H3PW12O40 acid dispersed on its Cs salt: improvement of its catalytic properties by mechanical mixture and grinding

Acidic cesium salts Cs_x H_3-xPW₁₂O₄₀ have been prepared by grinding together amounts of H₃PW₁₂O₄₀ and porous Cs₃PW₁₂O₄₀ compounds in varying stoichiometries. It is shown that this procedure leads to a dispersion of the acid on top of the high surface area Cs₃PW₁₂O₄₀ salt (160 m² g^-1), and, subsequently, yields high surface area materials which exhibit a much higher catalytic activity for n-butane isomerisation at 473 K when compared with samples prepared directly by chemical precipitation. This improvement holds particularly true with low Cs content (x < 2). This revised version was published online in July 2006 with corrections to the Cover Date.     

Ligand‐Free Synthesis of Aluminum‐Doped Zinc Oxide Nanocrystals and their Use as Optical Spacers in Color‐Tuned Highly Efficient Organic Solar Cells

The color of polymer solar cells using an opaque electrode is given by the reflected light, which depends on the composition and thickness of each layer of the device. Metal‐oxide‐based optical spacers are intensively studied in polymer solar cells aiming to optimize the light absorption. However, the low conductivity of materials such as ZnO and TiO₂ limits the thickness of such optical spacers to tenths of nanometers. A novel synthesis route of cluster‐free Al‐doped ZnO (AZO) nanocrystals (NCs) is presented for solution processing of highly conductive layers without the need of temperature annealing, including thick optical spacers on top of polymer blends. The processing of 80 nm thick optical spacers based on AZO nanocrystal solutions on top of 200 nm thick polymer blend layer is demonstrated leading to improved photocurrent density of 17% compared to solar cells using standard active layers of 90 nm in combination with thin ZnO‐based optical spacers. These AZO NCs also open new opportunities for the processing of high‐efficiency color tuned solar cells. For the first time, it is shown that applying solution‐processed thick optical spacer with polymer blends of different thicknesses can process solar cells of similar efficiency over 7% but of different colors.     

A Complete Separation of Hexane Isomers by a Functionalized Flexible Metal Organic Framework

The separation ability of branched alkane isomers (nHEX, 3MP, 22DMB) of the flexible and functionalized microporous iron(III) dicarboxylate MIL‐53(Fe)‐(CF₃)₂ solid is evaluated through a combination of breakthrough experiments (binary or ternary mixtures), adsorption isotherms, X‐ray diffraction temperature analysis, quasi‐elastic neutron scattering measurements and molecular dynamics simulations. A kinetically controlled molecular sieve separation between the di‐branched isomer of hexane 22DMB from a mixture of paraffins is achieved. The reported total separation between mono‐ and di‐branched alkanes which was neither predicted nor observed so far in any class of porous solids is spectacular and paves the way towards a potential unprecedented upgrading of the RON of gasoline.     

Chemometric analysis of combined NIR and MIR spectra to characterize French olives

Chemometric treatment of near‐infrared (NIR) and mid‐infrared (MIR) combined spectra was used firstly to predict oil and water contents in fresh olive fruit samples (n = 223) and secondly to classify these samples into five principal French cultivar origins (Aglandau, Cailletier, Olivière, Salonenque, and Tanche). The study was carried out during four crop years (2005/2006 to 2008/2009) to take into account the seasonal variations. The comparison of the results obtained in the combined range (REP = 2.6% for the water content and 3.5% for the oil content) provides an obvious advantage compared to the NIR and MIR techniques used separately. Fresh olive fruit cultivars were satisfactorily classified with the partial least squares‐discriminant analysis (PLS‐DA) method in the combined range. After use of the K‐means clustering on the PLS‐DA scores, all the samples were well classified into their five groups of origin. The use of infrared combined spectra allows a considerable improvement in estimating olive fruit quality (oil and water contents, varietal origins).     

Early age deformations of concrete with high content of mineral additions

Under the project “EcoBéton” (Green concrete) funded by the French National Agency (ANR), concrete mixtures with a high quantity of mineral additions, such as blast-furnace slag and fly ash were studied. A first approach to quantify their cracking risk was to measure their plastic shrinkage evolution. In parallel, the evolution of other parameters such as setting, capillary depression and porosity were also monitored to relate this deformation to the evolution of the microstructure of the studied mixtures. Setting monitoring by means of ultrasonic measurements allows obtaining significant macroscopic information such as hardening process and rigidity evolution. The correlation between these different parameters shows that the plastic shrinkage evolution can be divided into three phases driven by different mechanisms. Moreover, it appears that the use of mineral additions has an effect on the plastic shrinkage behaviour, but this impact is not proportional to the percentage of additions. It depends on the hydration process and the microstructure of the cementitious materials. So, it seems that an optimum content of cement replacement by mineral additions must be sought to limit the development of plastic shrinkage of concretes with mineral additions at early age. However, a high rate of substitution of cement may affect the early age compressive strength of the concrete. So these mixtures were also optimised to obtain a significant compressive strength at an early age, but this optimisation leads to a higher risk of cracking for some of them.     

Naturalistic study of rider's behaviour in initial training in France: Evidence of limitations in the educational content

This paper analyses motorcycle educational content in a number of French motorcycle schools on the basis of a naturalistic study of riders’ and trainers’ behaviour. The aim is to specify the situations delivered in motorcycle schools and to study the rider's activity in these situations. The methodology includes ethnographic observation within the motorcycle schools and the longitudinal monitoring of 14 trainee motorcyclists during their initial training. The training situations were described by the combination of audio–visual recordings and interviews data (i.e. concomitant or interruptive verbalization, and self-confrontation data). The results permit to (1) compare the “real” and “official” durations of track and on-road training, (2) characterize the real training situations, (3) describe the preferred forms of instruction, and (4) conduct an in-depth analysis of the situations used during training in traffic. The discussion show, in first, the poverty of the training situations which are based on the repetition of the exercises in the test, and, in second, disparities between the riding situations encountered during training and the demands made by riding in natural traffic. The usefulness and the applications of this type of approach – based on the integration of the rider's point of view notably by self-confrontation interview – for understanding real riding behaviours and how such approaches could supplement vehicle-based data are discussed in a large conclusion.     

Statistical analysis of concrete transport properties

Results of a statistical analysis of transport properties measurements carried out on a number of concrete mixtures are presented. Migration and drying experiments were performed to evaluate the ionic diffusion coefficients and permeability of concrete mixtures. Seven concrete mixtures were tested. The mixtures were either batched under laboratory conditions or sampled from construction sites. For each mixture, approximately eighty concrete samples from a single batch were tested. Ionic diffusion coefficients were calculated by analyzing the evolution of the electrical current passing through concrete samples during the migration tests. Calculations took into account the volume of permeable pores of the materials and the pore solution chemistry. Permeability was calculated from mass loss measured during drying tests. The study indicates that the coefficient of variation of ionic diffusion coefficients is 11.1 % on average, with a maximum of 23.5 %, and that the coefficient of variation of permeability is 20.6 % on average, with a maximum of 37.3 %.     

L'Alphabétisation technoscientifique et la démocratisation de la démocratie

Résumé

La métaphore du changement de guide proposée par Fensham (2002a) constitue un véritable faux‐fuyant. Cette solution aux présumés problèmes d'une alphabétisation technoscientifique pour tous et toutes fait l'impasse sur une interrogation plus générale à propos de la socialite des technosciences. Ainsi, l'auteur reconduit la séculaire séparation entre le monde de la science et celui de la société, qui justifie que seuls des ? experts ?, scientifiques ou sociétaux, puissent servir de médiateurs entre ces univers incommensurables. Il élimine donc d'emblée, en évoquant la complexité des problèmes, la possibilité pour les citoyens et les citoyennes ordinaires de s'engager dans les controverses sociotechniques qui traversent inévitablement nos sociétés. En conséquence, il se rabat sur une forme d'alphabétisation technoscientifique à deux vitesses ; l'une pour la populace, l'autre pour une élite qui, à terme, aura le privilège de pénétrer dans l'univers mystérieux et ésotérique de la science. Autrement dit, les contenus des curriculums pourront varier sans que la hiérarchie sociale des savoirs, de même que les pouvoirs forcément politiques des experts, soient menacés.     

Effects of Speeds,Materials, and Tool Rake Angles on Metallic Particle Emission During Orthogonal Cutting

Dry high speed machining has been proposed as a viable and cost-effective process in metal cutting industries. However, it produces fine and ultra-fine metallic particles, also referred to as dust, which can be harmful to the machine-tool operator. The risk associated with exposure to metallic particles increases as the particle size decreases. For machining processes, little data exist on the size and distribution of dust generated during the shaping of materials. In order to reduce or eliminate the generation of these particles, it is necessary to understand how and under which conditions they are formed, as well as to be able to make predictions. In this study, the effects exerted by tool geometry, material, and machining parameters on dust emission were studied experimentally in order to understand the mechanisms of dust generation and to develop a predictive model. The particle sizes studied include the PM2.5 (particles with aerodynamique diameter below 2.5 μm) and a distribution of nanoparticles varying in size from 10 nm to 10 μm. Using dry machining and reducing the amount of dust generated should improve the air quality in machine shops in addition to helping protect the environment.