Prediction of Nontrivial Band Topology and Superconductivity in Mg2_2Pb

The interplay of BCS superconductivity and nontrivial band topology is expected to give rise to opportunities for creating topological superconductors, achieved through pairing spin-filtered boundary modes via superconducting proximity effects. The thus-engineered topological superconductivity can, for example, facilitate the search for Majorana fermion quasiparticles in condensed matter systems. Here we report a first-principles study of Mg$_2$Pb and predict that it should be a superconducting topological material. The band topology of Mg$_2$Pb is identical to that of the archetypal quantum spin Hall insulator HgTe, while isostructural and isoelectronic Mg$_2$Sn is topologically trivial; a trivial to topological transition is predicted for Mg$_2$Sn$_{1-x}$Pb$_x$ for x~0.77. We propose that Mg$_2$Pb-Mg$_2$Sn quantum wells should generate robust spin-filtered edge currents in analogy to HgTe/CdTe quantum wells. In addition, our calculations predict that Mg$_2$Pb should become superconducting upon electron doping. Therefore, Mg$_2$Pb is expected to provide a practical material platform for studying emergent phenomena arising from the interplay of superconductivity and band topology.Comment: 5 figure

Disintermediation of traditional chemical intermediary roles in the Electronic Business-to-Business (e-B2B) exchange world

The traditional chemical distribution industry is a multi-billion dollar business and with the introduction of Electronic Business-to-Business (e-B2B) exchanges to the global chemical industry there is some concern about the future roles of traditional intermediaries (TI). The objectives of this research paper are to investigate the possibility of disintermediation of roles of TI by e-B2B exchanges and to identify the value adding role of TI as perceived by chemical distributors and buyers. If these value adding roles may be the key to future survival for TI in the marketplace. International data collected from e-B2B exchanges, chemical distributors and buyers are used. Content analysis of e-B2B exchanges was conducted while survey questionnaires were used for distributors and buyers using a cross-sectional approach. The research shows that whilst the e-B2B exchanges have a role to play in the chemical supply chain management there were still sub-functions which the buyers viewed that the TI could offer to them. So the supplier-buyer relationships could be maintained between the buyers and the TI, at least for the time being, until newer business models of e-B2B exchanges begins to compete with the TI's to offer these sub-functions. The research holds valuable implications for TI in the chemical industry regarding the need for differentiation with a view building new competences to survive the encroachment of their traditional business base by e-B2B exchanges. The impact of e-B2B exchanges on TI in the chemical industry has not previously been studied in-depth. This paper provides new knowledge and makes a contribution by providing evidence of evolution in the chemical distribution channels. © 2010 Elsevier B.V. All rights reserved

Holographic injection locking of a broad area laser diode via a photorefractive thin-film device

We demonstrate locking of a high power broad area laser diode to a single frequency using holographic feedback from a photorefractive polymer thin-film device for the first time. A four-wave mixing setup is used to generate feedback for the broad area diode at the wavelength of the single frequency source (Ti:Sapphire laser) while the spatial distribution adapts to the preferred profile of the broad area diode. The result is an injection-locked broad area diode emitting with a linewidth comparable to the Ti:Sapphire laser

Red blood cells and other non-spherical capsules in shear flow: oscillatory dynamics and the tank-treading-to-tumbling transition

We consider the motion of red blood cells and other non-spherical microcapsules dilutely suspended in a simple shear flow. Our analysis indicates that depending on the viscosity, membrane elasticity, geometry and shear rate, the particle exhibits either tumbling, tank-treading of the membrane about the viscous interior with periodic oscillations of the orientation angle, or intermittent behavior in which the two modes occur alternately. For red blood cells, we compute the complete phase diagram and identify a novel tank-treading-to-tumbling transition at low shear rates. Observations of such motions coupled with our theoretical framework may provide a sensitive means of assessing capsule properties.Comment: 11 pages, 4 figure

Multivariate dynamic kernels for financial time series forecasting

The final publication is available at http://link.springer.com/chapter/10.1007/978-3-319-44781-0_40We propose a forecasting procedure based on multivariate dynamic kernels, with the capability of integrating information measured at different frequencies and at irregular time intervals in financial markets. A data compression process redefines the original financial time series into temporal data blocks, analyzing the temporal information of multiple time intervals. The analysis is done through multivariate dynamic kernels within support vector regression. We also propose two kernels for financial time series that are computationally efficient without a sacrifice on accuracy. The efficacy of the methodology is demonstrated by empirical experiments on forecasting the challenging S&P500 market.Peer ReviewedPostprint (author's final draft