Electrocatalytic oxidation of ethanol on Pt–Mo bimetallic electrodes in acid medium

Pt–Mo alloy electrocatalysts were prepared by an arc-melting furnace process to investigate the origin of their enhanced activity toward ethanol oxidation. Two Mo contents were chosen in zones of the binary phase diagram where they are supposed to form either a pure alloy mixture or a solid solution. Pt–Mo alloy catalysts were more active than Pt-alone. Gradual Mo dissolution at the electrode surface was observed after voltammetric and chronoamperometric measurements. The dissolved Mo contributed to the catalytic effect of the electrode as underpotentially deposited (upd) adatoms. This dissolution probably also leads to an increase in the electrode surface roughness. Low molybdenum content in the electrode material enhances the activity toward ethanol oxidation when compared to Pt-alone. Ethanol oxidation was also investigated by in situ infrared reflectance spectroscopy in order to determine the presence of adsorbed intermediates like CO species. Acetaldehyde, acetic acid and CO₂ were also found by spectroscopic experiments.     

The distribution and phylogenetic significance of desmethylsterols inChenopodium andAtriplex: Coexistence of Δ7- and Δ5 -sterols

Twenty-one species in the Chenopodiaceae were analyzed for sterol composition. In ten of eleven species ofChenopodium, the major desmethylsterols were Δ⁷-sterols accompanied by lower proportions of Δ⁵-sterols. InC. fremontii this pattern was reversed. The sterol profiles of five species ofAtriplex were characterized by the coexistence of Δ⁷- and Δ⁵-sterols in ratios of 0.3∶1 to 0.4∶1. MaleAtriplex plants contained higher proportions of Δ⁵-sterols than femaleAtriplex plants. OneCeratoides and twoSalicornia species contained Δ⁵-sterols as their predominant sterols.     

Glutarimide acrylic copolymer: A new route to high heat PVC

PVC is the second largest polymer produced and used in the U.S. It is a self-extinguishing material with excellent chemical resistance and good dimensional stability. It's greatest asset, however, is it's versatility. By specifically formulating PVC with the numerous types of additives available, a balance of properties can be tailored for a wide range of applications. The most serious disadvantage of PVC is it's low heat resistance which limits the service temperature of finished articles to about 70°C. Now an additive is available that can be formulated with PVC to form miscible, transparent blends with increased service temperature. With proper formulating, the higher HDT can be achieved without sacrificing other properties. It is especially important in clear PVC applications where no increase in haze was noted with the addition of the acrylic imide copolymer. Indications are that substantial market opportunities exist for a high heat PVC. Major market segments include clear packaging with it's need for hot-fill containers, building products where the desire to use darker colors provides the driving force, and in custom injection molding applications where improved heat resistance would allow vinyl to compete more effectively with FR-styrenics.     

Quantitative Characterization of Indentation Crack Path in a Cubic Zirconia-10 vol% Alumina Composite

Stereological measurements were performed to characterize the indentation crack path in a cubic zirconia-10 vol% alumina (c-ZrO₂-10 vol% Al₂O₃) composite. Cracks were generated using Vickers indentation, and the crack propagation behavior was characterized as a function of the indentation loading/unloading rates. Cracks that were produced by Vickers indentation formed at higher crack velocities as the loading/unloading rates increased. The amount of contact between the crack and the Al₂O₃ particles increased as the indentation rate decreased. The total number of crack-particle interactions per unit crack length also increased as the indentation rate decreased, because of an increase in the number of particles that were fractured per unit crack length, whereas the number of particles that were debonded remained relatively constant as the indentation rate changed. These results suggest that residual thermal mismatch stresses have predominant control of the crack path at lower crack velocities (low indentation loading/unloading rate), whereas elastic mismatch stresses predominate at higher crack velocities (high indentation loading/unloading rate).     

Sterols of the oyster,Crassostrea virginica

A commericial sample of the oyster,Crassostrea virginica, obtained from Maryland waters of the Chesapeake Bay, contained 31 desmethylesterols and at least eight 4-monomethylsterols. The combined gas liquid chromatography-mass spectra of the minor components showed the presence of 6 unusual sterols, 24-ethylcholest-22-en-3β ol, 4α-methyl-24-ethylcholestan-3β-ol, occelasterol, (24E)-24-propylidene-cholest-5-en-3β-ol, (24ZO-24-propylidene-cholest-5-en-3β-ol, and 24-methylene-cholestanol. The C-24 configuration of 24-ethylcholest-5-enol, 24-methyl-cholesta-5,22-dienol, and 24-ethylcholesta-5,22 dienol were elucidated by 220 MHz nuclear magnetic resonance spectrometry.     

Analysis of polymer blend morphology by transmission and reflection light scattering techniques

Optical inspection is a potentially powerful and practical tool to collect information on polymer blend morphology for on-line quality and process control. This paper describes two approaches for the characterization of polymer blend materials by multiple light scattering. A quantitative evaluation of spectral turbidimetry (scattering of transmitted light) is presented and an adaptation of this technique for monitoring particle size, independent of the volume fraction is demonstrated. Such a procedure is applicable to materials in film form. A different approach is presented for the analysis of nearly spherical particles in optically thick samples: the diffuse reflection pattern surrounding the position of incidence of a focused light beam on the surface of the turbid medium is scanned by a single side imaging system. A spectral pseudo-transmittance signal processing technique provides particle size information again independent of the volume fraction: Both techniques have been tested using well characterized polystyrene microspheres suspended in water as well as poly(methyl) (methacrylate)/polystyrene polymer blends.     

Debinding injection molded materials by melt wicking

For metal and ceramic injection molding procedures which use wax binders in the production of powder-based parts, melt wicking is commonly employed to debind the components prior to sintering. Because debinding is often a time-consuming procedure, the influence of such process variables as powder size, part height, green density and temperature have been investigated to reduce the amount of time required for debinding by melt wicking.     

激光熔区中应力缓解的X射线衍射法测定

AISI 304奥氏体不锈钢表面经激光熔化处理,引入一个大的张应力,它可用注Ne的方法使其缓解本文介绍测量0.1μm薄层应力变化的原理和技术,由测得的应力分布曲线证明了注Ne缓解表面张应力的效果     

Three-dimensional automated nanoparticle tracking using Mie scattering in an optical microscope

The forward scattering of light in a conventional inverted optical microscope by nanoparticles ranging in diameter from 10 to 50nm has been used to automatically and quantitatively identify and track their location in three-dimensions with a temporal resolution of 200ms. The standard deviation of the location of nominally stationary 50-nm-diameter nanoparticles was found to be about 50nm along the light path and about 5nm in the plane perpendicular to the light path. The method is based on oscillating the microscope objective along the light path using a piezo actuator and acquiring images with the condenser aperture closed to a minimum to enhance the effects of diffraction. Data processing in the time and spatial domains allowed the location of particles to be obtained automatically so that the technique has potential applications both in the processing of nanoparticles and in their use in a variety of fields including nanobiotechnology, pharmaceuticals and food processing where a simple optical microscope maybe preferred for a variety of reasons.