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  Partner: UNT Libraries
 Decade: 1990-1999
 Collection: UNT Theses and Dissertations
O-Acetylserine Sulhydralase-A from Salmonella typhimurium LT-2: Thermodynamic Properties and SPectral Identification of Intermediates

O-Acetylserine Sulhydralase-A from Salmonella typhimurium LT-2: Thermodynamic Properties and SPectral Identification of Intermediates

Date: August 1993
Creator: Simmons, James Walter
Description: O-Acetylserine Sulfhydrylase (OASS) is a pyridoxal phosphate enzyme that catalyzes the reaction of O-acetyl-Lserine with sulfide to give L-cysteine. OASS is present as two isoforms, designated -A and -B. The kinetic mechanism of OASS-A is well known and there is also much known concerning the acid-base chemistry of the enzyme. However, little is known concerning the location of the rate determining steps, the sequencing of chemical steps that occur at the active site, or the nature of the rate determining transition states. The studies performed to help elucidate these aspects of the OASS-A mechanism included determination of the thermodynamics of both half reactions, along with studies utilizing substrate analogs of OAS halting the reaction at specific points along the reaction pathway allowing the identification of reaction intermediates. The free energy change of the first half reaction was shown to be -5.7 Kcal/mole while the second half reaction was shown to be, for all intents and purposes, irreversible. Intermediates along the reaction pathway that have been previously identified include the internal Schiff base and the a-aminoacrylate. The external Schiff base was identified using the analogs cysteine, alanine, and glycine while the geminal diamine was identified using the analog serine. Formation of ...
Contributing Partner: UNT Libraries
Active or Passive Voice: Does It Matter?

Active or Passive Voice: Does It Matter?

Date: December 1993
Creator: Watson, Rose E.
Description: None
Contributing Partner: UNT Libraries
The Activities of Disaster Relief Organizations During the Permanent Housing Phase of Recovery: a Case Study Analysis

The Activities of Disaster Relief Organizations During the Permanent Housing Phase of Recovery: a Case Study Analysis

Date: August 1992
Creator: Ephraim, Melinda M. H.
Description: None
Contributing Partner: UNT Libraries
Acts of Survival: the Plight and Prospects of Dallas Theatre

Acts of Survival: the Plight and Prospects of Dallas Theatre

Date: December 1993
Creator: Leeman, Patricia Diane
Description: None
Contributing Partner: UNT Libraries
N-Acylethanolamines and Plant Phospholipase D

N-Acylethanolamines and Plant Phospholipase D

Date: December 1998
Creator: Brown, Shea Austin
Description: Recently, three distinct isoforms of phospholipase D (PLD) were identified in Arabidopsis thaliana. PLD α represents the well-known form found in plants, while PLD β and γ have been only recently discovered (Pappan et al., 1997b; Qin et al., 1997). These isoforms differ in substrate selectivity and cofactors required for activity. Here, I report that PLD β and γ isoforms were active toward N-acylphosphatidylethanolamine (NAPE), but PLD α was not. The ability of PLD β and γ to hydrolyze NAPE marks a key difference from PLD α. N-acylethanolamines (NAE), the hydrolytic products of NAPE by PLD β and γ, inhibited PLD α from castor bean and cabbage. Inhibition of PLD α by NAE was dose-dependent and inversely proportional to acyl chain length and degree of unsaturation. Enzyme kinetic analysis suggested non-competitive inhibition of PLD α by NAE 14:0. In addition, a 1.2-kb tobacco (Nicotiana tabacum L.) cDNA fragment was isolated that possessed a 74% amino acid identity to Arabidopsis PLD β indicating that this isoform is expressed in tobacco cells. Collectively, these results provide evidence for NAE producing PLD activities and suggest a possible regulatory role for NAE with respect to PLD α.
Contributing Partner: UNT Libraries
Ádám's Conjecture and Its Generalizations

Ádám's Conjecture and Its Generalizations

Date: August 1990
Creator: Dobson, Edward T.
Description: None
Contributing Partner: UNT Libraries
An Adaptive Linearization Method for a Constraint Satisfaction Problem in Semiconductor Device Design Optimization

An Adaptive Linearization Method for a Constraint Satisfaction Problem in Semiconductor Device Design Optimization

Date: May 1999
Creator: Chang, Chih-Hui, 1967-
Description: The device optimization is a very important element in semiconductor technology advancement. Its objective is to find a design point for a semiconductor device so that the optimized design goal meets all specified constraints. As in other engineering fields, a nonlinear optimizer is often used for design optimization. One major drawback of using a nonlinear optimizer is that it can only partially explore the design space and return a local optimal solution. This dissertation provides an adaptive optimization design methodology to allow the designer to explore the design space and obtain a globally optimal solution. One key element of our method is to quickly compute the set of all feasible solutions, also called the acceptability region. We described a polytope-based representation for the acceptability region and an adaptive linearization technique for device performance model approximation. These efficiency enhancements have enabled significant speed-up in estimating acceptability regions and allow acceptability regions to be estimated for a larger class of device design tasks. Our linearization technique also provides an efficient mechanism to guarantee the global accuracy of the computed acceptability region. To visualize the acceptability region, we study the orthogonal projection of high-dimensional convex polytopes and propose an output sensitive algorithm for ...
Contributing Partner: UNT Libraries
Addition, Omission and Revision: the Stylistic Changes Made to Zehn Variationen über ein Präludium von Chopin by Ferruccio Busoni

Addition, Omission and Revision: the Stylistic Changes Made to Zehn Variationen über ein Präludium von Chopin by Ferruccio Busoni

Date: December 1994
Creator: Yoon, Soomee
Description: This study examines what Busoni meant by "formal deficiencies" when he described his 1884 version of Chopin Variations, and reveals that changes made to the 1884 version during its process of revision in 1922 correct the "formal deficiencies" and show a fundamental change in Busoni's compositional style and perception of musical motion. Including a detailed analysis of the modifications, omissions, and additions made to the 1922 version (including an examination of the Chopin Prelude in C minor, op. 28, No. 20 as a theme to reveal aspects of its construction used in the variation process), which shows how these changes affect the work's compositional structure.
Contributing Partner: UNT Libraries
Adhesion/Diffusion Barrier Layers for Copper Integration: Carbon-Silicon Polymer Films and Tantalum Substrates

Adhesion/Diffusion Barrier Layers for Copper Integration: Carbon-Silicon Polymer Films and Tantalum Substrates

Date: December 1999
Creator: Chen, Li
Description: The Semiconductor Industry Association (SIA) has identified the integration of copper (Cu) with low-dielectric-constant (low-k) materials as a critical goal for future interconnect architectures. A fundamental understanding of the chemical interaction of Cu with various substrates, including diffusion barriers and adhesion promoters, is essential to achieve this goal. The objective of this research is to develop novel organic polymers as Cu/low-k interfacial layers and to investigate popular barrier candidates, such as clean and modified tantalum (Ta) substrates. Carbon-silicon (C-Si) polymeric films have been formed by electron beam bombardment or ultraviolet (UV) radiation of molecularly adsorbed vinyl silane precursors on metal substrates under ultra-high vacuum (UHV) conditions. Temperature programmed desorption (TPD) studies show that polymerization is via the vinyl groups, while Auger electron spectroscopy (AES) results show that the polymerized films have compositions similar to the precursors. Films derived from vinyltrimethyl silane (VTMS) are adherent and stable on Ta substrates until 1100 K. Diffusion of deposited Cu overlayers is not observed below 800 K, with dewetting occurred only above 400 K. Hexafluorobenzene moieties can also be incorporated into the growing film with good thermal stability. Studies on the Ta substrates demonstrate that even sub-monolayer coverages of oxygen or carbide on polycrystalline ...
Contributing Partner: UNT Libraries
Adjustment of Kindergarten Children through Play Sessions Facilitated by Fifth Grade Students Trained in Child-Centered Play Therapy Procedures and Skills

Adjustment of Kindergarten Children through Play Sessions Facilitated by Fifth Grade Students Trained in Child-Centered Play Therapy Procedures and Skills

Date: May 1999
Creator: Baggerly, Jennifer N. (Jennifer Nalini)
Description: This research study investigated the effectiveness of the application of child-centered play therapy procedures and skills by trained fifth grade students in play sessions with kindergarten children who had adjustment difficulties. Specifically, this research determined if play sessions with trained fifth grade students facilitated change in kindergarten children's self concept, internalizing behavior, and externalizing behavior and their parents' stress level.
Contributing Partner: UNT Libraries