Rôle de la fréquence des prélèvements de la biomasse produite sur les capacités épuratrices de Lemna minor L.

Les Lemnaceae en général, Lemna minor L. et L. gibba L. en particulier, font l'objet de recherches importantes au niveau international sur le rôle positif ou négatif que ces espèces peuvent jouer dans le domaine de l'épuration des eaux usées urbaines par les diverses techniques extensives.Selon les travaux scientifiques réalisés en vraie grandeur comme en pilote, les auteurs insistent soit sur l'intérêt de ces espèces (productivité élevée, haute teneur en protéines, capacité de bioaccumulation de métaux lourds, prélèvements périodiques aisés, bonnes capacités épuratrices en N et P. ...) soit sur leurs inconvénients (effets néfastes sur l'épuration dans les lagunages à microphytes, anaérobiose de la nappe aquatique, prélèvements périodiques difficiles - ! -, capacités épuratrices médiocres, voire nulles, ...).Dans ce contexte de résultats apparemment contradictoires, qui ne se limitent d'ailleurs pas aux seules Lemnaceae - loin s'en faut-, nous avons comparé, sous climat local, les rendements épuratoires de deux systèmes de bassins miniatures en série, rigoureusement identiques, alimentés par le même débit des mémos eaux usées urbaines durant toute la période de végétation : l'un des systèmes était peuplé de Lemna minor, l'autre n'en contenait pas.Nos résultats font apparaître que l'efficacité épuratrice de Lemna minor dépend, entre autres, de la fréquence des prélèvements périodiques de la biomasse produite.1. Lorsque les prélèvements sont peu fréquents (7 fois sur la période de végétation), le système à Lemna épure sensiblement mieux que le témoin non « planté » en ce qui concerne les matières en suspension et la charge organique. Il influence défavorablement, par contre, l'épuration tertiaire au niveau de l'azote et surtout du phosphore.2. Lorsque les prélèvements sont fréquents (24 fois sur la période de végétation), le système à Lemna améliore considérablement la rétention des matières en suspension et celle de la charge organique. II augmente nettement l'épuration tertiaire au niveau de l'azote et reste sans effet pour le phosphore.The affect of Lemnaceae, and in particular of Lemna miner L. and L. gibba L. on various extensive urban sewage treatment techniques is currently the subject of intense international research.Researches on both full-scale and pilot plants stress either these species' advantages (high productivity, high protein content, heavy metal bioaccumulation, easy harvesting, high N and P purification efficiency, ...) or disadvantages (detrimental effect on microphyte ponding, anaerobiosis in the water layer, difficult harvesting, poor or non-existent purification capacity).Against this background of apparently conflicting results (and in this respect, Lemnaceae are far from being the only case), we have compared the performances of two systems under local climate, bath consisting of 4 strictly identical ponds in series (4 x 0.96 m2) supplied with an identical influx of the came urban sewage, one with a population of Lemna miner and the other without.Each series of ponds was supplied with a hydraulic load of wastewater corresponding to the use of 6 square metres of pond per capita.The two series of ponds were monitored in 1985 and 1986 during the periods of vegetative growth (from May to October inclusive).In 1985, the duckweed biomass was harvested 7 times during the experimental period : each lime, 50 % of the plant cover was removed; this frequency amounts to roughly one harvest every fortnight in June, July, August and September.In 1986, the duckweed biomass was harvested 24 times during the experimental period in the same manner as the previous year; this frequency amounts to 1 or 2 harvests every week in May, June, July, August and September.The parameters chosen to characterize the pollutant load at the inflow and the outflow of each ponding system were measured twice monthly.An amount of wastewater proportional to the volume in circulation was sampled automatically at each level. Our protocol required on sample of inflow every 30 minutes and one sample per litre of outflow. Consequently, average concentrations of the various parameters were assessed on the basis of a mixture of 14 x 48 inflow samples and a mixture of outflow samples equal in number to the volume in litres flowing through the system in two weeks.Taking into account the automatically recorded hydraulic flow rates, theses average concentrations were then converted into absolute loads (flow rates) for each parameter and for every 14-day period. They are expressed in gram per 14 days.Four parameters are discussed :- suspended solids (S.S.)- total chemical oxygen demand (total COD) on unfiltered samples, i. e. the total organic load- total nitrogen on unfiltered samples (total N)- total phosphorus on unfiltered samples (total P).Our results show that the purification efficiency of Lemna minor does depend on the frequency of the biomass production removal.1. When the removal is less frequent (7 times during the period of vegetative growth), the system with Lemna minor has purification rates that are significantly better than those of the unplanted control system as far as suspended solids and organic load are concerned. However, it has a negative impact on tertiary retention for nitrogen and especially phosphorus.2. When the biomass production is frequently removed (24 times during the period of vegetative growth, the system with Lemna minor considerably improves the retention of suspended solids and of organic load. It also improves significantly tertiary purification as far as nitrogen is concerned, but bas no effect on phosphorus

Fragment Hotspot Mapping to Identify Selectivity-Determining Regions between Related Proteins.

Funder: ExscientiaFunder: Diamond Light SourceFunder: Kungliga Tekniska HoegskolanFunder: Chinese Center for Disease Control and PreventionFunder: European Federation of Pharmaceutical Industries and AssociationsFunder: European CommissionFunder: Kennedy Trust for Rheumatology ResearchFunder: Ontario Institute for Cancer ResearchFunder: Royal Institution for the Advancement of Learning McGill UniversityFunder: UCBSelectivity is a crucial property in small molecule development. Binding site comparisons within a protein family are a key piece of information when aiming to modulate the selectivity profile of a compound. Binding site differences can be exploited to confer selectivity for a specific target, while shared areas can provide insights into polypharmacology. As the quantity of structural data grows, automated methods are needed to process, summarize, and present these data to users. We present a computational method that provides quantitative and data-driven summaries of the available binding site information from an ensemble of structures of the same protein. The resulting ensemble maps identify the key interactions important for ligand binding in the ensemble. The comparison of ensemble maps of related proteins enables the identification of selectivity-determining regions within a protein family. We applied the method to three examples from the well-researched human bromodomain and kinase families, demonstrating that the method is able to identify selectivity-determining regions that have been used to introduce selectivity in past drug discovery campaigns. We then illustrate how the resulting maps can be used to automate comparisons across a target protein family

Conformal geometry of the supercotangent and spinor bundles

We study the actions of local conformal vector fields X∈conf(M,g) on the spinor bundle of (M,g) and on its classical counterpart: the supercotangent bundle M of (M,g). We first deal with the classical framework and determine the Hamiltonian lift of conf(M,g) to M. We then perform the geometric quantization of the supercotangent bundle of (M,g), which constructs the spinor bundle as the quantum representation space. The Kosmann Lie derivative of spinors is btained by quantization of the comoment map. The quantum and classical actions of conf(M,g) turn, respectively, the space of differential operators acting on spinor densities and the space of their symbols into conf(M,g)-modules. They are filtered and admit a common associated graded module. In the conformally flat case, the latter helps us determine the conformal invariants of both conf(M,g)-modules, in particular the conformally odd powers of the Dirac operator.Peer reviewe

Mapping of Submerged Aquatic Vegetation in Rivers From Very High Resolution Image Data, Using Object Based Image Analysis Combined with Expert Knowledge

The use of remote sensing for monitoring of submerged aquatic vegetation (SAV) in fluvial environments has been limited by the spatial and spectral resolution of available image data. The absorption of light in water also complicates the use of common image analysis methods. This paper presents the results of a study that uses very high resolution (VHR) image data, collected with a Near Infrared sensitive DSLR camera, to map the distribution of SAV species for three sites along the Desselse Nete, a lowland river in Flanders, Belgium. Plant species, including Ranunculus aquatilis L., Callitriche obtusangula Le Gall, Potamogeton natans L., Sparganium emersum L. and Potamogeton crispus L., were classified from the data using Object-Based Image Analysis (OBIA) and expert knowledge. A classification rule set based on a combination of both spectral and structural image variation (e.g. texture and shape) was developed for images from two sites. A comparison of the classifications with manually delineated ground truth maps resulted for both sites in 61% overall accuracy. Application of the rule set to a third validation image, resulted in 53% overall accuracy. These consistent results show promise for species level mapping in such biodiverse environments, but also prompt a discussion on assessment of classification accuracy

Scrapie-Specific Pathology of Sheep Lymphoid Tissues

Transmissible spongiform encephalopathies (TSEs) or prion diseases often result in accumulation of disease-associated PrP (PrPd) in the lymphoreticular system (LRS), specifically in association with follicular dendritic cells (FDCs) and tingible body macrophages (TBMs) of secondary follicles. We studied the effects of sheep scrapie on lymphoid tissue in tonsils and lymph nodes by light and electron microscopy. FDCs of sheep were grouped according to morphology as immature, mature or regressing. Scrapie was associated with FDC dendrite hypertrophy and electron dense deposit or vesicles. PrPd was located using immunogold labelling at the plasmalemma of FDC dendrites and, infrequently, mature B cells. Abnormal electron dense deposits surrounding FDC dendrites were identified as immunoglobulins suggesting that excess immune complexes are retained and are indicative of an FDC dysfunction. Within scrapie-affected lymph nodes, macrophages outside the follicle and a proportion of germinal centre TBMs accumulated PrPd within endosomes and lysosomes. In addition, TBMs showed PrPd in association with the cell membrane, non-coated pits and vesicles, and also with discrete, large and random endoplasmic reticulum networks, which co-localised with ubiquitin. These observations suggest that PrPd is internalised via the caveolin-mediated pathway, and causes an abnormal disease-related alteration in endoplasmic reticulum structure. In contrast to current dogma, this study shows that sheep scrapie is associated with cytopathology of germinal centres, which we attribute to abnormal antigen complex trapping by FDCs and abnormal endocytic events in TBMs. The nature of the sub-cellular changes in FDCs and TBMs differs from those of scrapie infected neurones and glial cells suggesting that different PrPd/cell membrane interactions occur in different cell types

Supersymmetric QCD corrections to e+e−→tbˉH−e^+e^-\to t\bar{b}H^- and the Bernstein-Tkachov method of loop integration

The discovery of charged Higgs bosons is of particular importance, since their existence is predicted by supersymmetry and they are absent in the Standard Model (SM). If the charged Higgs bosons are too heavy to be produced in pairs at future linear colliders, single production associated with a top and a bottom quark is enhanced in parts of the parameter space. We present the next-to-leading-order calculation in supersymmetric QCD within the minimal supersymmetric SM (MSSM), completing a previous calculation of the SM-QCD corrections. In addition to the usual approach to perform the loop integration analytically, we apply a numerical approach based on the Bernstein-Tkachov theorem. In this framework, we avoid some of the generic problems connected with the analytical method.Comment: 14 pages, 6 figures, accepted for publication in Phys. Rev.

Clinical anticancer drug development: targeting the cyclin-dependent kinases

Cell division involves a cyclical biochemical process composed of several step-wise reactions that have to occur once per cell cycle. Dysregulation of cell division is a hallmark of all cancers. Genetic and epigenetic mechanisms frequently result in deranged expression and/or activity of cell-cycle proteins including the cyclins, cyclin-dependent kinases (Cdks), Cdk inhibitors and checkpoint control proteins. The critical nature of these proteins in cell cycling raises hope that targeting them may result in selective cytotoxicity and valuable anticancer activity