Thermal expansion stress in a metallic matrix composite:in situ TEM observations

A metallic matrix composite material (2024-type aluminium alloy reinforced with 25 vol % SiC whiskers) wasin situ thermally cycled in a transmission electron microscope. Dislocation movements were observed between 180 and 400 °C. The local shear stress due to the difference between the thermal expansion coefficient of matrix and fibres is estimated from the radius of curvature of mobile dislocations. The experimental values of the internal stress are discussed.     

Study of interlayer spacing collapse during polymer/clay nanocomposite melt intercalation

The influence of the chemical structure of alkylammonium organo-modifying montmorillonite clays on the ability to form nanocomposites by melt blending, depending on the processing temperature and the organoclay thermal treatment, has been investigated. On one side chlorinated polyethylene/Cloisite 30B (nano)composite has been prepared by melt intercalation at 175 degrees C and its wide angle X-ray diffraction pattern revealed that the peak characteristic of the interlayer spacing of the organoclay was shifted to lower d-spacing, indicating a collapse of the organoclay structure. On the other side, (nano)composites based on ethylene-vinyl acetate copolymer/Cloisite 30B have been prepared by melt intercalation at 140 degrees C. At this temperature, exfoliation was observed with the as-received organoclay while the same organo-modified clay, simply dried at 180 degrees C for 2 hours, induced again the formation of a composite with a collapsed structure. The effect of the Cloisite 30B thermal treatment on the morphology and mechanical properties of ethylene-vinyl acetate-based (nano)composites was investigated using wide angle X-ray diffraction and tensile tests. In order to shed some light on the origin of this clay interlayer collapse, organoclay modified with various ammonium cations bearing long alkyl chains with different amounts of unsaturations were studied using wide angle X-ray diffraction and X-ray photoelectron spectroscopy before and after thermal treatment at 180 degrees C for 2 hours. Isothermal thermogravimetric analysis of all organoclays was also investigated. The layers collapse effect is discussed depending upon the level of unsatured hydrocarbon present in the organic surfactant.     

Widely tunable continuous-wave mid-infrared radiation (5.5-11 microm) by difference-frequency generation in LiInS2 crystal

The first demonstration, to the best of our knowledge, of continuous-wave (cw) difference-frequency generation (DFG) in LiInS2 crystal is reported. Wide spectral coverage (5.5-11.3 microm) has been obtained with angle and wavelength tuning for type II (eoe) critically phase-matched parametric interaction. The phase-matching conditions in cw DFG have been investigated, which allowed us to improve the Sellmeier parameters by use of a two-pole dispersion equation. An effective nonlinear coefficient deff = 6.9 +/- 0.8 pm/V has been determined at approximately 7 microm relative to the well-known nonlinear coefficient d36 of AgGaS2, which yields a power-conversion efficiency of approximately 12.4 microW/(W2 cm). We evaluated the high-resolution spectral characteristics of the DFG source by recording C2H2 and SO2 spectra.     

Etudes des transformations des formes du carbone, azote, phosphore, soufre, et des principaux elements mineraux au cours de la mesure de la demande totale en oxygene—I. Transformation des formes du carbone et des principaux cations

Les expériences réalisées sur le D.T.O. mètre de laboratoire IONICS 225 de la Dow Chemical, ont permis de caractériser, aprés l'action catalytique à haute température, les formes stables du carbone, de l'hydrogéne et des cations sodium, potassium, calcium, magnésium.Dans l'intervalle 0–250 mg O₂ l ou la réponse du capteur d'oxygène est proportionnelle à la concentration en matière organique nous avons démontré expérimentalement que le carbone organique ou minéral est transformé en CO₂ l'hydrogène en H₂O, et les cations sodium, potassium, calcium, magnésium en leurs oxyde et hydroxyde correspondants.Les ions bicarbonates et carbonates sont réduits et créent une interference négative: par contre les cations sont oxydés et creent une interférence positive dans la mesure de l'équivalent oxygéne par le D.T.O. métre.     

Lighting transfer across multiple views through local color transforms

Computational Visual Media - We present a method for transferring lighting between photographs of a static scene. Our method takes as input a photo collection depicting a scene with varying...     

Effect of bacterial interactions on the spoilage of cold-smoked salmon

Cold-smoked salmon is a lightly preserved fish product in which a mixed microbial flora develops during storage and where the interactive behaviour of micro-organisms may contribute to their growth and spoilage activity. The aim of this study was to assess the effect of the bacterial interactions between the main species contaminating the cold-smoked salmon on bacterial growth, chemical and sensory changes, and spoilage. First, Carnobacterium piscicola, Photobacterium phosphoreum, Lactobacillus sakei, Vibrio sp., Brochothrix thermosphacta and Serratia liquefaciens-like were inoculated as pure cultures on sterile cold-smoked salmon. All bacterial species grew well; Vibrio sp. was the fastest and L. sakei strains developed very rapidly as well with a high maximum cell density on cold-smoked salmon blocks (up to 10(9) cfu g(-1) after 10 days at 8 degrees C). Based on sensory analysis, Vibrio sp. was identified as non-spoilage bacteria, C. piscicola as very lightly and B. thermosphacta as lightly spoiling. L. sakei and S. liquefaciens-like were found to be the most spoiling bacteria. Secondly, C. piscicola and L. sakei, two species frequently occurring in the lactic flora of the product, were inoculated together and each of them in mixed cultures with respectively P. phosphoreum, Vibrio sp., B. thermosphacta, and S. liquefaciens-like. The growth of L. sakei was shown to strongly inhibit most of the co-inoculated strains i.e. P. phosphoreum, B. thermosphacta, S. liquefaciens-like and, to a lesser extent, Vibrio sp. The growth of C. piscicola seemed to be enhanced with B. thermosphacta and to develop earlier with P. phosphoreum and Vibrio sp. Conversely, S. liquefaciens-like and P. phosphoreum were weakly inhibited by C. piscicola. The main observation resulting from the sensory evaluation was the delay in the appearance of the spoilage characteristics in the mixed cultures with L. sakei, in particular L. sakei/ S. liquefaciens-like. On the other hand, the spoilage activity of the non-spoiler strains Vibrio sp. or the moderate spoilage strains B. thermosphacta and C. piscicola was increased when they were associated together. It is concluded that the spoilage behaviour of micro-organisms in mixed culture is significantly different from pure culture and explain the difficulty to find robust quality indices for this product.     

Poisoning of platinum surfaces by hexamethyldisiloxane (HMDS): application to catalytic methane sensors

The evolution of the catalytic activity of platinum ribbons towards methane oxidation has been studied as a function of the exposure to hexamethyldisiloxane (HMDS) at various temperatures. Below 950 K, and at moderate exposure, HMDS acts as an inhibitor, the surface is progressively covered by patches of silica and the number of active sites decreases as the exposure to HMDS is increased. Above 950 K, the interaction of platinum with HMDS produces irreversibly the formation of a silica overlayer, the mechanism of the catalytic oxidation of methane is deeply modified. The consequences on the resistance of catalytic methane sensors are analysed as a function of the working conditions.     

Structural, microstructural and transport properties study of lanthanum lithium titanium perovskite thin films grown by Pulsed Laser Deposition

Lanthanum lithium titanate thin films were grown by Pulsed Laser Deposition. La_0.57Li_0.29TiO₃ dense films with smooth surfaces were obtained after optimization of the growth parameters. Such films deposited at 700 °C under 15 Pa are nano-crystalline with domains corresponding to the cubic and tetragonal modifications of this phase. In relation to the measured conductivities/activation energy and to previous works, we clearly underlined that the films of practical interest, prepared at relatively low temperature, are predominantly formed from the tetragonal ordered phase.