363 Matching Results

Results open in a new window/tab.

The Stopping of Energetic Si, P and S Ions in Ni, Cu, Ge and GaAs Targets

Access: Use of this item is restricted to the UNT Community
Accurate knowledge of stopping powers is essential for these for quantitative analysis and surface characterization of thin films using ion beam analysis (IBA). These values are also of interest in radiobiology and radiotherapy, and in ion- implantation technology where shrinking feature sizes puts high demands on the accuracy of range calculations. A theory that predicts stopping powers and ranges for all projectile-target combinations is needed. The most important database used to report the stopping powers is the SRIM/TRIM program developed by Ziegler and coworkers. However, other researchers report that at times, these values differ significantly from experimental values. In this study the stopping powers of Si, P and S ions have been measured in Ni, Cu, Ge and GaAs absorbers in the energy range ~ 2-10 MeV. For elemental films of Ni, Cu and Ge, the stopping of heavy ions was measured using a novel ERD (Elastic Recoil Detection) based technique. In which an elastically recoiled lighter atom is used to indirectly measure the energy of the incoming heavy ion using a surface barrier detector. In this way it was possible to reduce the damage and to improve the FWHM of the detector. The results were compared to SRIM-2000 predictions …
Date: December 2001
Creator: Nigam, Mohit
Object Type: Thesis or Dissertation
System: The UNT Digital Library

A laboratory course in experimental genetics for the biology major.

Access: Use of this item is restricted to the UNT Community
This manual has been designed for a class of twenty- four students concurrently enrolled in the lecture course. The laboratory aids in the learning process and fosters an interest in the science of genetics. This manual and the experiments contained within are both informative and fun. The manual correlates with and expands upon the genetics course. Each investigation, with the exception of the Drosophila melanogaster project, can be completed in a 3-4 hour timeframe. This manual provides a “hands on” experience of theories simply discussed in the lecture course. This manual is intended to be a one-source manual where each investigation is designed to include an adequate introduction. Special attention has been given for each investigation with both the student and instructor in mind.
Date: December 2001
Creator: Lux, Melissa McNeil
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Quantization Dimension for Probability Definitions

Access: Use of this item is restricted to the UNT Community
The term quantization refers to the process of estimating a given probability by a discrete probability supported on a finite set. The quantization dimension Dr of a probability is related to the asymptotic rate at which the expected distance (raised to the rth power) to the support of the quantized version of the probability goes to zero as the size of the support is allowed to go to infinity. This assumes that the quantized versions are in some sense ``optimal'' in that the expected distances have been minimized. In this dissertation we give a short history of quantization as well as some basic facts. We develop a generalized framework for the quantization dimension which extends the current theory to include a wider range of probability measures. This framework uses the theory of thermodynamic formalism and the multifractal spectrum. It is shown that at least in certain cases the quantization dimension function D(r)=Dr is a transform of the temperature function b(q), which is already known to be the Legendre transform of the multifractal spectrum f(a). Hence, these ideas are all closely related and it would be expected that progress in one area could lead to new results in another. It would …
Date: December 2001
Creator: Lindsay, Larry J.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The Effects of Color Concentrate in Polyolefins.

Access: Use of this item is restricted to the UNT Community
Throughout history consumer products were generally manufactured from wood and metal. They either had to hold their natural color or become subject to painting. When plastics entered the industry, it was recognized for its ease of shaping, re-usability, physical properties and its low cost. One of plastics' greatest benefits is its ability to hold a given color from within allowing it to avoid use of paint. This paper will give a brief overview on the effects of pigments when incorporated in a polyolefin. It will provide a classification of the main types of pigments and how each effect the properties of the product through: crystallization, weatherability, opacity, coloristic values and of course viscosity.
Date: December 2001
Creator: Flora, Paul
Object Type: Thesis or Dissertation
System: The UNT Digital Library

An Etiology of Juvenile Homicide in Dallas, Texas: 1988-1997

Access: Use of this item is restricted to the UNT Community
This research analyzed all juveniles involved in a homicide, both victims and offenders, in the city of Dallas, Texas from the years 1988 through 1997. This study addressed several research questions including the identification of risk factors common to both victims and offenders. Data for this study was obtained from the homicide files of the Dallas Police Department. The findings in part identify specific profiles of the victims and offenders, as well as identifying comparisons of risk factors between the two groups. Also identified are the relationships between the offenders and victims. Conclusions from this research present implications for law enforcement agencies, as well as furthering the etiology of juvenile homicide.
Date: December 2001
Creator: Haynes, Joseph
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Electroencephalographic (EEG) biofeedback treatment for children with attention deficit disorders in a school setting.

Access: Use of this item is restricted to the UNT Community
The purpose of this study was to explore the use of EEG biofeedback in a school setting to assist students who had attentional challenges. The equipment for implementing biofeedback was relatively inexpensive and was easily integrated into the school setting. Twenty students ranging in age from 7 to 17 were recruited for this study. Data was used from 14 subjects, 12 males (2 Hispanic, 1 African American, and 10 Caucasian) and 2 females (1 Hispanic, 1 Caucasian.) The subject pool was reduced due to non-compliance or the students. moving from the school district. Significant effect size was obtained in the treatment group in areas pertaining to visual perception and motor coordination. However, significant effect sizes in other areas were obtained when the control group scores worsened. The inclusion of student subjects who, perhaps, did not meet stringent criterion of attention deficit may have skewed the results. The small number of students in the study may have hindered accurate measures of statistical significance. Conversely, the information obtained from this study may offer insight to school districts in providing their students an alternate/adjunct to psychopharmacological medication and a non- invasive method of helping students with psycho-social challenges.
Date: December 2001
Creator: Mosse, Leah Kathryn
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Development of a Pre-Impact Environmental Site Characterization for the Bryan Mound, Texas Strategic Petroleum Reserve

Access: Use of this item is restricted to the UNT Community
This thesis presents a model for developing site-specific contingency plans to be used during spill response, remediation, and post-spill monitoring using the Strategic Petroleum Reserve's Bryan Mound site as a case study. Bird and vegetation observations provide baseline data for biological conditions, and sediment sampling for total petroleum hydrocarbons serves as a chemical component of the model. Results demonstrate previously unknown conditions that would hinder remediation and affect the persistence of petroleum contaminants. Results also established previously unmapped dominant bird and vegetation types likely to be impacted by a spill at the site. This model points to a reconsideration of individual facilities' responsibilities when planning for large-scale disasters and protecting the sensitive ecosystems surrounding their sites.
Date: December 2001
Creator: Hernandez, Sylvia A.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Characterization of Moraxella bovis Aspartate Transcarbamoylase

Access: Use of this item is restricted to the UNT Community
Aspartate transcarbamoylase (ATCase) catalyzes the first committed step in the pyrimidine biosynthetic pathway. Bacterial ATCases have been divided into three classes, class A, B, and C, based on their molecular weight, holoenzyme architecture, and enzyme kinetics. Moraxella bovis is a fastidious organism, the etiologic agent of infectious bovine keratoconjunctivitis (IBK). The M. bovis ATCase was purified and characterized for the first time. It is a class A enzyme with a molecular mass of 480 to 520 kDa. It has a pH optimum of 9.5 and is stable at high temperatures. The ATCase holoenzyme is inhibited by CTP > ATP > UTP. The Km for aspartate is 1.8 mM and the Vmax 1.04 µmol per min, where the Km for carbamoylphosphate is 1.05 mM and the Vmax 1.74 µmol per min.
Date: December 2001
Creator: Hooshdaran, Sahar
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Development, Validation, and Evaluation of a Continuous, Real-time, Bivalve Biomonitoring System

Access: Use of this item is restricted to the UNT Community
A biological monitoring tool to assess water quality using bivalve gape behavior was developed and demonstrated. The purpose of this work was to develop methodologies for screening water quality appropriate to the goals of the watershed paradigm. A model of bivalve gape behavior based on prediction of behavior using autoregressive techniques was the foundation of the bivalve biomonitoring system. Current technology was used in developing the system to provide bivalve gape state data in a continuous real-time manner. A laboratory version of the system, including data collection and analysis hardware and software, was developed for use as a toxicological assay for determination of effective concentrations of toxicant(s) or other types of stress on bivalve gape behavior. Corbicula fluminea was monitored and challenged with copper, zinc, and chlorpyrifos using the system. Effective concentrations of 176±23µg/L copper, 768±412µg/L zinc, and 68µg/L chlorpyrifos were observed using a natural water with high dissolved organic carbon concentrations. A rugged field version of the bivalve biomonitoring system was developed and deployed in two locations. The field systems were fitted with a photovoltaic array, a single board computer, and a CDPD telemetry modem for robust remote operation. Data were telemetered at a time relevant rate of once …
Date: December 2002
Creator: Allen, H. Joel
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The relationship between training in learning style adaptation and successful completion of entry-level community college classes.

Access: Use of this item is restricted to the UNT Community
The purpose of this study was to determine if there was a relationship between training in learning style adaptation and successful completion of community college courses. The rationale for conducting this study was based on the need for students to learn how to adapt their learning style in order to more effectively learn in any situation. It is also important that community colleges implement strategies that assist in student retention. The learning styles of entry-level community college students were measured using Kolb's Learning Style Inventory Version 3. Students enrolled in entry-level college courses at a small North Texas community college were studied. The Chi-square Test of Independence with a 2 x 2 design was employed. Findings indicated that there was no statistically significant difference in the relationship between students receiving training in learning styles adaptation and successful completion of entry-level college courses, and that students who attended a learning styles training session and those who did not attend a learning styles training session had an equal chance of succeeding in entry-level community college courses. Findings also indicated that students with Accommodating and Assimilating learning styles are less likely to successfully complete an entry-level college course than are students with Diverging …
Date: December 2002
Creator: Ferrell, Dawn M.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The Effects of Reinforcing Operant Variability on Task Acquisition

Access: Use of this item is restricted to the UNT Community
Neuringer, Deiss, and Olson (2000) was replicated and extended to determine the effect of variability contingencies on task acquisition for twelve 7-9 year old children. Subjects first learned to press a computer's shift keys with increasing response variation. Each subject was then exposed to one of three experimental conditions during which they received a point for target responses. Variability condition subjects received additional points on a variable interval schedule for nontarget responses occurring less than 3% of the time. The any condition subjects received additional points on a variable interval schedule for any nontarget response. Control subjects received points only for target responses. All variability condition and two control subjects learned the target response. All any condition subjects and two control subjects did not.
Date: December 2002
Creator: Seymour, Kail H.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Investigations of Thermochemistry and the Kinetics of H Atom Radical Reactions

Access: Use of this item is restricted to the UNT Community
The thermochemistry of several species, and the kinetics of various H atom radical reactions relevant to atmospheric and combustion chemistry were investigated using ab initio theoretical techniques and the flash photolysis / resonance fluorescence technique. Using ab initio quantum mechanical calculations up to the G3 level of theory, the C-H bond strengths of several alkanes were calculated. The bond strengths were calculated using two working reactions. From the results, it is apparent that the bond strengths decrease as methyl groups are added to the central carbon. The results are in good agreement with recent experimental halogenation kinetic studies. Hydrogen bond strengths with sulfur and oxygen were studied via CCSD(T) theory, together with extrapolation to the complete basis set limit. The results for the bond dissociation energies (ground state at 0 K, units: kJ mol-1) are: S-H = 349.9, S-D = 354.7, HS-H = 376.2, DS-D = 383.4, and HO-H = 492.6. These data compare well with experimental literature. The rate constants for the isotopic reactions of H + H2S, D + H2S, H + D2S, and D + D2S are studied at the QCISD(T)/6-311+G(3df,2p) level of theory. The contributions of the exchange reaction versus abstraction are examined through transition state …
Date: December 2002
Creator: Peebles, Lynda Renee
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The Role of the Vice-Chancellor in the Nigerian University and the Factors Essential for Effective Administration as Perceived by Vice-Chancellors and Members of University Governing Councils in Nigeria

Access: Use of this item is restricted to the UNT Community
The purposes of this study were to determine 1) the tasks that the Nigerian university vice-chancellor should perform personally, 2) the functions that the vice-chancellor should delegate to other university staff to achieve effective administration, 3) the factors that should be considered in the selection of a vice-chancellor, and 4) the criteria that should be considered in the evaluation of the vice-chancellor's job performance effectiveness. Chapter 1 includes a statement of the problem, purposes, research questions, background, significance of the study, definition of terms, limitations of the study, and basic assumptions. Chapter II is a review of related literature, and Chapter III presents information on the procedure followed in the collection and treatment of data. The analysis and evaluation of the findings are presented in Chapter IV; and the summary, findings, implications, and recommendations of the study are presented in Chapter V.
Date: December 1985
Creator: Ugwonali, Felix Chima
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Performance Evaluation of MPLS on Quality of Service in Voice Over IP (VoIP) Networks

Access: Use of this item is restricted to the UNT Community
The transmission of voice data over Internet Protocol (IP) networks is rapidly gaining acceptance in the field of networking. The major voice transmissions in the IP networks are involved in Internet telephony, which is also known as IP telephony or Voice Over IP (VoIP). VoIP is undergoing many enhancements to provide the end users with same quality as in the public switched telephone networks (PSTN). These enhancements are mostly required in quality of service (QoS) for the transmission of voice data over the IP networks. As with recent developments in the networking field, various protocols came into market to provide the QoS in IP networks - of them, multi protocol label switching (MPLS) is the most reliable and upcoming protocol for working on QoS. The problem of the thesis is to develop an IP-based virtual network, with end hosts and routers, implement MPLS on the network, and analyze its QoS for voice data transmission.
Date: December 2002
Creator: Chetty, Sharath
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Integrating life cycle analysis and the ecological footprint calculator to foster sustainable behaviors

Access: Use of this item is restricted to the UNT Community
Many tools have been developed to assess global, national or regional sustainable development policies. However, as governments develop sustainable policies, individuals must also feel empowered to affect their personal impact on the planet. This thesis integrates three sustainability concepts that lend themselves to individual sustainability: The natural step, life cycle assessment, and the ecological footprint. TNS serves to provide the meaning and substance toward sustainable development. LCA helps provide the framework for assessing sustainability. The EF calculator determines the driving components and measures the qualitative decisions made through TNS and LCA. From the analysis of the household footprint calculator a simplified footprint calculator was developed to assist individuals and communities in setting benchmarks and goals as they move away from over-consumption and towards a sustainable lifestyle.
Date: December 2002
Creator: Anderle, Kathryn
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Ranges of consideration: crossing the fields of ecology, philosophy and science studies.

Access: Use of this item is restricted to the UNT Community
Environmental issues are often complex with many different constituents operating according to a broad range of communication techniques. In order to foster negotiations, different perspectives need to be articulated in lucid ways sensitive to various viewpoints and circumstances. In my thesis I investigate how certain approaches to environmental discourse effect dialogue and negotiation. My first two chapters focus on environmental problems surrounding rangeland ecology along the U.S./Mexico border; whereas the last two chapters explore more theoretical conflicts concerning the philosophy of nature. Throughout the thesis I show the significance of nonhumans (prairie dogs, cattle, biological assessment sheets, environmental laws, etc.) in the human community. Only by considering the roles of nonhumans do we broaden and enrich the conversation between ourselves concerning environmental issues.
Date: December 2002
Creator: Dinneen, Nathan
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Ensuring Authenticity and Integrity of Critical Information Using XML Digital Signatures

Access: Use of this item is restricted to the UNT Community
It has been noticed in the past five years that the Internet use has been troubled by the lack of sufficient security and a legal framework to enable electronic commerce to flourish. Despite these shortcomings, governments, businesses and individuals are using the Internet more often as an inexpensive and ubiquitous means to disseminate and obtain information, goods and services. The Internet is insecure -- potentially millions of people have access, and "hackers" can intercept anything traveling over the wire. There is no way to make it a secure environment; it is, after all, a public network, hence the availability and affordability. In order for it to serve our purposes as a vehicle for legally binding transactions, efforts must be directed at securing the message itself, as opposed to the transport mechanism. Digital signatures have been evolved in the recent years as the best tool for ensuring the authenticity and integrity of critical information in the so called "paperless office". A model using XML digital signatures is developed and the level of security provided by this model in the real world scenario is outlined.
Date: December 2002
Creator: Korivi, Arjun
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Server load balancing.

Access: Use of this item is restricted to the UNT Community
Server load balancing technology has obtained much attention as much business proceeded towards e-commerce. The idea behind is to have set of clustered servers that share the load as against a single server to achieve better performance and throughput. In this problem in lieu of thesis, I propose and evaluate an implementation of a prototype scalable server. The prototype consists of a load-balanced cluster of hosts that collectively accept and service TCP connections. The host IP addresses are advertised using the Round Robin DNS technique, allowing any host to receive requests from any client. Once a client attempts to establish a TCP connection with one of the hosts, a decision is made as to whether or not the connection should be redirected to a different host namely, the host with the lowest number of established connections. This problem in lieu of thesis outlines the history of load balancing, various options available today and finally approach for implementing the prototype and the corresponding findings.
Date: December 2002
Creator: Kanuri, Jaichandra
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Implementation of Back Up Host in TCP/IP

Access: Use of this item is restricted to the UNT Community
This problem in lieu thesis is considering a TCP client H1 making a connection to distant server S and is downloading a file. In the midst of the downloading, if H1 crashes, the TCP connection from H1 to S is lost. In the future, if H1 restarts, the TCP connection from H1 to S will be reestablished and the file will be downloaded again. This cannot happen until host H1 restarts. Now consider a situation where there is a standby host H2 for the host H1. H1 and H2 monitor the health of each other by heartbeat messages (like SCTP). If H2 detects the failure of H1, then H2 takes over. This implies that all resources assigned to H1 are now reassigned or taken over by H2. The host H1 and H2 transmit data between each other when any one of it crashed. Throughout the data transmission process, heart beat chunk is exchanged between the hosts when one of the host crashes. In particular, the IP addresses that were originally assigned to H1 are assigned to H2. In this scenario, movement of the TCP connection between H1 and S to a connection between H2 and S without disrupting the TCP …
Date: December 2002
Creator: Golla,Mohan
Object Type: Thesis or Dissertation
System: The UNT Digital Library

A Quality of Service Aware Protocol for Power Conservation in Wireless Ad Hoc and Mobile Networks

Access: Use of this item is restricted to the UNT Community
Power consumption is an important issue for mobile computers since they rely on the short life of batteries. Conservation techniques are commonly used in hardware design of such systems but network interface is a significant consumer of power, which needs considerable research to be devoted towards designing a low-power design network protocol stack. Due to the dynamic nature of wireless networks, adaptations are necessary to achieve energy efficiency and a reasonable quality of service. This paper presents the application of energy-efficient techniques to each layer in the network protocol stack and a feedback is provided depending on the performance of this new design. And also a comparison of two existing MAC protocols is done showing a better suitability of E2MAC for higher power conservation. Multimedia applications can achieve an optimal performance if they are aware of the characteristics of the wireless link. Relying on the underlying operating system software and communication protocols to hide the anomalies of wireless channel needs efficient energy consumption methodology and fair quality of service like E2MAC. This report also focuses on some of the various concerns of energy efficiency in wireless communication and also looks into the definition of seven layers as defined by International …
Date: December 2002
Creator: Gangidi, Murali
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Discovering the Parameters of a Successful Piece: While Developing a Body of Work that Represents My Passion for Clay and My Enthusiasm for Life

Access: Use of this item is restricted to the UNT Community
Chapter I describes the purpose of the project, which was to develop a body of work that exhibits all that I am at this point in time. The questions I presented to myself were the following: 1. A successful piece is defined by what parameters? 2. What visual qualities indicate my passion for clay and my enthusiasm for life? Chapter II lists and explains the five parameters of a successful piece, which are composition, firing, mark making, color contrast, and movement. Furthermore there is an explanation on how these parameters visually display my passion for clay and my enthusiasm for life. Chapter III is a summary concluding that by discovering my five parameters of a successful piece I now understand the elements that I am searching for in my work. My work will grow from this understanding as long as I have the same passion for clay and enthusiasm for life.
Date: December 2002
Creator: Lichman, Brenda C.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

A Physiological Age-Grading System for Female Hydrellia pakistanae Deonier (Diptera: Ephydridae)

Access: Use of this item is restricted to the UNT Community
Conflicting opinions about the effectiveness of H. pakistanae as a biological control agent for hydrilla prompt researchers to find a method for assessing the fly's success. Developing a physiological age-grading system for the fly using ovarian morphology to detect changes in reproductive activity is useful for evaluating reproductive status of the fly in field populations. Changes in the appearance of follicular relics in ovaries with oviposition provide a reliable method to estimate fecundity. Characteristics of follicular relics were used to develop a system with eight physiological age classes, three nulliparous and five parous. Changes that occur in the fat body were used to assist in classification of nulliparous females or those with low egg counts.
Date: December 2002
Creator: Lenz, Jennifer Marie
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The Impact of Drug Testing on Secondary School Students

Access: Use of this item is restricted to the UNT Community
The purpose of this study determined whether use of student random drug testing provided an effective means to reduce drug usage by secondary school students. The participants included 50,214 7th through 12th grade students in 12 selected public schools. All school districts participated in the Texas School Survey of Substance Use in 1994, 1996, 1998, and 2000. The six districts in the experimental group used drug testing as a method of reducing drug usage among students. The six districts in the control group did not use drug testing. Although athletes and students involved in extracurricular activities remain the focus of random dug testing, this research focused on an entire school population to determine whether drug testing only a select group of students reduced reported drug usage in the entire school. Two questions guided the research: First, does the use of random drug testing have an impact on student drug usage? Second, does the year of implementation of random drug testing have an impact on students' self-reported drug usage? The findings for each research question were categorized according to nine illegal drugs. The researcher used a one-way repeated measures factorial design. The data were analyzed via the univariate (split-plot) 2 x …
Date: December 2002
Creator: Lee, Elton David
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Removal of selected water disinfection byproducts, and MTBE in batch and continuous flow systems using alternative sorbents.

Access: Use of this item is restricted to the UNT Community
A study was conducted to evaluate the sorption characteristics of six disinfection byproducts (DBPs) on four sorbents. To investigate sorption of volatile organic compounds (VOCs), specially designed experimental batch and continuous flow modules were developed. The investigated compounds included: chloroform, 1,2-dichloroethane (DCE), trichloroethylene (TCE), bromodichloromethane (BDCM), methyl tertiary butyl ether (MTBE), bromate and bromide ions. Sorbents used included light weight aggregate (LWA), an inorganic porous material with unique surface characteristics, Amberlite® XAD-16, a weakly basic anion exchange resin, Amberjet®, a strongly basic anion exchange resin, and granular activated carbon (GAC). Batch experiments were conducted on spiked Milli-Q® and lake water matrices. Results indicate considerable sorption of TCE (68.9%), slight sorption of bromate ions (19%) and no appreciable sorption for the other test compounds on LWA. The sorption of TCE increased to 75.3% in experiments utilizing smaller LWA particle size. LWA could be a viable medium for removal of TCE from contaminated surface or groundwater sites. Amberlite® was found unsuitable for use due to its physical characteristics, and its inability to efficiently remove any of the test compounds. Amberjet® showed an excellent ability to remove the inorganic anions (>99%), and BDCM (96.9%) from aqueous solutions but with considerable elevation of pH. …
Date: December 2002
Creator: Kadry, Ahmed Y.
Object Type: Thesis or Dissertation
System: The UNT Digital Library