Aberdeen beat Ross County 3-1 to move back into second place in the Scottish Premiership, profiting from Hearts' 2-2 draw at Motherwell.
Mixu Paatelainen says he needs "stronger characters" in his Dundee United squad after they suffered a fourth successive loss on Saturday.
Former Liverpool forward Florent Sinama Pongolle has agreed a six-month contract with Dundee United.
Dundee United have signed former West Ham defender Guy Demel for the remainder of the season.
Hearts failed to close the gap on Scottish Premiership leaders Celtic after drawing 1-1 with Dundee, as Dundee United lost again.
Mixu Paatelainen remains confident Dundee United can stay up despite them sliding six points adrift.
Gavin Gunning has returned to Dundee United as Mixu Paatelainen's first signing since he took charge of the club.
Mario Bilate has left Dundee United by mutual consent after suffering a season-ending injury earlier this year.
More of the games that matter on Sky Sports
A Day Pass for only £6.99. No contract
All the gossip from the morning editions
Listen to the latest Premier League news
Who is your player of November?