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Mathematical models for infrared analysis applied to cultural heritage
No full textActive pulsed infrared thermography is an effective technique consisting in moderately heating the specimen by means of the absorption of a visible light pulse and, then, in detecting the transient variation in the emitted infrared radiation by an infrared camera. Inhomogeneities and buried features eventually located into the specimen volume can be revealed by the recorded infrared images. Such a technique has been successfully applied to the analysis of cultural heritage artifacts like ancient bronzes and manuscripts. The former belong to the category of optically opaque materials, whereas the second to the one of optically semi-transparent materials. For both the two considered categories, a mathematical model for the analysis of the thermographic signal is here presented, together with an implementation in Matlab environment using the finite element technique. The developed models are then used to analyse the experimental results and, hence, to obtain both qualitative and quantitative information about the investigated items
Time resolved calorimetric investigations of photoinduced isomeric molecular changes in the nematic phase of an azobenzene compound
No full textBy monitoring the time dependence of the thermal conductivity of a p,p’-diheptylazobenzene sample irradiated with UV light of various intensities, a quantitative study is presented on the effects played by the photo-induced trans to cis isomerization on the degree of the homeotropic alignment in its nematic phase. In particular, the kinetics of the changes eventually leading to the nematic–isotropic phase transformation has been investigated. Unlike the case of the thermal diffusivity analyzed in a recent study, the thermal conductivity analysis has enabled the quantitative evaluation of the trans–cis transformation rates since it is not affected by the specific heat critical behavior and, therefore, it is determined only by changes in the molecular structure induced by the photo-isomerization. The study has been possible thanks to the peculiarity of the adopted photopyroelectric calorimetric setup that enabled both the calorimetric evaluations, as well as the sample texture characterization, to be performed during the UV illumination of the sample
Photothermal approach for cultural heritage research
No full textOver the last few years, there has been an increasing interest in the application of photothermal techniques to the investigation of cultural heritage. Thanks to their peculiar ability of depth-resolving the position of subsurface features, these techniques are in fact well suited for a nondestructive analysis of multi-layer structures such as the one typical of artwork. In addition, the recent availability of highly developed instrumentation makes it possible to effectively carry out in situ investigations into different kinds of artwork. Such circumstances have created new opportunities in both theoretical and experimental research whose development is still in progress. In this work, we report an overview of the results that have been obtained on several kinds of artwork and of further developments that can be used to improve the effectiveness of the application of photothermal techniques to this field
A note on the early thermographic approaches for the investigation of the Cultural Heritage
No full textIn this paper, we present an overview of some of the early applications of Infrared Thermography (IRT) to Cultural Heritage (CH) where Ermanno Grinzato, to whom the present issue is dedicated, was the leading scientist. In such a presentation, the works of arts have been divided into two main categories, namely movable and immovable CH. For each kind of CH, the good quality of the results that have been obtained despite the technical limitations of the adopted experimental equipment is highlighted, having such early results played a crucial role in the subsequent developments, thanks to which IRT has been nowadays established as a valuable technique for the CH surveys
Photopyroelectric Investigation of the trans–cis Isomerization Effect on the Nematic- Isotropic Phase Transition of a Liquid Crystalline Azobenzene
Full text linkPhotopyroelectric calorimetry has been applied to the study of the effects of different concentration of photo-induced cis isomeric molecules on the characteristics of the nematic – isotropic phase transition in p,p’-diheptylazobenzene (7AB) samples. The investigations could be carried out by monitoring the behavior of the thermal diffusivity over the phase transition before and during the sample irradiation with UV light of varying intensity. Among other, it is shown that the monitoring of the time dependence of the thermal diffusivity at fixed sample temperature enabled the comparative study of the dynamics of the trans–cis and cis–trans isomeric transitions. It was shown that the increasing cis isomers concentration caused an increase in the fraction of material undergoing the phase transitions and increased the cis–trans conversion rate. Finally, polarization microscopy observations of the sample texture, which could be carried out together with the calorimetric evaluations proved useful for a more comprehensive analysis of the obtained results
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
La Lupa Capitolina: indagini termografiche per lo studio delle tecniche di formatura e delle finiture del bronzo dopo la fusione
No full textVariations 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
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