Dialogue Nord-Sud, plurilinguisme et perspective écologique : pour le développement de la recherche et de la formation d'enseignants en sciences humaines

<div><p>The cross-section of a cell in a monolayer epithelial tissue can be modeled mathematically as a <i>k</i>-sided polygon. Empirically studied distributions of the proportions of <i>k</i>-sided cells in epithelia show remarkable similarities in a wide range of evolutionarily distant organisms. A variety of mathematical models have been proposed for explaining this phenomenon. The highly parsimonious simulation model of (Patel et al., PLoS Comput. Biol., 2009) that takes into account only the number of sides of a given cell and cell division already achieves a remarkably good fit with empirical distributions from <i>Drosophila</i>, <i>Hydra</i>, <i>Xenopus</i>, Cucumber, and <i>Anagallis</i>. Within the same modeling framework as in that paper, we introduce additional options for the choice of the endpoints of the cleavage plane that appear to be biologically more realistic. By taking the same data sets as our benchmarks, we found that combinations of some of our new options consistently gave better fits with each of these data sets than previously studied ones. Both our algorithm and simulation data are made available as research tools for future investigations.</p></div

Structure elucidation and NMR assignments of a new 6,9-cyclotetrahydrofuranlignan from <i>Syringa pinnatifolia</i>

<p>A new 6,9-cyclotetrahydrofuranlignan, 3,3′-dimethoxy-4,4′-dihydroxy-8β,9β,8′α-6,9-cyclotetrahydrofuranlignan, was isolated from the stem of <i>Syringa pinnatifolia</i> Hems1.var. <i>alashanensis</i> MA. et S. Q. ZHOU. Its structures were elucidated on the basis of spectroscopic methods including UV, IR, ESI-MS, 1D NMR and 2D NMR.</p

SEM images (a); TEM and HRTEM images (b) as well as the corresponding SAED patterns (insets) for CO, CO–SC, ME and ME–SC.

<p>SEM images (a); TEM and HRTEM images (b) as well as the corresponding SAED patterns (insets) for CO, CO–SC, ME and ME–SC.</p

Significant Improvement of Thermal Stability for CeZrPrNd Oxides Simply by Supercritical CO₂ Drying

<div><p>Pr and Nd co-doped Ce-Zr oxide solid solutions (CZPN) were prepared using co-precipitation and microemulsion methods. It is found that only using supercritical CO₂ drying can result in a significant improvement of specific surface area and oxygen storage capacity at lower temperatures for CZPN after aging at 1000°C for 12 h in comparison with those using conventional air drying and even supercritical ethanol drying. Furthermore, the cubic structure was obtained in spite of the fact that the atomic ratio of Ce/(Ce+Zr+Pr+Nd) is as low as 29%. The high thermal stability can be attributed to the loosely aggregated morphology and the resultant Ce enrichment on the nanoparticle surface, which are caused by supercritical CO₂ drying due to the elimination of surface tension effects on the gas-liquid interface.</p></div

Textural properties and compositions.

a<p>t-plot external surface area;</p>b<p>t-plot micropore volume;</p>c<p>Calculated standard deviations from Le Bail fitting are given in parentheses.</p

XPS analysis results.

a<p>Adsorbed oxygen/(Adsorbed and lattice oxygen, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088236#pone.0088236.s005" target="_blank">Figure S5c</a>).</p

H₂–TPR and total OSC results.

a<p>µmol O₂/g sample;</p>b<p>µmol O₂/g CeO₂.</p

N₂ adsorption/desorption isotherms (a) and pore size distribution plots (b) for CO, CO–SC, ME and ME–SC.

<p>N₂ adsorption/desorption isotherms (a) and pore size distribution plots (b) for CO, CO–SC, ME and ME–SC.</p

Raman spectra of CO, CO–SC, ME and ME–SC.

<p>Raman spectra of CO, CO–SC, ME and ME–SC.</p

H₂–TPR spectra (a) and initial H₂ consumption rate per gram sample (b) for CO, CO–SC, ME and ME–SC during the first cycle.

<p>H₂–TPR spectra (a) and initial H₂ consumption rate per gram sample (b) for CO, CO–SC, ME and ME–SC during the first cycle.</p