Known as lead white, lead carbonates were used as white pigment or cosmetics from the 4th century BC to the 20th century AD. Lead white was produced by the corrosion of metallic lead by vinegar and horse manure up to the 19th c. In order to document the incorporation of carbon in the corrosion mechanism, lead carbonates were produced in the laboratory under monitored experimental conditions using materials with different isotope signatures in 14C and 13C. Six experimental setups were defined combining vinegar, acetic acid, horse manure and fossil CO2 gas. The corrosion products were characterized by X-ray diffraction. 14C content and δ13C values of the initial reactants and the final products were measured by accelerator and isotopic ratio mass spectrometry (AMS and IRSM). The reaction between lead and vinegar or acetic acid resulted in lead acetates with a carbon isotopic signature close to that of the corrosive reagent. In the presence of CO2, the carbonatation reaction occurred and the cerussite produced had a predominant 14C signature of the carbon dioxide source. These experiments demonstrate that the CO2 produced by horse manure fermentation is incorporated into the corrosion products, allowing the absolute dating of lead white by the radiocarbon method.

Se presentan los resultados de fluorescencia de rayos-X realizados a 12 artefactos provenientes de contextos funerarios Chinchorro, Arica, norte de Chile, focalizándose la discusión en el manganeso (Mn). La muestra con mayor concentración de Mn fue analizada con espectrometría Raman, para avanzar en la identificación estructural del cromóforo negro correspondiente. Todos los artefactos dieron positivo para la presencia de Mn con un rango de 1,11%-63,66%, considerándose antrópico sobre 2% (83,33% del total) y el pigmento analizado fue identificado como criptomelano y goetita.

Lead white is a man-made white pigment commonly used in works of art. In this study, the possibility of radiocarbon dating lead white pigments alone and in oil paints was explored using well-dated lead white pigments and paints. Resulting 14C ages on lead white pigments produced following the traditional stack process, where carbonate groups results from the incorporation of CO2 originating from fermentation, matched the production years, while radiocarbon dating of lead white made using other industrial processes indicate that 14C depleted CO2 was used in their production. The method was applied to two case studies, where lead carbonate samples were dated in two oil paintings, one Baroque and one from the 20th century. We hereby show that the lead white pigment can be dated by 14C and used as proxy for the time of creation of an artwork. Additionally, a two-step method was developed to allow 14C analysis of both the lead white pigment and oil binder from the same sample. A single lead white paint sample can yield two distinct radiocarbon ages, one from the carbonate and one from the natural organic binder. This study thus proposes new strategies for 14C dating of artworks.

Visible derivative spectroscopy (VDS) analysis of sediment from Cleland Lake, Southeastern British Columbia provides a reconstruction of paleolimnological productivity and hydrologic change during the past 14,000 calibrated 14C years before present (cal yr BP). The first five principal components (PC) of the VDS data explain 97% of the variance in the VDS data set. Four PCs correlate with standard reflectance derivative spectra for diatom, dinoflagellate algae, and cyanophyte pigments that record ecological change, while two PCs are paleohydrologic indicators. Dinoflagellate algae are predominant from 11,600 to 8600 cal yr BP then decrease to low levels after ~ 8500 cal yr BP. PCs 3–5 represent variations in cyanophyte abundance and exhibit peaks from 14,000 to 11,600, 14,000 to 9500, and 6100 to 5400 cal yr BP, respectively. Conditions shifted toward favoring diatoms around 9400 and lasted until 170 cal yr BP. Higher dinoflagellate-related pigment concentrations suggest a lower lake level from 11,600 to 8600 cal yr BP, followed by higher water levels and wetter conditions after 8500 cal yr BP. We propose that drier conditions transitioning from the late glacial into the Holocene were caused by summer insolation-driven, non-linear feedbacks between the northern hemisphere subtropical high-pressure systems, vegetation, and soil moisture.

X-ray fluorescence spectrometry (XRF) and micro-X-ray diffraction (μXRD) were used to analyze the composition of pigments on a pastel drawing, Special No. 32, by Georgia O’Keeffe. XRF analyses showed that, among other pigments present in the drawing, the red, orange, and yellow pigments may possibly be identified with lead- and chromium-based pigments: lead chromates, red and yellow lead oxides, and/or lead carbonates, plus calcium-based pastel fillers, such as whiting or gypsum. XRD examination of a sample removed from a dark mottled area of coral red pastel confirmed that this pigment layer, which is associated with a darkened appearance and high Pb:Cr ratios, matches the red lead oxide, minium (2PbO⋅PbO2).

Cutmarks on the bones of ten individuals from Körtik Tepe, a Pre-Pottery Neolithic site in Southeastern Anatolia, were analysed using a bioarchaeological approach. Half of the ten individuals possess cutmarks on their crania only while the other five have cutmarks on both their cranial and postcranial bones. Diagnoses of these cutmarks suggest they were made on fresh cadavers, while skeletal data and burial customs reveal that the individuals with cutmarks were subject to human intervention in the decomposition process, understood as post-burial practices rather than secondary burials. This conclusion is supported by the application of plaster and paint as part of the burial customs. The process of defleshing is interpreted as an attempt to purify the corpse and to separate death from life.

The crustose lichen genus Mycoblastus in the Northern Hemisphere includes eight recognized species sharing large, simple ascospores produced 1–2 per ascus in strongly pigmented biatorine apothecia. The monophyly of Mycoblastus and the relationship of its various species to Tephromelataceae have never been studied in detail. Data from ITS rDNA and the genes coding for translation elongation factor 1-α and DNA replication licensing factor mini-chromosome maintenance complex 7 support the distinctness of Mycoblastus s. str. from the core of the Tephromelataceae, but recover M. fucatus and an undescribed Asian species as strongly supported within the latter group. We propose accommodating these two species in a new genus, Violella, which is characterized by its brownish inner ascospore walls, Fucatus-violet hymenial pigment granules and secondary chemistry, and discuss the position of Violella relative to Calvitimela and Tephromela. We describe the new species Violella wangii T. Sprib. & Goffinet to accommodate a new species with roccellic acid from Bhutan, China, India and the Russian Far East. We also exclude Mycoblastus indicus Awasthi & Agarwal from the genus Mycoblastus and propose for it the new combination Malmidea indica (Awasthi & Agarwal) Hafellner & T. Sprib.

A petroglyph showing a human face found in East Timor is dated to the late Pleistocene. It recalls ancient Australian forms and raises the possibility of connecting early cave art with the better known painted figures of Lapita/Austronesian art ten millennia later. This new discovery at a known cave shows what precious evidence still lies in store even in well-trodden places.

Introduction. In Mexico, the Myrtillocactus fruit production levels are substantial, yet fruits are often under-used. Although the focus of interest is on their potential as food colourings, the fruits deserve more attention for their other food properties but information on their physico-chemical composition is scarce. To offer a baseline for the development of Myrtillocactus cultivation, we reviewed the information so far available. Botanical description. Four Myrtillocactus species have been identified and reported in the literature. They differ in shape, colour and other phenotypic characteristics. In Mexico, the predominant species is M. geometrizans, but M. schenckii also grows abundantly throughout the arid and semi-arid lands of the country. Cytological analyses performed on M. geometrizans showed that the plant is diploid (2n = 22). Agronomic aspects. Myrtillocactus species belong to the Cactaceae family. Because of their Crassulacean acid metabolism, they are able to grow in the arid and semi-arid highlands of Mexico. Myrtillocactus species have been propagated asexually by explants or cloning. Under controlled conditions, in vitro micropropagation from apical and basal explants gives rise to high yields. For cultivation, attention should be paid especially to minimum winter temperatures. Description of fruits and biochemical characterisation. The edible fruit is globular, with diameters reaching 1.5 cm. The pulp is gel-like, ranging in colour from glowing red to bluish. Chemical characterisation has mainly focused on betalain compounds, the predominant ones of which are betanin and betaxanthins. Contents are reported to be about 2.3 mg betalain·100 g–1of pulp. Colour appears to be more stable than for red beets. Human consumption and commercial importance. In the production season (June to September), the fruits are found in all public markets in the states where they are grown. They are eaten either fresh or in processed forms. The commercialisation of the fruit is restricted mainly to rural production areas in certain states of Mexico. Conclusions. Our review establishes that published information on Myrtillocactus species is scarce and incomplete. The plant is under-utilised, despite its nutritional properties and commercial potential. Because they adapt easily to severely dry conditions, the Myrtillocactus species merit much more research.

Avian eggs differ so much in their colour and patterning from species to species that any attempt to account for this diversity might initially seem doomed to failure. Here I present a critical review of the literature which, when combined with the results of some comparative analyses, suggests that just a few selective agents can explain much of the variation in egg appearance. Ancestrally, bird eggs were probably white and immaculate. Ancient diversification in nest location, and hence in the clutch's vulnerability to attack by predators, can explain basic differences between bird families in egg appearance. The ancestral white egg has been retained by species whose nests are safe from attack by predators, while those that have moved to a more vulnerable nest site are now more likely to lay brown eggs, covered in speckles, just as Wallace hypothesized more than a century ago. Even blue eggs might be cryptic in a subset of nests built in vegetation. It is possible that some species have subsequently turned these ancient adaptations to new functions, for example to signal female quality, to protect eggs from damaging solar radiation, or to add structural strength to shells when calcium is in short supply. The threat of predation, together with the use of varying nest sites, appears to have increased the diversity of egg colouring seen among species within families, and among clutches within species. Brood parasites and their hosts have probably secondarily influenced the diversity of egg appearance. Each drives the evolution of the other's egg colour and patterning, as hosts attempt to avoid exploitation by rejecting odd-looking eggs from their nests, and parasites attempt to outwit their hosts by laying eggs that will escape detection. This co-evolutionary arms race has increased variation in egg appearance both within and between species, in parasites and in hosts, sometimes resulting in the evolution of egg colour polymorphisms. It has also reduced variation in egg appearance within host clutches, although the benefit thus gained by hosts is not clear.

Introduction. The peel of lychee fruit turns from its attractive bright red color to a dull brown color when the fruit starts to age. This study reports how the color change of lychee pericarp from red to brown is associated with several factors and may be reversed depending on its pH, anthocyanin content and brown pigments. Materials and methods. After transport by air transit from China to Canada, arriving 4 d after harvest, the anthocyanin, brown pigment concentrations and the pH values in the lychee (Litchi chinensis Sonn.) pericarp were determined over a period of 5 d at 25 °C and 65% RH. The macromolecular sizes of the brown pigment extract were measured in solutions between a pH of 4 and 6. Results and discussion. The acidity in the lychee pericarp decreased from a pH of 4.3 to 5.3, at the end of the 5-day period. The anthocyanins in the lychee pericarp decreased and the brown pigment increased. Polyphenol oxidase in the pericarp was active when its pH was between 4.1 and 4.6, and became less active when its pH was above 4.6. The diameter of the brown pigment molecules in the solutions increased when the pH of the solutions was increased and maintained for 5 d. The anthocyanins returned to their original redness and concentrations if they were placed in solutions with a pH value ranging between 4 and 6 for 10 min or they were placed in solutions with a pH value of 4 for 5 d. However, the anthocyanins did not return to their original redness and concentration if they were placed in solutions with a pH value ranging between 5 and 6 for 5 d. Conclusion. This study suggests that the bright red color of lychee peel could be maintained if its pericarp pH could be maintained at a pH of 4. If the pericarp pH is above 4, the reversibility of its bright red color from brown pigments is dependent on storage time.

Although mat-forming cyanobacteria dominate many freshwater ecosystems in the Arctic and Antarctic, their optimal temperature for growth (Topt) is usually much higher than the temperature range of their native habitat. The present study compared the temperature dependence of growth, pigment composition and absorbance, photosynthesis and photosynthate partitioning for two strains of cyanobacteria with contrasting Topt values; Phormidium subfuscum, isolated from McMurdo Ice Shelf, Antarctica, and Phormidium tenue, collected from the Kuparuk River in the tundra region of northern Alaska. Phormidium subfuscum grew between 5 and 20°C with a Topt of 15°C whereas P. tenue showed detectable growth from 10 to 40°C and a Topt of 30°C. Light utilization efficiency, photosynthetic capacity and the irradiance at the onset of light saturation increased with increasing temperature up to Topt in both strains. The cellular concentrations of chlorophyll a (Chl a) and carotenoid (CAR) and the in vivo absorbance maxima for Chl a, CAR, C-phycocyanin and allophycocyanin changed little for P. subfuscum but all these variables increased across the temperature range up to Topt for P. tenue. Neither P. subfuscum nor P. tenue showed changes in relative carbon allocation with varying temperature, suggesting that gross biochemical alterations are not a characteristic of temperature acclimation in these cyanobacteria. We conclude that the eurythermal cyanobacterium P. tenue optimizes growth over a wide range of temperatures by adjusting its light-capturing as well as carbon fixation characteristics, whereas stenothermal P. subfuscum relies on changes in carbon fixation without concomitant shifts in pigment content.

The edge and isthmus of the mantle of Pinctada margaritifera (Mollusc, Bivalvia) were studied using light and electron microscopy from a morphological and histochemical point of view. Six areas with several subareas were differentiated in the mantle edge. One of these areas is similar to the epithelium isthmus. Trials to elucidate the nature of the pigment responsible for the black colour of the shell and pearl indicate a melanin-like material. Possible functions of the distinctive epithelial areas in Pinctada margaritifera mantle are discussed according to available data on the secretion of organic matrix of the shell, protein selerotization and deposition of crystals in some pearl-forming molluscs. Three different epithelial areas in the outer mantle edge of Pinctada margaritifera are probably involved in the sequential processes of deposition of calcite prisms, aragonite fibres and aragonite rhombs.