Note 6 - Embedded Derivatives and Derivative Warrant Liabilities (Tables)

3 Months Ended

Mar. 31, 2018

Schedule of Assumptions Used [Table Text Block]

	March 31,			December 31,
	2018			2017
Stock price	$	0.46			0.59
Conversion Rate per $1,000		1,358.90			1,358.90
Conversion Price	$	0.74		$	0.74
Maturity date	March 15, 2020			March 15, 2020
Risk-free interest rate		2.24	%		1.89	%
Estimated stock volatility		75	%		75	%
Estimated credit spread		28	%		28	%

Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]

	Issuance Date	Expiration Date	Exercise Price as of March 31, 2018			Shares Underlying Warrants on Issuance Date		Shares Issued upon Warrant Exercises as of March 31, 2018		Shares Underlying Warrants Outstanding as of March 31, 2018 (4)
2013 Warrants	12/16/2013	12/16/2018	$	8.99			71,013		15,239		55,774
2014 Warrants	08/05/2014	08/05/2019	$	6.83			50,000		30,538		19,462
Series A Warrants	02/03/2015	02/03/2020	$	0.68			110,833		99,416		11,417
Series B Warrants	02/03/2015	08/03/2015		-	(1)		110,833		110,833		-
Series C Warrants	05/19/2015	05/19/2020	$	5.50			21,500		-		21,500
Series D Warrants	12/11/2015	12/11/2020	$	2.00			502,500		501,570		930
Series E Warrants	12/11/2015	12/11/2020		-	(1)		400,000		400,000		-
Series F Warrants	04/01/2016	04/01/2021	$	2.00			514,644		233,857		280,787
Series G Warrants	04/01/2016	04/01/2017		-	(1)		328,571		328,571		-
Series H Warrants	04/01/2016	10/01/2016		-	(1)		1,029,286		1,029,286		-
Series I Warrants	09/13/2016	09/13/2021	$	11.00			712,503		-		712,503
Series J Warrants	09/13/2016	09/13/2017		-	(1)		185,000		185,000		-
Series K Warrants	02/17/2017	2/17/2022	$	0.60			6,250,000		160,000		6,090,000
Series L Warrants	02/17/2017	02/17/2018		-	(1)		570,000		570,000		-
Series M-A Warrants	02/17/2017	11/17/2017		-	(1), (2)		2,305,000		1,485,000		-
Series M-B Warrants	02/17/2017	11/17/2017		-	(1), (3)		3,945,000		3,945,000		-
							17,106,683		9,094,310		7,192,373

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details