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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archive of applied mechanics 65 (1995), S. 548-563 
    ISSN: 1432-0681
    Keywords: Key words nonlinear dynamics ; annular jet ; gravitational fluctuations ; adaptive finite difference method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary  The nonlinear dynamics of axisymmetric, inviscid, incompressible, thin, annular liquid jets subjected to fluctuating body forces is studied numerically by means of an adaptive finite difference method which maps the time-dependent, curvilinear geometry of the jet into a unit square. The fluctuating body forces may arise from fluctuations in the gravitational acceleration in inertial frames or from the acceleration of a non-inertial frame of reference which translates parallelly to an inertial one. It is shown that both the pressure coefficient and the axial location at which the annular jet becomes a solid one are periodic functions of time with a period equal to that of the imposed body force fluctuations, and that their magnitude increases as the amplitude of the body force fluctuations is increased. It has also been shown that, for both intermittent, sinusoidal or rectangular excitations, increases in the frequency of the excitation result in the creation of superharmonics, broad, albeit peaked, spectra, and closed phase planes with many loops.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cultures of dissociated embryonic rat mesencephalic cells were exposed to 10 μM 1-methyl-4-phenylpyridinium (MPP+), a concentration shown earlier to result in loss of 〉85% of tyrosine hydroxylase (TH)-positive neurons without affecting the total number of cells observed by phase-contrast microscopy. To characterize better the selectivity of the toxic action of MPP+, other parameters were measured reflecting survival and function of dopaminergic or nondopaminergic neurons. Exposure of cultures to 10 μM MPP+ for 48 h reduced TH activity to 11% of control values without reducing protein levels. [3H]Dopamine uptake was reduced to 〈 4% of control values, whereas the uptake of γ-[3H]aminobutyric acid ([3H]GABA) was not affected in these cultures. This same treatment failed to reduce the number of cholinergic cells visualized in septal cultures and did not affect either choline acetyltransferase activity or high-affinity choline uptake. To assess for possible recovery of dopaminergic neurons, cultures were exposed to 10, 1.0, or 0.1 μM MPP+ for 48 h and then kept for up to 6 days in MPP+-free medium. After exposure to 10 μM MPP+, the number of TH-positive neurons, their neurite density, TH activity, and [3H]dopamine uptake remained at constant, reduced levels throughout the period of observation after termination of exposure, whereas GABA uptake remained normal. Treatment with lower concentrations of MPP+, i.e., 1.0 and 0.1 μM, induced less pronounced dopaminergic toxic effects. However, no recovery was seen after posttreatment incubation in toxin-free medium. These findings provide evidence that MPP+ treatment results in highly selective and irreversible toxicity for cultured dopaminergic neurons.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 317-325 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2692-2700 
    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
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 10 (1977), S. 989-992 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5307-5310 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical properties of Eu3+ ions in oxyfluoride glass ceramics and in the precursor glasses (30 SiO2, 15 Al2O3, 29 CdF2, 22 PbF2, 1.5 YF3, and 2.5 EuF3, in mol %) have been analyzed and compared. The Eu3+ ions in the glass ceramics are incorporated into a crystalline environment with higher symmetry and lower energy coupled phonons. Emission measurements indicate that this crystalline phase is EuF3, instead of PbxCd1−xF2 as generally considered. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    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
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 4561-4566 
    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
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  • 9
    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
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 5087-5095 
    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
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