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Articles 1 - 30 of 40
Full-Text Articles in Physical Sciences and Mathematics
Fate And Reactivity Of Natural And Manufactured Nanoparticles In Soil/Water Environments, Allison Vandevoort
Fate And Reactivity Of Natural And Manufactured Nanoparticles In Soil/Water Environments, Allison Vandevoort
All Dissertations
Nanoparticles (NPs), < 100 nm in diameter, make up the smallest component of solid material. This small size often causes increased reactivity in soil/water environments, which is true for both natural NPs, such as very fine clay particles, and for manufactured nanoparticles, such as silver nanoparticles (AgNPs). As the importance of these particles is more widely recognized, and as manufactured nanoparticles, especially AgNPs, are increasing in production, it is essential to consider their effect on terrestrial and aquatic environments. The studies presented in this dissertation show that both the physicochemical characteristics of the NPs (e.g., particle size, surface coating, elemental composition), as well as soil-water interfacial chemistry (e.g., ionic strength, ligand concentration, pH), are instrumental in predicting environmental fate and reactivity.
Ligand type and concentration were especially important in NP reactivity and bioavailability. Using the hard/soft acid/base concept, the effect of phosphate ligand (hard base) on Fe/Al (hard acid) oxyhydroxide natural NPs was investigated in Chapters 2 and 3. Adding phosphate to soil NPs and reference nano-minerals (Fe-(oxyhydr)oxides and kaolinite) caused coagulation or dispersion, changing the particle size of the NPs, as well as affecting the amount of phosphate in its bioavailable (i.e., dissolved) form. A review of the literature in Chapters 1 and 3 revealed that changes in the soil conditions, and therefore, soil colloids/NPs (e.g., increasing organic …
Planet Formation In Transition Disks: Modeling, Spectroscopy, And Theory, Joseph Liskowsky
Planet Formation In Transition Disks: Modeling, Spectroscopy, And Theory, Joseph Liskowsky
All Dissertations
An important field of modern astronomy is the study of planets. Literally for millennia, careful observers of the night sky have tracked these 'wanderers', with their peculiar motions initiating avenues of inquiry not able to elucidated by a study of the stars alone: we have discovered that the planets (as well as Earth) orbit the sun and that the stars are so far away, even their relative positions do not seem to shift perceptibly when Earth's position moves hundreds of millions of miles. With the advent of the telescope, and subsequent improvements upon it over the course of centuries, accelerating …
Sample Preparation Techniques For The Improvement Of Analytical Measurements: Capillary-Channeled Polymer Fibers Employed In Protein Solid Phase Extraction Applications And Characterization Of Active Components In Botanical Dietary Supplements, Carolyn Burdette
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The task of sample preparation encompasses many challenges and demands for analytical techniques. Appropriate preparative steps can be the determining factor between successful measurements and failures. Too little preparation can lead to the inability to detect analytes due to low concentrations, insufficient extraction of analytes, and/or strong matrix effects; exhaustive preparation steps increases analysis times, the potential for analyte losses, and the difficulty to obtain consistent reproducible results. Discussed here are several examples of analytical techniques where sample preparation is critical and can be used to improve existing techniques. Capillary-channeled polymer (C-CP) fibers used for solid phase extraction (SPE) protein …
Understanding Nanoparticle-Cell Interaction, Ran Chen
Understanding Nanoparticle-Cell Interaction, Ran Chen
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Nanotechnology has revolutionalized the landscape of modern science and technology, including materials, electronics, therapeutics, bioimaging, sensing, and the environment. Along with these technological advancements, there arises a concern that engineered nanomaterials, owing to their high surface area and high reactivity, may exert adverse effects upon discharge to compromise biological and ecological systems. Research in the past decade has examined the fate of nanomaterials in vitro and in vivo, as well as the interactions between nanoparticles and biological and ecosystems using primarily toxicological and ecotoxicological approaches. However, due to the versatility in the physical and physicochemical properties of nanoparticles, and due …
Conservation Needs Of Nearshore Seabirds In The Southeastern U.S. Addressed Through Habitat Use Surveys And Assessments Of Health And Mercury Concentrations, Lisa Eggert
All Dissertations
Seabirds encounter a range of natural and anthropogenic stressors in the nearshore environment and are ideal candidate species for long-term monitoring of changes to coastal systems. The mitigation of threats to nearshore seabirds requires management of essential coastal habitat and monitoring population health and trends. In this dissertation, I first evaluated intertidal habitat use for a suite of coastal species as it relates to management practices at a seabird nesting island in South Carolina. Specifically, my objectives were (1) to determine intertidal areas of high bird abundance, (2) to examine course-scale habitat characteristics and human use of intertidal areas associated …
Sensitivity Analysis In Magnetic Resonance Elastography And A Local Wavelength Reconstruction Based On Wave Direction, Christopher Gillam
Sensitivity Analysis In Magnetic Resonance Elastography And A Local Wavelength Reconstruction Based On Wave Direction, Christopher Gillam
All Dissertations
or the detection of early stage cancer. MRE utilizes interior data for its inverse problems, which greatly reduces the ill-posedness from which most traditional inverse problems suffer.
In this thesis, we first establish a sensitivity analysis for viscoelastic scalar medium with complex wave number and compare it with the purely elastic case. Also we estimate the smallest detectable inclusion for breast and liver, which is about twice larger than using the purely elastic model. We also found the existence of optimal frequency (50 Hz) that maximizes the detectability when the Voigt model is used.
Second, we propose a local wavelength …
Asymptotics For The Arc Length Of A Multivariate Time Series And Its Applications As A Measure Of Risk, Tharanga Wickramarachchi
Asymptotics For The Arc Length Of A Multivariate Time Series And Its Applications As A Measure Of Risk, Tharanga Wickramarachchi
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The necessity of more trustworthy methods for measuring the risk (volatility) of financial assets has come to the surface with the global market downturn This dissertation aims to propose sample arc length of a time series, which provides a measure of the overall magnitude of the one-step-ahead changes over the observation time period, as a new approach for quantifying the risk. The Gaussian functional central limit theorem is proven under finite second moment conditions. Without loss of generality we consider equally spaced time series when first differences of the series follow a variety of popular stationary models including autoregressive moving …
Sorption And Enantiomerization Of Current Use Chiral Pesticides, April Hall
Sorption And Enantiomerization Of Current Use Chiral Pesticides, April Hall
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Chiral pesticides are prevalent in the environment today and are known to react selectively with chiral environmental components such as microbes, enzymes, and other naturally occurring chiral materials. In addition, chiral sorption is a process that has been occasionally investigated in the study of homochirality (the exclusive presence of one enantiomer in living organisms), but almost overlooked in environmental science. For chiral sorption to occur, the sorbent and sorbate must be chiral entities. In the environment, there are abundant natural surfaces that are chiral, including clay minerals and organic matter present in soil, sediment and aqueous solution. A knowledge of …
The Behavior And Toxicity Of Metal Oxide Nanoparticles In Aqueous Solution, Phenny Mwaanga
The Behavior And Toxicity Of Metal Oxide Nanoparticles In Aqueous Solution, Phenny Mwaanga
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The dissolution and aggregation of metal oxides nanoparticles (NPs) in aqueous solution not only alter the abundance and toxicology of NPs, but also makes the effective assessment and the correct interpretation of effects of NPs on organisms challenging. The extent to which these processes (dissolution and aggregation) occur largely depend on pH, ionic strength, dissolved natural organic matter (NOM) and NPs characteristics. This study investigated the dissolution and aggregation behavior of the four metal oxide NPs (nZnO, nCuO, nFe2O3 and nTiO2) in aqueous solution as influenced by pH, ionic strength and NOM and examined the toxicity of these NPs to …
Solvation Energy Of Biomolecular Structures: A Study Of The Effect Of Salt On Biomolecules Through Implicit As Well As Explicit Solvation Methods, Mihir Date
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In the current dissertation, studies related to solvation energy of protein structures using implicit as well explicit solvation methods have been discussed. Special focus is given to explore effect of salt on the fold stability of proteins and enzymes. Salt plays a crucial role in the functioning of all proteins, enzymes and nucleic acids. Change in salt concentration of the medium has large impact on stability and activity of these biological macromolecules. Therefore exploring mechanism of salt effect on them and development of an efficient model to calculate the salt effect has fundamental as well as practical importance in the …
Spider Mediation Of Polychlorinated Biphenyl Transport And Transformation Across Riparian Ecotones, Diana Delach
Spider Mediation Of Polychlorinated Biphenyl Transport And Transformation Across Riparian Ecotones, Diana Delach
All Dissertations
Polychlorinated biphenyls (PCBs) contaminate the sediment of the Twelvemile Creek / Lake Hartwell Superfund Site, and are known to be transported throughout the resident biota via trophic transport. Riparian spiders have recently become of interest because they are terrestrial organisms that have significant PCB exposures derived from aquatic sources. Many riparian spiders primarily consume insects emerging from contaminated aquatic systems, and these spiders can have a body burden as high as 2900 ng/g lipid. These emergent insects carry contaminants out of the river and into the riparian zone where they are captured by spiders, which effectively directs the contamination towards …
Spectroscopic Signature For Bundling, Edge States And Impurities In 1d And 0d Materials, Kiran Kumar Lingam
Spectroscopic Signature For Bundling, Edge States And Impurities In 1d And 0d Materials, Kiran Kumar Lingam
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Study of nanomaterials has gained interest of researchers from various fields of science and technology due to their unique electronic and vibrational properties as compared to their bulk counterparts. In particular, carbon nanotechnology has evolved rapidly over the past few decades and nowadays, carbon nanotubes are used in various fields such as energy storage, electronics etc. However, the quest for new properties of this material is never ending and the invention of graphene generated enormous interest in the scientific community due to its excellent properties such as strength, high electron mobility, thermal conductivity etc. In this thesis, I aim at …
Polyhedral Approximations Of Quadratic Semi-Assignment Problems, Disjunctive Programs, And Base-2 Expansions Of Integer Variables, Frank Muldoon
Polyhedral Approximations Of Quadratic Semi-Assignment Problems, Disjunctive Programs, And Base-2 Expansions Of Integer Variables, Frank Muldoon
All Dissertations
This research is concerned with developing improved representations for special families of mixed-discrete programming problems. Such problems can typically be modeled using different mathematical forms, and the representation employed can greatly influence the problem's ability to be solved. Generally speaking, it is desired to obtain mixed 0-1 linear forms whose continuous relaxations provide tight polyhedral outer-approximations to the convex hulls of feasible solutions. This dissertation makes contributions to three distinct problems, providing new forms that improve upon published works.
The first emphasis is on devising solution procedures for the classical quadratic semi-assignment problem(QSAP), which is an NP-hard 0-1 quadratic program. …
Sensitivity Anaylsis And Detectability For Magnetic Resonance Elastography, Catherine White
Sensitivity Anaylsis And Detectability For Magnetic Resonance Elastography, Catherine White
All Dissertations
This thesis is for a sensitivity analysis of magnetic resonance elastography, a hybrid imaging technique used in early-stage cancer screening. To quantitatively analyze the sensitivity, we introduce a notion of detectability, which is dened as a relative amplitude
drop in a small sti tumor region. This analysis is accomplished in both the full elastic and viscoelastic models and compared with that of the simpler scalar model which is frequently used in the actual application.
Some of the highlights are 1) a useful formula for detectability in terms of physical parameters, which will help the design of experiments; 2) the discrepancy …
Synthesis And Characterization Of Magnetic Solids Featuring 3d-4f Heterometallic Oxides Comprised Of Spin Chains And 3d-6p Noncentrosymmetric Oxides Templated By Acentric Salt Units, Jennings West
All Dissertations
The studies and syntheses presented in this dissertation were primarily aimed at exploring new magnetic solids comprised of special framework oxides with novel magnetic properties. Low-dimensional magnetic behavior has been of great interest, especially pertaining to molecular solids having single magnetic domains where slow relaxation and quantum properties of magnetization are evident. In attempts to mimic molecular magnets and achieve reduced dimensionality of, in this case 3d-;4f magnetic sublattices, diamagnetic oxyanions, XOmn-, and A-site cations (A = alkali and alkaline-earth metals) were used as nonmagnetic spacers in hopes of disrupting or confining magnetic interactions in certain dimensions. The …
Physicic-Based Algorithms And Divergence Free Finite Elements For Coupled Flow Problems, Nicholas Wilson
Physicic-Based Algorithms And Divergence Free Finite Elements For Coupled Flow Problems, Nicholas Wilson
All Dissertations
This thesis studies novel physics-based methods for
simulating incompressible fluid flow described by the Navier-Stokes equations (NSE) and
magnetohydrodynamics equations (MHD).
It is widely accepted in computational fluid dynamics (CFD) that numerical schemes which are more
physically accurate lead to more precise flow simulations especially over long time intervals.
A prevalent theme throughout will be the inclusion of as much
physical fidelity in numerical solutions as efficiently possible. In algorithm design, model
selection/development, and element choice, subtle changes can provide better physical accuracy,
which in turn provides better overall accuracy (in any measure). To this end we develop and study …
The Power Of Thermonuclear Supernovae After One Year, Ginger Bryngelson
The Power Of Thermonuclear Supernovae After One Year, Ginger Bryngelson
All Dissertations
Type Ia supernovae (SNe Ia), the thermonuclear explosion of a white dwarf, shape our understanding of the expansion of the universe with the use of their uniformity in distance determinations. Powered by radioactivity synthesized in the explosion, they fade slowly over hundreds of days. Sometime after 200 days, the continually expanding ejecta allows γ-rays from 56 Ni and 56 Co decays to escape, and soon any radioactive power contributing to lighting up the SN comes from positrons formed in 19% of 56 Co
decays.
While at first it seemed that positrons escaped through the thinning ejecta, it has become apparent …
Sparsity Regularization In Diffuse Optical Tomography, John Cooper
Sparsity Regularization In Diffuse Optical Tomography, John Cooper
All Dissertations
The purpose of this dissertation is to improve image reconstruction in Diffuse Optical Tomography (DOT), a high contrast imaging modality that uses a near infrared light source. Because the scattering and absorption of a tumor varies significantly from healthy tissue, a reconstructed spatial representation of these parameters serves as tomographic image of a medium. However, the high scatter and absorption of the optical source also causes the inverse problem to be severely ill posed, and currently only low resolution reconstructions are possible, particularly when using an unmodulated direct current (DC) source.
In this work, the well posedness of the forward …
Avian Phenology, Climate, And Land-Use Conservation Assessed At Broad Spatial And Temporal Scales Using Interdisciplinary Approaches And Citizen Science, Jason Courter
All Dissertations
Current natural resource challenges include global alteration of land cover, loss of biodiversity, impacts from increasing demands for agricultural products, and climate change. Birds are often used to assess the effects of ecological stressors because they are sensitive to environmental changes, ubiquitous and charismatic, and long-term monitoring programs have been in place for more than a century. I demonstrate the effects of climate change on avian migration and nesting dates and the potential value of using interdisciplinary approaches and citizen science to address contemporary ecological challenges. I examine Ruby-throated Hummingbird (Archilochus colubris) migration in the eastern United States from 1880-2010 …
Environmental Implications And Applications Of Nanomaterials, Priyanka Bhattacharya
Environmental Implications And Applications Of Nanomaterials, Priyanka Bhattacharya
All Dissertations
Recent advances in material science and nanotechnology have given rise to a myriad of developments, while in the meantime call for research into the impacts of nanomaterials on the environment and human health. Although considerable progress has been made in the past decade concerning the behavior of nanomaterials in biological systems, such understanding is critically lacking with respect to the fate of nanomaterials in ecosystems.
Accordingly, this dissertation addresses the interactions between nanomaterials and algae--the major constituent of the aquatic food chain (Part I, Chapter two), and exploits the physicochemistry of nanoscaled synthetic dendritic polymers for environmental applications, especially for …
The Influence Of Flagship Species On In Situ And Ex Situ Wildlife Tourists' Connection To Wildlife And Pro-Conservation Behaviors, Jeffrey Skibins
The Influence Of Flagship Species On In Situ And Ex Situ Wildlife Tourists' Connection To Wildlife And Pro-Conservation Behaviors, Jeffrey Skibins
All Dissertations
Annually, millions of tourists visit natural areas and zoos primarily to view flagship species such as lions and elephants. Venues rely on the inherent charisma of these species to increase visitation and anchor conservation efforts. Expected visitor outcomes from the use of flagships include raised levels of awareness and pro-conservation behaviors. However, the role of flagships in wildlife tourism has been criticized for not delivering conservation benefits for species of interest or biodiversity, and producing negative site impacts. Furthermore, little is known about how the connection to a species influences conservation behaviors. This dissertation addresses this gap in knowledge by …
The Influence Of Land Use On Fish Health And Fish Communities In Wadeable Steams In South Carolina, Andrew Sayer
The Influence Of Land Use On Fish Health And Fish Communities In Wadeable Steams In South Carolina, Andrew Sayer
All Dissertations
In 2011 the State of South Carolina population was over 4.6 million people and has increased at a rate of around 15% (1.5% per year) throughout the last decade. While the population density per square mile is relatively low compared to other US states, it seems certain the population will further increase in years to come. Increasing population density leads to urbanization resulting in an increase in impervious surfaces such as roadways, parking lots, and building roofs. This changing land use can have dramatic effects on smaller streams and creeks which form the upper reaches of watersheds. Although water systems …
Fast And Efficient Classification, Tracking, And Simulation In Wireless Sensor Networks, Hao Jiang
Fast And Efficient Classification, Tracking, And Simulation In Wireless Sensor Networks, Hao Jiang
All Dissertations
Wireless sensor networks are composed of large numbers of resource-lean sensors that collect low-level inputs from the physical world. The applications present challenges for programmers. On the one hand, lightweight algorithms are required given the limited capacity of the constituent devices. On the other, the algorithms must be scalable to accommodate large networks. In this thesis, we focus on the design and implementation of fast and lean (yet scalable) algorithms for classification, simulation, and target tracking in the context of wireless sensor networks. We briefly consider each of these challenges in turn.
The first challenge is to achieve high precision …
Probing And Controlling Fluid Rheology At Microscale With Magnetic Nanorods, Alexander Tokarev
Probing And Controlling Fluid Rheology At Microscale With Magnetic Nanorods, Alexander Tokarev
All Dissertations
This Dissertation is focused on the development of new methods for characterization and control of fluid rheology using magnetic nanorods. This Dissertation consists of five chapters. In the first chapter, we review current microrheologial methods and develop a Magnetic Rotational Spectroscopy (MRS) model describing nanorod response to a rotating magnetic field. Using numerical modeling, we analyze the effects of materials parameters of nanorods and fluids on the MRS characteristic features. The model is designed for a specific experimental protocol. We introduce and examine physical parameters which can be measured experimentally. The model allows identification of MRS features enabling the calculation …
Mass Latex Balloon Releases And The Potential Effects On Wildlife, Stephan Irwin
Mass Latex Balloon Releases And The Potential Effects On Wildlife, Stephan Irwin
All Dissertations
The first component of the study examined the fate of balloons after release to determine aspects of where, in what state, and how long they persist in the environment to assess potential risk of exposure to wildlife. Tagged balloons from sporting events gave estimates of mean distances traveled from releases. Effects on the structural integrity of the latex balloon as it reaches the upper atmosphere were also tested to determine the physical state when fragments landed. Degradation studies were conducted to determine the length of time latex can persist in the environment after exposure to various environmental conditions (sun, shade, …
Thermoelectric Properties Of Silicon Germanium: An In-Depth Study To The Reduction Of Lattice Thermal Conductivity, Daniel Thompson
Thermoelectric Properties Of Silicon Germanium: An In-Depth Study To The Reduction Of Lattice Thermal Conductivity, Daniel Thompson
All Dissertations
Thermoelectric materials provide a solid state route for the direct conversion between thermal and electrical energy. Hence, thermal gradients can be used to generate power of up to several KW, or driven DC power can be used to pump heat in or out of a system. Recent pushes in thermoelectric research are for power generation materials with higher efficiency. These materials can be used to recover energy from the waste heat of vehicles' exhaust systems, and as power generators for extraterrestrial exploration when coupled with a radioactive heat source.
The goal of this dissertation will be to demonstrate a new …
Surface Modifications Of Capillary-Channeled Polymer (C-Cp) Fibers For Applications In Highly Selective Separations, Jennifer Pittman
Surface Modifications Of Capillary-Channeled Polymer (C-Cp) Fibers For Applications In Highly Selective Separations, Jennifer Pittman
All Dissertations
High Performance Liquid Chromatography (HPLC) is a key component in the purification and separation of biological samples. Stationary phases in HPLC are generally silica based porous particles or monoliths designed with high surface area and high capacities in mind. However, in the field of macromolecule separations, specifically proteins, the porous based stationary phases have inherent issues that include slow mass transfer, high operating back pressures, and analyte carryover. Recent research has looked to non-porous polymeric materials as stationary phases in HPLC to overcome these challenges. Specifically, fibrous based polymer stationary phases exhibit significant benefits for macromolecules that include improved mass …
Finding A New Continent Versus Mapping All The Rivers: Recognition, Ownership, And The Scientific Epistemological Development Of Practicing Scientists And Engineers, Andrea Verdan
All Dissertations
Maintaining our nation's standing as a leader of innovative and premier science and engineering research requires that those on the trajectory of these careers receive both rigorous and exceptional training. In addition to educating students in the content knowledge of these disciplines, it is also necessary to train them in the professional skills associated with being competent and conscientious scientists and engineers. In the attempts to understand the best strategies to teach these skills, research during the past few decades has shown a steadily increasing interest in improving the scientific literacy of students in science and engineering disciplines. Researchers agree …
Modular Forms, Elliptic Curves And Drinfeld Modules, Catherine Trentacoste
Modular Forms, Elliptic Curves And Drinfeld Modules, Catherine Trentacoste
All Dissertations
In this thesis we explore three different subfields in the area of number theory. The first topic we investigate involves modular forms, specifically nearly holomorphic eigenforms. In Chapter 3, we show the product of two nearly holomorphic eigenforms is an eigenform for only a finite list of examples. The second type of problem we analyze is related to the rank of elliptic curves. Specifically in Chapter 5 we give a graph theoretical approach to calculating the size of 3-Selmer groups for a given family of elliptic curves. By calculating the size of the 3-Selmer groups, we give an upper bound …
On Factoring Hecke Eigenforms, Nearly Holomorphic Modular Forms, And Applications To L-Values, Jeff Beyerl
On Factoring Hecke Eigenforms, Nearly Holomorphic Modular Forms, And Applications To L-Values, Jeff Beyerl
All Dissertations
This thesis is a presentation of some of my research activities while at Clemson University. In particular this includes joint work on the factorization of eigenforms and their relationship to Rankin- Selberg L-values, and nearly holomorphic eigenforms. The main tools used on the factorization of eigenforms are linear algebra, the j function, and the Rankin-Selberg Method. The main tool used on nearly holomorphic modular forms is the Rankin-Cohen bracket operator.