Materials Literature
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Optical-absorption and emission spectra and fluorescence lifetimes were measured for Nd3+ in tellurite glasses containing various alkali and higher valence state cations and in a series of new phosphotellurite glasses. Judd-Ofelt intensity parameters were determined and used to calculate radiative lifetimes and stimul…
Abstract Polymers such as polyacetylene, which have an extended π‐electron system in their backbone, or like poly( p ‐phenylene) consist of a sequence of aromatic rings are excellent insulators in their native state and can be transformed by oxidation or reduction in the solid state into conductive CT‐complexes which…
Some of the difficulties in using x‐ray photoelectron spectroscopy (XPS) for the chemical characterization of surfaces are considered. XPS chemical shifts are often quite small, compared to spectral line widths and to the accuracy of the reference data. Moreover, subtle differences in peak shape are often degraded by…
A mathematical model of ductile hole growth under the application of a mean tensile stress is developed and applied to the problem of spallation in solids. The object is to describe dynamic ductile fracture under a wide range of tensile loading conditions. The mathematical model presented here describes both plate-imp…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectrochromism in the mixed-valence hexacyanides. 1. Voltammetric and spectral studies of the oxidation and reduction of thin films of Prussian blueD. Ellis, M. Eckhoff, and V. D. NeffCite this: J. Phys. Chem. 1981, 85, 9, 1225–1231Publication Date (Print):April 1, 1981Publ…
ADVERTISEMENT RETURN TO ISSUEArticleNEXTCrystallographic refinement and atomic models of a human Fc fragment and its complex with fragment B of protein A from Staphylococcus aureus at 2.9- and 2.8-.ANG. resolutionJohann DeisenhoferCite this: Biochemistry 1981, 20, 9, 2361–2370Publication Date (Print):April 1, 1981Publ…
The Rietveld [J. Appl. Cryst. (1969), 2, 65–71] method of structure refinement from powder diffraction patterns is widely used with neutron data and increasingly so with X-ray data. A computer program for the application of the method with X-ray data, or with neutron nuclear scattering data, has been written ab initio…
A broad review of recent research work on the preparation and the remarkable properties of intercalation compounds of graphite, covering a wide range of topics from the basic chemistry, physics and materials science to engineering applications.
Escherichia coli dihydrofolate reductase was shown to follow slow transient kinetics (hysteresis). Nonlinear reaction velocities were detected during the enzyme assay and required 10-15 min to reach a steady-state rate. The degree of hysteresis was influenced by the enzyme concentration and the order of substrate addi…
An analysis is made of the theory of the luminescence spectra of semiconductors with direct optical transitions involving recombination of nonequilbrium carriers whose energies are close to the band gap edges. The usual formulation of the theory of recombination is employed, i.e., given densities of free electrons and…
The information contained in an Auger-electron-photoelectron coincidence spectroscopy (AEPECS) experiment for $\mathrm{XXV}$, $\mathrm{XYV}$, and $\mathrm{XYZ}$ Auger processes when a single $X$ level is involved is discussed. For finite systems AEPECS gives information about the spatial character of the excited state…
Abstract PE spectral comparisons of the title compounds with the corresponding O ‐ and N ‐methyl fixed derivatives show that both 2‐ and 4‐quinolone exist as the NH forms in the vapour phase: none of the OH tautomers could be detected.
Evidence for superconductivity in the organic conductor di-(tetramethyltetraselenafulvalenium)-perchlorate [${(\mathrm{TMTSF})}_{2}$Cl${\mathrm{O}}_{4}$] has been found by resistance measurements in the absence of applied pressure. For different crystals the transitions are approximately 0.3 K wide and are centered ar…
Polarised Raman spectra of chloro- and bromo-sodalite (Na 4 Al 3 (SiO 4 ) 3 Br) 2 single crystals have been recorded, and 28 of the predicted 32 Raman-active phonon modes observed. A full group-theoretical analysis of the zone-centre phonons is given. The internal modes are assigned using as a basis the normal mode fr…
Abstract A historical survey about the development of Ziegler‐Natta catalysts for polymerization of propylene is given. After having employed catalysts based on titaniumtrichloride for several years, in the 70's catalysts of the so‐called second generation were introduced, which are more effective and yield products o…
New developments in Cu2S thin-film technology allow, in principle, the combination of Cu2S with semiconductors other than CdS or Cd1−xZnxS for solar cell purposes. We discuss here a pn+-type Cu2S-ZnO structure that offers some basic advantages over existing structures. Our analysis predicts a practically achievable ef…
Natural ultramarine and alkali borate glasses doped with sulphur are investigated by means of ESR and optical spectroscopy. A comparison of optical and ESR spectra makes it possible to conclude that the blue colouring (absorption band within the range 585 nm) and the anisotropic ESR signal (g1 = 2.003, g2 = 2.032, g3…
The macroscopic properties of the plastic deformation of a simple model crystal which obeys the Friedel relation are compared with computer simulation data and some in the literature unnoticed differences are discussed. It is pointed out that the random distribution of obstacles causes on average activation energy ΔG0…
There is increasing interest in the measurements of the dielectric absorption of compressed solid powders. A theoretical analysis is reported which highlights the problems which may arise due to “lack of contact” between the material and the electrodes. It is demonstrated, both theoretically and experimentally, that s…
It is observed that a reversible step period rearrangement on clean nickel single-crystal surfaces occurs in the immediate vicinity of the Curie temperature. Reversible carbon segregation is observed on the same crystal surfaces below the Curie point. The segregated carbon is carbidic, not graphitic, and indicates a c…