The effects of air velocity and direction and of wetness on rate of heat transfer were studied in tests with samples of fur from five caribou calves. The rate of heat transfer through this fur increased by a factor of two to three with increase in air velocity from a negligible level (natural convection) to 23 m/second (direction parallel to sample). The effect of air velocity varied markedly (up to ±50% at 23 m/second) with inclination of the sample to the direction of air movement. Spraying water on the fur increased its rate of heat transfer markedly; addition of water equivalent to 10–12% of the volume of the fur doubled the rate of heat transfer. Other factors, such as erectness of the fur, direction of the hairs or "grain" of the fur with respect to the direction of air movement, and wetness of the skin also affected heat transfer. Differences between samples were large and did not appear to depend directly on the physical characteristics measured.
A standard vegetative inoculum of Aspergillus niger has been developed for the submerged citric acid fermentation of sugar beet molasses. Increasing the ferrocyanide content and the pH of the seed mash, within limits, decreased the rate of development of the mold pellets whereas increasing the spore inoculum increased the rate of development. Using this "standard" inoculum, an average yield of 8.9% anhydrous citric acid (68.5% conversion of available sugar) was obtained in 116 hr. The standard deviation between runs was 4.5% of the mean citric acid yield. An abrupt breakdown of the fermentation process decreased the yield by 50% and increased the standard deviation to 28.5% of the mean yield. The breakdown was overcome by changing the sporulation medium from a chemically-defined synthetic type to a nutritionally-richer type. Results indicate that serial transfer on a synthetic medium weakened the culture and made the fermentation unstable.
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