Brent oil prices slid in Asian trade on Tuesday as concern about a sluggish economy in China bringing down demand outweighed the impact of a blockade of oil production facilities in Libya.Brent crude futures were down 37 cents, or 0.48%, to $77.15 a barrel.US West Texas Intermediate crude, which did not have a Monday settlement because of the US Labor Day holiday, was 28 cents up from its Friday close of $73.55Source: Qatar News Agency