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Dynamical approximations for composite quantum systems: assessment of error estimates for a separable ansatz
No full textInternational audienceAbstract Numerical studies are presented to assess error estimates for a separable (Hartree) approximation for dynamically evolving composite quantum systems which exhibit distinct scales defined by their mass and frequency ratios. The relevant error estimates were formally described in our previous work Burghardt et al (2021 J. Phys. A: Math. Theor. 54 414002). Specifically, we consider a representative two-dimensional tunneling system where a double well and a harmonic coordinate are cubically coupled. The time-dependent Hartree approximation is compared with a fully correlated solution, for different parameter regimes. The impact of the coupling and the resulting correlations are quantitatively assessed in terms of a time-dependent reaction probability along the tunneling coordinate. We show that the numerical error is correctly predicted on moderate time scales by a theoretically derived error estimate
Etude des multiples rôles des phosphatidylinositol-4-kinases betas dans la morphogenèse et les réponses de défense d'Arabidopsis thaliana
No full textPhosphatidylinositol 4-kinases (PI4Ks) are the first enzymes that commit phosphatidylinositol into the phosphoinositide pathway. Phosphoinositides (PPI), minor components of plasma membrane, are the phosphorylated derivatives of phosphatidylinositol (PI), such as phosphatidylinositol-4-phosphate (PI4P) and phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). In the Arabidopsis thaliana genome, twelve putative PI4K isoforms have been identified. Eight belong to type-II (AtPI4Kγ1-8), and four belong to type-III (AtPI4Kα1 and α2 and AtPI4Kβ1 and β2).To study the role of PI4Ks, I have worked with a double mutant defective plant in both the PI4Kβ genes. I show that the Arabidopsis thaliana pi4kβ1β2 double mutant exhibits several root phenotypes: impaired root growth, a lower sensitivity of roots to exogenous IAA (indole-3-acetic acid), impaired gravistimulation, and misshapen root hair growth. These changes appeared to coincide with a less stable actin cytoskeleton and an alteration in intracellular trafficking dynamics in pi4kβ1β2 roots. The content of bioactive auxin in the pi4kβ1β2 roots was similar to that in wild-type ones. Yet, an enhanced auxin-conjugating activity was detected and the auxin level reporter DII-VENUS did not respond to exogenous auxin in pi4kβ1β2 mutant. These data, therefore, link altered PI4K activity to the modification of vesicular trafficking and actin filaments organization one the one hand to altered auxin response likely due to alteration in auxin homeostasis one the other hand.The second part of my thesis was related to the Blumeria graminis (Bgh) interaction with pi4kβ1β2 double mutant. It is known that Arabidopsis has non-host resistance to Bgh. It means that plants build a special resistance structure - papillae - that acts as a barrier between fungi and plant cells. The pi4kβ1β2 double mutant showed an enhanced successful penetration of Bgh 24 hpi. The sid2 mutation affects the ISOCHORISMATE SYNTHASE 1 gene necessary for the synthesis of salicylic acid (SA). A similar defect in penetration resistance was seen in sid2/pi4kβ1β2, indicating the SA-independent character of this phenomenon. Deficiency of PI4Kbetas led to decreased accumulation of PI4P level in papillae. During pathogen attack, plenty of phospholipids and proteins were shown to accumulate in papillae. My hypothesis was that PI4Ks are essential for plant successful defense against Bgh, and more specifically for the formation of a successful papilla.The third part of my thesis concerns the mechanism leading to a constitutively active immunity in pi4kβ1β2 double mutant. In 4-week-old pi4kβ1β2 plants, an accumulation SA occurs. This SA accumulation was shown to be responsible for the dwarf stature of 4-week-old pi4kβ1β2 plants. The question is therefore to understand why the immunity system is constitutively switched on. The immunity system could be activated through cell-membrane or nuclear localized receptors. To study the role of type β PI4Ks in the regulation of defense mechanisms, I first crossed the pi4kβ1β2 double mutant with several mutants affected in different receptors or regulators of immunity. The use of different types of receptors or regulators of immunity will cover a wide range of pathways associated with the both - cell-surface and intracellular immunity. As a control, I used the sid2/pi4kβ1β2 triple mutant that does not accumulate SA, in contrast to pi4kβ1β2 plants. For phenotype describing rosette size was measured. After that typical immunity features were tested: resistance level to hemibiotroph Pseudomonas syringae pv tomato DC3000, PR1 expression and callose accumulation level. If any of these receptors/regulators is upstream to SA accumulation, I hoped to obtain a reverted plant phenotype with wild-type features. The dwarf pi4kβ1β2 phenotype was preserved for all mutants except one - wrky70/pi4kβ1β2, which indicates a possible role of WRKY70 factor in the constitutive SA accumulation.Les phosphatidylinositol 4-kinases (PI4K) sont les premières enzymes qui engagent le phosphatidylinositol dans la voie des phosphoinositides. Dans le génome d'Arabidopsis thaliana, douze isoformes putatives de PI4K ont été identifiées. Huit appartiennent au type II (AtPI4Kγ1-8) et quatre appartiennent au type III (AtPI4Kα1 et α2 et AtPI4Kβ1 et β2).Pour étudier le rôle des PI4K, j'ai travaillé avec une plante double mutante défectueuse dans les deux gènes PI4Kβ. J’ai montré que le double mutant d'Arabidopsis thaliana pi4kβ1β2 présente plusieurs phénotypes racinaires: une croissance racinaire altérée, une moindre sensibilité des racines à l'IAA exogène (acide indole-3-acétique), une gravistimulation altérée et une croissance des poils. Ces changements semblaient coïncider avec un cytosquelette d'actine moins stable et une altération de la dynamique du trafic intracellulaire dans les racines pi4kβ1β2. La teneur en auxine bioactive dans les racines pi4kβ1β2 était similaire à celle des racines de type sauvage. Ces données relient donc l'activité PI4K altérée à la modification du trafic vésiculaire et de l'organisation des filaments d'actine d'une part, et à la réponse altérée de l'auxine probablement due à l'altération de l'homéostasie de l'auxine d'autre part.La deuxième partie de ma thèse portait sur l'interaction de Blumeria graminis (Bgh) avec le double mutant pi4kβ1β2. On sait qu'Arabidopsis a une résistance non hôte à Bgh. Papilles - qui agit comme une barrière entre les champignons et les cellules végétales. Le double mutant pi4kβ1β2 a montré une meilleure pénétration de Bgh 24 hpi, donc une moindre résistance de la plante. La mutation sid2 touche le gène ISOCHORISMATE SYNTHASE 1nécessaire à la synthèse d’acide salicylique (SA). Un défaut similaire de résistance à la pénétration a été observé dans sid2/pi4kβ1β2, indiquant le caractère indépendant de SA de ce phénomène. La carence en PI4Kbetas a entraîné une diminution de l'accumulation du niveau de PI4P dans les papilles. Au cours de l'attaque pathogène, il a été démontré que de nombreux phospholipides et protéines s'accumulent dans les papilles. Mon hypothèse était que les PI4K sont essentielles pour une défense réussie des plantes contre la Bgh, et plus spécifiquement pour la formation d'une papille efficace.La troisième partie de ma thèse concerne le mécanisme conduisant à une immunité constitutivement active chez le double mutant pi4kβ1β2. Chez les plantes pi4kβ1β2 âgées de 4 semaines, une accumulation de SA. Cette accumulation de SA s'est avérée responsable de la stature naine des plantes pi4kβ1β2 âgées de 4 semaines. La question est donc de comprendre pourquoi le système immunitaire est constitutivement enclenché. Le système immunitaire pourrait être activé par l'intermédiaire de récepteurs localisés dans la membrane cellulaire ou solubles. Pour étudier le rôle des PI4K de type β dans la régulation des mécanismes de défense, j'ai d'abord croisé le double mutant pi4kβ1β2 avec plusieurs mutants affectés dans différents récepteurs ou régulateurs de l'immunité. Comme témoin, j'ai utilisé le triple mutant sid2/pi4kβ1β2 qui n'accumule pas de SA, contrairement aux plantes pi4kβ1β2. Pour le phénotype décrivant la taille de la rosette a été mesurée. Après cela, les caractéristiques typiques de l'immunité ont été testées : niveau de résistance à l'hémibiotrophe Pseudomonas syringae pv tomato DC3000, expression de PR1 et niveau d'accumulation de callose. Si l'un de ces récepteurs/régulateurs est en amont de l'accumulation de SA, j'espérais obtenir un phénotype végétal inversé avec des caractéristiques de type sauvage. Le phénotype nain pi4kβ1β2 a été préservé pour tous les mutants sauf un - wrky70/pi4kβ1β2_ ce qui indique un rôle possible du facteur de transcription WRKY70 dans l'accumulation constitutive de SA
Résultats de l'enquête sur les pratiques d'enseignement des mathématiques, PRAESCO, en classe de CM2 en 2019
No full textNational audienceL’enquête nationale sur les pratiques d’enseignement des mathématiques en classe de CM2 fait partie des enquêtes « PRAtiques d’Enseignement Spécifiques aux Contenus » (PRAESCO) que conduit la Direction de l’évaluation, de la prospective et de la performance (DEPP) en partenariat avec des équipes de recherche. L’enquête PRAESCO Mathématiques CM2 a été conduite en 2019, elle vise à documenter les pratiques d’enseignement des professeurs de ce niveau en mathématiques d’un point de vue général quant à cette discipline et de façon plus approfondie sur certains thèmes du programme scolaire. Cette enquête apporte également un certain nombre d’informations sur leur formation, leur ancienneté ou leur contexte de travail. Les données d’enquête ont été analysées, croisées et soumises à des traitements statistiques afin d’apporter, dans leurs convergences et leurs différences, une description précise et complète des pratiques d’enseignement des mathématiques à ce niveau scolaire
Weak and strong error analysis for mean-field rank based particle approximations of one dimensional viscous scalar conservation law
No full text47 pagesInternational audienceIn this paper, we analyse the rate of convergence of a system of interacting particles with mean-field rank based interaction in the drift coefficient and constant diffusion coefficient. We first adapt arguments by Kolli and Shkolnikhov to check trajectorial propagation of chaos with optimal rate to the associated stochastic differential equations nonlinear in the sense of McKean. We next relax the assumptions needed by Bossy to check convergence in with rate of the empirical cumulative distribution function of the Euler discretization with step of the particle system to the solution of a one dimensional viscous scalar conservation law. Last, we prove that the bias of this stochastic particle method behaves in . We provide numerical results which confirm our theoretical estimates
Fast improvement of macrofauna communities and soil quality in plantain crops converted to agroecological practices
No full textInternational audiencePlantain (Musa paradisiaca AAB) is one of the main staple food crops in tropical areas, particularly in the Caribbean region. Therefore, supporting a sustainable production of plantain in this zone is crucial to secure food and to provide income to millions of people. We hypothesized that agroecological practices based on multifunctionality and biodiversity and that preserve soil should i) increase macrofauna abundance, ii) enhance soil chemical fertility, iii) improve soil physical structure, iv) reduce plant infestation by parasitic nematodes, and v) immediately achieve similar yield as in conventional systems. For this purpose, we compared plantain conventional and agroecological systems at the farm scale. The agroecological system consisted in a combination of three innovations: i) inputs of vermicompost to replace mineral fertilizers, ii) use of healthy planting material and iii) use of a mulching of living crop to control weeds. Ten months after the plantation, soil macrofauna abundance had doubled and taxonomic richness had increased by 45% in the agroecological system. In addition, soil structure was improved in the agroecological system (52% of biogenic aggregates in the agroecological system vs. 21 % in conventional systems), as well as the abundance of free-living nematodes associated to plantain roots increased by 73 % in the agroecological system. The abundance of Radopholus similis, one of main plant parasitic nematodes, decreased in the agroecological system. Moreover, the agroecological system achieved similar crop yield level than conventional systems. Agroecological practices are thus an efficient option to allow a fast transition from conventional to environmentally friendly cropping system
Easy way for fabricating calcium carbonate hybrid microparticles-supported carrier: Focus on the loading of several hydrosoluble cargos all at once
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A new biaxial apparatus for tensile tests on Poly Ethylene Terephthalate optimized specimen at stretch blow molding conditions
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Reactivity of performic acid with organic micropollutants and model compounds
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Cyclic hardening/softening and deformation mechanisms of a twip steel under reversed loading
No full textInternational audiencePush-pull tests at fixed plastic strain amplitude or fixed stress amplitude were run on a TWIP steel, and followed by TEM observations, to analyze its cyclic behavior in relation with the deformation mechanisms. The kinematic and isotropic components of the flow stress were measured throughout the whole cyclic hardening/softening stages, and their evolution with the cumulated plastic strain was compared to those measured in tension. The rise of the internal stress was found responsible for the initial cyclic hardening, but this stress reached at most 50 % of the flow stress, as compared to nearly 70% in tension. Special constitutive equations were identified to capture these evolutions, as well as the transition from hardening to softening. Both components of the flow stress slightly decrease during the softening stage, whose origin is discussed, based on TEM observations at peak stress amplitude, or after softening. The present measurements and TEM observations, combined with those from a previous study of twinning/detwinning kinetics in push-pull on the same steel [29], suggest that under cyclic loading, mechanical twinning cannot be responsible for significant kinematic hardening of intragranular nature (or "dynamic Hall-Petch effect"), but rather contributes to a back stress of intergranular origin
Decimations for One- and Two-dimensional Ising and Rotator Models II: Continuous versus Discrete Symmetries
No full text16 pages, 1 figureWe show how decimated Gibbs measures which have an unbroken continuous symmetry due to the Mermin-Wagner theorem, although their discrete equivalents have a phase transition, still can become non-Gibbsian. The mechanism rests on the occurrence of a spin-flop transition with a broken discrete symmetry, once the model is constrained by the decimated spins in a suitably chosen "bad" configuration