Chemistry Commons^™

Study On Electrochemical Behavior Of Copper In Nh3 ·H2O Solution Medium Including K3[Fe(Cn)6] During Cmp, Yue-Hua Hu, Han-Wei He, Ke-Long Huang

Journal of Electrochemistry

Influence of medium pH value and passivator concentrations on the copper passivation and CMP process were studied by electrochemical measurement technologies, relations of the film thickness and tightness with polishing process and polishing rates were investigated. Electrochemical variables influencing polishing process and rates were found out. Electochemical mechanism of polishing processes were explained by corrosion potential and corrosion current density. A recipe of K₃[Fe(CN)₆] as passivator and nano sized γ-Al₂O₃ as abrasives in medium of NH₃·H₂O solution was confirmed reasonable. It is shown that the conditions of polishing process …

Study On The Anticorrosion Of Ld-2 Compound Inhibitor On Reinforcing Steel In Seawater, Rong-Gui Du, Zhou-Cheng Wang, Ruo-Shuang Huang, Rong-Gang Hu, Bing Zhao, Jian-Guang Tan, Chang-Jian Lin

Journal of Electrochemistry

The effect of LD-2 compound inhibitor developed in our laboratory on its anticorrosion action on the reinforcing steel in concrete immersed in seawater was shown in this paper. The corrosion behavior of the reinforcing steel in seawater was studied using electrochemical techniquesand immersion tests. The polarization curve of the reinforcing steel immersed in seawater showedthe free corrosion potential of the steel increased by 0. 220 V (vs. SCE), and the corrosion current decreased by two orders of magnitude by adding 25 g⋅L^-1 compound inhibitor to the seawater. The potentiodynamic anodic polarization curve of reinforcing steel in the seawater with …

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials: Aaa Task-4 Quarterly (September 1 – November 30, 2001) Report, Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The primary objective of this task is to evaluate the effect of hydrogen on environment-assisted cracking of candidate materials for applications in spallation-neutron-target (SNT) systems such as accelerator production of tritium (APT) and accelerator transmutation of waste (ATW). The materials selected for evaluation and characterization are martensitic stainless steels including HT- 9, EP 823 and 422. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of these alloys will be evaluated in environments of interest using tensile specimens under constant load and slow-strain-rate (SSR) conditions. The extent and morphology of cracking of these alloys will further be evaluated …

Sulfur Dioxide Uptake And Oxidation In Sea-Salt Aerosol, William Hoppel, Louise Pasternack, Peter F. Caffrey, Glendon Frick, James Fitzgerald, Dean A. Hegg, Song Gao, John Ambrusko, Thomas Albrechcinski

Chemistry and Physics Faculty Articles

Measurements of SO₂ and O₃ uptake by sea-salt and NaCl aerosol were made in a 600 m³environmental chamber by measuring the rate of SO₂ and O₃ depletion during nebulization of seawater and NaCl solutions. The experiments were carried out with starting relative humidity between 80% and 92%, with SO₂ concentrations between 35 and 60 ppb, and ozone concentrations between O and 110 ppb. For NaCl, no SO₂ or O₃uptake was observed. For sea-salt aerosol, uptake in the range of 0.21 and 1.2 millimoles of S per liter of (nebulized) seawater …

Particle Formation And Growth From Ozonolysis Of Α-Pinene, William Hoppel, James Fitzgerald, Glendon Frick, Peter F. Caffrey, Louise Pasternack, Dean A. Hegg, Song Gao, W. Richard Leaitch, Nicole Shantz, Chris Cantrell, Thomas Albrechcinski, John Ambrusko, William Sullivan

Chemistry and Physics Faculty Articles

Observations of particle nucleation and growth during ozonolysis of α-pinene were carried out in Calspan's 600 m³ environmental chamber utilizing relatively low concentrations of α-pinene (15 ppb) and ozone (100 ppb). Model simulations with a comprehensive sectional aerosol model which incorporated the relevant gas-phase chemistry show that the observed evolution of the size distribution could be simulated within the accuracy of the experiment by assuming only one condensable product produced with a molar yield of 5% to 6% and a saturation vapor pressure (SVP) of about 0.01 ppb or less. While only one component was required to simulate the …

In-Cloud Oxidation Of So2 By O3 And H2o2: Cloud Chamber Measurements And Modeling Of Particle Growth, Peter F. Caffrey, William Hoppel, Glendon Frick, Louise Pasternack, James Fitzgerald, Dean A. Hegg, Song Gao, W. R. Leaitch, Nicole Shantz, Thomas Albrechcinski, John Ambrusko

Chemistry and Physics Faculty Articles

Controlled cloud chamber experiments were conducted to measure particle growth resulting from the oxidation of SO₂ by O₃ and H₂O₂ in cloud droplets formed on sulfuric acid seed aerosol. Clouds were formed in a 590 m³ environmental chamber with total liquid water contents ranging from 0.3–0.6 g m⁻³ and reactant gas concentrations <10 ppbv for SO₂ and H₂O₂ and <70 ppbv for O₃. Aerosol growth was measured by comparison of differential mobility analyzer size distributions before and after each 3–4 min cloud cycle. Predictions of aerosol growth were then made with a full microphysical cloud …

Experimental And Modeling Studies Of Secondary Organic Aerosol Formation And Some Applications To The Marine Boundary Layer, Song Gao, Dean A. Hegg, Glendon Frick, Peter F. Caffrey, Louise Pasternack, Chris Cantrell, William Sullivan, John Ambrusko, Thomas Albrechcinski, Thomas W. Kirchstetter

Chemistry and Physics Faculty Articles

A series of controlled experiments were carried out in the Calspan Corporation's 600 m³environmental chamber to study some secondary organic aerosol formation processes. Three precursor-ozone systems were studied: cyclopentene-ozone, cyclohexene-ozone, and α-pineneozone. Additionally, SO₂ was added to the initial gas mixture in several instances and was likely present at trace levels in the ostensibly organic-only experiments. It was found that all three systems readily formed new submicron aerosols at very low reactant levels. The chemical composition of formed aerosols was consistent with some previous studies, but the yields of organic products were found to be lower in …

Magnetic Ordering In An Organic Polymer, Andrzej Rajca, Jirawat Wongsriratanakul, Suchada Rajca

Andrzej Rajca Publications

We describe preparation and magnetic properties of an organic p-conjugated polymer with very large magnetic moment and magnetic order at low temperatures. The polymer is designed with a large density of cross-links and alternating connectivity of radical modules with unequal spin quantum numbers (S), macrocyclic S = 2 and, cross-linking S = ½ modules, which permits large net S values for either ferromagnetic or antiferromagnetic exchange couplings between the modules. In the highly cross-linked polymer, an effective magnetic moment corresponding to an average S of about 5000 and slow reorientation of the magnetization by a small magnetic field …

Micromagnetics Simulation Of Deep-Submicron Supermalloy Disks, Scott L. Whittenburg, Ngocnga Dao, R. P. Cowburn

Chemistry and Biochemistry Faculty Publications

The results of recent micromagnetic simulations of deep submicron supermalloy disks are presented. A recent experimental measurement of the hysteresis and magnetic domain structure in supermalloy disks with diameters ranging from 55 to 500 nm and thickness ranging from 6 to 15 nm has been reported. Our micromagnetic simulations show remarkable agreement with the experimental hysteresis loops. The simulation results show that for thin or small diameter disks a single magnetic domain exists with all spins aligned. The hysteresis loop represents free rotation of these spins. For larger diameter disks or as the thickness increases the hysteresis loops change shape …

Analysis Of Corrosion Of Steel By Lead Bismuth Eutectic, John Farley, Dale L. Perry

Transmutation Sciences Materials (TRP)

We examined stainless samples that were exposed to LBE in experiments conducted by the Russians, under contract to Los Alamos. We examined both corroded and uncorroded samples using the Scanning Electron Microscope (SEM), the Energy Dispersive X-Ray (EDAX) Spectroscopy, and the X-ray Photoelectron Spectrometer (XPS). We found that the surface of the corroded sample is covered by oxygen-containing compounds, presumably mostly iron oxide. In samples exposed for shorter times or lower temperatures, we found that some areas were covered by an oxide layer, and some areas was uncovered. We found that the level of Cr in the uncovered area is …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics: Quarterly Progress Report August 16,2001- November 15, 2001, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The Lead-Bismuth eutectic (LBE) has been determined from previous experimental studies by the Russians and the European scientific community to be a potential material that can be used as a spallation target and coolant for the AAA proposed application.

Properly controlling the oxygen content in LBE can drastically reduce the LBE corrosion to structural steels. However, existing knowledge of material corrosion performance was obtained from point-wise testing with very limited density. The transport of oxygen and corrosion products, their interaction and variation of corrosion/precipitation along the flow are not well understood.

The first subtask of this project involves using a …

Monte Carlo Simulation Of Homogeneous Binary Vapor–Liquid Nucleation: Mutual Enhancement Of Nucleation In A Partially Miscible System, S. Yoo, K.J. Oh, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Gibbs free energy of ij-cluster formation ΔG_ij is obtained via the relation n_ij=Ne^{-ΔG_ij /k_BT}, where N is the number of molecules in the system, T is temperature, and kB is the Boltzmann constant. The saddle point on the free energy surface ΔG_ij versus i and j provides a measure of the activation barrier to nucleation ΔG *. A statistical mechanical formula of ΔG_ij is derived based on the physical-cluster theory of nucleation, and from which a molecular interpretation of ΔG_{ij …}

Synthesis Of A New Hollandite-Type Manganese Oxide With Framework And Interstitial Cr(Iii), Stanton Ching, Peter F. Driscoll, Katarzyna S. Krukowska, Michael R. Marvel, Steven L. Suib

Chemistry Faculty Publications

Hollandite with Cr(III) in both tunnel and framework sites has been prepared hydrothermally from layered manganese oxide precursors.

Ca4Iro6, Ca3Mgiro6 And Ca3Zniro6, Matthew J. Davis, Mark D. Smith, Hans Conrad Zur Loye

Faculty Publications

Single crystals of tetracalcium iridium hexaoxide, Ca₄IrO₆, tricalcium magnesium iridium hexaoxide, Ca₃MgIrO₆, and tricalcium zinc iridium hexaoxide, Ca₃ZnIrO₆, were prepared via high-temperature flux growth and structurally characterized by single-crystal X-ray diffraction. The three compounds are isostructural and adopt the K₄CdCl₆ structure type, comprised of chains of alternating face-shared [CaO₆], [MgO₆] or [ZnO₆] trigonal prisms and [IrO₆] octahedra, surrounded by columns of Ca²⁺ ions.

Formula: Ca₄IrO₆, Ca_3.34Mg_0.66IrO₆ and …

Variational Transition State Theory Evaluation Of The Rate Constant For Proton Transfer In A Polar Solvent, Robin P. Mcrae, Gregory K. Schenter, Bruce C. Garrett, Zoran Svetlicic, Donald G. Truhlar

Chemistry and Biochemistry Faculty Publications

Variational transition state theory (VTST) is used to calculate rate constants for a model proton transfer reaction in a polar solvent. We start from an explicit description of the reacting solute in a solvent, and we model the effects of solvation on the reaction dynamics by a generalized Langevin equation (GLE) for the solute. In this description, the effects of solvation on the reaction energetics are included in the potential of mean force, and dynamical, or nonequilibrium, solvation is included by solvent friction. The GLE solvation dynamics are approximated by a collection of harmonic oscillators that are linearly coupled to …

Micromagnetics Simulation Of Deep-Submicron Supermalloy Disks, Scott Whittenburg

Chemistry Faculty Publications

The results of recent micromagnetic simulations of deep submicron supermalloy disks are presented. A recent experimental measurement of the hysteresis and magnetic domain structure in supermalloy disks with diameters ranging from 55 to 500 nm and thickness ranging from 6 to 15 nm has been reported. Our micromagnetic simulations show remarkable agreement with the experimental hysteresis loops. The simulation results show that for thin or small diameter disks a single magnetic domain exists with all spins aligned. The hysteresis loop represents free rotation of these spins. For larger diameter disks or as the thickness increases the hysteresis loops change shape …

A Dipolar Coupling Based Strategy For Simultaneous Resonance Assignment And Structure Determination Of Protein Backbones, Fang Tian, Homayoun Valafar, James H. Prestegard

Faculty Publications

A new approach for simultaneous protein backbone resonance assignment and structure determination by NMR is introduced. This approach relies on recent advances in high-resolution NMR spectroscopy that allow observation of anisotropic interactions, such as dipolar couplings, from proteins partially aligned in field ordered media. Residual dipolar couplings are used for both geometric information and a filter in the assembly of residues in a sequential manner. Experimental data were collected in less than one week on a small redox protein, rubredoxin, that was 15N enriched but not enriched above 1% natural abundance in 13C. Given the acceleration possible with partial 13C …

The Tetramethylpiperidinyl-1-Oxide Anion (Tmpo-) As A Ligand In Lanthanide Chemistry: Synthesis Of The Per(Tmpo-) Complex [(Onc5h6me4)2sm(Μ-Onc5h6me4)]2, William J. Evans, Jeremy M. Perotti, Robert J. Doedens, Joseph W. Ziller

Chemistry and Physics Faculty Articles

(C₅Me₅)₃Sm reacts with the free radical 2,2,6,6-tetramethylpiperidinyl-1-oxy (TMPO) to form (C₅Me₅)₂ and the per nitroxide [(η¹-ONC₅H₆Me₄)₂ Sm(μ-η¹∶η²-ONC₅H ₆Me₄)]₂

Simultaneous Determination Of Enantiomers Of Structurally Related Anticholinergic Analogs In Human Serum By Liquid Chromatography–Electrospray Ionization Mass Spectrometry With On-Line Sample Cleanup, Vladimı́R Čápka, Yan Xu

Chemistry Faculty Publications

Trihexyphenidyl, biperiden and procyclidine are anticholinergic drugs produced as racemates for the treatment of Parkinson’s disease. This paper describes a simple and sensitive LC–MS method for the simultaneous determination of these compounds in human serum. An on-line sample clean-up procedure was used, where serum samples were directly injected into a “restricted-access media” pre-column. After the exclusion of the serum proteins, the drug molecules were eluted to a β-cyclodextrin analytical column for chiral separation. The quantitation was done by electrospray ionization MS using diphenidol as an internal standard. The method developed has limits of detection of 1 ng/ml, at least two-orders-of-magnitude …

Alpha-Alkyl-Alpha-Amino-Beta-Sulphone Hydroxamates As Potent Mmp Inhibitors That Spare Mmp-1, Daniel Becker, Gary A. Decrescenzo, John Freskos, Daniel P. Getman

Chemistry: Faculty Publications and Other Works

A series of α-alkyl-α-amino-β-sulphone hydroxamates was prepared and evaluated for potency versus MMP-2 and MMP-13, and for selectivity versus MMP-1. Low nanomolar potency was obtained with selectivity versus MMP-1 ranging from >10 to >1000. Selected compounds were orally bioavailable.

Highly Plasma Etch-Resistant Photoresist Composition Containing A Photosensitive Polymeric Titania Precursor, Tony D. Flaim, Douglas J. Guerrero, Michelle R. Fowler, William Joseph James, Vladimir Petrovsky, Harlan U. Anderson

Chemistry Faculty Research & Creative Works

A composition is derived from an addition polymerizable organotitanium polymer which upon exposure to an oxygen plasma or baking in air, is converted to titanium dioxide (titania) or is converted to a mixed, titanium-containing metal oxide. The metal oxide formed in situ imparts etch- resistant action to a patterned photoresist layer. The composition may also be directly deposited and patterned into permanent metal oxide device features by a photolithographic process.

Structural Evidence That The Methionyl Aminopeptidase From Escherichia Coli Is A Mononuclear Metalloprotease, Nathaniel J. Cosper, Ventris M. D'Souza, Robert A. Scott, Richard C. Holz

Chemistry Faculty Research and Publications

The Co and Fe K-edge extended X-ray absorption fine structure (EXAFS) spectra of the methionyl aminopeptidase from Escherichia coli (EcMetAP) have been recorded in the presence of 1 and 2 equiv of either Co(II) or Fe(II) (i.e., [Co(II)_(EcMetAP)], [Co(II)Co(II)(EcMetAP)], [Fe(II)_(EcMetAP)], and [Fe(II)Fe(II)(EcMetAP)]). The Fourier transformed data of both [Co(II)_(EcMetAP)] and [Co(II)Co(II)(EcMetAP)] are dominated by a peak at ca. 2.05 Å, which can be fit assuming 5 light atom (N,O) scatterers at 2.04 Å. Attempts to include a Co−Co interaction (in the 2.4−4.0 Å range) in the …

Two Different One-Dimensional Structural Motifs In The Same Coordination Polymer: A Novel Interpenetration Of Infinite Ladders By Bundles Of Infinite Chains, Badruz Zaman, Mark D. Smith, Hans Conrad Zur Loye

Faculty Publications

A coordination polymer with a novel structural motif
consisting of stacks of infinite ladders interpenetrated by
bundles of infinite chains is described; geometrical arguments
are made for the requirements that can lead to such
interpenetration as a function of ligand dimensions.

Effect Of Surface Charges On The Rates Of Intermolecular Electron-Transfer Between De Novo Designed Metalloproteins, Anna Y. Kornilova, James F. Wishart, Michael Y. Ogawa

Chemistry Faculty Publications

A de novo designed coiled-coil metalloprotein was prepared that uses electrostatic interactions to control both its conformational and bimolecular electron-transfer properties. The title protein exists as a coiled-coil heterodimer of the [Ru(trpy)(bpy)-KK(37-mer)] and [Ru(NH3)(5)-EE(37-mer)] polypeptides which is formed by interhelix electrostatic attractions. Circular dichroism studies show that the electrostatic heterodimer has Kd 0.19 +/- 0.03 muM and is 96% helical at high concentrations. Intercomplex electron-transfer reactions were studied that involve the [Ru(NH3)(5)-H21](2+) electron-donor and the [Ru(trpy)(bpy)H21](3+) electron-acceptor belonging to different electrostatic dimers. An important feature of the designed metalloprotein is its two cationic redox centers embedded within protein surfaces having …

Energetics And Cooperativity In Three-Center Hydrogen Bonding Interactions. I. Diacetamide-X Dimers .X=Hcn, Ch3Oh., Ruben D. Parra, Makoto Furukawa, Bing Gong, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

High level ab initio calculations are carried out on diacetamide–X (DA–X) dimers, X=HCN, CH₃OH. The dimers are used as model systems to investigate the energetics and cooperative phenomomena in intermolecular three-center hydrogen-bond (H-bond) interactions relative to two-center H-bond interactions. The trans–trans conformer of diacetamide is chosen as a suitable model for intermolecular three-center H bonding where one H atom is interacting with two acceptor atoms. The proton–acceptor atoms are rigidly held in the same molecule. For both model systems, it is found that the calculated interaction energy per H bond is appreciably smaller in the three-center than in …

Crystal Structure Of Mtan, A Global Multidrug Transporter Gene Activator, Michael H. Godsey, Natalya N. Baranova, Alexander A. Neyfakh, Richard G. Brennan

CUP Faculty Research

MtaN (Multidrug Transporter Activation, N terminus) is a constitutive, transcriptionally active 109-residue truncation mutant, which contains only the N-terminal DNA-binding and dimerization domains of MerR family member Mta. The 2.75 Å resolution crystal structure of apo-MtaN reveals a winged helix-turn-helix protein with a protruding 8-turn helix (α5) that is involved in dimerization by the formation of an antiparallel coiled-coil. The hydrophobic core and helices α1 through α4 are structurally homologous to MerR family member BmrR bound to DNA, whereas one wing (Wing 1) is shifted. Differences between the orientation of α5 with respect to the core and the revolution of …

Energetics And Cooperativity In Three-Center Hydrogen Bonding Interactions. Ii. Intramolecular Hydrogen Bonding Systems, Ruben D. Parra, Bing Gong, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

High level ab initio calculations have been carried out on a number of intramolecular two- and three-center H-bonding structures containing the amide motif, NHC=O. These structures serve as model systems for probing the stability of intramolecular three-center H bonds of the type A₁HA₂. Particular attention is given to cooperative effects in the three-center H-bonding structures. A systematic assessment of cooperativity for intramolecular H-bonding systems is presented.

Unlv Magazine, Barbara Cloud, Laurie Fruth, Mae Worthey-Flennoy

UNLV Magazine

No abstract provided.

Α-Amino-Β-Sulphone Hydroxamates As Potent Mmp-13 Inhibitors That Spare Mmp-1, Daniel P. Becker Ph.D., Thomas E. Barta, Louis Bedell, Gary Decrescenzo, John Freskos, Daniel P. Getman, Susan L. Hockerman, Madeleine Li, Pramod Mehta, Brent Mischke, Grace E. Munie, Craig Swearingen, Clara I. Villamil

Chemistry: Faculty Publications and Other Works

A series of α-amino-β-sulphone hydroxamates was prepared and evaluated for potency versus MMP-13 and selectivity versus MMP-1. Various substituents were employed on the α-amino group (P1 position), as well as different groups attached to the sulphone group extending into P1′. Low nanomolar potency was obtained for MMP-13 with selectivity versus MMP-1 of >1000× for a number of analogues.

α-Amino-β-sulphone hydroxamates were prepared, which are potent MMP-13 inhibitors with selectivity versus MMP-1 of >1000× for a number of analogues. Selected compounds exhibited oral bioavailability.

Synthesis Of Cyclopropane Containing Natural Products, William A. Donaldson

Chemistry Faculty Research and Publications

The synthesis of select cyclopropane containing natural products is presented.