Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Theses and Dissertations

Discipline
Institution
Keyword
Publication Year
File Type

Articles 5641 - 5670 of 8341

Full-Text Articles in Physical Sciences and Mathematics

Physical And Chemical Properties Of Ice In A Main Valley Glacier And A Tributary Glacier, Gornergletscher, Canton Valais, Switzerland, Annika M. Quick Jul 2010

Physical And Chemical Properties Of Ice In A Main Valley Glacier And A Tributary Glacier, Gornergletscher, Canton Valais, Switzerland, Annika M. Quick

Theses and Dissertations

Glacier models often fail to incorporate the geometry and/or physical properties of tributaries included in complex glaciers. Tributary glaciers have different source areas and flow conditions than the adjacent main valley glacier. Ice cores (~3m depth) and surface samples (<0.5m depth) were collected from Grenzgletscher (main valley glacier) and Zwillingsgletscher (tributary glacier) in the Gornergletscher system of the Swiss Alps. Stable water isotopes indicate seasonal variation, showing 1-2 annual layers. The mean d18O for Grenzgletscher is ~4.8‰ lower than for Zwillingsgletscher. This difference may be accounted for in part by elevation differences between the accumulation areas (~1.1‰ δ18O), increased avalanching in Grenzgletscher (~1.8 ‰ δ18O), and by varying climatic conditions at the time of precipitation (~0.9-1.4‰ variation in δ18O). Using a kinematic ice flow model, core ages were estimated using effective annual layer thickness (based on seasonal variations), annual accumulation rate and ice thickness. The Grenzgletscher core is ~4 years older than the Zwillingsgletscher core. Based on ages and flow distances, the tributary has a lower flow velocity (63-87 m/yr) compared to Grenzgletscher (61-134 m/yr). To understand thermal properties of the tributary, a 775 m GPR survey (200 MHz) was conducted along a flow line of Zwillingsgletscher. Topographic waves (ogives) observed on the surface are mimicked by the onset of reflectivity 10-20 m below the surface. Reflective regions are interpreted as warmer ice at the pressure melting point, overlain by colder ice. This thermal structure is likely related to acceleration through an ice fall. Since most tributary glaciers include ice falls, thermal properties of tributary glaciers may be different from those of the main valley glacier. The properties and geometry of tributary glaciers are significantly different from main valley glaciers and should therefore be incorporated into glacier models in the future.

Go to article

A Probabilistic Morphological Analyzer For Syriac, Peter J. Mcclanahan Jul 2010

A Probabilistic Morphological Analyzer For Syriac, Peter J. Mcclanahan

Theses and Dissertations

We show that a carefully crafted probabilistic morphological analyzer significantly outperforms a reasonable, naive baseline for Syriac. Syriac is an under-resourced Semitic language for which there are no available language tools such as morphological analyzers. Such tools are widely used to contribute to the process of annotating morphologically complex languages. We introduce and connect novel data-driven models for segmentation, dictionary linkage, and morphological tagging in a joint pipeline to create a probabilistic morphological analyzer requiring only labeled data. We explore the performance of this model with varying amounts of training data and find that with about 34,500 tokens, it can …

Go to article

In Search Of Empty Places: Voids In The Distribution Of Galaxies, Brian K. Bucklein Jul 2010

In Search Of Empty Places: Voids In The Distribution Of Galaxies, Brian K. Bucklein

Theses and Dissertations

We investigate several techniques to identify voids in the galaxy distribution of matter in the universe. We utilize galaxy number counts as a function of apparent magnitude and Wolf plots to search a two- or three-dimensional data set in a pencil-beam fashion to locate voids within the field of view. The technique is able to distinguish between voids that represent simply a decrease in density as well as those that show a build up of galaxies on the front or back side of the void. This method turns out to be primarily useable only at relatively short range (out to …

Go to article

Oh Megamasers In Merging Galaxies: A Multi-Frequency Study Of Iizw096, Kirstin Marie Cooprider Jul 2010

Oh Megamasers In Merging Galaxies: A Multi-Frequency Study Of Iizw096, Kirstin Marie Cooprider

Theses and Dissertations

OH Megamasers (OHMs) generally appear in luminous infrared regions i.e. merging galaxies. In this study we assume that OHMs may not be represented by their association with star formation solely, because of the possibility of a compact AGN source in the merging galaxies. In fact, previously classified starburst galaxies where OHMs are found are now optically observed as AGN. OHMs may also serve as a reasonable criterion for the evolutionary stage of the merger. This project focuses on observations from a multi-frequency analysis of merging regions with known OHMs. Optically, Hα and BVRI filters provided an environmental perspective of the …

Go to article

Impact Of Nickel Doping On Hydrogen Storage In Porous Metal-Organic Frameworks, Tanushree Banerjee Jul 2010

Impact Of Nickel Doping On Hydrogen Storage In Porous Metal-Organic Frameworks, Tanushree Banerjee

Theses and Dissertations

A supply of clean, carbon neutral and sustainable energy is the most scientific and technical challenge that humanity is facing in the 21st century. Though there is enough fossil fuels available for a few centuries, their use would increase the level of CO2 in the atmosphere. This would lead to global warming and may pose serious threats such as rising of sea level, change in hydrological cycle, etc. Hence there is a need for an alternative source of fuel that is clean and sustainable. Among the many resources considered as an alternative power source, hydrogen is considered one of the …

Go to article

Electronic Library Database Application, Visar Nura Jul 2010

Electronic Library Database Application, Visar Nura

Theses and Dissertations

It's probably fair to say that most business-oriented computer applications work with data in one form or another. This data often is stored in one or more databases. Visual Basic can create powerful data management programs with a little planning and effort. The most fundamental part of that planning is in how the data is structured. A poorly designed database can doom even the most well-intentioned program from the start. On the other hand, a well-designed database can make a programmer's life much easier. Creating an organized data structure requires you to learn about two separate tasks. First, you must …

Go to article

Mechanistic Studies On The Electrochemistry Of Proton Coupled Electron Transfer And The Influence Of Hydrogen Bonding, Timothy Alligrant Jun 2010

Mechanistic Studies On The Electrochemistry Of Proton Coupled Electron Transfer And The Influence Of Hydrogen Bonding, Timothy Alligrant

Theses and Dissertations

This research has investigated proton-coupled electron transfer (PCET) of quinone/hydroquinone and other simple organic PCET species for the purpose of furthering the knowledge of the thermodynamic and kinetic effects due to reduction and oxidation of such systems. Each of these systems were studied involving the addition of various acid/base chemistries to influence the thermodynamics and kinetics upon electron transfer. It is the expectation that the advancement of the knowledge of acid/base catalysis in electrochemistry gleaned from these studies might be applied in fuel cell research, chemical synthesis, the study of enzymes within biological systems or to simply advance the knowledge …

Go to article

An Inferential Framework For Network Hypothesis Tests: With Applications To Biological Networks, Phillip Yates Jun 2010

An Inferential Framework For Network Hypothesis Tests: With Applications To Biological Networks, Phillip Yates

Theses and Dissertations

The analysis of weighted co-expression gene sets is gaining momentum in systems biology. In addition to substantial research directed toward inferring co-expression networks on the basis of microarray/high-throughput sequencing data, inferential methods are being developed to compare gene networks across one or more phenotypes. Common gene set hypothesis testing procedures are mostly confined to comparing average gene/node transcription levels between one or more groups and make limited use of additional network features, e.g., edges induced by significant partial correlations. Ignoring the gene set architecture disregards relevant network topological comparisons and can result in familiar n<

Go to article

Practical Improvements In Applied Spectral Learning, Adam C. Drake Jun 2010

Practical Improvements In Applied Spectral Learning, Adam C. Drake

Theses and Dissertations

Spectral learning algorithms, which learn an unknown function by learning a spectral representation of the function, have been widely used in computational learning theory to prove many interesting learnability results. These algorithms have also been successfully used in real-world applications. However, previous work has left open many questions about how to best use these methods in real-world learning scenarios. This dissertation presents several significant advances in real-world spectral learning. It presents new algorithms for finding large spectral coefficients (a key sub-problem in spectral learning) that allow spectral learning methods to be applied to much larger problems and to a wider …

Go to article

Automatic Extraction From And Reasoning About Genealogical Records: A Prototype, Charla Jean Woodbury Jun 2010

Automatic Extraction From And Reasoning About Genealogical Records: A Prototype, Charla Jean Woodbury

Theses and Dissertations

Family history research on the web is increasing in popularity, and many competing genealogical websites host large amounts of data-rich, unstructured, primary genealogical records. It is labor-intensive, however, even after making these records machine-readable, for humans to make these records easily searchable. What we need are computer tools that can automatically produce indices and databases from these genealogical records and can automatically identify individuals and events, determine relationships, and put families together. We propose here a possible solution—specialized ontologies, built specifically for extracting information from primary genealogical records, with expert logic and rules to infer genealogical facts and assemble relationship …

Go to article

Targeting Complex Cyclic Peptides For Synthesis: The Celogentin And Theonellamide Families, Joshua Wayne Robinson Jun 2010

Targeting Complex Cyclic Peptides For Synthesis: The Celogentin And Theonellamide Families, Joshua Wayne Robinson

Theses and Dissertations

Celogentin C and theonellamide F are a class of natural products that have potential antimitotic behavior. They both contain interesting bicyclic structures with unusual linkages within a central moiety. Celogentin C's highly functionalized tryptophan moiety has two unusual linkages, a β-substituted Leu connection to the C6 of the indole structure that makes up the left-hand ring, and a τ-N connection of the imidazole to the C2 of the indole constructing the right-hand ring. This right-hand ring connection was solved via a novel oxidative coupling procedure developed in our group and the left-hand ring was initially constructed via a radical conjugated …

Go to article

Developing A Hybrid Virtualization Platform Design For Cyber Warfare And Simulation, Kyle E. Stewart Jun 2010

Developing A Hybrid Virtualization Platform Design For Cyber Warfare And Simulation, Kyle E. Stewart

Theses and Dissertations

Virtualization is a technique used to model and simulate the cyber domain, as well as train and educate. Different types of virtualization techniques exist that each support a unique set of benefits and requirements. This research proposes a novel design that incorporates host and network virtualization concepts for a cyber warfare training platform. At the host level, hybrid virtualization combines full and operating system virtualization techniques in order to leverage the benefits and minimize the drawbacks of each individual technique. Network virtualization allows virtual machines to connect in flexible topologies, but it also incurs additional processing overhead. Quantitative analysis falls …

Go to article

Electronic Structure Of Lithium Tetraborate, David J. Wooten Jun 2010

Electronic Structure Of Lithium Tetraborate, David J. Wooten

Theses and Dissertations

Due to interest as neutron detection material, an investigation of Li2B4O7(110) and Li2B4O7(100) was undertaken, utilizing photoemission and inverse photoemission spectroscopic techniques. The measured band gap depended on crystallographic direction with the band gaps ranging from 8.9±0.5 eV to 10.1±0.5 eV. The measurement yielded a density of states that qualitatively agreed with the theoretical results from model bulk band structure calculations for Li2B4O7; albeit with a larger band gap than predicted, but consistent with the known deficiencies of LDA and DFT calculations. …

Go to article

Deterministic, Efficient Variation Of Circuit Components To Improve Resistance To Reverse Engineering, Daniel F. Koranek Jun 2010

Deterministic, Efficient Variation Of Circuit Components To Improve Resistance To Reverse Engineering, Daniel F. Koranek

Theses and Dissertations

This research proposes two alternative methods for generating semantically equivalent circuit variants which leave the circuit's internal structure pseudo-randomly determined. Component fusion deterministically selects subcircuits using a component identification algorithm and replaces them using a deterministic algorithm that generates canonical logic forms. Component encryption seeks to alter the semantics of individual circuit components using an encoding function, but preserves the overall circuit semantics by decoding signal values later in the circuit. Experiments were conducted to examine the performance of component fusion and component encryption against representative trials of subcircuit selection-and-replacement and Boundary Blurring, two previously defined methods for circuit obfuscation. …

Go to article

An Application Of Automated Theorem Provers To Computer System Security: The Schematic Protection Model, Mitchell D.I. Hirschfeld Jun 2010

An Application Of Automated Theorem Provers To Computer System Security: The Schematic Protection Model, Mitchell D.I. Hirschfeld

Theses and Dissertations

The Schematic Protection Model is specified in SAL and theorems about Take-Grant and New Technology File System schemes are proven. Arbitrary systems can be specified in SPM and analyzed. This is the first known automated analysis of SPM specifications in a theorem prover. The SPM specification was created in such a way that new specifications share the underlying framework and are configurable within the specifications file alone. This allows new specifications to be created with ease as demonstrated by the four unique models included within this document. This also allows future users to more easily specify models without recreating the …

Go to article

The Combined Effects Of Radio Frequency And Gamma Irradiation On P-Channel Mosfets, Joshua D. Daniel Jun 2010

The Combined Effects Of Radio Frequency And Gamma Irradiation On P-Channel Mosfets, Joshua D. Daniel

Theses and Dissertations

The purpose of this research was to investigate the combined effects of continuous gigahertz radio frequency signals and gamma irradiation on the threshold voltage of metal oxide semiconductor field effect transistors. The combined effects of gigahertz radio frequency waves and gamma irradiation on electronics presents a new challenge in electronic warfare and little is known of the combined effect on threshold voltage damage and recovery. The Fairchild NDS352AP, a commonly used commercial device, was irradiated by a cobalt-60 source under a +5 V bias with and without a radio frequency signal applied to the gate. The threshold voltage was measured …

Go to article

Realistic Vertical Atmospheric Profiles And Effects From Limited Surface Observations, Dane P. Ranney Jun 2010

Realistic Vertical Atmospheric Profiles And Effects From Limited Surface Observations, Dane P. Ranney

Theses and Dissertations

The ability to accurately describe the atmospheric conditions around us is not only important to the Air Force, but to anyone involved in signal propagation. The programs currently utilized to describe the atmosphere take into account a variety of measures. The LEEDR (Laser Environmental Effects Definition and Reference) program in particular, allows the user to select a location, aerosol and molecular effects model, numerous cloud and precipitation events, as well as other features. Even with the control that the user has, the output that the program provides can vary from actual conditions on a day to day basis. This is …

Go to article

Sediment Flux Through The Rio Grande River: A Monsoonal Effect, Troy C. Hiatt Jun 2010

Sediment Flux Through The Rio Grande River: A Monsoonal Effect, Troy C. Hiatt

Theses and Dissertations

Climate has historically been recognized as an influence on sediment flux and deposition. The North American Monsoon is suggested as the forcing mechanism of deltaic progradational events of the Rio Grande River delta. Interpretations of reflection seismic profiles reveal that eustatic rise in sea-level from the Last Glacial Maximum to present is accompanied by several regressional events of the Rio Grande delta 5.5, 9.5, and 11.5 ka BP. Much of the migration of depositional facies within a delta system is forced by hinterland tectonics and base-level rise and fall. However, we suggest that the movement of facies within the Rio …

Go to article

The Minimum Rank, Inverse Inertia, And Inverse Eigenvalue Problems For Graphs, Mark Condie Kempton Jun 2010

The Minimum Rank, Inverse Inertia, And Inverse Eigenvalue Problems For Graphs, Mark Condie Kempton

Theses and Dissertations

For a graph G we define S(G) to be the set of all real symmetric n by n matrices whose off-diagonal zero/nonzero pattern is described by G. We show how to compute the minimum rank of all matrices in S(G) for a class of graphs called outerplanar graphs. In addition, we obtain results on the possible eigenvalues and possible inertias of matrices in S(G) for certain classes of graph G. We also obtain results concerning the relationship between two graph parameters, the zero forcing number and the path cover number, related to the minimum rank problem.

Go to article

Characterization Of Stabilized Palladium Nanocatalysts, Meghann Broderick Jun 2010

Characterization Of Stabilized Palladium Nanocatalysts, Meghann Broderick

Theses and Dissertations

Metal nanoparticles have received much interest for their application in catalysis due to high surface-to-volume ratios resulting in more available active sites. Ideally these catalysts are heterogeneous and allow for facile separation from the catalytic reaction mixture making them ideal for industrial application. Dispersed metal nanoparticles are explored due to their high reactivity in solution and are stabilized by surfactants and polymers. However, it is difficult to determine whether or not a catalyst is truly heterogeneous as a certain degree of leaching from the metal nanoparticle is inevitable. Determining the mechanisms involved in nanocatalysis is also a challenge. In this …

Go to article

Celogentin C And Thioviridamide: Synthetic And Structural Studies, Dmitry Nikolayevich Litvinov Jun 2010

Celogentin C And Thioviridamide: Synthetic And Structural Studies, Dmitry Nikolayevich Litvinov

Theses and Dissertations

Project I Celogentin C, isolated by Kobayashi from the seeds of Celosia argentea in 2001 exhibits strong inhibitory behavior towards polymerization of tubulin – globular protein, which plays crucial role during the cell division cycle. We have attempted synthesis of the left-hand ring of celogentin C via the intramolecular alkylation and the Knoevenagel condensation strategies. Utilizing synthetic methodologies in the field of nitroacetyl chemistry, developed by Kornblum and Rajappa we have successfully prepared the intermolecular Knoevenagel condensation product – the late-stage precursor to the left-hand ring of celogentin C. Synthesis of this key intermediate subsequently led to the preparation of …

Go to article

Wild Low-Dimensional Topology And Dynamics, Mark H. Meilstrup Jun 2010

Wild Low-Dimensional Topology And Dynamics, Mark H. Meilstrup

Theses and Dissertations

In this dissertation we discuss various results for spaces that are wild, i.e. not locally simply connected. We first discuss periodic properties of maps from a given space to itself, similar to Sharkovskii's Theorem for interval maps. We study many non-locally connected spaces and show that some have periodic structure either identical or related to Sharkovskii's result, while others have essentially no restrictions on the periodic structure. We next consider embeddings of solenoids together with their complements in three space. We differentiate solenoid complements via both algebraic and geometric means, and show that every solenoid has an unknotted embedding …

Go to article

The Google Search Engine, Ganimete Perçuku Jun 2010

The Google Search Engine, Ganimete Perçuku

Theses and Dissertations

Përgjithësisht makina kërkuese Google paraqitet si sistemi i kompjuterëve të projektuar për kërkimin e informatave në ueb. Google mundohet t’i kuptojë kërkesat e njerëzve në mënyrë “njerëzore”, dhe t’iu kthej atyre përgjigjen në formën të qartë. Por, ky synim nuk është as afër ideales dhe realizimi i tij sa vjen e vështirësohet me zgjerimin eksponencial që sot po përjeton ueb-i. Google, paraqitet duke ngërthyer në vetvete shqyrtimin e pjesëve që e përbëjnë, atyre në të cilat sistemi mbështetet, dhe rrethinave tjera që i mundësojnë sistemit të funksionojë pa probleme apo të përtërihet lehtë nga ndonjë dështim eventual. Procesi i grumbullimit …

Go to article

A Case Study Of Network Design For Middle East Water Distribution, Rachel Bullene May 2010

A Case Study Of Network Design For Middle East Water Distribution, Rachel Bullene

Theses and Dissertations

The Middle Eastern region encompassing Israel, Jordan, and the Palestinian Territories (West Bank and Gaza) is an arid region with fast growing populations. Adequate and equitable access to water for all the people of the region is crucial to the future of Middle East peace. However, the current water distribution system not only fails to provide an adequate and equitable allocation of water, but also results adverse impacts on the environment. This project involves building a mathematical model to aid decision-makers in designing an optimal water distribution network. A new method for incorporating uncertainty in optimization that is based on …

Go to article

Inhomogeneity-Induced Spin Current In Atomic And Condensed Matter Systems, Bailey Hsu May 2010

Inhomogeneity-Induced Spin Current In Atomic And Condensed Matter Systems, Bailey Hsu

Theses and Dissertations

I derive and apply quantum propagator techniques to atomic and condensed matter systems. I observe many interesting features by following the evolution of a wavepacket. In atomic systems, I revisit the Stern-Gerlach effect and study the spin dynamics inside an inhomogeneous magnetic field. The results I obtained are not exactly the same as the textbook description of the effect which is usually a manifestation of a perfect space and spin entanglement. This discovery can provide insight on more reliable quantum computation device designs. In condensed matter systems, the doping concentration inhomogeneity leads to the Rashba spin-orbit interaction. This makes it …

Go to article

An Empirical Approach To Evaluating Sufficient Similarity: Utilization Of Euclidean Distance As A Similarity Measure, Scott Marshall May 2010

An Empirical Approach To Evaluating Sufficient Similarity: Utilization Of Euclidean Distance As A Similarity Measure, Scott Marshall

Theses and Dissertations

Individuals are exposed to chemical mixtures while carrying out everyday tasks, with unknown risk associated with exposure. Given the number of resulting mixtures it is not economically feasible to identify or characterize all possible mixtures. When complete dose-response data are not available on a (candidate) mixture of concern, EPA guidelines define a similar mixture based on chemical composition, component proportions and expert biological judgment (EPA, 1986, 2000). Current work in this literature is by Feder et al. (2009), evaluating sufficient similarity in exposure to disinfection by-products of water purification using multivariate statistical techniques and traditional hypothesis testing. The work of …

Go to article

Density Functional Studies Of The Stability Of Clusters, Penee Clayborne May 2010

Density Functional Studies Of The Stability Of Clusters, Penee Clayborne

Theses and Dissertations

Theoretical studies using the Kohn-Sham density functional formalism have been carried out to identify and investigate the stability of a variety of atomic clusters for their use in cluster assembled materials. The stable behavior found in a cluster system provides a way to classify inorganic clusters. The clusters in this study can be categorized in one of the following, jellium, all-metal aromatic, Zintl analogue or as a covalent metal-carbide. By understanding the electronic structure and ultimately the stable nature of a cluster first, it is proposed one can construct assemblies based on the stable cluster. The methodology presented is a …

Go to article

Transformation Learning: Modeling Transferable Transformations In High-Dimensional Data, Christopher R. Wilson May 2010

Transformation Learning: Modeling Transferable Transformations In High-Dimensional Data, Christopher R. Wilson

Theses and Dissertations

The goal of learning transfer is to apply knowledge gained from one problem to a separate related problem. Transformation learning is a proposed approach to computational learning transfer that focuses on modeling high-level transformations that are well suited for transfer. By using a high-level representation of transferable data, transformation learning facilitates both shallow transfer (intra-domain) and deep transfer (inter-domain) scenarios. Transformations can be discovered in data using manifold learning to order data instances according to the transformations they represent. For high-dimensional data representable with coordinate systems, such as images and sounds, data instances can be decomposed into small sub-instances based …

Go to article

A Lift Of Cohomology Eigenclasses Of Hecke Operators, Brian Francis Hansen May 2010

A Lift Of Cohomology Eigenclasses Of Hecke Operators, Brian Francis Hansen

Theses and Dissertations

A considerable amount of evidence has shown that for every prime p &neq; N observed, a simultaneous eigenvector v_0 of Hecke operators T(l,i), i=1,2, in H^3(Γ_0(N),F(0,0,0)) has a “lift” v in H^3(Γ_0(N),F(p−1,0,0)) — i.e., a simultaneous eigenvector v of Hecke operators having the same system of eigenvalues that v_0 has. For each prime p>3 and N=11 and 17, we construct a vector v that is in the cohomology group H^3(Γ_0(N),F(p−1,0,0)). This is the first construction of an element of infinitely many different cohomology groups, other than modulo p reductions of characteristic zero objects. We proceed to show that v …

Go to article

Cost And Accuracy Comparisons In Medical Testing Using Sequential Testing Strategies, Anwar Ahmed May 2010

Cost And Accuracy Comparisons In Medical Testing Using Sequential Testing Strategies, Anwar Ahmed

Theses and Dissertations

The practice of sequential testing is followed by the evaluation of accuracy, but often not by the evaluation of cost. This research described and compared three sequential testing strategies: believe the negative (BN), believe the positive (BP) and believe the extreme (BE), the latter being a less-examined strategy. All three strategies were used to combine results of two medical tests to diagnose a disease or medical condition. Descriptions of these strategies were provided in terms of accuracy (using the maximum receiver operating curve or MROC) and cost of testing (defined as the proportion of subjects who need 2 tests to …

Go to article

First Prev Next Last