Mucosal-associated invariant T (MAIT) cells are innate MHC-unrestricted cells that regulate inflammatory responses through the rapid production of cytokines. In this article, we show that circulating MAIT cells are depleted in obese adults, and depletion is associated with diabetic status. Circulating MAIT cells more frequently produced IL-17 upon stimulation ex vivo, a cytokine implicated in insulin resistance. MAIT cells were enriched in adipose tissue (AT) compared with blood. AT MAIT cells, but not circulating MAIT cells, were capable of producing IL-10. In AT from obese subjects, MAIT cells were depleted, were less likely to produce IL-10, and more frequently produced IL-17. Finally, we show that IL-17+ MAIT cells are also increased in childhood obesity, and altered MAIT cell frequencies in obese children are positively associated with insulin resistance. These data indicate that MAIT cells are enriched in human AT and display an IL-17+ phenotype in both obese adults and children, correlating with levels of insulin resistance. The alterations in MAIT cells may be contributing to obesity-related sterile inflammation and insulin resistance.

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The formation of saw-tooth chips is one of the primary characteristics in the machining of hardened steels with geometrically defined cutting tools. Catastrophic failure within the primary shear zone during saw-tooth chip formation is usually attributed to either cyclic crack initiation and propagation or to the occurrence of a thermo-plastic instability. The results presented here show that the primary instability resulting in the formation of saw-tooth chips is initiation of adiabatic shear at the tool tip and propagation partway towards the free surface. Depending on the work material hardness and cutting conditions, catastrophic failure within the upper region of the primary shear zone occurs through either ductile fracture or large strain plastic deformation. Prior to the onset of chip segmentation, which occurs with increases in work material hardness and cutting speed, there is a transition in the morphology of the free surface of continuous chips, from the familiar lamellar structure to what has been termed a “fold-type” structure. This transition is attributed to the operation of thermally softened micro-shear zones, which, it is suggested, are a precursor to adiabatic shear initiation.

Synopsis This preliminary study was undertaken to provide data from which a more comprehensive investigation to establish the safety in-use of cosmetic talcs could be designed. Methods for collecting and analysing respirable talc generated during the use of loose face powder and adult and baby dusting powders were established. Respirable particles in the air were separated from larger size particles by means of a cyclone and were collected on membrane filters. The collected dust was dissolved in acid and the solution was analysed for magnesium by atomic absorption spectroscopy. From the results the concentrations of talc in the air samples were calculated. The method was used to monitor the in-use levels of a range of cosmetic talcs. Mean concentrations in air sampled for 5 min from the start of use of Chinese grades and Italian 00000 grades of talc formulated for use as loose face powder, adult dusting powder and baby dusting powder were 0.48, 1.13 and 0.21 mg m(-3), respectively. Higher levels were found with micronised adult dusting powder (mean concentration 1.9 mg m(-3)). There was no evidence that the presence of perfume in the talc or the ambient relative humidity in the range 54-74% during use affected the levels of respirable talc, but high relative humidity <90% reduced the amount of respirable talc.