COMMON STOCK WARRANT LIABILITY (Tables)

6 Months Ended

Jun. 30, 2013

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Changes in Fair Value of Common Stock Warrant Liability

The following table presents changes in the fair value of the common stock warrant liability during the periods indicated:

	Three Months Ended June 30,				Six Months Ended June 30,
(Dollars in thousands)	2013		2012		2013		2012
Beginning balance	$	3,800	$	1,400	$	2,350	$	1,403
Change in fair value of common stock warrant liability		3,700		600		5,150		597
Ending balance	$	7,500	$	2,000	$	7,500	$	2,000

Summary of Assumptions Used to Estimate Fair Value of Common Stock Warrant Liability

The following table summarizes the assumptions used to estimate the fair value of the common stock warrant liability during the periods indicated:

	Three Months Ended June 30,						Six Months Ended June 30,
(Weighted averages)	2013			2012			2013			2012
Expected term (years)		5.2			7.6			5.9			7.7
Volatility		53.0	%		49.0	%		52.0	%		48.8	%
Risk-free rate		1.47	%		1.22	%		1.18	%		1.51	%
Exercise multiple		2.8			2.8			2.8			2.8
Fair value of Signature common stock	$	0.91		$	0.37		$	0.74		$	0.31
Exercise price	$	0.68		$	0.68		$	0.68		$	0.68