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Articles 1411 - 1440 of 2496

Full-Text Articles in Physical Sciences and Mathematics

New Methods For Trace Analysis Of Iodine And Perchlorate In Biological Fluids, Charles Phillip Shelor Jan 2014

New Methods For Trace Analysis Of Iodine And Perchlorate In Biological Fluids, Charles Phillip Shelor

Chemistry & Biochemistry Dissertations

Iodine is an essential element necessary for the production of the thyroid hormones T3 and T4. These hormones are necessary for metabolism and are especially important for brain development in infants and young children. Iodine is transported into the thyroid by the sodium iodide symporter. Perchlorate is known to inhibit iodine uptake into the thyroid by binding to the sodium iodide symporter, thus acting as a potential neurotoxicant for developing children.The research in this dissertation consists of two goals. The primary is the development of novel methods for measuring iodine and perchlorate and the second is performing analyses to determine …

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Supporting Traditional Instructional Methods With A Constructivist Approach To Learning: Promoting Conceptual Change And Understanding Of Stoichiometry Using E-Learning Tools, Kenneth Munoz Abayan Jan 2014

Supporting Traditional Instructional Methods With A Constructivist Approach To Learning: Promoting Conceptual Change And Understanding Of Stoichiometry Using E-Learning Tools, Kenneth Munoz Abayan

Chemistry & Biochemistry Dissertations

Stoichiometry is a fundamental topic in chemistry that measures a quantifiable relationship between atoms, molecules, etc. Stoichiometry is usually taught using expository teaching methods. Students are passively given information, in the hopes they will retain the transmission of information to be able to solve stoichiometry problems masterfully. Cognitive science research has shown that this kind of instructional teaching method is not very effecting in meaningful learning practice. Instead, students must take ownership of their learning. The students need to actively construct their own knowledge by receiving, interpreting, integrating and reorganizing that information into their own mental schemas. In the absence …

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Development Of Paired Ion Electrospray Ionization Mass Spectrometry For Ultrasensitive Detection Of Anions, Chengdong Xu Jan 2014

Development Of Paired Ion Electrospray Ionization Mass Spectrometry For Ultrasensitive Detection Of Anions, Chengdong Xu

Chemistry & Biochemistry Dissertations

Mass spectrometry (MS) has emerged as an essential analytical technique over the last several decades. It is a widely applicable and powerful tool for determination and identification of different types of molecules. Electrospray ionization (ESI) is one of the most commonly used ionization sources for mass spectrometry. ESI-MS has advantages for the analysis of both small molecules and macromolecules due to its outstanding sensitivity, specificity, speed, and the capability for analyte structure elucidation. Currently, one challenging aspect in ESI-MS is the qualitative and quantitative determination of anionic species. This is due to the inherently poor detection sensitivity in the negative …

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Mechanistic Study Of Cysteine Dioxygenase, A Non-Heme Mononuclear Iron Enzyme, Wei Li Jan 2014

Mechanistic Study Of Cysteine Dioxygenase, A Non-Heme Mononuclear Iron Enzyme, Wei Li

Chemistry & Biochemistry Dissertations

Cysteine dioxygenase (CDO) is an non-heme mononuclear iron enzymes that catalyzes the O2-dependent oxidation of L-cysteine (Cys) to produce cysteine sulfinic acid (CSA). CDO controls cysteine levels in cells and is a potential drug target for some diseases such as Parkinson's and Alzhermer's. Several crystal structures of CDO have been determined and they reveal a ferrous iron active site coordinated by three histidine residues. This feature is divergent from the monoanionic 2-histidine-1-carboxylate coordination typically observed within the non-heme mononuclear iron super family of oxidase/oxygenase enzymes. Furthermore, within 3.3 Å of the CDO active site iron is an unusual covalently crosslinked …

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Determination Of Nicotine And Its Metabolites Accumulated In Fish Tissue Using Quechers And Hydrophilic Interaction Liquid Chromatography And Tandem Mass Spectrometry, Yun-Wei Chang Jan 2014

Determination Of Nicotine And Its Metabolites Accumulated In Fish Tissue Using Quechers And Hydrophilic Interaction Liquid Chromatography And Tandem Mass Spectrometry, Yun-Wei Chang

Chemistry & Biochemistry Theses

The quantitative determination of nicotine and its major metabolites (cotinine and anabasine) in fish tissue was performed using hydrophilic interaction liquid chromatography (HILIC) coupled with tandem mass spectrometry. Marine and freshwater fish were purchased from local grocery stores and were prepared based on the well-known QuEChERS (quick, easy, cheap, effective, rugged, safe) sample preparation protocol. There were significant suppressions on measured nicotine signals (10%) due to the matrix effects from marine fish, but no obvious effects on freshwater fish signals. Method validation was incorporated with internal standards and carried out with matrix-matched calibration. The detection limits for nicotine, cotinine, and …

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Development, Characterization And Application Of Chiral Stationary Phases, Muhammad Abdul Momin Khan Jan 2014

Development, Characterization And Application Of Chiral Stationary Phases, Muhammad Abdul Momin Khan

Chemistry & Biochemistry Theses

Cyclofructans are cyclic oligosaccharides consisting of a crown ether core with pendent fructofuranose units. These unique macrocycles were reported recently to be powerful chiral selectors. Native cyclofructans show little enantioselectivity. However, when they are derivatized and bonded to silica, they make excellent chiral selectors for HPLC. In this study, several new derivatives of cyclofructan 6 were prepared by introducing aromatic selectors with electron-withdrawing chloro and nitro group(s) and electron-donating methyl group. Their enantioselectivities were evaluated in the normal phase mode in comparison to the commercially available cyclofructan columns (LARIHC CF6-P, LARIHC CF6-RN and LARIHC CF7-DMP). In several cases, the new …

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Cutoff Frequencies For Alfven Waves In The Solar Atmosphere, B L Harsha Kalpanie Perera Jan 2014

Cutoff Frequencies For Alfven Waves In The Solar Atmosphere, B L Harsha Kalpanie Perera

Physics Dissertations

Propagation of linear Alfven waves in the isothermal and non-isothermal solaratmosphere is investigated numerically and analytically. It is shown that thetwo wave variables, the velocity and magnetic field perturbations, behave differently and that there is a range of wave frequencies for which the wave behavior changes from propagating to non-propagating. The so-called transition and turning points corresponding to this change are determined analytically, and their locations in the atmosphere are calculated and verified against the numerical results. The transition and turning points are then used to introduce cutoff frequencies, which are different for different wave variables. The main result is …

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Orbital Stability Analysis And Chaotic Dynamics Of Exoplanets In Multi-Stellar Systems, Suman Satyal Jan 2014

Orbital Stability Analysis And Chaotic Dynamics Of Exoplanets In Multi-Stellar Systems, Suman Satyal

Physics Dissertations

The advancement in detection technology has substantially increased the discovery rate of exoplanets in the last two decades. The confirmation of thousands of exoplanets orbiting the solar type stars has raised new astrophysical challenges, including the studies of orbital dynamics and long-term stability of such planets. Continuous orbital stability of the planet in stellar habitable zone is considered vital for life to develop. Hence, these studies furthers one self-evident aim of mankind to find an answer to the century old question: Are we alone?This dissertation investigates the planetary orbits in single and binary star systems. Within binaries, a planet could …

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Experimental Studies Of Fundamental Aspects Of Auger Emission Process In Cu(100) And Ag(100), Prasad Vivek Joglekar Jan 2014

Experimental Studies Of Fundamental Aspects Of Auger Emission Process In Cu(100) And Ag(100), Prasad Vivek Joglekar

Physics Dissertations

Auger spectra at the low energies are accompanied by large contributions unrelated to the Auger transition. The Auger unrelated contributions can obscure the Auger peak and affect the quantitative analysis of the materials under investigation. In this dissertation we present a methodology to measure experimentally the Auger unrelated contributions and eliminate it from the Auger spectrum for obtaining an Auger spectrum inherent to the Auger transition. We used Auger Photoelectron Coincidence Spectroscopy (APECS) to obtain the Auger spectrum. APECS measures the Auger spectrum in coincidence with the core energy level and thus discriminating the contributions arising from secondary electrons and …

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Biological Damage Of Uv Radiation In Environments Of F-Type Stars, Satoko Sato Jan 2014

Biological Damage Of Uv Radiation In Environments Of F-Type Stars, Satoko Sato

Physics Dissertations

I investigate the general astrobiological significance of F-type main-sequence stars with special consideration to stellar evolutionary aspects due to nuclear evolution. DNA is taken as a proxy for carbon-based macromolecules following the assumption that exobiology is most likely based on hydrocarbons. The DNA action spectrum is utilized to represent the relative damage of the stellar UV radiation. Planetary atmospheric attenuation is taken into account in the form of parameterized attenuation functions. My work is motivated by previous studies indicating that the UV environment of solar-like stars is one of the most critical elements in determining the habitability of exoplanets and …

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First Principles Computational Modeling Of The Surface Properties Of Uranium Dioxide, Megan Hoover Jan 2014

First Principles Computational Modeling Of The Surface Properties Of Uranium Dioxide, Megan Hoover

Physics Theses

The interaction of uranium dioxide (UO₂) with environmental elements occurs at its exposed surface and a fundamental understanding of this interaction process begins at the atomic scale. In this regard, atomic scale modeling of the properties of clean and adsorbate-covered uranium dioxide (UO₂) surfaces can be used to elucidate UO₂ surface mechanisms such as corrosion and the formation of complex species via environmental gas adsorption. In this thesis, structural and electronic properties of clean and adsorbatecovered low index UO₂ surfaces were modeled using regular and hybrid density functional theory. Specifically, the properties of the clean (111) and (110) surfaces were …

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The Use Of Liquid Chromatography And Subcritical Fluid Chromatography For Chiral Separations Using Macrocyclic Chiral Stationary Phases: Insights Into Mechanisms Of Retention And Chiral Discrimination, Ross M. Woods Jan 2014

The Use Of Liquid Chromatography And Subcritical Fluid Chromatography For Chiral Separations Using Macrocyclic Chiral Stationary Phases: Insights Into Mechanisms Of Retention And Chiral Discrimination, Ross M. Woods

Chemistry & Biochemistry Dissertations

Enantiomeric separations are an essential component of pharmaceutical drug development, not only at the analytical scale, but also to separate usable quantities for further analysis. The field of asymmetric synthesis is also heavily dependent on chromatographic methods to separate and quantitate the results of asymmetric transformations as well as characterize new ligands and catalysts. This dissertation focuses on the use of macrocyclic chiral stationary phases for use in high performance liquid chromatography as well as subcritical fluid chromatography to separate individual enantiomers of molecules of importance to the scientific community. Optimized separation conditions are provided for many of these important …

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Fundamental And Applied Studies Of An Ambient Ionization Technique: Continuous Flow-Extractive Desorption Electrospray Ionization - Mass Spectrometry, Li Li Jan 2014

Fundamental And Applied Studies Of An Ambient Ionization Technique: Continuous Flow-Extractive Desorption Electrospray Ionization - Mass Spectrometry, Li Li

Chemistry & Biochemistry Dissertations

Continuous flow extractive desorption electrospray ionization (CF-EDESI) is a novel ambient ionization technique that was developed to help analyze samples from non-ESI-friendly solvents, manipulate protein charge states, and couple to a flowing sample solution stream. CF-EDESI is performed by introducing a sample solution through a hypodermic needle set orthogonal to an on-axis electrospray ionization source. Samples dissolved in non-ESI-friendly solvents such as hexanes, ethyl acetate etc. can be successfully detected in CF-EDESI which then makes it an attractive detection technique for normal phase separation. Additionally, introducing samples separated from electrospray has provided freedom to optimize both the sample solvents and …

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Efficient Frameworks For Lifetime Maximization In Tree Based Sensor Networks, Sk Kajal Arefin Imon Jan 2014

Efficient Frameworks For Lifetime Maximization In Tree Based Sensor Networks, Sk Kajal Arefin Imon

Computer Science and Engineering Dissertations

In most wireless sensor network (WSN) applications, data are typically gathered by the sensor nodes and reported to a data collection point, called the sink. In order to support such data collection, a tree structure rooted at the sink is usually defined. Based on different aspects, including the actual WSN topology and the available energy budget, the energy consumption of nodes belonging to different paths in the data collection tree may vary significantly. This affects the overall network lifetime, defined in terms of when the first node in the network runs out of energy. In this thesis, we address the …

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Graph Embedding Discriminative Unsupervised Dimensionality Reduction, Yun Liu Jan 2014

Graph Embedding Discriminative Unsupervised Dimensionality Reduction, Yun Liu

Computer Science and Engineering Theses

In this thesis, a novel graph embedding unsupervised dimensionality reduction method was proposed. Simultaneously, we assigned the adaptive and optimal neighbors on the basis of the projected local distances, thus we developed the dimensionality reduction along with the graph construction. The clustering results could be directly exhibited from the learnt graph which has the explicit block diagonal structure.The analysis of experimental result on different databases also determines that the proposed dimensionality reduction method is superior to other related dimensionality reduction methods, like PCA and LPP. In this study, we use synthetic data and real-world benchmark data sets. Also experimental results …

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A Hmm-Based Prediction Model For Spatio-Temporal Trajectories, Sakthi Kumaran Shanmuganathan Jan 2014

A Hmm-Based Prediction Model For Spatio-Temporal Trajectories, Sakthi Kumaran Shanmuganathan

Computer Science and Engineering Theses

Spatio-temporal trajectories are time series data that represent movement of an object over the time. Hidden Markov Models (HMM), a variant of Markov Models (MM), were first applied at a large scale to speech recognition but have also been used in time series prediction by analyzing trends in historical time series data. In this research, we propose a storm prediction model using a HMM built from overall storm trajectories derived from raw rainfall data. This HMM is built by assuming the states are associated with clusters created by clustering the locations of each storm from the overall storm trajectories. Then …

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Improving Tor Performance By Modifying Path Selection, Mehrdad Amirabadi Jan 2014

Improving Tor Performance By Modifying Path Selection, Mehrdad Amirabadi

Computer Science and Engineering Theses

Tor is a popular volunteer-based overlay network that provides anonymity andprivacy for Internet users. Using the Onion Proxy (OP) client, users connect to anetwork of Onion Routers (ORs) and send their traffic through an encrypted path ofthree ORs. One of the main problems of the Tor network is its slow performance, anda key cause of this is the Tor path selection algorithm. In Tor, ORs are selected basedprimarily on their bandwidth. In this work, we improve on the Tor path selectionalgorithm by proposing a new algorithm that besides bandwidth, uses distance as afactor to help reduce propagation delay. In our …

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Linking Entity Profiles, Ramesh Venkataraman Jan 2014

Linking Entity Profiles, Ramesh Venkataraman

Computer Science and Engineering Theses

Entity linking allows one to have collections of data from multiple sources as a global dataset and then query those data. Entity linking allows us to do knowledge discovery on this global dataset which might result in the discovery of some interesting facts and information. Microsoft Academic Search (MAS) is a free public search engine for academic papers and contains the bibliographic information for papers published in journals, conference proceedings and respective citations. As of February 2014, it has indexed over 40 million publications and 20 million authors. LinkedIn is a social networking service used for professional networking. LinkedIn has …

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Estimation Myopia: Tinkering With Perception In Software Estimation And Placebo Estimation In Edw, Hazem Hasan Yassin Jan 2014

Estimation Myopia: Tinkering With Perception In Software Estimation And Placebo Estimation In Edw, Hazem Hasan Yassin

Computer Science and Engineering Theses

The goal of this study is to explore an effective way to provide timely and accurate size estimates for software and for an enterprise data warehouse (EDW). Several research papers attempt to adapt function point (FP) analysis to EDW, but there is not much research in comprehensive techniques to estimate large EDW projects. Despite the generality of FP, it is challenging to employ in an EDW environment. This thesis describes such a technique. Additionally, the thesis provides an overview of general estimating approaches, techniques, models, and tools.This work presents a software tool that is a custom built estimation utility that …

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A Method To Evade Keyword Based Censorship, Ritu R. Patil Jan 2014

A Method To Evade Keyword Based Censorship, Ritu R. Patil

Computer Science and Engineering Theses

Many countries block the content of web pages which are deemed against the morals, religious rules or policies set by government or organization. Countries like China block the post which is against their government interest. Germany blocks contents related to Neo-Nazi group. Most of these web pages are subjected to IP address blocking, DNS poisoning and keyword based filtering. We mainly focus on keyword based filtering as it is fine grained filtering technique where the contents of web pages are filtered using blacklisting. So with increase in surveillance over network, arms race for circumvention techniques has also increased. We propose …

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A Cloud Based Automated Anomaly Detection Framework, Prathibha Datta Kumar Jan 2014

A Cloud Based Automated Anomaly Detection Framework, Prathibha Datta Kumar

Computer Science and Engineering Theses

A machine-to-machine (M2M) communications network hosts millions of heterogeneous devices such as for vehicle tracking, medical services, and home automation and security services. These devices exchange thousands of messages over cellular networks. These messages are Signaling System No. 7 (SS7) messages of various types like authentication, mobility management, and many more, resulting in tera bytes of SS7 signaling traffic data over a period of days. The data generated is diverse, depending on several factors like device activity, hardware manufacturers, and radio / tower interaction. This inherent diversity makes anomaly detection in a M2M network challenging. With millions of messages to …

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Evidence Of A Positron Bound State On The Surface Of A Topological Insulator, Karthik Shastry Jan 2014

Evidence Of A Positron Bound State On The Surface Of A Topological Insulator, Karthik Shastry

Physics Dissertations

We describe experiments aimed at probing the sticking of positrons to the surfaces of topological insulators performed at university of Texas at Arlington using the Positron Annihilation induced Auger electron Spectrometer. A magnetically guided beam was used to deposit positrons at the surface of Bi₂Te₂Se sample at energy of ~2eV. Peaks observed in the energy spectra and intensities of electrons emitted as a result of positron annihilation showed peaks at energies corresponding to Auger peaks in Bi and Te providing clear evidence of Auger emission associated with the annihilation of positrons in a surface bound state. Theoretical estimates of the …

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Phenomenological Studies Of Dark Matter, Miguel Alejandro Gomez Ramirez Jan 2014

Phenomenological Studies Of Dark Matter, Miguel Alejandro Gomez Ramirez

Physics Dissertations

It is common knowledge that eighty percent of the matter in our Universe consists of a mysterious substance called ``dark matter'' (DM) which has only been detected through its gravitational interactions. The ``Standard Model'' (SM) of particle physics, despite its extremely impressive successes, does not have a good candidate particle to fit the DM requirements. If DM is made up of a particle which interacts weakly and it has a mass on the same scale as other SM particles, it should be detectable.In this work, two different phenomenological studies of DM are performed. The first possibility is a weakly-interacting particle …

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Investigating The Global Geospace Response To A Period Of Solar Wind High Speed Streams Using The Lyon-Fedder-Mobarry Mhd Simulation, Kevin Pham Jan 2014

Investigating The Global Geospace Response To A Period Of Solar Wind High Speed Streams Using The Lyon-Fedder-Mobarry Mhd Simulation, Kevin Pham

Physics Dissertations

As the solar wind flows past the Earth, it interacts with the Earth's magnetic field and transfers energy and momentum to the geospace environment. During times when the solar cycle is near a minimum, there is a tendency for the Sun to produce high speed streams (HSSs), which are solar wind flows that are faster than the ambient solar wind. The HSSs contain properties that are not typically found in slower ambient solar wind, such as large amplitude Alfvén waves, that affect the transfer of energy and momentum. Large transfers of energy and momentum into the geospace environment that could …

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Investigation Of How Microbes Involved In Anerobic Digestion Of Vinasse Change As Functions Of Temperature, Vinasse Compositions And Time, Madhu Sanjog Sabnis Jan 2014

Investigation Of How Microbes Involved In Anerobic Digestion Of Vinasse Change As Functions Of Temperature, Vinasse Compositions And Time, Madhu Sanjog Sabnis

Earth & Environmental Sciences Dissertations

Recent fossil fuel supply crunches and price spikes have prompted increased interest in ethanol as an alternative transportation fuel. However, vinasse, the liquid residue left from the distillation of ethanol, poses serious disposal challenges due to its high acidity, chemical oxygen demand, and concentrations of solids, nitrogen, phosphorous, and potassium. On average, 12-14 liters of vinasse are produced per liter of ethanol. Brazilian production of ethanol is estimated as 15.1 billion liters per year, meaning that the vinasse treatment and disposal problem for Brazil is particularly significant.Degradation via anaerobic microbes has been demonstrated as a viable option for vinasse treatment, …

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Application Of In-Situ Remediation By Using Soil Phosphate Amendments At Three Lead Contaminated Soil Sites (Residential Yards) In New Orleans, La., Dhary Saad Alkandary Jan 2014

Application Of In-Situ Remediation By Using Soil Phosphate Amendments At Three Lead Contaminated Soil Sites (Residential Yards) In New Orleans, La., Dhary Saad Alkandary

Earth & Environmental Sciences Dissertations

Lead (Pb) contamination of soil continues as a threat to public health. The problem exists, in part, due to the abundance of lead in soil in certain contexts which has the potential to cause adverse health effects in children at relatively low exposure levels. The dominant source of lead in soils in the city of New Orleans, in the older urban areas close to residences, is old deteriorated lead-based paint. A cost-effective intervention method to address the problem of lead in these soils is needed to reduce the Pb exposure risk for people in these areas.Excavation and removal of lead …

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Social Data Analytics Using Tensors And Sparse Techniques, Miao Zhang Jan 2014

Social Data Analytics Using Tensors And Sparse Techniques, Miao Zhang

Computer Science and Engineering Dissertations

The development of internet and mobile technologies is driving an earthshaking social media revolution. They bring the internet world a huge amount of social media content, such as images, videos, comments, etc. Those massive media content and complicate social structures require the analytic expertise to transform those flood of information into actionable strategies, because mining those data can help organizations take control of those data, therefore organizations can improve customer satisfaction, identify patterns and trends, and make smarter marketing strategies. Mining those data can also help the consumers to grasp the most important and convenient information from the overwhelming data …

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Online Efficient And Effective Search In Large And Noisy Sequence Databases, Alexios Kotsifakos Jan 2014

Online Efficient And Effective Search In Large And Noisy Sequence Databases, Alexios Kotsifakos

Computer Science and Engineering Dissertations

This thesis investigates the problem of similarity search in large and noisy sequence databases. A key application domain of interest in this work is the very challenging Query-By-Humming (QBH) problem, according to which, given a hummed part of a song, we would like to identify the closest matches in a large music repository. The problem of selecting the most appropriate, based on each specific query, distance measure out of a pool of measures for classification in time series data is also investigated. In addition, searching time series databases via examples, which may be either time series or models, is also …

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Source Characterization Of African Soils Using Computer Controlled Sem Analysis, Robert Mace Rogers Jan 2014

Source Characterization Of African Soils Using Computer Controlled Sem Analysis, Robert Mace Rogers

Earth & Environmental Sciences Dissertations

An investigation is underway to determine whether African dust can be chemically distinguished by regions and whether it is developed through Pedogenic or Aeolian processes. A total of 29 dust samples were taken from the Sahel and Saharan region of Africa and are to be analyzed using computer controlled scanning electron microscopy (CCSEM). CCSEM collects data on size shape and chemical composition on individual microscopic dust particles present in a media sample analyzed in a scanning electron microscope (SEM). Back-scattered electron imaging (BEI) in the SEM is accomplished using a four-quadrants backscatter electron detector. This method of imaging the particles …

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Sensitivity Of The Late Permian Climate To Tectonic And Radiative Forcing Changes: Implications For The Mass Extinction, Angela Osen Jan 2014

Sensitivity Of The Late Permian Climate To Tectonic And Radiative Forcing Changes: Implications For The Mass Extinction, Angela Osen

Earth & Environmental Sciences Dissertations

The largest mass extinction occurred near the Permian-Triassic boundary (ca. 252 Ma). Significant carbon isotope shifts indicate that perturbations in the carbon cycle occurred during the Late Permian and persisted into the Early Triassic. The loss of biodiversity within the terrestrial and marine realms coincided with the eruption of the Siberian Flood Basalts and magma intrusion into coal beds, leading to the emission of greenhouse, sulfur, and other gases into the atmosphere. In this study, climate model output from the Community Climate System Model Version 3 with improved topographic features, along with a prediction of patterns of oceanic water masses …

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