"... a group of us have been studying ways to make sense of large amounts of language data generated by people on the ground in Libya. ... You won't be surprised when I tell you what event coincides with the most obvious peak in positive emotion as well as in volume of tweet traffic: Gaddafi's death. Specifically, the vertical dashed black line marks the time when news of Gadaffi's capture and death were first made public."
Their report, Evolution of Sentiment in the Libyan Revolution, is here (PDF): https://webspace.utexas.edu/dib97/Libya-report-10-30-11.pdf
