Der Einfluß wechselnder Temperaturen auf das Zeitfestigkeitsverhalten von Stählen

Mechanische und thermische Beanspruchungen, die zu überelastischen Verformungen führen und ein frühzeitiges Versagen eines Bauteiles verursachen können, treten im Betrieb häufig gemeinsam auf. Es war zu untersuchen, ob eine überlagerte Beanspruchung zu einer größeren Schädigung führt als eine Beanspruchung bei konstanter Höchsttemperatur. Dazu wurden Torsionswechselversuche durchgeführt, wobei in Axialrichtung eine freie Wärmedehnung gewährleistet war. Aus dem Vergleich der Ergebnisse aus Konstant- und Wechseltemperaturversuchen konnte für Wechseltemperaturversuche eine ?äquivalente Konstanttemperatur“ definiert werden.     

On the existence of polyadenylated histone mRNA in Xenopus laevis oocytes

In a variety of systems, histone mRNA has been shown to lack poly(A) (Adesnik and Darnell, 1972; Grunstein et al., 1973). We have found, however, that in Xenopus laevis oocytes, poly (A)-containing mRNA codes for histones, in a wheat germ cell-free system, based on the following criteria: first, co-migration with authentic X. laevis oocyte histones on polyacrylamide gels; second, no detectable incorporation of tryptophan; third, differential incorporation of lysine and methionine into histone fraction H2A; fourth, resistance of histone fraction H2A to cleavage with cyanogen bromide; and fifth, correspondence of tryptic peptide maps of partially purified cell-free products with authentic X. laevis oocyte histone. RNA which directs the synthesis of histones in the cell-free system is retained on oligo(dT)-cellulose, even after denaturation in 80% DMSO at 70 degrees C, thereby demonstrating the covalent attachment of polyadenylic acid sequences to the mRNA. Poly (A)- RNA (7S-14S fraction) was also found to code for histones using the same criteria. We discuss the significance of the finding that X. laevis oocytes contain two classes of histone mRNA as well as the potential developmental implications of this observation.     

Validation and adjustment of the mathematical prediction model for human sweat rate responses to outdoor environmental conditions

Under outdoor conditions this model was over estimating sweat loss response in shaded (low solar radiation) environments, and underestimating the response when solar radiation was high (open field areas). The present study was conducted in order to adjust the model to be applicable under outdoor environmental conditions. Four groups of fit acclimated subjects participated in the study. They were exposed to three climatic conditions (30 degrees, 65% rh; 31 degrees C, 40% rh; and 40 degrees C, 20% rh) and three levels of metabolic rate (100, 300 and 450 W) in shaded and sunny areas while wearing shorts, cotton fatigues (BDUs) or protective garments. The original predictive equation for sweat loss was adjusted for the outdoor conditions by evaluating separately the radiative heat exchange, short-wave absorption in the body and long-wave emission from the body to the atmosphere and integrating them in the required evaporation component (Ereq) of the model, as follows: Hr = 1.5SL0.6/I(T) (watt) H1 = 0.047Me.th/I(T) (watt), where SL is solar radiation (W.m-2), Me.th is the Stephan Boltzman constant, and I(T) is the effective clothing insulation coefficient. This adjustment revealed a high correlation between the measured and expected values of sweat loss (r = 0.99, p < 0.0001).