Digital Commons Network^™

Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James

Physics Faculty Research & Creative Works

ErNi_5-xCo_x alloys were prepared by RF induction melting and analyzed using neutron powder diffraction. Rietveld analysis neutron diffraction data indicates the unit cell volume increases with Co content while the a and c lattice parameters show different dependencies on the composition. the Co atoms show higher affinity for the 3g sites than for the 2c sites. the Co sublattice tends to couple antiferromagnetically to the Er sublattice. the easy magnetization direction is along the c axis.

Neutron Investigations Of Novel Magnetic Phases, William B. Yelon

Physics Faculty Research & Creative Works

Recent years have seen a renewed search for Fe based permanent magnets, spurred by the discovery of Nd2Fe14B and interstitially modified rare-earth iron binaries. The insights derived from those compounds have suggested a number of routes to the development of such systems, including selective site substitution and combinations of site substitution and interstitial modification. Neutron diffraction is an essential component of this work, since it provides systematic information about the location of substitutional and interstitial atoms, and about the effects these changes have on the magnetic interactions in the systems of interest

A Diamond Thin Film Flow Sensor, Sacharia Albin, John C. Hagwood, John B. Cooper, David L. Gray, Scott D. Martinson, Michael A. Scott

Electrical & Computer Engineering Faculty Publications

We present the results of theoretical modeling and experimental testing of a diamond thin film sensor for flow studies. It is shown that the high thermal conductivity of a diamond film can enhance the frequency response of the flow sensor. One-dimensional heat diffusion equation was solved using the finite difference method for determining the frequency response. Two different sensor structures were analyzed: a Ni film on a quartz substrate (Ni/Q) and an intermediate layer of diamond film between the Ni film and quartz substrate (Ni/D/Q). The theoretical model predicts a frequency response for the Ni/D/Q sensor higher than that of …

Free Α-Oxiranyl Amino Acids, David B. Berkowitz, Michelle L. Pedersen

David Berkowitz Publications

Analogues of natural amino acids, in which the α-proton is replaced by an unsubstituted epoxide ring, are potential mechanism-based inhibitors for pyridoxal phosphate dependent enzymes.¹ Yet, free α-oxiranyl amino acids have remained elusive until now. The synthesis of an α-(phenyl-substituted)oxiranyl amino ester has been reported. However, the accessibility and stability of the corresponding free, zwitterionic α-oxiranyl amino acid remained an open question.⁹

Preparations Of Polycarbynes, Reuben D. Rieke

Department of Chemistry: Faculty Publications

Polycarbynes prepared from a soluble source of electrons and an organic monomer or co-monomer containing at least one carbyne group in an ethereal, polyethereal, or hydrocarbon solvent are presented. A wide variety of arylcarbyne and/or alkylcarbyne monomers and co-monomers can be combined with a source of electrons soluble in an ethereal, polyethereal, or hydro-carbon solvent to form novel polycarbyne polymers. These polycarbyne polymers can be used to form synthetic diamond materials, fibers, and other materials that can withstand extreme conditions.

Preparation Of Doped Polycarbynes, Reuben D. Rieke

Department of Chemistry: Faculty Publications

Polycarbynes, such as doped polycarbynes, prepared from a soluble source of electrons and an organic monomer or co-monomer containing at least one carbyne group and, optionally, containing a doping agent, in an ethereal, poly ethereal, or hydrocarbon solvent are presented. A wide variety of arylcarbyne and/or alkylcarbyne monomers and co-monomers can be combined with a source of electrons soluble in an ethereal, polyethereal, or hydrocarbon solvent to form novel polycarbyne polymers. These polycarbyne polymers can be used to form synthetic diamond materials, fibers, and other materials that can withstand extreme con ditions.

Baseline Water Quality Data Inventory And Analysis: Lake Mead National Recreation Area, Volume Ii Of Ii, National Park Service

Publications (WR)

This document presents the results of surface-water-quality data retrievals for Lake Mead National Recreation Area (LAME) from five of the United States Environmental Protection Agency's (EPA) national databases: (1) Storage and Retrieval (STORET) database management system; (2) River Reach File (RF3); (3) Industrial Facilities Discharge (IFD); (4) Drinking Water Supplies (DRINKS); and (5) Flow Gages (GAGES). This document is one product resulting from a cooperative contractual endeavor between the National Park Service's Servicewide Inventory and Monitoring Program, the National Park Service's Water Resources Division (WRD), and Horizon Systems Corporation to retrieve, format, and analyze water quality data for all units …

Baseline Water Quality Data Inventory And Analysis: Lake Mead National Recreation Area, Volume I Of Ii, National Park Service

Publications (WR)

This document presents the results of surface-water-quality data retrievals for Lake Mead National Recreation Area (LAME) from five of the United States Environmental Protection Agency's (EPA) national databases: (1) Storage and Retrieval (STORET) database management system; (2) River Reach File (RF3); (3) Industrial Facilities Discharge (IFD); (4) Drinking Water Supplies (DRINKS); and (5) Flow Gages (GAGES). This document is one product resulting from a cooperative contractual endeavor between the National Park Service's Servicewide Inventory and Monitoring Program, the National Park Service's Water Resources Division (WRD), and Horizon Systems Corporation to retrieve, format, and analyze water quality data for all units …

The Reaction Of Caffeic Acid And Copper (Ii) In Natural Water, Ling Xiaozheng Xu

Masters Theses

The interaction of the lignin precursor compound caffeic acid with copper(lI) in aqueous solution was studied. In the presence of a reducible transition metal, such as copper, caffeic acid undergoes oxidation. Oxygen was shown to play an important role in the reaction. The UV-visible data demonstrated that the conjugated double bond in the propenoic acid side chain of caffeic acid slowly disappeared during the reaction. The molecular weight experiments indicated that the product was a dimer. FTIR spectrum agreed with two possible dimer structures involving the side chain of caffeic acid. In addition, the reaction was shown to be reversible. …

Foam Flotation Enrichment Of Enantiomers, Daniel W. Armstrong, Eve Y. Zhou, Shushi Chen, Kang Le, Yubing Tang

Chemistry Faculty Research & Creative Works

Adsorptive bubble separation methods are known to be useful for processing large amounts of material at a relatively low cost These techniques have been used to enrich components from both heterogeneous and homogeneous solutions. There is a need for economical process-scale enantiomeric separations. Thus far there has been little evidence to support the feasibility of using an adsorptive bubble process to enrich enantiomers. We demonstrate that foam-forming chiral collectors can be used in conjunction with an inexpensive glass device to enantiomerically enrich some pharmaceutically important compounds as well as derivatized and underivatized amino acids. Factors that appeared to affect this …

Application Of Fractals And Kinetic Equation In Modelling Cluster And Ultrafine Particle Size Distributions, Joseph Chaiken, Jerry Goodisman

Chemistry - All Scholarship

We briefly describe a model which seems to be applicable to a variety of coalescence growth systems. Spanning cluster growth, particle growth and hillock formation in thin metal films, this model is based on the Smoluchowski kinetic equations and fractals. We describe how this model has been able to suggest the effect of translational to internal energy conversion in coalescing systems in determining the shape of particle size distributions. We also suggest how this model can be employed to account for the behavior of hillocks in supersaturated alloy films under thermal annealing conditions.

Semiclassical Quantization Of A Nonintegrable System: Pushing The Fourier Method Into The Chaotic Regime, Karl Sohlberg, Randall B. Shirts

Faculty Publications

Semiclassical Einstein–Brillouin–Keller (EBK) quantization of the nonintegrable Hénon–Heiles Hamiltonian succeeds using the Fourier transform method of Martens and Ezra. Two innovations are required for this success: (1) the use of tunneling corrected quantizing actions obtained from an approximate, one-dimensional Hamiltonian and (2) exploitation of intermediate-time approximate quasiperiodicity or "vague tori'' wherein the Fourier transform of chaotic motion over 10–100 vibrational periods allows the determination of frequencies and amplitudes which approximate motion during the time interval. Approximate tori, actions, and EBK energy levels are then straightforward. We use an interpolation method to smooth over small resonance zones that are not expected …

A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of The Nd₂Fe₁₇₋ₓalₓ Solid Solutions, Gary J. Long, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean

Chemistry Faculty Research & Creative Works

The magnetic properties of a series of Nd₂Fe_17-xAl_x solid solutions, with x equal to 2.04, 4.01, 5.97, 7.94, and 9.06, have been studied by magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. Magnetization studies indicate that the Curie temperature increases from 330 K in Nd₂Fe₁₇ to a maximum of ~470 K at an x of 3.5. The compounds crystallize in the Th₂Zn₁₇ structure with lattice parameters and unit cell volumes which increase linearly with increasing aluminum content. The neutron diffraction results indicate that aluminum atoms are excluded from the 9d …

Neutron Diffraction And Mössbauer Effect Study Of Several Nd₂Fe₁₇₋ₓalₓ Solid Solutions, William B. Yelon, H. Xie, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. J. Buschow

Physics Faculty Research & Creative Works

Aluminum-substituted Nd₂Fe_17-xAl_x solid solutions with x=2.30, 4.44, 6.13, 8.00, and 9.40 have been studied by neutron diffraction and Mössbauer spectroscopy. A Rietveld analysis of the neutron scattering indicates that the aluminum atoms have a high initial affinity for the 18h site, show a high affinity for the 6c site at high aluminum concentrations, and are absent from the 9d site at all aluminum concentrations. The Mössbauer spectra show a maximum in both the maximum and weighted average hyperfine field for x≅2. This indicates that the lattice expansion which occurs with aluminum substitution is sufficient, at …

A Study Of Euplotes Crassus Telomere Proteins And Related Genes, John Scott Perez

Department of Chemistry: Dissertations, Theses, and Student Research

A novel PCR technique used to amplify Euplotes crassus macronuclear chromosomes was developed to provide scientific proof that an Euplotes crassus 1.0 kb gene is not genetically related to an Oxytricha nova 1.8 kb β-telomere protein gene. Theories and experimental procedures associated with the development of this PCR technique were the product of research that will have a profound impact on future studies of telomere protein genes and telomeric DNA in a multitude of eukaryotic cells. The hypothesis that a β-telomere protein does not exist in Euplotes crassus was supported by the result of this study.

Expression of the recombinant …

Three-Body Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra

Chemistry Faculty Publications

Large basis set ab initio calculations have been carried out for a dense grid of points on the He, potential energy surface. Three-body contributions were extracted at every point, and a number of concise functional representations for the three-body potential surface were then examined. Three-body multipolar dispersion terms and other radial and angular terms were used in the representations, and an assessment of relative importance of the different terms is presented. Combined with a two-body He-He potential, the results of this work should offer a high quality interaction potential for simulations of aggregated helium.

Investigation Of New Methods For The Synthesis Of Pyrrolidines And The Generation Of Novel Heterocumulenes, Travis R. Taylor

Undergraduate Honors Capstone Projects

The following paper is a summary of the research completed from March to August of 1990. This research project proceeded through the guidance of Dr. Eric Edstrom incorporating a senior thesis in conjunction with the Honors Program.

Sensitivity Of Second Harmonic Generation To Space Charge Effects At Si(111)/Electrolyte And Si(111)/Sio2/Electrolyte Interfaces, P. R. Fischer, J. L. Daschbach, D. E. Gragson, G. L. Richmond

Chemistry and Biochemistry

The potential dependence in the surface second harmonic response from hydrogen terminated n‐Si(111) and oxidized n‐Si(111) surfaces has been examined in aqueous NH₄F and H₂SO₄ solutions. The relative phase of the nonlinear response as measured by rotational anisotropy experiments is found to be highly sensitive to the presence of the oxide and the field applied across the Si(111)/oxide/electrolyte interface. These observations are attributed to field effects within the space–charge region of the semiconductor which vary with the presence and thickness of the insulating oxide layer on the Si(111) surface.

Use Of An Oriented Transmembrane Protein To Probe The Assembly Of A Supported Phospholipid Bilayer, Paul Brian Contino, Carol A. Hasselbacher, J. B. Alexander Ross, Yale Nemerson

Chemistry and Biochemistry Faculty Publications

Planar-supported phopholipid bilayers formed by te adsorpton of vesicles are increasingly used in the investigation of lipK-ependent reactis. We have studied the way in which these bilayers are forned with phopholipid vesicles coaining the btranembrane protein Tssue Factor (TF). TF complexed with te senne protease, factor Vlla, is the primary initiator of bklod coagulation by way of activation of the zymogen factor X. TF has been shown to orient randomly on the inner and outer leaflets of vesicles. We used proteolytic digestion to produce vesicles in which the exracellular domain of TF is located on the inner leaflet These vesicles …

Chromium(Vi) Reduction By Ascorbate: Role Of Reactive Intermediates In Dna Damage In Vitro, D M. Stearns, K D. Courtney, P H. Giangrande, L S. Phieffer, Karen E. Wetterhahn

Dartmouth Scholarship

Reaction of chromium(VI) with one equivalent of ascorbate was studied by electron paramagnetic resonance spectroscopy in the presence of 0.10 M 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) at room temperature in 0.10 M (N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid]) (HEPES) and 0.05 M tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffers (pH 7.0 room temperature). Chromium(V), ascorbyl radical, and carbon-based DMPO-radical adducts were observed. A higher level of Cr(V) was observed in HEPES buffer and a higher level of the DMPO-radical adducts was observed in Tris-HCl buffer. Chromium-DNA binding studies were carried out in vitro for calf thymus DNA incubated with Cr(VI) and ascorbate in both buffers at 37 degrees C. Higher …

Exposure Of A Food Crop To Trichloroethylene From A Contaminated Aquifer, Richard G. Baringer

Theses and Dissertations

This research developed a methodology for assessment of the exposure of a mature corn crop to trichloroethylene from a contaminated aquifer. The methodology was then applied to the case of Hill AFB to determine the ability of the methodology to provide information about a specific exposure. Current procedures sample for food contamination but do not attempt to predict exposure problems. A review of the potential exposure pathways from the aquifer to the crop was conducted. Based on this review, the exposures due to soil gas and irrigation were modeled. Empirical estimated were used to approximate the expected flux of soil …

Modeling Trihalomethane Formation Potential From Wastewater Chlorination, Carol A. Mccormick

Theses and Dissertations

The deletion of federally mandated fecal coliform limits has led many states to review and modify their wastewater disinfection requirements. One issue in analyzing wastewater disinfection is the discharge of potentially carcinogenic halogenated organics formed during the chlorination process. This research investigates the formation of one class of the halogenated organics, the trihalomethanes. The applicability of using drinking water trihalomethane formation models for use with wastewater effluent is examined. Three models are compared for predictive capability by using measured trihalomethane values from previous research data. The results show that a previously developed model is applicable for use based on assumptions …

Tucson Intersection Study Of Automobile Emissions, Amber K. Hodgson, Yi Zhang, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

Neutron-Diffraction And Mössbauer Effect Study Of The Tb₂Fe₁₇₋ₓalₓ Solid Solutions, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Gary J. Long, Zhong Bo Hu, William B. Yelon, Fernande Grandjean, D. P. Middleton, K. H. J. Buschow

Physics Faculty Research & Creative Works

The magnetic properties of a series of Tb₂Fe_17-xAl_x solid solutions, with nominal x compositions of 0, 2, 3, 4, 5, 6, 7, and 8, have been studied by neutron diffraction and Mössbauer spectroscopy. Neutron-diffraction data indicate that the compounds all crystallize with the Th₂Zn₁₇ structure and that the aluminum atoms are excluded from the 9d site and show a distinct preference for the 6c site only for an aluminum content greater than 6. The unit-cell volume increases by approximately 1% per aluminum atom substituted in the formula unit. The magnetic moment per …

The Structure And Dynamics Of The Cs2 Molecular Ion, Karl Sohlberg, Chan Yibai

Faculty Publications

Several common elementary methods of computing molecular properties, prerequisite to molecular dynamics studies, are tested for their validity for CS+2. Judged sufficiently accurate, these methods are then used to aid in investigating the collisionally activated dissociation of CS+2 upon impact with xenon. Rice–Ramsperger–Kassel–Marcus (RRKM) unimolecular decay rate calculations are presented and compared to experimental studies employing collisional activation. RRKM theory is shown to reproduce the experimental results for collision energies near threshold. When corrected for vibrational anharmonicity, the RRKM calculation shows agreement with the experimental results over a slightly wider range of energies. A discussion is given on the applicability …

Careers In Chemical Information And Science Librarianship, Philip Barnett

Publications and Research

The ceaseless growth of chemical information has created a need for chemical professionals who can organize and disseminate this vast knowledge. If you like to read, enjoy being in a library, or like to work with information on computers, you may want to consider a career in chemical information. While only a small fraction of chemists choose this nontraditional career, they have found fulfillment in many different roles. Chemical information scientists and librarians using the powerful computerized databases now available either provide chemists and other research scientists the information they need, or teach researchers and students how to use these …

Studies In Fluorine Chemistry: 13c Nmr Investigation Of Sf5/So2f Fluorinated Systems, Yoon S. Choi

Dissertations and Theses

The purpose of this thesis was two fold: (i) The synthesis and characterization of SF5 containing dienes. (ii) The characterization of hydro/fluorocarbon compounds containing SF5/S02F groups via their 13C NMR spectra. A new SF5CH2CHBrCH2CF=CF2 was prepared and characterized as a precursor to new dielectric polymers. This new adduct was made from the reaction of pentafluorothio bromide with l,l,2-trifluoro-1,4-pentadiene. A SF5-diene was prepared from the reaction of pentafluorothio chloride with acetylene. This reaction involves a radical addition mechanism. The SF5 group is bonded to the carbon atom carrying the most hydrogens. SF5 - dienes are capable of undergoing different reactions, such …

Dissection Of An Antibody-Catalyzed Reaction, Jon D. Stewart, Joseph F. Krebs, Gary Siuzdak, Anthony J. Berdis, David B. Smithrud, Stephen J. Benkovic

Chemistry Faculty Publications

Antibody 43C9 accelerates the hydrolysis of a p-nitroanilide by a factor of 2.5 x 10(5) over the background rate in addition to catalyzing the hydrolysis of a series of aromatic esters. Since this represents one of the largest rate accelerations achieved with an antibody, we have undertaken a series of studies aimed at uncovering the catalytic mechanism of 43C9. The immunogen, a phosphonamidate, was designed to mimic the geometric and electronic characteristics of the tetrahedral intermediate that forms upon nucleophilic attack by hydroxide on the amide substrate. Further studies, however, revealed that the catalytic mechanism is more complex and involves …

Photoionization With Excitation Of The 4s And 4p Subshells In Krypton, Ahmad Farhat

Masters Theses

High-resolution photoelectron spectra of the nd, Rydberg satellites in krypton have been measured for the first time for six different angles and for photon energies between 68.5 and 250 eV. The relative intensities of these satellites with respect to the 4s and 4p main lines are in very good accord with the most recent measurements of Krause et al. (1992) at 68.5 eV. They also confirm that the theoretical predictions for the relative intensity of these satellites are too high. We determine the ratios for nd satellites with respect to the 4s and 4p main lines, and extract the angular …

36th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Program, abstracts, and information about the 36th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 31 - August 5, 1994.