Topology on the Spaces Of Orderings of Groups

A natural topology on the space of left orderings of an arbitrarysemi-group is introduced here. This space is proved to be compact,and for free abelian groups it is shown to be homeomorphic tothe Cantor set. An application of this result is a new proofof the existence of universal Gröbner bases. 2000 MathematicsSubject Classification 06F15, 13P10 (primary), 06F05, 20F60(secondary).     

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.     

High lying energy positions of doubly (2pns) P° and (2pnd) P° excited states of the beryllium atom

The Screening Constant by Unit Nuclear Charge (SCUNC) method is used to study (2pns) ^1,3P° and (2pnd) ^1,3P° autoionizing states of the beryllium atom. Energy positions are reported up to n=20. In addition, resonance widths of the (2pns) ¹P° states also presented. The current results compared very well to available theoretical and experimental literature values up to n=15. The accurate data presented in this work may be of interest for future experimental and theoretical studies in the photoabsorption spectrum of Be.     

Synthesis and Sorption Performance of Novel Sorbents for Selective Solid-Phase Extraction of Eu(III) Ions from Aqueous Solutions

Russian Journal of Applied Chemistry - Magnesium-cadmium hydroxyapatite [(Mg-Cd)HAP] and novel multi-wall carbon nanotubes Mg-Cd hydroxyapatite (CNTs/(Mg-Cd)HAP) composites were synthesized by a...