On the applicability of the Heliosat-2 method to assess surface solar irradiance in the Intertropical Convergence Zone,French Guiana

Measurements of daily means of surface solar irradiance made at four ground stations in French Guiana are compared to estimates from the HelioClim-3 database produced by the Heliosat-2 method applied to Meteosat satellite images. The bias ranges from 12 W m^?2 (6% of the mean of measurements) to 23 W m^?2 (12%), depending on the stations. The root mean square difference ranges between 23 W m^?2 (11%) and 35 W m^?2 (18%). The correlation coefficient (r) is close to 0.9. Better results are observed during the rainy season than during the dry season. Uncertainties are mainly due to the presence of clouds, large viewing angles of the Meteosat satellite, and limitations of the atmospheric transmittance model under the tropical atmospheric conditions. It is concluded that the Heliosat-2 method provides new knowledge about solar radiation in French Guiana.     

New hypotheses for hydrogenase implication in the corrosion of mild steel

The influence of [Fe]-hydrogenase from Clostridium acetobutylicum was studied on the anaerobic corrosion of mild steel. Two short-circuited mild steel electrodes were exposed to the same solution and hydrogenase was retained on the surface of only one electrode thanks to a dialysis membrane. The galvanic current and the electrode potential were measured as a function of time in order to monitor the difference in electrochemical behaviour induced by the presence of hydrogenase. A sharp potential decrease of around 500 mV was controlled by the deoxygenating phase. When hydrogenase was introduced after complete deoxygenation, significant heterogeneous corrosion was observed under the vivianite deposit on the electrode in contact with hydrogenase, while the other electrode only showed the vivianite deposit, which was analysed by MEB and EDX. The effect of hydrogenase was then confirmed by monitoring the free potential of single coupons exposed or not to the enzyme in a classical cell after complete deoxygenating. In both phosphate and Tris-HCl buffers, the presence of hydrogenase increased the free potential around 60 mV and induced marked general corrosion. It was concluded that [Fe]-hydrogenase acts in the absence of any final electron acceptor by catalysing direct proton reduction on the mild steel surface.     

Electroactive biofilms: new means for electrochemistry

This work demonstrates that electrochemical reactions can be catalysed by the natural biofilms that form on electrode surfaces dipping into drinking water or compost. In drinking water, oxygen reduction was monitored with stainless steel ultra-microelectrodes under constant potential electrolysis at −0.30 V/SCE for 13 days. 16 independent experiments were conducted in drinking water, either pure or with the addition of acetate or dextrose. In most cases, the current increased and reached 1.5–9.5 times the initial current. The current increase was attributed to biofilm forming on the electrode in a similar way to that has been observed in seawater. Epifluorescence microscopy showed that the bacteria size and the biofilm morphology depended on the nutrients added, but no quantitative correlation between biofilm morphology and current was established. In compost, the oxidation process was investigated using a titanium based electrode under constant polarisation in the range 0.10–0.70 V/SCE. It was demonstrated that the indigenous micro-organisms were responsible for the current increase observed after a few days, up to 60 mA m⁻². Adding 10 mm acetate to the compost amplified the current density to 145 mA m⁻² at 0.50 V/SCE. The study suggests that many natural environments, other than marine sediments, waste waters and seawaters that have been predominantly investigated until now, may be able to produce electrochemically active biofilms.     

From technological acceptability to appropriation by users: Methodological steps for device assessment in road safety

This article presents the methodology developed within the framework of the research project SARI (Automated Road Surveillance for Driver and Administrator Information). This methodology is based on the logic of action research. The article presents the different stages in the development of technological innovation addressing vehicle control loss when driving on a curve. The results observed in speed reduction illustrate that no matter how optimal an innovation may be technologically speaking, it is only as effective as it is acceptable from a user standpoint. This acceptability can only be obtained if the technology is developed by engineers in liaison with social science specialists.     

1 H and 29Si NMR Spectroscopy as a Powerful Analytical Tool to Evaluate the Activity of Various Platinum-Based Catalysts in Model Olefin Hydrosilylation

The structure of polysiloxane copolymers obtained by hydrosilylation of 1-octene with polymethylhydrosiloxane (PMHS) was analyzed by ²⁹Si NMR spectroscopy and revealed a tendency to form block copolymers. Although all the platinum catalysts that were used showed a tendency to form some block structures, only Karstedt catalyst led to well defined block copolymers. However, the tacticity of these copolymers could not be determined using Heteronuclear Multiple Bond Correlation (HMBC) 2D (¹H/ ²⁹Si) NMR technique. The following criteria were found to affect the structure of the hydrosilylation product: low SiH conversion, the “age” of the Karstedt catalyst (low TON) and high octene/SiH ratios.     

Solubility and mobility of phosphorus recycled from dairy effluents and pig manures in incubated soils with different characteristics

Phosphorus (P) nutrition of plants in croplands is managed by fertilization. Commercial P fertilizers are manufactured from phosphate rocks, which are non-renewable and the only fossil resource of P. As an alternative, P in human and animal wastes can be recovered and concentrated in products that can be used as P fertilizers. Here, we studied four recycled P products derived from pig manures (hereafter referred as “RPPM”) and another one derived from dairy effluents (“RPDE”). The RPDE product is composed of Ca–P (partly as hydroxyapatite, HA), while RPPM products include recovered struvite (ST) and Ca–P in variable proportions. The objective was to assess the ability of RPPM and RPDE products to increase available P in a range of soils differing in their characteristics (seven soils used), and to compare these recycled P products with a standard fertilizer [commercial triple super phosphates (TSP)], reference HA and reference ST. To this end, products were mixed to the soils and the mixtures were incubated at 75 % water holding capacity and 28 °C. After incubation, the amounts of phosphate ions (iP) in solution (Q_W) and isotopically exchangeable iP (E) in soils were quantified using an isotopic labeling (³²P) and dilution procedure. In each soil, Q_W and E were significantly affected by treatments (control and P-treated soils) and increased due to the application of the different products. However, reference HA and RPDE products were generally less effective than TSP, reference ST and RPPM products. The soil response (variation in Q_W or E) in TSP treatment was compared to those in other treatments. It enabled the calculation of a relative effectiveness index. Relative effectiveness of HA and RPDE varied among soils (from 5 to 124 %) and increased with decreasing soil pH. Results however showed that the RPDE product tends to be more effective than reference HA, probably due to different degrees of crystallization of Ca–P. Relative effectiveness of RPPM products (80–116 %) was high in all soils and was similar to that of reference ST (90–104 %). To conclude, the present study suggests that RPDE products are effective only in acidic or slightly acidic soils. In contrast, P recycling from pig manures through chemical precipitation can provide effective P fertilizers, independently on soil conditions.     

Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (E_oc) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of E_oc ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended essentially on the nature of the material. This effect was due to the capacity of G. sulfurreducens to create a direct cathodic reaction on steel surfaces, extracting the electrons directly from material. The presence of bacterial cells modified the corrosion features of mild steel and ferritic steel, so that corrosion attacks were gathered in determined zones of the surface. Local corrosion was significantly enhanced on ferritic steel. Potential ennoblement was not sufficient to induce corrosion on austenitic steels. In contrast G. sulfurreducens delayed the occurrence of pitting on 304L steel because of its capability to oxidize acetate at high potential values. The electrochemical behaviour of 304L steel was not affected by the concentration of soluble electron donor (acetate, 1–10 mM) or the amount of planktonic cells; it was directly linked to the biofilm coverage. After polarization pitting curves had been recorded, microscopic observations showed that pits propagated only in the surface zones where cell settlement was the densest. The study evidenced that Geobacter sulfurreducens can control the electrochemical behaviour of steels in complex ways that can lead to severe corrosion. As Geobacteraceae are ubiquitous species in sediments and soils they should now be considered as possible crucial actors in the microbial corrosion of buried equipment.     

Gender stereotypes and superior conformity of the self in a sample of cyclists

In the field of driving, people tend to think they are more competent and more cautious than others. This is the superior conformity of the self (SCS). Our main hypothesis was that, among cyclists, women would show a higher SCS on cautiousness, though men would show a higher SCS concerning competence. 1799 cyclists provided a self-assessment of their own cautiousness and of other people's cautiousness. The same procedure was used for competence. Consistent with the hypothesis, the SCS was gender-specific: it was more prominent for women concerning cautiousness and more prominent for men concerning competence. These results could explain why people tend to ignore the safety campaigns. They also indicate the importance of adapting messages concerning safety measures to gender.     

Treatment of dairy wastes with a microbial anode formed from garden compost

Garden compost has already been identified as a source of efficient electro-active (EA) biofilms. The work described here consisted of lixiviating the compost and then using the leachate as a microbial source. This procedure gave promising results for the treatment of yogurt waste (YW) in a microbial fuel cell (MFC). Experiments performed in MFC set-ups were compared with electrochemical cells under polarization at +0.1 V versus SCE. Different parameters were tested to optimize the microbial anode. Preliminary acclimation of the compost microbial flora to YW was revealed to be unnecessary. Forming biofilms firstly in pure leachate before exposing them to YW showed that high concentrations of this type of substrate were detrimental to current generation. Pre-treatment of the electrode by pre-adsorbing YW led to a 10-fold increase in the current density. The highest current densities were obtained at 40 and 60 °C, revealing the diversity of electro-active microorganisms coming from soils. Values up to 1,450 mA m^?2 were reached at 40 °C.