Utilisation De La Radiographie De La Gammadensimetrie Et Du Microscope Electronique A Balayage Pour L’etude Des Sediments Marins. Interet Pour La Geologie De L’ingenieur

Résumé Ce travail montre l’application de nouvelles méthodes sédimentologiques pour l’étude des faciès macroscopiques (échelle 1/1), par radiographie des carottes, et de la structure microscopique par microscope électronique à balayage sur des vases préalablement lyophilisées. La gammadensimétrie est de même largement utilisée. Une abondante illustration montre les principaux faciès observés. On tente de les relier aux propriétés physiques des sédiments.

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On this paper some new sedimentological methods are applied for studying the macroscopic structures (1/1 scale) by radiography of the long cores, and microscopic textures by Scanning Electron Microscopy on formerly dry freezed muds. Gammadensimetry is till largerly used in these studies. The main observed types are copiously illustrated and related to the properties of sediments.

     

Causes of Instability and Aging of Piezoelectric Power Ceramics

A simple model of substituted perovskites of the PZT type involving the presence of centers which can act both as donors and acceptors provides an explanation of the cancellation of space charge density (ρ=−div     ) in polarized ceramics. A cause of instability can be avoided by incorporating substitutions in the cation lattice to form these centers and lock them in position. These substitutions insure the nonconductive state of the material although they allow a short-range electron transfer between the centers.     

Immunocytochemical localization of lingual lipase in serous cells of the developing rat tongue

The ontogeny of the rat lingual serous and mucous glands was explored by light and electron immune microscopy using the peroxidase-antiperoxidase and streptavidin-gold techniques. Tissues from fetal and neonatal rats from day 18 of gestation through 4 wk after birth were fixed and embedded in paraffin or Epon for light and transmission electron microscopy, respectively. Electron microscopy revealed that the only cells containing lingual lipase were the developing serous cells; secretory granules containing lingual lipase of varying degrees of maturity were seen. Mucous cells did not show immunospecific staining in rats of any age. The neonatal “mixed” lingual glands secrete lingual lipase from serous components immediately after birth to aid in fat digestion.     

Computer-assisted experimental design for the optimization of electrostatic separation processes

Electrostatic separation is a typical multifactorial process. Its efficiency depends on the characteristics of the granular mixtures to be sorted, the feed rate, the configuration of the electrode system, the applied high voltage, the environmental conditions, and so on. The aim of this paper is to demonstrate the usefulness of computer-assisted experimental design in the optimization of such a process. The example analyzed in the paper was suggested by a typical application of electrostatic separation technique in the recycling industry: the selective sorting of metals and insulating materials from chopped wire and cable waste. The objective was to maximize the benefits from the recycling of both constituents of a binary copper-polyvinyl chloride granular mixture. A preliminary set of electrostatic separation tests, performed on a custom-designed laboratory unit, guided the choice of the starting values of the parameters considered in the computer-assisted experimental procedure of process optimization. The results of a first experiment, carried out in conformity with a fractional factorial scheme, were used for the computation of the coefficients of a linear mathematical model of the electrostatic process. The model was then employed to predict the values of the operating variables for which the optimum of the process is attained. A second experiment was performed in order to confirm the accuracy of the prediction. The procedure presented in this paper and the accompanying computer programs can be easily adapted to other electrostatic process applications.     

Effects of ionizing treatments on packaging -food simulant combinations

Research relating to ionizing treatment has been carried out on ‘food simulants polyethylene film’ combinations. Pouches have been irradiated by gamma photons or accelerated electrons at a 10kGy dose. Overall, the migration test has given some interesting results, particularly in the case of acid simulant, where a limit of validity has been found for the overall migration method. Many radiolytic products and degradation reactions have been indicated, and it has been established that the high permeability of packaging film to oxygen had influenced the radiolytic product yields. The results show some interactions between packaging film and food simulant under irradiation conditions.     

Etude du diagramme de phases et cristallogenese des phosphovanadates de plomb

The phase diagram of lead phosphovanadate Pb₃(P_xV_1?xO₄)₂ for 0.5 ≤ x ≤ 1 has been investigated. Liquidus and solidus have been determined by means of differential thermal analysis and X-ray techniques. These results are confirmed through a molecular absorption spectrophotometry analysis of phosphor and vanadium, by comparing the compositions of lead phosphovanadate single crystals, grown by Czochralski pulling, with that of the starting melts. Good optical and crystallographic quality crystals of large size are obtained for x = 0 and x = 0.5, while for other compositions, they are still suitable for physical measurements. A definite, congruently melting compound with trigonal symmetry at room temperature is found for x = 0.5.