The Electronic Ground State Energy Problem: a New Reduced Density Matrix Approach

We present here a formulation of the electronic ground-state energy in terms of the second order reduced density matrix, using a duality argument. It is shown that the computation of the ground-state energy reduces to the search of the projection of some two-electron reduced Hamiltonian on the dual cone of $N$-representability conditions. Some numerical results validate the approach, both for equilibrium geometries and for the dissociation curve of N$_2$

A Compact Model for the Ballistic Subthreshold Current in Ultra-Thin Independent Double-Gate MOSFETs

International audienceWe present an analytical model for the subthreshold characteristic of ultra-thin Independent Double-Gate (IDG) MOSFET working in the ballistic regime. This model takes into account short-channel effects, quantization effects and source-to-drain tunneling (WKB approximation) in the expression of the subthreshold drain current. Important device parameters, such as off-state current or subthreshold swing, can be easily evaluated through this full analytical approach. The model can be successfully implemented in a TCAD circuit simulator for the simulation of IDG MOSFET based-circuits

Modélisation numérique directe et des grandes échelles des écoulements turbulents gaz-particules dans le formalisme eulérien mésoscopique

Une nouvelle approche eulérienne aux grandes échelles (LES) pour simuler un nuage de particules inertielles soumis à une turbulence fluide est présentée. Elle est basée sur le formalisme eulérien mésoscopique (Février et al. (2005)) qui permet de décomposer la vitesse de chaque particule en une partie spatialement corrélée et une partie décorrélée. La dérivation des équations LES particulaires comprend deux étapes : une moyenne d'ensemble conditionnée par une réalisation du champ fluide turbulent est suivie d'un filtrage spatial LES classique des équations de transport. En conséquence, les termes à modéliser sont de deux sortes : ceux provenant de la moyenne d'ensemble sont modélis es par analogie avec les fermetures statistiques de la méthode aux moments, alors que l'effet des termes de sous-maille est prédit par des modèles similaires à ceux employés en turbulence monophasique compressible. Les différents modèles sont testés a priori à l'aide de résultats de simulations lagrangiennes pour la phase dispersée couplées à une résolution numérique directe du fluide en turbulence homogène isotrope décroissante. Les nombres de Stokes des écoulements simulés correspondent à des régimes de concentration préférentielle des particules. Le couplage inverse ainsi que les collisions interparticulaires ne sont pas pris en compte. L'interprétation de ces résultats lagrangiens en terme de champs eulériens mésoscopiques nécessite l'emploi d'une procédure de projection. Une projection de type gaussienne, spécialement développée permet de limiter les erreurs spatiales et statistiques. Les champs mésoscopiques sont, tout d'abord analysés en détail : évolution des grandeurs moyennes, spectres de vitesses, champs locaux instantanés. Puis ces champs sont filtrés spatialement. Les tests a priori des modèles de sous-mailles sont effectués et donnent des résultats similaires aux tests effectués en écoulements monophasiques en ce qui concerne le tenseur de sous-maille. ABSTRACT : The purpose of the paper is to develop a new large eddy simulation (LES) approach for a dispersed phase suspended in a fluid turbulent flow in the framework of the Eulerian modelling for inertial particles. Local instantaneous Eulerian equations for the particles are first written using the Mesoscopic Eulerian Formalism, which accounts for the contribution of an uncorrelated velocity component for inertial particles with relaxation time larger than the Kolmogorov time scale. Then, particle LES equations are obtained by volume filtering of mesoscopic Eulerian equations. In such approach, the particulate flow at larger scales than the filter width is recovered while subgrid effects need to be modelled. Particle eddy-viscosity, scale similarity and mixed subgrid stress (SGS) models derived from fluid compressible turbulence SGS models are presented. Evaluation of the proposed modelling approaches is performed using seven sets of particle Lagrangian results computed from discret particle simulation (DPS) coupled with fluid direct numerical simulation (DNS) of homogeneous isotropic decaying turubulence. Fluid acts on the particle through the Stokes drag force, two-way coupling and inter-particle collisions are not considered. Simulated Stokes numbers corresponds to prefential concentration regimes. Mesoscopic Eulerian fields are extracted from Lagrangian results by a projection process, which is equivalent to a spatial filter. A specific projector is develop to limit statistical bias and spatial error and is validated. First mesoscopic fields are analysed in detail including correlated velocity power spectra and uncorrelated energy modelling. The mesoscopic fields measured from DPS+DNS are then filtered to obtain large scale fields. A priori evaluation of particle subgrid stress models gives comparable agreement than fluid compressible turbulence tests. The standard Smagorinsky eddy-viscosity model exhibits the smaller correlation coefficients. The scale similarity model shows very good correlation coefficient but strongly underestimates the subgrid dissipation. The mixed model is on the whole superior to pure eddy-viscosity mode

A Lower Bound and a Near-Optimal Algorithm for Bilevel Empirical Risk Minimization

Bilevel optimization problems, which are problems where two optimization problems are nested, have more and more applications in machine learning. In many practical cases, the upper and the lower objectives correspond to empirical risk minimization problems and therefore have a sum structure. In this context, we propose a bilevel extension of the celebrated SARAH algorithm. We demonstrate that the algorithm requires $\mathcal{O}((n+m)^{\frac12}\varepsilon^{-1})$ gradient computations to achieve $\varepsilon$-stationarity with $n+m$ the total number of samples, which improves over all previous bilevel algorithms. Moreover, we provide a lower bound on the number of oracle calls required to get an approximate stationary point of the objective function of the bilevel problem. This lower bound is attained by our algorithm, which is therefore optimal in terms of sample complexity

Increased precision in the intravascular arterial input function with flow compensation

Abstract: Purpose: In this study, we investigate the effects of pulsatile flow and inflow on dynamic susceptibility-contrast MRI (DSC-MRI) intravascular arterial input function (AIF) measurement in human brain arteries and measure how they are affected by first-order flow compensation (FC). Methods: A dual-echo single-shot EPI sequence with alternating FC gradients was used to acquire DSC-MRI data with electrocardiogram monitoring. The dynamic signal variations measured inside the middle- (MCA) and internal cerebral arteries (ICA) was associated to the pulsatile arterial blood velocities measured with a single-slice quantitative flow sequence throughout the cardiac cycle. Results: Major inverse correlations between intravascular signal and blood velocity were found for the standard SS-EPI sequence. FC reduces these correlated variations that contribute to signal physiological noise. It causes a significant two-fold increase of intravascular SNR in the MCA and the ICA, (2.3 ± 0.9, P = 0.03) and (2.0 ± 0.9, P = 0.04) respectively; and reduced phase standard deviation for the ICA (0.72 ± 0.14, P = 0.004). The correction proposed in this work translates into a quantitative AIF with reduced noise in the ICA. Conclusion: The physiological noise added by pulsatile flow and inflow for intravascular AIF measurement in the brain arteries is significantly reduced by FC

Examining high school students’ personality traits of extraversion and emotional stability in relation to their academic expectation and value appraisals

Abstract : Both personality and motivational characteristics can be considered to estimate individuals’ potential for adjustment and development. That said, these characteristics are rarely studied in conjunction. In this study, we examine how personality and motivational characteristics relate one to the other and influence how students approach learning. More precisely, we analyzed the additive and interactive effects of two intimately related traits (extraversion and emotional stability) from the Big Five model of personality on five motivational dimensions reflecting academic expectations (sense of competence) and values (interest, utility, and mastery and performance goal orientations). Data was collected from a sample of 303 students in tenth and eleventh grade (108 boys and 195 girls; Mage = 16.275 years, SD = 1.149) in a French-Canadian public high school in the greater Quebec City area. Primary analyses included both bivariate correlation and hierarchical regression analyses. Correlations indicated that emotionally stable students were more interested in learning. Hierarchical regression showed that emotionally stable students were more likely to exhibit a performance goal orientation, especially when they were extroverted. These analyses also revealed that emotionally stable students were more interested in learning, especially when they had a strong sense of competence. Results are discussed in light of the limited but relevant existing literature

Marquage de molécules biologiques par des complexes de radiométaux à base de polyamines macrocycliques

Ce travail de thèse réalisé à l Institut de Chimie Moléculaire de l Université de Bourgogne porte dans un premier temps sur la synthèse d agents chélatants bifonctionnels adaptés à la chélation de radiométaux trivalents, notamment l indium-111. La plus grande partie de ce travail a ensuite consisté à réaliser le greffage d un agent chélatant bifonctionnel dérivé du DOTA sur différents anticorps ou fragments d anticorps monoclonaux : le trastuzumab (anti HER2, traitement de cancers du sein), le cétuximab (anti EGFR, traitement de nombreux cancers, dont le cancer colorectal) et l abciximab (antiagrégant plaquettaire). Une attention particulière a été apportée à la caractérisation des différents immunoconjugués. La dernière étape de ce travail de thèse porte sur le radiomarquage à l indium-111 de deux immunoconjugués préparés : le trastuzumab et le cétuximab. Ces étapes de radiomarquage nous ont permis de déterminer la fraction immunoréactive et l affinité de chaque radiotraceur. Nous avons ainsi pu étudier la biodistribution in vivo de ces radiotraceurs chez la souris par imagerie SPECT-CT. Nous avons également développé une méthode de greffage originale pour le marquage d un fragment d anticorps de type Fab, l abciximab, dans le but de suivre la biodistribution de cet antiagrégant plaquettaire. Enfin, nous avons également validé le concept d imagerie multimodale à travers le greffage et le radiomarquage d un agent bimodal pour l imagerie optique et la SPECT sur des lipopolysaccharides bactériens. Les travaux réalisés nous ont permis d acquérir un savoir faire en matière de greffage d anticorps et de radiomarquage. Les résultats obtenus permettent d envisager le greffage d autres anticorps ou biomolécules, ainsi que l utilisation d autres radionucléides pour l imagerie PET ou la radioimmunothérapieThis work conducted at the Institut de Chimie Moléculaire de l Université de Bourgogne carries at first on the synthesis of bifunctional chelating agents suitable for the chelation of trivalent radiometals, including indium-111. The greater part of this work was then dedicated to the grafting of a DOTA derivative bifunctional chelating agent on different antibodies or fragments of monoclonal antibodies: trastuzumab (anti-HER2 treatment of breast cancer), cetuximab (anti EGFR, treatment of many cancers, including colorectal cancer) and abciximab (antiplatelet). Particular attention was paid to the characterization of various immunoconjugates. The critical step of this thesis consisted in the indium-111 radiolabeling of two previously prepared immunoconjugates: trastuzumab and cetuximab. These steps of radiolabelling allowed us to determine the immunoreactive fraction and affinity of each radiotracer. Thus, we were able to study the in vivo biodistribution of the radiotracers in tumour-bearing mice by SPECT-CT. We also developed an original method for the labeling of a Fab antibody fragment in order to monitor the biodistribution of the antiplatelet agent (abciximab). Finally, we also validated the concept of multimodal imaging through grafting and radiolabeling of a bimodal agent for optical and SPECT imaging on bacterial lipopolysaccharide. Thank s to this work, we gained an expertise in antibodies radiolabeling. The results obtained allow to consider the labeling of antibodies or other biomolecules, and the use of other radionuclides for PET imaging and radioimmunotherapyDIJON-BU Doc.électronique (212319901) / SudocSudocFranceF

FEDSM2008-55143 EULER-EULER LARGE-EDDY SIMULATION APPROACH FOR NON ISOTHERMAL PARTICLE-LADEN TURBULENT JET

ABSTRACT This paper presents an Euler-Euler Large-Eddy Simulation (LES) approach for the numerical modeling of non isothermal dispersed turbulent two-phase flows. The proposed approach is presented and validated by a priori tests from an EulerLagrange database, provided using discrete particle simulation (DPS) of the particle phase coupled with direct numerical simulation (DNS) of the turbulent carrier flow, in a non isothermal particle-laden temporal jet configuration. A statistical approach, the Mesoscopic Eulerian Formalism (MEF) [Février et al., J. Fluid Mech., 2005, vol. 533, pp. 1-46], is used to write local and instantaneous Eulerian equations for the dispersed phase and then, by spatial averaging, to derive the LES equations governing the filtered variables. In this work, the MEF approach is extended to scalar variables transported by the particles in order to develop LES for reactive turbulent dispersed two-phase flows with mass and heat turbulent transport. This approach leads to separate the instantaneous particle temperature distribution in a Mesoscopic Eulerian field, shared by all the particles, and a Random Uncorrelated distribution which may be characterized in terms of Eulerian fields of particle moments such as the uncorrelated temperature variance. In this paper, the DPS-DNS numerical database is presented, LES Eulerian equations for the dispersed phase are derived in the frame of the Mesoscopic approach and models for the unresolved subgrid and random uncorrelated terms are proposed and a priori tested using the DPS-DNS database

An improved genome of the model marine alga Ostreococcus tauri unfolds by assessing Illumina de novo assemblies

Background: Cost effective next generation sequencing technologies now enable the production of genomic datasets for many novel planktonic eukaryotes, representing an understudied reservoir of genetic diversity. O. tauri is the smallest free-living photosynthetic eukaryote known to date, a coccoid green alga that was first isolated in 1995 in a lagoon by the Mediterranean sea. Its simple features, ease of culture and the sequencing of its 13 Mb haploid nuclear genome have promoted this microalga as a new model organism for cell biology. Here, we investigated the quality of genome assemblies of Illumina GAIIx 75 bp paired-end reads from Ostreococcus tauri, thereby also improving the existing assembly and showing the genome to be stably maintained in culture. Results: The 3 assemblers used, ABySS, CLCBio and Velvet, produced 95% complete genomes in 1402 to 2080 scaffolds with a very low rate of misassembly. Reciprocally, these assemblies improved the original genome assembly by filling in 930 gaps. Combined with additional analysis of raw reads and PCR sequencing effort, 1194 gaps have been solved in total adding up to 460 kb of sequence. Mapping of RNAseq Illumina data on this updated genome led to a twofold reduction in the proportion of multi-exon protein coding genes, representing 19% of the total 7699 protein coding genes. The comparison of the DNA extracted in 2001 and 2009 revealed the fixation of 8 single nucleotide substitutions and 2 deletions during the approximately 6000 generations in the lab. The deletions either knocked out or truncated two predicted transmembrane proteins, including a glutamate-receptor like gene. Conclusion: High coverage (>80 fold) paired-end Illumina sequencing enables a high quality 95% complete genome assembly of a compact ~13 Mb haploid eukaryote. This genome sequence has remained stable for 6000 generations of lab culture