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  • Author or Editor: J. Millet x
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Abstract  

The transformation of VOHPO40.5H2O (VPO) precursor doped with cobalt or iron for n-butane oxidation to maleic anhydride was investigated by thermogravimetric analysis under air and nitrogen, with and without n-butane in the flow. While almost no effect was observed in nitrogen or air, a strong influence of the doping was observed when n-butane was added to the nitrogen or air. This resulted in a delay of the decomposition of the precursor and a further reoxidation of the VPO catalyst, particularly for doping with cobalt at low percentage (1%). This shows that doping can change the oxidation state of vanadium phosphorus oxide catalysts, which can explain differences in their catalytic performances and the favourable effect of doping by cobalt.

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The solid ⇌ solid equilibria in the binary system Ca3(PO4)2-CaNaPO4 have been studied. Different diagrams have been proposed for this system. The differences relate to the limits of the field of existence of a non-stoichiometric phase (phase A) stable at high temperature and undergoing eutectoid decomposition during cooling; they can be explained by the existence of two metastable equilibria diagrams which are superposed in the stable diagram. These metastabilities depend on both the cooling rates and the maximum temperatures reached before this cooling.

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The phase diagram of solid-solid equilibria in the system Ca3(PO4)-CaNaPO4 has been studied by thermal analysis. The results are confirmed by X-ray diffraction at different temperatures. This study was limited to that of mixtures in a temperature range determined by previous results. The present work confirms the existence of two metastable diagrams which are superimposed on the stable diagram.

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Otitis externa in dogs and cats is always caused by a combination of yeasts and bacteria, among which the most important are Malassezia pachydermatis, Staphylococcus intermedius and Pseudomonas species. These organisms often develop resistance to classical antimicrobial agents. Therefore, the aim of this study was to investigate the antimicrobial activities of an ethyl acetate leaf extract of Harungana madagascariensis against the organisms cited, to carry out the phytochemical investigation of this extract and to determine its bioactive chemical class using dilution techniques, the bioautography method and the standard phytochemical method described by Harborne (1973). Phytochemical analysis revealed the presence of saponins, tannins, flavonoids, alkaloids and anthracenic derivatives. The bioassay showed that the antimicrobial properties may be attributed to astilbin, a flavanone derivative identified on the basis of its spectroscopic data. The results suggest that the extract could be used in an antimicrobial preparation effective against the whole range of organisms incriminated in otitis externa in dogs and cats, with a minimal inhibitory concentration (MIC) of 250 μg/ml.

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