Calculation of point defects in rutile TiO 2 by the screened-exchange hybrid functional

The formation energies of the oxygen vacancy and titanium interstitial in rutile TiO 2 were calculated by the screened-exchange (sX) hybrid density functional method, which gives a band gap of 3.1 eV, close to the experimental value. The oxygen vacancy gives rise to a gap state lying 0.7 eV below the conduction band edge, whose charge density is localized around the two of three Ti atoms next to the vacancy. The Ti interstitial (Ti int) generates four defect states in the gap, whose unpaired electrons lie on the interstitial and the adjacent Ti 3d orbitals. The formation energy for the neutral oxygen vacancy is 1.9 eV for the O-poor chemical potential. The neutral Ti interstitial has a lower formation energy than the O vacancy under O-poor conditions. This indicates that both the O vacancy and Ti int are relevant for oxygen deficiency in rutile TiO 2 but the O vacancy will dominate under O-rich conditions. This resolves questions about defect localization and defect predominance in the literature. © 2012 American Physical Society.

Coexistence of high-bit-rate quantum key distribution and data on optical fiber

Quantum key distribution (QKD) uniquely allows distribution of cryptographic keys with security verified by quantum mechanical limits. Both protocol execution and subsequent applications require the assistance of classical data communication channels. While using separate fibers is one option, it is economically more viable if data and quantum signals are simultaneously transmitted through a single fiber. However, noise-photon contamination arising from the intense data signal has severely restricted both the QKD distances and secure key rates. Here, we exploit a novel temporal-filtering effect for noise-photon rejection. This allows high-bit-rate QKD over fibers up to 90 km in length and populated with error-free bidirectional Gb/s data communications. With high-bit rate and range sufficient for important information infrastructures, such as smart cities and 10 Gbit Ethernet, QKD is a significant step closer towards wide-scale deployment in fiber networks.

Multiplexed classical and quantum transmission for high bitrate quantum key distribution systems

We report the operation of a gigahertz clocked quantum key distribution system, with two classical data communication channels using coarse wavelength division multiplexing over a record fibre distance of 80km. © 2012 OSA.

The night purging of a two-storey atrium building

We examine the fluid mechanics of night purging in a two-storey naturally ventilated atrium building. We develop a mathematical model of a simplified atrium building and focus on the rate at which warm air purges from each storey and the atrium by displacement ventilation into a still cool night environment of a constant temperature. To develop a first insight into how the geometry of the building influences the rate at which warm air purges from each storey via the atrium we neglect heat exchange with the fabric (so there is no thermal buffering) and furthermore assume that the warm air layers in each storey and the atrium are of uniform temperature. The plumes of warm air that rise from the storeys into the atrium, causing the atrium to fill with warm air, have a very strong influence on the night purge. Modelling these as axisymmetric turbulent plumes, we identify three forms of purging behaviour. Each purge is characterised by five key times identified in the progression of the night purge and physical rationale for these differing behaviours is given. An interface velocity deficit and volumetric purge deficit are introduced as measures of the efficiency of a night purge. © 2010 Elsevier Ltd.

Accurate screened exchange band structures for the transition metal monoxides MnO, FeO, CoO and NiO.

We report calculations of the band structures and density of states of the four transition metal monoxides MnO, FeO, CoO and NiO using the hybrid density functional sX-LDA ('screened exchange local density approximation'). Late transition metal oxides are prototypical examples of strongly correlated materials, which pose challenges for electronic structure methods. We compare our results with available experimental data and show that our calculations generally yield accurate predictions for the fundamental band gaps and valence bands, in favourable agreement with previously reported theoretical studies. For MnO, the band gaps are still underestimated, suggesting additional many-body effects that are not captured by our screened hybrid functional approach.

Key principles for developing industrially relevant strategic technology management toolkits

When considering the potential uptake and utilization of technology management tools by industry, it must be recognized that companies face the difficult challenges of selecting, adopting and integrating individual tools into a toolkit that must be implemented within their current organizational processes and systems. This situation is compounded by the lack of sound advice on integrating well-founded individual tools into a robust toolkit that has the necessary degree of flexibility such that they can be tailored for application to specific problems faced by individual organizations. As an initial stepping stone to offering a toolkit with empirically proven utility, this paper provides a conceptual foundation to the development of toolkits by outlining an underlying philosophical position based on observations from multiple research and commercial collaborations with industry. This stance is underpinned by a set of operationalized principles that can offer guidance to organizations when deciding upon the appropriate form, functions and features that should be embodied by any potential tool/toolkit. For example, a key objective of any tool is to aid decision-making and a core set of powerful, flexible, scaleable and modular tools should be sufficient to allow users to generate, explore, shape and implement possible solutions across a wide array of strategic issues. From our philosophical stance, the preferred mode of engagement is facilitated workshops with a participatory process that enables multiple perspectives and structures the conversation through visual representations in order to manage the cognitive load in the collaborative environment. The generic form of the tools should be configurable for the given context and utilized in a lightweight manner based on the premise of 'start small and iterate fast'. © 2012 Elsevier Inc.

Efficient decoy-state quantum key distribution with quantified security

We analyse the finite-size security of the efficient Bennett-Brassard 1984 protocol implemented with decoy states and apply the results to a gigahertz-clocked quantum key distribution system. Despite the enhanced security level, the obtained secure key rates are the highest reported so far at all fibre distances.

High bit rate quantum key distribution with 100 dB security

We report the operation of a gigahertz clocked quantum key distribution system featuring high composable and quantifiable security while maintaining more than 1 Mbit/s secure key rate over a 50 km quantum channel. © OSA 2013.

Histone H2A Has a Novel Variant in Fish Oocytes

Histone variants and their modification have significant roles in many cellular processes. In this study, we identified and characterized the histone H2A variant h2af1o in fish and revealed its oocyte-specific expression pattern during oogenesis and embryogenesis. Moreover, posttranslational modification of H2af1o was observed that results from phosphorylation during oocyte maturation. To understand the binding dynamics of the novel core histone variant H2af1o in nucleosomes, we cloned ubiquitous gibel carp h2afx as a conventional histone control and investigated the dynamic exchange difference in chromatin by fluorescence recovery after photobleaching. H2af1o has significantly higher mobility in nucleosomes than ubiquitous H2afx. Compared with ubiquitous H2afx, H2af1o has a tightly binding C-terminal and a weakly binding N-terminal. These data indicate that fish oocytes have a novel H2A variant that destabilizes nucleosomes by protruding its N-terminal tail and stabilizes core particles by contracting its C-terminal tail. Our findings suggest that H2af1o may have intrinsic ability to modify chromatin properties during fish oogenesis, oocyte maturation, and early cleavage.

The effect of cationic, non-ionic and amphiphilic surfactants on the intercalation of bentonite

Surfactant-clay interactions are key for the development of new clay applications and inorganic-organic nanocomposites. Bentonite, with montmorillonite as the principal clay mineral constituent, was modified with varying concentrations of hexadecethyltrimethylammonium chloride (HDTMA), as a reference cationic surfactant, polypropylene glycol (PPG) 1200 and 2000, as non-ionic surfactants, and lecithin and Topcithin®, as amphiphilic phospholipid surfactants, according to the cation exchange capacity (CEC). The modified bentonites were characterised by X-ray diffraction, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectrometry, specific surface area and pore volume. Three intercalation regions have been identified depending on the surfactant. The non-ionic surfactant caused only a crystalline expansion of bentonite interlayers, while the cationic surfactant induced an osmotic intercalation. The amphiphilic lecithin derivatives intercalated more extensively with the bentonite matrix. The TGA and the FTIR spectra showed that, at lower concentrations, the PPGs and HDTMA adopted a disordered conformation that required more energy to degrade, while at higher concentrations, the surfactants were ordered in the interlayer space of the bentonite. The lecithin derivative surfactant had a greater thermal and conformation stability. The specific surface area reduced with increasing surfactant concentrations. This study highlights the effect of surfactant type on the interlayer space of montmorillonite in the perspective of developing novel clay functions. © 2013.