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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 176 (1995), S. 379-389 
    ISSN: 1432-1351
    Keywords: Neural network ; Evolution strategy ; Salamander ; Optic tectum ; Orienting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Simulander is a feedforward neural network simulating the orientation movement of salamanders. The orientation movement is part of the prey capture behavior; it is performed with the head alone. Simulander is a network which consists of 300 neurons incorporating several cytoarchitectonic and electrophysiological features of the salamander brain. The network is trained by means of an evolution strategy. Although only 100 tectum neurons with fairly large receptive fields are used (“coarse coding”), Simulander is able to localize an irregularly moving prey precisely. It is demonstrated that large receptive field neurons are important for successful prey localization. The removal of a model tectum hemisphere leads to a network which accounts for investigations made in living monocular salamanders. The model also yields an understanding of electrical stimulation experiments in toads.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 56 (1993), S. 169-174 
    ISSN: 1432-0630
    Keywords: 61.50 ; 61.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A new fullerene-containing van der Waals-compound, C60S16, has been synthesized and its crystal structure determined from single-crystal X-ray diffraction data collected at room temperature. The compound is monoclinic, space group C 2/c with a=20.867(4) Å, b=21.062(4) Å, c=10.508(2) Å, β=111.25(7)° and four formula units per cell. The C60 molecules form a three-dimensional framework with one-dimensional channels along c which contain crown-shaped S8 rings. The structure has been determined by direct methods and has been refined to atomic resolution on the C60 molecule. The two independent C-C bond distances, averaged under the idealized point symmetry of the “free” C60 molecule, amount to 1.340(8) Å and 1.448(8) Å, corresponding to a “bond alternation” as large as 0.108(8) Å. The bond lengths are compared with the results of theoretical calculations of the molecular structure of C60 as well as with bond lengths from various experimental sources.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 292 (1998), S. 47-56 
    ISSN: 1432-0878
    Keywords: Key words: Plethodontids ; Urodeles ; Optic tectum ; Electrophysiology ; Biocytin ; Salamander ; Plethodon jordani ; Hydromantes genei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The amphibian optic tectum and pretectum have been analyzed in detail anatomically and physiologically, and a specific model for tecto-pretectal interaction in the context of the visual guidance of behavior has been proposed. However, anatomical evidence for this model, particularly the precise pattern of pretecto-tectal connectivity, is lacking. Therefore, we stained pretectal neurons intracellularly in an in-vitro preparation of the salamanders Plethodon jordani and Hydromantes genei. Our results demonstrate that the projections of neurons of the nucleus praetectalis profundus are divergent and widespread. Individual neurons may project divergently to telencephalic (ipsilateral amygdala and striatum), diencephalic (ipsi-and contralateral thalamus, contralateral pretectum), and mesencephalic (ipsi- and contralateral tectum and tegmentum) centers, and to the ipsi- and contralateral medulla oblongata and rostral spinal cord. The projection of pretectal cells to the optic tectum is bilateral; axonal structures do not show discernible patterns and are present in all layers of the superficial white matter. A classification of pretectal neurons on the basis of axonal termination pattern or dendritic arborization has not been possible. Our results do not support the hypothesis that a distinct class of pretectal neurons projects to a particular subset of tectal cells. Rather, the pretectum appears to influence the tectum indirectly, acting either on retinal afferents or modulating inhibitory interneurons.
    Type of Medium: Electronic Resource
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