In the structured finance sector, FirstMac on Friday launched what will be the last mortgage-backed security deal that draws on the second round of funding from the Australian government.The structure appears designed to cater to a small number of private investors looking for short-term yield pick up on the first of the five tranches, for $188 million and with a weighted average life of 0.8 years.The Australian Office of Financial Management will no doubt be the investor in the second tranche covering $250 million of loans and with an average life of 3.5 years.A third tranche, for A$17 million, like the first two, carries a AAA credit rating. The fourth tranche, for A$14 million is rated AA- and even the equity tranche of $2 million carries a AA- rating from one of the agencies.FirstMac and its investment bankers expect to price the transaction on November 10.   On the subject of structured finance, the European Union has passed legislation requiring credit rating agencies to differentiate the ratings assigned to structured finance instruments from those assigned to other securities. The legislation will come into force before year end.