Effet de la matrice de l'eau sur l'élimination des micropolluants organiques par ozonation. Partie 1. Consommation spécifique de l'ozone dans un réacteur

A partir des réactions possibles entre l'ozone, les radicaux et les principaux composants d'une eau à potabiliser, des formules théoriques de formations de radicaux et de décomposition de l'ozone sont établies. La matière organique est schématisée par les composés qui réagissent avec l'ozone (Si), les initiateurs, les promoteurs et les inhibiteurs de la réaction radicalaire (SIi, Sp,i, Ss,i). La décomposition de l'ozone est ensuite mesurée pour 56 eaux naturelles caractérisées par les analyses suivantes (pH, Absorbance à 254 nm, COT, Alcalinité). En se basant sur les connaissances acquises et les valeurs expérimentales du taux spécifique de consommation de l'ozone w, l'équation théorique est simplifiée et on obtient:-(d[O3]/dt)=([O3](∑kDlSl,i)(∑klDP,i[SP,i])) / ([HCO3-](k9+k10 10pH-10,25))En prenant le COT comme représentatif des [Sp,i] (attaque radicalaire non sélective) et l'absorbance à 254 nm comme representative de SI,i (attaque directe sur les cycles aromatiques), une analyse multifactorielle permet d'obtenir l'expression:log10w = -3,93 + 0,24pH + 0,75 log10 Absorbance à 254 mm + 1,08 log10 COT - 0,19 log10 alcalinitéL'équation ainsi obtenue peut être utilisée dans tous les modèles prédictifs faisant appel aux bilans massiques sur l'oxydant.From the numerous reactions between ozone and other components of raw water in a drinking water plant, we obtain theoretical equations for hydroxy radical concentrations (1) and for the disappearance of ozone (2). Dissolved organic matter is divided in to four components: substances which react with ozone by a direct mechanism (Si), initiators, promotors, and scavengers ofradical reactions (SI,i, SP,i, SS,i). We also take into account the reactions between hydrogen peii*iâô. orThe, and free radicals to simulate advanced oxidation processes.[OH∘]= ([O3]{2k1∙10pH-14+2k2 10pH-11,6 [H2O2] + ∑kdl,i [Sl,i]}) / (klD[P]+[HCO3-] (k9+k10∙10pH-10,25)+∑klDS,i [Ss,i])   (1)-(d[O3])/(dt) = {kD[P]+∑kD,i[Si]+∑kDl,i[Sl,i]+3k110pH-14+k210pH-11,6H2O2]}[O3]+[OH∘]{k8[O3]+[H2O2](k210pH-11,6+K7)+∑klDP,i[SP,i]   (2)For 56 natural water samples, we measured the disappearence of ozone directly in a completely stirred batch reactor. Water samples were characterized by pH, TOC, 254 nm UV absorbance and alkalinity. Kinetics were first order with respect to ozone(d[O3])/(dt) = -w[O3]with w : specific ozone disappearence rate.Each term of equation 2 is discussed and, based on the experimental values of w, a simplified equation 3 obtained :-(d[O3])/(dt) = ([O3](∑kDISl,i)(∑klDP,i[SP,i))/([HCO3](k9+k10 10pH-10,25))The TOC parameter can represent [SP,i] because radical reactions are non selective, where as the 254 nm UV absorbance can represent [Si] because organic matter (Fulvic and Humic acid) can react directly with ozone via its constituent aromatic rings.Using the data set of 56 w values measured in natual water samples, mathematical correlations can be calculated :log10w = -3,93 + 0,24pH + 0,75 log10 Absorbance à 254 mm + 1,08 log10 COT - 0,19 log10 alcalinityA strong correlation between experimental measurements and predicted w values is obtained

Effet de la matrice de l'eau sur l'élimination des micropolluants organiques par ozonation. Partie 2. Simulation de l'élimination d'un micropolluant dans les réacteurs idéaux

L'équation cinétique qui permet de calculer l'oxydation d'un micropolluant dans les réacteurs d'ozonation s'écrit:-(d[P]/dt)=(KD[O3]L+KID[OH∘])[P]Kd et Kid: constantes de vitesse de l'ozone et des radicaux hydroxyles sur le micropolluant P.Dans la première partie, l'approche théorique de la concentration en radicaux hydroxyles a montré que [OH·] est proportionnel à la concentration en ozone ([OH·] = k'[03]). On a donc:(d[P]/dt)=KG[O3]L[P] with KG=KD+KIDK'Dans un réacteur parfaitement agité, les concentrations en ozone et en micropolluant sont constantes et l'élimination s'écrit: ([P]/[Po])=(1/1+KG[O3]L τ) with τ=(V/Q)Dans un réacteur piston, les concentrations varient tout au long de la colonne et il est habituel de modéliser un tel réacteur comme un grand nombre de R.P.A. en série de volume DeltaV et de hauteur DeltaH (Dans notre approche DeltaH = 0,01 m).Dans les deux cas, la simulation de l'élimination du micropolluant est basée sur la connaissance de la valeur de kG et de la concentration en ozone dans l'eau [03]L[03]L est obtenue de la résolution des bilans massiques dans un volume V ou ~V. ozone à l'entrée + ozone transféré = ozone à la sortie + ozone consomméL'ozone transféré utilise pour son calcul des relations semi-empiriques donnant la constante de Henry et la valeur du kLa.L'ozone consommé est déduit de la relation établie dans la partie 1:(d[O3]L/dt)=w[O3]LLes résultats de la simulation sont comparés aux résultats expérimentaux obtenus avec un pesticide organo-phosphoré, le parathion. Les paramètres variables sont le temps de contact (300 - 600 s), le pH (6,7 - 8,2) et le taux de traitement (1 à 5 g/m3).Une valeur de kG comprise entre 500 et 600 M-¹s-¹ donne une bonne corrélation entre les valeurs expérimentales et calculées. Cependant, on peut noter quelques différences, en particulier dans la partie basse de la colonne, ce qui montre la nécessité de prendre en compte pour des calculs plus précis l'hydrodynamique du réacteur. L'emploi du programme de simulation permet de tracer deux abaques qui montrent l'influence pour n'importe quel micropolluant des facteurs kGteta et w.Micropollutant (P) oxidation in an ideal ozonation reactor uses the kinetic équation:(d[P]/dt)=(KD[O3]L+KID[OH∘])[P]kD and kID : kinetic rate constant of ozone and hydroxy radicals on the micro -pollutant P.In part 1, the theoritical équation shows that [OH°] is proportional to the ozone concentration ([OH°] = k'[O3]) and thus the following equation is obtained :(d[P]/dt)=KG[O3]L[P] with KG=KD+KIDK'In a completely stirred tank reactor, ozone concentration in liquid phase is constant and pesticide elimination is given by the equation :([P]/[Po])=(1/1+KG[O3]L τ) with τ=(V/Q)In a plug flow reactor, ozone concentration in liquid phase varies along the column. To modelize them, we use the model of completely stirred tank reactors in series where the unit volume is ∆V. In our calculations, this volume is obtained by S (reactor cross section area) and ∆h equal to 0,01 m. In this volume ∆V, ozone and micropoliutant concentrations are considerad as a constant.Simulation calculations are based on the knowledge of global kinetic constant kG and ozone concentration.The value of the ozone concentration is obtain from mass balances on the oxklant (on a ∆V or V volume reactor) :ozone inlet + transferred ozone = consumed ozone + ozone outletThe quantifies of transferred ozone are calculated from the Henry law and a semi empirical kLa equation.The quantity of consumed ozone is calculated from the equation in part I(d[O3]L/dt)=w[O3]LExperimental results are obtained with parathion, an organo-phosphorus pesticide on a bubble column pilot plant:Parameters are contact time (300-600 s), pH (6,7-8-2) and ozone treatment rate (1 to 5 g/m3).A kG value of 500 or 600 M-l s-l shows a good correlation between predicted and simulated pesticide concentrations.However, there are noticable differences, especially at the bottom of the column. This shows the necessity to take into account the hydrodynamic properties of the reactor during next works. The use of the simulation program lets to calculate the elimination of pesticide versus the two main parameters : the factor kGteta and the value of w

Tree-level scattering amplitudes from the amplituhedron

7 pages, 2 figures, to be published in the Journal of Physics: Conference Series. Proceedings for the "7th Young Researcher Meeting", Torino, 2016A central problem in quantum field theory is the computation of scattering amplitudes. However, traditional methods are impractical to calculate high order phenomenologically relevant observables. Building on a few decades of astonishing progress in developing non-standard computational techniques, it has been recently conjectured that amplitudes in planar N=4 super Yang-Mills are given by the volume of the (dual) amplituhedron. After providing an introduction to the subject at tree-level, we discuss a special class of differential equations obeyed by the corresponding volume forms. In particular, we show how they fix completely the amplituhedron volume for next-to-maximally helicity violating scattering amplitudes.Peer reviewe

Evidence for Hydrodynamic Evolution in Proton-Proton Scattering at LHC Energies

In $pp$ scattering at LHC energies, large numbers of elementary scatterings will contribute significantly, and the corresponding high multiplicity events will be of particular interest. Elementary scatterings are parton ladders, identified with color flux-tubes. In high multiplicity events, many of these flux tubes are produced in the same space region, creating high energy densities. We argue that there are good reasons to employ the successful procedure used for heavy ion collisions: matter is assumed to thermalizes quickly, such that the energy from the flux-tubes can be taken as initial condition for a hydrodynamic expansion. This scenario gets spectacular support from very recent results on Bose-Einstein correlations in $pp$ scattering at 900 GeV at LHC.Comment: 11 pages, 20 figure

Glutathione determination by the Tietze enzymatic recycling assay and its relationship to cellular radiation response.

Large fluctuations in glutathione content were observed on a daily basis using the Tietze enzyme recycling assay in a panel of six human cell lines of varying radiosensitivity. Glutathione content tended to increase to a maximum during exponential cell proliferation, and then decreased at different rates as the cells approached plateau phase. By reference to high-performance liquid chromatography and flow cytometry of the fluorescent bimane derivative we were able to verify that these changes were real. However, the Tietze assay was occasionally unable to detect glutathione in two of our cell lines (MGH-U1 and AT5BIVA), although the other methods indicated its presence. The existence of an inhibitory activity responsible for these anomalies was confirmed through spiking our samples with known amounts of glutathione. We were unable to detect a direct relationship between cellular glutathione concentration and aerobic radiosensitivity in our panel of cell lines

Design and evaluation of the immunogenicity and efficacy of a biomimetic particulate formulation of viral antigens

Subunit viral vaccines are typically not as efficient as live attenuated or inactivated vaccines at inducing protective immune responses. This paper describes an alternative 'biomimetic' technology; whereby viral antigens were formulated around a polymeric shell in a rationally arranged fashion with a surface glycoprotein coated on to the surface and non-structural antigen and adjuvant encapsulated. We evaluated this model using BVDV E2 and NS3 proteins formulated in poly-(D, L-lactic-co-glycolic acid) (PLGA) nanoparticles adjuvanted with polyinosinic:polycytidylic acid (poly(I:C) as an adjuvant (Vaccine-NP). This Vaccine-NP was compared to ovalbumin and poly(I:C) formulated in a similar manner (Control-NP) and a commercial adjuvanted inactivated BVDV vaccine (IAV), all inoculated subcutaneously and boosted prior to BVDV-1 challenge. Significant virus-neutralizing activity, and E2 and NS3 specific antibodies were observed in both Vaccine-NP and IAV groups following the booster immunisation. IFN-γ responses were observed in ex vivo PBMC stimulated with E2 and NS3 proteins in both vaccinated groups. We observed that the protection afforded by the particulate vaccine was comparable to the licenced IAV formulation. In conclusion, the biomimetic particulates showed a promising immunogenicity and efficacy profile that may be improved by virtue of being a customisable mode of delivery

Molecular characterization of dissolved organic matter linked to microbial (Bacteria and Archaea) diversity in the main water masses of the Eastern North Atlantic Ocean

The microbe-dissolved organic matter (DOM) interactions include microbial uptake and DOM reworking and release, affecting the composition of the heterogeneous DOM pool. In turns, this distinct DOM composition can select for microbial assemblages. We investigated the diversity of microbial (both Bacteria and Archaea) communities (combining Illumina tag sequencing of 16S rRNA gen -amplicon sequencing variants, ASVs- and metagenomics) and the chemodiversity of dissolved organic molecules (extracted by solid phase extraction and analyzed by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, FT-ICR-MS) in the Eastern North Atlantic Ocean off the Galician coast (43oN, 9o-15oW). Sampling ranged from 100 m to 5000 m, thereby encompassing a wide variety of water masses with contrasting origins and different aging. Applying diversity ecological metrics to both organic compounds and ASVs, we found that microbial diversity and richness were negatively correlated with DOM concentration and chemo-diversity. Besides, our results demonstrated the link between this trend and water mass aging, which enhances biosphere taxonomic diversity but reduces molecular variety. DOM diversity, decreasing along the water mass aging gradient, would likely reflect the persistence of the most refractory molecules, generated as by- product of the DOM degradation by microbes. In two PCoAs based on the metagenomic data, combined PCoA axis 1 and PCoA axis 2, explained the 80% and 20% of the microbial gene ́s structural variability among water masses. The oldest water masses, originated at high latitudes, such as NADW and LDW, were associated to higher abundance of genes involved in metabolism of aromatic compound. Intermediate waters such as ENACWst were related to sulphur/iron/phosphorous metabolism related genes. Surface waters were linked to genes involved in photosynthesis, autotrophy and cell division. Taken together, the observed increase of DOM homogenization along water mass aging was associated to differences in the functional diversity of microbial communities

Towards the Amplituhedron Volume

21 pages; v2: version published in JHEPIt has been recently conjectured that scattering amplitudes in planar N=4 super Yang-Mills are given by the volume of the (dual) amplituhedron. In this paper we show some interesting connections between the tree-level amplituhedron and a special class of differential equations. In particular we demonstrate how the amplituhedron volume for NMHV amplitudes is determined by these differential equations. The new formulation allows for a straightforward geometric description, without any reference to triangulations. Finally we discuss possible implications for volumes related to generic N^kMHV amplitudes.Peer reviewe

Bacterial community composition and optical signature of DOM shape empirical leucine-to-carbon conversion factors in north-eastern Atlantic waters (0-4000 m)

Oral communicationMicrobial heterotrophic activity is a major process regulating the flux of dissolved organic matter (DOM) in the ocean. DOM quantity and quality strongly influence its microbial utilization and fate in the ocean. In order to broaden the vertical resolution of leucine-to-carbon conversion factors (CFs), needed for converting substrate incorporation into biomass production by heterotrophic bacteria, nine dilution experiments were performed in the north Atlantic. We found a very consistent depth-stratification in empirical CFs values from epipelagic to bathypelagic waters (3.95 ± 0.05 to 0.90 ± 0.51 kg C mol Leu-1). Our results demonstrated that the customarily used CF of 1.55 kg C mol Leu-1 in oceanic waters leads to an underestimation of prokaryotic heterotrophic production in epi- and mesopelagic waters, while it causes a severe overestimation in bathypelagic waters. Pearson correlations showed that CFs were related not only to hydrographic variables but also to specific phylogenetic groups and DOM quality and quantity indicators. Furthermore, a multiple linear regression model predicting CFs from relatively simple hydrographic and optical spectroscopic measurements is provided. Taken together, our results suggest that differences in CFs throughout the water column might be mostly associated to the quality of DOM affecting the response of particular phylogenetic groups.ASL

Vision and Foraging in Cormorants: More like Herons than Hawks?

Background Great cormorants (Phalacrocorax carbo L.) show the highest known foraging yield for a marine predator and they are often perceived to be in conflict with human economic interests. They are generally regarded as visually-guided, pursuit-dive foragers, so it would be expected that cormorants have excellent vision much like aerial predators, such as hawks which detect and pursue prey from a distance. Indeed cormorant eyes appear to show some specific adaptations to the amphibious life style. They are reported to have a highly pliable lens and powerful intraocular muscles which are thought to accommodate for the loss of corneal refractive power that accompanies immersion and ensures a well focussed image on the retina. However, nothing is known of the visual performance of these birds and how this might influence their prey capture technique. Methodology/Principal Findings We measured the aquatic visual acuity of great cormorants under a range of viewing conditions (illuminance, target contrast, viewing distance) and found it to be unexpectedly poor. Cormorant visual acuity under a range of viewing conditions is in fact comparable to unaided humans under water, and very inferior to that of aerial predators. We present a prey detectability model based upon the known acuity of cormorants at different illuminances, target contrasts and viewing distances. This shows that cormorants are able to detect individual prey only at close range (less than 1 m). Conclusions/Significance We conclude that cormorants are not the aquatic equivalent of hawks. Their efficient hunting involves the use of specialised foraging techniques which employ brief short-distance pursuit and/or rapid neck extension to capture prey that is visually detected or flushed only at short range. This technique appears to be driven proximately by the cormorant's limited visual capacities, and is analogous to the foraging techniques employed by herons