Nanofiltration de solutions de nitrate d'ammonium. Etude des paramètres influents

Cet article propose une étude de la rétention du nitrate d'ammonium par une membrane commerciale de nanofiltration (Nanomax 50). Les effets de la pression, de la concentration et de la vitesse d'écoulement tangentiel ont été étudiés avec le souci d'une meilleure compréhension du mécanisme de transport des ions nitrate et en vue d'une optimisation de la rétention. Le taux de rétention des ions nitrate augmente dans un premier temps avec la pression, atteint un maximum puis diminue. La rétention, pour des pressions élevées, peut cependant être améliorée en augmentant la vitesse d'écoulement tangentiel. La séparation résulterait d'un rapport de différentes forces : une force d'entraînement radial dans le pore (illustrée par l'effet de la pression transmembranaire), une force d'entraînement tangentiel vers le rétentat (illustrée par l'effet de la vitesse d'écoulement tangentiel) et une force de surface traduisant les interactions membrane-soluté (illustrée par l'effet de la concentration). L'équation de Spiegler et Kedem est proposée en première approche de modélisation pour une valeur limite de pression.Many water sources deal with the problem of increasing nitrate concentrations above authorised levels for drinking water. In order to minimise this amount of pollution and to achieve high quality of water and reused water in the distribution system, membrane processes are becoming a promising technology. Indeed, they present the major advantages of a small land area requirement, low temperature operation, continuous separation, better effluent quality, little or no sludge production and a large reduction in the quantities of chemical additives. Reverse osmosis has already been used to remove most of the nitrates together with the other solutes, but the disadvantage is that this technique induces a total demineralisation of the treated water. Another possible filtration process, nanofiltration, has been investigated in this study while no extensive research has been carried out on its nitrate removal potential. Theories cannot adequately predict the influence of operating parameters on membrane performance. Consequently, new membranes and modules must be experimentally evaluated for each new application. The main objective of this study was to provide fundamental data for designing an operation of nanofiltration under various operating conditions such as transmembrane pressure, cross-flow velocity and initial feed concentration for drinking water and water reuse purposes.The retention rate rises with an increase of the applied pressure, reaches a maximum and then decreases. Such a result is quite different from those usually mentioned in the literature where the retention increases and reaches a plateau when the pressure grows. The singular decrease of the retention rate observed in this study could be explained in terms of a concentration polarization phenomenon. However, since the volumetric flux increased linearly with the pressure and remained close to the pure water flux, it might be thought that such an assumption is not valid in the case of this work. Therefore, another hypothesis has to be provided to explain the variation of the retention with transmembrane pressure. As the size of NH4+ ion (ionic radius=0.148 nm) is lower than that of the pore of membrane (diameter=1 nm), cations can enter the pores where they are partially retained due to surface forces (electrostatic and friction forces). When the pressure increases, these forces remain constant while drag forces increase due to the flux in the pore. At low pressure (∆P < 5 bars), the surface forces are stronger than the drag forces. Therefore, the solute flux remains low while the solvent flux increases with the pressure, leading to an increase in the solute retention. Above a given pressure (≅ 5 bars), the drag forces become higher than the surface forces. Consequently, the retention rate decreases.As can be observed in the obtained results, the retention rate decreased when the feed concentration was increased regardless of the operating pressure. This effect is mainly attributed to the cation shielding of the effective charge of the membrane. This characteristic can be explained by the fact that the electric repulsion becomes less efficient at higher concentration. It has been recognized that the effective charge density of the membrane decreases with an increase in the feed concentration of an ionic solution. Consequently, the retention rate of the co-ion due to charge effect is reduced. It follows that a greater amount of nitrate ions could permeate when feed solutions of higher concentration are applied.The effect of cross-flow velocity on the fluxes is insignificant since the permeate flux depends only on transmembrane pressure. However, the retention performance increases with velocity. The lower the cross-flow velocity, the higher the interaction between the solute and the membrane. Therefore, at low cross-flow rate, the solute amount that enters the membrane pores is high. When the drag forces become stronger than the surface forces, as explained above, the retention sharply decreases. At high cross-flow velocity, the feed circulation transports a large solute amount and therefore, the solute amount that enters the pores is reduced and is less sensitive to operating pressure. In consequence, the sensitivity of the retention to transmembrane pressure is not so marked. It might be thought that for a very high cross-flow velocity, the retention increases and then remains constant.It was demonstrated in this work that nanofiltration can be successfully used to remove nitrates from water. The retention was shown to depend strongly on operating parameters such as feed solution concentration, applied pressure and circulation cross-flow rate. In fact, the retention is mainly determined by the intensity of the solute / membrane interaction. This interaction comes from two main forces: a tangential one due to the feed solute flow (illustrated by the cross-flow velocity effect) and a radial one in the pores due to drag forces (illustrated by the transmembrane pressure effect). Moreover, it was observed that the valence of the associated ions is an important factor that can affect nitrate retention. It can be expected that the optimization of the separation performance will result of the best combination of all these parameters. Therefore, with a view to a future industrial application, it will be necessary to take into consideration the chemical composition of the resource and to adapt the operating conditions to the desired objectives

First isolation of a rhabdovirus from perch Perca fluviatilis in Switzerland

Perca fluviatilis is a fish species of increasing interest to the Swiss fish farming industry. In recent years, recirculation systems have been specifically set up to increase production. In one of these farms, abnormal spiral swimming associated with elevated mortalities occurred in repeated batches of imported perch shortly after stocking on several occasions. No bacterial or parasitic etiology was detected, but a virus grown in bluegill fry (BF-2) cells was identified as perch rhabdovirus. Subsequent investigations of other samples suggested a viral tropism for the central nervous system (CNS). Phylogenetic analysis of the partial N and entire G gene sequences positioned this isolate in genogroup C of the species Perch rhabdovirus, with high nucleotide and amino acid (aa) sequence identities with the DK5533 strain isolated in Denmark in 1989. Comparative studies using other closely related isolates allowed the distinction of 2 serological Patterns among perch rhabdoviruses and the identification of a proline substitution by a serine in Position 147 of the glycoprotein potentially involved in antigenic differentiation. Even if perch imported onto the farm tested negative by virus isolation prior to transport, they may have been the origin of this outbreak since CNS tissue was not included in the samples that were analyzed. Another possibility might be a sub-clinical infection with a viral load in resident fish too low to be detected. This study reports the first isolation of a perch rhabdovirus in Switzerland, and emphasizes the necessity of optimizing diagnostic tools that facilitate better control of the risks associated with fish translocation

Model evaluation for glycolytic oscillations in yeast biotransformations of xenobiotics

Anaerobic glycolysis in yeast perturbed by the reduction of xenobiotic ketones is studied numerically in two models which possess the same topology but different levels of complexity. By comparing both models' predictions for concentrations and fluxes as well as steady or oscillatory temporal behavior we answer the question what phenomena require what kind of minimum model abstraction. While mean concentrations and fluxes are predicted in agreement by both models we observe different domains of oscillatory behavior in parameter space. Generic properties of the glycolytic response to ketones are discussed

Fungal planet description sheets: 951–1041

Novel species of fungi described in this study include those from various countries as follows: Antarctica , Apenidiella antarctica from permafrost, Cladosporium fildesense fromanunidentifiedmarinesponge. Argentina , Geastrum wrightii onhumusinmixedforest. Australia , Golovinomyces glandulariae on Glandularia aristigera, Neoanungitea eucalyptorum on leaves of Eucalyptus grandis, Teratosphaeria corymbiicola on leaves of Corymbia ficifolia, Xylaria eucalypti on leaves of Eucalyptus radiata. Brazil, Bovista psammophila on soil, Fusarium awaxy on rotten stalks of Zea mays, Geastrum lanuginosum on leaf litter covered soil, Hermetothecium mikaniae-micranthae (incl. Hermetothecium gen. nov.)on Mikania micrantha, Penicillium reconvexovelosoi in soil, Stagonosporopsis vannaccii from pod of Glycine max. British Virgin Isles , Lactifluus guanensis onsoil. Canada , Sorocybe oblongispora on resin of Picea rubens. Chile, Colletotrichum roseum on leaves of Lapageria rosea. China, Setophoma caverna fromcarbonatiteinKarstcave. Colombia , Lareunionomyces eucalypticola on leaves of Eucalyptus grandis. Costa Rica, Psathyrella pivae onwood. Cyprus , Clavulina iris oncalcareoussubstrate. France , Chromosera ambigua and Clavulina iris var. occidentalis onsoil. French West Indies , Helminthosphaeria hispidissima ondeadwood. Guatemala , Talaromyces guatemalensis insoil. Malaysia , Neotracylla pini (incl. Tracyllales ord. nov. and Neotra- cylla gen. nov.)and Vermiculariopsiella pini on needles of Pinus tecunumanii. New Zealand, Neoconiothyrium viticola on stems of Vitis vinifera, Parafenestella pittospori on Pittosporum tenuifolium, Pilidium novae-zelandiae on Phoenix sp. Pakistan , Russula quercus-floribundae onforestfloor. Portugal , Trichoderma aestuarinum from salinewater. Russia , Pluteus liliputianus on fallen branch of deciduous tree, Pluteus spurius on decaying deciduouswoodorsoil. South Africa , Alloconiothyrium encephalarti, Phyllosticta encephalarticola and Neothyrostroma encephalarti (incl. Neothyrostroma gen. nov.)onleavesof Encephalartos sp., Chalara eucalypticola on leaf spots of Eucalyptus grandis × urophylla, Clypeosphaeria oleae on leaves of Olea capensis, Cylindrocladiella postalofficium on leaf litter of Sideroxylon inerme , Cylindromonium eugeniicola (incl. Cylindromonium gen. nov.)onleaflitterof Eugenia capensis , Cyphellophora goniomatis on leaves of Gonioma kamassi , Nothodactylaria nephrolepidis (incl. Nothodactylaria gen. nov. and Nothodactylariaceae fam. nov.)onleavesof Nephrolepis exaltata , Falcocladium eucalypti and Gyrothrix eucalypti on leaves of Eucalyptus sp., Gyrothrix oleae on leaves of Olea capensis subsp. macrocarpa , Harzia metro sideri on leaf litter of Metrosideros sp., Hippopotamyces phragmitis (incl. Hippopota- myces gen. nov.)onleavesof Phragmites australis , Lectera philenopterae on Philenoptera violacea , Leptosillia mayteni on leaves of Maytenus heterophylla , Lithohypha aloicola and Neoplatysporoides aloes on leaves of Aloe sp., Millesimomyces rhoicissi (incl. Millesimomyces gen. nov.) on leaves of Rhoicissus digitata , Neodevriesia strelitziicola on leaf litter of Strelitzia nicolai , Neokirramyces syzygii (incl. Neokirramyces gen. nov.)onleafspots o

SIRNA-Directed In Vivo Silencing of Androgen Receptor Inhibits the Growth of Castration-Resistant Prostate Carcinomas

BACKGROUND: Prostate carcinomas are initially dependent on androgens, and castration or androgen antagonists inhibit their growth. After some time though, tumors become resistant and recur with a poor prognosis. The majority of resistant tumors still expresses a functional androgen receptor (AR), frequently amplified or mutated. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis that AR is not only expressed, but is still a key therapeutic target in advanced carcinomas, we injected siRNA targeting AR into mice bearing exponentially growing castration-resistant tumors. Quantification of siRNA into tumors and mouse tissues demonstrated their efficient uptake. This uptake silenced AR in the prostate, testes and tumors. AR silencing in tumors strongly inhibited their growth, and importantly, also markedly repressed the VEGF production and angiogenesis. CONCLUSIONS/SIGNIFICANCE: Our results demonstrate that carcinomas resistant to hormonal manipulations still depend on the expression of the androgen receptor for their development in vivo. The siRNA-directed silencing of AR, which allows targeting overexpressed as well as mutated isoforms, triggers a strong antitumoral and antiangiogenic effect. siRNA-directed silencing of this key gene in advanced and resistant prostate tumors opens promising new therapeutic perspectives and tools

Rémy Ollier And Imperial Citizenship

This essay discusses Rémy Ollier’s (1816–45) journalism. As an early claimant of citizenship through (rather than against) the British Empire during the 1840s, Ollier attempted to redress a gap that he perceived between the institutionalization of rights in Britain and Mauritius. Established accounts of Ollier’s political intervention provide a rich narrative of how his efforts are implicated in the development of rights in Mauritius and broader postcolonial nationalisms. However, I argue that facets of his expression of imperial citizenship reside apart from this genealogy. To explore how Ollier uniquely created imperial citizenship, an “acts”-influenced approach to citizenship is adopted. By analyzing his writings in La Sentinelle de Maurice, I reveal how imperial citizenship is generated through a subversive loyalism to Britain and an orientalist portrayal of indentured labourers. I conclude by mobilizing Ollier’s struggle as a challenge to the notion that citizenship realizes itself in teleological fashion