ACSB: A minimum performance assessment

Amplitude companded sideband (ACSB) is a new modulation technique which uses a much smaller channel width than does conventional frequency modulation (FM). Among the requirements of a mobile communications system is adequate speech intelligibility. This paper explores this aspect of minimum required performance. First, the basic principles of ACSB are described, with emphasis on those features that affect speech quality. Second, the appropriate performance measures for ACSB are reviewed. Third, a subjective voice quality scoring method is used to determine the values of the performance measures that equate to the minimum level of intelligibility. It is assumed that the intelligibility of an FM system operating at 12 dB SINAD represents that minimum. It was determined that ACSB operating at 12 dB SINAD with an audio-to-pilot ratio of 10 dB provides approximately the same intelligibility as FM operating at 12 dB SINAD

The influence of binarity on the morpho-kinematics of planetary nebulae

The role of central star binarity in the shaping of planetary nebulae (PNe) has been the subject of much debate, with single stars believed to be incapable of producing the most highly collimated morphologies. However, observational support for binary-induced shaping has been sadly lacking. Here, we highlight the results of a continuing programme to spatio-kinematically model the morphologies of all PNe known to contain a close binary central star. Spatio-kinematical modelling is imperative for these objects, as it circumvents the degeneracy between morphology and orientation which can adversely affect determinations of morphology based on imaging alone. Furthermore, spatio-kinematical modelling accurately determines the orientation of the nebular shell, allowing the theoretically predicted perpendicular alignment, between nebular symmetry axis and binary orbital plane, to be tested. To date, every PN subjected to this investigation has displayed the predicted alignment, indicating that binarity has played an important role in the formation and evolution of these nebulae. The further results from this programme will be key, not only in determining whether binary interaction is responsible for shaping the studied PNe, but also in assessing the importance of binarity in the formation and evolution of all PNe in general.Comment: 2 pages, 2 tables, proceedings of the IAU Symposium No. 283, Planetary Nebulae: An Eye to the Futur

A study of the kinematics and binary-induced shaping of the planetary nebula HaTr 4

We present the first detailed spatio-kinematical analysis and modelling of the planetary nebula HaTr 4, one of few known to contain a post-common-envelope central star system. Common envelope evolution is believed to play an important role in the shaping of planetary nebulae, but the exact nature of this role is yet to be understood. High spatial- and spectral- resolution spectroscopy of the [OIII]5007 nebular line obtained with VLT-UVES are presented alongside deep narrowband Ha+[NII]6584 imagery obtained using EMMI-NTT, and together the two are used to derive the three-dimensional morphology of HaTr 4. The nebula is found to display an extended ovoid morphology with an enhanced equatorial region consistent with a toroidal waist - a feature believed to be typical amongst planetary nebulae with post-common-envelope central stars. The nebular symmetry axis is found to lie perpendicular to the orbital plane of the central binary, concordant with the idea that the formation and evolution of HaTr 4 has been strongly influenced by its central binary.Comment: 9 pages, 5 figures, accepted for publication in MNRA

Formal Synthesis of (±)-Allocolchicine Via Gold-Catalysed Direct Arylation: Implication of Aryl Iodine(III) Oxidant in Catalyst Deactivation Pathways

Abstract A concise formal synthesis of racemic allocolchicine has been developed, centred on three principal transformations: a retro-Brook alkylation reaction to generate an arylsilane, a gold-catalysed arylative cyclisation to generate the B-ring via biaryl linkage, and a palladium-catalysed carbonylation of an aryl chloride to generate an ester. 1H NMR monitoring of the key gold-catalysed cyclisation step reveals that a powerful catalyst deactivation process progressively attenuates the rate of catalyst turnover. The origins of the catalyst deactivation have been investigated, with an uncatalysed side-reaction, involving the substrate and the iodine(III) oxidant, identified as the source of a potent catalyst poison. The side reaction generates 1–4% of a diaryliodonium salt, and whilst this moiety is shown not to be an innate catalyst deactivator, when it is tethered to the arylsilane reactant, the inhibition becomes powerful. Kinetic modelling of processes run at two different catalyst concentrations allows extraction of the partitioning of the gold catalyst between the substrate and its diaryliodonium salt, with a rate of diaryliodonium salt generation consistent with that independently determined in the absence of catalyst. The high partition ratio between substrate and diaryliodonium salt (5/1) results in very efficient, and ultimately complete, diversion of the catalyst off-cycle. Graphical Abstract </jats:sec

Universal simulation of Hamiltonian dynamics for qudits

What interactions are sufficient to simulate arbitrary quantum dynamics in a composite quantum system? Dodd et al. (quant-ph/0106064) provided a partial solution to this problem in the form of an efficient algorithm to simulate any desired two-body Hamiltonian evolution using any fixed two-body entangling N-qubit Hamiltonian, and local unitaries. We extend this result to the case where the component systems have D dimensions. As a consequence we explain how universal quantum computation can be performed with any fixed two-body entangling N-qudit Hamiltonian, and local unitaries.Comment: 13 pages, an error in the "Pauli-Euclid-Gottesman Lemma" fixed, main results unchange

Gold-Catalyzed Direct Arylation

Gently Coupled Linked aryl rings are found in a broad range of commercial chemical products. Currently, the most versatile synthetic route to this motif involves cross-coupling of one ring with a halide substituent to another ring with a boron or metal-based substituent. Recent research has focused on eliminating the need for one or both of these activating substituents, but for the most part, the emerging methods have required high temperatures and high concentrations of one coupling partner. Ball et al. (p. 1644 ) now present a gold catalyst that can couple silyl-activated arenes to unactivated arenes in comparable concentrations at room temperature. </jats:p

Implementation of a Deutsch-like quantum algorithm utilizing entanglement at the two-qubit level, on an NMR quantum information processor

We describe the experimental implementation of a recently proposed quantum algorithm involving quantum entanglement at the level of two qubits using NMR. The algorithm solves a generalisation of the Deutsch problem and distinguishes between even and odd functions using fewer function calls than is possible classically. The manipulation of entangled states of the two qubits is essential here, unlike the Deutsch-Jozsa algorithm and the Grover's search algorithm for two bits.Comment: 4 pages, two eps figure