The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
W H Matthaeus - One of the best experts on this subject based on the ideXlab platform.
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kinetic dissipation and anisotropic heating in a turbulent collisionless plasma
Physics of Plasmas, 2009Co-Authors: T N Parashar, M A Shay, P A Cassak, W H MatthaeusAbstract:The kinetic evolution of the Orszag–Tang vortex is studied using collisionless hybrid simulations. In magnetohydrodynamics (MHD) this configuration leads rapidly to broadband turbulence. At large length scales, the evolution of the hybrid simulations is very similar to MHD, with magnetic power spectra displaying scaling similar to a Kolmogorov scaling of −5/3. At small scales, differences from MHD arise, as energy dissipates into heat almost exclusively through the magnetic field. The magnetic energy spectrum of the hybrid simulation shows a break where linear theory predicts that the Hall term in Ohm’s law becomes significant, leading to dispersive kinetic Alfven waves. A key result is that protons are heated preferentially in the Plane Perpendicular to the mean magnetic field, creating a proton temperature anisotropy of the type observed in the corona and solar wind.
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kinetic dissipation and anisotropic heating in a turbulent collisionless plasma
arXiv: Plasma Physics, 2007Co-Authors: T N Parashar, M A Shay, P A Cassak, W H MatthaeusAbstract:The kinetic evolution of the Orszag-Tang vortex is studied using collisionless hybrid simulations. In the magnetohydrodynamic regime this vortex leads rapidly to broadband turbulence. Significant differences from MHD arise at small scales, where the fluid scale energy dissipates into heat almost exclusively through the magnetic field because the protons are decoupled from the magnetic field. Although cyclotron resonance is absent, the protons heat preferentially in the Plane Perpendicular to the mean field, as in the corona and solar wind. Effective transport coefficients are calculated.
Richard R. Ernst - One of the best experts on this subject based on the ideXlab platform.
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Orientation of the Chemical Shielding Anisotropy Tensor of the Carbonate Carbon in Diphenyl Carbonate and Its Consequences for NMR Studies on Polycarbonate
Macromolecules, 1998Co-Authors: P. Robyr, Marcel Utz, Z. Gan, Christoph Scheurer, M. Tomaselli, Ulrich W. Suter, Richard R. ErnstAbstract:The orientation of the chemical shielding anisotropy tensor of the carbonate carbon in diphenyl carbonate was determined by using solid state NMR spectroscopy. The same tensor orientation was obtained from quantum mechanical calculation based on density functional theory. The most shielded direction of the tensor is along the CO double bond. The least shielded direction is for the carbonate Plane Perpendicular to the CO double bond. Chemical shielding calculations in diphenyl carbonate fragments with different conformations show that the tensor orientation measured in crystalline diphenyl carbonate also applies to the carbonate groups of bisphenol A polycarbonate. However, this orientation is not identical to that assumed so far in the work on bisphenol A polycarbonate. The consequences of this incorrect assumption in previous studies are examined.
T N Parashar - One of the best experts on this subject based on the ideXlab platform.
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kinetic dissipation and anisotropic heating in a turbulent collisionless plasma
Physics of Plasmas, 2009Co-Authors: T N Parashar, M A Shay, P A Cassak, W H MatthaeusAbstract:The kinetic evolution of the Orszag–Tang vortex is studied using collisionless hybrid simulations. In magnetohydrodynamics (MHD) this configuration leads rapidly to broadband turbulence. At large length scales, the evolution of the hybrid simulations is very similar to MHD, with magnetic power spectra displaying scaling similar to a Kolmogorov scaling of −5/3. At small scales, differences from MHD arise, as energy dissipates into heat almost exclusively through the magnetic field. The magnetic energy spectrum of the hybrid simulation shows a break where linear theory predicts that the Hall term in Ohm’s law becomes significant, leading to dispersive kinetic Alfven waves. A key result is that protons are heated preferentially in the Plane Perpendicular to the mean magnetic field, creating a proton temperature anisotropy of the type observed in the corona and solar wind.
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kinetic dissipation and anisotropic heating in a turbulent collisionless plasma
arXiv: Plasma Physics, 2007Co-Authors: T N Parashar, M A Shay, P A Cassak, W H MatthaeusAbstract:The kinetic evolution of the Orszag-Tang vortex is studied using collisionless hybrid simulations. In the magnetohydrodynamic regime this vortex leads rapidly to broadband turbulence. Significant differences from MHD arise at small scales, where the fluid scale energy dissipates into heat almost exclusively through the magnetic field because the protons are decoupled from the magnetic field. Although cyclotron resonance is absent, the protons heat preferentially in the Plane Perpendicular to the mean field, as in the corona and solar wind. Effective transport coefficients are calculated.
H T Nguyen - One of the best experts on this subject based on the ideXlab platform.
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x ray measurement of the twist grain boundary angle in the liquid crystal analog of the abrikosov phase
Physical Review Letters, 1993Co-Authors: L Navailles, P Barois, H T NguyenAbstract:We report the first experimental observation of the commensurate state of the recently discovered helical smectic-C phase. The projection of the reciprocal lattice on the Plane Perpendicular to the pitch axis consists of a ring of equispaced Bragg spots, as predicted by Renn and Lubensky for the «twist grain boundary» phase. On cooling, the number of spots q jumps from 16 to 18 and 18 to 20. A noticeable thermal hysteresis is observed on heating. The corresponding symmetries are quasicrystalline since the q-fold screw axes are not crystallographically allowed. These observations allow an accurate determination of all the parameters of the twisted lattice of screw dislocations
P. Robyr - One of the best experts on this subject based on the ideXlab platform.
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Orientation of the Chemical Shielding Anisotropy Tensor of the Carbonate Carbon in Diphenyl Carbonate and Its Consequences for NMR Studies on Polycarbonate
Macromolecules, 1998Co-Authors: P. Robyr, Marcel Utz, Z. Gan, Christoph Scheurer, M. Tomaselli, Ulrich W. Suter, Richard R. ErnstAbstract:The orientation of the chemical shielding anisotropy tensor of the carbonate carbon in diphenyl carbonate was determined by using solid state NMR spectroscopy. The same tensor orientation was obtained from quantum mechanical calculation based on density functional theory. The most shielded direction of the tensor is along the CO double bond. The least shielded direction is for the carbonate Plane Perpendicular to the CO double bond. Chemical shielding calculations in diphenyl carbonate fragments with different conformations show that the tensor orientation measured in crystalline diphenyl carbonate also applies to the carbonate groups of bisphenol A polycarbonate. However, this orientation is not identical to that assumed so far in the work on bisphenol A polycarbonate. The consequences of this incorrect assumption in previous studies are examined.