Physical Sciences and Mathematics Commons^™

An Evaluation Of Disturbance-Induced Nutrient Changes And Climate Responses Of Loblolly Pine Xylem, Rebecca Lynne Stratton

Doctoral Dissertations

Dendrochronological techniques are currently limited to the identification of visible fire scars. However, through the development of new dendrochemical techniques, the potential exists to provide insight into a broader array of pyric ecosystems. In addition, the ability to identify historic climate-growth responses provides a better understanding of the conditions under which historic fire regimes occurred.

This study provides the groundwork for the identification of a dendrochemical nutrient fire signature in xylem and identifies the climate-radial growth responses of loblolly pine (Pinus taeda L.) on five sites in the Piedmont of South Carolina. Changes in N, P, K, Ca, Mg, …

Development And Application Of Liquid Chromatography-Tandem Mass Spectrometry Methods To The Understanding Of Metabolism And Cell-Cell Signaling In Several Biological Systems, Jessica Renee Gooding

Doctoral Dissertations

Liquid chromatography tandem mass spectrometry has become a powerful tool for investigating biological systems. Herein we describe the development of both isotope dilution mass spectrometry methods and targeted metabolomics methods for the study of metabolic and cell-cell signaling applications.

A putative yeast enzyme was characterized by discovery metabolite profiling, kinetic flux profiling, transcriptomics and structural biology. These experiments demonstrated that the enzyme shb17 was a sedoheptulose bisphosphatase that provides a thermodynamically dedicated step towards riboneogenesis, leading to the redefinition of the canonical pentose phosphate pathway.

An extension of metabolic profiling and kinetic flux profiling methods was developed for a set …

A Geospatial Based Decision Framework For Extending Marssim Regulatory Principles Into The Subsurface, Robert Nathan Stewart

Doctoral Dissertations

The Multi-Agency Radiological Site Survey Investigation Manual (MARSSIM) is a regulatory guidance document regarding compliance evaluation of radiologically contaminated soils and buildings (USNRC, 2000). Compliance is determined by comparing radiological measurements to established limits using a combination of hypothesis testing and scanning measurements. Scanning allows investigators to identify localized pockets of contamination missed during sampling and allows investigators to assess radiological exposure at different spatial scales. Scale is important in radiological dose assessment as regulatory limits can vary with the size of the contaminated area and sites are often evaluated at more than one scale (USNRC, 2000). Unfortunately, scanning is …

A Time-And-Space Parallelized Algorithm For The Cable Equation, Chuan Li

Doctoral Dissertations

Electrical propagation in excitable tissue, such as nerve fibers and heart muscle, is described by a nonlinear diffusion-reaction parabolic partial differential equation for the transmembrane voltage $V(x,t)$, known as the cable equation. This equation involves a highly nonlinear source term, representing the total ionic current across the membrane, governed by a Hodgkin-Huxley type ionic model, and requires the solution of a system of ordinary differential equations. Thus, the model consists of a PDE (in 1-, 2- or 3-dimensions) coupled to a system of ODEs, and it is very expensive to solve, especially in 2 and 3 dimensions.

In order to …

Optimal Theory Applied In Integrodifference Equation Models And In A Cholera Differential Equation Model, Peng Zhong

Doctoral Dissertations

Integrodifference equations are discrete in time and continuous in space, and are used to model the spread of populations that are growing in discrete generations, or at discrete times, and dispersing spatially. We investigate optimal harvesting strategies, in order to maximize the profit and minimize the cost of harvesting. Theoretical results on the existence, uniqueness and characterization, as well as numerical results of optimized harvesting rates are obtained. The order of how the three events, growth, dispersal and harvesting, are arranged also affects the harvesting behavior.

Cholera remains a public health threat in many parts of the world and improved …

Adaptation And Stochasticity Of Natural Complex Systems, Roy David Dar

Doctoral Dissertations

The methods that fueled the microscale revolution (top-down design/fabrication, combined with application of forces large enough to overpower stochasticity) constitute an approach that will not scale down to nanoscale systems. In contrast, in nanotechnology, we strive to embrace nature’s quite different paradigms to create functional systems, such as self-assembly to create structures, exploiting stochasticity, rather than overwhelming it, in order to create deterministic, yet highly adaptable, behavior. Nature’s approach, through billions of years of evolutionary development, has achieved self-assembling, self-duplicating, self-healing, adaptive systems. Compared to microprocessors, nature’s approach has achieved eight orders of magnitude higher memory density and three orders …

The ‘Helper’ Phenotype: A Symbiotic Interaction Between Prochlorococcus And Hydrogen Peroxide Scavenging Microorganisms, James Jeffrey Morris

Doctoral Dissertations

The unicellular cyanobacterium Prochlorococcus is the numerically dominant photosynthetic organism throughout the temperate and tropical open oceans, but it is difficult to grow in pure cultures. We developed a system for rendering spontaneous streptomycin-resistant mutants of Prochlorococcus axenic by diluting them to extinction in the presence of “helper” heterotrophic bacteria, allowing them to grow to high cell concentrations, and then killing the helpers with streptomycin. Using axenic strains obtained in this fashion, we demonstrated that Prochlorococcus experiences a number of growth defects in dilute axenic culture, including reduced growth rate, inability to form colonies on solid media, and higher incidence …