Materials Literature
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The natures of radiation-induced defects and defect generation processes in optical glasses are critically reviewed. Materials of interest here include silica, silicates, and fluorides, hence encompassing glasses now in use or contemplated for fiber optics, lenses, mirrors, windows, and other optical applications. The…
The tracer diffusion coefficient is investigated for a correlated diffusion of a tracer, which is a particle of the lattice gas. The lattice gas consists of particles of arbitrary concentration hopping on a two-dimensional honeycomb lattice, which interact only as repulsing point hard cores. Exchange between different…
The low-temperature ferroelectric-paraelectric phase transition occurring in lead scandium tantalate (PbSc 1 2/Ta 1 2/O 3 ) has been investigated by X-ray diffraction. The symmetry of the low-temperature phase is shown to be rhombohedral and the lattice parameters are given over the temperature range 30-300K. The atom…
The phase behavior of multicomponent polymeric materials is a crucial factor in determining their physical properties and subsequently their utility. For systems forming separate phases, the important issues are phase morphology (size and shape) and the nature of the interface (wetting and adhesion) between phases. Fo…
This report was produced by a scientific committee of eight members, chaired by Richard C. McCall. It is a reference manual dealing with the problem of neutron production that results from the operation of high-energy electron linear accelerators used in radiation therapy. As radiation therapy becomes more sophisticat…
A model for the paramagnetic ${E}_{2}^{\ensuremath{'}}$ center in alpha quartz is tested by means of semiempirical molecular-orbital calculations. The ${E}_{2}^{\ensuremath{'}}$ center is proposed to be a variant of the ${E}_{4}^{\ensuremath{'}}$ center (a hydrogen atom substituted for an oxygen atom) with one silicon…
Resume- On passe en revue des donn6es sur la structure d'un certain nombre de solides amorphes repr6sentatifs- m6taux purs et semiconducteurs, alliages amorphes et verres d'oxydes- et on se propose de sugggrer quels sont les modbles les plus adkquats. Historiquement, les empilements denses algatoires…
Abstract With highly orientd and isotropic samples of iostactic polypropylene the thermo‐oxidative stability in air and in fumic nitric acid was studied. The rate of chain scission was found to be higher with isotropic than with oriented samples. Thermo‐oxidation in air and etching of amorphous regions leads to format…
X-ray absorption spectra of Fe and Ni K edges have been obtained at room temperature by means of a total electron yield technique for a clean Fe foil on which Ni was subsequently deposited, and a Ni foil. This technique involves the measurement of the specimen current. The total yield is found to be ∼1×10−2 electron p…
Audio frequency complex admittance has been used to investigate electrical relaxation in poly(ethylene oxide). The complex admittance measurements were performed at seventeen frequencies from 10 Hz to 100 kHz in approximately equal logarithmic intervals using a fully automated dielectric spectrometer and measurements…
The dislocation-enhanced Snoek effect - DESE in nitrogen doped iron is reported. The nitrogen DESE shows similar properties as already reported carbon DESE in iron. Thermal instability of the DESE in iron is clearly shown. A general discussion on the DESE in bcc metals is given.
Abstract Die bisher unbekannte Verbindung Cu 6 Mo 5 O 18 wurde in einkristalliner Form dargestellt und röntgenographisch untersucht (a = 18,884(19), b = 6,273(7), c = 15,259(23) Å, β = 130,40(5)°, Raumgruppe C –C2/c, Z = 4). Die charakteristischen Strukturmerkmale werden beschrieben und im Zusammenhang mit Oxocupraten…
Abstract The colourless com pound NaLiS has been prepared and its structure determined by single crystal X-ray diffraction techniques. The very hygroscopic NaLiS crystallizes in the tetragonal space group P4/nmm (Z = 2) with the cell parameters a = 402.6(1), c = 649.5(2) pm. The structure was solved from 720 counter r…
A generalized effectiveness factor equation (Eq. (32)), in terms of modified Bessel functions, is derived for a catalyst pellet of arbitrary shape. The derivation is based on utilizing an appropriate one-dimensional approximation for the Laplacian in an arbitrary shaped body subjected to a uniform external concentrati…
We present a theory of quasiperiodic tilings and more general quasiperiodic patterns with long range orientational order. We explain our "strip method" (a variant of the projection methods) on a one dimensional model. Then the icosahedral case is investigated in view of the quasicrystals of the type Al-Mn. Our method…
Resting spores of Thalassiosira scotia Fryx. et Hoban were abundant in phytoplankton net hauls collected from the Scotia Sea south of South Georgia in December 1981. Primary valves are distinguished from secondary valves by the presence of marginal striae with rounded, shoelike protrusions, villi surrounding marginal…
We suggest that the staging transformation in graphite intercalation compounds takes place through metastable, partly disordered states. A specific mechanism, involving nucleation of defect sandwiches of stage n\ifmmode\pm\else\textpm\fi{}1 in the stage-n phase, is proposed. We predict that the staging disorder is ass…
The occurrence of sepiolite and palygorskite in soils, Eocene limestones and the Asmari dolomitic limestone of Iran has been described by many workers (Bentor et al. , 1963; Martin Vivaldi & Robertson, 1971; Abtahi, 1977, 1980). No studies have been carried out on the genesis of these minerals in Iranian soils, ho…
The increasing interest in introducing cheaper forms of reinforcement for use with glass fibers within the latter quarter of this century has stimulated research in hard cellulosic fibers, their diversification, and their potential use in such areas. At present, hard cellulosic fibers are flax, jute, hemp, and ramie (…
Lead zirconate‐titanate (Pb(Zr 0.54 Ti 0.46 )O 3 ) was doped with varied concentrations of Ta 5+ and La 3+ and sintered at 1200°C for 2 h. Dense ceramic materials were obtained when the cation stoichiometry was adjusted to allow for charge compensation of the donor ions by Pb vacancies. Bulk density, capacitance at 1…