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  • 1
    Electronic Resource
    Electronic Resource
    Unit analysis of hippocampal population spikes (1971)
    Springer
    Experimental brain research 13 (1971), S. 208-221 
    Details
    ISSN: 1432-1106
    Keywords: Hippocampal formation ; Single units ; Population spike ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The assumption that the negative extracellular population spikes recorded from the pyramidal or granular layers in the hippocampal formation in response to appropriate afferent volleys is due to the sum of individual unitary discharges was tested by recording unit activity and population spike with microelectrodes, using normal and ultrashort amplifier time constants. 2. Unit spikes were correlated in time with the population spike. 3. The size of the population spike was altered by varying the stimulus strength, or by using a conditioning-test technique. In either case the number of units recorded followed the change in the size of the population spike. For very large population spikes, the technique failed since unit spikes could then no longer be clearly distinguished. 4. The theoretically expected shape of the population spike as a summation of individual unit discharges was derived, and discussed in terms of the observed results. 5. We conclude that over a wide range the height of the population spike is an increasing function of the number of discharging cells and can thus be used as a measure of the extent to which an afferent volley discharges a cell population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234086
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  • 2
    Electronic Resource
    Electronic Resource
    Lamellar organization of hippocampal excitatory pathways (1971)
    Springer
    Experimental brain research 13 (1971), S. 222-238 
    Details
    ISSN: 1432-1106
    Keywords: Hippocampal formation ; Excitatory pathways ; Lamellar organization ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Entorhinal activation of the hippocampal cortex involves the sequential activation of a four-membered pathway: the perforant path from the entorhinal area — the mossy fibres from the dentate granule cells — the Schaffer collaterals of the CA3 pyramidal cells and finally, the CA1 pyramidal cell axons in the alveus. 2. The spatial orientation of these four fibre bundles has been studied by recording the extracellular field potentials (population spike), signalling the discharge of neurones in response to orthodromic or antidromic impulses. The height of the population spike was taken as an indicator of the number of cells discharged (see the previous paper). 3. The perforant path fibres from neighbouring parts of the entorhinal area run in a parallel fashion in a direction nearly transversely to the longitudinal axis of the hippocampus. In the dorsal part of the hippocampus, this direction was nearly sagittal, confirming Lømo (1971 a). The mossy fibres as well as the Schaffer collaterals and the alvear fibres were all found to run in the same direction. Thus, a point source of entorhinal activity projects its impulses through the four-membered pathway along a slice, or lamella, of hippocampal tissue oriented normally to the alvear surface and nearly sagittally in the dorsal part of the hippocampal formation. Also with more temporal locations of the stimulating and recording electrodes, the lamellar organization was maintained, but with a different orientation, matching the curving of the hippocampus so that the angle between the plane of the lamella and the longitudinal axis remained the same. 4. By injection of a quick-setting solution of vinyl acetate, the direction of the arteries and veins in the hippocampal formation was displayed. The branches from the artery running in the hippocampal fissure are nearly straight and are oriented in a direction similar to that of the lamellae. 5. The hippocampal cortex seems to be organized in parallel lamellae, both with regard to the neuronal and the vascular system. By means of this lamellar organization, small strips of the hippocampal cortex may operate as independent functional units, although excitatory and inhibitory transverse connections may modify the behaviour of the neighbouring lamellae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234087
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  • 3
    Electronic Resource
    Electronic Resource
    Flow-induced crystallization of polypropylene in stretched ribbons (1976)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 16 (1976), S. 217-221 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ribbons of molten polypropylene have been extruded into a thermostatted chamber and subjected to elongations ranging as high as 4400-fold. Some of these ribbons have been shown to possess the unusual ability of recovering nearly all of the strain from large levels of stretch (≤100 percent). This property, as well as the magnitude of the tensile yield drop, has been found to be directly proportional to the uniaxial character of the flow present at the moment of crystallization. The structure in the final solid films has been characterized by wide angle X-ray diffraction and crystal orientation distribution. Both of these factors have been found to be proportional to the character of flow at the moment of crystallization. Finally, the temperature in the thermostatted chamber has been shown to affect the character of the flow.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760160316
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  • 4
    Electronic Resource
    Electronic Resource
    Crystal nucleation in sheared polymer melts (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 215-221 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A semiquantitative procedure has been developed for analyzing crystal nucleation in undercooled polymer melts that are undergoing flow. This analysis was applied to the specific ease of molten high density polyethylene experiencing low levels of shearing flow. A custom-made concentric cylinder viscometer, which could be operated by the Rheometrics mechanical spectrometer instrument, was used to make simultaneous measurements of transmitted torque and optical anisotropy in isothermal melts, The result of the analytical procedure developed here was molecular Size-dependence of chain distensions caused by prevailing shear. This distribution function was verified by testing against experimentally obtained values of birefringence. Total entropy reduction resulting from this distorted state was then calculated, and the corresponding increase in free energy was found to be at least enough to account for comparable crystal nucleation rates in flowing melts at higher temperatures and in quiescent melts at lower temperatures.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760180308
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    Paper (German National Licenses)
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