Preheating Sensitization of a TATB Composition Part one: Chemical Evolution

We analyze the evolution of the sensitivity of a TATB composition after thermal cycles at elevated temperatures. Sensitization due to thermal cycles is of variable magnitude depending on the kind of the second stimulus (mechanical or thermal). In order to investigate the possible mechanisms which govern these phenomena, we perform an extensive study of the evolution of the chemistry and microstructure of our composition and we determine the sensitivity of our explosive to various stimuli after various temperature/duration cycles. This first paper is devoted to the study of TATB chemical evolutions. We present the results obtained for explosive decomposition, furazan generation, gas analyses and solid residue characterization.     

Greffage de molécules à la surface du silicium par voie électrochimique

The hydrogentated surface of silicon exhibits remarkable properties, but poor resistance to oxidation. To improve its stability, surface hydrogen has been replaced by several organic groups. Such grafting can be carried out chemically by a multi-step reaction scheme. However, an electrochemical approach allows direct reaction with the hydrogenated surface. The porous-silicon surface has been partially methoxylated by a controlled anodic dissolution. If has also been methylated using a non-destructive anodic process, with a yield of 80%, limited only by steric hindrance. The methylated surface of porous silicon exhibits a stability against oxidation increased by an order of magnitude.     

Osmotic cracking in unsaturated polyester matrices under humid environment

Glass fiber reinforced polyester composites are widely used in marine applications where they may undergo chemical and physical aging. For this kind of laminates, the durability is governed mainly by the matrix degradation. The mechanical property reduction is not induced only by hydrolytic aging but rather by the formation of cracks or blisters. That is the reason why it became of major interest to understand the microcrack nucleation mechanism in neat matrices, to study the crack propagation, and to evaluate the incidence of cracking on the tensile property loss. We first put forward a nucleation mechanism based on polyester‐organic molecule phase separation, and drew a simple kinetic model to take into account the existence of a crack induction time that is dependent on temperature and matrix structure. Crack propagation results from the build up of an osmotic pressure in microcavities, which is proportional to solute concentration. This second step has been studied in terms of crack density evolution and crack propagation rate. Finally, there is a good correlation between tensile mechanical properties variation and crack parameters. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2517–2526, 2001     

Building maps of local apparent conductivity of the epicardium with a 2-D electrophysiological model of the heart

In this paper, we address the problem of estimating the parameters of an electrophysiological model of the heart from a set of electrical recordings. The chosen model is the reaction-diffusion model on the transmembrane potential proposed by Aliev and Panfilov. For this model of the transmembrane, we estimate a local apparent two-dimensional conductivity from a measured depolarization time distribution. First, we perform an initial adjustment including the choice of initial conditions and of a set of global parameters. We then propose a local estimation by minimizing the quadratic error between the depolarization time computed by the model and the measures. As a first step we address the problem on the epicardial surface in the case of an isotropic version of the Aliev and Panfilov model. The minimization is performed using Brent method without computing the derivative of the error. The feasibility of the approach is demonstrated on synthetic electrophysiological measurements. A proof of concept is obtained on real electrophysiological measures of normal and infarcted canine hearts.     

Combined GC/MS analytical procedure for the characterization of glycerolipid, waxy, resinous, and proteinaceous materials in a unique paint microsample

A novel GC/MS analytical procedure for the identification of lipids, waxes, proteins, and resinous materials in the same microsample from painted works of art has been optimized. It is based on a sample multistep chemical pretreatment (solvent extractions and microwave-assisted chemolysis) that is able to separate the various organic components into different fractions, which are suitably treated and derivatized before analysis. In particular, the procedure allows the complete saponification of wax esters and the completeness of the Cannizzaro type reaction of shellac acids in conditions that are suitable also for glycerides saponification. The method was tested on reference materials for the identification of proteinaceous binders (egg, collagen, casein) on the basis of the quantitative determination of the amino acid profile and the identification of glycerolipids (linseed oil, poppy seed oil, walnut oil, and egg), plant resins (Pinaceae resins, sandarac, mastic, and dammar), animal resins (shellac), tars or pitches, and natural waxes (beeswax, carnauba wax) on the basis of the determination of fatty acid, alcohol, and hydrocarbon profiles and of significant terpenic molecular markers. The procedure was applied to the characterization of three old paint microsamples. Animal glue, egg, linseed oil, beeswax, Pinaceae resin, dammar, and shellac were the identified materials found in mixtures and recognized as original and/or restoration substances.     

Pressure control in a PEM fuel cell via second order sliding mode

Pressure difference inside the Polymer Electrolyte Membrane Fuel Cells (PEMFC) arises due to load variations, during which the pressure difference between anode and cathode rises. Practically, this problem can be avoided by equalizing anode and cathode pressures, to protect the fuel cell from permanent damage. This paper focuses on pressure regulation in the anode and cathode sides of the PEMFC. The control objective is achieved using second order sliding mode multi-input multi-output (MIMO) controller based on “Twisting algorithm”. Parametric uncertainty is formally presented and included in a nonlinear dynamic fuel cell model. The resultant nonlinear controller is robust and is proved to guarantee performance around any equilibrium point and under parametric uncertainty. Simulation results show that the proposed controller has a good transient response under load variations.     

Correction to Tremblay et al (2009).

Reports an error in "Work Extrinsic and Intrinsic Motivation Scale: Its value for organizational psychology research" by Maxime A. Tremblay, Céline M. Blanchard, Sara Taylor, Luc G. Pelletier and Martin Villeneuve (Canadian Journal of Behavioural Science/Revue canadienne des sciences du comportement, 2009[Oct], Vol 41[4], 213-226). In this article, line 2 of the second table was missing from the printed article. The correct table is reprinted in this correction. (The following abstract of the original article appeared in record 2009-18333-004.) The Work Extrinsic and Intrinsic Motivation Scale (WEIMS) is an 18-item measure of work motivation theoretically grounded in self-determination theory (Deci & Ryan, 2000). The purpose of the present research was twofold. First, the applicability of the WEIMS in different work environments was evaluated. Second, its factorial structure and psychometric properties were assessed. Two samples of workers (military: N = 465; civilians: N = 192) voluntarily completed questionnaires. Using the WEIMS’s 3 indexes (work self-determination index, work self-determined and nonself-determined motivation, respectively), results of regression analyses were supportive of its ability to predict positive and negative criteria in the workplace. Results also showed the adequacy of both its construct validity and internal consistency. Its factorial structure was also invariant across samples. Finally, its quasi-simplex pattern and relationships with psychological correlates further supported the self-determination continuum. Overall, these findings provide evidence for the applicability as well as the reliability and validity of the WEIMS in organisational settings. Results are discussed in regard to the applicability of self-determination theory to the workplace. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Theoretical analysis of the influence of defect parameters on photovoltaic performances of composition graded InGaN solar cells

In this paper, we have used simulations to evaluate the impact of the distribution of electrically active defects on the photovoltaic performances of InGaN-based solar cell. The simulations were carried out using Silvaco's ATLAS software. We have modeled a P-GaN/Grad-InGaN/i-In_0.53Ga_0.47N/Grad-InGaN/N-ZnO where Grad-InGaN corresponds to an InGaN layer with a graded composition. This layer is inserted to eliminate the band discontinuities at the interface between InGaN and the GaN and ZnO layers. The defects were modeled through the introduction of band tails and a Gaussian distribution of defects in i-InGaN material. We have evaluated the influence of band tail widths as well as the parameters of the Gaussian distribution (i.e. defect density, mean position and standard deviation) on the short-circuit current, the open-circuit voltage and the fill-factor (efficiency) of the solar cell. These results have allowed us to identify key structural parameters useful for the optimization of InGaN solar cells, as well as to give realistic estimates of the performances of such cells.     

Large scale synthesis of single-crystal and polycrystalline boron nitride nanosheets

Boron nitride nanosheets (BNNSs) have an identical crystal structure and similar lattice parameter to those of graphene sheets. However, growing quality BNNSs consisting of only several atomic layers remains a challenge. Here, we report on the synthesis of BNNSs at a temperature of 350 °C using a CO₂ pulsed laser plasma deposition (CO₂-PLD) technique by irradiating a pyrolytic hexagonal boron nitride (h-BN) target. The deposition was performed either in vacuum at a pressure of 0.2 Pa, for which we obtained polycrystalline BN, or in hydrogen (H₂) atmosphere at a pressure of 26 Pa for which we obtained single-crystal BNNSs. The presence of H₂ seems to minimize the side effects of sputtering and the material shows higher purity and better crystallinity. High resolution transmission electron microscopy (HRTEM) showed the sheets to be mostly defect-free and to have the characteristic honeycomb structure of six-membered B₃-N₃ hexagon. HRTEM, electron diffraction, X-ray diffraction, Raman scattering, and Fourier transform infrared spectroscopy clearly identified h-BN.     

Surface characterization of GSH-CdTe quantum dots

The surface characterization of CdTe QDs synthesized by a novel procedure using glutathione (GSH), low temperatures (60–90 °C) and K₂TeO₃ as the –Te precursor is reported. Fluorescence of the produced QDs is stable in the pH range 6–13 and QDs inside eukaryotic cells are highly fluorescent. The surface composition of GSH-CdTe QDs with different spectroscopic properties and particle size distributions was determined by XPS. The XPS analysis indicated that the QDs are essentially CdTe, although all nanoparticles contain 12–24% of CdO (and in one case also TeO₂). GSH decomposes with reaction time releasing small amounts of S⁻² ions that react with Cd(Te) to yield Cd(Te)S in a smaller amount than that of CdTe. Finally, the use of QDs in fluorescence mediated immunodetection of bacterial pathogens has been evaluated.