1,720,974 research outputs found
13C Solid State Nuclear Magnetic Resonance and μ-Raman Spectroscopic Characterization of Sicilian Amber
No full text13C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) and μ-Raman spectroscopy were applied to characterize Sicilian amber samples. The main goal of this work was to supply a complete study of simetite, highlighting discriminating criteria useful to distinguish Sicilian amber from fossil resins from other regions and laying the foundations for building a spectroscopic database of Sicilian amber. With this aim, a private collection of unrefined simetite samples and fossil resins from the Baltic region and Dominican Republic was analyzed. Overall, the obtained spectra permitted simetite to be distinguished from the other resins. In addition, principal component analysis (PCA) was applied to the spectroscopic data, allowing the clustering of simetite samples with respect to the Baltic and Dominican samples and to group the simetite samples in two sets, depending on their maturity. Finally, the analysis of loadings allowed for a better understanding of the spectral features that mainly influenced the discriminating characteristics of the investigated ambers
Nuclear Magnetic Resonance to investigate inorganic porous materials of interest in the cultural heritage field
No full textNuclear Magnetic Resonance (NMR) can be successfully applied to a wide number of organic, inorganic, and hybrid materials regarding cultural heritage. High-resolution solid-state NMR provides information on the structure of materials, and portable NMR devices allow non-destructive and non-invasive in situ investigation of variably sized objects. This result is possible by combining open magnets and surface radiofrequency coils to generate a sensitive volume external to the sensor and inside the object under investigation. In this paper we focus on the application of NMR to investigate inorganic porous materials such as pottery, plasters, and stones from cultural heritage sites. 27Al MAS and 3QMAS, and 29Si MAS high-resolution solid-state NMR along with spectral deconvolution allowed for the investigation of the chemical structure of ancient pottery. Portable unilateral NMR was used to investigate, in a non-invasive and non-destructive way, the porous structure of pottery. The effect of protective-consolidating treatments on plaster was carefully investigated by 1H NMR depth profiles that allowed for scanning with micrometric resolution of plaster specimens. Changes occurring in the total open porosity after treatments were also evaluated. NMR diffusion measurements provided information on the restricted geometry of the porous structure of two types of biocalcarenite and tuff. A suitable processing of collected data enabled us to define the average pore radius and pores' interconnection in these material
Advanced NMR methodologies and micro-analytical techniques to investigate the stratigraphy and materials of 14th century Sienese wooden paintings
No full textIn this study a multi-analytical approach was used to characterize ancient and modem constitutive materials and the stratigraphy of a Sienese wooden painting consisting of four cusps belonging to a lost Polyptych, by Andrea di Bartolo dated back to the late 14th century, repainted in the 16th century and partially restored and cleaned in the 20th century. In order to distinguish the original layers from the other ones, a comparison with the painting Adorazione dei Magi by Bartolo di Fredi (Andrea's father) dated to the 14th century, was performed. The painting Adorazione dei Magi was found to be in a very good state of conservation and provided a model of the artistic technique used in Sienese painting in the 14th century. In situ measurements by portable NMR were performed to investigate the stratigraphy of the paintings in a non-destructive and non-invasive way. By means of this technique, information about all layers constituting the paintings were obtained and used to plan the successive micro-sampling. High resolution NMR spectroscopy was applied on a few samples to characterize binders and organic substances. Specifically, solid state C-13 and P-31 CPMAS NMR spectroscopy and H-1 NMR spectroscopy in solution were applied to characterize original and non-original materials. Other techniques such as ToF-SIMS, HPLC, IR and Raman spectroscopy were also applied
1H-1H NMR 2D-TOCSY, ATR FT-IR and SEM-EDX for the identification of organic residues on Sicilian prehistoric pottery
No full textInsights into the diets of early societies can be gained, indirectly, from the cultural evidence of artefacts related to food procurement, preparation and consumption and human skeletal remains. However, more direct evidence for dietary constituents derives from the identification of intact plant and animal remains collected during the excavations but also from the exam of the amorphous remains of foodstuff associated with artefacts. Organic residues adhering to the surface or absorbed into the porous fabric of an unglazed cooking vessel should provide important information both about the usage of the vessel and dietary practices. This contribute deals with the results of a combined analytical research via 1H-1H NMR 2D-TOCSY, ATR FT-IR and SEM-EDX on organic residues on pottery from two Sicilian prehistoric sites of Monte Kronio and Sant'Ippolito. The goal was that to shed new light on the use of certain ceramic shapes and infer some hypothesis about ancient dietary habit
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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