Low-cost sensor system for online monitoring during laser cleaning

The self-limiting effect during laser cleaning only occurs in a limited amount of specific applications in restoration (e.g. removal of black crust from white marble). In all the other cases, a control of the removal process will be necessary either by the operator himself or by the employment of sensor equipment. Various methods, mainly spectroscopic (e.g. LIBS), have been investigated and proposed by others. Despite the fact that these have been shown to be promising, they all have in common rather high investment cost close to that of the cleaning equipment. Furthermore, this highly sophisticated control equipment is not easy to handle by conservators in practice. As an alternative low-cost method, we employed a simple photodiode to detect the scattered light from the irradiation area on the artwork surface. In many cases, this signal contains several pieces of information on the layer just being removed. The scattered radiation detected by the photodiode originates from the laser-induced plasma as well as reflected laser radiation. A separation, if necessary in order to separate the information, is possible by spectral filters. First applications during laser cleaning of corroded metal, encrusted glass and stone were promising. It has turned out that there is a distinct influence on the scattered light amplitude or even the pulse-bandwidth once the laser has removed the encrustation completely. The corresponding signal can be used in a closed loop control or for online monitoring.     

Fashioning the Discipline: History of Science in the European Intellectual Tradition

This paper offers personal reflections on the fashioning of the history of science in Europe. It presents the history of science as a discipline emerging in the twentieth century from an intellectual and political context of great complexity, and concludes with a plea for tolerance and pluralism in historiographical methods and approaches.Robert Fox held the chair of the history of science at Oxford University between 1988 and 2006. He has been active in a number of international organizations, including the International Union of the History and Philosophy of Science, of which he is a past president, and the European Society for the History of Science, whose founding president he became in 2004.     

What do plastics emit? HS-SPME-GC/MS analyses of new standard plastics and plastic objects in museum collections

In recent years, plastics are designated as a source of indoor pollution and particular attention has thus been devoted to the identification of emitting low molecular weight compounds. Headspace-solid phase microextraction-gas chromatography coupled with mass spectrometry (HS-SPME-GC/MS) has been already successfully applied for screening emissions from synthetic materials. This analytical tool being also non-invasive, it has been already successfully applied in the field of cultural heritage science for the identification of volatile organic compounds (VOCs) emitted from various museum objects made of natural materials. In this research, we aimed at assessing the use of HS-SPME-GC/MS as an in situ non-invasive analytical tool for a better knowledge of the volatile organic compounds emitted by plastics in collections. The possibility of characterizing plastics based on their emission signatures was also evaluated. Twelve new standard plastic samples, belonging to seven main polymer families widely present in museum collections as well as three naturally aged museum objects, were investigated. In this paper, we provide a survey of the VOCs emitted, and the use of HS-SPME-GC/MS for identifying volatile marker compounds, degradation products, additives, and monomer residues of the plastic synthesis is evaluated. More than 200 different VOCs were identified from the new standard samples. Two categories of VOCs were distinguished: “non-specific” and “specific” ones. We showed that based on the “specific” VOCs, it was possible to identify the nature of the polymeric matrix itself or at least to unambiguously distinguish a plastic by family. Emissions from the museum objects were then characterised, and main volatile degradation compounds considered as degradation markers of the natural deterioration of polymeric matrices, were identified. This identification procedure could be further exploited for the characterization of VOCs emitted by objects made of multiple synthetic polymers. Complementary to other techniques, this analytical tool is an interesting way to assess the risk for the objects stored in the vicinity of emitting plastics.     

Tert-butyl amine borane complex: An unusual application of a reducing agent on model molecules of cellulose based materials

The need to preserve cultural heritage on paper requires the setting up of methods and treatments that can be applied to original documents. The cellulose main degradation processes are hydrolysis and oxidation. Only the first one has been widely investigated. The Istituto Centrale per la Patologia del Libro (ICPL) focused its attention on oxidation phenomena and studied a particular class of reducing agents, namely the borane-amine complexes. During the investigation it was found that the borane tert-butylamine complex, besides being the most promising reducing agent, was also able to react with carboxylic functions. In the present study ¹H and ¹³C NMR, Pulsed field gradient NMR spectroscopy as well as Raman spectroscopy were used as analytical tools to disclose the mechanism of the interaction between the borane tert-butylamine complex and the carboxylic functions. Given the complexity of the paper/environment interactions and the subsequent degradation phenomena, we worked on simplified models based on small carbohydrate molecules in order to reproduce the behavior of degraded paper after reductive restoration. Modified D-glucose and D-cellobiose were used in this first step in order to set up the analytical methods before approaching more complex systems such as microcrystalline cellulose and paper. Our results give the experimental evidence that borane tert-butylamine complex is also able to neutralize acidic functions. This finding has important perspectives in paper restoration.     

Appraisal models of intercultural communication apprehension among sojourners

We used R. S. Lazarus’ (Emotion and Adaptation. Oxford: Oxford University Press, 1991) appraisal theory of emotions to propose a theoretical model of anxiety, upon which we built two empirical models centering on intercultural communication apprehension (ICA), distinguished by timing. We tested the models in three samples: Chinese in the US (N?=?268), US Americans who studied abroad (N?=?419), and US Americans in the US (N?=?515). The models achieved good fit. The results showed that during an anticipated or actual intercultural interaction, people had multiple, potentially conflicting goals. The goal-related appraisals of the situation resulted in emotional reactions, such as ICA, as well as coping strategies. ICA and coping further influenced people’s immediacy behaviors and the intention to interact. Our empirical models supported the utility of the theoretical framework for all three samples, and provided advice for practitioners to improve sojourners’ time abroad.     

Degrees of influence: the politics of honorary degrees in the universities of oxford and cambridge, 1900–2000

Minerva - The universities of Oxford and Cambridge had developed different attitudes towards the award of honorary degrees through the early and middle decades of the twentieth century. Recently,...     

Non-invasive multi-technique investigation of artworks: A new tool for on-the-spot data documentation and analysis

The main advantage of a multi-technique non-invasive artwork investigations relies on the use of different spectroscopic techniques that give rise to complementary information. Despite the artworks complexity, this approach allows great insight into the artwork composition and alteration phases. However, difficulties arise from the great amount of heterogeneous interconnected data that has to be stored for a prompt analysis and preserved. A suitable tool to handle and analyse all the information on the fly is therefore crucial to optimize work, specially in in situ investigations. In this paper we present MOVIDA, a new tool for the data management and analysis of non-invasive investigations in the Cultural Heritage field that not only allows the digital preservation of all the information and knowledge, but can also be used as an analytical tool while the investigation is being developed. The software can be installed on any computer to record, elaborate and analyse the data on-the-spot. All the data generated can be managed within the same application and the information can be easily consulted, compared and related to the corresponding areas of the artwork. The software is self-comprehensive and user-friendly and can be used by all the professionals involved in the investigation and preservation of Cultural Heritage whatever their background and computer skills are.     

Making words Flesh: Changing Roles of University Learning and the Professions in 19th Century England

In 19th century Oxford and Cambridge, university learning, with itsemphasis on the Classics, is often thought to have been at odds with thetendencies of the modern world. Sometimes its influence is even seen aspernicious, bearing an anti-entrepreneurial bias that stifled Britain'seconomic development. This article argues that, on the contrary, anindeterminate body of learning in the universities cooperated withindeterminate social values in the professions to produce a new,deliberative liberalism: a kind of cultural capital that embraced a newmodernity, and gave a new authority to British administration andgovernment in the 20th century.     

Documentation of cultural heritage using digital photogrammetry and laser scanning

Precise documentation of cultural heritage status is essential for its protection and scientific studies carried out during the restoration and renovation process. The close range photogrammetry has been used successfully for documentation of cultural heritage. With recent developments in computer and information technologies, this well-known traditional method has been replaced with digital close-range photogrammetry. This new method offers us new opportunities such as automatic orientation and measurement procedures, generation of 3D vector data, digital ortho-image and digital surface model. Terrestrial laser scanning is another technology that in recent years has become increasingly popular for documentation which provides very dense 3D points on an object surface with high accuracy. In addition, the 3D model and digital ortho-image can be easily generated using generated 3D point cloud and recorded digital images.     

Initial results on laser cleaning at the Victoria & Albert Museum,Natural History Museum and Tate Gallery

A collaborative project between the Materials Department of Imperial College, the Victoria & Albert Museum, Natural History Museum and the Tate Gallery was initiated with the objective of introducing laser cleaning in these London-based museums and establishing a long-term research collaboration. An access to these material conservation departments means that materials like traditional statuary materials, heavily corroded metals, ivory, palaeontological samples, textiles, stained glass, plaster and some modern materials can be used to investigate the usefulness of laser cleaning and study their effects using a wide range of analytical techniques.     

Femtosecond laser cleaning of historical paper with sizing

Lasers have served as cleaning tools for historical objects and artworks for about 40 years. In many cases, superior results of laser cleaning were achieved with respect to traditional methods. In this technique, contaminations on the surface of the object are ablated by laser irradiation. In order to apply laser cleaning method to fragile materials such as paper made of cellulose or parchment, heat deposition to the bulk should be minimal, to prevent damage. In this work, it is demonstrated that laser pulses with femtosecond (fs) duration can exhibit non-thermal ablation of contaminants on paper samples. In particular, laser cleaning studies are concentrated on paper samples with sizing. Fs laser cleaning is performed on artificially soiled and aged samples, as well as on historical ones. The laser used in the experiments has pulse duration of 550 fs and 1030 nm center wavelength. The fluence of the laser is varied and the post-cleaning statuses of samples are investigated. The analyses are color changes, fiber integrity, chemical composition changes and mechanical strengths. These results show that fs lasers can be very efficient in cleaning paper samples, yielding minimal discoloration and no damage to fibers distinguishable on microscopic examination. The presence of sizing also provides further protection against possible side effects.     

Excimer laser removal of beeswax from galician granite monuments

The paper presents the use of laser radiation for cleaning of beeswax treated granite stone. In the early sixties, prestigious restorers decided to apply molten beeswax on the granite surface of valuable monuments with the aim of preventing the erosive action of atmospheric agents. An interesting example of this treatment is the Renaissance Frieze in the Cloister of the Cathedral of Santiago de Compostela in Galicia (Northwest Spain). With time, salt accumulation beneath the beeswax layer has caused an intense surface disintegration of granite. Conventional cleaning methods can destroy sculptured details of these emblematic monuments. For this reason, excimer laser cleaning has been chosen as a promising non contact, selective and environmentally friendly cleaning technique to be studied.The cleaning tests have been carried out using an excimer laser (ArF, 193 nm), with fluences between 0.5 and 2 J cm⁻² pulse⁻¹ and a spot area of 0.025 cm². Samples representing beeswax films over Roan granite have been irradiated and their degree of cleaning has been studied as a function of the number of pulses and the laser fluence.Cleaning efficiency has been evaluated by FT-Raman Spectroscopy, allowing to establish the beeswax ablation threshold and the ablation rate.Excimer laser cleaning allows a progressive and controlled removal of a few tenths of micrometers of beeswax per pulse without damaging the underlying granite stone.     

Electronic paramagnetic resonance as a tool for studying the blackening of Carrara marble due to irradiation by a Q-switched YAG laser

Several authors or practitioners have remarked that Q-switched lasers have an immediate blackening effect on mineral pigments such as vermilion (HgS), minium (Pb₃O₄), white lead [2PbCO₃. Pb(OH)₂], malachite [Cu₂CO₃.(OH)₂] and yellow ochre (FeOH₂). A similar blackening effect can also be obtained on veined Carrara marble. This stone contains several trace elements, particularly iron and manganese. The latter is responsible for a particular response in electronic paramagnetic resonance spectroscopy (EPRS). We investigated the effect of a Q-switched Nd:YAG laser irradiation on the EPRS trace of Carrara marble. Further experiments were performed with the same analytical tool on synthetic calcite powders that had been doped with iron or manganese. It appeared that no significant change of EPRS trace could be put into evidence after laser irradiation of both bulk Carrara marble or doped calcite powders, although some samples had actually blackened. It is concluded that the blackening effect is not due to an oxidation of manganese ions. Colour measurements were also performed within the framework of this investigation. They showed that the colour shift to black is proportional to the fluence applied to the stone surface     

The analysis of polychrome works of art: 40 years of infrared spectroscopic investigations

In this paper a synthetic chronological survey of analytical applications of infrared spectroscopy for the characterization of the materials of polychrome works of art and archaeology is outlined. Various sampling methods are described and some relevant examples, drawn from the published cases, are presented. The various methods prove to be very effective in characterizing both the inorganic and organic constituents of a wide variety of artworks, giving an insight into the materials and techniques of execution of the artifacts and, in the case of infrared mapping techniques, pinpointing the analytical data within a precise layer of the stratigraphy of the cross-sectioned samples. Overall, the great analytical potential and wide field of application of this technique is fully brought to light.     

What is Basic Research? Insights from Historical Semantics

For some years now, the concept of basic research has been under attack. Yet although the significance of the concept is in doubt, basic research continues to be used as an analytical category in science studies. But what exactly is basic research? What is the difference between basic and applied research? This article seeks to answer these questions by applying historical semantics. I argue that the concept of basic research did not arise out of the tradition of pure science. On the contrary, this new concept emerged in the late 19th and early 20th centuries, a time when scientists were being confronted with rising expectations regarding the societal utility of science. Scientists used the concept in order to try to bridge the gap between the promise of utility and the uncertainty of scientific endeavour. Only after 1945, when United States science policy shaped the notion of basic research, did the concept revert to the older ideals of pure science. This revival of the purity discourse was caused by the specific historical situation in the US at that time: the need to reform federal research policy after the Second World War, the new dimension of ethical dilemmas in science and technology during the atomic era, and the tense political climate during the Cold War.     

HMTY-KM (black copper) and the Egyptian bronzes' collection of the Musée du Louvre

At the instigation of the Musée du Louvre's Department of Egyptian Antiquities, an intensive programme to study black bronze has been carried out at the Centre de Recherche et de Restauration des Musées de France. Systematic research has been undertaken on the museum's collection to identify objects that might have an intentional black patina.The same experimental protocol has been applied to all the objects, alllowing this study to be one of the most important coherent investigation on this type of bronze decoration. It involves the use of non-invasive analytical methods in order to obtain the maximum amount of information possible about the chemical nature and structure of the surface layer. The protocol makes it possible to compare objects and to propose an interpretation of how this decorative technique evolved during the Egyptian period.Based on previous stylistic investigations (by J. Cooney, 1966) and personal observation, sixteen objects dating from the Middle Kingdom to the Late Period were selected. Thanks to elemental analyses, twelve of them were identified as being intentionally patinated. Only ten of these could be described as hmty-km, because the base patinated alloy contains small amounts of gold and/or silver and the black patina is made up mainly of cuprous oxide Cu₂O (cuprite). Among the four other objects, one patina is very close to the black bronze patina, but contains neither gold nor silver. Three other pieces have an unusual patina. A lack of other comparable examples makes it very difficult to determine whether the patinas are of ancient origin.     

Epistemic Living Spaces,International Mobility,and Local Variation in Scientific Practice

This article explores local variations in scientific practice through the lens of scientists’ international mobility. Its aim is twofold: to explore how the notion of epistemic living spaces may be mobilised as a tool for systematically exploring differences in scientific practice across locations, and to contribute to literature on scientific mobility. Using material from an interview study with scientists with experience of international mobility, and epistemic living spaces as an analytical frame, the paper describes a set of aspects of life in science that interviewees described as being different in different places. These axes of variation were: embodied routines of research; resource levels and salaries; daily or longer-term rhythms of scientific life (and their relation to rhythms of home or family); ‘efficiency’ and how work time is used; degree of hierarchy; the nature of social interactions between colleagues; the purposes of research; the social and interpersonal organisation of knowledge production; and the scale or ambition of research. In presenting an exploratory overview of these variations, the article points the way for future comparative investigation of epistemic cultures through studies of international mobility.

     

The craft of urgency: performing prosperity,running capital,and the making of a buying crowd in home presales in Nanjing,China

ABSTRACT

This article examines home presales – the selling of future residential properties – at the urban fringe of Nanjing, China. It argues for an analytical focus on urgency as a temporal quality that creates the local housing market and facilitates urban accumulation. I examine how urgency, grounded in a linear imagination of urban development, motivates home presales for developers, estate agents, and homebuyers. In particular, to speed up the turnaround time of investment, developers conjure up a vision of prosperity by building extravagant sales centers to organize home presales. Estate agents working at the sales center organize promotional events to attract, register, and manage a buying crowd. If properly managed, the buying crowd could reach the size of a festival-like presale, whereby hundreds of apartments are sold within one day. Capital at the urban fringe accumulates through the synchronization of these activities in which the sales center crafts an affective temporality of transaction by cultivating and managing an exuberant buying crowd. The craft of urgency emphasizes the performative agencement that assembles the condition for urgency to come into being.     

Characterization of the organic materials used in the painting of the vaulted ceiling at the Saadian Tomb of Mulay Ahmed Al-Mansour (Marrakech)

The Saadian tombs from the era of sultan Ahmed al-Mansour (1574–1603) are beautifully decorated and have always been a major attraction for visitors to Marrakesh. The central mausoleum, named the Hall of Twelve Columns, encloses the tombs of Ahmed al-Mansour and his family. The hall has a huge vaulted ceiling, carved cedar doors, opening windows with wooden marquetry screen (Mashrabiya), and grey Italian marble columns. This paper presents the first attempt to identify the organic materials used by the Moroccan artisans. A GC/MS analytical procedure was used for the characterization of lipids, waxes, resins, pitch, tar, proteinaceous and saccharide materials in the same paint micro-sample. The analytical study identified the organic materials used in the polychrome and gilded decorations of the walls, ceiling and dome of the hall. Data showed that the polychrome decorations were painted using animal glue as a binder, and highlighted the treatment of the wall surface with linseed oil and the retouching of the paintings based on a saccharide binder. The use of a proteinaceous-resinous-oil mixture, applied on a proteinaceous preparation layer, for the gilded decorations revealed a very similar technique to that used at the time in Europe for mural paintings.     

Spectroscopic analyses of Hellenistic painted plasters from 2nd century B.C., Sicily (South Italy)

In the present work, an analytical characterization of painted plaster samples coming from ancient buildings dated back to 2nd cent. B.C., located in Licata (Sicily, Southern Italy), has been carried out. The investigation has been performed through different spectroscopic techniques: X-ray fluorescence (XRF) using an handheld energy-dispersive XRF analyzer, scanning electron microscopy equipped with an Energy Dispersive Spectrometry microanalysis detector (SEM-EDS) and Fourier transform infrared absorbance spectroscopy (FT-IR). The main goal is to identify the plaster and pigments material. In particular, the XRF investigation of surfaces is the first step for a preliminary elemental characterization. Then, through SEM-EDS measurements, a quantitative analysis of the chemical composition of the plaster and the pigmenting agents along with eventual components related to deterioration processes has been obtained. Finally, FT-IR absorbance spectra have proven to be a useful tool to investigate the molecular nature of the used materials.