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Creators/Authors contains: "Yu, Hang"

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  1. ; ; ( , The Astrophysical Journal)
    Abstract High-eccentricity tidal migration is a potential formation channel for hot Jupiters. During this process, the planetary f-mode may experience a phase of diffusive growth, allowing its energy to quickly build up to large values. In Yu et al., we demonstrated that nonlinear mode interactions between a parent f-mode and daughter f- and p-modes expand the parameter space over which the diffusive growth of the parent is triggered. We extend that study by incorporating (1) the angular momentum transfer between the orbit and the mode, and consequently the evolution of the pericenter distance; (2) a prescription to regulate the nonlinearmore »frequency shift at high parent mode energies; and (3) dissipation of the parent’s energy due to both turbulent convective damping of the daughter modes and strongly nonlinear wave-breaking events. The new ingredients allow us to follow the coupled evolution of the mode and orbit over ≳10 4 yr, covering the diffusive evolution from its onset to its termination. We find that the semimajor axis shrinks by a factor of nearly 10 over 10 4 yr, corresponding to a tidal quality factor  ∼ 10 . The f-mode’s diffusive growth terminates while the eccentricity is still high, at around e = 0.8–0.95. Using these results, we revisit the eccentricity distribution of proto-hot Jupiters. We estimate that less than 1 proto-HJ with eccentricity >0.9 should be expected in Kepler's data once the diffusive regime is accounted for, explaining the observed paucity of this population.« less
    Free, publicly-accessible full text available April 1, 2023
  2. ; ; ; ; ; ; ( , Additive Manufacturing)
    Free, publicly-accessible full text available April 1, 2023
  3. ; ; ( , The Astrophysical Journal)
    Free, publicly-accessible full text available August 1, 2022
  4. ; ; ; ; ( , Physical Review D)
    Free, publicly-accessible full text available September 1, 2022
  5. ; ; ; ; ; ; ; ( , Materialia)
    Free, publicly-accessible full text available August 1, 2022
  6. ; ; ; ; ( , Genetics)
    Freitag, M (Ed.)
    Abstract Heterochromatin, a transcriptionally silenced chromatin domain, is important for genome stability and gene expression. Histone 3 lysine 9 methylation (H3K9me) and histone hypoacetylation are conserved epigenetic hallmarks of heterochromatin. In fission yeast, RNA interference (RNAi) plays a key role in H3K9 methylation and heterochromatin silencing. However, how RNAi machinery and histone deacetylases (HDACs) are coordinated to ensure proper heterochromatin assembly is still unclear. Previously, we showed that Dpb4, a conserved DNA polymerase epsilon subunit, plays a key role in the recruitment of HDACs to heterochromatin during S phase. Here, we identified a novel RNA-binding protein Dri1 that interacts withmore »Dpb4. GFP-tagged Dri1 forms distinct foci mostly in the nucleus, showing a high degree of colocalization with Swi6/Heterochromatin Protein 1. Deletion of dri1+ leads to defects in silencing, H3K9me, and heterochromatic siRNA generation. We also showed that Dri1 physically associates with heterochromatic transcripts, and is required for the recruitment of the RNA-induced transcriptional silencing (RITS) complex via interacting with the complex. Furthermore, loss of Dri1 decreases the association of the Sir2 HDAC with heterochromatin. We further demonstrated that the C-terminus of Dri1 that includes an intrinsically disordered (IDR) region and three zinc fingers is crucial for its role in silencing. Together, our evidences suggest that Dri1 facilitates heterochromatin assembly via the RNAi pathway and HDAC.« less
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  7. ; ; ( , Physical Review D)
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  8. ; ( , Physical Review Letters)
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  9. ; ; ; ( , Physical Review D)
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  10. ; ; ; ; ; ; ( , Materialia)
    Among metal additive manufacturing technologies, additive friction stir deposition stands out for its ability to create freeform and fully-dense structures without melting and solidification. Here, we employ a comparative approach to investigate the process-microstructure linkages in additive friction stir deposition, utilizing two materials with distinct thermomechanical behavior—an Al-Mg-Si alloy and Cu—both of which are challenging to print using beam-based additive processes. The deposited Al-Mg-Si is shown to exhibit a relatively homogeneous microstructure with extensive subgrain formation and a strong shear texture, whereas the deposited Cu is characterized by a wide distribution of grain sizes and a weaker shear texture. Wemore »show evidence that the microstructure in Al-Mg-Si primarily evolves by continuous dynamic recrystallization, including geometric dynamic recrystallization and progressive lattice rotation, while the heterogeneous microstructure of Cu results from discontinuous recrystallization during both deposition and cooling. In Al-Mg-Si, the continuous recrystallization progresses with an increase of the applied strain, which correlates with the ratio between the tool rotation rate and travel velocity. Conversely, the microstructure evolution in Cu is found to be less dependent on , instead varying more with changes to . This difference originates from the absence of Cu rotation in the deposition zone, which reduces the influence of tool rotation on strain development. We attribute the distinct process-microstructure linkages and the underlying mechanisms between Al-Mg-Si and Cu to their differences in intrinsic thermomechanical properties and interactions with the tool head.« less
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