Fulvio Mercuri

In this work, we discuss the unique capability of photopyroelectric (PPE) calorimetry to investigate optically induced phase transitions in phototropic liquid crystals. To this end, we present experimental results obtained for two mixtures consisting of 4-octyl-4-cyanobiphenyl (8CB) liquid-crystal hosting methyl 8-(49-pentylbiphenyl-4-yl)-2-phenyl-2-(4-fluorophenyl)-2H-naphtho[1,2-b]pyran-5-carboxylate and p,p′-diheptylazobenzene, respectively, being such molecules characterized by opposite UV-induced photoisomerization behavior. We demonstrate that the combined analysis of the investigated thermal parameters, supported by the simultaneous optical imaging of the sample texture, provides valuable insights into the underlying photoinduced processes. In particular, the temperature dependence of the specific heat allows us to quantify the light-induced shifts of the phase transition temperatures and to assess the influence played by the different isomeric states of the photoactive molecule on the critical behavior of the 8CB phase transitions. On the other hand, thermal conductivity measurements enable the investigation of optically driven changes in the average molecular orientation and, in addition, the determination of characteristic timescales associated with these reorientation processes. These results highlight the effectiveness of PPE calorimetry as a powerful tool for probing both the thermodynamic and kinetic aspects of optically stimulated phase transitions in liquid crystals.

In this paper, an innovative method for the digital representation of ancient books is proposed. Specifically, this approach consists of the reconstruction of the three-dimensional geometry of the codex through images obtained from different viewpoints, using Structure from Motion techniques. In addition, both reflectograms in the midwave infrared spectral range and thermograms, recorded by pulse thermography, have been adopted since they enable a depth-resolved characterization of the book. The final result is a 4D digital model of the codex, which allows both the visualization of the geometry of the book and the stratigraphic exploration of the features buried beneath the surface. Data obtained from humanistic studies and diagnostic survey have been also mapped onto this model in the form of semantic annotations. Finally, several outputs were developed, including a 3DWeb platform and a holographic showcase designed for museums, with the goal of creating an interdisciplinary experience with the ancient codex.

In the manufacture of ancient books, it was quite common to insert written scraps belonging to earlier library material into bookbindings. For scholars like codicologists and paleographers, it is extremely important to have the possibility of reading the text lying on such scraps without dismantling the book. In this regard, in this paper, we report on the detection of these texts by means of infrared (IR) pulsed thermography (PT), which, in recent years, has been specifically proven to be an effective tool for the investigation of Cultural Heritage. In particular, we present a quantitative analysis based, for the first time, on PT images obtained from books of historical relevance preserved at the Biblioteca Angelica in Rome. The analysis has been carried out by means of a theoretical model for the PT signal, which makes use of two image parameters, namely, the distortion and the contrast, related to the IR readability of the buried texts. As shown in this paper, the good agreement between the experimental data obtained in the historical books and the theoretical analysis proved that the capability of the adopted PT method could be fruitfully applied, in real case studies, to the detection of buried texts and to the quantitative characterization of the parameters affecting their thermal readability.

This paper sheds light on the manufacturing processes, techniques, and materials used in the splendid illuminations of the oldest surviving copy of De Balneis Puteolanis, preserved at the Angelica Library in Rome (Ms. 1474). The codex is one of the masterpieces of mid-13th-century Italian-Southern illumination, traditionally referred to as the commission of Manfredi, son of Frederick II. The findings reported in the article result from the interdisciplinary study conducted in 2021–2023 in the framework of “Codex 4D: journey in four dimensions into the manuscript”, a multidisciplinary project involving many competences and dealing with art-historical studies on manuscripts, diagnostic and conservative analyses, scientific dissemination, storytelling, and public engagement. The considerations we present aims at increasing the knowledge of book artefacts while respecting their extraordinary complexity; data from non-invasive diagnostic investigations (X-ray fluorescence, Vis-NIR reflectance and Raman spectroscopies, hyperspectral imaging, and multi-band imaging techniques as ultraviolet, reflectography, and thermography), carried out in situ with portable instruments on the book, have been integrated with observations resulting from the historical-artistic study, and the reading of some ancient treatises on the production and use of the pigments and dyes employed in illumination.

Non-destructive techniques for the analysis of cultural heritage items are of the outmost importance in order to understand better the artworks, to assess their conservation conditions and to evaluate a possible restoration intervention. Among these techniques, pulsed infrared thermography plays an important role, since it is simple and quite powerful. A standard experimental setup employs flash lamps for the delivery of a pulse of visible light to heat the sample and an infrared camera to record the consequent radiation emission. In this study, this technique was applied for studying ancient manuscripts and, in particular, for revealing hidden text buried under the end leaves of the book. A mathematical model developed by the authors is briefly detailed. The finite element method was employed to numerically solve the model equations and perform numerical simulations. The numerical results highlight the influence of some parameters involved in this phenomenon and can be used for a quantitative analysis of the experimental findings.

Photopyroelectric 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.

Among the different forms of art, the puppet theatre constitutes a long-standing and often little-known tradition. The use of puppets as support for acting dates back to the Greek age, and it was mainly developed during the modern period. The reason for such a large diffusion was due to the possibility of using affordable materials, such as papier-mâché, for the puppets’ manufacture. In this paper, a method based on the combined use of pulsed thermography (PT) and mid-wave infrared reflectography (MIR) is, for the first time, proposed for the characterization of papier-mâché artworks. In particular, some puppets belonging to the collection of the Museo delle Civiltà in Rome and made by Olga Lampe Minelli, a 20th-century puppet master, were investigated in order to detect damaged areas, such as those affected by insect attacks, and, consequently, to specifically plan suitable restoration works. Finally, the investigations were also carried out after the restoration to evaluate the effectiveness of the adopted treatments.