Scientists have captured an image of the Aids virus in a biological handshake with the immune cells it attacks, and said on Wednesday they hope this can help lead to a better vaccine against the incurable disease. They pinpointed a place on the outside of the human immunodeficiency virus that could be vulnerable to antibodies that could block it from infecting human cells.

Scientists have found a way to use the cotton plant, long a source of fibre for clothing but inedible by humans, to feed potentially half a billion people a year. Plant biotechnologist Keerti Rathore and colleagues reported on Monday they have genetically altered the plant to reduce the levels of the toxic chemical gossypol.

Initial tests of air samples taken by United States planes near North Korea found no evidence of radiation, but the US is not ready to declare that Pyongyang did not detonate a nuclear device, a US government intelligence official said on Friday. Monday’s announcement by North Korea that it had tested a nuclear bomb sharply escalated world concerns.