Origin of {112} < 111 > antitwinning in a Ti-24Nb-4Zr-8Sn superelastic single crystal

Journal of Materials Science - $${\left\{112\right\}\langle {111}\rangle }_{\beta }$$ twins are observed in a superelastic β Ti-24Nb-4Zr-8Sn (wt.%) single crystal after tensile test. A careful...     

Fair cost-sharing methods for the minimum spanning tree game

We study the problem of sharing in a fair manner the cost of a service provided to a set of players in the context of Cooperative Game Theory. We introduce a new fairness measure capturing the dissatisfaction (or happiness) of each player and we propose two cost sharing methods minimizing the maximum or average dissatisfaction of the clients for the classical minimum spanning tree game.     

Multiresolution atomistic simulations of dynamic fracture in nanostructured ceramics and glasses

Multimillion atom molecular-dynamics (MD) simulations are performed to investigate dynamic fracture in glasses and nanostructured ceramics. Using multiresolution algorithms, simulations are carried out for up to 70 ps on massively parallel computers. MD results in amorphous silica (a-SiO₂) reveal the formation of nanoscale cavities ahead of the crack tip. With an increase in applied strain, these cavities grow and coalesce and their coalescence with the advancing crack causes fracture in the system. Recent AFM studies of glasses confirm this behavior. The MD value for the critical stress intensity factor of a-SiO₂ is in good agreement with experiments. Molecular dynamics simulations are also performed for nanostructured silicon nitride (n-Si₃N₄). Structural correlations in n-Si₃N₄ reveal that interfacial regions between nanoparticles are amorphous. Under an external strain, nanoscale cavities nucleate and grow in interfacial regions while the crack meanders through these regions. The fracture toughness of n-Si₃N₄ is found to be six times larger than that of crystalline -Si₃N₄. We also investigate the morphology of fracture surfaces. MD results reveal that fracture surfaces of n-Si₃N₄ are characterized by roughness exponents 0.58 below and 0.84 above a certain crossover length, which is of the order of the size of Si₃N₄ nanoparticles. Experiments on a variety of materials reveal this behavior. The final set of simulations deals with the interaction of water with a crack in strained silicon. These simulations couple MD with a quantum-mechanical (QM) method based on the density functional theory (DFT) so that chemical processes are included. For stress intensity factor K=0.4 MPa m^1/2, we find that a decomposed water molecule becomes attached to dangling bonds at the crack or forms a Si-O-Si structure. At K=0.5 MPa m^1/2, water molecules decompose to oxidize Si or break Si-Si bonds.     

Analyzing the physiological signature of anabolic steroids in cattle urine using pyrolysis/metastable atom bombardment mass spectrometry and pattern recognition

Pyrolysis coupled to metastable atom bombardment (MAB) and time-of-flight mass spectrometry (TOFMS) is used for generating mass spectra from bovine urine samples obtained from cattle treated with anabolic steroids. These spectra constitute fingerprints, which can be discriminated by multivariate statistical analysis. Four main conclusions can be drawn from this work: (i) The use of different metastable gases, such as Xe*, Kr*, or N2*, as an energy-tunable ionization beamline allows control of the internal energy and the dissociation processes of the produced odd electron molecular ions, thus giving rise to complementary mass spectra fingerprints. (ii) A variable transformation depending on the biofluid matrix suitably contracts the frequency distribution of the generated data for low m/z ratios holding information related to endogenous metabolites encountered in urine. (iii) Coupling variable selection to statistical pattern recognition methods results in low error rates (< 1%) for predicting MAB mass fingerprints, especially using lineardiscriminant analysis (LDA). (iv) LDA discriminates controls from treated animals and also correlates to quantitative physiological responses induced by anabolic steroids. This work shows that Py-MAB-TOFMS could be a suitable method for complementary monitoring anabolic use in sports, medicine, and cattle breeding, as well as monitoring many other long-lasting although weak physiological disruptions.     

EXAFS and XANES studies of retention of copper and lead by a lignocellulosic biomaterial

Lignocellulosic substrate (LS), which is a low cost biomaterial, has a strong complexing ability and can be used in the treatment of wastewaters as biosorbentto remove heavy metals. The speciation of copper and lead to this biomaterial has been studied by X-ray absorption spectroscopy. The copper(II) has a 6-coordinate structure with four oxygen atoms in the equatorial plane at 1.95 A and two in axial position at 2.35 A. In the case of lead a particularly low coordination number of about 3 has been obtained. The combination of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) suggested that Cu and Pb are bound to the surface of LS through carboxylic moieties.     

Use of a Plackett-Burman design with multivariate calibration for the analysis of polycyclic aromatic hydrocarbons in micellar media by synchronous fluorescence

This work describes the use of a multilevel Plackett-Burman design (PB) for the creation of a calibration set for partial least square regression (PLS). The PB calibration set was compared to a collinear analogue by testing these two PLS models for the analysis of six polycyclic aromatic hydrocarbons (PAHs). These compounds were analyzed in micellar media by synchronous fluorescence after determination of the experimental conditions (choice of surfactant, analytical conditions such as deltalambda, step, and scan range). The external validation shows that the collinear set is inappropriate to quantify PAH in real samples, but the PB calibration set affords optimal results.     

Reject Strategies Driven Combination of Pattern Classifiers

This article deals with the combination of pattern classifiers with two reject options. Such classifiers operate in two steps and differ on the managing of ambiguity and distance rejection (independently or not). We propose to combine the first steps of these classifiers using concepts from the theory of evidence. We propose some intelligent basic probability assignment to reject classes before using the combination rule. After combination, a decision rule is proposed for classifying or rejecting patterns either for distance or for ambiguity. We emphasize that rejection is not related to a lack of consensus between the classifiers, but to the initial reject options. In the case of ambiguity rejection, a class-selective approach has been used. Some illustrative results on artificial and real data are given. Received: 21 November 2000, Received in revised form: 25 October 2001, Accepted: 26 November 2001     

Tip‐mould microcontact printing for functionalisation of optical microring resonator

We present an approach to functionalise optical microring resonators as hybridisation platforms, using tip‐mould reactive microcontact printing process. Derived from reactive microcontact printing using an ad hoc mould of polydimethylsiloxane (PDMS), the method functionalises single microring resonator with a target‐specific capture agent. The authors report the functionalisation of silicon nitride (SiN) 200μm diameter microring resonator with single‐strand DNA and the hybridisation detection of 100 nM target analyte, while concurrently monitoring not‐functionalised microring as a control sensor. Results show that the functionalisation approach permits to address single microring resonators with mutual distance lower than 100μm with high precision, enabling a better integration of multiple spotting zones on the chip concerning traditional functionalisation procedures.Inspec keywords: DNA, molecular biophysics, biosensors, microsensors, optical resonators, microcavities, soft lithography, polymers, silicon compounds, integrated optics, optical sensors, micro‐opticsOther keywords: tip‐mould reactive microcontact printing, optical microring resonator, hybridisation platforms, polydimethylsiloxane, PDMS, target‐specific capture agent, single‐strand DNA, hybridisation detection, multiple spotting zones, chip, size 200 mum, SiN     

Securing communications overAtm networks: the remoteAtm private networks interconnection example

When remoteAtm sites communicate through anAtm public network, a number of security problems arise, such as hacking, eavesdropping and traffic tampering. This paper proposes three contributions to these security problems. Firstly, risks due toAtm technology usage are detailed. Secondly, a survey of existing techniques aiming at securingAtm communications is presented with emphasis on theAtm Forum’s security specifications. Thirdly, a new solution called Safe (which stands for Solution for anAtm Frequent communications Environment) developed in the Démostène project is described. Safe realizes both firewall’s filtering functions and communications protection over theAtm network. The main idea of Safe is to use signaling (Uni 3.1) as a means to exchange security information over the network. This idea has been implemented and introduced to theAtm Forum.     

Fracture toughness behavior of weldments with mis-matched properties at elevated temperature

High temperature fracture toughness tests were performed on welded specimens of 1Cr-1Mo-14 V steel with different levels of mismatch between the base metal and the weld metal and the cracks lying along the fusion line. A wide range of fracture toughness values were obtained for weldments, as opposed to a unique value of J_IC and a unique J-R curve typically obtained for homogeneous materials. Detailed observations of the crack path within the weldments were made to understand the wide scatter in the fracture toughness behavior. The yield strength mismatch between the base metal and the weld metal was found to directly influence the stable crack path, and hence the fracture toughness behavior. The denomination of ‘apparent fracture toughness’ was used to describe the variability of the fracture toughness in the weld region due to microstructure and mechanical property gradients. The apparent fracture toughness exhibited a minima at a fixed distance from the fusion line for a specific weld. The relative position of the fatigue precrack with respect to the fusion line and the region of low fracture toughness was also shown to influence the measured fracture toughness behavior of the specimen. A frame-work is provided for representing the weld fracture toughness behavior and the associated variability due to microstructural gradients. This revised version was published online in August 2006 with corrections to the Cover Date.