1,721,329 research outputs found
La mort des Sirènes dans la littérature grecque de l'époque classique
No full textThis paper deals with the post-Homeric tradition on the death of the Sirens
after the passage of Odysseus’ ship, due to their failure in charming him. The
representation of their suicide on a stamnos dating back to the 5th century
(London 1943.11-3.31) shows that this legend was quite known in Antiquity and
so it could help in the understanding of three much debated literary occurrences
according to which the Sirens dwell in the Hades (Eur. Hel 168-78; Soph. fr. 861
Radt; Plat. Crat 403d). Rather than explaining these texts with the reference to
the “funerary Siren”, a quite common decoration for tombs, it could be possible
to compare them with a mythical tradition on this topic which was popular at
that time.Cette contribution porte sur la tradition posthomérique de la mort des
Sirènes, après le passage du bateau d’Ulysse, parce qu’elles n’ont pas été capables
de le charmer. La représentation de leur suicide sur un stamnos du ve siècle avant
J.-C. (Londres BM 1943.11-3.31) montre que cette légende était assez connue
dans l’Antiquité ; elle peut donc aider dans l’interprétation de quelques passages
littéraires très débattus où les Sirènes se trouvent dans l’Hadès (Eur. Hel 168-78 ;
Soph. fr. 861 Radt ; Plat. Crat 403d). Plutôt que d’expliquer ces textes avec la
référence à la figure de la « Sirène funéraire », une décoration pour les tombes
assez commune, on pourrait les comparer avec la tradition mythique connue à
l’époque sur ce sujet
AUCTORICTAS HOMERICA? OMERO E LA CULTURA GRECA D'ETA' CLASSICA
No full textQuesto lavoro ha per oggetto il trattamento degli episodi del ciclo troiano presenti, da un lato, nei poemi omerici, e, dall’altro, nella letteratura e nell’arte figurativa di età classica. L’obiettivo è quello di stabilire quale fosse l’autorità dell’Iliade e dell’Odissea nel V e IV secolo per gli autori e gli artisti che si trovavano a riprendere i medesimi argomenti. Attraverso un esame attento dei casi in cui si riscontrano differenze tra la riproposizione di età classica e la versione dei poemi omerici, è emerso, da un lato, che le differenze rispetto a Omero non costituiscono casi sporadici, ma sono documentabili in numerosi testi e in numerose rappresentazioni. Dall’altro, che, soppesando prudentemente le diverse possibilità, ne risulta un quadro diversificato, in cui l’influenza della versione omerica può essere considerata possibile o da escludere. Il valore canonico che è attribuito ai poemi omerici in età successive non è quindi rintracciabile già nell’età classica: la versione omerica non era che una tra le tante a cui era possibile ispirarsi nella trattazione di un episodio del ciclo troiano.This research focuses on the handling of the episodes belonging to the Trojan cycle which appear both in the Homeric epics and in the literature and iconography of the classical period. It aims at showing if an ipothetic authority of the Iliad and the Odyssey in the 5th and 4th century was determining for artists and authors who dealt with the same subjects. Through a careful analysis of the differences between the version which appears in the classical age and in the Homeric one, it is possible to state that these differences are not sporadic, but they can be found in a number of texts and representations. Moreover, taking into account every possible explanation, the resulting picture is a variegated one, made up of cases where the influence of the Homeric version may be considered as possible and cases where it has to be excluded. In conclusion, the canonical value which is attributed to the poems in later times can’t be detected in the classical age: the Homeric version is just one out of many legends to which it was possible to make reference while dealing with an episode of the Trojan cycle
A comparative study of the NH3-SCR reactions over a Cu-zeolite and a Fe-zeolite catalyst
No full textOn board catalytic NOx control: mechanistic aspects of the regeneration of Lean NOx Traps with H2
No full textThe chemistry of NH3-NO/NO2 - Fast SCR reaction over Fe-ZSM-5 investigated by dynamic reaction experiments
No full textMechanistic and kinetic study of the NO/NO2-NH3 SCR reaction over a V-based catalyst for Diesel exhaust after treatment
No full textThe low-temperature interaction of NH3/NO/NO2 + O2 with Fe-ZSM-5 + BaO/Al2O3 and H-ZSM-5 + BaO/Al2O3: Influence of phase separation and relevance for the NH3-SCR chemistry
Full text linkIn an effort to elucidate mechanism and intermediates of Standard SCR over metal-zeolite catalysts, we apply Transient Response Methods (TRM) to identify the mediating species in the low-temperature (120 °C) interaction of NO2 + O2, NO + O2 and NO + NO2 + O2 (NO/NO2 = 10/1 v/v) with a composite Fe-ZSM-5 (Fe = 1% w/w) + BaO/Al2O3 system in different configurations (physical mixture versus double-bed), corresponding to different degrees of separation of the two component phases. The results clearly indicate for the first time that the strong interaction between the two system components, already demonstrated in previous work, survives their complete segregation, proceeds via the gas phase, and is mediated by stable gaseous NOx species. The nature of the NOx species trapped on the BaO phase is identified by TPD experiments: in line with previous data, they include primarily nitrates for NO2 adsorption, and nitrites for NO + O2 adsorption at short exposure times. A new, striking finding is that formation of nitrites on BaO upon exposure of Fe-ZSM-5 + BaO/Al2O3 to NO + O2, which involves the oxidative activation of NO on Fe-sites, is fully equivalent to the formation of nitrites observed upon exposing only BaO/Al2O3 to NO2 in excess NO. This suggests that NO2 (possibly in the form of N2O3) may play the role of mediating gas-phase species generated by the oxidative activation of NO on Fe centers. The reactivity with NH3 of nitrites trapped on BaO is probed by Temperature Programmed Surface Reaction (NH3-TPSR) runs, which show rapid dinitrogen formation from low temperatures when Fe-ZSM-5 is not only mixed with, but also placed downstream from BaO/Al2O3, thus confirming the stability of the NOx intermediate formed on Fe-centers, and linking it to the Standard SCR reactivity. Finally, in order to study the role of the metal redox sites in the reactivity of nitrites stored on BaO with ammonia, we compare NH3-TPSR experiments over a Fe-ZSM-5 catalyst and over a parent H-ZSM-5 zeolite with a drastically reduced Fe content (Fe ≅ 0.02% w/w). Results show that nitrites on BaO react with NH3 to dinitrogen equally well on Fe- and on H-ZSM-5, which questions the role of the metal sites and therefore of the oxidative activation of NH3 in such a step. The present data emphasize the bifunctional (redox + acid) nature of the NH3-SCR catalytic chemistry at low temperatures, and should be considered in the development of comprehensive mechanisms for the Standard SCR reaction over Fe-zeolite catalysts
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