Assumptions used to value the options granted and warrants issued using the Black-Scholes option pricing model (Details) - $ / shares	Jun. 30, 2015	Dec. 31, 2014
Series E and G
Stock price volatility	111.60%	0.00%
Risk-free rate of return	4.26%	0.00%
Annual dividend yield	0.00%	0.00%
Expected life (in years)	0.5	0
Series F and H
Stock price volatility	111.60%	0.00%
Risk-free rate of return	4.26%	0.00%
Annual dividend yield	0.00%	0.00%
Expected life (in years)	3.0	0
Mentor warrants in years	23.00	23.4
Weighted average outstanding warrant exercise price per share	$ 1.87	$ 1.84