Note 4 - Warrants (Tables)

6 Months Ended

Jun. 30, 2024

Notes Tables

Schedule of Warrants or Rights, Assumptions Used [Table Text Block]

	June 30, 2024	December 31, 2023
Risk-free interest rate	4.3% to 5.2%	3.8% to 5.4%
Volatility	87.9% to 94.9%	79.5% to 108.7%
Expected life (years)	0.6 to 4.5	0.3 to 5.0
Dividend yield	—%	—%

Schedule of Warrant Activity [Table Text Block]

	Number of Shares			Range of Warrant Exercise				Weighted Average		Weighted Average Remaining Contractual
	Under Warrant			Price per Share				Exercise Price		Life (Years)
Balance at January 1, 2024		1,082,895		$	9.60	$	157.50	$	24.32		5.1
Expired warrants		(75,909	)	$	99.00	$	99.00	$	99.00		—
Balance at June 30, 2024		1,006,986		$	9.60	$	94.50	$	—		4.4
Exercisable at June 30, 2024		1,006,986		$	9.60	$	94.50	$	15.31		4.4