Tune shift with amplitude of the system. When the tune reaches resonant values, it can be unstable, and thus a tune-shift with amplitude can limit the stability region, or dynamic aperture. In classical mechanics, a simple example of a system with tune shift with amplitude is a pendulum. In accelerator physics, both the transverse and the longitudinal dynamics show tune shift with amplitude. A simple model of the transverse dynamics is of an oscillator with a single sextupole, it is referred to as the Hénon map. Another model for this case is the Standard Map. An important example is the typical case of distributed
Cassandra (metaphor) representing the human moral conscience whose main task is to issue warnings. Cassandra as moral conscience, "predicts ill to come and warns that punishment will follow and grief arise". Cassandra's need to point out moral infringements and subsequent social consequences is driven by what Klein calls "the destructive influences of the cruel super-ego", which is represented in the Greek myth by the god Apollo, Cassandra's overlord and persecutor. Klein's use of the metaphor centers on the moral nature of certain predictions, which tends to evoke in others "a refusal to believe what at the same time they know to be