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In this paper, the multi-transverse mode competition rate equation model of the Tm:YLF slab laser is established based on the cavity structure of multi-pass gain. As the pump power increased, the changing trend of the number of particles in each mode is analyzed. The direction of beam quality change is also mastered, verified by the three-pass gain laser with the evolution of pump power. Due to the limited compression capacity of the x-axial output spot of the three-pass gain laser, the output spot changes significantly under different cavity lengths and output mirror curvatures. By discussing the output spot evolution, it is known that the large curvature output mirror and the appropriate cavity length can optimize the output spot. Finally, under the pump power of 72 W, the four-pass gain laser obtains a laser output of 1.8 W. It's beam quality is M X 2 = 1.77; M Y 2 = 1.99, the optical–optical conversion efficiency is 2.5 %, and the slope efficiency is 15 %. The beam quality of a three-pass gain laser is M X 2 = 2.67; M Y 2 = 1.70, the optical–optical conversion efficiency is 3.2 %, and the slope efficiency is 11 %. It is verified that the compression of the four-pass gain laser is stronger than that of the three-pass gain laser on the x-axis, laying the foundation for developing a compact multi-pass gain laser. [ABSTRACT FROM AUTHOR]

Protein Kinase A catalytic subunit α (PKACα), plays an important role in the PKA and NF-κB signaling pathway in mammals. However, the function of PKACα in teleost fish remains largely unknown. In this study, PKACα from black carp (bcPKACα) has been cloned and its role in the innate immune antiviral signaling pathway was investigated. The open reading frame of bcPKACα gene contains 1056 nucleotides and the immunofluorescence assay verified that PKACα was mainly distributed in the cytoplasm. The reporter assay showed that bcPKACα expression and co-expression of bcPKACα and black carp TAK1 (bcTAK1) could activate the transcription of NF-κB. However, bcTAK1/bcIRF7-mediated IFN transcription was inhibited by bcPKACα. Knockdown of bcPKACα showed slightly enhanced antiviral activity against spring viremia of carp virus (SVCV) compared with control group. Accordingly, the antiviral activity against SVCV and grass carp reovirus (GCRV) of EPC cells co-expressing bcPKACα, bcTAK1 and bcIRF7 was obviously lower than that of EPC cells co-expressing bcTAK1 and bcIRF7. The similar subcellular distribution and interaction between bcPKACα and bcTAK1 were detected by immunofluorescent staining and co-immunoprecipitation assay separately. The data generated in this study demonstrates that bcPKACα associates with bcTAK1 and positively regulates NF-κB signaling, however, negatively regulates TAK1/IRF7 signaling pathway. • bcPKACα interacted with bcTAK1. • bcPKACα positively regulates NF-κB signaling pathway. • bcPKACα negatively regulates TAK1/IRF7 signaling pathway. [ABSTRACT FROM AUTHOR]