Frequency of exceedance any peak exceeding is . Its complement, is the probability of exceedance, the probability that has been exceeded at least once by time . This probability can be useful to estimate whether an extreme event will occur during a specified time period, such as the lifespan of a structure or the duration of an operation. If is small, for example for the frequency of a rare event occurring in a short time period, then Under this assumption, the frequency of exceedance is equal to the probability of exceedance per unit time, , and the probability of exceedance can be computed
Vibration theory of olfaction effect in no way argues exclusively for a vibrational theory of olfaction. A study published in 2011 by Franco, Turin, Mershin and Skoulakis shows both that flies can smell deuterium, and that to flies, a carbon-deuterium bond smells like a nitrile, which has a similar vibration. The study reports that drosophila melanogaster (fruit fly), which is ordinarily attracted to acetophenone, spontaneously dislikes deuterated acetophenone. This dislike increases with the number of deuteriums. (Flies genetically altered to lack smell receptors could not tell the difference.) Flies could also be trained by electric shocks either to avoid the deuterated molecule or to