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Note 4 - Investments - Investments (Details) - USD ($) $ in Thousands | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Investments at cost | $ 790,592 | $ 766,774
Investments at fair value | 689,553 | 697,891
Biotechnology Sector [Member] |  |
Investments at cost | 138,360 | 118,221
Investments at fair value | 116,174 | 97,562
Medical Device Sector [Member] |  |
Investments at cost | 220,360 | 213,564
Investments at fair value | 192,105 | 205,634
Communications Sector [Member] |  |
Investments at cost | 518 | 11,711
Investments at fair value | 3,547 | 14,763
Consumer-related Sector [Member] |  |
Investments at cost | 74,805 | 74,421
Investments at fair value | 27,362 | 36,667
Data Storage Sector [Member] |  |
Investments at cost | 417 | 417
Investments at fair value | 322 | 350
Internet and Media Sector [Member] |  |
Investments at cost | 329 | 329
Investments at fair value | 911 | 999
Networking Sector [Member] |  |
Investments at cost | 10,076 | 10,070
Investments at fair value | 9,826 | 9,827
Semiconductor Sector [Member] |  |
Investments at cost | 45 | 45
Investments at fair value | 0 | 0
Software Sector [Member] |  |
Investments at cost | 161,916 | 154,040
Investments at fair value | 159,213 | 151,043
Energy Efficiency [Member] |  |
Investments at cost | 9,824 | 9,818
Investments at fair value | 9,713 | 9,712
Other Sustainability Sector [Member] |  |
Investments at cost | 65,329 | 66,151
Investments at fair value | 64,109 | 66,079
Diagnostics Sector [Member] |  |
Investments at cost | 17,252 | 16,704
Investments at fair value | 14,661 | 13,701
Other Healthcare Sector [Member] |  |
Investments at cost | 39,552 | 39,533
Investments at fair value | 40,166 | 40,144
Software, Healthcare Information and Service [Member] |  |
Investments at cost | 51,809 | 51,750
Investments at fair value | 51,444 | 51,410
Debt [Member] |  |
Investments at cost | 699,761 | 678,167
Investments at fair value | 643,567 | 638,779
Warrant [Member] |  |
Investments at cost | 16,120 | 15,956
Investments at fair value | 18,603 | 18,277
Other Debt Obligations [Member] |  |
Investments at cost | 36,723 | 36,709
Investments at fair value | 13,697 | 14,637
Equity Securities [Member] |  |
Investments at cost | 37,988 | 35,942
Investments at fair value | $ 13,686 | $ 26,198

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