STOCKHOLDERS' EQUITY (Tables)

12 Months Ended

Dec. 31, 2018

Stockholders' Equity:

Schedule of warrant activity

Summary of our Warrant activity during the year ended December 31, 2018:

	Number of Shares Under Warrants			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years		Aggregate Intrinsic Value
Balance at December 31, 2017		3,115,905		$	2.58		1.8	$	11,348,273
Granted		175,000		$	5.16
Exercised		—
Expired		(283,334	)	$	2.01
Cancelled/Forfeited		—
Balance at December 31, 2018		3,007,571		$	2.78		1.58	$	4,826,403
Vested and Exercisable at December 31, 2018		2,963,818		$	2.75		1.54	$	4,826,403
Unvested at December 31, 2018		43,753		$	5.16		4.21	$	0

Schedule of assumptions used in the Black-Scholes Model of warrants issued

The weighted average fair value per share of warrants issued and the assumptions used in the Black-Scholes Model during the years ended December 31, 2018, 2017, and 2016 are set forth in the table below.

	2018			2017			2016
Weighted average exercise price	$	5.16		$	6.83		$	7.90
Weighted average grant date fair value	$	2.79		$	3.67		$	4.78
Risk-free interest rate		2.36	%		1.47	%		1.04-1.28	%
Volatility		62.12	%		63.24	%		74.10-74.15	%
Term (in years)		5			5			5
Dividend yield		0.00	%		0.00	%		0.00	%

Schedule of assumptions used in the Black-Scholes Model of stock options

The ranges of assumptions used in the Black-Scholes Model during the years ended December 31, 2018, 2017, and 2016 are set forth in the table below.

	2018			2017			2016
Weighted average exercise price	$	5.45		$	6.60		$	6.22
Weighted average grant date fair value	$	3.24		$	3.82		$	3.94
Risk-free interest rate		2.38-2.89	%		1.84-2.05	%		1.13-1.90	%
Volatility		59.45-64.04	%		61.56-64.25	%		70.26-73.34	%
Term (in years)		5.1-6.25			5.5-6.25			5.5-6.25
Dividend yield		0.00	%		0.00	%		0.00	%

Schedule of activity of 2009 and 2012 Plans

A summary of activity under the 2009 and 2012 Plans and related information during the year ended December 31, 2018 is as follows:

	Number of Shares Under Warrants			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years		Aggregate Intrinsic Value
Balance at December 31, 2017		23,365,225		$	3.78		5.13	$	64,664,821
Granted		3,264,500		$	5.45
Exercised		(5,454,526	)	$	0.31			$	27,534,623
Expired		(25,000	)	$	7.76
Cancelled/Forfeited		(277,375	)	$	5.47
Balance at December 31, 2018		20,872,824		$	4.93		5.94	$	12,239,876
Vested and Exercisable at December 31, 2018		16,068,991		$	4.61		5.09	$	12,239,876
Unvested at December 31, 2018		4,803,833		$	5.99		8.8	$	0