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91.
Jean-Luc Caillaud Stphane Deguillaume Michel Vincent Jean-Claude Giannotta Jean-Michel Widmaier 《Polymer International》1996,40(1):1-7
The addition of metallic fillers is recognized to impart improvement of acoustic properties to polyurethane-based materials used for marine applications. The system under consideration was obtained by the reaction of a triisocyanateterminated prepolymer with 1,4-butanediol, in the presence of various concentrations of lead powder. With increasing lead content, gelation time is reduced and an Einstein-type law does not apply. The kinetics of the reaction were determined by Fourier transform infrared spectroscopy. Deviation from the classic second order is observed for the filled systems, and the higher the lead content, the more important the deviation is, showing undoubtedly the catalytic effect of the metallic powder. 相似文献
92.
Walter P Welcomme E Hallégot P Zaluzec NJ Deeb C Castaing J Veyssière P Bréniaux R Lévêque JL Tsoucaris G 《Nano letters》2006,6(10):2215-2219
Lead-based chemistry was initiated in ancient Egypt for cosmetic preparation more than 4000 years ago. Here, we study a hair-dyeing recipe using lead salts described in text since Greco-Roman times. We report direct evidence about the shape and distribution of PbS nanocrystals that form within the hair during blackening. It is remarkable that the composition and supramolecular organization of keratins can control PbS nanocrystal growth inside a hair. 相似文献
93.
Romaner L Heimel G Gruber M Brédas JL Zojer E 《Small (Weinheim an der Bergstrasse, Germany)》2006,2(12):1468-1475
Density functional theory (DFT) calculations based on band structure are used to investigate the electromechanical properties of a molecular junction consisting of a dithiolbenzene molecule sandwiched between two gold slabs. This represents a prototypical system for the field of molecular electronics; such a system has previously been studied in break-junction measurements and electron-transport calculations. The stretching and breaking behavior of the junction is analyzed for different geometric conformations, and it is found that the breakage occurs through dissociation of one of the sulfur-gold bonds with a maximum force of 1.25 nN. The molecular electronic states shift during stretching, and, at the point of highest stress in the junction, the highest occupied molecular orbital (HOMO) of the molecule is located exactly at the Fermi level. 相似文献
94.
Nicolle M Fusco T Michau V Rousset G Beuzit JL 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(9):2233-2245
Multiconjugate adaptive optics is one of the major challenges in adaptive optics. It requires the measurement of the volumic distribution of the turbulence. Two wavefront sensing (WFS) concepts have been proposed to perform the wavefront analysis for such systems: the star-oriented and layer-oriented approaches. We give a performance analysis and a comparison of these two concepts in the framework of the simplest of the multi-guide-star adaptive optics systems, that is, ground layer adaptive optics. A phase-related criterion is proposed to assess analytically the performance of both concepts. This study highlights the main advantages and drawbacks of each WFS concept and shows how it is possible to optimize the concepts with respect to the signal to noise ratio on the phase measurement. A comparison of their optimized versions is provided and shows that one can expect very similar performance with the two optimized concepts. 相似文献
95.
Thiffeault JL Finn MD 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2006,364(1849):3251-3266
Stirring of fluid with moving rods is necessary in many practical applications to achieve homogeneity. These rods are topological obstacles that force stretching of fluid elements. The resulting stretching and folding is commonly observed as filaments and striations, and is a precursor to mixing. In a space-time diagram, the trajectories of the rods form a braid, and the properties of this braid impose a minimal complexity in the flow. We review the topological viewpoint of fluid mixing, and discuss how braids can be used to diagnose mixing and construct efficient mixing devices. We introduce a new, realizable design for a mixing device, the silver mixer, based on these principles. 相似文献
96.
Lee CS Cojocaru CS Moujahid W Lebental B Chaigneau M Châtelet M Normand FL Maurice JL 《Nanotechnology》2012,23(26):265603
Post-growth transfer and high growth temperature are two major hurdles that research has to overcome to get graphene out of research laboratories. Here, using a plasma-enhanced chemical vapour deposition process, we demonstrate the large-area formation of continuous transparent graphene layers at temperatures as low as 450?°C. Our few-layer graphene grows at the interface between a pre-deposited 200 nm Ni catalytic film and an insulating glass substrate. After nickel etching, we are able to measure the optical transmittance of the layers without any transfer. We also measure their sheet resistance directly and after inkjet printing of electrical contacts: sheet resistance is locally as low as 500 Ω sq?1. Finally the samples equipped with printed contacts appear to be efficient humidity sensors. 相似文献
97.
The automaticity of evaluative processing is one of the most important issues in cognitive psychology of emotions. The affective priming paradigm has been created specifically in order to provide some evidence regarding this issue. For 20 years, this paradigm has resulted in a significant number of studies. Originally focused on the automaticity of evaluation, investigation rapidly moved to the underlying mechanisms and it has led to a theoretical dichotomy. Some studies suggest that a spreading activation mechanism underlies affective priming effects, whereas other studies suggest that this priming effect is determined by a response competition mechanism similar to that found in compatibility tasks such as the Stroop task. The clarification of the theoretical models of affective priming therefore appears to be necessary in order to improve the understanding of the effect, possibly leading to its justified use as an indirect measure. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
Despite evidence of formation of brominated compounds in seawater swimming pools treated with chlorine, no data about exposure levels to these compounds have been reported. To address this issue, a survey has been carried out in four establishments (representing 8 pools) fed with seawater and devoted to relaxing and cure treatments (thalassotherapy centres located in Southeast of France). Carcinogenic and mutagenic brominated disinfection byproducts (trihalomethanes -THM- and halogenated acetic acids -HAA-) were quantified at varying levels, statistically related to organic loadings brought by bathers, and not from marine organic matter, and also linked to activities carried out in the pools (watergym vs swimming). Bromoform and dibromoacetic acid, the most abundant THM and HAA detected, were measured at levels up to 18-fold greater than the maximum contaminant levels of 60 and 80 μg/L fixed by US.EPA in drinking waters. The correlations between these disinfection byproducts and other environmental factors such as nitrogen, pH, temperature, free residual chlorine, UV254, chloride and bromide concentrations, and daily frequentation were examined. Because thalassotherapy and seawater swimming pools (hotels, cruise ships,…) are increasing in use around the world and because carcinogenic and mutagenic brominated byproducts may be produced in chlorinated seawater swimming pools, specific care should be taken to assure cleanliness of users (swimmers and patients taking the waters) and to increase water circulation through media filters to reduce levels of brominated byproducts. 相似文献
99.
Cooper D de la Peña F Béché A Rouvière JL Servanton G Pantel R Morin P 《Nano letters》2011,11(11):4585-4590
In order to improve the performance of today's nanoscaled semiconductor devices, characterization techniques that can provide information about the position and activity of dopant atoms and the strain fields are essential. Here we demonstrate that by using a modern transmission electron microscope it is possible to apply multiple techniques to advanced materials systems in order to provide information about the structure, fields, and composition with nanometer-scale resolution. Off-axis electron holography has been used to map the active dopant potentials in state-of-the-art semiconductor devices with 1 nm resolution. These dopant maps have been compared to electron energy loss spectroscopy maps that show the positions of the dopant atoms. The strain fields in the devices have been measured by both dark field electron holography and nanobeam electron diffraction. 相似文献
100.
Andrea Bianchi Sandrine Dufort François Lux Arnaud Courtois Olivier Tillement Jean-Luc Coll Yannick Crémillieux 《Magma (New York, N.Y.)》2014,27(4):303-316