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  • Springer Nature  (76)
  • American Institute of Physics (AIP)  (45)
  • Oxford University Press  (38)
  • American Chemical Society (ACS)
  • 1995-1999  (90)
  • 1985-1989  (43)
  • 1955-1959  (22)
  • 1930-1934  (4)
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  • 1
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    BBC microcomputer controlled field inversion gel electrophoresis (1988)
    Oxford University Press
    Details
    Publikationsdatum: 1988-01-01
    Print ISSN: 1367-4803
    Digitale ISSN: 1460-2059
    Thema: Biologie , Informatik , Medizin
    Publiziert von Oxford University Press
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    AKTUELLE ARTIKEL
  • 2
    Digitale Medien
    Digitale Medien
    Nonperturbative calculation of energies and widths of predissociative states of diatomic molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3057-3062 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A nonperturbative theory of predissociation based upon an effective Hamiltonian is presented. For a model diatomic system in which a (bound-state) Morse potential-energy curve is crossed by an (unbound-state) exponential potential-energy curve, the exact effective Hamiltonian may be obtained in high precision for any well behaved interaction potential. The real and imaginary parts of the eigenvalues of the effective Hamiltonian give the (shifted) energies and widths, respectively, of the predissociative states. Numerical results are obtained and compared with both a semiclassical approximation and those derived from solutions of coupled Schrödinger equations. In the weak-coupling regime the agreement between the present method and semiclassical results is good, and better in general than the coupled-equations results, which apparently suffer from instability problems. For couplings of intermediate strength, the semiclassical method breaks down, as do fully quantum-mechanical first-order perturbation approximations, as is demonstrated by comparison with the converged nonperturbative results. Fixed points of the spectrum appear at "resonance'' values of the coupling strength which bring the exact energy eigenvalue into resonance with one of the adiabatic levels so that the imaginary part (level width) of the former vanishes. Thus beyond a critical coupling strength, stronger coupling enhances the stability of a resonance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.454961
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  • 3
    Digitale Medien
    Digitale Medien
    The application of electrochemistry to the measurement of selected intrinsic properties of polyacetylene (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5102-5107 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Electrochemical techniques are applied to a study of selected intrinsic physical properties (independent of dopant) of polyacetylene, (CH)x. Electrochemical voltage spectroscopy (EVS) is used to characterize the energies of charge injection and removal for both cis-(CH)x and trans-(CH)x. The difference in charge injection and ejection potentials is shown to give a direct measure of the approximate semiconductor band gap and the results are compared with similar data from optical measurements. Charge injection and ejection potentials are used to define the redox potentials of (CH)x and are used in conjunction with equilibrium potential measurements at varying oxidation or reduction levels of polyacetylene to present a unifying concept to the electrochemistry of (CH)x.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.456552
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  • 4
    Digitale Medien
    Digitale Medien
    Comment on: "Total scattering, surface ionization, and photoionization of a beam of H3 metastable molecules'' (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5984-5985 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The nature of the metastable state of hydrogen trimers described by Ga and Kuppermann (ref.1) is further discussed. The analysis is based on linewidth measurements in the emission spectrum of the trimer, the quantum mechanical selection rules, and earlier beam and photoionization measurements.(AIP)
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.454517
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  • 5
    Digitale Medien
    Digitale Medien
    The nuclear displacement operator and formulation of the Born couplings of molecular Born–Oppenheimer wave functions (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4949-4956 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The nuclear displacement operator (NDO) for Born–Oppenheimer electronic wave functions (BOEWF) is introduced and some recurrence formulas are obtained. The formulas for Born couplings and higher derivatives of BOEWF with respect to nuclear coordinates are derived from very general considerations and relations among these quantities are given. The series form, exponential, and integral forms of the NDO are exhibited. Particularly, it is proven that for the two-state systems the NDO has a very simple form by which it is convenient to study two-state dynamical processes. It is shown that the NDO satisfies a differential equation which is analogous to that for the time-evolution operator in the presence of a time-dependent perturbation. The physical meanings of these two operators are compared. It is demonstrated that the NDO is uniquely determined by the vector Born coupling matrix, and that the nuclear motion may be analyzed in terms of a local non-Abelian gauge transformation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.454706
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  • 6
    Digitale Medien
    Digitale Medien
    Inertial range structures in decaying compressible turbulent flows (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 237-245 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Simulations of decaying compressible turbulent flows have been performed using the PPM algorithm on grids of 5123 and 10243 computational cells. Although the run on the finer grid has not yet been carried out to a time large enough for the spectra to relax fully, it adds significantly to the results on the coarser grid by lengthening the range of wave numbers in which the flow exhibits a self-similar character. There is an inertial range of scales in the decaying flow on the finer mesh that is free from direct effects of dissipation, forcing, boundary conditions, or initial conditions. Favre averaging of the high resolution data is performed on different scales from which the vorticity structures in the inertial range may be visualized and characterized without confusion from the smaller-scale features of the near dissipation range. We find that the vorticity structures of the inertial range are filamentary as well, but qualitatively different—shorter and more curved—than those of the dissipation range. Quantitative evidence of the action of vortex stretching in developed turbulence is also presented. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.869563
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  • 7
    Digitale Medien
    Digitale Medien
    Characterization of the separatrix plasma parameters in DIII-D (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1410-1422 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Characterization of the plasma density and temperature at the last closed flux surface (the separatrix) of a tokamak requires accurate knowledge of the location of the separatrix. In this paper we discuss the effect of inaccuracy in the separatrix location on the measured parameters in DIII-D [Luxon et al., International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1986), p. 159] An uncertainty in the separatrix position of ±0.5 cm, as expected in this device using magnetic reconstruction to determine the location of the separatrix, leads to unacceptably large uncertainty in the plasma parameters. Several techniques to improve the accuracy obtained from magnetic reconstruction are discussed. A new technique that is based on a characterization of the electron temperature profile is proposed. A comparison of the separatrix location defined in this manner with that obtained using magnetic reconstruction techniques suggests a systematic error in the reconstruction when the plasma is far from the walls and magnetic diagnostics. Determination of the perpendicular transport coefficients is given as an example of the improved statistics obtained using the new technique of defining the separatrix position.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872830
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  • 8
    Digitale Medien
    Digitale Medien
    Radiative divertor plasmas with convection in DIII-D : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1736-1743 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The radiation of divertor heat flux on DIII-D [J. Luxon et al., in Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1987), p. 159] is shown to greatly exceed the limits imposed by assumptions of energy transport dominated by electron thermal conduction parallel to the magnetic field. Approximately 90% of the power flowing into the divertor is dissipated through low-Z radiation and plasma recombination. The dissipation is made possible by an extended region of low electron temperature in the divertor. A one-dimensional analysis of the parallel heat flux finds that the electron temperature profile is incompatible with conduction-dominated parallel transport. Plasma flow at up to the ion acoustic speed, produced by upstream ionization, can account for the parallel heat flux. Modeling with the two-dimensional fluid code UEDGE [T. Rognlien, J. L. Milovich, M. E. Rensink, and G. D. Porter, J. Nucl. Mater. 196–198, 347 (1992)] has reproduced many of the observed experimental features. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872842
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  • 9
    Digitale Medien
    Digitale Medien
    The role of radial particle flow on power balance in DIII-D (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 4311-4320 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The importance of radial particle flow on the power flowing across the last closed flux surface (separatrix) in DIII-D [Luxon et al., International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1986), Vol. I, p. 159] is considered. The perpendicular thermal diffusivity at the separatrix is near 1 m2/s in low confinement operation (L-mode), and 0.1 m2/s in high confinement (H-mode). The particle diffusivity is about one-fourth of the thermal diffusivity producing radial particle fluxes of the order of kilo-amperes. The particle flux is 10 to 100 times the particle input from neutral beam sources, consistent with core fueling being dominated by neutral recycling. The radial particle flux scales with the neutral pressure in the private flux region, suggesting the core is fueled predominantly from neutrals which recycle from the divertor, through the private flux, and into the core near the singular point where the poloidal field is zero (X-point). There is significant core power loss associated with the large particle flux across the separatrix. The electron temperature measured at the top of the edge pedestal in H-mode operation scales inversely with the particle flux. In turn, the core energy confinement scales with the pedestal temperature, and hence inversely with the particle flux. The results presented here indicate the global particle confinement time is between 0.5 and 2 times the global energy confinement time. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.873169
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  • 10
    Digitale Medien
    Digitale Medien
    Two-dimensional electric fields and drifts near the magnetic separatrix in divertor tokamaks : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1851-1857 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A two-dimensional calculation is presented for the transport of plasma in the edge region of a divertor tokamak solving continuity, momentum, and energy balance fluid equations. The model uses classical processes of parallel transport along the magnetic field and cross-field drifts together with anomalous radial diffusion, including perpendicular ion viscosity. The self-consistent electrostatic potential is calculated on both sides of the magnetic separatrix via quasineutrality and current continuity. Outside the separatrix, the model extends to material divertor plates where the incident plasma is recycled as neutral gas and where the plate sheath and parallel currents dominate the potential structure. Inside the separatrix, various radial current terms—from anomalous viscosity, collisional damping, inertia, and ∇B drifts—contribute to determining the potential. The model rigorously enforces cancellation of gyroviscous and magnetization terms from the transport equations. The results emphasize the importance of E×B particle flow under the X-point which depends on the sign of the toroidal magnetic field. Radial electric field profiles at the outer midplane show strong variation with the magnitude of the anomalous diffusion coefficients and the core toroidal rotation velocity, indicating that shear stabilization of edge turbulence can likewise be sensitive to these parameters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.873488
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