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Gond, V., Bartholome, E., Ouattara, F., Nonguierma, A., & Bado, L. (2004). Monitoring and mapping of waters and wetlands in arid regions using the SPOT-4 VEGETATION imaging system. Int. J. Remote Sens., 25(5), 987–1004.
Abstract: Monitoring the state of small waterbodies and wetlands is very useful in dry regions, because their existence is entirely controlled by the rhythm of local rainfall. On VEGETATION image colour composites, waterbodies and marshy vegetation show up clearly. Yet simple image classification does not yield sufficiently good results because 'spectral signatures' vary significantly together with the ecological conditions of these surfaces. A robust contextual procedure taking into account local contrast was successfully developed and tested. A systematic validation was carried out and a map of waterbodies and wetlands was produced for Burkina Faso and neighbouring regions.
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Lebrini, M., Roos, C., Vezin, H., & Robert, F. (2011). Electrochemical and theoretical studies of adsorption of some indole derivates at C38 Steel/Sulfuric acid interface as corrosion inhibitors. Int.J.Electrochem.Sci., 6(9), 3844–3857.
Abstract: The inhibitive action of 9H-pyrido[3,4-b]indole (norharmane) and 1-Methyl-9H-pyrido[3,4-b]indole (harmane) on corrosion of C38 steel in 0.5 M H2SO4 solution was investigated through electrochemical techniques. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution for all concentrations studied. Polarization measurements indicate that the examined compounds act as a mixed inhibitor and its inhibition efficiency increases with inhibitor concentration. Data obtained from ac impedance technique show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE), has been used. The adsorption of used compounds on the steel surface obeys Langmuir's isotherm. The ΔG°ads values were calculated and discussed for both inhibitors. Significant correlations are obtained between inhibition efficiency and quantum chemical parameters using quantitative structure-activity relationship (QSAR) method. © 2011 by ESG.
Keywords: Acidic media; Adsorption; C38 steel; Corrosion inhibitors; Theoretical calculations
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Faustin, M., Lebrini, M., Robert, F., & Roos, C. (2011). Corrosion studies of C38 steel by alkaloids extract of a tropical plant type. Int.J.Electrochem.Sci., 6(9), 4095–4113.
Abstract: Alkaloids extract of Aspidosperma album was tested as corrosion inhibitor for C38 steel in 1 M HCl by using polarization and electrochemical impedance spectroscopy (EIS). Potentiodynamic polarization curves indicated that the plant extract behaves as mixed-type inhibitors. Impedance measurements showed that the double-layer capacitance decreased and charge-transfer resistance increased with increase in the inhibitors concentration and hence increasing in inhibition efficiency. The effect of temperature on the corrosion behavior of C38 steel in 1 M HCl with and without addition of plant extract was studied in the temperature range 25 – 55°C. The adsorption of the inhibitor molecules was in accordance with the Langmuir adsorption isotherm. The results obtained show that this plant extract could serve as an effective inhibitor for the corrosion of C38 steel in hydrochloric acid. © 2011 by ESG.
Keywords: Acidic media; C38 steel; Corrosion inhibitor; Plant extract
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Lecante, A., Robert, F., Lebrini, M., & Roos, C. (2011). Inhibitive Effect of Siparuna Guianensis Extracts on the Corrosion of Low Carbon Steel in Acidic Media. Int.J.Electrochem.Sci., 6(11), 5249–5264.
Abstract: The present study examines the effect of alkaloids extract from Siparuna guianensis leaves and stems on corrosion of C38 steel in 0.1 M HCl using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization technique and Raman spectroscopy. The protection efficiency is better with stems alkaloids extract. The inhibition was assumed to occur via adsorption of inhibitor molecules on the metal surface. The influence of stems alkaloids extract concentration on corrosion of low carbon steel in 0.1 M HCl was studied. The inhibition efficiency obtained from impedance and polarization measurements was in a good agreement and was found to increase with increasing concentration of alkaloids extract up to 50 mg/L for stems extract. The adsorption of the extract on the low carbon steel surface obeys the Langmuir adsorption.
Keywords: Alkaloids extract; corrosion inhibition; C38 steel; EIS; raman spectroscopy
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Ntienoue, J. K., Reguer, A., Robert, F., Nait-Rabah, O., & Roos, C. (2013). Electrochemical behaviour of a super austenitic stainless steel in amazonian aqueous environment. Int.J.Electrochem.Sci., 8(4), 4761–4775.
Abstract: The electrochemical behaviour of 254 SMO super austenitic stainless steel in natural seawater collected from river mouth of French Guiana was investigated. A comparative study of samples immersed during 22 days in this environment was made including influences of scraped biofilm introduced in experiments and of stirring. Electrochemical measurements – open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and linear polarisation (LP) – are used to characterize the metal/medium interface included biofilms adhesion. The EDX analysis (EDAX system) shows that the chemical composition of adhered biofilm consists mostly of iron, oxygen, silicon and aluminium and seem preferentially bind on metal defects. © 2013 by ESG.
Keywords: Cyclic voltammetry; Eis; Esem; Passive films; Stainless steel
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Vastra, M., Salvin, P., & Roos, C. (2016). MIC of carbon steel in Amazonian environment: Electrochemical, biological and surface analyses. International Biodeterioration and Biodegradation, 112, 98–107.
Abstract: In this study, the corrosion of S355 carbon steel was monitored for 50 days in equatorial environment. The experiments were conducted under three complementary approaches in a natural environment: (i) bacterial diversity was assessed with Miseq sequencing, (ii) observations of the surface and identifications of deposit compounds were realised with scanning electron microscopy (SEM), Raman spectrometry and EDX analyses, (iii) electrochemical measurements were used to calculate corrosion rate and to identify the phenomena which control corrosion. The results showed that the bacterial population had changed over immersion time from a dominance of β-proteobacteria to α-proteobacteria. This evolution decreased charge transfer resistance at the metal/deposit from 41.6 to 20.8 Ω/cm2 in 50 days, caused an increase in the corrosion rate by a factor of 2, from 0.13 to 0.27 mm/year. Surface analyses showed a progressive appearance of MIC markers in the deposit such as iron sulphide and manganese oxides that were detected after 30 days of immersion in the natural environment. In conclusion, this study describes in detail, the first stage of MIC activity on carbon steel surface in an equatorial brackish water, under aerobic conditions. © 2016 Elsevier Ltd.
Keywords: Biology; Electrochemistry; Mic; Short term; Surface analyses
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Leba, L. - J., Popovici, J., Estevez, Y., Pelleau, S., Legrand, E., Musset, L., et al. (2017). Antiplasmodial activities of dyes against Plasmodium falciparum asexual and sexual stages: Contrasted uptakes of triarylmethanes Brilliant green, Green S (E142), and Patent Blue V (E131) by erythrocytes. International Journal for Parasitology: Drugs and Drug Resistance, 7(3), 314–320.
Abstract: The search for safe antimalarial compounds acting against asexual symptom-responsible stages and sexual transmission-responsible forms of Plasmodium species is one of the major challenges in malaria elimination programs. So far, among current drugs approved for human use, only primaquine has transmission-blocking activity. The discovery of small molecules targeting different Plasmodium falciparum life stages remains a priority in antimalarial drug research. In this context, several independent studies have recently reported antiplasmodial and transmission-blocking activities of commonly used stains, dyes and fluorescent probes against P. falciparum including chloroquine-resistant isolates. Herein we have studied the antimalarial activities of dyes with different scaffold and we report that the triarylmethane dye (TRAM) Brilliant green inhibits the growth of asexual stages (IC50 ≤ 2 μM) and has exflagellation-blocking activity (IC50 ≤ 800 nM) against P. falciparum reference strains (3D7, 7G8) and chloroquine-resistant clinical isolate (Q206). In a second step we have investigated the antiplasmodial activities of two polysulfonated triarylmethane food dyes. Green S (E142) is weakly active against P. falciparum asexual stage (IC50 ≃ 17 μM) whereas Patent Blue V (E131) is inactive in both antimalarial assays. By applying liquid chromatography techniques for the culture supernatant analysis after cell washings and lysis, we report the detection of Brilliant green in erythrocytes, the selective uptake of Green S (E142) by infected erythrocytes, whereas Patent Blue V (E131) could not be detected within non-infected and 3D7-infected erythrocytes. Overall, our results suggest that two polysulfonated food dyes might display different affinity with transporters or channels on infected RBC membrane. © 2017 The Authors
Keywords: Antimalarial dyes; Brilliant green; Drug uptake; Food dyes; Transmission blocking; Triarylmethanes
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Fayad, I., Baghdadi, N., Guitet, S., Bailly, J. - S., Herault, B., Gond, V., et al. (2016). Aboveground biomass mapping in French Guiana by combining remote sensing, forest inventories and environmental data. International Journal of Applied Earth Observation and Geoinformation, 52, 502–514.
Abstract: Mapping forest aboveground biomass (AGB) has become an important task, particularly for the reporting of carbon stocks and changes. AGB can be mapped using synthetic aperture radar data (SAR) or passive optical data. However, these data are insensitive to high AGB levels (>150 Mg/ha, and >300 Mg/ha for P-band), which are commonly found in tropical forests. Studies have mapped the rough variations in AGB by combining optical and environmental data at regional and global scales. Nevertheless, these maps cannot represent local variations in AGB in tropical forests. In this paper, we hypothesize that the problem of misrepresenting local variations in AGB and AGB estimation with good precision occurs because of both methodological limits (signal saturation or dilution bias) and a lack of adequate calibration data in this range of AGB values. We test this hypothesis by developing a calibrated regression model to predict variations in high AGB values (mean >300 Mg/ha) in French Guiana by a methodological approach for spatial extrapolation with data from the optical geoscience laser altimeter system (GLAS), forest inventories, radar, optics, and environmental variables for spatial inter- and extrapolation. Given their higher point count, GLAS data allow a wider coverage of AGB values. We find that the metrics from GLAS footprints are correlated with field AGB estimations (R2 = 0.54, RMSE = 48.3 Mg/ha) with no bias for high values. First, predictive models, including remote-sensing, environmental variables and spatial correlation functions, allow us to obtain “wall-to-wall” AGB maps over French Guiana with an RMSE for the in situ AGB estimates of ∼50 Mg/ha and R2 = 0.66 at a 1-km grid size. We conclude that a calibrated regression model based on GLAS with dependent environmental data can produce good AGB predictions even for high AGB values if the calibration data fit the AGB range. We also demonstrate that small temporal and spatial mismatches between field data and GLAS footprints are not a problem for regional and global calibrated regression models because field data aim to predict large and deep tendencies in AGB variations from environmental gradients and do not aim to represent high but stochastic and temporally limited variations from forest dynamics. Thus, we advocate including a greater variety of data, even if less precise and shifted, to better represent high AGB values in global models and to improve the fitting of these models for high values. © 2016 Elsevier B.V.
Keywords: Aboveground biomass mapping; Forests; French Guiana; ICESat GLAS; LiDAR
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Djenontin Tindo, S., Amusant, N., Dangou, J., Wotto, D. V., Avlessi, F., Dahouénon-Ahoussi, E., et al. (2012). Screening of Repellent, Termiticidal and Preventive activities on Wood, of Azadirachta indica and Carapa procera (Meliaceae) seeds oils. ISCA J. Biological Sci., 1(3), 25–29.
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Peay, K. G., Baraloto, C., & Fine, P. V. A. (2013). Strong coupling of plant and fungal community structure across western Amazonian rainforests. Isme J., 7(9), 1852–1861.
Abstract: The Amazon basin harbors a diverse ecological community that has a critical role in the maintenance of the biosphere. Although plant and animal communities have received much attention, basic information is lacking for fungal or prokaryotic communities. This is despite the fact that recent ecological studies have suggested a prominent role for interactions with soil fungi in structuring the diversity and abundance of tropical rainforest trees. In this study, we characterize soil fungal communities across three major tropical forest types in the western Amazon basin (terra firme, seasonally flooded and white sand) using 454 pyrosequencing. Using these data, we examine the relationship between fungal diversity and tree species richness, and between fungal community composition and tree species composition, soil environment and spatial proximity. We find that the fungal community in these ecosystems is diverse, with high degrees of spatial variability related to forest type. We also find strong correlations between α- and β-diversity of soil fungi and trees. Both fungal and plant community β-diversity were also correlated with differences in environmental conditions. The correlation between plant and fungal richness was stronger in fungal lineages known for biotrophic strategies (for example, pathogens, mycorrhizas) compared with a lineage known primarily for saprotrophy (yeasts), suggesting that this coupling is, at least in part, due to direct plant-fungal interactions. These data provide a much-needed look at an understudied dimension of the biota in an important ecosystem and supports the hypothesis that fungal communities are involved in the regulation of tropical tree diversity. © 2013 International Society for Microbial Ecology.
Keywords: coexistence; diversity; Janzen-Connell; natural enemies; negative feedback
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