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The development of micro-alloyed high-purity aluminum for low-temperature superconductor stabilizer applications is described. The base aluminum is 99.9998% pure; the micro-alloy levels range from 5 up to 90 wt ppm. Individual elements are added to the base in binary form; the solute elements used are B, Ca, Ce, Ga or Y. The effects of solute elements and solute concentration on electrical, mechanical, and crystallographic properties and on cyclic-strain resistivity degradation at 4.2 K are presented. The addition of low levels of various elements changes these properties with minimal effects on resistivity, and alloyed materials exhibit lower levels of cyclic-strain resistivity degradation than the base high-purity aluminum. Our results show that this improvement in resistivity degradation is closely related to grain refinement resulting from the addition of solute elements and sample preparation procedures. Optical micrographs show the presence of particles that occurred as a result of micro-segregation during the initial solidification.

In the fermentation of cucumbers, naturally occurring strains of Lactobacillus plantarum decarboxylate malic acid (MDC+) to form lactic acid and CO2. Since CO2buildup in the brine contributes to bloater damage of the cucumbers, it is desirable to have strains of L. plantarum that do not decarboxylate malic acid (MDC-1). Two MDC-mutants, obtained by N-methyl-N′-nitro-N-nitrosoguanidine mutagenesis of different MDC+strains, and their parent strains of L. plantarum wre evaluated in laboratory fermentations of filter-sterilized cucumber juice and of whole cucumbers as to growth rate, end-products, residual malic acid, and competitiveness with the natural flora. Effects of temperature (15 to 40°C) and NaCl concentration (0-6%) on growth in cucumber juice were determined. One MDC-1strain, designated MOP3-M6, was selected for further development because of its relative dominance in cucumber ferementations, high residual malic acid concentration after fermentation and greater salt tolerance as compared to its closest rival mutant culture. Growth lag and generation times averaged 1·6 and 1·2 times greater, respectively, for the MOP3-M6 mutant than its parent. However, this mutant may still have application as a starter culture for cucumber fermentation, particularly under relatively aseptic conditions.