Physical Sciences and Mathematics Commons^™

Study On The New Type Fe_3o_4 Composite Anode, Xiongxin-Yong Xiongxin-Yong

Journal of Electrochemistry

An ultrafine powder of magnetite has been prepared, and used to prepare the composite anode of Fe_(3)O_(4)-Fe by sintering method. The voltage of chlorine evolution、polarization curves、service life and mass loss, and the optimum sintering temperature and the weight ratio of the sintered powder have been investigated. All results showed that the method of preparing the practical Fe_(3)O_(4)-Fe composite uniform anode is feasible.

Investigation On Ru-Ti-Ir-Sn Oxide Anode Coatings For Electrolyzing Seawater, Wang Ke

Journal of Electrochemistry

The anode coatings of Ru-Ti-Ir-Sn oxide with various compositions were prepared by thermal decomposition. The physical and electrochemical properties of the coatings were characterized by scanning electron microscope (SEM), energy dispersive X-ray detector (EDX), accelerated life, current efficiency, anti-Mn~(2+)contamination, polarization curveandcyclic voltammetry tests. The results showed thatthe anode coating with optimized formula possessed excellent overall properties for electrolyzing seawater.

Electrochemical Stability Of Pva Alkaline Gel Polymer Electrolyte Membranes, Jun-Hong Wang, Jian-Min Liu, Hua-Bin Yang, Zuo-Xiang Zhou

Journal of Electrochemistry

Polyvinyl alcohol (PVA) alkaline polymer gel electrolyte(GPE) membranes were successfully prepared by a solution-casting technique and their electrochemical stabilities were investigated. The electrochemical impedance spectrum (EIS) results showed that the ionic conductivity of the PVA alkaline GPE membranes first increased with the increase of KOH content, then decreased with the further increase of KOH. When the weight percentage of the KOH in the PVA alkaline GPE membrane approached to 42%, it exhibitedthe highest ionic conductivity of 2.01×10~(-3 ) S/cm at room temperature (R.T.). The X-ray diffraction (XRD) results revealed that with the increase of KOH the crystalline of the PVA …

A Comparison On Structural Sensitive Adsorption Of Sb On Au Single Crystalline Electrodes, Jia-Wei Yang, Wang-Huo Shang, Qiong Wu, Bing-Wei Mao

Journal of Electrochemistry

We compare the behaviors of irreversible adsorption of Sb(III) and its reduction, underpotential deposition of Sbon Au(111) and Au(100) as well as mutual interactions of the processes. Based on in-situ scanning tunneling microscopic and cyclic voltammetric results, the substrate structure not only influence anion adsorptionbehavior and thus the Sb adsorption structure, but also the stability of its own structure. On Au(111) surface,the irreversibly adsorbed dense and disordered SbO~(+ )film structure remains after reduction of the film; while on Au(100)surface, due to the coadsorption of SO_4~(2-),an ordered(2×2)structure is formed after reduction.UPD of Sb on Au(111)is accompanied by significant surface alloying, which …

The Preparation And Performance Of The Aqueous Matrix For Molten Carbonate Fuel Cells, Hua-Xin Lin

Journal of Electrochemistry

PVA matrix of MCFC was prepared from the α-LiAlO_(2 )powder, and polyvinylalcohol(PVA), Compared with the conventional PVB matrix, higher porosity,higher thermal weight loss and smaller maximum pore diameter were achieved for PVA matrix. Single cell was assembled with PVA matrix. At reaction gas pressure of 0.9MPa, under reaction gas utilization of 20%, at 300 and 428.57mA·cm~(-2), the cell voltage was 0.849 and (0.739) V respectively, and the output power density was 254.7 and 316.7mW·cm~(-2 )respectively, which are higher than those of the cell assembled with PVB matrix. During thermal cycles, the cell performance shows a slightly decreasing-rising-stabilizing process, which might …

Preparation And Characterization Of Mcm-41/ Pvdf-Hfp Composite Microporous Polymer Electrolytes For Li-Ion Batteries, Zuo-Feng Chen

Journal of Electrochemistry

MCM-41/vinylidine fluoride-hexafluropropene copolymer (PVdF-HFP) composite microporous polymer electrolytes were prepared with mixed solvent of N, N-Dimethylformamide (DMF) and acetone. The influence of MCM-41 and nano-SiO_(2) on the porous structure of the microporous polymer electrolytes were studied with SEM. The results show that MCM-41 could take the place of the plasticizer in the process of making pores, and bring the preparation of microporous membranes easily. The preliminary electrochemical tests showed that the ion conductivity of composite microporous polymer electrolyte with 10% MCM-41 was about 10~(-3) S cm~(-1), and the performance of batteries was improved. The mesoporous MCM-41selected in the paper possesses …

Application Of Nickel Foam Electrode For Electroreduction Intermediate Of Purine, Hui-Wen Yang, Xi-En Hu, Xue-Jun Wang

Journal of Electrochemistry

Nickel foam with weight uniformity, good porosity ,pore size and low resistivity as a three-dimensional cathode was used in a filter-press electrochemical reactor. The H_(2)SO_(4) as supporting electrolyte, separator of cation ion exchange membrane, and the lead plate as an anode were used. The cyclic system consisted of electroreduction reactor, pump, store tank and ampere meter. NAU was electroreduced in the cathode chamber of the reactor. Purine intermediate was synthesized with DAU, and the results were compared with those of iron powder reduction process. A peak current in the electroreduction process was detected. The current density of nickel foam increased …

Influence Of Dc Electric Field On The Oil-Water Relative Permeability In Water-Drive Reservoir, Zhangji-Hong Zhangji-Hong

Journal of Electrochemistry

The effectsof DC electric field strength and direction on oil-water relative permeability and the influence mechanism in reservoir were studied and analysed.The results of experiments indicated that, with the application of external electric field, the core samplesbecomes more hydrohilic, irreducible water saturation increasesand residual oil saturation decreases. Meanwhile, oil relative permeability increases and water relative permeability decreases with increasingof the strength of external electric field. It is demonstrated as well that the different seepage flow behaviors, the structure change of double-electric-layer surface and the electric-viscous effect of polar and non-polar phaseare the main factors influencingoil-water relative permeability.

Oscillographic Determination Of Ethamsylate, Hong-Gang Ni, Hong-Fang Zhang, Jian-Bin Zheng

Journal of Electrochemistry

In 0.2 mol L~(-1) NaOH solution, ethamsylate can yield a sensitive incision on cathodic branch of dE/dt-E osillogram at 0.3V (vs. SCE). Based on the oscillographic characteristic, a second order differential simple oscillographic voltammetry for determination of ethamsylate in tablet and injection is presented in this paper. The peak height on second order differential simple oscillographic voltammogram is linearly proportional to concentration of the ethamsylate in the range of 1.5×10~(-5)～3.4×10~(-4) mol·L~(-1 )with a 0.9921 correlation coefficient and a detection limit of 6.0×10~(-6 )mol·L~(-1 ) for ethamsylate. The relative standard deviation is 2.1% for the determination of 3.0 10~(-5) mol L~(-1) …

Initial Process Of Pyrophosphate Copper Electroplating, Shao-Bin Feng, Shi-Bo Shang, Li-Ting Feng

Journal of Electrochemistry

The relationship between the type of on changes of copper electroplating potential~time and the adhesion of coating layer was examined by chronopotentiometry. The conception of critical initial current density (D_(KC)) was put forward. When the initial working current (D_(KI)) was higher than the critical initial current, the iron electrodewas polarized to activation potential of iron surface firstly, then to the activation of the substratesurface, and finally to depositionpotentialof copper ion. The coating deposited on the active surface and had goodadhesion.On the contrary,when D_(KI) was lower than D_(KC), the coating deposits on the surface of "passivated" iron substrate, and bad coating …

Ab Initio Calculation Of Bowl, Cage, And Ring Isomers Of C20 And C20-, Wei An, Yi Gao, Satya S. Bulusu, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

High-level ab initio calculations have been carried out to reexamine relative stability of bowl, cage, and ring isomers of C₂₀ and C₂₀^-. The total electronic energies of the three isomers show different energy orderings, strongly depending on the hybrid functionals selected. It is found that among three popular hybrid density-functional (DF) methods B3LYP, B3PW91, PBE1PBE, and a new hybrid-meta-DF method TPSSKCIS, only the PBE1PBE method (with cc-pVTZ basis set) gives qualitatively correct energy ordering as that predicted from ab initio CCSD(T)/cc-pVDZ [CCSD(T)—coupled-cluster method including singles, doubles, and noniterative perturbative triples; cc-pVDZ—correlation consistent polarized valence double zeta] …

An Investigation Of The Chemistry Of Ship Emission Plumes During Itct 2002, G. Chen, L. G. Huey, M. Trainer, D. Nicks, J. Corbett, T. Ryerson, D. Parrish, J. A. Neuman, J. Nowak, D. Tanner, J. Holloway, C. Brock, J. Crawford, J. R. Olson, A. Sullivan, R. Weber, S. Schauffler, Stephen G. Donnelly Ph.D., E. Atlas, J. Roberts, F. Flocke, G. Hübler, F. Fehsenfeld

Chemistry Faculty Publications

A ship emission plume experiment was conducted about 100 km off the California coast during the NOAA Intercontinental Transport and Chemical Transformation (ITCT) 2K2 airborne field campaign. Measurements of chemical species were made from the NOAA WP-3D aircraft in eight consecutive transects of a ship plume around midday during 2.5 hours of flight. The measured species include NOx, HNO3, peroxyacetylnitrate (PAN), SO2, H2SO4, O3, CO, CO2, nonmethane hydrocarbons (NMHC), and particle number and size distributions. Observations demonstrate a NOx lifetime of ∼1.8 hours inside the ship plume compared to ∼6.5 hours (at noontime) in the moderately polluted background marine boundary …

Integrated Quantum Mechanical Approaches For Extended Π Systems: Multicentered Qm/Qm Studies Of The Cyanogen And Diacetylene Trimers, Brian W. Hopkins, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

A multicentered integrated quantum mechanical (MC QM/QM) scheme that can accurately treat extended π systems is presented. The trimers of cyanogen (NC-CN) and diacetylene (H-CC-CC-H) are studied in seven geometries. MC QM/QM calculations reproduce CCSD(T) binding energies within 0.04 kcal mol^-1. In contrast, MP2 substantially overestimates these interaction energies. An MC QM/QM version of the substituent value test is introduced, and the error in MC QM/QM results is discussed in this context. The results for these systems suggest that MC QM/QM may be a powerful tool in the study of extended π systems and other weakly bound clusters. …

Cisplatin Carbonato Complexes. Implications For Uptake, Antitumor Properties, And Toxicity, Corey R. Centerwall, Jerry Goodisman, Deborah J. Kerwood, James C. Dabrowiak

Chemistry - All Scholarship

The reaction of aquated cisplatin with carbonate which is present in culture media and blood is described. The first formed complex is a monochloro monocarbonato species, which upon continued exposure to carbonate slowly forms a biscarbonato complex. The formation of carbonato species under conditions that simulate therapy may have important implications for uptake, antitumor properties, and toxicity of cisplatin.

Using Databases And Computational Techniques To Infer The Function Of Novel Proteins, Viswanathan Ramanathan, Kelly A. Mercier, Robert Powers, Peter Revesz

Chemistry Department: Faculty Publications

The Human Genome Project and similar efforts have resulted in the identification of an abundance of novel proteins. There is a need to expedite the process of assigning function to novel proteins. Nuclear magnetic resonance (NMR) spectroscopy can be used to infer a general biological function for a protein of unknown function by identifying compounds that preferentially bind the protein and comparing these results against proteins with defined structure and function. The Functional NMR screen generates hundreds of data sets and a manual analysis of these data sets is laborious and time- consuming. It is hypothesized that several sub-tasks of …

Cyclopropylcarbinyl → Homoallyl-Type Ring Opening Of Ketyl Radical Anions. Structure/Reactivity Relationships And The Contribution Of Solvent/Counterion Reorganization To The Intrinsic Barrier, J. M. Tanko, Jason G. Gillmore, Robert Friedline, M'Hamed Chahma

Faculty Publications

Following a protocol developed by Mathivanan, Johnston, and Wayner (J. Phys. Chem. 1995, 99, 8190−8195), the radical anions of several cyclopropyl- and oxiranyl-containing carbonyl compounds were generated in an effort to measure the rate constants for their ring opening (ko) by laser flash photolysis. The results of these experiments are compared to those obtained from earlier electrochemical studies, and the combined data set is used to rationalize the kinetics of radical anion ring opening in a general context by using Savéant's theory pertaining to stepwise dissociative electron transfer (Acc. Chem. Res. 1993, 26, 455−461). Compared to cyclopropylcarbinyl → homoallyl rearrangements …

Two-Neutron Transfer In The 6he + 209bi Reaction Near The Coulomb Barrier, Paul A. Deyoung, Patrick J. Mears, J. J. Kolata, E. F. Aguilera, F. D. Becchetti, Y. Chen, M. Cloughesy, H. Griffin, C. Guess, J. D. Hinnefeld, H. Jiang, Scott R. Jones, U. Khadka, D. Lizcano, E. Martinez-Quiroz, M. Ojaniega, Graham F. Peaslee, A. Pena, J. Reith, S. Vandendriessche, J. A. Zimmerman

Faculty Publications

The cross section for α-particle emission in the He6+Bi209 reaction at energies near the Coulomb barrier is remarkably large. Possible reactions that may produce the observed α particles include two-neutron transfer, one-neutron transfer, and direct projectile breakup. Each of these mechanisms results in a distinctive angular correlation between the α particle and the outgoing neutron(s). A neutron-α-particle coincidence experiment was performed to study two-neutron transfer to unbound states of Bi211. It is shown that approximately 55% of the observed α-particle yield at and beyond the grazing angle is because of this process. This is more than 2.5 times the fraction …

Preparation, Structural Characterization, And Dynamic Properties Investigation Of Permalloy Antidot Arrays, Andriy Vovk, Leszek M. Malkinski, Scott L. Whittenburg, Charles O'Connor, Jin-Seung Jung, Suk-Hong Min

Chemistry and Biochemistry Faculty Publications

Regular nanosized structures are considered to be promising materials for magnetic information storage media with high density of information. Recently attention was paid to static and dynamic magnetic properties arising from dimensional confinement in such nanostructures. Here we present an investigation of permalloy antidot arrays of different thicknesses. Thin permalloyfilms of thickness ranging from were deposited on nanoporous membranes with a pore size of . It was found that additional ferromagnetic resonance peaks appear for film thicknesses below , while films with larger thicknesses show resonanceproperties similar to continuous films. A comparison between the filmsdeposited onto Si wafers and porous …

Cooperative Effects In Two-Dimensional Ring-Like Networks Of Three-Center Hydrogen Bonding Interactions, Ruben D. Parra, Satya S. Bulusu, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Cooperative effects in two-dimensional cyclic networks containing intermolecular three-centered hydrogen bonding interactions of the type H₁&#;A&#;H₂ are investigated by means of ab intio molecular orbital and density functional theory calculations. Ring-like clusters consisting of three and up to nine monomers of the cis–cis isomer of carbonic acid H₂CO₃ are used as basic models, where each unit acts simultaneously as a double hydrogen-bond donor and double hydrogen-bond acceptor. Cooperative effects based on binding energies are evident for (H₂CO₃)_n, where n goes from 2 to 9. Thus, the ZPVE-corrected dissociation …

Stereoselective Allylation Of Chiral Monoperoxyacetals, Aqeel Ahmed, Patrick Dussault

Patrick Dussault Publications

Neighboring iodo-, alkoxy-, acetoxy- and silyl groups impart useful levels of diastereoselection in the Lewis acid-mediated allylation of monoperoxyacetals. Although monoperoxyacetals are found to be considerably less reactive than corresponding nonperoxidic acetals, similar stereochemical trends are observed in the two series.

Guest-Host Chemistry Of P-Sulfonatocalix[6]Arene And Nizatidine, Galia Debelouchina

Honors Theses

This work investigates the guest-host chemistry in water of p-sulfonatocalix[6]arene and a number of guests related to the amino acids arginine and lysine. Two questions are particularly important: what are the interactions that drive guest-host binding and what is the role of the solvent. The answers to these questions are investigated with isothermal titration calorimetry (lTC), which gives K, ?H, and ?S, and pressure perturbation calorimetry (PPC), which allows the calculation of the thermal coefficient of expansion ? and relating it to a molecule's structure-breaking or structure-making properties. The ITC data suggests that hydrogen bonding and charge-charge interactions are the …

Improvement Of Long Range Order In Diblock Copolymer Templates For Nanostructure Deposition, Scott Michael Fontana

Doctoral Dissertations

This dissertation presents work that examines the use of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer thin films as nanoporous templates. Diblock copolymer thin films are able to microphase separate to produce microdomains on the nanometer length scale. Cylindrical domains can be perpendicularly oriented when cast as a thin film on a neutral surface. From the perpendicularly oriented cylindrical microdomains, nanoporous templates can be created.

Cylindrical domain block copolymer templates can lead to the production of nanostructures, but the lack of long range ordering prevents the use of diblock copolymer template for some industrial applications. Graphoepitaxy utilizes a …

Atomistic Investigation Of Anomalous Diffusion On Surfaces: A Deterministic Approach, James Wesley Mancillas

Doctoral Dissertations

The observation of anomalous diffusion rates on surfaces by recent experiments has renewed interest in diffusion mechanics. In order to provide a better understanding of the atomistic motions resulting in anomalous diffusion, we have investigated the diffusion dynamics of sodium on a copper surface using conservative molecular dynamics. The properties of diffusing adatoms transitioning between normal diffusive motion and anomalous motion have then been examined. Utilizing short time approximation Lyapunov exponents, stable cantori within chaotic manifolds are identified. At the periphery of these stable cantori from which anomalous diffusion originates, we have examined the transition properties of diffusive motions with …

Overcoming Statistical Error And Bias In Quantum Monte Carlo: Application To Metal-Doped Helium Clusters, Gary Lee Warren Jr.

Doctoral Dissertations

Quantum Monte Carlo (QMC) methods are a class of powerful computer simulation techniques for solving the many-body Schrӧdinger equation. These techniques deliver essentially exact results and boast favorable computational scaling with system size. Calculations provide a full quantum mechanical treatment and may be carried to arbitrary precision. These characteristics make QMC a promising choice for the investigation of doped helium clusters, where quantum effects are substantial.

Stochastic in nature, QMC methods are susceptible to statistical bias and error, which must be carefully controlled. Moreover, the relationship between the finite sampling error and the statistical uncertainty in observables has never been …

Syntheses, Structures, And Reactivities Of Early-Transition-Metal Silyl, Amide, And Imide Complexes, Xianghua Yu

Doctoral Dissertations

This dissertation describes syntheses, characterization, and reactivities of Groups 4 and 5 metal amide silyl complexes free of anionic π-ligands such as cyclopentadienyl (Cp).

A summary of the research in this dissertation is provided in Chapter 1. Chapter 2 reports unusual equilibria involving zirconium amides, silyl anions, and zirconium silyl complexes through amide-silyl ligand exchange reactions. Silyl anion SiBu^{tPh_{2− (}}2) was found to substitute an amide ligand in Zr(NMe2)4 (3) to give (Me2N)3Zr(SiButPh2)2− (1a) and Zr(NMe2)5− (1b) in THF. Silyl anion 2 also selectively attacks the –N(SiMe3)2 ligand in (Me2N)3Zr[N(SiMe3)2] …

Development Of Novel Synthetic Methods Utilizing Group Iii And Iv Reagents, Gang Dong

Doctoral Dissertations

This dissertation summarizes the development of novel synthetic methods involving Group III & IV reagents. These newly discovered reactions include the rhodium-catalyzed direct cross-coupling of allylic alcohols with aryl- and vinylboronic acids; palladium-catalyzed coupling reaction of Baylis-Hillman acetate adducts with both potassium organotrifluoroborate reagents and organosiloxanes; efficient syntheses of functionalized allylmetals such as allylboranes, allylsilanes, and allylgermanes; application of allylboranes to the synthesis of homoallylic alcohols; syntheses of 4-(1-alkynyl)-2(5H)-furanones and coumarins; utilization of potassium alkynyltrifluoroborates in the synthesis of conjugated enediynes; and application of potassium alkynyltrifluoroborates as reagents in the Petasis reaction.

The new synthetic methodologies involving Group III & …

Determination Of The Cyanide Metabolite 2-Aminothiazoline-4-Carboxylic Acid In Urine And Plasma By Gas Chromatography–Mass Spectrometry, Brian A. Logue, Nicholas P. Kirschten, Ilona Petrikovics, Matthew A, Moser, Gary A. Rockwood, Steven I. Baskin

Chemistry and Biochemistry Faculty Publications

The cyanide metabolite 2-aminothiazoline-4-carboxylic acid (ATCA) is a promising biomarker for cyanide exposure because of its stability and the limitations of direct determination of cyanide and more abundant cyanide metabolites. A simple, sensitive, and specific method based on derivatization and subsequent gas chromatography–mass spectrometry (GC–MS) analysis was developed for the identification and quantification of ATCA in synthetic urine and swine plasma. The urine and plasma samples were spiked with an internal standard (ATCA-d2), diluted, and acidified. The resulting solution was subjected to solid phase extraction on a mixed-mode cation exchange column. After elution and evaporation of the solvent, a silylating …

An Entry To A Chiral Dihydropyrazole Scaffold:  Enantioselective [3 + 2] Cycloaddition Of Nitrile Imines, Mukund P. Sibi, Levi M. Stanley, Craig P. Jasperse

Levi M. Stanley

We have developed a versatile strategy to access dihydropyrazoles in highly enantioenriched form. Dipolar cycloaddition of electron-deficient acceptors and in situ-generated nitrile imines proceeds with high regio- and enantioselectivity using 10 mol % chiral Lewis acid catalyst. A variety of dihydropyrazoles that incorporate functionality for further manipulation have been prepared.

Hinge-Like Motions In Rna Kink-Turns: The Role Of The Second A-Minor Motif And Nominally Unpaired Bases, Neocles B. Leontis, Filip Rázga, Jaroslav Koča, Jiří Šponer

Chemistry Faculty Publications

Kink-turn (K-turn) motifs are asymmetric internal loops found at conserved positions in diverse RNAs, with sharp bends in phosphodiester backbones producing V-shaped structures. Explicit-solvent molecular dynamics simulations were carried out for three K-turns from 23S rRNA, i. e., Kt-38 located at the base of the A-site. nger, Kt-42 located at the base of the L7/L12 stalk, and Kt-58 located in domain III, and for the K-turn of human U4 snRNA. The simulations reveal hinge-like K-turn motions on the nanosecond timescale. The first conserved A-minor interaction between the K-turn stems is entirely stable in all simulations. The angle between the helical …

Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin

Chemistry Faculty Publications

The present report describes the preparation and characterization of several N-2-(trimethylsilyl)ethyl-N-nitrosocarbamates, designed as precursors to thermally unstable secondary N-nitrosocarbamate anions via fluoride-assisted cleavage. X-ray structural studies demonstrate that the core N-nitrosocarbamate moiety has a nearly planar geometry, with an s-E orientation at the N–N bond. DFT calculations (B3LYP/6-31+G(d)) reproduce accurately the structural features of the title compounds and detailed conformational analysis at the same level of theory addresses the long-standing issue of preferred geometries for three classes of related structures: N-nitrosocarbamates, N-nitrosoureas and N-nitrosoamides. Desilylation studies demonstrate that both the …