Physical Sciences and Mathematics Commons^™

17. Hermann Klare, Otto Vogl, Burkart Philipp

Otto Vogl

No abstract provided.

Models For Molybdenum Coordination During The Catalytic Cycle Of Periplasmic Nitrate Reductase From Paracoccus Denitrificans Derived From Epr And Exafs Spectroscopy, Clive S. Butler, John M. Charnock, Brian Bennett, Heather J. Sears, Ann J. Reilly, Stuart J. Ferguson, C. David Garner, David J. Lowe, Andrew J. Thomson, Ben C. Berks, David J. Richardson

Physics Faculty Research and Publications

The periplasmic nitrate reductase from Paracoccus denitrificans is a soluble two-subunit enzyme which binds two hemes (c-type), a [4Fe-4S] center, and a bis molybdopterin guanine dinucleotide cofactor (bis-MGD). A catalytic cycle for this enzyme is presented based on a study of these redox centers using electron paramagnetic resonance (EPR) and extended X-ray absorption fine structure (EXAFS) spectroscopies. The Mo(V) EPR signal of resting NAP (High g [resting]) has g_av = 1.9898 is rhombic, exhibits low anisotropy, and is split by two weakly interacting protons which are not solvent-exchangeable. Addition of exogenous ligands to this resting …

Zinc Speculation And Ligand Fluxes In Chesapeake Bay And Elizabeth River Pore Waters, Duncan Glover Byers

Chemistry & Biochemistry Theses & Dissertations

Presented here are the first data on the vertical concentrations, complexation, speciation, and fluxes of total dissolved zinc and zinc complexing ligands, and zinc speciation in sediment pore waters in the Chesapeake Bay and Elizabeth River, Virginia.

Sediment pore waters were collected in mid and southern Chesapeake Bay in November 1997 and in the Elizabeth River (Pinner's Point) in March, April, and July 1998. Flux experiments were conducted in Elizabeth River sediment cores in April and July 1998. [TDZn] and zinc complexation were determined using differential pulse anodic stripping voltammetry at a hanging mercury drop electrode (DPASV-HMDE).

[TDZn] in the …

Intermediate Species Possessing Bent Dna Are Present Along The Pathway To Formation Of A Final Tbp-Tata Complex, Kay M. Parkhurst, Robyn M. Richards, Michael Brenowitz, Lawrence J. Parkhurst

Lawrence Parkhurst Publications

Binding of the TATA-binding protein (TBP) to the “TATA” sequences present in the promoters of eukaryotic class II genes is the first step in the sequential assembly of transcription pre-initiation complexes. Myriad structural changes, including severe bending of the DNA, accompany TBP-TATA complex formation. A detailed kinetic study has been conducted to elucidate the mechanistic details of TBP binding and DNA bending. The binding of Saccharomyces cerevisiae TBP to the adenovirus major late promoter (AdMLP) was followed in real-time through a range of temperatures and TBP concentrations using fluorescence resonance energy transfer (FRET) and stopped-flow mixing. The results of association …

The Benign Hamburger, Graham F. Peaslee, Juliette Lantz, Mary Walczak

Faculty Publications

In this dilemma case study, the executives of a popular restaurant chain must decide whether to use irradiated meat, in this case, beef, to protect its customers from the bacteria, E. coli. Students learn about food irradiation and discuss issues related to food safety and the public’s acceptance of new food technologies. As developed, the case could be used in a variety of introductory science courses in chemistry, physics, biology, environmental science, and agricultural science.

High-Performance Liquid Chromatographic Separation Of Novel Atropic Α,Α-Disubstituted-Β-Amino Acids, Either On Different Β-Cyclodextrin-Bonded Phases Or As Their 1-Fluoro-2,4-Dinitrophenyl-5-L-Alanine Amide Derivatives, Gabriella Török, Antal Péter, Anne Gaucher, Michel Wakselman, Jean Paul Mazaleyrat, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

The high-performance liquid chromatographic enantioresolution of free and N- and/or C-protected derivatives of (R, S)-2',1':1,2;1',2':3,4-dinaphthcyclohepta-1,3-diene-6-aminomethyl-6 -carboxylic acid (β2-Bin) by direct and indirect methods is reported. The direct separation was carried out on native and different derivatized β -cyclodextrin-bonded phases. The indirect resolution was achieved by applying pre-column derivatization with 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide. The effects of different parameters such as the mobile phase composition and the structures of the compounds on the enantiomeric resolution are discussed.

Methylene-Only Subspectra In 13C Cpmas Using A New Double Quantum Filtering Sequence, Paola Rossi, Raju Subramanian, Gerard S. Harbison

Gerard Harbison Publications

Methodology for the assignment of ¹³C CPMAS spectra is still in its infancy. Previous methods of CPMAS spectral editing have utilized differences in the strength of the ¹³C–¹H dipolar interaction or the rate and spin thermodynamics of crosspolarization from protons to carbon, to differentiate between quaternary, tertiary, and methylene carbons. We introduce a different approach, which is based on the fact that double-quantum coherence develops between the protons of a methylene group considerably faster than between most other proton spin pairs in an organic solid. We generate this coherence, filter it, convert it back to single …

Phd Thesis (Doctorat De Spécialité): Université De Ouagadougou, 1999. Dr. Mamoudou H. Dicko. Purification Et Propriétés Physico-Chimiques Des Enzymes De Curculigo Pilosa, Gladiolus Klattianus Et Boscia Senegalensis Catalysant L'Hydrolyse Des Polysaccharides (Amidon Et Béta-Glucanes), Mamoudou H. Dicko Prof.

Pr. Mamoudou H. DICKO, PhD

The objective of this study was the research of novel and inexpensive sources of polysaccharides degrading enzymes such as amylases and glucanases from local plants in order to justify their biotechnological applications. The isolation of two l3-amylases and an endo-1,3-ß-D-glucanase was reached using common protein purification methods such as buffer extraction, ammonium sulfate fractionation, ionexchange and gel filtration chromatographies. The methods used were simple and easily reproducible, suggesting the possibilfty of large-scale production. ln the crude extract of Curculigo pilosa tuber, only ß-amylase was detected as starch degrading enzyme and its activity was approximately 282 Uig of fresh material. The …

18. Dieter Freitag, Otto Vogl, Karina Rigby

Otto Vogl

No abstract provided.

Media Coverage Of Epa's Draft Dioxin Reassessment Report, Sharon M. Friedman, Megan A. Fitzpatrick, Brenda P. Egolf

RISK: Health, Safety & Environment (1990-2002)

Using content analysis, the authors examine the utility of news media in democratic decision making.

The Binding Of Fluorophores To Beta-Cyclodextrin Derivatives, Kellie J. Forrestall

Honors Theses

β-cyclodextrin (β-CD) is a seven-unit cyclic sugar molecule with a toroidal shape, a hydrophilic exterior and a hydrophobic cavity. It has been suggested that pyrene (P) forms a 2:1 (P(β-CD)2) complex with β-CD, where pyrene lies in-between the two wider rims of the β-CD. We examined this hypothesis by comparing the spectral properties of pyrene in the presence of substituted β-CDs. These properties include the shape and lifetime of pyrene fluorescence and the effect on pyrene fluorescence of added iodide quencher and alcohol. The derivatives studied included those with substituents only on the narrow rim, and those with substitution on …

The Characterization Of Methylene-Blue-Doped Sol Gels And The Development Of A Fluorenscence-Based Fiber-Optic Sensor For Sulfite, Tara K. Morcone

Honors Theses

The purpose of this research was to develop a fiber-optic sensor for sulfite via immobilizing Methylene Blue (MB) within a sol-gel matrix. MB is a redox-indicating dye. In the oxidized form, the dye is a blue color, but reduction causes a change to the colorless, leuco form. This property is advantageous for the detection of reducing agents, such as sulfite. In solution, leuco-MB reverts to its blue form in the presence of an oxidizing agent. The method of MB immobilization is through the use of sol gels. The environment of a sol gel is chemically inert and small analytes can …

The Dynamic Interactions Of Actin Stress Fibers And Microtubutes, Daniel Jason Kelmanovich

Honors Theses

The regulation of actin stress fibers (SF) are linked to the stability of microtubule (M1) structures. The exact method of interaction is not understood. To study the interaction, live cells containing fluorescent α-actinin were observed and treated with MT perturbing drugs as well as ATP-depletion. These treatments affect the stability of the microtubules and stress fibers respectively. A plasmid coding for fluorescent tubulin was also inserted into these cells to aid in observing both the MTs and SFs simultaneously. The observation relies on fluorescent microscopy and digital imaging. By observing the changes in the MTs and SFs in live cells, …

The Polymerization Of Aniline On Transition-Metal Cation Exchanged Hectorite Films, Charity Mcmanaman

Honors Theses

Inorganic-organic materials often exhibit enhanced flexibility and thermal stability over their individual inorganic and organic precursors. We are studying the polymerization of organic aniline monomers on inorganic hectorite clay thin film supports. Previous research has shown that aniline polymerizes on the surface and intergallery regions of Cu(II)-exchanged hectorite films. We have synthesized a library of first row transition-metal exchanged hectorite thin film hosts and are probing the effects of the different transition metal cations on aniline polymerization. We have used infrared spectroscopy, X-ray diffraction and digital photography to characterize the extent of aniline polymerization on the films. Utilizing the transition …

Photochemistry And Pinhole Photography: An Interdisciplinary Experiment, Angeliki A. Rigos, Kevin Salemme

Visual & Performing Arts Faculty Publications

This interdisciplinary activity combines chemistry and art through the construction and use of a pinhole camera. We focused on the chemistry of the black and white photographic process as the science component of this activity. The reactions involved are good examples of photochemistry and multiphase chemical reactions, since the light sensitive materials (silver halides) are in the form of a gelatin emulsion of microscopic crystals.

Spectroscopic And Kinetic Investigation Of Carbocation Reactivity In Supercritical Carbon Dioxide, Hongshu Jin

Masters Theses

Recent interest in the use of supercritical CO₂ as an environmentally benign reaction medium has included the development of solvent systems that may support polar and ionic chemistry. Carbocations are key intermediate in a variety of synthetically important reactions and characterization of their reactivity is the focus of this work. UV-visible absorption, and steady-state and time-resolved fluorescence spectroscopy has been used to identify and monitor the reaction kinetics of 9- phenylxanthenium carbocation. The arylcarbocation is conveniently generated from 9- phenylxanthen-9-ol in supercritical CO₂ under mildly acidic conditions. Under these conditions 9-phenylxanthenium ion is extremely stable and persists for …

4-Methoxybenzaldehyde Pentafluorophenyl-Methylidenehydrazone, Michael A. Lewis, Charles Leslie Barnes, Bruce A. Hathaway, Rainer Glaser

Chemistry Faculty Research & Creative Works

The crystal structure of the mixed azine C₁₅H₉F₅N₂O is described. The molecule has a high degree of planarity. The two phenyl rings deviate from perfect planarity by less than 2° and the dihedral angles between the ipso-C atoms and the azine bridge also show a minute deviation from planarity of less than 2°. The only dihedral angle that indicates any significant twisting is the dihedral angle about the azine bridge [C1-N1-N2-C8 174.8 (6)°], and even this one is relatively small. Face-to-face arene-arene contacts are the dominant intermolecular interactions. There are double …

Overview: Nonlinear Dynamics Related To Polymeric Systems, Irving R. Epstein, John A. Pojman

Faculty Publications

No abstract provided.

Period-Doubling Behavior In Frontal Polymerization Of Multifunctional Acrylates, Jonathan Masere, Felicia Stewart, Timothy Meehan, John A. Pojman

Faculty Publications

Front dynamics in the frontal polymerization of two multifunctional acrylate monomers, 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane ethoxylate triacrylate (TMPTA), with Lupersol 231 [1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane] as the initiator, are studied. In most frontal polymerization systems, the dynamics are associated with a planar front propagating through the sample. However, in some cases, front behavior can be altered: the front becomes nonplanar characterized by complex patterns like spin modes and pulsations. To determine how these periodic and aperiodic modes arise, reactant solutions consisting of HDDA diluted with diethyl phthalate (DEP) and TMPTA diluted with dimethyl sulfoxide (DMSO) were used in the study. …

Cross-Linking Of Polystyrene By Friedel–Crafts Chemistry To Improve Thermal Stability, Zhitao Wang, David D. Jiang, Michael A. Mckinney, Charles Wilkie

Chemistry Faculty Research and Publications

Copolymers which contain either alcohol or chloride functionalized polystyrene units have been prepared and they participate in Friedel–Crafts chemistry to give cross-linked polymers by the evolution of either hydrogen chloride or water. Proof of cross-linking comes from the identification of the evolved gas, the insolubility of the product, and the thermal resistance of the newly formed polymer. The onset temperature for the degradation is raised by about 100°C relative to that of polystyrene and the fraction which is not volatile at 800°C ranges from 10% for the alcohol copolymers to 20% for the chloride copolymers.

Reference Materials For Calorimetry And Differential Thermal Analysis, R. Sabbah, An Xu-Wu, J.S. Chickos, M.L.Planas Leitão, M.V. Roux, L.A. Torres

James Chickos

No abstract provided.

Catalyctic Reduction Of Nitric Oxide By Copper Catalyzed Granular Activated Carbon In The Presence Of Oxygen, Shan Xiao

Theses

The catalytic reduction of nitric oxides by solid carbonaceous material consisting primarily of granular activated carbon or (GAC) was studied in a fix bed catalytic reactor in order to develop the technology for removing NO and soot simultaneously from diesel engine exhaust. The catalytic activity and conversion of NO as a function of reaction temperature was evaluated as a function of space velocity. The results show that at lean condition and high gaseous hourly space velocity, vis., 50,000 ~ 80,000, Cu-ZSM-5 does not perform as well with CO and GAC as it does with gaseous hydrocarbons(HC). Plain GAC has low …

Sustainable Green Manufacturing Of Energetic Materials, Ted Alex Formeza

Theses

Pollution from manufacturing processes of the major energetic materials currently used in the U.S., 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7 tetraazacyclooctane (HMX) was briefly evaluated. It was found that acetic acid was a major pollutant. It appeared that the British Process could be controlled to reduce the polluting effluents better than the Bachmann Process used in the U.S. Most of the effort for producing the next generation of energetic materials is currently centered around the production of 1,3,3-trinitroazetidine (TNAZ). We evaluated five synthetic routes for producing TNAZ. We reduced the number of potential processes by carefully considering possible changes in the schemes that …

The Influence Of Heat On The Measurement Of Photocurrent At The Anodic Film Of Nickel Electrode, Hang Chen, Zhiyu Jiang

Journal of Electrochemistry

The influence of heat on the measurement of photocurrent for nickel electrode in 1 mol/L NaOH solution was investigated by using the photocurrent,photothermal and thermal current methods. It was found that the appearance of photocurrent in potential region of -0.750.20 V(vs. Hg/HgO electrode) was due to the p_type semiconductor properties of Ni(OH)2 film in which is agree with the previous report. In the Ni(OH)2/NiOOH redox potential region, the increase of temperature at the surface of working electrode during irradiation significantly promoted the electrochemical reaction strongly. The photocurrent observed in potential region 0.200.57 V is mainly attributed to the influence of …

Investigation Of Solution Chemistry In Crevice Of Carbon Steel And Its Anodic Polarization Behavior, Zhuo Chen, Cuiwei Du, Bei Cao, Yinshun Wu, Hai Yang, Zhengrong Zhang

Journal of Electrochemistry

A self_made wedge_shaped simulated crevice apparatus was designed to investigate the solution chemistry in crevice of carbon steel and its anodic polarization behavior. For carbon steel with 3.5%(wt) NaCl , the change and the distribution of electrode potential , concentration of Cl- and pH value of solution in the crevice, and the current density of metal in the crevice were measured respectively under various conditions of anodic polarization. The results showed that without polarization the metal about 2 cm away from the opening of the crevice was attacked preferentially because of its lowest free corrosion potential. The anodic polarization promoted …

A Study On The Cathode Protection Potential Against Pitting Corrosion, Chunchun Xu, Youping Liu, Xiaobo Zhang, Xuhui Zhao

Journal of Electrochemistry

The methods have been developed to determine the protection potential against pitting corrosion. They are based on the theory that the pitting protection potential(Ep) is actually the transition potential of the direction of current between the occluded cell and the external surface (ET).ET lasts from -220 mV to -440 mV(SCE), the lowest of which can be considered as cathode protection potential. The Ep values determined with cyclic potentiodynamic polarization method is included in the ET with above methods.

Preparation And Application Of Gold_Film On The Surface Of Bacterial_Modified Carbon Paste Electrode, Rongzong Hu, Yanping Ruan, Hao Xu, Jinkun Fu, Weide Zhang, Wenyun Hu

Journal of Electrochemistry

A novel method for preparation of gold_film composed of ultra_fine gold particles was reported in this paper. The gold_film was prepared by electrochemical method on the surface of the paste electrode modified with the strain Bacillus sp. D01 which has strong ability to absorb and reduce Au3+. In addition, this paper reported an experimental method of determining trace amount of Cu2+ in water solution using cathodic stripping analysis to estimate the performances of the obtained gold_film. The experimental results indicated that this new method for preparation of gold_film is simple. The obtained gold_film electrode is stable and sensitive to determining …

Electochemical Measuments Of Defective Coatingson Buried Steel Substrates, Shizhe Song, Shijiu Jin, Xiaoping Song, Yunhai Xu, Jian Li

Journal of Electrochemistry

An electrochemical technique to detect the defects and detachments of the protective coating on the steel structures with electrochemical impedance spectroscopy (EIS) was offered. A new parameter K,which was defined as the ratio of the electrode resistance amplitude at a certain frequency to that at minimal frequency was obtained in present paper. The results indicated that the change of K at a certain range of frequency reflected the condition of protective coating.The technique was found to be very useful in estimating the different conditions of protective coating after being applied to the carbon steel samples covered with tar asphalt which …

Oxidation And Adsorption Of Deoxyribonucleic Acid At Highly Ordered Pyrolytic Graphite And Glass Carbon Electrode, Jianzhang Zhou, Lingling Wu, Jin Luo, Zhonghua Lin

Journal of Electrochemistry

It is shown that calf thymus DNA(CT DNA) can be adsorbed at highly ordered pyrolytic graphite(HOPG) electrode and detected by differential pulse voltammetry(DPV) and electrochemical atomic force microscopy(ECAFM). It is found that controlled potential pre-polarization influences largely the adsorption of dsDNA while it has little influence on ssDNA. It is demonstrated that ECAFM is useful to exploit adsorption of DNA at HOPGE. The pattern of adsorption of DNA at HOPG electrode that fits best with the experimental data is proposed. The results aslo shows that UV/Vis reflection spectroscopy, which has not been used in studying electrochemical behavior of DNA, is …

Study On The Hydrogen Permeation Through Zinc Electrodeposit, Jiangli Cao, Jixun Wu, Yanping Lu, Jie Shi

Journal of Electrochemistry

The electrochemical hydrogen_permeation technique was used to study hydrogen permeation through zinc electrodeposit with bilayer specimens of Fe substrate/zinc electrodeposit.The effect of coating thickness on hydrogen diffusion coefficient and hydrogen steady-state flux was studied. The results showed that hydrogen diffusion coefficient was approximately in the range of 10-11 cm2s-1 rank and zinc coating could retard hydrogen permeation. Accordingly, hydrogen steady_state flux and effective diffusion coefficient declined while the coating thickness increased.