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  • 1
    ISSN: 1432-1246
    Keywords: Sleep length ; Sleep quality ; Sleep timing ; Watchkeeping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Sleep length and sleep quality scores were collected on board ships over periods of up to two weeks from 38 watchkeepers working a ‘4-on/8-off routine’ and 29 dayworkers. All watchkeepers exhibited fragmented sleeping patterns, which indicated a lack of adaptation of the sleep/wakefulness cycle to the hours of work. There were only slight differences in total sleep length between watchkeepers and dayworkers, however, both groups did not obtain an adequate amount of sleep. Within the watchkeeping crews the 3rd Officers had by far the shortest sleep length. Concerning sleep quality, daytime sleep was generally given the lowest ratings, whereas sleep starting before midnight was on average evaluated as the best, both by watchkeepers and dayworkers. Watchkeeping personnel do not normally have any “days off” during a voyage so that missed sleep might even amount to a sleep deficit. A solution for this problem could perhaps be a new, stabilized system that allows a single uninterrupted sleep, which is required for full recuperation, to be taken each day.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 16 (1977), S. 317-321 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Ausrichtungs- und Aggregationseffekte in Kugelsuspensionen mit viskoelastischer Suspensionsflüssigkeit werden aufgezeigt. Bei einem Teil der Bilder handelt es sich um Mikroaufnahmen von ebenen Schichtenströmungen zwischen zwei Glasplatten. Die Kugeln richten sich in Strömungsrichtung aus und kommen einander näher. Bei Berührung verschwindet die Rotationsgeschwindigkeit der Kugeln. Diese Ausrichtung und Anlagerung wird auch in der Dehn- und Rohrströmung beobachtet. Der Orientierungsvorgang ist ein Normalspannungseffekt. Nicht die absolute Höhe der ersten Normalspannungsdifferenz, sondern das Verhältnis der ersten Normalspannungsdifferenz zur Schubspannung ist der wesentliche Parameter. Auf praktische Folgerungen wird kurz hingewiesen.
    Notes: Summary Photographs are presented which demonstrate the alignment and aggregation effects in suspensions of spheres in viscoelastic media. Pictures were taken from plane shear flows between two glass plates. The spheres line up in flow direction and come into contact. If the spheres touch, the rotation ceases. This alignment and association was also observed and photographed in elongational and in pipe flow. The alignment process could be related to normal stresses. A further observation is that the ratio of the first normal stress difference to the shear stress is the determining parameter. Practical aspects are mentioned.
    Type of Medium: Electronic Resource
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