Talk about the biggest improvement in world athletics. Nicholas Bett powered to victory in the men's 400m hurdles in 47.79sec at the World Championships in Beijing last night to increase Kenya's lead atop the medals table, aided by 800m winner David Rudisha.But Bett couldn't even win this race at the SA Open meet in Potchefstroom in early May, when he managed just 49.91. At the time his personal best was 49.03.Jean Verster noticed Bett labouring over every hurdle three months ago, his technique suggesting he was a steeplechaser rather than a hurdler."He could be good if he learned to hurdle," Verster commented on the athlete at the time.But Bett, 23, who broke 49sec for the first time in his career at the beginning of this month, wasn't just good last night - he was blessed with superhuman stamina.He outsprinted Russian Denis Kudryavtsev (48.05) and Jeffery Gibson (48.17) of Bahamas on the final straight.Fellow Kenyan Boniface Tumuti was fifth in 48.33.South Africa has been Africa's leading nation in the 400m hurdles for years, but not last night.The only South African athletes in action at the Bird's Nest on the day were Anaso Jobodwana and Akani Simbine, who both qualified for tonight's 200m semifinals.But South Africa's attention tonight will be on Wenda Nel and Wayde van Niekerk, who seek to land the country's first medals of this championship.Nel could be a dark horse in the women's 400m hurdles, while Van Niekerk competes in what has the potential to be the most competitive men's 400m race in history.Jobodwana, who made the 200m final at the last championships in 2013 and at the London Olympics the year before, won his heat comfortably in 20.22.Simbine advanced as a fastest loser after finishing fourth in his heat in a 20.23 personal best, which caught him by surprise."That was a shock," he said.Simbine, also a 100m semifinalist here, is not famous - not yet, anyhow - but he is known by the top sprinters in the world.American superstar Justin Gatlin diverted his march through the mixed zone just to fist-bump Simbine."We've been on the circuit for a while now," explained Simbine."Most of the 100m guys know each other well."US-based Jobodwana, who was disqualified from the 100m on Saturday night for a false start, has faded in the final 50m in some races this season, was optimistic for tonight, however."To come out of the heat the way I felt gave me a bit of confidence going into the semifinal," the sprinter said.Beijing scheduleToday (Wednesday evening):Women's pole vault, final (1pm)Men's javelin throw, final (1.05pm)Women's 200m, heats (1.15pm)Women's 400m hurdles, final (Wenda Nel - 2.10pm)Men's 200m, semifinals (Anaso Jobodwana and Akani Simbine - 2.30pm)Women's 3000m steeplechase, final (3pm)Men's 400m, final (Wayde van Niekerk - 3.25pm)Tomorrow (Thursday) morning:Men's discus, qualification groups A and B (Victor Hogan - 3.30am and 4.50am)Women's high jump, qualification (3.35am)Women's 5000m, heats (3.40am)Women's long jump, qualification (4.20am)Men's 1500m, heats (Johan Cronje - 4.35am)Women's 100m hurdles, heats (5.15am)..