1,721,035 research outputs found
OH-related infrared absorption bands in oxide glasses
No full textWe report the infrared activity, in the spectral region of the OH stretching modes, of different composite silicate glasses whose chemical composition is established by X-ray fluorescence measurements. The analysis of the absorption line profiles is made in terms of different spectral contributions, Gaussian in shape. The comparison with analogous spectra obtained in vitreous silica samples with impurity concentrations < 100 part per million moles is evidence of the effects of the different oxides on the vibrational properties of the OH groups. In particular, for oxide glasses a red shift of the composite band at about 3670 cm(-1), assigned to the OH stretching modes of free Si-OH groups and of water molecules, is found with respect to those silica samples with the smallest impurity concentrations. Moreover, for oxide glasses the absorption activity in the 2500-3200 cm-1 region shows several spectral contributions that depend on the chemical composition of each sample. Also in view of the fact that in this zone no significant absorption activity is revealed in the case of silica samples, these spectral components are assigned to OH stretching modes of Si-OH groups in interaction with the different atoms present (Na, Ca, K, Al, etc.) and/or in modified sites of the vitreous structure
Le anfore fenicio-puniche prodotte nel Mediterraneo occidentale: caratteristiche petrografiche degli impasti siciliani e spagnoli.
No full textThe aim of this paper is to provide well-stated petrographic reference groups for the recognition of several Sicilian and
Spanish Phoenician-Punic production centres in order to facilitate an instrument of further objective support for amphorae
provenance. This instrument is based on the crosschecking between data provided by typological studies and the thinsection
analysis of amphorae fabrics. It is worth noting that this is only a first step within the framework of a larger research
project focused in the creation of an Atlas of Phoenician and Punic Amphorae in the Western Mediterranean including both
archaeological and petrographic data. In this context a systematical work on the known production centres characterizing
fabrics, pastes and raw materials is the proper way to define workshops and their manufactures and to study their
technological choices. Thus we shall give primarily references to well-define workshops as Mozya and Solunto in Sicily and
Cadiz and Ebussus in Spain. However, some other petrographic data not obtained from the above cited workshops are also
included. In those cases, the reference fabric has to be taken only as a general trend on the petrographic features of a
certain large compositional space
Caracterización petrográfica de cerámicas a mano y a torno del yacimiento protohistórico de la Plaza de la Catedral (Ceuta)
No full textINDIGENOUS TABLEWARE PRODUCTION DURING THE ARCHAIC PERIOD IN WESTERN SICILY: NEW RESULTS FROM PETROGRAPHIC ANALYSIS.
No full textIndagini archeologiche e archeometriche preliminari sulle anfore di alcuni relitti della Sicilia (metà III-I sec. a.C.)
No full textPetrographic and Geochemical Characterization of Archaic- Hellenistic Tableware Production at Solunto, Sicily
No full textRelitti della Sicilia (metà III-I sec. a.C.): primi dati delle analisi archeometriche sulle anfore
No full textThe majolica production of Northern central Sicily (16th - 18th Century AD): Archaeometric evidence
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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