Jetting of a near-wall cavitation bubble induced by another tandem bubble

Double bubbles near a rigid wall surface collapse to produce a significant jet impact,with potential applications in surface cleaning and ultrasonic lithotripsy.However,the dynamic behaviors of near-wall bubbles remain unexplored.In this study,we investigate the jetting of a near-wall bubble induced by another tandem bubble.We define two dimensionless standoff distances,γ_(1),γ_(2),to represent the distances from the center of the near-wall bubble to the rigid wall and the center of controlling bubble to the center of the near-wall bubble,respectively.Our observations reveal three distinct jetting regimes for the near-wall bubble:transferred jetting,double jetting,and directed jetting.To further investigate the jetting mechanism,numerical simulations are conducted using the compressibleInterFoam solver in the open-source framework of OpenFOAM.A detailed analysis shows that the transferred jet flow is caused by the pinch-off resulting from the axial contraction velocity at the lower end of the near-wall bubble being greater than the vertical contraction velocity,leading to a maximum jet velocity of 682.58 m/s.In the case of double jetting,intense stretching between the controlling bubble and the wall leads to a pinch-off and a double jetting with a maximum velocity of 1096.29 m/s.The directed jet flow is caused by the downward movement of the high-pressure region generated by the premature collapse of the controlling bubble,with the maximum jet velocity reaching 444.62 m/s.

Palladium-catalyzed relay C–H functionalization to construct novel hybrid-arylcyclophosphorus ligand precursors

A new relay C–H functionalization of di([1,1'-biphenyl]-2-yl)phosphine oxide to obtain esterified and hy-droxylated products with different hypervalent iodines as oxidants under palladium catalysis is disclosed.This reaction provides a more effective and concise strategy for the synthesis of novel structural hybrid-arylcyclophosphorus ligand precursors with a wide range of substrates and good functional group toler-ance.

Phosphine oxide directing-group-enabled atroposelective C-H bond acyloxylation via an eight-membered palladacycle intermediate

Herein,we report the first atroposelective C(sp^(2))-H bond acyloxylation enabled by a phosphine oxide directing group.Uniquely,this transformation is shown to proceed through an eight-membered palladacycle intermediate,as opposed to the kinetically and thermodynamically favored five-membered palladacycle intermediate.Additionally,L-pGlu-OH,a cheap and abundant chiral amino acid derivative,was identified as the best chiral ligand to promote this atroposelective remote C-H functionalization reaction.

Solvent-controlled regioselective arylation of indoles and mechanistic explorations

The ability to manipulate the site selectivity in C–H bond functionalization reactions is an important goal in modern chemistry.Herein,we report a new reaction strategy for the regioselective arylation of indoles at C2 or C3 positions,achieved by adjusting the solvent and with P(O)^(t) Bu_(2) as an auxiliary group.