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364 Matching Results
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Characterization of Low Barrier Hydrogen Bonds in Enzyme Catalysis: an Ab Initio and DFT Investigation
Hartree-Fock, Moller-Plesset, and density functional theory calculations have been carried out using 6-31+G(d), 6-31+G(d,p) and 6-31++G(d,p) basis sets to study the properties of low-barrier or short-strong hydrogen bonds (SSHB) and their potential role in enzyme-catalyzed reactions that involve proton abstraction from a weak carbon-acid by a weak base. Formic acid/formate anion, enol/enolate and other complexes have been chosen to simulate a SSHB system. These complexes have been calculated to form very short, very short hydrogen bonds with a very low barrier for proton transfer from the donor to the acceptor. Two important environmental factors including small amount of solvent molecules that could possibly exist at the active site of an enzyme and the polarity around the active site were simulated to study their energetic and geometrical influences to a SSHB. It was found that microsolvation that improves the matching of pK as of the hydrogen bond donor and acceptor involved in the SSHB will always increase the interaction of the hydrogen bond; microsolvation that disrupts the matching of pKas, on the other hand, will lead to a weaker SSHB. Polarity surrounding the SSHB, simulated by SCRF-SCIPCM model, can significantly reduce the strength and stability of a SSHB. The residual strength …
Date:
August 1999
Creator:
Pan, Yongping
System:
The UNT Digital Library
Chaucer and the Rhetorical Limits of Exemplary Literature
Though much has been made of Chaucer's saintly characters, relatively little has been made of Chaucer's approach to hagiography. While strictly speaking Chaucer produced only one true saint's life (the Second Nun's Tale), he was repeatedly intrigued and challenged by exemplary literature. The few studies of Chaucer's use of hagiography have tended to claim either his complete orthodoxy as hagiographer, or his outright parody of the genre. My study mediates the orthodoxy/parody split by viewing Chaucer as a serious, but self-conscious, hagiographer, one who experimented with the possibilities of exemplary narrative and explored the rhetorical tensions intrinsic to the genre, namely the tensions between transcendence and imminence, reverence and identification, and epideictic deliberative discourse.
Date:
May 1999
Creator:
Youmans, Karen DeMent
System:
The UNT Digital Library
Chemotactic Response of Lumbricus terrestris Coelomocytes to Larval and Adult Stages of Rhabditis pellio
Access:
Use of this item is restricted to the UNT Community
Experiments were performed to assess the suitability of Rhabditis pellio, a nematode found in earthworms, as a challenge organism for use in development of a biomarker assay to determine the potential of chemicals to suppress the immunocompetence of the non-specific immune system. To accomplish this goal, information on the life cycle of R. pellio was determined; including effects of incubation time and temperature on growth rates; along with information on the immune response elicited in the earthworm, Lumbricus terrestris. Immune parameters measured were coelomocyte migration toward and attachment to R. pellio larvae and adults. Preliminary background information showed that R. pellio has potential as a challenge organism for development of a biomarker assay.
Date:
December 1999
Creator:
Medrano, Jennifer Centurion
System:
The UNT Digital Library
Children and Childhood in Hawthorne's Fiction
This paper explores the role of children and childhood in Nathaniel Hawthorne's fiction. Moreover, it asserts that the child and childhood are keys to a better understanding of Hawthorne's fiction.
Date:
August 1999
Creator:
Sitz, Shirley Ann Ellis
System:
The UNT Digital Library
Chiral separation of pharmaceutical compounds using electrochemically modulated liquid chromatography (EMLC)
This research explores the application of a new technique, termed electrochemically modulated liquid chromatography (EMLC), to the chiral separations of pharmaceutical compounds. The introduction section provides a literature review of the technique and its applications, as well as brief overview of the research described in each of the next two chapters. Chapter 2 investigates the EMLC-based enantiomeric separation of a group of chiral benzodiazepines with {beta}-cyclodextrin as a chiral mobile phase additive. Chapter 3 demonstrates the effects of several experimental parameters on the separation efficiency of drug enantiomers. The author concludes with a general summary and possible directions for future studies. Chapters 2 and 3 are processed separately.
Date:
February 12, 1999
Creator:
Wang, S.
System:
The UNT Digital Library
Classification of Toolmark Surfaces on Zipper Teeth
This study proposes the classification of the toolmark under the heads of zipper teeth as a subclass characteristic as outlined by the Association of Firearm and Toolmark Examiners (AFTE). Two separate cases in which zipper teeth were found at crime scenes prompted this study. Brass zipper teeth manufactured by YKK were taken from 20 pairs of jeans and studied using a Reichert comparison microscope at 4X power. Photographs were taken and over 750 comparisons made. It was found that the toolmarks on each side on the 20 zippers were unique and independent of all other sides. The observations made in this study indicate that classifying zipper teeth toolmarks as a subclass characteristic is valid.
Date:
December 1999
Creator:
Jacobsen, Dawn
System:
The UNT Digital Library
Client/Server Systems Performance Evaluation Measures Use and Importance: a Multi-Site Case Study of Traditional Performance Measures Applied to the Client/Server Environment
This study examines the role of traditional computing performance measures when used in a client/server system (C/SS) environment. It also evaluates the effectiveness of traditional computing measures of mainframe systems for use in C/SS. The underlying problem was the lack of knowledge about how performance measures are aligned with key business goals and strategies. This research study has identified and evaluated client/server performance measurements' importance in establishing an effective performance evaluation system. More specifically, this research enables an organization to do the following: (1) compare the relative states of development or importance of performance measures, (2) identify performance measures with the highest priority for future development, (3) contrast the views of different organizations regarding the current or desired states of development or relative importance of these performance measures.
Date:
May 1999
Creator:
Posey, Orlando Guy
System:
The UNT Digital Library
Cognitive Interference in the Perception of Pitch and Loudness in a Five-note Musical Pattern
The purpose of the study was to explore whether musicians experience Garner interference among the auditory dimensions of pitch and loudness. Specifically, the study explored whether the dimensions of intonation and loudness, when presented to musicians in a five-note musical pattern, were perceived as integral or separable in nature.
Date:
May 1999
Creator:
Cattley, Gary Thomas
System:
The UNT Digital Library
Collision-induced dissociation reactions and pulsed field ionization photoelectron
This report summarized the four parts of the research study and describes the general conclusions. Individual chapters have been removed for separate processing. The chapter titles are: A study of the dissociation of CH{sub 3}SH{sup +} by collisional activation: Observation of non-statistical behavior; High resolution vacuum ultraviolet pulsed field ionization photoelectron band for OCS{sup +}(X{sup 2}{Pi}): An experimental and theoretical study; Rotationally resolved pulsed field ionization photoelectron bands of H{sub 2}{sup +} ({Chi}{sup 2}{Sigma}{sup +}{sub g}, v{sup +} = 0--18); and Rotationally resolved pulsed field ionization photoelectron bands of HD{sup +} ({Chi}{sup 2}{Sigma}{sup +}, v{sup +} = 0--21).
Date:
February 12, 1999
Creator:
Stimson, S.
System:
The UNT Digital Library
A Comparative Analysis of Intensive Individual Play Therapy and Intensive Sibling Group Play Therapy with Child Witnesses of Domestic Violence
This study was designed to determine the effectiveness of intensive sibling group play therapy in: (a) improving the self-concept of child witnesses of domestic violence; (b) reducing internalizing behavior problems, such as withdrawal, somatic complaints, anxiety and depression, of child witnesses of domestic violence; (c) reducing externalizing behavior problems, such as aggression and delinquency, of child witnesses of domestic violence; and (d) reducing overall behavior problems of child witnesses of domestic violence. A second objective of this study was to compare the effectiveness of intensive sibling group play therapy and intensive individual play therapy on the above identified dimensions.
Date:
May 1999
Creator:
Tyndall-Lind, Ashley
System:
The UNT Digital Library
Comparative Biochemistry and Evolution of Aspartate Transcarbamoylase from Diverse Bacteria
Aspartate transcarbamoylase (ATCase) catalyzes the first committed step in pyrimidine biosynthesis. Bacterial ATCases are divided into three classes, A, B and C. Class A ATCases are largest at 450-500, are. dodecamers and represented by Pseudomonas ATCase. The overlapping pyrBC' genes encode the Pseudomonases ATCase, which is active only as a 480 kDa dodecamer and requires an inactive pyrC'-encoded DHOase for ATCase activity. ATCase has been studied in two non-pathogenic members of Mycobacterium, M. smegmatis and M. phlei. Their ATCases are dodecamers of molecular weight 480 kDa, composed of six PyrB and six PyrC polypeptides. Unlike the Pseudomonas ATCase, the PyrC polypeptide in these mycobacteria encodes an active DHOase. Moreover, the ATCase: DHOase complex in M. smegmatis is active both as the native 480 kDa and as a 390 kDa complex. The latter lacks two PyrC polypeptides yet retains ATCase activity. The ATCase from M. phlei is similar, except that it is active as the native 480 kDa form but also as 450,410 and 380 kDa forms. These complexes lack one, two, and three PyrC polypeptides, respectively. By contrast,.ATCases from pathogenic mycobacteria are active only at 480 kDa. Mycobacterial ATCases contain active DHOases and accordingly. are placed in class A1 . …
Date:
May 1999
Creator:
Hooshdaran, Massoumeh Ziba
System:
The UNT Digital Library
Comparative Mitochondrial DNA Sequence Diversity in Isolated and Open Populations of Southern Flying Squirrels
Access:
Use of this item is restricted to the UNT Community
Three populations of Southern flying squirrels were studied in the Ouachita Mountains of Arkansas to assess the impact of population subdivision-due to island formation--on the population genetics of Glaucomys volans. One island, one mainland, and one open population were investigated. A 367 nucleotide hypervariable region of mitochondrial DNA was sequenced in individuals from each population. Individuals and populations were compared to assess relatedness. Higher sequence diversity was detected in the open and island populations. One island individual shared characters with both the island and mainland populations. Results support the hypothesis that the mainland population may have reduced gene flow. Also, the island population may have been originally founded by at least two maternal lineages.
Date:
August 1999
Creator:
Cook, Melaney Birdsong
System:
The UNT Digital Library
A Comparison of Economic Development in Latin America, Middle Eastern Europe and Asia in the 1990s
The 1990s were characterized by severe turbulence in the global economy. Economic and financial crises occurred in Latin America, Middle and Eastern Europe and Asia. This analysis distinguishes between the two socioeconomic criteria "transitional" and "emerging" region. Transitional countries are former centrally planned socialist economies and emerging countries former agricultural-oriented classical developing economies with mostly a history of military or some other kind of autocratic dictatorship. The resources for the analysis are data sets regarding investment, exchange rate behavior, government finance, international liabilities of monetary authorities and inflation. The study reveals macroeconomic patterns associated with economic development in each socioeconomic region. It is shown that similar patterns are responsible for successful and non-successful performance in each region. A comparison of different regions shows many parallels between emerging economies, but only little similarity between transitional economies.
Date:
May 1999
Creator:
Marktanner, Marcus
System:
The UNT Digital Library
A Comparison of Multivariate Normal and Elliptical Estimation Methods in Structural Equation Models
In the present study, parameter estimates, standard errors and chi-square statistics were compared using normal and elliptical estimation methods given three research conditions: population data contamination (10%, 20%, and 30%), sample size (100, 400, and 1000), and kurtosis (kappa =1,10, 20).
Date:
August 1999
Creator:
Cheevatanarak, Suchittra
System:
The UNT Digital Library
A Comparison of Points Versus Sounds as Reinforces in Human Operant Research
Research shows that human operant behavior typically differs from non-human operant behavior on schedules of reinforcement. These differences in performance may be related to differences between the experimental preparations used to study human and non-human operant behavior. One such difference is the type of reinforcer used. This experiment analyzed the differential effects of points alone, points backed up by money, and sounds on schedule performance of human subjects. Results show that sounds generated moderate rates of responding, capable of change in either direction. When points backed up with money were the reinforcers, however, high rates of behavior were generated, disrupting the previously established baseline performance. This suggests that while points may be effective in generating high rates of behavior, they may be ineffective in producing sensitive baselines needed to study human operant behavior on schedules of reinforcement.
Date:
August 1999
Creator:
Rouse, Susan L.
System:
The UNT Digital Library
A Comparison of Predicted and Actual Trophic Status of Lake Ray Roberts, Texas Based on Chlorophyll A
Two years before impoundment, the trophic status of Lake Ray Roberts was predicted by applying the total phosphorus input into the Organization for Economic Cooperation and Development (OECD) eutrophication model. Predicted mean summer epilimnetic (MSE) chlorophyll a of Elm Fork arm, Isle duBois arm and Main Body were in the eutrophic category of the OECD model. Observed MSE chlorophyll a two years after impoundment of Elm Fork arm, Isle duBois and Main Body had not reached their predicted means and were at the mesotrophic-eutrophic boundary of the OECD model. Six years after impoundment, observed MSE chlorophyll a for Main Body, was closer to its predicted mean and in the eutrophic category of the OECD model. Six years after impoundment, Elm Fork arm was the most productive area of Lake Ray Roberts. Observed means of chlorophyll a, total phosphates, suspended solids and turbidity were often highest in the Elm Fork arm. Wastewater effluent from Gainesville and Valley View, TX, had an impact on productivity in Elm Fork arm.
Date:
May 1999
Creator:
Lytle, Lili Lisa
System:
The UNT Digital Library
A comparison of thermoelectric phenomena in diverse alloy systems
The study of thermoelectric phenomena in solids provides a wealth of opportunity for exploration of the complex interrelationships between structure, processing, and properties of materials. As thermoelectricity implies some type of coupled thermal and electrical behavior, it is expected that a basic understanding of transport behavior in materials is the goal of such a study. However, transport properties such as electrical resistivity and thermal diffusivity cannot be fully understood and interpreted without first developing an understanding of the material's preparation and its underlying structure. It is the objective of this dissertation to critically examine a number of diverse systems in order to develop a broad perspective on how structure-processing-property relationships differ from system to system, and to discover the common parameters upon which any good thermoelectric material is based. The alloy systems examined in this work include silicon-germanium, zinc oxide, complex intermetallic compounds such as the half-Heusler MNiSn, where M = Ti, Zr, or Hf, and rare earth chalcogenides.
Date:
January 1, 1999
Creator:
Cook, Bruce
System:
The UNT Digital Library
The Computation of Ultrapowers by Supercompactness Measures
The results from this dissertation are a computation of ultrapowers by supercompactness measures and concepts related to such measures. The second chapter gives an overview of the basic ideas required to carry out the computations. Included are preliminary ideas connected to measures, and the supercompactness measures. Order type results are also considered in this chapter. In chapter III we give an alternate characterization of 2 using the notion of iterated ordinal measures. Basic facts related to this characterization are also considered here. The remaining chapters are devoted to finding bounds fwith arguments taking place both inside and outside the ultrapowers. Conditions related to the upper bound are given in chapter VI.
Date:
August 1999
Creator:
Smith, John C.
System:
The UNT Digital Library
A Computer-Based Process Control System for a Target Station in a LINAC Facility
An event-driven, sequential, process control system was designed for International Isotopes, Inc., to automate and remotely control a target station at the company's linear accelerator facility. The designed system consisted of two major sections: a software program (virtual instrument), which was developed by LabVIEW, and a hardware interface (FieldPoint Modular Distributed I/O System by National Instrument), which had to be a pre-developed system that did not require customization. The designed virtual instrument was tested on a simulation model that mimed the target station. The result was a valid design.
Date:
May 1999
Creator:
Al-Shantaf, Abdulraouf O.
System:
The UNT Digital Library
Conceptualizations of Young, Middle-aged, and Older Adults and the Ingroup-outgroup Complexity Effect
The purpose of the present study was to investigate Linville's (1982) ingroup-outgroup complexity hypothesis through descriptive card sorts created by young, middle-aged, and older adults regarding their own and other age groups.
Date:
August 1999
Creator:
Curtiss, Karin (Karin Elizabeth)
System:
The UNT Digital Library
Construction of a Physical Map of Moraxella (Branhamella) catarrhalis Strain ATCC25238
In order to gain a better understanding of this microorganismand its role in human pathogenesis, a physical map of Moraxella catarrhalis type strain ATCC25238 was constructed using pulsed field gel electrophoresis (PFGE) in combination with Southern hybridization techniques. Restriction endonucleases Not I, Rsr II, and Sma I were used to digest the chromosomal DNA. An overlapping circular map was generated by cross-hybridization of isolated radiolabeled fragments of Moraxella catarrhalis genomic DNA to dried PFGE gels. The number and location of the 16S and 23S ribosomal RNA genes were determined by digestion with l-Ceul enzyme and by Southern hybridization. Virulence-associated genes, the gene for β-lactamase, and housekeeping genes were also placed onto the physical map.
Date:
May 1999
Creator:
Nguyen, Kim Thuy
System:
The UNT Digital Library
Constructions: An Investigation into Childhood From a Perspective of Loss
The interaction of the construction and the images was the focus of my proposed exploration. Previously, I viewed the images as the vehicle for content with little thought to the construction. I thought of the construction as a painter might think of his or her canvas, a place for the images to reside. The relationship between constructions as part of my content is essential. Exploration of form and image will push the limits of how the images and constructions may interact. Now that I was conscious of the construction being included in the content, I wanted to discover how the ideation process would change. I was also hoping to determine how the imagery would be affected by the redirection of my decision making process concerning the construction as part of the content.
Date:
May 1999
Creator:
Moss, Christopher H.
System:
The UNT Digital Library
Continuity Expectations in Vertical Marketing Systems: a Dyadic Perspective of Domestic and International Franchising
An emerging paradigm shift in the marketing discipline has prompted renewed research interest in the nature and scope of exchange. A common theme in the research to date is a departure from the traditional transactional orientation to a relational perspective of exchange. The relational emphasis is particularly germane to contractual Vertical Marketing Systems (VMS) where the emphasis is on long-term, mutually beneficial interaction between various channel members. The franchisor-franchisee relationship, a type of contractual VMS, is governed by norms that impact system efficiency and effectiveness. Despite the unprecedented growth of international franchising systems in the marketplace, a paucity of empirical attention has focused on cross-national franchisor-franchisee relationships. With many U.S.-based business format franchisors penetrating foreign markets, the primary purpose of the dissertation is to provide insights into tools which franchisors, and franchisees can use during the evolution of the exchange relationship. To identify differences across geographic boundaries, the dissertation simultaneously studies domestic and cross-border franchisor-franchisee relationships.
Date:
May 1999
Creator:
Mehta, Sanjay S. (Sanjay Subhash)
System:
The UNT Digital Library
Contributing Risk Factors in the Association Between Sexual Abuse Experiences and Disturbed Eating Patterns in College Females
This study examined two theoretical factors proposed to explain the relationship between sexual abuse experiences and disturbed eating patterns. Over 300 women completed questionnaires designed to assess sexual abuse histories, bodily shame, body disparagement, and disordered eating behaviors. Multivariate analyses indicated that bodily shame, body image dysphoria, and bodily dissatisfaction were significantly higher in participants with previous sexual violations. In addition, disordered eating symptoms and behaviors were related to reported severity of sexual abuse experiences. However, the relationship between the severity of disturbed eating patterns and sexual abuse histories appears to be more meaningful in relation to the presence of bodily shame and body dissatisfaction, as proposed in previous research. Future research implications are discussed.
Date:
August 1999
Creator:
Tripp, Margaret Murphy
System:
The UNT Digital Library