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1999

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Articles 61 - 90 of 328

Full-Text Articles in Chemistry

Calculation Of Corrosion Rate Of Passive Metals With Charge Curve Analysis Technique, Yuan-Sheng Zhang, Min Gong Aug 1999

Calculation Of Corrosion Rate Of Passive Metals With Charge Curve Analysis Technique, Yuan-Sheng Zhang, Min Gong

Journal of Electrochemistry

This work contains two parts: (1) A charge curve equation having no appro-ximation for passivated metal corrosion systems is derived and compared with the routine charge curve equation, which is virtual only when the polarization is minim(linear range). (2) It is simpler to analyze charge curve data by from of charge differential equation than from charge curve equation. After the charge curve data are measured, the slope of charge curve is computed by numerical differentiation method, then the charge differential equation may be transformed to a set of linear equations using polynomial approximation. The electrochemical parameters of corrosion system would …

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Direct Electrolysis Of Seawater On Conducting Film For Microbial Anticorrosion 1. Simulation And Measurement Technique, Wei-Ling Hu, Ling-Ling Wu, Jing Zhou, Jing-Xin Li, Jin Luo, Zhong-Hua Lin Aug 1999

Direct Electrolysis Of Seawater On Conducting Film For Microbial Anticorrosion 1. Simulation And Measurement Technique, Wei-Ling Hu, Ling-Ling Wu, Jing Zhou, Jing-Xin Li, Jin Luo, Zhong-Hua Lin

Journal of Electrochemistry

Based on the electrochemical micro probe and the weak signal detection technique, simulated test and measurement system were set up by the use of four-electrode cell(including a micro electrode), bipotentiostat, lock-in amplifier and three-dimensional micro manipulating device. Based on the system, the micrometer scale concentration distribution of trace hypochlorite, which is produced by direct electrolysis of seawater on the conducting film for preventing microbial corrosion has been obtained for the first time. Both relationships between concentration of hypochlorite and its reduction current, which is termed an working curve, and between the reduction current of hypochlorite and measured time are reported.

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The Techniques Of The Paired Electrosynthesis, Hong-Kun Zhang, Deng-Ping Gu Aug 1999

The Techniques Of The Paired Electrosynthesis, Hong-Kun Zhang, Deng-Ping Gu

Journal of Electrochemistry

In this Paper, we introduce our work on paired electrosynthesis. In conjunction with our research practice, we introduce electrolytic conditions,such as material of electrode ,courrent density and electrolytic temperature etc,as reference for researcher. We categorize the paired electrosynthesis techniques to widen our view on the paired electroorganic synthesis and to promote the deveopments of paired electrosynthesis techniques.

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A Study Of The Corrosion On Bronze, Hong-Fan Zhu, Hao Zhou Aug 1999

A Study Of The Corrosion On Bronze, Hong-Fan Zhu, Hao Zhou

Journal of Electrochemistry

The bronze is the treasure in chinese metallic antique, which was typified by product in Shang-Zhou period (three thousands years ago). Because of corrosion, archaeological messages, such as inscription and pattern on the surface of bronze, would be damaged then the value of bronze antique decreased. The bronze disease is a common disease which forms powdery rust on the surface of bronze in atmospheric environment, the powdery rust emerge from under incrusted rust, then spreads, and eventually leads to bronze damaged. This paper investigates the bronze disease. According to the chemical and electrochemical tests in simulated occluded cell, the variation …

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A Study Self-Passivation Of Passivie Film Of Stainless Steel In Vinylon Aldehyde Solution, Si-Fu Hu, Chuan-Bi Xu, Zhu-Qiu Cheng Aug 1999

A Study Self-Passivation Of Passivie Film Of Stainless Steel In Vinylon Aldehyde Solution, Si-Fu Hu, Chuan-Bi Xu, Zhu-Qiu Cheng

Journal of Electrochemistry

Properties of self-passivation for the anodic passive film of 1Cr18Ni9Ti and the firsthand passive film of SUS 36 stainless steel in vinylon aldehyde solution(H2SO4(240 g/L)+Na2SO4(70 g/L)+HCHO(25 g/L)+[Fe3+](35.4 mg/L)+[Cl-](240 mg/L) at 70 ℃ were studied by galvanostatic and potentiostatic polarization mesurements. The effects of compponents of vinylon aldehyde solution, i.e. Fe3+ and Cl-, on the passivation behaviours of stainless steel have also been investigated. The experimental results showed there is a conversion zone of the active/passive state if the area ratio of active/passive state on these …

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Effects Of The Surfactant And Ph On Linear Potential Scan Of Aqueous Na2S Solution, Qing-Feng Yi, Qi-Yuan Chen, Ping-Min Zhang Aug 1999

Effects Of The Surfactant And Ph On Linear Potential Scan Of Aqueous Na2S Solution, Qing-Feng Yi, Qi-Yuan Chen, Ping-Min Zhang

Journal of Electrochemistry

In presence of a cationic surfactant HTAB,linear potential scans for Na2S at graphite anode in both saturated sodium tetra-borate solution and 1 mol·L-1 NaOH solution, have been investigated. Results show that anodic current density increases and peak potentials shift to more negative with the increase of HTAB concentrations. The anodic current densities increased by addition of HTAB are larger in 1 mol·L-1 NaOH than those in saturated sodium tetra-borate solution, resulting from different acting forces of HTAB with various charged electro-active species. Both oxidation and reduction peaks in cyclic voltammograms for Na2S containing solution …

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Influence Of Thiourea And Its Derivate On The Process Of Cathodic Electrodeposition Of Copper, Yun-Hui Dong, Ai-Hong Zou, Yun-Xia Zhao Aug 1999

Influence Of Thiourea And Its Derivate On The Process Of Cathodic Electrodeposition Of Copper, Yun-Hui Dong, Ai-Hong Zou, Yun-Xia Zhao

Journal of Electrochemistry

The effects of thiourea and its derivate on the electrodeposition of copper from the dilute acid sulphate solutions have been studied by using potential sweep techniques at quasisteady state. Limiting current densities (Id), exchange current densities (i0) and αn are obtained by data processing with the least square method. Thiourea has a depolarizing effect on the copper depositing at concentrations below 8 mg·L-1, and a polarizing effect at higher concentration (>10 mg·L-1), and it changes the mechanism of copper deposition reaction. Propenyltiourea and Phenylthiourea have a depolarizing effect on the …

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The Effects Of Metallic Cobalt Abbition On The Performance Of Pasted Nickel Electrodes, An-Bao Yuan, Jian-Qing Zhang, Wan-Chun Ding, Shao-An Cheng, Chu-Nan Cao Aug 1999

The Effects Of Metallic Cobalt Abbition On The Performance Of Pasted Nickel Electrodes, An-Bao Yuan, Jian-Qing Zhang, Wan-Chun Ding, Shao-An Cheng, Chu-Nan Cao

Journal of Electrochemistry

The Ni-foam pasted nickel electrodes prepared by coprecipitated Ni1-XZnX(OH)2 with and without cobalt power addition have been studied. The electrode with addition of metallic cobalt showed a higher performance both in discharge capacity and cycle life. It is known from the experiment results that the addition of Co can remarkably increase the active material utilization which is suggested to be improvement of discharge depth due to the conducting CoOOH formed in the first activation charging. The superior capacity during cycling could be attributed to the synergistic action of zinc and cobalt addition ,especially to the …

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A New Method For Preparing Self-Assembled Lipid Bilayers On Pt Electrode, Peng Diao, Dian-Lu Jiang, Xiao-Li Cui, Deng-Ping Gu, Ru-Ting Tong Aug 1999

A New Method For Preparing Self-Assembled Lipid Bilayers On Pt Electrode, Peng Diao, Dian-Lu Jiang, Xiao-Li Cui, Deng-Ping Gu, Ru-Ting Tong

Journal of Electrochemistry

A new method for preparing Pt-supported bilayer lipid membrane (Pt-BLM) on Pt electrode cleaned by high power ultrasound was reported. The reported method was convenient, costing less platinum and could be used to form large-area Pt-BLM as compared with the traditional Pt-wire-cutting method. The electrical properties of Pt-BLM were studied using electrochemical impedance spectroscopy and cyclic voltammetry. Experimental results showed that the values of membrane capacitance and the voltammetric characteristics were consistent with those of Pt-BLM prepared by traditional method.

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Study On Synthesizing Of 2-Methylbutanoic Acid By Indirect Electrooxidation, Chong-Tao Zhao, Ze-Shan Zhu Aug 1999

Study On Synthesizing Of 2-Methylbutanoic Acid By Indirect Electrooxidation, Chong-Tao Zhao, Ze-Shan Zhu

Journal of Electrochemistry

The working conditions of synthesizing 2-methylbutanoic acid by oxidizing 2-methyl-1-butanol with tetrabutylammonium hydrosulfate (TBAS) or tetrabutylammonium perchlorate (TBAP) as phase transfer catalyst in sulfuric acid Cr(Ⅵ) oxidation medium was studied. The Cr(Ⅵ) oxidation medium could be electrolytic regenerated from Cr(Ⅲ), during above oxidation reaction. Under the optinum condition, the yield of 2-methylbutanoic acid is more than 95%.

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The Ac-Impedance Analysis For Pluse Oxide Film Of Aluminium Alloy, Ai-Ling Du, Xi-Cheng Ma, He-Ming Zhang Aug 1999

The Ac-Impedance Analysis For Pluse Oxide Film Of Aluminium Alloy, Ai-Ling Du, Xi-Cheng Ma, He-Ming Zhang

Journal of Electrochemistry

Bode diagrams for aluminum PC (abbreviated from pulse current) oxide films were first obtained by AC-impedance measurements in a wide range of frequency. The experimental results show that different kinds of electrical equivalent circuits can be used for representing PC films and DC (abbreviated from direct current) oxide films separately, the main differences between them are their porous layers, the PC films are more even with little defects.Those are also verified by SEM and V-I characteristic curve measurements.

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Electrochemical Synthesis Of Fes Electrode And Its Behavior Measurement, Cong-Sheng Guan Aug 1999

Electrochemical Synthesis Of Fes Electrode And Its Behavior Measurement, Cong-Sheng Guan

Journal of Electrochemistry

The Potential for the electrochemical synthesis of FeS electrode has been obtained by cyclic voltammetry. FeS electrodes were synthesiaed by controlling Fe electrode at -1.0 V in LiCl-KCl-Li2S and Li(FClI)-Li2S melts and their behavior were measured also. The FeS electrode synthesized in molten Li(FClI)-Li2S has the best charge and discharge properties.

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Studies On The Inclusion Complexes Of Rhein With Cds By Oscilloscope Polarography, Xiang-Jun Li, Jun Lian, Yong Zhang, Jing-Hao Pan Aug 1999

Studies On The Inclusion Complexes Of Rhein With Cds By Oscilloscope Polarography, Xiang-Jun Li, Jun Lian, Yong Zhang, Jing-Hao Pan

Journal of Electrochemistry

Inclusion action of rhein with CDs was studied by linear sweep oscilloscope polarography. The molar ratio of inclusion complexes of rhein with CDs are 1:1, the inclusion constants in different temperature have been determined and the thermodynamics parameter of some inclusion complexes have also been obtained. It indicates that in normal temperature, the inclusion procedure go on spontaneously, improving temperature is unfavorable to the formation of inclusion complexes.

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A Patching Model For Surface Tension And The Tolman Length, T.V. Bykov, Xiao Cheng Zeng Aug 1999

A Patching Model For Surface Tension And The Tolman Length, T.V. Bykov, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

In the framework of density functional theory (DFT), a patching model for the density profile of the liquid–vapor interface is developed. The patching is based on analytical expressions of the asymptote of the density profiles. Derived from the model the surface tension of planar liquid–vapor interface as well as the Tolman length can be computed from analytic expressions. Two prototype systems are considered; the Yukawa and the Lennard-Jones. As a result, the temperature dependence of the surface tension as well as the Tolman length are obtained. The results are compared with numerical DFT calculations.

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Assignment Of The Infrared Spectra Of The Methanol Trimer, Gregory S. Tschumper, Jason M. Gonzales, Henry F. Schaefer Aug 1999

Assignment Of The Infrared Spectra Of The Methanol Trimer, Gregory S. Tschumper, Jason M. Gonzales, Henry F. Schaefer

Chemistry Faculty Research & Creative Works

Second-order Möller-Plesset perturbation theory (MP2) and density functional theory (DFT) were employed to optimize two cyclic conformations of the methanol trimer, denoted "bowl" and "chair," as well as a third noncyclic, "open-chain" conformation. This is the first time all three methanol trimer conformations have been studied at the same level of theory. Harmonic vibrational frequencies confirm that all stationary points are minima on the intermolecular potential energy hypersurface. The chair is consistently predicted to be the most stable conformer. The bowl and open-chain conformers are only slightly less stable and lie within 3 kcal/mol. Results indicate that the bowl structure …

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Two-Dimensional Nuclear Magnetic Resonance Correlation Spectroscopy At Zero Field, Ming-Yuan Liao, Gerard S. Harbison Aug 1999

Two-Dimensional Nuclear Magnetic Resonance Correlation Spectroscopy At Zero Field, Ming-Yuan Liao, Gerard S. Harbison

Gerard S. Harbison Publications

Three methods for two-dimensional correlation nuclear magnetic resonance spectroscopy at zero field are discussed. All three involve coherence transfer via longitudinal polarization, double quantum coherence, or both in parallel. The double quantum pulse sequences exploit the spinor property of spin states. These sequences have been applied to connected Δm=1 transitions, as well as for the indirect detection of forbidden or nearly forbidden Δm.1 transitions.

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1H Nmr Studies On The Cua Center Of Nitrous Oxide Reductase From Pseudomonas Stutzeri, Richard C. Holz, Marcela L. Alvarez, Walter G. Zumft, David M. Dooley Aug 1999

1H Nmr Studies On The Cua Center Of Nitrous Oxide Reductase From Pseudomonas Stutzeri, Richard C. Holz, Marcela L. Alvarez, Walter G. Zumft, David M. Dooley

Chemistry Faculty Research and Publications

1H NMR spectra of the CuA center of N2OR from Pseudomonas stutzeri, and a mutant enzyme that contains only CuA, were recorded in both H2O- and D2O-buffered solution at pH 7.5. Several sharp, well-resolved hyperfine-shifted 1H NMR signals were observed in the 60 to −10 ppm chemical shift range. Comparison of the native and mutant N2OR spectra recorded in H2O-buffered solutions indicated that several additional signals are present in the native protein spectrum. These signals are attributed to a dinuclear copper(II) center. At least …

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The Methionyl Aminopeptidase From Escherichia Coli Can Function As An Iron(Ii) Enzyme, Ventris M. D'Souza, Richard C. Holz Aug 1999

The Methionyl Aminopeptidase From Escherichia Coli Can Function As An Iron(Ii) Enzyme, Ventris M. D'Souza, Richard C. Holz

Chemistry Faculty Research and Publications

The identity of the physiologically relevant metal ions for the methionyl aminopeptidase (MetAP) from Escherichia coli was investigated and is suggested to be Fe(II). The metal content of whole cells in the absence and presence of expression of the type I MetAP from E. coli was determined by inductively coupled plasma (ICP) emission analysis. The observed change in whole cell concentrations of cobalt, cadmium, copper, nickel, strontium, titanium, and vanadium upon expression of MetAP was negligible. On the other hand, significant increases in the cellular metal ion concentrations of chromium, zinc, manganese, and iron were observed with the increase in …

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Electrodeposition Of Cerium-Based Coatings For Corrosion Protection Of Aluminum Alloys, James O. Stoffer, Thomas J. O'Keefe, Xuan Lin, Eric L. Morris, Pu Yu, Srinivas Pravin Sitaram Aug 1999

Electrodeposition Of Cerium-Based Coatings For Corrosion Protection Of Aluminum Alloys, James O. Stoffer, Thomas J. O'Keefe, Xuan Lin, Eric L. Morris, Pu Yu, Srinivas Pravin Sitaram

Chemistry Faculty Research & Creative Works

A process for enhancing the corrosion resistance of an aluminum-containing component with a cerium based coating. An aluminum-containing cathode and an oxygen- evolving anode are immersed in an electrolyte comprising water, solvent, oxidizing agent and cerium ions. An electrical current is passed through the electrolyte by applying electrical current to deposit a cerium based coating onto the cathode. An electrolyte for use in depositing a cerium based coating. An electrodeposited cerium-based coating. An aluminum aircraft structural component having a cerium-based coating thereon.

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Is Hyperconjugation Responsible For The "Gauche Effect" In 1-Fluoropropane And Other 2-Substituted-1-Fluoroethanes?, Paul R. Rablen, R. W. Hoffman, D. A. Hrovat, W. T. Borden Aug 1999

Is Hyperconjugation Responsible For The "Gauche Effect" In 1-Fluoropropane And Other 2-Substituted-1-Fluoroethanes?, Paul R. Rablen, R. W. Hoffman, D. A. Hrovat, W. T. Borden

Chemistry & Biochemistry Faculty Works

The energies and geometries of a series of 2-substituted-1-fluoroethanes were computed at the MP2/6-311++G**(6D)//MP2/6-31+G* level of theory for both the maxima and minima of the rotation about the C-C bond. The results did not support the predictions of a hyperconjugative model, that both 1,2-difluoroethane and 1-chloro-2-fluoroethane would strongly prefer a gauche conformation, and that 1-fluoro-2-silylethane would strongly prefer an anti conformation. The existence of competing electrostatic interactions between the fluorine and the substituents at C-2 was indicated by the detailed geometries of the gauche conformers and by the calculated sensitivity of the gauche-anti energy differences to the presence of a …

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Induced Changes In Solvent Structure By Phospholipid Monolayer Formation At A Liquid–Liquid Interface, R. A. Walker, D. E. Gragson, G. L. Richmond Aug 1999

Induced Changes In Solvent Structure By Phospholipid Monolayer Formation At A Liquid–Liquid Interface, R. A. Walker, D. E. Gragson, G. L. Richmond

Chemistry and Biochemistry

Vibrational sum frequency spectroscopy has been used in conjunction with dynamic surface tension measurements to study formation of a 1,2-dilauroyl-sn-phosphatidylcholine (DLPC) monolayer at a water–carbon tetrachloride interface. Surface tension measurements show that an aqueous solution of liquid crystalline phosphocholine vesicles (4.5 μM DLPC) requires several hours to form a tightly packed, fully equilibrated monolayer of DLPC monomers. Vibrational spectra of the interfacial region at different stages in the monolayer formation process indicate that the solvent structure undergoes dramatic re-organization as the monolayer forms. Initial adsorption of DLPC monomers severely disrupts the interfacial hydrogen bonding. Intensity in the OH …

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Analysis Of Galvanized Steel Plates Using Glow Discharge-Atomic Emission Spectrometry, Liang Wang Aug 1999

Analysis Of Galvanized Steel Plates Using Glow Discharge-Atomic Emission Spectrometry, Liang Wang

Masters Theses & Specialist Projects

Combining an intense emission source and a high-speed sputtering source in one, glow discharge atomic emission spectrometer (GD-AES) provides an efficient technique for analyzing surfaces, coatings and bulk solids. The purpose of our work is to explore the optimum lamp operation parameters of SA-2000 for analysis of galvanized steel plate and to investigate the method for qualitatively and quantitatively analyzing the zinc coating. Under the optimum experimental conditions found in our study, which are current of 19-21 mA; voltage of 900-1200 V; pressure 2.0-2.5 torr, the calibration curve is constructed, so that specific zinc concentration can be assign to the …

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Comparison Of An Advanced Mercury Analyzer With The Cold Vapor Atomic Absorption Technique For The Determination Of Mercury In Coal, Dong Li Aug 1999

Comparison Of An Advanced Mercury Analyzer With The Cold Vapor Atomic Absorption Technique For The Determination Of Mercury In Coal, Dong Li

Masters Theses & Specialist Projects

For over 30 years the industry standard method for mercury analysis has been the cold vapor atomic absorption spectrometric technique (CVAAS). Recent developments in improving this technique have focused on procedures for concentrating mercury in the analyte or materials to improve detection. The LECO Corporation produces an Advanced Mercury Analyzer, the AMA-254, for analysis of the solid and liquid samples. The system allows for the thermal heating of the sample to decompose the sample and release mercury, which is concentrated in a gold amalgam. Thermal desorption of the mercury from the amalgam is detected by atomic absorption spectroscopy. A comparison …

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Folding Dynamics Of Single Gcn-4 Peptides By Fluorescence Resonant Energy Transfer Confocal Microscopy, Yiwei Jia, David Talaga, Wai Leung Lau, Helen S.M. Lu, William F. Degrado, Robin M. Hochstrasser Aug 1999

Folding Dynamics Of Single Gcn-4 Peptides By Fluorescence Resonant Energy Transfer Confocal Microscopy, Yiwei Jia, David Talaga, Wai Leung Lau, Helen S.M. Lu, William F. Degrado, Robin M. Hochstrasser

Department of Chemistry and Biochemistry Faculty Scholarship and Creative Works

We have prepared a bichromophoric crosslinked variant of GCN4-P1 for single-molecule fluorescence energy transfer experiments (GCN4-Pf). The folding and unfolding fluctuations of single GCN4-Pf molecules are measured in a two-channel confocal microscope with which donor and acceptor fluorescence trajectories are measured simultaneously. The energy transfer efficiency is thereby determined and its probability distributions as a function of added denaturant [urea] are calculated. The distributions indicate that single molecule GCN4-Pf is in dynamic folding equilibrium with the position of the equilibrium being altered by the concentration of urea.

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The Discovery-Oriented Approach To Organic Chemistry. 2. Selectivity In Alcohol Oxidation. An Exercise In 1H Nmr Spectroscopy For Sophomore Organic Laboratories, Ram Mohan, Steven Shadwick Aug 1999

The Discovery-Oriented Approach To Organic Chemistry. 2. Selectivity In Alcohol Oxidation. An Exercise In 1H Nmr Spectroscopy For Sophomore Organic Laboratories, Ram Mohan, Steven Shadwick

Scholarship

We have developed a simple oxidation experiment that presents the student with a puzzle and is a good exercise in 1H NMR spectroscopy. The experiment, which illustrates the important concept of selectivity in organic synthesis, involves selective oxidation of a mixture of 1-heptanol and 2-heptanol using commercial swimming pool chlorine. 1H NMR analysis of the product mixture allows the student to determine the selectivity exhibited by the reagent.

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Hydrogen Dynamics In The Hydrides Of Pr₂Fe₁₇ As Revealed By Mössbauer Spectroscopy, Dimitri Hautot, Gary J. Long, Fernande Grandjean, Olivier Isnard, Salvatore Miraglia Aug 1999

Hydrogen Dynamics In The Hydrides Of Pr₂Fe₁₇ As Revealed By Mössbauer Spectroscopy, Dimitri Hautot, Gary J. Long, Fernande Grandjean, Olivier Isnard, Salvatore Miraglia

Chemistry Faculty Research & Creative Works

The rhombohedral Pr2Fe17Hx compounds with the Th2Zn17 structure have been prepared for x =0-5. Their lattice parameters and Curie temperatures have been determined from powder x-ray diffraction and thermomagnetic measurements, respectively, and their Mössbauer spectra have been measured between 4.2 and 295 K. The Mössbauer spectra for x=0, 1, and 2, obtained between 4.2 and 295 K, and those of Pr2Fe17H3, obtained above 90 K, have been analyzed with a seven sextet model, indicative of a basal magnetization in these compounds. The Mössbauer spectra of Pr …

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41st Rocky Mountain Conference On Analytical Chemistry Aug 1999

41st Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 41st annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 1-5, 1999.

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Rank-Order Of Potencies For Inhibition Of The Secretion Of Aβ40 And Aβ42 Suggests That Both Are Generated By A Single Γ-Secretase, John T. Durkin, Seetha Murthy, E. Jean Husten, Stephen P. Trusko, Mary J. Savage, David Rotella, Barry D. Greenberg, Robert Siman Jul 1999

Rank-Order Of Potencies For Inhibition Of The Secretion Of Aβ40 And Aβ42 Suggests That Both Are Generated By A Single Γ-Secretase, John T. Durkin, Seetha Murthy, E. Jean Husten, Stephen P. Trusko, Mary J. Savage, David Rotella, Barry D. Greenberg, Robert Siman

Department of Chemistry and Biochemistry Faculty Scholarship and Creative Works

The Alzheimer's disease amyloid peptide Aβ has a heterogeneous COOH terminus, as variants 40 and 42 residues long are found in neuritic plaques and are secreted constitutively by cultured cells. The proteolytic activity that liberates the Aβ COOH terminus from the β-amyloid precursor protein is called γ-secretase. It could be one protease with dual specificity or two distinct enzymes. By using enzyme-linked immunosorbent assays selective for Aβ40 or Aβ42, we have measured Aβ secretion by a HeLa cell line, and we have examined the dose responses for a panel of five structurally diverse γ- secretase inhibitors. The inhibitors lowered Aβ …

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Protein Adducts Of Iso[4]Levuglandin E2, A Product Of The Isoprostane Pathway, In Oxidized Low Density Lipoprotein, Robert G. Salomon, Wei Sha, Cynthia Brame, Kamaljit Kaur, Ganesamoorthy Subbanagounder, June O'Neil, Henry F. Hoff, L. Jackson Roberts Ii Jul 1999

Protein Adducts Of Iso[4]Levuglandin E2, A Product Of The Isoprostane Pathway, In Oxidized Low Density Lipoprotein, Robert G. Salomon, Wei Sha, Cynthia Brame, Kamaljit Kaur, Ganesamoorthy Subbanagounder, June O'Neil, Henry F. Hoff, L. Jackson Roberts Ii

Pharmacy Faculty Articles and Research

Levuglandin (LG) E2, a cytotoxic seco prostanoic acid co-generated with prostaglandins by nonenzymatic rearrangements of the cyclooxygenase-derived endoperoxide, prostaglandin H2, avidly binds to proteins. That LGE2-protein adducts can also be generated nonenzymatically is demonstrated by their production during free radical-induced oxidation of low density lipoprotein (LDL). Like oxidized LDL, LGE2-LDL, but not native LDL, undergoes receptor-mediated uptake and impaired processing by macrophage cells. Since radical-induced lipid oxidation produces isomers of prostaglandins, isoprostanes (isoPs), via endoperoxide intermediates, we postulated previously that a similar family of LG isomers, isoLGs, is cogenerated with isoPs. Now …

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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 Jul 1999

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 gav = 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 …

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