Transport equations with disparate advection fields. Application to the gyrokinetic models in plasma physics

The subject matter of this paper concerns the asymptotic regimes for transport equations with advection fields having components of very disparate orders of magnitude. The main purpose is to derive the limit models: we justify rigorously the convergence towards these limit models and we investigate the well-posedness of them. Such asymptotic analysis arises in the magnetic confinement context, where charged particles move under the action of strong magnetic fields. In these situations we distinguish between a slow motion driven by the electric field and a fast motion around the magnetic lines.     

Bootstrap inference for misspecified moment condition models

We study the standard-bootstrap, the centered-bootstrap, and the empirical-likelihood bootstrap tests of hypotheses used in conjunction with generalized method of moments inference in correctly specified and misspecified moment condition models. We show that, under correct specification, the standard-bootstrap estimator of the null distribution of the J-test converges in distribution to a random distribution, verifying its inconsistency, while the centered and the empirical-likelihood bootstrap estimators are consistent. We provide higher-order expansions of the size distortions of the analytic and the bootstrap tests. We show that the standard-bootstrap parameter-tests are consistent under misspecification, while the centered-bootstrap parameter-tests are inconsistent. We propose a general bootstrap methodology which is highly accurate under correct specification and consistent under misspecification. In a simulation study, we explore the finite sample behavior of the analytic and the bootstrap tests for a panel data model and we apply our methodology on a real-world data set.     

Direct C2-trifluoromethylation of indole derivatives catalyzed by copper acetate

Direct C2-selective trifluoromethylation of indole derivatives was achieved with Togni’s hypervalent iodine reagent and CuOAc as a catalyst in MeOH under mild conditions, affording the desired C2-trifluoromethylated indoles in good yield (up to 90%).     

Nanocatalysis on tailored shape supports: Au and Pd nanoparticles supported on MgO nanocubes and ZnO nanobelts

Active gold and palladium nanoparticles supported on MgO nanocubes and ZnO nanobelts and transition-metal-containing MgO nanobelts were synthesized by combining evaporation and deposition-precipitation techniques. The high activity and stability of the Au/CeO2 and Pd/CeO2 nanoparticle catalysts deposited on the MgO cubes are remarkable and imply that a variety of efficient catalysts can be designed and tested using this approach. The significant increase in the concentration of corner and edge sites in MgO nanocubes make them well-defined supports to study the detailed mechanism of the catalytic activity enhancement.     

The DFT rationalization of exchange and anisotropy in one-dimensional d-p magnets: The [MnIII(porphyrin)][TCNE] case study

We report here numerical experiments, modeling and interpretations dealing with the magnetic interactions necessary for building nano-scale magnets in quasi-one-dimensional systems based on the assembling of [Mn(porphyrin)]⁺ magnetically anisotropic d units and TCNE-p-type spin carriers. The magnetic ordering and its coupling parameter are studied by Broken Symmetry DFT calculations for various model structures, allowing for the rationalization of geometry dependence of the effective exchange. The roles of the phenyl substituent, as well as of the basis set and the DFT functional used in the computation are discussed. The intrinsic anisotropy of these systems is studied in an original manner, extracting Ligand Field and Spin Orbit parameters by combined fits to non-relativistic and relativistic DFT calculations, allowing the explicit estimation of the Zero Field Splitting parameters.     

On exact 2-para Sasakian manifolds

Paracontact and para Sasakian manifoldsM carryingr(1<r≤dimM) Reed vector filds ξ _r have been especially studied by A. Bucki [2], [3], [4]. In the present paper, we consider a (2m+2)-dimensional para Sasakian manifoldM(ϕ, ξ _r , η ^r g), whose Reed convectors η ^r =ξ _r ^b are exact 1-forms and the covariant derivatives of ξ _r are given by ∇ξ _r =f _r dp ^⊺, wheredp ^⊤ means the horizontal component of the soldering formdp andf _r∈C^∞M satisfydf _r =cη ^r ,c=constant. It is proved that such a manifold may be viewed as the local Riemannian productM=M ^⊥×M^⊤, where

Higher Dimensional Aztec Diamonds and a (2d + 2)-Vertex Model

Motivated by the close relationship between the number of perfect matchings of the Aztec diamond graph introduced in [5] and the free energy of the square-ice model, we consider a higher dimensional analog of this phenomenon. For d 1, we construct d-uniform hypergraphs which generalize the Aztec diamonds and we consider a companion d-dimensional statistical model (called the 2d + 2-vertex model) whose free energy is given by the logarithm of the number of perfect matchings of our hypergraphs. We prove that the limit defining the free energy per site of the 2d + 2-vertex model exists and we obtain bounds for it. As a consequence, we obtain an especially good asymptotical approximation for the number of matchings of our hypergraphs.     

Application of Brønsted-type LFER in the study of the phospholipase C mechanism

Phosphatidylinositol-specific phospholipase C cleaves the phosphodiester bond of phosphatidylinositol to form inositol 1,2-cyclic phosphate and diacylglycerol. This enzyme also accepts a variety of alkyl and aryl inositol phosphates as substrates, making it a suitable model enzyme for studying mechanism of phosphoryl transfer by probing the linear free-energy relationship (LFER). In this work, we conducted a study of Br?nsted-type relationship (log k = beta(lg) pK(a) + C) to compare mechanisms of enzymatic and nonenzymatic reactions, confirm the earlier proposed mechanism, and assess further the role of hydrophobicity in the leaving group as a general acid-enabling factor. The observation of the high negative Br?nsted coefficients for both nonenzymatic (beta(lg) = -0.65 to -0.73) and enzymatic cleavage of aryl and nonhydrophobic alkyl inositol phosphates (beta(lg) = -0.58) indicates that these reactions involve only weak general acid catalysis. In contrast, the enzymatic cleavage of hydrophobic alkyl inositol phosphates showed low negative Br?nsted coefficient (beta(lg) = -0.12), indicating a small amount of the negative charge on the leaving group and efficient general acid catalysis. Overall, our results firmly support the previously postulated mechanism where hydrophobic interactions between the enzyme and remote parts of the leaving group induce an unprecedented negative-charge stabilization on the leaving group in the transition state.