Month

Carbon Nanotube/Microwave Interactions and Applications to Hydrogen Fuel Cells.

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One of the leading problems that will be carried into the 21st century is that of alternative fuels to get our planet away from the consumption of fossil fuels. There has been a growing interest in the use of nanotechnology to somehow aid in this progression. There are several unanswered questions in how to do this. It is known that carbon nanotubes will store hydrogen but it is unclear how to increase that storage capacity and how to remove this hydrogen fuel once stored. This document offers some answers to these questions. It is possible to implant more hydrogen in a nanotube sample using a technique of ion implantation at energy levels ~50keV and below. This, accompanied with the rapid removal of that stored hydrogen through the application of a microwave field, proves to be one promising avenue to solve these two unanswered questions.
Date: May 2004
Creator: Imholt, Timothy James
System: The UNT Digital Library

Study of Conductance Quantization by Cross-Wire Junction

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The thesis studied quantized conductance in nanocontacts formed between two thin gold wires with one of the wires coated by alkainthiol self assembly monolayers (SAM), by using the cross-wire junction. Using the Lorenz force as the driving force, we can bring the two wires in contact in a controlled manner. We observed conductance with steps of 2e2 / h. The conductance plateaus last several seconds. The stability of the junction is attributed to the fact that the coating of SAM improves the stability and capability of the formed contact.
Date: May 2004
Creator: Zheng, Tao
System: The UNT Digital Library

Electrodeposition of adherent copper film on unmodified tungsten.

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Adherent Cu films were electrodeposited onto polycrystalline W foils from purged solutions of 0.05 M CuSO4 in H2SO4 supporting electrolyte and 0.025 M CuCO3∙Cu(OH)2 in 0.32 M H3BO3 and corresponding HBF4 supporting electrolyte, both at pH = 1. Films were deposited under constant potential conditions at voltages between -0.6 V and -0.2 V vs Ag/AgCl. All films produced by pulses of 10 s duration were visible to the eye, copper colored, and survived a crude test called "the Scotch tape test", which stick the scotch tape on the sample, then peel off the tape and see if the copper film peels off or not. Characterization by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray photon spectroscopy (XPS) confirmed the presence of metallic Cu, with apparent dendritic growth. No sulfur impurity was observable by XPS or EDX. Kinetics measurements indicate that the Cu nucleation process in the sulfuric bath is slower than in the borate bath. In both baths, nucleation kinetics do not correspond to either instantaneous or progressive nucleation. Films deposited from 0.05 M CuSO4/H2SO4 solution at pH > 1 at -0.2 V exhibited poor adhesion and decreased Cu reduction current. In both borate and sulfate baths, small …
Date: May 2004
Creator: Wang, Chen
System: The UNT Digital Library

Synthesis of cubic boron nitride thin films on silicon substrate using electron beam evaporation.

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Cubic boron nitride (cBN) synthesis has gained lot of interest during the past decade as it offers outstanding physical and chemical properties like high hardness, high wear resistance, and chemical inertness. Despite of their excellent properties, every application of cBN is hindered by high compressive stresses and poor adhesion. The cost of equipment is also high in almost all the techniques used so far. This thesis deals with the synthesis of cubic phase of boron nitride on Si (100) wafers using electron beam evaporator, a low cost equipment that is capable of depositing films with reduced stresses. Using this process, need of ion beam employed in ion beam assisted processes can be eliminated thus reducing the surface damage and enhancing the film adhesion. Four sets of samples have been deposited by varying substrate temperature and the deposition time. scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) techniques have been used to determine the structure and composition of the films deposited. X-ray diffraction (XRD) was performed on one of the samples to determine the thickness of the film deposited for the given deposition rate. Several samples showed dendrites being formed as …
Date: May 2004
Creator: Vemuri, Prasanna
System: The UNT Digital Library

Richard Strauss's Duett-Concertino: A Study of the Programmatic Elements for the Performer

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Richard Strauss's Duett-Concertino for Clarinet and Bassoon with Strings and Harp, AV 147 was one of the last works written by this celebrated composer. This double concerto has been largely unrecognized by performers and scholars until a recent surge in recorded performances. Some factors that hinder performances of the Duett-Concertino include unusual scoring and difficult rhythmic passages, as well as a lack of acknowledgement or understanding of the programmatic elements represented in the music. Sketches and letters show that the Duett-Concertino was inspired by a fairytale, which may have been the popular Beauty and the Beast. The programmatic analysis in this study examines the musical gestures of the piece, which, when combined with the cues provided in the sketches and letters, construct a musical interpretation of the fairytale. Recognition of the extra-musical features of the Duett-Concertino is essential for an effective performance and, in turn, creates additional performance possibilities such as narration and choreography.
Date: May 2004
Creator: Turley, Sarah Leigh
System: The UNT Digital Library

Supplemental Studies for Mastering Extended Techniques in Three Late Twentieth-Century Works for Solo Trombone: Luciano Berio's Sequenza V, Folke Rabe's Basta and Mark Phillips' T. Rex, Together with Three Recitals of Selected Works by Wagenseil, Grøndahl, Gotkovsky, and Others

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Many, if not most, student trombonists have perhaps had little or no previous experience with "extended techniques"-novel or unconventional modes of sound production. To address this deficiency of experience, this document sets forth a progressive sequence of descriptive explanations and supplementary studies, which are specifically designed to assist trombonists in mastering the particular extended techniques that will prepare them to perform three of the most popular late Twentieth-Century pieces for trombone that include extended techniques-Luciano Berio's Sequenza V, Folke Rabe's Basta, and Mark Phillips' T.Rex. Following the introductory chapter, the body of the document consists of three chapters, each of which deals with one of the three solos, presenting descriptive explanations of relevant extended techniques interspersed with performance commentary (solicited from prominent trombonists) and supplementary studies (composed by the author). The studies presented in each chapter are specifically geared toward mastering the extended techniques as they relate to the music of each particular solo. They are also especially focused toward learning the more difficult passages of music in each solo.
Date: May 2004
Creator: Scott, Deb
System: The UNT Digital Library

Pedagogical style and influence of Nadia Boulanger on music for wind symphony, an analysis of three works by her students: Copland, Bassett, and Grantham.

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An examination of the influences on twentieth-century wind music would be incomplete without the consideration of composer, organist, pianist, conductor, teacher, and critic Nadia Boulanger (1887-1979). Students from the United States began studying with Boulanger between World War I and World War II, and continued to travel to study with her for over fifty years. The respect awarded this legendary French woman was gained as a result of her effectiveness as a teacher, her influence on the development of each student's unique compositional style, and her guidance of an emerging American musical style. The correlation between the teacher's lessons and the compositional output of her students must be explored. Boulanger did not compose specifically for winds, and she did not encourage her students to compose for the wind symphony. However, this document will outline the influence that this powerful pedagogue exerted over the creation of repertoire by her students by providing insight into the pedagogical style and philosophical foundations of Boulanger as reflected in the literature and by the writings, comments, and compositions of three successful students who composed literature for the wind symphony: Aaron Copland (1900-1990), Leslie Bassett (b. 1923), and Donald Grantham (b. 1947). Three significant works for …
Date: May 2004
Creator: McCallum, Wendy M.
System: The UNT Digital Library

Passivation effects of surface iodine layer on tantalum for the electroless copper deposition.

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The ability to passivate metallic surfaces under non-UHV conditions is not only of fundamental interests, but also of growing practical importance in catalysis and microelectronics. In this work, the passivation effect of a surface iodine layer on air-exposed Ta for the copper electroless deposition was investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Although the passivation effect was seriously weakened by the prolonged air exposure, iodine passivates the Ta substrate under brief air exposure conditions so that enhanced copper wetting and adhesion are observed on I-passivated Ta relative to the untreated surface.
Date: May 2004
Creator: Liu, Jian
System: The UNT Digital Library

Cyanide Assimilation in Pseudomonas Fluorescens: Characterization of Cyanide Oxygenase as a Pterin-Dependent Multicomponent Enzyme Complex

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Cyanide utilization in Pseudomonas fluorescens NCIMB 11764 occurs via oxidative conversion to carbon dioxide and ammonia, the latter satisfying the nitrogen requirement. Substrate attack is initiated by an enzyme referred to as cyanide oxygenase (CNO), previously shown to require components in both high (H) (>30 kDa) and low (L) (<10 kDa) molecular weight cell fractions. In this study, tetrahydrobiopterin (H4biopterin) was identified as a cofactor in fraction L, thus making CNO appear as a pterin- dependent hydroxylase. CNO was purified 150-fold (specific activity 0.9 U/mg) and quantitatively converted cyanide to formate and ammonia as reaction products. When coupled with formate dehydrogenase, the complete enzymatic system for cyanide oxidation to carbon dioxide and ammonia was reconstituted. CNO was found to be an aggregate of known enzymes that included NADH oxidase (Nox), NADH peroxidase (Npx), cyanide dihydratase (CynD) and carbonic anhydrase (CA). A complex multi-step reaction mechanism is proposed in which Nox generates hydrogen peroxide which in turn is utilized by Npx to catalyze the oxygenation of cyanide to formamide accompanied by the consumption of one and two molar equivalents of oxygen and NADH, respectively. The further hydrolysis of formamide to ammonia and formate is thought to be mediated by CynD. The …
Date: May 2004
Creator: Fernandez, Ruby
System: The UNT Digital Library

Bioavailability and toxicity of 2,4,6-trinitrotoluene in sediment.

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TNT (2,4,6-trinitrotoluene) is a persistent contaminant at many military installations and poses a threat to aquatic ecosystems. Data from environmental fate and toxicity studies with TNT revealed that sediment toxicity test procedures required modification to accurately assess sediment TNT toxicity. Key modifications included aging TNT-spiked sediments 8-14 d, basing lethal dose on measured sediment concentrations of the molar sum of TNT and its main nitroaromatic (NA) transformation products (SNA), basing sublethal dose on average sediment SNA concentrations obtained from integration of sediment SNA transformation models, avoiding overlying water exchanges, and minimizing toxicity test durations. Solid phase microextraction fibers (SPMEs) were investigated as a biomimetic chemical measure of toxicity and bioavailability. Both organism and SPME concentrations provided measures of lethal dose independent of exposure scenario (TNT-spiked sediment or TNT-spiked water) for Tubifex tubifex. Among all benthic organisms tested (Chironomus tentans, Ceriodaphnia dubia, T. tubifex) and matrixes, median lethal dose (LC50) estimates based on SPME and organism concentrations ranged from 12.6 to 55.3 mmol SNA/ml polyacrylate and 83.4 to 172.3 nmol SNA/g tissue, ww, respectively. For Tubifex, LC50s (95% CI) based on SNA concentrations in sediment and SPMEs were 223 (209-238) nmol SNA/g, dw and 27.8 (26.0-29.8) mmol SNA/ml, respectively. Reproductive effects …
Date: May 2004
Creator: Conder, Jason M.
System: The UNT Digital Library

The Effect of Breastfeeding Education on Breastfeeding Initiation Rates Among Teenage Mothers

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The purpose of this study was to examine the effect of a breastfeeding education program on breastfeeding initiation rates, breastfeeding knowledge, and attitude towards breastfeeding among teenage mothers at an urban school for pregnant and parenting teens. Breastfeeding initiation rose from 35.7% in the control group to 85.2% in the treatment group. The mean score on the Breastfeeding Knowledge Subscale was significantly higher for the treatment group but not the control group. There was not a significant increase in mean scores on the Breastfeeding Attitude Subscale. Participants who initiated breastfeeding scored also had a significant increase in scores from pretest to posttest on the Breastfeeding Knowledge Subscale, while participants who did not initiate breastfeeding did not.
Date: May 2004
Creator: Brown, Amber L.
System: The UNT Digital Library

Hopfield Networks as an Error Correcting Technique for Speech Recognition

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I experimented with Hopfield networks in the context of a voice-based, query-answering system. Hopfield networks are used to store and retrieve patterns. I used this technique to store queries represented as natural language sentences and I evaluated the accuracy of the technique for error correction in a spoken question-answering dialog between a computer and a user. I show that the use of an auto-associative Hopfield network helps make the speech recognition system more fault tolerant. I also looked at the available encoding schemes to convert a natural language sentence into a pattern of zeroes and ones that can be stored in the Hopfield network reliably, and I suggest scalable data representations which allow storing a large number of queries.
Date: May 2004
Creator: Bireddy, Chakradhar
System: The UNT Digital Library

The Effect of Information Literacy Instruction on Library Anxiety Among International Students

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This study explored what effect information literacy instruction (ILI) may have on both a generalized anxiety state and library anxiety specifically. The population studied was international students using resources in a community college. Library anxiety among international students begins with certain barriers that cause anxiety (i.e., language/communication barriers, adjusting to a new education/library system and general cultural adjustments). Library Anxiety is common among college students and is characterized by feelings of negative emotions including, ruminations, tension, fear and mental disorganization (Jiao & Onwuegbuzie, 1999a). This often occurs when a student contemplates conducting research in a library and is due to any number of perceived inabilities about using the library. In order for students to become successful in their information seeking behavior this anxiety needs to be reduced. The study used two groups of international students enrolled in the English for Speakers of other Languages (ESOL) program taking credit courses. Each student completed Bostick's Library Anxiety Scale (LAS) and Spielberger's State-Trait Anxiety Inventory (STAI) to assess anxiety level before and after treatment. Subjects were given a research assignment that required them to use library resources. Treatment: Group 1 (experimental group) attended several library instruction classes (the instruction used Kuhltau's information search …
Date: May 2004
Creator: Battle, Joel C.
System: The UNT Digital Library

The Effects of Parent Training on the Amount and Variety of Food Consumed By a Child with Autism.

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The current study assessed the effectiveness of a training package, delivered in the form of a manual, to teach a parent to increase the variety and amount of food consumed by her son. The participant was a 5-year-old boy with Pervasive Developmental Disorder and limited food consumption. A changing criterion design across two variables, variety of food and quantity of food, was used. Results were that the parent who used the manual, with limited assistance from the experimenter, did succeed in increasing food variety and quantity of target foods.
Date: May 2004
Creator: VanKirk, Tessa Schreiber
System: The UNT Digital Library

Preparation and characterization of praseodymium oxide films and powders.

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Nanocrystalline praseodymium oxide films have been successfully generated on stainless steel substrates. The electrochemical deposition was performed in the cathode compartment of a divided electrochemical cell with a regular three-electrode configuration. The green films obtained by electrodeposition were then annealed at high temperatures for 1-3 hours. X-ray diffraction revealed the fluorite structure of Pr6O11 and the crystallite size was calculated. X-ray photoelectron spectroscopy was employed to study the composition of the oxide films and also the oxidation state of Pr. Scanning electron microscopy was utilized to study the surface texture and microstructure of deposits. Fourier transform infrared spectrometery was used to investigate the composition of the films. The effects of different conditions on the green films were also studied such as different pH values of the electrolyte solution, different deposition modes, different supporting electrolytes and different applied current densities. Sintering experiments were conducted to investigate the properties of the green films. Praseodymium oxide powders were also successfully prepared by combining electrochemical methods with sintering processes. The praseodymium oxide powders were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The crystallite sizes of the powders were evaluated.
Date: May 2004
Creator: Shang, Yajuan
System: The UNT Digital Library

Use of Fading Procedures and Positive Reinforcement to Increase Consumption of Non-Preferred Food in a Child with Autism

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Traditionally children with developmental disabilities who develop feeding issues can be at great risk for malnutrition. Failure to eat adequate amounts of food and/or insistence on eating a limited range of foods can be detrimental to a child's health and can lead to other behavioral difficulties. Feeding problems are difficult to treat because high levels of physical prompting can quickly create an aversion to eating as well as cause stress for both parents and children. Behavioral problems that range from moderate to extremely maladaptive can ensue. The question the present study addressed was whether or not a treatment package including only positive reinforcement and fading for a non-preferred food would result in independent eating of the targeted non-preferred food.
Date: May 2004
Creator: Vorpahl, Cresse Merchant
System: The UNT Digital Library

Culturing Vallisneria americana for Restoration Efforts

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Robust Vallisneria americana was cultured for restoration purposes. Preliminary studies, with various iron treatments, were conducted to ascertain the amount of phosphorous release into the water column from sediments. There was a significant difference in the amount of phosphorous released if commercial sediment was used with a low iron amendment or without an iron amendment. The second study consisted of planting V. americana on two different sediment types while supplying half of the plants with additional CO2. Plants grown on pond sediment with additional CO2 had significantly more biomass. In the third study all plants were grown on pond sediment, and half were treated with CO2. All plants that were treated with additional CO2 had significantly more biomass than those that were aerated.
Date: May 2004
Creator: Tanski, Erin M.
System: The UNT Digital Library

Key Components of a Comprehensive Visual Information System for College-Level Design Education Curriculum Analysis

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Electronic and computer technology have advanced and transformed graphic design. New technologies are forcing design educators to constantly monitor and update their programs, creating a need for a system to be adopted by college-level institutions to better investigate, evaluate and plan art and design curriculum. The author identifies metaphorical approaches to designing a two-part solution, which includes a Comprehensive Visual Information System (CVIS) and Three-Dimensional Virtual Database (3DVDb), which assign volumetric form to education components based on the form, structure and content of a discipline. Research and development of the conceptual design for the CVIS and 3DVDb are intended to aid in the development of an electronic media solution to be made accessible to students, faculty and administrators.
Date: May 2004
Creator: Short, Scott Allen
System: The UNT Digital Library

Exhaustivity, continuity, and strong additivity in topological Riesz spaces.

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In this paper, exhaustivity, continuity, and strong additivity are studied in the setting of topological Riesz spaces. Of particular interest is the link between strong additivity and exhaustive elements of Dedekind s-complete Banach lattices. There is a strong connection between the Diestel-Faires Theorem and the Meyer-Nieberg Lemma in this setting. Also, embedding properties of Banach lattices are linked to the notion of strong additivity. The Meyer-Nieberg Lemma is extended to the setting of topological Riesz spaces and uniform absolute continuity and uniformly exhaustive elements are studied in this setting. Counterexamples are provided to show that the Vitali-Hahn-Saks Theorem and the Brooks-Jewett Theorem cannot be extended to submeasures or to the setting of Banach lattices.
Date: May 2004
Creator: Muller, Kimberly O.
System: The UNT Digital Library

Instigating a Necessary Epiphany in Visual Message-Making for Design Educators and Future Communication Designers

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Man has used graphic signs and symbols to express a variety of thoughts and feelings since before the invention of writing; they have helped him to preserve the ideologies that have enabled him to articulate his conception of the world. Every culture in every historical era has invested the objects, animals and plants around it with a multitude of different psychological meanings to communicate its essential belief systems and social aspirations. In my document, I chose to shed light on the responsibility I believe design educators must assume regarding their ability to understand and teach the importance of how similar graphic signs, symbols, ideograms and icons are perceived differently by different cultures in the hyper-connected, inter-global economy of 21st century. It is very crucial not to discount the influence and correlation of symbolic, fundamental building blocks of design with the basic psychological functions that inform our subconscious, and are also informed by our individual social and cultural upbringings. People from different cultures may cognate these shapes similarly, but they perceive and encode their meanings based on their particular social and cultural influences. One-size-fits-all communication design solutions rarely work, especially when they are distributed to culturally diverse audiences, because various ethnic …
Date: May 2004
Creator: Sarkaria, Gagandeep
System: The UNT Digital Library

Effects of Thickness and Indenter Tip Geometry in Nanoindentation of Nickel Films

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Nanoindentation has become a widely used technique to measure the mechanical properties of materials. Due to its capability to deform materials in micro- and nano-scale, nanoindentation has found more applications in characterizing the deformation behavior and determining the mechanical properties of thin films and coatings. This research deals with the characterization of samples received from Center for Advanced Microstructures and Devices (CAMD) and Integran Technologies Inc., Toronto, Canada and the objective of this investigation was to utilize the experimental data obtained from nanoindentation to determine the deformation behavior, mechanical properties of thin films on substrates and bulk materials, and the effect of geometrically different indenters (Berkovich, cubecorner, and conical). X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) analysis were performed on these materials to determine the crystal orientation, grain size of the material, and also to measure any substrate effects like pile-up or sin-in respectively. The results indicate that indentation size effect (ISE) strongly depends on shape of the indenter and less sensitive to penetration depth where as the hardness measurements depends on shape of indenter and depth of penetration. There is a negligible strain rate dependency of hardness at deeper depths …
Date: May 2004
Creator: Parakala, Padma
System: The UNT Digital Library

Design of Power Amplifier Test Signals with a User-Defined Multisine

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Cellular radio communication involves wireless transmission and reception of signals at radio frequencies (RF). Base stations house equipment critical to the transmission and reception of signals. Power amplifier (PA) is a crucial element in base station assembly. PAs are expensive, take up space and dissipate heat. Of all the elements in the base station, it is difficult to design and operate a power amplifier. New designs of power amplifiers are constantly tested. One of the most important components required to perform this test successfully is a circuit simulator model of an entire communication system that generates a standard test signal. Standard test signals 524,288 data points in length require 1080 hours to complete one test of a PA model. In order to reduce the time taken to complete one test, a 'simulated test signal,' was generated. The objective of this study is to develop an algorithm to generate this 'simulated' test signal such that its characteristics match that of the 'standard' test signal.
Date: May 2004
Creator: Nagarajan, Preeti
System: The UNT Digital Library

The Relationship of Acculturation Stress and Leisure Satisfaction of Hispanic College Students

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Hispanics are the fastest growing minority group in the U.S. and signs indicate a similar trend in their college enrollment. Leisure activities are known to have a moderating effect on individuals experiencing stress in their lives. Hispanic organizations registered with a major 4-year metropolitan university were targeted. The hypothesis for this study was there is no relationship between acculturation stress and leisure satisfaction. Results indicate no relationship between acculturation stress and leisure satisfaction. One explanation for this lack of a significant relationship between these two measures might be that these college students had obtained a high level of acculturation, which would explain the relatively low level of acculturation stress reported.
Date: May 2004
Creator: Pacleb, Selverio V.
System: The UNT Digital Library

Spaces of Compact Operators

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In this dissertation we study the structure of spaces of operators, especially the space of all compact operators between two Banach spaces X and Y. Work by Kalton, Emmanuele, Bator and Lewis on the space of compact and weakly compact operators motivates much of this paper. Let L(X,Y) be the Banach space of all bounded linear operators between Banach spaces X and Y, K(X,Y) be the space of all compact operators, and W(X,Y) be the space of all weakly compact operators. We study problems related to the complementability of different operator ideals (the Banach space of all compact, weakly compact, completely continuous, resp. unconditionally converging) operators in the space of all bounded linear operators. The structure of Dunford-Pettis sets, strong Dunford-Pettis sets, and certain spaces of operators is studied in the context of the injective and projective tensor products of Banach spaces. Bibasic sequences are used to study relative norm compactness of strong Dunford-Pettis sets. Next, we use Dunford-Pettis sets to give sufficient conditions for K(X,Y) to contain c0.
Date: May 2004
Creator: Ghenciu, Ioana
System: The UNT Digital Library