URS Corp (NYSE:URS), Whiting Petroleum Corp (NYSE:WLL) and Turtle Beach Corp (NASDAQ:HEAR) are having a strong start to the week and are today’s biggest gainers midday. The losers are Harmonic Inc (NASDAQ:HLIT), Uniqure NV (NASDAQ:QURE) and Allied Nevada Gold Corp. (NYSEMKT:ANV).

URS, Whiting Petroleum

URS, WLL Surge on Merger News

Up +10.8%, today’s top midday gainer is URS Corp (NYSE:URS), a provider of engineering, construction and technical services. Over the weekend, news broke that the company is to be bought by AECOM Technology Corp (NYSE:ACM) in a deal worth $4 billion. David Einhorn initiated a position in URS during the second quarter of 2013 and increased his allocation in both Q4 2013 and Q1 2014. Ray Dalio has a small allocation – just 5,000 shares – in URS as well.

Whiting Petroleum Corp (NYSE:WLL) also got a boost off of weekend merger news, its price up +7.5% midday. The John Paulson and Ray Dalio pick said on Sunday that it will buy Kodiak Oil & Gas Corporation (NYSE:KOG) – also a Paulson holding – for $3.8 billion in stock.

Turtle Beach Corp (NASDAQ:HEAR) takes the last spot on today’s list of midday gainers, its price climbing +7.14%. A new Q1 pick for billionaire investor George Soros, the company has gained +5.93% over the past month.

Harmonic Inc. Dives After Disappointing on Results

Harmonic Inc (NASDAQ:HLIT) posted a loss of -10.66% midday today after announcing preliminary second quarter results. The video infrastructure technologist missed the mark on per-share earnings and revenue and lowered its Q3 guidance as well.

Farallon Capital holding Uniqure NV (NASDAQ:QURE) dipped -7.32% today. The biopharmaceutical firm is down -14.99% YTD, though its price has climbed +12.81% over the last month.

Allied Nevada Gold Corp. (NYSEMKT:ANV) is the day’s third-biggest loser midday, its price declining -6.12%. A long-time holding of billionaire investor John Paulson, ANV took a hit today as August gold futures fell 2.2%. The gold and silver producer is still up +3.1% in 2014.