Thermal carbosilylation of endohedral dimetallofullerene La(2)@I(h)-C(80) with silirane

Thermal carbosilylation of endohedral dimetallofullerene La(2)@I(h)-C(80) with silirane (silacyclopropane) is reported herein for the first time. Two diastereomers of the carbosilylated La(2)@I(h)-C(80) have been isolated and characterized. The fascinating molecular structure of one diastereomer of the carbosilylated derivatives has been determined unambiguously using X-ray crystallographic analysis. Detailed characteristics of the molecular structures including their metal atom movements have also been revealed using NMR spectroscopic studies and computational calculations. Results revealed that two La atoms move dynamically inside the carbon sphere. Furthermore, electrochemical study has demonstrated that carbosilylation is effective to fine-tune the La(2)@I(h)-C(80) electronic properties.     

Devitrification behaviour of Cu-Zr-Ti-Pd bulk glassy alloys

The glass formation, mechanical properties and devitrification of the Cu-Zr-Ti-Pd glassy alloys are studied. The formation of a nanoscale icosahedral phase in Cu-based alloys is observed. The nanoscale particles with icosahedral symmetry are primarily formed in the Cu-Zr-Ti-Pd glassy alloys in the initial stage of the devitrification process. As the icosahedral phase is metastable it transforms to the equilibrium oC68 (Cu, Pd)₁₀(Zr, Ti)₇ single phase or its mixture with the oP44 Cu₈Zr₃ phase, depending upon the alloy composition, through an intermediate crystalline compound. The structure changes on heating were studied by X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry.     

Characterization of Ce@C82 and its anion

Ce@C(82) is isolated by high-performance liquid chromatography (HPLC) and the cage symmetry is determined as C(2)(v)() by measuring the (13)C NMR spectra of its anion. The (13)C NMR peaks of [Ce@C(82)](-) show temperature-dependent shifts ascribed to the f electron remaining on the Ce atom. Both Ce@C(82) and [Ce@C(82)](-) are silent in electron spin resonance spectroscopy (ESR) because of the highly anisotropic g matrix as well as of the fast relaxation process originating from the orbital angular momentum of the f electron. This is the complementary relationship to the observation of the paramagnetic shift in (13)C NMR. [Ce@C(82)](-) has lower stability in air than [La@C(82)](-).     

Characterization of acid sites on the external surface of zeolites

Styrene oligomerization in the presence of Pd(acac)₂+PPh₃+BF₃OEt₂ catalytic system (acac—acetylacetonate) has been studied. Styrene conversion at optimum conditons (T=343 K, B/Pd=7, P/Pd=2) was as high as 75,000 mol of C₃H₃ per mol of Pd in 7 h with a selectivity to dimers, mostly 1,3-diphenylbut-1-ene, up to 93%.     

Advances in quantum dots for classical and non-classical light sources Invited Paper

Recent advances in quantum dots (QDs) for classical and non-classical light sources are presented. We have established metal organic chemical vapor deposition (MOCVD) technology for InAs-based QD lasers at 1.3 μm and achieved ultralow threshold in QD lasers with photonic crystal (PhC) nanocavity. In addition, single photon emitters at 1.55/μm, GaN-based single photon sources operating at 200 K, and high-Q PhC nanocavity have been demonstrated.     

Proximity theorems of discrete convex functions

A proximity theorem is a statement that, given an optimization problem and its relaxation, an optimal solution to the original problem exists in a certain neighborhood of a solution to the relaxation. Proximity theorems have been used successfully, for example, in designing efficient algorithms for discrete resource allocation problems. After reviewing the recent results for L-convex and M-convex functions, this paper establishes proximity theorems for larger classes of discrete convex functions, L₂-convex functions and M₂-convex functions, that are relevant to the polymatroid intersection problem and the submodular flow problem.Mathematics Subject Classification (2000): 90C27, 05B35