Materials Literature
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X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and electrochemical potentiodynamic experiments have been used to study the pretreatment of 2024–T3 aluminium alloy before conversion coating. The pretreatment process included vapour degreasing, alkaline cleaning and Cr based acidic deoxidising ste…
The three-dimensional structure of the Saccharomyces cerevisie fatty acid synthase was computed from electron microscopy of stain images. The barrel-shaped structure (point group symmetry 32) has major and minor axes of approximately 245 x 220 A, respectively, and consists of two different subunits organized in an alp…
Designs are given for gallium-arsenide subwavelength grating retarders operating at 10.6 μm. A design procedure is detailed that takes into account the reflections at all surfaces and that uses numerical optimization to improve the transmittance of the retarders to nearly 100%. It is shown that the homogeneous uniaxia…
A second virial theory is presented to study the influence of a slight flexibility on the nematic-smectic A transition in fluids of freely rotating hard rods. The spinodal is located by performing a bifurcation analysis of the equation describing the single-particle distribution function. A closed expression for the s…
A photolithographic process has been used to form cross-shaped patterns in 3-μm-thick nickel foils. Patterns with cross arm dimensions in the 10-20-μm range, and with periodicities in the 16-26-μm range, yield self-resonant bandpass filters for wavelengths in the 20-25-μm region. Transmittances as high as 80% were ach…
Abstract The radical polymerization of acrylic acid and sodium 4‐styrenesulfonate in the presence of chitosan as a template gives insoluble products, identified as the polyelectrolyte complexes chitosan‐poly(acrylic acid) and chitosan‐poly(4‐styrenesulfonate). Kinetic results do not permit to propose any mechanism in…
Abstract A backscattered electron energy spectrometer, based on a toroidal energy analyser and an annular detector, has been devised and adapted for use in a scanning electron microscope. Computer simulations have been carried out for equipotentials and trajectories of electrons in the toroidal deflector, which permit…
We have studied the scaling behavior of the bulk structure in a symmetric diblock copolymer system using small-angle scattering. We have identified a crossover between the inter mediate-segregation regime and the strong-segregation limit at χ N ≃ 29. In the inter mediate-segregation regime (χ N ≃ 5 − 29), the characte…
Abstract Ferroelectricity and thus piezoelectricity are well known features of low molar mass chiral smectic C (S c * ) liquid crystals. We present a new technique to orientate macroscopically the director as well as the smectic layers of a S c * ‐polymer network by applying a suitable mechanical field. The uniform or…
Interposition of a fine-scale X-ray absorbing mesh between a Laue-diffracting crystal specimen and the photographic plate recording its topographic image splits the diffracted beam into an array of individually identifiable microbeam elements. Direction differences between the microbeams in the array, which are twice…
Using light scattering, the thickness dependence of the isotropic-nematic phase transition temperature ${\mathit{T}}_{\mathit{NI}}$ in a thin film of octylcyanobiphenyl (8CB) is studied in two distinct geometries: with and without strain. We observed a large stress induced shift in ${\mathit{T}}_{\mathit{NI}}$, as a f…
Recent experiments on the Tokamak Fusion Test Reactor have afforded an opportunity to measure the retention of tritium in a graphite limiter that is subject to erosion, codeposition, and high neutron flux. The tritium was injected by both gas puff and neutral beams. The isotopic mix of hydrogenic recycling was measure…
Current‐voltage ( I‐V ) and anodic polarization characteristics were measured for the H 2 ‐fueled solid oxide fuel cell with an 8 mole percent yttria‐stabilized zirconia (YSZ) electrolyte and Ni‐YSZ anode. For a H 2 ‐rich H 2 ‐ H 2 O system, the I‐V curve was characterized by a high open‐circuit voltage and significan…
Systematic studies of the specific-heat anomaly and of the entropy changes at the Verwey transition in the ${\mathrm{Fe}}_{3\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ti}}_{\mathit{x}}$${\mathrm{O}}_{4}$ and ${\mathrm{Fe}}_{3\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Zn}}_{\mathit{y}}$${\mathrm{O}}_{4}$ series are…
Observations of the expanding vapor cloud generated by the hypervelocity impact have been carried out. Under usual laboratory conditions, rock or ice materials cannot be vaporized completely. In order to investigate the expansion of a large amount of the vapor by complete vaporization caused by hypervelocity impact, w…
We have used a high-intensity tunable picosecond infrared laser source to measure the spectral content of light scattered near the second harmonic for two well-known organic dyes, p-Nitroaniline and Disperse Red 1, at a number of wavelengths in the near infrared. We found that in Disperse red 1 a broad two-photon fluo…
Solid solutions along the magnesite-siderite join have been synthesized from mechanical mixtures of iron oxalate and basic magnesium carbonate using hydrothermal synthesis techniques at 500°C and about 2 kilobars. The double capsule method was used to provide the atmosphere necessary to prevent decomposition and oxida…
All articles of this category Improved procedures are described for the synthesis of meso -tetrakis(2,6-dichlorophenyl)porphyrin and for subsequent perhalogenation of the porphyrin ring. halogenated porphyrins - metalloporphyrins halogenation - oxidation catalysts
The frequencies of the Si-Si, Si-Ge, and Ge-Ge Raman modes in ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Ge}}_{\mathit{x}}$${\mathrm{C}}_{\mathit{y}}$ alloys with y\ensuremath{\leqslant}0.03 have been measured. All frequencies are found to increase as a function of t…
The exciton binding energy ɛb for a conducting polymer can only be defined unambiguously in the long chain limit. In that limit it can be taken as the difference between the bandgap or the ‘single particle bandgap’ — the former if the exciton dissociates into a free electron and hole, the latter if it dissociates into…