Warrants (Tables)

9 Months Ended

Sep. 30, 2013

Number of Warrants Outstanding

The number of warrants outstanding at September 30, 2013 and December 31, 2012 were as follows:

	September 30, 2013		December 31, 2012
Liability-classified warrants		8,050,709		8,050,709
Equity-classified warrants		2,341,678		3,146,745
Total warrants		10,392,387		11,197,454

Assumptions Used in Binomial and Monte Carlo Valuation Model

The following assumptions were used in the Binomial/Monte Carlo valuation model at September 30, 2013 and 2012:

	September 30, 2013	September 30, 2012
Risk-free interest rate	0.10%	0.23%
Expected life in years	1.19	2.19
Expected volatility	75%	70%
Expected dividend yield	0	0
Steps per year	13	12

Warrant Exercises

During the nine months ended September 30, 2013, warrant exercises were as follows:

(in thousands, except share data)	Equity Warrants		Liability Warrants		Common Stock Issued		Liability Reclassed to Equity		Cash Received
Cash exercises		98,359		—		98,359	$	—	$	201
Cashless exercises		—		—		—		—		—
		98,359		—		98,359	$	—	$	201

During the nine months ended September 30, 2012, warrant exercises were as follows:

(in thousands, except share data)	Equity Warrants		Liability Warrants		Common Stock Issued		Liability Reclassed to Equity		Cash Received
Cash exercises		161,639		—		161,639	$	—	$	330
Cashless exercises		24,658		373,617		98,021		412		—
		186,297		373,617		259,660	$	412	$	330