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Electron spin echo envelope modulation (ESEEM) spectroscopy, a pulsed electron spin resonance technique, was used to analyze the N coordination of the iron-molybdenum (FeMo) cofactor contained within the nitrogenase MoFe protein.... more
Electron spin echo envelope modulation (ESEEM) spectroscopy, a pulsed electron spin resonance technique, was used to analyze the N coordination of the iron-molybdenum (FeMo) cofactor contained within the nitrogenase MoFe protein. Comparison of spectra obtained from whole cells and purified MoFe protein established that the N coordination of the FeMo cofactor provided by the MoFe-protein polypeptide matrix can be unambiguously recognized in whole cells. ESEEM spectra of altered MoFe proteins, which were produced in certain mutant strains of Azotobacter vinelandii, showed that the N coordination to FeMo cofactor requires His-195 of the MoFe protein alpha subunit. Moreover, this requirement for His-195 was shown to be essential for biological nitrogen fixation.
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Multiple-quantum NMR coherences created from the coherent excitation of the soliton nuclear hyperfine interactions are generated and detected by electron-spin echoes in polyacetylene, (CH)x. The multiple-quantum spectra observed for both... more
Multiple-quantum NMR coherences created from the coherent excitation of the soliton nuclear hyperfine interactions are generated and detected by electron-spin echoes in polyacetylene, (CH)x. The multiple-quantum spectra observed for both trans- and cis-(CH)x are identical from 4 to 300 K, establishing that both the soliton spin-density distribution and on-chain mobility are identical in these isomers throughout this temperature range.
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ABSTRACT We propose a model for the ground state of La2-zCuO4-y in which next-nearest-neighbor Cu2+ spins in the orthorhombic a-c plane are coupled ferromagnetically, due partly to a cooperative ring-exchange process. The orthorhombic... more
ABSTRACT We propose a model for the ground state of La2-zCuO4-y in which next-nearest-neighbor Cu2+ spins in the orthorhombic a-c plane are coupled ferromagnetically, due partly to a cooperative ring-exchange process. The orthorhombic lattice distortion breaks the spin rotational invariance, favoring a spin alignment in the c-axis direction in the Néel state for y>ymin. For y=z=0, the ground state is a resonating state of triplet electron pairs. Several scenarios for superconductivity in La2-x-zSrxCuO4-y are suggested.
... Standard Article. ElectronNuclear Multiple Resonance Spectroscopy. Hans Thomann,; Marcelino Bernardo. Published Online: 15 MAR 2007. DOI: 10.1002/9780470034590.emrstm0153. Copyright © 1996, 2000, 2002, 2007 John Wiley & Sons,... more
... Standard Article. ElectronNuclear Multiple Resonance Spectroscopy. Hans Thomann,; Marcelino Bernardo. Published Online: 15 MAR 2007. DOI: 10.1002/9780470034590.emrstm0153. Copyright © 1996, 2000, 2002, 2007 John Wiley & Sons, Ltd. Book Title. ...
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Research Interests: Cognitive Science, Biomedical Engineering, Water, Magnetic Resonance Imaging, Nuclear Magnetic Resonance, and 21 moreRheology, Two Phase Flow, X-ray Tomography, Magnetic Resonance Spectroscopy, DISTRIBUTION, Tomography, Oils, Computer Simulation, Oil, Diffusion, Mathematical Analysis, Technique, Clinical Sciences, Distribution, Porous Medium, Nuclear Magnetic Resonance Imaging, Silicon Dioxide, Simulation Model, Capillary Pressure, Water Saturation, and Tomografía(Rheology, Two Phase Flow, X-ray Tomography, Magnetic Resonance Spectroscopy, DISTRIBUTION, Tomography, Oils, Computer Simulation, Oil, Diffusion, Mathematical Analysis, Technique, Clinical Sciences, Distribution, Porous Medium, Nuclear Magnetic Resonance Imaging, Silicon Dioxide, Simulation Model, Capillary Pressure, Water Saturation, and Tomografía)
(Rheology, Two Phase Flow, X-ray Tomography, Magnetic Resonance Spectroscopy, DISTRIBUTION, Tomography, Oils, Computer Simulation, Oil, Diffusion, Mathematical Analysis, Technique, Clinical Sciences, Distribution, Porous Medium, Nuclear Magnetic Resonance Imaging, Silicon Dioxide, Simulation Model, Capillary Pressure, Water Saturation, and Tomografía)
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... 1985, 153, 459-467. Brook, Stony Brook, NY 11794. (3) Coyle, CL; Zumft, W. G.; Kroneck, PMH; Korner, H.; Jakob, ... (12) (a) Mims, W. B.; Peisach, J. In Biological Magnetic Resonance; Berliner, L. J., Reuben, J., Eds.; Plenum Press:... more
... 1985, 153, 459-467. Brook, Stony Brook, NY 11794. (3) Coyle, CL; Zumft, W. G.; Kroneck, PMH; Korner, H.; Jakob, ... (12) (a) Mims, W. B.; Peisach, J. In Biological Magnetic Resonance; Berliner, L. J., Reuben, J., Eds.; Plenum Press: New York, 1981; Vol. 3, pp 213-263. ...
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ABSTRACT Electron Spin Echo (ESE) experiments have been performed on 9956 l3C-enriched trans-(CH)x. Strong modulation 1s observed In the envelope traced by the decay of the spin echoes. This modulation arises from the interaction of the... more
ABSTRACT Electron Spin Echo (ESE) experiments have been performed on 9956 l3C-enriched trans-(CH)x. Strong modulation 1s observed In the envelope traced by the decay of the spin echoes. This modulation arises from the interaction of the paramagnetic defect with 13C nuclei. The electron-nuclear hyperfine coupling may be determined by Fourier transformation of the time domain signal. At 6K we find a maximum hyperfine coupling of 1.75 Mhz.
... Samples were investigated as a function of Fe content and after variable-temperature dehydration and rehydration. Transitions characteristic of tetrahedrally coordinated Fe3+ were observed in the diffuse reflectance spectra of all Fe... more
... Samples were investigated as a function of Fe content and after variable-temperature dehydration and rehydration. Transitions characteristic of tetrahedrally coordinated Fe3+ were observed in the diffuse reflectance spectra of all Fe zeolites except for FeFAU. ...
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The theory of Karplus and Fraenkel is employed to analyze the effect of on-site PU electron Coulombic interactions in determining the 13C and'H hyperfine interaction tensors for polyacetylene. Relative signs of hyperfine tensors have... more
The theory of Karplus and Fraenkel is employed to analyze the effect of on-site PU electron Coulombic interactions in determining the 13C and'H hyperfine interaction tensors for polyacetylene. Relative signs of hyperfine tensors have been determined by electron-...
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Electron Spin Echo (ESE) experiments have been performed on 9956 C-enriched trans-(CH)x. Strong modulation 1s observed In the envelope traced by the decay of the spin echoes. This modulation arises from the interaction of the paramagnetic... more
Electron Spin Echo (ESE) experiments have been performed on 9956 C-enriched trans-(CH)x. Strong modulation 1s observed In the envelope traced by the decay of the spin echoes. This modulation arises from the interaction of the paramagnetic defect with C nuclei. The electron-nuclear hyperfine coupling may be determined by Fourier transformation of the time domain signal. At 6K we find a
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... Phys. 65, 3006(1976). 1 AH Beth, R. Wilder, LS Wilkerson, R. С Perkins, BP Meriwether, LR Dalton, С. R. Park, and JH Park. .1. Chem. Phys. ... 49 AH Beth, R. С Perkins, Jr., SD Venkataramu, DE Pearson, CR Park, JH Park, and LR Dalton,... more
... Phys. 65, 3006(1976). 1 AH Beth, R. Wilder, LS Wilkerson, R. С Perkins, BP Meriwether, LR Dalton, С. R. Park, and JH Park. .1. Chem. Phys. ... 49 AH Beth, R. С Perkins, Jr., SD Venkataramu, DE Pearson, CR Park, JH Park, and LR Dalton, Chem. Phys. Lett. 69, 24 (1980).