Materials Literature
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Abstract The weathering of chlorite, one of the major minerals of the host rock in the uranium ore deposit at Koongarra, Australia, was examined by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), electron microprobe analysis, and transmission electron microscopy (TEM). The conversion sequence of…
The energy density crystallization threshold of amorphous GeSb films has been studied for the first time as a function of the laser pulse duration in the range from 170 fs to 8 ns. The results obtained provide evidence of the existence of enhanced crystallization upon irradiation with pulses shorter than 800 fs, which…
Theoretical and practical information on galvanic corrosion of zinc and its alloys, coupled to other metals, particularly steel, is organized and presented, along with a conceptual and elemental analysis of galvanic coupling between zinc and steel. Various factors which may play roles in galvanic action between zinc a…
An NAD(P)-glucose dehydrogenase from the extremely halophilic Archaeon, Haloferax mediterranei, has been purified to electrophoretic homogeneity. The purified enzyme has been characterised with respect to its cofactor specificity, subunit composition and its salt and thermal stability. The N-terminal amino acid sequen…
Abstract Toluene‐ d 8 solutions of methylaluminoxane (MAO) after the addition of different amounts of trimethylaluminium (TMA) have been studied by means of 1 H and 13 C NMR at a temperature as low as −78°C to freeze out some of the fluxional equilibria of the molecule. A comparison of the half height width of the NMR…
A microrheological model for the consolidation of aggregated colloidal dispersion is presented. Interparticle forces are responsible for the formation of the fractal-like network of particles chains. Aggregation is supposed to be weak in that the chains are gradually created and annihilated. In the framework of this m…
A surface model was developed for diamondlike-carbon film deposition, and was connected in a self-consistent way with a one-dimensional plasma chemistry and physics model for a CH4 radio-frequency (rf) discharge. The surface model considers the adsorption of multiple species (CH3, CH2, and H), and solves for the surfa…
The existence of an orientationally disordered cubic phase of solid ethanol is revealed by x-ray diffraction and Raman spectroscopic measurements. Such a phase, whose existence was postulated some time ago on the basis of specific-heat measurements, is produced by quenching below some 95 K a plastic crystal formed upo…
Vascular grafts, devices designed to augment inefficiently functioning vascular systems, represent a significant part of implantable medical devices, with major participation in over a million vascular surgeries performed worldwide. By definition accepted in the art, a small caliber graft is a conduit with internal di…
Oxygen self-diffusion coefficients were determined in polycrystals of α-alumina either ‘undoped’ or doped with 500wt.ppm (225molppm) Y2O3 in the temperature range 1460-1720°C, with 18O2 and secondary-ion mass spectrometry. Oxygen grain-boundary diffusion coefficients obey the relations for ‘undoped’ alumina and for ‘y…
To determine when secondary structure forms as two chains coalesce to form an alpha-helical dimer, the folding rates of variants of the coiled coil region of GCN4 were compared. Residues at non-perturbing positions along the exterior length of the helices were substituted one at a time with alanine and glycine to vary…
We propose, based on recent experimental results, a polyyne ring nucleus (PRN) growth model for the synthesis of single-layer nanotubes (SLN's). The PRN model assumes that (i) the critical nuclei are the planar carbon polyyne rings that are observed to be most stable for sizes in the range ${\mathrm{C}}_{10}$ to ${\ma…
The molecular anchoring and orientational wetting properties of a liquid crystal close to the nematic-isotropic transition temperature confined to the 0.2 \ensuremath{\mu}m cylindrical channels of alumina membranes are investigated for various surface preparations. The cavity walls of the confining pores are chemicall…
The dc resistivity, magnetoresistance, and magnetic susceptibility of ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CoO}}_{3}$ compounds have been investigated in the temperature range of 4--300 K for magnetic fields up to 7 T. In the doping range studied (0.05\ensuremath{\l…
The formation processes of unfilled and filled interpenetrating polymer networks (IPNs) and some of their physico-mechanical properties have been investigated. The IPN formation kinetics and the constituent network curing rates determine the rate and degree of microphase separation. This in turn determines the boundar…
Abstract The influence of molecular weight and its distribution on the nucleation density, crystallization, thermal and mechanical behavior of isotactic polypropylene based composites has been investigated. The composites were prepared by compression molding. The ability of carbon and Kevlar fibers to nucleate the pol…
A reversible thermally induced conformational transition of the beta2 subunit of tryptophan synthase from Salmonella typhimurium has been detected by use of the pyridoxal 5'-phosphate coenzyme as a spectroscopic probe. Increasing the temperature converts the major form of pyridoxal 5'-phosphate bound to the beta2 subu…
We report x-ray photoemission spectra of poly(tetrafluoroethylene) (PTFE). XPS spectra were measured with the SSI, SSX-100 model, using monochromated Al Kα x-rays. We present the survey spectrum (binding energy range of 0–1000 eV) and narrow scans of C 1s and F 1s. The polymer is used as a reference to study the influ…
Abstract The new technique of measuring radial expansion of a crater as a function of time on a shaped charge jet that penetrates water is explained in this paper. Radial expansion of the crater in the frame of experimentation can, in this case, be easily described with a modified Bernoulli equation under the conditio…
The microstructure of a cross-woven CSiC composite and its effect on tensile behavior was studied in terms of damage and damage development. Microstructure characterization revealed that the composite contained processing-induced cracks and nonuniform fiber bundle sections with different fiber-matrix distributions. T…