Defect Structure of NiO-CoO Solid Solutions

Measurements at high temperature of integrated intensities of Bragg peaks were used to examine the defect structure in two NiO-CoO solid solutions. The results indicate that the concentrations of vacant cation sites at 1100° to 1500°C are 4 to 10% and the tetrahedral occupations 2 to 5%. The concentration of these defects increases with temperature and partial pressure of O₂. The mean-square displacements of oxygen ions and cations increase with temperature and CoO concentration.     

Interdiffusion in CoO-NiO Solid Solutions

Interdiffusion coefficients were measured in CoO-NiO solid solutions over the range 1000° to 1600°C in air and at po₂=5×10⁻⁸ atm. Isothermal values of the interdiffusion coefficients in this system increased exponentially with the CoO concentration. Comparison of the present results with cation-tracer diffusion coefficients for this system measured under similar conditions by Chen and Peterson shows that a Darken-type equation relating the interdiffusion coefficient to the cation-tracer diffusivities is valid for these data.     

Control Requirements for Control Systems: Matching Surety To Risk

Abstract

Auditing Software Development: A Manual With Case Studies, by S. Rao Vallabhaneni. John Wiley and Sons (605 Third Avenue, New York, 10158-0012), 1990, 439 pp. Includes a glossary and bibliography. Price: $75.00, plus shipping and handling charges.

Computer Crime: Techniques For Preventing And Detecting Crime In Financial Institutions, by Gregory Wold and Robert Shriver. Bankers Publishing (60 Gould Center, Rolling Meadows IL 60008), 1989, 255 pp. Includes a glossary. Price: $49, with a discount for BAI members.     

A laboratory investigation of a physical rnechanisim for the extended infrared absorption (‘red shift‘) in wheat

Laboratory spectral measurements, on the components of both greenhouse and field grown winter wheat, were performed to identify the component and its appropriate response which gave rise to the extended infrared absorption or ‘red shift’ reported by Collins. Results of this study indicated that inherent intraplant adaxial (upper) leaf reflectances were of sufficient variability to suggest that an admixture of mechanisms may have utility on identifying the booting and head emergence stages in the life cycle of wheat. The physical mechanism for the shift was found to be relatively independent of the inherent variability in leaf spectra, and to be dependent upon the difference in the mode of deposition of cuticle upon the abaxial (lower) surface relative to that of the adaxial (upper) surface, ihe position of the flag leaf, and thus the surface exposed to the incident light during heading and after emergence of the head.     

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Measurement of the Lattice Parameter of Wustite at High Temperatures

The lattice parameter of wustite (Fe₂O) single crystals was measured at high temperatures. Plots of both lattice parameter vs composition and lattice parameter vs temperature were linear, and no appreciable changes in slope were detected at the boundaries of the subphases suggested by Vallet and Raccah.     

Diffraction from a Natural Grain Boundary in a Magnetite Bicrystal

The structure of a natural small-angle boundary in a magnetite bicrystal was investigated by X-ray diffraction. This boundary was a "general" type with a mixed twist and tilt character. The grain-boundary reflections observed around an 040 matrix reflection were in good agreement with those predicted by Boll-mann's O-lattice theory. These extra reflections appear to arise from a predominantly planar dislocation network. The structural width of the boundary, determined from the length of the relrods of the grain-boundary reflections, was of the order of four unit cells, close to the average spacing of the expected dislocation network.