Dynamics of mussel plaque detachment

Mussels are well known for their ability to generate and maintain strong, long-lasting adhesive bonds under hostile conditions. Many prior studies attribute their adhesive strength to the strong chemical interactions between the holdfast and substrate. While chemical interactions are certainly important, adhesive performance is also determined by contact geometry, and understanding the coupling between chemical interactions and the plaque shape and mechanical properties is essential in deploying bioinspired strategies when engineering improved adhesives. To investigate how the shape and mechanical properties of the mussel's plaque contribute to its adhesive performance, we use a custom built load frame capable of fully characterizing the dynamics of the detachment. With this, we can pull on samples along any orientation, while at the same time measuring the resulting force and imaging the bulk deformations of the plaque as well as the holdfast-substrate interface where debonding occurs. We find that the force-induced yielding of the mussel plaque improves the bond strength by two orders of magnitude and that the holdfast shape improves bond strength by an additional order of magnitude as compared to other simple geometries. These results demonstrate that optimizing the contact geometry can play as important a role on adhesive performance as optimizing the chemical interactions as observed in other organisms and model systems

Portrayals of the Holocaust in English history textbooks, 1991–2016: continuities, challenges and concerns

This study examines portrayals of the Holocaust in a sample of 21 secondary school history textbooks published in England between 1991 and 2016. Evaluated against internationally recognized criteria and guidelines, the content of most textbooks proved very problematic. Typically, textbooks failed to provide clear chronological and geographical frameworks and adopted simplistic Hitler-centric, perpetrator-oriented narratives. Furthermore, textbooks paid limited attention to pre-war Jewish life, the roots of antisemitism, the complicity of local populations and collaborationist regimes, and the impact of the Holocaust on people across Europe. Based on these critical findings, the article concludes by offering initial recommendations for textbook improvement

The role of re-aggregation on the performance of electrochemically exfoliated many-layer graphene for Li-ion batteries

AbstractTwo potential pathways for Li+ diffusion occur within graphitic carbon with typically in-plane diffusion dominating (∼10−7cm2s−1) over diffusion along the crystallite grain boundaries (∼10−11cm2s−1). Reducing the flake thickness of microcrystalline graphite powders via electrochemical exfoliation offers a method to overcome the latter, sluggish grain boundary Li+ diffusion, thereby increasing the overall rate capability of the graphite negative electrode in a the Li-ion battery. Six micron particulate graphite was electrochemically exfoliated to give flakes of which ∼90% had a thickness of <10 graphene layers. This exfoliated material was then prepared as an ink and allowed to dry prior to forming a battery electrode. Analysis of the electrode and dried exfoliated powder using powder X-ray diffraction, scanning electron microscopy and Brunauer–Emmett–Teller isotherm analysis show that the material has, apart from a significant reduction of the rhombohedral fraction from 41% to 14%, near-identical properties to that of original starting graphite powder. Thus, once the exfoliated powder has been dried from the exfoliation process, as anticipated, major restacking of the multi-layer graphene flakes had occurred. Likewise there was no significant improvement in using the exfoliated material at high rates of delithiation and lower specific capacity, when tested within a half cell vs. lithium metal. In situ Raman analysis showed that the exfoliated material displayed similar spectral features to the pristine sample during lithiation, as did multi point measurements on differently disordered areas shown from the varying ID/IG-band intensity ratios, indicating that local surface disorder does not influence the course of lithium insertion. The re-aggregation of graphenic material is widely recognised, but seldom evaluated. This work shows the importance of keeping graphenic material dispersed at all stages of production