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 Department: Department of Chemistry
 Collection: UNT Theses and Dissertations
Kinetics and Mechanism Study of Diphenylketene Cycloadditions

Kinetics and Mechanism Study of Diphenylketene Cycloadditions

Date: August 1967
Creator: O'Neal, Hubert Ronald
Description: From a review of the published work in the field of cycloadditions, it is evident that further research is needed to establish the mechanism of ketene cycloadditions. This work was initiated with the intent of obtaining kinetic data which will contribute to the elucidation of the mechanism of ketene cycloadditions.
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Kinetics and Mechanisms of Ligand Exchange Reactions of Chelate Complexes

Kinetics and Mechanisms of Ligand Exchange Reactions of Chelate Complexes

Date: May 1989
Creator: Cortés, José E. (José Enrique)
Description: Certain ligand substitution reactions proceed to a complete displacement of the chelate ligand. Certain reactions proceed through a mechanism involving an initial fission of the tungsten-sulfur bond to afford a coordinatively-unsaturated intermediate which is rapidly attacked by chlorobenzene. The resulting solvated intermediate establishes an equilibrium which involves desolvation-solvation. Although main group organometallic chemistry has received a great deal of attention, this discussion will be centered in organotransition metal chemistry, in particular, metal carbonyls.
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Kinetics and Mechanisms of Metal Carbonyls

Kinetics and Mechanisms of Metal Carbonyls

Date: May 1998
Creator: Ladogana, Santino
Description: Pulsed laser flash photolysis with both visible and infrared detection has been applied to the study of the displacement of weakly coordinating ligands (Lw) by strongly "trapping" nucleophiles (Ls) containing either an olefinic functionality (Ls = 1-hexene, 1-decene, 1-tetradecene) or nitrogen (Ls = acetonitrile, hydrocinnamonitrile) from the photogenerated 16 electron pentacarbonylchromium (0) intermediate. 5-Chloropent-l-ene (Cl-ol), a potentially bidentate ligand, has been shown to form (ol-Cl) pentacarbonylchromium (0), in which Cl-ol is bonded to Cr via a lone pair on the chlorine, and isomerize to (Cl-ol) pentacarbonylchromium (0), in which Cl-ol is bonded to the olefinic functionality on the submillisecond time scale. This process has been studied in both the infrared and visible region employing both fluorobenzene or n-heptane as the "inert" diluent. Parallel studies employing 1-chlorobutane and 1-hexene were also evaluated and showed great similiarity with the Cl-ol system. The data supported a largely dissociative process with a possibility of a small interchange process involving the H's on the alkyl chain. Studies were also carried out for various Cr(CO)6/arene/Ls systems (arene = various alkyl or halogenated substituted benzenes). The data indicated that for both C6H5R (R=various alkyl chains) or multi-alkyl substituted arenes (i.e. o-xylene, 1,2,3-trimethylbenzene) containing an "unhindered" ring-edge, bonding ...
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Kinetics and Thermochemistry of Halogenated Species

Kinetics and Thermochemistry of Halogenated Species

Date: May 1997
Creator: Misra, Ashutosh
Description: Gas phase kinetics and thermochemistry of several halogenated species relevant to atmospheric, combustion and plasma chemistry were studied using experimental and ab initio theoretical techniques.
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Kinetics of Reactions of Substituted Group VI B Metal Carbonyls with Phosphites

Kinetics of Reactions of Substituted Group VI B Metal Carbonyls with Phosphites

Date: August 1972
Creator: Rettenmaier, Albert J.
Description: The problem with which this investigation is concerned is twofold. The initial part of the problem was to prepare a non-sterically demanding bidentate phosphine ligand, 1,2-bis-(Phosphino)ethane, (P-en), and to determine the kinetics of (P-en)Mo(CO)4 with phosphites via spectrophotometric methods in an attempt to determine if steric effects are directing the type of mechanism followed.
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Kinetics of Sulfur: Experimental Study of the Reaction of Atomic Sulfur with Acetylene and Theoretical Study of the Cn + So Potential Energy Surface

Kinetics of Sulfur: Experimental Study of the Reaction of Atomic Sulfur with Acetylene and Theoretical Study of the Cn + So Potential Energy Surface

Date: May 2013
Creator: Ayling, Sean A.
Description: The kinetics of the reaction of atomic sulfur with acetylene (S (3P) + C2H2) were investigated experimentally via the flash photolysis resonance fluorescence method, and the theoretical potential energy surface for the reaction CN + SO was modeled via the density functional and configuration interaction computational methods. Sulfur is of interest in modern chemistry due to its relevance in combustion and atmospheric chemistry, in the Claus process, in soot and diamond-film formation and in astrochemistry. Experimental conditions ranged from 295 – 1015 K and 10 – 400 Torr of argon. Pressure-dependence was shown at all experimental temperatures. The room temperature high-pressure limit second order rate constant was (2.10 ± 0.08) × 10-13 cm3 molecule-1 s-1. The Arrhenius plot of the high-pressure limit rate constants gave an Ea of (11.34 ± 0.03) kJ mol-1 and a pre-exponential factor of (2.14 ± 0.19) × 10-11 cm3 molecule-1 s-1. S (3P) + C2H2 is likely an adduct forming reaction due to pressure-dependence (also supported by a statistical mechanics analysis) which involves intersystem crossing. The potential energy surface for CN + SO was calculated at the B3LYP/6-311G(d) level and refined at the QCISD/6-311G(d) level. The PES was compared to that of the analogous reaction ...
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Kinetics Studies of Substituted Tungsten Carbonyl Complexes

Kinetics Studies of Substituted Tungsten Carbonyl Complexes

Date: August 1989
Creator: Wang, I-Hsiung, 1950-
Description: Thermal reactions and flash photolysis are used to study the olefin bond-migration promoted by tungsten carbonyls. Substitution of piperidine (pip) by 2- allylphenyldiphenylphosphine (adpp) in the cis-(pip)(η^1- adpp)W(CO)-4 complex was investigated, and no olefin bond-migration was observed. This suggests that a vacant coordinated site adjacent to the coordinated olefin is an essential requirement for olefin bond rearrangement. The rates of olefin attack on the photogenerated coordinatively unsaturated species, cis-[(CB)(η^1-ol- P)W(CO)-4] (CB = chlorobenzene, p-ol = Ph-2P(CH-2)-3CH=CH-2; n = 1-4) were measured. Kinetics data obtained both in pure CB and in CB/cyclohexane mixtures support a dissociative mechanism in which the W-CB bond is broken in the transition state. In contrast to results observed in studies of other related systems, no olefin bond-migration is noted. This observation is attributed to P-W coordination at all stages of the reaction, which precludes formation of a reactive intermediate containing a vacant coordination site adjacent to a P-ol bond.
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Knowledge Discovery of Nanotube Mechanical Properties With an Informatics-Molecular Dynamics Approach

Knowledge Discovery of Nanotube Mechanical Properties With an Informatics-Molecular Dynamics Approach

Date: May 2012
Creator: Borders, Tammie L.
Description: Carbon nanotubes (CNT) have unparalleled mechanical properties, spanning several orders of magnitude over both length and time scales. Computational and experimental results vary greatly, partly due to the multitude of variables. Coupling physics-based molecular dynamics (MD) with informatics methodologies is proposed to navigate the large problem space. The adaptive intermolecular reactive empirical bond order (AIREBO) is used to model short range, long range and torsional interactions. A powerful approach that has not been used to study CNT mechanical properties is the derivation of descriptors and quantitative structure property relationships (QSPRs). For the study of defected single-walled CNTs (SWCNT), two descriptors were identified as critical: the density of non-sp2 hybridized carbons and the density of methyl groups functionalizing the surface. It is believed that both of these descriptors can be experimentally measured, paving the way for closed-loop computational-experimental development. Informatics can facilitate discovery of hidden knowledge. Further evaluation of the critical descriptors selected for Poisson’s ratio lead to the discovery that Poisson’s ratio has strain-varying nonlinear elastic behavior. CNT effectiveness in composites is based both on intrinsic mechanical properties and interfacial load transfer. In double-walled CNTs, inter-wall bonds are surface defects that decrease the intrinsic properties but also improve load transfer. ...
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Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Raman Spectroscopy Imaging of Biological Tissues

Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Raman Spectroscopy Imaging of Biological Tissues

Date: May 2016
Creator: Gorishek, Emma
Description: Laser Ablation Inductively coupled plasma mass spectrometry (LA-ICP-MS) and Raman spectroscopy are both powerful imaging techniques. Their applications are numerous and extremely potential in the field of biology. In order to improve upon LA-ICP-MS an in-house built cold cell was developed and its effectiveness studied by imaging Brassica napus seeds. To further apply LA-ICP-MS and Raman imaging to the field of entomology a prong gilled mayfly (Ephemeroptera: Leptophlebiidae) from the Róbalo River, located on Navarino Island in Chile, was studied. Analysis of both samples showcased LA-ICP-MS and Raman spectroscopy as effective instruments for imaging trace elements and larger molecules in biological samples respectively.
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Layered Double Hydroxides and the Origins of Life on Earth

Layered Double Hydroxides and the Origins of Life on Earth

Access: Use of this item is restricted to the UNT Community.
Date: May 2001
Creator: Brister, Brian
Description: A brief introduction to the current state of research in the Origins of Life field is given in Part I of this work. Part II covers original research performed by the author and co-workers. Layered Double Hydroxide (LDH) systems are anion-exchanging clays that have the general formula M(II)xM(III)(OH)(2x+2)Y, where M(II) and M(III) are any divalent and trivalent metals, respectively. Y can be nearly any anion, although modern naturally occuring LDH systems incorporate carbonate (CO32-), chloride (Cl-), or sulfate (SO42-) anions. Intercalated cobalticyanide anion shows a small yet observable deviation from local Oh symmetry causing small differences between its oriented and non-oriented infrared spectra. Nitroprusside is shown to intercalate into 2:1 Mg:Al LDH with decomposition to form intercalated ferrocyanide and nitrosyl groups of an unidentified nature. The [Ru(CN)6]4- anion is shown to intercalate into layered double hydroxides in the same manner as other hexacyano anions, such as ferrocyanide and cobalticyanide, with its three-fold rotational axis perpendicular to the hydroxide sheets. The square-planar tetracyano-nickelate(II), -palladate(II), and platinate(II) anions were intercalated into both 2:1 and 3:1 Mg:Al layered double hydroxides (LDH). The basal spacings in the 2:1 hosts are approximately 11 Å, indicating that the anions are inclined approximately 75 degrees relative to ...
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Layered Double Hydroxides as Anion- and Cation-Exchanging Materials

Layered Double Hydroxides as Anion- and Cation-Exchanging Materials

Date: May 2007
Creator: Richardson, Mickey Charles
Description: Layered double hydroxides (LDH) have been principally known as anion-exchanging, clay-like materials for several decades, and continues to be the main driving force for current and future research. The chemical interactions of LDH, with transition metallocyanides, have been a popular topic of investigation for many years, partly due to the use of powder x-ray diffraction and infrared spectroscopy as the main characterization tools. Each transition metallocyanide has a characteristic infrared stretching frequency that can be easily observed, and their respective sizes can be observed while intercalated within the interlayer of the LDH. The ability of LDH to incorporate metal cations or any ions/molecules/complexes, that have a postive charge, have not been previously investigated, mainly due to the chemical and physical nature of LDH. The possibility of cationic incorporation with LDH would most likely occur by surface adsorption, lattice metal replacement, or by intercalation into the LDH interlayers. Although infrared spectroscopy finds it main use through the identification of the anions incorporated with LDH, it can also be used to study and identify the various active and inactive bending and stretching modes that the metal hydroxide layers have.
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Layered Double Hydroxides: Morphology, Interlayer Anion, and the Origins of Life

Layered Double Hydroxides: Morphology, Interlayer Anion, and the Origins of Life

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Date: December 2002
Creator: Halcom-Yarberry, Faith Marie
Description: The preparation of layered double hydroxides via co-precipitation of a divalent/trivalent metal solution against a base results in 1 mm LDH particles with a disorganized metal lattice. Research was performed to address these morphological issues using techniques such as Ostwald ripening and precipitation via aluminate. Another interesting issue in layered double hydroxide materials is the uptake and orientation of anions into the interlayer. Questions about iron cyanide interlayer anions have been posed. Fourier transform infared spectroscopy and powder x-ray diffraction have been used to investigate these topics. It was found that factors such as orientation, anion charge, and anion structure depended on the divalent/trivalent metal ratio of the hydroxide layer and reactivity time. The cyanide self-addition reaction is an important reaction of classical prebiotic chemistry. This reaction has been shown to give rise to amino acids, purines and pyrimidines. At cyanide concentrations similar to that expected on the early earth, hydrolysis to formamide rather than self-addition occurs. One theory to alleviate this side reaction is the use of minerals or clays that are thought to concentrate and catalyze prebiotics of interest. Layered double hydroxides have been studied as a catalyst for this reaction.
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Layered Double Hydroxides: Synthesis, Characterization, and Interaction of Mg-Al Systems with Intercalated Tetracyanonickelate(II)

Layered Double Hydroxides: Synthesis, Characterization, and Interaction of Mg-Al Systems with Intercalated Tetracyanonickelate(II)

Date: August 2004
Creator: Brister, Fang Wei
Description: The square-planar tetracyanonickelate(II) anion was intercalated into 2:1 and 3:1 Mg-Al layered double hydroxide systems (LDHs). In the 2:1 material, the anion holds itself at an angle of about 30° to the layers, whereas in the 3:1 material it lies more or less parallel to the layers. This is confirmed by orientation effects in the infrared spectra of the intercalated materials and by X-ray diffraction (XRD) data. The measured basal spacings for the intercalated LDH hosts are approximately 11 Å for the 2:1 and approximately 8 Å for the 3:1. The IR of the 2:1 material shows a slight splitting in the ν(CN) peak, which is suppressed in that compound's oriented IR spectrum, indicating that at least some of the intercalated anion's polarization is along the z-axis. This effect is not seen in the 3:1 material. A comparison between chloride LDHs and nitrate LDHs was made with respect to intercalation of tetracyanonickelate(II) anions. Both XRD data and atomic absorption spectroscopy (AAS) data of the LDH tetracyanonickelates confirms that there are no significant differences between the products from the two types of starting materials. The presence of a weak ν(NO) peak in the IR spectra of those samples made from nitrate ...
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Ligand Substitution Studies in the Tetracobalt Cluster Co₄(CO)₁₀([mu]₄-PPh₂) and Synthesis and Reactivity Studies in the Fe₂Pt and FeCo₂ Mixed-metal Clusters

Ligand Substitution Studies in the Tetracobalt Cluster Co₄(CO)₁₀([mu]₄-PPh₂) and Synthesis and Reactivity Studies in the Fe₂Pt and FeCo₂ Mixed-metal Clusters

Date: August 1991
Creator: Don, Ming-jaw
Description: The kinetics of ligand substitution for CO in Co4(CO)10(mu4-PPh2) , 1, have been investigated for the ligands P(OMe)3, P(OEt)3, PPh2H, P(0-i-Pr)3, P(n-Bu)3, PPh3, P(i-Pr)3, and PCy3 over a wide temperature range.
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The Light Sensitivity of some Nitrogen-containing Furfural Derivatives

The Light Sensitivity of some Nitrogen-containing Furfural Derivatives

Date: 1940
Creator: Tittle, Charles William
Description: This study describes the creation of various furfural derivatives and their respective light sensitivity.
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Lipidomic Analysis of Single Cells and Organelles Using Nanomanipulation Coupled to Mass Spectrometry

Lipidomic Analysis of Single Cells and Organelles Using Nanomanipulation Coupled to Mass Spectrometry

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Date: May 2016
Creator: Bowman, Amanda
Description: The capability to characterize disease states by way of determining novel biomarkers has led to a high demand of single cell and organelle analytical methodologies due to the unexpected heterogeneity present in cells of the same type. Lipids are of particular interest in the search for biomarkers due to their active roles in cellular metabolism and energy storage. Analyzing localized lipid chemistry from individual cells and organelles is challenging however, due to low analyte volume, limited discriminate instrumentation, and common requirements of separation procedures and expenditure of cell sample. Using nanomanipulation in combination with mass spectrometry, individual cells and organelles can be extracted from tissues and cultures in vitro to determine if heterogeneity at the cellular level is present. The discriminate extraction of a single cell or organelle allows the remainder of cell culture or tissue to remain intact, while the high sensitivity and chemical specificity of mass spectrometry provides structural information for limited volumes without the need for chromatographic separation. Mass analysis of lipids extracted from individual cells can be carried out in multiple mass spectrometry platforms through direct-inject mass spectrometry using nanoelectrospray-ionization and through matrix-assisted laser/desorption ionization.
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Magnetic Exchange in Oxovanadium(IV) Complexes with N-Salicylideneamino Acids

Magnetic Exchange in Oxovanadium(IV) Complexes with N-Salicylideneamino Acids

Date: January 1968
Creator: Hu, James Hung-Jen
Description: Copper(II) and oxovanadium(IV) ions resemble one another magnetically in having one unpaired electron in their complexes irrespective of their geometrical structures and bond types involved. Copper(II) complexes with antiferromagnetic exchange are well known. On the contrary, antiferromagnetic exchange in oxovanadium(IV) complexes is rather new and not well established. Very few oxovanadium(IV) complexes have been reported to have this anomalous magnetic property. In the investigation of the magnetic properties of oxovanadium(IV) complexes, we have successfully prepared two series of new oxovanadium(IV) complexes with N-salicylideneamino acids.
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Magnetic Properties of Copper (II) Complexes of N-(Hydroxyalkyl) Pyrrole-2-Aldimines

Magnetic Properties of Copper (II) Complexes of N-(Hydroxyalkyl) Pyrrole-2-Aldimines

Date: December 1973
Creator: Pauley, Charles Richard
Description: In this work magnetic properties of copper(II) complexes on N-(hydroxyalkyl) pyrrole-2-aldimines were investigated by various techniques, one of which was magnetic susceptibility. Magnetic moments are not directly determined experimentally, but magnetic susceptibilities are.
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Magnetic Properties of Copper (II) Complexes of Schiff Bases

Magnetic Properties of Copper (II) Complexes of Schiff Bases

Date: August 1975
Creator: Jones, William James
Description: The synthesis and characterization of two new Schiff base copper(II) complexes are reported. These are Cu(acac: 2-amino-l-phenylethanol) and Cu(acac:2-amino-l-butanol). The ligands, derived from acetylacetone and the appropriate aminoalcohol, are dibasic tridentates with 0,N,O donor atoms. The magnetic properties of the complexes were studied at several temperatures between 78 OK and 296 OK. The magnetic moment of Cu(acac:2-amino-l-phenylethanol) varied little with temperature, and that of Cu(acac:2-amino-lbutanol) increased as the temperature was lowered. This is in contrast to the magnetic moment of Cu(acac:ethanolamine), which decreases as the temperature decreases. Molecular weight data, infrared spectra, magnetic data, electronic spectra, and electron spin resonance spectra of both complexes are reported and discussed.
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Magnetic Properties of Metal(II) Schiff Base Complexes

Magnetic Properties of Metal(II) Schiff Base Complexes

Date: May 1976
Creator: Hines, Mary Katherine
Description: Ligands prepared from various combinations of aldehydes and ketones with the appropriate aminealcohol were complexed with cupric acetate monohydrate. The complexes with O,NO or N,N,O donor atoms were synthesized to study the influences of the ligand on molecular structure, spin-spin interaction, and on the value of the exchange integral. The magnetic data indicated that of the eight Cu(II) complexes discussed, two behaved differently from known analogous compounds. Cu (benzoylacetone :ethanolamine) was compared to Cu(acac:ethanolamine), and Cu(pyrr:oaminophenol) was compared to Cu(acac:o-aminophenol). Each pair of complexes was postulated to have the same molecular structure. The synthesis and characterization of Mn(pyrr:oaminophenol) 2H2 is also discussed. The following physical data were collected and discussed: elemental analysis, melting point, molecular weight, infrared spectra, electronic spectra, and magnetic susceptibility.
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Magnetic Properties of Oxovanadium(IV) Complexes of Substituted N-(Hydroxylalkyl) Salicylideneimines

Magnetic Properties of Oxovanadium(IV) Complexes of Substituted N-(Hydroxylalkyl) Salicylideneimines

Date: May 1972
Creator: Carey, Elbert Franklin
Description: A series of oxovanadium(IV) complexes of Schiff bases derived from substituted salicylaldehyde and aminoalcohols has been prepared and characterized. The Schiff bases coordinate through 0, N, and 0 as tridentate bivalent ligands. The primary purpose of the investigation is to describe the structure and bonding in these complexes. The subnormal magnetic properties of the complexes provide much information about both the structure and the bonding in the complexes.
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Manufacturer [Sic] of Densified-Refuse Derived Fuel (d-RDF) Pellets and Methods for the Determination of d-RDF Pellet Densities

Manufacturer [Sic] of Densified-Refuse Derived Fuel (d-RDF) Pellets and Methods for the Determination of d-RDF Pellet Densities

Date: December 1986
Creator: Attili, Bassam Saleem
Description: There are 150 million tons of Municipal Solid Waste (MSW) annually produced in the United States, which is approximately equivalent to 150 million barrels of oil. MSW production is inexhaustible, and is increasing on an annual per capita basis of approximately three per cent. After controlling the moisture and adding a binder, the combustible portion of MSW was converted to pellets. The objects of this project were to 1) evaluate the binder, 2) prepare the pellets, and 3) evaluate the pellets with regard to density. The manufacture of pellets was conducted at the Naval Air Station, Jacksonville, Florida. The evaluation of the binders and the pellets was done at North Texas State University (NTSU). There were three procedures for measuring the density. The first, using water displacement, was from the American Society for Testing and Material (ASTM). The second, using wax coating, was also from ASTM. The third, using sharply-cut cylindrical pellets, was developed at NTSU.
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A Materials Approach to Silicon Wafer Level Contamination Issues from the Wet Clean Process

A Materials Approach to Silicon Wafer Level Contamination Issues from the Wet Clean Process

Date: December 1996
Creator: Hall, Lindsey H. (Lindsey Harrison)
Description: Semiconductor devices are built using hyperpure silicon and very controlled levels of doping to create desired electrical properties. Contamination can alter these precisely controlled electrical properties that can render the device non-functional or unreliable. It is desirable to determine what impurities impact the device and control them. This study consists of four parts: a) determination of acceptable SCI (Standard Clean 1) bath contamination levels using VPD-DSE-GFAAS (Vapor Phase Decomposition Droplet Surface Etching Graphite Furnace Atomic Absorption Spectroscopy), b) copper deposition from various aqueous HF solutions, c) anion contamination from fluoropolymers used in chemical handling and d) metallic contamination from fluoropolymers and polyethylene used in chemical handling. A technique was developed for the determination of metals on a silicon wafer source at low levels. These levels were then correlated to contamination levels in a SCI bath. This correlation permits the determination of maximum permissible solution contaminant levels. Copper contamination is a concern for depositing on the wafer surface from hydrofluoric acid solutions. The relationship between copper concentration on the wafer surface and hydrofluoric acid concentration was determined. An inverse relationship exists and was explained by differences in diffusion rates between the differing copper species existing in aqueous hydrofluoric acid solutions. Finally, ...
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The Mechanisms of Human Glutathione Synthetase and Related Non-Enyzmatic Catalysis

The Mechanisms of Human Glutathione Synthetase and Related Non-Enyzmatic Catalysis

Date: May 2015
Creator: Ingle, Brandall L.
Description: Human glutathione synthetase (hGS) is a homodimeric enzymes that catalyzes the second step in the biological synthesis of glutathione, a critical cellular antioxidant. The enzyme exhibits negative cooperativity towards the γ-glutamylcysteine (γ-GC) substrate. In this type of allosteric regulation, the binding of γ-GC at one active site significantly reduces substrate affinity at a second active site over 40 Å away. The presented work explores protein-protein interactions, substrate binding, and allosteric communication through investigation of three regions of hGS: the dimer interface, the S-loop, and the E-loop. Strong electrostatic interactions across the dimer interface of hGS maintain the appropriate tertiary and quaternary enzymatic structure needed for activity. The S-loop and E-loop of hGS form walls of the active site near γ-GC, with some residues serving to bind and position the negatively cooperative substrate. These strong interactions in the active site serve as a trigger for allosteric communication, which then passes through hydrophobic interactions at the interface. A comprehensive computational and experimental approach relates hGS structure with activity and regulation. ATP-grasp enzymes, including hGS, utilize ATP in the nucleophilic attack of a carboxylic acid in a reaction thought to proceed through the formation of an acylphosphate intermediate. Small metal cations are known ...
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