Microbial fuel cells (MFCs), which use living microbes as catalysts for the conversion of fuels (e.g., organic compounds) into electricity, have recently attracted wide attention as sustainable bioenergy systems. The diverse catabolic activities of bacteria provide MFCs with a great advantage over chemical fuel cells that can utilize only purified reactive fuels (e.g., hydrogen). MFCs are expected to be applied to the recovery of energy from biomass wastes and wastewater. Electron transfer to electrodes by microbes requires distinct mechanisms to transfer electrons from intracellular electron donors to extracellular electron acceptors because microbial cells are insulated by cell membrane and extracellular structures. Extensive studies have been performed to understand the mechanisms underlying extracellular electron transfer (EET), revealing that some current-generating microbes have intrinsic EET pathways that consist of conductive membrane proteins. Studies have also demonstrated that low potential-poised electrodes can supply electrons into microbial cells via EET pathways, thereby promoting intracellular reductive reactions for chemical production. These studies suggest the wide applicability of microbial EET reactions for valuable biotechnological processes.
This is a brief overview of recent progress in understanding basic properties of higher dimensional black holes. Particular focus is on asymptotically flat, vacuum solutions to higher dimensional general relativity.
Ultrafast photoinduced transitions of a one-dimensional Mott insulator to two distinct electronic phases, metal and charge-density-wave (CDW) phases, were successfully achieved in a bromine-bridged Pd-chain compound. By the high-energy excitation in the Mott insulator phase, free electron and hole carriers are produced, giving rise to an insulator to metal transition. By the resonant excitation of the Mott-gap transition, excitonic states are initially generated in the Mott insulator phase, and subsequently converted to one-dimensional CDW domains. Photoinduced Mott insulator to CDW transition is quite intriguing because it is the transition from a higher-symmetry phase to a lower-symmetry phase. Such selectivity in photoconversions by the choice of the initial photoexcited states opens a new possibility for the developments of advanced optical switching and memory functions.