Generally, fracture toughness and fracture stress of ceramics depend on crack length, notch root radius and grain size. These three parameters are most important when assessing the integrity of structural ceramic members and developing high-performance ceramics. A new failure criterion called the process zone size failure criterion, has been proposed based on the existence of a crack-tip process zone. Using this criterion, it is shown that theoretical values are in good agreement with many test results quoted from many papers. It is concluded that this failure criterion is useful when evaluating crack length and notch root radius problems. The effect of grain size on both the fracture toughness and on the toughening mechanism is also considered.

Five kinds of silicon nitride samples with different microstructure were prepared in order to examine the effect of sintering condition on grain size and mechanical properties. The degradation in strength of ceramics caused by grinding is investigated in detail. It is shown that the critical process zone size is closely related to the grinding process. Futhermore, the crack size caused by grinding is estimated by the process zone size failure criterion and the Newman-Raju formula. It can be concluded that the process zone size failure criterion is useful when evaluating the sensitivity of ceramics to grinding.

BackgroundSingle cell RNA sequencing (scRNA-seq) of kidney tissues in patients with lupus has led to landscape of complete cellular composition and states for immune and non-immune cells. These studies suggested type I interferon (IFN) signatures prime inflammatory responses. However, there is a lack of knowledge regarding the characteristics of subsets of IFN stimulating genes (ISG) high expressed cells.ObjectivesHere we investigated immune cell compositions between peripheral blood mononuclear cells (PBMCs), skin and kidney tissues in patients with lupus using scRNA-seq. We characterized a subset of ISG high CD4 T cells, which are commonly expressed across PBMCs, skins and kidneys of lupus but not skins of healthy.MethodsscRNA-seq dataset of PBMCs, skin and kidney tissues in patients with lupus were collected. We integrated and analyzed immune cell compositions from this scRNA-seq dataset. We focused on subset of ISG high expressed CD4 T cells and characterized top 200 genes of this subset.ResultsThere is one subset of ISG high expressed CD4 T cells in the lupus PBMCs, kidneys, and skins but not in the healthy skins. This ISG high expressed CD4 T cells have the greatest number of type I interferon signatures and gasdermin D gene, which is related to pyroptosis of cells, among top 200 genes. We further investigated pyroptosis pathway genes in the subsets of CD3 T cells. Interestingly, the subset of ISG high expressed CD4 T cells have most increased pyroptosis related upstream regulating genes including IRF1, GBP1, CASP4 and CASP1. Furthermore, this subset highly expressed inflammasome gene such as NLRC5 not NLRP3ConclusionThere are ISG high expressed CD4 T cells across tissues of lupus. Those cells highly expressed pyroptosis pathway related genes. Further investigation is needed to characterize association between ISG and pyroptosis.Reference[1]Arazi A, Rao DA, Berthier CC, Davidson A, Liu Y, Hoover PJ, et al. The immune cell landscape in kidneys of patients with lupus nephritis. Nat Immunol 2019;20:902-14.Acknowledgements:NIL.Disclosure of InterestsNone Declared.