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Previous studies have shown a strong correspondence between long bone bilateral asymmetry and reported handedness. Here, we compare the pattern of asymmetry in mechanical properties of the humerus and second metacarpal of Pan troglodytes, recent British industrial and medieval populations, and a broad range of human hunter-gatherers, to test whether technological variation corresponds with lateralization in bone function. The results suggest that P. troglodytes are left-lateralized in the morphology of the humerus and right-lateralized in the second metacarpal, while all human populations are predominantly right-biased in the morphology of these bones. Among human populations, the second metacarpals of 63% of hunter-gatherers show right-hand bias, a frequency similar to that found among chimpanzees. In contrast, the medieval and recent British populations show over 80% right-lateralization in the second metacarpal. The proportion of individuals displaying right-directional asymmetry is less than the expected 90% among all human groups. The variation observed suggests that the human pattern of right-biased asymmetry developed in a mosaic manner throughout human history, perhaps in response to technological development.

A piezoelectric nanogenerator has been fabricated using a simple, fast and scalable template-assisted electrodeposition process, by which vertically aligned zinc oxide (ZnO) nanowires were directly grown within a nanoporous polycarbonate (PC) template. The nanowires, having average diameter 184 nm and length 12 μm, are polycrystalline and have a preferred orientation of the [100] axis parallel to the long axis. The output power density of a nanogenerator fabricated from the as-grown ZnO nanowires still embedded within the PC template was found to be 151 ± 25 mW m−3 at an impedance-matched load, when subjected to a low-level periodic (5 Hz) impacting force akin to gentle finger tapping. An energy conversion efficiency of ∼4.2% was evaluated for the electrodeposited ZnO nanowires, and the ZnO–PC composite nanogenerator was found to maintain good energy harvesting performance through 24 h of continuous fatigue testing. This is particularly significant given that ZnO-based nanostructures typically suffer from mechanical and/or environmental degradation that otherwise limits their applicability in vibrational energy harvesting. Our template-assisted synthesis of ZnO nanowires embedded within a protective polymer matrix through a single growth process is thus attractive for the fabrication of low-cost, robust and stable nanogenerators.

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751 14- and 15-year old children completed a 3-year, double-blind, caries preventive program. The effects of daily, supervised toothbrushing with an 0.76% sodium monofluorophosphate dentifrice, rinsing with a 0.05% sodium fluoride mouthrinse, and the combined effects of the two treatments were investigated. Both the dentifrice and mouthrinse reduced the incidence of dental caries, but their combined use at the same time had no greater effect than either used alone.