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Articles 1561 - 1590 of 2906

Full-Text Articles in Physical Sciences and Mathematics

Social Capital In Online Communities, Matthew Scott Smith May 2011

Social Capital In Online Communities, Matthew Scott Smith

Theses and Dissertations

Social capital is the value of the relationships we create and maintain within our social networks to gain access to and mobilize needed resources (e.g., jobs, moral support). Quantifying, and subsequently leveraging, social capital are challenging problems in the social sciences. Most work so far has focused on analyses from static surveys of limited numbers of participants. The explosion of online social media means that it is now possible to collect rich data about people's connections and interactions, in a completely ubiquitous, non-intrusive manner. Such dynamic social data opens the door to the more accurate measuring and tracking of social …

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Accelerated Large-Scale Multiple Sequence Alignment With Reconfigurable Computing, G Scott Lloyd May 2011

Accelerated Large-Scale Multiple Sequence Alignment With Reconfigurable Computing, G Scott Lloyd

Theses and Dissertations

Multiple Sequence Alignment (MSA) is a fundamental analysis method used in bioinformatics and many comparative genomic applications. The time to compute an optimal MSA grows exponentially with respect to the number of sequences. Consequently, producing timely results on large problems requires more efficient algorithms and the use of parallel computing resources. Reconfigurable computing hardware provides one approach to the acceleration of biological sequence alignment. Other acceleration methods typically encounter scaling problems that arise from the overhead of inter-process communication and from the lack of parallelism. Reconfigurable computing allows a greater scale of parallelism with many custom processing elements that have …

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Adaptive Threat Detector Testing Using Bayesian Gaussian Process Models, Bradley Thomas Ferguson May 2011

Adaptive Threat Detector Testing Using Bayesian Gaussian Process Models, Bradley Thomas Ferguson

Theses and Dissertations

Detection of biological and chemical threats is an important consideration in the modern national defense policy. Much of the testing and evaluation of threat detection technologies is performed without appropriate uncertainty quantification. This paper proposes an approach to analyzing the effect of threat concentration on the probability of detecting chemical and biological threats. The approach uses a probit semi-parametric formulation between threat concentration level and the probability of instrument detection. It also utilizes a bayesian adaptive design to determine at which threat concentrations the tests should be performed. The approach offers unique advantages, namely, the flexibility to model non-monotone curves …

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Coherent Turbulence: Synthesizing Tree Motion In The Wind Using Cfd And Noise, Anthony Frank Selino May 2011

Coherent Turbulence: Synthesizing Tree Motion In The Wind Using Cfd And Noise, Anthony Frank Selino

Theses and Dissertations

Animating trees in wind has long been a problem in computer graphics. Progress on this problem is important for both visual effects and biomechanics and may inform future work on two-way coupling between turbulent flows and deformable objects. Synthetic turbulence added to a coarse fluid simulation has been used to produce convincing animations of turbulent flows, but only considers one-way coupling between fluid and solid. We produce accurate animations of tree motion by creating a two-way coupling between synthetic turbulence and semipermeable proxy geometry. The resulting animations exhibit global wind sheltering effects and branch tips have motion paths which match …

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A Speculative Approach To Parallelization In Particle Swarm Optimization, Matthew J. Gardner Apr 2011

A Speculative Approach To Parallelization In Particle Swarm Optimization, Matthew J. Gardner

Theses and Dissertations

Particle swarm optimization (PSO) has previously been parallelized primarily by distributing the computation corresponding to particles across multiple processors. In this thesis we present a speculative approach to the parallelization of PSO that we refer to as SEPSO. In our approach, we refactor PSO such that the computation needed for iteration t+1 can be done concurrently with the computation needed for iteration t. Thus we can perform two iterations of PSO at once. Even with some amount of wasted computation, we show that this approach to parallelization in PSO often outperforms the standard parallelization of simply adding particles to the …

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Outdoor Scenes For Data Visualization, Benjamin A. Hillery Apr 2011

Outdoor Scenes For Data Visualization, Benjamin A. Hillery

Theses and Dissertations

Recent cognitive research indicates that the human brain possesses special abilities for processing information relating to outdoor scenes. Simulated outdoor scenes are presented as an effective method of displaying higher dimensional data in an efficient and comprehensible manner. We demonstrate novel methods of using outdoor objects and scenes to display multidimensional content in a way that that is intuitive for humans to understand, and to exploit various cues commonly found in scenes from the natural world to communicate the values of multiple variables.

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Geologic Mapping Of Exhumed, Mid-Cretaceous Paleochannel Complexes Near Castle Dale, Emery County, Utah: On The Correlative Relationship Between The Dakota Sandstone And The Mussentuchit Member Of The Cedar Mountain Formation, Amanda Elizabeth Mackay Sorensen Apr 2011

Geologic Mapping Of Exhumed, Mid-Cretaceous Paleochannel Complexes Near Castle Dale, Emery County, Utah: On The Correlative Relationship Between The Dakota Sandstone And The Mussentuchit Member Of The Cedar Mountain Formation, Amanda Elizabeth Mackay Sorensen

Theses and Dissertations

Numerous well-preserved, exhumed paleochannels in the Morrison, Cedar Mountain and Dakota Sandstone formations are exposed east of Castle Dale, Utah. These channels consist primarily of point bar complexes and scattered, low sinuosity channels. To determine the vertical and lateral relationships of these channels within the Cedar Mountain and Dakota Sandstone formations, a 1:24,000 scale geologic map covering ~140 km2 was created showing the fluvial sandstones. In the study area the Cedar Mountain Formation consists, from bottom to top, of 2.5-10 m of Buckhorn Conglomerate Member equivalent units, ~80 m of the Ruby Ranch Member, and ~30 m of the Mussentuchit …

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Differentiation Of Bacillus Endospores From Gas Chromatography-Mass Spectrometry Of Biomarkers Produced By Thermochemolysis Methylation, Tai Van Truong Apr 2011

Differentiation Of Bacillus Endospores From Gas Chromatography-Mass Spectrometry Of Biomarkers Produced By Thermochemolysis Methylation, Tai Van Truong

Theses and Dissertations

Methods for fast, simple detection of biomarkers to detect and differentiate closely related Bacillus endospores including Bacillus anthracis (BA), Bacillus thuringiensis (BT), Bacillus atrophaeus (BG), and Bacillus cereus (BC) using thermochemolysis and methylation (TCM), coiled wire filament (CWF), solid phase micro extraction (SPME) and gas chromatography-mass spectrometry (GC-MS) were developed. The main biomarkers detected and used for differentiation include dipicolinic acid methyl ester (DPAME), fatty acid methyl esters (FAMEs), 3-methyl-2-butenoic acid methyl ester (3M2BAME), 2-butenoic acid methyl ester (2BAME), and several methylated sugars. TCM of endospores was performed based on hydrolysis and methylation at elevated temperature after the endospores were …

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Polymer Molded Templates For Nanostructured Amorphous Silicon Photovoltaics, Lei Pei, Amy Balls, Cary Tippets, Jonathan Abbott, Matthew R. Linford, David D. Allred, Richard R. Vanfleet, Robert C. Davis, Jian Hu, Arun Madan Apr 2011

Polymer Molded Templates For Nanostructured Amorphous Silicon Photovoltaics, Lei Pei, Amy Balls, Cary Tippets, Jonathan Abbott, Matthew R. Linford, David D. Allred, Richard R. Vanfleet, Robert C. Davis, Jian Hu, Arun Madan

Faculty Publications

Here, the authors report the fabrication of transparent polymer templates for nanostructured amorphous silicon photovoltaics using low-cost nanoimprint lithography of polydimethylsiloxane. The template contains a square two-dimensional array of high-aspect-ratio nanoholes (300 nm diameter by 1 µm deep holes) on a 500X500 nm^2 pitch. A 100 nm thick layer of a-Si:H was deposited on the template surface resulting in a periodically nanostructured film. The optical characterization of the nanopatterned film showed lower light transmission at 600-850 nm wavelengths and lower light reflection at 400-650 nm wavelengths, resulting in 20% higher optical absorbance at AM 1.5 spectral irradiance versus a nonpatterned …

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Easy To Find: Creating Query-Based Multi-Document Summaries To Enhance Web Search, Rani Majed Qumsiyeh Mar 2011

Easy To Find: Creating Query-Based Multi-Document Summaries To Enhance Web Search, Rani Majed Qumsiyeh

Theses and Dissertations

Current web search engines, such as Google, Yahoo!, and Bing, rank the set of documents S retrieved in response to a user query Q and display each document with a title and a snippet, which serves as an abstract of the corresponding document in S. Snippets, however, are not as useful as they are designed for, i.e., to assist search engine users to quickly identify results of interest, if they exist, without browsing through the documents in S, since they (i) often include very similar information and (ii) do not capture the main content of the corresponding documents. …

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Impact Of A Finite-Temperature Equation Of State On Neutron Stars, Christian D. Draper Mar 2011

Impact Of A Finite-Temperature Equation Of State On Neutron Stars, Christian D. Draper

Theses and Dissertations

In this research, we study how a finite-temperature nuclear equation of state suitable for astrophysical simulations impacts the oscillation modes of neutron stars. We chose the Shen equation of state (EOS) because it accurately describes both stable and unstable nuclei as well as nuclear incompressibilities. I modified the existing MHD code at BYU, the HAD code, to call a lookup table for the Shen EOS for use at run time, and added a Newton-Raphson method algorithm to convert conserved variables to primitive variables. The algorithm was tested and verified by evolving a stable neutron star for several dynamical times and …

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High-Quality Broadband Bvri Photometry Of Benchmark Open Clusters, Michael Deloss Joner Mar 2011

High-Quality Broadband Bvri Photometry Of Benchmark Open Clusters, Michael Deloss Joner

Theses and Dissertations

Photometric techniques are often used to observe stars and it can be demonstrated that fundamental stellar properties can be observationally determined using calibrated sets of photometric data. Many of the most powerful techniques utilized to calibrate stellar photometry employ the use of stars in clusters since the individual stars are believed to have many common properties such as age, composition, and approximate distance. Broadband photometric Johnson/Cousins BVRI observations are presented for several nearby open clusters. The new photometry has been tested for consistency relative to archival work and shown to be both accurate and precise. The careful use of a …

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Human Endogenous Sodium Pump Inhibitors Measurement, Source, Synthesis And Regulation, Jie Ma Mar 2011

Human Endogenous Sodium Pump Inhibitors Measurement, Source, Synthesis And Regulation, Jie Ma

Theses and Dissertations

The sodium pump (SP or Na+,K+-ATPase) is a membrane embedded protein complex that pumps 3 sodium ions out and 2 potassium ions into the cell per cycle and in so doing creates a cell membrane electrochemical potential. The membrane potential is critical for any functional cell. In the vasculature, reduction in the voltage potential causes vascular smooth muscle contraction and a narrowing of blood vessels (vasoconstriction) which can lead to increased blood pressure (hypertension). Substantial research over the past several decades has provided a vast amount of research on SP inhibitors, sometimes called endogenous digitalis-like factors (EDLF). Increased levels of …

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Super Collision Energy Transfer Studies In Single Collisions Between Vibrationally Hot Benzene Like Molecules And Ground State Bath Molecules: The Effect Of Physical Properties Of Donor And Bath Molecules On Super Collision Energy Transfer, Kilyoung Kim Mar 2011

Super Collision Energy Transfer Studies In Single Collisions Between Vibrationally Hot Benzene Like Molecules And Ground State Bath Molecules: The Effect Of Physical Properties Of Donor And Bath Molecules On Super Collision Energy Transfer, Kilyoung Kim

Theses and Dissertations

This research is focused on single-collision energy transfer events between highly vibrationally excited benzene-like donor molecules and small bath molecules, CO2 and N2O in the vibrational ground level. Measuring how much energy is transferred from donors to bath molecules was accomplished by probing bath molecules scattered into specific-rotational states using a tunable Δv=0.0003 cm-1 solid state diode laser. The normalized energy transfer probability distribution function, P(E,E'), determined from energy gain information, is very useful in comparing collisional energy transfer efficiency between various collision systems. P(E,E') is also used to investigate the effects of donor and bath physical properties on collisional …

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Evolution And Emergence Of The Hinterland In The Active Banda Arc-Continent Collision: Insights From The Metamorphic Rocks And Coral Terraces Of Kisar, Indonesia, Jonathan R. Major Mar 2011

Evolution And Emergence Of The Hinterland In The Active Banda Arc-Continent Collision: Insights From The Metamorphic Rocks And Coral Terraces Of Kisar, Indonesia, Jonathan R. Major

Theses and Dissertations

Coral terrace surveys and U-series ages of coral and mollusk shells yield a surface uplift rate of ~0.6 m/ka for Kisar Island. The small island is located NE of Timor in the active Banda Arc of Indonesia. Based on this rate, Kisar first emerged from the ocean as recently as ~450 ka. Terrace surveys show warping that follows a pattern of east-west striking folds, which are along strike of thrust-related folds of similar wavelength imaged by a seismic reflection profile just offshore. This deformation shows that the emergence of Kisar can be attributed to forearc closure along the south-dipping Kisar …

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Identifying Complex Fluvial Sandstone Reservoirs Using Core, Well Log, And 3d Seismic Data: Cretaceous Cedar Mountain And Dakota Formations, Southern Uinta Basin, Utah., William H. Hokanson Mar 2011

Identifying Complex Fluvial Sandstone Reservoirs Using Core, Well Log, And 3d Seismic Data: Cretaceous Cedar Mountain And Dakota Formations, Southern Uinta Basin, Utah., William H. Hokanson

Theses and Dissertations

The Cedar Mountain and Dakota Formations are significant gas producers in the southern Uinta Basin of Utah. To date, however, predicting the stratigraphic distribution and lateral extent of potential gas-bearing channel sandstone reservoirs in these fluvial units has proven difficult due to their complex architecture, and the limited spacing of wells in the region. A new strategy to correlate the Cedar Mountain and Dakota Formations has been developed using core, well-log, and 3D seismic data. The detailed stratigraphy and sedimentology of the interval were interpreted using descriptions of a near continuous core of the Dakota Formation from the study area. …

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Variable Selection And Parameter Estimation Using A Continuous And Differentiable Approximation To The L0 Penalty Function, Douglas Nielsen Vanderwerken Mar 2011

Variable Selection And Parameter Estimation Using A Continuous And Differentiable Approximation To The L0 Penalty Function, Douglas Nielsen Vanderwerken

Theses and Dissertations

L0 penalized likelihood procedures like Mallows' Cp, AIC, and BIC directly penalize for the number of variables included in a regression model. This is a straightforward approach to the problem of overfitting, and these methods are now part of every statistician's repertoire. However, these procedures have been shown to sometimes result in unstable parameter estimates as a result on the L0 penalty's discontinuity at zero. One proposed alternative, seamless-L0 (SELO), utilizes a continuous penalty function that mimics L0 and allows for stable estimates. Like other similar methods (e.g. LASSO and SCAD), SELO produces sparse solutions because the penalty function is …

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A Novel Use Of Digoxin Immune Fab Fragment In Identification And Isolation Of An Endogenous Digitalis-Like Factor Found In Preeclampsia, Moana Lee Hopoate-Sitake Mar 2011

A Novel Use Of Digoxin Immune Fab Fragment In Identification And Isolation Of An Endogenous Digitalis-Like Factor Found In Preeclampsia, Moana Lee Hopoate-Sitake

Theses and Dissertations

The mechanisms mediating the hypertension of preeclampsia (PE) are unclear. Endogenous digitalis-like factors (EDLFs) are specific sodium pump (SP) inhibitors implicated in essential and experimental hypertension, but they have not been fully explored in the setting of PE. This study uses a digoxin antibody Fab fragment to address the question of whether such factors are present and increased in PE, to investigate a possible treatment of PE, and to isolate and characterize all EDLFs present in PE. Sera and placenta from women with PE did show a significant increase in SP inhibition in comparison to women with normal pregnancy and …

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Time-Series Observations Of The High Mass X-Ray Binary 4u 2206+54 To Monitor Light Variation, Jessica Lynn Bugno Mar 2011

Time-Series Observations Of The High Mass X-Ray Binary 4u 2206+54 To Monitor Light Variation, Jessica Lynn Bugno

Theses and Dissertations

The high mass X-ray binary 4U 2206+54 has been a very controversial system due to variability in spectral data as well as photometric data. We, at Brigham Young University, have been observing this system in multiple filters with several telescopes. This thesis presents our methods of observations, reductions, and results. It also compares what we have been detecting to other groups looking at the same target in different wavelengths. Furthermore, this thesis discusses some of the peculiarities of 4U 2206+54 and possible theories to explain these phenomena. Based on our photometric observations for the past three years, we believe the …

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Surface Modification, Fabrication, And Characterization Of Silicon, Polymer, And Nanotube Composite Materials, Lei Pei Mar 2011

Surface Modification, Fabrication, And Characterization Of Silicon, Polymer, And Nanotube Composite Materials, Lei Pei

Theses and Dissertations

In my research, I have performed many characterization and fabrication experiments that are based on tools of analytical chemistry, materials chemistry, and surface science. My research projects are as follows. (1) Fabrication of transparent polymer templates for nanostructured amorphous silicon photovoltaics was done using low-cost nanoimprint lithography of polydimethylsiloxane. This approach provides a test bed for absorption studies in nanostructured film geometries and should result in improved light capturing designs in thin-film solar cells. Nanopatterned polymer films were characterized by scanning electron microscopy and optical measurements. (2) A straightforward method for fabricating freely suspended, thin, carbon nanotube (CNT) membranes infiltrated …

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Mean Square Estimate For Primitive Lattice Points In Convex Planar Domains, Ryan D. Coatney Mar 2011

Mean Square Estimate For Primitive Lattice Points In Convex Planar Domains, Ryan D. Coatney

Theses and Dissertations

The Gauss circle problem in classical number theory concerns the estimation of N(x) = { (m1;m2) in ZxZ : m1^2 + m2^2 <= x }, the number of integer lattice points inside a circle of radius sqrt(x). Gauss showed that P(x) = N(x)- pi * x satisfi es P(x) = O(sqrt(x)). Later Hardy and Landau independently proved that P(x) = Omega_(x1=4(log x)1=4). It is conjectured that inf{e in R : P(x) = O(x^e )}= 1/4. I. K atai showed that the integral from 0 to X of |P(x)|^2 dx = X^(3/2) + O(X(logX)^2). Similar results to those of the circle have been obtained for regions D in R^2 which contain the origin and whose boundary dD satis fies suff cient smoothness conditions. Denote by P_D(x) the similar error term to P(x) only for the domain D. W. G. Nowak showed that, under appropriate conditions on dD, P_D(x) = Omega_(x1=4(log x)1=4) and that the integral from 0 to X of |P_D(x)|^2 dx = O(X^(3/2)). A result similar to Nowak's mean square estimate is given in the case where only "primitive" lattice points, {(m1;m2) in Z^2 : gcd(m1;m2) = 1 }, are counted in a region D, on assumption of the Riemann Hypothesis.

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Hierarchical Bayesian Methods For Evaluation Of Traffic Project Efficacy, Andrew Nolan Olsen Mar 2011

Hierarchical Bayesian Methods For Evaluation Of Traffic Project Efficacy, Andrew Nolan Olsen

Theses and Dissertations

A main objective of Departments of Transportation is to improve the safety of the roadways over which they have jurisdiction. Safety projects, such as cable barriers and raised medians, are utilized to reduce both crash frequency and crash severity. The efficacy of these projects must be evaluated in order to use resources in the best way possible. Five models are proposed for the evaluation of traffic projects: (1) a Bayesian Poisson regression model; (2) a hierarchical Poisson regression model building on model (1) by adding hyperpriors; (3) a similar model correcting for overdispersion; (4) a dynamic linear model; and (5) …

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Facies Analysis And Reservoir Characterization Of Subtidal, Intertidal, And Supratidal Zones Of The Mudstone-Rich Entrada Sandstone, South-Central Utah, Tanner Charles Hicks Mar 2011

Facies Analysis And Reservoir Characterization Of Subtidal, Intertidal, And Supratidal Zones Of The Mudstone-Rich Entrada Sandstone, South-Central Utah, Tanner Charles Hicks

Theses and Dissertations

Understanding thickness variation and facies transitions in the mudstone-rich part of the Upper Middle Jurassic (Callovian) Entrada Sandstone depositional system is critical for constraining the paleogeography and evaluating the economic potential of Utah's Entrada Sandstone. Facies of the Entrada Sandstone in south-central Utah are dominated by mudstone-rich intertidal facies that were widespread within the Jurassic seaway. Intertidal deposits interfinger basinward with subtidal ooid-bearing shoals and bars, and landward supratidal sabkha, and erg-margin eolian deposits. Three sections were measured to improve understanding of the lateral and vertical facies transitions. Variations in thickness indicate the rate of developing accommodation space was high …

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Parameter Estimation For The Two-Parameter Weibull Distribution, Mark A. Nielsen Mar 2011

Parameter Estimation For The Two-Parameter Weibull Distribution, Mark A. Nielsen

Theses and Dissertations

The Weibull distribution, an extreme value distribution, is frequently used to model survival, reliability, wind speed, and other data. One reason for this is its flexibility; it can mimic various distributions like the exponential or normal. The two-parameter Weibull has a shape (γ) and scale (β) parameter. Parameter estimation has been an ongoing search to find efficient, unbiased, and minimal variance estimators. Through data analysis and simulation studies, the following three methods of estimation will be discussed and compared: maximum likelihood estimation (MLE), method of moments estimation (MME), and median rank regression (MRR). The analysis of wind speed data from …

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Utilizing Universal Probability Of Expression Code (Upc) To Identify Disrupted Pathways In Cancer Samples, Michelle Rachel Withers Mar 2011

Utilizing Universal Probability Of Expression Code (Upc) To Identify Disrupted Pathways In Cancer Samples, Michelle Rachel Withers

Theses and Dissertations

Understanding the role of deregulated biological pathways in cancer samples has the potential to improve cancer treatment, making it more effective by selecting treatments that reverse the biological cause of the cancer. One of the challenges with pathway analysis is identifying a deregulated pathway in a given sample. This project develops the Universal Probability of Expression Code (UPC), a profile of a single deregulated biological path- way, and projects it into a cancer cell to determine if it is present. One of the benefits of this method is that rather than use information from a single over-expressed gene, it pro- …

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Development Of Monolithic Stationary Phases For Cation-Exchange Capillary Liquid Chromatography Of Peptides And Proteins, Xin Chen Feb 2011

Development Of Monolithic Stationary Phases For Cation-Exchange Capillary Liquid Chromatography Of Peptides And Proteins, Xin Chen

Theses and Dissertations

This dissertation focuses on the preparation of polymeric monolithic capillaries for ion exchange chromatography of peptides and proteins, since polymeric monoliths have shown promise for providing improved protein separations. Characteristics of monolithic columns include low back pressure, simplicity of fabrication and biocompatibility. Preparation of strong and weak cation-exchange monolithic stationary phases in 75 μm I.D. capillaries by direct in situ copolymerization was achieved using various functional monomers including sulfopropyl methacrylate, phosphoric acid 2-hydroxyethyl methacrylate, bis[2-(methacryloyloxy)ethyl] phosphate and 2-carboxyethyl acrylate with polyethylene glycol diacrylate and other PEG materials. The resulting monoliths provided excellent ion exchange capillary LC of peptides and proteins …

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Programming Language Fragmentation And Developer Productivity: An Empirical Study, Jonathan L. Krein Feb 2011

Programming Language Fragmentation And Developer Productivity: An Empirical Study, Jonathan L. Krein

Theses and Dissertations

In an effort to increase both the quality of software applications and the efficiency with which applications can be written, developers often incorporate multiple programming languages into software projects. Although language specialization arguably introduces benefits, the total impact of the resulting language fragmentation (working concurrently in multiple programming languages) on developer performance is unclear. For instance, developers may solve problems more efficiently when they have multiple language paradigms at their disposal. However, the overhead of maintaining efficiency in more than one language may outweigh those benefits. This thesis represents a first step toward understanding the relationship between language fragmentation and …

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Relationships Among Learning Algorithms And Tasks, Jun Won Lee Jan 2011

Relationships Among Learning Algorithms And Tasks, Jun Won Lee

Theses and Dissertations

Metalearning aims to obtain knowledge of the relationship between the mechanism of learning and the concrete contexts in which that mechanisms is applicable. As new mechanisms of learning are continually added to the pool of learning algorithms, the chances of encountering behavior similarity among algorithms are increased. Understanding the relationships among algorithms and the interactions between algorithms and tasks help to narrow down the space of algorithms to search for a given learning task. In addition, this process helps to disclose factors contributing to the similar behavior of different algorithms. We first study general characteristics of learning tasks and their …

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Parallel Particle Swarm Optimization And Large Swarms, Andrew W. Mcnabb Jan 2011

Parallel Particle Swarm Optimization And Large Swarms, Andrew W. Mcnabb

Theses and Dissertations

Optimization is the search for the maximum or minimum of a given objective function. Particle Swarm Optimization (PSO) is a simple and effective evolutionary algorithm, but it may take hours or days to optimize difficult objective functions which are deceptive or expensive. Deceptive functions may be highly multimodal and multidimensional, and PSO requires extensive exploration to avoid being trapped in local optima. Expensive functions, whose computational complexity may arise from dependence on detailed simulations or large datasets, take a long time to evaluate. For deceptive or expensive objective functions, PSO must be parallelized to use multiprocessor systems and clusters efficiently. …

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Density And Temperature Scaling Of Disorder-Induced Heating In Ultracold Plasmas, Scott D. Bergeson, A. Denning, M. Lyon, F. Robicheaux Jan 2011

Density And Temperature Scaling Of Disorder-Induced Heating In Ultracold Plasmas, Scott D. Bergeson, A. Denning, M. Lyon, F. Robicheaux

Faculty Publications

We report measurements and simulations of disorder-induced heating in ultracold neutral plasmas. Fluorescence from plasma ions is excited using a detuned probe laser beam while the plasma relaxes from its initially disordered nonequilibrium state. This method probes the wings of the ion velocity distribution. The simulations yield information on time-evolving plasma parameters that are difficult to measure directly and make it possible to connect the fluorescence signal to the rms velocity distribution. The disorder-induced heating signal can be used to estimate the electron and ion temperatures ~100 ns after the plasma is created. This is particularly interesting for plasmas in …

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