Materials Literature
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Abstract Microcellular foam is a polymeric foam with bubble sizes of 10 microns or less that is produced by saturating a polymer with gas and then utilizing the thermodynamic instabilities that result when the polymer is heated and the pressure is reduced to nucleate the cells. A model for the nucleation of microcellu…
A computer program has been written for the purpose of standardizing crystal structure data according to rules formulated by Parthé & Gelato [Acta Cryst. (1984). A40, 169–183]. From input consisting of space-group symbol, unit-cell parameters and positional coordinates of the atoms, a reordered and renumbered list of…
The application of the Rietveld refinement technique to synchrotron X-ray data collected from a capillary sample of Al2O3 in Debye–Scherrer geometry is described. The data were obtained at the Cornell High Energy Synchrotron Source (CHESS) with an Si(111) double-crystal monochromator and a Ge(111) crystal analyzer. Fi…
A room-temperature nematic liquid crystal cell is prepared in the homeotropic geometry using dielectrically positive pentyl cyanobiphenyl. The indium tin oxide electrodes are treated to increase locally their surface resistance. At high frequencies (ω>ωc) the border of these regions behaves as capacitance edge,…
The band structures of zincblende, hexagonal and wurtzite BN have been calculated using the full-potential linear augmented-plane-wave (FLAPW) method systematically. The present results for zincblende and hexagonal BN are compared with earlier calculations. For the wurtzite structure, the work is the first ab initio c…
The astonishing smoothness of the superdeformed rotational spectrum in $^{152}\mathrm{Dy}$, from I=22 to I=60, is used as a basis for inferring a liquid-to-solid transition as the centrifugal force drives the nuclear shape into a closed-shell configuration.
The most significant feature in the transition from the quasicrystalline to the amorphous state is the loss of long-range bond-orientational order. Disclinations are candidates for elementary excitations which destroy angular correlations. Generalizing the topological defect classification, we investigate point singul…
The electrical conduction in thin-film diamond synthesized by microwave plasma enhanced chemical vapor deposition has been studied with metal-diamond-silicon metal-insulator-semiconductor structures. Measurements over a wide temperature range provide evidence for space-charge-limited current in the presence of traps.…
We show that large piezoelectrically induced electric fields strongly modify the optical properties of [111] growth axis strained-layer superlattices with growth axis along [111]. These internal fields reduce the superlattice band gap, change optical matrix elements, and cause a spatial separation of photoexcited elec…
Diamond thin films have been formed by dc plasma chemical vapor deposition with a high growth rate (∼20 μm/h). The diamond has been grown from methane (CH4) and hydrogen (H2) mixed gases on Si and α-Al2O3 substrates at a pressure of 200 Torr without surface scratching by diamond or c-BN powder. The obtained films have…
A two-dimensional Euclidean plane can be identified with the Gauss-Argan plane, so that a two-dimensional triangular lattice can be identified, apart from a scaling factor, with a set of 'triangular integers' of the complex quadratic field associated with a complex cubic root of 1. It is shown that a two-dimensional m…
The luminescence spectra and decay curves of Sb 3+ -doped Cs 2 NaMBr 6 (M=Sc,Y,La) are presented. In this lattice the Sb 3+ ion (5s 2 ) is octahedrally surrounded by six bromide ions. The emission consists of one band. The Stokes shift increases in going from Sc to La. This is connected to the larger space available f…
((NH4)1–xKx)2SO4 powdered crystals with x = 0.0, 0.1, 0.15, 0.25, 0.32, 0.6, 0.7, and 1.0 are studied by X-ray diffraction from room temperature down to 73 K. It is found that the mixed crystals are isomorphous to (NH4)2SO4 and K2SO4. The phase transition temperature decreases with the increase of the substituted ions…
Cross-slip of partial dislocations via the formation of stair rod dislocations at the line of intersection of two {111} planes is studied. General formulae are derived for the calculation of activation energies. It is shown that local stress concentrations due to a pile-up or a microtwin tip makes such cross-slip proc…
Magnetic susceptibility of an organic ion-radical salt, triethylammonium[TCNQ] 2 , has precisely been measured in the temperature range between 4.2 and 360K. It shows a shallow but obvious dip near 215 K. Such anomaly in the susceptibility of the salt has been found for the first time. The anomaly may result from the…
ABSTRACT This paper describes a recently developed standardized system for dull grading natural diamond, PDC, and TSP (Thermally Stable Polycrystalline diamond) bits, otherwise known as fixed cutter bits. The new system is consistent with the recently revised dull grading system for roller bits. It describes the condi…
The transmission spectra of the amorphous semiconductor system (${\mathrm{GeS}}_{2}$${)}_{\mathrm{x}}$(${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$${)}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$ are measured under hydrostatic pressure, and the dependence of the optical gap ${E}_{0}$ and the refractive index n on the pressure is s…
The CNDO/S3 molecular orbital model is applied to describe the electronic structure of aniline, (C6H5)NH2, emeraldine, (C6H5)N(C6H4)N(C6H4)NH(C6H4)NH2, its hydrogenated and dehydrogenated forms, and its singly and doubly protonated forms. The cation eigenvalue spectrum, i.e., density of valence states (DOVS), is found…
A recombinant plasmid carrying an 11 kb restriction-endonuclease-ClaI fragment of genomic DNA from Escherichia coli ML308 was constructed. This plasmid complements an aceA mutation. The plasmid encodes the structural genes of the glyoxylate bypass operon, namely malate synthase A (aceB), isocitrate lyase (aceA) and is…
X-ray scattering and electron-transmission microscopy of melt-spun Al-Si-Mn alloys reveal that the Al-Mn icosahedral phase itself can grow congruently over a range of composition varying from 16 to 20 at.?Mn, and Si atoms substitute Al atoms selectively. The Q dependences of linewidth \ensuremath{\Delta}Q suggest that…