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  • Springer  (56)
  • 1980-1984  (56)
  • 1
    Electronic Resource
    Electronic Resource
    Development of visual sensitivity in the fly,Sarcophaga bullata (1983)
    Springer
    Cellular and molecular life sciences 39 (1983), S. 1318-1319 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ontogeny of light response in the compound eyes of the fly,Sarcophaga bullata was investigated. Even though the eyes are structurally differentiated before eclosion they become electrophysiologically functional only after eclosion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01990392
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  • 2
    Electronic Resource
    Electronic Resource
    Genetic definition of a further gene region and identification of at least three different histocompatibility genes in the rat major histocompatibility system (1980)
    Springer
    Immunogenetics 11 (1980), S. 483-490 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two new recombinant haplotypes of the rat major histocompatibility system,RT1, have been detected in [LEW.1A (RT1 a ) ×LEW.1W (RT1 u )] × LEW 1N(RT1 n ) segregating hybrids. Recombinantr3 carries theRTL1. A region (determining classical transplantation antigens) and theRT1.B region (determining strong mixed lymphocyte reactivity and genetic control of antipolypeptide immune responsiveness) of the RT1a parent, bur rejects RT1a skin grafts. Recombinantr4 carries theA andB regions of the RT1u parent, but rejects RT1u skin grafts. The two histocompatibility genes detected are allelic to each other. The relevant locus, designated asH-C, maps to theB-region side of theRT1 system and appears to mark a thirdRT1 gene region,RT1.C. Availability of haplotypes r3 andr4 allowed the definition of a histocompatibility locus in theB region,H-B. The products ofH-C, H-B and of the previously describedH-A gene vary in antigenic strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01567816
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  • 3
    Electronic Resource
    Electronic Resource
    Sensitivity analysis and optimization for a head movement model (1981)
    Springer
    Biological cybernetics 41 (1981), S. 33-45 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A sixth order nonlinear model for horizontal head rotations in humans is analyzed using an extended parameter sensitivity analysis and a global optimization algorithm. The sensitivity analysis is used in both the direct sense, as a model fitting tool, and in the indirect sense, as a guide to experimental design. Resolution is defined in terms of the sensitivity table, and is used to interpret the sensitivity results. Using sensitivity analyses, the head and eye movement systems are compared and contrasted. Controller signal parameters are the most influential. Their variations and effects on head movement trajectories and accelerations are investigated, and the conclusions are compared with clinical neurological findings. The global optimization algorithm, in addition to automating the fitting of various types of data, is combined with time optimality theory to give theoretical time-optimal inputs to the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01836125
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  • 4
    Electronic Resource
    Electronic Resource
    Simulation of head movement trajectories: model and fit to main sequence (1981)
    Springer
    Biological cybernetics 41 (1981), S. 19-32 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A sixth order nonlinear model for horizontal head rotations in humans is presented and investigated using experimental results on head movement trajectories and neck muscle EMG. The controller signals, structured in accordance with time optimal control theory, are parameterized, and controller signal parameter variations show a dominating influence on different aspects of the head movement trajectory. The model fits the common head acceleration types over a wide range of amplitudes, and also less common (dynamic overshoot) trajectories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01836124
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  • 5
    Electronic Resource
    Electronic Resource
    A model for nonlinear stochastic behavior of the pupil (1982)
    Springer
    Biological cybernetics 45 (1982), S. 13-21 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract In this paper we present new experimental results that show pupillary noise to be multiplicative in a particular fashion with greatest variance in midrange and smaller variance at high and low ranges. This confirms the finding of multiplicative noise by Stanten and Stark (1966), but modifies and extends the relationship they suggested between standard deviation and mean pupil diameter. We propose a parametric model of the iris muscle which not only describes the static characteristics of pupil response to given stimuli, but also explains its random fluctuations in terms of probability density functions. We emphasize the point that the range nonlinearity is not due to decreased gain at the extrema of the pupil range, but is operational over a wide portion of the pupillary behavioral range, hence its name — “expansive range nonlinearity”. We conclude that noise amplitude, which is a function of the pupil diameter, closely parallels the changes in deterministic gain. Thus pupil noise can be simply considered as cross-talk additive Gaussian noise injected into the pupil system at midbrain level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387209
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  • 6
    Electronic Resource
    Electronic Resource
    Multipulse controller signals (1983)
    Springer
    Biological cybernetics 48 (1983), S. 5-8 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We apply minimum time as an optimality criterion for human saccadic eye movements. This constrains the class of admissable controller signals to those taking only their maximum and minimum values. We then assume set numbers of switchings between maximum and minimum for each extraocular muscle, and explore the space of switching times to find the fastest model-generated trajectory, for each number of switches. We find that controller signals with bursts of antagonist “braking” activity cause much faster movements than do simple pulse-step patterns, and that signals with an extra pulse of agonist innervation produce still faster movements. The slight increase in speed for still more pulses is at the expense of unreasonably short final pulses. The use of the global optimization algorithm confirms and extends our previous study of multipulse control using a parallel processor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336878
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  • 7
    Electronic Resource
    Electronic Resource
    Multipulse controller signals (1983)
    Springer
    Biological cybernetics 48 (1983), S. 1-4 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Although eye movement saccades are stereotyped, repeatable movements, the shape of the neural controller signal innervating the extraocular muscles is a matter of controversy. Different lines of evidence — single motoneuron recordings, electromyograms, and dynamics — lead to different conclusions. Although all agree that the controller is, in outline, a pulse-step of net activity, neither the pulse width nor shape of the trailing edge of the pulse is clear. We use a mathematical model of the eye and two extraocular muscles to link the dynamical data to the electrophysiological evidence. We conjecture a multipulse controller signal, based on the application of an optimality principle to our model. This multi-pulse controller signal raises new possibilities for resolution of the pulse shape ambiguities, and resolves the controversy over pulse width.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336877
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  • 8
    Electronic Resource
    Electronic Resource
    Multipulse controller signals (1983)
    Springer
    Biological cybernetics 48 (1983), S. 9-10 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We compare model trajectories driven by different orders of controller signals to statistics on shapes of human saccadic eye movements. The commonly recorded dynamic overshoot must be driven by a multipulse controller signal, but multipulse controller signals need not always produce observable dynamic overshoots. Thus it is possible that a single strategy — multipulse control — produces all saccades, but that the strategy is not always apparent in the recorded movements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336879
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  • 9
    Electronic Resource
    Electronic Resource
    Experimental study of quantum size effects in very thin metal films (1980)
    Springer
    Applied physics 21 (1980), S. 397-406 
    Details
    ISSN: 1432-0630
    Keywords: 73 ; 79.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The influence of the quantum size effect (QSE) in very thin Pd and Au films (0.5〈d〈10 [nm]) deposited on glass tips is studied by means of field emission at various anode potentials. The thickness-dependent field emission current characteristics show short periodic variations with a period of about 0.3 nm for both Pd and Au. The measured QSE oscillations and their amplitudes differ strongly from those expected qualitatively from model calculations for the smallest thicknesses. A model for the metal film based on a modification of the uniform background model is presented, and the thickness dependence of the conductance and the field emission current density are qualitatively discussed. Possible explanations of some discrepancies between calculations and the measured field emission current characteristics are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00895932
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  • 10
    Electronic Resource
    Electronic Resource
    A systems model for the pupil size effect (1983)
    Springer
    Biological cybernetics 48 (1983), S. 101-108 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The human pupillary control system is a paradigm for linearized biological control systems. It also exhibits a series of interesting nonlinear behaviors, particularly asymmetry, “pupillary escape”, and “pupillary capture.” We present a nonlinear model in which a signal dependent upon pupil size is fed back internally to cause a change in system parameters related to gains and rates of light adaptation. The model was simulated on a digital computer, a variety of experimental data was well matched, and improvements over previous pupil models demonstrated. A candidate physiological mechanism for adaptive components of the model might have the form of an inverse “Henneman coded” neuronal pool.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00344393
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