Physical Sciences and Mathematics Commons^™

Preparation Of Nanocomposites From Styrene And Modified Graphite Oxides, Fawn Marie Uhl, Charles A. Wilkie

Chemistry Faculty Research and Publications

Graphite oxide was prepared and modified with several ammonium salts and these modified graphite oxides were used to prepare nanocomposites with polystyrene by in situ polymerization of styrene monomer and by melt blending with polystyrene. Nanocomposites were characterized by X-ray diffraction, cone calorimetry, thermogravimetric analysis and the evaluation of mechanical properties. Nanocomposites are formed by in situ polymerization but not by melt blending; the graphite oxide undergoes thermal degradation at the temperature of melt blending so nanocomposite formation would be unlikely. Mechanical properties of the melt blended nanocomposites are improved relative to the virgin polystyrene while those prepared by in …

Synthesis And Reactivity Of Tricarbonyl(1-Methoxycarbonyl-5-Phenylpentadienyl)Iron(1+) Cation, Subhabrata Chaudhury, William Donaldson, Dennis W. Bennett, Daniel T. Haworth, Tasneem Siddiquee, Jennifer M. Kloss

Chemistry Faculty Research and Publications

Tricarbonyl(1-methoxycarbonyl-5-phenylpentadienyl)iron(1+) hexafluorophosphate (7) was prepared in two steps from tricarbonyl(methyl 6-oxo-2,4-hexadienoate)iron. While addition of carbon and heteroatom nucleophiles to 7 generally occurs at the phenyl-substituted dienyl carbon to afford (2,4-dienoate)iron products, the addition of phthalimide proceeded at C2 to afford a (pentenediyl)iron product (18). Complex 18 was structurally characterized by X-ray diffraction analysis.

The reaction of the title cation with carbon and heteroatom nucleophiles was examined. In general, the products arise from nucleophilic attack at C5 to give E,E- or E,Z-dienoate iron complexes. Addition of phthalimide anion proceeds at C2 …

Dynamic Correction Of A Distorted Image Using A Photorefractive Polymeric Composite, Jeffrey G. Winiarz, Fassil Ghebremichael, Jayan Sanders Thomas, Gerald R. Meredith, Nasser N. Peyghambarian

Chemistry Faculty Research & Creative Works

We demonstrate, for the first time, the dynamic correction of aberrated images in real-time using a polymeric composite with fast response times. The current novel experimental design is capable of restoring a phase aberrated, image carrying laser beam, to nearly its original quality. The ability to reconstruct images in real-time is demonstrated through the changing of the aberrating medium at various speeds. In addition, this technique allows for the correction of images in motion, demonstrated through the oscillatory movement of the resolution target. We also have demonstrated that important parameters of the materials in the study such as response times, …

Self-Assembly Of Inorganic Membranes: Attachment Of Gold Nanoparticles To A Mesoporous Silica Membrane, Jennifer K. Saucier

Honors College

The purpose of this study was to investigate the self-assembly of gold nanoparticles to create thin, densely packed structures several monolayers thick for the synthesis of a membrane. Silica membrane synthesis was examined as a support for deposition of the nanoparticles. Pore size formation and thickness were controlled to promote high flux, defect free layer formation while providing for optimum separation. Silica mesoporous membranes were created through the acid-catalyzed hydrolysis of tetraethyl orthosilicate. An ionic block co-polymer was used to control a networked pore formation. The silica sols were dip coated on macroporous alumina supports. The silica membranes were characterized …

Synthesis Of Nanocrystalline Nickel-Zinc Ferrites Via A Microemulsion Route, Vuk Uskoković, Miha Drofenik

Pharmacy Faculty Articles and Research

Nanostructured NiZn-ferrites were synthesized using a low-temperature co-precipitation method within the reverse micelles of ternary CTAB/1-hexanol/water microemulsions. The influence of pH on the precipitation reaction was investigated. It was found that a higher pH resulted in more crystalline particles. Subsequent oxidation of the ferrous ions precipitate, which leads to the formation of spinel ferrites, is discussed. Diffraction-lines broadening and specific surface area measurements yielded an average particle size of ~ 3 nm. The saturation magnetization of the samples was 20 times smaller than for traditionally synthesized NiZn-ferrites, while the coercivities were 10 - 100 times larger than bulk NiZn-ferrites, which …

Directed Ortho Metalation In Hydrocarbon Solvents: Opposing Pi-Resonance Effects, Barry Woosley

Masters Theses & Specialist Projects

Hydrocarbon solvents are known to be unreactive toward organolithium reagents and do not typically support ortho-metalation reactions without the aid of a promoter. An exception would be an arene substrate having the capability to bidentate complex to the reactive alkyllithium dimer, which enables ortho-metalation to occur in high yields. A second, more limiting exception, would be that the arene substrate possesses localized lone pairs of electrons, as is the case when the directed ortho metalating group (DMG) is located in the benzyl position. The work reported here centers upon developing a third and larger class of arene substrates that are …

Cesium Effect: A Mild And Efficient Synthesis Of Secondary And Tertiary Phosphines, Matthew Honaker

Masters Theses & Specialist Projects

A mild and efficient method to synthesize a variety of secondary and tertiary, as well as disecondary and ditertiary phosphines has been developed. Using reaction conditions that include cesium hydroxide, molecular sieves, and DMF, at room temperature, a wide range of alkyl halides has been coupled to primary or secondary phosphines to yield secondary or tertiary phosphines. Included were activated and aliphatic halides, as well as base sensitive functional groups. In addition, examples of disecondary and ditertiary ligands have also been prepared using similar reaction conditions. The synthesis of a P-N-P ligand was also accomplished with these procedures. Optically active …

Spectroscopic Studies Of Chlorophyll A Complexes With Trinitro-Substituted Flourene Derivatives, Stephanie Smalley

Masters Theses & Specialist Projects

Absorption, fluorescence, and excited-state lifetime studies of chlorophyll a (Chl a) with fluorene, 2-(2,4,7-Trinitro-fluoren-9-ylideneaminooxy)-propionic acid (TFPR), 2- (2,4,7-Trinitro-fluoren-9-ylidenemethyl)-phenol, (TFPH), and 9-Isopropylidene-2,4,7- trinitro-9H-fluorene (ITNF) have been investigated. These systems were studied in acetonitrile and dichloromethane at room temperature. Absorption data were analyzed with the Nash plot. Linearity of the Nash plots proved that a 1:1 complex was formed between the donor and acceptor. Ground state binding constants (Ka) of each system were also determined from the y-intercept of these plots. Fluorescence data were analyzed with a Stern-Volmer plot. The quenching constants (Ksv) were obtained from the slope of these plots. These …

Arenediazonium Salts As Versatile (Meso-Ionic) Tectons. Charge-Transfer Intercalates And Clathrates In Unusual Crystalline Networks Self-Assembled With Neutral Aromatic Π-Donors, Sergey Lindeman, Jay K. Kochi

Chemistry Faculty Research and Publications

Synopsis

Arenediazonium salts as tectonic building elements for crystal engineering possess a unique array of binding properties, including (a) strong acceptor affinity toward electronegative or neutral σ-donors; (b) enhanced C−H acidity for extensive formation of C−H···X bonds; and (c) π-acceptor properties of the electron-deficient arene substituent for charge-transfer complex formation with appropriate aromatic π-donors. Shown: Donor/acceptor intercalate in the layered structure of 3,5(NO₂)C₆H₃N₂⁺ BF₄^- with naphthalene.

Abstract

The surprisingly uniform crystal packings of various arenediazonium salts (ArN₂⁺X^-) largely consist of two-dimensional ionic layers from …

Polybutadiene Modified Clay And Its Nanocomposites, Shengpei Su, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

A butadiene-modified clay was prepared by ionic exchange between sodium montmorillonite and a butadiene surfactant; the butadiene surfactant was obtained from the reaction of vinylbenzyl chloride grafted polybutadiene with a tertiary amine. Nanocomposites of polystyrene, high impact polystyrene, acrylonitrile–butadiene–styrene terpolymer, poly(methyl methacrylate), polypropylene and polyethylene were prepared by melt blending this modified clay with the virgin polymers. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, cone calorimetry and the evaluation of mechanical properties. A morphological study of PBD-modified clay–polymer nanocomposites shows that all the composites are immiscible micro-composites. The consistency of the result from XRD and …

Study On The Thermal Stability Of Polystyryl Surfactants And Its Modified Clay Nanocomposites, Shengpei Su, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

Five oligomeric styrene surfactants, N,N,N-trimethylpolystyrylammonium, N,N-dimethyl-N-benzylpolystyrylammonium, N,N-dimethyl-N-hexadecylpolystyrylammonium, 1,2-dimethyl-3-polystyrylimidazolium, and triphenylpolystyrylphosphonium chlorides were synthesized and used to prepare organically modified clays. Both styrene and methyl methacrylate nanocomposites were prepared by melt blending and the type of nanocomposite was evaluated by X-ray diffraction and transmission electron microscopy. The thermal stability of the organically modified clays and the nanocomposites were studied by thermogravimetric analysis; these systems do give clays which have good thermal stability and may be useful for melt blending with polymers that must be processed at …

Studies Of Reversible Inhibition, Irreversible Inhibition And Activation Of Alkaline Phosphatase By Capillary Electrophoresis, Angela Randall Whisnant

Masters Theses

Reversible inhibition, irreversible inhibition, and activation of calf intestinal alkaline phosphatase (EC 3.1.3.1) have been studied by capillary electrophoresis. The capillary electrophoretic enzyme-inhibitor assays were performed by electrophoretically mixing zones of inhibitor and enzyme in a substrate-filled capillary. Enzyme inhibition was indicated by a decrease in product formation detected in the capillary by laser-induced fluorescence. Reversible enzyme inhibitors could be quantified by Michaelis-Menten treatment of the electrophoretic data. Reversible, competitive inhibition of alkaline phosphatase by sodium vanadate and sodium arsenate has been examined. The calculated K_i value for the capillary electrophoretic enzyme-inhibitor assays was 2.1 µM for sodium vanadate …

Synthetic Studies On Anticancer Compounds: The Tylophorinines, Conrad Gracjan Kaczmarek

Masters Theses

This thesis describes synthetic studies in the area of alkaloid chemistry, specifically, potent anticancer compounds: the tylophorinines.

Tylophorinine is a naturally occurring compound found in the Monarch butterfly and plants of the genus Tylophora. Described here is a concise methodology for stereoselective synthesis of this compound, and analogs, starting from simple, naturally occurring compounds. The synthetic strategy represents a simplification in synthesizing tylophorinines, and would allow numerous other tylophorinines with similar chemical structure to be conveniently synthesized in an analogous fashion.

Further, the tylophorinines are convenient compounds for determining where a cancer cell may be most effectively attacked. Numerous …

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Organic Matrix, Spencer M. Steinberg

Separations Campaign (TRP)

The recovery of iodine released during the processing of used nuclear fuel poses a significant challenge to the transmutation of radioactive iodine. During the first two years of this program the use of Fullerene Containing Carbon (FCC) compounds and Natural Organic Matter (NOM) as potential sorbents for iodine release from the reprocessing of nuclear fuel was examined. This work also included the development of bench-scale testing capabilities at UNLV to allow the testing of the FCC and NOM materials in a simulated process off-gas environment. In the final year of the project we will complete studies of FCC and NOM …

Identification Of An Il-17-Producing Nk1.1neg Inkt Cell Population Involved In Airway Neutrophilia, Paul B. Savage, Marie-Laure Michel, Alexandre Castro Keller, Christophe Paget, Masakazu Fujio, Francois Trottein, Chi-Huey Wong, Elke Schneider, Michael Dy, Maria C. Leite-De-Moraes

Faculty Publications

Invariant natural killer T (iNKT) cells are an important source of both T helper type 1 (Th1) and Th2 cytokines, through which they can exert beneficial, as well as deleterious, effects in a variety of inflammatory diseases. This functional heterogeneity raises the question of how far phenotypically distinct subpopulations are responsible for such contrasting activities. In this study, we identify a particular set of iNKT cells that lack the NK1.1 marker (NK1.1neg) and secrete high amounts of interleukin (IL)-17 and low levels of interferon (IFN)-{gamma} and IL-4. NK1.1neg iNKT cells produce IL-17 upon synthetic ({alpha}-galactosylceramide [{alpha}-GalCer] or PBS-57), as well …

Real Versus Artifactual Symmetry-Breaking Effects In Hartree-Fock, Density-Functional, And Coupled-Cluster Methods, Nicholas J. Russ, T. Daniel Crawford, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

The relative abilities of Hartree-Fock, density-functional theory (DFT) and coupled-cluster theory were used to investigate symmetry breaking in polyatomic molecules. It was observed that for degenerate electronic states, symmetry breaking in the nuclear framework may result from first-order Jahn-Teller (SOJT) effects. Displacements along Non totally symmetric nuclear coordinates, however, may lead to mixing of the states if their respective irreducible representations correlate in the reduced symmetry point group. Coupled-cluster theory correctly describes the strength of SOJT coupling, assuming that the full CCSDT method provides a reasonable approximation of the exact wave function.

Fluorescence Detectors For Proteins And Toxic Heavy Metals, Uchenna Prince Paul

Theses and Dissertations

An inexpensive detector for proteins is described. The detection technique was based on two-photon excitation intrinsic protein fluorescence using a visible 532 nm diode-pumped nano laser as the excitation source. Proteins that exhibit intrinsic fluorescence must contain at least one tryptophan, tyrosine, or phenylalanine residue in their amino acid sequences. The detector was characterized and was found to have a detection limit of 4 micro-molar for tryptophan, 22 micro-molar for tyrosine and 500 micro-molar for phenylalanine. Bovine serum albumin, a serum protein with 3 tryptophan residues in its amino acid sequence was also used to characterize the detector. It was …

Determining The Biosynthetic Sequence In The Early Steps Of The Fumonisin Pathway By Use Of Three Gene-Disruption Mutants Of Fusarium Verticillioides, Ravi S. Bojja, Ronald Cerny, Robert H. Proctor, Liangcheng Du

Ronald Cerny Publications

Fumonisins are polyketide-derived mycotoxins produced by Fusarium verticillioides, a fungal pathogen of corn plants. Although a gene cluster for the biosynthesis of fumonisins has been cloned, the biosynthetic pathway is still not clear. We have used three gene-disrupted mutants, designated ΔFUM1, ΔFUM6, and ΔFUM8, to study the early steps of the pathway. Fumonisins were not produced in single-strain cultures of the ΔFUM1, ΔFUM6, and ΔFUM8 mutants. However, fumonisins were produced by ΔFUM1 or ΔFUM8 mutants when they were cocultured with the ΔFUM6 mutant. No fumonisins were produced when the ΔFUM1 and ΔFUM8 mutants were cocultured. These results suggest that …

Analysis Of Clinically Important Compounds Using Electrophoretic Separation Techniques Coupled To Time-Of-Flight Mass Spectrometry, Zlatuse Durda Peterson

Theses and Dissertations

Capillary electrophoretic (CE) separations were successfully coupled to time-of-flight mass spectrometric (TOFMS) detection for the analysis of three families of biological compounds that act as mediators and/or indicators of disease, namely, catecholamines (dopamine, epinephrine, norepinephrine) and their O-methoxylated metabolites (3-methoxytyramine, norepinephrine, and normetanephrine), indolamines (serotonin, tryptophan, and 5-hydroxytryptophan), and angiotensin peptides. While electrophoretic separation techniques provided high separation efficiency, mass spectrometric detection afforded specificity unsurpassed by other types of detectors.

Both catecholamines and indolamines are present in body fluids at concentrations that make it possible for them to be determined by capillary zone electrophoresis coupled to TOFMS without employing any …

Ab Initio Studies Of Π⋯Π Interactions: The Effects Of Quadruple Excitations, Brian W. Hopkins, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

To examine the effects of including quadruple excitations in the electron correlation treatment when computing the binding energy of van der Waals dimers, we have calculated MP2, CCSD, CCSD(T), and CCSD(TQ) interaction energies for several van der Waals complexes ranging from helium dimer to furan dimer. Through comparison of CCSD(TQ) and CCSD(T) binding energies the first direct assessment of the effects of quadruple excitations on π⋯π interactions is presented. The influence of triple excitations is assessed not only in the conventional manner that permeates the literature (comparison of CCSD(T) and MP2 interaction energies) but also via comparison of CCSD(T) and …

Bohmian Dynamics On Subspaces Using Linearized Quantum Force, Vitaly A. Rassolov, Sophya Garashchuk

Faculty Publications

In the de Broglie–Bohm formulation of quantum mechanics the time-dependent Schrödinger equation is solved in terms of quantum trajectories evolving under the influence of quantum and classical potentials. For a practical implementation that scales favorably with system size and is accurate for semiclassical systems, we use approximate quantum potentials. Recently, we have shown that optimization of the nonclassical component of the momentum operator in terms of fitting functions leads to the energy-conserving approximate quantum potential. In particular, linear fitting functions give the exact time evolution of a Gaussian wave packet in a locally quadratic potential and can describe the dominant …

In Situ Magnetoresistance Of Ni Nanocontacts, C-S Yang, Chunjuan Zhang, Jody G. Redepenning, Bernard Doudin

Chemistry Department: Faculty Publications

Magnetoresistance properties of Ni nanocontacts in the ballistic quantum regime are investigated in situ during closure and opening of electrochemically grown planar electrodes. The magnitude of conductance change when sweeping the magnetic field is of the order of the quantum conductance e²/h for conductance values spanning 1–100 quanta. The relative orientation of electric current and applied magnetic field changes the magnetoresistance sign, with symmetry properties reminiscent of bulk anisotropy magnetoresistance. Ex situ investigations of samples of higher conductance values, of the order of 1000 quanta, unambiguously show the analogy with bulk anisotropy magnetoresistance.

Hybrid Atomistic-Coarse-Grained Treatment Of Thin-Film Lubrication. I, Z.-B. Wu, Dennis J. Diestler, Ruqiang Feng, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A technique that melds an atomistic description of the interfacial region with a coarse-grained description of the far regions of the solid substrates is presented and applied to a two-dimensional model contact consisting of planar solid substrates separated by a monolayer fluid film. The hybrid method yields results in excellent agreement with the “exact” (i.e., fully atomistic) results. The importance of a proper accounting for the elastic response of the substrates, which is reliably and efficiently accomplished through coarse-graining of the far regions, is demonstrated.

Measurement Of The Anticancer Agent Gemcitabine And Its Deaminated Metabolite At Low Concentrations In Human Plasma By Liquid Chromatography-Mass Spectrometry, Yan Xu, Bruce Keith, Jean L. Grem

Chemistry Faculty Publications

A liquid chromatography/mass spectrometry (LC-MS) method has been developed and validated for the determination of the anticancer agent gemcitabine (dFdC) and its metabolite 2′,2′-difluoro-2′-deoxyuridine (dFdU) in human plasma. An Oasis® HLB solid phase extraction cartridge was used for plasma sample preparation. Separation of the analytes was achieved with a YMC ODS-AQ (5 μm, 120 Å, mm) column. The initial composition of the mobile phase was 2% methanol/98% 5 mM ammonium acetate at pH 6.8 (v/v), and the flow rate was 0.2 ml/min. An isocratic gradient was used for 3 min, followed by a linear gradient over 4 min to 30% …

Self-Assembled Arrays Of Zno Nanoparticles And Their Application As Varistor Materials, Suresh Pillai, Declan Mccormack, John Kelly, Raghavendra Ramesh

Articles

Linear arrays of ZnO nanoparticles have been successfully prepared by a simple sol–gel condensation reaction involving chemical modifiers, followed by drying (80oC) and calcination (500 oC). The calcined material (nanoarray ZnO) is composed of approximately spherical nanoparticles of average diameter 21+/-3 nm, selfassembled to form arrays extending in length to 2–4 mm. The morphology of the ZnO is found to depend sensitively on the amounts of chemical modifiers present. In their absence the ZnO produced (nano-ZnO) is an unstructured agglomerate of nanoparticles. The mechanism for formation of these linear arrays has been investigated by examining the intermediates formed at 80 …

Fum3p, A 2-Ketoglutarate-Dependent Dioxygenase Required For C-5 Hydroxylation Of Fumonisins In Fusarium Verticillioides, Yousong Ding, Ravi S. Bojja, Liangcheng Du

Liangcheng Du Publications

Fumonisins are polyketide-derived mycotoxins produced by several agriculturally important Fusarium species. The B series fumonisins, FB₁, FB₂, FB₃, and FB₄, are fumonisins produced by wild-type Fusarium verticillioides strains, differing in the number and location of hydroxyl groups attached to the carbon backbone. We characterized the protein encoded by FUM3, a gene in the fumonisin biosynthetic gene cluster. The 33-kDa FUM3 protein (Fum3p) was heterologously expressed and purified from Saccharomyces cerevisiae. Yeast cells expressing the Fum3p converted FB₃ to FB₁, indicating that Fum3p catalyzes the C-5 hydroxylation of fumonisins. …

Pictures From My Life With Polymer Science: Album 08, Otto Vogl

Otto Vogl

No abstract provided.

Consequences Of Block Number On The Order-Disorder Transition And Viscoelastic Properties Of Linear (Ab)N Multiblock Copolymers, Lifeng Wu, Eric W. Cochran, Timothy P. Lodge, Frank S. Bates

Eric W. Cochran

The effect of block number on the order-disorder transition (ODT) and viscoelastic properties were studied for linear (AB) n multiblock copolymers. A series of symmetric poly(styrene-b-isoprene) n multiblocks ((SI) n, n = 1-10) were synthesized by anionic polymerization, and their order-disorder transition temperatures (T ODT) were located using dynamic mechanical spectroscopy. As n increases, T ODT approaches an asymptotic value, consistent with random phase approximation calculations. A systematic difference between the experimental and theoretical results is attributable to the effects of fluctuations, independent of the number of blocks. Addition of up to 20 vol % of a nonselective solvent depresses …

Developmental Changes In Pedunculopontine Nucleus (Ppn) Neurons, T. Kobayashi, C. Good, J. Biedermann, Christina B. Cooley, R. D. Skinner, E. E. García-Rill

Chemistry Faculty Research

The developmental decrease in rapid-eye-movement (REM) sleep in man occurs between birth and after puberty. We hypothesize that if this decrease in REM sleep does not occur, lifelong increases in REM sleep drive may ensue. Such disorders are characterized by hypervigilance and sensory-gating deficits, such as are present in postpubertal onset disorders like schizophrenia, panic attacks (a form of anxiety disorder), and depression. The decrease in REM sleep in the rat occurs between 10 and 30 days of age. We studied changes in size and physiological properties of pedunculopontine nucleus (PPN) cells involved in the control of arousal, i.e., waking …

A Reoptimization Of The Five-Site Water Potential (Tip5p) For Use With Ewald Sums, Steven W. Rick

Chemistry Faculty Publications

The five-site transferable interaction potential (TIP5P) for water [M. W. Mahoney and W. L. Jorgensen, J. Chem. Phys. 112, 8910 (2000)] is most accurate at reproducing experimental data when used with a simple spherical cutoff for the long-ranged electrostatic interactions. When used with other methods for treating long-ranged interactions, the model is considerably less accurate. With small modifications, a new TIP5P-like potential can be made which is very accurate for liquid water when used with Ewald sums, a more physical and increasingly more commonly used method for treating long-ranged electrostatic interactions. The new model demonstrates a density maximum near 4 …