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Articles 2761 - 2790 of 3436

Full-Text Articles in Physical Sciences and Mathematics

Development Of A Model For The Kinetics And Mechanism Of Nitrogenase, Phillip E. Wilson Jul 2005

Development Of A Model For The Kinetics And Mechanism Of Nitrogenase, Phillip E. Wilson

Theses and Dissertations

Nitrogenase has a central role in the global nitrogen cycle as the enzyme that catalyzes the reduction of atmospheric N2 to NH3. Fixed nitrogen is generally limiting in the environment and in agriculture, so nitrogenase has received much attention as an alternative to nitrogen fertilizers. Characterizing the mechanism of nitrogenase is the goal of this work. The molybdenum nitrogenase enzyme system is comprised of the MoFe protein and the Fe protein. Interactions between these proteins and nucleotides are crucial to catalysis. An important approach to characterize these interactions is to correlate the kinetics of nitrogenase catalysis to a mechanism based …

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Angiotensin Ii-Mediated Regulation Of The Human Angiotensin Ii Type 1 Receptor Gene, Xylophone Vijai Aasee Victor Jul 2005

Angiotensin Ii-Mediated Regulation Of The Human Angiotensin Ii Type 1 Receptor Gene, Xylophone Vijai Aasee Victor

Theses and Dissertations

The physiological responses of angiotensin II (Ang II) are mediated across the cell membrane through the angiotensin II type 1 receptor (AT1R), a heptahelical membrane protein coupled to trimeric G-proteins on the cytosolic side. AT1R on binding its ligand, Ang II, leads to downregulation of cell-surface receptor and also its mRNA. We have investigated whether the 3'- and 5'-untranslated regions of the human AT1R mRNA mediate the degradation of hAT1R mRNA by post-transcriptional mechanisms in human adrenocortical carcinoma cell line (H295R cells). Protein kinase C (PKC) activator, phorbol-12-myristate-13-acetate (PMA), showed that the downregulation of hAT1R mRNA is mediated by the …

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Elevation, Longitudinal Profile, And Schmidt Hammer Analysis Of Strath Terraces Through Capitol Reef National Park, Utah: Bedrock Channel Response To Climate Forcing?, James L. Eddleman Jul 2005

Elevation, Longitudinal Profile, And Schmidt Hammer Analysis Of Strath Terraces Through Capitol Reef National Park, Utah: Bedrock Channel Response To Climate Forcing?, James L. Eddleman

Theses and Dissertations

Elevation, longitudinal profile, and Schmidt hammer data indicate that strath terraces (specifically the lower elevation terraces) mapped in the Fremont River drainage of Capitol Reef National Park are correlative to the terraces of the smaller Pleasant Creek drainage located approximately ten miles to the south. This correlation suggests that drainage development in this area of the Colorado Plateau was strongly dependent upon a regional-scale forcing mechanism (e.g. climate) rather than strictly independent basin-scale processes. Elevations of mapped strath terraces and their associated black volcanic boulder deposits were calculated from geologic maps, Digital Elevation Models (DEM), and Digital Orthophoto Quadrangles of …

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Effects Of Hurricane Fault Architecture On Groundwater Flow In The Timpoweap Canyon Of Southwestern, Utah, Sarah J. Dutson Jul 2005

Effects Of Hurricane Fault Architecture On Groundwater Flow In The Timpoweap Canyon Of Southwestern, Utah, Sarah J. Dutson

Theses and Dissertations

Hydrogeologically important features of fault zones include undamaged country rock, the damage zone, and the core zone. Fault cores generally have low porosity and permeability, and often act as a barrier to groundwater flow. The damage zone, by contrast, consists of small faults and fracture networks, which can act as conduits. Timpoweap Canyon near Hurricane, Utah has superb exposures of the fault core and damage zone of the Hurricane Fault. Also within the canyon, springs discharge from the damage zone into the Virgin River, providing an ideal natural laboratory for the study of groundwater discharge from a fault zone. The …

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Establishing Public Confidence In The Viability Of Fingerprint Biometric Technology, Nathan Alan Green Jul 2005

Establishing Public Confidence In The Viability Of Fingerprint Biometric Technology, Nathan Alan Green

Theses and Dissertations

The most common personal authentication techniques used for identity management employ a secret PIN or password that must be remembered. The challenge, for a given user, is that a multitude of such codes must be recalled over the course of the day for transactions involving distinct computer applications. Password mania prevails. Fingerprint biometric technology is an ideal alternate solution to this password recall problem. In spite of their availability for nearly thirty years, fingerprint biometric systems still remain uncommon in public sectors of industry such as education, government, and technology. Technology has improved sufficiently that false acceptance and rejection rates …

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Representations For Understanding The Stern-Gerlach Effect, Jared R. Stenson Jul 2005

Representations For Understanding The Stern-Gerlach Effect, Jared R. Stenson

Theses and Dissertations

The traditional explanation of the Stern-Gerlach effect carries with it several very subtle assumptions and approximations. We point out the degree to which this fact has affected the way we practice and interpret modern physics. In order to gain a more complete understanding of the Stern-Gerlach effect beyond the standard approximations and assumptions it typically carries, we introduce the inhomogeneous Stern-Gerlach effect in which the strong uniform field component is removed. This change allows us to easily identify precession as a critical concept. It also provides us with a means by which to study precession and analyze it critically. By …

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A Mathematical Model Of Adhesion Interactions Between Living Cells, Casey P. Johnson Jul 2005

A Mathematical Model Of Adhesion Interactions Between Living Cells, Casey P. Johnson

Theses and Dissertations

This thesis presents a simple force-based model of moving and interacting cells that incorporates a realistic description of cell adhesion and applies it to a system of spherical cells. In addition, several results in matrix theory are proved with the end of showing that the equations produced by the model uniquely determine the motion of the system or cells.

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An Improved Flexible Neutron Detector For Powder Diffraction Experiments, Thomas Kevin Mcknight Jul 2005

An Improved Flexible Neutron Detector For Powder Diffraction Experiments, Thomas Kevin Mcknight

Theses and Dissertations

Large amounts of money are being applied to the construction of the next generation of spallation sources for neutron scattering. Neutron powder diffraction instruments will be an important element of these facilities and the incorporation of detectors into these instruments with a high neutron capture efficiency is desirable. A new detector design named the Flexible Embedded Fiber Detector (FEFD) has been developed and tested for this thesis. This detector is based on wavelength shifting fibers embedded in a zinc-sulfide lithium-fluoride based scintillator. The virtue of this design is that the detecting surface can be curved around the Debye-Scherrer rings. This …

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Black Spaghetti: A Numerical Model Of Gravitational Collapse In 4 + 1 Spacetime, Michael P. Christenson Jul 2005

Black Spaghetti: A Numerical Model Of Gravitational Collapse In 4 + 1 Spacetime, Michael P. Christenson

Theses and Dissertations

We investigate spherically-symmetric gravitational collapse in the presence of a single "large" extra dimension through the use of analytical and numerical techniques. This has bearing on higher-dimensional ideas concerning hypothetical objects called "black strings," or black holes extending into an extra circular dimension, which dimension we hereinafter label zeta. These putative objects were first seriously considered as elements of string theory but have relevance in simpler, higher-dimensional generalization of Einstein's general relativity. We assume a universe topologically consisting of a two-dimensional Lorentzian manifold crossed with the sphere, crossed again with the circle. We model the formation of a uniform black …

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Accelerated Ray Traced Animations Exploiting Temporal Coherence, Darwin Tarry Baines Jul 2005

Accelerated Ray Traced Animations Exploiting Temporal Coherence, Darwin Tarry Baines

Theses and Dissertations

Ray tracing is a well-know technique for producing realistic graphics. However, the time necessary to generate images is unacceptably long. When producing the many frames that are necessary for animations, the time is magnified. Many methods have been proposed to reduce the calculations necessary in ray tracing. Much of the effort has attempted to reduce the number of rays cast or to reduce the number of intersection calculations. Both of these techniques exploit spatial coherence. These acceleration techniques are expanded not only to exploit spatial coherence but also to exploit temporal coherence in order to reduce calculations by treating animation …

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Task Localization, Similarity, And Transfer; Towards A Reinforcement Learning Task Library System, James Lamond Carroll Jul 2005

Task Localization, Similarity, And Transfer; Towards A Reinforcement Learning Task Library System, James Lamond Carroll

Theses and Dissertations

This thesis develops methods of task localization, task similarity discovery, and task transfer for eventual use in a reinforcement learning task library system, which can effectively “learn to learn,” improving its performance as it encounters various tasks over the lifetime of the learning system.

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Suitability Of The Nist Shop Data Model As A Neutral File Format For Simulation, Gregory Brent Harward Jul 2005

Suitability Of The Nist Shop Data Model As A Neutral File Format For Simulation, Gregory Brent Harward

Theses and Dissertations

Due to the successful application in internet related fields, Extensible Markup Language (XML) and its related technologies are being explored as a revolutionary software file format technology used to provide increased interoperability in the discrete-event simulation (DES) arena. The National Institute of Standards and Technology (NIST) has developed an XML-based information model (XSD) called the Shop Data Model (SDM), which is used to describe the contents of a neutral file format (NFF) that is being promoted as a means to make manufacturing simulation technology more accessible to a larger group of potential customers. Using a two step process, this thesis …

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Novel Neutron Detector For N-N Scattering Length Measurement, Eva Wilcox Jul 2005

Novel Neutron Detector For N-N Scattering Length Measurement, Eva Wilcox

Theses and Dissertations

The neutron-neutron (n-n) scattering length is a fundamental parameter in nuclear physics; however, measurements are plagued with large uncertainties caused by neutron detector cross talk. Many experimentalists also rely upon computer code to calibrate their neutron detectors. Experiments give one of two different numbers but there is still no adequate explanation for this discrepancy. We have developed a new neutron detector expressly for the purpose of improving the n-n scattering length measurement. It offers two important advantages: 1) minimal cross talk and 2) high counting efficiency. We calibrated the detector from 1 MeV to 6 MeV at 1 MeV increments. …

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Gps Velocity Field In The Transition From Subduction To Collision Of The Eastern Sunda And Banda Arcs, Indonesia, Hendro Nugroho Jul 2005

Gps Velocity Field In The Transition From Subduction To Collision Of The Eastern Sunda And Banda Arcs, Indonesia, Hendro Nugroho

Theses and Dissertations

Campaign GPS measurements during 2001-2003 in the transition between subduction and collision of the Banda arc reveal how strain is partitioned away from the trench and distributed to other parts of the arc-trench system. Genrich, et. al. (1996) conducted a GPS campaign (1992-1994) throughout the Eastern Sunda and Banda arcs that demonstrated partial accretion of the arc to the Australian plate. We reoccupied many of the sites from this earlier study and 7 additional stations, 3 of which are new benchmarks. Our study shortened many baselines and extended the observation epoch to ten years for many key stations. The resulting …

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Long-Term Surface Uplift History Of The Active Banda Arc-Continent Collision: Depth And Age Analysis Of Foraminifera From Rote And Savu Islands, Indonesia, Nova Roosmawati Jul 2005

Long-Term Surface Uplift History Of The Active Banda Arc-Continent Collision: Depth And Age Analysis Of Foraminifera From Rote And Savu Islands, Indonesia, Nova Roosmawati

Theses and Dissertations

Analysis of foraminifera for synorogenic pelagic units of Rote and Savu Islands, Indonesia, reveals high rates of surface uplift in the past 1.5 Ma of the incipient Banda arc-continent collision. Paleodepth estimates are derived from benthonic forams and ages from planktonic forams. But estimates are complicated, however, by abundant reworking; yet several distinctive species have been found. Synorogenic deposits in western Rote yield forams of biozone Neogene (N) 18 and depths from 5000-5700 meters at the base of the section, and 3600 meters at the top of the section. Eastern Rote yields forams of N 19/20 - N 22 and …

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Phase-Matching Optimization Of Laser High-Order Harmonics Generated In A Gas Cell, Julia Robin Miller Sutherland Jul 2005

Phase-Matching Optimization Of Laser High-Order Harmonics Generated In A Gas Cell, Julia Robin Miller Sutherland

Theses and Dissertations

Ten-millijoule, thirty-five femtosecond, 800 nm (~40 nm bandwidth) laser pulses are used to study high-order harmonic generation in helium- and neon-filled gas cells of various lengths. Harmonic orders in the range of 50 to 100 are investigated. A semi-infinite cell geometry produces brighter harmonics than cells of sub-centimeter length. In the semi-infinite geometry, the gas occupies the region from the focusing lens to a thin exit foil near the laser focus. Counter-propagating light is used to directly probe where the high harmonics are generated within the laser focus and to investigate phase matching. The phase matching under optimized harmonic generation …

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Detecting Similar Html Documents Using A Fuzzy Set Information Retrieval Approach, Yiu-Kai D. Ng, Rajiv Yerra Jul 2005

Detecting Similar Html Documents Using A Fuzzy Set Information Retrieval Approach, Yiu-Kai D. Ng, Rajiv Yerra

Faculty Publications

Web documents that are either partially or completely duplicated in content are easily found on the Internet these days. Not only do these documents create redundant information on the Web, which take longer to filter unique information and cause additional storage space, but also they degrade the efficiency of Web information retrieval. In this paper, we present a new approach for detecting similar Web documents, especially HTML documents. Our detection approach determines the odd ratio of any two documents, which makes use of the degrees of resemblance of the documents, and graphically displays the locations of similar (not necessarily the …

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Validating Human–Robot Interaction Schemes In Multitasking Environments, Jacob W. Crandall, Michael A. Goodrich, Curtis W. Nielsen, Dan R. Olsen Jr. Jul 2005

Validating Human–Robot Interaction Schemes In Multitasking Environments, Jacob W. Crandall, Michael A. Goodrich, Curtis W. Nielsen, Dan R. Olsen Jr.

Faculty Publications

The ability of robots to autonomously perform tasks is increasing. More autonomy in robots means that the human managing the robot may have available free time. It is desirable to use this free time productively, and a current trend is to use this available free time to manage multiple robots. We present the notion of neglect tolerance as a means for determining how robot autonomy and interface design determine how free time can be used to support multitasking, in general, and multirobot teams, in particular. We use neglect tolerance to 1) identify the maximum number of robots that can be …

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Comparing High-Order Boolean Features, Adam Drake, Dan A. Ventura Jul 2005

Comparing High-Order Boolean Features, Adam Drake, Dan A. Ventura

Faculty Publications

Many learning algorithms attempt, either explicitly or implicitly, to discover useful high-order features. When considering all possible functions that could be encountered, no particular type of high-order feature should be more useful than any other. However, this paper presents arguments and empirical results that suggest that for the learning problems typically encountered in practice, some high-order features may be more useful than others.

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Effectively Using Recurrently-Connected Spiking Neural Networks, Eric Goodman, Dan A. Ventura Jul 2005

Effectively Using Recurrently-Connected Spiking Neural Networks, Eric Goodman, Dan A. Ventura

Faculty Publications

Recurrently-connected spiking neural networks are difficult to use and understand because of the complex nonlinear dynamics of the system. Through empirical studies of spiking networks, we deduce several principles which are critical to success. Network parameters such as synaptic time delays and time constants and the connection probabilities can be adjusted to have a significant impact on accuracy. We show how to adjust these parameters to fit the type of problem.

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Time Invariance And Liquid State Machines, Eric Goodman, Dan A. Ventura Jul 2005

Time Invariance And Liquid State Machines, Eric Goodman, Dan A. Ventura

Faculty Publications

Time invariant recognition of spatiotemporal patterns is a common task of signal processing. Liquid state machines (LSMs) are a paradigm which robustly handle this type of classification. Using an artificial dataset with target pattern lengths ranging from 0.1 to 1.0 seconds, we train an LSM to find the start of the pattern with a mean absolute error of 0.18 seconds. Also, LSMs can be trained to identify spoken digits, 1-9, with an accuracy of 97.6%, even with scaling by factors ranging from 0.5 to 1.5.

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Categorizing And Extracting Information From Multilingual Html Documents, Yiu-Kai D. Ng, Seungjin Lim Jul 2005

Categorizing And Extracting Information From Multilingual Html Documents, Yiu-Kai D. Ng, Seungjin Lim

Faculty Publications

The amount of online information written in different natural languages and the number of non-English speaking Internet users have been increasing tremendously during the past decade. In order to provide high-performance access of multilingual information on the Internet, we have developed a data analysis and querying system (DatAQs) that (i) analyzes, identifies, and categorizes languages used in HTML documents, (ii) extracts information from HTML documents of interest written in different languages, (iii) allows the user to submit queries for retrieving extracted information in the same natural language provided by the query engine of DatAQs using a menu-driven user interface, and …

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Maximal Surfaces In Complexes, Allen J. Dickson Jun 2005

Maximal Surfaces In Complexes, Allen J. Dickson

Theses and Dissertations

Cubical complexes are defined in a manner analogous to that for simplicial complexes, the chief difference being that cubical complexes are unions of cubes rather than of simplices. A very natural cubical complex to consider is the complex C(k_1,...,k_n) where k_1,...,k_n are nonnegative integers. This complex has as its underlying space [0,k_1]x...x[0,k_n] subset of R^n with vertices at all points having integer coordinates and higher dimensional cubes formed by the vertices in the natural way. The genus of a cubical complex is defined to be the maximum genus of all surfaces that are subcomplexes of the cubical complex. A formula …

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An Exposition Of The Deterministic Polynomial-Time Primality Testing Algorithm Of Agrawal-Kayal-Saxena, Robert Lawrence Anderson Jun 2005

An Exposition Of The Deterministic Polynomial-Time Primality Testing Algorithm Of Agrawal-Kayal-Saxena, Robert Lawrence Anderson

Theses and Dissertations

I present a thorough examination of the unconditional deterministic polynomial-time algorithm for determining whether an input number is prime or composite proposed by Agrawal, Kayal and Saxena in their paper [1]. All proofs cited have been reworked with full details for the sake of completeness and readability.

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Upper Mantle Reflectivity Beneath An Intracratonic Basin: Insights Into The Behavior Of The Mantle Beneath Illinois Basin., Maxwell Sunday Okure Jun 2005

Upper Mantle Reflectivity Beneath An Intracratonic Basin: Insights Into The Behavior Of The Mantle Beneath Illinois Basin., Maxwell Sunday Okure

Theses and Dissertations

Reflectivity images of the lower crust and uppermost mantle beneath the Illinois basin have been derived from reprocessing of several hundred kilometers of industry seismic reflection data using extended vibroseis recorrelation. The recorrelation was based on extending an originally 4-s correlated record, acquired with a 16-s sweep from 14 to 126 Hz, to the absolute limit of the full 20 s (~70 km) listening travel time. The reconstructed bandwidth includes frequency components suitable for imaging structures from signals received from both sedimentary basin reflectors and those received from reflectors in the deep crust and upper mantle. Mantle and sub-Moho reflectors …

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Matrix Representations Of Automorphism Groups Of Free Groups, Ivan B. Andrus Jun 2005

Matrix Representations Of Automorphism Groups Of Free Groups, Ivan B. Andrus

Theses and Dissertations

In this thesis, we study the representation theory of the automorphism group Aut (Fn) of a free group by studying the representation theory of three finite subgroups: two symmetric groups, Sn and Sn+1, and a Coxeter group of type Bn, also known as a hyperoctahedral group. The representation theory of these subgroups is well understood in the language of Young Diagrams, and we apply this knowledge to better understand the representation theory of Aut (Fn). We also calculate irreducible representations of Aut (Fn) in low dimensions and for small n.

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Statistical Properties Of Thompson's Group And Random Pseudo Manifolds, Benjamin M. Woodruff Jun 2005

Statistical Properties Of Thompson's Group And Random Pseudo Manifolds, Benjamin M. Woodruff

Theses and Dissertations

The first part of our work is a statistical and geometric study of properties of Thompson's Group F. We enumerate the number of elements of F which are represented by a reduced pair of n-caret trees, and give asymptotic estimates. We also discuss the effects on word length and number of carets of right multiplication by a standard generator x0 or x1. We enumerate the average number of carets along the left edge of an n-caret tree, and use an Euler transformation to make some conjectures relating to right multiplication by a generator. We describe a computer algorithm which produces …

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Classifying Homotopy Types Of One-Dimensional Peano Continua, Mark H. Meilstrup Jun 2005

Classifying Homotopy Types Of One-Dimensional Peano Continua, Mark H. Meilstrup

Theses and Dissertations

Determining the homotopy type of one-dimensional Peano continua has been an open question of some interest. We give a complete invariant of the homotopy type of such continua, which consists of a pair of subspaces together with a relative homology group. Along the way, we describe reduced forms for one-dimensional Peano continua.

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Three Pension Cost Methods Under Varying Assumptions, Linda S. Grizzle Jun 2005

Three Pension Cost Methods Under Varying Assumptions, Linda S. Grizzle

Theses and Dissertations

A pension plan administrator promises certain benefits in the future in exchange for labor today. In order to budget for this expense and create more security for the participant, the administrator uses a pension cost method. Each cost method assigns a portion of the future liability to the current year. This is called the normal cost. We calculate the normal cost under three cost methods using different annuity, interest and inflation assumptions. Then we make comparisons between cost methods as well as between assumption changes. The cost methods considered in this paper are the unit credit cost method, projected unit …

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Explicit Computations Supporting A Generalization Of Serre's Conjecture, Brian Francis Hansen Jun 2005

Explicit Computations Supporting A Generalization Of Serre's Conjecture, Brian Francis Hansen

Theses and Dissertations

Serre's conjecture on the modularity of Galois representations makes a connection between two-dimensional Galois representations and modular forms. A conjecture by Ash, Doud, and Pollack generalizes Serre's to higher-dimensional Galois representations. In this paper we discuss an explicit computational example supporting the generalized claim. An ambiguity in a calculation within the example is resolved using a method of complex approximation.

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