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Articles 2821 - 2850 of 3417

Full-Text Articles in Physical Sciences and Mathematics

Simulating Protein Evolution Via Thermodynamic Models, Yanlong Xu Jan 2006

Simulating Protein Evolution Via Thermodynamic Models, Yanlong Xu

LSU Doctoral Dissertations

Natural proteins are results of evolution and they need to maintain certain thermodynamic stabilities in order to carry out their biological functions. By simulating protein evolution based on thermodynamic rules, we could reconstruct the evolution trajectory and analyze the evolutionary dynamics of a protein population, and further understand the protein sequence-structure-function relationship. In this study, we have used both a simplified lattice model and a high-resolution atomic model to simulate protein evolution processes. With the lattice model, we have investigated general theoretical questions about how protein structural designability would affect protein evolution, particularly how it would affect protein recombination and …

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Extension Of Shor's Period-Finding Algorithm To Infinite Dimensional Hilbert Spaces, Jeremy James Becnel Jan 2006

Extension Of Shor's Period-Finding Algorithm To Infinite Dimensional Hilbert Spaces, Jeremy James Becnel

LSU Doctoral Dissertations

Over the last decade quantum computing has become a very popular field in various disciplines, such as physics, engineering, and mathematics. Most of the attraction stemmed from the famous Shor period--finding algorithm, which leads to an efficient algorithm for factoring positive integers. Many adaptations and generalizations of this algorithm have been developed through the years, some of which have not been ripened with full mathematical rigor. In this dissertation we use concepts from white noise analysis to rigorously develop a Shor algorithm adapted to find a hidden subspace of a function with domain a real Hilbert space. After reviewing the …

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On The Nature Of Connectivity Types, Miao Xu May 2005

On The Nature Of Connectivity Types, Miao Xu

Honors Theses

No abstract provided.

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Dynamical Systems And The Logistic And Tent Maps, Kathleen Larkin Spires May 2005

Dynamical Systems And The Logistic And Tent Maps, Kathleen Larkin Spires

Honors Theses

No abstract provided.

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Ensight, Jonathan Hefner May 2005

Ensight, Jonathan Hefner

Honors Theses

No abstract provided.

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An Investigation Of Modified Superconductivity Through Structural Alteration Of Mgcni3 And Mgb2, Nathan L. Henderson Apr 2005

An Investigation Of Modified Superconductivity Through Structural Alteration Of Mgcni3 And Mgb2, Nathan L. Henderson

Honors Theses

No abstract provided.

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Shear Induced Orientation In Polymer-Clay Solutions And Their Influence On The Structure In Multilayered Films, Matthew Michael Malwitz Jan 2005

Shear Induced Orientation In Polymer-Clay Solutions And Their Influence On The Structure In Multilayered Films, Matthew Michael Malwitz

LSU Doctoral Dissertations

The influence of shear on viscoelastic solutions of poly(ethylene oxide) (PEO) and clay (Cloisite, CNA) was investigated by rheology and small angle neutron scattering (SANS) under shear. These measurements determined the shear-induced orientation of the clay and the polymer as well as their relaxation behavior after cessation of shear. Comparison of PEO-CNA solutions (~100 nm diameter platelets) to previously studied PEO-Laponite gels (~30 nm diameter platelets) found that the orientation of CNA platelets occurs at much lower shear rates. Additionally, the relaxation times were much longer for CNA platelets than for Laponite platelets. From these solutions and gels, multilayered nanocomposite …

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Multiscale Strain Analysis, Timothy Donald Breitzman Jan 2005

Multiscale Strain Analysis, Timothy Donald Breitzman

LSU Doctoral Dissertations

The mathematical homogenization and corrector theory relevant to prestressed heterogeneous materials in the linear-elastic regime is discussed. A suitable corrector theory is derived to reconstruct the local strain field inside the composite. Based on this theory, we develop an inexpensive numerical method for multi scale strain analysis within a prestressed heterogeneous material. The theory also provides a characterization of the macroscopic strength domain. The strength domain places constraints on the homogenized strain field which guarantee that the actual strain in the heterogeneous material lies inside the strength domain of each material participating in the structure.

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An Empirical Study Of Imputation Techniques For Software Data Sets, Sumanth Yenduri Jan 2005

An Empirical Study Of Imputation Techniques For Software Data Sets, Sumanth Yenduri

LSU Doctoral Dissertations

Software Project Effort/Cost/Time Estimation has been one of the hot topics of research in the current software engineering industry. Solutions for effort/cost/time estimation are in great demand. Knowledge of accurate effort/cost/time estimates early in the software project life cycle enables project managers manage and exploit resources efficiently. The constraints of cost and time can also be met. To this day, most companies rely on their historical database of past project data sets to predict estimates for future projects. Like other data sets, software project data sets also suffer from numerous problems. The most important problem is they contain missing/incomplete data. …

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Hydrophobic Guar Gum Derivatives Prepared By Controlled Grafting Processes For Hydraulic Facturing Applications, Ahmad Bahamdan Jan 2005

Hydrophobic Guar Gum Derivatives Prepared By Controlled Grafting Processes For Hydraulic Facturing Applications, Ahmad Bahamdan

LSU Doctoral Dissertations

The synthesis of new water soluble guar gum derivatives is described. Introduction of polyalkoxyalkyleneamide grafts to guar gum or hydroxyopropyl guar was achieved in a three step process: carboxymethylation with sodium chloroacetate, esterification with dimethyl sulfate and amidation with a series of polyalkoxyalkylene-amines. The process steps were followed using infrared spectroscopy; the grafted guar derivatives were characterized using FT-IR and 1H NMR. A series of hydroxypropyl guar derivatives with degrees of carboxymethylations ranging from 0.15-0.25 were modified with polyalkoxyalkyleneamines with molecular weights ranging from 300-3000. The ratio of oxypropylene to oxoethylene units in the polyalkoxyalkyleneamines was varied from 9/1 …

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Analytical Separations Using Polymetric Surfactants, Mary Waithira Kamande Jan 2005

Analytical Separations Using Polymetric Surfactants, Mary Waithira Kamande

LSU Doctoral Dissertations

The goal of the research presented in this dissertation is to develop effective analytical methods for the separation of both achiral and chiral analytes using polymeric surfactants. Three analytical techniques are employed to accomplish this objective: open-tubular capillary electrochromatography (OT-CEC), open-tubular capillary electrochromatography coupled to mass spectrometry (OT-CEC/MS), and micellar affinity gradient focusing (MAGF). This research work presents novel application of polymeric surfactants that contributes to improved separations of difficult to separate analytes. The first part focuses on the application of an achiral polyelectrolyte multilayer (PEM) coating using OT-CEC. The PEM coating consisting of the cationic polymer poly (diallyldimethylammonium chloride), …

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Laguerre Functions Associated To Euclidean Jordan Algebras, Michael Aristidou Jan 2005

Laguerre Functions Associated To Euclidean Jordan Algebras, Michael Aristidou

LSU Doctoral Dissertations

Certain differential recursion relations for the Laguerre functions, defined on a symmetric cone Ω, can be derived from the representations of a specific Lie algebra on L2(Ω,dμv). This Lie algebra is the corresponding Lie algebra of the Lie group G that acts on the tube domain T(Ω)=Ω+iV, where V is the associated Euclidean Jordan algebra of Ω. The representations involved are the highest weight representations of G on L2(Ω,dμv). To obtain these representations, we start from the highest weight representations of G on Hv(T(Ω)), the Hilbert space of holomorphic functions …

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Efficient Automatic Correction And Segmentation Based 3d Visualization Of Magnetic Resonance Images, Mikhail V. Milchenko Jan 2005

Efficient Automatic Correction And Segmentation Based 3d Visualization Of Magnetic Resonance Images, Mikhail V. Milchenko

LSU Doctoral Dissertations

In the recent years, the demand for automated processing techniques for digital medical image volumes has increased substantially. Existing algorithms, however, still often require manual interaction, and newly developed automated techniques are often intended for a narrow segment of processing needs. The goal of this research was to develop algorithms suitable for fast and effective correction and advanced visualization of digital MR image volumes with minimal human operator interaction. This research has resulted in a number of techniques for automated processing of MR image volumes, including a novel MR inhomogeneity correction algorithm derivative surface fitting (dsf), automatic tissue detection algorithm …

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Parallel Molecular Dynamics Simulations Of Pressure-Induced Structural Transformations In Cadmium Selenide Nanocrystals, Nicholas Jabari Ouma Lee Jan 2005

Parallel Molecular Dynamics Simulations Of Pressure-Induced Structural Transformations In Cadmium Selenide Nanocrystals, Nicholas Jabari Ouma Lee

LSU Doctoral Dissertations

Parallel molecular dynamics (MD) simulations are performed to investigate pressure-induced solid-to-solid structural phase transformations in cadmium selenide (CdSe) nanorods. The effects of the size and shape of nanorods on different aspects of structural phase transformations are studied. Simulations are based on interatomic potentials validated extensively by experiments. Simulations range from 105 to 106 atoms. These simulations are enabled by highly scalable algorithms executed on massively parallel Beowulf computing architectures. Pressure-induced structural transformations are studied using a hydrostatic pressure medium simulated by atoms interacting via Lennard-Jones potential. Four single-crystal CdSe nanorods, each 44Å in diameter but varying in length, in the …

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Boundary Effects On Non-Equilibrium Localized Structures In Spatially Extended Systems, Aniruddha Yadav Jan 2005

Boundary Effects On Non-Equilibrium Localized Structures In Spatially Extended Systems, Aniruddha Yadav

LSU Doctoral Dissertations

A study of the effects of system boundaries on bistable front propagation in nonequilibrium reaction-diffusion systems is presented. Two model partial differential equations displaying bistable fronts, with distinct experimental motivations and mathematical structure, are examined in detail utilizing simulations and perturbation techniques. We see that propagating fronts in both models bounce, trap, pin, or oscillate at the boundary, contingent on the imposed boundary condition, initial front speed and distance from the boundary. The similarities in front boundary interactions in these two models is traced to the fact that they display the same front instability (Ising-Bloch bifurcation) that controls the speed …

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Carbonate Records Of Submarine Hydrocarbon Venting: Northern Gulf Of Mexico, Matthew S. Hackworth Jan 2005

Carbonate Records Of Submarine Hydrocarbon Venting: Northern Gulf Of Mexico, Matthew S. Hackworth

LSU Doctoral Dissertations

Hydrocarbon seep sediments are examined from 3 sites in the Gulf of Mexico (Green Canyon Lease Blocks 232, 185, and 272) to relate the effects of gas hydrates and hydrocarbons on microbial process, pore fluid chemistry, and the processes of authigenic carbonate formation. Hydrocarbon-fueled microbial reactions result in pore fluids with lowered SO42- (all consumed by –10 cm) and enrichments in H2S, alkalinity, and DIC (up to 20 mmol, 30 meq/L, and 18 mmol/L, respectively) which promote carbonate formation. Pore fluid d13CDIC (PDB) is influenced by thermogenic hydrocarbons and crude oil in GC …

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Wavelet Sets With And Without Groups And Multiresolution Analysis, Mihaela Dobrescu Jan 2005

Wavelet Sets With And Without Groups And Multiresolution Analysis, Mihaela Dobrescu

LSU Doctoral Dissertations

In this dissertation we study a special kind of wavelets, the so-called minimally supported frequency wavelets and the associated wavelet sets. Most of the examples of wavelet sets are for dilation sets which are groups. In this work we construct wavelet sets for which the dilation set, D, is of the form D=MN, where the product is direct, and so D is not necessarily group. In the second part of this dissertation we construct multiwavelets associated with MRA's and we generalize the rotations in the dilation sets to Coxeter groups.

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Active Security Mechanisms For Wireless Sensor Networks And Energy Optimization For Passive Security Routing, Lydia Ray Jan 2005

Active Security Mechanisms For Wireless Sensor Networks And Energy Optimization For Passive Security Routing, Lydia Ray

LSU Doctoral Dissertations

Wireless sensor networks consisting of numerous tiny low power autonomous sensor nodes provide us with the remarkable ability to remotely view and interact with the previously unobservable physical world. However, incorporating computation intensive security measures in sensor networks with limited resources is a challenging research issue. The objective of our thesis is to explore different security aspects of sensor networks and provide novel solutions for significant problems. We classify security mechanisms into two categories - active category and passive category. The problem of providing a secure communication infrastructure among randomly deployed sensor nodes requires active security measurements. Key pre-distribution is …

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Characterization Of A Modified Poly(Propylene Imine) Dendrimer Host System, Amy D. Morara Jan 2005

Characterization Of A Modified Poly(Propylene Imine) Dendrimer Host System, Amy D. Morara

LSU Doctoral Dissertations

The research in this dissertation focuses on the design of a novel redox-responsive host system that has the ability to encapsulate guest molecules. The host at hand is a tri(ethylene oxide), TEO, pyrrole-terminated PPI dendrimer that possesses water-solubility as a result of the presence of the TEO chains on the pyrrole groups and redox-responsive activity from the pyrrole groups after their oligomerization. The pyrrole moieties at the periphery of the dendrimer exhibit the ability to be oligomerized by oxidation chemistry, and this is shown to aid in the retention and egress of guest molecules located within the dendrimer interior. These …

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Characterization Of Aged Polymer Modified Asphalt Cements For Recycling Purposes, Codrin Daranga Jan 2005

Characterization Of Aged Polymer Modified Asphalt Cements For Recycling Purposes, Codrin Daranga

LSU Doctoral Dissertations

Since polymer modified asphalt cement (PMAC) has been employed for a decade, the lifetime and wear on some of these pavements is reaching a stage where resurfacing is necessary. This research focuses on the characterization of aged polymer modified asphalt cements (PMAC) to evaluate their potential for recycling. A styrene-butadiene-styrene tri-block (SBS) polymer modified asphalt cement was selected and characterized using standard asphalt binder qualification techniques, i.e., the Superpave PG protocol. We developed a procedure to characterize the relative concentration of polymer in asphalt cements by gel permeation chromatography (GPC). Infrared spectrographic, thermogravimetric and rheological techniques were used to identify …

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Radiative Transfer Modeling Of Thermal Infrared Emissivity Spectra: Applications To Martian Regolith Observations, Karly Mariah Pitman Jan 2005

Radiative Transfer Modeling Of Thermal Infrared Emissivity Spectra: Applications To Martian Regolith Observations, Karly Mariah Pitman

LSU Doctoral Dissertations

Satellite and rover remote sensing of planetary regolith surfaces, in the form of thermal infrared emissivity spectra taken at nadir and off-nadir angles of emergence from the surface, requires use of theoretical models for interpretation of constituent grain physical properties. However, such models have remained in stasis in recent years, with nearly a ten-year gap in significant advances. To date, no radiative transfer model (semiempirical, exact, or hybrid solution) has been able to adequately predict the nadir emissivity behavior of simple mineral assemblages. Few measurements have been attempted in the laboratory or field regarding directional emissivity effects of planetary regoliths; …

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Learning Discrete Hidden Markov Models From State Distribution Vectors, Luis G. Moscovich Jan 2005

Learning Discrete Hidden Markov Models From State Distribution Vectors, Luis G. Moscovich

LSU Doctoral Dissertations

Hidden Markov Models (HMMs) are probabilistic models that have been widely applied to a number of fields since their inception in the late 1960’s. Computational Biology, Image Processing, and Signal Processing, are but a few of the application areas of HMMs. In this dissertation, we develop several new efficient learning algorithms for learning HMM parameters. First, we propose a new polynomial-time algorithm for supervised learning of the parameters of a first order HMM from a state probability distribution (SD) oracle. The SD oracle provides the learner with the state distribution vector corresponding to a query string. We prove the correctness …

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Detection Of Biologically Important Molecules, Kyukwang Kim Jan 2005

Detection Of Biologically Important Molecules, Kyukwang Kim

LSU Doctoral Dissertations

Anions play important roles in biological systems. The design of anion sensors has been of great interest. The selective detection of a specific anion is particularly challenging. In the first chapter, I describe the synthesis of a TBS-protected fluorescein dye (1.1) and its use for the selective detection of fluoride. Solutions of 1.1 either in DCM or in aqueous media at physiological pH show the excellent selectivity towards fluoride to afford color formation while solutions of other interfering anions remain colorless. The monitoring of homocysteine (Hcy) and cysteine (Cys) levels is important since they are biomarkers associated with Alzheimer’s and …

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Roc Comparison Of Acquisition Parameters For Two Pet/Ct Scanners Based On Lesion Detectability In A Torso Phantom, Kenneth Bernstein Jan 2005

Roc Comparison Of Acquisition Parameters For Two Pet/Ct Scanners Based On Lesion Detectability In A Torso Phantom, Kenneth Bernstein

LSU Master's Theses

Positron emission tomography (PET) and computed tomography (CT) are well established and powerful tools for medical diagnostics but even integrated PET/CT scanner images still lack the necessary quality and resolution that would make medical diagnoses flawless. In this thesis experiments were performed to statistically determine the effect that image acquisition parameters have upon diagnostic accuracy. Images from different PET/CT scanners were assessed by comparing subject human diagnostic accuracy from a sample of both professional and student volunteers. The assessment results were compared to the objective NEMA-standards performance data provided by the manufacturers for each scanner. The data analysis method is …

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Using Ground Penetrating Radar, Light Detection And Ranging, Geodetic Leveling, And Area Hydrogeology To Study The Baton Rouge And Scotlandville Faults, East Baton Rouge Parish, La, Angela Mooi Thomas Jan 2005

Using Ground Penetrating Radar, Light Detection And Ranging, Geodetic Leveling, And Area Hydrogeology To Study The Baton Rouge And Scotlandville Faults, East Baton Rouge Parish, La, Angela Mooi Thomas

LSU Master's Theses

East Baton Rouge Parish, Louisiana, is situated on at least two faults, the Baton Rouge Fault and the Denham Springs-Scotlandville Fault. These faults have surface expressions in the form of escarpments and damage to man-made structures. The purpose of this thesis is to study these faults in the shallow subsurface, in climate and soils found in Louisiana, and to study their ability to block fluid flow and whether groundwater withdrawal influences the amount and rate of subsidence along these faults. Techniques used to gather field data or to research and compile previously acquired data for this thesis includes: Ground Penetrating …

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Environmental Factors Influencing Incubation Constancy And Recess Frequency In Gadwall (Anas Strepera) In The Prairie Pothole Region Of North Dakota, Nicole F. Lorenz Jan 2005

Environmental Factors Influencing Incubation Constancy And Recess Frequency In Gadwall (Anas Strepera) In The Prairie Pothole Region Of North Dakota, Nicole F. Lorenz

LSU Master's Theses

I examined nest attendance patterns for 132 Gadwall (Anas strepera) females breeding in the prairie pothole region located in Towner County, North Dakota from May to July 2000 - 2001. Overall, Gadwall had a daily incubation constancy of 76.5 ± 10.8%, and daily recess frequency of 2.2 ± 1.1 with each recess lasting 179.8 ± 133.8 minutes. Unlike other waterfowl species, Gadwall increased incubation constancy and decreased recess frequency as daily high temperature increased and showed no change in constancy with precipitation. Gadwall incubation constancy did not fit the body-size hypothesis, as Gadwall have a lower incubation constancy compared to …

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Energy-Rate Based Mac Protocol For Wireless Sensor Networks And Key Pre-Distribution Schemes, Ramaraju Kalidindi Jan 2005

Energy-Rate Based Mac Protocol For Wireless Sensor Networks And Key Pre-Distribution Schemes, Ramaraju Kalidindi

LSU Master's Theses

Sensor networks are typically unattended because of their deployment in hazardous, hostile or remote environments. This makes the problem of conserving energy at individual sensor nodes challenging. S-MAC and PAMAS are two MAC protocols which periodically put nodes (selected at random) to sleep in order to achieve energy savings. Unlike these protocols, we propose an approach in which node duty cycles (i.e sleep and wake schedules) are based on their criticality. A distributed algorithm is used to find sets of winners and losers, who are then assigned appropriate slots in our TDMA based MAC protocol. We introduce the concept of …

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Effect Of Estradiol-17b On The Gonadal Developemnt Of Diploid And Triploid Female Eastern Oysters, Roberto Quintana Jan 2005

Effect Of Estradiol-17b On The Gonadal Developemnt Of Diploid And Triploid Female Eastern Oysters, Roberto Quintana

LSU Master's Theses

Declines in annual oyster landings and problems associated with seasonal reduction of oyster meat yields have increased interest for development of techniques to produce oysters with enhanced growth characteristics. Research interest has been focused on developing improved lines by induction of polyploidy. The goal of the present study was to evaluate the enhancement of gonadal development of triploid oysters, by the use of the hormone estradiol 17-â (E2) to produce viable eggs for the development of tetraploid broodstocks. Previous studies with the Pacific oyster, Crassostrea gigas, have shown: (1) the need to use the larger eggs of triploid females to …

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Experimental Method Development For Direct Dosimetry Of Permanent Interstitial Prostate Brachytherapy Implants, John Michael Jarrett Jan 2005

Experimental Method Development For Direct Dosimetry Of Permanent Interstitial Prostate Brachytherapy Implants, John Michael Jarrett

LSU Master's Theses

Purpose: To ascertain if PET image data of a positron tracer can be used for the quantitative description of dose distribution in support of direct prostate seed dosimetry. Materials and Methods: Simulated brachytherapy seeds were constructed containing trace amounts of a positron emitter, F-18, such that all annihilation events took place in the encapsulation wall. An acrylic prostate phantom containing these seeds was imaged with a GE Discovery ST PET/CT scanner in 2D and 3D acquisition modes and several image reconstruction methods. The PET scan data was used as the input for Monte Carlo calculation of dose distribution due to …

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Performance Evaluation Of Two Czt Gamma Ray Imaging Systems, Laurie Kelly Jan 2005

Performance Evaluation Of Two Czt Gamma Ray Imaging Systems, Laurie Kelly

LSU Master's Theses

The purpose of this research was to evaluate the performance of the imaging characteristics of two versions of a cadmium zinc telluride (CZT) gamma radiation detector system called the Laboratory Radioactive Assay Tracer (LabRAT). The performance evaluation follows the National Electrical Manufacturers Association standards for pixellated detector cameras. The LabRAT detector system hardware was developed by Mosaic Imaging Technology, Inc. LabRAT is a portable nuclear medicine imaging detector system intended for small field of view applications such as small animal imaging, portable radioisotope imaging in emergency room or intensive care units, and as an instruction tool for radiology residents and …

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