Physical Sciences and Mathematics Commons^™

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 …

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.

Characterization Of Surface Structure And Interactions By Polarization Modulation Fitr And The Quartz Crystal Microbalance, Mark Anderson, Minhui Zhang

Mark R. Anderson

No abstract is currently available.

Xith Symposium On Cationic Polymerization And Related Ionic Processes, Otto Vogl, Ivan M. Panayotov, Christo B. Tsvetanov

Otto Vogl

No abstract provided.

Polymer Science In Australia Ii. Brisbane And Queensland, Otto Vogl, James H. O'Donnell, David J. T. Hill

Otto Vogl

No abstract provided.

Studies Toward Understanding The Relationship Between Structure And Function Of Modified Electrodes, Mark Anderson

Mark R. Anderson

No abstract is available at this time.

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.

Participation Of The Β Phosphonate Group In Carbocation Formation, Joseph B. Lambert, Robert W. Embridge, Yan Zhao

Yan Zhao

Diethyl (2-(tosyloxy)cyclohexyl)phosphonates have been prepared to test the hypothesis that the strongly electron-withdrawing phosphonate group can stabilize the formation of a /3 carbocation through hyperconjugation. Systems were constructed with the 180" dihedral angle between phosphonate and tosyloxy that is optimal for such participation and with the 60" dihedral angle that minimizes it. Reactions were carried out in aqueous mixtures of ethanol, trifluoroethanol, and hexafluoro-2-propanol. The 60" case had the standard profile for bimolecular reaction with solvent (kB),w ith a slower rate that is sensitive to solvent nucleophilicity. The 180" case had the standard profile for a carbocation pathway (kc), with …

9th Bratislava Conference On Modification Of Thermoplastic Polymers, Otto Vogl, Lyda Matisova-Rychla

Otto Vogl

No abstract provided.

Polymer Science In Australia Iii. Csiro And Other Government Institutions, Otto Vogl, Ezio Rizzardo, Carolyn Morris

Otto Vogl

No abstract provided.

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 …

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 …

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 …

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 …

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 …

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 …

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 …

Two-Fragment Correlation Functions With Directional Cuts For Central 36ar + 197au Collisions At E/A=50 Mev, T. Glasmacher, L. Phair, D. R. Bowman, C. K. Gelbke, W. G. Gong, Y. D. Kim, M. A. Lisa, W. G. Lynch, Graham F. Peaslee, R. T. De Souza, M. B. Tsang, F. Zhu

Faculty Publications

Two-fragment correlation functions observed in central collisions of Ar36+197Au at E/A=50 MeV are compared to many-body trajectory calculations. For the present reaction, ambiguities between source size and lifetime can be reduced by employing directional emission cuts and describing observed differences between longitudinal and transverse correlation functions. For fragments emitted above the Coulomb barrier, E/A≥6 MeV, many-body Coulomb-trajectory calculations with a surface emission model indicate emission from an extended source of short lifetime.

Two-Proton Correlation Functions For 36ar + 45sc At E/A=80 Mev, D. O. Handzy, M. A. Lisa, C. K. Gelbke, W. Bauer, F. C. Decowski, W. G. Gong, E. Gualtieri, S. Hannuschke, R. Lacey, T. Li, W. G. Lynch, C. M. Mader, Graham F. Peaslee, T. Reposeur, S. Pratt, A. M. Vander Molen, G. D. Westfall, J. Yee, S. J. Yennello

Faculty Publications

Impact-parameter filtered longitudinal and transverse two-proton correlation functions measured for 36Ar+ 45Sc collisions at E/A=80 MeV are compared to predictions of the BUU transport model. For a cut on large transverse energies, the overall trends of the measured correlated functions are rather well reproduced by calculations for central collisions. Systematic discrepancies become visible, however, for calculations with larger impact parameters.

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 …

Investigation Of The Charge Transfer Properties Of Electrodes Modified By The Spontaneous Adsorption Of Unsymmetrical Dialkyl Sulfides, Minhui Zhang, Mark Anderson

Mark R. Anderson

Electrodes modified by the spontaneous adsorption of unsymmetrical dialkyl sulfides are used to investigate two monolayer properties, structural disorder and solvent compatibility, that may be of importance in determining the ability for faradaic charge transport to occur in the presence of the monolayer. Two groups of dialkyl sulfides are prepared and studied: a purely hydrocarbon dialkyl sulfide with the structure CH3(CH2)17S(CH2)nCH3, where n, = 7,9, and 17, and an acid containing dialkyl sulfide with the structure CH3(CH2)17S(CH2)mCOOH, where m = 7, 10, and 15. Reflection infrared spectroscopy of the hydrocarbon dialkyl sulfide reveals that the monolayer structure is disordered, when …

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.

The Relationship Between Structure And Function Of Modified Interfaces, Mark Anderson

Mark R. Anderson

No abstract is available at this time.

Surface-Induced Ordering In Asymmetric Block Copolymers, Y. Liu, W. Zhao, X. Zheng, Alexander H. King, A. Sing, M. H. Rafailovich, J. Sokolov, K. H. Dai, E. J. Kramer, S. A. Schwarz, O. Gebizlioglu, S. K. Sinha

Alexander H. King

The surface-induced ordering in thin films of asymmetric deuterated polystyrene (dPS)- poly(viny1pyridine) (PVP) diblock and triblock copolymers of comparable polymerization index and PVP volume fraction - 0.25) was studied using transmission electron microscopy, atomic force microscopy, secondary ion massspectrometry, and neutron reflectivity. The morphology of both di- and triblock copolymer films was found to be cylindrical except for the layer adjacent to the silicon oxide surface, which due to the strong interaction of silica with PVP, was lamellar. The spacing between adjacent cylindrical layers was found to be consistent with mean field theory predictions. In the triblock copolymer films the …

A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of Nd₂Fe₁₅Ga₂ And The Tb₂Fe₁₇₋ₓgaₓ Solid Solutions, Zhong Bo Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean

Physics Faculty Research & Creative Works

An x-ray diffraction study of the substitution of gallium in Tb ₂Fe₁₇ to form the Tb₂Fe_17-xGa_x solid solutions indicates that the compounds adopt the rhombohedral Th₂Zn₁₇ structure. The unit cell volume and the a-axis lattice parameter increase linearly with increasing gallium content. The c-axis lattice parameter increases linearly from x=0 to 6 and then decreases between x=7 and 8. Magnetic studies show the Curie temperature increases by ~150° above that of Tb₂Fe₁₇ to reach a maximum between x=3 and 4, and then decreases with further increases in …

Axial Asymmetry In The Nuclear Magnetic Resonance Spectra Of Deuterated Methyl Groups: An Alternative Explanation, Mieng-Hua Wann, Gerard S. Harbison

Gerard Harbison Publications

The deuterium nuclear magnetic resonance (NMR) powder spectra of methyl groups at ambient temperatures are invariably averaged by rotation or hopping about the C₃ axis. The canonical result for a perfectly threefold symmetric methyl is an axially symmetric Pake doublet whose splitting, in the case of perfect tetrahedral angles around the group, is averaged by a factor of exactly three. However, deuterium NMR spectra of methyl groups are often somewhat axially asymmetric, indicating a significant deviation either of the methyl group, or of its environment, from threefold symmetry. Previous explanations for this phenomenon have hinged on either an additional …

Analysis Of The Potential For Plant Uptake Of Trichloroethylene And An Assessment Of The Relative Risk From Different Crop Types, Roy-Alan C. Agustin

Theses and Dissertations

This research expands our limited knowledge on the influence of plants on the fate and effects of trichloroethylene (TCE), providing a screening tool on which to base decisions regarding the need for actual sampling of plants. First, physicochemical properties of TCE--vapor pressure, Henry's Law constant, water solubility, octanol-water partition coefficient, molecular weight, and half-life--were screened against relationships reported in literature to evaluate TCE plant uptake potential. This screening approach indicated TCE may be transferred to plants via retention by root surfaces, root uptake and translocation, and foliar uptake. Next, the PLANTX model developed by Trapp and others was applied to …

Determination Of Pancreatic And Salivary Amylase By Enzyme Immunoassay And Their Prevalence In Hyperamylasemic Patients, Sabdra Borgens Ward

Theses and Dissertations in Biomedical Sciences

Currently, amylase determinations are nonspecific for the organ source and are based entirely on the enzymatic properties of amylase to produce a measurable product or byproduct. The determination of pancreatic amylase is important in the diagnosis of acute pancreatitis. Most commercially available tests for amylase employ the measurement of the change in NADH absorbance at 280 nm or of the p-nitrophenol released from a maltotetrose substrate. These are nonspecific measurements of pancreatic amylase and often necessitate other tests to be run such as a serum lipase.

The two predominant isoenzymes of amylase are pancreatic (p-amylase) and salivary (s-amylase); the most …