Interactive Boundary Element Analysis for Engineering Design

Structural design of mechanical components is an iterative process that involves multiple stress analysis runs; this can be time consuming and expensive. Significant improvements in the eciency of this process can be made by increasing the level of interactivity. One approach is through real-time re-analysis of models with continuously updating geometry. Three primary areas need to be considered to accelerate the re-solution of boundary element problems. These are re-meshing the model, updating the boundary element system of equations and re-solution of the system. Once the initial model has been constructed and solved, the user may apply geometric perturbations to parts of the model. The re-meshing algorithm must accommodate these changes in geometry whilst retaining as much of the existing mesh as possible. This allows the majority of the previous boundary element system of equations to be re-used for the new analysis. For this problem, a GMRES solver has been shown to provide the fastest convergence rate. Further time savings can be made by preconditioning the updated system with the LU decomposition of the original system. Using these techniques, near real-time analysis can be achieved for 3D simulations; for 2D models such real-time performance has already been demonstrated

Clinical and Demographic Factors Associated with COVID-19, Severe COVID-19, and SARS-CoV-2 Infection in Adults: A Secondary Cross-Protocol Analysis of 4 Randomized Clinical Trials

Importance: Current data identifying COVID-19 risk factors lack standardized outcomes and insufficiently control for confounders. Objective: To identify risk factors associated with COVID-19, severe COVID-19, and SARS-CoV-2 infection. Design, Setting, and Participants: This secondary cross-protocol analysis included 4 multicenter, international, randomized, blinded, placebo-controlled, COVID-19 vaccine efficacy trials with harmonized protocols established by the COVID-19 Prevention Network. Individual-level data from participants randomized to receive placebo within each trial were combined and analyzed. Enrollment began July 2020 and the last data cutoff was in July 2021. Participants included adults in stable health, at risk for SARS-CoV-2, and assigned to the placebo group within each vaccine trial. Data were analyzed from April 2022 to February 2023. Exposures: Comorbid conditions, demographic factors, and SARS-CoV-2 exposure risk at the time of enrollment. Main Outcomes and Measures: Coprimary outcomes were COVID-19 and severe COVID-19. Multivariate Cox proportional regression models estimated adjusted hazard ratios (aHRs) and 95% CIs for baseline covariates, accounting for trial, region, and calendar time. Secondary outcomes included severe COVID-19 among people with COVID-19, subclinical SARS-CoV-2 infection, and SARS-CoV-2 infection. Results: A total of 57692 participants (median [range] age, 51 [18-95] years; 11720 participants [20.3%] aged ≥65 years; 31058 participants [53.8%] assigned male at birth) were included. The analysis population included 3270 American Indian or Alaska Native participants (5.7%), 7849 Black or African American participants (13.6%), 17678 Hispanic or Latino participants (30.6%), and 40745 White participants (70.6%). Annualized incidence was 13.9% (95% CI, 13.3%-14.4%) for COVID-19 and 2.0% (95% CI, 1.8%-2.2%) for severe COVID-19. Factors associated with increased rates of COVID-19 included workplace exposure (high vs low: aHR, 1.35 [95% CI, 1.16-1.58]; medium vs low: aHR, 1.41 [95% CI, 1.21-1.65]; P <.001) and living condition risk (very high vs low risk: aHR, 1.41 [95% CI, 1.21-1.66]; medium vs low risk: aHR, 1.19 [95% CI, 1.08-1.32]; P <.001). Factors associated with decreased rates of COVID-19 included previous SARS-CoV-2 infection (aHR, 0.13 [95% CI, 0.09-0.19]; P <.001), age 65 years or older (aHR vs age <65 years, 0.57 [95% CI, 0.50-0.64]; P <.001) and Black or African American race (aHR vs White race, 0.78 [95% CI, 0.67-0.91]; P =.002). Factors associated with increased rates of severe COVID-19 included race (American Indian or Alaska Native vs White: aHR, 2.61 [95% CI, 1.85-3.69]; multiracial vs White: aHR, 2.19 [95% CI, 1.50-3.20]; P <.001), diabetes (aHR, 1.54 [95% CI, 1.14-2.08]; P =.005) and at least 2 comorbidities (aHR vs none, 1.39 [95% CI, 1.09-1.76]; P =.008). In analyses restricted to participants who contracted COVID-19, increased severe COVID-19 rates were associated with age 65 years or older (aHR vs <65 years, 1.75 [95% CI, 1.32-2.31]; P <.001), race (American Indian or Alaska Native vs White: aHR, 1.98 [95% CI, 1.38-2.83]; Black or African American vs White: aHR, 1.49 [95% CI, 1.03-2.14]; multiracial: aHR, 1.81 [95% CI, 1.21-2.69]; overall P =.001), body mass index (aHR per 1-unit increase, 1.03 [95% CI, 1.01-1.04]; P =.001), and diabetes (aHR, 1.85 [95% CI, 1.37-2.49]; P <.001). Previous SARS-CoV-2 infection was associated with decreased severe COVID-19 rates (aHR, 0.04 [95% CI, 0.01-0.14]; P <.001). Conclusions and Relevance: In this secondary cross-protocol analysis of 4 randomized clinical trials, exposure and demographic factors had the strongest associations with outcomes; results could inform mitigation strategies for SARS-CoV-2 and viruses with comparable epidemiological characteristics

Interface effects on the fracture mechanism of a high toughness aluminum composite laminate

The microstructure and the mechanical properties of a multilayer composite laminate based on aluminum 7075 and 2024 alloys produced by hot roll-bonding were examined. The composite laminate has been tested at room temperature under impact Charpy tests, three-point bend tests and shear tests on the interfaces. The toughness of the post-rolling tempered and T6 treated composite laminate, measured by impact absorbed energy in the crack arrester orientation, was more than twenty times higher than that of the monolithic Al 7075 alloy and seven times higher than that of Al 2024 alloy. The outstanding toughness increase of the composite laminate in the post-rolling tempered and T6 treated condition is mainly due to the mechanism of “interface predelamination”. By this fracture mechanism the interfaces are debonded before the main crack reaches them, warranting delamination in all interfaces. Therefore, delamination and crack renucleation in every layer are responsible for the improvement in toughness.Financial support from CICYT (Project MAT2003-01172) is gratefully acknowledged. C.M. Cepeda-Jiménez and J.M. García-Infanta thank the Spanish Ministry of Education and Science for a Juan de la Cierva contract and a FPI fellowship respectively. We also thank L. del Real-Alarcón for the welding work, F.F. González-Rodríguez for assistance during hot rolling and J. Chao-Hermida for assistance with the Charpy impact test.Peer reviewe

Evaluation of learning and exposure in the undergraduate interventional radiology curriculum (ELIXIR)

Aim: To gauge current final year medical students' exposure to interventional radiology (IR)and assess their perceptions of IR as a prospective career option. Materials and methods: An online questionnaire comprising of questions that gauge final-year medical students' understanding of and exposure to IR based on the recommendations set out by the British Society of Interventional Radiology (BSIR), was sent out to final-year students across 34 UK medical schools. Results: Five hundred and ten responses were collected from 33 out of 34 eligible medical schools. Sixty-four per cent of respondents rated their own IR knowledge as inadequate. On average, only 50% of all subtopics proposed in the BSIR undergraduate curriculum was covered during medical school and 32.7% of respondents were not exposed to any fundamental IR principles and techniques recommended by the BSIR during medical school. Regarding careers, 2.7% of respondents reported a definite interest in pursuing a career in IR. Most respondents (89.8%) felt that there was insufficient undergraduate teaching on IR and that they lacked information to consider pursuing a career in IR (87.5%). Conclusion: Insufficient exposure and teaching on IR throughout medical schools have led to a lack of awareness and consideration of IR as a future career choice amongst UK medical students. The re-evaluation of IR teaching in the medical school curricula is needed. In the long-term, such recommendations could provide the much-needed solution to the workforce shortages seen in IR

A non-consequentialist alternative to economics

Providing an up-to-date synthesis of knowledge relevant to the climate change issue, this book ranges from the basic science documenting the need for policy action to the technologies, economic instruments and political strategies that can be employed in response to climate change. Ethical and cultural issues constraining the societal response to climate change are also discussed. This book covers a very wide range of disciplines – core biophysical sciences involved with climate change (geosciences, atmospheric sciences, ocean sciences, ecology/biology) as well as economics, political science, health sciences, institutions and governance, sociology, ethics and philosophy, and engineering