Dr Jim Gray, a Turing Award winner in 1998, and currently a technical fellow for Microsoft Research in San Francisco, is missing at sea.

Dr Gray, the first ever recipient of a PhD from Berkeley's Computer Science Department, was last seen sailing out to sea to scatter the ashes of his recently deceased mother.

The scientist was sailing towards the Farallon Islands, 43 kilometres off San Francisco, and was formally declared missing three days ago.

"He's a maverick," his daughter Heather told the San José Mercury News. "He's had close calls. It's just that it is so out of character for him to disappear, and in such calm weather. I really don't know what happened."

A huge air and sea search was launched but coast guard officials said that, after covering 40,000 square miles, they had found no trace of him or his 40ft yacht, Tenacious.

But when they proposed calling off the search, offers of help flooded in from Silicon Valley.

Google co-founder Sergey Brin and employees from Amazon called in to help, additional flights have been scheduled and Microsoft and Cingular Wireless have been analysing data on the last time his PDA was detected at 7:30pm on 28 January.

Dr Gray was one of the pioneers of database technology, writing much of the original SQL code.

He was awarded the Turing Prize in 1998, the industry's equivalent of the Nobel Prize, for his work on databases.

Dr Gray was currently developing the world's largest astronomy database, the Sloan Digital Sky Survey, which cross referenced astronomical databases.