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Does Gender Affect Scientific Productivity ? A Critical Review of the Empirical Evidence and a Panel Data Econometric Analysis for FrenchPhysicists
No full textInternational audienceThe paper revisits the issue of the gender gap in scientific productivity, oftenreferred as the “productivity puzzle” by economists and sociologists of science. Afterproviding a critical review of the empirical evidence, the paper presents the relevantresults of a panel data econometric analysis of individual publication productivitydifferences for two large samples of French cnrs and university physicists. Weobserve in both cases that the productivity of women in terms of number ofpublications is, by about one third in average, largely lower than that of men. Weconclude, however, that female physicists appear as productive as their malecolleagues in cnrs, and even more productive in French universities, when we takeinto account several factors, in particular unequal chances of promotion and frequentnon-publishing spells, which can reflect strong family engagements
Radial Junction Architecture: A New Approach to Stable and Highly Efficient Silicon Thin Film Solar Cells
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Many-Body Quantum Electrodynamics Networks: Non-Equilibrium Condensed Matter Physics with Light
No full text30 pages, Invited Review Submitted to Comptes Rendus de l'Acad\'emie des Sciences, topical issue on polaritons. Comments are welcomeWe review recent developments concerning non-equilibrium quantum dynamics and many-body physics with light, in superconducting circuits and Josephson analogues. We start with quantum impurity models summarizing the effect of dissipation and of driving the system. We mention theoretical and experimental efforts to characterize these non-equilibrium quantum systems. We show how Josephson junction systems can implement the equivalent of the Kondo effect with microwave photons. The Kondo effect is characterized by a renormalized light-frequency and a peak in the Rayleigh elastic transmission of a photon. We also address the physics of hybrid systems comprising mesoscopic quantum dot devices coupled to an electromagnetic resonator. Then, we discuss extensions to Quantum Electrodynamics (QED) Networks allowing to engineer the Jaynes-Cummings lattice and Rabi lattice models. This opens the door to novel many-body physics with light out of equilibrium, in relation with the Mott-superfluid transition observed with ultra-cold atoms in optical lattices. Then, we summarize recent theoretical predictions for realizing topological phases with light. Synthetic gauge fields and spin-orbit couplings have been successfully implemented with ultra-cold atoms in optical lattices --- using time-dependent Floquet perturbations periodic in time, for example --- as well as in photonic lattice systems. Finally, we discuss the Josephson effect related to Bose-Hubbard models in ladder and two-dimensional geometries. The Bose-Hubbard model is related to the Jaynes-Cummings lattice model in the large detuning limit between light and matter. In the presence of synthetic gauge fields, we show that Meissner currents subsist in an insulating Mott phase
Near-tip strain evolution under cyclic loading: In situ experimental observation and numerical modelling
No full textInternational audienceThe concept of ratchetting strain as a crack driving force in controlling crack growth has previously been explored at Portsmouth using numerical approaches for nickel-based superalloys. In this paper, we report the first quantitative experimental evidence of near-tip strain ratchetting with cycles, as captured in situ by digital image correlation (DIC) technique on a compact tension specimen of stainless steel 316L, using both Stereo and SEM systems. The evolution of the near-tip strains with loading cycles was monitored whilst the crack tip was kept stationary. The strains normal to the crack plane were examined over selected distances from 6 to 57 lm to the crack tip for a number of cycles. The results show that strain ratchetting occurs with loading cycles, and is particularly evident close to the crack tip and under higher loads. 3D finite element models have also been developed to simulate the experiments and the results from the simulation are compared with those from the DIC measurements. This is the first time that near-tip strain ratchetting has been captured in situ at the peak loads during cyclic loading
About the use of standard integration schemes for X-FEM in solid mechanics plasticity
No full textInternational audienceHighlights • A new integration method for X-FEM elements cut by an interface is proposed. • The Heaviside function is replaced by an equivalent continuous higher order polynomial function. • A generic numerical strategy to compute this polynomial function is proposed. • This new integration method integrates correctly mechanical fields in elasticity and plasticity. Abstract The introduction of plasticity in an extended finite element (X-FEM) framework is very recent and arises several technical and scientific difficulties due to the moving position of integration points as the crack proceeds if a fixed grid is not used. Currently, the existing analyses in plasticity with X-FEM are limited to monotonic plasticity approximated by non-linear elasticity using the HRR field decomposition. However, such an analysis cannot be applied in fatigue where cyclic plasticity plays a major role in crack propagation. The aim of this study is to tackle one of the difficulties induced by cyclic plastic computation: the projection of the internal variables during crack propagation. The discontinuous Heaviside function in the elements cut by the crack is replaced by a new continuous enrichment function. This new function is polynomial and its degrees and coefficients depend on the type of element and on the position of the interface in the element. The automatic determination of the new enrichment and its introduction in a linear and non-linear framework have been implemented for linear elements in two dimensions and three dimensions and tested with convergence tests in elasticity and plasticity
Identification of a second GTP-bound magnesium ion in archaeal initiation factor 2
No full textInternational audienceEukaryotic and archaeal translation initiation processes involve a heterotrimeric GTPase e/aIF2 crucial for accuracy of start codon selection. In eu-karyotes, the GTPase activity of eIF2 is assisted by a GTPase-activating protein (GAP), eIF5. In ar-chaea, orthologs of eIF5 are not found and aIF2 GT-Pase activity is thought to be non-assisted. However , no in vitro GTPase activity of the archaeal factor has been reported to date. Here, we show that aIF2 significantly hydrolyses GTP in vitro. Within aIF2␥, H97, corresponding to the catalytic histidine found in other translational GTPases, and D19, from the GKT loop, both participate in this activity. Several high-resolution crystal structures were determined to get insight into GTP hydrolysis by aIF2␥. In particular, a crystal structure of the H97A mutant was obtained in the presence of non-hydrolyzed GTP. This structure reveals the presence of a second magnesium ion bound to GTP and D19. Quantum chemical/molecular mechanical simulations support the idea that the second magnesium ion may assist GTP hydrolysis by helping to neutralize the developing negative charge in the transition state. These results are discussed in light of the absence of an identified GAP in archaea to assist GTP hydrolysis on aIF2
Optimal fares and capacity decisions for crowded public transport systems
No full textInternational audienceThere is a large operations research literature on public transit system design. An extensive economic literature has also developed on public transit capacity investments, service frequency, and optimal pricing and subsidy policy. These two branches of literature have made significant advances in understanding public transit systems. However, in contrast to the literature on automobile traffic congestion, most of the studies have employed static models that cannot account for travelers' time-of-use decisions and the dynamics of transit congestion and crowding. The time profile of ridership is driven by the trade-off that users face between traveling at peak times and suffering crowding, and avoiding the peak by traveling earlier or later than they would like. A few studies have explored this trade-off using simple microeconomic models that combine trip-scheduling preferences as introduced by Vickrey (1969) with a crowding cost function that describes how utility from travel decreases with passenger loads. In this paper we use this modeling framework to analyze usage of a rail transit line, and assess the potential benefits from internalizing crowding externalities by setting differential train fares. We also present results on optimal train capacity and the number of trains put into service
Synthesis of an Artificial Cornea Allowing In Vitro Colonization of the Host Cells
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Proceedings Tenth International Workshop on Logical Frameworks and Meta Languages: Theory and Practice
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Disproving Using the Inverse Method by Iterative Refinement of Finite Approximations
No full textInternational audienceIn first-order logic, forward search using a complete strategy such as the inverse method can get stuck deriving larger and larger consequence sets when the goal query is unprovable. This is the case even in trivial theories where backward search strategies such as tableaux methods will fail finitely. We propose a general mechanism for bounding the consequence sets by means of finite approximations of infinite types. If the inverse method also implements forward subsumption and globalization, then the search space under this approximation is finite. We therefore obtain a type-directed iterative refinement algorithm for disproving queries. The method has been implemented for intuitionistic first-order logic, and we discuss its performance on a variety of problems