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Pourret O.,Polytechnic Institute of LaSalle Beauvais | Davranche M.,French National Center for Scientific Research
Journal of Colloid and Interface Science | Year: 2013

Manganese oxides are important scavengers of rare earth elements (REE) in hydrosystems. However, it has been difficult to include Mn oxides in speciation models due to the lack of a comprehensive set of sorption reactions consistent with a given surface complexation model (SCM), as well as discrepancies between published sorption data and predictions using the available models. Surface complexation reactions for hydrous Mn oxide were described using a two surface site model and the diffuse double layer SCM. The specific surface area, surface side density, and pHzpc were fixed to 746m2/g, 2.1mmol/g, and 2.2, respectively. Two site types (XOH and YOH) were also used with pKa2 values of 2.35 (XOH) and 6.06 (YOH). The fraction of the high affinity sites was fixed at 0.36. Published REE sorption data were subsequently used to determine the equilibrium surface complexation constants, while considering the influence of pH, ionic strength, and metal loading. LogK increases from light REE to heavy REE and, more specifically, displays a convex tetrad effect. At low metal loading, the YOH site type strongly expresses its affinity toward REE, whereas at higher metal loading, the same is true for the XOH site type. This study thus provides evidence for heterogeneity in the distribution of the Mn oxide binding sites among REE. © 2012 Elsevier Inc. Source

Roman M.,CNR Institute of Neuroscience | Jitaru P.,Polytechnic Institute of LaSalle Beauvais | Barbante C.,CNR Institute of Neuroscience
Metallomics | Year: 2014

Despite its very low level in humans, selenium plays an important and unique role among the (semi)metal trace essential elements because it is the only one for which incorporation into proteins is genetically encoded, as the constitutive part of the 21st amino acid, selenocysteine. Twenty-five selenoproteins have been identified so far in the human proteome. The biological functions of some of them are still unknown, whereas for others there is evidence for a role in antioxidant defence, redox state regulation and a wide variety of specific metabolic pathways. In relation to these functions, the selenoproteins emerged in recent years as possible biomarkers of several diseases such as diabetes and several forms of cancer. Comprehension of the selenium biochemical pathways under normal physiological conditions is therefore an important requisite to elucidate its preventing/therapeutic effect for human diseases. This review summarizes the most recent findings on the biochemistry of active selenium species in humans, and addresses the latest evidence on the link between selenium intake, selenoproteins functionality and beneficial health effects. Primary emphasis is given to the interpretation of biochemical mechanisms rather than epidemiological/observational data. In this context, the review includes the following sections: (1) brief introduction; (2) general nutritional aspects of selenium; (3) global view of selenium metabolic routes; (4) detailed characterization of all human selenoproteins; (5) detailed discussion of the relation between selenoproteins and a variety of human diseases. © 2014 The Royal Society of Chemistry. Source

Sorba A.,Polytechnic Institute of LaSalle Beauvais | Sopade P.A.,University of Queensland
Starch/Staerke | Year: 2013

Changes in the rapid visco-analysis (RVA) viscosity of potato and waxy maize starches during digestion were studied using amyloglucosidase and α-amylase (60-1700 U/mL), and three solids contents (3-20%) of the starch dispersions in a replicated randomised experiment. The starches were gelatinised in the RVA before digestion at 50°C at a shear rate of 17 s-1 for 5 min. Control dispersions effectively did not change (<10%) in viscosity with time. With the enzyme-treated gels, irrespective of the starch, enzyme or concentration, the RVA viscosity reduced with time as low molecular weight (MW) products were produced. A modified first-order kinetic model suitably described (r2>0.9) the starch viscosity-digestograms. The rate of change in starch viscosity, KVIS (an index of the rate of starch digestion), was significantly (p<0.05) inversely related to the solids content, and directly related to the enzyme concentration. KVIS of the waxy maize starch was higher than that of the potato starch, and a higher KVIS was measured with the α-amylase than with the amyloglucosidase. Differences in potato and waxy maize starch structures, specificity of enzymes and enzyme:substrate ratios can explain the results, and rheology is proposed as valuable in starch digestion. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Zghibi A.,Institute National Agronomique Of Tunisie | Zouhri L.,Polytechnic Institute of LaSalle Beauvais | Tarhouni J.,Institute National Agronomique Of Tunisie
Hydrological Processes | Year: 2011

This article studies the effect of drought and pumping discharge on groundwater supplies and marine intrusion in the Korba aquifer (Cap-Bon peninsula, Tunisia). The Groundwater Modelling System has been used to model the groundwater flow and to simulate the seawater intrusion. The calibration is based on the groundwater levels in the steady state from 1963, and in the transient state from the groundwater levels from 1963 to 2005. The main objective is to quantify the components of the groundwater mass balance and to estimate the hydraulic conductivity distribution. The impact of pumping discharge on the groundwater level evolution has been examined by two pumping scenarios P1 (no. 8420) and P2 (no. 8862) wells. The hydrodynamic modelling shows the increasing drawdowns after 14 years of pumping: 4 m in P1 well and about 5 m in P2 well below sea level. The drawdowns are accompanied by the inverse hydraulic gradient. The numerical model was used to discuss the management of the groundwater resources of Cap-Bon. As the population continues to grow and the demand for groundwater pumping intensifies beyond the 1963 level, it can be expected that the actual extent of seawater intrusion in the future would be more severe than the model prediction. Better strategies for groundwater development and management will be necessary to protect the freshwater aquifers to the marine intrusion. © 2011 John Wiley & Sons, Ltd. Source

Ton X.-A.,Compiegne University of Technology | Acha V.,Polytechnic Institute of LaSalle Beauvais | Haupt K.,Compiegne University of Technology | Tse Sum Bui B.,Compiegne University of Technology
Biosensors and Bioelectronics | Year: 2012

A rapid, robust, sensitive and economic sensing method, based on a molecularly imprinted polymer (MIP) synthetic antibody mimic, and fluorescence polarization analysis, for the direct detection of UV-excited fluorescent analytes in food and environmental samples was developed. Fluoroquinolone (FQ) antibiotics were used as fluorescent model analytes. Water-compatible MIP nanoparticles were synthesized with enrofloxacin (ENRO) as the imprinting template. Fluorescence polarization measurements then allow the direct determination of the amount of ENRO and other structurally related piperazine-based fluoroquinolones that bind to the MIP. No separation step was required since this technique distinguishes in situ analyte molecules bound to the MIP from the free analyte in solution. This assay was successfully applied for the first time to determine FQs in real samples, i.e. tap water and milk, without any prior concentration step, by simply adding a known amount of MIP. No interference by the sample components was observed even though the excitation was in the UV region. In tap water, a low limit of detection of 0.1nM for ENRO was achieved with 5μgmL -1 of MIP. In milk, ENRO and danofloxacin, whose MRLs have been fixed at 0.28μM and 0.08μM, respectively, could be selectively measured and distinguished from other families of antibiotics. The procedure is very easy and practical as it consists of simply precipitating the milk proteins with acetonitrile and adding buffer and MIP to the supernatant before reading the polarization values with a spectrofluorimeter. © 2012 Elsevier B.V. Source

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