High strain rate in situ micropillar compression of a Zr-based metallic glass

Abstract: High strain rate micromechanical testing can assist researchers in elucidating complex deformation mechanisms in advanced material systems. In this work, the interactions of atomic-scale chemistry and strain rate in affecting the deformation response of a Zr-based metallic glass was studied by varying the concentration of oxygen dissolved into the local structure. Compression of micropillars over six decades of strain rate uncovered a remarkable reversal of the strain rate sensitivity from negative to positive above ~ 5 s−1 due to a delocalisation of shear transformation events within the pre-yield linear regime for both samples, while a higher oxygen content was found to generally decrease the strain rate sensitivity effect. It was also identified that the shear band propagation speed increases with the actuation speed, leading to a transition in the deformation behaviour from serrated to apparent non-serrated plastic flow at ~ 5 s−1. Graphic abstract: [Figure not available: see fulltext.

Post-yield and failure properties of cortical bone

Ageing and associated skeletal diseases pose a significant challenge for health care systems worldwide. Age-related fractures have a serious impact on personal, social and economic wellbeing. A significant proportion of physiological loading is carried by the cortical shell. Its role in the fracture resistance and strength of whole bones in the ageing skeleton is of utmost importance. Even though a large body of knowledge has been accumulated on this topic on the macroscale, the underlying micromechanical material behaviour and the scale transition of bone's mechanical properties are yet to be uncovered. Therefore, this review aims at providing an overview of the state-of-the-art of the post-yield and failure properties of cortical bone at the extracellular matrix and the tissue level

Is transcranial alternating current stimulation effective in modulating brain oscillations?

Transcranial alternating current stimulation (tACS) is a promising tool for modulating brain oscillations, as well as a possible/ntherapeutic intervention. However, the lack of conclusive evidence on whether tACS is able to effectively affect cortical/nactivity continues to limit its application. The present study aims to address this issue by exploiting the well-known/ninhibitory alpha rhythm in the posterior parietal cortex during visual perception and attention orientation. Four groups of/nhealthy volunteers were tested with a Gabor patch detection and discrimination task. All participants were tested at the/nbaseline and selective frequencies of tACS, including Sham, 6 Hz, 10 Hz, and 25 Hz. Stimulation at 6 Hz and 10 Hz over the/noccipito-parietal area impaired performance in the detection task compared to the baseline. The lack of a retinotopically/norganised effect and marginal frequency-specificity modulation in the detection task force us to be cautious about the/neffectiveness of tACS in modulating brain oscillations. Therefore, the present study does not provide significant evidence for/ntACS reliably inducing direct modulations of brain oscillations that can influence performance in a visual task