Physical Sciences and Mathematics Commons^™

Molecular Dynamics Simulation Of The Order- Disorder Phase Transition In Solid Nano2, Wei-Guo Yin, Chun-Gang Duan, Wai-Ning Mei, Jianjun Liu, Robert W. Smith, John R. Hardy

Physics Faculty Publications

We present molecular dynamics simulations of solid NaNO2 using pair potentials with the rigid-ion model. The crystal potential surface is calculated by using an a priori method which integrates the ab initio calculations with the Gordon-Kim electron gas theory. This approach is carefully examined by using different population analysis methods and comparing the intermolecular interactions resulting from this approach with those from the ab initio Hartree-Fock calculations. Our numerics show that the ferroelectric-paraelectric phase transition in solid NaNO2 is triggered by rotation of the nitrite ions around the crystallographical c axis, in agreement with recent x-ray experiments @Gohda et al., …

Dynamics Of Bulk And Adsorbed Poly(Vinyl Acetate), Frank D. Blum, Robert D. O'Connor

Materials Science and Engineering Faculty Research & Creative Works

We have recently completed a series of experiments on methyl-labeled poly(vinyl acetate)-d3, (PVAc-d3)1 and poly(methyl acrylate)-d3 (PMA-d3).234 the systems have been studied as a function of the adsorbed amount, molecular weight, and presence of a protonated overlayer. Using deuterium line shape analysis, we have found that around the glass transition temperature, the adsorbed polymers show the presence of a motional gradient. Polymer segments near the silica-polymer interface have less mobility than the bulk polymer and those near the polymer-air interface are more mobile than those of the bulk polymer. A schematic representation of the motional gradient is shown in Figure …

Flanking Sequences Modulate Diepoxide Cross-Linking Efficiencies At The 5'-Gnc Sste, Gregory A. Sawyer

Honors Theses

Diepoxybutane, diepoxyoctane, and mechlorethamine are cytotoxic DNA crosslinking agents that vary in their carcinogenic versus chemotherapeutic potentials. Interstrand cross-linking occurs between the N7 positions of deoxyguanosine residues on opposite strands of the DNA duplex. Each synthetic DNA oligomer used in this study contained four 5'-N\GN2CN3 sites (within a 32 base sequence) and we have systematically varied the bases in the N1 and N2 positions to determine the resulting cross-linking efficiencies of each cytotoxic agent. Each duplex was 5' -end labeled and incubated with cross-linking agent. Interstrand cross-links were purified through denaturing polyacrylamide gel electrophoresis and then subjected to piperidine cleavage. …

Application Of The Chan-Evans Diaryl Ether Synthesis To The Formation Of Bis(Bibenzyls), Eric Rosenthal

Honors Theses

Alkene (6) was produced in three steps from 3-hydroxybenzaldehyde (8), and 3-bromobenzyl bromide (10). A variety of strategies were employed to synthesize the desired boronic acid (13), but as of this time none have been successful. The synthesis of this boronic acid is necessary to study the feasibility of applying the Chan-Evans copper mediated formation of diaryl ethers to a bis(bibenzyl) synthesis. In seeking to exploit the advantages of the Chan-Evans ether synthesis over the Ullman ether synthesis, we have encountered some of the associated difficulties. The utilization of an arylboronic acid to produce a diaryl ether first requires the …

Quantitative Analysis Of Diepoxybutane Damage Within The Chicken Β-Globin Domain, André M. Pilon

Honors Theses

In industrial polymer and synthetic rubber production facilities, workers are exposed to 1,3-butadiene. This compound is converted in vivo to 1,2,3,4-diepoxybutane (DEB) and has been linked to increased incidences of cancer in these individuals. Carcinogenesis has been attributed to formation of DEB induced DNA interstrand cross-links. Previous studies have demonstrated that DEB cross-links deoxyguanosine residues within 5'-GNC sequences in synthetic DNA, in restriction fragments, and in defined sequence nucleosomes. The current study utilized the polymerase chain reaction (PCR) to examine DEB damage frequencies within nuclear genes, found within "open" regions of chromatin, as compared to regions of unexpressed sequence that …

Sedimentological And Plant Taphonomic Evaluation Of The Early Middle Devonian Trout Valley Formation, Jonathan Allen

Honors Theses

The Trout Valley Formation of Emsian-Eifelian age, outcropped in Baxter State Park, Maine, consists offluvial and coastal deposits preserving early land plants. Massive, crudely bedded conglomerate represents deposits of proximal braided channels on an alluvial fan complex. Lithic sandstone bodies in channel-form geometries represent deposits of river channels draining the Acadian highlands whereas associated siltstones represent overbank deposits, intertidal flats, and tidal channels. Localized lenticular quartz arenites represent nearshore shelf bar deposits that were storm influenced. The majority of plant assemblages preserved mainly in siltstone lithologies are allochthonous and parautochthonous, with only one autochthonous assemblage identified in the sequence. Plant …

Iron-Mediated Preparation Of Vinylcyclopropanes. Scope, Mechanism, And Applications, Young K. Yun, Kamil Godula, Yeyu Cao, William A. Donaldson

Chemistry Faculty Research and Publications

The addition of stabilized carbon nucleophiles to tricarbonyl(1-methoxycarbonylpentadienyl)iron(1+) cation (1a) proceeds via attack at C2 on the face of the ligand opposite the Fe(CO)₃ group to generate tricarbonyl(pentenediyl)iron complexes 2. Oxidation of complexes 2 affords vinylcyclopropanecarboxylates in good yield. In general, the relative stereochemistry about the cyclopropane ring reflects reductive elimination with retention of configuration. In cases where the C2 substituent is bulky (i.e., 2b) the major cyclopropane product 9b represents ring closure with inversion at C3. A mechanism involving π−σ−π rearrangement of the initially oxidized (pentenediyl)iron species is proposed to account for these results. …

Preparation And Flammability Properties Of Polyethylene-Clay Nanocomposites, Jinguo Zhang, Charles A. Wilkie

Chemistry Faculty Research and Publications

Polyethylene (PE)–clay nanocomposites have been prepared using melt blending in a Brabrender mixer. X-ray diffraction and transmission electron microscopy were used to characterize the nano-structure of these composites while the thermal stability was evaluated from thermogravimetric analysis and the flammability parameters using cone calorimetry. It is found that the PE–clay nanocomposites have a mixed immiscible-intercalated structure and there is better intercalation when maleic anhydride is combined with the polymer and clay to be melt blended. The reduction in peak heat release rate is 30–40%.

A Stibonium-Modified Clay And Its Polystyrene Nanocomposite, Dongyan Wang, Charles A. Wilkie

Chemistry Faculty Research and Publications

Triphenylhexadecylstibonium trifluoromethylsulfonate has been prepared and ion-exchanged with sodium montmorillonite to obtain a new organically-modified clay. The clay has higher thermal stability than an ammonium clay; only a portion of the alkyl chain is lost during degradation and all of the antimony is retained. This clay has been used to prepare a polystyrene nanocomposite in which the clay is not uniformly distributed throughout the polymer. Nonetheless the polymer does insert into the clay layers and the d-spacing of the clay expands from 2.0 to 3.0 nm. The enhanced thermal stability of this system may mean that it could be …

Utilizing Structure Property Correlations To Predict And Analyze Two Derivatives Of An Ampicillin Homologous Series, C. Malesa, J. Stoddard, Ronald Bartzatt

Chemistry Faculty Publications

Structure Property Correlation methods such as regression analysis and pattern recognition are applied to predict the molecular properties of two members of an ampicillin homologous series. The pentyl and hexyl esters of ampicillin are also evaluated for their similarity to other penicillins by use of multiple regression, contingency tables, cluster analysis, correspondence analysis, self organizing tree algorithms, factor analysis, principal component analysis, box plots, and other graphing methods. Other members of the homologous series include methyl, ethyl, propyl, and butyl esters of ampicillin which have been previously synthesized and tested in tissue culture against Escherichia coli. All of the tested …

Measuring The Pore Sizes Of Sol-Gels Using Argon Effusion Techniques, Thomas J. Noel Ii, Krista Mincey, Catrena Higginbotham

The Corinthian

The rate of effusion of argon through a sol-gel scaffold will be measured to determine the size of the pores. The effusion rate will then be used to correlate initial pore size to any pore shrinkage that occurs. We will attempt to control the initial pore size by using various-sized paraffin beads as templates throughout the organically modified tetramethoxysilane (TMOS) gel scaffold. Polyethylene glycol (PEG) will also be used to prop open the pore openings and keep them from closing during the drying process.

The Photochemistry Of Nitrous Acid In An Aqueous Matrix, Jay S. Ratliff '03

Honors Projects

The thermal and photochemical decomposition of aqueous solutions of nitrous acid and nitrite ion were studied, with a focus on the production and subsequent reaction of hydroxyl radicals. The production of these radicals in aqueous solution may be determined indirectly by disappearance of nitrous acid, or more directly by their interaction with a radical scavenger. Benzene was used to scavenge hydroxyl radical and the products of reactions with hydroxyl radical as well as nitrous acid were characterized. The roles of temperature and dissolved gases were also examined.

Tribromo(3,5-Dimethyl-2-Nitrophenyl-J2 C1 ,O)Tellurium(Iv), Bromo(3,5-Dimethyl-2-Nitrophenyl-J2 C1 ,O)Tellurium(Ii) And Bromo(3,5-Dimethyl-2-Nitrosophenyl-J2 C1 ,O)Tellurium(Ii), Prabodhika R. Mallikaratchy, Richard E. Norman, Frank R. Fronczek, Thomas Junk

Publications and Research

All three title compounds, prepared from bis(3,5-dimethyl-2- nitrophenyl)ditellurium, exhibit high degrees of intramolecular TeÐO coordination. Their TeÐO distances increase in the order C8H8BrNOTe < C8H8BrNO2Te < C8H8Br3NO2Te, with distances of 2.165 (3), 2.306 (1) and 2.423 (6) AÊ , respectively, indicating that C8H8BrNOTe may be more aptly described as 1-bromo-4,6-dimethyl-2,1,3-benzoxatellurazole.

Modeling And Design Of Polythiophene Gate Electrode Chemfets For Environmental Pollutant Sensing, T. V. Krishna, Jeffrey R. Jessing, Dale D. Russell, Jonathan Scaggs, Lisa R. Warner, Joe A. Hartman

Chemistry and Biochemistry Faculty Publications and Presentations

Water-borne pollutants such as volatile organic compounds are a serious environmental concern, which has increased the demand for chemical sensing elements. Solidstate sensors based on catalytic gate devices are a subject of current research, however they are restricted in practical applications because of their inability to operate at room temperature. Conducting polymer FETs, which employ a conducting gate polymer, have received much attention due to their unique electronic and optical properties. Polythiophene is chosen as the semi-conductive gate polymer in this work. A functional group attached to the polythiophene is used to detect analytes (i.e., mercury in this work) of …

Development Of A Simple Method To Detect And Quantify Benzoylecgonine, A Cocaine Metabolite, In Urine, Kylee E. Billings '03

Honors Projects

Benzoylecgonine (BE) is the most abundant metabolite of cocaine found in the human body. Analysis of BE in urine by gas chromatography/mass spectrometry is the most common method currently used to detect cocaine abuse. This current method is costly and time consuming, so the investigation of an easier and more cost-effective approach is the goal of this research. Because BE is a zwitterion, it is highly soluble in water and very difficult to extract from urine. Once the pKa values of BE are determined, either the cation or anion form of BE can be formed from the zwitterion by adjusting …

Bismuth Compounds In Organic Synthesis. Synthesis Of Resorcinarenes Using Bismuth Triflate, Ram Mohan, Katherine Peterson, Russell Smith

Scholarship

Bismuth triflate (5 mol%) smoothly catalyzes the condensation of aromatic and aliphatic aldehydes with resorcinol to give tetrameric cyclic products, resorcinarenes. With benzaldehyde, the product is obtained as a mixture of two diastereomers and the ratio of the diastereomers depends on reaction time. On the other hand, a single diastereomer is obtained with aliphatic aldehydes. The low toxicity and ease of handling of bismuth compounds coupled with fast reaction times make this method an attractive alternative to the existing methods for resorcinarene formation

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

Transmutation Sciences Materials (TRP)

Materials for transmuter systems must be able to tolerate high neutron fluxes, great temperatures, and chemical corrosion. For lead bismuth eutectic (LBE) systems, there is an additional challenge in that the corrosive behaviors of materials in LBE are not well understood. Most of the available information on LBE systems has come from the Russians, who have over 80 reactor-years experience with LBE coolant in their Alpha-class submarine reactors. The Russians found that the presence of small amounts of oxygen (on the order of parts per million) in the LBE significantly reduced corrosion. However, a fundamental understanding and verification of its …

Surface Studies Of Corrosion Of Stainless Steel By Lead Bismuth Eutectic, Daniel Koury, Brian D. Hosterman, John Farley, Dale L. Perry, D. Parsons, J. Manzerova, Allen L. Johnson

Transmutation Sciences Materials (TRP)

Why is Lead Bismuth Eutectic Important?

• Changing national security stances have led to reexamination of nuclear waste reprocessing

• Dangerous actinides can be separated and

• Transmuted into safer products, creating a waste form dangerous for only hundreds of years, in addition to the production (up to 1/3 of the original fission energy) of useful energy

• Non-moderating coolants or spallation targets for production of fast neutrons is required for transmutation

• Russian experience with LBE coolants in their nuclear submarine fleet makes LBE an attractive possible transmutation coolant technology

• Corrosion of steel by LBE is an important …

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials, Ajit K. Roy, Brendan O'Toole, Zhiyong Wang, David W. Hatchett

Transmutation Sciences Materials (TRP)

The primary objective of this task is to evaluate the potential for the environmentally-assisted cracking of candidate target materials for applications in spallation-neutron-target systems, such as accelerator-driven system for the transmutation of waste. The materials selected for evaluation and characterization are martensitic stainless steels (SS) including Alloys HT- 9, EP 823 and Type 422 stainless steel.

More recently, this experimental program has been expanded to evaluate the effect of molten lead-bismuth eutectic (LBE) on the corrosion behavior of target materials in the presence of oxygen. Since the materials performance laboratory (MPL) at UNLV currently cannot accommodate this type of testing, …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The corrosion of structural materials is a major concern for the use of lead-bismuth eutectic (LBE) systems for nuclear applications such as in transmuter targets or fast reactors. Corrosion in liquid metal systems can occur through various processes, including, for example, dissolution, formation of inter-metallic compounds at the interface, and penetration of liquid metal along grain boundaries. Predicting the rate of these processes depends on numerous system operational factors: temperature, system geometry, thermal gradients, solid and liquid compositions, and velocity of the liquid metal, to name a few. Corrosion, along with mechanical and/or hydraulic factors, often contributes to component failure. …

Modeling Of Corrosion In Oxygen Controlled Lead Bismuth Eutectic Systems With The Coupling Of Chemical Kinetics And Hydrodynamics, Samir Moujaes, Yitung Chen, Kanthi Kiran Dasika, Chao Wu

Transmutation Sciences Materials (TRP)

Objectives:

• To simulate a 2-D model of the Materials Test Loop by approximating it to be a toroid with a pie cross section for the purpose of comparing the simulated results with the analytical results.
• The temperature and concentration profiles on the wall boundaries imposed are similar to the actual test model.
• Geometry effects have great influence on local corrosion rate.
• A 2-D benchmark problem and a sudden expansion case are studied which show good consistency to analytical solution.
• Results from 2-D sudden expansion problem are similar to experimental data obtained by other researchers.

Nuclear Criticality, Shielding, And Thermal Analyses Of Separations Processes For The Transmutation Fuel Cycle, William Culbreth, Denis Beller

Separations Campaign (TRP)

The first step in any transmutation strategy is the separation of radionuclides in used nuclear fuel. The current separation strategy supporting the Advanced Fuel Cycle Initiative (AFCI) program is based on the use of a solvent extraction separation process to separate the actinides, fission products, and uranium from used commercial nuclear fuel, and on the use of pyrochemical separation technologies to process used transmuter fuels. To separate the fission products and transuranic elements from the uranium in used fuel, the national program is developing a new solvent extraction process, the Uranium Extraction Plus, or UREX+, process, based on the traditional …

Evaluation Of Fluorapatite As A Waste-Form Material, Dennis W. Lindle, Dale L. Perry

Separations Campaign (TRP)

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal is for renewal of the UNLV portion of a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF₄, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and …

Evaluation Of Fluorapatite As A Waste-Form Material, Dennis W. Lindle, Dale L. Perry

Separations Campaign (TRP)

Argonne National Laboratory has proposed a new extraction procedure to handle TRISO-coated fuels, the Fluoride Extraction Process, or FLEX. The FLEX process is designed to separate the uranium in the fuel from the actinides and most fission products by taking advantage of the unique properties of uranium hexafluoride (UF₆). In the FLEX process, the used TRISO fuel is reacted with zirconium fluoride salt, forming UF₆ and the fluoride salts of the actinides and fission products. At process temperatures, the UF6 volatizes into a gas, and is released from the molten salt mixture. This leaves behind the actinides …

Comparison Between Hydrogen And Dihydrogen Bonds Among H3bnh3, H2bnh2, And Nh3, T. Kar, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Several possible binary complexes among ammonia-borane, aminoborane, and ammonia, via hydrogen and/or dihydrogen bonds, have been investigated to understand the effect of different hybridization. Møller–Plesset second-order perturbation theory with aug-cc-pVDZ basis set was used. The interaction energy is corrected for basis set superposition error, and the Morokuma–Kitaura method was employed to decompose the total interaction energy. Like H₃BNH₃, the sp² hybridized H₂BNH₂ also participates in H- and dihydrogen bond formation. However, such bonds are weaker than their sp³ analogs. The contractions of BN bonds are associated with blueshift in …

A Phase I And Pharmacologic Study Of Weekly Gemcitabine In Combination With Infusional 5-Fluorodeoxyuridine And Oral Calcium Leucovorin, Jean L. Grem, Mary G. Quinn, Bruce Keith, Brian P. Monahan, J. Michael Hamilton, Yan Xu, Nancy Harold, Dat Nguyen, Chris H. Takimoto, Anthony Rowedder, Janet Pang, Geraldine Morrison, Alice Chen

Chemistry Faculty Publications

Purpose: Since preclinical studies have shown more than additive cytotoxicity and DNA damage with the combination of gemcitabine and 5-fluoro-2′-deoxyuridine (FUDR), we studied this combination in a phase I trial. Methods: Gemcitabine alone was given in cycle 1 as a 24-h, 2-h or 1-h i.v. infusion weekly for 3 of 4 weeks; if tolerated, a 24-h i.v. infusion of FUDR was added with oral leucovorin. The cycle was aborted for grade 3 thrombocytopenia, grade 4 neutropenia, and grade 2 or worse nonhematologic toxicity. Results: During cycle 1, six of eight patients who received 150 or 100 mg/m2 over 24 h …

Steady‐State Absorption Rate Models For Use In Relaxation Rate Studies With Continuous Laserexcited Photothermal Lens Spectrometry, Stephen E. Bialkowski

Stephen E. Bialkowski

This paper examines the solutions of kinetic rate equations for prediction of the photothermal lens signals under irradiance conditions that can lead to optical saturation or bleaching. The relaxation kinetics resulting from forcing excited state populations in multiple levels by high excitation irradiance continuous lasers is examined and irradiance-dependent photothermal lens signals are predicted. The analyses described in this paper are based on simple kinetic models for optical excitation and subsequent excited state relaxation. Dark-state relaxation is assumed to be extremely fast compared to limiting kinetics resulting in simplified excited state models. Kinetic models are derived for two, four and …

Genomic Instability Induced By Two Chemical Carcinogens, Cadmium And Nickel And By Particulate Titanium Debris From An Implant, Natasha Coen

Doctoral

It has been established that cells surviving radiation may produce descendants many cell divisions post-exposure in which, there are high incidences of chromosomal aberrations arising de novo, gene mutation and lethal mutations/delayed cell death. These effects are collectively known as genomic instability and are induced at frequencies greater than that of spontaneous mutations. Formally this syndrome ‘genomic instability’ has only been definitively proven to occur following irradiation. This leads us to the consideration that heavy metals could also induce the genomic instability phenotype, and if so, it could have implications for those exposed through their occupation, through smoking or for …

Infrared-Active Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde

Chemistry Publications and Other Works

We present a model for the line shapes of infrared-active Q₁(0) vibron bands observed in solid parahydrogen doped with low concentrations of spherical substitutional impurities. The line shapes are highly sensitive to the H₂ vibrational dependence of the dopant–H₂ interaction. When this vibrational dependence is strong, the dopant can trap the infrared-active vibron in its first solvation shell; in this case, the trapped vibron manifests itself in the absorption spectrum as a narrow feature to the red of the pure solid’s vibron band.

Reactions Of Boranes And Metallaboranes With Phosphines, Lawrence Barton, Oleg Volkov, Mitsuhiro Hata, Paul Mcquade, Nigam Rath

Chemistry & Biochemistry Faculty Works

This paper reports extensions of the well-established field of phosphine–borane chemistry. Linked clusters, for example, {[(PPh3)2(CO)OsB4H7-3-BH2-PPh2]2 [(Fe(C5H4)2]}, are formed in reactions of rigid backboned bidentate phosphines with {2,2,2-(PPh3)2(CO)-nido-2-OsB5H9]. Reaction of bidentate phosphines with the unsaturated clusters [8,8-PPh3)2-nido-8,7-RhSB9H10] and [9,9-(PPh3)2-nido-9,7,8-RhC2B8 H11] leads to the isolation of novel species such as {1-(PPh3)[1,3-(µ-dppm)]-closo -1,2-RhSB9H8},with a dppm molecule bridging adjacent metal and boron vertices in the cage, [1,1-(ç2-dppe)-3-(ç1-dppm)-closo-1,2-RhSB 9H8], a mixed ligand system, and {9,9-ç2-[(ç2-BH3)PPh2PCH2 PPh2]-nido- 9,7,8-RhC2B8H11} which contains a bidentate dppm BH3 moiety. The formation of bidentate phosphine-linked main group transition-metal moieties such as [BH3PPh2(CH)nPPh2IrCp*Cl2] is also described as is an example of …