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Articles 26041 - 26070 of 34740

Full-Text Articles in Physical Sciences and Mathematics

Isothermal Titration Calorimetry And Transmission Electron Microscopy Of Main-Chain Viologen Polymer Containing Bromide As Counerions, Pradip K. Bhowmik, Marcos A. Cheney, Haesook Han, Longzhou Ma Jan 2006

Isothermal Titration Calorimetry And Transmission Electron Microscopy Of Main-Chain Viologen Polymer Containing Bromide As Counerions, Pradip K. Bhowmik, Marcos A. Cheney, Haesook Han, Longzhou Ma

Transmission Electron Microscope

Polyelectrolytes are an important class of macromolecules that contain dissociable ionic groups. When introduced into polar solvent, usually the universal solvent water, dissociation takes place so that electrically charged macromolecule is suspended in solution. The electrostatic interaction is operative between ionized groups inside the macromolecule, between the macromolecules, between the counterions, and between the macromolecule and counterion. Since this interaction is characterized by its long-range nature, the solution exhibits various interesting properties including the polyelectrolyte behavior very different from solutions of neutral polymers.

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Interaction Between Metal Fission Products And Triso Coating Materials: A Study Of Chemical Bonding And Interdiffusion: 1st Quarterly Report, 2006, Clemens Heske Jan 2006

Interaction Between Metal Fission Products And Triso Coating Materials: A Study Of Chemical Bonding And Interdiffusion: 1st Quarterly Report, 2006, Clemens Heske

Fuels Campaign (TRP)

This project is devoted to an in-depth study of the chemical and electronic impact of metal fission products on the coating layers in TRISO nuclear fuel. In particular, there is a focus on the investigation of Pd, Cs, and Ag and their interface formation with SiC and carbon-based substrates. A variety of surface and near-surface bulk sensitive probes that investigate the occupied and unoccupied electronic states of the substrate and the metal overlayer have been utilized. By a controlled and stepwise deposition of the metal overlayer, it is possible to gain substantial insight into the formation of interfaces and their …

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Solution-Based Synthesis Of Nitride Fuels, Kenneth Czerwinski, Thomas Hartmann Jan 2006

Solution-Based Synthesis Of Nitride Fuels, Kenneth Czerwinski, Thomas Hartmann

Fuels Campaign (TRP)

A wide variety of fuel concepts are considered for advanced reactor technology including metals, metal oxides or metal nitrides as solid solutions or composite materials. Nitride fuels have appropriate properties for advanced fuels including high thermal conductivity, thermal stability, solid-state solubility of actinides, fissile metal density, and suitable neutronic properties. A drawback of nitride fuels involves their synthesis. A key parameter for preparing oxide fuels is the precipitation step in the sol-gel process. For nitride fuels, the current synthetic route is carbothermic reduction from the oxide to the nitride. This process step is based on solid phase reactions and for …

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Trans-Atlantic Correlation Of Upper Cretaceous Marine Sediments, Marcus R. Ross, David E. Fastovsky Jan 2006

Trans-Atlantic Correlation Of Upper Cretaceous Marine Sediments, Marcus R. Ross, David E. Fastovsky

Faculty Publications and Presentations

Upper Cretaceous marine deposits from the Mid-Atlantic region of North America (Delaware, Maryland, and New Jersey) and the Maastricht area (southern Netherlands, and nearby Belgium and Gennany) are correlated across the Atlantic using a variety of macro invertebrates, nannofossils, and sequence stratigraphy. Four late Cretaceous Mid-Atlantic sequences, the Marshalltown, Englishtown, Merchantville, and Navesink, span the upper Santonian to lowennost Danian, and have direct correlatives in the Maastricht area. Correlations between the Mid-Atlantic and the Maastricht regions (respectively) are as follows: the upper Santonian to lower Campanian Merchantville and Matawan formations with the Achen and lower Vaals fonnations; the middle Campanian …

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Mechanism Of Shifts Of Potentials Of Hemosorbents Based On Activated Carbons Caused By Adsorption Of Organic Toxicants, Mark Goldin, Yury Goldfarb, Mikhail M. Goldin Jan 2006

Mechanism Of Shifts Of Potentials Of Hemosorbents Based On Activated Carbons Caused By Adsorption Of Organic Toxicants, Mark Goldin, Yury Goldfarb, Mikhail M. Goldin

Faculty Publications and Presentations

No abstract provided.

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Recent Developments Inthe Mechanistic Enzymology Of The Atp-Dependent Lon Protease From Escherichia Coli: Highlights From Kinetic Studies, Irene Lee, Anthony J. Berdis, Carolyn K. Suzuki Jan 2006

Recent Developments Inthe Mechanistic Enzymology Of The Atp-Dependent Lon Protease From Escherichia Coli: Highlights From Kinetic Studies, Irene Lee, Anthony J. Berdis, Carolyn K. Suzuki

Chemistry Faculty Publications

Lon protease, also known as protease La, is one of the simplest ATP-dependent proteases that plays vital roles in maintaining cellular functions by selectively eliminating misfolded, damaged and certain short-lived regulatory proteins. Although Lon is a homo-oligomer, each subunit of Lon contains both an ATPase and a protease active site. This relatively simple architecture compared to other hetero-oligomeric ATP-dependent proteases such as the proteasome makes Lon a useful paradigm for studying the mechanism of ATP-dependent proteolysis. In this article, we survey some recent developments in the mechanistic characterization of Lon with an emphasis on the utilization of pre-steady-state enzyme kinetic …

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Bis([Mu]-Thio­Phene-2-Carbaldehyde Thio­Semicarbazonato)Bis­[Acetonitrile­Copper(I)] Bis­(Tetra­Fluoro­Borate), Robert D. Pike, Austin B. Wiles, Tristan A. Tronic Jan 2006

Bis([Mu]-Thio­Phene-2-Carbaldehyde Thio­Semicarbazonato)Bis­[Acetonitrile­Copper(I)] Bis­(Tetra­Fluoro­Borate), Robert D. Pike, Austin B. Wiles, Tristan A. Tronic

Arts & Sciences Articles

The title compound, [Cu2(C6H7N3S2)2(C2H3N)2](BF4)2, is a dimer with a central Cu2S2 core resulting from thio­semi­carbazone sulfur bridging. Both Cu-TCT units (TCT is the thio­phene-2-carboxaldehyde thio­semicarbazone anion) are roughly planar and are parallel to one another and perpendicular to the Cu2S2 plane.

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Solubilisation, Purification And Processing Of Single Walled Carbon Nanotubes Using Organic Molecules, Theresa Hedderman Jan 2006

Solubilisation, Purification And Processing Of Single Walled Carbon Nanotubes Using Organic Molecules, Theresa Hedderman

Doctoral

The aims of this research are seven fold; • To enhance the solubility of SWNTs in organic solvents. • To purify an untreated sample of SWNTs that contains many side products. • To gain a greater understanding of the interaction between the polycyclic aromatic hydrocarbons and SWNTs. • To debundle and disperse SWNTs. • To select SWNTs of a specific structure based on the structures of the polycyclic aromatic hydrocarbons used. • To observe and compare the interaction of polycyclic aromatic hydrocarbons with SWNTs produced by different methods. • To elucidate factors which contribute to different degrees of interaction between …

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Population Size Bias In Descendant-Weighted Diffusion Quantum Monte Carlo Simulations, G. Lee Warren, Robert J. Hinde Jan 2006

Population Size Bias In Descendant-Weighted Diffusion Quantum Monte Carlo Simulations, G. Lee Warren, Robert J. Hinde

Chemistry Publications and Other Works

We consider the influence of population size on the accuracy of diffusion quantum Monte Carlo simulations that employ descendant weighting or forward walking techniques to compute expectation values of observables that do not commute with the Hamiltonian. We show that for a simple model system, the d-dimensional isotropic harmonic oscillator, the population size must increase rapidly with d in order to ensure that the simulations produce accurate results. When the population size is too small, expectation values computed using descendant-weighted diffusion quantum Monte Carlo simulations exhibit significant systematic biases.

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Optical Susceptibilities Of Supported Indium Tin Oxide Thin Films, Jonathan L. Humphrey, Darius Kuciauskas Jan 2006

Optical Susceptibilities Of Supported Indium Tin Oxide Thin Films, Jonathan L. Humphrey, Darius Kuciauskas

Chemistry Publications

The third-order nonlinear optical susceptibility of indium tin oxide (ITO) thin films on glass substrates, χ(3)ITO, was determined in the near-IR spectral region using degenerate four wave mixing (DFWM)spectroscopy with 100fs laser pulses. A DFWM method for measuring thin films on thick substrates was refined for the characterization of films less than 100nm thick and applied to ∼25nm thick ITO films. It was found that χ(3)ITO is purely electronic at 900–1300nm (11000–7700cm−1) and has a value of (2.16±0.18)×10−18m2V−2. Theχ(3)ITO value reaches (3.36±0.28)×10−18m2V−2 at 1500nm (6700cm−1) due to two-photon absorption by free carriers (electrons). Ultrafast electron relaxation was also observed. The …

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Characterization Of The Wheat Grain Pkaba1-Interacting Protein Tawd40, Natalie Wayne Jan 2006

Characterization Of The Wheat Grain Pkaba1-Interacting Protein Tawd40, Natalie Wayne

Honors Theses

Abscisic acid (ABA)-mediated gene expression is a critical component of plant responses to this important hormone, which affects plant growth, development, and responses to environmental stresses. Plant responses to ABA are mediated by a number of factors including PKABA 1> an ABA-induced protein kinase involved in ABA-suppressed gene expression in cereal grains, and TaWD40, which has previously been shown to physically interact with PKABA1. A full-length 1.9 kb TaWD40 cDNA, CK210682, was sequenced as part of this project. Based on the deduced protein sequence, it is thought that TaWD40 may belong to the family of E3 ubiquitin ligases, possibly targeting …

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A Chloride Selective Calix[4]Arene Optical Sensor Combining Urea Functionality With Pyrene Excimer Transduction, Benjamin Schazmann, Dermot Diamond Jan 2006

A Chloride Selective Calix[4]Arene Optical Sensor Combining Urea Functionality With Pyrene Excimer Transduction, Benjamin Schazmann, Dermot Diamond

Articles

A neutral 2-site chloride selective compound has been developed (3), based on a 1,3- alternate tetrasubstituted calix[4]arene providing a preorganised supramolecular scaffold. The resultant supramolecular cavity is amongst the first to combine urea functional groups bridged with single methylene spacers to pyrene moieties. It combines a naturally and synthetically proven H-bonding system with the elegant ratiometric fluorescent signalling properties of an intramolecular pyrene excimer system, triggered by conformational changes upon anion coordination. The excimer emission of 3 is quenched, with a simultaneous rise in the monomer emission solely by the chloride anion amongst a wide variety of anions tested. 3 …

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Development Of A Calix[4]Arene Sensor For Soft Metals Based On Nitrile Functionality, Benjamin Schazmann, Dermot Diamond Jan 2006

Development Of A Calix[4]Arene Sensor For Soft Metals Based On Nitrile Functionality, Benjamin Schazmann, Dermot Diamond

Articles

The current work is amongst the first to examine the potential usefulness of the nitrile functional group in potentiometric analytical sensors for soft metals. Nitrile functionality has hereby been incorporated into a calix[4]arene skeleton to give a series of new cation selective hosts. The analytical sensing behaviour of these hosts was examined by Ion Selective Electrode (ISE) based potentiometry. In all cases a preference for soft metals was observed, explained primarily in terms of soft–soft compatibility between calix[4]arene nitrile hosts and metal guests in combination with a classical ‘lock and key’ best fit mechanism. Hosts 2, 3 and 4 showed …

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Synthesis Of An Aza-Cope Rearrangement - Mannich Cyclization Precursor From L-Proline, Patricia T. Sinawe Jan 2006

Synthesis Of An Aza-Cope Rearrangement - Mannich Cyclization Precursor From L-Proline, Patricia T. Sinawe

Senior Honors Theses and Projects

No abstract provided.

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Lipid Metabolism In A549 And 9hte Cells Quantitation Of Lipid Peroxidation, Elizabeth Quintus Jan 2006

Lipid Metabolism In A549 And 9hte Cells Quantitation Of Lipid Peroxidation, Elizabeth Quintus

Senior Honors Theses and Projects

No abstract provided.

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Polystyrene Nanocomposites Based On An Oligomerically-Modified Clay Containing Maleic Anhydride, Xiaoxia Zheng, David D. Jiang, Charles A. Wilkie Jan 2006

Polystyrene Nanocomposites Based On An Oligomerically-Modified Clay Containing Maleic Anhydride, Xiaoxia Zheng, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

An oligomerically-modified clay containing maleic anhydride was used to prepare polystyrene-clay nanocomposites by melt blending and the effect of this modified clay on the thermal stability and fire performance was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed immiscible/intercalated/delaminated morphology. The maleic anhydride modified clay improved the compatibility between the clay and the polystyrene.

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Ligand-Promoted Solvent-Dependent Ionization And Conformational Equilibria Of Re(Co)3Br[Ch2(S-Tim)2] (Tim = 1-Methylthioimidazolyl). Crystal Structures Of Re(Co)3Br[Ch2(S-Tim)2] And {Re(Co)3(Ch3Cn)[Ch2(S-Tim)2]}(Pf6), Rosalice M. Silva, Brendan J. Liddle, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier Jan 2006

Ligand-Promoted Solvent-Dependent Ionization And Conformational Equilibria Of Re(Co)3Br[Ch2(S-Tim)2] (Tim = 1-Methylthioimidazolyl). Crystal Structures Of Re(Co)3Br[Ch2(S-Tim)2] And {Re(Co)3(Ch3Cn)[Ch2(S-Tim)2]}(Pf6), Rosalice M. Silva, Brendan J. Liddle, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier

Chemistry Faculty Research and Publications

The compounds Re(CO)3Br[CH2(S-tim)2] (1) and {Re(CO)3(CH3CN)[CH2(S-tim)2]}(PF6) (2), where tim is 1-methylthioimidazolyl, were prepared in high yields and characterized both in the solid state and in solution. The solid-state structures show that the ligand acts in a chelating binding mode where the eight-member chelate ring adopts twist-boat conformations in both compounds. A comparison of both solid-state IR data for CO stretching frequencies and the solution-phase voltammetric measurements for the Re1+/2+ couples between 1, 2, …

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Highly Cooperative Tetrametallic Ruthenium-Μ-Oxo-Μ-Hydroxo Catalyst For The Alcohol Oxidation Reaction, Chae S. Yi, Tonya N. Zeczycki, Ilia A. Guzei Jan 2006

Highly Cooperative Tetrametallic Ruthenium-Μ-Oxo-Μ-Hydroxo Catalyst For The Alcohol Oxidation Reaction, Chae S. Yi, Tonya N. Zeczycki, Ilia A. Guzei

Chemistry Faculty Research and Publications

The tetrametallic ruthenium-oxo-hydroxo-hydride complex {[(PCy3)(CO)RuH]4(μ4-O)(μ3-OH)(μ2-OH)} (1) was synthesized in two steps from the monomeric complex (PCy3)(CO)RuHCl (2). The tetrameric complex 1 was found to be a highly effective catalyst for the transfer dehydrogenation of alcohols. Complex 1 showed a different catalytic activity pattern toward primary and secondary benzyl alcohols, as indicated by the Hammett correlation for the oxidation reaction of p-X-C6H4CH2OH (ρ = −0.45) and p-X-C6H4CH(OH)CH3 (ρ = +0.22) (X = …

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Enhancing The Third-Order Nonlinear Optical Properties Of Porphyrins And Molecular Wires, Jonathan L. Humphrey Jan 2006

Enhancing The Third-Order Nonlinear Optical Properties Of Porphyrins And Molecular Wires, Jonathan L. Humphrey

Theses and Dissertations

The third-order nonlinear optical (NLO) properties of indium tin oxide (ITO) thin films, Fe3+, Mn3+, Co2+ 5,10,15,20-tetrakis-4hydroxytetraphenyl)porphyrin (TPP) films, and a series of ethynyl-linked azobenzene oligomers were investigated using degenerate four wave mixing (DFWM) with 100 fs laser pulses. To measure the NLO of ITO thin films, A DFWM method for measuring thin films on thick substrates was refined for the characterization of films less than 100 nm thick and applied to ITO films ~25 nm thick. It was found that the third-order nonlinear susceptibility of ITO, χ(3)ITO, is purely electronic at 900 - 1300 nm (11000 - 7700 cm-1) …

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Janus Scorpionates:  Supramolecular Tectons For The Directed Assembly Of Hard−Soft Alkali Metallopolymer Chains, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier Jan 2006

Janus Scorpionates:  Supramolecular Tectons For The Directed Assembly Of Hard−Soft Alkali Metallopolymer Chains, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier

Chemistry Faculty Research and Publications

A new scorpionate ligand [HB(mtda)3-] containing mercaptothiadiazolyl (mtda) heterocyclic rings with both hard nitrogen donors and soft sulfur donors has been prepared. This new ligand, the Janus scorpionate, is a hybrid of a tris(pyrazolyl)borate and a tris(mercaptoimidazolyl)borate. The differential hard/soft character of the dissimilar donor groups in this bridging ligand was exploited for the controlled solid-state organization of homometallic and heterometallic alkali metal coordination polymers. Remarkably, in the case of sodium, coordination polymers with both acentric (with NaS3N3H kernels) and centric (with alternating NaN6 and NaS6H2 kernels) chains are …

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A Practical Synthesis Of Bridged Diarylacetylenes, Ruchi Shukla, Daniel M. Brody, Sergey V. Lindeman, Rajendra Rathore Jan 2006

A Practical Synthesis Of Bridged Diarylacetylenes, Ruchi Shukla, Daniel M. Brody, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

An efficient and practical synthesis of bridged diarylacetylenes in multigram quantities has been successfully carried out using high-yielding (classical) synthetic methods and readily available starting materials. The structural analysis of the representative bridged diarylacetylenes by X-ray crystallography strongly suggests that conformations, bending of the linear triple bond, and the angle between the mean planes of aromatic rings in various bridged diarylacetylenes are governed by the p−π conjugation among the aromatic rings and the ethereal groups. Furthermore, the synthetic scheme also allows the preparation of (appropriately) bromo-substituted bridged diarylacetylenes which hold potential for their future usage for the preparation of polymeric …

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Development Of Dirhodium Sugar-Substituted Carboxylate And Acetamide Complexes And Evaluation Of Their Potential As Lectin Inhibitors, Bethany Masten Jan 2006

Development Of Dirhodium Sugar-Substituted Carboxylate And Acetamide Complexes And Evaluation Of Their Potential As Lectin Inhibitors, Bethany Masten

Undergraduate Review

No abstract provided.

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Effects Of Salinity Changes On The Photodegradation And Ultraviolet-Visible Absorbance Of Terrestrial Dissolved Organic Matter, E. C. Minor, J. Pothen, B. J. Dalzell, H. Abdulla, K. Mopper Jan 2006

Effects Of Salinity Changes On The Photodegradation And Ultraviolet-Visible Absorbance Of Terrestrial Dissolved Organic Matter, E. C. Minor, J. Pothen, B. J. Dalzell, H. Abdulla, K. Mopper

Chemistry & Biochemistry Faculty Publications

We performed laboratory studies to determine the effects of salinity on the photodegradation of dissolved organic matter (DOM) from the Great Dismal Swamp, Virginia, an important source of terrestrial DOM to the lower Chesapeake Bay. Samples were created by mixing Great Dismal Swamp water (ionic strength approximate to 0 mol L-1) with modified artificial seawater solutions of differing salinities while keeping the final dissolved organic carbon (DOC) concentration constant. These samples were then irradiated for 24 h in a light box providing ultraviolet (UV) light similar to that of natural sunlight. Light absorbance and DOC concentrations decreased after …

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Open-Ocean Carbon Monoxide Photoproduction, Aron Stubbins, Günther Uher, Cliff S. Law, Kenneth Mopper, Carol Robinson, Robert C. Upstill-Goddard Jan 2006

Open-Ocean Carbon Monoxide Photoproduction, Aron Stubbins, Günther Uher, Cliff S. Law, Kenneth Mopper, Carol Robinson, Robert C. Upstill-Goddard

Chemistry & Biochemistry Faculty Publications

Sunlight-initiated photolysis of chromophoric dissolved organic matter (CDOM) is the dominant source of carbon monoxide (CO) in the open-ocean. A modelling study was conducted to constrain this source. Spectral solar irradiance was obtained from two models (GCSOLAR and SMARTS2). Water-column CDOM and total light absorption were modelled using spectra collected along a Meridional transect of the Atlantic ocean using a 200-cm pathlength liquid waveguide UV-visible spectrophotometer. Apparent quantum yields for the production of CO (AQYCO) from CDOM were obtained from a parameterisation describing the relationship between CDOM light absorption coefficient and AQYCO and the CDOM spectra collected. …

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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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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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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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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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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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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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