Miami-based investment banking firm Cassel Salpeter & Co. released this week its quarterly review of technology investment activity, which highlights a recent cluster of initial public offerings amid a mostly stagnant year. The report covers the period between July 1 and September 30. It finds that a bulk of public offerings occurred during Q3 — five in September (Nutanix, Tabula Rasa Healthcare, The Trade Desk, Everbridge and Apptio) and Impinj in the previous month. The activity overwhelmed…