Chemistry Commons^™

Planar-To-Tubular Structural Transition In Boron Clusters: B20 As The Embryo Of Single-Walled Boron Nanotubes, Boggavarapu Kiran, Satya S. Bulusu, Hua-Jin Zhai, Soohaeng Yoo, Xiao Cheng Zeng, Lai-Sheng Wang

Xiao Cheng Zeng Publications

Experimental and computational simulations revealed that boron clusters, which favor planar (2D) structures up to 18 atoms, prefer 3D structures beginning at 20 atoms. Using global optimization methods, we found that the B₂₀ neutral cluster has a double-ring tubular structure with a diameter of 5.2 Å. For the B₂₀^- anion, the tubular structure is shown to be isoenergetic to 2D structures, which were observed and confirmed by photoelectron spectroscopy. The 2D-to-3D structural transition observed at B₂₀, reminiscent of the ring-to-fullerene transition at C₂₀ in carbon clusters, suggests it may be considered as the embryo …

In Situ Anomalous Small-Angle X-Ray Scattering From Metal Particles In Supported-Metal Catalysts. Ii. Results, H. Brumberger, D. Hagrman, Jerry Goodisman, K. D. Finkelstein

Chemistry - All Scholarship

Information about the metal phase in a supported-metal catalyst can be obtained using anomalous small-angle X-ray scattering (ASAXS). The difference between the scattering profiles for SAXS at two different wavelengths near the metal's absorption edge is essentially the scattering of the metal alone. Novel in situ ASAXS measurements are made on mordenite impregnated with platinum metal while the temperature and composition of gas in the sample cell are changed. Measurements are made 62 times during treatment of the catalyst. The metal particles are assumed to be randomly distributed spheres with N(R)dR = number of spheres with radii between R and …

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Organic Matrix: Quaterly Report October-December 2004, Spencer M. Steinberg

Separations Campaign (TRP)

We have conducted a large number of experiments to determine the possible reaction of iodate with sphagnum peat moss. These experiments indicate that the natural organic material reacts with iodate resulting in the formation of organically bound iodine and/or iodide in solution.

In the last quarter, we have conducted a number of experiments at various pHs and several temperatures (70oC, 60oC and 40oC). The reaction of iodate with peat follows pseudo first-order kinetics, although the reaction rate does appear to decrease significantly with reaction time. As noted in a previous report organically bound iodine appears to go through a maximum …

Impact Of Alteration Phase Formation And Microbial Activity On The Fate And Transport Of The Actinides And Fission Products: Alteration Phase Analysis, James Cizdziel, Klaus J. Stetzenbach, Thomas Williams, Abe Van Luik

Publications (YM)

The study of the behavior and movement of radionuclides in the environment is significant to many projects of interest to Southern Nevada, especially for the proposed Yucca Mountain Repository, as well as to the nation-wide issues of radiological releases from a variety of scenarios. Understanding and predicting the release, transport, and fate of radionuclides, particularly the actinide elements, in the Mojave/Great Basin geology is an extremely challenging, multi-faceted problem. In support of the national program to deepen our understanding of the behavior of radionuclides in the environment and to better predict the performance of a geological repository at Yucca Mountain, …

Characterization Of Microbial Activity, Mark P. Buttner, Patricia Cruz, Klaus J. Stetzenbach, Abe Van Luik, Thomas Williams, Amy J. Smiecinski

Publications (YM)

The overall goal of this study is to investigate the phenomena that affect the fate and transport of radionuclides in the environment. The objective of this task, “Characterization of Microbial Activity”, is to develop a molecular biological method for the characterization of the microbial population indigenous to the Yucca Mountain Project site, with emphasis in detection and measurement of species or groups of microorganisms that could be involved in actinide and/or metal reduction, and subsurface transport. Subtasks consist of QA planning and preparation, and literature review. This task is part of a cooperative agreement between the UNLV Research Foundation and …

Thermodynamics Of Folding And Association Of Lattice-Model Proteins, Troy Cellmer, Dusan Bratko, John M. Prausnitz, Harvey Blanch

Chemistry Publications

Closely related to the “protein folding problem” is the issue of protein misfolding and aggregation. Proteinaggregation has been associated with the pathologies of nearly 20 human diseases and presents serious difficulties during the manufacture of pharmaceutical proteins. Computational studies of multiprotein systems have recently emerged as a powerful complement to experimental efforts aimed at understanding the mechanisms of proteinaggregation. We describe the thermodynamics of systems containing two lattice-model 64-mers. A parallel tempering algorithm abates problems associated with glassy systems and the weighted histogram analysis method improves statistical quality. The presence of a second chain has a substantial effect on single-chain …

Kinetics Of Ion-Induced Nucleation In A Vapor-Gas Mixture, Sergey P. Fisenko, David B. Kane, M. Samy El-Shall

Chemistry Publications

A general solution for the steady-state ion-induced nucleation kinetics has been derived, considering the differences between ion-induced nucleation and homogeneous nucleation. This solution includes a new effect for nucleation kinetics, the interaction of charged clusters with vapor molecules. Analytical expressions for the ion-induced nucleation rate have been obtained for the limiting cases of high and low thermodynamic barriers. The physical explanation of the so-called sign effect is proposed based on multipole expansion of an electric field of the cluster ion. This theory gives good agreement with experiments and is used to elucidate experimentally observed phenomena.

Sulfoxides As An Intramolecular Sulfenylating Agent For Indoles And Diverse Applications Of The Sulfide-Sulfoxide Redox Cycle In Organic Chemistry, Parag V. Jog

Dissertations, Master's Theses and Master's Reports - Open

This dissertation involves study of various aspects of sulfoxide chemistry. Specifically designed t-butyl and propanenitrile sulfoxides tethered to indole-2-carboxamide were used as a source of intramolecular sulfenylating agents to synthesize novel indolo[3,2-b]-1-5-benzothiazepinones which are structurally analogous to the other biologically active benzothiazepinones. This study reveals that the intramolecular cyclization of sulfoxide follows an electrophilic sulfenylation (Sulfoxide Electrophilic Sulfenylation, SES) reaction pathway. Evidence of the absence of sulfenic acid as a transient reactive intermediate in such intramolecular cyclization is also provided.

In another study, sulfoxide was used as a “protecting group” of thioether to synthesize 8-membered, indole substituted, thiazocine-2-acetic acid derivative …

Test Of 3He Implanted Target, Caleb Dyer

The Corinthian

The proton-proton chains (p-p chains), a series of nuclear reactions were proposed several decades ago as a way in which hydrogen burning can occur in smaller main sequence stars. The ³He + ⁴He? ⁷Be reaction determines the path that the p-p chains follow. At present the cross section for this reaction has not been precisely determined. To measure this cross section a ³He target and ⁴He beam are to be used. ³He exists as a gas so a method to manufacture a solid ³He target was needed. A ³He beam was used …

"Middle Georgia Waters:" Chemical Analysis By Gc&Su Undergraduates, Melanie Mobley, Lance Cramer, Daniel Brooks, Catrena Higginbotham Ph.D

The Corinthian

Every living organism on Earth depends on water, many of which must consume liters of fresh water daily. Unfortunately, a readily available source of clean, fresh water is diminishing. Over the years, the fresh water supply has been polluted by biological and chemical sources. The nutrient levels and pesticide chemical contamination of several water locations in the Middle Georgia area were analyzed and monitored by chemistry majors at GC&SU over the past two years.

Temperature And Ph Dependence Of The Cyclization Of Creatine: A Study Via Mass Spectrometry, Brian J. Diamond

Theses, Dissertations and Capstones

The creatine to creatinine cyclization is of significant biological importance, providing energy for muscle cells and indicating proper renal function. From a chemical perspective, the rate at which creatine cyclizes to form creatinine has interested researchers since the late 1920s, but the cyclization is poorly understood both energetically and mechanistically. Mass spectroscopy was used to determine the rate of creatine cyclization as a function of temperature and pH. Using these values, the energetic parameters, activation energy and Arrhenius factor, were determined as a function of pH to better understand this reaction and ultimately determine the mechanistic process for this reaction. …

2,2':6',2"-Terpyridine 1,1"-Dioxide Dihydrate, Kraig A. Wheeler, Scott E. Mckay, Robert W. Lashlee Iii

Faculty Research and Creative Activity

No abstract provided.

Nature's Assembly Line Logic For Natural Products, Christopher T. Walsh, Ryan G. Kruger, David A. Vosburg

All HMC Faculty Publications and Research

Nature fashions a very large number of diverse products (molecular weights ranging from ca. 200 to 2000 daltons) from simple monomeric metabolites used in primary metabolism. These include polyketide scaffolds generated from the simple C₃ malonyl CoA and C₄ methylmalonyl CoA monomers and nonribosomal peptides made from both the 20 proteinogenic amino acids and dozens of nonpoteinogenic amino acids.¹ A large family of terpenoid skeletons are built from the Δ²- and Δ³-alkene isomers of the biological isoprene monomer, isoprenyl-pyrophosphate.²

A Theoretical Investigation Of Charge Transfer In Several Substituted Acridinium Ions, Jason Lappe '00, Robert J. Cave, Marshall D. Newton, I.V. Rostov

All HMC Faculty Publications and Research

We present calculations for various properties of the ground and excited states of several arylamine-substituted acridinium ion systems that have been studied experimentally. Using ab initio and semiempirical quantum mechanical methods together with the generalized Mulliken−Hush (GMH) model, we examine the excitation energies, dipole moment shifts, and electronic coupling elements for the vertical charge shift (CSh) processes in these systems. We also examine solvent effects on these properties using a dielectric continuum reaction field model. The results are in generally good agreement with available experimental results and indicate that there is strong electronic coupling in these systems over a wide …

Two Purified Domains Of Telomerase Reverse Transcriptase Reconstitute Sequence-Specific Interactions With Rna, C. M. O'Connor, Cary K. Lai, Kathleen Collins

Biology Faculty Publications

Telomerase reverse transcriptase (TERT) and telomerase RNA (TER) function together to create a uniquely specialized polymerase. Here we have described for the first time domains of bacterially expressed Tetrahymena TERT that interacted directly with TER in the absence of assembly chaperones. We used quantitative binding assays to define TER sequence requirements for recognition by the high affinity RNA binding domain and an independent N-terminal RNA interaction domain. The TERT RNA binding domain and N-terminal RNA interaction domain had distinct, nonoverlapping requirements for TER sequence and structure that together accounted for all of the sites of TER contact inferred for full-length …

Yba2cu3o7 Electro-Magneto-Optic Effects In Ba L2,3 X-Ray Absorption Near Tc, Juana Vivó Acrivos

Faculty Publications, Chemistry

The onset of electro magneto-optic effects, observed at the Ba L2,3 edges synchrotron X-ray absorption by a YBa2Cu3O7 single crystal, 10 K above the transition temperature to superconductivity, Tc ~ 92 K is used to identify the role played by the Ba donor layer in the transition to superconductivity in the CuO2 layers. Negative permeability leads to Faraday rotation of the transmitted beam below T = 112 to 56 K for the 22 μm thick single crystal (c-axis orientation of 8π/18 relative to εX-rays) and sharp changes in the density of empty final states lead to zero transmitted radiation in …

Removal Of P-Cresol Sulfate By Hemodialysis, Andres W. Martinez, Natalie S. Recht, Thomas H. Hostetter, Timothy W. Meyer

Chemistry and Biochemistry

Protein-bound solutes are poorly cleared by dialysis. Among the most extensively studied of these solutes is p-cresol, which has been shown to be toxic in vitro. This study examined the form in which p-cresol circulates and quantified its removal by hemodialysis. HPLC analysis of plasma from hemodialysis patients contained a peak whose mobility corresponded to synthetic p-cresol sulfate (PCS) but no detectable unconjugated p-cresol. Treatment with sulfatase resulted in recovery of this peak as p-cresol, confirming its identity. Subsequent studies compared the removal of PCS and another protein-bound solute, indican, to the removal of urea during clinical hemodialysis treatments. …

Nonlinear Dynamics Of Piezoelectric High Displacement Actuators In Cantilever Mode, Timothy Usher, Alec Sim

Physics Faculty Publications

Experimental results of the nonlinear dynamic response of a piezoelectric high displacement actuator known as thin-layer composite unimorph ferroelectric driver and sensor were compared to a theoretical model, which utilizes the multiple scales method to connect the effective spring constant to higher-order stiffness constants c4 of the piezoelectric layer. This type of actuator has prestress gradients resulting from the manufacturing process that have been reported to play an important role in enhanced actuation. A value of c₄=−4.7x10²⁰ N/m² was obtained for the higher-order lead zirconate titanate (PZT) stiffness coefficient, which is higher than other published results …

Reduced Macrophage Apoptosis Is Associated With Accelerated Atherosclerosis In Low-Denstiy Lipoprotein Receptor-Null Mice, Michael Sinensky, J. Liu, D. P. Thweke, Y. R. Su, M. F. Linton, S. Fazio

Faculty Publications, Biological Sciences

Objective— The majority of apoptotic cells in atherosclerotic lesions are macrophages. However, the pathogenic role of macrophage apoptosis in the development of atherosclerosis remains unclear. Elevated expression of Bax, one of the pivotal proapoptotic proteins of the Bcl-2 family, has been found in human atherosclerotic plaques. Activation of Bax also occurs in free cholesterol-loaded and oxysterol-treated mouse macrophages. In this study, we examined the effect of Bax deficiency in bone marrow-derived leukocytes on the development of atherosclerosis in low-density lipoprotein receptor-null (LDLR−/−) mice. Methods and Results— Fourteen 8-week-old male LDLR−/− mice were lethally irradiated and reconstituted with either wild-type (WT) …

Characterization Of The Electronic Excited-State Energetics And Solution Structure Of Lanthanide(Iii) Complexes With The Polypyridine Ligand 6,6'-Bis[Bis(2-Pyridylmethyl)Aminomethyl]-2,2'-Bipyridine, Gilles Muller, P. Gawryszewska, J. Sokolnicki, A. Dossing, J. P. Riehl, J. Legendziewicz

Faculty Publications, Chemistry

Absorption, emission, and excitation spectra for solid-state and solution of Tb(III), Dy(III), and Gd(III) complexes with the polypyridine ligand 6,6‘-bis[bis(2-pyridylmethyl)-aminomethyl]-2,2‘-bipyridine (C36H34N8) are presented. Measurements of excited-state lifetimes and quantum yields in various solvents at room temperature and 77 K are also reported and used to characterize the excited-state energetics of this system. Special attention is given to the characterization of metal-to-ligand energy transfer efficiency and mechanisms. The measurement of circularly polarized luminescence (CPL) from the solution of the Dy(III) complex following circularly polarized excitation confirms the chiral structure of the complexes under study. No CPL is present in the luminescence …

Comparative Study Of Structural Properties Of Yba2cu3o7 Thin Films On Srtio3 Single Crystal And Bicrystal Substrates By X- Ray Diffraction, M. Navacerrada, A. Mehta, H. Sahibudeen, Juana Acrivos

Faculty Publications, Chemistry

We present a comparative study in terms of structural properties deduced from X - ray diffraction diagrams between YBa2Cu3O7 (YBCO) thin films fabricated on SrTiO3 (STO) single crystal substrates and bicrystallines substrates with a symmetrical tilt angle of 24 degrees. Periodic Lattice Distortions (PLD) have been observed around different Bragg peaks in YBCO thin films deposited on STO bicrystals while only diffraction peaks have been measured in the diagrams corresponding to the YBCO thin films deposited on STO single crystal substrates. Only in regions situated a 3.5 mm at both sides of the grain boundary the PDL have been investigated. …

Differential Tethering Of Log Phase Trypanosoma Brucei Onto Chemically Distinct Surfaces, Darrell R. Fry, Lydia Archuleta, Ashley Dunham, Justin Rains

Faculty Publications

Our long-term objective is to understand and model the motility of T. brucei. Obtaining high quality images of T. brucei that allow one to differentiate between cell body movement and flagallar movement is difficult with T. brucei because the flagellum is attached along the cell body. Currently, our approach his to tether T. brucei onto a microscope friendly surface. The contributions to the ISIS our progress to date. Specifically, we look at the adhesion density of T. brucei to numerous microscope friendly surfaces and at the optimum adhesion conditions for T. brucei.

Mass Spectrometric And Computational Study Of Snpb In The Gas Phase, G Gigli, Giovanni Meloni, M Carrozzino

Chemistry Faculty Publications

The SnPb molecule has been identified in a Knudsen effusion mass spectrometry experiment. The direct dissociation reaction and two isomolecular exchange reactions involving the Sn(2) and Pb(2) molecules have been studied, in the 1426-1705 K range of temperatures, using both second and third law procedures. The D(degree)0(SnPb,g) has been derived, for the first time, as (122.6+/-4.0) kJ mol(-1). Density functional and ab initio calculations up to the coupled clusters level of theory were also performed. In addition, the anion dissociation energy D(degree)0(SnPb(-),g) of (179.2+/-4.2) kJ mol(-1) was determined using the D(degree)0(SnPb,g) mass spectrometric value derived in this investigation and literature …

Gallium Oxide And Dioxide: Investigation Of The Ground And Low-Lying Electronic States Via Anion Photoelectron Spectroscopy, Giovanni Meloni, S M. Sheehan, D M. Neumark

Chemistry Faculty Publications

The GaO and GaO2 molecules were investigated using negative ion photoelectron spectroscopy. All the photoelectron spectra showed vibrationally resolved progressions. With the aid of electronic structure calculations and Franck-Condon spectral simulations, different molecular parameters and energetics of GaO-/GaO and GaO2-/GaO2 were determined, including the electron affinity of GaO, the vibrational frequency of GaO-, and the term energy, spin-orbit splitting, and vibrational frequency for the first excited A 2PiOmega state of GaO. The GaO2- photoelectron spectra comprised three bands assigned as transitions from the linear X 1Sigma(g)+ ground state of GaO2- to three linear neutral states: the A 2Pi(g), B 2Pi(u), …

Response To "Kinetic And Mechanistic Studies Of The Recombination Of Oh With No2: Vibrational Deactivation, Isotopic Scrambling And Product Isomer Branching Ratios", J. Stutz, A. R. Ravishankara, J. A. Pyle, A. Tuck, M. J. Evans, H. Herrmann, M. P. Chipperfield, R. Zellner, H. Roscoe, D. E. Shallcross, R. A. Cox, P. S. Monks, S. R. Arnold, D. S. Stevenson, D. E. Heard, J. J. Remedios, R. P. Wayne, E. A. Cohen, T. Brauers, A. J. Orr-Ewing, M. A. Blitz, L. Wang, G. Duxbury, T. Dibble, C. A. Taatjes, W. Eisfeld, P. W. Seakins, A. Kovács, S. Dóbé, E. Farkas, T. Ingham, D. Rowley, C. E. Kolb, Thomas Alex Stephenson, A. J. Hynes, N. M. Donahue, I. W. M. Smith, D. Self, D. J. Donaldson

Chemistry & Biochemistry Faculty Works

No abstract provided.

Computational Study Of A Novel Dinuclear Metal Complex, Dragos Seghete

Inquiry: The University of Arkansas Undergraduate Research Journal

The first compound containing an M-H-M was recently reported by Vicic et al. With recent availability of large computational resources, molecular modeling has become a reliable tool for confirming experimental results. The novel dinuclear Ni complex [( dippm)2Ni2Br2]( 0 -H) was investigated in this work from a theoretical perspective. Full geometry optimization was carried on the dinuclear Ni complex at the DFT/B3LYP with the 6-31G* basis set. The result verifies the linear Ni-H-Ni bond. Two different starting structures that converged to the same geometry confirm that a global minimum was reached. The computed structure differs from the experimentally determined one …

Synthesis And Characterization Of Mercury Vapor Coordination Species Using 1,3-Benzenedioethanethiolate (Bdet), Elizabeth Zuchek, Harvest L. Collier

Opportunities for Undergraduate Research Experience Program (OURE)

Mercury is a major pollutant in the air today. Some possible chelators that have been used are British anti-Lewisite (BAL) 2,3-dimercaptopropanol, dimercaptosuccinic acid (DMSA). diinercaptopropanesulfonic acid (DMPS). and 1,3-benzenediamidoethanethiolate (BDE'I1. All contain two thiol groups, which 'capture' the heavy mercury element. Due to their structure, they all differ in how well they bind to the mercury atom. BDET is the most recent and efficient chelate used. Statistics show that coal-fired power plants are the nation's largest mercury polluter. Steps have been taken to lower the emission of this toxic metal by the Clean Air Act. However, recently The Bush Administration's …

Recovery Of Hydrogen And Helium From Their Mixtures Using Metal Hydrides, Muzaffer Tonguc Oztek

Electronic Theses and Dissertations

Waste streams of hydrogen and helium mixtures are produced at the Kennedy Space Center during purging of the hydrogen systems and supply lines. This process is done prior to and after hydrogen servicing. The purged waste gases are lost to the atmosphere, resulting in an annual loss of 2 million and 0.1 million standard cubic meters of helium and hydrogen, respectively. Recovery of these gases will have an economic benefit. Metals, alloys, and intermetallics are known to react with hydrogen in favorable conditions; therefore, they have the possibility of serving as separating and recovery agents. In this study, Mg2Ni, VTiNi …

Simulation Of Electronic And Geometric Degrees Of Freedom Using A Kink-Based Path Integral Formulation: Application To Molecular Systems, Randall W. Hall

Collected Faculty Scholarship

A kink-based path integral method, previously applied to atomic systems, is modified and used to study molecular systems. The method allows the simultaneous evolution of atomic and electronic degrees of freedom. Results for CH₄, NH₃, and H₂O demonstrate this method to be accurate for both geometries and energies. Comparison with DFT and MP2 level calculations show the path integral approach to produce energies in close agreement with MP2 energies and geometries in close agreement with both DFT and MP2 results.

Solvent Extraction Separation And Determination Of Yttrium With Cyanex272, Manjusha Karve, Bhagyashree P. Vaidya

Department of Chemistry and Biochemistry Faculty Scholarship and Creative Works

A simple and selective method for the liquid - liquid extraction of yttrium with Cyanex272 is presented. The influence of the pH of aqueous phase, concentration of extractant, nature of diluent, extraction time, type of stripping agent and stripping time were evaluated to optimize the conditions for quantitative extraction of yttrium. The effect of certain foreign ions on the extraction of yttrium was studied. Yttrium was quantitatively extracted at pH = 7.0 with 5 x 10-4 M Cyanex272 in xylene. It was stripped from the organic phase with 4M nitric acid and determined spectrophotometrically with Arsenazo (Ill) at 650nm.