Chemistry Commons^™

Analysis Of Liquid-Phase Chemical Detection Using Guided Shear Horizontal-Surface Acoustic Wave Sensors, Zhonghui Li, Yolanda Jones, Jeanne M. Hossenlopp, Richard Cernosek, Fabien Josse

Chemistry Faculty Research and Publications

Direct chemical sensing in liquid environments using polymer-guided shear horizontal surface acoustic wave sensor platforms on 36° rotated Y-cut LiTaO3 is investigated. Design considerations for optimizing these devices for liquid-phase detection are systematically explored. Two different sensor geometries are experimentally and theoretically analyzed. Dual delay line devices are used with a reference line coated with poly (methyl methacrylate) (PMMA) and a sensing line coated with a chemically sensitive polymer, which acts as both a guiding layer and a sensing layer or with a PMMA waveguide and a chemically sensitive polymer. Results show the three-layer model provides higher sensitivity than the …

Angiotensin Ii-Mediated Regulation Of The Human Angiotensin Ii Type 1 Receptor Gene, Xylophone Vijai Aasee Victor

Theses and Dissertations

The physiological responses of angiotensin II (Ang II) are mediated across the cell membrane through the angiotensin II type 1 receptor (AT1R), a heptahelical membrane protein coupled to trimeric G-proteins on the cytosolic side. AT1R on binding its ligand, Ang II, leads to downregulation of cell-surface receptor and also its mRNA. We have investigated whether the 3'- and 5'-untranslated regions of the human AT1R mRNA mediate the degradation of hAT1R mRNA by post-transcriptional mechanisms in human adrenocortical carcinoma cell line (H295R cells). Protein kinase C (PKC) activator, phorbol-12-myristate-13-acetate (PMA), showed that the downregulation of hAT1R mRNA is mediated by the …

Development Of A Model For The Kinetics And Mechanism Of Nitrogenase, Phillip E. Wilson

Theses and Dissertations

Nitrogenase has a central role in the global nitrogen cycle as the enzyme that catalyzes the reduction of atmospheric N2 to NH3. Fixed nitrogen is generally limiting in the environment and in agriculture, so nitrogenase has received much attention as an alternative to nitrogen fertilizers. Characterizing the mechanism of nitrogenase is the goal of this work. The molybdenum nitrogenase enzyme system is comprised of the MoFe protein and the Fe protein. Interactions between these proteins and nucleotides are crucial to catalysis. An important approach to characterize these interactions is to correlate the kinetics of nitrogenase catalysis to a mechanism based …

Tris(Ethylenediamine)Cobalt(Iii) Nonaiododibismuthate, Andrea M. Goforth, Rachael E. Hipp, Mark D. Smith, Leroy Peterson Jr., Hans-Conrad Zur Loye

Faculty Publications

The asymmetric unit of the title compound, [Co(C₂H₈N₂)₃][Bi₂I₉], crystallizes in the orthorhombic space group Cmc2₁. The asymmetric unit contains half of a [Co(en)₃]³⁺ cation (en is ethylenediamine) and half of a [Bi₂I₉]^3- anion. Both species are located on mirror planes, requiring the [Co(en)₃]³⁺ cation to be present as a statistically disordered mixture of both enantiomeric forms. Crystals were grown solvothermally from an ethanol-water solvent mixture using rac-[Co(en)₃]I₃ and bismuth triiodide …

Keto-Carboxylic Acids In Carbonaceous Meteorites, Aliah C. Dugas

Electronic Dissertations and Theses

The Murchison meteorite is the best-characterized carbonaceous meteorite with respect to organic chemistry and is generally used as references for organic compounds in extraterrestrial material. Among the classes of organic compounds found in the meteorite are amino acids, carboxylic acids, hydroxy acids, purines, and pyrimidines. Absent among today's critically important biological compounds reported in carbonaceous meteorites are keto acids, i.e., pyruvic acid, acetoacetic acid, and higher homologs. These compounds are key intermediates in such critical processes as glycolysis and the citric acid cycle. In this study several individual meteoritic keto acids were identified by gas chromatography-mass spectrometry (GC-MS). All compounds …

Photoinduced One-Electron Reduction Of Alkyl Halides By Dirhodium(Ii,Ii) Tetraformamidinates And A Related Complex With Visible Light, Dean Johnston

Chemistry Faculty Scholarship

Various substituted dirhodium tetraformamidinate complexes, Rh(2)(R-form)(4) (R = p-CF(3), p-Cl, p-OCH(3), m-OCH(3); form = N,N'-diphenylformamidinate), and the new complex Rh(2)(tpgu)(4) (tpgu = 1,2,3-triphenylguanidinate) have been investigated as potential agents for the photoremediation of saturated halogenated aliphatic compounds, RX (R = alkyl group). The synthesis and characterization of the complexes is reported, and the crystal structure of Rh(2)(tpgu)(4) is presented. The lowest energy transition of the complexes is observed at approximately 870 nm and the complexes react with alkyl chlorides and alkyl bromides under low energy irradiation (lambda(irr) > or = 795 nm), but not when kept in the dark. The metal-containing …

Melting Temperature Of Ice IH Calculated From Coexisting Solid-Liquid Phases, J. Wang, S. Yoo, Jaeil Bai, James R. Morris, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

The purpose of this paper is twofold: (1) to compute the melting temperature (T_m) of ice I_h with both TIP4P and TIP5P models by using the two-phase coexistence method and to compare with previously obtained T_m; (2) to compute the T_m using recently improved TIP4P and TIP5P models, namely, the TIP4P-Ew (Ref. 6) and TIP5P-Ew (Ref. 7) models. Both models are developed specifically for use with Ewald techniques. The TIP4P-Ew model, in particular, has shown substantial improvement over the original TIP4P model as it can reproduce the density maximum at about 274 K, …

Spm Oxidation And Parallel Writing On Zirconium Nitride Thin Films, N. Farkas, J. R. Comer, G. Zhang, Edward A. Evans, R. D. Ramsier, J. A. Dagata

Chemical, Biomolecular, and Corrosion Engineering Faculty Research

Systematic investigation of the SPM oxidation process of sputter-deposited ZrN thin films is reported. During the intrinsic part of the oxidation, the density of the oxide increases until the total oxide thickness is approximately twice the feature height. Further oxide growth is sustainable as the system undergoes plastic flow followed by delamination from the ZrN-silicon interface keeping the oxide density constant. ZrN exhibits superdiffusive oxidation kinetics in these single tip SPM studies. We extend this work to the fabrication of parallel oxide patterns 70 nm in height covering areas in the square centimeter range. This simple, quick, and well-controlled parallel …

Promoting Learning Through Peer Group Work, Christine O'Connor, Renli Ma

Conference Papers

The session aimed to help the Summer School participants develop tasks and assessment strategies of peer group work in their own teaching.

Protection Against Experimental Autoimmune Myocarditis Is Mediated By Interleukin-10-Producing T Cells That Are Controlled By Dendritic Cells, Ya Li, Janet S. Heuser, Stanley D. Kosanke, Mark E. Hemric, Madeleine W. Cunningham

Faculty Publications and Presentations

Experimental autoimmune myocarditis (EAM) can be induced in the Lewis rat by cardiac myosin or its cryptic S2-16 peptide epitope (amino acids1052 to 1076). To investigate cellular mechanisms and the role of antigen-presenting cells in regulation of myocarditis, we induced protection against EAM in Lewis rats by administration of S2-16 peptide in incomplete Freund’s adjuvant (IFA). Protection to EAM was associated with activation of S2-16-reactive splenocytes secreting high levels of interleukin (IL)-10 and reduced levels of interferon- and IL-2. Adoptive transfer of S2-16:IFA-induced splenocytes producing IL-10 suppressed myocarditis induction in syngeneic recipients, suggesting their regulatory cell nature. However, exposure of …

Deconvolution Of The Co3O4(110) Fuchs–Kliewer Phonon Spectrum, E.M. Marsh, S.C. Petitto, G.S. Harbison, K.W. Wulser, Marjorie Langell

Marjorie A. Langell Publications

The Fuchs–Kliewer phonon spectrum of single crystal Co₃O₄(110) has been treated with a Fourier transform log deconvolution method, which removes multiple scattering features from the single loss spectrum. Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) were first used to characterize the Co₃O₄ crystal establishing the cleanliness, composition, and order of the (110) surface. High resolution electron energy loss spectroscopy (HREELS) was then used to obtain the phonon spectrum for an incident electron energy of 3.77 eV. Due to the strong dipole cross section for the Fuchs–Kliewer phonon …

Expandable Graphite/Polyamide-6 Nanocomposites, Fawn Marie Uhl, Qiang Yao, Hiroyoshi Nakajima, Evangelos Manias, Charles A. Wilkie

Chemistry Faculty Research and Publications

Polyamide-6 (PA-6)/graphite nanocomposites were prepared by melt blending, using a variety of graphites, including virgin graphite, expandable graphites and expanded graphite. The resulting nanocomposites were characterized by X-ray diffraction, thermogravimetric analysis, cone calorimetry, and tensile mechanical analysis. Nanocomposite formation does occur, as denoted by the nanometre dispersion of graphite layers in the polymer matrix, and the dispersion depends on the graphite treatment. The material properties of the resulting composites are improved relative to the virgin/unfilled polymer; in particular, there is an enhancement of the thermal stability without any significant deterioration of the mechanical properties.

Fire Retardancy Of Vinyl Ester Nanocomposites: Synergy With Phosphorus-Based Fire Retardants, Grace Chigwada, Panchatapa Jash, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

Vinyl ester (PVE) nanocomposites were prepared using both clay and polyhedral oligosilsesquioxanes (POSS) as the nano-dimensional material. From cone calorimetric data, it was shown that both POSS and clay affect the flammability of the nanocomposites to the same extent. To improve on the flame retardancy, the nanocomposites were combined with phosphorous-containing fire retardants (FRs) and the result compared to the benchmark halogen-containing system. The use of the cone calorimeter to investigate the fire properties of these nanocomposites showed a great reduction in peak heat release rate (PHRR) in the presence of phosphate and slight improvements in average mass loss rate …

An Analysis Of The Chemical Processes In The Smoke Plume From A Savanna Fire, Jorg Trentmann, Robert J. Yokelson, Peter V. Hobbs, Tanja Winterrath, Ted J. Christian, Meinrat O. Andreae, Sherri A. Mason

Chemistry and Biochemistry Faculty Publications

[1] Photochemistry in young plumes from vegetation fires significantly transforms the initial fire emissions within the first hour after the emissions are injected into the atmosphere. Here we present an investigation of field measurements obtained in a smoke plume from a prescribed savanna fire during the SAFARI 2000 field experiment using a detailed photochemical box-dilution model. The dilution used in the model simulations was constrained by measurements of chemically passive tracers (e.g., CO) near and downwind of the fire. The emissions of the dominant carbonaceous compounds, including oxygenated ones, were taken into account. The field measurements revealed significant production of …

Synthesis And Characterization Of Azole Isoflavone Inhibitors Of Aromatase, John C. Hackett, Young Woo Kim, Bin Su, Robert W. Brueggemeier

Chemistry Faculty Publications

The synthesis and biological evaluation of a series of 2-azole and 2-thioazole isoflavones as potential aromatase inhibitors are described. Differences in inhibitory activity of triazole and imidazole inhibitors are rationalized with density functional theory to expose a key difference in the electronic structure of these molecules. In addition, difference binding spectra of inhibitors to immunoaffinity-purified aromatase produces classical Type II spectra consistent with coordination of the nitrogen lone pair electrons to the aromatase P450 heme.

Fluorescence-Dip Infrared Spectroscopy And Predissociation Dynamics Of Oh A (V=4) Radicals, Erika L. Derro, Ilana B. Pollack, Logan P. Dempsey, Margaret E. Greenslade, Yuxiu Lei, Dragana C. Radenovic, Marsha I. Lester

Chemistry

Fluorescence-dip infrared spectroscopy, an UV-IR double-resonance technique, is employed to characterize the line positions, linewidths, and corresponding lifetimes of highly predissociative rovibrational levels of the excited A  electronic state of the OH radical. Various lines of the 4←2 overtone transition in the excited A  state are observed, from which the rotational, centrifugal distortion, and spin-rotation constants for the A  (v = 4) state are determined, along with the vibrational frequency for the overtone transition. Homogeneous linewidths of 0.23–0.31 cm⁻¹ full width at half maximum are extracted from the line profiles, demonstrating that the N = …

Photoinduced One-Electron Reduction Of Alkyl Halides By Dirhodium(Ii,Ii) Tetraformamidinates And A Related Complex With Visible Light, Dean Johnston

Chemistry Faculty Scholarship

Various substituted dirhodium tetraformamidinate complexes, Rh(2)(R-form)(4) (R = p-CF(3), p-Cl, p-OCH(3), m-OCH(3); form = N,N'-diphenylformamidinate), and the new complex Rh(2)(tpgu)(4) (tpgu = 1,2,3-triphenylguanidinate) have been investigated as potential agents for the photoremediation of saturated halogenated aliphatic compounds, RX (R = alkyl group). The synthesis and characterization of the complexes is reported, and the crystal structure of Rh(2)(tpgu)(4) is presented. The lowest energy transition of the complexes is observed at approximately 870 nm and the complexes react with alkyl chlorides and alkyl bromides under low energy irradiation (lambda(irr) > or = 795 nm), but not when kept in the dark. The metal-containing …

Sensing Of Antipyretic Carboxylates By Simple Chromogenic Calix[4]Pyrroles, Ryuhei Nishiyabu, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

We present a simple, two- or three-step method for the synthesis of chromogenic octamethylcalix[4]pyrrole-based (OMCP) sensors for anions. Electrophilic aromatic substitution allows for converting the pyrrole moieties of OMCP into a dye. The formation of a sensor-anion complex results in partial charge transfer and a dramatic change in color. The absorption (UV-vis) and NMR titration experiments show that the chromogenic OMCPs sense anions administered as aqueous solutions, even at high ionic strength ( approximately 0.1 M NaCl), while displaying selectivity for pyrophosphate and carboxylate anions. The experiments with polyurethane sensor films show a strong response for aqueous carboxylates, such as …

Cu(I) Luminescence From The Tetranuclear Cu4s4 Cofactor Of A Synthetic 4-Helix Bundle, Olesya A. Kharenko, David C. Kennedy, Borries Demeler, Michael J. Maroney, Michael Y. Ogawa

Chemistry Faculty Publications

The addition of Cu(I) to the random-coil peptide, C16C19-GGY, produces a self-organized, metal-bridged 4-helix bundle which displays an intense room-temperature luminescence at 600 nm. Emission, UV, and CD titrations along with X-ray absorption studies indicate that the luminescent cofactor is likely a Cu4S4 cluster in which each Cu atom is bridged by the side chains of two cysteine residues and has terminal N/O ligation.

Synthesis And Spectroscopic Characterization Of Manganese Doped Zinc Sulfide Quantum Dot Nanocrystals, Pedro A. Gonzalez Beerman

Dissertations

Zinc sulphide quantum dots were synthesized in aqueous media using sodium polyphosphate as the stabilizer. The nanoparticles were 2.5 ± 0.5 nm and 5.0 ± 0.5 nm diameter depending on the synthetic procedure employed and the amount of Mn doped varied from 0.003 to 0.32% (w/w). The nanoparticles were characterized by UV-Vis absorption, luminescence, EPR, near edge x-ray absorption fine structure (NEXAFS), and x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD), and transmission electron microscopy (TEM). These quantum dots show a strong emission at 590 nm due to the ⁴T₁ -⁶A₁ transition characteristic of Mn …

Acylpyrazolones: Synthesis, Self-Assembly And Lanthanide Metal Ion Separation, Jun Yang

Dissertations

The central hypothesis that nanoscale self-assemblies can provide excellent metal ion recognition has been substantiated by employing acylpyrazolones and trivalent lanthanide metal ions as model systems. Several novel acylpyrazolones and their amphiphilic analogs have been designed, synthesized, and characterized. Their lanthanide metal ion recognition efficacies have been demonstrated through baseline separations of a mixture of light, middle, and heavy lanthanide metal ions by employing them in the aqueous mobile phase of high performance liquid chromatography (HPLC) with octadecylsilanized silica (ODS) as the stationary phase. The complex separation mechanism is influenced by the structures of acylpyrazolone and amphiphilic moieties, and spontaneous …

Radiolytic Damage To Freeze-Dried Human Amniotic Membrane, Chester C. Deocaris, Lucille B. Abad, Erwin P. Enriquez, Zenaida M. De Guzman, Ann A. Aliganga, Marianne B. Tangonan, Mitos M. Tolentino, Luzviminda V. Ignacio, Custer C. Deocaris

Chemistry Faculty Publications

Radiation-sterilization at 25 and 35 kGy of freeze-dried human amniotic membranes caused degradative effects in the biologic dressing. The decrease in pH and increase in UV absorption showed that radiation may have caused possible radiolytic changes in this biomaterial. Total nitrogen content, tensile strength, and [H3]water-retention capacity of the irradiated membranes remained invariable. Molecular topography analysis by atomic force microscopy showed radiation-induced defrayment of the collagen fibers, the major structural protein in amnion.

1,12-Diferrocenyldodecane At 100 K, Danielle M. Bequeath, Richard L. Porter, Michael W. Lufaso, Timothy R. Wagner, Rachel L. Kusnic, Matthias Zeller, Larry S. Curtin

Chemistry Faculty Research and Scholarship

1,12-Diferrocenyldodecane, [Fe₂(C₅H₅)₂(C₂₂H₃₂)], was synthesized from ferrocene and 1,12-dodecanedioyl chloride, followed by Clemmensen reduction. The single-crystal structure was determined at 100 K by X-ray diffraction and the spectroscopic and cyclic voltammetric data of 1,12-diferrocenyldodecane and its precursor are reported.

Biologically Active Fluorescent Farnesol Analogs, Roman Shchepin, Razvan Dumitru, Kenneth W. Nickerson, Miranda Lund, Patrick Dussault

Patrick Dussault Publications

We describe ten polyene analogs of farnesol, typified by 3,7,11-trimethyl-2,4,6,8,10-dodecapentenaldehyde oxime, which preserve the length, cross-section, and approximate hydrophobicity of farnesol. Four of the ten display strong quorum- sensing activity in the human pathogen Candida albicans, with IC₅₀ values for inhibition of germ-tube formation as low as 10 μM. The polyenes display absorption maxima between 320 and 380 nm, with the extinction coefficients for the oximes approaching 100,000. All but two of the analogs are fluorescent, with excitation maxima varying over the range of 320–370 nm. Oxime anti-4, which can undergo fluorescence excitation at wavelengths beyond 400 …

Ionic Liquid As Catalysts In The Cycloaddition Of Co2 To Styrene Oxide In Supercritical And Subcritical States, Joy Mwalimu

Masters Theses

Supercritical fluids (SCFs) have fascinated researchers ever since the discovery of a critical temperature more than a century ago.¹ Initial studies focused mainly on the physical properties of supercritical phases.² However, their use as reaction media has sparked mainly during the last five to ten years.²

The coupling of CO₂ and Ionic Liquids (ILs) in the synthesis of cyclic carbonates comes from an increasing need for environmentally and toxicologically benign processes for the production of high-value compounds. In my research, CO₂ was utilized as both a replacement solvent and a C₁ feedstock in its …

Afci Quarterly Input – Unlv April Through June, 2005, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects, activities and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

The Electrochemical Separation Of Curium And Americium: Quaterly Report April - June, 2005, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium.

Results

• We have completed the electrochemical investigation in of the Ce³⁺/Ce⁴⁺ redox couple and have determined the optimum experimental conditions.

• Computer modeling of the cerium using the JChess speciation-modeling program has been completed for the Ce redox couple. Traditional complexing ligands such as EDTA, oxalate, NTA, phosphate, acetate, and sulfate have been purchased and will be used to initiate the complexation and electrochemical characterization.

• Electrochemical investigations have continued on the Eu²⁺/Eu³⁺ redox …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix: Neutronic Evaluation Of Zro2-Mgo Inert Fuels, E. Shwageraus, A. Galperin, E. Fridman, S. Kolesnikov

Fuels Campaign (TRP)

This report presents results of the analysis performed within the framework of “Dissolution, Reactor, and Environmental Behavior of ZrO₂-MgO Inert Fuel Matrix” project managed by University of Nevada at Las Vegas, Harry Reid Center for Environmental Studies. The main objective of the study was to explore the basic neutronic feasibility of using MgO-ZrO₂ as inert fuel matrix for Pu recycling in conventional Light Water Reactors (LWR).

Synergy Between Nanocomposite Formation And Low Levels Of Bromine On Fire Retardancy In Polystyrenes, Grace Chigwada, Panchatapa Jash, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

An organically-modified clay has been prepared using ammonium salts which contain an oligomeric material consisting of vinylbenzyl chloride, styrene and dibromostyrene. The presence of dibromostyrene enhances the flame retardancy of polystyrene nanocomposites compared to both the virgin polymer and polystyrene nanocomposites prepared from non-halogen-containing organically-modified clays. The nanocomposites were prepared both by bulk polymerization and melt blending and they were evaluated by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry measurements. Bulk polymerization produced nanocomposites with reduced peak heat release rate, reduced total heat release and improved thermal stability. It is noteworthy that all these improvements were obtained …

Effects Of Surfactants On The Thermal And Fire Properties Of Poly(Methyl Methacrylate)/Clay Nanocomposites, Panchatapa Jash, Charles A. Wilkie

Chemistry Faculty Research and Publications

Nanocomposites of poly(methyl methacrylate) (PMMA) with layered silicates and with polyhedral oligosilsesquioxanes (POSS) were prepared by bulk polymerization. The thermal and fire stabilities of the various organically-modified clay and POSS nanocomposites were evaluated using both thermogravimetric analysis (TGA) and cone calorimetry. Thermogravimetric analysis is not a good criteria for evaluating nanocomposite formation but cone calorimetry can be. For montmorillonite systems, when more than 4% clay is present, the expected reduction in peak heat release rate is observed. For hectorite, a minimum of 6% clay concentration is required to achieve the same reduction in peak heat release rate. POSS has the …