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Substituent Effects: A Computational Study on Stabilities of Cumulenes and Low Barrier Hydrogen Bonds

Substituent Effects: A Computational Study on Stabilities of Cumulenes and Low Barrier Hydrogen Bonds

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Date: August 2000
Creator: Kumar, Ganesh Angusamy
Description: The effect of substituents on the stabilities of cumulenes-ketenes, allenes, diazomethanes and isocyanates and related systems-alkynes, nitriles and nitrile oxides is studied using the density functional theory (B3LYP, SVWN and BP86) and ab initio (HF, MP2) calculations at the 6-31G* basis set level. Using isodesmic reactions, correlation between stabilization energies of cumulenes and substituent group electronegativities (c BE) is established and the results from DFT and MP2 methods are compared with the earlier HF calculations. Calculations revealed that the density functional methods can be used to study the effect of substituents on the stabilities of cumulenes. It is observed that the cumulenes are stabilized by electropositive substituent groups from s -electron donation and p -electron withdrawal and are destabilized by electronegative substituent groups from n-p donation. The calculated geometries of the cumulenes are compared with the available experimental data.High level ab initio and density functional theory calculations have been used to study the energetics of low-barrier hydrogen bond (LBHB) systems. Using substituted formic acid-formate anion complexes as model LBHB systems, hydrogen bond strength is correlated to the pKa mismatch between the hydrogen bond donor and the hydrogen bond acceptor. LBHB model systems are characterized by the 1H-NMR chemical shift calculations. ...
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Supercritical Silylation and Stability of Silyl Groups

Supercritical Silylation and Stability of Silyl Groups

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Date: May 2006
Creator: Nerusu, Pawan Kumar
Description: Methylsilsesquioxane (MSQ) and organosilicate glass (OSG) are the materials under this study because they exhibit the dielectric constant values necessary for future IC technology requirements. Obtaining a low-k dielectric value is critical for the IC industry in order to cope time delay and cross talking issues. These materials exhibit attractive dielectric value, but there are problems replacing conventional SiO2, because of their chemical, mechanical and electrical instability after plasma processing. Several techniques have been suggested to mitigate process damage but supercritical silylation offers a rapid single repair step solution to this problem. Different ash and etch damaged samples were employed in this study to optimize an effective method to repair the low-k dielectric material and seal the surface pores via supercritical fluid processing with various trialkylchlorosilanes. Fourier transform infrared spectroscopy (FTIR), contact angle, capacitance- voltage measurements, and x-ray photoemission spectroscopy, dynamic secondary ion mass spectroscopy (DSIMS), characterized the films. The hydrophobicity and dielectric constant after exposure to elevated temperatures and ambient conditions were monitored and shown to be stable. The samples were treated with a series of silylating agents of the form R3-Si-Cl where R is an alkyl groups (e.g. ethyl, propyl, isopropyl). Reactivity with the surface hydroxyls was inversely ...
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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

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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Date: May 2004
Creator: Scott, Deb
Description: 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.
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Suppressive effects of a stimulus correlated with reprimands for automatically-maintained eye poking.

Suppressive effects of a stimulus correlated with reprimands for automatically-maintained eye poking.

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Date: May 2003
Creator: McKenzie, Scott Daniel
Description: A functional analysis, conducted to assess the variables maintaining the chronic eye poking of a female diagnosed with profound mental retardation, indicated that the behavior persisted in the absence of social contingencies. A procedure was initiated in a training environment in which a punisher (mild reprimand) was delivered contingent on eye poking in the presence, but not in the absence, of a neutral stimulus (wristbands). Using a combination of multiple baseline and multielement experimental designs, it was determined that that eye poking was suppressed in the presence of the previously neutral stimulus, even in environments in which the reprimand contingency was inoperative.
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Surface Plasmon Based Nanophotonic Optical Emitters

Surface Plasmon Based Nanophotonic Optical Emitters

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Date: December 2005
Creator: Vemuri, Padma Rekha
Description: Group- III nitride based semiconductors have emerged as the leading material for short wavelength optoelectronic devices. The InGaN alloy system forms a continuous and direct bandgap semiconductor spanning ultraviolet (UV) to blue/green wavelengths. An ideal and highly efficient light-emitting device can be designed by enhancing the spontaneous emission rate. This thesis deals with the design and fabrication of a visible light-emitting device using GaN/InGaN single quantum well (SQW) system with enhanced spontaneous emission. To increase the emission efficiency, layers of different metals, usually noble metals like silver, gold and aluminum are deposited on GaN/InGaN SQWs using metal evaporator. Surface characterization of metal-coated GaN/InGaN SQW samples was carried out using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Photoluminescence is used as a tool for optical characterization to study the enhancement in the light emitting structures. This thesis also compares characteristics of different metals on GaN/InGaN SQW system thus allowing selection of the most appropriate material for a particular application. It was found out that photons from the light emitter couple more to the surface plasmons if the bandgap of former is close to the surface plasmon resonant energy of particular metal. Absorption of light due to gold reduces the ...
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Surface Topography and Aesthetics of Recycled Cross-Linked Polyethylene Wire and Cable Coatings

Surface Topography and Aesthetics of Recycled Cross-Linked Polyethylene Wire and Cable Coatings

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Date: December 2014
Creator: Xie, Wa
Description: Our research focuses on re-using a waste a material, cross-linked polyethylene abbreviated XLPE, which is a widely used coating for wires. XLPE is strong and has excellent thermal properties due to its chemical structure - what leads to the significance of recycling this valuable polymer. Properties of XLPE include good resistance to heat, resistance to chemical corrosion, and high impact strength. A wire is usually composed of a metal core conductor and polymeric coating layers. One creates a new coating, including little pieces of recycled XLPE in the lower layer adjacent to the wire, and virgin XLPE only in the upper layer. Industries are often wasting materials which might be useful. Mostly, some returned or excess products could be recycled to create a new type of product or enable the original use. This method helps cleaning the waste, lowers the costs, and enhances the income of the manufacturing company. With the changing of the thickness of the outer layer, the roughness changes significantly. Moreover, different processing methods result in surfaces that look differently.
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Survey of Texas Public Universities and University Systems Involvement in State Public Policy Making

Survey of Texas Public Universities and University Systems Involvement in State Public Policy Making

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Date: August 2004
Creator: Wolf, David Fletcher
Description: This study investigated the perceptions of influential relationships between Texas public university presidents, university system chancellors, and state legislators. The study's purpose was to examine Texas public universities engagement in lobbying type behaviors and whether public policy is affected through interaction and communication with legislative leaders. Moreover, of importance for this study was to identifying if Texas public universities actively work to influence the Texas legislature and if lobbying behavior exists whether or not that behavior influences public policy formation within the Texas legislative process. Lastly, this study focused on perceptions dealing with the Texas statute prohibiting state governmental agencies, including public universities and university systems, from influencing legislation through use of state funds. The study was conducted in the winter of 2003 and had 29 president / chancellor respondents and 88 legislator respondents. Three survey instruments were developed by the researcher to determine Texas public university president, system chancellor, and state legislator perceptions and attitudes concerning lobbying type activities, influence, and state statute compliance. Data reported consist of percentages, t-Test of significance, and Cohen's d effect size measure. Results from the study show agreement between the groups in areas of activities utilized to influence the legislative process and actual ...
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The Symbolic Representation of Latinos: A Content Analysis of Prime-Time Television

The Symbolic Representation of Latinos: A Content Analysis of Prime-Time Television

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Date: August 2001
Creator: McKenzie-Elliott, Tracey M.
Description: The media are powerful agents of socialization in modern society influencing values, beliefs, and attitudes of the culture that produces them. Both the quantity and quality of Latino images in the media may reflect and reinforce the place of Latinos in United States society. This study examines how Latinos are portrayed in television entertainment programming by addressing two major research questions: 1) What is the extent of Latino recognition on prime-time television? and 2) What is the extent of respect accorded Latinos on prime-time television? A one-week sample of prime-time television programming airing on three networks yielded 47 programs and 807 characters for analysis. Using content analysis methodology, recognition is identified by examining the frequency and proportional representation of Latino television portrayals and respect is measured by examining the types and significance of these roles. The results indicate an overall lack of diversity on prime-time television with only 11 of the 47 programs analyzed reaching 50% or more of the maximum possible diversity in their racial and ethnic portrayals. Specifically, Latinos represent only 3% of primetime television characters, less than one-fourth of their proportion of the nation's population. Compared to non-Hispanic Whites, Blacks, and Asians, Latinos are the group least ...
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Symmetrical Features of Nikolai Medtner's Language: The Grzovaya Sonata, Opus 53 No. 2

Symmetrical Features of Nikolai Medtner's Language: The Grzovaya Sonata, Opus 53 No. 2

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Date: December 1999
Creator: Pitts, James L.
Description: Nikolai Medtner's works evidence an intense interest in symmetrical designs. This concern is manifest at all levels, from the large scale proportions of his numerous ingenious sonata forms to the symmetrically constructed themes and motives. Medtner's works include several instances of palindromic themes and periods. Some palindromic contours are achieved through immediate inversion, creating expansive, symmetrical waves. One of Medtner's thumbprints, symmetrical contrary voice-leading, consists of two or more voices which systematically expand or contract in exact mirror fashion. The contrary movement is usually stepwise, and may be either chromatic or diatonic. Occasionally even larger intervals, such as thirds and fourths, are subjected to this favourite mirroring technique. Such symmetrical expansion and contraction often controls the harmonic progression of several consecutive bars. One of the most striking aspects of Medtner's music is his sophisticated harmonic language. He was fascinated with symmetrical harmonic designs, such as the tritone, the French sixth chord, and the octatonic scale, and made endless and increasingly intricate explorations into these stuctures and the ways in which these apparently nontonal, non-hierarchical forms could be coordinated with the fundamental hierarchy of asymmetrical tonal forms, including triads, major and minor scales, and tonic-dominant relations. Medtner's late work, the Grozovaya ...
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Synchrotron Radiation X-Ray Diffraction of Nickel-Titanium Shape Memory Alloy Wires during Mechanical Deformation

Synchrotron Radiation X-Ray Diffraction of Nickel-Titanium Shape Memory Alloy Wires during Mechanical Deformation

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Date: December 2015
Creator: Zhang, Baozhuo
Description: Shape memory alloys (SMAs) are a new generation material which exhibits unique nonlinear deformations due to a phase transformation which allows it to return to its original shape after removal of stress or a change in temperature. It shows a shape memory effect (martensitic condition) and pseudoelasticity (austenitic condition) properties depends on various heat treatment conditions. The reason for these properties depends on phase transformation through temperature changes or applied stress. Many technological applications of austenite SMAs involve cyclical mechanical loading and unloading in order to take advantage of pseudoelasticity, but are limited due to poor fatigue life. In this thesis, I investigated two important mechanical feature to fatigue behavior in pseudoelastic NiTi SMA wires using high energy synchrotron radiation X-ray diffraction (SR-XRD). The first of these involved simple bending and the second of these involved relaxation during compression loading. Differential scanning calorimetry (DSC) was performed to identify the phase transformation temperatures. Scanning electron microscopy (SEM) images were collected for the initial condition of the NiTi SMA wires and during simple bending, SEM revealed that micro-cracks in compression regions of the wire propagate with increasing bend angle, while tensile regions tend to not exhibit crack propagation. SR-XRD patterns were analyzed ...
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