Nakajima varieties and repetitive algebras

We realize certain graded Nakajima varieties of finite Dynkin type as orbit closures of repetitive algebras of Dynkin quivers. As an application, we obtain that the perverse sheaves introduced by Nakajima for describing irreducible characters of quantum loop algebras are isomorphic to the intersection cohomology sheaves of these orbit closures.Comment: 26 pages, v2 : Minor corrections. Final version to appear in PRIMS (Publications of the Research Institute for Mathematical Sciences, Kyoto

Macé – Les Hernies

Date de l'opération : 2007 (FP) Inventeur(s) : Leclerc Guy (BEN) Les opérations menées en 2005 et 2006 avaient permis de répertorier treize bâtiments à fonction cultuelle dans une aire sacrée (cour 1) limitée par un péribole doté d’un porche monumental et d’une galerie. La campagne 2007 a, dans un premier temps, complété l’étude du mur d’enceinte de la cour principale sur son côté sud-ouest. Ce péribole F 13, dont l’élévation a été volée, n’y subsiste plus que par une fondation partiellement ..

Les occupations rurales gallo-romaines de la plaine d’Argentan

En 2012, la poursuite de la prospection dans la plaine d’Argentan s’est intéressée au territoire de quatre nouvelles communes (Commeaux, Montabard, Ri, Rônai) localisées dans le secteur nord en bordure de l’espace sédimentaire. Quantitativement, le bilan de l’opération s’établit à 13 sites et indices inédits qui se répartissent entre Commeaux (2), Montabard (3), Ri (3) et Ronai (2), auxquels il faut ajouter deux entités identifiées sur Occagnes, commune incomplètement prospectée en 2011, et u..

Occupations rurales antiques de la plaine d'Argentan-Mortrée

Date de l'opération : 2009 (PT) L’opération 2009 s’est intéressée au territoire de quatre nouvelles communes situées au sud-ouest de la plaine ; trois d’entre-elles sont adossées au massif forestier d’Écouves en limite du bassin sédimentaire. Quantitativement, le bilan 2009 s’établit à 18 sites inédits répartis ainsi par commune :    - Saint-Christophe-le-Jajolet : 2 ;     - Vrigny : 6 ;     - Fleuré : 5 ;     ..

Real-time RT-PCR analysis of mRNA decay: half-life of Beta-actin mRNA in human leukemia CCRF-CEM and Nalm-6 cell lines

BACKGROUND: We describe an alternative method to determine mRNA half-life (t(1/2)) based on the Real-Time RT-PCR procedure. This approach was evaluated by using the β-actin gene as a reference molecule for measuring of mRNA stability. RESULTS: Human leukemia Nalm-6 and CCRF-CEM cells were treated with various concentrations of Actinomycin D to block transcription and aliquots were removed periodically. Total RNA was isolated and quantified using the RiboGreen(®) fluorescent dye with the VersaFluor Fluorometer System. One μg of total RNA was reverse transcribed and used as template for the amplification of a region of the β-actin gene (231 bp). To generate the standard curve, serial ten-fold dilutions of the pBactin-231 vector containing the cDNA amplified fragment were employed, β-actin mRNAs were quantified by Real-Time RT-PCR using the SYBR(®) Green I fluorogenic dye and data analyzed using the iCycle iQ system software. Using this method, the β-actin mRNA exhibited a half-life of 6.6 h and 13.5 h in Nalm-6 and CCRF-CEM cells, respectively. The t(1/2) value obtained for Nalm-6 is comparable to those estimated from Northern blot studies, using normal human leukocytes (5.5 h). CONCLUSIONS: We have developed a rapid, sensitive, and reliable method based on Real-Time RT-PCR for measuring mRNA half-life. Our results confirm that β-actin mRNA half-life can be affected by the cellular growth rate

L’établissement rural antique du Grand-Herbage à Sées (Orne)

L’étude de l’occupation rurale gallo-romaine du Grand-Herbage, à Sées (Orne), a restitué l’organisation d’une entité agricole implantée au ier siècle de notre ère, caractérisée par un habitat en dur et par des installations agricoles en matériaux périssables. Suite à son abandon dans la seconde moitié du iiie siècle, l’établissement est réorganisé sous une forme plus modeste.The Antique farmstead of Le Grand-Herbage at Sées (Orne). The study of the rural occupation of Le Grand-Herbage at Sées (Orne) revealed the organization of an agricultural unit established in the 1st century A.D. and characterized by a stone built residence and lighter agricultural installations of perishable materials. Following its desertion in the second half of the third century, the farmstead is reorganised in a more modest form

The role of chemistry in the oscillating combustion of hydrocarbons : an experimental and theoretical study

The stable operation of low-temperature combustion processes is an open challenge, due to the presence of undesired deviations from steady-state conditions: among them, oscillatory behaviors have been raising significant interest. In this work, the establishment of limit cycles during the combustion of hydrocarbons in a wellstirred reactor was analyzed to investigate the role of chemistry in such phenomena. An experimental investigation of methane oxidation in dilute conditions was carried out, thus creating quasi-isothermal conditions and decoupling kinetic effects from thermal ones. The transient evolution of the mole fractions of the major species was obtained for different dilution levels (0.0025 <= X-CH4 <= 0.025), inlet temperatures (1080K <= T <= 1190K) and equivalence ratios (0.75 <= Phi <= 1). Rate of production analysis and sensitivity analysis on a fundamental kinetic model allowed to identify the role of the dominating recombination reactions, first driving ignition, then causing extinction. A bifurcation analysis provided further insight in the major role of these reactions for the reactor stability. One-parameter continuation allowed to identify a temperature range where a single, unstable solution exists, and where oscillations were actually observed. Multiple unstable states were identified below the upper branch, where the stable (cold) solution is preferred. The role of recombination reactions in determining the width of the unstable region could be captured, and bifurcation analysis showed that, by decreasing their strength, the unstable range was progressively reduced, up to the full disappearance of oscillations. This affected also the oxidation of heavier hydrocarbons, like ethylene. Finally, less dilute conditions were analyzed using propane as fuel: the coupling with heat exchange resulted in multiple Hopf Bifurcations, with the consequent formation of intermediate, stable regions within the instability range in agreement with the experimental observations