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Full-Text Articles in Physics
Observation Of Turbulent Intermittency Scaling With Magnetic Helicity In An Mhd Plasma Wind Tunnel, David A. Schaffner, A. Wan, M. R. Brown
Observation Of Turbulent Intermittency Scaling With Magnetic Helicity In An Mhd Plasma Wind Tunnel, David A. Schaffner, A. Wan, M. R. Brown
Physics Faculty Research and Scholarship
The intermittency in turbulent magnetic field fluctuations has been observed to scale with the amount of magnetic helicity injected into a laboratory plasma. An unstable spheromak injected into the MHD wind tunnel of the Swarthmore Spheromak Experiment displays turbulent magnetic and plasma fluctuations as it relaxes into a Taylor state. The level of intermittency of this turbulence is determined by finding the flatness of the probability distribution function of increments for magnetic pickup coil fluctuations B_ðtÞ. The intermittency increases with the injected helicity, but spectral indices are unaffected by this variation. While evidence is provided which supports the hypothesis that …
Solid State 1 H Spin - Lattice Relaxation And Isolated - Molecule And Cluster Electronic Structure Calculations In Organic Molecular Solids: The Relationship Between Structure And Methyl Group And T - Butyl Group Rotation, Xianlong Wang, Frank B. Mallory, Clelia W. Mallory, Hosanna R. Odhner, Peter A. Beckmann
Solid State 1 H Spin - Lattice Relaxation And Isolated - Molecule And Cluster Electronic Structure Calculations In Organic Molecular Solids: The Relationship Between Structure And Methyl Group And T - Butyl Group Rotation, Xianlong Wang, Frank B. Mallory, Clelia W. Mallory, Hosanna R. Odhner, Peter A. Beckmann
Physics Faculty Research and Scholarship
We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state 1H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl …
I-127 And Pb-207 Solid-State Nmr Spectroscopy And Nuclear Spin Relaxation In Lead Iodide: A Preliminary Study, R. E. Taylor, Peter A. Beckmann, Shi Bai, C. Dybowski
I-127 And Pb-207 Solid-State Nmr Spectroscopy And Nuclear Spin Relaxation In Lead Iodide: A Preliminary Study, R. E. Taylor, Peter A. Beckmann, Shi Bai, C. Dybowski
Physics Faculty Research and Scholarship
Lead iodide is a layered structure that experiences polytypism. The 2H polytype contains high rates of iodine vacancies but retains its stoichiometry. This characteristic feature makes it potentially useful for many practical applications. The hopping of iodine ions among vacancies is the dominant motion in the 2H polytype. We present a preliminary 127I and 207Pb solid-state nuclear magnetic resonance (NMR) spectroscopy and spin–lattice relaxation study of the 2H polytype below 400 K. We present reasonable models for the solid-state NMR results in terms of the effects of iodine hopping and lattice vibrations.