Welcome to this forum and thank you for your question. This logic negation symbol meaning “not” is not listed in the Nemeth Code. You may substituted the tilde for this symbol (the tilde also means “not” in logic) as long as the tilde does not appear elsewhere in this transcription. You must explain the substitution in a transcriber’s note. If this is not an option, devise a symbol. Explain in a transcriber’s note and list the transcriber-devised symbol on the special symbols page.