1,720,958 research outputs found
I pigmenti pittorici: una risposta della chimica
No full textSono state effectuate misure non distruttive per la caratterizzazione del materiale pittorico e della tecnica di preparazione usata nel sarcofago di Paherienaset
Caratterizzazione chimico fisica di legni bagnati e confronto con legni archeologici
No full textQuesto lavoro presenta una metodica per la diagnostica e la caratterizzazione di legni
bagnati basata sull’uso di alcune tecniche di indagine chimico fisica: diffrazione dei
raggi X (XRD), analisi termica differenziale (DTA) e termogravimetrica (TG), calorimetria
a scansione differenziale (DSC), misure di colore, spettroscopia infrarossa in
trasformata di Fourier (FTIR), fluorescenza dei raggi X (XRF). Castagno (hardwood) e abete
(softwood) sono stati i tipi di legno presi in esame per verificare tale metodica. I campioni di
castagno e abete, tal quali e dopo l’inserimento di chiodi metallici, sono stati immersi in acqua
deionizzata e acqua di mare sintetica a temperatura ambiente e a 40°C per effettuare una impregnazione
preliminare.
Il periodo di immersione è durato per tempi variabili ed al minimo per otto settimane. I chiodi
usati sono stati di ferro e rame, metalli molto diffusi in antichità. La penetrazione degli ioni
metallici è stata controllata tramite misure di fluorescenza dei raggi X.
Ogni settimana sono state eseguite misure di colore e di peso sui campioni e si è provveduto
alla sostituzione dell’acqua con altra fresca.
Dopo l’immersione, tramite operazioni di segatura e macinatura sono stati ottenuti campioni
polverizzati. La macinatura provoca, come noto, una diminuzione del grado di cristallinità della
cellulosa nei legni, ma non vi è alcun dato quantitativo circa tale effetto, che ci proponiamo
di valutare tramite un proseguimento della nostra ricerca. Lamacinatura è, comunque, necessaria
per ottenere campioni omogenei e misure riproducibili.
Le analisi diffrattometriche, termiche e calorimetriche hanno permesso di mettere in evidenza
l’effetto di degrado provocato sulle due specie lignee da parte dell’acqua di mare e dei metalli.
Per studiare il deterioramento del legno si è proceduto alla misura del grado di cristallinità dei
campioni tramite XRD tenendo in considerazione il picco principale della cellulosa (002) che
cade a circa 22,4° di 2θ. Sui legni archeologici è stata ripetuta la stessa serie di indagini e i risultati
sono stati confrontati con quelli ottenuti per i legni campione. Inoltre la spettroscopia infrarossa
in trasformata di Fourier (FTIR) è stata utilizzata quale ulteriore convalida dei confronti effettuati.
Infine, la sequenza delle reazioni di decomposizione termica è stata valutata tramite una serie
di prove condotte eseguendo combustioni parziali di campioni di abete a temperature via via
crescenti, comprese tra 225° e 350°C, in ambiente ossidante. I prodotti sono stati caratterizzati
mediante misure di perdita in peso e di cristallinità, che hanno permesso di individuare le principali
frazioni, amorfe o cristalline, coinvolte nei processi ossidativi
Caratterizzazione Archeometrica
No full textCaratterizzazione mediante tecniche non invasive di due opere pittoriche
Thermal, XRD and spectrophotometric study on artificially degraded woods
No full textThermogravimetry, differential thermal analysis, differential scanning calorimetry in oxygen flux were used to characterize two wood types: fir and chestnut woods. They were characterized by the peak temperatures of DTA, DTG and DSC curves and by the
different mass losses evaluated on the basis of the measured thermal data. The samples were woods in powder obtained during sawing. Complementary characterization of the woods was performed by estimating the crystallinity of cellulose by means of X-ray powder diffraction. In order to simulate the degradation of wet woods, fir and chestnut woods were put into deionised water and into artificial sea water for several weeks; some samples of woods contained Cu and Fe nails to ascertain the effect of these metals on the degradation process. The thermal and X-ray diffraction measurements were then performed on the wet woods, following the same previous procedure. X-ray fluorescence was used to investigate the penetration of metals into wood samples
Study of artificially degraded woods simulating natural ageing of archaeological findings
No full textSimulation of waterlogged archaeological woods was carried out by immersion of fir and chestnut wood samples into sea water at different
temperatures (room temperature and 40°C). The effects of metals in contact with woods were simulated by inserting in some
specimens of the two types of wood copper or iron nails, the most important metals from the archaeological point of view. The effects
of this ageing simulation on woods were studied by different characterization methods. At first we have performed gravimetric analyses,
controlling the mass increase of immersed wood in function of the time of immersion and the temperature of the bath. Then,
thermogravimetry, differential thermal analysis, differential scanning calorimetry in oxygen flux were used. The alteration of wood was
observed by means of the peak temperatures of DTA, DTG and DSC variation and by the mass losses observed during heating, evaluated
on the basis of the measured thermal data. The samples were woods powder obtained by milling. Complementary characterization
of the woods was performed by evaluating the crystallinity of cellulose by means of X-ray powder diffraction. The change in colour of
woods during ageing was checked by means of spectrophotometric measurements in the visible region.
X-ray fluorescence was used to investigate the penetration of metals into wood samples. An artificial ageing treatment with
NaOH and O3 was also performed.
Finally, a comparison between the effects of artificial alteration realised in our specimens and natural degradation observed in
archaeological woods, was performed
I dipinti murali di Luca Cambiaso nella Villa Imperiale di Terralba: la conoscenza delle tecniche attraverso le indagini di laboratorio
No full textLe indagini in fluorescenza dei raggi X e in spettrofotometria per riflettano hanno permesso una completa caratterizzazione dei dipinti murali in studio
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
Variations on the Author
Full text link“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
Full text linkWe 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
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