A theoretical and numerical investigation of a family of immersed finite element methods

In this article we consider the widely used immersed finite element method (IFEM), in both explicit and implicit form, and its relationship to our more recent one-field fictitious domain method (FDM). We review and extend the formulation of these methods, based upon an operator splitting scheme, in order to demonstrate that both the explicit IFEM and the one-field FDM can be regarded as particular linearizations of the fully implicit IFEM. However, the one-field FDM can be shown to be more robust than the explicit IFEM and can simulate a wider range of solid parameters with a relatively large time step. In addition, it can produce results almost identical to the implicit IFEM but without iteration inside each time step. We study the effect on these methods of variations in viscosity and density of fluid and solid materials. The advantages of the one-field FDM within the IFEM framework are illustrated through a selection of parameter sets for two benchmark cases

Insights from the NeurIPS 2021 NetHack Challenge

In this report, we summarize the takeaways from the first NeurIPS 2021 NetHack Challenge. Participants were tasked with developing a program or agent that can win (i.e., ‘ascend’ in) the popular dungeon-crawler game of NetHack by interacting with the NetHack Learning Environment (NLE), a scalable, procedurally generated, and challenging Gym environment for reinforcement learning (RL). The challenge showcased community-driven progress in AI with many diverse approaches significantly beating the previously best results on NetHack. Furthermore, it served as a direct comparison between neural (e.g., deep RL) and symbolic AI, as well as hybrid systems, demonstrating that on NetHack symbolic bots currently outperform deep RL by a large margin. Lastly, no agent got close to winning the game, illustrating NetHack’s suitability as a long-term benchmark for AI research

Validation of a modified 28-day rat study to evidence effects of test compounds of the immune system

The toxicology profile of new test compounds is ascertained in repeat-dose toxicity studies with exposure over 4 weeks or 3 months which yield a range between a high dose causing overt toxicity and a low dose with no observable (toxic) effect. In recent years, the immune system has been identified as a target of the direct toxic action of chemicals (Dean et al., 1989). A first step to the EU level to developed a test program to detected undesired effects on the immune system was undertaken in Luxembourg in 1984 (Berlin et al., 1987) . In consequence of this international activity, a number of collaborative studies were initiated. The aim of these studies was to select and validate available testing procedures in a tiered approach to find out their appropriateness of indicating adverse effects on the immune system after exposure to chemicals (Vos and vanLoveren, 1987; Hess et al., 1990). In a collaborative toxicity study initiated and coordinated by the Federal Institute for Health Prot ection of Consumers and Veterinary Medicine, four industrial laboratorys and one independent institute participated. The purpose of this study was to qualify and validate additional investigation (i.e., enhanced pathology, functional tests) within an ordinary subacute toxicity test protocol (Annex V, 67/548/EEC; OECD 407) to identify the effects of chemicals on the immune system during their regular safety evaluation