249 research outputs found
Données nouvelles sur le contenu organique des dépÎts phosphatés du gisement de Ras-Draù (Tunisie) New data on the organic matter associated to phosphatic ores of the Ras-Draù deposit (Tunisia)
International audienceL'Ă©tude de la matiĂšre organique (MO) associĂ©e aux sĂ©diments phosphatĂ©s a Ă©tĂ© conduite sur des fractions sĂ©parĂ©es â grains phosphatĂ©s (pellets) et leurs matrices â de strates riches en phosphate du gisement de Ras-DraĂą. Cette Ă©tude a rĂ©uni des analyses gĂ©ochimiques Ă©lĂ©mentaires C, N, S, des analyses par pyrolyse Rock-Eval (RE) et des extractions des substances humiques (SH). Les donnĂ©es gĂ©ochimiques fournies par l'analyse CNS et par la pyrolyse RE indiquent : (i) des teneurs en carbone organique total (COT) plus Ă©levĂ©es dans les matrices (atteignant 4,00 %) que dans les pellets (†1,62 % ) ; (ii) la prĂ©sence, dans les deux fractions, d'une MO se rattachant Ă la lignĂ©e II, planctonique marine, plus ou moins oxydĂ©e ; (iii) une faible Ă©volution diagĂ©nĂ©tique subie par la MO dans chacune des fractions (Tmax, globalement < 430 °C). Les donnĂ©es quantitatives de l'extraction et du fractionnement des SH en acides fulviques, humiques et humine, indiquent une forte abondance de composĂ©s humiques extractibles (CH) dans les pellets (CCH not, vert, similar 70 % de la somme du COT des fractions sĂ©parĂ©es COTfr) et une prĂ©sence occasionnelle, en faibles quantitĂ©s, de CH extractibles dans les matrices. Cette situation exclut que ces pellets se soient constituĂ©s de façon authigĂ©nique au sein de leur matrice, ce qui est pleinement conforme Ă la possibilitĂ©, rĂ©cemment formulĂ©e, qu'il s'agisse de fĂšces de poissons. Abstract The study of the organic matter (OM) content of phosphatic sediments from the Ras-DraĂą 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 300Â K. The respective nanoparticles sizes in the three systems studied in this work are 1.5, 4, and 2Â 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 Ï(1) in the range 0.5â0.8Â ns, whereas the other decays much more slowly, with a time Ï(2) in the range 1â3Â ns. The weak activation energy (32â37Â 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 âpelletsâ (Tunisia)
9-14 September 2007International audienceHumic substances (HS) were extracted from faecal âpelletsâ - ovoid phosphatic grains 50-200 ”m 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
Testing the Relationships between Energy Consumption, CO2 Emissions and Economic Growth in 24 African Countries: A Panel ARDL Approach
Detection of viable but non cultivable Escherichia coli after UV irradiation using a lytic QÎČ phage
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