Additions dipolaires-1,3 en serie germaniee: Action de nitrilimines, oxydes de nitrile, et nitrones sur les germanones et germathiones

A new aspect of the reactivity of germanones and germathiones towards nitrilimines, nitriloxides and nitrones is investigated. The regioselectivity of the dipolar 1,3-cycloaddition reactions between germanones or germathiones and diphenylnitrilimine is discussed.

The structure of the adducts is determined from chemical or spectroscopic studies (¹³C NMR, IR).

Germa-oxa- or -thia-diazolines, germaoxathiazoles and germaoxathiazolidines are obtained and the thermal stability of these adducts reported.     

Orthogonality properties of iterated polynomial mappings

We consider a measure defined on a complex contour and its associated orthogonal polynomials. The action of a polynomial transformation on the measure and the transformation laws of the corresponding orthogonal polynomials are given. Iterating the transformation provides an invariant measure, whose support is the Julia set corresponding to the polynomial transformation. It appears that, up to a constant, the iterated polynomials generated by the initial mapping form a subset of the invariant set of orthogonal polynomials, which fulfill a three term recursion relation. An algorithm is given to compute the coefficients of this recursion relation, which can be interpreted as a linear extension of the iterative procedure.     

Experimental determination of the spin-wave spectrum of the two-dimensional ferromagnet K2CuF4

K₂CuF₄ is a quasi-bidimensional ferromagnet with an easy magnetization plane. The Curie temperature is 6.25 K. We have measured the spin-wave spectrum from 2 to 14 K, and found an exchange integral of 11.4 K between the first neighbours in the basal plane. No measurable dispersion was found along the axis perpendicular to that plane. We have observed a shift in the energy of the magnons, and a broadening of the magnon peak both of which behave differently below and above the Curie temperature.     

Preparation of113mIn radiocolloid for liver scanning

Kits were developed for the preparation of a sterile^113mIn colloid as a radiopharmaceutical for liver scanning. 2.5 ml of^113mIn sterile generator eluate was added to 0.5 ml of ferric chloride dissolved in 0.04N HCl (40 g/ml). The pH was adjusted by addition of 2 ml of phosphate buffer. The optimal pH for the formation of^113mIn colloid was found to be equal to 7.5–8.5. Liver uptake in mice was determined to be 85–90%.     

Field-induced ferromagnetic metallic state in the bilayer manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7, probed by neutron scattering

The bilayer manganite La1.2Sr1.8Mn2O7 exhibits a phase transition from a paramagnetic insulating (PI) to a ferromagnetic metallic (FM) state with a colossal magnetoresistance (CMR) effect. Upon 60% Pr substitution, magnetic order and PI to FM transition are suppressed. Application of a moderate magnetic field restores an FM state with a CMR effect. Neutron scattering by a single crystal of (La0.4Pr0.6)1.2Sr1.8Mn2O7, under a magnetic field of 5 T, has revealed a long-range and homogeneous ferromagnetic order. In the PI phase, under zero field, correlated lattice polarons have been detected. At 28 K, under 5 T, the spin wave dispersion curve determines an in-plane isotropic spin wave stiffness constant of 146 meV A(2). So the magnetic field not only generates a homogeneous ferromagnetic ground state, but also restores a magnetic coupling characteristic of FM CMR manganites.     

Sequential photo-addition of glycine methyl-ester to [60]fullerene

While direct photo-addition of glycine-methyl-esters (GME) to [60]fullerene (C₆₀) can yield a complex product mixture, only a fulleropyrrolidine (FP) mono-adduct has been characterized and the mechanism remains to be ascertained. We show here that visible light irradiation of a mixture of C₆₀ and GME in the presence of oxygen is a direct route to synthesize sequentially higher FP poly-adducts through an unprecedented cyclization–deamination mechanism. Each step of this mechanism leads to a FP adduct involving the correlated addition of two GME radicals and the departure of an ammonia molecule.