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  • 1
    Electronic Resource
    Electronic Resource
    Difference in excitability along geometrically inhomogeneous structures and occurrence of “hot spots” (1991)
    Springer
    Biological cybernetics 66 (1991), S. 185-189 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The differences in excitability along geometrically inhomogeneous, electrically excitable structures as well as the possibility of occurrence of “hot spots” at certain branch points were theoretically analysed on the basis of the Hodgkin-Huxley model assuming uniform specific membrane parameters along the structure length. It was shown that the “hot spots” conditioned by geometrical inhomogeneities should be not only morphological but also functional formations. The excitability at the branch point could be higher than that at the rest of the structure when the branch point was an electrical equivalent of a step decrease in the cable diameter. The stronger the diameter decrease, the higher the excitability at the branch point and thus the higher is the possibility of observation of “hot spots” in the nerve cells whose dendrites have a profuse branching. The realization of the “hot spots”, however, depended on the distance from the site of the stimulus application (synapse) to the branch point and on the stimulus (synaptic current) strength, as well. The closer the synaptic current strength to the threshold value, and the shorter the synapse-branch point distance, the higher was the possibility of a propagating action potential origin at the branch point but not at the site of the stimulus application and thus the higher was the possibility of realization of “hot spots”. The conclusion that the geometrical position of the initial segment contributes to its higher excitability (as compared to the rest of the cell) in the case of orthodromic activation of the neuron was also made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243294
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  • 2
    Electronic Resource
    Electronic Resource
    Solving Linear Systems with Error Control: Minisymposium within the 4th International Conference NMA'98 (1999)
    Springer
    Reliable computing 5 (1999), S. 97-100 
    Details
    ISSN: 1573-1340
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026449926367
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  • 3
    Electronic Resource
    Electronic Resource
    Power spectra of single infinite fibre extracellular potentials recorded by a bipolar electrode (1990)
    Springer
    Medical & biological engineering & computing 28 (1990), S. 537-543 
    Details
    ISSN: 1741-0444
    Keywords: Bipolar recording ; Extracellular action potential ; Fibre-electrode distance ; Intracellular action potential duration ; Power spectrum ; Propagation velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The power spectra of bipolarly recorded extracellular action potentials (EAPs) generated by an infinite, homogeneous, excitable fibre in an infinite, resistive, isotropic and homogeneous volume conductor were theoretically analysed. The changes in the power spectrum of EAP, which occurred as a result of alterations in the propagation velocity v and duration Tin of the intracellular action potential IAP, were analytically determined for bipolar parallel and radial electrodes with a small interpole distance. It was found that the sensitivity of the spectral characteristics to alteration in v, Tin and/or the IAP asymmetry substantially depends on the fibre-electrode distance; information on the IAP fast changes, that seems to be lost in unipolar recording as a result of the filtering effect of the fibre-electrode distance, can be restored. The orientation of the recording electrode need not be taken into account when a qualitative analysis is carried out, but when a quantitative analysis has to be performed, then the electrode orientation has a significant influence. A method is suggested for determination of the fibres' orientation by means of the spectrum of EAPs recorded bipolarly. The selectivity of the bipolar electrodes is analysed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02442604
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  • 4
    Electronic Resource
    Electronic Resource
    Radial changes of extracellular potential amplitude and integral characteristics and the inverse problem in electroneurography (1992)
    Springer
    Medical & biological engineering & computing 30 (1992), S. 357-363 
    Details
    ISSN: 1741-0444
    Keywords: Activated fibres' territory ; Desynchronisation ; Extracellular potential amplitude ; Extracellular potential integral ; Fibre-electrode distance ; Fibre excitation parameters ; Inverse problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The possibility of solving the inverse problem in electroneurography, i.e. of estimating the main parameters specifying the activated fibre's functional state, using the amplitude and integral characteristics of the surface potentials generated by infinite homogeneous fibres, has been analysed. An analytical expression has been found for the amplitude of the negative phase Anph of the single fibre extracellular action potential (SFEAP) as a function of the wavelength b, the fibre-electrode distance y and a scale factor Ao proportional to the intracellular action potential amplitude Vm, to the square of the fibre radius a and to the ratio of the axoplasm conductivity τa and volume conductor conductivity τe. For a large fibre-electrode distance, typical of surface recordings, an analytical expression of the integral of the negative phase Inph of the SFEAP as a function of Ao, b, y and the propagation velocity v was also found. Simple methods are proposed for estimating v, the location of the electrical centre of the activated fibres' territory and the product of the number of activated fibres N, duration Tin of the intracellular action, potential and of the factor Ao. The estimation errors due to the temporal and spatial dispersion of the activated fibres were analysed as a function of the fibre-electrode distance and the territory shape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02446975
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  • 5
    Electronic Resource
    Electronic Resource
    Use of surface potential spectral characteristics for solving the inverse problem in electroneurography (1992)
    Springer
    Medical & biological engineering & computing 30 (1992), S. 399-405 
    Details
    ISSN: 1741-0444
    Keywords: Activated fibres' territory ; Anisotropy ratio ; Desynchronisation ; Frequency-dependent volume conductor ; Inverse problem ; Power spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The changes in the power spectra of single-fibre extracellular action potentials (SFEAPs) generated in an infinite anisotropic frequency-dependent volume conductor, which occurred as a result of alterations in the propagation velocity v and duration Tin of the intracellular action potential (IAP) were analytically determined. Effects of the temporal and spatial dispersions of almost synchronously activated fibres on the power spectrum of compound extracellular potentials (CEPs) were analysed for different shapes and sizes of the activated fibres' territory. It was found that, as a result of desynchronisation in the fibres' activation, dips existed in the CEP power spectra and that the frequencies of the dips depended on the degree of desynchronisation but did not depend on the velocity. It was shown that the hypothetical power spectrum of compound IAP was sensitive to the variations in the desynchronisation in the fibres' activation and in the risetime and duration of IAP even at a great fibre electrode distance typical for surface recordings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02446167
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  • 6
    Electronic Resource
    Electronic Resource
    Schnelle Anionenaustauschertrennung des Molybdäns von Bor für die Analyse von Molybdänboriden (1974)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 268 (1974), S. 207-207 
    Details
    ISSN: 1618-2650
    Keywords: Best. von Molybdän und Bor in Molybdänborid ; Ionen-austausch, Volumetrie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00430608
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  • 7
    Electronic Resource
    Electronic Resource
    Power spectra of extracellular potentials generated by an infinite, homogeneous excitable fibre (1990)
    Springer
    Medical & biological engineering & computing 28 (1990), S. 24-30 
    Details
    ISSN: 1741-0444
    Keywords: Extracellular potential ; Intracellular action potential duration ; Mathematical model ; Power spectrum ; Propagation velocity ; Radial distance ; Single fibre
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The power spectra of the extracellular potentials (EPs) generated under activation of an infinite, homogeneous excitable fibre immersed into an infinite, resistive, isotropic and homogeneous volume conductor are theoretically analysed. The changes in the power spectrum related to the changes in the propagation velocity v, amplitudes Vm and duration Tin of the intracellular action potential (IAP) are analytically determined. It is found that in the ultra-low-frequency region the EP spectral power follows the course of alteration in the square of the modified Bessel function of the second kind and order zero multiplied by the fourth power of the frequency, and the Tin can be assessed by the deviation of the EP power spectrum from this function. It is shown why the sensitivity of the spectral characteristics depends substantially on the radial distance y0 from the activated fibre to the point of observation; why the total spectral amplitude depends directly on the IAP wavelength but the total spectral power depends on the IAP wavelength as well as on its duration and propagation velocity; and why the EPs are not proportional to the IAP second spatial derivative even in close proximity to the fibre.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441673
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  • 8
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    Difference in excitability along geometrically inhomogeneous structures and occurrence of “hot spots” (1991)
    Springer
    Details
    Publication Date: 1991-12-01
    Print ISSN: 0340-1200
    Electronic ISSN: 1432-0770
    Topics: Biology , Computer Science , Physics
    Published by Springer
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  • 9
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    Schnelle Anionenaustauschertrennung des Molybd�ns von Bor f�r die Analyse von Molybd�nboriden (1974)
    Springer
    Details
    Publication Date: 1974-01-01
    Print ISSN: 0016-1152
    Topics: Chemistry and Pharmacology
    Published by Springer
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