Local search pivoting rules and the landscape global structure

In local search algorithms, the pivoting rule determines which neighboring solution to select and thus strongly influences the behavior of the algorithm and its capacity to sample good-quality local optima. The classical pivoting rules are first and best improvement, with alternative rules such as worst improvement and maximum expansion recently studied on hill-climbing algorithms. This article conducts a thorough empirical comparison of five pivoting rules (best, first, worst, approximated worst and maximum expansion) on two benchmark combinatorial problems, NK landscapes and the unconstrained binary quadratic problem (UBQP), with varied sizes and ruggedness. We present both a performance analysis of the alternative pivoting rules within an iterated local search (ILS) framework and a fitness landscape analysis and visualization using local optima networks. Our results reveal that the performance of the pivoting rules within an ILS framework may differ from their performance as single climbers and that worst improvement and maximum expansion can outperform classical pivoting rules

Exiting the Anthropocene : Achieving personal and planetary health in the 21st century

Planetary health provides a perspective of ecological interdependence that connects the health and vitality of individuals, communities, and Earth's natural systems. It includes the social, political, and economic ecosystems that influence both individuals and whole societies. In an era of interconnected grand challenges threatening health of all systems at all scales, planetary health provides a framework for cross-sectoral collaboration and unified systems approaches to solutions. The field of allergy is at the forefront of these efforts. Allergic conditions are a sentinel measure of environmental impact on human health in early life-illuminating how ecological changes affect immune development and predispose to a wider range of inflammatory noncommunicable diseases (NCDs). This shows how adverse macroscale ecology in the Anthropocene penetrates to the molecular level of personal and microscale ecology, including the microbial systems at the foundations of all ecosystems. It provides the basis for more integrated efforts to address widespread environmental degradation and adverse effects of maladaptive urbanization, food systems, lifestyle behaviors, and socioeconomic disadvantage. Nature-based solutions and efforts to improve nature-relatedness are crucial for restoring symbiosis, balance, and mutualism in every sense, recognizing that both personal lifestyle choices and collective structural actions are needed in tandem. Ultimately, meaningful ecological approaches will depend on placing greater emphasis on psychological and cultural dimensions such as mindfulness, values, and moral wisdom to ensure a sustainable and resilient future.Peer reviewe

Cabbage and fermented vegetables : From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19

Large differences in COVID-19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS-CoV-2 binds to its receptor, the angiotensin-converting enzyme 2 (ACE2). As a result of SARS-CoV-2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT(1)R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID-19. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT(1)R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof-of-concept of dietary manipulations that may enhance Nrf2-associated antioxidant effects, helpful in mitigating COVID-19 severity.Peer reviewe

Nrf2-interacting nutrients and COVID-19 : time for research to develop adaptation strategies

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPAR gamma:Peroxisome proliferator-activated receptor, NF kappa B: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2 alpha:Elongation initiation factor 2 alpha). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT(1)R axis (AT(1)R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity

Fitness landscape exploration strategies : application of combinatorial optimization problems to the approximate solution of combinatorial optimization problems

De nombreux problèmes d'optimisation combinatoire sont difficiles à résoudre et mettent en échec les méthodes de résolution exactes. Parmi les algorithmes de résolution approchée, les métaheuristiques sont des algorithmes génériques largement étudiés dans la littérature. La capacité d’une métaheuristique donnée à trouver de bonnes solutions varie selon la nature des problèmes traités et selon les données qui les composent, et il est difficile d’étudier efficacement la dynamique de ces algorithmes pour des instances de grandes tailles. L'étude proposée porte sur les métaheuristiques de type recherche locale. Des mécanismes basiques sont étudiés afin d'améliorer la compréhension de leur comportement et d'évaluer leur capacité à trouver de bonnes solutions sur différents types de problèmes. Nous abstrayons plusieurs problèmes d'optimisation, munis d’une relation de voisinage entre solutions, sous forme de paysages de fitness afin d’analyser la dynamique des méthodes selon des caractéristiques générales de ces paysages. Nous étudions la navigation dans ces paysages, en se restreignant en premier lieu aux mouvements strictement améliorants. En particulier, nous proposons le critère d’expansion pour guider la recherche et évaluons sa pertinence pour guider les descentes vers de bonnes solutions. Différentes variantes approchant ce principe sont proposées et évaluées, offrant divers compromis entre efficacité et coût calculatoire permettant d’envisager de les intégrer dans des métaheuristiques plus complexes. Enfin nous étudions des recherches locales à voisinage partiel qui acceptent les mouvements détériorant et montrons que dans ce contexte des règles pivot simples peuvent suffire à obtenir de bons compromis entre intensification et diversification, et ainsi atteindre de très bonnes solutions sur divers paysages.Many combinatorial optimization problems are hard to solve and in many cases, exact approaches are impracticable. Among partial search algorithms, metaheuristics are generic algorithms, widely studied in the literature. Their ability to find good solutions varies in function of the problems’ nature et data composing problem instances, and studying efficiently the dynamics of such algorithms is challenging, especially for large instances. We restrain our metaheuristic study to local search algorithms. Basic mechanisms are studied to improve their understanding and assess their ability to find good solutions. We abstract optimization problems into fitness landscapes, thanks to a neighborhood relation between solutions, in order to analyze the dynamics of methods in function of several landscapes characteristics.We study the navigation on these landscapes, firstly by constraining moves to be strictly improving. In particular, we propose the expansion criterion to guide the search process and assess its relevance to guide climbers through good solutions. Variants approximating this principle are proposed and studied, leading to many trade-offs between the ability to find good solutions and the computational cost making them integrable into more complex metaheuristics. Last, we study partial neighborhood local searches, which accept deteriorating moves. In this context, experiments show that simple pivoting rules are sufficient to attain good trade-offs between intensification and diversification and thus reaching good solutions

Stratégies d'exploration de paysages de fitness : application à la résolution approchée de problèmes d'optimisation combinatoire

Many combinatorial optimization problems are hard to solve and in many cases, exact approaches are impracticable. Among partial search algorithms, metaheuristics are generic algorithms, widely studied in the literature. Their ability to find good solutions varies in function of the problems’ nature et data composing problem instances, and studying efficiently the dynamics of such algorithms is challenging, especially for large instances. We restrain our metaheuristic study to local search algorithms. Basic mechanisms are studied to improve their understanding and assess their ability to find good solutions. We abstract optimization problems into fitness landscapes, thanks to a neighborhood relation between solutions, in order to analyze the dynamics of methods in function of several landscapes characteristics.We study the navigation on these landscapes, firstly by constraining moves to be strictly improving. In particular, we propose the expansion criterion to guide the search process and assess its relevance to guide climbers through good solutions. Variants approximating this principle are proposed and studied, leading to many trade-offs between the ability to find good solutions and the computational cost making them integrable into more complex metaheuristics. Last, we study partial neighborhood local searches, which accept deteriorating moves. In this context, experiments show that simple pivoting rules are sufficient to attain good trade-offs between intensification and diversification and thus reaching good solutions.De nombreux problèmes d'optimisation combinatoire sont difficiles à résoudre et mettent en échec les méthodes de résolution exactes. Parmi les algorithmes de résolution approchée, les métaheuristiques sont des algorithmes génériques largement étudiés dans la littérature. La capacité d’une métaheuristique donnée à trouver de bonnes solutions varie selon la nature des problèmes traités et selon les données qui les composent, et il est difficile d’étudier efficacement la dynamique de ces algorithmes pour des instances de grandes tailles. L'étude proposée porte sur les métaheuristiques de type recherche locale. Des mécanismes basiques sont étudiés afin d'améliorer la compréhension de leur comportement et d'évaluer leur capacité à trouver de bonnes solutions sur différents types de problèmes. Nous abstrayons plusieurs problèmes d'optimisation, munis d’une relation de voisinage entre solutions, sous forme de paysages de fitness afin d’analyser la dynamique des méthodes selon des caractéristiques générales de ces paysages. Nous étudions la navigation dans ces paysages, en se restreignant en premier lieu aux mouvements strictement améliorants. En particulier, nous proposons le critère d’expansion pour guider la recherche et évaluons sa pertinence pour guider les descentes vers de bonnes solutions. Différentes variantes approchant ce principe sont proposées et évaluées, offrant divers compromis entre efficacité et coût calculatoire permettant d’envisager de les intégrer dans des métaheuristiques plus complexes. Enfin nous étudions des recherches locales à voisinage partiel qui acceptent les mouvements détériorant et montrons que dans ce contexte des règles pivot simples peuvent suffire à obtenir de bons compromis entre intensification et diversification, et ainsi atteindre de très bonnes solutions sur divers paysages

L'imperfect

En este proyecto se cuestiona el ideal de belleza femenino impuesto por los medios de comunicación de masas. Una seductora trampa que controla a las mujeres y logra que se sientan insatisfechas con su propio cuerpo. El trabajo consta de una parte teórica en la que se desarrolla una investigación breve del canon de belleza a lo largo de la historia y en el arte, y una parte gráfica en la que a través de una serie de experimentaciones con el collage se pretende mostrar el tema escogid