The effect of aluminium coating on elemental standards in X-ray microanalysis

The standardisation of frozen hydrated bulk biological specimens using gelatin standards is described. The relationship between corrected elemental X-ray counts and ionic concentration was found to be linear, and minimum detectable limits for each element are stated. Variations in uncorrected standard curves were found to be due to changes in aluminium coating thickness. There was an inverse relationship between coating thickness and elemental X-ray counts. The factors causing this are discussed. To avoid errors arising from inconsistent aluminium thickness, experimental material should only be compared with standards of similar aluminium net counts. This can be achieved most easily by mounting and analysing specimen and standard together.     

Ionization of Acetylacetone in Me2SO—Water Mixtures. Reactivity—Selectivity Principle or Principle of Imperfect Synchronization?

Rate constants for the reversible deprotonation of acetylacetone were measured in carboxylate and amine buffers in water and in 50%, 90% and 95% Me₂SO at 20°C. The Brønsted plot for the carboxylate ions is curved in the Me₂SO—water mixtures, but straight in water. The curvature is in the direction predicted by the Reactivity—Selectivity Principle (RSP). However, the Brønsted plot for the reaction with primary amines is straight in all solvents. This suggests that the curvature observerd with the carboxylate ions is caused by loss of solvation of the base; this loss of solvation is ahead of bond formation in the transition state rather than being a manifestation of the RSP. (Note that all Brønsted plots are based on pK_a values measured in the respective solvents.) The intrinsic rate constant (k₀) for proton transfer increases with the addition of Me₂SO, and more so with the carboxylate buffers than with the amines. This increase in k₀ is attributed to delayed solvation of the developing enolate ion in the transition state; with the carboxylate buffers, an additional factor is the early loss of solvation of the base. The various solvation effects observed in this study can all be understood in the context of the Principle of Imperfect Synchronization (PIS).     

Heterogeneous structure of cis-isoprene rubber and oligodiene diisocyanate blends

The structural peculiarities of cis-1,4-isoprene rubber, oligodiene diisocyanate, and derivative of phenol–formaldehyde resin blends have been studied by WAXS and SAXS methods and electron microscopy. It has been demonstrated that the addition of modifiers and further thermal treatment under conventional curing conditions change considerably the microheterogeneous structure and morphology and contribute to the improvement of the short-range order in the rubber matrix.     

Effect of Contact Residual Stress Relaxation on Fracture Strength of Indented Soda-Lime Glass

The strength of Vickers-indented soda-lime glass measured in air at room temperature steadily increases with time after indentation, whereas optical retardation steadily decreases in the same interval. Annealing after indentation causes further strength increase and retardation decrease. The results are consistent with Marshall and Lawn's treatment of the slow crack growth of indentation flaws driven by the combined influence of residual contact stress and applied stress. Post-indentation strengthening of indentation flaws can be explained without recourse to flaw blunting.     

Synthesis of Si3N4 with Emphasis on Si-S-N Chemistry

Industrial production of Si₃N₄ from SiCI₄, is increasing. An element rivaling CI in abundance and cheapness with potentially suitable chemistry for this application is sulfur. Thus, Si–S–N chemistry was investigated to determine its usefulness in producing Si₃N₄. Bifunctionality in S, as opposed to mono-functionality in CI, may allow special routes via polymers to become important.     

Knowledge-based understanding of radiology text

A data acquisition tool which will extract pertinent diagnostic information from radiology reports has been designed and implemented. Pertinent diagnostic information is defined as that clinical data which is used by the HELP medical expert system. The program uses a memory-based semantic parsing technique to 'understand' the text. Moreover, the memory structures and lexicon necessary to perform this action are automatically generated from the diagnostic knowledge base by using a special purpose compiler. The result is a system where data extraction from free text is directed by an expert system whose goal is diagnosis.     

The 1987-8 Taulbee Survey report

This report describes the results of a survey completed in December 1988 on the production and employment of PhDs and faculty in PhD-granting computer science/engineering departments during the 1987-8 academic year. All 127 computer science (CS) departments (115 US and 12 Canadian) participated. In addition, 34 departments offering the PhD in computer engineering (CE) were included. Throughout the report. CE statistics are reported separately so that comparisons with previous years can be made for CS. The intent is to merge all statistics for CS and CE after several years     

Semiconductor-insulator structures in the phototargets of vidicons sensitive in the middle infrared region of the spectrum

The kinetics of electronic processes in vidicon phototargets based on semiconductor-insulator structures with a narrow-gap semiconductor is considered taking into account charge drain in the insulator layer and relaxation of the nonequilibrium depletion region in the semiconductor layer. The integration time, threshold sensitivity, and resolution at various intensities of incident radiation are estimated.     

Field observations on the occurrence of new indicators of disinfection efficiency

This paper summarizes studies on the presence of acid-fast and yeast organisms in wastewater and water treatment plants and in surface water. These organisms were found to satisfy three of Bonde's criteria for indicator organisms: presence whenever pathogens are likely to be present; resistance at least equal to that of pathogens; and lack of regrowth in the post-treatment environment. This, plus prior data, indicates that these organisms are at least as acceptable as indicators of disinfection efficiency than the coliform group.