FlexShares, the Chicago-based exchange-traded funds unit of Northern Trust, expanded its product line-up with the recent launch of the passively-managed FlexShares Disciplined Duration MBS Index Fund (MBSD). Though FlexShares has a wide array of products in the traditional equity and fixed-income segments, MBSD is the first mortgage-backed securities product from the company. The new fund tracks the BofA Merrill Lynch …