Dix wins 200m ahead of Gay
Sprinter Tyson Gay finished second in his first 200m of the year at Eugene's Diamond League meeting in Oregon.
American Walter Dix clocked 19.72 seconds to win, while Gay, returning from a hamstring injury, was 0.04 secs behind, with Ryan Bailey in third.
In the 110m hurdles, American David Oliver ran within 0.03 secs of Dayron Robles' world record when timing 12.90.
In doing so Oliver, the 2008 Olympic bronze medallist, equalled Dominique Arnold's all-time third quickest mark.
Ryan Wilson (13.16 secs) and Ronnie Ash (13.19 secs) completed an American one-two-three.
In the women's 100m Jamaican Veronica Campbell-Brown ran the fastest time in the world this year and a personal best of 10.78 seconds, ahead of her compatriot Shelly-Ann Fraser (10.82 secs).
Carmelita Jeter, who remains top of the league over the distance by a point, was third (10.83 secs).
Two-time world champion Abubaker Kaki ran the fifth fastest 1,000m time in history, and the fastest this year, but failed in his world record attempt.
Felix wins close 400m in Eugene
The Sudanese clocked two minutes 13.62 secs, well outside Kenyan Noah Ngeny's 11-year-old 2:11.96 mark.
Kenya's Boaz Lalang was second in 2:14.83, with American Nick Symmonds third (2:16.35).
African athletes, and in particular Ethiopians, were to the fore in an extremely fast men's 5,000m.
Tariku Bekele powered to victory in 12:58.93, while second-placed Dejen Gebremeskel went under 13 minutes for the first time with 12:59.30, with Imane Merga (13:00.18.) completing Ethiopia's clean-sweep in third.
Mariya Savinova of Russia ran 1:57.56 - the fastest time in the world this year - winning the women's 800m ahead of second and third-placed Kenyans Nancy Jebet Langat (1:57.75) and Janeth Jepkosgei (1:57.84).
Campbell-Brown impresses with 100m win
In the women's 3,000m steeplechase Briton Barbara Parker, who claimed the UK national title over the distance in Birmingham last Sunday, ran a personal best 9:35.17 in a race won by Kenya's 2009 world bronze medallist Milcah Chemos Cheiywa (9:26.70).
The Prefontaine Classic at Hayward Field in Eugene was the sixth stop on the 14-meet IAAF Diamond League series which moves to Lausanne in Switzerland on Thursday before next Sunday's meeting at Gateshead International Stadium on 11 July.