The relativistic hydrogen atom: a theoretical laboratory for structure functions

Thanks to the Dirac equation, the hydrogen-like atom at high $Z$ offers a precise model of relativistic bound state, allowing to test properties of unpolarized and polarized structure functions analogous to the hadronic ones, in particular: Sivers effect, sum rules for the vector, axial, tensor charges and for the magnetic moment, positivity constraints, sea contributions and fracture function

The High-Z hydrogen-like atom: a model for polarized structure functions

The Dirac equation offers a precise analytical description of relativistic two-particle bound states, when one of the constituent is very heavy and radiative corrections are neglected. Looking at the high-Z hydrogen-like atom in the infinite momentum frame and treating the electron as a "parton", various properties usually attributed to the quark distributions in the nucleon are tested, in particular: Bj{\o}rken scaling; charge, helicity, transversity and momentum sum rules; existence of the parton sea; Soffer inequality; correlation between spin and transverse momentum (Sivers and Boer-Mulders effects); transverse displacement of the center-of-charge and its connection with the magnetic moment. Deep inelastic experiments with photon or positron beams at MeV energies, analogous to DIS or Drell-Yan reactions, are considered

A Lagrangian heuristic for a real-life integrated planning problem of railway transportation resources

International audienceRailway planning requires three scarce and heterogeneous resources: train paths (infrastructure), rolling stock and train drivers. In the current industrial approach at SNCF (French National Railway Company), these resources are essentially planned through a sequential approach which typically starts from (1) train paths and goes further on to (2) rolling stock and finally (3) train drivers. SNCF has already developed optimization tools for Steps (2) and (3). In this paper, we built upon the work previously presented at IAROR-RAILROME 2011. We presented a mixed integer linear programming model with coupling constraints for a simplified integrated problem of railway production resources. We also proposed a Lagrangian relaxation heuristic. In this approach, sub-problems were solved thanks to a standard mathematical programming solver. First numerical experiments were conducted on a reduced data set, extracted from an actual instance from a French region (Bretagne). The results obtained were promising but showed that the resolution with a standard solver was too costly in terms of computational times for real-world instances and that the model had to be improved for implementation in a Lagrangian relaxation framework. Since 2011, the mathematical model has been improved and numerous operational constraints have been integrated in order to tackle real-life integrated planning problems at SNCF. The Lagrangian relaxation heuristic has been updated consequently. As already mentioned, SNCF has already developed two independent optimization tools for planning rolling stock and train drivers. The Lagrangian approach has also been adapted so that the resulting sub-problems of this mathematical decomposition method can now be solved with the two dedicated tools. We thus can now address real-life instances and solve each sub-problem of the specific Lagrangian heuristic with proprietary software. Preliminary computational results show the interest of our method. Compared to a sequential approach, the Lagrangian heuristic leads to substantial cost reductions and generates good solutions in a reasonable CPU time. This is thus an interesting tool for human planners who want to experiment and quantitatively evaluate different scenarios (e.g. other train-path distribution, specific rolling stock, train drivers with other capabilities...)

numerical study of steady flow inside a lid-driven square cavity for Reynolds number up to 50000

The flow inside a lid-driven square cavity have been imposed a wide controversy during these last decades.Multiple studies found to exist in the literature included this case, which is widely used for benchmarking in computational fluid dynamic due to the simplicity of geometry. some classes of studies have investigated the existence of steady flow in the driven cavity, they found a steady 2D numérical solution until 35000 value of Reynolds number.However, other classes of studies have stated that the flow in driven cavity submitted to a hydrodynamic instability and they illustrated a continuation méthode to locate the point at which a Hopf bifurcation occurs leading to a transition from a steady flow to unsteady.In the shade of these studies and with this uncertainty surrounding this subject we wanted to get more clarification especially for steady flow solutions.The present study represents a numerical computation for steady flow inside a lid-driven square cavity, the governing equation is solved using a finite volume method based on second order scheme of accuracy. Steady solutions are obtained for Reynolds numbers ascending from 100 to 50000, using a resolution of 1024 x1024 grid point. A good agreement with previous results in the literature, the work was done in this paper including proprieties of flow in the center of primary and secondary vortices, velocity components and numérical values for stream function and vorticity which assure a good example for benchmarking purposes

Planification intégrée des ressources en transport ferroviaire : de la théorie à la mise en œuvre

Cet article présente les travaux réalisés sur l'optimisation du plan de transport par planification intégrée des ressources engins et Agents de Conduite. Pour résoudre de façon satisfaisante le modèle mathématique proposé sur des instances de taille industrielle, nous avons proposé une approche par relaxation lagrangienne des contraintes couplantes. Plusieurs schémas de relaxation sont ainsi proposés et étudiés expérimentalement. Nous avons retenu, pour la mise en œuvre, celui qui offrait le meilleur compromis entre les performances et la compatibilité avec des briques logicielles existantes à la SNCF pour la planification optimisée et séparée des engins et des AdC. Les résultats préliminaires sont encourageants; des tests plus intensifs de qualification industrielle sont en cours et seront présentés au congrès. Ces travaux réalisés offrent des perspectives par rapport à la prise en compte de modifications des horaires des trains dans la recherche de solutions optimisées par un processus de planification intégrée des ressources engins et AdC

Activation of Hepatic Lipase Expression by Oleic Acid: Possible Involvement of USF1

Polyunsaturated fatty acids affect gene expression mainly through peroxisome proliferator-activated receptors (PPARs) and sterol regulatory element binding proteins (SREBPs), but how monounsaturated fatty acids affect gene expression is poorly understood. In HepG2 cells, oleate supplementation has been shown to increase secretion of hepatic lipase (HL). We hypothesized that oleate affects HL gene expression at the transcriptional level. To test this, we studied the effect of oleate on HL promoter activity using HepG2 cells and the proximal HL promoter region (700 bp). Oleate increased HL expression and promoter activity 1.3–2.1 fold and reduced SREBP activity by 50%. Downregulation of SREBP activity by incubation with cholesterol+25-hydroxycholesterol had no effect on HL promoter activity. Overexpression of SREBP2, but not SREBP1, reduced HL promoter activity, which was effected mainly through the USF1 binding site at -307/-312. Oleate increased the nuclear abundance of USF1 protein 2.7 ± 0.6 fold, while USF1 levels were reduced by SREBP2 overexpression. We conclude that oleate increases HL gene expression via USF1. USF1 may be an additional fatty acid sensor in liver cells

INTEGRATED PLANNING OF RAILWAY TRANSPORTATION RESOURCES

La production des circulations ferroviaires a la sncf repose actuellement sur un processus essentiellement sequentiel dans lequel la conception des grilles horaires de circulation (reservation de l'infrastructure pour la circulation des trains de l'offre de transport de la sncf) conditionne largement la conception des planifications des engins ferroviaires (les roulements engins), puis celle des agents de conduite (adc) (les grilles de service des adc). cette strategie de planification sequentielle des ressources ferroviaires a ete massivement adoptee pour des raisons pratiques et scientifiques (historique, savoir-faire, complexite du systeme ferroviaire, etc.). toutefois, cette strategie de planification sequentielle genere des solutions qui peuvent etre de cout eleve et moins robustes aux aleas, car les decisions prises a une etape donnee peuvent reduire considerablement l'ensemble des solutions realisables aux etapes suivantes. face a ce constat et a la forte interaction entre ces trois ressources heterogenes et tres couteuses, la sncf a souhaite investiguer la praticabilite et les apports d'une demarche d'optimisation du plan de transport par planification integree de ces ressources critiques. dans cette optique, les travaux de these ont porte sur l'etude de faisabilite, le prototypage et la validation d'une demarche de planification integree des ressources permettant d'ameliorer l'efficacite globale du plan de transport, d'accroitre la competitivite de la sncf et d'ameliorer la qualite de ses services. nous avons propose une formalisation du probleme de planification integree engins/adc et des algorithmes performants qui s'appuient sur une approche par relaxation lagrangienne pour resoudre de maniere efficace la problematique etudiee. cette approche repose sur l'exploitation de deux briques logicielles developpees a la sncf pour resoudre chacun des sous-problemes de planification des engins et des adc. les algorithmes ont ete testes experimentalement avec des donnees reelles de la region ter bretagne. differentes evolutions des modeles et des algorithmes ont ete etudiees pour rendre ces derniers plus efficaces. les tests de validation sur des jeux de donnees reelles a une echelle industrielle sont encourageants et montrent des gains potentiels allant jusqu'a 4% des adc exploites par rapport a une approche traditionnelle (sequentielle).The planning of railway production at the french national railways (sncf) is currently based on a mainly sequential process in which the design of railway timetabling widely conditioning design planning of railway equipment (rolling stock), then one of the train drivers (driver rosters). this strategy of sequential planning of railway resources massively adopted for practical and scientific reasons (expertise, complexity of the railway system, etc.). however, this strategy generates solutions which can be more expensive and less robust to uncertainties, because decisions taken at any given stage can significantly reduce the overall feasible solutions of the following steps.given this situation and the strong interaction between these heterogeneous and very expensive resources, the thesis deals with the feasibility and inputs of a process where these critical resources could be planned and optimized in an integrated way. the thesis focuses on the feasibility study, prototyping and validation of an integrated approach for planning rolling stocks and drivers, so as to improve the efficiency of the overall transportation plan, increase sncf competitiveness and enhance the quality of its services. we propose a mixed integer linear programming formulation of the rolling stock/ train drivers integrated planning problem. in this mathematical model, each planning sub-problem is formalized and coupling constraints are further introduced to model the interdependencies of these two resources when they are simultaneously used for train production. in this heuristic, the solution of the lagrangian dual and the calculation of feasible solutions are performed by calling two proprietary software modules available at sncf for planning rolling stocks and train drivers. the heuristic is tested experimentally with real data from the ter bretagne region, and several evolutions are introduced in the models and algorithms so as to improve their performances.validation tests on of real data sets at an industrial scale are encouraging and, when compared to a traditional (sequential) approach, show gain of up to 4% for train drivers used