A Narrowband Pulse-Echo Technique for In Vivo Ultrasonic Attenuation Estimation

The principles of a narrowband technique for pulse echo attenuation measurements are presented. Experiments are described which compare the attenuation in tissue-mimicking phantoms, measured by known methods, to the attenuation measured by the present technique. The effects of various experimental parameters on the results are investigated. The attenuation in spleens of canine models and in livers of human volunteers is presented.     

Angular conversion electron Mössbauer spectroscopy (ACEMS) — a method for surface layer study

A method to study the composition and depth distribution of phases present in surface layers of 0–500 Å is described. The method is based on the analysis of the Mössbauer spectra taken by means of conversion electrons emerging at approximately the initial energy at different angles relative to the layer surface.     

Changing the hydrogen content of alloy steel in relation to the technology used to cool cast slabs

Results are reported from the production of two trial heats of alloy steel in which the cast slabs were cooled in a thermostatted chamber and in a dense stack. It is shown that cooling slabs in such a chamber makes it possible to reduce the hydrogen content of the steel 30% compared to slabs that are cooled while stacked.     

Book review

Published in 1989, 585 pages, $180; Available from the American Institute of Chemical Engineers, 345 East 47th St., Publication Sales Department, New York, NY 10017.     

Spouted and spout-fluid bed combustors 1: Devolatilization and combustion of coal volatiles

The devolatilization and volatile combustion of a single coal particle in spouted and spout-fluid beds have been studied. The results showed that the flame extinction time increases with the particle diameter, and decreases with the bed temperature. When the bed temperature and the air flow rate were fixed, the operation modes (spouted or spout-fluid bed) showed less effect on the mean flame extinction time. A mathematical model of the spouted bed mode for preignition and postignition periods has also been developed assuming the devolatilization rate to be controlled by heat transfer and multireaction pyrolysis kinetics based on volatile products. Ignition, heat transfer back from the volatile flame to the particle surface, variation in flame temperature, and the hydrodynamics of SB are taken into account. The model predictions, with some adjusting parameters, were in good agreement with experimental results.     

Facts and figures on interlibrary lending in Dutch-speaking Belgium in 1989

A survey of interlending activities in Dutch-speaking Belgium was taken in order to cordinate future developments. Data on a broad range of topics were collected. The processing of numerical data is outlined. The figures must be put in perspective, due to the presence of estimates. The investigation remains however the first serious attempt to get an overall picture of interlending in Flemish libraries.     

Methods to assess physical activity with special reference tomotion sensors and accelerometers

Motion sensors may be applied for the assessment of physical activity. This paper reviews the evolution of these instruments from the mechanical pedometer to the electronic accelerometer. We conclude that for accurate assessment of physical activity under free living conditions the recently introduced accelerometer looks most promising, although little information was available regarding the reliability of these instruments. Subsequently, reliability of an accelerometer with a three-directional sensor was examined. Intrainstrument variation in a bench test was less than 8% during four measurements over a week. Interinstrument variation during treadmill experiments while subjects wore two accelerometers at the same time was on average 22% and was not improved after adjustment for differences found in the bench test. Reproducibility in the treadmill experiment was approximately 76, 85, and 95% at 3, 5, and 7 km/h, respectively. Bench testing revealed that the sensitivity of a piezoelectric element is prone to shifts, probably due to mechanical, electromagnetic, and/or temperature shock, which may be encountered during outdoor application. However, the relevance of the bench test in this study may be questioned, as results did not correspond with the findings in subjects. This needs further investigation.     

Synthesis and characterisation of N-toluyl methacrylatoethyl carbamates,homopolymers and copolymers with methyl methacrylate

The paper describes the synthesis of N-2/4-toluyl methacrylatoethyl carbamates using 2/4-toluyl isocyanate and 2-hydroxyethyl methacrylate. Homopolymerisation and copolymerisation of these novel monomers with methyl methacrylate was carried out using benzoyl peroxide as an initiator and tetrahydrofuran as solvent. Photopolymerisation of N-4-toluyl methacrylatoethyl carbamate could be carried out without the use of photosensitiser. Structural characterisation of copolymers was done using ¹H-NMR. Thermal stability of copolymers was evaluated in a nitrogen atmosphere by dynamic thermogravimetry.