Optimality in Quantum Data Compression using Dynamical Entropy

In this article we study lossless compression of strings of pure quantum states of indeterminate-length quantum codes which were introduced by Schumacher and Westmoreland. Past work has assumed that the strings of quantum data are prepared to be encoded in an independent and identically distributed way. We introduce the notion of quantum stochastic ensembles, allowing us to consider strings of quantum states prepared in a more general way. For any identically distributed quantum stochastic ensemble we define an associated quantum Markov chain and prove that the optimal average codeword length via lossless coding is equal to the quantum dynamical entropy of the associated quantum Markov chain

Radial Kinematics of Isolated Elliptical Galaxies

Ellipticals in very low density environments are extremely rare but hold important clues about galaxy formation and evolution. In this paper we continue our study of isolated elliptical galaxies, presenting results on the radial stellar kinematics for 13 isolated early-type galaxies. We derive radial rotation velocity, velocity dispersion and hermite terms to ~1 effective radius. We observe a dichotomy in kinematic properties similar to that in the elliptical population as a whole, where low luminosity ellipticals tend to be rotationally supported. For all galaxies the V/sigma ratio increases with radius. We find kinematically distinct cores (KDCs), or velocity substructure, in ~40% of the galaxies for which we have major axis spectra. Such a fraction is similar to that observed for ellipticals in higher density environments. Most galaxies in the sample reveal kinematic evidence for a nuclear disk. The non-relaxed kinematics in several galaxies suggests that they have undergone a merger or accretion event. Isolated ellipticals generally follow the fundamental plane defined by cluster ellipticals -- exceptions being those galaxies with evidence for young stellar populations. Overall, we find isolated ellipticals have similar kinematic properties to their counterparts in higher density environments.Comment: 11 pages, 6 figures, MNRAS accepte

The threats of social networking : old wine in new bottles?

Despite the many potential benefits to its users, social networking appears to provide a rich setting for criminal activities and other misdeeds. In this paper we consider whether the risks of social networking are unique and novel to this context. Having considered the nature and range of applications to which social networks may be applied, we conclude that there are no exploits or fundamental threats inherent to the social networking setting. Rather, the risks and associated threats treat this communicative and social context as an enabler for existing, long established and well-recognised exploits and activities

CMB temperature lensing power reconstruction

We study reconstruction of the lensing potential power spectrum from CMB temperature data, with an eye to the Planck experiment. We work with the optimal quadratic estimator of Okamoto and Hu, which we characterize thoroughly in application to reconstruction of the lensing power spectrum. We find that at multipoles L<250 our current understanding of this estimator is biased at the 15% level by beyond-gradient terms in the Taylor expansion of lensing effects. We present the full lensed trispectrum to fourth order in the lensing potential to explain this effect. We show that the low-L bias, as well as a previously known bias at high-L, is relevant to the determination of cosmology and must be corrected for in order to avoid significant parameter errors. We also investigate the covariance of the reconstructed power, finding broad correlations of ~0.1%. Finally, we discuss several small improvements which may be made to the optimal estimator to mitigate these problems.Comment: straightforward bias mitigation on pg. 14, matches version accepted by PR

Analysis and correction of the helium speech effect by autoregressive signal processing

SIGLELD:D48902/84 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

A magnetically isolated gate driver for high-speed voltage sharing in series-connected MOSFETs

A scalable resonant gate drive circuit is described, suitable for driving series-connected MOSFETs in high-voltage, high-speed inverter applications for resistive and capacitive loads. Galvanic isolation is provided by a loop of high voltage wire, which also serves as the resonant inductor in the circuit. Fast dynamic voltage sharing is achieved by delivering equal current to each gate. A prototype is built and tested, demonstrating a 75ns switching time at 5kV using 900V MOSFETs

High-Tensile Wire or Cable Tobacco Field Curing Structure

Producers are rapidly adopting field curing structures, and several variations in construction methods and materials exist to achieve low cost or low maintenance and long life. One of the construction methods, pioneered by a producer and now being used by others in the state, uses high-tensile wire strands or cable to support the tobacco sticks