These conventions are used in combinatorics, although Knuth's underline/overline notations formula 4 are increasingly popular. Abbreviations are commonplace, mostly marked with an overline and/or superscript. In computational neuroscience, an overline is used to indicate the 'maximal' conductances in Hodgkin-Huxley models. Long vowels are marked with an overline. An active low signal is designated by an overline, e.g. , representing logical negation. The OpenType math table allows to add this overline following the radical symbol. The overline station building was removed during the late 1990s. In mathematics, an overline can be used as a vinculum. Overline Gaming has released an arcade joystick attachment, named The Shaft.