Note 3 - Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Fair Value, by Balance Sheet Grouping [Table Text Block]

	As of December 31, 2019
	Level 1		Level 2		Level 3		Total
Assets:
Cash and cash equivalents	$	—	$	—	$	—	$	—
Short-term investments		—		452,301		—		452,301
Total assets	$	—	$	452,301	$	—	$	452,301
Liabilities:
Accrued warrant liability	$	—	$	—	$	6,414	$	6,414

	As of December 31, 2018
	Level 1		Level 2		Level 3		Total
Assets:
Cash and cash equivalents	$	1,130	$	—	$	—	$	1,130
Short-term investments		—		503,810		—		503,810
Total assets	$	1,130	$	503,810	$	—	$	504,940
Liabilities:
Accrued warrant liability	$	—	$	—	$	78,637	$	78,637

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

	Year Ended December 31, 2019
Beginning Balance	$	78,637
Total (gains) or losses, realized and unrealized, included in earnings (1)		(72,223	)
Balance at December 31, 2019	$	6,414

	Year Ended December 31, 2018
Beginning Balance	$	1,041,455
Total (gains) or losses, realized and unrealized, included in earnings (1)		(962,818	)
Balance at December 31, 2018	$	78,637

Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques [Table Text Block]

	December 31, 2019
Description	Fair Value		Valuation Technique	Unobservable Input	Range in years
Accrued warrant liability	$	6,414	Black-scholes pricing model	Expected term		1.04-1.60

Warrant [Member]

Notes Tables

Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]

	December 31,
	2019			2018
Stock Price	$	0.60		$	1.01
Exercise Price	$	3.64 - 20.40		$	3.64 - 24.40
Term in years		1.04-1.60			0.04 - 2.60
Volatility		84.59 - 98.24	%		88.07 - 108.18	%
Annual rate of quarterly dividends		0	%		0	%
Discount rate- bond equivalent yield		1.58 - 1.59	%		0.12 - 2.48	%