Dendrite morphology of several steady state unidirectionally solidified iron base alloys

The experimental data are presented of the dendrite morphology of steady state unidirectionally solidified steels. The dendrite arm spacings were correlated with the equation A =KR ^mG^mwhereR is the growth rate and G the temperature gradient. The exponentsm andn for the primary arms are fairly close to the theoretical values (m = -0.25,n = -0.5). For the secondary arms they are about the same (-0.4). The primary arm spacings do not depend much on composition. The secondary arm spacings, however, decrease at fixed carbon content with increasing content of substitutional elements, and they were found to be smaller in a steel freezing as ferrite compared to steels freezing as austenite. All the authors were with Max-Planck Institut für Eisenforschung, 4 Düsseldorf 1, Max-Planck-Str. 1, Germany, at the time this investigation was carried out.     

Listeria monocytogenes Survival Model Validated in Simulated Uncooked-Fermented Meat Products for Effects of Nitrite and pH

Previous modeling studies in broth cultures demonstrated that acidity and nitrite increased the inactivation rate of Listeria monocytogenes. To validate this effect during storage of simulated uncooked-fermented meat products, lean beef was ground with salt, adjusted to pH 4.0–5.1, and treated with nitrite at 0–300 μg/mL. Samples were immediately inoculated with L. monocytogenes (10⁷ CFU/g) and survivors were enumerated over 21 days storage at 37°C. The time to achieve a four log decline as greatly affected by pH, ranging from 21 days at pH 5.0 to < 1.0 day at pH 4.0. Growth occurred at pH 5.1 after a long lag period. Nitrite additions did not affect survival, suggesting that the effective concentration was the rapidly decreasing residual nitrite level.