Synthesis of alkenes from tertiary esters utilizing the triphenylphosphine-iodine system

The treatment of tertiary esters with triphenylphosphine and iodine under mild conditions gives the most stable alkene in good yield. Formates, acetates and trifluoroacetates were studied.     

Synthesis,dynamic light scattering,and luminescence properties of copolymers containing iridium(III) bisterpyridine in the side chain

Supramolecular block‐random copolymers containing [Ir(terpy)₂]³⁺ in the side chain were synthesized via postfunctionalization of a P(S‐b‐AC_terpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐AC_terpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007     

Anomalies of the external and internal gravitational fields of the Earth’s isostatically balanced crust in the quadratic approximation

Formulas that include the contribution from dipole-distributed anomalous masses represented as layers distributed in height relative to the reference ellipsoid to the gravitational field in the quadratic approximation have been derived. The relationships between the expansion coefficients of some function and its square in terms of spherical functions have been established. The contribution from the relief masses and the density jump at the Mohorovicic discontinuity is used to illustrate the results.     

100-TW femtosecond laser based on parametric amplification

In experiments on the parametrical amplification of femtosecond pulses in wide-aperture DKDP crystals, a power of more than 100 TW has been reached, which is much higher than the record level achieved in such lasers. The energy efficiency obtained for the parametric amplifier is equal to 27%. The energy of a 72-fs pulse is equal to 10 J.     

A dynamic finite volume scheme for large-eddy simulation on unstructured grids

In recent years there has been considerable progress in the application of large-eddy simulation (LES) to increasingly complex flow configurations. Nevertheless a lot of fundamental problems still need to be solved in order to apply LES in a reliable way to real engineering problems, where typically finite-volume codes on unstructured meshes are used. A self-adaptive discretisation scheme, in the context of an unstructured finite-volume flow solver, is investigated in the case of isotropic turbulence at infinite Reynolds number. The Smagorinsky and dynamic Smagorinsky sub-grid scale models are considered. A discrete interpolation filter is used for the dynamic model. It is one of the first applications of a filter based on the approach presented by Marsden et al. In this work, an original procedure to impose the filter shape through a specific selection process of the basic filters is also proposed. Satisfactory results are obtained using the self-adaptive scheme for implicit LES. When the scheme is coupled with the sub-grid scale models, the numerical dissipation is shown to be dominant over the sub-grid scale component. Nevertheless the effect of the sub-grid scale models appears to be important and beneficial, improving in particular the energy spectra. A test on fully developed channel flow at Re_τ = 395 is also performed, comparing the non-limited scheme with the self-adaptive scheme for implicit LES. Once again the introduction of the limiter proves to be beneficial.     

Study of the vibrational states of nanocrystalline carbon by diffuse reflection spectroscopy

The possibility of performing a quantitative analysis of vibrational states of nanocrystalline carbon has been explored by using the spectroscopic method of diffuse IR reflection. An expression derived from the Kubelka-Munk relation has been proposed and employed to investigate the effect of the original parameters of a sample (absorber concentration, sample dispersion, radiation frequency, scattering factors) on the characteristic features of IR spectra. The IR absorption bands observed in the diffuse reflection spectrum of pyrographite were assigned.     

Cluster approach in first-principle calculations for ferroelectrics

It is shown that, proceeding from the first principles, it is possible to separate the contributions from short-and long-range interactions to the lattice dynamics and dielectric properties of crystalline dielectrics. The cluster calculations of local force constants and potentials for the matrix and impurity atoms in ferroelectrics with the perovskite structure were made by the Hartree-Fock MOLCAO-SCF method. The parameters of the Devonshire-Slater-Barrett single-ion model are calculated for barium titanate and potassium niobate. The influence of the quantum statistics on the Curie temperature in these ferroelectrics and the isotope effect in barium titanate are also considered.