CLSA Americas LLC, the U.S. brokerage owned by China’s Citic Group Corp., shut down its equity-research operations Monday. “It is with a heavy heart that I tell you that as of today my client CLSA Americas is no longer open for business,” Melissa Sheer, a spokeswoman for the firm at Kent Place Communications, wrote in an e-mail, referencing the U.S. arm of Hong-Kong based CLSA Ltd. “As such, Equity Research is completely shut down in the U.S.” CLSA asked its 1,500 workers globally in September to take as many as 10 days of unpaid leave through March as it sought ways to cut costs.