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  • 1990-1994  (57)
  • 1985-1989  (41)
  • 1970-1974  (36)
  • 1965-1969  (26)
  • 1
    Electronic Resource
    Electronic Resource
    A model of beam–plasma discharge in a nonuniform plasma (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 3562-3568 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents a model of beam–plasma discharge resulting from the quasilinear heating of plasma electrons by Langmuir waves which are excited by beam–plasma interactions. The heating is made possible by the spectral transformation of waves propagating radially from the central beam-occupied region toward the region of lower plasma density. In this paper equations describing the wave spectral density, the distribution function of a high-energy electron tail, and its stationary density profile are obtained and numerically solved; to do so a balanced diffusion and ionization is assumed. The possibility of significant plasma density enhancement in beam–plasma discharge is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860363
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Wave collapse at the lower-hybrid resonance (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3148-3162 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The modulational instability and collapse of waves in the vicinity of the lower-hybrid resonance including both magnetosonic and lower-hybrid waves are investigated by analytical and numerical methods. The mechanism leading to the modulational instability is the nonlinear coupling of lower-hybrid waves with the much lower-frequency quasineutral density perturbations via the ponderomotive force. The result is a filamentation of the high-frequency field producing elongated, cigar-shaped nonlinear wave packets aligned along the magnetic field with the plasma expelled outside (cavities). The analytical self-similar solutions describing cavity collapse are obtained and compared with the results of numerical simulation for both two- and three-dimensional cavity geometries. It is shown that in three-dimensional solutions the transverse, with respect to the magnetic field, contraction remains prevailing. The possibility of ion acceleration as the result of the lower-hybrid collapse is discussed and detailed comparison is made with the observations of the phenomena in the auroral ionosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860652
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Reply to "Comment on ‘Peeling of convection cells and the generation of sheared flow' [Phys. Fluids B 4, 488 (1992)]'' (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 658-658 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The comments of Montgomery and Matthaeus on the authors' paper1, have been answered. The results do not contradict those of Montgomery and Matthaeus but for simple case considered, transition to shear flow state and shape of initial vortices is explained. (AIP)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860501
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  • 4
    Electronic Resource
    Electronic Resource
    Theory of wave activity occurring in the AMPTE artificial comet (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1728-1738 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: One of the main experiments of the Active Magnetospheric Particle Tracer Explorers (AMPTE) [J. Geophys. Res. 91, 10013 (1986)] satellite mission was the release of neutral barium atoms in the solar wind. The barium atoms ionized by photoionization extremely rapidly forming a dense, expanding, plasma cloud that interrupted the solar wind flow creating diamagnetic cavities. On the upstream side of the cavity a region of compressed plasma and enhanced magnetic field was created as the result of being produced by the slowing down and deflection of the solar wind, and magnetic field line draping. Intense electrostatic and magnetic turbulence was observed by both the IRM [J. Geophys. Res. 91, 10 013 (1986)] and UKS [J. Geophys. Res. 91, 1320 (1986)] satellites at the boundary of the diamagnetic cavity, with the most intense waves being detected near the outer boundary of the compressed region. This paper examines how the newly created expanding plasma couples to the solar wind by means of plasma–beam and current-driven instabilities. In particular, it is shown how lower-hybrid and lower-hybrid drift waves are generated by cross-field proton–barium streaming instabilities and cross-field electron currents. The saturation mechanism for these waves is considered to be the modulational instability, this instability can also lead to filamentation and coupling to magnetosonic modes, which are also observed. As the result of modulational instability the k(parallel) component increases, which allows the heating and acceleration of electrons that is consistent with the observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859984
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Peeling of convection cells and the generation of sheared flow (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 488-491 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A periodic array of convection cells is subject to a "shear flow'' instability. The generation of the sheared flow is a consequence of "peeling'' of the convection cells. Fluid simulations demonstrate that the efficiency of shear flow generation is high. Implications for understanding poloidal rotation in tokamaks are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860246
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  • 6
    Electronic Resource
    Electronic Resource
    Vega spacecraft encounters with comet Halley (1986)
    [s.l.] : Nature Publishing Group
    Nature 321 (1986), S. 259-262 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The spacecraft Vega 1 and Vega 2 encountered comet Halley on 6 and 9 March 1986. Their scientific payload comprised 14 instruments, which collected data concerning the comet's optical characteristics, dust emission, and neutral gas, plasma and electromagnetic field environment. The main ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/321259a0
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  • 7
    Electronic Resource
    Electronic Resource
    Dust coma structure of comet Halley from SP-1 detector measurements (1986)
    [s.l.] : Nature Publishing Group
    Nature 321 (1986), S. 274-276 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Each dust particle that hits the solid target of the SP-1 detector gives rise to a charged plasma cloud5; the amplitude of each charge pulse is measured and recorded by decade counters. A preliminary estimate for the mass range Amn of the nth channel is obtained by using an empirical conversion ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/321274a0
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  • 8
    Electronic Resource
    Electronic Resource
    Comet Halley dust environment from SP-2 detector measurements (1986)
    [s.l.] : Nature Publishing Group
    Nature 321 (1986), S. 276-278 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The techniques used evolved from the near-Earth cosmic dust studies carried out on Kosmos satellites from 1966 to 19723. The SP-2 experiment4 comprises two types of particle impact sensor: an acoustic sensor and an ionization (plasma) sensor. The acoustic sensor consists of a thin circular plate ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/321276a0
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  • 9
    Electronic Resource
    Electronic Resource
    Interaction between chemical mutagens with a delayed effect and metabolites of seeds (1971)
    Springer
    Theoretical and applied genetics 41 (1971), S. 21-24 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A study was made of the cytogenetic effect of mutagens with a delayed effect (ethylenimine and ethyl methanesulphonate) on Crepis capillaris seeds. The effect was found to depend on the physiological condition of the seeds. In seeds not subjected to prolonged storage, where only chromatid aberrations were occurring spontaneously, mutagens also induced chromatid aberrations only. If, however, because of physiological changes in the seeds (e.g. upon prolonged storage or when seeds were kept at an elevated temperature and humidity) a large number of chromosome-type aberrations appeared, they also appeared when the seeds were acted upon by mutagens with a delayed effect. The action of such mutagens was also found to depend on spontaneous mutation in seeds with different rates of germination. Special experiments showed that the interaction of ethylenimine with the metabolites of seeds in vitro leads to the formation of secondary active mutagens differing from ethylenimine in the nature of their action. The induction of chromosome-type aberrations by treating seeds with alkylating compounds may be due to the action of secondary mutagens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00279294
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  • 10
    Electronic Resource
    Electronic Resource
    Interaction between chemical mutagens with a delayed effect and metabolites of seeds (1971)
    Springer
    Theoretical and applied genetics 41 (1971), S. 52-56 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A study was made of chromosome aberrations in Crepis capillaris seedlings, induced by the reaction products of chemical mutagens with seed metabolites. Interaction between ethylenimine and seed metabolites of some plants of the family Compositae (C. capillaris, Taraxacum officinale, Pyrethrum carneum, Helianthus annuus) has been found to lead to the formation of highly active secondary mutagens whose action remains similar to that of ethylenimine, although the effect of ethylenimine is enhanced dozens of times. The substances responsible for this „enhancement effect” are contained in the fruit coating of the seed. The metabolites of seeds of other plants studied (Triticum vulgare, Hordeum vulgare, Fagopyrum esculentum) enhanced the effect of ethylenimine only 1.5–2.0 times. Unlike ethylenimine, the effect of its derivatives (thioTEP and phosphazine) and of ethyl methanesulphonate, HN2 and maleic hydrazide is not enhanced after their interaction with metabolites of compositae plant seeds. Experiments with HN2 revealed an almost complete inactivation of the mutagenic action of NH2 by metabolites of C. capillaris seeds. The observed modification of the mutagenic action of ethylenimine and NH2 after successive treatment of seedlings with mutagens and metabolites of seeds points to the preservation of the mutagen in the cell. It is concluded that when chemical mutagens act on the cells, chromosome aberrations are induced not only by the chemical agent itself, but also by its reaction with cell metabolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277045
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