Mechanical configurational effects

Erdemir, M. M., Edwards, R. H. McCarthy, K. L. (1992). Effect of screw configuration on mechanical energy transfer in twin-screw extrusion of rice flour. Lebensm fFtss. Technol, 25, 502-508. 

Stereochemical analysis can add detail to the mechanistic picture of the Sj l substitution reaction. The ionization mechanism results in foimation of a caibocation intermediate which is planar because of its hybridization. If the caibocation is sufficiently long-lived under the reaction conditions to diffirse away from the leaving group, it becomes symmetrically solvated and gives racemic product. If this condition is not met, the solvation is dissymmetric, and product with net retention or inversion of configuration may be obtained, even though an achiral caibocation is formed. The extent of inversion or retention depends upon the details of the system. Examples of this effect will be discussed in later sections of the chapter. 

Louver Failure - Inadvertent louver closure may result from automatic control failure or mechanical linkage failure. The effect on heat transfer will depend on the degree of restriction to air flow in the closed position and the configuration of louvers in relation to tube bundles (e.g., louvers may not be installed over all tube bundles in a given service). 

---