Prime Finance is Business Insider’s midday summary of the top stories of the past 24 hours.

The big news of the day, once again, is China.

China shut down its stock market for the second time in four days after a 7% meltdown in 15 minutes. It has since said that the so-called circuit-breaker rule that brought an early end to trading would be suspended.

The country also revealed that it burned $3.5 billion a day in December trying to manage the devaluation of the yuan.

On Wall Street, the path has been cleared for Morgan Stanley executive Colm Kelleher. The departure of Greg Fleming puts Kelleher – now the sole president at Morgan Stanley – in prime position to succeed CEO James Gorman.

Here’s the full letter Fleming sent to his Morgan Stanley team last night

In other news, Bill Gross thinks things are about to get so bad we’re all going to need a Xanax, George Soros thinks it is just like the 2008 financial crisis all over again, and Saudi Arabia’s state-owned oil behemoth could be coming to the public markets.

Oh, and Yahoo is prepping to cut 10% or more of its staff.

Here are the top Wall Street headlines at midday –

Passport Global’s head quant is leaving the hedge fund – Passport Global’s head quant, Tim Garry, is leaving the $4.4 billion San Francisco-based hedge fund, according to a letter to investors from the fund’s founder, John Burbank.

Morgan Stanley execs keep swapping jobs — and it says something important about the future of the firm – The strategy here is to bring wealth management closer together with the investment bank both culturally and from a business perspective.

Deutsche Bank won’t say what this chart means, but it doesn’t look good – “Given our desire to discuss today’s employment data and the proverb ‘a picture is worth a thousand words,’ we are deafeningly silent on what the below chart implies,” Deutsche Bank’s chief US economist, Joseph LaVorgna, said in a note.

A startup that wants to change the way we test for cancer just raised nearly $100 million – Guardant Health, a Redwood City-based cancer diagnostics company, said it’s completed a series D funding round led byOrbiMed.

This Tesla analyst has an incredibly out-there thesis about the company’s future – Tesla has a way of bringing out the creativity in Wall Street analysts.

Detroit is selling more cars than ever — but Wall Street doesn’t careWhat a time it is to be a major automaker. General Motors and Ford have just capped off the best year in the history of US auto sales.

HEDGE FUND: Here’s what’s going to happen at Yahoo – Yahoo is under pressure. Its shares have fallen by 35% over the past year, and shareholders are pushing for the company to split off its core business from a $30 billion investment in Alibaba Group.

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