Scientists divided on new research into Alzheimer's: Correction

In an article on research into Alzheimer's disease, published on 5 November, Professor Bob Williams of Oxford University was quoted as saying that 'his own data suggests that the nuclear microscope is sensitive down to a level of about 60 parts per million, and not the 15 ppm claimed'. He has asked us to point out that the 60 ppm figure referred to one sample and the actual sensitivity is 15 ppm.