Rating activity turned net positive, with upgrades at double the number of downgrades (excluding transitions to default). Speculative-grade-rated issuers dominated this week’s rating activity, accounting for all downgrades and all but one upgrade. Upgrades included a rising star--the second this year--Castlelake Aviation Ltd., an aircraft leasing company, following its acquisition by Avolon Holdings Ltd. (BBB-). On the downside, there were three defaults last week, all due to distressed exchanges. Two defaults were on U.S.-based issuers (Aimbridge Acquisition Co. Inc., Physician Partners LLC) and one on an Irish issuer (Trinseo PLC).