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Warrant Liability (Tables)

12 Months Ended

Dec. 31, 2012

Warrant Liability [Abstract]

Assumptions used for Black-Scholes option pricing model

The assumptions used for the Black-Scholes option pricing model are as follows:


		To Calculate Fair Value of Warrant Liability at December 31,
		2012				2011
Expected life (years)			1.4				2.4
Risk-free interest rate			0.2	%			0.3	%
Expected volatility			108.2	%			74.1	%
Expected dividend yield			0	%			0	%


		At December 31, 2012				At December 31, 2011				Change in Fair Value of Warrant Liability in Year 2012
Fair value of warrant liability		$	44,628			$	2,224			$	42,404

The assumptions used for the Black-Scholes option pricing model are as follows:


		To Calculate Fair Value of Warrant Liability at
		December 31, 2012				December 31, 2011
Expected life (years)			2.3				3.3
Risk-free interest rate			0.3	%			0.5	%
Expected volatility			94.5	%			90.8	%
Expected dividend yield			0	%			0	%


		At December 31, 2012				At December 31, 2011				Change in Fair Value of Warrant Liability in Year 2012
Fair value of warrant liability		$	63,340			$	28,971			$	34,369

Assumptions used for simulation model

The assumptions used for the Monte Carlo simulation model to value the outstanding Series A Warrants at December 31, 2012 are as follows:


Risk-free interest rate per year			0.5	%
Expected volatility per year			86.0	%
Expected dividend yield			0	%
Expected life (years)			4.0

Summary of changes in fair value of warrant liability

The following table is a summary of the changes in fair value of warrant liability for the Series A and Series B Warrants in 2012:


		Series A								Series B
		Number of Warrants				Fair value $				Number of Warrants				Fair value $
Balance at December 31, 2011			8,000,000			$	3,790,160				8,000,000			$	2,220,960
Add issued			2,700,000				1,714,436				—				—
Less exercised			(2,198,571	)			(3,340,155	)			(2,700,000	)			(1,095,802	)
Less expired			—				—				(5,300,000	)			—
Changes in fair value			—				6,992,956				—				(1,125,158	)

Balance at December 31, 2012			8,501,429			$	9,157,397				—			$	—

Summary of outstanding warrants and fair value of warrant liability

The following table is a summary of our outstanding warrants and fair value of our warrant liability as of December 31, 2012:


Warrants		Number Outstanding				Exercise Price ($) per share				Fair value
Warrants issued in 2008			1,034,483				23.00			$	44,628
Warrants issued in 2009			400,000				15.00				63,340
Series A Warrants			8,501,429				1.40				9,157,397

Total			9,935,912							$	9,265,365