Signature of Transition between Granular Solid and Fluid: Rate-Dependent Stick Slips in Steady Shearing.

Despite extensive studies on either smooth granular-fluid flow or the solidlike deformation at the slow limit, the change between these two extremes remains largely unexplored. By systematically investigating the fluctuations of tightly packed grains under steady shearing, we identify a transition zone with prominent stick-slip avalanches. We establish a state diagram, and propose a new dimensionless shear rate based on the speed dependence of interparticle friction and particle size. With fluid-immersed particles confined in a fixed volume and forced to "flow" at viscous numbers J decades below reported values, we answer how a granular system can transition to the regime sustained by solid-to-solid friction that goes beyond existing paradigms based on suspension rheology.

Cooperative effect of two metals: CoPd(OAc)4-catalyzed C-H amination and aziridination.

The first Co/Pd-cocatalyzed intramolecular C-H amination and aziridination reactions were developed. Sulfamate esters were converted to oxathiazinanes by using CoPd(OAc)4 as catalyst and PhI(OAc)2 as oxidant. The mutual presence of both Co and Pd is crucial for the catalytic activity. This combination of two metals with simple acetate ligands provides an economical alternative to the Rh-catalyzed insertion of nitrenoids into C-H bonds.