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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archive of applied mechanics 62 (1992), S. 158-171 
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary Mechanical systems are considered which are subject to temporary constraints. This is the case in stick-slip processes and impacts. The use of the first Lagrangian method requires the calculation of Lagragian multipliers whenever one of the additional constraints becomes active. In this paper a method is presented and illustrated by examples which takes all possible constraints into account à priori, without calculating constraint forces explicitly. However, the latter are easily calculated by a simple equation, if necessary.
    Notes: Übersicht Es werden mechanische Systeme behandelt, die über begrenzte Zeit wirksamen Zwängen unterworfen sind. Dies sind typischerweise Haft-Gleit-Übergänge und Stöße. Die Verwendung der Lagrangeschen Gleichungen erster Art bedarf bei Aktivwerden der Bindungen der Ermittlung der Langrangeschen Multiplikatoren. In der vorliegenden Arbeit wird ein Verfahren vorgestellt und an Beispielen erläutert, das die möglichen Bindungen à priori erfaßt, ohne daß Zwangskräfte explizit in Erscheinung treten. Letztere lassen sich jedoch im Bedarfsfall durch eine einfache Beziehung angeben.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: E. coli ; dnaA ; pBR322
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The in vivo role of the Escherichia coli protein DnaA in the replication of plasmid pBR322 was investigated, using a plasmid derivative carrying an inducible dnaA + gene. In LB medium without inducer, the replication of this plasmid, like that of pBR322, was inhibited by heat inactivation of chromosomal DnaA46 protein so that plasmid accumulation ceased 1 to 2 h after the temperature shift. This inhibition did not occur when the plasmid dnaA + gene was expressed in the presence of the inducer isopropyl-1-thin-β-d-galactopyranoside (IPTG). Inhibition was also not observed in glycerol minimal medium or in the presence of low concentrations of rifampicin or chloramphenicol. Deletion of the DnaA binding site and the primosome assembly sites (pas, rri) downstream of the replication origin did not affect the plasmid copy number during exponential growth at 30° C, or after inactivation of DnaA by a shift to 42° C in a dnaA46 host, or after oversupply of DnaA, indicating that these sites are not involved in a rate-limiting step for replication in vivo. The accumulation of the replication inhibitor, RNAI, was independent of DnaA activity, ruling out the possibility that DnaA acts as a repressor of RNAI synthesis, as has been suggested in the literature. Changes in the rate of plasmid replication in response to changes in DnaA activity (in LB medium) could be resolved into an early, rom-dependent, and a late, rom-independent component. Rom − plasmids show only the late effect. After heat inactivation of DnaC, plasmid replication ceased immediately. These results, together with previously published reports, suggest that DnaA plays no specific role during in vivo replication of ColE1 plasmids and that the gradual cessation of plasmid replication after heat inactivation of DnaA in LB medium results from indirect effects of the inhibition of chromosome replication and the ensuing saturation of promoters with RNA polymerase under nonpermissive growth conditions.
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  • 3
    ISSN: 1436-6215
    Keywords: protein-energymalnutrition ; vitaminE status ; children ; Sudan ; developingcountries ; Protein-Energie-Mangelernährung ; Vitamin-E-Status ; Kinder ; Sudan ; Entwicklungsländer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Das Gesamttocopherol und alpha-Tocopherol wurden im Plasma von Kindern mit schwerer Mangelernährung (14 Maramus; 11 marantischer kwashiorkor; 5 kwashiorkor) bestimmt und auf die Gesamtlipide des Plasmas und auf die verschiedenen Plasmalipidklassen bezogen. Wenn die reinen Plasmakonzentrationen als ein Index des Vitamin-E-Status genommen würden, so wären 5 Kinder mit Marasmus, 5 Kinder mit marantischem kwashiorkor und 2 Kinder mit kwashiorkor als defizitär (〈500 μg/dl) anzusehen. Werden jedoch Gesamttocopherol und alpha-Tocopherol auf die Gesamtlipide bezogen, so zeigten alle mangelernährten Kinder — bis auf eines — Werte, die innerhalb der Grenzen lagen, die für gesunde amerikanische Kinder gefunden wurden. Die Studie zeigt, daß niedrige Tocopherol-Lipid-Verhältnisse kein konstantes Merkmal bei schwer mangelernährten Kindern sind.
    Notes: Summary Total tocopherols and alpha-tocopherols were estimated in the plasma of children with severe malnutrition (14 marasmus; 11 marasmic kwashiorkor; five kwashiorkor) and related to the total plasma lipids and different plasma lipid classes. If the mere plasma concentrations were taken as an index of the vitamin E status, five children with marasmus, five children with marasmic kwashiorkor, and two children with kwashiorkor would have been regarded as deficient (〈500 μg/dl). However, if total tocopherols and alpha-tocopherols were related to the total plasma lipids, all malnourished children — except one — showed values within the limits found in healthy American children. The study shows that low tocopherol/lipid ratios are not a constant feature in severely malnourished children.
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