Heck reactions using segmented flow conditions

Various Heck couplings have been carried out using segmented flow conditions to accelerate the reactions. Aryl iodides and aryl bromides as well as anilines in diazonium-type Heck reactions have been used successfully.     

Measurement of deeply virtual compton scattering with a polarized-proton target

The longitudinal target-spin asymmetry AUL for the exclusive electroproduction of high-energy photons was measured for the first time in ep-->e;'pgamma. The data have been accumulated at JLab with the CLAS spectrometer using 5.7 GeV electrons and a longitudinally polarized NH3 target. A significant azimuthal angular dependence was observed, resulting from the interference of the deeply virtual Compton scattering and Bethe-Heitler processes. The amplitude of the sinvarphi moment is 0.252+/-0.042stat+/-0.020sys. Theoretical calculations are in good agreement with the magnitude and the kinematic dependence of the target-spin asymmetry, which is sensitive to the generalized parton distributions H and H.     

Composite Particles From Pickering‐Stabilized Radical Mediated Thiol‐Ene Suspension Polymerizations

Pickering stabilization is a facile method to create composite colloidal particles. Inorganic colloidal SiO₂ nanoparticles are often used as the stabilizer for particles instead of the more common amphiphilic surfactants. Here the use of this approach in radical‐mediated thiol‐ene suspension polymerizations using monomers 1,3,5‐triallyl‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione (TTT) and pentaerythritol tetrakis (3‐mercaptopropionate) (PETMP) is described. The resulting micron‐sized crosslinked poly(thioether) colloidal particles are coated with 80 nm silica nanoparticles. The addition of a small amount of various costabilizers is examined (hexadecane, cetyl alcohol and toluene), and while all yielded particles, cetyl alcohol provide more consistent results. Scanning electron microscopy and thermal analysis of the composite particles demonstrate morphologies that are consistent with a raspberry‐like structure. No significant changes to the glass transition temperature are observed, which is consistent with the silica nanoparticles being located at the surface of the polymer particles.     

Cosmological singularities and analytical solutions in varying vacuum cosmologies

We investigate the dynamical features of a large family of running vacuum cosmologies for which \(\Lambda \) evolves as a polynomial in the Hubble parameter. Specifically, using the critical point analysis we study the existence and the stability of singular solutions which describe de-Sitter, radiation and matter dominated eras. We find several classes of \(\Lambda (H)\) cosmologies for which new analytical solutions are given in terms of Laurent expansions. Finally, we show that the Milne universe and the \(R_{h}=ct\) model can be seen as perturbations around a specific \(\Lambda (H)\) model, but this model is unstable.