The hollowing out of Canada's tech sector continues with the sale of two Montreal-based companies to US buyers. Both are mid-sized companies — the type experts say are crucial to developing a mature and sustainable technology sector with global reach. 20-20 Technologies has been purchased by Vector Capital Corp, San Francisco, for $77 million. The developer of specialized computer-aided design software for the furniture design and interior design manufacturing chain was founded in 1987 and has approximately 500 employees. Last month, Miranda Technologies Inc was purchased by Belden Inc, St Louis MO for $35 million. Miranda is a developer and manufacturer of professional digital video/audio interfaces and advanced display products and hardware for broadcast post-production facilities. Ottawa-based Branham Group — a market research firm for the information and communications technology industry — reports that 45 Canadian tech firms were sold to foreign interests in 2011, up from 32 in 2010. Veteran technology executive and entrepreneur, Dr Adam Chowaniec, has flagged the loss of mid-size tech firms as the greatest challenge facing the tech sector (R$, January 20/12)....