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  • 1
    Electronic Resource
    Electronic Resource
    A nonequilibrium ensemble formalism: Criterion for truncation of description (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2692-2700 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the framework of a nonequilibrium statistical ensemble formalism, consisting of the so-called Nonequilibrium Statistical Operator Method, we discuss the question of the choice of the space of thermohydrodynamic states. We consider in particular the relevant question of the truncation of description (reduction of the dimension of the state space). A criterion for justifying the different levels of truncation is derived. It depends on the range of wavelengths and frequencies which are the relevant ones for the characterization, in terms of normal modes, of the thermohydrodynamic motion in a nonequilibrium open system. Applications to the cases of thermal-sensitive resins and of n-doped polar semiconductors are done, numerical results are presented, and experimental observation is discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480843
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  • 2
    Electronic Resource
    Electronic Resource
    Identification of Mercier instabilities in Alcator C-Mod tokamak (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 5087-5095 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: During current ramp-up discharges, highly localized magnetohydrodynamic (MHD) fluctuations were observed on the electron cyclotron emission diagnostics of Alcator C-Mod tokamak [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)]. The electron temperature profile was hollow, while the density profile was weakly decreasing. Assuming that the equilibration time was short enough to quickly thermalize ions the pressure profile was also found to be hollow. Using this pressure profile as an additional constraint to the EFIT program, an equilibrium with reversed shear was constructed having a q(0)(very-much-greater-than)1. The localized MHD activity was observed near the inner q=5 rational surface in this reconstructed equilibrium, where the Mercier criterion for ideal MHD stability was violated because of the reversed pressure gradient (dp/dr〉0), q〉1 and moderate shear. When kinetic effects were added, the ideal Mercier mode was finite ion Larmor radius stabilized. However, ion Landau damping was found to be strong enough to drive a kinetic Mercier instability. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1323758
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of strong radial variation of the ion diamagnetic frequency on internal ballooning modes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 4561-4566 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formalism for internal ballooning modes in a tokamak is extended to retain the strong radial variation of the ion diamagnetic drift frequency characteristic of edge plasmas in the pedestal region. The resulting finite Larmor radius (FLR) stabilization is modified and can be weaker than in the case of constant diamagnetic frequency. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310201
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  • 4
    Electronic Resource
    Electronic Resource
    Stability criterion for edge-localized, high-n external modes in tokamaks : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2029-2032 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ideal-magnetohydrodynamics (MHD) energy principle is used to derive a necessary stability criterion for high-toroidal-number (n) external modes in axisymmetric equilibria. The corresponding trial functions are expressed in the ballooning representation, but have a finite amplitude at the plasma boundary and can apply to equilibria where the conventional, high-n internal ballooning criterion predicts stability. These trial functions are constructed by solving the standard local ballooning equation at the plasma boundary flux surface with the radial wave number parameter as a complex eigenvalue, such that the radial envelope of the mode is an exponential decaying into the plasma. The resulting stability criterion includes the surface and vacuum contributions to the MHD potential energy associated with the mode finite edge amplitude, and provides a framework for analyzing free-boundary ballooning and peeling modes. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347038
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  • 5
    Electronic Resource
    Electronic Resource
    Suicidal Genetic Elements and their Use in Biological Containment of Bacteria (1993)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 47 (1993), S. 139-166 
    Details
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.mi.47.100193.001035
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  • 6
    Electronic Resource
    Electronic Resource
    Calculations of the direct electromagnetic enhancement in surface enhanced Raman scattering on random self-affine fractal metal surfaces (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 317-325 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the classical electromagnetic enhancement at the excitation wavelength related to surface enhanced Raman scattering (SERS) experimental configurations in the vicinity of random rough metal surfaces possessing self-affine scaling behavior. The scattered electromagnetic intensity is obtained by means of numerical calculations based on the rigorous integral equations formulation of the electromagnetic wave scattering, free from the limitations of electrostatic and/or dipolar approximations. From the enhancement of the scattered field intensity in the immediate vicinity of the surface, originated in the excitation of transversal-magnetic surface plasmon polaritons, the SERS electromagnetic mechanism on substrates of Ag, Au, and Cu is explored as a function of the surface fractal dimension, rms height, and excitation wavelength. It is found that fractality favors the occurrence of large electromagnetic enhancements, which in turn appear to be maximum at an optimum wavelength as a result of the compromise between roughness-induced light coupling into surface plasmons and absorptive losses. This optimum wavelength is shorter for Ag than for Au and Cu. Maximum local enhancements on the order of 103 are encountered for the three metals being considered. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475394
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetohydrodynamic channel flow study (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 992-997 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A finite-difference study of a steady, incompressible, viscous, magnetohydrodynamic (MHD) channel flow which has direct application to dc electromagnetic pumps is presented. The study involves the numerical solution of the coupled Navier–Stokes and Maxwell equations at low magnetic Reynolds numbers. It is shown that the axial velocity profiles have a characteristic M shape as the fluid approaches and passes the electrode. The electric potential varies almost linearly from the channel centerline to the channel wall. The current shows a steep gradient near the electrodes. Comparison between the finite-difference solution and a quasi-one-dimensional approach are presented. The two-dimensional numerical calculations predict a larger pressure rise, a smaller net current, and a smaller pump efficiency than the quasi-one-dimensional model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865695
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  • 8
    Electronic Resource
    Electronic Resource
    Theory of the tokamak beta limit and implications for second stability (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2247-2250 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive picture of the tokamak stability limits against ideal magnetohydrodynamic (MHD) pressure-gradient-driven modes is put forward. The approach is based on scaling arguments for large q, and affords a first principle understanding of the Troyon limit once the normalized ratio βaB/I is modified by an extra q0 factor. The effects related to a possible access to the second stability region are clarified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859643
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  • 9
    Electronic Resource
    Electronic Resource
    Access to the second stability region in a high-shear, low-aspect-ratio tokamak (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 2674-2682 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is known that tokamaks display a second region of stability to ideal magnetohydrodynamic (MHD) internal modes. An important determining factor for MHD properties is the radial profile of toroidal current. Here it is shown that in a low-aspect-ratio tokamak with high on-axis safety factor (q0(approximately-equal-to)2) and high shear, a path to high beta can be obtained that remains completely stable against ideal MHD modes. By maintaining high shear this scenario avoids fixed boundary instabilities for both high and low toroidal mode numbers for beta values well above the Troyon limit (stability was tested up to εβp=1.4, β=10.8%). For a close fitting wall (awall/aplasma(approximately-equal-to)1.2) this configuration is also stable to low toroidal mode number balloon-kink modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866545
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  • 10
    Electronic Resource
    Electronic Resource
    Fast ECE correlation radiometry for fluctuation measurements in JET and PBX-M : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4619-4621 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We discuss the fluctuation characteristics expected from MHD modes including ballooning modes and show how they can be studied using measurements of ECE. A novel technique, ECE correlation radiometry, which enables the location and spatial structure of long wavelength (L(approximately-greater-than)0.1×a) MHD modes to be determined, is described. Measurements on JET with a 44-channel ECE heterodyne radiometer are presented and show the existence of high-frequency (high n number) MHD modes under high poloidal beta, pellet-enhanced performance (PEP) plasma conditions. Similar measurements are planned for PBX-M and the measurement system is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143689
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