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Note 9 - Share-based Compensation - Share-based Compensation Expense (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Allocated Share-based Compensation Expense | $ 554 | $ 1,584 | $ 3,152
SEED 2022 Share Incentive Plan [Member] |  |  |
Allocated Share-based Compensation Expense | 216 | 81 |
Research and Development Expense [Member] |  |  |
Allocated Share-based Compensation Expense | (181) | 859 | 901
Research and Development Expense [Member] | SEED 2022 Share Incentive Plan [Member] |  |  |
Allocated Share-based Compensation Expense | 89 | 71 |
General and Administrative Expense [Member] |  |  |
Allocated Share-based Compensation Expense | 735 | 725 | $ 2,251
General and Administrative Expense [Member] | SEED 2022 Share Incentive Plan [Member] |  |  |
Allocated Share-based Compensation Expense | $ 127 | $ 10 |

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- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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