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Missouri University of Science and Technology

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Articles 811 - 840 of 1553

Full-Text Articles in Chemistry

Structural And Magnetic Properties Of La Mn₁₋ₓfeₓo₃ (0 < X < 1.0), X.-D. Zhou, L. R. Pederson, Qingsheng Cai, Jinbo Yang, B. J. Scarfino, M. Kim, William B. Yelon, William Joseph James, Harlan U. Anderson, C. Wang Apr 2006

Structural And Magnetic Properties Of La Mn₁₋ₓfeₓo₃ (0 < X < 1.0), X.-D. Zhou, L. R. Pederson, Qingsheng Cai, Jinbo Yang, B. J. Scarfino, M. Kim, William B. Yelon, William Joseph James, Harlan U. Anderson, C. Wang

Materials Science and Engineering Faculty Research & Creative Works

Electronic, structural, and magnetic properties of Mn-doped lanthanum ferrites were studied by neutron diffraction, superconducting quantum interference device, and impedance spectroscopy. Neutron diffraction refinements were performed with the constraint of full La occupancy, which showed the presence of excess oxygen when x < 0.4. Mixed valent Mn cations and cation vacancies, therefore, exist in all the samples. The samples with x > 0.7 are magnetically ordered at room temperature with orthorhombic symmetry (Pbnm). When x < 0.3 the structure is rhombohedral and magnetically disordered above 16 K. The majority carriers, electron holes, correspond to high oxidation states of Mn. The carrier concentration is determined from the Seebeck coefficients, and is a function of temperature and Fe concentration. The measurements of conductivity and Seebeck coefficients show polaron hopping at elevated temperatures.

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Macrocyclic Antibiotics As Separation Agents, Daniel W. Armstrong Mar 2006

Macrocyclic Antibiotics As Separation Agents, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

Macrocyclic antibiotics having ring structures with at least 10 members act as separation agents in crystallization, precipitation, filtration, electrophoresis, and chromatography. The macrocyclic antibiotics include ansamacrolides, macrolides, macrocyclic peptides, polyenes and derivatives thereof. The process has been found to be especially advantageous for separation of optical isomers by electrophoresis and chromatography.

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Nanometal Containing Nanocomposites And Photolithographic Polyaniline Nanofibers, Frank D. Blum, Sunil K. Pillalamarri, Lalani K. Werake, J. Greg Story, Massimo F. Bertino, Akira Tokuhiro Mar 2006

Nanometal Containing Nanocomposites And Photolithographic Polyaniline Nanofibers, Frank D. Blum, Sunil K. Pillalamarri, Lalani K. Werake, J. Greg Story, Massimo F. Bertino, Akira Tokuhiro

Chemistry Faculty Research & Creative Works

A report on recent progress from our laboratories on the nanostructures produced from novel synthesis techniques will be discussed. Using high-energy radiation (γ-rays) we have been able to produce conducting polymer nanofibers and nanorods of polyaniline and polypyrrole without the use of a separate template or capping agent. This technique has been extended, with the addition of metal ions, to a "one pot" synthesis, producing conducting nanocomposites. These nanocomposites contain metal nanoparticles which decorate the conducting nanofibers. We have also recently shown that these systems can be photopatterned to produce novel structures. We believe that these systems will be useful …

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Reliable Electron Affinities Of Perfluorocyclopropane And Perfluorocyclobutane From Convergent Ab Initio Computations, Adel M. Elsohly, Macey L. Renault, Gregory S. Tschumper Feb 2006

Reliable Electron Affinities Of Perfluorocyclopropane And Perfluorocyclobutane From Convergent Ab Initio Computations, Adel M. Elsohly, Macey L. Renault, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

To resolve discrepancies concerning the magnitude of the electron affinities of perfluoro cyclopropane and perfluorocyclobutane, quantum chemical calculations have been carried out with the MP2 and CCSD(T), methods in conjunction with augmented correlation consistent basis sets (aug-cc-pVX Z, X = D, T, Q). Though no experimental values have been found for perfluoro cyclopropane, we estimate its electron affinity to be 0.17 eV (0.00 eV without zero-point vibrational energy corrections). In addition, determination of the electron affinity of perfluorocyclobutane (0.61 and 0.44 eV with and without zero-point vibrational energy corrections, respectively) is in good agreement with experimental values reported by Miller …

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(±)-1-Methyl-1,3,6-Triphenyl-7-(2-Phenylpropenyl)-1, 2-Dihydronaphthalene, Yongqiang Sui, Charles Leslie Barnes, Rainer Glaser Feb 2006

(±)-1-Methyl-1,3,6-Triphenyl-7-(2-Phenylpropenyl)-1, 2-Dihydronaphthalene, Yongqiang Sui, Charles Leslie Barnes, Rainer Glaser

Chemistry Faculty Research & Creative Works

The crystal structure of the title compound, C38H32, presents a novel framework that combines the functionalities of a 1,6-diarene-substituted 1,2-dihydronaphthalene (DHN) with a 1,4-distyrylbenzene (DSB) to form a crossed bis-diarene. The lamellar crystal structure is held together by arene-arene interactions. While the orientations of the phenyl rings of the DSB units alternate within both the R and the S substructures, the homochiral substructures feature opposing polarity along the long axes of the DHN-based diarenes.

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Electrochemical Deposition And Characterization Of Fe₃O₄ Films Produced By The Reduction Of Fe(Iii)-Triethanolamine, Hiten M. Kothari, Elizabeth A. Kulp, Steven J. Limmer, Philippe Poizot, Eric W. Bohannan, Jay A. Switzer Jan 2006

Electrochemical Deposition And Characterization Of Fe₃O₄ Films Produced By The Reduction Of Fe(Iii)-Triethanolamine, Hiten M. Kothari, Elizabeth A. Kulp, Steven J. Limmer, Philippe Poizot, Eric W. Bohannan, Jay A. Switzer

Chemistry Faculty Research & Creative Works

In this paper, we demonstrate that films of magnetite, Fe3O4, can be deposited by the electrochemical reduction of a Fe(III)-triethanolamine complex in aqueous alkaline solution. the films were deposited with a columnar microstructure and a [100] preferred orientation on stainless steel substrates. In-plane electrical transport and magnetoresistance measurements were performed on the films after they were stripped off onto glass substrates. the resistance of the films was dependent on the oxygen partial pressure. We attribute the increase in resistance in O2 and the decrease in resistance in Ar to the oxidation and reduction of grain …

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Acid-Catalyzed Time-Efficient Synthesis Of Resorcinol-Formaldehyde Aerogels And Crosslinking With Isocyanates, Sudhir Mulik, Chariklia Sotiriou-Leventis, Nicholas Leventis Jan 2006

Acid-Catalyzed Time-Efficient Synthesis Of Resorcinol-Formaldehyde Aerogels And Crosslinking With Isocyanates, Sudhir Mulik, Chariklia Sotiriou-Leventis, Nicholas Leventis

Chemistry Faculty Research & Creative Works

Aerogels are open-cell foams derived from supercritical fluid (SCF) drying of wet gels. Their large internal void space is responsible for low thermal conductivity, high surface area and high acoustic impedance. Most aerogels are based on inorganic metal or semimetal oxide frameworks. Pekala and co-workers synthesized resorcinol-formaldehyde (RF) organic aerogels by poly-condensation of resorcinol with formaldehyde in the presence of Na2CO3 as base catalyst, followed by drying with SCF CO2. Low-density RF aerogels prepared by this method exhibit high porosities (>80%), high surface areas (400-900 m2g-1), ultrafine cell-size (<500 > Å) …

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Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum Jan 2006

Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum

Chemistry Faculty Research & Creative Works

For a polymer film deposited on a surface, the strength of the surfacesegment interaction affects the mobility of polymer-chain segments. The selfconsistent field lattice model of Scheutjens and Fleer,1 based on mean-field lattice models of polymer at interfaces,2 has been used to describe the distribution of conformations of polymers on surfaces. Adsorbed-polymer segments may be classified as belonging to loops, trains or tails. There are different techniques used to study the molecular motion of the polymer including modulated differential scanning calorimetry (MDSC)3 and nuclear magnetic resonance (NMR).4,5 in this work, solid-state deuterium (2H) NMR was used to characterize the polymer …

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Segmental Dynamics In Poly(Methyl Acrylate) On Silica: Molecular-Mass Effects, Burak Metin, Frank D. Blum Jan 2006

Segmental Dynamics In Poly(Methyl Acrylate) On Silica: Molecular-Mass Effects, Burak Metin, Frank D. Blum

Chemistry Faculty Research & Creative Works

The effect of molecular mass on the segmental dynamics of poly(methyl acrylate) (PMA) adsorbed on silica was studied using deuterium quadrupole-echo nuclear magnetic resonance (NMR) and modulated differential scanning calorimetry. Samples adsorbed on silica (all about 1.5 mg PMA/m2 silica) were shown to have more restricted segmental mobility, and higher Tg's, than the corresponding bulk PMA samples. Around the glass-transition region, adsorbed samples exhibited segmental mobility, which could be classified as heterogeneous due to a superposition of more-mobile and less-mobile components present in the deuterium NMR spectra. This heterogeneity was consistent with a motional gradient with more-mobile segments near the …

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Segmental Dynamics Of Poly(Vinyl Acetate)- D₃ Absorbed On Silica By Solid State 2hnmr: Effect Of Small Molecule Plasticizer, Rakesh R. Nambiar, Frank D. Blum Jan 2006

Segmental Dynamics Of Poly(Vinyl Acetate)- D₃ Absorbed On Silica By Solid State 2hnmr: Effect Of Small Molecule Plasticizer, Rakesh R. Nambiar, Frank D. Blum

Chemistry Faculty Research & Creative Works

There has been significant progress in understanding the behavior of polymeric thin films on surfaces. The change in the apparent glass transition temperature (Tg) of supported thin polymer films with thickness (Tg -nanoconfinement effect) has been widely studied over the last fifteen years. While many studies focused on the thickness dependence of Tg, there are other aspects which are important to understand in a nanoconfined polymer system. For example, polymeric photoresists contain small-molecule photoactive compounds, plasticizers, and processing aids. These components interact with the polymer chains and affect the segmental mobility, which, in turn, affects the Tg - nanoconfinement effect. …

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Effect Of Processing Conditions On Chemical Makeup Of Di-Isocyanate Crosslinked Silica Aerogels, Mary Ann B. Meador, Nicholas Leventis, Lynn A. Capadona, Plousia Vassilaras Jan 2006

Effect Of Processing Conditions On Chemical Makeup Of Di-Isocyanate Crosslinked Silica Aerogels, Mary Ann B. Meador, Nicholas Leventis, Lynn A. Capadona, Plousia Vassilaras

Chemistry Faculty Research & Creative Works

Sol-gel derived silica aerogels are attractive candidates for many unique thermal, optical, catalytic, and chemical applications1 because of their low density and high mesoporosity. However, their inherent fragility has restricted their use to, for example, insulation in extreme temperature environments such as Mars. We have previously reported crosslinking the mesoporous silica structure of an aerogel with di-isocyanates reacted with silanols on the surface,2,3 or epoxies reacting with an amine decorated silica surface.4 Either approach has been shown to significantly increase the strength of the aerogel with only a small effect on density or porosity. Thus, these hybrid materials may be …

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Molecular Mass And Dynamics Of Poly(Methyl Acrylate) In The Glass Transition Region, Burak Metin, Frank D. Blum Jan 2006

Molecular Mass And Dynamics Of Poly(Methyl Acrylate) In The Glass Transition Region, Burak Metin, Frank D. Blum

Chemistry Faculty Research & Creative Works

The segmental dynamics of bulk poly(methyl acrylate) (PMA) were studied as a function of molecular mass in the glass-transition region using 2H NMR and modulated differential scanning calorimetry (MDSC). Quadrupole-echo 2H NMR spectra were obtained for four samples of methyl-deuterated PMA-d3 with different molecular masses. The resulting spectra were fit using superpositions of simulated spectra generated from the MXQET simulation program, based on a model incorporating nearest-neighbor jumps from positions on the vertices of a truncated icosahedron (soccer-ball shape). The lower molecular-mass samples, influenced by the presence of more chain ends, showed more heterogeneity (broader distribution) and lower glass transitions …

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A Comparative Study Of The Properties Of Polar And Nonpolar Solvent/Solute/Polystyrene Solutions In Microwave Fields Via Molecular Dynamics, Mark J. Purdue, Macduff O. Okuom, Frank D. Blum, James M. D. Macelroy, D. F. O'Shea Jan 2006

A Comparative Study Of The Properties Of Polar And Nonpolar Solvent/Solute/Polystyrene Solutions In Microwave Fields Via Molecular Dynamics, Mark J. Purdue, Macduff O. Okuom, Frank D. Blum, James M. D. Macelroy, D. F. O'Shea

Chemistry Faculty Research & Creative Works

The influence of an applied microwave field on the dynamics of methylamine-dichloromethane (DCM) mixtures bound within atactic polystyrene (a-PS) over a range of polymer densities from 30 to 94 wt % polymer was examined using atomistic molecular dynamics simulations. This study is an extension of previous studies on methylamine transport in relatively polar polystyrene solutions of methanol and dimethylformamide [M. J. Purdue et al., J. Chem. Phys. 124, 204904 (2006)]. A direct comparison is made across the three types of polystyrene solutions. Consideration is given to both solvent and reagent transport within the polymer solutions under zero-field conditions and in …

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Segmental Mobility Of Chain Ends In Poly(Methyl Acrylate)-D3, Burak Metin, Frank D. Blum Jan 2006

Segmental Mobility Of Chain Ends In Poly(Methyl Acrylate)-D3, Burak Metin, Frank D. Blum

Chemistry Faculty Research & Creative Works

Better control of polymeric materials can be achieved with a thorough understanding of the dynamics of their constituents. In the present study, we consider polymer chains as composed of chain middles and chain ends. Even though chain ends do not comprise much of the sample by mass, they may play a crucial role in the ultimate properties of the polymers. Although chain ends have been assigned a higher mobility, as compared to chain middles, there have not been a large number of experimental studies that directly probe their mobility. Among those, the studies of Kitahara et al.1 and Miwa et …

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Separation And Quantification Of N-Acetylcysteine-Amide (Naca) By Hplc With Fluorescence Detection, Wei Wu, Glenn Goldstein, Craig D. Adams, Richard H. Matthews, Nuran Ercal Jan 2006

Separation And Quantification Of N-Acetylcysteine-Amide (Naca) By Hplc With Fluorescence Detection, Wei Wu, Glenn Goldstein, Craig D. Adams, Richard H. Matthews, Nuran Ercal

Chemistry Faculty Research & Creative Works

N-acetyl-l-cysteine (NAC) is a well-known antioxidant that is capable of facilitating glutathione (GSH) biosynthesis and replenishing intracellular GSH under oxidatively challenging circumstances. N-acetyl-cysteine-amide (NACA), the amide form of NAC, is a newly designed and synthesized thiol-containing compound which is believed to be more lipophilic and permeable through cell membranes than NAC. The metabolic and antioxidant effects of these compounds in vitro and in vivo are under investigation. However, an analytical method that can separate and quantify both compounds simultaneously is not yet available, to the best of our knowledge. Because of their structural similarities, the two compounds are difficult to …

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Synthesis And Thermal Behavior Of Poly(Methyl Acrylate) Attached To Silica By Surface-Initiated Atrp, Manikantan B. Nair, Frank D. Blum Jan 2006

Synthesis And Thermal Behavior Of Poly(Methyl Acrylate) Attached To Silica By Surface-Initiated Atrp, Manikantan B. Nair, Frank D. Blum

Chemistry Faculty Research & Creative Works

The modification of the surface of an object dictates the response of the object to an external environment.1 Surface-modified materials and nanoparticles have attracted immense interest due to the various desirable electronic, optical and magnetic properties they possess.2 Silica is widely used as an inorganic filler. Surface modification of the silica, with a variety of organic moieties, facilitates the utilization of silica in conjunction with organic systems. The resulting organic/inorganic hybrid materials have significant potential applications. This work reports the synthesis and characterization of modified silica, and poly(methyl acrylate) attached to the modified silica. An observation of the thermal behavior …

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Conformal Internal Coating Of Macroporous Co-Continuous Mcf-Silicas With Isocyanate Derived Polymers, Nicholas Leventis, Chariklia Sotiriou-Leventis, Xiaojiang Wang, Sudhir Mulik Jan 2006

Conformal Internal Coating Of Macroporous Co-Continuous Mcf-Silicas With Isocyanate Derived Polymers, Nicholas Leventis, Chariklia Sotiriou-Leventis, Xiaojiang Wang, Sudhir Mulik

Chemistry Faculty Research & Creative Works

Since their discovery in 1992,1,2 templating sol-gel silica with structuredirecting agents has resulted in new materials with ordered mesoporous (2-50 nm) structure that is investigated for application in areas as diverse as high surface area supports for caralysts or as nanostructured drug storage and release platforms.3 Structure-directing agents are typically surfactants ranging from cationic detergents such as alkyl-trimethylammonium salts with C8-C18 hydrocarbon chains to non-ionic tertiary amines, polyethylene oxide or amphiphilic triblock copolymers such as poly(ethyleneoxide)-blockpoly( propyleneoxide)-block-poly(ethyleneoxide) (e.g., Pluronic P123). Depending on the surfactant and the conditions (e.g., kind and concentration of catalyst) the structure of the mesopores may vary …

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Residual Stress Distribution, Intermolecular Force, And Frictional Coefficient Maps In Diamond Films: Processing-Structure-Mechanical Property Relationship, Sanju Gupta, Oliver Williams, R. J. Patel, Eric W. Bohannan, P. W. May Jan 2006

Residual Stress Distribution, Intermolecular Force, And Frictional Coefficient Maps In Diamond Films: Processing-Structure-Mechanical Property Relationship, Sanju Gupta, Oliver Williams, R. J. Patel, Eric W. Bohannan, P. W. May

Chemistry Faculty Research & Creative Works

Carbon in its various forms, specifically nanocrystalline diamond, may become a key material for the manufacturing of micro- and nano-electromechanical (M/NEMS) devices in the 21st Century. in order to utilize effectively these materials for M/NEMS applications, understanding of their microscopic structure and physical properties (mechanical, in particular) become indispensable. the micro- and nanocrystalline diamond films were grown using hot-filament and microwave chemical vapor deposition techniques involving novel CH4 / [TMB for boron doping and H2S for sulfur incorporation] in high hydrogen dilution chemistry. to investigate residual stress distribution and intermolecular forces at the nanoscale, the films were characterized using Raman …

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Adapting User Interface To Expedite Physician Order Entry: A Frontline To Ensure Patient Safety, Chiang S. Jao, Daniel B. Hier Jan 2006

Adapting User Interface To Expedite Physician Order Entry: A Frontline To Ensure Patient Safety, Chiang S. Jao, Daniel B. Hier

Chemistry Faculty Research & Creative Works

Preventable Medical Errors Are a Major Problem in Healthcare. Maintenance of Accurate Problem Lists and Drug Lists in the Electronic Medical Record is Critical to the Practice of Medicine and Patient Safety. We Built a Simulator of a Clinical Decision Support System that Automates the Process of Maintaining an Electronic Problem List by Processing Drug Order Requests from a Simulated Computerized Physician Order Entry System. Preliminary Results Revealed that the Productivity of the System Increased When the User Interface Was Improved. This Study Highlights the Importance of an Enhanced User Interface as a Frontline in Expediting Physician Data Entry, Streamlining …

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Crystal And Electronic Structures Of Linh₂, Jinbo Yang, X.-D. Zhou, Qingsheng Cai, William Joseph James, William B. Yelon Jan 2006

Crystal And Electronic Structures Of Linh₂, Jinbo Yang, X.-D. Zhou, Qingsheng Cai, William Joseph James, William B. Yelon

Materials Science and Engineering Faculty Research & Creative Works

The crystal structure of LiNH2 was reinvestigated using powder neutron diffraction with high sensitivity. The compound crystallizes in the tetragonal space group I4 with lattice parameters α = b= 5.034 42 (24) Å, c = 10.255 58 (52) Å. It is found that H atoms occupy 8g1(0.2429, 0.1285, 0.1910) and 8g2 (0.3840, 0.3512, 0.1278) sites. The bond lengths between the nearest nitrogen and hydrogen atoms are 0.986 and 0.942 Å, respectively. The bond angle between H-N-H is about 99.97°. These results are significantly different from those of previous experiments. The electronic structure was calculated according to the revised structural …

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Intrinsic Conformational Preferences Of Substituted Cyclohexanes And Tetrahydropyrans Evaluated At The Ccsd(T) Complete Basis Set Limit: Implications For The Anomeric Effect, Abby Jones Weldon, Trisha L. Vickrey, Gregory S. Tschumper Dec 2005

Intrinsic Conformational Preferences Of Substituted Cyclohexanes And Tetrahydropyrans Evaluated At The Ccsd(T) Complete Basis Set Limit: Implications For The Anomeric Effect, Abby Jones Weldon, Trisha L. Vickrey, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

A series of MP2 and CCSD(T) computations have been carried out with correlation consistent basis sets as large as aug-cc-pV5Z to determine the intrinsic equatorial-axial conformational preference of CH 3-, F-, OCH 3-, and OH-substituted cyclohexane and tetrahydropyran rings. The high-accuracy relative electronic energies reported here shed new light on the intrinsic energetics of these cyclic prototypes for the anomeric effect. At the CCSD(T) complete basis set (CBS) limit, the energy of the equatorial conformation relative to the axial position (ΔE CCSD(T)CBC) is -0.75, -0.20, -0.21, and -0.56 kcal mol -1 in methyl-, fluoro-, methoxy-, and hydroxy cyclohexane, respectively, while …

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Exafs Studies Of Bimetallic Ag-Pt And Ag-Pd Nanorods, Debdutta Lahiri, Soma Chattopadhyay, B. A. Bunker, Cm Doudna, Massimo F. Bertino, Frank D. Blum, Akira Tokuhiro, J. Terry Dec 2005

Exafs Studies Of Bimetallic Ag-Pt And Ag-Pd Nanorods, Debdutta Lahiri, Soma Chattopadhyay, B. A. Bunker, Cm Doudna, Massimo F. Bertino, Frank D. Blum, Akira Tokuhiro, J. Terry

Physics Faculty Research & Creative Works

Nanoparticles of Ag-Pt and Ag-Pd with high aspect ratios were synthesized using a radiolysis method. Gamma rays at dose rates below 0.5 kGy/h were used for irradiation. the nanoparticles were characterized by transmission electron microscopy (TEM), optical absorption spectroscopy and x-ray Absorption Fine Structure (XAFS) spectroscopy. Bright field micrographs show that Ag-Pt nanowires are composed of large particles with diameters ranging from 20-30 nm and joined by filaments of diameter between 2-5 nm. the Ag-Pd nanowires have diameters of 20-25 nm and lengths of 1.5 μm. for XAFS measurements, the Pt L3 edge (11.564 keV), Ag K-edge (25.514 keV) and …

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Neutron And Nuclear Inelastic Scattering Study Of The Einstein Oscillators In Ba-, Sr-, And Eu-Filled Germanium Clathrates, Raphaël P. Hermann, Werner Schweika, Olaf Leupold, Rudolf Rüffer, George S. Nolas, Fernande Grandjean, Gary J. Long Nov 2005

Neutron And Nuclear Inelastic Scattering Study Of The Einstein Oscillators In Ba-, Sr-, And Eu-Filled Germanium Clathrates, Raphaël P. Hermann, Werner Schweika, Olaf Leupold, Rudolf Rüffer, George S. Nolas, Fernande Grandjean, Gary J. Long

Chemistry Faculty Research & Creative Works

Inelastic neutron scattering measurements on Ba8Ga16Ge30 and Sr8Ga16Ge30 indicate the presence of soft local modes with Einstein oscillator energies of 4.9±0.1 and 4.4±0.1meV, modes which are associated with the lowest “rattling” mode of the Ba(B) and Sr(B) guests, respectively. Nuclear inelastic scattering measurements on Eu8Ga16Ge30 yield Einstein oscillator energies of between 3.0±0.3 and 7.5±1.2meV for the different modes of the Eu guests. Further, the resonant character of the measurements on Eu8Ga16Ge30 reveals, without question, that neither of the Eu guests …

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Pm Emission From A Commercial Jet Engine -- Project Apex, Donald E. Hagen, Philip D. Whitefield, Prem Lobo, Max B. Trueblood Aug 2005

Pm Emission From A Commercial Jet Engine -- Project Apex, Donald E. Hagen, Philip D. Whitefield, Prem Lobo, Max B. Trueblood

Physics Faculty Research & Creative Works

Project APEX (Aircraft Particle Emissions eXperiment) was a multi-agency commercial aircraft emission characterization and technology demonstration experiment. Its objective was to characterize particle and trace gas precursor species in the emissions from a NASA DC-8 aircraft with General Electric CFM56-2C1 engines at the engine exit plane as well as selected down stream locations. This was to advance the understanding of particle emissions and their evolution in the atmosphere from a current in-service turbofan engine. The test was conducted at the NASA Dryden Flight Research Center at Edwards Air Force Base California during April 15-30, 2004. Participants included the National Aeronautics …

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Computational And Esr Studies Of Electron Attachment To Decafluorocyclopentane, Octafluorocyclobutane, And Hexafluorocyclopropane: Electron Affinities Of The Molecules And The Structures Of Their Stable Negative Ions As Determined From ¹³C And 19f Hyperfine Coupling Constants, Adel M. Elsohly, Gregory S. Tschumper, Richard A. Crocombe, Jih Tzong Wang, Ffrancon Williams Aug 2005

Computational And Esr Studies Of Electron Attachment To Decafluorocyclopentane, Octafluorocyclobutane, And Hexafluorocyclopropane: Electron Affinities Of The Molecules And The Structures Of Their Stable Negative Ions As Determined From ¹³C And 19f Hyperfine Coupling Constants, Adel M. Elsohly, Gregory S. Tschumper, Richard A. Crocombe, Jih Tzong Wang, Ffrancon Williams

Chemistry Faculty Research & Creative Works

High-resolution ESR spectra of the ground-state negative ions of hexafluoro cyclopropane (c-C3F6.-), octafluorocyclobutane (c-C4F8.-), and decafluorocyclopentane (c-C5F10.-) are reported and their isotropic 19F hyperfine coupling constants (hfcc) of 198.6 ± 0.4 G, 147.6 ± 0.4 G, and 117.9 ± 0.4 G, respectively, are in inverse ratio to the total number of fluorine atoms per anion. Together with the small value of 5.2 ± 0.4 G determined for the isotropic 13C hfcc of c-C4F8.-, these results indicate that in each case the singly occupied molecular orbital (SOMO) is delocalized over the equivalent fluorine's and possesses a nodal plane through the carbon …

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Integrated Quantum Mechanical Approaches For Extended Π Systems: Multicentered Qm/Qm Studies Of The Cyanogen And Diacetylene Trimers, Brian W. Hopkins, Gregory S. Tschumper May 2005

Integrated Quantum Mechanical Approaches For Extended Π Systems: Multicentered Qm/Qm Studies Of The Cyanogen And Diacetylene Trimers, Brian W. Hopkins, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

A multicentered integrated quantum mechanical (MC QM/QM) scheme that can accurately treat extended π systems is presented. The trimers of cyanogen (NC-CN) and diacetylene (H-CC-CC-H) are studied in seven geometries. MC QM/QM calculations reproduce CCSD(T) binding energies within 0.04 kcal mol-1. In contrast, MP2 substantially overestimates these interaction energies. An MC QM/QM version of the substituent value test is introduced, and the error in MC QM/QM results is discussed in this context. The results for these systems suggest that MC QM/QM may be a powerful tool in the study of extended π systems and other weakly bound clusters. …

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Microwave Reflectometry As A Novel Diagnostic Method For Detection Of Skin Cancers, Kundan Chand, Pratik Mehta, Daryl G. Beetner, R. Zoughi, William V. Stoecker May 2005

Microwave Reflectometry As A Novel Diagnostic Method For Detection Of Skin Cancers, Kundan Chand, Pratik Mehta, Daryl G. Beetner, R. Zoughi, William V. Stoecker

Electrical and Computer Engineering Faculty Research & Creative Works

More than one million people are diagnosed with skin cancer each year in the United States and more than ten thousand people die from the disease. Currently, there are some methods for early detection of skin cancers, like visual inspection, but improvements are needed. This paper presents a method involving microwave reflectometry as a diagnostic tool for detection of skin cancers. The results of measurements and simulations for normal and wet skin have been shown to distinguish among skin samples with different properties. Microwave measurements from lesions have also been presented which are used to distinguish between cancerous and benign …

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Bimetallic Pt-Ag And Pd-Ag Nanoparticles, Frank D. Blum, Akira Tokuhiro, Massimo F. Bertino, Carmen M. Doudna Apr 2005

Bimetallic Pt-Ag And Pd-Ag Nanoparticles, Frank D. Blum, Akira Tokuhiro, Massimo F. Bertino, Carmen M. Doudna

Chemistry Faculty Research & Creative Works

We report studies of bimetallic nanoparticles with 15%-16% atomic crystal parameters size mismatch. The degree of alloying was probed in a 2-nm Pt core (smallest attainable core size) of Pt-Ag nanoparticles (completely immiscible in bulk) and 20-nm-diameter Pd-Ag nanowires (completely miscible in bulk). Particles were synthesized radiolytically, and depending on the initial parameters, they assume spherical or cylindrical (nanowire) morphologies. In all cases, the metals are seen to follow their bulk alloying characteristics. Pt and Ag segregate in both spherical and wire forms, which indicates that strain due to crystallographic mismatch overcomes the excess surface free energy in the small …

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How To Choose One-Dimensional Basis Functions So That A Very Efficient Multidimensional Basis May Be Extracted From A Direct Product Of The One-Dimensional Functions: Energy Levels Of Coupled Systems With As Many As 16 Coordinates, Richard Dawes, Tucker Carrington Jr. Apr 2005

How To Choose One-Dimensional Basis Functions So That A Very Efficient Multidimensional Basis May Be Extracted From A Direct Product Of The One-Dimensional Functions: Energy Levels Of Coupled Systems With As Many As 16 Coordinates, Richard Dawes, Tucker Carrington Jr.

Chemistry Faculty Research & Creative Works

In this paper we propose a scheme for choosing basis functions for quantum dynamics calculations. Direct product bases are frequently used. The number of direct product functions required to converge a spectrum, compute a rate constant, etc., is so large that direct product calculations are impossible for molecules or reacting systems with more than four atoms. It is common to extract a smaller working basis from a huge direct product basis by removing some of the product functions. We advocate a build and prune strategy of this type. the one-dimensional (1D) functions from which we build the direct product basis …

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Strongly Decoupled Europium And Iron Vibrational Modes In Filled Skutterudites, Gary J. Long, Raphäel P. Hermann, Fernande Grandjean, Ercan E. Alp, Wolfgang Sturhahn, Charles E. Johnson, Dennis E. Brown, Olaf Leupold, Rudolf Rüffer Apr 2005

Strongly Decoupled Europium And Iron Vibrational Modes In Filled Skutterudites, Gary J. Long, Raphäel P. Hermann, Fernande Grandjean, Ercan E. Alp, Wolfgang Sturhahn, Charles E. Johnson, Dennis E. Brown, Olaf Leupold, Rudolf Rüffer

Chemistry Faculty Research & Creative Works

The europium partial vibrational density of states (DOS) in EuFe4Sb12 and the iron partial vibrational DOS in both EuFe4Sb12 and Ce57Fe4Sb12 have been obtained by nuclear inelastic scattering. The results reveal the strong independence of the iron and rare-earth vibrational modes. The cage filling europium only participates significantly to the low-energy local vibrational modes. The force constants have been obtained from the measured probability of nuclear absorption. The energies of the peaks in the europium and iron DOS are in excellent agreement with the calculated DOS in LaFe4 …

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