PARTISN results for the C5G7 MOX benchmark problems

In early 2001 the Nuclear Energy Agency solicited participants for a proposed new benchmark. The benchmark, known as C5G7 MOX, is intended to be a basis to measure current transport code abilities in the treatment of reactor core problems without spatial homogenization. We have participated with the code transport code PARTISN. PARTISN (PARallel TIme Dependent SN), PARTISN solves the linear Boltzmann transport equation in static and time dependent forms on one, two and three dimensional orthogonal grids using the deterministic (SN) method. A variety of spatial discritization methods are incorporated into PARTISN, however all calculations performed here used the diamond difference approach, coupled with a volume fraction method for non-Cartesian problem geometries. Acceleration of the source iterations is accomplished with diffusion synthetic acceleration (DSA)

N2-H2 capacitively coupled radio-frequency discharges at low pressure. Part I. Experimental results: Effect of the H2 amount on electrons, positive ions and ammonia formation

The mixing of N2 with H2 leads to very different plasmas from pure N2 and H2 plasma discharges. Numerous issues are therefore raised involving the processes leading to ammonia (NH3) formation. The aim of this work is to better characterize capacitively-coupled radiofrequency plasma discharges in N2 with few percents of H2 (up to 5%), at low pressure (0.3-1 mbar) and low coupled power (3-13 W). Both experimental measurements and numerical simulations are performed. For clarity, we separated the results in two complementary parts. The actual one (first part), presents the details on the experimental measurements, while the second focuses on the simulation, a hybrid model combining a 2D fluid module and a 0D kinetic module. Electron density is measured by a resonant cavity method. It varies from 0.4 to 5 109 cm-3, corresponding to ionization degrees from 2 10-8 to 4 10-7. Ammonia density is quantified by combining IR absorption and mass spectrometry. It increases linearly with the amount of H2 (up to 3 1013 cm-3 at 5% H2). On the contrary, it is constant with pressure, which suggests the dominance of surface processes on the formation of ammonia. Positive ions are measured by mass spectrometry. Nitrogen-bearing ions are hydrogenated by the injection of H2, N2H+ being the major ion as soon as the amount of H2 is >1%. The increase of pressure leads to an increase of secondary ions formed by ion/radical-neutral collisions (ex: N2H+, NH4 +, H3 +), while an increase of the coupled power favours ions formed by direct ionization (ex: N2 +, NH3 +, H2 +).N. Carrasco acknowledges the financial support of the European Research Council (ERC Starting Grant PRIMCHEM, Grant agreement no. 636829). A. Chatain acknowledges ENS Paris-Saclay Doctoral Program. A. Chatain is grateful to Gilles Cartry and Thomas Gautier for fruitful discussions on the MS calibration. L.L. Alves acknowledges the financial support of the Portuguese Foundation for Science and Technology (FCT) through the project UID/FIS/50010/2019. L. Marques and M. J. Redondo acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2019

Targeting of T/Tn Antigens with a Plant Lectin to Kill Human Leukemia Cells by Photochemotherapy

Photochemotherapy is used both for solid tumors and in extracorporeal treatment of various hematologic disorders. Nevertheless, its development in oncology remains limited, because of the low selectivity of photosensitizers (PS) towards human tumor cells. To enhance PS efficiency, we recently covalently linked a porphyrin (TrMPyP) to a plant lectin (Morniga G), known to recognize with high affinity tumor-associated T and Tn antigens. The conjugation allowed a quick uptake of PS by Tn-positive Jurkat leukemia cells and efficient PS-induced phototoxicity. The present study was performed: (i) to evaluate the targeting potential of the conjugate towards tumor and normal cells and its phototoxicity on various leukemia cells, (ii) to investigate the mechanism of conjugate-mediated cell death. The conjugate: (i) strongly increased (×1000) the PS phototoxicity towards leukemic Jurkat T cells through an O-glycan-dependent process; (ii) specifically purged tumor cells from a 1∶1 mixture of Jurkat leukemia (Tn-positive) and healthy (Tn-negative) lymphocytes, preserving the activation potential of healthy lymphocytes; (iii) was effective against various leukemic cell lines with distinct phenotypes, as well as fresh human primary acute and chronic lymphoid leukemia cells; (iv) induced mostly a caspase-independent cell death, which might be an advantage as tumor cells often resist caspase-dependent cell death. Altogether, the present observations suggest that conjugation with plant lectins can allow targeting of photosensitizers towards aberrant glycosylation of tumor cells, e.g. to purge leukemia cells from blood and to preserve the normal leukocytes in extracorporeal photochemotherapy

Real-Space Mesh Techniques in Density Functional Theory

This review discusses progress in efficient solvers which have as their foundation a representation in real space, either through finite-difference or finite-element formulations. The relationship of real-space approaches to linear-scaling electrostatics and electronic structure methods is first discussed. Then the basic aspects of real-space representations are presented. Multigrid techniques for solving the discretized problems are covered; these numerical schemes allow for highly efficient solution of the grid-based equations. Applications to problems in electrostatics are discussed, in particular numerical solutions of Poisson and Poisson-Boltzmann equations. Next, methods for solving self-consistent eigenvalue problems in real space are presented; these techniques have been extensively applied to solutions of the Hartree-Fock and Kohn-Sham equations of electronic structure, and to eigenvalue problems arising in semiconductor and polymer physics. Finally, real-space methods have found recent application in computations of optical response and excited states in time-dependent density functional theory, and these computational developments are summarized. Multiscale solvers are competitive with the most efficient available plane-wave techniques in terms of the number of self-consistency steps required to reach the ground state, and they require less work in each self-consistency update on a uniform grid. Besides excellent efficiencies, the decided advantages of the real-space multiscale approach are 1) the near-locality of each function update, 2) the ability to handle global eigenfunction constraints and potential updates on coarse levels, and 3) the ability to incorporate adaptive local mesh refinements without loss of optimal multigrid efficiencies.Comment: 70 pages, 11 figures. To be published in Reviews of Modern Physic

« Croître ou périr : un dilemne pour les firmes agro-alimentaires prises entre les prix agricoles, la distribution et les multinationales »

Alcouffe Alain. « Croître ou périr : un dilemne pour les firmes agro-alimentaires prises entre les prix agricoles, la distribution et les multinationales ». In: Revue d'économie industrielle, vol. 31, 1er trimestre 1985. Les restructurations de l'industrie française. pp. 33-42

Modes d'organisation et efficacité : le cas des groupes agro-alimentaires en France

National audienceCet article étudie l'influence de l'organisation sur les performances des entreprises. Il examine, dans une première partie, le mode d'organisation français en groupes de sociétés et le situe entre la forme en M américaine et le modèle J de la firme japonaise. Deux caractéristiques sont particulièrement mises en évidence : le mode de financement, le type de coordination et sa flexibilité. Les industries agro-alimentaires fournissent un cadre pour évaluer l'influence de ces facteurs que l'on a préalablement reliés au type de contrôle final. Dans une deuxième partie, l'hypothèse d'une relation positive entre organisation et performances est testée dans le même cadre sectoriel. Celui-ci comprend une grande diversité de formes organisationnelles distribuées suivant les différentes classes de taille, ce qui permet d'éliminer les biais liés à la taille. Les résultats indiquent qu'il existe une corrélation entre forme d'organisation et efficacité. Ils suggèrent que la forme d'organisation est aujourd'hui une variable stratégique qui joue un rôle majeur dans les structures industrielles

Modes d'organisation et efficacité : le cas des groupes agro-alimentaires en France

National audienceCet article étudie l'influence de l'organisation sur les performances des entreprises. Il examine, dans une première partie, le mode d'organisation français en groupes de sociétés et le situe entre la forme en M américaine et le modèle J de la firme japonaise. Deux caractéristiques sont particulièrement mises en évidence : le mode de financement, le type de coordination et sa flexibilité. Les industries agro-alimentaires fournissent un cadre pour évaluer l'influence de ces facteurs que l'on a préalablement reliés au type de contrôle final. Dans une deuxième partie, l'hypothèse d'une relation positive entre organisation et performances est testée dans le même cadre sectoriel. Celui-ci comprend une grande diversité de formes organisationnelles distribuées suivant les différentes classes de taille, ce qui permet d'éliminer les biais liés à la taille. Les résultats indiquent qu'il existe une corrélation entre forme d'organisation et efficacité. Ils suggèrent que la forme d'organisation est aujourd'hui une variable stratégique qui joue un rôle majeur dans les structures industrielles

Les grandes etapes de la previsions economique.

previsions economiques ; cycles economiques