pH-Driven Mechanistic Switching from Electron Transfer to Energy Transfer between [Ru(bpy)] and Ferrocene Derivatives.

The metal-to-ligand charge transfer excited states of [Ru(bpy)] (bpy = 2,2'-bipyridine) may be deactivated via energy transfer or electron transfer with ferrocene derivatives in aqueous conditions. Stern-Volmer quenching analysis revealed that the rate constant for [Ru(bpy)] excited-state quenching depends on solution pH when a ferrocenyl-amidinium derivative (Fc-am) containing a proton-responsive functionality tethered to the ferrocene center was present. By contrast, the rate constant with which the [Ru(bpy)] excited state is quenched by an analogous ferrocene derivative (ferrocenyl-trimethylammonium, Fc-mam) that lacks a protonic group does not depend on pH.

Estimating the population-level impact of vaccines using synthetic controls.

When a new vaccine is introduced, it is critical to monitor trends in disease rates to ensure that the vaccine is effective and to quantify its impact. However, estimates from observational studies can be confounded by unrelated changes in healthcare utilization, changes in the underlying health of the population, or changes in reporting. Other diseases are often used to detect and adjust for these changes, but choosing an appropriate control disease a priori is a major challenge.