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Dakar, Senegal

Oviposition site selection by females of various groundnut seed-beetle strains, Caryedon serratus, bred from different hosts was studied in labratory. Tests of choice on pods of various host plants were made at first. Egg distributions among hosts are compared. The levels of adaptation of the wild strains (Bauhinia rufescens, Cassia sieberiana, Piliostigma reticulatum and Tamarindus indica) on the groundnut and the capacities of development of "groundnut" strain on the seeds of the wild hosts are also tested. The results indicate that strains may be considered as developing according to Hopkins' host selection principle because females lay preferentially their eggs on the host they were bred from. "Piliostigma " strain deposits its eggs undifferentially on pods of P. reticulatum or on groundnut pods. Results obtained from the levels of adaptation tests reveal from the point of view of the duration of development, that the various strains as identical as for their intrinsic possibilities of development on the groundnut. The parameter weight of the adults indicates that the "Bauhinia" strain is adapted intrinsically less well than the other strains to the development on the groundnut. The fecundity rates reveal that the various strains are identical as for their intrinsic possibilities of development on the groundnut but, here also, "Bauhinia" seems less good adapted to the groundnut. The passage of the groundnut strain to the wild hosts is possible but, raised on wild seeds, this one behaves although on groundnut. Source

Seydi A.,University Ca Diop | Biet J.,French National Center for Scientific Research | Delfau J.L.,French National Center for Scientific Research | Vovelle C.,French National Center for Scientific Research
Bulletin of the Chemical Society of Ethiopia

To better understand the chemistry involved in the lean-fuel combustion, the chemical structure of lean premixed propene-oxygen-nitrogen flames stabilized on a flat-flame burner at atmospheric pressure was determined experimentally. The species mole fraction profiles were also computed by the Premix code and three detailed reaction mechanisms. A very good agreement was observed for the main properties: reactants consumption, final products (CO 2, H 2O) and the main intermediates: CO and H 2. Only a general agreement is also observed between predicted and measured mole fraction profiles for minor intermediates. Marked differences occurred in the prediction of active intermediate species present in small concentrations. Pathways analyses were performed to identify the origins of these discrepancies. It was shown that the same reactions were involved in the three mechanisms to describe the consumption of propene, but with marked differences in their importance. C 2H 5, C 2H 4, and C 3H 5 are the main species formed in the first step and their consumption increases the differences between the mechanisms either by the use of different kinetics data for common reactions or by differences in the nature of the consumption reactions. © 2012 Chemical Society of Ethiopia. Source

Diaw P.A.,University Ca Diop | Maroto A.,French National Center for Scientific Research | Mbaye O.M.A.,University Ca Diop | Gaye-Seye M.D.,University Ca Diop | And 6 more authors.

A direct Laser Photo-Induced Fluorescence (DL-PIF) method is developed for the determination of two phenylurea pesticides, namely fenuron and diflubenzuron. The DL-PIF method uses a tunable Nd:YAG-OPO Laser to obtain the photoproduct(s) and to simultaneously analyse their fluorescence in a short acquisition time on an intensified CCD camera. Compared to classical PIF methods, the use of a tunable laser improves the selectivity (by choosing the suitable excitation wavelength), increases the sensitivity (due to the high energy of the beam) and also reduces the time of analysis. The analytical performances of this method for the determination of both pesticides are satisfactory in comparison to other classical PIF methods published for the determination of phenylurea pesticides. The calibration curves were linear over one order of magnitude and the limits of detection were in the ng mL -1 range. Satisfactory recoveries were obtained in the analysis of both pesticides in river and sea water spiked samples. © 2013 Elsevier B.V. Source

Mbaye O.M.A.,University Ca Diop | Maroto A.,University of Western Brittany | Gaye-Seye M.D.,University Ca Diop | Stephan L.,University of Western Brittany | And 3 more authors.

A new direct laser photo-induced fluorescence high performance liquid chromatography (DL-PIF-HPLC) method is developed for the simultaneous determination of three anilide pesticides, namely carboxin, monalide and propanil. DL-PIF-HPLC uses a tunable Nd:YAG-OPO laser to obtain fluorescent photoproduct(s) and to simultaneously analyze their fluorescence in a short acquisition time with an intensified CCD camera, which improves the selectivity (by choosing the suitable excitation wavelength), increases the sensitivity (due to the high energy of the laser beam) and reduces the time of analysis, relative to the classical PIF methods. However, one of the main drawbacks of PIF methods is the presence of interferences with other compounds, such as other pesticides from the same group yielding similar fluorescent photoproducts, which reduces their selectivity. The analytical interest of DL-PIF-HPLC to avoid these interferences is demonstrated. The DL-PIF spectra, chromatographic conditions and analytical performances of DL-PIF-HPLC are presented for the simultaneous determination of three anilide pesticides. The calibration curves are linear over one order of magnitude and the limits of detection are in the ng mL-1 range. The new DL-PIF-HPLC system has the advantage to combine the performances of both techniques, DL-PIF and liquid chromatography, and to improve the analysis selectivity. © 2014 Elsevier Ltd. All rights reserved. Source

Lo C.,University of Marne-la-Vallee | Lo C.,University Ca Diop | Doucoure B.I.,University Ca Diop | Aaron J.-J.,University of Marne-la-Vallee | And 6 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

The synthesis and optical properties of three new fluorescent alkoxy-substituted thieno[3,2-b]indole (TI) derivatives, including 7-methoxy thieno[3,2-b]indole (7-MeOTI), 6,7- methylenedioxythieno[3,2-b]indole (6,7-MDTI) and 6,7-dihexyloxythieno[3,2-b]indole, (6,7-DHTI), were investigated. Electronic absorption spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (ΦF), lifetimes (τF), and other photophysical parameters of the three TI derivatives were measured in DMSO solutions at room temperature. Theoretical electronic absorption and fluorescence spectra were also calculated by means of a molecular orbital (MO) method. For all three alkoxy-TI derivatives, the fluorescence emission maximum wavelength was significantly red shifted relative to un-substituted TI, which was attributed to delocalization of the fused hetero-aromatic ring π electronic system by the electron-donating alkoxy group(s). ΦF values varied from 0.12 to 0.19, according to the compound. τF were short, in the range 0.56-1.13 ns. © 2013 Elsevier B.V. All rights reserved. Source

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