The Photoelectron Spectra of Some Tl-Sb Sulphosalts

The results of X-ray induced photoelectron spectroscopy (XPS) experiments on several phases of the ternary system Tl-Sb-S are reported. The binding energies of the inner S, Sb and Tl electrons increase with increasing quantities of Sb and decreasing amounts of Tl in these compounds. This is explained by the influences of the proportions of the bonded metals on the effective electron affinity of S. The higher proportions of the more electronegative element bonded to S cause the increase of its effective electron affinity. The results for Tl2S (carlinite), Tl3SbS3, TlSbS2 (weissbergite), TlAsS2 (lorandite) and Sb2S3 (antimonite) can be interpreted in this way. The results for Tl4S3 suggest a predominantly covalent character of bonding for both Tl(III) and Tl(I), which are present in this sulfide. From comparison with Tl3SbS4 it could be supposed that Tl(III)-S bond has a more covalent character than Sb(V)-S bond. The results for Tl3SbS4 are in agreement with crystal structure data and the results of Moessbauer spectroscopy. For AsS (realgar) the binding energies of the inner electrons of As and S significantly increase, showing that the electrons in molecular orbitals are less strongly bonded to individual atoms, as compared to pure elements. The results for the amorphous TlSb5S8 (corresponding in composition to parapierrotite) suggest that in amorphous compound the Tl-S bonding is stronger and the coordination of Tl more regular than in a crystalline one. © 1993 Springer-Verlag

Fragmentations of protonated cyclic-glycylglycine and cyclic-alanylalanine

Collision-induced dissociation has been used to study the fragmentations of two protonated diketopiperazines, protonated cyclic-glycylglycine and cyclic-alanylalanine. Protonated cyclo-AA lost CO and (CO + NH3) at low collision energies, channels attributed to dissociation of the O-protonated tautomer. Higher collision energies were required to dissociate protonated cyclo-GG, and the two lowest-energy products were the result of losses of one CO and two CO molecules. These occur from the higher-energy N-protonated tautomer, which is formed from the O-protonated tautomer by a 1,4-proton shift that has a high barrier (54.5 kcal mol(-1)) due to constraints imposed by the ring. Mechanistic schemes for four different dissociation channels, three from the N-protonated tautomer and one from the O-protonated tautomer, have been computed using density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. Comparison of the potential energy surfaces for the two protonated diketopiperazines reveals the factors behind this dichotomy of fragmentation pathways. The infrared multiple-photon dissociation spectrum of the [M+H-NH3-CO](+) ion (m/z 98) from protonated cyclo-M shows this product to be an oxazole, the lowest-energy isomer. (C) 2012 Elsevier B.V. All rights reserved

Fragmentations of protonated cyclic-glycylglycine and cyclic-alanylalanine

Collision-induced dissociation has been used to study the fragmentations of two protonated diketopiperazines, protonated cyclic-glycylglycine and cyclic-alanylalanine. Protonated cyclo-AA lost CO and (CO + NH3) at low collision energies, channels attributed to dissociation of the O-protonated tautomer. Higher collision energies were required to dissociate protonated cyclo-GG, and the two lowest-energy products were the result of losses of one CO and two CO molecules. These occur from the higher-energy N-protonated tautomer, which is formed from the O-protonated tautomer by a 1,4-proton shift that has a high barrier (54.5 kcal mol−1) due to constraints imposed by the ring. Mechanistic schemes for four different dissociation channels, three from the N-protonated tautomer and one from the O-protonated tautomer, have been computed using density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. Comparison of the potential energy surfaces for the two protonated diketopiperazines reveals the factors behind this dichotomy of fragmentation pathways. The infrared multiple-photon dissociation spectrum of the [M+H-NH3-CO]+ ion (m/z 98) from protonated cyclo-AA shows this product to be an oxazole, the lowest-energy isomer

Contro le nuove guerre

Sempre più calcolo e progetto sembrano aver sostituito tattica e strategia, mentre la guerra asserve tecniche e scienza in un viluppo di morte affondando la politica dei cittadini. Ma qualcuno degli addetti ai lavori - Scienziate e scienziati contro la guerra - rilutta, si organizza e denuncia con la forza della dimostrazione il programma di distruzione, tanto insensato quanto micidiale e criminale, di cui è principale responsabile la maggiore potenza imperiale del pianeta, ben spalleggiata peraltro dai suoi alleati europei. Questo libro fa seguito a Imbrogli di guerra; è la sua continuazione e il suo approfondimento risultando il frutto di un convegno intenso e appassionato (Torino, Politecnico, 22 e 23 giugno 2000) che ha visto il confronto stringente di studiose e studiosi di varie discipline, dalle scienze naturali alla storia e all'ingegneria, dalla sociologia alla matematica e alla medicina. Esso mantiene intatto il suo contenuto d'informazione ponderata anche e soprattutto dopo il ricambio al vertice di Belgrado. Se la guerra è la sospensione del diritto, le nuove guerre tendono a rendere indefinita e permanente la situazione di squilibrio politico impedendo la libertà di comunicazione e di controllo, devastando progressivamente e irrimediabilmente l'ambiente e asservendo l'economia e lo sviluppo delle relazioni umane alla logica militare di dominio planetario