Communities, knowledge creation, and information diffusion

NOTICE: this is the pre-print version of a work deposited in arXiv (arXiv:0909.2481v1 [physics.soc-ph]) and submitted to the Journal of Informetrics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in JOURNAL OF INFORMETRICS, [VOL 3, ISSUE 3, (2009)] DOI 10.1016/j.joi.2009.03.00