Impact of Intramolecular Hydrogen Bonding on the Reactivity of Cupric Superoxide Complexes with O−H and C−H Substrates

The dioxygen reactivity of a series of TMPA‐based copper(I) complexes (TMPA=tris(2‐pyridylmethyl)amine), with and without secondary‐coordination‐sphere hydrogen‐bonding moieties, was studied at ?135 °C in 2‐methyltetrahydrofuran (MeTHF). Kinetic stabilization of the H‐bonded [( TMPA)Cu^II(O₂^.?)]⁺ cupric superoxide species was achieved, and they were characterized by resonance Raman (rR) spectroscopy. The structures and physical properties of [( TMPA)Cu^II(N₃^?)]⁺ azido analogues were compared, and the O₂^.? reactivity of ligand–Cu^I complexes when an H‐bonding moiety is replaced by a methyl group was contrasted. A drastic enhancement in the reactivity of the cupric superoxide towards phenolic substrates as well as oxidation of substrates possessing moderate C?H bond‐dissociation energies is observed, correlating with the number and strength of the H‐bonding groups.     

Squeezed states parametrized by elements of noncommutative algebras

By analogy with the conventional (q=1) case, a squeezed vacuum state for theq-bosonic oscillator is constructed. It can be shown that this obeys quantum noise relations similar to those found in the undeformed state. Using the unitary displacement operator for theq-boson algebra, we show that it is possible to construct aq-squeezed state which is parameterised by elements of a noncommutative algebra. These states satisfy the Robertson-Schrödinger Uncertainty Relation and can be generalised toq-analogues of correlated coherent states.Presented at the 4th Colloquium Quantum Groups and Integrable Systems, Prague, 22–24 June 1995.One of the authors (RJM) would like to thank the organizers of this colloquium for giving him the opportunity to attend this meeting. He would also like to thank the Carnegie Trust for support in travelling expenses.     

Improved acoustic signals discrimination using fractional Fourier transform based phase-space representations

In this communication we propose performing two-dimensional correlation operation between phase-space representations based on the fractional Fourier transform, instead of correlating the signals themselves. A numerical examples clearly indicates superior discrimination performance.     

Nanocrystalline GdBa2HfO5.5 perovskite dielectric material—A single-step synthesis and its characterization

Nanocrystals of GdBa₂HfO_5.5 perovskite ceramic materials, of the family A₂(BB′)O₆, were synthesized using an auto-igniting combustion of a precursor solution containing metal ions, oxidant and a fuel. Phase purity and particulate properties of the as-prepared powder were examined using X-ray diffraction, differential thermal and thermogravimetric analyses, Fourier-transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopic techniques. These nanocrystals were sintered to high density (～98% of the theoretical density) at ～1620 °C for 2 h.The sintering behavior, dielectric constant and dielectric loss factor of the samples showed variations in magnitude with that of the samples prepared by conventional solid-state route.