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 biofilm

Evolution of Linear Absorption and Nonlinear Optical Properties in V-Shaped Ruthenium(II)-Based Chromophores

In this article, we describe a series of complexes with electron-rich cis-{Ru^(II)(NH_3)_4}^(2+) centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845−4859). They have been isolated as their PF_6− salts and characterized by using various techniques including ^1H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru^(III/II) waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities β have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d → π^* metal-to-ligand charge-transfer (MLCT) and π → π^* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant β_0 responses as high as ca. 600 × 10^(−30) esu. These pseudo-C_(2v) chromophores show two substantial components of the β tensor, β_(zzz) and β_(zyy), although the relative significance of these varies with the physical method applied. According to HRS, β_(zzz) dominates in all cases, whereas the Stark analyses indicate that β_(zyy) is dominant in the shorter chromophores, but β_(zzz) and β_(zyy) are similar for the extended species. In contrast, finite field calculations predict that β_(zyy) is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand π-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al. J. Am. Chem. Soc. 2004, 126, 3880−3891)

Enhanced tumour antiangiogenic effects when combining gefitinib with the antivascular agent ZD6126

Current experimental and clinical knowledge supports the optimisation of endothelial cell targeting using a strategy combining anti-EGFR drugs with antivascular agents. The purpose of the present study was to examine the effects of the association of ZD6126, an antivascular microtubule-destabilising agent, with gefitinib and irradiation on the growth of six head and neck human cancer cell lines xenografted in nude mice and to study predictive and molecular factors responsible for antitumour effects. CAL33- and Hep-2-grafted cell lines were the most sensitive to ZD6126 treatment, with VEGF levels significantly higher (P=0.0336) in these tumour xenografts compared to Detroit 562- and CAL27-grafted cell lines with relatively low VEGF levels that were not sensitive to ZD6126. In contrast, neither IL8 levels nor EGFR expression was linked to the antitumour effects of ZD6126. ZD6126 in combination with gefitinib resulted in a synergistic cytotoxic interaction with greater antitumour effects than gefitinib alone. The synergistic interaction between ZD6126 and gefitinib was corroborated by a significant decrease in CD31 labelling. The present study may serve for future innovative clinical applications, as it suggests that VEGF tumour levels are possible predictors for ZD6126 antitumour efficacy. It also supports the notion of antitumour supra-additivity when combining gefitinib and ZD6126, and identifies neoangiogenesis as the main determinant of this synergistic combination

The Relative Importance of Topography and RGD Ligand Density for Endothelial Cell Adhesion

The morphology and function of endothelial cells depends on the physical and chemical characteristics of the extracellular environment. Here, we designed silicon surfaces on which topographical features and surface densities of the integrin binding peptide arginine-glycine-aspartic acid (RGD) could be independently controlled. We used these surfaces to investigate the relative importance of the surface chemistry of ligand presentation versus surface topography in endothelial cell adhesion. We compared cell adhesion, spreading and migration on surfaces with nano- to micro-scaled pyramids and average densities of 6×102–6×1011 RGD/mm2. We found that fewer cells adhered onto rough than flat surfaces and that the optimal average RGD density for cell adhesion was 6×105 RGD/mm2 on flat surfaces and substrata with nano-scaled roughness. Only on surfaces with micro-scaled pyramids did the topography hinder cell migration and a lower average RGD density was optimal for adhesion. In contrast, cell spreading was greatest on surfaces with 6×108 RGD/mm2 irrespectively of presence of feature and their size. In summary, our data suggest that the size of pyramids predominately control the number of endothelial cells that adhere to the substratum but the average RGD density governs the degree of cell spreading and length of focal adhesion within adherent cells. The data points towards a two-step model of cell adhesion: the initial contact of cells with a substratum may be guided by the topography while the engagement of cell surface receptors is predominately controlled by the surface chemistry

Municipal Waste Selection and Disposal: Evidences from Lombardy

This article exploit a data base of 1.522 observations related to Lombardy’s municipalities to run a cross sectional estimation of the drivers of MW selection. We find no evidence of a significant correlation between the percentage of selected MW selection and market variables such as the unit charge for waste management, a result probably affected by the high degree of integration existing in Lombardy among collectors and disposal operators. On the contrary, we discover robust and significant correlation with a set of geographical, socio-economic, and political variables. Among the latter ones, we have a confirmations on the influence of party competition on the percentage of household recycling, with the left wing ruling parties more addressed to it than the rivals, and on the high correlation existing between MW selection and the implementation of a unit pricing scheme. Other positive correlations with the independent variable are shown by per-capita income, while quite surprisingly the education level of citizens seems to play no role

Opérations de maîtrise des pollutions dans les élevages de 1987 à 1993 : analyse des travaux et des coûts. Résultats dans quelques départements français

Local operations aimed at reducing animal wastes took place in France from 1987 to 1993. These operations vary in their goal, their financing and their duration, but they all bring some help to farmers constructing installations on their farms. The analysis of this aid to reduce animal wastes in the 12 studied departments, shows a large variability in the unit cost of the undertaken installations. This variability may be explained by the size of the built installations, and the materials used; big differences in the technical choices for the realization of these installations in the various departments. A more precise analysis of the files describing, in detail, the installations and the costs, provides a good indication of the cost of the main types of installations. A reference unit price for each main type of installation has been provided from the information contained in these files. Given the size of the control program (PMPOA), there is an uncertainty on the prices evolution, which need to be monitored. A cost observation center may be the measurement tool for this evolution. Some indications are provided to quickly compare, for a large number of files, installations per type, to evaluate the yearly cost variations of each type of installation, and to promote the most efficient and cheapest technical solutions. / Des opérations locales visant à réduire la pollution due aux élevages ont été menées en France de 1987 à 1993. Ces opérations diffèrent par leurs objectifs, leurs financements, leurs durées, mais elles apportent toutes une aide aux éleveurs pour la réalisation d'ouvrages au siège d'exploitation. Le dépouillement des dossiers d'aide à cette réduction des pollutions dues aux élevages dans les 12 départements étudiés a permis de mettre en évidence une très grande variabilité du coût unitaire des travaux. Cette varabilité peut être expliquée par : la taille des ouvrages construits et les matériaux employés ; de grandes différences dans les choix techniques pour les réalisations d'ouvrages selon les départements. Une analyse plus précise des dossiers comportant une description détaillée des ouvrages réalisés et des coûts permet cependant de dégager des ordres de grandeur significatifs du coût des principaux types d'ouvrages. Un coût unitaire de référence, par grand type d'ouvrage a pu être établi d'après les informations contenues dans ces dossiers. Compte tenu de l'ampleur du programme de maîtrise (PMPOA), il existe une incertitude sur l'évolution des prix, qu'il apparaît nécessaire de suivre. Un observatoire des coûts peut être l'instrument de mesure de cette évolution. Des indications sont fournies permettant de comparer rapidement, sur un nombre important de dossiers, des ouvrages par types, de dégager les variations annuelles du coût de chaque type d'ouvrage, et de promouvoir les solutions techniques les plus efficaces au meilleur coût

Influence of stainless steel surface treatment on the oxygen reduction reaction in seawater

cited By 105International audienceThe oxygen reduction reaction on stainless steels (SSs) was studied in natural seawater with a rotating disk electrode and a rotating ring-disk electrode. Different surface treatments have been performed: prereduction, polishing, passivation and chemical treatment. X-ray photoelectron spectroscopy has been used to characterize the oxide films. The processes of O2 reduction are markedly influenced by the surface oxides and the reduction rate increases in the following order: chemically treated surface<passivated surface<mechanically polished surface<prereduced surface. An effect of the content of iron (FeII) in the oxide films and of Ni are suggested. On prereduced surfaces, O2 is reduced mainly through the four electron pathway, whereas the 2e- and 4e- occur on polished SS. On prereduced and on polished surfaces, O2 reduction is limited by the mass transport in the solution. On passivated surfaces, the oxygen reduction is not limited by the mass transport in the solution. It may be due to a limited access of oxygen to the metal surface and/or to a modification of the electronic conductivity of the oxide film. In both cases, about 10% and 20% of oxygen is reduced to hydrogen peroxide. On passivated surfaces, O2 reduction occurs simultaneously with the reduction of ferric oxide