S. Paoloni

Hidden Text Detection by Infrared Thermography / Anwendung der aktiven Infrarotthermographie (IRT) zur Erfassung von verdeckten Texten / Utilisation de la thermographie infrarouge (IRT) pour détecter des textes cachés

Abstract We present an opto-thermal approach based on the use of active infrared thermography (IRT) for the study of texts hidden inside the bookbinding structure of ancient books. In particular we focus our investigation on the detection and characterization of texts on paper scraps, belonging to earlier handwritten or printed leaves, used for the making of bookbindings and lying between the end papers and the cover. A qualitative description of the physical mechanisms allowing the identification of texts is proposed and a comparative analysis of the results obtained by means of different IRT experimental configurations is presented. The results show that active IRT can be a very useful tool for the detection and the identification of underlying texts whose reading can provide useful information on the specific history of ancient books. Zusammenfassung Die Anwendung von aktiver Infrarotthermographie (IRT) zur Erfassung von Texten, die in Einbandstrukturen verborgen sind, wird vorgestellt. Insbesondere wurden Texte auf Fragmenten, die fur die Buchdeckenherstellung verwendet wurden, beziehungsweise sich zwischen Vorsatz und Buchdeckel befinden. Eine Beschreibung der physikalischen Grundlagen fur die Texterfassung mit IRT wird gegeben ebenso wie die Prasentation ausgewahlter Untersuchungen an historischen Objekten. Die prasentierten Resultate zeigen, dass aktive Infrarotthermographie eine geeignete Methode fur die Erfassung von verdeckten Textfragmenten darstellt und wichtige Informationen zur Geschichte historischer Bucher beziehungsweise Bucheinbande liefern kann. Résumé Nous présentons une approche qui se base sur l’utilisation active de la thermographie infrarouge (IRT) pour l’étude de textes cachés à l’intérieur de la structure reliée des livres anciens. L’examen s’est centre surtout sur la détection et la caractérisation de textes sur les fragments de papier provenant de feuilles écrites auparavant à la main ou imprimées et qui ont servi dans la fabrication des reliures et qui se trouvent entre les dernières feuilles de garde et la couverture des livres. On présentera une description des mécanismes physiques permettant l’identification des textes et une analyse comparative des résultats obtenus au moyen de différentes configurations expérimentales d’IRT. Les résultats présentés démontrent que La thermographie infrarouge active s’avère être un outil très utile dans la détection et la caractérisation de textes sous-jacents dont la lecture peut fournir de précieuses informations sur l’histoire spécifique de livres anciens.

Latent heat investigation by photopyroelectric calorimetry

We report on an approach for photopyroelectric calorimetry enabling a frequency dependence detection of the specific heat and of the latent heat exchanged over first order transitions. It has been applied to the nematic-isotropic transition of 4-n-octyl-4′-cyanobiphenyl liquid crystal confined in a silica nanoparticles network, where the specific heat shows a double peak structure. The larger strain involved with the nematic nucleating over the low temperature peak induces a considerable lower latent heat than the one involved over the higher temperature peak. The frequency dependent measurements have shown a different dynamics of the nematic nucleating over the two peaks.

Thermographic analysis of bronze sculptures

In this work we investigate various aspects of the finishing process in ancient bronze sculptures by means of active infrared thermography (IRT). Active IRT provides information on surface and sub-surface features of the investigated artefact, by analysing the heat diffusion process induced within the sample by appropriate thermal stimulations usually produced by absorption of light emitted by different sources. The aim of this research is, in particular, to investigate the processing of bronze surfaces, revealing repairs like plugs, fillings, local castings and concealed marks.

Simultaneous specific heat, thermal conductivity and imaging evaluations in thin samples of 8CB liquid crystal dispersed with microemulsion of DDAB/water micelles

In this work we use a photopyroelectric calorimetric set up to analyze the transformations occurring in thin samples of liquid crystal-microemulsion system by combining the results of the simultaneously performed high temperature resolution polarization microscopy observations and the temperature dependence of the specific heat, and of the thermal conductivity. This enabled an accurate direct correlation of the observations concerning the different measured quantities for a most comprehensive interpretation of the obtained results. It is found that the I-N conversion progresses in the entire nematic range because of the micelles expelled from the nucleating nematic volumes remaining confined in the residual isotropic material. A hysteretic behavior is observed in the nematic range between cooling and heating run because of the different micelle content in the material during the cooling and heating runs. A moderate hysteresys also over the N-A transition indicated an additional material refinement from micelles during the transition. Finally in samples with different micelle concentration the same maximum micelle content is retained in the nematic and smectic phases.

Active infrared thermography applied to the study of a painting on paper representing the Chigi's family tree

Abstract In this work, active infrared thermography was applied to study a seventeenth-century painting on paper, namely the Chigis family tree, housed at Palazzo Chigi in Ariccia (Rome). Thermography was performed before and after restoration to obtain information used in planning the restoration and also to assess its effectiveness. Infrared thermography provided important information on the artifact structure, areas of damage, structural defects, and the state of adhesion between different layers of the composite artifact before and after the treatment.

Communication: Optically induced decoupling of the smectic-A and nematic order parameters at the AN phase transition in phototropic liquid crystals

In the present work, by means of the photopyroelectric calorimetric investigations in liquid crystal/naphtopyran (NP) molecule mixtures, the effect of the photoisomerization of NP by UV light on the critical behavior of specific heat could be studied over the smectic-nematic phase transition. It is shown that the UV light irradiation of the sample can shift the critical exponent from a non-universal value typical of the non-irradiated mixture to one close to that of the 3D-XY universality class, predicted for such a transition. This witnesses the optically triggered reduction of the coupling between the smectic and nematic order parameters responsible for the deviation from the XY-like behavior. A tentative explanation is provided based on the weakening of the order parameter coupling caused by the NP molecules entering the smectic layers following the UV light illumination.