Note 11 - Warrant Liability (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

Schedule of Derivative Instruments [Table Text Block]

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

	As of
	March 31,			December 31,
Assumption	2020			2019
Expected price volatility		191	%		184	%
Expected term (in years)		0.58			0.83
Risk-free interest rate		0.15	%		1.59	%
Dividend yield		0.00	%		0.00	%
Weighted-average fair value of warrants	$	0.46		$	0.49

	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
	March 31,			December 31,
Assumption	2020			2019
Expected price volatility		175.35	%		154.10	%
Expected term (in years)		4.88			5.13
Risk-free interest rate		0.37	%		1.70	%
Dividend yield		0.00	%		0.00	%
Weighted-average fair value of warrants	$	0.56		$	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
	March 31,			December 31,
Assumption	2020			2019
Expected price volatility		179.77	%		159.94	%
Expected term (in years)		4.36			4.61
Risk-free interest rate		0.34	%		1.69	%
Dividend yield		0.00	%		0.00	%
Weighted-average fair value of warrants	$	0.55		$	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
	March 31,			December 31,
Assumption	2020			2019
Expected price volatility		175.35	%		154.10	%
Expected term (in years)		4.88			5.13
Risk-free interest rate		0.37	%		1.70	%
Dividend yield		0.00	%		0.00	%
Weighted-average fair value of warrants	$	0.56		$	0.57

Class of Warrant or Right [Table Text Block]

	Shares		Warrant
			Liability
Warrant liability - current
October 2015 Warrants		38	$	17
		38	$	17
Warrant liability – non-current
2019 Domestic Warrants		4,199	$	2,339
2019 Foreign Warrants		2,700		1,504
2019 Ladenburg Warrants		168		92
		7,067	$	3,935