Preserving or escaping? On the welfare effects of environmental self-protective choices

In modern societies individuals often try to alleviate their personal damages from environmental degradation by increasing their consumption of private goods. Although this “self-protective” behavior is very frequent in industrial economies, insufficient attention has been paid to its economic and environmental consequences. In this paper we show that such a behavior can give rise to a self-reinforcing growth process in which environmental degradation increases economic growth and vice-versa, leading the economy on a welfare-reducing path. For this purpose, we first provide several examples of environmental self-protective choices to give a heuristic view of this phenomenon and then examine their effects through a two-islands evolutionary model that leads the reader beyond a purely intuitive understanding of the argument. Although the proposed model is deliberately very simple, it may provide some interesting insights on an aspect that has been mainly ignored in the literature so far.Self-protective choices; defensive expenditures; environmental degradation; negative externalities; economic growth.

A reactive molecular dynamics study

We report the results of a computational study regarding the mechanical properties of a lithiated Si/SiO2 interface using reactive molecular dynamics. The study is motivated by an intended application of SiO2-coated Sinanotubes as fibers in structural batteries with a fiber-reinforced composite architecture while serving as anodes. According to the results, main failure properties due to partly irreversible bond breakage during mechanical deformation are identified, indicating agreement with bond energy/bond order based estimates. Microscopic failure properties are also identified and interpreted in view of the observed processes of bonding degradation. In particular, the effect of Li distribution on the shear deformation response is evaluated as significant

Absorbing processes in Richardson diffusion: analytical results

We consider the recently addressed problem of a passive particle (a predator), being the center of a ``sphere of interception'' of radius $R$ and able to absorb other passive particles (the preys) entering into the sphere. Assuming that all the particles are advected by a turbulent flow and that, in particular, the Richardson equation properly describes the relative dispersion, we calculate an analytical expression for the flux into the sphere as a function of time, assuming an initial constant density of preys outside the sphere. In the same framework, we show that the distribution of times of first passage into the sphere has a $t^{-5/2}$ power law tail, seen in contrast to the $t^{-3/2}$ appearing in standard 3D diffusion. We also discuss the correction due to the integral length scale on the results in the stationary case.Comment: 6 pages, 3 figures, sunbmitted to Physics of Fluid

Partition of unity-based discontinuous finite elements: GFEM, PUFEM, XFEM

International audienceIn this paper we review some basic notions of partition of unity-based discontinuous finite elements showing their relation to the Generalized Finite Element Method. A minimal one-dimensional example illustrates some of the issues related to the computer implementation of the method and highlights the relative simplicity of the approach. The ability of the approach in describing displacement discontinuities independently of the finite element mesh is shown in a classical crack propagation problem in an elastic medium. We also illustrate some limitations of this method when used in conjunction with the dummy stiffness approach.Dans cet article, nous présentons les principes élémentaires des éléments finis discontinus basés sur la méthode de la partition de l'unité en montrant leur relation avec la méthode des éléments finis généralisée. Les aspects liés à l'implantation dans un code ainsi que la simplicité de cette méthode sont illustrés sur un exemple unidimensionnel. La capacité de cette approche à représenter des discontinuités en déplacement indépendamment du maillage élément fini est montrée sur la propagation d'une fissure dans un milieu élastique. Nous montrons aussi certaines limitations de cette méthode quand elle est utilisée avec l'approche "dummy stiffness"

Biodiversity and Economic Growth: Stabilization Versus Preservation of the Ecological Dynamics

This work examines the impact that economic growth can have on biodiversity and on the ecological dynamics that would naturally emerge in the absence of human activity. The loss of biodiversity may induce policy-makers to implement defensive actions that prevent single species from extinction. These defensive actions, however, may deeply alter the natural dynamics of interaction between species, leading to an ecological equilibrium that is completely different from the one that would exist in the absence of human intervention. This suggests that there might exist a conflict between preserving biodiversity (through stabilization of the ecological system) and preserving the intrinsic features of the ecological dynamics. To investigate this issue more deeply, we analyze the impact that different objective functions and defensive technologies can have on the natural ecological dynamics, and show that human action can modify the stability of the ecological fixed points. From the simple analytical formulations adopted in the paper, it emerges that it is possible to stabilize the ecological fixed point and consequently to avoid the extinction of a species, even in the absence of defensive expenditures specifically finalized at the protection of that species. The stabilizing. effect of human intervention, however, turns out to be enhanced when specific defensive expenditures are implemented. Finally, numerical simulations suggest that human activity can have an even deeper impact on the ecological dynamics, substantially modifying not only the stability of the fixed points, but also their number.Biodiversity, Growth, Defensive actions, Ecological dynamics

Detrital events within pelagic deposits of the Umbria-Marche basin (Northern Apennines, Italy). Further evidence of Early Cretaceous tectonics

Re-sedimented deposits characterize different stratigraphical intervals in the pelagic successions of the Umbria-Marche-Sabina Domain (Central and Northern Apennines, Italy). Three stratigraphic sections of the Maiolica and Marne a Fucoidi Formations, characterized by breccias and calcarenites embedded in pelagic sediments, were sampled across the Mt. Primo area (Umbria- Marche Ridge, Northern Apennines). Facies analysis indicates a gravity-driven origin for the clastic levels, interpreted as debris-flows, or turbidity flows. The massive lensoid-to-tabular levels are composed of loose shallow-water benthic material, sourced from an unknown carbonate platform, associated with: i) lithoclasts made of Lower Jurassic and Lower Cretaceous shallow-water carbonates; ii) Jurassic mudstones and wackestones referable to the pelagic succession; iii) calpionellid/radiolarian-rich soft pebbles (Maiolica-type facies). The compositional features of the studied detrital deposits imply submarine exposure and dismantling of portions of the stratigraphic succession older than the Barremian/Aptian, which had to be buried in the late Early Cretaceous. Such evidence led us to refer the investigated clastic event to an extensional tectonic phase. Our interpretation well fits with data coming from different geological settings of Italy, strongly suggesting the occurrence of a widespread extensional phase in the late Early Cretaceous

Understanding the mechanism of binding between Gab2 and the C terminal SH3 domain from Grb2

Gab2 is a large disordered protein that regulates several cellular signalling pathways and is overexpressed in different forms of cancer. Because of its disordered nature, a detailed characterization of the mechanisms of recognition between Gab2 and its physiological partners is particularly difficult. Here we provide a detailed kinetic characterization of the binding reaction between Gab2 and the C-terminal SH3 domain of the growth factor receptor-bound protein 2 (Grb2). We demonstrate that Gab2 folds upon binding following an induced fit type mechanism, whereby recognition is characterized by the formation of an intermediate, in which Gab2 is primarily disordered. In this scenario, folding of Gab2 into the bound conformation occurs only after binding. However, an alanine scanning of the proline residues of Gab2 suggests that the intermediate contains some degree of native-like structure, which might play a role for the recognition event to take place. The results, which represent a fundamental step forward in the understanding of this functional proteinprotein interaction, are discussed on the light of previous structural works on these proteins

Diatoms synthesize sterols by inclusion of animal and fungal genes in the plant pathway

Diatoms are ubiquitous microalgae that have developed remarkable metabolic plasticity and gene diversification. Here we report the first elucidation of the complete biosynthesis of sterols in the lineage. The study has been carried out on the bloom-forming species Skeletonema marinoi and Cyclotella cryptica that synthesise an ensemble of sterols with chemotypes of animals (cholesterol and desmosterol), plants (dihydrobrassicasterol and 24-methylene cholesterol), algae (fucosterol) and marine invertebrates (clionasterol). In both species, sterols derive from mevalonate through cyclization of squalene to cycloartenol by cycloartenol synthase. The pathway anticipates synthesis of cholesterol by enzymes of the phytosterol route in plants, as recently reported in Solanaceae. Major divergences stem from reduction of Δ24(28) and Δ24(25) double bonds which, in diatoms, are apparently dependent on sterol reductases of fungi, algae and animals. Phylogenetic comparison revealed a good level of similarity between the sterol biosynthetic genes of S. marinoi and C. cryptica with those in the genomes of the other diatoms sequenced so far