Cascade development

In early copiers, deposition of the toner particles onto the photoreceptor surface was accomplished simply bv cascading the particles over the photoreceptor surface. Cascade development was first described by Walkup (1952) and used in all earl) Xerox copiers. Figure 15 shows a cascade development process. Carriers for cascade development were usually glass or metal beads with diameters of several hundred pm. The limitations of cascade development... 

Figure 15 A cascade development system. Cascade development operates by cascading developer particles across the photoreceptor surface under the force of gravity.

Brown, K. R, and Bacon, L. G., 2000, Cascade development and mineral extraction -alternatives to reinjection. In Environmental Safety and Health Issues in Geothermal Development in World Geothermal Congress, Kazuno, Japan. 

Finally, there is also a relevant example of an intermolecular conjugate Friedel-Crafts/electrophilic amination cascade developed very recently by Melchiorre in which 2-methyl-IH-indole reacted with a variety of a,p-unsatu-rated aldehydes and dialkyl azodicarboxylates in the presence of a primary amine catalyst, leading to the formation of a family of products containing two contiguous stereocenters, one of them a quaternary one (Scheme 7.43). This reaction started with the conjugate addition of 2-methyl-lH-indole to the enal... 

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