4,807 research outputs found
Radiative hydrodynamical simulations of super-Eddington accretion flow in tidal disruption event: the accretion flow and wind
One key question in tidal disruption events theory is that how much of the
fallback debris can be accreted to the black hole. Based on radiative
hydrodynamic simulations, we study this issue for efficiently `circularized'
debris accretion flow. We find that for a black hole disrupting a solar type
star, of the debris can be accreted for a solar mass ()
black hole. While for a black hole, the value is . We find
that wind can be launched in the super-Eddington accretion phase regardless of
the black hole mass. The maximum velocity of wind can reach (with
being speed of light). The kinetic power of wind is well above . The results can be used to study the interaction of wind and
the circumnuclear medium around quiescent super-massive black holes.Comment: 10 pages, 15 figures, accepted by MNRA
Radio emission of tidal disruption events from wind-cloud interaction
Winds can be launched in tidal disruption event (TDE). It has been proposed
that the winds can interact with the cloud surrounding the black hole, produce
bow shocks, accelerate electrons, and produce radio emission. We restudy the
wind-cloud interaction model. We employ the properties of winds found by the
radiation hydrodynamic simulations of super-Eddington circularized accretion
flow in TDEs. We can calculate the peak radio emission frequency, the
luminosity at the peak frequency, and their time-evolution based on the TDEs
wind-cloud interaction model. We find that the model predicted peak radio
emission frequency, the luminosity at peak frequency, and their time evolution
can be well consistent with those in TDEs AT2019dsg and ASASSN-14li. This
indicates that in these two radio TDEs, the wind-cloud interaction mechanism
may be responsible for the radio emission.Comment: 11 pages, 10 figures, accepted to MNRA
Catalytic Asymmetric Dihydroxylation of Olefins Using a Recoverable and Reusable Ligand
A free bis-cinchona alkaloid derivative ligand was prepared by a simple synthetic manipulation.
With ligand/olefin mole ratio of 1%, the asymmetric dihydroxylation reactions of six olefins
proceeded smoothly to give the chiral vicinal diols in high chemical yields and optical yields.
The ligand itself could be recovered quantitatively by a simple operation and reused five times
without loss of enantioselectivity
What Differs on the Enzymatic Acetylation Mechanisms for Arylamines and Arylhydrazines Substrates? A Theoretical Study
The acetylation mechanisms of several selected typical substrates from experiments, including arylamines and arylhydrazines, are investigated with the density functional theory in this paper. The results indicate that all the transition states are characterized by a four-membered ring structure, and hydralazine (HDZ) is the most potent substrate. The bioactivity for all the compounds is increased in a sequence of PABA ≈ 4-AS < 4-MA < 5-AS ≈ INH < HDZ. The conjunction effect and the delocalization of the lone pairs of N atom play a key role in the reaction. All the results are consistent with the experimental data
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