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  • 1985-1989  (10)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Identification of MGB cells by Volterra kernels (1987)
    Springer
    Biological cybernetics 56 (1987), S. 261-268 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Neuronal systems can be described by their transfer functions, which can be represented by a Volterra series expansion. While the high level of abstraction which characterizes this representation enables a global description, it is problematic, to some extent, in the context of linking the formal representation of the system to its actual structure. The formal representation is unique, yet there are multiple physical realizations of this representation. Separating the system's output into its logical components (linear, cross-linear, and self nonlinear, in this study), and inspecting the relative contribution of these components, might provide a key towards a linkage between the formal and actual representations. Based on results drawn from identification of MGB cells of the squirrel monkey, it is shown that the relative contributions can be described in neurobiological terms such as excitation and inhibition and thus be attributed to actual sybsystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365221
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Identification of MGB cells by Volterra kernels (1985)
    Springer
    Biological cybernetics 51 (1985), S. 383-390 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The function of CNS sites is frequently explored by an analysis of its input-output relationships. However, such research are often confined to a qualitative and subjective inspection of raw data. System Identification methods can be used to formalize the stimulus-response relations, and one of them, the Volterra approach, is employed here in order to define these relations in the MGB of the squirrel monkey, natural vocalizations being the stimuli. In order to validate the formal representation of the system under study, the predictibility power of the model is tested. Having the distances between responses (PSTH) and predicted response quantified, it is found that the predictions made by the model are, in general, “closer” to the actual responses then some arbitrarily chosen responses. It is concluded that there are cells in the MGB that can be characterized by their Volterra kernels, and further research on the cell's functional role can be based on these kernels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350778
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic and electronic properties of HOPG/MoF6 graphite intercalation compounds: An ESR study (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 3859-3862 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The diamagnetic MoF6 molecule intercalates into graphite (HOPG) according to the reaction nC+MoF6 → C+xn(MoF−6)x (MoF6)1−x. Combination of ESR and magnetic susceptibility measurements indicate that the charge transfer is incomplete with x∼0.2. The system HOPG/MoF6 is unique in that ESR resonances due to both the 4d1 intercalant species (MoF−6) and conduction carriers can be detected. The ESR spectra of stage III exhibit an additional resonance which is probably associated with graphite interior layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449096
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Magnetic relaxation and critical current in an YBaCuO crystal (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5797-5799 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the temperature dependence of magnetic relaxation and critical current in an YBaCuO single crystal. Unusually strong time-logarithmic magnetic relaxation is observed. The relaxation rate increases initially with temperature, peaks at (approximately-equal-to)25 K and slows down at higher temperatures. The results, interpreted with a thermally activated flux model, yield a low-temperature pinning energy U0(approximately-equal-to)0.02 eV. This low pinning energy results in an unusually rapid decrease of the critical current as temperature is increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342208
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    New glassy features in high-Tc superconductors (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4182-4184 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic measurements on a high-Tc superconductor YBa2Cu3O7 reveal new spin-glass-like features. At low temperatures and low fields the irreversible part of the field-cooled magnetization Mirr rotates with the sample as a rigid entity. The rigidity is broken and part of Mirr disappears above an angle φ* which decreases with increasing temperature or field. This behavior resembles that of spin glasses and differs qualitatively from the behavior found for Nb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340243
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Release behavior of shock loaded commercial alumina (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1844-1846 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plate impact experiments were conducted on AD-85 alumina specimens (manufactured by Coors) in the low shock stress region. The experimental configuration consisted of impacting a thin flyer disc (either copper or alumina) on a relatively thick specimen disc (the target). A thin manganin stress gauge was placed at the back face of the specimen supported by a thick polymethylmethacrylate disc. After recording the initial shock at the specimen-PMMA interface, the gauge showed an unusually fast compressional wave preceding the main release wave which originates at the flyer's back surface. This wave appeared for all the shots with copper flyers and impact velocities resulting shock stresses in the 0–30 kb range. They did not appear when alumina flyers were used. Our explanation for the origin of this fast compressional wave is based on the possible occurrence of dilatancy in the specimen upon stress unloading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337231
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of the dynamic response of AD-85 alumina with in-material Manganin gauges (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3077-3080 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plate impact experiments were performed on commercial alumina disks (AD-85, manufactured by Coors), with in-material Manganin gauges, in order to determine the dynamic response of this material in the 0–100 kb range. The measured stress signals showed that the transmitted waves, at the high stress range, are composed of an initial elastic jump, to about 60 kb, followed by a dispersive rise to the final stress level. This behavior was found recently for pure alumina but not for AD-85. We used the gauges to determine the Hugoniot curve of AD-85 in the 0–100 kb range and its spall strength in this region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335807
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Shear strength of shock-loaded alumina as determined with longitudinal and transverse manganin gauges (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 1120-1122 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The shear strength of shock-loaded commercial alumina (AD-85 manufactured by Coors) is determined in the 0–140-kbar range of shock stresses. Longitudinal and transverse manganin gauges were used to determine the principal stresses in the shocked specimens. Shear strengths were determined from the difference between the longitudinal and lateral stresses. It was found that the shear strength remains essentially constant at about 27 kbar for shock stresses between 60 kbar (the Hugoniot elastic limit) and the maximum shock amplitude tested in this series (142 kbar). The source for the high shear strength is attributed to the confining pressures that strengthen the comminuted ceramic. Evidence for this interpretation is obtained by considering the release profiles as recorded by the longitudinal gauges when the free-surface rarefactions reach gauge location.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339721
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Prediction of linear and non-linear responses of MGB neurons by system identification methods (1989)
    Springer
    Bulletin of mathematical biology 51 (1989), S. 337-346 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In sensory physiology, various System Identification methods are implemented to formalized stimulus-response relationships. We applied the Volterra approach for characterizing input-output relationships of cells in the medial geniculate body (MGB) of an awake squirrel monkey. Intraspecific communication calls comprised the inputs and the corresponding cellular evoked responses—the outputs. A set of vocalization was used to calculate the kernels of the transformation, and these kernels subserved to predict the responses of the cell to a different set of vocalizations. It was found that it is possible to predict the response (PSTH) of MGB cells to natural vocalizations, based on envelopes of the spectral components of the vocalization. Some of the responses could be predicted by assuming a linear transformation function, whereas other responses could be predicted by non-linear (second order) kernels. These two modes of transformation, which are also reflected by a distinct spatial distribution of the linearvis-à-vis non-linear responding cells, apparently representa new revelation of parallel processing of auditory information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460112
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Identification of MGB cells by volterra kernels (1987)
    Springer
    Biological cybernetics 56 (1987), S. 203-208 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract System Identification methods can be implemented in sensory physiology to formalize stimulus-response relationships. We apply the Volterra approach in order to define input-output relations of Medial Geniculate Body (MGB) cells in the awake squirrel monkey. The transfer functions (kernels) of MGB cells are computed using input output pairs. The inputs are intraspecific communication sounds, represented by their spectral components at a 1 or 1/3 octave resolution, yielding thus a multi input system. The outputs are represented by the responses of single neurons expressed as the smoothed Peri Stimulus Time Histograms (PSTHs). The kernels are computed for various combinations of the model: linear and quadratic Volterra expansions respectively 1 and 1/3 octave resolution of the input. Judging by the predictions of these models, it can be concluded that the model predictibility power is systematically improved as the order of the model and its spectral resolution are increased. An analysis of the predicted responses reveals that in certain cases, the quality of the predictions might be related primarily to either the order of the model, or alternatively to the spectral resolution of the input. The quality of the predictions, and their “Linearity”, are associated with the spatial location of the cells within the MGB. Cells located at the medial aspect of the nucleus exhibit more “linear” responses, which are also better predicted, compared with most other cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317995
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    Paper (German National Licenses)
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