GERALi) T. CARGO, ANI) ROBERT R. ERNST. Kinetics of heat activation and of thermal death of bacterial spores. Appl.-Microbiol. 11:485-487. 1963. Hypotheses concerning kinetics of heat activation and of thermal death of bacterial spores were formulated, and were employed to derive equations describing nonlogarithmic thermal death curves. The equations permitted evaluationi of the validity of experimental data and provided a means for testing the hypotheses presented.

SummaryAlthough the basic parameters for ethylene oxide sterilization are established, it is sometimes difficult to attain in practice where the principal limiting factor is moisture availability. There are situations which can limit or enhance the dynamics of sterilization. Such factors, if overlooked, could upset experiments and lead to erroneous conclusions, or defeat the sterilization process entirely.

Tandem-L is a highly innovative SAR satellite mission for the global observation of dynamic processes on the Earth's surface with hitherto unknown quality and resolution. Thanks to its novel imaging techniques and its unprecedented acquisition capacity, Tandem-L will deliver urgently needed information for the solution of pressing scientific questions in the areas of the biosphere, geosphere, cryosphere and hydrosphere. The feasibility of Tandem-L has been analyzed and confirmed in the scope of a phase A study, which has been conducted in close cooperation between the German Aerospace Center (DLR) and the German space industry. This paper provides an overview of the Tandem-L mission concept and summarizes the actual development status.

SHULL, JAMES J. (Wilmot Castle Co., Rochester, N. Y.) AND ROBERT R. ERNST. Graphical procedure for comparing thermal death of Bacillus stearothermophilus spores in saturated and superheated steam. Appl. Microbiol. 10:452-457. 1962-The thermal death curve of dried spores of Bacillus stearothermophilus in saturated steam was characterized by three phases: (i) a sharp initial rise in viable count; (ii) a low rate of death which gradually increased; and (iii) logarithmic death at maximal rate. The first phase was a reflection of inadequate heat activation of the spore population. The second and third phases represented the characteristic thermal death curve of the spores in saturated steam. A jacketed steam sterilizer, equipped with a system for initial evacuation of the chamber, was examined for superheat during normal operation. MNeasurements of spore inactivation and temperature revealed superheat in surface layers of fabrics being processed in steam at 121 C. The high temperature of the fabric surfaces was attributed to absorption of excess heat energy from superheated steam. The superheated steam was produced at the beginning of the normal sterilizing cycle by transfer of heat from the steam-heated jacket to saturated steam entering the vessel.

The resistance to destruction of spores of Bacillus subtilis var. niger occluded in crystals of calcium carbonate and exposed to ethylene oxide and moist and dry heat was determined and compared with the destruction of unoccluded spores. Occluded spores could not be inactivated with ethylene oxide. Resistance to inactivation was approximately 900 and 9 times higher for occluded than for unoccluded spores subjected to moist and dry heat, respectively, at 121 C. The protective effect may be due either to the unavailability of oxygen for destruction by oxidation or to inhibition of the loss of essential cell constituents by vaporization. Evidence also implicates the crystal structure as a thermal conductivity barrier. Occluded spores retained viability over a 3-year period compared with unoccluded spores which decreased over 90% during this period. Occluded spores in insoluble materials are seldom encountered in the technology of sterilization, but could be the most critical factor in the sterilization of interplanetary vehicles. Entrapped spores in insoluble materials are usually difficult to detect, and are very stable as well as extremely resistant to destruction by heat and ethylene oxide.