3,191 Matching Results

Search Results

Advanced search parameters have been applied.

The Crystal and Molecular Structures of Tri-(p-Fluorophenyl)-Amine and Tri-(p-Iodophenyl)-Amine

Description: Because of the need for data on the geometry of nitrogen in arylamines, the determination of the crystal and molecular structures of tri-(p-fluorophenyl)-amine (TFPA) and tri-(p-iodophenyl)-amine (TIPA) was undertaken as the subject of this dissertation.
Date: January 1970
Creator: Freeman, Gerald R. (Gerald Richard)
Partner: UNT Libraries

An Interactive Tool to Investigate the Inference Performance of Network Dynamics From Data

Description: Network structure plays a significant role in determining the performance of network inference tasks. An interactive tool to study the dependence of network topology on estimation performance was developed. The tool allows end-users to easily create and modify network structures and observe the performance of pole estimation measured by Cramer-Rao bounds. The tool also automatically suggests the best measurement locations to maximize estimation performance, and thus finds its broad applications on the optimal design of data collection experiments. Finally, a series of theoretical results that explicitly connect subsets of network structures with inference performance are obtained.
Date: August 2012
Creator: Veenadhar, Katragadda
Partner: UNT Libraries

Newspaper Ownership Structure and the Quality of Local Political News Coverage

Description: This research sought to ascertain how newspaper ownership structures influence the quality of local political news coverage. More specifically, do independently owned newspapers tend to produce larger quantities of quality local political reporting than do corporately owned and publicly traded newspapers? In the thesis, I develop an understanding of "quality" news coverage as being coverage that is thematic, or providing interpretive analysis and supplying contextual information. Additionally, I tackle the question of quality news coverage from three angles: whether or not independently owned newspapers provide more quality local political news stories per edition than corporately owned papers; whether or not the percentage of quality local political news stories of total political news stories within an edition is higher for independently owned or corporately owned newspapers; and whether or not the percentage of total political news stories of total news stories is higher for independently owned or corporately owned newspapers.
Date: May 2012
Creator: Clark, Karla Christine Marie
Partner: UNT Libraries

Calibration of 3D Upper Mantle Structure in Eurasia Using Regional and Teleseismic Full Waveform Seismic Data

Description: Adequate path calibrations are crucial for improving the accuracy of seismic event location and origin time, size, and mechanism, as required for CTBT monitoring. There is considerable information on structure in broadband seismograms that is currently not fully utilized. The limitations have been largely theoretical. the development and application to solid earth problems of powerful numerical techniques, such as the Spectral Element Method (SEM), has opened a new era, and theoretically, it should be possible to compute the complete predicted wavefield accurately without any restrictions on the strength or spatial extent of heterogeneity. This approach requires considerable computational power, which is currently not fully reachable in practice. We propose an approach which relies on a cascade of increasingly accurate theoretical approximations for the computation of the seismic wavefield to develop a model of regional structure for the area of Eurasia located between longitudes of 30 and 150 degrees E, and latitudes of -10 to 60 degrees North. The selected area is particularly suitable for the purpose of this experiment, as it is highly heterogeneous, presenting a challenge for calibration purposes, but it is well surrounded by earthquake sources and, even though they are sparsely distributed, a significant number of high quality broadband digital stations exist, for which data are readily accessible through IRIS (Incorporated Research Institutions for Seismology) and the FDSN (Federation of Digital Seismic Networks). The starting models used will be a combination of a-priori 3D models recently developed for this region, combining various geophysical and seismological data, and a major goal of this study will be to refine these models so as to fit a variety of seismic waveforms and phases.
Date: April 23, 2005
Creator: Romanowicz, Barbara & Panning, Mark
Partner: UNT Libraries Government Documents Department

Calibration of 3D Upper Mantle Structure in Eurasia Using Regional and Teleseismic Full Waveform Seismic Data

Description: Adequate path calibrations are crucial for improving the accuracy of seismic event location and origin time, size, and mechanism, as required for CTBT monitoring. There is considerable information on structure in broadband seismograms that is currently not fully utilized. The limitations have been largely theoretical. the development and application to solid earth problems of powerful numerical techniques, such as the Spectral Element Method (SEM), has opened a new era, and theoretically, it should be possible to compute the complete predicted wavefield accurately without any restrictions on the strength or spatial extent of heterogeneity. This approach requires considerable computational power, which is currently not fully reachable in practice. We propose an approach which relies on a cascade of increasingly accurate theoretical approximations for the computation of the seismic wavefield to develop a model of regional structure for the area of Eurasia located between longitudes of 30 and 150 degrees E, and latitudes of -10 to 60 degrees North. The selected area is particularly suitable for the purpose of this experiment, as it is highly heterogeneous, presenting a challenge for calibration purposes, but it is well surrounded by earthquake sources and, even though they are sparsely distributed, a significant number of high quality broadband digital stations exist, for which data are readily accessible through IRIS (Incorporated Research Institutions for Seismology) and the FDSN (Federation of Digital Seismic Networks). The starting models used will be a combination of a-priori 3D models recently developed for this region, combining various geophysical and seismological data, and a major goal of this study will be to refine these models so as to fit a variety of seismic waveforms and phases.
Date: April 23, 2005
Creator: Romanowicz, Barbara & Panning, Mark
Partner: UNT Libraries Government Documents Department

Invariant patterns in crystal lattices: Implications for protein folding algorithms

Description: Crystal lattices are infinite periodic graphs that occur naturally in a variety of geometries and which are of fundamental importance in polymer science. Discrete models of protein folding use crystal lattices to define the space of protein conformations. Because various crystal lattices provide discretizations of the same physical phenomenon, it is reasonable to expect that there will exist invariants across lattices related to fundamental properties of the protein folding process. This paper considers whether performance-guaranteed approximability is such an invariant for HP lattice models. The authors define a master approximation algorithm that has provable performance guarantees provided that a specific sublattice exists within a given lattice. They describe a broad class of crystal lattices that are approximable, which further suggests that approximability is a general property of HP lattice models.
Date: June 1, 2000
Creator: HART,WILLIAM E. & ISTRAIL,SORIN
Partner: UNT Libraries Government Documents Department

A Determination of the Fine Structure Constant Using Precision Measurements of Helium Fine Structure

Description: Spectroscopic measurements of the helium atom are performed to high precision using an atomic beam apparatus and electro-optic laser techniques. These measurements, in addition to serving as a test of helium theory, also provide a new determination of the fine structure constant α. An apparatus was designed and built to overcome limitations encountered in a previous experiment. Not only did this allow an improved level of precision but also enabled new consistency checks, including an extremely useful measurement in 3He. I discuss the details of the experimental setup along with the major changes and improvements. A new value for the J = 0 to 2 fine structure interval in the 23P state of 4He is measured to be 31 908 131.25(30) kHz. The 300 Hz precision of this result represents an improvement over previous results by more than a factor of three. Combined with the latest theoretical calculations, this yields a new determination of α with better than 5 ppb uncertainty, α-1 = 137.035 999 55(64).
Date: August 2010
Creator: Smiciklas, Marc
Partner: UNT Libraries

Polycyclic Aromatic Hydrocarbon Solute Probes. Part 10: Evaluation of Select Hydrogenated Pyrene, Benzo[ghi]perylene, and Naphthacene Derivatives as Possible Solvent Polarity Probes

Description: Article on polycyclic aromatic hydrocarbon solute probes and the evaluation of select hydrogenated pyrene, benzo[ghi]perylene, and naphthacene derivatives as possible solvent polarity probes.
Date: February 16, 1993
Creator: Tucker, Sheryl A. (Sheryl Ann); Acree, William E. (William Eugene); Fetzer, John Charles, 1953- & Mitchell, Reginald H.
Partner: UNT College of Arts and Sciences

Chlorido(4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine)platinum(II) chloride toluene monosolvate

Description: In the title compound, [PtCl(C₂₇H₃₅N₃)]Cl·C₇H₈, the Ptᴵᴵ atom is coordinated in a pseudo-square-planar fashion by the N atoms of a 4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine ligand and a Cl atom.
Date: November 22, 2010
Creator: Batrice, Rami J.; Nesterov, Vladimir N. & Smucker, Bradley W.
Partner: UNT College of Arts and Sciences

Social Area Analysis and Transportation Patterns: Dallas, Texas, 1960

Description: When the heterogeneity of the city is considered, the sociological implications which stem from this heterogeneity become important to understanding the social structure of the city. One of these sociological implications is intrinsic in the patterns of transportation. This is an ecological study of the structure and changing structure of parts of the city. We will study the relationship between two variables; social area characteristics and patterns of transportation.
Date: May 1969
Creator: Byler, Don L.
Partner: UNT Libraries

Spectroscopic Investigation of Fluorescence Quenching Agents: Effect of Nitromethane on the Fluorescence Emission Behavior of Select Cyclopenta-PAH, Aceanthrylene, and Fluorene Derivatives

Description: Article on a spectroscopic investigation of fluorescence quenching agents and the effect of nitromethane on the fluorescence emission behavior of select cyclopenta-PAH, aceanthrylene, and fluorene derivatives.
Date: March 2, 1992
Creator: Amszi, Vicki L.; Cordero, Yvonne; Smith, Bradley; Tucker, Sheryl A. (Sheryl Ann); Acree, William E. (William Eugene); Yang, Chengxi et al.
Partner: UNT College of Arts and Sciences

Layered nickel based superconductors

Description: We review the properties of Ni-based superconductors which contain Ni{sub 2}X{sub 2} (X=As, P, Bi, Si, Ge, B) planes, a common structural element to the recently discovered FeAs superconductors. We also compare the properties ofthe Ni-and Fe-based systems from a perspective ofelectronic structure as well as structure-property relations.
Date: January 1, 2009
Creator: Ronning, Filip; Bauer, Eric D; Park, Tuson; Kurita, Nobuyuki; Klimczuk, T; Movshovich, R et al.
Partner: UNT Libraries Government Documents Department

Near-edge x-ray absorption fine structure examination of chemical bonding in sputter deposited boron and boron-nitride films

Description: Near-edge x-ray absorption fine structure (NEXAFS) is used to examine the chemical bonding in boron and boron-nitride films sputter deposited from a fully-dense, pure boron target. Reactive sputtering is used to prepare the boron-nitride and multilayered films. Although the process of sputter deposition often produces films that lack long range order, NEXAFS reveals the distinguishing features of sp{sup 2} and sp{sup 3} hybridization that are associated with different crystalline structures. The sensitivity of NEXAFS to local order further provides details in bonding modifications that exist in these films.
Date: May 1, 1996
Creator: Jankowski, A.F.; Hayes, J.P. & Suthreland, D.G.J.
Partner: UNT Libraries Government Documents Department

X-ray absorption spectroscopic studies of mononuclear non-heme iron enzymes

Description: Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s{yields}3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been applied to the study of non-heme iron enzyme active sites.
Date: January 1, 1996
Creator: Westre, T.E.
Partner: UNT Libraries Government Documents Department

Local Structure of La1-xSrxCoO3 determined from EXAFS and neutron PDF studies

Description: The combined local structure techniques, extended x-ray absorption fine structure (EXAFS) and neutron pair distribution function analysis, have been used for temperatures 4<= T<= 330 K to rule out a large Jahn-Teller (JT) distortion of the Co-O bond in La1?xSrxCoO3 for a significant fraction of Co sites (x<= 0.35), indicating few, if any, JT-active, singly occupied eg Co sites exist.
Date: January 26, 2009
Creator: Sundaram, N.; Jiang, Y.; Anderson, I. E.; Belanger, D. P.; Booth, C. H.; Bridges, F. et al.
Partner: UNT Libraries Government Documents Department

Localized Electron States Near a Metal-SemiconductorNanocontact

Description: The electronic structure of nanowires in contact withmetallic electrodes of experimentally relevant sizes is calculated byincorporating the electrostatic polarization potential into the atomisticsingle particle Schrodinger equation. We show that the presence of anelectrode produces localized electron/hole states near the electrode, aphenomenon only exhibited in nanostructures and overlooked in the past.This phenomenon will have profound implications on electron transport insuch nanosystems. We calculate several electrode/nanowire geometries,with varying contact depths and nanowire radii. We demonstrate the changein the band gap of up to 0.5 eV in 3 nm diameter CdSe nanowires andcalculate the magnitude of the applied electric field necessary toovercome the localization.
Date: April 25, 2007
Creator: Demchenko, Denis O. & Wang, Lin-Wang
Partner: UNT Libraries Government Documents Department

MPSA 2004 Final Report

Description: This proposal was to support a portion of the costs of Methods in Protein Structure Analysis 2004 (MPSA2004). MPSA2004 was the 15th in the series of MPSA international conferences on protein structure analysis that began in 1974. MPSA2004 was held on the campus of the University of Washington, Seattle, WA August 29 through September 2, 2004. Twenty-four internationally recognized speakers gave invited presentations; additional participants were chosen to present short talks in the 10 topics that were addressed. The aim of MPSA conferences is to communicate the latest, cutting-edge techniques in protein structure analysis and proteomics through science success stories as told by the scientific leaders who developed the technologies. Biotechnology vendors are present to explain currently available commercial technology through workshops and demonstrations booths. The overall aim is to provide a forum for exchanging the latest methods and ideas in protein structure analysis and proteomics to current and future practitioners. The conference supported the missions of the DOE Office of Science and the Office of Biological and Environmental Research (BER) in at least two ways: by enabling the above forum, and by encouraging young researchers who might otherwise not attend to meet leading researchers and to learn about the most current ideas, technologies, products, and services relevant to protein structure analysis. Topics covered in MPSA2004 were highly relevant to the BER Genomics: GTL initiative and several National Laboratory scientists were among the invited speakers.
Date: February 18, 2006
Creator: Anderson, Carl W.
Partner: UNT Libraries Government Documents Department

The interfacial bioscience grand challenge.

Description: This report is broken down into the following 3 sections: (1) Chemical Cross-linking and Mass Spectrometry Applied to Determination of Protein Structure and Dynamics; (2) Computational Modeling of Membrane Protein Structure and Dynamics; and (3) Studies of Toxin-Membrane Interactions using Single Molecule Biophysical Methods.
Date: March 1, 2004
Creator: Lane, Pamela; Stevens, Mark Jackson; Jacobsen, Richard B.; Hong, Joohee; Ayson, Marites J.; Crozier, Paul Stewart et al.
Partner: UNT Libraries Government Documents Department