Reduction and emulation of ADMS Urban

International audienceADMS Urban is a non-linear static model whose input data $p$ varies one simulated hour after the other. The model computes a high-dimensional concentration vector $y= ℳ(p)$ which can contain 10⁵ concentrations. A full-year simulation of $NO_2$ concentrations can take dozens of days of computations, which greatly limits the range of methods that can be applied to the model, especially for uncertainty quantification. This work proposes a method to replace ADMS Urban with a so-called emulator, i.e., a close approximation of ADMS Urban whose computational cost is negligible. First, the output concentration field $y$ is projected on a few modes of a proper orthogonal decomposition $[Ψ_1 ... Ψ_N]$, so that $y \simeq ∑^N_{j=1} \alpha_j Ψ_j$ where \apha_j is the projection coefficient on $j$-th mode and $N$ smaller than 10. Then, the reduced model $f(p) = Ψ^T ℳ(p)$ is replaced by a statistical emulator $\hat{f}$ so that $\hat{f}(p) \simeq f(p)$ and the computational cost of $\hat{f}(p)$ is negligible

BLUE-based NO2 data assimilation at urban scale

International audienceWe aim at optimally combining air quality computations, from the Gaussian model ADMS Urban, and ground observations at urban scale. An ADMS simulation generated NO2 concentration fields across Clermont-Ferrand (France) down to street level, every 3 h for the full year 2008. A monitoring network composed of nine fixed stations provided hourly observations to be assimilated. Every 3 h, we compute the so-called BLUE (best linear unbiased estimator), which is a concentration field merging ADMS outputs and ground observations. Its error variance is supposed to be minimal under given assumptions regarding the errors on observations and model simulations. A key step lies in the modeling of error covariances between the computed NO2 concentrations across the city. We introduce a parameterized covariance which heavily relies on the road network. The covariance between two locations depends on the distance of each location to the road network and on the distance between the locations along the road network. Efficient parameters for the covariances are primarily chosen according to prior assumptions, χ2 diagnosis and leave-one-out cross-validations. According to the cross-validations, the improvements due to the assimilation seem moderately far from the observation network, but the root mean square error roughly decreases by 30-50% in the main city where the station density is high. The method is computationally tractable for the generation of improved concentration fields over a long period, or for day-to-day forecasts

Stepwise Development of MAIT Cells in Mouse and Human

Mucosal-associated invariant T (MAIT) cells display two evolutionarily conserved features: an invariant T cell receptor (TCR)α (iTCRα) chain and restriction by the nonpolymorphic class Ib major histocompatibility complex (MHC) molecule, MHC-related molecule 1 (MR1). MR1 expression on thymus epithelial cells is not necessary for MAIT cell development but their accumulation in the gut requires MR1 expressing B cells and commensal flora. MAIT cell development is poorly known, as these cells have not been found in the thymus so far. Herein, complementary human and mouse experiments using an anti-humanVα7.2 antibody and MAIT cell-specific iTCRα and TCRβ transgenic mice in different genetic backgrounds show that MAIT cell development is a stepwise process, with an intra-thymic selection followed by peripheral expansion. Mouse MAIT cells are selected in an MR1-dependent manner both in fetal thymic organ culture and in double iTCRα and TCRβ transgenic RAG knockout mice. In the latter mice, MAIT cells do not expand in the periphery unless B cells are added back by adoptive transfer, showing that B cells are not required for the initial thymic selection step but for the peripheral accumulation. In humans, contrary to natural killer T (NKT) cells, MAIT cells display a naïve phenotype in the thymus as well as in cord blood where they are in low numbers. After birth, MAIT cells acquire a memory phenotype and expand dramatically, up to 1%–4% of blood T cells. Finally, in contrast with NKT cells, human MAIT cell development is independent of the molecular adaptor SAP. Interestingly, mouse MAIT cells display a naïve phenotype and do not express the ZBTB16 transcription factor, which, in contrast, is expressed by NKT cells and the memory human MAIT cells found in the periphery after birth. In conclusion, MAIT cells are selected by MR1 in the thymus on a non-B non-T hematopoietic cell, and acquire a memory phenotype and expand in the periphery in a process dependent both upon B cells and the bacterial flora. Thus, their development follows a unique pattern at the crossroad of NKT and γδ T cells

Reduction of ethanol yield and improvement of glycerol formation by adaptive evolution of the wine yeast Saccharomyces cerevisiae under hyperosmotic conditions

There is a strong demand from the wine industry for methodologies to reduce the alcohol content of wine without compromising wine's sensory characteristics. We assessed the potential of adaptive laboratory evolution strategies under hyperosmotic stress for generation of Saccharomyces cerevisiae wine yeast strains with enhanced glycerol and reduced ethanol yields. Experimental evolution on KCl resulted, after 200 generations, in strains that had higher glycerol and lower ethanol production than the ancestral strain. This major metabolic shift was accompanied by reduced fermentative capacities, suggesting a trade-off between high glycerol production and fermentation rate. Several evolved strains retaining good fermentation performance were selected. These strains produced more succinate and 2,3-butanediol than the ancestral strain and did not accumulate undesirable organoleptic compounds, such as acetate, acetaldehyde, or acetoin. They survived better under osmotic stress and glucose starvation conditions than the ancestral strain, suggesting that the forces that drove the redirection of carbon fluxes involved a combination of osmotic and salt stresses and carbon limitation. To further decrease the ethanol yield, a breeding strategy was used, generating intrastrain hybrids that produced more glycerol than the evolved strain. Pilot-scale fermentation on Syrah using evolved and hybrid strains produced wine with 0.6% (vol/vol) and 1.3% (vol/vol) less ethanol, more glycerol and 2,3-butanediol, and less acetate than the ancestral strain. This work demonstrates that the combination of adaptive evolution and breeding is a valuable alternative to rational design for remodeling the yeast metabolic network

Chemically Modified Cyclodextrins: An Attractive Class of Supramolecular Hosts for the Development of Aqueous Biphasic Catalytic Processes

During these last years, cyclodextrins have contributed greatly to the development of catalytic processes in water. These cyclic oligosaccharides composed of 6(α), 7(β) or 8(γ) glucopyranose units improve the mass transfer in aqueous-organic two-phase systems and are useful compounds to design new catalysts. Thus, chemically modified cyclodextrins can be used to: (i) increase significantly the rate and selectivity of reactions catalyzed by water-soluble organometallic complexes, (ii) design new water-soluble ligands for aqueous organometallic catalysis, (iii) stabilize catalytically active noble metal nanoparticles in water and (iv) favour the dispersion and activation of the palladium on charcoal in water

Institutions sectorielles et management environnemental : une étude sur données françaises

Cet article analyse les déterminants sectoriels des politiques environnementales des firmes. La décomposition statistique proposée permet d'isoler l'influence de l'environnement sectoriel des autres facteurs expliquant les initiatives des entreprises en matière de protection de l’environnement. À partir des données de l'OCDE, nous construisons des indicateurs sectoriels qui appréhendent les spécificités des industries métallurgiques, chimiques, et mécaniques dans le domaine environnemental. Nos résultats suggèrent que l'environnement sectoriel propre à l'industrie métallurgique est plus propice à l'adoption de systèmes de management environnementaux que ceux des industries chimiques et mécaniques. Notre analyse invite donc le législateur et les partenaires de l'entreprise à affiner leurs exigences environnementales en fonction des caractéristiques sectorielles des firmes concernées.<br>This article focuses on the sectoral influence of firms’ environmental policies. The statistical decomposition assesses particularly the sectoral environment in directly, as distinct from other institutional, organizational or physical factors. Using an OECD dataset, we compute sectoral values that grasp the environmental specificities of metallurgical, chemical, and mechanical industries. Our results suggest that metallurgical industry is better for the adoption of environmental management system than the chemical and mechanical industries. It follows from our analysis that public authorities and the partners of the company have to refine their environmental requirements according to the sectoral characteristics of the firms

Meta-modeling of ADMS-Urban by dimension reduction and emulation

International audienc

Complexation of Monosulfonated Triphenylphosphine with Chemically Modified β-Cyclodextrins: Effect of Substituents on the Stability of Inclusion Complexes

International audienceno abstrac