The absolute dating of mortar by accelerator mass spectrometry (AMS) has been the subject of renewed interest for several years. International intercomparison campaigns, called MODIS (MOrtar Dating Intercomparison Study), have been carried out. The first MODIS-1 campaign highlighted limitations in mortar dating, due to the similarity between the primary material to be dated (binder) and the contaminant (exogenous CaCO3). Methods have since emerged to overcome this problem and the need for a good preliminary characterization has been proven. The Laboratoire de Mesure du Carbone 14 (LMC14) took part in the second intercomparison campaign, MODIS2, by applying thermal decomposition increments to distinguish the carbonated binder, the organic matter contaminants (late in formation pyrogenic carbonate, LDH) and limestone. The LMC14 results on MODIS2 are quite conclusive on “pure” re-carbonated lime mortar binders containing little contaminant geological limestone but show their weaknesses for mortars heavily contaminated in Dolomites, which are difficult to discern from the binder. Recommendations for users of radiocarbon (14C) dating on mortar-based materials are made in the conclusion.

Spermaceti is a waxy substance found in the head cavities of sperm whales (Physeter macrocephalus and P. catodon). This substance had a variety of commercial applications from the end of the 18th to the beginning of the 20th century, such as candles, soap, cosmetics and other compounds. Spermaceti was also occasionally used as wax for modeling sculptures. In order to date such artworks the marine reservoir effect (MRE) has to be considered. The chemical library of the Muséum national d’Histoire naturelle (Paris, France) contains samples of spermaceti studied by the French chemist M. E. Chevreul (1786–1889) at the beginning of the 19th century. Eight samples of substances preserved in their original containers were 14C dated. According to the whaling practices and the publications of Chevreul, we estimated that the spermaceti samples came from whales caught between 1805 and 1815. AMS 14C dating results are from 550 to 1180 ± 30 BP, R values between 393 and 1023 (± 34) 14C yr and ΔR between –168 and 504 (± 60) 14C yr. The values presented here are the first ever obtained for spermaceti. However, being based on museum specimens, further measurements on crude material would be necessary to refine these results.

The direct dating of rock paintings is not always possible due to the lack of organic carbon compounds in pigments, or because sampling from a heritage site is often restricted. To overcome these limitations, dating laboratories have to develop new approaches. In this study, we consider sampling calcium oxalate crusts covering the painted artworks as a way to indirectly date the rock art. This stratigraphic approach includes isolating and extracting pure oxalate from the crusts. The approach was tested on natural bulk accretions collected in the open-air sites of Erongo Mountains in Namibia. The accretions were separated into two phases (pure oxalate and the remaining residues) with a special pretreatment. This process removes carbonates through acidification (HCl 6N) and dissolves the oxalate into the supernatant, leaving the minerals and windblown organic compounds in the residue. The efficiency of the separation was checked on the two phases by FTIR analyses and by 14C dating and showed that pure oxalate powders were indeed obtained. AMS radiocarbon results of various accretions on the same art panels provided ages from modern periods to 2410 ± 35 BP. From these first results, more targeted sampling campaigns can be considered to provide a terminus ante quem for the rock art.

Quality control procedures have been developed at the Laboratoire de Mesure du Carbone 14 (LMC14) national laboratory throughout the years of operation. Routine procedures are applied to sample preparation depending on their composition and their size. The tuning of the ARTEMIS AMS facility, hosted by the LMC14 laboratory, uses an accurate procedure. A batch of unknown samples is measured with accompanying samples (primary and secondary standards and blanks), which give a powerful set of data to control the quality of each measurement. A homemade database has been created to store the sample information and study the evolution of the accompanying samples. The LMC14 laboratory participated in the Sixth International Radiocarbon Intercomparison, SIRI. The results are presented here, with statistical tests to assess the quality of the preparations and measurements done at the LMC14 national laboratory. To obtain a reliable radiocarbon (14C) age by AMS, 1 mg of sample is required in routine analysis. Recently, the LMC14 developed a new procedure dedicated to microsamples, allowing the size of samples to be reduced and contributing to opening 14C dating to materials that were previously unreachable. This new procedure has been successfully tested on valuable Cultural Heritage samples: lead white mural paintings.

Lead carbonates were used as cosmetic and pigment since Antiquity. The pigment, known as lead white, was generally composed of cerussite and hydrocerussite. Unlike most ancient pigments, lead white was obtained by a synthetic route involving metallic lead, vinegar and organic matter. Fermentation of organic matter produces heat and CO2 emission, leading to the formation of carbonates. As lead white is formed by trapping CO2, radiocarbon (14C) dating can thus be considered. We have developed a protocol to prepare lead white. We selected modern pigments for the experiment implementation and ancient cosmetic and paintings for dating. After characterization of the samples by XRD, thermal decomposition of cerussite at various temperatures was explored in order to select the appropriate conditions for painting samples. CO2 extraction yield, SEM and XPS were used to characterize the process. Thermal decomposition at 400°C was successfully applied to mixtures of lead white with other paint components (oil as binder, calcite as filler/extender) and to historical samples. We obtained radiocarbon measurements in agreement with the expected dates, demonstrating that thermal decomposition at 400°C is efficient for a selective decomposition of lead white and that paintings can be directly 14C-dated by dating lead white pigment.

Absolute dating of mortars is crucial when trying to pin down construction phases of archaeological sites and historic stone buildings to a certain point in time or to confirm, but possibly also challenge, existing chronologies. To evaluate various sample preparation methods for radiocarbon (14C) dating of mortars as well as to compare different dating methods, i.e. 14C and optically stimulated luminescence (OSL), a mortar dating intercomparison study (MODIS) was set up, exploring existing limits and needs for further research. Four mortar samples were selected and distributed among the participating laboratories: one of which was expected not to present any problem related to the sample preparation methodologies for anthropogenic lime extraction, whereas all others addressed specific known sample preparation issues. Data obtained from the various mortar dating approaches are evaluated relative to the historical framework of the mortar samples and any deviation observed is contextualized to the composition and specific mineralogy of the sampled material.

A growing body of literature has explored the influence of physical activity on brain structure and function. While the mechanisms of this relationship remain largely speculative, recent research suggests that one of the effects of physical exercise is an increase in synaptic long-term potentiation (LTP). This has not yet been explored directly in humans due to the difficulty of measuring LTP non-invasively. However, we have previously established that LTP-like changes in visual-evoked potentials (VEPs) can be measured in humans. Here, we investigated whether physical fitness status affects the degree of visual sensory LTP. Using a self-report measure of physical activity, participants were split into two groups: a high-activity group, and a low-activity group. LTP was measured and compared between the two groups using the previously established electroencephalography-LTP paradigm, which assesses the degree to which the N1b component of the VEP elicited by a sine grating is potentiated (enhanced) following a rapid “tetanic” presentation of that grating. Both groups demonstrated increased negativity in the amplitude of the N1b component of the VEP immediately after presentation of the visual “tetanus,” indicating potentiation. However, after a 30-min rest period, the N1b for the high-activity group remained potentiated while the N1b for the low-activity group returned to baseline. This study presents the first evidence for the impact of self-reported levels of physical activity on LTP in humans, and sheds light on potential neurological mechanisms underlying the relationship between physical fitness and cognition. (JINS, 2015, 21, 831–840)

Radiocarbon dating of the carbonate remaining in calcined bones is widely regarded as a viable alternative to date skeletal remains in situations where collagen is no longer present. However, anomalously low δ13C values measured in calcined bones prompted questions about the origin of the carbon used for dating. The goal of this study was to quantify the magnitude of carbon isotope exchange between bone carbonate and environmental CO2 for bones calcined under natural conditions. Four archaeological bones ranging in age between the Neolithic and the Medieval period were combusted on a separate open fire for up to 4 hr and subsamples of calcined bones were taken every hour. All the bones experienced a significant increase in IRSF values and decrease in carbonate content and δ13C values. 14C ages measured in the carbonate fraction of well-calcined bones indicate that 67 ± 3% to 91 ± 8% of the carbon present in bone carbonate was replaced by carbon from the atmosphere of combustion. This finding confirms previous results obtained under laboratory conditions and has serious implications for 14C dating of calcined bones found in archaeological contexts. The 14C age obtained on a calcined bone will only reflect the true age of the bone sample if the age difference between the bone and the charcoal can be neglected. Our results show also that δ13C values of calcined bones can be used to estimate the degree of C exchange and control for post-burial diagenetic alteration.

Single Walled Carbon Nanotubes (SWNTs) dispersions are obtained after ultrasonication in Cellulose Nanocrystals (CNs) colloidal suspensions and they are found to be stable during several months. Similarly to CNs suspensions, SWNTs/CNs dispersions are used to elaborate multilayered thin films by the layer by layer method. Characterizations of the growth pattern, Raman and optical properties of the films are investigated. The presence of isolated SWNTs in each bi-layer is attested by characteristic Raman and luminescence signals. These films may be interesting for sensing applications.

The Bay of Bourgneuf, France, is a main site of shellfish production. In the marshes along the bay, oyster intensive rearing and fattening need the mass production of microalgae. Salt groundwaters, available in this region, support a large part of this production for aquaculture. Studies carried out by local authorities have brought to the fore the accumulation of lead (Pb) in several samples of algal pastes derived from cultures using salt groundwater. The aim of this study was to compare growth, nutritional value and metal (Cd, Cu, Pb and Zn) uptake of four microalgae grown in two salt groundwaters or in enriched coastal seawater. Cultures of microalgae used in aquaculture (Haslea ostrearia, Phaeodactylum tricornutum, Skeletonema costatum and Tetraselmis suecica) were realised at the laboratory under controlled experimental conditions. Results indicated that salt groundwaters provided cultures with, at least, an equal biomass and a nutritional value similar to cultures grown in enriched seawater. There was no difference regarding metal accumulation whatever the culture medium, except when S. costatum was grown in one of the salt groundwater in which case its cadmium levels were higher and could be above the French guideline level. These observations questioned on the bioavailability of metals in salt groundwaters. It also underlines the specificity of metal uptake and accumulation by microalgae.

Three major lithographic applications have emerged for electron beam exposure tools: optical mask fabrication, direct writing for device fabrication, and more recently projection e-beam printing. The traditional mask making process uses poly(butenesulfone) resist. A wet etch process was adopted to generate patterns on chrome. Recently, shrinking dimensions, optical proximity correction features, and the complexity of phase shift masks have forced the industry to a chrome dry etch process. ZEP, a poly(methyl α-chloroacrylate-co-α-methylstyrene) based resist, has been well accepted for most of the >180 nm device mask making. The acceptance of ZEP comes in spite of its low contrast, marginal etch resistance, organic solvent development, and concerns of resist heating associated with its high dose requirements. These issues have spawned interest in using chemically amplified resist (CAR) systems for direct write and mask making applications. We have developed a high contrast resist based on ketal protecting groups, KRS-XE, which is robust against airborne contamination and can be used for all forms of e-beam exposure in both chrome mask and silicon processing. This high contrast resist is processed with aqueous base developer and has a wide bake latitude. The development of KRS-XE has provided the capability of fabricating chrome masks for future generation (< 180 nm) devices and has potential for use with projection beam exposure systems.