Growth and characterization of Ca5(BO3)3F fiber crystals, a new nonlinear optical material for UV light generation

For the first time, Ca₅(BO₃)₃F (CBF) fiber crystals were grown by the micro-pulling down technique from LiF-based flux. Regular and transparent fibers were obtained with good optical quality. Characterization by Raman spectroscopy and EDX microprobe showed fibers compositionally homogeneous. The specific heat capacity of the fibers was measured indicating a laser damage threshold slightly lower, at room temperature, than for crystals belonging to the related rare earth calcium oxoborate family.     

Half-conductive coupling interconnection technology for digitaltransmission between CMOS chips

This paper describes how to use half-conductive coupling (HC-coupling) to obtain digital interconnections between two flip-chip standard CMOS integrated circuits. For process simplicity, the HC-layer can be unpatterned and the CMOS chips do not require any post-processing steps. Measurements of a complete HC-coupling, digital communication link show reliable operation up to 100 Mb/s channel speed. The two flipped prototype CMOS chips were fabricated in 0.8-μm, 5-V CMOS. The I/O pads' pitch was 150 μm     

Kinetic Study of Hydroperoxide Degradation in Edible Oils Using Electron Spin Resonance Spectroscopy

Lipid oxidation is a complex phenomenon involving free radicals which are highly reactive molecular species. The life-time of these radical species is extremely short and their detection is therefore difficult. Several electron spin resonance (ESR) spectroscopy methodologies make it possible to identify, quantify and measure the reactivity of radical species formed during oxidation–reduction reactions. In this study we took advantage of the specificity of ESR spectroscopy to detect radical compounds in order to determine the rate constants of hydroperoxide degradation, a key reaction involved in lipid oxidation. The interaction of 5-doxyl stearic acid and lipid-derived radicals was studied by following the intensity of ESR spectra. A kinetic model was developed to simulate data analysis obtained by ESR and values of rate constants for hydroperoxide degradation were determined at 100 and 110 °C. This quantitative approach of ESR spectroscopy has produced useful information about new rate estimates for hydroperoxide degradation in edible oils.     

Preparation of methanol oxidation electrocatalysts: ruthenium deposition on carbon-supported platinum nanoparticles

Methanol oxidation electrocatalysts were prepared from Ru electrochemical or spontaneous deposition on commercial-grade carbon-supported Pt nanoparticles (Pt-Vulcan XC72, E-TEK). The resulting Ru coverage was estimated by cyclic voltammetry in supporting electrolyte. The maximum electrocatalytic activity for methanol oxidation at room temperature was observed at lower Ru coverage for spontaneous deposition than for electrodeposition; _Ru 10% vs 20%, respectively. On the other hand, higher current densities for methanol oxidation were obtained in the case of electrodeposited Ru. These two results were related to the presence of non-reducible ruthenium oxides in the spontaneous deposit. The present work provides evidence that (i) efficient DMFC electrocatalysts can be achieved by Ru deposition on Pt nanoparticles, and (ii) formation of a PtRu alloy is not a required condition for effective methanol electrooxidation.     

Online Mesh Refinement for Parallel Atmospheric Models

Forecast precisions of climatological models are limited by computing power and time available for the executions. As more and faster processors are used in the computation, the resolution of the mesh adopted to represent the Earth’s atmosphere can be increased, and consequently the numerical forecast is more accurate. However, a finer mesh resolution, able to include local phenomena in a global atmosphere integration, is still not possible due to the large number of data elements to compute in this case. To overcome this situation, different mesh refinement levels can be used at the same time for different areas of the domain. Thus, our paper evaluates how mesh refinement at run time (online) can improve performance for climatological models.The online mesh refinement (OMR) increases dynamically mesh resolution in parts of a domain,when special atmosphere conditions are registered during the execution. Experimental results show that the execution of a model improved by OMR provides better resolution for the meshes, without any significant increase of execution time. The parallel performance of the simulations is also increased through the creation of threads in order to explore different levels of parallelism.     

Further insights into the durability of Pt3Co/C electrocatalysts: Formation of “hollow” Pt nanoparticles induced by the Kirkendall effect

This paper provides further insights into the degradation mechanisms of nanometer-sized Pt₃Co/C particles under various proton-exchange membrane fuel cell (PEMFC) operating conditions. We confirm that Co atoms are continuously depleted from the mother Pt₃Co/C electrocatalyst because they can diffuse from the bulk to the surface of the material. The structure of the Pt–Co/C nanoparticles in the long-term is determined by a balance between Co surface segregation and formation of oxygenated species from water splitting. When the PEMFC is operated at high current density (low cathode potential, below the onset of surface oxide formation from water), a steady-state is reached between the rate of Co dissolution at the surface and Co surface segregation. Consequently, Co and Pt atoms remain homogeneously distributed within the Pt–Co/C particles and the thickness of the Pt-shell is maintained to a small value not detectable by atomic-resolution high-angle annular dark-field scanning transmission electron microscopy. When the PEMFC is operated at low current density (high cathode potential), the formation of surface oxides from water and the resulting “place-exchange” mechanism enhance the rate of diffusion of Co atoms to the surface. Consequently, the fresh Pt₃Co/C particles form core/shell particles with thick Pt-shells and Co content < 5 at% and, ultimately, “hollow” Pt nanoparticles (Kirkendall effect). To the best of our knowledge, this is the first report on the formation of “hollow” Pt particles in a PEMFC.     

Study of the R-(Zr,W)-(O,N) (R = Y, Nd, Sm, Gd, Yb) oxynitride system

The replacement of tantalum by the couple Zr/W within the RTa-O-N systems (R = Y, Nd, Sm, Gd, Yb), enables the preparation of novel oxide and oxynitride phases in the R-Zr-W-O-N system. R₂Zr_2−xW_xO_7+x oxides exhibit the fluorite-type (x < 0.9) and scheelite (x ∼ 1) structures. Corresponding oxynitride compositions are of the fluorite-type and show different colors, for example in the case of ytterbium: pale yellow (x = 0.2 or 0.25), green (x = 0.5-0.8) and brown for the tungsten-rich samples (x = 0.9, 1). Photocatalytic activity measurements have been performed to investigate the overall water splitting behavior of these colored phases.     

Genomic organization, fine-mapping, and expression of the human islet-brain 1 (IB1)/c-Jun-amino-terminal kinase interacting protein-1 (JIP-1) gene

Islet-brain 1 (IB1), a regulator of the pancreatic beta-cell function in the rat, is homologous to JIP-1, a murine inhibitor of c-Jun amino-terminal kinase (JNK). Whether IB1 and JIP-1 are present in humans was not known. We report the sequence of the 2133-bp human IB1 cDNA, the expression, structure, and fine-mapping of the human IB1 gene, and the characterization of an IB1 pseudogene. Human IB1 is 94% identical to rat IB1. The tissue-specific expression of IB1 in human is similar to that observed in rodent. The IB1 gene contains 12 exons and maps to chromosome 11 (11p11.2-p12), a region that is deleted in DEFECT-11 syndrome. Apart from an IB1 pseudogene on chromosome 17 (17q21), no additional IB1-related gene was found in the human genome. Our data indicate that the sequence and expression pattern of IB1 are highly conserved between rodent and human and provide the necessary tools to investigate whether IB1 is involved in human diseases.     

An investigation into the antimicrobial mechanisms of action of two contact lens biocides using electron microscopy.

Polyquaternium-1 (PQ-1) and myristamidopropyl dimethylamine (MAPD) are biocides used commercially in a contact lens disinfecting solutions. Electron microscopy was used to provide further evidence on the mechanism(s) of action of these agents against a wide range of ocular pathogens including bacteria, fungi and protozoa. Both PQ-1 and MAPD caused multiple forms of damage to the organisms tested, evidenced by structural alterations, blebbing, leakage and cell destruction. The extent of damage and the selectivity against specific type of microorganisms was consistent with the antimicrobial activity of these agents. Although electron microscopy is a powerful tool, it has its limitations when used to examine the mode of action of biocides. Indeed, there was no evidence of gross structural alteration to Acanthamoeba castellani or Aspergillus fumigatus following treatment.     

La recherche de granulats en region centre

This study was made on the reaction between aggregate and cement paste in autoclaved concrete and its influence on compressive strength. The specimens mixed with cement and various crushed minerals (149–74 μm) were autoclaved at 181°C for 1–168 hours. Quartz and feldspars (microcline, albite and anorthite) reacted to cement paste, whereas hornblende, augite and olivine did not react. The reaction rate of minerals were, in order, anorthite > quartz > microcline=albite. 11A tobermorite was formed by the reaction between cement paste and quartz, and feldspars. Hydrogarnet was also formed by the reaction between cement paste and anorthite. The compressive strength of the specimens containing quartz and feldspars increased as the curing time was prolonged.