First ZnGa2O4 transparent ceramics

Transparent polycrystalline ZnGa₂O₄ ceramics are synthesized, for the first time, by combining high-energy ball milling, solid-state reaction and spark plasma sintering. They appear transparent in both the visible and near infrared (up to 9 μm) ranges after a post-SPS annealing in air converting the raw semiconductor into an electrical insulator. The maximum of transmittance is reached in the near infrared region, at around 2.5 μm, with a value of 78 % (1 mm thick sample) close to the maximum value of transmittance previously measured for single crystals. These transparent ceramics present a classic cubic spinel ZnGa₂O₄ structure and a dense microstructure (> 99 %) attained without sintering aids, with an average grain size of 600 nm and a random orientation of the crystallites. TEM observations performed on thin foils have revealed limited nanometer scale intergranular porosity which does not affect much the transparency. As a proof of interest, red long-lasting luminescence arising from the entire sample volume is observed in these Cr³⁺ doped transparent ceramics. This innovative work is anticipated to further drive the development of transparent ZnGa₂O₄ ceramics towards a wider range of performing optical applications such as laser emission.     

Thermodynamic and experimental approach of the effect of Si on the sintering of Y3NbO7

The effect of silicon on the natural sintering of Y₃NbO₇ powders is studied. Characterizations shows that Si increases densification rate and grain growth but it also leads to the apparition of a secondary silicate phase. The silicate precipitation results from the segregation of silicon favored by matter transport through a liquid phase. The distribution of the secondary phase have been studied by electronic microscopy and mapped by micro-luminescence. Thermodynamic calculations of Gibbs energy of the different phase as well as binary and ternary phase diagrams have been conducted to support interpretation of the sintering experimental results.     

The impact of implementing continuous improvement upon stress within a Lean production framework

The purpose of this research is to understand the impact of implementing continuous improvement upon the occupational stress of employees within the framework of Lean management. The outcomes of empirical research mobilising a mixed methodology prove that continuous improvement can help attenuate stress levels, whilst achieving or surpassing economic performance objectives, if its implementation means an effective and satisfactory participation by both employees as well as by management. Conversely, when there is no continuous improvement or it is ill-suited, Lean results in greater stress. These findings confirm the interest in furthering insight into Lean management by moving from a global approach to an approach integrating the effects of its various pillars, especially continuous improvement.     

Experimental quantum cryptography

We describe results from an apparatus and protocol designed to implement quantum key distribution, by which two users, who share no secret information initially: (1) exchange a random quantum transmission, consisting of very faint flashes of polarized light; (2) by subsequent public discussion of the sent and received versions of this transmission estimate the extent of eavesdropping that might have taken place on it, and finally (3) if this estimate is small enough, distill from the sent and received versions a smaller body of shared random information, which is certifiably secret in the sense that any third party's expected information on it is an exponentially small fraction of one bit. Because the system depends on the uncertainty principle of quantum physics, instead of the usual mathematical assumptions such as the difficulty of factoring, it remains secure against an adversary with unlimited computing power.This paper was accepted prior to the present Editor-in-Chief taking responsibility. A preliminary version of this paper was presented at Eurocrypt '90, May 21–24, Århus, Denmark, and has appeared in the proceedings, pp. 253–265. François Bessette was supported in part by an NSERC Postgraduate Scholarship. Gilles Brassard was supported in part by Canada's NSERC. This work was performed while John Smolin was visiting IBM Research.     

Forced‐ and Self‐Rotation of Magnetic Nanorods Assembly at the Cell Membrane: A Biomagnetic Torsion Pendulum

In order to provide insight into how anisotropic nano‐objects interact with living cell membranes, and possibly self‐assemble, magnetic nanorods with an average size of around 100 nm × 1 µm are designed by assembling iron oxide nanocubes within a polymeric matrix under a magnetic field. The nano–bio interface at the cell membrane under the influence of a rotating magnetic field is then explored. A complex structuration of the nanorods intertwined with the membranes is observed. Unexpectedly, after a magnetic rotating stimulation, the resulting macrorods are able to rotate freely for multiple rotations, revealing the creation of a biomagnetic torsion pendulum.     

A simple multi‐directional absorbing layer method to simulate elastic wave propagation in unbounded domains

The numerical analysis of elastic wave propagation in unbounded media may be difficult due to spurious waves reflected at the model artificial boundaries. This point is critical for the analysis of wave propagation in heterogeneous or layered solids. Various techniques such as Absorbing Boundary Conditions, infinite elements or Absorbing Boundary Layers (e.g. Perfectly Matched Layers) lead to an important reduction of such spurious reflections. In this paper, a simple absorbing layer method is proposed: it is based on a Rayleigh/Caughey damping formulation which is often already available in existing Finite Element softwares. The principle of the Caughey Absorbing Layer Method is first presented (including a rheological interpretation). The efficiency of the method is then shown through 1D Finite Element simulations considering homogeneous and heterogeneous damping in the absorbing layer. 2D models are considered afterwards to assess the efficiency of the absorbing layer method for various wave types and incidences. A comparison with the PML method is first performed for pure P‐waves and the method is shown to be reliable in a more complex 2D case involving various wave types and incidences. It may thus be used for various types of problems involving elastic waves (e.g. machine vibrations, seismic waves, etc.). Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis and observation,on an atomic resonance,of the frequency shift due to the length modulation of an optical cavity

The frequency shift of the light owing to a cavity length modulation has been observed with the spectroscopy of the 1S-3S two-photon transition in hydrogen. The excitation of this transition occurs at a wavelength of 205 nm. One produces this radiation by frequency doubling a 410-nm radiation in an enhancement ring cavity. The length modulation of this cavity induces frequency shifts and a splitting of the observed 1S-3S line. We obtain a good agreement between the experiment and the theoretical analysis.     

Toward the link between structural and mechanical properties of fiber aggregates in paper materials

Journal of Materials Science - Mechanical properties of fiber-based materials, such as paper, are governed by the heterogeneous microstructure induced by the formation process. For example, in...     

Gallium bismuth halide GaBi-X2 (X = I,Br, Cl) monolayers with distorted hexagonal framework: Novel room-temperature quantum spin Hall insulators

Quantum spin Hall (QSH) insulators with a large topologically nontrivial bulk gap are crucial for future applications of the QSH effect.Among these,group Ⅲ-Ⅴ monolayers and their halides,which have a chair structure (regular hexagonal framework),have been widely studied.Using first-principles calculations,we formulate a new structure model for the functionalized group Ⅲ-Ⅴ monolayers,which consist of rectangular GaBi-X2 (X =I,Br,Cl) monolayers with a distorted hexagonal framework (DHF).These structures have a far lower energy than the GaBi-X2 monolayers with a chair structure.Remarkably,the DHF GaBi-X2 monolayers are all QSH insulators,which exhibit sizeable nontrivial band gaps ranging from 0.17 to 0.39 eV.The band gaps can be widely tuned by applying different spin-orbit coupling strengths,resulting in a distorted Dirac cone.