Adaptive Algorithms for Relaxed Pareto Set Identification

In this paper we revisit the fixed-confidence identification of the Pareto optimal set in a multi-objective multi-armed bandit model. As the sample complexity to identify the exact Pareto set can be very large, a relaxation allowing to output some additional near-optimal arms has been studied. In this work we also tackle alternative relaxations that allow instead to identify a relevant subset of the Pareto set. Notably, we propose a single sampling strategy, called Adaptive Pareto Exploration, that can be used in conjunction with different stopping rules to take into account different relaxations of the Pareto Set Identification problem. We analyze the sample complexity of these different combinations, quantifying in particular the reduction in sample complexity that occurs when one seeks to identify at most $k$ Pareto optimal arms. We showcase the good practical performance of Adaptive Pareto Exploration on a real-world scenario, in which we adaptively explore several vaccination strategies against Covid-19 in order to find the optimal ones when multiple immunogenicity criteria are taken into account

Adaptive Algorithms for Relaxed Pareto Set Identification

International audienceIn this paper we revisit the fixed-confidence identification of the Pareto optimal set in a multi-objective multi-armed bandit model. As the sample complexity to identify the exact Pareto set can be very large, a relaxation allowing to output some additional near-optimal arms has been studied. In this work we also tackle alternative relaxations that allow instead to identify a relevant subset of the Pareto set. Notably, we propose a single sampling strategy, called Adaptive Pareto Exploration, that can be used in conjunction with different stopping rules to take into account different relaxations of the Pareto Set Identification problem. We analyze the sample complexity of these different combinations, quantifying in particular the reduction in sample complexity that occurs when one seeks to identify at most k Pareto optimal arms. We showcase the good practical performance of Adaptive Pareto Exploration on a real-world scenario, in which we adaptively explore several vaccination strategies against Covid-19 in order to find the optimal ones when multiple immunogenicity criteria are taken into account

Microbiological contamination of cooked meals in collective and commercial catering of public universities of Abidjan in Côte d’Ivoire

In Côte d'Ivoire, the absence of legislation in university catering increases the risk of collective food poisoning. The aim of this study was to assess the level of contamination of cooked meals in university catering in the city of Abidjan. To do this, 160 cooked meals samples were taken in the two public universities of Abidjan. The search of mesophilic aerobic germs; Enterobacteriaceae and of Staphylococcus aureus was carried out. The results showed that in general, the microbial loads of the cooked meals analyzed were higher than the criteria required by the regulations. 40.33% of the presumptive Staphylococcus aureus strains tested are confirmed. 20 species belonging to 14 genera of Enterobacteriaceae were isolated from the different cooked meals. The species most frequently isolated from cooked meals is Klebsiella pneumoniae (19.4%) followed by Klebsiella oxytoca (17%) and Serratia liquefaciens (14.5%). In general, efforts still need to be made to improve the level of hygiene in institutional catering and commercial catering. Constant monitoring of the application of hygienic rules must be instituted, in order to prevent the occurrence of food poisoning. The use of microbiologic results of cooked meals in the universities will provide an example for similar collective catering

A new method to determine the diet of pygmy hippopotamus in Taï National Park, Côte d’Ivoire

Diet determination of endangered species is an essential element in defining successful conservation strategies and optimising captive breeding programmes. In this study, we developed a new diet identification system, derived from standard faecal analysis, to determine the diet of an elusive and endangered herbivore, the pygmy hippopotamus (Choeropsis liberiensis). We collected faecal samples from 10 free-ranging individuals covering a combined home range area of about 50 km2 in Taï National Park, Côte d’Ivoire. In subsequent laboratory analyses, we extracted a large number of leaf epidermis fragments from spatially separated faecal samples and compared them with a reference plant database. Using Multiple Correspondence Analysis (MCA) of epidermis fragments combined with direct visual inspection, we identified the most frequently consumed plant species, which revealed that pygmy hippopotami qualified as intermediate feeders. Their diet was based on at least seven species of monocotyledonae, dicotyledonae and fern groups, with a preference for a small number of other plant species. We evaluate the merit of our method and discuss our findings for developing effective conservation and captive breeding strategies in an endangered species with a wild population of less than 2500 adult individuals.‘Fond des donations’ of the University of Neuchâtel and the ‘Willy Müller Award’ of the Centre Suisse de Recherches Scientifiques en Côte d’Ivoire.http://www.wileyonlinelibrary.com/journal/ajehj2022Mammal Research Institut