The growth rate of flagellar hooks in Salmonella typhimurium was analyzed by computer-aided simulation of the length distributions of mutant hooks of uncontrolled length (polyhooks). The wild-type hook has a relatively well-controlled length, with an average of 55 nm and a standard deviation of 6 nm. Mutations in the fliK gene give rise to polyhooks. A histogram of the lengths of polyhooks from a fliK mutant shows a peak at 55 nm with a long monotonic tail extending out to 1 microm. To analyze the growth rate, we employed the population balance method. Regression analysis showed that the histogram could fit a combination of two theoretical curves. In the first phase of growth, the hook starts with a very fast growth rate (40 nm/min), and then the rate exponentially slows until the length reaches 55 nm. In the second phase of growth, where the hook length is over 55 nm, the hook grows at a constant rate of 8 nm/min. Second mutations in either the fliK or flhB genes, as found in pseudorevertants from fliK mutants, give rise to polyhook filaments (phf). The ratio between the numbers of hooks with and without filament was 6:4. The calculated probability of filament attachment to polyhooks was low so that the proportion of hooks that start filament growth was only 2% per minute. The lengths of polyhooks with and without filaments were measured. A histogram of hook length in phf's was the same as that for polyhooks in single-site fliK mutants, against the expectation that the distribution would shift to a shorter average. The role of FliK in hook length control is discussed.

In the expendable pattern casting (EPC) process for the aluminum alloy casting, the thermal decomposition rate of the expendable pattern is smaller than the cast iron, therefore the misrun by the temperature drop at the melt surface occurs easily. This study takes account of the control of the heat release to the mold to investigate numerically and experimentally the effect of the coat permeability on the molten aluminum alloy temperature during mold filling in the EPC process. An aluminum alloy plate was cast by the EPC process, and the temperature change of the melt surface to the melt flow direction was measured. The use of high permeability coat led to a higher melt velocity and a smaller temperature drop at the melt surface than the case of the normal permeability coat. The temperature of molten metal filling into the cavity was numerically simulated, and the obtained temperature drop at the melt surface agreed relatively well with the experimental values.

MethodCreeping flow past a square and an equilateral triangular array of cylinders and mass transfer between the fluid and the surface of the cylinders were studied theoretically. A numerical solution for the drag coefficient of the cylinders was obtained and found to be in good agreement with the asymptotic analytical solutions for very small and very large values of the dimensionless pitch respectively. Anumerical solution for the Sherwood number was obtained as a function of the Peclet number, the dimensionless pitch, and the number of rows of cylinders in square and triangular arrays. Theoretical predictions for the drag coefficient of the cyh'nders and the Sherwood number were compared with approximate analytical solutions based on the free-surface model by Happel.

Kato, Y.; Nishiwakl, A.; Kago, T.; Fukuda, T.; Tanaka, S. Int. Chem. Eng. Kim, S. D.; Baker, C. G. J.; Bergougnou, M. A. Can. J . Chem. Eng. 1972, Kumar, A.; Oegaleesan, T. E.; Laddha, G. S.; Hoelscher, H. E. Can. J . Oels, U.; Lucke, J.; Buchholz, R.; Schugerl, K.Solubility and diffusivity of carbon dioxide in 10-43 wt % aqueous kaolin slurries were measured at 15, 25, and 35 O C and at atmospheric pressure. The effects of the addition of electrolytes (sodium chloride, sodium sulfate, and magnesium chloride) in 15-44 wt % aqueous kaolin slurries on carbon dioxide solubility and diffusivity were determined at 25 OC. The electrolyte concentration ranged from 0.5 to 1.7 kmol/m3. The carbon dioxide solubilities in aqueous slurries of 12-42 wt % zircon and 7-21 wt % sulfur were also measured at 25 OC. All the solubility

The generation of machining defects and their effect on bending strength characteristics are discussed with respect to a TiAl intermetallic compound, which is attracting much attention as a high-temperature structural material because of its high specific strength. The discussion focuses on the mechanism of the formation of edge chipping and machined surface cracks during cutting of a TiAl intermetallic compound. Also, some effects of these machining defects on the bending strength are clarified. The comparison of cutting results with abrasive machining results helps clarify the dependence of strength on undeformed chip thickness during chip generation of machining processes.