Comfortably beating analysts' forecasts, Goldman Sachs earned second-quarter net profits of $3.44 billion, or $4.93 a share, the bank announced on Tuesday.The results continue a robust turnaround for the firm since it rode out the final tumultuous months of last year with the aid of a federal rescue. They come just one month after it paid back its $10 billion in federal aid.Goldman's profit was lifted by record quarterly revenues of $6.8 billion in its fixed income, currency and commodities unit, where mortgage and other credit instruments are traded, the bank said in a statement. This business has performed well since the bank has taken on greater levels of risk since the end of last year.Its equity underwriting business also generated record net revenues, worth $736 billion in the second quarter, it said, as Goldman benefited among other things from a rush by other troubled banks to issue shares and raise their capital levels."While markets remain fragile and we recognize the challenges the broader economy faces, our second-quarter results reflected the combination of improving financial market conditions and a deep and diverse client franchise," Lloyd C. Blankfein, Goldman's chief executive, said in a news release. Over all, Goldman's net revenues were $13.76 billion, compared with $9.43 billion in the first quarter.