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  • Polymer and Materials Science  (3)
  • Stimulus transduction  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Periodic firing pattern in afferent discharges from electroreceptor organs of catfish (1995)
    Springer
    Pflügers Archiv 429 (1995), S. 378-385 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Stimulus transduction ; Bursting ; Temperature dependence ; Calcium entry blockers ; Siluriformes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Spontaneous afferent activity was recorded from 26 single ampullary electroreceptive organs of freshwater catfish (Ictalurus nebulosus LeS) at various temperatures. Regular grouping of action potentials was apparent in this secondary sensory system at 35°C and occasionally at 30°C. Impulse groups consisted of up to seven impulses. The precise timing of impulse generation and the temporal sequence of impulses indicated that oscillating processes are involved. Expectation density functions were calculated for records of afferent activity obtained at various temperatures below 35°C. In the majority of records the function was periodic. Impulse grouping and expectation density functions became more distinct in units exhibiting extremely high thresholds (i.e. being insensitive) to electrical stimuli. The results suggest that the oscillations originate from the postsynaptic membrane. The temporal pattern of impulse generation within impulse groups of ampullary electroreceptor organs and of specific warm and cold receptors was compared and found to be similar. Application of cadmium and menthol, which both reduce calcium entry, suppressed spontaneous activity in normal and insensitive electroreceptor systems, attenuated the sensitivity of normal receptors and modified the periodic pattern. This indicates that calcium is implicated in sensory transduction and in postsynaptic mechanisms. The data suggest that an oscillating process is one component of signal transmission in ampullary electroreceptor organs of teleost fish.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00374153
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  • 2
    Digitale Medien
    Digitale Medien
    Ampullary electroreceptors in catfish (Teleostei): temperature dependence of stimulus transduction (1990)
    Springer
    Pflügers Archiv 417 (1990), S. 100-105 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Catfish ; Ampullary electroreceptors ; Stimulus transduction ; Temperature dependence ; Calcium channels
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The response properties of ampullary electroreceptors have been studied in the catfish Ictalurus nebulosus at skin temperatures between 5 and 35 °C. A unimodal relationship between spontaneous activity and temperature was obtained. Mean (±SEM) peak discharge rate was 57.3 ±1.8 impulses s−1 at 25 ° C; the receptors were active at 5 °C (15.0 impulses s−1) and at 35 °C (31.5 impulses s−1). There were no dynamic responses to temperature changes in either the warming or cooling direction. The shape of the frequency characteristic depended on temperature: the peak of the gain curve shifted to low frequencies at low temperatures. There was a concomitant change of the phase characteristic: the intersection at zero degree phase angle shifted to higher frequencies with an increase of temperature, thus increasing the lead at lower frequencies and decreasing the lag at higher frequencies. Latency after combined excitatory and inhibitory impulse stimulation was temperature dependent, ranging from 16.4 ms (5 °C) to 5.6 ms (35 °C). Application of the specific calcium channel blocker menthol (0.2 mM) suppressed spontaneous activity, the effect becoming more prominent at higher temperatures. Sensitivity to sinusoidal electrical stimulation was also impaired, but to a lesser degree and mainly at lower temperatures. We conclude that the filter properties of the receptor organ can be modelled by a band-pass filter in series with a latency, both of which are temperature dependent. These filter properties might be partially based on the activation kinetics of the tranduction channels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00370776
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  • 3
    Digitale Medien
    Digitale Medien
    Über die Anwendung von Zirkonium im chemischen Apparatebau (1969)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 20 (1969), S. 30-35 
    Details
    ISSN: 0947-5117
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Application of zirconium in chemical plant constructionIt ist in this decade only, that zirconium has become an established special material in chemical plant construction. Zirconium is used in particular where high corrosion resistance is required, e.g. with processes involving sulfuric, hydrochloric, nitric and phosphoric acids, chlorides (except ferric and cupric chlorides), alkalies, urea, hydrogen peroxide and lactic acid. Preferred types of equipment are reaction columns, pump casing, heat exchangers and tubing, e.g. in connection with the production of dyes, pigments (erosion resistance), foods, hydrogen peroxide and urea. The price of zirconium, though still high if compared with that of nickel-base alloys or high-alloy stainless steels is soon amortized as a consequence of the low maintenance requirement.
    Notizen: Zirkonium ist im Laufe von nur 10 Jahren zu einem fest eingeführten Sonderwerkstoff des Apparatebaues geworden. Es wird vor allem bei hohen Ansprüchen an die Korrosionsbeständigkeit eingesetzt, z.B. bei Verfahren mit Schwefel-, Salz-, Salpeter- und Phosphorsäure, Chloriden (außer Eisen-III- und Kupfer-II-chlorid), Alkalien, Harnstoff, Wasserstoffsuperoxid, Milchsäure. Bevorzugte Apparaturen sind Reaktionstürme, Pumpengehäuse, Wärmeaustauscher und Rohrleitungen, z.B. bei der Herstellung von Farbstoffen, Pigmenten (Erosionsbeständigkeit), Nahrungsmitteln, Wasserstoffsuperoxid und Harnstoff. Der noch immer höhere Preis des Zirkoniums im Verleich mit Legierungen auf Bickelbasis oder hochlegierten nichtrostenden Stählen amortisiert sich bald aufgrund des geringen Wartungsbedarfs.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/maco.19690200109
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  • 4
    Digitale Medien
    Digitale Medien
    Flow behavior of symmetrical P (S-b-MMA) block copolymers: Rheological problems arising from shear modified morphology (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 487-499 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: In this article, symmetrical, narrow distribution P (S-b-MMA) block copolymers are characterized rheologically, using a dynamic spectrometer and a stress rheometer. The shear induced morphology changes are investigated by off-line electron microscopy and SAXS. We tried to correlate the results of dynamics and long-time creep experiments with morphological and rheological features. Summarizing, one can point out that the examined block copolymers reveal the well-known low frequency behavior of phase separated blends. Additionally, we observed a significant shear influence on the morphology, i.e. a shear induced structuring and alignment of lamellae. This considerable change in morphology is also reflected by the characteristic rheological properties (retardation time, yield stress). Therefore, problems concerning the validity range of linear viscoelastic behavior arise, which are discussed in brief. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1993.070490313
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  • 5
    Digitale Medien
    Digitale Medien
    Production, properties, and application of polyurethane RRIM (1988)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 8 (1988), S. 17-26 
    Details
    ISSN: 0730-6679
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: The production of automotive exterior body panels in the PUR-RRIM process is a comparatively new technology that provides a great potential for further improvements and makes it possible to produce plastic components for the automotive industry that, at relatively thin wall thicknesses, meet maximum requirements in regard to part geometrydimensional stabilitythe high industrial standards valid in the automotive industrysurface quality (avoidance of sink marks, pores, etc.)durable fastening For a better acceptance of RRIM moldings, cost reductions in the production process are necessary which, in turn, require noticeable progress in the material and process development. Due to the improvements made in the field of both raw materials and production units, the PUR-RRIM process has, in the last few years, become interesting also for high-volume production. A handicap in this connection is that the development of the RRIM process is, to a large extent, based on the practical experience of a few experts. For its use in high-volume production it is, however, inevitable to have at hand through scientific data on material, design, process and resulting correlations. It is the objective of the Institute for Polymer Testing and Polymer Science in Stuttgart to help establish these data and, through close contacts to the industry, make them usable in practice.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/adv.1988.060080104
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