Material point method for crack propagation in anisotropic media: a phase field approach

A novel phase field formulation implemented within a material point method setting is developed to address brittle fracture simulation in anisotropic media. The case of strong anisotropy in the crack surface energy is treated by considering an appropriate variational, i.e., phase field approach. Material point method is utilized to efficiently treat the resulting coupled governing equations. The brittle fracture governing equations are defined at a set of Lagrangian material points and subsequently interpolated at the nodes of a fixed Eulerian mesh where solution is performed. As a result, the quality of the solution does not depend on the quality of the underlying finite element mesh and is relieved from mesh-distortion errors. The efficiency and validity of the proposed method is assessed through a set of benchmark problems

Out-of-plane response of masonry walls strengthened using textile-mortar system

The out-of-plane response of masonry walls strengthened with textile-reinforced mortar (TRM) is experimentally investigated in this work. Medium-scale three-point bending tests were carried out on 18 specimens comprising a set of 9 single-wythe and 9 double-wythe brick masonry walls. Key investigated parameters involved the textile reinforcement ratio, the textile material, the coating of the textile reinforcement with epoxy resin, and the wall thickness. Experimental results suggest that TRM significantly increase the load bearing capacity of masonry walls. The amount of reinforcement utilised affects both the strength and deformation characteristics of the corresponding specimens, while it may alter the failure mode. Resin coating on the textile is found to be beneficial for the performance of the TRM overlays

A discontinuous extended Kalman filter for non-smooth dynamic problems

Problems that result into locally non-differentiable and hence non-smooth state-space equations are often encountered in engineering. Examples include problems involving material laws pertaining to plasticity, impact and highly non-linear phenomena. Estimating the parameters of such systems poses a challenge, particularly since the majority of system identification algorithms are formulated on the basis of smooth systems under the assumption of observability, identifiability and time invariance. For a smooth system, an observable state remains observable throughout the system evolution with the exception of few selected realizations of the state vector. However, for a non-smooth system the observable set of states and parameters may vary during the evolution of the system throughout a dynamic analysis. This may cause standard identification (ID) methods, such as the Extended Kalman Filter, to temporarily diverge and ultimately fail in accurately identifying the parameters of the system. In this work, the influence of observability of non-smooth systems to the performance of the Extended and Unscented Kalman Filters is discussed and a novel algorithm particularly suited for this purpose, termed the Discontinuous Extended Kalman Filter (DEKF), is proposed

MerTK expressing hepatic macrophages promote the resolution of inflammation in acute liver failure

Objective: Acute liver failure (ALF) is characterised by overwhelming hepatocyte death and liver inflammation with massive infiltration of myeloid cells in necrotic areas. The mechanisms underlying resolution of acute hepatic inflammation are largely unknown. Here, we aimed to investigate the impact of Mer tyrosine kinase (MerTK) during ALF and also examine how the microenvironmental mediator, secretory leucocyte protease inhibitor (SLPI), governs this response. Design: Flow cytometry, immunohistochemistry, confocal imaging and gene expression analyses determined the phenotype, functional/transcriptomic profile and tissue topography of MerTK+ monocytes/macrophages in ALF, healthy and disease controls. The temporal evolution of macrophage MerTK expression and its impact on resolution was examined in APAP-induced acute liver injury using wild-type (WT) and Mer-deficient (Mer−/−) mice. SLPI effects on hepatic myeloid cells were determined in vitro and in vivo using APAP-treated WT mice. Results: We demonstrate a significant expansion of resolution-like MerTK+HLA-DRhigh cells in circulatory and tissue compartments of patients with ALF. Compared with WT mice which show an increase of MerTK+MHCIIhigh macrophages during the resolution phase in ALF, APAP-treated Mer−/− mice exhibit persistent liver injury and inflammation, characterised by a decreased proportion of resident Kupffer cells and increased number of neutrophils. Both in vitro and in APAP-treated mice, SLPI reprogrammes myeloid cells towards resolution responses through induction of a MerTK+HLA-DRhigh phenotype which promotes neutrophil apoptosis and their subsequent clearance. Conclusions: We identify a hepatoprotective, MerTK+, macrophage phenotype that evolves during the resolution phase following ALF and represents a novel immunotherapeutic target to promote resolution responses following acute liver injury

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Out-of-plane response of masonry walls strengthened using textile-mortar system

The out-of-plane response of masonry walls strengthened with textile-reinforced mortar (TRM) is experimentally investigated in this work. Medium-scale three-point bending tests were carried out on 18 specimens comprising a set of 9 single-wythe and 9 double-wythe brick masonry walls. Key investigated parameters involved the textile reinforcement ratio, the textile material, the coating of the textile reinforcement with epoxy resin, and the wall thickness. Experimental results suggest that TRM significantly increase the load bearing capacity of masonry walls. The amount of reinforcement utilised affects both the strength and deformation characteristics of the corresponding specimens, while it may alter the failure mode. Resin coating on the textile is found to be beneficial for the performance of the TRM overlays. © 2018 Elsevier Lt