earthquakes, And Afterslip In The Framework Of The Frenkel-Kontorova Model, Naum I. Gershenzon, V. G. Bykov, Gust Bambakidis May 2009

Strain Waves, Earthquakes, Slow Earthquakes, And Afterslip In The Framework Of The Frenkel-Kontorova Model, Naum I. Gershenzon, V. G. Bykov, Gust Bambakidis

Physics Faculty Publications

The one-dimensional Frenkel-Kontorova (FK) model, well known from the theory of dislocations in crystal materials, is applied to the simulation of the process of nonelastic stress propagation along transform faults. Dynamic parameters of plate boundary earthquakes as well as slow earthquakes and afterslip are quantitatively described, including propagation velocity along the strike, plate boundary velocity during and after the strike, stress drop, displacement, extent of the rupture zone, and spatiotemporal distribution of stress and strain. The three fundamental speeds of plate movement, earthquake migration, and seismic waves are shown to be connected in framework of the continuum FK model. The …

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Measuring The Permeability Of Open-Framework Gravel, James Thomas Ferreira Jr. Jan 2009

Measuring The Permeability Of Open-Framework Gravel, James Thomas Ferreira Jr.

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Open-framework gravel has permeability, k, above the measurement range of most conventional constant-head permeameters used in laboratories. Here I addressed the challenge of measuring such high k by using a permeameter long enough that the differences in head across it were on the order of 10-3 m and therefore measurable. I collected data over the range from linear-laminar flow to non-linear, non-Darcian flow. In doing so, I verified that k was measured under Darcian flow. I measured k between 4,000 and 100,000 Darcies among experiments using different sediments.

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Porosity And Permeability In Ternary Sediment Mixtures, Jason Dennis Esselburn Jan 2009

Porosity And Permeability In Ternary Sediment Mixtures, Jason Dennis Esselburn

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Porosity and permeability were measured in mixtures of fine, medium, and coarse sand, where the volume fraction of each of the three components was systematically varied. The porosity varies non-linearly with the volume fractions, and can be modeled with a piecewise-linear approach. The permeability also varies non-linearly with the volume fractions. Permeability can be modeled with the Kozeny-Carman equation using a recursive approach for computing the representative grain size from those of the components in the mixture.

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A Morphometric Analysis Of The Highly Variable Clypeasteroid, Periarchus Lyelli, Lauren Elizabeth Williamson Jan 2009

A Morphometric Analysis Of The Highly Variable Clypeasteroid, Periarchus Lyelli, Lauren Elizabeth Williamson

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The Late Eocene echinoid, Periarchus lyelli (Conrad, 1834), known for its wide geographic range, high abundance, and specific stratigraphic range, is an ideal example of a guide fossil. However, due to its highly variable test morphology, many have questioned if, in fact, this sand dollar is actually two or three distinct species that have been misclassified. A preliminary study on this subject has been performed on specimens from Mississippi, North Carolina and South Carolina (Williamson, 2006), showing significant separation in test shapes. Continuing previous research, this study analyzes the test shapes of P. lyelli over its entire North American geographic …

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Bench-Scale Conversion Of Carbon Dioxide To A Hydrocarbon Fuel, Melissa L. Kennedy Jan 2009

Bench-Scale Conversion Of Carbon Dioxide To A Hydrocarbon Fuel, Melissa L. Kennedy

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There is a growing concern about the effects of global warming that many believe is anthropogenically caused. As such, scientists are trying to uncover a viable alternative fuel source and establish a way to reduce atmospheric carbon dioxide levels. A potential solution that addresses both of these aspects would be to capture atmospheric carbon dioxide and convert it into a natural gas, in particular methane, which could be used as an energy source. A laboratory-scale experiment using 6 160 mL microcosms (3 with anaerobic wetland soil and 3 relatively soil free) and 2 7.2 L bioreactors was conducted to learn …

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Using Morphometrics, Phylogenetic Systematics And Parsimony Analysis To Gain Insight Into The Evolutionary Affinities Of The Calymenidae Trilobita, Alex J. Chestnut Jan 2009

Using Morphometrics, Phylogenetic Systematics And Parsimony Analysis To Gain Insight Into The Evolutionary Affinities Of The Calymenidae Trilobita, Alex J. Chestnut

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The most common trilobite in the Silurian carbonates of Ohio - especially the Springfield Dolomite - is a species that has been assigned to at least five genera over the past 100 years. This trilobite has been variously referred to as Calymene celebra, Apocalymene celebra, Flexicalymene celebra, Gravicalymene celebra, and Sthenarocalymene celebra. Reexamination of the species "Calymene" celebra through parsimony and morphometric analysis was conducted to properly place this calymenid species within the correct genus. What compounds the confusion is that the characters used to seperate the genera within the family Calymenidae, and therefore create the basis for the argument …

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