The Casimir force is the attraction between uncharged metallic surfaces as a result of quantum mechanical vacuum fluctuations of the electromagnetic field. We demonstrate the Casimir effect in microelectromechanical systems using a micromachined torsional device. Attraction between a polysilicon plate and a spherical metallic surface results in a torque that rotates the plate about two thin torsional rods. The dependence of the rotation angle on the separation between the surfaces is in agreement with calculations of the Casimir force. Our results show that quantum electrodynamical effects play a significant role in such microelectromechanical systems when the separation between components is in the nanometer range.

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The Casimir force between uncharged metallic surfaces originates from quantum mechanical zero point fluctuations of the electromagnetic field. We demonstrate that this quantum electrodynamical effect has a profound influence on the oscillatory behavior of microstructures when surfaces are in close proximity (≤ 100 nm). Frequency shifts, hysteretic behavior and bistability caused by the Casimir force are observed in the frequency response of a periodically driven micromachined torsional oscillator.

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As NaHCO3 ingestion does not increase resting muscle pH or beta(in vitro), it is likely that the improved performance is a result of the greater extracellular buffer concentration increasing H efflux from the muscles into the blood. The significant increase in posttest muscle [La] in NaHCO3 suggests that an increased anaerobic energy contribution is one mechanism by which NaHCO3 ingestion improved RSA.

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ObjectiveTo systematically review, summarise and appraise findings of published meta-analyses that examined the effects of caffeine on exercise performance.DesignUmbrella review.Data sourcesTwelve databases.Eligibility criteria for selecting studiesMeta-analyses that examined the effects of caffeine ingestion on exercise performance.ResultsEleven reviews (with a total of 21 meta-analyses) were included, all being of moderate or high methodological quality (assessed using the Assessing the Methodological Quality of Systematic Reviews 2 checklist). In the meta-analyses, caffeine was ergogenic for aerobic endurance, muscle strength, muscle endurance, power, jumping performance and exercise speed. However, not all analyses provided a definite direction for the effect of caffeine when considering the 95% prediction interval. Using the Grading of Recommendations Assessment, Development and Evaluation criteria the quality of evidence was generally categorised as moderate (with some low to very low quality of evidence). Most individual studies included in the published meta-analyses were conducted among young men.Summary/conclusionSynthesis of the currently available meta-analyses suggest that caffeine ingestion improves exercise performance in a broad range of exercise tasks. Ergogenic effects of caffeine on muscle endurance, muscle strength, anaerobic power and aerobic endurance were substantiated by moderate quality of evidence coming from moderate-to-high quality systematic reviews. For other outcomes, we found moderate quality reviews that presented evidence of very low or low quality. It seems that the magnitude of the effect of caffeine is generally greater for aerobic as compared with anaerobic exercise. More primary studies should be conducted among women, middle-aged and older adults to improve the generalisability of these findings.

Over the past decade, discussion of the interaction between superconductivity and magnetism has been overshadowed by the omnipresence of the oxide-based, high-temperature superconductors. But interest in the interaction between these two generally competing effects has a history that predates high-Tc materials by several decades. Starting with seminal work by Bernd Matthias and his coworkers, it was found that magnetic impurities strongly suppress superconductivity in pure elements and binary compounds. This rapid suppression of the superconducting transition temperature Tc was due to the local magnetic moment of the impurity preventing the formation of the spin-up/spin-down conduction-electron pairs that are responsible for superconductivity. The early measurements were made on dilute alloys, and for many solid-state physicists of the time, the quest was to find compounds in which superconductivity coexists with an ordered lattice of local magnetic moments.