Supercontinuum generation of ultrashort laser pulses in air at different central wavelengths

Supercontinuum generation by femtosecond filaments in air is investigated for different laser wavelengths ranging from ultraviolet to infrared. Particular attention is paid on the role of third-harmonic generation and temporal steepening effects, which enlarge the blue part of the spectrum. A unidirectional pulse propagation model and nonlinear evolution equations are numerically integrated and their results are compared. Apart from the choice of the central wavelength, we emphasize the importance of the saturation intensity reached by self-guided pulses, together with their temporal duration and propagation length as key players acting on both supercontinuum generation of the pump wave and emergence of the third harmonics. Maximal broadening is observed for large wavelengths and long filamentation ranges.Comment: 10 pages, 11 figure

Interactions between β-lactoglobulin and pectins during in vitro gastric hydrolysis

International audienceThis paper deals with the influence of different levels of three pectins, low-methylated pectin (LMP), high-methylated pectin (HMP), and low-methylated and amidated pectin (LMA), on the in vitro gastric hydrolysis of â-lactoglobulin (â-lg). Proteolysis by pepsin consisted of a 2-h progressive reduction of pH. A turbidity measurement of â-lg-pectin mixtures was carried out during the proteolysis. The influence of pectins on pepsin enzymatic activity was also evaluated. â-Lg was resistant to peptic digestion. The presence of each of the three pectins at a concentration of 50 wt % increased the N release at all pH values considered, despite a significant inhibition of the pepsin enzymatic activity with the pectins. The turbidity of â-lg solutions during proteolysis was reduced by the addition of pectins, because of the formation of electrostatic complexes between this protein and pectins. The increase of N release could be a false positive result due to the difficulty of precipitating protein by trichloroacetic acid because of the formation of electrostatic complexes demonstrated by the decrease of turbidity

La chaîne alimentaire vecteur de polluants organiques persistants

L’activité agricole est en interaction avec d’autres activités anthropiques potentiellement émettrices de Polluants Organiques Persistants (POP). Ces molécules posent des problèmes de transfert dans la chaîne alimentaire, notamment vers les produits animaux. Les POP sont caractérisés par une forte rémanence, une volatilité élevée et une lipophilicité marquée entraînant leur accumulation potentielle dans les tissus adipeux. Ce groupe de molécules potentiellement toxiques pour l’homme et l’environnement fait l’objet d’une attention internationale. L’objectif de cette synthèse est d’aborder le devenir de trois familles de composés POP, de type hydrocarbures polycycliques : les dioxines-furanes (PCDD/F), les polychlorobiphényls (PCB) et les hydrocarbures aromatiques polycycliques (HAP). Les résultats de recherche montrent une contamination significative des fourrages situés en zones exposées aux polluants par comparaison avec des zones isolées. Ils mettent également en évidence un transfert différentiel de ces molécules toxiques vers les matrices biologiques dont le laitHuman activities produce polluting compounds such as the Persistent Organic Pollutants group (POPs) which may interact with agriculture. These molecules raised concern about risk of transfer through the food chain via the animal product. The POPs are characterised by a strong persistence in the environment, a high volatility and a lipophilicity which lead to their accumulation in fat tissues. These compounds are enlisted in international conventions to organise the information about their potential toxicity for humans and the environment. The aim of this paper is to study transfer in the food chain of three groups of POPs: the dioxins-furans (PCDD/F), the polychlorobiphenyls (PCB) and the Polycyclic Aromatic Hydrocarbons (PAH). The results show that the contamination of fodder by these compounds is observed when they are exposed to emission sources compared to remote areas. They also show that a differential transfer of the molecules is detected towards biological matrices (milk

Different Genotypes of Anatoxin-Producing Cyanobacteria Coexist in the Tarn River, France▿ †

Repeated dog deaths occurred in 2002, 2003, and 2005 after the animals drank water from the shoreline of the Tarn River in southern France. Signs of intoxication indicated acute poisoning due to a neurotoxin. Floating scum and biofilms covering pebbles were collected in the summers of 2005 and 2006 from six different sites along 30 km from the border of this river. The cyanobacterial neurotoxic alkaloid anatoxin-a and/or its methyl homolog, homoanatoxin-a, was detected in the extracts of most samples examined by gas chromatography-mass spectrometry. Fifteen filamentous cyanobacteria of the order Oscillatoriales were isolated and displayed four distinct phenotypes based on morphological characteristics and pigmentation. Three of the phenotypes can be assigned to the genus Oscillatoria or Phormidium, depending on the taxonomic treatises (bacteriological/botanical) employed for identification. The fourth phenotype is typical of the genus Geitlerinema Anagnostidis 1989. Eight strains rendered axenic were analyzed for production of anatoxin-a and homoanatoxin-a, and all strains of Oscillatoria/Phormidium proved to be neurotoxic. The genetic relatedness of the new isolates was evaluated by comparison of the intergenic transcribed spacer sequences with those of six oscillatorian strains from the Pasteur Culture Collection of Cyanobacteria. These analyses showed that the neurotoxic representatives are composed of five different genotypes, three of which correspond to phenotypes isolated in this study. Our findings prove that neurotoxic oscillatorian cyanobacteria exist in the Tarn River and thus were most likely implicated in the reported dog poisonings. Furthermore, they reemphasize the importance of monitoring benthic cyanobacteria in aquatic environments to fully assess the health risks associated with these organisms

Les plantes, sources d’acides gras essentiels oméga 3

L’acide α-linolénique (ALA) fait partie de la famille des acides gras dits oméga 3. Il est dit essentiel parce qu’il ne peut pas être synthétisé dans notre organisme et doit donc être fourni par l’alimentation. Les plantes, sous forme de fruits, de légumes verts, de graines ou d’huiles issues de ces graines constituent une source majeure d’ALA. Cette synthèse a pour but de rappeler l’importance relative des végétaux quant à leur capacité à nous fournir des acides gras essentiels. Elle vise à faire le point sur les différentes voies développées par l’industrie agroalimentaire et à envisager les développements futurs

Les plantes, sources d’acides gras essentiels oméga 3

L’acide α-linolénique (ALA) fait partie de la famille des acides gras dits oméga 3. Il est dit essentiel parce qu’il ne peut pas être synthétisé dans notre organisme et doit donc être fourni par l’alimentation. Les plantes, sous forme de fruits, de légumes verts, de graines ou d’huiles issues de ces graines constituent une source majeure d’ALA. Cette synthèse a pour but de rappeler l’importance relative des végétaux quant à leur capacité à nous fournir des acides gras essentiels. Elle vise à faire le point sur les différentes voies développées par l’industrie agroalimentaire et à envisager les développements futurs

Les plantes, sources d'acides gras essentiels omega 3

National audienceElonging to the omega-3 fatty acid group, alpha -linolenic acid (ALA) is considered an essential fatty acid since it can not be produced by the body and must be provided by diet. Plants are important sources of ALA, from fruits and seeds to green vegetables. This survey showed the relative importance of plant material as ALA sources.L'acide α-linolénique (ALA) fait partie de la famille des acides gras dits oméga 3. Il est dit essentiel parce qu'il ne peut pas être synthétisé dans notre organisme et doit donc être fourni par l'alimentation. Les plantes, sous forme de fruits, de légumes verts, de graines ou d'huiles issues de ces graines constituent une source majeure d'ALA. Cette synthèse a pour but de rappeler l'importance relative des végétaux quant à leur capacité à nous fournir des acides gras essentiels. Elle vise à faire le point sur les différentes voies développées par l'industrie agroalimentaire et à envisager les développements futur

SIRANERISK: Modelling dispersion of steady and unsteady pollutant releases in the urban canopy

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