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Measurement of the neutron ({sup 3}He) spin structure functions at low Q{sup 2}: A CONNECTION BETWEEN THE BJORKEN AND GERASIMOV-DRELL-HEARN SUM RULE

Description: This dissertation presents results of experiment E94-010 performed at Jefferson Laboratory (simply known as JLab) in Hall A. The experiment aimed to measure the low Q{sup 2} evolution of the Gerasimov-Drell-Hearn (GDH) integral from Q{sup 2} = 0.1 to 0.9 GeV{sup 2}. The GDH sum rule at the real photon point provides an important test of Quantum Chromodynamics (QCD). The low Q{sup 2} evolution of the GDH integral contests various resonance models, Chiral Perturbation Theory ({chi}#31;PT) and lattice QCD calculations, but more importantly, it helps us understand the transition between partonic and hadronic degrees of freedom. At high Q{sup 2}, beyond 1 GeV{sup 2}, the difference of the GDH integrals for the proton and the neutron is related to the Bjorken sum rule, another fundamental test of QCD. In addition, results of the measurements for the spin structure functions g{sub 1} and g{sub 2}, cross sections, and asymmetries are presented. E94-010 was the first experiment of its kind at JLab. It used a high-pressure, polarized {sup 3}He target with a gas pressure of 10 atm and average target polarization of 35%. For the first time, the polarized electron source delivered an average beam polarization of 70% with a beam current of 15 {micro}#22;A. The limit on the beam current was only imposed by the target. The experiment required six different beam energies from 0.86 to 5.1 GeV. This was the first time the accelerator ever reached 5.1 GeV. Both High-Resolution Spectrometers of Hall A, used in singles mode, were positioned at 15.5#14;{deg} each.
Date: December 1, 2002
Creator: Djawotho, Pibero
Partner: UNT Libraries Government Documents Department

Evaluating Radionuclide Air Emission Stack Sampling Systems

Description: The Pacific Northwest National Laboratory (PNNL) operates a number of research and development (R&D) facilities for the U.S. Department of Energy at the Hanford Site, Washington. These facilities are subject to Clean Air Act regulations that require sampling of radionuclide air emissions from some of these facilities. A revision to an American National Standards Institute (ANSI) standard on sampling radioactive air emissions has recently been incorporated into federal and state regulations and a re-evaluation of affected facilities is being performed to determine the impact. The revised standard requires a well-mixed sampling location that must be demonstrated through tests specified in the standard. It also carries a number of maintenance requirements, including inspections and cleaning of the sampling system. Evaluations were performed in 2000 – 2002 on two PNNL facilities to determine the operational and design impacts of the new requirements. The evaluation included inspection and cleaning maintenance activities plus testing to determine if the current sampling locations meet criteria in the revised standard. Results show a wide range of complexity in inspection and cleaning activities depending on accessibility of the system, ease of removal, and potential impact on building operations (need for outages). As expected, these High Efficiency Particulate Air (HEPA)-filtered systems did not show deposition significant enough to cause concerns with blocking of the nozzle or other parts of the system. The tests for sampling system location in the revised standard also varied in complexity depending on accessibility of the sample site and use of a scale model can alleviate many issues. Previous criteria to locate sampling systems at eight duct diameters downstream and two duct diameters upstream of the nearest disturbances is no guarantee of meeting criteria in the revised standard. A computational fluid dynamics model was helpful in understanding flow and contaminant mixing in an exhaust system ...
Date: December 16, 2002
Creator: Ballinger, Marcel Y.
Partner: UNT Libraries Government Documents Department

Development of trigger software for the silicon and fibre trackers and a study of B meson lifetimes for the D0 experiment

Description: The D0 detector has recently undergone a major upgrade to maximize its potential to fully exploit Run II at the Tevatron 2 TeV proton-antiproton collider. The upgrade includes a completely new central tracking system with an outer scintillating fiber tracker and an inner silicon vertex detector. This thesis describes the development of the software to ''unpack'' the raw data from the central tracking detectors into a useful form, and the development of the Level 3 trigger algorithms to cluster the hit information from these detectors. One of the many areas of physics that is being studied by the D0 experiment is the physics of B mesons, particularly that involving CP violation. The second part of the thesis details a constrained mass fitting tool written to aid the reconstruction of B particles, and a Monte Carlo study into measuring the lifetime of B{sup +} and B{sup 0} mesons. This thesis lays the foundations for the means by which physics is extracted from the vast amount of Tevatron data--the trigger--and illustrates how analyses will proceed through the key reconstruction of heavy quarks.
Date: January 1, 2002
Creator: Illingworth, Robert Arthur & /Imperial Coll., London
Partner: UNT Libraries Government Documents Department

Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

Description: Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To address concerns on the effect of natural air drying process ...
Date: September 18, 2002
Creator: Wang, Tong
Partner: UNT Libraries Government Documents Department

Topics in Hadronic Physics

Description: Hadron production cross sections are calculated in the perturbative QCD frame work. Parton distribution functions are obtained from a strip-soliton model. The fragmentation functions are derived from the Lund model of string breaking.
Date: August 1, 2002
Creator: Tang, Alfred
Partner: UNT Libraries Government Documents Department

A study of B(s)0 to J/psi phi in the D0 experiment and an example of HEP technology transfer

Description: After years of preparation, data taking with the upgraded D0 detector at the Tevatron proton-antiproton collider has begun. The large amount of data produced in a p{bar p}-collider requires sophisticated triggers to filter out the interesting events. Described in this thesis is the development of trigger software for the newly implemented Silicon Microstrip Tracker. D0 is a multi-purpose detector with a broad physics program. one area being studied at D0 is B mesons. An algorithm for reconstructing the B{sub s}{sup 0} and B{sub d}{sup 0} mesons and for measuring their lifetimes has been developed and is described in this thesis. The results suggest that an improvement of the current lifetime measurements can be achieved within the next two years. The reconstruction of a J/{psi} meson forms the basis for a wide range of b-physics. Data taken with the muon system during the commissioning period of the detector has been analyzed and a signal for the J/{psi} meson has been found. Systematic transfer of HEP technologies into other areas and their commercial exploitation plays an important role in the future of particle physics. An area of particular interest is DNA sequencing as shown by the recent completion of the sequencing of the human genome. The final part of this thesis details the development of a simulation for a high throughput sequencing device which is currently being developed at Imperial College.
Date: January 1, 2002
Creator: Bauer, Daniela Ursula & /Imperial Coll., London
Partner: UNT Libraries Government Documents Department

Studies in High Current Density Ion Sources for Heavy Ion FusionApplications

Description: This dissertation develops diverse research on small (diameter {approx} few mm), high current density (J {approx} several tens of mA/cm{sup 2}) heavy ion sources. The research has been developed in the context of a programmatic interest within the Heavy Ion Fusion (HIF) Program to explore alternative architectures in the beam injection systems that use the merging of small, bright beams. An ion gun was designed and built for these experiments. Results of average current density yield (<J>) at different operating conditions are presented for K{sup +} and Cs{sup +} contact ionization sources and potassium aluminum silicate sources. Maximum <J> values for a K{sup +} beam of {approx}90 mA/cm{sup 2} were observed in 2.3 {micro}s pulses. Measurements of beam intensity profiles and emittances are included. Measurements of neutral particle desorption are presented at different operating conditions which lead to a better understanding of the underlying atomic diffusion processes that determine the lifetime of the emitter. Estimates of diffusion times consistent with measurements are presented, as well as estimates of maximum repetition rates achievable. Diverse studies performed on the composition and preparation of alkali aluminosilicate ion sources are also presented. In addition, this work includes preliminary work carried out exploring the viability of an argon plasma ion source and a bismuth metal vapor vacuum arc (MEVVA) ion source. For the former ion source, fast rise-times ({approx} 1 {micro}s), high current densities ({approx} 100 mA/cm{sup 2}) and low operating pressures (< 2 mtorr) were verified. For the latter, high but acceptable levels of beam emittance were measured ({var_epsilon}{sub n} {le} 0.006 {pi} mm {center_dot} mrad) although measured currents differed from the desired ones (I {approx} 5mA) by about a factor of 10.
Date: June 1, 2002
Creator: Chacon-Golcher, E.
Partner: UNT Libraries Government Documents Department

Educational Corporate Social Responsibility in Mexico

Description: Thesis written by a student in the UNT Honors College discussing Mexico's educational system and corporate social responsibility programs and whether these actually respond to the needs of Mexican schools.
Date: Spring 2002
Creator: Cunningham, Kenda
Partner: UNT Honors College

Social Implications of Modeling

Description: Thesis written by a student in the UNT Honors College discussing the interaction of humans with the environment, including issues with water, consumption, reproduction, and groundwater in Texas.
Date: Spring 2002
Creator: Reams, Randall S.
Partner: UNT Honors College

Kevin

Description: Short story written by a student in the UNT Honors College about a group of people observing a friend as he delves into films and the occult.
Date: March 18, 2002
Creator: Saxon, Jared
Partner: UNT Honors College

A Study of Atomic Ordering in III-V Semiconductors

Description: Thesis written by a student in the UNT Honors College discussing semiconductors and band structure, the temperature-induced variation of the band structure, the atomic structure of III-V materials, atomic ordering of the band structure, and experimental techniques regarding atomic ordering of CuPt-B.
Date: Summer 2002
Creator: Cottier, Ryan J.
Partner: UNT Honors College

Flames II

Description: Thesis written by a student in the UNT Honors College discussing the authors composition of a musical piece called Flames II. He includes his influences, techniques, and sheet music.
Date: Summer 2002
Creator: Reagan, Brenton S.
Partner: UNT Honors College

Evolutions: A Study of George Crumb and Vox Balaenae

Description: Thesis written by a student in the UNT Honors College discussing the life of George Crumb, his compositions, and the natural world as his inspiration for Vox Balaenae.
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Date: Summer 2002
Creator: Wilhelms, Jennifer Ann
Partner: UNT Honors College

The Austen Women: A Look at Character

Description: Thesis written by a student in the UNT Honors College discussing female characters of Jane Austin's novels and how they achieve happiness.
Date: Autumn 2002
Creator: Henderson, Angela
Partner: UNT Honors College

Women under Monasticism in Renaissance Italy

Description: Honors thesis written by a student in the UNT Honors College discussing the marginalization experienced by women in the Catholic Church in Renaissance Italy.
Date: Autumn 2002
Creator: Lloyd, Leslie
Partner: UNT Honors College

Autonomic Control of Heat Rate Variability in Emu (Dromaius novaehollandiae) Hatchlings

Description: Thesis written by a student in the UNT Honors College discussing the role of the autonomic nervous system in the heart rate variability of day-old emu hatchlings. Atropine and propranolol were administered to block the action of cholinegric and adrenegric pathways and thereby reduce heart rate.
Date: Autumn 2002
Creator: Motiwala, Rajesh
Partner: UNT Honors College

Texas Public School Principals' Application of Procedures in Identification and Prevention of Sexual Harassment

Description: The procedural survey on sexual harassment procedures sent to 300 Texas principals had a response rate of 48.3 %. The mean score on the procedural survey for all 300 principals was 69.30 %. Eighteen research questions were addressed in detail in Chapter 4. Only five showed a significant correlation or effect size. Question 5 asked if there was a correlation between gender and the mean score of the survey instrument regarding sexual harassment procedures. The mean score of women was significantly higher than men. Question 6 asked if there was a correlation between the number of students in a school and the mean score of the survey instrument regarding sexual harassment procedures. This revealed that a significant correlation appeared between principals who worked at larger schools. Question 10 asked if there was a correlation between the location of the school, whether rural, urban, or metroplex and the mean score of the survey instrument. Principals of urban and metroplex schools scored significantly higher. Question 13 asked if there was a correlation between the hours of sexual harassment training attended in the last year and the mean score of the survey instrument regarding sexual harassment procedures. The results of this analysis revealed that a correlation approaching a medium effect size of .237 was present. Question 18 asked if there was a correlation between the total number of hours a principal had attended training and the mean score of the survey instrument. Neither the Pearson's correlation or the Spearman's rho was statistically significant. However, due to the large variation in responses on the sum of hours of training about sexual harassment, it was suspected that there might be a covariate accounting for sub-populations within the principals who participated in the survey. For ages 30-43.5, as the number of total training hours increased, the ...
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Date: May 2002
Creator: Cramer, Conita K. Markel
Partner: UNT Libraries

Fluorination Effect on the Conformational Properties of Alkanes

Description: A Series of fluorophores of the general formular P(CF2)nP and P(CF2)n-1CF3 has been synthesized. Copper catalyzed coupling of 1-bromopyrene and the corresponding mono and di-iodoperfluoroalkanes were used in most cases. For the n=3 dimer, a novel 1,w-perfluoroalkylation of pyrene via bis-decarboxylation of hexafluorogultaric acid was utilized. These compounds, along with suitable hydrocarbon analogs, are being used to study the flexibility of fluorocarbon chains using emission. We have found that the excimer formation for the fluorinated pyrene monomers is highly dependent on concentration and is less efficient than for pyene. Excimer formation for the fluorinated pyrene dimers is much more efficient than for the fluorocarbon monomers and is only slightly concentraion dependent. Steady-state emission spectra indicate hydrocarbon dimers-models form excimers more efficiently than the fluorinated dimers suggesting the fluorinated chains are stiffer than the hydrocarbons. We conducted the temperature-dependent studies and quantified the conformational difference.
Date: May 2002
Creator: Xu, Wenjian
Partner: UNT Libraries

Teacher-directed student use of the Internet for curricular activities: Profiles of frequent and infrequent use.

Description: The purpose of this study was to develop profiles that described teachers with infrequent and frequent teacher-directed student use of the Internet for curricular purposes. Responses to the teachers' self-reported needs, beliefs, demographics, Internet skill levels, and other information were examined as the basis for the study. The study was descriptive in nature, utilized correlation and causal-comparative methods, and employed a convenience sample. The population consisted of 3,187 public school teachers from Nebraska and four service regions in upstate New York. Data related to the research questions were gathered using an online survey. After minimum access was determined, frequencies, percentages, t tests, and correlations were used to examine the data. Teachers with infrequent (<15 mins. /week) teacher-directed student use of the Internet comprised 63% of the sample. Teachers from elementary and high school levels were almost equally represented in the infrequent use group. The majority of the high school level teachers were assigned to language arts, mathematics or science courses. Teachers in the frequent (>. 90 mins. /week) use group were predominately (75%) high school level, with the majority teaching computer and business subjects. Significant differences were found between the use groups regarding beliefs about the Internet's effect on students and schools and feelings about designing lessons that included the Internet or technology. Within the infrequent use group, significant correlations were found between comparative Internet skill levels and (a) hours of technology-related professional development and (b) willingness to use the Internet for professional development. Further study should be given to the question of how these differences and correlations may affect the amount of teacher-directed student use of the Internet. The profiles developed in this study provide a starting point to assist regional, district, and school-level personnel in assessing local needs and focusing resources on developing strategies to increase teacher-directed student ...
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Date: May 2002
Creator: Charles, Joan T.
Partner: UNT Libraries

Managerial self-awareness and its impact on leadership in high-performing managers.

Description: Managerial self-awareness is thought to impact leadership. A multi-rater feedback instrument was used to gather performance data on 70 managers in a large multi-national airline in regards to five leadership dimensions: making sound decisions, driving for results, effective communication, self-management, and innovation. Difference scores between self and direct reports were calculated and used as the operational definition of managerial self-awareness. T-tests were run to examine the difference between high performers and average performers. No significant differences were found. Additionally, correlational measures between the five leadership competencies and the managerial self-awareness measure indicated statistically weak relationships.
Date: May 2002
Creator: Yancey, Margaret
Partner: UNT Libraries