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Published guidelines for sports restriction for children with a bicuspid aortic valve remain controversial. We sought to describe practice variation and factors influencing sports restrictions in these children.
This retrospective single-centre study included children (7–18 years old) with an isolated bicuspid aortic valve at baseline from 1 January, 2005 to 31 December, 2014. Sports restrictions, factors potentially influencing decision-making, and outcomes were collected. Descriptive statistics and multivariable mixed-effects logistic regression models were performed with providers and patients as random effects. Provider variation was estimated using intraclass correlation coefficients. Odds ratios, 95% confidence intervals, and p-values were reported from the models.
In 565 encounters (253 children; 34 providers), 41% recommended no sports restrictions, 40% recommended high-static and high-dynamic restrictions, and 19% had no documented recommendations. Based on published guidelines, 22% of children were inappropriately restricted while 30% were not appropriately restricted. The paediatric cardiology provider contributed to 37% of observed practice variation (p < 0.001). Sports restriction was associated with older age, males, greater ascending aorta z-score, and shorter follow-up interval. There were no aortic dissections or deaths and one cardiac intervention.
Physicians frequently fail to document sports restrictions for children with a bicuspid aortic valve, and documented recommendations often conflict with published guidelines. Despite this, no adverse outcomes occurred. Providers accounted for a significant proportion of the variation in sports restrictions. Further research to provide evidence-based guidelines may improve provider compliance with activity recommendations in this population.
Reconstruction of a complete Quaternary record of climatic changes in the northeastern Qinghai-Tibetan Plateau is not well obtained, because of high relief and extensive surface erosion. In this study, two long cores obtained from thick loess deposits in the region, both contain clear alternations of loess and paleosols, indicating distinct climate changes during the Quaternary. The palaeomagnetic stratigraphy and optically stimulated luminescence dating indicate that the loess deposition began approximately 2.0 Ma ago, with continuous accumulation until the Holocene. Dust accumulation rates in this region are much higher than those in the central Chinese Loess Plateau, suggesting an extended dust source and/or robust transport agent. Variations of magnetic susceptibility of the loess are a good proxy index of warm/wet and cold/dry alternations and are correlated with the intensity of pedogensis. The magnetic susceptibility record reveals that a relatively cold/dry climate dominated the northeastern Qinghai-Tibetan Plateau in the Quaternary, punctuated by warm/wet phases. A stepwise strengthening of the plateau summer monsoon, with a significant strengthening at around 1200-1000 ka and at least 7 phases of strengthening of the plateau summer monsoon in the past 800 ka are interpreted from the core data. The cores provide evidence that strengthened warm/wet climates occurred at around 80-130, 190-250, 290-340, 385-420, 500-625, 690-720 and 755-780 ka, which may correlate to warm/wet phases in the Qinghai-Tibetan Plateau. The palaeoclimate changes probably were regulated by the glacial-interglacial alternations.
A highly deformable Zr–Al–Cu–Ni–Sn alloy system without any catastrophic failure has been developed and the underling mechanism for exceptional plasticity has been investigated in terms of structural characteristics and atomic movement kinetics. The as-cast Zr61.7Al8Ni13Cu17Sn0.3 bulk metallic glass has many local nanoscale ordering features. They can play a critical role in nucleating abundant shear bands that sufficiently accommodate global plasticity. During deformation at room temperature, the ordered regions do not grow, providing a structural stability, possibly from the sluggish atomic movement kinetics. Thermal activation energy for crystallization of the Zr61.7Al8Ni13Cu17Sn0.3 alloy is estimated as 3.96 eV, which is about 2.8 times higher than that of the Z41.2Ti13.8Cu12.5Ni10Be22.5 alloy [Vitreloy 1 (Vit1)] and the dynamic mass flow rate is around 10 times slower than that of Vit1. A thermomechanical estimation of compressive strain rates under constant stress shows a sluggish atomic movement upon the addition of Sn.
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