Search results for "ESA"
showing 10 items of 11914 documents
Self-Assembly of Water-Mediated Supramolecular Cationic Archimedean Solids
2013
Understanding the self-assembly of small structural units into large supramolecular assemblies remains one of the great challenges in structural chemistry. We have discovered that tetrahedral supramolecular cages, exhibiting the shapes of Archimedean solids, can be self-assembled by hydrogen bonding interactions using tricationic N-donors (1 or 2) in cooperation with water (W). Single crystal X-ray analysis shows that cage (2)4(W)6, assembled in an aqueous solution of cation 2 and KPF6, consists of four tripodal trications linked by six water monomers and resembles the shape of a truncated tetrahedron. Similarly, cage (1)4(W6)4 spontaneously self-assembles in an aqueous solution of cation 1…
Synthesis, vibrational and NMR spectroscopic characterization of [N(CH3)4][IO2F2] and X-ray crystal structure of [N(CH3)4]2[IO2F2][HF2]
2004
Abstract The salt, [N(CH3)4][IO2F2], was prepared from [N(CH3)4][IO3] and 49% aqueous HF, and characterized by Raman, infrared, and 19F NMR spectroscopy. Crystals of [N(CH3)4]2[IO2F2][HF2] were obtained by reduction of [N(CH3)4][cis-IO2F4] in the presence of [N(CH3)4][F] in CH3CN solvent and were characterized by Raman spectroscopy and single-crystal X-ray diffraction: C2/m, a = 14.6765(2) A, b = 8.60490(10) A, c = 13.9572(2) A, β = 120.2040(10)°, V = 1523.35(3) A3, Z = 4 and R = 0.0192 at 210 K. The crystal structure consists of two I O 2 F 2 − anions that are symmetrically bridged by two H F 2 − anions, forming a [F2O2I(FHF)2IO2F2]4− dimer. The symmetric bridging coordination for the H F …
Thermodynamics of Solubilization of Pentanol in Sodium Dodecyl Sulfate-Dodecyldimethylamine Oxide Mixed Micelles
1994
Abstract Heat capacity and density measurements of pentanol (PeOH)-sodium dodecyl sulfate (NaDS)-dodecyldimethylamine oxide-water mixtures were carried out at 0.03 m PeOH as a function of the total surfactants concentration (mc) at different ratios (XNaDS). From experimental data, the apparent molar volumes (VΦ,R) and heat capacities (CΦ,R) of PeOH in the surfactants mixture solutions were calculated. As a general feature, at a given mixture composition, VΦ,R increases monotonically with mt as observed in pure surfactants. In the cases of XNaDS = 0.1 and 0.3, VΦ,R drops at about 0.1 and 0.15 mt respectively. The decreasing CΦ,R VS mt curve shows peculiarities which were ascribed to the pres…
Alunni della perdizione. Chiesa e potere in Sicilia durante il grande scisma (1372-1416)
2008
Micro-Raman spectroscopy of pigments contained in different calcium carbonate polymorphs from freshwater cultured pearls
2008
The metastable calcium carbonate polymorph vaterite has recently been found to occur commonly in freshwater cultured pearls from Japan and China. Organic pigment molecules in these vaterite regions of freshwater cultured pearls were analysed by resonance and near-resonance micro-Raman spectroscopy, in single spectra and in mapping modes and are compared with their aragonitic counterparts. Four different excitation wavelengths (487.9, 514.5, 532.2 and 632.8 nm) were used, resulting in differential increase of resolution for the pigments. Although vaterite areas were always lightly coloured (light yellow, light brown or white), ten different pigments were identified and a single colour is for…
On Functions of Integrable Mean Oscillation
2005
Given we denote by the modulus of mean oscillation given by where is an arc of , stands for the normalized length of , and . Similarly we denote by the modulus of harmonic oscillation given by where and stand for the Poisson kernel and the Poisson integral of respectively. It is shown that, for each , there exists such that
Un nuovo insediamento rurale nel territorio dei Monti Sicani tra epoca bizantina e normanna: dati preliminari sul sito di lunga durata di Contrada Ca…
2018
Negli ultimi anni (2015-2017) sono state avviate delle ricerche archeologiche sulle dinamiche diacroniche dei paesaggi di una porzione di territorio localizzata a sud del comune di Corleone corrispondente alle contrade Castro e Giardinello delimitate a nord dal massiccio promontorio di Pizzo Castro o Rocche di Mezzogiorno e ad est dalle pendici del Monte Barraù. Il progetto Harvesting Memories ha previsto diverse fasi di studio relative alle traiettorie ecologiche e alle trasformazioni del paesaggio (Università di Palermo) e indagini archeologiche (Soprintendenza BB. CC. AA. di Palermo). In questo contributo si presentano i risultati preliminari di una prima campagna di scavo (marzo-maggio …
IL SITO PREISTORICO DELLO ZUBBIO DI COZZO SAN PIETRO S.I.C. RUPI DI CATALFANO E CAPO ZAFFERANO
2014
All’interno del S.I.C, “Rupi di Catalfano e Capo Zafferano”, alcune delle grotte presenti sono state frequentate dall’uomo fin dalla preistoria. Mettendo a confronto la genesi delle cavità e la loro ubicazione topografica, è evidente che la scelta dei siti consoni a essere usati dall’uomo è marcatamente strategica e ponderata. L’indagine è stata condotta dapprima individuando e raggiungendo i siti noti in bibliografia, dai quali si è cercato di elaborare un modello per individuare nuovi siti che potessero presentare evidenze di frequentazione umana risalenti alla preistoria, soprattutto recente. All’interno di una grotta, Zubbio di Cozzo San Pietro, ubicata ad una quota di 300 m s.l.m sul v…
Julien : les années parisiennes
2009
This article intends to scrutinize in what ways Julian’s stay in Gaul as a Caesar were decisive in Julian’s political and military education, and whether a specific ruling style and manner may be detected in the Parisian years of Julian’s government. Relying on a critical analysis of the documentation (Julian himself, Mamertinus, Ammianus, Libanios), the author examines the military and civilian aspects of Julian’s training as an apparently inexperienced ruler but quick learner. She carries out a prosopographical study of the Caesar’s circle and the administrative staff which was then on duty, combining friendly and hostile persons. Gaul offered him a training ground and he became even the …
El prestigio de los objetos: mangos de marfil en el mundo ibérico
2020
El estudio se centra en una serie de mangos de marfil de características morfotécnicas similares, recuperados en espacios de hábitat y funerarios ibéricos y datados entre el s. IV y el s. II a. C. Se trata de objetos de prestigio al alcance de una élite aristocrática, que han sido elaborados con materias primas exóticas (marfil) y técnicas decorativas inusuales que indican una especialización. A través de análisis de composición por infrarrojo cercano por Transformada de Fourier (FT-NIR) y de fluorescencia de rayos X (pXRF) se ha podido documentar la presencia de incrustaciones de ámbar adheridas a la superficie de los mangos mediante el uso del estaño como soldadura blanda y el empleo de a…