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Articles 1 - 30 of 59
Full-Text Articles in Physical Sciences and Mathematics
A Horizontal Edges Bound For The Independence Number Of A Graph, Michelle Grigsby
A Horizontal Edges Bound For The Independence Number Of A Graph, Michelle Grigsby
Theses and Dissertations
The independence number alpha of a graph is the size of a maximum independent set of vertices. An independent set is a set of vertices where every pair of vertices in non-adjacent. This number is known to be hard to compute. The bound we worked with is defined as epsilon = max[e(v)-eh(v)] over all the vertices in the vertex set, V(G). e(v) is the number of vertices at even distance from v. eh(v) is the number of edges both of whose endpoints are at even distance from v. Epsilon can be calculated in polynomial time. Siemion Fajtlowicz proved that alpha …
A Hierarchical Image Processing Approach For Diagnostic Analysis Of Microcirculation Videos, Nazanin Mirshahi
A Hierarchical Image Processing Approach For Diagnostic Analysis Of Microcirculation Videos, Nazanin Mirshahi
Theses and Dissertations
Knowledge of the microcirculatory system has added significant value to the analysis of tissue oxygenation and perfusion. While developments in videomicroscopy technology have enabled medical researchers and physicians to observe the microvascular system, the available software tools are limited in their capabilities to determine quantitative features of microcirculation, either automatically or accurately. In particular, microvessel density has been a critical diagnostic measure in evaluating disease progression and a prognostic indicator in various clinical conditions. As a result, automated analysis of the microcirculatory system can be substantially beneficial in various real-time and off-line therapeutic medical applications, such as optimization of resuscitation. …
Synthesis And Characterization Of Highly Porous Borazine-Linked Polymers Via Dehydrogenation/Dehydrocoupling Of Borane-Amine Adducts And Their Applications To Gas Storage, Karl Jackson
Theses and Dissertations
A new class of porous polymers has been designed and successfully synthesized by thermal dehydrogenation of several polytopic arylamine-borane adducts and has been designated Borazine-Linked Polymers (BLPs). The polymers reported are constructed of linear, triangular, and tetrahedral amine building units to form 2D and 3D frameworks. The boron sites of the pores are aligned with hydrogen atoms contrasted with the recently reported halogenated BLPs which consist of pore channels aligned with bromine or chlorine atoms. One of the reported BLPs, BLP-2(H), was proven to be crystalline by PXRD, matching the experimental pattern to theoretical patterns calculated from modeled structures. BLPs …
Designed Synthesis Of Halogenated Borazine-Linked Polymers And Their Applications In Gas Storage And Separation, Thomas Reich
Designed Synthesis Of Halogenated Borazine-Linked Polymers And Their Applications In Gas Storage And Separation, Thomas Reich
Theses and Dissertations
The synthesis of highly porous organic polymers with predefined porosity has attracted considerable attention due to their potential in a wide range of applications. Of particular interest in porous organic polymers is their potential use in automotive applications as well as separation processes whereby advancements could result in a reduction in carbon dioxide emissions and the production of natural gas in a more economically friendly manner. Along these pursuits, seven borazine-linked polymers (BLPs) have been synthesized through the introduction of p-phenylenediamine, 1,3,5-tris-(4-aminophenyl)benzene, benzidine, or tetra-(4-aminophenyl)methane with boron tribromide or boron trichloride followed by the thermolysis reaction of the resulting in …
Fast Parallel Machine Learning Algorithms For Large Datasets Using Graphic Processing Unit, Qi Li
Fast Parallel Machine Learning Algorithms For Large Datasets Using Graphic Processing Unit, Qi Li
Theses and Dissertations
This dissertation deals with developing parallel processing algorithms for Graphic Processing Unit (GPU) in order to solve machine learning problems for large datasets. In particular, it contributes to the development of fast GPU based algorithms for calculating distance (i.e. similarity, affinity, closeness) matrix. It also presents the algorithm and implementation of a fast parallel Support Vector Machine (SVM) using GPU. These application tools are developed using Compute Unified Device Architecture (CUDA), which is a popular software framework for General Purpose Computing using GPU (GPGPU). Distance calculation is the core part of all machine learning algorithms because the closer the query …
The Effect Of Oxidation And Support On Tio2(110)-Supported Pdn (N=1-7) Clusters, S. Vincent Ong
The Effect Of Oxidation And Support On Tio2(110)-Supported Pdn (N=1-7) Clusters, S. Vincent Ong
Theses and Dissertations
First principles theoretical studies based on a gradient-corrected density functional approach have been carried out on the atomic and electronic properties and oxidation of Pdn (n=1-7) clusters supported on the TiO2(110) surface. The studies are aimed to address some of the fundamental issues related to the properties of supported Pdn clusters used as catalysts in oxidation reactions. Of those issues are the following: What are the atomic structures of Pdn clusters on the TiO2 surface? Upon oxidation, do O atoms from a dissociated O2 molecule spill over onto the underlying TiO2 sup- port? How strongly does spillover oxygen bind? What …
Design Of Control Release Drug Delivery System (Dds) For Imaging And Therapeutic Applications, Sweta Naik
Design Of Control Release Drug Delivery System (Dds) For Imaging And Therapeutic Applications, Sweta Naik
Theses and Dissertations
The main challenge in disease treatment is no more the discovery of new therapeutic drugs, but to provide targeted delivery of therapeutic drugs to specific sites without incurring systemic toxicity effects. An efficient way of reducing the toxicity is by encapsulating the drug with a biodegradable matrix that can provide controlled release of the drug along with local heating of the drug. Local heating can be obtained by incorporating magnetic iron oxide particles that heat upon exposure to AC electromagnetic fields. The magnetic iron oxide nanoparticles are also gaining much attention as MRI contrast agents. Thus it would be of …
Wetting Transitions At Nanostructured Surfaces, Yazdi Jamileh Seyed
Wetting Transitions At Nanostructured Surfaces, Yazdi Jamileh Seyed
Theses and Dissertations
Shape of a droplet atop a surface heterogeneity at a nanoscale. Small aqueous droplets on homogeneous surfaces, surrounded by a reservoir of vapor are inherently unstable. In contact with supersaturated vapor, the drops will keep growing until they coalesce and form a contiguous aqueous phase. Alternatively, if vapor pressure is below that of the droplets, the droplets gradually evaporate. Departing from this common picture, when nanoscale droplets sit above hydrophilic patches on a heterogeneous surface, at certain conditions they can maintain a stable volume, determined by the pertinent contact angle and the size of the patches. Only the region under …
The Independent Set Decision Problem Is Np-Complete, Andrew Bristow Iv
The Independent Set Decision Problem Is Np-Complete, Andrew Bristow Iv
Theses and Dissertations
In the 1970's computer scientists developed the theory of computational complexity. Some problems seemed hard-to-compute, while others were easy. It turned out that many of the hard problems were equally hard in a way that could be precisely specified. They became known as the NP-complete problems. The SATISFIABILITY problem (SAT) was the first problem to be proved NP-complete in 1971. Since then numerous other hard-to-solve problems have been proved to be in NP-complete. In this paper we will examine the problem of how to find a maximum independent set of vertices for a graph. This problem is known as Maximum …
Synthesis Of Cyclen Based Receptors And Their Use In Separations Biotechnology., Vivek Kaushik
Synthesis Of Cyclen Based Receptors And Their Use In Separations Biotechnology., Vivek Kaushik
Theses and Dissertations
A number of purification techniques such as adsorption, centrifugation, chromatography, extraction, distillation, filtration, precipitation etc. to name a few, are commonly used for the purification. However, due to a constant need of purification of even more complex crude mixtures, be it reaction mixtures, various proteins and DNA from cell extracts or medicinal compounds and fragrances from plant extracts, scientists needed to consistently develop new and improved techniques of purification. One such great advancement in the field of chromatography was the development of affinity chromatography. It revolutionized the field of bioseparations technology, and the dream of single stage purification of complex …
Bounds For The Independence Number Of A Graph, William Willis
Bounds For The Independence Number Of A Graph, William Willis
Theses and Dissertations
The independence number of a graph is the maximum number of vertices from the vertex set of the graph such that no two vertices are adjacent. We systematically examine a collection of upper bounds for the independence number to determine graphs for which each upper bound is better than any other upper bound considered. A similar investigation follows for lower bounds. In several instances a graph cannot be found. We also include graphs for which no bound equals $\alpha$ and bounds which do not apply to general graphs.
Ecological Profiling Of Bird-Mosquito Interactions In Central Virginia, Anna Riggan
Ecological Profiling Of Bird-Mosquito Interactions In Central Virginia, Anna Riggan
Theses and Dissertations
Current methods of mosquito surveillance estimate general population abundances, but fail to represent the relationship of vector abundance to host density important to determining transmission risk of mosquito-borne pathogens (MBP). We sought to address this limitation by creating a novel mosquito trap that directly sampled mosquitoes seeking to feed on nesting birds. The primary objectives of this study were to (1) assess the efficiency of the Nest Mosquito Trap (NMT) and how this is affected by nest box size. (2) assess whether the NMT affects bird, specifically nest success in Prothonotary Warblers (Protonotaria citrea), and adult behavior. (3) compare our …
Growth Of Age-0 Atlantic Menhaden (Brevoortia Tyrannus) In Two Tidal Freshwater Tributaries Of Chesapeake Bay, Peter M. Sturke
Growth Of Age-0 Atlantic Menhaden (Brevoortia Tyrannus) In Two Tidal Freshwater Tributaries Of Chesapeake Bay, Peter M. Sturke
Theses and Dissertations
Few studies have described growth rates of age-0 Atlantic menhaden (Brevoortia tyrannus). Growth rates from tidal freshwater habitats of the Mattaponi and James Rivers, Virginia in 2009 were described and compared using otolith microstructural analyses. Larval tidal freshwater growth rates were significantly faster in the culturally eutrophic James River when compared to those collected from the Mattaponi River (p-value < 0.001). Elevated primary production within tidal freshwater habitats promotes favorable conditions for larval Atlantic menhaden growth. No differences between river habitats for juvenile growth rates were evident. Comparisons of age-0 growth rates to higher salinity habitats indicate that tidal freshwater habitats should be considered essential habitat for age-0 Atlantic menhaden.
Microbial Community Function In Freshwater Wetland Soils: Using Extracellular Enzyme Analysis To Study The Effect Of Moisture And Vegetation, Aaron Porter
Theses and Dissertations
Differences in microbial function via extracellular enzyme activity (EEA) were investigated to determine the potential effects of hydrology and plant-soil-microbe interactions in a young non-tidal freshwater riparian wetland. To study these relationships, three plots were established along a moisture gradient (Wet, Intermediate, Dry) within VCU Rice Center Within each main plot, five subplots were left undisturbed while another five were cleared of all above-ground plant biomass. Homogenized soil cores (top 10 cm) were analyzed for pH, redox, C:N, soil organic matter (SOM) content, saturation, and temperature. Microbial function was assessed using extracellular enzyme analysis. For most enzymes, a site difference …
Parity Domination In Product Graphs, Christopher Whisenant
Parity Domination In Product Graphs, Christopher Whisenant
Theses and Dissertations
An odd open dominating set of a graph is a subset of the graph’s vertices with the property that the open neighborhood of each vertex in the graph contains an odd number of vertices in the subset. An odd closed r-dominating set is a subset of the graph’s vertices with the property that the closed r-ball centered at each vertex in the graph contains an odd number of vertices in the subset. We first prove that the n-fold direct product of simple graphs has an odd open dominating set if and only if each factor has an odd open dominating …
Modeling The Homeschool Timetabling Problem Using Integer Programming, Subhashini Srinivasan
Modeling The Homeschool Timetabling Problem Using Integer Programming, Subhashini Srinivasan
Theses and Dissertations
Home schooling has steadily been increasing in the past decade. According to a survey in 2007, about 2.5 million children were being home schooled in the US. Typically, parents provide education at the convenience of their home and in some cases an instructor is appointed for the same. The Home School Timetabling problem (HSTP) deals with assigning subjects, timeslots and rooms to every student. In doing so, there are certain hard and specialty constraints that are to be satisfied. Integer programming (IP) has been used in solving the HSTP as it has the advantage of being able to provide information …
Synthesis Of Nanocomposites By Laser Ablation, Stephen Mutisya
Synthesis Of Nanocomposites By Laser Ablation, Stephen Mutisya
Theses and Dissertations
Immunoglobulin E (IgE)-conjugated gold nanoparticles were produced via in situ conjugation of gold nanoparticles with immunoglobulin E by laser ablation of Au in a liquid solution. The colloidal stability and the size distribution of the resulting bio-nanoconjugates were examined with UV-Visible spectroscopy (UV-Vis), dynamic light scattering (DLS), and transmission electron microscopy (TEM). These techniques showed that the Au nanoparticles in aqueous solutions were highly monodispersed spherical particles with a very narrow size distribution. The particles net diameter using TEM, was found to be D5 =3.8±0.9nm and D10 =4.7±1.3nm while the hydrodynamic diameter obtained with DLS was found to be h5 …
Growth Mechanisms Of Complex Organics In The Gas Phase And On Metal Nanoparticles Generated By A Laser Vaporization Process, Abdel Rahman Soliman
Growth Mechanisms Of Complex Organics In The Gas Phase And On Metal Nanoparticles Generated By A Laser Vaporization Process, Abdel Rahman Soliman
Theses and Dissertations
In this dissertation, the ion mobility mass spectrometry technique is used to study the possible mechanisms of formation of polyaromatic hydrocarbons (PAHs) and polyaromatic nitrogen-containing hydrocarbons (PANHs) via the ion-molecule reactions of acetylene neutrals with different aromatic cations, in order to infer the possible mechanisms of formation of PAHs and PANHs in different environments such as interstellar media under different ionizing conditions. Furthermore, this technique is used to probe structures, address the thermochemistry, and measure the kinetics of the product ions originated from these reactions. Reactions of benzene radical cations with acetylene produce styrene and naphthalene-type cations at high temperatures. …
Development Of Free-Label Sensing In Plastic Microfluidic Platforms Using Pulsed Streaming Potentials (Psp), Vera Fernando Luna
Development Of Free-Label Sensing In Plastic Microfluidic Platforms Using Pulsed Streaming Potentials (Psp), Vera Fernando Luna
Theses and Dissertations
This work deals with the development of a new label-free detection technique called Pulsed Streaming Potential (PSP). Its novelty relies on the adaptation of a classical electrokinetic phenomenon (streaming potential) into a tool which can evaluate molecular interplay in label-free fashion. Implementation of PSP to microfluidic platforms allowed the label-free sensing of binding events to plastic (modified and unmodified) surfaces. It was demonstrated the use of real time PSP in plastic microfluidic platforms for determination of kinetic parameters of the interaction of proteins and plastic surfaces. Moreover, initial change of PSP after adsorption of proteins showed to be proportional to …
The Superfund Program Past And Present Funding Implications, Nicole Franklin
The Superfund Program Past And Present Funding Implications, Nicole Franklin
Theses and Dissertations
The present research examines the impact of not reauthorizing the Superfund taxes on the operations of the program. EPA NPL site status data were obtained from the EPA CERCLIS database for analysis in this study. Data were selected for the fiscal years 1981 to 2009 in four NPL listing status categories: proposal to the NPL, final NPL listing, deletion from the NPL, and achievement of construction completion. Since the Superfund tax expired in 1995, data from the 1981 to 1995 fiscal years and data from the 1996 to 2009 fiscal years were analyzed to determine if there were mean differences …
Aging Effect In The Wettability Of Nickel Nanorod Arrays, Nahla Albarakati
Aging Effect In The Wettability Of Nickel Nanorod Arrays, Nahla Albarakati
Theses and Dissertations
The time-dependent wettability of nickel nanorod arrays was studied by measuring their water contact angles as a function of "aging" time in air. The nickel nanorod arrays were deposited on silicon substrates by DC magnetron sputtering using an oblique angle of 85° with respect to the substrate normal. By changing the deposition time from 10 to 90 min., the diameter, height, and separation of the nanorods were varied. The water contact angles of each sample were then periodically measured from a minimum aging time of 30 min. after deposition and exposure to air, up to a maximum aging time of …
Three Quarter Plackett-Burman Designs For Estimating All Main Effects And Two-Factor Interactions, Bridgette Briggs
Three Quarter Plackett-Burman Designs For Estimating All Main Effects And Two-Factor Interactions, Bridgette Briggs
Theses and Dissertations
Plackett-Burman designs and three quarter fractional factorial designs are both well established in the statistical literature yet have never been combined and studied. Plackett-Burman designs are often non-regular and are thus subject to complex aliasing. However, Plackett-Burman designs have the advantage of run-size efficiency (over the usual 2^(k) factorials) and taking three quarters of a Plackett-Burman design further improves this benefit. By considering projections of these designs, we constructed a catalog of designs of resolution V and ranked by D-efficiency.
Inducing Active Sites In Clusters: Reactivity Of Al13ix- And Al14iy- (X=0-2, Y=2-4) With Methanol, Christopher Powell
Inducing Active Sites In Clusters: Reactivity Of Al13ix- And Al14iy- (X=0-2, Y=2-4) With Methanol, Christopher Powell
Theses and Dissertations
Size selective reactivity has been observed in pure aluminum cluster anions as a result of Lewis acid and base pairs. Using this a starting point, the goal of this study has been to explore how reactivity is affected with the addition of one or more ligand, which may induce active sites on the surface of the metal clusters. To study this, a theoretical investigation was undertaken on Al13Ix- and Al14Iy- (x=0-2, y=2-4) and their reactivity with methanol. The hypothesis was that iodine can induce a Lewis base site on the opposite side of the cluster, which may enhance reactivity. In …
Stability And Spectroscopic Properties Of Negative Ions, Swayamprabha Behera
Stability And Spectroscopic Properties Of Negative Ions, Swayamprabha Behera
Theses and Dissertations
Negative ions play an important role in chemistry as building blocks of salts and oxidizing agents. Halogen atoms, due to their ability to attract electrons, readily form negative ions. Considerable interest exists in the design and synthesis of new negative ions called superhaogens whose electron affinities are much higher than those of halogen atoms. This thesis deals with the design of such species. Using density functional theory I have studied two classes of superhalogens. First one involves d1 transition metal (Sc, Y, La) atoms surrounded by Cl while the second one involves simple metals (Na, Mg, Al) surrounded by pseudohalogens …
The Effect Of Ambient On Photoluminescence From Gan, Iwona Ruchala
The Effect Of Ambient On Photoluminescence From Gan, Iwona Ruchala
Theses and Dissertations
The effect of ambient on photoluminescence (PL) from GaN was studied. We found that the PL intensity in vacuum was nearly four times higher than in air. The PL intensity also increased after etching the sample in Aqua Regia and BOE to remove the native oxide layer. After etching, the PL intensity was very stable in vacuum, but substantially degraded in air ambient. In HCl vapor (low pH), the PL intensity increased as compared to air ambient, while in NH3 vapor (high pH) it decreased. The quantum efficiency of the exciton and blue luminescence bands increased significantly with increasing excitation …
Computational Modeling Of Mulitsensory Processing Using Network Of Spiking Neurons, Hun Ki Lim
Computational Modeling Of Mulitsensory Processing Using Network Of Spiking Neurons, Hun Ki Lim
Theses and Dissertations
Multisensory processing in the brain underlies a wide variety of perceptual phenomena, but little is known about the underlying mechanisms of how multisensory neurons are generated and how the neurons integrate sensory information from environmental events. This lack of knowledge is due to the difficulty of biological experiments to manipulate and test the characteristics of multisensory processing. By using a computational model of multisensory processing this research seeks to provide insight into the mechanisms of multisensory processing. From a computational perspective, modeling of brain functions involves not only the computational model itself but also the conceptual definition of the brain …
Cumulative Risks To Eastern Oysters, Crassostrea Virginica In The James River, Va, Vrushali Lele
Cumulative Risks To Eastern Oysters, Crassostrea Virginica In The James River, Va, Vrushali Lele
Theses and Dissertations
In an effort to apply Cumulative Risk Assessment (CRA) as developed by the U.S. EPA, the present study investigates the cumulative risks to Eastern oysters due to multiple stressors such as salinity, temperature and oxygen and carbon dioxide. I also compared the effectiveness of the Hazard Quotient Method (HQ) in CRA. Ambient conditions in the James River, VA were obtained from the Virginia DEQ database and respiratory responses were estimated using values from the literature. The multiple environmental stresses are evaluated using a probabilistic analysis that combines the environmental conditions. It was concluded that salinity was the most influential stressor …
Pcal1: An R Package Of Principal Component Analysis Using The L1 Norm, Sapan Jot
Pcal1: An R Package Of Principal Component Analysis Using The L1 Norm, Sapan Jot
Theses and Dissertations
Principal component analysis (PCA) is a dimensionality reduction tool which captures the features of data set in low dimensional subspace. Traditional PCA uses L2-PCA and has much desired orthogonality properties, but is sensitive to outliers. PCA using L1 norm has been proposed as an alternative to counter the effect of outliers. The R environment for statistical computing already provides L2-PCA function prcomp(), but there are not many options for L1 norm PCA methods. The goal of the research was to create one R package with different options of PCA methods using L1 norm. So, we choose three different L1-PCA algorithms: …
Embeddings Of Product Graphs Where One Factor Is A Hypercube, Bethany Turner
Embeddings Of Product Graphs Where One Factor Is A Hypercube, Bethany Turner
Theses and Dissertations
Voltage graph theory can be used to describe embeddings of product graphs if one factor is a Cayley graph. We use voltage graphs to explore embeddings of various products where one factor is a hypercube, describing some minimal and symmetrical embeddings. We then define a graph product, the weak symmetric difference, and illustrate a voltage graph construction useful for obtaining an embedding of the weak symmetric difference of an arbitrary graph with a hypercube.
Phytoremediation Of Pcb Contaminated Soil: Effectiveness And Regulatory Policy, Nathan Pinsker
Phytoremediation Of Pcb Contaminated Soil: Effectiveness And Regulatory Policy, Nathan Pinsker
Theses and Dissertations
The purpose of this paper was to combine available peer-reviewed literature on PCB phytoremediation and make direct comparisons using ANCOVA statistics in order to determine if and what plants are presently a viable option for the remediation of PCB contaminated soils. Pumpkin (Curbita pepo cv Howden) consistently had the top root and shoot concentrations, as well as total plant accumulation. Their consistency shows that they can be reliable in the field and the most viable option. Tall fescue and sedge were also top contenders. Due to the small sample size for many plants and accounting for several confounding variables, very …