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in subjects: "Structural Chemical Analysis"

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Structural characterization of a polymer substituted fullerene (flagellene) by small angle neutron scattering

Small-angle neutron scattering (SANS) can structurally characterize fullerenes in solvents with strong SANS contrast (e.g. CS{sub 2}). Deuterated solvents (e.g. toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60} and C{sub 70} moieties. Hence, there is virtually no SANS contrast with the solvent and these particles are practically ``invisible`` in such media. On the other hand, the negative scattering length of hydrogen means that the SLD of H{sup … more

Date: December 31, 1994

Creator: Affholter, K. A.; Bunick, G. J.; Wignall, G. D.; Desimone, J. M.; Hunt, M. O., Jr.; Menceloglu, Y. Z. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Conformational Diversity in (Octaethylporphinato) (trichloroacetato)iron(III) Derivatives

Treatment of [Fe(OEP)]20 with trichloroacetic acid results in ruffled formation of (octaethylporphinato trichloroacetato)iron(HI). Various crystalline solvates can be isolated, depending on the crystallization solvent. Initial crystallization with CHC13/hexanes resulted in the isolation of an unsolvated form. [Fe(OEP)(02C2C13 )]. This form contains distinct porphyrin core conformations at the same site: one is domed and the other is ruffled. Crystal data for [Fe(OEP)(02C2C13 )]: Q = 14.734(4) .… more

Date: October 19, 1998

Creator: Cheng, B.; Ma, J.; Neal, T.J.; Scheidt, W.R.; Schulz, C.E. & Shelnutt, J.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The role of recycle oil in direct coal liquefaction process development

It has long been recognized that use of a recycle oil is a convenient and perhaps necessary feature of a practical direct coal liquefaction process. The recycle oil performs a number of important functions. It serves as a vehicle to convey coal into the liquefaction reactor and products from the reactor. It is a medium for mass and heat transfer among the solid, liquid, and gaseous components of the reactor inventory. It can act as a reactant or intermediate in the liquefaction process. Therefo… more

Date: August 1, 1995

Creator: Burke, F. P.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Photoelectron holography applied to surface structural determination

Photoemitted electron waves are used as coherent source waves for angstrom-scale holographic imaging of local atomic geometry at surfaces. Electron angular distribution patterns are collected above a sample surface and serve as a record of the interference between source wave and waves scattered from surrounding ion cores. Using a mathematical imaging integral transformation, the three-dimensional structural information is obtained directly from these collected patterns. Patterns measured with … more

Date: May 1, 1995

Creator: Petersen, B.L.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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Characterization of coal/waste coprocessing samples from HRI Run POC-2

Coal and waste materials (plastics and rubber) were co-liquefied during Run POC-2 in HRI`s 3 T/D direct liquefaction process development unit under the DOE sponsored Proof-of-Concept program. Analytical characterizations were conducted of well-defined samples from representative periods of the run to provide information on the chemical transformation of these feedstocks and their distribution in product and recycle streams. The characteristics of the products and process streams were dependent … more

Date: August 1, 1995

Creator: Robbins, G.A.; Winschel, R.A. & Burke, F.P.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

In this study, oriented Photosystem II (PS II) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy (XAS) to determine more details of the structure of the oxygen evolving complex (OEC). The nature of halide binding to Mn is also studied with Cl K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-Cl model compounds, and with Mn EXAFS of oriented PS II in which Br has replaced Cl. Attention is focused on the… more

Date: August 1, 1995

Creator: Andrews, J.C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Characterization of carbon nitride films produced by pulsed laser deposition

Carbon Nitride (CN{sub x}) films have been grown by ion-assisted pulsed-laser deposition (IAPLD). Graphite targets were laser ablated while bombarding the substrate with ions from a broad-beam Kaufman-type ion source. Ion voltage, current density, substrate temperature, and feed gas composition (N{sub 2} in Ar) were varied. Resultant films were characterized by Raman. Fourier transform infrared (FTIR), and Rutherford back scattering (RBS) spectroscopy. Samples with {approximately} 30% N/C ratio… more

Date: July 1, 1995

Creator: Friedmann, T. A.; Tallant, D. R.; Barbour, J. C.; Sullivan, J. P.; Siegal, M. P.; Simpson, R. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Spectroscopic studies of U(VI) sorption at the kaolinite-water interface. Final report

Efficient use of U as a resource and safe handling, recycling and disposal of U-containing wastes require an understanding of the factors controlling the fate of U, where fate refers to the destination of U, typically expressed as an environmental medium or a process phase. The sorption process constitutes a change in elemental fate. Partitioning of an element from solution to a solid phase, or sorption, can be divided into three broad categories: adsorption, surface precipitation, and absorpti… more

Date: June 1, 1994

Creator: Thompson, Hillary A.; Parks, George A. & Brown, Gordon E., Jr.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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A characterization and evaluation of coal liquefaction process streams. Status assessment

A review of the literature dealing with the modeling of fossil-fuel resid conversion to product oils and an updated assessment of the physico-chemical analytical methodology applicable to coal-liquefaction product streams is presented in this document. Analytical methodologies included here are either those which are different than those previously surveyed or are improvements on, or significantly different applications of methods previously surveyed. The literature cited spans the time period … more

Date: July 1, 1995

Creator: Brandes, S. D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Mitigating crosslinking reactions through preconversion strategies. Final report

The primary objective of this project was to determine the effect of reductive pretreatments of low-rank coals through the use of electron-transfer agents. This potential was explored in laboratory studies through determination of the impact on the evolution of oxygen functions, crosslinking, and conversion. The pretreatments explored include treatment with CO/water/base and hydroquinones or other electron-transfer agents in various combinations. The effects of these pretreatments on functional… more

Date: July 1, 1994

Creator: McMillen, D.F. & Malhotra, R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Temperature Effects on Chemical Structure and Motion in Coal. Quarterly Report, April--June, 1995

As described in previous reports, the effects of moderate temperatures (up to 230 C) is to increase molecular/macromolecular mobility in coals, as determined by {sup 1}H CRAMPS (Combined Rotation And Multiple Pulse Spectroscopy) measurements, especially dipolar-dephasing experiments. Pyridine-saturated coals have also been studied with the same kinds of NMR experiments. The author found that thermal activation and solvent saturation promote the molecular mobility of coals in quite different way… more

Date: June 30, 1995

Creator: Maciel, G.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Neutron scattering characterization of homopolymers and graft-copolymer micelles in supercritical carbon dioxide

Supercritical fluids are becoming an attractive alternative to the liquid solvents traditionally used as polymerization media. As the synthesis proceeds, a wide range of colloidal aggregates form, but there has hitherto been no way to measure such structures directly. We have applied small-angle neutron scattering (SANS) to characterize such systems, and although SCF polymerizations are carried out at high pressures, the penetrating power of the neutron beam means that typical cell windows are … more

Date: December 1995

Creator: Chillura-Martino, D.; Triolo, R. & McClain, J. B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Biological sources for phenylalkane hydrocarbons

Linear alkylbenzenes (phenylalkanes) represent an important class of molecular compounds used widely in today`s society as building blocks for detergent manufacture. Evidence is presented to support the proposition in that phenylalkanes in some Australian crude oils and sediments are of geochemical origin rather than resulting from contamination from byproducts of the petrochemical synthesis of surfactants. Evidence presented shows: (1) an unexposed sediment core was found to contain phenylalka… more

Date: August 1, 1996

Creator: Ellis, L.; Winans, R.E. & Langworthy, T.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Refining and end use study of coal liquids. Quarterly report, July-- September 1995

Bechtel, with Southwest Research Institute, Amoco Oil R&D, and the M.W. Kellogg Co. as subcontractors, initiated a study on November 1, 1993, for the US Department of Energy`s (DOE`s) Pittsburgh Energy Technology Center (PETC) to determine the most cost effective and suitable combination of existing petroleum refinery processes needed to make specification transportation fuels or blending stocks, from direct and indirect coal liquefaction product liquids. A key objective is to determine the mos… more

Date: December 31, 1995

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Direct experimental determination of the atomic structure at internal interfaces

A crucial first step in understanding the effect that internal interfaces have on the properties of materials is the ability to determine the atomic structure at the interface. As interfaces can contain atomic disorder, dislocations, segregated impurities and interphases, sensitivity to all of these features is essential for complete experimental characterization. By combining Z-contrast imaging and electron energy loss spectroscopy (EELS) in a dedicated scanning transmission electron microscop… more

Date: July 1, 1995

Creator: Browning, N. D. & Pennycook, S. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Diffraction anomalous fine structure analysis on (Bi,Pb){sub 2}PtO{sub 4} powders

The Diffraction Anomalous Fine Structure (DAFS) method can provide site selective and chemical selective structural information. The possibilities of DAFS experimental and data analysis procedures are demonstrated for (Bi{sub 1.67},Pb{sub 0.33}) powder samples. Experiments have been performed at both L{sub III} and K Pt edges (11.56.564keV and 78keV), using several data collection set-ups (analyser crystals, 1D-detector, 2D-detector). Based on this example, a comparison between these experiment… more

Date: December 31, 1995

Creator: Vacinova, J.; Hodeau, J.L. & Bordet, P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Characterization of polyxylylenes with solid state {sup 13}C nuclear magnetic resonance spectroscopy

Polyxylylenes are thermoplastics used as encapsulants for electronic devices. Five polyxylylenes were prepared by pyrolysis of [2.2]paracyclophanes and characterized by solid state {sup 13}C NMR spectroscopy. The chemical shift data, in combination with interrupted decoupling experiments, allowed assignment of resonances to their carbon sources in the polymers. This confirmed the integrity of the xylylene building block in the polymers and is consistent with linear polymers. No crosslinking cou… more

Date: February 1, 1996

Creator: Loy, D. A.; Assink, R. A.; Jamison, G. M.; McNamara, W. F.; Schneider, D. A. & Prabakar, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Structural elucidation of Argonne premium coals: Molecular weights, heteroatom distributions and linkages between clusters

The objective of this study is to create a statistically accurate picture of important structural features for a group of coals representing a broad rank range. Mass spectrometric techniques are used to study coals, coal extracts and chemically modified coals and extracts. Laser desorption mass spectrometry is used to determine molecular weight distributions. Desorption chemical ionization high resolution mass spectrometry provides detailed molecular information on compound classes of molecules… more

Date: December 31, 1995

Creator: Winans, R. E.; Kim, Y.; Hunt, J. E. & McBeth, R. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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EXAFS studies of lanthanide coordination in crystalline phosphates and amorphous phytates

As part of the DOE Efficient Separations and Processing Integrated Program, techniques are being developed to stabilize radioactive and hazardous contaminants to prevent their migration from buried wastes. This report is part of a study to immobilize actinide ions in the near-surface environment by reacting them with organophosphorus complexants that decompose to phosphates. Nd and Gd ions were used as models for Pu, Am, and Cm ions; phytic acid was used as the complexant. Solid Nd and Gd phyta… more

Date: December 31, 1995

Creator: Morss, L. R.; Schmidt, M. A. J. & Nash, K. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Angle-resolved photoemission extended fine structure study of chemisorbed c(2{times}2)P/Fe(100): Comparison with self-consistent- field X{alpha} scattered wave calculations

Angle-resolved photoemission extended fine structure (ARPEFS) was used to determine the structure of c(2x2)P/Fe(100). P 1s core-level photoemission data were collected normal to the (100) surface and 45{degree} off-normal along the [011] direction at room temperature. Close analysis of the auto-regressive linear prediction based Fourier transform and multiple-scattering spherical-wave calculations indicate that the P atoms adsorb in the high-coordination fourfold hollow sites. The P atoms bond … more

Date: February 1, 1996

Creator: Huff, W.R.A.; Chen, Y. & Zhang, X.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The chemical constitution of Pocahontas No. 3 coal

A new method for the definition of the larger aromatic structural elements in high-rank coals has been developed. The procedure involves the oxidative decom-position of the coal with oxygen in basic solution and the subsequent decarboxylation of the aromatic arboxylic acids to yield a mixture of aromatic compounds that can readily be analyzed by conventional methods. This approach has been tested with pure compounds and applied to Pocahontas No. 3 coal.

Date: December 31, 1995

Creator: Stock, L.M. & Obeng, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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X-ray spectroscopy of manganese clusters

Much of this thesis represents the groundwork necessary in order to probe Mn clusters more productively than with conventional Mn K-edge XAS and is presented in Part 1. Part 2 contains the application of x-ray techniques to Mn metalloproteins and includes a prognosis at the end of each chapter. Individual Mn oxidation states are more readily distinguishable in Mn L-edge spectra. An empirical mixed valence simulation routine for determining the average Mn oxidation state has been developed. The … more

Date: June 1, 1996

Creator: Grush, M. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Intense Pulsed Neutron Source: Progress report 1991--1996. 15. Anniversary edition -- Volume 2

The 15th Anniversary Edition of the IPNS Progress Report is being published in recognition of the Intense Pulsed Neutron Source`s first 15 years of successful operation as a user facility. To emphasize the importance of this milestone, the author shave made the design and organization of the report significantly different from previous IPNS Progress Reports. This report consists of two volumes. For Volume 1, authors were asked to prepare articles that highlighted recent scientific accomplishmen… more

Date: May 1, 1996

Item Type: Report

Partner: UNT Libraries Government Documents Department

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The in-situ generation of silica reinforcement in modified polydimethylsiloxane elastomers

Structure and properties of a series of modified polydimethylsiloxane (PDMS) elastomers reinforced by {ital in situ} generated silic particles were investigated. The PDMS elastomer was modified by systematically varying the molecular weight between reactive groups incorporated into the backbone. Tetraethoxysilane (TEOS) and partial hydrolyzate of TEOS were used to generate silic particles. Chemistry and phase structure of the materials were investigated by {sup 29}Si magic angle spinning nuclea… more

Date: June 1, 1996

Creator: Prabakar, S; Bates, S.E.; Black, E.P. & Ulibarri, T.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department