Stem cell research in the U.S. has been on a roller coaster ride the past few weeks.

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Since September 11, the day of the disaster, the rental car companies have gone on a roller coaster ride.

CNN: Car rentals, like airlines, hard hit after attacks

If investors allow their emotions to take them on a roller coaster ride, they can quickly become their own worst enemy.

FORBES: Understand The Cycle Of Market Emotions To Make Better Investing Decisions

As we start the last week of March, seasonal factors are likely to create a very volatile stock market through April, taking investors on a roller coaster ride.

FORBES: Stock Market Volatility In April Is Coming, Here's Why

Like many country funds, this one has been on a roller-coaster ride since its inception in 1981, but over the long haul it has rewarded its believers.

FORBES: South-of-the-border buys

Since then, they have been on a roller-coaster ride.

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Intuitive Surgical has had a roller coaster ride since we initiated coverage on the robotic surgical systems developer last December.

FORBES: How Intuitive Surgical Can Carve Its Way To $610

For Frankel, offering millions of strangers a front row seat on the often messy and exhausting roller coaster ride that is her life, proved the ticket to building her multi-million dollar business empire.

FORBES: Bethenny Frankel And The One Question She's Never Been Asked: 'Are You Happy?'