We generally agree with Burt's thesis. However, we note that the author did not discuss epigenetics, the study of how the environment can alter gene structure and function. Given epigenetic mechanisms, the utility of polygenic risk scores (PRS) is limited in studies of development and mental illness. Finally, in this commentary we expand upon the risks of reliance upon PRSs.

We present a mathematical model of a fishery on several sites with a variable price. The model takes into account the evolution during the time of the resource, fishes and boats movements between the different sites, fishing effort and price that varies with respect to supply and demand. We suppose that boats and fishes movements as well as prices variations occur at a fast time scale. We use methods of aggregation of variables in order to reduce the number of variables and we derive a reduced model governing two global variables, respectively the biomass of the resource and the fishing effort of the whole fishery. We look for the existence of equilibria of the aggregated model. We show that the aggregated model can have 1, 2 or 3 non trivial equilibria. We show that a variation of the total number of sites can induce a switch from over-exploitation to sustainable fisheries.

Plusieurs laboratoires et centres techniques ont commencé à travailler sur la possibilité de réaliser des composés multimatériaux via la Métallurgie des Poudres. Dans un tel cas, ce procédé permet d'éviter le problème de l'assemblage et d'obtenir une production aux cotes. Les compressions dynamique (CGV) et conventionnelle sont deux voies possibles qui pourront être comparées grâce à une presse de laboratoire instrumentée pour l'analyse des phénomènes. Pour certaines poudres, la CGV permet d'améliorer les propriétés à vert et de modifier favorablement les conditions de frittage. La compression est suivie d'un frittage conventionnel. Différents types de poudres (poudres métalliques, poudres dures mais également des poudres céramiques) sont utilisés dans ce projet permettant ainsi de proposer de nombreuses applications. Cette présentation montre les premiers résultats obtenus par le groupe de recherche.

This paper is devoted to the study of a predator-prey model in a patchy environment. The model represents the interactions between phytoplankton and zooplankton in the water column. Two patches are considered with respect to light availability: one patch is associated to the surface layer, the second patch describes the bottom layer. We show that this spatial heterogeneity may destabilize the predator-prey system, even in oligotrophic system where the nutrient is low enough to avoid ”paradox-enrichment” phenomenon. Indeed, in this case, an heterogeneity index can be used as a bifurcation parameter, leading to a Hopf bifurcation. Moreover, we assume that individuals can be dispersed in both patches via hydrodynamism processes, like in a mixed layer. The effect of mixing intensity is analysed as well as interactions between dispersion and enrichment. We also show that, in some cases, spatial heterogeneity has a stabilizing effect. These contrasted results are examined by considering the non linear interaction between heterogeneity, dispersal and enrichment and some mechanisms leading to stabilization/destabilization are exhibited.

We study a reaction-diffusion equation with an integral term describing nonlocal consumption of resources in population dynamics. We show that a homogeneous equilibrium can lose its stability resulting in appearance of stationary spatial structures. They can be related to the emergence of biological species due to the intra-specific competition and random mutations. Various types of travelling waves are observed.

Mechanical properties, such as hardness and impact toughness, of ferrite-containing stainless steels are greatly affected by long-term aging at intermediate temperatures. It is known that the α-α′ spinodal decomposition occurring in the iron–chromium-based ferrite is responsible for this aging susceptibility. This decomposition can be characterized unambiguously by atom probe analysis, allowing comparison both with the existing theories of spinodal decomposition and the evolution of some mechanical properties. It is then possible to predict the evolution of hardness of industrial components during service, based on the detailed knowledge of the involved aging process.

The merging of two independent populations of heterotrophs and autotrophs into a single population of mixotrophs has occurred frequently in evolutionary history. It is an example of a wide class of related phenomena, known as symbiogenesis. The physiological basis is almost always (reciprocal) syntrophy, where each species uses the products of the other species. Symbiogenesis can repeat itself after specialization on particular assimilatory substrates. We discuss quantitative aspects and delineate eight steps from two free-living interacting populations to a single fully integrated endosymbiotic one. The whole process of gradual interlocking of the two populations could be mimicked by incremental changes of particular parameter values. The role of products gradually changes from an ecological to a physiological one. We found conditions where the free-living, epibiotic and endobiotic populations of symbionts can co-exist, as well as conditions where the endobiotic symbionts outcompete other symbionts. Our population dynamical analyses give new insights into the evolution of cellular homeostasis. We show how structural biomass with a constant chemical composition can evolve in a chemically varying environment if the parameters for the formation of products satisfy simple constraints. No additional regulation mechanisms are required for homeostasis within the context of the dynamic energy budget (DEB) theory for the uptake and use of substrates by organisms. The DEB model appears to be closed under endosymbiosis. This means that when each free-living partner follows DEB rules for substrate uptake and use, and they become engaged in an endosymbiotic relationship, a gradual transition to a single fully integrated system is possible that again follows DEB rules for substrate uptake and use.

We try to explain the large differences observed in the proportion of needles colonized by fungal species in coniferous litter by spore dispersal properties. We constructed a population dynamics model, assuming that litter is a resource that is fragmented into ephemeral units, periodically produced. Spore dispersion on needles on a small spatial scale was assumed to follow a Poisson distribution. The model was compared with an experimental system using Thysanophora penicillioides on Abies alba needles and its relevance to field conditions is discussed.