Note 11 - Warrant Liability (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Derivative Instruments [Table Text Block]

	As of
	December 31,			December 31,
Assumption	2019			2018
Expected price volatility		115	%		77	%
Expected term (in years)		0.18			1.18
Risk-free interest rate		1.52	%		2.60	%
Dividend yield		0.00	%		0.00	%
Weighted-average fair value of warrants	$	0.44		$	0.29

	As of
	December 31,
Assumption	2018
Expected price volatility		77	%
Expected term (in years)		1.18
Risk-free interest rate		2.60	%
Dividend yield		0.00	%
Weighted-average fair value of warrants	$	0.24

	As of
	December 31,
Assumption	2018
Expected price volatility		77	%
Expected term (in years)		1.18
Risk-free interest rate		2.60	%
Dividend yield		0.00	%
Weighted-average fair value of warrants	$	0.29

	As of
	December 31,			December 31,
Assumption	2019			2018
Expected price volatility		184	%		73	%
Expected term (in years)		0.83			1.83
Risk-free interest rate		1.59	%		2.51	%
Dividend yield		0.00	%		0.00	%
Weighted-average fair value of warrants	$	0.49		$	0.38

	As of
	August 13,
Assumption	2019
Expected price volatility		149.29	%
Expected term (in years)		5.50
Risk-free interest rate		1.58	%
Dividend yield		0.00	%
Weighted-average fair value of warrants	$	0.75

	As of
	December 31,
Assumption	2019
Expected price volatility		154.10	%
Expected term (in years)		5.13
Risk-free interest rate		1.70	%
Dividend yield		0.00	%
Weighted-average fair value of warrants	$	0.57

	As of
	August 13,
Assumption	2019
Expected price volatility		155.19	%
Expected term (in years)		5.00
Risk-free interest rate		1.57	%
Dividend yield		0.00	%
Weighted-average fair value of warrants	$	0.74

	As of
	December 31,
Assumption	2019
Expected price volatility		159.94	%
Expected term (in years)		4.61
Risk-free interest rate		1.69	%
Dividend yield		0.00	%
Weighted-average fair value of warrants	$	0.57

	As of
	August 13,
Assumption	2019
Expected price volatility		149.29	%
Expected term (in years)		5.50
Risk-free interest rate		1.58	%
Dividend yield		0.00	%
Weighted-average fair value of warrants	$	0.75

	As of
	December 31,
Assumption	2019
Expected price volatility		154.10	%
Expected term (in years)		5.13
Risk-free interest rate		1.70	%
Dividend yield		0.00	%
Weighted-average fair value of warrants	$	0.57

Class of Warrant or Right [Table Text Block]

			Warrant
( shares and dollars in thousands )	Shares		Liability
Warrant liability - current
July 2011 Warrants		35	$	15
October 2015 Warrants		38		19
		73	$	34
Warrant liability – non-current
2019 Domestic Warrants		4,199	$	2,410
2019 Foreign Warrants		2,700		1,550
2019 Ladenburg Warrants		168		95
		7,067	$	4,055