On the Virtual Element Method for Topology Optimization on polygonal meshes: a numerical study

It is well known that the solution of topology optimization problems may be affected both by the geometric properties of the computational mesh, which can steer the minimization process towards local (and non-physical) minima, and by the accuracy of the method employed to discretize the underlying differential problem, which may not be able to correctly capture the physics of the problem. In light of the above remarks, in this paper we consider polygonal meshes and employ the virtual element method (VEM) to solve two classes of paradigmatic topology optimization problems, one governed by nearly-incompressible and compressible linear elasticity and the other by Stokes equations. Several numerical results show the virtues of our polygonal VEM based approach with respect to more standard methods

The conforming virtual element method for polyharmonic and elastodynamics problems: a review

In this paper, we review recent results on the conforming virtual element approximation of polyharmonic and elastodynamics problems. The structure and the content of this review is motivated by three paradigmatic examples of applications: classical and anisotropic Cahn-Hilliard equation and phase field models for brittle fracture, that are briefly discussed in the first part of the paper. We present and discuss the mathematical details of the conforming virtual element approximation of linear polyharmonic problems, the classical Cahn-Hilliard equation and linear elastodynamics problems.Comment: 30 pages, 7 figures. arXiv admin note: text overlap with arXiv:1912.0712

Impact of COVID-19 on emergency department visits among palliative home care recipients: a retrospective population-based cohort study in the Piedmont region, Italy

Background: Integrated palliative home care (IHPC) is delivered to patients with progressive end-stage diseases. During the COVID-19 pandemic, IHPC needed to provide high-quality home care services for patients who were treated at home, with the goal of avoiding unnecessary care, hospital admissions, and emergency department (ED) visits. This study aimed to compare the ED visits of IHPC recipients in a large Italian region before and during the first two waves of the COVID-19 pandemic and to find sociodemographic or clinical characteristics associated with changes in ED visits during the first two waves of COVID-19 pandemic, compared with the period before. Methods: Administrative databases were used to identify sociodemographic and clinical variables of IHPC recipients admitted before and during the pandemic. The obtained data were balanced by applying a propensity score. The average number of ED visits before and during the pandemic was calculated by using the Welch's t test and stratified by all the variables. Results: Before and during the pandemic, 5155 and 3177 recipients were admitted to IHPC, respectively. These individuals were primarily affected by neoplasms. ED visits of IHPC recipients reduced from 1346 to 467 before and during the pandemic, respectively. A reduced mortality among IHCP patients who had at least one ED visit during the pandemic (8% during the pandemic versus 15% before the pandemic) was found. The average number of ED visits decreased during the pandemic [0.143, confidence interval (CI) = (0.128-0.158) versus 0.264, CI = (0.242-0.286) before the pandemic; p < 0.001] for all ages and IHPC duration classes. The presence of a formal caregiver led to a significant decrease in ED use. Medium and high emergency ED admissions showed no difference, whereas a decrease in low-level emergency ED admissions during the pandemic [1.27, CI = (1.194-1.345) versus 1.439, CI = (1.3-1.579) before the pandemic; p = 0.036] was found. Conclusion: ED visits among IHPC recipients were significantly decreased during the first two waves of the COVID-19 pandemic, especially in those individuals characterized by a low level of emergency. This did not result in an increase in mortality among IHPC recipients. These findings could inform the reorganization of home care services after the pandemic

Impact of the Timing of Integrated Home Palliative Care Enrolment on Emergency Department Visits

Background: The association between timing of integrated home palliative care (IHPC) enrolment and emergency department (ED) visits is still under debate, and no studies investigated the effect of the timing of IPHC enrolment on ED visits, according to their level of emergency. This study aimed to investigate the impact of the timing of IHPC enrolment on different acuity ED visits. Methods: A retrospective, pre-/post-intervention study was conducted from 2013 to 2019 in Italy. Analyses were stratified by IHPC duration (short 90 days) and triage tags (white/green: low level of emergency visit; yellow/red: medium to-high level). The impact of the timing of IHPC enrolment was evaluated in two ways: incidence rate ratios (IRR) of ED visits were determined 1) before and after IHPC enrolment in each group and 2) post-IHPC among groups. Results: A cohort of 17983 patients was analysed. Patients enrolled early in the IHPC programme had a significantly lower incidence rate of ED visits than the pre-enrolment period (IRR=0.65). The incidence rates of white/green and yellow/red ED visits were significantly lower post-IHPC enrolment for patients enrolled early (IRR= 0.63 and 0.67, respectively). All results were statistically significant (p<0.001). Comparing the IHPC groups after enrolment versus the short group, medium and long IHPC groups had a significant reduction of ED visits (IRR=0.37, IRR=0.14 respectively), showing a relation between the timing of IHPC enrolment and the incidence of ED visits. A similar trend was observed after accounting for triage tags of ED visits. Conclusion: The timing of IHPC enrolment is related with a variation of the incidence of ED visits. Early IHPC enrolment is related to a high significant reduction of ED visits when compared to the 90-day pre-IHPC enrolment period and to late IHPC enrolment, accounting for both low-level and medium-to-high level emergency ED visits

Virtual Element Method and Topology Optimization on polygonal meshes

Topology optimization is a fertile area of research that is mainly concerned with the automatic generation of optimal layouts to solve design problems in Engineering. The classical formulation addresses the problem of finding the best distribution of an isotropic material that minimizes the work of the external loads at equilibrium, while respecting a constraint on the assigned amount of volume. This is the so-called minimum compliance formulation that can be conveniently employed to achieve stiff truss-like layout within a two-dimensional domain. A classical implementation resorts to the adoption of four node displacement-based finite elements that are coupled with an elementwise discretization of the (unknown) density field. When regular meshes made of square elements are used, well-known numerical instabilities arise, see in particular the so-called checkerboard patterns. On the other hand, when unstructured meshes are needed to cope with geometry of any shape, additional instabilities can steer the optimizer towards local minima instead of the expected global one. Unstructured meshes approximate the strain energy of truss-like members with an accuracy that is strictly related to the geometrical features of the discretization, thus remarkably affecting the achieved layouts. In this talk we will consider several benchmarks of truss design and explore the performance of the Virtual Element Method (VEM) in driving the topology optimization procedure. In particular, we will show how the capability of VEM of efficiently approximating elasticity equations on very general polygonal meshes can contribute to overcome the aforementioned mesh-dependent instabilities exhibited by classical finite element based discretization techniques

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

Abstract 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

C1 C^1 -VEM for some variants of the Cahn-Hilliard equation: A numerical exploration

We consider the C1-Virtual Element Method (VEM) for the conforming numerical approximation of some variants of the Cahn-Hilliard equation on polygonal meshes. In particular, we focus on the discretization of the advective Cahn-Hilliard problem and the Cahn-Hilliard inpainting problem. We present the numerical approximation and several numerical results to assess the efficacy of the proposed methodology