Stocks calm; Yellen in the hot seat; Trouble for Toshiba and Samsung

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1. Roses are red, markets are too: There's a fair bit of red in the stock markets right now, but losses aren't so steep that they'll break your heart.

U.S. stock futures are flat.

Most Asian markets closed in negative territory. Stocks are mixed in Europe.

The lackluster action comes after U.S. stocks hit fresh record highs on Monday.

The Dow Jones industrial average and S&P 500 have both rallied by between 3% to 4% since the start of the year. The Nasdaq is up a whopping 7%.

Shares in iPhone maker Apple (AAPL) are trading near their highest level ever.

2. Janet Yellen in the hot seat: Federal Reserve chief Janet Yellen is giving semi-annual testimony to the U.S. Senate at 10 a.m. ET.

The Fed is considered the driving force behind the multi-year bull market rally in stocks since the Great Recession.

What Yellen says about the timing and magnitude of future interest rate hikes could keep the rally going full steam ahead -- or stop it dead in its tracks.

The Fed last raised rates in December.

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3. Stocks to watch -- GM, Credit Suisse, Rolls-Royce: Shares in General Motors (GM) are getting a 4% boost premarket after automaker PSA Group said it's considering buying GM's Opel business unit in Europe.

Shares in Credit Suisse (CS) are rising by about 3% after the European bank said it would cut up to 6,500 jobs. It also reported that it lost 2.4 billion Swiss francs ($2.4 billion) in 2016.

Rolls-Royce (RYCEY)is having a tough day in London trading. Shares in the aircraft engine-maker fell by about 4% after the firm warned that pre-tax profits in 2016 were down 49%.

The British engineering giant said in January that it reached settlements with authorities in the U.K., the U.S. and Brazil over bribery allegations. These large settlements contributed to the drop in profit.

4. Tech trouble: Toshiba's (TOSYY) chairman is stepping down as the firm revealed a $6.3 billion writedown at its troubled U.S. nuclear business.

The Japanese conglomerate missed its own deadline to report earnings earlier on Tuesday, sending shares down 8% in Tokyo.

Toshiba stock has lost about half its value since the company warned in December that it was expecting billion of dollars in nuclear-related losses.

In South Korea, prosecutors are again seeking an arrest warrant for the heir to the Samsung (SSNLF) business empire.

Lee Jae-yong, Samsung's de facto leader, has been under investigation as part of a huge political corruption scandal that has rocked South Korea.

Prosecutors are also seeking an arrest warrant for Samsung Electronics President Park Sang-jin.

A judge will decide whether the arrest warrants are valid.

5. Earnings and economics: Dr Pepper Snapple (DPS), Molson Coors (TAP), and T-Mobile (TMUS) are releasing earnings before the open Tuesday, while Caesars Entertainment (CZR) and Fossil (FOSL) plan to report earnings after the close.

On the economic front, new data shows the U.K. economy is experiencing higher inflation following its decision to leave the European Union.

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6. Coming this week:

Tuesday - Janet Yellen testifies before the U.S. Senate; T-Mobile (TMUS) earnings
Wednesday - Cisco (CSCO), PepsiCo (PEP), TripAdvisor (TRIP) and Kraft Heinz (KHC) earnings
Thursday - Labor secretary nominee Andrew Puzder has his Senate confirmation hearing; Wendy's (WEN) earnings
Friday - Campbell Soup (CPB) and Deere (DE) earnings; Wells Fargo (WFC) CEO expected to answer Senate's letter about its latest controversies