Championship - Demel joins West Ham United
In a deal finalised minutes before the European summer transfer window closed on Wednesday, the French-born Demel joins relegated West Ham after spending the last 10 years in the Bundesliga with Borussia Dortmund and Hamburg.
The 30-year-old, who had a brief unsuccessful spell at Arsenal in 2000, can play in any position at the back but was not part of Hamburg coach Michael Oenning's plans for this season and had been training with the reserves.
The out-of-favour midfielder moved to Upton Park hours after Scott Parker made a £5million switch in the opposite direction.
Bentley was joined at Upton Park by Arsenal midfielder Henri Lansbury on an initial season-long loan.
England Under-21 international Lansbury wants regular first-team football having failed to make the breakthrough with Arsenal.
The 21-year-old, who has represented England at Under-19, 20 and 21 level, has penned a three-year deal.
Stanislas struggled with a hernia problem in 2010/11 and he has made just two appearances this season - scoring in the Carling Cup defeat to Aldershot at Upton Park.
Meanwhile Swindon manager Paolo Di Canio raided his former club to sign rookie midfielder Ahmed Abdulla on loan and Aldershot have signed defender Jordan Brown on loan.