Three-dimensional unstructured grid generation via incremental insertion and local optimization

Algorithms for the generation of 3D unstructured surface and volume grids are discussed. These algorithms are based on incremental insertion and local optimization. The present algorithms are very general and permit local grid optimization based on various measures of grid quality. This is very important; unlike the 2D Delaunay triangulation, the 3D Delaunay triangulation appears not to have a lexicographic characterization of angularity. (The Delaunay triangulation is known to minimize that maximum containment sphere, but unfortunately this is not true lexicographically). Consequently, Delaunay triangulations in three-space can result in poorly shaped tetrahedral elements. Using the present algorithms, 3D meshes can be constructed which optimize a certain angle measure, albeit locally. We also discuss the combinatorial aspects of the algorithm as well as implementational details

Clinical course and outcomes of COVID-19 in kidney transplant recipients

Introduction: Kidney transplant recipients (KTR) are at increased risk of morbidity and mortality due to coronavirus disease 2019 (COVID-19). This study aimed to explore the clinical characteristics and outcomes of COVID-19 in KTR. Methods: We reviewed the clinical profile, outcomes, and immunological responses of recipients admitted with COVID-19. We determined the risk factors for mortality and severe COVID-19. Results: Out of 452 recipients on follow-up, 60 were admitted with COVID-19. Prevalent comorbidities were hypertension (71%), diabetes (40%), lung disease (17%). About 27% had tuberculosis. The median Sequential Organ Failure Assessment score at presentation was 3 (interquartile range [IQR] 1–5). There was a high incidence of diarrhea (52%) and anemia (82%). Treatment strategies included antimetabolite withdrawal (85%), calcineurin inhibitor decrease or withdrawal (64%), increased steroids (53%), hydroxychloroquine (21%), remdesivir (28.3%), and tocilizumab (3.3%). Severe COVID-19 occurred in 34 (56.4%) patients. During a median follow-up of 42.5 days (IQR 21–81 days), 83% developed acute kidney injury (AKI) and eight (13%) died. Mortality was associated with the baseline graft dysfunction, hypoxia at admission, lower hemoglobin and platelets, higher transaminases, higher C reactive protein, diffuse radiological lung involvement, hypotension requiring inotropes, and Kidney Diseases Improving Global Outcomes (KDIGO) stage 3 AKI (univariate analysis). Around 57% of patients remained RT-PCR positive at the time of discharge. By the last follow-up, 66.6% of patients developed IgM (immunoglobulin M) antibodies and 82.3% of patients developed IgG antibodies. Conclusion: COVID-19 in kidney transplant recipients is associated with a high risk of AKI and significant mortality