Physical Sciences and Mathematics Commons^™

Future Of Semiconductor Based Thermal Neutron Detectors, R. J. Nikolić, Chin Li Cheung, C. E. Reinhardt, T. F. Wang

Barry Chin Li Cheung Publications

Thermal neutron detectors have seen only incremental improvements over the last decades. In this paper we overview the current technology of choice for thermal neutron detection – ³He tubes, which suffer from, moderate to poor fieldability, and low absolute efficiency. The need for improved neutron detection is evident due to this technology gap and the fact that neutrons are a highly specific indicator of fissile material. Recognizing this need, we propose to exploit recent advances in microfabrication technology for building the next generation of semiconductor thermal neutron detectors for national security requirements, for applications requiring excellent fieldability of small …

High-Resolution Studies Of Tropolone In The S 0 And S 1 Electronic States: Isotope Driven Dynamics In The Zero-Point Energy Levels, John C. Keske, Wei Lin, Wallace C. Pringle, Stewart E. Novick, Thomas A. Blake, David F. Plusquellic

Chemistry Faculty Publications and Presentations

Rotationally resolved microwave (MW) and ultraviolet (UV) spectra of jet-cooled tropolone have been obtained in S0 and S1 electronic states using Fourier-transform microwave and UV-laser/molecular-beam spectrometers. In the ground electronic state, the MW spectra of all heavy-atom isotopomers including one O18 and four C13 isotopomers were observed in natural abundance. The OD isotopomer was obtained from isotopically enriched samples. The two lowest tunneling states of each isotopomer except O18 have been assigned. The observed inversion splitting for the OD isotopomer is 1523.227(5) MHz. For the asymmetric C13 structures, the magnitudes of tunneling-rotation interactions are found to diminish with decreasing distance …

Measurement, Characterization, And Source Apportionment Of The Major Chemical Components Of Fine Particulate Material, Including Semi-Volatile Species, Brett D. Grover

Theses and Dissertations

The promulgation of revised standards for atmospheric fine particles (PM2.5) by the US EPA has sparked renewed interest in the ability to accurately measure and characterize suspended atmospheric particulate matter. Semi-volatile material (SVM), consisting of ammonium nitrate and semi-volatile organic material (SVOM), is not accurately measured by EPA accepted methods such as the Federal reference method (FRM) or Tapered Element Oscillating Microbalance (TEOM). However, SVM is often a major fraction of urban aerosols. Recent advances in atmospheric sampling instrumentation allowed for the semi-continuous characterization of urban PM2.5, including SVM. The Filter Dynamic Measurement System (FDMS) was shown to measure total …

Determining The Redox Properties Of Yucca Mountain-Related Groundwater Using Trace Element Speciation For Predicting The Mobility Of Nuclear Waste, James Cizdziel, Amy J. Smiecinski

Publications (YM)

The objective of this task is to determine the principal oxidation state (redox) species of select elements in samples of groundwater in the vicinity of Yucca Mountain (YM), which is being evaluated as a site for geologic storage of the nation’s spent nuclear fuel and high-level nuclear waste. Samples to be analyzed include, but are not limited to, groundwater from wells of the Nye County Early Warning Drilling Program. Elements to be studied include arsenic (As), antimony (Sb), selenium (Se), chromium (Cr), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), vanadium (V), tungsten (W), rhenium (Re), and uranium (U). The …

Rhodium-Catalyzed Asymmetric Hydrogenation Using Self-Assembled Chiral Bidentate Ligands, James M. Takacs, Kittichai Chaiseeda, Shin A. Moteki, D. Sahadeva Reddy, Di Wu, Kusumlata Chandra

James Takacs Publications

The chirality-directed self-assembly of bifunctional subunits around a structural metal-typically, zinc(II)-is used to form a heteroleptic complex in which a second set of ligating groups are suitably disposed to bind a second metal, forming a heterobimetallic catalyst system. We find that subtle changes in the structural backbone (i.e., ligand scaffold) of such chiral bidentate self-assembled ligands (SALs) can be used to manipulate the ligand topography and chiral environment around catalytic metal; thus, the scaffold can be optimized to maximize asymmetric induction. Using this combinatorial strategy for ligand synthesis, a preliminary study was carried out in which a library of 110 …

A Topology-Constrained Distance Network Algorithm For Protein Structure Determination From Noesy Data, Yuanpeng Janet Huang, Roberto Tejero, Robert Powers, Gaetano T. Montelione

Robert Powers Publications

This article formulates the multidimensional nuclear Overhauser effect spectroscopy (NOESY) interpretation problem using graph theory and presents a novel, bottom-up, topology-constrained distance network analysis algorithm for NOESY cross peak interpretation using assigned resonances. AutoStructure is a software suite that implements this topology- constrained distance network analysis algorithm and iteratively generates structures using the three-dimensional (3D) protein structure calculation programs XPLOR/CNS or DYANA. The minimum input for AutoStructure includes the amino acid sequence, a list of resonance assignments, and lists of 2D, 3D, and/or 4D-NOESY cross peaks. AutoStructure can also analyze homodimeric proteins when X-filtered NOESY experiments are available. The quality …

Pyrrolizidine Esters And Amides As 5-Ht4 Receptor Agonists And Antagonists, Daniel Becker, Daniel L. Flynn, Alan E. Moormann, Roger Nosal

Chemistry: Faculty Publications and Other Works

A series of pyrrolizidine esters, amides, and ureas was prepared and tested for 5-HT(4) and 5-HT(3) receptor binding, 5-HT(4) receptor agonism in the rat tunica muscularis mucosae (TMM) assay, and for 5-HT(3) receptor-mediated functional antagonism in the Bezold-Jarisch reflex assay. Several pyrrolizidine derivatives were identified with high affinity for the 5-HT(4) receptor, including benzamide 12a (SC-53116), a potent and selective 5-HT(4) partial agonist that exhibits efficacy in promoting antral contractions and activity in promoting gastric emptying in canine models. Also discovered were 5-HT(4) receptor antagonists, including imidazopyridine amide 12h (SC-53606), which is a potent and selective 5-HT(4) receptor antagonist with …

Reliable Electron Affinities Of Perfluorocyclopropane And Perfluorocyclobutane From Convergent Ab Initio Computations, Adel M. Elsohly, Macey L. Renault, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

To resolve discrepancies concerning the magnitude of the electron affinities of perfluoro cyclopropane and perfluorocyclobutane, quantum chemical calculations have been carried out with the MP2 and CCSD(T), methods in conjunction with augmented correlation consistent basis sets (aug-cc-pVX Z, X = D, T, Q). Though no experimental values have been found for perfluoro cyclopropane, we estimate its electron affinity to be 0.17 eV (0.00 eV without zero-point vibrational energy corrections). In addition, determination of the electron affinity of perfluorocyclobutane (0.61 and 0.44 eV with and without zero-point vibrational energy corrections, respectively) is in good agreement with experimental values reported by Miller …

Dynamic Contact Angle In Rim Instability Of Dewetting Holes, Sung-Hwan Choi, Bi-Min Zhang Newby

Chemical, Biomolecular, and Corrosion Engineering Faculty Research

The effects of dynamic contact angle (theta(d)), between a substrate and the melt of a dewetting polymer thin film, on the evolution of rim instabilities of dewetting holes were reported. Various theta(d)'s were achieved by covering SiOx surfaces with different coverage of octadecyltrichlorosilane. On each surface, the morphology of the dewetting holes was examined in detail as the hole grew to a certain size. Rim instabilities, in terms of undulations in both r and z directions, became more pronounced as theta(d) increased, under which condition, narrower and higher rims were also observed. Experimentally, atomic force microscopic scans of the rim …

Changes In Dna Bending And Flexing Due To Tethered Cations Detected By Fluorescence Resonance Energy Transfer, Sarah L. Williams, Laura K. Parkhurst, Lawrence J. Parkhurst

Lawrence Parkhurst Publications

Local DNA deformation arises from an interplay among sequence-related base stacking, intrastrand phosphate repulsion, and counterion and water distribution, which is further complicated by the approach and binding of a protein. The role of electrostatics in this complex chemistry was investigated using tethered cationic groups that mimic proximate side chains. A DNA duplex was modified with one or two centrally located deoxyuracils substituted at the 5-position with either a flexible 3-aminopropyl group or a rigid 3-aminopropyn-1-yl group. End-to-end helical distances and duplex flexibility were obtained from measurements of the time-resolved Fö̈rster resonance energy transfer between 5’- and 3’-linked dye pairs. …

A Bidomain Nonribosomal Peptide Synthetase Encoded By Fum14 Catalyzes The Formation Of Tricarballylic Esters In The Biosynthesis Of Fumonisins, Kathia Zaleta-Rivera, Chunping Xu, Fengan Yu, Robert A. E. Butchko, Robert H. Proctor, Maria E. Hidalgo-Lara, Ashraf S. Raza, Patrick Dussault, Liangcheng Du

Patrick Dussault Publications

Fumonisins are a group of polyketide-derived mycotoxins produced by Fusarium Verticillioides, a filamentous fungus infecting corn and contaminating food and feeds. Fumonisins contain two tricarballylic esters that are critical for toxicity. Here, we present genetic and biochemical data for the esterification mechanism. FUM14 in F. Verticillioides has been deleted by homologous recombination, and the resultant mutant lost the ability to produce fumonisins. Two new metabolites, HFB₃ and HFB₄, which are biosynthetic precursors of fumonisins lacking the tricarballylic esters, were detected in the mutant. The results suggest that FUM14 is required for the esterification of fumonisins. FUM14 …

Characterization, Functionalization And Applications Of Alkyl Monolayers On Silicon Surfaces, Guilin Jiang

Theses and Dissertations

Investigations were performed on the stability, mechanism of formation and an application of alkyl monolayers chemomechanically prepared on silicon surfaces. A new method of surface modification, laser-activation modification of surfaces (LAMS), and multivariate analyses of time-of-flight secondary ion mass spectrometry (ToF-SIMS) images of LAMS spots were also reported. X-ray photoelectron spectroscopy (XPS) and other data show that alkyl monolayers prepared by scribing silicon under 1-iodoalkanes and 1-alkenes were stable over extended periods of time to air, water, a boiling acid and Al Ka X-rays. The stability is attributed to direct Si-C bonding in the monolayers. The observation that the oxygen …

New Oscillating Reaction – Phenylacetylene Oxidative Carbonylation To Anhydride Of Phenylmaleic Acid (In Russian), Sergey N. Gorodsky, Olga V. Kasatkina, Lev G. Bruk, Oleg N. Temkin

Sergey N. Gorodsky

No abstract provided.

Annealing Effects On The Crystallite Size And Dielectric Properties Of Ultrafine Ba1-Xsrxtio3 (0 < X < 1) Powders Synthesized Through An Oxalate-Complex Precursor, Gabriel Caruntu, Charles J. O'Connor

Chemistry Faculty Publications

Nanocrystalline Ba12xSrxTiO3 (0 , x , 1) nanopowders were prepared through the oxalate route and the influence of the thermal history on their dielectric properties was investigated. For pelletized samples obtained by decomposing the corresponding oxalate intermediates at 600 uC and then annealed at different temperatures ranging from 600 to 1000 uC the dielectric constant decreases upon increasing the strontium content of the samples. Similar behavior was observed with decreasing the temperature of the thermal treatment of the pellets, a trend which is presumably ascribed to a synergic effect of decreasing the porosity of the samples, the increase of the …

Structures And Relative Stability Of Medium-Sized Silicon Clusters. Iv. Motif Based Low-Lying Clusters Si21–Si30, Soohaeng Yoo, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Structures and relative stability of four families of low-lying silicon clusters in the size range of Si_n(n=21–30) are studied, wherein two families of the clusters show prolate structures while the third one shows near-spherical structures. The prolate clusters in the first family can be assembled by connecting two small-sized magic clusters Si_n(n=6, 7, 9, or 10) via a fused-puckered-hexagonal-ring Si₉ unit (a fragment of bulk diamond silicon), while those in the second family can be constructed on the basis of a structural motif consisting of a puckered-hexagonal-ring Si₆ unit (also …

(±)-1-Methyl-1,3,6-Triphenyl-7-(2-Phenylpropenyl)-1, 2-Dihydronaphthalene, Yongqiang Sui, Charles Leslie Barnes, Rainer Glaser

Chemistry Faculty Research & Creative Works

The crystal structure of the title compound, C₃₈H₃₂, presents a novel framework that combines the functionalities of a 1,6-diarene-substituted 1,2-dihydronaphthalene (DHN) with a 1,4-distyrylbenzene (DSB) to form a crossed bis-diarene. The lamellar crystal structure is held together by arene-arene interactions. While the orientations of the phenyl rings of the DSB units alternate within both the R and the S substructures, the homochiral substructures feature opposing polarity along the long axes of the DHN-based diarenes.

Enzyme Dynamics Along The Reaction Coordinate: Critical Role Of A Conserved Residue, Evgueni Kovriguine, J. Patrick Loria

Chemistry Faculty Research and Publications

Conformational flexibility of the enzyme architecture is essential for biological function. These structural transitions often encompass significant portions of the enzyme molecule. Here, we present a detailed study of functionally relevant RNase A dynamics in the wild type and a D121A mutant form by NMR spin-relaxation techniques. In the wild-type enzyme, the dynamic properties are largely conserved in the apo, enzyme−substrate, and enzyme−product complexes. In comparison, mutation of aspartic acid 121 to alanine disrupts the timing of active-site dynamics, the product-release step, and global conformational changes, indicating that D121 plays a significant role in coordinating the dynamic events in RNase …

Fire Properties Of Styrenic Polymer–Clay Nanocomposites Based On An Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie

Chemistry Faculty Research and Publications

An oligomerically-modified clay has been used to fabricate nanocomposites with styrenic polymers, such as polystyrene, high-impacted polystyrene, poly(styrene-co-acrylonitrile) and acrylonitrile–butadiene–styrene by melt blending. The clay dispersion was evaluated by X-ray diffraction and bright field transmission electron microscopy. All of the nanocomposites have a mixed delaminated/intercalated structure. The fire properties of nanocomposites were evaluated by cone calorimetry and the mechanical properties were also evaluated.

Femtosecond Nuclear Motion Of Hcl Probed By Resonant X-Ray Raman Scattering In The Cl 1s Region, Marc Simon, Loic Journel, Stephane Carniato, Richard Taieb, I. Minkov, Faris Gel'mukhanov, P. Salek, H. Agren, Renaud Guillemin, Wayne C. Stolte, A. C. Hudson, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Femtosecond dynamics are observed by resonant x-ray Raman scattering (RXS) after excitation along the dissociative Cl 1s→6ơ* resonance of gas-phase HCl. The short core-hole lifetime results in a complete breakdown of the common nondispersive behavior of soft-x-ray transitions between parallel potentials. We evidence a general phenomenon of RXS in the hard-x-ray region: a complete quenching of vibrational broadening. This opens up a unique opportunity for superhigh resolution x-ray spectroscopy beyond vibrational and lifetime limitations.

1,3-Indane-Based Chromogenic Calixpyrroles With Push-Pull Chromophores: Synthesis And Anion Sensing, Ryuhei Nishiyabu, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

Knoevenagel condensation of 2-formyl-octamethylcalix[4]pyrrole with selected 1,3-indanedione derivatives yields calix[4]pyrrole anion sensors with push-pull chromophores displaying strong intramolecular charge transfer. The push-pull feature results in augmented signal output as well as in dramatic changes in anion selectivity exemplified by a 50-fold increase in acetate vs chloride selectivity compared to the parent calix[4]pyrrole.

Ligand-Based Design Of Dopamine Reuptake Inhibitors : Fuzzy Relational Clustering And 2-D And 3-D Qsar Modleing, Milind Misra

Dissertations

As the three-dimensional structure of the dopamine transporter (DAT) remains undiscovered, any attempt to model the binding of drug-like ligands to this protein must necessarily include strategies that use ligand information. For flexible ligands that bind to the DAT, the identification of the binding conformation becomes an important but challenging task. In the first part of this work, the selection of a few representative structures as putative binding conformations from a large collection of conformations of a flexible GBR 12909 analogue was demonstrated by cluster analysis. Novel structurebased features that can be easily generalized to other molecules were developed and …

Study Of Organic Reactions In Pyridinium-Based Ionic Liquids, Ying Xiao

Dissertations

Recently, ionic liquids have attracted a lot of attention as novel materials for organic transformations. This is due to their unique properties, which make them suitable substitutes for organic solvents. Most of the available literature is focused on the application of imidazolium-based ionic liquids for organic reactions, while very limited information is available on the application of pyridinium-based ionic liquids.

In this study, two different ionic liquids, 1 -ethyl-pyridinium tetrafluoroborate ([EtPy]⁺[BF₄]^-) and 1 -ethyl-pyridinium trifluoroacetate ([EtPy]⁺[CF₃COO]^-) have been investigated. Compared to previous reports, the synthetic technique for preparation …

Domain Architecture Of Protein-Disulfide Isomerase Facilitates Its Dual Role As An Oxidase And An Isomerase In Ero1p-Mediated Disulfide Formation, Mohini Kulp, Eva Maria Frickel, Lars Ellgaard, Jonathan S. Weissman

Chemistry: Faculty Publications

Native disulfide bond formation in eukaryotes is dependent on protein-disulfide isomerase (PDI) and its homologs, which contain varying combinations of catalytically active and inactive thioredoxin domains. However, the specific contribution of PDI to the formation of new disulfides versus reduction/rearrangement of non-native disulfides is poorly understood. We analyzed the role of individual PDI domains in disulfide bond formation in a reaction driven by their natural oxidant, Ero1p. We found that Ero1p oxidizes the isolated PDI catalytic thioredoxin domains, A and A′ at the same rate. In contrast, we found that in the context of full-length PDI, there is an asymmetry …

Global Characterization Of Porcine Intrauterine Proteins During Early Pregnancy, Jean-Patrick R. Kayser, Jong G. Kim, Ronald Cerny, Jeffrey L. Vallet

Ronald Cerny Publications

Total protein secreted in the intrauterine lumen increases between day 10 and 13 post-estrus in both cyclic and pregnant gilts. The objective of this experiment was to identify those intrauterine proteins whose secretion changes during this time period. Sixteen mature gilts were either mated (day 0) or remained cyclic and were slaughtered at either day 10 or day 13 (n = 4 per status by day). At slaughter, each uterine horn was flushed with 20 ml Minimal Essential Medium. Flushings were dialyzed extensively against distilled water. A 0.5 ml aliquot of each was lyophilized, subjected to two-dimensional PAGE, and protein …

Phase Change Enthalpies And Entropies Of Liquid Crystals, William Acree, James Chickos

Chemistry & Biochemistry Faculty Works

No abstract provided.

Phase Change Enthalpies And Entropies Of Liquid Crystals, William E. Acree, James S. Chickos

James Chickos

No abstract provided.

Evaluation Of The Vaporization, Fusion, And Sublimation Enthalpies Of The 1-Alkanols: The Vaporization Enthalpy Of 1-, 6-, 7-, And 9-Heptadecanol, 1-Octadecanol, 1-Eicosanol, 1-Docosanol, 1-Hexacosanol, And Cholesterol At T = 298.15 K By Correlation Gas Chromatography, Gary Nichols, Sasha Kweskin, Margaret Frericks, Sarah Reiter, Gin Wang, Jennifer Orf, Brett Carvallo, Dorothea Hillesheim, James Chickos

James Chickos

No abstract provided.

Lewis And Protic Acid Mediated Nicholas Reactions Of 3-Acetoxycyclohept-1-En-4-Ynedicobalt Hexacarbonyl: Site Selectivity Of Nucleophile Incorporation, Joseph Dimartino, James R. Green

Chemistry and Biochemistry Publications

Nicholas reactions on the cation derived from the cyclic allylic acetate alkynedicobalt complex 1 favour the gamma-site kinetically for most nucleophiles, with increasing amounts of of-products in cases with greater nucleophilicity. Some regiocontrol in introduction of a specific nucleophilic fragment is possible by using different nucleophiles. Under conditions where reversibility is possible, the thermodynamically favoured site is exclusively gamma-. (c) 2005 Elsevier Ltd. All rights reserved.

Direct Detection Of Double-Stranded Dna: Molecular Methods And Applications For Dna Diagnostics, Indraneel Ghosh, Cliff I. Stains, Aik T. Ooi, David J. Segal

Cliff Stains Publications

Methodologies to detect DNA sequences with high sensitivity and specificity have tremendous potential as molecular diagnostic agents. Most current methods exploit the ability of single-stranded DNA (ssDNA) to base pair with high specificity to a complementary molecule. However, recent advances in robust techniques for recognition of DNA in the major and minor groove have made possible the direct detection of double-stranded DNA (dsDNA), without the need for denaturation, renaturation, or hybridization. This review will describe the progress in adapting polyamides, triplex DNA, and engineered zinc finger DNA-binding proteins as dsDNA diagnostic systems. In particular, the sequence-enabled reassembly (SEER) method, involving …

Reversible Paramagnetism To Ferromagnetism In Transition Metal-Doped Tio2 Nanocrystals Prepared By Microwave Irradiation, Garry Glaspell, Asit B. Panda, M. S. El-Shall

Chemistry Publications

TiO2nanoparticlesdoped with 1%, 5%, and 10% M (M=Co, Fe, and Ni) were prepared by microwave irradiation and characterized using x-ray diffraction, transmission electron microscopy, and magnetometry. The as-prepared samples are found to be paramagnetic at room temperature, with the magnetic susceptibility following the Curie-Weiss law in the investigated range of 2–300K. However, transformation from paramagnetism to room-temperature ferromagnetism (RTFM) was observed by hydrogenating the samples at 400°C. Reheating in air converted the samples back to paramagnetic while rehydrogenating the samples again induced ferromagnetism. It is argued that the reversible RTFM observed is due to interaction between the dopant metal ions …