Modalités du transport des PCB dans la rivière Seine (France)

L'évolution de la pollution et les modalités du transport des P.C.B. en rivière ont été étudiées en Seine à Paris en relation avec les épisodes du cycle hydrologique durant un an.Les résultats analytiques montrent que la pollution occasionnée par les P.C.B. est supérieure à celle produite par les autres résidus de pesticides organochlorés, et ceci malgré la limitation réglementaire d'emploi des P.C.B. aux systèmes clos depuis 1975.Pour 88 % des échantillons analysés, les concentrations en P.C.B. dissous sont supérieures aux teneurs en P.C.B. adsorbés sur M.E.S. et atteignent jusqu'à 170 ng.l-1.Le transport se fait en solution pour 73 %, en moyenne, de la teneur totale, contrairement aux idées admises fondées sur la faible solubilité du polluant, mais qui ne prennent pas en compte le rapport en masse M.E.S./eau voisin de 25 x 10-6 en rivière.L'étude de la capacité d'adsorption des particules démontre qu'elle subit une évolution inverse de celle de la charge solide et du débit, ce qui explique la dominance des P.C.B. en phase aqueuse quelle que soit la teneur en M.E.S. Il en résulte que les valeurs élevées du coefficient de partage ne correspondent pas aux fortes teneurs en M.E.S. Les valeurs sont faibles pour la moitié d'entre elles et comprises entre 2 x 103 et 12 x 103 l.kg-1.The evolution of pollution by PCBs and their transport state in rivers was studied in the River Seine in Paris, in relation to the yearly hydrological cycle.Sampling took place just upstream of main waste waters (output) in the Paris area, and downstream from the junction of the Marne and the Seine, in order to establish the mean quality of water pumped upstream of these two rivers for drinking water production.Micropollutant concentrations were measured on 500 ml of raw water and 500 ml of water centrifuged at 6 000 G. Three extractions were carried out on these samples with a solvent mixture (85 % hexane, 15 % dichloromethane).In some cases extracts were purified on unactivated Florisil. After concentration down to 1 ml, extracts were measured through GC (falling needle injector; fused silica capillry column I.D. 0.25 mm, stationary phase SPB5; E.C.D. ni 63; vector gas He, make up Ar + 10 % CH4).Identification and quantification were carried out using an integrator and commercial Aroclor : 1242, 1254 and 1268 standards. In natural samples, the isomer composition is generally close to that of Aroclor 1254.Analytical data show that pollution linked to PCBs is higher than that due to other organochlorinated products, in spite of the official PCBs use limitation for closed systems since 1975.Except for a pollution peak of 990 ng.l-1, concentrations in raw water are irregular and vary from 25 to 250 ng.l-1.For 88 % of analyzed samples, dissolved PCB concentrations are higher than the concentrations of PCBs adsorbed onto suspended matter and reach 170 ng.1-1. The main transport (73 %) of the total flux is by solution, in contradiction with commonly accepted views based on the low solubility of PCBs.The study of adsorption capacity of solid particles demonstrates that its evolution is negatively correlated with the water flux and the solid load, which explains the prevalence of PCBs transport through solution, whatever the suspended matter concentration. Thereafter, it appears that high values of the partition coefficient are not linked to the concentration of suspended matter. For about half of them, values are low, between 2.102 and 12.101 l.kg-1

Synthesis of new 1- 2-azido-2-(2,4-dichlorophenyl)ethyl -1H/-imidazoles and in vitro evaluation of their antifungal activity

International audienc

q-Generalization of the inverse Fourier transform

A wide class of physical distributions appears to follow the q-Gaussian form, which plays the role of attractor according to a Central Limit Theorem generalized in the presence of specific correlations between the relevant random variables. In the realm of this theorem, a q-generalized Fourier transform plays an important role. We introduce here a method which univocally determines a distribution from the knowledge of its q-Fourier transform and some supplementary information. This procedure involves a recently q-generalized Dirac delta and the class of functions on which it acts. The present method conveniently extends the inverse of the standard Fourier transform, and is therefore expected to be very useful in the study of many complex systems.Comment: 6 pages, 3 figures. To appear in Physics Letters

Energetic flux and performance index in copaiba (Copaifera multijuga Hayne) and mahogany (Swietenia macrophylla King) seedlings grown under two irradiance environments

Plant adaptation under conditions of limited irradiance can be investigated by their efficiency while using the available energy with a minimal thermodynamic energy loss. For this reason, we compared the energetic fluxes and the performance index (PIABS) in copaiba (Copaifera multijuga) and mahogany (Swietenia macrophyla) seedlings under both sunlight and shade. The experiment was carried out in Manaus (3°8′S, 59°52′W), Amazonas State, Brazil. The fluorescence transients were obtained in intact and healthy leaves using a Plant Efficiency Analyser (PEA) between 1200 h and 1300 h. Using the O-J-I-P test, the following parameters were calculated: 1) density of reaction centers per cross section (RC/CS), 2) maximum quantum yield for primary photochemistry of photosystem II (φPo), and 3) probability of energy excitation (ψo) or that of an absorbed photon (φEo) to move an electron further than quinone A, and 4) the performance index (PIABS). The highest PIABS was found in seedlings under shade for both species. Mahogany seedlings exhibited values of PIABS about three-fold and 14-fold higher than copaiba seedlings under shade and sunlight, respectively. For RC/CS, reaction centers were inactive under sunlight, 58% for mahogany and 78% for copaiba. The high irradiance induced a decrease of φPo in mahogany (36%) and in copaiba (69%) when compared to shaded seedlings. This likely was a result of need for excess energy dissipation under sunlight. In addition, it was verified that seedlings under sunlight presented a severe decrease in φEo, particularly in copaiba (23-fold), when compared to mahogany (9-fold). Therefore, mahogany seedlings showed the highest performance in energy use under low and high irradiance, thus it may be proposed that mahogany presented lower entropy than copaiba seedlings, as demonstrated by the higher plasticity in the use of energy

Molecular insights into RmcA-mediated c-di-GMP consumption: Linking redox potential to biofilm morphogenesis in Pseudomonas aeruginosa

The ability of many bacteria to form biofilms contributes to their resilience and makes infections more difficult to treat. Biofilm growth leads to the formation of internal oxygen gradients, creating hypoxic subzones where cellular reducing power accumulates, and metabolic activities can be limited. The pathogen Pseudomonas aeruginosa counteracts the redox imbalance in the hypoxic biofilm subzones by producing redox-active electron shuttles (phenazines) and by secreting extracellular matrix, leading to an increased surface area-to-volume ratio, which favors gas exchange. Matrix production is regulated by the second messenger bis-(3′,5′)-cyclic-dimeric-guanosine monophosphate (c-di-GMP) in response to different environmental cues. RmcA (Redox modulator of c-di-GMP) from P. aeruginosa is a multidomain phosphodiesterase (PDE) that modulates c-di-GMP levels in response to phenazine availability. RmcA can also sense the fermentable carbon source arginine via a periplasmic domain, which is linked via a transmembrane domain to four cytoplasmic Per-Arnt-Sim (PAS) domains followed by a diguanylate cyclase (DGC) and a PDE domain. The biochemical characterization of the cytoplasmic portion of RmcA reported in this work shows that the PAS domain adjacent to the catalytic domain tunes RmcA PDE activity in a redox-dependent manner, by differentially controlling protein conformation in response to FAD or FADH2. This redox-dependent mechanism likely links the redox state of phenazines (via FAD/FADH2 ratio) to matrix production as indicated by a hyperwrinkling phenotype in a macrocolony biofilm assay. This study provides insights into the role of RmcA in transducing cellular redox information into a structural response of the biofilm at the population level. Conditions of resource (i.e. oxygen and nutrient) limitation arise during chronic infection, affecting the cellular redox state and promoting antibiotic tolerance. An understanding of the molecular linkages between condition sensing and biofilm structure is therefore of crucial importance from both biological and engineering standpoints.The authors would like to acknowledge Sapienza University of Rome [RM120172A7AD98EB to SR, RM1221815D52AB32 to APaiardini and AR12117A63EE6037; AR2221816C44C7B3 to CSR] for financial support. AUC experiments have received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004806. We thank Patrick England of the Plateforme de Biophysique Moléculaire of the C2RT (Institut Pasteur) for fruitful discussion

Septic cardiomyopathy

Depression of left ventricular (LV) intrinsic contractility is constant in patients with septic shock. Because most parameters of cardiac function are strongly dependent on afterload, especially in this context, the cardiac performance evaluated at the bedside reflects intrinsic contractility, but also the degree of vasoplegia. Recent advances in echocardiography have allowed better characterization of septic cardiomyopathy. It is always reversible providing the patient's recovery. Unlike classic cardiomyopathy, it is not associated with high filling pressures, for two reasons: improvement in LV compliance and associated right ventricular dysfunction. Although, it is unclear to which extent it affects prognosis, a hyperkinetic state is indicative of a profound and persistent vasoplegia associated with a high mortality rate. Preliminary data suggest that the hemodynamic response to a dobutamine challenge has a prognostic value, but large studies are required to establish whether inotropic drugs should be used to treat this septic cardiac dysfunction