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China wants greater global restrictions on the drug ketamine, where it is used as a club drug, leading in extreme cases to serious problems such as kidney failure, and even bladder removal. But ketamine also has perfectly legitimate uses as an anaesthetic all around the world, and low income countries in particular are reliant on it. Dr Bisola Onajin-Obembe, the President of the Nigerian Society of Anaesthetists, talks to Claudia Hammond about the consequences to surgery in her country if ketamine becomes a controlled substance.

Tracking Hannibal
A little over 2,200 years ago, Carthaginian general Hannibal Barca infamously led a huge army of elephants and horses across the Alps, almost to the gates of Rome. It has been celebrated as one of the most audacious military campaigns in history, but his exact route has always been subject to debate. This week further results from a consortium of disparate scientists have been published, supporting their preferred route taken by the grand army. Microbiologist Chris Allen from Queen's University Belfast talks Adam Rutherford through the analysis of animal faeces, which mark the passage of thousands of animals.

The Man Who Knew Infinity
A new film about the untrained Indian maths genius Srinivasa Ramanujan and his relationship with the Cambridge mathematician, G H Hardy, is about to be released worldwide. Ania Lichtarowicz discusses his life and work with Fields Medal winner Professor Manjul Bhargava of Princeton University.

Coral Bleaching
The Great Barrier Reef in Australia is the largest natural living structure on earth and home to more than one thousand five hundred species of fish. But rising sea temperatures and this year’s powerful El Niño have caused the worst mass bleaching event the reef has ever seen. A recent survey of its northern and most pristine section found that 95% of the top corals are now severely bleached. Scientists are still trying to find out where the south boundary of the bleaching even is. Laura Hampton is on Lizard Island, a research station two hundred kilometres north of Cairns, to see first-hand how bad the situation really is.

The Next Einstein
Will Einstein’s successors be African? It is very likely - and some of them will be women. Back in 2008, South African physicist Neil Turok gave a speech in which he declared his wish that the next Einstein would be from Africa. It was a rallying call for investment in maths and physics research in Africa. The ‘Next Einstein’ slogan became a mission for the organisation Neil Turok had founded to bring Africa into the global scientific community - through investment in maths and physics, the African Institute for Mathematical Sciences. That search for an African Einstein now has some results, with 15 ‘Next Einstein fellows’ and 54 ‘Next Einstein Ambassadors’. These are young African scientists, often leaders in their fields, working and studying in Africa. Julian Siddle reports from the ‘Next Einstein Forum’ – a meeting held in March 2016 in Senegal which celebrated the Next Einstein Fellows.

Sweeteners vs. Sugar
Are low-calorie sweeteners the guilt-free way to allow ourselves foods that taste sweet? Some argue that they help us to cut calories and lose weight. But others insist they do just the opposite. James Gallagher has been looking at the evidence with the help of Susan Swithers, Professor of Psychological Sciences at Purdue University in the US, and Peter Rogers, Professor of Biological Psychology at the University of Bristol in the UK.

(Photo caption: A man wounded by gunshot is undergoing surgery © Sia Kambou/AFP/Getty Images)

The Science Hour was presented by Claudia Hammond with comments from ´óÏó´«Ã½ Science reporter Jonathan Webb on an expedition to drill into the Chicxulub Crater off the coast of Mexico and how sugars are made in space.

Editor: Deborah Cohen