201 research outputs found
Synthèse d'un sulfatoferrate de potassium et son efficacité dans le traitement des eaux
Depuis le milieu du siècle dernier, nous savons que le fer existe à son degré d'oxydation supérieur VI dans l'ion tétraoxoferrate(VI) FeO42-, isostructural de SO42-, CrO42-, MnO42-. Cette espèce mise en solution aqueuse oxyde l'eau en O2, et ce quelque soit le pH de cette solution. La vitesse de cette réaction est très grande en milieu acide, plus lente en milieu alcalin où elle conduit à la précipitation de Fe(OH)3. On peut donc envisager son emploi comme réactif polyfonctionnel : oxydant et floculant, dans le traitement de certaines eaux. La première partie de ce travail décrit une voie originale de synthèse à l'état solide, à la température ambiante, du sel de formule K2(Fe,S)O4, appelé sulfatoferrate de potassium, qui contient l'entité FeO42-. En effet, jusqu'à ce jour seules des synthèses par voie aqueuse, à rendements très faibles, chimiques ou électrochimiques, ont été utilisées pour obtenir FeO42-.Dans une seconde partie, nous avons mesuré les propriétés oxydantes et floculantes du sulfatoferrate de potassium agissant sur deux types d'eaux usées urbaines, chargées (MEST=258 mg.L-1, DCO=549 mg.L-1) et peu chargées (MEST=9 mg.L-1, DCO=37 mg.L- 1). Cette étude effectuée en collaboration avec le Centre International de l'Eau de Nancy (NANC.I.E.) nous a permis de préciser les conditions optimales d'emploi de K2(Fe,S)O4 et de comparer ses performances à celles de FeCl3.6H2O et Al2(SO4)3.18H2O.Sur une eau chargée, l'abattement de la MEST est meilleur avec FeCl3.6H2O et Al2(SO4)3.18H2O, tandis que K2(Fe,S)O4 est plus efficace vis à vis de l'abattement de la DCO.Sur une eau peu chargée, c'est l'effet bactéricide de K2(Fe,S)O4 qui est le plus remarquable; une dose de 10 mg.L-1 en fer (VI) anéantit 99,70% des coliformes totaux et 99,90% des coliformes fécaux.Tetraoxoferrate(VI), FeO42-, possesses properties which make it potentially useful in certain areas of water purification: it is an excellent oxidizing agent, it has a powerful bactericidal action and it spontaneously decomposes over a short period of time. When reduced, the FeO42- ion generates base in solution and a Fe(OH)3 type gel which precipitates and carries down with it other ions (precipitation of hydroxide metal salts). These properties make ferrate(VI) useful in water disinfection and in wastewater treatment because it acts by an oxidation-coagulation-precipitation process. Iron, in its familiar form exists in the (II) and (III) oxidation states; ferrate(VI) ion has long been known, but, due to its instability and difficulty of preparation, it has not been studied extensively and has not been industrially produced. In this paper, we recommend a method of synthesis of alkali ferrate(VI) salts by a dry powder process, which occurs at room temperature and can be easily used for industrial production of Fe(VI). To minimize ferrate(VI) decomposition, we proceed in a strong alkaline medium (presence of a strong base like potash or caustic soda) where oxidation of an iron (bivalent or trivalent) containing salt becomes easier. By such a synthesis process, we produce stabilized ferrate(VI) which enters a solid solution with the formula:M2(Fe,X)O4where M designates Na or K, X is an element whose cation has the electronic structure of a rare gas, e.g. X=S. M2XO4 is an isomorph of K2FeO4 with closed unit cell parameters. The M2(Fe,X)O4 formula has been established by chemical means and by X-ray diffraction; [sup]57Fe Mössbauer spectrometry has been used to monitor the hexavalent iron oxidation state. This paper deals with sulfatoferrate K2(Fe,S)O4 properties for compounds having Fe/S ratios between 1 and 1.5. in aqueous solution, K2(Fe,S)O4 dissolves and gives rise to FeO42- and SO42- anions.In collaboration with NANC.I.E. (Centre International de l'Eau de Nancy), the effectiveness of K2(Fe,S)O4 in wastewater treatment has been studied. The product exhibits a real bactericidal effect on both coliforms and total bacteria. This bactericidal efficiency is reached in a short period of time with iron starting levels as low as 5-10 mg.L-¹. Comparative coagulation jar-tests were carried out on raw wastewater and on secondary effluent using FeCl3·6 H2O, Al2(SO4)3·18 H2O and K2(Fe[inf]0.54,S[inf]0.46)O4. Total suspended solids (TSS) removal on the raw wastewater was better with Al(III) and Fe(III) than with sulfatoferrate. On the secondary effluent, 40% removal was achieved with sulfatoferrate as well as with Fe(III). For removal of chemical oxygen demand (COD), better results were reached with Fe(VI) than with either Fe(III) or Al(III). The effectiveness of FeO42- after 30 minutes of contact with the bacterial medium (secondary effluent) has also been studied. At pH=8.5, a dose of 10 mg.L-¹ iron(VI) removes 99.70% of the total coliforms and 99.90% of the fecal coliforms
The feeding route (enteral or parenteral) affects the plasma response of the dipetide Ala-Gln and the amino acids glutamine, citrulline and arginine, with the administration of Ala-Gln in preoperative patients
Campagne océanographique EBENE à bord du N.O. l'Atalante : 21 octobre au 20 novembre 1996 : recueil de données : 2. Matière organique, pigments photosynthétiques, production primaire, micro- et mésozooplancton, profileur vidéo marin
Evolution of disease activity and biomarkers on and off rapamycin in 28 patients with autoimmune lymphoproliferative syndrome
The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Measurement of the BAO and growth rate of structure of the luminous red galaxy sample from the anisotropic power spectrum between redshifts 0.6 and 1.0
We analyse the clustering of the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 16 luminous red galaxy sample (DR16 eBOSS LRG) in combination with the high redshift tail of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 12 (DR12 BOSS CMASS).We measure the redshift space distortions (RSD) and also extract the longitudinal and transverse baryonic acoustic oscillation (BAO) scale from the anisotropic power spectrum signal inferred from 377 458 galaxies between redshifts 0.6 and 1.0, with the effective redshift of zeff = 0.698 and effective comoving volume of 2.72 Gpc3. After applying reconstruction, we measure the BAO scale and infer DH(zeff)/rdrag = 19.30 ± 0.56 and DM(zeff)/rdrag = 17.86 ± 0.37. When we perform an RSD analysis on the pre-reconstructed catalogue on the monopole, quadrupole, and hexadecapole we find, DH(zeff)/rdrag = 20.18 ± 0.78, DM(zeff)/rdrag = 17.49 ± 0.52 and fσ8(zeff) = 0.454 ± 0.046. We combine both sets of results along with the measurements in configuration space and report the following consensus values: DH(zeff)/rdrag = 19.77 ± 0.47, DM(zeff)/rdrag = 17.65 ± 0.30 and fσ8(zeff) = 0.473 ± 0.044, which are in full agreement with the standard CDM and GR predictions. These results represent the most precise measurements within the redshift range 0.6 ≤ z ≤ 1.0 and are the culmination of more than 8 yr of SDSS observations
The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey : pairwise-inverse probability and angular correction for fibre collisions in clustering measurements
HJS is supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0014329. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 693024).The completed extended Baryon Oscillation Spectroscopic Survey (eBOSS) catalogues contain redshifts of 344 080 quasars at 0.8 < z < 2.2, 174 816 luminous red galaxies between 0.6 < z < 1.0, and 173 736 emission-line galaxies over 0.6 < z < 1.1 in order to constrain the expansion history of the Universe and the growth rate of structure through clustering measurements. Mechanical limitations of the fibre-fed spectrograph on the Sloan telescope prevent two fibres being placed closer than 62 arcsec in a single pass of the instrument. These ‘fibre collisions’ strongly correlate with the intrinsic clustering of targets and can bias measurements of the two-point correlation function resulting in a systematic error on the inferred values of the cosmological parameters. We combine the new techniques of pairwise-inverse probability and the angular upweighting (PIP+ANG) to correct the clustering measurements for the effect of fibre collisions. Using mock catalogues, we show that our corrections provide unbiased measurements, within data precision, of both the projected wp(rp) and the redshift-space multipole ξ(ℓ = 0, 2, 4)(s) correlation functions down to 0.1h−1Mpc, regardless of the tracer type. We apply the corrections to the eBOSS DR16 catalogues. We find that, on scales s≳20h−1Mpcs≳20h−1Mpc for ξℓ, as used to make baryon acoustic oscillation and large-scale redshift-space distortion measurements, approximate methods such as nearest-neighbour upweighting are sufficiently accurate given the statistical errors of the data. Using the PIP method, for the first time for a spectroscopic program of the Sloan Digital Sky Survey, we are able to successfully access the one-halo term in the clustering measurements down to ∼0.1h−1Mpc scales. Our results will therefore allow studies that use the small-scale clustering to strengthen the constraints on both cosmological parameters and the halo occupation distribution models.Publisher PDFPeer reviewe
Potential controls of isoprene in the surface ocean
Isoprene surface ocean concentrations and vertical distribution, atmospheric mixing ratios, and calculated sea-to-air fluxes spanning approximately 125° of latitude (80°N–45°S) over the Arctic and Atlantic Oceans are reported. Oceanic isoprene concentrations were associated with a number of concurrently monitored biological variables including chlorophyll a (Chl a), photoprotective pigments, integrated primary production (intPP), and cyanobacterial cell counts, with higher isoprene concentrations relative to all respective variables found at sea surface temperatures greater than 20°C. The correlation between isoprene and the sum of photoprotective carotenoids, which is reported here for the first time, was the most consistent across all cruises. Parameterizations based on linear regression analyses of these relationships perform well for Arctic and Atlantic data, producing a better fit to observations than an existing Chl a-based parameterization. Global extrapolation of isoprene surface water concentrations using satellite-derived Chl a and intPP reproduced general trends in the in situ data and absolute values within a factor of 2 between 60% and 85%, depending on the data set and algorithm used
Resource Concentration Modulates the Fate of Dissimilated Nitrogen in a Dual-Pathway Actinobacterium
Respiratory ammonification and denitrification are two evolutionarily unrelated dissimilatory nitrogen (N) processes central to the global N cycle, the activity of which is thought to be controlled by carbon (C) to nitrate (NO_3^−) ratio. Here we find that Intrasporangium calvum C5, a novel dual-pathway denitrifier/respiratory ammonifier, disproportionately utilizes ammonification rather than denitrification when grown under low C concentrations, even at low C:NO_3^− ratios. This finding is in conflict with the paradigm that high C:NO_3^− ratios promote ammonification and low C:NO_3^− ratios promote denitrification. We find that the protein atomic composition for denitrification modules (NirK) are significantly cost minimized for C and N compared to ammonification modules (NrfA), indicating that limitation for C and N is a major evolutionary selective pressure imprinted in the architecture of these proteins. The evolutionary precedent for these findings suggests ecological importance for microbial activity as evidenced by higher growth rates when I. calvum grows predominantly using its ammonification pathway and by assimilating its end-product (ammonium) for growth under ammonium-free conditions. Genomic analysis of I. calvumfurther reveals a versatile ecophysiology to cope with nutrient stress and redox conditions. Metabolite and transcriptional profiles during growth indicate that enzyme modules, NrfAH and NirK, are not constitutively expressed but rather induced by nitrite production via NarG. Mechanistically, our results suggest that pathway selection is driven by intracellular redox potential (redox poise), which may be lowered when resource concentrations are low, thereby decreasing catalytic activity of upstream electron transport steps (i.e., the bc1 complex) needed for denitrification enzymes. Our work advances our understanding of the biogeochemical flexibility of N-cycling organisms, pathway evolution, and ecological food-webs
The relative effects of upwelling and river flow on the phytoplankton diversity patterns in the ria of A Coruña (NW Spain)
Phytoplankton species assemblages in estuaries are connected to those in rivers and marine environments by local hydrodynamics leading to a continuous flow of taxa. This study revealed differential effects of upwelling and river flow on phytoplankton communities observed in 2011 along a salinity gradient from a river reservoir connected to the sea through a ria-marine bay system in A Coruña (NW Spain, 43° 16-21’ N, 8° 16-22’ W). With 130 phytoplankton taxa identified, the assemblages were dominated in general by diatoms, particularly abundant in the bay and in the estuary, but also by chlorophycea and cyanobacteria in the reservoir. Considering the entire seasonal cycle, the local assemblages were mainly characterized by changes in cryptophytes and diatoms, small dinoflagellates and some freshwater chlorophycea. Salinity, nitrate, and organic matter variables, were the main environmental factors related to the changes in the phytoplankton communities through the system, while phosphate and nitrite were also important for local communities in the estuary and the bay, respectively. The corresponding local phytoplankton assemblages showed moderate levels of connectivity. The estuarine community shared a variable number of taxa with the adjacent zones, depending on the relative strength of upwelling (major influence from the bay) and river flow (major influence of the reservoir) but had on average 35% of unique taxa. Consequently, local and zonal diversity patterns varied seasonally and were not simply related to the salinity gradient driven by the river flow.ANILE (CTM2009-08396 and CTM2010-08804-E), FIOME (CTM2011-28792-C02-01-MAR), and MEFIO (CTM2011-28792-C02-02-MAR) of the Plan Nacional de I+D+i (Spain), and RADIALES of the Instituto Español de Oceanografía (IEO, Spain).Versión del editor2,01
- …