The 'black chair' stands ready in the centre of the Mastermind arena awaiting the presence of the 48 aspirants to the title 'Mastermind 1978', chosen from the many thousands of viewers who applied to take part in this year's series.The Open University at Milton Keynes is the venue for the first of these opening heats and the contenders are:Jean Robinson, nurse - life and works of W. S. GilbertAubrey Lawrence, assistant librarian - Britain between AD 350 and 600Jonathan Allum, civil servant - 20th-century British philosophyRaymond Fell, Detective Sergeant, New Scotland Yard - notable British poisoners