Physical Sciences and Mathematics Commons^™

Specific Heat And Thermodynamic Properties Of Metallic Systems: Instrumentation And Analysis, Brian E. Lang

Theses and Dissertations

A small-scale adiabatic calorimeter has been constructed as part of a larger project to study nano-particles and to facilitate specific heat measurements on samples where it is difficult to obtain enough material to run on the current large-scale adiabatic apparatus. This calorimeter is designed to measure sample sizes of less than 0.8 cc over a temperature range from 13 K to 350 K. Specific heat results on copper, sapphire, and benzoic acid show the accuracy of the measurements to be better than ±0.4% for temperatures higher than 50 K. The reproducibility of these measurements is generally better than ±0.25%. Experimental …

Nicholas Reactions With Carboxylic Acids For The Synthesis Of Macrocyclic Diolides, Kevin M. Shea, Kristina D. Closser, Miriam M. Quintal

Chemistry: Faculty Publications

We have developed a new strategy for the preparation of diolides using a cascade of Nicholas reactions. The carboxylic acid nucleophiles in these reactions are virtually unstudied participants in transformations of this type. Using this methodology, a 16-membered cobalt-complexed cyclic diyne is available in 28% yield over eight steps (an average of 85% per step). We can also easily access the uncomplexed diolide in one additional step.

Semiconductor Nanowire Laser And Nanowire Waveguide Electro-Optic Modulators, Andrew B. Greytak, Carl J. Barrelet, Yat Li, Charles M. Lieber

Faculty Publications

Electric field modulation of visible and ultraviolet nanoscale lasers consisting of single CdS or GaN nanowires has been achieved using integrated, microfabricated electrodes. Modulation of laser emission intensity is achieved with no detectable change in the laser wavelength. The devices can also be operated below the lasing threshold to modulate the intensity of light propagating within the nanowire waveguide. Studies of the electric field dependence in devices of varied geometry indicate that modulation is due to an electroabsorption mechanism. These findings expand opportunities for multicolor, nanowire-based photonic devices and circuits.

The Cytolethal Distending Toxin B Sub-Unit Of Helicobacter Hepaticus Is A Ca2+- And Mg2+-Dependent Neutral Nuclease, Rohana P. Dassanayake, Mark A. Griep, Gerald Duhamel

Mark Griep Publications

The cytolethal distending toxin B (CdtB) of the mouse pathogen Helicobacter hepaticus has cation binding and DNA catalysis residues in common with members of the mammalian deoxyribonuclease I (DNase I) family. The purpose of the present study was to characterize CdtB nuclease. To establish optimal digestion conditions and to evaluate co-factor requirements, a novel and sensitive fl uorometric assay that quantitatively determines double stranded DNA digestion was developed. Although the Ca²⁺- and Mg²⁺-dependence and neutral properties of CdtB were similar to DNase I, hydrolysis of DNA by CdtB was approximately 100-fold less active than DNase I …

Coarse-Grained Free-Energy-Functional Treatment Of Quasistatic Multiscale Processes In Heterogeneous Materials, H. Zhou, Ruqiang Feng, Dennis J. Diestler, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A new treatment of quasistatic (reversible) multiscale processes in heterogeneous materials at nonzero temperature is presented. The system is coarse grained by means of a finite-element mesh. The coarse-grained free-energy functional (of the positions of the nodes of the mesh) appropriate to the thermodynamic-state variables controlled in the relevant process is minimized. Tests of the new procedure on a Lennard-Jonesium crystal yield thermomechanical properties in good agreement with the “exact” atomistic results.

Chemistry & Biochemistry Newsletter, Department Of Chemistry & Biochemistry, South Dakota State University

Chemistry & Biochemistry Newsletter: 2002-2015

Inside:

Page 2 2010 Research Center Wins Big in Business Competition

Page 3 New Grad Students; Julee Driver to attend ACS Summer School on Green Chemistry

Page 4 New Staff; Foundation Donors

Page 5 Alumni News

Page 6 New Faculty Publications; Faculty Patents; Undergraduate Publications

Structures And Stability Of Medium-Sized Silicon Clusters. Iii. Reexamination Of Motif Transition In Growth Pattern From Si15 To Si20, Soohaeng Yoo, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

It has been established from experiments that stable medium-sized ionic clusters Si₁₅–Si₂₀ are prolate in shape. Density-functional theories (DFTs) also predict that nearly all low-lying neutral clusters in this size range are prolate in shape. Moreover, most of them are built onto two generic structural motifs, either the tricapped-trigonal-prism (TTP) Si₉ motif or the six/six Si₆/Si₆ (sixfold-puckered hexagonal ring Si₆ plus six-atom tetragonal bipyramid Si₆) motif. However, it appears that the exact location of the TTP-to-six/six motif transition is dependent on the functional (e.g., PBE or BLYP) used in the …

Microcapsule Biosensors Based On Competitive Binding And Fluorescence Resonance Energy Transfer Assays, Swetha Chinnayelka

Doctoral Dissertations

Fluorescent sensing systems offer the potential for minimally invasive monitoring with implantable devices, but they require carrier technologies that provide suitable immobilization, accessibility, and biocompatibility while maintaining adequate response characteristics. Towards the development of this goal, a general design of a biosensor with the capability of detecting different metabolites was investigated. The approach is based on the encapsulation of a competitive binding assay in microcapsules and monitoring the changes in fluorescence resonance energy transfer (FRET) in the presence of analyte. To experimentally demonstrate this type of sensing system, glucose was chosen as the model target analyte. The design, fabrication, and …

The Armstrong Chemical Bond, Armstrong Atlantic State University

Chemical Bond Newsletter (2004-2005)

No abstract provided.

Simple Electrooptical Sensors For Inorganic Anions, Pavel Anzenbacher Jr., Karolina Jursikova, Manuel Marquez

Chemistry Faculty Publications

Electrooptical sensors consisting of a conjugated chromophore undergoing a change in color and a redox-active moiety such as quinone fused to the chromophore were synthesized. Strong changes in colorimetric and electrochemical properties were observed in the presence of inorganic anions. A unique anion-specific response was observed for fluoride, pyrophosphate, and acetate. DFT (B3LYP/6-31G*) calculations performed for both "on/off" states of a sensor-fluoride model are in good agreement with the observed electrochemical and spectroscopic data.

Interaction Of Porphyrins With A Dendrimer Template: Self-Aggregation Controlled By Ph, Pavel Kubat, Kamil Lang, Pavel Janda, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

The interaction between self-aggregated porphyrins such as 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and 5,10,15,20-tetrakis(4-phosphonatophenyl)porphyrin (TPPP), and a generation 5 (G5) PAMAM dendrimer template is governed by minute differences of porphyrin acido-basic properties. While at neutral pH both monomeric TPPS and TPPP form complexes with G5, decreasing pH did not lead to porphyrin ring protonation (pK(a) approximate to 5) but rather to the preferential formation of H-aggregates (probably H-dimers), most likely due to protonation of the G5. Upon further acidification of the solution, this face-to-face orientation of the porphyrin units is being converted to edge-to-edge aligned J-aggregates with a tightly defined structure. This process …

Benzothiadiazoles And Dipyrrolyl Quinoxalines With Extended Conjugated Chromophores-Fluorophores And Anion Sensors, Dmitry Aldakov, Manuel A. Palacios, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

Stable fluorescent chromophores find use in a growing number of practical applications, including their utility as laser dyes,1 emitters in light-emitting diodes,2 photoconductors,3 optical data storage,4 and optical switches.5 Stable fluorophores with high quantum yields are widely used in fluorescent sensors6 and labels.7 These became very popular lately, owing to their potential for high sensitivity at low concentration coupled with decreased cost of the required equipment.8 Recently, we have described a new class of fluorescent anion sensors bearing extended conjugated chromophores9 with incorporated 2,3-di(1H-2-pyrrolyl)quinoxaline, (DPQ), as the anion recognition element.10 Literature shows that DPQ binds anions via hydrogen bonding between …

Natural And Synthetic Viniferins Associated With The Grapevine Disease Young Vine Decline, David Michael Mcginnis

Chemistry & Biochemistry Theses & Dissertations

Grapevine disease has been thc subject of intense research amongst viticulturists over the last few decades, especially during the 1990's. There has been discoveries that suggest grapevine disease is commonly caused by fungal pathogens. One of the most common fungi that the vine may become infected by is known as Botrytis cinerea. B. cinerea is capable of attacking the grapevine which in turn will lead to bunch rot in the grape clusters. This disease has been researched in great detail during the past several years and is one of only few microorganisms that have actually been identified. Phaeoacremrmium chnlmydospnrum …

Development And Application Of A Gg-Irms Reductive Pyrolysis Reactor Interface For The Δ34S Determination Of Sulfur In Individual Organic Compounds, N. Deborah Hewlett

Chemistry & Biochemistry Theses & Dissertations

The incorporation of sulfur into sedimentary organic matter is an important aspect of organic carbon preservation. A better understanding of the sulfur cycle and the formation of organo-sulfur compounds are necessary if we are to better understand the interaction of biogeochemical cycles of C, N, O, H. and S. Currently, the determination of ³⁴S/³²S in organic matter is limited to bulk organic samples. The sulfur isotopic analysis of individual organo-sulfur compounds within the sediments should allow for a more complete understanding of the sulfur cycle and the processes which lead to sulfur incorporation into organic matter. This …

Phases Found At Grain Boundary Of Yba2cu3o7-D 50 Nm Films On Srtio3 By Enhanced Anomalous Scattering At O:K, Cu:L2,3 And Ba:M4,5 Edges, Juana Acrivos

Faculty Publications, Chemistry

A new phase is detected within 100micrometers of 24 DEG ab grain boundary (GB) in YBa2Cu3O7-d 50 nm films on SrTiO3 by enhanced (001) anomalous scattering. Site identification and temperature dependence is interpreted using crystallographic weights to distinguish enhanced scattering from total electron yield and fluorescence spectra. The c-axis, c0 indicates that only ortho-I phase is present far from GB, both ortho-I and II phases are present near GB. The phase c0 is constant versus temperature across the transition to superconductivity.

Afci Quarterly Input – Unlv July 1 Through September 30, 2005, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects, activities and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

A Facile Synthesis Of (Tert-Alkoxy)Amines, Hasan Palandoken, Chris M. Bocian, Michelle R. Mccombs, Michael H. Nantz

Chemistry and Biochemistry

Tertiary alcohols react with stoichiometric BF₃·Et₂O and N-hydroxyphthalimide to yield N-alkoxyphthalimides. Subsequent hydrazinolyses afford the title compounds.

A Bacillus Thuringiensis Isolation Method Utilizing A Novel Stain, Low Selection And High Throughput Produced Atypical Results, Joanne Rampersad-Ammons, David R. Ammons

Chemistry Faculty Publications and Presentations

Background

Bacillus thuringiensis is a bacterium known for producing protein crystals with insecticidal properties. These toxins are widely sought after for controlling agricultural pests due to both their specificity and their applicability in transgenic plants. There is great interest in isolating strains with improved or novel toxin characteristics, however isolating B. thuringiensis from the environment is time consuming and yields relatively few isolates of interest. New approaches to B. thuringiensis isolation have been, and continue to be sought. In this report, candidate B. thuringiensis isolates were recovered from environmental samples using a combination of a novel stain, high throughput and …

Polymer Microchips For Capillary Electrophoresis And Electric Field Gradient Focusing Of Biomolecules, Ryan Thomas Kelly

Theses and Dissertations

Polymeric materials have seen increasing use as microfluidic device substrates due to their low cost and the simplicity of templated fabrication procedures. I showed that poly(methyl methacrylate) (PMMA) microdevices could be enclosed in a boiling water bath, which allowed the seal to form more quickly than in conventional approaches, and enabled microchannels to remain hydrated throughout the bonding process. Microchip capillary electrophoresis (µ-CE) devices were fabricated using water-based enclosure, and a mixture of fluorescently labeled amino acids was separated in 30 s in these microchips. To create more robust capillary electrophoresis (CE) microdevices with improved separation performance, phase-changing sacrificial materials …

Towards The Rational Design Of Mri Contrast Agents: A Practical Approach To The Synthesis Of Gadolinium Complexes That Exhibit Optimal Water Exchange, Mark Woods, Mauro Botta, Stefano Avedano, Jing Wang, A. Dean Sherry

Chemistry Faculty Publications and Presentations

The gadolinium(III) complex of S-SSSS-NO₂BnDOTMA exhibits water exchange kinetics that are optimal for use in high relaxivity or targeted contrast agents. However, the synthesis of this ligand is hampered by the steric encumbrance imparted upon the cyclen ring by the nitrobenzyl substituent. A relatively simple modification has been used to enable the synthesis of larger quantities of a bifunctional ligand that retains similar fast water exchange properties. The gadolinium complex of S-SSS-NO₂BnDO3MA-1A is shown to retain the rapid water exchange kinetics characteristic of a twisted square antiprismatic (TSAP) …

Catena-Poly[[Bis(Α-Thenoyltrifluoroacetonato)Copper(Ii)]-Μ-1,4-Di-4-Pyridyl-2,3-Diazabuta-1,3-Diene], William J. Perkins, Tamara Maxwell, Mark D. Smith, Leroy Peterson Jr., Hans-Conrad Zur Loye

Faculty Publications

In the one-dimensional title polymer, [Cu(C₈H₄F₃O₂S)₂(C₁₂H₁₀N₄)]_n or [Cu(L)₂(tta)₂] [tta is -thenoyltrifluoroacetonato and L is 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene], Cu²⁺ lies on a center of inversion. It is axially coordinated by two pyridyl N atoms from two different L ligands and equatorially coordinated by four O atoms from two chelating tta ligands. The ligand L propagates the one-dimensional chain structure by serving as a bridging ligand between two Cu octahedra via Cu-N coordinate bonds.

Enhanced Anomalous Scattering By Superconducting Nanofilms Vs T At O:K, Cu:L2,3 , Ba:M4,5 Edges, Juana Acrivos

Faculty Publications, Chemistry

Enhanced (001) anomalous scattering by YBa2Cu3O7-δ 50 nm films on SrTiO3 substrates with and without a grain boundary versus temperature is interpreted using crystallographic weights to distinguish it from total electron yield and fluorescence spectra. The power of diffraction enhancement is to ascertain the film oxygen composition from the changes in the c-axis, c0 as the film surface is scanned across the grain boundary, and to determine that c0 is constantversus temperature across the superconducting phase transition.

Activation Of Carboplatin By Carbonate, Anthony J. Di Pasqua, Jerry Goodisman, Deborah J. Kerwood, Bonnie B. Toms, James C. Dabrowiak

Chemistry - All Scholarship

Carboplatin, [Pt(NH3)2(CBDCA-O,O')], 1, where CBDCA is cyclobutane-1,1-dicarboxylate, is in wide clinical use for the treatment of ovarian, lung, and other types of cancer. Because carboplatin is relatively unreactive toward nucleophiles, an important question concerning the drug is the mechanism by which it is activated in vivo. Using [1H,15N] heteronuclear single quantum coherance spectroscopy (HSQC) NMR and 15N-labeled carboplatin, we show that carboplatin reacts with carbonate ion in carbonate buffer to produce ring-opened products, the nature of which depends on the pH of the medium. The assignment of HSQC NMR resonances was facilitated by studying the reaction of carboplatin in strong …

1,3-Bis(9-Ethyl­Carbazol-3-Yl)Propane, Erol Asker, John Masnovi

Chemistry Faculty Publications

In the title compund, C₃₁H₃₀N₂, π–π overlap is absent in the region where carbazole groups of two adjacent mol­ecules are inclined toward each other. The eth­yl groups which protrude from the plane of the carbazole groups and the alkyl­ene chain connecting the two carbazole groups are responsible for the poor mol­ecular stacking.

Electrochemical Attachment Of Motile Bacterial Cells To Gold, Sergey Rozhok, Richard C. Holz

Chemistry Faculty Research and Publications

Selective attachment of Escherichia coli K-12 bacterial cells to charged gold surfaces was demonstrated. Electrostatic binding of E. coli K-12 bacterial cells to positively charged surfaces was observed starting at +750 mV. The binding of E. coli K-12 cells to positively charged gold surfaces is proposed to occur due to long-range electrostatic interactions between the negatively charged O-chain of lipopolysaccharide (LPS) molecules protruding the bacterial cell body and the electrode surface. Removing LPS alters the cellular surface charge and results in cellular attachment to negatively charged surfaces. Thus, applying an electrical potential allows for the direct, real time detection of …

Digital Commons Presentation For Chemistry Department Faculty, Paul Royster

Department of Chemistry: Department Information

Why you should put your publications and other work online; how the Digital Commons can help you do that; copyright status of your publications; policies of publishers; policy of American Chemical Society.

Molecular Discrimination Of Type-I Over Type-Ii Methionyl Aminopeptidases, Krzysztof Swierczek, Alicja J. Copik, Sabina I. Swierczek, Richard C. Holz

Chemistry Faculty Research and Publications

Two residues that are conserved in type-I methionyl aminopeptidases (MetAPs) but are absent in all type-II MetAPs are the cysteine residues (Escherichia coli MetAP-I:   C59 and C70) that reside at the back of the substrate recognition pocket. These Cys residues are 4.4 Å apart and do not form a disulfide bond. Since bacteria and fungi contain only type-I MetAPs while all human cells contain both type-I and type-II MetAPs, type-I MetAPs represent a novel antibiotic/antifungal target if type-I MetAPs can be specifically targeted over type-II. Based on reaction of the thiol-specific binding reagent 5,5‘-dithio-bis(2-nitrobenzoic acid) (DTNB) with the type-I …

Quantum Amplified Isomerization:  A New Concept For Polymeric Optical Materials, Jason G. Gillmore, J. D. Neiser, K. A. Mcmanus, Y. Roh, G. W. Dombrowski, T. G. Brown, J. P. Dinnocenzo, S. Farid, D. R. Robello

Faculty Publications

The preparation and evaluation of a new class of photoresponsive polymers are described on the basis of a process called quantum amplified isomerization (QAI). The QAI process utilizes photoinitiated, cation radical isomerization chemistry in a polymeric medium. Two classes of materials are described:  one where the QAI reactant is molecularly doped in the polymer matrix and another where the reactant is part of a functionalized polymer. Quantum yield experiments demonstrate that the isomerization reaction can proceed by a chain process with modest efficiencies. Photochemical conversion experiments show that high extents of conversion of the QAI reactants are possible. The rate …

Origin Of Enantioselection In Chiral Alcohol Oxidation Catalyzed By Pd[(–)-Sparteine]Cl2, J. A. Mueller, Anne Cowell, Bert D. Chandler, M. S. Sigman

Chemistry Faculty Research

A kinetic investigation into the origin of enantioselectivity for the Pd[(–)-sparteine]Cl₂-catalyzed aerobic oxidative kinetic resolution (OKR) is reported. A mechanism to account for a newly discovered chloride dissociation from Pd[(–)-sparteine]Cl₂ prior to alcohol binding is proposed. The mechanism includes (1) chloride dissociation from Pd[(–)-sparteine]Cl₂ to form cationic Pd(–)-sparteine]Cl, (2) alcohol binding, (3) deprotonation of Pd-bound alcohol to form a Pd-alkoxide, and (4) β-hydride elimination of Pd–alkoxide to form ketone product and a Pd–hydride. Utilizing the addition of (–)-sparteine HCl to control the [Cl^–] and [H⁺] and the resulting derived rate law, …

Chemistry Weekly, Volume 1 Issue 23, September 5 - 9, 2005

Department of Chemistry: Department Information

COLLOQUIUM, Professor Bruce S. Hudson: “Vibrations of Molecules in Solids: Periodic DFT and Inelastic Neutron Scattering”
NEW CHEMISTRY DEPARTMENT STAFF; UNL EMPLOYEE SERVICE AWARDS; Hamilton Hall - Renovation News;
EHS COLLOQUIUM SERIES FOR RESEARCH PIs presents “Personal Protective Equipment (Laboratory),” Dr. Jim Zeigler, DuPont Personal Protection;
SEMINAR Sponsored By: Center for Materials Research & Analysis / NSF-MRSEC Title: Q & A on Synthesis of Nanoparticles and Nanotubes Speaker: Professor Stephen O'Brien, Dept. of Materials Science & Engineering, Columbia University;
Nebraska MRSEC 3rd Annual Review & Symposium—SEPT. 20-21