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This paper analyses the impact of networks on the structure of international migration flows to OECD countries. In particular, we look at whether diaspora effects are different across education levels and gender. Using new data allowing to include both dimensions, we are able to analyze the respective impact of networks on the proportion of each category of migrant. Therefore, unlike the preceding literature on macro determinants of international migration, we can identify the factors that influence the selection in terms skills and in terms of gender. We find that network effects vary by education level but not by gender.

Emigration affects institutions at home in a number of ways. While people may have fewer incentives to voice when they have exit options, emigrants can voice once abroad and contribute to the diffusion of democratic values and norms. We first document these channels and then consider dynamic-panel regressions to investigate the overall impact of emigration on institutions in the home country. We find that both openess to migration and human capital have a positive impact on institutions (as measured by standard democracy and economic freedom indices). This implies that unskilled migration has a positive effect on institutional quality while the effect of skilled migration (or brain drain) is ambiguous. Using the point estimates from our regressions, we simulate the marginal effect of skilled emigration on institutional quality. In general, the simulations confirm that the brain drain has an ambiguous impact on institutions, though a significant institutional gain obtains for a limited set of countries when incentive effects of the brain drain on human capital formation are taken into account.

The present work follows a series of investigations of ours aimed at understanding whether longrange intermolecular electrodynamic forces could play a role in accelerating the encounter of the cognate partners of biochemical reactions in living matter and by which experimental methods and available techniques these forces could be detected. After the experimental detection of collective intramolecular oscillations of protein molecules [that we reported in Phys. Rev.X8, 031061 (2018)] the possibility of observing the mentioned electrodynamic interactions appears more realistic and thus deserving a deeper theoretical investigation of possible experimental detection of these forces with new data at hand.

Methane, discovered in 1766 by Alessandro Volta, is an attractive energy source because of its high heat of combustion per mole of carbon dioxide. However, methane is the most abundant hydrocarbon in the atmosphere and is an important greenhouse gas, with a 21-fold greater relative radiative effectiveness than CO2 on a per-molecule basis. To avoid or limit the formation of pollutants that are dangerous for both human health and the atmospheric environment, the catalytic combustion of methane appears to be one of the most promising alternatives to thermal combustion. Total oxidation of methane, which is environmentally friendly at much lower temperatures, is believed to be an efficient and economically feasible way to eliminate pollutants. This work presents a literature review, a statu quo, on catalytic methane oxidation on transition metal oxide-modified ceria catalysts (MOx/CeO2). Methane was used for this study since it is of great interest as a model compound for understanding the mechanisms of oxidation and catalytic combustion on metal oxides. The objective was to evaluate the conceptual ideas of oxygen vacancy formation through doping to increase the catalytic activity for methane oxidation over CeO2. Oxygen vacancies were created through the formation of solid solutions, and their catalytic activities were compared to the catalytic activity of an undoped CeO2 sample. The reaction conditions, the type of catalysts, the morphology and crystallographic facets exposing the role of oxygen vacancies, the deactivation mechanism, the stability of the catalysts, the reaction mechanism and kinetic characteristics are summarized.

Background: tinnitus is a heterogeneous condition associated with audiological and/or mental disorders. Chronic, severe tinnitus is reported in 1% of the population and it shows a relevant heritability, according to twins, adoptees and familial aggregation studies. The genetic contribution to severe tinnitus is unknown since large genomic studies include individuals with self-reported tinnitus and large heterogeneity in the phenotype. The aim of this study was to identify genes for severe tinnitus in patients with extreme phenotype. Methods: for this extreme phenotype study, we used three different cohorts with European ancestry (Spanish with Meniere disease (MD), Swedes tinnitus and European generalized epilepsy). In addition, four independent control datasets were also used for comparisons. Whole-exome sequencing was performed for the MD and epilepsy cohorts and whole-genome sequencing was carried out in Swedes with tinnitus. Findings: we found an enrichment of rare missense variants in 24 synaptic genes in a Spanish cohort, the most significant being PRUNE2, AKAP9, SORBS1, ITGAX, ANK2, KIF20B and TSC2 (p < 2E 04), when they were compared with reference datasets. This burden was replicated for ANK2 gene in a Swedish cohort with 97 tinnitus individuals, and in a subset of 34 Swedish patients with severe tinnitus for ANK2, AKAP9 and TSC2 genes (p < 2E 02). However, these associations were not significant in a third cohort of 701 generalized epilepsy individuals without tinnitus. Gene ontology (GO) and gene-set enrichment analyses revealed several pathways and biological processes involved in severe tinnitus, including membrane trafficking and cytoskeletal protein binding in neurons. Interpretation: a burden of rare variants in ANK2, AKAP9 and TSC2 is associated with severe tinnitus. ANK2, encodes a cytoskeleton scaffolding protein that coordinates the assembly of several proteins, drives axonal branching and influences connectivity in neurons.

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International audience; We provide a new argument proving the reliability of the Bank-Weiser estimator for Lagrange piecewise linear finite elements in both dimension two and three. The extension to dimension three constitutes the main novelty of our study. In addition, we present a numerical comparison of the Bank-Weiser and residual estimators for a three-dimensional test case.

${\mathrm{BaZrO}}_{3}$ is a perovskite that remains in the simple cubic phase at all temperatures, hence with no first-order Raman-active phonon mode allowed by symmetry. Yet, it exhibits an intense Raman spectrum with sharp and well-defined features. Here, we report the evolution of the Raman spectrum of ${\mathrm{BaZrO}}_{3}$ single crystals in a broad temperature range (4--1200 K) and discuss its origin with the support of detailed first-principle calculations of the lattice dynamics. Phonon calculations are performed not only for the cubic phase of ${\mathrm{BaZrO}}_{3}$, but also for the low-symmetry phases with octahedra tilts that have been suspected to exist at the nanoscale. We show that the Raman spectrum shows no direct evidence for these nanodomains, but can instead be explained by classical second-order Raman scattering. We provide an assignment of the dominant features to phonon mode combinations. In particular, we show that the high frequency range of the spectrum is dominated by overtones and shows an image of the phonon density of states corresponding to the stretching modes of the oxygen octahedra.

The installation of internal insulation systems within the scope of refurbishment changes the hygrothermal behaviour of the existing masonry of a building in the long term. The internal insulation layer reduces the temperature of the masonry during the heating period and considerably reduces the drying potential. If the moisture content is too high due to the absorption of driving rain from the outside and moisture from the interior climate, the masonry may be permanently damaged and mould may form. The proof of function can be achieved by hygrothermal simulations. These simulations require the input of sensitive boundary conditions and different material parameters. In order to obtain precise simulation results, these input values should be validated by building physics measurements. In order to be able to better assess the simulation parameters, various physical measurements for the preparation of a field test for interior insulation systems in a conference room were carried out on behalf of the administration of the bâtiments publics at the University of Luxembourg as part of the research project "Possibilities and limitations of interior insulation in the renovation of public buildings in Luxembourg". Die Installation von Innendämmsystemen im Rahmen von Sanierungen verändert das hygrothermische Verhalten des Bestandsmauerwerkes eines Gebäudes nachhaltig. Durch die innenliegende Dämmschicht sinkt die die Temperatur des Mauerwerks in der Heizperiode stärker ab und das Abtrocknungspotential reduziert sich erheblich. Bei zu starker Auffeuchtung durch die Aufnahme von Schlagregen von außen und Feuchte aus dem Innenklima kann es zu dauerhafter Schädigung des Mauerwerkes sowie Schimmelbildung kommen. Der Funktionsnachweis kann durch hygrothermische Simulationen erreicht werden. Diese Simulationen erfordern die Eingabe sensitiver Rand-bedingungen und unterschiedlicher Materialparameter. Um präzise Simulationsergebnisse zu erhalten, sollten diese Eingabewerte über bauphysikalische Messungen validiert werden. Um die Simulationsparameter besser einschätzen zu können, wurden im Rahmen des Forschungsprojektes „Möglichkeiten und Grenzen der Innendämmung bei der Sanierung öffentlicher Gebäude in Luxemburg“ im Auftrag der Administration des bâtiments publics an der Universi-tät Luxemburg diverse physikalische Messungen zur Vor-bereitung eines Feldtests für Innendämmsysteme in einem Konferenzraum durchgeführt.

International audience; Ferroic materials naturally exhibit a rich number of functionalities, which often arise from thermally , chemically or mechanically induced symmetry breakings or phase transitions. Based on Density Functional Calculations, we demonstrate here that light can drive phase transitions as well in ferroelectric materials such as the perovskite oxides lead titanate and barium titanate. Phonon analysis and total energy calculations reveal that the polarization tends to vanish under illumination , to favor the emergence of non-polar phases, potentially antiferroelectric, and exhibiting a tilt of the oxygen octahedra. Strategies to tailor photo-induced phases based on phonon instabilities in the electronic ground state are also discussed.

We present a numerical study of the time-dependent motion of a two-dimensional vesicle in a channel under an imposed flow. In a Poiseuille flow the shape of the vesicle depends on the flow strength, the mechanical properties of the membrane, and the width of the channel as reported in the past. This study is focused on the centered snaking (CSn) shape, where the vesicle shows an oscillatory motion like a swimmer flagella even though the flow is stationary. We quantify this behavior by the amplitude and frequency of the oscillations of the vesicle's center of mass. We observe regions in parameter space, where the CSn coexists with the parachute or the unconfined slipper. The influence of an amplitude modulation of the imposed flow on the dynamics and shape of the snaking vesicle is also investigated. For large modulation amplitudes transitions to static shapes are observed. A smaller modulation amplitude induces a modulation in amplitude and frequency of the center of mass of the snaking vesicle. In a certain parameter range we find that the center of mass oscillates with a constant envelope indicating the presence of at least two stable states., Comment: 10 pages, 7 figures

Background The Pas-de-Calais mining basin is a predominantly urban conurbation of approximately 650,000 inhabitants, situated in the North of France, about 35 km south of Lille and at a reasonable distance of Paris, London and Brussels. The territory have been facing since the end of the mining activity in the 1980s an alarming socio-economic situation, ranked last in France for most of the indicators. Against this background, local and regional actors have created in 2009 a local association, Euralens, in order to use the implementation of the antenna of the Louvre in Lens as a catalyst for territorial development. The association has today two main missions: to prepare and to facilitate the emergence of a metropolis institution; to foster local development by supporting innovative local initiatives through a label process. Findings Created in 2009 at the regional level, Euralens is neither a classical (in France) top-down State intervention nor a genuine bottom-up local initiative. The association has taken a rising importance in the organisation of the territory, favouring the cooperation between local authorities, but also between institutional stakeholders at different levels, the civil society and private actors. Doing so, it gives the Pas-de-Calais mining basin a clearer and louder voice. The recent creation of a specific state policy towards the Mining Basin is a good example of such an assertion and demonstrates the clear redistributive impact of Euralens for the benefit of the locality in the national space. On the question of the distribu-tion of territorial engineering, another accomplishment of Euralens is its the capacity to mobilise external national and international expertise to imagine with local stakeholders policies supporting social and territorial development. Outlook However, the effort seems still insufficient over time. The enormous environmental impact of mining activity as well as the deep social impact of the collapse of this activity have let the territory dry. Albeit positive, the action of Euralens is relatively modest in comparison to the extent of the needs. At the social level in particular, the rebuilding of individuals trust is a long-term policy that deserves more attention. Too often, Euralens disregard the social and the procedural dimensions of injustice. It does not pay sufficient attention to the integration of the civil society to the decision-making in a time of democratic crisis. Yet, symbols, power balance, transparency should be cornerstones of Euralens action in the territory in order to better exemplify change in the locality. Joensuu: University of Eastern Finland

International audience; A large number of advanced finite element shell formulations have been developed, but their adoption is hindered by complexities of transforming mathematical formulations into computer code. Furthermore, it is often not straightforward to adapt existing implementations to emerging frontier problems in thin structural mechanics including nonlinear material behaviour, complex microstructures, multi-physical couplings, or active materials. We show that by using a high-level mathematical modelling strategy and automatic code generation tools, a wide range of advanced plate and shell finite element models can be generated easily and efficiently, including: the linear and non-linear geometrically exact Naghdi shell models, the Marguerre-von Karman shallow shell model, and the Reissner-Mindlin plate model. To solve shear and membrane-locking issues, we use: a novel re-interpretation of the Mixed Interpolation of Tensorial Component (MITC) procedure as a mixed-hybridisable finite element method, and a high polynomial order Partial Selective Reduced Integration (PSRI) method. The effectiveness of these approaches and the ease of writing solvers is illustrated through a large set of verification tests and demo codes, collected in an open-source library, FEniCS-Shells, that extends the FEniCS Project finite element problem solving environment.

Ferroic domain walls could play an important role in microelectronics, given their nanometric size and often distinct functional properties. Until now, devices and device concepts were mostly based on mobile domain walls in ferromagnetic and ferroelectric materials. A less explored path is to make use of polar domain walls in nonpolar ferroelastic materials. Indeed, while the polar character of ferroelastic domain walls has been demonstrated, polarization control has been elusive. Here, we report evidence for the electrostatic signature of the domain-wall polarization in nonpolar calcium titanate (CaTiO3). Macroscopic mechanical resonances excited by an ac electric field are observed as a signature of a piezoelectric response caused by polar walls. On the microscopic scale, the polarization in domain walls modifies the local surface potential of the sample. Through imaging of surface potential variations, we show that the potential at the domain wall can be controlled by electron injection. This could enable devices based on nondestructive information readout of surface potential., Comment: 30 pages, 12 figures

International audience; This work studies the performance of a cooperative network which consists of two channel-coded sources, multiple relays, and one destination. To achieve high spectral efficiency, we assume that a single time slot is dedicated to relaying. Conventional network-coded-based cooperation (NCC) selects the best relay which uses network coding to serve the two sources simultaneously. The bit error rate (BER) performance of NCC with channel coding, however, is still unknown. In this paper, we firstly study the BER of NCC via a closed-form expression and analytically show that NCC only achieves diversity of order two regardless of the number of available relays and the channel code. Secondly, we propose a novel partial relaying-based cooperation (PARC) scheme to improve the system diversity in the finite signal-to-noise ratio (SNR) regime. In particular, closed-form expressions for the system BER and diversity order of PARC are derived as a function of the operating SNR value and the minimum distance of the channel code. We analytically show that the proposed PARC achieves full (instantaneous) diversity order in the finite SNR regime, given that an appropriate channel code is used. Finally, numerical results verify our analysis and demonstrate a large SNR gain of PARC over NCC in the SNR region of interest.

The ability to generate efficient giga–terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic to complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary light waves (and vice versa), remain limited to the megahertz range. Here, using coherent acoustic waves generated at tens of gigahertz frequency by a femtosecond laser pulse, we reveal the mode conversion process and show its efficiency in ferroelectric materials such as BiFeO3 and LiNbO3. Further to the experimental evidence, we provide a complete theoretical support to this all-optical ultrafast mechanism mediated by acousto-optic interaction. By allowing the manipulation of light polarization with gigahertz coherent acoustic phonons, our results provide a novel route for the development of next-generation photonic-based devices and highlight new capabilities in using ferroelectrics in modern photonics., Electrically driven acousto-optic light modulators are limited to frequencies of a few hundred megahertz and are typically no smaller than a few micrometres. Here, the authors demonstrate gigahertz acousto-optic conversion of light polarization in a region of a few nanometres using pulsed laser stimulation of a ferroelectric.

The increasing part of renewable energy in the electricity production mix with its known fluctuations of wind and photovoltaic plants is leading to an enlarged discrepancy of production and consumption. Up to now the electricity production of biogas plants is more or less constant but could be used in future more to balance the energy production by using higher biogas storage capacity. An interesting alternative could be a 2 stage process. The 1st stage is operated at higher loadings and low pH where mainly substrate hydrolysis takes place and relatively small quantities of H2/CO2 gas are produced. The effluent shows high concentrations (total > 10 g FA/l) of mainly butyric and caproic acid which could easily and stable be temporarily stored in liquid-tanks. The transformation of the acidic intermediates from hydrolysis to biogas (and finally electricity) in the 2nd stage is faster compared to the traditional fermentation. The storage capacity for the acidic intermediates is more than 10 times smaller compared to the temporary storage of biogas.

The use of kitchen and food waste of which a great amount is disposed every year in EU is an interesting path for an energetic utilisation and as an alternative substrate. Compared to other substrates as energy crops or manure kitchen waste includes a higher content of proteins and fats which have a higher biogas and methane yield than carbohydrates. To exclude problems related to hygienisation a model kitchen waste (59% VS carbohydrates, 16% VS proteins and 25% VS fats) was used for the fermentation experiments at mesophilic conditions. Semi-continuous experiments in a 6 litres reactor with daily feeding shows a good degradation for loadings of 1 and 2 gVS/l/d but already a little reduced degradation at 4 gVS/l/d. The experiments with model kitchen waste as unique substrate needed the addition of trace elements and buffering agents. Therefor it would be reasonable to use kitchen waste as co-substrate.

The understanding of domain structures, specifically domain walls, currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM – electrons reflected) to Low Energy Electron Microscopy (LEEM – electrons backscattered) gives rise to a robust contrast between domains with upwards (Pup) and downwards (Pdown) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces, and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field.

International audience; This paper introduces an effective Static ProbabilisticTiming Analysis (SPTA) for multi-path programs. The analysis estimates the temporal contribution of an evict-on-miss, random replacement cache to the probabilistic Worst-Case Execution Time (pWCET) distribution of multi-path programs. The analysis uses a conservative join function that provides a proper overapproximation of the possible cache contents and the pWCET distribution on path convergence, irrespective of the actual path followed during execution. Simple program transformations are introduced that reduce the impact of path indeterminism while ensuring sound pWCET estimates. Evaluation shows that the proposed method is efficient at capturing locality in the cache, and substantially outperforms the only prior approach to SPTA for multi-path programs based on path merging. The evaluation results show incomparability with analysis for an equivalent deterministic system using an LRU cache.

International audience; Graphene flakes with giant shape anisotropy are extensively used to establish connectedness electrical percolation in various heterogeneous systems. However, the percolation behaviour of graphene flakes has been recently predicted to be far more complicated than generally anticipated on the basis of excluded volume arguments. Here we confirm experimentally that graphene flakes self-assemble into nematic liquid crystals below the onset of percolation. The competition of percolation and liquid crystal transition provides a new route towards high-k materials. Indeed, near-percolated liquid-crystalline graphene-based composites display unprecedented dielectric properties with a dielectric constant improved by 260-fold increase as compared with the polymer matrix, while maintaining the loss tangent as low as 0.4. This performance is shown to depend on the structure of monodomains of graphene liquid-crystalline phases. Insights into how the liquid crystal phase transition interferes with percolation transition and thus alters the dielectric constant are discussed.

International audience; Predictability is an important aspect in real-time and safety-critical systems, where non-functional properties – such as the timing behavior – have high impact on the system cor-rectness. As many safety-critical systems have a growing performance demand, simple, but outdated architectures are not sufficient anymore. Instead, multi-core systems are more and more popular, even in the real-time domain. To combine the performance benefits of a multi-core architecture with the required predictability, Time Division Multiple Access (TDMA) buses are often advocated. In this paper, we are interested in accesses to shared resources in such environments. Our approach uses SMT (Satisfiability Modulo Theory) to encode the semantics and execution time of the analyzed program in an environment with shared resources. We use an SMT-solver to find a solution that corresponds to the execution path with correct semantics and maximal execution time. We propose to model a shared bus with TDMA arbitration policy. Using examples, we show how the WCET estimation is enhanced by combining the semantics and the shared bus analysis in SMT.

This review devoted to multiferroic properties of Bismuth-based perovskites falls into two parts. The first part focuses on BiFeO3 and summarizes the recent progress made in the studies of its pressure-temperature phase diagram and magnetoelectric coupling phenomena. The second part discusses in a more general way the issue of polar - and multiferroic - phases in BiBO3 perovskites and the competition between ferroelectricity and other structural instabilities, from an inventory of recently synthetized compounds., Comment: 22 pages, 7 figures, to be published in Comptes Rendus Physique

Under which conditions do the electrical transport properties of one-dimensional (1D) carbon nanotubes (CNTs) and 2D graphene become equivalent? We have performed atomistic calculations of the phonon-limited electrical mobility in graphene and in a wide range of CNTs of different types to address this issue. The theoretical study is based on a tight-binding method and a force-constant model from which all possible electron-phonon couplings are computed. The electrical resistivity of graphene is found in very good agreement with experiments performed at high carrier density. A common methodology is applied to study the transition from 1D to 2D by considering CNTs with diameter up to 16 nm. It is found that the mobility in CNTs of increasing diameter converges to the same value, the mobility in graphene. This convergence is much faster at high temperature and high carrier density. For small-diameter CNTs, the mobility strongly depends on chirality, diameter, and existence of a bandgap., 12 pages

Outstanding paper award; International audience; In this paper, we introduce a Multicore Response Time Analysis (MRTA) framework. This framework is extensible to different multicore architectures, with various types and arrangements of local memory, and different arbitration policies for the common interconnects. We instantiate the framework for single level local data and instruction memories (cache or scratchpads), for a variety of memory bus arbitration policies, including: Round-Robin, FIFO, Fixed-Priority, Processor-Priority, and TDMA, and account for DRAM refreshes. The MRTA framework provides a general approach to timing verification for multicore systems that is parametric in the hardware configuration and so can be used at the architectural design stage to compare the guaranteed levels of performance that can be obtained with different hardware configurations. The MRTA framework decouples response time analysis from a reliance on context independent WCET values. Instead, the analysis formulates response times directly from the demands on different hardware resources.

International audience; Cette contribution retrace les grandes lignes et les grands enjeux de l'évolution de l'appareil policier en Belgique, depuis l'indépendance du pays. Elle en dresse une synthèse à partir de l'historiographie la plus récente

International audience; What is the on-line echo of the commemoration of the centenary of the 1st World War ? What is the behavior of Memorial/Heritage Institutions about the 1st World War on Twitter ? How do they pass information about the Centenary ? Is there an effect of the English predominance on Twitter about the Centenary on the way non-English twitter accounts are considering the 1st World War? Those questions are to be answered by a research project that is to be presented in this poster, which aims at harvesting tweets containing hashtags linked to the Centenary since April 2014.

This paper quantitatively investigates the short- and long-run effects of liberalizing global migration on the world distribution of income. We develop and parametrize a dynamic model of the world economy with endogenous migration, fertility and education decisions. We identify bilateral migration costs and their legal component for each pair of countries and two classes of worker. Our analysis reveals that the effects of a liberalization on human capital accumulation, income and inequality are gradual and cumulative. In case of a complete liberalization, the world average level of GDP per worker increases by 20 percent in the short-run, and by more than 55 percent after 50 years. The world average index of inequality decreases and the liberalization path has stochastic dominance over the Baseline-As-Usual. These results are very robust to our identifying assumptions. We also analyze partial liberalization shocks : efficiency and inequality effects are roughly proportional to the «liberalization rate».

We study theoretically two-dimensional single-crystalline sheets of semiconductors that form a honeycomb lattice with a period below 10 nm. These systems could combine the usual semiconductor properties with Dirac bands. Using atomistic tight-binding calculations, we show that both the atomic lattice and the overall geometry influence the band structure, revealing materials with unusual electronic properties. In rocksalt Pb chalcogenides, the expected Dirac-type features are clouded by a complex band structure. However, in the case of zinc-blende Cd-chalcogenide semiconductors, the honeycomb nanogeometry leads to rich band structures, including, in the conduction band, Dirac cones at two distinct energies and nontrivial flat bands and, in the valence band, topological edge states. These edge states are present in several electronic gaps opened in the valence band by the spin-orbit coupling and the quantum confinement in the honeycomb geometry. The lowest Dirac conduction band has S-orbital character and is equivalent to the pi-pi* band of graphene but with renormalized couplings. The conduction bands higher in energy have no counterpart in graphene; they combine a Dirac cone and flat bands because of their P-orbital character. We show that the width of the Dirac bands varies between tens and hundreds of meV. These systems emerge as remarkable platforms for studying complex electronic phases starting from conventional semiconductors. Recent advancements in colloidal chemistry indicate that these materials can be synthesized from semiconductor nanocrystals., 12 pages, 12 figures

It is known how to transform certain canonical three-pass identification schemes into signature schemes via the Fiat---Shamir transform. Pointcheval and Stern showed that those schemes are existentially unforgeable in the random-oracle model leveraging the, at that time, novel forking lemma. Recently, a number of 5-pass identification protocols have been proposed. Extending the above technique to capture 5-pass identification schemes would allow to obtain novel unforgeable signature schemes. In this paper, we provide an extension of the forking lemma (and the Fiat---Shamir transform) in order to assess the security of what we call $$n$$n-generic signature schemes. These include signature schemes that are derived from certain $$(2n+1)$$(2n+1)-pass identification schemes. In doing so, we put forward a generic methodology for proving the security of a number of signature schemes derived from $$(2n+1)$$(2n+1)-pass identification schemes for $$n\ge 2$$n?2. As an application of this methodology, we obtain two new code-based existentially-unforgeable signature schemes, along with a security reduction. In particular, we solve an open problem in multivariate cryptography posed by Sakumoto, Shirai and Hiwatari at CRYPTO 2011.

Background School is a multi-cultural setting where students need social, material, physical, and mental resources to attain school achievement. But they are often lacking, especially for immigrant students. In an early adolescence context, this study assessed risk for school difficulties among European and non-European immigrants and the roles of socioeconomic characteristics, physical health, psychological health, social relationships, living environment, and unhealthy behaviours. Methods This cross-sectional study included 1,559 middle-school adolescents from north-eastern France, who completed a self-administered questionnaire including socioeconomic characteristics (gender, age, family structure, father’s occupation, and family income), WHO-Quality of life (measuring the four dimensions physical health, psychological health, social relationships, and living environment), unhealthy behaviours (last-30-day uses of tobacco, alcohol, cannabis, and other illicit drugs and no regular sports/physical activities), grade repetition, low school performance ( Results Grade repetition affected 14.8% of students, low school performance 8.2%, and school dropout ideation 3.9%. European immigrants had a higher risk for grade repetition only with a gender-age-adjusted odds ratio (OR) of 2.44, vs. French students. This odds ratio decreased to 1.76 (contribution 47%) with further adjustment for all confounders (family structure, father’s occupation, family income, physical health, psychological health, social relationships, living environment, and unhealthy behaviours). Non-European immigrants had a statistically higher risk for all grade repetition, low school performance, and school dropout ideation with ORs of 3.29, 3.02, and 3.42, respectively vs. French students. These odds ratios decreased to 1.76, 1.54, and 1.54, respectively (contributions 66%, 73%, and 78%) with further adjustment for all confounders. Conclusions Compared with French students, European immigrant students were more affected only by grade repetition while non-European immigrant students by all grade repetition, low school performance, and school dropout ideation. The contribution of socioeconomic characteristics, physical health, psychological health, social relationships, living environment, and unhealthy behaviours was very high and much higher for non-European than for European immigrant students. Public policy should focus on these factors and services to reduce school difficulties.

International audience

The paper assesses the global effects of brain drain on developing economies and quantifies the relative sizes of various static and dynamic impacts. By constructing a unified generic framework characterized by overlapping generations dynamics and calibrated to real data, this study incorporates many direct impacts of brain drain whose interactions, along with other indirect effects, are endogenously and dynamically generated. Our findings suggest that the short-run impact of brain drain on resident human capital is extremely crucial, as it does not only determine the number of skilled workers available to domestic production, but it also affects the sending economy’s capacity to innovate or to adopt modern technologies. The latter impact plays an important role particularly in a globalized economy where capital investments are made in places with higher production efficiencies ceteris paribus. Hence, in spite of several empirically documented positive feedback effects, those countries with high skilled emigration rates are the most candid victims to brain drain since they are least likely to benefit from the “brain gain” effect, and thus suffering from declines of their resident human capital.

Recent theoretical studies suggest that migration prospects can raise the expected return to human capital and thus foster education investment at home or, in other words, induce a brain gain. In a recent paper (Beine, Docquier and Rapoport, Economic Journal, 2008) we used the Docquier and Marfouk (2006) data set on emigration rates by education level to examine the impact of brain drain migration on gross (pre-migration) human capital formation in developing countries. We found a positive effect of skilled migration prospects on human capital growth in a cross-section of 127 developing countries, with an elasticity of about 5 percent. In this paper we assess the robustness of our results to the use of alternative brain drain measures, definitions of human capital, and functional forms. We find that the results hold using the Beine et al. (2007) alternative brain drain measures controlling for whether migrants acquired their skills in the home or in the host country. We also regress other indicators of human capital investment on skilled migration rates and find a positive effect on youth literacy while the effect on school enrolment depends on the exact specification chosen.

International audience