Materials Literature
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Recent progress in the field of charge storage and charge transport in polymers irradiated with partially penetrating electron beams is discussed. The analytical model used to describe these phenomena takes the following physical parameters and processes into consideration: charge and energy deposition profiles, ohmic…
The use of an implanted, mass-separated carrier-free 105Ag radiotracer improves the sensitivity for measuring grain-boundary (GB) penetration profiles. In this way the GB self-diffusion coefficient DGB in silver was directly determined from experiments in type-C kinetics conditions. When multiplying the DGB values wit…
The extraction of pure-specimen X-ray diffraction-line broadening is described using a convolution of the instrumental profile and an exact Voigt function. Real Fourier coefficients were computed from the Cauchy and Gauss integral breadths and were input for Warren–Averbach analysis. Smooth surface-weighted and volume…
A force field (MSXX) for molecular dynamics simulations of silicon nitride is derived using the Hessian biased technique from ab initio calculations on N(SiH3)3 and Si(NH2)4 clusters. This is used to model the nitrogen and silicon centers of the α and β forms of crystalline Si3N4 for prediction of crystal structures,…
The metal-insulator transition in the orthorhombic perovskites PrNiO 3 and NdNiO 3 is accompanied by the sudden 3D magnetic ordering of the Ni ions (μ Ni ≈ 0.9 μ B ). The magnetic ground state, described by a commensurate κ = (1/2, 0, 1/2) spin density wave, is unprecedented in a perovskite structure. The coexistence…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis, self-assembly, and photophysical dynamics of stacked layers of porphyrin and viologen phosphonatesSolomon B. Ungashe, William L. Wilson, Howard E. Katz, Geoffrey R. Scheller, and Thomas M. PutvinskiCite this: J. Am. Chem. Soc. 1992, 114, 22, 8717–8719Publication D…
From a genomic library of Chromatium vinosum strain D in lambda L47, a 16.5-kbp EcoRI-restriction fragment was identified by hybridization with a DNA fragment harboring the operon for Alcaligenes eutrophus poly(3-hydroxyalkanoate) (PHA) synthesis. This fragment and subfragments thereof restored the ability to synthesi…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetic properties of high-nuclearity spin clusters. Fourteen- and fifteen-oxovanadium(IV) clustersAnne Laure Barra, Dante Gatteschi, Luca Pardi, Achim Mueller, and Joachim DoeringCite this: J. Am. Chem. Soc. 1992, 114, 22, 8509–8514Publication Date (Print):October 1, 1992P…
The microhardness, H, and Young’s modulus, E, of a polycrystalline diamond film and several amorphous diamondlike carbon (DLC) films were determined from force-displacement curves obtained using an ultralow-load microhardness instrument (UMIS-2000). Measurements were made at a constant loading rate of 3 mN/s, to a max…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMicrophase separation kinetics in segmented polyurethanes: effects of soft segment length and structureBenjamin Chu, Tong Gao, Yingjie Li, Jian Wang, C. Richard Desper, and Catherine A. ByrneCite this: Macromolecules 1992, 25, 21, 5724–5729Publication Date (Print):October 1,…
Abstract The Laves phase structures (MgCu 2 MgZn 2 and MgNi 2 types) are adopted by a large number of binary intermetallic compounds of composition AB 2 . These phases belong to the class of tetrahedrally closepacked alloys. Two of the structural features of the Laves phases which have aroused interest are, firstly th…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolymerization of silicon-containing diphenylacetylenes and high gas permeability of the product polymersKenji Tsuchihara, Toshio Masuda, and Toshinobu HigashimuraCite this: Macromolecules 1992, 25, 21, 5816–5820Publication Date (Print):October 1, 1992Publication History Pub…
From genomic libraries, the polyhydroxyalkanoate gene locus of Pseudomonas aeruginosa PAO1 was cloned and characterised at the molecular level. Two genes coding for polyhydroxyalkanoate synthases, phaC1Pa and phaC2Pa, a polyhydroxyalkanoate depolymerase gene, phaDPa, and four adjacent open reading frames (ORF1, ORF2,…
Macroscopic fluid motion can have dramatic consequences near the isotropic-nematic transition in fluids of nematogens. We explore some of these consequences using both deterministic and stochastic descriptions involving coupled hydrodynamic equations of motion for the nematic order parameter and fluid velocity fields.…
The clpB gene in Escherichia coli encodes a heat-shock protein that is a close homolog of the clpA gene product. The latter is the ATPase subunit of the multimeric ATP-dependent protease Ti (Clp) in E. coli, which also contains the 21-kDa proteolytic subunit (ClpP). The clpB gene product has been purified to near homo…
Hydrogenation of diamond has been carried out using the electron-cyclotron-resonance microwave plasma chemical-vapor deposition apparatus. According to reflection high-energy and low-energy electron diffraction and X-ray photoelectron spectroscopy measurements, the natural- and synthetic-diamond surfaces maintained th…
A study of the mechanical characteristics of a unidirectional fiber–reinforced calcium aluminosilicate matrix composite has been conducted. The properties have been related to the individual properties of the matrix, the fibers, and the interfaces, as well as the residual stress, using available models of matrix crack…
A versatile approach to dendritic polyesters and their use in the preparation of two different types of novel macromolecular architectures represent dendritic block copolymers is described. The chemistry developed for the synthesis of dendritic polyesters involves generation growth through an esterification step using…
Epitaxial growth of BaTiO3 and SrTiO3 films by the reactive evaporation method was investigated using reflection high-energy electron diffraction (RHEED). The investigations were carried out using two growth methods: coevaporation and alternate evaporation of the metal elements in an oxygen atmosphere. Atomic layer gr…
Abstract In 1984 physicists discovered a monster in the world of crystallography, a structure that appeared to contain five-fold symmetry axes, which cannot exist in strictly periodic structures. Such quasi-periodic structures became known as quasicrystals. A previously formulated theory in terms of higher dimensional…