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Angelov G.,Bulgarian Academy of Science | Gourdon C.,CNRS Chemical Engineering Laboratory
Chemical Engineering Research and Design | Year: 2012

A study on the pressure drop in pulsed extraction columns with internals of immobile discs and rings, usually called Discs and Doughnuts Columns (DDC) is carried out. The local pressure at a desired level of the column is obtained by resolving of turbulent flow model based on Reynolds equations coupled with k- e{open} model of turbulence. Consequently, the pressure drop for a column stage or for a unit of column length is determined. The results are used for development of correlations for determination of pressure drop as a function of plate free area, interplate distance and pulsation parameters - amplitude and frequency. Good correspondence to experimental data is observed. The developed quantitative relations are useful for non-experimental numerical optimization of stage geometry in view of lesser energy consumption. © 2011 The Institution of Chemical Engineers.

The comparative breakdown of passivity of tin by fluorides and chlorides highlight the significant slower kinetics of attack by the kosmotrope fluoride when compared to the chaotrope chloride at pH 5.7 and 10. The origin of this difference is ascribed to the predominant halide-dependent mechanism of attack, pitting with chlorides and film thinning with fluorides, which is conditioned according to the anion-specific hydration properties. © 2015 Elsevier Ltd.

Pfohl-Leszkowicz A.,CNRS Chemical Engineering Laboratory | Manderville R.A.,University of Guelph
Chemical Research in Toxicology | Year: 2012

Ochratoxin A (OTA) is a naturally occurring chlorophenolic fungal toxin that contaminates a wide range of food products and poses a cancer threat to humans. The mechanism of action (MOA) for OTA renal carcinogenicity is a controversial issue. In 2005, direct genotoxicity (covalent DNA adduct formation) was proposed as a MOA for OTA-mediated carcinogenicity [Manderville, R. A. (2005) Chem. Res. Toxicol. 18, 1091 - 1097]. At that time, inconsistent results had been published on OTA genotoxicity/mutagenicity, and conclusive evidence for OTA-mediated DNA adduction had been lacking. In this update, published data from the past 6 - 7 years are presented that provide new hypotheses for the MOA (Figure presented) of OTA-mediated carcinogenicity. While direct genotoxicity remains a controversial issue for OTA, new findings from the Umemura and Nohmi laboratories provide definitive results for the mutagenicity of OTA in the target tissue (outer medulla) of male rat kidney that rules out oxidative DNA damage. These findings, coupled with our own efforts that provide new structural evidence for DNA adduction by OTA, has strengthened the argument for involvement of direct genotoxicity in OTA-mediated renal carcinogenesis. This MOA should be taken into consideration for OTA human risk assessment. © 2011 American Chemical Society.

Fabre P.-L.,University Paul Sabatier | Reynes O.,CNRS Chemical Engineering Laboratory
Electrochemistry Communications | Year: 2010

The electrocarboxylation of chloroacetonitrile mediated by [Co(II)(phen)3]2+ has been investigated. Cyclic voltammetry studies of [Co(II)(phen)3]2+ have shown that [Co(I)(phen)3]+, an 18 electron complex, activates chloroacetonitrile by an oxidative addition through the loss of a phenanthroline ligand to give [RCo(III)(phen)2Cl]+. The unstable one-electron-reduced complex underwent Co-C bond cleavage. In carbon dioxide saturated solution, CO2 insertion proceeds after reduction of the alkylcobalt complex. A catalytic current is observed which corresponds to the electrocarboxylation of chloroacetonitrile into cyanoacetic acid. Electrolyses confirmed the process and gave faradic yield of 62% in cyanoacetic acid at potentials that are about 0.3 V less cathodic than the one required for Ni(salen). © 2010 Elsevier B.V.

Muzzarelli R.A.A.,Marche Polytechnic University | Boudrant J.,CNRS Chemical Engineering Laboratory | Meyer D.,Sensus Inc. | Manno N.,University of Padua | And 2 more authors.
Carbohydrate Polymers | Year: 2012

Two hundred years ago, Henri Braconnot described a polysaccharide containing a substantial percent of nitrogen, later to be called chitin: that discovery stemmed from investigations on the composition of edible mushrooms and their nutritional value. The present interdisciplinary article reviews the major research topics explored by Braconnot, and assesses their importance in the light of our most advanced knowledge. Thus, the value of fungi, seafoods and insects is described in connection with the significance of the presence of chitin itself in foods, and chitinases in the human digestive system. The capacity of chitin/chitosan to depress the development of microbial pathogens, is discussed in terms of crop protection and food preservation. Other topics cherished by Braconnot, such as the isolation of pectin from a large number of plants, and inulin from the Helianthus tubers, are presented in up-to-date terms. Acids isolated from plants at that early time, led to enormous scientific advancements, in particular the glyoxylic acid and levulinic acid used for the preparation of soluble chitosan derivatives that paved the way to a number of applications. An opportunity to trace the origins of the carbohydrate polymers science, and to appreciate the European scientific heritage. © 2011 Elsevier Ltd. All rights reserved.

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