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Kanemite, NaH [Si₂O₄ (OH)₂] • 2H₂O, was found, associated with trona and gaylussite in the interdunary depression of Andjia, on the northeastern edge of Chad Lake. Orthorhombic, D [2h] ⁷˗Pnmb, a₀ = 7.282, b₀ = 20.507, c₀ = 4.956 Å ; V = 740 ų ; Z = 4 ; ρcalc. = 1.933. Strongest lines of the X-ray powder pattern are : 10.3 (10), 4.014 (10), 3.435 (9) ; 3.162 (7), 3.093 (7), 2.480 (8) Å. Biaxial (— ), 2 V = 46°, ng = 1.478 (c), nm = 1.470 (a), np = 1.451 (b) ; dispersion r > v. White spherolites and platy crystals with (010) ; cleavage (010) perfect, (100) good ; hardness 4 ; ρmeas. = 1.926. Chemical composition : SiO₂ = 56.68, Al₂O₃ = 0.40, CaO = 0.20, Na₂O = 13.25, K₂O = 0,10, H₂O (> 280°) = 4.25, H₂O (170°-280°) = 8.45, H₂O (170°) = 16.30, total = 99.63. Differential thermal analysis shows sharp endothermic peaks at 160°, 220°, 600° C and a broad exothermic peak at 655° C. The products of dehydration have been studied. IR spectrum shows absorption bands at 3570, 3445, 1667, 1475, 1170, 1046, 900, 850, 774, 681, 609, 659 and 456 cm⁻¹. The name is taken from Kanem, the region where the salina is located., La kanemite, NaH [Si₂O₄ (OH)₂] • 2H₂O, a été trouvée dans la saline d'Andjia, Kanem, au Tchad, associée au trona et à la gaylussite. Orthorhombique, D [2h] ⁷˗Pnmb, a₀ = 7,282, b₀ = 20,507, c₀ = 4,956 Å ; V = 740 ų ; Z = 4 ; dx = 1,933. Les raies les plus intenses du diagramme de poudre sont : 10,3 (10), 4,014 (10), 3,435 (9), 3,162 (7), 3,093 (7), 2,480 (8) Å. Biaxe (— ), 2 V = 46°, ng = 1,478 (c), nm = 1,470 (a), np = 1,451 (b) ; dispersion r > v. En sphérolites blancs et en cristaux aplatis suivant (010) ; clivage (010) parfait, (100) bon ; dureté ~ 4 ; d[mes.] = 1,926. Composition chimique : SiO₂ = 56,68, Al₂O₃ = 0,40, CaO = 0,20, Na₂O = 13,25, K₂O = 0,10, H₂O (> 280°) = 4,25, H₂O (170°-280)° = 8,45, H₂O (170°) = 16,30, total = 99,63. L'ATD montre des maximums endothermiques à 160°, 220°, 600° C et un maximum exothermique à 655° C. Le spectre d'absorption infrarouge donne les bandes suivantes : 3570, 3445, 1667, 1475, 1170, 1046, 900, 850, 774, 681, 609, 569 et 456 cm⁻¹. Le minéral est nommé d'après la région de Kanem où est situé le gisement type., Johan Zdenek, Maglione Gilbert. La kanemite, nouveau silicate de sodium hydraté de néoformation. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 95, 3, 1972. pp. 371-382.

Lead zirconium titanium oxide (PZT) thin films are used for their ferroelectric and piezoelectric properties. The composition of the PZT is very important for these properties, and may also be influenced by inter- diffusion with the bottom electrode, on which the PZT film has been grown at rather elevated temperature (550°C-600°C). The bottom electrode is essentially made of RuO2 deposited on a chromium adhesion layer which also helps to block oxygen diffusion. A part of the multi-layer device is shown in Figure 1. Since now no comprehensive study concerning rnicroanalysis of the device have been made, the composition of the films as well as the other layers are not precisely known. It is therefore not possible to relate the composition to the functional properties of the device and to optimize the parameters of deposition. It was the aim of this work to study the composition of the Pb(Zr,Ti)O3 layer, and the bottom electrode by mean of energy dispersive X-ray analysis (EDX) and energy electron loss spectroscopy (EELS). The experiments were performed with the Hitachi HF 2000 equipped with a field emission gun located at the EPFL.

A simple geochemical balance of lateritization processes governing the development of several tens of meters of weathering profiles overlain by ferricretes is estimated on the basis of detailed mineralogical and geochemical data. The lateritic weathering mantle of the “Haut–Mbomou” area in Central Africa is composed of different weathering layers described from the base to the top of vertical profiles as a saprolite, a mottled clay layer, a soft nodular layer, a soft ferricrete, and a ferricrete in which kaolinite, gibbsite, goethite, and hematite occur in various quantities. Incongruent dissolution of kaolinite leads to the formation of gibbsite in the upper saprolite, whereas the hematite does not clearly replace the kaolinite according to an epigene process in the upper ferruginous layers of the profiles. Instead, that kaolinite is also transformed into gibbsite according to an incongruent dissolution under hydrated and reducing conditions induced by a relatively humid climatic pattern. The respective relations of the silica, iron, and aluminum balances and the Al substitution rate of the hematite on the one hand, and of RHG [RHG = 100 (hematite/hematite + goethite)] and the kaolinite on the other hand, to the consumption or the release of protons H+ permit differentiation of aggrading ferruginization and degradation processes operating in the different lateritic weathering profiles. The Al substitution rate of the Fe–oxyhydroxides varies according to the nature of lateritization processes, e.g., saprolitic weathering and aggrading ferruginization vs. degradation. The observations and results indicate that the ferruginization process of the weathering materials of parent rocks is not a simple ongoing process as often thought. This suggests that the actual lateritic weathering mantle of the Haut–Mbomou area may result from different stages of weathering and erosion during climatic changes.

In the course of an epidemiologic survey in Ecuador, the following collection of #Leishmania$ stocks was isolated : 28 from patients with clinical signs of leishmaniasis, 2 from sloths, 1 from a dog, and 4 from sand flies. For genetic characterization of these stocks, multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD) were used. Twenty six of the 35 stocks were identified as either #Leishmania (V.) panamensis$ or #L. (V.) guyanensis$, 2 stocks were identified as #L. (V.) braziliensis$, the 2 stocks from sloths showed specific genotypes, and 5 stocks were characterized as hybrids between #L. (V.) braziliensis$ and #L. (V.) guyanensis$. These data show that genetic diversity of #Leishmania$ in Ecuador is high and that #L. (V.) panamensis$/#guyanensis$ is the dominant group in this country. The genetic analysis questioned the distinctness between the two species #L. (V.) panamensis$ and #L. (V.) guyanensis$, since MLEE and RAPD data did not indicate that #L. (V.) panamensis$ and #L. (V.) guyanensis$ correspond to distinct monophyletic lines. Population genetic analysis performed on the #L. (V.) panamensis$/#guyanensis$ group favors the hypothesis of a basically clonal population structure. (Résumé d'auteur)

Analyse des diélectriques commerciaux : fluorescence X, Infrared absorption, EDX, X-ray Diffraction. Détermination des éléments, déduction des composés par détermination des phases de ceux ci. Tout ceci afin de déterminer les éléments responsables de l’adhérence des TF sur acier et titane.

Actes des 25èmes rencontres de l’Association Française pour l’Archéologie du Verre; International audience