Sur la catégorie Db,G(X) pour G réductif fini

In this Note, we are interested in the G-equivariant derived category of a smooth projective scheme over an algebraically closed field k, on which a reductive finite group G is acting. We compare the G-equivariant derived category of X with the derived category of the quotient by giving a descent criterion. The result generalizes a theorem of Lønsted in G-equivariant K-theory on curves (K. Lønsted, J. Math. Kyoto Univ. 23 (4) (1983) 775–793). We also give an equivariant version of Be??linson's equivalence of categories (Funct. Anal. Appl. 12 (1979) 214–216) and treat the exemple of the projective line. To cite this article: S. Térouanne, C. R. Acad. Sci. Paris, Ser. I 336 (2003).     

Propriété de Liouville et équation de Poisson pour le laplacien généralisé de Dunkl

Let Δ_k be the Dunkl generalized Laplacian associated to a root system R of $\text{R}{}^{\mathrm{N}}$ and a non-negative function k defined on R and invariant by the Weyl group. In this Note, we show that this differential-difference operator on $\text{R}{}^{\mathrm{N}}$ satisfies the Liouville property, then we solve the Poisson equation Δ_ku=?f by using a generalized Fourier analysis method. To cite this article: L. Gallardo, L. Godefroy, C. R. Acad. Sci. Paris, Ser. I 337 (2003).     

Synthesis of new nucleoside analogues comprising a methylenecyclobutane unit

Synthesis of eight nucleoside analogues 3-10 with a methylene cyclobutane unit is described. Wittig or Peterson reactions with protected 2-hydroxycyclobutanones 12 and 13 gave E- and Z-derivatives, respectively. After functional modifications the heterocyclic moieties were introduced via a Mitsunobu reaction either on the lateral chain or on the cycle. When adenine was used in this reaction only the N-9 substitution products were obtained. Removal of the protecting groups provided the target products.     

Quantitation of 35S promoter in maize DNA extracts from genetically modified organisms using real-time polymerase chain reaction, part 2: interlaboratory study

The European Committee for Standardization (CEN) and the European Network of GMO Working Laboratories have proposed development of a modular strategy for stepwise validation of complex analytical techniques. When applied to the quantitation of genetically modified organisms (GMOs) in food products, the instrumental quantitation step of the technique is separately validated from the DNA extraction step to better control the sources of uncertainty and facilitate the validation of GMO-specific polymerase chain reaction (PCR) tests. This paper presents the results of an interlaboratory study on the quantitation step of the method standardized by CEN for the detection of a regulatory element commonly inserted in GMO maize-based foods. This is focused on the quantitation of P35S promoter through using the quantitative real-time PCR (QRT-PCR). Fifteen French laboratories participated in the interlaboratory study of the P35S quantitation operating procedure on DNA extract samples using either the thermal cycler ABI Prism 7700 (Applied Biosystems, Foster City, CA) or Light Cycler (Roche Diagnostics, Indianapolis, IN). Attention was focused on DNA extract samples used to calibrate the method and unknown extract samples. Data were processed according to the recommendations of ISO 5725 standard. Performance criteria, obtained using the robust algorithm, were compared to the classic data processing after rejection of outliers by the Cochran and Grubbs tests. Two laboratories were detected as outliers by the Grubbs test. The robust precision criteria gave values between the classical values estimated before and after rejection of the outliers. Using the robust method, the relative expanded uncertainty by the quantitation method is about 20% for a 1% Bt176 content, whereas it can reach 40% for a 0.1% Bt176. The performances of the quantitation assay are relevant to the application of the European regulation, which has an accepted tolerance interval of about +/-50%. These data were fitted to a power model (r2 = 0.96). Thanks to this model, it is possible to propose an estimation of uncertainty of the QRT-PCR quantitation step and an uncertainty budget depending on the analytical conditions.     

Propriétés de lissité de certaines normes

Sans résumé     

The fate of mercury species injected into coelomic fluid of starfish Leptasterias polaris

Mature starfish Leptasterias polaris, collected in the St Lawrence Estuary (eastern Canada), were exposed to two mercury species (HgCI₂ and CH₃HgCI) via injections into the coelomic fluid. In vivo effects of some complexing agents (glutathione, mercaptoethanol and EDTA) on the distribution of ²⁰³Hg-labelled species in starfish organs and tissues and their possible role in mercury transport through membranes were studied over a 24 h period. The excretion of ammonia and mercury was also measured. When injected alone, inorganic mercury and methylmercury [CH₃Hg(II)] were distributed in all organs, with a preferential adsorption in gonads, pyloric caeca and stomach. Mercury excretion was very low under all conditions studied. Mercaptoethanol, a small thiol ligand, was very efficient in reducing both mercury species in the coelomic fluid and seems to have promoted translocation towards most organs of the starfish. Its action is attributed to the formation of small and neutral complexes, HgL₂ and CH₃HgL, which can diffuse through membranes preserving their integrity. Glutathione increased the translocation of CH₃Hg(II) towards surrounding organs, but had no apparent effect on inorganic mercury. EDTA promoted the transport of inorganic mercury only. These results highlight (1) the particular interest of starfish to workers studying in vivo chemical complexation of mercury species, and (2) the potential role of complexing molecules in the biotransport of mercury species through living membranes.     

Using the Hard Templating Method for the Synthesis of Metal‐Conducting Polymer Multi‐Segmented Nanowires

With the development of nanotechnology, there is a growing demand for advanced electronics based on functional nanomaterials. In this respect, owing to their unique properties, conducting polymers (CP) synthesized in the form of one‐dimensional (1D) nanostructures are of particular interest. In this feature paper, we first report one of the most powerful techniques, the hard templating synthesis, for elaborating a large number of uniform 1D CP nanotubes or nanowires with precise control over lengths and diameters. Then, recent advances in the preparation, through electrochemical template synthesis, of various multi‐segmented nanowires containing a combination of metallic and polymeric components are discussed. Hybrid metal‐CP nanowires are promising high tech materials as they exhibit enhanced performances compared to their bulk counterparts and are of direct interest for developing novel multifunctional systems for a wide range of applications. Finally, some future directions for research in the area of multi‐segmented nanowires are proposed.

     

Résolutions de singularités non-abéliennes en dimension trois

Let E be an elliptic curve and R be a real three dimensional root system. Let W be the Weyl group associated to R. Denote $W_{+}=W\cap {\mathrm{SL}}_3(\mathbb{C})$. The quotient $E?Q(\mathrm{R})/W_{+}$ admits two natural crepant resolutions. One is the result of a Jung process of desingularization of singularities, the other the equivariant Hilbert scheme. To compare these resolutions, we calculate the fibres over any singular point in both cases. We exhibit a McKay correspondence phenomenon for the Hilbert scheme resolution and construct a new family of vector bundles on E parametrized by the $W_{+}$-Hilbert scheme. To cite this article: S. Térouanne, C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

Neural correlates of intelligibility in speech investigated with noise vocoded speech--a positron emission tomography study

Functional imaging studies of speech perception in the human brain have identified a key role for auditory association areas in the temporal lobes (bilateral superior temporal gyri and sulci) in the perceptual processing of the speech signal. This is extended to suggest some functional specialization within this bilateral system, with a particular role for the left anterior superior temporal sulcus (STS) in processing intelligible speech. In the current study, noise-vocoded speech was used to vary the intelligibility of speech parametrically. This replicated the finding of a selective response to intelligibility in speech in the left anterior superior temporal sulcus, in contrast to the posterior superior temporal sulcus, which showed a response profile insensitive to the degree of intelligibility. These results are related to theories of functional organization in the human auditory system, which have indicated that there are separate processing streams, with different functional roles, running anterior and posterior to primary auditory cortex. Specifically, it is suggested that an anterior stream processing intelligibility can be distinguished from a posterior stream associated with transient representations, important in spoken repetition and working memory.