Les déterminants de la dynamique entrepreneuriale dans les régions françaises (1994-2003)

Cet article cherche à évaluer les déterminants de la dynamique entrepreneuriale dans les régions françaises pour la période 1993-2004. On estime dans ce but un modèle dynamique de panel par la méthode de Blundell et Bond (1998) pour expliquer le taux de création d'entreprise (rapporté à la population régionale). L'hypothèse d'Holcombe (1998) selon laquelle la création d'entreprise s'explique par elle-même est en premier lieu confirmée. Il apparaît également que le niveau de chômage et le revenu disponible ont un effet positif sur la création régionale d'entreprise. La taille des entreprises jouerait, à l'inverse, négativement comme une barrière à l'entrée. Enfin, l'importance statistique des effets spécifiques individuels amène à penser que les facteurs institutionnels et culturels doivent être mieux pris en considération au niveau régional.dynamique entrepreneuriale, modèle dynamique de panel, régions françaises

Assessing the mitigation potential of environmental impacts from circular economy strategies on an industrial sector and its value chain: a case study on the steel value chain in Quebec

ABSTRACT: This research project aims to evaluate the potential reduction of environmental impacts from circular economy strategies on an industrial sector at a regional scale with a case study on Greenhouse Gas (GHG) emissions in Quebec's steel industry and its value chain. To do so, an integrated model has been created based on the matrix approach, building on material flow analysis (MFA) tracking flows and stocks and on life cycle assessment (LCA) to compute direct (from the activity, e.g., combustion process) and indirect (from the supply chain, e.g., production of raw material inside or outside of region) emissions. This theoretical model is designed to be applied to any emissions or environmental impacts from a specific sector in a given region and enable to model the effects of circularity strategies to both flows and related environmental impacts. The overall mitigation potential of individual or combined circular economy strategies on a specific sector could thus be evaluated across its entire value chain. In the case study, a set of the most promising circular strategies applicable in the Quebec context were identified, and the GHG reduction potential within and outside the province is calculated and compared with actual emissions. Six circular strategies were analyzed acting at three different levers, namely, GHG/material (increase iron recycling rate, switch to hydrogen-based reduction production), material/product (reduce weight of vehicle, limit over-specification in building construction), and product/service (increase buildings and cars lifetime, increase car-sharing), and therefore impact rather direct or indirect emissions on different stages of the steel life cycle. Combining these six strategies into a consolidated scenario shows that a circular-driven economy allows to cut down GHG emissions of the cradle-to-gate steel industry value chain by −55%, i.e., 1.67 Mt CO2e. Taking into account use phase of steel, overall reductions are estimated at −6.03 Mt CO2e, i.e., −30% of the whole life cycle

Proto-Planetary Disk Chemistry Recorded by D-Rich Organic Radicals in Carbonaceous Chondrites

Insoluble organic matter (IOM) in primitive carbonaceous meteorites has preserved its chemical composition and isotopic heterogeneity since the solar system formed ~4.567 billion years ago. We have identified the carrier moieties of isotopically anomalous hydrogen in IOM isolated from the Orgueil carbonaceous chondrite. Data from high spatial resolution, quantitative isotopic NanoSIMS mapping of Orgueil IOM combined with data from electron paramagnetic resonance spectroscopy reveals that organic radicals hold all the deuterium excess (relative to the bulk IOM) in distinct, micrometer-sized, D-rich hotspots. Taken together with previous work, the results indicate that an isotopic exchange reaction took place between pre-existing organic compounds characterized by low D/H ratios and D-rich gaseous molecules, such as H_2D^+ or HD_2^+. This exchange reaction most likely took place in the diffuse outer regions of the proto-planetary disk around the young Sun, offering a model that reconciles meteoritic and cometary isotopic compositions of organic molecules

Neuron-Derived Semaphorin 3A Is an Early Inducer of Vascular Permeability in Diabetic Retinopathy via Neuropilin-1

SummaryThe deterioration of the inner blood-retinal barrier and consequent macular edema is a cardinal manifestation of diabetic retinopathy (DR) and the clinical feature most closely associated with loss of sight. We provide evidence from both human and animal studies for the critical role of the classical neuronal guidance cue, semaphorin 3A, in instigating pathological vascular permeability in diabetic retinas via its cognate receptor neuropilin-1. We reveal that semaphorin 3A is induced in early hyperglycemic phases of diabetes within the neuronal retina and precipitates initial breakdown of endothelial barrier function. We demonstrate, by a series of orthogonal approaches, that neutralization of semaphorin 3A efficiently prevents diabetes-induced retinal vascular leakage in a stage of the disease when vascular endothelial growth factor neutralization is inefficient. These observations were corroborated in TgCre-Esr1/Nrp1flox/flox conditional knockout mice. Our findings identify a therapeutic target for macular edema and provide further evidence for neurovascular crosstalk in the pathogenesis of DR

Évaluation du risque simplifiée du tomato brown rugose fruit virus pour la France métropolitaine: Avis de l'Anses. Rapport d'expertise collective

Évaluation du risque simplifiée du tomato brown rugose fruit virus pour la France métropolitaine. Avis de l'Anses. Rapport d'expertise collectiv

Combined fit to the spectrum and composition data measured by the Pierre Auger Observatory including magnetic horizon effects

The measurements by the Pierre Auger Observatory of the energy spectrum and mass composition of cosmic rays can be interpreted assuming the presence of two extragalactic source populations, one dominating the flux at energies above a few EeV and the other below. To fit the data ignoring magnetic field effects, the high-energy population needs to accelerate a mixture of nuclei with very hard spectra, at odds with the approximate E$^{-2}$ shape expected from diffusive shock acceleration. The presence of turbulent extragalactic magnetic fields in the region between the closest sources and the Earth can significantly modify the observed CR spectrum with respect to that emitted by the sources, reducing the flux of low-rigidity particles that reach the Earth. We here take into account this magnetic horizon effect in the combined fit of the spectrum and shower depth distributions, exploring the possibility that a spectrum for the high-energy population sources with a shape closer to E$^{-2}$ be able to explain the observations