Application of ToF-SIMS for sulfur isotopic fractionation in sulfide phases of iron corrosion layers: determination of bacterial impact on the formation of these phases

International audienceTo a better understanding of the iron corrosion mechanisms, it is crucial to elucidate the role of bacteria. Thus, in order to have a diagnosis of the action of bacteria in the iron corrosion, the objective of this study is to determine by ToF-SIMS the isotopic sulfur fractionation δ 34 S in iron sulfides of (sub)micrometric size located in the corrosion product layers of the ferrous objects corroded in anoxic soils and marine environment. These iron sulfides may have two origins: an abiotic origin resulting in the dissolution/reprecipitation of sulfides from the surrounding medium (for example from pyrite in a soil) or a biotic origin by the action of the sulfate-reducing bacteria that reduce sulfate ions into sulfides leading to the formation of iron sulfides with ferrous ions issued from the aqueous dissolution of metal iron. A difference in the isotopic sulfur fractionation δ 34 S in the sulfur phases according to the abiotic or biotic origin of these phases is reported in the literature. Thus in this study, the isotopic sulfur fractionation δ 34 S in the iron sulfides formed in the corrosion product layers of iron was determined to identify the formation origin of these phases and the role of bacteria in the iron corrosion. After characterization of the distribution of the different iron sulfides within the layers (optical microscopy, SEM-EDS, μRaman spectroscopy), the local isotopic fractionation of sulfur is measured by the imaging and spectroscopy ToF-SIMS technique. Some important results have been obtained. First of all, the reproducibility and the accuracy of the method were established by the choice and the validation of a hydrothermal pyrite sample calibrated relatively to the international sulfur isotopic standard Canon Diablo Troilite. Secondly, it was observed that there was no or little variation in the isotopic sulfur fractionation δ 34 S with the degree of oxidation of sulfur. Finally, a noticeable difference in the isotopic sulfur fractionation δ 34 S between iron sulfides formed in laboratory under abiotic or biotic conditions was evidenced: δ 34 S is close to 0 in abiotic conditions whereas in biotic conditions it is shifted from 0 with values up to up to some tens per mil. These first results being promising, the study is actually in progress to determine the formation origin (abiotic/biotic) of the Fe-S present in the corrosion product layers of natural systems of iron corrosion, from soils, subaquatic and marine environments

Access to artesunate-amodiaquine, quinine and other anti-malarials: policy and markets in Burundi

BACKGROUND: Malaria is the leading cause of morbidity and mortality in post-conflict Burundi. To counter the increasing challenge of anti-malarial drug resistance and improve highly effective treatment Burundi adopted artesunate-amodiaquine (AS-AQ) as first-line treatment for uncomplicated Plasmodium falciparum malaria and oral quinine as second-line treatment in its national treatment policy in 2003. Uptake of this policy in the public, private and non-governmental (NGO) retail market sectors of Burundi is relatively unknown. This study was conducted to evaluate access to national policy recommended anti-malarials. METHODS: Adapting a standardized methodology developed by Health Action International/World Health Organization (HAI/WHO), a cross-sectional survey of 70 (24 public, 36 private, and 10 NGO) medicine outlets was conducted in three regions of Burundi, representing different levels of transmission of malaria. The availability on day of the survey, the median prices, and affordability (in terms of number of days' wages to purchase treatment) of AS-AQ, quinine and other anti-malarials were calculated. RESULTS: Anti-malarials were stocked in all outlets surveyed. AS-AQ was available in 87.5%, 33.3%, and 90% of public, private, and NGO retail outlets, respectively. Quinine was the most common anti-malarial found in all outlet types. Non-policy recommended anti-malarials were mainly found in the private outlets (38.9%) compared to public (4.2%) and NGO (0%) outlets. The median price of a course of AS-AQ was US$0.16 (200 Burundi Francs, FBu) for the public and NGO markets, and 3.5-fold higher in the private sector (US$0.56 or 700 FBu). Quinine tablets were similarly priced in the public (US$1.53 or 1,892.50 FBu), private and NGO sectors (both US$1.61 or 2,000 FBu). Non-policy anti-malarials were priced 50-fold higher than the price of AS-AQ in the public sector. A course of AS-AQ was affordable at 0.4 of a day's wage in the public and NGO sectors, whereas, it was equivalent to 1.5 days worth of wages in the private sector. CONCLUSIONS: AS-AQ was widely available and affordable in the public and NGO markets of hard-to-reach post-conflict communities in Burundi. However greater accessibility and affordability of policy recommended anti-malarials in the private market sector is needed to improve country-wide policy uptake

Étude cristallographique et optique d'un certain nombre de minéraux des Pegmatites de Madagascar et de minéraux de l'Oural

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Contribution à l'étude des minéraux des pegmatites de Madagascar. Sur quelques minéraux d'Ambatofotsikely

Duparc Louis, Sabot R., Wunder Max. Contribution à l'étude des minéraux des pegmatites de Madagascar. Sur quelques minéraux d'Ambatofotsikely. In: Bulletin de la Société française de Minéralogie, volume 37, 1, 1914. pp. 19-30