What's better than momentum? Mo' momentum. Let's take a closer look at five of this past week's biggest scorchers.

Company

May 24

Weekly Gain

James River Coal (NASDAQOTH:JRCCQ)

$3.11

27%

MannKind (NASDAQ:MNKD)

$6.55

26%

FX Energy (NASDAQ:FXEN)

$4.26

23%

AcelRX Pharmaceuticals (NASDAQ:ACRX)

$7.86

18%

ServiceSource (NASDAQ:SREV)

$7.73

15%

Source: Barron's.

Let's start with James River Coal. Shares of the coal miner continue to rally after a financing deal that was announced on Friday of the prior week. James River is swapping out $243.4 million in convertible notes for $123.3 million in new debt.

It's not a perfect deal, but that can be expected from a convertible note swap that slashes debt in half. The new 10% interest rate is sharply higher than the notes being replaced. The conversion prices are dropping sharply. The new notes are secured by a subsidiary of the company. However, it ultimately pushes out some of the debt from 2015 to 2018, giving James River Coal more time to bet on a coal-industry recovery.

MannKind moved 17% higher a week earlier after analysts at MLV & Co. initiated coverage with a "buy" rating. There was no news to push the stock even higher this week, but clearly, speculative biotech investors want to make sure that they're long ahead of the summertime clinical trial data release for its promising inhalable insulin treatment.

FX Energy hit a gusher on an upbeat report of a production test at its Tuchola-3K well. The oil and gas explorer is seeing healthy gas flow at the Polish well, and additional seismic testing and drilling will verify the reserves before production begins at the site.

AcelRx moved higher after upbeat data from a late-stage clinical trial. The biotech revealed that its pain-management system met expectations in providing relief of post-operative pain when pitted against a placebo.

ServiceSource moved higher after a filing revealed that a director, Barry Reynolds, bought 115,000 more shares in the company at an average price of $6.81 apiece. Even though Reynolds has been a frequent buyer over the past year -- at much higher prices than where ServiceSource trades now -- Mr. Market always perceives insider buying as a positive.

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