Données nouvelles sur le contenu organique des dépôts phosphatés du gisement de Ras-Draâ (Tunisie) New data on the organic matter associated to phosphatic ores of the Ras-Draâ deposit (Tunisia)

International audienceL'étude de la matière organique (MO) associée aux sédiments phosphatés a été conduite sur des fractions séparées – grains phosphatés (pellets) et leurs matrices – de strates riches en phosphate du gisement de Ras-Draâ. Cette étude a réuni des analyses géochimiques élémentaires C, N, S, des analyses par pyrolyse Rock-Eval (RE) et des extractions des substances humiques (SH). Les données géochimiques fournies par l'analyse CNS et par la pyrolyse RE indiquent : (i) des teneurs en carbone organique total (COT) plus élevées dans les matrices (atteignant 4,00 %) que dans les pellets (≤ 1,62 % ) ; (ii) la présence, dans les deux fractions, d'une MO se rattachant à la lignée II, planctonique marine, plus ou moins oxydée ; (iii) une faible évolution diagénétique subie par la MO dans chacune des fractions (Tmax, globalement < 430 °C). Les données quantitatives de l'extraction et du fractionnement des SH en acides fulviques, humiques et humine, indiquent une forte abondance de composés humiques extractibles (CH) dans les pellets (CCH not, vert, similar 70 % de la somme du COT des fractions séparées COTfr) et une présence occasionnelle, en faibles quantités, de CH extractibles dans les matrices. Cette situation exclut que ces pellets se soient constitués de façon authigénique au sein de leur matrice, ce qui est pleinement conforme à la possibilité, récemment formulée, qu'il s'agisse de fèces de poissons. Abstract The study of the organic matter (OM) content of phosphatic sediments from the Ras-Draâ deposit, Tunisia, was carried on the two separated lithological fractions constituting the bulk sediments, namely phosphatic grains (pellets) and their associated matrices. The geochemical characterization of the OM present in pellets and in their matrices by CNS elemental analysis and RE pyrolysis indicates that: (i) the TOC content is higher in matrices (where it reaches 4.00%), than in pellets in the same strata where it does not exceed 1.62%; (ii) the presence of more or less oxidized marine planktonic OM in both fractions; (iii) a low degree of diagenetic evolution of the OM in both fractions (RE Tmax globally < than 430 °C). The chemical extraction of the humic substances (HS) from both fractions followed by the separation of fractions according to the IHSS procedure, systematically indicates a higher abundance of extractable humic compounds (HC) in the pellets (CHC not, vert, similar 70% of the sum of TOC in the separated fractions, TOCfr) and a variable but lower extraction yield in matrices (CHC not, vert, similar 18% TOCfr). This significant difference between both fractions excludes the possibility that pellets formed authigenically from, and within, their matrix. This is consistent with recent findings suggesting that these pellets could be fish feces

Time resolved and temperature dependence of the radiative properties of thiol-capped CdS nanoparticles films

In this work, we present the temperature-dependence and time-resolved photoluminescence (PL) of CdS nanoparticles capped independently with three different ligands thiophenol, thioglycerol, and l-cysteine over a broad temperature range from 10 to 300 K. The respective nanoparticles sizes in the three systems studied in this work are 1.5, 4, and 2 nm as determined from X-ray diffraction (XRD). From the analysis of AFM images, it was found that the lateral particle sizes of capped CdS nanoparticles are greater than those deduced from XRD or optical absorption measurements. The aim of this study is the investigation of the impact of the organic ligands on the radiative recombination dynamics in organically capped CdS nanoparticles. From the PL study and based on the temperature-dependence and time-resolved emission spectroscopy, we conclude that the emission of CdS QDs film originates from recombination of the delocalized carriers in the internal core states with a small contribution of the localized carriers at the interface. The PL decay reveals a biexponential behavior for the entire three samples at all temperatures. One of the two exponential components decays rapidly with a time τ(1) in the range 0.5–0.8 ns, whereas the other decays much more slowly, with a time τ(2) in the range 1–3 ns. The weak activation energy (32–37 meV) deduced from the temperature dependence of the PL intensity suggests the involvement of shallow traps. The analysis of the experimental results reveals a relatively narrow size distribution, an efficient surface passivation, and a satisfactory thermal stability of CdS nanocrystals

A forward genetics approach integrating genome-wide association study and expression quantitative trait locus mapping to dissect leaf development in maize (Zea mays)

The characterization of the genetic basis of maize (Zea mays) leaf development may support breeding efforts to obtain plants with higher vigor and productivity. In this study, a mapping panel of 197 biparental and multiparental maize recombinant inbred lines (RILs) was analyzed for multiple leaf traits at the seedling stage. RNA sequencing was used to estimate the transcription levels of 29\ua0573 gene models in RILs and to derive 373\ua0769 single nucleotide polymorphisms (SNPs), and a forward genetics approach combining these data was used to pinpoint candidate genes involved in leaf development. First, leaf traits were correlated with gene expression levels to identify transcript\u2013trait correlations. Then, leaf traits were associated with SNPs in a genome-wide association (GWA) study. An expression quantitative trait locus mapping approach was followed to associate SNPs with gene expression levels, prioritizing candidate genes identified based on transcript\u2013trait correlations and GWAs. Finally, a network analysis was conducted to cluster all transcripts in 38 co-expression modules. By integrating forward genetics approaches, we identified 25 candidate genes highly enriched for specific functional categories, providing evidence supporting the role of vacuolar proton pumps, cell wall effectors, and vesicular traffic controllers in leaf growth. These results tackle the complexity of leaf trait determination and may support precision breeding in maize

New data on the characterization of humic substances extracted from phosphatised faecal “pellets” (Tunisia)

9-14 September 2007International audienceHumic substances (HS) were extracted from faecal “pellets” - ovoid phosphatic grains 50-200 µm in size - collected from commercially mined phosphatic sediments, in the Gafsa Basin. The phosphatic constituents were characterized by C, H, O, N, and S elemental analysis, Rock-Eval VI pyrolysis, Fourier-transformed infrared spectroscopy (FTIR) and solid state 13C CPMAS NMR

Successful treatment of fusarium solani ecthyma gangrenosum in a patient affected by leukocyte adhesion deficiency type 1 with granulocytes transfusions

<p>Abstract</p> <p>Background</p> <p>Ecthyma gangrenosum (EG) manifests as a skin lesion affecting patients suffering extreme neutropenia and is commonly associated with <it>Pseudomonas aeruginosa </it>in immunocompromised patients. Leukocyte adhesion deficiency I (LAD I) which count among primary immunodeficiency syndromes of the innate immunity, is an autosomal recessive disorder characterized in its severe phenotype by a complete defect in CD18 expression on neutrophils, delayed cord separation, chronic skin ulcers mainly due to recurrent bacterial and fungal infections, leucocytosis with high numbers of circulating neutrophils and an accumulation of abnormally low number of neutrophils at sites of infection.</p> <p>Case Presentation</p> <p>We report at our knowledge the first case of a child affected by LAD-1, who experienced during her disease course a multi-bacterial and fungal EG lesion caused by <it>fusarium solani</it>. Despite targeted antibiotics and anti-fungi therapy, the lesion extended for as long as 18 months and only massive granulocytes pockets transfusions in association with G-CSF had the capacity to cure this lesion.</p> <p>Conclusion</p> <p>We propose that granulocytes pockets transfusions will be beneficial to heal EG especially in severely immunocompromised patients.</p

Interior Regularity Estimates in High Conductivity Homogenization and Application

In this paper, uniform pointwise regularity estimates for the solutions of conductivity equations are obtained in a unit conductivity medium reinforced by a epsilon-periodic lattice of highly conducting thin rods. The estimates are derived only at a distance epsilon^{1+tau} (for some tau>0) away from the fibres. This distance constraint is rather sharp since the gradients of the solutions are shown to be unbounded locally in L^p as soon as p>2. One key ingredient is the derivation in dimension two of regularity estimates to the solutions of the equations deduced from a Fourier series expansion with respect to the fibres direction, and weighted by the high-contrast conductivity. The dependence on powers of epsilon of these two-dimensional estimates is shown to be sharp. The initial motivation for this work comes from imaging, and enhanced resolution phenomena observed experimentally in the presence of micro-structures. We use these regularity estimates to characterize the signature of low volume fraction heterogeneities in the fibred reinforced medium assuming that the heterogeneities stay at a distance epsilon^{1+tau} away from the fibres

Research of the origin of a particular Tunisian group using a physical marker and Alu insertion polymorphisms

The aim of this study was to show how, in some particular circumstances, a physical marker can be used along with molecular markers in the research of an ancient people movement. A set of five Alu insertions was analysed in 42 subjects from a particular Tunisian group (El Hamma) that has, unlike most of the Tunisian population, a very dark skin, similar to that of sub-Saharans, and in 114 Tunisian subjects (Gabes sample) from the same governorate, but outside the group. Our results showed that the El Hamma group is genetically midway between sub-Saharan populations and North Africans, whereas the Gabes sample is clustered among North Africans. In addition, The A25 Alu insertion, considered characteristic to sub-Saharan Africans, was present in the El Hamma group at a relatively high frequency. This frequency was similar to that found in sub-Saharans from Nigeria, but significantly different from those found in the Gabes sample and in other North African populations. Our molecular results, consistent with the skin color status, suggest a sub-Saharan origin of this particular Tunisian group