Energy conservation and numerical stability for the reduced MHD models of the non-linear JOREK code

In this paper we present a rigorous derivation of the reduced MHD models with and without parallel velocity that are implemented in the non-linear MHD code JOREK. The model we obtain contains some terms that have been neglected in the implementation but might be relevant in the non-linear phase. These are necessary to guarantee exact conservation with respect to the full MHD energy. For the second part of this work, we have replaced the linearized time stepping of JOREK by a non-linear solver based on the Inexact Newton method including adaptive time stepping. We demonstrate that this approach is more robust especially with respect to numerical errors in the saturation phase of an instability and allows to use larger time steps in the non-linear phase

Welfare Effects of Salary Caps in Sports Leagues with Win-Maximizing Clubs

This paper studies the welfare effect of a percentage-of-revenue salary cap in a European context with win-maximizing clubs. It shows that a percentage-of-revenue cap increases competitive balance and decreases the overall salary payments in the league, therefore contributing to financial stability. A percentage-of-revenue cap will always increase social welfare if the weight on aggregate club surplus in the welfare function is sufficiently high. Additionally, if fans’ preferences for aggregate talent are sufficiently high then the percentage-of-revenue cap will also increase social welfare; no matter how much weight the league puts on financial stability.Salary Caps, Social Welfare, Competitive Balance, Team Sports League

Organizational Differences between U.S. Major Leagues and European Leagues: Implications for Salary Caps

This paper outlines and compares the organizational structure of major sports leagues, explores the reasoning behind their formation, and derives implications for salary caps in European football. To understand why sports leagues have developed a specific organizational structure, one must take the economic peculiarities of team sports leagues into consideration. For this purpose, we analyze the production process and illuminate its major peculiarities. For example, we present the difference between economic competition and competition on the pitch and discuss the consequences of this distinction for an attractive final product. Furthermore, we show that a hold-up problem exists between the two stages of the production process and demonstrate how these problems are overcome by the organizational structure chosen by sports leagues. We also outline the differences between the U.S. major leagues and European leagues and document recent developments in that context. Finally, based on this comparative institutional analysis, we derive implications for the introduction of salary caps into European football.Sports leagues, organization, salary cap, hold-up problem

Comparative analysis of classical models (MARS3D, AZOV3D) and lattice Boltzmann models for shallow water hydrodynamics computations

Different numerical approaches of hydrodynamics of shallow water basins are considered and compared. Two approaches are developped in TIT-Russia: one of them is classical and based on numerical solution of the Navier-Stokes equations by Pressure-Correction method, another (developed several years ago) is  based on the solution of the Lattice Boltzmann kinetic equation. The comparative analysis of these two approaches with MARS3D is performed for a shallow water basin example: «Etang de Berre»

Salt-driven assembly of magnetic silica microbeads with tunable porosity.

HYPOTHESIS: Porous magnetic silica beads are promising materials for biological and environmental applications due to their enhanced adsorption and ease of recovery. This work aims to develop a new, inexpensive and environmentally friendly approach based on agglomeration of nanoparticles in aqueous droplets. The use of an emulsion as a geometrical constraint is expected to result in the formation of spherical beads with tunable composition depending on the aqueous phase content. EXPERIMENTS: Magnetic silica beads are produced at room temperature by colloidal destabilization induced by addition of CaCl2 to a water-in-oil emulsion containing SiO2 and Fe3O4 nanoparticles. The impact of the salt concentration, emulsification method, concentration of hydrophobic surfactant as well as silica content is presented in this paper. FINDINGS: This method enables the production of spherical beads with diameters between 1 and 9 µm. The incorporation of magnetic nanoparticles inside the bead's structure is confirmed using Energy Dispersive X-ray spectrometry (EDX) and Scanning Transmission Electron Microscopy (STEM) and results in the production of magnetic responsive beads with a preparation yield up to 84%. By incorporating the surfactant Span 80 in the oil phase it is possible to tune the roughness and porosity of the beads.W D Armstrong Studentship (internal Cambridge award

A minimal model for spontaneous cell polarization and edge activity in oscillating, rotating and migrating cells

How the cells break symmetry and organize their edge activity to move directionally is a fun- damental question in cell biology. Physical models of cell motility commonly rely on gradients of regulatory factors and/or feedback from the motion itself to describe polarization of edge activity. Theses approaches, however, fail to explain cell behavior prior to the onset of polarization. Our analysis using the model system of polarizing and moving fish epidermal keratocytes suggests a novel and simple principle of self-organization of cell activity in which local cell-edge dynamics depends on the distance from the cell center, but not on the orientation with respect to the front-back axis. We validate this principle with a stochastic model that faithfully reproduces a range of cell-migration behaviors. Our findings indicate that spontaneous polarization, persistent motion, and cell shape are emergent properties of the local cell-edge dynamics controlled by the distance from the cell center.Comment: 8 pages, 5 figure

09191 Abstracts Collection -- Fault Tolerance in High-Performance Computing and Grids

From June 4--8, 2009, the Dagstuhl Seminar 09191 ``Fault Tolerance in High-Performance Computing and Grids \u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available. Slides of the talks and abstracts are available online at url{http://www.dagstuhl.de/Materials/index.en.phtml?09191}

Anomalous polarization conversion in arrays of ultrathin ferromagnetic nanowires

We study optical properties of arrays of ultrathin nanowires by means of the Brillouin scattering of light on magnons. We employ the Stokes/anti-Stokes scattering asymmetry to probe the circular polarization of a local electric field induced inside nanowires by linearly polarized light waves. We observe the anomalous polarization conversion of the opposite sign than that in a bulk medium or thick nanowires with a great enhancement of the degree of circular polarization attributed to an unconventional refraction in the nanowire medium.Comment: 5 pages, 4 figure

A short diastereoselective total synthesis of (±)-vibralactone

A total synthesis of the (±)-vibralactone has been achieved in 11 steps and 16% overall yield from malonic acid. Key steps include a highly diastereoselective allylation of an α-formyl ester containing an all carbon α-quaternary center, a Pd-catalyzed deallylative β-lactonization, and an aldehyde-selective Wacker oxidation of a terminal alkene