Transparent varnishes on copper alloys dating from the 19th century: characterization and identification strategies

International audienceMany varnished copper-based artefacts dating from the 19th century can be found in museum collections. Although conservators deal on a daily basis with these surface finishes, few studies on this topic have been conducted during the last few decades on European objects. A more thorough understanding of these historical coatings would be helpful to establish accurate diagnoses and to contextualise the results with respect to the historical written sources. This paper presents the first results of the LacCa (Lacquered Copper Alloys) project currently being undertaken by an international multidisciplinary team. LacCa aims to develop a methodology that conservators can apply to identify and preserve these coatings. To this end, both historical objects and ancient varnish recipes have been studied. In a first step, the identification and characterisation protocol was validated using mock-ups, the results of which are presented in this paper

Distribution of the Octopamine Receptor AmOA1 in the Honey Bee Brain

Octopamine plays an important role in many behaviors in invertebrates. It acts via binding to G protein coupled receptors located on the plasma membrane of responsive cells. Several distinct subtypes of octopamine receptors have been found in invertebrates, yet little is known about the expression pattern of these different receptor subtypes and how each subtype may contribute to different behaviors. One honey bee (Apis mellifera) octopamine receptor, AmOA1, was recently cloned and characterized. Here we continue to characterize the AmOA1 receptor by investigating its distribution in the honey bee brain. We used two independent antibodies produced against two distinct peptides in the carboxyl-terminus to study the distribution of the AmOA1 receptor in the honey bee brain. We found that both anti-AmOA1 antibodies revealed labeling of cell body clusters throughout the brain and within the following brain neuropils: the antennal lobes; the calyces, pedunculus, vertical (alpha, gamma) and medial (beta) lobes of the mushroom body; the optic lobes; the subesophageal ganglion; and the central complex. Double immunofluorescence staining using anti-GABA and anti-AmOA1 receptor antibodies revealed that a population of inhibitory GABAergic local interneurons in the antennal lobes express the AmOA1 receptor in the cell bodies, axons and their endings in the glomeruli. In the mushroom bodies, AmOA1 receptors are expressed in a subpopulation of inhibitory GABAergic feedback neurons that ends in the visual (outer half of basal ring and collar regions) and olfactory (lip and inner basal ring region) calyx neuropils, as well as in the collar and lip zones of the vertical and medial lobes. The data suggest that one effect of octopamine via AmOA1 in the antennal lobe and mushroom body is to modulate inhibitory neurons

Perfluorohexane sulfonate (PFHxS) and a mixture of endocrine disrupters reduce thyroxine levels and cause antiandrogenic effects in rats

Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. The developmental toxicity of perfluorohexane sulfonate (PFHxS) is largely unknown despite widespread environmental contamination and presence in human serum, tissues and milk. To thoroughly investigate PFHxS toxicity in developing rats and to mimic a realistic human exposure situation, we examined a low dose close to human relevant PFHxS exposure, and combined the dose-response studies of PFHxS with a fixed dose of 12 environmentally relevant endocrine disrupting chemicals (EDmix). Two reproductive toxicity studies in time-mated Wistar rats exposed throughout gestation and lactation were performed. Study 1 included control, two doses of PFHxS, and two doses of PFHxS+EDmix (n=5-7). Study 2 included control, 0.05, 5, or 25 mg/kg body weight/day PFHxS, EDmix-only, 0.05, 5, or 25mg PFHxS/kg plus EDmix (n=13-20). PFHxS caused no overt toxicity in dams and offspring but decreased male pup birth weight and slightly increased liver weights at high doses and in combination with the EDmix. A marked effect on T4 levels was seen in both dams and offspring, with significant reductions from 5 mg/kg/day. The EDmix caused antiandrogenic effects in male offspring, manifested as slight decreases in anogenital distance, increased nipple retention and reductions of the weight of epididymides, ventral prostrate, and vesicular seminalis. PFHxS can induce developmental toxicity and in addition results of the co-exposure studies indicated that PFHxS and the EDmix potentiate the effect of each other on various endpoints, despite their different modes of action. Hence, risk assessment may underestimate toxicity when mixture toxicity and background exposures are not taken into account

Aluminium alloys in swiss public collections ::identification and development of diagnostic tools to assess their condition

Despite their presence in many museum collections as testimony to the great technological advances of the late 19th century, aluminium alloy objects are rarely exhibited or may even be discarded because of their unattractive surface appearance. Conservation professionals are often helpless when faced with these materials which they consider to be unalterable but whose composition, desired appearance during their manufacture, successive uses and corrosion forms developed over the long term are not well known. Any diagnosis is therefore extremely uncertain. The objective of this project was to cover this gap and provide conservation professionals with examination tools and diagnostic assistance. This approach has been applied to more than 400 objects preserved in four Swiss museum or private collections and considered sufficiently representative of the problems posed by aluminium alloys. The materials were systematically analysed, the corrosion forms developed identified, characterised and compared from one collection to another. Some alterations were examined in depth and the observed models were inserted into the MiCorr participatory database (micorr.org). The results obtained should make it possible to appreciate better the nature of the materials studied and understand their long-term performance in order to propose, if necessary, appropriate intervention

Characterization and identification of varnishes on copper alloys by means of UV Imaging and FTIR

The application of varnishes on the surface of metal objects has been a very common practice since antiquity, both for protective and aesthetic purposes. One specific case concerns the use of tinted varnishes on copper alloys in order to mimic gilding. This practice, especially flourishing in the 19th century for scientific instruments, decorative objects, and liturgical items, results in large museum collections of varnished copper alloys that need to be preserved. One of the main challenges for conservators and restorers deals with the identification of the varnishes through non-invasive and affordable analytical techniques. We hereby present the experimental methodology developed in the framework of the LacCA and VERILOR projects at the Haute École ARC of Neuchâtel for the identification of gold varnishes on brass. After extensive documentary research and analytical campaigns on varnished museum objects, various historic shellac-based varnishes were created and applied by different methods on a range of brass substrates with different finishes. The samples were then characterized by UV imaging and infrared spectroscopy before and after artificial ageing. The comparative study of these two techniques was performed for different thicknesses of the same varnish and for different shellac grades in order to implement an identification methodology based on simple non-invasive examination and analytical tools, which are accessible to conservator

Investigating five totalizing counters manufactured by the Alphonse Darras company of the CNAM collections in Paris

The paper reports the study of five totalizing counters preserved in the collections of the CNAM (museum of the Conservatoire National des Arts et Métiers) in Paris. These artefacts are part of a corpus of over forty counters attributed to the Darras company founded by the engineer Alphonse Darras (1860-1936). In the framework of the LacCA project at Haute Ecole Arc, Neuchâtel (Switzerland), dedicated to the characterization of lacquered copper-alloys, the focus of the study were the different aspects of the object’s coatings. Lacquers were frequently applied on technical objects with the double aim of protecting them from corrosion and to provide a specific esthetical appearance. Five totalizing counters showing various shapes and surface colors were chosen from the lot and examined with a non-invasive multi analytical approach. The comparative study – investigating lacquering processes and materials – contributes to the historical study of these artefactsEste artigo descreve o estudo de cinco contadores totalizadores conservados nas coleções do CNAM (museu do Conservatoire National des Arts et Métiers) em Paris. Estes artefactos fazem parte de um corpus de mais de 40 contadores atribuídos à empresa Darras, fundada pelo engenheiro Alphonse Darras (1860-1936). O estudo desenvolvido no âmbito do projecto LacCA da Haute Ecole Arc, Neuchâtel (Suíça) sobre caracterização de ligas de cobre lacadas, incidiu sobre as diferentes características dos revestimentos dos objetos. As lacas eram frequentemente aplicadas em objetos técnicos com o duplo intuito de proteção contra a corrosão e decoração. Cinco contadores totalizadores com diferentes formas e cores, foram selecionados e examinados através de diferentes técnicas analíticas não invasivas. O estudo comparativo – investigando os processos e os materiais de lacagem – contribui para o estudo histórico destes artefactos

Special Issue: The sixth international workshop on unstructured mesh numerical modelling of coastal, shelf and ocean flows

Special issue of the journal "Ocean Modelling" following the workshop on unstructured-mesh numerical modelling of coastal, shelf and ocean flows held at Imperial College (London, UK) on September 19-21, 2007. This special issue contains 16 peer-reviewed research articles

The Impact of Wetting-Heterogeneity Distribution on Capillary Pressure and Macroscopic Measures of Wettability

We investigate the effect of the length scale of wetting heterogeneities, close to the length scale of a pore, on capillary pressure saturation (CPS) curves and the United States Bureau of Mines (USBM) and Amott-Harvey (AH) wettability indices. These macroscopic wettability indices are used to describe bulk rock wettability, because the local contact angle (the standard physical measure of wettability) in a sample is difficult to access and might vary within and between pores caused by changes in mineralogy and the surface coverage of organic materials. Our study combines laboratory experiments and full-scale fluid-dynamics simulations using the multiphase stochastic-rotation dynamics (SRDmc) model. Four model systems were created using monodisperse glass beads. The surface properties of the beads were modified so that one-half of the surface area in each system was strongly hydrophilic and the other half was hydrophobic. However, each system had a different length scale of wetting heterogeneity, ranging from a fraction of a bead diameter to two bead diameters. There is excellent agreement between the experimental and simulation results. All systems are classified as intermediate-wet on the basis of their AH and USBM indices. An examination of the capillary pressure curves shows that the opening of the stable hysteresis loop decreases monotonically as the length scale of the wetting heterogeneities is increased. Thus, our results suggest that macroscopic wettability indices could be used as indicators of ultimate recovery, but they are not suited to discriminate between the different flows that occur earlier in a mixed-wettability displacement process