There's never a shortage of losers in the stock market. 

Let's take a closer look at five of this past week's biggest sinkers.

Company

May 18 Weekly Loss My Watchlist
Patriot Coal (NYSE: PCX) $3.29 (34%) Add
SmartHeat (Nasdaq: HEAT) $3.73 (32%) Add
Cellcom Israel (NYSE: CEL) $8.10 (29%) Add
Yingli Green Energy (NYSE: YGE) $2.52 (29%) Add
American Science & Engineering (Nasdaq: ASEI) $48.79 (28%) Add

Source: Barron's.

Patriot Coal was the biggest loser on the New York Stock Exchange, losing more than a third of its value after a weak forecast forced Standard & Poor's to downgrade the company's credit rating on liquidity concerns.

SmartHeat felt the heat after posting uninspiring quarterly results. The Chinese clean energy specialist announced a widening deficit on a 15% decline in revenue. 

Cellcom Israel took a hit after posting a 43% decline in quarterly earnings. In another piece of bad news for Israeli's largest wireless carrier, the stock will be booted from MSCI's Israel Index after shedding more than two-thirds of its value over the past year.

Yingli Green Energy joined many other solar companies on the way down after the U.S. Commerce Department stepped up its efforts regarding anti-dumping tariffs.

Finally, American Science & Engineering fell woefully short of Wall Street expectations in its latest quarter. The provider of X-ray inspection equipment posted a profit of $0.15 a share on $39.8 million. Analysts were banking on net income of $0.83 a share on $60.7 million in revenue. You don't need to X-ray those results to know that there's something wrong.

Ready for a bounce
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Motley Fool newsletter services have recommended buying shares of American Science & Engineering. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.

Longtime Fool contributor Rick Munarriz calls them as he sees them. He does not own shares in any of the stocks in this story. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.