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We assessed the subsistence-related variation of the human gut microbiome at a fine resolution for two of the main dimensions of microbiome variation, age and geography. For this, we investigated the fecal microbiome and metabolome in rural Bassa and urbanized individuals from Nigeria, including infants, and compared data with worldwide populations practicing varying subsistence. Our data highlight specific microbiome traits that are progressively lost with urbanization, such as the dominance of pristine fiber degraders and the low inter-individual variation. For the Bassa, this last feature is the result of their subsistence-related practices favoring microbial dispersal, such as their extensive environmental contact and the usage of untreated waters from the Usuma River. The high degree of microbial dispersal observed in the Bassa meta-community nullifies the differences between infant and adult intestinal ecosystems, suggesting that the infant-type microbiome in Western populations could be the result of microbiome-associated neotenic traits favored by urbanization.

A flywheel energy cache system (FECS) is a mechanical battery that can charge/discharge electricity by converting it into the kinetic energy of a rotating flywheel, and vice versa. Compared to a chemical battery, a FECS has great advantages in durability and lifetime, especially in hot or cold environments. Design simulations of the FECS were carried out to clarify the effects of the composition and dimensions of the flywheel rotor on the charge/discharge performance. The rotation speed of a flywheel is limited by the strength of the materials from which it is constructed. Three materials, carbon fiber-reinforced polymer (CFRP), Cr-Mo steel, and a Mg alloy were examined with respect to the required weight and rotation speed for a 3 MJ (0.8 kWh) charging/discharging energy, which is suitable for an FECS operating with a 3-5 kW photovoltaic device in an ordinary home connected to a smart grid. The results demonstrate that, for a stationary 3 MJ FECS, Cr-Mo steel was the most cost-effective, but also the heaviest, Mg-alloy had a good balance of rotation speed and weight, which should result in reduced mechanical loss and enhanced durability and lifetime of the system, and CFRP should be used for applications requiring compactness and a higher energy density. Finally, a high-speed prototype FW was analyzed to evaluate its fundamental characteristics both under acceleration and in the steady state.