KARACHI - The Pakistan Academy of Sciences (PAS) has conferred PAS gold medal on Prof Dr Khalid M Khan, a senior scientist of the International Centre for Chemical & Biological Sciences (ICCBS), Karachi University (KU), in recognition of his services in the field of chemistry. Spokesman to ICCBS, in a statement on Saturday, said that Dr Khan is considered one of the most senior scientists of the ICCBS.